title: Implications of the Universal Temperature Profile for Galaxy Clusters

abstract:
  We study the X-ray cluster gas density distribution in hydrostatic
equilibrium using the universal temperature profile obtained from recent
simulations involving only gravitational processes. If this temperature profile
is an indicator of the influence of gravitational processes alone on the
intracluster medium, then the comparison of various X-ray parameters expected
from this profile and the observed data would point towards any additional
physics that may be required. We compare the entropy at 0.1 R_{200} and
R_{500}, the scaled entropy profile, the gas fraction at 0.3 R_{200} and the
gas fraction profile with recent observations and discuss the implications of
this temperature profile in light of these data. We find that the entropy
imparted to the gas from gravitational processes alone is larger than
previously thought. The entropy at R_{500} for rich clusters is consistent with
data, whereas the entropy at 0.1R_{200} is still less than the observed values.
We also find that the gas fraction in the inner region of clusters, expected
from gravitational processes alone, is smaller than previously thought but
larger than the observed data. It does show a trend with the emission-weighted
temperature (<T>) as shown by data. We therefore find that the role of any
additional non-gravitational process influencing the physical state of ICM
would have to be revised in light of these findings.


title: A Search for Interstellar Pyrimidine

abstract:
  We have searched three hot molecular cores for submillimeter emission from
the nucleic acid building-block pyrimidine. We obtain upper limits to the total
pyrimidine (beam-averaged) column densities towards Sgr B2(N), Orion KL and W51
e1/e2 of 1.7E+14 cm^{-2}, 2.4E+14 cm^{-2} and 3.4E+14 cm^{-2}, respectively.
The associated upper limits to the pyrimidine fractional abundances lie in the
range (0.3-3)E-10. Implications of this result for interstellar organic
chemistry, and for the prospects of detecting nitrogen heterocycles in general,
are briefly discussed.


title:
The Angular Momentum of Gas in Proto-Galaxies: II -- The Impact of
  Preheating

abstract:
  We examine the effect of preheating of the intergalactic medium on galaxy
formation using cosmological hydrodynamical simulations. By performing
simulations both with and without a simple model for preheating, we analyse and
compare the angular momentum distributions of the dark matter and the baryons.
Preheating unbinds baryons from their dark matter haloes, yielding a baryonic
mass fraction that declines with decreasing halo mass. In addition, the spin
parameter of the gas is reduced with respect to the case without preheating,
while the misalignment between the angular momentum directions of the gas and
dark matter increases strongly. The angular momentum distributions of
individual haloes reveal that preheating decreases (increases) the mass
fraction with low (negative) specific angular momentum. We discuss the
implications of these findings for the formation of disk galaxies in a
preheated intergalactic medium, and compare our results to the predictions of
Maller & Dekel (2002), who propose an alternative interpretation for the origin
of the angular momentum of (proto)-galaxies.


title:
Constraining the dark energy dynamics with the cosmic microwave
  background bispectrum

abstract:
  We consider the influence of the dark energy dynamics at the onset of cosmic
acceleration on the Cosmic Microwave Background (CMB) bispectrum, through the
weak lensing effect induced by structure formation. We study the line of sight
behavior of the contribution to the bispectrum signal at a given angular
multipole $l$: we show that it is non-zero in a narrow interval centered at a
redshift $z$ satisfying the relation $l/r(z)\simeq k_{NL}(z)$, where the
wavenumber corresponds to the scale entering the non-linear phase, and $r$ is
the cosmological comoving distance. The relevant redshift interval is in the
range $0.1\lsim z\lsim 2$ for multipoles $1000\gsim\ell\gsim 100$; the signal
amplitude, reflecting the perturbation dynamics, is a function of the
cosmological expansion rate at those epochs, probing the dark energy equation
of state redshift dependence independently on its present value. We provide a
worked example by considering tracking inverse power law and SUGRA Quintessence
scenarios, having sensibly different redshift dynamics and respecting all the
present observational constraints. For scenarios having the same present
equation of state, we find that the effect described above induces a projection
feature which makes the bispectra shifted by several tens of multipoles, about
10 times more than the corresponding effect on the ordinary CMB angular power
spectrum.


title:
Analysis of two-point statistics of cosmic shear: II. Optimizing the
  survey geometry

abstract:
  We present simulations of a cosmic shear survey and show how the survey
geometry influences the accuracy of determination of cosmological parameters.
We numerically calculate the full covariance matrices Cov of two-point
statistics of cosmic shear, based on the expressions derived in the first paper
of this series. The individual terms are compared for two survey geometries
with large and small cosmic variance. We use analyses based on maximum
likelihood of Cov and the Fisher information matrix in order to derive expected
constraints on cosmological parameters. As an illustrative example, we simulate
various survey geometries consisting of 300 individual fields of 13'x13' size,
placed (semi-)randomly into patches which are assumed to be widely separated on
the sky and therefore uncorrelated. Using the aperture mass statistics, the
optimum survey consists of 10 patches with 30 images in each patch. If
\Omega_m, \sigma_8 and \Gamma are supposed to be extracted from the data, the
minimum variance bounds on these three parameters are 0.17, 0.25 and 0.04
respectively. These variances raise slightly when the initial power spectrum
index n_s is also to be determined from the data. The cosmological constant is
only poorly constrained.


title: Gleam: the GLAST Large Area Telescope Simulation Framework

abstract:
  This paper presents the simulation of the GLAST high energy gamma-ray
telescope. The simulation package, written in C++, is based on the Geant4
toolkit, and it is integrated into a general framework used to process events.
A detailed simulation of the electronic signals inside Silicon detectors has
been provided and it is used for the particle tracking, which is handled by a
dedicated software. A unique repository for the geometrical description of the
detector has been realized using the XML language and a C++ library to access
this information has been designed and implemented.


title:
HST and UKIRT imaging observations of z ~ 1 6C radio galaxies - I. The
  data

abstract:
  The results of Hubble Space Telescope and UKIRT imaging observations are
presented for a sample of 11 6C radio galaxies with redshifts 0.85 < z < 1.5.
The observations of the 6C sources reveal a variety of different features,
similar to those observed around the higher luminosity of the aligned emission
appears less extreme in the case of the 6C radio galaxies. For both samples,
the aligned emission clearly cannot be explained by a single emission
mechanism; line emission and related nebular continuum emission, however, often
provide a significant contribution to the aligned emission.


title:
Periodic Thermonuclear X-ray Bursts from GS 1826-24 and the Fuel
  Composition as a Function of Accretion Rate

abstract:
  We analyze 24 type I X-ray bursts from GS 1826-24 observed by the Rossi X-ray
Timing Explorer between 1997 November and 2002 July. The bursts observed
between 1997-98 were consistent with a stable recurrence time of 5.74 +/- 0.13
hr. The persistent intensity of GS 1826-24 increased by 36% between 1997-2000,
by which time the burst interval had decreased to 4.10 +/- 0.08 hr. In 2002
July the recurrence time was shorter again, at 3.56 +/- 0.03 hr. The bursts
within each epoch had remarkably identical lightcurves over the full approx.
150 s burst duration; both the initial decay timescale from the peak, and the
burst fluence, increased slightly with the rise in persistent flux. The
decrease in the burst recurrence time was proportional to Mdot^(-1.05+/-0.02)
(where Mdot is assumed to be linearly proportional to the X-ray flux), so that
the ratio alpha between the integrated persistent and burst fluxes was
inversely correlated with Mdot. The average value of alpha was 41.7 +/- 1.6.
Both the alpha value, and the long burst durations indicate that the hydrogen
is burning during the burst via the rapid-proton (rp) process. The variation in
alpha with Mdot implies that hydrogen is burning stably between bursts,
requiring solar metallicity (Z ~ 0.02) in the accreted layer. We show that
solar metallicity ignition models naturally reproduce the observed burst
energies, but do not match the observed variations in recurrence time and burst
fluence. Low metallicity models (Z ~ 0.001) reproduce the observed trends in
recurrence time and fluence, but are ruled out by the variation in alpha. We
discuss possible explanations, including extra heating between bursts, or that
the fraction of the neutron star covered by the accreted fuel increases with
Mdot.


title: Why do starless cores appear more flattened than protostellar cores?

abstract:
  We evaluate the intrinsic three dimensional shapes of molecular cores, by
analysing their projected shapes. We use the recent catalogue of molecular line
observations of Jijina et al. and model the data by the method originally
devised for elliptical galaxies. Our analysis broadly supports the conclusion
of Jones et al. that molecular cores are better represented by triaxial
intrinsic shapes (ellipsoids) than biaxial intrinsic shapes (spheroids).
However, we find that the best fit to all of the data is obtained with more
extreme axial ratios ($1:0.8:0.4$) than those derived by Jones et al.
  More surprisingly, we find that starless cores have more extreme axial ratios
than protostellar cores -- starless cores appear more `flattened'. This is the
opposite of what would be expected from modeling the freefall collapse of
triaxial ellipsoids. The collapse of starless cores would be expected to
proceed most swiftly along the shortest axis - as has been predicted by every
modeller since Zel'dovich - which should produce more flattened cores around
protostars, the opposite of what is seen.


title:
HST imaging and Keck Spectroscopy of z~6 I-band Drop-Out Galaxies in the
  ACS GOODS Fields

abstract:
  We measure the surface density of i'-band dropout galaxies at z~6 through
wide field HST/ACS imaging and ultra-deep Keck/DEIMOS spectroscopy. Using deep
HST/ACS SDSS-i' (F775W) and SDSS-z' (F850LP) imaging from GOODS-N (200
arcmin^2), we identify 9 i'-drops satisfying an (i'-z')_AB>1.5 selection
criterion to a depth of z'_AB=25.6 (corresponding to L*_UV at z~3-4). We use
HK' imaging data to improve the fidelity of our sample, discriminating against
lower redshift red galaxies and cool Galactic stars. Three i'-drops are
consistent with M/L/T dwarf stars. We present ultra-deep Keck/DEIMOS
spectroscopy of 10 objects from our combined GOODS-N and GOODS-S i'-drop
sample. We detect Lyman-alpha emission at z=5.83 from one object in the GOODS-S
field, which lies only 8arcmin away (i.e. 3Mpc/h_70) from the z=5.78 object
already confirmed by Bunker et al. (2003). One possible Lyman-alpha emitter at
z=6.24 is found in the GOODS-N field (although identification of this
spatially-offset emission line is ambiguous). Using the rest-frame UV continuum
from our 6 candidate z~6 galaxies from the GOODS-N field, we determine a lower
limit to the unobscured volume-averaged global star formation rate at z~6 of
(5.4+/-2.2)x10^-4 h_70 M_sun/yr/Mpc^3. We find that the cosmic star formation
density in galaxies with unobscured star formation rates 15M_sun/yr/h_70^2
falls by a factor of 8 between z~3 and z~6. Hence the luminosity function of
LBGs must evolve in this redshift interval: a constant integrated star
formation density at $z>3$ requires a much steeper faint-end slope, or a
brighter characteristic luminosity. This result is in agreement with our
previous measurement from the Chandra Deep Field South (Stanway et al. 2003),
indicating that cosmic variance is not a dominant source of uncertainty.


