title:
Multifrequency variability of the blazar AO 0235+164. The WEBT campaign
  in 2004-2005 and long-term SED analysis

abstract:
  A huge multiwavelength campaign targeting the blazar AO 0235+164 was
organized by the Whole Earth Blazar Telescope (WEBT) in 2003-2005 to study the
variability properties of the source. Monitoring observations were carried out
at cm and mm wavelengths, and in the near-IR and optical bands, while three
pointings by the XMM-Newton satellite provided information on the X-ray and UV
emission. We present the data acquired during the second observing season,
2004-2005, by 27 radio-to-optical telescopes. They reveal an increased near-IR
and optical activity with respect to the previous season. Increased variability
is also found at the higher radio frequencies, down to 15 GHz, but not at the
lower ones. The radio (and optical) outburst predicted to peak around
February-March 2004 on the basis of the previously observed 5-6 yr
quasi-periodicity did not occur. The analysis of the optical light curves
reveals now a longer characteristic time scale of 8 yr, which is also present
in the radio data. The spectral energy distributions corresponding to the
XMM-Newton observations performed during the WEBT campaign are compared with
those pertaining to previous pointings of X-ray satellites. Bright, soft X-ray
spectra can be described in terms of an extra component, which appears also
when the source is faint through a hard UV spectrum and a curvature of the
X-ray spectrum. Finally, there might be a correlation between the X-ray and
optical bright states with a long time delay of about 5 yr, which would require
a geometrical interpretation.


title:
Accretion states and radio loudness in Active Galactic Nuclei: analogies
  with X-ray binaries

abstract:
  Hardness-intensity diagrams (HIDs) have been used with great success to study
the accretion states and their connection to radio jets in X-ray binaries
(XRBs). The analogy between XRBs and active galactic nuclei (AGN) suggests that
similar diagrams may help to understand and identify accretion states in AGN
and their connection to radio loudness. We construct ``disc-fraction luminosity
diagrams'' (DFLDs) as a generalization of HIDs, which plot the intensity
against the fraction of the disc contribution in the overall spectral energy
distribution (SED). Using a sample of 4963 Sloan Digital Sky Survey (SDSS)
quasars with ROSAT matches, we show empirically that an AGN is more likely to
have a high radio:optical flux ratio when it has a high total luminosity or a
large non-thermal contribution to the SED. We find that one has to consider at
least two-dimensional diagrams to understand the radio loudness of AGN. To
extend our DFLD to lower luminosities we also include a sample of
low-luminosity AGN. Using a simulated population of XRBs we show that stellar
and supermassive BHs populate similar regions in the DFLD and show similar
radio/jet properties. This supports the idea the AGN and XRBs have the same
accretion states and associated jet properties.


title: Sensitive VLBI Studies of the OH Megamaser Emission from IRAS 17208-0014

abstract:
  We present phase-referenced VLBI results on the radio continuum and the OH 18
cm megamaser emission from the Ultra-Luminous Infrared Galaxy, IRAS
17208--0014. The observations were carried out at 1599 MHz using the Very Long
Baseline Array, the phased VLA, and the Green Bank Telescope. The highest
resolution radio continuum results show several compact sources with brightness
temperatures on the order of $10^{6}$ K. These sources are more likely to be
clustered supernova remnants and/or luminous radio supernovae. However, the
agreement between the number of observed and expected compact sources above the
5 $\sigma$ level supports the possibility that each one of the compact sources
could be dominated by a recently detonated luminous radio supernova. The
continuum results suggest that there is no radio-loud AGN in the nuclear region
of this galaxy. The OH 18 cm megamaser emission in IRAS 17208--0014 is detected
at various angular resolutions. It has an extent of $170 \times 110$ pc, and is
mostly localized in two regions separated by 61 pc. The structure and dynamics
of the maser emission seem to be consistent with a clumpy, rotating, ring-like
geometry, with the two dominant maser regions marking the tangential points of
the proposed rotating-ring distribution. Assuming Keplerian motion for the
rotating maser ring, the enclosed dynamical mass and the mass density within a
radius of 30.5 pc, are about {$3 \times 10^7 ({\rm sin}^{-2}i) M{_\odot}$}, and
$281 ({\rm sin}^{-2} i) M{_\odot} {\rm pc}^{-3}$, respectively.


title:
Spitzer/MIPS 24 micron Detection of Photoevaporating Protoplanetary
  Disks

abstract:
  We present 24 micron images of three protoplanetary disks being
photoevaporated around high mass O type stars. These objects have ``cometary''
structure where the dust pulled away from the disk by the photoevaporating flow
is forced away from the O star by photon pressure on the dust and heating and
ionization of the gas. Models of the 24 micron and 8 micron brightness profiles
agree with this hypothesis. These models show that the mass-loss rate needed to
sustain such a configuration is in agreement with or somewhat less than the
theoretical predictions for the photoevaporation process.


title: Dark Energy and Some Alternatives: a Brief Overview

abstract:
  The high-quality cosmological data, which became available in the last
decade, have thrusted upon us a rather preposterous composition for the
universe which poses one of the greatest challenges theoretical physics has
ever faced: the so-called dark energy. By focusing our attention on specific
examples of dark energy scenarios, we discuss three different candidates for
this dark component, namely, a decaying vacuum energy or time-varying
cosmological constant [$\Lambda(t)$], a rolling homogeneous quintessence field
($\Phi$), and modifications in gravity due to extra spatial dimensions. As
discussed, all these candidates [along with the vacuum energy or cosmological
constant ($\Lambda$)] seem somewhat to be able to explain the current
observational results, which hampers any definitive conclusion on the actual
nature of the dark energy.


title: Cosmological Constraints from the SDSS Luminous Red Galaxies

abstract:
  We measure the large-scale real-space power spectrum P(k) using luminous red
galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS) and use this measurement
to sharpen constraints on cosmological parameters from the Wilkinson Microwave
Anisotropy Probe (WMAP). We employ a matrix-based power spectrum estimation
method using Pseudo-Karhunen-Loeve eigenmodes, producing uncorrelated
minimum-variance measurements in 20 k-bands of both the clustering power and
its anisotropy due to redshift-space distortions, with narrow and well-behaved
window functions in the range 0.01h/Mpc < k < 0.2h/Mpc. Results from the LRG
and main galaxy samples are consistent, with the former providing higher
signal-to-noise. Our results are robust to omitting angular and radial density
fluctuations and are consistent between different parts of the sky. They
provide a striking confirmation of the predicted large-scale LCDM power
spectrum.
  Combining only SDSS LRG and WMAP data places robust constraints on many
cosmological parameters that complement prior analyses of multiple data sets.
The LRGs provide independent cross-checks on Om and the baryon fraction in good
agreement with WMAP. Within the context of flat LCDM models, our LRG
measurements complement WMAP by sharpening the constraints on the matter
density, the neutrino density and the tensor amplitude by about a factor of
two, giving Omega_m=0.24+-0.02 (1 sigma), sum m_nu < 0.9 eV (95%) and r<0.3
(95%). Baryon oscillations are clearly detected and provide a robust
measurement of the comoving distance to the median survey redshift z=0.35
independent of curvature and dark energy properties. Within the LCDM framework,
our power spectrum measurement improves the evidence for spatial flatness,
sharpening the curvature constraint Omega_tot=1.05+-0.05 from WMAP alone to
Omega_tot=1.003+-0.010. Assuming Omega_tot=1, the equation of state parameter
is constrained to w=-0.94+-0.09, indicating the potential for more ambitious
future LRG measurements to provide precision tests of the nature of dark
energy. All these constraints are essentially independent of scales k>0.1h/Mpc
and associated nonlinear complications, yet agree well with more aggressive
published analyses where nonlinear modeling is crucial.


title: The Weak Clustering of Gas-Rich Galaxies

abstract:
  We examine the clustering properties of HI-selected galaxies through an
analysis of the HI Parkes All-Sky Survey Catalogue (HICAT) two-point
correlation function. Various sub-samples are extracted from this catalogue to
study the overall clustering of HI-rich galaxies and its dependence on
luminosity, HI gas mass and rotational velocity. These samples cover the entire
southern sky Dec < 0 deg, containing up to 4,174 galaxies over the radial
velocity range 300-12,700 km/s. A scale length of r_0 = 3.45 +/- 0.25 Mpc/h and
slope of gamma = 1.47 +/- 0.08 is obtained for the HI-rich galaxy real-space
correlation function, making gas-rich galaxies among the most weakly clustered
objects known. HI-selected galaxies also exhibit weaker clustering than
optically selected galaxies of comparable luminosities. Good agreement is found
between our results and those of synthetic HI-rich galaxy catalogues generated
from the Millennium Run CDM simulation. Bisecting HICAT using different
parameter cuts, clustering is found to depend most strongly on rotational
velocity and luminosity, while the dependency on HI mass is marginal. Splitting
the sample around v_rot = 108 km/s, a scale length of r_0 = 2.86 +/- 0.46 Mpc/h
is found for galaxies with low rotational velocities compared to r_0 = 3.96 +/-
0.33 Mpc/h for the high rotational velocity sample.


