title:
Variable Quasi Periodic Oscillations during an outburst of the transient
  X-ray pulsar XTE J1858+034

abstract:
  We have investigated the Quasi Periodic Oscillation (QPO) properties of the
transient accreting X-ray pulsar XTE J1858+034 during the second outburst of
this source in April-May 2004. We have used observations made with the
Proportional Counter Array (PCA) of the Rossi X-ray Timing Explorer (RXTE)
during May 14-18 2004, in the declining phase of the outburst. We detected the
presence of low frequency QPOs in the frequency range of 140--185 mHz in all
the RXTE-PCA observations. We report evolution of the QPO parameters with the
time, X-ray flux, and X-ray photon energy. Though a correlation between the QPO
centroid frequency and the instantaneous X-ray flux is not very clear from the
data, we point out that the QPO frequency and the one day averaged X-ray flux
decreased with time during these observations. We have obtained a clear energy
dependence of the RMS variation in the QPOs, increasing from about 3% at 3 keV
to 6% at 25 keV. The X-ray pulse profile is a single peaked sinusoidal, with
pulse fraction increasing from 20% at 3 keV to 45% at 30 keV. We found that,
similar to the previous outburst, the energy spectrum is well fitted with a
model consisting of a cut-off power law along with an iron emission line.


title: Radio views of cosmic reionization

abstract:
  We use numerical simulations of cosmic reionization and radiative processes
related to the HI 21 cm emission line to produce synthetic radio maps as seen
by next generation radio telescopes that will operate at low radio frequencies
(e.g. LOFAR). Two different scenarios, in which the end of reionization occurs
early (z approx 13) or late (z approx 8) depending on the Initial Mass Function
(IMF) of the first stars and ionizing photon escape fraction, have been
explored. For each of these models we produce synthetic HI 21 cm emission maps
by convolving the simulation outputs with the provisional LOFAR sampling
function in the frequency range 76-140 MHz. If reionization occurs late, LOFAR
will be able to detect individual HI structures on arcmin scales, emitting at a
brightness temperature of approx 35 mK as a 3-sigma signal in about 1000 hours
of observing time. In the case of early reionization, the detection would be
unlikely, due to decreased sensitivity and increased sky temperatures. These
results assume that ionospheric, interference and foreground issues are fully
under control.


title: Physical origin of X-ray flares following GRBs

abstract:
  One of the major achievements of Swift is the discovery of the erratic X-ray
flares harboring nearly half of gamma-ray bursts (GRBs), both for long-duration
and short-duration categories, and both for traditional hard GRBs and soft
X-ray flashes (XRFs). Here I review the arguments in support of the suggestion
that they are powered by reactivation of the GRB central engine, and that the
emission site is typically ``internal'', i.e. at a distance within the forward
shock front. The curvature effect that characterizes the decaying lightcurve
slope during the fading phase of the flares provides an important clue. I will
then discuss several suggestions to re-start the GRB central engine and comment
on how future observations may help to unveil the physical origin of X-ray
flares.


title:
Spot patterns and differential rotation in the eclipsing pre-CV
  binary,V471 Tau

abstract:
  We present surface spot maps of the K2V primary star in the pre-cataclysmic
variable binary system, V471 Tau. The spot maps show the presence of large high
latitude spots located at the sub-white dwarf longitude region. By tracking the
relative movement of spot groups over the course of four nights (eight rotation
cycles), we measure the surface differential rotation rate of the system.Our
results reveal that the star is rotating rigidly with a surface shear rate,
dOmega = 1.6 +/- 6 mrad/d. The single active star AB Dor has a similar spectral
type, rotation period, and activity level as the K star in V471 Tau but
displays much stronger surface shear (46 < dOmega < 58 mrad/d). Our results
suggest that tidal locking may inhibit differential rotation; this reduced
shear, however, does not affect the overall magnetic activity levels in active
K dwarfs.


title:
Prediction of Supersoft X-ray Phase during the 2006 Outburst of RS
  Ophiuchi

abstract:
  RS Ophiuchi is one of the well-observed recurrent novae and also a candidate
progenitor of Type Ia supernovae. Its sixth recorded outburst was discovered on
12 February 2006. Detection of a supersoft X-ray phase will provide a firm
confirmation of hydrogen shell-burning on the white dwarf and its
turn-on/turn-off dates strongly constrain a mass range of the white dwarf,
which clarify whether or not RS Oph becomes a Type Ia supernova. For a timely
detection of its supersoft X-ray phase, we have calculated outburst evolution
of RS Oph based on the optically thick wind theory and predicted a supersoft
X-ray phase for the 2006 outburst: it will most probably start on day 80-90 and
continue until day 110-120 after the optical maximum. Its duration is so short
as only a month or so. We strongly recommend multiple observations during
April, May, and June of 2006 to detect turn-on and turn-off times of the
supersoft X-ray phase.


title: The dust disk dynamics in week-nonlinear regime

abstract:
  We investigate the problem of self-gravitating dust disk dynamics in a static
state taking into account nonlinear effects. For this purpose Schrodinger-type
equation including the mass conservation law is used for the whole description
of hydrodynamic flows of self-gravitating dust. We have shown a purely
hydrodynamic mechanism of ring formation in the radial direction by taking into
account nonlinearity in the lowest order of expansion parameter, which
determines an order of magnitude of flow.


title: The asymmetric structure of the Galactic halo

abstract:
  Using the stellar photometry catalogue based on the latest data release (DR4)
of the Sloan Digital Sky Survey (SDSS), a study of the Galactic structure using
star counts is carried out for selected areas of the sky. The sample areas are
selected along a circle at a Galactic latitude of +60$^\circ$, and 10 strips of
high Galactic latitude along different longitudes. Direct statistics of the
data show that the surface densities of $\ell$ from $180^{\circ}$ to
$360^{\circ}$ are systematically higher than those of $\ell$ from $0^{\circ}$
to $180^{\circ}$, defining a region of overdensity (in the direction of Virgo)
and another one of underdensity (in the direction of Ursa Major) with respect
to an axisymmetric model. It is shown by comparing the results from star counts
in the $(g-r)$ colour that the density deviations are due to an asymmetry of
the stellar density in the halo. Theoretical models for the surface density
profile are built and star counts are performed using a triaxial halo of which
the parameters are constrained by observational data. Two possible reasons for
the asymmetric structure are discussed.


title:
Suppressing cluster cooling flows by self-regulated heating from
  spatially distributed population of AGNs

abstract:
  (Abridged) Existing models invoking AGN activty to resolve the cooling flow
conundrum in galaxy clusters focus exclusively on the role of the central
galaxy. Such models require fine-tuning of highly uncertain microscopic
transport properties to distribute the thermal thermal over the entire cluster
cooling core. We propose that the ICM is instead heated by multiple, spatially
distributed AGNs. There is mounting observational evidence for multiple AGNs in
cluster environments. Active AGNs drive bubbles into the ICM. We identify three
distinct interactions between the bubble and the ICM: (1) Upon injection, the
bubbles expand rapidly in situ to reach pressure equilibrium with their
surroundings, generating shocks and waves whose dissipation is the principal
source of ICM heating. (2) Once inflated, the bubbles rise buoyantly at rate
determined by a balance with the viscous drag force, which itself results in
some additional heating. (3) Rising bubbles expand and compress their
surroundings. This process is adiabatic and does not contribute to any
additional heating; rather, the increased ICM density due to compression
enhances cooling. Our model sidesteps the ``transport'' issue by relying on the
spatially distributed galaxies to heat the cluster core. We include self
regulation in our model by linking AGN activity in a galaxy to cooling
characteristics of the surrounding ICM. We use a spherically symmetric
one-dimensional hydrodynamical code to carry out a preliminary study
illustrating the efficacy of the model. Our self-regulating scenario predicts
that there should be enhanced AGN activity of galaxies inside the cooling
regions compared to galaxies in the outer parts of the cluster. This prediction
remains to be confirmed or refuted by observations.


title:
CCD photometric search for peculiar stars in open clusters. VII.
  Berkeley 11, Berkeley 94, Haffner 15, Lynga 1, NGC 6031, NGC 6405, NGC 6834
  and Ruprecht 130

abstract:
  The detection of magnetic chemically peculiar (CP2) stars in open clusters of
the Milky Way can be used to study the influence of different galactic
environments on the (non-)presence of peculiarities, which has to be taken into
account in stellar evolution models. Furthermore it is still unknown if the CP2
phenomenon evolves, i.e. does the strength of the peculiarity feature at 5200A,
increase or decrease with age. We have observed eight young to intermediate age
open clusters in the Delta a photometric system. This intermediate band
photometric system samples the depth of the 5200A, flux depression by comparing
the flux at the center with the adjacent regions having bandwidths of 110A, to
230A. The Delta a photometric system is most suitable to detect CP2 stars with
high efficiency, but is also capable of detecting a small percentage of
non-magnetic CP objects. Also, the groups of (metal-weak) lambda Bootis, as
well as classical Be/shell stars, can be successfully investigated. This
photometric system allows one to determine the age, reddening and distance
modulus by fitting isochrones. Among the presented sample of eight galactic
clusters, we have detected twenty three CP2, eight Be/Ae and eight metal-weak
stars. Another six objects show a peculiar behaviour which is most probably due
to a non-membership,variability or duplicity. Fitting isochrones to Delta a
photometry yields estimates of the age, reddening and distance that are in
excellent agreement with published values.


title:
Magnetohydrodynamic Shocks in Non-Equatorial Plasma Flows around a Black
  Hole

abstract:
  We study magnetohydrodynamic (MHD) standing shocks in inflowing plasmas in a
black hole magnetosphere. Fast and intermediate shock formation is explored in
Schwarzschild and Kerr geometry to illustrate general relativistic effects. We
find that non-equatorial standing MHD shocks are physically possible, creating
a very hot plasma region close to the event horizon. Shocked downstream plasmas
can be heated or magnetized depending on the values of various magnetic
field-aligned parameters. Then we may expect high-energy thermal/nonthermal
emissions from the shocked region. We present the properties of non-equatorial
MHD shocks and discuss the shocked plasma region in the black hole
magnetosphere. We also investigate the effects of the poloidal magnetic field
and the black hole spin on the properties of shocks, and show that both effects
can modify the distribution of the shock front and shock strength. We find for
strong MHD shock formation that fast rotating magnetic fields are necessary.
The physics of non-equatorial MHD shocks in the black hole magnetosphere could
be very important when we are to construct the central engine model of various
astrophysical phenomena.