title:
Characteristics and classification of A-type supergiants in the Small
  Magellanic Cloud

abstract:
  We address the relationship between spectral type and physical properties for
A-type supergiants in the SMC. We first construct a self-consistent
classification scheme for A supergiants, employing the calcium K to H epsilon
line ratio as a temperature-sequence discriminant. Following the precepts of
the `MK process', the same morphological criteria are applied to Galactic and
SMC spectra with the understanding there may not be a correspondence in
physical properties between spectral counterparts in different environments. We
then discuss the temperature scale, concluding that A supergiants in the SMC
are systematically cooler than their Galactic counterparts at the same spectral
type, by up to ~10%. Considering the relative line strengths of H gamma and the
CH G-band we extend our study to F and early G-type supergiants, for which
similar effects are found. We note the implications for analyses of
extragalactic luminous supergiants, for the flux-weighted gravity-luminosity
relationship and for population synthesis studies in unresolved stellar
systems.


title: Cool White Dwarfs Revisited -- New Spectroscopy and Photometry

abstract:
  In this paper we present new and improved data on 38 cool white dwarfs
identified by Oppenheimer et al. 2001 (OHDHS) as candidate dark halo objects.
Using the high-res spectra obtained with LRIS, we measure radial velocities for
13 WDs that show an H alpha line. We show that the knowledge of RVs decreases
the UV-plane velocities by only 6%. The radial velocity sample has a W-velocity
dispersion of sig_W = 59 km/s--in between the values associated with the thick
disk and the stellar halo. We also see indications for the presence of two
populations by analyzing the velocities in the UV plane. In addition, we
present CCD photometry for half of the sample, and with it recalibrate the
photographic photometry of the remaining WDs. Using the new photometry in
standard bands, and by applying the appropriate color-magnitude relations for H
and He atmospheres, we obtain new distance estimates. New distances of the WDs
that were not originally selected as halo candidates yield 13 new candidates.
On average, new distances produce velocities in the UV plane that are larger by
10%, with already fast objects gaining more. Using the new data, while applying
the same UV-velocity cut (94 km/s) as in OHDHS, we find a density of cool WDs
of 1.7e-4 pc^-3, confirming the value of OHDHS. In addition, we derive the
density as a function of the UV-velocity cutoff. The density (corrected for
losses due to higher UV cuts) starts to flatten out at 150 km/s (0.4e-4 pc^-3),
and is minimized (thus minimizing a possible non-halo contamination) at 190
km/s (0.3e-4 pc^-3). These densities are in a rough agreement with the
estimates for the stellar halo WDs, corresponding to a factor of 1.9 and 1.4
higher values.


title:
Occurrence and Stability of Apsidal Resonance in Multiple Planetary
  Systems

abstract:
  With the help of the Laplace-Lagrange solution of the secular perturbation
theory in a double-planet system, we study the occurrence and the stability of
apsidal secular resonance between the two planets. The explicit criteria to
predict whether two planets are in apsidal resonance is derived. The pobability
of two planets falling in apsidal resonance is given in the initial element
space. We verify the criteria with numerical integrations for the HD12661
system, and find they give good predictions except at the boundary of the
criteria or when the planet eccentricities are too large. The nonlinear
stability of the two planets in HD12661 system are studied by calculating the
Lyapunov exponents of their orbits in a general three-body model. The
applications of the criteria to the other multiple planetary systems are
discussed.


title: The cluster environments of radio-loud quasars at 0.6 < z < 1.1

abstract:
  We have carried out multicolour imaging of a complete sample of radio-loud
quasars at 0.6 < z < 1.1 and find groups or clusters of galaxies in the fields
of at least 8 and possibly 13 of the 21 sources. There is no evidence for an
evolution in the richness of the environments of radio-loud quasars from other
low-redshift studies to z >~ 0.9. The quasars associated with groups and
clusters in our sample do not necessarily reside in the centre of the galaxy
distribution which rarely displays a spherical geometry. Clustering is
preferentially associated with small or asymmetric steep-spectrum radio
sources. The quasars with the largest projected angular size are, in nearly all
cases, found in non-clustered environments. Radio-based selection (including
source size) of high-redshift groups and clusters can be a very efficient
method of detecting rich environments at these redshifts.
  We find that in optical searches for galaxy overdensities above z ~ 0.6
multiple filters must be used. If the single-filter counting statistics used by
groups at lower redshift are applied to our data, uncertainties are too large
to make accurate quantifications of cluster richness. This means that genuine
clustering of galaxies about quasars will be missed and, in ~10% of cases,
putative clusters turn out to be false detections. The statistics are further
diluted by the fact that galaxy overdensities are generally not centred on the
quasar.


title: Optical Activity From Extra Dimension

abstract:
  Optical activity, like Faraday effect, is a rotation of the plane of
polarization of propagating light in a medium and can be attributed to
different sources with distinct signatures. In this note we discuss the effect
of optical activity {\it{in vacuum}} due to Kaluza-Klein scalar field $\phi$,
in the presence of an external electro-magnetic field. The astrophysical
implication of this effect is indicated. We also point out the possibility of
observing the same in laboratory conditions.


title:
The Ks-band Luminosity and Stellar Mass Functions of Galaxies in z~1
  Clusters

abstract:
  We present the near-infrared (Ks-band) luminosity function of galaxies in two
z~1 cluster candidates, 3C336 and Q1335+28. A third cluster, 3C289, was
observed but found to be contaminated by a foreground system. Our wide field
imaging data reach to Ks=20.5 (5sigma), corresponding to ~M*+2.7 with respect
to the passive evolution. The near-infrared luminosity traces the stellar mass
of a galaxy due to its small sensitivity to the recent star formation history.
Thus the luminosity function can be transformed to the stellar mass function of
galaxies using the $J-K$ colours with only a small correction (factor<2) for
the effects of on-going star formation. The derived stellar mass function spans
a wide range in mass from ~3 x 10^{11}Msun down to ~6 x 10^{9}Msun (set by the
magnitude limit). The form of the mass function is very similar to lower
redshift counterparts such as that from 2MASS/LCRS clusters (Balogh et al.
2001) and the z=0.31 clusters (Barger et al. 1998). This indicates little
evolution of galaxy masses from z=1 to the present-day. Combined with colour
data that suggest star formation is completed early (z>>1) in the cluster core,
it seems that the galaxy formation processes (both star formation and mass
assembly) are strongly accerelated in dense environments and has been largely
completed by z=1. We investigate whether the epoch of mass assembly of massive
cluster galaxies is earlier than that predicted by the hierarchical galaxy
formation models. These models predict the increase of characteristic mass by
more than factor ~3 between z=1 and the present day. This seems incompatible
with our data.


title: Ram pressure stripping and the formation of cold fronts

abstract:
  Chandra and XMM-Newton observations of many clusters reveal sharp
discontinuities in the surface brightness, which, unlike shocks, have lower gas
temperature on the X-ray brighter side of the discontinuity. For that reason
these features are called ``cold fronts''. It is believed that some cold fronts
are formed when a subcluster merges with another cluster and the ram pressure
of gas flowing outside the subcluster gives the contact discontinuity the
characteristic curved shape. While some edges may not arise directly from
mergers (e.g., A496, Dupke & White, 2003), this paper focuses on those which
arise as contact discontinuities between a merging subcluster and the ambient
cluster gas. We argue that the flow of gas past the merging subcluster induces
slow motions inside the cloud. These motions transport gas from the central
parts of the subcluster towards the interface. Since in a typical cluster or
group (even an isothermal one) the entropy of the gas in the central regions is
significantly lower than in the outer regions, the transport of the low entropy
gas towards the interface and the associated adiabatic expansion makes the gas
temperature immediately inside the interface lower than in any other place in
the system, thus enhancing the temperature jump across the interface and making
the ``tip'' of the contact discontinuity cool. We illustrate this picture with
the XMM-Newton gas temperature map of the A3667 cluster.


title:
Quasars as probes of the submillimetre cosmos at z>5: I. Preliminary
  SCUBA photometry

abstract:
  We present submillimetre continuum observations of a sample of some of the
highest redshift quasars currently known, made with the SCUBA bolometer array
on the JCMT. The median redshift of the sample is 5.3. Two z>5 objects are
strong (6 sigma) detections, with S(850um)>10mJy. A firm (5 sigma) detection is
obtained for the z=5.7 quasar SDSS J1044-0125; and SDSS J1306+0356, at z=6.0,
is detected with a signal-to-noise approx. 4. For the remainder of the sample
we have obtained sensitive (sigma=1.5mJy) upper limits. Submm spectral indices
measured for two of the sources are consistent with thermal reradiation from
dust, rather than from synchrotron emission. Sensitive 450um upper limits imply
that the dust is cool,suggesting large dust masses only 1Gyr after the Big
Bang.


title:
The mass function and distribution of velocity dispersions for UZC
  groups of galaxies

abstract:
  We measure the distribution of velocity dispersions of groups of galaxies
identified in the UZC catalog; we use the distribution to derive the group mass
function. We introduce a new method which makes efficient use of the entire
magnitude limited catalog. Our determination of \nst includes a significant
contribution from low luminosity systems that would be missing in a volume
limited sample. We start from a model for the probability density function of
the total number of group members and reproduce the observed distribution. We
take several effects like the local fluctuations in volume density, limited
sampling and group selection into account. We estimate the relation between
total number of members, total luminosity and true velocity dispersion. We can
then reproduce not only the observed distribution of \sv but also the
distributions of the number of group members, the total groups luminosity, and
virial mass. The best fit to the data in the true velocity dispersion range 100
km/s < \sigma < 750 km/s is a power law model with a slope -3.4 and a
normalization (1.27 +/- 0.21) x 10^{-5} h^3 Mpc^{-3}. The predictions of CDM
models are consistent with the mass function we derive from this distribution
of velocity dispersions.


title: Fueling Gas to the Central Region of Galaxies

abstract:
  Supplying gas to the galactic central regions is one of key ingredients for
AGN activity. I will review various fueling mechanisms for a R ~ 1 kpc region,
determined mainly by numerical simulations over the last decade. I will also
comment on the bars-within-bars mechanism. Observations suggest that the
stellar bar is not a sufficient condition for gas fueling. Moreover,
considering the various factors for the onset of gas accretion, stellar bars
would not even be a necessary condition. I introduce recent progress obtained
through our two- and three-dimensional, high resolution hydrodynamical
simulations of the ISM in the central 0.1--1 kpc region of galaxies. Possible
structure of the obscuring molecular tori around AGNs is also shown. The
nuclear starburst is an important factor in determining the structure of the
molecular tori and the mass accretion rate to the nucleus. It is natural that
the ISM in the central 100 pc region is a highly inhomogeneous and turbulent
structure. As a result, gas accretion to the central parsec region should be
time dependent and stochastic. The conventional picture of gas fueling and the
AGN unified model may be modified in many respects.


