title: The H.E.S.S. View of the Central 200 Parsecs

abstract:
  The inner few hundred parsecs of our galaxy provide a laboratory for the
study of the production and propagation of energetic particles.
Very-high-energy gamma-rays provide an effective probe of these processes and,
especially when combined with data from other wave-bands, gamma-rays
observations are a powerful diagnostic tool. Within this central region, data
from the H.E.S.S. instrument have revealed three discrete sources of
very-high-energy gamma-rays and diffuse emission correlated with the
distribution of molecular material. Here I provide an overview of these recent
results from H.E.S.S.


title:
On some peculiarities of cosmic gamma-radiation in the energy range ~
  10^14 - 10^15 eV

abstract:
  The distribution of EAS hadronic component energy fluxes through the
ionization calorimeter in the primary energy range ~ 3x10^13 - 10^16 eV is
considered. The EAS, carrying the zero or the minimal flux of the hadron
component energy are extracted. The conclusion supports the existence of
izotropic gamma-radiation in the primary energy region E_0 ~ 1x10^14 - 2x10^15
eV. This radiation has a spectrum of a form, close to the bell-like one, with
the maximum at E_0 ~ 2.2x10^14 ev and with an additional local maximum at E_0 ~
1.6x10^15 eV.


title: Gamma-ray bursts and collisionless shocks

abstract:
  Particle acceleration in collisionless shocks is believed to be responsible
for the production of cosmic-rays over a wide range of energies, from few GeV
to >10^{20}eV, as well as for the non-thermal emission of radiation from a wide
variety of high energy astrophysical sources. A theory of collisionless shocks
based on first principles does not, however, exist. Observations of gamma-ray
burst (GRB) "afterglows" provide a unique opportunity for diagnosing the
physics of relativistic collisionless shocks. Most GRBs are believed to be
associated with explosions of massive stars. Their "afterglows," delayed low
energy emission following the prompt burst of gamma-rays, are well accounted
for by a model in which afterglow radiation is due to synchrotron emission of
electrons accelerated in relativistic collisionless shock waves driven by the
explosion into the surrounding plasma. Within the framework of this model, some
striking characteristics of collisionless relativistic shocks are implied.
These include the generation of downstream magnetic fields with energy density
exceeding that of the upstream field by ~8 orders of magnitude, the survival of
this strong field at distances ~10^{10} skin-depths downstream of the shock,
and the acceleration of particles to a power-law energy spectrum, d\log n/d\log
E ~ -2, possibly extending to 10^{20}eV. I review in this talk the
phenomenological considerations, based on which these characteristics are
inferred, and the challenges posed to our current models of particle
acceleration and magnetic field generation in collisionless shocks. Some recent
theoretical results derived based on the assumption of a self-similar shock
structure are briefly discussed.


title:
Swift/XRT follow-up observations of TeV sources of the HESS Inner Galaxy
  survey

abstract:
  In order to provide a firm identification of the newly discovered Galactic
TeV sources, a search for counterparts in a broad band from soft X-ray to soft
gamma-rays is crucial as data in these wavebands allow us to distinguish
between different types of suggested models (for example leptonic versus
hadronic) and, in turn, to disentangle their nature. In this paper, we report
the results of a set of follow-up observations performed by the Swift/X-Ray
Telescope (XRT) on seven sources recently discovered by HESS, in the range from
few hundred GeV to about 10 TeV, during the inner Galaxy survey (Aharonian et
al. 2006). In all, but one case, we detect X-ray sources inside or close-by the
extended TeV emitting region. All these putative X-ray counterparts have
accurate arc-second location and are consistent with being point sources. The
main result of our search is the discovery that three of them are located at
the center of the diffuse radio emission of the supernova remnants, which have
been spatially associated to these TeV objects. HESS J1640-465, HESS J1834-087
and HESS J1813-178 show this evidence, suggestive of a possible Pulsar Wind
Nebula association.


title:
The All-wavelength Extended Groth Strip International Survey (AEGIS)
  Data Sets

abstract:
  In this the first of a series of Letters, we present a description of the
panchromatic data sets that have been acquired in the Extended Groth Strip
region of the sky. Our survey, the All-wavelength Extended Groth strip
International Survey (AEGIS), is intended to study the physical properties and
evolutionary processes of galaxies at z ~ 1. It includes the following deep,
wide-field imaging data sets: Chandra/ACIS X-ray (0.5 - 10 keV), GALEX
ultraviolet (1200 - 2500 Angstrom), CFHT/MegaCam Legacy Survey optical (3600 -
9000 Angstroms), CFHT/CFH12K optical (4500 - 9000 Angstroms), Hubble Space
Telescope/ACS optical (4400 - 8500 Angstroms), Palomar/WIRC near-infrared (1.2
- 2.2 microns), Spitzer/IRAC mid-infrared (3.6 - 8.0 microns), Spitzer/MIPS
far-infrared (24 - 70 microns), and VLA radio continuum (6 - 20 cm). In
addition, this region of the sky has been targeted for extensive spectroscopy
using the DEIMOS spectrograph on the Keck II 10 m telescope. Our survey is
compared to other large multiwavelength surveys in terms of depth and sky
coverage.


title: Interferometric Mapping of Magnetic fields: NGC2071IR

abstract:
  We present polarization maps of NGC2071IR from thermal dust emission at 1.3
mm and from CO J=$2 \to 1$ line emission. The observations were obtained using
the Berkeley-Illinois-Maryland Association array in the period 2002-2004. We
detected dust and line polarized emission from NGC2071IR that we used to
constrain the morphology of the magnetic field. From CO J=$2 \to 1$ polarized
emission we found evidence for a magnetic field in the powerful bipolar outflow
present in this region. We calculated a visual extinction $A_{\rm{v}} \approx
26$ mag from our dust observations. This result, when compared with early
single dish work, seems to show that dust grains emit polarized radiation
efficiently at higher densities than previously thought. Mechanical alignment
by the outflow is proposed to explain the polarization pattern observed in
NGC2071IR, which is consistent with the observed flattening in this source.


title: Interferometric mapping of Magnetic fields: G30.79 FIR 10

abstract:
  We present polarization maps of G30.79 FIR 10 (in W43) from thermal dust
emission at 1.3 mm and from CO J=$2 \to 1$ line emission. The observations were
obtained using the Berkeley-Illinois-Maryland Association array in the period
2002-2004. The G30.79 FIR 10 region shows an ordered polarization pattern in
dust emission, which suggests an hourglass shape for the magnetic field. Only
marginal detections for line polarization were made from this region.
Application of the Chandrashkar-Fermi method yielded $B_{pos} \approx 1.7$ mG
and a statistically corrected mass to magnetic flux ratio $\lambda_{C} \approx
0.9$, or essentially critical.


title: Microlensing towards LMC: a study of the LMC halo contribution

abstract:
  We carry on a new analysis of the sample of MACHO microlensing candidates
towards the LMC. Our main purpose is to determine the lens population to which
the events may belong. We give particular emphasis to the possibility of
characterizing the Milky Way dark matter halo population with respect to the
LMC one. Indeed, we show that only a fraction of the events have
characteristics that match those expected for lenses belonging to the MACHO
population of the Milky Way halo. This suggests that this component cannot
explain all the candidates. Accordingly, we challenge the view that the dark
matter halo fraction of both the Milky Way and the LMC halos are equal, and
indeed we show that, for a MACHO mass in the range 0.1-0.3 M$_\odot$, the LMC
halo fraction can be significantly larger than the Milky Way one. In this
perspective, our main conclusion is that up to about half of the observed
events could be attributed to the LMC MACHO dark matter halo.


title: Critical state of phantom universe

abstract:
  The late-time evolution behavior of the autonomous system in the SO(1,1) dark
energy model with power-law potential is studied. Big Rip may be a critical
point of the autonomous system. This means that such a Big Rip may be
considered as the middle state between the expanding and contracting phases of
phantom universe. This result is also valid for some special interactions
between matter and dark energy.


title: Scale-Free Thin Discs with an Isopedic Magnetic Field

abstract:
  Global stationary configurations of both aligned and logarithmic spiral MHD
perturbations are constructed analytically within an axisymmetric background
ofrazor-thin scale-free gas disc, which is embedded in an axisymmetric
gravitational potential of a dark matter halo and involves an isopedic magnetic
field almost vertically threaded through the disc plane. The scale-free index
$\beta$ of the disc rotation speed $v_{\theta}\propto R^{-\beta}$ falls in the
rangeof $(-1/2 , 1/2)$ where $R$ is the cylindrical radius. With the
holding-back of a deep background dark matter halo potential, the isopedic
magnetic field may be strong enough to allow for the magnetic tension force
overtaking the disc self-gravity, which can significantly influence global
stationary MHD perturbation configurations and stability properties of the
scale-free disc system. Only for stationary logarithmic spiral MHD
perturbations with a perturbation scale-free index $\beta_1=1/4$ or for aligned
stationary MHD perturbations, can the MHD disc maintain a constant radial flux
of angularmomentum. The variable radial flux of angular momentum in the radial
direction corresponds to a complex dispersion relation. The marginal
instabilities foraxisymmetric MHD disturbances are also examined for a special
case as an example. When the magnetic tension force overtakes the disc
self-gravity, the scale-free disc can be completely stable against axisymmetric
MHD disturbances of all wavelengths. We predict the possible existence of an
isopedicallymagnetized gas disc system in rotation primarily confined by a
massive dark matter halo potential.


title: Width of the 511 KeV Line from the Bulge of the Galaxy

abstract:
  In this paper I present the detail estimations for the width of the 511 keV
line produced by a mechanism when dark matter is represented by macroscopically
large dense nuggets. I argue that the width of 511 keV emission in this
mechanism is very narrow (in a few keV range) in agreement with all
observations. The dominant mechanism of the annihilation in this case is the
positronium formation e^+e^-to ^1S_0 to 2\gamma rather than a direct e^+e^- to
2\gamma$ annihilation. I also discuss some generic features of the \gamma rays
spectrum (in few MeV range) resulting from this mechanism.


title: The Virial Balance of Clumps and Cores in Molecular Clouds

abstract:
  We study the instantaneous virial balance of clumps and cores (CCs) in 3D
simulations of driven, MHD, isothermal molecular clouds (MCs). The models
represent a range of magnetic field strengths in MCs from subcritical to
non-magnetic regimes. We identify CCs at different density thresholds, and for
each object, we calculate all the terms that enter the Eulerian form of the
virial theorem (EVT). A CC is considered gravitationally bound when the
gravitational term in the EVT is larger than the amount for the system to be
virialized, which is more stringent than the condition that it be large enough
to make the total volume energy negative. We also calculate, quantities
commonly used in the observations to indicate the state of gravitational
boundedness of CCs such as the Jeans number J_c, the mass-to magnetic flux
ratio mu_c, and the virial parameter alpha_vir. Our results show that: a) CCs
are dynamical out-of-equilibrium structures. b) The surface energies are of the
same order than their volume counterparts c) CCs are either in the process of
being compressed or dispersed by the velocity field. Yet, not all CCs that have
a compressive net kinetic energy are gravitationally bound. d) There is no
1-to-1 correspondence between the state of gravitational boundedness of a CC as
described by the virial analysis or as implied by the classical indicators. In
general, in the virial analysis, we observe that only the inner regions of the
objects are gravitationally bound, whereas J_c, alpha_vir, and mu_c estimates
tend to show that they are more gravitationally bound at the lowest threshold
levels and more magnetically supercritical. g) We observe, in the non-magnetic
simulation, the existence of a bound core with structural and dynamical
properties that resemble those of the Bok globule Barnard 68 (B68).


