#  A comparative study of ultraluminous infrared galaxies in the IRAS and SDSS
Surveys

Shaohua Zhang (张少华) Shanghai Key Lab for Astrophysics, Shanghai Normal
University, Shanghai 200234, People’s Republic of China  Zhijian Luo (罗智坚)
Shanghai Key Lab for Astrophysics, Shanghai Normal University, Shanghai
200234, People’s Republic of China  Xiheng Shi (史习珩) MNR Key Laboratory for
Polar Science, Polar Research Institute of China, Shanghai 200136, People’s
Republic of China  Chenggang Shu (束成钢)  Shanghai Key Lab for Astrophysics,
Shanghai Normal University, Shanghai 200234, People’s Republic of China
Hubing Xiao (肖胡兵) Shanghai Key Lab for Astrophysics, Shanghai Normal
University, Shanghai 200234, People’s Republic of China  Hongyan Zhou (周宏岩)
MNR Key Laboratory for Polar Science, Polar Research Institute of China,
Shanghai 200136, People’s Republic of China  CAS Key Laboratory for Research
in Galaxies and Cosmology, Department of Astronomy, University of Sciences and
Technology of China, Hefei, Anhui 230026, People’s Republic of China

###### Abstract

We present a comprehensive study of Ultraluminous Infrared Galaxies (ULIRGs),
leveraging data from the IRAS Faint Source Catalogue (FSC) and the
spectroscopic catalog in the Sloan Digital Sky Survey (SDSS) DR16. Our
meticulous cross-matching technique significantly enhances the reliability of
ULIRG identification, resulting in the identification of 283 reliable ULIRGs,
including 102 new detections, while discarding 120 previously reported false
sources. Covering a redshift range of $z=0.018-0.996$, with a median redshift
of $\bar{z}=0.259$, our uniform sample reveals apparent interaction features
in approximately 40% of ULIRGs, increasing to 92% for those with $z<0.1$.
Through optical spectra analysis, it is indicated that over 58% of ULIRGs host
an AGN, which is twice as high as the detections based solely on infrared
colors. Moreover, a pronounced excess of radio emissions associated with AGN
activity results in a steeper radio-far-infrared correlation. Notably, Type I
ULIRGs exhibit properties similar to those of narrow-line Seyfert 1 galaxies
(NLS1s), with an elevated incidence rate of Mg II BALs (16.7%), surpassing
that of typical optically selected quasars by over tenfold, consistent with
current evolutionary models. We anticipate that forthcoming telescopes such as
the China Space Station Telescope (CSST) and Leighton Chajnantor Telescope
(LCT) will provide deeper insights into ULIRG morphology, dust distribution,
molecular gas, and AGN activity.

Starburst galaxies (1570), Galaxy formation (595), Infrared galaxies (790),
Active galaxies (17)

##  1 Introduction

Ultraluminous infrared galaxies (ULIRGs) stand out as remarkable celestial
objects, characterized by their intense infrared luminosity in the 8 $\mu$m –
1000 $\mu$m wavelength band, classically exceeding $\rm 10^{12}~{}L_{\sun}$,
comparable to the bolometric luminosity of quasars (see Sanders & Mirabel 1996
for an in-depth review). As one of the significant outcomes of the Infrared
Astronomical Satellite (IRAS) mission (Neugebauer et al. 1984), ULIRGs were
discovered in large numbers, and appeared as bright, pointlike sources at 60
$\mu$m, lacking visible counterparts (Houck et al. 1984; Soifer et al. 1984).

Efforts to unveil the mysteries surrounding ULIRGs have surged, exploring
their origin, infrared power source, and evolutionary path (Lonsdale et al.
2006; Perez-Torres et al. 2021). Prevailing consensus attributes ULIRG
formation to intense galactic collisions and mergers, as demonstrated by the
study of Soifer et al. (1984), which meticulously examined 86 infrared
galaxies, revealing a substantial fraction as interacting spiral galaxies.
Additionally, New Technology Telescope (NTT) images of all 16 southern ULIRGs
reveal strongly interacting systems showing double nuclei, wisps, and tails
that are characteristic of advanced mergers (Melnick & Mirabel 1990).

Observations further reveal post-merger ULIRGs with active galactic nuclei
(AGN) manifestations in the later stages of merging (Clements et al. 1996;
Murphy et al. 1996; Zheng et al. 1999; Canalizo & Stockton 2001; Cui et al.
2001; Bushouse et al. 2002; Veilleux et al. 2002). The enormous infrared
radiation emitted by ULIRGs results from the re-emission of dust, heated by
intense star formation and AGN activity triggered and fueled by these merger
events (Leech et al. 1988; Sanders et al. 1988a; Veilleux et al. 1995; Genzel
et al. 1998; Farrah et al. 2003). In this dynamic astronomical panorama,
ULIRGs have been observed in association with submillimeter galaxies (SMGs;
Hughes et al. 1998; Barger et al. 1998; Efstathiou & Rowan-Robinson 2003;
Rowan-Robinson et al. 2018), quasars and hot dust-obscured galaxies (Hot DOGs;
Eisenhardt et al. 2012; Bridge et al. 2013; Casey et al. 2014; Farrah et al.
2017; Efstathiou et al. 2021). ULIRGs play a pivotal role in the evolution
path from galaxy mergers to elliptical galaxies and quasars, offering
essential insights into the evolutionary connection between circumnuclear
massive starbursts and AGNs.

Nevertheless, the complexity of the astronomical landscape is apparent.
According to Jones et al. (2014), the investigation revealed that
submillimeter-detected WISE-selected Hot DOGs qualify as hyperluminous
infrared galaxies (HyLIRGs; $L\rm_{IR}>10^{13}~{}L_{\sun}$), harboring very
powerful AGN. Chen & Liu (2024) observed that the majority of DOGs are
characterized by AGN dominance in the mid-IR, far-IR, and submillimeter
wavelengths, whereas ULIRGs are marked by a prevalence of star formation in
the far-IR. Efstathiou et al. (2022) contributed to this narrative by
discovering that all HERUS ULIRGs exhibit high rates of star formation, with
bolometrically significant AGNs present in every galaxy of the sample, and
dual AGNs identified in two sources. Importantly, there is no evidence that
strong AGN appears either at the beginning or end of a starburst episode or
that starbursts and AGN affect each other.

Despite the significant progress in understanding ULIRGs, previous
investigations identified specific issues related to the use of IRAS data.
These issues mainly stem from the positional uncertainty of IRAS sources,
leading to notable overestimation in the infrared luminosity of numerous
sources, consequently misclassifying them as ULIRGs. This discrepancy arises
from the presence of multiple optical and near-infrared counterparts within
the positional uncertainty ellipse, contributing to challenges in precisely
determining the true characteristics of these objects. This study aims to
overcome these challenges by generating a comprehensive and reliable ULIRG
sample, leveraging optical images, multi-band colors, and AGN activity
analysis based on photometric and spectroscopic data. Section 2 provides an
overview of the data and the ULIRG identification method, followed by the
presentation and discussion of results in Section 3, and concluding remarks in
Section 4. Adopting standard cosmological parameters
($H\rm_{0}=70kms^{-1}~{}Mpc^{-1}$, $\Omega\rm_{m}=0.3$, and
$\Omega\rm_{\Lambda}=0.7$), this work seeks to contribute to a deeper
understanding of ULIRGs and their pivotal role in the cosmic tapestry.

##  2 Identification of ULIRGs

###  2.1 Samples and cross-matching

This work starts from the IRAS Faint Source Catalog (FSC92, $|b|>10^{\circ}$,
Version 2.0, Moshir et al. 1992) and the Sloan Digital Sky Survey (SDSS) Data
Release 16 (DR16; Ahumada et al. 2020). The IRAS survey, a remarkable feat in
thermal infrared sky coverage, provided comprehensive data through multiple
detectors. The cornerstone of IRAS, the FSC92 catalog, comprises information
on 173,044 sources in unconfused regions, featuring flux densities typically
exceeding 0.2 Jy at 12, 25, and 60 $\mu$m, and above 1.0 Jy at 100 $\mu$m. The
catalog ensures reliabilities of at least 98.5% at 12 and 25 $\mu$m and
approximately 94% at 60 $\mu$m. Notably, the FSC92 achieves a limiting
magnitude approximately one magnitude deeper than the IRAS Point Source
Catalog (PSC, Version 2.0, IPAC 1986), positioning it more favorably for
distant sources like galaxies and quasars. However, FSC92 sources present
substantial positional uncertainties, ranging from $1-13$ arcsec in the in-
scan direction (typical value of 5 arcsecs) to $3-55$ arcsec in the cross-scan
direction (typical value of 16 arcsecs), described as “error ellipses.”

The SDSS DR16 release is distinguished as the latest and final data release of
optical spectra from the SDSS extended Baryon Oscillation Spectroscopic Survey
(eBOSS; Dawson et al. 2016). Despite being the fourth data release of SDSS-IV,
SDSS DR16 incorporates spectroscopically-confirmed sources from SDSS-I/II/III.
Covering 5,789,200 optical spectra of stars, galaxies, and quasars, SDSS DR16
is a substantial resource. Post filtering out spectra marked as
“STAR”111https://www.sdss.org/dr16/spectro/catalogs/. in the “CLASS”
parameter, over 4.5 million spectra with effective redshift measurements
remain. After cross-referencing astrometric positions, 386,462 sources with
repeated spectral observations are identified within the catalog, totaling
4,044,951 sources across 9,376 deg2. The catalog serves as an extensive
repository of galaxies and quasars within SDSS. While the catalog may still
contain sources classified as
“Unknown”222https://www.sdss.org/dr16/scope/#Opticalspectroscopydatastatistics;
however, it is unnecessary to worry about those distracters, which will be
gradually eliminated in the following analysis.

Previous studies have favored the positional uncertainty ellipse of each IRAS
source to identify their SDSS counterparts (e.g., Cao et al. 2006; Hwang et
al. 2007; Hou et al. 2009), considering an SDSS source within the $3\sigma$
error ellipse of an IRAS source as a match. This method is used in this work.
Since the positional uncertainty of the SDSS is much smaller than that of
IRAS, the positional uncertainty of the optical identification itself is
negligible. The cross-matching reveals 17,428 IRAS sources with SDSS
counterparts in DR16, including 3,996 with more than one counterpart within
the 3$\sigma$ error ellipse. Notably, we abandon the conventional ”likelihood
ratio (LR)” method for confirming the most probable counterpart (e.g.,
Sutherland & Saunders 1992; Cao et al. 2006; Hwang et al. 2007 and Hou et al.
2009), and instead opt for a robust approach—cross-matching with the Wide-
field Infrared Survey Explorer (WISE; Wright et al. 2010) photometry database.
This ensures reliable identification of counterparts and mitigates
uncertainties associated with flux intensity and source brightness in the
infrared waveband.

###  2.2 Luminosity selection criteria

Figure 1: Distribution of the primary ULIRG candidates in Equatorial
coordinates (map centered at $\rm RA=8h$).

To reduce the workload, we initially rejected the majority of IRAS sources
using ULIRG luminosity selection criteria. As the 12 and 25 $\mu$m flux
qualities for the matched IRAS sources are primarily upper limits, our
subsequent analysis focuses on sources with reliable 60 $\mu$m detections.
From the total list of 17,428 matched IRAS sources, we narrowed down our
selection to 17,235 sources with “high” or “moderate” quality index for their
60 $\mu$m flux densities, following the FSC92 catalog conventions (where upper
limits, moderate quality, and high quality are marked as numbers 1, 2, and 3,
respectively). Following methods similar to Cao et al. (2006) and Hou et al.
(2009), we calculate the far-infrared (FIR) luminosity ($L_{\rm FIR}$) using
the 60 and 100 $\mu$m flux densities (Helou et al. 1988; Sanders & Mirabel
1996), which is then converted to the total infrared luminosity ($L_{\rm IR}$;
Calzetti et al. 2000).

The formulae are as follows:

$F_{\rm FIR}=1.26\times 10^{-14}~{}\left[2.58~{}f_{60~{}\mu m}+f_{100~{}\mu
m}\right]~{}\rm(W~{}m^{-2}),$ (1) $L_{\rm FIR}=4~{}\pi~{}D_{\rm
L}^{2}~{}F_{\rm FIR}~{}\rm(L_{\sun}),$ (2) $L_{\rm IR}{\rm(1-1000~{}\mu
m)}=1.75~{}L_{\rm FIR},$ (3)

where $f_{\rm 60~{}\mu m}$, $f_{\rm 100~{}\mu m}$ are the IRAS flux densities
in Jy at 60 and 100 $\mu$m, $D_{\rm L}$ is the luminosity distance based on
the counterpart’s redshift, and the luminosities are in $\rm L_{\sun}$.
Notably, approximately 41% of the sources have upper limits for their 100
$\mu$m flux qualities. Given that the 100 $\mu$m flux has a minimal impact on
$L_{\rm IR}$ calculations, as pointed out by Cao et al. (2006) and
corroborated by Kim & Sanders (1998) and Hwang et al. (2007), we do not impose
quality limits on the 100 $\mu$m flux density.

From the pool of 17,235 reliable sources, we identify the primary sample,
comprising 2,715 ULIRG candidates with infrared luminosities exceeding
$10^{12}~{}\rm L_{\sun}$. Of these, 254 still have multiple optical
counterparts. At this stage, we refrain from designating the “true” IRAS-SDSS
association, retaining all associations for further analysis.

Figure 1 displays the sky coverage of these ULIRG candidates in equatorial
coordinates, illustrating comprehensive coverage across nearly the entire SDSS
DR16 spectroscopic survey regions. A comparison with the ULIRG candidate
sample from Hou et al. (2009), who identified 308 ULIRGs from the SDSS DR6
catalog, reveals a recovery of 306 out of their 308 ULIRGs. Two sources in
their sample, F10212+2506 and F14336-0147, are excluded from our study due to
their lower infrared luminosities, identified as $\rm 10^{11.53}~{}L_{\sun}$
and $\rm 10^{11.09}~{}L_{\sun}$, respectively. Further examining the optical
spectra of their counterparts, we find that the redshift of F10212+2506 was
overestimated by Hou et al. (2009), while that of F14336-0147 is
underestimated in the DR16 catalog. This primary sample serves as the basis
for our Catalog, providing a foundation for detailed identification and
subsequent in-depth analysis.

Figure 2: The infrared luminosity of the primary ULIRG candidates versus
redshift. The primary candidates’ redshift and infrared luminosity
distributions are shown in the upper and right-hand panels. As the SDSS-III/IV
depth increases, many SDSS sources at high redshift are matched, and the
estimated infrared luminosity also tends to be higher.

In Figure 2, we illustrate the infrared luminosities of the 2715 primary ULIRG
candidates identified in this study plotted against their redshifts. The upper
and right-hand panels display their redshift and luminosity distributions,
respectively. The redshift range of the primary candidates spans from $z\sim
0.02$ to $4.0$ with a median value of approximately $0.56$. This range is
notably broader and extends further than the redshift range of $0.02-0.6$ with
a median redshift $z\simeq 0.2$ observed in previously known ULIRGs (e.g., Cao
et al. 2006; Hwang et al. 2007; Hou et al. 2009). This difference could be
attributed to distinct selection criteria for spectroscopic targets. The SDSS-
III/IV has probed up to two magnitudes deeper than SDSS-I/II and other bright
galaxy surveys employed in previous studies. Consequently, the parent sample
of our primary ULIRG candidates, namely the DR16 spectroscopic catalog,
encompasses a substantial number of fainter and more distant (higher redshift)
sources. Moreover, thus, the primary ULIRG candidates in this study exhibit
significantly larger infrared luminosities compared to those of previously
known ULIRGs. Their median infrared luminosity is approximately
$L\rm_{IR}\simeq 10^{13}~{}L_{\sun}$, nearly approaching the maximum value
observed in previously known ULIRGs.

