title: Non-LTE neutral carbon spectral line formation in late-type stars

abstract:
  We present non-Local Thermodynamic Equilibrium (non-LTE) calculations for
neutral carbon spectral line formation, carried out for a grid of model
atmospheres covering the range of late-type stars. The results of our detailed
calculations suggest that the carbon non-LTE corrections in these stars are
higher than usually adopted, remaining substantial even at low metallicity. For
the most metal-poor stars in the sample of Akerman et al. (2004), the non-LTE
abundance corrections are of the order of -0.35...-0.45 dex (when neglecting H
collisions). Applying our results to those observations, the apparent [C/O]
upturn seen in their LTE analysis is no longer present, thus revealing no need
to invoke contributions from Pop. III stars to the carbon nucleosynthesis.


title:
First detection of [CII]158um at high redshift: vigorous star formation
  in the early universe

abstract:
  We report the detection of the 2P_3/2 -> 2P_1/2 fine-structure line of C+ at
157.74 micron in SDSSJ114816.64+525150.3 (hereafter J1148+5251), the most
distant known quasar, at z=6.42, using the IRAM 30-meter telescope. This is the
first detection of the [CII] line at high redshift, and also the first
detection in a Hyperluminous Infrared Galaxy (L_FIR > 10^13 Lsun). The [CII]
line is detected at a significance level of 8 sigma and has a luminosity of 4.4
x 10^9 Lsun. The L_[CII]/L_FIR ratio is 2 x 10^-4, about an order of magnitude
smaller than observed in local normal galaxies and similar to the ratio
observed in local Ultraluminous Infrared Galaxies. The [CII] line luminosity
indicates that the host galaxy of this quasar is undergoing an intense burst of
star formation with an estimated rate of ~3000 Msun/yr. The detection of C+ in
SDSS J1148+5251 suggests a significant enrichment of metals at z ~ 6 (age of
the universe ~870 Myr), although the data are consistent with a reduced carbon
to oxygen ratio as expected from chemical evolutionary models of the early
phases of galaxy formation.


title: RATAN-600 new zenith field survey and CMB problems

abstract:
  We present new RATAN-600 data on the synchrotron Galaxy radiation at the
PLANCK Mission and WMAP frequencies at high Galactic latitudes upto l=3000. The
difference between the standard synchrotron template (l<50) of the WMAP group
and RATAN-600 data was detected with the strong synchrotron ``longitude
quadrant asymmetry''. It may change the WMAP estimates of z_{reheating} from
low l polarization data. The polarized synchrotron noise for very deep
observations (<< 1 microK) at the PLANCK HFI was not detected at l>200 scales.
``Sakharov Oscillations'' in the E-mode (500<l<2000) should be well visible
even at ~10 GHz. The polarized noise from relic gravitational waves (l~80) may
be confused with B-mode of synchrotron Galaxy polarized noise at the
frequencies below 100 GHz, but there are no problems at HFI-band.


title:
Polarization of Quasars: Electron Scattering in the Broad Absorption
  Line Region

abstract:
  It is widely accepted that the broad absorption line region (BALR) exists in
most (if not all) quasars with a small covering factor. Recent works showed
that the BALR is optically thick to soft and even medium energy X-rays, with a
typical hydrogen column density of a few 10$^{23}$ to $>$ 10$^{24}$ cm$^{-2}$.
The electron scattering in the thick absorber might contribute significantly to
the observed continuum polarization for both BAL QSOs and non-BAL QSOs. In this
paper, we present a detailed study of the electron scattering in the BALR by
assuming an equatorial and axisymmetric outflow model. Monte-Carlo simulations
are performed to correct the effect of the radiative transfer. Assuming an
average covering factor of 0.2 of the BALR, which is consistent with
observations, we find the electron scattering in the BALR with a column density
of $\sim$ 4 $\times$ 10$^{23}$ cm$^{-2}$ can successfully produce the observed
average continuum polarization for both BAL QSOs and non-BAL QSOs. The observed
distribution of the continuum polarization of radio quiet quasars (for both BAL
QSOs and non-BAL QSOs) is used to constrain the dispersal distribution of the
BALR. We find that, to match the observations, the maximum continuum
polarization produced by the BALR (while viewed edge-on) peaks at $P$ = 0.34%,
which is much smaller than the average continuum polarization of BAL QSOs ($P$
= 0.93%). The discrepancy can be explained by a selection bias that the BAL
with larger covering factor, and thus producing larger continuum polarization,
is more likely to be detected. A larger sample of radio quiet quasars with
accurate measurement of the continuum polarization will give better constraints
to the distribution of the BALR properties.


title:
Submillimeter Imaging of RCS022434-0002.5: Intense Activity in a
  High-Redshift Cluster?

abstract:
  We present deep 850micron imaging of the z=0.773 strong lensing galaxy
cluster RCSJ022434-0002.5 from the Red-Sequence Cluster Survey (RCS). These
data are part of a larger submillimeter survey of RCS clusters, with SCUBA on
the JCMT. We find five objects at 850micron, all of which are also detected at
either 1.4-GHz, 450micron or both. The number density of objects in this field
is in general agreement with the blank-field source counts; however, when
combined with other cluster surveys a general tendency of cluster fields
towards higher submm number densities is seen, which may be the result of
unrecognized submillimeter luminous cluster galaxies. Primarily employing
optical photometric redshifts we show that two of the five submillimeter
galaxies in this field are consistent with being cluster members, while two are
more likely background systems.


title:
Non-LTE modelling of the HeI 10830A line in early-type main sequence
  stars

abstract:
  The near-IR HeI 10830A transition is a highly sensitive diagnostic for
non-LTE effects in the helium atom. So far, non-LTE line-formation computations
have failed to quantitatively reproduce observations of this line in the entire
range of early-A to late-O main sequence stars. It is shown that the non-LTE
modelling was insufficient, for the most part either because of inaccurate
photoionization cross-sections for the 2s 3S state or the neglect of line
blocking. New calculations based on state-of-the-art atomic data give excellent
agreement with observation for the HeI 10830 A feature, while profiles of the
HeI lines in the visual are retained.


title: Hierarchical Object Formation in the Peculiar Velocity Field

abstract:
  Using the initial peculiar velocity field, we analytically study the
hierarchical formation of gravitationally bound objects. The field is smoothed
over a scale that corresponds to the mass of a given class of objects. Through
the Zel'dovich approximation, the smoothed field determines how the objects
cluster together to form a new class of more massive objects. The standard
cosmological parameters lead to the evolution of primordial clouds with 10^6
M(sun) -> galaxies with 10^12 M(sun) -> clusters of galaxies with 10^15 M(sun)
-> superclusters of galaxies with 10^16 M(sun). The epochs obtained for the
formation of these classes of objects are consistent with observations.


title:
The Time Delays of Gravitational Lens HE0435-1223: An Early-Type Galaxy
  With a Rising Rotation Curve

abstract:
  We present Hubble Space Telescope images and 2 years of optical photometry of
the quadruple quasar HE0435-1223. The time delays between the intrinsic quasar
variations are 14.4+/-0.8 (A-D), 8.0+/-0.8 (A-B) and 2.1+/-0.8 (A-C) days. We
also observed non-intrinsic variations of ~0.1 mag/yr that we attribute to
microlensing. Instead of the traditional approach of assuming a rotation curve
for the lens galaxy and then deriving the Hubble constant (H_0), we assume
H_0=(72+/-7) km/s/Mpc and derive constraints on the rotation curve. On the
scale over which the lensed images occur (1.2"=5kpc/h=1.5R_e), the lens galaxy
must have a rising rotation curve, and it cannot have a constant mass-to-light
ratio. These results add to the evidence that the structures of early-type
galaxies are heterogeneous.


title: The Swift X-ray Telescope

abstract:
  The Swift Gamma-Ray Explorer is designed to make prompt multiwavelength
observations of Gamma-Ray Bursts (GRBs) and GRB afterglows. The X-ray Telescope
(XRT) enables Swift to determine GRB positions with a few arcseconds accuracy
within 100 seconds of the burst onset.
  The XRT utilizes a mirror set built for JET-X and an XMM/EPIC MOS CCD
detector to provide a sensitive broad-band (0.2-10 keV) X-ray imager with
effective area of > 120 cm^2 at 1.5 keV, field of view of 23.6 x 23.6
arcminutes, and angular resolution of 18 arcseconds (HPD). The detection
sensitivity is 2x10^-14 erg cm^-2 s^-1 in 10^4 seconds. The instrument is
designed to provide automated source detection and position reporting within 5
seconds of target acquisition. It can also measure the redshifts of GRBs with
Fe line emission or other spectral features. The XRT operates in an
auto-exposure mode, adjusting the CCD readout mode automatically to optimize
the science return for each frame as the source intensity fades. The XRT will
measure spectra and lightcurves of the GRB afterglow beginning about a minute
after the burst and will follow each burst for days or weeks.


title: The Faint End of the HI Mass Function

abstract:
  We study the faint end of the HI mass function (HIMF) in order to test the
predictions of the CDM theory on the number density of objects with small
(dark) masses. The neutral hydrogen is much better tracer of the underlying
mass distribution compared to the luminous matter and can be used to test the
existence of a population of small galaxies in which the star formation has
been partially or completely suppressed during cosmic evolution. Due to
technical limitations, the existing HI surveys are not very sensitive to HI
masses below 10^8 M_sun. We designed a blind HI survey to be sensitive to
objects with small HI masses. The surveyed area is in the Canis Venatici groups
of galaxies and covers in total ~ 86 deg^2 of sky, with observed velocities in
the range -350 < cz < 1400 km/s. We detected 69 objects, 22 of them for the
first time in HI. All new HI detections fall in the lower part of the
mass-histogram, confirming our ability to detect galaxies with small HI masses.
The calculated HIMF is flat in the faint end regime (slope ~ -1), different
from the steep rise predicted by CDM models. Possible effects of the
environment on the estimated HIMF parameters are discussed.


title:
A low level of extragalactic background light as revealed by gamma-rays
  from blazars

abstract:
  The diffuse extragalactic background light consists of the sum of the
starlight emitted by galaxies through the history of the Universe, and it could
also have an important contribution from the first stars, which may have formed
before galaxy formation began. Direct measurements are difficult and not yet
conclusive, owing to the large uncertainties caused by the bright foreground
emission associated with zodiacal light. An alternative approach is to study
the absorption features imprinted on the gamma-ray spectra of distant
extragalactic objects by interactions of those photons with the background
light photons. Here we report the discovery of gamma-ray emission from the
blazars H 2356-309 and 1ES 1101-232, at redshifts z=0.165 and z=0.186,
respectively. Their unexpectedly hard spectra provide an upper limit on the
background light at optical/near-infrared wavelengths that appears to be very
close to the lower limit given by the integrated light of resolved galaxies.
The background flux at these wavelengths accordingly seems to be strongly
dominated by the direct starlight from galaxies, thus excluding a large
contribution from other sources -- in particular from the first stars formed.
This result also indicates that intergalactic space is more transparent to
gamma-rays than previously thought.


