title:
Lyman-alpha forest-CMB cross-correlation and the search for the ionized
  baryons at high redshift

abstract:
  The intergalactic neutral hydrogen which is responsible for the Lyman alpha
forest of quasar absorption is a tracer of much larger amounts of ionised
hydrogen. The ionised component has yet to be detected directly, but is
expected to scatter CMB photons via the Sunyaev-Zel'dovich (SZ) effect. We use
hydrodynamic simulations of a LambdaCDM universe to create mock quasar spectra
and CMB sky maps. We find that the high-z Lya forest gas causes temperature
fluctuations of the order of 1 muK rms in the CMB on arcmin scales. The kinetic
and thermal SZ effects have a similar magnitude at z=3, with the thermal effect
becoming relatively weaker as expected at higher z. The CMB signal associated
with lines of sight having HI column densities > 10^18 cm^-2 is only marginally
stronger than that for lower column densities. The strong dependence of rms
temperature fluctuation on mean Lya absorbed flux, however, suggests that the
CMB signal effectively arises in lower density material. We investigate the use
of the cross-correlation of the Lya forest and the microwave background to
detect the SZ effect at redshifts 2-4. In so doing we are able to set direct
limits on the density of diffuse ionised intergalactic baryons. We carry out a
preliminary comparison at a mean redshift z=3 of 3488 quasar spectra from SDSS
Data Release 3 and the WMAP first year data. Assuming that the baryons are
clustered as in a LambdaCDM cosmology, and have the same mean temperature, the
cross-correlation yields a weak limit on the cosmic density of ionised baryons
Omega_(b,I), which is Omega_(b,I) < 0.8 at 95% confidence. With data from
upcoming CMB telescopes, we anticipate that a direct detection of the high
redshift ionised IGM will soon be possible, providing an important consistency
check on cosmological models.


title:
Dynamical flows through Dark Matter Haloes: Inner perturbative dynamics,
  secular evolution, and applications

abstract:
  We investigate statistically the dynamical consequences of cosmological
fluxes of matter and related moments on progenitors of today's dark matter
haloes. Their dynamics is described via canonical perturbation theory which
accounts for two types of perturbations: the tidal field corresponding to
fly-bys and accretion of dark matter through the halo's outer boundary. he
dynamical equations are solved linearly, order by order, projecting on a
biorthogonal basis to consistently satisfy the field equation. Since our
solution of the Boltzmann Poisson equations is explicit, it allows statistical
predictions for the ensemble distribution of the inner dynamical features of
haloes. The secular evolution of open galactic haloes is investigated: we
derive the kinetic equation which governs the quasi-linear evolution of dark
matter profile induced by infall and its corresponding gravitational
correlations. This yields a Fokker Planck-like equation for the angle-averaged
underlying distribution function. We show how these extensions to the classical
theory could be used to (i) observationally constrain the statistical nature of
the infall (ii) predict the observed distribution and correlations of
substructures in upcoming surveys, (iii) predict the past evolution of the
observed distribution of clumps, and finally (iv) weight the relative
importance of the intrinsic (via the unperturbed distribution function) and
external (tidal and/ or infall) influence of the environment in determining the
fate of galaxies.


title:
Large Area Mapping at 850 Microns. IV. Analysis of the Clump
  Distribution in the Orion B South Molecular Cloud

abstract:
  We present results from a survey of a 1300 arcmin^2 region of the Orion B
South molecular cloud, including NGC 2024, NGC 2023, and the Horsehead Nebula
(B33), obtained using the Submillimetre Common-User Bolometer Array (SCUBA) on
the James Clerk Maxwell Telescope. Submillimeter continuum observations at 450
microns and 850 microns are discussed. Using an automated algorithm, 57
discrete emission features (``clumps'') are identified in the 850 micron map.
The physical conditions within these clumps are investigated under the
assumption that the objects are in quasi-hydrostatic equilibrium. The best fit
dust temperature for the clumps is found to be T_d = 18 +/- 4 K, with the
exception of those associated with the few known far infrared sources residing
in NGC 2024. The latter internally heated sources are found to be much warmer.
In the region surrounding NGC 2023, the clump dust temperatures agree with
clump gas temperatures determined from molecular line excitation measurements
of the CO molecule. The bounding pressure on the clumps lies in the range
log(k^-1 P cm^3 K^-1) = 6.1 +/- 0.3. The cumulative mass distribution is steep
at the high mass end, as is the stellar Initial Mass Function. The distribution
flattens significantly at lower masses, with a turn-over around 3 -- 10 M_sun.


title: Two Populations of Young Massive Star Clusters in Arp 220

abstract:
  We present new optical observations of young massive star clusters in Arp
220, the nearest ultraluminous infrared galaxy, taken in UBVI with the Hubble
Space Telescope ACS/HRC camera. We find a total of 206 probable clusters whose
spatial distribution is centrally concentrated toward the nucleus of Arp 220.
We use model star cluster tracks to determine ages, luminosities, and masses
for 14 clusters with complete UBVI indices or previously published
near-infrared data. We estimate rough masses for 24 additional clusters with I
< 24 mag from BVI indices alone. The clusters with useful ages fall into two
distinct groups: a ``young'' population (< 10 Myr) and an intermediate-age
population (~300 Myr). There are many clusters with masses clearly above 10^6
Msun and possibly even above 10^7 Msun in the most extreme instances. These
masses are high enough that the clusters being formed in the Arp 220 starburst
can be considered as genuine young globular clusters. In addition, this study
allows us to extend the observed correlation between global star formation rate
and maximum cluster luminosity by more than an order of magnitude in star
formation rate.


title: Galaxy Formation

abstract:
  I summarize current knowledge of galaxy formation with emphasis on the
initial conditions provided by the Lambda CDM cosmology, integral constraints
from cosmological quantities, and the demographics of high-redshift
protogalaxies. Tables are provided summarizing the number density, star
formation rate and stellar mass per object, cosmic star formation rate and
stellar mass densities, clustering length and typical dark matter halo masses
for Lyman break galaxies, Lyman alpha emitting galaxies, Distant red galaxies,
Sub-millimeter galaxies, and Damped Lyman alpha absorption systems. I also
discuss five key unsolved problems in galaxy formation and prognosticate
advances that the near future will bring.


title:
The origin of the double main sequence in Omega Centauri: Helium
  enrichment due to gas fueling from its ancient host galaxy ?

abstract:
  Recent observational studies of $\omega$ Centauri by {\it Hubble Space
Telescope} have discovered a double main sequence in the color magnitude
diagrams (CMDs) of its stellar populations. The stellar population with the
blue main sequence (bMS) is observationally suggested to have a helium
abundance much larger, by $\Delta Y\sim 0.12$, than that of the red main
sequence (rMS). By using somewhat idealized models in which stars of the bMS
are formed from gas ejected from those of the rMS, we quantitatively
investigate whether the helium overabundance of the bMS can result from
self-enrichment from massive AGB stars, from mass loss of very massive young
stars, or from type II supernovae within $\omega$ Cen. We show that as long as
the helium enrichment is due to ejecta from the rMS formed earlier than the
bMS, none of the above three enrichment scenarios can explain the observed
properties of the bMS self-consistently for reasonable IMFs. The common,
serious problem in all cases is that the observed number fraction of the bMS
can not be explained without assuming unusually top-heavy IMFs. This failure of
the self-enrichment scenarios implies that most of the helium-enriched gas
necessary for the formation of the bMS originated from other external sources.
We thus suggest a new scenario that most of the second generation of stars
(i.e., the bMS) in $\omega$ Cen could be formed from gas ejected from field
stellar populations that surrounded $\omega$ Cen when it was a nucleus of an
ancient dwarf galaxy.


title:
Impact of dark matter subhalos on extended HI disks of galaxies:
  Possible formation of HI fine structures and stars

abstract:
  Recent observations have discovered star formation activities in the extreme
outer regions of disk galaxies. However it remains unclear what physical
mechanisms are responsible for triggering star formation in such low-density
gaseous environments of galaxies. In order to understand the origin of these
outer star-forming regions, we numerically investigate how the impact of dark
matter subhalos orbiting a gas-rich disk galaxy embedded in a massive dark
matter halo influences the dynamical evolution of outer HI gas disk of the
galaxy. We find that if the masses of the subhalos ($M_{\rm sb}$) in a galaxy
with an extended HI gas disk are as large as $10^{-3} \times M_{\rm h}$, where
$M_{\rm h}$ is the total mass of the galaxy's dark halo, local fine structures
can be formed in the extended HI disk. We also find that the gas densities of
some apparently filamentary structures can exceed a threshold gas density for
star formation and thus be likely to be converted into new stars in the outer
part of the HI disk in some models with larger $M_{\rm sb}$. These results thus
imply that the impact of dark matter subhalos (``dark impact'') can be
important for better understanding the origin of recent star formation
discovered in the extreme outer regions of disk galaxies. We also suggest that
characteristic morphologies of local gaseous structures formed by the dark
impact can indirectly prove the existence of dark matter subhalos in galaxies.
We discuss the origin of giant HI holes observed in some gas-rich galaxies
(e.g., NGC 6822) in the context of the dark impact.


title:
The Galactic black hole transient H1743-322 during outburst decay:
  connections between timing noise, state transitions and radio emission

abstract:
  Multi-wavelength observations of Galactic black hole transients during
outburst decay are instrumental for our understanding of the accretion geometry
and the formation of outflows around black hole systems. H1743-322, a black
hole transient observed intensely in X-rays and also covered in the radio band
during its 2003 decay, provides clues about the changes in accretion geometry
during state transitions and also the general properties of X-ray emission
during the intermediate and the low-hard states. In this work, we report on the
evolution of spectral and temporal properties in X-rays and the flux in the
radio band with the goal of understanding the nature of state transitions
observed in this source. We concentrate on the transition from the thermal
dominant state to the intermediate state that occurs on a timescale of one day.
We show that the state transition is associated with a sudden increase in
power-law flux. We determine that the ratio of the power-law flux to the
overall flux in the 3--25 keV band must exceed 0.6 to observe strong timing
noise. Even after the state transition, once this ratio was below 0.6, the
system transited back to the thermal dominant state for a day. We show that the
emission from the compact radio core does not turn on during the transition
from the thermal dominant state to the intermediate state but does turn on when
the source reaches the low-hard state, as seen in 4U 1543-47 and GX 339-4. We
find that the photon index correlates strongly with the QPO frequency and
anti-correlates with the rms amplitude of variability. We also show that the
variability is more likely to be associated with the power-law emission than
the disk emission.