###  2.3 Examining candidates through WISE detections

Figure 3: The number distribution of the WISE counterparts for each primary
ULIRG candidate, these primary candidates have 8 WISE counterparts within
3$\sigma$ error ellipse on average.

To verify the reliability of the IRAS-SDSS associations, we conducted an
additional examination by scrutinizing WISE detections within the positional
uncertainty ellipse of each IRAS source. In comparison to IRAS, WISE
extensively mapped the entire sky at 3.4, 4.6, 12, and 22 $\mu$m, denoted as
$W1$, $W2$, $W3$, and $W4$, with higher angular resolutions of 6.1, 6.4, 6.5,
and 12.0 arcsec in the four bands, and higher photometric sensitivities of
0.068, 0.098, 0.86, and 5.4 mJy ($5\sigma$) for the four bands, respectively.

The comprehensive AllWISE source
catalog333http://wise2.ipac.caltech.edu/docs/release/allwise/ encompasses
attributes for over 747 million point-like and resolved objects detected on
coadded Atlas Images (Cutri et al. 2013). Through the IRAS-WISE cross-matching
process, we successfully identified 24,341 WISE counterparts in the AllWISE
source catalog for the 2715 primary ULIRG candidates within the $3\sigma$
error ellipse. Figure 3 illustrates the distribution of the number of WISE
counterparts for each primary ULIRG candidate. On average, the primary ULIRG
candidates exhibit 8 WISE counterparts, with a maximum of 24 WISE
counterparts. The far-infrared fluxes detected by IRAS are attributed to the
contributions of all WISE counterparts within the 3$\sigma$ error ellipse.

Figure 4: The distribution of the angular separation between the brightest
WISE sources at $W4$ band and the SDSS counterpart for each primary ULIRG
candidate. The size of each bin of the histogram is 2 arcsec.

We systematically organized the WISE counterparts for each ULIRG candidate
based on their magnitudes in the $W4$ band, selecting the most luminous
sources in the mid-infrared. The WISE $W4$ band centers at a wavelength of 22
$\mu$m, which is close to the IRAS 60 $\mu$m band. Our working assumption is
that the brightest WISE source in the W4 band is likely the WISE counterpart
of the IRAS source. We computed the distances between the brightest WISE
source and the SDSS counterpart for each ULIRG candidate, illustrating the
angular separation distribution in Figure 4. The distribution reveals two
distinct bimodal patterns—a narrow, sharp peak at zero offsets and an
exceptionally broad peak spanning from 6 to 170 arcsec.

For a valid WISE-SDSS association, the maximum angular separation is set to
2.0 arcsec, a commonly adopted criterion in SDSS quasar catalogs (e.g., Pâris
et al. 2014, 2017, 2018). This choice helps minimize false-positive matches,
maintaining the rate at a low level of approximately $1\%$ (Krawczyk et al.
2013; Pâris et al. 2018). This approach effectively addresses the issue of one
IRAS source having multiple SDSS counterparts, except the source F08449+2332.

In the case of F08449+2332, we examined its $gri$ composite image using the
SDSS DR16 Image List Tool (Figure 5). F08449+2332 exhibits two closely
situated SDSS counterparts, namely, SDSS J084750.17+232108.6 and SDSS
J084750.26+232110.9, with an angular separation of only 2.5 arcsecs
(approximately half to one-third of the angular resolutions of WISE), thus,
they cannot be resolved by WISE. In conclusion, our WISE-SDSS association
resulted in 432 matches, classifying the corresponding 431 IRAS sources as
reliable ULIRG candidates.

Figure 5: The $1\times 1$ arcmin2 finding chart of F08449+2332 extracted from
the SDSS $gri$ composite image. The IRAS object names are presented in the
bottom left-hand corner. The finding chart centered on the IRAS source
position. The North is up, and the east is to the left-hand side. The ellipses
represent 1, 2, and 3$\sigma$ positional uncertainty, and the red cross
denotes the WISE counterpart. Two SDSS counterparts (SDSS J084750.17+232108.6
and SDSS J084750.26+232110.9) in the SDSS are marked by the squares, which
positional separation is only 2.5 arcsec, less than the angular resolutions of
WISE.

Figure 6: Distributions of redshift (top panel), infrared luminosity (middle
panel), and flux ratio (bottom panel) of the reliable ULIRG candidates. The
shadow regions are the distributions of the final ULIRGs with a flux ratio
larger than 50%.

Mirroring the presentation of primary ULIRG candidates, we depict the redshift
and infrared luminosity distributions of reliable ULIRG candidates in Figure
6. Notably, a substantial number of IRAS sources with high-redshift SDSS
counterparts have been excluded, resulting in the predominance of credible
ULIRG candidates with redshifts below 1.0. Furthermore, their infrared
luminosities generally fall below $\rm 10^{13}~{}L_{\sun}$.

To quantitatively evaluate the contribution of SDSS counterparts in infrared,
we computed the total flux from all matched WISE sources within the $3\sigma$
uncertainty ellipse. We derived the flux ratio (at the WISE $W4$ band) of the
brightest source to all sources, presenting the flux ratio distribution of the
431 reliable ULIRG candidates in the bottom panel of Figure 6. Of these, 285
sources with a flux ratio exceeding 50%, indicative of dominance in IRAS
emission, were preliminarily selected to constitute our ULIRG sample.
Subsequently, a meticulous examination of the spectroscopic commissioning data
of the SDSS counterpart for all sources was conducted to verify their
redshifts. Notably, the redshifts of three high-redshift sources (F08409+4153,
F08519+2017, and F15346+1409) were significantly overestimated in the SDSS
DR16 release. Correct redshift values derived from their optical spectra are
0.0071, 0.3060, and 0.0002, respectively. Consequently, sources F08409+4153
and F15346+1409 were deemed invalid, and redshift and infrared luminosity
values for F08519+2017 underwent subsequent revisions. Our refined ULIRG
sample comprises 283 sources, with their redshift, infrared luminosity, and
flux ratio distributions displayed in the shaded regions of the panels in
Figure 6.

Table 1 provides a comprehensive list of our ULIRGs, encompassing details such
as the names of IRAS sources, identifications of their optical counterparts,
redshifts, IRAS flux densities and qualities, and infrared luminosities. To
facilitate visual understanding, Figure 7 displays $2.5\times 2.5$ arcmin2
finding charts for all sources within our ULIRG sample. These charts are
extracted from the SDSS $gri$ composite images, with each image centered on
the position of the corresponding IRAS source. The SDSS counterpart is denoted
by a black square, and the red crosses represent WISE sources found within the
$3\sigma$ error ellipse.

Figure 7: Finding charts of the 285 ULIRGs. The $2.5\times 2.5$ arcmin2
finding charts extracted from the SDSS $gri$ composite images centered on IRAS
sources’ positions. Same as Figure 5, the north is up, and the east is to the
left-hand side, and the ellipses represent 1, 2, and 3$\sigma$ positional
uncertainty. The square and red crosses represent the SDSS counterpart and the
$WISE$ sources within the $3\sigma$ error ellipse. For F111388+0108, the scale
of the image is $\rm 5\times 5~{}arcmin^{2}$. Figure 7: Continued.  Figure 7:
Continued.  Figure 7: Continued.  Figure 7: Continued.  Figure 7: Continued.
Figure 7: Continued.

The criteria for ULIRG selection are stringent, potentially leading to the
inadvertent exclusion of certain “true” ULIRGs. Typically, ULIRGs are
categorized as either “cool” or “warm” systems, based on the dominant power
source of mid-/far-infrared radiation, such as starburst and AGN activity
(Sanders et al. 1988b; Veilleux et al. 2002). In the context of pure type I
AGN, the flux difference between the $W4$ and 60 $\mu$m bands shows only a
marginal variation, constituting approximately $20-30\%$ of the total flux.
Conversely, in star-forming templates, this factor could increase by a factor
of $2\sim 6$ at 60 $\mu$m compared to the $W4$ band (Polletta et al. 2007). It
is crucial to recognize that an elevation in this factor also results in a
proportional increase in the overall brightness of the system. This
observation implies that AGNs are more likely to be identified as ULIRGs due
to their greater luminosity in the mid-infrared waveband compared to star-
forming galaxies.

To explore potential selection bias, we opted for the second brightest source
at the $W4$ band for each primary ULIRG candidate. In Figure 8’s top panel, we
depict the separation distribution between the second brightest WISE sources
at the $W4$ band and the SDSS counterpart for each primary ULIRG candidate.
This distribution closely resembles that of the brightest WISE sources, with
366 effective matches within 2.0 arcsec. We computed the flux ratio of the
effective WISE source at the $W4$ band to all WISE sources within a 3$\sigma$
uncertainty ellipse for these 366 effective matches. The distribution of this
flux ratio is presented in the bottom panel of Figure 8. It is worth noting
that, despite being the second brightest source within the corresponding
uncertainty ellipse, their fluxes remain relatively faint. The distribution of
flux ratios peaks at approximately 10%, with the majority of sources
displaying ratios below 20%. Only four sources exceed 30%. This analysis
suggests that the aforementioned concerns regarding selection bias may not be
well-founded.

We have carried out detailed quantitative analyses to assess the impact of
positional uncertainties on our method. To simulate potential inaccuracies, we
artificially shifted the positions of the IRAS sources by 5 degrees in
arbitrary directions, then executed cross-matching using the method we
previously described. This exercise reveals 3,640 IRAS sources have
corresponding SDSS counterparts. Notably, 314 of these sources are associated
with multiple counterparts within the $3\sigma$ error ellipses. Furthermore,
we experimented with shifting the positions by various distances, yet the
counts of IRAS-SDSS matches remained basically consistent. The substantial
number of matches for the artificially shifted IRAS positions can be mainly
ascribed to the average number density of extragalactic sources within the
SDSS and the large positional uncertainties inherent in the IRAS. Upon
refining the selection to IRAS sources with “high” or “moderate” quality for
their 60 $\mu m$ flux densities, the count was reduced to 2,923. Applying an
infrared luminosity threshold, we selected 2,234 “primary ULIRG candidates”
with infrared luminosities of $L\rm_{IR}\geq 10^{12}~{}\rm L_{\sun}$. These
“primary ULIRG candidates” show higher redshifts than the genuine ones,with a
range from $z=0.05$ to $6.87$, and a median redshift of $z=0.67$. The corss-
matching with the WISE data has exposed that approximately a quarter of the
SDSS counterparts are missing corresponding entries in the AllWISE catalog.
After imposing the flux ratio threshold at W4, we have further refined the
IRAS-SDSS-WISE matches to 32, which could be considered potential error
introduced by our method, mainly due to the uncertainties in the IRAS-SDSS
matching process. Similarly, considering the $1\%$ false matching rate in the
SDSS-WISE data, we estimate that there would be approximately 27 suprious
matchs in our primary sample of 2,715 ULIRG candidates. Assuming that the same
proportion of these false matches would pass the W4 flux ratio threshold, we
anticipate that roughly 18 of these matches would incorrectly be classified as
valid.

Figure 8: Top panel: Distribution of the angular separation between the second
bright WISE sources at the $W4$ band and the SDSS counterpart for each primary
ULIRG candidate. The size of each bin of the histogram is 2 arcsec. Bottom
panel: Flux ratio distribution of the second bright WISE sources within 2
arcsec of the SDSS counterparts.

##  3 Results and Discussion

###  3.1 Interaction Features in Optical Images

Figure 9: The $30\times 30$ arcsec2 optical images of ULIRGs with obvious
interacting features, which are centered on their SDSS counterparts’
positions. For 5 cases of them (F09320+6134, F10565+2448, F13428+5608,
F14394+5332, and F15327+2340), the scales of the images are $1\times 1$
arcmin2.  Figure 9: Continued.  Figure 9: Continued.

Previous works have revealed that ULIRGs have a wide morphological
distribution, and their structures generally vary from ellipsoid to multiple
nuclei. Some of them exhibit the appearance of a merger of two nuclei or the
gas bridges and the tidal asymmetries structures in the optical and near-
infrared images, and this indicates that there has been an interaction and
merger process in the history of ULIRGs (e.g., Sanders et al. 1988a; Farrah et
al. 2001; Veilleux et al. 2002; Xia et al. 2012). In this study, we employed
the SDSS DR16 Image List
Tool444https://skyserver.sdss.org/dr16/en/tools/chart/list.aspx to examine
ULIRG images. Only 114 cases show apparent interaction features in their SDSS
images, and the fraction is slightly lower than previous similar findings
(e.g., Hou et al. 2009). Due to the limited resolution of the SDSS image, we
can only mark the ULIRGs with a noticeable interaction feature.

The relative fractions of interacting and merging systems varied across
different subsamples of ULIRGs, ranging from as low as $10\%-20\%$ in some
cases to as high as $80\%$ or more in others (e.g., Sanders et al. 1988a;
Melnick & Mirabel 1990; Zou et al. 1991; Leech et al. 1994; Clements et al.
1996; Murphy et al. 1996; Bushouse et al. 2002; Perna et al. 2021). Perna et
al. (2021) observed 25 nearby ($z<0.165$) ULIRGs using the integral field
spectrograph MUSE, revealing systems with both AGN and Starburst (SB) nuclear
activity in pre- and post-coalescence phases of major mergers. Five of their
ULIRGs are included in our sample, with MUSE images providing detailed
insights. For instance, F01572+0009 exhibits ordered disk-like rotations and a
merger classification with a single nucleus and small nearby companions.
F10190+1322 displays two overlapping disks centered at the positions of the
two nuclei, separated by $\sim 7$ kpc. F12112+0305 is identified as an
interacting system, while F13451+1232 presents tidal tails and two nuclei
separated by $\sim 4.18$ kpc. F15327+2340 shows a disturbing kpc-scale disk in
the innermost nuclear regions and two nuclei separated by $\sim 0.37$ kpc.

Figure 9 provides $30\times 30$ arcsec2 finding charts extracted from SDSS
$gri$ composite images. Interaction types of ULIRGs were classified the
interaction types of ULIRGs using zoom-in images, revealing that nearly half
of ULIRGs show one nucleus with tail features, approximately 35% have two
identified nuclei with well-developed tidal tails or bridges, and the
remaining 18% have two close or even overlapped nuclei. It is unclear whether
the latter are galaxy pairs. In almost all cases, only one source in the
system has effective redshift measurements. ULIRGs exhibit clearer interaction
features, with a percentage of about 92% for $z<0.1$, 66% for $0.1\leq z<0.2$,
32% for $0.2\leq z<0.3$, 18% for $0.3\leq z<0.4$, and 11% for $z\geq 0.4$. The
fraction decreases with increasing redshift, suggesting a selection effect in
classifying interactive features. Notably, the ULIRGs identified in this study
generally have higher redshifts than previous findings, resulting in a lower
percentage of sources with interactive features.

Due to the limit of the spatial resolution and survey depth of most ground-
based imaging surveys, most previous studies on galaxy mergers are often
limited to the early stages of galactic gravitational convergence. In
contrast, signs such as large-scale asymmetric structures or tidal tails and
stellar streams produced by galaxy mergers tend to dissipate in the late
stages. However, high-resolution images ($\sim 0.1^{\prime\prime}$) have
revealed dual-core structures at the kpc scale in the galaxy’s central region
(e.g., Bushouse et al. 2002; Koss et al. 2018). This dual-core design is
likely linked to the two phases of galaxy mergers and black hole mergers. By
comparing the ratio of AGN, galaxy morphology, and stellar population of dual-
core galaxies, galaxy pairs, and isolated galaxies, a comprehensive
understanding of galaxy merging into black hole pre-merging can be
established. This approach may reveal a series of frontier problems, including
the formation of nuclear spheres and the mechanism of black hole triggering.
High-resolution imaging observations are imperative for clarifying these
issues.

