title:
INTEGRAL spectroscopy of three powerful radio galaxies: Jet-cloud
  interactions seen in 3-D

abstract:
  Integral-field spectroscopic observations are presented for three powerful
radio galaxies, namely 3C277.3 (Coma A; z=0.0857), 3C171 (z=0.2384) and 3C265
(z=0.811), which are known to be undergoing jet-cloud interactions. The
morphology, kinematics and ionization of the gas in the emission-line structure
of these sources are mapped and analysed. One-dimensional spectra are also
extracted and integrated over the different emission-line regions in each
galaxy. In two of the galaxies (3C277.3 and 3C171) the radio sizes are of
similar extent to the emission-line structure. For these, enhanced
emission-line regions are found associated with the radio structures, in
addition to complex kinematics and low ionization states close to the radio
hotspots, indicating that jet-induced shocks disturb and ionize the gas.
Interestingly, the bright -- presumably shock-ionized -- emission-line region
coincident with the radio jet knot in 3C277.3 shows quiescent kinematics and
high ionization state. Possible explanations for this puzzling result are
proposed. The images of 3C171 and 3C265 indicate that the lateral expansion of
the cocoon has a significant effect on the kinematics and ionization of the
gas, showing for the first time that the effects of the radio source are felt
far from the jet axis. In addition, the presence of a stellar-photoionized HII
region is detected in the extended emission-line nebula of the radio galaxy
3C277.3.


title: The Microwave Anisotropy Probe (MAP) Mission

abstract:
  The purpose of the MAP mission is to determine the geometry, content, and
evolution of the universe via a 13 arcmin full-width-half-max (FWHM) resolution
full sky map of the temperature anisotropy of the cosmic microwave background
radiation with uncorrelated pixel noise, minimal systematic errors,
multifrequency observations, and accurate calibration. These attributes were
key factors in the success of NASA's Cosmic Background Explorer (COBE) mission,
which made a 7 degree FWHM resolution full sky map, discovered temperature
anisotropy, and characterized the fluctuations with two parameters, a power
spectral index and a primordial amplitude. Following COBE considerable progress
has been made in higher resolution measurements of the temperature anisotropy.
With 45 times the sensitivity and 33 times the angular resolution of the COBE
mission, MAP will vastly extend our knowledge of cosmology. MAP will measure
the physics of the photon-baryon fluid at recombination. From this, MAP
measurements will constrain models of structure formation, the geometry of the
universe, and inflation. In this paper we present a pre-launch overview of the
design and characteristics of the MAP mission. This information will be
necessary for a full understanding of the MAP data and results, and will also
be of interest to scientists involved in the design of future cosmic microwave
background experiments and/or space science missions.


title: The MAP Satellite Feed Horns

abstract:
  We present the design, manufacturing methods, and characterization of 20
microwave feed horns currently in use on the Microwave Anisotropy Probe (MAP)
satellite. The nature of the cosmic microwave background (CMB) anisotropy
requires a detailed understanding of the properties of every optical component
of a microwave telescope. In particular, the properties of the feeds must be
known so that the forward gain and sidelobe response of the telescope can be
modeled and so that potential systematic effects may be computed. MAP requires
low emissivity, azimuthally symmetric, low-sidelobe feeds in five microwave
bands (K, Ka, Q, V, and W) that fit within a constrained geometry. The beam
pattern of each feed is modeled and compared with measurements; the agreement
is generally excellent to the -60 dB level (80 degrees from the beam peak).
This agreement verifies the beam-predicting software and the manufacturing
process. The feeds also affect the properties and modeling of the microwave
receivers. To this end, we show that the reflection from the feeds is less than
-25 dB over most of each band and that their emissivity is acceptable. The
feeds meet their multiple requirements.


title:
The Optical Design and Characterization of the Microwave Anisotropy
  Probe

abstract:
  The primary goal of the MAP satellite, now in orbit, is to make high fidelity
polarization sensitive maps of the full sky in five frequency bands between 20
and 100 GHz. From these maps we will characterize the properties of the cosmic
microwave background (CMB) anisotropy and Galactic and extragalactic emission
on angular scales ranging from the effective beam size, <0.23 degree, to the
full sky. MAP is a differential microwave radiometer. Two back-to-back shaped
offset Gregorian telescopes feed two mirror symmetric arrays of ten corrugated
feeds. We describe the prelaunch design and characterization of the optical
system, compare the optical models to the measurements, and consider multiple
possible sources of systematic error.


title:
Detailed atmosphere modelling for the neutron star 1E1207.4-5209:
  Evidence of Oxygen/Neon atmosphere

abstract:
  We present a comprehensive investigation of the two broad absorption features
observed in the X-ray spectrum of the neutron star 1E1207.4-5209 based on a
recent analysis of the 260 ksec XMM-Newton data by Mori et al. 2005. Expanding
on our earlier work (Hailey & Mori 2002) we have examined all previously
proposed atmospheric models for 1E1207.4-5209. Using our atomic code, which
rapidly solves Schrodinger's equation for arbitrary ion in strong magnetic
field (Mori & Hailey 2002), we have systematically constructed atmospheric
models by calculating polarization-dependent LTE opacities and addressed all
the physics relevant to strongly-magnetized plasmas. We have been able to rule
out virtually all atmospheric models because they either do not sustain an
ionization balance consistent with the claimed atmosphere composition or
because they predict line strengths and line widths which are inconsistent with
the data. Only Oxygen or Neon atmospheres at B~10^{12} G provide
self-consistent atmospheric solutions of appropriate ionization balance and
with line widths, strengths and energies consistent with the observations. The
observed features are likely composed of several bound-bound transition lines
from highly-ionized oxygen/neon and they are broadened primarily by motional
Stark effects and magnetic field variation over the line-emitting region.
Further considerations of plausible mechanisms for the formation of a mid-Z
atmosphere likely rule out Neon atmospheres, and have important implications
for the fallback mechanism in supernova ejecta. Future high resolution
spectroscopy missions such as Constellation-X will be able to resolve predicted
substructure in the absorption features and will measure magnetic field
strength and gravitational redshift independently to better than 10% accuracy.


title: Luminous Supersoft X-Ray Sources in External Galaxies

abstract:
  We use a set of conservative criteria to identify luminous supersoft X-ray
sources(SSSs) in external galaxies. We test this approach on blackbody models,
and then apply it to {\it Chandra} data from 4 galaxies: an elliptical (NGC
4967), 2 face-on spirals (M101 and M83), and an interacting galaxy (M51).
  We find SSSs in every galaxy, and estimate that the total SSS population of
sources with $L > 10^{37}$ erg s$^{-1}$ in each galaxy is at least several
hundred and could be significantly larger. In addition, we discover two
intriguing features of galactic populations of SSSs. First, there are
significant subpopulations of high-luminosity sources; the bolometric
luminosities can exceed $10^{39}$ erg s$^{-1}.$ Second, in the spiral galaxies
M101, M83 and M51, SSSs appear to be associated with the spiral arms. This may
indicate that some SSSs are young systems, possibly younger than $10^8$ years.


title: X-ray spectroscopy and time variability of Narrow Line Seyfert 1

abstract:
  We present the main results of broad band (0.1-10 keV) BeppoSAX observations
of a selected sample of Narrow Line Seyfert 1 galaxies (NLS1s). We have
performed a spectroscopic analysis of LECS and MECS data to test their average
spectral properties, and timing analysis to study their amplitude variability.
The steep average spectral indices and the high amplitude time variability are
in agreement with a scenario where NLS1s, with respect to the Broad Line
Seyfert 1 (BLS1s) host a smaller black hole mass surrounded by hotter accretion
disc.


title: Design, Implementation and Testing of the MAP Radiometers

abstract:
  The Microwave Anisotropy Probe (MAP) satellite, launched June 30, 2001, will
produce full sky maps of the cosmic microwave background radiation in 5
frequency bands spanning 20 - 106 GHz. MAP contains 20 differential radiometers
built with High Electron Mobility Transistor (HEMT) amplifiers with passively
cooled input stages. The design and test techniques used to evaluate and
minimize systematic errors and the pre-launch performance of the radiometers
for all five bands are presented.


title:
The Recurrent Nova U Scorpii in the 1999 Outburst: the First Detection
  of a Significant Orbital-Period Change

abstract:
  In this paper we present and discuss our time-resolved photometry of an
eclipsing recurrent nova, U Sco, during an outburst in 1999, which was
conducted from immediately after the optical maximum to the final fading toward
the quiescence. In the first-ever complete light-curve, a few primary and
secondary eclipses of the binary system were detected, and the timings of the
minima were determined. We found that the eclipses showed no totality during
the outburst. The depth of the primary eclipses was 0.4-0.8 mag, much shallower
than that in quiescence. In the plateau phase, very little irradiation (< 0.1
mag) was observed in the orbital light curve, which implies the existence and a
large flaring rim of the accretion disk during the outburst. The minima of the
eclipses were detected at earlier orbital phases for the predicted ephemerides.
Thus, we obtained an orbital period change of the binary system as \dot{P}/P =
-1.7 (+/- 0.7) x 10^{-6} yr^{-1} from the O-C. Assuming that this period change
is a result of the conservative mass transfer between the component stars, its
mass-transfer rate reaches \dot{M} = 2.4 (+/- 1.0) x 10^{-6} M_solar yr^{-1}
for a 1.37 M_solar white dwarf and a 2.0 M_solar mass-donor companion, which is
too high to cause shell flashes, even on a massive white dwarf. Therefore, this
large rate of the period change strongly indicates a non-conservative mass
transfer in the binary system.


title: Parameters of core-collapse

abstract:
  This paper considers the phenomenon of deep core collapse in collisional
stellar systems, with stars of equal mass. The collapse takes place on some
multiple, $\xi ^{-1}$, of the central relaxation time, and produces a density
profile in which $\rho \propto r^{-\alpha}$, where $\alpha$ is a constant. The
parameters $\alpha$ and $\xi$ have usually been determined from simplified
models, such as gas and Fokker-Planck models, often with the simplification of
isotropy. Here we determine the parameters directly from N-body simulations
carried out using the newly completed GRAPE-6.


title: Polarisation Observations at Jodrell Bank Observatory

abstract:
  Some of the issues concerning polarisation calibration in the context of
pulsar observations are outlined along with the existing calibration system in
Jodrell Bank Observatory. The principle behind the back-calibration of the
Jodrell Bank database of 16 years is presented along with plans for exploiting
the database in the future.


title:
Dwarf Nova Oscillations and Quasi-Periodic Oscillations: Extension of
  the Two-QPO Diagram of X-Ray Binaries, and a new kind of DNO

abstract:
  Seventeen examples are given of Cataclysmic Variable (CV) stars possessing
both Dwarf Nova Oscillations (DNOs) and Quasi-Periodic Oscillations (QPOs).
These form an extension of the X-Ray Two-QPO correlation to frequencies three
orders of magnitude lower. We draw attention to the existence of a second type
of DNO in CVs, which is probably caused by magnetically channelled accretion
onto the white dwarf.