title: The Rise Time of Type Ia Supernovae from the Supernova Legacy Survey

abstract:
  We compare the rise times of nearby and distant Type Ia supernovae (SNe Ia)
as a test for evolution using 73 high-redshift spectroscopically-confirmed SNe
Ia from the first two years of the five year Supernova Legacy Survey (SNLS) and
published observations of nearby SN. Because of the ``rolling'' search nature
of the SNLS, our measurement is approximately 6 times more precise than
previous studies, allowing for a more sensitive test of evolution between
nearby and distant supernovae. Adopting a simple $t^2$ early-time model (as in
previous studies), we find that the rest-frame $B$ rise times for a fiducial SN
Ia at high and low redshift are consistent, with values
$19.10^{+0.18}_{-0.17}({stat}) \pm 0.2 ({syst})$ and $19.58^{+0.22}_{-0.19}$
days, respectively; the statistical significance of this difference is only 1.4
\sg . The errors represent the uncertainty in the mean rather than any
variation between individual SN. We also compare subsets of our high-redshift
data set based on decline rate, host galaxy star formation rate, and redshift,
finding no substantive evidence for any subsample dependence.


title: Spin-down Rate of Pinned Superfluid

abstract:
  The spinning down (up) of a superfluid is associated with a radial motion of
its quantized vortices. In the presence of pinning barriers against the motion
of the vortices, a spin-down may be still realized through ``random unpinning''
and ``vortex motion,'' as two physically separate processes, as suggested
recently. The spin-down rate of a pinned superfluid is calculated, in this
framework, by directly solving the equation of motion applicable to only the
unpinned moving vortices, at any given time. The results indicate that the
pinned superfluid in the crust of a neutron star may as well spin down at the
same steady-state rate as the rest of the star, through random unpinning
events, while pinning conditions prevail and the superfluid rotational lag is
smaller than the critical lag value.


title:
A Search for Dense Gas in Luminous Submillimeter Galaxies with the 100-m
  Green Bank Telescope

abstract:
  We report deep K-band (18-27GHz) observations with the 100-m Green Bank
Telescope of HCN(1-0) line emission towards the two submillimeter-selected
galaxies (SMGs) SMMJ02399-0136 (z=2.81) and SMMJ16359+6612 (z=2.52). For both
sources we have obtained spectra with channel-to-channel rms noise of <=0.5mJy,
resulting in velocity-integrated line fluxes better than < 0.1 Jy km/s,
although we do not detect either source. Such sensitive observations -- aided
by gravitational lensing of the sources -- permit us to put upper limits of
L_HCN(1-0) < 2x10^10 K km/s pc^2 on the intrinsic HCN(1-0) line luminosities of
the two SMGs. The far-infrared (FIR) luminosities for all three SMGs with
sensitive HCN(1-0) observations to date are found to be consistent with the
tight FIR-HCN luminosity correlation observed in Galactic molecular clouds,
quiescent spirals and (ultra) luminous infrared galaxies in the local Universe.
Thus, the observed HCN luminosities remain in accordance with what is expected
from the universal star formation efficiency per dense molecular gas mass
implied by the aforementioned correlation, and more sensitive observations with
today's large aperture radio telescopes hold the promise of detecting HCN(1-0)
emission in similar objects in the distant Universe.


title: Redshift Degeneracy in the Eiso-Epeak Relation of Gamma-Ray Bursts

abstract:
  In this Letter we show that there is a redshift degeneracy in the Eiso-Epeak
relation of gamma-ray bursts (GRBs). If a GRB has a redshift solved from the
Eiso-Epeak relation that lies in the range of 0.9<z<20, a GRB that has the same
observed fluence and peak spectral energy but is at a different redshift in
that range also satisfies the Eiso-Epeak relation within 1-sigma error,
implying an extremely large error in the calculated redshift. Even if the data
scatter in the Eiso-Epeak relation is reduced by a factor of 2, the error in
the predicted redshift is still large enough to prevent constraining the
redshift meaningfully. Hence, the Eiso-Epeak relation is not useful for
determining the GRB distance.


title: Power spectrum of HI intensity fluctuations in DDO 210

abstract:
  We measure the power spectrum of HI intensity fluctuations in the extremely
faint (M_B ~ -10.9) dwarf galaxy DDO 210 using a visibility based estimator
that is well suited in very low signal to noise ratio regimes. DDO 210's HI
power spectrum is well fit by a power law $P_HI(U)= A U^{\alpha}$ with
$\alpha=-2.75 \pm0.45$ over the length-scales 80 pc to 500 pc. We also find
that the power spectrum does not change with an increase in the velocity
channel width, indicating that the measured fluctuations correspond mainly to
density fluctuations. However, Kolmogorov turbulence (with a velocity structure
function spectral slope of 2/3) cannot be ruled out from the present
observations. The value of the slope $\alpha$ is similar to that obtained in
the Milkyway. In contrast to the Milkyway, DDO 210 has three orders of
magnitude less HI, no spiral arms, and also no measurable ongoing star
formation. The fact that the power spectrum slope is nonetheless similar in
these two galaxies (and also similar to the values measured for the LMC and
SMC) suggests that there is some universal, star formation independent,
phenomenon responsible for producing fine scale structure in the gas.


title:
LS I +61 303 as a potential neutrino source on the light of MAGIC
  results

abstract:
  Very high energy $\gamma$-rays have recently been detected from the
microquasar LS I +61 303 using the MAGIC telescope. A phenomenological study on
the concomitant neutrinos that would be radiated if the $\gamma$-ray emission
is hadronic in origin is herein presented. Neutrino oscillations are
considered, and the expected number of events in a km-scale detector such as
ICECUBE is computed under different assumptions including orbital periodicity
and modulation, as well as different precision in the modeling of the detector.
We argue that the upper limits already imposed on the neutrino emission of LS I
+61 303 using AMANDA-II and the forthcoming measurements by ICECUBE may
significantly constrain -in an independent and unbiased way- the $\gamma$-ray
to neutrino flux ratio, and thus the possibility of a hadronic origin of the
$\gamma$-rays. The viability of hadronic models based on wind-jet interactions
in the LS + 61 303 system after MAGIC measurements is discussed.


title:
A possible interrelation between the estimated luminosity distances and
  internal extinctions of type Ia supernovae

abstract:
  We studied the statistical properties of the luminosity distance and internal
extinction data of type Ia supernovae in the lists published by Tonry et al.
(2003) and Barris et al. (2004). After selecting the luminosity distance in an
empty Universe as a reference level we divided the sample into low $z<0.25$ and
high $z \ge 0.25$ parts. We further divided these subsamples by the median of
the internal extinction. Performing sign tests using the standardized residuals
between the estimated logarithmic luminosity distances and those of an empty
universe, on the four subsamples separately, we recognized that the residuals
were distributed symmetrically in the low redshift region, independently from
the internal extinction. On the contrary, the low extinction part of the data
of $z \ge 0.25$ clearly showed an excess of the points with respect to an empty
Universe which was not the case in the high extinction region. This diversity
pointed to an interrelation between the estimated luminosity distance and
internal extinction. To characterize quantitatively this interrelation we
introduced a hidden variable making use of the technics of factor analysis.
After subtracting that part of the residual which was explained by the
hiddenmaking use of the technics of factor analysis. After subtracting that
part of the residual which was explained by the hidden variable we obtained
luminosity distances which were already free from interrelation with internal
extinction. Fitting the corrected luminosity distances with cosmological models
we concluded that the SN Ia data alone did not exclude the possibility of the
$\Lambda=0$ solution.


title: Isotherms clustering in cosmic microwave background

abstract:
  Since the strong clustering of luminous matter in the observable universe is
a consequence of an initial non-uniformity of the baryon-photon fluid in the
last scattering surface, an investigation of clustering of the isotherms in the
cosmic microwave background has been performed. The isotherms clustering has
been related to the baryon-photon fluid dynamics and the Taylor-microscale
Reynolds number of this motion is estimated to be $10^2$. 3-year WMAP cosmic
microwave background map has been used in this investigation.


title:
Two 3-Branes in Randall-Sundrum Setup and Current Acceleration of the
  Universe

abstract:
  Five-dimensional spacetimes of two orbifold 3-branes are studied, by assuming
that {\em the two 3-branes are spatially homogeneous, isotropic, and
independent of time}, following the so-called "bulk-based" approach. The most
general form of the metric is obtained, and the corresponding field equations
are divided into three groups, one is valid on each of the two 3-branes, and
the third is valid in the bulk. The Einstein tensor on the 3-branes is
expressed in terms of the discontinuities of the first-order derivatives of the
metric coefficients. Thus, once the metric is known in the bulk, the
distribution of the Einstein tensor on the two 3-branes is uniquely determined.
As applications, we consider two different cases, one is in which the bulk is
locally $AdS_{5}$, and the other is where it is vacuum. In some cases, it is
shown that the universe is first decelerating and then accelerating. The global
structure of the bulk as well as the 3-branes is also studied, and found that
in some cases the solutions may represent the collision of two orbifold
3-branes. The applications of the formulas to the studies of the cyclic
universe and the cosmological constant problem are also pointed out.


title:
GRAVITY: The adaptive optics assisted, two object beam combiner for the
  VLTI

abstract:
  We present the adaptive optics assisted, near-infrared VLTI instrument -
GRAVITY - for precision narrow-angle astrometry and interferometric phase
referenced imaging of faint objects. Precision astrometry and phase-referenced
interferometric imaging will realize the most advanced vision of
optical/infrared interferometry with the VLT. Our most ambitious science goal
is to study motions within a few times the event horizon size of the Galactic
Center massive black hole and to test General Relativity in its strong field
limit. We define the science reference cases for GRAVITY and derive the top
level requirements for GRAVITY. The installation of the instrument at the VLTI
is planned for 2012.