title: Spectroscopic Analysis of sdB Binaries from the SPY Project

abstract:
  In the course of our search for double degenerate binaries as potential
progenitors of type Ia supernovae with the ESO VLT (ESO SN Ia Progenitor SurveY
SPY) several new subdwarf B (sdB) binaries with sdB primary components were
discovered. In this paper, we present detailed analyses of six radial velocity
variable sdB stars. Radial velocity curves have been measured. From the mass
functions we derive lower limits to the masses of the unseen companions and we
discuss their nature. In addition, stellar parameters like effective
temperatures, surface gravities and helium abundances were determined as well
as metal abundances.


title: Deceleration from Entrainment in the jet of the quasar 1136-135?

abstract:
  Modeling the multiwavelength emission of successive regions in the jet of the
quasar PKS 1136-135 we find indication that the jet suffers deceleration near
its end on a (deprojected) scale of ~400 kpc. Adopting a continuous flow
approximation we discuss the possibility that the inferred deceleration from a
Lorentz factor Gamma=6.5 to Gamma=2.5 is induced by entrainment of external
gas. Some consequences of this scenario are discussed.


title: New method for determining the thickness of non-edge-on disk galaxies

abstract:
  In this paper we report a new method for determining the thickness of the
non-edge-on disk galaxies. Our method is based on the observation comparing
with the theoretical researches of the distribution of the vertical velocity
dispersion, which is obtained from the solutions of three dimensional Poisson's
equation and the galactic dynamical equation. This method also allows us to
investigate the mass-to-light ratio of the disk. As examples, the thickness and
mass-to-light ratio of two disk galaxies, NGC 1566 and NGC 5247, which have
been extensively studied in spectroscopy, have been calculated and the results
are presented.


title:
The evolution of the star formation activity in galaxies and its
  dependence on environment

abstract:
  We study how the proportion of star-forming galaxies evolves between z=0.8
and z=0 as a function of galaxy environment, using the [OII] line in emission
as a signature of ongoing star formation. Our high-z dataset comprises 16
clusters, 10 groups and another 250 galaxies in poorer groups and the field at
z=0.4-0.8 from the ESO Distant Cluster Survey, plus another 9 massive clusters
at similar redshifts. As a local comparison, we use samples of galaxy systems
selected from the Sloan Digital Sky Survey at 0.04< z < 0.08. At high-z most
systems follow a broad anticorrelation between the fraction of star-forming
galaxies and the system velocity dispersion. At face value, this suggests that
at z=0.4-0.8 the mass of the system largely determines the proportion of
galaxies with ongoing star formation. At these redshifts the strength of star
formation (as measured by the [OII] equivalent width) in star-forming galaxies
is also found to vary systematically with environment. Sloan clusters have much
lower fractions of star-forming galaxies than clusters at z=0.4-0.8 and, in
contrast with the distant clusters, show a plateau for velocity dispersions $
\ge 550 km s^-1$, where the fraction of galaxies with [OII] emission does not
vary systematically with velocity dispersion. We quantify the evolution of the
proportion of star-forming galaxies as a function of the system velocity
dispersion and find it is strongest in intermediate-mass systems (sigma ~
500-600 km s^-1 at z=0). To understand the origin of the observed trends, we
use the Press-Schechter formalism and the Millennium Simulation and show that
galaxy star formation histories may be closely related to the growth history of
clusters and groups. We propose a scheme that is able to account for the
observed relations between the star-forming fraction and \sigma [abridged].


title: Swift and XMM observations of the dark GRB 050326

abstract:
  We present Swift and XMM observations of GRB 050326, detected by Swift-BAT.
The fluence was 7.7x10^-6 erg cm^-2 (20-150 keV), and its spectrum was hard,
with a power law photon index 1.25. The afterglow light curve did not show any
break nor flares between ~1 hr and ~6 d after the burst, and decayed with a
slope 1.70. The afterglow spectrum is well fitted by a power-law model,
suffering absorption both in the Milky Way and in the host galaxy. The
rest-frame Hydrogen column density is significant, N_H_z > 4x10^21 cm^-2, and
the redshift of the absorber is z > 1.5. There was good agreement between the
Swift-XRT and XMM results. By comparing the prompt and afterglow fluxes, we
found that an early break occurred before the XRT observation. The properties
of the GRB 050326 afterglow are well described by a spherical fireball
expanding in a uniform external medium, so a further steepening is expected at
later times. The lack of such a break constrains the jet angle to be >7 deg.
Using the redshift constraints provided by the X-ray analysis, we also
estimated that the beaming-corrected gamma-ray energy was >3x10^51 erg, at the
high end of GRB energies. Despite the brightness in X rays, only deep limits
could be placed by Swift-UVOT at optical/UV wavelengths. Thus, this GRB was
"truly dark", with the optical-to-X-ray spectrum violating the synchrotron
limit. The optical and X-ray observations are consistent either with an
absorbed event or with a high-redshift one. To obey the Ghirlanda relation, a
moderate/large redshift z>4.5 is required. (abridged)


title:
Observational evidence for the link between the variable optical
  continuum and the jet of a radio-loud galaxy 3C 390.3

abstract:
  The ``central engine'' of AGN is thought to be powered by accretion on a
central nucleus believed to be a super-massive black hole. The localization and
exact mechanism of the energy release in AGN are still not well understood. We
present observational evidence for the link between variability of the radio
emission of the compact jet, optical and X-ray continua emission and ejections
of new jet components in the radio galaxy 3C 390.3. The time delays between the
light curves of the individual jet components and the light curve of the
optical continuum are estimated by using minimization methods and the discret
correlation function. We find that the variations of the optical continuum are
correlated with radio emission from a stationary feature in the jet. This
correlation indicates that the source of variable non-thermal continuum
radiation is located in the innermost part of the relativistic jet. We suggest
that the continuum emission from the jet and counterjet ionizes material in a
subrelativistic outflow surrounding the jet, which results in a formation of
two conical regions with broad emission lines (in addition to the conventional
broad line region around the central nucleus) at a distance more or equal to
0.4 parsecs from the central engine. Implications for modeling of the
broad-line regions are discussed.


title:
Investigating a Fluctuating-accretion Model for the Spectral-timing
  Properties of Accreting Black Hole Systems

abstract:
  The fluctuating accretion model of Lyubarskii (1997) and its extension by
Kotov et al. (2001), seeks to explain the spectral-timing properties of the
X-ray variability of accreting black holes in terms of inward-propagating mass
accretion fluctuations produced at a broad range of radii. The fluctuations
modulate the X-ray emitting region as they move inwards and can produce
temporal-frequency-dependent lags between energy bands, and energy-dependent
power spectral densities (PSDs) as a result of the different emissivity
profiles, which may be expected at different X-ray energies. Here we use a
simple numerical implementation to investigate in detail the X-ray
spectral-timing properties of the model and their relation to several
physically interesting parameters, namely the emissivity profile in different
energy bands, the geometrical thickness and viscosity parameter of the
accretion flow, the strength of damping on the fluctuations and the temporal
coherence (measured by the `quality-factor', Q) of the fluctuations introduced
at each radius. We find that a geometrically thick flow with large viscosity
parameter is favoured, and confirm that the predicted lags are quite robust to
changes in the emissivity profile, and physical parameters of the accretion
flow, which may help to explain the similarity of the lag spectra in the
low/hard and high/soft states of Cyg X-1. We also demonstrate the model regime
where the light curves in different energy bands are highly spectrally
coherent. We compare model predictions directly to X-ray data from the Narrow
Line Seyfert~1 galaxy NGC 4051 and the BHXRB Cyg X-1 in its high/soft state and
show that this general scheme can reproduce simultaneously the time lags and
energy-dependence of the PSD.


title:
Magnetic flux in the inter-network quiet Sun from comparison with
  numerical simulations

abstract:
  Khomenko et al. estimate the mean magnetic field strength of the quiet Sun to
be 20 G. The figure is smaller than several existing estimates, and it comes
from the comparison between observed Zeeman polarization signals and synthetic
signals from numerical simulations of magneto-convection. The numerical
simulations require an artificially large magnetic diffusivity, which smears
out magnetic structures smaller than the grid scale. Assuming a turbulent
cascade for the unresolved artificially smeared magnetic fields, we find that
their unsigned magnetic flux is at least as important as that explicitly shown
in the simulation. The unresolved fields do not produce Zeeman polarization but
contribute to the unsigned flux.Since they are not considered by Khomenko et
al., their mean magnetic field strength has to be regarded as a lower limit.
This kind of bias is not specific of a particular numerical simulation or a
spectral line. It is to be expected when observed quiet Sun Zeeman signals are
compared with synthetic signals from simulations.


title:
A Lyman-alpha blob in the GOODS South field: evidence for cold accretion
  onto a dark matter halo

abstract:
  We report on the discovery of a z = 3.16 Lyman-alpha emitting blob in the
GOODS South field. The blob has a total Ly-alpha luminosity of ~ 10^(43) erg
s^(-1) and a diameter larger than 60 kpc. The available multi-wavelength data
in the GOODS field consists of 13 bands from X-rays (Chandra) to infrared
(Spitzer). Unlike other discovered Ly-alpha blobs, this blob shows no obvious
continuum counter-part in any of the broad-bands. In particular, no optical
counter-parts are found in the deep HST/ACS imaging available. For previously
published blobs, AGN (Active Galactic Nuclei) or 'superwind' models have been
found to provide the best match with the data. We here argue that the most
probable origin of the extended Ly-alpha emission from the blob in the GOODS
South field is cold accretion onto a dark matter halo.


title:
Analysis of a multi-wavelength time-resolved observation of a coronal
  loop

abstract:
  Several items on the diagnostics and interpretation of coronal loop
observations are under debate. In this work, we analyze a well-defined loop
system detected in a time-resolved observation in several spectral bands. The
dataset includes simultaneous images in the TRACE 171 A, 195 A and 284 A bands,
and Yohkoh/SXT, and two rasters taken with SoHO/CDS in twelve relevant lines.
The loop is initially best visible in the TRACE 195 A filter band, and later in
the 171 A filter band, with correspondence with the CDS raster images at log T
\~ 6.0-6.1. We have taken as pixel-by-pixel background the latest TRACE, Yohkoh
and CDS images where the loop has faded out. We examine the loop morphology
evolution, the light curves, the TRACE filter ratio distribution and evolution,
the images and emission measure from the CDS spectral lines. Our analysis
detects that, after background subtraction, the emission along the loop and its
evolution are non-uniform, especially in the 171 A filter band, and that the
TRACE 195/171 filter ratio has a moderately non-uniform distribution along the
loop and evolves in time. Both the light curves and the filter ratio evolution
indicate a globally cooling loop. Relatively hot plasma may be present at the
beginning while, during the first CDS raster, the data indicate a rather
moderate thermal structuring of the loop. Our data analysis supports a coherent
scenario across the different bands and instruments, points out difficulties in
diagnostic methods and puts quantitative basis for detailed forward modeling.


