title:
The Millennium Arecibo 21-cm Absorption Line Survey. III. Techniques for
  Spectral Polarization and Results for Stokes V

abstract:
  We outline the theory and practice of measuring the four Stokes parameters of
spectral lines in emission/absorption observations. We apply these concepts to
our Arecibo HI absorption line data and present the results. We include a
detailed discussion of instrumental effects arising from polarized beam
structure and its interaction with the spatially extended emission line
structure. At Arecibo, linear polarization (Stokes (Q,U)) has much larger
instrumental effects than circular (Stokes V). We show how to reduce the
instrumental contributions to V and to evaluate upper limits to its remaining
instrumental errors by using the (Q,U) results. These efforts work well for
opacity spectra but not for emission spectra. Arecibo's large central blockage
exacerbates these effects, particularly for emission profiles, and other
telescopes with weaker sidelobes are not as susceptible. We present graphical
results for 41 sources; we analyze these absorption spectra in terms of
Gaussian components, which number 136, and present physical parameters
including magnetic field for each.


title: The Planetary Nebula System and Dynamics in the Outer Halo of NGC 5128

abstract:
  The halos of elliptical galaxies are faint and difficult to explore, but they
contain vital clues to both structure and formation. We present the results of
an imaging and spectroscopic survey for planetary nebulae (PNe) in the nearby
elliptical NGC 5128. We extend the work of Hui et al.(1995) well into the halo
of the galaxy--out to distances of 100 and 50 kpc along the major and minor
axes. We now know of 1141 PNe in NGC 5128, 780 of which are confirmed. Of these
780 PNe, 349 are new from this survey, and 148 are at radii beyond 20 kpc. PNe
exist at distances up to 80 kpc (~15 r_e), showing that the stellar halo
extends to the limit of our data. This study represents by far the largest
kinematic study of an elliptical galaxy to date, both in the number of velocity
tracers and in radial extent. We confirm the large rotation of the PNe along
the major axis, and show that it extends in a disk-like feature into the halo.
The rotation curve of the stars flattens at ~100 km/s with V/sigma between 1
and 1.5, and with the velocity dispersion of the PNe falling gradually at
larger radii. The two-dimensional velocity field exhibits a zero-velocity
contour with a pronounced twist, showing that the galaxy potential is likely
triaxial in shape, tending toward prolate. The total dynamical mass of the
galaxy within 80 kpc is ~5 x 10^{11} M_sun, with M/L_B ~ 13. This mass-to-light
ratio is much lower than what is typically expected for elliptical galaxies.


title: High-Resolution Infrared Spectroscopy of the Brown Dwarf Epsilon Indi Ba

abstract:
  We report on the analysis of high-resolution infrared spectra of the newly
discovered brown dwarf Epsilon Indi Ba. This is the closest known brown dwarf
to the solar system, with a distance of 3.626 pc. Spectra covering the ranges
of 2.308-2.317 microns and 1.553-1.559 microns were observed at a spectral
resolution of R=50,000 with the Phoenix spectrometer on the Gemini South
telescope. The physical paramters of effective temperature and surface gravity
are derived by comparison to model spectra calculated from atmospheres computed
using unified cloudy models. An accurate projected rotational velocity is also
derived.


title: High resolution X-ray observations of 3C 58

abstract:
  As the presumed remnant of SN1181, 3C 58 houses one of the youngest known
neutron stars in the Galaxy. The properties of this young pulsar and its
associated wind nebula differ considerably from those of the Crab, and may well
offer a more typical example of the endpoint of massive star collapse. High
resolution X-ray studies reveal structures in the inner nebula that may be
associated with the pulsar wind termination shock, a jet that may be aligned
with the rotation axis, and other regions of enhanced emission. Spectral
variations in the PWN are consistent with the expected evolution of the
postshock flow, and complex loops of emission are seen in the nebula interior.
Limits on the NS surface temperature fall below standard cooling models,
indicating that some more rapid neutrino cooling process is required. The outer
regions of 3C 58 show thermal emission with enhanced levels of Ne, indicative
of shocked ejecta bounding the PWN.


title:
Rest-frame optical continua of L ~ L*, z>3 quasars: probing the faint
  end of the high z quasar luminosity function

abstract:
  Near-IR photometry for 20 radio-loud z>3 quasars, 16 of which are radio-
selected, are presented. These data sample the rest-frame optical/UV continuum,
which is commonly interpreted as emission from an accretion disk. In a previous
study, we compared the rest-frame optical/UV continuum shapes of 15 optically
bright (V<17.5) z>3 quasars with those of 27 low redshift (z~0.1) ones that
were matched to the high redshift sample in evolved luminosity (i.e. having
luminosities ranging from 1-7 times the characteristic luminosity, L*, where
L*~(1+z)^{~3}) to look for signs of evolution in the central engines. We found
the continuum shapes at z~0.1 and z>3 similar, consistent with no significant
change in the ratio mdot/M, where mdot is the accretion rate with respect to
the Eddington rate and M is the black hole mass. This study expands our earlier
high redshift sample to lower luminosity, away from extreme objects and towards
a luminosity overlap with lower redshift samples. The distribution of
rest-frame optical/UV continuum shapes for this fainter sample is broader,
extending further to the red than that of the brighter z>3 one. Three quasars
from this fainter sample, two radio-selected and one optically-selected, have
optical continuum slopes alpha<-1 (F_{nu}~nu^{alpha}). The optically-selected
one, LBQS0056+0125, appears to be reddened by dust along the line of sight or
in the host galaxy, whereas the radio-selected ones, PKS2215+02 and
TXS2358+189, could derive their red continua from the contribution of a
relatively strong synchrotron component to the rest-frame optical. These
objects may represent a bridge to a population of very red high redshift
quasars to which ongoing or future near-IR, optical and deep X-ray surveys will
be sensitive.


title: Pulsar velocities and dark matter hint at a singlet neutrino

abstract:
  Two astrophysical puzzles, the origin of pulsar velocities and that of dark
matter, may have a simultaneous explanation if there exists a sterile neutrino
with a mass in the 1-20 keV range and a small mixing (of order 10^{-4}) with
the electron neutrino. Although the mixing is too small for direct detection,
future observations of the X-ray telescopes, as well as the gravity waves
detectors, such as LIGO and LISA, may be able to confirm or rule out the
existence of such a neutrino.


title: Shell Structure in the Fornax Dwarf Spheroidal Galaxy

abstract:
  We present initial results from a wide field photometric survey of the Fornax
dwarf spheroidal (dSph) galaxy. The focus here is on a small overdensity of
stars located approximately 17 arcmin (670 pc in projection) from the centre of
Fornax. Based on imaging data in both V and I bands down to approximately V =
21, the dimensions of the feature are approximately 1.7 arcmin by 3.2 arcmin
(68 pc by 128 pc) with an average surface brightness of 25.8 mag/arcsec^2 in V.
A follow-up analysis using the deep B and R band data obtained by Stetson et
al. (1998) indicates that the overdensity is apparently dominated by a
relatively young stellar population with an age of approximately 2 Gyr, though
the current data do not rule out the presence of older stars. Our preferred
interpretation is that the overdensity represents shell structure in the Fornax
dSph galaxy, a phenomenon previously unseen in dwarf galaxies. The shell may be
the remnant of a merger with Fornax of a smaller, gas-rich system that occured
approximately 2 Gyr ago. The comparitively recent star formation seen in some
dSph and dE galaxies may then also be the result of infall of small relatively
gas-rich systems.


title:
Possibility of Magnetic Mass Detection by the Next Generation of
  Microlensing Experiments

abstract:
  We study the possibility of magnetic mass detection by the gravitational
microlensing technique. Recently the theoretical effect of magnetic mass in the
NUT space on the microlensing light curve has been studied. It was shown that
in the low photometric signal to noise and sampling rate of MACHO experiment
light curves, no signature of NUT factor has been found. In order to increase
the sensitivity of magnetic mass detection, we propose a systematic search for
microlensing events, using the currently running alert systems and
complementary telescopes for monitoring the Large Magellanic Clouds stars. In
this strategy of observation, we obtain the magnetic mass detection efficiency
and also the lowest observable limit of the NUT factor. This method of survey
for gravitational microlensing detection can also be used as a tool for
searching other exotic space-times.


title:
The Cygnus X region XXII. A probable HAeBe star with a giant bipolar
  outflow in DR 16

abstract:
  From medium-resolution radio images, DR 16 was suspected to be a large
cometary nebula. To test this suggestion we obtained a higher resolution
(15\arcsec) VLA continuum map. We also analyzed data from the Canadian Galactic
Plane Survey in continuum, H I line, and IR. These data were supplemented by
published near-infrared (J, H, K) stellar photometric results and MSX 8.28
micrometer data. We suggest that DR 16 is the diffuse H II region of an ongoing
star formation site at a distance of about 3 kpc. The complicated radio picture
arises from the superposition of diffuse H II with the remains of a giant
bipolar outflow. The outflow was generated by a probable Herbig AeBe star, and
the lobes are the remnants of its working surfaces. Additional ring-like
features are discussed. DR 16 is part of a larger volume of space in the local
spiral arm where star formation is an ongoing process.


title: Sub-Quantum Dark Energy

abstract:
  A procedure is considered which upgrades the Lagrangian description of
quantum relativistic particles to the Lagrangian of a proper field theory in
the case that the Klein-Gordon wave equation is classically interpreted in
terms of a relativistic sub-quantum potential. We apply the resulting field
theory to cosmology and show that the relativistic version of the Bohm's
subquantum potential which can be associated with a homogeneous and isotropic
distribution of particles behaves like though it was a cosmological constant
responsible for the current accelerating expansion of the universe, at least in
the limit where the field potential vanishes.


title: Symmetries, magnetic fields, and the shape of molecular cloud cores

abstract:
  We develop a formalism wherein the solution of the equations of equilibrium
for a self-gravitating, magnetized interstellar cloud may be accomplished
analytically, under the only hypotheses that (a) the cloud is scale-free, and
(b) is electrically neutral. All variables are represented as series of scalar
and vector spherical harmonics, and the equilibrium equations are reduced to a
set of coupled algebraic equations for the expansion coefficients of the
density and the magnetic vector potential. Previously known axisymmetric
solutions are recovered and new non-axisymmetric solutions are found and
discussed as models for pre-protostellar molecular cloud cores.


title: The Physical and Chemical Structure of Hot Molecular Cores

abstract:
  We have made self-consistent models of the density and temperature profiles
of the gas and dust surrounding embedded luminous objects using a detailed
radiative transfer model together with observations of the spectral energy
distribution of hot molecular cores. Using these profiles we have investigated
the hot core chemistry which results when grain mantles are evaporated, taking
into account the different binding energies of the mantle molecules, as well a
model in which we assume that all molecules are embedded in water ice and have
a common binding energy. We find that most of the resulting column densities
are consistent with those observed toward the hot core G34.3+0.15 at a time
around 10$^4$ years after central luminous star formation. We have also
investigated the dependence of the chemical structure on the density profile
which suggests an observational possibility of constraining density profiles
from determination of the source sizes of line emission from desorbed
molecules.


