title:
The Role of Polycyclic Aromatic Hydrocarbons in Ultraviolet Extinction.
  I. Probing small molecular PAHs

abstract:
  We have obtained new STIS/HST spectra to search for structure in the
ultraviolet interstellar extinction curve, with particular emphasis on a search
for absorption features produced by polycyclic aromatic hydrocarbons (PAHs).
The presence of these molecules in the interstellar medium has been postulated
to explain the infrared emission features seen in the 3-13 $\mu$m spectra of
numerous sources. UV spectra are uniquely capable of identifying specific PAH
molecules. We obtained high S/N UV spectra of stars which are significantly
more reddened than those observed in previous studies. These data put limits on
the role of small (30-50 carbon atoms) PAHs in UV extinction and call for
further observations to probe the role of larger PAHs. PAHs are of importance
because of their ubiquity and high abundance inferred from the infrared data
and also because they may link the molecular and dust phases of the
interstellar medium. A presence or absence of ultraviolet absorption bands due
to PAHs could be a definitive test of this hypothesis. We should be able to
detect a 20 \AA wide feature down to a 3$\sigma$ limit of $\sim$0.02 A$_V$. No
such absorption features are seen other than the well-known 2175 \AA bump.


title: Carbon Monoxide Depletion in Orion B Molecular Cloud Cores

abstract:
  We have observed several cloud cores in the Orion B (L1630) molecular cloud
in the 2-1 transitions of C18O, C17O and 13C18O. We use these data to show that
a model where the cores consist of very optically thick C18O clumps cannot
explain their relative intensities. There is strong evidence that the C18O is
not very optically thick. The CO emission is compared to previous observations
of dust continuum emission to deduce apparent molecular abundances. The
abundance values depend somewhat on the temperature but relative to `normal
abundance' values, the CO appears to be depleted by about a factor of 10 at the
core positions. CO condensation on dust grains provides a natural explanation
for the apparent depletion both through gas-phase depletion of CO, and through
a possible increase in dust emissivity in the cores. The high brightness of
HCO+ relative to CO is then naturally accounted for by time-dependent
interstellar chemistry starting from `evolved' initial conditions. Theoretical
work has shown that condensation of H2O, which destroys HCO+, would allow the
HCO+ abundance to increase while that of CO is falling.


title: XMM observation of the dynamically young galaxy cluster CL 0939+4713

abstract:
  We present an XMM observation of the distant galaxy cluster CL 0939+4713. The
X-ray image shows pronounced substructure, with two main subclusters forming
the cluster core. This is an indication that the cluster is a dynamically young
system. This conclusion is supported by the temperature distribution: a hot
region is found between the two main subclusters indicating that they are at
the beginning of a major merger, and that they will collide in a few hundreds
of Myr. The intra-cluster gas of CL 0939+4713 shows inhomogeneities in the
metal distribution, with the optically richer subcluster having a higher
metallicity.


title:
An I-Band-Selected Sample of Radio-Emitting Quasars: Evidence for a
  Large Population of Red Quasars

abstract:
  We present a new sample of 35 quasars selected from the FIRST radio survey
and the Deeprange I-band survey (Postman et al. 1998, 2002). A comparison with
the FIRST Bright Quasar survey samples reveals that this I-band selected sample
is redder by 0.25-0.5 mag in B-R, and that the color difference is not
explained by the higher mean redshift of this sample but must be intrinsic. Our
small sample contains five quasars with unusually red colors, including three
that appear very heavily reddened. Our data are fitted well with normal blue
quasar spectra attenuated by more than 2.5 magnitudes of extinction in the
I-band.
  The red quasars are only seen at low redshifts (z<1.3). Even with a magnitude
limit I<20.5, our survey is deep enough to detect only the most luminous of
these red quasars at z~1; similar objects at higher redshifts would fall below
our in I-band limit. Indeed, the five most luminous objects (using dereddened
magnitudes) with z<1.3 are all red. Our data strongly support the hypothesis
that radio quasars are dominated by a previously undetected population of red,
heavily obscured objects. Unless highly reddened quasars are preferentially
also highly luminous, there must be an even larger, as yet undiscovered,
population of red quasars at lower luminosity. We are likely to be finding only
the most luminous tip of the red quasar iceberg.
  Five of our six z<1 quasars are associated with Deeprange cluster candidates
of similar estimated redshifts. This association is very unlikely to be the
result of chance. It has some surprising implications, including the
possibility that up to half of the Deeprange clusters at z~1 have associated
quasars.


title:
About the nature of dark matter and dark energy and a model of cosmology
  that may solve the cosmic coincidence problem

abstract:
  A model of cosmology, that arises from the hypothesis that ordinary matter,
dark matter and dark energy are made of the same stuff, is studied. It is
argued that this hypothesis is a consequence of considering space and time in
the same footing. The model provides a solution to the cosmic coincidence
problem predicting without fine-tuning values in agreement with observations.
Besides, the model does not suffer from neither the flatness nor the horizon
problems, does not appear to spoil the successes of cosmic nucleosynthesis
calculations and allows for the formation of galaxies and clusters.


title: Relationship Between Cepheid and Tully-Fisher Distance Calculations

abstract:
  A correlation between (1) the difference between the Tully-Fisher calculated
distance and Cepheid calculated distance for a target galaxy and (2) the
magnitude and distance of galaxies close to the target galaxy is described. The
result is based on a sample of 31 galaxies that have published Cepheid
distances with a wide range of characteristics and distances from 2.02 Mpc to
49.7 Mpc. The energy impinging on a target galaxy from neighboring galaxies is
related to the residual between Tully-Fisher and Cepheid distance calculations
of the target galaxy. These relations have four different zones dependent on
the value of the impinging energy. The correlation coefficients are 0.77, 0.87,
0.81, and 0.98, respectively. This relationship is of interest not only for its
ability to reduce the Tully-Fisher to Cepheid distance residual but also
because it suggests neighboring galaxies have a strong influence on the
apparent luminosity of galaxies and it suggests the Tully-Fisher relationship
assumption that the intrinsic mass to intrinsic luminosity ratio is constant
among galaxies is valid for z < 0.006.


title:
Galaxy Luminosity Functions from Deep Spectroscopic Samples of Rich
  Clusters

abstract:
  Using a new spectroscopic sample and methods accounting for spectroscopic
sampling fractions that vary in magnitude and surface brightness, we present
R-band galaxy luminosity functions (GLFs) for six nearby galaxy clusters with
redshifts 4000 < cz < 20000 km/s and velocity dispersions 700 < sigma < 1250
km/s. In the case of the nearest cluster, Abell 1060, our sample extends to
M_R=-14 (7 magnitudes below M*), making this the deepest spectroscopic
determination of the cluster GLF to date. Our methods also yield composite GLFs
for cluster and field galaxies to M_R=-17 (M*+4), including the GLFs of
subsamples of star forming and quiescent galaxies. The composite GLFs are
consistent with Schechter functions (M*_R=-21.14^{+0.17}_{-0.17},
alpha=-1.21^{+0.08}_{-0.07} for the clusters, M*_R=-21.15^{+0.16}_{-0.16},
alpha=-1.28^{+0.12}_{-0.11} for the field). All six cluster samples are
individually consistent with the composite GLF down to their respective
absolute magnitude limits, but the GLF of the quiescent population in clusters
is not universal. There are also significant variations in the GLF of quiescent
galaxies between the field and clusters that can be described as a steepening
of the faint end slope. The overall GLF in clusters is consistent with that of
field galaxies, except for the most luminous tip, which is enhanced in clusters
versus the field. The star formation properties of giant galaxies are more
strongly correlated with the environment than those of fainter galaxies.


title:
Probing the Complex and Variable X-ray Absorption of Markarian 6 with
  XMM-Newton

abstract:
  We report on an X-ray observation of the Seyfert 1.5 galaxy Mrk 6 obtained
with the EPIC instruments onboard XMM-Newton. Archival BeppoSAX PDS data from
18-120 keV were also used to constrain the underlying hard power-law continuum.
The results from our spectral analyses generally favor a double
partial-covering model, although other spectral models such as absorption by a
mixture of partially ionized and neutral gas cannot be firmly ruled out. Our
best-fitting model consists of a power law with a photon index of 1.81+/-0.20
and partial covering with large column densities up to 10^{23} cm**-2. We also
detect a narrow emission line consistent with Fe Kalpha fluorescence at
6.45+/-0.04 keV with an equivalent width of ~93+/-25 eV. Joint analyses of
XMM-Newton, ASCA, and BeppoSAX data further provide evidence for both spectral
variability (a factor of ~2 change in absorbing column) and
absorption-corrected flux variations (by ~60%) during the ~4 year period probed
by the observations.


title:
Near-IR Properties of Galaxy Clusters: Luminosity as a Binding Mass
  Predictor and the State of Cluster Baryons

abstract:
  We explore the near-infrared properties of galaxies within 27 galaxy clusters
using data from the Two Micron All Sky Survey (2MASS). For a subsample of 13
clusters with available X-ray imaging data, we examine both the properties of
the galaxies and the intracluster medium. We show that the K-band luminosity is
correlated with cluster mass, providing a binding mass estimate accurate to
45%. The mass to light ratio in our ensemble increases by a factor of ~2 over
the cluster mass range (10^{14}-10^{15}M_sun). We examine the total baryon
fraction, showing that it is an increasing function of cluster mass. Using the
mass to light ratio of massive clusters, we find that Omega_M=0.19+/-0.03;
using the total baryon fraction we find that Omega_M=0.28+/-0.03, in good
agreement with recent cosmic microwave background anisotropy constraints.
Differences between these two estimates suggest that the K-band mass to light
ratio in massive clusters may be lower than that in the universe by as much as
\~30%.
  We examine the stellar mass fraction, the ICM mass to stellar mass ratio and
the cluster iron mass fraction. The stellar mass fraction decreases by a factor
of 1.8 from low to high mass clusters, and the ICM to stellar mass ratio
increases from 5.9 to 10.4 over the same mass range. Together, these
measurements suggest a decrease of star formation efficiency with increasing
cluster mass and provide constraints on models of the thermodynamic history of
the intracluster medium. The cluster iron mass to total mass ratio is constant
and high, suggesting that some efficient, and uniform enrichment process may
have taken place before the bulk of stars in cluster galaxies formed.