title: Baryonic Pinching of Galactic Dark Matter Halos

abstract:
  High resolution cosmological N-body simulations of four galaxy-scale dark
matter halos are compared to corresponding N-body/hydrodynamical simulations
containing dark matter, stars and gas. The simulations without baryons share
features with others described in the literature in that the dark matter
density slope continuously decreases towards the center, with a density
\rho~r^{-1.3+/-0.2}, at about 1% of the virial radius for our Milky Way sized
galaxies. The central cusps in the simulations which also contain baryons
steepen significantly, to \rho~r^{-1.9+/-0.2}, with an indication of the inner
logarithmic slope converging. Models of adiabatic contraction of dark matter
halos due to the central build-up of stellar/gaseous galaxies are examined. The
simplest and most commonly used model, by Blumenthal et al., is shown to
overestimate the central dark matter density considerably. A modified model
proposed by Gnedin et al. is shown to be a considerable improvement, but not
perfect. Moreover it is found that the contraction parameters not only depend
on the orbital structure of the dark-matter-only halos but also on the stellar
feedback prescription which is most relevant for the baryonic distribution.
Implications for dark matter annihilation at the galactic center are discussed
and it is found that although our simulations show a considerable reduced halo
contraction as compared to the Blumenthal et al. model, the fluxes from dark
matter annihilation is still expected to be enhanced by at least a factor of a
hundred as compared to dark-matter-only halos. Finally, it is shown that while
dark-matter-only halos are typically prolate, the dark matter halos containing
baryons are mildly oblate with minor-to-major axis ratios of c/a=0.73+/-0.11,
with their flattening aligned with the central baryonic disks.


title: Measuring the matter density using baryon oscillations in the SDSS

abstract:
  We measure the cosmological matter density by observing the positions of
baryon acoustic oscillations in the clustering of galaxies in the Sloan Digital
Sky Survey (SDSS). We jointly analyse the main galaxies and LRGs in the SDSS
DR5 sample, using over half a million galaxies in total. The oscillations are
detected with 99.74% confidence (3.0sigma assuming Gaussianity) compared to a
smooth power spectrum. When combined with the observed scale of the peaks
within the CMB, we find a best-fit value of Omega_m=0.256+0.029-0.024 (68%
confidence interval), for a flat Lambda cosmology when marginalising over the
Hubble parameter and the baryon density. This value of the matter density is
derived from the locations of the baryon oscillations in the galaxy power
spectrum and in the CMB, and does not include any information from the overall
shape of the power spectra. This is an extremely clean cosmological measurement
as the physics of the baryon acoustic oscillation production is well
understood, and the positions of the oscillations are expected to be
independent of systematics such as galaxy bias.


title: The shape of the SDSS DR5 galaxy power spectrum

abstract:
  We present a Fourier analysis of the clustering of galaxies in the combined
Main galaxy and Luminous Red Galaxy (LRG) Sloan Digital Sky Survey (SDSS) Data
Release 5 (DR5) sample. The aim of our analysis is to consider how well we can
measure the cosmological matter density using the signature of the horizon at
matter-radiation equality embedded in the large-scale power spectrum. The new
data constrains the power spectrum on scales 100--600h^-1Mpc with significantly
higher precision than previous analyses of just the SDSS Main galaxies, due to
our larger sample and the inclusion of the LRGs. This improvement means that we
can now reveal a discrepancy between the shape of the measured power and linear
CDM models on scales 0.01<k<0.15hMpc^-1, with linear model fits favouring a
lower matter density (Omega_m=0.22+/-0.04) on scales 0.01<k<0.06hMpc^-1 and a
higher matter density (Omega_m=0.32+/-0.01) when smaller scales are included,
assuming a flat LCDM model with h=0.73 and n_s=0.96. This discrepancy could be
explained by scale-dependent bias and, by analysing subsamples of galaxies, we
find that the ratio of small-scale to large-scale power increases with galaxy
luminosity, so all of the SDSS galaxies cannot trace the same power spectrum
shape over 0.01<k<0.2hMpc^-1. However, the data are insufficient to clearly
show a luminosity-dependent change in the largest scale at which a significant
increase in clustering is observed, although they do not rule out such an
effect. Significant scale-dependent galaxy bias on large-scales, which changes
with the r-band luminosity of the galaxies, could potentially explain
differences in our Omega_m estimates and differences previously observed
between 2dFGRS and SDSS power spectra and the resulting parameter constraints.


title:
The structure of dark matter halos: self-similar models versus N-body
  simulations

abstract:
  We derive the density profile of cold dark matter halos using a self-similar
accretion model. We show that if the clumpiness of the infalling matter is
taken into account, then the inner density slope, d(log{rho})/d(log{r}), is
close to -1. Compared with the density profiles predicted by different
numerical simulations, we find that outside ~0.1% of the virial radius, our
solutions agree best with the fitting formula proposed by Navarro et al.
(2004), d(ln{rho})/d(ln{r})=-2(r/R)^0.17, where R is a characteristic radius,
inside which the density profile becomes shallower than isothermal.


title: Some Pattern Recognition Challenges in Data-Intensive Astronomy

abstract:
  We review some of the recent developments and challenges posed by the data
analysis in modern digital sky surveys, which are representative of the
information-rich astronomy in the context of Virtual Observatory. Illustrative
examples include the problems of an automated star-galaxy classification in
complex and heterogeneous panoramic imaging data sets, and an automated,
iterative, dynamical classification of transient events detected in synoptic
sky surveys. These problems offer good opportunities for productive
collaborations between astronomers and applied computer scientists and
statisticians, and are representative of the kind of challenges now present in
all data-intensive fields. We discuss briefly some emergent types of scalable
scientific data analysis systems with a broad applicability.


title: Lightcurves of Type Ia Supernovae from Near the Time of Explosion

abstract:
  We present a set of 11 type Ia supernova (SN Ia) lightcurves with dense,
pre-maximum sampling. These supernovae (SNe), in galaxies behind the Large
Magellanic Cloud (LMC), were discovered by the SuperMACHO survey. The SNe span
a redshift range of z = 0.11 - 0.35. Our lightcurves contain some of the
earliest pre-maximum observations of SNe Ia to date. We also give a functional
model that describes the SN Ia lightcurve shape (in our VR-band). Our function
uses the "expanding fireball" model of Goldhaber et al. (1998) to describe the
rising lightcurve immediately after explosion but constrains it to smoothly
join the remainder of the lightcurve. We fit this model to a composite observed
VR-band lightcurve of three SNe between redshifts of 0.135 to 0.165. These SNe
have not been K-corrected or adjusted to account for reddening. In this
redshift range, the observed VR-band most closely matches the rest frame
V-band. Using the best fit to our functional description of the lightcurve, we
find the time between explosion and observed VR-band maximum to be
17.6+-1.3(stat)+-0.07(sys) rest-frame days for a SN Ia with a VR-band Delta
m_{-10} of 0.52mag. For the redshifts sampled, the observed VR-band
time-of-maximum brightness should be the same as the rest-frame V-band maximum
to within 1.1 rest-frame days.


title: Limits to Tertiary Astrometric Companions in Binary Systems

abstract:
  The Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES)
has monitored 37 sub-arcsecond binary systems to determine whether their
Keplerian orbits are perturbed by faint astrometric companions to either star.
Software has been developed to evaluate the regions in a companion mass-period
phase space in which the PHASES observations can exclude the possibility of
face-on orbit perturbations. We present results for 8 systems for which
astrometric companions with masses as small as those of giant planets can be
excluded.


title: Performance of the AMS-02 Transition Radiation Detector

abstract:
  For cosmic particle spectroscopy on the International Space Station the AMS
experiment will be equipped with a Transition Radiation Detector (TRD) to
improve particle identification. The TRD has 20 layers of fleece radiator with
Xe/CO2 proportional mode straw tube chambers. They are supported in a conically
shaped octagon structure made of CFC-Al-honeycomb. For low power consumption VA
analog multiplexers are used as front-end readout. A 20 layer prototype built
from final design components has achieved proton rejections from 100 to 2000 at
90% electron efficiency for proton beam energies up to 250 GeV with cluster
counting, likelihood and neural net selection algorithms.