title:
Acceleration parameter of the Universe expansion and cosmological
  equation of state

abstract:
  This paper has been withdrawn by the author, due an error in Eq.(4.4),
wherein a term of cosmological constant added into a theory of gravitation by
Ref.[8], in which such the term is truly forbidden.


title: Hypernovae and Other Black-Hole-Forming Supernovae

abstract:
  During the last few years, a number of exceptional core-collapse supernovae
(SNe) have been discovered. Their kinetic energy of the explosions are larger
by more than an order of magnitude than the typical values for this type of
SNe, so that these SNe have been called `Hypernovae'. We first describe how the
basic properties of hypernovae can be derived from observations and modeling.
These hypernovae seem to come from rather massive stars, thus forming black
holes. On the other hand, there are some examples of massive SNe with only a
small kinetic energy. We suggest that stars with non-rotating black holes are
likely to collapse "quietly" ejecting a small amount of heavy elements (Faint
supernovae). In contrast, stars with rotating black holes are likely to give
rise to very energetic supernovae (Hypernovae). We present distinct
nucleosynthesis features of these two types of "black-hole-forming" supernovae.
Hypernova nucleosynthesis is characterized by larger abundance ratios
(Zn,Co,V,Ti)/Fe and smaller (Mn,Cr)/Fe. Nucleosynthesis in Faint supernovae is
characterized by a large amount of fall-back. We show that the abundance
pattern of the most Fe deficient star, HE0107-5240, and other extremely
metal-poor carbon-rich stars are in good accord with those of
black-hole-forming supernovae, but not pair-instability supernovae. This
suggests that black-hole-forming supernovae made important contributions to the
early Galactic (and cosmic) chemical evolution.


title:
Cosmological Implications and Physical Properties of an X-Ray
  Flux-Limited Sample of Galaxy Clusters

abstract:
  The original abstract significantly exceeds the space available here, so
here's a brief summary.
  The abstract is similar to the abstract of astro-ph/0111285 (ApJ, 567, 716)
which describes the X-ray galaxy cluster sample HIFLUGCS, the X-ray
luminosity--gravitational mass relation, the cluster mass function, and the
derived cosmological constraints. Additionally, the fraction of the total
gravitating mass in the universe which is contained in intracluster gas is
quantified.
  Furthermore, physical properties of the cluster sample have been studied and
analyses of relations between different cluster parameters (including the gas
mass fraction, gas temperature, X-ray luminosity, gas mass, gravitational mass,
beta, and core radius) are discussed.
  Also, results from an analysis of XMM-Newton performance verification phase
data of Abell 1835 are described.


title: Type Ia Supernovae: Progenitors and Diversities

abstract:
  A key question for supernova cosmology is whether the peak luminosities of
Type Ia supernovae (SNe Ia) are sufficiently free from the effects of cosmic
and galactic evolution. To answer this question, we review the currently
popular scenario of SN Ia progenitors, i.e., the single degenerate scenario for
the Chandrasekhar mass white dwarf (WD) models. We identify the progenitor's
evolution with two channels: (1) the WD+RG (red-giant) and (2) the WD+MS (near
main-sequence He-rich star) channels. The strong wind from accreting WDs plays
a key role, which yields important age and metallicity effects on the
evolution.
  We suggest that the variation of the carbon mass fraction $X$(C) in the C+O
WD (or the variation of the initial WD mass) causes the diversity of SN Ia
brightness. This model can explain the observed dependence of SNe Ia brightness
on the galaxy types. We then predict how SN Ia brightness evolves along the
redshift (with changing metallicity and age) for elliptical and spiral
galaxies. Such evolutionary effects along the redshift can be corrected as has
been made for local SNe Ia.
  We also touch on several related issues: (1) the abundance pattern of stars
in dwarf spheroidal galaxies in relation to the metallicity effect on SNe Ia,
(2) effects of angular momentum brought into the WD in relation to the
diversities and the fate of double degenerates, and (3) possible presence of
helium in the peculiar SN Ia 2000cx in relation to the sub-Chandrasekhar mass
model.


title:
Galaxies in group and field environments: a comparison of optical-NIR
  luminosities and colors

abstract:
  We compare properties of galaxies in loose groups with those in field
environment by analyzing the Nearby Optical Galaxy (NOG) catalog of galaxy
systems. We consider as group galaxies, objects belonging to systems with at
least five members identified by means of the "friends of friends method", and,
as field galaxies, all galaxies with no companions. We analyze both a
magnitude--limited sample of 959 and 2035 galaxies (groups vs. field galaxies,
respectively, B<14 mag, and 2000<cz<6000 km/s) and a volume-limited sample (M_B
<-19.01 mag, 2000<cz<4000 km/s 369 group and 548 field galaxies). For all these
galaxies, blue corrected magnitudes and morphological types are available. The
cross-correlation of NOG with the 2MASS second release allow us to assign K
magnitudes and obtain B-K colors for about half of the galaxies in our samples.
We analyze luminosity and color segregation-effects in relation with the
morphological segregation. For both B and K bands, we find that group galaxies
are, on average, more luminous than field galaxies and this effect is not
entirely a consequence of the morphological segregation. After taking into
account the morphological segregation, the luminosity difference between group
and field galaxies is about 10%. When considering only very early-type galaxies
(T<-2) the difference is larger than 30%. We also find that group galaxies are
redder than field galaxies, Delta(B-K) about 0.4 mag. However, after taking
into account the morphological segregation, we find a smaller B-K difference,
poorly significant (only at the c.l. of about 80%).


title:
Cosmological Evolution of the Hard X-ray AGN Luminosity Function and the
  Origin of the Hard X-ray Background

abstract:
  We investigate the cosmological evolution of the hard X-ray luminosity
function (HXLF) of Active Galactic Nuclei (AGN) in the 2-10 keV luminosity
range of 10^{41.5} - 10^{46.5} erg s^-1 as a function of redshift up to 3. From
a combination of surveys conducted at photon energies above 2 keV with HEAO1,
ASCA, and Chandra, we construct a highly complete (>96%) sample consisting of
247 AGNs over the wide flux range of 10^{-10} - 3.8*10^{-15} erg cm^-2 s^-1
(2-10 keV). For our purpose, we develop an extensive method of calculating the
intrinsic (before-absorption) HXLF and the absorption (N_H) function. This
utilizes the maximum likelihood method fully correcting for observational
biases with consideration of the X-ray spectrum of each source. We find that
(i) the fraction of X-ray absorbed AGNs decreases with the intrinsic luminosity
and (ii) the evolution of the HXLF of all AGNs (including both type-I and
type-II AGNs) is best described with a luminosity dependent density evolution
(LDDE) where the cutoff redshift increases with the luminosity. Our results
directly constrain the evolution of AGNs that produce a major part of the hard
X-ray background, thus solving its origin quantitatively. A combination of the
HXLF and the NH function enables us to construct a purely "observation based"
population synthesis model. We present basic consequences of this model, and
discuss the contribution of Compton-thick AGNs to the rest of the hard X-ray
background.


title: The effects of discreteness of galactic cosmic rays sources

abstract:
  Most studies of GeV Galactic Cosmic Rays (GCR) nuclei assume a steady
state/continuous distribution for the sources of cosmic rays, but this
distribution is actually discrete in time and in space. The current progress in
our understanding of cosmic ray physics (acceleration, propagation), the
required consistency in explaining several GCRs manifestation (nuclei,
$\gamma$,...) as well as the precision of present and future space missions
(e.g. INTEGRAL, AMS, AGILE, GLAST) point towards the necessity to go beyond
this approximation. A steady state semi-analytical model that describes well
many nuclei data has been developed in the past years based on this
approximation, as well as others. We wish to extend it to a time dependent
version, including discrete sources. As a first step, the validity of several
approximations of the model we use are checked to validate the approach: i) the
effect of the radial variation of the interstellar gas density is inspected and
ii) the effect of a specific modeling for the galactic wind (linear vs
constant) is discussed. In a second step, the approximation of using continuous
sources in space is considered. This is completed by a study of time
discreteness through the time-dependent version of the propagation equation. A
new analytical solution of this equation for instantaneous point-like sources,
including the effect of escape, galactic wind and spallation, is presented.
Application of time and space discretness to definite propagation conditions
and realistic distributions of sources will be presented in a future paper.


title: Tidal Streams around External Galaxies

abstract:
  We have the unique opportunity to observe and model nearby streams around the
two large Local Group spirals Milky Way and M31 in great detail. However, the
detection of streams around other external galaxies is required to verify the
general application of the derived results. We give a short summary of streams
around other galaxies known in the literature, measuring for the first time the
surface brightness of Malin's M83 stream with modern CCD imaging. In addition,
we present four new detections of possible stellar streams around disk
galaxies.


title:
Envelope Structure of Starless Core L694-2 Derived from a Near-Infrared
  Extinction Map

abstract:
  We present a near-infrared extinction study of the dark globule L694-2, a
starless core that shows strong evidence for inward motions in molecular line
profiles. The J,H, and K band data were taken using the European Southern
Observatory New Technology Telescope. The best fit simple spherical power law
model has index p=2.6 +/- 0.2, over the 0.036--0.1 pc range in radius sampled
in extinction. This power law slope is steeper than the value of p=2 for a
singular isothermal sphere, the initial condition of the inside-out model for
protostellar collapse. Including an additional extinction component along the
line of sight further steepens the inferred profile. Fitting a Bonnor-Ebert
sphere results in a super-critical value of the dimensionless radius xi_max=25
+/- 3. The unstable configuration of material may be related to the observed
inward motions. The Bonnor-Ebert model matches the shape of the observed
profile, but significantly underestimates the amount of extinction (by a factor
of ~4). This discrepancy in normalization has also been found for the nearby
protostellar core B335 (Harvey et al. 2001). A cylindrical density model with
scale height H=0.0164+/- 0.002 pc viewed at a small inclination to the cylinder
axis provides an equally good radial profile as a power law model, and
reproduces the asymmetry of the core remarkably well. In addition, this model
provides a basis for understanding the discrepancy in the normalization of the
Bonnor-Ebert model, namely that L694-2 has prolate structure, with the full
extent (mass) of the core being missed by assuming symmetry between the
profiles in the plane of the sky and along the line-of-sight. If the core is
sufficiently magnetized then fragmentation may be avoided, and later evolution
might produce a protostar similar to B335.