title:
The calm after the storm: XMM-Newton observation of SGR 1806-20 two
  months after the Giant Flare of 2004 December 27

abstract:
  XMM-Newton observed the soft gamma repeater SGR 1806-20 about two months
after its 2004 December 27 giant flare. A comparison with the previous
observations taken with the same instrument in 2003-2004 shows that the pulsed
fraction and the spin-down rate have significantly decreased and that the
spectrum slightly softened. These changes may indicate a global reconfiguration
of the neutron star magnetosphere. The spectral analysis confirms that the
presence of a blackbody component in addition to the power-law is required.
Since this additional component is consistent with being constant with respect
to the earlier observations, we explore the possibility of describing the
long-term spectral evolution as only due to the power-law variations. In this
case, the slope of the power-law does not significantly change and the spectral
softening following the giant flare is caused by the increase of the relative
contribution of the blackbody over the power-law component.


title:
The Opacity of Spiral Galaxy Disks V: dust opacity, HI distributions and
  sub-mm emission

abstract:
  The opacity of spiral galaxy disks, from counts of distant galaxies, is
compared to HI column densities. The opacity measurements are calibrated using
the ``Synthetic Field Method'' from Gonzalez et al (1998) and Holwerda et al.
(2005a).
  When compared for individual disks, the HI column density and dust opacity do
not seem to be correlated as HI and opacity follow different radial profiles.
  To improve statistics, an average radial opacity profile is compared to an
average HI profile. Compared to dust-to-HI estimates from the literature, more
extinction is found in this profile. This difference may be accounted for by an
underestimate of the dust in earlier measurements due to their dependence on
dust temperature. Since the SFM is insensitive to the dust temperature, the
ratio between the SFM opacity and HI could very well be indicative of the true
ratio.
  Earlier claims for a radially extended cold dust disk were based on sub-mm
observations. A comparison between sub-mm observations and counts of distant
galaxies is therefore desirable. We present the best current example of such a
comparison, M51, for which the measurements seem to agree. However, this
remains an area where improved counts of distant galaxies, sub-mm observations
and our understanding of dust emissivity are needed.


title:
Level set simulations of turbulent thermonuclear deflagration in
  degenerate carbon and oxygen

abstract:
  We study the dynamics of thermonuclear flames propagating in fuel stirred by
stochastic forcing. The fuel consists of carbon and oxygen in a state which is
encountered in white dwarfs close to the Chandrasekhar limit. The level set
method is applied to represent the flame fronts numerically. The computational
domain for the numerical simulations is cubic, and periodic boundary conditions
are imposed. The goal is the development of a suitable flame speed model for
the small-scale dynamics of turbulent deflagration in thermonuclear supernovae.
Because the burning process in a supernova explosion is transient and spatially
inhomogeneous, the localised determination of subgrid scale closure parameters
is essential. We formulate a semi-localised model based on the dynamical
equation for the subgrid scale turbulence energy $k_{\mathrm{sgs}}$. The
turbulent flame speed $s_{\mathrm{t}}$ is of the order
$\sqrt{2k_{\mathrm{sgs}}}$. In particular, the subgrid scale model features a
dynamic procedure for the calculation of the turbulent energy transfer from
resolved toward subgrid scales, which has been successfully applied to
combustion problems in engineering. The options of either including or
suppressing inverse energy transfer in the turbulence production term are
compared. In combination with the piece-wise parabolic method for the
hydrodynamics, our results favour the latter option. Moreover, different
choices for the constant of proportionality in the asymptotic flame speed
relation,
  $s_{\mathrm{t}}\propto\sqrt{2k_{\mathrm{sgs}}}$, are investigated.


title:
The Opacity of Spiral Galaxy Disks VII: the accuracy of galaxy counts as
  an extinction probe

abstract:
  The ``Synthetic Field Method'' (SFM) was introduced by Gonzalez et al. (1998)
to calibrate numbers of distant galaxies as a probe of extinction in a
foreground spiral disk. Gonzalez et al. (2003) studied the effect of the
foreground disk on these numbers using simulations of current and future
instruments for fields in the LMC, M31 and NGC 4536, a galaxy in Virgo. They
concluded that: (1) the brighter centers of disks were unsuitable, (2) the
granularity of the disk at a fixed surface brightness is the limiting factor in
the detection of distant galaxies, and (3) the optimum distance for
measurements would be that of the Virgo cluster for the current instruments on
board HST. At this distance the foreground disk is smoothed with distance,
improving detection of distant background galaxies. Holwerda et al. (2005a)
automated the SFM and Holwerda et al. (2005b) applied it to a large set of
WFPC2 fields. In this paper, the quality of the extinction measurement in these
fields is compared to their distance, granularity, surface brightness and
structure. The average surface brightness of the of a field is shown to
directly influence the accuracy of the SFM. This restricts meaningful
measurements to the disks of spiral galaxies. Large structures such as spiral
arms have a similar effect. The granularity or small scale structure in a field
influences the detection of distant galaxies, limiting the SFM measurements in
nearby disks. From the trends in the accuracy and maximum practical
field-of-view considerations, the minimum and maximum distance for SFM
application, approximately 5 and 35 Mpc respectively. Using the same instrument
and detection method, the relations with SFM parameters and field
characteristics can be used to forgo the synthetic fields altogether.


title: Charge Exchange Spectra of Hydrogenic and He-like Iron

abstract:
  We present H-like Fe XXVI and He-like Fe XXV charge-exchange spectra
resulting from collisions of highly charged iron with N2 gas at an energy of 10
eV/amu in an electron beam ion trap. Although individual high-n emission lines
are not resolved in our measurements, we observe that the most likely level for
Fe25+ --> Fe24+ electron capture is n~9, in line with expectations, while the
most likely value for Fe26+ --> Fe25+ charge exchange is significantly higher.
In the Fe XXV spectrum, the K-alpha emission feature dominates, whether
produced via charge exchange or collisional excitation. The K-alpha centroid is
lower in energy for the former case than the latter (6666 versus 6685 eV,
respectively), as expected because of the strong enhancement of emission from
the forbidden and intercombination lines, relative to the resonance line, in
charge-exchange spectra. In contrast, the Fe XXVI high-n Lyman lines have a
summed intensity greater than that of Ly-alpha, and are substantially stronger
than predicted from theoretical calculations of charge exchange with atomic H.
We conclude that the angular momentum distribution resulting from electron
capture using a multi-electron target gas is significantly different from that
obtained with H, resulting in the observed high-n enhancement. A discussion is
presented of the relevance of our results to studies of diffuse Fe emission in
the Galactic Center and Galactic Ridge, particularly with ASTRO-E2/Suzaku.


title:
Metal abundances of RR Lyrae stars in the metal rich globular cluster
  NGC 6441

abstract:
  Low resolution spectra have been used to measure individual metal abundances
of RR Lyrae stars in NGC 6441, a Galactic globular cluster known to have very
unusual horizontal branch morphology and periods of the RR Lyrae stars for its
high metallicity. We find an average metal abundance of [Fe/H]=-0.69 +/- 0.06
(r.m.s.=0.33 dex) and [Fe/H]=-0.41 +/- 0.06 (r.m.s.=0.36 dex) on Zinn & West
and Carretta & Gratton metallicity scales, respectively, consistent with the
cluster metal abundance derived by Armandroff & Zinn. Most of the metallicities
were extrapolated from calibration relations defined for [Fe/H] < -1; however,
they are clearly high and contrast with the rather long periods of the NGC 6441
variables, thus confirming that the cluster does not fit in the general
Oosterhoff classification scheme. The r.m.s. scatter of the average is larger
than observational errors (0.15-0.16 dex) possibly indicating some spread in
metallicity. However, even the metal poor variables, if confirmed to be cluster
members, are still more metal rich than those commonly found in the Oosterhoff
type II globular clusters.


title: Panchromatic Studies of Distant Clusters of Galaxies

abstract:
  High redshift (z >~ 1) clusters are ideal probes to study the formation and
evolution of large scale structures and galaxies in the universe. A 10-m class
ground based telescope, X-ray observatories (Chandra, XMM-Newton) and HST/ACS
are allowing us to perform an unprecedented study of distant massive clusters
of galaxies in the redshift range 0.84<z<1.3, selected from X-rays surveys. In
this paper we summarize our results on the structure and dynamics of two of
these clusters derived from imaging and spectroscopic data as well as our
results on the evolution of early-type galaxies.


title: Testing the Rate of False Planetary Transits due to Binary Star Blending

abstract:
  We investigate the rate of false planetary transit detection due to blending
with eclipsing binaries. Our approach is purely empirical and is based on the
analysis of the artificially blended light curves of the eclipsing binary stars
in the Large Magellanic Cloud from the archive of the Optical Gravitational
Lensing Experiment (OGLE). Employing parameters that characterize the
significance of the transit and the amplitude of the variation out of the
transit, we can substantially limit the number of potential false positives.
Further constraint comes from the expected length of the transit by a possible
planetary companion. By the application of these criteria we are left only with
18 candidates from the full sample of 2495 stars. Visual inspection of these
remaining variables eliminates all of them for obvious reasons (e.g., for
visible fingerprints of orbital eccentricity). We draw the attention to the
short-period stars, where the false alarm rate is especially low.


title:
Kelu-1 is a Binary L Dwarf: First Brown Dwarf Science from Laser Guide
  Star Adaptive Optics

abstract:
  (Abridged) We present near-IR imaging of the nearby L dwarf Kelu-1 obtained
with the Keck sodium laser guide star adaptive optics (LGS AO) system as part
of a high angular resolution survey for substellar binaries. Kelu-1 was one of
the first free-floating L dwarfs identified, and the origin of its
overluminosity compared to other similar objects has been a long-standing
question. Our images clearly resolve Kelu-1 into a 0.29'' (5.4 AU) binary, and
a previous non-detection by HST demonstrates that the system is a true physical
pair. Binarity explains the properties of Kelu-1 that were previously noted to
be anomalous compared to other early-L dwarfs. We estimate spectral types of
L1.5-L3 and L3-L4.5 for the two components, giving model-derived masses of
0.05-0.07 Msun and 0.045-0.065 Msun for an estimated age of 0.3-0.8 Gyr. More
distant companions are not detected to a limit of 5-9 Mjup. The presence of
lithium absorption indicates that both components are substellar, but the
weakness of this feature relative to other L dwarfs can be explained if only
Kelu-1B is Li-bearing. Determining whether both or only one of the components
possesses lithium could constrain the age of Kelu-1 (and other Li-bearing L
binaries) with higher precision than is possible for most ultracool field
objects. These results are the first LGS AO observations of brown dwarfs and
demonstrate the potential of this new instrumental capability for substellar
astronomy.