title: Partial rip scenario - a cosmology with a growing cosmological term

abstract:
  A cosmology with the growing cosmological term is considered. If there is no
exchange of energy between vacuum and matter components, the requirement of
general covariance implies the time dependence of the gravitational constant
$G$. Irrespectively of the exact functional form of the cosmological term
growth, the universe ends in a de Sitter regime with a constant asymptotic
$\Lambda$, but vanishing $G$. Although there is no divergence of the scale
factor in finite time, such as in the "Big Rip" scenario, gravitationally bound
systems eventually become unbound. In the case of systems bound by
non-gravitational forces, there is no unbounding effect, as the asymptotic
$\Lambda$ is insufficiently large to disturb these systems.


title: Collisions between carbonaceous grains in the interstellar medium

abstract:
  Semi-empirical molecular dynamics is used to simulate hydrocarbon grain
sputtering and collisions which are extremely difficult to study
experimentally. This microscopic and dynamic approach is particularly suited to
high velocity impacts, where target destruction occurs far from equilibrium. A
wide variety of processes are encountered, depending on grain size and
velocity: vaporization, fragmentation, atomic implantation, sticking, elastic
recoil, atomic chemisorption, H abstraction and H2 formation, etc. The
impact-velocity threshold is about 10 km/s but complete grain destruction
requires much higher velocities and nearly equal grain sizes. The main outcome
of strong collisions is vaporization, i.e. formation of small molecules rather
than solid fragments; most of the impact energy is carried away by these
molecules in the form of kinetic energy. As a consequence, the energy left in
the bulk is insufficient for shattering or even thermal processing. Grain size
distribution is hardly affected by such collisions. These results cast doubt on
the notion that collisions reduce grain lifetime so much as to require
efficient growth processes in the interstellar medium.


title: UBVI photometry of the intermediate age open cluster NGC 6939

abstract:
  We present CCD UBVI photometry of the nearby, intermediate age open cluster
NGC 6939. Using the synthetic Colour - Magnitude Diagrams technique we estimate
the following parameters: age between 1.3 and 1.0 Gyr (depending on whether or
not overshooting is considered), reddening 0.34<E(B-V)<0.38 and distance
modulus 11.3<mod_0<11.4 .


title: The traditional approximation in general relativity

abstract:
  We discuss the generalisation of the so-called traditional approximation,
well known in geophysics, to general relativity. We show that the approximation
is applicable for rotating relativistic stars provided that one focuses on
relatively thin radial shells. This means that the framework can be used to
study waves in neutron star oceans. We demonstrate that, once the effects of
the relativistic frame-dragging are accounted for, the angular problem reduces
to Laplace's tidal equation. We derive the dispersion relation for various
classes of waves in a neutron star ocean and show that the combined effects of
the frame-dragging and the gravitational redshift typically lower the frequency
of a mode by about 20%.


title: AGN and starburst radio activity in the A3558 cluster complex

abstract:
  In this paper we present Very Large Array (VLA) 1.4 GHz (21 cm) observations
of the region between the centres of A3558 and A3562, in the majorcluster
merger complex of the Shapley Concentration. Our final catalogue includes a
total of 174 radio sources above the flux density limit of 0.25 mJy b$^{-1}$.
By cross-correlation with optical and spectroscopic catalogues we found 33
optical counterparts belonging to the Shapley Concentration. We investigated
the effects of cluster merger on the radio emission properties of the galaxy
population by means of the radio source counts and the radio luminosity
functions (RLF). We found that the radio source counts are consistent with the
field source counts.The RLF of elliptical and S0 galaxies in the region
surveyed here, is consistent with the ``universal'' RLF for early--type
galaxies.This result suggests that the deficit in radio galaxies found in
ourprevious works over the whole A3558 chain, is entirely due to the cluster
A3558. A population of faint radio galaxies (logP$_{1.4 GHz}$(W Hz$^{-1}$)
\ltsim 22) is also found.Half of these objects are also blue, suggesting that
starburst is the main mechanism driving the radio emission. Finally, we
detected 14 spiral radio galaxies, whose ratio between radio and optical
emission is similar to those found in galaxies located in rich and dynamically
evolved clusters. Our results are briefly discussed in the light of the age and
stage of the merger in the A3558 cluster complex.


title:
Prompt GRB spectra: detailed calculations and the effect of pair
  production

abstract:
  We present detailed calculations of the prompt spectrum of gamma-ray bursts
(GRBs) predicted within the fireball model framework, where emission is due to
internal shocks in an expanding relativistic wind. Our time dependent numerical
model describes cyclo-synchrotron emission and absorption, inverse and direct
Compton scattering, and e^\pm pair production and annihilation (including the
evolution of high energy electro-magnetic cascades). It allows, in particular,
a self-consistent calculation of the energy distribution of e^\pm pairs
produced by photon annihilation, and hence a calculation of the spectra
resulting when the scattering optical depth due to pairs, \tau_\pm, is high. We
show that emission peaks at ~1MeV for moderate to large \tau_\pm, reaching
\tau_\pm ~ 10^2. In this regime of large compactness we find that (i) A large
fraction of shock energy can escape as radiation even for large \tau_\pm; (ii)
The spectrum depends only weakly on the magnetic field energy fraction; (iii)
The spectrum is hard, epsilon^2 dN/depsilon \propto epsilon^\alpha with
0.5<\alpha<1, between the self absorption (epsilon_{ssa}= 10^{0.5\pm0.5} keV)
and peak (epsilon_{peak}= 10^{0.5\pm0.5} MeV) photon energy, (iv) and shows a
sharp cutoff at ~10 MeV; (v) Thermal Comptonization leads to emission peaking
at epsilon_peak>=30 MeV, and can not therefore account for observed GRB
spectra. For small compactness, spectra extend to >10 GeV with flux detectable
by GLAST, and the spectrum at low energy depends on the magnetic field energy
fraction. Comparison of the flux at ~1 GeV and ~ 100 keV may therefore allow to
determine the magnetic field strength. For both small and large compactness,
the spectra depend only weakly on the spectral index of the energy distribution
of accelerated electrons.


title:
Rapid Growth of Dust Particles in the Vicinity of Local Gas Density
  Enhancements in a Solar Nebula

abstract:
  The results of a numerical study of the growth of solid particles, ranging
from 1 micron to 1 millimeter in size, in the vicinity of an azimuthally
symmetric density enhancement of a protostellar disk are presented. It is shown
that the combined effect of gas drag and pressure gradients, which causes solid
objects to rapidly migrate toward the location of the local maximum density,
can also enhance the rate of growth of dust particles to larger objects. The
results of numerical simulations of such growth processes are presented and the
effects of the changes of the physical properties of particles on the rates of
their growth are also discussed.


title:
High-angular resolution HC_3N and CS observations of the dense core in
  the cirrus cloud MCLD123.5+24.9

abstract:
  We report on high-angular resolution observations of a dense core in the
cirrus cloud MCLD123.5+24.9 obtained with the PdB and the OVRO interferometers.
Our maps show substructures down to the scale of the beam (~ 1000 AU). The
chosen molecules CS(2-1) and HC_3N(10-9) trace different regions in the core.
This can be explained by time-dependent chemical evolution of the cloud and
therefore provides constraints on the timescales of the fragmentation and core
formation processes. Our data demonstrate that the chemical evolution plays the
decisive role in our attempt to interpret observational data of different gas
density tracers.


title: The Proximity Effect Around High Redshift Galaxies

abstract:
  Recent observations have shown that the intergalactic medium (IGM) is more
transparent to Lyalpha photons close to Lyman Break Galaxies (LBGs) than at
large distance from them, ie a proximity effect. Cosmological simulations
including winds from LBGs have been so far unable to explain this trend. By
coupling such simulations with the radiative transfer code CRASH, we
investigate whether the addition of the ionizing radiation emitted by LBGs can
increase the transmissivity by decreasing the neutral hydrogen fraction in the
inner Mpc of the galaxy halo. The transmissivity as a function of distance is
roughly reproduced only if LBGs are identified with dwarf galaxies (with masses
< 10^9 solar masses), which are undergoing a vigorous (50 solar masses/yr)
burst of star formation. Similar star formation rates in larger galaxies are
not sufficient to overwhelm the large recombination rates associated with their
denser environment. If so, photoionization partly reconciles theory with
observations, although we discuss a number of uncertainties affecting both
approaches.


title: Neutrinos as astrophysical probes

abstract:
  The aim of these notes is to provide a brief review of the topic of neutrino
astronomy and in particular of neutrinos from core collapse supernovae. They
are addressed to a curious reader, beginning to work in a multidisciplinary
area that involves experimental neutrino physics, astrophysics, nuclear physics
and particle physics phenomenology. After an introduction to the methods and
goals of neutrinos astronomy, we focus on core collapse supernovae, as (one of)
the most promising astrophysical source of neutrinos. The first part is
organized almost as a tale, the last part is a bit more technical. We discuss
the impact of flavor oscillations on the supernova neutrino signal (=the change
of perspective due to recent achievements) and consider one specific example of
signal in detail. This shows that effects of oscillations are important, but
astrophysical uncertainties should be thought as an essential systematics for a
correct interpretation of future experimental data. Three appendices
corroborate the text with further details and some basics on flavor
oscillations; but no attempt of a complete bibliographical survey is done (in
practice, we selected a few references that we believe are useful for a
`modern' introduction to the subject. We suggest the use of public databases
for papers as SPIRES or NASA/ESO or for experiments as SPIRES or PaNAGIC to get
a more complete information).


title: Dark energy from backreaction

abstract:
  We consider the effect of inhomogeneities on the expansion of the Einstein-de
Sitter universe. We find that the backreaction of linear scalar metric
perturbations results in apparent dark energy with a mixture of equations of
state between 0 and -4/3. We discuss the possibility that backreaction could
account for present-day acceleration.


title:
Molecular Gas in Nearby Dwarf Galaxies: Single Dish and Interferometric
  Results

abstract:
  We present results from an extensive survey of molecular gas in nearby dwarf
galaxies. This survey consists of a single-dish search for CO emission at the
UASO Kitt Peak 12m telescope and interferometric follow-up using the
Berkeley-Illinois-Maryland Array. We have detected 41 new sources,
approximately doubling the number of detections of such objects in the
literature. In this paper we discuss two results from the survey that lead us
to agree with recent suggestions that, above a metallicity of 12+log[O/H]~8.0,
there appears to be little variation in the CO-to-H2 conversion factor for
star-forming molecular gas. We find two major pieces of evidence for this
result: 1) the virial mass to molecular mass ratio found from the
interferometer observations in a variety of sources shows no clear trend with
metallicity; and 2) dwarf galaxies appear to exhibit a CO-to-radio continuum
relationship that is similar to that observed in larger, presumably metal-rich,
galaxies leaving little room for a large systematic variation of the CO-to-H2
conversion factor with metallicity in the star-forming gas.