title:
Parametric versus non-parametric modelling? Statistical evidence based
  on P-value curves

abstract:
  In astrophysical (inverse) regression problems it is an important task to
decide whether a given parametric model describes the observational data
sufficiently well or whether a non-parametric modelling becomes necessary.
However, in contrast to common practice this cannot be decided by solely
comparing the quality of fit due to possible over-fitting by the non-parametric
method. Therefore, in this paper we present a resampling algorithm which allows
to decide whether deviations between a parametric and a non-parametric model
are systematic or due to noise. The algorithm is based on a statistical
comparison of the corresponding residuals, under the assumption of the
parametric model as well as under violation of this assumption. This yields a
graphical tool for a robust decision making of parametric versus non-parametric
modelling.
  Moreover, our approach can be used for the selection of the most proper model
among several competitors (model selection). The methods are illustrated by the
problem of recovering the luminosity density in the Milky Way [MW] from
near-infrared [NIR] surface brightness data of the DIRBE experiment on board of
the COBE satellite. Among the parametric models investigated one with 4-armed
spiral structure performs best. In this model the Sagittarius-Carina arm and
its counter-arm are significantly weaker than the other pair of arms.
Furthermore, we find statistical evidence for an improvement over a range of
parametric models with different spiral structure morphologies by a
non-parametric model of Bissantz & Gerhard (2002).


title:
Recombination rate coefficients for astrophysical applications from
  storage-ring experiments

abstract:
  The basic approach for measuring electron-ion recombination rate coefficients
in merged-beams electron-ion collision experiments at heavy-ion storage rings
is outlined. As an example experimental results for the low temperature
recombination of C IV ions are compared with the recommended theoretical rate
coefficient by Mazzotta et al. The latter deviates by factors of up to 5 from
the experimental one.


title: Runaway migration and the formation of hot Jupiters

abstract:
  [Abridged] We evaluate the coorbital corotation torque on a migrating
protoplanet. The coorbital torque is assumed to come from orbit crossing fluid
elements which exchange angular momentum with the planet when they execute a
U-turn at the end of horseshoe streamlines. When the planet migrates inward,
the fluid elements of the inner disk undergo one such exchange as they pass to
the outer disk. The angular momentum they gain is removed from the planet, and
this corresponds to a negative contribution to the corotation torque, which
scales with the drift rate. In addition, the material trapped in the coorbital
region drifts radially with the planet giving a positive contribution to the
corotation torque, which also scales with the drift rate. These two
contributions do not cancel out if the coorbital region is depleted, in which
case there is a net corotation torque which scales with the drift rate and the
mass deficit in the coorbital region, and which has same sign as the drift
rate. This leads to a positive feedback on the migrating planet. In particular,
if the coorbital mass deficit is larger than the planet mass, the migration
rate undergoes a runaway which can vary the protoplanet semi-major axis by 50%
over a few tens of orbits. This can happen only if the planet mass is
sufficient to create a dip or gap in its surrounding region, and if the
surrounding disk mass is larger than the planet mass. This typically
corresponds to planet masses in the sub-Saturnian to Jovian mass range embedded
in massive protoplanetary disks. Runaway migration is a good candidate to
account for the orbital characteristics of close orbiting giant planets, most
of which have sub-Jovian masses. Further, we show that in the runaway regime,
migration can be directed outwards.


title: The high frequency power spectrum of Markarian 766

abstract:
  An analysis is presented of the power spectrum of X-ray variability of the
bright Seyfert 1 galaxy Mrk 766 as observed by XMM-Newton. Over the 0.2-10 keV
energy range the power spectral density (PSD) is well-represented by a
power-law with a slope of alpha_low ~ 1 at low frequencies, breaking to a slope
of alpha_hi = 2.8 (-0.4/+0.2) at a frequency f_br ~ 5 x 10^-4 Hz. As has been
noted before this broken power-law PSD shape is similar to that observed in the
Galactic black hole candidate Cygnus X-1. If it is assumed that Mrk 766 shows a
power spectrum similar in form to that of Cyg X-1, and that the break timescale
scales linearly with black hole mass, then the mass of the black hole in Mrk
766 is inferred to be < 5 x 10^5 M_sun. This rather low mass would mean Mrk 766
radiates above the Eddington limit. The coherence between different energy
bands is significantly below unity implying that variations in the different
energy bands are rather poorly correlated. The low coherence can be explained
in the framework of standard Comptonisation models if the properties of the
Comptonising medium are rapidly variable or if there are several distinct
emission sites.


title:
Highly accurate calculation of rotating neutron stars: Detailed
  description of the numerical methods

abstract:
  We give a detailed description of the recently developed multi-domain
spectral method for constructing highly accurate general-relativistic models of
rapidly rotating stars. For both "ordinary" and "critical" configurations, it
is exhibited by means of representative examples, how the accuracy improves as
the order of the approximation increases. Apart from homogeneous fluid bodies,
we also discuss models of polytropic and strange stars.


title: The Crab glitches: incidence and cumulative effect

abstract:
  The fourteen glitches observed during 33 years do not show the simple pattern
expected from a relaxation oscillator. They may however be regarded as three
major events separated by about 12 years, the third being a group of smaller
glitches. There is a step increase in slowdown rate at each glitch, whose
cumulative effect makes a significant contribution to the second differential
nu-ddot. The braking index "n" has previously been evaluated only between
glitches: the effect of the glitches is to reduce "n" from 2.51 to 2.45. This
extra effect due to the glitches would be explained by an increase in dipole
field at the fractional rate of 1.5x10^-5 per annum.


title:
Quantitative spectral analysis of early B-type supergiants in the
  Sculptor galaxy NGC 300

abstract:
  The spectra of two early B-type supergiant stars in the Sculptor spiral
galaxy NGC 300 are analysed by means of non-LTE line blanketed unified model
atmospheres, aimed at determining their chemical composition and the
fundamental stellar and wind parameters. For the first time a detailed chemical
abundance pattern (He, C, N, O, Mg and Si) is obtained for a B-type supergiant
beyond the Local Group. The derived stellar properties are consistent with
those of other Local Group B-type supergiants of similar types and
metallicities. One of the stars shows a near solar metallicity while the other
one resembles more a SMC B supergiant. The effects of the lower metallicity can
be detected in the derived wind momentum.


title: On E.D.Jones' Microcosmology

abstract:
  By taking seriously the limits on observability which come from combining
relativistic quantum mechanics with general relativity, Ed Jones has shown that
the current measurements of the cosmological constant density
$\Omega_{\Lambda}\sim 0.7$ imply that the temperature scale at which it becomes
possible to discuss cosmological models is $\sim 5 Tev$ ($5.8\times 10^{16} \
^oK$). This is self-consistent with the assumption that the number of Planck
masses which make some sort of ``phase transition'' to this state is
$N_{Pk}\sim 4\times 10^{61}$. We review Jones' argument and the {\it bit-string
physics} calculation which gives the baryon-photon ratio at nucleosynthesis as
$\sim 2/256^4$, the dark matter-baryon ratio as $\sim 12.7$, and hence
$\Omega_m \sim 0.3$, in agreement with current observations. Accepting these
values for the two energy densities $\Omega_{\Lambda}+\Omega_m \sim 1$ in
accord with recent analyses of fluctuations in the CMB showing that space is
flat to about 6%. We conclude that experiments with particle accelerators in
the 5-10 Tev range must either show that current theory can adequately describe
the currently observed structure of our universe or force us to revise our
ideas about physics at a very fundamental level.


title: Primordial Gravity Waves and Weak Lensing

abstract:
  Inflation produces a primordial spectrum of gravity waves in addition to the
density perturbations which seed structure formation. We compute the signature
of these gravity waves in the large scale shear field. In particular, the shear
can be divided into a gradient mode (G or E) and a curl mode (C or B). The
former is produced by both density perturbations and gravity waves, while the
latter is produced only by gravity waves, so the observations of a non-zero
curl mode could be seen as evidence for inflation. We find that the expected
signal from inflation is small, peaking on the largest scales at
$l(l+1)C_l/2\pi < 10^{-11}$ at $l=2$ and falling rapidly there after. Even for
an all-sky deep survey, this signal would be below noise at all multipoles.
Part of the reason for the smallness of the signal is a cancellation on large
scales of the standard line-of-sight effect and the effect of ``metric shear.''


title: Hot plasma in clusters of galaxies, the largest objects in the universe

abstract:
  Clusters of galaxies are the largest organized structures in the Universe.
They are important cosmological probes, since they are large enough to contain
a fair sample of the materials in the Universe, but small enough to have
achieved dynamical equilibrium. Clusters were first discovered as
concentrations of hundreds of bright galaxies in a region about 3 megaparsecs
(10 million light years) across. However, the dominant observed form of matter
in clusters is hot, diffuse intergalactic gas. This intracluster plasma has
typical temperatures of T ~ 7e7 K, and typical electron densities of n_e ~
10^{-3} cm^{-3}. This intracluster plasma mainly emits X-rays, and typical
cluster X-ray luminosities are L_X ~ 10^{43} - 10^{45} erg/s. The basic
properties of and physical processes in the intracluster plasma will be
reviewed. Important observational constraints on plasma processes in these
systems will be discussed. Recent X-ray observations of clusters of galaxies
with the orbiting Chandra X-ray Observatory will be highlighted.


title:
Blue Supergiants as a Tool for Extragalactic Distances - Empirical
  Diagnostics

abstract:
  Blue supergiant stars can be exceptionally bright objects in the optical,
making them prime targets for the determination of extragalactic distances. I
describe how their photometric and spectroscopic properties can be calibrated
to provide a measurement of their luminosity. I first review two well-known
techniques, the luminosity of the brightest blue supergiants and, with the aid
of recent spectroscopic data, the equivalent width of the Balmer lines. Next I
discuss some recent developments concerning the luminosity dependence of the
wind momentum and of the flux-weighted gravity, which can provide, if properly
calibrated, powerful diagnostics for the determination of the distance to the
parent galaxies.


title:
Relation between source and temperature fluctuations in photoionized
  nebulae

abstract:
  The magnitude of the temperature fluctuations (t^2) required to explain the
observed inconsistencies between metallicities inferred from recombination
lines and from forbidden lines cannot be attained by steady-state equilibrium
photoionization models. If on the other hand the nebular ionizing source was
variable, the temperature fluctuations t^2 would be significantly larger. We
investigate the time-dependent response of the nebular ionization and
temperature structure when photoionized by a periodically varying source. We
study how the asymptotic mean value, <t^2>, behaves as a function of the period
or amplitude of the source variability. We find that the temperature
fluctuations occur only in the outer section of the nebula, close to the
ionization front, within a zone corresponding to 8-20% of the ionized layer's
thickness. We conclude that the amplitude of the exciting star variations
required to achieve a <t^2> = 0.025 (as in the Orion nebula) is unacceptably
large. Source variability is therefore not a viable mechanism to explain the
observed values of t^2. We reach a similar conclusion from studies of the
temporal variability resulting from intermittent shadows behind opaque
condensations. We find that photoionized nebulae are on average less massive
but somewhat hotter in the case of cyclicly variable ionizing sources.