title: Properties of SN-host galaxies

abstract:
  It is of prime importance to recognize evolution and extinction effects in
supernovae results as a function of redshift, for SN Ia to be considered as
distance indicators. This review surveys all observational data searching for
an evolution and/or extinction, according to host morphology. For instance, it
has been observed that high-z SNe Ia have bluer colours than the local ones:
although this goes against extinction to explain why SN are dimmer with
redshift until z ~ 1, supporting a decelerating universe, it also demonstrates
intrinsic evolution effects. -- SNe Ia could evolve because the age and
metallicity of their progenitors evolve. The main parameter is carbon
abundance. Smaller C leads to a dimmer SN Ia and also less scatter on peak
brightness, as it is the case in elliptical galaxy today. Age of the progenitor
is an important factor: young populations lead to brighter SNe Ia, as in spiral
galaxies, and a spread in ages lead to a larger scatter, explaining the
observed lower scatter at high z. -- Selection biases also play a role, like
the Malmquist bias; high-z SNe Ia are found at larger distance from their host
center: there is more obscuration in the center, and also detection is easier
with no contamination from the center. This might be one of the reason why less
obscuration has been found for SNe Ia at high z. -- There is clearly a sample
evolution with z: currently only the less bright SNe Ia are detected at high z,
with less scatter. The brightest objects have a slowly declining light-curve,
and at high z, no slow decline has been observed. This may be interpreted as an
age effect, high-z SN having younger progenitors.


title:
The Multi-Colored Hot Interstellar Medium of "The Antennae" Galaxies
  (NGC 4038/39)

abstract:
  We report the results of the analysis of the extended soft emission
discovered in the Chandra ACIS pointing at the merging system NGC 4038/39 (the
Antennae). We present a `multi-color' X-ray image that suggests both extensive
absorption by the dust in this system, peaking in the contact region, as well
as variations in the temperature of different emitting regions of the hot
interstellar medium (ISM). Spectral fits to multi-component thermal emission
models confirm this picture and give a first evaluation of the parameters of
the hot plasma. We compare the diffuse X-ray emission with radio continuum
(6cm), HI, CO, and H$\alpha$ images to take a first look at the multi-phase ISM
of the Antennae galaxies. We find that the hot (X-ray) and cold (CO) gas have
comparable thermal pressures in the two nuclear regions. We also conclude that
the displacement between the peak of the diffuse X-ray emission in the north of
the galaxy system, towards the inner regions of the northern spiral arm (as
defined by H$\alpha$, radio continuum and HI), could result from ram pressure
of infalling HI clouds.


title:
A two-arm gaseous spiral in the inner 200 pc of the early-type galaxy
  NGC 2974: signature of an inner bar

abstract:
  TIGER integral-field spectrography and HST/WFPC2 imaging of the E3 galaxy NGC
2974 are used to derive the kinematics of the stellar and ionized gas
components in its central 500 pc. We derive a numerical two-integral
distribution function from a MGE mass model using the HQ formalism. The TIGER
as well as published long-slit stellar kinematics are well fitted with this
self-consistent model, requiring neither the addition of a significant mass
contribution from a hidden disc structure, nor the presence of a central dark
mass. The data reveal the presence of a striking, highly contrasted, two-arm
gaseous spiral structure within a radius of ~200 pc, corresponding to a total
mass of 6.8x10^4 Msun of ionized gas. We use a deconvolved TIGER datacube to
probe its kinematics at a resolution of about 0.35 arcsec. Strong departures
from circular motions are observed, as well as high velocity dispersion values
on the inner side of the arms. We interpret the observed gas morphology and
kinematics as the signature of streaming gas flows driven by a ~540 pc diameter
bar with Ome=700+/-100 km/s/kpc. This hypothesis is strongly supported by the
predictions of a density wave model. This model predicts that the bar should
lie at about 35 degree from the line of nodes, and implies gas inflow towards
the central ~50 pc. The quadrupole pertubation due to this bar is estimated to
represent less than 2% of the underlying gravitational potential. Despite its
weakness, the inner bar of NGC 2974 may be able to drive some gas within a 10
pc radius. We suggest that the presence of such inner bars might be more common
among early-type disk galaxies than is generally thought, and that deep
high-resolution emission-line imagery may be the best way to detect such
structures.


title: Constraints on extended quintessence from high-redshift Supernovae

abstract:
  We obtain constraints on quintessence models from magnitude-redshift
measurements of 176 type Ia Supernovae. The considered quintessence models are
ordinary quintessence, with Ratra-Peebles and SUGRA potentials, and extended
quintessence with a Ratra-Peebles potential. We compute confidence regions in
the $\Omega_{m0}-\alpha$ plane and find that for SUGRA potentials it is not
possible to obtain useful constraints on these parameters; for the
Ratra-Peebles case, both for the extended and ordinary quintessence we find
$\alpha\mincir 0.8$, at the $1\sigma$ level. We also consider simulated dataset
for the SNAP satellite for the same models: again, for a SUGRA potential it
will not be possible to obtain constraints on $\alpha$, while with a
Ratra-Peebles potential its value will be determined with an error $\mincir
0.6$. We evaluate the inaccuracy made by approximating the time evolution of
the equation of state with a linear or constant $w\diz$, instead of using its
exact redshift evolution. Finally we discuss the effects of different
systematic errors in the determination of quintessence parameters.


title: Neutron Stars as Type-I Superconductors

abstract:
  In a recent paper by Link, it was pointed out that the standard picture of
the neutron star core composed of a mixture of a neutron superfluid and a
proton type-II superconductor is inconsistent with observations of a long
period precession in isolated pulsars. In the following we will show that an
appropriate treatment of the interacting two-component superfluid (made of
neutron and proton Cooper pairs), when the structure of proton vortices is
strongly modified, may dramatically change the standard picture, resulting in a
type-I superconductor. In this case the magnetic field is expelled from the
superconducting regions of the neutron star leading to the formation of the
intermediate state when alternating domains of superconducting matter and
normal matter coexist.


title: Age constraints and fine tuning in variable-mass particle models

abstract:
  VAMP (variable-mass particles) scenarios, in which the mass of the cold dark
matter particles is a function of the scalar field responsible for the present
acceleration of the Universe, have been proposed as a solution to the cosmic
coincidence problem, since in the attractor regime both dark energy and dark
matter scale in the same way. We find that only a narrow region in parameter
space leads to models with viable values for the Hubble constant and dark
energy density today. In the allowed region, the dark energy density starts to
dominate around the present epoch and consequently such models cannot solve the
coincidence problem. We show that the age of the Universe in this scenario is
considerably higher than the age for noncoupled dark energy models, and
conclude that more precise independent measurements of the age of the Universe
would be useful in distinguishing between coupled and noncoupled dark energy
models.


title:
Chandra Observation of the Edge-on Galaxy NGC 3556 (M 108): Violent
  Galactic Disk-halo Interaction Revealed

abstract:
  We present a 60 ks Chandra ACIS-S observation of the isolated edge-on spiral
NGC 3556, together with a multiwavelength analysis of various discrete X-ray
sources and diffuse X-ray features. Among 33 discrete X-ray sources detected
within the I_B = 25 mag per square arcsec isophote ellipse of the galaxy, we
identify a candidate for the galactic nucleus, an ultraluminous X-ray source
that might be an accreting intermediate-mass black hole, a possible X-ray
binary with a radio counterpart, and two radio-bright giant HII regions. We
detect large amounts of extraplanar diffuse X-ray emission, which extends about
10 kpc radially in the disk and >~ 4 kpc away from the galactic plane. The
diffuse X-ray emission exhibits significant substructures, possibly
representing various blown-out superbubbles or chimneys of hot gas heated in
massive star forming regions. This X-ray-emitting gas has temperatures in the
range of ~ 2-7 x 10^6 K and has a total cooling rate of ~ 2 x 10^40 erg/s. The
energy can be easily supplied by supernova blast-waves in the galaxy. These
results demonstrate NGC 3556 as being a galaxy undergoing vigorous disk-halo
interaction. The halo in NGC 3556 is considerably less extended, however, than
that of NGC 4631, in spite of many similarities between the two galaxies. This
may be due to the fact that NGC 3556 is isolated whereas NGC 4631 is
interacting. Thus NGC 3556 presents a more pristine environment for studying
the disk-halo interaction.


title:
The bispectrum of the Lyman-alpha forest at z~2-2.4 from a Large sample
  of UVES QSO Absorption Spectra (LUQAS)

abstract:
  We present a determination of the bispectrum of the flux in the Lyman-alpha
forest of QSO absorption spectra obtained from LUQAS which consists of spectra
observed with the high resolution Echelle spectrograph UVES. Typical errors on
the observed bispectrum as obtained from a jack-knife estimator are ~ 50%. For
wavenumbers in the range 0.03 s/km <k < 0.1 s/km the observed bispectrum agrees
within the errors with that of the synthetic absorption spectra obtained from
numerical hydro-simulations of a LCDM model with and without feedback from star
formation. Including galactic feedback changes the bispectrum by less than 10%.
At smaller wavenumbers the associated metal absorption lines contribute about
50% to the bispectrum and the observed bispectrum exceeds that of the
simulations. At wavenumbers k< 0.03 (s/km) second-order perturbation theory
applied to the flux spectrum gives a reasonable (errors smaller than 30%)
approximation to the bispectra of observed and simulated absorption spectra.
The bispectrum of the observed absorption spectra also agrees, within the
errors, with that of a randomized set of absorption spectra where a random
shift in wavelength has been added to absorption lines identified with VPFIT.
This suggests that for a sample of the size presented here, the errors on the
bispectrum are too large to discriminate between models with very different 3D
distribution of Lyman-alpha absorption. If it were possible to substantially
reduce these errors for larger samples of absorption spectra, the bispectrum
might become an important statistical tool for probing the growth of
gravitational structure in the Universe at redshift z>2.


title: Gravitomagnetic Resonance Shift due to a Slowly Rotating Compact Star

abstract:
  The effect of a slowly rotating mass on a forced harmonic oscillator with two
degrees of freedom is studied in the weak field approximation. It is found that
according to the general theory of relativity there is a shift in the resonat
frequency of the oscillator which depends on the density and rotational
frequency of the gravitational source. The proposed shift is quite small under
normal physical situations however it is estimated that for compact x-ray
sources such as white dwarfs, pulsars, and neutron stars the shift is quite
appreciable.


