title:
Is it possible to tell the difference between fermionic and bosonic hot
  dark matter?

abstract:
  We study the difference between thermally produced fermionic and bosonic hot
dark matter in detail. In the linear regime of structure formation, their
distinct free-streaming behaviours can lead to pronounced differences in the
matter power spectrum. While not detectable with current cosmological data,
such differences will be clearly observable with upcoming large scale weak
lensing surveys for particles as light as m_HDM ~ 0.2 eV. In the nonlinear
regime, bosonic hot dark matter is not subject to the same phase space
constraints that severely limit the amount of fermionic hot dark matter infall
into cold dark matter halos. Consequently, the overdensities in fermionic and
bosonic hot dark matter of equal particle mass can differ by more than a factor
of five in the central part of a halo. However, this unique manifestation of
quantum statistics may prove very difficult to detect unless the mass of the
hot dark matter particle and its decoupling temperature fall within a very
narrow window, 1 < m_HDM/eV < 4 and g* < 30. In this case, hot dark matter
infall may have some observable consequences for the nonlinear power spectrum
and hence the weak lensing convergence power spectrum at l ~ 10^3 - 10^4 at the
percent level.


title: PPN-limit of Fourth Order Gravity inspired by Scalar-Tensor Gravity

abstract:
  Based on the {\it dynamical} equivalence between higher order gravity and
scalar-tensor gravity the PPN-limit of fourth order gravity is discussed. We
exploit this analogy developing a fourth order gravity version of the Eddington
PPN-parameters. As a result, Solar System experiments can be reconciled with
higher order gravity, if physical constraints descending from experiments are
fulfilled.


title: Inhomogeneous systematic signals in cosmic shear observations

abstract:
  We calculate the systematic errors in the weak gravitational lensing power
spectrum which would be caused by spatially varying calibration (i.e.
multiplicative) errors, such as might arise from uncorrected seeing or
extinction variations. The systematic error is fully described by the angular
two-point correlation function of the systematic in the case of the 2D lensing
that we consider here. We investigate three specific cases: Gaussian,
``patchy'' and exponential correlation functions. In order to keep systematic
errors below statistical errors in future LSST-like surveys, the spatial
variation of calibration should not exceed 3% rms. This conclusion is
independently true for all forms of correlation function we consider. The
relative size the E- and B-mode power spectrum errors does, however, depend
upon the form of the correlation function, indicating that one cannot repair
the E-mode power spectrum systematics by means of the B-mode measurements.


title: Bivariate Galaxy Luminosity Functions in the Sloan Digital Sky Survey

abstract:
  Bivariate luminosity functions (LFs) are computed for galaxies in the New
York Value-Added Galaxy Catalogue, based on the Sloan Digital Sky Survey Data
Release 4. The galaxy properties investigated are the morphological type,
inverse concentration index, Sersic index, absolute effective surface
brightness, reference frame colours, absolute radius, eClass spectral type,
stellar mass and galaxy environment. The morphological sample is flux-limited
to galaxies with r < 15.9 and consists of 37,047 classifications to an RMS
accuracy of +/- half a class in the sequence E, S0, Sa, Sb, Sc, Sd, Im. These
were assigned by an artificial neural network, based on a training set of 645
eyeball classifications. The other samples use r < 17.77 with a median redshift
of z ~ 0.08, and a limiting redshift of z < 0.15 to minimize the effects of
evolution. Other cuts, for example in axis ratio, are made to minimize biases.
A wealth of detail is seen, with clear variations between the LFs according to
absolute magnitude and the second parameter. They are consistent with an early
type, bright, concentrated, red population and a late type, faint, less
concentrated, blue, star forming population. This bimodality suggests two major
underlying physical processes, which in agreement with previous authors we
hypothesize to be merger and accretion, associated with the properties of
bulges and discs respectively. The bivariate luminosity-surface brightness
distribution is fit with the Choloniewski function (a Schechter function in
absolute magnitude and Gaussian in surface brightness). The fit is found to be
poor, as might be expected if there are two underlying processes.


title:
Toward the Detection of Transiting Hot Earths and Hot Neptunes in Open
  Clusters

abstract:
  Radial velocity searches for extrasolar planets have recently detected
several very low mass (7-20M_Earth) planets in close orbits with periods <10
days. We consider the prospects for detecting the analogs of these planets in
Galactic open clusters via transits. We outline the requirements for
constructing a transit survey that would allow one to probe such ``Hot Earths''
and ``Hot Neptunes.'' Specifically, we present a simple criterion for detection
that defines the minimum aperture required to detect planets of a given radius
in a cluster at a given distance. Adopting photometric precisions that have
been demonstrated in state-of-the-art variability surveys, we then predict the
number of planets one could potentially detect with ambitious transit surveys
toward several open clusters. Dedicated surveys lasting more than 20 nights
with Pan-STARRS toward the Hyades and Praesepe could detect a handful of Hot
Earths, if the majority of stars host such planets. Similar surveys with larger
aperture telescopes (e.g. CFHT, MMT), toward M67, M35, M50, and M37 could
detect Hot Neptunes, provided that their frequency is >1%. The majority of
planets will be detected around M dwarfs; detecting Hot Neptunes around such
primaries requires photometric precisions of ~1%, whereas Hot Earths require
\~0.1%. We discuss potential hurdles in detecting and confirming small planets
in ground-based surveys, including correlated noise, false positives, and
intrinsic stellar variability.


title: A possible black hole in the gamma-ray microquasar LS 5039

abstract:
  The population of high energy and very high energy gamma-ray sources,
detected with EGRET and the new generation of ground-based Cherenkov
telescopes, conforms a reduced but physically important sample. Most of these
sources are extragalactic (e.g., blazars), while among the galactic ones there
are pulsars and SN remnants. The microquasar LS 5039, previously proposed to be
associated with an EGRET source by Paredes et al. (2000), has recently been
detected at TeV energies, confirming that microquasars should be regarded as a
class of high energy gamma-ray sources. To model and understand how the
energetic photons are produced and escape from LS 5039 it is crucial to unveil
the nature of the compact object, which remains unknown. Here we present new
intermediate-dispersion spectroscopy of this source which, combined with values
reported in the literature, provides an orbital period of 3.90603+/-0.00017 d,
a mass function f(M)=0.0053+/-0.0009 M_sun, and an eccentricity e=0.35+/-0.04.
Atmosphere model fitting to the spectrum of the optical companion, together
with our new distance estimate of d=2.5+/-0.1 kpc, yields R_opt=9.3+0.7-0.6
R_sun, log (L_opt/L_sun)=5.26+/-0.06, and M_opt=22.9+3.4-2.9 M_sun. These,
combined with our dynamical solution and the assumption of
pseudo-synchronization, yield an inclination i=24.9+/-2.8 degree and a compact
object mass M_X=3.7+1.3-1.0 M_sun. This is above neutron star masses for most
of the standard equations of state and, therefore, we propose that the compact
object in LS 5039 is a black hole. We finally discuss about the implications of
our orbital solution and new parameters of the binary system on the CNO
products, the accretion/ejection energetic balance, the SN explosion scenario,
and the behaviour of the TeV emission with the new orbital period.


title:
Multi-Dimensional Density Estimation and Phase Space Structure Of Dark
  Matter Halos

abstract:
  We present a method to numerically estimate the densities of a discretely
sampled data based on binary space partitioning tree. We start with a root node
containing all the particles and then recursively divide each node into two
nodes each containing roughly equal number of particles,until each of the nodes
contains only one particle. The volume of such a leaf node provides an estimate
of the local density. We implement an entropy-based node splitting criterion
that results in a significant improvement in the estimation of densities
compared to earlier work. The method is completely metric free and can be
applied to arbitrary number of dimensions. We apply this method to determine
the phase space densities of dark matter halos obtained from cosmological
N-body simulations. We find that contrary to earlier studies, the volume
distribution function $v(f)$ of phase space density $f$ does not have a
constant slope but rather a small hump at high phase space densities. We
demonstrate that a model in which a halo is made up by a superposition of
Hernquist spheres is not capable in explaining the shape of $v(f)$ vs $f$
relation, whereas a model which takes into account the contribution of the main
halo separately roughly reproduces the behavior as seen in simulations. The use
of the presented method is not limited to calculation of phase space densities,
but can be used as a general-purpose data-mining tool and due to its speed and
accuracy it is ideally suited for analysis of large multidimensional data sets.


title: Metal-Poor Globular Clusters and the Formation of Their Host Galaxies

abstract:
  We have determined the total numbers and specific frequencies of blue,
metal-poor globular clusters (GCs) in eight spiral and early-type galaxies.
These data, along with five measurements from the literature, show a trend of
increasing blue GC specific frequency with increasing mass of the host galaxy.
The increase is not accounted for in a simple galaxy formation model in which
ellipticals and their GC systems are formed by the merger of typical spiral
galaxies. The data appear broadly consistent with hierarchical formation
scenarios in which metal-poor GCs are formed over a finite period in the early
Universe during the initial stages of galaxy assembly. In this picture, the
observed trend is related to biasing, in the sense that the more massive
galaxies of today began assembling earlier and therefore formed relatively more
GCs during this early epoch of metal-poor GC formation. We discuss how
comparisons of the observed specific frequency of metal-poor GCs with model
calculations can constrain the formation redshift of these objects.


title: A Spitzer/IRAC Survey of the Orion Molecular Clouds

abstract:
  We present initial results from a survey of the Orion A and B molecular
clouds made with the InfraRed Array Camera (IRAC) onboard the Spitzer Space
Telescope. This survey encompasses a total of 5.6 square degrees with the
sensitivity to detect objects below the hydrogen burning limit at an age of 1
Myr. These observations cover a number of known star forming regions, from the
massive star forming clusters in the Orion Nebula and NGC 2024, to small groups
of low mass stars in the L1641. We combine the IRAC photometry with photometry
from the 2MASS point source catalog and use the resulting seven band data to
identify stars with infrared excesses due to dusty disks and envelopes. Using
the presence of an infrared excess as an indicator of youth, we show the
distribution of young stars and protostars in the two molecular clouds. We find
that roughly half of the stars are found in dense clusters surrounding the two
regions of recent massive star formation in the Orion clouds, NGC 2024 and the
Orion Nebula.


