title:
A Subaru/Suprime-Cam wide-field survey of globular cluster populations
  around M87 - I: Observation, data analysis, and luminosity function

abstract:
  In this paper and a companion paper, we report on a wide-field imaging survey
of the globular cluster (GC) populations around M87 carried out with
Suprime-Cam on the 8.2m Subaru telescope. Here we describe the observations,
data reduction, and data analysis and present luminosity functions of GC
populations around M87 and NGC 4552, another luminous Virgo elliptical in our
survey field. The imaging data were taken in the B, V, and I bands with a sky
coverage out to 0.5 Mpc from the M87 centre. GC candidates were selected by
applying a colour criterion on the B-V and V-I diagram to unresolved objects,
which greatly reduces contamination. The data from control fields taken with
Subaru/Suprime-Cam were also analyzed for subtraction of contamination in the
GC sample. We investigate GC luminosity functions (GCLFs) within 10' (~ 45 kpc)
from the host galaxy centre in detail. The V-band turnover magnitude (V_TO) is
estimated to be 23.62 +-0.06 mag and 23.56 +- 0.20 mag for the GC population in
M87 and NGC 4552, respectively. The GCLF is found to be a function of GC
colour; V_TO of the red GC subpopulation (V-I > 1.1) is fainter than that of
the blue GC subpopulation (V-I < 1.1) in both M87 and NGC 4552, as expected if
the colour differences are primarily due to a metallicity effect and the mass
functions of the two subpopulations are similar. The radial dependence of the
GCLF is also investigated for the GC population in M87. The GCLF of each
subpopulation at 1' < R < 5' is compared with that at 5' < R < 10' but no
significant trend with distance is found in the shape of the GCLF. We also
estimate GC specific frequencies (S_N) for M87 and NGC 4552. The S_N of the M87
GC population is estimated to be 12.5 +- 0.8 within 25'. The S_N value of the
NGC 4552 GC population is estimated to be 5.0 +- 0.6 within 10'.


title:
The Galaxy Mass Function up to z=4 in the GOODS-MUSIC sample: into the
  epoch of formation of massive galaxies

abstract:
  The goal of this work is to measure the evolution of the Galaxy Stellar Mass
Function and of the resulting Stellar Mass Density up to redshift ~4, in order
to study the assembly of massive galaxies in the high redshift Universe. We
have used the GOODS-MUSIC catalog, containing ~3000 Ks-selected galaxies with
multi-wavelength coverage extending from the U band to the Spitzer 8 micron
band, of which 27% have spectroscopic redshifts and the remaining fraction have
accurate photometric redshifts. On this sample we have applied a standard
fitting procedure to measure stellar masses. We compute the Galaxy Stellar Mass
Function and the resulting Stellar Mass Density up to redshift ~4, taking into
proper account the biases and incompleteness effects. Within the well known
trend of global decline of the Stellar Mass Density with redshift, we show that
the decline of the more massive galaxies may be described by an exponential
timescale of ~6 Gyrs up to z~1.5, and proceeds much faster thereafter, with an
exponential timescale of ~0.6 Gyrs. We also show that there is some evidence
for a differential evolution of the Galaxy Stellar Mass Function, with low mass
galaxies evolving faster than more massive ones up to z~1-1.5 and that the
Galaxy Stellar Mass Function remains remarkably flat (i.e. with a slope close
to the local one) up to z~1-1.3. The observed behaviour of the Galaxy Stellar
Mass Function is consistent with a scenario where about 50% of present-day
massive galaxies formed at a vigorous rate in the epoch between redshift 4 and
1.5, followed by a milder evolution until the present-day epoch.


title: Cryogenic tests of volume-phase holographic gratings: results at 100 K

abstract:
  We present results from cryogenic tests of Volume-Phase Holographic(VPH)
gratings at 100 K. The aims of these tests are to see whether the diffraction
efficiency as a function of wavelength is significantly different at a low
temperature from that at room temperature and to see how the performance of a
VPH grating is affected by a number of thermal cycles. We have completed 10
cycles between room temperature and 100 $K$, and find no clear evidence that
the diffraction efficiency changes with temperature or with successive thermal
cycle.


title:
A Subaru/Suprime-Cam wide-field survey of globular cluster populations
  around M87 - II: Colour and spatial distribution

abstract:
  We have performed a wide-field imaging survey of the globular cluster (GC)
populations around M87 out to a radius of ~ 0.5 Mpc with Suprime-Cam on the
8.2m Subaru Telescope. By investigating the GC colour distribution as a
function of distance from M87 and NGC 4552, another luminous Virgo elliptical
in our survey field, it is found that clear bimodality ((V-I)_peak ~ 1.0 and
1.2) is seen only in the inner regions (< 10 kpc) of the host galaxies and that
it becomes weaker with radius due to the decreasing contribution of the red GC
(V-I > 1.1) subpopulation. It is also found (both around M87 and NGC 4552) that
while the spatial distribution of the red GCs is as centrally concentrated as
the host galaxy halo light distribution, the distribution of the blue GCs (V-I
< 1.1) tends to be more extended. However, the blue GC distribution around M87
is not as extended as the Virgo cluster mass density profile. Based on these
facts, we argue that the contribution of GCs associated with the Virgo cluster
(e.g., intergalactic GCs) is not significant around M87 and is not the primary
reason for the high S_N value of M87. Instead, most of the blue GCs around
luminous ellipticals, as well as the red GCs, are presumed to be associated
with the host galaxy. We model the radial profile of GC surface densities out
to ~ 0.5 Mpc from M87 by a superposition of the GC populations associated with
M87 and with NGC 4552, suggesting the existence of an additional intergalactic
GC (i-GC) population independent of the luminous ellipticals. We obtain a crude
estimate of i-GC specific frequency S_N = 2.9 (+4.2, -1.5), which may indicate
the contribution of tidally captured GCs in the GC population of M87 is low to
be consistent with the high S_N value of M87.


title:
Radial variation of attenuation and star formation in the largest
  late-type disks observed with GALEX

abstract:
  For a sample of 43 nearby, late-type galaxies, we have investigated the
radial variation of both the current star formation rate and the dust-induced
UV light attenuation. To do this we have cross-correlated IRAS images and GALEX
observations for each of these galaxies, and compiled observations of the gas
(CO and HI) and metal-abundance gradients found in the literature. We find that
attenuation correlates with metallicity. We then use the UV profiles, corrected
for attenuation, to study several variants of the Schmidt law and conclude that
our results are compatible with a simple law similar to the one of Kennicutt
but extending smoothly to lower surface densities, but with considerable
scatter. We do not detect an abrupt break in the UV light at the threshold
radius derived from H-alpha data (at which the H-alpha profile shows a break
and beyond which only a few HII regions are usually found). We interpret the
H-alpha sudden break not as a change in the star formation regime (as often
suggested) but as the vanishingly small number of ionizing stars corresponding
to low levels of star formation.


title:
Indirect search for dark matter with AMS in positrons, gamma and
  antiprotons channels

abstract:
  The Alpha Magnetic Spectrometer (AMS), to be installed on the International
Space Station, will provide data on cosmic radiations in a large energy range.
The main physics goals in the astroparticle domain are the antimatter and the
dark matter searches. Dark matter should be composed of non baryonic weakly
interacting massive particles, a good candidate being the lightest SUSY
particle in R-parity conserving models. As a prototype for the AMS-02
experiment, the AMS-01 particle spectrometer was flown on the Space Shuttle
Discovery in near earth orbit for a ten day mission in June 1998. The direct
identification of positrons in AMS-01 was limited to energies below 3 GeV due
to the vast proton background and the characteristics of the subdetectors, but
the sensitivity towards higher energies (up to 40 GeV) was extended by
identifying positrons through the conversion of bremsstrahlung photons. AMS-02
will greatly improve the accuracy on the positron spectrum, which will be
measured up to 300 GeV, together with the antiproton and $\gamma$-ray flux,
thus providing a unique chance to measure all relevant neutralino decay
channels with the same experiment.


title:
A general relativistic model for the light propagation in the
  gravitational field of the Solar System: the dynamical case

abstract:
  Modern astrometry is based on angular measurements at the micro-arcsecond
level. At this accuracy a fully general relativistic treatment of the data
reduction is required. This paper concludes a series of articles dedicated to
the problem of relativistic light propagation, presenting the final
microarcsecond version of a relativistic astrometric model which enable us to
trace back the light path to its emitting source throughout the non-stationary
gravity field of the moving bodies in the Solar System. The previous model is
used as test-bed for numerical comparisons to the present one. Here we also
test different versions of the computer code implementing the model at
different levels of complexity to start exploring the best trade-off between
numerical efficiency and the micro-arcsecond accuracy needed to be reached.


title: On the stability of accelerating relativistic shock waves

abstract:
  We consider the corrugation instability of the self-similar flow with an
accelerating shock in the highly relativistic regime. We derive the correct
dispersion relation for the proper modes in the self-similar regime, and
conclude that this solution is unstable.


title: Baryon Acoustic Oscillations and Dynamical Dark Energy

abstract:
  We compute the impact of dark energy at last scattering on measurements of
baryon acoustic oscillations (BAOs). We show that an early dark energy
component can contribute a systematic uncertainty to BAO measurements of up to
2.5%. Whilst this effect turns out to only slightly affect current BAO surveys,
the results of future BAO surveys might become biased. We find that BAO surveys
alone appear unable to resolve this systematic uncertainty, so supplementary
measurements are necessary.


title: The Tully-Fisher relation for S0 galaxies

abstract:
  We present a study of the local B and K-band Tully-Fisher Relation (TFR)
between absolute magnitude and maximum circular speed in S0 galaxies. To make
this study, we have combined kinematic data, including a new high-quality
spectral data set from the Fornax Cluster, with homogeneous photometry from the
RC3 and 2MASS catalogues, to construct the largest sample of S0 galaxies ever
used in a study of the TFR. Independent of environment, S0 galaxies are found
to lie systematically below the TFR for nearby spirals in both optical and
infrared bands. This offset can be crudely interpreted as arising from the
luminosity evolution of spiral galaxies that have faded since ceasing star
formation. However, we also find a large scatter in the TFR. We show that most
of this scatter is intrinsic, not due to the observational uncertainties. The
presence of such a large scatter means that the population of S0 galaxies
cannot have formed exclusively by the above simple fading mechanism after all
transforming at a single epoch. To better understand the complexity of the
transformation mechanism, we have searched for correlations between the offset
from the TFR and other properties of the galaxies such as their structural
properties, central velocity dispersions and ages (as estimated from line
indices). For the Fornax Cluster data, the offset from the TFR relates with the
estimated age of the stars in the individual galaxies, in the sense and of the
magnitude expected if S0 galaxies had passively faded since being converted
from spirals. This correlation implies that a significant part of the scatter
in the TFR arises from the different times at which galaxies began their
transformation.