title:
Parameter study of the diamagnetic relativistic pulse accelerator (DRPA)
  in slab geometry I: Dependence on initial frequency ratio and slab width

abstract:
  Two-and-a-half-dimensional particle-in-cell plasma simulations are used to
study the particle energization in expanding magnetized electron-positron
plasmas with slab geometry. When the magnetized relativistic plasma with high
temperature (initial electron and positron temperature are
$k_{B}T_{e}=k_{B}T_{p}=5MeV$) is expanding into a vacuum, the electromagnetic
(EM) pulse with large amplitude is formed and the surface plasma particles are
efficiently accelerated in the forward direction owing to the energy conversion
from the EM field to the plasma particles. We find that the behavior of the
DRPA (Diamagnetic Relativistic Pulse Accelerator) depends strongly on the ratio
of the electron plasma frequency to the cyclotron frequency
$\omega_{pe}/\Omega_{e}$ and the initial plasma thickness. In the high
$\omega_{pe}/\Omega_{e}$ case, the EM pulse is rapidly damped and the plasma
diffuses uniformly without forming density peaks because the initial thermal
energy of the plasma is much larger than the field energy. On the contrary, in
the low $\omega_{pe}/\Omega_{e}$ case, the field energy becomes large enough to
energize all the plasma particles, which are confined in the EM pulse and
efficiently accelerated to ultrarelativistic energies. We also find that a
thicker initial plasma increases the maximum energy of the accelerated
particles.


title:
Outburst and Post-Outburst Active Phase of the Black Hole X-ray Binary
  V4641 Sgr in 2002

abstract:
  The black hole X-ray binary V4641 Sgr experienced an outburst in 2002 May
which was detected at X-ray, optical, and radio wavelengths. The outburst
lasted for only 6 days, but the object remained active for the next several
months. Here we report on the detailed properties of light curves during the
outburst and the post-outburst active phase. We reveal that rapid optical
variations of ~100 s became more prominent when a thermal flare weakened and
the optical spectrum flattened in the Ic, Rc, and V-band region. In conjunction
with the flat spectrum in the radio range, this strongly indicates that the
origin of rapid variations is not thermal emission, but synchrotron emission.
Just after the outburst, we detected repeated flares at optical and X-ray
wavelengths. The optical and X-ray light curves exhibited a strong correlation,
with the X-rays, lagging by about 7 min. The X-ray lag can be understood in
terms of a hot region propagating into the inner region of the accretion flow.
The short X-ray lag, however, requires modifications of this simple scenario to
account for the short propagation time. We also detected rapid optical
variations with surprisingly high amplitude 50 days after the outburst, which
we call optical flashes. During the most prominent optical flash, the object
brightened by 1.2 mag only within 30 s. The released energy indicates that the
emission source should be at the innermost region of the accretion flow.


title:
Constrained Simulations of the Magnetic Field in the Local Supercluster
  and the Propagation of UHECR

abstract:
  Magnetic fields (MF) in the Local Supercluster (LSC) of galaxies may have
profound consequences for the propagation of Ultra High Energy Cosmic Rays
(UHECR). Faraday rotations measurements provide some informations about MF in
compact clusters. However, very few is known about less dense regions and about
the global structure of MF in the LSC. In order to get a better knowledge of
these fields we are performing constrained magnetohydrodynamical simulations of
the LSC magnetic field. We will present the results of our simulation and
discuss their implications for the angular distribution of expected UHECR
deflections.


title: Photometrical Review of Open Cluster M25

abstract:
  The young open star cluster M25 (IC 4725) is located in the direction of the
galactic center in a crowded region, near much irregular absorption features on
Sagittarius arm. This cluster has some difficult observing problems due to its
southern location. The mass data available in the literature have been gathered
to reinvestigate this cluster using most photometric tools to determine its
main photometric parameters. This system is found to be at a distance of 600 pc
from the sun, of -52.82 pc from the galactic plane; and the median age is 9.45
x 10^(7) yr. More than 220 stars with mean reddening of 0.50 mag and absorption
of 1.62 mag are found within the cluster.


title: BeppoSAX serendipitous discovery of the X-ray pulsar SAX J1802.7-2017

abstract:
  We report on the serendipitous discovery of a new X-ray source, SAX
J1802.7-2017, ~22' away from the bright X-ray source GX 9+1, during a BeppoSAX
observation of the latter source on 2001 September 16-20. SAX J1802.7-2017
remained undetected in the first 50 ks of observation; the source count rate in
the following ~300 ks ranged between 0.04 c/s and 0.28 c/s, corresponding to an
averaged 0.1-10 keV flux of 3.6 10^{-11} ergs cm^{-2} s^{-1}. We performed a
timing analysis and found that SAX J1802.7-2017 has a pulse period of 139.612
s, a projected semimajor axis of a_x sin i ~ 70 lt-s, an orbital period of ~4.6
days, and a mass function f(M) ~ 17 Msun. The new source is thus an accreting
X-ray pulsar in a (possibly eclipsing) high mass X-ray binary. The source was
not detected by previous X-ray astronomy satellites, indicating that it is
likely a transient system.


title: Energy Release in Air Showers

abstract:
  A simulation study of the energy released in air due to the development of an
extensive air shower has been carried out using the CORSIKA code. The
contributions to the energy release from different particle species and
energies as well as the typical particle densities are investigated. Special
care is taken of particles falling below the energy threshold of the simulation
which contribute about 10% to the total energy deposition. The dominant
contribution to the total deposition stems from electrons and positrons from
sub-MeV up to a few hundred MeV, with typical transverse distances between
particles exceeding 1 mm for 10 EeV showers.


title:
Making other Earths: Dynamical Simulations of Terrestrial Planet
  Formation and Water Delivery

abstract:
  We present results from 42 simulations of late stage planetary accretion,
focusing on the delivery of volatiles (primarily water) to the terrestrial
planets. Our simulations include both planetary "embryos" (defined as Moon to
Mars sized protoplanets) and planetesimals, assuming that the embryos formed
via oligarchic growth. We investigate volatile delivery as a function of
Jupiter's mass, position and eccentricity, the position of the snow line, and
the density (in solids) of the solar nebula.
  In all simulations, we form 1-4 terrestrial planets inside 2 AU, which vary
in mass and volatile content. In 42 simulations we have formed 43 planets
between 0.8 and 1.5 AU, including 11 "habitable" planets between 0.9 and 1.1
AU. These planets range from dry worlds to "water worlds" with 100+ oceans of
water (1 ocean = 1.5x10^24 g), and vary in mass between 0.23 and 3.85 Earth
masses.
  There is a good deal of stochastic noise in these simulations, but the most
important parameter is the planetesimal mass we choose, which reflects the
surface density in solids past the snow line. A high density in this region
results in the formation of a smaller number of terrestrial planets with larger
masses and higher water content, as compared with planets which form in systems
with lower densities.
  We find that an eccentric Jupiter produces drier terrestrial planets with
higher eccentricities than a circular one. In cases with Jupiter at 7 AU, we
form what we call "super embryos," 1-2 Earth mass protoplanets which can serve
as the accretion seeds for 2+ Earth mass planets with large water contents.


title: Do We Live in a Vanilla Universe? Theoretical Perspectives on WMAP

abstract:
  I discuss the theoretical implications of the WMAP results, stressing WMAP's
detection of a correlation between the E-mode polarization and temperature
anisotropies, which provides strong support for the overall inflationary
paradigm. I point out that almost all inflationary models have a ``vanilla
limit,'' where their parameters cannot be distinguished from a genuinely de
Sitter inflationary phase. Because its findings are consistent with vanilla
inflation, WMAP cannot exclude entire classes of inflationary models. Finally,
I summarize hints in the current dataset that the CMB contains relics of new
physics, and the possibility that we can use observational data to reconstruct
the inflaton potential.


title: Accelerating expansion of the universe may be caused by inhomogeneities

abstract:
  We point out that, due to the nonlinearity of the Einstein equations, a
homogeneous approximation in cosmology leads to the appearance of an additional
term in the Friedmann equation. This new term is associated with the spatial
inhomogeneities of the metric and can be expressed in terms of density
fluctuations. Although it is not constant, it decays much slower (as t^(-2/3))
than the other terms (like density) which decrease as t^(-2). The presence of
the new term leads to a correction in the scale factor that is proportional to
t^2 and may give account of the recently observed accelerating expansion of the
universe without introducing a cosmological constant.


title: Evolution of angular momenta and energy of the Earth-Moon system

abstract:
  We have developed a model for the evolution of the Earth-Moon angular
momenta, energy dissipation and tidal torque valid for the entire history of
the Earth-Moon system. The model is supported by present observational data.


title: Nucler star formation in NGC 6240

abstract:
  We have made use of archival HST BVIJH photometry to constrain the nature of
the three discrete sources, A1, A2 and B1, identified in the double nucleus of
NGC 6240. STARBURST99 models have been fitted to the observed colours, under
the assumption, first, that these sources can be treated as star clusters (i.e.
single, instantaneous episodes of star formation), and subsequently as
star-forming regions (i.e. characterised by continuous star formation). For
both scenarios, we estimate ages as young as 4 million years, integrated masses
ranging between 7x10^6 Msun (B1) and 10^9 Msun (A1) and a rate of 1 supernova
per year, which, together with the stellar winds, sustains a galactic wind of
44 Msun/yr. In the case of continuous star formation, a star-formation rate has
been derived for A1 as high as 270 Msun/yr, similar to what is observed for
warm Ultraluminous Infrared Galaxies (ULIRGs) with a double nucleus. The A1
source is characterised by a mass density of about 1200 Msun/pc^3 which
resembles the CO molecular mass density measured in cold ULIRGs and the stellar
density determined in ``elliptical core'' galaxies. This, together with the
recent discovery of a supermassive binary black hole in the double nucleus of
NGC 6240, might indicate that the ongoing merger could shape the galaxy into a
core elliptical.


title:
New search strategy for high z intervening absorbers: GRB021004, a pilot
  study

abstract:
  We present near-infrared narrow- and broad-band imaging of the field of
GRB021004, performed with ISAAC on the UT1 of the ESO Very Large Telescope. The
narrow-band filters were chosen to match prominent emission lines at the
redshift of the absorption-line systems found against the early-time afterglow
of GRB021004: [OIII] at z=1.38 and Halpha at z=1.60, respectively. For the
z=1.38 system we find an emission-line source at an impact parameter of 16",
which is somewhat larger than the typical impact parameters of a sample of MgII
absorbers at redshifts around unity. Assuming that this tentative
redshift-identification is correct, the star formation rate of the galaxy is 13
+- 2 Msun/year. Our study reaches star-formation rate limits (5 sigma) of 5.7
Msun/year at z=1.38, and 7.7 Msun/year at z=1.60. These limits correspond to a
depth of roughly 0.13 L*. Any galaxy counterpart of the absorbers nearer to the
line of sight either has to be fainter than this limit or not be an
emission-line source.