title: EMMA - A New Underground Cosmic-Ray Experiment

abstract:
  A new type of cosmic-ray experiment is under construction in the Pyh\"asalmi
mine in the underground laboratory of the University of Oulu, Finland. It aims
to study the composition of cosmic rays at and above the knee region. The
experiment, called EMMA, will cover approximately 150 square-metres of detector
area. The array is capable of measuring the multiplicity and the lateral
distribution of underground muons, and the arrival direction of the air shower.
The full-size detector is expected to run by the end of 2007.


title:
Unveiling the nature of INTEGRAL objects through optical spectroscopy.
  III. Observations of seven southern sources

abstract:
  Context. The detection, thanks to the INTEGRAL satellite, of a number of new
hard X-ray sources calls for the identification of their nature by means of
observations at longer wavelengths.
  Aims. In our continuing campaign to identify longer-wavelength counterparts
of these newly-discovered hard X-ray sources detected by INTEGRAL, we observed
the putative optical counterparts of seven southern sources at the South
African Astronomical Observatory and at the European Southern Observatory.
  Methods. Optical spectroscopy was performed on all candidates of these X-ray
sources. For two of these objects, optical photometry was also acquired.
  Results. These observations firmly established the nature of four of these
sources: we found that IGR J10404-4625 (=LEDA 93974), 4U 1344-60 and IGR
J16482-3036 are Active Galactic Nuclei (AGNs) at redshifts z = 0.0237, 0.013
and 0.0313, respectively, and that 2RXP J130159.6-635806 is a Galactic
High-Mass X-ray Binary (HMXB). We also give possible optical identifications
for three further objects, namely IGR J11215-5952, IGR J11305-6256 and IGR
J16207-5129, which are consistent with being Galactic HMXBs. Physical
parameters for these objects are also evaluated by collecting and discussing
the available multiwavelength information.
  Conclusions. The detection of four definite or likely HMXBs out of seven
objects in our sample further stresses INTEGRAL's crucial contribution in
hunting this class of object. Also, the determination of the extragalactic
nature of a substantial fraction of the INTEGRAL survey sources underlines the
importance of hard X-ray observations for the study of background AGNs located
beyond the 'Zone of Avoidance' of the Galactic Plane.


title:
Shapiro Effect as a Possible Cause of the Low-Frequency Pulsar Timing
  Noise in Globular Clusters

abstract:
  A prolonged timing of millisecond pulsars has revealed low-frequency
uncorrelated noise, presumably of astrophysical origin, in the pulse arrival
time (PAT) residuals for some of them. In most cases, pulsars in globular
clusters show a low-frequency modulation of their rotational phase and spin
rate. The relativistic time delay of the pulsar signal in the curved space time
of randomly distributed and moving globular cluster stars (the Shapiro effect)
is suggested as a possible cause of this modulation.
  Given the smallness of the aberration corrections that arise from the
nonstationarity of the gravitational field of the randomly distributed ensemble
of stars under consideration, a formula is derived for the Shapiro effect for a
pulsar in a globular cluster. The derived formula is used to calculate the
autocorrelation function of the low-frequency pulsar noise, the slope of its
power spectrum, and the behavior of the $\sigma_z$ statistic that characterizes
the spectral properties of this noise in the form of a time function. The
Shapiro effect under discussion is shown to manifest itself for large impact
parameters as a low-frequency noise of the pulsar spin rate with a spectral
index of n=-1.8 that depends weakly on the specific model distribution of stars
in the globular cluster. For small impact parameters, the spectral index of the
noise is n=-1.5.


title: XMM-Newton Spectroscopy of the Cluster of Galaxies 2A 0335+096

abstract:
  We present here the results of a deep (130 ks) XMM-Newton observation of the
cluster of galaxies 2A 0335+096. The deep exposure allows us to study in detail
its temperature structure and its elemental abundances. We fit three different
thermal models and find that the multi-temperature wdem model fits our data
best. We find that the abundance structure of the cluster is consistent with a
scenario where the relative number of Type Ia supernovae contributing to the
enrichment of the intra-cluster medium is ~25%, while the relative number of
core collapse supernovae is ~75%. Comparison of the observed abundances to the
supernova yields does not allow us to put any constrains on the contribution of
Pop III stars to the enrichment of the ICM. Radial abundance profiles show a
strong central peak of both Type Ia and core collapse supernova products. Both
the temperature and iron abundance maps show an asymmetry in the direction of
the elongated morphology of the surface brightness. In particular the
temperature map shows a sharp change over a brightness edge on the southern
side of the core, which was identified as a cold front in the Chandra data.
This suggests that the cluster is in the process of a merger with a subcluster.
Moreover, we find that the blobs or filaments discovered in the core of the
cluster by Chandra are, contrary to the previous results, colder than the
ambient gas and they appear to be in pressure equilibrium with their
environment.


title:
Two-dimensional models of layered protoplanetary discs - II. The effect
  of a residual viscosity in the dead zone

abstract:
  We study axisymmetric models of layered protoplanetary discs taking radiative
transfer effects into account, and allowing for a residual viscosity in the
dead zone. We also explore the effect of different viscosity prescriptions. In
addition to the ring instability reported in the first paper of the series we
find an oscillatory instability of the dead zone, accompanied by variations of
the accretion rate onto the central star. We provide a simplified analytical
description explaining the mechanism of the oscillations. Finally, we find that
the residual viscosity enables stationary accretion in large regions of layered
discs. Based on results obtained with the help of a simple 1-D hydrocode we
identify these regions, and discuss conditions in which layered discs can give
rise to FU~Orionis phenomena.


title: The Infrared Glow of First Stars

abstract:
  Kashlinsky et al. (2005) find a significant cosmic infrared background
fluctuation excess on angular scales >50 arcsec that cannot be explained by
instrumental noise or local foregrounds. The excess has been tentatively
attributed to emission from primordial very massive (PopIII) stars formed <200
Myr after the Big Bang. Using an evolutionary model motivated by independent
observations and including various feedback processes, we find that PopIII
stars can contribute <40% of the total background intensity (\nu J_\nu ~ 1-2 nW
m^-2 sr^-1 in the 0.8-8 \mum range) produced by all galaxies (hosting both
PopIII and PopII stars) at z>5. The infrared fluctuation excess is instead very
precisely accounted by the clustering signal of galaxies at z>5, predominantly
hosting PopII stars with masses and properties similar to the present ones.


title: The PAH Emission Deficit In Low-Metallicity Galaxies - A Spitzer View

abstract:
  Archival observations of 18 starburst galaxies that span a wide range in
metallicity reveal for the first time a correlation between the ratio of
emission line fluxes of [FeII] at 26 microns and [NeII] at 12.8 microns and the
7.7 micron PAH strength, with the [FeII]/[NeII] flux ratio decreasing with
increasing PAH strength. We also find a strong correlation between the
[FeII]/[NeII] flux ratio and the host galaxy metallicity, with the flux ratio
decreasing with increasing metallicity.
  Since [FeII] emission has been linked primarily to supernova shocks, we
attribute the high [FeII]/[NeII] ratios in low-metallicity galaxies to enhanced
supernova activity. We consider this to be a dominant mechanism for PAH
destruction, rather than grain destruction in photoionized regions surrounding
young massive stars. We also consider whether the extreme youth of the
low-metallicity galaxies is responsible for the lack of PAH emission.


title:
Numerical action reconstruction of the dynamical history of dark matter
  haloes in N-body simulations

abstract:
  We test the ability of the numerical action method (NAM) to recover the
individual orbit histories of mass tracers in an expanding universe in a region
of radius 26Mpc/h, given the masses and redshift-space coordinates at the
present epoch. The mass tracers are represented by dark matter haloes
identified in a high resolution N-body simulation of the standard LCDM
cosmology. Since previous tests of NAM at this scale have traced the underlying
distribution of dark matter particles rather than extended haloes, our study
offers an assessment of the accuracy of NAM in a scenario which more closely
approximates the complex dynamics of actual galaxy haloes. We show that NAM can
recover present-day halo distances with typical errors of less than 3 per cent,
compared to 5 per cent errors assuming Hubble flow distances. The total halo
mass and the linear bias were both found to be constained at the 50 per cent
level. The accuracy of individual orbit reconstructions was limited by the
inability of NAM, in some instances, to correctly model the positions of haloes
at early times solely on the basis of the redshifts, angular positions, and
masses of the haloes at the present epoch. Improvements in the quality of NAM
reconstructions may be possible using the present-day three-dimensional halo
velocities and distances to further constrain the dynamics. This velocity data
is expected to become available for nearby galaxies in the coming generations
of observations by SIM and GAIA.


title: Reconstructing K-essence

abstract:
  We present a model independent method of reconstructing the Lagrangian for
the k-essence field driving the present acceleration of the universe. We
consider the simplest k-essence model for which the potential is constant.
Later we use three parametrizations for the Hubble parameter $H(z)$, consistent
with the recent SN1a data, to yield the Lagrangian $F$. Our reconstruction
program does not generate any physically realistic Lagrangian for models that
allow phantom crossing, whereas models without phantom crossing, yield well
behaved Lagrangian.


title: Binary and Multiple O-Type Stars in the Cas OB6 Association

abstract:
  We present the results of time-resolved spectroscopy of 13 O-type stars in
the Cas OB6 stellar association. We conducted a survey for radial velocity
variability in search of binary systems, which are expected to be plentiful in
young OB associations. Here we report the discovery of two new single-lined
binaries, and we present new orbital elements for three double-lined binaries
(including one in the multiple star system HD 17505). One of the double-lined
systems is the eclipsing binary system DN Cas, and we present a preliminary
light curve analysis that yields the system inclination, masses, and radii. We
compare the spectra of the single stars and the individual components of the
binary stars with model synthetic spectra to estimate the stellar effective
temperatures, gravities, and projected rotational velocities. We also make fits
of the spectral energy distributions to derive E(B-V), R=A_V/E(B-V), and
angular diameter. A distance of 1.9 kpc yields radii that are consistent with
evolutionary models. We find that 7 of 14 systems with spectroscopic data are
probable binaries, consistent with the high binary frequency found for other
massive stars in clusters and associations.


title: The mass of cosmic rays above 1017 eV

abstract:
  Interpretation of the energy spectrum and arrival distribution of cosmic rays
is complicated by lack of knowledge of the nature of the primaries. We review
claims for the mass composition above 1017 eV where it can be determined only
indirectly from air-shower observables. Difficulties in comparisons between
data arise because, inevitably, a set of measurements is interpreted using the
best model of hadronic interactions available at the time of analysis. We
discuss the situation and conclude that the evidence for a proton-dominated
mass composition, even at the highest energies, is unconvincing. However, it
may be that there are consistent differences between mass measurements from
optical techniques and those based upon other shower observables. We also find
that iron nuclei of ultra high energy can probably escape from the galaxies
that host GRBs, possible cosmic ray accelerators. The accelerators must lie
nearby.