title:
Physics of Gamma-Ray Bursts: Turbulence, Energy Transfer and
  Reconnection

abstract:
  Understanding of the nature of gamma-ray bursts (GRBs) is one of the
challenging problem facing the astrophysics community. The field of gamma ray
bursts is a rapidly developing one and we expect that new missions, like SWIFT
and GLAST will bring the field to a new quantitative level. The detail of the
explosion, the formation of the fireball, its propagation, the generation of
the shocks, the source of the magnetic fields and soft photons, the particle
acceleration process, and the details of the radiation process are all still
outstanding questions. The goal of this review is to attract the attention of
the community to a number of physical processes (MHD turbulence and particle
acceleration, magnetic reconnection, etc.) that seem to be very relevant for
these sources.


title: Quantitative Spectroscopy of Supergiants

abstract:
  Blue supergiants of spectral types B and A are the visually brightest stars
in spiral and irregular galaxies, with their most luminous members (at M_V=-10)
outshining entire dwarf galaxies. This characteristic allows us to use them as
probes to study the Local Universe in great detail. In principle, already the
existing large telescopes and instrumentation facilitate quantitative
spectroscopy of these objects as far as the Virgo and Fornax clusters of
galaxies. Beyond their challenging stellar atmospheres and opportunities for
testing sophisticated non-LTE physics they offer numerous applications to
modern astrophysics. Quantitative spectroscopy of supergiants can contribute to
improve our understanding of massive star evolution. Galactic abundance
gradients and abundance patterns, as can be obtained from studies of large
ensembles of supergiants in our own and other galaxies, will foster the
understanding of galactochemical evolution. Finally, they are promising
independent indicators for calibrating the extragalactic distance scale, by
application of the wind momentum-luminosity and the flux-weighted
gravity-luminosity relationships. In view of this large potential, the
objective of this thesis is to improve the status of quantitative spectroscopy
of BA-type supergiants and to provide first applications on a sample of
Galactic and extragalactic targets, within the Local Group and beyond.


title: X-Ray IGM in the Local Group

abstract:
  Recent observations with the dispersive X-ray spectrometers aboard Chandra
and Newton Observatory have begun to probe the properties of the X-ray
intergalactic medium (IGM) at small redshifts. Using large quantities (~950
ksec) of spectroscopic data acquired using the RGS aboard Newton Observatory,
we investigated the intervening material toward three low redshift, high
Galactic latitude AGNs with nominally featureless spectra: Mrk421, PKS2155-304
and 3C273. Each spectrum provides clear evidence for what appears to be a local
(z~0), highly ionized absorbing medium betrayed by the OVII 1s-2p resonance
transition feature seen at 21.6A (N[OVII] ~ 1E16 cm-2). Measurements are also
made for the Lyman alpha transition of the adjacent ionization state, (OVIII;
18.97A), which potentially constrains the absorber's temperature. Finally, in a
collisional equilibrium approximation, upper limits to diffuse emission
intensities place upper limits on the electron density (ne < 2E-4 cm-3), lower
limits on the scale length of the absorber (L > 140 kpc) and lower limits on
its mass (M > 5E10 M[sun]). Limits on the absorber's scale length and its
velocity distribution lead us to identify it with the Local Group.


title:
The phase coherence of light from extragalactic sources - direct
  evidence against first order Planck scale fluctuations in time and space

abstract:
  We present a method of directly testing whether time continues to have its
usual meaning on scales of <= t_P = sqrt(hbar G/c^5) ~ 5.4E-44 s, the Planck
time. According to quantum gravity, the time t of an event cannot be determined
more accurately than a standard deviation of the form sigma_t/t = a_o
(t_P/t)^a, where a_o and a are positive constants ~1; likewise distances are
subject to an ultimate uncertainty c \sigma_t, where c is the speed of light.
As a consequence, the period and wavelength of light cannot be specified
precisely; rather, they are independently subject to the same intrinsic
limitations in our knowledge of time and space, so that even the most
monochromatic plane wave must in reality be a superposition of waves with
varying omega and {\bf k}, each having a different phase velcocity omega/k. For
the entire accessible range of the electromagnetic spectrum this effect is
extremely small, but can cumulatively lead to a complete loss of phase
information if the emitted radiation propagated a sufficiently large distance.
Since, at optical frequencies, the phase coherence of light from a distant
point source is a necessary condition for the presence of diffraction patterns
when the source is viewed through a telescope, such observations offer by far
the most sensitive and uncontroversial test. We show that the HST detection of
Airy rings from the active galaxy PKS1413+135, located at a distance of 1.2
Gpc, secures the exclusion of all first order (a=1) quantum gravity
fluctuations with an amplitude a_o > 0.003. The same result may be used to
deduce that the speed of light in vacuo is exact to a few parts in 10^32.


title: SDSS Catalog of Stars in the Draco Dwarf Spheroidal Galaxy

abstract:
  The Sloan Digital Sky Survey (SDSS) has scanned the entire region containing
the Draco dwarf spheroidal galaxy to 23rd magnitude in g*. We present a catalog
of stars found in a 453 square arcminute, elliptical region centered on the
Draco dwarf spheroidal galaxy. Objects in the catalog are matched with five
previously published catalogs. The catalog contains SDSS photometry for 5634
individual objects, and also the photometry from matches to any of the other
catalogs. A comparison of the photometry between catalogs allows us to identify
142 candidate variable objects. One hundred and twelve of the suspected
variables have colors consistent with RR Lyrae variables.


title: The Lyman-alpha Forest as a Cosmological Tool

abstract:
  We review recent developments in the theory of the Lyman-alpha forest and
their implications for the role of the forest as a test of cosmological models.
Simulations predict a relatively tight correlation between the local Lya
optical depth and the local gas or dark matter density. Statistical properties
of the transmitted flux can constrain the amplitude and shape of the matter
power spectrum at high redshift, test the assumption of Gaussian initial
conditions, and probe the evolution of dark energy by measuring the Hubble
parameter H(z). Simulations predict increased Lya absorption in the vicinity of
galaxies, but observations show a Lya deficit within Delta_r ~ 0.5 Mpc/h
(comoving). We investigate idealized models of "winds" and find that they must
eliminate neutral hydrogen out to comoving radii ~1.5 Mpc/h to marginally
explain the data. Winds of this magnitude suppress the flux power spectrum by
\~0.1 dex but have little effect on the distribution function or threshold
crossing frequency. In light of the stringent demands on winds, we consider the
alternative possibility that extended Lya emission from target galaxies
replaces absorbed flux, but we conclude that this explanation is unlikely.
Taking full advantage of the data coming from large telescopes and from the
Sloan Digital Sky Survey will require more complete understanding of the galaxy
proximity effect, careful attention to continuum determination, and more
accurate numerical predictions, with the goal of reaching 5-10% precision on
key cosmological quantities.


title:
The Hubble Space Telescope WFPC2 B-Band Parallel Survey: A Study of
  Galaxy Morphology for 18 < B < 27 mag

abstract:
  [Abridged] We present the results of the HST B-Band Parallel Survey (BBPS).
It covers 0.0370 sq. deg. and consists of 31 shallow (4-6 orbit), randomly
selected high latitude HST WFPC2 parallel fields with images taken in both the
B (F450W) and I (F814W) filters. The goal is to morphologically classify the
galaxies in a homogeneous manner and study galaxy properties as a function of
type and B-band magnitude for 18<b_J<23.5 mag. The B-band selected galaxies are
classified using an artificial neural network (ANN) galaxy classifier on the
higher S/N I-band images. These provide reliable types for I<24 mag (or b_J<26
mag), since these I-band classifications are less subject to the uncertain
redshifted rest-frame UV morphology. The ANN classification depends on the
shape of the surface brightness profile, but not on color. These results are
combined with deeper studies in the HDF-N and the deep WFPC2 field surrounding
the radio galaxy 53W002, for which galaxies have been classified to b_J<27 mag.
The galaxy counts for the combined B-band selected samples show adequate
statistics for a range 19<b_J<27 mag, and are in good agreement with other
studies in the flux range where they overlap, while showing improved statistics
at the bright end. The galaxies are divided into 3 morphological classes: E/S0,
Sabc and Sd/Irr, and the B-band counts are presented for each class, as well as
the total counts. The faint end of the counts is dominated by the Sd/Irr
galaxies. These type dependent counts are compared to models based on local
luminosity functions which include the effects of the Cosmological Constant.
The BBPS sample, along with the two deeper fields, is used to delineate the
general trends of effective radius and (B-I) color as a function of both
morphological type and apparent magnitude 18<b_J<27 mag.


title: Direct Detection Constraints on Superheavy Dark Matter

abstract:
  The dark matter in the Universe might be composed of superheavy particles
(mass >~ 10^10 GeV). These particles can be detected via nuclear recoils
produced in elastic scatterings from nuclei. We estimate the observable rate of
strongly interacting supermassive particles (simpzillas) in direct dark matter
search experiments. The simpzilla energy loss in the Earth and in the
experimental shields is taken into account. The most natural scenarios for
simpzillas are ruled out based on recent EDELWEISS and CDMS results. The dark
matter can be composed of superheavy particles only if these interact weakly
with normal matter or if their mass is above 10^15 GeV.


title:
Multi-transonic Black Hole Accretion Discs with Isothermal Standing
  Shocks

abstract:
  In this work we would like to address the issue of shock formation in black
hole accretion discs. We provide a {\it generalized two parameter solution
scheme} for multi-transonic, accretion and wind around Schwarzschild black
holes, by mainly concentrating on accretion solutions which may contain steady,
standing isothermal shocks. Such shocks conserve flow temperature by the
dissipation of energy at the shock location.Unlike previous works in this
field, our calculation is {\it not} restricted to any particular kind of
post-Newtonian gravitational potentials, rather we use {\it all} available
pseudo-Schwarzschild potentials to formulate and solve the equations governing
the accretion and wind only in terms of flow temperature $T$ and specific
angular momentum $\lambda$ of the flow. Our generalized formalism assures that
the shock formation is not just an artifact of a particular type of
gravitational potential, rather inclusion of all available black-hole
potentials demonstrates a substantially extended zone of parameter space
allowing for the possibility of shock formation. We thus arrive at the
conclusion that the standing shocks are essential ingredients in rotating,
advective accretion flows of isothermal fluid around a non-spinning
astrophysical black hole. Types of shocks discussed in this paper may appear to
be `bright' because of the huge amount of energy dissipation at shock, and the
quick removal of such energy to maintain the isothermality may power the strong
X-ray flares recently observed to be emerged from our Galactic centre.
  The results are discussed in connection to other astrophysical phenomena of
related interest, such as the QPO behaviour of galactic black hole candidates.
(Abridged).