title: Growth of structure seeded by primordial black holes

abstract:
  We discuss the possibilities for primordial black holes (PBHs) to grow via
the accretion of dark matter. In agreement with previous works, we find that
accretion during the radiation-dominated era does not lead to a significant
mass increase. However, during matter-domination, PBHs may grow by up to two
orders of magnitude in mass through the acquisition of large dark matter halos.
We discuss the possibility of PBHs being an important component in dark matter
halos of galaxies as well as their potential to explain the ultra-luminous
x-ray sources (ULXs) observed in nearby galactic disks. We point out that
although PBHs are ruled out as the dominant component of dark matter, there is
still a great deal of parameter space open to them playing a role in the
modern-day universe. For example, a primordial halo population of PBHs each at
$10^{2.5} M_\odot$ making up 0.1% of the dark matter grow to $10^{4.5} M_\odot$
via the accumulation of dark matter halos to account for $\sim 10%$ of the dark
matter mass by a redshift of $z \approx 30$. These intermediate mass black
holes may then ``light up'' when passing through molecular clouds, becoming
visible as ULXs at the present day, or they may form the seeds for supermassive
black holes at the centers of galaxies.


title:
The Shear TEsting Programme 2: Factors affecting high precision weak
  lensing analyses

abstract:
  The Shear TEsting Programme (STEP) is a collaborative project to improve the
accuracy and reliability of weak lensing measurement, in preparation for the
next generation of wide-field surveys. We review sixteen current and emerging
shear measurement methods in a common language, and assess their performance by
running them (blindly) on simulated images that contain a known shear signal.
We determine the common features of algorithms that most successfully recover
the input parameters. We achieve previously unattained discriminatory precision
in our analysis, via a combination of more extensive simulations, and pairs of
galaxy images that have been rotated with respect to each other, thus removing
noise from their intrinsic ellipticities. The robustness of our simulation
approach is also confirmed by testing the relative calibration of methods on
real data.
  Weak lensing measurement has improved since the first STEP paper. Several
methods now consistently achieve better than 2% precision, and are still being
developed. However, the simulations can now distinguish all methods from
perfect performance. Our main concern continues to be the potential for a
multiplicative shear calibration bias: not least because this can not be
internally calibrated with real data. We determine which galaxy populations are
responsible and, by adjusting the simulated observing conditions, we also
investigate the effects of instrumental and atmospheric parameters. We have
isolated several previously unrecognised aspects of galaxy shape measurement,
in which focussed development could provide further progress towards the
sub-percent level of precision desired for future surveys.
  [ABRIDGED]


title: Wolfgang Priester: from the big bounce to the Lambda-dominated universe

abstract:
  Wolfgang Priester was one of Germany's most versatile and quixotic
astrophysicists, re-inventing himself successively as a radio astronomer, space
physicist and cosmologist, and making a lasting impact on each field. We focus
in this personal account on his contributions to cosmology, where he will be
most remembered for his association with quasars, his promotion of the idea of
a nonsingular "big bounce" at the beginning of the current expansionary phase,
and his recognition of the importance of dark energy (Einstein's cosmological
constant Lambda) well before this became the standard paradigm in cosmology.


title: 9.7 um Silicate Features in AGNs: New Insights into Unification Models

abstract:
  We describe observations of 9.7 um silicate features in 97 AGNs, exhibiting a
wide range of AGN types and of X-ray extinction toward the central nuclei. We
find that the strength of the silicate feature correlates with the HI column
density estimated from fitting the X-ray data, such that low HI columns
correspond to silicate emission while high columns correspond to silicate
absorption. The behavior is generally consistent with unification models where
the large diversity in AGN properties is caused by viewing-angle-dependent
obscuration of the nucleus. Radio-loud AGNs and radio-quiet quasars follow
roughly the correlation between HI columns and the strength of the silicate
feature defined by Seyfert galaxies. The agreement among AGN types suggests a
high-level unification with similar characteristics for the structure of the
obscuring material. We demonstrate the implications for unification models
qualitatively with a conceptual disk model. The model includes an inner
accretion disk (< 0.1 pc in radius), a middle disk (0.1-10 pc in radius) with a
dense diffuse component and with embedded denser clouds, and an outer clumpy
disk (10-300 pc in radius).


title:
A collimated jet and an infalling-rotating disk in G192.16-3.84 traced
  by H2O maser emission

abstract:
  We report H2O masers associated with the massive-star forming region
G192.16-3.84 observed with the new Japan VLBI network at three epochs spanned
for two months, which have revealed the three-dimensional kinematical structure
of the whole \h2o maser region in G192.16-3.84, containing two young stellar
objects separated by ~1200 AU. The maser spatio-kinematical structure has well
persisted since previous observations, in which the masers are expected to be
associated with a highly-collimated bipolar jet and an infalling-rotating disk
in the northern and southern clusters of H2O maser features, respectively. We
estimated a jet expansion speed of ~100 km/s and re-estimated a dynamical age
of the whole jet to be 5.6x10^4 yrs. We have investigated the spatial
distribution of Doppler velocities during the previous and present observations
and relative proper motions of H2O maser features in the southern cluster, and
a relative bulk motion between the two maser clusters. They are well explained
by a model of an infalling-rotating disk with a radius of ~1000 AU and a
central stellar mass of 5-10 M_sun, rather than by a model of a bipolar jet
perpendicular to the observed CO outflow. Based on the derived H2O maser
spatio-kinematical parameters, we discuss the formation mechanism of the
massive young stellar objects and the outflow development in G192.16-3.84.


title:
NICMOS/HST Observations of the Embedded Cluster Associated with Mon R2:
  Constraining the sub-stellar Initial Mass Function

abstract:
  We have analyzed HST/NICMOS2 F110W, F160W, F165M, and F207M band images
covering the central 1'x1' of the cluster associated with Mon R2 in order to
constrain the Initial Mass Function (IMF) down to 20 Mjup. The flux ratio
between the F165M and F160W bands was used to measure the strength of the water
band absorption feature and select a sample of 12 out of the total sample of
181 objects that have effective temperatures between 2700 K and 3300 K. These
objects are placed in the HR diagram together with sources observed by
Carpenter et al. (1997) to estimate an age of ~1 Myr for the low mass cluster
population. By constructing extinction limited samples, we are able to
constrain the IMF and the fraction of stars with a circumstellar disk in a
sample that is 90% complete for both high and low mass objects. For stars with
estimated masses between 0.1 Msun and 1.0 Msun for a 1 Myr population with Av <
19 mag, we find that 27+-9% have a near-infrared excess indicative of a
circumstellar disk. The derived fraction is similar to, or slightly lower than,
the fraction found in other star forming regions of comparable age. We
constrain the number of stars in the mass interval 0.08-1.0Msun to the number
of objects in the mass interval 0.02-0.08 Msun by forming the ratio,
R**=N(0.08-1Msun)/N(0.02-0.08Msun) for objects in an extinction limited sample
complete for Av < 7 mag. The ratio is found to be R^**=2.2+-1.3 assuming an age
of 1 Myr, consistent with the similar ratio predicted by the system IMF
proposed by Chabrier (2003). The ratio is similar to the ratios observed
towards the Orion Nebula Cluster and IC 348 as well as the ratio derived in the
28 square degree survey of Taurus by Guieu et al. (2006).


title: A ULX associated with a cloud collision in M99

abstract:
  The Sc galaxy M99 in the Virgo cluster has been strongly affected by tidal
interactions and recent close encounters, responsible for an asymmetric spiral
pattern and a high star formation rate. Our XMM-Newton study shows that the
inner disk is dominated by hot plasma at kT ~ 0.30 keV, with a total X-ray
luminosity ~ 10^{41} erg/s in the 0.3--12 keV band. At the outskirts of the
galaxy, away from the main star-forming regions, there is an ultraluminous
X-ray source (ULX) with an X-ray luminosity ~ 2 x 10^{40} erg/s and a hard
spectrum well fitted by a power law of photon index Gamma ~ 1.7. This source is
close to the location where a massive HI cloud appears to be falling onto the
M99 disk at a relative speed > 100 km/s. We suggest that there may be a direct
physical link between fast cloud collisions and the formation of bright ULXs,
which may be powered by accreting black holes with masses ~ 100 Msun. External
collisions may trigger large-scale dynamical collapses of protoclusters,
leading to the formation of very massive (>~ 200 Msun) stellar progenitors; we
argue that such stars may later collapse into massive black holes if their
metal abundance is sufficiently low.