title:
The angular momentum transport by the strato-rotational instability in
  simulated Taylor-Couette flows

abstract:
  Aims: To investigate the stability and angular momentum transport by the
strato-rotational instability in the nonlinear regime. Methods: The
hydrodynamic compressible equations are solved in a cartesian box in which the
outer cylinder is embedded. Gravity along the rotation axis leads to density
stratification. No-slip boundary conditions are used in the radial direction,
while free-slip conditions are used on the two ends of the cylinders. Results:
The strato-rotational instability is confirmed and the Reynolds stress is shown
to transport angular momentum away from the axis. However, the growth rate
decreases with increasing Reynolds number. This, as well as the presence of
boundaries renders this instability less relevant for astrophysical
applications.


title:
Inner-shell Absorption Lines of Fe~VI-- Fe~XVI: A Many-body Perturbation
  Theory Approach

abstract:
  We provide improved atomic calculation of wavelengths, oscillator strengths,
and autoionization rates relevant to the $2\to 3$ inner-shell transitions of
Fe~VI--XVI, the so-called Fe~M-shell unresolved transition array (UTA). A
second order many-body perturbation theory is employed to obtain accurate
transition wavelengths, which are systematically larger than previous
theoretical results by 15--45~m{\AA}. For a few transitions of Fe~XVI and Fe~XV
where laboratory measurements exist, our new wavelengths are accurate to within
a few m{\AA}. Using these new calculations, the apparent discrepancy in the
velocities between the Fe~M-shell UTA and other highly ionized absorption lines
in the outflow of NGC 3783 disappears. The oscillator strengths in our new
calculation agree well with the previous theoretical data, while the new
autoionization rates are significantly larger, especially for lower charge
states. We attribute this discrepancy to the missing autoionization channels in
the previous calculation. The increased autoionization rates may slightly
affect the column density analysis of the Fe~M-shell UTA for sources with high
column density and very low turbulent broadening. The complete set of atomic
data is provided as an electronic table.


title: Stringent Constraint on Galactic Positron Production

abstract:
  The intense 0.511 MeV gamma-ray line emission from the Galactic Center
observed by INTEGRAL requires a large annihilation rate of nonrelativistic
positrons. If these positrons are injected at even mildly relativistic
energies, higher-energy gamma rays will also be produced. We calculate the
gamma-ray spectrum due to inflight annihilation and compare to the observed
diffuse Galactic gamma-ray data. Even in a simplified but conservative
treatment, we find that the positron injection energies must be $\lesssim 3$
MeV, which strongly constrains models for Galactic positron production.


title: Extended Stromgren Photoelectric Photometry in NGC 752

abstract:
  Photoelectric photometry on the extended Stromgren system (uvbyCa) is
presented for 7 giants and 21 main sequence stars in the old open cluster, NGC
752. Analysis of the hk data for the turnoff stars yields a new determination
of the cluster mean metallicity. From 10 single-star members, [Fe/H] = -0.06
+/- 0.03, where the error quoted is the standard error of the mean and the
Hyades abundance is set at [Fe/H] = +0.12. This result is unchanged if all 20
stars within the limits of the hk metallicity calibration are included. The
derived [Fe/H] is in excellent agreement with past estimates using
properly-zeroed m1 data, transformed moderate-dispersion spectroscopy, and
recent high dispersion spectroscopy.


title:
The Radio and X-ray Luminous SN 2003bg and the Circumstellar Density
  Variations Around Radio Supernovae

abstract:
  We report extensive radio and X-ray observations of SN 2003bg whose
spectroscopic evolution shows a transition from a broad-lined Type Ic to a
hydrogen-rich Type II and later to a typical hydrogen-poor Type Ibc. We show
that the extraordinarily luminous radio emission is well described by a
self-absorption dominated synchrotron spectrum while the observed X-ray
emission at t~30 days is adequately fit by Inverse Compton scattering of the
optical photons off of the synchrotron emitting electrons. Our radio model
implies a sub-relativistic ejecta velocity, v ~ 0.24c, at t_0 ~ 10 days after
the explosion which emphasizes that broad optical absorption lines do not imply
relativistic ejecta. We find that the total energy of the radio emitting region
evolves as E ~ 7.3 x 10^{48} (t/t_0)^{0.4} erg assuming equipartition of energy
between relativistic electrons and magnetic fields (e_e=e_B=0.1). The
circumstellar density is well described by a stellar wind profile with modest
(factor of ~2) episodic density enhancements which produce abrupt achromatic
flux variations. We estimate an average progenitor mass loss rate of M_dot ~ 3
x 10^{-4} solar masses per year (assuming a wind velocity of 1000 km/s),
consistent with the observed values for Galactic Wolf-Rayet stars. Comparison
with other events reveals that ~50% of radio supernovae show similar short
timescale flux variations attributable to circumstellar density irregularities.
Specifically, the radio light-curves of SN 2003bg are strikingly similar to
those of the Type IIb SN 2001ig, suggestive of a common progenitor evolution.
We conclude that their progenitors experienced quasi-periodic mass loss
episodes just prior to the SN explosion. [ABRIDGED]


title:
INTEGRAL observation of the high-mass X-ray transient V0332+53 during
  the 2005 outburst decline

abstract:
  The decline of the high mass X-ray transient V0332+53 during the Dec. 2004 to
Feb. 2005 outburst is analysed from the data recorded by INTEGRAL. The flux is
shown to decrease exponentially until 2005 Feb. 10, with a decay time scale of
\~30 days above 20 keV and ~20 days at lower energies, and to decrease linearly
thereafter.
  The energy spectrum is well modelled throughout the decay by a power law with
a folding energy of ~7.5 keV, and with two cyclotron absorption features. The
folding energy does not vary significantly over the decay, but the spectrum
becomes harder with time. Most importantly, we show that the parameters
describing the fundamental cyclotron line around 27 keV do vary with time: its
energy and depth increase (by about 17% for the energy in ~6 weeks), while its
width decreases. These changes of the cyclotron line parameters are interpreted
as resulting from a change in the extent of the cyclotron scattering region.
  Two quasi-periodic oscillations are also observed at various times during the
observations, one at 0.05 Hz and another one near the pulsation frequency
around 0.23 Hz.


title: Rejuvenation of spiral bulges

abstract:
  We seek to understand whether the stellar populations of galactic bulges show
fingerprints of secular evolution triggered by the presence of the disc. For
this purpose we re-analyse the sample of Proctor and Sansom, deriving stellar
population ages and element abundances from absorption line indices. We obtain
very consistent constraints on ages from the three Balmer indices Hbeta,
Hgamma, and Hdelta, in good agreement with those of Proctor and Sansom based on
a completely different method. Like other studies in the literature, we find
that bulges have relatively low luminosity weighted ages, the lowest age
derived for the smallest bulges being 1.3 Gyr. Hence bulges are not generally
old but actually rejuvenated systems. We discuss evidence that this might be
true also for the bulge of the Milky Way. We show that the smallest bulges,
being the youngest with the lowest alpha/Fe ratios, must have experienced star
formation events involving 10-30 per cent of their total mass in the past 1-2
Gyr. No significant correlations of the stellar population parameters with
Hubble Type are found instead. We show that the relationships with sigma
coincide perfectly with those of early-type galaxies. Hence, bulges are
typically seen younger, metal-poorer and less alpha/Fe enhanced than early-type
galaxies, only because of their smaller masses. At a given velocity dispersion,
bulges and elliptical galaxies are indistinguishable as far as their stellar
populations are concerned. These results favour an inside-out formation
scenario and indicate that the discs in spiral galaxies of Hubble types Sbc and
earlier cannot have a significant influence on the evolution of the stellar
populations in the bulge component. The phenomenon of pseudobulge formation
must be restricted to spirals of types later than Sbc.


title:
The Dependence of Halo Clustering on Halo Formation History,
  Concentration, and Occupation

abstract:
  We investigate the dependence of dark matter halo clustering on halo
formation time, density profile concentration, and subhalo occupation number,
using high-resolution numerical simulations of a LCDM cosmology. We confirm
results that halo clustering is a function of halo formation time, and that
this trend depends on halo mass. For the first time, we show unequivocally that
halo clustering is a function of halo concentration and show that the
dependence of halo bias on concentration, mass, and redshift can be accurately
parameterized in a simple way: b(c,M|z) = b(M|z) b(c|M/M*). The scaling between
bias and concentration changes sign with the value of M/M*: high concentration
(early forming) objects cluster more strongly for M <~ M* while low
concentration (late forming) objects cluster more strongly for rare high-mass
halos, M >~ M*. We show the first explicit demonstration that host dark halo
clustering depends on the halo occupation number (of dark matter subhalos) and
discuss implications for halo model calculations of dark matter power spectra
and galaxy clustering statistics. The effect of these halo properties on
clustering is strongest for early-forming dwarf-mass halos, which are
significantly more clustered than typical halos of their mass. Our results
suggest that isolated low-mass galaxies (e.g. low surface-brightness dwarfs)
should have more slowly-rising rotation curves than their clustered
counterparts, and may have consequences for the dearth of dwarf galaxies in
voids. They also imply that self calibrating richness-selected cluster samples
with their clustering properties might overestimate cluster masses and bias
cosmological parameter estimation.


title:
Effects of Gravitational Lensing and Companion Motion on the Binary
  Pulsar Timing

abstract:
  The measurement of the Shapiro time delay in binary pulsar systems with
highly inclined orbit can be affected both by the motion of the pulsar's
companion because of the finite time it takes a photon to cross the binary, and
by the gravitational light bending if the orbit is sufficiently edge-on
relative to the line of sight. Here we calculate the effect of retardation due
to the companion's motion on various time delays in pulsar binaries, including
the Shaipro delay, the geometric lensing delay, and the lens-induced delays
associated with the pulsar rotation. Our results can be applied to systems so
highly inclined that near conjunction gravitational lensing of the pulsar
radiation by the companion becomes important (the recently discovered double
pulsar system J0737-3039 may exemplify such a system). To the leading order,
the effect of retardation is to shift all the delay curves backward in time
around the orbit conjunction, without affecting the shape and amplitude of the
curves. The time shift is of order the photon orbit crossing time, and ranges
from a second to a few minutes for the observed binary pulsar systems. In the
double pulsar system J0737-3039, the motion of the companion may also affect
the interpretation of the recent correlated interstellar scintillation
measurements. Finally, we show that lensing sets an upper limit on the
magnitude of the frame-dragging time delay caused by the companion's spin, and
makes this delay unobservable in stellar-mass binary pulsar systems.


title: The Black Hole - Bulge Relationship for QSOs at High Redshift

abstract:
  We examine the black hole mass - galaxy bulge relationship in high-redshift
QSOs. Black hole masses are derived from the broad emission lines, and the host
galaxy stellar velocity dispersion sigma is estimated from the widths of the
radio CO emission lines. At redshifts z > 3, the CO line widths are narrower
than expected for the black hole mass, indicating that these giant black holes
reside in undersized bulges by an order of magnitude or more. The largest black
holes (above 10^9 solar masses) evidently grow rapidly in the early universe
without commensurate growth of their host galaxies. CO line widths offer a
unique opportunity to study AGN host galaxy dynamics at high redshift.


