title:
An accurate analytic He-H2 potential energy surface from a greatly
  expanded set of ab initio energies

abstract:
  The interaction potential energy surface (PES) of He-H2 is of great
importance for quantum chemistry, as the simplest test case for interactions
between a molecule and a closed-shell atom. It is also required for a detailed
understanding of certain astrophysical processes, namely collisional excitation
and dissociation of H2 in molecular clouds, at densities too low to be
accessible experimentally. A new set of 23703 ab initio energies was computed,
for He-H2 geometries where the interaction energy was expected to be
non-negligible. These have an estimated rms "random" error of about 0.2
millihartree and a systematic error of about 0.6 millihartree (0.4 kcal/mol). A
new analytic He-H2 PES, with 112 parameters, was fitted to 20203 of these new
ab initio energies (and to an additional 4862 points generated at large
separations). This yielded an improvement by better than an order of magnitude
in the fit to the interaction region, relative to the best previous surfaces
(which were accurate only for near-equilibrium H2 molecule sizes). This new PES
has an rms error of 0.95 millihartree (0.60 kcal/mole) relative to the the
14585 ab initio energies that lie below twice the H2 dissociation energy, and
2.97 millihartree (1.87 kcal/mole) relative to the full set of 20203 ab initio
energies (the fitting procedure used a reduced weight for high energies,
yielding a weighted rms error of 1.42 millihartree, i.e., 0.89 kcal/mole).
These rms errors are comparable to the estimated error in the ab initio
energies themselves; the conical intersection between the ground state and the
first excited state is the largest source of error in the PES.


title: Gravitational Lensing of Epoch-of-reionization Gas

abstract:
  I present a weak lensing sensitivity estimate for upcoming high redshift
(epoch of reionization and beyond) 21cm surveys. Instruments such as PAST,
LOFAR and SKA should be able to measure the weak lensing power spectrum to
precisions far exceeding conceivable optical surveys. Three types of sources
are detectable, which include the re-ionization stromgren spheres, large scale
structure, and minihalos.
  Tomography allows the measurement of the time evolution of the dark matter
power spectrum. Raw sensitivities allow measurement of many cosmological
parameters, including dark energy, neutrino mass and cosmic equations of state,
to percent accuracy. It also has the potential for inflationary gravity wave
measurements.
  Ultimate limits may be achievable through radio observations of 10^18
minihalos. Inflationary Hubble parameters H_I down to 10^-9 M_Planck can be
detected through this effect. Second order effects may also be observable,
allowing tests for backreaction and the quantum mechanical origin of
perturbations.


title: Using globular clusters to test gravity in the weak acceleration regime

abstract:
  We have carried out a study of the velocity dispersion of the stars in the
outskirts of the globular cluster Omega Centauri, finding that the velocity
dispersion remains constant at large radii rather than decrease monotonically.
The dispersion starts to be constant for an acceleration of gravity of a =
2.1e-8 cm/s/s. A similar result is obtained reanalyzing existing data for the
globular cluster M15 where the profile flattens out for a = 1.7e-8 cm/s/s. In
both cases the acceleration is comparable to that at which the effect of dark
matter becomes relevant in galaxies. Explanations for this result within
Newtonian dynamics exist (e.g. cluster evaporation, tidal effects, presence of
dark matter) but require ad hoc tuning of the relevant parameters in order to
make in both clusters the dispersion profile flat starting exactly at the same
acceleration. We suggest that this result, together with a similar one for
Palomar 13 and the anomalous behavior of spacecrafts outside the solar system,
may indicate a breakdown of Newton's law in the weak acceleration regime.
Although not conclusive, these data prompt for the accurate determination of
the internal dynamics of as many GCs as possible.


title: Pierre Auger Atmosphere-Monitoring Lidar System

abstract:
  The fluorescence-detection techniques of cosmic-ray air-shower experiments
require precise knowledge of atmospheric properties to reconstruct air-shower
energies. Up to now, the atmosphere in desert-like areas was assumed to be
stable enough so that occasional calibration of atmospheric attenuation would
suffice to reconstruct shower profiles. However, serious difficulties have been
reported in recent fluorescence-detector experiments causing systematic errors
in cosmic ray spectra at extreme energies. Therefore, a scanning backscatter
lidar system has been constructed for the Pierre Auger Observatory in Malargue,
Argentina, where on-line atmospheric monitoring will be performed. One lidar
system is already deployed at the Los Leones fluorescence detector site and the
second one is currently (April 2003) under construction at the Coihueco site.
Next to the established ones, a novel analysis method with assumption on
horizontal invariance, using multi-angle measurements is shown to unambiguously
measure optical depth, as well as absorption and backscatter coefficient.


title:
Covariant Wigner Function Approach to the Boltzmann Equation for Mixing
  Fermions in Curved Spacetime

abstract:
  Based on the covariant Wigner function approach we derive the quantum
Boltzmann equation for fermions with flavor mixing in general curved spacetime.
This work gives a rigorous theoretical framework to investigate the flavor
oscillation phenomena taking the gravitational effect into account. It is shown
that the Boltzmann equation of the lowest order of the expansion with respect
to $\hbar$ reproduces the previous result which was derived in the relativistic
limit on the Minkowski background spacetime. It is demonstrated that the
familiar formula for the vacuum neutrino oscillation can be obtained by solving
the Boltzmann equation. Higher order effects of the $\hbar$-expansion is also
briefly discussed.


title: Ratio of color and effective temperatures in X-ray burst spectra

abstract:
  We present model atmospheres and theoretical spectra for X-ray bursters. Our
models include the effects of Compton scattering on free electrons. The
atmospheres have compositions that are mixtures of hydrogen, helium, and iron.
For our models the ratio of color temperature, $T_c$, to effective temperature,
$T_{eff}$, is in the range 1.2 - 1.8. This ratio depends on $T_{eff}$, surface
gravity, and iron abundance. For fixed $T_{eff}$ and surface gravity, models
with non-zero iron abundance exhibit values of $T_c/T_{eff}$ that are slightly
lower than pure hydrogen-helium models.


title:
Cosmological constraints in Lambda-CDM and Quintessence paradigms with
  Archeops

abstract:
  We review the cosmological constraints put by the current CMB experiment
including the recent ARCHEOPS data, in the framework of Lambda-CDM and
quintessence paradigm. We show that well chosen combinations of constraints
from different cosmological observations lead to precise measurements of
cosmological parameters. The Universe seems flat with a 70 percents
contribution of dark energy with an equation of state very close to those of
the vacuum.


title: The structure of voids

abstract:
  Using high resolution N-body simulations we address the problem of emptiness
of giant 20 Mpc/h diameter voids found in the distribution of bright galaxies.
Are the voids filled by dwarf galaxies? Do cosmological models predict too many
small dark matter haloes inside the voids? Can the problems of cosmological
models on small scales be addressed by studying the abundance of dwarf galaxies
inside voids? We find that voids in the distribution of 10^12 Msun/h haloes
(expected galactic magnitudes ~ M_*) are almost the same as the voids in 10^11
Msun/h haloes. Yet, much smaller haloes with masses 10^9 Msun/h and circular
velocities v_circ about 20 km/s readily fill the voids: there should be almost
1000 of these haloes in a 20 Mpc/h void. A typical void of diameter 20 Mpc/h
contains about 50 haloes with v_circ > 50 km/s. The haloes are arranged in a
pattern, which looks like a miniature Universe: it has the same structural
elements as the large-scale structure of the galactic distribution of the
Universe. There are filaments and voids; larger haloes are at the intersections
of filaments. The only difference is that all masses are four orders of
magnitude smaller. There is severe (anti)bias in the distribution of haloes,
which depends on halo mass and on the distance from the centre of the void.
Large haloes are more antibiased and have a tendency to form close to void
boundaries. The mass function of haloes in voids is different from the
``normal'' mass function. It is much steeper for high masses resulting in very
few M33-type galaxies (v_circ about 100 km/s). We present an analytical
approximation for the mass function of haloes in voids.


title: The evolution of lithium depletion in young open clusters: NGC 6475

abstract:
  We have carried out a high resolution spectroscopic survey of the 220-250 Myr
old cluster NGC 6475: our main purpose is to investigate Li evolution during
the early stages of the Main Sequence. We have determined Li abundances for 33
late F to K-type X-ray selected cluster candidates, extending the samples
already available in the literature; for part of the stars we obtained radial
and rotational velocities, allowing us to confirm the membership and to check
for binarity. We also estimated the cluster metallicity which turned out to be
over-solar ([Fe/H]=+0.14 +/-0.06). Our Li analysis evidenced that (i) late
F-type stars (Teff > 6000 K) undergo a very small amount of Li depletion during
the early phases on the ZAMS; (ii) G-type stars (6000 > Teff > 5500 K) instead
do deplete lithium soon after arrival on the ZAMS. Whereas this result is not
new, we show that the time scale for Li depletion in these stars is almost
constant between 100 and 600 Myr; (iii) we confirm that the spread observed in
early K-type stars in younger clusters has converged by 220 Myr. No constraints
can be put on later-type stars. (iv) Finally, we investigate the effect of
metallicity on Li depletion by comparing NGC 6475 with the similar age cluster
M 34, but we show that the issue remains open, given the uncertain metallicity
of the latter cluster. By using the combined NGC 6475 + M 34 sample together
with the Hyades and the Pleiades, we compare quantitatively Li evolution from
the ZAMS to 600 Myr with theoretical predictions of standard models.


title: Odin observations of H2O in the Galactic Centre

abstract:
  The Odin satellite has been used to detect emission and absorption in the
557-GHz H2O line in the Galactic Centre towards the Sgr A* Circumnuclear Disk
(CND), and the Sgr A +20 km/s and +50 km/s molecular clouds. Strong broad H2O
emission lines have been detected in all three objects. Narrow H2O absorption
lines are present at all three positions and originate along the lines of sight
in the 3-kpc Spiral Arm, the -30 km/s Spiral Arm and the Local Sgr Spiral Arm.
Broad H2O absorption lines near -130 km/s are also observed, originating in the
Expanding Molecular Ring. A new molecular feature (the ``High Positive Velocity
Gas'' - HPVG) has been identified in the positive velocity range of ~ +120 to
+220 km/s, seen definitely in absorption against the stronger dust continuum
emission from the +20 km/s and +50 km/s clouds and possibly in emission towards
the position of Sgr A* CND. The 548-GHz H2_18O isotope line towards the CND is
not detected at the 0.02 K (rms) level.


