title:
Constraints on holographic dark energy models using the differential
  ages of passively evolving galaxies

abstract:
  Using the absolute ages of passively evolving galaxies observed at different
redshifts, one can obtain the differential ages, the derivative of redshift $z$
with respect to the cosmic time $t$ (i.e. ${\rm d} z/{\rm d}t$). Thus, the
Hubble parameter $H(z)$ can be measured through the relation $H(z)=-({\rm d}
z/{\rm d}t)/(1+z)$. By comparing the measured Hubble parameter at different
redshifts with the theoretical one containing free cosmological parameters, one
can constrain current cosmological models. In this paper, we use this method to
present the constraint on a spatially flat Friedman-Robert-Walker Universe with
a matter component and a holographic dark energy component, in which the
parameter $c$ plays a significant role in this dark energy model. Firstly we
consider three fixed values of $c$=0.6, 1.0 and 1.4 in the fitting of data. If
we set $c$ free, the best fitting values are $c=0.26$, $\Omega_{\rm m0}=0.16$,
$h=0.9998$. It is shown that the holographic dark energy behaves like a
quintom-type at the $1\sigma$ level. This result is consistent with some other
independent cosmological constrains, which imply that $c<1.0$ is favored. We
also test the results derived from the differential ages using another
independent method based on the lookback time to galaxy clusters and the age of
the universe. It shows that our results are reliable.


title: Toward Resolving the Outflow Engine: An Observational Perspective

abstract:
  Jets from young stars represent one of the most striking signposts of star
formation. The phenomenon has been researched for over two decades and there is
now general agreement that such jets are generated as a by-product of
accretion; most likely by the accretion disk itself. Thus they mimic what
occurs in more exotic objects such as active galactic nuclei and micro-quasars.
The precise mechanism for their production however remains a mystery. To a
large degree, progress is hampered observationally by the embedded nature of
many jet sources as well as a lack of spatial resolution: Crude estimates, as
well as more sophisticated models, nevertheless suggest that jets are
accelerated and focused on scales of a few AU at most.
  It is only in the past few years however that we have begun to probe such
scales in detail using classical T Tauri stars as touchstones. Application of
adaptive optics, data provided by the HST, use of specialised techniques such
as spectro-astrometry, and the development of spectral diagnostic tools, are
beginning to reveal conditions in the jet launch zone. This has helped
enormously to constrain models. Further improvements in the quality of the
observational data are expected when the new generation of interferometers come
on-line. Here we review some of the most dramatic findings in this area since
Protostars and Planets~IV including indications for jet rotation, i.e. that
they transport angular momentum. We will also show how measurements, such as
those of width and the velocity field close to the source, suggest jets are
initially launched as warm magneto-centrifugal disk winds. (abridged)


title: Results from the Exoplanet Search Programmes with BEST and TEST

abstract:
  Thueringer Landessternwarte Tautenburg (TLS) has started to operate a small
dedicated telescope - the Tautenburg Exoplanet Search Telescope (TEST) -
searching for transits of extrasolar planets in photometric time series
observations. In a joint effort with the Berlin Exoplanet Search Telescope
(BEST) operated by the Institut fuer Planetenforschung of the "Deutsches
Zentrum fuer Luft- und Raumfahrt (DLR)" at the Observatoire de Haute-Provence
(OHP), France, two observing sites are used to optimise transit search. Here,
we give a short overview of these systems and the data analysis. We describe a
software pipeline that we have set up to identify transit events of extrasolar
planets and variable stars in time series data from these and other telescopes,
and report on some first results.


title: Surface brightness in plasma-redshift cosmology

abstract:
  In 2001 Lori M. Lubin and Allan Sandage, using big-bang cosmology for
interpreting the data, found the surface brightness of galaxies to be inversely
proportional to about the third power of (1+z), while the contemporary big-bang
cosmology predicts that the surface brightness is inversely proportional to the
fourth power of (1+z). In contrast, these surface brightness observations are
in agreement with the predictions of the plasma-redshift cosmology. Lubin and
Sandage (2001) and Barden et al. (2005), who surmised the big-bang expansion,
interpreted the observations to indicate that the diameters of galaxies are
inversely proportional to (1+z). In contrast, when assuming plasma-redshift
cosmology, the diameters of galaxies are observed to be constant independent of
redshift and any expansion. Lubin and Sandage (2001) and Barden et al. (2005),
when using big-bang cosmology, observed the average absolute magnitude of
galaxies to decrease with redshift; while in plasma redshift cosmology it is a
constant. Lubin and Sandage and Barden et al. suggested that a coherent
evolution could explain the discrepancy between the observed relations and
those predicted in the big-bang cosmology. We have failed to find support for
this explanation. We consider the observed relations between the redshift and
the surface-brightness, the galaxy diameter, and the absolute magnitude to be
robust confirmations of plasma-redshift cosmology.


title: Origin of the Counter-Rotating Gas in NGC 1596

abstract:
  We present Australia Telescope Compact Array (ATCA) HI imaging of the edge-on
galaxy NGC 1596, which was recently found to have counter-rotating ionized gas
in its center (<15"). We find a large HI envelope associated with a nearby
companion, the dwarf irregular galaxy NGC 1602. The HI covers a region
\~11.9'x13.4' (62x70 kpc^2) and the total HI mass detected is 2.5+/-0.1x10^9
Msun (assuming an 18 Mpc distance). The HI is centered on NGC 1602 but appears
to have two tidal tails, one of which crosses over NGC 1596. The HI located at
the position of NGC 1596 has a velocity gradient in the same sense as the
ionized gas, i.e. opposite to the stellar rotation. Both the existence of a
large gas reservoir and the velocity gradient of the HI and the ionized gas
strongly suggest that the ionized gas in NGC 1596 originated from NGC 1602.
  From the length of the HI tails we conclude that the interaction started at
least 1 Gyr ago, but the unsettled, asymmetric distribution of the ionized gas
suggests that the accretion occured more recently. NGC 1596 thus provides a
good example where the presence of counter-rotating gas can be directly linked
to an accretion event. After the accretion has stopped or the merging is
complete, NGC 1596 may evolve to a system with more extended counter-rotating
gas but no obvious signature of interaction. There is a substantial local HI
peak in one of the two tails, where we also find a faint stellar counterpart.
The M_HI/L_B ratio in this region is too high for a normal dwarf elliptical or
a low surface brightness galaxy, so we conclude that a tidal dwarf is currently
forming there.


title:
Accretion Disks around Young Stars: Lifetimes, Disk Locking and
  Variability

abstract:
  We report the findings of a comprehensive study of disk accretion and related
phenomena in four of the nearest young stellar associations spanning 6-30
million years in age, an epoch that may coincide with the late stages of planet
formation. We have obtained ~650 multi-epoch high-resolution optical spectra of
100 low-mass stars that are likely members of the eta Chamaeleontis (~6 Myr),
TW Hydrae (~8 Myr), beta Pictoris (~12 Myr) and Tucanae-Horologium (~30 Myr)
groups. Our data were collected over 12 nights between 2004 December - 2005
July on the Magellan Clay 6.5m telescope. Based on H$\alpha$ line profiles,
along with a variety of other emission lines, we find clear evidence of
on-going accretion in three out of 11 eta Cha stars and two out of 32 TW Hydrae
members. None of the 57 beta Pic or Tuc-Hor members shows measurable signs of
accretion. Together, these results imply significant evolution of the disk
accretion process within the first several Myr of a low-mass star's life. While
a few disks can continue to accrete for up to ~10 Myr, our findings suggest
that disks accreting for beyond that timescale are rather rare. This result
provides an indirect constraint on the timescale for gas dissipation in inner
disks and, in turn, on gas giant planet formation. All accretors in our sample
are slow rotators, whereas non-accretors cover a large range in rotational
velocities. This may hint at rotational braking by disks at ages up to ~8 Myr.
Our multi-epoch spectra confirm that emission-line variability is common even
in somewhat older T Tauri stars, among which accretors tend to show
particularly strong variations. Thus, our results indicate that accretion and
wind activity undergo significant and sustained variations throughout the
lifetime of accretion disks.


title: The Asymmetrical Wind of the Candidate Luminous Blue Variable MWC 314

abstract:
  We present the results of long-term spectropolarimetric and spectroscopic
monitoring of MWC 314, a candidate Luminous Blue Variable star. We detect the
first evidence of H$\alpha$ variability in MWC 314, and find no apparent
periodicity in this emission. The total R-band polarization is observed to vary
between 2.21% and 3.00% at a position angle consistently around
$\sim0^{\circ}$, indicating the presence of a time-variable intrinsic
polarization component, hence an asymmetrical circumstellar envelope. We find
suggestive evidence that MWC 314's intrinsic polarization exhibits a
wavelength-independent magnitude varying between 0.09% and 0.58% at a
wavelength-independent position angle covering all four quadrants of the Stokes
Q-U plane. Electron scattering off of density clumps in MWC 314's wind is
considered as the probable mechanism responsible for these variations.


title: The Formation and Evolution of Intracluster Light

abstract:
  Using N-body simulations, we have modeled the production and evolution of
diffuse, low surface brightness intracluster light (ICL) in three simulated
galaxy clusters. Using an observational definition of ICL to be luminosity at a
surface brightness mu_V>26.5 mag/sq.arcsec, we have found that the fraction of
cluster luminosity contained in ICL generally increases as clusters evolve,
although there are large deviations from this trend over short timescales,
including sustained periods of decreasing ICL luminosity. Most ICL luminosity
increases come in short, discrete events which are highly correlated with group
accretion events within the cluster. In evolved clusters we find that ~10-15%
of the clusters' luminosity is at ICL surface brightness. The morphological
structure of the ICL changes with time, evolving from a complex of filaments
and small-scale, relatively high surface brightness features early in a
cluster's history, to a more diffuse and amorphous cluster-scale ICL envelope
at later times. Finally, we also see a correlation between the evolution of ICL
at different surface brightnesses, including a time delay between the evolution
of faint and extremely faint surface brightness features which is traced to the
differing dynamical timescales in the group and cluster environment.


title: Nflation: multi-field inflationary dynamics and perturbations

abstract:
  We carry out numerical investigations of the dynamics and perturbations in
the Nflation model of Dimopoulos et al. (2005). This model features large
numbers of scalar fields with different masses, which can cooperate to drive
inflation according to the assisted inflation mechanism. We extend previous
work to include random initial conditions for the scalar fields, and explore
the predictions for density perturbations and the tensor-to-scalar ratio. The
tensor-to-scalar ratio depends only on the number of e-foldings and is
independent of the number of fields, their masses, and their initial
conditions. It therefore always has the same value as for a single massive
field. By contrast, the scalar spectral index has significant dependence on
model parameters. While normally multi-field inflation models make predictions
for observable quantities which depend also on the unknown field initial
conditions, we find evidence of a `thermodynamic' regime whereby the predicted
spectral index becomes independent of initial conditions if there are enough
fields. Only in parts of parameter space where the mass spectrum of the fields
is extremely densely packed is the model capable of satisfying the tight
observational constraints from WMAP3 observations.


