# Extended HNCO, SiO, and HC3N emission in 43 southern star-forming regions

Yu-Xin He Xinjiang Astronomical Observatory, Chinese Academy of Sciences,
Urumqi 830011, PR China  Key Laboratory of Radio Astronomy, Chinese Academy of
Sciences, Urumqi 830011, PR China  Chinese Academy of Sciences South America
Center for Astronomy, National Astronomical Observatories, CAS, Beijing
100012, China  Departmento de Astronomía, Facultad de Ciencias Físicas y
Matemáticas, Universidad de Concepción, Concepción, Chile  Christian Henkel
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011,
PR China  Astron. Dept., King Abdulaziz University, P.O. Box 80203, 21589
Jeddah, Saudi Arabia  Jian-Jun Zhou  Xinjiang Astronomical Observatory,
Chinese Academy of Sciences, Urumqi 830011, PR China  Key Laboratory of Radio
Astronomy, Chinese Academy of Sciences, Urumqi 830011, PR China  Jarken
Esimbek  Xinjiang Astronomical Observatory, Chinese Academy of Sciences,
Urumqi 830011, PR China  Key Laboratory of Radio Astronomy, Chinese Academy of
Sciences, Urumqi 830011, PR China  Amelia M. Stutz  Departmento de Astronomía,
Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción,
Concepción, Chile  Max-Planck-Institute for Astronomy, Königstuhl 17, 69117
Heidelberg, Germany  Hong-Li Liu  Departmento de Astronomía, Facultad de
Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción, Chile
Wei-Guang Ji  Xinjiang Astronomical Observatory, Chinese Academy of Sciences,
Urumqi 830011, PR China  Key Laboratory of Radio Astronomy, Chinese Academy of
Sciences, Urumqi 830011, PR China  Da-Lei Li  Xinjiang Astronomical
Observatory, Chinese Academy of Sciences, Urumqi 830011, PR China  Key
Laboratory of Radio Astronomy, Chinese Academy of Sciences, Urumqi 830011, PR
China  Gang Wu  Xinjiang Astronomical Observatory, Chinese Academy of
Sciences, Urumqi 830011, PR China  Key Laboratory of Radio Astronomy, Chinese
Academy of Sciences, Urumqi 830011, PR China  Xin-Di Tang  Xinjiang
Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, PR China
Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Urumqi 830011,
PR China  Toktarkhan Komesh  Xinjiang Astronomical Observatory, Chinese
Academy of Sciences, Urumqi 830011, PR China  Department of Solid State
Physics and Nonlinear Physics, Faculty of Physics and Technology, Al-Farabi
Kazakh National
University, Almaty, 050040, Kazakhstan  University of the Chinese Academy of
Sciences, Beijing 100080, People’s Republic of China  Serikbek Sailanbek
Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011,
PR China  Department of Solid State Physics and Nonlinear Physics, Faculty of
Physics and Technology, Al-Farabi Kazakh National
University, Almaty, 050040, Kazakhstan  University of the Chinese Academy of
Sciences, Beijing 100080, People’s Republic of China

###### Abstract

We have selected 43 southern massive star-forming regions to study the spatial
distribution of HNCO 404–303, SiO 2–1 and HC3N 10–9 line emission and to
investigate their spatial association with the dust emission. The morphology
of HNCO 404–303 and HC3N 10–9 agrees well with the dust emission. HC3N 10–9
tends to originate from more compact regions than HNCO 404–303 and SiO 2–1. We
divided our sources into three groups: those in the Central Molecular Zone
(CMZ), those associated with bubbles (Bubble), and the remaining sources,
which are termed ’normal star forming regions’ (NMSFR). These three groups,
subdivided into three different categories with respect to line widths,
integrated intensities, and column densities, hint at the presence of
different physical and chemical processes. We find that the dust temperature
$T_{\rm d}$, and the abundance ratios of $N_{\rm HNCO}/N_{\rm SiO}$ and
$N_{\rm HNCO}/N_{\rm HC3N}$ show a decreasing trend towards the central dense
regions of CMZ sources, while $N_{\rm HC3N}/N_{\rm SiO}$ moves into the
opposite direction. Moreover, a better agreement is found between $T_{\rm d}$
and $N_{\rm HC3N}/N_{\rm SiO}$ in Bubble and NMSFR category sources. Both
outflow and inflow activities have been found in eight of the sixteen bubble
and NMSFR sources. The low outflow detection rate indicates that in these
sources the SiO 2–1 line wing emission is either below our sensitivity limit
or that the bulk of the SiO emission may be produced by the expansion of an H
ii region or supernova remnant, which has pushed molecular gas away forming a
shock and yielding SiO.

astrochemistry — stars: formation — ISM: abundances — ISM: clouds C– ISM:
molecules — radio lines: ISM

††software: GILDAS/CLASS (Pety, 2005; Gildas Team, 2013), Matplotlib (Hunter,
2007), astropy (Astropy Collaboration et al., 2013)

##  1 Introduction

Shocks are a ubiquitous phenomenon in the interstellar medium (ISM) of
galaxies. They may be driven by supernova explosions, the pressure of
photoionized gas, stellar winds, and collisions between fast-moving clumps of
interstellar gas, where the fluid-dynamical disturbances proceed at a velocity
that exceeds the local sound speed because of the presence of large pressure
gradients (Draine & McKee, 1993). The processes of birth, evolution and death
of stars are always associated with shocks (Gusdorf, 2015). Therefore, a
systematic study of shocks in regions of star formation is of great importance
for our general understanding of the physical and chemical boundary conditions
of star formation.

Isocyanic acid (HNCO), which was detected for the first time in the Galactic
radio source Sgr B2 by Snyder & Buhl (1971), is a ubiquitous molecule. Based
on the morphology of the emission, the HNCO abundance with respect to H2 and
the relation to SiO emission, several authors tested the hypothesis that HNCO
could be a good tracer of interstellar shocks (e.g. Zinchenko et al., 2000;
Meier & Turner, 2005; Minh & Irvine, 2006). Afterwards, Rodríguez-Fernández et
al. (2010) tested this hypothesis by observing several transitions of HNCO
towards a well-known shocked Galactic source, L1157–mm, and proposed that HNCO
is a good shock tracer and the gas phase abundance of HNCO is achieved by both
grain mantle evaporation through shock waves and by neutral-neutral reactions
in the gas phase involving CN and O2.

The silicon monoxide (SiO) molecule is an excellent tracer of molecular gas
processed by the action of high-velocity ($\sim$20 – 50 km s-1) shocks in
regions of star formation (Martin-Pintado et al., 1992; Schilke et al., 1997;
Codella et al., 1999; Gusdorf et al., 2008a, b; López-Sepulcre et al., 2016).
Martin-Pintado et al. (1992) reported that this molecule is enhanced by large
factors (in some cases by $>$ 106) towards molecular outflows, which strongly
suggests that grain disruption by shocks is the major mechanism for releasing
SiO into the gas phase (Martin-Pintado et al., 1992). Furthermore, SiO
emission can also trace Photon Dominated Regions (PDRs) with $\sim$10 – 20 km
s-1 shocks (e.g. Schilke et al., 2001). In the Galactic center region, the gas
is characterized by large line widths, indicating a high degree of turbulence.
There, SiO is widespread (see e.g. the surveys in the J = 1–0 transition by
Martín-Pintado et al. 1997 and Jones et al. 2013, and in the J = 2–1
transition by Jones et al. 2012), which was interpreted as evidence for large
scale or ubiquitous (fast) shocks. Hüttemeister et al. (1998) observed 33
targets in the Galactic center region and found that at least some SiO is
detected in all cloud cores, mostly associated with cool gas. They proposed
that this was due to shocks caused by local turbulence and/or cloud-cloud
collisions. In the Galactic disc, quasithermal SiO emission is tightly
correlated with high temperature regions (e.g. Ziurys et al., 1989). In
addition, observations indicate that the properties of molecular peaks in the
Galactic center region are markedly different from the Galactic disk, where
thermal SiO emission is confined to very small regions in the vicinity of
outflows associated with star formation (Downes et al., 1982; Hüttemeister et
al., 1998).

Interstellar cyanoacetylene (HC3N) was first detected in Sgr B2 by Turner
(1971). It is an excellent dense gas tracer (Morris et al., 1976, 1977; Chung
et al., 1991; Bergin et al., 1996). Both chemical models and observations
indicate that the abundance of HC3N is enhanced towards hot cores (through the
gas-phase reaction C2H2 \+ CN $\rightarrow$ HC3N + H, see van Dishoeck &
Hogerheijde 1999 and Chapman et al. 2009 for details).

Shocks are often related to outflowing gas. The above mentioned tracers,
however, are not ideal when trying to study the entire velocity field
encompassing both quiescent, outflowing and inflowing gas. For this purpose
the HCO+ $J$ = 1–0 line has been chosen. With its skewed line profiles in case
of outflow or inflow, it provides the required signature (Wu et al., 2007; He
et al., 2015, 2016; Li et al., 2019).

The two shock tracers HNCO and SiO are chemically different. HNCO is thought
to arise from dust ice mantle sublimation under soft shocks (Meier & Turner,
2005), while SiO can be significantly enhanced in the gas phase by strong
shocks due to a partial/total evaporation of the SiO present in both the grain
mantles and the grain cores (e.g. Jiménez-Serra et al., 2005, 2008; Schilke et
al., 1997; Gusdorf et al., 2008b). Moreover, HNCO and HC3N are easily
dissociated by UV radiation and are hot core tracers (Martín et al., 2008;
Miettinen, 2014; Rodriguez-Franco et al., 1998), while SiO is more robust
against UV radiation. In past years, some HNCO or SiO molecular line surveys
of massive galactic dense clumps have already been published (Harju et al.,
1998; Zinchenko et al., 2000; Li et al., 2013; Csengeri et al., 2016).
However, most of the line surveys of massive Galactic dense clumps performed
so far are based on single-pointing observations in which case the spatial
distribution of HNCO and SiO emissions cannot be explored. Furthermore, beside
sources in the Galactic center region, the large-scale SiO J = 2–1 line
emission has been measured only in a few regions of the Galactic disk, such as
the filamentary infrared dark cloud (IRDC) G035.39$-$00.33 (Jiménez-Serra et
al., 2010) and the three IRDCs G028.37$+$00.07, G034.43$+$00.24, and
G034.77$-$00.55 (Cosentino et al., 2018), with the IRDC G034.77$-$00.55 being
further studied in detail by using ALMA data (Cosentino et al., 2019).
Therefore, it is clear that high-sensitivity mapping observations of HNCO, SiO
and HC3N are needed to characterise the spatial distributions of these species
and their relation to physical properties of dense clumps. This paper presents
a systematic study of a sample of 43 massive dense clumps. The spectral-line
mapping data used here were taken from the Millimetre Astronomy Legacy Team 90
GHz (MALT90) survey (Foster et al., 2011; Jackson et al., 2013). After
describing the sample selection and observations in Sect. 2, the observational
results are presented in Sect. 3. In Sects. 4 and 5, we analyze and discuss
the results and summarize the paper in Sect. 6.

##  2 Data

###  2.1 Observations

In the following, we will study a sample of 43 massive southern dense clumps
using data taken from the Millimetre Astronomy Legacy Team 90 GHz (MALT90)
Survey, the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), and the
Herschel infrared Galactic Plane Survey (Hi-GAL).

MALT90 is a large international project aimed at characterizing the physical
conditions, chemical, and evolutionary state of over 2,000 high-mass dense
cores in the southern sky at 90 GHz with the ATNF Mopra 22 m telescope (Foster
et al., 2011, 2013; Jackson et al., 2013). With the full 8 GHz bandwidth of
MOPS and the OTF mapping mode of Mopra, 3 arcmin $\times$ 3 arcmin maps can be
efficiently obtained simultaneously in 16 molecular lines. The angular
resolution and typical rms noise of this project are about 38′′ and
$T$${}_{\rm A}^{\ast}$ = 0.25 K per 0.11 km s-1 channel, respectively (for the
main beam efficiency, see Sect. 2.2). The data cubes of HNCO 404–303, SiO 2–1,
HC3N 10–9, and HCO+ 1–0, which will be used in the following analysis, were
downloaded from the MALT90 online archive 111http://atoa.atnf.csiro.au/MALT90.

ATLASGAL is the first systematic survey of the inner Galactic plane in the
sub-millimetre aimed at studying continuum emission from the highest density
regions of dust at 345 GHz with the APEX 12 m telescope (Schuller et al.,
2009; Contreras et al., 2013). The angular resolution of the APEX telescope at
this frequency is 19′′.2, and the r.m.s. is 50-70 mJy beam-1 in the final 870
$\mu$m survey images.

Hi-GAL is an unbiased photometric survey of the inner Galactic plane at 70 and
160 $\mu$m with PACS (Poglitsch et al., 2010), and at 250, 350, and 500 $\mu$m
with SPIRE (Griffin et al., 2010) on board of the Herschel satellite, aimed to
catalogue star-forming regions and studying cold structures across the
interstellar medium (Molinari et al., 2010). While we will not use the 70
$\mu$m band, which may trace a high temperature but low mass dust component,
the corresponding angular resolutions for the longer wavelength bands are
12′′, 18′′, 25′′, and 37′′, respectively. The PACS and SPIRE photometric maps
used here, processed by Molinari et al. (2016), were taken from the online
archive 222http://tools.asdc.asi.it/HiGAL.jsp.

###  2.2 Sample selection

The source sample of the present paper was selected from the MALT90
observations applying the following criteria: (i) at the peak of each HNCO
404–303, SiO 2–1 and HC3N 10–9 integrated intensity emission map, the averaged
intensity over a circular area with a diameter roughly equal to the Mopra
beamwidth (38′′, see Sect. 2.1) must lie above the detection threshold of
$3\sigma$. (ii) The HNCO 404–303 line presents relatively simple profiles,
which means no more than two velocity components, along the line of sight
towards the peak position of its integrated intensity emission map.

Using these criteria, all those 43 sources with extended molecular line
emissions have been selected for our sample. In the following these sources
were divided into three subsamples: 27 sources are part of the Central
Molecular Zone (CMZ) of the Galaxy, 10 sources are associated with expanding
bubbles of ionized gas (Bubble), and 6 are ”normal” star forming (NMSFR)
clouds with no obvious star-formation and interaction signatures from the
surrounding Spitzer 8$\mu$m continuum emissions (Benjamin et al., 2003;
Churchwell et al., 2009). Moreover, 4 Bubble sources (G322.159+00.635,
G327.293$-$00.579, G345.004$-$00.224 and G350.101+00.083) and 3 NMSFR sources
(G329.030$-$00.202, G335.586$-$00.289 and G348.754$-$00.941) in our sample are
identified as infrared dark clouds (IRDCs) by analysing Spitzer data in
Peretto & Fuller (2009).

In the following, the statistical results including only 10 Bubble and even
less NMSFR clouds would be not fully sufficient to provide reliable
statistical results, so that we will also compare our findings with additional
measurements taken from the literature in Sect. 5. The basic information is
summarized in Tables 1 and 2. Spectral line data were reduced using CLASS
(Continuum and Line Analysis Single-Disk Software), a part of the GILDAS
(Grenoble Image and Line Data Analysis Software) software 333GILDAS is a radio
astronomy software developed by IRAM. See http://www.iram.fr/IRAMFR/GILDAS/..
After baseline subtraction, the final spectra were converted to units of main
beam brightness temperature ($T_{\rm mb}$) according to the usual expression
$T_{\rm mb}=T_{\rm a}^{*}/\eta_{\rm mb}$, where $\eta_{\rm mb}$ is the
frequency-dependent beam efficiency. The main beam efficiency of Mopra at 86
GHz is 0.49, and at 110 GHz it is 0.44 (Ladd et al., 2005). Unless otherwise
specified, we use $T_{\rm mb}$ throughout the paper. ATLASGAL and Hi-GAL data
were also analysed towards our 43 southern massive dense clumps (see Sect. 3).

##  3 Dust temperature and molecular column density

###  3.1 Dust temperature

Combining the _Herschel_ Hi-GAL observations at 160, 250, 350, 500 $\mu$m, and
the APEX ATLASGAL observations at 870 $\mu$m, we obtained dust temperature
maps pixel by pixel from a single temperature gray-body dust emission model
which is given by

$I_{\nu}(T_{d},N_{\rm H_{2}})\,=\,B_{\nu}(T_{d})\left(1-e^{{\rm R}\times\mu
m_{\rm H}N_{\rm H_{2}}\kappa_{\nu}}\right),$ (1)

where $I_{\nu}$ is the observed intensity, $B_{\nu}(T_{d})$ is the Planck
function at a dust temperature $T_{d}$, $N_{\rm H_{2}}$ is the column density
of molecular hydrogen, R is the gas to dust mass ratio (assumed to be 100),
$\mu$ = 2.8 is the mean molecular weight of the interstellar medium (Kauffmann
et al., 2008), and $\kappa_{\nu}$ is the dust absorption coefficient. The
$\kappa_{\nu}$ curve is approximated by a power-law of
$\kappa_{\nu}=\kappa_{0}(\nu/\nu_{0})^{\beta}$, which depends on frequency
($\nu$ $<$ 1THz) and spectral index $\beta$ (Hildebrand, 1983). Guzmán et al.
(2015) tested 14 IRAS sources selected from the 1.1 mm Bolocam Galactic Plane
Survey (Rosolowsky et al., 2010; Ginsburg et al., 2013) and the ATLASGAL
catalog, and found that $\overline{\beta}$ = 1.6 is in agreement with the
absorption coefficient law of silicate-graphite grains, with 3$\times$104
years of coagulation, and without ice coatings analyzed by Ormel et al.
(2011). This choice of $\beta$ is also consistent with previous studies (see
e.g. Battersby et al., 2011). The sources in this paper can also be considered
as a subsample of the targets analysed by Guzmán et al. (2015), who determined
dust temperatures for all molecular clumps from the MALT90 survey using the
aforementioned absorption coefficient law presented by Ormel et al. (2011).
However, Guzmán et al. (2015) just provide average and peak dust temperature
for each source in their work, so we calculate dust temperature maps here. We
follow their method without fitting $\beta$ and directly use
$\kappa_{\nu}$=32.9, 13.9, 7.7, 4.3 and 1.7 cm2 g-1 values for the 160, 250,
350, 500, and 870 $\mu$m data, which were extracted from Ormel et al. (2011).
Before performing Spectral Energy Distribution (SED) fitting, we made use of
the routine 444https://github.com/esoPanda/FTbg/. developed by Wang et al.
(2015) to remove emission from the background and foreground. Next, all
previously mentioned images are convolved to the SPIRE 500 $\mu$m data
resolution (i.e., to 37′′) using the kernels provided by Aniano et al. (2011),
and then re-gridded to the same pixelization ($\sim$12′′).