title:
A Spectroscopic Survey of Faint Quasars in the SDSS Deep Stripe: I.
  Preliminary Results from the Co-added Catalog

abstract:
  In this paper we present the first results of a deep spectroscopic survey of
faint quasars in the Sloan Digital Sky Survey (SDSS) Southern Survey, a deep
survey carried out by repeatedly imaging a 270 deg^2 area. Quasar candidates
were selected from the deep data with good completeness over 0<z<5, and 2 to 3
magnitudes fainter than the SDSS main survey. Spectroscopic follow-up was
carried out on the 6.5m MMT with Hectospec. The preliminary sample of this SDSS
faint quasar survey (hereafter SFQS) covers ~ 3.9 deg^2, contains 414 quasars,
and reaches g=22.5. The overall selection efficiency is ~ 66% (~ 80% at
g<21.5); the efficiency in the most difficult redshift range (2<z<3) is better
than 40%. We use the 1/V_{a} method to derive a binned estimate of the quasar
luminosity function (QLF) and model the QLF using maximum likelihood analysis.
The best model fits confirm previous results showing that the QLF has steep
slopes at the bright end and much flatter slopes (-1.25 at z<2.0 and -1.55 at
z>2.0) at the faint end, indicating a break in the QLF slope. Using a
luminosity-dependent density evolution model, we find that the quasar density
at M_{g}<-22.5 peaks at z~2, which is later in cosmic time than the peak of
z~2.5 found from surveys of more luminous objects. The SFQS QLF is consistent
with the results of the 2dF QSO Redshift Survey, the SDSS, and the 2dF-SDSS LRG
and QSO Survey, but probes fainter quasars. We plan to obtain more quasars from
future observations and establish a complete faint quasar sample with more than
1000 objects over 10 deg^2.


title:
A comprehensive Nbody study of mass segregation in star clusters: Energy
  equipartition and escape

abstract:
  We address the dynamical evolution of an isolated self--gravitating system
with two stellar mass groups. We vary the individual ratio of the heavy to
light bodies, $\mu$ from 1.25 to 50 and alter also the fraction of the total
heavy mass $\MH$ from 5% to 40% of the whole cluster mass. Clean-cut properties
of the cluster dynamics are examined, like core collapse, the evolution of the
central potential, as well as escapers. We present in this work collisional
$N$-body simulations, using the high--order integrator NBODY6++ with up to
${\cal N}_{\star}=2\cdot 10^4$ particles improving the statistical significancy
of the lower--${\cal N}_{\star}$ simulations by ensemble averages.
Equipartition slows down the gravothermal contraction of the core slightly.
Beyond a critical value of $\mu \approx 2$, no equipartition can be achieved
between the different masses; the heavy component decouples and collapses. For
the first time the critical boundary between Spitzer--stable and --unstable
systems is demonstrated in direct $N$-body models.


title:
Neutral Hydrogen Clouds near Early-Type Dwarf Galaxies of the Local
  Group

abstract:
  Parkes neutral hydrogen 21 cm line (HI) observations of the surroundings of 9
early-type Local Group dwarfs are presented. We detected numerous HI clouds in
the general direction of those dwarfs and these clouds are often offset from
the optical center of the galaxies. Although all the observed dwarfs, except
Antlia, occupy phase-space regions where the High-Velocity Cloud (HVC) density
is well above average, the measured offsets are smaller than one would expect
from a fully random cloud distribution. Possible association is detected for 11
of the 16 investigated clouds, while, for two galaxies, Sextans and Leo I, no
HI was detected. The galaxies where HI clouds were found not to coincide with
the optical, yet have a significant probability of being associated are:
Sculptor dSph, Tucanna, LGS3, Cetus, and Fornax. If the clouds are indeed
associated, these galaxies have HI masses of $M_{HI} = 2\times10^5 M_{\odot}$,
$M_{HI} = 2\times10^6 M_{\odot}$, $M_{HI} = 7\times10^5 M_{\odot}$, $M_{HI} =
7\times10^5 M_{\odot}$, and $M_{HI} = 1\times10^5 M_{\odot}$, respectively.
However, neither ram pressure nor tidal stripping can easily explain the
offsets. In some cases, large offsets are found where ram pressure should be
the least effective.


title:
Cepheid Distances to SNe Ia Host Galaxies based on a Revised Photometric
  Zero-Point of the HST-WFPC2 and New P-L Relations and Metallicity Corrections

abstract:
  With this paper we continue the preparation for a forthcoming summary report
of our experiment with the Hubble Space Telescope (HST) to determine the Hubble
constant using type Ia supernovae as standard candles. Two problems are
addressed. (1) We examine the need for, and determine the value of, the
corrections to the apparent magnitudes of our program Cepheids in the eleven
previous calibration papers due to sensitivity drifts and charge transfer
effects of the HST WFPC2 camera over the life time of the experiment from 1992
to 2001. (2) The corrected apparent magnitudes are applied to all our previous
photometric data from which revised distance moduli are calculated for the
eight program galaxies that are parents to the calibrator Ia supernovae. Two
different Cepheid P-L relations are used; one for the Galaxy and one for the
LMC. These differ both in slope and zero-point at a fixed period. The
procedures for determining the absorption and reddening corrections for each
Cepheid are discussed. Corrections for the effects of metallicity differences
between the program galaxies and the two adopted P-L relations are derived and
applied. The distance moduli derived here for the eight supernovae program
galaxies, and for 29 others, average 0.20 mag fainter (more distant) than those
derived by Gibson et al. and Freedman et al. in their 2000 and 2001 summary
papers for reasons discussed in this paper. The effect on the Hubble constant
is the subject of our forthcoming summary paper.


title:
GalaxyCount: a JAVA calculator of galaxy counts and variances in
  multiband wide-field surveys to 28 AB mag

abstract:
  We provide a consistent framework for estimating galaxy counts and variances
in wide-field images for a range of photometric bands. The variances include
both Poissonian noise and variations due to large scale structure. We
demonstrate that our statistical theory is consistent with the counts in the
deepest multiband surveys available. The statistical estimates depend on
several observational parameters (e.g. seeing, signal to noise ratio), and
include a sophisticated treatment of detection completeness. The JAVA
calculator is freely available and offers the user the option to adopt our
consistent framework or a different scheme. We also provide a summary table of
statistical measures in the different bands for a range of different fields of
view.
  Reliable estimation of the background counts has profound consequences in
many areas of observational astronomy. We provide two such examples. One is
from a recent study of the Sculptor galaxy NGC 300 where stellar photometry has
been used to demonstrate that the outer disc extends to 10 effective radii, far
beyond what was thought possible for a normal low-luminosity spiral. We confirm
this finding by a reanalysis of the background counts. Secondly, we determine
the luminosity function of the galaxy cluster Abell 2734, both through
spectroscopically determined cluster membership, and through statistical
subtraction of the background galaxies using the calculator and offset fields.
We demonstrate very good agreement, suggesting that expensive spectroscopic
follow-up, or off-source observations, may often be bypassed via determination
of the galaxy background with GalaxyCount.


title:
A method to identify the companion stars of type Ia supernovae in young
  supernova remnants

abstract:
  We propose a method to identify the companion stars of type Ia supernovae
(SNe Ia) in young supernova remnants (SNRs) by recognizing distinct features of
absorption lines due to Fe I appearing in the spectrum. If a sufficient amount
of Fe I remains in the ejecta, Fe I atoms moving toward us absorb photons by
transitions from the ground state to imprint broad absorption lines exclusively
with the blue-shifted components in the spectrum of the companion star. To
investigate the time evolution of column depth of Fe I in the ejecta, we have
performed hydrodynamical calculations for SNRs expanding into the uniform
ambient media, taking into account collisional ionizations, excitations, and
photo-ionizations of heavy elements. As a result, it is found that the
companion star in Tycho's SNR will exhibit observable features in absorption
lines due to Fe I at $\lambda\lambda = 371.9935$ nm and 385.9911 nm if a carbon
deflagration SN model is taken. However, these features may disappear by taking
another model that emits a few times more intense ionizing photons from the
shocked outer layers. To further explore the ionization states in the freely
expanding ejecta, we need a reliable model to describe the structure of the
outer layers.


title: The Alignments of Disk Galaxies with the Local Pancakes

abstract:
  We analyze the Tully catalog of nearby galaxies to investigate the local
pancaking effect on the orientation of disk galaxies. We first select only
those edge-on disk galaxies in the catalog whose axis-ratios are less than 0.1
to measure their spin axes unambiguously. A local pancake at the location of
each selected galaxy is found as a plane encompassing the two nearest neighbor
disks. Then, we examine statistically the inclinations of the galaxy spin axes
relative to the local pancake planes. It is detected that the Tully disk
galaxies tend to be inclined onto the local pancake planes, and the average
inclination angles decrease with the pancake scale. We also construct a
theoretical model for the inclination of disk galaxies relative to the local
pancakes in the frame of the linear tidal torque theory. The comparison of the
theoretical prediction with the observational result demonstrates a good
agreement. Finally, we conclude that it is a first detection of the local
pancaking effect on the orientation of disk galaxies, which is consistent with
the scenario that the gravitational tidal field promotes the formation of
pancakes on small mass scale.


title:
The buildup of stellar mass and the 3.6 micron luminosity function in
  clusters from z=1.25 to z=0.2

abstract:
  We have measured the 3.6 micron luminosity evolution of about 1000 galaxies
in 32 clusters at 0.2<z<1.25, without any a priori assumption about luminosity
evolution, i.e. in a logically rigorous way. We find that the luminosity of our
galaxies evolves as an old and passively evolving population formed at high
redshift without any need for additional redshift-dependent evolution. Models
with a prolonged stellar mass growth are rejected by the data with high
confidence. The data also reject models in which the age of the stars is the
same at all redshifts. Similarly, the characteristic stellar mass evolves, in
the last two thirds of the universe age, as expected for a stellar population
formed at high redshift. Together with the old age of stellar populations
derived from fundamental plane studies, our data seems to suggest that
early-type cluster galaxies have been completely assembled at high redshift,
and not only that their stars are old. The quality of the data allows us to
derive the LF and mass evolution homogeneously over the whole redshift range,
using a single estimator. The Schechter function describes the galaxy
luminosity function well. The characteristic luminosity at z=0.5 is is found to
be 16.30 mag, with an uncertainty of 10 per cent.


title: CMB constraints on the fine structure constant

abstract:
  We study constraints on time variation of the fine structure constant alpha
from cosmic microwave background (CMB) taking into account simultaneous change
in alpha and the electron mass m_e which might be implied in unification
theories. We obtain the constraints -0.097 < Delta alpha/alpha < 0.034 at 95%
C.L. using WMAP data only, and -0.042 < Delta alpha/alpha < 0.026 combining
with the constraint on the Hubble parameter by the HST Hubble Key Project.
These are improved by 15% compared with constraints assuming only alpha varies.
We discuss other relations between variations in alpha and m_e but we do not
find evidence for varying alpha.


title: Adapting and expanding interferometric arrays

abstract:
  We outline here a simple yet efficient method for finding optimized
configurations of the elements of radio-astronomical interferometers with fixed
pad locations. The method can be successfully applied, as we demonstrate, to
define new configurations when changes to the array take place. This may
include the addition of new pads or new antennas, or the loss of pads or
antennas. Our method is based on identifying which placement of elements
provides the most appropriate uv plane sampling for astronomical imaging.