title: Small-scale turbulent dynamo - a numerical investigation

abstract:
  We present the results of a numerical investigation of the turbulent
kinematic dynamo problem in a high Prandtl number regime. The scales of the
magnetic turbulence we consider are far smaller than the Kolmogorov dissipative
scale, so that the magnetic wavepackets evolve in a nearly smooth velocity
field. Firstly, we consider the Kraichnan-Kazantsev model (KKM) in which the
strain matrix is taken to be independent of coordinate and Gaussian white in
time. To simulate the KKM we use a stochastic Euler-Maruyama method. We test
the theoretical predictions for the growth of rates of the magnetic energy and
higher order moments (Kazantsev, 1968; Kulsrud & Anderson, 1992; Chertkov et
al., 1999), the shape of the energy spectrum (Kazantsev, 1968; Kulsrud &
Anderson, 1992; Schekochihin et al., 2000a; Nazarenko et al., 2003) and the
behaviour of the polarisation and spectral flatness Nazarenko et al., 2003). In
general, the results appear to be in good agreement with the theory, with the
exception that the predicted decay of the polarisation in time is not
reproduced well in the stochastic numerics. Secondly, in order to study the
sensitivity of the KKM predictions to the choice of strain statistics, we
perform additional simulations for the case of a Gaussian strain with a finite
correlation time and also for a strain taken from a DNS data set. These
experiments are based on non-stochastic schemes, using a timestep that is much
smaller than the correlation time of the strain. We find that the KKM is
generally insensitive to the choice of strain statistics and most KKM results,
including the decay of the polarisation, are reproduced well. The only
exception appears to be the flatness whose spectrum is not reproduced in
accordance with the KKM predictions in these simulations.


title:
Rotational periods of very young brown dwarfs and very low-mass stars in
  ChaI

abstract:
  We have studied the photometric variability of very young brown dwarfs and
very low-mass stars (masses well below 0.2 M_sun) in the ChaI star forming
region. We have determined photometric periods in the Gunn i and R band for the
three M6.5-M7 type brown dwarf candidates ChaHa2, ChaHa3 and ChaHa6 of 2.2 to
3.4 days. These are the longest photometric periods found for any brown dwarf
so far. If interpreted as rotationally induced they correspond to moderately
fast rotational velocities, which is fully consistent with their v sini values
and their relatively large radii. We have also determined periods for the two
M5-M5.5 type very low-mass stars B34 and CHXR78C. In addition to the Gunn i and
R band data, we have analysed JHK_s monitoring data of the targets, which have
been taken a few weeks earlier and confirm the periods found in the optical
data. Upper limits for the errors in the period determination are between 2 and
9 hours. The observed periodic variations of the brown dwarf candidates as well
as of the T Tauri stars are interpreted as modulation of the flux at the
rotation period by magnetically driven surface features, on the basis of a
consistency with v sini values as well as (R-i) color variations typical for
spots. Furthermore, the temperatures even for the brown dwarfs in the sample
are relatively high (>2800K) because the objects are very young. Therefore, the
atmospheric gas should be sufficiently ionized for the formation of spots on
one hand and the temperatures are too high for significant dust condensation
and hence variabilities due to clouds on the other hand.


title: The X-ray Halo of G21.5-0.9

abstract:
  The emission of the plerion G21.5-0.9 appears more extended in X rays than in
radio. This is an unexpected result because it would imply that short-lived
X-ray electrons may reach distances even larger than radio electrons. Applying
an empirical relationship between dust scattering optical depth and
photoelectric column density, the measured column density leads to a large
optical depth at 1 keV, of about 1. Therefore we investigate the hypothesis
that the detected halo be an effect of dust scattering, re-analyzing an Cal/PV
XMM-Newton observation of G21.5-0.9 and critically examining it in terms of a
dust scattering model. We also present a spectral analysis of a prominent
extended feature in the northern sector of the halo.


title: Some aspects of Relativistic Astrometry from within the Solar System

abstract:
  In this article we outline the structure of a general relativistic
astrometric model which has been developed to deduce the position and proper
motion of stars from 1-microarcsecond optical observations made by an
astrometric satellite orbiting around the Sun. The basic assumption of our
model is that the Solar System is the only source of gravity, hence we show how
we modeled the satellite observations in a many-body perturbative approach
limiting ourselves to the order of accuracy of $(v/c)^2$. The microarcsecond
observing scenario outlined is that for the GAIA astrometric mission.


title: An ISOCAM survey through gravitationally lensing galaxy clusters

abstract:
  ISOCAM was used to perform a deep survey through three gravitationally
lensing clusters of galaxies. Nearly seventy sq. arcmin were covered over the
clusters A370, A2218 and A2390. We present maps and photometry at 6.7 & 14.3
microns, showing a total of 145 mid-IR sources and the associated source
counts. The 15 micron counts reach the faintest level yet recorded. All sources
have counterparts in the optical or near-IR. Models of the clusters were used
to correct for the effects of lensing, which increases the sensitivity of the
survey. Seven of fifteen SCUBA sources were detected at 15 microns. Five have
redshift between 0.23 & 2.8, with a median of 0.9. The field sources were
counted to a lensing-corrected sensitivity of 30 microJy at 15 microns, and 14
microJy at 7 microns. The counts, corrected for completeness, contamination by
cluster sources and lensing, confirm and extend findings of an excess by a
factor of ten in the 15 micron population with respect to source models with no
evolution. Source redshifts are mostly between 0.4 and 1.5. For the counts at 7
microns, integrating from 14 microJy to 460 microJy, we resolve 0.49+/-0.2
nW.m^(-2).sr^(-1) of the infrared background light (IBL) into discrete sources.
At 15 microns we include the counts from other ISOCAM surveys to integrate from
30 microJy to 50 mJy, two to three times deeper than unlensed surveys, to
resolve 2.7+/-0.62 nW.m^(-2).sr^(-1) of the IBL. These values are 10% and 55%,
respectively, of the upper limit to the IBL, derived from photon-photon pair
production of the TeV gamma rays from BL-Lac sources on the IBL photons.
However, recent detections of TeV gamma rays from the z=0.129 BL Lac H1426+428
suggest that the 15 micron background reported implies substantial absorption
of TeV photons from that source.


title: PKS 0537-441: extended [O II] emission and a binary QSO?

abstract:
  We present high-resolution imaging and low-resolution spectroscopy of the BL
Lac object PKS 0537-441 (z = 0.893) and its environment. The observations were
designed to clarify, whether the properties of PKS 0537-441 are affected by
gravitational microlensing, or whether PKS 0537-441 and its environment act as
a lensing system itself. Our observations show that neither case seems to be
likely. We did not find a galaxy along the line-of-sight to the BL Lac as
claimed previously, our spectroscopy shows that none of the four closest
companion galaxies is at high redshift. Two of the four nearby companion
galaxies to PKS 0537-441 are within 200 km/s of the systemic velocity of the BL
Lac (z = 0.892 and 0.895, respectively). The third companion galaxy is at
higher redshift (z = 0.947). The fourth companion galaxy shows evidence of Mg
II absorption redwards of its systemic velocity and is perhaps a mini low
ionization BAL QSO at z = 0.885. If the latter can be confirmed, PKS 0537-441
is the first BL Lacertae object being a member of a binary Quasar. We also
detected extended [O II] emission in the off-nuclear spectrum of PKS 05371-441,
which is most likely due to photoionization from the active nucleus.
Alternatively, the extended [O II] emission is due to jet-cloud interaction
with the counterjet of PKS 0537-441. Our clustering analysis indicates that PKS
0537-441 is located in a cluster environment as rich as Abell type 0-1. This is
supported by the detection of four galaxies in the field with similar redshifts
as the BL Lac (Delta z < 0.002). We found serendipitously even more galaxies at
somewhat higher redshifts (z = 0.9-1). Thus, PKS0537-441 might be located in
front of a galaxy cluster at somewhat higher redshift or even be part of a
large-scale structure with an extension towards the BL Lac.


title: High-Latitude HI in the Low Surface Brightness Galaxy UGC7321

abstract:
  From the analysis of sensitive HI 21-cm line observations, we find evidence
for vertically extended HI emission (|z|<~2.4 kpc) in the edge-on, low surface
brightness spiral galaxy UGC7321. Three-dimensional modelling suggests that the
HI disk of UGC7321 is both warped and flared, but that neither effect can fully
reproduce the spatial distribution and kinematics of the highest z-height gas.
We are able to model the high-latitude emission as an additional HI component
in the form of a ``thick disk'' or ``halo'' with a FWHM~3.3 kpc. We find
tentative evidence that the vertically extended gas declines in rotational
velocity as a function of z, although we are unable to completely rule out
models with constant V(z). In spite of the low star formation rate of UGC7321,
energy from supernovae may be sufficient to sustain this high-latitude gas.
However, alternative origins for this material, such as slow, sustained infall,
cannot yet be excluded.


title: The WSRT wide-field HI survey: I. The background galaxy sample

abstract:
  We have used the Westerbork array to carry out an unbiased wide-field survey
for HI emission features, achieving an RMS sensitivity of about 18 mJy/Beam at
a velocity resolution of 17 km/s over 1800 deg^2 and between -1000 <
V_Hel<+6500 km/s. The primary data consists of auto-correlation spectra with an
effective angular resolution of 49' FWHM. We detect 155 external galaxies in
excess of 8 sigma in integrated HI flux density. Plausible optical associations
are found within a 30' search radius for all but one of our HI detections in
DSS images, although several are not previously cataloged or do not have
published red-shift determinations. Twenty-three of our objects are detected in
HI for the first time. We classify almost half of our detections as
``confused'', since one or more companions is cataloged within a radius of 30'
and a velocity interval of 400 km/s. We identify a handful of instances of
significant positional offsets exceeding 10 kpc of unconfused optical galaxies
with the associated HI centroid, possibly indicative of severe tidal
distortions or uncataloged gas-rich companions. A possible trend is found for
an excess of detected HI flux in unconfused galaxies within our large survey
beam relative to that detected previously in smaller telescope beams, both as
function of increasing distance and increasing gas mass. This may be an
indication for a diffuse gaseous component on 100 kpc scales in the environment
of massive galaxies or a population of uncataloged low mass companions. We use
our galaxy sample to estimate the HI mass function from our survey volume. Good
agreement is found with the HIPASS BGC results, but only after explicit
correction for galaxy density variations with distance.


title:
Limitations on Space-based Air Fluorescence Detector Apertures obtained
  from IR Cloud Measurements

abstract:
  The presence of clouds between an airshower and a space-based detector can
dramatically alter the measured signal characteristics due to absorption and
scattering of the photonic signals. Furthermore, knowledge of the cloud cover
in the observed atmosphere is needed to determine the instantaneous aperture of
such a detector. Before exploring the complex nature of cloud-airshower
interactions, we examine a simpler issue. We investigate the fraction of
ultra-high energy cosmic ray events that may be expected to occur in volumes of
the viewed atmosphere non-obscured by clouds. To this end, we use space-based
IR data in concert with Monte Carlo simulated $10^{20}$ eV airshowers to
determine the acceptable event fractions. Earth-observing instruments, such as
MODIS, measure detailed cloud configurations via a CO$_2$-slicing technique
that can be used to determine cloud-top altitudes over large areas. Thus,
events can be accepted if their observed 3-dimensional endpoints occur above
low clouds as well as from areas of cloud-free atmosphere. An initial analysis
has determined that by accepting airshowers that occur above low clouds, the
non-obscured acceptance can be increased by approximately a factor of 3 over
that obtained using a cloud-free criterion.