title: Dark Matter in Dwarf Galaxies: High Resolution Observations

abstract:
  We present observations and analysis of rotation curves and dark matter halo
density profiles in the central regions of four nearby dwarf galaxies. This
observing program has been designed to overcome some of the limitations of
other rotation curve studies that rely mostly on longslit spectra. We find that
these objects exhibit the full range of central density profiles between
constant density and NFW halos. This result suggests that there is a
distribution of central density slopes rather than a unique halo density
profile.


title: A hierarchy of voids: Much ado about nothing

abstract:
  We present a model for the distribution of void sizes and its evolution in
the context of hierarchical scenarios of gravitational structure formation. We
find that at any cosmic epoch the voids have a size distribution which is
well-peaked about a characteristic void size which evolves self-similarly in
time. This is in distinct contrast to the distribution of virialized halo
masses which does not have a small-scale cut-off.
  In our model, the fate of voids is ruled by two processes. The first process
affects those voids which are embedded in larger underdense regions: the
evolution is effectively one in which a larger void is made up by the mergers
of smaller voids, and is analogous to how massive clusters form from the
mergers of less massive progenitors. The second process is unique to voids, and
occurs to voids which happen to be embedded within a larger scale overdensity:
these voids get squeezed out of existence as the overdensity collapses around
them. It is this second process which produces the cut-off at small scales.
  In the excursion set formulation of cluster abundance and evolution, solution
of the cloud-in-cloud problem, i.e., counting as clusters only those objects
which are not embedded in larger clusters, requires study of random walks
crossing one barrier. We show that a similar formulation of void evolution
requires study of a two-barrier problem: one barrier is required to account for
voids-in-voids, and the other for voids-in-clouds. Thus, in our model, the void
size distribution is a function of two parameters, one of which reflects the
dynamics of void formation, and the other the formation of collapsed objects.


title: Imaging the Sunyaev Zel'dovich Effect using ACBAR on Viper

abstract:
  During 2001 and 2002, observations of several X-ray bright clusters of
galaxies were conducted using the ACBAR Bolometer Array on the South Pole Viper
telescope. A multi-frequency analysis of these clusters is currently underway.
This multi-frequency analysis includes 150, 220 and 275 GHz data from ACBAR,
X-ray imaging and spectroscopy from Chandra and XMM-Newton, and weak lensing
data from the CTIO 4m Blanco telescope. We describe here how ACBAR can be used
to create fully sampled cluster images and present such images for four of the
clusters in our sample; Abell 3266, Abell 3827, Abell S1063 and 1E0657-56. In
these images, the Sunyaev-Zel'dovich Effect is clearly detected.


title:
Using Multiwavelength Observations to Estimate the Black Hole Masses and
  Accretion Rates in Seyfert Galaxies

abstract:
  We model the spectral energy distribution of the type 1 Seyfert galaxies,
fitting data from simultaneous optical, UV, and X-ray monitoring observations.
We assume a geometry consisting of a hot central Comptonizing region surrounded
by a thin accretion disk. The properties of the disk and the hot central region
are determined by the feedback occurring between the hot Comptonizing region
and thermal reprocessing in the disk that, along with viscous dissipation,
provides the seed photons for the Comptonization process. The constraints
imposed upon this model by existing multiwavelength data allow us to derive
limits on the central black hole mass, the accretion rate, and the radius of
the transition region between the thin outer disk and the geometrically thick,
hot inner region in these objects.


title: Sunyaev-Zeldovich Observations of Massive Clusters of Galaxies

abstract:
  We present detections of the Sunyaev-Zeldovich Effect (SZE) at 150GHz and
275GHz for the X-ray luminous z=0.299 cluster 1E0657-67. These observations
were obtained as part of an X-ray, weak lensing, and SZE survey of nearby X-ray
bright clusters. The SZE maps were made with the ACBAR (150, 210, 275 GHz)
bolometer array installed at the Viper telescope located at the South Pole. We
also present preliminary results from a blind SZE cluster survey.


title: The Globular Cluster System of NGC 5128 I. Survey and Catalogs

abstract:
  We present the results of a photometric and spectroscopic survey of the
globular cluster system of NGC 5128 (Centaurus A), a galaxy whose proximity
makes it an important target for early-type galaxy studies. We imaged three
fields in UBVRI that extend 50 and 30 kpc along the major and minor axes,
respectively. We used both color and size information to develop efficient
selection criteria for differentiating between star clusters and foreground
stars. In total, we obtained new velocities for 138 globular clusters, nearly
tripling the number of known clusters, and bringing the confirmed total in NGC
5128 to 215. We present a full catalog of all known GCs, with their positions,
photometry, and velocities. In addition, we present catalogs of other objects
observed, such as foreground stars, background galaxies, three Galactic white
dwarfs, seven background QSOs, and 52 optical counterparts to known X-ray point
sources. We also report an observation of the cluster G169, in which we confirm
the existence of a bright emission line object. This object, however, is
unlikely to be a planetary nebula, but may be a supernova remnant.


title:
The Globular Cluster System of NGC 5128 II. Ages, Metallicities,
  Kinematics, and Formation

abstract:
  We present a study of the nearby post-merger giant elliptical galaxy, NGC
5128 (Centaurus A), in which we use the properties of its globular cluster (GC)
and planetary nebula (PN) systems to constrain its evolution. Using photometric
and spectroscopic data for 215 GCs presented in Paper I, we study trends in
age, metallicity, and kinematics for the GC system. We confirm that the GC
metallicity distribution is bimodal, and show that these two sub-populations
have different properties. Using spectral line index measurements of the
brightest clusters, the metal-poor GCs have old ages like the Milky Way
globular clusters, while the metal-rich GCs have H-beta line-strengths that
could be interpreted as a mean age of ~5 (+3/-2) Gyr. Both populations appear
to have [Mg/Fe] ratios consistent with that of the Galactic GC system, although
this quantity is not very well-constrained. The kinematics of the metal-rich
GCs are similar to those of the planetary nebulae, exhibiting significant
rotation about a misaligned axis, while the metal-poor GCs have a higher
velocity dispersion and show a weaker kinematic correlation with the field
stars. The total gravitating mass of NGC 5128 derived from the GCs is in
excellent agreement with the value derived from stellar (PN) kinematics. We
suggest that these and other data support a picture in which the main body of
NGC 5128 was formed 3-8 Gyr ago by the dissipational merger of two unequal-mass
disk galaxies supplemented by the continual accretion of both gas-rich and
gas-poor satellites.


title:
The origin of optical emission from super-Eddington accreting Active
  Galactic Nuclei: the case of Ton S 180

abstract:
  Self-gravitating accretion discs have only been studied in a few nearby
objects using maser spots at the parsec-scale. We find a new spectral window
for observing the self-gravitating accretion disc in super-Eddington accreting
Active Galactic Nuclei (AGNs). This window is determined by calculating the
outermost radius (rsg) of a non self-gravitating disc and the corresponding
emission wavelength (lsg) as a function of various disc parameters. We find
that lsg reaches ~ 4000 AA for alpha=0.1, when Mdot > 70 (M_BH / 10^7 M_Sun)^-1
L_Edd/c^2 (where alpha, Mdot, M_BH and L_Edd are, respectively, the viscosity
parameter, gas accretion rate onto the central black hole (BH), the BH mass and
the Eddington luminosity). Moreover, lsg is as small as 1500 AA for alpha =
0.001, which is the smallest alpha case in this study. Therefore, the window
for observing the self-gravitating part of an AGN accretion disc is from 2
micron to lsg. Incidentally, rsg can be less than the photon trapping radius
for Mdot >~ 10^3.3 L_Edd/c^2. Namely, a self-gravitating, optically-thick,
advection-dominated accretion disc is expected to appear in the extremely high
accretion rate regime.
  Next, we demonstrate that the Mid-Infrared to X-ray spectrum of a bright,
well-studied Narrow-Line Seyfert 1 galaxy, Ton S 180, is indeed well fitted by
the spectrum arising from the following three components: an inner slim disc
(with a corona), an outer, self-gravitating non-Keplerian disc and a dusty
torus. The total mass, BH mass plus the entire disc mass, is found to be about
(1.4 - 8.0) M_BH. If the surface density varies with radius r in proportion to
r^-0.6, the total mass is consistent with the central mass estimated by H_beta
and [O III] widths.


title: Monopolar Pulsar Spin-Down

abstract:
  A multipole spin-down equation based on a monopolar term is derived from the
general expression $\dot{\nu} = -f(\nu,t)$ and used to study pulsar evolution.
We show that the time-independent version of such equation cannot reproduce the
observed properties of pulsars and conclude that there is no equation of the
form $\dot{\nu} = -f(\nu)$ consistent with the \pp diagram and braking index
measurements. We explore the time-dependent model under the hypothesis of
decaying magnetic fields, showing that an inverse linear decay gives reasonable
evolutionary trajectories. This model distinguishes the evolution of Vela from
that of the other three young pulsars considered. We discuss the origin of the
monopolar term, which cannot be attributed to radiative processes, pointing to
the importance of particle acceleration and/or mass loss processes in the
dynamical evolution of pulsars.


title: On the Steady Nature of Line-Driven Disk Winds

abstract:
  We perform an analytic investigation of the stability of line-driven disk
winds, independent of hydrodynamic simulations. Our motive is to determine
whether or not line-driven disk winds can account for the wide/broad UV
resonance absorption lines seen in cataclysmic variables (CVs) and
quasi-stellar objects (QSOs). In both CVs and QSOs observations generally
indicate that the absorption arising in the outflowing winds has a steady
velocity structure on time scales exceeding years (for CVs) and decades (for
QSOs). However, published results from hydrodynamic simulations of line-driven
disk winds are mixed, with some researchers claiming that the models are
inherently unsteady, while other models produce steady winds. The analytic
investigation presented here shows that if the accretion disk is steady, then
the line-driven disk wind emanating from it can also be steady. In particular,
we show that a gravitational force initially increasing along the wind
streamline, which is characteristic of disk winds, does not imply an unsteady
wind. The steady nature of line-driven disk winds is consistent with the 1D
streamline disk-wind models of Murray and collaborators and the 2.5D
time-dependent models of Pereyra and collaborators. This paper emphasizes the
underlying physics behind the steady nature of line-driven disk winds using
mathematically simple models that mimic the disk environment


title:
Reconstructing the Peak Distribution in the Sunyaev-Zeldovich Effect
  Surveys

abstract:
  We examine the ability of the Sunyaev-Zel'dovich effect (SZE) statistics
proposed by Lee (2002) using numerical simulations. The statistics describe the
distribution of the peak heights in the noise-contaminated SZE sky maps, and
provide an analysis technique to sort out the noise-contamination effect and
estimate the number density of real clusters. The method is devised to be
suitable for the interferometric SZE observations in drift-scanning mode like
AMiBA experiment. We apply the proposed method to a set of realistic SZE sky
maps constructed from large-scale cosmological simulations, and show that the
method indeed allows us to estimate the number density of clusters efficiently.
The efficiency of the method is demonstrated in two aspects: (i) it can
reconstruct the number density of clusters even though the clusters contribute
only a small fraction (10%) of the total number of peaks in each SZE map; (ii)
it can count even those clusters whose amplitudes are low enough to be
compatible with the noise level while conventional method of cluster
identification using the threshold cutoff cannot count them properly within the
same observation time. Thus, the proposed method may be useful for the study of
cluster abundance exploiting future interferometric SZE surveys such as AMiBA.