title:
Definitive Identification of the Transition between Small- to
  Large-Scale Clustering for Lyman Break Galaxies

abstract:
  We report angular correlation function (ACF) of Lyman Break Galaxies (LBGs)
with unprecedented statistical quality on the basis of 16,920 LBGs at z=4
detected in the 1 deg^2 sky of the Subaru/XMM-Newton Deep Field. The ACF
significantly departs from a power law, and shows an excess on small scale.
Particularly, the ACF of LBGs with i'<27.5 have a clear break between the small
and large-scale regimes at the angular separation of ~7'' whose projected
length corresponds to the virial radius of dark halos with a mass of 10^11-12
Mo, indicating multiple LBGs residing in a single dark halo. Both on small
(2''<theta<3'') and large (40''<theta<400'') scales, clustering amplitudes
monotonically increase with luminosity for the magnitude range of i'=24.5-27.5,
and the small-scale clustering shows a stronger luminosity dependence than the
large-scale clustering. The small-scale bias reaches b~10-50, and the outskirts
of small-scale excess extend to a larger angular separation for brighter LBGs.
The ACF and number density of LBGs can be explained by the cold dark matter
model.


title:
About the correlation between solar micro bursts and the change of the
  solar wind parameters

abstract:
  The Sun is the closest star to our planet and it is the most studied,
perhaps, there exist too much procesess not-understood. One of the solar
processes that have a direct interaction with the earth is the solar wind. The
solar wind is defined as the plasma expulsed from the solar atmosphere, this
wind was cataloged and is considered that have three components:
  - Passive solar wind: Is the constant component of the solar wind. -
Supersonic and quasistady flux. - Sporadic supersonic flux.
  We present and brief explanation of the Parker's model of the solar wind and
a correlation analysis between solar micro radio bursts and the change of the
solar wind parameters.


title:
Numerical Galaxy Catalog -I. A Semi-analytic Model of Galaxy Formation
  with N-body simulations

abstract:
  We construct the Numerical Galaxy Catalog ($\nu$GC), based on a semi-analytic
model of galaxy formation combined with high-resolution N-body simulations in a
$\Lambda$-dominated flat cold dark matter ($\Lambda$CDM) cosmological model.
The model includes several essential ingredients for galaxy formation, such as
merging histories of dark halos directly taken from N-body simulations,
radiative gas cooling, star formation, heating by supernova explosions
(supernova feedback), mergers of galaxies, population synthesis, and extinction
by internal dust and intervening HI clouds. As the first paper in a series
using this model, we focus on basic photometric, structural and kinematical
properties of galaxies at present and high redshifts. Two sets of model
parameters are examined, strong and weak supernova feedback models, which are
in good agreement with observational luminosity functions of local galaxies in
a range of observational uncertainty. Both models agree well with many
observations such as cold gas mass-to-stellar luminosity ratios of spiral
galaxies, HI mass functions, galaxy sizes, faint galaxy number counts and
photometric redshift distributions in optical pass-bands, isophotal angular
sizes, and cosmic star formation rates. In particular, the strong supernova
feedback model is in much better agreement with near-infrared (K'-band) faint
galaxy number counts and redshift distribution than the weak feedback model and
our previous semi-analytic models based on the extended Press-Schechter
formalism. (Abridged)


title:
Black hole X-ray binaries LMC X-1 and X-3: observations confront
  spectral models

abstract:
  We present a comprehensive spectral analysis of black hole X-ray binaries,
LMC X-1 and LMC X-3, based on BeppoSAX observations. We test both the
multi-color disk plus power law (MCD+PL) model and a newly-developed
Monte-Carlo simulation- based model for a Comptonized MCD (CMCD) with either a
spherical or a slab-like corona, by comparing the inferred parameters with
independent direct measurements. While all models give an adequate description
of the spectra, we find a significant discrepancy between the MCD+PL inferred
X-ray-absorbing gas column density and the absorption-edge measurement based on
dispersed X-ray spectra. The MCD+PL fits to the LMC X-1 spectra also require a
change in the inner disk radius during the BeppoSAX observation, which may be
due to the nonphysical effects inherited in the model. In contrast, the CMCD
model with the spheric corona gives the predictions of both the disk
inclination angle and the absorption that are consistent with the direct
measurements, and only slightly under-predicts the black hole mass of LMC X-3.
The model explains the spectral state evolution of LMC X-1 within the BeppoSAX
observation as a change in the accretion rate, which leads to an increase in
both the inner disk temperature and the Comptonization opacity. On the other
hand, the CMCD model with the slab-like corona is more problematic in the test
and is thus not recommended.


title: Reverse Shock Emission as a Probe of GRB Ejecta

abstract:
  We calculate the reverse shock (RS) synchrotron emission in the optical and
the radio wavelength bands from electron-positron pair enriched gamma-ray burst
ejecta with the goal of determining the pair content of GRBs using early time
observations. We take into account an extensive number of physical effects that
influence radiation from the reverse-shock heated GRB ejecta. We find that
optical/IR flux depends very weakly on the number of pairs in the ejecta, and
there is no unique signature of ejecta pair enrichment if observations are
confined to a single wavelength band. It may be possible to determine if the
number of pairs per proton in the ejecta is > 100 by using observations in
optical and radio bands; the ratio of flux in the optical and radio at the peak
of each respective reverse-shock light curve is dependent on the number of
pairs per proton. We also find that over a large parameter space, RS emission
is expected to be very weak; GRB 990123 seems to have been an exceptional burst
in that only a very small fraction of the parameter space produces optical
flashes this bright. Also, it is often the case that the optical flux from the
forward shock is brighter than the reverse shock flux at deceleration. This
could be another possible reason for the paucity of prompt optical flashes with
a rapidly declining light curve at early times as was seen in 990123 and
021211. Some of these results are a generalization of similar results reported
in Nakar & Piran (2004).


title:
Detection of a young stellar population in the background of open
  clusters in the Third Galactic Quadrant

abstract:
  We report the detection of a young stellar population ($\leq$100 Myrs) in the
ba ckground of 9 young open clusters belonging to a homogenoeous sample of 30
star clusters in the Third Galactic Quadrant (at $217^o \leq l \leq 260^o$).
Deep and accurate UBVRI photometry allows us to measure model-independent age
and distance for the clusters and the background population with high
confidence. This population is exactly the same population (the Blue Plume)
recently detected in 3 intermediate-age open clusters and suggested to be a
$\leq$ 1-2 Gyr old population belonging to the Canis Major (CMa) over-density
(Bellazzini et al. 2004, Mart\'inez-Delgado et al. 2005). However, we find that
the young population in those three and in six clusters of our sample follows
remarkably well the pattern of the Norma-Cygnus spiral arm as defined by CO
clouds, while in the other three program clusters it lies in the Perseus arm.
We finally provide one example (out of 21) of a cluster which does not show any
background population, demonstrating that this population is not ubiquitous
toward CMa.


title:
Cosmic infrared background from Population III stars and its effect on
  spectra of high-z gamma-ray bursts

abstract:
  We discuss the contribution of Population III stars to the near-IR (NIR)
cosmic infrared background (CIB) and its effect on spectra of high-$z$
high-energy gamma-ray bursts (GRBs). It is shown that if Population III were
massive stars, the claimed NIR CIB excess will be reproduced if only ~ 4+/-2%
of all baryons went through these stars. Regardless of the precise value of the
NIR CIB produced by them, they would leave enough photons to provide a large
optical depth for high-energy photons from high-z GRBs. Observations of such
GRBs are expected following the planned launch of NASA's GLAST mission. The
presence or absence of such damping in the spectra of high-$z$ GRBs will then
provide important information on the emissions from the Population III. The
location of this cutoff may also serve as an indicator of the GRB's redshift.


title:
The Large-scale and Small-scale Clustering of Lyman-Break Galaxies at
  3.5 < z< 5.5 from the GOODS survey

abstract:
  We report on the angular correlation function of Lyman-break galaxies (LBGs)
at z~4 and 5 from deep samples obtained from the Great Observatories Deep
Origins Survey (GOODS). Similar to LBGs at z~3, the shape of w(theta) of the
GOODS LBGs is well approximated by a power-law with slope beta~0.6 at angular
separation theta > 10 arcsec. The clustering strength of z~4, 5 LBGs also
depends on the rest-frame UV luminosity, with brighter galaxies more strongly
clustered than fainter ones, implying a general correlation between halos' mass
and LBGs' star-formation rate. At smaller separations, w(theta) of deep samples
significantly exceeds the extrapolation of the large-scale power-law fit,
implying enhanced spatial clustering at scales r < 1 Mpc. We also find that
bright LBGs statistically have more faint companions on scales theta < 20
arcsec than fainter ones, showing that the enhanced small-scale clustering is
very likely due to sub-structure, namely the fact that massive halos can host
multiple galaxies. A simple model for the halo occupation distribution and the
CDM halo mass function reproduce well the observed w(theta). The scaling
relationship of the clustering strength with volume density and with redshift
is quantitatively consistent with that of CDM halos. A comparison of the
clustering strength of three samples of equal luminosity limit at z ~ 3, 4 and
5 shows that the LBGs at z~5 are hosted in halos about one order of magnitude
less massive than those in the lower redshift bins, suggesting that
star-formation was more efficient at higher-redshift.


title:
Exploring Halo Substructure with Giant Stars VIII: The Extended
  Structure of the Sculptor Dwarf Spheroidal Galaxy

abstract:
  (Abridged) We explore the spatial distribution of stars in the Sculptor dwarf
spheroidal (dSph) galaxy over an area of 7.82 deg^2. We identify red giant
branch (RGB) starts via Washington M, T_2+DDO51 photometry and a blue
horizontal branch (BHB) population to map the spatial structure of the dSph. A
spectroscopically observed subset of Sculptor candidate stars yield a systemic
heliocentric velocity for the system of v_{hel}=110.43 km/s, in good agreement
with previous studies, and a global velocity dispersion of sigma_v=8.8 km/s,
which may rise slightly past 0.4r_{lim}. To a limit of M~19, we find 94% of the
photometrically-selected Sculptor giant star candidates with spectrocopic
measurements are kinematically associated with Sculptor, and four of ten stars
not selected photometrically are selected kinematically; our candidate samples
are likely to be very pure. We take considerable care in assessing the
contaminating background level in our photometric sample to ensure accurate
density profiles. These assessments verify that we detect a considerable
stellar density of Sculptor stars to the limits of our survey area in both the
RGB and BHB samples. We find the Sculptor density profile is well-fit by a King
profile of limiting radius r_{lim} = 79.6 within ~60 arcmin, beyond which a
"break" to a power law profile occurs. This break population must be either a
bound group of "halo stars" around the Sculptor dSph or unbound tidal debris.
The latter is supported by 2D distribution analyses and, if true, implies a
fractional mass-loss rate of ~0.042 Gyr^{-1} for Sculptor. Finally, likely more
metal-poor RGB stars (as selected by color and magnitude) are significantly
less centrally concentrated and, therefore, constitute the primary contributor
to the likely tidally-stripped parts of the dSph.