The line optical thickness ($\tau_{\nu}$) of HNCO 404–303 could not be derived
through fitting the hyperfine structure, because the hyperfine structure is
not spectrally resolved. With limited bandwith, we also could not derive
$\tau_{\nu}$ of HNCO 404–303, SiO 2–1 and HC3N 10–9 by comparing the
intensities of two different isotopologues of the same species. Therefore, we
calculate the value of optical depth using equation 2. Assuming local
thermodynamic equilibrium (LTE) conditions, all levels are populated according
to the same excitation temperature ($T_{\rm ex}$). In addition, we performed
checks on the mean volume densities of the H2 molecule, which is given by
$n_{\rm H_{2}}=\frac{N_{\rm H_{2}}}{\theta\times d}$, combining column density
($N_{\rm H_{2}}$, see Sect. 3.2) with source size ($\theta$, see Sect. 4), and
find that about 75% of the sources are denser than 1.2$\times$104 cm-3, which
indicates that the gas and dust are thermally coupled (see Merello et al. 2019
for details). Distances ($d$) for CMZ sources are assumed to be 8.15 kpc (Reid
et al., 2019), and are taken from SIMBAD555http://simbad.u-strasbg.fr/simbad/
for the remaining sources. Therefore we assumed that $T_{\rm ex}$ is equal to
the temperature of the dust, $T_{\rm d}$. The optical thickness of the line
emission ($\tau$) can then be derived from the equation (Hernandez et al.,
2011):

$T_{\rm MB}\,=\,\frac{h\nu}{k_{\rm B}}\left[F(T_{\rm ex})-F(T_{\rm
bg})\right]\left(1-e^{-\tau_{\nu}}\right)\,,$ (2)

where $T_{\rm MB}$ is the main-beam brightness temperature, h is the Planck
constant, kB is the Boltzmann constant, $\nu$ is the transition frequency,
$T_{\rm ex}$ is the line excitation temperature, $T_{\rm bg}$ is the
background temperature, and $F(T_{\rm ex})$ is the (average) photon occupation
number, which is given by $F(T)=1/(e^{h\nu/k_{\rm B}T}-1)$. With $T_{\rm ex}$
from $T_{\rm d}$, and $T_{\rm mb}$ and $T_{\rm bg}$ being known from the
observations, the optical depths $\tau_{\nu}$ can also be determined.

###  3.2 Column densities and fractional abundances

The beam-averaged column densities of the three molecules (the size of the
beam is 38′′), $N_{\rm MOL}$, can be derived from Garden et al. (1991):

$N_{\rm MOL}\,=\,\frac{8\pi\nu^{3}}{c^{3}}\frac{Q_{\rm rot}}{g_{\rm u}A_{\rm
ul}}\frac{\exp(E_{{}_{l}}/k_{\rm B}T_{\rm ex})}{[1-\exp(-h\nu/k_{\rm B}T_{\rm
ex})]}\int\tau_{\rm\nu}\,dv~{},$ (3)

where $g_{\rm u}$ is the statistical weight of the upper level, $A_{\rm ul}$
is the Einstein coefficient for spontaneous emission, $E_{{}_{l}}$ is the
energy of the lower state, and $Q_{\rm rot}$ is the partition function. All
the above parameters of HNCO 404–303, SiO 2–1 and HC3N 10–9 are presented in
detail by Sanhueza et al. (2012). The calculated $\tau_{\nu}$ and column
densities of these three molecules are listed in Table 1, column 10 and Table
2, column 7, respectively.

The hydrogen column density, $N_{\rm H_{\rm 2}}$, can be derived from the
ATLASGAL dust continuum maps smoothed to the MALT90 resolution of 38′′
(Kauffmann et al., 2008):

$N_{\rm H_{\rm 2}}\,=\,\frac{S_{\rm{\nu}}\,\rm{R}}{B_{\rm\nu}(T_{\rm
d})\,\Omega\,\kappa_{\rm{\nu}}\,\mu\,m_{\rm H}}\,,$ (4)

where Sν is the 870 $\rm\mu$m continuum flux, $\rm\Omega$ is the beam solid
angle (which has been smoothed to the MALT90 resolution of 38′′), and
${\rm\kappa_{\nu}}$ is the dust-absorption coefficient (taken as 1.7 cm2 g-1,
see Sect. 3.1).

The fractional abundances of the molecules were calculated by dividing the
beam-averaged molecular column density by the hydrogen column density, $x_{\rm
MOL}$ = $N_{\rm MOL}$/$N_{\rm H_{\rm 2}}$. The calculated fractional
abundances of HNCO, SiO and HC3N are listed in Table 2, column 9.

##  4 Individual target analysis

Figs. 13–34 show the diagrams of the HNCO, SiO and HC3N 3 $\times$ 3 arcmin2
integrated intensity maps superposed on the ATLASGAL 870 $\mu$m emission
images and dust temperature maps, the beam averaged spectra of HNCO 404–303,
SiO 2–1 and HC3N 10–9 at the position marked by yellow crosses on the maps,
and the trends of normalized abundance ratios of $N_{\rm HNCO}/N_{\rm SiO}$,
$N_{\rm HNCO}/N_{\rm HC3N}$ and $N_{\rm HC3N}/N_{\rm SiO}$ along Galactic
longitude and latitude passing through the yellow cross for the 43 southern
sources, respectively. The HNCO lines, and a part of the strong SiO and HC3N
lines, which show single Gaussian profiles, were fitted with a single Gaussian
using CLASS. Sources showing more than one velocity were fitted using two
Gaussian components. For instance, CMZ sources G359.977$-$00.072,
G359.895$-$00.069, G359 .868$-$00.085, G359.453$-$00.112, G000.067$-$00.077,
G000.104$-$00.080, G000.106$-$00.001, G000.908$+$00.116, G001.655$-$00.062 and
G001.883$-$00.062, Bubble sources G345.004$-$00.224, G351.443$+$00.659 and
G351.775$-$00.537, and NMSFR sources G329.030$-$00.202 and G335.586$-$00.289
showing more than one velocity component were fitted with two Gaussian
components (the two Gaussian components and total fits are shown with red and
green lines in Figs. 13–34, respectively). The Gaussian fitting velocity
components with full-width half-maximum (FWHM) linewidth ($\Delta$V) of HNCO
404–303, SiO 2–1 and HC3N 10–9 emission are presented in Table 1. The
integrated line intensity ($\int{T_{\rm MB}}dv$ ) is derived by integrating
the area underneath the lines over the velocity range indicated in Table 2,
column 6. The details of the individual 43 sources are described in Appendix
A. In most CMZ sources, we find that the abundance ratios of $N_{\rm
HNCO}/N_{\rm SiO}$ and $N_{\rm HNCO}/N_{\rm HC3N}$ show a decreasing trend
towards the yellow cross, which is similar to the dust temperature, while
$N_{\rm HC3N}/N_{\rm SiO}$ moves into the opposite direction. In Bubble and
NMSFR category sources, dust temperature and $N_{\rm HC3N}/N_{\rm SiO}$
roughly follow a similar trend towards the center, where stars are forming
(see Sect. 5.4).

We characterize the size of HNCO 404–303, SiO 2–1 and HC3N 10–9 emission using
a beam deconvolved angular diameter of a circle with the same area as the
half-peak intensity, which is given by
$\theta=2(\frac{A}{\pi}-\frac{\theta_{beam}^{2}}{4})^{1/2}$, where A is the
area within the half-peak intensity, and $\theta_{beam}$ is the FWHM beam
size. The angular diameters of HNCO range from 25′′ to 200′′, with a mean
value of 102′′$\pm$45′′, the error being the standard deviation of an
individual measurement. Nearly all the angular diameters of HNCO are well
above the beam size. The angular diameters of SiO range from 14′′ to 196′′,
with a mean value of 97′′$\pm$48′′. Molecular lines of HNCO 404–303 and SiO
2–1 show similar sizes for most sources. The angular diameters of HC3N range
from 18′′ to 151′′, with a mean value of 81′′$\pm$37′′. Nearly half of the
angular diameters of HC3N are smaller than the telescope beam size. The
average angular diameters of NMSFR, Bubble and CMZ sources are 63′′$\pm$23′′,
61′′$\pm$24′′ and 124′′$\pm$38′′ for HNCO, 43′′$\pm$7′′, 51′′$\pm$20′′ and
122′′$\pm$37′′ for SiO, and 39′′$\pm$10′′, 48′′$\pm$24′′ and 100′′$\pm$28′′
for HC3N, respectively. That HC3N turns out to be more compact than HNCO and
SiO cannot be an effect of relatively weak HC3N lines which are not detected
in the outskirts of the clouds due to the limited sensitivity of our data. To
the contrary, the line tending to be weakest in our study is SiO, thus
suggesting that HC3N really originates from a smaller volume than HNCO and
SiO. Besides, these three species show more spatially extended emission
towards the CMZ sources as compared with the other two categories. The
distributions of the angular diameters for HNCO 404–303, SiO 2–1 and HC3N 10–9
are shown in Fig. 1.

##  5 Discussion

###  5.1 Previous studies

In order to investigate relations between properties of HNCO 404–303, SiO 2–1
and HC3N 10–9 and to compare our results with previous studies, we introduce a
number of comparisons with previous publications directly related to our data
in this section. Moreover, we also discuss inflow and outflow activities in
the Bubble and NMSFR sources (see Sect. 5.3).

In recent years, statistical studies of molecular clumps in the Milky Way have
mainly relied on samples associated with infrared dark clouds (IRDCs) in
Miettinen (2014), Sanhueza et al. (2012), Sakai et al. (2008) and Sakai et al.
(2010). IRDCs are extinction features against the background mid-IR emission
(e.g. Simon et al., 2006; Carey et al., 1998), and clumps therein are cold
(10-20 K) compared to clumps severely affected by ongoing massive star
formation (Carey et al., 1998). However, observations show that clumps found
in IRDCs can also be in various evolutionary stages or subject to H ii region
(bubble) feedback (Sanhueza et al., 2012), which are similar to Bubble and
NMSFR category sources defined by us in this study (see Sect. 2.2). Seven
sources (4 in the Bubble category and 3 in the NMSFR category) in our sample
have been identified as IRDCs by Peretto & Fuller (2009). Besides, 18 out of
35 clumps of IRDCs studied by Miettinen (2014) are located in the CMZ. All
this suggests that IRDCs are the most natural sources for comparisons with our
data. Sakai et al. (2008) and Sakai et al. (2010) assumed that $T_{\rm ex}$ is
equal to the rotation temperatures of NH3 and CH3OH, and found clump kinetic
temperatures in the range 10.3–20.8 K (15.5 K on average) and 13.4–24.5 K
(17.3 K on average), respectively. In this work we determine (see Sect. 3)
only slightly higher dust temperatures in the range 18–33 K (20 K on average),
so that the IRDCs provide a suitable sample with which our data can be
compared. As most sources studied by Sanhueza et al. (2012) show obvious signs
of massive star-forming activities, they derived even higher dust temperatures
in the range 17–52 K (average value 31 K). All of the above mentioned works
have been carried out in a single pointing mode. Because peak positions tend
to be strong, the following comparison is not dependent on the observational
sensitivity.

To derive column densities, Miettinen (2014) assumed that $T_{\rm ex}$ is
equal to $E_{\rm u}$/kB in the case of the linear molecules SiO and HC3N, 6.3
K and 24.0K, and that $T_{\rm ex}$ = 2/3 $\times$ $E_{\rm u}$/kB, 7 K, in the
case of HNCO, where $E_{\rm u}$ is the energy of the upper state. They derived
HNCO column densities of 5.4$\times$1012–7.9$\times$1014 cm-2. Their mean
value, 2.2$\times$1014 cm-2, is about one order of magnitude higher than the
value, 3.36$\times$1013 cm-2, obtained by Sanhueza et al. (2012). For HC3N
column densities, Miettinen (2014) found a median value of 1.6$\times$1014
cm-2 towards 11 embedded clumps in two IRDCs, almost an order of magnitude
higher than the highest value of 5.4$\times$1013 cm-2 found by Sakai et al.
(2008). Furthermore, Sanhueza et al. (2012) determined an even lower median
value of 4.77$\times$1012 cm-2 in 22 clumps. Because of these differences, we
tested HNCO and HC3N column density calculations using Eq. 3 with different
excitation temperature. We only find less than a factor of three differences
between the column densities determined with 10 K and 30 K. So the significant
difference is mainly caused by the spectral line intensity. By checking source
positions in Miettinen (2014), where HNCO and HC3N emissions are detected, we
find almost all of them located in the CMZ. Consistent with our data analyzed
in Sect. 5.2, higher spectral line intensities in the CMZ will result in one
order of magnitude higher column densities than those in the other two
categories.

Sakai et al. (2010) and Miettinen (2014) derived values of
4.6$\times$1012–3.8$\times$1013 cm-2 and 5.5$\times$1012–4.8$\times$1013 cm-2,
with average values of 1.5$\times$1013 cm-2 and 1.9$\times$1013 cm-2, for the
column densities of SiO, respectively. Sanhueza et al. (2012) have no CMZ
sources, thus obtaining smaller SiO column densities of
1.36$\times$1012–3.47$\times$1013 cm-2 with a median of 7.72$\times$1012 cm-2
in IRDC clumps. Moreover, there are two sources, G1.87$-$SMM 1 and G1.87$-$SMM
23, that have been studied by Miettinen (2014) analysing the same MALT90
survey data also used by us. The molecular properties of the corresponding
sources of G001.655$-$00.062 and G001.833$-$00.062 derived in this work are
similar to the values they found.

Here we will also compare our results with those obtained by Kelly et al.
(2017) and Aladro et al. (2015) in external galaxies in the following
discussions. All of the above mentioned works have carried out their
observation and analysis in a single pointing mode except Kelly et al. (2017)
in mapping the circumnuclear disk of the Seyfert galaxy NGC1068. By mapping
analysis, we can more directly understand spatial variations in HNCO, SiO and
HC3N emission as already emphasized in Sect. 4. Kelly et al. (2017) found that
the mean ratios of $I_{\rm HNCO}/I_{\rm SiO}$ are 0.35$\pm$0.13 and
2.5$\pm$1.3 in the heavily shocked East Knot and mildly shocked West Knot of
NGC1068, respectively. In nearby active galaxies, Aladro et al. (2015)
determined source-averaged column densities of simultaneously detected HNCO
404–303, SiO 2–1 and HC3N 10–9 with signal-to-noise ratios S/N $>$ 3 in the
starburst galaxies of M 83, NGC 253 (see also Martín et al., 2006), and M 82,
the AGN and starburst galaxy NGC 1068, and the ultra-luminous infrared galaxy
(ULIRG) Arp220. The mean abundance ratios of $N_{\rm HNCO}/N_{\rm SiO}$,
$N_{\rm SiO}/N_{\rm HC_{3}N}$, and $N_{\rm HNCO}/N_{\rm HC_{3}N}$ in starburst
galaxies are 10.94, 0.18, and 1.73, respectively. The corresponding values for
AGN and ULIRGs are 4.71, 0.45, and 2.13, and 2.86, 0.23, and 0.07,
respectively.

For purposes of comparison with above mentioned works, the HNCO 404–303, SiO
2–1 and HC3N 10–9 line properties have been extracted at the yellow crosses of
all our 43 sources (see Figs. 13–34 and Table 1 and 2).

###  5.2 Molecular line properties and column densities

Fig. 2 shows a comparison of line widths between HNCO and SiO, HNCO and HC3N,
as well as SiO and HC3N. We find that SiO has larger line widths, which agrees
with previous research of Zinchenko et al. (2000). In addition, the line
widths of HNCO and HC3N are similar. The mean values of the HNCO line widths
are 3.81$\pm$1.34, 5.71$\pm$1.63 and 18.19$\pm$7.46 km s-1 for the NMSFR,
Bubble, and CMZ samples, respectively. Separately for SiO and HC3N, the
corresponding values are 4.86$\pm$1.64, 8.80$\pm$2.08 and 23.83$\pm$9.11 km
s-1, and 3.87$\pm$0.57, 5.40$\pm$1.26 and 17.36$\pm$7.53 km s-1. For NMSFR and
CMZ sources, the SiO line widths are about 1.3 times larger than those of HNCO
and HC3N, while for sources in the Bubble category they are 1.4 to 1.6 times
larger. SiO has the highest line widths, since it is tracing the strongest
shocks.

Fig. 3 shows a comparison of integrated intensities (in K km s-1) averaged
over a circular area positioned on the yellow cross of each map with a
diameter corresponding to the $\sim$38′′ Mopra beamwidth. We find a tight
correlation between SiO and HC3N (r = 0.89), and a linear fitting
relationship:

$I_{\rm HC_{3}N}=(1.15\pm 0.09)\times I_{\rm SiO}+(1.08\pm 2.45)\,.$ (5)

I${}_{\rm HC_{3}N}$ and, to a lesser extent, ISiO also show linear
relationships with the integrated intensity of HNCO, with linear Pearson
correlation coefficients of r = 0.81 and 0.66, respectively. The relationships
are:

$I_{\rm HC_{3}N}=(0.75\pm 0.08)\times I_{\rm HNCO}+(6.00\pm 2.92)\,.$ (6)

$I_{\rm SiO}=(0.47\pm 0.08)\times I_{\rm HNCO}+(8.49\pm 2.89)\,.$ (7)

Applying equation 2, Fig. 4 plots optical depths. We find that the three
molecular lines studied here are all optically thin ($\tau$ $\ll$ 1) in our
star-forming regions, which agrees with the previous study of Miettinen
(2014). For sources in the CMZ, the optical depths of the HNCO lines are
similar to those of the HC3N lines. The optical depths of the HC3N and SiO
lines appear to be higher relative to HNCO in NMSFR and Bubble sources.

Using the equations in Sect. 3.2, column densities and abundances of HNCO, SiO
and HC3N are derived and presented in columns 7 and 9 of Table 2. The column
densities of HNCO, SiO and HC3N for their whole sample to be compared with
those by other groups, summarized in Sect. 5.1, range from
1.91$\times$1013–1.39$\times$1015 cm-2, 6.30$\times$1012–1.83$\times$1014 cm-2
and 1.83$\times$1013–4.50$\times$1014 cm-2, with mean values of
2.93$\times$1014 cm-2, 4.83$\times$1013 cm-2 and 1.19$\times$1014 cm-2,
respectively. The corresponding median values are 1.98$\times$1014 cm-2,
3.00$\times$1013 cm-2, and 5.92$\times$1013 cm-2. The mean abundances of HNCO,
SiO, and HC3N are 3.13$\times$10-9, 5.24$\times$10-10, and 1.14$\times$10-9,
respectively. The corresponding median values are 3.44$\times$10-9,
3.28$\times$10-10, and 8.96$\times$10-10. Sanhueza et al. (2012) derived an
SiO abundance comparable to that of ours for our whole sample.

The mean HNCO column density we find, 2.93$\times$1014 cm-2, is quite similar
to those derived by Miettinen (2014) towards their IRDC sources. Our median
column density of 1.98$\times$1014 cm-2 is about five times higher than the
median value found by Sanhueza et al. (2012). Because most sources of our work
are part of the CMZ or associated with bubbles, the surrounding environment
may cause this difference. The average HNCO column densities of NMSFR, Bubble
and CMZ are 3.75$\times$1013, 5.81$\times$1013 and 4.37$\times$1014 cm-2,
respectively. The corresponding median values are 3.97$\times$1013,
5.60$\times$1013 and 3.03$\times$1014 cm-2. We find that the average and
median column densities of HNCO for each category increase as in the case of
SiO monotonically from the NMSFR sources to the Bubble sources, to the CMZ
sources. This suggests that shocks in the Bubble category are strong enough to
evaporate a significant amount of HNCO from grain mantles without dissociating
them in comparison with sources of the NMSFR category. HNCO in the CMZ is much
more abundant than the other two species, SiO and HC3N, and seems to react
more sensitively to its extreme environment.

The mean values of SiO peak column densities of NMSFR, Bubble and CMZ clouds
we derive are 9.58$\times$1012 cm-2, 2.88$\times$1013 cm-2, and
6.97$\times$1013 cm-2, respectively. The corresponding median values are
8.15$\times$1012 cm-2, 1.89$\times$1013 cm-2, and 4.76$\times$1013 cm-2. The
NMSFR values are similar to those found by Sakai et al. (2010) for their
sample of clumps within IRDCs, and by Miettinen (2014) for their sample of
massive clumps (see Sect. 5.1).