The upcoming China Space Station Telescope (CSST), a 2-meter space telescope
boasting a large field of view ( $\rm\sim 1.1~{}deg^{2}$) and sharing the same
orbit as the Chinese Space Station, is poised for launch. The CSST Optical
Survey (CSS-OS; Zhan 2011, 2018, 2021; Cao et al. 2018; Gong et al. 2019) will
undertake a comprehensive multi-band survey with high spatial resolution
(approximately $0.15^{\prime\prime}$ for the survey camera). This survey
encompasses the NUV, $u$, $g$, $r$, $i$, $z$, and $y$ bands, spanning the
wavelength range of $255-1000$ nm, from the NUV to NIR. Over the next
approximately ten years, the CSS-OS is projected to cover an extensive sky
area of $\rm 17,500~{}deg^{2}$ with deep limiting magnitudes, reaching around
$26$ AB mag or higher in the $g$ and $r$ bands for $5\sigma$ point source
detection. The high-resolution, high-quality, and deep images captured by the
CSST are expected to provide a more detailed understanding of the morphology
and interactions of ULIRGs. The investigation of the interacting and merger
processes of supermassive binary black holes and galaxies stands out as one of
the pivotal scientific focuses for the CSST.

###  3.2 Infrared Colours

Figure 10: The infrared luminosity and color diagrams for the ULIRGs. The open
circles represent the sources with flux upper limits and high/moderate flux
qualities with the open-circle-arrows and the filled circles, respectively.
Top-left panel: The dotted line represents the boundary between galaxies and
stars (Kim & Sanders 1998). Top-right panel: For the sources with flux upper
limits, we use the WISE $W4$ magnitudes (centered at 22 $\mu$m) to replace the
upper limits at 25 $\mu$m; the green filled circles represent the colors of
$W4/f60$. The dotted lines represent the boundaries between normal galaxies,
Seyfert 2, and quasars (Neff & Hutchings 1992). Bottom-left panel: The dotted
line represents the selection criteria (${\rm log}~{}f60/f100>-0.3$) of the
1-Jy sample of ULIRGs (Kim & Sanders 1998). The squares are at the mean color
and the central luminosity of ULIRGs in the three luminosity bins. The
vertical error bars define the limiting luminosities of the bins, and the
horizontal error bars represent the standard deviation of ${\rm
log}~{}f60/f100$ colors in each bin. Bottom-right panel: WISE color-color
diagram for the ULIRGs. The red, blue, and green filled circles symbolize the
galaxies (not included in the Milliquas catalog), Type I and II (distinguished
by the presence or absence of broad emission lines as per Paliya et al. (2024)
and Wu &Shen (2022), see details in Section 4). The plotted isodensity
contours refer to WISE thermal sources and locations of various source classes
are also highlighted. The contour data are adopted from Massaro et al. (2011).

The classification of infrared sources has long relied on the infrared colors
of $f12/f60$, $f25/f60$, and $f60/f100$. Following the approach of Hwang et
al. (2007), we extended our examination to the infrared colors of ULIRGs. The
top-left panel of Figure 10 illustrates the relationship between infrared
luminosity and the color of $f12/f60$ for ULIRGs. The $f12/f60$ color proves
effective in distinguishing stars from galaxies (e.g., Cohen et al. 1987),
particularly as infrared-bright stars typically exhibit spectral energy
distributions peaking around 12 $\mu$m, characterized by a logarithmic slope
of ${\rm log}~{}f12/f60>0$ (e.g., Cohen et al. 1987; Kim & Sanders 1998). In
this panel, open circles with arrows represent the 268 sources with flux upper
limits at 12 $\mu$m, while the filled circles represent the remaining 15
ULIRGs with high or moderate flux qualities at 12 $\mu$m. Notably, none of the
ULIRGs fall into the region of ${\rm log}~{}f12/f60>0$, indicating that our
ULIRG sample is free from contamination by infrared-bright stars. This result
is consistent with our approach during the construction of the ULIRG sample,
where all objects labeled as “STAR” were initially removed from the SDSS DR16
spectral catalog (see Section 2.1).

In the bottom-left panel of Figure 10, we illustrate the relationship between
infrared luminosity and the color of $f60/f100$ for ULIRGs. Open circles
represent the sources with flux upper limits at 100 $\mu$m with the arrows,
while filled circles represent sources with high or moderate flux qualities.
For subsequent analysis, we focus on sources with high or moderate flux
qualities. The color of ${\rm log}~{}f60/f100$ ranges from $-0.50$ to $+0.22$
with a mean value of $-0.18$. Notably, $86\%$ (123 out of 143) of ULIRGs
exhibit colors of ${\rm log}~{}f60/f100$ surpassing $-0.3$. This aligns with
the fourth selection criterion for “warm” sources proposed by Kim & Sanders
(1998), aimed at including genuine ULIRGs while excluding a significant
fraction of less luminous galaxies. The distribution range and mean value of
$f60/f100$ color in our study fall intermediate to those of other ULIRG
samples (e.g., Soifer & Neugebauer 1991; Kim & Sanders 1998; Hwang et al.
2007).

Soifer & Neugebauer (1991) demonstrated an increasing mean $f60/f100$ color
with rising infrared luminosity in the IRAS Bright Galaxy Survey. We plotted
the mean colors in each luminosity bin using filled squares to explore any
dependence of color on infrared luminosity. Our sample exhibits no significant
infrared luminosity dependence of the ${\rm log}~{}f60/f100$ color, up to $\rm
10^{12.8}~{}L_{\sun}$; nevertheless, our colors are warmer than those
typically found in less infrared-luminous galaxies, which tend to have cooler
$f60/f100$ colors.

Additionally, we focus on the distribution of the $f25/f60$ color. Given the
tendency of ULIRGs in interacting systems to undergo collisions and mergers,
these processes are believed to be the primary mechanisms responsible for a
significant portion of the infrared emission. In Veilleux et al. (2002), it
was found that Seyfert galaxies, particularly Type I, warm ULIRGs
($f25/f60>0.2$), and more luminous sources ($\rm>10^{12.5}~{}L_{\sun}$) showed
a strong inclination toward advanced mergers with a single nucleus. In
essence, the $f25/f60$ color effectively distinguishes the dominant energy
source in ULIRGs (i.e., starburst and AGNs) and categorizes ULIRGs into ”cool”
and ”warm” systems (e.g., Sanders et al. 1988b; Veilleux et al. 2002).

The top-right panel of Figure 10 depicts the relationship between infrared
luminosity and the color of $f25/f60$ for ULIRGs. The two vertical lines
(${log}~{}f25/f60=-0.8$ and $-0.65$) represent the boundaries for the
classification of normal galaxies, Seyfert 2 galaxies, and quasars as
suggested by Neff & Hutchings (1992). Among these ULIRGs, black-filled circles
represent 70 sources with high or moderate flux qualities at 25 $\mu$m, while
open circles with arrows represent others with flux upper limits at 25 $\mu$m.
The AllWISE source catalog provides effective detections of upper limit
sources at the $W4$ band, represented by green-filled circles.

The number ratio of objects is then
$N{\rm(Galaxy)}:N{\rm(Sy2)}:N{\rm(Quasar)}=204:26:53$. Adopting $f25/f60=0.2$
as the classification boundary between “cool” and “warm” ULIRGs (Sanders et
al. 1988b), the number ratio for our ULIRG sample becomes
$N{\rm(Cool)}:N{\rm(Warm)}=225:58$. This ratio is comparable to that of the
1-Jy sample ($N{\rm(Cool)}:N{\rm(Warm)}=90:25$, Kim & Sanders 1998), and much
higher than that of ULIRGs with high or moderate flux qualities
($N{\rm(Cool)}:N{\rm(Warm)}=38:30$, Hwang et al. 2007). The differences may be
related to the distinct selection criteria and the exclusion (or not) of
sources with flux upper limits at 25 $\mu$m.

We conducted a cross-match between our ULIRG catalog and the latest release of
the Million Quasars
(Milliquas555https://heasarc.gsfc.nasa.gov/w3browse/all/milliquas.html) v8
catalog (Flesch 2023). Milliquas comprises 907,144 type-I Quasars & AGNs,
along with 2814 blazars, 45,816 type-II objects, and 66,026 radio/X-ray
associated quasar candidates with $p\rm_{quasar}=99\%$ and is largely complete
based on literature sources. The cross-match resulted in 163 matches within a
3-arcsec radius, including 38 quasars (‘Q’ type), 99 type-I Seyferts/host-
dominated AGNs (‘A’ type), 22 type-II narrow-line core-dominated (‘N’ type), 3
type-II Seyferts/host-dominated (‘K’ type), and 1 BL Lac-type object (‘B’
type). That is, more than half of the ULIRGs exhibit an active core at their
centers. On the face of it, the fraction of AGNs among them is approximately
twice as high as that indicated by the $f25/f60$ classification. The possible
reason is that although the central black holes of these ULIRGs have been
ignited, part of these ULIRGs perhaps do not produce enough energy in the
nucleus to dominate the infrared emission of the whole galaxy. They have not
yet transitioned from the “cool” to the “warm” systems in the $f25/f60$
diagnosis.

In the mid-infrared (MIR) waveband, spectroscopy presents a diagnostic avenue
for distinguishing between AGN and starburst activities. This is due to the
strong emission features at 6.2, 7.7, 8.6, and 11.3 $\mu$m that are
characteristic of starburst galaxies, which are attributed to aromatic
carbonaceous material. In contrast, AGNs exhibit a strong continuum with low-
contrast emission features in the nuclear region of the galaxy. Genzel et al.
(1998) and Lutz et al. (1998) proposed employing the line-to-continuum ($L/C$)
ratio of the 7.7 $\mu$m band to distinguish between starburst- and AGN-
dominated ULIRGs. Tran et al. (2001) suggested applying spectral decomposition
to quantitatively characterize the relative contribution of star formation and
AGN activity to the MIR emission of ULIRGs. This involved analyzing the
spectra by overlaying a starburst and an AGN spectrum, both of which could be
obscured to varying degrees. Their studies revealed that approximately half of
high-luminosity ULIRGs are dominated by starburst activity, while AGNs
primarily influence the other half. This ratio aligns with the findings of our
sample, as both sets exhibit a similar range in infrared luminosity, estimated
to be around $\rm\sim 10^{12}-10^{13.1}~{}L_{\sun}$ according to Tran et al.
(2001). Moreover, starbursts are the primary contributors to bolometric
luminosity at the lower end of the spectrum, while AGNs take precedence at the
higher end.

In general, the fraction of systems containing AGNs seems to escalate with
infrared luminosity (e.g., Klaas 1989; Klass & Elsasser 1993; Rowan-Robinson
et al. 1991; Kim et al. 1998; Veilleux et al. 1999a,b). Our sample also
indicates that the fraction of AGNs increases with infrared luminosity. The
transition between star-dominated and AGN-dominated occurs at $\rm\sim
10^{12.4}~{}L_{\sun}$, with AGN fractions ranging from approximately
$43\%-56\%$ when the infrared luminosity is below this threshold, jumping to
around $\sim 76\%-92\%$ afterward. Then, we constructed a [3.4]-[4.6]-[12]
$\mu$m color-color diagram using magnitudes from the WISE Catalog for ULIRGs
in the bottom-right panel of Figure 10. Contour data are adopted from Massaro
et al. (2011), corresponding to WISE thermal sources detected in a 56 deg2
region at high Galactic latitude. ULIRG sources are classified into three
subclasses: galaxies (red), Type I (blue), and Type II (green). The former
group includes 120 sources not in the Milliquas catalog. In contrast, the
latter two groups, totaling 163 sources, are further divided based on the
presence or absence of broad emission lines, as per Paliya et al. (2024) and
Wu & Shen (2022). Additional details can be found in Section 3.4. Type I
sources occupy overlapping regions predominantly populated by luminous quasars
and Seyfert galaxies, while galaxy and Type II sources overlap regions
dominated by ULIRGs and Liners. A small fraction of sources extends into
regions occupied by starburst galaxies and obscured AGNs.

###  3.3 Infrared to Radio Correlation

Figure 11: Distribution of the 1.4 GHz radio luminosity (left panel) and
q-value (right panel) of the ULIRGs plotted as a function of the 60 $\mu$m FIR
luminosity. The sources in our ULIRG sample with detections of FIRST and NVSS
are represented by black and green filled circles, and the IRAS 2 Jy sample
galaxies are overplotted by gray crosses for contrast. In the left panel, the
dashed line means the best-fitting line for an all-sky sample of infrared-
detected galaxies from IRAS (Yun et al. 2001). In the right panel, the dashed
line is at $q=2.34$ which is the mean value obtained by Yun et al. (2001), the
above and below dotted lines are limits for five times FIR excess and radio
excess from the mean respectively.

It has been suggested that AGN activities can be distinguished from starbursts
by using the FIR/radio correlation, a possible connection between the host
galaxy and nuclear activity was involved (e.g., Condon et al. 1982; Rush,
Malkan, & Edelson 1996). Objects displaying a radio excess are primarily
radio-loud AGNs, as suggested by Roy & Norris 1997, possibly involving complex
mechanisms such as jet emission. Objects displaying a radio excess are
primarily radio-loud AGNs, as suggested by Roy & Norris 1997, possibly
involving complex mechanisms such as jet emission. Dust heating by low-mass
stars (cirrus emission) might contribute solely to the observed FIR emission
(e.g., Helou 1986; Lonsdale Persson & Helou 1987; Fitt et al. 1988).
Observational evidence also indicates that the well-known correlation between
FIR and radio luminosity is observed only in star-forming ULIRGs (Yun et al.
2001).

To obtain the radio properties of our ULIRGs, we cross-identified them with
the latest catalogs of the Faint Images of Radio Sky at Twenty centimeters
(FIRST)666http://sundog.stsci.edu/first/catalogs/readme_14dec17.html (Becker
et al. 1995) and the NRAO VLA Sky Survey
(NVSS)777https://www.cv.nrao.edu/nvss/NVSSlist.shtml (Condon et al. 1998)
using a matching radius of 3.0 arcsec. In the preliminary sample, a total of
241 and 103 ULIRGs had counterparts in FIRST and NVSS, respectively, with flux
peak densities at 20 cm (1.4 GHz) and high signal-to-noise ratios. In the end,
245 ULIRGs exhibited effective radio detections, with 98 of them observed in
both surveys.

In Figure 11, we present the 1.4 GHz radio luminosity ($L_{\rm 1.4GHz}$) and
“$q$” parameter against the 60 $\mu$m FIR luminosity ($L_{\rm 60\mu m}$) of
our ULIRG sample. The 60 $\mu$m and 1.4 GHz luminosities and $q$ parameter are
calculated using the formulas (Condon et al. 1991; Yun et al. 2001):

${\rm log}~{}L_{\rm 60\mu m}~{}(L_{\sun})=6.014+2~{}{\rm log}~{}D_{\rm L}+{\rm
log}~{}f_{60\mu m},$ (4) ${\rm log}~{}L_{\rm 1.4GHz}~{}({\rm
WHz^{-1}})=20.08+2~{}{\rm log}~{}D_{\rm L}+{\rm log}~{}f_{\rm 1.4GHz},$ (5)
$q\equiv{\rm log}~{}(2.58~{}f_{\rm 60\mu m}+f_{100\mu m})/2.98-{\rm
log}~{}f_{\rm 1.4GHz},$ (6)

where $D_{\rm L}$ is the luminosity distance in Mpc, and $f_{\rm 60\mu m}$,
$f_{\rm 100\mu m}$ and $f_{\rm 1.4GHz}$ are the observed flux densities at 60
$\mu$m, 100 $\mu$m and 1.4 GHz in units of Jy.