title:
Invariants and solutions of Gurzadyan-Xue dark energy cosmological
  models

abstract:
  We have derived the invariants of cosmological models with Gurzadyan-Xue dark
energy, along with the solutions for any time dependent light speed and
gravitational constant. The correspondence of the invariants with the
separatrices found earlier for the GX-models in \cite{Ver06a} is shown, and
hence the basis of then detected hidden symmetry is now revealed. Solutions are
derived both for radiation and matter models, as well as with both components.
It is interesting that, the solutions for the scale factor do not depend on the
gravitational constant but only on the 'time evolution' of the speed of light.
GX-invariants act as efficient tools describing the models and the phases of
the cosmological expansion.


title:
Our distorted view of magnetars: application of the Resonant Cyclotron
  Scattering model

abstract:
  The X-ray spectra of the magnetar candidates are customarily fitted with an
empirical, two component model: an absorbed blackbody and a power-law. However,
the physical interpretation of these two spectral components is rarely
discussed. It has been recently proposed that the presence of a hot plasma in
the magnetosphere of highly magnetized neutron stars might distort, through
efficient resonant cyclotron scattering, the thermal emission from the neutron
star surface, resulting in the production of non-thermal spectra. Here we
discuss the Resonant Cyclotron Scattering (RCS) model, and present its XSPEC
implementation, as well as preliminary results of its application to Anomalous
X-ray Pulsars and Soft Gamma-ray Repeaters.


title:
A statistical analysis of X-ray variability in pre-main sequence objects
  of the Taurus Molecular Cloud

abstract:
  This work is part of a systematic X-ray survey of the Taurus star forming
complex with XMM-Newton. We study the time series of all X-ray sources
associated with Taurus members, to statistically characterize their X-ray
variability, and compare the results to those for pre-main sequence stars in
the Orion Nebula Cluster and to expectations arising from a model where all the
X-ray emission is the result of a large number of stochastically occurring
flares. We find that roughly half of the detected X-ray sources show
variability above our sensitivity limit, and in ~ 26 % of the cases this
variability is recognized as flares. Variability is more frequently detected at
hard than at soft energies. The variability statistics of cTTS and wTTS are
undistinguishable, suggesting a common (coronal) origin for their X-ray
emission. We have for the first time applied a rigorous maximum likelihood
method in the analysis of the number distribution of flare energies on pre-main
sequence stars. In its differential form this distribution follows a power-law
with index alpha = 2.4 +- 0.5, in the range typically observed on late-type
stars and the Sun. The flare energy distribution is probably steep enough to
explain the heating of stellar coronae by nano-flares (alpha > 2), albeit
associated with a rather large uncertainty that leaves some doubt on this
conclusion.


title:
Procyon-A and Eta-Bootis: Observational Frequencies Analyzed by the
  Local-Wave Formalism

abstract:
  In the present analysis of Procyon-A and Eta-Bootis, we use the local-wave
formalism which, despite its lack of precision inherent to any semi-analytical
method, uses directly the model profile without any modification when
calculating the acoustic mode eigenfrequencies. These two solar-like stars
present steep variations toward the center due to the convective core
stratification, and toward the surface due to the very thin convective zone.
Based on different boundary conditions, the frequencies obtained with this
formalism are different from that of the classical numerical calculation. We
point out that (1) the frequencies calculated with the local-wave formalism
seem to agree better with observational ones. All the frequencies detected with
a good confident level including those classified as 'noise' find an
identification, (2) some frequencies can be clearly identified here as
indications of the core limit.


title: Timing Studies on RXTE Observations of SAX J2103.5+4545

abstract:
  SAX J2103.5+4545 has been continuously monitored for $\sim $ 900 days by
Rossi X-ray Timing Explorer (RXTE) since its outburst in July 2002. Using these
observations and previous archival RXTE observations of SAX J2103.5+4545, we
refined the binary orbital parameters and find the new orbital period as P=
(12.66536 $\pm $ 0.00088) days and the eccentricity as 0.4055$\pm$ 0.0032. With
these new orbital parameters, we constructed the pulse frequency and pulse
frequency derivative histories of the pulsar and confirmed the correlation
between X-ray flux and pulse frequency derivative presented by Baykal, Stark
and Swank (2002). We constructed the power spectra for the fluctuations of
pulse frequency derivatives and found that the power law index of the noise
spectra is 2.13 $\pm$ 0.6. The power law index is consistent with random walk
in pulse frequency derivative and is the steepest among the HMXRBs.
  X-ray spectra analysis confirmed the inverse correlation trend between
power-law index and X-ray flux found by Baykal, Stark and Swank (2002).


title: Recovering the star formation rate in the solar neighborhood

abstract:
  This paper develops a method for obtaining the star formation histories of a
mixed, resolved population through the use of color-magnitude diagrams (CMDs).
The method provides insight into the local star formation rate, analyzing the
observations of the Hipparcos satellite through a comparison with synthetic
CMDs computed for different histories with an updated stellar evolution
library. Parallax and photometric uncertainties are included explicitly and
corrected using the Bayesian Richardson-Lucy algorithm. We first describe our
verification studies using artificial data sets. From this sensitivity study,
the critical factors determining the success of a recovery for a known star
formation rate are a partial knowledge of the IMF and the age-metallicity
relation, and sample contamination by clusters and moving groups (special
populations whose histories are different than that of the whole sample).
Unresolved binaries are less important impediments. We highlight how these
limit the method. For the real field sample, complete to Mv < 3.5, we find that
the solar neighborhood star formation rate has a characteristic timescale for
variation of about 6 Gyr, with a maximum activity close to 3 Gyr ago. The
similarity of this finding with column integrated star formation rates may
indicate a global origin, possibly a collision with a satellite galaxy. We also
discuss applications of this technique to general photometric surveys of other
complex systems (e.g. Local Group dwarf galaxies) where the distances are well
known.


title: Dust in High-Velocity Clouds : relevance for Planck

abstract:
  The recent detection of dust emission in Complex C, the largest High-Velocity
Cloud (HVC) on the sky, opens a very interesting perspective for Planck. The
HVC dust temperature determined using IRAS and Spitzer observations is low
(T~10.7 K) in accordance with its great distance from the Galaxy (> 5 kpc).
Peak column density in 30 arcmin beam is NH ~10^20 cm-2 which is typical of
HVCs and similar to cirrus column density in diffuse regions. On the other hand
HVCs appear to be very clumpy at smaller angular scales; several observations
at the arcminute scale resolution show significant structure and higher
brightness contrasts than in typical cirrus emission. In this contribution we
show that, even with their moderate column density, the cold temperature, high
emissivity and high column density contrast of HVCs should lead to significant
and detectable emission in the Planck-HFI frequency range. In order to separate
the HVC emission from the Galactic cirrus emission, the use of 21 cm
observations will be mandatory.


title: 0.5 Mpc-scale extended X-ray emission in 4C 23.56

abstract:
  We present an XMM-Newton observation of the radio galaxy 4C 23.56 at z=2.48
which reveals extended X-ray emission coincident with the radio lobes spanning
\~0.5 Mpc. These are the largest X-ray-bright lobes known at z>2. Under the
assumption that these features result from inverse-Compton scattering of cosmic
microwave background photons by relativistic electrons in the radio source
lobes, the measured luminosity of L_0.5-8 keV=7.5x10^44 erg s^-1 implies a
minimum energy stored within the lobes of ~10^59 erg. We discuss the potential
of the large-scale radio/X-ray lobes to influence evolution of the host galaxy
and proto-cluster environment at high redshift.


title: Extremely compact massive galaxies at z~1.4

abstract:
  The optical rest-frame sizes of 10 of the most massive
(~5x10^{11}h_{70}^{-2}M_sun) galaxies found in the near-infrared MUNICS survey
at 1.2<z<1.7 are analysed. Sizes were estimated both in the J and K' filters.
These massive galaxies are at least a factor of 4_{-1.0}^{+1.9} (+-1 sigma)
smaller in the rest-frame V-band than local counterparts of the same stellar
mass. Consequently, the stellar mass density of these objects is (at least) 60
times larger than massive ellipticals today. Although the stellar populations
of these objects are passively fading, their structural properties are rapidly
changing since that redshift. This observational fact disagrees with a scenario
where the more massive and passive galaxies are fully assembled at z~1.4 (i.e.
a monolithic scenario) and points towards a dry merger scenario as the
responsible mechanism for the subsequent evolution of these galaxies.