For the HC3N peak column densities of NMSFR, Bubble and CMZ sources we derive
mean values of 3.49$\times$1013, 5.81$\times$1013, and 1.60$\times$1014 cm-2,
and median values of 3.08$\times$1013, 5.09$\times$1013, and 1.18$\times$1014
cm-2, respectively. Again column densities are rising from the NMSFR to the
CMZ sources. The median HC3N column density found by Miettinen (2014) (11 out
of their 12 detections are in the CMZ) is quite similar to our value for the
CMZ clouds. Our average value is almost an order of magnitude higher than the
highest value found by Sakai et al. (2008) towards massive clumps associated
with IRDCs located in the Galactic disk. Our median column density in NMSFR
(3.08$\times$1013 cm-2) exceeds the value found by Sanhueza et al. (2012) by a
factor of five. From the foregoing, we find that the CMZ contains large
reservoirs of SiO, HNCO and HC3N gas, with almost one order of magnitude
higher column densities than in the disc, especially when being compared to
the sources in the NMSFR category.

Fig. 5 confirms that column densities of our three molecules increase from
NMSFR, to Bubble, and on to sources with CMZ classification. A particularly
strong correlation coefficient r = 0.88 is found for the column densities of
SiO and HC3N for the entire sample. However, the differences between the
Pearson correlation coefficients are not that large, so that this is not a
finding we will emphasize. Least squares fitting yields

$log(N_{\rm HC_{3}N})=(2.24\pm 0.98)+(0.86\pm 0.07)\times log(N_{\rm SiO})\,.$
(8)

Moreover, a slightly weaker correlation is obtained between the column
densities of HNCO and SiO (r = 0.71) for the whole sample, as well as between
the column densities of HNCO and HC3N (r = 0.79). Results given by linear
fitting are

$log(N_{\rm SiO})=(5.33\pm 1.26)+(0.58\pm 0.09)\times log(N_{\rm HNCO})\,,$
(9)

and

$log(N_{\rm HC_{3}N})=(4.97\pm 1.07)+(0.63\pm 0.08)\times log(N_{\rm
HNCO})\,.$ (10)

The high correlations between SiO and HC3N in integrated intensities and
column densities above indicate that there is a close relationship during the
process of their chemical evolution. This argument will contribute to
determine the dominant chemical model through numerical simulations of star-
forming regions, where large scale shocks are generated, e.g. due to external
star forming activities or outflows from embedded young stellar objects.

###  5.3 The ratios of integrated intensity and abundances

Fig. 6 represents a comparison of the fractional abundances of HNCO, SiO and
HC3N. Two obvious clusters are seen between the CMZ sources and the other two
categories, implying that the chemical properties of sources in the CMZ are
different from sources far from the Galactic Center. A high correlation (right
panel of Fig. 6) is obtained between the fractional abundances of SiO and HC3N
(r = 0.93) for the whole sample, possibly because their parent species Si and
C2H2 are both released from dust grains due to a sudden increase in
temperature or to the erosion of dust grains via sputtering or grain-grain
collisions in shocks. The linear fitting result (red dashed line) is

$log(x_{\rm HC_{3}N})=(-0.94\pm 0.50)+(0.86\pm 0.05)\times log(x_{\rm
SiO})\,.$ (11)

The upper cluster only contains CMZ sources, while the lower cluster contains
NMSFR and Bubble sources. Moreover, Fig. 6 shows that HNCO is the most
abundant molecule in the CMZ category, while the fractional abundance of SiO
tends to be the lowest in the whole sample. For sources in the Bubble and
NMSFR category, the fractional abundances of HNCO and HC3N present a linear
distribution with a slope of almost unity, while SiO is slightly less
abundant..

In order to have a brief understanding of chemical properties of the three
molecules HNCO, SiO and HC3N, we computed integrated intensity and abundance
ratios. ${I_{\rm HNCO}/I_{\rm SiO}}$, ${I_{\rm SiO}/I_{\rm HC_{3}N}}$,
${I_{\rm HNCO}/I_{\rm HC_{3}N}}$, ${N_{\rm HNCO}/N_{\rm SiO}}$, ${N_{\rm
SiO}/N_{\rm HC_{3}N}}$, and ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ ratios are listed
for the whole sample in Table 3. Statistics provided in Table 4 include the
mean, median and standard deviation (std), as well as minimum and maximum
values of the sample.

From the left panel of Fig. 7, we deduce no correlation between the integrated
intensities of ${I_{\rm HNCO}/I_{\rm SiO}}$ and ${I_{\rm SiO}/I_{\rm
HC_{3}N}}$. It is interesting to find from Figs. 7 and 8 that ${I_{\rm
HNCO}/I_{\rm SiO}}$, ${I_{\rm HNCO}/I_{\rm HC_{3}N}}$, ${N_{\rm HNCO}/N_{\rm
SiO}}$, and ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ ratios for Bubble sources present
two separate groups, one of which (G322.159+00.635, G327.293$-$00.579,
G345.004$-$00.224, G351.443+00.659, and G351.775$-$00.537) has smaller ratios,
while the others (G008.671$-$00.357, G010.473+00.028, G326.653+00.618,
G350.101+00.083, and G351.582$-$00.352) have higher ratios, compared to those
of the NMSFR sources. Inflow and outflow activities have been simultaneously
detected in three (G345.004$-$00.224, G351.443+00.659, G351.775$-$00.537) out
of five sources in the group with smaller ratio (see Sect. 5.4). This may
indicate that the combined action of star formation activities and H ii region
(bubble) feedback will enhance the abundances of SiO and HC3N. The middle
panel of Fig. 7 plots ${I_{\rm HNCO}/I_{\rm HC3N}}$ as a function of ${I_{\rm
HNCO}/I_{\rm SiO}}$. A strong positive correlation is found, and the fitted
linear relationship is of the form ${log(I_{\rm HNCO}/I_{\rm
HC_{3}N})}=(-0.08\pm 0.03)+(0.78\pm 0.08)\times{log(I_{\rm HNCO}/I_{\rm
SiO})}$, with a Pearson’s r = 0.84. This is due to the good linear correlation
between ${I_{\rm SiO}}$ and ${I_{\rm HC_{3}N}}$ shown in Fig. 3. Moreover, the
integrated intensity ratios of our three molecules, shown in the middle panel
of Fig. 7, increase from the Bubble sources with small ratios to the NMSFR
sources, then to the Bubble sources with higher ratios and finally to the CMZ
sources. The integrated intensity ratio of ${I_{\rm HNCO}/I_{\rm HC_{3}N}}$
shows no obvious correlation with ${I_{\rm SiO}/I_{\rm HC_{3}N}}$ in the right
panel of Fig. 7. As shown in the left panel of Fig. 8, there is a weak hint
that the abundance ratio of ${N_{\rm SiO}/N_{\rm HC_{3}N}}$ decreases with an
increasing ${N_{\rm HNCO}/N_{\rm SiO}}$ abundance ratio. Instead, a high
correlation coefficient, 0.84, is obtained for the abundance ratio of ${N_{\rm
HNCO}/N_{\rm HC_{3}N}}$ versus ${N_{\rm HNCO}/N_{\rm SiO}}$ for the whole
sample in the middle panel of Fig. 8. The red dashed line indicates the least-
squares fit expressed as ${log(N_{\rm HNCO}/N_{\rm HC_{3}N})}=(-0.19\pm
0.06)+(0.72\pm 0.07)\times{log(N_{\rm HNCO}/N_{\rm SiO})}$ with r = 0.84. The
abundance ratio of ${N_{\rm SiO}/N_{\rm HC_{3}N}}$ shows no obvious trend as a
function of the ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ abundance ratio.

The average abundance ratios of ${N_{\rm HNCO}/N_{\rm SiO}}$ and ${N_{\rm
HNCO}/N_{\rm HC_{3}N}}$ we find in the CMZ and the Bubble sources are 8.79 and
3.33, and 3.30 and 1.35, respectively. These are quite similar to those
derived by Aladro et al. (2015) towards starburst galaxies. But their average
${N_{\rm SiO}/N_{\rm HC_{3}N}}$ abundance ratio is almost three times lower
than the corresponding values in the CMZ. Interestingly, abundance ratios in
the AGN NGC 1068 appear to be similar to the NMSFR sources. Beside the central
region of our Galaxy we suggest that star formation regions having extended
SiO and HNCO emissions in the Galactic disk can also be testbeds for studies
of the chemistry of the interstellar medium in the nuclear regions of
galaxies. It would be worthwhile to carry out high-sensitivity observations
and to perform large sample statistics in the future.

We find that the mean ${I_{\rm HNCO}/I_{\rm SiO}}$ ratios and their standard
deviations obtained from the Bubble, NMSFR and CMZ sources are 0.64$\pm$0.43,
0.75$\pm$0.38, and 1.76$\pm$1.15, respectively. As already mentioned (Sect.
5.1), Kelly et al. (2017) found that the mean ratios of ${I_{\rm HNCO}/I_{\rm
SiO}}$ are 0.35$\pm$0.13 and 2.5$\pm$1.3 in the heavily shocked East Knot and
mildly shocked West Knot of NGC1068, respectively. In the IRDC clumps studied
by Miettinen (2014), the ${I_{\rm HNCO}/I_{\rm SiO}}$ ratio was found to be
2.37$\pm$0.74, comparable to our average value within the error limits towards
the CMZ category. Moreover, the median abundance ratio ${N_{\rm HNCO}/N_{\rm
SiO}}$, 6.47, found by Miettinen (2014), is very similar to 7.38 derived in
this work towards the CMZ group of sources. This is explained by the fact that
most of the clumps with simultaneously detected HNCO and SiO lines (by
Miettinen, 2014) are also located in the Galactic center region.

In order to characterize the integrated intensity ratios of ${I_{\rm
HNCO}/I_{\rm SiO}}$, ${I_{\rm HNCO}/I_{\rm HC_{3}N}}$, ${I_{\rm
HC_{3}N}/I_{\rm SiO}}$ and their relationship with hydrogen column density and
gas kinetic temperature, we have applied a RADEX (van der Tak et al., 2007)
analysis. We separately analyzed sources in the NMSFR, Bubble and CMZ
category, using averaged HNCO line widths of 3.92, 5.61 and 17.82 km s-1 ,
respectively. The corresponding input values for the HNCO column densities are
3.75$\times$1013, 5.81$\times$1013 and 4.37$\times$1014 cm-2 as derived from
the results of Table 2. The corresponding column densities for SiO and HC3N
are 9.58$\times$1012 and 3.49$\times$1013, 2.88$\times$1013 and
5.81$\times$1013, and 6.97$\times$1013 and 1.60$\times$1014 cm-2. Our grid of
models includes varying hydrogen number densities from 103 cm-3 to 106 cm-3
and temperatures from 10 K to 60 K. The results are displayed in Fig. 9. In
each column of Fig. 9, we find that the integrated intensity ratios in
different classes show similar trends. ${I_{\rm HNCO}/I_{\rm SiO}}$ and
${I_{\rm HNCO}/I_{\rm HC_{3}N}}$, shown in the left and middle column of Fig.
9, are most sensitive to the hydrogen volume density n, while ${I_{\rm
HC_{3}N}/I_{\rm SiO}}$, shown in the right column of Fig. 9 is more sensitive
to the kinetic temperature $T_{\rm kin}$.

The Central Molecular Zone contains, for its limited volume, a large amount of
molecular gas, existing under extreme physical conditions with respect to
pressure and kinetic temperature (Ginsburg et al., 2016). From the Mopra
telescope HNCO, SiO and NH3 mapping data towards the Central Molecular Zone of
our Galaxy, Ott et al. (2014) found that there exists a distinct pattern of
alternating strong SiO or HNCO lines. They suggested that the difference is
due to the strength of the shocks. In order to quantitatively study this
phenomenon, we plot the integrated intensity ratio ${I_{\rm HNCO}/I_{\rm
SiO}}$ (black squares) and abundance ratios ${N_{\rm HNCO}/N_{\rm SiO}}$ (red
points) for seven separate Galactic longitude segments. The averaged ${I_{\rm
HNCO}/I_{\rm SiO}}$ indicated by cyan segments in Fig. 10 from left to right
are 2.51, 0.41, 1.29, 3.38, 1.31 and 2.57, respectively. The corresponding
averaged ${N_{\rm HNCO}/N_{\rm SiO}}$ ratios indicated by green segments are
12.29, 2.06, 6.46, 17.10, 6.66 and 13.16. This variation is compatible with
alternating stronger and weaker shocks affected by the motion of clouds and
the dynamics of the $x_{1}$ and $x_{2}$ orbits in the Central Molecular Zone
(e.g. Dale et al., 2019), and is also compatible with the data from Ott et al.
(2014).

###  5.4 Origin of the SiO emission: Outflow activity versus H II/SNR-induced
shocks

SiO is an excellent tracer of recent shock activity (e.g. active outflows).
When Si is liberated from dust grains, it then reacts with other species
observable from the ground to form SiO within $\sim$ 104 yr (Pineau des Forets
et al., 1997). Widmann et al. (2016) indeed proposed that most detected SiO
emission is likely to be a result of outflow activity. However, models and
observations also suggest that SiO emission could be caused by the UV
illumination of ices in Photon Dominated Regions (PDR; Schilke et al., 2001;
Shepherd et al., 2004) or by the expansion of HII regions or Supernova
Remnants (SNR; Cosentino et al., 2019, 2020), and not by an outflow. In
Schilke et al. (2001), narrow SiO emission (average line width of 2.0 km s-1)
with abundances of the order of 10-11 – 10-10 is produced directly by the
photo-desorption of a small fraction of silicon from the mantles of dust
grains by the intense UV radiation field originating from the massive stars in
the Trapezium. However, here we propose a different scenario: molecular gas
affected by the expansion of an H ii region or an SNR could induce low-
velocity shocks in the surrounding molecular environment that inject SiO into
the gas phase. This is more in line with the proposed scenario by Cosentino et
al. (2019) for spectrally narrow SiO emission (average line width of 1.6 km
s-1) detected toward IRDC G034.77$-$00.55, where the observed narrow SiO
emission is produced by low-velocity shocks induced by the expansion of a
supernova remnant. As star formation properties in the CMZ are complicated,
here we focus on dynamical processes (i.e. inflow and outflow activities) in
our Bubble and NMSFR sources.

To estimate the fraction of sources where SiO is produced by outflow activity,
we use HCO+ which is a suitable species to trace both inflow and outflow
activities by analyzing its line profile (Rawlings et al., 2004; Fuller et
al., 2005; He et al., 2015, 2016). To identify HCO+ outflow features, we
followed the method that was presented by Wu et al. (2005). HCO+ (1-0) spectra
near the source position should have high-velocity wings and position-velocity
(P-V) diagrams should show intensities of the wing emission decreasing
smoothly towards the edge of the mapped region. Also, we have checked the
optically thin H13CO+ 1–0 or HNCO 404–303 lines to avoid multiple velocity
components causing wing emission. As a result, we identify 4 outflow
candidates (G008.671$-$00.357, G345.004$-$00.224, G351.443$+$00.659,
G351.775$-$00.537) from 10 sources in the Bubble category and 4 outflow
candidates (G329.030$-$00.202, G331.708$+$00.583, G331.709$+$00.602,
G335.586$-$00.289) from the 6 sources in the NMSFR category. The detection
rates of outflow candidates in the Bubble and NMSFR categories are 40% and
67%, respectively. The difference between 40% and 67% is not significant in a
statistical sense and may be an effect of sensitivity limitations of the Mopra
observations. The wing emission is weak and it may not have been detected in
all sources. Therefore, it is necessary to investigate the outflow detection
rate on the basis of a larger sample and with higher sensitivity to check if
surrounding bubbles or cloud heating by shock waves can yield not only outflow
activity but also an enhancement of SiO emission.

The mean SiO abundances in the Bubble and NMSFR categories are
9.37$\times$10-11 and 8.70$\times$10-11, respectively. In combination with the
abundances derived by Schilke et al. (2001) from SiO 2–1 in the photon
dominated region of the Orion Bar, in the range 3$-$7$\times$10-11, this
suggests that the pressure of photoionized gas from the surrounding bubbles or
cloud heating by shock waves yields an enhancement of SiO emission for sources
in the Bubble category besides the outflow activity. The HCO+ (1-0) position
velocity (P-V) diagrams of these eight outflow candidates showing distinct
wing emission are shown in Figs. 11 and 12. Among these, G345.004-00.224 was
identified by Yu & Wang (2014), while G008.671$-$00.357, G329.030$-$00.202,
G331.708$+$00.583, G331.709$+$00.602, G335.586$-$00.289, G351.443$+$00.659 and
G351.775$-$00.537 are newly identified in this work. As the HCO+ spectrum in
G345.004$-$00.224 exhibits an obvious self-absorption dip, the wide SiO 2–1
line emission has been added to show outflow activities in Fig. 11. All the
P-V diagrams were cut along the $l$ direction in the Galactic coordinate
system except for the P-V diagram of G351.443+00.659 which was cut along
Galactic latitude where the HCO+ 1–0 wing emission is more pronounced.

Ren et al. (2012) proposed that inflow and outflow motions should be closely
related and interact with each other throughout the star-formation process. We
followed the inflow identification criterion used in He et al. (2015). Inflow
motions have been studied by investigating the profile of the optically thick
HCO+ 1–0 line, which would then show a double peak with a brighter blue peak
or a skewed single blue peak. Meanwhile, the optically thin single peak of the
H13CO+ 1–0 line should be located at the dip of the optically thick HCO+ 1–0
line to rule out a double peak caused by two velocity components along the
line of sight. After checking the spatial variation of optically thick line
profile asymmetries across the mapped region, we identified eight reliable
inflow candidates. The extracted spectra of HCO+ 1–0 and H13CO+ 1–0 from the
yellow cross of each source are shown in the lower panels of 11 and 12. Five
(G008.671$-$00.357, G331.708$+$00.583, G331.709$+$00.602, G335.586$-$00.289
and G351.443$+$00.659) of them have been identified as inflow candidates by He
et al. (2015, 2016) and the other three (G329.030$-$00.202, G345.004$-$00.224
and G351.775$-$00.537) are newly identified in this work. Interestingly, all
these inflow candidates have been detected to simultaneously show outflow
activities. Therefore, our results are also consistent with the coexistence of
in- and outflowing molecular gas.

##  6 Conclusions

We have performed a study of 43 southern star-forming regions in HNCO 404–303,
SiO 2–1 and HC3N 10–9, based on the MALT90 survey, the 870 $\mu$m ATLASGAL
survey and Herschel 160 $\mu$m, 250 $\mu$m, 350 $\mu$m, 500 $\mu$m data. Our
sample was divided into three categories: 27 sources in the Central Molecular
Zone (CMZ) of the Galaxy, 10 sources associated with expanding bubbles of
ionized gas, and 6 ”normal” star forming (NMSFR) clouds. The spatial
distributions of the three measured molecular lines and their properties are
analysed. Integrated intensity ratios, abundance ratios, outflow activity and
inflow activity are discussed. Our main results can be summarized as follows.

(i) The integrated intensity images show that the distribution of all three
molecular lines are compact and consistent with condensed dust structures
except for SiO in G000.110+00.148, G000.497+00.021, G001.610-00.172,
G001.655-00.062, G001.694-00.385 and G003.240+00.635. The derived angular
diameters of the three species indicate that HC3N traces denser gas than HNCO
and SiO.