title:
VLBI astrometry of circumstellar OH masers; proper motions and
  parallaxes of four AGB stars

abstract:
  The main-line OH masers around 4 AGB stars have been observed with the NRAO
Very Long Baseline Array (VLBA) at 8 epochs over a period of 2.5 years. Using a
phase referencing technique, the position of the most compact maser spot of
each star was monitored with respect to two extragalactic reference sources.
For U Her and W Hya, we observe the most blue-shifted maser spot, while for R
Cas and S CrB we only detect a compact red-shifted maser spot. We managed to
determine an accurate proper motion and parallax for U Her, R Cas and S CrB,
while additional motion of the compact blue-shifted maser of W Hya is shown to
possibly be related to the stellar pulsation. The motion and radio position are
compared with the stellar trajectory and absolute optical position determined
by the Hipparcos satellite. For U Her and W Hya, the most blue-shifted maser is
consistent with the amplified stellar image. The new distances are compared
with several published P--L relations, and in this respect the VLBI distances
seem an improvement upon the Hipparcos distances.


title: The Century Survey Galactic Halo Project I: Stellar Spectral Analysis

abstract:
  The Century Survey Galactic Halo Project is a photometric and spectroscopic
survey from which we select relatively blue stars (V-R<0.30 mag) as probes of
the Milky Way halo. The Survey strip spans the range of Galactic latitude
35<b<88 deg, allowing us to study the nature of populations of stars and their
systematic motions as a function of Galactic latitude. One of our primary goals
is to use blue horizontal-branch stars to trace potential star streams in the
halo, and to test the hierarchical model for the formation of the Galaxy.
  In this paper we discuss spectroscopy and multi-passband photometry for a
sample of 764 blue stars in the Century Survey region. Our sample consists
predominantly of A- and F-type stars. We describe our techniques for
determination of radial velocities, effective temperatures, metallicities, and
surface gravities. Based on these measurements, we derive distance estimates by
comparison with a set of calibrated isochrones. We devote special attention to
the classification of blue horizontal-branch stars, and compare the results
obtained from the application of the techniques of Kinman et al., Wilhelm et
al., and Clewley et al. We identify 55 blue horizontal-branch stars. Our large
sample of stars also uncovers a number of unusual objects, including three
carbon-enhanced stars, a late B-type star located 0.8 kpc above the Galactic
plane, and a DZ white dwarf.


title: Chandra Observations of the X-ray Environment of BL Lacs

abstract:
  We present Chandra observations of the X-ray environment of a sample of 6 BL
Lacertae objects. The improved sensitivity of the ACIS experiment allows us to
separate the core X-ray emission from the contribution of diffuse emission from
the host galaxy/cluster scales. Within the short (2-6 ks) ACIS exposures, we
find evidence for diffuse X-ray emission in 3 sources (BL Lac, PKS 0548-322,
and PKS 2005-489). The diffuse emission can be modeled with a King profile with
beta~0.3-0.6, core radii rc~15-28 kpc, and 0.4-5 keV luminosities in the range
10^{41}-10^{42} erg/s. In the remaining 3 sources, one (3C 371) has a radial
profile entirely consistent with an unresolved source, while two (1ES 2344+514
and 1ES 2321+419) show evidence for weak diffuse emission on kpc scales. These
results support current models for radio-loud AGN unifying BL Lacs and FRI
radio galaxies through the orientation of their jets. In PKS 0548-322 and PKS
2005-489, we also find evidence for diffuse emission on cluster scales,
although the spatial properties of this emission are not constrained. The
temperature and luminosity of the cluster gas are typical of normal clusters.
Interestingly, these are the two brightest sources of the sample, suggesting a
link between environment and nuclear activity.


title:
High Velocity Cloud Complex H: A Satellite of the Milky Way in a
  Retrograde Orbit?

abstract:
  Observations with the Green Bank Telescope of 21cm HI emission from the
high-velocity cloud Complex H suggest that it is interacting with the Milky
Way. A model in which the cloud is a satellite of the Galaxy in an inclined,
retrograde circular orbit reproduces both the cloud's average velocity and its
velocity gradient with latitude. The model places Complex H at approximately 33
kpc from the Galactic Center on a retrograde orbit inclined about 45 degrees to
the Galactic plane. At this location it has an HI mass > 6 10^6 Msun and
dimensions of at least 10 by 5 kpc. Some of the diffuse HI associated with the
cloud has apparently been decelerated by interaction with Galactic gas. Complex
H has similarities to the dwarf irregular galaxy Leo A and to some compact
high-velocity clouds, and has an internal structure nearly identical to parts
of the Magellanic Stream, with a pressure P/k about 100 cm^{-3} K.


title:
Star formation rate and metallicity of damped Lyman-alpha absorbers in
  cosmological SPH simulations

abstract:
  We study the distribution of the star formation rate and metallicity of
damped Lyman-alpha absorbers using cosmological SPH simulations of the Lambda
cold dark matter model in the redshift range z=0-4.5. Our approach includes a
phenomenological model of galactic wind. We find that there is a positive
correlation between the projected stellar mass density and the neutral hydrogen
column density (NHI) of DLAs for high NHI systems, and that there is a good
correspondence in the spatial distribution of stars and DLAs in the
simulations. The evolution of typical star-to-gas mass ratios in DLAs can be
characterised by an increase from about 2 at z=4.5 to 3 at z=3, to 10 at z=1,
and finally to 20 at z=0. We also find that the projected SFR density in DLAs
follows the Kennicutt law well at all redshifts, and the simulated values are
consistent with the recent observational estimates of this quantity by Wolfe et
al. (2003a,b). The rate of evolution in the mean metallicity of simulated DLAs
as a function of redshift is mild, and is consistent with the rate estimated
from observations. The predicted metallicity of DLAs is generally sub-solar in
our simulations, and there is a significant scatter in the distribution of DLA
metallicity for a given NHI. However, we find that the median metallicity of
simulated DLAs is close to that of Lyman-break galaxies, which is higher than
the values typically observed for DLAs by nearly an order of magnitude. This
discrepancy with observations could be due to an inadequate treatment of SN
feedback in our current simulations, perhaps indicating that metals are not
expelled efficiently enough from DLAs by outflows. Alternatively, the current
observations might be missing the majority of the high metallicity DLAs due to
selection effects. (abridged)


title:
Polarization of prompt GRB emission: evidence for
  electromagnetically-dominated outflow

abstract:
  Observations by the {\RHESSI} satellite of large polarization of the prompt
$\gamma$-ray emission from the Gamma Ray Burst GRB021206 \citep{coburn03} imply
that the magnetic field coherence scale is larger than the size of the visible
emitting region, $\sim R/\Gamma$, where $R$ is the radius of the flow, $\Gamma$
is the associated Lorentz factor.
  Such fields cannot be generated in a causally disconnected, hydrodynamically
dominated outflow. Electromagnetic models of GRBs \citep{lyutikov02}, in which
large scale, dynamically dominant, magnetic fields are present in the outflow
from the very beginning, provide a natural explanation of this large reported
linear polarization. We derive Stokes parameters of synchrotron emission of a
relativistically moving plasma with a given magnetic field configuration and
calculate the pulse averaged polarization fraction of the emission from a
relativistically expanding shell carrying global toroidal magnetic field. For
viewing angles larger than $1/\Gamma$ the observed patch of the emitting shell
has almost homogeneous magnetic field, producing a large fractional
polarization ($56% $ for a power-law energy distribution of relativistic
particles $dn/d\epsilon \propto \epsilon^{-3}$). The maximum polarization is
smaller than the theoretical upper limit for a stationary plasma in uniform
magnetic field due to relativistic kinematic effects.


title:
The Detectability of Departures from the Inflationary Consistency
  Equation

abstract:
  We study the detectability, given CMB polarization maps, of departures from
the inflationary consistency equation, r \equiv T/S \simeq -5 n_T, where T and
S are the tensor and scalar contributions to the quadrupole variance,
respectively. The consistency equation holds if inflation is driven by a
slowly-rolling scalar field. Departures can be caused by: 1) higher-order terms
in the expansion in slow-roll parameters, 2) quantum loop corrections or 3)
multiple fields. Higher-order corrections in the first two slow-roll parameters
are undetectably small. Loop corrections are detectable if they are nearly
maximal and r \ga 0.1. Large departures (|\Delta n_T| \ga 0.1) can be seen if r
\ga 0.001. High angular resolution can be important for detecting non-zero
r+5n_T, even when not important for detecting non-zero r.


title: A Disk Census for Young Brown Dwarfs

abstract:
  Recent surveys have identified sub-stellar objects down to planetary masses
in nearby star-forming regions. Reliable determination of the disk frequency in
young brown dwarfs is of paramount importance to understanding their origin.
Here we report the results of a systematic study of infrared L'-band
(3.8-micron) disk excess in ~50 spectroscopically confirmed objects near and
below the sub-stellar boundary in several young clusters. Our observations,
using the ESO Very Large Telescope, Keck I and the NASA Infrared Telescope
Facility, reveal that a significant fraction of brown dwarfs harbor disks at a
very young age. Their inner disk lifetimes do not appear to be vastly different
from those of disks around T Tauri stars. Our findings are consistent with the
hypothesis that sub-stellar objects form via a mechanism similar to solar-mass
stars.


title: The C IV Mass Density of the Universe at Redshift 5

abstract:
  In order to search for metals in the Lyman alpha forest at redshifts z > 4,
we have obtained spectra of high S/N and resolution of three QSOs at z > 5.4
discovered by the Sloan Digital Sky Survey. These data allow us to probe to
metal enrichment of the intergalactic medium at early times with higher
sensitivity than previous studies. We find 16 C IV absorption systems with
column densities log N(C IV) = 12.50 - 13.98 over a total redshift path Delta X
= 3.29. In the redshift interval z = 4.5-5.0, where our statistics are most
reliable, we deduce a comoving mass density of C IV ions Omega(C IV) = (4.3 +/-
2.5) x 10(-8) (90% confidence limits) for absorption systems with log N(C IV) >
13.0 (for an Einstein-de Sitter cosmology with h = 0.65). This value of Omega(C
IV) is entirely consistent with those measured at z < 4; we confirm the earlier
finding by Songaila (2001) that neither the column density distribution of C IV
absorbers nor its integral show significant redshift evolution over a period of
time which stretches from 1.25 to 4.5 Gyr after the big bang. This somewhat
surprising conclusion may be an indication that the intergalactic medium was
enriched in metals at redshifts much greater than 5, perhaps by the sources
responsible for its reionization. Alternatively, the C IV systems we see may be
associated with outflows from massive star-forming galaxies at later times,
while the truly intergalactic metals may reside in regions of the Lyman alpha
forest of lower density than those probed up to now.