title:
A near zero velocity dispersion stellar component in the Canes Venatici
  dwarf spheroidal galaxy

abstract:
  We present a spectroscopic survey of the newly-discovered Canes Venatici
dwarf galaxy using the Keck/DEIMOS spectrograph. Two stellar populations of
distinct kinematics are found to be present in this galaxy: an extended,
metal-poor component, of half-light radius 7'.8(+2.4/-2.1), which has a
velocity dispersion of 13.9(+3.2/-2.5) km/s, and a more concentrated
(half-light radius 3'.6(+1.1/-0.8) metal-rich component of extremely low
velocity dispersion. At 99% confidence, the upper limit to the central velocity
dispersion of the metal-rich population is 1.9 km/s. This is the lowest
velocity dispersion ever measured in a galaxy. We perform a Jeans analysis on
the two components, and find that the dynamics of the structures can only be
consistent if we adopt extreme (and unlikely) values for the scale length and
velocity dispersion of the metal-poor population. With a larger radial velocity
sample and improved measurements of the density profile of the two populations,
we anticipate that it will be possible to place strong constraints on the
central distribution of the dark matter in this galaxy.


title: Five years of SGR 1900+14 observations with BeppoSAX

abstract:
  We present a systematic analysis of all the BeppoSAX data of the soft
gamma-ray repeater SGR 1900+14: these observations allowed us to study the long
term properties of the source quiescent emission. In the observation carried
out before the 1998 giant flare the spectrum in the 0.8-10 keV energy range was
harder and there was evidence for a 20-150 keV emission, possibly associated
with SGR 1900+14. This possible hard tail, if compared with the recent INTEGRAL
detection of SGR 1900+14, has a harder spectrum (power-law photon index ~1.6
versus ~3) and a 20-100 keV flux ~4 times larger. In the last BeppoSAX
observation (April 2002), while the source was entering the long quiescent
period that lasted until 2006, the 2-10 keV flux was ~25% below the historical
level. We also studied in detail the spectral evolution during the 2001 flare
afterglow. This was characterized by a softening that can be interpreted in
terms of a cooling blackbody-like component.


title:
The ACS Virgo Cluster Survey. XIV. Analysis of Color-Magnitude Relations
  in Globular Cluster Systems

abstract:
  We examine the correlation between globular cluster (GC) color and magnitude
using HST/ACS imaging for a sample of 79 early-type galaxies (-21.7<M_B<-15.2
mag) with accurate SBF distances from the ACS Virgo Cluster Survey. Using the
KMM mixture modeling algorithm, we find a highly significant correlation,
d(g-z)/dz = -0.037 +- 0.004, between color and magnitude for the subpopulation
of blue GCs in the co-added GC color-magnitude diagram of the three brightest
Virgo galaxies (M49, M87 and M60): brighter GCs are redder than their fainter
counterparts. For the single GC systems of M87 and M60, we find similar
correlations; M49 does not appear to show a significant trend. There is no
correlation between (g-z) and M_z for GCs of the red subpopulation. The
correlation d(g-z)/dg for the blue subpopulation is much weaker than d(g-z)/dz.
Using Monte Carlo simulations, we attribute this to the fact that the blue
subpopulation in M_g extends to higher luminosities than the red subpopulation,
which biases the KMM fits. The correlation between color and M_z thus is a real
effect. This conclusion is supported by biweight fits to the same color
distributions. We identify two environmental dependencies of the
color-magnitude relation: (1) the slope decreases in significance with
decreasing galaxy luminosity; and (2) the slope is stronger for GCs at smaller
galactocentric distances. We examine several mechanisms that might give rise to
the observed color-magnitude relation: (1) presence of contaminators; (2)
accretion of GCs from low-mass galaxies; (3) stochastic effects; (4) capture of
field stars by individual GCs; and (5) GC self-enrichment. We conclude that
self-enrichment and field-star capture, or a combination of these processes,
offer the most promising means of explaining our observations.


title:
RASS-SDSS Galaxy Cluster Survey. VI. The dependence of the cluster SFR
  on the cluster global properties

abstract:
  Using a subsample of 79 nearby clusters from the RASS-SDSS galaxy cluster
catalogue of Popesso et al. (2005a), we perform a regression analysis between
the cluster integrated star formation rate (Sigma_SFR) the cluster total
stellar mass (M_star), the fractions of star forming (f_SF) and blue (f_b)
galaxies and other cluster global properties, namely its richness (N_gal, i.e.
the total number of cluster members within the cluster virial radius), velocity
dispersion (sigma_v), virial mass (M_200), and X-ray luminosity (L_X). All
cluster global quantities are corrected for projection effects before the
analysis. Galaxy SFRs and stellar masses are taken from the catalog of
Brinchmann et al. (2004), which is based on SDSS spectra. We only consider
galaxies with M_r <= -20.25 in our analysis, and exclude AGNs. We find that
both Sigma_SFR and M_star are correlated with all the cluster global
quantities. A partial correlation analysis show that all the correlations are
induced by the fundamental one between Sigma_SFR and N_gal, hence there is no
evidence that the cluster properties affect the mean SFR or M_star per galaxy.
The relations between Sigma_SFR and M_star, on one side, and both N_gal and
M_200, on the other side, are linear, i.e. we see no evidence that different
clusters have different SFR or different M_star per galaxy and per unit mass.
The fraction f_SF does not depend on any cluster property considered, while f_b
does depend on L_X. We note that a significant fraction of star-forming cluster
galaxies are red (~25% of the whole cluster galaxy population). We conclude
that the global cluster properties are unable to affect the SF properties of
cluster galaxies, but the presence of the X-ray luminous intra-cluster medium
can affect their colors, perhaps through the ram-pressure stripping mechanism.


title: Probing the growth of supermassive black holes at z>6 with LOFAR

abstract:
  HII regions surrounding supermassive black holes (BHs) in an otherwise still
neutral intergalactic medium (IGM) are likely to be the most easily detectable
sources by future 21cm experiments like LOFAR. We have made predictions for the
size distribution of such HII regions for several physically motivated models
for BH growth at high redshift and compared this to the expected LOFAR
sensitivity to these sources. The number of potentially detectable HII regions
does not only depend on the ionisation state of the intergalactic medium and
the decoupling of the spin temperature of the neutral hydrogen from the cosmic
microwave background (CMB) temperature, but is also strongly sensitive to the
rate of growth of BHs at high redshift. If the supermassive BHs at redshift 6
were built up via continuous Eddington-limited accretion from low mass seed BHs
at high redshift, then LOFAR is not expected to detect isolated QSO HII regions
at redshifts much larger than 6, and only if the IGM is still significantly
neutral. If the high-redshift growth of BHs starts with massive seed BHs and is
driven by short-lived accretion events following the merging of BH hosting
galaxies then the detection of HII regions surrounding supermassive BHs may
extend to redshifts as large as 8-9 but is still very sensitive to the redshift
to which the IGM remains significantly neutral. The most optimistic predictions
are for a model where the supermassive BHs at z>6 have grown slowly. HII
regions around supermassive BHs may then be detected to significantly larger
redshifts.


title:
Further Evidence for Collimated Particle Beams from Pulsars, and
  Precession

abstract:
  We follow up on our (Radhakrishnan & Deshpande, 2001: RD01) radically
different interpretation of the observed structures and morphologies in the
x-ray observations of the nebulae around young pulsars (PWNe). In our general
model for PWNe (RD01), originally motivated by the Chandra observations of the
Vela X-ray nebula, the bright arcs, the jet-like feature and the diffuse
components in such nebulae can be explained together in detail, wherein the
arcs are understood as traces of the particle beams from the two magnetic poles
at the shock front. We consider this as important evidence for collimated
particle beams from pulsars' magnetic poles. In this paper, we discuss the
variability in the features in the Vela X-ray nebula observed by Pavlov et al.
(2003), and assess the relevance and implication of our model to the
observations on the Crab and other remnants. Our basic picture after
incorporating the signatures of free precession of the central compact object
can readily account for the variability and significant asymmetries, including
the bent jet-like features, in the observed morphologies. The implications of
these findings are discussed.


title: The Spitzer IRS view of V4334 Sgr (Sakurai's Object)

abstract:
  We present an observation of the very late thermal pulse object V4334 Sgr
(Sakurai's Object) with the Infrared Spectrometer (IRS) on the Spitzer Space
Telescope. The emission from 5-38 microns is dominated by the still-cooling
dust shell. A number of features are seen in absorption against the dust shell,
which we attribute to HCN and polyyne molecules. We use these features to
determine the 12C/13C ratio for the absorbing gas to be ~ 3.2 (+3.2,-1.6}; this
implies that, despite the H-content of the molecules, the hydrocarbon-bearing
gas must have originated in material produced in the very late thermal pulse.
We see no evidence of emission lines, despite the recently-reported optical and
radio observations that suggest the effective temperature of the stellar
remnant is rising.


title:
Looking for Mister Goodstar (A preliminary analysis of stars with S IV,
  V and VI wind lines)

abstract:
  The winds of stars with very specific temperatures and luminosities are ideal
for determining the magnitude and nature of mass loss in OB stars. I identify
these stars and analyze their wind lines. The results are discussed within the
context of recent findings which appear to indicate that the mass-loss rates of
OB stars may as much as an order of magnitude less than commonly accepted
values.


title: Measuring Omega_m using clusters evolution

abstract:
  The constraints obtained by several authors (Eke et al. 1998; Henry 2000) on
the estimated values of $\Omega_{\rm m}$, $n$ and $\sigma_8$ are revisited in
the light of recent theoretical developments: 1) new theoretical mass
functions; 2) a more accurate mass-temperature relation, also determined for
arbitrary $\Omega_{\rm m}$ and $\Omega_{\rm \Lambda}$. I re-derive the X-ray
Temperature Function (XTF), similarly to Henry (2000) and Eke et al. (1999),
re-obtaining the constraints on $\Omega_{\rm m}$, $n$, $\sigma_8$. The result
shows that changes in the mass function and M-T relation produces an increase
in $\Omega_{\rm m}$ of $ \simeq 20%$ and similar results in $\sigma_8$ and $n$.


title: Spectroscopy of planetary mass brown dwarfs in Orion

abstract:
  We report the results of near infrared spectroscopy of 11 luminosity selected
candidate planetary mass objects (PMOs) in the Trapezium Cluster with Gemini
South/GNIRS and Gemini North/NIRI. 6 have spectral types >=M9, in agreement
with expectations for PMOs. 2 have slightly earlier types, and 3 are much
earlier types which are probably field stars. 4/6 sources with types >= M9 have
pseudo-continuum profiles which confirm them as low gravity cluster members.
The gravity status of the other cool dwarfs is less clear but these remain
candidate PMOs. The derived number fraction of PMOs with M=3-15 Mjup is 1-14%,
these broad limits reflecting the uncertainty in source ages. However, the
number fraction with M<20 Mjup is at least 5%. These detections add
significantly to the body of evidence that a planetary mass population is
produced by the star formation process.