title:
Curvaton reheating mechanism in inflation on warped
  Dvali-Gabadadze-Porrati brane

abstract:
  An impressed feature of inflation on warped Dvali-Gabadadze-Porrati (DGP)
brane is that the inflationary phase exits spontaneously for a scalar inflaton
field with exponential potential, which presents a graceful exit mechanism for
the inflation. But its reheating mechanism leaves open. We investigate the
curvaton reheating in inflation on warped DGP brane model. The reheating may
occur in effctively 5 dimensional or 4 dimensional stage. We study the
permitted parameter space of the curvaton field in detail. We demonstrate how
the inflation model of the warped DGP brane is improved by the curvaton
mechanism.


title:
Astrocladistics: a phylogenetic analysis of galaxy evolution II.
  Formation and diversification of galaxies

abstract:
  This series of papers is intended to evaluate astrocladistics in
reconstructing phylogenies of galaxies. The objective of this second paper is
to formalize the concept of galaxy formation and to identify the processes of
diversification. We show that galaxy diversity can be expected to organize
itself in a hierarchy. In order to better understand the role of mergers, we
have selected a sample of 43 galaxies from the GALICS database built from
simulations with a hybrid model for galaxy formation studies. These simulated
galaxies, described by 119 characters and considered as representing still
undefined classes, have experienced different numbers of merger events during
evolution. Our cladistic analysis yields a robust tree that proves the
existence of a hierarchy. Mergers, like interactions (not taken into account in
the GALICS simulations), are probably a strong driver for galaxy
diversification. Our result shows that mergers participate in a branching type
of evolution, but do not seem to play the role of an evolutionary clock.


title:
Astrocladistics: a phylogenetic analysis of galaxy evolution I.
  Character evolutions and galaxy histories

abstract:
  This series of papers is intended to present astrocladistics in some detail
and evaluate this methodology in reconstructing phylogenies of galaxies. Being
based on the evolution of all the characters describing galaxies, it is an
objective way of understanding galaxy diversity through evolutionary
relationships. In this first paper, we present the basic steps of a cladistic
analysis and show both theoretically and practically that it can be applied to
galaxies. For illustration, we use a sample of 50 simulated galaxies taken from
the GALICS database, which are described by 91 observables (dynamics, masses
and luminosities). These 50 simulated galaxies are indeed 10 different galaxies
taken at 5 cosmological epochs, and they are free of merger events. The
astrocladistic analysis easily reconstructs the true chronology of evolution
relationships within this sample. It also demonstrates that burst characters
are not relevant for galaxy evolution as a whole. A companion paper is devoted
to the formalization of the concepts of formation and diversification in galaxy
evolution.


title: Chemical evolution in Sersic 159-03 observed with XMM-Newton

abstract:
  Using a new long X-ray observation of the cluster of galaxies Sersic 159-03
with XMM-Newton, we derive radial temperature and abundance profiles using
single- and multi-temperature models. The fits to the EPIC and RGS spectra
prefer multi-temperature models especially in the core. The radial profiles of
oxygen and iron measured with EPIC/RGS and the line profiles in RGS suggest
that there is a dip in the O/Fe ratio in the centre of the cluster compared to
its immediate surroundings. A possible explanation for the large scale
metallicity distribution is that SNIa and SNII products are released in the ICM
through ram-pressure stripping of in-falling galaxies. This causes a peaked
metallicity distribution. In addition, SNIa in the central cD galaxy enrich
mainly the centre of the cluster with iron. This excess of SNIa products is
consistent with the low O/Fe ratio we detect in the centre of the cluster. We
fit the abundances we obtain with yields from SNIa, SNII and Population-III
stars to derive the clusters chemical evolution. We find that the measured
abundance pattern does not require a Population-III star contribution. The
relative contribution of the number of SNIa with respect to the total number of
SNe which enrich the ICM is about 25-50%. Furthermore, we discuss the possible
presence of a non-thermal component in the EPIC spectra. A potential source of
this non-thermal emission can be inverse-Compton scattering between Cosmic
Microwave Background (CMB) photons and relativistic electrons, which are
accelerated in bow shocks associated with ram-pressure stripping of in-falling
galaxies.


title: XMM-Newton observations of the Coma cluster relic 1253+275

abstract:
  Using XMM Newton data, we investigate the nature of the X-ray emission in the
radio relic 1253+275 in the Coma cluster. We determine the conditions of the
cluster gas to check current models of relic formation, and we set constraints
on the intracluster magnetic field. Both imaging and spectral analysis are
performed, and the X-ray emission is compared with the radio emission. We found
that the emission is of thermal origin and is connected to the sub-group around
NGC 4839. The best-fit gas temperature in the region of the relic and in its
vicinity is in the range 2.8 - 4.0 keV, comparable to the temperature of the
NGC 4839 sub-group. We do not detect any high temperature gas, resulting from a
possible shock in the region of the Coma relic. We therefore suggest that the
main source of energy for particles radiating in the radio relic is likely to
be turbulence. From the X-ray data, we can also set a flux upper limit of 3.2 x
10e-13 erg/cm^2 s, in the 0.3 - 10 keV energy range, to the non-thermal
emission in the relic region. This leads to a magnetic field B > 1.05 microG.


title: Nonextensive theory of dark matter and gas density profiles

abstract:
  Pronounced core-halo patterns of dark matter and gas density profiles,
observed in relaxed galaxies and clusters, were hitherto fitted by empirical
power-laws. On the other hand, similar features are well known from
astrophysical plasma environments, subject to long-range interactions, modeled
in the context of nonextensive entropy generalization. We link nonextensive
statistics to the problem of density distributions in large-scale structures
and provide fundamentally derived density profiles, representing accurately the
characteristics of both, dark matter and hot plasma distributions, as observed
or generated in simulations. The bifurcation of the density distribution into a
kinetic dark matter and thermodynamic gas branch turns out as natural
consequence of the theory and is controlled by a single parameter kappa,
measuring physically the degree of coupling within the system. Consequently, it
is proposed to favor nonextensive distributions, derived from the fundamental
physical context of entropy generalization and accounting for nonlocality and
long-range interactions in gravitationally coupled systems, when modeling
observed density profiles of astrophysical structures.


title: Searching for X-ray luminous 'normal' galaxies in 2dfGRS

abstract:
  We cross-correlated the Chandra XASSIST and XMM-Newton Serendipitous Source
Catalogues with the 2 degree Field Galaxy Redshift Survey (2dfGRS) database.
Our aim was to identify the most X-ray luminous (L_X > 10^42 erg s^-1) examples
of galaxies in the local Universe whose X-ray emission is dominated by stellar
processes rather than AGN activity ('normal' galaxies) as well as to test the
empirical criterion log(f_X/f_O) < -2 for separating AGN from NGs. With
XMM-Newton (Chandra) we covered an area of ~8.2 (~5.8)deg^2 down to a flux
limit of ~10^-15 (~1.6 x 10^-15) erg cm^-2 s^-1 and found 18 (20) 2dfGRS
galaxies. Using emission-line intensity ratios, we classified 6 2dfGRS spectra
as star-forming, H II nuclei, and 2 spectra as possible H II nuclei. The rest
of the objects are absorption-line galaxies and AGN, including 3 possible
LINERs. No luminous 'normal' galaxies have been found but out of 19 'normal'
galaxies in this sample 5 H II and 3 absorption-line galaxies have log(f_X/f_O)
> -2. We performed a similar search in two nearby-galaxy samples from the
literature. All 44 galaxies in the Zezas (2001) sample have log(f_X/f_O) < -2
and L_X < 10^42 erg s^-1. In the Fabbiano et al. (1992) sample, out of a total
of 170 'normal' galaxies, we found 16 galaxies with log(f_X/f_O) >-2, the
majority of which are massive ellipticals. Three of these have L_X > 10^42 erg
s^-1 .


title: H_2D^+: a light on baryonic dark matter?

abstract:
  It has been suggested that the dark halos of galaxies are constituted by
cloudlets of cold (< 10 K) H_2 and dense (> 10^7$ cm^{-3}) molecular gas. Such
gas is extremely difficult to detect, because the classical tracers of
molecular gas, CO and/or dust grains, have very low abundances and their
emission is exceedingly weak. For this reason, the cloudlet hypothesis remains
so far substantially unproven. In this Letter we propose a new method to probe
the presence of cold H_2 clouds in galactic halos: the ground transition of
ortho-H_2D^+ at 372 GHz. We discuss why the H_2D^+ is abundant under the
physical conditions appropriate for the cloudlets, and present a chemical model
that predicts the H_2D^+ abundance as function of four key parameters: gas
density and metallicity, cosmic ray ionization rate and dust grain size. We
conclude that current ground-based instruments might detect the ortho-H_2D^+
line emitted by the cloudlets halo, and prove, therefore, the existence of
large quantities of dark baryonic matter around galaxies.


title:
The scaling relation of early-type galaxies in clusters. II:
  Spectroscopic data for galaxies in eight nearby clusters

abstract:
  AIMS: We present in this work low and intermediate resolution spectroscopic
data collected for 152 early type galaxies in 8 nearby clusters with z $\leq$
0.10.
  METHODS: We use low resolution data to produce the redshift and the
K-correction for every individual galaxy, as well as to give their overall
spectral energy distribution, and some spectral indicators, including the
4000\AA break, the Mg$_2$ strength, and the NaD equivalent width.We have also
obtained higher resolution data for early type galaxies in three of the
clusters, to determine their central velocity dispersion.
  RESULTS: The effect of the resolution on the measured parameters is
discussed.
  CONCLUSIONS: New accurate systemic redshift and velocity dispersion is
presented for four of the surveyed clusters, A98, A3125, A3330, and DC2103-39.
We have found that the K-correction values for E/S0 bright galaxies in a given
nearby clusters are very similar. We also find that the distribution of the
line indicators significantly differ from cluster to cluster.


title: Systematic effects induced by a flat isotropic dielectric slab

abstract:
  The instrumental polarization induced by a flat isotropic dielectric slab in
microwave frequencies is faced. We find that, in spite of its isotropic nature,
such a dielectric can produce spurious polarization either by transmitting
incoming anisotropic diffuse radiation or emitting when it is thermally
inhomogeneous. We present evaluations of instrumental polarization generated by
materials usually adopted in Radioastronomy, by using the Mueller matrix
formalism. As an application, results for different slabs in front of a 32 GHz
receiver are discussed. Such results are based on measurements of their complex
dielectric constant. We evaluate that a 0.33 cm thick Teflon slab introduces
negligible spurious polarization ($< 2.6 \times 10^{-5}$ in transmission and $<
6 \times 10^{-7}$ in emission), even minimizing the leakage ($< 10^{-8}$ from
$Q$ to $U$ Stokes parameters, and viceversa) and the depolarization ($\sim 1.3
\times 10^{-3}$).