title:
Steady-State Electrostatic Layers from Weibel Instability in
  Relativistic Collisionless Shocks

abstract:
  It is generally accepted that magnetic fields generated in the nonlinear
development of the transverse Weibel instability provide effective
collisionality in unmagnetized collisionless shocks. Recently, extensive two
and three dimensional simulations improved our understanding of the growth and
saturation of the instability in colliding plasma shells. However, the
steady-state structure of the shock wave transition layers remains poorly
understood. We use basic physical considerations and order-of-magnitude
arguments to study the steady state structure in relativistic unmagnetized
collisionless shocks in pair plasmas. The shock contains an electrostatic layer
resulting from the formation of stationary, magnetically-focused current
filaments. The filaments form where the cold upstream plasma and the
counterstreaming thermal plasma interpenetrate. The filaments are not entirely
neutral and strong electrostatic fields are present. Most of the downstream
particles cannot cross this layer into the upstream because they are trapped by
the electrostatic field. We identify the critical location in the shock
transition layer where the electromagnetic field ceases to be static. At this
location, the degree of charge separation in the filaments reaches a maximum
value, the current inside the filaments comes close to the Alfv\'en limit, and
the phase space distribution function starts to isotropize. We argue that the
radius of the current filaments upstream of the critical location is about
twice the upstream plasma skin depth. Finally, we show that some downstream
particles cross the electrostatic layer and run ahead of the shock into the
preshock medium without causing instability. These particles may play an
important role in particle acceleration.


title:
Discovery of Five New R Coronae Borealis Stars in the MACHO Galactic
  Bulge Database

abstract:
  We have identified five new R Coronae Borealis (RCB) stars in the Galactic
bulge using the MACHO Project photometry database, raising the total number of
known Galactic RCB stars to about 40. We have obtained spectra to confirm the
identifications. The fact that four out of the five newly identified RCB stars
are ``cool'' (T(eff) < 6000 K) rather than ``warm'' (T(eff) > 6000 K) suggests
that the preponderance of warm RCB stars among the existing sample is a
selection bias. These cool RCB stars are redder and fainter than their warm
counterparts and may have been missed in surveys done with blue plates. Based
on the number of new RCB stars discovered in the MACHO bulge fields, there may
be ~250 RCB stars in the reddened "exclusion" zone toward the bulge.


title:
Measuring the Growth of Structure with Spectroscopically Identified
  Groups and Clusters

abstract:
  Number counts of galaxy clusters offer a very promising probe of the Dark
Energy (DE) equation-of-state parameter, $w$. The basic goal is to measure
abundances of these objects as a function of redshift, compare this to a
theoretical prediction, and infer the values of cosmological parameters.
Various teams have proposed such a measurement, including the South Pole
Telescope, the Dark Energy Survey and the Red-Sequence Cluster Survey. The
specific study discussed here detects clusters and smaller galaxy groups in the
three-dimensional distribution of galaxies inferred from a large spectroscopic
redshift survey. This method allows the abundance, $N$, of groups and clusters
to be measured as a function of \emph{velocity dispersion}, as well as of
redshift, permitting a more sensitive test of cosmology.


title: Black-Hole Transients : From QPOs to Relativistic Jets

abstract:
  Due to the impressive amount of new data provided by the RXTE satellite in
the past decade, our knowledge of the phenomenology of accretion onto black
holes has increased considerably. In particular, it has been possible to
schematize the outburst evolution of transient systems on the basis of their
spectral and timing properties, and link them to the ejection of relativistic
jets as observed in the radio. Here, I present this scheme, concentrating on
the properties of the quasi-periodic oscillations observed in the light curves
and on the link with jet ejection.


title:
Resonant Cyclotron Scattering and Comptonization in Neutron Star
  Magnetospheres

abstract:
  Resonant cyclotron scattering of the surface radiation in the magnetospheres
of neutron stars may considerably modify the emergent spectra and impede
efforts to constraint neutron star properties. Resonant cyclotron scattering by
a non-relativistic warm plasma in an inhomogeneous magnetic field has a number
of unusual characteristics: (i) in the limit of high resonant optical depth,
the cyclotron resonant layer is half opaque, in sharp contrast to the case of
non-resonant scattering. (ii) The transmitted flux is on average Compton
up-scattered by ~ $1+ 2 beta_T$, where $\beta_T$ is the typical thermal
velocity in units of the velocity of light; the reflected flux has on average
the initial frequency. (iii) For both the transmitted and reflected fluxes the
dispersion of intensity decreases with increasing optical depth. (iv) The
emergent spectrum is appreciably non-Plankian while narrow spectral features
produced at the surface may be erased.
  We derive semi-analytically modification of the surface Plankian emission due
to multiple scattering between the resonant layers and apply the model to
anomalous X-ray pulsar 1E 1048.1--5937. Our simple model fits just as well as
the ``canonical'' magnetar spectra model of a blackbody plus power-law.


title:
16 micron Imaging around the Hubble Deep Field North with the Spitzer
  IRS

abstract:
  We present a pilot study of 16 micron imaging within the GOODS northern
field. Observations were obtained using the PeakUp imaging capability of the
Spitzer IRS. We survey 35 square arcminutes to an average 3 sigma depth of
0.075 mJy and detect 149 sources. The survey partially overlaps the area imaged
at 15 microns by ISO, and we demonstrate that our photometry and galaxy-number
counts are consistent with their measurements. We infer the total infrared
luminosity of 16 micron detections using a comparison to local templates and
find a wide range of L_IR} from ~10^9 to 10^{12} L_sun. Approximately one fifth
of the detected sources have counterparts in the Chandra 2 Msec catalog, and we
show that the hard band (2-8 keV) detected sources are likely to have strong
AGN contributions to the X-ray flux. The ultradeep sensitivity of Chandra
implies some X-ray detections may be purely starbursting objects. We examine
the 16 to 24 micron flux ratio and conclude that it shows evidence for the
detection of redshifted PAH emission at z~0.5 and z>0.8.


title: Mass-radius relations for massive white dwarf stars

abstract:
  We present detailed theoretical mass-radius relations for massive white dwarf
stars with oxygen-neon cores. This work is motivated by recent observational
evidence about the existence of white dwarf stars with very high surface
gravities. Our results are based on evolutionary calculations that take into
account the chemical composition expected from the evolutionary history of
massive white dwarf progenitors. We present theoretical mass-radius relations
for stellar mass values ranging from 1.06 to 1.30 Mo with a step of 0.02 Mo and
effective temperatures from 150000 K to approx. 5,000 K. A novel aspect
predicted by our calculations is that the mass-radius relation for the most
massive white dwarfs exhibits a marked dependence on the neutrino luminosity.
Extensive tabulations for massive white dwarfs, accessible from our web site,
are presented as well.


title: Cooling of Akmal-Pandharipande-Ravenhall neutron star models

abstract:
  We study the cooling of superfluid neutron stars whose cores consist of
nucleon matter with the Akmal-Pandharipande-Ravenhall equation of state. This
equation of state opens the powerful direct Urca process of neutrino emission
in the interior of most massive neutron stars. Extending our previous studies
(Gusakov et al. 2004a, Kaminker et al. 2005), we employ phenomenological
density-dependent critical temperatures T_{cp}(\rho) of strong singlet-state
proton pairing (with the maximum T_{cp}^{max} \sim 7e9 K in the outer stellar
core) and T_{cnt}(\rho) of moderate triplet-state neutron pairing (with the
maximum T_{cnt}^{max} \sim 6e8 K in the inner core). Choosing properly the
position of T_{cnt}^{max} we can obtain a representative class of massive
neutron stars whose cooling is intermediate between the cooling enhanced by the
neutrino emission due to Cooper pairing of neutrons in the absence of the
direct Urca process and the very fast cooling provided by the direct Urca
process non-suppressed by superfluidity.


title:
Power Spectrum and Intermittency of Ly${\alpha}$ Transmitted Flux of QSO
  He2347-4342

abstract:
  We have studied the power spectrum and the intermittent behavior of the
fluctuations in the transmitted flux of HE2347-4342 ${\rm Ly}{\alpha}$
absorption in order to investigate if there is any discrepancy between the LCDM
model with parameters given by the WMAP and observations on small scales. If
the non-Gaussianity of cosmic mass field is assumed to come only from halos
with an universal mass profile of the LCDM model, the non-Gaussian behavior of
mass field would be effectively measured by its intermittency, because
intermittency is a basic statistical feature of the cuspy structures. We have
shown that the Ly$\alpha$ transmitted flux field of HE2347-4342 is
significantly intermittent on small scales. With the hydrodynamic simulation,
we demonstrate that the LCDM model is successful in explaining the power
spectrum and intermittency of ${\rm Ly}{\alpha}$ transmitted flux. Using
statistics ranging from the second to eighth order, we find no discrepancy
between the LCDM model and the observed transmitted flux field, and no evidence
to support the necessity of reducing the power of density perturbations
relative to the standard LCDM model up to comoving scales as small as about
$0.08 {\rm h}^{-1} {\rm Mpc}$. Moreover, our simulation samples show that the
intermittent exponent of the Ly$\alpha$ transmitted flux field is probably
scale-dependent. This result is different from the prediction of universal mass
profile with a constant index of the central cusp. The scale-dependence of the
intermittent exponent indicates that the distribution of baryonic gas is
decoupled from the underlying dark matter.


title:
XMM-Newton Observations of Ultraluminous X-Ray Sources in Nearby
  Galaxies

abstract:
  We examined X-ray spectral and timing properties of ultraluminous X-ray
sources (ULXs) in nearby galaxies in XMM-Newton archival data. There appear to
be three distinct classes of spectra. One class shows emission from hot,
diffuse plasma. This thermal emission is similar to that seen from recent
supernovae; the temperatures are in the range 0.6-0.8 keV and the luminosities
are the lowest in our sample, near 10^39 erg/s. Three sources have spectra
which are strongly curved at high energies and have the highest temperatures in
our sample, 1.0-1.4 keV. These spectra are well fitted with a power-law plus
multicolor disk blackbody model with the power-law dominant at low energies or
a Comptonization model. The remainder of the sources are best fitted with a
power-law plus multicolor disk blackbody model, as is commonly used to describe
the spectra of accreting black holes. These sources have the lowest thermal
component temperatures, 0.1-0.4 keV, and extend to the highest luminosities,
above 10^40 erg/s. The temperature of the thermal component is in three
distinct ranges for the three source classes. This diversity of spectral shapes
and the fact that the sources lie in three distinct temperature ranges suggests
that the ULXs are a diverse population. Two ULXs which show state transitions
stay within a single class over the course of the transition. However, we
cannot conclude with certainty that the classes represent distinct types of
objects rather than spectral states of a single population of objects. We also
searched for timing noise from the sources and report detection of noise above
the Poisson level from five sources. In three of the sources, the power density
spectrum increases with decreasing frequency as a power-law down to the lowest
frequencies observed, below 10^-4 Hz.


title: The effects of thermal conduction on the hot accretion flows

abstract:
  Thermal conduction has been suggested as a possible mechanism by which
sufficient extra heating is provided in radiation-dominated accretion flows. We
consider the extreme case in which the generated energy due to the viscosity
and the energy transported by a saturated form of thermal conduction are
balanced by the advection cooling. For the steady-state structure of such
accretion flows a set of self-similar solution are presented. Based on these
solutions while the radial and the rotational velocities are both
sub-Keplerian, increasing the level of thermal conduction has the effects of
decreasing the rotational velocity, but increasing the radial velocity.
Conduction provides extra heating and the temperature of the gas increases with
thermal conduction.


