title: Atmospheric parameters and abundances of sdB stars

abstract:
  We summarize recent results of quantitative spectral analyses using NLTE and
metal line-blanketed LTE model atmospheres. Temperatures and gravities derived
for hundreds of sdB stars are now available and allow us to investigate
systematic uncertainties of teff, log g scales and to test the theory of
stellar evolution and pulsations. Surface abundance patterns of about two dozen
sdB stars are surprisingly homogenous. In particular the iron abundance is
almost solar for most sdBs. We highlight one iron deficient and three super
metal-rich sdBs, a challenge to diffusion theory. SdB stars are slowly rotating
stars unless they are in close binary systems which is hard to understand if
the sdB stars were formed in merger events. The only exception is the pulsator
PG 1605+072 rotating at v sin i = 39km/s. Signatures of stellar winds from sdB
stars have possibly been found.


title: Understanding Core-Collapse Supernovae

abstract:
  I summarize, in the form of an extended abstract, the ongoing efforts at the
University of Arizona (and in collaboration) to understand core-collapse
supernovae theoretically. Included are short discussions of 1D (SESAME) and 2D
(VULCAN/2D) codes and results, as well as discussions of the possible role of
rotation. Highlighted are recent developments in multi-dimensional radiation
hydrodynamics and the essential physics of the neutrino-driven mechanism.


title: CMB 3-point functions generated by non-linearities at recombination

abstract:
  We study the 3-point functions generated at recombination in the squeezed
triangle limit, when one mode has a wavelength much larger than the other two
and is outside the horizon. The presence of the long wavelength mode cannot
change the physics inside the horizon but modifies how a late time observer
sees the anisotropies. The effect of the long wavelength mode can be divided
into a redefinition of time and spatial scales, a Shapiro time delay and
gravitational lensing. The separation is gauge dependent but helps develop
intuition. We show that the resulting 3-point function corresponds to an f_NL <
1 and that its shape is different from that created by the f_NL (or local)
model.


title: Tidal Torques and the Orientation of Nearby Disk Galaxies

abstract:
  We use numerical simulations to investigate the orientation of the angular
momentum axis of disk galaxies relative to their surrounding large scale
structure. We find that this is closely related to the spatial configuration at
turnaround of the material destined to form the galaxy, which is often part of
a coherent two-dimensional slab criss-crossed by filaments. The rotation axis
is found to align very well with the intermediate principal axis of the inertia
momentum tensor at this time. This orientation is approximately preserved
during the ensuing collapse, so that the rotation axis of the resulting disk
ends up lying on the plane traced by the protogalactic material at turnaround.
This suggests a tendency for disks to align themselves so that their rotation
axis is perpendicular to the minor axis of the structure defined by surrounding
matter. One example of this trend is provided by our own Galaxy, where the
Galactic plane is almost at right angles with the supergalactic plane (SGP)
drawn by nearby galaxies; indeed, the SGP latitude of the North Galactic Pole
is just 6 degrees. We have searched for a similar signature in catalogs of
nearby disk galaxies, and find a significant excess of edge-on spirals (for
which the orientation of the disk rotation axis may be determined
unambiguously) highly inclined relative to the SGP. This result supports the
view that disk galaxies acquire their angular momentum as a consequence of
early tidal torques acting during the expansion phase of the protogalactic
material.


title:
Studying the decay of the vacuum energy with the observed density
  fluctuation spectrum

abstract:
  One of the major problems in cosmology today is to explain the observed
acceleration of the universe. The present observational data are consistent
with the simplest solution to this problem, which is based on the vacuum
energy. A decaying vacuum energy is a very attractive solution. It could link
the value of the present vacuum energy, that is accelerating the universe
today, with the value that created the inflationary epoch in the past. We
investigate here models that suggest that the vacuum energy decays into cold
dark matter (CDM) and show that the density fluctuation spectrum obtained from
the cosmic microwave background (CMB) data together with large galaxy surveys
(e.g., the Sloan Digital Sky Survey), puts strong limits on the rate of decay
of the vacuum energy. CDM produced by a decaying vacuum energy would dilute the
density fluctuation spectrum, created in the primordial universe and observed
with large galaxy surveys at low redshifts. Our results indicate that the decay
rate of the vacuum energy into CDM is extremely small.


title:
The Non-Relativistic Evolution of GRBs 980703 and 970508:
  Beaming-Independent Calorimetry

abstract:
  We use the Sedov-Taylor self-similar solution to model the radio emission
from the gamma-ray bursts (GRBs) 980703 and 970508, when the blastwave has
decelerated to non-relativistic velocities. This approach allows us to infer
the energy independent of jet collimation. We find that for GRB 980703 the
kinetic energy at the time of the transition to non-relativistic evolution,
t_NR ~ 40 d, is E_ST ~ (1-6)e51 erg. For GRB 970508 we find E_ST ~ 3e51 erg at
t_NR ~ 100 d, nearly an order of magnitude higher than the energy derived in
Frail, Waxman and Kulkarni (2000). This is due primarily to revised
cosmological parameters and partly to the maximum likelihood fit we use here.
Taking into account radiative losses prior to t_NR, the inferred energies agree
well with those derived from the early, relativistic evolution of the
afterglow. Thus, the analysis presented here provides a robust,
geometry-independent confirmation that the energy scale of cosmological GRBs is
about 5e51 erg, and additionally shows that the central engine in these two
bursts did not produce a significant amount of energy in mildly relativistic
ejecta at late time. Furthermore, a comparison to the prompt energy release
reveals a wide dispersion in the gamma-ray efficiency, strengthening our
growing understanding that E_gamma is a not a reliable proxy for the total
energy.


title:
Discovery of Massive Evolved Galaxies at z > 3 in the Hubble Ultra Deep
  Field

abstract:
  We have identified six early-type galaxies at z>2.8 in the central 5.76
arcmin^2 Hubble Ultra Deep Field NICMOS region based on a pronounced broad-band
discontinuity between the NICMOS F110W and F160W bandpasses. These galaxies
have red observed optical and near-infrared colors (AB_F775W - AB_F160W >= 2)
that cannot be explained entirely by dust reddening (indicating advanced age),
and their luminosities at rest-frame optical wavelengths suggest a substantial
stellar mass. One of the galaxies is detected in X-ray and is likely to have an
active nuclear region, while the rest are estimated to be at least 1 Gyr old at
z ~ 3 and contain total stellar mass of (0.4 - 9.1) x 10^{10} h^{-2} M_\odot.
We calculate a cumulative comoving stellar mass density of rho_star = 0.7 - 1.2
x 10^7 h M_\odot Mpc^{-3} for massive evolved galaxies of M > 10^9 h^{-2}
M_\odot at z>2.5. Comparison of the stellar mass density confined in galaxies
of different types shows that massive evolved galaxies contribute ~ 16 - 28% of
total stellar mass density even at these early epochs. Finally, an analysis of
their morphology observed in the ACS and NICMOS images shows that the active
galaxy has compact structure, while the rest are less concentrated. The
presence of massive evolved galaxies at z ~ 3, when the universe was only 2 Gyr
old, suggests that early star formation may have been particularly efficient in
massive halos.


title: Microquasar-AGN-GRB Connections

abstract:
  I review the progress made on the physics of black hole systems in the
context of the analogy between AGN and microquasars that was proposed one
decade ago. If the emerging empirical correlations between the observational
properties of stellar and supermassive black holes will become more robust, we
will use them to determine the mass and spin of black holes, independently of
theoretical models. Microquasars are fossils of sources of Gamma-ray bursts
(GRBs) of long duration, and their kinematics provides observational clues on
the physics of collapsars. If jets in GRBs, microquasars and AGN are due to a
unique universal magnetohydrodynamic mechanism, synergy between the research on
these three different classes of cosmic objects will lead to further progress
in black hole physics and astrophysics.
  The potential contributions with INTEGRAL in this field of research are also
discussed. It is shown that the Galactic Plane Survey (GPS) with INTEGRAL is
unraveling new extragalactic sources of hard x-rays behind the Milky Way, as
well as new black hole high-mass binaries that were hidden by large columns of
gas and dust.


title: Feedback in AGN heating of galaxy clusters

abstract:
  One of the challenges that models of AGN heating of the intracluster medium
(ICM) face, is the question how the mechanical luminosity of the AGN is tuned
to the radiative losses of the ICM. Here we implement a simple 1D model of a
feedback mechanism that links the luminosity of the AGN to the accretion rate.
We demonstrate how this simple feedback mechanism leads to a quasi-steady state
for a broad range of parameters. Moreover, within this feedback model, we
investigate the effect of thermal conduction and find that its relative
importance depends strongly on the cluster mass.


title: Warm molecular gas in galaxy-galaxy merger NGC6090

abstract:
  We present observations of the CO 2-1 and 3-2 transitions toward the merging
galaxies of NGC6090 with the Submillimeter Array (SMA) (The Submillimeter Array
(SMA) is a joint project between the Smithsonian Astrophysical Observatory and
the Academia Sinica Institute of Astronomy and Astrophysics, and is funded by
the Smithsonian Institution and the Academia Sinica.). The high resolution CO
data reveal three gas concentrations. The main component is peaking in the
overlap region between the two galaxies, where the near-IR a nd radio continuum
emission are weak. The CO 2-1 emission from the face-on galaxy NGC6090E is
somewhat stronger than that from the edge-o n galaxy NGC6090W.
  The CO 3-2 emission peaks in the overlap region, similar to the CO 2-1
emission . More than 50% of the CO 3-2 emission arises from the 2$''$ (1.2 kpc)
area of the overlap region. There appears to be CO 3-2 emission toward the
nuclear region and the north-west arm of NGC6090E, while no CO 3-2 emission is
detected toward NGC6090W. Unlike the CO gas, most of the radio continuum
emission comes from NGC6090E. The strong CO emission, together with the weak
radio continuum emission, suggests that star formation in the overlap region
has not proceeded long enoug h to produce significant numbers of supernovae
which would be detectable due to their radio continuum emission.


title:
An X-Ray Jet from a White Dwarf - Detection of the Collimated Outflow
  from CH Cygni with Chandra

abstract:
  Most symbiotic stars consist of a white dwarf accreting material from the
wind of a red giant. An increasing number of these objects have been found to
produce jets. Analysis of archival Chandra data of the symbiotic system CH
Cygni reveals faint extended emission to the south, aligned with the optical
and radio jets seen in earlier HST and VLA observations. CH Cygni thus contains
only the second known white dwarf with an X-ray jet, after R Aquarii. The
X-rays from symbiotic-star jets appear to be produced when jet material is
shock-heated following collision with surrounding gas, as with the outflows
from some protostellar objects and bipolar planetary nebulae.