(ii) The dust temperature images show that all the 27 CMZ sources are cold
with $\thicksim$14 K towards the central 870 $\mu$m continuum emission
regions, while the dust is warmer in the more diffuse surrounding regions. For
CMZ sources, the variations of ${I_{\rm HNCO}/I_{\rm SiO}}$ and ${N_{\rm
HNCO}/N_{\rm SiO}}$ as a function of Galactic longitude are compatible with
alternating stronger and weaker shocks affected by the motion of clouds and
the dynamics of the $x_{1}$ and $x_{2}$ orbits in the Central Molecular Zone.

(iii) From analyzing the centers of each cold dense clump in Section 4, the
dust temperature $T_{\rm d}$, and the abundance ratios of ${N_{\rm
HNCO}/N_{\rm SiO}}$ and ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ show a decreasing
trend with increasing column densities, while ${N_{\rm HC_{3}N}/N_{\rm SiO}}$
reveals the opposite. This characteristic property appears to be most common
for sources in the Central Molecular Zone. In Bubble and NMSFR category
sources, dust temperature and $N_{\rm HC3N}/N_{\rm SiO}$ roughly follow a
similar trend towards the center, where stars are forming.

(iv) The line widths of HNCO and HC3N correlate well with each other and
ratios are close to unity for the 43 star-forming regions. SiO lines tend to
be wider than lines from HNCO and HC3N, apparently being most sensitive to the
presence of outflowing gas. HC3N provides, in the average, the most compact
spatial distributions. SiO and HC3N may have similar excitation mechanisms as
is suggested by the good correlation between line widths, integrated
intensities, column densities, and fractional abundances of these two species,
though the critical density of SiO is about four times higher than that of
HC3N at 20 K.

(v) Eight star-forming sources, G008.671$-$00.357, G345.004$-$00.224,
G351.443$+$00.659 and G351.775$-$00.537 in the Bubble category, and
G329.030$-$00.202, G331.708$+$00.583, G331.709$+$00.602 and G335.586$-$00.289
in the NMSFR category (see Sect. 2.2) are found to have simultaneously outflow
and inflow motions. And seven new outflow candidates (G008.671$-$00.357,
G329.030$-$00.202, G331.708$+$00.583, G331.709$+$00.602, G335.586$-$00.289,
G351.443$+$00.659 and G351.775$-$00.537) and three new inflow candidates
(G329.030$-$00.202, G345.004$-$00.224 and G351.775$-$00.537) have been
identified in this work.

We thank the referee for careful comments of this paper. This work was mainly
funded by the National Natural Science foundation of China (NSFC) under grant
11703073. It was also partially funded by the NSFC under grants 11433008,
11973076, 11703074, and 11603063, The CAS ”Light of West China” Program
2016-QNXZ-B-22, 2018-XBQNXZ-B-024. The ”TianShan Youth Plan” under grant
2018Q084. The Heaven Lake Hundred-Talent Program of Xinjiang Uygur Autonomous
Region of China. C. Henkel has been funded by Chinese Academy of Sciences
President’s International Fellowship Initiative with grant No. 2021VMA0009.
Moreover, this work is sponsored (in part) by the Chinese Academy of Sciences
(CAS), through a grant to the CAS South America Center for Astronomy (CASSACA)
in Santiago, Chile. AS acknowledges funding through Fondecyt Regular (project
code 1180350) and Chilean Centro de Excelencia en Astrofísica y Tecnologías
Afines (CATA) BASAL grant AFB-170002. This research has made use of the data
products from the MALT90 survey, the SIMBAD data base, operated at CDS,
Strasbourg, France, the data from _Herschel_ , a European Space Agency space
observatory with science instruments provided by European led consortia, and
the ATLASGAL survey, which is a collaboration between the Max-Planck-
Gesellschaft, the European Southern Observatory (ESO) and the Universidad de
Chile.

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Figure 1: The beam deconvolved angular diameter distributions for HNCO 404–303, SiO 2–1 and HC3N 10–9. The median values of each molecule are indicated by dashed black vertical lines. Figure 2: Comparison of the line width for HNCO and SiO (left), HNCO and HC3N (middle), and SiO and HC3N (right). NMSFR sources are plotted as green triangles. Sources associated with bubbles are plotted as red points, while sources in the CMZ are shown as black squares. The slopes of the black solid lines are 1. Figure 3: Same as Fig. 2, but for integrated intensity. The red dashed lines indicate the best-fit relation. The slopes of the black solid lines are 1. Figure 4: Same as Fig. 3, but for optical depth. The slopes of the black solid lines are 1. Figure 5: Same as Fig. 3, but for column density. The slopes of the black solid lines are 1. Figure 6: Same as Fig. 3, but for fractional abundance. The slopes of the black solid lines are 1. Figure 7: Left: plot of the integrated intensity ratios of SiO to HC3N vs. the integrated intensity ratios of HNCO to SiO. Middle: plot of the integrated intensity ratios of HNCO to HC3N vs. the integrated intensity ratios of HNCO to SiO. Right: plot of the integrated intensity ratios of SiO to HC3N vs. the integrated intensity ratios of HNCO to HC3N. For the color of the plotted intensity ratios, see the caption to Fig. 2. The red dashed line in the central panel represents the least-squares fitting result. Figure 8: Same as Fig. 7, but for column density. The open circles represent the starburst galaxies of M 83, NGC 253, and M 82, and the AGN and starburst galaxy NGC 1068. The black arrows point to the ultraluminous infrared galaxy Arp 220. The red dashed line in the central panel indicates the least-squares fit. Figure 9: Integrated intensity ratios of ${I_{\rm HNCO}/I_{\rm SiO}}$, ${I_{\rm HNCO}/I_{\rm HC_{3}N}}$ and ${I_{\rm HC_{3}N}/I_{\rm SiO}}$ from RADEX models for sources of CMZ, Bubble, and NMSFR category with varying temperature from 10 K to 60 K and hydrogen number density from 103 cm-3 to 106 cm-3. The corresponding averaged input HNCO line widths and column densities are 17.49, 5.20 and 3.62 km s-1, and 4.37$\times$1014, 5.81$\times$1013 and 3.75$\times$1013 cm-2. While the input line widths are the same for SiO and HC3N, their column densities used for the plots are 9.58$\times$1012 and 3.49$\times$1013, 2.88$\times$1013 and 5.81$\times$1013, and 6.97$\times$1013 and 1.60$\times$1014 cm-2, respectively. Horizontal isophotes indicate density, while vertical isophotes show kinetic temperature tracers. Figure 10: Integrated intensity ratios ${I_{\rm HNCO}/I_{\rm SiO}}$ (black squares) and abundance ratios ${N_{\rm HNCO}/N_{\rm SiO}}$ (red points) for seven separate Galactic longitude segments (top panel; the abcissa is in units of degrees). The averaged ${I_{\rm HNCO}/I_{\rm SiO}}$ indicated by cyan segments from left to right are 2.51, 0.41, 1.29, 3.38, 1.31 and 2.57, respectively. The corresponding averaged ${N_{\rm HNCO}/N_{\rm SiO}}$ ratios indicated by green segments are 12.29, 2.06, 6.46, 17.10, 6.66 and 13.16. The central two panels show the peak brightness images of the HNCO 404-303 and SiO 2-1 lines in units of K in the CMZ, taken from Fig. 1 of Ott et al. (2014). The bottom panel shows the gas temperature map derived from NH3 (also Ott et al., 2014). The regions with weak and strong shocks are marked in blue and red rectangles, respectively. The green rectangle centers on the star forming region Sgr B2 and marks the likely point where the $x_{1}$ orbits accrete on the 100 pc ring, the location of the $x_{2}$ orbits. Figure 11: The upper four panels show the HCO+ (1–0) P-V diagrams of the three outflow candidates G008.671$-$00.357, G351.443+00.659 and G351.775$-$00.537, and the SiO (2–1) P-V diagrams of the outflow candidate G345.004$-$00.224 in the Bubble category. All the P-V diagrams were cut along the east-west direction except for the P-V diagram of G351.443+00.659 which was cut along the south-north direction. Here the four cardinal directions, north, south, east and west, are meant with respect to the Galactic coordinates ($l^{\rm II}$, $b^{\rm II}$), and not with respect to Right Ascension and Declination. The lower four panels show the extracted spectra of HCO+(1–0) and H13CO+(1–0) from the yellow cross position (see Figs. 27 and 29 – 31) of each outflow candidate. Red dashed lines indicate the central velocity of the sources. Figure 12: The upper four panels show the HCO+ (1–0) P-V diagrams of four outflow candidates in the NMSFR category. All the P-V diagrams were cut along the east-west direction. Here the four cardinal directions, north, south, east and west, are meant with respect to the Galactic coordinates ($l^{\rm II}$, $b^{\rm II}$), and not with respect to Right Ascension and Declination. The lower four panels show the extracted spectra of HCO+(1–0) and H13CO+(1–0) from the yellow cross position (see Figs. 32 and 33) of each outflow candidate. Red dashed lines indicate the central velocity of the sources. Table 1: Derived parameters for sources. Quantities in parentheses give the uncertainties. The columns are as follows: (1) MALT90 names; (2) and (3) Galactic longitude and Galactic latitude of the yellow crosses on maps of Figs. 13 to 34; (4) molecular species; (5) beam deconvolved angular diameter; (6) dust temperature $T_{\rm d}$; (7) centroid velocities; (8) main beam brightness temperatures; (9) full width to half power line width; (10) optical thickness of the line emission; (11) source category (see Sect. 2.2). The central Galactic coordinate of each map is used for the source name (e.g. MALT90 names in column 1 of Table 1). Sourcea | l | b | MOL | $\theta$ |  Td |  vLSR |  TMB |  $\Delta$v | $\tau$ | comment
---|---|---|---|---|---|---|---|---|---|---
| deg | deg |  | $\prime\prime$ | $K$ | $km\ s^{-1}$ | K | $km\ s^{-1}$ |  |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11)
G000.067$-$00.077 | 0.065 |  $-$0.078 | HNCO | 116 | 15.1 |  48.47 $\pm$ 0.31, 51.62 $\pm$ 2.19 | 1.89, 0.61 |  20.85 $\pm$ 1.37, 44.63 $\pm$ 5.19 | 0.17 | CMZ
| 0.065 |  $-$0.078 | SiO | 118 |  |  50.56 $\pm$ 0.43, 75.73 $\pm$ 1.88 | 1.73, 0.32 |  23.17 $\pm$ 1.02, 17.20 $\pm$ 4.12 | 0.16 |
| 0.065 |  $-$0.078 |  HC3N | 105 |  |  49.50 $\pm$ 0.20 | 2.40 |  24.39 $\pm$ 1.81 | 0.22 |
G000.104$-$00.080 | 0.107 |  $-$0.085 | HNCO | 98 | 15.2 |  52.66 $\pm$ 0.09, 53.53 $\pm$ 0.05 | 2.50, 0.56 |  15.91 $\pm$ 0.07, 34.12 $\pm$ 1.83 | 0.23 | CMZ
| 0.107 |  $-$0.085 | SiO | 107 |  |  55.18 $\pm$ 0.21, 45.45 $\pm$ 2.22 | 1.74, 0.72 |  18.52 $\pm$ 0.93, 36.81 $\pm$ 1.88 | 0.16 |
| 0.107 |  $-$0.085 |  HC3N | 54 |  |  52.85 $\pm$ 0.11, 36.55 $\pm$ 0.82 | 3.01, 0.26 |  18.23 $\pm$ 0.32, 4.83 $\pm$ 2.27 | 0.29 |
G000.106$-$00.001 | 0.104 |  $-$0.004 | HNCO | 114 | 15.4 |  51.07 $\pm$ 0.22, 53.68 $\pm$ 1.24 | 1.34, 0.62 |  13.61 $\pm$ 1.14, 34.01 $\pm$ 3.19 | 0.12 | CMZ
| 0.104 |  $-$0.004 | SiO | 119 |  |  51.00 $\pm$ 0.20 | 1.16 |  24.11 $\pm$ 2.30 | 0.10 |
| 0.104 |  $-$0.004 |  HC3N | 90 |  |  50.83 $\pm$ 0.17, 67.98 $\pm$ 1.09 | 2.12, 0.24 |  17.27 $\pm$ 0.37, 20.20 $\pm$ 1.28 | 0.19 |
G000.110$+$00.148 | 0.113 | 0.152 | HNCO | 113 | 15.2 |  99.85 $\pm$ 0.34 | 0.76 |  15.07 $\pm$ 1.14 | 0.07 | CMZ
| 0.113 | 0.152 | SiO | 140 |  |  99.59 $\pm$ 0.76 | 0.45 |  12.72 $\pm$ 1.50 | 0.04 |
| 0.113 | 0.152 |  HC3N | 105 |  |  98.91 $\pm$ 0.31 | 0.69 |  10.95 $\pm$ 0.78 | 0.06 |
G000.314$-$00.100 | 0.314 |  $-$0.096 | HNCO | 90 | 15.8 |  73.88 $\pm$ 1.69, 82.80 $\pm$ 0.59 | 0.44, 0.40 |  43.90 $\pm$ 2.68, 7.20 $\pm$ 1.71 | 0.04 | CMZ
| 0.314 |  $-$0.096 | SiO | 97 |  |  80.79 $\pm$ 1.24, 81.56 $\pm$ 1.87 | 0.48, 0.11 |  40.89 $\pm$ 2.35, 6.92 $\pm$ 3.26 | 0.04 |
| 0.314 |  $-$0.096 |  HC3N | 73 |  |  78.03 $\pm$ 2.09, 81.21 $\pm$ 0.63 | 0.30, 0.27 |  38.50 $\pm$ 3.00, 3.98 $\pm$ 1.78 | 0.02 |
G000.497$+$00.021 | 0.497 | 0.018 | HNCO | 177 | 15.0 |  30.56 $\pm$ 0.46, 12.58 $\pm$ 0.46 | 2.65, 0.23 |  22.54 $\pm$ 0.46, 27.82 $\pm$ 0.46 | 0.25 | CMZ
| 0.497 | 0.018 | SiO | 186 |  |  35.56 $\pm$ 0.64, 16.12 $\pm$ 0.82 | 0.62, 0.37 |  20.46 $\pm$ 2.67, 21.17 $\pm$ 2.08 | 0.05 |
| 0.497 | 0.018 |  HC3N | 151 |  |  32.48 $\pm$ 0.26, 11.51 $\pm$ 2.22 | 2.06, 0.22 |  18.46 $\pm$ 0.60, 16.05 $\pm$ 4.89 | 0.19 |
G000.645$+$00.027 | 0.647 | 0.032 | HNCO | 190 | 14.9 |  54.31 $\pm$ 0.09 | 3.94 |  26.89 $\pm$ 0.66 | 0.41 | CMZ
| 0.647 | 0.032 | SiO | 196 |  |  56.02 $\pm$ 0.64 | 0.68 |  45.60 $\pm$ 1.43 | 0.06 |
| 0.647 | 0.032 |  HC3N | 146 |  |  52.53 $\pm$ 0.20 | 1.99 |  27.60 $\pm$ 1.87 | 0.19 |
G000.892$+$00.143 | 0.894 | 0.142 | HNCO | 70 | 14.5 |  76.80 $\pm$ 0.39 | 0.76 |  26.25 $\pm$ 0.81 | 0.07 | CMZ
| 0.894 | 0.142 | SiO | 86 |  |  77.45 $\pm$ 0.63 | 0.50 |  31.06 $\pm$ 1.41 | 0.04 |
| 0.894 | 0.142 |  HC3N | 71 |  |  76.84 $\pm$ 0.49 | 0.55 |  25.56 $\pm$ 1.09 | 0.05 |
G000.908$+$00.116 | 0.919 | 0.116 | HNCO | 82 | 14.4 |  64.64 $\pm$ 0.81, 75.78 $\pm$ 6.23 | 0.61, 0.21 |  12.44 $\pm$ 2.23, 23.40 $\pm$ 6.54 | 0.06 | CMZ
| 0.919 | 0.116 | SiO | 79 |  |  66.18 $\pm$ 3.22, 75.83 $\pm$ 2.15 | 0.17, 0.14 |  27.32 $\pm$ 1.06, 32.29 $\pm$ 2.49 | 0.02 |
| 0.919 | 0.116 |  HC3N | 79 |  |  63.68 $\pm$ 0.69, 78.60 $\pm$ 3.42 | 0.28, 0.13 |  9.67 $\pm$ 1.48, 27.51 $\pm$ 7.74 | 0.03 |
G001.226$+$00.059 | 1.233 | 0.061 | HNCO | 149 | 14.0 |  103.87 $\pm$ 0.48 | 0.61 |  18.42 $\pm$ 1.79 | 0.06 | CMZ
| 1.233 | 0.061 | SiO | 130 |  |  113.73 $\pm$ 0.33 | 1.15 |  36.32 $\pm$ 1.70 | 0.11 |
| 1.233 | 0.061 |  HC3N | 75 |  |  109.38 $\pm$ 0.34 | 0.83 |  23.22 $\pm$ 1.39 | 0.08 |
G001.344$+$00.258 | 1.348 | 0.262 | HNCO | 112 | 13.7 |  105.58 $\pm$ 0.49 | 0.82 |  28.85 $\pm$ 1.76 | 0.08 | CMZ
| 1.348 | 0.262 | SiO | 110 |  |  102.74 $\pm$ 0.47 | 1.41 |  38.43 $\pm$ 1.25 | 0.14 |
| 1.348 | 0.262 |  HC3N | 88 |  |  100.65 $\pm$ 0.26 | 1.36 |  25.42 $\pm$ 0.98 | 0.14 |
G001.381$+$00.201 | 1.381 | 0.187 | HNCO | 165 | 13.8 |  102.80 $\pm$ 0.87 | 0.40 |  21.89 $\pm$ 2.42 | 0.04 | CMZ
| 1.381 | 0.187 | SiO | 156 |  |  100.16 $\pm$ 0.65 | 0.69 |  36.29 $\pm$ 2.47 | 0.07 |
| 1.381 | 0.187 |  HC3N | 113 |  |  100.14 $\pm$ 1.05 | 0.37 |  25.99 $\pm$ 2.48 | 0.04 |
G001.510$+$00.155 | 1.522 | 0.144 | HNCO | 134 | 13.3 |  78.00 $\pm$ 0.19 | 1.75 |  15.15 $\pm$ 0.45 | 0.19 | CMZ
| 1.522 | 0.144 | SiO | 159 |  |  79.33 $\pm$ 0.46 | 0.84 |  18.11 $\pm$ 1.15 | 0.09 |
| 1.522 | 0.144 |  HC3N | 100 |  |  77.52 $\pm$ 0.25 | 1.43 |  13.15 $\pm$ 0.75 | 0.15 |
G001.610$-$00.172 | 1.607 |  $-$0.174 | HNCO | 159 | 13.1 |  46.85 $\pm$ 0.18, 37.09 $\pm$ 0.11 | 1.69, 0.77 |  9.08 $\pm$ 0.38, 10.68 $\pm$ 0.65 | 0.19 | CMZ
| 1.607 |  $-$0.174 | SiO | 107 |  |  47.05 $\pm$ 0.81, 38.65 $\pm$ 0.64 | 0.42, 0.40 |  7.91 $\pm$ 1.75), 6.02 $\pm$ 1.98 | 0.04 |
| 1.607 |  $-$0.174 |  HC3N | 89 |  |  48.46 $\pm$ 0.25, 41.51 $\pm$ 0.66 | 0.75, 0.42 |  4.63 $\pm$ 0.57, 7.75 $\pm$ 1.43 | 0.08 |
Table 1: \- continued. Sourcea | l | b | MOL | $\theta$ |  Td |  vLSR |  TMB |  $\Delta$v | $\tau$ | comment
---|---|---|---|---|---|---|---|---|---|---
| deg | deg |  | $\prime\prime$ | $K$ | $km\ s^{-1}$ | K | $km\ s^{-1}$ |  |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11)
G001.655$-$00.062 | 1.661 |  $-$0.053 | HNCO | 200 | 12.4 |  52.21 $\pm$ 0.07, 44.66 $\pm$ 0.03 | 3.08, 1.58 |  10.55 $\pm$ 0.51, 8.58 $\pm$ 0.25 | 0.40 | CMZ
G1.87$-$SMM 1∗ |  |  |  |  |  |  |  |  |  |
| 1.661 |  $-$0.053 | SiO | 196 |  |  55.81 $\pm$ 0.34, 44.84 $\pm$ 0.49 | 0.67, 0.55 |  7.62 $\pm$ 0.91, 8.77 $\pm$ 1.01 | 0.07 |
| 1.661 |  $-$0.053 |  HC3N | 150 |  |  51.74 $\pm$ 0.50, 44.77 $\pm$ 2.23 | 1.48, 0.43 |  7.00 $\pm$ 0.24,8.54 $\pm$ 3.54 | 0.17 |
G001.694$-$00.385 | 1.694 |  $-$0.388 | HNCO | 144 | 13.1 |  $-$35.36 $\pm$ 0.28 | 1.37 |  18.88 $\pm$ 0.91 | 0.15 | CMZ
| 1.694 |  $-$0.388 | SiO | 37 |  |  $-$24.52 $\pm$ 0.83 | 0.63 |  29.95 $\pm$ 1.72 | 0.07 |
| 1.694 |  $-$0.388 |  HC3N | 83 |  |  $-$34.31 $\pm$ 0.27 | 1.51 |  13.87 $\pm$ 0.65 | 0.16 |
G001.699$-$00.366 | 1.700 |  $-$0.367 | HNCO | 101 | 13.0 |  $-$32.62 $\pm$ 0.21 | 1.47 |  16.13 $\pm$ 0.52 | 0.16 | CMZ
| 1.700 |  $-$0.367 | SiO | 133 |  |  $-$24.31 $\pm$ 0.34, $-$40.97 $\pm$ 3.31 | 0.74, 0.27 |  13.69 $\pm$ 1.22, 30.37 $\pm$ 7.69 | 0.08 |
| 1.700 |  $-$0.367 |  HC3N | 86 |  |  $-$31.67 $\pm$ 0.14 | 2.05 |  16.76 $\pm$ 0.36 | 0.23 |
G001.734$-$00.410 | 1.737 |  $-$0.412 | HNCO | 110 | 12.5 |  $-$38.74 $\pm$ 0.17 | 2.36 |  14.98 $\pm$ 0.77 | 0.29 | CMZ
| 1.737 |  $-$0.412 | SiO | 112 |  |  $-$36.85 $\pm$ 0.43 | 0.92 |  19.49 $\pm$ 0.85 | 0.10 |
| 1.737 |  $-$0.412 |  HC3N | 90 |  |  $-$37.88 $\pm$ 0.08 | 2.24 |  11.87 $\pm$ 0.27 | 0.27 |
G001.883$-$00.062 | 1.887 |  $-$0.063 | HNCO | 88 | 13.5 |  35.79 $\pm$ 0.30, 44.45 $\pm$ 3.21 | 1.18, 0.28 |  7.94 $\pm$ 0.58, 12.82 $\pm$ 4.20 | 0.12 | CMZ
G1.87$-$SMM 23∗ |  |  |  |  |  |  |  |  |  |
| 1.887 |  $-$0.063 | SiO | 75 |  |  37.32 $\pm$ 0.58, 42.55 $\pm$ 0.80 | 0.55, 0.28 |  5.85 $\pm$ 1.20, 4.36 $\pm$ 1.96 | 0.05 |
| 1.887 |  $-$0.063 |  HC3N | 60 |  |  36.17 $\pm$ 0.30, 41.15 $\pm$ 0.51 | 0.84, 0.38 |  6.67 $\pm$ 0.89, 3.03 $\pm$ 1.03 | 0.08 |
G003.240$+$00.635 | 3.241 | 0.635 | HNCO | 44 | 12.6 |  41.39 $\pm$ 0.81 | 0.36 |  18.38 $\pm$ 1.90 | 0.04 | CMZ
| 3.241 | 0.635 | SiO | 91 |  |  42.50 $\pm$ 0.52 | 0.59 |  20.05 $\pm$ 1.47 | 0.06 |
| 3.241 | 0.635 |  HC3N | 106 |  |  42.23 $\pm$ 0.51 | 0.45 |  16.18 $\pm$ 1.27 | 0.05 |
G003.338$+$00.419 | 3.339 | 0.425 | HNCO | 132 | 12.4 |  28.80 $\pm$ 0.44 | 0.90 |  21.24 $\pm$ 1.52 | 0.10 | CMZ
| 3.339 | 0.425 | SiO | 152 |  |  35.84 $\pm$ 0.75, 16.03 $\pm$ 0.82 | 1.02, 0.58 |  23.80 $\pm$ 1.82, 14.74 $\pm$ 1.56 | 0.12 |
| 3.339 | 0.425 |  HC3N | 120 |  |  29.22 $\pm$ 0.18 | 1.75 |  17.44 $\pm$ 0.60 | 0.21 |
G359.445$-$00.054 | 359.446 |  $-$0.058 | HNCO | 117 | 15.7 |  $-$102.71 $\pm$ 0.22 | 1.29 |  15.96 $\pm$ 0.73 | 0.11 | CMZ
| 359.446 |  $-$0.058 | SiO | 115 |  |  $-$103.16 $\pm$ 0.71 | 0.39 |  17.72 $\pm$ 1.95 | 0.03 |
| 359.446 |  $-$0.058 |  HC3N | 113 |  |  $-$101.97 $\pm$ 0.36 | 0.71 |  13.48 $\pm$ 0.82 | 0.06 |
G359.453$-$00.112 | 359.455 |  $-$0.112 | HNCO | 107 | 15.6 |  $-$52.00 $\pm$ 0.19, $-$61.60 $\pm$ 0.42 | 1.43, 0.50 |  8.36 $\pm$ 0.53, 5.32 $\pm$ 0.81 | 0.12 | CMZ
| 359.455 |  $-$0.112 | SiO | 106 |  |  $-$51.69 $\pm$ 0.40 | 0.66 |  13.44 $\pm$ 1.02 | 0.05 |
| 359.455 |  $-$0.112 |  HC3N | 103 |  |  $-$51.07 $\pm$ 0.33, $-$62.12 $\pm$ 0.90 | 1.01, 0.26 |  12.17 $\pm$ 0.97, 6.43 $\pm$ 1.28 | 0.08 |
G359.565$-$00.161 | 359.551 |  $-$0.166 | HNCO | 84 | 15.8 |  $-$57.78 $\pm$ 0.34 | 0.92 |  16.85 $\pm$ 1.15 | 0.08 | CMZ
| 359.551 |  $-$0.166 | SiO | 87 |  |  $-$55.33 $\pm$ 0.93 | 0.36 |  19.86 $\pm$ 1.26 | 0.03 |
| 359.551 |  $-$0.166 |  HC3N | 67 |  |  $-$54.69 $\pm$ 0.72 | 0.51 |  17.57 $\pm$ 1.35 | 0.04 |
G359.868$-$00.085 | 359.866 |  $-$0.082 | HNCO | 177 | 15.3 |  9.21 $\pm$ 0.05, 0.53 $\pm$ 0.17 | 4.89, 1.24 |  9.55 $\pm$ 0.13, 6.27 $\pm$ 0.27 | 0.52 | CMZ
| 359.866 |  $-$0.082 | SiO | 149 |  |  5.82 $\pm$ 0.21 | 1.86 |  22.23 $\pm$ 0.49 | 0.17 |
| 359.866 |  $-$0.082 |  HC3N | 148 |  |  8.69 $\pm$ 0.26, 0.58 $\pm$ 0.60 | 3.49, 1.29 |  12.57 $\pm$ 0.49, 10.28 $\pm$ 1.82 | 0.34 |
G359.895$-$00.069 | 359.892 |  $-$0.076 | HNCO | 134 | 15.2 |  17.40 $\pm$ 0.06, 5.11 $\pm$ 0.66 | 4.32, 0.38 |  16.64 $\pm$ 0.14, 15.36 $\pm$ 0.20 | 0.44 | CMZ
| 359.892 |  $-$0.076 | SiO | 137 |  |  15.20 $\pm$ 0.10 | 2.78 |  21.34 $\pm$ 0.23 | 0.26 |
| 359.892 |  $-$0.076 |  HC3N | 137 |  |  16.24 $\pm$ 0.05 | 4.59 |  18.49 $\pm$ 0.13 | 0.48 |
G359.977$-$00.072 | 359.980 |  $-$0.070 | HNCO | 135 | 16.6 |  49.88 $\pm$ 0.14, 36.37 $\pm$ 0.56 | 2.75, 0.69 |  14.93 $\pm$ 0.34, 12.65 $\pm$ 0.91 | 0.23 | CMZ
| 359.980 |  $-$0.070 | SiO | 114 |  |  51.80 $\pm$ 0.02, 37.00 $\pm$ 0.53 | 1.66, 1.20 |  25.39 $\pm$ 0.70, 21.08 $\pm$ 0.37 | 0.13 |
| 359.980 |  $-$0.070 |  HC3N | 108 |  |  48.50 $\pm$ 0.47, 38.42 $\pm$ 1.33 | 3.63, 0.66 |  20.92 $\pm$ 0.52, 25.50 $\pm$ 4.12 | 0.32 |
G008.671$-$00.357 | 8.677 |  $-$0.360 | HNCO | 75 | 14.8 |  36.09 $\pm$ 0.19 | 0.79 |  5.69 $\pm$ 0.44 | 0.07 | Bubble
| 8.677 |  $-$0.360 | SiO | 67 |  |  35.99 $\pm$ 0.32 | 0.55 |  7.39 $\pm$ 0.85 | 0.05 |
| 8.677 |  $-$0.360 |  HC3N | 69 |  |  35.46 $\pm$ 0.08 | 1.86 |  4.88 $\pm$ 0.19 | 0.17 |
G010.473$+$00.028 | 10.480 | 0.030 | HNCO | 65 | 15.5 |  65.79 $\pm$ 0.23 | 0.63 |  6.37 $\pm$ 0.61 | 0.05 | Bubble
| 10.480 | 0.030 | SiO | 49 |  |  65.82 $\pm$ 1.36 | 0.21 |  23.41 $\pm$ 3.13 | 0.02 |
| 10.480 | 0.030 |  HC3N | 18 |  |  66.31 $\pm$ 0.19 | 0.79 |  6.96 $\pm$ 0.55 | 0.07 |
G322.159$+$00.635† | 322.159 | 0.637 | HNCO | 96 | 19.4 |  $-$56.94 $\pm$ 0.27 | 0.45 |  4.02 $\pm$ 0.61 | 0.03 | Bubble
| 322.159 | 0.637 | SiO | 14 |  |  $-$56.34 $\pm$ 0.15 | 1.12 |  7.75 $\pm$ 0.44 | 0.07 |
| 322.159 | 0.637 |  HC3N | 43 |  |  $-$56.89 $\pm$ 0.05 | 2.67 |  4.99 $\pm$ 0.11 | 0.18 |
Table 1: \- continued.