title: Halting Type I planet migration in non-isothermal disks

abstract:
  Aims: We investigate the effect of including a proper energy balance on the
interaction of a low-mass planet with a protoplanetary disk. Methods: We use a
three-dimensional version of the RODEO method to perform hydrodynamical
simulations including the energy equation. Radiation is included in the
flux-limited diffusion approach. Results: The sign of the torque depends
sensitively on the ability of the disk to radiate away the energy generated in
the immediate surroundings of the planet. In the case of high opacity,
corresponding to the dense inner regions of protoplanetary disks, migration is
directed \emph{outward}, instead of the usual inward migration that was found
in locally isothermal disks. For low values of the opacity we recover inward
migration, and we show that torques originating in the coorbital region are
responsible for the change in migration direction.


title:
Are isolated planetary-mass objects really isolated? A brown
  dwarf-exoplanet system candidate in the sigma Orionis cluster

abstract:
  The recent detection by direct imaging of three giant planets at wide
separation (50-250 AU) from their primaries has raised the question about the
``true isolation'' of planetary-mass objects in clusters. Our goal was to test
the possibility that some free-floating planetary-mass object could in fact be
part of wide planetary systems. We searched in the literature for stellar and
brown-dwarf member candidates of the sigma Orionis cluster at small angular
separations from published candidate planetary-mass objects. We found one
candidate planetary system, SE 70, composed of an X-ray source and a
planetary-mass object, namely S Ori 68, separated by only 4.6 arcsec. In order
to assess the cluster membership of the X-ray source, we obtained
mid-resolution optical spectroscopy using ISIS on the William Herschel
Telescope. We also compiled additional data on the target from available
astronomical catalogues. We have found that SE 70 follows the
spectrophotometric sequence of the cluster and displays spectroscopic features
of youth, such as lithium in absorption and chromospheric Halpha emission. The
radial velocity is consistent with cluster membership. Hence, SE 70 is very
probably a sigma Orionis cluster member. The projected physical separation
between SE 70 and S Ori 68 is 1700+/-300 AU at the distance of the cluster. If
the common proper motion is confirmed in the near future, the system would be
composed of an M5-6 brown dwarf with an estimated mass of ~45 M_Jup and an
L5+/-2 giant planet with an estimated mass of ~5 M_Jup. It would be the widest
and one of the lowest-mass planetary systems known so far.


title: Simulating planet migration in globally evolving disks

abstract:
  Numerical simulations of planet-disk interactions are usually performed with
hydro-codes that -- because they consider only an annulus of the disk, over a
2D grid -- can not take into account the global evolution of the disk. However,
the latter governs planetary migration of type II, so that the accuracy of the
planetary evolution can be questioned.
  To develop an algorithm that models the local planet-disk interactions
together with the global viscous evolution of the disk, we surround the usual
2D grid with a 1D grid ranging over the real extension of the disk. The 1D and
2D grids are coupled at their common boundaries via ghost rings, paying
particular attention to the fluxes at the interface, especially the flux of
angular momentum carried by waves. The computation is done in the frame
centered on the center of mass to ensure angular momentum conservation.
  The global evolution of the disk and the local planet-disk interactions are
both well described and the feedback of one on the other can be studied with
this algorithm, for a negligible additional computing cost with respect to
usual algorithms.


title:
The Globular Cluster Kinematics and Galaxy Dark Matter Content of NGC
  4649 (M60)

abstract:
  From observations with the GMOS multi-slit spectrograph on the Gemini North
telescope, we have obtained spectra for 39 globular cluster candidates in the
Virgo giant elliptical galaxy NGC 4649 (M60), of which 38 are confirmed
globular clusters. The clusters extend out to a radius of 260" (3.5 effective
radii). We find no rotation of the globular cluster system, with an upper limit
of v/sigma < 0.6 at a confidence level of 95%. The globular cluster velocity
dispersion is constant with radius, within the uncertainties. We fit isotropic
models to the globular cluster and stellar kinematics; these models yield a
M/L_V around 16 at 200" radius (16 kpc), an increase of a factor of two from
the central M/L. We also use the mass profile as derived from X-rays to
determine the orbital structure. Using axisymmetric orbit-based models and the
X-ray mass profile, we find the orbital distribution is close to isotropic
within 100", and becomes tangentially biased beyond. Furthermore, when using
the X-ray profile, we find a better fit to the kinematics compared to using a
constant M/L model. Thus, both isotropic and axisymmetric orbit-based models
give support for the presence of a dark matter halo in NGC 4649.


title: Pure pseudo-C_l estimators for CMB B-modes

abstract:
  Fast heuristically weighted, or pseudo-C_l, estimators are a frequently used
method for estimating power spectra in CMB surveys with large numbers of
pixels. Recently, Challinor & Chon showed that the E-B mixing in these
estimators can become a dominant contaminant at low noise levels, ultimately
limiting the gravity wave signal which can be detected on a finite patch of
sky. We define a modified version of the estimators which eliminates E-B mixing
and is near-optimal at all noise levels.


title: Pulse profiles of millisecond pulsars and their Fourier amplitudes

abstract:
  Approximate analytical formulae are derived for the pulse profile produced by
small hot spots on a rapidly rotating neutron star. Its Fourier amplitudes and
phases are calculated. The proposed formalism takes into account gravitational
bending of light, Doppler effect, anisotropy of emission, and time delays. Its
accuracy is checked with exact numerical calculations.


title:
The Luminosity Function of high-redshift QSOs - A combined analysis of
  GOODS and SDSS

abstract:
  Aims: In this work the luminosity function of QSOs is measured in the
redshift range 3.5<z<5.2 for the absolute magnitude interval -21<M_{145}<-28.
The determination of the faint end of the luminosity function at these
redshifts provides important constraints on models of joint evolution of
galaxies and AGNs. Methods: We have defined suitable criteria to select faint
QSOs in the GOODS fields, checking in detail their effectiveness and
completeness. Spectroscopic follow-up of the resulting QSO candidates has been
carried out. The confirmed sample of faint QSOs is compared with a brighter one
derived from the SDSS. We have used a Monte-Carlo technique to estimate the
properties of the luminosity function, checking various parameterizations for
its shape and evolution. Results: Models based on Pure Density Evolution show
better agreement with observation than models based on Pure Luminosity
Evolution. However a different break magnitude with respect to z~2.1 is
required at 3.5<z<5.2. Models with a steeper faint end score a higher
probability. We do not find any evidence for a flattening of the bright end at
redshift z>3.5. Conclusions: The estimated space density evolution of QSOs
indicates a suppression of the formation and/or feeding of Supermassive Black
Holes at these redshifts. The QSO contribution to the UV background is
insufficient to ionize the IGM at 3.5<z<5.2.


title: Dynamics of Barred Galaxies

abstract:
  Some 30% of disc galaxies have a pronounced central bar feature in the disc
plane and many more have weaker features of a similar kind. Kinematic data
indicate that the bar constitutes a major non-axisymmetric component of the
mass distribution and that the bar pattern tumbles rapidly about the axis
normal to the disc plane. The observed motions are consistent with material
within the bar streaming along highly elongated orbits aligned with the
rotating major axis. A barred galaxy may also contain a spheroidal bulge at its
centre, spirals in the outer disc and, less commonly, other features such as a
ring or lens. Mild asymmetries in both the light and kinematics are quite
common. We review the main problems presented by these complicated dynamical
systems and summarize the effort so far made towards their solution,
emphasizing results which appear secure. (Truncated)


title: A Search for Nitrogen-Enhanced Metal-Poor Stars

abstract:
  Theoretical models of very metal-poor intermediate-mass Asymptotic Giant
Branch (AGB) stars predict a large overabundance of primary nitrogen. The very
metal-poor, carbon-enhanced, s-process-rich stars, which are thought to be the
polluted companions of now-extinct AGB stars, provide direct tests of the
predictions of these models. Recent studies of the carbon and nitrogen
abundances in metal-poor stars have focused on the most carbon-rich stars,
leading to a potential selection bias against stars that have been polluted by
AGB stars that produced large amounts of nitrogen, and hence have small [C/N]
ratios. We call these stars Nitrogen-Enhanced Metal-Poor (NEMP) stars, and
define them as having [N/Fe] > +0.5 and [C/N] < -0.5. In this paper, we report
on the [C/N] abundances of a sample of 21 carbon-enhanced stars, all but three
of which have [C/Fe] < +2.0. If NEMP stars were made as easily as
Carbon-Enhanced Metal-Poor (CEMP) stars, then we expected to find between two
and seven NEMP stars. Instead, we found no NEMP stars in our sample. Therefore,
this observational bias is not an important contributor to the apparent dearth
of N-rich stars. Our [C/N] values are in the same range as values reported
previously in the literature (-0.5 to +2.0), and all stars are in disagreement
with the predicted [C/N] ratios for both low-mass and high-mass AGB stars. We
suggest that the decrease in [C/N] from the low-mass AGB models is due to
enhanced extra-mixing, while the lack of NEMP stars may be caused by
unfavorable mass ratios in binaries or the difficulty of mass transfer in
binary systems with large mass ratios.