title:
Phase-Induced Amplitude Apodization of Telescope Pupils for Extrasolar
  Terrestrial Planet Imaging

abstract:
  In this paper, an alternative to the classical pupil apodization techniques
(use of an amplitude pupil mask) is proposed. It is shown that an apodized
pupil suitable for imaging of Extrasolar planets can be obtained by reflection
of an unapodized flat wavefront on 2 mirrors. By carefully choosing the shape
of these 2 mirrors, it is possible to obtain a contrast better than 10^{9} at a
distance smaller than 2 \lambda/d from the optical axis. Because this technique
preserves both the angular resolution and light gathering capabilities of the
unapodized pupil, it allows efficient detection of terrestrial extrasolar
planets with a 1.5m telescope in the visible.


title: The Frequency and Radio Properties of Broad Absorption Line Quasars

abstract:
  A sample of 67 Broad Absorption Line quasars (BALQSOs) from the Large Bright
Quasar Survey (LBQS) is used to estimate the observed and intrinsic fraction of
BAL quasars in optically--selected samples at intermediate (B_J \simeq 18.5)
magnitudes. The observed BALQSO fraction in the redshift range 1.5 < z < 3.0 is
15\pm3%. A well--determined, empirical, k--correction, to allow for the
differences in the spectral energy distributions of non--BALQSOs and BALQSOs
shortward of \simeq 2100A in the restframe, is applied to the sample. The
result is an estimate of the intrinsic fraction of BALQSOs, in the redshift
range 1.5 < z < 3.0, of 22+/-4%. This value is twice that commonly cited for
the occurrence of BALQSOs in optically--selected samples and the figure is in
reasonable agreement with that from a preliminary analysis of the SDSS Early
Data Release. The fraction of BALQSOs predicted to be present in an optical
survey with flux limits equivalent to that of the FIRST Bright Quasar Survey
(FBQS) is shown to be \simeq 20%. The BALQSO fractions derived from the FBQS
and the LBQS suggest that optically--bright BALQSOs are half as likely as
non-BALQSOs to be detectable as S_1.4GHz > 1mJy radio sources.


title:
Probing dark energy with the CMB: projected constraints from WMAP and
  Planck

abstract:
  We investigate the accuracy attainable by forthcoming space-based
observations of the cosmic microwave background (CMB) temperature and
polarization anisotropy in constraining the dark energy density parameter $\Oq$
and equation of state $\wq=p_{\rm Q}/\rho_{\rm Q}$. Despite degeneracies among
parameters, it is possible for high precision observations such as those from
WMAP and Planck to provide interesting information on the nature of the dark
energy. Furthermore, we show that imposing a flat universe constraint makes it
possible to obtain tight limits in the space of dark energy parameters even
from the CMB alone.


title:
New Constraints on the Energetics, Progenitor Mass, and Age of the
  Supernova Remnant G292.0+1.8 Containing PSR J1124-5916

abstract:
  We present spatially resolved spectroscopy of the supernova remnant (SNR)
G292.0+1.8 with the Chandra X-ray observatory. This SNR contains the 135 ms
pulsar, J1124-5916. We apply non-equilibrium ionization (NEI) models to the
data. By comparing the derived abundances with those predicted from
nucleosynthesis models, we estimate a progenitor mass of 30-40 solar masses. We
also derive the intrinsic parameters of the supernova explosion such as its
energy, the age of the SNR, the blast wave velocity, and the swept-up mass. In
the Sedov interpretation, our estimated SNR age of 2,600 years is close to the
pulsar's characteristic age of 2,900 years. This confirms the pulsar/SNR
association and relaxes the need for the pulsar to have a non-canonical value
for the braking index, a large period at birth or a large transverse velocity.
We discuss the properties of the pulsar wind nebula (PWN) in the light of the
Kennel and Coroniti model and estimate the pulsar wind magnetization parameter.
We also report the first evidence for steepening of the power law spectral
index with increasing radius from the pulsar.


title: The little galaxy that could: Kinematics of Camelopardalis B

abstract:
  We present deep, high velocity resolution (1.6 km/s) GMRT HI as well as
optical data for the faint (M_B ~ -10.9) galaxy Camelopardalis B. We find that
the HI in the galaxy has a regular velocity field, consistent with rotational
motion. The implied kinematical major axis is well aligned with the major axis
of both the HI and optical images. Cam B is the faintest known galaxy with such
relatively well behaved kinematics. From the HI velocity field we derive a
rotation curve for the galaxy. The peak (inclination corrected) rotation
velocity is only 7km/s, comparable to the observed velocity dispersion. After
correcting the observed rotation velocities for random motions (the "asymmetric
drift" correction) we find a corrected peak rotation velocity of ~ 20 km/s. On
fitting mass models to corrected rotation curve we find that the kinematics of
Cam B is well fit with a modified isothermal halo with central density $\rho_0$
approximately 12.0 $M_\odot$ pc$ ^{-3}$. This derived central density has only
a very weak dependence on the assumed M/L ratio of the stellar disk. We also
find that the corrected rotation curve cannot be fit with an NFW halo
regardless of the assumed M/L ratio. We compile from the literature a sample of
galaxies with rotation curves obtained from HI synthesis observations. From
this sample (which has an absolute magnitude range of ~ 12) we find (i) that
Cam B lies on the Tully-Fisher relation defined by these galaxies, provided we
use the corrected rotation velocity, and (ii) a weak trend for increasing halo
central density with decreasing galaxy size. Such a trend is expected in
hierarchical models of halo formation.


title: Hard X-ray timing and spectral properties of PSR B0540-69

abstract:
  We report the hard X-ray properties of the young Crab-like LMC pulsar PSR
B0540-69, using archival RXTE PCA (2 - 60 keV) and RXTE HEXTE (15 - 250 keV)
data. Making use of the very long effective exposure of 684 ks, we derived a
very detailed master pulse profile for energies 2 - 20 keV. We confirm the
broad single-pulse shape with a dip in the middle and with a significant fine
structure to the left of the dip. For the first time pulse profiles in the 10 -
50 keV energy interval are shown. Remarkably, the coarse pulse shape is stable
from the optical up to X-ray energies analogous to the case of the Crab pulsar
(PSR B0531+21). The profiles can be described with two Gaussians with a phase
separation of ~0.2; the distribution of the ratios between the two components
from the optical to the X-ray range is consistent with being flat. Therefore we
cannot conclude that the profile consists of two distinct components. We also
derived a new total pulsed spectrum in the ~0.01 - 50 keV range in a consistent
analysis including also archival ROSAT PSPC (0.01 - 2.5 keV) data. This
spectrum cannot be described by a single power-law, but requires an additional
energy dependent term. The bending of the spectrum around 10 keV resembles that
of the Crab pulsar spectrum. Although model calculations using Outer Gap
scenarios could probably explain the high-energy characteristics of PSR
B0540-69 as they successfully do for the Crab, our measurements do not entirely
agree with the latest calculations by Zhang & Cheng (2000). The small
discrepancies are likely to be caused by uncertainties in the pulsar's
geometry.


title: Cosmic Ray Astrophysics and Hadronic Interactions

abstract:
  Research in cosmic rays is now nearly a century old, but most of the
fundamental questions in this field remain unanswered, on the other hand the
perspectives of future studies in the next decade are very bright. New
detectors will provide higher quality data in the entire energy range from 10^8
to 10^{20} eV (or more if particles of higher energy have non negligible
fluxes), moreover cosmic ray astrophysics must now be considered, together with
gamma, neutrino and gravitational wave astronomy, as one of the subfields of
high energy astrophysics, and using information from these four "messengers"
there is the potential of a detailed understanding of the origin of the high
energy radiation in the universe. High energy cosmic rays are measured
indirectly observing the showers they generate in the atmosphere, and a correct
and detailed interpretation of these measurements will require an improved
understanding of the properties of hadronic interactions. The new collider
experiments, and in particular the LHC project at CERN offer the unique
possibility to perform measurements of great value for cosmic ray astrophysics.
It is of great importance for cosmic research that this possibility is fully
exploited with the appropriate instrumentation and analysis.


title:
Changes in the measured image separation of the gravitational lens
  system, PKS 1830-211

abstract:
  We present eight epochs of 43 GHz, dual-polarisation VLBA observations of the
gravitational lens system PKS 1830-211, made over fourteen weeks. A bright,
compact ``core'' and a faint extended ``jet'' are clearly seen in maps of both
lensed images at all eight epochs.
  The relative separation of the radio centroid of the cores (as measured on
the sky) changes by up to 87 micro arcsec between subsequent epochs.
  A comparison with the previous 43 GHz VLBA observations (Garrett et al. 1997)
made 8 months earlier show even larger deviations in the separation of up to
201 micro arcsec. The measured changes are most likely produced by changes in
the brightness distribution of the background source, enhanced by the
magnification of the lens. A relative magnification matrix that is applicable
on the milliarcsecond scale has been determined by relating two vectors (the
``core-jet'' separations and the offsets of the polarised and total intensity
emission) in the two lensed images. The determinant of this matrix,
  -1.13 +/-0.61, is in good agreement with the measured flux density ratio of
the two images. The matrix predicts that the 10 mas long jet, that is clearly
seen in previous 15 and 8.4 GHz VLBA observations (Garrett et al. 1997,
  Guirado et al. 1999), should correspond to a 4 mas long jet trailing to the
south-east of the SW image. The clear non-detection of this trailing jet is a
strong evidence for sub-structure in the lens and may require more realistic
lens models to be invoked, e.g. Nair & Garrett (2000).


title: Ly-alpha emission from GRB host galaxies

abstract:
  Ly-alpha emission is indicative of on-going star formation in a dust-poor
environment. Ly-alpha imaging is therefore a probe of the star formation rate
and of the dust-content of Gamma-Ray Burst host galaxies. Both of these
parameters are central to our understanding of GRB progenitors and of how the
environments affect the propagation of afterglow emission out of host galaxies.
We have started a program aimed at imaging high redshift (z>2) host galaxies of
GRBs at the Ly-alpha resonance line from neutral hydrogen. Here were report the
results from imaging of the fields of GRB 000301C and GRB 000926 and outline
upcoming observations of further hosts.


title: Time Since the Beginning

abstract:
  While there is no consensus about the history of time since the beginning, in
this paper I will discuss some possibilities. We have a pretty clear picture of
cosmic history from the electroweak phase transition through the time of
recombination, a period which includes the QCD phase transition and big bang
nucleosynthesis. This paper includes a quantitative discussion of the age of
the universe, of the radiation-matter transition, and of hydrogen
recombination. There is much evidence that at earlier times the universe
underwent inflation, but the details of how and when inflation happened are
still far from certain. There is even more uncertainty about what happened
before inflation, and how inflation began. I will describe the possibility of
``eternal'' inflation, which proposes that our universe evolved from an
infinite tree of inflationary spacetime. Most likely, however, inflation can be
eternal only into the future, but still must have a beginning.