title:
Ultraviolet Through Far-Infrared Spatially Resolved Analysis of the
  Recent Star Formation in M81 (NGC3031)

abstract:
  The recent star formation (SF) in the early-type spiral galaxy M81 is
characterized using imaging observations from the far-ultraviolet (UV) to the
far-infrared (IR). We compare these data with models of the stellar, gas, and
dust emission for sub-galactic regions. Our results suggest the existence of a
diffuse dust emission not directly linked to the recent SF. We find a radial
decrease of the dust temperature and dust mass density, and in the attenuation
of the stellar light. The IR emission in M81 can be modeled with three
components: 1) cold dust with a temperature <T_c>=18+-2 K, concentrated near
the HII regions but also presenting a diffuse distribution; 2) warm dust with
T_w=53+-7 K, directly linked with the HII regions; and 3) aromatic molecules,
with diffuse morphology peaking around the HII regions. We derive several
relationships to obtain total IR luminosities from IR monochromatic fluxes, and
we compare five different star formation rate (SFR) estimators for HII regions
in M81 and M51: the UV, Halpha, and three estimators based on Spitzer data. We
find that the Halpha luminosity absorbed by dust correlates tightly with the 24
microns emission. The correlation with the total IR luminosity is not as good.
Important variations from galaxy to galaxy are found when estimating the total
SFR with the 24 microns or the total IR emission alone. The most reliable
estimations of the total SFRs are obtained by combining the Halpha emission (or
the UV) and an IR luminosity (especially the 24 microns emission), which probe
the unobscured and obscured SF, respectively. For the entire M81 galaxy, about
50% of the total SF is obscured by dust. The percentage of obscured SF ranges
from 60% in the inner regions of the galaxy to 30% in the outer zones.


title: Discovery of a Binary Centaur

abstract:
  We have identified a binary companion to (42355) 2002 CR46 in our ongoing
deep survey using the Hubble Space Telescope's High Resolution Camera. It is
the first companion to be found around an object in a non-resonant orbit that
crosses the orbits of giant planets. Objects in orbits of this kind, the
Centaurs, have experienced repeated strong scattering with one or more giant
planets and therefore the survival of binaries in this transient population has
been in question. Monte Carlo simulations suggest, however, that binaries in
(42355) 2002 CR46 -like heliocentric orbits have a high probability of survival
for reasonable estimates of the binary's still-unknown system mass and
separation. Because Centaurs are thought to be precursors to short period
comets, the question of the existence of binary comets naturally arises; none
has yet been definitively identified. The discovery of one binary in a sample
of eight observed by HST suggests that binaries in this population may not be
uncommon.


title: Supernova constraints on decaying vacuum cosmology

abstract:
  There is mounting observational evidence that the expansion of our Universe
is undergoing a late-time acceleration. Among many proposals to describe this
phenomenon, the cosmological constant seems to be the simplest and the most
natural explanation. However, despite its observational successes, such a
possibility exacerbates the well known cosmological constant problem, requiring
a natural explanation for its small, but nonzero, value. In this paper we
consider a cosmological scenario driven by a varying cosmological term, in
which the vacuum energy density decays linearly with the Hubble parameter. We
show that this model is indistinguishable from the standard one in that the
early radiation phase is followed by a long dust-dominated era, and only
recently the varying cosmological term becomes dominant, accelerating the
cosmic expansion. In order to test the viability of this scenario we have used
the most recent type Ia supernova data, i.e., the High-Z SN Search (HZS) Team
and the Supernova Legacy Survey (SNLS) Collaboration data. In particular, for
the SNLS sample we have found the present matter density and Hubble parameters
in the intervals [0.27, 0.37] and [0.68, 0.72], respectively (at 95% c.l.),
which is in good agreement with the currently accepted estimates for these
parameters.


title: Understanding the Cosmic Mass Function High Mass Behaviour

abstract:
  We claim that the discrepancy found between theoretical predictions for the
cosmic mass function and those found in numerical simulations is due to the
fact that in deriving the former all mass elements are assumed to be at the
center of the object they belong to (the all-mass-at-center problem). By an
appropriate treatment of this problem, using the spherical collapse model
(which is not a bad approximation in the high mass limit), we obtain both the
high mass behaviour found in simulations and the true assymptotic behaviour of
the mass function (for arbitrarily high masses). Therefore, we conclude that by
combining ellipsoidal dynamics with a suitable treatment of the
all-mass-at-center problem (that we will show in a follow up work) a
theoretical prediction for the cosmic mass function in full agreement with
simulations may be obtained.


title: A Method To Remove Fringes From Images Using Wavelets

abstract:
  We have developed a new method that uses wavelet analysis to remove
interference fringe patterns from images. This method is particularly useful
for flat fields in the common case where fringes vary between the calibration
and object data. We analyze the efficacy of this method by creating fake flats
with fictitious fringes and removing the fringes. We find that the method
removes 90% of the fringe pattern if its amplitude is equal to the random noise
level and 60% if the fringe amplitude is $\approx 1/10$ of the noise level. We
also present examples using real flat field frames. A routine written in the
Interactive Data Language (IDL) that implements this algorithm is available
from the authors and as an attachment to this paper.


title: Binary Stellar Population Synthesis Study of Elliptical Galaxies

abstract:
  We determine relative stellar ages and metallicities mainly for about 80
elliptical galaxies in low and high density environments via the latest binary
stellar population (BSP) synthesis model and test a latest hierarchical
formation model of elliptical galaxies which adopted the new $\Lambda$CDM
cosmology for the first time. The stellar ages and metallicities of galaxies
are estimated from two high-quality published spectra line indices, i.e.
H$\beta$ and [MgFe]. The results show that elliptical galaxies have stellar
populations older than 3.9 Gyr and more metal rich than 0.02. Most of our
results are in agreement with predictions of the model: First, elliptical
galaxies in denser environment are redder and have older populations than field
galaxies. Second, elliptical galaxies with more massive stellar components are
redder while have older and more metal rich populations than less massive ones.
Third, the most massive galaxies are shown to have the oldest and most metal
rich stars. However, some of our results are found to be different with
predictions of the galaxy formation model, i.e. the metallicity distributions
of low- and high-density elliptical galaxies and the relations relating to
cluster-centric distance.


title:
The outermost gravitationally bound orbit around a mass clump in an
  expanding Universe: implication on rotation curves and dark matter halo sizes

abstract:
  Conventional treatment of cold dark matter halos employs the
Navarro-Frenk-White (NFW) profile with a maximum radius set at $r=r_{200}$,
where the enclosed matter has an overdensity of 200 times the critical density.
The choice of $r=r_{200}$ is somewhat arbitrary. It is not the collapsed
(virial) radius, but does give $r \sim$ 1 Mpc for rich clusters, which is a
typical X-ray size. Weak lensing measurements, however, reveal halo radii well
in excess of $r_{200}$. Is there a surface that places an absolute limit on the
extension of a halo? To answer the question, we derived analytically the
solution for circular orbits around a mass concentration in an expanding flat
Universe, to show that an outermost orbit exists at $v/r = H$, where $v$ is the
orbital speed and $H$ is the Hubble constant. The solution, parametrized as
$r_2$, is independent of model assumptions on structure formation, and {\it is
the radius at which the furthest particle can be regarded as part of the bound
system}. We present observational evidence in support of dark matter halos
reaching at least as far out as $r=r_2$. An interesting consequence that
emerges concerns the behavior of rotation curves. Near $r=r_2$ velocities will
be biased low. As a result, the mass of many galaxy groups may have been
underestimated. At $r=r_2$ there is an abrupt cutoff in the curve, irrespective
of the halo profile. An important cosmological test can therefore be performed
if velocity disperion data are available out to 10 Mpc radii for nearby
clusters (less at higher redshifts). For Virgo it appears that there is no such
cutoff.


title: The Age and Metallicity Relation of Omega Centauri

abstract:
  We present a metallicity distribution based on photometry and spectra for 442
omega Cen cluster members that lie at the main sequence turnoff region of the
color-magnitude diagram. This distribution is similar to that found for the red
giant branch. The distribution shows a sharp rise to a mean of [Fe/H] = -1.7
with a long tail to higher metallicities. Ages have then been determined for
the stars using theoretical isochrones enabling the construction of an
age-metallicity diagram. Interpretation of this diagram is complicated by the
correlation of the errors in the metallicities and ages. Nevertheless, after
extensive Monte-Carlo simulations, we conclude that our data show that the
formation of the cluster took place over an extended period of time: the most
metal-rich stars in our sample ([Fe/H] ~ -0.6) are younger by 2-4 Gyrs than the
most metal-poor population.


title: NGC922 - A new drop-through ring galaxy

abstract:
  We have found the peculiar galaxy NGC922 to be a new drop-through ring galaxy
using multi-wavelength (UV-radio) imaging and spectroscopic observations. Its
`C'-shaped morphology and tidal plume indicate a recent strong interaction with
its companion which was identified with these observations. Using numerical
simulations we demonstrate that the main properties of the system can be
generated by a high-speed off-axis drop-through collision of a small galaxy
with a larger disk system, thus making NGC922 one of the nearest known
collisional ring galaxies. While these systems are rare in the local Universe,
recent deep HST images suggest they were more common in the early Universe.


title: Is the cosmic UV background fluctuating at redshift z ~ 6 ?

abstract:
  We study the Gunn-Peterson effect of the photo-ionized intergalactic
medium(IGM) in the redshift range 5< z <6.4 using semi-analytic simulations
based on the lognormal model. Assuming a rapidly evolved and spatially uniform
ionizing background, the simulation can produce all the observed abnormal
statistical features near redshift z ~ 6. They include: 1) rapidly increase of
absorption depths; 2) large scatter in the optical depths; 3) long-tailed
distributions of transmitted flux and 4) long dark gaps in spectra. These
abnormal features are mainly due to rare events, which correspond to the
long-tailed probability distribution of the IGM density field, and therefore,
they may not imply significantly spatial fluctuations in the UV ionizing
background at z ~ 6.