title: High-resolution observations of water masers in Bok globules

abstract:
  We present Very Large Array observations at 1.3 cm of several water maser
detections obtained by previous single-dish studies of Bok globules in the
Clemens & Barvainis (1988; CB) catalog. We report water maser emission in CB 3
(CB3-mm), CB 54 (IRAS 07020-1618), CB 101 (IRAS 17503-0833), and CB 232 (IRAS
21352+4307), and non-detection towards CB 65 (IRAS 16277-2332) and CB 205 (IRAS
19433+2743). These are the first reported interferometric observations of water
masers in Bok globules of the CB catalog. We also present single-dish
observations of millimeter and centimeter spectral lines towards CB 101 (IRAS
17503-0833) and CB 65 (IRAS 16277-2332). All the maser emission seems to be
associated with star forming regions hosting bipolar molecular outflows, except
IRAS 17503-0833 in CB 101, which we suggest to be a possible Mira evolved star,
and IRAS 16277-2332 in CB 65, of unknown nature. We have used the precise
position of the maser emission to derive information about the powering source
of the masers. By analyzing the spatio-kinematical distribution of the water
masers, we confirm the millimeter source CB 3-mm as the most likely powering
source of the CB 3 masers. We propose the near-IR source CB 232 YC1-I as the
best candidate for pumping the maser emission observed in CB 232, while in CB
54, we suggest that the pumping source of the masers could be located at the
position of an elongated feature observed in near-infrared maps.


title:
The MODEST questions: challenges and future directions in stellar
  cluster research

abstract:
  We present a review of some of the current major challenges in stellar
cluster research, including young clusters, globular clusters, and galactic
nuclei. Topics considered include: primordial mass segregation and runaway
mergers, expulsion of gas from clusters, the production of stellar exotica seen
in some clusters (eg blue stragglers and extreme horizontal--branch stars),
binary populations within clusters, the black--hole population within stellar
clusters, the final parsec problem, stellar dynamics around a massive black
hole, and stellar collisions. The Modest Questions posed here are the outcome
of discussions which took place at the Modest-6A workshop held in Lund, Sweden,
in December, 2005. Modest-6A was organised as part of the activities of the
Modest Collaboration (see www.manybody.org for further details)


title:
Kinematics of planet-host stars and their relation with dynamical
  streams in the solar neighbourhood

abstract:
  We present a detailed study on the kinematics of metal-rich stars with and
without planets, and their relation with the Hyades, Sirius and Hercules
dynamical streams in the solar neighbourhood. Accurate kinematics have been
derived for all the stars belonging to the CORALIE planet search survey. We
used precise radial velocity measurements and CCF parameters from the CORALIE
database, and parallaxes, photometry and proper motions from the HIPPARCOS and
Tycho-2 catalogues. The location of stars with planets in the thin or thick
discs has been analysed using both kinematic and chemical constraints. We
compare the kinematic behaviour of known planet-host stars to the remaining
targets belonging to the volume-limited sample, in particular to its metal-rich
population. The high average metallicity of the Hyades stream is confirmed. The
planet-host targets show a kinematic behaviour similar to that of the
metal-rich comparison subsample, rather than to that of the comparison sample
as a whole, thus supporting a primordial origin for the metal excess observed
in stars with known planetary companions. According to the scenarios proposed
as an explanation for the dynamical streams, systems with giant planets could
have formed more easily in metal-rich inner Galactic regions and then been
brought into the solar neighbourhood by dynamical streams.


title: The Hybrid Activities of the Pierre Auger Observatory

abstract:
  The Pierre Auger Observatory detects ultra-high energy cosmic rays by
implementing two complementary air-shower techniques. The combination of a
large ground array and fluorescence detectors, known as the hybrid concept,
means that a rich variety of measurements can be made on a single shower,
providing much improved information over what is possible with either detector
alone. In this paper I describe the hybrid reconstruction approach and the
latest hybrid measurements.


title: On the origin of the ultramassive white dwarf GD50

abstract:
  We argue on the basis of astrometric and spectroscopic data that the
ultramassive white dwarf GD50 is associated with the star formation event that
created the Pleiades and is possibly a former member of this cluster. Its
cooling age (~60Myrs) is consistent with it having evolved essentially as a
single star from a progenitor with a mass M>6Msun so we find no need to invoke
a white dwarf-white dwarf binary merger scenario to account for its existence.
This result may represent the first direct observational evidence that single
star evolution can produce white dwarfs with M>1.1Msun, as predicted by some
stellar evolutionary theories. On the basis of its tangential velocity we also
provisionally identify the ultramassive (M~1.2Msun) white dwarf PG0136+251 as
being related to the Pleiades. These findings may help to alleviate the
difficulties in reconciling the observed number of hot nearby ultramassive
white dwarfs with the smaller number predicted by binary evolution models under
the assumption that they are the products of white dwarf mergers.


title: Enhanced mergers of galaxies in low-redshift clusters

abstract:
  An ensemble cluster has been formed from a data set comprising a complete
magnitude-limited sample of 680 giant galaxies (M(B) < -19) in 8 low-redshift
clusters, normalised by the velocity dispersions and virial radii for the
early-type cluster populations. Distinct galaxy populations have been
identified, including an infall population. A majority (50-70% or greater) of
the infall population are found to be in interacting or merging systems
characterised by slow gravitational encounters. The observed enhancement of
galaxy-galaxy encounters in the infall population compared to the field can be
explained by gravitational shocking. It is shown that disc galaxy mergers in
the infall population integrated over the estimated lifetime of the cluster (~
10 Gyr) can readily account for the present cluster S0 population.


title:
Test of Thick Pixelated Orbotech Detectors with and without Steering
  Grids

abstract:
  We report here on the optimization of 0.5 cm thick pixelated Orbotech CZT
detectors with regards to the best contacting materials and the use of steering
grids. We evaluated the performance of different contacting materials. Our
study differs from earlier ones in that we investigated the performance of
different anode and cathode materials separately. We obtain the best
performance with Au cathodes. For different anode materials Ti and In give the
best energy resolutions. The detector (2.0 x 2.0 x 0.5 cm, 8 x 8 pixels) shows
excellent 59 keV, 122 keV and 662 keV energy resolutions of 1.4 keV, 1.9 keV,
and 7.4 keV, respectively. Furthermore, we report on using steering grids to
improve on the performance of the pixelated detectors. Previously, the benefit
of steering grids had been limited by additional electronic noise associated
with currents between the negatively biased steering grids and the anode
pixels. We are currently exploring the possibility to isolate the steering grid
from the CZT substrates by a thin layer of Al$_2$O$_3$. We performed a series
of measurements to determine by how much the isolation layer reduces the
grid-pixel currents. Comparing the currents between two Au contacts before and
after isolating one of the two contacts from the CZT with a 700 nm thick layer
of Al2O3, we measure that the isolation layer reduces the currents by a factor
of about 10 at 500 V. We present some results from a detector before and after
deposition of an isolated steering grid. The grid indeed improves on the
detectors energy resolution and detection efficiency. We show that simulations
can be used to model the anode to cathode charge correlation in excellent
agreement with the experimental results.


title:
A VLT/NACO Survey for Triple and Quadruple Systems among Visual Pre-Main
  Sequence Binaries

abstract:
  This paper describes a systematic search for high-order multiplicity among
wide visual Pre-Main Sequence (PMS) binaries. We conducted an Adaptive Optics
survey of a sample of 58 PMS wide binaries from various star-forming regions,
which include 52 T Tauri systems with mostly K- and M-type primaries, with the
NIR instrument NACO at the VLT. Of these 52 systems, 7 are found to be triple
(2 new) and 7 quadruple (1 new). The new close companions are most likely
physically bound based on their probability of chance projection and, for some
of them, on their position on a color-color diagram. The corresponding degree
of multiplicity among wide binaries (number of triples and quadruples divided
by the number of systems) is 26.9 +/- 7.2% in the projected separation range
0.07-12 arcsec, with the largest contribution from the Taurus-Auriga cloud. We
also found that this degree of multiplicity is twice in Taurus compared to
Ophiuchus and Chamaeleon for which the same number of sources are present in
our sample. Considering a restricted sample composed of systems at distance
140-190pc, the degree of multiplicity is 26.8 +/- 8.1%, in the separation range
10/14 AU - 1700/2300 AU (30 binaries, 5 triples, 6 quadruples). The observed
frequency agrees with results from previous multiplicity surveys within the
uncertainties, although a significant overabundance of quadruple systems
compared to triple systems is apparent. Tentatively including the spectroscopic
pairs in our restricted sample and comparing the multiplicity fractions to
those measured for solar-type main-sequence stars in the solar neighborhood
leads to the conclusion that both the ratio of triples to binaries and the
ratio of quadruples to triples seems to be in excess among young stars. [...]