title: The formation history of the Galactic bulge

abstract:
  The distributions of the stellar metallicities of K giant stars in several
fields of the Galactic bulge, taken from the literature are compared with a
simple model of star formation and chemical evolution. Our model assumes a
Schmidt law of star formation and is described by only a few parameters that
control the infall and outflow of gas and the star formation efficiency. We
find that very short infall timescales are needed, with durations of infall and
star formation greater than 1 Gyr being ruled out at the 90% confidence level.
The metallicity distributions are compatible with an important amount of gas
and metals being ejected in outflows, although a detailed quantification of the
ejected gas fraction is strongly dependent on a precise determination of the
absolute stellar metallities. The recent bulge data from Zoccali et al. are
also analyzed, and the subsample with subsolar metallicities still rules out
infall timescales around 1 Gyr at the 90% confidence level. Hence, the short
timescales we derive based on the observed distribution of metallicities are
robust and should be taken as stringent constraints on bulge formation models.


title:
Meissner Effect and Vortex Dynamics in Quark Stars -- A Model for Soft
  Gamma-Ray Repeaters

abstract:
  We present a new model for soft gamma-ray repeaters based on a quark star
born with temperatures above the critical value (T_c) for the onset of the
colour-flavor locked superconductivity. The quark star then quickly cools below
T_c, expelling a fraction of the surface magnetic field via the Meissner
effect. We show that if a small fraction (\leq 10%) of the surface magnetic
field (10^{14} - 10^{15} {\rm G}) is expelled, it quickly decays via magnetic
reconnection and heats up the quark star surface to temperatures > 10^9 {\rm
K}. Created (e^{+},e^{-}) pairs annihilate into gamma rays emitted in a giant
burst (the first burst in our model), with a luminosity of \sim 10^{45} {\rm
ergs} {\rm s}^{-1}. Subsequent bursts result from the restructuring of the
surface magnetic field following the formation and relaxation of a vortex
lattice which confines the internal magnetic field. During this phase, energy
is sporadically released as a consequence of magnetic reconnection events in
the entangled surface magnetic field as it evolves into a smooth, more stable,
configuration. The star eventually enters a quiescent phase in which energy is
continuously supplied by vortex annihilation at the surface. As the star spins
down, the outermost vortex lines will be pushed to the surface where they
annihilate and release their confined magnetic field. We show that the
corresponding luminosity is L_v \sim 10^{36} {\rm ergs} {\rm s}^{-1} for a
typical soft gamma-ray repeater spinning with a period of 8 {\rm s} and a
surface magnetic field not exceeding 10^{15} {\rm G}. Our model can be applied
to any situation where a T>T_{\rm c} quark star is generated. We discuss the
connection between anomalous X-ray pulsars and soft gamma-ray repeaters in the
context of our model.


title:
Stationary Nonaxisymmetric Configurations of Magnetized Singular
  Isothermal Disks

abstract:
  We construct both aligned and unaligned (logarithmic spiral) stationary
configurations of nonaxisymmetric magnetohydrodynamic (MHD) disks from either a
full or a partial razor-thin power-law axisymmetric magnetized singular
isothermal disk (MSID) that is embedded with a coplanar azimuthal magnetic
field $B_{\theta}$ of a non-force-free radial scaling $r^{-1/2}$ and that
rotates differentially with a flat rotation curve of speed $aD$, where $a$ is
the isothermal sound speed and $D$ is the dimensionless rotation parameter.
Analytical solutions and stability criteria for determining $D^2$ are derived.


title: Multi-wavelength Cosmological Simulations of Elliptical Galaxies

abstract:
  We study the chemodynamical evolution of elliptical galaxies and their X-ray
and optical properties using high-resolution cosmological simulations. Our Tree
N-body/SPH code includes a self-consistent treatment of radiative cooling, star
formation, supernovae feedback, and chemical enrichment. We present a series of
LCDM cosmological simulations which trace the spatial and temporal evolution of
abundances of heavy element in both the stellar and gas components of galaxies.
A giant elliptical galaxy formed in the simulations is quantitatively compared
with the observational data in both the X-ray and optical regime. X-ray spectra
of the hot gas are constructed via the use of the vmekal plasma model, and
analysed using XSPEC with the XMM EPN response function. Optical properties are
derived by the population synthesis for the stellar component. We find that
radiative cooling is important to interpret the observed X-ray luminosity,
temperature, and metallicity of the hot gas of elliptical galaxies. However,
this cooled gas also leads to excessive star formation at low redshift, and
therefore results in underlying galactic stellar populations which are too blue
with respect to observations. Time variation and radial dependence of X-ray
properties and abundance ratios, such as [O/Fe] and [Si/Fe], of the X-ray
emitting hot gas are also discussed.


title: Non-commutative inflation and the CMB

abstract:
  Non-commutative inflation is a modification of standard general relativity
inflation which takes into account some effects of the space-time uncertainty
principle motivated by ideas from string theory. The corrections to the
primordial power spectrum which arise in a model of power-law inflation lead to
a suppression of power on large scales, and produce a spectral index that is
blue on large scales and red on small scales. This suppression and running of
the spectral index are not imposed ad hoc, but arise from an early-Universe
stringy phenomenology. We show that it can account for some loss of power on
the largest scales that may be indicated by recent WMAP data. Cosmic microwave
background anisotropies carry a signature of these very early Universe
corrections, and can be used to place constraints on the parameters appearing
in the non-commutative model. Applying a likelihood analysis to the WMAP data,
we find the best-fit value for the critical wavenumber k_* (which involves the
string scale) and for the exponent p (which determines the power-law
inflationary expansion). The best-fit value corresponds to a string length of
L_s \sim 10^{-28} cm.


title:
Inelastic H+Li and H^-+Li^+ collisions and non-LTE Li I line formation
  in stellar atmospheres

abstract:
  Rate coefficients for inelastic collisions between Li and H atoms covering
all transitions between the asymptotic states
Li(2s,2p,3s,3p,3d,4s,4p,4d,4f)+H(1s) and Li^+ +H^- are presented for the
temperature range 2000-8000 K based on recent cross-section calculations. The
data are of sufficient completeness for non-LTE modelling of the Li I 670.8 nm
and 610.4 nm features in late-type stellar atmospheres. Non-LTE radiative
transfer calculations in both 1D and 3D model atmospheres have been carried out
for test cases of particular interest. Our detailed calculations show that the
classical modified Drawin-formula for collisional excitation and de-excitation
(Li*+H <-> Li*'+H) over-estimates the cross-sections by typically several
orders of magnitude and consequently that these reactions are negligible for
the line formation process. However, the charge transfer reactions collisional
ion-pair production and mutual neutralization (Li*+H <-> Li^+ +H^-) are of
importance in thermalizing Li. In particular, 3D non-LTE calculations of the Li
I 670.8 nm line in metal-poor halo stars suggest that 1D non-LTE results
over-estimate the Li abundance by up to about 0.1 dex, aggrevating the
discrepancy between the observed Li abundances and the primordial Li abundance
as inferred by the WMAP analysis of the cosmic microwave background.


title: On the impossibility of advection dominated accretion

abstract:
  Using only the assumption that all interactions between particles in an
accretion flow are electromagnetically mediated, it is shown that the time to
establish equipartition between ions and electrons is shorter than the
characteristic accretion time. Consequently, two-temperature fits to the
spectra of accreting objects are unphysical, and models in which significant
thermal energy is carried across the event horizon are effectively ruled out.


title: On the origin of the galaxy luminosity function

abstract:
  Evidence is summarized that suggests that when a protogalaxy collapses, a
fraction $f$ of its gas fails to heat to the virial temperature, where $f$ is
large for haloes less massive than the value $M^*$ associated with $L^*$
galaxies. Stars and galaxies form only from the cool gas fraction. Hot gas is
ejected from low-mass systems as in conventional semi-analytic models of galaxy
formation. In high-mass systems it is retained but does not cool and form
stars. Instead it builds up as a largely inert atmosphere, in which cooling is
inhibited by an episodically active galactic nucleus. Cold gas frequently falls
into galactic haloes. In the absence of a dense atmosphere of
virial-temperature gas it builds up on nearly circular orbits and forms stars.
When there is a sufficiently dense hot atmosphere, cold infalling gas tends to
be ablated and absorbed by the hot atmosphere before it can form stars. The
picture nicely explains away the surfeit of high-luminosity galaxies that has
recently plagued semi-analytic models of galaxy formation, replacing them by
systems of moderate luminosity from old stars and large X-ray luminosities from
hot gas.


title: The Integral Burst Alert System (IBAS)

abstract:
  We describe the INTEGRAL Burst Alert System (IBAS): the automatic software
for the rapid distribution of the coordinates of the Gamma-Ray Bursts detected
by INTEGRAL. IBAS is implemented as a ground based system, working on the
near-real time telemetry stream. During the first six months of operations, six
GRB have been detected in the field of view of the INTEGRAL instruments and
localized by IBAS. Positions with an accuracy of a few arcminutes are currently
distributed by IBAS to the community for follow-up observations within a few
tens of seconds of the event.


title:
Spectral analysis of a large sample of BeppoSAX Seyfert spectra with
  Comptonization models: Preliminary results

abstract:
  We present preliminary results of the spectral analysis of a large sample of
Seyfert galaxies observed by BeppoSAX. The only selection criterium was a
sufficiently large S/N ratio (>10) in the PDS band (12-200 keV) to allow good
detection up to the highest energy. The resulting sample is composed of 28
objects (17 Seyfert 1, 11 Seyfert 2) and 50 observations. Our main effort here
is to adopt Comptonization models to fit the different spectra on a truly broad
band basis (0.1-200 keV). We use two distinct disc-corona configurations, an
anisotropic slab and an isotropic spherical one. We discuss the distributions
of the physical parameters, like temperature and optical depth of the corona
and the reflection component, among this sample. We also discussed the
existence (or inexistence) of correlations between these parameters.


title: Database of optical properties of cosmic dust analogues (DOP)

abstract:
  We present a database containing information on different aspects of
calculation and usage of the optical properties of small non-spherical
particles -- cosmic dust analogues. The main parts of the DOP are a review of
available methods of the light scattering theory, collection of light
scattering codes, special computational tools, a graphic library of the optical
properties (efficiencies, albedo, asymmetry factors, etc.), a database of the
optical constants for astronomy, a bibliographic database of light scattering
works, and links to related Internet resources. The general purpose of the DOP
having the address http://www.astro.spbu.ru/DOP is twofold -- to help
scientists to apply the light scattering theory in astronomy and to give
students and beginners a possibility quickly to get necessary knowledge on the
subject.


title: The XMM/BeppoSAX observation of Mkn 841

abstract:
  Mkn 841 has been observed simultaneously by XMM and BeppoSAX in January 2001.
Due to operational contingency, the 30ks XMM observation was split into two
parts, separated by about 15 hours. We first report the presence of a narrow
iron line which appears to be rapidly variable between the two pointings,
requiring a non-standard interpretation. We then focus on the analysis of the
broad band (0.3-200 keV) continuum using the XMM/EPIC, RGS and SAX/PDS data.
The Mkn 841 spectrum is well fitted by a comptonization model in a geometry
more photon-fed than a simple slab geometry above a passive disk. It presents a
relatively large reflection (R>2) which does not agree with an apparently weak
iron line. It also show the presence of a strong soft excess wellfitted by a
comptonized spectrum in a cool plasma, suggesting the presence of a
multi-temperature corona.