title: Elemental abundances in the atmosphere of clump giants

abstract:
  The aim of this paper is to provide the fundamental parameters and abundances
for a large sample of local clump giants with a high accuracy. The selection of
clump stars for the sample group was made applying a color - absolute magnitude
window to nearby Hipparcos stars. The abundances of carbon and nitrogen were
obtained from molecular synthetic spectrum, the Mg and Na abundances were
derived using the non-LTE approximation. The "classical" models of stellar
evolution without atomic diffusion and rotation-induced mixing were employed.
The atmospheric parameters (Teff, log g, [Fe/H], Vt) and Li, C, N, O, Na, Mg,
Si, Ca and Ni abundances in 177 clump giants of the Galactic disc were
determined. The underabundance of carbon, overabundance of nitrogen and
"normal" abundance of oxygen were detected. A small sodium overabundance was
found. A possibility of a selection of the clump giants based on their chemical
composition and the evolutionary tracks was explored. The theoretical
predictions based on the classical stellar evolution models are in good
agreement with the observed surface variations of the carbon and nitrogen just
after the first dredge-up episode. The giants show the same behavior of the
dependencies of O, Mg, Ca, Si (alpha-elements) and Ni (iron-peak element)
abundances vs. [Fe/H] as dwarfs do. This allows one to use such abundance
ratios to study the chemical and dynamical evolution of the Galaxy.


title: Kinematic structure in the young Sigma Orionis association

abstract:
  We have used precise radial velocity measurements for a large number of
candidate low-mass stars and brown dwarfs, to show that the young Sigma Ori
``cluster'' consists of two spatially superimposed components which are
kinematically separated by 7 km/s in radial velocity, and which have different
mean ages. We examine the relationship of these two kinematic groups to other
populations in the Orion OB1 association and briefly discuss the consequence of
mixed age samples for ongoing investigations of the formation and evolution of
low-mass objects in this much-observed region.


title: The Monitor project: Rotation of low-mass stars in the open cluster M34

abstract:
  We report on the results of a V and i-band time-series photometric survey of
M34 (NGC 1039) using the Wide Field Camera (WFC) on the Isaac Newton Telescope
(INT), achieving better than 1% precision per data point for 13 <~ i <~ 17.
Candidate cluster members were selected from a V vs V-I colour-magnitude
diagram over 14 < V < 24 (0.12 <~ M/Msun <~ 1.0), finding 714 candidates, of
which we expect ~ 400 to be real cluster members (taking into account
contamination from the field). The mass function was computed, and found to be
consistent with a log-normal distribution in dN/dlogM. Searching for periodic
variable objects in the candidate members gave 105 detections over the mass
range 0.25 < M/Msun < 1.0. The distribution of rotation periods for 0.4 <
M/Msun < 1.0 was found to peak at ~ 7 days, with a tail of fast rotators down
to periods of ~ 0.8 days. For 0.25 < M/Msun < 0.4 we found a peak at short
periods, with a lack of slow rotators (eg. P >~ 5 days, consistent with the
work of other authors (eg. Scholz & Eisloffel 2004) at very low masses. Our
results are interpreted in the context of previous work, finding that we
reproduce the same general features in the rotational period distributions. A
number of rapid rotators were found with velocities ~ a factor of two lower
than in the Pleiades, consistent with models of angular momentum evolution
assuming solid body rotation without needing to invoke core-envelope
decoupling.


title:
Transverse and longitudinal correlation functions in the Intergalactic
  Medium from 32 close pairs of high-redshift quasars

abstract:
  We present the transverse flux correlation function of the Lyman-alpha forest
in quasar absorption spectra at z~2.1 from VLT-FORS and VLT-UVES observations
of a total of 32 pairs of quasars; 26 pairs with separations in the range
0.6<theta<4 arcmin and 6 pairs with 4<theta<10 arcmin. Correlation is detected
at the 3sigma level up to separations of the order of ~4 arcmin (or ~4.4 h^{-1}
Mpc comoving at z=2.1 for Omega_{m}=0.3 and Omega_{Lambda}=0.7). We have,
furthermore, measured the longitudinal correlation function at a somewhat
higher mean redshift (z=2.39) from 20 lines of sight observed with high
spectral resolution and high signal-to-noise ratio with VLT-UVES. We compare
the observed transverse and longitudinal correlation functions to that obtained
from numerical simulations and illustrate the effect of spectral resolution,
thermal broadening and peculiar motions. The shape and correlation length of
the correlation functions are in good agreement with those expected from
absorption by the filamentary and sheet-like structures in the photoionized
warm intergalactic medium predicted in CDM-like models for structures
formation. Using a sample of 139 C_{iv} systems detected along the lines of
sight toward the pairs of quasars we also investigate the transverse
correlation of metals on the same scales. The observed transverse correlation
function of intervening C_{iv} absorption systems is consistent with that of a
randomly distributed population of absorbers. This is likely due to the small
number of pairs with separation less than 2 arcmin. We detect, however, a
significant overdensity of systems in the sightlines towards the quartet
Q0103-294A&B, Q0102-2931 and Q0102-293 which extends over the redshift range
1.5<z<2.2 and an angular scale larger than 10 arcmin.


title: Merging of a massive binary due to ejection of bound stars

abstract:
  From the results of numerical scattering experiments and simulations of a
massive black hole binary in spherically symmetric and shallow cores it has
been deduced that most likely the shrinking process stalls due to loss-cone
depletion before emission of gravitational radiation becomes important. Here we
follow a different approach and focus on the population of stars which is bound
to the binary and so far has not received much attention. With simple
assumptions which should not be sensitive to initial conditions we derive a
lower limit for the mass of stars which needs to be ejected by the binary in
order to coalesce. We also compute this mass in dependence on the steepness of
the density profile according to which the stars are distributed. Our results
are not as pessimistic as earlier conclusions and actually suggest that the BHs
merge.


title:
New light on the old problem of lithium pre--MS depletion: models with
  2D RHD convection

abstract:
  The Teff location of Pre-Main Sequence (PMS) evolutionary tracks depends on
the treatment of over-adiabaticity. We present here the PMS evolutionary tracks
computed by using the mixing length theory of convection (MLT) in which the
alpha_MLT=l/H_p parameter calibration is based on 2D--hydrodynamical models
(Ludwig et al. 1999). These MLT--\alpha^2D stellar models and tracks are very
similar to those computed with non--grey ATLAS9 atmospheric boundary conditions
and Full Spectrum of Turbulence (FST) convection model both in the atmosphere
and in the interior. The comparison of the new tracks with the location on the
HR diagram of pre--MS binariesis not completely satisfactory, as some binary
components are located at too low \teff. Besides, the pre--MS lithium depletion
in the MLT--\alpha^2D tracks is still much larger than that expected from the
observations of lithium in young open clusters. This result is similar to that
of FST models. Thus, in spite of the fact that 2D RHD models should provide a
better convection description than any local model, their introduction is not
sufficient to reconcile theory and observations. Lithium depletion in young
clusters points towards a convection efficiency which, in pre--MS, should be
smaller than in the MS. The pre--MS lithium depletion decreases significantly
in FST models if we reduce the solar metallicity down to the value suggested by
Asplund et al.(2004), but the corresponding solar model does not reproduce the
depth of the convective zone as determined by helioseismology.


title: Mass functions in coupled Dark Energy models

abstract:
  We evaluate the mass function of virialized halos, by using Press & Schechter
(PS) and/or Steth & Tormen (ST) expressions, for cosmologies where Dark Energy
(DE) is due to a scalar self-interacting field, coupled with Dark Matter (DM).
We keep to coupled DE (cDE) models known to fit linear observables. To
implement the PS-ST approach, we start from reviewing and extending the results
of a previous work on the growth of a spherical top-hat fluctuation in cDE
models, confirming their most intriguing astrophysical feature, i.e. a
significant baryon-DM segregation, occurring well before the onset of any
hydrodynamical effect. Accordingly, the predicted mass function depends on how
halo masses are measured. For any option, however, the coupling causes a
distortion of the mass function, still at z=0. Furthermore, the z-dependence of
cDE mass functions is mostly displaced, in respect to LambdaCDM, in the
opposite way of uncoupled dynamical DE. This is an aspect of the basic
underlying result, that even a little DM-DE coupling induces relevant
modifications in the non-linear evolution. Therefore, without causing great
shifts in linear astrophysical observables, the DM-baryon segregation induced
by the coupling can have an impact on a number of cosmological problems, it
e.g., galaxy satellite abundance, spiral disk formation, apparent baryon
shortage, entropy input in clusters, etc..


title:
Central stellar populations of early-type galaxies in low-density
  environments

abstract:
  We have investigated the properties of a volume and magnitude limited sample
of nearby early type galaxies that were carefully selected from the AAO two
degree field galaxy redshift survey. We used images from the DSS to confirm the
E/S0 morphologies, and augmented this sample with field galaxies from Colbert
et al. 2001. We present spectroscopic observations of 22 galaxies from the
combined sample, from which central velocity dispersions and the Lick stellar
population indices were measured. After carefully correcting the spectra for
nebular emission we derived luminosity-weighted ages, metallicities, and
alpha-element abundance ratios. We compare these isolated galaxies with samples
of early-type galaxies in the Virgo and Coma clusters, and also with the sample
of galaxies in low-density regions of Kuntschner et al. (2002). We find that
galaxies in low-density environments are younger and have a greater spread of
ages compared to cluster galaxies. They also show a wider range of
metallicities at a given velocity dispersion than cluster galaxies, which
display only super-solar metallicities. On average cluster, as well as,
isolated galaxies show non-solar abundance ratios in alpha-elements, suggesting
that, independent of galactic environment, star formation occurred on short
time-scales. We reason that early-type galaxies in low-density environments
experienced merging-induced star-formation episodes over a longer and more
recent period of time compared to a cluster environment, and speculate that a
considerable fraction of their stars formed out of low-metallicity halo gaseous
material during the slow growth of a stellar disk between merging events.


title:
Extragalactic chemistry of molecular gas: lessons from the local
  universe

abstract:
  Observational constraints provided by high resolution and high sensitivity
observations of external galaxies made in the millimeter and submillimeter
range have started to put on a firm ground the study of extragalactic chemistry
of molecular gas. In particular, the availability of multi-species and
multi-line surveys of nearby galaxies is central to the interpretation of
existent and forthcoming millimeter observations of the high redshift universe.
Probing the physical and chemical status of molecular gas in starbursts and
active galaxies (AGN) requires the use of specific tracers of the relevant
energetic phenomena that are known to be at play in these galaxies: large-scale
shocks, strong UV fields, cosmic rays and X-rays. We present below the first
results of an ongoing survey, allying the IRAM 30m telescope with the Plateau
de Bure interferometer(PdBI), devoted to study the chemistry of molecular gas
in a sample of starbursts and AGN of the local universe. These observations
highlight the existence of a strong chemical differentiation in the molecular
disks of starbursts and AGN.