title:
Gravitational Lensing in Modified Gravity and the Lensing of Merging
  Clusters without Dark Matter

abstract:
  Gravitational lensing in a modified gravity (MOG) is derived and shown to
describe lensing without postulating dark matter. The recent data for merging
clusters identified with the interacting cluster 1E0657-56 is shown to be
consistent with a weak lensing construction based on MOG without exotic dark
matter.


title:
Spectropolarimetry of the Deep Impact target comet 9P/Tempel 1 with
  HiVIS

abstract:
  High resolution spectropolarimetry of the Deep Impact target, comet 9P/
Tempel 1, was performed during the impact event on July 4th, 2005 with the
HiVIS Spectropolarimeter and the AEOS 3.67m telescope on Haleakala, Maui. We
observed atypical polarization spectra that changed significantly in the few
hours after the impact. The polarization of scattered light as a function of
wavelength is very sensitive to the size and composition (complex refractive
index) of the scattering particles as well as the scattering geometry. As
opposed to most observations of cometary dust, which show an increase in the
linear polarization with the wavelength (at least in the visible domain and for
phase angles greater than about 30%, a red polarization spectrum) observations
of 9P/Tempel 1 at a phase angle of 41 degrees beginning 8 minutes after impact
and centered at 6:30UT showed a polarization of 4% at 650 nm falling to 3% at
950 nm. The next observation, centered an hour later showed a polarization of
7% at 650 nm falling to 2% at 950nm. This corresponds to a spectropolarimetric
gradient, or slope, of -0.9% per 1000 Angstroms 40 minutes after impact,
decreasing to a slope of -2.3% per 1000 Angstroms an hour and a half after
impact. This is an atypical blue polarization slope, which became more blue 1
hour after impact. The polarization values of 4% and 7% at 650nm are typical
for comets at this scattering angle, whereas the low polarization of 2% and 3%
at 950nm is not. We compare observations of comet 9P/Tempel 1 to that of a
typical comet, C/2004 Machholz, at a phase angle of 30 degrees which showed a
typical red slope, rising from 2% at 650nm to 3% at 950nm in two different
observations (+1.0 and +0.9% per 1000 Angstroms).


title:
The Distance to the Virgo Cluster from a Recalibrated Tully-Fisher
  Relation Based on HST Cepheids and a Demonstrated Teerikorpi Cluster
  Incompleteness Bias

abstract:
  The importance of the distance of the Virgo cluster in the ongoing debate on
the value of the Hubble constant is reviewed. A new calibration of the
Tully-Fisher 21-cm line width-absolute magnitude relation is made using Cepheid
distances to 25 galaxies determined in various HST programs and reduced with
the new Cepheid P-L relations that vary from galaxy-to galaxy. The calibration
is applied to a complete sample of Virgo cluster spirals for the purpose of
demonstrating the Teerikorpi cluster incompleteness bias. A diagnostic test is
shown that should be useful in identifying the presence of bias in incompletely
sampled data for distant clusters. The bias-free TF distance modulus for the
Virgo cluster is m - M = 31.67 (D = 21.6 Mpc). A systematic correction of 0.07
mag is made because the cluster members are redder in B I on average than the
calibrators at a given line width, giving a final adopted modulus for the Virgo
cluster core of 31.60 + 0.09. If we assign a generous range of systematic error
of ~ 0.3 mag, the distance D = 20.9 Mpc (m - M = 31.60) has a range from 24.0
Mpc to 18.2 Mpc (m - M between 31.9 and 31.3), and a Hubble constant of Ho = 56
between the limits of 49 and 65 when used with a cosmic expansion velocity of
1175 km s-1 determined by the method of distance ratios of remote clusters to
Virgo. This range overlaps our preferred value of Ho = 62 from the HST Cepheid
calibration of type Ia supernovae recently determined. The TF modulus of Virgo
determined here cannot be reconciled with the recent high value of Ho = 72 from
Freedman et al.


title: Could GRB 060614 and its presumed host galaxy be a chance superposition?

abstract:
  The lack of an observed supernova associated with GRB 060614 appears to
require a new paradigm for the formation of (a subset of) long-duration GRBs.
This requirement is based on the presumed low redshift of the burst, which was
inferred from the spatial coincidence of the afterglow with a z=0.125 galaxy.
We explore the possibility that this low-redshift galaxy is a chance
superposition along the line of sight to GRB 060614. We examine the galaxy
distribution of the field of GRB 060614 and find that the probability of a
chance association with a galaxy at least as bright as the putative host is
only ~ 0.5 - 1.9%. However, for the current ensemble of ~180 Swift GRBs it is
likely that several such coincidences have occurred, and given the
"non-standard" nature of GRB 060614 it is not implausible that this is one such
occurrence. Thus the conclusion that GRB 060614 requires a revision to the
formation paradigm for long-duration GRBs should be approached with caution.


title: Efficient Cosmological Parameter Estimation with Hamiltonian Monte Carlo

abstract:
  Traditional Markov Chain Monte Carlo methods suffer from low acceptance rate,
slow mixing and low efficiency in high dimensions. Hamiltonian Monte Carlo
resolves this issue by avoiding the random walk. Hamiltonian Monte Carlo (HMC)
is a Markov chain Monte Carlo (MCMC) technique built upon the basic principle
of Hamiltonian mechanics. Hamiltonian dynamics allows the chain to move along
trajectories of constant energy, taking large jumps in the parameter space with
relatively inexpensive computations. This new technique improves the acceptance
rate by a factor of 4 and boosts up the efficiency by at least a factor of D in
a D-dimensional parameter space. Therefor shorter chains will be needed for a
reliable parameter estimation comparing to a traditional MCMC chain yielding
the same performance. Besides that, the HMC is well suited for sampling from
non-Gaussian and curved distributions which are very hard to sample from using
the traditional MCMC methods. The method is very simple to code and can be
easily plugged into standard parameter estimation codes such as CosmoMC. In
this paper we demonstrate how the HMC can be efficiently used in cosmological
parameter estimation.


title:
A High-Resolution Spectrum of the Extremely Metal-Rich Bulge G-Dwarf
  OGLE-2006-BLG-265

abstract:
  We present an R=45,000 Keck spectrum of the microlensed Galactic bulge
G-dwarf OGLE-2006-BLG-265, which has a high (~60) signal-to-noise ratio despite
its short (15 min) exposure time because the source was magnified by A~135.
While it is very metal-rich ([Fe/H]=0.56), the higher temperature of this star
compared with the luminous red giants usually measured in the bulge gives its
spectrum many unblended atomic lines. We measure the abundances of 17 elements,
including the first abundances for S and Cu in a bulge star. The [alpha/Fe]
ratios are subsolar, while the odd-Z elements are slightly supersolar, trends
that are also seen in the more metal-rich stars in the bulge and the local
Galactic disk. Because the star is a dwarf, the [O/Fe], [Na/Fe], and [Al/Fe]
ratios cannot be attributed to internal mixing, as is sometimes claimed for
giants. Similar high-resolution spectra could be obtained for about a dozen
bulge dwarf stars per year by means of well-designed target-of-opportunity
observations.


title:
Separating Dark Physics from Physical Darkness: Minimalist Modified
  Gravity vs. Dark Energy

abstract:
  The acceleration of the cosmic expansion may be due to a new component of
physical energy density or a modification of physics itself. Mapping the
expansion of cosmic scales and the growth of large scale structure in tandem
can provide insights to distinguish between the two origins. Using Minimal
Modified Gravity (MMG) - a single parameter gravitational growth index
formalism to parameterize modified gravity theories - we examine the
constraints that cosmological data can place on the nature of the new physics.
For next generation measurements combining weak lensing, supernovae distances,
and the cosmic microwave background we can extend the reach of physics to allow
for fitting gravity simultaneously with the expansion equation of state,
diluting the equation of state estimation by less than 25% relative to when
general relativity is assumed, and determining the growth index to 8%. For weak
lensing we examine the level of understanding needed of quasi- and nonlinear
structure formation in modified gravity theories, and the trade off between
stronger precision but greater susceptibility to bias as progressively more
nonlinear information is used.