title:
On the incidence of chemically peculiar stars in the Large Magellanic
  cloud

abstract:
  With the aim to corroborate the result of a search for chemically peculiar
stars in the Large Magellanic Cloud (LMC) we present measurements obtained from
CCD-imaging of two fields, one containing a young open cluster (NGC 1711).
While for the latter field, including its surrounding we obtain a contribution
of three percent of chemically peculiar stars detectable by Delta a photometry
(i.e. the magnetic objects of this group), the second field yields about half
of this value in good accordance with the finding for NGC 1866 (Maitzen et al.,
2001, A&A, 371, L5) the surrounding field of which has been found to exhibit a
very low value of such stars - 0.3%. Thus we are faced with the fact, that our
incipient impression about a substantially lower appearance of magnetic
chemically peculiar stars in the LMC as compared to the Galaxy continues to be
valid. Most of the photometrically identified peculiar stars (from their
historical origin denominated Ap-stars) are located in the domain of the B-type
stars. But this is a selection effect due to the limiting magnitude of our
observing conditions impeding the observation of fainter main sequence stars.
In addition to objects showing up as positive deviators in Delta a photometry
we also discuss nine stars which appear opposite the main line of normal stars,
hence are negative deviators. For most of them the interpretation as emission
stars of B-type seems to be appropriate. The statistically relevant number of
observations obtained so far in the LMC supports the view that the formation of
magnetic peculiar stars has occurred there at a significantly lower rate.


title:
GeV gamma-rays and TeV neutrinos from very massive compact binary
  systems: The case of WR 20a

abstract:
  Massive Wolf-Rayet stars in a compact binary systems are characterised by
very strong winds which collide creating a shock wave. If the wind nuclei
accelerated at the shock can reach large enough energies, they suffer
disintegration in collisions with soft thermal radiation from the massive stars
injecting relativistic protons and neutrons. Protons collide with the matter of
the wind and a fraction of neutrons colide with the massive stars producing
gamma-rays and neutrinos. We calculate the gamma-rays fluxes from the inverse
Compton pair cascades, initiated by primary gamma-rays and leptons produced by
protons, and the neutrino fluxes produced by protons and neutrons for the
example compact massive binary WR 20a. From normalization of the gamma-ray
spectra to the fluxes of the EGRET sources, 2EG J1021-5835 and 2EG J1049-5847,
we conclude that this massive binary can be detected by the IceCube type
neutrino detector with the event rate between a few up to a few tens per km^2
per yr.


title: Can bars be destroyed by a central mass concentration? I. Simulations

abstract:
  We study the effect of a central mass concentration (CMC) on the secular
evolution of a barred disc galaxy. Unlike previous studies, we use fully
self-consistent 3D $N$-body simulations with live haloes, which are known to be
important for bar evolution. The CMC is introduced gradually, to avoid
transients. In all cases where the mass of the CMC is of the order of, or more
than, a few per cent of the mass of the disc, the strength of the bar decreases
noticeably. The amount of this decrease depends strongly on the bar type. For
the same CMC, bars with exponential surface-density profile, which formed in a
disk-dominated galaxy (MD-type bars), can be totally destroyed, while strong
bars with a flat surface-density profile, whose evolution is largely due to the
halo (MH-type bars), witness only a decrease of their strength. This decrease
occurs simultaneously from both the innermost and outermost parts of the bar.
The CMC has a stronger effect on the Fourier components of higher azimuthal
wave number $m$, leading to fatter and/or less rectangular bars. Furthermore,
the CMC changes the side-on outline from peanut-shaped to boxy or, for massive
CMCs, to elliptical. Similarly, side-on initially boxy outlines can be
destroyed. The CMC also influences the velocity dispersion profiles. Most of
the decrease of the bar strength occurs while the mass of the CMC increases and
it is accompanied by an increase of the pattern speed. In all our simulations,
the mass of the CMC necessary in order to destroy the bar is at least several
per cent of the mass of the disc. This argues that observed super-massive black
holes are not likely to destroy pre-existing bars.


title: Formation of Structure in Molecular Clouds: A Case Study

abstract:
  Molecular clouds (MCs) are highly structured and ``turbulent''. Colliding gas
streams of atomic hydrogen have been suggested as a possible source of MCs,
imprinting the filamentary structure as a consequence of dynamical and thermal
instabilities. We present a 2D numerical analysis of MC formation via
converging HI flows. Even with modest flow speeds and completely uniform
inflows, non-linear density perturbations as possible precursors of MCs arise.
Thus, we suggest that MCs are inevitably formed with substantial structure,
e.g., strong density and velocity fluctuations, which provide the initial
conditions for subsequent gravitational collapse and star formation in a
variety of galactic and extragalactic environments.


title:
Magnetic-Reconnection and Current-Sheet Model for the Radio Arc and
  Threads in the Galactic Center

abstract:
  We propose a new mechanism to explain the radio Arc and threads in the
Galactic Center by current sheets produced by local magnetic shears due to
interaction of a moving cloud and the vertical field based on three-dimensional
magneto-hydrodynamical simulations. Magnetic reconnetion and acceleration of
cosmic-ray electrons in the current sheet will result in high contrast of radio
emissivity inside and outside the Arc and threads.


title:
Rotational velocities of the giants in symbiotic stars: I. D'-type
  symbiotics

abstract:
  We have measured the rotational velocities (v.sini) of the mass donors in a
number of D'--type symbiotic stars, using the cross-correlation function
method. Four from five D' symbiotic stars with known v.sini, appeared to be
very fast rotators compared with the catalogues of v.sini for the corresponding
spectral types. At least three of these stars rotate at a substantial fraction
(>=0.5) of the critical velocity. This means that at least in D'-type
symbiotics the cool components rotate faster than isolated giants. If these
binary stars are synchronized, their orbital periods should be relatively short
(4-60 days). We also briefly discuss the possible origin of the rapid rotation
and its connection with mass loss and dust formation.


title: Numerical simulations of quasar absorbers

abstract:
  The physical state of the intergalactic medium can be probed in great detail
with the intervening absorption systems seen in quasar spectra. The properties
of the Hydrogen absorbers depend on many cosmological parameters, such as the
matter-power spectrum, reionisation history, ionising background and the nature
of the dark matter. The spectra also contain metal lines, which can be used to
constrain the star formation history and the feedback processes acting in large
and small galaxies. Simulations have been instrumental in investigating to what
extent these parameters can be unambiguously constrained with current and
future data. This paper is meant as an introduction to this subject, and
reviews techniques and methods for simulating the intergalactic medium.


title: Dust-enshrouded giants in clusters in the Magellanic Clouds

abstract:
  We present the results of an investigation of post-Main Sequence mass loss
from stars in clusters in the Magellanic Clouds, based around an imaging survey
in the L'-band (3.8 micron) performed with the VLT at ESO. The data are
complemented with JHKs and mid-IR photometry. The goal is to determine the
influence of initial metallicity and initial mass on the mass loss and
evolution during the latest stages of stellar evolution. Dust-enshrouded giants
are identified by their reddened near-IR colours and thermal-IR dust excess
emission. Most of these objects are Asymptotic Giant Branch (AGB) carbon stars
in intermediate-age clusters, with progenitor masses between 1.3 and about 5
Msun. Red supergiants with circumstellar dust envelopes are found in young
clusters, and have progenitor masses between 13 and 20 Msun. Post-AGB objects
(e.g., Planetary Nebulae) and massive stars with detached envelopes and/or hot
central stars are found in several clusters. We model the spectral energy
distributions of the cluster IR objects to estimate their bolometric
luminosities and mass-loss rates. The IR objects are the most luminous cluster
objects, and have luminosities as expected for their initial mass and
metallicity. They experience mass-loss rates in the range from a few 1e-6 up to
1e-4 Msun/yr (or more), with most of the spread being due to evolutionary
effects and only a weak dependence on progenitor mass and/or initial
metallicity. About half of the mass lost by 1.3--3 Msun stars is shed during
the superwind phase, which lasts of order 1e5 yr. Objects with detached shells
are found to have experienced the highest mass-loss rates, and are therefore
interpreted as post-superwind objects. We also propose a simple method to
measure the cluster mass from L'-band images.


title: CCD-Delta a and BVR photometry of NGC 7296

abstract:
  The first CCD photometric investigation of the open cluster NGC 7296 up to
now was performed within the narrow band Delta a photometric system, which
enables us to detect peculiar objects. A deeper investigation of that cluster
followed, using the standard BVR-Bessel filter set. The age and E(B-V) was
determined independently to log t= 8.0 and 0.15 respectively by using Delta a
and broadband photometry. In total five Be/Ae objects and two metal-weak stars
showing significant negative Delta a-values as well as one classical chemically
peculiar star could be identified within that intermediate age open cluster.


title:
Post-inflation increase of the cosmological tensor-to-scalar
  perturbation ratio

abstract:
  We investigate the possibility that the amplitude of scalar density
perturbations may be damped after inflation. This would imply that CMB
anisotropies do not uniquely fix the amplitude of the perturbations generated
during inflation and that the present tensor-to-scalar ratio might be larger
than produced in inflation, increasing the prospects of detection of primordial
gravitational radiation. It turns out, however, that the damping of density
perturbations is hard to achieve.


title:
Search for Point Sources of Ultra--High-Energy Cosmic Rays Above 10^19
  eV Using a Maximum Likelihood Ratio Test

abstract:
  We present the results of a search for cosmic ray point sources at energies
above 10^19 eV in the HiRes stereo data set. The analysis is based on a maximum
likelihood ratio test using the probability density function for each event
rather than requiring an a priori choice of a fixed angular bin size. The
search is extended to the combined data set of HiRes data above 10^19 eV and
AGASA data above 4.0 10^19 eV. In both cases, no statistically significant
clustering of events consistent with a point source is found.