Sourcea | l | b | MOL | $\theta$ |  Td |  vLSR |  TMB |  $\Delta$v | $\tau$ | comment
---|---|---|---|---|---|---|---|---|---|---
| deg | deg |  | $\prime\prime$ | $K$ | $km\ s^{-1}$ | K | $km\ s^{-1}$ |  |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11)
G326.653$+$00.618 | 326.640 | 0.615 | HNCO | 88 | 15.3 |  $-$39.78 $\pm$ 0.27 | 0.60 |  5.88 $\pm$ 0.69 | 0.05 | Bubble
| 326.640 | 0.615 | SiO | 89 |  |  $-$39.45 $\pm$ 0.32 | 0.58 |  6.95 $\pm$ 1.13 | 0.05 |
| 326.640 | 0.615 |  HC3N | 98 |  |  $-$39.02 $\pm$ 0.06 | 1.79 |  3.30 $\pm$ 0.16 | 0.16 |
G327.293$-$00.579† | 327.296 |  $-$0.577 | HNCO | 25 | 16.9 |  $-$44.73 $\pm$ 0.24 | 0.58 |  5.55 $\pm$ 0.67 | 0.04 | Bubble
| 327.296 |  $-$0.577 | SiO | 34 |  |  $-$44.29 $\pm$ 0.21 | 1.01 |  7.64 $\pm$ 0.60 | 0.08 |
| 327.296 |  $-$0.577 |  HC3N | 52 |  |  $-$44.88 $\pm$ 0.05 | 3.10 |  5.76 $\pm$ 0.11 | 0.26 |
G345.004$-$00.224† | 345.007 |  $-$0.220 | HNCO | 32 | 16.5 |  $-$26.43 $\pm$ 0.36 | 0.44 |  8.02 $\pm$ 0.85 | 0.03 | Bubble
| 345.007 |  $-$0.220 | SiO | 50 |  |  $-$24.91 $\pm$ 0.34, $-$34.45 $\pm$ 0.36 | 0.77, 0.42 |  9.23 $\pm$ 0.96 | 0.06 |
| 345.007 |  $-$0.220 |  HC3N | 30 |  |  $-$27.07 $\pm$ 0.11 | 1.46 |  7.11 $\pm$ 0.27 | 0.12 |
G350.101$+$00.083† | 350.110 | 0.096 | HNCO | 55 | 16.0 |  $-$68.53 $\pm$ 0.35 | 0.57 |  8.07 $\pm$ 0.70 | 0.05 | Bubble
| 350.110 | 0.096 | SiO | 58 |  |  $-$69.38 $\pm$ 0.60 | 0.46 |  12.46 $\pm$ 1.65 | 0.04 |
| 350.110 | 0.096 |  HC3N | 44 |  |  $-$69.84 $\pm$ 0.25 | 0.66 |  6.97 $\pm$ 0.76 | 0.05 |
G351.443$+$00.659 | 351.451 | 0.654 | HNCO | 67 | 15.7 |  $-$4.41 $\pm$ 0.11 | 1.29 |  4.32 $\pm$ 0.29 | 0.11 | Bubble
| 351.451 | 0.654 | SiO | 49 |  |  $-$3.84 $\pm$ 0.09, $-$3.86 $\pm$ 0.46 | 1.90, 0.76 |  5.58 $\pm$ 0.40, 14.73 $\pm$ 1.90 | 0.16 |
| 351.451 | 0.654 |  HC3N | 64 |  |  $-$4.23 $\pm$ 0.13 | 7.29 |  4.02 $\pm$ 0.05 | 0.87 |
G351.582$-$00.352 | 351.579 |  $-$0.355 | HNCO | 69 | 17.9 |  $-$95.72 $\pm$ 0.11 | 1.09 |  4.60 $\pm$ 0.23 | 0.08 | Bubble
| 351.579 |  $-$0.355 | SiO | 58 |  |  $-$96.03 $\pm$ 0.44 | 0.47 |  6.68 $\pm$ 1.48 | 0.03 |
| 351.579 |  $-$0.355 |  HC3N | 27 |  |  $-$95.51 $\pm$ 0.10 | 1.40 |  4.93 $\pm$ 0.24 | 0.10 |
G351.775$-$00.537 | 351.773 |  $-$0.539 | HNCO | 35 | 20.7 |  $-$2.64 $\pm$ 0.16, $-$6.84 $\pm$ 0.28 | 1.01, 0.47 |  3.58 $\pm$ 0.42, 1.77 $\pm$ 0.61 | 0.06 | Bubble
| 351.773 |  $-$0.539 | SiO | 39 |  |  $-$2.83 $\pm$ 0.56, 5.40 $\pm$ 1.22 | 1.97, 0.71 |  9.45 $\pm$ 94, 7.75 $\pm$ 1.48 | 0.12 |
| 351.773 |  $-$0.539 |  HC3N | 32 |  |  $-$2.41 $\pm$ 0.10 | 1.94 |  6.22 $\pm$ 0.28 | 0.12 |
G329.030$-$00.202† | 329.031 |  $-$0.201 | HNCO | 55 | 15.4 |  $-$44.47 $\pm$ 0.17 | 0.83 |  3.86 $\pm$ 0.37 | 0.07 | NMSFR
| 329.031 |  $-$0.201 | SiO | 49 |  |  $-$43.17 $\pm$ 0.33, $-$50.46 $\pm$ 0.62 | 0.90, 0.41 |  6.99 $\pm$ 0.58, 6.16 $\pm$ 1.89 | 0.08 |
| 329.031 |  $-$0.201 |  HC3N | 51 |  |  $-$44.08 $\pm$ 0.08 | 1.79 |  4.95 $\pm$ 0.22 | 0.16 |
G331.708$+$00.583 | 331.709 | 0.582 | HNCO | $-$ | 14.0 |  $-$67.61 $\pm$ 0.22 | 0.50 |  2.48 $\pm$ 0.59 | 0.05 | NMSFR
| 331.709 | 0.582 | SiO | $-$ |  |  $-$66.99 $\pm$ 0.47 | 0.39 |  7.89 $\pm$ 1.39 | 0.04 |
| 331.709 | 0.582 |  HC3N | $-$ |  |  $-$66.84 $\pm$ 0.15 | 0.79 |  4.23 $\pm$ 0.37 | 0.08 |
G331.709$+$00.602 | 331.709 | 0.602 | HNCO | $-$ | 14.4 |  $-$66.93 $\pm$ 0.25 | 0.61 |  4.90 $\pm$ 0.71 | 0.06 | NMSFR
| 331.709 | 0.602 | SiO | $-$ |  |  $-$67.22 $\pm$ 0.32 | 0.45 |  4.60 $\pm$ 0.72 | 0.04 |
| 331.709 | 0.602 |  HC3N | $-$ |  |  $-$67.62 $\pm$ 0.11 | 1.03 |  3.34 $\pm$ 0.27 | 0.10 |
G335.586$-$00.289† | 335.584 |  $-$0.288 | HNCO | 35 | 16.7 |  $-$46.43 $\pm$ 0.15 | 0.78 |  3.26 $\pm$ 0.46 | 0.06 | NMSFR
| 335.584 |  $-$0.288 | SiO | 39 |  |  $-$46.08 $\pm$ 0.16, $-$52.48 $\pm$ 0.59 | 0.91, 0.32 |  4.55 $\pm$ 0.45, 4.92 $\pm$ 1.17 | 0.07 |
| 335.584 |  $-$0.288 |  HC3N | 30 |  |  $-$46.45 $\pm$ 0.06 | 1.98 |  3.41 $\pm$ 0.15 | 0.16 |
G348.754$-$00.941† | 348.761 |  $-$0.948 | HNCO | 86 | 13.7 |  $-$14.06 $\pm$ 0.32 | 0.56 |  5.44 $\pm$ 0.76 | 0.05 | NMSFR
| 348.761 |  $-$0.948 | SiO | 48 |  |  $-$12.66 $\pm$ 0.32 | 0.56 |  5.45 $\pm$ 1.03 | 0.05 |
| 348.761 |  $-$0.948 |  HC3N | 32 |  |  $-$13.24 $\pm$ 0.19 | 0.85 |  4.73 $\pm$ 0.50 | 0.08 |
G351.157$+$00.701 | 351.155 | 0.709 | HNCO | 75 | 17.5 |  $-$6.48 $\pm$ 0.18 | 0.75 |  3.57 $\pm$ 0.54 | 0.05 | NMSFR
| 351.155 | 0.709 | SiO | 34 |  |  $-$6.48 $\pm$ 0.12 | 1.05 |  3.17 $\pm$ 0.34 | 0.08 |
| 351.155 | 0.709 |  HC3N | 41 |  |  $-$6.66 $\pm$ 0.04 | 3.54 |  3.42 $\pm$ 0.09 | 0.28 |

_Note_. a $\ast$ indicates the source name is adopted from Miettinen (2014).
${\dagger}$ indicates a source is identified as an IRDC by Peretto & Fuller
(2009).