In the left panel, we present the linear relation of the 60 $\mu$m and 1.4 GHz
luminosities for ULIRGs with a solid line. A formal fit to the observed radio-
FIR luminosity correlation yields:

${\rm log}~{}L_{\rm 1.4GHz}=(2.03\pm 0.11)~{}{\rm log}~{}L_{60\mu m}+(0.59\pm
1.13).$ (7)

When combined with the IRAS 2 Jy galaxy sample to view the FIR and radio
luminosity distribution comprehensively, as reported by Yun et al. (2001),
most sources in star-forming ULIRGs follow the radio-FIR luminosity
correlation with a unity slope (dashed line). However, a steepening relation
exists at low luminosities ($L\rm_{60\mu m}\leq 10^{9}~{}L_{\sun}$), and a
higher dispersion for luminosities above $\rm 10^{10.5}~{}L_{\sun}$ (also see
Fig. 5a in Yun et al. (2001)). In other words, two notable features emerge: a
downward trend at the low-luminosity end and an upturn at the high-luminosity
end.

The deviations at low/high luminosities are more intuitively presented in the
distribution of $q$ values (see the right panel of Figure 11). $q$ is a
measure of the difference between the logarithmic FIR/radio flux density
(Equation 6). It should be noted that the value of $q$ is overestimated for
sources with flux upper limits at 100 $\mu m$. The dashed line represents
$q=2.34$, the mean value obtained by Yun et al. (2001), while the above and
below dotted lines are limits for five times FIR excess and radio excess from
the mean, respectively. Deviations from the linear relation can occur if the
FIR or radio luminosity is not directly proportional to star-forming activity.
It is essential to acknowledge a potential bias toward sources with higher
FIR/radio flux density ratios in FIR-selected samples, with the selection
effect being particularly severe at low luminosities (e.g., Condon & Broderick
1986; Yun et al. 2001).

Furthermore, the IRAS 2 Jy sample spans over five decades in luminosity, with
the majority of galaxies having $L_{\rm 60\mu m}$ between $10^{8}$ and
$10^{11.5}~{}L_{\sun}$. In contrast, our ULIRGs are collected at the highest
luminosity ($L\rm_{60\mu m}\gtrsim 10^{11.4}~{}L_{\sun}$). Upon categorizing
the ULIRGs based on AGN activity into three subclasses and analyzing their
distributions within the radio-FIR diagrams, it becomes apparent that AGN-free
ULIRGs (represented by red filled circles) adhere to the Yun et al. radio-FIR
relation. However, both Type I and Type II ULIRGs (represented by blue and
green filled circles) exhibit a significant deviation from this pattern. The
steeper radio-FIR relation (Equation 7) is predominantly attributed to AGNs.
This result is consistent with that of Hou et al. (2009). Therefore, the
radio-FIR relation originates from starburst-related non-thermal radiation,
and the radio excess objects are due to AGN-related radio emission (Roy &
Norris 1997).

###  3.4 Type I AGNs in ULIRGs

Figure 12: Comparisons of various optical spectroscopic parameters
measured/derived for Type I ULIRGs (red), NLS1 (green), and BLS1 (blue)
sources. All measurements are obtained from Paliya et al. (2024).

As mentioned in the third paragraph of Section 3.2, a cross-match with the
Milliquas catalog identified 163 sources in the ULIRG sample displaying
significant AGN activity at their nuclei. The AGN parameter properties are
extracted from the following two articles.

Paliya et al. (2024) meticulously conducted spectral decomposition on over two
million optical spectra of extragalactic sources at low redshifts ($z\leq 0.8$
for SDSS-I/II, and $z\leq 0.9$ for SDSS-III/IV) from the SDSS Data Release 17
(DR17). Their exhaustive work yielded a catalog containing 22,656 narrow-line
Seyfert 1 (NLS1) galaxies and 52,273 broad-line Seyfert 1 (BLS1) galaxies. The
optical spectra underwent meticulous replication to account for multi-
component contributions from both AGN and host galaxies, involving
simultaneous fitting of both emission line and continuum features.

Wu & Shen (2022) presented a catalog of continuum and emission-line properties
for 750,414 broad-line quasars included in the SDSS DR16 quasar catalog
(DR16Q; Lyke et al. 2020), measured from optical spectroscopy. These quasars
cover broad ranges in redshift ($0.1\lesssim z\lesssim 6$) and luminosity
($44\lesssim{\rm log~{}}L{\rm{}_{bol}[erg~{}s^{-1}]}\lesssim 48$). In contrast
to Paliya et al. (2024), Wu & Shen (2022) focused on high redshift, luminous
quasars. The quasars’ spectra were fitted with a global continuum+emission
lines model using the public code PyQSOFIT (e.g., Guo et al. 2018), and the
model does not include host galaxy emission in the spectral fits. Thus, the
measurement reliability for the sources at low redshift with strong host
galaxy starlight is yet to be verified.

Guided by redshift information, we selected the spectral continuum and
emission-line properties of the three sources with redshifts exceeding 0.9
(namely F08105+2554, F10026+4949, and F13080+3237) from the catalog of the
DR16Q properties. The measurements for the remaining 160 low-redshift sources
were obtained from Paliya et al. (2024). Among these, the optical spectra of
55 sources showcase broad H$\alpha$ and/or H$\beta$ emission lines. As a
result, our sample encompasses 58 Type I and 105 Type 2 AGNs within a total of
283 ULIRGs. In a prior investigation, Hou et al. (2009) identified 308 ULIRGs,
with 62 sources classified as Type I. The percentage of Type I ULIRGs in their
study was approximately 20%, a figure consistent with our findings.

Figure 12 presents various parameters and physical properties of Type I ULIRGs
and Type I AGNs. Leveraging measurements conducted by Paliya et al. (2024), we
have redrawn the parameter distribution for Type I AGNs, specifically NLS1s
and BLS1s, to enable more effective comparative analysis. In the top-left
panel, the redshift distribution indicates an increase in the number of Type I
AGNs with redshift, whereas Type I ULIRGs are more frequently observed within
the redshift range of $z<0.55$, peaking at $z=0.28$.

Furthermore, the distribution of black hole masses in Type I ULIRGs is similar
to that in BLS1s, with the average value surpassing that of NLS1s by 0.83 dex.
Type I ULIRGs exhibit significantly larger bolometric luminosities compared to
Type I AGNs. The average bolometric luminosities for NLS1, BLS1s, and Type I
ULIRGs gradually increases from $5.1\times 10^{44}$ erg s-1 to $9.3\times
10^{44}$ erg s-1, and then to $4.4\times 10^{45}$ erg s-1. Consequently, Type
I ULIRGs have exceptionally high accretion rates, with the mean value
($\overline{L_{\rm bol}/L_{\rm Edd}}=0.92$) being approximately 1.5 times
higher than that of NLS1s ($\overline{L_{\rm bol}/L_{\rm Edd}}=0.63$). When
compared with previous studies, the black hole mass distributions in Type I
ULIRGs from both Hou et al.’s and our study show largely identical profiles,
with mean values of $\rm 7.6\times 10^{7}~{}M_{\sun}$ and $\rm 5.8\times
10^{7}~{}M_{\sun}$, respectively. These values are systematically smaller than
those of DR16Q quasars (with a mean value of $\rm 8.3\times
10^{8}~{}M_{\sun}$). However, the average accretion rate for Hou et al.’s Type
I ULIRGs is relatively low, comparable only to that of NLS1s but significantly
larger than that of BLS1s and DR16Q quasars (with mean Eddington ratios of
about 0.16 and 0.23, respectively). In addition, the relative strength of
$R_{4570}$ $\rm(=FeII\lambda\lambda 4434-4684/H\beta)$ in NLS1s is generally
about twice that in normal AGNs on average (e.g., Zhou et al. 2006; Rakshit et
al. 2017; Paliya et al. 2024). We found the median $R_{4570}$ parameter value
of Type I ULIRGs to be even a quarter higher than NLS1s. These findings align
with the prevalent evolutionary model suggesting that ULIRGs are in a pre-QSO
phase, and their central black holes are still in a growing phase.

Furthermore, the bottom-right panel of Figure 12 illustrates a comparison of
the radio-loudness ($RL$) parameters. The overall distributions reveal
similarities between BLS1s and NLS1s, with median average $RL$ values of
approximately 51 and 17, respectively. In contrast, Type 1 ULIRGs demonstrate
relatively low $RL$ parameters, depicting a narrow distribution peaking at
about 13. Remarkably, all sources are below 100, with only two exceptions. The
most noteworthy case is F16413+3954, distinguished by an exceptionally high
$RL$, just below that of merely 10 sources in NLS1 and BLS1 catalogs. Its
optical counterpart, SDSS J164258.80+394837.0, also known as 3C 345, has been
detected in the Fermi-Large Area Telescope’s all-sky gamma-ray survey (Abdo et
al. 2009; Paliya et al. 2018). Recognized as a flat spectrum radio quasar in
the constellation of Hercules, it is renowned for hosting a superluminal jet
and displaying variability across almost all wave bands. The second-highest
radio-loudness source is F09220+2759, associated with the optical counterpart
SDSS J092501.78+274607.9. This extremely red quasar is classified as a radio-
detected Type 1 quasar (Ross et al. 2015). Notably, it exhibits weak broad
H$\beta$ and anomalous [O III] profiles in the optical spectrum (Boroson &
Lauer 2010).

Figure 13: SDSS spectra in restframe of 3 ULIRGs with Mg II BAL features. The
main emission lines are represented by dashed lines, and the gray shaded
regions illustrate the Mg II BAL troughs.

Broad Absorption Lines (BALs) are frequently observed in quasars,
characterized by specific spectral features such as a narrower H$\beta$
emission line, weaker [O III], [Ne III], and [Ne V] emission lines, along with
stronger optical Fe II multiplets (Boroson 2002; Trump et al. 2006; Ganguly et
al. 2007; Gibson et al. 2009; Zhang et al. 2010). The BAL fraction is
significantly higher in quasars with elevated Eddington ratios and luminosity
compared to those with lower values. In Figure 12, we observe that Type I
ULIRGs exhibit similar spectral lines and parameter characteristics,
suggesting a potential connection between AGN outflows and Type I ULIRGs.
Subsequently, we examined the SDSS spectra of the optical counterparts of Type
I ULIRGs and identified three sources displaying Mg II BAL features in their
spectra (Figure 13).

Among these Type I ULIRGs, 18 sources have redshifts of $z\geqslant 0.4$, with
this redshift cutoff chosen to ensure that Mg II falls within the wavelength
coverage of the SDSS spectrograph. Consequently, the fraction of Mg II BALs in
Type I ULIRGs is approximately 16.7%. Typically, previous studies report a
fraction of about 1% for Mg II BAL quasars (e.g., Turnshek et al. 1997; Trump
et al. 2006; Zhang et al. 2010). Considering the bias of the optically
selected sample, the fraction of Mg II BAL quasars ranges from 2% to 7% in
quasars (see more details in Section 3.3 of Zhang et al. 2010). This high
anomaly in the fraction of Mg II BALs within Type I ULIRGs aligns with the
evolutionary scenario of BAL quasars, indicating an early stage of quasar
evolution with a gas/dust richer nuclear environment (Voit et al. 1993; Hamann
et al. 1993; Egami et al. 1996).

##  4 Conclusion

We present a novel dataset of ULIRGs identified through the cross-matching of
IRAS sources in the FSC92 with the spectroscopic sample of the SDSS DR16. The
combination of the reliability and extensive sky coverage of both surveys
provides a uniformly sampled collection suitable for investigating the
distinctive properties of ULIRGs, such as color, morphology, and AGN activity,
using archived photometric and spectroscopic data.

A total of 283 ULIRGs have been identified, with 102 newly discovered within
the SDSS DR16 coverage area. Notably, 120 false ULIRGs previously reported by
Hwang et al. (2007) and Hou et al. (2009) have been excluded. In prior
research, the application of the likelihood ratio method led to the
misidentification of SDSS counterparts for IRAS sources and the acquisition of
incorrect redshifts. Moreover, all infrared emissions from IRAS detections
were erroneously attributed to their likelihood-selected optical counterpart,
resulting in a significant overestimation of the infrared luminosities of
these false sources and their erroneous classification as ULIRGs. To address
this, we employed cross-matching with the AllWISE source catalog and validated
the reliability of IRAS-SDSS associations based on positional uncertainty
ellipses. We also evaluated the infrared contribution from the SDSS
counterpart for each IRAS source, yielding a high-confidence ULIRG sample.

A detailed examination of the SDSS $gri$ composite images revealed that 40%
(114 out of 283) of ULIRGs exhibit apparent interaction features.
Approximately half of them display a single nucleus with tail features, while
the rest show two nuclei with well-defined tidal tails or bridges, or closely
situated nuclei, possibly overlapping. Notably, the higher redshifts of ULIRGs
in this study, compared to previous research, have led to a slightly lower
fraction of sources with interaction features, which decreases with increasing
redshift (92% for $z<0.1$ and 11% for $z\geq 0.4$), likely due to selection
effects. We expect that the forthcoming CSST will provide high-resolution,
high signal-to-noise ratio, and deep images, enabling a more detailed
understanding of ULIRG morphology and interactions.

Our investigation into the infrared colors of these ULIRGs revealed that the
fraction of AGNs, as defined by the $f_{25}/f_{60}$ classification, is 26%
(79/283). However, when matched with Milliquas, this fraction increases to 58%
(163/283), more than doubling the initial value. Interestingly, the fraction
of AGNs appears to correlate with infrared luminosity. Within the radio band,
both Type I and Type II ULIRGs demonstrate an overabundance of radio emission
attributable to AGN activity, resulting in a steeper radio-FIR relationship.
Analysis of the [3.4]-[4.6]-[12] $\mu$m color-color diagram revealed that Type
I ULIRGs predominantly occupy regions associated with luminous quasars and
Seyfert galaxies. Conversely, regions dominated by ULIRGs and Liners overlap
with those occupied by Type II ULIRGs and those lacking AGN activity. These
intriguing patterns imply that while central black holes in certain ULIRGs
have been ignited, they may not produce sufficient energy within the nucleus
to dominate the entire galaxy’s infrared emission.

Moreover, spectral decomposition conducted by Paliya et al. (2024) and Wu &
Shen (2022) identified 58 ULIRGs with significant H$\alpha$ and/or H$\beta$
broad emission lines. Approximately 20% of these ULIRGs are thus classified as
Type I. Comparative analysis revealed various parameter properties between
Type I ULIRGs and Type I AGNs. Type I ULIRGs share similarities with NLS1s,
particularly in terms of higher accretion rate $L_{\rm bol}/L_{\rm Edd}$ and
larger relative strength of $R_{4570}$. However, their black hole masses align
more closely with those of BLS1s and are still systematically smaller than
those of DR16Q quasars, while their bolometric luminosities are even larger
than those of NLS1s and BLS1s. Moreover, the fraction of Mg II BALs in Type I
ULIRGs is approximately 16.7%, over ten times that observed in quasars. These
results are consistent with the current evolutionary model, indicating that
ULIRGs are still in a pre-QSO phase and their central black holes are still
growing.