title:
On the search of electromagnetic cosmological counterparts to
  coalescences of massive black hole binaries

abstract:
  We explore the nature of possible electromagnetic counterparts of
coalescences of massive black hole binaries at cosmological distances
detectable by the Laser Interferometer Space Antenna (LISA). An electromagnetic
precursor, during the last year of gravitational wave (GW)-driven inspiral, or
an afterglow within few years after coalescence, may highlight the position in
the sky of galaxies hosting LISA sources. We show that observations of
precursors and afterglows are mutually exclusive, depending on the mass of the
primary black hole. Precursors are expected to occur in binaries where the
primary (more massive) black hole is heavier than ~10^7 \Msun. They may
correspond to on-off states of accretion, i.e., to a bright X-ray source
decaying into quiescence before black hole coalescence, and are likely
associated to disturbed galaxies showing signs of ongoing starbursts.
Coalescences of lighter binaries, with masses <5x10^6 \Msun, lack of any
precursor, as gas is expected to be consumed long before the GW-driven orbital
decay. Such events would not be hosted by (massive) galaxies with an associated
starburst, given the slow binary inspiral time compared to the typical time
scale of starbursts. By contrast, coalescence, for such light binaries, is
followed by an electromagnetic afterglow, i.e., an off-on accretion state
rising in <20 yrs. Using a cosmological merger tree algorithm, we show that
future X-ray missions such as XEUS will be able to identify, in 20 yrs
operation, almost all the massive BH binary detectable by LISA, and, in only 5
yrs, all the LISA sources at z>6.


title:
Shadows and Photoevaporated Flows from Neutral Clumps Exposed to Two
  Ionizing Sources

abstract:
  Neutral clumps immersed in HII regions are frequently found in star formation
regions. We investigate here the formation of tail of neutral gas, which are
not reached by the direct ionizing flux coming from two massive stars, using
both an analytical approximation, that allows us to estimate the shadow
geometry behind the clumps for different initial geometric configurations, and
three-dimensional numerical simulations. We found a good agreement between both
approaches to this theoretically interesting problem. A particularly important
application could be the proplyds that are found in the Trapezium cluster in
Orion, which are being photoevaporated primordially by the O stars theta-1 Ori
C and theta-2 Ori A.


title: Binary central stars of planetary nebula

abstract:
  Only a handful of binary central stars of planetary nebulae (PNe) are known
today, due to the difficulty of detecting their companions. Preliminary results
from radial velocity surveys, however, seem to indicate that binarity plays a
fundamental,rather than marginal role in the evolution of PNe and that the
close binary fraction might be much larger than the currently known value of
10-15%. In this review, we list all the known binary central stars, giving an
updated census of their numbers and selected characteristics. A review is also
given of the techniques used to detect binaries as well as selected
characteristics of related stellar classes which might provide constraints (or
additional puzzles) to the theory of PN evolution. Finally, we will formulate
the conjecture that all PNe derive from binary interactions and suggest that
this is not inconsistent with our current knowledge.


title: Magnetohydrodynamic Simulation of Solar Supergranulation

abstract:
  Three-dimensional magnetohydrodynamical large eddy simulations of solar
surface convection using realistic model physics is conducted. The effects of
magnetic fields on thermal structure of convective motions into radiative
layers, the range of convection cell sizes and penetration depths of convection
is investigated. We simulate a some portion of the solar photosphere and the
upper layers of the convection zone, a region extending 30 x 30 Mm horizontally
from 0 Mm down to 18 Mm below the visible surface. We solve equations of the
fully compressible radiation magnetohydrodynamics with dynamical viscosity and
gravity. For numerical simulation we use: 1)realistic initial model of Sun and
equation of state and opacities of stellar matter, 2) high order conservative
TVD scheme for solution magnetohydrodynamics, 3) diffusion approximation for
solution radiative transfer 4) calculation dynamical viscosity from subgrid
scale modelling. Simulations are conducted on horizontal uniform grid of 320 x
320 and with 144 nonuniformly spaced vertical grid points on the 128 processors
of supercomputer MBC-1500 with distributed memory multiprocessors in Russian
Academy of Sciences.


title:
Poynting Flux out of Rotating Black Hole and Accretion Flow through
  Force-Free Magnetosphere

abstract:
  The basic features of the Poynting flux from the horizon and the ergosphere
of a black hole and from the accreting flow onto a black hole are discussed for
the force-free magnetosphere. The accretion flow dominated by the Poynting flux
is discussed and the possible Poynting flux from the equatorial plane inside
the ergosphere is discussed.


title: X-ray nature of the LINER nuclear sources

abstract:
  We report the results from an homogeneous analysis of the X-ray
(Chandra-ACIS) data available for a sample of 51 LINER galaxies selected from
the catalogue by Carrillo et al. (1999) and representative of the population of
bright LINER sources. The nuclear X-ray morphology has been classified
attending to their nuclear compactness in the hard band (4.5-8.0 keV) into 2
categories: Active Galactic Nuclei (AGN) candidates (with a clearly identified
unresolved nuclear source) and Starburst (SB) candidates (without a clear
nuclear source). 60% of the total sample are classified as AGNs, with a median
luminosity of LX(2-10 keV)=2.5 x 10^(40)erg/s, which is an order of magnitude
higher than that for SB-like nuclei. The spectral fitting allows to conclude
that most of the objects need a non-negligible power-law contribution. When no
spectral fitting can be performed (data with low signal-to-noise ratio), the
Color-Color diagrams allow us to roughly estimate physical parameters such as
column density, temperature of the thermal model or spectral index for a
power-law and therefore to better constrain the origin of the X-ray emission.
All together the X-ray morphology, the spectra and the Color-Color diagrams
allow us to conclude that a high percentage of LINER galaxies, at least ~60%,
could host AGN nuclei, although contributions from High Mass X-ray Binaries or
Ultra-luminous X-ray sources cannot be ruled out for some galaxies.


title:
The Cryogenic Dark Matter Search Experiment, results from the 2004
  campaign and status of the current update

abstract:
  The CDMS II experiment uses Z-dependent Ionization Phonon (ZIP) detectors
made of Germanium and Silicon to identify nuclear recoils from Weakly
Interacting Massive Particles (WIMPs) with near complete event-by-event
rejection of various radioactive backgrounds. In 2004 CDMS II operated 6 Ge
ZIPs and 6 Si ZIPs. The 74.5 live days of operation gave after cuts 34 kg*d
exposure for the Ge ZIPs and 15 kg*d exposure for Si ZIPs. All criteria for
identifying a signal from nuclear recoil due to WIMPs were developed blind with
respect to the WIMP search data. The new 90% C.L. upper limit on the
spin-independent WIMP-nucleon cross section is 1.6e-43 cm2 from Si, for a WIMP
mass of 60 GeV/c2. The experiment has recently upgraded to 19 Ge ZIPs totaling
4.8 kg, and 11 Si ZIPs totaling 1.9 kg. The goal is to increase sensitivity
with running in 2006 and 2007 by one order of magnitude.


title:
Analysing Globular Cluster observations - Models and Analysis Tools for
  Lick/IDS indices

abstract:
  We have extended our evolutionary synthesis code, GALEV, to include Lick/IDS
absorption-line indices for both simple and composite stellar population models
(star clusters and galaxies), using the polynomial fitting functions of Worthey
et al. (1994) and Worthey & Ottaviani (1997). We present a mathematically
advanced Lick Index Analysis Tool (LINO) for the determination of ages and
metallicities of globular clusters (CGs): An extensive grid of GALEV models for
the evolution of star clusters at various metallicities over a Hubble time is
compared to observed sets of Lick indices of varying completeness and
precision. A dedicated chi^2 - minimisation procedure selects the best model
including 1-sigma uncertainties on age and metallicity. We discuss the age and
metallicity sensitivities of individual indices and show that these
sensitivities themselves depend on age and metallicity; thus, we extend
Worthey's (1994) concept of a "metallicity sensitivity parameter" for an old
stellar population at solar metallicity to younger clusters of different
metallicities. We find that indices at low metallicity are generally more age
sensitive than at high metallicity. Our aim is to provide a robust and reliable
tool for the interpretation of star cluster spectra becoming available from 10m
class telescopes in a large variety of galaxies: metal-rich & metal-poor,
starburst, post-burst, and dynamically young. We test our analysis tool using
observations from various authors for Galactic and M31 GCs, for which reliable
age and metallicity determinations are available in the literature, and discuss
in how far the observational availability of various subsets of Lick indices
affects the results. For M31 GCs, we discuss the influence of non-solar
abundance ratios on our results.


title: Cosmological acceleration from structure formation

abstract:
  We discuss the Buchert equations, which describe the average expansion of an
inhomogeneous dust universe. In the limit of small perturbations, they reduce
to the Friedmann-Robertson-Walker equations. However, when the universe is very
inhomogeneous, the behaviour can be qualitatively different from the FRW case.
In particular, the average expansion rate can accelerate even though the local
expansion rate decelerates everywhere. We clarify the physical meaning of this
paradoxical feature with a simple toy model, and demonstrate how acceleration
is intimately connected with gravitational collapse. This provides a link to
structure formation, which in turn has a preferred time around the era when
acceleration has been observed to start.


title: Population III Generated Cosmic Rays and the Production of Li6

abstract:
  We calculate the evolution of Li6 generated from cosmic rays produced by an
early population of massive stars. The computation is performed in the
framework of hierarchical structure formation and is based on cosmic star
formation histories constrained to reproduce the observed star formation rate
at redshift z \la 6, the observed chemical abundances in damped Lyman alpha
absorbers and in the intergalactic medium, and to allow for an early
reionization of the Universe at z\sim 11 by Pop III stars as indicated by the
third year results released by WMAP. We show that the pregalactic production of
the Li6 isotope in the IGM via these Pop III stars can account for the Li6
plateau observed in metal poor halo stars without additional over-production of
Li7. Our results depend on the efficiency of cosmic rays to propagate out of
minihalos and the fraction of supernovae energy deposited in cosmic rays. We
also compute the cosmic ray heating of the IGM gas. In general, we find
somewhat high temperatures (of order 10^5 K) implying that the cosmic rays
production of Li6 may be required to be confined to the so-called warm-hot IGM.


title:
Multiwavelength Observations of EXO 0748--676 -- II. Emission Line
  Behavior

abstract:
  We present optical and ultraviolet spectra, lightcurves, and Doppler
tomograms of the low-mass X-ray binary EXO 0748-676. Using an extensive set of
15 emission line tomograms, we show that, along with the usual emission from
the stream and ``hot spot'', there is extended non-axisymmetric emission from
the disk rim. Some of the emission and Halpha and beta absorption features lend
weight to the hypothesis that part of the stream overflows the disk rim and
forms a two phase medium. The data are consistent with a 1.35M_sun neutron star
with a main sequence companion and hence a mass ratio q~0.34.