title: The B band luminosities of QSO host galaxies

abstract:
  We report on the analysis of B band imaging data of 57 low-redshift QSOs and
Seyfert 1 galaxies selected from the Hamburg/ESO-Survey, for which host galaxy
dependent selection biases are greatly reduced compared to other optical
surveys. Only one object in the sample is known to be radio-loud.
  We adopted a procedure to remove the AGN contribution by subtracting a scaled
point spread functions from each QSO image. To reclaim the integrated host
galaxy flux we correct for oversubtraction based on simulations. This method
shows to be quite insensitive to the host galaxy morphological type, which we
can unambiguously established for 15 of the 57 objects.
  The quasar host galaxies are detected in all cases. The hosts are very
luminous, ranging in absolute magnitude M_B from -19.0 to -23.8, with an
average of M_B,gal = -21.5, considerably above L* for field galaxies. For the
luminous QSO subsample with M_B < -23 the average host absolute magnitude is
M_B,gal = -23.0, while for the complementary low-luminosity AGN we get M_B,gal
= -21.2, roughly equal to L*.
  The luminous host galaxies in the sample are typically approx. 1 mag brighter
than expected when inferring B band luminosities from studies of similar
objects at longer wavebands. We argue that this mismatch is not likely to be
explained by selection effects, but favor host galaxy colours significanlty
bluer than those of inactive galaxies. Although published B band data are
scant, this result and the findings of other authors are in good agreement.


title:
The near-IR properties and continuum shapes of high redshift quasars
  from the Sloan Digital Sky Survey

abstract:
  We present J-H-K' photometry for a sample of 45 high redshift quasars found
by the Sloan Digital Sky Survey. The sample was originally selected on the
basis of optical colors and spans a redshift range from 3.6 to 5.03. Our
photometry reflects the rest-frame
  SED longward of Ly alpha for all redshifts. The results show that the near-IR
colors of high redshift quasars are quite uniform. We have modelled the
continuum shape of the quasars (from just beyond Ly alpha to ~4000 A) with a
power law of the form f_nu \propto nu^alpha, and find <alpha > =-0.57 with a
scatter of 0.33. This value is similar to what is found for lower redshift
quasars over the same restframe wavelength range, and we conclude that there is
hardly any evolution in the continuum properties of optically selected quasars
up to redshift 5. The spectral indices found by combining near-IR with optical
photometry are in general consistent but slightly flatter than what is found
for the same quasars using the optical spectra and photometry alone, showing
that the continuum region used to determine the spectral indices can somewhat
influence the results.


title: Sonic-Point and Spin-Resonance Model of the Kilohertz QPO Pairs

abstract:
  KHz QPOs have now been detected in more than twenty accreting neutron stars
in low-mass binary systems. Two kHz QPOs are usually detected in each star.
Burst oscillations and two kHz QPOs have recently been detected in the 401 Hz
accretion-powered X-ray pulsar SAX J1808.4-3658. In this star the frequency of
the burst oscillation is approximately equal to the star's spin frequency
nu_spin whereas the frequency separation of the two kHz QPOs is approximately
nu_spin/2. If as expected the frequency of the burst oscillations in other
stars is also approximately nu_spin, the frequency separation is approximately
nu_spin in some stars but approximately nu_spin/2 in others. A frequency
separation approximately equal to nu_spin/2 is unexplained in all existing
models of the kHz QPOs. Here we propose a modified version of the sonic-point
beat-frequency model that can explain within a single framework why the
frequency separation is close to nu_spin in some stars but close to nu_spin/2
in others. As in the original sonic-point model, the frequency nu_QPO2 of the
upper kHz QPO is close to the orbital frequency nu_orb at the radius r_{sp} of
the sonic point in the disk flow. We show that magnetic and radiation fields
rotating with the star will preferentially excite vertical motions in the disk
at the "spin-resonance'' radius r_{sr} where nu_orb - nu_spin is equal to the
vertical epicyclic frequency, producing vertical motions in the disk that
modulate the X-ray flux at approximately nu_QPO2 - nu_spin or approximately
nu_QPO2 - nu_spin/2, depending on whether the disk flow at r_{sr} is smooth or
clumped. This sonic-point and spin-resonance model can also explain
quantitatively the decrease of the kHz QPO frequency separation with increasing
accretion rate that is observed in many sources.


title: Gemini Mid-Infrared Imaging of Massive Young Stellar Objects in NGC 3576

abstract:
  We present a mid-infrared study of NGC 3576. The high-resolution images were
taken at the Gemini South Observatory through narrow and broad band filters
centered between 7.9 micron and 18 micron. The nearly diffraction limited
images show IRS 1 resolved into 4 sources for the first time in the 10 micron
band. The positions of the sources are coincident with massive young stellar
objects detected previously in the near infrared. The properties of each
object, such as spectral energy distribution, silicate absorption feature,
color temperature and luminosities were obtained and are discussed. We also
report observations of two other YSO candidates and the detection of a new
diffuse MIR source without a NIR counterpart. We conclude that none of these
sources contributes significantly to the ionization of the HII region. A
possible location for the ionization source of NGC 3576 is suggested based on
both radio and infrared data.


title: Light element evolution resulting from WMAP data

abstract:
  The recent determination of the baryon-to-photon ratio from WMAP data by
Spergel et al. (2003) allows one to fix with unprecedented precision the
primordial abundances of the light elements D, 3He, 4He and 7Li in the
framework of the standard model of big bang nucleosynthesis. We adopt these
primordial abundances and discuss the implications for Galactic chemical
evolution, stellar evolution and nucleosynthesis of the light elements. The
model predictions on D, 3He and 4He are in excellent agreement with the
available data, while a significant depletion of 7Li in low-metallicity stars
is required to reproduce the Spite plateau.


title:
Contributions to the Nearby Stars (NStars) Project: Spectroscopy of
  Stars Earlier than M0 within 40 parsecs: The Northern Sample I

abstract:
  We have embarked on a project, under the aegis of the Nearby Stars (NStars)/
Space Interferometry Mission Preparatory Science Program to obtain spectra,
spectral types, and, where feasible, basic physical parameters for the 3600
dwarf and giant stars earlier than M0 within 40 parsecs of the sun. In this
paper we report on the results of this project for the first 664 stars in the
northern hemisphere. These results include precise, homogeneous spectral types,
basic physical parameters (including the effective temperature, surface gravity
and the overall metallicity, [M/H]) and measures of the chromospheric activity
of our program stars. Observed and derived data presented in this paper are
also available on the project's website at http://stellar.phys.appstate.edu/ .


title: Dark energy and dark matter from an inhomogeneous dilaton

abstract:
  A cosmological scenario is proposed where the dark matter (DM) and dark
energy (DE) of the universe are two simultaneous manifestations of an
inhomogenous dilaton. The equation of state of the field is scale-dependent and
pressureless at galactic and larger scales and it has negative pressure as a DE
at very large scales. The dilaton drives an inflationary phase followed by a
kinetic energy-dominated one, as in the "quintessential inflation" model
introduced by Peebles & Vilenkin, and soon after the end of inflation particle
production seeds the first inhomogeneities that lead to galaxy formation. The
dilaton is trapped near the minimum of the potential where it oscillates like a
massive field, and the excess of kinetic energy is dissipated via the mechanism
of "gravitational cooling" first introduced by Seidel & Suen. The
inhomogeneities therefore behave like solitonic oscillations around the minimum
of the potential, known as "oscillatons", that we propose account for most DM
in galaxies. Those regions where the dilaton does not transform enough kinetic
energy into reheating or carry an excess of it from regions that have cooled,
evolve to the tail of the potential as DE, driving the acceleration of the
universe.


title: Theoretical UBVRI colors of iron core white dwarfs

abstract:
  We explore photometric properties of hypothetical iron core white dwarfs and
compute their expected colors in UBVRI Johnson broadband system. Atmospheres of
iron core WDs in this paper consist of pure iron covered by a pure hydrogen
layer of an arbitrary column mass. LTE model atmospheres and theoretical
spectra are calculated on the basis of Los Alamos TOPS opacities and the
equation of state from the OPAL project, suitable for nonideal Fe and H gases.
We have also computed UBVRI colors of the models and determined an area on the
B-V vs. U-B and U-B vs. V-I planes, occupied by both pure Fe, and pure H model
atmospheres of WD stars. Finally, we search for iron core white dwarf
candidates in the available literature.


title:
Identification of Type Ia Supernovae at Redshift 1.3 and Beyond with the
  Advanced Camera for Surveys on HST

abstract:
  We present discoveries of SNe Ia at z > 1 and the photometric diagnostic used
to discriminate them from other types of SNe detected during the GOODS Hubble
Space Telescope Treasury program with the Advanced Camera for Surveys (ACS).
Photometric redshift measurements of the hosts combined with deep f606w, f775w,
and f850lp imaging discriminates hydrogen-rich SNe II from SNe I at z > 1 by
exploiting the ultraviolet (UV) deficit in the energy distributions of SNe Ia.
This sorting allows rapid follow-up of space-based discoveries. Subsequent
spectroscopy of 11 GOODS SNe Ia obtained from the ground and with the grism on
ACS confirmed the reliability of our photometric screening. We present the
highest-redshift spectrum of any supernova published to date,
  SN Ia 2002fw at z = 1.3 observed near maximum brightness with the ACS grism.
  The lack of UV flux for true SNe Ia provides an effective tool for our
ongoing efforts to build a sample of SNe Ia at 1.2 < z < 1.8 which will extend
the useful range of the magnitude-redshift relation of SNe Ia.


title:
The effects of low temporal frequency modes on minimum variance maps
  from PLANCK

abstract:
  We estimate the effects of low temporal frequency modes in the time stream on
sky maps such as expected from the PLANCK experiment -- a satellite mission
designed to image the sky in the microwave band. We perform the computations in
a semi-analytic way based on a simple model of PLANCK observations, which
permits an insight into the structure of noise correlations of PLANCK-like
maps, without doing exact, computationally intensive numerical calculations. We
show that, for a set of plausible scanning strategies, marginalization over
temporal frequency modes with frequencies lower than the spin frequency of the
satellite (= 1/60 Hz) causes a nearly negligible deterioration of a quality of
the resulting sky maps. We point out that this observation implies that it
should be possible to successfully remove effects of long-term time domain
parasitic signals from the PLANCK maps during the data analysis stage.