title: High Resolution Spectra of Novae and the Quadratic Zeeman Effect

abstract:
  High resolution spectra of novae after outburst reveal distinctive
characteristics in the line profiles and intensities. The higher Balmer lines
are often broader than the lower members of the series, and the relative
profiles and intensities of the [O I] \lambda\lambda6300, 6364 doublet differ
from normal values. We suggest these features may be caused by the Quadratic
Zeeman Effect from magnetic fields exceeding B=10^6 gauss. Taken together the
emission and absorption lines point to multiple origins for the ejecta on both
the erupting white dwarf and the cool secondary star.


title: Quintom cosmologies admitting either tracking or phantom attractors

abstract:
  In this paper we investigate the evolution of a class of cosmologies fuelled
by quintom dark energy and dark matter. Quintom dark energy is a hybrid of
quintessence and phantom which involves the participation of two reals scalar
fields playing the roles of those two types of dark energy. In that framework
we examine from a dynamical systems perspective the possibility that those
fields are coupled among them by considering an exponential potential with an
interesting functional dependence similar but not identical to others studied
before. The model we consider represents a counterexample to the typical
behavior of quintom models with exponential potentials because it admits either
tracking attractors ($w=0$), or phantom attractors ($w<-1$).


title: How extreme are the Wolf-Rayet clusters in NGC3125?

abstract:
  We reinvestigate the massive stellar content of NGC3125 (Tol3) using
VLT/FORS1 imaging & spectroscopy, plus archival VLT/ISAAC, HST/FOC and HST/STIS
datasets. Narrow-band imaging confirms that A and B knots represent the primary
sites of Wolf-Rayet (WR) stars, whilst HST imaging reveals that both regions
host multiple clusters. Clusters A1 + A2 within region A host WR stars. altough
is not clear which cluster within region B hosts WR stars. Nebular properties
infer an LMC-like metallicity. LMC template WN5-6 & WC4 spectra are matched to
the observed optical WR bumps of A1 and B, permitting the contribution of WC
stars to the blue bump to be quantified. We obtain N(WN5-6:WC4)=105:20, 55:0,
40:20 for clusters A1, A2 and B1+B2, a factor of 3 lower than optical studies,
as a result of a lower E(B-V). Using Starburst99 models to estimate O star
populations for individual clusters, we find N(WR)/N(O)=0.2 for A1 and 0.1 for
A2 and B1+B2. From Halpha imaging, the O star content of the Giant HII regions
A and B is found to be a factor of 5-10 times higher than that derived
spectroscopically for the UV/optically bright clusters, suggesting that NGC3125
hosts optically obscured young massive clusters, further supported by VLT/ISAAC
K band imaging. Archival HST/STIS UV spectroscopy confirms the low E(B-V)
towards A1, for which we have determined an SMC extinction law, in preference
to an LMC or starburst law. We obtain N(WN5-6)=110 from the slit-loss corrected
HeII 1640 line flux, in excellent agreement with optical result. However, this
is a factor of 35 times lower than that inferred from the same dataset by
Chandar et al. due to their use of a starburst extinction law. Highly
discrepant stellar populations may result in spatially resolved star forming
regions from UV and optical studies through use of different extinction laws.


title:
Extrasolar planets and brown dwarfs around A-F type stars. IV. A
  candidate brown dwarf around the A9V pulsating star HD180777

abstract:
  We present here the detection of a brown dwarf orbiting the A9V star
HD180777. The radial velocity measurements, obtained with the ELODIE echelle
spectrograph at the Haute-Provence Observatory, show a main variation with a
period of 28.4 days. Assuming a primary mass of 1.7 Mo, the best Keplerian fit
to the data leads to a minimum mass of 25 MJup for the companion (the true mass
could be significantly higher). We also show that, after substraction of the
Keplerian solution from the radial velocity measurements, the residual radial
velocities are related to phenomena intrinsic to the star, namely pulsations
with typical periods of Gamma Dor stars. These results show that in some cases,
it is possible to disentangle radial velocity variations due to a low mass
companion from variations intrinsic to the observed star.


title: Helium preenrichment in the star-forming regions

abstract:
  We show that element diffusion can produce large fluctuations in the initial
helium abundance of the star-forming clouds. Diffusion time-scale, which in
stars is much larger than the Hubble time, can fall below 10^8 years in the
neutral gas clouds dominated by collisionless dark matter or with dynamically
important radiation or magnetic pressure. Helium diffusion may therefore
explain the recent observations of globular clusters, which are inconsistent
with initially homogeneous helium distribution.


title: Prospects for direct detection of primordial gravitational waves

abstract:
  We study the primordial gravitational wave background produced in models of
single field inflation. Using the inflationary flow approach, we investigate
the amplitude of gravitational wave spectrum in the frequency range 1 mHz - 1
Hz pertinent to future space-based laser interferometers. For models that
satisfy the current observational constraint on the tensor-to-scalar ratio,
r<0.36, we derive a strict upper bound of omega_{gw}<1.6 x 10^{-15},
independent of the form of the inflationary potential. Applying, in addition,
the observational constraints on the spectral index and its running, omega_{gw}
is expected to be considerably lower than this bound unless the shape of the
potential is finely tuned. We contrast our numerical results with those based
on simple power-law extrapolation of the tensor power spectrum from CMB scales.
In addition to single field inflation, we summarise a number of other possible
cosmological sources of primordial gravitational waves and assess what might be
learnt from direct detection experiments such as LISA, Big Bang Observer and
beyond.


title: Where are the ``Missing'' Galactic Baryons?

abstract:
  Based on 19 high-resolution N-body/gas-dynamical galaxy formation simulations
in the LCDM cosmology it is shown, that for a galaxy like the Milky Way, in
addition to the baryonic mass of the galaxy itself, about 70% extra baryonic
mass should reside around the galaxy (inside of the virial radius), chiefly in
the form of hot gas. Averaging over the entire field galaxy population, this
``external'' component amounts to 64-85% of the baryonic mass of the population
itself. These results are supported by the recent detection of very extended,
soft X-ray emission from the halo of the quiescent, massive disk galaxy NGC
5746.
  Some of the hot gas may, by thermal instability, have condensed into mainly
pressure supported, warm clouds, similar to the Galactic High Velocity Clouds
(HVCs). Based on an ultra-high resolution cosmological test simulation of a
Milky Way like galaxy (with a gas particle mass and gravity softening length of
only 7600 h^-1 Msun and 83 h^-1 pc,respectively), it is argued, that the hot
gas phase dominates over the warm gas phase, in the halo. Finally, an origin of
HVCs as ``leftovers'' from filamentary, ``cold'' accretion events, mainly
occurring early in the history of galaxies, is proposed.


title:
Star Formation and Extinction in Redshift z~2 Galaxies: Inferences from
  Spitzer MIPS Observations

abstract:
  Using very deep Spitzer/MIPS 24 micron observations, we present an analysis
of the bolometric luminosities (L[bol]) and UV extinction properties of more
than 200 spectroscopically identified, optically selected (UGR) z~2 galaxies in
the GOODS-N field. The large spectroscopic sample is supplemented with near-IR
selected (BzK/DRG) galaxies and submm sources at similar redshifts in the same
field, providing a representative collection of relatively massive (M*>1e10
Msun) galaxies at high redshifts. We focus on the redshift range 1.5-2.6, where
MIPS is sensitive to the strength of the mid-IR PAH features in the galaxy
spectra (rest-frame 5-8.5 micron). We demonstrate, using stacked X-ray data and
a subset of galaxies with H-alpha measurements, that L(5-8.5) provides a
reliable estimate of L(IR) for most star forming galaxies at z~2. The range of
L(IR) in the samples considered extends from ~1e10 to >1e12 Lsun, with a mean
of 2e11 Lsun. Using 24 micron observations to infer dust extinction in high
redshift galaxies, we find that, as in the local universe, the obscuration
(L[IR]/L[1600]) is strongly dependent on L(bol), and ranges in value from <1 to
\~1000. However, the obscuration is ~10 times smaller at a given L(bol) at z~2
than at z=0. We show that the values of L(IR) and obscuration inferred from the
UV spectral slope beta generally agree well with the values inferred from
L(5-8.5) for L(bol)<1e12 Lsun. For galaxies with L(bol)>1e12 Lsun, it is common
for UV-based estimates to underpredict L(IR) by a factor of ~10-100. Using the
specific SFR as a proxy for cold gas fraction, we find a wide range in the
evolutionary state of galaxies at z~2, from those which have just begun to form
stars to those which have already accumulated most of their stellar mass and
are about to become, or already are, passively-evolving. [Abridged]


title: Primordial Stellar Feedback and the Origin of Hyper Metal-Poor Stars

abstract:
  The apparent absence of stars in the Milky Way halo with -5 ~< [Fe/H] ~< -4
suggests that the gas out of which the halo stars were born experienced a
period of low or delayed star formation after the local universe was lit up by
the first, metal-free generation of stars (Pop III). Negative feedback owed to
the Pop III stars could initially have prevented the pre-Galactic halo from
cooling, which thereby delayed the collapse and inhibited further star
formation. During this period, however, the nucleosynthesis products of the
first supernovae (SNe) had time to mix with the halo gas. As a result, the
initially primordial gas was already weakly enriched in heavy elements, in
particular iron, at the time of formation of the Galactic halo. The very high,
observed C/Fe ratios in the two recently discovered hyper metal-poor stars
([Fe/H]<-5) HE 0107-5240 and HE 1327-2326 as well as the diversity of C/Fe
ratios in the population of extremely metal-poor stars ([Fe/H]<-3) are then
naturally explained by a combination of pre-enrichment by Pop III stars and
local enrichment by subsequent generations of massive, rotating stars, for
which the most massive ones end their lives as black hole-forming SNe, only
ejecting their outer (carbon-rich) layers. The possible existence of
populations of mega metal-poor/iron-free stars ([Fe/H]<-6) is also discussed.


title: A Cosmological Test of Standard Gravity by Weak Lensing

abstract:
  The large scale structure formation in the standard Einstein gravity at later
time is uniquely determined by the expansion history H(z) measured by the
geometrical factor. A possible departure from the expected standard structure
formation is detectable by growth structure test. We design new deviation
parameters to test standard gravity at large scales and estimate the expected
errors by weak lensing experiment. The effective Newtonian constant G_N at the
present time can be constrained around 10% accuracy by measuring the difference
curvature perturbations (\Phi-\Psi)/2 within 2% accuracy.


title:
Wind signatures in the X-ray emission line profiles of the late O
  supergiant $\zeta$ Orionis

abstract:
  X-ray line profile analysis has proved to be the most direct diagnostic of
the kinematics and spatial distribution of the very hot plasma around O stars.
In this paper we apply several analysis techniques to the emission lines in the
Chandra HETGS spectrum of the late-O supergiant zeta Ori (O9.7 Ib), including
the fitting of a simple line-profile model. We show that there is distinct
evidence for blue shifts and profile asymmetry, as well as broadening in the
X-ray emission lines of zeta Ori. These are the observational hallmarks of a
wind-shock X-ray source, and the results for zeta Ori are very similar to those
for the earlier O star, zeta Pup, which we have previously shown to be well-fit
by the same wind-shock line-profile model. The more subtle effects on the
line-profile morphologies in zeta Ori, as compared to zeta Pup, are consistent
with the somewhat lower density wind in this later O supergiant. In both stars,
the wind optical depths required to explain the mildly asymmetric X-ray line
profiles imply reductions in the effective opacity of nearly an order of
magnitude, which may be explained by some combination of mass-loss rate
reduction and large-scale clumping, with its associated porosity-based effects
on radiation transfer. In the context of the recent reanalysis of the
helium-like line intensity ratios in both zeta Ori and zeta Pup, and also in
light of recent work questioning the published mass-loss rates in OB stars,
these new results indicate that the X-ray emission from zeta Ori can be
understood within the framework of the standard wind-shock scenario for hot
stars.