title:
Lines in the Cosmic Microwave Background Spectrum from the Epoch of
  Cosmological Hydrogen Recombination

abstract:
  We compute the spectral distortions of the Cosmic Microwave Background (CMB)
arising during the epoch of cosmological hydrogen recombination within the
standard cosmological (concordance) model for frequencies in the range 1
GHz-3500 GHz. We follow the evolution of the populations of the hydrogen levels
including states up to principle quantum number $n=30$ in the redshift range
$500\leq z\leq 3500$. All angular momentum sub-states are treated individually,
resulting in a total number of 465 hydrogen levels. The evolution of the matter
temperature and the fraction of electrons coming from HeII are also included.
We present a detailed discussion of the distortions arising from the main
dipolar transitions, e.g. Lyman and Balmer series, as well as the emission due
to the two-photon decay of the hydrogen 2s level. Furthermore, we investigate
the robusteness of the results against changes in the number of shells
considered. The resulting spectral distortions have a characteristic
oscillatory behaviour, which might allow experimentalists to separate them from
other backgrounds. The relative distortion of the spectrum exceeds a value of
$10^{-7}$ at wavelengths longer than 21cm. Our results also show the importance
of detailed follow-up of the angular momentum sub-states, and their effect on
the amplitude of the lines. The effect on the residual electron fraction is
only moderate, and mainly occurs at low redshifts. The CMB angular power
spectrum is changed by less than 1%. Finally, our computations show that if the
primordial radiation field is described by a pure blackbody, then there is no
significant emission from any hydrogen transition at redshifts greater than $z
\sim 2000$. This is in contrast to some earlier works, where the existence of a
`pre-recombination' peak was claimed.


title:
Continuum gamma-ray emission from light dark matter positrons and
  electrons

abstract:
  The annihilation of light dark matter was recently advocated as a possible
explanation of the large positron injection rate at the Galactic center deduced
from observations by the SPI spectrometer aboard INTEGRAL. The modelling of
internal Bremsstrahlung and in-flight annihilation radiations associated to
this process drastically reduced the mass range of this light dark matter
particle. We estimate critically the various energy losses and radiations
involved in the propagation of the positron before its annihilation --in-
flight or at rest.
  Using a simple model with mono-energetic positrons injected and confined to
the Galactic bulge, we compute energy losses and gamma-ray radiations caused by
ionization, Bremsstrahlung interactions as well as in-flight and at rest
annihilation and compare these predictions to the available observations, for
various injection energies.
  Confronting the predictions with observations by the CGRO/EGRET,
CGRO/COMPTEL, INTEGRAL/SPI and INTEGRAL/IBIS/ISGRI instruments, we deduce a
mass upper bound of 3 to 7.5 MeV/c^2 for the hypothetical light dark matter
particle. The most restrictive limit is in agreement with the value previously
found by Beacom and Yuksel and was obtained under similar assumptions, while
the 7.5 MeV/c^2 value corresponds to more conservative choices and to a
partially ionized propagation medium. We stress how the limit depends on the
degree of ionization of the propagation medium and how its precision could be
improved by a better appraisal of data uncertainties.


title:
Molecular line emission in HH54: a coherent view from near to far
  infrared

abstract:
  Aims. We present a detailed study of the infrared line emission (1-200
micron) in the Herbig-Haro object HH54. Our database comprises: high- (R~9000)
and low- (R~600) resolution spectroscopic data in the near-infrared band (1-2.5
micron); mid-infrared spectrophotometric images (5-12 micron); and, far-IR
(45-200 micron, R~200) spectra acquired with the ISO satellite. As a result, we
provide the detection of and the absolute fluxes for more than 60 molecular
features (mainly from H2 in the near- and mid-infrared and from H2O, CO and OH
in the far-infrared) and 23 ionic lines. Methods. The H2 lines, coming from
levels from v=0 to v=4 have been interpreted in the context of a state-of-art
shock code, whose output parameters are adopted as input to a Large Velocity
Gradient computation in order to interpret the FIR emission of CO, H2O and OH.
Results. The H2 emission can be interpreted as originating in either
steady-state J-type shocks or in quasi-steady J-type shocks with magnetic
precursor. However, our multi-species analysis shows that only a model of a
J-type shock with magnetic precursor (v_shock=18 km/s, n_H=10^4 cm^-3, B=100
microG, age=400 yr) can account for both the observed H2 emission and the CO
and H2O lines. Such a model predicts a H2O abundance of ~ 7 10^-5, in agreement
with estimations from other shock models for outflows associated with low mass
protostars. We can exclude the possibility that the observed atomic lines arise
in the same shock as the molecular lines, and give arguments in favour of the
presence of a further high-velocity, fully dissociative shock component in the
region. Finally, in view of the forthcoming spectroscopic facilities on board
of the Herschel satellite, we provide predictions for H2O lines considered to
be the most suitable for diagnostic purposes.


title:
Metallicity as a criterion to select H2 bearing Damped Lyman-alpha
  systems

abstract:
  We characterize the importance of metallicity on the presence of molecular
hydrogen in damped Lyman-alpha (DLA) systems. We construct a representative
sample of 18 DLA/sub-DLA systems with log N(HI)>19.5 at high redshift
(zabs>1.8) with metallicities relative to solar [X/H]>-1.3(with[X/H]=
logN(X)/N(H)-log(X/H)solar and X either Zn, S or Si). We gather data covering
the expected wavelength range of redshifted H2 absorption lines on all systems
in the sample from either the literature (10 DLAs), the UVES-archive or new
VLT-UVES observations for four of them. The sample is large enough to discuss
for the first time the importance of metallicity as a criterion for the
presence of molecular hydrogen in the neutral phase at high-z. From the new
observations, we report two new detections of molecular hydrogen in the systems
at zabs=2.431 toward Q2343+125 and zabs=2.426 toward Q2348-011. We compare the
H2 detection fraction in the high-metallicity sample with the detection
fraction in the overall sample from Ledoux et al. (2003). We show that the
fraction of DLA systems with logf=log 2N(H2)/(2N(H2)+N(HI))>-4 is as large as
50% for [X/H]>-0.7 when it is only about 5% for [X/H]<-1.3 and about 15% in the
overall sample (with -2.5<[X/H]<-0.3). This demonstrates that the presence of
molecular hydrogen at high redshift is strongly correlated with metallicity.


title:
Chandra monitoring observations of the ultraluminous X-ray source NGC
  5204 X-1

abstract:
  We report the results of a 2-month campaign conducted with the Chandra X-ray
observatory to monitor the ultraluminous X-ray source (ULX) NGC 5204 X-1. This
was composed of a 50-ks observation, followed by ten 5-ks follow-ups spaced
initially at ~ 3, then at ~ 10 day intervals. The ULX flux is seen to vary by
factors ~ 5 on timescales of a few days, but no strong variability is seen on
timescales shorter than an hour. There is no evidence for a periodic signal in
the X-ray data. An examination of the X-ray colour variations over the period
of the campaign shows the ULX emission consistently becomes spectrally harder
as its flux increases. The X-ray spectrum from the 50-ks observation can be
fitted by a number of disparate spectral models, all of which describe a smooth
continuum with, unusually for a ULX, a broad emission feature evident at 0.96
keV. The spectral variations, both within the 50-ks observation and over the
course of the whole campaign, can then be explained solely by variations in the
continuum component. In the context of an optically-thick corona model (as
found in other recent results for ULXs) the spectral variations can be
explained by the heating of the corona as the luminosity of the ULX increases,
consistent with the behaviour of at least one Galactic black hole system in the
strongly-Comptonised very high state. We find no new evidence supporting the
presence of an intermediate-mass black hole in this ULX.


title:
A log-quadratic relation for predicting supermassive black hole masses
  from the host bulge Sersic index

abstract:
  We reinvestigate the correlation between black hole mass and bulge
concentration. With an increased galaxy sample, updated estimates of galaxy
distances, black hole masses, and Sersic indices `n' - a measure of
concentration - we perform a least-squares regression analysis to obtain a
relation suitable for the purpose of predicting black hole masses in other
galaxies. In addition to the linear relation, log(M_bh) = 7.81(+/-0.08) +
2.69(+/-0.28)[log(n/3)] with epsilon_(intrin)=0.31 dex, we investigated the
possibility of a higher order M_bh-n relation, finding the second order term in
the best-fitting quadratic relation to be inconsistent with a value of zero at
greater than the 99.99% confidence level. The optimal relation is given by
log(M_bh) = 7.98(+/-0.09) + 3.70(+/-0.46)[log(n/3)] -
3.10(+/-0.84)[log(n/3)]^2, with epsilon_(intrin)=0.18 dex and a total absolute
scatter of 0.31 dex. Extrapolating the quadratic relation, it predicts black
holes with masses of ~10^3 M_sun in n=0.5 dwarf elliptical galaxies, compared
to ~10^5 M_sun from the linear relation, and an upper bound on the largest
black hole masses in the local universe, equal to 1.2^{+2.6}_{-0.4}x10^9
M_sun}. In addition, we show that the nuclear star clusters at the centers of
low-luminosity elliptical galaxies follow an extrapolation of the same
quadratic relation. Moreover, we speculate that the merger of two such
nucleated galaxies, accompanied by the merger and runaway collision of their
central star clusters, may result in the late-time formation of some
supermassive black holes. Finally, we predict the existence of, and provide
equations for, a relation between M_bh and the central surface brightness of
the host bulge.


title: On the angular momentum evolution of merged white dwarfs

abstract:
  We study the angular momentum evolution of binaries containing two white
dwarfs which merge and become cool helium-rich supergiants. Our object is to
compare predicted rotation velocities with observations of highly evolved stars
believed to have formed from such a merger, including RCrB and extreme helium
stars. The principal study involves a binary containing a 0.6 solar mass CO
white dwarf, and a 0.3 solar mass He white dwarf. The initial condition for the
angular momentum distribution is defined where the secondary fills its Roche
Lobe. We assume conservation of angular momentum to compute the angular
momentum distribution in a collisionless disk and subsequently in the giant
envelope. At the end of shell-helium burning, the giant contracts to form a
white dwarf. We derive the surface rotation velocity during this contraction.
The calculation is repeated for a range of initial mass ratios, and also for
the case of mergers between two helium white dwarfs; the latter will contract
to the helium main-sequence rather than the white dwarf sequence. Assuming
complete conservation of angular momentum, we predict acceptable angular
rotation rates for cool giants and during the initial subsequent contraction.
However such stars will only survive spin-up to reach the white dwarf sequence
(CO+He merger) if the initial mass ratio is close to unity. He+He merger
products must lose angular momentum in order to reach the helium main sequence.
Minimum observed rotation velocities in extreme helium stars are lower than our
predictions by at least one half, indicating that CO+He mergers must lose at
least one half of their angular momentum.


title:
Solving the Problem of Time in General Relativity and Cosmology with
  Phantoms and k -- Essence

abstract:
  We show that if the Lagrangean for a scalar field coupled to General
Relativity only contains derivatives, then it is possible to completely
deparametrise the theory. This means that 1.Physical observables, i.e.
functions which Poisson commute with the spatial diffeomorphism and Hamiltonian
constraints of General Relativity, can be easily constructed. 2. The physical
time evolution of those observables is generated by a natural physical
Hamiltonian which is (constrained to be) positive. The mechanism by which this
works is due to Brown and Kucha\v{r}. In order that the physical Hamiltonian is
close to the Hamiltonian of the standard model and the one used in cosmology,
the required Lagrangean must be that of a Dirac -- Born -- Infeld type. Such
matter has been independently introduced previously by cosmologists in the
context of k -- essence due to Armendariz-Picon, Mukhanov and Steinhardt in
order to solve the cosmological coincidence (dark energy) problem. We arrive at
it by totally unrelated physical considerations originating from quantum
gravity. Our manifestly gauge invariant approach leads to important
modifictaions of the interpretation and the the analytical appearance of the
standard FRW equations of classical cosmology in the late universe. In
particular, our concrete model implies that the universe should recollapse at
late times on purely classical grounds.