title:
Exploring Halo Substructure with Giant Stars: A diffuse star cloud or
  tidal debris around the Milky Way in Triangulum-Andromeda

abstract:
  We report here the discovery of an apparent excess of 2MASS M giant
candidates with dereddened 0.85 < J-K_S < 1.2 spanning a considerably large
area of the celestial sphere between, at least, $100\degr < l < 150\degr$ and
$-20\degr > b > -40\degr$, and covering most of the constellations of
Triangulum and Andromeda. This structure does not seem to be preferentially
distributed around a clear core, but rather lies in a tenuous, clumpy
cloud-like structure tens of kiloparsecs away. The reduced proper-motion
diagram as well as spectroscopy of a subsample shows these excess stars to be
real giants, not contaminating dwarfs. Radial velocity measurements indicate
among those M giants the presence of a coherent kinematical structure with a
velocity dispersion $\sigma < 17$ km s$^{-1}$. Our findings support the
existence of a quite dispersed stellar structure around the Milky Way that, due
to its coreless and sparse distribution, could be part of a tidal stream or a
new kind of satellite galaxy.


title: Spectral Properties of Brown Dwarfs and Hot Jupiters

abstract:
  Brown dwarfs bridge the gap between the stellar and planetary mass regimes.
Evolving from conditions very similar to the lowest-mass stars, the atmospheres
of older brown dwarfs closely resemble those expected in close-in extrasolar
giant planets, and with cooler BDs still being discovered, more and more
approach the properties of gas giants at wider separation. Interpreting the
spectra of BDs is therefore a crucial step towards understanding and predicting
the spectral and thermal properties of EGPs.
  Essential properties of substellar atmospheres are massive molecular
line-blanketing and the condensation of species with decreasing Teff, changing
the chemical equilibrium composition and causing absorption from dust grains.
More complex details involve the distribution of dust clouds over the surface
giving rise to temporal variability, and possible deviations from chemical
equilibrium conditions. In the case of close-in EGPs and some BDs in binary
systems, the effect of irradiation from the primary significantly affects the
spectral properties and thermal evolution.


title:
Is the Initial Mass Function of Low Surface Brightness Galaxies
  Dominated by Low Mass Stars?

abstract:
  The rotation curves of low surface brightness (LSB) galaxies suggest that
they possess significantly higher mass-to-light (M/L) ratios than their high
surface brightness counterparts, indicating that LSB galaxies may be dark
matter dominated. This interpretation is hampered by the difficulty of
disentangling the disc and dark halo contributions from the disc dynamics of
LSB galaxies. Recently, Fuchs (2002) has attempted such a disentanglement using
spiral arm density wave and swing amplification theory, allowing an independent
measurement of the disc mass; this work suggests that LSB discs are
significantly more massive than previously believed. This would considerably
reduce the amount of matter required in the dark halos in fitting the rotation
curves. Interestingly, the high mass-to-light ratios derived for the discs
appear inconsistent with standard stellar population synthesis models. In this
paper, we investigate whether the high M/L ratios for the Fuchs LSB discs might
be understood by adopting a very ``bottom heavy'' initial mass function (IMF).
We find that an IMF with a power law exponent of around alpha=3.85 (compared to
the standard Salpeter IMF, alpha=2.35) is sufficient to explain the unusually
high M/L ratios of the Fuchs sample. Within the context of the models, the blue
colours ((B-R)_0 < 1.0) of the sample galaxies result from being metal-poor
([Fe/H] = -1.5 ~ -1.0) and having undergone recent (~1-3 Gyr ago) star
formation.


title: The Current Status of Primary Distance Indicators

abstract:
  A review is given of the current status of the primary distance indicators.
The relevance of these indicators for determining the local expansion rate and
the age of globular clusters is briefly outlined.


title:
A new determination of the extragalactic diffuse gamma-ray background
  from EGRET data

abstract:
  We use the GALPROP model for cosmic-ray propagation to obtain a new estimate
of the Galactic component of gamma rays, and show that away from the Galactic
plane it gives an accurate prediction of the observed EGRET intensities in the
energy range 30 MeV - 50 GeV. On this basis we re-evaluate the extragalactic
gamma-ray background. We find that for some energies previous work
underestimated the Galactic contribution at high latitudes and hence
overestimated the background. Our new background spectrum shows a positive
curvature similar to that expected for models of the extragalactic emission
based on the blazar population.


title: Figure Rotation of Cosmological Dark Matter Halos

abstract:
  We have analyzed galaxy and group-sized dark matter halos formed in a high
resolution LCDM numerical N-body simulation in order to study the rotation of
the triaxial figure, a property in principle independent of the angular
momentum of the particles themselves. Such figure rotation may have
observational consequences, such as triggering spiral structure in extended gas
disks. The orientation of the major axis is compared at 5 late snapshots of the
simulation. Halos with significant substructure or that appear otherwise
disturbed are excluded from the sample. We detect smooth figure rotation in 278
of the 317 halos in the sample. The pattern speeds follow a log normal
distribution centred at 0.148 h km/s/kpc with a width of 0.83. These speeds are
an order of magnitude smaller than required to explain the spiral structure of
galaxies such as NGC 2915. The axis about which the figure rotates aligns very
well with the halo minor axis, and also reasonably well with its angular
momentum vector. The pattern speed is correlated with the halo spin parameter,
but shows no correlation with the halo mass. The halos with the highest pattern
speeds show particularly strong alignment between their angular momentum
vectors and their figure rotation axes. The figure rotation is coherent outside
0.12 r_vir. The measured pattern speed and degree of internal alignment of the
figure rotation axis drops in the innermost region of the halo, which may be an
artifact of the numerical force softening. The axis ratios show a weak tendency
to become more spherical with time.


title: Subsonic propellers in a strong wind as anomalous X-ray pulsars

abstract:
  The appearance of subsonic propellers situated in a strong wind is discussed.
We show that it is similar to the appearance of anomalous X-ray pulsars (AXPs)
provided the mass and the magnetic moment of neutron stars are 1.4 solar
masses, and 2E+30 G cm^3, respectively, and the strength of the wind is M_c =
3E+17 g/s. Under these conditions, the spin periods of subsonic propellers are
limited within the range of 5-15 s, and the expected spin-down rates are close
to 7E-11 s/s. The mass accretion rate onto the stellar surface is limited to
the rate of plasma penetration into its magnetosphere at the boundary. As this
process is governed by the reconnection of the field lines, the accretion rate
onto the stellar surface constitutes 1-2% of M_c. In this case the X-ray
luminosity of the objects under consideration can be evaluated as 4E+35 erg/s.
The model predicts the existence of at least two spatially separated sources of
the X-ray emission: hot spots at the stellar surface, and the hot atmosphere
surrounding the magnetosphere of the star. The ages of the subsonic propellers
under the conditions of interest are limited to 10^5 yr.


title: Gravitationally coupled scale-free discs

abstract:
  In a composite fluid system of two gravitationally coupled barotropic
scale-free discs bearing a rotation curve $v\propto r^{-\beta}$ and a power-law
surface mass density $\Sigma_0\propto r^{-\alpha}$ with $\alpha=1+2\beta$, we
construct coplanar stationary aligned and spiral perturbation configurations in
the two discs. Due to the mutual gravitational interaction, there are two
independent classes of perturbation modes with surface mass density
disturbances in the two coupled discs being either in-phase or out-of-phase. We
derive analytical criteria for such perturbation modes to exist and show
numerical examples. We compute the aligned and spiral perturbation modes
systematically to explore the entire parameter regime. For the axisymmetric
$m=0$ case with radial oscillations, there are two unstable regimes of
ring-fragmentation and collapse corresponding to short and long radial
wavelengths, respectively. Only within a certain range of the rotation
parameter $D_s^2$ (square of the effective Mach number for the stellar disc),
can a composite disc system be stable against all axisymmetric perturbations.
Compared with a single-disc system, the coupled two-disc system becomes less
stable against such axisymmetric instabilities.


title: Fast Identification of Bound Structures in Large N-body Simulations

abstract:
  We present an algorithm which is designed to allow the efficient
identification and preliminary dynamical analysis of thousands of structures
and substructures in large N-body simulations. First we utilise a refined
density gradient system (based on DENMAX) to identify the structures, and then
apply an iterative approximate method to identify unbound particles, allowing
fast calculation of bound substructures. After producing a catalog of separate
energetically bound substructures we check to see which of these are
energetically bound to adjacent substructures. For such bound complex subhalos,
we combine components and check if additional free particles are also bound to
the union, repeating the process iteratively until no further changes are
found. Thus our subhalos can contain more than one density maximum, but the
scheme is stable: starting with a small smoothing length initially produces
small structures which must be combined later, and starting with a large
smoothing length produces large structures within which sub-substructure is
found. We apply this algorithm to three simulations. Two which are using the
TPM algorithm by Bode et al. (2000) and one on a simulated halo by Diemand
(2004). For all these halos we find about 5-8% of the mass in substructures.


title: Model independent analysis of dark energy I: Supernova fitting result

abstract:
  The nature of dark energy is a mystery to us. This paper uses the supernova
data to explore the property of dark energy by some model independent methods.
We first Talyor expanded the scale factor $a(t)$ to find out the deceleration
parameter $q_0<0$. This result just invokes the Robertson-Walker metric. Then
we discuss several different parameterizations used in the literature. We find
that $\Omega_{\rm DE0}$ is almost less than -1 at $1\sigma$ level. We also find
that the transition redshift from deceleration phase to acceleration phase is
$z_{\rm T}\sim 0.3$.


title:
Contribution of the Disk Emission to the Broad Emission Lines in AGNs:
  Two-component model

abstract:
  We present an investigation of the structure of the emission line region in a
sample of 12 single-peaked Active Galactic Nuclei (AGNs). Using the high
resolution H-beta and H-alpha line profiles observed with the Isaac Newton
Telescope (La Palma) we study the substructure in the lines (such as shoulders
or bumps) which can indicate a disk or disk-like emission in Broad Line Regions
(BLRs). Applying Gaussian analysis we found that both kinds of emission
regions, BLR and NLR, are complex. In this sample the narrow [OIII] lines are
composites of two components; NLR1 which have random velocities from \sim 200
to 500 km/s and systematic velocities toward the blue from 20 to 350 km/s, and
NLR2 with smaller random velocities (\sim 100-200 km/s) and a redshift
corresponding to the cosmological one. The BLR also have complex structure and
we apply a two-component model assuming that the line wings originate in a very
broad line region (VBLR) and the line core in an intermediate line region
(ILR). The VBLR is assumed to be an accretion disk and the ILR a spherical
emission region.
  The model fits very well the H-alpha and H-beta line profiles of the AGNs.