ULIRGs have been proposed as the future quasar activity sites once the AGN,
which is obscured by the massive gas and dust driven to the galactic center by
the merger, has emerged. Additionally, they are viewed as local analogs of the
SMGs discovered at large redshifts. Submillimeter observations, particularly
sensitive to star-forming regions, dust distribution, molecular gas, and AGNs,
offer superior resolution and more detailed insights. This distinctive class
of galaxies is valuable and well-suited for submillimeter observations in the
study of galaxy evolution. Shanghai Normal University (ShNU) is currently
collaborating with the California Institute of Technology (Caltech) and the
University of Concepcion (UdeC) to promote the Leighton Chajnantor Telescope
(LCT) project. This project involves relocating the 10.4-meter Caltech
submillimeter telescope (CSO) from Mauna Kea in Hawaii to the Atacama Desert
in Chile for terminal upgrades, with operations slated to commence in 2026. We
believe that multiband and spectral submillimeter observations with LCT on
this uniform and high-confidence sample will help improve the current paradigm
of galaxy formation and evolution.

This work was supported in part by the National Natural Science Foundation of
China (Grant No. 12173026 and 12141302), the National Key Research and
Development Program of China (Grant No. 2022YFC2807303), the Shanghai Science
and Technology Fund (Grant No. 23010503900). SHZ acknowledges support from the
Program for Professor of Special Appointment (Eastern Scholar) at Shanghai
Institutions of Higher Learning and the Shuguang Program (23SG39) of the
Shanghai Education Development Foundation and Shanghai Municipal Education
Commission. ZJL acknowledges the support from the Shanghai Science and
Technology Foundation (Grant No. 20070502400) and the science research grants
from the China Manned Space Project. HBX acknowledges support from the
National Natural Science Foundation of China (Grant No. 12203034) and the
Shanghai Science and Technology Fund (Grant No. 22YF1431500). This publication
uses data products from the Infra-Red Astronomical Satellite, the Sloan
Digital Sky Survey, the Wide-field Infrared Survey Explorer, the VLA Faint
Images of the Radio Sky at Twenty-Centimeters, and the NRAO VLA Sky Survey.
Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P.
Sloan Foundation, the U.S. Department of Energy Office of Science, and the
Participating Institutions. SDSS-IV acknowledges support and resources from
the Center for High-Performance Computing at the University of Utah. The SDSS
website is www.sdss.org. The Wide-field Infrared Survey Explorer is a joint
project of the University of California, Los Angeles, and the Jet Propulsion
Laboratory/California Institute of Technology, funded by the National
Aeronautics and Space Administration. The VLA is operated by the National
Radio Astronomy Observatory, which is a facility of the National Science
Foundation under a cooperative agreement by Associated Universities, Inc.

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Table 1: Parameters of the ULIRG Sample