title:
Understanding High-Density Matter Through Analysis of Surface Spectral
  Lines and Burst Oscillations from Accreting Neutron Stars

abstract:
  We discuss millisecond period brightness oscillations and surface atomic
spectral lines observed during type I X-ray bursts from a neutron star in a low
mass X-ray binary system. We show that modeling of these phenomena can
constrain models of the dense cold matter at the cores of neutron stars. We
demonstrate that, even for a broad and asymmetric spectral line, the stellar
radius-to-mass ratio can be inferred to better than 5%. We also fit our
theoretical models to the burst oscillation data of the low mass X-ray binary
XTE J1814-338, and find that the 90% confidence lower limit of the neutron
star's dimensionless radius-to-mass ratio is 4.2.


title:
Primitive Variable Solvers for Conservative General Relativistic
  Magnetohydrodynamics

abstract:
  Conservative numerical schemes for general relativistic magnetohydrodynamics
(GRMHD) require a method for transforming between ``conserved'' variables such
as momentum and energy density and ``primitive'' variables such as rest-mass
density, internal energy, and components of the four-velocity. The forward
transformation (primitive to conserved) has a closed-form solution, but the
inverse transformation (conserved to primitive) requires the solution of a set
of five nonlinear equations. Here we discuss the mathematical properties of the
inverse transformation and present six numerical methods for performing the
inversion. The first method solves the full set of five nonlinear equations
directly using a Newton-Raphson scheme and a guess from the previous timestep.
The other methods reduce the five nonlinear equations to either one or two
nonlinear equations that are solved numerically. Comparisons between the
methods are made using a survey over phase space, a two-dimensional explosion
problem, and a general relativistic MHD accretion disk simulation. The run-time
of the methods is also examined. Code implementing the schemes is available for
download on the web.


title:
Exoplanet Imaging with a Phase-induced Amplitude Apodization Coronagraph
  III. Hybrid Approach: Optical Design and Diffraction Analysis

abstract:
  Properly apodized pupils can deliver point spread functions (PSFs) free of
Airy rings, and are suitable for high dynamical range imaging of extrasolar
terrestrial planets (ETPs). To reach this goal, classical pupil apodization
(CPA) unfortunately requires most of the light gathered by the telescope to be
absorbed, resulting in poor throughput and low angular resolution.
Phase-induced amplitude apodization (PIAA) of the telescope pupil (Guyon 2003)
combines the advantages of classical pupil apodization (particularly low
sensitivity to low order aberrations) with full throughput, no loss of angular
resolution and little chromaticity, which makes it, theoretically, an extremely
attractive coronagraph for direct imaging of ETPs. The two most challenging
aspects of this technique are (1) the difficulty to polish the required optics
shapes and (2) diffraction propagation effects which, because of their
chromaticity, can decrease the spectral bandwidth of the coronagraph. We show
that a properly designed hybrid system combining classical apodization with the
PIAA technique can solve both problems simultaneously. For such a system, the
optics shapes can be well within today's optics manufacturing capabilities, and
the $10^{-10}$ PSF contrast at $\approx 1.5 \lambda/D$ required for efficient
imaging of ETPs can be maintained over the whole visible spectrum. This updated
design of the PIAA coronagraph maintains the high performance of the earlier
design, since only a small part of the light is lost in the classical
apodizer(s).


title: Isolating the decay rate of cosmological gravitational potential

abstract:
  The decay rate of cosmological gravitational potential measures the deviation
from Einstein-de Sitter universe and can put strong constraints on the nature
of dark energy and gravity. Usual method to measure this decay rate is through
the integrated Sachs-Wolfe (ISW) effect-large scale structure (LSS) cross
correlation. However, the interpretation of the measured correlation signal is
complicated by the galaxy bias and matter power spectrum. This could bias
and/or degrade its constraints to the nature of dark energy and gravity. But,
combining the lensing-LSS cross correlation measurements, the decay rate of
gravitational potential can be isolated. For any given narrow redshift bin of
LSS, the ratio of the two cross correlations directly measures $[d\ln
D_{\phi}/d\ln a]H(z)/W(\chi,\chi_s)$, where $D_{\phi}$ is the linear growth
factor of the gravitational potential, $H$ is the Hubble constant at redshift
$z$, $W(\chi,\chi_s)$ is the lensing kernel and $\chi$ and $\chi_s$ are the
comoving angular diameter distance to lens and source, respectively. This
method is optimal in the sense that (1) the measured quantity is essentially
free of systematic errors and is only limited by cosmic variance and (2) the
measured quantity only depends on several cosmological parameters and can be
predicted from first principles unambiguously. Though fundamentally limited by
inevitably large cosmic variance associated with the ISW measurements, it can
still put useful independent constraints on the amount of dark energy and its
equation of state. It can also provide a powerful test of modified gravity and
can distinguish the Dvali-Gabadadze-Porrati model from $\Lambda$CDM at
$>2.5\sigma$ confidence level.


title:
Techniques for measuring atmospheric aerosols at the High Resolution
  Fly's Eye experiment

abstract:
  We describe several techniques developed by the High Resolution Fly's Eye
experiment for measuring aerosol vertical optical depth, aerosol horizontal
attenuation length, and aerosol phase function. The techniques are based on
measurements of side-scattered light generated by a steerable ultraviolet laser
and collected by an optical detector designed to measure fluorescence light
from cosmic-ray air showers. We also present a technique to cross-check the
aerosol optical depth measurement using air showers observed in stereo. These
methods can be used by future air fluorescence experiments.


title:
The evolution of galaxies from primeval irregulars to present-day
  ellipticals

abstract:
  The current understanding of galaxy formation is that it proceeds in a
'bottom up' way, with the formation of small clumps of gas and stars that merge
hierarchically until giant galaxies are built up. The baryonic gas loses the
thermal energy by radiative cooling and falls towards the centres of the new
galaxies, while supernovae (SNe) blow gas out. Any realistic model therefore
requires a proper treatment of these processes, but hitherto this has been far
from satisfactory. Here we report an ultra-high-resolution simulation that
follows evolution from the earliest stages of galaxy formation through the
period of dynamical relaxation. The bubble structures of gas revealed in our
simulation ($< 3\times10^8$ years) resemble closely the high-redshift Lyman
$\alpha$ emitters (LAEs). After $10^9$ years these bodies are dominated by
stellar continuum radiation and look like the Lyman break galaxies (LBGs) known
as the high-redshift star-forming galaxies at which point the abundance of
elements heavier than helium ("metallicity") appears to be solar. After
$1.3\times10^{10}$ years, these galaxies resemble present-day ellipticals.


title: Refining MOND interpolating function and TeVeS Lagrangian

abstract:
  The phenomena customly called Dark Matter or Modified Newtonian Dynamics
(MOND) have been argued by Bekenstein (2004) to be the consequences of a
covariant scalar field, controlled by a free function (related to the MOND
interpolating function) in its Lagrangian density. In the context of this
relativistic MOND theory (TeVeS), we examine critically the interpolating
function in the transition zone between weak and strong gravity. Bekenstein's
toy model produces too gradually varying functions and fits rotation curves
less well than the standard MOND interpolating function. However, the latter
varies too sharply and implies an implausible external field effect (EFE).
These constraints on opposite sides have not yet excluded TeVeS, but made the
zone of acceptable interpolating functions narrower. An acceptable "toy"
Lagrangian density function with simple analytical properties is singled out
for future studies of TeVeS in galaxies. We also suggest how to extend the
model to solar system dynamics and cosmology, and compare with strong lensing
data (see also astro-ph/0509590).


title:
The influence of baryons on the clustering of matter and weak lensing
  surveys

abstract:
  Future weak lensing measurements of cosmic shear will reach such high
accuracy that second order effects in weak lensing modeling, like the influence
of baryons on structure formation, become important. We use a controlled set of
state of the art cosmological simulations to quantify this effect by comparing
pure N-body dark matter runs with corresponding hydrodynamical simulations,
carried out both in non-radiative, and in dissipative form with cooling and
star formation. In both hydrodynamical simulations, the clustering of the gas
is suppressed while that of dark matter is boosted at scales k>1 h/Mpc. Despite
this counterbalance between dark matter and gas, the clustering of the total
matter is suppressed by up to 1 percent at 1<k<10 h/Mpc, while for k ~ 20 h/Mpc
it is boosted, up to 2 percent in the non-radiative run and 10 percent in the
run with star formation. The stellar mass formed in the latter is highly biased
relative to the dark matter in the pure N-body simulation. Using our power
spectrum measurements to predict the effect of baryons on the weak lensing
signal at 100<l<10000, we find that baryons may change the lensing power
spectrum by less than 0.5 percent at l<1000, but by 1 to 10 percent at
1000<l<10000. The size of the effect exceeds the predicted accuracy of future
lensing power spectrum measurements and will likely be detected. Precise
determinations of cosmological parameters with weak lensing, and studies of
small-scale fluctuations and clustering, therefore rely on properly including
baryonic physics.


title: Have We Detected Patchy Reionization in Quasar Spectra?

abstract:
  The Lyman-alpha forest at z >~ 5.5 shows strong scatter in the mean
transmission even when smoothed over very large spatial scales, >~ 50 Mpc/h.
This has been interpreted as a signature of strongly fluctuating radiation
fields, or patchy reionization. To test this claim, we calculate the scatter
arising solely from density fluctuations, with a uniform ionizing background,
using analytic arguments and simulations. This scatter alone is comparable to
that observed. It rises steeply with redshift and is of order unity by z ~ 6,
even on ~ 50 Mpc/h scales. This arises because: i) at z ~ 6, transmission
spectra, which are sensitive mainly to rare voids, are highly biased (with a
linear bias factor b >~ 4-5) tracers of underlying density fluctuations, and
ii) projected power from small-scale transverse modes is aliased to long
wavelength line-of-sight modes. Inferring patchy reionization from quasar
spectra is therefore subtle and requires much more detailed modeling.
Similarly, we expect order unity transmission fluctuations in the z ~ 3 HeII
Lyman-alpha forest from density fluctuations alone, on the scales over which
these measurements are typically made.