title:
Novae as a Mechanism for Producing Cavities around the Progenitors of SN
  2002ic and Other SNe Ia

abstract:
  We propose that a nova shell ejected from a recurrent nova progenitor system
created the evacuated region around the explosion center of SN 2002ic. In this
picture, periodic shell ejections due to nova explosions on a white dwarf sweep
up the slow wind from the binary companion, creating density variations and
instabilities that lead to structure in the circumstellar medium (CSM). Our
model naturally explains the observed gap between the supernova explosion
center and the CSM in SN 2002ic, accounts for the density variations observed
in the CSM, and resolves the coincidence problem of the timing of the explosion
of SN 2002ic with respect to the apparent cessation of mass-loss in the
progenitor system. We also consider such nova outburst sweeping as a generic
feature of Type Ia supernovae with recurrent nova progenitors.


title: Halo assembly bias and its effects on galaxy clustering

abstract:
  The clustering of dark halos depends not only on their mass but also on their
assembly history, a dependence we term `assembly bias'. Using a galaxy
formation model grafted onto the Millennium Simulation of the LCDM cosmogony,
we study how assembly bias affects galaxy clustering. We compare the original
simulation to `shuffled' versions where the galaxy populations are randomly
swapped among halos of similar mass, thus isolating the effects of correlations
between assembly history and environment at fixed mass. Such correlations are
ignored in the halo occupation distribution models often used populate dark
matter simulations with galaxies, but they are significant in our more
realistic simulation. Assembly bias enhances 2-point correlations by 10% for
galaxies with M_bJ-5logh brighter than -17, but suppresses them by a similar
amount for galaxies brighter than -20. When such samples are split by colour,
assembly bias is 5% stronger for red galaxies and 5% weaker for blue ones. Halo
central galaxies are differently affected by assembly bias than are galaxies of
all types. It almost doubles the correlation amplitude for faint red central
galaxies. Shuffling galaxies among halos of fixed formation redshift or
concentration in addition to fixed mass produces biases which are not much
smaller than when mass alone is fixed. Assembly bias must reflect a correlation
of environment with aspects of halo assembly which are not encoded in either of
these parameters. It induces effects which could compromise precision
measurements of cosmological parameters from large galaxy surveys.


title: Gravitational polarization and the phenomenology of MOND

abstract:
  The modified Newtonian dynamics (MOND) has been proposed as an alternative to
the dark matter paradigm; the philosophy behind is that there is no dark matter
and we witness a violation of the Newtonian law of dynamics. In this article,
we interpret differently the phenomenology sustaining MOND, as resulting from
an effect of "gravitational polarization", of some cosmic fluid made of dipole
moments, aligned in the gravitational field, and representing a new form of
dark matter. We invoke an internal force, of non-gravitational origin, in order
to hold together the microscopic constituents of the dipole. The dipolar
particles are weakly influenced by the distribution of ordinary matter; they
are accelerated not by the gravitational field, but by its gradient, or tidal
gravitational field.


title:
Hard X-ray Bursts Detected by the IBIS Telescope Onboard the INTEGRAL
  Observatory in 2003-2004

abstract:
  All of the observations performed with the IBIS telescope onboard the
INTEGRAL observatory during the first one and a half years of its in-orbit
operation (from February 10, 2003, through July 2, 2004) have been analyzed to
find X-ray bursts. IBIS/ISGRI detector lightcurves total count rate in the
energy range 15-25 keV revealed 1077 bursts of durations from ~5 to ~500 s
detected with a high statistical significance (only one event over the entire
period of observations could be detected by a chance with a probability of
20%). Apart from the events associated with cosmic gamma-ray bursts (detected
in the field of view or passed through the IBIS shield), solar flares, and
activity of the soft gamma repeater SGR1806-20, we were able to localize 105
bursts and, with one exception, to identify them with previously known
persistent or transient X-ray sources (96 were identified with known X-ray
bursters). In one case, the burst source was a new burster in a low state. We
named it IGR J17364-2711. Basic parameters of the localized bursts and their
identifications are presented in the catalog of bursts. Curiously enough, 61
bursts were detected from one X-ray burster - GX 354-0. The statistical
distributions of bursts in duration, maximum flux, and recurrence time have
been analyzed for this source. Some of the bursts observed with the IBIS/ISGRI
telescope were also detected by the JEM-X telescope onboard the INTEGRAL
observatory in the standard X-ray energy range 3-20 keV.


title:
A Spitzer Infrared Spectrograph (IRS) Spectral Sequence of M, L, and T
  Dwarfs

abstract:
  We present a low-resolution (R = 90), 5.5-38 micron spectral sequence of a
sample of M, L, and T dwarfs obtained with the Infrared Spectrograph (IRS)
onboard the Spitzer Space Telescope. The spectra exhibit prominent absorption
bands of H_2O at 6.27 microns, CH_4 at 7.65 microns, and NH_3 at 10.5 microns
and are relatively featureless at lambda > 15 microns. Three spectral indices
that measure the strengths of these bands are presented; H_2O absorption
features are present throughout the MLT sequence while the CH_4 and NH_3 bands
first appear at roughly the L/T transition. Although the spectra are, in
general, qualitatively well matched by synthetic spectra that include the
formation of spatially homogeneous silicate and iron condensate clouds, the
spectra of the mid-type L dwarfs show an unexpected flattening from roughly 9
to 11 microns. We hypothesize that this may be a result of a population of
small silicate grains that are not predicted in the cloud models. The spectrum
of the peculiar T6 dwarf 2MASS J0937+2931 is suppressed from 5.5-7.5 microns
relative to typical T6 dwarfs and may be a consequence of its mildly
metal-poor/high surface gravity atmosphere. Finally, we compute bolometric
luminosities of a subsample of the M, L, and T dwarfs by combining the IRS
spectra with previously published 0.6-4.1 micron spectra and find good
agreement with the values of Golimowski et al. who use L'- and M'-band
photometry and to account for the flux emitted at lambda > 2.5 microns.


title:
The Araucaria Project. VLT spectra of blue supergiants in WLM:
  classification and first abundances

abstract:
  As part of the Araucaria Project, we present the first spectral catalog of
supergiant stars in the Local Group dwarf irregular galaxy WLM. In assigning a
spectral classification to these stars we accounted for the low metal content
of WLM relative to the galactic standards used in the MK process, by using
classification criteria developed for B and A supergiants contained in the
Small Magellanic Cloud. Our spectral catalog shows that our higher S/N
spectroscopic sample of 19 objects contains at least 6 early-B (B0-B5)
supergiants and 6 late-B and early-A (B8-A2) stars of luminosity class between
Ia and II, as well as an O7~V star and an O9.7 Ia star. The spectra of several
of these stars is of sufficiently high quality for a determination of the
stellar parameters and abundances. We have acquired also a second set of lower
S/N spectra for mostly BA stars, however their quality does not allow a further
analysis. We have carried out a quantitative analysis for three early-B
supergiants. The mean oxygen abundance we derive is 12+log(O/H)=7.83 +/- 0.12.
This value agrees very well with the measurement that is obtained from HII
regions. We therefore find no additional evidence for the discrepancy between
stellar and nebular oxygen abundances measured for a single A-type supergiant
by Venn et al. The analysis of B- and A-type supergiants yields compatible
results for nitrogen, silicon and magnesium. We show that the photometric
variability of the blue supergiants included in our spectroscopic sample is
negligible for the use of these stars as distance indicators.


title:
Synchrotron emission in small scale magnetic field as possible
  explanation for prompt emission spectra of gamma-ray bursts

abstract:
  Synchrotron emission is believed to be a major radiation mechanism during
gamma-ray bursts' (GRBs) prompt emission phase. A significant drawback of this
assumption is that the theoretical predicted spectrum, calculated within the
framework of the ``internal shocks'' scenario using the standard assumption
that the magnetic field maintains a steady value throughout the shocked region,
leads to a slope F_\nu \propto \nu^{-1/2} below 100 keV, which is in
contradiction to the much harder spectra observed. This is due to the electrons
cooling time being much shorter than the dynamical time. In order to overcome
this problem, we propose here that the magnetic field created by the internal
shocks decays on a length scale much shorter than the comoving width of the
plasma. We show that under this assumption synchrotron radiation can reproduce
the observed prompt emission spectra of the majority of the bursts. We
calculate the required decay length of the magnetic field, and find it to be
\~10^4 - 10^5 cm (equivalent to 10^5 - 10^6 skin depths), much shorter than the
characteristic comoving width of the plasma, ~3*10^{9} cm. We implement our
model to the case of GRB050820A, where a break at <~ 4 keV was observed, and
show that this break can be explained by synchrotron self absorption. We
discuss the consequences of the small scale magnetic field scenario on current
models of magnetic field generation in shock waves.


title: The star formation history of luminous infrared galaxies

abstract:
  We constrain the past star formation histories of a sample of 25 distant
(z~0.7) luminous infrared galaxies (LIRGs) detected with the mid infrared
cameras ISOCAM and MIPS onboard the ISO and Spitzer satellites.
  We use high resolution VLT-FORS2 spectroscopy in addition to a comprehensive
library of 200,000 model optical spectra to derive Bayesian likelihood
estimates of the star formation histories of these galaxies based on the
analysis of Balmer absorption lines and the 4000 A break.
  The locus of distant LIRGs in the diagram defined by Hdelta_A and D4000 is
roughly comparable to that of local LIRGs observed with IRAS, suggesting that
no trend for an evolution is detected between the local and distant LIRGs. We
obtain similar results when using either the H8 or the H$\delta_A$ Balmer
absorption-line indices in combination with D4000.
  We compute a birthrate parameter (b=SFR/<SFR>) of 4\pm1, confirming that the
distant LIRGs are currently experiencing a major phase of star formation. The
most likely duration of the bursts is 0.10 Gyr, during which the LIRGs produce
5-10 % of their current stellar mass. No evidence is found for successive
starbursts on the scale of a few times $10^7$ yr, such as those predicted by
some numerical simulations of major mergers. However, the large number density
of those galaxies suggest that they could experience between two and four LIRG
phases until the present epoch.


title: Diffraction-Based Sensitivity Analysis of Apodized Pupil Mapping Systems

abstract:
  Pupil mapping is a promising and unconventional new method for high contrast
imaging being considered for terrestrial exoplanet searches. It employs two (or
more) specially designed aspheric mirrors to create a high-contrast amplitude
profile across the telescope pupil that does not appreciably attenuate
amplitude. As such, it reaps significant benefits in light collecting
efficiency and inner working angle, both critical parameters for terrestrial
planet detection. While much has been published on various aspects of pupil
mapping systems, the problem of sensitivity to wavefront aberrations remains an
open question. In this paper, we present an efficient method for computing the
sensitivity of a pupil mapped system to Zernike aberrations. We then use this
method to study the sensitivity of a particular pupil mapping system and
compare it to the concentric-ring shaped pupil coronagraph. In particular, we
quantify how contrast and inner working angle degrade with increasing Zernike
order and rms amplitude. These results have obvious ramifications for the
stability requirements and overall design of a planet-finding observatory.