title: New direction for gamma-rays

abstract:
  The origin of energetic gamma-ray bursts is still unknown. But the detection
of polarization of gamma-rays provides fresh insight into the mechanism driving
these powerful explosions.


title: Weighting CMB and Galactic synchrotron polarisation

abstract:
  We review the present knowledge of the diffuse Galactic synchrotron emission
in polarisation. At microwave frequencies, we assess the expected contamination
to the CMB polarisation angular power spectrum, for $E$ and $B$ modes, as
expected after the WMAP first year measurements.


title: Stellar populations and star formation histories in late-type dwarfs

abstract:
  Studies of the resolved stellar populations in nearby systems are crucial to
understand galaxy evolution. Here, we summarize how the interpretation of the
colour-magnitude diagrams of field stars in late-type dwarfs inside and outside
the Local Group has allowed us to infer their star formation histories and put
useful constraints on the evolution of this type of galaxies.


title:
A Method for Mapping the Temperature Profile of X-ray Clusters Through
  Radio Observations

abstract:
  Many of the most luminous extragalactic radio sources are located at the
centers of X-ray clusters, and so their radiation must be scattered by the
surrounding hot gas. We show that radio observations of the highly-polarized
scattered radiation (which depends on the electron density distribution) in
combination with the thermal Sunyaev-Zeldovich effect (which measures the
electron pressure distribution), can be used to determine the radial profile of
the electron temperature within the host cluster. The sensitivity levels
expected from current instruments will allow radio measurements of
mass-weighted cluster temperature profiles to better than roughly 1 keV
accuracy, as long as the central radio source is steady over several million
years. Variable or beamed sources will leave observable signatures in the
scattered emission. For clusters with a central point source brighter than
about 1 mJy, the scattered polarization signal is stronger than competing
effects due to the cosmic microwave background.


title: Intrinsic Spectra of the TeV Blazars Mrk 421 and Mrk 501

abstract:
  Energy spectra of gamma-ray blazars may contain an imprint from the cosmic
infrared background radiation due to gamma-ray absorption (pair-production) by
soft photons constituting the extragalactic background light (EBL). The
signature of this imprint depends on the spectral shape of the EBL. In this
work we correct the observed spectra of Mrk 421 and Mrk 501 for absorption
using different possible realizations of the EBL, consistent with the most
recent detections and limits. We present the intrinsic gamma-ray spectrum of
these sources for the different EBL scenarios. These spectra reveal their true
peak energy and luminosities, which provide important information on the nature
and physical characteristics of the particle acceleration mechanism operating
in these sources.


title: Hourly Spectral Variability of Mrk 421

abstract:
  Mrk 421 is the first TeV blazar found to exhibit significant spectral
variability during strong flaring activity, showing hardening of the TeV
spectrum in high emission states. Mrk 421 is also known to exhibit flux
variability on time scales as short as 15 minutes. In this paper we present
studies of hourly spectral variability of Mrk 421 in 2001 using data from the
Whipple Observatory 10m gamma-ray telescope.


title: Probing the Edge of the Solar System: Formation of an Unstable Jet-Sheet

abstract:
  The Voyager spacecraft is now approaching the edge of the solar system. Near
the boundary between the solar system and the interstellar medium we find that
an unstable ``jet-sheet'' forms. The jet-sheet oscillates up and down due to a
velocity shear instability. This result is due to a novel application of a
state-of-art 3D Magnetohydrodynamic (MHD) code with a highly refined grid. We
assume as a first approximation that the solar magnetic and rotation axes are
aligned. The effect of a tilt of the magnetic axis with respect to the rotation
axis remains to be seen. We include in the model self-consistently magnetic
field effects in the interaction between the solar and interstellar winds.
Previous studies of this interaction had poorer spatial resolution and did not
include the solar magnetic field. This instability can affect the entry of
energetic particles into the solar system and the intermixing of solar and
interstellar material. The same effect found here is predicted for the
interaction of rotating magnetized stars possessing supersonic winds and moving
with respect to the interstellar medium, such as O stars.


title: Bondi Accretion and the Problem of the Missing Isolated Neutron Stars

abstract:
  A large number of neutron stars (NSs), ~10^9, populate the Galaxy, but only a
tiny fraction of them is observable during the short radio pulsar lifetime. The
majority of these isolated NSs, too cold to be detectable by their own thermal
emission, should be visible in X-rays as a result of accretion from the
interstellar medium. The ROSAT all sky survey has however shown that such
accreting isolated NSs are very elusive: only a few tentative candidates have
been identified, contrary to theoretical predictions that up to several
thousands should be seen. We suggest that the fundamental reason for this
discrepancy lies in the use of the standard Bondi formula to estimate the
accretion rates. We compute the expected source counts using updated estimates
of the pulsar velocity distribution, realistic hydrogen atmosphere spectra, and
a modified expression for the Bondi accretion rate as suggested by recent MHD
simulations, and supported by direct observations in the case of accretion
around supermassive black holes in nearby galaxies and in our own. We find
that, whereas the inclusion of atmospheric spectra partly compensates for the
reduction in the counts due to the higher mean velocities of the new
distribution, the modified Bondi formula dramatically suppresses the source
counts. The new predictions are consistent with a null detection at the ROSAT
sensitivity.


title:
Launching jets from the boundary layer of accretion disks in young
  stellar objects

abstract:
  We reexamine a previously proposed model for thermal pressure acceleration of
collimated outflows in young stellar objects (YSO). We are motivated by new
results from recent X-ray observations of YSO. These show that there is
essentially no difference between the properties of X-ray emission from YSO
with and without outflows, imposing quite severe constraints on models based on
magnetic launching of jets. In our scenario the magnetic fields are weak, and
serve only to recollimate the outflow at large distances from the source. We
perform time scale estimates and an analytical calculation of the acceleration
of gas originating in the boundary layer (BL) of an accretion disk. By applying
global energy conservation considerations we find that the mass escaping the
system is compatible with observations. A crucial ingredient of the proposed
model is that the accreted material is strongly shocked, and then cools down on
a time scale longer than its ejection time from the disk. By using appropriate
properties of accretion disks boundary layers around YSO, we show that the
conditions for the proposed scenario to work are reasonably met. We find also
that the thermal acceleration mechanism works only when the accretion rate in
YSO accretion disk is large enough and the `alpha' parameter of the disk small
enough - otherwise the cooling time is too short and significant ejection does
not take place. This result appears to be compatible with observations as well
as theoretical considerations.


title:
The Stellar Cusp Around the Supermassive Black Hole in the Galactic
  Center

abstract:
  We analyze deep near-IR adaptive optics imaging as well as new proper motion
data of the nuclear star cluster of the Milky Way. The surface density
distribution of faint stars peaks within 0.2" of the black hole candidate
SgrA*. The radial density distribution of this stellar 'cusp' follows a power
law of exponent 1.3-1.4. The K-band luminosity function of the overall nuclear
stellar cluster (within 9" of SgrA*) resembles that of the large scale,
Galactic bulge, but shows an excess of stars at K<14.
  We find that most of the massive early type stars at distances 1-10" from
SgrA* are located in two rotating and geometrically thin disks. These disks are
inclined at large angles and counter-rotate with respect to each other. Their
stellar content is essentially the same, indicating that they formed at the
same time.
  The star closest to SgrA* in 2002, S2, exhibits a 3.8 micron excess. We
propose that the mid-IR emission either comes from the accretion flow around
the black hole itself, or from dust in the accretion flow that is heated by the
ultra-violet emission of S2.


title:
XMM-Newton discovery of O VII emission from warm gas in clusters of
  galaxies

abstract:
  XMM-Newton recently discovered O VII line emission from ~2 million K gas near
the outer parts of several clusters of galaxies. This emission is attributed to
the Warm-Hot Intergalactic Medium. The original sample of clusters studied for
this purpose has been extended and two more clusters with a soft X-ray excess
have been found. We discuss the physical properties of the warm gas, in
particular the density, spatial extent, abundances and temperature.


title: Solar-like Oscillations (Invited Review)

abstract:
  The five-minute oscillations in the Sun have provided a wealth of information
about the solar interior. After many attempts, positive detections of similar
oscillations in solar-type stars have now been made. This review discusses the
properties of solar-like oscillations, the methods used to observe them and the
results on individual stars. We conclude that the study of solar-like
oscillations from the ground and space has an exciting future.


title: GRB 030226 in a Density-Jump Medium

abstract:
  We present an explanation for the unusual temporal feature of the GRB 030226
afterglow. The R-band afterglow of this burst faded as ~ t^{-1.2} in ~ 0.2 days
after the burst, rebrightened during the period of ~ 0.2 - 0.5 days, and then
declined with ~ t^{-2.0}. To fit such a light curve, we consider an
ultrarelativistic jetted blast wave expanding in a density-jump medium. The
interaction of the blast wave with a large density jump produces relativistic
reverse and forward shocks. In this model, the observed rebrightening is due to
emissions from these newly forming shocks, and the late-time afterglow is
caused by sideways expansion of the jet. Our fitting implies that the
progenitor star of GRB 030226 could have produced a stellar wind with a large
density jump prior to the GRB onset.


title:
A Technique for Separating the Gravitational Torques of Bars and Spirals
  in Disk Galaxies

abstract:
  We describe a Fourier-based method of separating bars from spirals in
near-infrared images. The method takes advantage of the fact that a bar is
typically a feature with a relatively fixed position angle, and uses the simple
assumption that the relative Fourier amplitudes due to the bar decline with
radius past a maximum in the same or a similar manner as they rose to that
maximum. With such an assumption, the bar can be extrapolated into the spiral
region and removed from an image, leaving just the spiral and the axisymmetric
background disk light. The procedure allows us to estimate the maximum
gravitational torque per unit mass per unit square of the circular speed for
the bar and spiral forcing separately, parameters which quantitatively define
the bar strength Q_b and the spiral strength Q_s following the recent study of
Buta & Block. We outline the complete procedure here using a 2.1 micron image
of NGC 6951, a prototypical SAB(rs)bc spiral. We justify our assumption on how
to make the bar extrapolation using an analysis of NGC 4394, a barred spiral
with only weak near-infrared spiral structure, and we justify the number of
needed Fourier terms using NGC 1530, one of the most strongly-barred galaxies
(bar class 7) known. We also evaluate the main uncertainties in the technique.
Allowing for uncertainties in vertical scaleheight, bar extrapolation, sky
subtraction, orientation parameters, and the asymmetry in the spiral arms
themselves, we estimate Q_b=0.28\pm0.04 and Q_s=0.21\pm0.06 for NGC 6951.
(abridged)


title: Goodness--of--fit Statistics and CMB Data Sets

abstract:
  Application of a Goodness--of--fit (GOF) statistic is an essential element of
parameter estimation. We discuss the computation of GOF when estimating
parameters from anisotropy measurements of the cosmic microwave background
(CMB), and we propose two GOF statistics to be used when employing approximate
band--power likelihood functions. They are based on an approximate form for the
distribution of band--power estimators that requires only minimal experimental
information to construct. Monte Carlo simulations of CMB experiments show that
the proposed form describes the true distributions quite well. We apply these
GOF statistics to current CMB anisotropy data and discuss the results.


