title: On measuring the Tully-Fisher relation at $z > 1$

abstract:
  The evolution of the line width - luminosity relation for spiral galaxies,
the Tully-Fisher relation, strongly constrains galaxy formation and evolution
models. At this moment, the kinematics of z>1 spiral galaxies can only be
measured using rest frame optical emission lines associated with star
formation, such as Halpha and [OIII]5007/4959 and [OII]3727. This method has
intrinsic difficulties and uncertainties. Moreover, observations of these lines
are challenging for present day telescopes and techniques. Here, we present an
overview of the intrinsic and observational challenges and some ways way to
circumvent them. We illustrate our results with the HST/NICMOS grism sample
data of z ~ 1.5 starburst galaxies. The number of galaxies we can use in the
final Tully-Fisher analysis is only three. We find a ~2 mag offset from the
local rest frame B and R band Tully-Fisher relation for this sample. This
offset is partially explained by sample selection effects and sample specifics.
Uncertainties in inclination and extinction and the effects of star formation
on the luminosity can be accounted for. The largest remaining uncertainty is
the line width / rotation curve velocity measurement. We show that high
resolution, excellent seeing integral field spectroscopy will improve the
situation. However, we note that no flat rotation curves have been observed for
galaxies with z>1. This could be due to the described instrumental and
observational limitations, but it might also mean that galaxies at z>1 have not
reached the organised motions of the present day.


title: Indirect Search for Dark Matter in M31 with the CELESTE Experiment

abstract:
  If dark matter is made of neutralinos, annihilation of such Majorana
particles should produce high energy cosmic rays, especially in galaxy halo
high density regions like galaxy centres. M31 (Andromeda) is our nearest
neighbour spiral galaxy, and both its high mass and its low distance make it a
source of interest for the indirect search for dark matter through gamma-ray
detection. The ground based atmospheric Cherenkov telescope CELESTE observed
M31 from 2001 to 2003, in the mostly unexplored energy range 50-500 GeV. These
observations provide an upper limit on the flux above 50 GeV around
$10^{-10}\rm{cm}^{-2}\rm{s}^{-1}$ in the frame of supersymmetric dark matter,
and more generally on any gamma emission from M31.


title:
Big bang nucleosynthesis constraints on scalar-tensor theories of
  gravity

abstract:
  We investigate BBN in scalar-tensor theories of gravity with arbitrary matter
couplings and self-interaction potentials. We first consider the case of a
massless dilaton with a quadratic coupling to matter. We perform a full
numerical integration of the evolution of the scalar field and compute the
resulting light element abundances. We demonstrate in detail the importance of
particle mass thresholds on the evolution of the scalar field in a radiation
dominated universe. We also consider the simplest extension of this model
including a cosmological constant in either the Jordan or Einstein frame.


title:
Spitzer and Magellan Observations of NGC 2264: A Remarkable Star Forming
  Core Near IRS-2

abstract:
  We analyze {\it Spitzer} and Magellan observations of a star forming core
near IRS-2 in the young cluster NGC 2264. The submillimeter source IRAS 12 S1,
previously believed to be an intermediate mass Class 0 object is shown to be a
dense collection of embedded, low mass stars. We argue that this group of stars
represents the fragmenting collapse of a dense, turbulent core, based on a
number of indicators of extreme youth. With reasonable estimates for the
velocity dispersion in the group, we estimate a dynamical lifetime of only a
few x 10$^{4}$ years. Spectral energy distributions of stars in the core are
consistent with Class I or Class 0 assignments. We present observations of an
extensive system of molecular hydrogen emission knots. The luminosity of the
objects in the core region are consistent with roughly solar mass protostars.


title: A Chandra View of Dark Matter in Early-Type Galaxies

abstract:
  We present a Chandra study of mass profiles in 7 elliptical galaxies, of
which 3 have galaxy-scale and 4 group-scale halos demarcated at 1E13Msun. These
represent the best available data for nearby objects with comparable X-ray
luminosities. We measure ~flat mass-to-light (M/L) profiles within an optical
half-light radius (Reff), rising by an order of magnitude at ~10Reff, which
confirms the presence of dark matter (DM). The data indicate hydrostatic
equilibrium, which is also supported by agreement with studies of stellar
kinematics in elliptical galaxies. The data are well-fitted by a model
comprising an NFW DM profile and a baryonic component following the optical
light. The distribution of DM halo concentration parameters (c) versus Mvir
agrees with LCDM predictions and our observations of bright groups.
Concentrations are slightly higher than expected, which is most likely a
selection effect. Omitting the stellar mass drastically increases c, possibly
explaining large concentrations found by some past observers. The stellar M/LK
agree with population synthesis models, assuming a Kroupa IMF. Allowing
adiabatic compression (AC) of the DM halo by baryons made M/L more discrepant,
casting some doubt on AC. Our best-fitting models imply total baryon fractions
\~0.04--0.09, consistent with models of galaxy formation incorporating strong
feedback. The groups exhibit positive temperature gradients, consistent with
the "Universal" profiles found in other groups and clusters, whereas the
galaxies have negative gradients, suggesting a change in the evolutionary
history of the systems around Mvir=1E13 Msun.


title:
Multidimensional Supernova Simulations with Approximative Neutrino
  Transport I. Neutron Star Kicks and the Anisotropy of Neutrino-Driven
  Explosions in Two Spatial Dimensions

abstract:
  By means of two-dimensional (2D) simulations we study hydrodynamic
instabilities during the first seconds of neutrino-driven supernova explosions,
using a PPM hydrodynamics code, supplemented with a gray, non-equilibrium
approximation of radial neutrino transport. We consider three 15 solar mass
progenitors with different structures and one rotating model, in which we
replace the dense core of the newly formed neutron star (NS) by a contracting
inner grid boundary, and trigger neutrino-driven explosions by systematically
varying the neutrino fluxes emitted at this boundary. Confirming more idealized
studies as well as supernova simulations with spectral transport, we find that
random seed perturbations can grow by hydrodynamic instabilities to a globally
asymmetric mass distribution, leading to a dominance of dipole (l=1) and
quadrupole (l=2) modes in the explosion ejecta. Anisotropic gravitational and
hydrodynamic forces are found to accelerate the NS on a timescale of 2-3
seconds. Since the explosion anisotropies develop chaotically, the magnitude of
the corresponding kick varies stochastically in response to small differences
in the fluid flow. Our more than 70 models separate into two groups, one with
high and the other with low NS velocities and accelerations after 1s of
post-bounce evolution, depending on whether the l=1 mode is dominant in the
ejecta or not. This leads to a bimodality of the distribution when the NS
velocities are extrapolated to their terminal values. The fast group has an
average velocity of about 500 km/s and peak values in excess of 1000 km/s.
Establishing a link to the measured distribution of pulsar velocities, however,
requires a much larger set of calculations and ultimately 3D modeling.
(abridged)


title:
Determining Central Black Hole Masses in Distant Active Galaxies and
  Quasars. II. Improved Optical and UV Scaling Relationships

abstract:
  We present four improved empirical relationships useful for estimating the
central black hole mass in nearby AGNs and distant luminous quasars alike using
either optical or UV single-epoch spectroscopy. These mass-scaling
relationships between line widths and luminosity are based on recently improved
empirical relationships between the broad-line region size and luminosities in
various energy bands and are calibrated to the improved mass measurements of
nearby AGNs based on emission-line reverberation mapping. The mass-scaling
relationship based on the Hbeta line luminosity allows mass estimates for
low-redshift sources with strong contamination of the optical continuum
luminosity by stellar or non-thermal emission, while that based on the C IV
lambda 1549 line dispersion allows mass estimates in cases where only the line
dispersion (as opposed to the FWHM) can be reliably determined. We estimate
that the absolute uncertainties in masses given by these mass-scaling
relationships are typically around a factor of 4. We include in an Appendix
mass estimates for all the Bright Quasar Survey (PG) quasars for which direct
reverberation-based mass measurements are not available.


title:
The X-ray Structure of the Pulsar Bow Shock G189.22+2.90 in the
  Supernova Remnant IC 443

abstract:
  We present a deep observation with the Chandra X-ray Observatory of the
neutron star bow shock G189.22+2.90 in the supernova remnant (SNR) IC 443. Our
data confirm the cometary morphology and central point source seen previously,
but also reveal considerable new structure. Specifically, we find that the
X-ray nebula consists of two distinct components: a "tongue" of bright emission
close to the neutron star, enveloped by a larger, fainter "tail". We interpret
the tongue and tail as delineating the termination shock and the post-shock
flow, respectively, as previously identified also in the pulsar bow shock
G359.23-0.82 ("the Mouse"). However, for G189.22+2.90 the tongue is much less
elongated than for the Mouse, while the tail is much broader. These differences
are consistent with the low Mach number, M >~ 2, expected for a neutron star
moving through the hot gas in a SNR's interior, supporting the case for a
physical association between G189.22+2.90 and IC 443. We resolve the stand-off
distance between the star and the head of the bow shock, which allows us to
estimate a space velocity for the neutron star of ~230 km/s, independent of
distance. We detect thermal emission from the neutron star surface at a
temperature of 102 +/- 22 eV, which is consistent with the age of SNR IC 443
for standard neutron star cooling models. We also identify two compact knots of
hard emission located 1-2 arcsec north and south of the neutron star.


title: The Mystery Deepens: Spitzer Observations of Cool White Dwarfs

abstract:
  We present 4.5$\mu$m and 8$\mu$m photometric observations of 18 cool white
dwarfs obtained with the Spitzer Space Telescope. Our observations demonstrate
that four white dwarfs with T_eff< 6000 K show slightly depressed mid-infrared
fluxes relative to white dwarf models. In addition, another white dwarf with a
peculiar optical and near-infrared spectral energy distribution (LHS 1126) is
found to display significant flux deficits in Spitzer observations. These
mid-infrared flux deficits are not predicted by the current white dwarf models
including collision induced absorption due to molecular hydrogen. We postulate
that either the collision induced absorption calculations are incomplete or
there are other unrecognized physical processes occuring in cool white dwarf
atmospheres. The spectral energy distribution of LHS 1126 surprisingly fits a
Rayleigh-Jeans spectrum in the infrared, mimicking a hot white dwarf with
effective temperature well in excess of 10$^5$ K. This implies that the source
of this flux deficit is probably not molecular absorption but some other
process.