title:
A comprehensive asteroseismic modelling of the high-amplitude delta
  Scuti star RV Arietis

abstract:
  We present a comprehensive asteroseismic study of the double-mode
high-amplitude delta Scuti star HD 187642 (RV Arietis). The modelling includes
some of the most recent techniques: 1) effects of rotation on both equilibrium
models and adiabatic oscillation spectrum, 2) non-adiabatic study of radial and
non-radial modes, 3) relationship between the fundamental radial mode and the
first overtone in the framework of Petersen diagrams. The analysis reveals that
two of the observed frequencies are very probably identified as the fundamental
and first overtone radial modes. Analysis of the colour index variations,
together with theoretical non-adiabatic calculations, points to models in the
range of [7065,7245] K in effective temperature and of [1190, 1270] Myr in
stellar age. These values were found to be compatible with those obtained using
the three other asteroseismic techniques.


title:
Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star
  IRC+10216

abstract:
  In this paper we study the oxygen chemistry in the C-rich circumstellar
shells of IRC+10216. The recent discoveries of oxygen bearing species (water,
hydroxyl radical and formaldehyde) toward this source challenge our current
understanding of the chemistry in C-rich circumstellar envelopes. The presence
of icy comets surrounding the star or catalysis on iron grain surfaces have
been invoked to explain the presence of such unexpected species. This detailed
study aims at evaluating the chances of producing O-bearing species in the
C-rich circumstellar envelope only by gas phase chemical reactions. For the
inner hot envelope, it is shown that although most of the oxygen is locked in
CO near the photosphere (as expected for a C/O ratio greater than 1), some
stellar radii far away species such as H2O and CO2 have large abundances under
the assumption of thermochemical equilibrium. It is also shown how non-LTE
chemistry makes very difficult the CO-->H2O,CO2 transformation predicted in
LTE. Concerning the chemistry in the outer and colder envelope, we show that
formaldehyde can be formed through gas phase reactions. However, in order to
form water vapor it is necessary to include a radiative association between
atomic oxygen and molecular hydrogen with a quite high rate constant. The
chemical models explain the presence of HCO+ and predict the existence of SO
and H2CS (which has been detected in a 3 mm line survey to be published). We
have modeled the line profiles of H2CO, H2O, HCO+, SO and H2CS using a
non-local radiative transfer model and the abundance profiles predicted by our
chemical model. The results have been compared to the observations and
discussed.


title:
On the Iron content of NGC 1978 in the LMC: a metal rich, chemically
  homogeneous cluster

abstract:
  We present a detailed abundance analysis of giant stars in NGC 1978, a
massive, intermediate-age stellar cluster in the Large Magellanic Cloud,
characterized by a high ellipticity and suspected to have a metallicity spread.
We analyzed 11 giants, all cluster members, by using high resolution spectra
acquired with the UVES/FLAMES spectrograph at the ESO-Very Large Telescope. We
find an iron content of [Fe/H]=-0.38 dex with very low (0.07 dex) dispersion,
and a mean heliocentric radial velocity Vr=293.1 (with an error of 0.9 km/s)
and a velocity dispersion (3.1 km/s), thus excluding the presence of a
significant metallicity, as well as velocity, spread within the cluster.


title: The Sun's Interior Metallicity Constrained by Neutrinos

abstract:
  Observed solar neutrino fluxes are employed to constrain the interior
composition of the Sun. Including the effects of neutrino flavor mixing, the
results from Homestake, Sudbury, and Gallium experiments constrain the Mg, Si,
and Fe abundances in the solar interior to be within a factor 0.89 to 1.34 of
the surface values with 68% confidence. If the O and/or Ne abundances are
increased in the interior to resolve helioseismic discrepancies with recent
standard solar models, then the nominal interior Mg, Si, and Fe abundances are
constrained to a range of 0.83 to 1.24 relative to the surface. Additional
research is needed to determine whether the Sun's interior is metal poor
relative to its surface.


title:
Dynamical Formation of the Dark Molecular Hydrogen Clouds around Diffuse
  HII Regions

abstract:
  We examine the triggering process of molecular cloud formation around diffuse
HII regions. We calculate the time evolution of the shell as well as of the HII
region in a two-phase neutral medium, solving the UV and FUV radiative
transfer, the thermal and chemical processes in the time-dependent
hydrodynamics code. In the cold neutral medium, the ambient gas is swept up in
the cold (T \sim 30-40K) and dense (n \sim 10^3 cm^-3) shell around the HII
region. In the shell, H_2 molecules are formed from the swept-up HI gas, but CO
molecules are hardly formed. The reformation of H_2 molecules is more efficient
with a higher-mass central star. The physical and chemical properties of gas in
the shell are just intermediate between those of the neutral medium and
molecular clouds observed by the CO emission. The dense shell with cold HI/H_2
gas easily becomes gravitationally unstable, and breaks up into small clouds.
The cooling layer just behind the shock front also suffers from thermal
instability, and will fragment into cloudlets with some translational motions.
We suggest that the predicted cold ``dark'' HI/H_2 gas should be detected as
the HI self-absorption (HISA) feature. We have sought such features in recent
observational data, and found shell-like HISA features around the giant HII
regions, W4 and W5. The shell-like HISA feature shows good spatial correlation
with dust emission, but poor correlation with CO emission. Our quantitative
analysis shows that the HISA cloud can be as cold as T \sim a few x 10K.
(abridged)


title:
Polarisation measurements with a CdTe pixel array detector for Laue hard
  X-ray focusing telescopes

abstract:
  Polarimetry is an area of high energy astrophysics which is still relatively
unexplored, even though it is recognized that this type of measurement could
drastically increase our knowledge of the physics and geometry of high energy
sources. For this reason, in the context of the design of a Gamma-Ray Imager
based on new hard-X and soft gamma ray focusing optics for the next ESA Cosmic
Vision call for proposals (Cosmic Vision 2015-2025), it is important that this
capability should be implemented in the principal on-board instrumentation. For
the particular case of wide band-pass Laue optics we propose a focal plane
based on a thick pixelated CdTe detector operating with high efficiency between
60-600 keV. The high segmentation of this type of detector (1-2 mm pixel size)
and the good energy resolution (a few keV FWHM at 500 keV) will allow high
sensitivity polarisation measurements (a few % for a 10 mCrab source in 106s)
to be performed. We have evaluated the modulation Q factors and minimum
detectable polarisation through the use of Monte Carlo simulations (based on
the GEANT 4 toolkit) for on and off-axis sources with power law emission
spectra using the point spread function of a Laue lens in a feasible
configuration.


title:
CCD photometry and visual observations of V1663 Aquilae (Nova Aquilae
  2005)

abstract:
  We present CCD V and I band photometry and visual observations of V1663
Aquilae (Nova Aquilae 2005). This was a classical fast nova, probably of type
Ba, observed for the first time on 2005 June 9. Maximum light occurred at HJD=
2453531.2 +/- 0.2, when the apparent V magnitude was 10.7 +/- 0.1 and the V-I
colour index 3.1. Decline times were t2,V= 17d, t2,I= 18d, t3,V= 32d and t3,I=
35d. We derived a maximum absolute V magnitude of -7.8 +/- 0.2, colour excess
E(B-V)= 2, extinction AV= 6 magnitudes and distance d= 2.9 +/- 0.4 kpc. After
maximum the V-I colour index remained between 3.1 and 3.4 for 50 days, then
gradually reduced as the nova became bluer with increasing age. We saw no
direct evidence of dust emission although this could have contributed to the
high extinction in the direction of the nova.


title:
Cosmological Simulations of Intergalactic Medium Enrichment from
  Galactic Outflows

abstract:
  We investigate models of self-consistent chemical enrichment of the
intergalactic medium (IGM) from z=6 to 1.5, based on hydrodynamic simulations
of structure formation that incorporate galactic outflows. Our main result is
that outflow parameterizations based on momentum-driven winds as seen in local
starburst galaxies provide the best agreement with observations of CIV
absorption at z~2-5. Such models sufficiently enrich the high-z IGM to produce
a global mass density of CIV absorbers that is relatively invariant from z=5.5
to 1.5, in agreement with observations. This occurs despite an increase in the
volume-averaged metallicity by x5-10 over this redshift range, because energy
input from outflows causes a drop in the global ionization fraction of CIV.
Comparisons to observed CIV column density and linewidth distributions and
CIV-based pixel optical depth ratios provide significant constraints on wind
models. Our best-fitting models show mean IGM temperatures only slightly above
our no-outflow case, metal filling factors of just a few % with volume-weighted
metallicities around 0.001 at z~3, significant amounts of collisionally-ionized
CIV absorption, and a metallicity-density relationship that rises rapidly at
low overdensities and flattens at higher ones. In general, we find that outflow
speeds must be high enough to enrich the low-density IGM at early times but low
enough not to overheat it, and concurrently must significantly suppress early
star formation while still producing enough early metals. It is therefore
non-trivial that locally-calibrated momentum-driven wind scenarios naturally
yield the desired strength and evolution of outflows, and suggest that such
models represent a significant step towards understanding the impact of
galactic outflows on galaxies and the IGM across cosmic time.


title:
Feedback-Driven Evolution of the Far-Infrared Spectral Energy
  Distributions of Luminous and Ultraluminous Infrared Galaxies

abstract:
  We calculate infrared spectral energy distributions (SEDs) from simulations
of major galaxy mergers and study the effect of AGN and starburst driven
feedback on the evolution of the SED as a function of time. We use a
self-consistent three-dimensional radiative equilibrium code to calculate the
emergent SEDs and to make images. To facilitate a simple description of our
findings, we describe our results in reference to an approximate analytic
solution for the far-IR SED. We focus mainly on the luminous infrared galaxy
(LIRG) and ultraluminous infrared galaxy (ULIRG) phases of evolution. We
contrast the SEDs of simulations performed with AGN feedback to simulations
performed with starburst driven wind feedback. We find that the feedback
processes critically determine the evolution of the SED. Changing the source of
illumination (whether stellar or AGN) has virtually no impact on the
reprocessed far-infrared SED. We find that AGN feedback is particularly
effective at dispersing gas and rapidly injecting energy into the ISM. The
observational signature of such powerful feedback is a warm SED. In general,
simulations performed with starburst driven winds have colder spectra and
reprocess more of their emission into the infrared, resulting in higher
infrared to bolometric luminosities compared to (otherwise equivalent)
simulations performed with AGN feedback. We depict our results in IRAS bands,
as well as in Spitzer's MIPS bands, and in Herschel's PACS bands.


title: Are Red Tidal Features Unequivocal Signatures of Major Dry Mergers?