title:
A Wide-field Hubble Space Telescope Survey of the Cluster Cl 0024+16 at
  z=0.4. III: Spectroscopic Signatures of Environmental Evolution in Early Type
  Galaxies

abstract:
  We report results from a panoramic spectroscopic survey of 955 objects in the
field of the rich cluster Cl 0024+1654 (z~0.4), complementing the HST imaging
presented in the first paper in this series. Our new spectroscopic sample
includes over 200 high quality spectra of cluster members, spread across an
area 10 Mpc in diameter. We examine the properties of a large sample of 104
cluster early-types as a function of cluster radius and local density, using
them as sensitive tracers of the various physical processes that may be
responsible for galaxy evolution. By constructing the Fundamental Plane of Cl
0024, we infer an evolution in the mean mass to light ratio of early-types
equal to \Delta<Log (M/L_V)> = -0.14 +- 0.02. In the cluster center, we detect
a significantly increased scatter in the relationship compared to that seen in
local clusters. Moreover, we observe a clear radial trend in the mass to light
ratios of individual early types, with the oldest galaxies located in the
cluster core. Galaxies are apparently younger at larger radius, with E+S0s in
the periphery having M/L_V ratios that nearly match values seen in the field at
a similar redshift. Independent spectral indicators used in combination reveal
an abrupt interaction with the cluster environment which occurs near the virial
radius of Cl 0024, revealed by small bursts of star formation in a population
of dim early-types, as well as by enhanced Balmer absorption for a set of
larger E+S0s closer to the cluster core. We construct a simple infall model
used to compare the timescales and strengths of the observed interactions in
this cluster. We examine the possibility that bursts of star formation are
triggered when galaxies suffer shocks as they encounter the intra-cluster
medium, or by the onset of galaxy harassment.


title:
Deep optical observations of the supernova remnants G 126.2+1.6, G
  59.8+1.2 and G 54.4-0.3

abstract:
  Optical CCD imaging and spectroscopic observations of three supernova
remnants are presented. Optical emission from G 54.4-0.3 and G 59.8+1.2 is
detected for the first time, while the first flux calibrated CCD images of the
supernova remnant G 126.2+1.6 were performed in the optical emission lines of
Halpha+[N II], [O III] and [S II]. A mixture of filamentary and diffuse
structures is observed in G 54.4-0.3 and G 59.8+1.2, mainly in Halpha+[N II],
while the deep optical images of G 126.2+1.6 reveal several new filamentary and
diffuse structures inside the extent of the remnant as defined by its known
radio emission. In all cases, the radio emission is found to be well correlated
with the optical filaments. [O III] emission was not detected at G 54.4-0.3 and
G 59.8+1.2 while in G 126.2+1.6, significant morphological differences between
the low and medium ionization images are present suggesting incomplete shock
structures. Deep long-slit spectra were taken at different positions of the
remnants. Both the flux calibrated images and the long-slit spectra clearly
show that the emission originates from shock-heated gas, while some spectra of
G 126.2+1.6 are characterized by large [O III]/Hbeta ratios. This remnant's [O
III] flux suggests shock velocities into the interstellar "clouds" between 100
and 120 km/s, while the [O III] absence in the other two remnants indicates
slower shock velocities. For all remnants, the [S II]6716/6731 ratio indicates
electron densities below 600 cm^{-3} with particularly low densities for G
54.4-0.3 (below 50 cm^{-3}). Finally, the Halpha emission has been measured to
be between 3.0 to 15.2x10^{-17} erg/s/cm^2/ arcsec^2, 3.2x10^{-17} erg/s/cm^2/
arcsec^2 and between 6.5 to 16.8x10^{-17} erg/s/cm^2/ arcsec^2 for G 54.4-0.3,
G 59.8+1.2 and G 126.2+1.6, respectively.


title:
Magnetic reconnection with anomalous resistivity in two-and-a-half
  dimensions I: Quasi-stationary case

abstract:
  In this paper quasi-stationary, two-and-a-half-dimensional magnetic
reconnection is studied in the framework of incompressible resistive
magnetohydrodynamics (MHD). A new theoretical approach for calculation of the
reconnection rate is presented. This approach is based on local analytical
derivations in a thin reconnection layer, and it is applicable to the case when
resistivity is anomalous and is an arbitrary function of the electric current
and the spatial coordinates. It is found that a quasi-stationary reconnection
rate is fully determined by a particular functional form of the anomalous
resistivity and by the local configuration of the magnetic field just outside
the reconnection layer. It is also found that in the special case of constant
resistivity reconnection is Sweet-Parker and not Petschek.


title:
New clues on outburst mechanisms and improved spectroscopic elements of
  the black-hole binary V4641 Sagittarii

abstract:
  We present spectroscopic observations of the black-hole binary V4641
Sagittarii, obtained between 4th July 2004 and 28th March 2005, which cover the
minor outburst of the star in early July 2004 and quiescence variations on 19
nights scattered over six months. During the outburst, the star peaked
approximately 3 magnitudes brighter than usual, and our spectra were dominated
by broad hydrogen, helium and iron emission lines. The very first spectra
showed P Cygni profiles, which disappeared within a few hours, indicating rapid
changes in matter ejection. The H-alpha line had multiple components, one being
a broad blue-shifted wing exceeding 5000 km/s. During a simultaneously observed
10-min photometric flare-up, the equivalent width of the H-alpha line
temporarily decreased, implying that it was a flare of the continuum. The
overall spectral appearance was similar to that observed in the 1999 September
active phase, which suggests that similar mass-ejection processes were
associated with both eruptions. In quiescence, the spectra were those of the
early-type secondary star showing its orbital motion around the primary. By
measuring cross-correlation radial velocities, we give an improved set of
spectroscopic elements. Whereas we measure the same velocity amplitude
(K_2=211.3+/-1.0 km/s), within errors, as Orosz et al. (2001), our
centre-of-mass velocity (v_gamma=72.7+/-3.3 km/s) differs significantly from
the previously published value (107.4+/-m2.9 km/s). However, we find evidence
that the difference is caused by a systematic error in data reduction in the
previous study, rather than by gravitational effects of an invisible third
component.


title: Line bisectors and radial velocity jitter from SARG spectra

abstract:
  We present an analysis of spectral line bisector variations for a few stars
observed in the SARG high precision radial velocity planet survey, and discuss
their relationship with differential radial velocities. The spectra we consider
are the same used for determining radial velocities. The iodine cell lines
employed in the measurement of radial velocities were removed before bisector
analysis. The line bisectors were then computed from average absorption
profiles obtained by cross correlation of the stellar spectra with a mask made
from suitable lines of a solar catalog. Bisector velocity spans were then
determined: errors in these quantities compare well with theoretical
expectations based on resolution, S/N and line shape. The plot of bisector
velocity span against radial velocity was studied to search for correlations
between line asymmetries and radial velocity variations. A correlation was seen
for HD 166435 due to stellar activity, and for HD 8071B due to spectral
contamination by the companion. No correlation was seen for 51 Peg and rho CrB,
stars hosting planets. We conclude that this technique may be useful to
separate radial velocity variations due to barycenter motion from spurious
signals in spectra acquired with the iodine cell.


title: Multicomponent Decompositions for a Sample of S0 galaxies

abstract:
  We have estimated the bulge-to-total ($B/T$) light ratios in the $K_s$-band
for a sample of 24 S0, S0/a and Sa galaxies by applying a 2-dimensional
multicomponent decomposition method. For the disk an exponential function is
used, the bulges are fitted by a S\'ersic's $R^{1/n}$ function and the bars and
ovals are described either by a S\'ersic or a Ferrers function. In order to
avoid non-physical solutions, preliminary characterization of the structural
components is made by inspecting the radial profiles of the orientation
parameters and the low azimuthal wavenumber Fourier amplitudes and phases. In
order to identify also the inner structures, unsharp masks were created:
previously undetected inner spiral arms were found in NGC 1415 and marginally
in NGC 3941. Most importantly, we found that S0s have a mean $<B/T>_K$-ratio of
0.24 $\pm$ 0.11, which is significantly smaller than the mean $<B/T>_R$ = 0.6
generally reported in the literature. Also, the surface brightness profiles of
the bulges in S0s were found to be more exponential-like than generally
assumed, the mean shape parameter of the bulge being $<n>$ = 2.1 $\pm$ 0.7. We
did not find examples of barred S0s lacking the disk component, but we found
some galaxies (NGC 718, NGC 1452, NGC 4608) having a non-exponential disk in
the bar region. To our knowledge our study is the first attempt to apply a
multicomponent decomposition method for a moderately sized sample of early-type
disk galaxies


title:
The Circumstellar Environment of High Mass Protostellar Objects. III
  Evidence of Infall?

abstract:
  The results are presented of a molecular line survey to search for the
spectral signature of infall towards 77 850 micron continuum sources believed
to be candidate high mass protostellar objects. Up to six different
transitions, HCO+ 1-0, 3-2 and 4-3, H2CO 2_12-1_11, N2H+ and H13CO+ 3-2, were
observed towards each source. Towards the peak of the 850 micron emission, N2H+
was typically strong, with a peak antenna temperature of ~1.5K, with a typical
linewidth of ~2km/s. The good agreement between the velocity and velocity width
of the N2H+ and H13CO+ emission suggests that both species are tracing similar
material in the sources. With respect to the velocity of the N2H+, there is a
statistically significant excess of blue asymmetric line profiles in both the
HCO+ 1-0 and H2CO transitions. This excess reaches levels similar to that seen
towards samples of low mass protostars, and suggests that the material around
these high mass sources is infalling. We identify 22 promising candidate infall
sources which show at least one blue asymmetric line profile and no red
asymmetric profiles. The infall velocity is estimated to be in the range of 0.1
km/s to 1 km/s with an implied mass accretion rate of between 2x10^{-4} Msol/yr
and 10^{-3}Msol/yr.


title: Violent star and star cluster formation in nearby and distant galaxies

abstract:
  I present recent observations and analyses of star cluster formation in a
wide variety of environments -- from young star clusters and super star
clusters in normal actively star-forming spirals and irregulars to starbursting
dwarfs and spiral-spiral mergers. Star cluster formation in interacting
galaxies can be restricted to central starburst region, extend over the entire
body of the merger, or even all along extended tidal structures. I address
methods and results for the determination of star cluster ages, metallicities,
masses, and sizes and discuss the nature, possible lifetimes and future
signatures of these star cluster populations, as well as the relative
importance of field star formation vs. star cluster formation.