title:
ASMOOTH: A simple and efficient algorithm for adaptive kernel smoothing
  of two-dimensional imaging data

abstract:
  An efficient algorithm for adaptive kernel smoothing (AKS) of two-dimensional
imaging data has been developed and implemented using the Interactive Data
Language (IDL). The functional form of the kernel can be varied (top-hat,
Gaussian etc.) to allow different weighting of the event counts registered
within the smoothing region. For each individual pixel the algorithm increases
the smoothing scale until the signal-to-noise ratio (s.n.r.) within the kernel
reaches a preset value. Thus, noise is suppressed very efficiently, while at
the same time real structure, i.e. signal that is locally significant at the
selected s.n.r. level, is preserved on all scales. In particular, extended
features in noise-dominated regions are visually enhanced. The ASMOOTH
algorithm differs from other AKS routines in that it allows a quantitative
assessment of the goodness of the local signal estimation by producing
adaptively smoothed images in which all pixel values share the same
signal-to-noise ratio above the background.
  We apply ASMOOTH to both real observational data (an X-ray image of clusters
of galaxies obtained with the Chandra X-ray Observatory) and to a simulated
data set. We find the ASMOOTHed images to be fair representations of the input
data in the sense that the residuals are consistent with pure noise, i.e. they
possess Poissonian variance and a near-Gaussian distribution around a mean of
zero, and are spatially uncorrelated.


title: Cosmic Microwave Background Mini-Review

abstract:
  A compact overview of the status of CMB anisotropy results and their
cosmological interpretation up until the end of 2005. Sections headings:
Introduction; Description of CMB Anisotropies; Cosmological Parameters; Physics
of Anisotropies; Current Anisotropy Data; CMB Polarization; Complications;
Constraints on Cosmologies; Particle Physics Constraints; Fundamental Lessons;
and Future Directions.


title:
Further Evidence for a Merger Origin for the Thick Disk: Galactic Stars
  Along Lines-of-sight to Dwarf Spheroidal Galaxies

abstract:
  The history of the Milky Way Galaxy is written in the properties of its
stellar populations. Here we analyse stars observed as part of surveys of local
dwarf spheroidal galaxies, but which from their kinematics are highly probable
to be non-members. The selection function -- designed to target metal-poor
giants in the dwarf galaxies, at distances of ~100kpc -- includes F-M dwarfs in
the Milky Way, at distances of up to several kpc. Thestars whose motions are
analysed here lie in the cardinal directions of Galactic longitude l ~ 270 and
l ~ 90, where the radial velocity is sensitive to the orbital rotational
velocity. We demonstrate that the faint F/G stars contain a significant
population with V_phi ~ 100km/s, similar to that found by a targeted, but
limited in areal coverage, survey of thick-disk/halo stars by Gilmore, Wyse &
Norris (2002). This value of mean orbital rotation does not match either the
canonical thick disk or the stellar halo. We argue that this population,
detected at both l ~ 270 and l ~ 90, has the expected properties of `satellite
debris' in the thick-disk/halo interface, which we interpret as remnants of the
merger that heated a pre-existing thin disk to form the thick disk.


title:
The Araucaria Project. The Distance to the Local Group Galaxy IC 1613
  from Near-Infrared Photometry of Cepheid Variables

abstract:
  We have measured accurate near-infrared magnitudes in the J and K bands of 39
Cepheid variables in IC 1613 with well-determined periods and optical VI light
curves. Using the template light curve approach of Soszy{\'n}ski, Gieren and
Pietrzy{\'n}ski, accurate mean magnitudes were obtained from these data which
allowed to determine the distance to IC 1613 relative to the LMC from a
multiwavelength period-luminosity solution in the optical VI and near-IR JK
bands, with an unprecedented accuracy. Our result for the IC 1613 distance is
$(m-M)_{0} = 24.291 \pm 0.014$ (random error) mag, with an additional
systematic uncertainty smaller than 2%. From our multiwavelength approach, we
find for the total (average) reddening to the IC 1613 Cepheids $E(B-V) = 0.090
\pm 0.007$ mag,which is significantly higher than the foreground reddening of
about 0.03 mag,showing the presence of appreciable dust extinction inside the
galaxy. Our data suggest that the extinction law in IC 1613 is very similar to
the galactic one.Our distance result agrees, within the uncertainties, with two
earlier infrared Cepheid studies in this galaxy of Macri et al. (from HST data
on 4 Cepheids), and McAlary et al. (from ground-based H-band photometry of 10
Cepheids), but our result has reduced the total uncertainty on the distance to
IC 1613 (relative to the LMC) to less than 3%. With distances to nearby
galaxies from Cepheid infrared photometry at this level of accuracy, which are
currently being obtained in our Araucaria Project, it seems possible to
significantly reduce the systematic uncertainty of the Hubble constant as
derived from the HST Key Project approach, by improving the calibration of the
metallicity effect on PL relation zero points, and by improving the distance
determination to the LMC.


title:
Dispersion relation for electromagnetic wave propagation in a strongly
  magnetized plasma

abstract: This paper is withdrawn because it is a duplicate of astro-ph/0601311


abstract:
  A dispersion relation for electromagnetic wave propagation in a strongly
magnetized cold plasma is deduced, taking photon-photon scattering into
account. It is shown that the combined plasma and quantum electrodynamic effect
is important for understanding the mode-structures in magnetar and pulsar
atmospheres. The implications of our results are discussed.


title: Nucleosynthesis results from INTEGRAL

abstract:
  Since its launch in October 2002, ESA's INTEGRAL observatory has enabled
significant advances to be made in the study of Galactic nucleosynthesis. In
particular, the imaging Ge spectrometer SPI combines for the first time the
diagnostic powers of high resolution gamma-ray line spectroscopy and moderate
spatial resolution. This review summarizes the major nucleosynthesis results
obtained with INTEGRAL so far. Positron annihilation in our Galaxy is being
studied in unprecented detail. SPI observations yield the first sky maps in
both the 511 keV annihilation line and the positronium continuum emission, and
the most accurate spectrum at 511 keV to date, thereby imposing new constraints
on the source(s) of Galactic positrons which still remain(s) unidentified. For
the first time, the imprint of Galactic rotation on the centroid and shape of
the 1809 keV gamma-ray line due to the decay of 26Al has been seen, confirming
the Galactic origin of this emission. SPI also provided the most accurate
determination of the gamma-ray line flux due to the decay of 60Fe. The combined
results for 26Al and 60Fe have important implications for nucleosynthesis in
massive stars, in particular Wolf-Rayet stars. Both IBIS and SPI are searching
the Galactic plane for young supernova remnants emitting the gamma-ray lines
associated with radioactive 44Ti. None have been found so far, which raises
important questions concerning the production of 44Ti in supernovae, the
Galactic supernova rate, and the Galaxy's chemical evolution.


title:
The near-infrared spectrum of Mrk 1239: direct evidence of the dusty
  torus?

abstract:
  We report 0.8-4.5 micron SpeX spectroscopy of the narrow-line Seyfert 1
galaxy Mrk1239. The spectrum is outstanding because the nuclear continuum
emission in the near-infrared is dominated by a strong bump of emission peaking
at 2.2 micron, with a strength not reported before in an AGN. A comparison of
the Mrk1239 spectrum to that of Ark564 allowed us to conclude that the
continuum is strongly reddened by E(B-V)=0.54. The excess of emission,
confirmed by aperture photometry and additional NIR spectroscopy, follows a
simple blackbody curve at T=1200 K. This suggest that we may be observing
direct evidence of dust heated near to the sublimation temperature, likely
produced by the putative torus of the unification model. Although other
alternatives are also plausible, the lack of star formation, the strong
polarization and low extinction derived for the emission lines support the
scenario where the hot dust is located between the narrow line region and the
broad line region.


title:
Spitzer/MIPS Infrared Imaging of M31: Further Evidence for a Spiral/Ring
  Composite Structure

abstract:
  New images of M31 at 24, 70, and 160 micron taken with the Multiband Imaging
Photometer for Spitzer (MIPS) reveal the morphology of the dust in this galaxy.
This morphology is well represented by a composite of two logarithmic spiral
arms and a circular ring (radius ~10 kpc) of star formation offset from the
nucleus. The two spiral arms appear to start at the ends of a bar in the
nuclear region and extend beyond the star forming ring. As has been found in
previous work, the spiral arms are not continuous but composed of spiral
segments. The star forming ring is very circular except for a region near M32
where it splits. The lack of well defined spiral arms and the prominence of the
nearly circular ring suggests that M31 has been distorted by interactions with
its satellite galaxies. Using new dynamical simulations of M31 interacting with
M32 and NGC 205 we find that, qualitatively, such interactions can produce an
offset, split ring like that seen in the MIPS images.


title:
Large Scale CO Observations of a Far-Infrared Loop in Pegasus; Detection
  of a Large Number of Very Small Molecular Clouds Possibly Formed via Shocks

abstract:
  We have carried out large scale 12CO and 13CO observations with a mm/sub-mm
telescope NANTEN toward a loop-like structure in far infrared whose angular
extent is about 20x20 degrees around (l, b) ~ (109, -45) in Pegasus. The 12CO
distribution is found to consist of 78 small clumpy clouds whose masses range
from 0.04 Mo to 11 Mo. About 83% of the 12CO clouds have very small masses less
than 1.0 Mo. 13CO emission shown in the 19 of the 78 12CO clouds was detected
in the region where the column density of H2 derived from 12CO is greater than
5x10(20) cm(-2), corresponding to Av of ~ 1 mag, which takes into account that
of HI. We find no indication of star formation in these clouds in IRAS and
2MASS Point Source Catalogs. The very low mass clouds, M < 1 Mo, identified are
unusual in the sense that they have very weak 12CO peak temperature of 0.5 K to
2.7 K and that they aggregate in a region of a few pc with no main massive
clouds of ~ 100 Mo. A comparison with a theoretical work on molecular cloud
formation (Koyama & Inutsuka 2002) suggests that the very low-mass clouds may
have been formed in the shocked layer through the thermal instability. The star
HD886 (B2IV) may be the source of the mechanical luminosity via stellar winds
to create shocks, forming the loop-like structure where the very low-mass
clouds are embedded.


title: Constraints on the Star Formation Rate in Active Galaxies

abstract:
  The [O II] 3727 emission line is often used as an indicator of star formation
rate in extragalactic surveys, and it can be an equally effective tracer of
star formation in systems containing luminous active galactic nuclei (AGNs). In
order to investigate the ongoing star formation rate of the host galaxies of
AGNs, we measured the strength of [O II] and other optical emission lines from
a large sample (~ 3600) of broad-line (Type 1) AGNs selected from the Sloan
Digital Sky Survey. We performed a set of photoionization calculations to help
evaluate the relative contribution of stellar and nonstellar photoionization to
the observed strength of [O II]. Consistent with the recent study of Ho (2005),
we find that the observed [O II] emission can be explained entirely by
photoionization from the AGN itself, with little or no additional contribution
from HII regions. This indicates that the host galaxies of Type 1 AGNs
experience very modest star formation concurrent with the optically active
phase of the nucleus. By contrast, we show that the sample of ``Type 2''
quasars selected from the Sloan Digital Sky Survey does exhibit substantially
stronger HII emission consistent with an elevated level of star formation, a
result that presents a challenge to the simplest form of the AGN unification
model.