title: A Fast Hybrid Approach to Air Shower Simulations and Applications

abstract:
  The SENECA model, a new hybrid approach to air shower simulations, is
presented. It combines the use of efficient cascade equations in the energy
range where a shower can be treated as one-dimensional, with a traditional
Monte Carlo method which traces individual particles. This allows one to
reproduce natural fluctuations of individual showers as well as the lateral
spread of low energy particles. The model is quite efficient in computation
time.
  As an application of the new approach, the influence of the low energy
hadronic models on shower properties for AUGER energies is studied. We conclude
that these models have a significant impact on the tails of lateral
distribution functions, and deserve therefore more attention.


title: Neutrinos from the pulsar wind nebulae

abstract:
  In the recent paper we calculated the $\gamma$-ray spectra from pulsar wind
nebulae (PWNe), assuming that a significant amount of the pulsar rotational
energy is converted into relativistic nuclei. These nuclei accelerate leptons
which are responsible for most of the observed electromagnetic emission from
PWNe. Small part of nuclei also interact with the matter of the supernova
producing $\gamma$-rays, which can also contribute to the observed spectra of
young nebulae. Here we calculate the spectra of neutrinos from the interaction
of nuclei inside the nebula and the expected neutrino event rates in the 1
km$^2$ neutrino detector from: the Crab Nebula (PSR 0531+21), the Vela SNR (PSR
0833-45), G 343.1-2.3 (PSR 1706-44), MSH15-52 (PSR 1509-58), 3C58 (PSR
J0205+6449), and CTB80 (PSR 1951+32). It is shown that only the Crab Nebula can
produce the neutrino event rate above the sensitivity limit of the 1 km$^2$
neutrino detector, provided that nuclei take most of the rotational energy lost
by the pulsar. The neutrino event rate expected from the Vela SNR is comparable
to that from the Crab Nebula but these neutrinos are less energetic and emitted
from a much larger region on the sky. Therefore it may be difficult to subtract
the Vela SNR signal from the higher background of the atmospheric neutrinos.


title:
On the efficiency of the Ultra Steep Spectrum technique in finding
  High-z Radiogalaxies

abstract:
  In the last three decades, the Ultra Steep spectrum tecnique has been
exploited by many groups since it was demonstrated that radio sources with very
steep spectra (Alpha < -1.0) are good tracers of high-z radio galaxies (HzRGs;
z>2). Though more than 150 HzRGs have been discovered up to now with this
tecnique, little is known about its real effectiveness, as most of the ongoing
searches still have incomplete follow-up programs. By selecting a new
appropriate sample of USS sources from the MRC survey, the true searching
efficiency of the USS tecnique has been quantitatively demonstrated for the
first time in this paper. Moreover it was compared with that of an optical
search of HzRGs based on a simple cut of the galaxies r-band magnitude
distribution. When no bias other than the radio-spectrum steepness is applied,
the USS tecnique may be up to 4 times more efficient in selecting HzRGs with
respect to an optical search. Nevertheless, when the search is limited to
objects fainter than the POSS-II plates (r~21), the USS tecnique is still 2.5
times more efficient (epsilonUSS =0.52 vs. epsilon_OPT= 0.19). For an optical
search to reach a comparable efficiency it is necessary to select objects
fainter than r=23, but this implies that about half of the HzRGs are lost
because of the imposed magnitude bias. The advantage of the USS tecnique is
that a ~0.5 search efficiency is already reached at the POSS-II plates limit,
where all the optical identification work is done without telescopes. However,
this tecnique has the drawback that up to 40% of the HzRGs of the sample are
lost simply because of the applied spectral index bias.


title: Long Period Variables in NGC 5128: I. Catalogue

abstract:
  The first variable star catalogue in a giant elliptical galaxy NGC 5128
(Centaurus A) is presented. Using multi-epoch observations with ISAAC at the
VLT we have detected 1504 red variables in two halo fields covering 10.46
arcmin square. For the variables with at least 10 good measurements, periods
and amplitudes were determined using Fourier analysis and non-linear sine-curve
fitting algorithms. The final catalogue contains 1146 long period variables
with well established light curve parameters. Periods, amplitudes, JsHKs
photometry as well as individual Ks-band magnitudes are provided for all the
variables. The distribution of amplitudes ranges from 0.3 to a few magnitudes
in the Ks-band, with a median value around 0.7 mag. The amplitudes, mean
magnitudes and periods indicate that the majority of variables belong to the
class of long period variables with semiregular and Mira variables. Exhaustive
simulations were performed in order to assess the completeness of our catalogue
and the accuracy of the derived periods.


title: Scaling properties of the cosmic background plasma and radiation

abstract:
  Scaling properties of the cosmic microwave background (CMB) radiation are
studied using satellite (COBE-DMR maps), balloon-borne and ground-based
(combined QMASK map) data. Quantitative consistency is found between the
multiscaling properties of the COBE-DMR and QMASK CMB maps. Surprisingly, it is
found that the observed CMB temperature multiscaling resembles quantitatively
the multiscaling properties of fluid turbulence, that indicates primordial
plasma turbulence as an origin of the CMB temperature space anisotropy.


title:
The CORALIE survey for southern extra-solar planets XI. The return of
  the giant planet orbiting HD192263

abstract:
  The presence of a planet around the K dwarf HD192263 was recently called into
question by the detection of a periodic photometric signal with the same period
as the one observed in radial velocity. In this paper, we investigate this
possibility, using a combination of radial-velocity, photometry, and bisector
measurements obtained simultaneously. The results show that while the observed
radial-velocity variation is always very stable in phase, period, and
amplitude, the photometric signal changes with time. The combined information
strongly suggests that the observed radial-velocity variation is being produced
by the presence of a planet, as firstly proposed. The photometric variations
are either not connected to the planetary companion, or can eventually be
induced by the interaction between the planet and the star. Finally, the
radial-velocity data further show the presence of a long term trend, whose
origin, still not clear, might be related to the presence of another companion
to the system.


title: Thermal Radiation from Cooling Neutron Stars

abstract:
  Observations of thermal radiation from neutron stars allow one to measure the
surface temperatures and confront them with cooling scenarios. Detection of
gravitationally redshifted spectral lines can yield the mass-to-radius ratio.
In the few cases when the distance is known, one can measure the neutron star
radius, which is particularly important to constrain the equation of state of
the superdense matter in the neutron star interiors. Finally, one can infer the
chemical composition of the neutron star surface layers, which provides
information about formation of neutron stars and their interaction with the
environments. We present the observational results on thermal radiation from
active pulsars and radio-quiet neutron stars, with emphasis on the results
obtained with the Chandra X-ray Observatory and discuss some implications of
these results. In particular, we present a new interpretation of the thermal
emission detected in the broad energy range (from optical to X-rays) from the
puzzling object RX J1856.5-3754


title: Uses of Linear Polarization as a Probe of Extrasolar Planet Atmospheres

abstract:
  We point out some advantages of making observations of extrasolar planets in
linearly polarized (LP) light. Older cool stars have quite low levels (~ 10^-4
to 10^-5) of fractional LP, while extrasolar planets can have relatively high
fractional LP (~0.1). Observations in LP light can therefore significantly
enhance contrast between the planet and its parent star. Data on LP as a
function of planetary orbital phase can be used to diagnose the properties
(e.g., composition, size, and shape) of the scatterers in the planetary
atmosphere. We discuss the feasibility of LP observations of extrasolar
planets.


title: SINGS: The SIRTF Nearby Galaxies Survey

abstract:
  The SIRTF Nearby Galaxy Survey is a comprehensive infrared imaging and
spectroscopic survey of 75 nearby galaxies. Its primary goal is to characterize
the infrared emission of galaxies and their principal infrared-emitting
components, across a broad range of galaxy properties and star formation
environments. SINGS will provide new insights into the physical processes
connecting star formation to the interstellar medium properties of galaxies,
and provide a vital foundation for understanding infrared observations of the
distant universe and ultraluminous and active galaxies. The galaxy sample and
observing strategy have been designed to maximize the scientific and archival
value of the data set for the SIRTF user community at large. The SIRTF images
and spectra will be supplemented by a comprehensive multi-wavelength library of
ancillary and complementary observations, including radio continuum, HI, CO,
submillimeter, BVRIJHK, H-alpha, Paschen-alpha, ultraviolet, and X-ray data.
This paper describes the main astrophysical issues to be addressed by SINGS,
the galaxy sample and the observing strategy, and the SIRTF and other ancillary
data products.


title: Rapid Cooling of Dusty Gas in Elliptical Galaxies

abstract:
  We propose a stellar origin for the central dust clouds observed in most
giant elliptical galaxies. Dusty gas ejected from evolving red giant stars in E
or cD galaxies can cool rapidly even after entering the hot, X-ray emitting
gas. Cooling by thermal collisions with dust grains can be faster than either
the dynamical time in the galactic potential or the grain sputtering time. Some
grains survive in the cooled gas. Dusty stellar outflows cool more efficiently
in the central regions where the stellar metallicity is higher. Mergers with
gas and dust-rich dwarf galaxies may occasionally occur but are not required to
explain the observed dust clouds.


title: Eternal inflation and energy conditions in de Sitter spacetime

abstract:
  Eternal inflation is shown to require violations of the Null Energy Condition
(NEC) on superhorizon scales. With light scalar fields as the matter sources in
a de Sitter background, there can be no classical or semiclassical violations
of the NEC. However, quantum fluctuations of the energy-momentum tensor,
described by an expectation value of four field operators, do lead to
large-scale NEC violations. The backreaction of such quantum fluctuations on
the inflating spacetime is generally deduced at a heuristic level and leads to
the eternal inflation scenario. A rigorous treatment of the backreaction will
necessarily include fluctuations of the metric, and several new effects are
expected to come into play.


title: Multi-dimensional nucleosynthesis calculations of Type II SNe

abstract:
  We investigate explosive nuclear burning in core collapse supernovae by
coupling a tracer particle method to one and two-dimensional Eulerian
hydrodynamic calculations. Adopting the most recent experimental and
theoretical nuclear data, we compute the nucleosynthetic yields for 15 Msun
stars with solar metallicity, by post-processing the temperature and density
history of advected tracer particles. We compare our results to 1D calculations
published in the literature.