title:
Trapping of magnetic flux by the plunge region of a black hole accretion
  disk

abstract:
  The existence of the radius of marginal stability means that accretion flows
around black holes invariably undergo a transition from a MHD turbulent
disk-like flow to an inward plunging flow. We argue that the plunging inflow
can greatly enhance the trapping of large scale magnetic field on the black
hole, and therefore may increase the importance of the Blandford-Znajek (BZ)
effect relative to previous estimates that ignore the plunge region. We support
this hypothesis by constructing and analyzing a toy-model of the dragging and
trapping of a large scale field by a black hole disk, revealing a strong
dependence of this effect on the effective magnetic Prandtl number of the MHD
turbulent disk. Furthermore, we show that the enhancement of the BZ effect
depends on the geometric thickness of the accretion disk. This may be, at least
in part, the physical underpinnings of the empirical relation between the
inferred geometric thickness of a black hole disk and the presence of a radio
jet.


title:
Anisotropy studies around the galactic centre at EeV energies with the
  Auger Observatory

abstract:
  Data from the Pierre Auger Observatory are analyzed to search for
anisotropies near the direction of the Galactic Centre at EeV energies. The
exposure of the surface array in this part of the sky is already significantly
larger than that of the fore-runner experiments. Our results do not support
previous findings of localized excesses in the AGASA and SUGAR data. We set an
upper bound on a point-like flux of cosmic rays arriving from the Galactic
Centre which excludes several scenarios predicting sources of EeV neutrons from
Sagittarius $A$. Also the events detected simultaneously by the surface and
fluorescence detectors (the `hybrid' data set), which have better pointing
accuracy but are less numerous than those of the surface array alone, do not
show any significant localized excess from this direction.


title:
Physical properties of two compact high-velocity clouds possibly
  associated with the Leading Arm of the Magellanic System

abstract:
  We observed two compact high-velocity clouds HVC 291+26+195 and HVC
297+09+253 to analyse their structure, dynamics, and physical parameters. In
both cases there is evidence for an association with the Leading Arm of the
Magellanic Clouds. The goal of our study is to learn more about the origin of
the two CHVCs and to use them as probes for the structure and evolution of the
Leading Arm. We have used the Parkes 64 m radio telescope and the Australia
Telescope Compact Array (ATCA) to study the two CHVCs in the 21 cm line
emission of neutral hydrogen. We present a method to estimate the distance of
the two CHVCs. The investigation of the line profiles of HVC 297+09+253 reveals
the presence of two line components in the spectra which can be identified with
a cold and a warm gas phase. In addition, we find a distinct head-tail
structure in combination with a radial velocity gradient along the tail,
suggesting a ram-pressure interaction of this cloud with an ambient medium. HVC
291+26+195 has only a cold gas phase and no head-tail structure. The ATCA data
show several cold, compact clumps in both clouds which, in the case of HVC
297+09+253, are embedded in the warm, diffuse envelope. All these clumps have
very narrow HI lines with typical line widths between 2 and 4 km/s FWHM,
yielding an upper limit for the kinetic temperature of the gas of T_max = 300
K. We obtain distance estimates for both CHVCs of the order of 10 to 60 kpc,
providing additional evidence for an association of the clouds with the Leading
Arm.


title: The secondary star and distance of the polar V1309 Ori

abstract:
  The first phase-resolved JHK light curves of the eclipsing polar (AM Herculis
binary) V1309 Ori are presented and interpreted. We separate the contributions
from the secondary star and from other sources with the aim of determining a
photometric distance. Simple model calculations show that the accretion stream
and the cyclotron source on the accreting white dwarf are minor contributors to
the infrared light, allowing an accurate determination of spectral type and
absolute flux of the secondary star. The unilluminated backside of the
secondary star as seen in eclipse has spectral type dM0 to dM0+. Its dereddened
magnitude is K = 13.58 at orbital phase phi = 0 (eclipse). Using the calibrated
surface brightness of M-stars and the published mass of the secondary, M2 =
0.46 Msun, we obtain a distance d = 600 +/- 25 pc which scales as M2^(1/2). The
radius of the Roche-lobe filling secondary exceeds the main-sequence radius of
an M0 star by 21 +11/-6 %. The debated origin of the infrared light of V1309
Ori has been settled in favor of the secondary star as the main contributor and
an accurate distance has been derived that will place estimates of the
luminosity and synchronization time scale on a more secure basis.


title: Galaxies in front of Quasars: Mrk 1456 and SDSS J114719.90+522923.2

abstract:
  The chance projection of the disk of Mrk~1456 onto a background QSO is
similar to the case of SBS 1543+593/HS 1543+5921. Mrk~1456 is a luminous,
late-type spiral at z ~ 0.05. Though the QSO, SDSS J114719.90+522923.2 at z ~
2, has not yet been observed with ultraviolet spectroscopy, it shows strong Ca
II absorption at the redshift of Mrk 1456 which gives evidence that it is a
possible Damped Lyman Alpha absorber. Spectroscopy of the star-forming nucleus
of Mrk~1456 allows us to apply emission-line diagnostics to infer the chemical
abundances at the center of the galaxy, and to make a prediction of the
expected metallicity on the sightline to the QSO.


title: Vlbi Diagnostics of Jet Instabilities in 0836+710

abstract:
  In this paper, we present new VLBA observations of the radio jet in the
quasar S5 0836+710 at 8 and 22 GHz. The identification of the ridge lines allow
us to interpret the jet structure in terms of Kelvin-Helmholtz instability.
Combined with previous epochs of VLBA and VSOP data at 1.6 and 5 GHz, these new
observations will allow us to study the evolution of the instabilities in the
jet. We have detected signatures of possible jet disruption in the jet due to
the growth of instabilities, which points towards a possible morphological
classification of the source as an FRI, contrary to what previously thought in
terms of luminosity criteria.


title: Disks around young stars with VLTI/MIDI

abstract:
  We report on observations of circumstellar disks around young stars that have
been obtained with the MIDI instrument, which is mounted on the VLT
Interferometer and operates in the 10 micrometer atmospheric window. The
maximum spatial resolution of 5 milli-arcsec corresponds to sub-AU scales at
the distance to nearby star formation regions. Thus, we can study the disks on
the spatial scales at which important processes occur, such as accretion, dust
processing, and planet formation. The main results obtained so far can be
summarized as follows: 1. The measured interferometric visibilities are in good
qualitative agreement with those predicted by models of circumstellar disks. In
particular, a predicted correlation between the strength of the far-infrared
excess and the spatial structure of the disk is confirmed by direct
measurements; 2. In several objects strong evidence for deviations from
circular symmetry is present, indicating that an inclined disk is indeed the
dominant component seen in the mid-infrared; 3. The dust properties are not
uniform over the disk, but are instead a strong function of distance to the
central star. The dust in the innermost disk regions is observed to be more
``processed'' than the dust further out, both in Herbig Ae star disks and in
those around T-Tauri stars.


title: First broad band study of the mysterious source 1E 1743.1-2843

abstract:
  In the last years, the persistent source 1E 1743.1-2843 has been observed in
the X-rays, but never above 20 keV. In previous works, it was stressed that a
possible high energy emission could give further indications on the accreting
object nature which remains still unknown. We present here more than two years
of 1E 1743.1-2843 monitoring with INTEGRAL/IBIS as well as public XMM-Newton
and Chandra X-ray observations. The temporal study in the 20-40 keV band shows
a rather constant flux on few months time scale. Based on this result we have
performed the broad-band spectral analysis using EPIC/IBIS non simultaneous
data and ACIS-I/IBIS data collected during 2004. In ~2 Ms, we report a
detection of 6 sigma in the energy range 35-70 keV. The first broad-band study
(2-70 keV) shows a steep slope (~3) and a black body temperature of 1.7 keV.
Combining spectral parameters and discussion about the luminosity evaluations
for different possible distances, our conclusions are in favour of a LMXB
system with a neutron star at distance higher than the Galactic Centre, even
though a firm conclusion can not be stated.


title:
The nature of the close magnetic white dwarf + probable brown dwarf
  binary SDSS J121209.31+013627.7

abstract:
  Optical time series photometry of the short period magnetic white dwarf +
probable brown dwarf binary SDSS 121209.31+013627.7 reveals pulse-like
variability in all bands from i' to u', peaking at u'. These modulations are
most likely due to a self-eclipsing accretion hot spot on the white dwarf,
rotating into view every 88.43 minutes. This period is commensurate with the
radial velocity period determined by Schmidt et al. 2005 of ~90 minutes, and
consistent with the rotation period of the accretor being equal to the binary
orbital period. We combine our observations with those recently published by
Koen and Maxted 2006 to provide an accurate ephemeris. We also detect the
system in X-rays with Swift, and estimate the accretion rate at ~1x10^-13Msun
per year. We suggest that SDSS1212 is most likely a magnetic cataclysmic
variable in an extended state of very low accretion, similar to the
well-studied Polar EF Eri. Alternatively, the putative brown dwarf is not
filling its Roche Lobe and the system is a detached binary in which the white
dwarf is efficiently accreting from the wind of the secondary. Six such
post-common envelope, ``pre-Polar'' systems - termed ``low accretion rate
Polars (LARPs)'' by Schwope et al. 2002 - have previously been identified
through optical cyclotron emission lines. Cyclotron emission from SDSS1212 has
recently been detected in the near-IR Debes et al. 2006 but, if detached, it
would be the first ``LARP'' with a probably sub-stellar secondary. It is
unclear whether an L-dwarf wind is strong enough to provide the measured
accretion rate. We suggest further observations to distinguish between the
Roche Lobe over-flow and wind accretion scenarios.


title: $m=1$ Ideal Internal Kink Modes in a Line-tied Screw Pinch

abstract:
  It is well known that the radial displacement of the $m=1$ internal kink mode
in a periodic screw pinch has a steep jump at the resonant surface where
$\mathbf{k}\cdot\mathbf{B}=0$. In a line-tied system, relevant to solar and
astrophysical plasmas, the resonant surface is no longer a valid concept. It is
then of interest to see how line-tying alters the aforementioned result for a
periodic system. If the line-tied kink also produces a steep gradient,
corresponding to a thin current layer, it may lead to strong resistive effects
even with weak dissipation. Numerical solution of the eigenmode equations shows
that the fastest growing kink mode in a line-tied system still possesses a jump
in the radial displacement at the location coincident with the resonant surface
of the fastest growing mode in the periodic counterpart. However, line-tying
thickens the inner layer and slows down the growth rate. As the system length
$L$ approaches infinity, both the inner layer thickness and the growth rate
approach the periodic values. In the limit of small $\epsilon\sim
B_{\phi}/B_{z}$, the critical length for instability $L_{c}\sim\epsilon^{-3}$.
The relative increase in the inner layer thickness due to line-tying scales as
$\epsilon^{-1}(L_{c}/L)^{2.5}$.