title:
Alfvenic reacceleration of relativistic particles in galaxy clusters in
  the presence of secondary electrons and positrons

abstract:
  In a previous paper (Brunetti et al. 2004) we presented the first
self-consistent calculations of the time-dependent coupled equations for the
electrons, hadrons and Alfv\'en waves in the intracluster medium, which
describe the stochastic acceleration of the charged particles and the
corresponding spectral modification of the waves. Under viable assumptions,
this system of mutually interacting components was shown to accurately describe
several observational findings related to the radio halos in clusters of
galaxies. In this paper, we add to the self-consistency of the calculations by
including the generation and re-energization of secondary electrons and
positrons, produced by the inelastic interactions of cosmic rays with the
thermal gas in the intracluster medium. The bulk of Cosmic rays is expected to
be confined within the cluster volume for cosmological times, so that the rate
of production of secondary electrons, as well as gamma rays, may become
correspondingly enhanced. If MHD waves are present, as it may be expected in
the case of a recent merger event, then the reacceleration of secondary
electrons and positrons can significantly affect the phenomenology of the non
thermal processes in clusters. We investigate here these effects for the first
time.


title:
Spectral analyses of DO white dwarfs and PG1159 stars from the Sloan
  Digital Sky Survey

abstract:
  We present a model atmosphere analysis of ten new DO white dwarfs and five
new PG 1159 stars discovered in the Sloan Digital Sky Survey DR1, DR2 and DR3.
This is a significant increase in the number of known DOs and PG 1159 stars. DO
white dwarfs are situated on the white dwarf cooling sequence from the upper
hot end Teff ~ 120 000 K down to the DB gap (Teff ~ 45 000 K). PG 1159 stars on
the other hand feature effective temperatures which exceed Teff = 65 000 K with
an upper limit of Teff = 200 000 K and are the proposed precursors of DO white
dwarfs. Improved statistics are necessary to investigate the evolutionary link
between these two types of stars. From optical SDSS spectra effective
temperatures, surface gravities and element abundances are determined by means
of non-LTE model atmospheres.


title:
XMM-Newton Surveys of the Canada-France Redshift Survey Fields - III:
  The Environments of X-ray Selected AGN at 0.4<z<0.6

abstract:
  The environmental properties of a sample of 31 hard X-ray selected AGN are
investigated, from scales of 500 kpc down to 30 kpc, and are compared to a
control sample of inactive galaxies. The AGN all lie in the redshift range
0.4<z<0.6. The accretion luminosity-density of the Universe peaks close to this
redshift range, and the AGN in the sample have X-ray luminosities close to the
knee in the hard X-ray luminosity function, making them representative of the
population which dominated this important phase of energy conversion.
  Using both the spatial clustering amplitude and near neighbour counts it is
found that the AGN have environments that are indistinguishable from normal,
inactive galaxies over the same redshift range and with similar optical
properties. Typically, the environments are of sub-cluster richness, in
contrast to similar studies of high-z quasars, which are often found in
clusters with comparable richness to the Abell R>=0 clusters.
  It is suggested that minor mergers with low mass companions is a likely
candidate for the mechanism by which these modest luminosity AGN are fuelled.


title:
2-D Monte Carlo simulations of H I line formation in massive YSO disk
  winds

abstract:
  Massive young stellar objects (YSOs) are powerful infrared H I line emitters.
It has been suggested that these lines form in a outflow from a disk
surrounding the YSO. Here, new two-dimensional Monte Carlo radiative transfer
calculations are described which test this hypothesis. Infrared spectra are
synthesised for a YSO disk wind model based on earlier hydrodynamical
calculations. The model spectra are in qualitative agreement with the observed
spectra from massive YSOs, and therefore provide support for a disk wind
explanation for the H I lines. However, there are some significant differences:
the models tend to overpredict the Br alpha/Br gamma ratio of equivalent-widths
and produce line profiles which are slightly too broad and, in contrast to
typical observations, are double-peaked. The interpretation of these
differences within the context of the disk wind picture and suggestions for
their resolution via modifications to the assumed disk and outflow structure
are discussed.


title:
The entrainment matrix of a superfluid neutron-proton mixture at a
  finite temperature

abstract:
  The entrainment matrix (also termed the Andreev-Bashkin matrix or the
mass-density matrix) for a neutron-proton mixture is derived at a finite
temperature in a neutron star core. The calculation is performed in the frame
of the Landau Fermi-liquid theory generalized to account for superfluidity of
nucleons. It is shown, that the temperature dependence of the entrainment
matrix is described by a universal function independent on an actual model of
nucleon-nucleon interaction employed. The results are presented in the form
convenient for their practical use. The entrainment matrix is important, e.g.,
in kinetics of superfluid nucleon mixtures or in studies of the dynamical
evolution of neutron stars (in particular, in the studies of star pulsations
and pulsar glitches).


title:
Constraints on the dense matter EOS from the measurements of PSR
  J0737-3039A moment of inertia and PSR J0751+1807 mass

abstract:
  The moment of inertia of the pulsar A in the neutron star binary J0737-3039
will soon be measurable through detailed measurements of the periastron
advance. We present the calculation of the moment of inertia of neutron stars
with the masses of the components of the binary J0737-3039 for a broad range of
equations of state of dense matter and discuss the implications of such
measurement for constraining the equation of state. An observational
determination of the moment of inertia of the pulsar A in J0737-3039 with the
accuracy of 10% shall narrow down considerably the range of viable equations of
state. We also show that limits on maximal mass of a neutron star provide a
complementary set of constraints on the properties of dense nuclear matter.


title: Stellar Processes Near the Massive Black Hole in the Galactic Center

abstract:
  A massive black hole resides in the center of most, perhaps all galaxies. The
one in the center of our home galaxy, the Milky Way, provides a uniquely
accessible laboratory for studying in detail the connections and interactions
between a massive black hole and the stellar system in which it grows; for
investigating the effects of extreme density, velocity and tidal fields on
stars; and for using stars to probe the central dark mass and probe
post-Newtonian gravity in the weak- and strong-field limits. Recent results,
open questions and future prospects are reviewed in the wider context of the
theoretical framework and physical processes that underlie them.
  Contents: [1] Introduction (1.1) Astrophysical context (1.2) Science
questions (1.3) Scope and connections to related topics [2] Observational
overview: Stars in the Galactic center (2.1) The central 100 parsecs (2.2) The
central parsec [3] Stellar dynamics at extreme densities (3.1) Physical
processes and scales (3.2) The stellar cusp in the Galactic center (3.3) Mass
segregation (3.4) Stellar Collisions [4] Probing the dark mass with stellar
dynamics (4.1) Weighing and pinpointing the dark mass (4.2) Constraints on
non-BH dark mass alternatives (4.3) Limits on MBH binarity (4.4) High-velocity
runaway stars [5] Probing post-Newtonian gravity near the MBH (5.1)
Relativistic orbital effects (5.2) Gravitational lensing [6] Strong star-MBH
interactions (6.1) Tidal disruption (6.2) Dissipative interactions with the MBH
[7] The riddle of the young stars (7.1) The difficulties of forming or
importing stars near a MBH (7.2) Proposed solutions (7.3) Feeding the MBH with
stellar winds [8] Outlook (8.1) Progress report (8.2) Future directions


title: Simulations of galactic winds and starbursts in galaxy clusters

abstract:
  We present an investigation of the metal enrichment of the intra-cluster
medium (ICM) by galactic winds and merger-driven starbursts. We use combined
N-body/hydrodynamic simulations with a semi-numerical galaxy formation model.
The mass loss by galactic winds is obtained by calculating transonic solutions
of steady state outflows, driven by thermal, cosmic ray and MHD wave pressure.
The inhomogeneities in the metal distribution caused by these processes are an
ideal tool to reveal the dynamical state of a galaxy cluster. We present
surface brightness, X-ray emission weighted temperature and metal maps of our
model clusters as they would be observed by X-ray telescopes like XMM-Newton.
We show that X-ray weighted metal maps distinguish between pre- or post-merger
galaxy clusters by comparing the metallicity distribution with the
galaxy-density distribution: pre-mergers have a metallicity gap between the
subclusters, post-mergers a high metallicity between subclusters. We apply our
approach to two observed galaxy clusters, Abell 3528 and Abell 3921, to show
whether they are pre- or post-merging systems. The survival time of the
inhomogeneities in the metallicity distribution found in our simulations is up
to several Gyr. We show that galactic winds and merger-driven starbursts enrich
the ICM very efficiently after z=1 in the central (~ 3 Mpc radius) region of a
galaxy cluster.


title:
Light and heavy metal abundances in hot central stars of planetary
  nebulae

abstract:
  We present new results from our spectral analyses of very hot central stars
achieved since the last IAU Symposium on planetary nebulae held in Canberra
2001. The analyses are mainly based on UV and far-UV spectroscopy performed
with the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer
but also on ground-based observations performed at the Very Large Telescope and
other observatories. We report on temperature, gravity, and abundance
determinations for the CNO elements of hydrogen-rich central stars. In many
hydrogen-deficient central stars (spectral type PG1159) we discovered
particular neon and fluorine lines, which are observed for the very first time
in any astrophysical object. Their analysis strongly confirms the idea that
these stars exhibit intershell matter as a consequence of a late helium-shell
flash.


title: On the potential of extrasolar planet transit surveys

abstract:
  We analyse the respective benefits and drawbacks of ground-based and
space-based transit surveys for extrasolar planets. Based on simple but
realistic assumptions about the fraction of lower main sequence stars harboring
telluric and giant planets within the outer limit of the habitable zone, we
predict the harvests of fictitious surveys with three existing wide field
optical and near-IR cameras: the CFHT-Megacam, SUBARU-Suprime and VISTA-IR. An
additional promising instrument is considered, VISTA-Vis, currently under
development. The results are compared with the harvests predicted under exactly
the same assumptions, for the space missions COROT and KEPLER. We show that
ground-based wide field surveys may discover more giant planets than space
missions. However, space surveys seem to constitute the best strategy to search
for telluric planets. In this respect, the KEPLER mission appears 50 times more
efficient than any of the ground--based surveys considered here. KEPLER might
even discover telluric planets in the habitable zone of their host star.


title: Hierarchical Star Formation in M51: Star/Cluster Complexes

abstract:
  We report on a study of young star cluster complexes in the spiral galaxy
M51. Recent studies have confirmed that star clusters do not form in isolation,
but instead tend to form in larger groupings or complexes. We use {\it HST}
broad and narrow band images (from both {\it WFPC2} and {\it ACS}), along with
{\it BIMA}-CO observations to study the properties and investigate the origin
of the e complexes. We find that the complexes are all young ($< 10$ Myr), have
sizes between $\sim$85 and $\sim$240 pc, and have masses between 3-30 $\times
10^{4} M_{\odot}$. Unlike that found for isolated young star clusters, we find
a strong correlation between the complex mass and radius, namely $M\propto
R^{2.33 \pm 0.19}$. This is similar to that found for giant molecular clouds
(GMCs). By comparing the mass-radius relation of GMCs in M51 to that of the
complexes we can estimate the star formation efficiency within the complexes,
although this value is heavily dependent on the assumed CO-to-H$_2$ conversion
factor. The complexes studied here have the same surface density distribution
as individual young star clusters and GMCs. If star formation within the
complexes is proportional to the gas density at that point, then the shared
mass-radius relation of GMCs and complexes is a natural consequence of their
shared density profiles. We briefly discuss possibilities for the lack of a
mass-radius relation for young star clusters. We note that many of the
complexes show evidence of merging of star clusters in their centres,
suggesting that larger star clusters can be produced through the build up of
smaller clusters.