title: Quantifying the Uncertainty in the Orbits of Extrasolar Planets

abstract:
  Precise radial velocity measurements have led to the discovery of ~100
extrasolar planetary systems. We investigate the uncertainty in the orbital
solutions that have been fit to these observations. Understanding these
uncertainties will become more and more important as the discovery space for
extrasolar planets shifts to longer and longer periods. While detections of
short period planets can be rapidly refined, planets with long orbital periods
will require observations spanning decades to constrain the orbital parameters
precisely. Already in some cases, multiple distinct orbital solutions provide
similarly good fits, particularly in multiple planet systems. We present a
method for quantifying the uncertainties in orbital fits and addressing
specific questions directly from the observational data rather than relying on
best fit orbital solutions. This Markov chain Monte Carlo (MCMC) technique has
the advantage that it is well suited for the high dimensional parameter spaces
necessary for the multiple planet systems. We apply the MCMC technique to
several extrasolar planetary systems, assessing the uncertainties in orbital
elements for several systems. Our MCMC simulations demonstrate that for some
systems there are strong correlations between orbital parameters and/or
significant non-Gaussianities in parameter distributions, even though the
measurement errors are nearly Gaussian. Once these effects are considered the
actual uncertainties in orbital elements can be significantly larger or smaller
than the published uncertainties. We also present simple applications of our
methods such as predicting the times of possible transits for GJ 876.


title:
Collisions and Mergers of Disk Galaxies: Hydrodynamics of Star Forming
  Gas

abstract:
  We summarize the results of numerical simulations of colliding gas-rich disk
galaxies in which the impact velocity is set parallel to the spin axes of the
two galaxies. The effects of varying the impact speed are studied with
particular attention to the resulting gaseous structures and shockwave
patterns, and the time needed to produce these structures. The simulations
employ an N-body treatment of the stars and dark matter, together with an SPH
treatment of the gas, in which all components of the models are gravitationally
active. The results indicate that for such impact geometries, collisions can
lead to the very rapid formation of a central, rapidly rotating, dense gas
disk, and that in all cases extensive star formation is predicted by the very
high gas densities and prevalence of shocks, both in the nucleus and out in the
galactic disks. As the dense nucleus is forming, gas and stars are dispersed
over very large volumes, and only fall back towards the nucleus over long
times. In the case of low impact velocities, this takes an order of magnitude
more time than that needed for the formation of a dense nucleus.


title: A Chandra X-ray Study of the Globular Cluster M80

abstract:
  We report our analysis of a Chandra X-ray observation of the rich globular
cluster M80, in which we detect some 19 sources to a limiting 0.5-2.5 keV X-ray
luminosity of 7*10^30 ergs/s within the half-mass radius. X-ray spectra
indicate that two of these sources are quiescent low-mass X-ray binaries
(qLMXBs) containing neutron stars. We identify five sources as probable
cataclysmic variables (CVs), one of which seems to be heavily absorbed,
implying high inclination. The brightest CV may be the X-ray counterpart of
Nova 1860 T Sco. The concentration of the X-ray sources within the cluster core
implies an average mass of 1.2+/-0.2 Msun, consistent with the binary nature of
these systems and very similar to the radial distribution of the blue
stragglers in this cluster. The X-ray and blue straggler source populations in
M80 are compared to those in the similar globular cluster 47 Tuc.


title:
The HDF-North SCUBA Super-map I: Submillimetre maps, sources and number
  counts

abstract:
  We investigate the emission of sub-millimetre-wave radiation from galaxies in
a 165 square arcminute region surrounding the Hubble Deep Field North. The data
were obtained from dedicated observing runs from our group and others using the
SCUBA camera on the James Clerk Maxwell Telescope, and combined using
techniques specifically developed for low signal-to-noise source recovery. The
resulting `Super-map' is derived from about 60 shifts of JCMT time, taken in a
variety of observing modes and chopping strategies, and combined here for the
first time. At 850 micron we detect 19 sources at >4 sigma, including 5 not
previously reported. We also list an additional 15 sources between 3.5 and 4.0
sigma (where 2 are expected by chance). The 450 micron map contains 5 sources
at >4 sigma. We present a new estimate of the 850 micron and 450 micron source
counts. The number of sub-mm galaxies we detect account for approximately 40%
of the 850 micron sub-mm background, and we show that mild extrapolations can
reproduce it entirely. A clustering analysis fails to detect any significant
signal in this sample of SCUBA detected objects. A companion paper describes
the multiwavelength properties of the sources.


title:
Analysis of the Quiescent Low-Mass X-ray Binary Population in Galactic
  Globular Clusters

abstract:
  Quiescent low-mass X-ray binaries (qLMXBs) containing neutron stars have been
identified in several globular clusters using Chandra or XMM X-ray
observations, using their soft thermal spectra. We report a complete census of
the qLMXB population in these clusters, identifying three additional probable
qLMXBs in NGC 6440. We conduct several analyses of the qLMXB population, and
compare it with the harder, primarily CV, population of low-luminosity X-ray
sources with 10^31<L_X<10^32.5 ergs/s. The radial distribution of our qLMXB
sample suggests an average system mass of 1.5^{+0.3}_{-0.2} Msun, consistent
with a neutron star and low-mass companion. Spectral analysis reveals that no
globular cluster qLMXBs, other than the transient in NGC 6440, require an
additional hard power-law component as often observed in field qLMXBs. We
identify an empirical lower luminosity limit of 10^32 ergs/s among globular
cluster qLMXBs. The bolometric luminosity range of qLMXBs implies (in the deep
crustal heating model of Brown and collaborators) low time-averaged mass
transfer rates, below the disk stability criterion. The X-ray luminosity
functions of the CV populations alone in NGC 6397 and 47 Tuc are shown to
differ. The distribution of qLMXBs among globular clusters is consistent with
their dynamical formation by either tidal capture or exchange encounters,
allowing us to estimate that seven times more qLMXBs than bright LMXBs reside
in globular clusters. The distribution of harder sources (primarily CVs) has a
weaker dependence upon density than that of the qLMXBs. Finally, we discuss
possible effects of core collapse and globular cluster destruction upon X-ray
source populations.


title:
A Unified Treatment of the Gamma-Ray Burst 021211 and Its Afterglow
  Emissions

abstract:
  The Gamma-Ray Burst (GRB) 021211 detected by the High Energy Transient
Explorer (HETE) II had a simple light-curve in the x-ray and gamma-ray energy
bands containing one peak and little temporal fluctuation other than the
expected Poisson variation. Such a burst offers the best chance for a unified
understanding of the gamma-ray burst and afterglow emissions. We provide a
detailed modeling of the observed radiation from GRB 021211 both during the
burst and the afterglow phase. The consistency between early optical emission
(prior to 11 minutes), which presumably comes from reverse shock heating of the
ejecta, and late afterglow emission from forward shock (later than 11 minutes)
requires the energy density in the magnetic field in the ejecta, expressed as
fraction of the equipartition value or $\epsilon_B$, to be larger than the
forward shock at 11 minutes by a factor of about 10$^3$. We find that the only
consistent model for the gamma-ray emission in GRB 021211 is the synchrotron
radiation in the forward shock; to explain the peak flux during the GRB
requires $\epsilon_B$ in forward shock at deceleration to be larger than the
value at 11 minutes by a factor of about 10$^2$.
  These results suggest that the magnetic field in the reverse shock and early
forward shock is most likely frozen-in-field from the explosion, and therefore
a large fraction of the energy in the explosion was initially stored in
magnetic field. We can rule out the possibility that the ejecta from the burst
for GRB 021211 contained more than 10 electron-positron pairs per proton.


title: Fast n-point correlation functions and three-point lensing application

abstract:
  We present a new algorithm to rapidly compute the two-point (2PCF),
three-point (3PCF) and n-point (n-PCF) correlation functions in roughly O(N log
N) time for N particles, instead of O(N^n) as required by brute force
approaches. The algorithm enables an estimate of the full 3PCF for as many as
10^6 galaxies. This technique exploits node-to-node correlations of a recursive
bisectional binary tree. A balanced tree construction minimizes the depth of
the tree and the worst case error at each node. The algorithm presented in this
paper can be applied to problems with arbitrary geometry.
  We describe the detailed implementation to compute the two point function and
all eight components of the 3PCF for a two-component field, with attention to
shear fields generated by gravitational lensing. We also generalize the
algorithm to compute the n-point correlation function for a scalar field in k
dimensions where n and k are arbitrary positive integers.


title:
The Librating Companions in HD 37124, HD 12661, HD 82943, 47 Uma and GJ
  876: Alignment or Antialignment?

abstract:
  We investigated the apsidal motion for the multi-planet systems. In the
simulations, we found that the two planets of HD 37124, HD 12661, 47 Uma and HD
82943 separately undergo apsidal alignment or antialignment. But the companions
of GJ 876 and $\upsilon$ And are only in apsidal lock about $0^{\circ}$.
Moreover, we obtained the criteria with Laplace-Lagrange secular theory to
discern whether a pair of planets for a certain system are in libration or
circulation.


title: Metal Rich Stars in omega Centauri

abstract:
  I present some preliminary results from a high-resolution spectroscopic
observing campaign conducted with UVES at the ESO VLT, devoted to the study of
the newly discovered, metal-rich red giant branch (RGB-a) in omega Centauri. In
particular, I derive and discuss accurate abundances of iron-peak elements,
alpha-elements and s-process elements. The main results discussed in this
contribution are: (i) the RGB-a is the most metal-rich component of the RGB
stellar mix in omega Cen, with [Fe/H]=-0.62+/-0.06; (ii) the RGB-a has a lower
alpha-enhancement compared to the other red giants, possibly due to SNe type Ia
pollution and (iii) the s-process elements overabundance of the RGB-a is
similar to that of the other red giants in omega Cen, and unusually high for
globular cluster stars, due to pollution by low mass AGB stars.


title:
Evolution and Nucleosynthesis of Massive Stars and Related Nuclear
  Uncertainties

abstract:
  Properties of atomic nuclei important for the prediction of astrophysical
reaction rates are reviewed. In the first part, a recent simulation of
evolution and nucleosynthesis of stars between 15 and 25 solar masses is
presented. This study is used to illustrate the required nuclear input as well
as to give examples of the sensitivity to certain rates. The second part
focusses on the prediction of nuclear rates in the statistical model
(Hauser-Feshbach) and direct capture (DWBA). Some of the important ingredients
are addressed. Discussed in more detail are approaches to predict level
densities, parity distributions, and optical alpha+nucleus potentials.