title:
Abundances of Baade's Window Giants from Keck/HIRES Spectra: II. The
  Alpha- and Light Odd Elements

abstract:
  We report detailed chemical abundance analysis of 27 RGB stars towards the
Galactic bulge in Baade's Window for elements produced by massive stars: O, Na,
Mg, Al, Si, Ca and Ti. All of these elements are overabundant in the bulge
relative to the disk, especially Mg, indicating that the bulge is enhanced in
Type~II supernova ejecta and most likely formed more rapidly than the disk. We
attribute a rapid decline of [O/Fe] to metallicity-dependent yields of oxygen
in massive stars, perhaps connected to the Wolf-Reyet phenomenon. he explosive
nucleosynthesis alphas, Si, Ca and Ti, possess identical trends with [Fe/H],
consistent with their putative common origin. We note that different behaviors
of hydrostatic and explosive alpha elements can be seen in the stellar
abundances of stars in Local Group dwarf galaxies. We also attribute the
decline of Si,Ca and Ti relative to Mg, to metallicity- dependent yields for
the explosive alpha elements from Type~II supernovae. The starkly smaller
scatter of [<SiCaTi>/Fe] with [Fe/H] in the bulge, as compared to the halo, is
consistent with expected efficient mixing for the bulge. The metal-poor bulge
[<SiCaTi>/Fe] ratios are higher than ~80% of the halo. If the bulge formed from
halo gas, the event occured before ~80% of the present-day halo was formed. The
lack of overlap between the thick and thin disk composition with the bulge does
not support the idea that the bulge was built by a thickening of the disk
driven by the bar. The trend of [Al/Fe] is very sensitive to the chemical
evolution environment. A comparison of the bulge, disk and Sgr dSph galaxy
shows a range of ~0.7 dex in [Al/Fe] at a given [Fe/H], presumably due to a
range of Type~II/Type~Ia supernova ratios in these systems.


title:
Off-center ignition in type Ia supernova: I. Initial evolution and
  implications for delayed detonation

abstract:
  The explosion of a carbon-oxygen white dwarf as a Type Ia supernova is known
to be sensitive to the manner in which the burning is ignited. Studies of the
pre-supernova evolution suggest asymmetric, off-center ignition, and here we
explore its consequences in two- and three-dimensional simulations. Compared
with centrally ignited models, one-sided ignitions initially burn less and
release less energy. For the distributions of ignition points studied, ignition
within two hemispheres typically leads to the unbinding of the white dwarf,
while ignition within a small fraction of one hemisphere does not. We also
examine the spreading of the blast over the surface of the white dwarf that
occurs as the first plumes of burning erupt from the star. In particular, our
studies test whether the collision of strong compressional waves can trigger a
detonation on the far side of the star as has been suggested by Plewa et al.
(2004). The maximum temperature reached in these collisions is sensitive to how
much burning and expansion has already gone on, and to the dimensionality of
the calculation. Though detonations are sometimes observed in 2D models, none
ever happens in the corresponding 3D calculations. Collisions between the
expansion fronts of multiple bubbles also seem, in the usual case, unable to
ignite a detonation. "Gravitationally confined detonation" is therefore not a
robust mechanism for the explosion. Detonation may still be possible in these
models however, either following a pulsation or by spontaneous detonation if
the turbulent energy is high enough.


title:
The quest for Type 2 quasars: Chandra observations of luminous obscured
  quasars in the Sloan Digital Sky Survey

abstract:
  We report on new Chandra exploratory observations of six candidate Type 2
quasars at z=0.49-0.73 selected among the most [OIII] luminous emitters from
the Sloan Digital Sky Survey (SDSS). Under the assumption that [OIII] is a
proxy for the intrinsic luminosity of the central source, their predicted
rest-frame X-ray luminosities are L(2-10keV)~10^45 erg/s. For two of the
targets, the photon statistics are good enough to allow for basic X-ray
spectral analyses, which indicate the presence of intrinsic absorption
(~10^{22-23} cm^-2) and luminous X-ray emission (L_X>10^44 erg/s). Of the
remaining four targets, two are detected with only a few (3-6) X-ray counts,
and two are undetected by Chandra. If these four sources have the large
intrinsic X-ray luminosities predicted by the [OIII] emission, then their
nuclei must be heavily obscured (N_H>few 10^23 cm^-2) and some might be Compton
thick (N_H>1.5 10^24 cm^-2). We also present the results for two Type 2 quasar
candidates serendipitously lying in the fields of the Chandra targets, and
provide an up-to-date compilation of the X-ray properties of eight additional
SDSS Type 2 quasars from archival Chandra and XMM-Newton observations (five
with moderate-quality X-ray data). The combined sample of 16 SDSS Type 2
quasars (10 X-ray detections) provides further evidence that a considerable
fraction of optically selected Type 2 quasars are obscured in the X-ray band
(at least all the objects with moderate-quality X-ray spectra), lending further
support to the findings presented in Vignali, Alexander and Comastri (2004a)
and unification schemes of Active Galactic Nuclei, and confirms the reliability
of [OIII] emission in predicting the X-ray emission in obscured quasars.


title:
A Survey of Galaxy Kinematics to z ~ 1 in the TKRS/GOODS-N Field. I.
  Rotation and Dispersion Properties

abstract:
  We present kinematic measurements of a large sample of galaxies from the TKRS
Survey in the GOODS-N field. We measure line-of-sight velocity dispersions from
integrated emission for 1089 galaxies with median z=0.637, and spatially
resolved kinematics for a subsample of 380 galaxies. This is the largest sample
of galaxies to z ~ 1 with kinematics to date, and allows us to measure
kinematic properties without morphological pre-selection. Emission linewidths
provide kinematics for the bulk of blue galaxies. To fit the spatially resolved
kinematics, we fit models with both line-of-sight rotation amplitude and
velocity dispersion. Integrated linewidth correlates well with a combination of
the rotation gradient and dispersion, and is a robust measure of galaxy
kinematics. The spatial extents of emission and continuum are similar and there
is no evidence that linewidths are affected by nuclear or clumpy emission. The
measured rotation gradient depends strongly on slit PA alignment with galaxy
major axis, but integrated linewidth does not. Even for galaxies with
well-aligned slits, some have kinematics dominated by dispersion (V/sigma<1)
rather than rotation. These are probably objects with disordered velocity
fields, not dynamically hot stellar systems. About 35% of the resolved sample
are dispersion dominated; galaxies that are both dispersion dominated and
bright exist at high redshift but appear rare at low redshift. This kinematic
morphology is linked to photometric morphology in HST/ACS images: dispersion
dominated galaxies include a higher fraction of irregulars and chain galaxies,
while rotation dominated galaxies are mostly disks and irregulars. Only
one-third of chain/hyphen galaxies are dominated by rotation; high-z elongated
objects cannot be assumed to be inclined disks. (Abridged)


title:
A Survey of Galaxy Kinematics to z ~ 1 in the TKRS/GOODS-N Field. II.
  Evolution in the Tully-Fisher Relation

abstract:
  We use kinematic measurements of a large sample of galaxies from the Team
Keck Redshift Survey in the GOODS-N field to measure evolution in the optical
and near-IR Tully-Fisher relations to z = 1.2. We construct Tully-Fisher
relations with integrated line-of-sight velocity widths of ~ 1000 galaxies in B
and ~ 670 in J-band; these relations have large scatter, and we derive a
maximum-likelihood least squares method for fitting in the presence of scatter.
The B-band Tully-Fisher relations, from z=0.4 to z=1.2, show evolution of ~
1.0-1.5 mag internal to our sample without requiring calibration to a local TF
relation. There is evolution in both Tully-Fisher intercept and slope,
suggesting differential luminosity evolution. In J-band, there is evolution in
slope but little evolution in overall luminosity. The slope measurements imply
that bright, massive blue galaxies fade {\it more strongly} than fainter blue
galaxies from z ~ 1.2 to now. This conclusion runs counter to some previous
measurements and to our naive expectations, but we present a simple set of star
formation histories to show that it arises naturally if massive galaxies have
shorter timescales of star formation, forming most of their stars before z ~ 1,
while less massive galaxies form stars at more slowly declining rates. This
model predicts that the higher global star formation rate at z ~ 1 is mostly
due to higher SFR in massive galaxies. The amount of fading in B-band
constrains star formation timescale more strongly than redshift of formation.
Tully-Fisher and color-magnitude relations can provide global constraints on
the luminosity evolution and star formation history of blue galaxies.


title: Observational Limits on X-ray Bursts from RRAT J1911+00

abstract:
  (abridged) The high radio-flux brightness temperature of the recently
discovered class of sources known as Rotating RAdio Transients (RRATs)
motivates detailed study in the X-ray band. We describe analyses of historical
X-ray data, searching for X-ray phenomena (sources, behaviors), finding no
sources or behaviors which may unequivocally be associated with RRAT J1911+00.
We put forward a candidate X-ray counterpart to RRAT J1911+00, discovered in a
Chandra observation in Feb 2001, which fades by a factor >5 prior to April
2004. The X-ray flux and optical (F_X/F_R>12) and near infra-red (F_X/F_J>35)
limits, as well as the X-ray flux itself, are consistent with an AGN origin,
unrelated to RRAT J1911+00. Searches for msec X-ray bursts found no evidence
for such a signal, and we place the first observational upper-limit on the
X-ray to radio flux ratio of RRAT bursts: F_X/F_{radio} <6e-11 ergs cm-2 s-1
mJy-1. The upper-limit on the X-ray burst flux (corresponding to <2.2e37 (d/3.3
kpc)^2 erg s-1, 2-10 keV) requires a limit on the spectral energy density
power-law slope of \alpha<-0.3 between the radio and X-ray bands. We place a
limit on the time-average X-ray burst luminosity, associated with radio bursts,
of < 3.4e30 (d/3.3 kpc)^2 erg s-1.


title:
Evolution of black-hole intermediate-mass X-ray binaries: the influence
  of a circumbinary disc

abstract:
  Justham, Rappaport & Podsiadlowski (2006) recently suggested that black-hole
low-mass X-ray binaries (BHLMXBs) with short orbital periods may have evolved
from black-hole intermediate-mass X-ray binaries (BHIMXBs). In their model the
secondaries in BHIMXBs are assumed to possess anomalously high magnetic fields,
so that magnetic braking can lead to substantial loss of angular momentum. In
this paper we propose an alternative mechanism for orbital angular momentum
loss in BHIMXBs. We assume that a small fraction $\delta$ of the transferred
mass from the donor star form a circumbinary disc surrounding the binary
system. The tidal torques exerted by the disc can effectively drain orbital
angular momentum from the binary. We have numerically calculated the
evolutionary sequences of BHIMXBs, to examine the influence of the circumbinary
disc on the binary evolution. Our results indicate when $\delta\la 0.01-0.1$
(depending on the initial orbital periods), the circumbinary disc can cause
secular orbital shrinking, leading to the formation of compact
  BHLMXBs, otherwise the orbits always expand during the evolution. This
scenario also suggests the possible existence of luminous, persistent BHLMXBs,
but it suffers the same problem as in Justham, Rappaport & Podsiadlowski (2006)
that, the predicted effective temperatures of the donor stars are significantly
higher than those of the observed donor stars in BHLMXBs.