title: GRB Variability-Luminosity Correlation Confirmed

abstract:
  Recently, Guidorzi et al. (2005) expanded the size of the sample of GRBs for
which variabilities and peak luminosities have been measured, from 11 to 32.
They confirm the existence of a correlation, but find a dramatically different
relationship between L and V than had originally been found. We find that this
is the result of improper statistical methodology. When we fit a model to the
data that accommodates both statistical variance (in two dimensions) and sample
variance, we find that L ~ V^3.4(+0.9,-0.6) with a sample variance of
sigma_logV = 0.20(+0.04,-0.04), which is consistent with the original finding
of Reichart et al. (2001) -- L ~ V^3.3(+1.1,-0.9) with a sample variance of
sigma_logV = 0.18(+0.07,-0.05) -- and inconsistent with the finding of Guidorzi
et al. (2005): L ~ V^1.3(+0.8,-0.4) with sample variance assumed to be zero.


title: A Chandra X-Ray Survey of Ultraluminous Infrared Galaxies

abstract:
  We present results from Chandra observations of 14 ultraluminous infrared
galaxies (ULIRGs; log(L_IR/L_Sun) >= 12) with redshifts between 0.04 and 0.16.
The goals of the observations were to investigate any correlation between
infrared color or luminosity and the properties of the X-ray emission and to
attempt to determine whether these objects are powered by starbursts or active
galactic nuclei (AGNs). The sample contains approximately the same number of
high and low luminosity objects and ``warm'' and ``cool'' ULIRGs. All 14
galaxies were detected by Chandra. Our analysis shows that the X-ray emission
of the two Seyfert 1 galaxies in our sample are dominated by AGN. The remaining
12 sources are too faint for conventional spectral fitting to be applicable.
Hardness ratios were used to estimate the spectral properties of these faint
sources. The photon indices for our sample plus the Chandra-observed sample
from Ptak et al.(2003) peak in the range of 1.0-1.5, consistent with
expectations for X-ray binaries in a starburst, an absorbed AGN, or hot
bremsstrahlung from a starburst or AGN. The values of photon index for the
objects in our sample classified as Seyferts (type 1 or 2) are larger than 2,
while those classified as HII regions or LINERs tend to be less than 2. The
hard X-ray to far-infrared ratios for the 12 weak sources are similar to those
of starbursts, but we cannot rule out the possibility of absorbed, possibly
Compton-thick, AGNs in some of these objects. Two of these faint sources were
found to have X-ray counterparts to their double optical and infrared nuclei.


title:
An infrared study of galactic OH/IR stars. II. The `GLMP sample' of red
  oxygen-rich AGB stars

abstract:
  We present optical and near-infrared finding charts taken from the DSS and
2MASS surveys of 94 IRAS sources selected from the GLMP catalogue
(Garc\'{\i}a-Lario 1992), and accurate astrometry (~0.2") for most of them.
Selection criteria were very red IRAS colours representative for OH/IR stars
with optically thick circumstellar shells and the presence of variability
according to the IRAS variability index (VAR>50). The main photometric
properties of the stars in this `GLMP sample' are presented, discussed and
compared with the correspondent properties of the `Arecibo sample' of OH/IR
stars studied in Jim\'enez-Esteban et al. (2005a). We find that 37% of the
sample (N=34) have no counterpart in the 2MASS, implying extremely high optical
depths of their shells. Most of the sources identified in the 2MASS are faint
(K>~8) and of very red colour in the near-infrared, as expected. The brightest
2MASS counterpart (K=5.3mag) was found for IRAS 18299--1705. Its blue colour
H--K=1.3 suggests that IRAS 8299--1705 is a post-AGB star. A couple of GLMP
sources have faint but relatively blue counterparts. They might be misidentifed
field stars or stars hich experienced recently a drop of their mass loss rates.
The `GLMP sample' in general is made of oxygen-rich AGB stars, which are highly
obscured by their circumstellar shells. They belong to the same population as
the reddest OH/IR stars in the `Arecibo sample'.


title: The Effect of Baryons on Halo Shapes

abstract:
  Observational evidence indicates a mismatch between the shapes of
collisionless dark matter (DM) halos and those of observed systems. Using
hydrodynamical cosmological simulations we investigate the effect of baryonic
dissipation on halo shapes. We show that dissipational simulations produce
significantly rounder halos than those formed in equivalent dissipationless
simulations. Gas cooling causes an average increase in halo principal axis
ratios of ~ 0.2-0.4 in the inner regions and a systematic shift that persists
out to the virial radius, alleviating any tension between theory and
observations. Although the magnitude of the effect may be overestimated due to
overcooling, cluster formation simulations designed to reproduce the observed
fraction of cold baryons still produce substantially rounder halos. Subhalos
also exhibit a trend of increased axis ratios in dissipational simulations.
Moreover, we demonstrate that subhalos are generally rounder than corresponding
field halos even in dissipationless simulations. Lastly, we analyze a series of
binary, equal-mass merger simulations of disk galaxies. Collisionless mergers
reveal a strong correlation between DM halo shape and stellar remnant
morphology. In dissipational mergers, the combination of strong gas inflows and
star formation leads to an increase of the DM axis ratios in the remnant. All
of these results highlight the vital role of baryonic processes in comparing
theory with observations and warn against over-interpreting discrepancies with
collisionless simulations on small scales.


title:
The afterglow and elliptical host galaxy of the short gamma-ray burst
  GRB 050724

abstract:
  Despite a rich phenomenology, gamma-ray bursts (GRBs) are divided into two
classes based on their duration and spectral hardness -- the long-soft and the
short-hard bursts. The discovery of afterglow emission from long GRBs was a
watershed event, pinpointing their origin to star forming galaxies, and hence
the death of massive stars, and indicating an energy release of about 10^51
erg. While theoretical arguments suggest that short GRBs are produced in the
coalescence of binary compact objects (neutron stars or black holes), the
progenitors, energetics, and environments of these events remain elusive
despite recent localizations. Here we report the discovery of the first radio
afterglow from a short burst, GRB 050724, which unambiguously associates it
with an elliptical galaxy at a redshift, z=0.257. We show that the burst is
powered by the same relativistic fireball mechanism as long GRBs, with the
ejecta possibly collimated in jets, but that the total energy release is
10-1000 times smaller. More importantly, the nature of the host galaxy
demonstrates that short GRBs arise from an old (>1 Gyr) stellar population,
strengthening earlier suggestions, and providing support for coalescing compact
object binaries as the progenitors.


title:
Observations of Chemically Enriched QSO Absorbers near z ~ 2.3 Galaxies:
  Galaxy-Formation Feedback Signatures in the IGM

abstract:
  We present a study of galaxies and intergalactic gas toward the z=2.73 quasar
HS1700+6416, to explore the effects of galaxy formation feedback on the IGM.
Our observations and ionization simulations indicate that the volume within
100-200 h_71^{-1} physical kpc of high-redshift galaxies contains very small,
dense, and metal-rich absorption-line regions. These systems often contain
shock-heated gas seen in OVI, and may exhibit [Si/C] abundance enhancements
suggestive of Type II supernova enrichment. We argue that the absorbers
resemble thin sheets or bubbles, whose physical properties can be explained
with a simple model of radiatively efficient shocks propegating through the
IGM. Their high metallicities suggest that these shocks are being expelled
from--rather than falling into--star forming galaxies. There is a dropoff in
the IGM gas density at galaxy impact parameters beyond ~300 physical kpc that
may trace boundaries of gas structures where the galaxies reside. The local
heavy-element enhancement covers 100-200 kpc; beyond this the observed
abundances blend into the general IGM. Supernova-driven winds or dynamical
stripping of interstellar gas appears to affect the IGM near massive galaxies,
even at R>~100 kpc. However, these feedback systems represent only a few
percent of the Lya forest mass at z~2.5. Their mass could be larger if the more
numerous metal-poor CIV systems at >~200 kpc are tepid remnants of very
powerful winds. Based on present observations it is not clear that this
scenario is to be favored over one involving pre-enrichment by smaller galaxies
at z>~6.


title: A High Resolution Mosaic of Molecular Gas in Stephan's Quintet

abstract:
  We present high resolution CO J=1-0 observations of the molecular gas in the
Hickson Compact Group Stephan's Quintet (HCG92). Our observations consist of
multiple pointing and mosaics covering all the regions where CO and star
formation has been detected. Within the 100'' field of view centered on the
eastern-most tidal tail, we detect three clumps of emission that may be
partially resolved at our resolution of 8''; two of these are new detections
not previously seen in ISM studies of this region. Two of these clumps lie in
the optical tidal tail, while the third lies to the southeast and is coincident
with a large HI feature, but does not correspond to any features at other
wavelengths. We also tentatively detect CO emission from the star forming
regions in the ``Old Tail'' corresponding to recent star formation activity
detected in recent UV and H$\alpha$ observations. Observations of the rest of
the compact group do not show detections even though strong emission was
detected with single dish telescopes, which suggests the CO emission originates
from a diffuse molecular gas cloud or from more at least three separate clumps
with separations of greater than around 3 kpc.


title:
Characterizing the Shapes of Galaxy Clusters Using Moments of the
  Gravitational Lensing Shear

abstract:
  We explore the use of the tangential component of weak lensing shear to
characterize the ellipticity of clusters of galaxies. We introduce an
ellipticity estimator, and quantify its properties for isolated clusters from
LCDM N-body simulations. We compare the N-body results to results from smooth
analytic models. The expected distribution of the estimator for mock
observations is presented, and we show how this distribution is impacted by
contaminants such as noise, line of sight projections, and misalignment of the
central galaxy used to determine the orientation of the triaxial halo. We
examine the radial profile of the estimator and discuss tradeoffs in the
observational strategy to determine cluster shape.


title: Exploring Large-scale Structure with Billions of Galaxies

abstract:
  We consider cosmological applications of galaxy number density correlations
to be inferred from future deep and wide multi-band optical surveys. We mostly
focus on very large scales as a probe of possible features in the primordial
power spectrum. We find the proposed survey of the Large Synoptic Survey
Telescope may be competitive with future all-sky CMB experiments over a broad
range of scales. On very large scales the inferred power spectrum is robust to
photometric redshift errors, and, given a sufficient number density of
galaxies, to angular variations in dust extinction and photometric calibration
errors. We also consider other applications, such as constraining dark energy
with the two CMB-calibrated standard rulers in the matter power spectrum, and
controlling the effect of photometric redshift errors to facilitate the
interpretation of cosmic shear data. We find that deep photometric surveys over
wide area can provide constraints that are competitive with spectroscopic
surveys in small volumes.