title:
The Spatial Homogeneity of Nebular and Stellar Oxygen Abundances in the
  Local Group Dwarf Irregular Galaxy NGC 6822

abstract:
  To test the existence of a possible radial gradient in oxygen abundances
within the Local Group dwarf irregular galaxy NGC 6822, we have obtained
optical spectra of 19 nebulae with the EFOSC2 spectrograph on the 3.6-m
telescope at ESO La Silla. The extent of the measured nebulae spans
galactocentric radii in the range between 0.05 kpc and 2 kpc (over four
exponential scale lengths). In five H II regions (Hubble I, Hubble V, Kalpha,
Kbeta, KD28e), the temperature-sensitive [O III] 4363 emission line was
detected, and direct oxygen abundances were derived. Oxygen abundances for the
remaining H II regions were derived using bright-line methods. The oxygen
abundances for three A-type supergiant stars are slightly higher than nebular
values at comparable radii. Linear least-square fits to various subsets of
abundance data were obtained. When all of the measured nebulae are included, no
clear signature is found for an abundance gradient. A fit to only newly
observed H II regions with [O III] 4363 detections yields an oxygen abundance
gradient of -0.14 +/- 0.07 dex/kpc. The gradient becomes slightly more
significant (-0.16 +/- 0.05 dex/kpc) when three additional H II regions with [O
III] 4363 measurements from the literature are added. Assuming no abundance
gradient, we derive a mean nebular oxygen abundance 12+log(O/H) = 8.11 +/- 0.10
from [O III] 4363 detections in the five H II regions from our present data;
this mean value corresponds to [O/H] = -0.55.


title: The VIMOS-VLT Deep Survey: Luminosity dependence of clustering at z~1

abstract:
  We investigate the dependence of galaxy clustering on the galaxy intrinsic
luminosity at high redshift, using the data from the First Epoch VIMOS-VLT Deep
Survey (VVDS). The size (6530 galaxies) and depth (I_{AB}<24) of the survey
allows us to measure the projected two-point correlation function of galaxies,
w_p(r_p) for a set of volume-limited samples up to an effective redshift
<z>=0.9 and median absolute magnitude -19.6< M_B < -21.3. Fitting w_p(r_p) with
a single power-law model for the real-space correlation function
xi(r)=(r/r_0)^{-gamma}, we measure the relationship of the correlation length
r_0 and the slope gamma with the sample median luminosity for the first time at
such high redshift. Values from our lower-redshift samples (0.1<z<0.5) are
fully consistent with the trend observed by larger local surveys. In our high
redshift sample (0.5<z<1.2), we find that the clustering strength is suddenly
rising around M_B^*, apparently with a sharper turn than at low redshifts.
Galaxies in the faintest sample (<M_B>=-19.6) have a correlation length
r_0=2.7^{+0.3}_{-0.3} h^{-1} Mpc, compared to r_0=5.0^{+1.5}_{-1.6} h^{-1} Mpc
at <M_B>=-21.3. Correspondingly the slope of the correlation function is
observed to steepen significantly from \gamma=1.6^{+0.1}_{-0.1} to
\gamma=2.4^{+0.4}_{-0.2}. This is not observed neither by large local surveys
nor in our lower-redshift sample and seems to imply a significant change in the
way luminous galaxies trace dark-matter halos at z~1 with respect to z~0. At
our effective median redshift z~0.9 this corresponds to a strong difference of
the relative bias, from b/b* < 0.7 for galaxies with L < L*, to b/b*~1.4 for
galaxies with L > L*.


title:
Discovery of a low-eccentricity, high-inclination Kuiper belt object at
  58 AU

abstract:
  We report the discovery of the first trans-neptunian object, designated 2004
XR190, with a nearly-cirular orbit beyond the 2:1 mean-motion resonance.
Fitting an orbit to 23 astrometric observations spread out over 12 months
yields an orbit of a=57.2\pm0.4, e=0.08\pm0.04, and i=46.6 deg. All viable
orbits have perihelia distances q>49 AU. The very high orbital inclination of
this extended scattered disk object might be explained by several models, but
its existence again points to a large as-yet undiscovered population of
transneptunian objects with large orbital perihelia and inclination.


title: Nature of nuclear rings in unbarred galaxies: NGC 7742 and NGC 7217

abstract:
  We have studied the unbarred Sb galaxy with a nuclear star-forming ring, NGC
7742, by means of 2D spectroscopy, long-slit spectroscopy, and imaging, and
have compared the results with the properties of another galaxy of this type,
NGC 7217, which is studied by us earlier. Both galaxies have many peculiar
features in common: each has two global exponential stellar disks with
different scalelengths, each possesses a circumnuclear inclined gaseous disk
with a radius of 300 pc, and each has a global counterrotating subsystem,
gaseous one in NGC 7742 and stellar one in NGC 7217. We suggest that past minor
merger is the probable cause of all these peculiarities, including appearance
of the nuclear star-forming rings without global bars; the rings might be
produced as resonance features by tidally induced oval distortions of the
global stellar disks.


title:
Lateral distribution of Cherenkov light in extensive air showers at high
  mountain altitude produced by different primary particles in wide energy
  range

abstract:
  The general aim of this work is to obtain the lateral distribution of
atmospheric Cherenkov light in extensive air showers produced by different
primary particles precisely by. protons, Helium, Iron, Oxygen, Carbon,
Nitrogen, Calcium, Silicon and gamma quanta in wide energy range at high
mountain observation level of Chacaltaya cosmic ray station. The simulations
are divided generally in two energy ranges 10GeV-10 TeV and 10 TeV-10 PeV. One
large detector has been used for simulations, the aim being to reduce the
statistical fluctuations of the obtained characteristics. The shape of the
obtained lateral distributions of Cherenkov light in extensive air showers is
discussed and the scientific potential for solution of different problems as
well.


title: On the Viability of Bianchi Type VIIh Models with Dark Energy

abstract:
  We generalize the predictions for the CMB anisotropy patterns arising in
Bianchi type VIIh universes to include a dark energy component. We consider
these models in light of the result of Jaffe et al. (2005a,b) in which a
correlation was found on large angular scales between the WMAP data and the
anisotropy structure in a low density Bianchi universe. We find that by
including a term Omega_L > 0, the same best-fit anisotropy pattern is
reproduced by several combinations of cosmological parameters. This sub-set of
models can then be further constrained by current observations that limit the
values of various cosmological parameters. In particular, we consider the
so-called geometric degeneracy in these parameters imposed by the peak
structure of the WMAP data itself. Apparently, despite the additional freedom
allowed by the dark energy component, the modified Bianchi models are ruled out
at high significance.


title:
Photon air showers at ultra-high energy and the photonuclear
  cross-section

abstract:
  Experimental conclusions from air shower observations on cosmic-ray photons
above 10^19 eV are based on the comparison to detailed shower simulations. For
the calculations, the photonuclear cross-section needs to be extrapolated over
several orders of magnitude in energy. The uncertainty from the cross-section
extrapolation translates into an uncertainty of the predicted shower features
for primary photons and, thus, into uncertainties for a possible data
interpretation. After briefly reviewing the current status of ultra-high energy
photon studies, the impact of the uncertainty of the photonuclear cross-section
for shower calculations is investigated. Estimates for the uncertainties in the
main shower observables are provided. Photon discrimination is shown to be
possible even for rapidly rising cross-sections. When photon-initiated showers
are identified, it is argued that the sensitivity of photon shower observables
to the photonuclear cross-section can in turn be exploited to constrain the
cross-section at energies not accessible at colliders.


title:
Colour corrections for high redshift objects due to intergalactic
  attenuation

abstract:
  Corrections to the magnitudes of high redshift objects due to intergalactic
attenuation are computed using current estimates of the properties of the
intergalactic medium. The results of numerical simulations are used to estimate
the contributions to resonant scattering from the higher order Lyman
transitions. Differences of 0.5-1 magnitude from the previous estimate of Madau
(1995) are found. Intergalactic k_IGM-corrections and colours are provided for
high redshift starburst galaxies and Type I and Type II QSOs for several filter
systems used in current and planned deep optical and infra-red surveys.


title: The formation of brown dwarfs

abstract:
  We review four mechanisms for forming brown dwarfs: (i) turbulent
fragmentation (producing very low-mass prestellar cores); (ii) gravitational
instabilities in discs; (iii) dynamical ejection of stellar embryos from their
placental cores; and (iv) photo-erosion of pre-existing cores in HII regions.
We argue (a) that these are simply the mechanisms of low-mass star formation,
and (b) that they are not mutually exclusive. If, as seems possible, all four
mechanisms operate in nature, their relative importance may eventually be
constrained by their ability to reproduce the binary statistics of brown
dwarfs, but this will require fully 3-D radiative magneto-hydrodynamic
simulations.


title: The possible detection of high redshift Type II QSOs in deep fields

abstract:
  The colours of high redshift Type II QSOs are synthesized from observations
of moderate redshift systems. It is shown that Type II QSOs are comparable to
starbursts in their success at matching the colours of z_850-dropouts and
i_775-drops in the Hubble Ultra Deep Field, and more naturally account for the
bluest objects detected. Type II QSOs may also account for some of the
i_775-drops detected in the GOODS fields. It is shown that by combining imaging
data from the Hubble Space Telescope and the James Webb Space Telescope, it
will be possible to clearly separate Type II QSOs from Type I QSOs and
starbursts based on their colours. Similarly, it is shown that the UKIDSS ZYJ
filters may be used to discriminate high redshift Type II QSOs from other
objects. If Type II QSOs are prevalent at high redshifts, then AGN may be major
contributors to the re-ionization of the Intergalactic Medium.


title: The origin of ultra high energy cosmic rays

abstract:
  We briefly discuss some open problems and recent developments in the
investigation of the origin and propagation of ultra high energy cosmic rays
(UHECRs).


title:
Strongly Interacting Neutrinos as the Highest Energy Cosmic Rays: A
  Quantitative Analysis

abstract:
  Scattering processes in the cosmic microwave background limit the propagation
of ultra high energy charged particles in our Universe. For extragalactic
proton sources resonant photopion production results in the famous
Greisen-Zatsepin-Kuzmin (GZK) cutoff at about 4x10^10 GeV expected in the
spectrum observed on Earth. The faint flux of ultra high energy cosmic rays of
less than one event per year and cubic kilometer and the large systematic
uncertainties in the energy calibration of cosmic ray showers is a challenge
for cosmic ray observatories and so far the GZK cutoff has not been
unambiguously confirmed. We have investigated the possibility that the
primaries of super-GZK events are strongly interacting neutrinos which are not
subject to the GZK cutoff. For the flux of protons and neutrinos from
extragalactic optically thin sources and a flexible parameterization of the
neutrino-nucleon cross section we have analyzed the cosmic ray spectra observed
at AGASA and HiRes taking also into account results from horizontal events at
AGASA and contained events at RICE. We find that scenarios of strongly
interacting neutrinos are still compatible with the data requiring a steep
increase of the inelastic neutrino-nucleon cross section by four order of
magnitude within one energy decade compared to the Standard Model predictions.
We also discuss the impact of the preliminary cosmic ray spectrum observed by
the Pierre Auger Observatory.