title:
Envelope Expansion with Core Collapse. I. Spherical Isothermal
  Similarity Solutions

abstract:
  We investigate self-similar dynamical processes in an isothermal
self-gravitational fluid with spherical symmetry. In reference to earlier
complementary solution results of Larson, Penston, Shu, Hunter and Whitworth &
Summers, we further explore the `semi-complete solution space' from an initial
instant $t\to 0^{+}$ to a final stage $t\to +\infty$. These similarity
solutions can describe and accommodate physical processes of radial inflow,
core collapse, oscillations and envelope expansion (namely, outflow or wind) or
contraction as well as shocks. In particular, we present new classes of
self-similar solutions, referred to as `envelope expansion with core collapse'
(EECC) solutions, that are featured by an interior core collapse and an
exterior envelope expansion concurrently. The interior collapse towards the
central core approaches a free-fall state as the radius $r\to 0$, while the
exterior envelope expansion gradually approaches a constant radial flow speed
as $r\to +\infty$. There exists at least one spherical stagnation surface of
zero flow speed that separates the core collapse and the envelope outflow and
that travels outward at constant speed, either subsonically or supersonically,
in a self-similar manner.


title: Structure and kinematics of candidate double-barred galaxies

abstract:
  Results of optical and NIR spectral and photometric observations of a sample
of candidate double-barred galaxies are presented. Velocity fields and velocity
dispersion maps of stars and ionized gas, continuum and emission-line images
were constructed from integral-field spectroscopy observations carried out at
the 6m telescope (BTA) of SAO RAS, with the MPFS spectrograph and the scanning
Fabry-Perot Interferometer. NGC2681 was also observed with the long-slit
spectrograph of the BTA. Optical and NIR images were obtained at the BTA and at
the 2.1m telescope (OAN, M\'exico). High-resolution images were retrieved from
the HST data archive. Morphological and kinematic features of all 13 sample
objects are described in detail. Attention is focused on the interpretation of
observed non-circular motions of gas and stars in circumnuclear (one
kiloparsec- scale) regions. We have shown first of all that these motions are
caused by the gravitational potential of a large-scale bar. NGC3368 and NGC3786
have nuclear bars only, their isophotal twist at larger radii being connected
with the bright spiral arms. Three cases of inner polar disks in our sample
(NGC2681, NGC3368 and NGC5850) are considered. We found ionized-gas
counter-rotation in the central kiloparsec of the lenticular galaxy NGC3945.
Seven galaxies (NGC470, NGC2273, NGC2681, NGC3945, NGC5566, NGC5905, and
NGC6951) have inner mini-disks nested in large-scale bars. Minispiral
structures occur often in these nuclear disks. It is interesting that the
majority of the observed, morphological and kinematical, features in the sample
galaxies can be explained without the secondary bar hypothesis. Thus we suggest
that a dynamically independent secondary bar is a rarer phenomenon than follows
from isophotal analysis of the images only.


title: The Roche problem: some analytics

abstract:
  Some exact analytical formulas are derived for the potential and mass ratio
as a function of Lagrangian points position, in the classical Roche model of
the close binary stars.


title:
Numerical simulation of the three-dimensional structure and dynamics of
  the non-magnetic solar chromosphere

abstract:
  Three-dimensional numerical simulations with CO5BOLD, a new radiation
hydrodynamics code, result in a dynamic, thermally bifurcated model of the
non-magnetic chromosphere of the quiet Sun. The 3-D model includes the middle
and low chromosphere, the photosphere, and the top of the convection zone,
where acoustic waves are excited by convective motions. While the waves
propagate upwards, they steepen into shocks, dissipate, and deposit their
mechanical energy as heat in the chromosphere. Our numerical simulations show
for the first time a complex 3-D structure of the chromospheric layers, formed
by the interaction of shock waves. Horizontal temperature cross-sections of the
model chromosphere exhibit a network of hot filaments and enclosed cool
regions. The horizontal pattern evolves on short time-scales of the order of
typically 20 - 25 seconds, and has spatial scales comparable to those of the
underlying granulation. The resulting thermal bifurcation, i.e., the
co-existence of cold and hot regions, provides temperatures high enough to
produce the observed chromospheric UV emission and -- at the same time --
temperatures cold enough to allow the formation of molecules (e.g., carbon
monoxide). Our 3-D model corroborates the finding by Carlsson & Stein (1994)
that the chromospheric temperature rise of semi-empirical models does not
necessarily imply an increase in the average gas temperature but can be
explained by the presence of substantial spatial and temporal temperature
inhomogeneities.


title:
WMAP constraints on scalar-tensor cosmology and the variation of the
  gravitational constant

abstract:
  We present observational constraints on a scalar-tensor gravity theory by
$\chi^2$ test for CMB anisotropy spectrum. We compare the WMAP temperature
power spectrum with the harmonic attractor model, in which the scalar field has
its harmonic effective potential with curvature $\beta$ in the Einstein
conformal frame and the theory relaxes toward Einstein gravity with time. We
found that the present value of the scalar coupling, i.e. the present level of
deviation from Einstein gravity $(\alpha_0^2)$, is bounded to be smaller than
$5\times 10^{-4-7\beta}$ ($2\sigma$), and $10^{-2-7\beta}$ ($4\sigma$) for $0<
\beta<0.45$. This constraint is much stronger than the bound from the solar
system experiments for large $\beta$ models, i.e., $\beta> 0.2$ and 0.3 in
$2\sigma$ and $4\sigma$ limits, respectively. Furthermore, within the framework
of this model, the variation of the gravitational constant at the recombination
epoch is constrained as $|G(z=z_{rec})-G_0|/G_0 < 0.05(2\sigma)$, and
$0.23(4\sigma)$.


title:
Particle acceleration in cooling flow clusters of galaxies: the case of
  Abell 2626

abstract:
  It has recently been proposed a theoretical model which accounts for the
origin of radio mini-halos observed in some cooling flow clusters as related to
electron re-acceleration by MHD turbulence (Gitti, Brunetti & Setti 2002). The
MHD turbulence is assumed to be frozen into the flow of the thermal ICM and
thus amplified in the cooling flow region. Here we present the application of
this model to a new mini-halo candidate, the cluster A2626, and compare the
results with those obtained for the mini-halo in the Perseus cluster. We
present VLA data at 330 MHz and 1.5 GHz of the diffuse radio emission observed
in A2626, and we show that its main properties can be explained by the model.
We find that the power necessary for the re-acceleration of the relic electron
population is only a factor ~ 0.7% of the maximum power that can be extracted
by the cooling flow (as estimated on the basis of the standard model). We also
discuss the observational properties of known mini-halos in connection with
those of host clusters, showing that the radio power of mini--halos increases
with the maximum power of cooling flows. This trend is expected in the
framework of the model. Possible effects of new Chandra and XMM-Newton
estimates of $\dot{M}$ on this trend are considered: we conclude that even if
earlier derived cooling rates were overestimated, cooling flow powers are still
well above the radio powers emitted by mini-halos.


title: On the origin of ionising photons emitted by T Tauri stars

abstract:
  We address the issue of the production of Lyman continuum photons by T Tauri
stars, in an attempt to provide constraints on theoretical models of disc
photoionisation. By treating the accretion shock as a hotspot on the stellar
surface we show that Lyman continuum photons are produced at a rate
approximately three orders of magnitude lower than that produced by a
corresponding black body, and that a strong Lyman continuum is only emitted for
high mass accretion rates. When our models are extended to include a column of
material accreting on to the hotspot we find that the accretion column is
extremely optically thick to Lyman continuum photons. Further, we find that
radiative recombination of hydrogen atoms within the column is not an efficient
means of producing photons with energies greater than 13.6eV, and find that an
accretion column of any conceivable height suppresses the emission of Lyman
continuum photons to a level below or comparable to that expected from the
stellar photosphere. The photospheric Lyman continuum is itself much too weak
to affect disc evolution significantly, and we find that the Lyman continuum
emitted by an accretion shock is similarly unable to influence disc evolution
significantly. This result has important consequences for models which use
photoionisation as a mechanism to drive the dispersal of circumstellar discs,
essentially proving that an additional source of Lyman continuum photons must
exist if disc photoionisation is to be significant.


title: Time-sequenced Multi-Radio-Frequency Observations of Cygnus X-3 in Flare

abstract:
  Multifrequency observations from the VLA, VLBA and OVRO Millimeter Array of a
major radio outburst of Cygnus X-3 in 2001 September are presented, measuring
the evolution of the spectrum of the source over three decades in frequency,
over a period of six days. Following the peak of the flare, as the intensity
declines the high-frequency spectrum at frequency nu steepens from nu^{-0.4} to
nu^{-0.6}, after which the spectral index remains at this latter terminal
value; a trend previously observed but hitherto not satisfactorily explained.
VLBA observations, for the first time, track over several days the expansion of
a sequence of knots whose initial diameters are approximately 8
milliarcseconds. The light-crossing time within these plasmons is of the same
order as the time-scale over which the spectrum is observed to evolve. We
contend that properly accounting for light-travel time effects in and between
plasmons which are initially optically thick, but which after expansion become
optically thin, explains the key features of the spectral evolution, for
example the observed timescale. Using the VLBA images, we have directly
measured for the first time the proper motions of individual knots, analysis of
which shows a two-sided jet whose axis is precessing. The best-fit jet speed is
roughly beta = 0.63 and the precession period is about 5 days, significantly
lower than fitted for a previous flare. Extrapolation of the positions of the
knots measured by the VLBA back to zero-separation shows this to occur
approximately 2.5 days after the detection of the rise in flux density of
Cygnus X-3.