title:
AGN heating, thermal conduction and Sunyaev-Zeldovich effect in galaxy
  groups and clusters

abstract:
  (abridged) We investigate in detail the role of active galactic nuclei on the
physical state of the gas in galaxy groups and clusters, and the implications
for anisotropy in the CMB from Sunyaev-Zeldovich effect. We include the effect
of thermal conduction, and find that the resulting profiles of temperature and
entropy are consistent with observations. Unlike previously proposed models,
our model predicts that isentropic cores are not an inevitable consequence of
preheating. The model also reproduces the observational trend for the density
profiles to flatten in lower mass systems. We deduce the energy E_agn required
to explain the entropy observations as a function of mass of groups and
clusters M_cl and show that E_agn is proportional to M_cl^alpha with alpha~1.5.
We demonstrate that the entropy measurements, in conjunction with our model,
can be translated into constraints on the cluster--black hole mass relation.
The inferred relation is nonlinear and has the form M_bh\propto M_cl^alpha.
This scaling is an analog and extension of a similar relation between the black
hole mass and the galactic halo mass that holds on smaller scales. We show that
the central decrement of the CMB temperature is reduced due to the enhanced
entropy of the ICM, and that the decrement predicted from the plausible range
of energy input from the AGN is consistent with available data of SZ decrement.
We show that AGN heating, combined with the observational constraints on
entropy, leads to suppression of higher multipole moments in the angular power
spectrum and we find that this effect is stronger than previously thought.


title: High-Mass Cloud Cores in the eta Carinae Giant Molecular Cloud

abstract:
  We carried out an unbiased survey for massive dense cores in the giant
molecular cloud associated with eta Carinae with the NANTEN telescope in 12CO,
13CO, and C18O 1-0 emission lines. We identified 15 C18O cores. Two of the 15
cores are associated with IRAS point sources whose luminosities are larger than
10^4 Lo, which indicates that massive star formation is occuring within these
cores. Five cores including the two with IRAS sources are associated with MSX
point sources. We detected H13CO+ (1-0) emission toward 4 C18O cores, one of
which is associated with neither IRAS nor MSX point sources. This core shows
the presence of a bipolar molecular outflow in 12CO (2-1), which indicates that
star formation is also occuring in the core. In total, six C18O cores out of 15
are experienced star formation, and at least 2 of 15 are massive-star forming
cores in the eta Car GMC. We found that massive star formation occurs
preferentially in cores with larger column density, mass, number density, and
smaller ratio of virial mass to LTE mass Mvir/M. We also found that the cores
in the eta Car GMC are characterized by large line width and Mvir/M on average
compared to the cores in other GMCs. We investigated the origin of a large
amount of turbulence in the eta Car GMC. We propose the possibility that the
large turbulence was pre-existing when the GMC was formed, and is now
dissipating. Mechanisms such as multiple supernova explosions in the Carina
flare supershell may have contributed to form a GMC with a large amount of
turbulence.


title: Super-horizon primordial black holes

abstract:
  We discuss a new class of solutions to the Einstein equations which describe
a primordial black hole (PBH) in a flat Friedmann background. Such solutions
arise if a Schwarzschild black hole is patched onto a Friedmann background via
a transition region. They are possible providing the black hole event horizon
is larger than the cosmological apparent horizon. Such solutions have a number
of strange features. In particular, one has to define the black hole and
cosmological horizons carefully and one then finds that the mass contained
within the black hole event horizon decreases when it is larger than the
Friedmann cosmological apparent horizon, although its area always increases.
These solutions involve two distinct future null infinities and are interpreted
as the conversion of a white hole into a black hole. Although such solutions
may not form from gravitational collapse in the same way as standard PBHs,
there is nothing unphysical about them, since all energy and causality
conditions are satisfied. Their conformal diagram is a natural amalgamation of
the Kruskal diagram for the extended Schwarzschild solution and the conformal
diagram for a black hole in a flat Friedmann background. In this paper, such
solutions are obtained numerically for a spherically symmetric universe
containing a massless scalar field, but it is likely that they exist for more
general matter fields and less symmetric systems.


title:
Searching for the Sources Responsible for Cosmic Reionization: Probing 7
  < z < 10 and Beyond

abstract:
  (Abridged) We review recent observations that suggest the star formation rate
density is declining over 3$<z<$7 and illustrate the challenges that this poses
in explaining the assembled stellar mass in z$\sim$6 galaxies deduced from
Spitzer data. A plausible conclusion is a vigorous period of earlier star
formation. Prior to JWST and TMT, strong lensing offers a unique probe of the
extent of this earlier activity. We discuss the first results of a blind
spectroscopic survey of lensing clusters for 8.5$<z<$10 Ly$\alpha$ emitters
using NIRSPEC which is achieving a limiting star formation rate of 0.1
$M_{\odot}$ yr$^{-1}$. A companion HST/IRAC survey is targeting lensed $z$ and
$J$-band dropouts and probes a $\simeq$1 arcmin$^2$ region 1 magnitude deeper
than the UDF/NICMOS observations. Both surveys will constrain the contribution
of early, low luminosity, sources to cosmic reionization.


title:
The evolution of the ultraviolet and infrared luminosity densities in
  the universe at 0<z<1

abstract:
  The ratio between far-ultraviolet (FUV) and infrared (IR) luminosity
densities from z=0 to z=1 is discussed by using the luminosity functions (LFs)
of both wavelengths. The FUV LF (z=0-1) based on GALEX has been reported by
Arnouts et al. (2005), whilst for the IR LF, we used the IRAS PSCz 60-um LF for
the local universe and the Spitzer 15-um LF at higher-z as used by Le Floch et
al. (2005). Both luminosity densities show a significant evolutionary trend,
but the IR evolves much faster than the FUV. Consequently, the ratio
$\rho_{dust}/\rho_{FUV}$ increases toward higher-z, from 4 (local) to 15 (z =
1). It is also shown that more than 70% of the star formation activity in the
universe is obscured by dust at 0.5 < z < 1.2.


title:
Beryllium Enhancement as Evidence for Accretion in a Lithium-Rich F
  Dwarf

abstract:
  The early F dwarf star ``J37'' in the open cluster NGC6633 shows an unusual
pattern of photospheric abundances, including an order of magnitude enhancement
of lithium and iron-peak elements, but an under-abundance of carbon. As a
consequence of its thin convection zone these anomalies have been attributed to
either radiative diffusion or the accretion of hydrogen-depleted material. By
comparing high resolution VLT/UVES spectra of J37 (and other F stars in NGC
6633) with syntheses of the Be ii doublet region at 3131 Ang, we establish that
J37 also has a Be abundance (A(Be)=3.0+/-0.5) that is at least ten times the
cosmic value. This contradicts radiative diffusion models that produce a Li
over-abundance, as they also predict photospheric Be depletion. Instead, since
Be is a highly refractory element, it supports the notion that J37 is the first
clear example of a star that has accreted volatile-depleted material with a
composition similar to chondritic meteorites, although some diffusion may be
necessary to explain the low C and O abundances.


title: Gamma-ray bursts: Restarting the Engine

abstract:
  Recent gamma-ray burst observations have revealed late-time, highly energetic
events which deviate from the simplest expectations of the standard fireball
picture. Instead they may indicate that the central engine is active or
restarted at late times. We suggest that fragmentation and subsequent accretion
during the collapse of a rapidly rotating stellar core offers a natural
mechanism for this.


title: The bound $r \leq 16\epsilon$ on the primordial tensor perturbation

abstract:
  I recall the well-known sufficient conditions for the bound $r<16\epsilon$ on
the spectrum of the primordial tensor perturbation. Two recent papers claim a
violation of this bound, without stating explicitely any violation of the
sufficient conditions.


title:
A Persistent High-Energy Flux from the Heart of the Milky Way :
  Integral's view of the Galactic Center

abstract:
  The Ibis/Isgri imager on Integral detected for the first time a hard X-ray
source, IGR J17456-2901, located within 1' of Sgr A* over the energy range
20-100 keV. Here we present the results of a detailed analysis of ~7 Ms of
Integral observations of the GC. With an effective exposure of 4.7 Ms we have
obtained more stringent positional constraints on this HE source and
constructed its spectrum in the range 20-400 keV. Furthermore, by combining the
Isgri spectrum with the total X-ray spectrum corresponding to the same physical
region around SgrA* from XMM data, and collected during part of the Integral
observations, we constructed and present the first accurate wide band HE
spectrum for the central arcmins of the Galaxy. Our complete analysis of the
emission properties of IGR shows that it is faint but persistent with no
variability above 3 sigma contrary to what was alluded to in our first paper.
This result, in conjunction with the spectral characteristics of the X-ray
emission from this region, suggests that the source is most likely not
point-like but, rather, that it is a compact, yet diffuse, non-thermal emission
region. The centroid of IGR is estimated to be R.A.=17h45m42.5,
decl.=-28deg59'28'', offset by 1' from the radio position of Sgr A* and with a
positional uncertainty of 1'. Its 20-400 keV luminosity at 8 kpc is L=5.4x10^35
erg/sec. Very recently, Hess detected of a source of ~TeV g-rays also located
within 1' of Sgr A*. We present arguments in favor of an interpretation
according to which the photons detected by Integral and Hess arise from the
same compact region of diffuse emission near the central BH and that the
supernova remnant Sgr A East could play an important role as a contributor of
very HE g-rays to the overall spectrum from this region.


title:
Absorption and scattering by interstellar dust: XMM-Newton observation
  of Cyg X-2

abstract:
  We present results of the XMM-Newton observation on the bright X-ray binary
Cyg X-2. In our analysis we focus upon the absorption and scattering of the
X-ray emission by interstellar dust. The scattering halo around Cyg X-2,
observed with the CCD detector EPIC-pn, is well detected up to ~7 arcmin and
contributes ~5-7% to the total source emission at 1 keV, depending on the dust
size distribution model considered. For the first time spatially resolved
spectroscopy of a scattering halo is performed. In the halo spectrum we clearly
detect the signature of the interstellar dust elements: O, Mg, and Si. The
spectral modeling of the halo shows a major contribution of silicates (olivine
and pyroxene). The spatial analysis of the halo shows that the dust is smoothly
distributed toward Cyg X-2 at least for ~60% of the path to the source. Within
the instrumental limits, the data do not show preference for a specific dust
size distribution; namely the Mathis, Rumpl & Nordsieck (1977) or the
Weingartner & Draine (2001) model. We used the Mie theory to compute the
differential scattering cross section. The RGS data were used to investigate
the ISM absorption, in particular the region of the oxygen edge. Combining the
RGS results with the information on dust grains provided by the EPIC-pn
spectrum of the halo we estimate a column density for dust absorption by
oxygen, provided that it is locked in silicate grains (abridged).


title:
The first wide ultracool binary dwarf in the field:
  DENIS-J055146.0-443412.2 (M8.5 + L0)

abstract:
  We present observations of a new very low mass field binary, discovered
during an infrared imaging survey of 250 DENIS L and very late-M dwarfs.
DENIS-J055146.0-443412.2 is an M8.5+L0 pair, with a physical separation of over
200 AU. This makes it the widest very low mass binary known in the field, by an
order of magnitude. Such a system is fragile, and it would not have survived a
close encounter with a third body. Its existence demonstrate that some very low
mass stars/brown dwarfs form without ejection from a multiple system, or any
other strong dynamical interaction.