title:
Three-Point Correlations in Weak Lensing Surveys: Model Predictions and
  Applications

abstract:
  We use the halo model of clustering to compute two- and three-point
correlation functions for weak lensing, and apply them in a new statistical
technique to measure properties of massive halos. We present analytical results
on the eight shear three-point correlation functions constructed using
combination of the two shear components at each vertex of a triangle. We
compare the amplitude and configuration dependence of the functions with
ray-tracing simulations and find excellent agreement for different scales and
models. These results are promising, since shear statistics are easier to
measure than the convergence. In addition, the symmetry properties of the shear
three-point functions provide a new and precise way of disentangling the
lensing E-mode from the B-mode due to possible systematic errors.
  We develop an approach based on correlation functions to measure the
properties of galaxy-group and cluster halos from lensing surveys. Shear
correlations on small scales arise from the lensing matter within halos of mass
M > 10^13 solar masses. Thus the measurement of two- and three-point
correlations can be used to extract information on halo density profiles,
primarily the inner slope and halo concentration. We demonstrate the
feasibility of such an analysis for forthcoming surveys. We include covariances
in the correlation functions due to sample variance and intrinsic ellipticity
noise to show that 10% accuracy on profile parameters is achievable with
surveys like the CFHT Legacy survey, and significantly better with future
surveys. Our statistical approach is complementary to the standard approach of
identifying individual objects in survey data and measuring their properties.


title:
Red galaxy overdensities and the varied cluster environments of powerful
  radio sources with z~1.6

abstract:
  The environments of a complete subsample of 6 of the most powerful radio-loud
AGN at redshifts z~1.6 are investigated, using deep RJK imaging to depths of
R~26, J~22.4 and K~20.6. An excess of galaxy counts in the K-band is seen
across these fields; these are predominantly associated with red galaxies
(R-K>4) of magnitudes 17.5<K<20.5 found within radial distances of ~1 Mpc of
the AGN host. These are exactly (though not uniquely) the magnitudes, colours
and locations that would be expected of old passive elliptical galaxies in
cluster environments at the redshifts of these AGN. Using both an Abell-style
classification scheme and investigations of the angular and spatial
cross-correlation functions of the galaxies, the average environment of the
fields around these AGN is found to be consistent with Abell cluster richness
classes 0 to 1. The amplitude of the angular cross-correlation function around
the AGN is a strong function of galaxy colour, and is highest when only those
galaxies with the colours expected of old elliptical galaxies at these
redshifts are considered.
  The galaxy overdensities are found on two scales around the AGN: (i)
pronounced central concentrations on radial scales within 150 kpc; where
present, these are composed almost entirely of red (R-K>4) galaxies, suggesting
that the morphology-density relation is imprinted into the centres of clusters
at a high redshift. (ii) weaker large-scale excesses extending out to between 1
and 1.5 Mpc radius. The presence or absence of galaxy excesses on these two
scales, however, differs greatly between the six different fields. The
implications of these results for both cluster formation and the nature of high
redshift AGN are discussed (abridged).


title:
The Galactic Inner Halo: Searching for White Dwarfs and Measuring the
  Fundamental Galactic Constant, Vo/Ro

abstract:
  We establish an extragalactic, zero-motion frame of reference within the
deepest optical image of a globular star cluster, an HST 123-orbit exposure of
M4 (GO 8679, cycle 9). The line of sight beyond M4 (l,b (deg) = 351,16)
intersects the inner halo (spheroid) of our Galaxy at a tangent-point distance
of 7.6 kpc (for Ro = 8 kpc). We isolate these spheroid stars from the cluster
based on their proper motions over the 6-year baseline between these and
previous epoch HST data (GO 5461, cycle 4). Distant background galaxies are
also found on the same sight line using image-morphology techniques. This fixed
reference frame allows us to independently determine the fundamental Galactic
constant, Vo/Ro = 25.3 +/- 2.6 km/s/kpc, thus providing a velocity of the Local
Standard of Rest, v = 202.7 +/- 24.7 km/s for Ro = 8.0 +/- 0.5 kpc. Secondly,
the galaxies allow a direct measurement of M4's absolute proper motion,
mu_total = 22.57 +/- 0.76 mas/yr, in excellent agreement with recent studies.
The clear separation of galaxies from stars in these deep data also allow us to
search for inner-halo white dwarfs. We model the conventional Galactic
contributions of white dwarfs along our line of sight and predict 7.9 (thin
disk), 6.3 (thick disk) and 2.2 (spheroid) objects to the limiting magnitude at
which we can clearly delineate stars from galaxies (V = 29). An additional 2.5
objects are expected from a 20% white dwarf dark halo consisting of 0.5 Mo
objects, 70% of which are of the DA type. After considering the kinematics and
morphology of the objects in our data set, we find the number of white dwarfs
to be consistent with the predictions for each of the conventional populations.
However, we do not find any evidence for dark halo white dwarfs.


title:
XMM-Newton observations of Broad FeKalpha emission from a Seyfert 1.9
  galaxy MCG-5-23-16

abstract:
  XMM-Newton observations of the bright Seyfert 1.9 galaxy MCG-5-23-16 have
revealed a broad FeKalpha emission line which is nearly symmetric in contrast
to the broad and red-shifted asymmetric FeKalpha line sometimes observed from
Seyfert 1 galaxies. The FeKalpha line has two distinct components - a narrow
unresolved component with equivalent width of 40 eV and a broad component with
full width at half maximum of 40000 km/s and equivalent width of 120 eV. An
absorption feature at 7.1 keV has also been observed. The energies of the
emission and absorption features are consistent with those arising from neutral
iron. The broad component is consistent with an FeKalpha emission line expected
from a relativistic accretion disk around a Schwarzschild or a Kerr black hole.
Alternatively, most of the flux in the broad component could also be modeled as
reflection emission which mimics emission line like feature due to the presence
of iron K-shell edge at 7.1eV, however, the reflection fraction is much higher
than that inferred from the BeppoSax observations. The disk inclination angle
of about 47 deg, inferred from the disk-line fits, and the absorption column of
about 10^{22} cm^{-2}, inferred from the low-energy spectral curvature due to
photoelectric absorption, suggest that our line of sight passes through the
outer edge of a putative torus and are consistent with those expected for a
Seyfert 1.9 galaxy falling within the unification scheme. The strength of the
narrow iron Kalpha emission and the optical depth of the iron K absorption edge
suggest their origin in the putative torus with N_H about 10^{24} cm^{-2} in
the inner regions and N_H about 10^{22} cm^{-2} in the outer edges.


title: Formation of Massive Black Holes in Dense Star Clusters

abstract:
  We review possible dynamical formation processes for central massive black
holes in dense star clusters. We focus on the early dynamical evolution of
young clusters containing a few thousand to a few million stars. One natural
formation path for a central seed black hole in these systems involves the
development of the Spitzer instability, through which the most massive stars
can drive the cluster to core collapse in a very short time. The sudden
increase in the core density then leads to a runaway collision process and the
formation of a very massive merger remnant, which must then collapse to a black
hole. Alternatively, if the most massive stars end their lives before core
collapse, a central cluster of stellar-mass black holes is formed. This cluster
will likely evaporate before reaching the highly relativistic state necessary
to drive a runaway merger process through gravitational radiation, thereby
avoiding the formation of a central massive black hole. We summarize the
conditions under which these different paths will be followed, and present the
results of recent numerical simulations demonstrating the process of rapid core
collapse and runaway collisions between massive stars.


title:
New evolutionary models for massive ZZ Ceti stars: I. First results for
  their pulsational properties

abstract:
  We present new and improved evolutionary calculations for carbon-oxygen white
dwarf (WD) stars appropriate for the study of massive ZZ Ceti stars. We follow
the complete evolution of massive WD progenitors from the zero-age main
sequence through the thermally pulsing and mass loss phases to the WD regime.
Abundance changes are accounted for by means of a full coupling between nuclear
evolution and time-dependent mixing due to diffusive overshoot, semiconvection
and salt fingers. In addition, time-dependent element diffusion for
multicomponent gases has been considered during the WD stage. We find that
before the ZZ Ceti stage is reached, element diffusion has strongly smoothed
out the chemical profile to such a degree that the resulting internal abundance
distribution does not depend on the occurrence of overshoot episodes during the
thermally pulsing phase. The mass of the hydrogen envelope left at the ZZ Ceti
domain amounts to $M_H \approx 2.3 \times 10^{-6}$ \msun. This is about half as
large as for the case when element diffusion is neglected. The implications of
our new models for the pulsational properties of massive ZZ Ceti stars are
discussed. In this regard, we find that the occurrence of core overshooting
during central helium burning leaves strong imprints on the theoretical period
spectrum of massive ZZ Ceti stars. Finally, we present a simple new
prescription for calculating the He/H profile which goes beyond the trace
element approximation.


title:
CII* Absorption in Damped Lyman Alpha Systems: (I) Star Formation Rates
  in a Two-Phase Medium

abstract:
  We describe a technique that for the first time measures star formation rates
(SFRs) in damped Lyman alpha systems(DLAs) directly. We assume that massive
stars form in DLAs, and that the FUV radiation they emit heats the gas by the
grain photoelectric mechanism. We infer the heating rate from the cooling rate
measured by the strength of CII* 1335.7 absorption. Since the heating rate is
proportional to the dust-to-gas ratio and the SFR per unit area, we deduce the
SFR per unit area for DLAs in which both quantities have been measured. We
consider models in which the the dust comprises carbonaceous or silicate
grains. We present two-phase models where the cold neutral medium (CNM) and
warm neutral medium (WNM) are in pressuer equilibrium. In the CNM model the the
sightline goes throught the CNM and WNM, while in the WNM model it goes only
through the WNM. Since the grain photoelectric heating efficiency is at least
10 times higher in the CNM than in the WNM, CII* absorption mainly arises in
the CNM in the CNM model. But in the WNM model all of the CII* absorption
arises in the WNM. We use CII* absorption lines to derive the SFR per unit area
for a sample of ~ 30 DLAs in which the dust-to-gas ratio has been inferred from
element depletion patterns. We show that the resulting SFR per unit area
corresponds to an average over the star forming volume of galaxy hosting the
DLA rather than to local star formation along the line of sight. We find the
average SFR per unit area and equals10$^{-2.2}$ M$_{\odot}$yr$^{-1}$kpc$^{-2}$
for the CNM model and 10$^{-1.3}$ M$_{\odot}$yr$^{-1}$kpc$^{-2}$ for the WNM
model. The SFR per unit area in the CNM solution is similar to that measured in
the Milky Way ISM.


title: Planetary migration in protoplanetary disks

abstract:
  In the current paper, we further develop the model for the migration of
planets introduced in Del Popolo et al. (2001) and extended to time-dependent
accretion discs in Del Popolo and Eksi (2002). We use a method developed by
Stepinski and Valageas (1996, 1997), that is able to simultaneously follow the
evolution of gas and solid particles for up to $10^7 {\rm yr}$. The disc model
is coupled to the migration model introduced in Del Popolo et al. (2001) in
order to obtain the migration rate of the planet in the planetesimal disc. We
find that in the case of discs having total mass of $10^{-3}-0.1 M_{\odot}$,
and $0.1<\alpha<0.0001$, planets can migrate inward a large distance while if
$M<10^{-3} M_{\odot}$ the planets remain almost in their initial position for
$0.1<\alpha<0.01$ and only in the case $\alpha<0.001$ the planets move to a
minimum value of orbital radius of $\simeq 2 {\rm AU}$. The model gives a good
description of the observed distribution of planets in the period range 0-20
days.