title:
Comparison of EISCAT Radar Data on Space Debris with Model Prediction by
  the MASTER Model of ESA

abstract:
  In the effort to obtain low cost routine space debris observations in low
Earth orbit, ESA plans to utilise the radar facilities of the European
Incoherent Scatter Scientific Association. First demonstration measurements
were performed from 11 to 23 February 2001. In total $16{\rm hours}$ of radar
signals were collected. Here we compare these initial measurements with the
predictions of the ESA MASTER/PROOF'99 model in order to assess the sensitivity
as well as the reliability of the data. We find that while the determination of
object size needs to be reviewed, the altitude distribution provides a good fit
to the model prediction. The absolute number of objects detected in the various
altitude bins indicates that the coherent integration method indeed increases
the detection sensitivity when compared to incoherent integration. In the data
presented here integration times from 0.1 to $0.3{\rm s}$ were used. As
expected, orbit information cannot be obtained from the measurements if they
are linked to ionospheric measurements as planned. In addition routine space
debris observations provide also useful information for the validation of
large-object catalogues.


title:
A mid-infrared spectroscopic survey of starburst galaxies: excitation
  and abundances

abstract:
  We present spectroscopy of MIR emission lines in twelve starburst regions,
located in eleven starburst galaxies, for which a significant number of lines
between 2.38 and 45micron were observed with the ISO Short Wavelength
Spectrometer, with the intention of providing a reference resource for MIR
spectra of starburst galaxies. The observation apertures were centred on
actively star forming regions, including those which are inaccessible at
optical wavelengths due to high levels of obscuration. We use this data set,
which includes fine structure and hydrogen recombination lines, to investigate
excitation and to derive gas phase abundances of neon, argon, and sulphur of
the starburst galaxies. The derived Ne abundances span approximately an order
of magnitude, up to values of ~3 times solar. The excitation ratios measured
from the Ne and Ar lines correlate well with each other (positively) and with
abundances (negatively). Both in excitation and abundance, a separation of
objects with visible Wolf-Rayet features (high excitation, low abundance) is
noted from those without (low excitation, high abundance). For a given
abundance, the starbursts are of relatively lower excitation than a comparative
sample of HII regions, possibly due to ageing stellar populations. By
considering the abundance ratios of S with Ne and Ar we find that, in our
higher metallicity systems, S is relatively underabundant by a factor of ~3. We
discuss the origin of this deficit and favour depletion of S onto dust grains
as a likely explanation. This weakness of the MIR fine structure lines of S has
ramifications for future infrared missions such as SIRTF and Herschel since it
indicates that the S lines are less favourable tracers of star formation than
is suggested by nebular models which do not consider this effect.


title:
On the Coupling between Helium Settling and Rotation-Induced Mixing in
  Stellar Radiative Zones: I- Analytical Approach

abstract:
  In the presence of rotation-induced mixing, element diffusion still occurs in
stellar radiative zones, although at a slower rate than in the case of a
complete stability of the stellar gas. As a consequence, helium settling leads
to vertical $\displaystyle \mu $-gradients which, due to the meridional
circulation, turn into horizontal fluctuations. Up to now, the feed-back effect
of this process on the rotation-induced mixing was currently neglected in the
computations of abundance variations in stellar surfaces, or artificially
reduced. Here we analyse its consequences and derive an approximate analytical
solution in a quasi-stationary case. We also discuss the relative importance of
the various physical effects which influence the meridional circulation
velocity. In a second paper (Th\'eado and Vauclair 2002a), we will present a
complete 2D numerical simulation of this process while a third paper (Th\'eado
and Vauclair 2002b) will be devoted to special applications to Pop I stars.


title:
On the Coupling between Helium Settling and Rotation-Induced Mixing in
  Stellar Radiative Zones: II- Application to light elements in population I
  main-sequence stars

abstract:
  In the two previous papers of this series, we have discussed the importance
of t he $\mu$-gradients due to helium settling on rotation-induced mixing,
first in a n approximate analytical way, second in a 2D numerical simulation.
We have found that, for slowly rotating low mass stars, a process of ``creeping
paralysis" in which the circulation and the diffusion are nearly frozen may
take place below the convective zone. Here we apply this theory to the case of
lithium and beryll ium in galactic clusters and specially the Hyades. We take
into account the rota tional braking with rotation velocities adjusted to the
present observations. We find that two different cells of meridional
circulation appear on the hot side of the "lithium dip" and that the "creeping
paralysis" process occurs, not dir ectly below the convective zone, but deeper
inside the radiative zone, at the to p of the second cell. As a consequence,
the two cells are disconnected, which ma y be the basic reason for the lithium
increase with effective temperature on thi s side of the dip. On the cool side,
there is just one cell of circulation and t he paralysis has not yet set down
at the age of the Hyades; the same modelisatio n accounts nicely for the
beryllium observations as well as for the lithium ones .


title: Circumstellar features in hot DA white dwarfs

abstract:
  We present a phenomenological study of highly ionised, non-photospheric
absorption features in high spectral resolution vacuum ultraviolet spectra of
23 hot DA white dwarfs. Prior to this study, four of the survey objects (Feige
24, REJ 0457-281, G191-B2B and REJ 1614-085) were known to possess these
features. We find four new objects with multiple components in one or more of
the principal resonance lines: REJ 1738+665, Ton 021, REJ 0558-373 and WD
2218+706. A fifth object, REJ 2156-546 also shows some evidence of multiple
components, though further observations are required to confirm the detection.
We discuss possible origins for these features including ionisation of the
local interstellar environment, the presence of material inside the
gravitational well of the white dwarf, mass loss in a stellar wind, and the
existence of material in an ancient planetary nebula around the star. We
propose ionisation of the local interstellar medium as the origin of these
features in G191-B2B and REJ 1738+665, and demonstrate the need for higher
resolution spectroscopy of the sample, to detect multiple ISM velocity
components and to identify circumstellar features which may lie close to the
photospheric velocity.


title: Gamma-ray emission from Cassiopeia A produced by accelerated cosmic rays

abstract:
  The nonlinear kinetic model of cosmic ray (CR) acceleration in supernova
remnants (SNRs) is used to describe the relevant properties of Cassiopeia A
(Cas A). In order to reproduce the SNR's observed size, expansion rate and
thermal X-ray emission we employ a piecewise homogeneous model for the
progenitor's circumstellar medium developed by Borkowski et al. (1996). It
consists of a tenuous inner wind bubble, a dense shell of swept-up red
supergiant wind material, and a subsequent red supergiant wind region. A quite
large SNR interior magnetic field B_d approx 1 mG is required to give a good
fit for the radio and X-ray synchrotron emission. The steep radio spectrum is
consistent with efficient proton acceleration which produces a significant
shock modification and leads to a steep electron spectrum at energies E_e < 1
GeV. The calculated integral gamma-ray flux from Cas A, F propto E_gamma^-1, is
dominated by pi^0-decay gamma-rays due to relativistic protons. It extends up
to roughly 30 TeV if CR diffusion is as strong as the Bohm limit. At TeV
energies it satisfactorily agrees with the value 5.8 x 10^-13 cm^-2 s^-1
detected by the HEGRA collaboration.


title: Deep images of cluster radio halos

abstract:
  New radio data are presented for the clusters A401, A545, A754, A1914, A2219
and A2390, where the presence of diffuse radio emission was suggested from the
images of the NRAO VLA Sky Survey. Sensitive images of these clusters, obtained
with the Very Large Array (VLA)at 20 cm confirm the existence of the diffuse
sources and allow us to derive their fluxes and intrinsic parameters.The
correlation between the halo radio power and cluster X-ray luminosity is
derived for a large sample of halo clusters, and is briefly discussed.


title: Crowding in the GAIA spectrograph focal plane

abstract:
  Superpositions of stellar tracings are present in every slitless
spectrograph. The probability for such overlaps in the GAIA RVS spectrograph
focal plane is estimated using photometric observations of 66 stellar fields,
mostly close to the Galactic plane. It is shown that overlaps of bright stars
(V<17) are common near the Galactic plane, and no spectrum is free from
superpositions of faint star tracings. Most overlappers are of spectral type K.


title:
Spectral variations of the X-ray binary pulsar LMC X-4 during its long
  period intensity variation and a comparison with Her X-1

abstract:
  We present spectral variations of the binary X-ray pulsar LMC X-4 using the
RXTE/PCA observations at different phases of its 30.5 day long super-orbital
period. Only out of eclipse data were used for this study. During the high
state of the super-orbital period of LMC X-4, the spectrum is well described by
a high energy cut-off power-law with a photon index in the range of 0.7-1.0 and
an iron emission line. In the low state, the spectrum is found to be flatter
with power-law photon index in the range 0.5-0.7. A direct correlation is
detected between the continuum flux in 7-25 keV energy band and the iron
emission line flux. The equivalent width of the iron emission line is found to
be highly variable during low intensity state, whereas it remains almost
constant during the high intensity state of the super-orbital period. It is
observed that the spectral variations in LMC X-4 are similar to those of Her
X-1 (using RXTE/PCA data). These results suggest that the geometry of the
region where the iron line is produced and its visibility with respect to the
phase of the super-orbital period is similar in LMC X-4 and Her X-1. A
remarkable difference between these two systems is a highly variable absorption
column density with phase of the super-orbital period that is observed in Her
X-1 but not in LMC X-4.


title: Information recovery from overlapping GAIA spectra

abstract:
  The RVS instrument aboard GAIA is a slitless spectrograph, so some spectral
tracing overlap is inevitable. We show that this background can be accurately
modeled and subtracted. Radial velocity accuracy is not degraded significantly
unless the star density is higher than the value typical for the Galactic
plane.


title:
The Optical Gravitational Lensing Experiment. Planetary and
  Low-Luminosity Object Transits in the Carina Fields of the Galactic Disk

abstract:
  We present results of the second planetary and low-luminosity object transit
campaign conducted by the OGLE-III survey. Three fields (35'x35' each) located
in the Carina regions of the Galactic disk (l~290) were monitored continuously
in February-May 2002. About 1150 epochs were collected for each field. The
search for low depth transits was conducted on about 103000 stars with
photometry better than 15 mmag. In total, we discovered 62 objects with shallow
depth (<0.08 mag) flat-bottomed transits. For each of these objects several
individual transits were detected and photometric elements were determined.
Also lower limits on radii of the primary and companion were calculated. The
2002 OGLE sample of stars with transiting companions contains considerably more
objects that may be Jupiter-sized (R<1.6 R_Jup) compared to our 2001 sample.
There is a group of planetary candidates with the orbital periods close to or
shorter than one day. If confirmed as planets, they would be the shortest
period extrasolar planetary systems. In general, the transiting objects may be
extrasolar planets, brown dwarfs, or M-type dwarfs. One should be, however,
aware that in some cases unresolved blends of regular eclipsing stars can mimic
transits. Future spectral analysis and eventual determination of the amplitude
of radial velocity should allow final classification. High resolution
spectroscopic follow-up observations are, therefore, strongly encouraged. All
photometric data are available from the OGLE Internet archive.
  Note added for astro-ph version: One of the best planetary candidates from
the OGLE 2001 campaign, OGLE-TR-56, has recently been confirmed as a planetary
system by Konacki, Torres, Jha and Sasselov [astro-ph/0301052].