title: A Common Origin for Cosmic Explosions Inferred from Fireball Calorimetry

abstract:
  Past studies suggest that long-duration gamma-ray bursts (GRBs) have a
standard energy of E_gamma ~ 10^51 erg in ultra-relativistic ejecta when
corrected for asymmetry ("jets"). However, recently a group of sub-energetic
bursts, including the peculiar GRB 980425 associated with SN 1998bw (E_gamma ~
10^48 erg), has been identified. Here we report radio observations of GRB
030329, the nearest burst to date, which allow us to undertake calorimetry of
the explosion. Our observations require a two-component explosion: a narrow (5
degrees) ultra-relativistic component responsible for the gamma-rays and early
afterglow, and a wide, mildly relativistic component responsible for the radio
and optical afterglow beyond 1.5 days. While the gamma-rays are energetically
minor, the total energy release, dominated by the wide component, is similar to
that of other GRBs. Given the firm link of GRB 030329 with SN 2003dh our result
suggests a common origin for cosmic explosions in which, for reasons not
understood, the energy in the highest velocity ejecta is highly variable


title:
Millimeter Observations of GRB 030329: Continued Evidence for a
  Two-Component Jet

abstract:
  We present the results of a dedicated campaign on the afterglow of GRB 030329
with the millimeter interferometers of the Owens Valley Radio Observatory
(OVRO), the Berkeley-Illinois-Maryland Association (BIMA), and with the MAMBO-2
bolometer array on the IRAM 30-m telescope. These observations allow us to
trace the full evolution of the afterglow of GRB 030329 at frequencies of 100
GHz and 250 GHz for the first time. The millimeter light curves exhibit two
main features: a bright, constant flux density portion and a steep power-law
decline. The absence of bright, short-lived millimeter emission is used to show
that the GRB central engine was not actively injecting energy well after the
burst. The millimeter data support a model, advocated by Berger et al., of a
two-component jet-like outflow in which a narrow angle jet is responsible for
the high energy emission and early optical afterglow, and a wide-angle jet
carrying most of the energy is powering the radio and late optical afterglow
emission


title: A Late-Time Flattening of Afterglow Light Curves

abstract:
  We present a sample of radio afterglow light curves with measured decay
slopes which show evidence for a flattening at late times compared to optical
and X-ray decay indices. The simplest origin for this behavior is that the
change in slope is due to a jet-like outflow making a transition to
sub-relativistic expansion. This can explain the late-time radio light curves
for many but not all of the bursts in the sample. We investigate several
possible modifications to the standard fireball model which can flatten
late-time light curves. Changes to the shock microphysics which govern particle
acceleration, or energy injection to the shock (either radially or azimuthally)
can reproduce the observed behavior. Distinguishing between these different
possibilities will require simultaneous optical/radio monitoring of afterglows
at late times.


title:
The Nature of Damped Ly-alpha Absorbing Galaxies at z<=1--A Photometric
  Redshift Survey of Damped Ly-alpha Absorbers

abstract:
  We study the nature of damped Lya absorption (DLA) systems at z<=1 using a
sample of 11 DLA galaxies, for which accurate redshift measurements are
available. We demonstrate that the precision of photometric redshifts is
sufficient for identifying DLA galaxies, because DLAs are rare and their
intrinsically high column density implies a small impact parameter of the host
galaxy to the QSO line of sight. We adopt this first large DLA galaxy sample to
study the neutral gas cross section of intermediate-redshift galaxies and
examine the optical properties of DLA galaxies at z<=1. The results of our
study are: (1) the extent of neutral gas around intermediate-redshift galaxies
scales with B-band luminosity as R/R_* = [L_B/L_{B_*}]^{\beta} with R_*=24-30
h^{-1} kpc and \beta = 0.26_{-0.06}^{+0.24} at N(HI)=10^{20} cm^{-2}; (2) the
observed incidence of the DLAs versus the B-band luminosity of the DLA galaxies
is consistent with models derived from adopting a known galaxy B-band
luminosity function and the best-fit scaling relation of the neutral gas cross
section at M_B - 5\log h <= -17; (3) comparison of the observed and predicted
number density of DLAs supports that luminous galaxies can explain most of the
DLAs found in QSO absorption line surveys and a large contribution of dwarfs
(M_B - 5\log h >= -17) to the total neutral gas cross section is not necessary;
(4) of the 11 DLAs studied, 45% are disk dominated, 22% are bulge dominated,
11% are irregular, and 22% are in galaxy groups, indicating that galaxies that
give rise to the DLAs span a wide range of morphological types and arise in a
variety of galaxy environment; (Abridged)


title:
High-Precision Photometry of the Gamma-Ray Burst 020813: The Smoothest
  Afterglow Yet

abstract:
  We report results of our precise reduction of the high signal-to-noise VRI
observations of the optical afterglow of the gamma-ray burst GRB 020813
obtained by Gladders & Hall with the Magellan 6.5-m telescope 3.9-4.9 hours
after the burst. These observations are very well fitted locally by a power-law
curve, providing the tightest constraints yet on how smooth the afterglows can
be in some cases: the rms deviations range from 0.005 mag (0.5%) for the R-band
to 0.007 mag for the I-band, only marginally larger than the rms scatter for
nearby non-variable stars. This scatter is a factor of several smaller then the
smallest reported rms of 0.02 mag for GRB 990510 (Stanek et al). These
observations are in strong contrast to those of afterglows of GRB 011211 and
GRB 021004, for which large > 10% variability has been observed on timescales
from ~20 minutes to several hours. If interstellar medium (ISM) density
fluctuations near the GRB are indeed causing the bumps and wiggles observed in
some bursts, very uniform regions of ISM near some bursts must be present as
well. This result also constrains the intrinsic smoothness of the afterglow
itself.


title: The sub-millimeter properties of broad absorption line quasars

abstract:
  We have carried out the first systematic survey of the sub-millimeter
properties of broad absorption line (BAL) quasars. 30 BAL quasars drawn from a
homogeneously selected sample from the Sloan Digital Sky Survey at redshifts
2<z<2.6 were observed with the SCUBA array at the JCMT to a typical rms
sensitivity of 2.5 mJy. Eight quasars were detected at > 2 sigma significance,
four of which are at > 3 sigma significance. The far-infrared luminosities of
these quasars are > 10^{13} L_solar. There is no correlation of sub-millimeter
flux with either the strength of the broad absorption feature or with absolute
magnitude in our sample. We compare the sub-millimeter flux distribution of the
BAL quasar sample with that of a sample of quasars which do not show BAL
features in their optical spectra and find that the two are indistinguishable.
BAL quasars do not have higher sub-millimeter luminosities than non-BAL
quasars. These findings are consistent with the hypothesis that all quasars
would contain a BAL if viewed along a certain line-of-sight. The data are
inconsistent with a model in which the BAL phenomenon indicates a special
evolutionary stage which co-incides with a large dust mass in the host galaxy
and a high sub-millimeter luminosity. Our work provides constraints on
alternative evolutionary explanations of BAL quasars.


title:
Imaging and spectroscopy of galaxies associated with two z~0.7 damped
  Lyman-alpha absorption systems

abstract:
  We have identified galaxies near two quasars which are at the redshift of
damped Lyman-alpha (DLA) systems in the UV spectra of the quasars. Both
galaxies are actively forming stars. One galaxy has a luminosity close to the
break in the local galaxy luminosity function, L*, the other is significantly
fainter than L* and appears to be interacting with a nearby companion. Despite
the strong selection effects favoring spectroscopic identification of the most
luminous DLA galaxies, many of the spectroscopically-identified DLA galaxies in
the literature are sub-L*, suggesting that the majority of the DLA population
is probably sub-L*, in contrast to MgII absorbers at similar redshifts whose
mean luminosity is close to L*.


title:
The Formation and Evolution of Massive Star Clusters: Historical
  Overview

abstract:
  Some factors connecting the evolutionary histories of galaxies with the
characteristics of their cluster systems are reviewed. Unanswered questions
include: How is one to understand the observation that some globular cluster
systems have disk kinematics whereas others do not? Why do some galaxies have
cluster systems with unimodal metallicity distributions, whereas others have
bimodal metallicity distributions? What caused the average ellipticity of
individual clusters to differ from galaxy to galaxy?


title: Classifications of the Host Galaxies of Supernovae, Set II

abstract:
  Classifications on the DDO system are given for an additional 231 host
galaxies of supernovae that have been discovered during the course of the Lick
Observatory Supernova Search with the Katzman Automatic Imaging Telescope
(KAIT). This brings the total number of hosts of supernovae discovered (or
independently rediscovered) by KAIT, which have so far been classified on a
homogeneous system, to 408. The probability that SNe Ia and SNe II have a
different distribution of host galaxy Hubble types is found to be 99.7%. A
significant difference is also found between the distributions of the host
galaxies of SNe Ia and of SNe Ibc (defined here to include SNe Ib, Ib/c, and
Ic). However, no significant difference is detected between the frequency
distributions of the host galaxies of SNe II and SNe IIn. This suggests that
SNe IIn are generally not SNe Ia embedded in circumstellar material that are
masquerading as SNe II. Furthermore, no significant difference is found between
the distribution of the Hubble types of the hosts of SNe Ibc and of SNe II.
Additionally, SNe II-P and SNe II-L are found to occur among similar stellar
populations. The ratio of the number of SNe Ia-pec to normal SNe Ia appears to
be higher in early-type galaxies than it is in galaxies of later morphological
types. This suggests that the ancestors of SNe Ia-pec may differ systematically
in age or composition from the progenitors of normal SNe Ia. Unexpectedly, five
SNe of Types Ib/c, II, and IIn (all of which are thought to have massive
progenitors) are found in host galaxies that are nominally classified as types
E and S0. However, in each case the galaxy classification is uncertain, or
newly inspected images show evidence suggesting a later classification
(abridged) ...


title: Probing reionization with Lyman-alpha emission lines

abstract:
  Lyman-alpha emission from high-redshift galaxies may be a powerful probe of
the ionization history of the IGM at z>6: the observed Lyman-alpha emission
line is sensitive to the neutral fraction of IGM hydrogen in the range 0.1-1.
We present calculations of observed Lyman-alpha emission lines from z>6
galaxies, illustrating the effect of varying the many free parameters
associated with the emitting galaxy, its halo, and the IGM around the galaxy.
In particular, we use a dynamic model of the IGM that includes the effect of
IGM infall toward the emitting galaxy. Galactic winds may play a crucial role
in determining observed Lyman-alpha line fluxes. We compare our model
predictions with observations of two z=6.5 galaxies and conclude that, if
galactic winds are allowed for, existing observations place no constraint on
the neutral fraction of the IGM at z=6.5. Future space-based observations will
constrain the importance of galactic winds; if winds are unimportant for the
observed z=6.5 galaxies, our models suggest that the IGM neutral fraction at
z=6.5 is <~0.1.