title:
On class visualisation for high dimensional data: Exploring scientific
  datasets

abstract:
  Parametric Embedding (PE) has recently been proposed as a general-purpose
algorithm for class visualisation. It takes class posteriors produced by a
mixture-based clustering algorithm and projects them in 2D for visualisation.
However, although this fully modularised combination of objectives (clustering
and projection) is attractive for its conceptual simplicity, in the case of
high dimensional data, we show that a more optimal combination of these
objectives can be achieved by integrating them both into a consistent
probabilistic model. In this way, the projection step will fulfil a role of
regularisation, guarding against the curse of dimensionality. As a result, the
tradeoff between clustering and visualisation turns out to enhance the
predictive abilities of the overall model. We present results on both synthetic
data and two real-world high-dimensional data sets: observed spectra of
early-type galaxies and gene expression arrays.


title: Blending in Future Space-based Microlensing Surveys

abstract:
  We investigate the effect of blending in future gravitational microlensing
surveys by carrying out simulation of Galactic bulge microlensing events to be
detected from a proposed space-based lensing survey. From this simulation, we
find that the contribution of the flux from background stars to the total
blended flux will be equivalent to that from the lens itself despite the
greatly improved resolution from space observations, implying that
characterizing lenses from the analysis of the blended flux would not be easy.
As a method to isolate events for which most of the blended flux is
attributable to the lens, we propose to use astrometric information of source
star image centroid motion. For the sample of events obtained by imposing a
criterion that the centroid shift should be less than three times of the
astrometric uncertainty among the events for which blending is noticed with
blended light fractions $f_{\rm B}>0.2$, we estimate that the contamination of
the blended flux by background stars will be less than 20% for most ($\sim
90%$) of the sample events. The expected rate of these events is $\gtrsim 700$
events/yr, which is large enough for the statistical analysis of the lens
populations.


title: Dynamical Effects of CDM Subhalos on a Galactic Disk

abstract:
  We investigate the dynamical interaction between a galactic disk and
surrounding numerous dark subhalos as expected for a galaxy-sized halo in the
cold dark matter (CDM) models. Our particular interest is to what extent
accretion events of subhalos into a disk are allowed in light of the observed
thinness of a disk. Several models of subhalos are considered in terms of their
internal density distribution, mass function, and spatial and velocity
distributions. Based on a series of N-body simulations, we find that the disk
thickening quantified by the change of its scale height, Delta z_d, depends
strongly on the individual mass of an interacting subhalo M_{sub}. This is
described by the relation, Delta z_d / R_d = 8 Sum_{j=1}^N (M_{sub,j}/M_d)**2,
where R_d is a disk scale length, M_d is a disk mass, and N is the total number
of accretion events of subhalos inside a disk region (< 3R_d). Using this
relation, we find that an observed thin disk has not ever interacted with
subhalos with the total mass of more than 15% disk mass. Also, a less massive
disk with smaller circular velocity V_c is more affected by subhalos than a
disk with larger V_c, in agreement with the observation. Further implications
of our results for the origin of a thick disk component are also discussed.


title: The anomalous Cepheid XZ Ceti

abstract:
  XZ Ceti is the only known anomalous Cepheid in the Galactic field. Being the
nearest and brightest such variable star, a detailed study of XZ Ceti may shed
light on the behaviour of anomalous Cepheids whose representatives have been
mostly detected in external galaxies. CCD photometric and radial velocity
observations have been obtained. The actual period and amplitude of pulsation
were determined by Fourier analysis. The long time scale behaviour of the
pulsation period was studied by the method of the O-C diagram using the
archival Harvard photographic plates and published photometric data. XZ Ceti
differs from the ordinary classical Cepheids in several respects. Its most
peculiar feature is cycle-to-cycle variability of the light curve. The radial
velocity phase curve is not stable either. The pulsation period is subjected to
strong changes on various time scales including a very short one. The ratio of
amplitudes determined from the photometric and radial velocity observations
indicates that this Cepheid performs an overtone pulsation, in accord with the
other known anomalous Cepheid in our Galaxy, BL Boo (V19 in the globular
cluster NGC 5466). Continued observations are necessary to study the deviations
from regularity, to determine their time scale, as well as to confirm binarity
of XZ Ceti and to study its role in the observed peculiar behaviour.


title:
From nuclear clusters to halo globulars: Star clusters as basic galactic
  building blocks

abstract:
  I assess the similarities and differences between the star-formation modes in
quiescent spiral galaxies versus those in violent starburst regions, including
galactic nuclei. As opposed to the quiescent star-formation mode, current
empirical evidence on the star-formation processes in the extreme,
high-pressure environments induced by galaxy encounters strongly suggests that
star cluster formation is an important and perhaps even the dominant mode of
star formation in such starburst events. This implies that by using star
clusters as unique diagnostic probes, we can trace a galaxy's most violent star
formation history very well, at least for the past few Gyr. The sizes,
luminosities, and mass estimates of the young massive star clusters are
entirely consistent with what is expected for young Milky Way-type globular
clusters (GCs). Recent evidence lends support to the scenario that GCs, which
were once thought to be the oldest building blocks of galaxies, are still
forming today.


title: Is Dark Energy Abnormally Weighting?

abstract:
  We present a new interpretation of dark energy in terms of an
\textit{Abnormally Weighting Energy} (AWE). This means that dark energy does
not couple to gravitation in the same way as ordinary matter, yielding a
violation of the weak and strong equivalence principles on cosmological scales.
The resulting cosmological mechanism accounts for the Hubble diagram of type Ia
supernovae in terms of both cosmic acceleration and variation of the
gravitational constant while still accounting for the present tests of general
relativity. This explanation allows to build dark energy models (i) without
violation of the strong energy condition $p<-\rho c^2/3$ (ii) with
non-negligible direct couplings to gravitation and (iii) natural convergence
mechanism toward general relativity.


title: On the Average Comoving Number Density of Halos

abstract:
  I compare the numerical multiplicity function given in Yahagi, Nagashima &
Yoshii (2004) with the theoretical multiplicity function obtained by means of
the excursion set model and an improved version of the barrier shape obtained
in Del Popolo & Gambera (1998), which implicitly takes account of total angular
momentum acquired by the proto-structure during evolution and of a non-zero
cosmological constant. I show that the multiplicity function obtained in the
present paper, is in better agreement with Yahagi, Nagashima & Yoshii (2004)
simulations than other previous models (Sheth & Tormen 1999; Sheth, Mo & Tormen
2001; Sheth & Tormen 2002; Jenkins et al. 2001) and that differently from some
previous multiplicity function models (Jenkins et al. 2001; Yahagi, Nagashima &
Yoshii 2004) it was obtained from a sound theoretical background.


title: Evolution of the cosmological mass function in a moving barrier model

abstract:
  I calculate the mass function evolution in a $\Lambda$CDM model by means of
the excursion set model and an improved version of the barrier shape obtained
in Del Popolo & Gambera (1998), which implicitly takes account of the total
angular momentum acquired by the proto-structure during evolution and of a
non-zero cosmological constant. I compare the result with Reed et al. (2003),
who used a high resolution $\Lambda$CDM numerical simulation to calculate the
mass function of dark matter haloes down to the scale of dwarf galaxies, back
to a redshift of fifteen. I show that the mass function obtained in the present
paper, gives similar predictions to the Sheth & Tormen mass function but it
does not show the overprediction of extremely rare objects shown by the Sheth
and Tormen mass function. The results confirm previous findings that the
simulated halo mass function can be described solely by the variance of the
mass distribution, and thus has no explicit redshift dependence.


title: X-ray and HeI 1.0830 mu emission from protostellar jets

abstract:
  Context. The high energies of protostellar jets, implied by recent
observations of X-rays from such flows, came very much as a surprise. Inferred
shock velocities are considerably higher than what was previously known, hence
putting even larger energy demands on the driving sources of the jets. The
statistics of X-ray emitting jets are still poor, yet a few cases exist which
seem to imply a correlation between the presence of HeI 1.0830 mu emission and
X-ray radiation in a given source. Aims. This tentative correlation needs
confirmation and explanation. If the jet regions of HeI 1.0830 mu emission are
closely associated with those producing X-rays, high resolution infared
spectroscopy can be used to observationally study the velocity fields in the
hot plasma regions of the jets. This would provide the necessary evidence to
test and further develop theoretical models of intermediately fast (> 500 -
1500 km/s) interstellar shock waves. Methods. The HH 154 jet flow from the
embedded protostellar binary L 1551 IRS 5 provides a case study, since adequate
IR and X-ray spectroscopic data are in existence. The thermal X-ray spectrum is
fed into a photoionization code to compute, in particular, the line emission of
HeI and HI and to account for the observed unusual line intensity ratios.
Results. The advanced model is capable of accounting for most observables, but
shows also major weaknesses. It seems not unlikely that these could, in
principle, be overcome by a time dependent hydrodynamical calculation with
self-consistent cooling. However, such sophisticated model development is
decisively beyond the scope of the present work. Conclusions. Continued X-ray
observations, coordinated with simultaneous high resolution infrared
spectroscopy, are highly desirable.


title: The role of tidal forces in star cluster disruption

abstract:
  Star clusters are subject to density irregularities in their host galaxy,
such as giant molecular clouds (GMCs), the galactic disc and spiral arms, which
are largely ignored in present day (N-body) simulations of cluster evolution.
Time dependent external potentials give rise to tidal forces that accelerate
stars leading to an expansion and more rapid dissolution of the cluster. I
explain the basic principles of this tidal heating in the impulse approximation
and show how related disruption time-scales depend on properties of the
cluster.


title:
The Virgo stellar over-density: Mapping the infall of the Sagittarius
  tidal stream onto the Milky Way disk

abstract:
  The recently discovered Virgo stellar over-density, which expands over
\~1000deg^2 perpendicularly to the Galactic disk plane (7< Z <15 kpc, R~7 kpc),
is the largest clump of tidal debris ever detected in the outer halo and is
likely related with the accretion of a nearby dwarf galaxy by the Milky Way. We
carry out N-body simulations of the Sagittarius stream to show that this giant
stellar over-density is a confirmation of theoretical model predictions for the
leading tail of the Sagittarius stream to cross the Milky Way plane in the
Solar neighborhood. Radial velocity measurements are needed to confirm this
association and to further constrain the shape of the Milky Way dark matter
halo through a new generation of theoretical models. If the identification of
Virgo over-density and the Sagittarius leading arm is correct, we predict
highly negative radial velocities for the stars of Virgo over-density. The
detection of this new portion of the Sagittarius tidal stream would represent
an excellent target for the on-going and future kinematic surveys and for dark
matter direct detection experiments in the proximity of the Sun.