title: Thermal Structure and Radius Evolution of Irradiated Gas Giant Planets

abstract:
  We consider the thermal structure and radii of strongly irradiated gas giant
planets over a range in mass and irradiating flux. The cooling rate of the
planet is sensitive to the surface boundary condition, which depends on the
detailed manner in which starlight is absorbed and energy redistributed by
fluid motion. We parametrize these effects by imposing an isothermal boundary
condition $T \equiv T_{\rm deep}$ below the photosphere, and then constrain
$T_{\rm deep}$ from the observed masses and radii. We compute the dependence of
luminosity and core temperature on mass, $T_{\rm deep}$ and core entropy,
finding that simple scalings apply over most of the relevant parameter space.
These scalings yield analytic cooling models which exhibit power-law behavior
in the observable age range $0.1-10 {\rm Gyr}$, and are confirmed by
time-dependent cooling calculations. We compare our model to the radii of
observed transiting planets, and derive constraints on $T_{\rm deep}$. Only HD
209458 has a sufficiently accurate radius measurement that $T_{\rm deep}$ is
tightly constrained; the lower error bar on the radii for other planets is
consistent with no irradiation. More accurate radius and age measurements will
allow for a determination of the correlation of $T_{\rm deep}$ with the
equilibrium temperature, informing us about both the greenhouse effect and
day-night asymmetries.


title: The correlations between the twin kHz QPO frequencies of LMXBs

abstract:
  We analyzed the recently published kHz QPO data in the neutron star low-mass
X-ray binaries (LMXBs), in order to investigate the different correlations of
the twin peak kilohertz quasi-eriodic oscillations (kHz QPOs) in bright Z
sources and in the less luminous Atoll sources. We find that a power-law
relation $\no\sim\nt^{b}$ between the upper and the lower kHz QPOs with
different indices: $b\simeq$1.5 for the Atoll source 4U 1728-34 and
  $b\simeq$1.9 for the Z source Sco X-1. The implications of our results for
the theoretical models for kHz QPOs are discussed.


title:
The First Type Ia Supernovae: An Empirical Approach to Taming
  Evolutionary Effects In Dark Energy Surveys from SNe Ia at z>2

abstract:
  Future measurements of the nature of dark energy using Type Ia supernovae
will require a precise characterization of systematic sources of error.
  Evolutionary effects remain the most uncertain contributor to the overall
systematic error budget. Present plans to probe evolution with
cosmology-independent explosion parameters could yield absence of evidence for
evolution without definitive evidence of its absence. Here we show that
observations of Type Ia supernovae in the redshift interval 1.5 < z < 3.0,
where dark energy-dependent effects are relatively negligible, should provide
direct evidence to discern evolutionary effects. As examples of our approach to
constraining evolution, we examine the impact of changing progenitor
metallicity and age on the degree of potential luminosity evolution. We show
that the observations we propose can be carried out by existing space
telescopes, or ones that are already under development.


title:
Effects of the size of cosmological N-Body simulations on physical
  quantities -- I: Mass Function

abstract:
  N-Body simulations are a very important tool in the study of formation of
large scale structures. Much of the progress in understanding the physics of
galaxy formation and comparison with observations would not have been possible
without N-Body simulations. Given the importance of this tool, it is essential
to understand its limitations as ignoring these can easily lead to interesting
but unreliable results. In this paper we study the limitations due to the
finite size of the simulation volume. We explicitly construct the correction
term arising due to a finite box size and study its generic features for
clustering of matter and also on mass functions. We show that the correction to
mass function is maximum near the scale of non-linearity, as a corollary we
show that the correction to the number density of haloes of a given mass
changes sign at this scale; the number of haloes at small masses is over
estimated in simulations. This over estimate results from a delay in mergers
that lead to formation of more massive haloes. The same technique can be used
to study corrections to other physical quantities. The corrections are
typically small if the scale of non-linearity is much smaller than the
box-size. However, there are some cases of physical interest in which the
relative correction term is of order unity even though a simulation box much
larger than the scale of non-linearity is used. Within the context of the
concordance model, our analysis suggests that it is very difficult for present
day simulations to resolve mass scales smaller than 100 solar masses accurately
and the level of difficulty increases as we go to even smaller masses, though
this constraint does not apply to multi-scale simulations.


title:
Stellar and Gas properties of High HI Mass-to-Light Ratio Galaxies in
  the Local Universe

abstract:
  We present a multi-wavelength study (BVRI band photometry and HI line
interferometry) of nine late-type galaxies selected from the HIPASS Bright
Galaxy Catalog on the basis of apparently high HI mass-to-light ratios (3
M_sun/L_sun < M_HI/L_B < 27 M_sun/L_sun). We found that most of the original
estimates for M_HI/L_B based on available photographic magnitudes in the
literature were too high, and conclude that genuine high HI mass-to-light ratio
(>5 M_sun/L_sun) galaxies are rare in the Local Universe. Extreme high M_HI/L_B
galaxies like ESO215-G?009 appear to have formed only the minimum number of
stars necessary to maintain the stability of their HI disks, and could possibly
be used to constrain galaxy formation models. They may to have been forming
stars at a low, constant rate over their lifetimes. The best examples all have
highly extended HI disks, are spatially isolated, and have normal baryonic
content for their total masses but are deficent in stars. This suggests that
high M_HI/L_B galaxies are not lacking the baryons to create stars, but are
underluminous as they lack either the internal or external stimulation for more
extensive star formation.


title: A key to the spectral variability of prompt GRBs

abstract:
  We demonstrate that the rapid spectral variability of prompt GRBs is an
inherent property of radiation emitted from shock-generated, highly anisotropic
small-scale magnetic fields. We interpret the hard-to-soft evolution and the
correlation of the soft index $\alpha$ with the photon flux observed in GRBs as
a combined effect of temporal variation of the shock viewing angle and
relativistic aberration of an individual thin, instantaneously illuminated
shell. The model predicts that about a quarter of time-resolved spectra should
have hard spectra, violating the synchrotron $\alpha=-2/3$ limit. The model
also naturally explains why the peak of the distribution of $\alpha$ is at
$\alpha\sim-1$. The presence of a low-energy break in the jitter spectrum at
oblique angles also explains the appearance of a soft X-ray component in some
GRBs and their paucity. We emphasize that our theory is based solely on the
first principles and contains no ad hoc (phenomenological) assumptions.


title: Bistability in Interstellar Gas-Phase Chemistry

abstract:
  We present an analysis of "bistability" in gas-phase chemical models of dark
interstellar clouds. We identify the chemical mechanisms that allow high- and
low-ionization solutions to the chemical rate-equations to coexist. We derive
simple analytic scaling relations for the gas densities and ionization rates
for which the chemistry becomes bistable. We explain why bistability is
sensitive to the H3+ dissociative recombination rate coefficient, and why it is
damped by gas-grain neutralization.


title:
Relics of metal-free low mass stars exploding as thermonuclear
  supernovae

abstract:
  Renewed interest in the first stars that were formed in the universe has led
to the discovery of extremely iron-poor stars. Since several competing
scenarios exist, our understanding of the mass range that determines the
observed elemental abundances remains unclear. In this study, we consider three
well-studied metal-poor stars in terms of the theoretical supernovae (SNe)
model. Our results suggest that the observed abundance patterns in the
metal-poor star BD +80 245 and the pair of stars HD 134439/40 agree strongly
with the theoretical possibility that these stars inherited their heavy element
abundance patterns from SNe initiated by thermonuclear runaways in the
degenerate carbon-oxygen cores of primordial asymptotic giant branch stars with
\~3.5-5 solar masses. Recent theoretical calculations have predicted that such
SNe could be originated from metal-free stars in the intermediate mass range.
On the other hand, intermediate mass stars containing some metals would end
their lives as white dwarfs after expelling their envelopes in the wind due to
intense momentum transport from outgoing photons to heavy elements. This new
pathway for the formation of SNe requires that stars are formed from the
primordial gas. Thus, we suggest that stars of a few solar masses were formed
from the primordial gas and that some of them caused thermonuclear explosions
when the mass of their degenerate carbon-oxygen cores increased to the
Chandrasekhar limit without experiencing efficient mass loss.


title: The Unusual Spectrum of the Ultra Luminous X-ray Source, M82 X-1

abstract:
  The results of a spectral analysis, using {\it XMM-Newton} and {\it Chandra}
data of the brightest ultra luminous X-ray source in the nearby galaxy M82, are
presented. The spectrum of M82 X-1, was found to be unusually hard (photon
spectral index $\Gamma \approx 1$) with a sharp cutoff at $\approx 6$ keV. Disk
black body emission model requires a nonphysically high temperature. Instead,
the spectrum is better described, with a lower reduced $\chi^2$, as emission
due to nearly saturated Comptonization of photons in an optically thick ($\tau
\approx 10-30$, depending on the geometry) plasma having a temperature $kT
\approx 2$ keV. This is in contrast to the high energy spectra of other black
hole systems, which are relatively steeper ($\Gamma > 1.5$) and hence are
modeled as un-saturated thermal and/or non-thermal Comptonization of soft
photons, in an optically thin ($\tau \approx 1$) high temperature plasma. An
Iron line emission which is marginally resolved ($\sigma \sim 0.2$ keV) is
required to fit the data. We argue that the standard geometries for the X-ray
producing region, which are an optically thin inner disk or an uniform/patchy
corona on top of a cold disk, are not applicable to this source. Alternatively,
the geometry of the X-ray producing region could be a large sphere surrounding
a cold accretion disk or an optically thick inner disk region which cools by
bremsstrahlung self-Comptonization. For the latter scenario, such an inner disk
region, whose effective optical depth to absorption is less than unity, is
expected in the standard accretion disk theory for near Eddington accretion
rates.


title:
Low and intermediate mass star yields.II: The evolution of nitrogen
  abundances

abstract:
  We analyze the impact on the Galactic nitrogen abundances of using a new set
of low and intermediate mass star yields. These yields have a significant yield
of primary nitrogen from intermediate mass stars. We use these yields as an
input to a Galactic Chemical Evolution model and study the nitrogen abundances
in the halo and in the disc, and compare them with models obtained using other
yield sets and with a large amount of observational data. We find that, using
these new yields, our model adequately reproduce the observed trends. In
particular, these yields solve the historical problem of the evolution of
nitrogen, giving the right level of relative abundance N/O by the production of
a primary component in intermediate mass stars. Moreover, using different
evolutionary rates in each radial region of the Galaxy, we may explain the
observed N dispersion.