Table 2: Derived parameters for sources. Quantities in parentheses give the uncertainties. The columns are as follows: (1) MALT90 names; (2) and (3) Galactic longitude and Galactic latitude of the yellow crosses on maps of Figs. 13 to 34; (4) molecular species; (5) velocity range; (6) integrated intensity is derived by integrating over the velocity range indicated in column 5; (7) beam-averaged column densities of the molecules discussed in this paper; (8)beam-averaged H2 column density; (9) fractional abundances relative to H2; (10) source category (see Sect. 2.2). Sourcea | l | b | MOL |  vrange | $\int{T_{\rm MB}}dv$ | N |  N${}_{\rm H_{2}}$ | $x$ | comment
---|---|---|---|---|---|---|---|---|---
| deg | deg |  | $km\ s^{-1}$ | $K\cdot km\ s^{-1}$ | $\times 10^{13}cm^{-2}$ | $\times 10^{22}cm^{-2}$ | $\times 10^{-10}$ |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10)
G000.067$-$00.077 | 0.065 |  $-$0.078 | HNCO | 16.86, 96.65 |  70.65 $\pm$ 1.54 |  88.15 $\pm$ 1.92 |  18.13 $\pm$ 1.56 |  48.62 $\pm$ 4.34 | CMZ
| 0.065 |  $-$0.078 | SiO | 26.22, 91.03 |  48.09 $\pm$ 1.32 |  11.84 $\pm$ 0.32 |  |  6.53 $\pm$ 0.59 |
| 0.065 |  $-$0.078 |  HC3N | 32.59, 69.68 |  51.26 $\pm$ 0.98 |  25.16 $\pm$ 0.48 |  |  13.88 $\pm$ 1.23 |
G000.104$-$00.080 | 0.107 |  $-$0.085 | HNCO | 32.75, 73.68 |  59.60 $\pm$ 0.65 |  74.70 $\pm$ 0.81 |  16.72 $\pm$ 2.11 |  44.68 $\pm$ 5.66 | CMZ
| 0.107 |  $-$0.085 | SiO | 17.44, 76.46 |  60.75 $\pm$ 0.79 |  15.01 $\pm$ 0.19 |  |  8.98 $\pm$ 1.13 |
| 0.107 |  $-$0.085 |  HC3N | 26.07, 72.01 |  76.95 $\pm$ 0.76 |  37.60 $\pm$ 0.37 |  |  22.49 $\pm$ 2.84 |
G000.106$-$00.001 | 0.104 |  $-$0.004 | HNCO | 27.84, 84.77 |  41.18 $\pm$ 0.67 |  52.09 $\pm$ 0.84 |  8.76 $\pm$ 1.22 |  59.44 $\pm$ 8.34 | CMZ
| 0.104 |  $-$0.004 | SiO | 30.31, 71.54 |  28.39 $\pm$ 0.53 |  7.06 $\pm$ 0.13 |  |  8.05 $\pm$ 1.13 |
| 0.104 |  $-$0.004 |  HC3N | 34.31, 72.77 |  42.33 $\pm$ 0.49 |  20.50 $\pm$ 0.23 |  |  23.39 $\pm$ 3.27 |
G000.110$+$00.148 | 0.113 | 0.152 | HNCO | 80.21, 121.25 |  13.96 $\pm$ 0.56 |  17.50 $\pm$ 0.70 |  4.81 $\pm$ 0.54 |  36.37 $\pm$ 4.39 | CMZ
| 0.113 | 0.152 | SiO | 87.88, 113.59 |  6.85 $\pm$ 0.52 |  1.69 $\pm$ 0.12 |  |  3.52 $\pm$ 0.48 |
| 0.113 | 0.152 |  HC3N | 90.06, 110.86 |  8.82 $\pm$ 0.39 |  4.31 $\pm$ 0.19 |  |  8.96 $\pm$ 1.09 |
G000.314$-$00.100 | 0.314 |  $-$0.096 | HNCO | 47.32, 104.77 |  21.71 $\pm$ 0.82 |  27.97 $\pm$ 1.05 |  7.09 $\pm$ 0.40 |  39.46 $\pm$ 2.69 | CMZ
| 0.314 |  $-$0.096 | SiO | 37.29, 112.58 |  21.95 $\pm$ 1.07 |  5.52 $\pm$ 0.26 |  |  7.79 $\pm$ 0.58 |
| 0.314 |  $-$0.096 |  HC3N | 51.79, 116.48 |  13.82 $\pm$ 0.86 |  6.58 $\pm$ 0.40 |  |  9.29 $\pm$ 0.78 |
G000.497$+$00.021 | 0.497 | 0.018 | HNCO | 3.51, 53.42 |  69.41 $\pm$ 0.72 |  86.21 $\pm$ 0.89 |  16.59 $\pm$ 2.84 |  51.96 $\pm$ 8.93 | CMZ
| 0.497 | 0.018 | SiO | 0.70, 51.31 |  22.14 $\pm$ 0.73 |  5.44 $\pm$ 0.17 |  |  3.28 $\pm$ 0.57 |
| 0.497 | 0.018 |  HC3N | 2.81, 53.42 |  43.80 $\pm$ 0.66 |  21.60 $\pm$ 0.32 |  |  13.02 $\pm$ 2.24 |
G000.645$+$00.027 | 0.647 | 0.032 | HNCO | 21.76, 81.95 |  112.17 $\pm$ 0.84 |  138.69 $\pm$ 1.03 |  15.67 $\pm$ 1.34 |  88.49 $\pm$ 7.62 | CMZ
| 0.647 | 0.032 | SiO | 22.45, 93.99 |  30.90 $\pm$ 0.81 |  7.56 $\pm$ 0.19 |  |  4.83 $\pm$ 0.43 |
| 0.647 | 0.032 |  HC3N | 26.92, 77.82 |  60.69 $\pm$ 0.76 |  30.08 $\pm$ 0.37 |  |  19.19 $\pm$ 1.66 |
G000.892$+$00.143 | 0.894 | 0.142 | HNCO | 57.39, 98.18 |  19.97 $\pm$ 0.52 |  24.25 $\pm$ 0.63 |  3.30 $\pm$ 0.41 |  73.46 $\pm$ 9.52 | CMZ
| 0.894 | 0.142 | SiO | 54.08, 108.93 |  16.16 $\pm$ 0.61 |  3.91 $\pm$ 0.14 |  |  11.84 $\pm$ 1.56 |
| 0.894 | 0.142 |  HC3N | 54.36, 92.40 |  14.11 $\pm$ 0.49 |  7.14 $\pm$ 0.24 |  |  21.62 $\pm$ 2.84 |
G000.908$+$00.116 | 0.919 | 0.116 | HNCO | 51.24, 88.10 |  12.73 $\pm$ 0.66 |  15.39 $\pm$ 0.79 |  3.53 $\pm$ 0.32 |  43.58 $\pm$ 4.60 | CMZ
| 0.919 | 0.116 | SiO | 41.22, 93.71 |  9.49 $\pm$ 0.69 |  2.29 $\pm$ 0.16 |  |  6.48 $\pm$ 0.76 |
| 0.919 | 0.116 |  HC3N | 56.05, 88.90 |  5.82 $\pm$ 0.46 |  2.96 $\pm$ 0.23 |  |  8.38 $\pm$ 1.01 |
G001.226$+$00.059 | 1.233 | 0.061 | HNCO | 77.97, 136.29 |  16.64 $\pm$ 0.67 |  19.76 $\pm$ 0.79 |  5.43 $\pm$ 1.05 |  36.39 $\pm$ 7.20 | CMZ
| 1.233 | 0.061 | SiO | 79.95, 147.82 |  41.61 $\pm$ 0.73 |  9.92 $\pm$ 0.17 |  |  18.27 $\pm$ 3.55 |
| 1.233 | 0.061 |  HC3N | 88.52, 131.35 |  22.60 $\pm$ 0.48 |  11.76 $\pm$ 0.24 |  |  21.66 $\pm$ 4.22 |
G001.344$+$00.258 | 1.348 | 0.262 | HNCO | 75.10, 131.08 |  26.14 $\pm$ 0.71 |  30.63 $\pm$ 0.83 |  5.65 $\pm$ 0.52 |  54.24 $\pm$ 5.25 | CMZ
| 1.348 | 0.262 | SiO | 66.91, 136.99 |  55.98 $\pm$ 0.86 |  13.23 $\pm$ 0.20 |  |  23.43 $\pm$ 2.20 |
| 1.348 | 0.262 |  HC3N | 76.01, 124.25 |  35.37 $\pm$ 0.60 |  18.75 $\pm$ 0.31 |  |  33.21 $\pm$ 3.13 |
G001.381$+$00.201 | 1.381 | 0.187 | HNCO | 75.30, 123.23 |  10.08 $\pm$ 0.61 |  11.86 $\pm$ 0.71 |  2.68 $\pm$ 0.17 |  44.31 $\pm$ 3.94 | CMZ
| 1.381 | 0.187 | SiO | 60.05, 133.58 |  26.93 $\pm$ 0.76 |  6.38 $\pm$ 0.18 |  |  23.84 $\pm$ 1.69 |
| 1.381 | 0.187 |  HC3N | 69.85, 121.05 |  11.24 $\pm$ 0.62 |  5.92 $\pm$ 0.32 |  |  22.11 $\pm$ 1.89 |
G001.510$+$00.155 | 1.522 | 0.144 | HNCO | 64.27, 95.39 |  28.51 $\pm$ 0.61 |  32.83 $\pm$ 0.70 |  3.04 $\pm$ 0.40 |  107.93 $\pm$ 7.35 | CMZ
| 1.522 | 0.144 | SiO | 66.14, 98.90 |  15.81 $\pm$ 0.63 |  3.69 $\pm$ 0.14 |  |  12.15 $\pm$ 1.70 |
| 1.522 | 0.144 |  HC3N | 66.37, 92.11 |  19.75 $\pm$ 0.61 |  10.76 $\pm$ 0.33 |  |  35.36 $\pm$ 4.88 |
G001.610$-$00.172 | 1.607 |  $-$0.174 | HNCO | 29.14, 55.45 |  26.24 $\pm$ 0.49 |  29.96 $\pm$ 0.55 |  4.53 $\pm$ 0.50 |  66.07 $\pm$ 7.42 | CMZ
| 1.607 |  $-$0.174 | SiO | 30.13, 55.94 |  6.29 $\pm$ 0.42 |  1.46 $\pm$ 0.09 |  |  3.22 $\pm$ 0.41 |
| 1.607 |  $-$0.174 |  HC3N | 34.80, 55.94 |  7.47 $\pm$ 0.37 |  4.13 $\pm$ 0.20 |  |  9.10 $\pm$ 1.10 |
Table 2: \- continued. Sourcea | l | b | MOL |  vrange | $\int{T_{\rm MB}}dv$ | N |  N${}_{\rm H_{2}}$ | $x$ | comment
---|---|---|---|---|---|---|---|---|---
| deg | deg |  | $km\ s^{-1}$ | $K\cdot km\ s^{-1}$ | $\times 10^{13}cm^{-2}$ | $\times 10^{22}cm^{-2}$ | $\times 10^{-10}$ |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10)
G001.655$-$00.062 | 1.661 |  $-$0.053 | HNCO | 36.36, 62.59 |  46.96 $\pm$ 0.47 |  52.08 $\pm$ 0.52 |  6.23 $\pm$ 0.61 |  83.63 $\pm$ 8.29 | CMZ
G1.87$-$SMM 1∗ |  |  |  |  |  |  |  |  |
| 1.661 |  $-$0.053 | SiO | 38.79, 64.65 |  10.48 $\pm$ 0.44 |  2.39 $\pm$ 0.10 |  |  3.84 $\pm$ 0.41 |
| 1.661 |  $-$0.053 |  HC3N | 39.36, 60.72 |  14.98 $\pm$ 0.39 |  8.76 $\pm$ 0.22 |  |  14.06 $\pm$ 1.43 |
G001.694$-$00.385 | 1.694 |  $-$0.388 | HNCO | -50.97, -22.28 |  25.33 $\pm$ 0.69 |  28.92 $\pm$ 0.78 |  6.38 $\pm$ 0.83 |  45.31 $\pm$ 6.03 | CMZ
| 1.694 |  $-$0.388 | SiO | -61.15, -15.18 |  19.66 $\pm$ 0.93 |  4.57 $\pm$ 0.21 |  |  7.16 $\pm$ 0.99 |
| 1.694 |  $-$0.388 |  HC3N | -47.89, -20.12 |  24.02 $\pm$ 0.70 |  13.27 $\pm$ 0.38 |  |  20.79 $\pm$ 2.77 |
G001.699$-$00.366 | 1.700 |  $-$0.367 | HNCO | -53.14, -19.61 |  26.66 $\pm$ 0.55 |  30.31 $\pm$ 0.62 |  6.70 $\pm$ 0.40 |  45.26 $\pm$ 2.91 | CMZ
| 1.700 |  $-$0.367 | SiO | -59.97, -10.30 |  19.35 $\pm$ 0.63 |  4.48 $\pm$ 0.14 |  |  6.70 $\pm$ 0.46 |
| 1.700 |  $-$0.367 |  HC3N | -49.41, -10.85 |  38.80 $\pm$ 0.54 |  21.60 $\pm$ 0.30 |  |  32.25 $\pm$ 2.02 |
G001.734$-$00.410 | 1.737 |  $-$0.412 | HNCO | -57.64, -24.24 |  36.06 $\pm$ 0.43 |  40.15 $\pm$ 0.47 |  11.75 $\pm$ 1.53 |  34.18 $\pm$ 4.49 | CMZ
| 1.737 |  $-$0.412 | SiO | -54.63, -20.53 |  18.80 $\pm$ 0.44 |  4.30 $\pm$ 0.10 |  |  3.66 $\pm$ 0.48 |
| 1.737 |  $-$0.412 |  HC3N | -49.99, -25.17 |  30.04 $\pm$ 0.36 |  17.41 $\pm$ 0.20 |  |  14.82 $\pm$ 1.94 |
G001.883$-$00.062 | 1.887 |  $-$0.063 | HNCO | 26.73, 49.74 |  13.22 $\pm$ 0.36 |  15.36 $\pm$ 0.41 |  4.07 $\pm$ 0.38 |  37.69 $\pm$ 3.69 | CMZ
G1.87$-$SMM 23∗ |  |  |  |  |  |  |  |  |
| 1.887 |  $-$0.063 | SiO | 30.10, 44.78 |  5.29 $\pm$ 0.38 |  1.24 $\pm$ 0.08 |  |  3.05 $\pm$ 0.36 |
| 1.887 |  $-$0.063 |  HC3N | 28.52, 43.79 |  6.74 $\pm$ 0.34 |  3.62 $\pm$ 0.18 |  |  8.89 $\pm$ 0.94 |
G003.240$+$00.635 | 3.241 | 0.635 | HNCO | 29.37, 56.47 |  6.47 $\pm$ 0.45 |  7.23 $\pm$ 0.50 |  3.17 $\pm$ 0.41 |  22.80 $\pm$ 3.40 | CMZ
| 3.241 | 0.635 | SiO | 23.88, 59.90 |  13.07 $\pm$ 0.52 |  3.00 $\pm$ 0.11 |  |  9.44 $\pm$ 1.30 |
| 3.241 | 0.635 |  HC3N | 28.68, 56.81 |  7.44 $\pm$ 0.45 |  4.28 $\pm$ 0.25 |  |  13.48 $\pm$ 1.95 |
G003.338$+$00.419 | 3.339 | 0.425 | HNCO | 9.00, 55.42 |  20.86 $\pm$ 0.72 |  23.13 $\pm$ 0.79 |  8.73 $\pm$ 0.30 |  26.51 $\pm$ 1.29 | CMZ
| 3.339 | 0.425 | SiO | 1.87, 60.94 |  35.05 $\pm$ 0.74 |  7.99 $\pm$ 0.16 |  |  9.16 $\pm$ 0.37 |
| 3.339 | 0.425 |  HC3N | 6.09, 56.72 |  34.77 $\pm$ 0.74 |  20.32 $\pm$ 0.43 |  |  23.29 $\pm$ 0.94 |
G359.445$-$00.054 | 359.446 |  $-$0.058 | HNCO | -121.35, -84.20 |  24.52 $\pm$ 0.58 |  31.45 $\pm$ 0.74 |  6.51 $\pm$ 1.02 |  48.32 $\pm$ 7.70 | CMZ
| 359.446 |  $-$0.058 | SiO | -121.35, -92.22 |  7.07 $\pm$ 0.47 |  1.77 $\pm$ 0.11 |  |  2.72 $\pm$ 0.46 |
| 359.446 |  $-$0.058 |  HC3N | -112.13, -92.52 |  9.24 $\pm$ 0.42 |  4.42 $\pm$ 0.20 |  |  6.79 $\pm$ 1.11 |
G359.453$-$00.112 | 359.455 |  $-$0.112 | HNCO | -65.95, -42.46 |  17.49 $\pm$ 0.49 |  22.33 $\pm$ 0.62 |  14.37 $\pm$ 1.09 |  15.53 $\pm$ 1.26 | CMZ
| 359.455 |  $-$0.112 | SiO | -62.96, -43.10 |  8.70 $\pm$ 0.41 |  2.18 $\pm$ 0.10 |  |  1.51 $\pm$ 0.13 |
| 359.455 |  $-$0.112 |  HC3N | -66.38, -42.46 |  14.00 $\pm$ 0.46 |  6.72 $\pm$ 0.22 |  |  4.68 $\pm$ 0.38 |
G359.565$-$00.161 | 359.551 |  $-$0.166 | HNCO | -75.68, -43.94 |  17.28 $\pm$ 0.53 |  22.26 $\pm$ 0.68 |  3.79 $\pm$ 0.18 |  58.67 $\pm$ 3.44 | CMZ
| 359.551 |  $-$0.166 | SiO | -70.39, -35.12 |  7.73 $\pm$ 0.57 |  1.94 $\pm$ 0.14 |  |  5.12 $\pm$ 0.45 |
| 359.551 |  $-$0.166 |  HC3N | -72.51, -43.23 |  9.99 $\pm$ 0.50 |  4.76 $\pm$ 0.23 |  |  12.54 $\pm$ 0.88 |
G359.868$-$00.085 | 359.866 |  $-$0.082 | HNCO | -9.51, 23.01 |  63.64 $\pm$ 0.54 |  80.13 $\pm$ 0.67 |  35.98 $\pm$ 2.52 |  22.27 $\pm$ 1.57 | CMZ
| 359.866 |  $-$0.082 | SiO | -14.66, 30.87 |  43.22 $\pm$ 0.69 |  10.71 $\pm$ 0.17 |  |  2.98 $\pm$ 0.21 |
| 359.866 |  $-$0.082 |  HC3N | -11.95, 22.20 |  61.99 $\pm$ 0.62 |  30.16 $\pm$ 0.30 |  |  8.38 $\pm$ 0.59 |
G359.895$-$00.069 | 359.892 |  $-$0.076 | HNCO | -4.15, 35.34 |  81.24 $\pm$ 0.55 |  101.83 $\pm$ 0.68 |  26.93 $\pm$ 3.12 |  37.81 $\pm$ 4.40 | CMZ
| 359.892 |  $-$0.076 | SiO | -12.52, 37.35 |  62.86 $\pm$ 0.58 |  15.53 $\pm$ 0.14 |  |  5.77 $\pm$ 0.67 |
| 359.892 |  $-$0.076 |  HC3N | -7.83, 35.67 |  89.48 $\pm$ 0.52 |  43.73 $\pm$ 0.25 |  |  16.24 $\pm$ 1.88 |
G359.977$-$00.072 | 359.980 |  $-$0.070 | HNCO | 26.79, 63.94 |  55.09 $\pm$ 0.79 |  73.64 $\pm$ 1.05 |  21.39 $\pm$ 0.87 |  34.43 $\pm$ 1.48 | CMZ
| 359.980 |  $-$0.070 | SiO | 19.59, 76.07 |  70.96 $\pm$ 0.93 |  18.29 $\pm$ 0.23 |  |  8.55 $\pm$ 0.36 |
| 359.980 |  $-$0.070 |  HC3N | 21.87, 71.52 |  97.20 $\pm$ 0.89 |  44.99 $\pm$ 0.41 |  |  21.03 $\pm$ 0.87 |
G008.671$-$00.357 | 8.677 |  $-$0.360 | HNCO | 31.47, 40.86 |  4.59 $\pm$ 0.27 |  5.65 $\pm$ 0.33 |  18.69 $\pm$ 7.45 |  3.02 $\pm$ 1.21 | Bubble
| 8.677 |  $-$0.360 | SiO | 28.63, 41.97 |  4.50 $\pm$ 0.35 |  1.10 $\pm$ 0.08 |  |  0.59 $\pm$ 0.23 |
| 8.677 |  $-$0.360 |  HC3N | 31.47, 42.47 |  9.71 $\pm$ 0.31 |  4.84 $\pm$ 0.15 |  |  2.59 $\pm$ 1.03 |
G010.473$+$00.028 | 10.480 | 0.030 | HNCO | 58.39, 71.82 |  4.37 $\pm$ 0.28 |  5.55 $\pm$ 0.35 |  25.54 $\pm$ 6.74 |  2.17 $\pm$ 1.15 | Bubble
| 10.480 | 0.030 | SiO | 55.54, 84.44 |  4.57 $\pm$ 0.47 |  1.14 $\pm$ 0.11 |  |  0.45 $\pm$ 0.23 |
| 10.480 | 0.030 |  HC3N | 59.21, 76.30 |  6.23 $\pm$ 0.35 |  3.00 $\pm$ 0.16 |  |  1.18 $\pm$ 0.62 |
G322.159$+$00.635† | 322.159 | 0.637 | HNCO | -59.93, -51.67 |  1.93 $\pm$ 0.25 |  2.93 $\pm$ 0.37 |  24.45 $\pm$ 3.76 |  1.20 $\pm$ 0.24 | Bubble
| 322.159 | 0.637 | SiO | -63.59, -45.31 |  9.83 $\pm$ 0.32 |  2.76 $\pm$ 0.08 |  |  1.13 $\pm$ 0.17 |
| 322.159 | 0.637 |  HC3N | -61.83, -52.08 |  13.57 $\pm$ 0.25 |  5.88 $\pm$ 0.10 |  |  2.40 $\pm$ 0.37 |
Table 2: \- continued.