Name | M-P-F | redshift | ${\rm log}~{}L\rm_{IR}$ | $F\rm_{12\mu m}$ | $F\rm_{25\mu m}$ | $F\rm_{60\mu m}$ | $F\rm_{100\mu m}$ | Quality | $N\rm_{WISE}$ | Flux Ratio | $F\rm_{FIRST}$ | $F\rm_{NVSS}$ | AGN
---|---|---|---|---|---|---|---|---|---|---|---|---|---
|  |  | $L_{\sun}$ | Jy | Jy | Jy | Jy |  |  | % | mJy | mJy |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11) | (12) | (13) | (14)
F00242+3344 | 56537-06530-0561 | 0.1734 | 12.14 | 0.0760 | 0.1142 | 0.6008 | 1.3310 | 1132 | 5 | 83 |  | 18.97 |
F00344-0130 | 52261-00690-0216 | 0.2936 | 12.38 | 0.0821 | 0.1722 | 0.3238 | 0.6836 | 1131 | 6 | 82 | 0.82 |  | II
F01093-1002 | 52199-00659-0597 | 0.1315 | 12.00 | 0.1140 | 0.1364 | 0.9330 | 1.4040 | 1132 | 5 | 67 | 4.89 |  |
F01329+1439 | 51882-00426-0333 | 0.2178 | 12.17 | 0.1870 | 0.1861 | 0.3769 | 0.8811 | 1131 | 11 | 64 |  |  |
F01478+1254 | 51820-00429-0011 | 0.1467 | 12.02 | 0.1273 | 0.1827 | 0.4800 | 1.9110 | 1131 | 3 | 91 |  |  |
F01501+0433 | 55536-04403-0167 | 0.4930 | 12.86 | 0.1004 | 0.1310 | 0.2516 | 0.7125 | 1131 | 13 | 52 | 0.68 |  | II
F01572+0009 | 51871-00403-0550 | 0.1635 | 12.52 | 0.1232 | 0.5416 | 2.2240 | 2.1640 | 2332 | 3 | 91 | 22.91 | 25.38 | I
F02394-0031 | 52199-00706-0101 | 0.2186 | 12.06 | 0.0991 | 0.1215 | 0.3058 | 0.6354 | 1132 | 7 | 62 | 0.95 |  |
F02417-0043 | 51871-00409-0315 | 0.2002 | 12.14 | 0.1053 | 0.1595 | 0.4822 | 0.8260 | 1132 | 6 | 67 | 9.46 | 9.65 | II
F02486-0714 | 51901-00457-0324 | 0.3267 | 12.32 | 0.0719 | 0.1422 | 0.2443 | 0.3989 | 1131 | 7 | 68 | 6.02 | 6.70 | I
F03209-0806 | 51924-00460-0093 | 0.1664 | 12.28 | 0.1003 | 0.1343 | 1.0050 | 1.6920 | 1132 | 2 | 97 | 5.55 |  | II
F03319-0800 | 54476-01630-0045 | 0.2870 | 12.53 | 0.0732 | 0.1379 | 0.4645 | 1.0700 | 1131 | 2 | 94 |  |  | II
F07384+4515 | 56323-06375-0554 | 0.2071 | 12.07 | 0.0951 | 0.1181 | 0.3009 | 0.8828 | 1131 | 5 | 64 | 1.77 |  |
F07407+2720 | 52592-01059-0220 | 0.2527 | 12.10 | 0.0729 | 0.2620 | 0.2539 | 0.4688 | 1131 | 7 | 84 | 0.72 |  | I
F07464+2841 | 52592-01059-0507 | 0.3370 | 12.45 | 0.1099 | 0.2025 | 0.2854 | 0.5497 | 1131 | 5 | 73 | 27.95 | 26.20 | II
F07548+4227 | 57391-08291-0871 | 0.2112 | 12.13 | 0.1104 | 0.2195 | 0.3263 | 0.9755 | 1131 | 8 | 80 | 1.81 |  | I
F07592+3736 | 52253-00758-0259 | 0.2385 | 12.14 | 0.1008 | 0.1287 | 0.2845 | 0.6625 | 1132 | 6 | 64 | 3.36 |  | II
F08025+4523 | 56243-06377-0949 | 0.3040 | 12.56 | 0.0783 | 0.1445 | 0.3482 | 1.2260 | 1131 | 2 | 78 | 2.07 |  |
F08030+5243 | 53297-01781-0309 | 0.0833 | 12.08 | 0.0954 | 0.1836 | 2.9880 | 4.3940 | 1232 | 2 | 91 | 15.36 | 14.50 | II
F08072+1622 | 53713-02267-0561 | 0.1855 | 12.15 | 0.1041 | 0.1604 | 0.2647 | 1.8220 | 1131 | 5 | 64 | 2.14 |  |
F08079+2822 | 55858-04457-0604 | 0.3358 | 12.43 | 0.0679 | 0.1705 | 0.2841 | 0.5190 | 1132 | 8 | 50 | 4.50 |  |
F08090+0849 | 54081-02570-0571 | 0.2836 | 12.12 | 0.0910 | 0.1451 | 0.2009 | 0.3853 | 1131 | 4 | 66 | 0.82 |  |
F08105+2554 | 52709-01266-0219 | 1.5099 | 14.03 | 0.1054 | 0.1453 | 0.2843 | 0.5380 | 1132 | 10 | 71 |  |  | I
F08162+2716 | 55888-04461-0564 | 0.2612 | 12.52 | 0.1327 | 0.1359 | 0.6348 | 1.0710 | 1132 | 2 | 79 | 5.94 | 5.99 | II
F08180+5612 | 53386-01783-0354 | 0.1588 | 12.08 | 0.0838 | 0.1618 | 0.6525 | 1.3350 | 1131 | 3 | 93 | 11.69 | 11.66 | II
F08201+2801 | 52932-01267-0383 | 0.1678 | 12.30 | 0.0850 | 0.1616 | 1.1710 | 1.4290 | 1132 | 4 | 88 | 4.74 |  |
F08209+2458 | 52962-01585-0627 | 0.2342 | 12.20 | 0.1175 | 0.1713 | 0.2795 | 0.9380 | 1131 | 9 | 64 | 0.94 |  |
F08219+1549 | 53713-02272-0548 | 0.2201 | 12.15 | 0.1293 | 0.1780 | 0.3602 | 0.7955 | 1131 | 2 | 91 | 3.11 |  | II
F08220+3842 | 52615-00894-0135 | 0.2058 | 12.09 | 0.0737 | 0.1133 | 0.3988 | 0.7057 | 1132 | 4 | 70 | 2.36 |  |
F08238+0752 | 53084-01758-0187 | 0.3114 | 12.41 | 0.1515 | 0.1803 | 0.2445 | 0.7888 | 1131 | 8 | 68 |  |  | I
F08252+4632 | 51986-00548-0541 | 0.2807 | 12.35 | 0.0672 | 0.1385 | 0.2481 | 0.9269 | 1131 | 3 | 65 | 1.29 |  |
F08266+3855 | 52312-00827-0408 | 0.1957 | 12.09 | 0.0570 | 0.1325 | 0.4636 | 0.7513 | 1132 | 4 | 64 | 2.51 | 2.56 |
F08274+1930 | 53709-02275-0389 | 0.1862 | 12.11 | 0.0722 | 0.1259 | 0.5817 | 0.7599 | 1132 | 2 | 86 |  |  |
F08280+5429 | 55925-05156-0656 | 0.2924 | 12.27 | 0.1067 | 0.0839 | 0.2516 | 0.5526 | 1131 | 5 | 66 | 5.37 |  | II
F08287+5254 | 55212-03695-0976 | 0.1694 | 12.02 | 0.0709 | 0.0767 | 0.6005 | 0.7565 | 1132 | 4 | 57 | 2.89 |  |
F08297+4728 | 51981-00549-0409 | 0.2996 | 12.38 | 0.1010 | 0.1309 | 0.2742 | 0.7420 | 1131 | 5 | 76 | 1.68 |  |
F08313+4855 | 51873-00443-0019 | 0.1745 | 12.21 | 0.0877 | 0.0931 | 0.3347 | 2.4260 | 1131 | 4 | 69 | 7.88 |  |
F08322+3609 | 52668-01197-0613 | 0.2012 | 12.03 | 0.0647 | 0.1358 | 0.3614 | 0.6634 | 1131 | 4 | 76 | 1.28 |  |
F08344+5105 | 51873-00445-0488 | 0.0969 | 12.05 | 0.0712 | 0.1330 | 2.1400 | 2.6940 | 1232 | 1 | 100 | 7.53 |  |
F08407+2630 | 53350-01932-0293 | 0.2576 | 12.10 | 0.0938 | 0.1119 | 0.2015 | 0.5487 | 1131 | 10 | 50 |  |  | I
F08435+3141 | 52991-01270-0423 | 0.3867 | 12.46 | 0.0855 | 0.0927 | 0.2021 | 0.4346 | 1131 | 11 | 54 |  |  | I
F08449+2332 | 53358-01931-0015 | 0.1519 | 12.09 | 0.1289 | 0.1539 | 0.8674 | 1.1950 | 1132 | 2 | 94 | 3.24 | 5.16 |
F08449+2332 | 53379-02085-0279 | 0.1517 | 12.09 | 0.1289 | 0.1539 | 0.8674 | 1.1950 | 1132 | 2 | 94 | 3.24 | 5.16 |
F08504+2538 | 53381-01933-0182 | 0.2560 | 12.38 | 0.0829 | 0.1053 | 0.4872 | 0.8258 | 1132 | 5 | 51 | 10.46 |  | II
F08507+3636 | 52643-00935-0179 | 0.2604 | 12.22 | 0.0728 | 0.1252 | 0.2497 | 0.7246 | 1131 | 7 | 51 | 16.16 | 32.45 | II
F08519+2017 | 53729-02283-0329 | 0.3060 | 12.78 | 0.2838 | 0.4335 | 0.8911 | 1.1580 | 3332 | 2 | 98 | 1182.12 | 1480.56 | II
F08542+1920 | 53711-02281-0618 | 0.3313 | 12.46 | 0.1143 | 0.1235 | 0.3316 | 0.5156 | 1132 | 7 | 77 | 4.43 |  | I
F08542+5132 | 55946-05155-0182 | 0.3660 | 12.84 | 0.0968 | 0.0618 | 0.5983 | 1.0920 | 1132 | 2 | 87 | 7.11 | 6.66 | II
F08559+1053 | 54085-02575-0125 | 0.1480 | 12.22 | 0.1047 | 0.1921 | 1.1190 | 1.9520 | 1232 | 1 | 100 | 12.72 | 11.83 | II
F08572+3915 | 52703-01199-0041 | 0.0582 | 12.05 | 0.3178 | 1.7030 | 7.4330 | 4.5880 | 3332 | 1 | 100 | 4.89 | 3.98 |
F08589+5733 | 56329-05150-0971 | 0.2848 | 12.51 | 0.0718 | 0.0828 | 0.4911 | 0.9441 | 1132 | 5 | 65 | 7.28 | 7.07 | II
F08591+4341 | 52294-00831-0377 | 0.7029 | 13.08 | 0.0936 | 0.1000 | 0.2006 | 0.4356 | 1131 | 5 | 67 | 3.87 |  | I
F08591+5248 | 51999-00553-0331 | 0.1573 | 12.21 | 0.0999 | 0.1617 | 1.0100 | 1.5260 | 1132 | 2 | 91 | 5.96 |  |
F09005+0223 | 51924-00471-0322 | 0.3291 | 12.56 | 0.0672 | 0.1037 | 0.3626 | 0.8260 | 1131 | 4 | 70 | 22.50 | 23.58 | II
F09029+2430 | 53401-02086-0149 | 0.2316 | 12.15 | 0.0519 | 0.0933 | 0.3613 | 0.5896 | 1131 | 3 | 71 | 3.48 | 3.37 |
F09039+0503 | 52649-01192-0115 | 0.1250 | 12.14 | 0.1681 | 0.2077 | 1.4840 | 2.0630 | 1132 | 3 | 86 | 4.92 | 5.76 |
F09105+4108 | 52668-01200-0073 | 0.4408 | 12.87 | 0.1297 | 0.3335 | 0.5254 | 0.4379 | 2331 | 1 | 100 | 8.30 | 14.44 | II
F09116+0334 | 52252-00567-0200 | 0.1453 | 12.18 | 0.0859 | 0.1406 | 1.0920 | 1.8220 | 1132 | 4 | 83 | 9.41 | 9.87 | II
F09117+3111 | 56353-05809-0016 | 0.3064 | 12.23 | 0.0903 | 0.2109 | 0.2764 | 0.2509 | 1131 | 4 | 79 | 5.45 | 6.24 | II
F09198+0323 | 52254-00568-0267 | 0.1741 | 12.05 | 0.1317 | 0.1074 | 0.2405 | 1.7090 | 1131 | 9 | 51 |  |  |
F09220+2759 | 58130-09632-0133 | 0.5316 | 12.93 | 0.0761 | 0.2147 | 0.3006 | 0.5403 | 1131 | 6 | 75 | 26.74 | 26.00 | I
F09246+0115 | 51965-00475-0296 | 0.1687 | 12.07 | 0.1024 | 0.1401 | 0.5049 | 1.2880 | 1132 | 4 | 71 | 2.66 |  |
F09320+6134 | 51910-00486-0231 | 0.0394 | 12.02 | 0.2499 | 1.0340 | 11.5400 | 20.2300 | 3332 | 1 | 100 | 146.74 | 144.78 | II
F09322+0432 | 52264-00569-0459 | 0.1978 | 12.13 | 0.0868 | 0.1714 | 0.5835 | 0.6059 | 1132 | 6 | 70 |  | 2.92 | II
F09382+1449 | 55978-05315-0118 | 0.3838 | 12.89 | 0.1012 | 0.2257 | 0.6485 | 0.9760 | 1132 | 1 | 100 | 7.64 | 6.35 | II
F09395+3939 | 52725-01215-0082 | 0.1944 | 12.14 | 0.0666 | 0.1020 | 0.4704 | 1.0140 | 1132 | 4 | 70 | 3.53 |  |
F09398+0013 | 51602-00266-0235 | 0.1459 | 12.06 | 0.0950 | 0.1137 | 0.5014 | 2.2160 | 1131 | 4 | 83 | 4.87 |  |
F09400+4338 | 55631-04569-0576 | 0.3634 | 12.48 | 0.0874 | 0.1754 | 0.2521 | 0.5185 | 1131 | 4 | 84 | 7.97 |  | II
F09418+1433 | 54139-02582-0393 | 0.2164 | 12.19 | 0.1941 | 0.2951 | 0.4059 | 0.9099 | 1131 | 3 | 89 | 5.44 |  |
F09438+4735 | 56686-07299-0377 | 0.5394 | 13.01 | 0.0576 | 0.1325 | 0.2476 | 0.8972 | 1131 | 10 | 57 | 2.84 |  | I
F09444+1019 | 52757-01305-0509 | 0.2020 | 12.01 | 0.0894 | 0.1579 | 0.2245 | 0.9271 | 1131 | 7 | 52 | 1.97 |  |
F09483+1443 | 54139-02582-0583 | 0.2333 | 12.20 | 0.1117 | 0.1301 | 0.2103 | 1.1370 | 1131 | 8 | 61 | 1.80 |  | I
F09496+5755 | 56625-07085-0500 | 0.3840 | 12.70 | 0.0619 | 0.1006 | 0.3720 | 0.7202 | 1132 | 3 | 79 | 6.48 | 5.96 |
F09510+2128 | 56269-05785-0070 | 0.2451 | 12.29 | 0.1569 | 0.2289 | 0.4152 | 0.7829 | 1132 | 4 | 80 | 2.99 |  | II
F09554+2718 | 56270-06467-0602 | 0.2499 | 12.21 | 0.1117 | 0.1636 | 0.3424 | 0.5894 | 1131 | 7 | 64 | 4.26 | 3.39 |
F09583+4714 | 52339-00872-0280 | 0.0859 | 12.02 | 0.0846 | 0.4819 | 2.6430 | 3.0610 | 1332 | 3 | 87 | 24.95 |  | II
F10015-0018 | 51581-00269-0182 | 0.2885 | 12.52 | 0.0821 | 0.1430 | 0.3203 | 1.3330 | 1131 | 5 | 63 | 2.65 |  | II
F10026+4347 | 57401-08287-0228 | 0.1783 | 12.07 | 0.1277 | 0.1848 | 0.5582 | 0.8740 | 1232 | 2 | 92 | 2.81 |  | I
F10026+4949 | 56660-07282-0898 | 1.1218 | 13.72 | 0.0858 | 0.1772 | 0.2655 | 0.6190 | 1231 | 3 | 85 |  |  | I
F10030+4126 | 52672-01217-0021 | 0.3285 | 12.49 | 0.0979 | 0.0892 | 0.3933 | 0.5044 | 1132 | 5 | 59 | 2.23 |  |
F10035+4852 | 52339-00872-0408 | 0.0651 | 12.03 | 0.0984 | 0.2827 | 4.5930 | 6.2420 | 2332 | 1 | 100 | 8.58 |  |
F10035+2740 | 53757-02347-0321 | 0.1656 | 12.30 | 0.1371 | 0.1698 | 1.1440 | 1.6300 | 1132 | 5 | 64 | 5.44 | 5.31 | II
F10037+1112 | 53053-01308-0483 | 0.2736 | 12.15 | 0.0804 | 0.2390 | 0.2596 | 0.3922 | 1131 | 5 | 68 | 1.14 |  |
F10040+0932 | 52751-01236-0534 | 0.1709 | 12.22 | 0.1366 | 0.2806 | 0.8290 | 1.4010 | 1132 | 1 | 100 | 2.58 |  |
F10077+1427 | 54174-02588-0309 | 0.1989 | 12.08 | 0.1221 | 0.2729 | 0.4673 | 0.6248 | 1231 | 2 | 98 | 8.82 | 10.96 | II
F10106+2227 | 53739-02365-0389 | 0.2739 | 12.15 | 0.0974 | 0.1321 | 0.2199 | 0.4779 | 1131 | 8 | 70 | 1.11 |  | I
F10107+4708 | 52339-00872-0021 | 0.2056 | 12.33 | 0.0911 | 0.1183 | 0.7034 | 1.2520 | 1132 | 1 | 100 | 2.15 |  |
F10124+2742 | 53757-02348-0020 | 0.2103 | 12.24 | 0.1465 | 0.1785 | 0.5816 | 0.8409 | 1132 | 4 | 73 | 5.36 | 5.03 |
F10124+1631 | 54174-02588-0551 | 0.2402 | 12.06 | 0.1144 | 0.2155 | 0.2475 | 0.5099 | 1131 | 7 | 62 | 2.47 |  | II
F10139+0429 | 55653-04801-0030 | 0.2661 | 12.51 | 0.0955 | 0.1746 | 0.5305 | 1.2110 | 1132 | 1 | 100 | 6.81 |  |
F10190+1322 | 53062-01746-0194 | 0.0763 | 12.07 | 0.0992 | 0.3785 | 3.3280 | 5.5740 | 1232 | 4 | 71 | 16.41 | 15.79 |
F10194+2427 | 53734-02349-0266 | 0.1882 | 12.04 | 0.1223 | 0.2014 | 0.3701 | 0.9331 | 1132 | 2 | 87 | 4.08 |  | II
F10211+2436 | 53734-02349-0233 | 0.2092 | 12.06 | 0.0678 | 0.1852 | 0.3724 | 0.6185 | 1131 | 4 | 81 |  |  |
F10234+3052 | 58161-10460-0253 | 0.3403 | 12.47 | 0.0592 | 0.1572 | 0.2588 | 0.6713 | 1131 | 8 | 63 | 1.82 |  | I