abstract:
  We use a cosmological numerical simulation to study the tidal features
produced by a minor merger with an elliptical galaxy. We find that the
simulated tidal features are quantitatively similar to the red tidal features,
i.e., dry tidal features, recently found in deep images of elliptical galaxies
at intermediate redshifts. The minor merger in our simulation does not trigger
star formation due to active galactic nuclei heating. Therefore, both the tidal
features and the host galaxy are red, i.e. a dry minor merger. The stellar mass
of the infalling satellite galaxy is about 10^10 Msun, and the tidal debris
reach the surface brightness of mu_R~27 mag arcsec^-2. Thus, we conclude that
tidal debris from minor mergers can explain the observed dry tidal features in
ellipticals at intermediate redshifts, although other mechanisms (such as major
dry mergers) may also be important.


title:
Viewing the Evolution of Massive Star Formation through FIR/Sub-mm/mm
  Eyes

abstract:
  In this paper, we present an overview of our method of constructing a family
of models for the far-infrared, sub-millimeter, and millimeter (FIR/sub-mm/mm)
line emission of molecular and atomic gas surrounding massive star formation in
starburst galaxies. We show the results of a case study, an expanding
supershell centered around a massive star cluster with a particular set of
input parameters and its application to nearby starburst galaxy M 82. This set
of models can be used not only to interpret the observations of FIR/sub-mm/mm
line emission from molecular and atomic gas, but also to investigate the
physical environment and the initial cloud conditions in massive star forming
regions as well as the ages of the starbursts through simulations for a wide
range of input parameters. Finally, we discuss limitations of our models, and
outline future work.


title: Toroidal Atmospheres around Extrasolar Planets

abstract:
  Jupiter and Saturn have extended, nearly toroidal atmospheres composed of
material ejected from their moons or rings. Here we suggest that similar
atmospheres must exist around giant extrasolar planets and might be observable
in a transit of the parent star. Observation of such an atmosphere would be a
marker for the presence of orbiting debris in the form of rings or moons that
might otherwise be too small to be detected.


title:
A New Probe of Dense Gas at High Redshift: Detection of HCO+(5-4) Line
  Emission in APM 08279+5255

abstract:
  We report the detection of HCO+(5-4) emission from the Broad Absorption Line
(BAL) quasar APM08279+5255 at z=3.911 based on observations conducted at the
IRAM Plateau de Bure interferometer. This represents the first detection of
this molecular ion at such a high redshift. The inferred line luminosity,
uncorrected for lensing, is L'(HCO+)=(3.5+-0.6)x10^10 Kkms^-1pc^2. The HCO+
J=5-4 source position coincides within the errors with that reported from
previous HCN J=5-4 and high-J CO line observations of this quasar. The HCO+
line profile central velocity and width are consistent with those derived from
HCN. This result suggests that HCO+(5-4) emission comes roughly from the same
circumnuclear region probed by HCN. However, the HCN(5-4)/HCO+(5-4) intensity
ratio measured in APM08279+5255 is significantly larger than that predicted by
simple radiative transfer models, which assume collisional excitation and equal
molecular abundances. This could imply that the [HCN]/[HCO^+] abundance ratio
is particularly large in this source, or that the J=5 rotational levels are
predominantly excited by IR fluorescent radiation.


title: Orbital Parameters for the X-ray Pulsar IGR J16393-4643

abstract:
  With recent and archival Rossi X-Ray Timing Explorer (RXTE) X-ray
measurements of the heavily obscured X-ray pulsar IGR J16393-4643, we carried
out a pulse timing analysis to determine the orbital parameters. Assuming a
circular orbit, we phase-connected data spanning over 1.5 years. The most
likely orbital solution has a projected semi-major axis of 43 +- 2 lt-s and an
orbital period of 3.6875 +- 0.0006 days. This implies a mass function of 6.5 +-
1.1 M_sun and confirms that this INTEGRAL source is a High Mass X-ray Binary
(HMXB) system. By including eccentricity in the orbital model, we find e < 0.25
at the 2 sigma level. The 3.7 day orbital period and the previously known ~910
s pulse period place the system in the region of the Corbet diagram populated
by supergiant wind accretors, and the low eccentricity is also consistent with
this type of system. Finally, it should be noted that although the 3.7 day
solution is the most likely one, we cannot completely rule out two other
solutions with orbital periods of 50.2 and 8.1 days.


title: CS 30322-023: an ultra metal-poor TP-AGB star?

abstract:
  With [Fe/H] = -3.5, CS 30322-023 is the most metal-poor star to exhibit a
clear s-process signature and the most metal-poor ``lead star'' known. CS
30322-023 is also remarkable in having the lowest surface gravity (log g <=
-0.3) among the metal-poor stars studied to date. The available evidence
indicates that this star is presently a thermally-pulsing asymptotic giant
branch (TP-AGB) star, with no strong indication of binarity thus far (although
a signal of period 192 d is clearly present in the radial-velocity data, this
is likely due to pulsation of the stellar envelope). We show that low-mass
TP-AGB stars are not expected to be exceedingly rare in a magnitude-limited
sample such as the HK survey, because their high luminosities make it possible
to sample them over a very large volume. The strong N overabundance and the low
12C/13C ratio (4) in this star is typical of the operation of the CN cycle.
Coupled with a Na overabundance and the absence of a strong C overabundance,
this pattern seems to imply that hot-bottom burning operated in this star,
which should then have a mass of at least 2 Msun. However, the luminosity
associated with this mass would put the star at a distance of about 50 kpc, in
the outskirts of the galactic halo. We explore alternative scenarios in which
the observed abundance pattern results from some mixing mechanism yet to be
identified occurring in a single low-metallicity 0.8 Msun AGB star, or from
pollution by matter from an intermediate-mass AGB companion which has undergone
hot-bottom burning. We stress, however, that our abundances may be subject to
uncertainties due to NLTE or 3D granulation effects which were not taken into
consideration.


title: Pulsation of the Lambda Bootis star HD 210111

abstract:
  CONTEXT. The Lambda Bootis stars are a small spectroscopic subgroup of
Population I A-type stars and show significant underabundances of metals. Many
are Delta Scuti pulsators.
  AIMS. HD 210111 was selected for a detailed multisite pulsation study to
determine whether its pulsation properties differ from those of normal A stars.
  METHODS. 262 hours of high-precision photometry were obtained at the SAAO and
SSO observatories.
  RESULTS. 13 statistically significant pulsation frequencies were detected
with very small photometric amplitudes from 1 to 7 millimag in the visual. A
comparison with earlier 1994 measurements indicates a small increase in
amplitude. As a byproduct, one of the comparison stars, HD 210571, was
discovered to be a millimag variable with a frequency of 1.235 c/d and is
probably a new Gamma Doradus variable. The observed wide range of excited
frequencies from 12 to 30 c/d in HD 210111 can be explained with both the
single- and double-star hypothesis. HD 210111 is in a similar evolutionary
status to FG Vir, which also shows a wide range of excited frequencies with a
similar frequency spacing near 4 c/d. This is interpreted as successive radial
orders of the excited nonradial modes. In the double-star hypothesis previously
evoked for HD 210111, the low and the high frequencies originate in different
stars: here HD 210111 would resemble Theta^2 Tau.
  CONCLUSIONS. The pulsation of the Lambda Bootis star HD 210111 does not
differ from that of normal Delta Scuti stars.


title: An I-band calibration of the SBF method at blue colours

abstract:
  The surface brightness fluctuation (SBF) method is a powerful tool to derive
distances to galaxies for which single stars cannot be resolved. Up to now, the
method has been calibrated mainly at red colours due to the intrinsic faintness
of blue early-type galaxies. In this paper we address the I-band calibration of
the SBF method at blue colours, the regime of dwarf elliptical galaxies (dEs).
We present deep and wide-field VI photometry of the central Fornax cluster
obtained at Las Campanas Observatory. With these data we perform an SBF
analysis of 25 dEs in the range -16.5<M_V<-11.2 mag, 0.8<(V-I)_0<1.10 mag. For
the calibration analysis we exclude eight dEs whose SBF measurement was
affected by poor seeing (FWHM ~ 1"). Our SBF data are inconsistent at the 3
sigma level with a colour independent absolute SBF magnitude Mbar_I, presenting
a problem for SBF models that predict such a flat relation. There is a weak
indication in our data (1.8 sigma) to favour a two-branch calibration over a
one-branch calibration with broad scatter in the Mbar_I - (V-I) plane. We
obtain the following one-branch empirical SBF calibration:
  Mbar_I=-2.13 (+/- 0.17) + 2.44 (+/- 1.94) * [(V-I)_0 - 1.00] mag.
  We deduce a 0.34 +/- 0.14 mag cosmic scatter of Mbar_I, which is
significantly larger than found at redder colours. This is in agreement with
those theoretical SBF models that predict Mbar_I to be more sensitive to
age-metallicity variations in the blue than in the red. We find evidence that
the fainter galaxies in our samples contain younger and more metal-rich stellar
populations than the brighter ones. The application of our empirical
calibration to published SBF measurements of Hydra and Centaurus cluster dEs
leaves the distances to both clusters unchanged.


title: The Galactic thick and thin disks: differences in evolution

abstract:
  Recent observations demonstrate that the thin and thick disks of the Galaxy
have different chemical abundance trends and evolution timescales. The relative
abundances of $\alpha$-elements in the thick Galactic disk are increased
relative to the thin disk. Our goal is to investigate the cause of such
differences in thick and thin disk abundances. We investigate the chemical
evolution of the Galactic disk in the framework of the open two-zone model with
gas inflow. The Galactic abundance trends for $\alpha$-elements (Mg, Si, O) and
Fe are predicted for the thin and thick Galactic disks. The star formation
histories of the thin and thick disks must have been different and the gas
infall must have been more intense during the thick disk evolution that the
thin disk evolution.


title: An equatorial wind from the massive young stellar object S140 IRS 1

abstract:
  The discovery of the second equatorial ionized stellar wind from a massive
young stellar object is reported. High resolution radio continuum maps of S140
IRS 1 reveal a highly elongated source that is perpendicular to the larger
scale bipolar molecular outflow. This picture is confirmed by location of a
small scale monopolar near-IR reflection nebula at the base of the blueshifted
lobe. A second epoch of observations over a five year baseline show little
ordered outward proper motion of clumps as would have been expected for a jet.
A third epoch, taken only 50 days after the second, did show significant
changes in the radio morphology. These radio properties can all be understood
in the context of an equatorial wind driven by radiation pressure from the
central star and inner disc acting on the gas in the surface layers of the disc
as proposed by Drew et al. (1998). This equatorial wind system is briefly
compared with the one in S106IR, and contrasted with other massive young
stellar objects that drive ionized jets.