title: The late time radio emission from SN 1993J at meter wavelengths

abstract:
  We present the investigations of SN 1993J using low frequency observations
with the Giant Meterwave Radio Telescope. We analyze the light curves of SN
1993J at 1420, 610, 325 and 243 MHz during $7.5-10$ years since explosion.The
supernova has become optically thin early on in the 1420 MHz and 610 MHz bands
while it has only recently entered the optically thin phase in the 325 MHz
band. The radio light curve in the 235 MHz band is more or less flat. This
indicates that the supernova is undergoing a transition from an optically thick
to optically thin limit in this frequency band. In addition, we analyze the SN
radio spectra at five epochs on day 3000, 3200, 3266, 3460 and 3730 since
explosion. Day 3200 spectrum shows a synchrotron cooling break. SN 1993J is the
only young supernova for which the magnetic field and the size of the radio
emitting region are determined through unrelated methods. Thus the mechanism
that controls the evolution of the radio spectra can be identified. We suggest
that at all epochs, the synchrotron self absorption mechanism is primarily
responsible for the turn-over in the spectra. Light curve models based on free
free absorption in homogeneous or inhomogeneous media at high frequencies
overpredict the flux densities at low frequencies. The discrepancy is
increasingly larger at lower and lower frequencies. We suggest that an extra
opacity, sensitively dependent on frequency, is likely to account for the
difference at lower frequencies. The evolution of the magnetic field
(determined from synchrotron self absorption turn-over) is roughly consistent
with $B \propto t^{-1}$. Radio spectral index in the optically thin part
evolves from $\alpha \sim 0.8-1.0$ at few tens of days to $\sim 0.6$ in about
10 years.


title: SN 2003lw and GRB 031203: A Bright Supernova for a Faint Gamma-ray Burst

abstract:
  Optical and near-infrared observations of the gamma-ray burst GRB 031203, at
z = 0.1055, are reported. A very faint afterglow is detected superimposed to
the host galaxy in our first infrared JHK observations, carried out ~9 hours
after the burst. Subsequently, a rebrightening is detected in all bands,
peaking in the R band about 18 rest-frame days after the burst. The
rebrightening closely resembles the light curve of a supernova like SN 1998bw,
assuming that the GRB and the SN went off almost simultaneously, but with a
somewhat slower evolution. Spectra taken close to the maximum of the
rebrightening show extremely broad features as in SN 1998bw. The determination
of the absolute magnitude of this SN (SN 2003lw) is difficult owing to the
large and uncertain extinction, but likely this event was brighter than SN
1998bw by 0.5 mag in the VRI bands, reaching an absolute magnitude M_V =
-19.75+-0.15.


title:
New Perspectives on the X-ray Emission of HD 104237 and Other Nearby
  Herbig Ae/Be Stars from XMM-Newton and Chandra

abstract:
  We present new X-ray observations of the nearby Herbig Ae star HD 104237 (=
DX Cha) with XMM-Newton, whose objective is to clarify the origin of the
emission. Several X-ray emission lines are clearly visible in the CCD spectra,
including the high-temperature Fe K-alpha complex. The emission can be
accurately modeled as a multi-temperature thermal plasma with cool (kT < 1 keV)
and hot (kT > 3 keV) components. The presence of a hot component is compelling
evidence that the X-rays originate in magnetically confined plasma, either in
the Herbig star itself or in the corona of an as yet unseen late-type
companion. The X-ray temperatures and luminosity (log Lx = 30.5 ergs/s) are
within the range expected for a T Tauri companion, but high resolution Chandra
and HST images constrain the separation of a putative companion to less than 1
arcsec. We place these new results into broader context by comparing the X-ray
and bolometric luminosities of a sample of nearby Herbig stars with those of T
Tauri stars and classical main-sequence Be stars. We also test the predictions
of a model that attributes the X-ray emission of Herbig stars to magnetic
activity that is sustained by a shear-powered dynamo.


title:
On the correlation between the recent star formation rate in the Solar
  Neighbourhood and the glaciation period record on Earth

abstract:
  Shaviv (2003) has shown evidence for a correlation between variations in the
Galactic cosmic ray flux reaching Earth and the glaciation period record on
Earth during the last 2 Gyr. If the flux of cosmic rays is mainly the result of
Type II supernovae, an additional correlation between the star formation
history of the Solar Neighbourhood and the timing of past ice ages is expected.
Higher star formation rate implies increased cosmic ray flux and this may
translate into colder climate through a rise in the average low altitude cloud
cover. Here we reanalyze the correlation between this star formation history
and the glaciation period record on Earth using a volume limited open cluster
sample. Numerical modeling and recent observational data indicate that the
correlation is rather strong but only if open clusters within 1.5 kpc from the
Sun are considered.


title:
Scattering in the vicinity of relativistic jets: a method for
  constraining jet parameters

abstract:
  Relativistic jets of radio loud active galactic nuclei (AGN) produce highly
directed, intense beams of radiation. A fraction of this beamed radiation
scatters on the thermal plasma generally surrounding an AGN. The morphology of
the scattered emission can thus provide constraints on the physical properties
of the jet. We present a model to study the feasibility of constraining the
parameters of a jet, especially its inclination angle and bulk Lorentz factor
in this way. We apply our model to the well studied jet of M87 and the
surrounding diffuse gas and find that the observational limits of the surface
brightness measured in the region of the putative counterjet provide the
tightest constraints on the jet parameters consistent with constraints derived
by other methods. We briefly discuss the applicability of our model to other
sources exhibiting relativistic motions


title: Mach number dependence of the onset of dynamo action

abstract:
  The effect of compressibility on the onset of nonhelical turbulent dynamo
action is investigated using both direct simulations as well as simulations
with shock-capturing viscosities, keeping however the regular magnetic
diffusivity. It is found that the critical magnetic Reynolds number increases
from about 35 in the subsonic regime to about 70 in the supersonic regime. In
the high resolution direct simulations the shock structures are much sharper
than in the low resolution shock-capturing simulations. Nevertheless, the
magnetic field looks roughly similar in both cases and does not show shock
structures. Similarly, the onset of dynamo action is not significantly affected
by the shock-capturing viscosity.


title:
The law of evolution of energy density in the universe imposed by
  quantum cosmology and its consequences

abstract:
  The quantum model of homogeneous and isotropic universe filled with the
uniform scalar field is considered. This model predicts effective inverse
square-law dependence of the mean total energy density <\rho> on the
expectation value of cosmological scale factor <a> where the averaging is
performed over the state with large quantum numbers. Such a law of decreasing
of <\rho> during the expansion of the universe allows to describe the observed
coordinate distances to type Ia supernovae and radio galaxies in the redshift
interval z = 0.01 - 1.8. A comparison with phenomenological models with the
cosmological constant (\Lambda CDM) and with zero dark energy component
(\Omega_{M} = 1) is made. It is shown that observed small deviations of the
coordinate distances to some sources from the predictions of above mentioned
simple quantum model can be explained by the fluctuations \delta a of the scale
factor about the average value <a>. These fluctuations can arise due to finite
widths of quasistationary states in the early universe. During expansion the
fluctuations \delta a grow with time and manifest themselves in the form of
observed relative increase or decrease of coordinate distances. The amplitudes
of fluctuations \delta a/<a> calculated from observed positions of individual
supernovae are in good agreement with their estimations in quantum theory.
Possible consequences from the conclusions of quantum theory are discussed.


title: Dark matter and dark energy production in quantum model of the universe

abstract:
  The quantum model of the homogeneous, isotropic, and spatially closed
universe predicts an existence of two types of collective quantum states in the
universe. The states of one type characterize a gravitational field, the others
describe a matter (uniform scalar) field. In the first stage of the evolution
of the universe a primordial scalar field evolves slowly into its vacuum-like
state. In the second stage the scalar field oscillates about an equilibrium due
to the quantum fluctuations. The universe is being filled with matter in the
form of elementary quantum excitations of the vibrations of the scalar field.
The separate quantum excitations are characterized by non-zero values of their
energies (masses). Under the action of gravitational forces mainly these
excitations decay into ordinary particles (baryons and leptons) and dark
matter. The elementary quantum excitations of the vibrations of the scalar
field which have not decayed up to now form dark energy. The numerical
estimations lead to realistic values of both the matter density \Omega_{M} =
0.29 (with the contributions from dark matter, \Omega_{DM} = 0.25, and
optically bright baryons, \Omega_{stars} = 0.0025) and the dark energy density
\Omega_{X} = 0.71 if one takes that the mean energy ~ 10 GeV is released in
decay of dark energy quantum and fixes baryonic component \Omega_{B} = 0.04
according to observational data. The energy (mass) of dark energy quantum is
equal to ~ 17 GeV and the energy > 2 x 10^{10} GeV is needed in order to detect
it. Dark matter particle has the mass ~ 6 GeV. The Jeans mass for dark matter
which is considered as a gas of such massive particles is equal to M_{J} ~
10^{5} M_{\odot}.


title: SZ effect from Dark Matter annihilation

abstract:
  We derive in this Letter the SZ effect induced by the secondary electrons
produced in the annihilation of Weakly Interacting Massive Particles (assumed
here to be neutralinos) in gravitationally bound structures dominated by Cold
Dark Matter (CDM). We show that the DM induced SZ effect has a specific
spectral shape and an amplitude which increases for decreasing neutralino mass
M_{chi}. The available SZ data on the Coma cluster set an upper limit on the
quantity <sigma V> n^2_{chi} which can be combined with the WMAP constraints on
Omega_m h^2 to restrict the available neutralino models in the <\sigma V> -
M_{chi} plane. We delineate various potential applications of this method to
constraint the physical properties of the Dark Matter particles from the study
of galaxy clusters and dwarf spheroidal galaxies in the light of the next
coming high-sensitivity SZ experiments.


title: Introducing BAX: a database for X-ray clusters and groups of galaxies

abstract:
  We present BAX, Base de Donnees Amas de Galaxies X
(http://webast.ast.obs-mip.fr/bax), a multi-wavelength database dedicated to
X-ray clusters and groups of galaxies allowing detailed information retrieval.
BAX is designed to support astronomical research by providing access to
published measurements of the main physical quantities and to the related
bibliographic references: basic data stored in the database are cluster/group
identifiers, equatorial coordinates, redshift, flux, X-ray luminosity (in the
ROSAT band) and temperature, and links to additional linked parameters (in
X-rays, such as spatial profile parameters, as well as SZ parameters of the hot
gas, lensing measurements,and data at other wavelengths, such as optical and
radio). The clusters and groups in BAX can be queried by the basic parameters
as well as the linked parameters or combinations of these. We expect BAX to
become an important tool for the astronomical community. BAX will optimize
various aspects of the scientific analysis of X-ray clusters and groups of
galaxies, from proposal planning to data collection, interpretation and
publication, from both ground based facilities like MEGACAM (CFHT), VIRMOS
(VLT) and space missions like XMM-Newton, Chandra and Planck.