title: Dark Matter Candidate from Conformality

abstract:
  Abelian quiver gauge theories provide candidates for the conformality
approach to physics beyond the standard model which possess novel cancellation
mechanisms for quadratic divergences. A $Z_2$ symmetry (R parity) can be
imposed and leads naturally to a dark matter candidate which is the Lightest
Conformality Particle (LCP), a neutral spin-1/2 state with weak interaction
annihilation cross section, mass in the 100 GeV region and relic density of
non-baryonic dark matter $\Omega_{dm}$ which can be consistent with the
observed value $\Omega_{dm} \simeq 0.24$.


title:
On radio-bright Active Galactic Nuclei in a complete Spectroscopic
  Redshift Survey

abstract:
  Analysis of the frequency and physical properties of galaxies with
star-formation and AGN activity in different environments in the local universe
is a cornerstone for understanding structure formation and galaxy evolution. We
have built a new multiwavelength catalog for galaxies in a complete redshift
survey (the 15R Survey), gathering information on their H-alpha, R-band, radio,
far-infrared, and X-ray emission, as well as their radio and optical
morphologies, and have developed a classification scheme to compare different
selection methods and to select accurately samples of radio emitting galaxies
with AGN and star-forming activity. While alternative classification schemes do
not lead to major differences for star-forming galaxies, we show that
spectroscopic and photometric classifications of AGN lead to incomplete
samples. In particular, a large population of AGN-containing galaxies with
absorption-line spectra, and in many cases extended radio structures (jets,
lobes), is missed in the standard Baldwin-Phillips-Terlevich emission-line
classification of active galaxies. This missed class of objects accounts for
roughly half of the radio AGN population. Similarly, for X-ray selected AGN in
our sample, we find that absorption-line AGN account for half of the sample.
Spectroscopically unremarkable, passive galaxies with AGN activity are not an
exception, but the norm, and we show that although they exist in all
environments, these systems preferentially reside in higher density regions.
Because of the existence of this population, the fractional abundance of AGN
increases with increasing density, in contrast to some published results based
on emission-line AGN extracted from the 15R, Sloan and 2DF redshift surveys.


title:
Chemical Evolution of the Galactic Bulge as Derived from High-Resolution
  Infrared Spectroscopy of K and M Red Giants

abstract:
  We present chemical abundances in K and M red-giant members of the Galactic
bulge derived from high-resolution infrared spectra obtained with the Phoenix
spectrograph on Gemini-South. The elements studied are carbon, nitrogen,
oxygen, sodium, titanium, and iron. The evolution of C and N abundances in the
studied red-giants show that their oxygen abundances represent the original
values with which the stars were born. Oxygen is a superior element for probing
the timescale of bulge chemical enrichment via [O/Fe] versus [Fe/H]. The
[O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with
[O/Fe] values falling above those of the disk. Titanium also behaves similarly
to oxygen with respect to iron. Based on these elevated values of [O/Fe] and
[Ti/Fe] extending to large Fe abundances, it is suggested that the bulge
underwent a more rapid chemical enrichment than the halo. In addition, there
are declines in both [O/Fe] and [Ti/Fe] in those bulge targets with the largest
Fe abundances, signifying another source affecting chemical evolution: perhaps
Supernovae of Type Ia. Sodium abundances increase dramatically in the bulge
with increasing metallicity, possibly reflecting the metallicity dependant
yields from supernovae of Type II, although Na contamination from H-burning in
intermediate mass stars cannot be ruled out.


title:
Dark Matter Halos of Disk Galaxies: Constraints from the Tully-Fisher
  Relation

abstract:
  We investigate structural properties of dark matter halos of disk galaxies in
LCDM cosmology, using a well-defined sample of 81 disk-dominated galaxies from
the SDSS redshift survey. We model the mass-velocity and fundamental plane
relations of these galaxies, which are constructed from the galaxy stellar
mass, disk scale length, and optical Halpha rotation velocity at 2.2 scale
lengths. We calculate a sequence of model galaxy populations, defined by the
distribution of the stellar disk-to-total mass fraction, m_d. We include the
effect of adiabatic contraction of dark matter halos in response to
condensation of baryons. We find that models with constant m_d underpredict the
intrinsic scatter of the TF and FP relations and predict an (unobserved) strong
correlation between TF residuals. Introducing a scatter of disk mass fractions
and allowing the mean value m_d to scale with the stellar surface density
significantly improves observational match of both the slope and intercept of
the TF relation and reduces the predicted residual correlation enough to be
consistent with the data. Our best-fit models with a Kroupa stellar IMF
over-produce the galaxy stellar mass function and predict the virial r-band
mass-to-light ratios, M_vir/L_r, systematically lower than those inferred from
galaxy-galaxy weak lensing and satellite dynamics. We investigate three
possible solutions to these problems: (1) ignoring the effects of adiabatic
contraction, (2) adopting a ``light'' stellar IMF, or (3) considering the lower
halo concentrations predicted for a low cosmological power spectrum
normalization. Any of these solutions yields acceptable residual correlations
and relieves most of the observational tension between the TF relation and the
galaxy stellar mass function (abridged).


title:
The Remarkable Stability of Probable Black Hole Low-Mass X-ray Binaries
  in Nearby Galaxies

abstract:
  The most luminous X-ray sources in nearby elliptical galaxies are likely
black hole low-mass X-ray binaries (BHLMXBs). In the Milky Way, such systems
are always transient, and with the exception of GRS1915+105 have burst
durations on the order of weeks or months. However, the low duty cycle of
short-duration outburst BHLMXBs makes it improbable that any one source would
be caught in an outburst during a single snapshot observation. Long-duration
outburst BHLMXBs, although much rarer, would be detectable in a series of
snapshot observations separated by several years. Our analysis of multi-epoch
Chandra observations of the giant elliptical galaxies NGC1399 and M87 separated
by 3.3 and 5.3 yr, respectively, finds that all 37 luminous (>8 x 10^38 ergs/s)
X-ray sources that were present in the first epoch observations were still in
outburst in all of the following observations. Many of these probable
long-duration outburst BHLMXBs reside within globular clusters of the galaxies.
Conversely, no definitive short-duration outburst BHLMXBs were detected in any
of the observations. This places an upper limit on the ratio of
short--to--long-duration outbursters that is slightly lower, but consistent
with what is seen in the Milky Way. The fact that none of the luminous sources
turned off between the first and last epochs places a 95 per cent lower limit
of 50 yr on the mean burst duration of the long-duration outburst sources. The
most likely scenario for the origin of these sources is that they are
long-period (>30 d) black hole binaries with a red giant donor, much like
GRS1915+105. However, unlike GRS1915+105, most of the sources show only modest
variability from epoch to epoch.


title: Phases of Swift X-ray Afterglows

abstract:
  The X-ray afterglows observed by Swift exhibit rich light-curves, with four
phases of different decay rate. The temporal and spectral properties for a set
of 47 bursts are used to identify the mechanisms which can explain these four
phases. The early, fast-decaying phase can be attributed to the same mechanism
which generated the burst emission (internal shocks in a relativistic outflow),
while the following phases of slower decay can be identified with synchrotron
emission from the forward shock sweeping the circumburst medium. Most likely,
the phase of slowest decay is due to a continuous energy injection in the
forward shock. That the optical power-law decay continues unabated after the
end of energy injection requires an ambient medium with a wind-like density
structure (n propto r^{-2}) and forward shock microphysical parameters that
change with the shock's Lorentz factor. A later break of the X-ray light-curve
can be attributed to a collimated outflow whose boundary becomes visible to the
observer (a jet) but the optical and X-ray decays are not always consistent
with the standard jet model expectations.


title:
Non-Equilibrium Ionization Model for Stellar Cluster Winds and its
  Application

abstract:
  We have developed a self-consistent physical model for super stellar cluster
winds based on combining a 1-D steady-state adiabatic wind solution and a
non-equilibrium ionization calculation. Comparing with the case of collisional
ionization equilibrium, we find that the non-equilibrium ionization effect is
significant in the regime of a high ratio of energy to mass input rate and
manifests in a stronger soft X-ray flux in the inner region of the star
cluster. Implementing the model in X-ray data analysis softwares (e.g., XSPEC)
directly facilitates comparisons with X-ray observations. Physical quantities
such as the mass and energy input rates of stellar winds can be estimated by
fitting observed X-ray spectra. The fitted parameters may then be compared with
independent measurements from other wavelengths. Applying our model to the star
cluster NGC 3603, we find that the wind accounts for no more than 50% of the
total "diffuse" emission, and the derived mass input rate and terminal velocity
are comparable to other empirical estimates. The remaining emission most likely
originate from numerous low-mass pre-main-sequence stellar objects.


title: Clustering of i-dropout galaxies at z=6 in GOODS and the UDF

abstract:
  We measured the angular clustering at z~6 from a large sample of i-dropout
galaxies (293 with z<27.5 from GOODS and 95 with z<29.0 from the UDF). Our
largest and most complete subsample (having L>0.5L*) shows the presence of
clustering at 94% significance. For this sample we derive a (co-moving)
correlation length of r_0=4.5^{+2.1}_{-3.2} h_{72}^{-1} Mpc and bias
b=4.1^{+1.5}_{-2.6}, using an accurate model for the redshift distribution. No
clustering could be detected in the much deeper but significantly smaller UDF,
yielding b<4.4 (1 sigma). We compare our findings to Lyman break galaxies at
z=3-5 at a fixed luminosity. Our best estimate of the bias parameter implies
that i-dropouts are hosted by dark matter halos having masses of ~10^11 M_sun,
similar to that of V-dropouts at z~5. We evaluate a recent claim that at z>5
star formation might have occurred more efficiently compared to that at z=3-4.
This may provide an explanation for the very mild evolution observed in the UV
luminosity density between z=6 and z=3. Although our results are consistent
with such a scenario, the errors are too large to find conclusive evidence for
this.