title: Giant Molecular Clouds in Local Group Galaxies

abstract:
  We present the first comparative study of extragalactic GMCs using complete
data sets for entire galaxies and a uniform set of reduction and analysis
techniques. We present results based on CO observations for the LMC, SMC, M33,
M31, IC10 and the nucleus of M64, and make comparisons with archival Milky Way
observations. Our sample includes large spirals and dwarf irregulars with
metallicities that vary by an order of magnitude. GMCs in HI rich galaxies are
seen to be well-correlated with HI filaments that pervade the galactic disks,
suggesting that they form from pre-existing HI structures. Virial estimates of
the ratio of CO line strength to H2 column density, XCO, suggests that a value
of 4 x 10^20 cm^-2 (K km/s)^-1 is a good value to use in most galaxies (except
the SMC) if the GMCs are virialized. However, if the clouds are only marginally
self-gravitating, as appears to be the case judging from their appearance, half
the virial value may be more appropriate. There is no clear trend of XCO with
metallicity. The clouds within a galaxy are shown to have the about the same H2
surface density and differences between galaxies seem to be no more than a
factor of ~2. We show that hydrostatic pressure appears to be the main factor
in determining what fraction of atomic gas is turned into molecules. In the
high-pressure regions often found in galactic centers, the observed properties
of GMCs appear to be different from those in the found in the Local Group. From
the association of tracers of star formation with GMCs in the LMC, we find that
about 1/4 of the GMCs exhibit no evidence of star formation and we estimate
that the lifetime of a typical GMC in these galaxies is 20--30 Myr.


title: Extragalactic Globular Clusters and Galaxy Formation

abstract:
  Globular cluster (GC) systems have now been studied in galaxies ranging from
dwarfs to giants and spanning the full Hubble sequence of morphological types.
Imaging and spectroscopy with the Hubble Space Telescope and large ground-based
telescopes have together established that most galaxies have bimodal color
distributions that reflect two subpopulations of old GCs: metal-poor and
metal-rich. The characteristics of both subpopulations are correlated with
those of their parent galaxies. We argue that metal-poor GCs formed in low-mass
dark matter halos in the early universe and that their properties reflect
biased galaxy assembly. The metal-rich GCs were born in the subsequent
dissipational buildup of their parent galaxies and their ages and abundances
indicate that most massive early-type galaxies formed the bulk of their stars
at early times. Detailed studies of both subpopulations offer some of the
strongest constraints on hierarchical galaxy formation that can be obtained in
the near-field.


title:
Detection of a 45 Degree Tidal Stream Associated with the Globular
  Cluster NGC 5466

abstract:
  We report on the detection in Sloan Digital Sky Survey data of a 45 degree
tidal stream of stars, extending from Bootes to Ursa Major, which we associate
with the halo globular cluster NGC 5466. Using an optimal contrast, matched
filter technique, we find a long, almost linear stellar stream with an average
width of 1.4 degrees. The stream is an order of magnitude more tenuous than the
stream associated with Palomar 5. The stream's orientation on the sky is
consistent to a greater or lesser extent with existing proper motion
measurements for the cluster.


title: X-ray Properties of Young Stars and Stellar Clusters

abstract:
  Although the environments of star and planet formation are thermodynamically
cold, substantial X-ray emission from 10-100 MK plasmas is present. In low mass
pre-main sequence stars, X-rays are produced by violent magnetic reconnection
flares. In high mass O stars, they are produced by wind shocks on both stellar
and parsec scales. The recent Chandra Orion Ultradeep Project, XMM-Newton
Extended Survey of Taurus, and Chandra studies of more distant high-mass star
forming regions reveal a wealth of X-ray phenomenology and astrophysics. X-ray
flares mostly resemble solar-like magnetic activity from multipolar surface
fields, although extreme flares may arise in field lines extending to the
protoplanetary disk. Accretion plays a secondary role. Fluorescent iron line
emission and absorption in inclined disks demonstrate that X-rays can
efficiently illuminate disk material. The consequent ionization of disk gas and
irradiation of disk solids addresses a variety of important astrophysical
issues of disk dynamics, planet formation, and meteoritics. New observations of
massive star forming environments such as M 17, the Carina Nebula and 30
Doradus show remarkably complex X-ray morphologies including the low-mass
stellar population, diffuse X-ray flows from blister HII regions, and
inhomogeneous superbubbles. X-ray astronomy is thus providing qualitatively new
insights into star and planet formation.


title:
A kinematically selected, metal-poor stellar halo in the outskirts of
  M31

abstract:
  We present evidence for a metal-poor, [Fe/H]$\sim-1.4$ $\sigma$=0.2 dex,
stellar halo component detectable at radii from 10 kpc to 70 kpc, in our
nearest giant spiral neighbor, the Andromeda galaxy. This metal-poor sample
underlies the recently-discovered extended rotating component, and has no
detected metallicity gradient. This discovery uses a large sample of 9861
radial velocities of Red Giant Branch (RGB) stars obtained with the Keck-II
telescope and DEIMOS spectrograph, with 827 stars with robust radial velocity
measurements isolated kinematically to lie in the halo component primarily by
windowing out the extended rotating component which dominates the photometric
profile of Andromeda out to $<$50 kpc (de-projected). The stars lie in 54
spectroscopic fields spread over an 8 square degree region, and are expected to
fairly sample the halo to a radius of $\sim$70 kpc. The halo sample shows no
significant evidence for rotation. Fitting a simple model in which the velocity
dispersion of the component decreases with radius, we find a central velocity
dispersion of $152\kms$ decreasing by $-0.90\kms/\kpc$. By fitting a
cosmologically-motivated NFW halo model to the halo stars we constrain the
virial mass of M31 to be greater than $9.0 \times 10^{11} \msun$ with 99%
confidence. The properties of this halo component are very similar to that
found in our Milky Way, revealing that these roughly equal mass galaxies may
have led similar accretion and evolutionary paths in the early Universe.


title:
Can the unresolved X-ray background be explained by emission from the
  optically-detected faint galaxies of the GOODS project?

abstract:
  The emission from individual X-ray sources in the Chandra Deep Fields and
XMM-Newton Lockman Hole shows that almost half of the hard X-ray background
above 6 keV is unresolved and implies the existence of a missing population of
heavily obscured active galactic nuclei (AGN). We have stacked the 0.5-8 keV
X-ray emission from optical sources in the Great Observatories Origins Deep
Survey (GOODS; which covers the Chandra Deep Fields) to determine whether these
galaxies, which are individually undetected in X-rays, are hosting the
hypothesised missing AGN. In the 0.5-6 keV energy range the stacked-source
emission corresponds to the remaining 10-20 per cent of the total background --
the fraction that has not been resolved by Chandra. The spectrum of the stacked
emission is consistent with starburst activity or weak AGN emission. In the 6-8
keV band, we find that upper limits to the stacked X-ray intensity from the
GOODS galaxies are consistent with the ~40 per cent of the total background
that remains unresolved, but further selection refinement is required to
identify the X-ray sources and confirm their contribution.


title:
Stellar abundances and molecular hydrogen in high-redshift galaxies -the
  far-ultraviolet view

abstract:
  FUSE spectra of star-forming regions in nearby galaxies are compared to
composite spectra of Lyman-break galaxies (LBGs), binned by strength of Lyman
alpha emission and by mid-UV luminosity. Several far-UV spectral features,
including lines dominated by stellar wind and by photospheric components, are
very sensitive to stellar abundances. Their measurement in Lyman-break galaxies
is compromised by the strong interstellar absorption features, allowing in some
cases only upper limits. The derived C and N abundances in the LBGs are no
higher than half solar (scaled to oxygen abundance for comparison with
emission-line analyses), independent of the strength of Lyman alpha emission. P
V absorption indicates abundances as low as 0.1 solar, with an upper limit near
0.4 solar in the reddest and weakest-emission galaxies. Unresolved interstellar
absorption components would further lower the derived abundances. Trends of
line strength, and derived abundances, are stronger with mid-UV luminosity than
with Lyman-alpha strength. H2 absorption in the Lyman and Werner bands is very
weak in the LBGs. Template H2 absorption spectra convolved to appropriate
resolution show that strict upper limits N(H2)< 10^18 cm^-2 apply in all cases,
with more stringent values appropriate for the stronger-emission composites and
for mixes of H2 level populations like those on Milky Way sight lines. Since
the UV-bright regions are likely to be widespread in these galaxies, these
results rule out massive diffuse reservoirs of H2, and suggest that the
dust/gas ratio is already fairly large at z~3.


title:
Spectrum of Cosmic Microwave Fluctuations and the Formation of Galaxies
  in a Modified Gravity Theory

abstract:
  A modified gravity (MOG) possesses a light, neutral vector particle called a
``phion'' associated with a vector field $\phi^\mu$, which forms a cold fluid
of Bose-Einstein condensates before recombination with zero pressure and zero
shear viscosity. The energy density associated with this Bose-Einstein
condensate fluid dominates the energy density before recombination and produces
a density parameter, $\Omega_\phi\sim 0.3$, that together with the fractional
baryon density $\Omega_b\sim 0.04$, and a cosmological constant parameter
$\Omega_\Lambda\sim 0.7$ yields an approximate fit to the data for the
acoustical oscillations in the CMB power spectrum. The quantum phion condensate
fluid is abundant well before recombination and can clump and form the
primordial structure for galaxies. At late times in the expanding universe, in
local bound systems such as galaxies ordinary baryonic matter dominates the
matter density. For galactic systems in the present epoch, the modified
Newtonian acceleration law determined by MOG describes well galaxy rotation
curve data and X-ray cluster mass profile data.


title:
A "super" star cluster grown old: the most massive star cluster in the
  Local Group

abstract:
  We independently redetermine the reddening and age of the globular cluster
037-B327 in M31 by comparing independently obtained multicolour photometry with
theoretical stellar population synthesis models. 037-B327 has long been known
to have a very large reddening value, which we confirm to be
E(B-V)=1.360+-0.013, in good agreement with the previous results. We
redetermine its most likely age at 12.4+- 3.2 Gyr.
  037-B327 is a prime example of an unusually bright early counterpart to the
ubiquitous ``super'' star clusters presently observed in most high-intensity
star-forming regions in the local Universe. In order to have survived for a
Hubble time, we conclude that its stellar IMF cannot have been top-heavy. Using
this constraint, and a variety of SSP models, we determine a photometric mass
of M_{GC}=(3.0+-0.5)*10^7, somewhat depending on the SSP models used, the
metallicity and age adopted and the IMF representation. This mass, and its
relatively small uncertainties, make this object the most massive star cluster
of any age in the Local Group. Assuming that the photometric mass estimate thus
derived is fairly close to its dynamical mass, we predict that this GC has a
(one-dimensional) velocity dispersion of order (72+-13)km/s. As a surviving
"super" star cluster, this object is of prime importance for theories aimed at
describing massive star cluster evolution.