title:
CII* Absorption in Damped Lyman Alpha Systems: (II) A New Window on the
  Star Formation History of the Universe

abstract:
  Starting from the SFR per unit physical area, determined for DLAs using the C
II* method, we obtain the SFR per unit comoving volume at $z$ $\approx$ 3, and
find that it agrees with that for the Lyman Break Galaxies (LBGs). Though the
mass of produced stars indicated by the SFRs is consistent with the current
densities of known stellar populations, the mass of metals produced by $z$=2.5
is 30 times larger than detected in absorption in DLAs. The most likely
solutions to this ``missing metals'' problem is that star formation occurs in
compact bulge regions. We search for evidence of feedback and find no
correlations between the SFR per unit area and N(H I), but possible
correlations between SFR per unit area and low-ion velocity width and SFR per
unit area and metal abundance. We show that (a) the correlation between cooling
rate and dust-to-gas ratio is positive evidence for grain photoelectric
heating, (b) the CMB does not significantly populate the C II excited
fine-structure states, and (c) the ratio of CII* to resonance-line optical
depths is a sensitive probe of the multi-phase structure of the DLA gas. We
address recent arguments that DLAs are comprised only of WNM gas, and show them
to be inconclusive. Despite the rough agreement between SFR per unit comoving
volume for DLAs and LBGs, current evidence indicates these are distinct
populations.


title: The z=2.51 Extremely Red Submillimeter Galaxy SMMJ04431+0210

abstract:
  We report the redshift measurement for the submillimeter selected galaxy
SMMJ04431+0210 (N4) using the Near Infrared Spectrograph on the Keck-II
telescope. The data show H-alpha, [NII]6583,6548, and [OIII]5007 lines at a
redshift of z=2.51. The high nuclear [NII]/H-alpha line ratio is consistent
with a LINER or Type-II AGN. The H-alpha emission is spatially resolved,
suggesting the presence of significant star-forming activity outside the
nucleus. From imaging with the Near Infrared Camera on the Keck-I telescope, we
find an extremely red near-infrared color of J-K=3.2 for N4. Follow-up
redshifted CO(3-2) observations with the Owens Valley Millimeter Array
constrain the mass of molecular gas to be less than 4x10^{10} Msun, after
correcting for lensing. The CO to sub-mm flux limit, the spectroscopic line
ratios, and the spectral energy distribution for N4 are all within the range of
properties found in other high-redshift sub-mm sources and local ultraluminous
infrared galaxies. After the correction for lensing, N4 is the weakest
intrinsic sub-mm selected source with a known redshift and represents the first
redshift for the <2mJy 850um sources which are responsible for the bulk of the
emission from the sub-mm population as a whole. We argue that N4 contains
either an AGN or LINER nucleus surrounded by an extended region of active
star-formation.


title:
Round Table Summary: Stellar interferometry as a tool to investigate
  atmospheres and to compare observations with models

abstract:
  Long-baseline interferometry at optical and near-infrared wavelengths is an
emerging technology which is quickly becoming a useful tool to investigate
stellar atmospheres and to compare observations with models. Stellar atmosphere
models have so far mainly been constrained by comparisons with stellar spectra
which are integrated over the stellar disks. Interferometric observations
provide spatially and spectrally resolved information and can thus provide
important complementary observational information which can be compared to
model predictions. Here, I summarize the different aspects on this topic which
were discussed at a round table on Thursday, June 20, 2002, during IAU
Symposium 210. This summary gives an overview on discussed interferometric
facilities and techniques, concepts to study atmospheres by optical
interferometry, and particular classes of objects. We conclude that more
frequent interactions between the efforts of atmosphere modelling and
interferometric observations promise to lead to increased confidence in stellar
model atmospheres and to further advancement of the field in the next years.


title:
Pseudo-Newtonion potential for the relativistic accretion disk around
  rotating central objects having hard surface

abstract:
  Here we furnish a pseudo-Newtonion potential for accretion disk modeling
around rotating central objects having hard sueface. That means, the potential
may be useful to describe the accretion disk around rotating neutron stars and
strange stars. The potential can describe the general relativistic effects in
accretion disk properly, essentially studying the relativistic hydrodynamics of
disk. As our intention lies in understanding the fluid dynamics of the
accretion disk around rotating central objects with hard surface, it is
necessary to incorporate the rotation of the central object which affects the
inner edge of the disk. We derive our potential, starting from the Hartle
Thorne metric. The potential can reproduce all the essential properties of
general relativity with 10% error at most, for slowly rotating neutron/strange
stars.


title: Discovery of the eclipse in the symbiotic binary Z Andromedae

abstract:
  Our photometric observations of the symbiotic binary Z And during its recent
(2000 -- 2003) active phase revealed a minimum in the U, B and V light curves
(LC) at the position of the inferior conjunction of its cool component (the
orbital phase 'phi' = 0). This fact and the behaviour of colour indices suggest
that the minimum was due to the eclipse of the active hot object by the red
giant. Physically plausible fit of the eclipse profile and a precise analysis
of the spectral energy distribution (SED) in the ultraviolet continuum suggest
a disk-like structure for the hot object during active phases. The present
knowledge of fundamental parameters of the system limits the orbital
inclination 'i' to 76 - 90 deg. The presence of the Rayleigh attenuated far-UV
continuum at 'phi' around 0 during quiescent phase confirms the very high
inclination of the Z And orbit.


title: Nuclear Partition Functions at Temperatures Exceeding 10^10 K

abstract:
  Nuclear partition functions were calculated for a grid of temperatures from
1.2x10^10 K to 2.75x10^11 K (1<=kT<=24 MeV) within a Fermi-gas approach,
including all nuclides from the proton-dripline to the neutron-dripline with
proton number 9<=Z<=85. The calculation is based on a nuclear level density
description published elsewhere, thus extending the previous tables of
partition functions beyond 10^10 K. Additional high temperature corrections had
to be applied.


title:
The Birmingham-CfA cluster scaling project - III: entropy and similarity
  in galaxy systems

abstract:
  We examine profiles and scaling properties of the entropy of the
intergalactic gas in a sample of 66 virialized systems, ranging in mass from
single elliptical galaxies to rich clusters, for which we have resolved X-ray
temperature profiles. Some of the properties we derive appear to be
inconsistent with any of the models put forward to explain the breaking of
self-similarity in the baryon content of clusters. In particular, the entropy
profiles, scaled to the virial radius, are broadly similar in form across the
sample, apart from a normalization factor which differs from the simple
self-similar scaling with temperature. Low mass systems do not show the large
isentropic cores predicted by preheating models, and the high entropy excesses
reported at large radii in groups by Finoguenov et al (2002) are confirmed, and
found to extend even to moderately rich clusters. We discuss the implications
of these results for the evolutionary history of the hot gas in clusters, and
suggest that preheating may affect the entropy of intracluster gas primarily by
reducing the density of material accreting into groups and clusters along
cosmic filaments.


title: Gamma-rays from the pulsar wind nebulae

abstract:
  We investigate the radiation processes inside supernova remnants which are
powered by young pulsars. Using recent model for particle acceleration by the
pulsar wind nebulae, we obtain the equilibrium spectra of leptons and nuclei
inside the nebula as a function of time. We calculate the multiwavelength
photon spectra produced by leptons and nuclei and compare them with the
observations of the PWNe, i.e. the Crab Nebula, the Vela Supernova Remnant, and
the nebula around PSR 1706-44. It is found that the emission from the Crab
Nebula can be well fitted by the composition of the gamma-ray emission produced
by leptons and nuclei. The model is further tested by successful fitting of the
high energy spectrum from the Vela SNR. However, considered model does not give
good fitting to the emission from PSR1706-44, for the likely parameters of this
source, unless additional target for relativistic leptons is present inside the
nebula, e.g. the thermal infrared emission. Based on the knowledge obtained
from these fittings, we predict the gamma-ray fluxes in the TeV energy range
from other PWNe, i.e. MSH15-52 (PSR 1509-58), 3C58 (PSR J0205+6449), and CTB80
(PSR 1951+32).


title: A fluctuating energy-momentum may produce an unstable world

abstract:
  Quantum gravitational effects may induce stochastic fluctuations in the
structure of space-time, to produce a characteristic foamy structure. It has
been known for some time now that these fluctuations may have observable
consequencies for the propagation of cosmic ray particles over cosmological
distances. We note here that the same fluctuations, if they exist, imply that
some decay reactions normally forbidden by elementary conservation laws, become
kinematically allowed, inducing the decay of particles that are seen to be
stable in our universe. Due to the strength of the prediction, we are led to
consider this finding as the most severe constraint on the classes of models
that may describe the effects of gravity on the structure of space-time. We
also propose and discuss several potential loopholes of our approach, that may
affect our conclusions. In particular, we try to identify the situations in
which despite a fluctuating energy-momentum of the particles, the reactions
mentioned above may not take place.


title: LISA observations of rapidly spinning massive black hole binary systems

abstract:
  Binary systems of massive black holes will be detectable by the Laser
Interferometer Space Antenna (LISA) throughout the entire Universe.
Observations of gravitational waves from this class of sources will have
important repercussions on our understanding of the behaviour of gravity in the
highly non-linear relativistic regime, the distribution and interaction of
massive black holes at high redshift and the formation and evolution of cosmic
structures. It is therefore important to address how accurately LISA can
measure the source parameters and explore the implications for astronomy and
cosmology. Present observations and theoretical models suggest that massive
black holes could be spinning, possibly rapidly in some cases. In binary
systems, the relativistic spin-orbit interaction causes the orbital plane to
precess in space producing a characteristic signature on the emitted
gravitational waves. In this paper we investigate the effect of spins on the
gravitational wave signal registered at the LISA output and the implications
for parameter estimation. We consider the in-spiral phase of binary systems in
circular orbit undergoing the so-called "simple precession" and we approximate
the gravitational radiation at the restricted 1.5PN order. We show that the
presence of spins changes dramatically the signature of the signal recorded by
LISA. As a consequence, the mean square errors associated to the parameter
measurements are significantly smaller than the ones obtained when the effect
of spins is neglected. For a binary system of two $10^6 \Ms$ black holes, the
angular resolution and the relative error on the luminosity distance improve by
a factor $\approx$ 3-to-10; the fractional errors on the chirp mass and the
reduced mass decrease by a factor $\sim 10$ and $\sim 10^3$, respectively.


title:
What Drives the Central Velocity Dispersion in Nearby Early-Type
  Galaxies?