title: XMM-Newton observations of high-luminosity radio-quiet QSOs

abstract:
  XMM Newton observations of five high-luminosity radio-quiet QSOs (Q
0144-3938, UM 269, PG 1634+706, SBS 0909+532 and PG 1247+267) are presented.
Spectral energy distributions were calculated from the XMM-Newton EPIC
(European Photon Imaging Camera) and OM (Optical Monitor) data, with bolometric
luminosities estimated in the range from 7 x 10^45 to 2 x 10^48 erg s^-1 for
the sample, peaking in the UV. At least four of the QSOs show a similar soft
excess, which can be well modelled by either one or two blackbody components,
in addition to the hard X-ray power-law. The temperatures of these blackbodies
(~100-500 eV) are too high to be direct thermal emission from the accretion
disc, so Comptonization is suggested. Two populations of Comptonizing
electrons, with different temperatures, are needed to model the broad-band
spectrum. The hotter of these produces what is seen as the hard X-ray
power-law, while the cooler (~0.25-0.5 keV) population models the spectral
curvature at low energies. Only one of the QSOs shows evidence for an
absorption component, while three of the five show neutral iron emission. Of
these, PG 1247+267 seems to have a broad line (EW ~ 250 eV), with a strong,
associated reflection component (R ~ 2), measured out to 30 keV in the rest
frame of the QSO. Finally, it is concluded that the X-ray continuum shape of
AGN remains essentially constant over a wide range of black hole mass and
luminosity.


title:
Affleck-Dine Baryogenesis and heavy elements production from
  Inhomogeneous Big Bang Nucleosynthesis

abstract:
  We study the impact of possible high density baryonic bubbles on the early
formed QSO, IGM, and metal poor stars. Such bubbles could be created, under
certain conditions, in Affleck-Dine model of baryogenesis and may occupy a
relatively small fraction of space, while the dominant part of the cosmological
volume has the normal observed baryon-to-photon ratio $\eta = 6\cdot 10^{-10}$.
The value of $\eta$ in the bubbles, could be much larger than the usually
accepted one (it might be even close to unity) without contradicting the
existing data on light element abundances and the observed angular spectrum of
CMBR. We find upper bounds on $\eta$ by comparing heavy elements' abundances
produced in BBN and those of metal poor stars. We conclude that $\eta$ should
be smaller than $10^{-5}$ in some metal poor star regions.


title: INTEGRAL Cross-calibration Status

abstract:
  The status of the INTEGRAL cross-calibration is presented for a standard
X-ray astronomy source, the Crab Nebula, as well as for some weaker sources.
The relative flux normalization for the different INTEGRAL instruments is
discussed together with spectral shape features.


title: Velocity Modification of Power Spectrum from Absorbing Medium

abstract:
  Quantitative description of the statistics of intensity fluctuations within
spectral line data cubes introduced in our earlier work is extended to the
absorbing media. A possibility of extracting 3D velocity and density statistics
from both integrated line intensity as well as from the individual channel maps
is analyzed. We find that absorption enables the velocity effects to be seen
even if the spectral line is integrated over frequencies. This regime that is
frequently employed in observations is characterized by a non-trivial relation
between the spectral index of velocities and the spectral index of intensity
fluctuations. For instance when density is dominated by fluctuations at large
scales, i.e. when correlations scale as r^{-\gamma}, \gamma<0, the intensity
fluctuations exhibit a universal spectrum of fluctuations ~K^{-3} over a range
of scales. When small scale fluctuations of density contain most of the energy,
i.e. when correlations scale as r^{-\gamma}, \gamma>0, the resulting spectrum
of the integrated lines depends on the scaling of the underlying density and
scales as K^{-3+\gamma}. We show that if we take the spectral line slices that
are sufficiently thin we recover our earlier results for thin slice data
without absorption. As the result we extend the Velocity Channel Analysis (VCA)
technique to optically thick lines enabling studies of turbulence in molecular
clouds. In addition, the developed mathematical machinery enables a
quantitative approach to solving other problems that involved statistical
description of turbulence within emitting and absorbing gas.


title: Fast and reliable MCMC for cosmological parameter estimation

abstract:
  Markov Chain Monte Carlo (MCMC) techniques are now widely used for
cosmological parameter estimation. Chains are generated to sample the posterior
probability distribution obtained following the Bayesian approach. An important
issue is how to optimize the efficiency of such sampling and how to diagnose
whether a finite-length chain has adequately sampled the underlying posterior
probability distribution. We show how the power spectrum of a single such
finite chain may be used as a convergence diagnostic by means of a fitting
function, and discuss strategies for optimizing the distribution for the
proposed steps. The methods developed are applied to current CMB and LSS data
interpreted using both a pure adiabatic cosmological model and a mixed
adiabatic/isocurvature cosmological model including possible correlations
between modes. For the latter application, because of the increased
dimensionality and the presence of degeneracies, the need for tuning MCMC
methods for maximum efficiency becomes particularly acute.


title:
The Most Exciting Massive Binary Cluster in NGC 5128: Clues to the
  Formation of Globular Clusters

abstract:
  VLT images in BVI are used to identify the ionizing source centered on Sersic
13, the largest HII region of the giant nearby galaxy NGC 5128 with log
L_Halpha=39.6 erg/s. This ionizing source turns out to be a close pair of
bright and blue star cluster candidates. Spectroscopy obtained with the
Magellan I telescope confirms that these are massive young clusters physically
associated with the giant HII region Sersic 13. The spectra of both clusters
show prominent Wolf-Rayet type emission features, and prominent lines of HI and
HeI, indicative of a very young age (t ~ few x 10^6 yr). Their luminosities
make each of them at least as luminous as the massive young cluster R136 in 30
Doradus in the LMC, and their individual masses are estimated to be 1-7.5x10^5
M_sun. In addition, the projected separation of the cluster pair is 42 pc. The
measured velocity difference between the clusters is small, \Delta V=49+/-21
km/s, and within 2 sigma of the expected orbital velocity V_orb=5-12 km/s if
they are bound. Dynamical models predict that binary clusters with these
properties would merge in a short timescale of a few orbital periods
(P=20-50x10^6 yr). The discovery of this binary cluster suggests that mergers
of young massive clusters could lead to the formation of the most massive
globular clusters such as omega Cen in our Galaxy and G1 in M31. Alternatively,
if they are not gravitationally bound, these objects would individually evolve
into two normal globular clusters.


title: Prediction on the very early Afterglow of X-ray Flashes

abstract:
  In the past two years, tremendous progresses to understand X-ray Flashes have
been made. Now it is widely believed that X-ray Flashes and Gamma-ray Bursts
are intrinsically the same, their much different peak energy and flux may be
just due to our different viewing angles to them. Here we analytically
calculate the very early afterglow of X-ray Flashes, i.e., the reverse shock
emission powered by the outflows interacting with the interstellar medium.
Assuming $z\sim 0.3$, we have shown that typically the R Band flux of reverse
shock emission can be bright to $16\sim 17$th magnitude (the actual values are
model dependent and sensitive to the initial Lorentz factor of the viewed
ejecta). That emission is bright enough to be detected by the telescope on work
today such as ROTSE-III or the upcoming UVOT carried by Swift Satellite,
planned for launching in later 2004.


title: The distance of M33 and the stellar population in its outskirts

abstract:
  We present deep V,I photometry of two $9.4' x 9.4' field in the outer regions
of the M33 galaxy. We obtain a robust detection of the luminosity of the Red
Giant Branch Tip (I{TRGB}=20.72 +- 0.08) from which we derived a new estimate
of the distance modulus of M33, (m-M)_0=24.64 +- 0.15, corresponding to a
distance D=847 +- 60 Kpc. By comparison of the color and magnitude of the
observed Red Giant Branch stars with ridge lines of template globular clusters
we obtained the photometric metallicity distribution of the considered fields
in three different metallicity scales. The derived metallicity distributions
are very similar over a range of distances from the galactic center 10' <= R <=
33', and are characterized by a well defined peak at [M/H] ~ -0.7 ([Fe/H] ~
-1.0, in the Zinn & West scale) and a weak metal-poor tail reaching [M/H] ~
-2.0. Our observations demonstrate that Red Giant Branch and Asymptotic Giant
Branch stars have a radial distribution that is much more extended than the
young MS stars associated with the star-forming disc.


title:
Dark matter in elliptical galaxies: I. Is the total mass density profile
  of the NFW form or even steeper?

abstract:
  Elliptical galaxies are modelled as Sersic luminosity distributions with
density profiles (DPs) for the total mass adopted from the DPs of haloes within
dissipationless LambdaCDM N-body simulations. Ellipticals turn out to be
inconsistent with cuspy low-concentration NFW models representing the total
mass, nor are they consistent with a steeper -1.5 inner slope, nor with the
shallower models proposed by Navarro et al. 04, nor with NFW models 10 times
more concentrated than predicted, as deduced from several X-ray observations:
the mass models, extrapolated inwards, lead to local mass-to-light ratios that
are smaller than the stellar value inside an effective radius (R_e), and to
central aperture velocity dispersions that are much smaller than observed. This
conclusion remains true as long as there is no sharp steepening (slope < -2) of
the dark matter (DM) DPs just inside 0.01 virial radii. The too low total mass
and velocity dispersion produced within R_e by an NFW-like total mass profile
suggests that the stellar component should dominate the DM one out to at least
R_e. It should then be difficult to kinematically constrain the inner slope of
the dark matter DP of ellipticals. The high concentration parameters deduced
from X-ray observations appear to be a consequence of fitting an NFW model to
the total mass DP made up of a stellar component that dominates inside and a DM
component that dominates outwards. An appendix gives the virial mass dependence
of the concentration parameter, central density, and total mass of the Navarro
et al. model. In a 2nd appendix are given single integral expressions for the
velocity dispersions averaged along the line-of-sight, in circular apertures
and in thin slits, for general luminosity density and mass distributions, with
isotropic orbits.