F10341+1312 | 53112-01748-0194 | 0.1740 | 12.06 | 0.0804 | 0.1764 | 0.5687 | 0.8803 | 1132 | 1 | 100 | 3.16 |  |
F10345+3809 | 53433-01998-0358 | 0.2028 | 12.05 | 0.0646 | 0.0787 | 0.2743 | 0.9466 | 1131 | 4 | 56 |  |  |
F10369+4913 | 52354-00875-0053 | 0.1755 | 12.06 | 0.0835 | 0.1110 | 0.6420 | 0.6584 | 1132 | 1 | 100 | 7.25 | 7.35 |
F10372+4801 | 52620-00962-0487 | 0.4861 | 12.81 | 0.0771 | 0.1488 | 0.2190 | 0.6733 | 1131 | 8 | 67 | 4.28 |  | II
F10378+1108 | 53090-01600-0061 | 0.1363 | 12.34 | 0.1141 | 0.2351 | 2.2810 | 1.8160 | 1232 | 4 | 87 | 8.55 | 8.17 |
F10425+2224 | 54058-02477-0010 | 0.2113 | 12.18 | 0.0573 | 0.1004 | 0.2321 | 1.4030 | 1131 | 6 | 64 | 2.56 |  |
F10445+4205 | 53047-01361-0036 | 0.1990 | 12.14 | 0.0863 | 0.0958 | 0.4289 | 0.9897 | 1131 | 4 | 69 | 1.00 |  |
F10482+1909 | 54175-02482-0430 | 0.2192 | 12.42 | 0.0664 | 0.1561 | 0.6850 | 1.4400 | 1132 | 3 | 73 | 3.08 |  |
F10494+4424 | 53053-01434-0052 | 0.0921 | 12.25 | 0.1171 | 0.1648 | 3.5270 | 5.4120 | 1232 | 1 | 100 | 20.74 | 20.39 | II
F10531+5531 | 52373-00907-0167 | 0.2564 | 12.01 | 0.0673 | 0.0857 | 0.1994 | 0.3728 | 1131 | 9 | 58 |  |  | I
F10558+3845 | 53474-02007-0610 | 0.2081 | 12.23 | 0.0516 | 0.0857 | 0.6240 | 0.7535 | 1132 | 4 | 71 | 2.25 |  |
F10565+2448 | 56354-06418-0766 | 0.0428 | 12.06 | 0.2170 | 1.1380 | 12.1200 | 15.1300 | 3332 | 2 | 99 | 51.80 | 51.61 |
F10594+3818 | 53469-01988-0235 | 0.1578 | 12.31 | 0.0853 | 0.1525 | 1.2930 | 1.8950 | 1132 | 2 | 88 | 9.60 | 9.18 |
F11028+3442 | 53466-02034-0230 | 0.5083 | 12.85 | 0.1025 | 0.1471 | 0.2375 | 0.6289 | 1231 | 6 | 86 |  |  | I
F11028+3130 | 53472-01990-0525 | 0.1988 | 12.43 | 0.0863 | 0.1182 | 1.0210 | 1.4440 | 1132 | 1 | 100 | 2.32 |  |
F11057+4053 | 53003-01439-0263 | 0.1657 | 12.08 | 0.1003 | 0.1304 | 0.6830 | 1.0170 | 1132 | 1 | 100 | 3.90 |  |
F11066+4242 | 53003-01439-0377 | 0.2317 | 12.11 | 0.1075 | 0.1234 | 0.2469 | 0.7610 | 1131 | 3 | 85 | 1.73 |  | I
F11070+4249 | 55652-04620-0744 | 0.2614 | 12.34 | 0.0663 | 0.1754 | 0.4693 | 0.5827 | 1132 | 3 | 90 | 16.96 | 15.20 | II
F11087+5351 | 52649-01012-0229 | 0.1429 | 12.03 | 0.0833 | 0.1100 | 0.8109 | 1.2820 | 1132 | 1 | 100 | 30.97 | 29.45 | II
F11119+3257 | 56367-06438-0524 | 0.1876 | 12.51 | 0.1672 | 0.3484 | 1.5880 | 1.5230 | 3332 | 3 | 90 | 107.77 | 106.80 | II
F11134+0225 | 52636-00511-0315 | 0.2109 | 12.01 | 0.1685 | 0.1889 | 0.3992 | 0.3291 | 1131 | 6 | 72 | 0.57 |  | I
F11162+6020 | 52398-00951-0410 | 0.2643 | 12.55 | 0.0792 | 0.1178 | 0.6751 | 1.1100 | 1132 | 3 | 77 | 56.22 |  | II
F11163+3207 | 53431-01979-0373 | 0.2618 | 12.22 | 0.0797 | 0.1414 | 0.2967 | 0.6030 | 1131 | 4 | 82 | 34.38 | 35.90 | II
F11188+1138 | 53062-01605-0093 | 0.1849 | 12.36 | 0.1228 | 0.2403 | 0.9126 | 1.7200 | 1132 | 4 | 76 | 6.53 |  | II
F11206+3639 | 53446-02037-0099 | 0.2425 | 12.42 | 0.0975 | 0.0872 | 0.4852 | 1.3410 | 1131 | 5 | 65 | 13.54 |  | II
F11213+6556 | 51942-00491-0088 | 0.2641 | 12.28 | 0.0941 | 0.1241 | 0.2404 | 0.9077 | 1131 | 11 | 50 |  |  |
F11215+1058 | 52781-01223-0325 | 0.1988 | 12.08 | 0.0816 | 0.1375 | 0.3249 | 0.9979 | 1131 | 6 | 59 | 1.38 |  |
F11273+4610 | 56390-06647-0298 | 0.2811 | 12.73 | 0.0920 | 0.0923 | 0.8939 | 1.4410 | 1132 | 1 | 100 | 6.19 |  |
F11277+2016 | 54169-02498-0590 | 0.1930 | 12.02 | 0.1110 | 0.1365 | 0.3215 | 0.8742 | 1131 | 6 | 53 |  |  |
F11370+4647 | 53050-01442-0025 | 0.1735 | 12.06 | 0.0815 | 0.1037 | 0.3227 | 1.5680 | 1131 | 3 | 89 | 4.95 | 4.08 |
F11387+4116 | 53062-01445-0242 | 0.1488 | 12.16 | 0.2003 | 0.1376 | 1.0250 | 1.5130 | 1132 | 2 | 95 | 5.39 |  |
F11388+0204 | 51994-00514-0285 | 0.3821 | 12.54 | 0.1078 | 0.1318 | 0.2230 | 0.6244 | 1131 | 6 | 50 |  |  | I
F11394+0108 | 51584-00283-0411 | 0.2450 | 12.22 | 0.1665 | 0.2659 | 0.4147 | 0.5166 | 1132 | 5 | 80 | 17.68 | 18.79 | II
F11417+1151 | 54894-03245-0248 | 0.2702 | 12.33 | 0.1542 | 0.2205 | 0.3674 | 0.6861 | 1132 | 5 | 91 | 3.01 |  | I
F11506+1331 | 53144-01610-0331 | 0.1273 | 12.39 | 0.0995 | 0.2949 | 2.5830 | 3.3230 | 1132 | 4 | 85 | 13.16 | 13.24 |
F11553-0259 | 52370-00330-0012 | 0.2145 | 12.06 | 0.1170 | 0.2981 | 0.3325 | 0.6266 | 1132 | 8 | 69 | 3.08 |  | I
F11579+0848 | 53089-01623-0321 | 0.2481 | 12.10 | 0.0914 | 0.4126 | 0.2540 | 0.5270 | 1131 | 9 | 55 | 1.66 |  |
F11588+2052 | 56067-05973-0482 | 0.5301 | 13.13 | 0.1316 | 0.1983 | 0.2791 | 1.3740 | 1131 | 10 | 60 | 5.35 |  | II
F11595+1144 | 53147-01611-0295 | 0.1937 | 12.34 | 0.1077 | 0.1573 | 0.9452 | 1.1500 | 1132 | 3 | 74 | 5.77 | 6.87 |
F12018+1941 | 54476-02609-0301 | 0.1679 | 12.45 | 0.1068 | 0.3735 | 1.7610 | 1.7760 | 1232 | 2 | 95 | 5.55 |  | II
F12043+5215 | 52370-00882-0065 | 0.3992 | 12.51 | 0.0993 | 0.0945 | 0.2220 | 0.4313 | 1131 | 7 | 70 | 1.32 |  | I
F12047+0233 | 52024-00517-0142 | 0.2217 | 12.14 | 0.1149 | 0.3462 | 0.4121 | 0.5774 | 1132 | 4 | 69 | 1.74 |  |
F12112+0305 | 52282-00518-0467 | 0.0730 | 12.38 | 0.1100 | 0.5093 | 8.5030 | 9.9760 | 1332 | 3 | 90 |  | 22.81 |
F12126+0943 | 52672-01230-0221 | 0.2632 | 12.09 | 0.0932 | 0.2684 | 0.2143 | 0.4491 | 1131 | 5 | 78 |  |  |
F12232+5532 | 52721-01020-0390 | 0.2324 | 12.36 | 0.2413 | 0.0954 | 0.6008 | 0.9410 | 1132 | 3 | 78 | 4.96 | 3.47 |
F12266+3240 | 53818-02013-0629 | 0.1730 | 12.03 | 0.0873 | 0.1533 | 0.5715 | 0.7624 | 1132 | 2 | 89 | 2.97 | 2.72 |
F12297+5222 | 52379-00885-0307 | 0.3907 | 12.61 | 0.0739 | 0.1188 | 0.2624 | 0.6350 | 1131 | 7 | 66 | 4.12 | 3.57 |
F12358+1807 | 54234-02599-0503 | 0.4522 | 12.67 | 0.1359 | 0.1279 | 0.2621 | 0.3896 | 1131 | 6 | 89 | 6.07 |  | I
F12375+3721 | 53495-02010-0621 | 0.2402 | 12.12 | 0.0534 | 0.0890 | 0.2478 | 0.6759 | 1131 | 6 | 65 | 6.13 | 7.21 | II
F12410+2344 | 54485-02648-0414 | 0.2120 | 12.03 | 0.0902 | 0.1115 | 0.3392 | 0.5528 | 1132 | 5 | 74 | 2.63 |  | I
F12433+6540 | 52316-00601-0479 | 0.3197 | 12.36 | 0.0594 | 0.0695 | 0.2081 | 0.6485 | 1131 | 10 | 61 |  |  | I
F12442+4550 | 53063-01373-0327 | 0.1957 | 12.28 | 0.0670 | 0.1374 | 0.7700 | 1.0400 | 1132 | 1 | 100 | 2.77 |  | II
F12447+3721 | 53772-01989-0282 | 0.1582 | 12.14 | 0.1155 | 0.1215 | 1.0430 | 0.8434 | 1132 | 1 | 100 | 2.15 | 2.55 |
F12465+4458 | 53063-01373-0197 | 0.2286 | 12.09 | 0.0669 | 0.0977 | 0.2094 | 0.8256 | 1131 | 6 | 71 |  |  | II
F12471+4759 | 53089-01455-0597 | 0.3043 | 12.55 | 0.1179 | 0.0672 | 0.3568 | 1.1680 | 1131 | 7 | 58 | 2.53 | 3.04 | I
F12484+6245 | 56444-06970-0269 | 0.4608 | 12.66 | 0.0617 | 0.0566 | 0.1875 | 0.5126 | 1131 | 3 | 83 | 10.84 | 10.40 | II
F12487+0235 | 52026-00523-0312 | 0.2533 | 12.38 | 0.0888 | 0.1270 | 0.4717 | 0.8864 | 1132 | 6 | 63 | 2.22 |  |
F12489+6619 | 51988-00495-0207 | 0.2817 | 12.17 | 0.0604 | 0.0712 | 0.1739 | 0.5768 | 1131 | 3 | 88 |  |  | I
F12510+2603 | 54505-02661-0518 | 0.4836 | 12.86 | 0.1253 | 0.1444 | 0.2168 | 0.8561 | 1131 | 11 | 63 | 2.89 |  | II
F12514+1027 | 55982-05415-0618 | 0.3190 | 12.70 | 0.0632 | 0.1904 | 0.7124 | 0.7553 | 1232 | 4 | 82 | 7.91 | 8.35 | II
F12532-0322 | 51694-00338-0287 | 0.1687 | 12.06 | 0.1279 | 0.1518 | 0.6741 | 0.8086 | 1132 | 2 | 90 | 3.74 |  | II
F12551+0825 | 54504-01794-0331 | 0.2724 | 12.49 | 0.0898 | 0.1191 | 0.5876 | 0.7789 | 1131 | 5 | 82 | 6.58 | 6.29 | I
F12559+2257 | 56066-05990-0641 | 0.2083 | 12.30 | 0.1521 | 0.0794 | 0.5616 | 1.3340 | 1132 | 5 | 69 | 3.79 | 3.87 |
F13080+3237 | 53819-02029-0602 | 0.9959 | 13.69 | 0.1744 | 0.2710 | 0.4198 | 0.5760 | 1232 | 1 | 100 | 1506.33 | 1618.18 | I
F13161+0927 | 53851-01798-0109 | 0.2821 | 12.22 | 0.0955 | 0.1573 | 0.2159 | 0.5929 | 1131 | 7 | 60 | 0.99 |  | II
F13190+4050 | 53112-01462-0140 | 0.1850 | 12.08 | 0.1039 | 0.1119 | 0.4423 | 1.0110 | 1132 | 5 | 78 | 2.62 |  | II
F13209+6353 | 52056-00603-0240 | 0.2000 | 12.21 | 0.0582 | 0.0687 | 0.5896 | 0.9138 | 1132 | 2 | 90 | 6.66 | 6.29 | II
F13218+0552 | 52375-00852-0367 | 0.2028 | 12.41 | 0.2621 | 0.4032 | 1.1740 | 0.7134 | 3332 | 1 | 100 | 4.26 |  | II
F13231+6235 | 52327-00784-0541 | 0.2376 | 12.31 | 0.0436 | 0.0643 | 0.3584 | 1.1900 | 1131 | 3 | 73 | 2.86 |  |
F13342+3932 | 53472-02005-0441 | 0.1791 | 12.37 | 0.1192 | 0.2528 | 1.1140 | 1.6340 | 1132 | 3 | 97 | 6.94 | 6.11 | I
F13372+2614 | 56089-05999-0984 | 0.3446 | 12.48 | 0.0855 | 0.1219 | 0.2343 | 0.7195 | 1131 | 6 | 62 | 8.22 | 8.42 | II
F13403-0038 | 51671-00299-0098 | 0.3256 | 12.39 | 0.1110 | 0.2365 | 0.2094 | 0.6905 | 1131 | 11 | 66 |  |  | I
F13428+5608 | 52764-01321-0638 | 0.0373 | 12.16 | 0.2352 | 2.2820 | 21.7400 | 21.3800 | 3332 | 1 | 100 | 132.02 | 134.58 | II
F13443+0802 | 54152-01803-0567 | 0.1350 | 12.17 | 0.1187 | 0.2351 | 1.2990 | 1.9350 | 1132 | 2 | 63 | 10.09 |  | II
F13446+3727 | 53858-02101-0622 | 0.2147 | 12.06 | 0.1069 | 0.0761 | 0.3377 | 0.5906 | 1132 | 7 | 59 | 2.02 |  | II
F13451+1232 | 53142-01701-0483 | 0.1205 | 12.18 | 0.1433 | 0.6695 | 1.9160 | 2.0600 | 1232 | 2 | 95 | 4859.88 | 5251.91 | II
F13464+1828 | 56038-05444-0671 | 0.1795 | 12.11 | 0.0677 | 0.0803 | 0.4818 | 1.2120 | 1132 | 6 | 61 | 4.53 | 4.72 |
F13469+5833 | 52668-01158-0429 | 0.1575 | 12.29 | 0.0517 | 0.0719 | 1.2670 | 1.7340 | 1132 | 2 | 89 | 3.02 |  |
F13485+3739 | 53476-02033-0373 | 0.2478 | 12.27 | 0.1096 | 0.0859 | 0.3043 | 0.9397 | 1131 | 4 | 73 | 1.84 |  |
F13515+0317 | 52026-00530-0616 | 0.2786 | 12.22 | 0.1139 | 0.1471 | 0.2298 | 0.5912 | 1131 | 6 | 67 | 2.53 |  | II
F13531+2005 | 56045-05868-0682 | 0.3143 | 12.53 | 0.1264 | 0.1434 | 0.4244 | 0.7346 | 1131 | 8 | 79 | 4.07 |  |
F13539+2920 | 53854-02116-0051 | 0.1088 | 12.12 | 0.0872 | 0.1224 | 1.8320 | 2.7290 | 1232 | 3 | 90 | 10.70 | 11.09 | II
F13583+2343 | 54529-02784-0436 | 0.2160 | 12.05 | 0.1082 | 0.1498 | 0.3149 | 0.6056 | 1131 | 4 | 72 | 1.97 |  |
F14014+3718 | 53115-01642-0490 | 0.2105 | 12.10 | 0.1432 | 0.1364 | 0.3811 | 0.7066 | 1132 | 6 | 71 | 1.96 |  |
F14026+4341 | 53115-01467-0216 | 0.3229 | 12.71 | 0.1178 | 0.2854 | 0.6217 | 0.9936 | 2332 | 3 | 86 | 1.46 |  | I
F14041+0117 | 51616-00302-0403 | 0.2363 | 12.48 | 0.1648 | 0.3190 | 0.8956 | 0.8293 | 1231 | 4 | 84 | 9.19 | 13.93 | II
F14060+2919 | 53794-02126-0307 | 0.1167 | 12.13 | 0.0959 | 0.1442 | 1.6110 | 2.4170 | 1232 | 1 | 100 | 7.86 | 9.11 |
F14079+4025 | 56045-05169-0304 | 0.4546 | 12.83 | 0.1018 | 0.1375 | 0.3363 | 0.6586 | 1131 | 5 | 71 | 49.62 | 49.34 |
F14082+0205 | 51993-00532-0064 | 0.2011 | 12.07 | 0.0711 | 0.1076 | 0.3062 | 0.9522 | 1131 | 9 | 55 | 2.09 |  | I
F14088+0212 | 51993-00532-0080 | 0.2023 | 12.05 | 0.1076 | 0.2348 | 0.3842 | 0.6646 | 1132 | 8 | 61 | 1.02 |  |
F14143+1244 | 56011-05458-0342 | 0.3278 | 12.56 | 0.1377 | 0.2589 | 0.4287 | 0.6601 | 1131 | 11 | 72 | 5.46 |  | II
F14167+4247 | 53108-01394-0044 | 0.4203 | 12.70 | 0.0976 | 0.0925 | 0.3073 | 0.5710 | 1231 | 5 | 77 | 1.25 |  | I
F14170+4545 | 52728-01287-0193 | 0.1502 | 12.02 | 0.0498 | 0.0809 | 0.7000 | 1.2010 | 1132 | 2 | 86 | 5.86 |  |
F14202+2615 | 53819-02131-0280 | 0.1587 | 12.36 | 0.1834 | 0.1522 | 1.4920 | 1.9860 | 1232 | 2 | 98 | 8.31 |  |
F14204+4533 | 52728-01287-0144 | 0.1673 | 12.01 | 0.0831 | 0.1138 | 0.5255 | 0.9385 | 1132 | 1 | 100 | 7.87 | 7.26 |
F14225+1044 | 56000-05460-0199 | 0.4801 | 12.92 | 0.0486 | 0.2529 | 0.4063 | 0.5923 | 1132 | 3 | 89 | 3.76 |  |
F14229+1636 | 54506-02760-0220 | 0.1850 | 12.12 | 0.1020 | 0.2495 | 0.5385 | 0.9784 | 1132 | 4 | 85 | 2.44 |  |
F14248-0045 | 51613-00305-0079 | 0.1623 | 12.18 | 0.1165 | 0.3196 | 0.9107 | 1.2810 | 1132 | 2 | 96 | 3.51 |  |