title:
Evolution of the Color-Magnitude Relation in High-Redshift Clusters:
  Blue Early-Type Galaxies and Red Pairs in RDCS J0910+5422

abstract:
  The color-magnitude relation has been determined for the RDCS J0910+5422
cluster of galaxies at redshift z = 1.106. Cluster members were selected from
HST ACS images, combined with ground--based near--IR imaging and optical
spectroscopy. The observed early--type color--magnitude relation (CMR) in
(i_775 -z_850) versus z_850 shows intrinsic scatters in color of 0.042 +/-
0.010 mag and 0.044 +/- 0.020 mag for ellipticals and S0s, respectively. From
the scatter about the CMR, a mean luminosity--weighted age t > 3.3 Gyr (z > 3)
is derived for the elliptical galaxies.
  Strikingly, the S0 galaxies in RDCS J0910+5422 are systematically bluer in
(i_775 - z_850) by 0.07 +/- 0.02 mag, with respect to the ellipticals. The
ellipticity distribution as a function of color indicates that the face-on S0s
in this particular cluster have likely been classified as elliptical. Thus, if
anything, the offset in color between the elliptical and S0 populations may be
even more significant.
  The color offset between S0 and E corresponds to an age difference of ~1 Gyr,
for a single-burst solar metallicity model. A solar metallicity model with an
exponential decay in star formation will reproduce the offset for an age of 3.5
Gyr, i.e. the S0s have evolved gradually from star forming progenitors.
  The early--type population in this cluster appears to be still forming. The
blue early-type disk galaxies in RDCS J0910+5422 likely represent the direct
progenitors of the more evolved S0s that follow the same red sequence as
ellipticals in other clusters.
  Thirteen red galaxy pairs are observed and the galaxies associated in pairs
constitute ~40% of the CMR galaxies in this cluster.


title: Magnetic fields in jets: ordered or disordered?

abstract:
  The question of the degree of order in the magnetic fields of relativistic
jets is important to any understanding of their production. Both vector-ordered
(e.g. helical) and disordered, but anisotropic fields can produce the high
observed degrees of polarization. We outline our models of jets in FR I radio
galaxies as decelerating relativistic flows. We then present theoretical
calculations of the synchrotron emission from different field configurations
and compare them with observed emission from FR I jets. We show that
large-scale helical fields (with significant poloidal and toroidal components)
are inconsistent with observations. The combination of an ordered toroidal and
disordered poloidal component is consistent with our data, as is an entirely
disordered field. Jets must also contain small, but significant amounts of
radial field.


title: The origin of cosmic rays at all energies

abstract:
  There is mounting evidence from observations of long duration gamma ray
bursts (GRBs), supernova remnants (SNR) and the supernova (SN) explosion 1987A,
that SN explosions eject highly relativistic bipolar jets of plasmoids
(cannonballs) of ordinary matter. Here we use the remarkably successful
cannonball (CB) model of GRBs to show that bipolar jets from Galactic SN
explosions can produce the bulk of the Galactic cosmic rays at energies below
the ankle, while the CRs which escape into the intergalactic space or are
deposited there directly by jets from SNe in external galaxies can produce the
observed cosmic ray flux with energies above the ankle. The model predict well
all the observed properties of cosmic rays: their intensity, their spectrum
including their elemental knees and ankle, their composition and the
distribution of their arrival directions. At energies above the CR ankle, the
Galactic magnetic fields can no longer delay the free escape of such ultra high
energy CRs (UHECRs) from the Galaxy. The UHECRs, which are injected into the
intergalactic medium (IGM) by the SN jets from our Galaxy and all the other
galaxies and are isotropized there by the IGM magnetic fields, dominate the
flux of UHECRs. Almost all the extragalactic UHECRs heavier than helium
photo-disintegrate in collisions with the far infrared (FIR), microwave and
radio background radiations. The CR protons and He nuclei however suffer a
Greisen-Zatsepin-Kuzmin (GZK) cutoff due to pion photo-production in collisions
with the FIR, microwave and radio background photons.


title:
Enhanced Mass-to-Light Ratios in UCDs through Tidal Interaction with the
  Centre of the Host Galaxy

abstract:
  A recent study of ultra-compact dwarf galaxies (UCDs) in the Virgo cluster
revealed that some of them show faint envelopes and have measured mass-to-light
ratios of 5 and larger, which can not be explained by simple population
synthesis models. It is believed that this proves that some of the UCDs must
possess a dark matter halo and may therefore be stripped nuclei of dwarf
ellipticals rather than merged star cluster complexes. Using an efficient
N-body method we investigate if a close passage of a UCD through the central
region of the host galaxy is able to enhance the measured mass-to-light ratio
by tidal forces leaving the satellite slightly out of virial equilibrium and
thereby leading to an overestimation of its virial mass. We find this to be
possible and discuss the general problem of measuring dynamical masses for
objects that are probably interacting with their hosts.


title: Barred Galaxies:Studying the chaotic and ordered nature of orbits

abstract:
  The chaotic or ordered character of orbits in galactic models is an important
issue, since it can influence dynamical evolution. This distinction can be
achieved with the help of the Smaller Alingment Index - (SALI). We describe
here briefly this method and its advantages. Then we apply it to that case of
2D and 3D barred galaxy potentials. In particular, we find the fraction of
chaotic and ordered orbits in such potentials and present how this fraction
changes when the main parameters of the model are varied. For this, we consider
models with different bar mass, bar thickness or pattern speed. Varying only
one parameter at a time, we find that bars that are more massive, or thinner,
or faster, have a larger fraction of chaotic orbits.


title: Short GRBs in old populations: Magnetars from WD-WD mergers

abstract:
  Recent progress on the nature of short duration gamma-ray bursts has shown
that a fraction of them originate in the local universe. These systems may well
be the result of giant flares from soft gamma-repeaters (highly magnetized
neutron stars commonly known as magnetars). However, if these neutron stars are
formed via the core collapse of massive stars then it would be expected that
the bursts should originate from predominantly young stellar populations, while
correlating the positions of BATSE short bursts with structure in the local
universe reveals a correlation with all galaxy types, including those with
little or no ongoing star formation. This is a natural outcome if, in addition
to magnetars formed via the core collapse of massive stars they also form via
Accretion Induced Collapse following the merger of two white dwarfs, one of
which is magnetic. We investigate this possibility and find that the rate of
magnetar production via WD-WD mergers in the Milky Way is comparable to the
rate of production via core-collapse. However, while the rate of production of
magnetars by core collapse is proportional to the star formation rate, the rate
of production via WD-WD mergers (which have long lifetimes) is proportional to
the stellar mass density, which is concentrated in early-type systems.
Therefore magnetars produced via WD-WD mergers may produce SGR giant flares
which can be identified with early type galaxies. We also comment on the
possibility that this mechanism could produce a fraction of the observed short
duration burst population at higher redshift.


title:
Constraints on the coupled quintessence from cosmic microwave background
  anisotropy and matter power spectrum

abstract:
  We discuss the evolution of linear perturbations in a quintessence model in
which the scalar field is non-minimally coupled to cold dark matter. We
consider the effects of this coupling on both cosmic microwave background
temperature anisotropies and matter perturbations. Due to the modification of
the scale of cold dark matter as $\rho_{c} = \rho_{c}^{(0)} a^{-3 + \xi}$, we
can shift the turnover in the matter power spectrum even without changing the
present energy densities of matter and radiation. This can be used to constrain
the strength of the coupling. We find that the phenomenology of this model is
consistent with current observations up to the coupling power $n_{c} \leq 0.01$
while adopting the current parameters measured by WMAP. Upcoming cosmic
microwave background observations continuing to focus on resolving the higher
peaks may put strong constraints on the strength of the coupling.


title:
Weak-Lensing Detection at z~1.3: Measurement of the Two Lynx Clusters
  with Advanced Camera for Surveys

abstract:
  (Abridged) We present a HST/ACS weak-lensing study of RX J0849+4452 and RX
J0848+4453, the two most distant (at z=1.26 and z=1.27, respectively) clusters
yet measured with weak-lensing. The two clusters are separated by ~4' from each
other and appear to form a supercluster in the Lynx field. Using our deep ACS
F775W and F850LP imaging, we detected weak-lensing signals around both clusters
at ~4 sigma levels. The mass distribution indicated by the reconstruction map
is in good spatial agreement with the cluster galaxies. From the SIS fitting,
we determined that RX J0849+4452 and RX J0848+4453 have similar projected
masses of ~2.0x10^14 solar mass and ~2.1x10^14 solar mass, respectively, within
a 0.5 Mpc (~60") aperture radius.


title: Total Solar Irradiance Variability and the Solar Activity Cycle

abstract:
  It is suggested that the solar variability is due to the perturbed nature of
the solar core and this variability is provided by the variability of the solar
neutrino flux from the solar neutrino detectors i.e., Homestake,
Superkamiokande, SAGE and GALLEX-GNO. The solar neutrino flux in the standard
solar model (SSM) was calculated on the assumption of L_nu (neutrino
luminosity) = L_gamma (optical luminosity) which implies that if there is a
change in optical luminosity then solar neutrino flux data will also be
changed. An internal dynamo due to the cyclic variation of nuclear energy
generation inside the core of the sun is responsible for the solar activity
cycle was suggested and thus the internal magnetic field is also variable.
Again the changes in the nuclear energy generation induce structural changes
that result in variations of the global solar parameters i.e., luminosity,
radius and temperatures etc. From the analysis of total solar irradiance (TSI)
data during the year from 1970 to 2003 we have found five phases within the
solar activity cycle. The first phase (I) starts before two years from the
sunspot minimum. The second phase (II) starts at the time of sunspot minimum
and phase (III) starts before 2/3 years from sunspot maximum whereas phase (IV)
starts at sunspot maximum and fifth phase (V) starts at after 2-3 years from
sunspot maximum.


title: Water Vapor around Sgr B2

abstract:
  We have conducted a study combining H2O lines in two spectral regions. First,
Infrared Space Observatory observations of several H2O thermal lines seen in
absorption toward Sgr B2(M) at a spectral resolution of 35 kms^-1 have been
analyzed. Second, an IRAM-30m telescope map of the para-H2O 3_13-2_20 line at
183.31 GHz, seen in emission, has also been obtained and analyzed. The H2O
lines seen in absorption are optically thick and are formed in the outermost
gas of the condensations in front of the far-IR continuum sources. They probe a
maximum visual extinction of ~5 to 10 mag. Radiative transfer models indicate
that these lines are quite insensitive to temperature and gas density, and that
IR photons from the dust play a dominant role in the excitation of the involved
H2O rotational levels. The water vapor abundance in the region is (1-2)x10^-5.
The relatively low H2O/OH abundance ratio in the region, 2-4, is a signature of
UV photon dominated surface layers traced by far-IR observations.