title:
Simultaneous Chandra and VLA Observations of Young Stars and Protostars
  in rho Ophiuchus Cloud Core A

abstract:
  A 96-ks Chandra X-ray observation of rho Ophiuchus cloud core A detected 87
sources, of which 60 were identified with counterparts at other wavelengths.
The X-ray detections include 12 of 14 known classical T Tauri stars in the
field, 15 of 17 known weak-lined TTS, and 4 of 15 brown dwarf candidates. The
X-ray detections are characterized by hard, heavily absorbed emission. The mean
photon energy of a typical source is 3 keV, and more than half of the
detections are variable. Prominent X-ray flares were detected in the unusual
close binary system Oph S1, the X-ray bright WTTS DoAr 21, and the brown dwarf
candidate GY 31. Time-resolved spectroscopic analysis of the DoAr~21 flare
clearly reveals a sequence of secondary flares during the decay phase which may
have reheated the plasma. We find that the X-ray luminosity distributions and
spectral hardnesses of CTTS and WTTS are similar. We also conclude that the
X-ray emission of detected brown-dwarf candidates is less luminous than T Tauri
stars, but spectroscopically similar. Simultaneous multifrequency VLA
observations detected 31 radio sources at 6 cm, of which ten were also detected
by Chandra. We report new radio detections of the optically invisible IR source
WLY 2-11 and the faint H-alpha emission line star Elias 24. We confirm circular
polarization in Oph S1 and report a new detection of circular polarization in
DoAr 21. We find no evidence that X-ray and radio luminosities are correlated
in the small sample of TTS detected simultaneously with Chandra and the VLA. We
describe a new non-parametric method for estimating X-ray spectral properties
from unbinned photon event.


title:
Chemical enrichment and star formation in the Milky Way disk III.
  Chemodynamical constraints

abstract:
  In this paper, we investigate some chemokinematical properties of the Milky
Way disk, by using a sample composed by 424 late-type dwarfs. We show that the
velocity dispersion of a stellar group correlates with the age of this group,
according to a law proportional to t^0.26, where t is the age of the stellar
group. The temporal evolution of the vertex deviation is considered in detail.
It is shown that the vertex deviation does not seem to depend strongly on the
age of the stellar group. Previous studies in the literature seem to not have
found it due to the use of statistical ages for stellar groups, rather than
individual ages. The possibility to use the orbital parameters of a star to
derive information about its birthplace is investigated, and we show that the
mean galactocentric radius is likely to be the most reliable stellar birthplace
indicator. However, this information cannot be presently used to derive radial
evolutionary constraints, due to an intrinsic bias present in all samples
constructed from nearby stars. An extensive discussion of the secular and
stochastic heating mechanisms commonly invoked to explain the age-velocity
dispersion relation is presented. We suggest that the age-velocity dispersion
relation could reflect the gradual decrease in the turbulent velocity
dispersion from which disk stars form, a suggestion originally made by Tinsley
and Larson (1978) and supported by several more recent disk evolution
calculations. A test to distinguish between the two types of models using
high-redshift galaxies is proposed.


title: Rotation of the pre-stellar core L1689B

abstract:
  The search for the onset of star formation in pre-stellar cores has focussed
on the identification of an infall signature in the molecular line profiles of
tracer species. The classic infall signature is a double peaked line profile
with an asymmetry in the strength of the peaks such that the blue peak is
stronger. L1689B is a pre-stellar core and infall candidate but new JCMT HCO+
line profile data, presented here, confirms that both blue and red asymmetric
line profiles are present in this source. Moreover, a dividing line can be
drawn between the locations where each type of profile is found. It is argued
that it is unlikely that the line profiles can be interpreted with simple
models of infall or outflow and that rotation of the inner regions is the most
likely explanation. A rotational model is developed in detail with a new 3D
molecular line transport code and it is found that the best type of model is
one in which the rotational velocity profile is in between solid body and
Keplerian. It is firstly shown that red and blue asymmetric line profiles can
be generated with a rotation model entirely in the absence of any infall
motion. The model is then quantitively compared with the JCMT data and an
iteration over a range of parameters is performed to minmize the difference
between the data and model. The results indicate that rotation can dominate the
line profile shape even before the onset of infall.


title:
Propagation of ionizing radiation in HII regions: the effects of
  optically thick density fluctuations

abstract:
  The accepted explanation of the observed dichotomy of two orders of magnitude
between in situ measurements of electron density in HII regions, derived from
emission line ratios, and average measurements based on integrated emission
measure, is the inhomogeneity of the ionized medium. This is expressed as a
"filling factor", the volume ratio of dense to tenuous gas, measured with
values of order 10^-3. Implicit in the filling factor model as normally used,
is the assumption that the clumps of dense gas are optically thin to ionizing
radiation. Here we explore implications of assuming the contrary: that the
clumps are optically thick. A first consequence is the presence within HII
regions of a major fraction of neutral hydrogen. We estimate the mean H^o/H^+
ratio for a population of HII regions in the spiral galaxy NGC 1530 to be the
order of 10, and support this inference using dynamical arguments. The
optically thick clumpy models allow a significant fraction of the photons
generated by the ionizing stars to escape from their HII region. We show, by
comparing model predictions with observations, that these models give an
account at least as good as, and probably better than that of conventional
models, of the radial surface brightness distribution and of selected spectral
line diagnostics for physical conditions within HII regions. These models
explain how an HII region can appear, from its line ratios, to be ionization
bounded, yet permit a major fraction of its ionizing photons to escape.


title: Structures in Dusty Disks

abstract:
  Optically thin dusty disks around Main Sequence stars consist of debris from
catastrophic collisions or from low erosion of long-lived planetesimals.
Resolved observations of dusty disks have systematically evidenced asymmetries
and annular structures. It has been proposed that some of these structures
could be signatures of undetected exoplanets. In this paper, I review and
discuss currently proposed models to account for the observed structures. These
include the impact of distant exoplanets and/or of stellar companions. The
Solar System serves as a reference case for these approaches and similarities
are pointed out along the paper as well as some limitations of current modeling
efforts.


title:
Dust-reddening and gravitational lensing of SDSS QSOs due to foreground
  damped Lyman-alpha systems

abstract:
  We use Sloan Digital Sky Survey Data Release 2 QSO spectra to constrain the
dust-reddening caused by intervening damped Lyman-alpha systems (DLAs).
Comparing the spectral index distribution of a 70 sight-line DLA sample with
that of a large control sample reveals no evidence for dust-reddening at z~3.
Our limit on the shift in spectral index, |Delta(alpha)| < 0.19 (3-sigma),
corresponds to a limit on the colour excess due to SMC-like dust-reddening,
E(B-V) < 0.02 mag (3-sigma). This is inconsistent with the early studies of
Fall, Pei and collaborators who used the small QSO and DLA samples available.
Comparison of the DLA and control magnitude distributions also reveals >2-sigma
evidence for an excess of bright and/or a deficit of faint QSOs with foreground
DLAs. Higher equivalent width DLAs give a stronger signal. We interpret this as
the signature of gravitational magnification due to the intervening DLAs.


title: GRB 990123 revisited: Further Evidence for a Reverse Shock

abstract:
  Recently we have presented a new theoretical analysis of the reverse shock
emission. We use this analysis here to revisit GRB 990123. We find new and
compelling evidences that the optical flash and the radio flare of GRB 990123
resulted from a reverse shock. This suggests that a significant fraction of the
energy of the relativistic ejecta must have been carried by baryons. It also
suggests that the external medium is an ISM and that in this burst the reverse
shock emission dominated at early time over other possible processes. We use
the early optical emission to constrain the physical parameters of the original
ejecta and the microscopic parameters in the emitting reverse shocked region.


title:
Distribution of Singularities in the Cosmic Microwave Background
  Polarization

abstract:
  The polarization of the cosmic microwave background radiation will have a
distribution of singularities and anti-singularities, points where the
polarization vanishes for topological reasons. The statistics of polarization
singularities provides a non-trivial scheme to analyze the polarization maps
that is distinct from the usual two-point correlation functions. Here we
characterize the statistics of the singularity distribution in simulated
polarization maps, and make predictions that can be compared with ongoing and
upcoming observations. We use three different characterizations: the nearest
neighbor distance between singularities, the critical exponent \nu that
captures the scaling of total charge q within a closed curve of length L (q
\propto L^\nu), and the angular two point angular correlation functions for
singularities of similar and opposite charge. In general, we find that the
distribution of singularities is random except on scales less than about 10
deg, where singularities of the same charge repel and those of opposite charge
attract. These conclusions appear to be extremely robust with respect to
variations in the underlying cosmological model and the presence of
non-Gaussianity; the only exception we found are cases where statistical
isotropy is grossly violated. This suggests that, within the assumption of
statistical isotropy, the distribution is a robust feature of the last
scattering surface and potentially may be used as a tool to discriminate
effects that occur during photon propagation from the last scattering surface
to the present epoch.


title: The Metal Content of the Bulge Globular Cluster NGC 6528

abstract:
  High resolution spectra of five stars in the bulge globular cluster NGC 6528
were obtained at the 8m VLT UT2-Kueyen telescope with the UVES spectrograph.
Out of the five stars, two of them showed evidence of binarity. The target
stars belong to the horizontal and red giant branch stages, at 4000<T_eff<4800
K. Multiband V,I,J,H,Ks photometry was used to derive initial effective
temperatures and gravities. The main purpose of this study is the determination
of metallicity and elemental ratios for this template bulge cluster, as a basis
for the fundamental calibration of metal-rich populations. The present analysis
provides a metallicity [Fe/H] = -0.1\pm0.2 and the alpha-elements O, Mg and Si,
show [alpha/Fe] ~ +0.1, whereas Ca and Ti are around the solar value or below,
resulting in an overall metallicity Z ~ Zsun.


title:
Neutrino oscillations, and the origin of pulsar velocities and dark
  matter

abstract:
  Neutrino oscillations in a core-collapse supernova may be responsible for the
observed rapid motions of pulsars. Three-dimensional numerical calculations
show that, in the absence of neutrino oscillations, the recoil velocities of
neutron stars should not exceed 200 km/s, while there exists a substantial
population of pulsars that move faster than 1000 km/s. A small asymmetry in the
neutrino emission may be the solution of this long-standing puzzle. Such an
asymmetry could arise from neutrino oscillations, but, given the present bounds
on the neutrino masses, the pulsar kicks require a sterile neutrino with a 1-20
keV mass and a small mixing with active neutrinos. The same particle can be the
cosmological dark matter. Its existence can be confirmed by X-ray telescopes if
they detect X-ray photons from the decays of the relic sterile neutrinos. One
can also verify the neutrino kick mechanism by observing gravity waves from a
nearby supernova.


title: The HI Detection of Low Column Density Clouds and Galaxies

abstract:
  The HIDEEP survey (Minchin et al. 2003) was done in an attempt to find
objects having low inferred neutral hydrogen column densities, yet they found a
distribution which was strongly peaked at 10^20.65 cm^-2. In an attempt to
understand this distribution and similar survey results, we model HI profiles
of gas discs and use simple simulations of objects having a wide range of HI
properties in the presence of an ionizing background. We find that inferred
column density (N_HI^o) values, which are found by averaging total HI masses
over some disc area, do not vary strongly with central column density (N_max)
for detectable objects, so that even a population having a wide range of N_max
values will give rise to a strongly peaked distribution of N_HI^o values. We
find that populations of objects, having a wide range of model parameters, give
rise to inferred column density distributions around 10^20.6+/-0.3 cm^-2.
However, populations of fairly massive objects having a wide range of central
column densities work best in reproducing the HIDEEP data, and these
populations are also consistent with observed Lyman limit absorber counts. It
may be necessary to look two orders of magnitude fainter than HIDEEP limits to
detect ionized objects having central column densities <10^20 cm^-2, but the
inferred column densities of already detected objects might be lower if their
radii could be estimated more accurately.