title:
Multi-frequency analysis of neutralino dark matter annihilations in the
  Coma cluster

abstract:
  We study the astrophysical implications of neutralino dark matter
annihilations in galaxy clusters, with a specific application to the Coma
cluster. We first address the determination of the dark halo models for Coma,
starting from structure formation models and observational data, and we discuss
in detail the role of sub-halos. We then perform a thorough analysis of the
transport and diffusion properties of neutralino annihilation products, and
investigate the resulting multi-frequency signals, from radio to gamma-ray
frequencies. We also study other relevant astrophysical effects of neutralino
annihilations, like the DM-induced Sunyaev-Zel'dovich effect and the
intracluster gas heating. As for the particle physics setup, we adopt a
two-fold approach, resorting both to model-independent bottom-up scenarios and
to benchmark, GUT-motivated frameworks. We show that the Coma radio-halo data
(the spectrum and the surface brightness) can be nicely fitted by the
neutralino-induced signal for peculiar particle physics models and for magnetic
field values, which we outline in detail. Fitting the radio data and moving to
higher frequencies, we find that the multi-frequency spectral energy
distributions are typically dim (with respect to the data) at EUV and X-ray
frequencies, but show a non-negligible gamma-ray emission, depending on the
amplitude of the Coma magnetic field. The best-fit particle physics models also
produce a detectable SZ effect, but do not yield substantial heating of the
intracluster gas in Coma. Due to the specific multi-frequency features of the
DM-induced spectral energy distribution in Coma, we find that supersymmetric
models can be significantly and optimally constrained either in the gamma-rays
or at radio and microwave frequencies.


title: Long-term Phase-coherent X-ray Timing of PSR B0540-69

abstract:
  We present a new phase-coherent timing analysis for the young, energetic
pulsar PSR B0540-69 using 7.6 yr of data from the Rossi X-Ray Timing Explorer.
We measure the braking index, n=2.140+/-0.009, and discuss our measurement in
the context of other discordant values reported in the literature. We present
an improved source position from the phase-coherent timing of the pulsar, to
our knowledge, the first of its kind from X-ray pulsar timing. In addition, we
detect evidence for a glitch which has been previously reported but later
disputed. The glitch occured at MJD 51335+/-12 with a fractional change in
frequency of (1.4+/-0.2)E{-9} and a fractional change in frequency derivative
of (1.33+/-0.02)E{-4}. We calculate that the glitch activity parameter for PSR
B0540-69 is two orders of magnitude smaller than that of the Crab pulsar which
has otherwise very similar properties. This suggests that neutron stars of
similar apparent ages, rotation properties and inferred dipolar B fields can
have significantly different internal properties.


title:
Optical Relative Calibration and Stability Monitoring for the Auger
  Fluorescence Detector

abstract:
  The stability of the fluorescence telescopes of the Pierre Auger Observatory
is monitored with the optical relative calibration setup. Optical fibers
distribute light pulses to three different diffuser groups within the optical
system. The total charge per pulse is measured for each pixel and compared with
reference calibration measurements. This allows monitoring the short and long
term stability with respect of the relative timing between pixels and the
relative gain for each pixel. The designs of the LED calibration unit (LCU) and
of the Xenon flash lamp used for relative calibration, are described and their
capabilities to monitor the stability of the telescope performances are
studied. We report the analysis of relative calibration data recorded during
2004. Fluctuations in the relative calibration constants provide a measure of
the stability of the FD.


title: The Disappearing Act of KH 15D: Photometric Results from 1995 to 2004

abstract:
  We present results from the most recent (2002-2004) observing campaigns of
the eclipsing system KH 15D, in addition to re-reduced data obtained at Van
Vleck Observatory (VVO) between 1995 and 2000. Phasing nine years of
photometric data shows substantial evolution in the width and depth of the
eclipses. The most recent data indicate that the eclipses are now approximately
24 days in length, or half the orbital period. These results are interpreted
and discussed in the context of the recent models for this system put forward
by Winn et al. and Chiang & Murray-Clay. A periodogram of the entire data set
yields a highly significant peak at 48.37 +/- 0.01 days, which is in accord
with the spectroscopic period of 48.38 +/- 0.01 days determined by Johnson et
al. Another significant peak, at 9.6 days, was found in the periodogram of the
out-of-eclipse data at two different epochs. We interpret this as the rotation
period of the visible star and argue that it may be tidally locked in
pseudosynchronism with its orbital motion. If so, application of Hut's theory
implies that the eccentricity of the orbit is e = 0.65 +/- 0.01. Analysis of
the UVES/VLT spectra obtained by Hamilton et al. shows that the v sin(i) of the
visible star in this system is 6.9 +/- 0.3 km/sec. Using this value of v sin(i)
and the measured rotation period of the star, we calculate the lower limit on
the radius to be R = (1.3 +/- 0.1), R_Sun, which concurs with the value
obtained by Hamilton et al. from its luminosity and effective temperature. Here
we assume that i = 90 degrees since it is likely that the spin and orbital
angular momenta vectors are nearly aligned.


title: Bulk motion Comptonization in black-hole accretion flows

abstract:
  We study spectra generated by Comptonization of soft photons by cold
electrons radially free-falling onto a black hole. We use a Monte Carlo method
involving a fully relativistic description of Comptonization in the Kerr
space-time. In agreement with previous studies, we find that Comptonization on
the bulk motion of free fall gives rise to power-law spectra with the photon
index of Gamma >~ 3. In contrast to some previous studies, we find that these
power-law spectra extend only to energies << 511 keV. We indicate several
effects resulting in generic cutoffs of such spectra at several tens of keV,
regardless of any specific values of physical parameters in the model. This
inefficiency of producing photons with energies > 100 keV rules out bulk motion
Comptonization as a main radiative process in soft spectral states of
black-hole binaries. The normalization of the power law (below the cutoff) with
respect to the peak of the blackbody emission of the surrounding disc is
typically very low, except for models with an overlap between the disc and the
plasma, in which case the spectra are very soft, Gamma >~ 4.


title: VITRUV - Science Cases

abstract:
  VITRUV is a second generation spectro-imager for the PRIMA enabled Very Large
Telescope Interferometer. By combining simultaneously up to 8 telescopes VITRUV
makes the VLTI up to 6 times more efficient. This operational gain allows two
novel scientific methodologies: 1) massive surveys of sizes; 2) routine
interferometric imaging. The science cases presented concentrate on the
qualitatively new routine interferometric imaging methodology. The science
cases are not exhaustive but complementary to the PRIMA reference mission. The
focus is on: a) the close environment of young stars probing for the initial
conditions of planet formation and disk evolution; b) the surfaces of stars
tackling dynamos, activity, pulsation, mass-loss and evolution; c) revealing
the origin of the extraordinary morphologies of Planetary Nebulae and related
stars; d) studying the accretion-ejection structures of stellar black-holes
(microquasars) in our galaxy; e) unveiling the different interacting components
(torus, jets, BLRs) of Active Galactic Nuclei; and f) probing the environment
of nearby supermassive black-holes and relativistic effects in the Galactic
Center black-hole.


title:
A FUSE Survey of Interstellar Molecular Hydrogen toward High-Latitude
  AGN

abstract:
  We report results from a FUSE survey of interstellar molecular hydrogen (H2)
along 45 sight lines to AGN at high Galactic latitudes (|b| > 20 degrees). Most
(39 of 45) of the sight lines show detectable Galactic H2 absorption from Lyman
and Werner bands between 1000 and 1126 A, with column densities ranging from
N(H2) = 10^(14.17-19.82) cm^-2. In the northern Galactic hemisphere, we
identify many regions of low column, N(H2) < 10^15 cm^-2, between longitude l =
60-180 degrees and at b > 54 degrees. These `"H2 holes" provide valuable,
uncontaminated sight lines for extragalactic UV spectroscopy, and a few may be
related to the "Northern Chimney" (low Na I absorption) and "Lockman Hole" with
low N(HI). A comparison of high-latitude H2 with 139 OB-star sight lines
surveyed in the Galactic disk suggests that high-latitude and disk H2 clouds
may have different rates of heating, cooling, and UV excitation. For rotational
states J = 0 and 1, the mean excitation temperature at high latitude,
<T_01(high)> = 124 +/- 8 K, is somewhat above that in the Galactic disk,
<T_01(disk)> = 86 +/- 20 K. For J = 2-4, the <T_exc> = 498 +/- 28 K, and the
column-density ratios, N(3)/N(1), N(4)/N(0), and N(4)/N(2), indicate a
comparable degree of UV excitation in the disk and low halo for sight lines
with N(H2) > 10^18. The distribution of molecular fractions at high latitude
shows a transition at lower total hydrogen column density, log N_H = 20.38 +/-
0.13, than in the Galactic disk, log N_H(disk) = 20.7. If the FUV radiation
fields are similar in disk and low halo, this suggests an enhanced
(dust-catalyzed) H2 formation rate in higher-density, compressed clouds, which
could be detectable as high-latitude, sheetlike infrared cirrus.


title:
Evidence for a fundamental stellar upper mass limit from clustered star
  formation, and some implications therof

abstract:
  Theoretical considerations lead to the expectation that stars should not have
masses larger than about m_{max*}=60-120Msun, while the observational evidence
has been ambiguous. Only very recently has a physical stellar mass limit near
150Msun emerged thanks to modern high-resolution observations of local
star-burst clusters. But this limit does not appear to depend on metallicity,
in contradiction to theory. Important uncertainties remain though. It is now
also emerging that star-clusters limit the masses of their constituent stars,
such that a well-defined relation between the mass of the most massive star in
a cluster and the cluster mass, m_{max}=F(M_ecl) \le m_{max*}\approx 150Msun,
exists. One rather startling finding is that the observational data strongly
favour clusters being built-up by consecutively forming more-massive stars
until the most massive stars terminate further star-formation. The relation
also implies that composite populations, which consist of many star clusters,
most of which may be dissolved, must have steeper composite IMFs than simple
stellar populations such as are found in individual clusters. Thus, for
example, 10^5 Taurus--Auriga star-forming groups, each with 20 stars, will ever
only sample the IMF below about 1Msun. This IMF will therefore not be identical
to the IMF of one cluster with 2 times 10^6 stars. The implication is that the
star-formation history of a galaxy critically determines its integrated
galaxial IMF and thus the total number of supernovae per star and its chemical
enrichment history. Galaxy formation and evolution models that rely on an
invariant IMF would be wrong.


title:
Cosmological parameters from CMB measurements and the final 2dFGRS power
  spectrum

abstract:
  We derive constraints on cosmological parameters using the power spectrum of
galaxy clustering measured from the final two-degree field galaxy redshift
survey (2dFGRS) and a compilation of measurements of the temperature power
spectrum and temperature-polarization cross-correlation of the cosmic microwave
background radiation. We analyse a range of parameter sets and priors, allowing
for massive neutrinos, curvature, tensors and general dark energy models. In
all cases, the combination of datasets tightens the constraints, with the most
dramatic improvements found for the density of dark matter and the
energy-density of dark energy. If we assume a flat universe, we find a matter
density parameter of $\Omega_{\rm m}=0.237 \pm 0.020$, a baryon density
parameter of $\Omega_{\rm b} = 0.041 \pm 0.002$, a Hubble constant of
$H_{0}=74\pm2 {\rm kms}^{-1}{\rm Mpc}^{-1}$, a linear theory matter fluctuation
amplitude of $\sigma_{8}=0.77\pm0.05$ and a scalar spectral index of $n_{\rm
s}=0.954 \pm 0.023$ (all errors show the 68% interval). Our estimate of $n_{\rm
s}$ is only marginally consistent with the scale invariant value $n_{\rm s}=1$;
this spectrum is formally excluded at the 95% confidence level. However, the
detection of a tilt in the spectrum is sensitive to the choice of parameter
space. If we allow the equation of state of the dark energy to float, we find
$w_{\rm DE}= -0.85_{-0.17}^{+0.18}$, consistent with a cosmological constant.
We also place new limits on the mass fraction of massive neutrinos: $f_{\nu} <
0.105$ at the 95% level, corresponding to $\sum m_{\nu} < 1.2$ eV.