title:
The effect of scattering on the structure and SED of protoplanetary
  disks

abstract:
  In this paper we investigate how the inclusion of scattering of the stellar
radiation into a passive flaring disk model affects its structure and spectral
energy distribution, and whether neglecting it could significantly decrease the
model reliability. In order to address these questions we construct a detailed
1+1D vertical structure model in which the scattering properties of the dust
can be varied. Models are presented with and without dust scattering, and for
different albedos and phase functions. It is found that scattering has the
effect of reducing the disk temperature at all heights, so that the disk
"shrinks", i.e., the the density at all intermediate heights decreases.
However, this effect in most cases is more than compensated by the increase of
the total extinction (absorption + scattering) cross section, so that the
surface scale height increases, and images in scattered light will see a
slightly thicker disk. The integrated infrared emission decreases as the albedo
increases, because an increasing part of the flux captured by the disk is
reflected away instead of absorbed and reprocessed. The reduction of the
infrared thermal emission of the disk is stronger at short wavelengths (near
infrared) and practically negligible at millimeter wavelengths. For relatively
low albedo (alb <~ 0.5), or for strongly forward-peaked scattering (g roughly
>0.8), the infrared flux reduction is relatively small.


title: Yet another galaxy identification for an ultraluminous X-ray source

abstract:
  We report on the identification of the optical and infrared counterparts of
the ultraluminous X-ray source (ULX) XMMU J121214.5+131248 (NGC4168-ULX1). The
optical spectrum yields a redshift of z=0.217, which implies that the ULX is
not associated with the nearby galaxy NGC 4168, but rather with a background
object. Optical spectral line ratios and the spectral energy distribution
constructed from the available data indicate that the source is likely a
starburst nucleus.


title: Multiscaling of galactic cosmic ray flux

abstract:
  Multiscaling analysis of differential flux dissipation rate of galactic
cosmic rays (Carbon nuclei) is performed in the energy ranges: 56.3-73.4
Mev/nucleon and 183.1-198.7 MeV/nucleon, using the data collected by ACE/CRIS
spacecraft instrument for 2000 year. The analysis reveals strong
(turbulence-like) intermittency of the flux dissipation rate for the short-term
intervals: 1-30 hours. It is also found that type of the intermittency can be
different in different energy ranges.


title: Multiscaling Anderson localization of cosmic electromagnetic fields

abstract:
  Multiscaling properties of the Anderson localization of the cosmic
electromagnetic fields before the recombination time are studied and results of
a numerical simulation for a random banded matrix ensemble are found to be in
good agreement with the large-scale cosmic data.


title: Self-Stark Limit of Brightness Temperature in Cosmic Masers

abstract:
  The radiation broadening of narrow maser lines by its own emission which can
be described as resonance Self-Stark effect puts an upper limit on the
brightness temperature of cosmic masers. It is shown that available results of
measurements of the brightness temperature of OH and water masers are
consistent with the observed narrow line widths only if the maser emission is
highly directive.


title:
Integration of the atmospheric fluctuations in a dual-field optical
  interferometer: the short exposure regime

abstract:
  Spatial phase-referencing in dual-field optical interferometry is
reconsidered. Our analysis is based on the 2-sample variance of the
differential phase between target and reference star. We show that averaging
over time of the atmospheric effects depends on this 2-sample phase variance
(Allan variance) rather than on the true variance. The proper expression for
fringe smearing beyond the isoplanatic angle is derived. With simulations of
atmospheric effects, based on a Paranal turbulence model, we show how the
performances of a dual-field optical interferometer can be evaluated in a
diagram 'separation angle' versus 'magnitude of faint object'. In this diagram,
a domain with short exposure is found to be most useful for interferometry,
with about the same magnitude limits in the H and K bands. With star counts
from a Galaxy model, we evaluate the sky coverage for differential astrometry
and detection of exoplanets, i.e. likelihood of faint reference stars in the
vicinity of a bright target. With the 2mass survey, we evaluate sky coverage
for phase-referencing, i.e. avaibility of a bright enough star for main delay
tracking in the vicinity of any target direction.


title: New varying speed of light theories

abstract:
  We review recent work on the possibility of a varying speed of light (VSL).
We start by discussing the physical meaning of a varying $c$, dispelling the
myth that the constancy of $c$ is a matter of logical consistency. We then
summarize the main VSL mechanisms proposed so far: hard breaking of Lorentz
invariance; bimetric theories (where the speeds of gravity and light are not
the same); locally Lorentz invariant VSL theories; theories exhibiting a color
dependent speed of light; varying $c$ induced by extra dimensions (e.g. in the
brane-world scenario); and field theories where VSL results from vacuum
polarization or CPT violation. We show how VSL scenarios may solve the
cosmological problems usually tackled by inflation, and also how they may
produce a scale-invariant spectrum of Gaussian fluctuations, capable of
explaining the WMAP data. We then review the connection between VSL and
theories of quantum gravity, showing how ``doubly special'' relativity has
emerged as a VSL effective model of quantum space-time, with observational
implications for ultra high energy cosmic rays and gamma ray bursts. Some
recent work on the physics of ``black'' holes and other compact objects in VSL
theories is also described, highlighting phenomena associated with spatial (as
opposed to temporal) variations in $c$. Finally we describe the observational
status of the theory. The evidence is currently slim -- redshift dependence in
the atomic fine structure, anomalies with ultra high energy cosmic rays, and
(to a much lesser extent) the acceleration of the universe and the WMAP data.
The constraints (e.g. those arising from nucleosynthesis or geological bounds)
are tight, but not insurmountable. We conclude with the observational
predictions of the theory, and the prospects for its refutation or vindication.


title:
Motivation and possibilities of affordable low-frequency radio
  interferometry in space

abstract:
  The motivation to build spaceborne interferometric arrays for low-frequency
radio astronomy is widely recognised because frequencies below the ionospheric
cutoff are inaccessible for ground-based radio telescopes. We discuss the
theoretical possibilities to use low-frequency spacecraft arrays to detect
signals from magnetized extrasolar planets, including earthlike ones. A major
uncertainty that prohibits us from knowing if it is possible to detect
exoplanet cyclotron maser signals is the incomplete knowledge of the properties
of the interstellar plasma.
  We also present some ideas of how to construct efficient and affordable
space-based radio telescopes. We discuss two possibilities, a log-periodic
antenna in the spin plane and a two-spacecraft concept where one spacecraft
holds a large parabolic wire mesh reflector and the other one contains the
receiver. In the latter case, the effective area could be of the order of 1
km$^2$. The purpose of the paper is to stress once more the importance of
spaceborne low-frequency measurements by bringing in the intriguing possibility
of detecting earthlike exoplanet radio emissions and to demonstrate that
building even very large low-frequency antennas in space is not necessarily too
expensive.


title: Simultaneous ASCA and HST/GHRS observations of Cygnus X-2/V1341 Cygni

abstract:
  We present results from ultraviolet and X-ray observations of the low mass
X-ray binary Cygnus X-2. The simultaneous HST/GHRS and ASCA observations took
place during the low state of an 82-day cycle. We compare our observations as
well as archival IUE and RXTE data with models that predict ultraviolet and
optical continuum emission from an X-ray heated disk and a Roche-lobe-filling
star. The model predictions are consistent with observed optical, ultraviolet,
and X-ray variations over both orbital and long-term periods. The X-ray
spectral state, the luminosities implied by fits to the X-ray data, the
ultraviolet continuum and line fluxes, and the mass accretion rates obtained
from fits to the ultraviolet continuum are consistent with location of our
observations on the normal and horizontal branches of the Z-shaped X-ray
color-color diagram. A combination of changes to mass accretion rate and
obstruction by a warped disk can be invoked as a possible explanation for the
motion of the ``Z'' in the color-color plane. The GHRS/G160M measurements
concentrated on NV and HeII. The low-resolution (GHRS/G140L) observations
captured SiIV, NIV, and CIV. Although the relative line fluxes are consistent
with emission from an X-ray heated accretion disk corona, predictions from
models of line emission from simple disks do not fit the observed emission line
profiles.The radial velocities (80-130 km s$^{-1}$) are consistent with
emission from the optical star at the orbital phase (0.70-0.74) of our
observations.


title: A 3-d simulation of the atmospheric neutrinos

abstract:
  The first AMS flight in June 1998 on board of the space shuttle Discovery at
an altitude of approximately 380 km unveiled unexpected features of the cosmic
rays spectra below the Earth geomagnetic cut-off. In addition to a secondary
flux of particles at all latitude, a ring of high energy particles (up to 6
GeV) and an anomalous ratio e+/e- as high as 4 was observed near the
geomagnetic equator. This paper describes a simulation of the interaction of
primary cosmic rays with atmosphere in which the effect of the Earth magnetic
field is included . Using the GEANT3 package for the tracking of particles with
the GFLUKA associated package for the physics of interactions, this simulation
reproduces quite well the AMS experimental results and the CAPRICE muon data at
ground level. The predictions of this model for the flux of atmospheric
neutrino are compared with the Super-Kamiokande results and with the results of
other atmospheric neutrino models.


title: Why Hot Horizontal Branch Stars Can Appear Redder Than Red Giants

abstract:
  In this paper we report on a curious feature in the V, (U-B) color-magnitude
diagrams of globular clusters. In our database, we find that a considerable
fraction of blue horizontal branch stars, hotter than the instability strip and
cooler than the Grundahl et al. (1999) jump (i.e., 6000 <~ T_eff K <~ 10000),
have (U-B) colors redder than their red giant progenitors. This red incursion
is not expected on theoretical grounds, as horizontal branch stars (whose
convective regions are less extended than in red giant structures) should not
``appear'' cooler than a red giant. Analyzing data from different telescopes we
show that: 1) the horizontal branch red incursion is strongly dependent on the
shape of the adopted U filter and to a lesser extent, on the B filter; 2) the
photometry done with U filters which do not encompass the Balmer jump, do not
show the blue horizontal branch red incursion; 3) the occurrence of this
feature is also due to the peculiar dependence of the U and B magnitudes on
stars effective temperature, gravity, and metallicity; 4) theoretical tracks
can reproduce the observed horizontal branch morphology, provided that the
appropriate (i.e. exactly responding to the filters effectively used in the
observations) transmission curve efficiencies are used for deriving color-T_eff
transformations; 5) the red incursion extent depends on metallicity.


title: The galactic evolution of the supernova rates

abstract:
  Supernova rates (hypernova, type II, type Ib/c and type Ia) in a particular
galaxy depend on the metallicity (i.e. on the galaxy age), on the physics of
star formation and on the binary population. In order to study the time
evolution of the galactic supernova rates, we use our chemical evolutionary
model that accounts in detail for the evolution of single stars and binaries.
In particular, supernovae of type Ia are considered to arise from exploding
white dwarfs in interacting binaries and we adopt the two most plausible
physical models: the single degenerate model and the double degenerate model.
Comparison between theoretical prediction and observations of supernova rates
in different types of galaxies allows to put constraints on the population of
intermediate mass and massive close binaries. The temporal evolution of the
absolute galactic rates of different types of SNe (including the SN Ia rate) is
presented in such a way that the results can be directly implemented into a
galactic chemical evolutionary model. Particularly for SNIa the inclusion of
binary evolution leads to results considerably different from those in earlier
population synthesis approaches, in which binary evolution was not included in
detail.