title: Hierarchical Structure Formation and Chemical Evolution of Galaxies

abstract:
  We present an analytical and phenomenological model for metal enrichment in
halos based on hierarchical structure formation. This model assumes that
astration of normal stellar populations along with SNe II already occurs at
very high redshift. For halos that are not disrupted by SN II explosions, the
chemical evolution of the gas and stars is explicitly determined by the rate of
gas infall as compared with the astration rate and the corresponding rate of
metal production by SNe II per H atom in the gas. This model provides a good
description of the data on [Fe/H] for damped Ly alpha systems over a wide range
of redshift 0.5 < z < 5. For all halos not disrupted by SN II explosions, if
there is a cessation of gas infall, the metallicities of stars follow a bimodal
distribution. This distribution is characterized by a sharp peak at the value
of [Fe/H] corresponding to the time of infall cessation and by a broad peak at
a higher value of [Fe/H] corresponding to the subsequent period of astration
during which the bulk of the remaining gas forms stars. Such a distribution may
be compared to that observed for the Galactic halo stars. If the gas in a halo
is rapidly lost upon cessation of infall, then an assemblage of stars with a
very sharply-defined [Fe/H] value will be left behind. This assemblage of stars
may be accreted by a larger system and become a globular cluster of the larger
system. We also discuss the masses and metallicities of the globular clusters
in this model. (Abridged)


title: Dark Matter Detection in Space

abstract:
  I review prospects for detecting dark matter in space-based experiments, with
an emphasis on recent developments. I propose the ``Martha Stewart criterion''
for identifying dark matter candidates that are particularly worth
investigation and focus on three that satisfy it: neutralino dark matter,
Kaluza-Klein dark matter, and superWIMP gravitino dark matter.


title:
The Metallicity Dependence of the Fourier Components of RR Lyrae Light
  Curves is the Oosterhoff/Arp/Preston Period Ratio Effect in Disguise

abstract:
  The correlation of particular Fourier components of the light curves of RR
Lyrae variables with metallicity, discovered by Simon and later by Kovacs and
his coworkers, is shown to have the same explanation as the period ratios
(period shifts in log P) between RRab Lyrae variables that have the same
colors, amplitudes, and light-curve shapes but different metallicities. A
purpose of this paper is to demonstrate that the model which predicts the
period-metallicity relations is the mediating parameters of colors, amplitudes,
and light-curve shapes also explains the Simon/Kovacs et al. correlation
between period, Phi_31, and metallicity. The proof is made by demonstrating
that the combination of the first and third phase terms in a Fourier
decomposition of RRab light curves, called Phi_31 by Simon and Lee, varies
monotonically across the RR Lyrae instability strip in the same way that
amplitude, color, and rise time vary with period within the strip. The premise
of the model is that if horizontal branches at the RR Lyrae strip are stacked
in luminosity according to the metallicity, then there necessarily must be a
log period shift between RR Lyraes with different metallicities at the same
Phi_31 values. However, there are exceptions to the model. (...)


title: Near-Infrared Spectroscopy of McNeil's Nebula Object

abstract:
  We present 0.8-5.2 micron spectroscopy of the compact source at the base of a
variable nebula (McNeil's Nebula Object) in the Lynds 1630 dark cloud that went
into outburst in late 2003. The spectrum of this object reveals an extremely
red continuum, CO bands at 2.3-2.5 microns in emission, a deep 3.0 micron ice
absorption feature, and a solid state CO absorption feature at 4.7 microns. In
addition, emission lines of H, Ca II, Mg I, and Na I are present. The Paschen
lines exhibit P Cygni profiles, as do two lines of He I, although the emission
features are very weak in the latter. The Brackett lines, however, are seen to
be purely in emission. The P Cygni profiles clearly indicate that mass outflow
is occurring in a wind with a velocity of ~400 km/s. The H line ratios do not
yield consistent estimates of the reddening, nor do they agree with the
extinction estimated from the ice feature (A_V ~ 11). We propose that these
lines are optically thick and are produced in a dense, ionized wind. The
near-infrared spectrum does not appear similar to any known FUor or EXor
object. However, all evidence suggests that McNeil's Nebula Object is a
heavily-embedded low-mass Class I protostar, surrounded by a disk, whose
brightening is due to a recent accretion event.


title:
Discovery of a Transient U-band Dropout in a Lyman-Break Survey: A
  Tidally-Disrupted Star at z = 3.3?

abstract:
  We report the discovery of a transient source in the central regions of
galaxy cluster Abell 267. The object, which we call "PALS1", was found in a
survey aimed at identifying highly-magnified Lyman-break galaxies in the fields
of intervening rich clusters. At discovery, the source had U>24.7 (2-sigma;
AB), g=21.96, and very blue g-r and r-i colors; i.e., PALS1 was a U-band
drop-out, characteristic of star-forming galaxies and quasars at z~3. However,
three months later the source had faded by more than three magnitudes. Further
observations showed a continued decline in luminosity, to R>26.4 seven months
after discovery. Though the apparent brightness is suggestive of a supernova at
roughly the cluster redshift, we show that the photometry and light curve argue
against any known type of supernova at any redshift. The spectral energy
distribution and location near the center of a galaxy cluster are consistent
with the hypothesis that PALS1 is a gravitationally-lensed transient at z~3.3.
If this interpretation is correct, the source is magnified by a factor of 4-7
and two counterimages are predicted. Our lens model predicts time delays
between the three images of 1-10 years and that we have witnessed the final
occurrence of the transient. The intense luminosity (M(AB) ~ -23.5 after
correcting for lensing) and blue UV continuum (implying T>50,000 K) argue the
source may have been a flare resulting from the tidal disruption of a star by a
10^6-10^8 solar-mass black hole. Regardless of its physical nature, PALS1
highlights the importance of monitoring regions of high magnification in galaxy
clusters for distant, time-varying phenomena.


title: Shocked molecular hydrogen towards the Tornado nebula

abstract:
  We present near-infrared and millimetre-line observations of the Tornado
nebula (G357.7-0.1). We detected 2.12 micron_m H2 1-0 S(1) line emission
towards the suspected site of interaction with a molecular cloud revealed by
the presence of an OH(1720 MHz) maser. The distribution of the H2 emission is
well correlated with the nonthermal radio continuum emission from the Tornado,
and the velocity of the H2 emission spans over 100 km/s, which both imply that
the H2 emission is shock excited. We also detected millimetre-lines from 12CO
and 13CO transitions at the velocity of the maser, and mapped the distribution
of the molecular cloud in a 2 x 2 arcmin^2 region around the maser. The peak of
the molecular cloud aligns well with an indentation in the nebula's radio
continuum distribution, suggesting that the nebula's shock is being decelerated
at this location, which is consistent with the presence of the OH(1720 MHz)
maser and shocked H2 emission at that location.


title: Exploring the Nucleus of the Gigamaser Galaxy TXS 2226-184

abstract:
  We present Very Long Baseline Array (VLBA) observations of the Gigamaser
galaxy TXS2226-184 at 1.3 and 5 GHz. These observations reveal the parsec-scale
radio structure of this Seyfert galaxy with exceptionally luminous water maser
emission. The source is found to be extended on scales of 10-100 pc with some
embedded compact sources, but has no readily identifiable flat-spectrum active
nucleus. This morphology resembles that of the nearby compact starburst galaxy
Mrk 273, although no significant FIR emission has been detected to support the
starburst scenario. The narrow (125 km/s) HI absorption in TXS2226-184
discovered with the VLA is also detected with the VLBA. This HI absorption is
distributed across the extended emission, probably co-spatial with the water
masers. The broad (420 km/s) line seen by the VLA is not detected, suggesting
that it arises from more extended gas which is absorbing the emission beyond
the central tens of parsecs.


title:
The isolated neutron star X-ray pulsars RX J0420.0-5022 and RX
  J0806.4-4123: new X-ray and optical observations

abstract:
  We report on the analysis of new X-ray data obtained with XMM-Newton and
Chandra from two ROSAT-discovered X-ray dim isolated neutron stars. RX
J0806.4-4123 was observed with XMM-Newton in April 2003, 2.5 years after the
first observation. The EPIC-pn data confirm that this object is an X-ray pulsar
with 11.371 s neutron star spin period. The X-ray spectrum is consistent with
absorbed black-body emission with a temperature kT = 96 eV and NH = 4x10^19
cm^-2 without significant changes between the two observations. Four XMM-Newton
observations of RX J0420.0-5022 between December 2002 and July 2003 did not
confirm the 22.7 s pulsations originally indicated in ROSAT data, but clearly
reveal a 3.453 s period. A fit to the X-ray spectrum using an absorbed
black-body model yields kT = 45 eV, the lowest value found from the small group
of XDINs and NH = 1.0x10^20 cm^-2. Including a broad absorption line improves
the quality of the spectral fits considerably for both objects and may indicate
the presence of absorption features similar to those reported from RBS1223, RX
J1605.3+3249 and RX J0720.4-3125. For both targets we derive accurate X-ray
positions from the Chandra data and present an optical counterpart candidate
for RX J0420.0-5022 with B = 26.6+/-0.3 mag from VLT imaging.


title:
Spectral and timing properties of the X-ray emission from the
  millisecond pulsar PSR B1821-24

abstract:
  We report results on the timing and spectral analysis of observations of the
millisecond pulsar PSR B1821-24 with RXTE, BeppoSAX and Chandra. The X-ray
light curve is characterized by two narrow peaks at a phase distance of
0.452+/-0.002. The average pulsed emission, over the range 1.6-20 keV, is well
represented by a single power law with a photon index alpha=1.30 +0.05 -0.02
and unabsorbed (2-10 keV) pulsed X-ray flux of 3.9x10^(-13) erg cm^(-2) s^(-1).
We searched for a possible bunching of X-ray photons to verify if the X ray
emission has a time structure similar to that of giant pulses and found a
negative result.