title: A Radio Pulsar Spinning at 716 Hz

abstract:
  We have discovered a 716-Hz eclipsing binary radio pulsar in the globular
cluster Terzan 5 using the Green Bank Telescope. It is the fastest-spinning
neutron star ever found, breaking the 23-year-old record held by the 642-Hz
pulsar B1937+21. The difficulty in detecting this pulsar, due to its very low
flux density and high eclipse fraction (~40% of the orbit), suggests that even
faster-spinning neutron stars exist. If the pulsar has a mass less than 2 Msun,
then its radius is constrained by the spin rate to be < 16 km. The short period
of this pulsar also constrains models that suggest gravitational radiation,
through an r-mode instability, limits the maximum spin frequency of neutron
stars.


title:
The evolution of the mass function split by morphology up to redshift 1
  in the FORS Deep and the GOODS-S Fields

abstract:
  We study the evolution of the stellar mass density for the separate families
of bulge-dominated and disk-dominated galaxies over the redshift range 0.25 < z
< 1.15. We derive quantitative morphology for a statistically significant
galaxy sample of 1645 objects selected from the FORS Deep and the GOODS-S
Fields. We find that the morphological mix evolves monotonically with time: the
higher the redshift, the more disk systems dominate the total mass content. At
redshift about 1, massive objects (M_stellar > 7E10 M_solar) host about half of
the mass contained in objects of similar mass in the local universe. The
contribution from early and late type galaxies to the mass budget at z about 1
is nearly equal. We show that in situ star formation is not sufficient to
explain the changing mass budget. Moreover we find that the star formation rate
per unit stellar mass of massive galaxies increases with redshift only for the
intermediate and early morphological types, while it stays nearly constant for
late-type objects. This suggests that merging and/or frequent accretion of
small mass objects has a key role in the shaping of the Hubble sequence as we
observe it now, and also in decreasing the star formation activity of the
bulge-dominated descendants of massive disk galaxies.


title: Initial conditions for reaching the critical velocity

abstract:
  The aim of this paper is to determine the initial rotational velocities
required on the ZAMS for single stars to reach the critical velocity, sometimes
called the break-up velocity, during the Main-Sequence (MS) phase. Some useful
relations between $\Omega/\Omega_{\rm crit}$, $\upsilon/\upsilon_{\rm crit}$
($\upsilon$ is the velocity at the equator), the moments of inertia, the
angular momenta, the kinetic energy in the rotation and various other basic
physical quantities are obtained.


title: K. Schwarzschild's problem in radiation transfer theory

abstract:
  We solve exactly the problem of a finite slab receiving an isotropic
radiation on one side and no radiation on the other side. This problem - to be
more precise the calculation of the source function within the slab - was first
formulated by K. Schwarzschild in 1914. We first solve it for unspecified
albedos and optical thicknesses of the atmosphere, in particular for an albedo
very close to 1 and a very large optical thickness in view of some
astrophysical applications. Then we focus on the conservative case (albedo =
1), which is of great interest for the modeling of grey atmospheres in
radiative equilibrium. Ten-figure tables of the conservative source function
are given. From the analytical expression of this function, we deduce 1) a
simple relation between the effective temperature of a grey atmosphere in
radiative equilibrium and the temperature of the black body that irradiates it,
2) the temperature at any point of the atmosphere when it is in local
thermodynamical equilibrium. This temperature distribution is the counterpart,
for a finite slab, of Hopf's distribution in a half-space. Its graphical
representation is given for various optical thicknesses of the atmosphere.


title:
On the accuracy of the ALI method for solving the radiative transfer
  equation

abstract:
  We solve the integral equation describing the propagation of light in an
isothermal plane-parallel atmosphere of optical thickness $\tau^*$, adopting a
uniform thermalization parameter $\epsilon$. The solution given by the ALI
method, widely used in the field of stellar atmospheres modelling, is compared
to the exact solution. Graphs are given that illustrate the accuracy of the ALI
solution as a function of the parameters $\epsilon$, $\tau^*$ and optical depth
variable $\tau$.


title: Integral equations for the H- X- and Y-functions

abstract:
  We come back to a non linear integral equation satisfied by the function H,
which is distinct from the classical H-equation. Established for the first time
by Busbridge (1955), it appeared occasionally in the literature since then.
First of all, this equation is generalized over the whole complex plane using
the method of residues. Then its counterpart in a finite slab is derived; it
consists in two series of integral equations for the X- and Y-functions. These
integral equations are finally applied to the solution of the albedo problem in
a slab.


title:
The finite Laplace transform for solving a weakly singular integral
  equation occurring in transfer theory

abstract:
  We solve a weakly singular integral equation by Laplace transformation over a
finite interval of R. The equation is transformed into a Cauchy integral
equation, whose resolution amounts to solving two Fredholm integral equations
of the second kind with regular kernels. This classical scheme is used to
clarify the emergence of the auxiliary functions expressing the solution of the
problem. There are four such functions, two of them being classical ones. This
problem is encountered while studying the propagation of light in strongly
scattering media such as stellar atmospheres.


title: Lost and found dark matter in elliptical galaxies

abstract:
  The kinematical properties of elliptical galaxies formed during the mergers
of equal mass, stars+gas+dark matter spiral galaxies are compared to the
observed low velocity dispersions found for planetary nebulae on the outskirts
of ellipticals, which have been interpreted as pointing to a lack of dark
matter in ellipticals (which poses a problem for the standard model of galaxy
formation). We find that the velocity dispersion profiles of the stars in the
simulated ellipticals match well the observed ones. The low outer stellar
velocity dispersions are mainly caused by the radial orbits of the outermost
stars, which, for a given binding energy must have low angular momentum to
reach their large radial distances, usually driven out along tidal tails.


title: Kinematical and Dynamical Modeling of Elliptical Galaxies

abstract:
  Elements of kinematical and dynamical modeling of elliptical galaxies (Es)
are presented. In projection, NFW models resemble Sersic models, but with a
very narrow range of shapes (m=3+/-1). The total density profile of Es cannot
be NFW-like because the predicted local M/L and aperture velocity dispersion
within an effective radius (Re) are much lower than observed. Stars must then
dominate Es out to a few Re. Fitting an NFW model to the total density profile
of Sersic+NFW (stars+dark matter [DM]) Es results in very high concentration
parameters, as found by X-ray observers. Kinematical modeling of Es assuming an
isotropic NFW DM model underestimates M/L at the virial radius by a factor of
1.6 to 2.4, because dissipationless LCDM halos have slightly different density
profiles and slightly radial velocity anisotropy. In N-body+gas simulations of
Es as merger remnants of spirals embedded in DM halos, the slope of the DM
density profile is steeper when the initial spiral galaxies are gas-rich. The
Hansen & Moore (2006) relation between anisotropy and the slope of the density
profile breaks down for gas and DM, but the stars follow an analogous relation
with slightly less radial anisotropies for a given density slope. Using
kurtosis (h_4) to infer anisotropy in Es is dangerous, as h_4 is also sensitive
to small levels of rotation. The stationary Jeans equation provides accurate
masses out to 8 Re. The discrepancy between the modeling of Romanowsky et al.
(2003), indicating a dearth of DM in Es, and the simulations analyzed by Dekel
et al. (2005), which match the spectroscopic observations of Es, is partly due
to radial anisotropy and to observing oblate Es face-on. However, one of the 15
solutions to the orbit modeling of Romanowsky et al. is found to have an amount
and concentration of DM consistent with LCDM predictions.


title:
Percolation Galaxy Groups and Clusters in the SDSS Redshift Survey:
  Identification, Catalogs, and the Multiplicity Function

abstract:
  We identify galaxy groups and clusters in volume-limited samples of the SDSS
redshift survey, using a redshift-space friends-of-friends algorithm. We
optimize the friends-of-friends linking lengths to recover galaxy systems that
occupy the same dark matter halos, using a set of mock catalogs created by
populating halos of N-body simulations with galaxies. Extensive tests with
these mock catalogs show that no combination of perpendicular and line-of-sight
linking lengths is able to yield groups and clusters that simultaneously
recover the true halo multiplicity function, projected size distribution, and
velocity dispersion. We adopt a linking length combination that yields, for
galaxy groups with ten or more members: a group multiplicity function that is
unbiased with respect to the true halo multiplicity function; an unbiased
median relation between the multiplicities of groups and their associated
halos; a spurious group fraction of less than ~1%; a halo completeness of more
than ~97%; the correct projected size distribution as a function of
multiplicity; and a velocity dispersion distribution that is ~20% too low at
all multiplicities. These results hold over a range of mock catalogs that use
different input recipes of populating halos with galaxies. We apply our
group-finding algorithm to the SDSS data and obtain three group and cluster
catalogs for three volume-limited samples that cover 3495.1 square degrees on
the sky. We correct for incompleteness caused by fiber collisions and survey
edges, and obtain measurements of the group multiplicity function, with errors
calculated from realistic mock catalogs. These multiplicity function
measurements provide a key constraint on the relation between galaxy
populations and dark matter halos.


title: Multiplicity, activity and fast rotation in early-type stars

abstract:
  There are obvious and direct ways in which the presence of binary companions
may affect activity in OB stars through tidal interactions. In this review,
however, I consider a more fundamental role for multiplicity and explore claims
that the Be phenomenon may be intimately linked to binarity. I describe the
binary channel for the formation of Be stars and the ongoing discussion about
the relative contribution of this channel to the population of Be stars. I also
present evidence suggesting that some environments are more favourable for the
appearance of Be stars and explore whether this may be connected to initial
conditions, such as the chemical composition or the distribution of rotational
velocities on the ZAMS.


title: Active Carbon and Oxygen Shell Burning Hydrodynamics

abstract:
  We have simulated 2.5$\times10^3$ s of the late evolution of a $23 \rm
M_\odot$ star with full hydrodynamic behavior. We present the first simulations
of a multiple-shell burning epoch, including the concurrent evolution and
interaction of an oxygen and carbon burning shell. In addition, we have evolved
a 3D model of the oxygen burning shell to sufficiently long times (300 s) to
begin to assess the adequacy of the 2D approximation. We summarize striking new
results: (1) strong interactions occur between active carbon and oxygen burning
shells, (2) hydrodynamic wave motions in nonconvective regions, generated at
the convective-radiative boundaries, are energetically important in both 2D and
3D with important consequences for compositional mixing, and (3) a spectrum of
mixed p- and g-modes are unambiguously identified with corresponding adiabatic
waves in these computational domains. We find that 2D convective motions are
exaggerated relative to 3D because of vortex instability in 3D. We discuss the
implications for supernova progenitor evolution and symmetry breaking in core
collapse.