title: Two-dimensional Kinematics of a Bar and Central Disk in NGC5448

abstract:
  We analyse SAURON kinematic maps of the inner kpc of the early-type (Sa)
barred spiral galaxy NGC 5448. The observed morphology and kinematics of the
emission-line gas is patchy and perturbed, indicating clear departures from
circular motion. The kinematics of the stars is more regular, and displays a
small inner disk-like system embedded in a large-scale rotating structure. We
focus on the [OIII] gas, and use a harmonic decomposition formalism to analyse
the gas velocity field. The higher-order harmonic terms and the main kinematic
features of the observed data are consistent with an analytically constructed
simple bar model, which is derived using linear theory. Our study illustrates
how the harmonic decomposition formalism can be used as a powerful tool to
quantify non-circular motions in observed gas velocity fields.


title: Observational constraints on the dark energy density evolution

abstract:
  We constrain the evolution of the dark energy density from Cosmic Microwave
Background, Large Scale Structure and Supernovae Ia measurements. While
Supernovae Ia are most sensitive to the equation of state $w_0$ of dark energy
today, the Cosmic Microwave Background and Large Scale Structure data best
constrains the dark energy evolution at earlier times. For the parametrization
used in our models, we find $w_0 < -0.8$ and the dark energy fraction at very
high redshift $\Omega_{early} < 0.03$ at 95 per cent confidence level.


title:
Is There an Imprint of Primordial Stars in the Tev Gamma-Ray Spectrum of
  Blazars?

abstract:
  The 1 - 5 micron diffuse sky emission from which local foreground emission
from the solar system and the Galaxy have been subtracted exceeds the
brightness that can be attributed to normal star forming galaxies. The nature
of this excess near-infrared background light (NIRBL) is still controversial.
On one hand, it has been interpreted as a distinct spectral feature created by
the redshifted emission from primordial (Population III) stars that have formed
at redshifts > 8. On the other hand, the NIRBL spectrum is almost identical to
that of the zodiacal cloud, raising the possibility that it is of local origin.
Blazars can, in principle, offer a simple test for the nature and origin of the
NIRBL. Very high energy gamma-ray photons emitted by these objects are
attenuated on route to earth by photon-photon interactions with the
extragalactic background light (EBL). This paper examines whether the
extragalactic nature of the NIRBL can be determined from the analysis of the
TeV spectra of blazars. (Abridged)


title: Directional Statistics for WIMP direct detection II: 2-d read-out

abstract:
  The direction dependence of the WIMP direct detection rate provides a
powerful tool for distinguishing a WIMP signal from possible backgrounds. We
study the the number of events required to discriminate a WIMP signal from an
isotropic background for a detector with 2-d read-out using non-parametric
circular statistics. We also examine the number of events needed to i) detect a
deviation from rotational symmetry, due to flattening of the Milky Way halo and
ii) detect a deviation in the mean direction due to a tidal stream. If the
senses of the recoils are measured then of order 20-70 events (depending on the
plane of the 2-d read out) will be sufficient to reject isotropy of the raw
recoil angles at 90% confidence. If the senses can not be measured these number
increase by roughly two orders of magnitude (compared with an increase of one
order of magnitude for the case of full 3-d read-out). The distributions of the
reduced angles, with the (time dependent) direction of solar motion subtracted,
are far more anisotropic, however, and if the isotropy tests are applied to
these angles then the numbers of events required are similar to the case of 3-d
read-out. A deviation from rotational symmetry will only be detectable if the
Milky Way halo is significantly flattened. The deviation in the mean direction
due to a tidal stream is potentially detectable, however, depending on the
density and direction of the stream.


title:
Development of a carbon fibre composite active mirror: Design and
  testing

abstract:
  Carbon fibre composite technology for lightweight mirrors is gaining
increasing interest in the space- and ground-based astronomical communities for
its low weight, ease of manufacturing, excellent thermal qualities and
robustness. We present here first results of a project to design and produce a
27 cm diameter deformable carbon fibre composite mirror. The aim was to produce
a high surface form accuracy as well as low surface roughness. As part of this
programme, a passive mirror was developed to investigate stability and coating
issues. Results from the manufacturing and polishing process are reported here.
We also present results of a mechanical and thermal finite element analysis, as
well as early experimental findings of the deformable mirror. Possible
applications and future work are discussed.


title: Galaxy-Quasar correlations between APM galaxies and Hamburg-ESO QSOs

abstract:
  We detect angular galaxy-QSO cross-correlations between the APM Galaxy
Catalogue and a preliminary release (consisting of roughly half of the
anticipated final catalogue) of the Hamburg-ESO Catalogue of Bright QSOs as a
function of source QSO redshift using multiple cross-correlation estimators.
Each of the estimators yield very similar results, implying that the APM
catalogue and the Hamburg-ESO survey are both fair samples of the respective
true galaxy and QSO populations. Though the signal matches the expectations of
gravitational lensing qualitatively, the strength of the measured
cross-correlation signal is significantly greater than the CDM models of
lensing by large scale structure would suggest. This same disagreement between
models and observation has been found in several earlier studies. We estimate
our confidence in the correlation detections versus redshift by generating 1000
random realizations of the Hamburg-ESO QSO survey: We detect physical
associations between galaxies and low-redshift QSOs at 99% confidence and
detect lensing associations at roughly 95% confidence for QSOs with redshifts
between 0.6 and 1. Control cross-correlations between Galactic stars and QSOs
show no signal. Finally, the overdensities (underdensities) of galaxies near
QSO positions relative to those lying roughly 135 - 150 arcmin away are
uncorrelated with differences in Galactic extinction between the two regions,
implying that Galactic dust is not significantly affecting the QSO sample.


title:
XMM-Newton Data Processing for Faint Diffuse Emission: Proton Flares,
  Exposure Maps and Report on EPIC MOS1 Bright CCDs Contamination

abstract:
  We present a study of the in-flight performance of the XMM-Newton EPIC MOS
and pn detectors, with focus on the influence of proton flares and vignetting
on the data. The very wide range in the conditions of our sample of
observations, in terms of exposure length and background intensities, allows
the detection of a wide range in the spectra of the proton flares, in contrast
to the hard-spectrum flares proposed by Lumb et al.(2002) or Read et al.(2003)
We also find an up to now unreported contamination in the low energy regime
(E<0.5 keV) of the MOS1 observations, consisting of a significant increase in
the measured intensities in two CCDs at the edges of the detector. This
contamination yields in "bright CCDs" in the observations. Its effect must be
taken into account for the study of sources detected in the affected CCDs. With
respect to vignetting, we present in-flight exposure maps and we propose a
method to repeat this calculation for user-definable energy bands. All the
results presented here, have the goal to enable the study of very faint
extended sources with XMM-Newton, like nearby galactic X-ray halos or the soft
X-ray background.


title:
Mergers of neutron star black hole binaries with small mass ratios:
  nucleosynthesis, gamma-ray bursts and electromagnetic transients

abstract:
  I discuss simulations of the coalescence of black hole neutron star binary
systems with black hole masses between 14 and 20 \msun. The calculations use a
three-dimensional smoothed particle hydrodynamics code, a
temperature-dependent, nuclear equation of state and a multi-flavor neutrino
scheme. General relativistic effects are mimicked using the \Pacz-Wiita
pseudo-potential and gravitational radiation reaction forces. Opposite to
previous, purely Newtonian calculations, in none of the explored cases episodic
mass transfer occurs. The neutron star is always completely disrupted after
most of its mass has been transferred directly into the hole. For black hole
masses between 14 and 16 \Msun an accretion disk forms, large parts of it,
however, are inside the last stable orbit and therefore falling with large
radial velocities into the hole. These disks are (opposite to the neutron star
merger case) thin and -apart from a spiral shock- essentially cold. For higher
mass black holes ($M_{\rm BH} \ge 18$ \msun) almost the complete neutron star
disappears in the hole without forming an accretion disk. In these cases the
surviving material is spun up by tidal torques and ejected as a half-ring of
neutron-rich matter. None of the investigated systems is a promising GRB
central engine. We find between 0.01 and 0.2 \Msun of the neutron star to be
dynamically ejected. Like in a type Ia supernova, the radioactive decay of this
material will power a light curve with a peak luminosity of a few times
$10^{44}$ erg/s. The maximum will be reached about three days after the
coalescence and will be mainly visible in the optical/near infrared band. The
coalescence itself may produce a precursor pulse with a thermal spectrum of
$\sim 10$ ms duration.


title: Early Tracking Behavior in Small-field Quintessence Models

abstract:
  We study several quintessence models which are singular at Q=0, and use a
simple initial constraint $Q_i\ge H_{inflation}/2\pi$ to see when they enter
tracking regime, disregarding the details of inflation. We find it can give
strong constraints for the inverse power-law potential $V=V_0Q^{-\alpha}$,
which has to enter tracking regime for ${\rm ln}z \sim 10$. While for the
supergravity model $V=V_0Q^{-\alpha}{\rm exp}(kQ^2/2)$, the constraint is much
weakened. For another kind inverse power-law potential $V=V_0{\rm
exp}(\lambda/Q)$, it exhibits no constraints.


title: The effect of stellar evolution on SiC dust grain sizes

abstract:
  Stars on the asymptotic giant branch (AGB) produce dust in their
circumstellar shells. The nature of the dust-forming environment is influenced
by the evolution of the stars, in terms of both chemistry and density, leading
to an evolution in the nature of the dust that is produced. Carbon-rich AGB
stars are known to produce silicon carbide (SiC). Furthermore, observations of
the ~11um SiC feature show that the spectral features change in a sequence that
correlates with stellar evolution. We present new infrared spectra of amorphous
SiC and show that the ~9um feature seen in both emission and absorption, and
correlated with trends in the ~11um feature, may be due to either amorphous SiC
or to nano-crystalline diamond with a high proportion of Si substituting for C.
Furthermore, we identify SiC absorption in three ISO spectra of extreme carbon
stars, in addition to the four presented by Speck et al. (1997). An accurate
description of the sequence in the IR spectra of carbon stars requires
accounting for both SiC emission and absorption features. This level of detail
is needed to infer the role of dust in evolution of carbon stars. Previous
attempts to find a sequence in the infrared spectra of carbon stars considered
SiC emission features, while neglecting SiC absorption features, leading to an
interpretation of the sequence inadequately describes the role of dust. We show
that the evolutionary sequence in carbon star spectra is consistent with a
grain size evolution, such that dust grains get progressively smaller as the
star evolves. The evolution of the grain sizes provides a natural explanation
for the shift of the ~11um SiC feature in emission and in absorption. Further
evidence for this scenario is seen in both post-AGB star spectra and in
meteoritic studies of presolar grains.