title: Cross Terms and Weak Frequency Dependent Signals in the CMB Sky

abstract:
  In this paper, we study the amplification of weak frequency dependent signals
in the CMB sky due to their cross correlation to intrinsic anisotropies. In
particular, we center our attention on mechanisms generating some weak signal,
of peculiar spectral behaviour, such as resonant scattering in ionic, atomic or
molecular lines, thermal SZ effect or extragalactic foreground emissions, whose
typical amplitude (denoted by $\epsilon$) is sufficiently smaller than the
intrinsic CMB fluctuations. We find that all these effects involve either the
autocorrelation of anisotropies generated during recombination ($z_{rec}$) or
the cross-correlation of those anisotropies with fluctuations arising at some
later redshift $z_i$. The degree of this correlation can be computed under the
assumption that density fluctuations were generated as standard inflationary
models dictate and that they evolved in time according to linear theory. In
case that the weak signal is frequency dependent, we show that, by substracting
power spectra at different frequencies, it is possible to avoid the limit
associated to Cosmic Variance and unveil weaker terms linear in $\epsilon$. We
find that the correlation term shows a different spectral dependence than the
squared ($\propto \epsilon^2$) term considered usually, making its extraction
particularly straightforward for the thermal SZ effect. Furthermore, we find
that in most cases the correlation terms are particularly relevant at low
multipoles and must be taken into account when characterising the power
spectrum associated to weak signals in the large angular scales.


title: Gamma-ray bursts from synchrotron self-Compton emission

abstract:
  The emission mechanism of the gamma-ray bursts (GRBs) is still a matter of
debates. The standard synchrotron energy spectrum of cooling electrons F_E ~
E^{-1/2} is much too soft to account for the majority of the observed spectral
slopes. An alternative in the form of quasi-thermal Comptonization in a high
compactness source has difficulties in reproducing the peak of the observed
photon distribution below a few hundred keV. We show here that for typical
parameters expected in the GRB ejecta the observed spectra in the 20-1000 keV
BATSE energy range can be produced by inverse Compton scattering of the
synchrotron radiation in a partially self-absorbed regime. If the particles are
continuously accelerated/heated over the life-time of a source rather than
being instantly injected, a prominent peak develops in their distribution at a
Lorentz factor gamma ~ 30-100, where synchrotron and inverse-Compton losses are
balanced by acceleration and heating due to synchrotron self-absorption. The
synchrotron peak should be observed at 10-100 eV, while the self-absorbed
low-energy tail with F_E ~ E^2 can produce the prompt optical emission (like in
the case of GRB 990123). The first Compton scattering radiation by nearly
monoenergetic electrons can then be as hard as F_E ~ E^1 reproducing the
hardness of most of the observed GRB spectra. The second Compton peak should be
observed in the high energy gamma-ray band, possibly being responsible for the
emission detected by EGRET in GRB 941017. A significant electron-positron pair
production reduces the available energy per particle, moving the spectral peaks
to lower energies as the burst progresses. The regime is very robust, operates
in a broad range of parameter space and can explain most of the observed GRB
spectra and their temporal evolution.


title: Evidence for new physics from clusters ?

abstract:
  The abundance of local clusters is a traditional way to derive the amplitude
of matter fluctuations. In the present work, by assuming that the observed
baryon content of clusters is representative of the universe, we show that the
mass temperature relation (M-T) can be specified for any cosmological model.
This approach allows one to remove most of the uncertainty coming from M-T
relation, and to provide an estimation of sigma\_8 whose uncertainty is
essentially statistical. The values we obtain are fortuitously almost
independent of the matter density of the Universe (sigma\_8 ~ 0.6-0.63) with an
accuracy better than 5%. Quite remarkably, the amplitude of matter fluctuations
can be also tightly constrained to similar accuracy from existing CMB
measurements alone. However, the amplitude inferred in this way in a
concordance model (Lambda-CDM) is significantly larger than the value derived
from the above method based on X-ray clusters. Such a discrepancy would almost
disappear if the actual optical thickness of the Universe was 0 but could also
be alleviated from more exotic solutions: the existence of a new dark component
in the Universe as massive neutrinos. However, recent other indications of
sigma\_8 favor a high normalization. In this case, the assumption that the
baryonic content observed in clusters actually reflects the primordial value
has to be relaxed : either there exists a large baryonic dark component in the
Universe or baryons in clusters have undergone a large depletion during the
formation of these structures. We concluded that the baryon fraction in
clusters is not representative and therefore that an essential piece of the
physics of baryons in clusters is missing in standard structure formation
scenario.


title:
Cosmological evolution of general scalar fields in a brane-world
  cosmology

abstract:
  We study the cosmology of a general scalar field and barotropic fluid during
the early stage of a brane-world where the Friedmann constraint is dominated by
the square of the energy density. Assuming both the scalar field and fluid are
confined to the brane, we find a range of behaviour depending on the form of
the potential. Generalising an approach developed for a standard Friedmann
cosmology, in \cite{delaMacorra:1999ff}, we show that the potential dependence
$V(\phi)$ can be described through a parameter $\lambda \equiv -\sqrt{2}
m_5^{3/2} V'/(\sqrt{H}V)$, where $m_5$ is the 5-dimensional Planck mass, $H$ is
the Hubble parameter and $V' \equiv \frac{dV}{d\phi}$. For the case where
$\lambda$ asymptotes to zero, we show that the solution exhibits stable
inflationary behaviour. On the other hand if it approaches a finite constant,
then $V(\phi) \propto \frac{1}{\phi^2}$. For $\lambda \to \infty$
asymptotically, we find examples where it does so both with and without
oscillating. In the latter case, the barotropic fluid dominates the scalar
filed asymptotically. Finally we point out an interesting duality which leads
to identical evolution equations in the high energy $\rho^2$ dominated regime
and the low energy $\rho$ dominated regime.


title:
Dark matter in elliptical galaxies: II. Estimating the mass within the
  virial radius

abstract:
  Elliptical galaxies are modelled with a a 4-component model: Sersic stars,
LCDM dark matter (DM), hot gas and central black hole. DM is negligible in the
inner regions, which are dominated by stars and the central black hole. This
prevents any kinematical estimate (using a Jeans analysis) of the inner slope
of the DM density profile. The gas fraction rises, but the baryon fraction
decreases with radius, at least out to 10 effective radii (R_e). Even with
line-of-sight velocity dispersion (VD) measurements at 4 to 6 R_e with 20 km/s
accuracy and perfectly known velocity anisotropy, the total mass within the
virial radius (r_v) is uncertain by a factor over 3. The DM distributions found
in LCDM simulations are consistent with the stellar VD profiles, but appear
inconsistent with the low VDs measured by Romanowsky et al. (2003) of planetary
nebulae between 2 and 5 R_e, which imply such low M/Ls that the baryon fraction
within r_v must be greater than the universal value. Replacing the NFW DM model
by the new model of Navarro et al. (2004) decreases slightly the VD at a given
radius. So, given the observed VD measured at 5 R_e, the inferred M/L within
r_v is 40% larger than predicted with the NFW model. Folding in the slight
(strong) radial anisotropy found in LCDM (merger) simulations, which is well
modelled (much better than with the Osipkov-Merritt formula) with beta(r) = 1/2
r/(r+a), the inferred M/L within r_v is another 1.6 (2.4) times higher than for
the isotropic NFW model. Thus, the DM model and radial anisotropy can partly
explain the low PN VDs, but not in full. In an appendix, single integral
expressions are derived for the VDs in terms of the tracer density and total
mass profiles, for 3 anisotropic models: radial, Osipkov-Merritt, and the model
above, for general radial profiles of luminosity density and mass.


title:
Spectral constraints on unidentified EGRET gamma-ray sources from
  COMPTEL MeV observations

abstract:
  We investigated the MeV properties of 173 unidentified or only tentatively
identified EGRET sources listed in the third EGRET catalogue, by analyzing the
simultaneously collected COMPTEL MeV data for each individual source. The
sources can generally be divided into 4 groups. In this paper we focus on one
of these, a group of 22 EGRET sources for which we can provide additional
constraining information: their spectral extrapolations from the energy range
above 100 MeV towards lower energies overshoot the fluxes or upper limits
derived simultaneously at MeV energies. This means that for these sources a
spectral turnover/break between 1 MeV and 100 MeV is required. At least two of
these sources, but most likely the majority of this sample, have the maxima of
their gamma-ray luminosities in this energy band. The sources have rather soft
EGRET spectra (average photon index: 2.72), and seem to spatially cluster in
the inner Galaxy. Variability analyses revealed 11 out of the 22 sources to be
significantly variable. Object classes proposed as possible counterparts for
the unidentified EGRET sources are discussed in the light of these additional
constraints.


title:
Feedback from Intra-Cluster Supernovae on the ICM in Cooling Flow Galaxy
  Clusters

abstract:
  We study the effect of heating and metal enrichment from supernovae (SNe)
residing between galaxies on the Intra-Cluster Medium (ICM). Recent
observations indicate that a considerable fraction (~20 %) of the SN Ia parent
stellar population in galaxy clusters is intergalactic. By considering their
effect on the relaxed progenitors of cooling flow clusters we propose that
intra-cluster SNe can act as a distributed heating source which may influence
the initial stages of the formation of cooling flows. We investigate the
increase in cooling time as a function of the energy input supplied by SNe and
their assumed spatial distribution, and conclude that intra-cluster SNe
represent a heating source which in some clusters can cause a delay of the
formation of cooling flows. This would imply that some cooling flows are
younger than previously thought. We also discuss the impact that a large
population of intra-cluster SNe could have on the chemical evolution of the ICM
in cooling flow clusters.


title:
All-sky component separation in the presence of anisotropic noise and
  dust temperature variations

abstract:
  We present an extension of the harmonic-space maximum-entropy component
separation method (MEM) for multi-frequency CMB observations that allows one to
perform the separation with more plausible assumptions about the receiver noise
and foreground astrophysical components. Component separation is considered in
the presence of spatially-varying noise variance and spectral properties of the
foreground components. It is shown that, if not taken properly into account,
the presence of spatially-varying foreground spectra, in particular, can
severely reduce the accuracy of the component separation. Nevertheless, by
extending the basic method to accommodate such behaviour and the presence of
anisotropic noise, we find that the accuracy of the component separation can be
improved to a level comparable with previous investigations in which these
effects were not present.


title: Galactic Distribution and the Luminosity Function of Pulsars

abstract:
  We have studied the radial distribution and luminosity function of normal
pulsars in the Galaxy, on the basis of the ATNF Pulsar Catalogue where the
distances are calculated according to the new electron density model NE2001. We
show that the maximum of galactocentric distribution of pulsars located near
3.5 kpc and the scale-length of this distribution is nearly 4 kpc. The surface
density of pulsars near the Galactic center (GC) is equal or slightly higher
than that in the solar neighborhood. The local density and birth-rate of
pulsars is 1.5 and 4 times higher than previous estimates, correspondingly
before and after beaming corrections. The dependence of these results on the
NE2001 model and recommendations for further improvement of the electron
density distribution are discussed. We derived the luminosity function of
pulsars at frequencies near 1400 MHz. In the limited band of luminosities, the
luminosity function has a slope near -1, but a new luminosity function may be
better fitted by a Log-Normal distribution.