F14290+1712 | 54534-02761-0235 | 0.2102 | 12.12 | 0.0514 | 0.1023 | 0.2859 | 1.0430 | 1131 | 5 | 68 | 1.76 |  |
F14305+0546 | 55682-04780-0710 | 0.2982 | 12.51 | 0.0934 | 0.1563 | 0.3058 | 1.1890 | 1131 | 2 | 89 | 9.79 | 9.19 | II
F14312+2825 | 53876-02134-0502 | 0.1748 | 12.22 | 0.1492 | 0.1035 | 0.7790 | 1.4110 | 1232 | 4 | 72 | 5.63 | 5.79 | II
F14315+2955 | 53917-02133-0019 | 0.5264 | 12.82 | 0.1269 | 0.1161 | 0.2020 | 0.5392 | 1131 | 9 | 66 |  |  | I
F14318-0252 | 52409-00919-0201 | 0.1865 | 12.11 | 0.0825 | 0.1827 | 0.3912 | 1.2390 | 1131 | 3 | 81 |  |  |
F14330+0141 | 52024-00536-0234 | 0.2325 | 12.16 | 0.1319 | 0.2227 | 0.3511 | 0.6480 | 1131 | 6 | 54 | 15.08 |  | II
F14379+5420 | 52668-01162-0095 | 0.2685 | 12.22 | 0.0645 | 0.0528 | 0.3328 | 0.4276 | 1132 | 4 | 70 | 1.93 |  |
F14390+6209 | 52368-00607-0625 | 0.2755 | 12.31 | 0.0595 | 0.0910 | 0.3153 | 0.6831 | 1131 | 4 | 77 | 2.86 |  | I
F14394+5332 | 52781-01327-0619 | 0.1050 | 12.08 | 0.0721 | 0.3464 | 1.9540 | 2.3950 | 1332 | 1 | 100 | 39.55 | 41.60 | II
F14401+6316 | 56447-06983-0612 | 0.2805 | 12.28 | 0.0657 | 0.0828 | 0.2666 | 0.6651 | 1131 | 3 | 82 | 7.93 |  | II
F14413+3730 | 53115-01382-0587 | 0.2598 | 12.20 | 0.0634 | 0.0679 | 0.3107 | 0.5328 | 1132 | 1 | 100 | 1.76 |  | II
F14424+1050 | 56011-05475-0494 | 0.4097 | 12.68 | 0.0690 | 0.1533 | 0.2765 | 0.6615 | 1131 | 9 | 54 | 4.63 |  | II
F14455+3507 | 53498-01646-0578 | 0.6624 | 13.10 | 0.0663 | 0.1049 | 0.2173 | 0.5833 | 1131 | 4 | 80 | 14.44 | 15.26 | I
F14481+4454 | 58171-08492-0889 | 0.6618 | 13.03 | 0.0764 | 0.0851 | 0.1897 | 0.5005 | 1231 | 7 | 86 | 11.06 | 11.26 | II
F14488+3521 | 53116-01383-0083 | 0.2057 | 12.30 | 0.0681 | 0.0928 | 0.6389 | 1.2120 | 1232 | 5 | 73 | 5.26 | 5.88 | II
F14501+0639 | 54560-01830-0380 | 0.2672 | 12.22 | 0.0493 | 0.1422 | 0.2917 | 0.5550 | 1131 | 6 | 63 | 291.60 | 289.40 | II
F14503+6006 | 56444-06982-0393 | 0.5748 | 12.91 | 0.0411 | 0.0788 | 0.2263 | 0.4721 | 1231 | 3 | 83 | 18.03 | 17.51 | II
F14513-0235 | 52380-00921-0139 | 0.2094 | 12.10 | 0.0851 | 0.1160 | 0.2545 | 1.0510 | 1131 | 6 | 56 | 1.19 |  |
F14538+1730 | 54535-02764-0521 | 0.1033 | 12.02 | 0.1012 | 0.1458 | 1.4420 | 3.0070 | 1132 | 4 | 82 | 12.68 | 11.50 | II
F14541+3813 | 58224-10748-0819 | 0.2833 | 12.01 | 0.0815 | 0.1295 | 0.1625 | 0.2905 | 1131 | 9 | 73 |  |  | I
F14541+4906 | 52736-01048-0505 | 0.2467 | 12.31 | 0.0825 | 0.1999 | 0.5303 | 0.5428 | 1332 | 2 | 85 | 6.35 | 6.64 | II
F14556+1328 | 56014-05478-0866 | 0.3341 | 12.48 | 0.0525 | 0.0596 | 0.2577 | 0.7606 | 1131 | 10 | 53 | 8.76 | 7.97 | II
F14560+5246 | 56390-06719-0072 | 0.6380 | 13.02 | 0.0532 | 0.0659 | 0.1560 | 0.6510 | 1131 | 8 | 52 | 2.07 |  | I
F14589+2340 | 54509-02149-0006 | 0.2578 | 12.08 | 0.0647 | 0.0845 | 0.1954 | 0.5151 | 1231 | 7 | 75 | 3.97 |  | I
F15001+1433 | 54535-02765-0287 | 0.1622 | 12.46 | 0.1220 | 0.1674 | 1.8710 | 2.0430 | 1232 | 2 | 98 | 16.74 | 14.85 |
F15002+4945 | 52767-01329-0103 | 0.3368 | 12.52 | 0.0533 | 0.0738 | 0.3952 | 0.5099 | 1232 | 5 | 80 | 3.09 |  |
F15004+0351 | 52055-00589-0197 | 0.2182 | 12.13 | 0.0876 | 0.0824 | 0.2327 | 1.0920 | 1131 | 9 | 53 | 2.10 |  |
F15043+5754 | 52056-00610-0060 | 0.1506 | 12.16 | 0.1221 | 0.0718 | 1.0190 | 1.5020 | 1232 | 2 | 90 | 2.64 | 2.31 |
F15069+1808 | 54556-02792-0089 | 0.1705 | 12.12 | 0.0914 | 0.1192 | 0.6851 | 1.0390 | 1232 | 3 | 91 | 11.87 | 11.40 | I
F15099+1521 | 54242-02766-0224 | 0.5007 | 12.82 | 0.0484 | 0.0691 | 0.1885 | 0.7123 | 1131 | 10 | 56 |  |  | I
F15101+5624 | 57894-08416-0020 | 0.2584 | 12.15 | 0.0467 | 0.0644 | 0.2450 | 0.5577 | 1132 | 2 | 59 |  |  |
F15104+3431 | 55691-04720-0744 | 0.8565 | 13.26 | 0.0576 | 0.0541 | 0.1893 | 0.4003 | 1132 | 6 | 51 |  |  | I
F15111+2458 | 53820-02155-0534 | 0.2200 | 12.19 | 0.0556 | 0.1732 | 0.5165 | 0.5627 | 1332 | 2 | 90 | 3.18 |  | II
F15206+3342 | 53118-01387-0458 | 0.1253 | 12.18 | 0.0812 | 0.3468 | 1.7670 | 1.8870 | 2332 | 1 | 100 | 9.96 |  |
F15206+3631 | 53470-01400-0254 | 0.1527 | 12.05 | 0.0629 | 0.0935 | 0.7706 | 1.0640 | 1232 | 2 | 91 | 4.82 | 4.61 | II
F15221+5619 | 54525-02883-0414 | 0.2438 | 12.02 | 0.0497 | 0.0706 | 0.2060 | 0.4726 | 1231 | 5 | 88 | 2.04 |  | II
F15225+2350 | 53878-02161-0373 | 0.1387 | 12.15 | 0.0686 | 0.1798 | 1.3000 | 1.4830 | 1332 | 2 | 89 | 5.53 | 6.38 |
F15239+4331 | 52468-01051-0123 | 0.3561 | 12.68 | 0.0481 | 0.0564 | 0.4869 | 0.6974 | 1132 | 1 | 100 | 6.85 |  |
F15261+5502 | 53437-00614-0213 | 0.2292 | 12.22 | 0.0478 | 0.0592 | 0.4616 | 0.6577 | 1232 | 1 | 100 | 1.50 |  |
F15320+0325 | 52026-00593-0145 | 0.2057 | 12.06 | 0.0715 | 0.0979 | 0.3285 | 0.7635 | 1132 | 8 | 65 | 2.95 | 3.85 | II
F15327+2340 | 53823-02163-0058 | 0.0184 | 12.22 | 0.4837 | 7.9070 | 103.8000 | 112.4000 | 3332 | 1 | 100 | 316.13 | 318.80 |
F15390+3913 | 53171-01680-0189 | 0.2394 | 12.02 | 0.0544 | 0.0786 | 0.1983 | 0.5398 | 1131 | 8 | 54 | 1.24 |  |
F15396+1715 | 54563-02795-0589 | 0.2570 | 12.12 | 0.0638 | 0.0931 | 0.2498 | 0.4837 | 1131 | 6 | 56 | 1.59 |  |
F15415+1633 | 55337-03932-0246 | 0.8483 | 13.36 | 0.0781 | 0.1170 | 0.2315 | 0.5459 | 1231 | 6 | 87 | 12.45 | 14.87 | I
F15432+3502 | 58223-10740-0291 | 0.5166 | 12.81 | 0.0509 | 0.0771 | 0.1787 | 0.6219 | 1131 | 8 | 65 | 15.93 | 17.68 | I
F15437+4647 | 52731-01168-0227 | 0.2284 | 12.05 | 0.0645 | 0.1076 | 0.2639 | 0.5625 | 1231 | 1 | 100 | 3.67 | 3.31 | II
F15438+0438 | 55679-04804-0808 | 0.2362 | 12.47 | 0.0649 | 0.1082 | 0.7833 | 1.0230 | 1132 | 3 | 81 | 6.54 |  | II
F15439+4855 | 57893-08429-0896 | 0.3997 | 12.58 | 0.0743 | 0.1082 | 0.2828 | 0.4475 | 1332 | 1 | 100 | 2.11 |  | I
F15453+1131 | 55737-04886-0146 | 0.2890 | 12.52 | 0.0519 | 0.1126 | 0.5145 | 0.8263 | 1132 | 5 | 54 | 7.51 |  | II
F15453+4316 | 56101-06042-0339 | 0.2973 | 12.41 | 0.0392 | 0.0567 | 0.3457 | 0.6949 | 1131 | 2 | 90 | 12.36 | 10.51 |
F15458+0041 | 51691-00342-0514 | 0.2524 | 12.05 | 0.0585 | 0.1265 | 0.1892 | 0.5158 | 1231 | 9 | 66 | 1.98 |  | II
F15478+5014 | 52401-00796-0022 | 0.1977 | 12.11 | 0.0520 | 0.0705 | 0.4178 | 0.9203 | 1132 | 3 | 86 | 2.44 |  |
F15496+0331 | 54592-02951-0294 | 0.1937 | 12.06 | 0.0837 | 0.1436 | 0.3519 | 0.9330 | 1231 | 7 | 74 | 29.37 |  | II
F15529+4545 | 52753-01169-0382 | 0.5164 | 12.81 | 0.0694 | 0.0548 | 0.2276 | 0.4863 | 1132 | 8 | 67 | 1.32 |  | I
F15531+2513 | 53786-01850-0565 | 0.1846 | 12.02 | 0.0601 | 0.0888 | 0.3025 | 1.1240 | 1131 | 8 | 53 |  |  |
F15554+5322 | 56799-07562-0403 | 0.5628 | 12.88 | 0.0532 | 0.0868 | 0.1820 | 0.5547 | 1131 | 3 | 86 | 8.78 | 7.35 | II
F15577+3816 | 52761-01055-0312 | 0.2181 | 12.14 | 0.0635 | 0.0829 | 0.4467 | 0.5607 | 1132 | 2 | 89 | 2.39 |  | II
F15583+4002 | 52516-01054-0072 | 0.2189 | 12.06 | 0.0901 | 0.1150 | 0.3149 | 0.6076 | 1231 | 3 | 91 | 2.02 |  |
F16006+0955 | 54582-02526-0302 | 0.1520 | 12.05 | 0.1176 | 0.1049 | 0.4826 | 1.8380 | 1131 | 3 | 89 | 3.89 |  |
F16019+0828 | 53858-01729-0457 | 0.2283 | 12.21 | 0.0860 | 0.0982 | 0.1959 | 1.3080 | 1131 | 6 | 50 |  |  |
F16048+1342 | 54568-02524-0064 | 0.2090 | 12.11 | 0.0570 | 0.0738 | 0.3835 | 0.7919 | 1132 | 3 | 57 |  |  | I
F16075+2838 | 53496-01578-0005 | 0.1696 | 12.16 | 0.0894 | 0.1064 | 0.8405 | 1.0060 | 1232 | 2 | 90 | 4.78 |  | II
F16098+2624 | 52824-01393-0113 | 0.1843 | 12.08 | 0.0705 | 0.0939 | 0.3054 | 1.4110 | 1131 | 7 | 52 | 1.61 |  |
F16109+1309 | 54569-02527-0172 | 0.1996 | 12.09 | 0.0805 | 0.0792 | 0.3166 | 1.0410 | 1131 | 3 | 83 | 1.84 |  |
F16122+1531 | 53918-02198-0475 | 0.3078 | 12.42 | 0.0541 | 0.1490 | 0.2671 | 0.8163 | 1231 | 7 | 81 | 20.27 | 23.13 | II
F16126+1953 | 53795-02206-0198 | 0.2529 | 12.27 | 0.0658 | 0.0980 | 0.3239 | 0.8370 | 1131 | 5 | 59 | 2.93 |  | II
F16133+2107 | 53566-01853-0227 | 0.0906 | 12.00 | 0.0827 | 0.1621 | 2.1640 | 2.9280 | 1332 | 1 | 100 | 11.24 |  | II
F16172+4432 | 57900-08525-0882 | 0.3351 | 12.41 | 0.0545 | 0.1131 | 0.2757 | 0.4972 | 1232 | 3 | 90 | 3.09 | 2.84 | I
F16184+5012 | 54526-02884-0145 | 0.2834 | 12.25 | 0.0638 | 0.0790 | 0.2685 | 0.5284 | 1132 | 5 | 74 | 2.35 |  | II
F16300+1558 | 53558-02207-0123 | 0.2418 | 12.77 | 0.0733 | 0.1240 | 1.4830 | 1.9900 | 1132 | 1 | 100 | 5.93 | 7.10 |
F16310+2254 | 53177-01572-0054 | 0.2217 | 12.06 | 0.1049 | 0.0710 | 0.2278 | 0.7851 | 1231 | 7 | 71 | 1.50 |  |
F16403+2537 | 53167-01423-0175 | 0.1602 | 12.04 | 0.0842 | 0.0584 | 0.3877 | 1.6780 | 1131 | 10 | 58 | 4.40 |  |
F16413+3954 | 56090-06038-0144 | 0.5934 | 13.39 | 0.1068 | 0.2918 | 0.5999 | 1.3840 | 3331 | 1 | 100 | 6598.19 | 6930.92 | I
F16533+6216 | 51695-00351-0329 | 0.1060 | 12.02 | 0.0588 | 0.1689 | 1.4800 | 2.5030 | 1322 | 2 | 94 | 14.43 | 16.26 |
F17040+6048 | 51703-00353-0377 | 0.3715 | 12.60 | 0.0700 | 0.1276 | 0.2959 | 0.6971 | 1311 | 1 | 100 |  |  | I
F17051+3824 | 52079-00633-0003 | 0.1683 | 12.23 | 0.0621 | 0.0788 | 0.9865 | 1.2060 | 1232 | 3 | 69 | 4.30 |  | II
F17081+3300 | 52426-00973-0039 | 0.2786 | 12.20 | 0.0722 | 0.0863 | 0.1956 | 0.6187 | 1132 | 7 | 66 |  |  | II
F17135+4153 | 58041-08545-0839 | 0.7274 | 13.34 | 0.0641 | 0.0526 | 0.2781 | 0.8838 | 1132 | 2 | 66 |  |  |
F17175+6603 | 51691-00350-0442 | 0.2926 | 12.25 | 0.0647 | 0.0478 | 0.2075 | 0.5919 | 1231 | 7 | 78 |  |  | I
F17234+6228 | 51694-00352-0082 | 0.2407 | 12.14 | 0.0435 | 0.0680 | 0.2587 | 0.6977 | 1131 | 2 | 95 | 1.93 |  | I
F20460-0035 | 52914-01115-0317 | 0.4327 | 12.82 | 0.1084 | 0.1045 | 0.3060 | 0.8955 | 1131 | 4 | 71 | 3.65 | 3.46 |
F20461+0043 | 52524-01022-0525 | 0.3487 | 12.82 | 0.0903 | 0.1166 | 0.3049 | 2.0140 | 1131 | 5 | 50 | 2.28 |  | II
F20522-0120 | 52443-00983-0044 | 0.1735 | 12.22 | 0.0527 | 0.1041 | 0.3907 | 2.4570 | 1131 | 10 | 54 |  |  |
F21292-0115 | 55450-04194-0246 | 0.3875 | 12.61 | 0.0720 | 0.1340 | 0.2586 | 0.6916 | 1131 | 6 | 76 | 4.41 |  | II
F21581-0053 | 55481-04199-0482 | 0.3566 | 12.66 | 0.1530 | 0.1350 | 0.3502 | 0.9194 | 1131 | 7 | 57 | 28.63 | 29.00 | II
F22032+0038 | 55481-04199-0750 | 0.2845 | 12.40 | 0.0802 | 0.1667 | 0.2154 | 1.1570 | 1131 | 11 | 67 | 3.52 | 4.52 | I
F22098-0748 | 52203-00719-0323 | 0.1427 | 12.00 | 0.0980 | 0.1693 | 0.7600 | 1.2240 | 1132 | 3 | 83 | 4.56 | 3.94 | II
F22288+1258 | 56187-05043-0287 | 0.1852 | 12.08 | 0.1500 | 0.1311 | 0.3195 | 1.3300 | 1131 | 4 | 60 |  |  | II
F22505+1704 | 56244-05033-0996 | 0.1786 | 12.30 | 0.0994 | 0.1415 | 0.5785 | 2.3600 | 1131 | 5 | 75 |  |  | II
F22559+0733 | 53710-02310-0458 | 0.3955 | 12.93 | 0.1211 | 0.2242 | 0.6066 | 1.1360 | 1231 | 7 | 69 | 27.70 | 33.04 | I
F23060+0505 | 55882-04414-0184 | 0.1728 | 12.26 | 0.1978 | 0.4258 | 1.1520 | 0.8329 | 3332 | 3 | 85 | 5.50 | 6.52 | II
F23233+2817 | 56537-06587-0910 | 0.1135 | 12.01 | 0.1287 | 0.2756 | 1.2620 | 2.1070 | 1332 | 4 | 84 |  | 34.76 | II

Note. — (1) Source name in the IRAS FSC92 catalog. (2) Mjd, plate, and fiberid
of the SDSS optical counterpart’s spectrum. (3) Spectroscopic redshift from
the SDSS pipeline. (4) Total infrared luminosity. (5-9) Observed flux
densities at 12 $\mu m$, 25 $\mu m$, 60 $\mu m$, 100 $\mu m$, and their
qualities from the IRAS survey. (10) Number of WISE counterparts within the
IRAS source’s positional uncertainty ellipse. (11) Flux ratio at the W4 band
of the optical counterpart to all WISE counterparts. (12-13) Radio flux
densities at 1.4 GHz from the FIRST and NVSS surveys. (14) Type I or Type II
AGNs.