abstract:
  The majority of nearby early-type galaxies contains detectable amounts of
emission-line gas at their centers. The emission-line ratios and gas kinematics
potentially form a valuable diagnostic of the nuclear activity and
gravitational potential well. The observed central gas velocity dispersion
often exceeds the stellar velocity dispersion. This could be due to either the
gravitational potential of a black hole or turbulent shocks in the gas. Here we
try to discriminate between these two scenarios.


title:
Period Changes in Galactic Classical Cepheids. Slow Evolution of
  Long-period Cepheids

abstract:
  We compared period changes derived from O-C diagrams for 63 classical
Cepheids from our Galaxy with model calculations. We found that for Cepheids
with log P > 1.0 the observed changes are smaller than predicted values, except
variable SZ Cas. However some of the first overtone Cepheids, particularly EU
Tau and Polaris, change its period much faster than it follows from theory.
Summary of the known data on the period changes in Cepheids from the Galaxy and
from the Magellanic Clouds (previous papers) leads to conclusion that none of
the 999 Cepheid is undergoing the first crossing of the instability strip. Also
the observed period changes for long-period Cepheids are a few times slower
than predicted by the models. These results imply that much larger fraction of
helium is burnt in the Cepheid stage than it is predicted by models.


title: A new catalogue of ISM content of normal galaxies

abstract:
  We have compiled a catalogue of the gas content for a sample of 1916
galaxies, considered to be a fair representation of `normality'. The definition
of 'normal' galaxy adopted in this work implies that we have purposely excluded
from the catalogue galaxies having distorted morphology (such as interaction
bridges, tails or lopsidedness) and/or any signature of peculiar kinematics
(such as polar rings, counterrotating disks or other decoupled components). In
contrast, we have included systems hosting active galactic nuclei (AGN) in the
catalogue. This catalogue revises previous compendia on the ISM content of
galaxies, and compiles data available in the literature from several small
samples of galaxies. Masses for warm dust, atomic and molecular gas, as well as
X-ray luminosities have been converted to a uniform distance scale taken from
the Catalogue of Principal Galaxies (PGC). We have used two different
normalization factors to explore the variation of the gas content along the
Hubble sequence: the blue luminosity and the square of linear diameter. Our
catalogue significantly improves the statistics of previous reference
catalogues and can be used in future studies to define a template ISM content
for 'normal' galaxies along the Hubble sequence. The catalogue can be accessed
on-line at http://dipastro.pd.astro.it/galletta/ismcat/


title: The quest for hot gas in the halo of NGC 1511

abstract:
  XMM-Newton observations of the starburst galaxy NGC 1511 reveal the presence
of a previously unknown extended hot gaseous phase of its ISM, which partly
extends out of the disk plane. The emission distribution is asymmetric, being
brightest in the eastern half of the galaxy, where also radio continuum
observations suggest the highest level of star formation. Spectral analysis of
the integral 0.2-12 keV X-ray emission from NGC 1511 indicates a complex
emission composition. A model comprising a power law plus thermal plasma
component, both absorbed by foreground gas, cannot explain all details of the
observed spectrum, requiring a third spectral component to be added. This
component can be a second thermal plasma, but other spectral models can be
fitted as well. Its X-ray properties characterize NGC 1511 as a starburst
galaxy. The X-ray-to-infrared luminosity ratio is consistent with this result.
Together with the X-ray data, XMM-Newton obtained UV images of NGC 1511,
tracing massive stars heating the ambient gas, which is then seen in H\alpha
emission. UV, H\alpha and near-infrared imagery suggest that NGC 1511 is
disturbed, most likely by its two small companions, NGC 1511a and NGC 1511b.


title: The Subdwarf Luminosity Function

abstract:
  Using data from the Sloan Digital Sky Survey Early Data Release and
SuperCOSMOS Sky Survey scans of POSS-I plates we identify a sample of 2600
subdwarfs using reduced proper motion methods and strict selection criteria.
This forms one of the largest and most reliable samples of candidate subdwarfs
known, and enables us to determine accurate luminosity functions along many
different lines of sight. We derive the subdwarf luminosity function with
unprecedented accuracy to M_V <= 12.5, finding good agreement with recent local
estimates but discrepancy with results for the more distant spheroid. This
provides further evidence that the inner and outer parts of the stellar halo
cannot be described by a single density distribution. We also find that the
form of the inner spheroid density profile within heliocentric distances of 2.5
kpc is closely matched by a power law with an index of -3.15 +/- 0.3.


title:
Narrow band survey for intragroup light in the Leo HI cloud. Constraints
  on the galaxy background contamination in imaging surveys for intracluster
  planetary nebulae

abstract:
  We have observed emission line objects located in a 0.26 deg^2 field in the
M96 (Leo) group, coincident with the intergalactic HI cloud. The emission line
objects were selected using the same procedure as used for the search for
intracluster planetary nebulae in the Virgo cluster, and their m_5007
luminosity function has a bright cut-off ~1.2 magnitude fainter than for the
PNLF associated with the elliptical galaxies in the M96 group.Therefore the
vast majority of these emission line objects are compatible with not being
intragroup planetary nebulae at the Leo group distance of 10 Mpc. Spectroscopic
follow-up of two emission line objects in this Leo field showed that indeed
these do not have the [OIII] doublet expected for a real PN. The brighter
source is identified as a starburst object at redshift z = 3.128, because of a
second emission in the near infrared, identified as FeII (\lambda 2220 AA).
  From these data we derive three main results: (i) from the absence of PN we
can determine a more stringent upper limit to the surface brightness in any old
stellar population associated with the Leo HI cloud. (ii) This translates to an
upper limit of 1.6% for the fraction of luminosity in a diffuse intragroup
component in the densest 3 x 2 deg area of the Leo group,relative to the light
in galaxies. (iii) Using this Leo field as a blank field, we derive an average
fraction of 13.6% background emission line objects that enter in surveys of
Virgo intracluster PN. The small fraction confirms the validity of the
selection criteria for intracluster PN candidates in Virgo.


title:
Particle transport in tangled magnetic fields and Fermi acceleration at
  relativistic shocks

abstract:
  This paper presents a new method of Monte-Carlo simulations of test particle
Fermi acceleration at relativistic shocks. The particle trajectories in tangled
magnetic fields are integrated out exactly from entry to exit through the
shock, and the conditional probability of return as a function of ingress and
egress pitch angles is constructed by Monte-Carlo iteration. These upstream and
downstream probability laws are then used in conjunction with the energy gain
formula at shock crossing to reproduce Fermi acceleration. For pure Kolmogorov
magnetic turbulence upstream and downstream, the spectral index is found to
evolve smoothly from s=2.09 +/- 0.02 for mildly relativistic shocks with
Lorentz factor Gamma=2 to s=2.26 +/- 0.04 in the ultra-relativistic limit Gamma
>> 1. The energy gain is ~Gamma^2 at first shock crossing, and ~2 in all
subsequent cycles as anticipated by Gallant & Achterberg (1999). The
acceleration timescale is found to be as short as a fraction of Larmor time
when Gamma >> 1.


title: A Search for Intraday Variability in the Blazar PKS 2005-489

abstract:
  Rapid, multi-color optical monitoring carried out for a multiwavelength
campaign during 22-27 August 2000 is presented for the bright and variable BL
Lac object PKS 2005-489. Previous multiwavelength monitoring campaigns of PKS
2005-489 have found complex variability behavior both in flux density and in
broadband spectrum, with different modes and timescales from days to hours.
During this campaign, PKS 2005-489 was observed to be in an unusual state,
bright in the optical but faint in the X-ray, just prior to an X-ray flare that
began on 2 September 2000. PKS 2005-489 was also observed to have a flatter
optical spectrum than prior epochs. A linear increase in optical flux density
was observed during the first 5.2 days of the campaign. However, intraday and
color variability were not detected. The large discrepancy between the ratio of
X-ray to optical flux density observed during this campaign and that observed
in prior epochs indicates a lack of long-term correlation between the two
wavebands; and it illustrates that simple particle injection events in the jet
are insufficient to explain the long-term variability behavior of this object.
Twenty-three in-field standard stars are identified for future optical
monitoring programs.


title: Scattering by Interstellar Dust Grains: Optical and Ultraviolet

abstract:
  Scattering and absorption properties at optical and ultraviolet wavelengths
are calculated for an interstellar dust model consisting of carbonaceous grains
and amorphous silicate grains. Polarization as a function of scattering angle
is calculated for selected wavelengths from the IR to the vacuum UV. The
widely-used Henyey-Greenstein phase function provides a good approximation for
the scattering phase function between ~0.4 and 1 micron, but fails to fit the
calculated phase functions at shorter wavelengths and longer wavelengths. A new
analytic phase function is presented. It is exact at long wavelengths, and
provides a good fit to the numerically-calculated phase function for lambda >
0.27um.
  Observational determinations of the scattering albedo and <cos(theta)> show
considerable disagreement, especially in the ultraviolet. Possible reasons for
this are discussed.


title:
Physical limits to the validity of synthesis models: The Lowest
  Luminosity Limit

abstract:
  (abriged) In this paper we establish a Lowest Luminosity Limit (LLL) for the
use of synthesis codes. The limit is defined by the following statement: The
total luminosity of the cluster modeled must be larger than the individual
contribution of any of the stars included in the assumed isochrones. This limit
is independent of the assumptions on the IMF and almost independent on the star
formation history. We have obtained the LLL for a wide range of ages (5 Myr to
20 Gyr) and metallicities (Z=0 to Z=0.019) from Girardi et al. (2002)
isochrones. Using the LLL and the results of evolutionary synthesis models we
have also obtained the minimal cluster mass, Mmin, for which the results of
synthesis models may suffer from a severe bias in the computation of colors. We
show that the results of synthesis models for clusters with mass equal to Mmin
have a relative dispersion about or larger than 32% (i.e. a dispersion of 0.35
mag) in the corresponding photometric bands. This effect is more important for
near infrared bands (except in the case where Asymptotic Giant Branch stars
dominate the luminosity in optical bands). In particular, Mmin takes values
between 10^4 and 10^5 Mo for the K band. From the observational point of view,
we show that in surveys that reach luminosities near the LLL, the color
distributions will be skewed toward the color with lower effective sources
(toward the red in general), and that the skewness is a signature of the
distribution of initial cluster masses in the survey. We also apply the LLL to
Globular Clusters showing that sampling effects are relevant in these clusters
and that they can explain (at least partially) the bias of the observed colors
with respect to the predictions of synthesis models.