Sourcea | l | b | MOL |  vrange | $\int{T_{\rm MB}}dv$ | N |  N${}_{\rm H_{2}}$ | $x$ | comment
---|---|---|---|---|---|---|---|---|---
| deg | deg |  | $km\ s^{-1}$ | $K\cdot km\ s^{-1}$ | $\times 10^{13}cm^{-2}$ | $\times 10^{22}cm^{-2}$ | $\times 10^{-10}$ |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10)
G326.653$+$00.618 | 326.640 | 0.615 | HNCO | -46.18, -34.80 |  3.87 $\pm$ 0.30 |  4.87 $\pm$ 0.37 |  25.46 $\pm$ 3.52 |  1.91 $\pm$ 0.30 | Bubble
| 326.640 | 0.615 | SiO | -48.69, -28.43 |  5.32 $\pm$ 0.37 |  1.32 $\pm$ 0.09 |  |  0.52 $\pm$ 0.08 |
| 326.640 | 0.615 |  HC3N | -43.34, -36.30 |  6.44 $\pm$ 0.23 |  3.13 $\pm$ 0.11 |  |  1.23 $\pm$ 0.17 |
G327.293$-$00.579† | 327.296 |  $-$0.577 | HNCO | -51.43, -39.94 |  3.74 $\pm$ 0.28 |  5.07 $\pm$ 0.37 |  59.52 $\pm$ 10.28 |  0.85 $\pm$ 0.30 | Bubble
| 327.296 |  $-$0.577 | SiO | -53.44, -35.71 |  8.43 $\pm$ 0.38 |  2.19 $\pm$ 0.09 |  |  0.37 $\pm$ 0.12 |
| 327.296 |  $-$0.577 |  HC3N | -50.62, -36.72 |  19.24 $\pm$ 0.30 |  8.82 $\pm$ 0.13 |  |  1.48 $\pm$ 0.51 |
G345.004$-$00.224† | 345.007 |  $-$0.220 | HNCO | -34.85, -20.90 |  3.70 $\pm$ 0.28 |  4.92 $\pm$ 0.37 |  19.83 $\pm$ 8.50 |  2.48 $\pm$ 1.08 | Bubble
| 345.007 |  $-$0.220 | SiO | -43.62, -11.96 |  12.96 $\pm$ 0.54 |  3.33 $\pm$ 0.13 |  |  1.68 $\pm$ 0.72 |
| 345.007 |  $-$0.220 |  HC3N | -35.63, -19.17 |  11.49 $\pm$ 0.32 |  5.34 $\pm$ 0.14 |  |  2.69 $\pm$ 1.15 |
G350.101$+$00.083† | 350.110 | 0.096 | HNCO | -74.50, -62.16 |  4.93 $\pm$ 0.36 |  6.41 $\pm$ 0.46 |  16.87 $\pm$ 3.76 |  3.80 $\pm$ 0.89 | Bubble
| 350.110 | 0.096 | SiO | -77.85, -58.98 |  5.65 $\pm$ 0.45 |  1.43 $\pm$ 0.11 |  |  0.85 $\pm$ 0.20 |
| 350.110 | 0.096 |  HC3N | -75.74, -62.16 |  4.83 $\pm$ 0.34 |  2.28 $\pm$ 0.16 |  |  1.35 $\pm$ 0.31 |
G351.443$+$00.659 | 351.451 | 0.654 | HNCO | -8.29, 2.03 |  6.05 $\pm$ 0.31 |  7.76 $\pm$ 0.39 |  45.35 $\pm$ 10.38 |  1.71 $\pm$ 0.78 | Bubble
| 351.451 | 0.654 | SiO | -16.13, 5.85 |  22.42 $\pm$ 0.48 |  5.62 $\pm$ 0.12 |  |  1.24 $\pm$ 0.56 |
| 351.451 | 0.654 |  HC3N | -11.73, 2.41 |  33.35 $\pm$ 0.35 |  15.95 $\pm$ 0.16 |  |  3.52 $\pm$ 1.61 |
G351.582$-$00.352 | 351.579 |  $-$0.355 | HNCO | -100.73, -90.92 |  5.18 $\pm$ 0.25 |  7.35 $\pm$ 0.35 |  31.87 $\pm$ 8.80 |  2.31 $\pm$ 0.64 | Bubble
| 351.579 |  $-$0.355 | SiO | -104.31, -92.48 |  3.60 $\pm$ 0.35 |  0.97 $\pm$ 0.09 |  |  0.30 $\pm$ 0.08 |
| 351.579 |  $-$0.355 |  HC3N | -101.04, -90.92 |  7.30 $\pm$ 0.30 |  3.26 $\pm$ 0.13 |  |  1.02 $\pm$ 0.28 |
G351.775$-$00.537 | 351.773 |  $-$0.539 | HNCO | -8.04, 1.36 |  4.73 $\pm$ 0.35 |  7.62 $\pm$ 0.56 |  50.86 $\pm$ 6.09 |  1.50 $\pm$ 0.37 | Bubble
| 351.773 |  $-$0.539 | SiO | -13.53, 11.97 |  25.98 $\pm$ 0.59 |  7.58 $\pm$ 0.17 |  |  1.49 $\pm$ 0.35 |
| 351.773 |  $-$0.539 |  HC3N | -8.53, 3.80 |  13.09 $\pm$ 0.40 |  5.57 $\pm$ 0.17 |  |  1.09 $\pm$ 0.26 |
G329.030$-$00.202† | 329.031 |  $-$0.201 | HNCO | -47.95, -39.93 |  3.50 $\pm$ 0.27 |  4.43 $\pm$ 0.34 |  22.03 $\pm$ 3.86 |  2.01 $\pm$ 0.38 | NMSFR
| 329.031 |  $-$0.201 | SiO | -56.70, -36.64 |  8.90 $\pm$ 0.37 |  2.21 $\pm$ 0.09 |  |  1.00 $\pm$ 0.18 |
| 329.031 |  $-$0.201 |  HC3N | -55.25, -38.65 |  10.63 $\pm$ 0.35 |  5.15 $\pm$ 0.16 |  |  2.34 $\pm$ 0.41 |
G331.708$+$00.583 | 331.709 | 0.582 | HNCO | -69.26, -62.52 |  1.61 $\pm$ 0.21 |  1.91 $\pm$ 0.24 |  8.32 $\pm$ 1.88 |  2.30 $\pm$ 0.60 | NMSFR
| 331.709 | 0.582 | SiO | -74.56, -59.08 |  3.72 $\pm$ 0.35 |  0.89 $\pm$ 0.08 |  |  1.07 $\pm$ 0.26 |
| 331.709 | 0.582 |  HC3N | -70.41, -61.80 |  3.59 $\pm$ 0.25 |  1.87 $\pm$ 0.13 |  |  2.25 $\pm$ 0.53 |
G331.709$+$00.602 | 331.709 | 0.602 | HNCO | -70.63, -60.74 |  3.26 $\pm$ 0.30 |  3.94 $\pm$ 0.36 |  10.13 $\pm$ 1.53 |  3.89 $\pm$ 0.68 | NMSFR
| 331.709 | 0.602 | SiO | -71.11, -58.98 |  2.63 $\pm$ 0.33 |  0.63 $\pm$ 0.07 |  |  0.63 $\pm$ 0.12 |
| 331.709 | 0.602 |  HC3N | -70.79, -63.77 |  3.59 $\pm$ 0.25 |  1.83 $\pm$ 0.12 |  |  1.80 $\pm$ 0.30 |
G335.586$-$00.289† | 335.584 |  $-$0.288 | HNCO | -49.02, -41.51 |  2.79 $\pm$ 0.24 |  3.75 $\pm$ 0.32 |  17.33 $\pm$ 3.99 |  2.16 $\pm$ 0.53 | NMSFR
| 335.584 |  $-$0.288 | SiO | -56.53, -41.92 |  6.02 $\pm$ 0.31 |  1.56 $\pm$ 0.08 |  |  0.90 $\pm$ 0.21 |
| 335.584 |  $-$0.288 |  HC3N | -52.31, -42.13 |  7.58 $\pm$ 0.28 |  3.50 $\pm$ 0.12 |  |  2.02 $\pm$ 0.47 |
G348.754$-$00.941† | 348.761 |  $-$0.948 | HNCO | -22.22, -10.53 |  3.81 $\pm$ 0.35 |  4.46 $\pm$ 0.41 |  9.80 $\pm$ 3.42 |  4.55 $\pm$ 1.64 | NMSFR
| 348.761 |  $-$0.948 | SiO | -16.89, -6.91 |  3.34 $\pm$ 0.35 |  0.79 $\pm$ 0.08 |  |  0.81 $\pm$ 0.29 |
| 348.761 |  $-$0.948 |  HC3N | -16.54, -4.68 |  5.02 $\pm$ 0.32 |  2.66 $\pm$ 0.16 |  |  2.71 $\pm$ 0.96 |
G351.157$+$00.701 | 351.155 | 0.709 | HNCO | -9.69, -2.76 |  2.86 $\pm$ 0.27 |  3.99 $\pm$ 0.37 |  23.82 $\pm$ 5.66 |  1.67 $\pm$ 0.42 | NMSFR
| 351.155 | 0.709 | SiO | -9.18, -2.38 |  3.54 $\pm$ 0.25 |  0.94 $\pm$ 0.06 |  |  0.39 $\pm$ 0.09 |
| 351.155 | 0.709 |  HC3N | -10.82, -1.87 |  13.08 $\pm$ 0.28 |  5.90 $\pm$ 0.12 |  |  2.47 $\pm$ 0.59 |

_Note_. a $\ast$ indicates the source name is adopted from Miettinen (2014).
${\dagger}$ indicates a source is identified as an IRDC by Peretto & Fuller
(2009).