title:
The SED of the TeV BLLac 1ES 1426+428 after correction for the TeV--IR
  absorption

abstract:
  The recent HEGRA detection and spectrum of 1ES 1426+428 at TeV energies, once
corrected for absorption using present estimates of the diffuse extragalactic
IR background, suggest that the high energy peak of the Spectral Energy
Distribution (SED) could be much higher than the synchrotron one
($L_c/L_s>10$), and lie at energies above 8-10 TeV. To see if such an SED could
be accounted for, we have applied a "finite injection time" SSC model, and
present here some preliminary results. Within this model, we found the need of
an external ("ambient") contribution to the energy density of seed photons, in
order to account for both the high Compton dominance and the hard spectrum.


title: Grids of synthetic spectra for the GAIA mission

abstract:
  Two sets of grids of Kurucz ATLAS~9 model spectra are presented. The first
one covers the GAIA spectral interval, while the second one which is still
being computed covers the whole range from 2500 -- 10500 \AA. Both grids
include parameters needed for realistic spectral simulation, e.g. stellar
rotation and are computed at R=20000 and lower spectral resolutions. They can
be useful for preparation of the GAIA and RAVE missions and also for a general
radial velocity correlation work


title: Observational tests of the GAIA expected harvest on eclipsing binaries

abstract:
  GAIA observations of eclipsing binary stars will have a large impact on
stellar astrophysics. Accurate parameters, including absolute masses and sizes
will be derived for $\sim 10^4$ systems, orders of magnitude more than what has
ever been done from the ground. Observations of 18 real systems in the
GAIA-like mode as well as with devoted ground-based campaigns are used to
assess binary recognition techniques, orbital period determination, accuracy of
derived fundamental parameters and the need to automate the whole reduction and
interpretation process.


title:
Detailed Kinematic Study of the Ionized and Neutral Gas in the Complex
  of Star Formation in the Galaxy IC 1613

abstract:
  We carried out detailed kinematic studies of the complex of multiple HI and
HII shells that represent the only region of ongoing star formation in the
dwarf irregular galaxy IC 1613. We investigated the ionized-gas kinematics by
using Fabry--Perot H-alpha observations with the 6-m Special Astrophysical
Observatory telescope and the neutral-gas kinematics by using VLA 21-cm radio
observations. We identified three extended (300-350 pc) neutral shells with
which the brightest HII shells in the complex of star formation are associated.
The neutral-gas kinematics in the complex has been studied for the first time
and the H~I shells were found to expand at a velocity of 15--18 km/s. We
constructed velocity ellipses for all HII shells in the complex and refined
(increased) the expansion velocities of most of them. The nature of the
interacting ionized and neutral shells is discussed.


title: Nature of Dark Energy and Polarization Measurements

abstract:
  High sensitivity polarization measures, on wide angular scales, together with
data on anisotropy, can be used to fix DE parameters. In this paper, first of
all, we aim to determine the sensitivity needed to provide significant limits.
Our analysis puts in evidence that there is a class of DE models that
polarization measures can possibly exclude soon. This class includes models
with DE due to a Ratra-Peebles (RP) potential. Using a likelihood analysis, we
show that it is possible to distinguish RP models from LCDM and other dynamical
DE models, already with the sensitivity of experiments like SPOrt or WMAP,
thanks to their negative TE correlation at low-l, when the optical depth tau is
sufficiently large. On the contrary, fixing the energy scale Lambda for RP
potentials or distinguishing between LCDM and other DE potentials requires a
much lower pixel noise, that no planned polarization experiment will achieve.
While reviewing this paper after the referee report, the first-year WMAP data
were released. WMAP finds large positive anisotropy-polarization correlations
at low l; this apparently excludes DE models with RP potentials.


title: Correlated long-term optical and X-ray variations in NGC 5548

abstract:
  We combine the long-term optical light curve of the Seyfert 1 galaxy NGC5548
with the X-ray light curve measured by the Rossi X-ray Timing Explorer over 6
years, to determine the relationship between the optical and X-ray continua.
The X-ray light curve is strongly correlated with the optical light curve on
long (~year) time-scales. The amplitude of the long-term optical variability in
NGC5548 is larger than that of the X-ray variability (after accounting for the
host galaxy contribution), implying that X-ray reprocessing is not the main
source of the optical/X-ray correlation. The correlated X-ray and optical
variations in NGC5548 may be caused by instabilities in the inner part of the
accretion flow, where both the X-ray and optical emission regions may be
located.


title: The Magnetic Field Geometry in DR21

abstract:
  We present broadband imaging polarimetry of DR21 at 2.2$\mu$m. Background
stars shining through the lobes of the bipolar outflow show polarization
aligned with the long axis of the outflow, indicating a magnetic field geometry
oriented along the flow axis. There is no indication of a spiral or turbulent
magnetic field geometry in the lobes. The polarization of stars in the central
cluster has a different position angle than the lobes and is in good agreement
with millimeter polarimetry. The nebulosity in the Eastern lobe has moderate to
high polarization consistent with scattering of continuum light from the
central cluster. We were unable to detect polarization of the nebulosity in the
Western lobe at the 4.2% (3sigma) level.


title:
Chandra X-ray analysis of the massive high-redshift galaxy clusters
  ClJ1113.1-2615 and ClJ0152.7-1357

abstract:
  We present an analysis of Chandra observations of two high-redshift clusters
of galaxies, ClJ1113.1-2615 at z=0.725 and ClJ0152.7-1357 at z=0.833. We find
ClJ1113 to be relaxed with kT=4.3^{+0.5}_{-0.4}keV and a mass (within the
virial radius) of 4.3^{+0.8}_{-0.7}*10^{14}Msol. ClJ0152, by contrast, is
resolved into a northern and southern subcluster, each massive and X-ray
luminous, in the process of merging. The temperatures of the subclusters are
found to be 5.5^{+0.9}_{-0.8}keV and 5.2^{+1.1}_{-0.9}keV respectively, and
their respective masses are 6.1^{+1.7}_{-1.5}*10^{14}Msol and
5.2^{+1.8}_{-1.4}*10^{14}Msol within the virial radii. 2D modelling of the
X-ray surface brightness reveals excess emission between the subclusters;
suggestive, but not conclusive evidence of a shock front.
  We make a first attempt at measuring the cluster M-T relation at z~0.8, and
find no evolution in its normalisation, supporting the previous assumption of
an unevolving M-T relation. We also find little or no evolution in the L-T
relation, the gas fraction-T relation, the beta-T relation or the metallicity.
These results suggest that, in at least some massive clusters, the hot gas was
in place, and containing its metals, at z~0.8.
  We also highlight the need to correct for the degradation of the Chandra ACIS
low energy quantum efficiency in high-redshift cluster studies when the low
energy absorption is often assumed to be the Galactic value, rather than
measured.


title: The Open Cluster Distance Scale: A New Empirical Approach

abstract:
  We present new BVRI photometry for a sample of 54 local G and K stars with
accurate Hipparcos parallaxes in the metallicity range -0.4 < [Fe/H] < +0.3. We
use this sample to develop a completely model-independent main sequence (MS)
fitting method which we apply to 4 open clusters - the Hyades, Praesepe, the
Pleiades and NGC 2516 - which all have direct Hipparcos parallax distance
determinations. Comparison of our MS-fitting results with distances derived
from Hipparcos parallaxes enables us to explore whether the discrepancy between
the Hipparcos distance scale and other MS-fitting methods found for some
clusters is a consequence of model assumptions. We find good agreement between
our results and the Hipparcos ones for the Hyades and Praesepe. For the
Pleiades and NGC 2516, when adopting the solar abundance determined from
spectroscopy, we find significant disagreement at a level similar to that found
by other MS-fitting studies. However, the colour-colour relationship for both
these clusters suggests that their metallicity is significantly subsolar. Since
the MS-fitting method relies on matching the cluster colours to a template MS,
we argue that, when applying this method, the appropriate metallicity to adopt
is the photometric subsolar one, not the solar abundance indicated by
spectroscopy. Adopting photometric metallicities for all 4 clusters, we find
complete agreement with the Hipparcos results and hence we conclude that the
mismatch between the spectroscopic and photometric abundances for the Pleiades
and NGC 2516 is responsible for the discrepancies in distance estimates found
by previous studies. The origin of this mismatch in abundance scales remains an
unsolved problem and some possible causes are discussed.


title: Non-Gaussianity: Comparing wavelet and Fourier based methods

abstract:
  In the context of the present and future Cosmic Microwave Background (CMB)
experiments, going beyond the information provided by the power spectrum has
become necessary in order to tightly constrain the cosmological model. The
non-Gaussian signatures in the CMB represent a very promising tool to probe the
early universe and the structure formation epoch. We present the results of a
comparison between two families of non-Gaussian estimators: The first act on
the wavelet space (skewness and excess kurtosis of the wavelet coefficients)
and the second group on the Fourier space (bi- and trispectrum). We compare the
relative sensitivities of these estimators by applying them to three different
data sets meant to reproduce the majority of possible non-Gaussian
contributions to the CMB. We find that the skewness in the wavelet space is
slightly more sensitive than the bispectrum. For the four point estimators, we
find that the excess kurtosis of the wavelet coefficients has very similar
capabilities than the diagonal trispectrum while a near-diagonal trispectrum
seems to be less sensitive to non-Gaussian signatures.


title: New infrared star clusters in the southern Milky Way with 2MASS

abstract:
  We carried out a 2MASS J, H and K_s survey of infrared star clusters in the
Milky Way sector 230$^{\circ}$ $< \ell <$ 350$^{\circ}$. This zone was the
least studied in the literature, previously including only 12 infrared clusters
or stellar groups with $|b|<$ 10$^{\circ}$, according to the recent catalogue
by Bica et al. (2003). We concentrated efforts on embedded clusters, which are
those expected in the areas of known radio and optical nebulae. The present
study provides 179 new infrared clusters and stellar groups, which are
interesting targets for detailed future infrared studies. The sample of
catalogued infrared clusters and stellar groups in the Galaxy is now increased
by 63%.