title:
On emission-line spectra obtained from evolutionary synthesis models I.
  Dispersion in the ionising flux and Lowest Luminosity Limits

abstract:
  (abriged) Stellar clusters with the same general physical properties (e.g.,
total mass, age, and star-formation mode) may have very different stellar mass
spectra due to the incomplete sampling of the underlying mass function; such
differences are especially relevant in the high-mass tail due to the smaller
absolute number of massive stars. The dispersion in the number of massive stars
also produces a dispersion in the properties of the corresponding ionising
spectra. In this paper, we lay the bases for the future analysis of this effect
by evaluating the dispersion in the ionising fluxes of synthetic spectra. As an
important consequence, we found that the intensities of synthetic fluxes at
different ionisation edges are strongly correlated, a fact suggesting that no
additional dispersion will result from the inclusion of sampling effects in the
analysis of diagnostic diagrams; this is true for HII regions on all scales.
Additionally, we find convincing suggestions that the He II lines are strongly
affected by sampling, and so cannot be used to constrain the evolutionary
status of stellar clusters. We also establish the range of applicability of
synthesis models set by the Lowest Luminosity Limit for the ionising flux, that
is the lowest limit in cluster mass for which synthesis models can be applied
to predict ionising spectra. This limit marks the boundary between the
situations in which the ionising flux is better modeled with a single star as
opposed to a star cluster; this boundary depends on the metallicity and age,
ranging from 10^3 to more than 10^6 Mo. As a consequence, synthesis models
should not be used to try to account for the properties of clusters with
smaller masses.


title:
Follow-Up HST/STIS Spectroscopy of Three Candidate Tidal Disruption
  Events

abstract:
  Large amplitude, high luminosity soft X-ray flares were detected by the ROSAT
All-Sky Survey in several galaxies with no evidence for Seyfert activity in
their ground-based optical spectra. These flares had the properties predicted
for a tidal disruption event by a central supermassive black hole: soft X-ray
spectrum, time-scale of months, and large X-ray luminosity (10^42 - 10^44 ergs
s^-1). In order to evaluate the alternative hypothesis that these flares could
have been some form of extreme AGN variability, we obtained follow-up optical
spectroscopy of three of the flaring galaxies a decade later with the Space
Telescope Imaging Spectrograph (STIS) and a narrow slit to search for or place
stringent limits on the presence of any persistent Seyfert-like emission in
their nuclei. Two of the galaxies, RX J1624.9+7554 and RX J1242.6-1119, show no
evidence for emission lines or a non-stellar continuum in their Hubble Space
Telescope (HST) nuclear spectra, consistent with their ground-based
classification as inactive galaxies. They remain the most convincing as hosts
of tidal disruption events. NGC 5905, previously known as a starburst H II
galaxy due to its strong emission lines, has in its inner 0."1 a nucleus with
narrow emission-line ratios requiring a Seyfert 2 classification. This weak
Seyfert 2 nucleus in NGC 5905, which was masked by the many surrounding H II
regions in ground-based spectra, requires a low level of prior non-stellar
photoionization, thus raising some uncertainty about the nature of its X-ray
flare, which may or may not have been a tidal disruption event. The absence of
both broad emission lines and nuclear X-ray absorption in NGC 5905 also
characterizes it as a ``true'' Seyfert 2 galaxy, yet one that has varied by
more than a factor of 100 in X-rays.


title: Binary Blue Metal-Poor Stars: Evidence for AGB Mass Transfer

abstract:
  We present new abundance analyses of six blue metal-poor (BMP) stars with
very low iron abundances ([Fe/H] < -2), based on new high resolution echelle
spectra. Three are spectroscopic binaries and three have constant radial
velocities. The chemical compositions of these two groups are very different,
as the binary BMP stars have large enhancements of carbon and neutron-capture
elements that are products of s-process nucleosynthesis. One star, CS
29497-030, has an extreme enhancement of lead, [Pb/Fe] = +3.7, the largest
abundance in any star yet discovered. It probably also has an oxygen
overabundance compared to the other BMP stars of our sample. The binary BMP
stars must have attained their status via mass transfer during the asymptotic
giant branch (AGB) evolutions of their companion stars, which are now unseen
and most likely are compact objects. We have not found any examples of AGB mass
transfer among BMP binaries with [Fe/H] > -2.


title:
Uniformity of foreground Galactic neutral Hydrogen over cooling flow
  clusters

abstract:
  Radio maps at 21 cm of foreground neutral hydrogen over three cooling flow
clusters of galaxies show that the foreground gas is uniform on scales from
about 1 -- 10 arcmin. Five sigma limits on fluctuations in the foreground
column density for Abell 3581, Sersic 159-03 and Abell 2597 are 6.2e19, 7.8e19
and 4.3e19 per sq cm, or 14, 43 and 17 per cent of the mean foreground column
density in the region of the system, respectively. Fluctuations in the column
density of neutral gas in the Galaxy are unlikely to account for any excesses
of photoelectric absorption in these or other cooling flow clusters.
Fluctuations in the foreground neutral gas on arcminute scales are also
unlikely to be the cause of excess EUV and soft X-ray emission from clusters.


title: A Review of The O--C Method and Period Change

abstract:
  The classical O--C curves are discussed in different cases in which various
period changes involved. Among them, the analytic O--C curves with frequency,
amplitude modulations and with double modes are closely inspected,
respectively. As a special, the light-time effect is illustrated. The features
of period change noise and period change to metallicity are added at the end.


title:
Solar Neutron Event in Association with a Large Solar Flare on November
  24, 2000

abstract:
  Solar neutrons have been detected using the neutron monitor located at Mt.
Chacaltaya, Bolivia, in association with a large solar flare on November 24,
2000. This is the first detection of solar neutrons by the neutron monitor that
have been reported so far in solar cycle 23. The statistical significance of
the detection is 5.5 sigma. In this flare, the intense emission of hard X-rays
and gamma-rays has been observed by the Yohkoh Hard X-ray Telescope (HXT) and
Gamma Ray Spectrometer (GRS), respectively. The production time of solar
neutrons is better correlated with those of hard X-rays and gamma-rays than
with the production time of soft X-rays. The observations of the solar neutrons
on the ground have been limited to solar flares with soft X-ray class greater
than X8 in former solar cycles. In this cycle, however, neutrons were detected
associated with an X2.3 solar flare on November 24, 2000. This is the first
report of the detection of solar neutrons on the ground associated with a solar
flare with its X-ray class smaller than X8.


title:
A Continuous Injection Plasma Model for the X-Ray/Radio Knots in
  Kpc-Scale Jets of AGN

abstract:
  We consider the evolution of a spherically expanding plasma cloud, where
there is continuous injection of non-thermal electrons. We compute the time
dependent electron distribution and resultant photon spectra taking into
account synchrotron, adiabatic and inverse Compton cooling. This model is
different from previous works where, instead of a continuous injection of
particles, a short injection period was assumed. We apply this model to the
radio/optical knots in the large scale jets of AGN, detected in X-rays by {\it
Chandra} and find that the overall broadband spectral features can be
reproduced. It is shown that for some sources, constraints on the X-ray
spectral index (by a longer {\it Chandra} observation) will be able to
differentiate between the different models. This in turn will put a strong
constraint on the acceleration mechanism active in these sources.


title:
Stellar evolution with rotation X: Wolf-Rayet star populations at solar
  metallicity

abstract:
  We examine the properties of Wolf--Rayet (WR) stars predicted by models of
rotating stars taking account of the new mass loss rates for O--type stars and
WR stars (Vink et al. \cite{Vink00}, \cite{Vink01}; Nugis & Lamers
\cite{NuLa00}) and of the wind anisotropies induced by rotation. We find that
the rotation velocities $v$ of WR stars are modest, i.e. about 50 km s$^{-1}$,
not very dependant on the initial $v$ and masses. For the most massive stars,
the evolution of $v$ is very strongly influenced by the values of the mass loss
rates; below $\sim$12 M$_\odot$ the evolution of rotation during the MS phase
and later phases is dominated by the internal coupling. Massive stars with
extreme rotation may skip the LBV phase.
  Models having a typical $v$ for the O--type stars have WR lifetimes on the
average two times longer than for non--rotating models. The increase of the WR
lifetimes is mainly due to that of the H--rich eWNL phase. Rotation allows a
transition WN/WC phase to be present for initial masses lower than 60
M$_\odot$. The durations of the other WR subphases are less affected by
rotation. The mass threshold for forming WR stars is lowered from 37 to 22
M$_\odot$ for typical rotation. The comparisons of the predicted number ratios
WR/O, WN/WC and of the number of transition WN/WC stars show very good
agreement with models with rotation, while this is not the case for models with
the present--day mass loss rates and no rotation. As to the chemical abundances
in WR stars, rotation brings only very small changes for WN stars, since they
have equilibrium CNO values. However, WC stars with rotation have on average
lower C/He and O/He ratios. The luminosity distribution of WC stars is also
influenced by rotation.


title: CI and CO in the nearby spiral galaxies IC 342 and Maffei 2

abstract:
  We present J=2-1, J=3-2, J=4-3 12CO and 492 GHz [CI] maps as well as J=2-1
and J=3-2 13CO measurements of the central regions in the nearby Sc galaxies IC
342 and Maffei 2. In both galaxies, the distribution of CO and [CI] is strongly
concentrated towards the modest starburst centers. Both galaxies have nearly
identical 12CO transitional ratios but the relative intensities of their 13CO
and [CI] emission lines differ significantly and require modelling with a
multi-component molecular gas. Both have a dense component (n(H2) = 10**4 -
10**5 cm**-3) with kinetic temperatures T(kin) = 10 - 20 K (IC 342) or 20 - 60
K (Maffei 2), and a less dense (IC 342: a few hundred cm**-3 at most; Maffei 2:
about 3 x 10**3 cm**-3 and hotter (T(kin) = 100 - 150 K) component. In both
galaxies, neutral and ionized atomic carbon amounts are between 1.5 and 2.5
times those of CO, and in both about half to two thirds of the molecular gas
mass is associated with a hot PDR phase. Within R = 0.25 kpc, the center of IC
342 contains an (atomic and molecular) gas mass of 1 x 10**7 M(sun) and a peak
face-on gas mass density of about 70 M(sun) pc**-2. For Maffei 2 these numbers
are less clearly defined, mainly because of its uncertain distance and carbon
abundance. We find a gass mass M(gas) > 0.5 x 10**7 M(sun) and a peak face-on
gas mass density of about 35 M(sun) pc**-2.


title: HST Astrometry of M4 and the Galactic Constant V_0/R_0

abstract:
  From multi-epoch WFPC2/HST observations we present astrometric measurements
of stars in the Galactic globular cluster M4 (NGC 6121) and in the
foreground/background. The presence of an extragalactic point source allows us
to determine the absolute proper motion of the cluster, and, through use of the
field stars in this region only 18 degree from the Galactic center, to measure
the difference between the Oort constants, A-B. We find: (mu_alpha cos dec,
mu_dec)_J2000 = (-13.21 +/- 0.35, -19.28 +/- 0.35) mas/yr, and A-B = V_0/R_0 =
27.6 +/- 1.7 km / s / kpc.