title: The Flare Activity of SgrA*; New Coordinated mm to X-Ray Observations

abstract:
  We report new simultaneous near-infrared/sub-millimeter/X-ray observations of
the SgrA* counterpart associated with the massive 3-4x10**6 solar mass black
hole at the Galactic Center. The main aim is to investigate the physical
processes responsible for the variable emission from SgrA*. The observations
have been carried out using the NACO adaptive optics (AO) instrument at the
European Southern Observatory's Very Large Telescope and the ACIS-I instrument
aboard the Chandra X-ray Observatory as well as the Submillimeter Array SMA on
Mauna Kea, Hawaii, and the Very Large Array in New Mexico. We detected one
moderately bright flare event in the X-ray domain and 5 events at infrared
wavelengths.


title:
An XMM-Newton observation of the young open cluster NGC 2547: coronal
  activity at 30 Myr

abstract:
  We report XMM-Newton observations of the young open cluster NGC 2547 which
allow us to characterise coronal activity in solar-type stars at an age of 30
Myr. X-ray emission peaks among G-stars at luminosities (0.3-3keV) of
Lx~10^{30.5} erg/s and declines to Lx<=10^{29.0} erg/s among M-stars. Coronal
spectra show evidence for multi-temperature differential emission measures and
low coronal metal abundances (Z~0.3). The G- and K-type stars follow the same
relationship between X-ray activity and Rossby number established in older
clusters and field stars, although most solar-type stars in NGC 2547 exhibit
saturated/super-saturated X-ray activity levels. Median levels of Lx and
Lx/Lbol in the solar-type stars of NGC 2547 are similar to T-Tauri stars of the
Orion Nebula cluster (ONC), but an order of magnitude higher than in the older
Pleiades. The spread in X-ray activity levels among solar-type stars in NGC
2547 is much smaller than in older or younger clusters. Coronal temperatures
increase with Lx, Lx/Lbol and surface X-ray flux. Active solar-type stars in
NGC 2547 have coronal temperatures between those in the ONC and the most active
older ZAMS stars. A flaring rate (for total flare energies [0.3-3keV] >10^{34}
erg) of 1 every 350^{+350}_{-120} ks was found for solar-type stars, similar to
rates found in the ONC and Pleiades. Comparison with ROSAT HRI data taken 7
years previously reveals that only 10-15 percent of solar-type stars or stars
with Lx>3x10^{29} erg/s exhibit X-ray variability by more than a factor of two.
The similar levels of X-ray activity and rate of occurrence for large flares in
NGC 2547 and the ONC demonstrate that the X-ray radiation environment around
young solar-type stars remains relatively constant over their first 30 Myr
(abridged).


title: Astronomy in Ukraine

abstract:
  The current and prospective status of astronomical research in Ukraine is
discussed. A brief history of astronomical research in Ukraine is presented and
the system organizing scientific activity is described, including astronomy
education, institutions and staff, awarding higher degrees/titles, government
involvement, budgetary investments and international cooperation. Individuals
contributing significantly to the field of astronomy and their accomplishments
are mentioned. Major astronomical facilities, their capabilities, and their
instrumentation are described. In terms of the number of institutions and
personnel engaged in astronomy, and of past accomplishments, Ukraine ranks
among major nations of Europe. Current difficulties associated with political,
economic and technological changes are addressed and goals for future research
activities presented.


title: Three-dimensional reconstruction of the intra-cluster medium

abstract:
  We propose and test a new method based on Richardson-Lucy deconvolution to
reconstruct three-dimensional gas density and temperature distributions in
galaxy clusters from combined X-ray and thermal Sunyaev-Zel'dovich
observations. Clusters are assumed to be axially symmetric and arbitrarily
inclined with respect to the line-of-sight. No equilibrium assumption other
than local thermal equilibrium is needed. We test the algorithm with synthetic
observations of analytically modeled and numerically simulated galaxy clusters
and discuss the quality of the density and temperature reconstructions in
idealised situations and in presence of observational noise, deviations from
axial symmetry and cluster substructure. We find that analytic and numerical
gas density and temperature distributions can be accurately reconstructed in
three dimensions, even if observational noise is present. We also discuss
methods for determining the inclination angle from data and show that it can be
constrained using X-ray temperature maps. For a realistic cluster and including
observational noise the three-dimensional reconstructions reach a level of
accuracy of about 15%.


title: A FUSE survey of high-latitude Galactic molecular hydrogen

abstract:
  Measurements of molecular hydrogen (H_2) column densities are presented for
the first six rotational levels (J=0 to 5) for 73 extragalactic targets
observed with FUSE. All of these have a final signal-to-noise ratio larger than
\snlimit, and are located at galactic latitude |b|>20 deg. The individual
observations were calibrated with the FUSE calibration pipeline CalFUSE version
2.1 or higher, and then carefully aligned in velocity. The final velocity
shifts for all the FUSE segments are listed. H_2 column densities or limits are
determined for the 6 lowest rotational (J) levels for each HI component in the
line of sight, using a curve-of-growth approach at low column densities ~16.5),
and Voigt-profile fitting at higher column densities. Detections include 73
measurements of low-velocity H_2 in the Galactic Disk and lower Halo. Eight
sightlines yield non-detections for Galactic H_2. The measured column densities
range from log N(H_2)=14 to log N(H_2)=20. Strong correlations are found
between log N(H_2) and T_01, the excitation temperature of the H_2, as well as
between log N(H_2) and the level population ratios (log (N(J')/N(J))). The
average fraction of nuclei in molecular hydrogen (f(H_2)) in each sightline is
calculated; however, because there are many HI clouds in each sightline, the
physics of the transition from HI to H_2 can not be studied. Detections also
include H2 in 16 intermediate-velocity clouds in the Galactic Halo (out of 35
IVCs). Molecular hydrogen is seen in one high-velocity cloud (the Leading Arm
of the Magellanic Stream), although 19 high-velocity clouds are intersected;
this strongly suggests that dust is rare or absent in these objects. Finally,
there are five detections of H_2 in external galaxies.


title: Comments on an argument of Tegmark and Bostrom

abstract: Withdrawn -- a revised version will appear in due course.


title:
On the Origin of [OII] Emission in Red Sequence and Post-starburst
  Galaxies

abstract:
  We investigate the emission-line properties of galaxies with red rest-frame
colors using spectra from SDSS DR4. Emission lines are detected in more than
half of the red galaxies. We focus on the relationship between two emission
lines commonly used as star formation rate indicators: Ha 6563 and [OII] 3727.
There is a strong bimodality in [OII]/Ha ratio in the full SDSS sample which
closely corresponds to the bimodality in rest-frame color. Nearly all of the
line-emitting red galaxies have line ratios typical of various types of AGN --
most commonly LINERs, a small fraction of transition objects and, more rarely,
Seyferts. Only ~6% of red galaxies display star-forming line ratios. A straight
line in the [OII]-Ha equivalent width plane separates LINER-like galaxies from
other categories. Quiescent galaxies with no detectable emission lines and
LINER-like galaxies combine to form a single, tight red sequence in
color-magnitude-concentration space. [OII] EWs in LINER- and AGN-like galaxies
can be as large as in star-forming galaxies. Thus, unless objects with
AGN/LINER-like line ratios are excluded, [OII] emission cannot be used directly
as a proxy for star formation rate. Lack of [OII] emission is generally used to
indicate lack of star formation when post-starburst galaxies are selected at
high redshift. Our results imply, however, that these samples have been cut on
AGN properties as well as star formation, and therefore may provide seriously
incomplete sets of post-starburst galaxies. Furthermore, post-starburst
galaxies identifed in SDSS by requiring minimal Ha EW generally exhibit weak
but nonzero line emission with ratios typical of AGNs; few of them show
residual star formation. This suggests that most post-starbursts may harbor
AGNs/LINERs.


title: The Supercritical Pile Model for GRBs

abstract:
  We present the spectral and temporal radiative signatures expected within the
"Supercritical Pile" model of Gamma Ray Bursts (GRB). This model is motivated
by the need for a process that provides the dissipation necessary in GRB and
presents a well defined scheme for converting the energy stored in the
relativistic protons of the Relativistic Blast Waves (RBW) associated with GRB
into radiation; at the same time it leads to spectra which exhibit a peak in
the burst $\nu F_{\nu}$ distribution at an energy $E_p \simeq 1$ MeV in the
observer's frame, in agreement with observation and largely independent of the
Lorentz factor $\Gamma$ of the associated relativistic outflow. Futhermore,
this scheme does not require (but does not preclude) acceleration of particles
at the shock other than that provided by the isotropization of the flow bulk
kinetic energy on the RBW frame. In the present paper we model in detail the
evolution of protons, electrons and photons from a RBW to produce detailed
spectra of the prompt GRB phase as a function of time from across a very broad
range spanning roughly $4 log_{10} \Gamma$ decades in frequency. The model
spectra are in general agreement with observations and provide a means for the
delineating of the model parameters through direct comparison with trends
observed in GRB properties.


title:
Spectral Methods for Time-Dependent Studies of Accretion Flows. II.
  Two-Dimensional Hydrodynamic Disks with Self-Gravity

abstract:
  Spectral methods are well suited for solving hydrodynamic problems in which
the self-gravity of the flow needs to be considered. Because Poisson's equation
is linear, the numerical solution for the gravitational potential for each
individual mode of the density can be pre-computed, thus reducing substantially
the computational cost of the method. In this second paper, we describe two
different approaches to computing the gravitational field of a two-dimensional
flow with pseudo-spectral methods. For situations in which the density profile
is independent of the third coordinate (i.e., an infinite cylinder), we use a
standard Poisson solver in spectral space. On the other hand, for situations in
which the density profile is a delta function along the third coordinate (i.e.,
an infinitesimally thin disk), or any other function known a priori, we perform
a direct integration of Poisson's equation using a Green's functions approach.
We devise a number of test problems to verify the implementations of these two
methods. Finally, we use our method to study the stability of polytropic,
self-gravitating disks. We find that, when the polytropic index Gamma is <=
4/3, Toomre's criterion correctly describes the stability of the disk. However,
when Gamma > 4/3 and for large values of the polytropic constant K, the
numerical solutions are always stable, even when the linear criterion predicts
the contrary. We show that, in the latter case, the minimum wavelength of the
unstable modes is larger than the extent of the unstable region and hence the
local linear analysis is inapplicable.


title:
Discovery of Five Very Low Mass Close Binaries, Resolved in the Visible
  with Lucky Imaging

abstract:
  We survey a sample of 32 M5-M8 stars with distance < 40pc for companions with
separations between 0.1 arcsec and 1.5 arcsec and with Delta m_i <5. We find
five new VLM binaries with separations between 0.15 arcsec and 1.1 arcsec,
including a candidate brown dwarf companion. The raw binary fraction is 16%
+8/-4% and the distance bias corrected fraction is 7% +7/-3%, for companions
within the surveyed range. No systems with contrast ratio Delta m_i>1 were
found, even though our survey is sensitive to up to Delta m=5 (well into the
brown dwarf regime). The distribution of orbital radii is in broad agreement
with previous results, with most systems at 1-5AU, but one detected binary is
very wide at 46.8+/-5.0AU. We also serendipitously imaged for the first time a
companion to Ross 530, a metal-poor single-lined spectroscopic binary. We used
the new Lucky Imaging system LuckyCam on the 2.5m Nordic Optical Telescope to
complete the 32 very low mass star i' and z' survey in only 5 hours of
telescope time.