title:
Radiative transfer in plane-parallel media and Cauchy integral equations
  II. The H-function

abstract:
  In the central part of this paper, we revisit the classical study of the
H-function defined as the unique solution, regular in the right complex
half-plane, of a Cauchy integral equation. We take advantage of our work on the
N-function published in the first article of this series. The H-function is
then used to solve a class of Cauchy integral equations occurring in transfer
problems posed in plane-parallel media. We obtain a concise expression of the
unique solution analytic in the right complex half-plane, then modified with
the help of the residue theorem for numerical calculations.


title: The Anomalous Early Afterglow of GRB 050801

abstract:
  The ROTSE-IIIc telescope at the H.E.S.S. site, Namibia, obtained the earliest
detection of optical emission from a Gamma-Ray Burst (GRB), beginning only 21.8
s from the onset of Swift GRB 050801. The optical lightcurve does not fade or
brighten significantly over the first ~250 s, after which there is an
achromatic break and the lightcurve declines in typical power-law fashion. The
Swift/XRT also obtained early observations starting at 69 s after the burst
onset. The X-ray lightcurve shows the same features as the optical lightcurve.
These correlated variations in the early optical and X-ray emission imply a
common origin in space and time. This behavior is difficult to reconcile with
the standard models of early afterglow emission.


title:
Radiative transfer in plane-parallel media and Cauchy integral equations
  III. The finite case

abstract:
  We come back to the Cauchy integral equations occurring in radiative transfer
problems posed in finite, plane-parallel media with light scattering taken as
monochromatic and isotropic. Their solution is calculated following the
classical scheme where a Cauchy integral equation is reduced to a couple of
Fredholm integral equations. It is expressed in terms of two auxiliary
functions $\zeta_+$ and $\zeta_-$ we introduce in this paper. These functions
show remarkable analytical properties in the complex plane. They satisfy a
simple algebraic relation which generalizes the factorization relation of
semi-infinite media. They are regular in the domain of the Fredholm integral
equations they satisfy, and thus can be computed accurately. As an
illustration, the X- and Y-functions are calculated in the whole complex plane,
together with the extension in this plane of the so-called Sobouti's functions.


title: Stellar Abundances: Recent and Foreseeable Trends

abstract:
  The determination of chemical abundances from stellar spectra is considered a
mature field of astrophysics. Digital spectra of stars are recorded and
processed with standard techniques, much like samples in the biological
sciences. Nevertheless, uncertainties typically exceed 20%, and are dominated
by systematic errors. The first part of this paper addresses what is being done
to reduce measurement errors; and what is not being done, but should be. The
second part focuses in some of the most exciting applications of stellar
spectroscopy in the arenas of galactic structure and evolution, the origin of
the chemical elements, and cosmology.


title:
Relativistic Proton Production During the 14 July 2000 Solar Event: The
  Case for Multiple Source Mechanisms

abstract:
  Protons accelerated to relativistic energies by transient solar and
interplanetary phenomena caused a ground-level cosmic ray enhancement on 14
July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux
directly and ground-based observatories measured the secondary responses to
higher energy protons. We have modelled the arrival of these relativistic
protons at Earth using a technique which deduces the spectrum, arrival
direction and anisotropy of the high-energy protons that produce increased
responses in neutron monitors. To investigate the acceleration processes
involved we have employed theoretical shock and stochastic acceleration
spectral forms in our fits to spacecraft and neutron monitor data. During the
rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum
between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In
contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining
phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We
propose that at least two acceleration processes were responsible for the
production of relativistic protons during the Bastille Day solar event: (1)
protons were accelerated to relativistic energies by a shock, presumably a
coronal mass ejection (CME). (2) protons were also accelerated to relativistic
energies by stochastic processes initiated by magnetohydrodynamic (MHD)
turbulence.


title: Data storage, processing and visualisation for the ATCA

abstract:
  We present three Virtual Observatory tools developed at the ATNF for the
storage, processing and visualisation of ATCA data. These are the Australia
Telescope Online Archive, a prototype data reduction pipeline, and the Remote
Visualisation System. These tools were developed in the context of the Virtual
Observatory and were intended to be both useful for astronomers and technology
demonstrators. We discuss the design and implementation of these tools, as well
as issues that should be considered when developing similar systems for future
telescopes.


title:
Active Galactic Nuclei in the mid-IR. Evolution and Contribution to the
  Cosmic Infrared Background

abstract:
  We study the evolution of the luminosity function (LF) of type-1 and type-2
AGN in the mid-infrared, and derive their contribution to the Cosmic InfraRed
Background (CIRB) and the expected deep source counts to be observed by Spitzer
at 24 micron. The sample of type-1 and type-2 AGN was selected at 15 micron
(ISO) and 12 micron (IRAS), and classified on the basis of their optical
spectra. Local templates of type-1 and type-2 AGN have been used to derive the
intrinsic 15 micron luminosities. We adopted an evolving smooth two-power law
shape of the LF, whose parameters have been derived using an un-binned maximum
likelihood method. We find that the LF of type-1 AGN is compatible with a pure
luminosity evolution (L(z)=L(0)(1+z)^k_L) model where k_L~2.9. A small
flattening of the faint slope of the LF with increasing redshift is favoured by
the data. A similar evolutionary scenario is found for the type-2 population
with a rate k_L ranging from ~1.8 to 2.6, depending significantly on the
adopted mid-infrared spectral energy distribution. Also for type-2 AGN a
flattening of the LF with increasing redshift is suggested by the data,
possibly caused by the loss of a fraction of type-2 AGN hidden within the
optically classified starburst and normal galaxies. The type-1 AGN contribution
to the CIRB at 15 micron is (4.2-12.1) x 10e-11 W m^-2 sr^-1, while the type-2
AGN contribution is (5.5-11.0) x 10e-11 W m^-2 sr^-1. We expect that Spitzer
will observe, down to a flux limit of S_24 = 0.01 mJy, a density of ~1200
deg^-2 type-1 and ~1000 deg^-2 type-2 optically classified AGN. The derived
total contribution of the AGN galaxies to the CIRB (4-10%) and Spitzer counts
should be considered as lower limits, because of a possible loss of type-2
sources caused by the optical classification.


title: Introduction: Paleoheliosphere versus PaleoLISM

abstract:
  Speculations that encounters with interstellar clouds modify the terrestrial
climate have appeared in the scientific literature for over 85 years. This
article introduces a series of articles that seek to give substance to these
speculations by examining the exact mechanisms that link the pressure and
composition of the interstellar medium surrounding the Sun to the physical
properties of the inner heliosphere at the Earth.


title:
Pulsar rotation measures and the large-scale structure of Galactic
  magnetic field

abstract:
  The large-scale magnetic field of our Galaxy can be probed in three
dimensions using Faraday rotation of pulsar signals. We report on the
determination of 223 rotation measures from polarization observations of
relatively distant southern pulsars made using the Parkes radio telescope.
Combined with previously published observations these data give clear evidence
for large-scale counterclockwise fields (viewed from the north Galactic pole)
in the spiral arms interior to the Sun and weaker evidence for a
counterclockwise field in the Perseus arm. However, in interarm regions,
including the Solar neighbourhood, we present evidence that suggests that
large-scale fields are clockwise. We propose that the large-scale Galactic
magnetic field has a bisymmetric structure with reversals on the boundaries of
the spiral arms. Streaming motions associated with spiral density waves can
directly generate such a structure from an initial inwardly directed radial
field. Large-scale fields increase toward the Galactic Center, with a mean
value of about 2~$\mu$G in the Solar neighbourhood and 4~$\mu$G at a
Galactocentric radius of 3 kpc.


title:
Global Three-Dimensional MHD Simulations of Galactic Gaseous Disks: I.
  Amplification of Mean Magnetic Fields in Axisymmetric Gravitational Potential

abstract:
  We carried out global three-dimensional resistive magnetohydrodynamic
simulations of galactic gaseous disks to investigate how the galactic magnetic
fields are amplified and maintained. We adopt a steady axisymmetric
gravitational potential given by \cite*{Miy80}. As the initial condition, we
assume a warm ($T\sim10^{5} \mathrm{K}$) rotating gas torus centered at
$\varpi=10 \mathrm{kpc}$ threaded by weak azimuthal magnetic fields. Numerical
results indicate that in differentially rotating galactic gaseous disks,
magnetic fields are amplified due to magneto-rotational instability and
magnetic turbulence develops. After the amplification of magnetic energy
saturates, the disk stays in a quasi-steady state. The mean azimuthal magnetic
field increases with time and shows reversals with period of 1Gyr (2Gyr for a
full cycle). The amplitude of $B_{\phi}$ near the equatorial plane is
$B_{\phi}\sim1.5\mu \mathrm{G}$ at $\varpi=5 \mathrm{kpc}$. The magnetic fields
show large fluctuations whose standard deviation is comparable to the mean
field. The mean azimuthal magnetic field in the disk corona has direction
opposite to the mean magnetic field inside the disk. The mass accretion rate
driven by the Maxwell stress is $\sim10^{-3}M_{\odot}/ \mathrm{yr}$ at
$\varpi=2.5 \mathrm{kpc}$ when the mass of the initial torus is
$\sim5\times10^{8}M_{\odot}$.


title: Short-term Variations in the Galactic Environment of the Sun

abstract:
  The galactic environment of the Sun varies over short timescales as the Sun
and interstellar clouds travel through space. Small variations in the dynamics,
ionization, density, and magnetic field strength of the interstellar medium
(ISM) surrounding the Sun yield pronounced changes in the heliosphere. We
discuss essential information required to understand short-term variations in
the galactic environment of the Sun, including the distribution and radiative
transfer properties of nearby ISM, and variations in the boundary conditions of
the heliosphere as the Sun traverses clouds. The most predictable transitions
are when the Sun emerged from the Local Bubble interior and entered the cluster
of local interstellar clouds flowing past the Sun, within the past 140,000
years, and again when the Sun entered the local interstellar cloud now
surrounding and inside of the solar system, sometime during the past 44,000
years.


title: Visibility retrieval in Michelson wide-field stellar interferometry

abstract:
  Wide field interferometry has become a subject of increasing interest in the
recent years. New methods have been suggested in order to avoid the drawbacks
of the standard wide-field method (homothetic mapping) which is not applicable
when the aperture is highly diluted; for this reason imaging with
non-homothetic arrays is being extensively studied [1], [2]. The field of view
of a pupil plane interferometer or a densified array consists only of a few
resolution elements; in order to improve these systems, we developed a new
method consisting of a Michelson pupil-plane combination scheme where a wide
field of view can be achieved in one shot. This technique, called "staircase
mirror" approach, has been described in a previous paper [3] and uses a
stair-shaped mirror in the intermediate image plane of each telescope in the
array, allowing for simultaneous correction of the differential delay for both
the on- and off-axis image positions. Experimental results have been obtained
showing the simultaneous recovering of the fringes of off-axis stars with an
appreciable angular separation, and with a contrast similar to that of the
on-axis reference star. With this example, we demonstrate an increase of the
field of view by a factor of five, with no need of extra observation time. In
this article, we present a further analysis of the method. We investigate how
to retrieve the visibility when a star is focused on the edge of a step of the
stair-shaped mirror. Even though the Optical Pathlength Difference (OPD)
correction is discontinuous, we show both numerically and analytically that the
visibility can be completely recovered, so that no information is lost. Our
experimental results demonstrate that the visibility can be retrieved to within
a 1% error.