title: The evolution of faint AGN between z~1 and z~5 from the COMBO-17 survey

abstract:
  We present a determination of the optical/UV AGN luminosity function and its
evolution, based on a large sample of faint (R<24) QSOs identified in the
COMBO-17 survey. Using multi-band photometry in 17 filters within 350nm <
lambda_obs < 930nm, we could simultaneously determine photometric redshifts
with an accuracy of sigma_z<0.03 and obtain spectral energy distributions. The
redshift range covered by the sample is 1.2<z<4.8, which implies that even at
z~3, the sample reaches below luminosities corresponding to M_B = -23,
conventionally employed to distinguish between Seyfert galaxies and quasars. We
clearly detect a broad plateau-like maximum of quasar activity around z~2 and
map out the smooth turnover between z~1 and z~4. The shape of the LF is
characterised by some mild curvature, but no sharp `break' is present within
the range of luminosities covered. Using only the COMBO-17 data, the evolving
LF can be adequately described by either a pure density evolution (PDE) or a
pure luminosity evolution (PLE) model. However, the absence of a strong L*-like
feature in the shape of the LF inhibits a robust distinction between these
modes. We present a robust estimate for the integrated UV luminosity generation
by AGN as a function of redshift. We find that the LF continues to rise even at
the lowest luminosities probed by our survey, but that the slope is
sufficiently shallow that the contribution of low-luminosity AGN to the UV
luminosity density is negligible. Although our sample reaches much fainter flux
levels than previous data sets, our results on space densities and LF slopes
are completely consistent with extrapolations from recent major surveys such as
SDSS and 2QZ.


title:
Long-term Properties of Accretion Disks in X-ray Binaries: II. Stability
  of Radiation-Driven Warping

abstract:
  A significant number of X-ray binaries are now known to exhibit long-term
``superorbital'' periodicities on timescales of $\sim$ 10 - 100 days. Several
physical mechanisms have been proposed that give rise to such periodicities, in
particular warping and/or precession of the accretion disk. Recent theoretical
work predicts the stability to disk warping of X-ray binaries as a function of
the mass ratio, binary radius, viscosity and accretion efficiency, and here we
examine the constraints that can be placed on such models by current
observations.
  In paper I we used a dynamic power spectrum (DPS) analysis of long-term X-ray
datasets (CGRO, RXTE), focusing on the remarkable, smooth variations in the
superorbital period exhibited by SMC X-1. Here we use a similar DPS analysis to
investigate the stability of the superorbital periodicities in the neutron star
X-ray binaries Cyg X-2, LMC X-4 and Her X-1, and thereby confront stability
predictions with observation. We find that the period and nature of
superorbital variations in these sources is consistent with the predictions of
warping theory.
  We also use a dynamic lightcurve analysis to examine the behaviour of Her X-1
as it enters and leaves the 1999 Anomalous Low State (ALS). This reveals a
significant phase shift some 15 cycles before the ALS, which indicates a change
in the disk structure or profile leading into the ALS.


title: Induced Formation of Primordial Low-Mass Stars

abstract:
  We show that the explosion of the first supernovae can trigger low-mass star
formation via gravitational fragmentation of the supernova-driven gas shell. If
the shell mass does not exceed the host galaxy gas mass, all explosions with
energies E_SN > 10^{51} erg can lead to shell fragmentation. However, the
minimum ambient density required to induce such fragmentation is much larger,
n_0 > 300 cm^{-3}, for Type II supernovae than for pair-instability ones, which
can induce star formation even at lower ambient densities. The typical mass of
the unstable fragments is 10^{4-7} Msun; their density is in the range
110-6x10^7 cm{-3}. Fragments have a metallicity strictly lower than 10^{-2.6}
Zsun and large values of the gravitational-to-pressure force ratio f ~ 8. Based
on these findings, we conclude that the second generation of stars produced by
such self-propagating star formation is predominantly constituted by low-mass,
long-living, extremely metal-poor (or even metal-free, if mixing is suppressed)
stars. We discuss the implications of such results for Pop III star formation
scenarios and for the most iron-poor halo star HE0107-5240.


title: Host galaxies of 2MASS-selected QSOs to redshift 0.3

abstract:
  We present and discuss optical imaging of 76 AGN which represent the
2MASS-selected sample for z<0.3, from a full list of 243. They are found to
have dust-obscured nuclei, residing in host galaxies that show a high fraction
(>70%) of tidal interactions. The derived luminosities of the AGN and host
galaxies are similar to traditionally-selected AGN, and they may comprise some
40% of the total AGN population at low redshift. We have measured a number of
host galaxy properties, and discuss their distributions and interrelations. We
compare the 2MASS AGN with optically selected samples and the IRAS-selected
galaxy samples, and discuss the differences in terms of merger processes and
initial conditions.


title:
RR Lyrae and short-period variable stars in the dwarf irregular galaxy
  NGC 6822

abstract:
  We report the discovery of a large number of short-period variable stars in
the dwarf irregular galaxy NGC6822, based on deep time-series imaging carried
out with the ESO Very Large Telescope. In particular, we found a modest
population of RR Lyrae stars tracing the presence of an old stellar component
in NGC6822. Measurements of the average luminosity of RR Lyrae stars provide a
new independent estimate of the distance to this galaxy based on a Pop.II
indicator, (m-M)o=23.36 +/-0.17. In addition, our new data show a significant
population of small-amplitude, short-period variable stars filling the
instability strip starting at luminosities only a few tenths of a magnitude
brighter than the RR Lyrae stars.


title: Variable Stars in Metal-Rich Globular Clusters. II. NGC 6316

abstract:
  We present time-series VI photometry of the metal-rich globular cluster NGC
6316. Our color-magnitude diagrams show a predominantly red-clump horizontal
branch morphology with no evidence of the blue extensions seen in NGC 6388 and
NGC 6441. Our data are in good agreement with published estimates of the
reddening and metallicity provided the cluster has an absolute distance modulus
of 15.50 mag. We have discovered more than one dozen long-period variable stars
in our field of view, and argue that at least seven of them are members of NGC
6316. We have also discovered four RR Lyrae variables, although only one of
them probably belongs to the cluster. The specific frequency of RR Lyrae stars
in NGC 6316 is found to be less than 0.4, making it clear that this cluster is
a normal, metal-rich globular and is not an analog of NGC 6388 and NGC 6441. We
recommend long-term photometric monitoring of NGC 6316 to clarify the nature of
the RR Lyrae member candidate as well as the pulsation classes of the
long-period variables.


title: Accretion in Young Stellar/Substellar Objects

abstract:
  We present a study of accretion in a sample of 45 young, low mass objects in
a variety of star forming regions and young associations, about half of which
are likely substellar. Based primarily on the presence of broad, asymmetric
Halpha emission, we have identified 13 objects (~30% of our sample) which are
strong candidates for ongoing accretion. At least 3 of these are substellar. We
do not detect significant continuum veiling in most of the accretors with late
spectral types (M5-M7). Accretion shock models show that lack of measurable
veiling allows us to place an upper limit to the mass accretion rates of <~
10^{-10} Msun/yr. Using magnetospheric accretion models with appropriate
(sub)stellar parameters, we can successfully explain the accretor Halpha
emission line profiles, and derive quantitative estimates of accretion rates in
the range 10^{-12} < Mdot < 10^{-9} Msun/yr. There is a clear trend of
decreasing accretion rate with stellar mass, with mean accretion rates
declining by 3-4 orders of magnitude over ~ 1 - 0.05 Msun.


title: OVI Emission in the Halos of Edge-on Spiral Galaxies

abstract:
  We have used the Far Ultraviolet Spectroscopic Explorer to search for OVI
1031.926, 1037.617 A emission in the halos of the edge-on spiral galaxies
NGC4631 and NGC891. In NGC4631, we detected OVI in emission toward a soft X-ray
bubble above a region containing numerous Halpha arcs and filaments. The
line-of-sight component of the motion of the OVI gas appears to match the
underlying disk rotation. The observed OVI luminosities can account for 0.2-2%
of the total energy input from supernovae (assuming a full OVI emitting halo)
and yield mass flux cooling rates between 0.48 and 2.8 M_sun/yr depending on
the model used in the derivations. Based on these findings, we believe it is
likely that we are seeing cooling, galactic fountain gas. No emission was
detected from the halo of NGC891, a galaxy in a direction with considerably
high foreground Galactic extinction.


title:
The Fe XXII I(11.92 A)/I(11.77 A) Density Diagnostic Applied to the
  Chandra High Energy Transmission Grating Spectrum of EX Hydrae

abstract:
  Using the Livermore X-ray Spectral Synthesizer, which calculates spectral
models of highly charged ions based primarily on HULLAC atomic data, we
investigate the temperature, density, and photoexcitation dependence of the
I(11.92 A)/I(11.77 A) line ratio of Fe XXII. We find that this line ratio has a
critical density n_c \approx 5x10^13 cm^-3, is approximately 0.3 at low
densities and 1.5 at high densities, and is very insensitive to temperature and
photoexcitation, so is a useful density diagnostic for sources like magnetic
cataclysmic variables in which the plasma densities are high and the efficacy
of the He-like ion density diagnostic is compromised by the presence of a
bright ultraviolet continuum. Applying this diagnostic to the Chandra High
Energy Transmission Grating spectrum of the intermediate polar EX Hya, we find
that the electron density of its T_e \approx 12 MK plasma is n_e =
1.0^{+2.0}_{-0.5} x 10^14 cm^-3, orders of magnitude greater than that
typically observed in the Sun or other late-type stars.


title: Massive Variability Surveys from Venezuela

abstract:
  At the Venezuela National Astronomical Observatory we are carrying out
variability surveys spanning many hundreds of square degrees near the celestial
equator, using an 8k x 8k CCD Mosaic Camera optimized for drift-scanning on a
1m Schmidt telescope. Among the initial efforts was a project to obtain the
first moderately deep, homogeneous sample of young stars over an area of
~180sqr.deg. encompassing the entire Orion OB1 association, one of the nearest
and most active regions of star formation. The results show that variability is
a powerful technique to identify pre-main sequence populations, specially in
sparse areas devoid of gas and dust. We are currently developing a massive
database, equipped with web-based data mining tools, that will make our data
and results available to the astronomical community.