title:
Self-gravitational Magnetohydrodynamics with Adaptive Mesh Refinement
  for Protostellar Collapse

abstract:
  A new numerical code, called SFUMATO, for solving self-gravitational
magnetohydrodynamics (MHD) problems using adaptive mesh refinement (AMR) is
presented. A block-structured grid is adopted as the grid of the AMR hierarchy.
The total variation diminishing (TVD) cell-centered scheme is adopted as the
MHD solver, with hyperbolic cleaning of divergence error of the magnetic field
also implemented. The self-gravity is solved by a multigrid method composed of
(1) full multigrid (FMG)-cycle on the AMR hierarchical grids, (2) V-cycle on
these grids, and (3) FMG-cycle on the base grid. The multigrid method exhibits
spatial second-order accuracy, fast convergence, and scalability. The numerical
fluxes are conserved by using a refluxing procedure in both the MHD solver and
the multigrid method. The several tests are performed indicating that the
solutions are consistent with previously published results.


title: Lithium and zirconium abundances in massive Galactic O-rich AGB stars

abstract:
  Lithium and zirconium abundances (the latter taken as representative for
s-process enrichment) are determined for a large sample of massive Galactic
O-rich AGB stars, for which high resolution optical spectroscopy has been
obtained (R=40,000-50,000). This is done by computing synthetic spectra based
on classical hydrostatic model atmospheres for cool stars using extensive line
lists. The results obtained are discussed in the framework of hot bottom
burning (HBB) and nucleosynthesis models. The complete sample is studied
attending to various observational properties such as the position of the stars
in the IRAS two-colour diagram ([12]-[25] vs [25]-[60]), Galactic distribution,
expansion velocity (derived from the OH maser emission) and period of
variability (when available). We conclude that a considerable fraction of the
sources observed are actually massive AGB stars (M > 3-4 solar masses)
experiencing HBB, as deduced from the strong Li overabundances found. A
comparison of our results with similar studies carried out in the past for the
Magellanic Clouds (MCs) reveals that, in contrast to MC AGB stars, our Galactic
sample does not show any indication of s-process element enrichment. The
differences observed are explained as a consequence of metallicity effects.
Finally, we discuss the results obtained in the framework of stellar evolution
by comparing our results with the data available in the literature for Galactic
post-AGB stars and PNe.


title:
First results of the XI Groups Project: Studying an unbiased sample of
  galaxy groups

abstract:
  X-ray observations of hot, intergalactic gas in galaxy groups provide a
useful means of characterizing the global properties of groups. However, X-ray
studies of large group samples have typically involved very shallow X-ray
exposures or have been based on rather heterogeneous samples. Here we present
the first results of the XI (XMM/IMACS) Groups Project, a study targeting, for
the first time, a redshift-selected, statistically unbiased sample of galaxy
groups using deep X-ray data. Combining this with radio observations of cold
gas and optical imaging and spectroscopy of the galaxy population, the project
aims to advance the understanding of how the properties and dynamics of group
galaxies relate to global group properties. Here, X-ray and optical data of the
first four galaxy groups observed as part of the project are presented. In two
of the groups we detect diffuse emission with a luminosity of L_X ~ 10^41
erg/s, among the lowest found for any X-ray detected group thus far, with a
comparable upper limit for the other two. Compared to typical X-ray selected
groups of similar velocity dispersion, these four systems are all surprisingly
X-ray faint. We discuss possible explanations for the lack of significant X-ray
emission in the groups, concluding that these systems are most likely
collapsing for the first time. Our results strongly suggest that, unlike our
current optically selected sample, previous X-ray selected group samples
represented a biased picture of the group population. This underlines the
necessity of a study of this kind, if one is to reach an unbiased census of the
properties of galaxy groups and the distribution of baryons in the Universe.


title:
Evershed clouds as precursors of moving magnetic features around
  sunspots

abstract:
  The relation between the Evershed flow and moving magnetic features (MMFs) is
studied using high-cadence, simultaneous spectropolarimetric measurements of a
sunspot in visible (630.2 nm) and near-infrared (1565 nm) lines. Doppler
velocities, magnetograms, and total linear polarization maps are calculated
from the observed Stokes profiles. We follow the temporal evolution of two
Evershed clouds that move radially outward along the same penumbral filament.
Eventually, the clouds cross the visible border of the spot and enter the moat
region, where they become MMFs. The flux patch farther from the sunspot has the
same polarity of the spot, while the MMF closer to it has opposite polarity and
exhibits abnormal circular polarization profiles. Our results provide strong
evidence that at least some MMFs are the continuation of the penumbral Evershed
flow into the moat. This, in turn, suggests that MMFs are magnetically
connected to sunspots.


title: Minivoids in the Local Volume

abstract:
  We consider a sphere of 7.5 Mpc radius, which contains 355 galaxies with
accurately measured distances, to detect the nearest empty volumes. Using a
simple void detection algorithm, we found six large (mini)voids in Aquila,
Eridanus, Leo, Vela, Cepheus and Octans, each of more than 30 Mpc^3. Besides
them, 24 middle-size "bubbles" of more than 5 Mpc^3 volume are detected, as
well as 52 small "pores". The six largest minivoids occupy 58% of the
considered volume. Addition of the bubbles and pores to them increases the
total empty volume up to 75% and 81%, respectively. The detected local voids
look like oblong potatoes with typical axial ratios b/a = 0.75 and c/a = 0.62
(in the triaxial ellipsoide approximation). Being arranged by the size of their
volume, local voids follow power law of volumes-rankes dependence. A
correlation Gamma-function of the Local Volume galaxies follows a power low
with a formally calculated fractal dimension D = 1.5. We found that galaxies
surrounding the local minivoids do not differ significantly from other nearby
galaxies on their luminosity, but have appreciably higher hydrogen
mass-to-luminosity ratio and also higher star formation rate. We recognize an
effect of local expansion of typical minivoid to be \Delta H/H_0~(25+-15)%.


title:
Asteroids as radial velocity and resolving power standards for medium
  and high resolution spectroscopy

abstract:
  Echelle spectra of 10 bright asteroids are presented and compared against an
observed twilight spectrum and a computed Solar spectrum. Spectra covering a
2130 A spectral range centered on 5785 A are of high resolving power and high
signal to noise ratio. So we focus on a comparison of detailed properties of
spectral lines and not on albedo variations. It is shown that the normalized
Solar and asteroid spectra are identical except for radial velocity (RV) shifts
which can be predicted at the accuracy level of 1 m/s. So asteroids are
proposed as new and extremely accurate radial velocity standards. Predicted and
measured RVs of observed asteroids indeed match within limits of accuracy of
the instrument. There are numerous absorption lines in the reflected Solar
spectrum. This allows a direct mapping of the resolving power of a spectrograph
between and along echelle spectral orders. So asteroid spectra can be used to
test wavelength calibration and resolving power of spectrographs on the ground
as well as in space, including the Gaia mission of ESA. All spectra are also
given in an electronic form.


title: Line formation regions of the UV spectrum of CI Cygni

abstract:
  We have examined radial velocities and fluxes of ultraviolet emission lines
at different epochs, deduced from archival IUE and GRHS/HST spectra. The line
fluxes give electron densities and were in addition used to calculate emission
measures, suggesting line formation in regions rather smaller than the binary
separation. Examination of the radial velocities led to us to find a systematic
redshift of the high ionization resonance lines with respect to the
intercombination, and HeII lines. Possible explanations of the redshift and the
high resolution GHRS CIV profile are discussed. We favour that involving
resonance line absorption by a circum-binary region most probably in an
asymmetric wind interaction shell or in a wind from the accretion disk.


title: Turning AGN Microlensing From a Curiosity Into a Tool

abstract:
  Microlensing of gravitationally lensed quasars by the stars in the foreground
lens galaxy can be used to probe the nature of dark matter, to determine the
mean stellar mass in the lens galaxy, and to measure the internal structure of
quasar accretion disks. Until recently, little progress has been made toward
using microlensing for these purposes because of the difficulty in obtaining
the necessary data and the lack of good analysis methods. In the last few
years, both problems have been solved. In particular, Bayesian analysis methods
provide a general approach to measuring quantities of physical interest and
their uncertainties from microlensing light curves. We discuss the data and the
analysis methods and show preliminary results for all three astrophysical
applications.


title:
The Hot Gas Content of Low-Luminosity Early-Type Galaxies and the
  Implications Regarding Supernova Heating and AGN Feedback

abstract:
  We have analyzed Chandra observations of 18 low-luminosity early-type
galaxies with L_B < 3 x 10e10 Lo. Thermal emission from hot gas with
temperatures between 0.2 and 0.8 keV comprises 5-70% of the total 0.5-2.0 keV
emission from these galaxies. We find that the total X-ray luminosity from
LMXBs (resolved plus the power-law component of the unresolved emission) scales
roughly linearly with the K-band luminosity of the galaxies with a
normalization comparable to that found in more luminous early-type galaxies.
All of the galaxies in our sample are gas poor with gas masses much less than
that expected from the accumulation of stellar mass loss over the life time of
the galaxies. The average ratio of gas mass to stellar mass in our sample is
M_{gas}/M_*=0.001, compared to more luminous early-type galaxies which
typically have M_{gas}/M_*=0.01. The time required to accumulate the observed
gas mass from stellar mass loss in these galaxies is typically 3 x 10e8 yr.
Since the cooling time of the gas is longer than the replenishment time, the
gas cannot be condensing out of the hot phase and forming stars, implying that
the gas is most likely being expelled from these galaxies in a wind (abridged).


title: Multi-band Astronomy with LISA

abstract:
  We discuss astrophysical scenarios relevant to the generation of
gravitational waves (GW) and effects expected to arise from the interaction of
GW and electromagnetic (EM) radiation. A strong programme of coordinated GW and
EM astrophysical studies must be established in order to ensure the
exploitation of the full scientific potential of the LISA mission. We describe
on-going astrophysical work, and suggest alternative approaches to current
studies, which are relevant to these considerations.


title: Optimizing WIMP directional detectors

abstract:
  We study the dependence of the exposure required to directly detect a WIMP
directional recoil signal on the capabilities of a directional detector.
Specifically we consider variations in the nuclear recoil energy threshold, the
background rate, whether the detector measures the recoil momentum vector in 2
or 3 dimensions and whether or not the sense of the momentum vector can be
determined. We find that the property with the biggest effect on the required
exposure is the measurement of the momentum vector sense. If the detector
cannot determine the recoil sense, the exposure required is increased by an
order of magnitude for 3-d read-out and two orders of magnitude for 2-d
read-out. For 2-d read-out the required exposure, in particular if the senses
can not be measured, can be significantly reduced by analyzing the reduced
angles with the, time dependent, projected direction of solar motion
subtracted. The background rate effectively places a lower limit on the WIMP
cross-section to which the detector is sensitive; it will be very difficult to
detect WIMPs with a signal rate more than an order of magnitude below the
background rate. Lowering the energy threshold also reduces the required
exposure, but only for thresholds above 20 keV.