title:
Pulsar Wind Nebulae and the Non-thermal X-Ray Emission of Millisecond
  Pulsars

abstract:
  The non-thermal, non-pulsed X-ray emission of MSPs is investigated. As in
young pulsars, MSPs emit a relativistic wind, which interacting with the
interstellar medium and/or a binary companion can significantly contribute to
the non-pulsed emission of these pulsars. An application and extension of a
simple model developed for young pulsars is applied to the old recycled MSP
B1957+20. It is found that the pulsar wind can, indeed, contribute to both the
resolved and unresolved X-ray emission. For other MSP in the Galactic field
where the spectral index of the non-pulsed component has been measured (i.e.,
PSR B1937+21, J0218+4232) the contribution of the pulsar wind to the non-pulsed
X-ray luminosity is estimated. For the MSPs in the core regions of globular
clusters, the pulsar wind nebula is likely affected by its interaction with the
dense stellar environment, possibly leading to a diminished contribution to the
total X-ray emission. In this case, the existence of non-thermal non-pulsed
X-ray emission is more likely for binary rather than isolated MSPs with the
emission arising from the interaction of the relativistic pulsar wind with a
binary companion. Our study suggests that the magnetization parameter in the
pulsar wind nebulae of MSPs is significantly larger than that of the Crab
nebula by about a factor of 10. The emission from MSPs moving at high
velocities may appear spatially extended with a tail-like morphology, which may
contribute to the faint filamentary X-ray source subpopulation in the Galaxy.


title:
Luminous Compact Blue Galaxies up to z~1 in the HST Ultra Deep Field: I.
  Small galaxies, or blue centers of massive disks?

abstract:
  We analyze 26 Luminous Compact Blue Galaxies (LCBGs) in the HST/ACS Ultra
Deep Field (UDF) at z ~ 0.2-1.3, to determine whether these are truly small
galaxies, or rather bright central starbursts within existing or forming large
disk galaxies. Surface brightness profiles from UDF images reach fainter than
rest-frame 26.5 B mag/arcsec^2 even for compact objects at z~1. Most LCBGs show
a smaller, brighter component that is likely star-forming, and an extended,
roughly exponential component with colors suggesting stellar ages >~ 100 Myr to
few Gyr. Scale lengths of the extended components are mostly >~ 2 kpc, >1.5-2
times smaller than those of nearby large disk galaxies like the Milky Way.
Larger, very low surface brightness disks can be excluded down to faint
rest-frame surface brightnesses (>~ 26 B mag/arcsec^2). However, 1 or 2 of the
LCBGs are large, disk-like galaxies that meet LCBG selection criteria due to a
bright central nucleus, possibly a forming bulge. These results indicate that
>~ 90% of high-z LCBGs are small galaxies that will evolve into small disk
galaxies, and low mass spheroidal or irregular galaxies in the local Universe,
assuming passive evolution and no significant disk growth. The data do not
reveal signs of disk formation around small, HII-galaxy-like LCBGs, and do not
suggest a simple inside-out growth scenario for larger LCBGs with a disk-like
morphology. Irregular blue emission in distant LCBGs is relatively extended,
suggesting that nebular emission lines from star-forming regions sample a major
fraction of an LCBG's velocity field.


title: Energetics and dynamics of an impulsive flare on March 10, 2001

abstract:
  We present the H$\alpha$ observations from ARIES, Nainital of a compact and
impulsive solar flare occurred on March 10, 2001 and associated with a CME. We
have also analysed HXT, SXT/Yohkoh observations as well as radio observations
from Nobeyama Radio Observatory to derive the energetics and dynamics of this
impulsive flare. We co-align the H$\alpha$, SXR, HXR, MW and magnetogram images
within the instrumental spatial resolution limit. We detect a single HXR source
in this flare, which is found spatially associated with one of the H$\alpha$
bright kernel. The unusual feature of HXR and H$\alpha$ sources, observed for
the first time, is the rotation during the impulsive phase in clockwise
direction. We propose that the rotation may be due to asymmetric progress of
the magnetic reconnection site or may be due to the change of peak point of the
electric field. In MW emission we found two sources, one is main source which
is at the main flare site and another is remote source located in South-West
direction. It appears that the remote source is formed by the impact of
accelerated energetic electrons from the main flare site. From the spatial
co-relation of multi-wavelength images of th


title: Further constraints on electron acceleration in solar noise storms

abstract:
  We reexamine the energetics of nonthermal electron acceleration in solar
noise storms. A new result is obtained for the minimum nonthermal electron
number density required to produce a Langmuir wave population of sufficient
intensity to power the noise storm emission. We combine this constraint with
the stochastic electron acceleration formalism developed by Subramanian &
Becker (2005) to derive a rigorous estimate for the efficiency of the overall
noise storm emission process, beginning with nonthermal electron acceleration
and culminating in the observed radiation. We also calculate separate
efficiencies for the electron acceleration -- Langmuir wave generation stage
and the Langmuir wave -- noise storm production stage. In addition, we obtain a
new theoretical estimate for the energy density of the Langmuir waves in noise
storm continuum sources.


title:
The Absence of Adiabatic Contraction of the Radial Dark Matter Profile
  in the Galaxy Cluster A2589

abstract:
  We present an X-ray analysis of the radial mass profile of the radio-quiet
galaxy cluster A2589 between 0.015-0.25 r_vir using an XMM-Newton observation.
Except for a ~16 kpc shift of the X-ray center of the R=45-60 kpc annulus,
A2589 possesses a remarkably symmetrical X-ray image and is therefore an
exceptional candidate for precision studies of its mass profile by applying
hydrostatic equilibrium. The total gravitating matter profile is well described
by the NFW model (fractional residuals <~10%) with c_vir=6.1 +/- 0.3 and M_vir
= 3.3 +/- 0.3 x 10^{14} M_sun (r_vir = 1.74 +/- 0.05 Mpc) in excellent
agreement with LCDM. When the mass of the hot ICM is subtracted from the
gravitating matter profile, the NFW model fitted to the resulting dark matter
(DM) profile produces essentially the same result. However, if a component
accounting for the stellar mass (M_*) of the cD galaxy is included, then the
NFW fit to the DM profile is substantially degraded in the central r ~50 kpc
for reasonable M_*/L_V. Modifying the NFW DM halo by adiabatic contraction
arising from the early condensation of stellar baryons in the cD galaxy further
degrades the fit. The fit is improved substantially with a Sersic-like model
recently suggested by high resolution N-body simulations but with an inverse
Sersic index, alpha ~0.5, a factor of ~3 higher than predicted. We argue that
neither random turbulent motions nor magnetic fields can provide sufficient
non-thermal pressure support to reconcile the XMM mass profile with adiabatic
contraction of a CDM halo assuming reasonable M_*/L_V. Our results support the
scenario where, at least for galaxy clusters, processes during halo formation
counteract adiabatic contraction so that the total gravitating mass in the core
approximately follows the NFW profile.


title: Ly Alpha Emitters at z=5.7 in the Subaru Deep Field

abstract:
  We present the properties of Ly Alpha emitters (LAEs) at z = 5.7 in the
Subaru Deep Field. A photometric sample of 89 LAE candidates is constructed
from narrow-band (NB816) data down to NB816 = 26.0 (AB) in a continuous 725
arcmin^2 area. Spectra of 39 objects satisfying the photometric selection
criteria for LAEs were obtained with Subaru and Keck II Telescopes, among which
28 were confirmed LAEs, one was a nearby galaxy, and eight were unclassified.
We also obtained spectra of another 24 NB816-excess objects in the field,
identifying six additional LAEs. We find that the Ly Alpha luminosity function
derived from the photometric sample is reproduced well by a Schechter function
with L* = (7.9+3.0-2.2) x 10^42 erg/s and phi* = (6.3+3.0-2.0) x 10^-4 Mpc^-3
for alpha = -1.5 (fixed) over the whole luminosity range of L ~= 3x10^42 -
3x10^43 erg/s. We then measure rest-frame Ly Alpha equivalent widths (EWs) for
the confirmed LAEs, to find that the median among the 28 objects satisfying the
photometric selection criteria is W_0^i = 233 A. We infer that 30% - 40% of
LAEs at z=5.7 exceed W_0^i = 240 A. These large-EW objects probably cannot be
accounted for by ordinary star-forming populations with a Salpeter IMF. We also
find that LAEs with fainter far-UV luminosities have larger EWs. Finally, we
derive the far-UV luminosity function of LAEs down to M_UV ~= -19.6 using the
photometric sample, and compare it with that of Lyman-break galaxies (LBGs). We
find that as high as about 80% of LBGs at z ~ 6 have W_0^i >= 100 A, in sharp
contrast to lower-z counterparts.


title:
Star formation in molecular cores III. The effect of the turbulent power
  spectrum

abstract:
  We investigate the effect of the turbulent power spectrum (P(k) \propto
k^{-n}, with n=3, 4 or 5) on the fragmentation of low-mass cores, by means of
SPH simulations. We adopt initial density profiles and low levels of turbulence
based on observation, and for each n-value we conduct an ensemble of
simulations with different initial seeds for the turbulent velocity field, so
as to obtain reasonable statistics. We find that when power is concentrated at
larger scales (i.e. for larger n), more protostellar objects form and there is
a higher proportion of low-mass stars and brown dwarfs. This is in direct
contrast with the recent results of Delgado Donate et al., presumably because
they adopted much higher levels of turbulence.


title:
The morphology of cosmological reionization by means of Minkowski
  Functionals

abstract:
  The morphology of the total gas and the neutral hydrogen (H I) distributions
during the cosmological epoch of reionization can be quantified with Minkowski
Functionals (MFs) of isodensity surfaces. We compute the MFs from the output of
a high-resolution numerical simulation which includes explicit treatment of
transfer of UV ionizing radiation. "Galaxies" identified in the simulation
using semi-analytic models of galaxy formation are assumed to be the sole
sources of UV photons. The MFs of the total gas distribution are well described
by the analytic expressions derived for lognormal random fields. The
statistical properties of the diffuse H I depend on the gas distribution and on
the way ionized regions propagate in the inter-galactic medium (IGM). The
deviations of the MFs of the H I distribution from those of a lognormal random
field are, therefore, caused by reionization. We use the MFs to discriminate
between the various stages of reionization in the simulation. We suggest a
simple model of reionization which reproduces the MFs derived from this
simulation. Using random realizations of lognormal density fields, we also
assess the ability of MFs to distinguish between different reionization
scenarios. Our results are relevant to the analysis of future cosmological
twenty-one centimeter maps.