title:
No Expanding Fireball: Resolving the Recurrent Nova RS Ophiuchi with
  Infrared Interferometry

abstract:
  Following the recent outburst of the recurrent nova RS Oph on 2006 Feb 12, we
measured its near-infrared size using the IOTA, Keck, and PTI Interferometers
at multiple epochs. The characteristic size of ~3 milliarcseconds hardly
changed over the first 60 days of the outburst, ruling out currently-popular
models whereby the near-infrared emission arises from hot gas in the expanding
shock. The emission was also found to be significantly asymmetric, evidenced by
non-zero closure phases detected by IOTA. The physical interpretation of these
data depend strongly on the adopted distance to RS Oph. Our data can be
interpreted as the first direct detection of the underlying RS Oph binary,
lending support to the recent ``reborn red giant'' models of Hachisu & Kato.
However, this result hinges on an RS Oph distance of ~< 540 pc, in strong
disagreement with the widely-adopted distance of ~1.6 kpc. At the farther
distance, our observations imply instead the existence of a non-expanding,
dense and ionized circumbinary gaseous disk or reservoir responsible for the
bulk of the near-infrared emission. Longer-baseline infrared interferometry is
uniquely suited to distinguish between these models and to ultimately determine
the distance, binary orbit, and component masses for RS Oph, one of the
closest-known (candidate) SNIa progenitor systems.


title: Population Synthesis Models for Late Build-Up of the Red Sequence

abstract:
  We present population synthesis models designed to represent the star
formation histories of L* red sequence galaxies (RSGs). Earlier work has shown
that single-burst stellar populations (SSPs) are unable to match Balmer line
strengths simultaneously at high and low redshift. We therefore consider
alternative star formation histories in which RSGs contain intermediate-aged
stars even at late epochs. The models are compared to Balmer Hdelta absorption
strengths, U-B color data, and the number density of red sequence galaxies from
z=1 to z=0. We find that quenched models (which consist of constant star
formation histories truncated at regularly-spaced intervals) average to an RSG
population that matches the data well, showing slow evolution in color and
Balmer line strength and a rise in number density by a factor of a few after
z=1. The data are best fit by a turn-on of quenching at redshifts z=1.5-2.


title: Are Proxima and Alpha Centauri Gravitationally Bound?

abstract:
  Using the most recent kinematic and radial velocity data in the literature,
we calculate the binding energy of Proxima Centauri relative to the center of
mass of the Alpha Centauri system. When we adopt the centroids of the observed
data, we find that the three stars constitute a bound system, albeit with a
semi-major axis that is on order the same size as Alpha Centauri AB's Hill
radius in the galactic potential. We carry out a Monte Carlo simulation under
the assumption that the errors in the observed quantities are uncorrelated. In
this simulation, 44% of the trial systems are bound, and systems on the 1-3
sigma tail of the radial velocity distribution can have Proxima currently
located near the apastron position of its orbit. Our analysis shows that a
further, very significant improvement in the characterization of the system can
be gained by obtaining a more accurate measurement of the radial velocity of
Proxima Centauri.


title:
Near Ultraviolet sources in the Great Observatories Origins Deep Survey
  Fields

abstract:
  We present an Ultraviolet (UV) selected sample of 268 objects in the two
fields of the Great Observatories Origins Deep Survey (GOODS). We used the
parallel observations taken with WFPC2 in the U--band (F300W) which covered 88%
of the GOODS fields to identify sources and selected only objects with
GOODS/ACS counterparts. Spectroscopic redshifts for 95 of these sources are
available and we have used the multiwavelength GOODS data to estimate
photometric redshifts for the others. Most of the objects are between
0.2<z<0.8. We used the spectral types obtained by the photometric redshift
fitting to identify the starburst galaxies. We have also visually checked all
objects and looked for tidal effects and nearby companions. We find that (i)
45% of the UV-selected galaxies are starbursts, (ii) nearly 75% of the
starbursts have tidal tails or show some peculiarity typical of interactions or
mergers, (iii) ~50% have companions within an area of 5x5 arcsec. The
UV-selected sample has an average rest-frame M_B=--19.9 +- 0.1. The bluest
objects in the sample (U-B < 0.2 and B-V < 0.1) are at 1.1<z<1.9 and have
peculiar morphologies that resembles either tadpoles, chains, or double-clump
galaxies. Starbursts with tadpole or clump morphology at z=0.8-1.3 have sizes
comparable to LBGs and compact Ultraviolet-luminous galaxies (UVLGs).


title:
Coherent Active-Sterile Neutrino Flavor Transformation in the Early
  Universe

abstract:
  We solve the problem of coherent Mikheyev-Smirnov-Wolfenstein (MSW) resonant
active-to-sterile neutrino flavor conversion driven by an initial lepton number
in the early universe. We find incomplete destruction of lepton number in this
process and a sterile neutrino energy distribution with a distinctive cusp and
high energy tail. These features imply alteration of the non-zero lepton number
primordial nucleosynthesis paradigm when there exist sterile neutrinos with
rest masses ~ 1 eV. This could result in better light element probes of
(constraints on) these particles.


title: WMAP 3-year primordial power spectrum

abstract:
  We constrain the form of the primordial power spectrum using Wilkinson
Microwave Anisotropy Probe (WMAP) 3-year cosmic microwave background (CMB) data
(+ other high resolution CMB experiments) in addition to complementary
large-scale structure (LSS) data: 2dF, SDSS, Ly-alpha forest and luminous red
galaxy (LRG) data from the SDSS catalogue. We compute the comparative Bayesian
evidence in addition to parameter estimates for a collection of seven models:
(i) a scale invariant Harrison-Zel'dovich (H-Z) spectrum; (ii) a power-law;
(iii) a running spectral index; (iv) a broken spectrum; (v) a power-law with an
abrupt cutoff on large-scales; (vi) a reconstruction of the spectrum in eight
bins in wavenumber; and (vii) a spectrum resulting from a cosmological model
proposed by Lasenby & Doran (L-D). Using a basic dataset of WMAP3 + other CMB +
2dF + SDSS our analysis confirms that a scale-invariant spectrum is disfavoured
by between 0.7 and 1.7 units of log evidence (depending on priors chosen) when
compared with a power-law tilt. Moreover a running spectrum is now
significantly preferred, but only when using the most constraining set of
priors. The addition of Ly-alpha and LRG data independently both suggest much
lower values of the running index than with basic dataset alone and
interestingly the inclusion of Ly-alpha significantly disfavours a running
parameterisation by more than a unit in log evidence. Overall the highest
evidences, over all datasets, were obtained with a power law spectrum
containing a cutoff with a significant log evidence difference of roughly 2
units. The natural tilt and exponential cutoff present in the L-D spectrum is
found to be favoured decisively by a log evidence difference of over 5 units,
but only for a limited study within the best-fit concordance cosmology.


title: Spitzer Observations of Nearby M Dwarfs

abstract:
  We present Spitzer IRAC and MIPS observations for a sample of eight M dwarfs:
six dMe, one dM, and one sdMe star. All of our targets are found to have SEDs
which are fitted within the error bars by a purely photospheric spectrum out to
24 micron. We find no evidence for IR excess. None of our targets is detected
in the MIPS 70 and 160 micron bands. The estimated ages for all are >10 Myr,
suggesting that enough disk dissipation has occurred within the inner several
AU of the star. For four of these, Mullan et al. (1989) had reported IRAS
detections at 12 micron, although the reported fluxes were below the 5-sigma
IRAS detection limit (~0.2 Jy). Mullan et al. also pointed out that V-K colors
in dMe stars are larger than those in dM stars, possibly because of the
presence of a chromosphere. Here we suggest that metallicity effects provide a
better explanation of the V-K data.
  For reasons of observational selection, our targets are not the most active
flare stars known, but being dMe stars indicates the presence of a
chromosphere. Scaling from Houdebine's model of the AU Mic chromosphere, we
have computed the free-free infrared excesses for a range of densities. Our
Spitzer 24 micron data shows that the chromospheres in two of our targets are
less dense than in AU Mic by a factor of 10 or more. This is consistent with
the fact that our sample includes the less active flare stars. Our models also
indicate that the chromospheric contribution to the observed AU Mic emission at
submillimeter wavelengths is only about 2%.


title:
Pupil plane optimization for single-mode multiaxial optical
  interferometry with a large number of telescopes

abstract:
  Incoming optical interferometers will allow spectro-imaging at high angular
resolution. Non-homothetic Fizeau concept combines good sensitivity and high
spectral resolution capabilities. However, one critical issue is the design of
the beam recombination scheme, at the heart of the instrument. We tackle the
possibility of reducing the number of pixels that are coding the fringes by
compressing the pupil plane. Shrinking the number of pixels -- which
drastically increases with the number of recombined telescopes -- is indeed a
key issue that enables to reach higher limiting magnitude, but also allows to
lower the required spectral resolution and fasten the fringes reading process.
By means of numerical simulations, we study the performances of existing
estimators of the visibility with respect to the compression process. We show
that, not only the model based estimator lead to better signal to noise ratio
(SNR) performances than the Fourier ones, but above all it is the only one
which prevent from introducing baseline mixing biases in the visibilities as
the pupil plane compression rate increases. Furthermore, we show that moderate
compression allows to keep the visibilities SNR unaffected. In the light of
these conclusions, we propose an optimized pupil arrangements for 6 and 8 beam
recombiners.


title:
Evolution of Galaxy Luminosity Function and Luminosity Function by
  Density Environment at 0.03<z<0.5

abstract:
  Using galaxy sample observed by the BATC large-field multi-color sky survey
and galaxy data of SDSS in the overlapped fields, we study the dependence of
the restframe $r$-band galaxy luminosity function on redshift and on
large-scale environment. The large-scale environment is defined by isodensity
contour with density contrast \delta\rho/\rho. The data set is a composite
sample of 69,671 galaxies with redshifts 0.03 < z < 0.5 and r < 21.5 mag. The
redshifts are composed by three parts: 1) spectroscopic redshifts in SDSS for
local and most luminous galaxies; 2) 20-color photometric redshifts derived
from BATC and SDSS; 3) 5-color photometric redshifts in SDSS. We find that the
faint-end slope \alpha steepens slightly from -1.21 at z ~ 0.06 to -1.35 at z ~
0.4, which is the natural consequence of the hierarchical formation of
galaxies. The luminosity function also differs with different environments. The
value of \alpha changes from -1.21 at underdense regions to -1.37 at overdense
regions and the corresponding M* brightens from -22.26 to -22.64. This suggests
that the fraction of faint galaxies is larger in high density regions than in
low density regions.


title:
The Distance to the Galactic Center Derived From Infrared Photometry of
  Bulge Red Clump Stars

abstract:
  On the basis of the near infrared observations of bulge red clump stars near
the Galactic center, we have determined the galactocentric distance to be R_0 =
7.52 +- 0.10 (stat) +- 0.35 (sys) kpc. We observed the red clump stars at |l| <
1.0 deg and 0.7 deg < |b| < 1.0 deg with the IRSF 1.4 m telescope and the
SIRIUS camera in the H and Ks bands. After extinction and population
corrections, we obtained (m - M)_0 = 14.38 +- 0.03 (stat) +- 0.10 (sys). The
statistical error is dominated by the uncertainty of the intrinsic local red
clump stars' luminosity. The systematic error is estimated to be +- 0.10
including uncertainties in extinction and population correction, zero-point of
photometry, and the fitting of the luminosity function of the red clump stars.
Our result, R_0 = 7.52 kpc, is in excellent agreement with the distance
determined geometrically with the star orbiting the massive black hole in the
Galactic center. The recent result based on the spatial distribution of
globular clusters is also consistent with our result. In addition, our study
exhibits that the distance determination to the Galactic center with the red
clump stars, even if the error of the population correction is taken into
account, can achieve an uncertainty of about 5%, which is almost the same level
as that in recent geometrical determinations.