title: Multi-wavelength spectroscopy of the bipolar outflow from Cepheus E

abstract:
  Cepheus E is the site of an exceptional example of a protostellar outflow
with a very young dynamical age and extremely high near infrared luminosity. We
combine molecular spectroscopic data from the submillimeter to the near
infrared in order to interpret the rotational excitation of CO and the
ro-vibrational excitation of H2. We conclude that C-type shocks with a
paraboloidal bow shock geometry can simultaneously explain all the molecular
excitations. Extinction accounts for the deviation of the column densities from
local thermodynamic equilibrium. A difference in the extinction between the red
and blue-shifted outflow lobes may account for the measured flux difference.
The outflow is deeply embedded in a clump of density 10^5cm^-3, yet a good
fraction of atomic hydrogen, about 40%, is required to explain the excitation
and statistical equilibrium. We propose that this atomic component arises,
self-consistently, from the dissociated gas at the apex of the leading bow
shocks and the relatively long molecule reformation time. At least 20 bow
shocks are required in each lobe, although these may be sub-divided into
smaller bows and turbulent shocked regions. The total outflow mechanical power
and cooling amounts to over 30L_\odot, almost half the source's bolometric
luminosity. Nevertheless, only about 6% of the clump mass has been set in
outward motion by the outflow, allowing a collapse to continue.


title:
The First Detection of Spatially Resolved Mid-Infrared Scattered Light
  from a Protoplanetary Disk

abstract:
  We report spatially resolved 11.8 micron images, obtained at the W. M. Keck
10 m telescope, of the protoplanetary disk around the pre--main-sequence star
HK Tau B. The mid-infrared morphology and astrometry of HK Tau B with respect
to HK Tau A indicate that the flux observed in the mid-infrared from HK Tau B
has been scattered off the upper surface of its nearly edge-on disk. This is
the first example of a protoplanetary disk observed in scattered light at
mid-infrared wavelengths. Monte Carlo simulations of this disk show that the
extent (FWHM =0."5, or 70 AU) of the scattered light nebula in the mid-infrared
is very sensitive to the dust size distribution. The 11.8 micron measurement
can be best modelled by a dust grain population that contains grains on the
order of 1.5-3 micron in size; grain populations with exclusively sub-micron
grain sizes or power law size distributions that extend beyond 5 micron cannot
reproduce the observed morphology. These grains are significantly larger than
those expected in the ISM implying that grain growth has occurred; whether this
growth is a result of dust evolution within the disk itself or had originally
occurred within the dark cloud remains an open question.


title:
Theoretical Limb Darkening for Classical Cepheids: II. Corrections for
  the Geometric Baade-Wesselink Method

abstract:
  The geometric Baade-Wesselink method is one of the most promising techniques
for obtaining a better calibration of the Cepheid period-luminosity relation by
means of interferometric measurements of accurate diameters. In this paper we
present new wavelength- and phase-dependent limb darkening corrections based on
our time-dependent hydrodynamic models of the classical Cepheid zeta Gem. We
show that a model simulation of a Cepheid atmosphere, taking into account the
hydrodynamic effects associated with the pulsation, shows strong departures
from the limb darkening otherwise predicted by a static model. For most of its
pulsational cycle the hydrodynamic model predicts a larger limb darkening then
the equivalent static model. The hydrodynamics affects the limb darkening
mainly at UV and optical wavelengths. Most of these effects evolve slowly as
the star pulsates, but there are phases, associated with shocks propagating
into the photosphere, in which significant changes in the limb darkening take
place on time-scales of the order of less than a day. We assess the implication
of our model LD corrections fitting the geometric Baade-Wesselink distance of
zeta Gem for the available near-IR PTI data. We discuss the effects of our
model limb darkening on the best fit result, and analyze the requirements
needed to test the time-dependence of the limb darkening with future
interferometric measurements.


title: A model for the jet-disk connection in BH accreting systems

abstract:
  Based on theoretical arguments and quasi-stationary radiative MHD
calculations, a model for an accretion-powered jet is presented. It is argued
that accretion disks around BHs consist of 1) a cold, Keplerian-rotating and
weakly magnetized mediumin the outer part, 2) a highly advective and
turbulent-free plasma inside $r_\mm{tr}=10-20$ Schwarzschild radii, where
magnetic fields are predominantly of large scale topology and in excess of
thermal equipartition, and 3) an ion-dominated torus in the vicinity of the
hole, where magnetic fields undergo a topological change into a monopole
like-configuration. The action of magnetic fields interior to $r_\mm{tr}$ is to
initiate torsional {\Alfven} waves that extract angular momentum from the
disk-plasma and deposit it into the transition layer (-TL) above the disk,
where the plasma is dissipative and tenuous. A significant fraction of the
shear-generated toroidal magnetic field reconnects in the TL, thereby heating
the plasma up to the virial-temperature and forming a super-Keplerian rotating,
and hence centrifugally accelerated outflow. The strong magnetic field in the
TL forces the electrons to cool rapidly yielding thereby an ion-dominated
outflow. The toroidal magnetic field in the TL is in thermal equipartition with
the ions, whereas the poloidal component is in equipartition with the
electrons. Such a strong toroidal magnetic field is essential for increasing
the jet-disk luminosity in the radio regime.


title: Early Optical Afterglows from Wind-Type Gamma-Ray Bursts

abstract:
  We study prompt optical emission from reverse shocks in the wind-type
gamma-ray bursts. The emission is evaluated in both the thick and thin shell
regimes. We discuss the angular time delay effect and the post-shock evolution
of the fireball ejecta, which determine the decay index of the prompt optical
emission and the duration of the radio flare. We discuss distinct emission
signatures of the wind environment compared with the constant interstellar
medium environment. We also present two recipes for directly constraining the
initial or early time Lorentz factor of the fireball using the reverse and
forward shock optical afterglow data for the wind case.


title:
Multi-frequency polarimetry of the Galactic radio background around 350
  MHz: II. A region in Horologium around l = 137, b = 7

abstract:
  We study a conspicuous ring-like structure with a radius of about 1.4 degrees
which was observed with the Westerbork Synthesis Radio Telescope (WSRT) at 5
frequencies around 350 MHz. This ring is very prominent in Stokes Q and U, and
less so in polarized intensity P. No corresponding structure is visible in
total intensity Stokes I, which indicates that the ring is created by Faraday
rotation and depolarization processes. The polarization angle changes regularly
from the center of the ring outwards to a radius of more than 1.7 degrees.
Thus, the structure in polarization angle is not ring-like but resembles a
disk, and it is larger than the ring in P. The rotation measure (RM) decreases
almost continuously over the disk, from RM = 0 rad/m2 at the edge, to -8 rad/m2
in the center, while outside the ring the RM is slightly positive. This radial
variation of RM yields stringent constraints on the nature of the ring-like
structure, because it rules out any spherically symmetrical magnetic field
configuration, such as might be expected from supernova remnants or wind-blown
bubbles. We discuss several possible connections between the ring and known
objects in the ISM, and conclude that the ring is a predominantly magnetic
funnel-like structure. This description can explain both the field reversal
from outside to inside the ring, and the increase in magnitude of RM towards
the center of the ring. The ring-structure in P is most likely caused by a lack
of depolarization due to a very uniform RM distribution at that radius. Beyond
the ring, the RM gradient increases, depolarizing the polarized emission, so
that P decreases. In the SW corner of the field a pattern of narrow filaments
of low polarization, aligned with Galactic longitude, is observed, indicative
of beam depolarization due to abrupt changes in RM.


title:
A broad absorption feature in the X-ray spectrum of the isolated neutron
  star RBS1223 (1RXS J130848.6+212708)

abstract:
  X-ray spectra of the isolated neutron star RBS1223 obtained with the
instruments on board XMM-Newton in December 2001 and January 2003 show
deviations from a Planckian energy distribution at energies below 500 eV. The
spectra are well fit when a broad, Gaussian-shaped absorption line with sigma =
100 eV and centered at an energy of 300 eV is added to an absorbed blackbody
model. The resulting equivalent width of the line is -150 eV. However, the
spectral resolution at these low energies of the EPIC detectors and the lower
statistical quality and restricted energy band of the RGS instruments are not
sufficient to exclude even broader lines at energies down to 100 eV or several
unresolved lines. The most likely interpretation of the absorption feature is a
cyclotron absorption line produced by protons in the magnetic field of the
neutron star. In this picture line energies of 100-300 eV yield a magnetic
field strength of 2-6x10^13 G for a neutron star with canonical mass and
radius. Folding light curves from different energy bands at a period of 10.31
s, which implies a double peaked pulse profile, shows different hardness ratios
for the two peaks. This confirms that the true spin period of RBS1223 is twice
as long as originally thought and suggests variations in cyclotron absorption
with pulse phase. We also propose that changes in photo-electric absorption
seen in phase resolved spectra of RX J0720.4-3125 by Cropper et al. (2001),
when formally fit with an absorbed blackbody model, are caused instead by
cyclotron absorption varying with pulse phase.


title: The effect of signal digitisation in CMB experiments

abstract:
  Signal digitisation may produce significant effects in balloon - borne or
space CMB experiments, since the limited bandwidth for downlink of data
requires imposes a large quantisation step q applied on board by the instrument
acquisition chain. In this paper we present a study of the impact of the
quantization error in CMB experiments using, as a working case, simulated data
from the Planck/LFI. At TOD level, the effect of the quantization can be
approximated as a source of nearly normally distributed noise. At map level,
the data quantization alters the noise distribution and the expectation of some
higher order moments. Finally, at the levell of power spectra, the quantization
introduces a power excess, that, although related to the instrument and mission
parameters, is weakly dependent on the multipole l at middle and large l and
can be quite accurately subtracted, leaving a residual uncertainty of few % of
the RMS uncertainty. Only for l<30 the quantization removal is less accurate.


title:
On the Correlated Spectral and Timing Properties of 4U 1636-53: an Atoll
  Source at High Accretion Rates

abstract:
  We analyze ~600 ks data from the X-ray observatory Rossi X-ray Timing
Explorer of the neutron star low mass X-ray binary and atoll source 4U 1636-53.
These observations span almost three years, from April 1996 to February 1999.
The color-color and hardness-intensity diagrams show significant secular shifts
of the atoll track, similar to what is observed for some Z sources. These are
most evident in the hardness-intensity diagram, where shifts in intensity up to
20% are observed. We find that the intensity shifts in the hardness-intensity
diagram are responsible for the parallel tracks observed in the kilohertz quasi
periodic oscillations frequency vs. intensity diagram. While the parallel
tracks in the frequency vs. color plane partially overlap, systematic long term
shifts are still evident. We also study the broad band power spectra of 4U
1636-53 as a function of the source position Sa along the track in the
color-color diagram. These power spectra are all characteristic of the lower
and upper banana state in atoll sources, showing very low frequency noise, band
limited noise, and sometimes one or two kHz QPOs. We find that the very low
frequency noise in some intervals is not well described by a power law because
of an excess of power between 20 and 30 mHz, which can be fitted by a
Lorentzian. Also, the characteristic frequency of the band limited noise shows
a trend to decrease with increasing Sa at high Sa values.