Table 3: The integrated intensity and abundance ratios of HNCO, SiO and HC3N. Source | ${I_{\rm HNCO}/I_{\rm SiO}}$ | ${I_{\rm HNCO}/I_{\rm HC_{3}N}}$ | ${I_{\rm SiO}/I_{\rm HC_{3}N}}$ | ${N_{\rm HNCO}/N_{\rm SiO}}$ | ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ | ${N_{\rm SiO}/N_{\rm HC_{3}N}}$ | comment
---|---|---|---|---|---|---|---
G000.067$-$00.077 |  1.47 $\pm$ 0.05 |  1.38 $\pm$ 0.04 |  0.94 $\pm$ 0.03 |  7.45 $\pm$ 0.26 |  3.50 $\pm$ 0.10 |  0.47 $\pm$ 0.02 | CMZ
G000.104$-$00.080 |  0.98 $\pm$ 0.02 |  0.77 $\pm$ 0.01 |  0.79 $\pm$ 0.01 |  4.98 $\pm$ 0.08 |  1.99 $\pm$ 0.03 |  0.40 $\pm$ 0.01 | CMZ
G000.106$-$00.001 |  1.45 $\pm$ 0.04 |  0.97 $\pm$ 0.02 |  0.67 $\pm$ 0.01 |  7.38 $\pm$ 0.18 |  2.54 $\pm$ 0.05 |  0.34 $\pm$ 0.01 | CMZ
G000.110$+$00.148 |  2.04 $\pm$ 0.17 |  1.58 $\pm$ 0.09 |  0.78 $\pm$ 0.07 |  10.36 $\pm$ 0.84 |  4.06 $\pm$ 0.24 |  0.39 $\pm$ 0.03 | CMZ
G000.314$-$00.100 |  0.99 $\pm$ 0.06 |  1.57 $\pm$ 0.11 |  1.59 $\pm$ 0.13 |  5.07 $\pm$ 0.31 |  4.25 $\pm$ 0.30 |  0.84 $\pm$ 0.06 | CMZ
G000.497$+$00.021 |  3.14 $\pm$ 0.11 |  1.58 $\pm$ 0.03 |  0.51 $\pm$ 0.02 |  15.85 $\pm$ 0.52 |  3.99 $\pm$ 0.07 |  0.25 $\pm$ 0.01 | CMZ
G000.645$+$00.027 |  3.63 $\pm$ 0.10 |  1.85 $\pm$ 0.03 |  0.51 $\pm$ 0.01 |  18.35 $\pm$ 0.48 |  4.61 $\pm$ 0.07 |  0.25 $\pm$ 0.01 | CMZ
G000.892$+$00.143 |  1.24 $\pm$ 0.06 |  1.42 $\pm$ 0.06 |  1.15 $\pm$ 0.06 |  6.20 $\pm$ 0.27 |  3.40 $\pm$ 0.14 |  0.55 $\pm$ 0.03 | CMZ
G000.908$+$00.116 |  1.34 $\pm$ 0.12 |  2.19 $\pm$ 0.21 |  1.63 $\pm$ 0.18 |  6.72 $\pm$ 0.58 |  5.20 $\pm$ 0.48 |  0.77 $\pm$ 0.08 | CMZ
G001.226$+$00.059 |  0.40 $\pm$ 0.02 |  0.74 $\pm$ 0.03 |  1.84 $\pm$ 0.05 |  1.99 $\pm$ 0.09 |  1.68 $\pm$ 0.08 |  0.84 $\pm$ 0.02 | CMZ
G001.344$+$00.258 |  0.47 $\pm$ 0.01 |  0.74 $\pm$ 0.02 |  1.58 $\pm$ 0.04 |  2.32 $\pm$ 0.07 |  1.63 $\pm$ 0.05 |  0.71 $\pm$ 0.02 | CMZ
G001.381$+$00.201 |  0.37 $\pm$ 0.02 |  0.90 $\pm$ 0.07 |  2.40 $\pm$ 0.15 |  1.86 $\pm$ 0.12 |  2.00 $\pm$ 0.16 |  1.08 $\pm$ 0.07 | CMZ
G001.510$+$00.155 |  1.80 $\pm$ 0.08 |  1.44 $\pm$ 0.05 |  0.80 $\pm$ 0.04 |  8.90 $\pm$ 0.39 |  3.05 $\pm$ 0.11 |  0.34 $\pm$ 0.02 | CMZ
G001.610$-$00.172 |  4.17 $\pm$ 0.29 |  3.51 $\pm$ 0.19 |  0.84 $\pm$ 0.07 |  20.52 $\pm$ 1.32 |  7.25 $\pm$ 0.38 |  0.35 $\pm$ 0.03 | CMZ
G001.655$-$00.062 |  4.48 $\pm$ 0.19 |  3.13 $\pm$ 0.09 |  0.70 $\pm$ 0.03 |  21.79 $\pm$ 0.94 |  5.95 $\pm$ 0.16 |  0.27 $\pm$ 0.01 | CMZ
G001.694$-$00.385 |  1.29 $\pm$ 0.07 |  1.05 $\pm$ 0.04 |  0.82 $\pm$ 0.05 |  6.33 $\pm$ 0.34 |  2.18 $\pm$ 0.09 |  0.34 $\pm$ 0.02 | CMZ
G001.699$-$00.366 |  1.38 $\pm$ 0.05 |  0.69 $\pm$ 0.02 |  0.50 $\pm$ 0.02 |  6.77 $\pm$ 0.25 |  1.40 $\pm$ 0.03 |  0.21 $\pm$ 0.01 | CMZ
G001.734$-$00.410 |  1.92 $\pm$ 0.05 |  1.20 $\pm$ 0.02 |  0.63 $\pm$ 0.02 |  9.34 $\pm$ 0.24 |  2.31 $\pm$ 0.04 |  0.25 $\pm$ 0.01 | CMZ
G001.883$-$00.062 |  2.50 $\pm$ 0.19 |  1.96 $\pm$ 0.11 |  0.78 $\pm$ 0.07 |  12.39 $\pm$ 0.86 |  4.24 $\pm$ 0.24 |  0.34 $\pm$ 0.03 | CMZ
G003.240$+$00.635 |  0.50 $\pm$ 0.04 |  0.87 $\pm$ 0.08 |  1.76 $\pm$ 0.13 |  2.41 $\pm$ 0.19 |  1.69 $\pm$ 0.15 |  0.70 $\pm$ 0.05 | CMZ
G003.338$+$00.419 |  0.60 $\pm$ 0.02 |  0.60 $\pm$ 0.02 |  1.01 $\pm$ 0.03 |  2.89 $\pm$ 0.11 |  1.14 $\pm$ 0.05 |  0.39 $\pm$ 0.01 | CMZ
G359.445$-$00.054 |  3.47 $\pm$ 0.24 |  2.65 $\pm$ 0.14 |  0.77 $\pm$ 0.06 |  17.77 $\pm$ 1.18 |  7.12 $\pm$ 0.36 |  0.40 $\pm$ 0.03 | CMZ
G359.453$-$00.112 |  2.01 $\pm$ 0.11 |  1.25 $\pm$ 0.05 |  0.62 $\pm$ 0.04 |  10.24 $\pm$ 0.55 |  3.32 $\pm$ 0.14 |  0.32 $\pm$ 0.02 | CMZ
G359.565$-$00.161 |  2.24 $\pm$ 0.18 |  1.73 $\pm$ 0.10 |  0.77 $\pm$ 0.07 |  11.47 $\pm$ 0.90 |  4.68 $\pm$ 0.27 |  0.41 $\pm$ 0.04 | CMZ
G359.868$-$00.085 |  1.47 $\pm$ 0.03 |  1.03 $\pm$ 0.01 |  0.70 $\pm$ 0.01 |  7.48 $\pm$ 0.13 |  2.66 $\pm$ 0.03 |  0.36 $\pm$ 0.01 | CMZ
G359.895$-$00.069 |  1.29 $\pm$ 0.01 |  0.91 $\pm$ 0.01 |  0.70 $\pm$ 0.01 |  6.56 $\pm$ 0.07 |  2.33 $\pm$ 0.02 |  0.36 $\pm$ 0.01 | CMZ
G359.977$-$00.072 |  0.78 $\pm$ 0.02 |  0.57 $\pm$ 0.01 |  0.73 $\pm$ 0.01 |  4.03 $\pm$ 0.08 |  1.64 $\pm$ 0.03 |  0.41 $\pm$ 0.01 | CMZ
G008.671$-$00.357 |  1.02 $\pm$ 0.10 |  0.47 $\pm$ 0.03 |  0.46 $\pm$ 0.04 |  5.14 $\pm$ 0.48 |  1.17 $\pm$ 0.08 |  0.23 $\pm$ 0.02 | Bubble
G010.473$+$00.028 |  0.96 $\pm$ 0.12 |  0.70 $\pm$ 0.06 |  0.73 $\pm$ 0.09 |  4.87 $\pm$ 0.56 |  1.85 $\pm$ 0.15 |  0.38 $\pm$ 0.04 | Bubble
G322.159$+$00.635 |  0.20 $\pm$ 0.03 |  0.14 $\pm$ 0.02 |  0.72 $\pm$ 0.03 |  1.06 $\pm$ 0.14 |  0.50 $\pm$ 0.06 |  0.47 $\pm$ 0.02 | Bubble
G326.653$+$00.618 |  0.73 $\pm$ 0.08 |  0.60 $\pm$ 0.05 |  0.83 $\pm$ 0.06 |  3.69 $\pm$ 0.38 |  1.56 $\pm$ 0.13 |  0.42 $\pm$ 0.03 | Bubble
G327.293$-$00.579 |  0.44 $\pm$ 0.04 |  0.19 $\pm$ 0.01 |  0.44 $\pm$ 0.02 |  2.32 $\pm$ 0.19 |  0.57 $\pm$ 0.04 |  0.25 $\pm$ 0.01 | Bubble
G345.004$-$00.224 |  0.29 $\pm$ 0.02 |  0.32 $\pm$ 0.03 |  1.13 $\pm$ 0.06 |  1.48 $\pm$ 0.13 |  0.92 $\pm$ 0.07 |  0.62 $\pm$ 0.03 | Bubble
G350.101$+$00.083 |  0.87 $\pm$ 0.09 |  1.02 $\pm$ 0.10 |  1.17 $\pm$ 0.12 |  4.48 $\pm$ 0.47 |  2.81 $\pm$ 0.28 |  0.63 $\pm$ 0.07 | Bubble
G351.443$+$00.659 |  0.27 $\pm$ 0.01 |  0.18 $\pm$ 0.01 |  0.67 $\pm$ 0.02 |  1.38 $\pm$ 0.08 |  0.49 $\pm$ 0.02 |  0.35 $\pm$ 0.01 | Bubble
G351.582$-$00.352 |  1.44 $\pm$ 0.16 |  0.71 $\pm$ 0.04 |  0.49 $\pm$ 0.05 |  7.58 $\pm$ 0.79 |  2.25 $\pm$ 0.14 |  0.30 $\pm$ 0.03 | Bubble
G351.775$-$00.537 |  0.18 $\pm$ 0.01 |  0.36 $\pm$ 0.03 |  1.98 $\pm$ 0.08 |  1.01 $\pm$ 0.08 |  1.37 $\pm$ 0.11 |  1.36 $\pm$ 0.05 | Bubble
G329.030$-$00.202 |  0.39 $\pm$ 0.03 |  0.33 $\pm$ 0.03 |  0.84 $\pm$ 0.04 |  2.00 $\pm$ 0.17 |  0.86 $\pm$ 0.07 |  0.43 $\pm$ 0.02 | NMSFR
G331.708$+$00.583 |  0.43 $\pm$ 0.07 |  0.45 $\pm$ 0.07 |  1.04 $\pm$ 0.12 |  2.15 $\pm$ 0.33 |  1.02 $\pm$ 0.15 |  0.48 $\pm$ 0.05 | NMSFR
G331.709$+$00.602 |  1.24 $\pm$ 0.19 |  0.91 $\pm$ 0.10 |  0.73 $\pm$ 0.11 |  6.25 $\pm$ 0.90 |  2.15 $\pm$ 0.24 |  0.34 $\pm$ 0.04 | NMSFR
G335.586$-$00.289 |  0.46 $\pm$ 0.05 |  0.37 $\pm$ 0.03 |  0.79 $\pm$ 0.05 |  2.40 $\pm$ 0.24 |  1.07 $\pm$ 0.10 |  0.45 $\pm$ 0.03 | NMSFR
G348.754$-$00.941 |  1.14 $\pm$ 0.16 |  0.76 $\pm$ 0.08 |  0.67 $\pm$ 0.08 |  5.65 $\pm$ 0.77 |  1.68 $\pm$ 0.18 |  0.30 $\pm$ 0.03 | NMSFR
G351.157$+$00.701 |  0.81 $\pm$ 0.10 |  0.22 $\pm$ 0.02 |  0.27 $\pm$ 0.02 |  4.24 $\pm$ 0.48 |  0.68 $\pm$ 0.06 |  0.16 $\pm$ 0.01 | NMSFR
Table 4: Statistics of integrated intensity and abundance ratios.

All sources
---
Quantity | Mean |  Stda | Median | Min. | Max.
${I_{\rm HNCO}/I_{\rm SiO}}$ | 1.36 | 1.07 | 1.14 | 0.18 | 4.48
${I_{\rm HNCO}/I_{\rm HC_{3}N}}$ | 1.07 | 0.77 | 0.90 | 0.14 | 3.51
${I_{\rm SiO}/I_{\rm HC_{3}N}}$ | 0.92 | 0.46 | 0.78 | 0.27 | 2.40
${N_{\rm HNCO}/N_{\rm SiO}}$ | 6.82 | 5.33 | 5.65 | 1.01 | 21.79
${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ | 2.58 | 1.70 | 2.15 | 0.49 | 7.25
${N_{\rm SiO}/N_{\rm HC_{3}N}}$ | 0.45 | 0.24 | 0.39 | 0.16 | 1.36
CMZ sources
Quantity | Mean |  Stda | Median | Min. | Max.
${I_{\rm HNCO}/I_{\rm SiO}}$ | 1.76 | 1.15 | 1.45 | 0.37 | 4.48
${I_{\rm HNCO}/I_{\rm HC_{3}N}}$ | 1.42 | 0.75 | 1.25 | 0.57 | 3.51
${I_{\rm SiO}/I_{\rm HC_{3}N}}$ | 0.98 | 0.49 | 0.78 | 0.50 | 2.40
${N_{\rm HNCO}/N_{\rm SiO}}$ | 8.79 | 5.71 | 7.38 | 1.86 | 21.79
${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ | 3.33 | 1.69 | 3.05 | 1.14 | 7.25
${N_{\rm SiO}/N_{\rm HC_{3}N}}$ | 0.46 | 0.22 | 0.39 | 0.21 | 1.08
Bubble sources
Quantity | Mean |  Stda | Median | Min. | Max.
${I_{\rm HNCO}/I_{\rm SiO}}$ | 0.64 | 0.43 | 0.59 | 0.18 | 1.44
${I_{\rm HNCO}/I_{\rm HC_{3}N}}$ | 0.47 | 0.29 | 0.42 | 0.14 | 1.02
${I_{\rm SiO}/I_{\rm HC_{3}N}}$ | 0.86 | 0.47 | 0.73 | 0.44 | 1.98
${N_{\rm HNCO}/N_{\rm SiO}}$ | 3.30 | 2.21 | 3.00 | 1.01 | 7.58
${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ | 1.35 | 0.78 | 1.27 | 0.49 | 2.81
${N_{\rm SiO}/N_{\rm HC_{3}N}}$ | 0.50 | 0.33 | 0.40 | 0.23 | 1.36
NMSFR sources
Quantity | Mean |  Stda | Median | Min. | Max.
${I_{\rm HNCO}/I_{\rm SiO}}$ | 0.75 | 0.38 | 0.64 | 0.39 | 1.24
${I_{\rm HNCO}/I_{\rm HC_{3}N}}$ | 0.51 | 0.27 | 0.41 | 0.22 | 0.91
${I_{\rm SiO}/I_{\rm HC_{3}N}}$ | 0.72 | 0.25 | 0.76 | 0.27 | 1.04
${N_{\rm HNCO}/N_{\rm SiO}}$ | 3.78 | 1.87 | 3.32 | 2.00 | 6.25
${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ | 1.24 | 0.56 | 1.05 | 0.68 | 2.15
${N_{\rm SiO}/N_{\rm HC_{3}N}}$ | 0.36 | 0.12 | 0.39 | 0.16 | 0.48

a Standard deviation of the mean.

##  Appendix A Individual targets analysis

Below we give comments on individual sources. Figs. 13–26, Figs. 27–31, and
Figs. 32–34 show the CMZ, Bubble, and NMSFR samples, respectively. It should
be understood that in the following the four cardinal directions, north,
south, east and west, are meant with respect to the Galactic coordinates
($l^{\rm II}$, $b^{\rm II}$), and not with respect to Right Ascension and
Declination.

_G359.977 $-$00.072_ and _G359.895 $-$00.069_. G359.977$-$00.072 is well known
under the name +50 km s-1 cloud. For the spectral line maps of
G359.977$-$00.072 and G359.895$-$00.069 shown in Fig. 13, there are single
cores towards the lower dust temperature region, but these have a slight
offset from the maximum of the dust continuum emission. The SiO spectra in
G359.977$-$00.072 are broader than those of HNCO and HC3N. The abundance ratio
of ${N_{\rm HC_{3}N}/N_{\rm SiO}}$ in these two sources shows a reverse trend
to that of the dust temperature.

_G359.868 $-$00.085_. From the top panel of Fig. 14, it can be seen that there
is no obvious molecular emission core at the centrally located brightest
clump, which is associated with water masers (Sjouwerman et al., 2002). The
SiO and HC3N molecular emissions clearly show two cores on each side of the
central clump. The abundance ratios of ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ and
${N_{\rm HC_{3}N}/N_{\rm SiO}}$ both show a similar trend as the dust
temperature.

_G359.565 $-$00.161_. Molecular line emissions show similar morphologies in
the lower panels of Fig. 14. Weak molecular line emission is found towards the
north-eastern high dust temperature region. All molecular line peaks have an
offset from the maximum of the 870 $\mu$m dust continuum emission. The SiO 2–1
data are noisy. Near the yellow cross position, ${N_{\rm HC_{3}N}/N_{\rm
SiO}}$ reaches maxima, while ${N_{\rm HNCO}/N_{\rm SiO}}$ and ${N_{\rm
HNCO}/N_{\rm HC_{3}N}}$ and the dust temperature are low.

_G359.453 $-$00.112_. As shown in the top panel of Fig. 15, SiO, HNCO and HC3N
exhibit a single core elongated from north-west to south-east in the velocity-
integrated intensity maps, consistent with the cometary shape of the low
temperature dust continuum emission. In the north-western high temperature
corner there is the H ii region G359.4$-$0.1 (i.e. Sgr C) (Kuchar & Clark,
1997). An additional velocity component can be distinguished at the eastern
side of the main component in all spectra. The ${N_{\rm HNCO}/N_{\rm
HC_{3}N}}$ abundance ratio (green lines) is closely related to changes in the
dust temperature.

_G359.445 $-$00.054_. G359.445$-$00.054 is part of the Sgr C Filament (Linden
et al., 2011). We find one isolated core in HNCO and HC3N and two compact
cores in the SiO line map. Moreover, the cores are slightly offset from the
maximum of dust continuum emission as it is shown in the lower panels of Fig.
15. In the case of the SiO 2–1 emission, the structure is complicated,
possibly because of low signal-to-noise ratios. There are two obviously
saturated areas in the Hi-GAL data (visible in gray in the image shown in the
lower left panel of G359.445$-$00.054), where the bubble MWP1G359450$-$000200S
(Simpson et al., 2012) and the H ii region Gal 359.43$-$00.09 (Giveon et al.,
2002) are found to be located on either side of the low temperature
filamentary structure of the dust. In addition, the velocity range appears to
be widest for the HNCO 404–303 spectrum. With respect to temperature
variations, the changes in abundance ratios are similar to source
G001.734$-$00.410. Near the yellow cross position, ${N_{\rm HNCO}/N_{\rm
HC_{3}N}}$ and dust temperature reach minima, while ${N_{\rm HNCO}/N_{\rm
SiO}}$ and ${N_{\rm HC_{3}N}/N_{\rm SiO}}$ are high.

_G000.067 $-$00.077_. As seen in the top panels of Fig. 16, the emissions of
the HNCO 404–303, SiO 2–1 and HC3N 10–9 lines show a similar morphology with a
centrally condensed structure. The emission peaks coincide with the 870 $\mu$m
continuum emission. At this position, the dust temperature is relatively low.
In addition, there are two higher dust temperature regions, in the north-east
and south-west of the 870 $\mu$m emission peak. The HC3N spectra have a simple
Gaussian shape. However, the HNCO and SiO lines towards the yellow cross
position show non-Gaussian wing emission, indicative of outflows/shocks. HNCO
and SiO are each fitted with two Gaussians. ${N_{\rm HNCO}/N_{\rm SiO}}$ and
${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ show a decreasing trend towards the central
lower dust temperature region.

_G000.104 $-$00.080_. The integrated intensity maps of the HNCO 404–303, SiO
2–1 and HC3N 10–9 lines show a similar morphology, and coincide well with the
ATLASGAL 870 $\mu$m emission where the dust temperature is relatively low. As
in G000.067-00.077, two higher dust temperature regions are located in the
north-east and south-west of the source. The HNCO, SiO and HC3N lines all show
an asymmetry and possess wing emission. The ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$
and dust temperature curves are similar towards the central region along
Galactic longitude direction shown in the last panel of Fig. 16.

_G000.106 $-$00.001_. All of the molecular line emissions have an offset of
$\sim$30′′ from the peak of the ATLASGAL 870 $\mu$m continuum emission and
show a large gradient towards the north-western higher dust temperature
region, which might be caused by external pressure from the arched filament H
ii complex (Lang et al., 2001). The SiO integrated intensity (white contours
in the lower left panel of the upper half of Fig. 17) and cold dust
temperature structures have a similar morphology. HNCO and HC3N show a line
wing on the redshifted side, and are each fitted with two Gaussians. In the
central part of G000.106$-$00.001, ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ and dust
temperature curves are similar.

_G000.110 $+$00.148_. From the lower panels of Fig. 17, HC3N and HNCO emission
peaks towards the lower dust temperature region, but is offset to the north-
east of the maximum of the 870 $\mu$m dust continuum emission ($\sim$36′′).
The structure is complex in the case of SiO 2–1, perhaps because of low
signal-to-noise ratios. A high dust temperature region appears in the lower
left corner. The HNCO 404–303 line shows a single Gaussian shape, while SiO
2–1 also shows wing emission.

_G000.314 $-$00.100_. The upper panels of Fig. 18 demonstrate that the HNCO
404–303 morphology shows a centrally condensed structure, with the emission
peak coinciding with the 870 $\mu$m emission, which shows low dust
temperatures. The SiO 2–1 and HC3N 10–9 emissions also have a centrally
condensed structure and show similar distributions, but the emission peaks are
offset ($\sim$20′′) from those of the HNCO 404–303 and 870 $\mu$m emission.
The spectral profiles have low signal-to-noise ratios in the HNCO 404–303 and
SiO 2-1 lines. HNCO, SiO and HC3N are each fitted with two Gaussians.
Abundance ratios of ${N_{\rm HC_{3}N}/N_{\rm SiO}}$ show an increasing trend
with respect to ${N_{\rm HNCO}/N_{\rm SiO}}$ and ${N_{\rm HNCO}/N_{\rm
HC_{3}N}}$ towards the central low dust temperature region.

_G000.497 $+$00.021_ and _G000.645 $+$00.027_. From the lower panels of Fig.
18 and the upper panels of Fig. 19, the SiO emission shows a complex
morphology in the observed area, while the other two molecular emission lines
reveal compact cores in the integrated intensity map. In addition, extended
SiO emission is seen particularly around the central core of HNCO emission in
source G000.497$+$00.021. As in G000.314$-$00.100, the dust emission regions
are cold, and the abundance ratio of ${N_{\rm HC_{3}N}/N_{\rm SiO}}$ shows an
increasing trend towards the central region.

_G000.892 $+$00.143_. The lower panels of Fig. 19 show a pronounced core
elongated from the south-east to the north-west in the three studied molecular
lines. Compared to the south-eastern 870 $\mu$m emission peak, the north-
western one shows a higher temperature and coincides with the local HNCO
404–303, SiO 2–1 and HC3N 10–9 peak positions. The SiO and HC3N spectra
exhibit asymmetric profiles. Abundance ratios of ${N_{\rm HNCO}/N_{\rm SiO}}$
and ${N_{\rm HNCO}/N_{\rm HC_{3}N}}$ decrease along the Galactic longitude
direction towards the central hot dust core, while ${N_{\rm HC_{3}N}/N_{\rm
SiO}}$ does the opposite.

_G000.908 $+$00.116_. Towards G000.908$+$00.116, shown in the upper panels of
Fig. 20, HNCO 404–303 shows a dense clump in the central map, with emission
peaking at a $\sim$29′′ offset from the maximum of the dust continuum
emission. However, the integrated intensity map of SiO 2–1 shows a more
complex structure. HC3N exhibits a simple morphology with a ridge elongated
from the south-east to the north-west. The abundance ratios of ${N_{\rm