title: The Origins of the Substellar Companion to GQ Lup

abstract:
  The recently discovered substellar companion to GQ Lup possibly represents a
direct test of current planet formation theories.
  We examine the possible formation scenarios for the companion to GQ Lup
assuming it is a $\sim$2 M$_{Jup}$ object. We determine that GQ Lup B most
likely was scattered into a large, eccentric orbit by an interaction with
another planet in the inner system.
  If this is the case, several directly observable predictions can be made,
including the presence of a more massive, secondary companion that could be
detected through astrometry, radial velocity measurements, or scuplting in GQ
Lup's circumstellar disk. This scenario requires a highly eccentric orbit for
the companion already detected. These predictions can be tested within the next
decade or so. Additionally, we look at scenarios of formation if the companion
is a brown dwarf. One possible formation scenario may involve an interaction
between a brown dwarf binary and GQ Lup. We look for evidence of any brown
dwarfs that have been ejected from the GQ Lup system by searching the 2MASS
all-sky survey.


title: INTEGRAL and RXTE Observations of Centaurus A

abstract:
  INTEGRAL and RXTE performed three simultaneous observations of the nearby
radio galaxy Cen A in 2003 March, 2004 January, and 2004 February with the
goals of investigating the geometry and emission processes via the
spectral/temporal variability of the X-ray/low energy gamma ray flux, and
intercalibration of the INTEGRAL instruments with respect to those on RXTE.
When combined with earlier archival RXTE results, we find the power law
continuum flux and the line-of-sight column depth varied independently, and the
iron line flux was essentially unchanging. Taking X-ray spectral measurements
from satellite missions since 1970 into account, we discover a variability in
the column depth between 1.0x10^23 cm^-2 and 1.5x10^23 cm^-2, and suggest that
variations in the edge of a warped accretion disk viewed nearly edge-on might
be the cause.


title:
The Double Helix Nebula: a magnetic torsional wave propagating out of
  the Galactic centre

abstract:
  Radioastronomical studies have indicated that the magnetic field in the
central few hundred parsecs of our Milky Way Galaxy has a dipolar geometry and
a strength substantially larger than elsewhere in the Galaxy, with estimates
ranging up to a milligauss. A strong, large-scale magnetic field can affect the
Galactic orbits of molecular clouds by exerting a drag on them, it can inhibit
star formation, and it can guide a wind of cosmic rays away from the central
region, so a characterization of the magnetic field at the Galactic center is
important for understanding much of the activity there. Here, we report Spitzer
Space Telescope observations of an unprecedented infrared nebula having the
morphology of an intertwined double helix. This feature is located about 100 pc
from the Galaxy's dynamical centre toward positive Galactic latitude, and its
axis is oriented perpendicular to the Galactic plane. The observed segment is
about 25 pc in length, and contains about 1.25 full turns of each of the two
continuous, helically wound strands. We interpret this feature as a torsional
Alfven wave propagating vertically away from the Galactic disk, driven by
rotation of the magnetized circumnuclear gas disk. As such, it offers a new
morphological probe of the Galactic center magnetic field. The direct
connection between the circumnuclear disk and the double helix is ambiguous,
but the MSX images show a possible meandering channel that warrants further
investigation.


title:
Light-cone anisotropy in 21cm fluctuations during the epoch of
  reionization

abstract:
  The delay in light travel time along the line of sight generates an
anisotropy in the power spectrum of 21cm brightness fluctuations from the epoch
of reionization. We show that when the fluctuations in the neutral hydrogen
fraction become non-linear at the later stages of reionization, the light-cone
anisotropy becomes of order unity on scales >50 comoving Mpc. During this
period the density fluctuations and the associated anisotropy generated by
peculiar velocities are negligible in comparison.


title: Dark matter from encapsulated atoms

abstract:
  We propose that dark matter consists of collections of atoms encapsulated
inside pieces of an alternative vacuum, in which the Higgs field vacuum
expectation value is appreciably smaller than in the usual vacuum. The
alternative vacuum is supposed to have the same energy density as our own.
Apart from this degeneracy of vacuum phases, we do not introduce any new
physics beyond the Standard Model. The dark matter balls are estimated to have
a radius of order 20 cm and a mass of order $10^{11}$ kg. However they are very
difficult to observe directly, but inside dense stars may expand eating up the
star and cause huge explosions (gamma ray bursts). The ratio of dark matter to
ordinary baryonic matter is estimated to be of the order of the ratio of the
binding energy per nucleon in helium to the difference between the binding
energies per nucleon in heavy nuclei and in helium. Thus we predict
approximately five times as much dark matter as ordinary baryonic matter!


title: Feedback Limits Rapid Growth of Seed Black Holes at High Redshift

abstract:
  Seed black holes formed in the collapse of population III stars have been
invoked to explain the presence of supermassive black holes at high redshift.
It has been suggested that a seed black hole can grow up to $10^{5\sim 6}\sunm$
through highly super-Eddington accretion for a period of $\sim 10^{6\sim 7}$ yr
between redshift $z=20\sim 24$. We studied the feedback of radiation pressure,
Compton heating and outflow during the seed black hole growth. It is found that
its surrounding medium fueled to the seed hole is greatly heated by Compton
heating. For a super-critical accretion onto a $10^3\sunm$ seed hole, a Compton
sphere (with a temperature $\sim 10^6$K) forms in a timescale of $1.6\times
10^3$yr so that the hole is only supplied by a rate of $10^{-3}$ Eddington
limit from the Compton sphere. Beyond the Compton sphere, the kinetic feedback
of the strong outflow heats the medium at large distance, this leads to a
dramatical decrease of the outer Bondi accretion onto the black hole and avoid
the accumulation of the matter. The highly super-critical accretion will be
rapidly halted by the strong feedback. The seed black holes hardly grow up at
the very early universe unless the strong feedback can be avoided.


title: Enhanced small-scale Faraday rotation in the Galactic spiral arms

abstract:
  We present an analysis of the rotation measures (RMs) of polarized
extragalactic point sources in the Southern Galactic Plane Survey. This work
demonstrates that the statistics of fluctuations in RM differ for the spiral
arms and the interarm regions. Structure functions of RM are flat in the spiral
arms, while they increase in the interarms. This indicates that there are no
correlated RM fluctuations in the magneto-ionized interstellar medium in the
spiral arms on scales larger than ~ 0.5 deg, corresponding to ~ 17 pc in the
nearest spiral arm probed. The non-zero slopes in interarm regions imply a much
larger scale of RM fluctuations. We conclude that fluctuations in the
magneto-ionic medium in the Milky Way spiral arms are not dominated by the
mainly supernova-driven turbulent cascade in the global ISM but are probably
due to a different source, most likely H II regions.


title: Constraining MgII absorbers with the SDSS

abstract:
  Using a large sample of MgII absorbers with 0.4<z<2.2 detected by Nestor et
al (2005) in the Early Data Release of the SDSS, we present new constraints on
the physical properties of these systems based on two statistical analyses: (i)
By computing the ratio between the composite spectra of quasars with and
without absorbers, we measure the reddening effects induced by these
intervening systems; and (ii) by stacking SDSS images centered on quasars with
strong MgII absorption lines and isolating the excess light around the PSF, we
measure the mean luminosity and colors of the absorbing galaxies. This
statistical approach does not require any spectroscopic follow up and allows us
to constrain the photometric properties of absorber systems.


title: Production of Axions by Cosmic Magnetic Helicity

abstract:
  We investigate the effects of an external magnetic helicity production on the
evolution of the cosmic axion field. It is shown that a helicity larger than
(few \times 10^{-15} G)^2 Mpc, if produced at temperatures above a few GeV, is
in contradiction with the existence of the axion, since it would produce too
much of an axion relic abundance.


title: Extragalactic H_2O masers and X-ray absorbing column densities

abstract:
  Having conducted a search for the 22 GHz water vapor line towards galaxies
with nuclear activity, large nuclear column densities or high infrared
luminosities, we present H_2O spectra for NGC2273, UGC5101 and NGC3393 with
isotropic luminosities of 7, 1500, and 400 L_sun. The H_2O maser in UGC5101 is
by far the most luminous yet found in an ultraluminous infrared galaxy. NGC3393
reveals the classic spectrum of a `disk maser', represented by three distinct
groups of Doppler components. As in all other known cases except NGC4258, the
rotation velocity of the putative masing disk is well below 1000 km/s. Based on
the literature and archive data, X-ray absorbing column densities are compiled
for the 64 galaxies with reported maser sources beyond the Magellanic Clouds.
For NGC2782 and NGC5728, we present Chandra archive data that indicate the
presence of an active galactic nucleus in both galaxies. The correlation
between absorbing column and H_2O emission is analyzed. There is a striking
difference between kilo- and megamasers with megamasers being associated with
higher column densities. All kilomasers (L_H_2O < 10 L_sun) except NGC2273 and
NGC5194 are Compton-thin, i.e. their absorbing columns are < 10^24 cm^-2. Among
the H_2O megamasers, 50% arise from Compton-thick and 85% from heavily obscured
(> 10^23 cm^-2) active galactic nuclei. These values are not larger but
consistent with those from samples of Seyfert 2 galaxies not selected on the
basis of maser emission. The similarity in column densities can be explained by
small deviations in position between maser spots and nuclear X-ray source and a
high degree of clumpiness in the circumnuclear interstellar medium.


title:
Observation of PeV Gamma Rays from the Monogem Ring with the Tibet Air
  Shower Array

abstract:
  We searched for steady PeV gamma-ray emission from the Monogem ring region
with the Tibet air shower array from 1997 February to 2004 October. No evidence
for statistically significant gamma-ray signals was found in a region
111$\degr$ $\leq$ R.A. $<$ 114$\degr$, 12$\fdg$5 $\leq$ decl. $<$ 15$\fdg$5 in
the Monogem ring where the MAKET-ANI experiment recently claimed a positive
detection of PeV high-energy cosmic radiation, although our flux sensitivity is
approximately 10 times better than MAKET-ANI's. We set the most stringent
integral flux upper limit at a 99% confidence level of 4.0 $\times$ 10$^{-12}$
cm$^{-2}$ s$^{-1}$ sr$^{-1}$ above 1 PeV on diffuse gamma rays extended in the
3$^{\circ}$ $\times$ 3$^{\circ}$ region.