title:
The NN2 Flux Difference Method for Constructing Variable Object Light
  Curves

abstract:
  We present a new method for optimally extracting point-source time
variability information from a series of images. Differential photometry is
generally best accomplished by subtracting two images separated in time, since
this removes all constant objects in the field. By removing background sources
such as the host galaxies of supernovae, such subtractions make possible the
measurement of the proper flux of point-source objects superimposed on extended
sources. In traditional difference photometry, a single image is designated as
the ``template'' image and subtracted from all other observations. This
procedure does not take all the available information into account and for
sub-optimal template images may produce poor results. Given N total
observations of an object, we show how to obtain an estimate of the vector of
fluxes from the individual images using the antisymmetric matrix of flux
differences formed from the N(N-1)/2 distinct possible subtractions and provide
a prescription for estimating the associated uncertainties. We then demonstrate
how this method improves results over the standard procedure of designating one
image as a ``template'' and differencing against only that image.


title: PHASES High Precision Differential Astrometry of delta Equulei

abstract:
  delta Equulei is among the most well-studied nearby binary star systems.
Results of its observation have been applied to a wide range of fundamental
studies of binary systems and stellar astrophysics. It is widely used to
calibrate and constrain theoretical models of the physics of stars. We report
27 high precision differential astrometry measurements of delta Equulei from
the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES).
The median size of the minor axes of the uncertainty ellipses for these
measurements is 26 micro-arcseconds. These data are combined with previously
published radial velocity data and other previously published differential
astrometry measurements using other techniques to produce a combined model for
the system orbit. The distance to the system is determined to within a
twentieth of a parsec and the component masses are determined at the level of a
percent. The constraints on masses and distance are limited by the precisions
of the radial velocity data; we outline plans improve this deficiency and
discuss the outlook for further study of this binary.


title: Lyman Alpha Radiative Transfer in a Multi-Phase Medium

abstract:
  Hydrogen Ly-alpha is our primary emission-line window into high redshift
galaxies. Surprisingly, despite an extensive literature, Ly-alpha radiative
transfer in the most realistic case of a dusty, multi-phase medium has not
received detailed theoretical attention. We investigate resonant scattering
through an ensemble of dusty, moving, optically thick gas clumps. We treat each
clump as a scattering particle and use Monte Carlo simulations of surface
scattering to quantify continuum and Ly-alpha surface scattering angles,
absorption probabilities, and frequency redistribution, as a function of the
gas dust content. This atomistic approach speeds up the simulations by many
orders of magnitude, making possible calculations which are otherwise
intractable. With these surface scattering results, we develop an analytic
framework for estimating escape fractions and line widths as a function of gas
geometry, motion, and dust content. We show that the key geometric parameter is
the average number of surface scatters for escape in the absence of absorption.
We consider two interesting applications: (i) Equivalent widths. Ly-alpha can
preferentially escape from a dusty multi-phase ISM if most of the dust lies in
cold neutral clouds, possibly explaining anomalously high EWs seen in many high
redshift/submm sources. (ii) Multi-phase galactic outflows. We show the
characteristic profile is asymmetric with a broad red tail, and relate the
profile features to the outflow speed and gas geometry. Many future
applications are envisaged. [Abridged]


title: Molecular Hydrogen in Infrared Cirrus

abstract:
  We combine data from our recent FUSE survey of interstellar molecular
hydrogen absorption toward 50 high-latitude AGN with COBE-corrected IRAS 100
micron emission maps to study the correlation of infrared cirrus with H2. A
plot of the H2 column density vs. IR cirrus intensity shows the same transition
in molecular fraction, f_H2, as seen with total hydrogen column density, N_H.
This transition is usually attributed to H2 self-shielding, and it suggests
that many diffuse cirrus clouds contain H2 in significant fractions, f_H2 =
1-30%. These clouds cover approximately 50% of the northern sky at latitudes b
> 30 degrees, at temperature-corrected 100 micron intensities D_100 > 1.5
MJy/sr. The sheetlike cirrus clouds, with hydrogen densities n_H > 30 cm^-3,
may be compressed by dynamical processes at the disk-halo interface, and they
are conducive to H2 formation on grain surfaces. Exploiting the correlation
between N(H2) and 100 micron intensity, we estimate that cirrus clouds at b >
30 contain approximately 3000 M_sun in H2. Extrapolated over the inner Milky
Way, the cirrus may contain 10^7 M_sun of H2 and 10^8 M_sun in total gas mass.
If elevated to 100 pc, their gravitational potential energy is ~10^53 erg.


title: The GRB Variability/Peak Luminosity Correlation: new results

abstract:
  We report test results of the correlation between time variability and peak
luminosity of Gamma-Ray Bursts (GRBs), using a larger sample (32) of GRBs with
known redshift than that available to Reichart et al. (2001), and using as
variability measure that introduced by these authors. The results are puzzling.
Assuming an isotropic-equivalent peak luminosity, as done by Reichart et al.
(2001), a correlation is still found, but it is less relevant, and inconsistent
with a power law as previously reported. Assuming as peak luminosity that
corrected for GRB beaming for a subset of 16 GRBs with known beaming angle, the
correlation becomes little less significant.


title: The Compression of Dark Matter Halos by Baryonic Infall

abstract:
  The initial radial density profiles of dark matter halos are laid down by
gravitational collapse in hierarchical structure formation scenarios and are
subject to further compression as baryons cool and settle to the halo centers.
We here describe an explicit implementation of the algorithm, originally
developed by Young, to calculate changes to the density profile as the result
of adiabatic infall in a spherical halo model. Halos with random motion are
more resistant to compression than are those in which random motions are
neglected, which is a key weakness of the simple method widely employed.
Young's algorithm results in density profiles in excellent agreement with those
from N-body simulations. We show how the algorithm may be applied to determine
the original uncompressed halos of real galaxies, a step which must be computed
with care in order to enable a confrontation with theoretical predictions from
theories such as LCDM.


title:
Measurement of the Lateral Distribution Function of UHECR Air Showers
  with the Pierre Auger Observatory

abstract:
  The Pierre Auger Observatory is being used to study cosmic rays with energies
larger than 10 EeV. An essential quantity that must be deduced from data is the
lateral distribution function (LDF). Knowledge of the LDF is important for the
reconstruction of the shower core and the shower direction. Here we describe
how the LDF is measured using the large sample of events recorded with the
surface detector (SD) array and with a small sample observed with the
fluorescence detectors (FD). For hybrid events, in which SD and FD measurements
of the same shower are available, the core position is much better constrained
than for SD-only events, thus providing an important cross-check on the LDF
determined from SD measurements alone.


title: Density Power Spectrum of Compressible Hydrodynamic Turbulent Flows

abstract:
  Turbulent flows are ubiquitous in astrophysical environments, and
understanding density structures and their statistics in turbulent media is of
great importance in astrophysics. In this paper, we study the density power
spectra, $P_{\rho}$, of transonic and supersonic turbulent flows through one
and three-dimensional simulations of driven, isothermal hydrodynamic turbulence
with root-mean-square Mach number in the range of $1 \la M_{\rm rms} \la 10$.
  From one-dimensional experiments we find that the slope of the density power
spectra becomes gradually shallower as the rms Mach number increases. It is
because the density distribution transforms from the profile with {\it
discontinuities} having $P_{\rho} \propto k^{-2}$ for $M_{\rm rms} \sim 1$ to
the profile with {\it peaks} having $P_{\rho} \propto k^0$ for $M_{\rm rms} \gg
1$. We also find that the same trend is carried to three-dimension; that is,
the density power spectrum flattens as the Mach number increases. But the
density power spectrum of the flow with $M_{\rm rms} \sim 1$ has the Kolmogorov
slope. The flattening is the consequence of the dominant density structures of
{\it filaments} and {\it sheets}. Observations have claimed different slopes of
density power spectra for electron density and cold H I gas in the interstellar
medium. We argue that while the Kolmogorov spectrum for electron density
reflects the {\it transonic} turbulence of $M_{\rm rms} \sim 1$ in the warm
ionized medium, the shallower spectrum of cold H I gas reflects the {\it
supersonic} turbulence of $M_{\rm rms} \sim$ a few in the cold neutral medium.


title:
A High Resolution HI Study of Selected Virgo Galaxies - Preliminary
  Results on Gas Morphology & Extra-Planar Gas

abstract:
  We present preliminary results of VLA HI imaging of selected Virgo cluster
galaxies. The goal is to study environmental effects on galaxy evolution. Our
sample of 41 galaxies is spread throughout the cluster and spans a wide range
in star formation properties. Here we present the total HI maps of 13 galaxies.
We find a number of galaxies with extended HI tails, almost all pointing away
from the cluster center. Truncated HI disks are found close to the center but
also in the outer region. Some galaxies near the cluster center show
compression of the gas on one side. Multiwavelength data of NGC 4569 and
kinematics on NGC 4396 indicate that some of the HI is extra-planar. These
preliminary results on the HI morphology already suggest that a variety of
environmental effects such as ICM-ISM interactions, harassment, tidal
interactions or mergers may be at work to affect the evolution of galaxies.


title:
Core-Collapse Very Massive Stars: Evolution, Explosion, and
  Nucleosynthesis of Population III 500 -- 1000 $M_{\odot}$ Stars

abstract:
  We calculate evolution, collapse, explosion, and nucleosynthesis of
Population III very-massive stars with 500$M_{\odot}$ and 1000$M_{\odot}$.
Presupernova evolution is calculated in spherical symmetry. Collapse and
explosion are calculated by a two-dimensional code, based on the bipolar jet
models. We compare the results of nucleosynthesis with the abundance patterns
of intracluster matter, hot gases in M82, and extremely metal-poor stars in the
Galactic halo. It was found that both 500$M_{\odot}$ and 1000$M_{\odot}$ models
enter the region of pair-instability but continue to undergo core collapse. In
the presupernova stage, silicon burning regions occupy a large fraction, more
than 20% of the total mass. For moderately aspherical explosions, the patterns
of nucleosynthesis match the observational data of both intracluster medium and
M82. Our results suggest that explosions of Population III core-collapse
very-massive stars contribute significantly to the chemical evolution of gases
in clusters of galaxies. For Galactic halo stars, our [O/Fe] ratios are smaller
than the observational abundances. However, our proposed scenario is naturally
consistent with this outcome. The final black hole masses are $\sim
230M_{\odot}$ and $\sim 500M_{\odot}$ for the $500M_{\odot}$ and
1000$M_{\odot}$ models, respectively. This result may support the view that
Population III very massive stars are responsible for the origin of
intermediate mass black holes which were recently reported to be discovered.