title: Screw dynamo in a time-dependent pipe flow

abstract:
  The kinematic dynamo problem is investigated for the flow of a conducting
fluid in a cylindrical, periodic tube with conducting walls. The methods used
are an eigenvalue analysis of the steady regime, and the three-dimensional
solution of the time-dependent induction equation. The configuration and
parameters considered here are close to those of a dynamo experiment planned in
Perm, which will use a torus-shaped channel. We find growth of an initial
magnetic field by more than 3 orders of magnitude. Marked field growth can be
obtained if the braking time is less than 0.2 s and only one diverter is used
in the channel. The structure of the seed field has a strong impact on the
field amplification factor. The generation properties can be improved by adding
ferromagnetic particles to the fluid in order to increase its relative
permeability,but this will not be necessary for the success of the dynamo
experiment. For higher magnetic Reynolds numbers, the nontrivial evolution of
different magnetic modes limits the value of simple `optimistic' and
`pessimistic' estimates.


title:
The Globular Cluster System of NGC 1399. I. A Wide-field Photometric
  Study

abstract:
  We present a photometric investigation of the globular cluster population of
NGC 1399, the central galaxy in the Fornax cluster, in Washington C and Kron R
filters within a field of 36'x36'. This is the largest area around this galaxy
ever studied with CCD photometry. The cluster system of NGC 1399 is found to
extend further than 100 kpc away from the galaxy. The color distribution
exhibits a pronounced bimodality. Within a radial distance of about 55 kpc, the
red clusters are more strongly concentrated to the center than the
blueclusters. At larger radii, the surface density profiles of the clusters are
indistinguishable and match well the distribution of the galaxy light. Over the
entire radial distance range, the surface brightness profile of NGC 1399 can be
very well fitted by a power law with an exponent of -1.85 and a core radius of
3.3". No steepening of the luminosity profile can be detected at large radii.
We suggest that the power law profile of NGC 1399 results from the galaxy being
embedded in a large dark matter halo, which prevents the stellar density
profile from steepening outwards. The cluster system contains 6450+-700
clusters and the specific frequency is found to be 5.1+-1.2 in the V band.
While NGC 1399 shows a pronounced color gradient. Using simple assumptions
about the underlying population that formed during the same star formation
event as the globular clusters, we presenta model in which we use radially
changing local specific frequencies for the red and blue subpopulations to fit
the observations. We find that within 7' the required specific frequency of the
blue clusters alone is a factor of approximately 3 larger than that of the red
ones. Outside this radius however, both populations have a high local specific
frequency of around 10.


title:
Simulations of Galaxy Formation in a Lambda CDM Universe III: The
  Dissipative Formation of an Elliptical Galaxy

abstract:
  We examine in detail the dynamical structure of an elliptical galaxy
simulated in the Lambda CDM scenario. The morphology of the galaxy evolves
dramatically over time in response to the mode and timing of mass accretion;
smooth deposition of cooled gas leads to the formation of centrifugally
supported disks, whilst major mergers disperse stellar disks into spheroids.
These two modes of accretion alternate successively until z~0.6, when the
galaxy undergoes one last major (1:2) merger that consumes much of the
remaining gas into stars. Little gas cools and accretes subsequently and, as a
result, most stars at z=0 are in a spheroidal component that resembles
present-day elliptical galaxies. Dynamically, the galaxy is well approximated
by an E4 oblate rotator. Boxy isophotes are obtained when the galaxy is seen
face-on and Vrot/sigma<<1. On the other hand, disky isophotes are found for
inclinations which maximize Vrot/sigma. The line-of-sight velocity distribution
is nearly Gaussian at all radii. The sign of the Gauss-Hermite skewness
parameter h3 is anti-correlated with the apparent sense of rotation, in
agreement with observed trends. The simulated galaxy has much higher effective
surface brightness than normal ellipticals of similar luminosity, in a way
reminiscent of the less common type of compact ellipticals. Our simulation
shows that repeated episodes of dissipational collapse, followed by merger
events, lead to stellar spheroids that are only mildly triaxial and of
relatively simple kinematic structure. This is in better agreement with
observation than earlier models based on dissipationless mergers of stellar
disks, and a positive step towards reconciling the observed structure of
ellipticals with the hierarchical merging scenario.


title:
Uses and limitations of relativistic jet proper motions: lessons from
  galactic microquasars

abstract:
  It is shown that the two-sided jet proper motions observed from the galactic
microquasars GRS 1915+105 and GRO J1655-40 in practice only allow us to place
lower limits on the Lorentz factors of the outflows. As a consequence, it is
not possible to rule out the possibility that jets from X-ray binaries are just
as relativistic as those from active galactic nuclei (AGN). This results from
the fact that distance estimates place the sources, within uncertainties, at
the maximum distance d(max) which corresponds to an intrinsic velocity v=c. The
general case is explored, for a range of intrinsic Lorentz factors and angles
to the line of sight, and it is shown that a source of significantly
relativistic jets will nearly always be observed close to d(max) and as a
result it is unlikely that we will ever be able to measure with any accuracy
the Lorentz factor of a jet from two-sided proper motions. We will generally
not be able to do more than place a lower limit on the Lorentz factor of the
flow, and this limit is naturally even lower in the cases where we only observe
the approaching jet. On the other hand, under the assumption that any two-sided
jets we see are intrinsically relativistic, we can confidently place the source
at a distance d ~ d(max). As a result, observations of two-sided proper motions
in relativistic jets from AGN would be extremely important for calibration of
the cosmological distance scale. (ABRIDGED).


title: Cosmological implications of APM 08279+5255, an old quasar at z = 3.91

abstract:
  The existence of old high-redshift objects provides an important tool for
constraining the expanding age of the Universe and the formation epoch of the
first objects. In a recent paper, Hasinger {\it et al.} (2002) reported the
discovery of the quasar APM 08279+5255 at redshift $z=3.91$ with an extremely
high iron abundance, and estimated age of 2 - 3Gyr. By assuming the lower limit
for this age estimate and the latest measurements of the Hubble parameter as
given by the HST key project, we study some cosmological implications from the
existence of this object. In particular, we derive new limits on the dark
matter and vacuum energy contribution. Our analysis is also extended to
quintessence scenarios in which the dark energy is parameterized by a smooth
component with an equation of state $p_x = \omega_x \rho_x$ ($-1\leq \omega_x <
0$). For flat models with a relic cosmological constant we show that the vacuum
energy density parameter is constrained to be $\Omega_\Lambda \geq 0.78$, a
result that is marginally compatible with recent observations from type Ia
supernovae (SNe Ia) and cosmic microwave background (CMB). For quintessence
scenarios the same analysis restricts the cosmic parameter to $\omega_x \leq
-0.22$. Limits on a possible first epoch of quasar formation are also briefly
discussed. The existence of this object pushes the formation era back to
extremely high redshifts.


title: What Types of Jets does Nature Make: A New Population of Radio Quasars

abstract:
  We use statistical results from a large sample of about 500 blazars, based on
two surveys, the Deep X-ray Radio Blazar Survey (DXRBS), nearly complete, and
the RASS-Green Bank survey (RGB), to provide new constraints on the spectral
energy distribution of blazars, particularly flat-spectrum radio quasars
(FSRQ). This reassessment is prompted by the discovery of a population of FSRQ
with spectral energy distribution similar to that of high-energy peaked BL
Lacs. The fraction of these sources is sample dependent, being ~ 10% in DXRBS
and ~ 30% in RGB (and reaching ~ 80% for the Einstein Medium Sensitivity
Survey). We show that these ``X-ray strong'' radio quasars, which had gone
undetected or unnoticed in previous surveys, indeed are the strong-lined
counterparts of high-energy peaked BL Lacs and have synchrotron peak
frequencies, nu_peak, much higher than ``classical'' FSRQ, typically in the UV
band for DXRBS. Some of these objects may be 100 GeV - TeV emitters, as are
several known BL Lacs with similar broadband spectra. Our large, deep, and
homogeneous DXRBS sample does not show anti-correlations between nu_peak and
radio, broad line region, or jet power, as expected in the so-called ``blazar
sequence'' scenario. However, the fact that FSRQ do not reach X-ray-to-radio
flux ratios and nu_peak values as extreme as BL Lacs and the elusiveness of
high nu_peak - high-power blazars suggest that there might be an intrinsic,
physical limit to the synchrotron peak frequency that can be reached by
strong-lined, powerful blazars. Our findings have important implications for
the study of jet formation and physics and its relationship to other properties
of active galactic nuclei.


title:
A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal
  Galaxies

abstract:
  The Wisconsin H Alpha Mapper has been used to set the first deep upper limits
on the intensity of diffuse H alpha emission from warm ionized gas in the Local
Group dwarf spheroidal galaxies (dSphs) Draco and Ursa Minor. Assuming a
velocity dispersion of 15 km/s for the ionized gas, we set limits for the H
alpha intensity of less or equal to 0.024 Rayleighs and less or equal to 0.021
Rayleighs for the Draco and Ursa Minor dSphs, respectively, averaged over our 1
degree circular beam. Adopting a simple model for the ionized interstellar
medium, these limits translate to upper bounds on the mass of ionized gas of
approximately less than 10% of the stellar mass, or approximately 10 times the
upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa
Minor dSphs could contain substantial amounts of interstellar gas, equivalent
to all of the gas injected by dying stars since the end of their main star
forming episodes more than 8 Gyr in the past, without violating these limits on
the mass of ionized gas.


title: Detecting dark matter using centrifuging techniques

abstract:
  A new and inexpensive technique for detecting self interacting dark matter in
the form of small grains in bulk matter is proposed. Depending on the
interactions with ordinary matter, dark matter grains in bulk matter may be
isolated by using a centrifuge and using ordinary matter as a filter. The case
of mirror matter interacting with ordinary matter via photon-mirror photon
kinetic mixing provides a concrete example of this type of dark matter
candidate.


title: Rest-Frame Ultraviolet Spectra of z~3 Lyman Break Galaxies

abstract:
  We present the results of a systematic study of the rest-frame UV
spectroscopic properties of Lyman Break Galaxies (LBGs). The database of almost
1000 LBG spectra proves useful for constructing high S/N composite spectra. The
composite spectrum of the entire sample reveals a wealth of features
attributable to hot stars, HII regions, dust, and outflowing neutral and
ionized gas. By grouping the database according to galaxy parameters such as
Lyman-alpha equivalent width, UV spectral slope, and interstellar kinematics,
we isolate some of the major trends in LBG spectra which are least compromised
by selection effects. We find that LBGs with stronger Lyman-alpha emission have
bluer UV continua, weaker low-ionization interstellar absorption lines, smaller
kinematic offsets between Lyman-alpha and the interstellar absorption lines,
and lower star-formation rates. There is a decoupling between the dependence of
low- and high-ionization outflow features on other spectral properties. Most of
the above trends can be explained in terms of the properties of the large-scale
outflows seen in LBGs. According to this scenario, the appearance of LBG
spectra is determined by a combination of the covering fraction of outflowing
neutral gas which contains dust, and the range of velocities over which this
gas is absorbing. Higher sensitivity and spectral resolution observations are
still required for a full understanding of the covering fraction and velocity
dispersion of the outflowing neutral gas in LBGs, and its relationship to the
escape fraction of Lyman continuum radiation in galaxies at z~3.