title:
A search for stellar X-ray sourcesin the Sagittarius and Carina dwarf
  galaxies - I: X-ray observations

abstract:
  ROSAT observations found no convincing evidence for X-ray sources located in
local dwarf spheroidal galaxies (dSph). Now with more sensitive instruments on
board Chandra and XMM-Newton we can reach fainter luminosity levels. We report
on an observation of the Sagittarius (Sgr) dSph made using Chandra and an
observation of the Carina (Car) dSph made using XMM-Newton. Our observations
are sensitive to sources with X-ray luminosities in the 0.1-10 keV band of
\~1x10^{32 ergs/s and 3x10^34 ergs/s for the Sgr and Car fields respectively.
We have identified a total of 80 sources in the Sgr field and 53 sources in the
Car field. Although the source numbers are roughly consistent with the expected
number of background AGN, we found a small fraction of X-ray sources which were
soft and could be located in the host dSph. Follow-up optical/IR observations
may help to identify their optical counterparts and hence determine their
nature.


title:
Long-Period Objects in the Extrasolar Planetary Systems 47 UMa and 14
  Her

abstract:
  The possible existence of additional long-period planetary-mass objects in
the extrasolar planetary systems 47 UMa and 14 Her is investigated. We combine
all available radial-velocity data on these stars, spanning up to 18 years. For
the 47 UMa system, we show that while a second planet improves the fit to all
available data, there is still substantial ambiguity as to the orbital
parameters of the proposed planetary companion 47 UMa c. We also present new
observations which clearly support a long-period companion in the 14 Her
system. With a period of 6906+/-70 days, 14 Her c may be in a 4:1 resonance
with the inner planet. We also present revised orbital solutions for 7
previously known planets incorporating recent additional data obtained with the
2.7m Harlan J. Smith Telescope at McDonald Observatory.


title: Ultra High Energy Cosmic Rays: Observations and Theoretical Aspects

abstract:
  We present a brief introduction to the physics of Ultra High Energy Cosmic
Rays (UHECRs), concentrating on the experimental results obtained so far and on
what, from these results, can be inferred about the sources of UHECRs.


title:
Mid-Infrared Imaging of the Herbig Ae Star AB Aurigae: Extended Emission
  on Several Scales

abstract:
  We present high sensitivity sub-arcsecond resolution images of the Herbig Ae
star AB Aurigae at 11.6 and 18.5 microns taken with Michelle on Gemini North.
Bright extended dust emission close to the star is resolved at both
wavelengths, with quadratically subtracted FWHM of 17+/-4 AU at 11.6 microns
and 22+/-5 AU at 18.5 microns. Additional, fainter emission is detected out to
a radius of 280 AU at 11.6 microns and 350 AU at 18.5 microns down to the
sensitivity limit of the observations. The latter value is identical to the
measured size of the millimeter-continuum disk, but much smaller than the CO
disk. Assuming moderately absorbing material, we find that larger particles (~
1 microns) dominate the mid-IR emission in the inner (< 100 AU) regions of the
disk, and smaller particles (< 0.3 microns) dominate in the outer regions of
the disk. A model of a nearly face-on passive flared disk with an inner rim
accounts well for our observations.


title: The effect of inhomogeneous expansion on the supernova observations

abstract:
  We consider an inhomogeneous but spherically symmetric Lemaitre-Tolman-Bondi
model to demonstrate that spatial variations of the expansion rate can have a
significant effect on the cosmological supernova observations. A model with no
dark energy but a local Hubble parameter about 15% larger than its global value
fits the supernova data better than the homogeneous model with the cosmological
constant. The goodness of the fit is not sensitive to inhomogeneities in the
present-day matter density, and our best fit model has Omega_M ~ 0.3, in
agreement with galaxy surveys. We also compute the averaged expansion rate,
defined by the Buchert equations, of the best fit model and show explicitly
that there is no average acceleration.


title:
Empirical Color Transformations Between SDSS Photometry and Other
  Photometric Systems

abstract:
  We present empirical color transformations between the Sloan Digital Sky
Survey (SDSS) ugriz photometry and Johnson-Cousins UBVRI system and Becker's
RGU system, respectively. Owing to the magnitude of data that is becoming
available in the SDSS photometric system it is particularly important to be
able to convert between this new system and traditional photometric systems.
Unlike earlier published transformations we based our calculations on stars
actually measured by the SDSS with the SDSS 2.5-m telescope. The photometric
database of the SDSS provides in a sense a single-epoch set of 'tertiary
standards' covering more than one quarter of the sky. Our transformations
should facilitate their use to easily and reliably derive the corresponding
approximate Johnson-Cousins or RGU magnitudes. The SDSS survey covers a number
of areas that were previously established as standard fields in the
Johnson-Cousins system, in particular, fields established by Landolt and by
Stetson. We used these overlapping fields to create well-photometered star
samples on which our calculated transformations are based. For the RGU
photometry we used fields observed in the framework of the new Basel
high-latitude field star survey. We calculated empirical color transformations
between SDSS photometry and Johnson-Cousins UBVRI and Becker's RGU system. For
all transformations we found linear relations to be sufficient. Furthermore we
showed that the transformations between the Johnson-Cousins and the SDSS system
have a slight dependence on metallicity.


title:
The Dust Properties of Eight Debris Disk Candidates as Determined by
  Submillimeter Photometry

abstract:
  The nature of far-infrared dust emission toward main sequence stars, whether
interstellar or circumstellar, can be deduced from submillimeter photometry. We
present JCMT/SCUBA flux measurements at 850 microns toward 8 stars with large
photospheric excesses at 60-100 microns. 5 sources were detected at 3-sigma or
greater significance and one was marginally detected at 2.5-sigma. The inferred
dust masses and temperatures range from 0.033 to 0.24 Earth masses and 43-65 K
respectively. The frequency behavior of the opacity, tau_nu ~ nu^beta, is
relatively shallow, beta < 1. These dust properties are characteristic of
circumstellar material, most likely the debris from planetesimal collisions.
The 2 non-detections have lower temperatures, 35-38 K and steeper opacity
indices, beta > 1.5, that are more typical of interstellar cirrus. The
confirmed disks all have inferred diameters > 2'', most lie near the upper
envelope of the debris disk mass distribution, and 4 are bright enough to be
feasible for high resolution imaging.


title: The X-ray emission of Lyman break galaxies

abstract:
  We present an analysis of the X-ray emission of a large sample of z~3 Lyman
break galaxies (LBGs), based on Chandra/ACIS observations of several LBG survey
fields. 24 LBGs are directly detected in the X-ray. 13 of the LBGs have optical
spectroscopic signatures of AGN activity, but almost all the other X-ray
detections are also likely to host an accreting black hole based on their X-ray
properties. The AGN exhibit a wide range in X-ray luminosity, from weak
Seyferts to bright QSOs. Optical spectroscopy identified approximately 1/3 of
the X-ray detected sources as broad line QSOs, 1/3 as narrow line AGN and 1/3
as normal star forming LBGs. The fraction of X-ray detected LBGs is 3%, much
lower than has been found for submm selected galaxies. 2 galaxies have X-ray
luminosities, spectra and f_x/f_opt values that are consistent with emission
from star formation processes and are candidate X-ray bright, pure starburst
galaxies at z~3. X-ray spectral analysis of the LBGs shows a mean photon index
1.96, similar to local AGN. There is evidence for absorption in at least 40% of
the objects. Significantly more absorption is evident in the narrow line AGN,
consistent with AGN unification schemes. After correction for absorption the
narrow and broad line objects show the same average luminosity. LBGs
spectroscopically classified as normal galaxies are less luminous in X-ray
indicating that the host galaxy is outshining any optical AGN signature. For
the LBGs without direct detections, stacking the X-ray flux in the 2 deepest
fields under consideration (the HDF-N and GWS) produced significant detections
in each. The detection in the HDF-N gives an X-ray derived SFR of 42.4+/-7.8
Msolar/yr per LBG and, by comparing with the UV SFR, the implied UV extinction
correction is 4.1+/-0.8. (abridged)


title:
Primordial non-Gaussianity and Dark Energy constraints from Cluster
  Surveys

abstract:
  Galaxy cluster surveys will be a powerful probe of dark energy. At the same
time, cluster abundance is sensitive to any non-Gaussianity of the primordial
density field. It is therefore possible that non-Gaussian initial conditions
might be misinterpreted as a sign of dark energy or at least degrade the
expected constraints on dark energy parameters. To address this issue, we
perform a likelihood analysis of an ideal cluster survey similar in size and
depth to the upcoming South Pole Telescope/Dark Energy Survey (SPT-DES). We
analyze a model in which the strength of the non-Gaussianity is parameterized
by the constant fNL; this model has been used extensively to derive Cosmic
Microwave Background (CMB) anisotropy constraints on non-Gaussianity, allowing
us to make contact with those works. We find that the constraining power of the
cluster survey on dark energy observables is not significantly diminished by
non-Gaussianity provided that cluster redshift information is included in the
analysis. We also find that even an ideal cluster survey is unlikely to improve
significantly current and future CMB constraints on non-Gaussianity. However,
when all systematics are under control, it could constitute a valuable cross
check to CMB observations.


title:
On the Proof of Dark Matter, the Law of Gravity and the Mass of
  Neutrinos

abstract:
  We develop a new method to predict the density associated with weak lensing
maps of (un)relaxed clusters in a range of theories interpolating between GR
and MOND (General Relativity and Modified Newtonian Dynamics). We apply it to
fit the lensing map of the bullet merging cluster 1E0657-56, in order to
constrain more robustly the nature and amount of collisionless matter in
clusters {\it beyond} the usual assumption of spherical equilibrium
(Pointecouteau & Silk 2005) and the validity of GR on cluster scales (Clowe et
al. 2006). Strengthening the proposal of previous authors we show that the
bullet cluster is dominated by a collisionless -- most probably non-baryonic --
component in GR as well as in MOND, a result consistent with the dynamics of
many X-ray clusters. Our findings add to the number of known pathologies for a
purely baryonic MOND, including its inability to fit the latest data from the
Wilkinson Microwave Anisotropy Probe. A plausible resolution of all these
issues and standard issues of Cold Dark Matter with galaxy rotation curves is
the "marriage" of MOND with ordinary hot neutrinos of 2eV. This prediction is
just within the GR-independent maximum of neutrino mass from current
$\beta$-decay experiments, and is falsifiable by the Karlsruhe Tritium Neutrino
(KATRIN) experiment by 2009. Issues of consistency with strong lensing arcs and
the large relative velocity of the two clusters comprising the bullet cluster
are also addressed.