title: TeV lightcurve of PSR B1259-63/SS2883

abstract:
  The inverse Compton scattering of ultrarelativistic electrons accelerated at
the pulsar wind termination shock is believed to be responsible for TeV
gamma-ray signal recently reported from the binary system PSR B1259-63/SS2883.
While this process can explain the energy spectrum of the observed TeV
emission, the detected gamma-ray fluxes do not agree with the published
theoretical predictions of the TeV lightcurve. The main objective of this paper
is to show that the HESS results can be explained, under certain reasonable
assumptions, by inverse Compton scenarios of gamma-ray production in the
system. In this paper we study evolution of the energy spectra of relativistic
electrons under different assumptions about the acceleration and energy-loss
rates of electrons, and the impact of these processes on the lightcurve of IC
gamma-rays. We demonstrate that the observed TeV lightcurve can be explained
(i) by adiabatic losses which dominate over the entire trajectory of the pulsar
with a significant increase towards the periastron, or (ii) by the sub-TeV
cutoffs in the energy spectra of electrons due to the enhanced rate of Compton
losses close to the periastron. The Compton deceleration of the pulsar wind
contributes to the decrease of the nonthermal power released in the accelerated
electrons, and thus to the reduction of the IC and synchrotron components of
radiation close to the periastron. Although this effect alone cannot explain
the observed lightcurves, the Comptonization of the pulsar wind leads to the
formation of gamma-radiation with a line-type energy spectrum. While the HESS
data already constrain the Lorentz factor of the wind, $\Gamma \le 10^6$,
future observations of this object with GLAST should allow a deep probe of the
wind Lorentz factor in the range between $10^4$ and $10^6$.


title: Mass-loss properties of S-stars on the AGB

abstract:
  We have used a detailed non-LTE radiative transfer code to model new APEX
CO(J=3-2) data, and existing CO radio line data, on a sample of 40 AGB S-stars.
The derived mass-loss-rate distribution has a median value of 2E-7 Msun/yr, and
resembles values obtained for similar samples of M-stars and carbon stars.
Possibly, there is a scarcity of high-mass-loss-rate (>=1E-5 Msun/yr) S-stars.
The distribution of envelope gas expansion velocities is similar to that of the
M-stars, the median is 7.5 km/s, while the carbon stars, in general, have
higher gas expansion velocities. The mass-loss rate correlates well with the
gas expansion velocity, in accordance with results for M-stars and carbon
stars.


title:
Stellar polytropes and Navarro-Frenk-White halo models: comparison with
  observations

abstract:
  Motivated by the possible conflict between the Navarro-Frenk-White(NFW) model
predictions for the dark matter contents of galactic systems and its
correlation with baryonic surface density, we will explore an alternative
paradigm for the description of dark matter halos. Such an alternative emerges
from Tsallis' non-extensive thermodynamics applied to self-gravitating systems
and leads to the so-called ``stellar polytrope'' (SP) model. We consider that
this could be a better approach to real structures rather than the isothermal
model, given the fact that the first one takes into account the non-extensivity
of energy and entropy present in these type of systems characterized by
long-range interactions. We compare a halo based on the Navarro-Frenk-White
(NFW) and one which follows the SP description. Analyzing the dark matter
contents estimated by means of global physical parameters of galactic disks,
obtained from a sample of actual galaxies, with the ones of the unobserved dark
matter halos, we conclude that the SP model is favored over the NFW model in
such a comparison.


title:
alpha-element enhanced opacity tables and low-mass metal-rich stellar
  models

abstract:
  We investigate the influence of both a new generation of low-temperature
opacities and of various amounts of alpha-element enhancements on stellar
evolution models. New stellar models with two different alpha-element mixtures
and two sets of appropriate opacity tables are computed and compared. The
influence of the different mixtures as well as that of the improved generation
of opacity tables is investigated. It is found that around solar metallicity
the new opacity tables have a drastic influence on stellar temperatures, which
is mainly an effect of the new low-temperature tables, and not of variations in
alpha-element enhancement factors. The latter, however, influence stellar
lifetimes via systematic opacity effects at core temperatures. We trace the
reason for the low-temperature table changes to errors in the old tables. We
conclude that variations in alpha-element abundance ratios affect the
main-sequence properties of super-solar metallicity stars significantly. Red
giant branch effective temperatures depend only slightly on the specific
mixture. Our older low-temperature opacity tables were shown to be erroneous
and should no longer be used for stellar models with near- or super-solar
metallicity. Corrected tables have already been produced.


title: Revealing the environs of the remarkable southern hot core G327.3-0.6

abstract:
  We present a submm study of the massive hot core G327.3-0.6 that constrains
its physical parameters and environment. The APEX telescope was used to image
CO and N2H+ emission, to observe lines from other molecules toward a hot and a
cold molecular core, and to measure the continuum flux density of the hot core.
In the C18O J=3-2 line, two clumps were found, one associated with the HII
region G327.3-0.5 and the other associated with the hot core. An additional
cold clump is found 30 arcsec (0.4 pc) northeast of the hot core in bright N2H+
emission. From the the continuum data, we calculate a mass of 420 Msol and a
size of 0.1 pc for the hot core. A new, more accurate position of the hot core
is reported, which allows the association of the core with a bright
mid-infrared source. The luminosity of the hot core is estimated to be between
5 and 15 10^4 Lsol. This study revealed several different evolutionary stages
of massive star formation in the G327.3-0.6 region.


title: Mid- and high-J CO observations towards UCHIIs

abstract:
  A study of 12 ultracompact HII regions was conducted to probe the physical
conditions and kinematics in the inner envelopes of the molecular clumps
harboring them. The APEX telescope was used to observe the sources in the CO
(4-3) and 13CO (8-7) lines. Line intensities were modeled with the RATRAN
radiative transfer code using power laws for the density and temperature to
describe the physical structure of the clumps. All sources were detected in
both lines. The optically thick CO (4-3) line shows predominantly blue skewed
profiles reminiscent of infall. Line intensities can be reproduced well using
the physical structure of the clumps taken from the literature. The optically
thick line profiles show that CO is a sensitive tracer of ongoing infall in the
outer envelopes of clumps harboring ultracompact HII regions and hot molecular
cores.


title: The Star Formation History of the Disk of the Starburst galaxy M82

abstract:
  Spectroscopic, photometric and dynamical data of the inner 3 kpc part of the
starburst galaxy M82 are analyzed in order to investigate the star formation
history of the stellar disk. The long-slit spectra along the major axis are
dominated by Balmer absorption lines in the region outside the nuclear
starburst all the way up to ~3.5 scalelengths (mu_B=22 mag/arcsec**2). Single
Stellar Population (SSP) spectra of age 0.4-1.0 Gyr match well the observed
spectra in the 1-3 kpc zone, with a mean age of the stellar population
marginally higher in the outer parts. The mass in these populations, along with
that in the gas component, make up for the inferred dynamical mass in the same
annular zone for a Kroupa initial mass function, with a low mass cut-off
m_l=0.4 Msun. The observed ratio of the abundances of alpha elements with
respect to Fe, is also consistent with the idea that almost all the stars in
M82 disk formed in a burst of short duration (0.3 Gyr) around 0.8 Gyr ago. We
find that the optical/near infrared colors and their gradients in the disk are
determined by the reddening with visual extinction exceeding 1 mag even in the
outer parts of the disk, where there is apparently no current star formation.
The disk-wide starburst activity was most likely triggered by the interaction
of M82 with its massive neighbor M81 around 1~Gyr ago. The properties of the
disk of M82 very much resemble the properties of the disks of luminous compact
blue galaxies seen at 0.2-1.0 redshift.


title:
A Keck/HIRES Doppler Search for Planets Orbiting Metal-Poor Dwarfs. I.
  Testing Giant Planet Formation and Migration Scenarios

abstract:
  We describe a high-precision Doppler search for giant planets orbiting a
well-defined sample of metal-poor dwarfs in the field. This experiment
constitutes a fundamental test of theoretical predictions which will help
discriminate between proposed giant planet formation and migration models. We
present here details on the survey as well as an overall assessment of the
quality of our measurements, making use of the results for the stars that show
no significant velocity variation.


title: Hot Molecular Gas in the Nuclear Region of IC 342

abstract:
  We present the first interferometric detection of extragalactic NH_3(6,6)
emission in the nearby galaxy IC 342 made using the VLA. The data have a
resolution of 7.8''x 5.0'' and trace hot (T ~ 412 K) and dense (> 10^{4}
cm^{-3}) molecular gas. We have covered a 170''x 300'' area, and detect two
very strong line emission peaks, likely associated with the two strongest star
formation regions of the central part of the galaxy. We compare these emission
peaks to CO (1-0) and (2-1) emission data, which are the most abundant CO
transitions and trace spatially extended emission. The NH_3(6,6) emission is
also compared to emission data from three high-density, nitrogen bearing
tracers: HNC(1-0), HC_3N(10-9) and N_2H^{+}. Our results suggest that the
molecular mass in the nuclear region of IC 342 has at least two different
components, a dense and cold component and a less dense and hotter component.


title:
Cosmological puzzle resolved by stellar feedback in high redshift
  galaxies

abstract:
  The standard cosmological model, now strongly constrained by direct
observation at early epochs, is very successful in describing the structure of
the evolved universe on large and intermediate scales. Unfortunately, serious
contradictions remain on smaller, galactic scales. Among the major small-scale
problems is a significant and persistent discrepancy between observations of
nearby galaxies, which imply that galactic dark matter (DM) haloes have a
density profile with a flat core, and the cosmological model, which predicts
that the haloes should have divergent density (a cusp) at the centre. Here we
use numerical N-body simulations to show that random bulk motions of gas in
small primordial galaxies, of the magnitude expected in these systems, result
in a flattening of the central DM cusp on short timescales (of order 10^8
years). Gas bulk motions in early galaxies are driven by supernova explosions
which result from ongoing star formation. Our mechanism is general and would
have operated in all star-forming galaxies at redshifts z>~ 10. Once removed,
the cusp cannot be reintroduced during the subsequent mergers involved in the
build-up of larger galaxies. As a consequence, in the present universe both
small and large galaxies would have flat DM core density profiles, in agreement
with observations.


title: An Atlas of STIS-HST Spectra of Seyfert Galaxies

abstract:
  We present a compilation of spectra of 101 Seyfert galaxies obtained with the
Space Telescope Imaging Spectrograph (HST-STIS), covering the UV and/or optical
spectral range. Information on all the available spectra have been collected in
a Mastertable, which is a very useful tool for anyone interested in a quick
glance at the existent STIS spectra for Seyfert galaxies in the HST archive,
and it can be recovered electronically at the URL address
www.if.ufrgs.br/~pat/atlas.htm. Nuclear spectra of the galaxies have been
extracted in windows of 0.2 arcsec for an optimized sampling (as this is the
slit width in most cases), and combined in order to improve the signal-to-noise
ratio and provide the widest possible wavelength coverage. These combined
spectra are also available electronically.