title: High-energy Astrophysics and the Virtual Observatory

abstract:
  The Virtual Observatory (VO) will revolutionise the way we do Astronomy by
allowing easy access to all astronomical data and by making the handling and
analysis of datasets at various locations across the globe much simpler and
faster. I report here on the need for the VO and its status in Europe,
concentrating on the recently started EURO-VO project, and then give two
specific applications of VO tools to high-energy astrophysics.


title: Clarifying Inflation Models: Slow-roll as an expansion in 1/N_{efolds}

abstract:
  Slow-roll inflation is studied as an effective field theory.We find as
consistent form of the inflaton potential V(phi)=N M^4 w(phi/[sqrt{N}M_P])
where phi is the inflaton field, M the inflation energy scale, M_P the Planck
mass, and N~50 the number of efolds since the relevant modes exited the horizon
till the end of inflation. The dimensionless function w(chi) and field chi are
O(1). The WMAP value for the amplitude of scalar adiabatic fluctuations
|\Delta_{k ad}^(S)| fixes the inflation scale M ~ 0.77 10^16 GeV precisely at
the GUT scale. This general form of the potential makes manifest that the slow
roll expansion is an expansion in 1/N. Powers of 1/N count the orders in the
slow roll expansion.This form of the inflaton potential suggests that the super
symmetry breaking scale is at the inflation and GUT scales.A Ginzburg-Landau
realization of this inflaton potential reveals that Hubble, inflaton mass and
non-linear couplings are of the see-saw form in terms of the small ratio M/M_P.
For example, the quartic coupling lambda ~ 1/N (M/M_P)^4.The smallness of the
non-linear couplings is not a result of fine tuning but a natural consequence
of the validity of the effective field theory. We clarify the Lyth bound which
relates the tensor/scalar ratio and the value of phi/M_P.Effective field theory
is valid for V(phi)<<M_P^4 allowing inflaton fields phi well beyond M_P.Thus,
no bounds based on the value of phi/M_P appear on r.In case one wishes to
restrict oneself to chi < 1 in the above potential, values for r larger than
the previous bounds are allowed thanks to the new factor sqrt{N}~7.Finally,it
is conjectured that inflation is hovering near a trivial gaussian infrared
fixed point during slow roll. Slow-roll inflation would then enjoy universality
properties as those of critical phenomena.


title:
Quantum corrections to the inflaton potential and the power spectra from
  superhorizon modes and trace anomalies

abstract:
  We obtain the effective inflaton potential during slow roll inflation by
including the one loop quantum corrections to the energy momentum tensor from
scalar curvature and tensor perturbations as well as quantum fluctuations from
light scalars and light Dirac fermions generically coupled to the inflaton.
During slow roll inflation there is a clean and unambiguous separation between
superhorizon and subhorizon contributions to the energy momentum tensor. The
superhorizon part is determined by the curvature perturbations and scalar field
fluctuations: both feature infrared enhancements as the inverse of a
combination of slow roll parameters which measure the departure from scale
invariance in each case.Fermions and gravitons do not exhibit infrared
divergences. The subhorizon part is completely specified by the trace anomaly
of the fields with different spins and is solely determined by the space-time
geometry. The one-loop quantum corrections to the amplitude of curvature and
tensor perturbations are obtained to leading order in slow-roll and in the
(H/M_PL)^2 expansion. This study provides a complete assessment of the
backreaction problem up to one loop including bosonic and fermionic degrees of
freedom. The result validates the effective field theory description of
inflation and confirms the robustness of the inflationary paradigm to quantum
fluctuations. Quantum corrections to the power spectra are expressed in terms
of the CMB observables:n_s, r and dn_s/dln k. Trace anomalies (especially the
graviton part) dominate these quantum corrections in a definite direction: they
enhance the scalar curvature fluctuations and reduce the tensor fluctuations.


title:
The Maximal Neutrino Flux from Neutralino Annihilation in the Galactic
  Center

abstract:
  We discuss a robust and fairly model-independent upper bound on the possible
neutrino flux produced by neutralino annihilation in the center of our galaxy,
and show that its detection with present or future neutrino telescopes is
highly improbable. This bound is obtained by relating the neutrino flux to the
gamma flux that would be produced in the same annihilation processes, for which
measurements do exist.


title: A New Version of Reimers' law of Mass Loss Based on a Physical Approach

abstract:
  We present a new semi-empirical relation for the mass loss of cool stellar
winds, which so far has frequently been described by "Reimers' law".
Originally, this relation was based solely on dimensional scaling arguments
without any physical interpretation. In our approach, the wind is assumed to
result from the spill-over of the extended chromosphere, possibly associated
with the action of waves, especially Alfven waves, which are used as guidance
in the derivation of the new formula. We obtain a relation akin to the original
Reimers law, but which includes two new factors. They reflect how the
chromospheric height depends on gravity and how the mechanical energy flux
depends, mainly, on effective temperature. The new relation is tested and
sensitively calibrated by modelling the blue end of the Horizontal Branch of
globular clusters. The most significant difference from mass loss rates
predicted by the Reimers relation is an increase by up to a factor of 3 for
luminous late-type (super-)giants, in good agreement with observations.


title: Flavoring Astrophysical Neutrinos: Flavor Ratios Depend on Energy

abstract:
  Electromagnetic (and adiabatic) energy losses of pions and muons modify the
flavor ratio (measured at Earth) of neutrinos produced by pion decay in
astrophysical sources, $\Phi_{\nu_e}:\Phi_{\nu_\mu}:\Phi_{\nu_\tau}$, from
1:1:1 at low energy to 1:1.8:1.8 at high energy. The transition occurs over 1-2
decades of nuetrino energy, and is correlated with a modification of the
neutrino spectrum. For gamma-ray bursts, e.g., the transition is expected at
\~100 TeV, and may be detected by km-scale neutrino telescopes. Measurements of
the transition energy and energy-width will provide unique probes of the
physics of the sources. pion and muon energy losses also affect the ratio of
$\bar\nu_e$ flux to total neutrino flux, which may be measured at the
W-resonance (6.3 PeV): It is modified from 1/6 (1/15) at low energy to 1/9
(practically 0) at high energy for neutrinos produced in pp ($p\gamma$)
interactions.


title:
Search for localized excess fluxes in Auger sky maps and prescription
  results

abstract:
  Using the first surface detector data of the Pierre Auger Observatory, we
present the results of a blind search for overdensities in the cosmic ray flux
with respect to isotropic expectations. We consider two energy bands: 1<E<5 EeV
and E>5 EeV at two angular scales: 5$^\circ$ and 15$^\circ$. We also report the
results of searches for excesses in target directions already defined in a set
of prescriptions presented at the ICRC in 2003. Both analyses give results that
are compatible with isotropy.


title:
Further empirical evidence for the non-linearity of the
  period-luminosity relations as seen in the Large Magellanic Cloud Cepheids

abstract:
  (abridged) Recent studies, using OGLE data for LMC Cepheids in the optical,
strongly suggest that the period-luminosity (PL) relation for the Large
Magellanic Cloud (LMC) Cepheids shows a break or non-linearity at a period of
10 days. In this paper we apply statistical tests, the chi-square test and the
F-test, to the Cepheid data from the MACHO project to test for a non-linearity
of the V- and R-band PL relations at 10 days, and extend these tests to the
near infrared (JHK-band) PL relations with 2MASS data. We correct the
extinction for these data by applying an extinction map towards the LMC. The
statistical test we use, the F-test, is able to take account of small numbers
of data points and the nature of that data on either side of the period cut at
10 days. With our data, the results we obtained imply that the VRJH-band PL
relations are non-linear around a period of 10 days, while the K-band PL
relation is (marginally) consistent with a single-line regression. The choice
of a period of 10 days, around which this non-linearity occurs, is consistent
with the results obtained when this "break" period is estimated from the data.
Long period Cepheids are supplemented from the literature to increase our
sample size. The photometry of these long period Cepheids is compared with our
data and no trend with period is found. Our main results remain unchanged when
we supplement our dataset with these long period Cepheids. By examining our
data at maximum light, we also suggest arguments why errors in reddening are
unlikely to be responsible for our results. The non-linearity of the mean
V-band PL relation as seen in both of the OGLE and MACHO data, using different
extinction maps, suggests that this non-linearity is real.


title: Proper identification of RR Lyrae Stars brighter than 12.5 mag

abstract:
  RR Lyrae stars are of great importance for investigations of Galactic
structure. However, a complete compendium of all RR-Lyraes in the solar
neighbourhood with accurate classifications and coordinates does not exist to
this day. Here we present a catalogue of 561 local RR-Lyrae stars V_max less
equal 12.5 mag according to the magnitudes given in the Combined General
Catalogue of Variable Stars (GCVS) and 16 fainter ones. The Tycho2 catalogue
contains about 100 RR Lyr stars. However, many objects have inaccurate
coordinates in the GCVS, the primary source of variable star information, so
that a reliable cross-identification is difficult. We identified RR Lyrae from
both catalogues based on an intensive literature search. In dubious cases we
carried out photometry of fields to identify the variable. Mennessier and
Colome (2002) have published a paper with Tyc2-GCVS identifications, but we
found that many of their identifications are wrong.
  Keywords: astrometry -- Stars: RR Lyrae stars -- Catalogues: Tycho-2
catalogue -- Catalogues: The HST Guide Star Catalogue, Version 1.2 --
Catalogues: Combined General Catalogue of Variable Stars


title: Contribution of HD molecules in cooling of the primordial gas

abstract:
  We study the effects of HD molecules on thermochemical evolution of the
primordial gas behind shock waves, possibly arised in the process of galaxy
formation. We find the critical shock velocity when deuterium transforms
efficiently into HD molecules which then dominate gas cooling. Above this
velocity the shocked gas is able to cool down to the temperature of the cosmic
microwave background. Under these conditions the corresponding Jeans mass
depends only on redshift and initial density of baryons $M_J \propto
\delta_c^{-0.5} (1+z)^{0.5}$. At $z\simgt 45$ HD molecules heat shocked gas,
and at larger redshift their contribution to thermal evolution becomes
negligible.