title: Prospects for direct dark matter detection in the Constrained MSSM

abstract:
  We outline the WIMP dark matter parameter space in the Constrained MSSM by
performing a comprehensive statistical analysis that compares with experimental
data predicted superpartner masses and other collider observables as well as a
cold dark matter abundance. We include uncertainties arising from theoretical
approximations as well as from residual experimental errors on relevant
Standard Model parameters.
  We present high-probability regions for neutralino dark matter direct
detection cross section, and we find that 10^-10 pb < sigma_p^SI < 10^-8 for
direct WIMP detection (with details slightly dependent on the assumptions
made). We highlight a complementarity between LHC and WIMP dark matter searches
in exploring the CMSSM parameter space. We conclude that most of the 95%
probability region for the cross section will be explored by future one-tonne
detectors, that will therefore cover most of the currently favoured region of
parameter space.


title: On the lambda Bootis spectroscopic binary hypothesis

abstract:
  It is still a matter of debate if the group of lambda Bootis stars is
homogeneously defined. A widely discussed working hypothesis formulates that
two apparent solar abundant stars of an undetected spectroscopic binary system
mimic a single metal-weak spectrum preventing any reliable analysis of the
group characteristics. Is the proposed spectroscopic binary model able to
explain the observed abundance pattern and photometric metallicity indices for
the group members? What is the percentage of undetected spectroscopic binary
systems? We have used the newest available stellar atmospheres to synthesize
105 hypothetical binary systems in the relevant astrophysical parameter range.
These models were used to derive photometric indices. As a test, values for
single stellar atmospheres, Vega and two typical lambda Bootis stars, HD 107233
and HD 204041, were generated. The synthesized indices fit the standard lines
and the observations of the three stars excellently. For about 90% of the group
members, the spectroscopic inary hypothesis can not explain the observations. A
carefully preselection of lambda Bootis stars results in a homogeneous group of
objects which can be used to investigate the group characteristics.


title: VLT-UVES abundance analysis of four giants in NGC 6553

abstract:
  Metal-rich globular clusters trace the formation of bulges. Abundance ratios
in the metal-rich globular clusters such as NGC 6553 can constrain the
formation timescale of the Galactic bulge. The purpose of this study is
determine the metallicity and elemental ratios in individual stars of the
metal-rich bulge globular cluster NGC 6553. A detailed abundance analysis of
four giants in NGC 6553 is carried out, based on optical high-resolution
echelle spectra obtained with UVES at the ESO VLT-UT2 Kueyen telescope. A
metallicity [Fe/H]= -0.20 dex is derived, together with $\alpha$-element
enhancement of Mg and Si ([Mg/Fe]=+0.28, [Si/Fe]=+0.21), solar Ca and Ti
([Ca/Fe]=+0.05, [Ti/Fe]=-0.01), and a mild enhancement of the r-process element
Eu with [Eu/Fe] = +0.10. A mean heliocentric radial velocity of -1.86 km
s$^{-1}$ is measured. We compare our results with previous investigations of
the cluster.


title: ZKDR Distance, Angular Size and Phantom Cosmology

abstract:
  The influence of mass inhomogeneities on the angular size-redshift test is
investigated for a large class of flat cosmological models driven by dark
energy plus a cold dark matter component. The results are presented in two
steps. First, the mass inhomogeneities are modeled by a generalized
Zeldovich-Kantowski-Dyer-Roeder (ZKDR) distance which is characterized by a
smoothness parameter $\alpha(z)$ and a power index $\gamma$, and, second, we
provide a statistical analysis to angular size data for a large sample of
milliarcsecond compact radio sources. By marginalizing over the characteristic
angular size $l$, fixing $\Omega_M = 0.26$ and assuming a Gaussian prior on
$\omega$, i.e., $\omega = -1 \pm 0.3$, the best fit values are $\omega = -1.03$
and $\alpha = 0.9$. By assuming a Gaussian prior on the matter density
parameter, i.e., $\Omega_M = 0.3 \pm 0.1$, the best fit model for a phantom
cosmology with $\omega = -1.2$ occurs at $\Omega_M = 0.29$ and $\alpha = 0.9$
when we marginalize over the characteristic size of the compact radio sources.
The results discussed here suggest that the ZKDR distance can give important
corrections to the so-called background tests of dark energy.


title: Magnetostatic penumbra models with field-free gaps

abstract:
  We present numerical 2D magnetostatic models for sunspot penumbrae consisting
of radially aligned field-free gaps in a potential magnetic field, as proposed
by Spruit and Scharmer (2006). The shape of the gaps and the field
configurations around them are computed consistently from the condition of
magnetostatic pressure balance between the gap and the magnetic field. The
results show that field-free gaps in the {\it inner} penumbra are cusp-shaped
and bounded by a magnetic field inclined by about $70^\circ$ from the vertical.
Here, the magnetic component has a Wilson depression on the order 200--300 km
relative to the top of the field-free gap; the gaps should thus appear as
noticeably elevated features. This structure explains the large variations in
field strength in the inner penumbra inferred from magnetograms and
two-component inversions, and the varying appearance of the inner penumbra with
viewing angle. In the {\it outer} penumbra, on the other hand, the gaps are
flat-topped with a horizontal magnetic field above the middle of the gap. The
magnetic field has large inclination variations horizontally, but only small
fluctuations in field strength, in agreement with observations.


title:
Three Dimensional Compressible Hydrodynamic Simulations of Vortices in
  Disks

abstract:
  We carry out three-dimensional, high resolution (up to $1024^2\times 256$)
hydrodynamic simulations of the evolution of vortices in vertically
unstratified Keplerian disks using the shearing sheet approximation. The
transient amplification of incompressible, linear amplitude leading waves
(which has been proposed as a possible route to nonlinear hydrodynamical
turbulence in disks) is used as one test of our algorithms; our methods
accurately capture the predicted amplification, converges at second-order, and
is free from aliasing. Waves expected to reach nonlinear amplitude at peak
amplification become unstable to Kelvin-Helmholtz modes when $\mid W_{\rm
max}\mid\gtrsim \Omega$ (where $W_{\rm max}$ is the local maximum of vorticity
and $\Omega$ the angular velocity). We study the evolution of a power-law
distribution of vorticity consistent with Kolmogorov turbulence; in
two-dimensions long-lived vortices emerge and decay slowly, similar to previous
studies. In three-dimensions, however, vortices are unstable to bending modes,
leading to rapid decay. Only vortices with a length to width ratio smaller than
one survive; in three-dimensions the residual kinetic energy and shear stress
is at least one order of magnitude smaller than in two-dimensions. No evidence
for sustained hydrodynamical turbulence and transport is observed in
three-dimensions. Instead, at late times the residual transport is determined
by the amplitude of slowly decaying, large-scale vortices (with horizontal
extent comparable to the scale height of the disk), with additional
contributions from nearly incompressible inertial waves possible. Evaluating
the role that large-scale vortices play in astrophysical accretion disks will
require understanding the mechanisms that generate and destroy them.


title: Chlorine in the Galactic ISM: Revised f-values with FUSE and STIS

abstract:
  Cl I is the atomic species most directly coupled to molecular hydrogen due to
its chemistry. Its weakest lines are thereby probably the best tracer of
optically thick H2 components in diffuse clouds. We report on the empirical
determination of the oscillator strengths for four Cl I absorption lines
predicted to be weak and often detected toward moderately reddened sight lines
observed with the Far Ultraviolet Spectroscopic Explorer (FUSE). We compared
our oscillator strength estimates with the oscillator strength calculations
listed in Morton (2003). We find that our empirical oscillator strength values
for the Cl I 1004, 1079, 1090 and 1094 A lines differ from the theoretical
predictions by factors of ~3.1, 1.2, 2.4 and 0.42, respectively. We briefly
discuss the value of Cl I as tracer of molecular gas for our star sample.


title:
Shock processing of interstellar dust and polycyclic aromatic
  hydrocarbons in the supernova remnant N132D

abstract:
  We observed the oxygen-rich Large Magellanic Cloud (LMC) supernova remnant
N132D (SNR 0525-69.6), using all instruments onboard the Spitzer Space
Telescope, IRS, IRAC, and MIPS (Infrared Spectrograph, Infrared Array Camera,
Multiband Imaging Photometer for Spitzer). The 5-40 micron IRS spectra toward
the southeastern shell of the remnant show a steeply rising continuum with
[NeIII] and [OIV] as well as PAH emission. We also present the spectrum of a
fast moving ejecta knot, previously detected at optical wavelengths, which is
dominated by strong [NeIII] and [OIV] emission lines. We interpret the
continuum as thermal emission from swept-up, shock-heated dust grains in the
expanding shell of N132D, which is clearly visible in the MIPS 24 micron image.
A 15-20 micron emission hump appears superposed on the dust continuum, and we
attribute this to PAH C-C-C bending modes. We also detect the well-known 11.3
micron PAH C-H bending feature, and find the integrated strength of the 15-20
micron hump about a factor of seven stronger than the 11.3 micron band in the
shell of the remnant. IRAC 3-9 micron images do not show clear evidence of
large-scale, shell-like emission from the remnant, partly due to confusion with
the ambient ISM material. However, we identified several knots of shocked
interstellar gas based on their distinct infrared colors. We discuss the bright
infrared continuum and the polycyclic aromatic hydrocarbon features with
respect to dust processing in young supernova remnants.


title:
Observations of Comet 9P/Tempel 1 with the Keck 1 HIRES Instrument
  During Deep Impact

abstract:
  We report high-spectral resolution observations of comet 9P/Tempel 1 before,
during and after the impact on 4 July 2005 UT of the Deep Impact spacecraft
with the comet. These observations were obtained with the HIRES instrument on
Keck 1. We observed brightening of both the dust and gas, but at different
rates. We report the behavior of OH, NH, CN, C$_{3}$, CH, NH$_{2}$ and C$_{2}$
gas. From our observations, we determined a CN outflow velocity of at least
0.51 km sec$^{-1}$. The dust color did not change substantially. To date, we
see no new species in our spectra, nor do we see any evidence of prompt
emission. From our observations, the interior material released by the impact
looks the same as the material released from the surface by ambient cometary
activity. However, further processing of the data may uncover subtle
differences in the material that is released as well as the time evolution of
this material.


title:
Gas-phase CO2 emission toward Cepheus A East: the result of shock
  activity?

abstract:
  We report the first detection of gas-phase CO2 emission in the star-forming
region Cepheus A East, obtained by spectral line mapping of the v2 bending mode
at 14.98 micron with the Infrared Spectrograph (IRS) instrument onboard the
Spitzer Space Telescope. The gaseous CO2 emission covers a region about 35'' x
25'' in extent, and results from radiative pumping by 15 micron continuum
photons emanating predominantly from the HW2 protostellar region. The gaseous
CO2 exhibits a temperature distribution ranging from 50 K to 200 K. A
correlation between the gas-phase CO2 distribution and that of H2 S(2), a
tracer of shock activity, indicates that the CO2 molecules originate in a cool
post-shock gas component associated with the outflow powered by HW2. The
presence of CO2 ice absorption features at 15.20 micron toward this region and
the lack of correlation between the IR continuum emission and the CO2 gas
emission distribution further suggest that the gaseous CO2 molecules are mainly
sputtered off grain mantles -- by the passage of slow non-dissociative shocks
with velocities of 15-30 km/s -- rather than sublimated through grain heating.