title:
Heavy elements abundances in turn-off stars and early subgiants in NGC
  6752

abstract:
  High resolution spectra (R > 40 000) for 9 main sequence turn-off stars and 9
subgiants in the globular cluster NGC 6752 were acquired with UVES on the
VLT-Kueyen (UT2). These data have been used to determine the abundances of some
heavy elements (strontium, yttrium, barium and europium). This paper presents
for the first time accurate results for heavy elements in this globular
cluster. We did not find any systematic effect between the abundances found in
turn-off stars, subgiants, and giants. We obtain the following mean abundances
for these elements in our sample (turn-off stars and subgiants): [Sr/Fe] = 0.06
+/- 0.16, [Y/Fe] = -0.01 +/- 0.12, [Ba/Fe] = 0.18 +/- 0.11, and [Eu/Fe] = 0.41
+/- 0.09. The dispersion in the abundance ratios of the different elements is
low and can be totally explained by uncertainties in their derivation. These
ratios are in agreement with the values found in field halo stars with the same
metallicity. We did not observe any correlation between the [n-capture/Fe]
ratios and the star-to-star variations of the O and Na abundances. The [Ba/Eu]
and [Sr/Ba] ratios show clearly that this globular cluster has also been
uniformly enriched by r- and s-process synthesis.


title: The Distribution of Lya-Emitting Galaxies at z=2.3

abstract:
  We present the detection of 34 Ly-alpha emission-line galaxy candidates in a
80x80x60 co-moving Mpc region surrounding the known z=2.38 galaxy cluster
J2143-4423. The space density of Ly-alpha emitters is comparable to that found
by Steidel et al. when targeting a cluster at redshift 3.09, but is a factor of
5.8 +/- 2.5 greater than that found by field samples at similar redshifts. The
distribution of these galaxy candidates contains several 5-10 Mpc scale voids.
We compare our observations with mock catalogs derived from the VIRGO
consortium Lambda-CDM n-body simulations. Fewer than 1% of the mock catalogues
contain voids as large as we observe. Our observations thus tentatively suggest
that the galaxy distribution at redshift 2.38 contains larger voids than
predicted by current models. Three of the candidate galaxies and one previously
discovered galaxy have the large luminosities and extended morphologies of
"Ly-alpha blobs".


title: Probing the variability of the fine-structure constant with the VLT/UVES

abstract:
  We assess the cosmological variability of the fine-structure constant from
the analysis of an ensemble of Fe II absorption lines at the redshift z=1.15
toward the QSO HE 0515-4414 by means of the standard many-multiplet (MM)
technique and its revision based on linear regression (RMM). This is the first
time the MM technique is applied to exceptional high-resolution and high
signal-to-noise QSO spectra recorded with the UV-Visual Echelle Spectrograph
(UVES) at the ESO Very Large Telescope (VLT). Our analysis results in the most
stringent bounds hitherto infered from QSO absorption lines. Our results
support the null hypothesis of a non-varying fine-structure constant at a
significance level of 91 percent, whereas the support for the results presented
in former MM studies indicating a variation in the fine-structure constant is
12 percent.


title: Timing properties and spectral states in Aquila X-1

abstract:
  We have analyzed five X-ray outbursts of the neutron-star soft X-ray
transient Aql X-1 and investigated the timing properties of the source in
correlation with its spectral states as defined by different positions in the
color-color and hardness-intensity diagrams. The hard color and the source
count rate serve as the distinguishing parameters giving rise to three spectral
states: a low-intensity hard state, an intermediate state and a high-intensity
soft state. These states are respectively identified with the extreme island,
island and banana states that characterize the atoll sources. The large amount
of data analyzed allowed us to perform for the first time a detailed timing
analysis of the extreme island state. Differences in the aperiodic variability
between the rise and the decay of the X-ray outbursts are found in this state:
at the same place in the color-color diagram, during the rise the source
exhibits more power at low frequencies (< 1 Hz), whereas during the decay the
source is more variable at high frequencies (> 100 Hz). The very-low frequency
noise that characterizes the banana-state power spectra below 1 Hz cannot be
described in terms of a single power law but a two-component model is required.
In two outbursts a new 6-10 Hz QPO has been discovered and tentatively
identified with the normal/flaring branch-like oscillation observed only at the
highest inferred mass accretion rates. We have compared the spectral and timing
properties of Aql X-1 with those of other atoll and Z sources. Our results
argue against a unification scheme for these two types of neutron-star X-ray
binaries.


title:
Evolution of the polarization of the optical afterglow of the gamma-ray
  burst GRB 030329

abstract:
  We report 31 polarimetric observations of the afterglow of GRB 030329 with
high signal-to-noise and high sampling frequency. We establish the polarization
light curve, detect sustained polarization at the percent level, and find
significant variability of polarization degree and angle. The data imply that
the afterglow magnetic field has small coherence length and is mostly random,
probably generated by turbulence.


title: Spin orientation of supermassive black holes in active galaxies

abstract:
  Accretion of gas onto a central supermassive black hole is generally accepted
to be the source of the emitted energy in active galactic nuclei.The broad
emission lines we observe in their optical spectra are probably formed in the
wind of an accretion disk at distances of light days to light years from the
central black hole. The variable fraction of the emission lines originates at
typical distances of only 1 to 50 light days from the central supermassive
black hole. We derived a central black hole mass of M_orbital = 1.8 +/-0.4 x
10^7 M_sun in the Seyfert galaxy Mrk110 assuming the broad emission lines are
generated in gas clouds orbiting within an accretion disk. This figure depends
on the inclination angle of the accretion disk. Here we report on the detection
of gravitational redshifted emission in the variable fraction of the broad
emission lines. We derive a central black hole mass of M_grav = 14.0 +/-3.0 x
10^7 M_sun. These measurements are independent on the orientation of the
accretion disk. The comparison of both black hole mass estimates allows to
determine the projection of the central accretion disk angle i to 21 +/-5 deg.
in Mrk110 and therefore the orientation of the spin axis of the central black
hole.


title: X-ray Cavities and Cooling Flows

abstract:
  Recent data have radically altered the X-ray perspective on cooling flow
clusters. X-ray spectra show that very little of the hot intracluster medium is
cooler than about 1 keV, despite having short cooling times. In an increasing
number of cooling flow clusters, the lobes of a central radio source are found
to have created cavities in the hot gas. Generally, the cavities are not
overpressured relative to the intracluster gas, but act as buoyant bubbles of
radio emitting plasma that drive circulation as they rise, mixing and heating
the intracluster gas. All this points to the radio source, i.e. an active
galactic nucleus, as the heat source that prevents gas from cooling to low
temperatures. However, heating due to bubbles alone seems to be insufficient,
so the energetics of cooling flows remain obscure. We briefly review the data
and theory supporting this view and discuss the energetics of cooling flows.


title: A Submm View of the Universe: Clues to the Formation of Massive Galaxies

abstract:
  We discuss recent advances in the study of dusty, massive galaxies at z>1
arising from the first extensive spectroscopic surveys.


title: Star Formation in Transient Molecular Clouds

abstract:
  We present the results of a numerical simulation in which star formation
proceeds from an initially unbound molecular cloud core. The turbulent motions,
which dominate the dynamics, dissipate in shocks leaving a quiescent region
which becomes gravitationally bound and collapses to form a small multiple
system. Meanwhile, the bulk of the cloud escapes due to its initial supersonic
velocities. In this simulation, the process naturally results in a star
formation efficiency of 50%. The mass involved in star formation depends on the
gas fraction that dissipates sufficient kinetic energy in shocks. Thus, clouds
with larger turbulent motions will result in lower star formation efficiencies.
This implies that globally unbound, and therefore transient giant molecular
clouds (GMCs), can account for the low efficiency of star formation observed in
our Galaxy without recourse to magnetic fields or feedback processes.
Observations of the dynamic stability in molecular regions suggest that GMCs
may not be self-gravitating, supporting the ideas presented in this letter.


title: On the Chandra X-ray Sources in the Galactic Center

abstract:
  Recent deep Chandra surveys of the Galactic center region have revealed the
existence of a faint, hard X-ray source population. While the nature of this
population is unknown, it is likely that several types of stellar objects
contribute. For sources involving binary systems, accreting white dwarfs and
accreting neutron stars with main sequence companions have been proposed. Among
the accreting neutron star systems, previous studies have focused on stellar
wind-fed sources. In this paper, we point out that binary systems in which mass
transfer occurs via Roche lobe overflow (RLOF) can also contribute to this
X-ray source population.
  A binary population synthesis study of the Galactic center region has been
carried out, and it is found that evolutionary channels for neutron star
formation involving the accretion induced collapse of a massive ONeMg white
dwarf, in addition to the core collapse of massive stars, can contribute to
this population. The RLOF systems would appear as transients with quiescent
luminosities, above 2 keV, in the range from 10^31-10^32 ergs/s. The results
reveal that RLOF systems primarily contribute to the faint X-ray source
population in the Muno et al. (2003) survey and wind-fed systems can contribute
to the less sensitive Wang et al. (2002) survey. However, our results suggest
that accreting neutron star systems are not likely to be the major contributor
to the faint X-ray source population in the Galactic center.


title: A search for close companions in Sco OB2

abstract:
  Using adaptive optics we study the binary population in the nearby OB
association Scorpius OB2. We present the first results of our near-infrared
adaptive optics survey among 199 (mainly) A- and B-type stars in Sco OB2. In
total 151 components other than the target stars are found, out of which 77 are
probably background stars. Our findings are compared with data collected from
literature. Out of the remaining 74 candidate physical companions 42 are new,
demonstrating that many stars A/B stars have faint, close companions.


title: He I 10830 as a Probe of Winds in Accreting Young Stars

abstract:
  He I 10830 profiles acquired with Keck's NIRSPEC for 6 young low mass stars
with high disk accretion rates (AS 353A, DG Tau, DL Tau, DR Tau, HL Tau and SVS
13) provide new insight into accretion-driven winds. In 4 stars the profiles
have the signature of resonance scattering, and possess a deep and broad
blueshifted absorption that penetrates more than 50% into the 1 micron
continuum over a continuous range of velocities from near the stellar rest
velocity to the terminal velocity of the wind, unlike inner wind signatures
seen in other spectral features. This deep and broad absorption provides the
first observational tracer of the acceleration region of the inner wind and
suggests that this acceleration region is situated such that it occults a
significant portion of the stellar disk. The remaining 2 stars also have blue
absorption extending below the continuum although here the profiles are
dominated by emission, requiring an additional source of helium excitation
beyond resonant scattering. This is likely the same process that produces the
emission profiles seen at He I 5876.


title: A Fast Algorithm for Cosmic Rays Removal from Single Images

abstract:
  We present a method for detecting cosmic rays in single images. The algorithm
is based on simple analysis of the histogram of the image data and does not use
any modeling of the picture of the object. It does not require a good signal to
noise ratio in the image data. Identification of multiple-pixel cosmic-ray hits
is realized by running the procedure for detection and replacement iteratively.
The tests performed by us, show that the method is very effective, when applied
to the images with the spectroscopic data. It is also very fast in comparison
with other single image algorithms found in astronomical data processing
packages. Practical implementation and examples of application are presented.