title: RR Lyrae stars: Kinematics, orbits and z-distribution

abstract:
  RR Lyrae stars in the Milky Way are good tracers to study the kinematic
behaviour and spatial distribution of older stellar populations. A recently
established well documented sample of 217 RR Lyr stars with V<12.5 mag, has
been used to reinvestigate these structural parameters. The kinematic
parameters allowed to calculate the orbits of the stars. Nearly 1/3 of the
stars of our sample has orbits staying near the Milky Way plane. Of the 217
stars, 163 have halo-like orbits fulfilling one of the following criteria:
Theta < 100 km/s, orbit eccentricity >0.4, and normalized maximum orbital
z-distance >0.45. Of these stars roughly half have retrograde orbits. The
z-distance probability distribution of this sample shows scale heights of 1.3
+-0.1 kpc for the disk component and 4.6 +-0.3 kpc for the halo component. With
our orbit statistics method we found a (vertical) spatial distribution which,
out to z=20 kpc, is similar to that found with other methods. This distribution
is also compatible with the ones found for blue (HBA and sdB) halo stars. The
circular velocity Theta, the orbit eccentricity, orbit z-extent and [Fe/H] are
employed to look for possible correlations. If any, it is that the metal poor
stars with [Fe/H] <1.0 have a wide symmetric distribution about Theta=0. We
conclude that the Milky Way possesses a halo component of old and metal poor
stars with a scale height of 4-5 kpc having random orbits. The presence in our
sample of a few metal poor stars (thus part of the halo population) with thin
disk-like orbits is statistically not surprising. The midplane density ratio of
halo to disk stars is found to be 0.16, a value very dependent on proper sample
statistics. Keywords: astrometry -- Stars: kinematics -- Stars: variables --
Stars: RR-Lyrae -- Galaxy: Halo -- Galaxy: structure


title: Enrichment of the ICM of galaxy clusters due to ram-pressure stripping

abstract:
  We investigate the impact of galactic mass loss triggered by ram-pressure
stripping of cluster galaxies on the evolution of the intra-cluster medium
(ICM). We use combined N-body and hydrodynamic simulations together with a
phenomenological galaxy formation model and a prescription of the effect of
ram-pressure stripping on the galaxies. We analyze the effect of galaxy -- ICM
interaction for different model clusters with different masses and different
merger histories. Our simulations show that ram-pressure stripping can account
for ~ 10% of the overall observed level of enrichment in the ICM within a
radius of 1.3 Mpc. The efficiency of metal ejection of cluster galaxies depends
at the first few Gyr of the simulation mainly on the cluster mass and is
significantly increased during major merger events. Additionally we show that
ram-pressure stripping is most efficient in the center of the galaxy cluster
and the level of enrichment drops quite fast at larger radii. We present
emission weighted metallicity maps of the ICM which can be compared with X-ray
observations. The resulting distribution of metals in the ICM shows a complex
pattern with stripes and plumes of metal rich material. The metallicity maps
can be used to trace the present and past interactions between the ICM and
cluster galaxies.


title:
First Results On Shear-Selected Clusters From the Deep Lens Survey:
  Optical Imaging, Spectroscopy, and X-ray Followup

abstract:
  We present the first sample of galaxy clusters selected on the basis of their
weak gravitational lensing shear. The shear induced by a cluster is a function
of its mass profile and its redshift relative to the background galaxies being
sheared; in contrast to more traditional methods of selecting clusters, shear
selection does not depend on the cluster's star formation history, baryon
content, or dynamical state. Because mass is the property of clusters which
provides constraints on cosmological parameters, the dependence on these other
parameters could induce potentially important biases in traditionally-selected
samples. Comparison of a shear-selected sample with optically and X-ray
selected samples is therefore of great importance. Here we present the first
step toward a new shear-selected sample: the selection of cluster candidates
from the first 8.6 deg$^2$ of the 20 deg$^2$ Deep Lens Survey (DLS), and
tabulation of their basic properties such as redshifts and optical and X-ray
counterparts.


title: The Potential of Multi-Colour Photometry for Pulsating Subdwarf B Stars

abstract:
  We investigate the potential of multi-colour photometry for partial mode
identification in both long- and short-period variable subdwarf B stars. The
technique presented is based on the fact that the frequency dependence of an
oscillation's amplitude and phase bears the signature of the mode's degree
index l, among other things. Unknown contributing factors can be eliminated
through the evaluation of the amplitude ratios and phase differences arising
from the brightness variation in different wavebands, theoretically enabling
the inference of the degree index from observations in two or more bandpasses.
Employing a designated model atmosphere code, we calculate the brightness
variation expected across the visible disk during a pulsation cycle in terms of
temperature, radius, and surface gravity perturbations to the emergent flux for
representative EC 14026 and PG 1716 star models. Nonadiabatic effects are
considered in detail and found to be significant from nonadiabatic pulsation
calculations applied to our state-of-the-art models of subdwarf B stars.


title: A Bound Concerning Primordial Non-Gaussianity

abstract:
  Seery and Lidsey have calculated the three-point correlator of the light
scalar fields, a few Hubble times after horizon exit during inflation. Lyth and
Rodriguez have calculated the contribution of this correlator to the
three-point correlator of the primordial curvature perturbation. We calculate
an upper bound on that contribution, showing that it is too small ever to be
observable.


title:
Newtonian and general relativistic contribution of gravity to surface
  tension of strange stars

abstract:
  Surface tension (S) is due to the inward force experienced by particles at
the surface and usually gravitation does not play an important role in this
force. But in compact stars the gravitational force on the particles is very
large and S is found to depend not only on the interactions in the strange
quark matter, but also on the structure of the star, i.e. on its mass and
radius. Indeed, it has been claimed recently that 511 keV photons observed by
the space probe INTEGRAL from the galactic bulge may be due to
electron-positron annihilation, and their source may be the positron cloud
outside of an antiquark star. Such stars, if they exist, may also go a long way
towards explaining away the antibaryon deficit of the universe. For that to
happen S must be high enough to allow for survival of quark/antiquark stars
born in early stages of the formation of the universe. High value of S may also
assist explanation of delayed gamma-ray burst after a supernova explosion, as
conversion from normal matter to strange matter takes place. The possibility of
some implications from formation of surface waves are also discussed.


title:
The Relationship Between Stellar and Black-Hole Mass in Submillimeter
  Galaxies

abstract:
  We analyze deep X-ray, optical and mid-infrared Spitzer observations of the
CDF-N/GOODS-N region to study 13 submillimeter-detected galaxies (SMGs) with
spectroscopic redshifts (median z=2.2). We find a correlation between the
estimated stellar and X-ray luminosity, implying that masses of the black holes
may be related to the stellar masses of their host galaxies. Although the
submillimeter emission implies that these galaxies are undergoing an epoch of
intense star-formation, the Spitzer data reveal a massive stellar population
already in place. These stellar masses are then compared to previously
published black hole mass estimates derived from the X-ray luminosities under
the assumption of Eddington-limit accretion. We find that the black hole masses
for our high-redshift sample are approximately 1-2 orders of magnitude smaller
than galaxies of comparable stellar mass in the local Universe. Although our
estimates of black hole masses will increase if the accretion is sub-Eddington,
and our stellar masses will decrease if we assume a much younger stellar
population or a different initial mass function, we find that only through a
combination of effects is it possible to shift the high redshift galaxies such
that they lie on the local relation. This suggests that the black holes need to
grow substantially between z=2.2 and the present-day, with much of the black
hole growth occurring after the current obscured, far-infrared luminous phase
of activity which is likely associated with the formation of the spheroid. This
interpretation supports a scenario where SMGs pass through a subsequent
accretion-dominated phase, where they would appear as optically bright quasars.
(ABRIDGED)


title:
On the migration-induced resonances in a system of two planets with
  masses in the Earth mass range

abstract:
  We investigate orbital resonances expected to arise when a system of two
planets, with masses in the range 1-4 Earth masses, undergoes convergent
migration while embedded in a section of gaseous disc where the flow is
laminar. We consider surface densities corresponding to 0.5-4 times that
expected for a minimum mass solar nebula at 5.2 AU. Using hydrodynamic
simulations we find that when the configuration is such that convergent
migration occurs the planets can become locked in a first order
commensurability for which the period ratio is (p+1)/p with p being an integer
and migrate together maintaining it for many orbits. Relatively rapid
convergent migration as tends to occur for disparate masses, results in
commensurabilities with p larger than 2. However, in these cases the dynamics
is found to have a stochastic character. When the convergent migration is
slower, such as occurs in the equal mass case, lower p commensurabilities such
as 3:2 are attained which show much greater stability. In one already known
example of a system with nearly equal masses in the several Earth mass range
(planets around pulsar PSR B1257+12) the two largest planets are intriguingly
close to a 3:2 commensurability. A very similar behaviour is obtained when the
systems are modeled using an N body code with simple prescriptions for the disc
planet interaction. Using that, we found that an 8:7 resonance established in a
hydrodynamic simulation run for 10-100 thousand orbits could be maintained for
more than million orbits. Resonant capture leads to a rise in eccentricities
that can be predicted using a simple analytic model constructed in this paper.
We find that the system with the 8:7 commensurability is fully consistent with
this prediction.


title:
The SCUBA HAlf Degree Extragalactic Survey (SHADES) -- I. Survey
  motivation, design and data processing

abstract:
  The SCUBA HAlf Degree Extragalactic Survey (SHADES) is a major blank-field
extragalactic sub-mm survey underway at the James Clerk Maxwell
telescope.SHADES aims to cover half a square degree at 450+850microns to a
4sigma depth of ~8mJy at 850microns. Two fields are being observed, the
Subaru/XMM--Newton Deep Field (SXDF) and the Lockman Hole East. The survey has
3 main aims to investigate: i) the cosmic history of massive dust enshrouded
star-formation activity, ii) the clustering properties of sub-mm-selected
galaxies in order to determine whether these objects could be progenitors of
present-day massive ellipticals, and iii) the fraction of sub-mm-selected
sources that harbour AGN. To achieve these aims requires the sub-mm data be
combined with co-spatial information spanning the radio-to-X-ray frequency
range, the resulting extensive multi-wavelength dataset providing complete
photometric redshift information accurate to delta z <~0.5 and detailed SEDs
for the vast majority of the sub-mm-selected sources. In this paper, the first
of a series on SHADES, we present an overview of the motivation for the survey,
describe the survey strategy and provide a detailed description of the primary
data analysis pipeline. As of Feb. 2004, 720arcmin^2 had been mapped with SCUBA
(about 40% of the anticipated final total) to a median 1sigma depth of 2.2mJy
per beam at 850microns (25mJy per beam at 450microns), and a source density of
650+/-50 sources/deg^2 >3sigma at 850microns, uncorrected for Eddington bias. A
refined re-analysis of the original 8-mJy survey Lockman hole data was carried
out in order to evaluate the new data reduction pipeline. Of the 17 most secure
sources in the original sample, 12 have been re-confirmed, including 10 of the
11 for which radio IDs were previously secured.(Abridged)


title:
Smoothed Particle Inference: A Kilo-Parametric Method for X-ray Galaxy
  Cluster Modeling

abstract:
  We propose an ambitious new method that models the intracluster medium in
clusters of galaxies as a set of X-ray emitting smoothed particles of plasma.
Each smoothed particle is described by a handful of parameters including
temperature, location, size, and elemental abundances. Hundreds to thousands of
these particles are used to construct a model cluster of galaxies, with the
appropriate complexity estimated from the data quality. This model is then
compared iteratively with X-ray data in the form of adaptively binned photon
lists via a two-sample likelihood statistic and iterated via Markov Chain Monte
Carlo. The complex cluster model is propagated through the X-ray instrument
response using direct sampling Monte Carlo methods. Using this approach the
method can reproduce many of the features observed in the X-ray emission in a
less assumption-dependent way that traditional analyses, and it allows for a
more detailed characterization of the density, temperature, and metal abundance
structure of clusters. Multi-instrument X-ray analyses and simultaneous X-ray,
Sunyaev-Zeldovich (SZ), and lensing analyses are a straight-forward extension
of this methodology. Significant challenges still exist in understanding the
degeneracy in these models and the statistical noise induced by the complexity
of the models.