title: The Redshift Evolution of the 2-8 keV X-ray Luminosity Function

abstract:
  The high angular resolution and sensitivity of the Chandra X-ray Observatory
has yielded large numbers of faint X-ray sources with measured redshifts in the
soft (0.5-2 keV) and hard (2-8 keV) energy bands. Many of these sources show
few obvious optical signatures of active galactic nuclei (AGN). We use Chandra
observations of the Hubble Deep Field North region, A370, and the Hawaii Survey
Fields SSA13 and SSA22, together with the ROSAT Ultra Deep Survey soft sample
and the ASCA Large Sky Survey hard sample, to construct rest-frame 2-8 keV
luminosity functions versus redshift for all the X-ray sources, regardless of
their optical AGN characteristics. At z=0.1-1 most of the 2-8 keV light density
arises in sources with luminosities in the 10^42 erg/s to 10^44 erg/s range. We
show that the number density of sources in this luminosity range is rising, or
is at least constant, with decreasing redshift. Broad-line AGN are the dominant
population at higher luminosities, and these sources show the well-known rapid
positive evolution with increasing redshift to z~3. We argue that the dominant
supermassive black hole formation has occurred at recent times in objects with
low accretion mass flow rates rather than at earlier times in more X-ray
luminous objects with high accretion mass flow rates.


title: Very High Redshift X-ray Selected AGN in the Chandra Deep Field-North

abstract:
  Deep Chandra X-ray exposures provide an efficient route for locating
optically faint active galactic nuclei (AGN) at high redshifts. We use deep
multicolor optical data to search for z>5 AGN in the 2 Ms X-ray exposure of the
Chandra Deep Field-North. Of the 423 X-ray sources bright enough (z'<25.2) for
a color-color analysis, at most one lies at z=5-6 and none at z>6. The z>5
object is spectroscopically confirmed at z=5.19. Only 31 of the 77 sources with
z'>25.2 are undetected in the B or V bands at the 2-sigma level and could lie
at z>5. There are too few moderate luminosity AGN at z=5-6.5 to ionize the
intergalactic medium.


title:
The bi-variate luminosity-color distribution of IRAS galaxies, and
  implications for the high redshift Universe

abstract:
  We present a characterization of the local luminosity-color, bi-variate
distribution of IRAS galaxies from the 1.2Jy sample, selected at 60 micron. The
S60/S100 infrared color is used as the best single parameter description of the
IR spectral energy distribution of galaxies. We derive an analytical form of
the distribution and use it to constrain the effect of the IR color
distribution on evolution models for high redshift, farIR luminous galaxies.
Our adopted evolution retains the locally observed correlation between
luminosity and color, such that the larger characteristic luminosities at
higher redshift have a warmer characteristic color. The width of the color
distribution at a given luminosity remains constant for all redshifts. We
demonstrate that there is the potential for both hotter and colder sources to
be missed in cosmological surveys. An evolving bi-variate luminosity function
coupled with the cold source bias of sub-mm selected surveys suggests the
existence of a large population of cold sources appearing in such surveys.
Likewise, a hot source bias for most SIRTF wavebands together with a bi-variate
model suggests an excess of hot sources being selected. We test the
evolutionary form against available data for higher redshift, farIR galaxies.
The data do not reveal evidence for any strong evolution in the characteristic
luminosity-color distribution as a function of redshift over 0<z<1. However,
there is marginal evidence for a broadening of the color distribution at higher
redshifts, consistent with our locally characterized trend of a broadening in
the IR color distribution at the highest luminosities.


title: Technique for detecting warm-hot intergalactic gas in quasar UV spectra

abstract:
  The ionizing spectral energy distribution of quasars exhibits a steepening of
the distribution shortward of ~ 1200 A. The change of the power-law index from
approximately -1 (near-UV) to -2 (far-UV) has so far been interpreted as being
intrinsic to quasars. We consider the possibility that the steepening may
result from a tenuous absorption component that is anticorrelated with large
mass overdensities. UV sensitive satellites, whose detectors can extend down to
1000 A, can set a useful limit to such an absorption component through the
search of a flux increase in the window 1050-1190 A (observer frame) with
respect to an extrapolation of the continuum above 1230 A. Since the recent
FUSE or HST-STIS data do not show any obvious discontinuity in this region,
this effectively rules out the possibility that intergalactic HI absorption is
very important, and it is concluded that most if not all of the steepening is
intrinsic to quasars. A smaller flux discontinuity of order 1% cannot, however,
be ruled out yet and would still be consistent with the warm-hot intergalactic
component if it amounts to 30% of the baryonic mass, as predicted by some
models of large scale structure formation, provided its temperature lies around
10^{5.5} K.


title:
X-ray Studies of Two Neutron Stars in 47 Tucanae: Toward Constraints on
  the Equation of State

abstract:
  We report spectral and variability analysis of two quiescent low mass X-ray
binaries (X5 and X7, previously detected with the ROSAT HRI) in a Chandra
ACIS-I observation of the globular cluster 47 Tuc. X5 demonstrates sharp
eclipses with an 8.666+-0.01 hr period, as well as dips showing an increased
N_H column. The thermal spectra of X5 and X7 are well-modeled by unmagnetized
hydrogen atmospheres of hot neutron stars. No hard power law component is
required. A possible edge or absorption feature is identified near 0.64 keV,
perhaps an OV edge from a hot wind. Spectral fits imply that X7 is
significantly more massive than the canonical 1.4 \Msun neutron star mass, with
M>1.8 \Msun for a radius range of 9-14 km, while X5's spectrum is consistent
with a neutron star of mass 1.4 \Msun for the same radius range. Alternatively,
if much of the X-ray luminosity is due to continuing accretion onto the neutron
star surface, the feature may be the 0.87 keV rest-frame absorption complex (O
VIII & other metal lines) intrinsic to the neutron star atmosphere, and a mass
of 1.4 \Msun for X7 may be allowed.


title: Relics of subluminous supernovae in metal-poor stars

abstract:
  The unique elemental abundance pattern of the carbon-rich stars CS29498-043
and CS22949-037 is characterized by a large excess of magnesium and silicon in
comparison with iron. This excess is investigated in the context of a
supernova-induced star formation scenario, and it is concluded that these stars
were born from the matter swept up by supernova remnants containing little iron
and that such supernovae are similar to the least-luminous SNe ever observed,
SNe 1997D and 1999br. Comparison of the observed abundance pattern in
iron-group elements of subluminous supernovae with those of other supernovae
leads to an intriguing implication for explosion, nucleosynthesis, and mixing
in supernovae. The observed invariance of these ratios can not be accounted for
by a spherically symmetric supernova model.


title: Spectroscopic and Spectropolarimetric Observations of V838 Mon

abstract:
  The spectroscopic and spectropolarimetric variability of the peculiar
variable V838 Monocerotis during the brighter phases of its multiple outbursts
in 2002 is presented. Significant line profile variability of H$\alpha$ and Si
II 6347.10\AA & 6371.36\AA occurred in spectra obtained between 2002 February 5
and 2002 March 14, and a unique secondary absorption component was observed
near the end of this time period. Our observations also suggest that multiple
shifts in ionization states occurred during the outbursts. Spectropolarimetric
observations reveal that V838 Mon exhibited both intrinsic and interstellar
polarization components during the initial stages of the second outburst,
indicating the presence of an asymmetric geometry; however, the intrinsic
component had significantly declined by February 14. We determine the
interstellar polarization to be $P_{max} = 2.746 \pm 0.011 %$, $\lambda_{max} =
5790 \pm 37\AA$, $PA = 153.43 \pm 0.12 ^{\circ} $, and we find the integrated
intrinsic V band polarization on February 5 to be $P = 0.983 \pm 0.012 %$ at a
position angle of $127.0 \pm 0.5^{\circ}$. The implications of these
observations for the nature of V838 Monocerotis, its distance, and its ejecta
are discussed.


title:
High-Resolution Spectroscopy of the Yellow Hypergiant Rho Cassiopeiae
  from 1993 Through the Outburst of 2000-2001

abstract:
  We present an overview of the spectral variability of the peculiar F-type
hypergiant Rho Cas, obtained from our long-term monitoring campaigns over the
past 8.5 years with four spectrographs in the northern hemisphere. Between 2000
June and September an exceptional variability phase occurred when the
V-brightness dimmed by about a full magnitude. The star recovered from this
deep minimum by 2001 April. It is the third outburst of Rho Cas on record in
the last century. We observe TiO absorption bands in high-resolution near-IR
spectra obtained with the Utrecht Echelle Spectrograph during the summer of
2000. TiO formation in the outer atmosphere occurred before the deep brightness
minimum. Atmospheric models reveal that the effective temperature decreases by
at least 3000 K, and the TiO shell is driven supersonically with Mdot ~= 5.4
10^{-2} Msun/yr. Strong episodic mass loss and TiO have also been observed
during the outbursts of 1945-47 and 1985-86.
  A detailed analysis of the exceptional outburst spectra is provided, by
comparing with high-resolution optical spectra of the early M-type supergiants
Mu Cep (Ia) and Betelgeuse (Iab). The outburst spectra indicate the formation
of a low-temperature, optically thick circumstellar gas shell of 3 10^{-2} Msun
during ~200 d, caused by dynamic instability of the upper atmosphere of this
pulsating massive supergiant near the Eddington luminosity limit. We observe
that the mass-loss rate during the outburst is of the same order of magnitude
as has been proposed for the outbursts of Eta Carinae. We present calculations
that correctly predict the outburst time-scale, whereby the shell ejection is
driven by the release of hydrogen ionization-recombination energy.


title:
A New Approach to Galaxy Morphology: I. Analysis of the Sloan Digital
  Sky Survey Early Data Release

abstract:
  In this paper we present a new statistic for quantifying galaxy morphology
based on measurements of the Gini coefficient of galaxy light distributions.
This statistic is easy to measure and is commonly used in econometrics to
measure how wealth is distributed in human populations. When applied to galaxy
images, the Gini coefficient provides a quantitative measure of the inequality
with which a galaxy's light is distributed amongst its constituent pixels. We
measure the Gini coefficient of local galaxies in the Early Data Release of the
Sloan Digital Sky Survey and demonstrate that this quantity is closely
correlated with measurements of central concentration, but with significant
scatter. This scatter is almost entirely due to variations in the mean surface
brightness of galaxies. By exploring the distribution of galaxies in the
three-dimensional parameter space defined by the Gini coefficient, central
concentration, and mean surface brightness, we show that all nearby galaxies
lie on a well-defined two-dimensional surface (a slightly warped plane)
embedded within a three-dimensional parameter space. By associating each galaxy
sample with the equation of this plane, we can encode the morphological
composition of the entire SDSS g-band sample using the following three numbers:
22.451, 5.366, 7.010. The i-band sample is encoded as: 22.149, 5.373, and
7.627.