title:
On the Nature of the Bright Short-Period X-ray Source in the Circinus
  Galaxy Field

abstract:
  The spectrum and light curve of the bright X-ray source CG X-1 in the field
of the Circinus galaxy are re-examined. Previous analyses have concluded that
the source is an accreting black hole of about 50 solar masses although it was
noted that the light curve resembles that of an AM Her system. Here we show
that the short period and an assumed main sequence companion constrain the mass
of the companion to less than one solar mass. Further a possible eclipse seen
during one of the Chandra observations and a subsequent XMM-Newton observation
constrains the mass of the compact object to less than about 60 solar masses.
If such a system lies in the Circinus galaxy, then the accreting object must
either radiate anisotropically or strongly violate the Eddington limit. Even if
the emission is beamed, then the companion star which intercepts this flux
during eclipse will be driven out of thermal equilibrium and evaporate within
about 1000 years. We find that the observations cannot rule out an AM Her
system in the Milky Way and that such a system can account for the variations
seen in the light curve.


title: Cosmic Renaissance: The First Sources of Light

abstract:
  I review recent progress in understanding the formation of the first stars
and quasars. The initial conditions for their emergence are given by the now
firmly established model of cosmological structure formation. Numerical
simulations of the collapse and fragmentation of primordial gas indicate that
the first stars formed at redshifts z ~ 20 - 30, and that they were
predominantly very massive, with M_* > 100 M_sun. Important uncertainties,
however, remain. Paramount among them is the accretion process, which builds up
the final stellar mass by incorporating part of the diffuse, dust-free envelope
into the central protostellar core. The first quasars, on the other hand, are
predicted to have formed later on, at z ~ 10, in more massive dark matter
halos, with total masses, ~ 10^8 M_sun, characteristic of dwarf galaxies.


title: Phantom Cosmologies

abstract:
  The dynamics of a minimally coupled scalar field in the expanding universe is
discussed with special reference to phantom cosmology. The evolution of the
universe with a phantom field vis-a-vis a quintessence field is compared.
Phantom cosmologies are found to have two special features i) occurrence of a
singularity where the scale factor, the energy density and Ricci curvature
scalar diverge to infinity. This singularity occurs at a finite time, depending
on w during cosmic evolution, ii) degeneracy in the determination of w(z_m) for
a particular transition redshift z_m which seems to impart similar
observational properties to corresponding phantom and quintessence models and
makes them compatible with the cosmological observations. Constraints over
phantom fields are derived using recent WMAP data and the range of $w$ is
narrowed down to -1.18 < w < -0.93 with the corresponding value of the
deceleration parameter lying in the range - 0.8 < q_0 < -0.52. An observational
test, based upon the observations of low redshift galactic clusters, is
suggested to discriminate between the quintessence and phantom dark energy.


title: Is There a Missing Galaxy Problem at High Redshift?

abstract:
  We study the evolution of the global stellar mass density in a Lambda cold
dark matter universe using two different types of hydrodynamical simulations
(Eulerian TVD and SPH) and the analytical model of Hernquist & Springel (2003).
We find that the theoretical calculations all predict both a higher stellar
mass density at z~3 than indicated by current observations, and that the peak
of the cosmic star formation rate history should lie at z~5. Such a star
formation history implies that as much as (70%, 30%) of the total stellar mass
density today must already have formed by z=(1, 3). Our results suggest that
current observations at z~3 are missing as much as 50% of the total stellar
mass density in the Universe, perhaps owing to an inadequate allowance for dust
obscuration in star-forming galaxies, limited sample sizes, or cosmic variance.
We also compare our results with some of the updated semi-analytic models of
galaxy formation.


title:
Photometric Properties of Lyman-break Galaxies at z=3 in Cosmological
  SPH Simulations

abstract:
  We study the photometric properties of Lyman-break galaxies (LBGs) formed by
redshift z=3 in a set of large cosmological smoothed-particle hydrodynamics
simulations of the Lambda cold dark matter (CDM) model. Our numerical
simulations include radiative cooling and heating with a uniform UV background,
star formation, supernova feedback, and a phenomenological model for galactic
winds. Analysing a series of simulations of varying boxsize and particle number
allows us to isolate the impact of numerical resolution on our results. We
compute spectra of simulated galaxies using a population synthesis model, and
derive colours and luminosity functions of galaxies at z=3 after applying local
dust extinction and absorption by the intergalactic medium (IGM). We find that
the simulated galaxies have U-G and G-R colours consistent with observations,
provided that intervening absorption by the IGM is applied. The observed
properties of LBGs, including their number density, colours, and luminosity
functions, can be explained if LBGs are identified with the most massive
galaxies at z=3, having typical stellar mass of M_{star} ~ 1e10 Msun/h, a
conclusion broadly consistent with earlier studies based on hydrodynamic
simulations of the Lamda CDM model. We also find that most simulated LBGs were
continuously forming stars at a high rate for more than one Gyr up until z=3,
but with numerous starbursts lying on top of the continuous component.
Interestingly, our simulations suggest that more than 50% of the total stellar
mass and star formation rate in the Universe are accounted for by galaxies that
are not detected in the current generation of LBG surveys.


title:
Heavy Neutron Stars? A Status Report on Arecibo Timing of Four
  Pulsar-White Dwarf Systems

abstract:
  Relativistic phenomena (orbital precession, Shapiro delay, and/or orbital
decay) have been measured in Arecibo timing observations of four pulsar-white
dwarf binaries, leading to constraints on the neutron star masses. We have
detected the decay of the PSR J0751+1807 orbit due to gravitational radiation
emission, the first such measurement in a binary with a low mass ratio
(m_2/m_1<<1). Timing data constrains the mass of this pulsar to bet between 1.6
and 2.8 solar masses. Masses of the other pulsars are in marginal agreement
with the canonical pulsar mass of 1.35 solar masses, but higher values are
preferred.


title: Globular Cluster Formation in M82

abstract:
  We present high resolution mid-infrared (mid-IR; 11.7 and 17.65 micron) maps
of the central 400 pc region of the starburst galaxy M82. Seven star forming
clusters are identified which together provide ~ 15% of the total mid-IR
luminosity of the galaxy. Combining the mid-IR data with thermal radio
measurements and near- and mid-IR line emission, we find that these young
stellar clusters have inferred masses and sizes comparable to globular
clusters. At least 20% of the star formation in M82 is found to occur in
super-star clusters.


title: Radiative Shock-Induced Collapse of Intergalactic Clouds

abstract:
  Accumulating observational evidence for a number of radio galaxies suggests
an association between their jets and regions of active star formation. The
standard picture is that shocks generated by the jet propagate through an
inhomogeneous medium and trigger the collapse of overdense clouds, which then
become active star-forming regions. In this contribution, we report on recent
hydrodynamic simulations of radiative shock-cloud interactions using two
different cooling models: an equilibrium cooling-curve model assuming solar
metallicities and a non-equilibrium chemistry model appropriate for primordial
gas clouds. We consider a range of initial cloud densities and shock speeds in
order to quantify the role of cooling in the evolution. Our results indicate
that for moderate cloud densities (>1 cm^{-3}) and shock Mach numbers (<20),
cooling processes can be highly efficient and result in more than 50% of the
initial cloud mass cooling to below 100 K. We also use our results to estimate
the final H_2 mass fraction for the simulations that use the non-equilibrium
chemistry package. This is an important measurement, since H_2 is the dominant
coolant for a primordial gas cloud. We find peak H_2 mass fractions of >0.01
and total H_2 mass fractions of >10^{-5} for the cloud gas. Finally, we compare
our results with the observations of jet-induced star formation in
``Minkowski's Object.'' We conclude that its morphology, star formation rate (~
0.3M_solar/yr) and stellar mass (~ 1.2 x 10^7 M_solar) can be explained by the
interaction of a 90,000 km/s jet with an ensemble of moderately dense (~ 10
cm^{-3}), warm (10^4 K) intergalactic clouds in the vicinity of its associated
radio galaxy at the center of the galaxy cluster.


title: Supernova Explosions: Lessons from Spectropolarimetry

abstract:
  Supernova can be polarized by an asymmetry in the explosion process, an
off-center source of illumination, scattering in an envelope distorted by
rotation or a binary companion, or scattering by the circumstellar dust.
Careful polarimetry is the most powerful tool to study the 3-D geometry of
supernovae. A deep understanding of the 3-D geometry of SNe is essential in
using them for calibrated distance indicators.


title: Short-Period Variable Stars in the M31 Halo

abstract:
  We report the findings of a new search for RR Lyraes in an M31 halo field
located 40 arcminutes from the nucleus of the galaxy along the minor axis. We
detected 37 variable stars, of which 24 are classified as RR Lyraes and the
others are ambiguous. Estimating a completeness fraction of ~24%, we calculate
that there are approximately 100 RR Lyraes in the field, which is consistent
with what is expected from deep HST color-magnitude diagrams. We calculate a
mean magnitude of g=25.15+/ 0.03, which we interpret to mean that the mean
metallicity of RR Lyraes is significantly lower than that of the M31 halo as a
whole. The presence of ancient, metal-poor stars opens the possibility that,
initially, the M31 halo appeared much like the Milky Way halo.


title: Gamma-Ray Bursts: Jets and Energetics

abstract:
  The relativistic outflows from gamma-ray bursts are now thought to be
narrowly collimated into jets. After correcting for this jet geometry there is
a remarkable constancy of both the energy radiated by the burst and the kinetic
energy carried by the outflow. Gamma-ray bursts are still the most luminous
explosions in the Universe, but they release energies that are comparable to
supernovae. The diversity of cosmic explosions appears to be governed by the
fraction of energy that is coupled to ultra-relativistic ejecta.


title:
Probable intermediate mass black holes in NGC4559: XMM-Newton spectral
  and timing constraints

abstract:
  We have examined X-ray and optical observations of two ultra-luminous X-ray
sources, X7 and X10 in NGC4559, using XMM-Newton, Chandra and HST. The UV/X-ray
luminosity of X7 exceeds 2.1e40 erg/s in the XMM-Newton observation, and that
of X10 is >1.3e40 erg/s. X7 has both thermal and power-law spectral components.
The characteristic temperature of the thermal component is 0.12 keV. The
power-law components in the two sources both have slopes with photon index
\~2.1. A timing analysis of X7 indicates a break frequency at 28 mHz in the
power spectrum, while that for X10 is consistent with an unbroken power law.
The luminosity of the blackbody component in the X-ray spectrum of X7 and the
nature of its time variability provides evidence that this object is an
intermediate mass black hole accreting at sub-Eddington rates, but other
scenarios which require high advection efficiencies from a hollowed-out disk
might be possible. The emission from X10 can be characterised by a single
power-law. This source can be interpreted either as an intermediate mass black
hole, or as a stellar-mass black hole with relativistically-beamed Comptonised
emission. There are four optical counterparts in the error circle of X7. No
counterparts are evident in the error circle for X10.