title:
The Photometric Performance and Calibration of the HST Advanced Camera
  For Surveys

abstract:
  We present the photometric calibration of the HST Advanced Camera for Surveys
(ACS). We give here an overview of the performance and calibration of the 2 CCD
cameras, the Wide Field Channel (WFC) and the High Resolution Channel (HRC),
and a description of the best techniques for reducing ACS CCD data.
  On-orbit observations of spectrophotometric standard stars have been used to
revise the pre-launch estimate of the instrument response curves to best match
predicted and observed count rates. Synthetic photometry has been used to
determine zeropoints for all filters in 3 magnitude systems and to derive
interstellar extinction values for the ACS photometric systems.
  Due to the CCD internal scattering of long wavelength photons, the width of
the PSF increases significantly in the near-IR and the aperture correction for
photometry with near-IR filters depends on the spectral energy distribution of
the source. We provide encircled energy curves and a detailed recipe to correct
for the latter effect.
  Transformations between the ACS photometric systems and the UBVRI and WFPC2
systems are presented. In general, two sets of transformations are available: 1
based on the observation of 2 star clusters; the other on synthetic photometry.
We discuss the accuracy of these transformations and their sensitivity to
details of the spectra being transformed.
  Initial signs of detector degradation due to the HST radiative environment
are already visible. We discuss the impact on the data in terms of dark rate
increase, charge transfer inefficiency, and hot pixel population.


title: The XBootes Chandra Survey Paper II: The X-ray Source Catalog

abstract:
  We present results from a Chandra survey of the nine square degree Bootes
field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists
of 126 separate contiguous ACIS-I observations each of approximately 5000
seconds in duration. These unique Chandra observations allow us to search for
large scale structure and to calculate X-ray source statistics o ver a wide,
contiguous field of view with arcsecond angular resolution and uniform
coverage. Optical spectroscopic follow-up observations and the rich NDWFS data
set will allow us to identify and classify these X-ray selected sources.
  Using wavelet decomposition, we detect 4642 point sources with n $\ge$ 2
counts. In order to keep our detections ~99% reliable, we limit our list to
sources with n $\ge$ 4 counts.
  The full 0.5--7 keV band n $\ge$ 4 count list has 3293 point sources. In
addition to the point sources, 43 extended sources have been detected
consistent, with the depth of these observations and the number counts of
clusters. We present here the X-ray catalog for the XBootes survey, including
source positions, X-ray fluxes, hardness ratios and their uncertainties.
  We calculate and present the differential number of sources per flux densit y
interval, $N(S)$, for the point sources.


title:
An Extreme Case of a Misaligned Highly Flattened Wind in the Wolf-Rayet
  Binary CX Cephei

abstract:
  CX Cep (WR 151) is the WR+O binary (WN5+O5V) with the second shortest period
known in our Galaxy. To examine the circumstellar matter distribution and to
better constraint the orbital parameters and mass-loss rate of the WR star, we
obtained broadband and multi-band (i.e. UBVRI) linear polarization observations
of the system. Our analysis of the phase-locked polarimetric modulation
confirms the high orbital inclination of the system (i.e. $i=65^o$). Using the
orbital solution of Lewis et al. (1993) we obtain masses of $33.9 M_{\odot}$
and $23.9 M_{\odot}$ for the O and WR stars respectively, which agree with
their spectral types. A simple polarimetric model accounting for finite stellar
size effects allowed us to derive a mass-loss rate for the WR star of
$0.3-0.5\times10^{-5} M_{\odot}/yr$. This result was remarkably independent of
the model's input parameters and favors an earlier spectral type for the WR
component (i.e. WN4). Finally, using our multi-band observations, we fitted and
subtracted from our data the interstellar polarization. The resulting constant
intrinsic polarization of $3-4%$ is misaligned in relation to the orbital plane
(i.e. $\theta_{CIP}=26^o$ vs. $\Omega=75^o$) and is the highest intrinsic
polarization ever observed for a WR star. This misalignment points towards a
rotational (or magnetic) origin for the asymmetry and contradicts the most
recent evolutionary models for massive stars (Meynet & Maeder 2003) which
predict spherically symmetric winds during the WR phase (i.e. $CIP=0%$).


title:
Wide-field prime-focus Imaging Atmospheric Cherenkov Telescopes: A
  systematic study

abstract:
  By means of third-order optical theory as well as ray-tracing simulations we
have investigated the feasibility of wide-field imaging atmospheric Cherenkov
telescopes with a reflective prime-focus design. For a range of desired optical
resolutions, we have determined the largest available field-of-view of
single-piece spherical, single-piece parabolic, tessellated spherical,
tessellated parabolic and Davies-Cotton designs, always considering a wide
range of design parameters. The Davies-Cotton design exhibits a surprising
similarity to the tessellated parabolic design in its qualitative behaviour.
Also, elliptic telescope designs with better off-axis imaging properties than
Davies-Cotton are presented. We show that by using f/2 optics it is possible to
build prime-focus telescopes with a full field-of-view of 10 degree at 0.1
degree resolution.


title: High-precision K-band photometry of the secondary eclipse of HD209458

abstract:
  Recently, mid-infrared Spitzer observations have been presented that show the
light decrement due to the passage of a planet behind its host star. These
measurements of HD209458b and TrES-1 are the first detections of direct light
from an extra-solar planet. Interpretation of these results in terms of planet
equipartition temperature and bond albedo is however strongly model dependent
and require additional observations at shorter wavelengths. Here we report on
two attempts to detect the secondary eclipse of HD209458b from the ground in
K-band, using the UK InfraRed Telescope (UKIRT). A photometry precision of
0.12% relative to two nearby reference stars was reached during both occasions,
but no firm detection of the eclipses were obtained. The first observation
shows a flux decrement of -0.13+-0.18%, and the second of -0.10+-0.10%. A
detailed description of the observing strategy, data reduction and analysis is
given, and a discussion on how the precision in ground-based K-band photometry
could be further improved. In addition we show that the relative photometry
between the target and the reference stars between the two epochs is consistent
down to the <0.1% level, which is interesting in the light of possible
near-infrared surveys to search for transiting planets around M and L dwarfs.


title: General Relativity Resolves Galactic Rotation Without Exotic Dark Matter

abstract:
  A galaxy is modeled as a stationary axially symmetric pressure-free fluid in
general relativity. For the weak gravitational fields under consideration, the
field equations and the equations of motion ultimately lead to one linear and
one nonlinear equation relating the angular velocity to the fluid density. It
is shown that the rotation curves for the Milky Way, NGC 3031, NGC 3198 and NGC
7331 are consistent with the mass density distributions of the visible matter
concentrated in flattened disks. Thus the need for a massive halo of exotic
dark matter is removed. For these galaxies we determine the mass density for
the luminous threshold as 10^{-21.75} kg.m$^{-3}.


title: Inductive acceleration of UHECRs in sheared relativistic jets

abstract:
  (Abridged)Relativistic outflows carrying large scale magnetic fields have
large inductive potential and may accelerate protons to ultra high energies. We
discuss a novel scheme of Ultra-High Energy Cosmic Ray (UHECR) acceleration due
to drifts in magnetized, cylindrically collimated, sheared jets of powerful
active galaxies (with jet luminosity $\geq 10^{46}$ erg s$^{-1}$). We point out
that a positively charged particle carried by such a plasma is in an unstable
equilibrium if ${\bf B} \cdot \nabla \times {\bf v}< 0$, so that kinetic drift
along the velocity shear would lead to fast, {\it regular} energy gain. We show
that if a seed of pre-accelerated particles with energy below the ankle $\leq
10^{18}$ eV is present, these particles can be boosted to energies above $
10^{19}$ eV. A key feature of the mechanism is that the highest rigidity
particles are accelerated most efficiently implying the dominance of light
nuclei for energies above the ankle in our model: from a mixed population of
pre-accelerated particle the drift mechanism picks up and boosts protons
preferably. In addition, after a particle traversed large fraction of the
available potential, its Larmor radius becomes of the order of the jet
thickness. In this case, {\it the maximum possible acceleration rate of inverse
relativistic gyro-frequency is achieved} and a particle finally become
unconfined and leave the jet.


title:
Probing the IGM-Galaxy Connection Toward PKS0405-123 II : A
  Cross-Correlation Study of Lya Absorbers and Galaxies at z<0.5

abstract:
  We present a pilot study of the clustering properties of Lya absorbers with
respect to known galaxies based on 112 Lya absorbers and 482 galaxies
identified at z<0.5 along the sightline toward PKS0405-123. The principal goal
is to determine the origin of Lya absorbers based on their cross-correlation
amplitude with known galaxies and investigate a possible N(HI) dependence of
the cross-correlation function. The main results of our study are as follows.
(1) The cross-correlation function xi_{ga} measured using only emission-line
dominated galaxies and Lya absorbers of log N(HI) >= 14 shows a comparable
strength to the galaxy auto-correlation function xi_{gg} on co-moving,
projection distance scales < 1 h^{-1} Mpc, while there remains a lack of
cross-correlation signal when using only absorption-line dominated galaxies.
This signifies a morphology-dependent xi_{ga} and indicates that strong
absorbers of log N(HI) >= 14 and emission-line galaxies reside in the same halo
population. (2) A maximum-likelihood analysis shows that Lya absorbers of log
N(HI) < 13.6 are consistent with being more randomly distributed with respect
to known galaxies. Finally, (3) we find based on this single sightline that the
amplitude of xi_{ga} does not depend sensitively on N(HI) for strong absorbers
of log N(HI) >= 13.6.