title:
Mid-infrared, spatially-resolved spectroscopy of the nucleus of the
  Circinus galaxy

abstract:
  High spatial resolution spectroscopy at 8-13microns with T-ReCS on Gemini-S
has revealed striking variations in the mid-infrared emission and absorption in
the nucleus of the Circinus galaxy on sub-arcsecond scales. The core of
Circinus is compact and obscured by a substantial column of cool silicate dust.
Weak extended emission to the east and west coincides with the coronal line
region and arises from featureless dust grains which are probably heated by
line emission in the coronal emission zone. The extended emission on the east
side of the nucleus displays a much deeper silicate absorption than that on the
west, indicating significant columns of cool material along the line of sight
and corresponding to an additional extinction of A(V) 25 mag. Emission bands
from aromatic hydrocarbons are not subject to this additional extinction, are
relatively weak in the core and in the coronal line region, and are much more
spatially extended than the continuum dust emission; they presumably arise in
the circumnuclear star-forming regions. These data are interpreted in terms of
an inclined disk-like structure around the nucleus extending over tens of
parsecs and possibly related to the inner disk found from observations of water
masers by Greenhill et al (2003).


title:
High frequency VLBI observations of the scatter broadened quasar
  B2005+403

abstract:
  The quasar B2005+403 located behind the Cygnus region, is a suitable object
for studying the interplay between propagation effects, which are extrinsic to
the source and source intrinsic variability. On the basis of VLBI experiments
performed at 1.6, 5, 8, 15, 22, and 43GHz between 1992-2003 and parallel
multi-frequency monitoring of the total flux density, we investigated the
variability of total flux density and source structure. Below 8 GHz, the
point-like VLBI source is affected by scatter-broadening of the turbulent
interstellar medium, which is located along the line of sight and likely
associated with the Cygnus region. We present and discuss the measured
frequency dependence of the source size, which shows a power-law with slope of
-1.91+/-0.05. From the measured scattering angle at 1GHz of 77.1+/-4.0mas a
SM=0.43+/-0.04 m^{-20/3} kpc is derived, consistent with the general properties
of the ISM in this direction. The decreasing effect of angular broadening
towards higher frequencies allows to study the internal structure of the
source. Above 8GHz new VLBI observations reveal a one-sided slightly
south-bending core-jet structure, with stationary and apparent superluminally
moving jet components. The jet components move on non-ballistic trajectories.
In AGN, total flux density variations are often related to the emergence of new
VLBI components. However, during almost eleven years no new component was
ejected in B2005+403. In the flux density variability a trough is observed at
5-37 GHz between 1996 and 2001. This can be explained as a blending effect of
jet component fluxes. Dense in time sampled flux density monitoring
observations reveal intra-day variability at 1.6GHz impling a second, less
dense or turbulent scattering screen at few to hundred parsec distance.


title:
Early-type stars observed in the ESO UVES Paranal Observatory Project: I
  -- Interstellar Na I UV, Ti II and Ca II K observations

abstract:
  We present an analysis of interstellar Na I (lambda=3302.37\AA, 3302.98\AA),
Ti II (lambda=3383.76\AA) and Ca II K (lambda=3933.66\AA) absorption features
for 74 sightlines towards O- and B-type stars in the Galactic disc. The data
were obtained from the UVES Paranal Observatory Project, at a spectral
resolution of 3.75km/s and with mean signal to noise ratios per pixel of 260,
300 and 430 for the Na I, Ti II and Ca II observations, respectively.
Interstellar features were detected in all but one of the Ti II sightlines and
all of the Ca II sightlines. The dependence of the column density of these
three species with distance, height relative to the Galactic plane, H I column
density, reddening and depletion relative to the solar abundance has been
investigated. We also examine the accuracy of using the Na I column density as
an indicator of that for H I. In general we find similar strong correlations
for both Ti and Ca, and weaker correlations for Na. Our results confirm the
general belief that Ti and Ca occur in the same regions of the interstellar
medium and also that the Ti II/Ca II ratio is constant over all parameters. We
hence conclude that the absorption properties of Ti and Ca are essentially
constant under the general interstellar medium conditions of the Galactic disc.


title: The decline and fall of GRS 1915+105: the end is nigh?

abstract:
  The galactic microquasar GRS 1915+105 has been in a continuous state of
outburst since 1992, over 20 times longer than any other black hole X-ray
transient. Assuming that the outburst is powered via accretion of an irradiated
gaseous disc, we calculate how the predicted outburst duration varies according
to the efficiency of the self-irradiation mechanism. At least one current model
leads to the conclusion that the end of the outburst is imminent. The timing of
the decline of GRS 1915+105, whenever it arrives, will be an excellent
discriminator of the self-irradiation mechanism in X-ray transients, allowing
us to infer the fraction of the disc that is heated by the incident X-rays and
the magnitude of the mass loss rate in the form of a wind.


title: From the Foucault pendulum to the galactical gyroscope and LHC

abstract:
  We consider the Foucault pendulum, isosceles triangle pendulum and the
general triangle pendulum rotating on the Earth. As an analogue, planet
orbiting in the rotating galaxy is considered as the giant galactical
gyroscope. The Lorentz and the Bargman-Michel-Telegdi equations are generalized
for the rotating system. These equations are inevitable for LHC where orbital
photons "feels" the Coriolis force caused by the rotation ofthe Earth.


title: The mass loss of C-rich giants

abstract:
  (Shortened version): The mass loss rates, expansion velocities and
dust-to-gas density ratios from millimetric observations of 119 carbon-rich
giants are compared, as functions of stellar parameters, to the predictions of
recent hydrodynamical models. Distances and luminosities previously estimated
from HIPPARCOS data, masses from pulsations and C/O abundance ratios from
spectroscopy, and effective temperatures from a new homogeneous scale, are
used. Predicted and observed mass loss rates agree fairly well, as functions of
effective temperature.(shortened). Four stars with detached shells, i.e.
episodic strong mass loss, and five cool infrared carbon-rich stars with
optically-thick dust shells, have mass loss rates much larger than predicted
values.(shortened). Recent drift models can contribute to minimize the
discrepancy since they include more dust. Simple approximate formulae are
proposed.


title:
The Great Observatories Origins Deep Survey VLT/FORS2 Spectroscopy in
  the GOODS-South Field: Part II

abstract:
  We present the second campaign of the ESO/GOODS program of spectroscopy of
faint galaxies in the GOODS-South field. Objects were selected as candidates
for VLT/FORS2 observations primarily based on the expectation that the
detection and measurement of their spectral features would benefit from the
high throughput and spectral resolution of FORS2. The reliability of the
redshift estimates is assessed using the redshift-magnitude and color-redshift
diagrams and comparing the results with public data. 807 spectra of 652
individua targets have been obtained in service mode with the FORS2
spectrograph at the ESO/VLT, providing 501 redshift determinations. The typical
redshift uncertainty is estimated to be sigma_z ~ 0.001. Galaxies have been
selected adopting three different color criteria and using the photometric
redshifts.The resulting redshift distribution typically spans two redshift
domains: from z=0.5 to 2 and z=3.5 to 6.2. In particular, 94 B435-,V606-,i775
"dropout" Lyman break galaxies have been observed, yielding redshifts for 65
objects in the interval 3.4<z<6.2. Three sources have been serendipitously
discovered in the redshift interval 4.8<z<5.5. Together with the previous
release, 930 sources have now been observed and 724 redshift determinations
have been carried out. The reduced spectra and the derived redshifts are
released to the community through the ESO web page
http://www.eso.org/science/goods/. Large scale structures are clearly detected
at z=0.666, 0.734, 1.096, 1.221, 1.300, and 1.614. A sample of 34 sources with
tilted [OII]3727 emission has been identified, 32 of them in the redshift range
0.9<z<1.5.


title: Bistable Profile Illumination in Pulsars B0919+06 & B1859+07

abstract:
  A new single pulse behaviour has been identified in two pulsars, B0919+06 and
B1859+07. Normally both starts emit bright subpulses in a region near the
trailing edge of heir profile. However, occasionally these stars exhibit
"events" wherein the emission longitude gradually decreases by about their
profile width, remains in this position for typically tens of pulses and then
gradually returns over a few pulses to the usual longitude. The effect bears
some resemblance to a profile "mode change", but here the effect is gradual and
episodic. When the separated profiles of the normal and "event" emission, they
reveal a broad and complex profile structure in each pulsar - but one which can
probably be understood correctly in terms of a single conical beam. Possibly
the effect entails an extreme example of "absorption"-induced profile
asymmetry, as suspected in other pulsars. Alternatively, shifting sources of
illumination within the pulsar beam may be responsible.


title: The Titius-Bode law of planetary distances: new approach

abstract:
  The new approach of the regular spacing of planetary orbits and planet mass
distribution in the Solar system is considered. The relative planetary
distances will be represented as the inverse composite probabilities of two
discrete distributions with one fitted parameter. Conceivable physical
interpretation of these distributions and fitted parameter will be suggested.
The parameters of the orbits of the newly discovered transneptunian objects are
compared with predicted planetary orbits.


title:
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses IV.
  Models of prospective time-delay lenses

abstract:
  Aims: To predict time delays for a sample of gravitationally lensed quasars
and to evaluate the accuracy that can be realistically achieved on the value of
H_0.
  Methods: We consider 14 lensed quasars that are candidates for time-delay
monitoring and model them in detail using pixelized lens models. For each
system, we provide a mass map, arrival-time surface and the distribution of
predicted time-delays in a concordance cosmology, assuming H_0^{-1}=14 Gyr
(H_0=70 in local units). Based on the predicted time-delays and on the
observational circumstances, we rate each lens as `excellent' or `good' or
`unpromising' for time-delay monitoring. Finally, we analyze simulated time
delays for the 11 lens rated excellent or good, and show that H_0 can be
recovered to a precision of 5%.
  Results: In combination with COSMOGRAIL paper I on the temporal sampling of
lensed quasar light curves, the present work will help design monitoring
campaigns of lensed quasars.