title: Low-Luminosity AGNs at the Highest Resolution: Jets or Accretion Flows?

abstract:
  Six low-luminosity active galactic nuclei have been imaged at multiple
frequencies from 1.7--43 GHz (2.3--15 GHz for three of the galaxies) using the
Very Long Baseline Array. In spite of dynamic ranges of about 100 in several
frequency bands, all six galaxies remain unresolved, with size limits at 8.4
GHz of 10^3--10^4 times the Schwarzschild radii of the black holes inferred at
their galactic centers. The galaxy spectra are roughly flat from 1.7 to 43 GHz,
rather than steepening to classical optically thin synchrotron spectra at high
frequencies. Although the spectral slopes somewhat resemble predictions for
advection-dominated accretion flows, the luminosities are too high for the
black hole masses of the galaxies and the slight spectral steepening at high
frequencies cannot be explained by standard simple models of such accretion
flows. In contrast, compact jets can accommodate the average spectral index,
the relatively high radio luminosity, and the unresolved appearance, but only
if the jets in all six galaxies are fairly close to our line of sight. This
constraint is in agreement with inclination angle predictions for five of the
six AGNs based on the dusty torus unification model.


title:
Discrete-dipole approximation with polarizabilities that account for
  both finite wavelength and target geometry

abstract:
  The discrete-dipole approximation (DDA) is a powerful method for calculating
absorption and scattering by targets that have sizes smaller than or comparable
to the wavelength of the incident radiation. We present a new prescription --
the Surface-Corrected Lattice Dispersion Relation (SCLDR) -- for assigning the
dipole polarizabilities that takes into account both target geometry and finite
wavelength. We test the SCLDR in DDA calculations using spherical and
ellipsoidal targets and show that for a fixed number of dipoles, the SCLDR
prescription results in increased accuracy in the calculated cross sections for
absorption and scattering. We discuss extension of the SCLDR prescription to
irregular targets.


title:
Multi-component power spectra estimation method for multi-detector
  observations of the Cosmic Microwave Background

abstract:
  We present a new method for multi-component power spectra estimation in
multi-frequency observations of the CMB. Our method is based on matching a
model to the cross and auto power spectra of observed maps. All the component
power spectra are estimated, as well as their mixing matrix. Noise power
spectra are also estimated. The method has been applied to full-sky Planck
simulations containing five astrophysical components and white noise. The beam
smoothing effect is taken into account.


title: Invisible Un-removable Field: A Search by Ultra-High Energy Cosmic Rays

abstract:
  A Toy model which introduces the different limiting velocities for each
particleis discussed: the differentiation of the universal limiting velocity is
implemented throgh the coupling with external tensor or vector field, something
like Higgs scalar field. GZK cut-off discussion could be altered due to the
violation of Lorentz symmetry.


title: Detection of Intergalactic HeII Absorption at Redshift 3.5

abstract:
  The large number of quasars found in the Sloan Digital Sky Survey has allowed
searches for elusive, clear lines of sight towards HeII Ly-alpha absorption, a
sensitive probe of the intergalactic medium. The few known systems indicate
that HeII reionization occurs at z>3. We report the detection of a HeII
Ly-alpha absorption edge in a quasar spectrum at z=3.50, the most distant such
feature found to date. The candidate quasar was selected from a z~3 sample in
the SDSS spectroscopic quasar survey and confirmed as part of an HST/STIS SNAP
survey. We discuss the general characteristics of the absorption feature, as
well as the probability for discovery of additional such objects.


title:
A spectral and spatial analysis of eta Carinae's diffuse X-ray emission
  using CHANDRA

abstract:
  The luminous unstable star (star system) eta Carinae is surrounded by an
optically bright bipolar nebula, the Homunculus and a fainter but much larger
nebula, the so-called outer ejecta. As images from the EINSTEIN and ROSAT
satellites have shown, the outer ejecta is also visible in soft X-rays, while
the central source is present in the harder X-ray bands. With our CHANDRA
observations we show that the morphology and properties of the X-ray nebula are
the result of shocks from fast clumps in the outer ejecta moving into a
pre-existing denser circumstellar medium. An additional contribution to the
soft X-ray flux results from mutual interactions of clumps within the ejecta.
Spectra extracted from the CHANDRA data yield gas temperatures kT of 0.6-0.76
keV. The implied pre-shock velocities of 670-760 km/s are within the scatter of
the velocities we measure for the majority of the clumps in the corresponding
regions. Significant nitrogen enhancements over solar abundances are needed for
acceptable fits in all parts of the outer ejecta, consistent with CNO processed
material and non-uniform enhancement. The presence of a diffuse spot of hard
X-ray emission at the S condensation shows some contribution of the highest
velocity clumps and further underlines the multicomponent, non-equilibrium
nature of the X-ray nebula. The detection of an X-ray ``bridge'' between the
northern and southern part of the X-ray nebula and an X-ray shadow at the
position of the NN bow can be attributed to a large expanding disk, which would
appear as an extension of the equatorial disk. No soft emission is seen from
the Homunculus, or from the NN bow or the ``strings''.


title: H-alpha variability of the recurrent nova T Coronae Borealis

abstract:
  We analyze H-alpha observations of the recurrent nova T CrB obtained during
the last decade. For the first time the H-alpha emission profile is analyzed
after subtraction of the red giant contribution. Based on our new radial
velocity measurements of the H-alpha emission line we estimate the component
masses of T CrB. It is found that the hot component is most likely a massive
white dwarf. We estimate the inclination and the component masses to be i~67
deg, Mwd = 1.37 +/-0.13 Msun and Msec=1.12 +/-0.23 Msun, respectively. The
radial velocity of the central dip in the H-alpha profile changes nearly in
phase with that of the red giant's absorption lines. This suggests that the dip
is most likely produced by absorption in the giant's wind.
  Our observations cover an interval when the H-alpha and the U-band flux vary
by a factor of ~6, while the variability in B and V is much smaller. Based on
our observations, and archival ultraviolet and optical data we show that the
optical, ultraviolet and H-alpha fluxes strongly correlate. We argue that the
presence of an accretion disc can account for most of the observed properties
of T CrB.


title: Spot Sizes on Sun-like Stars

abstract:
  The total area coverage by starspots is of interest for a variety of reasons,
but direct techniques only provide estimates of this important quantity.
Sunspot areas exhibit a lognormal size distribution irrespective of the phase
of the activity cycle, implying that most sunspots are small. Here we explore
the consequences if starspot areas were similarly distributed. The solar data
allow for an increase in the fraction of larger sunspots with increasing
activity. Taking this difference between the size distribution at sunspot
maximum and minimum, we extrapolate to higher activity levels, assuming
different dependencies of the parameters of the lognormal distribution on total
spot coverage. We find that even for very heavily spotted (hypothetical) stars
a large fraction of the spots are smaller than the current resolution limit of
Doppler images and might hence be missed on traditional Doppler maps.


title: Analyze This! A Cosmological Constraint Package for CMBEASY

abstract:
  We introduce a Markov Chain Monte Carlo simulation and data analysis package
that extends the CMBEASY software. We have taken special care in implementing
an adaptive step algorithm for the Markov Chain Monte Carlo in order to improve
convergence. Data analysis routines are provided which allow to test models of
the Universe against measurements of the cosmic microwave background,
supernovae Ia and large scale structure. We present constraints on cosmological
parameters derived from these measurements for a $\Lambda$CDM cosmology and
discuss the impact of the different observational data sets on the parameters.
The package is publicly available as part of the CMBEASY software at
www.cmbeasy.org.


title:
Accretion Driven Evolution of Quasars and Black Holes: Theoretical
  Models

abstract:
  We present a flexible framework for constructing physical models of quasar
evolution that can incorporate a variety of observational constraints, such as
multi-wavelength luminosity functions, estimated masses and accretion rates of
active black holes, space densities of quasar hosts, and the local black hole
mass function. We focus on the accretion rate distribution p(mdot|M,z), the
probability that a black hole of mass M at redshift z accretes at a rate mdot
in Eddington units. Given the radiative efficiency as a function of mdot, the
quasar luminosity function (QLF) is determined by a convolution of p(mdot|M,z)
with the black hole mass function n(M,z). In the absence of mergers p(mdot|M,z)
also determines the full evolution of n(M,z), given a "boundary value" of n(M)
at some redshift. Matching the observed decline of the QLF break luminosity at
z<2 requires either a shift towards lower characteristic accretion rates or an
evolving mass dependence of p(mdot) that preferentially shuts off accretion
onto high mass black holes. These two scenarios make different predictions for
the masses and accretion rates of active black holes. If the first mechanism
dominates, then the QLF changes character between z=2 and z=0, shifting from a
sequence of black hole mass towards a sequence of L/Ledd. We construct and
compare five models that illustrate different assumptions about the quasar
population: short and long lifetime models dominated by unobscured thin-disk
accretion, a model with a high fraction of obscured quasars, and models in
which mergers or ADAF accretion produce substantial black hole growth at low
redshift. We discuss the observational advances that would be most valuable for
distinguishing such models and for pinning down the physics that drives black
hole and quasar evolution. (Abridged)


title:
The Connection between W31, SGR 1806-20, & LBV 1806-20: Distance,
  Extinction, and Structure

abstract:
  We present new millimeter and infrared spectroscopic observations towards the
radio nebula G10.0-0.3, which is powered by the wind of the Luminous Blue
Variable star LBV 1806-20, also closely associated with the soft gamma-ray
repeater SGR 1806-20, and believed to be located in the giant Galactic HII
complex W31. Based on observations of CO emission lines and NH_3 absorption
features from molecular clouds along the line of sight to G10.0-0.3, as well as
the radial velocity and optical extinction of the star powering the nebula, we
determine its distance to be 15.1$^{+1.8}_{-1.3}$ kpc in agreement with Corbel
et al. (1997). In addition, this strengthens the association of SGR 1806-20
with a massive molecular cloud at the same distance. All soft gamma-ray
repeaters with precise location are now found to be associated with a site of
massive star formation or molecular cloud. We also show that W31 consists of at
least two distinct components along the line of sight. We suggest that
G10.2-0.3 and G10.6-0.4 are located on the -30 km/s spiral arm at a distance
from the Sun of 4.5 $\pm$ 0.6 kpc and that G10.3-0.1 may be associated with a
massive molecular cloud at the same distance as the LBV star, i.e.
15.1$^{+1.8}_{-1.3}$ kpc, implying that W31 could be decomposed into two
components along the line of sight.