title:
Early structure formation in quintessence models and its implications
  for cosmic reionisation from first stars

abstract:
  We present the first hydrodynamic N-body simulations of primordial gas clouds
responsible for the reionisation process in dark energy cosmologies. We compare
the cosmological constant scenario with a SUGRA quintessence model with marked
dynamics in order to highlight effects due to the different acceleration
histories imposed by the dark energy. We show that both the number density of
gas clouds and their clumpiness keep a record of the expansion rate during
evolution, similar to the non-linear dark matter profile at virialisation, as
was recently demonstrated by Dolag et al. (2004). Varying the shape of the
primordial power spectrum, we show how this effect is mitigated by a running
spectral index decreasing the power at small scales. Our results demonstrate
that, in order to constrain the dark energy from large scale structures, one
must track its effects down to the distribution of luminous matter.


title:
The optical to gamma-ray emission of the Crab pulsar: a multicomponent
  model

abstract:
  We present a multicomponent model to explain the features of the pulsed
emission and spectrum of the Crab Pulsar, on the basis of X and gamma-ray
observations obtained with BeppoSAX, INTEGRAL and CGRO. This model explains the
evolution of the pulse shape and of the phase-resolved spectra, ranging from
the optical/UV to the GeV energy band, on the assumption that the observed
emission is due to more components. The first component, C_O, is assumed to
have the pulsed double-peaked profile observed at the optical frequencies,
while the second component, C_X, is dominant in the interpeak and second peak
phase regions. The spectra of these components are modelled with log-parabolic
laws and their spectral energy distributions have peak energies at 12.2 and 178
keV, respectively. To explain the properties of the pulsed emission in the
MeV-GeV band, we introduce two more components, C_Ogamma and C_Xgamma, with
phase distributions similar to those of C_O and C_X and log-parabolic spectra
with the same curvature but peak energies at about 300 MeV and 2 GeV. This
multicomponent model is able to reproduce both the broadband phase-resolved
spectral behaviour and the changes of the pulse shape with energy. We also
propose some possible physical interpretations in which C_O and C_X are emitted
by secondary pairs via a synchrotron mechanism while C_Ogamma and C_Xgamma can
originate either from Compton scattered or primary curvature photons.


title: Modifying gravity with the Aether: an alternative to Dark Matter

abstract:
  There is evidence that Newton and Einstein's theories of gravity cannot
explain the dynamics of a universe made up solely of baryons and radiation. To
be able to understand the properties of galaxies, clusters of galaxies and the
universe on the whole it has become commonplace to invoke the presence of dark
matter. An alternative approach is to modify the gravitational field equations
to accommodate observations. We propose a new class of gravitational theories
in which we add a new degree of freedom, the Aether, in the form of a vector
field that is coupled covariantly, but non-minimally, with the space-time
metric. We explore the Newtonian and non-Newtonian limits, discuss the
conditions for these theories to be consistent and explore their effect on
cosmology.


title: Dielectronic recombination of Fe^{13+}: benchmarking the M-shell

abstract:
  We have carried-out a series of multi-configuration Breit-Pauli AUTOSTRUCTURE
calculations for the dielectronic recombination of Fe^{13+}. We present a
detailed comparison of the results with the high-energy resolution measurements
reported recently from the Heidelberg Test Storage Ring by Schmidt et al. Many
Rydberg series contribute significantly from this initial 3s^2 3p M-shell ion,
resulting in a complex recombination `spectrum'. While there is much close
agreement between theory and experiment, differences of typically 50% in the
summed resonance strengths over 0.1-10 eV result in the experimentally based
total Maxwellian recombination rate coefficient being a factor of 1.52-1.38
larger than theory over 10^4-10^5 K, which is a typical temperature range of
peak abundance for Fe^{13+} in a photoionized plasma. Nevertheless, this
theoretical recombination rate coefficient is an order of magnitude larger than
that used by modellers to-date. This may help explain the discrepancy between
the iron M-shell ionization balance predicted by photoionization modelling
codes such as ION and CLOUDY and that deduced from the iron M-shell
unresolved-transition-array absorption feature observed in the X-ray spectrum
of many active galactic nuclei. Similar data are required for Fe^{8+} through
Fe^{12+} to remove the question mark hanging over the atomic data though.


title: Dipole Straylight Contamination and Low Multipoles

abstract:
  Kinematic dipole signal originates from the motion of the Sun with respect to
the CMB rest frame. It is a remarkable signal, two orders of magnitude larger
than the observed pattern of CMB anisotropies. Therefore the dipole subtraction
from the main beam is of primary importance. But what happens to the dipole
signal entering the main spillover (i.e. the most relevant far antenna pattern
feature, responsible for the bulk of the straylight effect)? We present here an
analytical and statistical study of this systematic effect for a spinning
space-mission like {\sc Planck}.


title:
A RIAF Interpretation for the Past Higher Activity of the Galactic
  Center Black Hole and the 511 keV Annihilation Emission

abstract:
  There are several lines of evidence that the super-massive black hole at the
Galactic center had higher activities in the past than directly observed at
present. Here I show that these lines of evidence can quantitatively and
consistently be explained if the mean accretion rate during the past ~10^7 yrs
has been ~10^{3-4} times higher than the current rate, by the picture of
radiatively inefficient accretion flow (RIAF) and associated outflow that has
been successfully applied to Sgr A*. I argue that this increased rate and its
duration are theoretically reasonable in the Galactic center environment, while
the accretion rate suddenly dropped about 300 years ago most likely because of
the shell passage of the supernova remnant Sgr A East. The chance probability
of witnessing Sgr A* in such a low state is not extremely small (~0.5%). The
outflow energetics is sufficient to keep the hot (~8 keV) diffuse gas observed
in the Galactic center region. Then, I show that a significant amount of
positrons should have been created around the event horizon during the higher
activity phase, and injected into interstellar medium by the outflow. The
predicted positron production rate and propagation distance are close to those
required to explain the observed 511 keV annihilation line emission from the
Galactic bulge, giving a natural explanation for the large bulge-to-disk ratio
of the emission. The expected injection energy into interstellar medium is
about 1 MeV, which is also favorable as an explanation of the 511 keV line
emission.


title:
Photon-axion conversion in intergalactic magnetic fields and
  cosmological consequences

abstract:
  Photon-axion conversion induced by intergalactic magnetic fields causes an
apparent dimming of distant sources, notably of cosmic standard candles such as
supernovae of type Ia (SNe Ia). We review the impact of this mechanism on the
luminosity-redshift relation of SNe Ia, on the dispersion of quasar spectra,
and on the spectrum of the cosmic microwave background. The original idea of
explaining the apparent dimming of distant SNe Ia without cosmic acceleration
is strongly constrained by these arguments. However, the cosmic equation of
state extracted from the SN Ia luminosity-redshift relation remains sensitive
to this mechanism. For example, it can mimic phantom energy.


title:
A Spitzer Study of Comets 2P/Encke, 67P/Churyumov-Gerasimenko, and
  C/2001 HT50 (LINEAR-NEAT)

abstract:
  We present infrared images and spectra of comets 2P/Encke,
67P/Churyumov-Gerasimenko, and C/2001 HT50 (LINEAR-NEAT) as part of a larger
program to observe comets inside of 5 AU from the sun with the Spitzer Space
Telescope. The nucleus of comet 2P/Encke was observed at two vastly different
phase angles (20 degrees and 63 degrees). Model fits to the spectral energy
distributions of the nucleus suggest comet Encke's infrared beaming parameter
derived from the near-Earth asteroid thermal model may have a phase angle
dependence. The observed emission from comet Encke's dust coma is best-modeled
using predominately amorphous carbon grains with a grain size distribution that
peaks near 0.4 microns, and the silicate contribution by mass to the sub-micron
dust coma is constrained to 31%. Comet 67P/Churyumov-Gerasimenko was observed
with distinct coma emission in excess of a model nucleus at a heliocentric
distance of 5.0 AU. The coma detection suggests that sublimation processes are
still active or grains from recent activity remain near the nucleus. Comet
C/2001 HT50 (LINEAR-NEAT) showed evidence for crystalline silicates in the
spectrum obtained at 3.2 AU and we derive a silicate-to-carbon dust ratio of
0.6. The ratio is an order of magnitude lower than that derived for comets
9P/Tempel 1 during the Deep Impact encounter and C/1995 O1 (Hale-Bopp).


title:
Velocity Shear of the Thick Disk from SPM3 Proper Motions at the South
  Galactic Pole

abstract:
  The kinematical properties of the Galactic Thick Disk are studied using
absolute proper motions from the SPM3 Catalog and 2MASS near-infrared
photometry for a sample of ~1200 red giants in the direction of the South
Galactic Pole. The photometrically-selected sample is dominated by Thick Disk
stars, as indicated by the number-density distribution that varies with
distance from the Galactic plane as a single-valued exponential over the range
1<z<4 kpc. The inferred scale height of the Thick Disk is 0.783 +/- 0.048 kpc.
The kinematics of the sample are also consistent with disk-like motion. The
U-velocity component is roughly constant, reflecting the Sun's peculiar motion,
while a considerable shear is seen in the mean rotational velocity, V. The
V-velocity profile's dependence on z is linear, with a gradient of dV/dz = -30
+/- 3 km/s/kpc. The velocity dispersions, in both U and V, show a lesser
gradient of about 9 +/- 3 km/s/kpc. We demonstrate that the derived velocity
and velocity-dispersion profiles are consistent with the assumptions of
dynamical equilibrium and reasonable models of the overall Galactic potential.


title:
Inhomogeneous surface distribution of chemical elements in the eclipsing
  binary AR Aur: A new challenge for our understanding of HgMn stars

abstract:
  We present the results of a high spectral resolution study of the eclipsing
binary AR Aur. AR Aur is the only known eclipsing binary with a HgMn primary
star exactly on the ZAMS and a secondary star still contracting towards the
ZAMS. We detect for the first time in the spectra of the primary star that for
many elements the line profiles are variable over the rotation period. The
strongest profile variations are found for the elements Pt, Hg, Sr, Y, Zr, He
and Nd, while the line profiles of O, Na, Mg, Si, Ca, Ti, and Fe show only weak
distortions over the rotation period. The slight variability of He and Y is
also confirmed by the study of high resolution spectra of another HgMn star:
alpha And. A preliminary modelling of the inhomogeneous distribution has been
carried out for Sr and Y. Our analysis shows that these elements are very
likely concentrated in a fractured ring along the rotational equator. It may be
an essential clue for the explanation of the origin of the chemical anomalies
in HgMn stars (which are very frequently found in binary and multiple systems)
that one large fraction of the ring is missing exactly on the surface area
which is permanently facing the secondary, and another small one on the almost
opposite side. The results presented about the inhomogeneous distribution of
various chemical elements over the stellar surface of the primary suggest new
directions for investigations to solve the question of the origin of abundance
anomalies in B-type stars with HgMn peculiarity.