title: Growth of Dust as the Initial Step Toward Planet Formation

abstract:
  We discuss the results of laboratory measurements and theoretical models
concerning the aggregation of dust in protoplanetary disks, as the initial step
toward planet formation. Small particles easily stick when they collide and
form aggregates with an open, often fractal structure, depending on the growth
process. Larger particles are still expected to grow at collision velocities of
about 1m/s. Experiments also show that, after an intermezzo of destructive
velocities, high collision velocities above 10m/s on porous materials again
lead to net growth of the target. Considerations of dust-gas interactions show
that collision velocities for particles not too different in surface-to-mass
ratio remain limited up to sizes about 1m, and growth seems to be guaranteed to
reach these sizes quickly and easily. For meter sizes, coupling to nebula
turbulence makes destructive processes more likely. Global aggregation models
show that in a turbulent nebula, small particles are swept up too fast to be
consistent with observations of disks. An extended phase may therefore exist in
the nebula during which the small particle component is kept alive through
collisions driven by turbulence which frustrates growth to planetesimals until
conditions are more favorable for one or more reasons.


title: Accretion in the Rho-Oph pre-main sequence stars

abstract:
  The aim of this paper is to provide a measurement of the mass accretion rate
in a large, complete sample of objects in the core of the star forming region
Rho-Oph. The sample includes most of the objects (104 out of 111) with evidence
of a circumstellar disk from mid-infrared photometry; it covers a stellar mass
range from about 0.03 to 3 Msun and it is complete to a limiting mass of ~0.05
Msun. We used J and K-band spectra to derive the mass accretion rate of each
object from the intensity of the hydrogen recombination lines, Pab or Brg. For
comparison, we also obtained similar spectra of 35 diskless objects. The
results show that emission in these lines is only seen in stars with disks, and
can be used as an indicator of accretion. However, the converse does not hold,
as about 50% of our disk objects do not have detectable line emission. The
measured accretion rates show a strong correlation with the mass of the central
object (Macc ~ Mstar^1.8+-0.2) and a large spread, of two orders of magnitude
at least, for any interval of Mstar. A comparison with existing data for Taurus
shows that the objects in the two regions have similar behaviour, at least for
objects more massive than ~0.1Msun. The implications of these results are
briefly discussed.


title: Models of the Structure and Evolution of Protoplanetary Disks

abstract:
  We review advances in the modeling of protoplanetary disks. This review will
focus on the regions of the disk beyond the dust sublimation radius, i.e.
beyond 0.1 - 1 AU, depending on the stellar luminosity. We will be mostly
concerned with models that aim to fit spectra of the dust continuum or gas
lines, and derive physical parameters from these fits. For optically thick
disks, these parameters include the accretion rate through the disk onto the
star, the geometry of the disk, the dust properties, the surface chemistry and
the thermal balance of the gas. For the latter we are mostly concerned with the
upper layers of the disk, where the gas and dust temperature decouple and a
photoevaporative flow may originate. We also briefly discuss optically thin
disks, focusing mainly on the gas, not the dust. The evolution of these disks
is dominated by accretion, viscous spreading, photoevaporation, and dust
settling and coagulation. The density and temperature structure arising from
the surface layer models provide input to models of photoevaporation, which
occurs largely in the outer disk. We discuss the consequences of
photoevaporation on disk evolution and planet formation.


title: Rotation of 10 Be stars through Fourier transform analysis

abstract:
  Here we determine the projected rotational velocity of 10 Be stars using
Fourier Transform Method. Also, we discuss the gravity darkening and extend of
deviation from solid body rotation for our sample of stars. We found that 7 of
considered stars are affected by strong gravity darkening or/and solar
differential rotation.


title: IC 4200: a gas-rich early-type galaxy formed via a major merger

abstract:
  We present the result of radio and optical observations of the S0 galaxy IC
4200. We find that the galaxy hosts 8.5 billion solar masses of HI rotating on
a ~90 deg warped disk extended out to 60 kpc from the centre of the galaxy.
Optical spectroscopy reveals a simple-stellar-population-equivalent age of 1.5
Gyr in the centre of the galaxy and V- and R-band images show stellar shells.
Ionised gas is observed within the stellar body and is kinematically decoupled
from the stars and characterised by LINER-like line ratios.We interpret these
observational results as evidence for a major merger origin of IC 4200, and
date the merger back to 1-3 Gyr ago.


title: Magnetic Fields in the Center of the Perseus Cluster

abstract:
  We present Very Long Baseline Array (VLBA) observations of the nucleus of NGC
1275, the central, dominant galaxy in the Perseus cluster of galaxies. These
are the first observations to resolve the linearly polarized emission from
3C84, and from them we determine a Faraday rotation measure (RM) ranging from
6500 to 7500 rad/m^2 across the tip of the bright southern jet component. At 22
GHz some polarization is also detected from the central parsec of 3C84,
indicating the presence of even more extreme RMs that depolarize the core at
lower frequencies. The nature of the Faraday screen is most consistent with
being produced by magnetic fields associated with the optical filaments of
ionized gas in the Perseus Cluster.


title: Imaging the circumstellar envelopes of AGB stars

abstract:
  We report the results of an exploratory program to image the extended
circumstellar envelopes of asymptotic giant branch (AGB) stars in
dust-scattered galactic light. The goal is to characterize the morphology of
the envelopes as a probe of the mass-loss process. The observations consist of
short exposures with the VLT and longer exposures with 1-2m telescopes,
augmented with archival images from the Hubble Space Telescope. We observed 12
AGB stars and detected the circumstellar envelopes in 7. The detected envelopes
have mass loss rates more than about 5 10E-6 solar mass per year, and they can
be seen out to distances of about 1 kpc. The observations provide information
on the mass loss history on time scales up to about 10,000 years. For the five
AGB envelopes in which the circumstellar geometry is well determined by
scattered light observations, all except one (OH348.2-19.7) show deviations
from spherical symmetry. Two (IRC+10216 and IRC+10011) show roughly spherical
envelopes at large radii but asymmetry or bipolarity close to the star; one
(AFGL 2514) shows an extended, elliptical envelope, and one (AFGL 3068) shows a
spiral pattern. The non-spherical structures are all consistent with the
effects of binary interactions. Our observations are in accord with a scenario
in which binary companions play a role in shaping planetary nebulae, and show
that the circumstellar gas is already partly shaped on the AGB, before
evolution to the proto-planetary nebula phase.


title: The role of tidal interactions in driving galaxy evolution

abstract:
  We carry out a statistical analysis of galaxy pairs selected from chemical
hydrodynamical simulations with the aim at assessing the capability of
hierarchical scenarios to reproduce recent observational results for galaxies
in pairs. Particularly, we analyse the effects of mergers and interactions on
the star formation (SF) activity, the global mean chemical properties and the
colour distribution of interacting galaxies. We also assess the effects of
spurious pairs.


title: The neutron star soft X-ray transient 1H1905+000 in quiescence

abstract:
  In this Paper we report on our analysis of a ~25 ksec. Chandra X-ray
observation of the neutron star soft X-ray transient (SXT) 1H1905+000 in
quiescence. Furthermore, we discuss our findings of the analysis of optical
photometric observations which we obtained using the Magellan telescope and
photometric and spectroscopic observations which we obtained using the Very
Large Telescope at Paranal. The X-ray counterpart of 1H1905+000 was not
detected in our Chandra data, with a 95 per cent confidence limit to the source
count rate of 1.2x10^-4 counts s^-1. For different spectral models this yields
an upper limit on the luminosity of 1.8x10^31 erg s^-1 (for an upper limit on
the distance of 10 kpc.) This luminosity limit makes 1H1905+000 the faintest
neutron star SXT in quiescence observed to date. The neutron star luminosity is
so low that it is similar to the lowest luminosities derived for black hole
SXTs in quiescence. This low luminosity for a neutron star SXT challanges the
hypothesis presented in the literature that black hole SXTs in quiescence have
lower luminosities than neutron star SXTs as a result of the presence of a
black hole event horizon. Furthermore, the limit on the neutron star luminosity
obtained less than 20 years after the outburst has ceased, constrains the
thermal conductivity of the neutron star crust. Finally, the neutron star core
must be so cold that unless the time averaged mass accretion rate is lower than
2x10^-12 M_sun yr^-1, core cooling has to proceed via enhanced neutrino
emission processes. We derive a limit on the absolute I-band magnitude of the
quiescent counterpart of M_I>7.8 assuming the source is at 10 kpc. This is in
line with 1H1905+000 being an ultra-compact X-ray binary, as has been proposed
based on the low outburst V-band absolute magnitude.


title: How to move ionized gas: an introduction to the dynamics of HII regions

abstract:
  This review covers the dynamic processes that are important in the evolution
and structure of galactic HII regions, concentrating on an elementary
presentation of the physical concepts and recent numerical simulations of HII
region evolution in a non-uniform medium.
  The contents are as follows:
  (1) The equations (Euler equations; Radiative transfer; Rate equations; How
to avoid the dynamics; How to avoid the atomic physics).
  (2) Physical concepts (Static photoionization equilibrium; Ionization front
propagation; Structure of a D-type front; Photoablation flows; Other
ingredients - Stellar winds, Radiation pressure, Magnetic fields,
Instabilities).
  (3) HII region evolution (Early phases: hypercompact and ultracompact
regions; Later phases: compact and extended regions; Clumps and turbulence).


title: Stellar and Ionized Gas Kinematics of Peculiar Virgo Cluster Galaxies

abstract:
  We present the results of the stellar and ionized gas kinematics of 13 bright
peculiar Virgo cluster galaxies. The stellar velocity field are mostly
consistent with a rotation pattern, but some of them shows interesting features
such as; S-shaped stellar isovelocity contours in NGC 4064, and signatures of
kinematical distinct components in NGC 4429, and NGC 4698. This latter galaxy
and NGC 4424 exhibit extremely low (V/sigma)* values suggesting that these
galaxies are the result of mergers. The ionized gas velocity fields are more
disturbed than the stellar velocity fields, displaying non-circular motions.
Most galaxies in the sample reveals kinematical signatures that can be
associated to gravitational interactions such as; mergers or tidal
interactions, being specially clear in the "truncated/compact" galaxies.
Moreover, most of the sample galaxies show evidence for both gravitational
interactions, and ICM-ISM stripping. Thus the evolution of a significant
fraction of cluster galaxies is likely strongly impacted by both effects.