title:
Constraints on the Geometry of the VHE Emission in LS 5039 from
  Photon-Photon Deabsorption

abstract:
  A detailed parameter study of the gamma-gamma absorption effects in LS 5039
is presented. For a range of plausible locations of the VHE gamma-ray emission
region and the allowable range of viewing angles, the de-absorbed, intrinsic
VHE gamma-ray spectra and total VHE photon fluxes and luminosities are
calculated and compared to luminosity constraints based on wind accretion onto
the compact object in LS 5039. It is found that (1) it is impossible to choose
the viewing angle and location of the VHE emission region in a way that the
intrinsic (deabsorbed) fluxes and spectra in superior and inferior conjunction
are identical; consequently, the intrinsic VHE luminosities and spectral shapes
must be fundamentally different in different orbital phases, (2) if the VHE
luminosity is limited by wind accretion from the companion star and the system
is viewed at an inclination angle of i > 40 deg., the emission is most likely
beamed by a larger Doppler factor than inferred from the dynamics of the
large-scale radio outflows, (3) the still poorly constrained viewing angle
between the line of sight and the jet axis is most likely substantially smaller
than the maximum of ~ 64 deg. inferred from the lack of eclipses.(4)
Consequently, the compact object is more likely to be a black hole rather than
a neutron star. (5) There is a limited range of allowed configurations for
which the expected > 1 TeV neutrino flux would actually anti-correlate with the
observed VHE gamma-ray emission. If hadronic models for the gamma-ray
production in LS 5039 apply, a solid detection of the expected VHE neutrino
flux and its orbital modulation with km^3 scale water-Cherenkov neutrino
detectors might require the accumulation of data over more than 3 years.


title:
First results from the Arecibo Galactic HI Survey: the disk/halo
  interface region in the outer Galaxy

abstract:
  The consortium for Galactic studies with the Arecibo L-band Feed Array (ALFA)
is conducting a neutral hydrogen (HI) survey of the whole Arecibo sky
(declination range from -1 to 38 degrees), with high angular (3.5') and
velocity resolution (0.2 km/s). The precursor observations with ALFA of a
region in the Galactic anti-center reveal numerous isolated, small (a few pc in
size), and cold (T_k<400 K) HI clouds at low negative velocities, distinctly
separated from the HI disk emission (`low-velocity clouds', LVCs). These clouds
are most likely located in the transition region between the Galactic disk and
halo (at scale heights of 60--900 pc), yet they have properties of typical cold
neutral clouds. LVCs are colder and, most likely, smaller and less massive than
Lockman's clouds in the disk/halo interface region of the inner Galaxy. Our
observations demonstrate that the cloudy structure of the interface region is
most likely a general phenomenon, not restricted to the inner Galaxy. LVCs have
sizes and radial velocities in agreement with the expectations for clouds
formed in low-temperature fountain flows, although we measure a factor of ten
higher HI column densities. Alternatively, LVCs could represent the final
stages of the infalling intergalactic material in the on-going construction of
the Galaxy.
  In the same dataset at higher negative velocities, we have discovered a
`companion' HI cloud located 50' southwest of CHVC186+19-114. CHVC186+19-114 is
a typical compact high velocity cloud (HVC) with a well-defined core/envelope
structure. The companion cloud has a diameter of only 7'x9', and is one of the
smallest HVCs known, most likely stripped from the main cloud through the
interactions with the halo medium.


title:
Carbon-Enhanced Metal-Poor Stars. Osmium and Iridium Abundances in the
  Neutron-Capture-Enhanced Subgiants CS31062-050 and LP625-44

abstract:
  We have investigated the abundances of heavy neutron-capture elements,
including osmium (Os) and iridium (Ir), in the two Carbon-Enhanced Metal-Poor
(CEMP) subgiants CS31062-050 and LP625-44. CS31062-050 is known to be a
so-called CEMP-r/s star, which exhibits large excesses of s-process elements
such as barium (Ba) and lead (Pb), as well as a significant enhancement of
europium (Eu) that cannot be explained by conventional s-process production in
Asymptotic Giant Branch star models. Our analysis of the high-resolution
spectrum for this object has determined, for the first time, the abundances of
Ir and Os, elements in the third peak of the r-process nucleosynthesis. They
also exhibit significant excesses relative to the predictions of standard
s-process calculations. These two elements are not detected in a
similar-quality spectrum of LP625-44; the derived upper limits on their
abundances are lower than the abundances in CS31062-050. We compare the
observed abundance patterns of neutron-capture elements, including Os and Ir,
in these two stars with recent model calculations of the s-process, and discuss
possible interpretations.


title:
Positron Annihilations at the Galactic Center: Generating More Questions
  Than Answers

abstract:
  The bulge of our Galaxy is illuminated by the 0.511 MeV gamma-ray line flux
from annihilations of nonrelativistic positrons. The emission is strongly
concentrated at the Galactic Center, in contrast to gamma-ray maps tracing
nucleosynthesis (e.g., the 1.809 MeV line from decaying ^26Al) or cosmic ray
processes (e.g., the 1-30 MeV continuum), which reveal a bright disk with a
much less prominent central region. If positrons are generated at relativistic
energies, higher-energy gamma rays will also be produced from inflight
annihilation of positrons on ambient electrons. The comparison of the gamma-ray
spectrum from inflight annihilation to the observed diffuse Galactic gamma-ray
data constrains the injection energies of Galactic positrons to be less than 3
MeV.


title:
Planet formation around low mass stars: the moving snow line and
  super-Earths

abstract:
  We develop a semi-analytic model for planet formation during the pre-main
sequence contraction phase of a low mass star. During this evolution, the
stellar magnetosphere maintains a fixed ratio between the inner disk radius and
the stellar radius. As the star contracts at constant effective temperature,
the `snow line', which separates regions of rocky planet formation from regions
of icy planet formation, moves inward. This process enables rapid formation of
icy protoplanets that collide and merge into super-Earths before the star
reaches the main sequence. The masses and orbits of these super-Earths are
consistent with super-Earths detected in recent microlensing experiments.


title:
Spitzer 24 Micron Observations of Open Cluster IC 2391 and Debris Disk
  Evolution of FGK Stars

abstract:
  We present 24 micron Spitzer/MIPS photometric observations of the ~50 Myr
open cluster IC 2391. Thirty-four cluster members ranging in spectral type from
B3-M5 were observed in the central square degree of the cluster. Excesses
indicative of debris disks were discovered around 1 A star, 6 FGK stars, and
possibly 1 M dwarf. For the cluster members observed to their photospheric
limit, we find a debris disk frequency of 10 (-3,+17)% for B-A stars and 31
(-9,+13)% for FGK stars using a 15% relative excess threshold. Relative to a
model of decaying excess frequency, the frequency of debris disks around A-type
stars appears marginally low for the cluster's age while that of FGK stars
appears consistent. Scenarios that may qualitatively explain this result are
examined. We conclude that planetesimal activity in the terrestrial region of
FGK stars is common in the first ~50 Myr and decays on timescales of ~100 Myr.
Despite luminosity differences, debris disk evolution does not appear to depend
strongly on stellar mass.


title: The Supernova -- Gamma-Ray Burst Connection

abstract:
  Observations show that at least some gamma-ray bursts (GRBs) happen
simultaneously with core-collapse supernovae (SNe), thus linking by a common
thread nature's two grandest explosions. We review here the growing evidence
for and theoretical implications of this association, and conclude that most
long-duration soft-spectrum GRBs are accompanied by massive stellar explosions
(GRB-SNe). The kinetic energy and luminosity of well-studied GRB-SNe appear to
be greater than those of ordinary SNe, but evidence exists, even in a limited
sample, for considerable diversity. The existing sample also suggests that most
of the energy in the explosion is contained in nonrelativistic ejecta
(producing the supernova) rather than in the relativistic jets responsible for
making the burst and its afterglow. Neither all SNe, nor even all SNe of Type
Ibc produce GRBs. The degree of differential rotation in the collapsing iron
core of massive stars when they die may be what makes the difference.


title: Simulations of polarized dust emission

abstract:
  Our aim is to study the polarization of thermal dust emission to see if the
alignment of grain by radiative torques could explain the observed relation
between the degree of polarization and the intensity in dense cores.
Predictions are made for polarimetry observations with the Planck satellite.
Our results are based on model clouds derived from MHD simulations of
magnetized turbulent flows, while the continuum radiative transfer problem is
solved with Monte Carlo methods in order to estimate the three-dimensional
distribution of dust emission and the radiation field strength affecting the
grain alignment. The influence of grain alignment efficiency is examined in the
calculated polarization maps. We are able to reproduce the P/I-relation with
the grain alignment by radiative torques. The decrease in intrinsic
polarization and total emission means that sub-mm polarimetry carries only
little information about the magnetic fields in dense cores with high visual
extinction. The interpretation of the observations will be further complicated
by the unknown magnetic field geometry and the fact that what is observed as
individual cores may, in fact, be a superposition of several density
enhancements. According to our calculations, Planck will be able to map dust
polarization reliably when A_V > 2 mag at spatial resolution of 15'.


title: Binary Black Hole Accretion Flows in Merged Galactic Nuclei

abstract:
  We study the accretion flows from the circumbinary disks onto the
supermassive binary black holes in a subparsec scale of the galactic center,
using a smoothed particles hydrodynamics (SPH) code. Simulation models are
presented in four cases of a circular binary with equal and unequal masses, and
of an eccentric binary with equal and unequal masses. We find that the
circumblack-hole disks are formed around each black holes regardless of
simulation parameters. There are two-step mechanisms to cause an accretion flow
from the circumbinary disk onto supermassive binary black holes: First, the
tidally induced elongation of the circumbinary disk triggers mass inflow
towards two closest points on the circumbinary disk from the black holes. Then,
the gas is increasingly accumulated on these two points owing to the
gravitational attraction of black holes. Second, when the gas can pass across
the maximum loci of the effective binary potential, it starts to overflow via
their two points and freely infalls to each black hole. In circular binaries,
the gas continues to be supplied from the circumbinary disk (i.e. the gap
between the circumbinary disk and the binary black hole is always closed.) In
eccentric binaries, the mass supply undergoes the periodic on/off transitions
during one orbital period because of the variation of periodic potential. The
gap starts to close after the apastron and to open again after the next
periastron passage. Due to this gap closing/opening cycles, the mass-capture
rates are eventually strongly phase dependent. This could provide observable
diagnosis for the presence of supermassive binary black holes in merged
galactic nuclei.