title:
Multicomponent radiatively driven stellar winds IV. On the helium
  decoupling in the wind of sigma Ori E

abstract:
  We study the possibility of the helium decoupling in the stellar wind of
sigma Ori E. To obtain reliable wind parameters for this star we first
calculate an NLTE wind model and derive wind mass-loss rate and terminal
velocity. Using corresponding force multipliers we study the possibility of
helium decoupling. We find that helium decoupling is not possible for realistic
values of helium charge (calculated from NLTE wind models). Helium decoupling
seems only possible for a very low helium charge. The reason for this behaviour
is the strong coupling between helium and hydrogen. We also find that
frictional heating becomes important in the outer parts of the wind of sigma
Ori E due to the collisions between some heavier elements and the passive
components -- hydrogen and helium. For a metallicity ten times lower than the
solar one both hydrogen and helium decouple from the metals and may fall back
onto the stellar surface. However, this does not explain the observed chemical
peculiarity since both these components decouple together from the absorbing
ions. Although we do not include the effects of the magnetic field into our
models, we argue that the presence of a magnetic field will likely not
significantly modify the derived results because in such case model equations
describe the motion parallel to the magnetic field.


title:
The energy dependence of burst oscillations from the accreting
  millisecond pulsar XTE J1814-338

abstract:
  The nature of the asymmetry that gives rise to Type I X-ray burst
oscillations on accreting neutron stars remains a matter of debate. Of
particular interest is whether the burst oscillation mechanism differs between
the bursting millisecond pulsars and the non-pulsing systems. One means to
diagnose this is to study the energy dependence of the burst oscillations: here
we present an analysis of oscillations from 28 bursts observed during the 2003
outburst of the accreting millisecond pulsar XTE J1814-338. We find that the
fractional amplitude of the burst oscillations falls with energy, in contrast
to the behaviour found by Muno et al. (2003) in the burst oscillations from a
set of non-pulsing systems. The drop with energy mirrors that seen in the
accretion-powered pulsations; in this respect XTE J1814-338 behaves like the
other accreting millisecond pulsars. The burst oscillations show no evidence
for either hard or soft lags, in contrast to the persistent pulsations, which
show soft lags of up to 50 $\mu$s. The fall in amplitude with energy is
inconsistent with current surface mode and simple hot spot models of burst
oscillations. We discuss improvements to the models and uncertainties in the
physics that might resolve these issues.


title: On the current status of open-cluster parameters

abstract:
  We aim to characterize the current status of knowledge on the accuracy of
open-cluster parameters such as the age, reddening and distance. These
astrophysical quantities are often used to study the global characteristics of
the Milky Way down to very local stellar phenomena. In general, the errors of
these quantities are neglected or set to some kind of heuristic standard value.
We attempt to give some realistic estimates for the accuracy of available
cluster parameters by using the independent derived values published in the
literature. In total, 6437 individual estimates for 395 open clusters were used
in our statistical analysis. We discuss the error sources depending on
theoretical as well as observational methods and compare our results with those
parameters listed in the widely used catalogue by Dias et al. (2002). In
addition, we establish a list of 72 open clusters with the most accurate known
parameters which should serve as a standard table in the future for testing
isochrones and stellar models.


title: From progenitor to afterlife

abstract:
  The sequence of massive star supernova types IIP (plateau light curve), IIL
(linear light curve), IIb, IIn (narrow line), Ib, and Ic roughly represents a
sequence of increasing mass loss during the stellar evolution. The mass loss
affects the velocity distribution of the ejecta composition; in particular,
only the IIP's typically end up with H moving at low velocity. Radio and X-ray
observations of extragalactic supernovae show varying mass loss properties that
are in line with expectations for the progenitor stars. For young supernova
remnants, pulsar wind nebulae and circumstellar interaction provide probes of
the inner ejecta and higher velocity ejecta, respectively. Among the young
remnants, there is evidence for supernovae over a range of types, including
those that exploded with much of the H envelope present (Crab Nebula, 3C 58,
0540--69) and those that exploded after having lost most of their H envelope
(Cas A, G292.0+1.8).


title: Broken Isotropy from a Linear Modulation of the Primordial Perturbations

abstract:
  A linear modulation of the primordial perturbations is proposed as an
explanation for the observed asymmetry between the northern and southern
hemispheres of the Wilkinson Microwave Anisotropy Probe (WMAP) data. A cut sky,
reduced resolution third year "Internal Linear Combination" (ILC) map was used
to estimate the modulation parameters. A foreground template and a modulated
plus unmodulated monopole and dipole were projected out of the likelihood. The
effective chi squared is reduced by nine for three extra parameters. The mean
Galactic colatitude and longitude, of the modulation, with 68%, 95% and 99.7%
confidence intervals were 56^{+17 +36 +65}_{-17 -35 -51} and 63^{+28 +59
+105}_{-26 -58 -213}. The mean percentage change of the variance, across the
pole's of the modulation, was 62^{+18 +35 +57}_{-18 -35 -47}. Implications of
these results and possible generating mechanisms are discussed.


title: Black Hole Growth in Hierarchical Galaxy Formation

abstract:
  We incorporate a model for black hole growth during galaxy mergers into the
semi-analytical galaxy formation model based on Lambda-CDM proposed by Baugh et
al. (2005). Our black hole model has one free parameter, which we set by
matching the observed zeropoint of the local correlation between black hole
mass and bulge luminosity. We present predictions for the evolution with
redshift of the relationships between black hole mass and bulge properties. Our
simulations reproduce the evolution of the optical luminosity function of
quasars. We study the demographics of the black hole population and address the
issue of how black holes acquire their mass. We find that the direct accretion
of cold gas during starbursts is an important growth mechanism for lower mass
black holes and at high redshift. On the other hand, the re-assembly of
pre-existing black hole mass into larger units via merging dominates the growth
of more massive black holes at low redshift. This prediction could be tested by
future gravitational wave experiments. As redshift decreases, progressively
less massive black holes have the highest fractional growth rates, in line with
recent claims of "downsizing" in quasar activity.


title: XMM-LSS discovery of a z=1.22 galaxy cluster

abstract:
  We present details of the discovery of XLSSJ022303.0-043622, a z=1.2 cluster
of galaxies. This cluster was identified from its X-ray properties and selected
as a z>1 candidate from its optical/near-IR characteristics in the XMM
Large-Scale Structure Survey (XMM-LSS). It is the most distant system
discovered in the survey to date. We present ground-based optical and near IR
observations of the system carried out as part of the XMM-LSS survey. The
cluster has a bolometric X-ray luminosity of 1.1 +/- 0.7 x 10^44 erg/s, fainter
than most other known z>1 X-ray selected clusters. In the optical it has a
remarkably compact core, with at least a dozen galaxies inside a 125 kpc radius
circle centred on the X-ray position. Most of the galaxies within the core, and
those spectroscopically confirmed to be cluster members, have stellar masses
similar to those of massive cluster galaxies at low redshift. They have colours
comparable to those of galaxies in other z>1 clusters, consistent with showing
little sign of strong ongoing star formation. The bulk of the star formation
within the galaxies appears to have ceased at least 1.5 Gyr before the observed
epoch. Our results are consistent with massive cluster galaxies forming at z>1
and passively evolving thereafter. We also show that the system is
straightforwardly identified in Spitzer/IRAC 3.6 and 4.5 micron data obtained
by the SWIRE survey emphasising the power and utility of joint XMM and Spitzer
searches for the most distant clusters.


title: Current Status Of Velocity Field Surveys: A Consistency Check

abstract:
  We present an analysis comparing the bulk--flow measurements for six recent
peculiar velocity surveys, namely, ENEAR, SFI, RFGC, SBF and the Mark III
singles and group catalogs. We study whether the direction of the bulk--flow
estimates are consistent with each other and construct the full three
dimensional bulk--flow vectors for each survey. We show that although the
surveys differ in their geometry, galaxy morphologies, distance measures and
measurement errors, their bulk flow vectors are expected to be highly
correlated and in fact show impressive agreement in all cases. We found a
combined weighted mean bulk motion of 330 km s$^{-1}$ $\pm 101$ km s$^{-1}$
toward $l= 234^{\degree}\pm 11^{\degree}$ and $b=12^{\degree}\pm 9^{\degree}$
in a sphere with an effective depth of $\sim4000$ km s$^{-1}$.


title: Astrophysical implications of high energy neutrino limits

abstract:
  Second generation high energy neutrino telescopes are being built to reach
sensitivities of neutrino emission from galactic and extragalactic sources.
Current neutrino detectors are already able to set limits which are in the
range of some emission models. In particular, the Antarctic Muon And Neutrino
Detection Array (AMANDA) has recently presented the so far most restrictive
limit on diffuse neutrino emission (Achterberg et al. 2007). Stacking limits
which apply to AGN point source classes rather than to single point sources
(Achterberg et al. (IceCube Collab.) & P. L. Biermann 2006) are given as well.
In this paper, the two different types of limits will be used to draw
conclusions about different emission models. An interpretation of stacking
limits as diffuse limits to the emission from considered point source class is
presented. The limits can for instance be used to constrain the predicted
correlation of EGRET-detected diffuse emission and neutrino emission. Also, the
correlation between X-ray and neutrino emission is constrained. Further results
for source classes like TeV blazars and FR-II galaxies are presented. Starting
from the source catalogs so-far examined for the stacking method, we discuss
further potential catalogs and examine the possibilities of the second
generation telescopes IceCube and KM3NeT by comparing catalogs with respect to
northern and southern hemisphere total flux.


title:
Molecular line intensities as measures of cloud masses - I. Sensitivity
  of CO emissions to physical parameter variations

abstract:
  A reliable estimate of the molecular gas content in galaxies plays a crucial
role in determining their dynamical and star-forming properties. However, H2,
the dominant molecular species, is difficult to observe directly, particularly
in the regions where most molecular gas is thought to reside. Its mass is
therefore commonly inferred by assuming a direct proportionality with the
integrated intensity of the CO(J=1-0) emission line, using a CO-to-H2
conversion factor, X. Although a canonical value for X is used extensively in
such estimates, there is increasing evidence, both theoretical and
observational, that the conversion factor may vary by over an order of
magnitude under conditions different to those of the local neighbourhood. In an
effort to understand the influence of changing environmental conditions on the
conversion factor, we derive theoretical estimates of X for a wide range of
physical parameters using a photon-dominated region (PDR) time-dependent
chemical model, benchmarking key results against those of an independent PDR
code to ensure reliability. Based on these results, the sensitivity of the X
factor to change in each physical parameter is interpreted in terms of the
chemistry and physical processes within the cloud. In addition to confirming
previous observationally derived trends, we find that the time-dependence of
the chemistry, often neglected in such models, has a considerable influence on
the value of the conversion factor.