title:
Gas flow and dark matter in the inner parts of early-type barred
  galaxies

abstract:
  This paper presents the dynamical simulations run in the potential derived
from the light distribution of 5 late-type barred spiral galaxies. The aim is
to determine whether the mass distribution together with the hydrodynamical
simulations can reproduce the observed line-of-sight velocity curves and the
gas morphology in the inner regions of the sample barred galaxies. The light
distribution is obtained from the $H$-band and the $I$-band combined together.
The M/L is determined using population synthesis models. The observations and
the methodology of the mass distribution modelling are presented in a companion
paper. The SPH models using the stellar mass models obtained directly from the
$H$-band light distributions give a good representation of the gas distribution
and dynamics of the modelled galaxies, supporting the maximum disk assumption.
This result indicates that the gravitational field in the inner region is
mostly provided by the stellar luminous component. When 40% of the total mass
is transferred to an axisymmetric dark halo, the modelled kinematics clearly
depart from the observed kinematics, whereas the departures are negligible for
dark mass halos of 5% and 20% of the total mass. This result sets a lower limit
for the contribution of the luminous component of about 80%, which is in
agreement with the maximum disk definition of the stellar mass contribution to
the rotation curve (about 85%$\pm$10).


title: The Hierarchical Formation of the Galactic Disk

abstract:
  I review the results of recent cosmological simulations of galaxy formation
that highlight the importance of satellite accretion in the formation of
galactic disks. Tidal debris of disrupted satellites may contribute to the disk
component if they are compact enough to survive the decay and circularization
of the orbit as dynamical friction brings the satellite into the disk plane.
This process may add a small but non-negligible fraction of stars to the thin
and thick disks, and reconcile the presence of very old stars with the
protracted merging history expected in a hierarchically clustering universe. I
discuss various lines of evidence which suggest that this process may have been
important during the formation of the Galactic disk.


title:
The Ultra-Luminous X-ray Source Population from the Chandra Archive of
  Galaxies

abstract:
  One hundred fifty-four discrete non-nuclear Ultra-Luminous X-ray (ULX)
sources, with intrinsic X-ray luminosities >1e39 ergs/s, are identified in 82
galaxies observed with Chandra's Advanced CCD Imaging Spectrometer. Source
positions, X-ray luminosities, and spectral and timing characteristics are
tabulated. Statistical comparisons between these X-ray properties and those of
the weaker discrete sources in the same fields are made. Sources above ~1e38
erg/s display similar spatial, spectral, color, and variability distributions.
In particular, there is no compelling evidence in the sample for a new and
distinct class of X-ray object such as the intermediate-mass black holes.
Comparison of the cumulative X-ray luminosity functions of the ULXs to Chandra
Deep Field results suggests ~25% of the sources may be background objects
including 14% of the ULX candidates in the sample of spiral galaxies and 44% of
those in elliptical galaxies implying the elliptical galaxy ULX population is
severely compromised by background active galactic nuclei. Correlations with
host galaxy properties confirm the number and total X-ray luminosity of the
ULXs are associated with recent star formation and with galaxy merging and
interactions. The preponderance of ULXs in star-forming galaxies as well as
their similarities to less-luminous sources suggest they originate in a young
but short-lived population such as the high-mass X-ray binaries with a smaller
contribution (based on spectral slope) from recent supernovae. The number of
ULXs in elliptical galaxies scales with host galaxy mass and can be explained
most simply as the high-luminosity end of the low-mass X-ray binary population.


title: Identifying high redshift AGNs using X-ray hardness

abstract:
  The X-ray color (hardness ratio) of optically undetected X-ray sources can be
used to distinguish obscured active galactic nuclei (AGNs) at low and
intermediate redshift from viable high-redshift (i.e., z>5) AGN candidates.
This will help determine the space density, ionizing photon production, and
X-ray background contribution of the earliest detectable AGNs. High redshift
AGNs should appear soft in X-rays, with hardness ratio HR ~ -0.5, even if there
is strong absorption by a hydrogen column density N_H up to 10^23 cm^-2, simply
because the absorption redshifts out of the soft X-ray band in the observed
frame. Here the X-ray hardness ratio is defined as HR= (H-S)/(H+S), where S and
H are the soft and hard band net counts detected by Chandra. High redshift AGNs
that are Compton thick (N_H>~10^24 cm^-2) could have HR~0.0 at z>5. However,
these should be rare in deep Chandra images, since they have to be >~10 times
brighter intrinsically, which implies >~100 times drop in their space density.
Applying the hardness criterion (HR<0.0) can filter out about 50% of the
candidate high redshift AGNs selected from deep Chandra images.


title: Potential Direct Single-Star Mass Measurement

abstract:
  We analyze the lightcurve of the microlensing event
OGLE-2003-BLG-175/MOA-2003-BLG-45 and show that it has two properties that,
when combined with future high resolution astrometry, could lead to a direct,
accurate measurement of the lens mass. First, the lightcurve shows clear signs
of distortion due to the Earth's accelerated motion, which yields a measurement
of the projected Einstein radius \tilde r_E. Second, from precise astrometric
measurements, we show that the blended light in the event is coincident with
the microlensed source to within about 15 mas. This argues strongly that this
blended light is the lens and hence opens the possibility of directly measuring
the lens-source relative proper motion \vec\mu_\rel and so the mass
M=(c^2/4G)\mu_\rel t_E \tilde r_E, where t_E is the measured Einstein
timescale. While the lightcurve-based measurement of \tilde r_E is, by itself,
severely degenerate, we show that this degeneracy can be completely resolved by
measuring the direction of proper motion \vec\mu_\rel.


title:
SPI/INTEGRAL observation of 1809 keV gamma-ray line emission from the
  Cygnus X region

abstract:
  We present first results on the observation of 1809 keV gamma-ray line
emission from the Cygnus X region with the SPI imaging spectrometer. Our
analysis is based on data from the performance verification phase of the
INTEGRAL instruments and comprises 1.3 Ms of exposure time. We observe a 1809
keV line flux of (7.3 +/- 0.9) x 10-5 ph cm-2 s-1 from a region delimited by
galactic longitudes 73-93 deg and |b| < 7 deg at a significance level of 8
sigma. The 1809 keV line appears moderately broadened, with an intrinsic FWHM
of 3.3 +/- 1.3 keV. Although this broadening is only marginal (at the 2 sigma
level our data are compatible with an unbroadened line), it could reflect the
26Al ejecta kinematics.


title:
Gravitational instability in binary protoplanetary disks; new
  constraints on giant planet formation

abstract:
  We use high resolution 3D SPH simulations to study the evolution of
self-gravitating binary protoplanetary disks. Heating by shocks and cooling are
included. We consider different orbital separations and masses of the disks and
central stars. Isolated massive disks ($M \sim 0.1 M_{{\o}dot}$) fragment into
protoplanets as a result of gravitational instability for cooling times
comparable to the orbital time. Fragmentation does not occur in binary systems
with a separation of about 60 AU. This is because efficient heating owing to
strong tidally induced spiral shocks damps any overdensity. The resulting
temperatures, above 200 K, would vaporize water ice in the outer disk, posing a
problem even for the other model of giant planet formation, core-accretion.
Light disks ($M \sim 0.01 M_{\odot}$) do not fragment but remain cold because
their low self-gravity inhibits strong shocks. Core accretion would not be
hampered in the latter. At separations of about 120 AU the efficiency of
fragmentation by disk instability rises and approaches that in isolated
systems. If disk instability is the main formation mechanism for giant planets,
on going surveys targeting binary systems should find considerably fewer
planets in systems with separations below 100 AU.


title: The Physics of Gamma-Ray Bursts

abstract:
  Gamma-Ray Bursts (GRBs), short and intense pulses of low energy gamma-rays,
have fascinated astronomers and astrophysicists since their unexpected
discovery in the late sixties. During the last decade, several space missions:
BATSE (Burst and Transient Source Experiment) on Compton Gamma-Ray Observatory,
BeppoSAX and now HETE II (High-Energy Transient Explorer), together with ground
optical, infrared and radio observatories have revolutionized our understanding
of GRBs showing that they are cosmological, that they are accompanied by long
lasting afterglows and that they are associated with core collapse Supernovae.
At the same time a theoretical understanding has emerged in the form of the
fireball internal-external shocks model. According to this model GRBs are
produced when the kinetic energy of an ultra-relativistic flow is dissipated in
internal collisions. The afterglow arises when the flow is slowed down by
shocks with the surrounding circum-burst matter. This model has numerous
successful predictions like the prediction of the afterglow itself, the
prediction of jet breaks in the afterglow light curve and of an optical flash
that accompanies the GRBs themselves. In this review I focus on theoretical
aspects and on physical processes believed to take place in GRBs.


title: Analysis of UBV Photometry in Selected Area 133

abstract:
  We interpret the de-reddened UBV data for the field SA 133 to deduce the
stellar density and metallicity distributions function. The logarithmic local
space density for giants, $D^{*}(0)=6.40$, and the agreement of the luminosity
function for dwarfs and sub-giants with the one of Hipparcos confirms the
empirical method used for their separation. The metallicity distribution for
dwarfs gives a narrow peak at [Fe/H]=+0.13 dex, due to apparently bright
limiting magnitude, $V_{o}=16.5$, whereas late-type giants extending up to $z
\sim4.5$ kpc from the galactic plane have a multimodal distribution. The
metallicity distribution for giants gives a steep gradient $d[Fe/H]/dz=-0.75$
dex kpc$^{-1}$ for thin disk and thick disk whereas a smaller value for the
halo, i.e. $d[Fe/H]/dz=-0.45$ dex kpc$^{-1}$.


title:
Measuring the Radiative Histories of QSOs with the Transverse Proximity
  Effect

abstract:
  Since the photons that stream from QSOs alter the ionization state of the gas
they traverse, any changes to a QSO's luminosity will produce
outward-propagating ionization gradients in the surrounding intergalactic gas.
This paper shows that at redshift z~3 the gradients will alter the gas's
Lyman-alpha absorption opacity enough to produce a detectable signature in the
spectra of faint background galaxies. By obtaining noisy (S:N~4) low-resolution
(~7A) spectra of a several dozen background galaxies in an R~20' field
surrounding an isotropically radiating 18th magnitude QSO at z=3, it should be
possible to detect any order-of-magnitude changes to the QSO's luminosity over
the previous 50--100 Myr and to measure the time t_Q since the onset of the
QSO's current luminous outburst with an accuracy of ~5 Myr for t_Q<~50 Myr.
Smaller fields-of-view are acceptable for shorter QSO lifetimes. The major
uncertainty, aside from cosmic variance, will be the shape and orientation of
the QSO's ionization cone. This can be determined from the data if the number
of background sources is increased by a factor of a few. The method will then
provide a direct test of unification models for AGN.