title: The 3D skeleton of the SDSS

abstract:
  The length of the three-dimensional filaments observed in the fourth public
data-release of the SDSS is measured using the {\em local skeleton} method. It
consists in defining the set of points where the gradient of the smoothed
density field is extremal along its isocontours, with some additional
constraints on local curvature to probe actual ridges in the galaxy
distribution. A good fit to the mean filament length per unit volume,
$\cal{L}$, in the SDSS survey is found to be ${\cal{L}}=(52500\pm6500) (L/{\rm
Mpc})^{-1.75\pm0.06}\rm{Mpc}/(100 \rm{Mpc})^{3}$ for $8.2 \leq L \leq 16.4$
Mpc, where $L$ is the smoothing length in Mpc. This result, which deviates only
slightly, as expected, from the trivial behavior ${\cal{L}} \propto L^{-2}$, is
in excellent agreement with a $\Lambda$CDM cosmology, as long as the matter
density parameter remains in the range $0.25 < \Omega_{\rm matter} < 0.4$ at
one sigma confidence level, considering the universe is flat. These
measurements, which are in fact dominated by linear dynamics, are not
significantly sensitive to observational biases such as redshift distortion,
edge effects, incompleteness, and biasing between the galaxy distribution and
the dark matter distribution. Hence it is argued that the local skeleton is a
rather promising and discriminating tool for the analysis of filamentary
structures in three-dimensional galaxy surveys.


title: Abundance anomalies in NGC 2808

abstract:
  We present metallicity measurements of 25 stars in the blue horizontal branch
of the Galactic globular cluster NGC 2808. Our measurements are based on
moderate-resolution spectra taken with the multi-object fiber facility
FLAMES-UVES, mounted on Kueyen at the Very Large Telescope. We confirm that
stars hotter than a threshold temperature have super-solar abundance, while the
cooler ones respect the nominal metallicity of the cluster, i.e. [Fe/H] ~ -1.1.
The threshold temperature is estimated to be about 12000 K, corresponding to
the so called u-jump, and coincides with the sudden departure of the cluster
horizontal branch from the models. The metallicity increases with temperature
for star hotter than the jump, confirming the hypothesis that the process
responsible for this abrupt metallic enhancement is the levitation due to the
strong radiation field in absence of a significative convective envelope. A
metallicity dependence of the abundance enhancement is also suggested, with
more metal poor clusters having a higher increase in metal content. The slope
in the temperature vs. abundance diagram is higher than the errors involved,
and the metal content of the cluster plays possibly a role in determining the
amplitude of the jump (more metal poor clusters show more enhancement after the
jump), although other parameters, such as clusters' characteristics and even
the atomic species involved, may also someway contribute.


title: Evolution of supermassive black holes

abstract:
  Supermassive black holes (SMBHs) are nowadays believed to reside in most
local galaxies, and the available data show an empirical correlation between
bulge luminosity - or stellar velocity dispersion - and black hole mass,
suggesting a single mechanism for assembling black holes and forming spheroids
in galaxy halos. The evidence is therefore in favour of a co-evolution between
galaxies, black holes and quasars. In cold dark matter cosmogonies, small-mass
subgalactic systems form first to merge later into larger and larger
structures. In this paradigm galaxy halos experience multiple mergers during
their lifetime. If every galaxy with a bulge hosts a SMBH in its center, and a
local galaxy has been made up by multiple mergers, then a black hole binary is
a natural evolutionary stage. The evolution of the supermassive black hole
population clearly has to be investigated taking into account both the
cosmological framework and the dynamical evolution of SMBHs and their hosts.
The seeds of SMBHs have to be looked for in the early Universe, as very
luminous quasars are detected up to redshift higher than z=6. These black holes
evolve then in a hierarchical fashion, following the merger hierarchy of their
host halos. Accretion of gas, traced by quasar activity, plays a fundamental
role in determining the two parameters defining a black hole: mass and spin. A
particularly intriguing epoch is the initial phase of SMBH growth. It is very
challenging to meet the observational constraints at z=6 if BHs are not fed at
very high rates in their infancy.


title: First albedo determination of 2867 Steins, target of the Rosetta mission

abstract:
  We present the first albedo determination of 2867 Steins, the asteroid target
o f the Rosetta space mission together with 21 Lutetia. The data were obtained
in polarimetric mode at the ESO-VLT telescope with the FORS1 instrument in the
V and R filters. Observations were carried out from Jun e to August 2005
covering the phase angle range from 10.3 deg. to 28.3 deg., allowing the
determination of the asteroid albedo by the well known experimenta l
relationship between the albedo and the slope of the polarimetric curve at th e
inversion angle. The measured polarization values of Steins are small,
confirming an E-type cla ssification for this asteroid, as already suggested
from its spectral propertie s. The inversion angle of the polarization curve in
the V and R filters is resp ectively of 17.3 +/-1.5deg. and 18.4+/-1.0 deg.,
and the corresponding sl ope parameter is of 0.037+/-0.003 %/deg and
0.032+/-0.003 %/deg. On the basis of its polarimetric slope value, we have
derived an albedo of 0.45 +/-0.1, that gives an estimated diameter of 4.6 km,
assuming an absolute V ma gnitude of 13.18 mag.


title:
Is the dark matter interpretation of the EGRET gamma excess compatible
  with antiproton measurements?

abstract:
  We investigate the internal consistency of the halo dark matter model which
has been proposed by de Boer et al. to explain the excess of diffuse galactic
gamma rays observed by the EGRET experiment. Any model based on dark matter
annihilation into quark jets, such as the supersymmetric model proposed by de
Boer et al., inevitably also predicts a primary flux of antiprotons from the
same jets. Since propagation of the antiprotons in the unconventional,
disk-dominated type of halo model used by de Boer et al. is strongly
constrained by the measured ratio of boron to carbon nuclei in cosmic rays, we
investigate the viability of the model using the DarkSUSY package to compute
the gamma-ray and antiproton fluxes. We are able to show that their model is
excluded by a wide margin from the measured flux of antiprotons. We therefore
find that a model of the type suggested by Moskalenko et al., where the
intensities of protons and electrons in the cosmic rays vary with galactic
position, is far more plausible to explain the gamma excess.


title: A Long, Hard Look at the Low-Hard State in Accreting Black Holes

abstract:
  We present the first results of coordinated multi-wavelength observations of
the Galactic black hole GX 339-4 in a canonical low-hard state, obtained during
its 2004 outburst. XMM-Newton observed the source for 2 revolutions, or
approximately 280 ksec; RXTE monitored the source throughout this long stare.
The resulting data offer the best view yet obtained of the inner accretion flow
geometry in the low-hard state, which is thought to be analogous to the
geometry in low-luminosity active galactic nuclei. The XMM-Newton spectra
clearly reveal the presence of a cool accretion disk component, and a
relativistic Fe K emission line. The results of fits made to both components
strongly suggest that a standard thin disk remains at or near to the innermost
stable circular orbit, at least in bright phases of the low-hard state. These
findings indicate that potential links between the inner disk radius and the
onset of a steady compact jet, and the paradigm of a radially-recessed disk in
the low-hard state, do not hold universally. The results of our observations
can best be explained if a standard thin accretion disk fuels a corona which is
closely related to, or consistent with, the base of a compact jet. In a brief
examination of archival data, we show that Cygnus X-1 supports this picture of
the low/hard state. We discuss our results within the context of disk-jet
connections and prevailing models for accretion onto black holes.


title: Determining solar abundances using helioseismology

abstract:
  The recent downward revision of solar photospheric abundances of Oxygen and
other heavy elements has resulted in serious discrepancies between solar models
and solar structure as determined through helioseismology. In this work we
investigate the possibility of determining the solar heavy-element abundance
without reference to spectroscopy by using helioseismic data. Using the
dimensionless sound-speed derivative in the solar convection zone, we find that
the heavy element abundance, Z, of 0.0172 +/- 0.002, which is closer to the
older, higher value of the abundances.


title: Properties of dust and detection of Halpha emission in LDN 1780

abstract:
  We present ISOPHOT observations between 60 and 200 microns and a
near-infrared extinction map of LDN 1780. We have used the ISOPHOT data
together with the 25, 60 and 100 microns IRIS maps to disentangle the warm and
cold components of large dust grains that are observed in translucent and dense
clouds. The warm and cold components in LDN 1780 have different properties and
spatial distributions, with the warm component surrounding the cold component.
The cold component is associated with molecular gas at densities of ~1000
cm^-3. The warm component has a uniform colour temperature of 25 K, and the
colour temperature of the cold component slightly varies between 15.8 and 17.3
K (beta=2, Delta(T)=0.5 K). The ratio between the 200 microns emission of the
cold component and Av is Ic(200)/Av=12.1 MJy/sr/mag and the average ratio
tau(200)/Av=2.0x10^-4 mag^-1. The far-infrared emissivity of the warm component
is significantly lower than that of the cold component. The Halpha emission and
Av correlate very well; a ratio I(Halpha)/Av=2.2 Rayleigh/mag is observed. This
correlation indicates the presence of a source of ionisation that can penetrate
deeply into the cloud. Using the ratio I(Halpha)/Av we have estimated a
ionisation rate for LDN 1780 that results to be ~10^-16 photons/s. We interpret
this relatively high value as due to an enhanced cosmic ray flux of ~10 times
the standard value. The origin of the cosmic rays could be from supernovae in
the Scorpio-Centaurus OB association and/or the runaway zeta Ophiuchus.


title: A magnetically collimated jet from an evolved star

abstract:
  Planetary nebulae often have asymmetric shapes, which could arise due to
collimated jets from evolved stars before evolution to the planetary nebula
phase. The source of jet collimation in these stars is unknown. Magnetic fields
are thought to collimate outflows that are observed in many other astrophysical
sources, such as active galactic nuclei and proto-stars, although hitherto
there are no direct observations of both the magnetic field direction and
strength in any collimated jet. Theoretical models have shown that magnetic
fields could also be the dominant source of collimation of jet in evolved
stars. Here we report measurements of the polarization of water vapour masers
that trace the precessing jet emanating from the asymptotic giant branch star
W43A at 2.6 kpc from the Sun, which is undergoing rapid evolution into a
planetary nebula. The masers occur in two clusters at opposing tips of the
jets, ~1,000 AU from the star. We find direct evidence that the magnetic field
is collimating the jet.


title: New observational frontiers in the multiplicity of young stars

abstract:
  It has now been known for over a decade that low-mass stars located in
star-forming regions are very frequently members of binary and multiple
systems, even more so than main sequence stars in the solar neighborhood. This
high multiplicity rate has been interpreted as the consequence of the
fragmentation of small molecular cores into a few seed objects that accrete to
their final mass from the remaining material and dynamically evolve into stable
multiple systems, possibly producing a few ejecta in the process. Analyzing the
statistical properties of young multiple systems in a variety of environments
therefore represents a powerful approach to place stringent constraints on star
formation theories. In this contribution, we first review a number of recent
results related to the multiplicity of T Tauri stars. We then present a series
of studies focusing on the multiplicity and properties of optically-undetected,
heavily embedded protostars. These objects are much younger than the previously
studied pre-main sequence stars, and they therefore offer a closer look at the
primordial population of multiple systems. In addition to these observational
avenues, we present new results of a series of numerical simulations that
attempt to reproduce the fragmentation of small molecular cores into multiple
systems, and compare these results to the observations.