title:
Accretion and Dynamical Interactions in Small-N Star-Forming Clusters:
  I. N=5 case

abstract:
  We present results from high-resolution hydrodynamical simulations which
explore the effects of small scale clustering in star-forming regions. A large
ensemble of small-N clusters with 5 stellar seeds have been modelled and the
resulting properties of stars and brown dwarfs statistically derived and
compared with observational data.
  Close dynamical interactions between the protostars and competitive accretion
driven by the cloud collapse are shown to produce a distribution of final
masses which is bimodal, with most of the mass residing in the binary
components. When convolved with a suitable core mass function, the final
distribution of masses resembles the observed IMF, both in the stellar and
sub-stellar regime. Binaries and single stars are found to constitute two
kinematically distinct populations, with about half of the singles attaining
velocities > 2 km/s, which might deprive low mass star-forming regions of their
lightest members in a few crossing times. The eccentricity distribution of
binaries and multiples is found to follow a distribution similar to that of
observed long period (uncircularized) binaries.
  We predict that many close binary stars should have wide brown dwarfs
companions. Brown dwarfs and, in general, very low mass stars, would be rare as
pure binary companions. The binary fraction should be a decreasing function of
primary mass, with low-mass or sub-stellar primaries being scarce. Where such
binaries exist, they are either expected to be close enough (semi-major axis ~
10 AU) to survive strong interactions with more massive binaries or else born
in very small molecular cloud cores.


title:
How are Emerging Flux, Flares and CMEs Related to Magnetic Polarity
  Imbalance in MDI Data?

abstract:
  In order to understand whether major flares or coronal mass ejections (CMEs)
can be related to changes in the longitudinal photospheric magnetic field, we
study 4 young active regions during seven days of their disc passage. This time
period precludes any biases which may be introduced in studies that look at the
field evolution during the short-term flare or CME period only. Data from the
Michelson Doppler Imager (MDI) with a time cadence of 96 minutes are used.
Corrections are made to the data to account for area foreshortening and angle
between line of sight and field direction, and also the underestimation of the
flux densities. We make a systematic study of the evolution of the longitudinal
magnetic field, and analyze flare and CME occurrence in the magnetic evolution.
We find that the majority of CMEs and flares occur during or after new flux
emergence. The flux in all four active regions is observed to have deviations
from polarity balance both on the long-term (solar rotation) and on the short
term (few hours). The long-term imbalance is not due to linkage outside the
active region; it is primarily related to the east-west distance from central
meridian, with the sign of polarity closer to the limb dominating. The sequence
of short term imbalances are not closely linked to CMEs and flares and no
permanent imbalance remains after them. We propose that both kinds of imbalance
are due to the presence of a horizontal field component (parallel to the
photospheric surface) in the emerging flux.


title: A Dynamical Fossil in the Ursa Minor Dwarf Spheroidal Galaxy

abstract:
  The nearby Ursa Minor dwarf spheroidal (UMi dSph) is one of the most dark
matter dominated galaxies known, with a central mass to light ratio roughly
equal to 70. Somewhat anomalously, it appears to contain morphological
substructure in the form of a second peak in the stellar number density. It is
often argued that this substructure must be transient because it could not
survive for the > 10 Gyr age of the system, given the crossing time implied by
UMi's 8.8 km/s internal velocity dispersion. In this paper, however, we present
evidence that the substructure has a cold kinematical signature, and argue that
UMi's clumpiness could indeed be a primordial artefact. Using numerical
simulations, we demonstrate that substructure is incompatible with the cusped
dark matter haloes predicted by the prevailing Cold Dark Matter (CDM) paradigm,
but is consistent with an unbound stellar cluster sloshing back and forth
within the nearly harmonic potential of a cored dark matter halo. Thus CDM
appears to disagree with observation at the least massive, most dark matter
dominated end of the galaxy mass spectrum.


title: Relativistic Cosmology Number Counts and the Luminosity Function

abstract:
  This paper aims to connect the theory of relativistic cosmology number counts
with the astronomical data, practice, and theory behind the galaxy luminosity
function (LF). We treat galaxies as the building blocks of the Universe, but
ignore most aspects of their internal structures by considering them as point
sources. However, we do consider general morphological types in order to use
data from galaxy redshift surveys, where some kind of morphological
classification is adopted. We start with a general relativistic treatment for a
general spacetime, and then link the derived expressions with the LF definition
adopted in observational cosmology. Then equations for differential number
counts, the related relativistic density per source, and observed and total
relativistic energy densities of the universe, and other related quantities are
written in terms of the luminosity and selection functions. As an example of
how these theoretical/observational relationships can be used, we apply them to
test the LF parameters determined from the CNOC2 galaxy redshift survey, for
consistency with the Einstein-de Sitter (EdS) cosmology, which they assume, for
intermediate redshifts. We conclude that there is a general consistency for the
tests we carried out, namely both the observed relativistic mass-energy
density, and the observed relativistic mass-energy density per source, which is
equivalent to differential number counts, in an EdS Universe. In addition, we
find clear evidence of a large amount of hidden mass, as has been obvious from
many earlier investigations. At the same time, we find that the CNOC2 LF give
differential galaxy counts somewhat above the EdS predictions, indicating that
this survey observes more galaxies at 0.1 < z < 0.4 than the model's
predictions.


title: The Position, Motion, and Mass of Sgr A*

abstract:
  We report progress on measuring the position of Sgr A* on infrared images,
placing limits on the motion of the central star cluster relative to Sgr A*,
and measuring the proper motionof Sgr A* itself. The position of Sgr A* has
been determined to within 10 mas on infrared images. To this accuracy, the
gravitational source (sensed by stellar orbits) and the radiative source (Sgr
A*) are coincident. Proper motions of four stars measured both in the infrared
and radio indicate that the central star cluster moves with Sgr A* to within 70
km/s. Finally, combining stellar orbital information with an upper limit of 8
km/s for the intrinsic proper motion of Sgr A* (perpendicular to the Galactic
plane), we place a lower limit on the mass of Sgr A* of 4 x 10^5 Msun.


title: Metastable strange matter and compact quark stars

abstract:
  Strange quark matter in beta equilibrium at high densities is studied in a
quark confinement model. Two equations of state are dynamically generated for
the {\it same} set of model parameters used to describe the nucleon: one
corresponds to a chiral restored phase with almost massless quarks and the
other to a chiral broken phase. The chiral symmetric phase saturates at around
five times the nuclear matter density. Using the equation of state for this
phase, compact bare quark stars are obtained with radii and masses in the
ranges $R\sim 5 - 8$ km and $M\sim M_\odot$. The energy per baryon number
decreases very slowly from the center of the star to the periphery, remaining
above the corresponding values for the iron or the nuclear matter, even at the
edge. Our results point out that strange quark matter at very high densities
may not be absolutely stable and the existence of an energy barrier between the
two phases may prevent the compact quarks stars to decay to hybrid stars.


title: Sensitive observations at 1.4 and 250 GHz of z > 5 QSOs

abstract:
  We present 1.4 and 5 GHz observations taken with the Very Large Array (VLA),
and observations at 250 GHz obtained with the Max-Planck millimeter bolometer
(MAMBO) at the IRAM 30~m telescope, of ten optically selected Quasi-stellar
Objects (QSOs) at 5.0 < z < 6.28. Four sources are detected at 1.4 GHz two of
which are radio loud and are also detected at 5 GHz. These results are roughly
consistent with there being no evolution of the radio-loud QSO fraction out to
z~6.
  Three sources have been detected at 250 GHz or 350 GHz at much higher levels
than their 1.4 GHz flux densities suggesting that the observed mm emission is
likely thermal emission from warm dust, although more exotic possibilities
cannot be precluded.
  The highest redshift source in our sample (J1030+0524 at z=6.28) is not
detected at 1.4 or 250 GHz, but four fairly bright radio sources (flux density
at 1.4GHz > 0.2 mJy) are detected in a 2' field centered on the QSO, including
an edge-brightened ('FRII') double radio source with an extent of about 1'.
  A similar over-density of radio sources is seen in the field of the highest
redshift QSO J1148+5251. We speculate that these over-densities of radio
sources may indicate clusters along the lines-of-sight, in which case
gravitational lensing by the cluster could magnify the QSO emission by a factor
2 or so without giving rise to arcsecond-scale distortions in the optical
images of the QSOs.


title: Deep HST Imaging of Sextans A. III. The Star Formation History

abstract:
  We present a measurement of the star formation history of Sextans A, based on
WFPC2 photometry that is 50% complete to V=27.5 (M_V ~+ 1.9) and I=27.0. The
star formation history and chemical enrichment history have been measured
through modeling of the CMD. We find evidence for increased reddening in the
youngest stellar populations and an intrinsic metallicity spread at all ages.
Sextans A has been actively forming stars at a high rate for ~ 2.5 Gyr ago,
with an increased rate beginning ~ 0.1 Gyr ago. We find a non-zero number of
stars older than 2.5 Gyr, due to the limited depth of the photometry, a
detailed star formation history at intermediate and older ages has considerable
uncertainties. The mean metallicity was found to be [M/H] ~- 1.4 over the
measured history of the galaxy, with most of the enrichment happening at ages
of at least 10 Gyr. We also find that an rms metallicity spread of 0.15 dex at
all ages allows the best fits to the observed CMD. We revisit our determination
of the recent star formation history (age <= 0.7 Gyr) using BHeB stars and find
good agreement for all but the last 25 Myr, a discrepancy resulting primarily
from different distances used in the two analyses and the differential
extinction in the youngest populations. This indicates that star formation
histories determined solely from BHeB stars should be confined to CMD regions
where no contamination from reddened MS stars is present.


title: Radiatively Inefficient Accretion Flow Models of Sgr A*

abstract:
  I review radiatively inefficient accretion flow models for the 2.6 million
solar mass black hole (BH) in the Galactic Center. I argue for a 'concordance
model' of Sgr A*: both theory and observations suggest that hot ambient gas
around the BH is accreted at a rate of order 10^{-8} solar masses/year, much
less than the canonical Bondi rate. I interpret Chandra observations of Sgr A*
in the context of such a model: (1) the extended 'quiescent' X-ray emission is
due to thermal bremsstrahlung from gas in the vicinity of the Bondi accretion
radius, and (2) the ~ ksec long X-ray flares are due to synchrotron or
Inverse-Compton emission by non-thermal electrons accelerated in the inner 10
Schwarzschild radii of the accretion flow.


title:
Ultra-High Energy Cosmic Rays and Absolute Reference Frame defined by
  External Field

abstract:
  High-energy end of the cosmic-ray spectrum has provided us to check a
validity of the Lorentz Invariance and the Relativity principle, through the
observation of the so-called GZK cut-off. It is claimed in this report that the
comoving reference frame in the expanding universe might define the preferable
inertia frame, in contradiction to the relativity principle. If the present
universe has been permeated by tensor fields in a manner like it has been done
by Higgs scalar field, the limiting particle velocity of each species splits to
different values depending on the coupling coefficients to these external
fields.