title: Cosmic microwave background anisotropies in multi-connected flat spaces

abstract:
  This article investigates the signature of the seventeen multi-connected flat
spaces in cosmic microwave background (CMB) maps. For each such space it
recalls a fundamental domain and a set of generating matrices, and then goes on
to find an orthonormal basis for the set of eigenmodes of the Laplace operator
on that space. The basis eigenmodes are expressed as linear combinations of
eigenmodes of the simply connected Euclidean space. A preceding work, which
provides a general method for implementing multi-connected topologies in
standard CMB codes, is then applied to simulate CMB maps and angular power
spectra for each space. Unlike in the 3-torus, the results in most
multi-connected flat spaces depend on the location of the observer. This effect
is discussed in detail. In particular, it is shown that the correlated circles
on a CMB map are generically not back-to-back, so that negative search of
back-to-back circles in the WMAP data does not exclude a vast majority of flat
or nearly flat topologies.


title: Crowded Field 3D Spectroscopy

abstract:
  The quantitative spectroscopy of stellar objects in complex environments is
mainly limited by the ability of separating the object from the background.
Standard slit spectroscopy, restricting the field of view to one dimension, is
obviously not the proper technique in general. The emerging Integral Field (3D)
technique with spatially resolved spectra of a two-dimensional field of view
provides a great potential for applying advanced subtraction methods. In this
paper an image reconstruction algorithm to separate point sources and a smooth
background is applied to 3D data. Several performance tests demonstrate the
photometric quality of the method. The algorithm is applied to real 3D
observations of a sample Planetary Nebula in M31, whose spectrum is
contaminated by the bright and complex galaxy background. The ability of
separating sources is also studied in a crowded stellar field in M33.


title: The reprocessing features in the X-ray spectrum of the NELG MCG-5-23-16

abstract:
  We present results from the spectral analysis of the Seyfert 1.9 galaxy
MCG-5-23-16, based on ASCA, BeppoSAX, Chandra and XMM-Newton observations. The
spectrum of this object shows a complex iron Kalpha emission line, which is
best modeled by a superposition of a narrow and a broad (possibly relativistic)
iron line, together with a Compton reflection component. Comparing results from
all (six) available observations, we do not find any significant variation in
the flux of both line components. The moderate flux continuum variability
(about 25% difference between the brightest and faintest states), however, does
not permit us to infer much about the location of the line-emitting material.
The amount of Compton reflection is lower than expected from the total iron
line EW, implying either an iron overabundance or that one of the two line
components (most likely the narrow one) originates in Compton-thin matter.


title:
Discovery of another peculiar radial distribution of Blue Stragglers in
  Globular Clusters: The case of 47 Tuc

abstract:
  We have used high resolution WFPC2-HST and wide field ground-based
observations to construct a catalog of blue straggler stars (BSS) in the
globular cluster 47 Tuc spanning the entire radial extent of the cluster.
  The BSS distribution is highly peaked in the cluster center, rapidly
decreases at intermediate radii, and finally rises again at larger radii. The
observed distribution closely resembles that discovered in M3 by Ferraro et al
(1993,1997). To date, complete BSS surveys covering the full radial extent (HST
in the center and wide field CCD ground based observations of the exterior)
have been performed for only these two clusters. Both show a bimodal radial
distribution, despite their different dynamical properties. BSS surveys
covering the full spatial extent of more globular clusters are clearly required
to determine how common bimodality is and what its consequence is for theories
of BSS formation and cluster dynamics.


title:
Close Companions to Nearby Young Stars from Adaptive Optics Imaging on
  VLT and Keck

abstract:
  We report the results of VLT and Keck adaptive optics surveys of known
members of the Eta Chamaeleontis, MBM 12, and TW Hydrae (TWA) associations to
search for close companions. The multiplicity statistics of Eta Cha, MBM 12,
and TWA are quite high compared with other clusters and associations, although
our errors are large due to small number statistics. We have resolved S18 in
MBM 12 and RECX 9 in Eta Cha into triples for the first time. The tight binary
TWA 5Aab in the TWA offers the prospect of measuring the dynamical masses of
both components as well as an independent distance to the system within a few
years. The AO detection of the close companion to the nearby young star Chi^1
Orionis, previously inferred from radial velocity and astrometric observations,
has already made it possible to derive the dynamical masses of that system
without any astrophysical assumption.


title: Turbulent Fragmentation and Star Formation

abstract:
  We review the main results from recent numerical simulations of turbulent
fragmentation and star formation. Specifically, we discuss the observed scaling
relationships, the ``quiescent'' (subsonic) nature of many star-forming cores,
their energy balance, their synthesized polarized dust emission, the ages of
stars associated with the molecular gas from which they have formed, the mass
spectra of clumps, and the density and column density probability distribution
function of the gas. We then give a critical discussion on recent attempts to
explain and/or predict the star formation efficiency and the stellar initial
mass function from the statistical nature of turbulent fields. Finally, it
appears that turbulent fragmentation alone cannot account for the final stages
of fragmentation: although the turbulent velocity field is able to produce
filaments, the spatial distribution of cores in such filaments is better
explained in terms of gravitational fragmentation.


title:
The oscillation and stability of differentially rotating spherical
  shells: The initial value problem

abstract:
  An understanding of the oscillations of differentially rotating systems is
key to many areas of astrophysics. It is of particular relevance to the
emission of gravitational waves from oscillating neutron stars, which are
expected to possess significant differential rotation immediately after birth
or binary merger. In a previous paper we analysed the normal modes of a simple
system exhibiting differential rotation. In this complementary paper we address
the initial value problem for the same simple model using both analytical
methods and numerical time evolutions. We derive a necessary and sufficient
condition for dynamical shear instability. We discuss the dynamical behaviour
of the continuous spectrum in response to an initial perturbation, and show
that certain singular solutions within the continuous spectrum appear
physically indistinguishable from the discrete modes outside the continuous
spectrum.


title: Gamma-Ray Bursts: Progress, Problems & Prospects

abstract:
  The cosmological gamma-ray burst (GRB) phenomenon is reviewed. The broad
observational facts and empirical phenomenological relations of the GRB prompt
emission and afterglow are outlined. A well-tested, successful fireball shock
model is introduced in a pedagogical manner. Several important uncertainties in
the current understanding of the phenomenon are reviewed, and prospects of how
future experiments and extensive observational and theoretical efforts may
address these problems are discussed.


title: Were the LMC Globular Clusters Formed in a Disk?

abstract:
  The radial velocities of the 13 globular clusters in the Large Magellanic
Cloud have a dispersion of 28 km s$^{-1}$ relative to the HI rotation curve of
the LMC, compared to a dispersion of 30 km s$^{-1}$ with regard to the mean
globular cluster velocity. This shows that, contrary to a suggestion by
Schommer et al. (1992), one cannot yet rule out the possibility that the LMC
globular clusters formed in a pressure supported halo, rather than in rotating
disk. The globular clusters in the LMC may therefore, after all, exhibit a
relationship between age and kinematics that is similar to that of the clusters
in M33.


title:
Discovery of Globular Clusters in the Proto-Spiral NGC2915: Implications
  for Hierarchical Galaxy Evolution

abstract:
  We have discovered three globular clusters beyond the Holmberg radius in
Hubble Space Telescope Advanced Camera for Surveys images of the gas-rich dark
matter dominated blue compact dwarf galaxy NGC2915. The clusters, all of which
start to resolve into stars, have M_{V606} = -8.9 to -9.8 mag, significantly
brighter than the peak of the luminosity function of Milky Way globular
clusters. Their colors suggest a metallicity [Fe/H] ~ -1.9 dex, typical of
metal-poor Galactic globular clusters. The specific frequency of clusters is at
a minimum normal, compared to spiral galaxies. However, since only a small
portion of the system has been surveyed it is more likely that the luminosity
and mass normalized cluster content is higher, like that seen in elliptical
galaxies and galaxy clusters. This suggests that NGC2915 resembles a key phase
in the early hierarchical assembly of galaxies - the epoch when much of the old
stellar population has formed, but little of the stellar disk. Depending on the
subsequent interaction history, such systems could go on to build-up larger
elliptical galaxies, evolve into normal spirals, or in rare circumstances
remain suspended in their development to become systems like NGC2915.


title:
Blue horizontal branch stars in the Sloan Digital Sky Survey: I. Sample
  selection and structure in the Galactic halo

abstract:
  We isolate samples of 733 bright (g < 18) and 437 faint (g > 18)
high-Galactic latitude blue horizontal branch stars with photometry and
spectroscopy in the Sloan Digital Sky Survey (SDSS). Comparison of independent
photometric and spectroscopic selection criteria indicates that contamination
from F and blue-straggler stars is less than 10% for bright stars (g<18) and
about 25% for faint stars (g>18), and this is qualitatively confirmed by proper
motions based on the USNO-A catalog as first epoch. Analysis of repeated
observations shows that the errors in radial velocity are approximately 26
km/s.
  A relation between absolute magnitude and color is established using the
horizontal branches of halo globular clusters observed by SDSS. Bolometric
corrections and colors are synthesized in the SDSS filters from model spectra.
The redder stars agree well in absolute magitude with accepted values for RR
Lyrae stars. The resulting photometric distances are accurate to about 0.2
magnitudes, with a median of about 25 kpc. Modest clumps in phase space exist
and are consistent with the previously reported tidal stream of the Sagittarius
dwarf galaxy.
  The sample is tabulated in electronic form in the online version of this
article, or by request to the authors.


title:
Blue horizontal branch stars in the Sloan Digital Sky Survey: II.
  Kinematics of the Galactic halo

abstract:
  We carry out a maximum-likelihood kinematic analysis of a sample of 1170 blue
horizontal branch (BHB) stars from the Sloan Digital Sky Survey presented in
Sirko et al. (2003) (Paper I). Monte Carlo simulations and resampling show that
the results are robust to distance and velocity errors at least as large as the
estimated errors from Paper I. The best-fit velocities of the Sun (circular)
and halo (rotational) are 245.9 +/- 13.5 km/s and 23.8 +/- 20.1 km/s but are
strongly covariant, so that v_0 - v_halo = 222.1 +/- 7.7 km/s. If one adopts
standard values for the local standard of rest and solar motion, then the halo
scarcely rotates. The velocity ellipsoid inferred for our sample is much more
isotropic [(sigma_r,sigma_theta,sigma_phi) = (101.4 +/- 2.8, 97.7 +/- 16.4,
107.4 +/- 16.6) km/s] than that of halo stars in the solar neighborhood, in
agreement with a recent study of the distant halo by Sommer-Larsen et al.
(1997). The line-of-sight velocity distribution of the entire sample, corrected
for the Sun's motion, is accurately gaussian with a dispersion of 101.6 +/- 3.0
km/s.