title: Drifting subpulses and inner acceleration regions in radio pulsars

abstract:
  The classical vacuum gap model of Ruderman & Sutherland, in which
spark-associated subbeams of subpulse emission circulate around the magnetic
axis due to the EB drift, provides a natural and plausible physical mechanism
of the subpulse drift phenomenon. Recent progress in the analysis of drifting
subpulses in pulsars has provided a strong support to this model by revealing a
number of subbeams circulating around the magnetic axis in a manner compatible
with theoretical predictions. However, a more detailed analysis revealed that
the circulation speed in a pure vacuum gap is too high when compared with
observations. Moreover, some pulsars demonstrate significant time variations of
the drift rate, including a change of the apparent drift direction, which is
obviously inconsistent with the EB drift scenario in a pure vacuum gap. We
resolved these discrepancies by considering a partial flow of iron ions from
the positively charged polar cap, coexisting with the production of outflowing
electron-positron plasmas. By fitting the observationally deduced drift-rates
to the theoretical values, we managed to estimate polar cap surface
temperatures in a number of pulsars. The estimated surface temperatures
correspond to a small charge depletion of the order of a few percent of the
corotational charge density. We also argue that if the thermionic electron
outflow from the surface of a negatively charged polar cap is slightly below
the Goldreich-Julian density, then the resulting small charge depletion will
have similar consequences as in the case of the ions outflow. We thus believe
that the sparking discharge of a partially shielded acceleration potential drop
occurs in all pulsars, with both positively (``pulsars'') and negatively
(``anti-pulsars'') charged polar caps.


title: Gravitational force in weakly correlated particle distributions

abstract:
  We study the statistics of the gravitational (Newtonian) force in a
particular kind of weakly correlated distribution of point-like and unitary
mass particles generated by the so-called Gauss-Poisson point process. In
particular we extend to these distributions the analysis a' la Chandrasekhar
introduced for purely Poisson processes. In this way we can find the asymptotic
behavior of the probability density function of the force for large values of
the field as a generalization of the Holtzmark statistics. The validity of the
introduced approximations is positively tested through a direct comparison with
the analysis of the statistics of the gravitational force in numerical
simulations of Gauss-Poisson processes. Moreover the statistics of the force
felt by a particle due to only its first nearest neighbor is analytically a
numerical studied, resulting to be the dominant contribution to the total
force.


title: Sunyaev-Zel'dovich cluster surveys using a large beam

abstract:
  Sunyaev Zel'dovich cluster surveys can be used to constrain cosmological
parameters. Extracting clusters from the primary anisotropies and the
unresolved background from very faint clusters is simple when the telescope
beam size is small (1 arcmin), but could be difficult if the beam is larger (8
arcmin). By reference to examples, we show that this is possible by carefully
designing the depth of the survey.


title:
Physical changes during Z-track movement in Sco X-1 on the flaring
  branch

abstract:
  We present results of a detailed study of X-ray flaring in the Z-track source
Sco X-1 in a highly super-Eddington state made using high quality Rossi-XTE
data from the PCA and HEXTE instruments. The emission model successfully used
to explain the dipping LMXB, and other classes of LMXB in recent years, was
applied to study the physical evolution along the Z-track which remains a major
problem. This model consists of blackbody emission from the neutron star plus
Comptonized emission from an extended accretion disk corona. As found in
earlier work, major changes take place in the neutron star blackbody emission
with kT increasing in flaring, and the blackbody radius R_BB increasing
substantially to a maximum value of 9.4 +/- 0.6 km, consistent with the radius
of the neutron star, after which R_BB decreases. Thus this result is a
measurement of neutron star radius. The behaviour of Sco X-1 in flaring is
compared with our previous results for the strong flaring that takes place in
the bright dipping, flaring LMXB X 1624-490. Remarkably, during movement along
the Normal Branch towards the apex with the Flaring Branch, the luminosities of
both spectral components decrease, suggesting the possibility that Mdot may
decrease on the Normal Branch, contrary to the widely-held view that Mdot
increases monotonically along the Z-track. During flaring, we detect for the
first time an increase of the Comptonization cut-off energy which may suggest
heating of the ADC plasma by the neutron star flare. The energy of a broad
Gaussian line at 6.4 keV does not change, but the intensity of the line
increases in flaring suggesting either an increase in ADC size in flaring or
the effects of irradiation by the neutron star.


title: Galaxy-CMB Lensing

abstract:
  A long-standing problem in astrophysics is to measure the mass associated
with galaxies. Gravitational lensing provides one of the cleanest ways to make
this measurement. To date, the most powerful lensing probes of galactic mass
have been multiply imaged QSO's (strong lensing of a background point source)
and galaxy-galaxy lensing (weak deformation of many background galaxies). Here
we point out that the mass associated with galaxies also lenses the Cosmic
Microwave Background (CMB) and this effect is potentially detectable in small
scale experiments. The signal is small (roughly a few tenths of a microKelvin)
but has a characteristic shape and extends out well beyond the visible region
of the galaxy.


title:
Measurement of the gravitational potential evolution from the
  cross-correlation between WMAP and the APM Galaxy survey

abstract:
  Models with late time cosmic acceleration, such as the Lambda-dominated CDM
model, predict a freeze out for the growth of linear gravitational potential at
moderate redshift z<1, what can be observed as temperature anisotropies in the
CMB: the so called integrated Sachs-Wolfe (ISW) effect. We present a direct
measurement of the ISW effect based on the angular cross-correlation function,
w_{TG}, of CMB temperature anisotropies and dark-matter fluctuations traced by
galaxies. We cross-correlate the first-year WMAP data in combination with the
APM Galaxy survey. On the largest scales, theta = 4-10 deg, we detect a
non-vanishing cross-correlation at 98.8 % significance level, with a 1-sigma
error of w_{TG} = 0.35 +/- 0.14 microK, which favors large values of
Omega_Lambda \simeq 0.8 for flat FRW models. On smaller scales, theta < 1deg,
the correlations disappear. This is contrary to what would be expected from the
ISW effect, but the absence of correlations may be simply explained if the ISW
signal was being cancelled by anti-correlations arising from the thermal
Sunyaev-Zeldovich (SZ) effect.


title:
A deep survey of heavy element lines in planetary nebulae - I.
  Observations and forbidden-line densities, temperatures and abundances

abstract:
  We present spectrophotometry of 12 Galactic and 3 Magellanic Cloud planetary
nebulae (PNe). Nine of the Galactic PNe were observed by scanning the slit
across the PN. We use the fluxes of collisionally excited lines (CELs) to
derive electron densities (D's) and temperatures (T's), and ionic abundances.
We find that the D's derived from optical CEL ratios are systematically higher
than those derived from the ratios of the IR fine-structure (FS) lines of
[OIII], indicating the presence of significant density variations within the
PNe. We also compare T's obtained from the ratio of optical nebular to auroral
[OIII] lines with those obtained from the ratio of [OIII] optical to IR FS
lines. We find that when the latter are derived using D's based on the [OIII]
52um/88um ratio, they yield values that are significantly higher than the
optical [OIII] T's. Contrasting this, [OIII] optical/IR T's derived using the
higher D's obtained from [ClIII] 5517A/5537A ratios show much closer agreement
with optical [OIII] T's, implying that the observed [OIII] optical/IR ratios
are significantly weighted by D's in excess of the critical densities of both
[OIII] FS lines. Consistent with this, ionic abundances derived from [OIII] and
[NIII] FS lines using D's from optical CELs show much better agreement with
abundances derived for the same ions from optical and UV CELs than do
abundances derived from the FS lines using the lower D's obtained from the
52um/88um ratios. The behaviour of T's obtained making use of the T-insensitive
IR FS lines provides no support for significant T-fluctuations within the PNe
that could be responsible for derived Balmer jump T's being lower than those
obtained from the much more T-sensitive [OIII] optical lines.


title:
Gamma-Ray Bursts versus Quasars: Lyman-alpha Signatures of Reionization
  versus Cosmological Infall

abstract:
  Lyman-alpha absorption is a prominent cosmological tool for probing both
galactic halos and the intergalactic medium at high redshift. We consider a
variety of sources that can be used as the Lyman-alpha emitters for this
purpose. Among these sources, we argue that quasars are the best probes of the
evolution of massive halos, while gamma-ray bursts represent the cleanest
sources for studying the reionization of the intergalactic medium.


title:
Small-scale CMB Temperature and Polarization Anisotropies due to Patchy
  Reionization

abstract:
  We study contributions from inhomogeneous (patchy) reionization to arcminute
scale ($1000 < \ell < 10,000$) cosmic microwave background (CMB) anisotropies.
We show that inhomogeneities in the ionization fraction, rather than in the
mean density, dominate both the temperature and the polarization power spectra.
Depending on the ionization history and the clustering bias of the ionizing
sources, we find that rms temperature fluctuations range from 2 $\mu$K to 8
$\mu$K and the corresponding values for polarization are over two orders of
magnitude smaller. Reionization can significantly bias cosmological parameter
estimates and degrade gravitational lensing potential reconstruction from
temperature maps but not from polarization maps. We demonstrate that a simple
modeling of the reionization temperature power spectrum may be sufficient to
remove the parameter bias. The high-$\ell$ temperature power spectrum will
contain some limited information about the sources of reionization.


title:
An H-alpha survey aiming at the detection of extraplanar diffuse ionized
  gas in halos of edge-on spiral galaxies II. The H-alpha survey atlas and
  catalog

abstract:
  In this second paper on the investigation of extraplanar diffuse ionized gas
in nearby edge-on spiral galaxies we present the actual results of the
individual galaxies of our H-alpha imaging survey. A grand total of 74 galaxies
have been studied, including the 9 galaxies of a recently studied sub-sample
(Rossa & Dettmar 2000). 40.5% of all studied galaxies reveal extraplanar
diffuse ionized gas, whereas in 59.5% of the survey galaxies no extraplanar
diffuse ionized gas could be detected. The average distances of this extended
emission above the galactic midplane range from 1-2 kpc, while individual
filaments in a few galaxies reach distances of up to |z| ~ 6 kpc. In several
cases a pervasive layer of ionized gas was detected, similar to the Reynolds
layer in our Milky Way, while other galaxies reveal only extended emission
locally. The morphology of the diffuse ionized gas is discussed for each galaxy
and is compared with observations of other important ISM constituents in the
context of the disk-halo connection, in those cases where published results
were available. Furthermore, we present the distribution of extraplanar dust in
these galaxies, based on an analysis of the unsharp-masked R-band images. The
results are compared with the distribution of the diffuse ionized gas.