title:
A multifrequency angular power spectrum analysis of the Leiden
  polarization surveys

abstract:
  The Galactic synchrotron emission is expected to be the most relevant source
of astrophysical contamination in cosmic microwave background polarization
measurements, at least at frequencies < 100 GHz and at angular scales > 30'. We
present a multifrequency analysis of the Leiden surveys, linear polarization
surveys covering essentially the Northern Celestial Hemisphere at five
frequencies between 408 MHz and 1411 MHz. By implementing specific
interpolation methods to deal with these irregularly sampled data, we produced
maps of the polarized diffuse Galactic radio emission with pixel size of 0.92
deg. We derived the angular power spectrum (APS) (PI, E, and B modes) of the
synchrotron dominated radio emission as function of the multipole, l. We
considered the whole covered region and some patches at different Galactic
latitudes. By fitting the APS in terms of power laws (C_l = k l^a), we found
spectral indices that steepen with increasing frequency: from a = -(1-1.5) at
408 MHz to a = -(2-3) at 1411 MHz for 10 < l < 100 and from a = -0.7 to a =
-1.5 for lower multipoles (the exact values depending on the considered sky
region and polarization mode). The bulk of this steepening can be interpreted
in terms of Faraday depolarization effects. We then considered the APS at
various fixed multipoles and its frequency dependence. Using the APSs of the
Leiden surveys at 820 MHz and 1411 MHz, we determined possible ranges for the
rotation measure, RM, in the simple case of an interstellar medium slab model.
Taking also into account the polarization degree at 1.4 GHz, we could break the
degeneracy between the identified RM intervals. The most reasonable of them
turned out to be RM = 9-17 rad/m^2.


title:
The DPOSS II compact group survey: first spectroscopically confirmed
  candidates

abstract:
  This paper presents the results of a pilot redshift survey of 18 candidate
compact groups from the distant DPOSS survey that extends the available surveys
of compact groups of galaxies to z ~0.2 in redshift, mainly Hickson Compact
Groups and Southern Compact Groups. The goal of our survey was to confirm group
membership via redshift information and to measure the characteristic
parameters of a representative, albeit small, sample of DPOSS survey groups.
  Of the 18 candidates observed, seven are found to be indeed isolated compact
groups, i.e. groups with 3 or more concordant members and with no neighbouring
known cluster, while 7 are chance projection configurations on the sky. Three
remaining candidates, despite having 3 or more concordant member galaxies, are
located in the neighbourhood of known clusters, while another candidate turned
out to be a dense sub-condensation within Abell 0952.
  The median redshift of our 7 confirmed groups is z ~0.12, to be compared with
a median redshift of 0.03 for the local sample of compact groups by Hickson.
The typical group size is r~ 50 kpc, and the median radial velocity dispersion
is 167 km/s, while typical crossing times range from 0.005 H$_{0}^{-1}$ to 0.03
H$_{0}^{-1}$ with a median value of 0.018 H$_{0}^{-1}$, all similar to the
values usually found in the literature for such structures in the local
universe. The average mass-to-light ratio for our groups, M/L(B), is 92h,
higher than the value found for nearby Hickson compact groups but lower than
that found for loose groups. Our results suggest that, once full redshift
information for its members becomes available, the DPOSS sample will provide a
reference sample to study the properties of compact groups beyond the local
universe.


title:
Selection and 3D-Reconstruction of Gamma-Ray-induced Air Showers with a
  Stereoscopic System of Atmospheric Cherenkov Telescopes

abstract:
  A simple 3D-reconstruction method for gamma-ray induced air showers is
presented, which takes full advantage of the assets of a system of Atmospheric
Cherenkov Telescopes combining stereoscopy and fine-grain imaging like the High
Energy Stereoscopic System (H.E.S.S.). The rich information collected by the
cameras allows to select electromagnetic showers on the basis of their
rotational symmetry with respect to the incident direction, as well as of their
relatively small lateral spread. In the framework of a 3D-model of the shower,
its main parameters -- incident direction, shower core position on the ground,
slant depth of shower maximum, average lateral spread of Cherenkov photon
origins (or ``photosphere 3D-width'') and primary energy -- are fitted to the
pixel contents of the different images. For gamma-ray showers, the photosphere
3D-width is found to scale with the slant depth of shower maximum, an effect
related to the variation of the Cherenkov threshold with the altitude; this
property allows to define a dimensionless quantity omega (the ``reduced
3D-width''), which turns out to be an efficient and robust variable to
discriminate gamma-rays from primary hadrons. In addition, the omega
distribution varies only slowly with the gamma-ray energy and is practically
independent of the zenith angle. The performance of the method as applied to
H.E.S.S. is presented. Depending on the requirements imposed to reconstructed
showers, the angular resolution at zenith varies from 0.04 to 0.1 degrees and
the spectral resolution in the same conditions from 15% to 20%.


title:
Quasars near the line of sight towards Q 0302-003 and the transverse
  proximity effect

abstract:
  We report the discovery of the faint (V=21.7) quasar QSO03027-0010 at z=2.808
in the vicinity of Q0302-003, one of the few quasars observed with STIS to
study intergalactic HeII absorption. Together with another newly discovered QSO
at z=2.29, there are now 6 QSOs known near the line of sight towards Q0302-003,
of which 4 are located within the redshift region 2.76<=z<=3.28 covered by the
STIS spectrum. We correlated the opacity variations in the HI and HeII Lyman
forest spectra with the locations of known quasars. There is no significant
proximity effect in the HI Lyman alpha forest for any of the QSOs, except for
the well-known line of sight effect for Q0302-003 itself. By comparing the
absorption properties in HI and HeII, we estimated the fluctuating hardness of
the extragalactic UV radiation field along this line of sight. We find that
close to each foreground quasar, the ionizing background is considerably harder
than on average. In particular, our newly discovered QSO03027-0010 shows such a
hardness increase despite being associated with an overdensity in the HI Lyman
forest. We argue that the spectral hardness is a sensitive physical measure to
reveal the influence of QSOs onto the UV background even over scales of several
Mpc, and that it breaks the density degeneracy hampering the traditional
transverse proximity effect analysis. We infer from our sample that there is no
need for significantly anisotropic UV radiation from the QSOs. From the
transverse proximity effect detected in the sample we obtain minimum quasar
lifetimes in the range ~10-30 Myr.


title: Stellar Multiplicity and the IMF: Most Stars Are Single

abstract:
  In this short communication I compare recent findings suggesting a low binary
star fraction for late type stars with knowledge concerning the forms of the
stellar initial and present day mass functions for masses down to the hydrogen
burning limit. This comparison indicates that most stellar systems formed in
the galaxy are likely single and not binary as has been often asserted. Indeed,
in the current epoch two-thirds of all main sequence stellar systems in the
Galactic disk are composed of single stars. Some implications of this
realization for understanding the star and planet formation process are briefly
mentioned.


title: H-alpha Kinematics of the SINGS Nearby Galaxies Survey. I

abstract:
  This is the first part of an Halpha kinematics follow-up survey of the SINGS
sample. The data for 28 galaxies are presented. The observations were done on
three different telescopes with FaNTOmM, an integral field photon counting
spectrometer, installed in the respective focal reducer of each telescope. The
data reduction was done through a newly built pipeline with the aim of
producing the most homogenous data set possible. Adaptive spatial binning was
applied to the data cubes in order to get a constant signal-to-noise ratio
across the field of view. Radial velocity and monochromatic maps were generated
using a new algorithm and the kinematical parameters were derived using
tilted-ring models.


title: Large-Scale Bulk Motions Complicate the Hubble Diagram

abstract:
  We investigate the extent to which correlated distortions of the luminosity
distance-redshift relation due to large-scale bulk flows limit the precision
with which cosmological parameters can be measured. In particular, peculiar
velocities of type 1a supernovae at low redshifts may prevent a sufficient
calibration of the Hubble diagram necessary to measure the dark energy equation
of state to better than 10%, and diminish the resolution of the equation of
state time-derivative projected for planned surveys. We consider similar
distortions of the angular-diameter distance, as well as the Hubble constant.
We show that the measurement of correlations in the large-scale bulk flow at
low redshifts using these distance indicators may be possible with a cumulative
signal-to-noise ratio of order 7 in a survey of 300 type 1a supernovae spread
over 20,000 square degrees.


title:
The complex X-ray morphology of NGC 7618: A major group-group merger in
  the local Universe?

abstract:
  We present results from a short {\em Chandra}/ACIS-S observation of NGC 7618,
the dominant central galaxy of a nearby ($z$=0.017309, d=74.1 Mpc) group. We
detect a sharp surface brightness discontinuity 14.4 kpc N of the nucleus
subtending an angle of 130$^\circ$ with an X-ray tail extending $\sim$ 70 kpc
in the opposite direction. The temperature of the gas inside and outside the
discontinuity is 0.79$\pm$0.03 and 0.81$\pm$0.07 keV, respectively. There is
marginal evidence for a discontinuous change in the elemental abundance
($Z_{inner}$=0.65$\pm$0.25,$Z_{outer}$=0.17$\pm$0.21 at 90% confidence),
suggesting that this may be an `abundance' front. Fitting a two-temperature
model to the ASCA/GIS spectrum of the NGC 7618/UGC 12491 pair shows the
presence of a second, much hotter ($T$=$\sim$2.3 keV) component. We consider
several scenarios for the origin of the edge and the tail including a radio
lobe/IGM interaction, non-hydrostatic `sloshing', equal-mass merger and
collision, and ram-pressure stripping. In the last case, we consider the
possibility that NGC 7618 is falling into UGC 12491, or that both groups are
falling into a gas poor cluster potential. There are significant problems with
the first two models, however, and we conclude that the discontinuity and tail
are most likely the result of ram pressure stripping of the NGC 7618 group as
it falls into a larger dark matter potential.


title: Oscillation modes of relativistic slender tori

abstract:
  Accretion flows with pressure gradients permit the existence of standing
waves which may be responsible for observed quasi-periodic oscillations (QPO's)
in X-ray binaries. We present a comprehensive treatment of the linear modes of
a hydrodynamic, non-self-gravitating, polytropic slender torus, with arbitrary
specific angular momentum distribution, orbiting in an arbitrary axisymmetric
spacetime with reflection symmetry. We discuss the physical nature of the
modes, present general analytic expressions and illustrations for those which
are low order, and show that they can be excited in numerical simulations of
relativistic tori. The mode oscillation spectrum simplifies dramatically for
near Keplerian angular momentum distributions, which appear to be generic in
global simulations of the magnetorotational instability. We discuss our results
in light of observations of high frequency QPO's, and point out the existence
of a new pair of modes which can be in an approximate 3:2 ratio for arbitrary
black hole spins and angular momentum distributions, provided the torus is
radiation pressure dominated. This mode pair consists of the axisymmetric
vertical epicyclic mode and the lowest order axisymmetric breathing mode.