title: Proto-Neutron Star Winds with Magnetic Fields and Rotation

abstract:
  We solve the 1D neutrino-heated non-relativistic MHD wind problem for
conditions that range from slowly rotating (spin period P > 10 ms) protoneutron
stars (PNSs) with surface field strengths typical of radio pulsars (B < 10^13
G), to "proto-magnetars" with B ~ 10^14-10^15 G in their hypothesized rapidly
rotating initial states (P ~ 1 ms). We use the simulations of Bucciantini et
al. (2006) to map our monopole results onto a more physical dipole geometry and
to estimate the spindown of PNSs when their winds are relativistic. We then
quantify the effects of rotation and magnetic fields on the mass loss, energy
loss, and r-process nucleosynthesis in PNS winds. We describe the evolution of
PNS winds through the Kelvin-Helmholtz cooling epoch, emphasizing the
transition between (1) thermal neutrino-driven, (2) non-relativistic
magnetically-dominated, and (3) relativistic magnetically-dominated outflows.
We find that proto-magnetars with P ~ 1 ms and B > 10^15 G drive relativistic
winds with luminosities, energies, and Lorentz factors (magnetization sigma ~
0.1-1000) consistent with those required to produce long duration gamma-ray
bursts and hyper-energetic supernovae (SNe). A significant fraction of the
rotational energy may be extracted in only a few seconds, sufficiently rapidly
to alter the asymptotic energy of the SN remnant, its morphology, and,
potentially, its nucleosynthetic yield. Winds from PNSs with more modest
rotation periods (2 - 10 ms) and with magnetar-strength fields produce
conditions significantly more favorable for the r-process than winds from
slowly rotating PNSs. Lastly, we show that energy and momentum deposition by
convectively-excited waves further increase the likelihood of successful
r-process in PNS winds.


title:
CO line emission from Lyman Break Galaxies. Cosmological simulations and
  predictions for ALMA

abstract:
  [Abridged] The detection of the rotational lines of CO in proto-galaxies in
the early Universe provides one of the most promising ways of probing the
fundamental physical properties of a galaxy, such as its size, dynamical mass,
gas density, and temperature. While such observations are currently limited to
the most luminous galaxies, the advent of ALMA will change the situation
dramatically, resulting in the detection of numerous normal galaxies at high
redshifts. Maps and spectra of rotational CO line emission were calculated from
a cosmological N-body/hydrodynamical TreeSPH simulation of a z ~ 3 "Lyman break
galaxy'' of UV luminosity about one order of magnitude below L*. To simulate a
typical observation of our system with ALMA, we imposed characteristic noise,
angular, and spectral resolution constraints. The CO line properties predicted
by our simulation are in good agreement with the two Lyman break systems
detected in CO to date. We find that while supernovae explosions from the
ongoing star formation carve out large cavities in the molecular ISM, they do
not generate large enough gas outflows to make a substantial imprint on the CO
line profile. This implies that for most proto-galaxies - except possibly the
most extreme cases - stellar feedback effects do not affect CO as a dynamical
mass tracer. Detecting CO in sub-L* galaxies at z ~3 will push ALMA to the
limits of its cababilities, and whether a source is detected or not may depend
critically on its inclination angle. Both these effects (sensitivity and
inclination) will severely impair the ability of ALMA to infer the gas
kinematics and dynamical masses using line observations.


title:
Probing Cool and Warm Infrared Galaxies using Photometric and Structural
  Measures

abstract:
  We have analyzed a sample of nearby cool and warm infrared (IR) galaxies
using photometric and structural parameters. The set of measures include
far-infrared color ($C = \log_{10}[S_{60\mu m}/S_{100\mu m}]$), total IR
luminosity ($L_{TIR}$), radio surface brightness as well as radio,
near-infrared, and optical sizes. In a given luminosity range cool and warm
galaxies are considered as those sources that are found approximately $1
\sigma$ below and above the mean color in the far-infrared $C - L_{TIR}$
diagram. We find that galaxy radio surface brightness is well correlated with
color whereas size is less well correlated with color. Our analysis indicates
that IR galaxies that are dominated by cool dust are large, massive spirals
that are not strongly interacting or merging and presumably the ones with the
least active star formation. Dust in these cool objects is less centrally
concentrated than in the more typical luminous and ultra-luminous IR galaxies
that are dominated by warm dust. Our study also shows that low luminosity early
type unbarred and transitional spirals are responsible for the large scatter in
the $C - L_{TIR}$ diagram. Among highly luminous galaxies, late type unbarred
spirals are predominately warm, and early type unbarred and barred are
systematically cooler. We highlight the significance of $C - L_{TIR}$ diagram
in terms of local and high redshifts sub-millimeter galaxies.


title: Cluster-Supercluster Alignments

abstract:
  We study correlations in spatial orientation between galaxy clusters and
their host superclusters using a Hubble Volume N-body realization of a
concordance cosmology and an analytic model for tidally-induced alignments. We
derive an analytic form for distributions of the alignment angle as functions
of halo mass (M), ellipticity (epsilon), distance (r) and velocity (v) and show
that the model, after tuning of three parameters, provides a good fit to the
numerical results. The parameters indicate a high degree of alignment along
anisotropic, collapsed filaments. The degree of alignment increases with M and
epsilon while it decreases with r and is independent of v. We note the
possibility of using the cluster-supercluster alignment effect as a
cosmological probe to constrain the slope of the initial power spectrum.


title:
New Constraints on the Variable Equation of State Parameter from X-Ray
  Gas Mass Fractions and SNe Ia

abstract:
  Recent measurements are suggesting that we live in a flat Universe and that
its present accelerating stage is driven by a dark energy component whose
equation of state may evolve in time. Assuming two different parameterizations
for the function $\omega(z)$, we constrain their free parameters from a joint
analysis involving measurements from X-Ray luminosity of galaxy clusters and
SNe type Ia data.


title: Multiple dynamical components in Local Group dwarf spheroidals

abstract:
  The dwarf spheroidal (dSph) satellites of the Local Group have long been
thought to be simple spheroids of stars embedded within extended dark matter
halos. Recently, however, evidence for the presence of spatially and
kinematically distinct stellar populations has been accumulating. Here, we
examine the influence of such components on dynamical models of dwarf galaxies
embedded in cold dark matter halos. We begin by constructing a model of
Andromeda II, a dSph satellite of M31 which shows evidence for spatially
distinct stellar components. We find that the two-component model predicts an
overall velocity dispersion profile that remains approximately constant at
$\sim 10 - 11$ km s$^{-1}$ out to $\sim 1$ kpc from the center; this is despite
wide kinematic and spatial differences between the two individual components.
The presence of two components may also help to explain oddities in the
velocity dispersion profiles of other dSphs; we show that velocity dispersion
profiles which appear to rise from the center outwards before leveling
off--such as those of Leo I, Draco, and Fornax--can result from the gradual
transition from a dynamically cold, concentrated component to a second, hotter,
and more spatially extended one, both in equilibrium within the same dark halo.
Dwarf galaxies with two stellar components generally have a leptokurtic
line-of-sight velocity distribution which is well described by a double
Maxwellian. Interestingly, we find that multiple equilibrium components could
also provide a potential alternative origin for ``extra-tidal'' stars (normally
ascribed to tidal effects) in situations where corroborating evidence for tides
may be lacking.


title: Galactic chemical evolution: Carbon through Zinc

abstract:
  We calculate the evolution of heavy element abundances from C to Zn in the
solar neighborhood adopting our new nucleosynthesis yields. Our yields are
calculated for wide ranges of metallicity (Z=0-Z_\odot) and the explosion
energy (normal supernovae and hypernovae), based on the light curve and spectra
fitting of individual supernovae. The elemental abundance ratios are in good
agreement with observations. Among the alpha-elements, O, Mg, Si, S, and Ca
show a plateau at [Fe/H] < -1, while Ti is underabundant overall. The observed
abundance of Zn ([Zn/Fe] ~ 0) can be explained only by the high energy
explosion models, which requires a large contribution of hypernovae. The
observed decrease in the odd-Z elements (Na, Al, and Cu) toward low [Fe/H] is
reproduced by the metallicity effect on nucleosynthesis. The iron-peak elements
(Cr, Mn, Co, and Ni) are consistent with the observed mean values at -2.5 <
[Fe/H] < -1$, and the observed trend at the lower metallicity can be explained
by the energy effect. We also show the abundance ratios and the metallicity
distribution functions of the Galactic bulge, halo, and thick disk. Our results
suggest that the formation timescale of the thick disk is ~ 1-3 Gyr.


title: On the role of the current loss in radio pulsar evolution

abstract:
  The aim of this article is to draw attention to the importance of the
electric current loss in the energy output of radio pulsars. We remind that
even the losses attributed to the magneto-dipole radiation of a pulsar in
vacuum can be written as a result of an Ampere force action of the electric
currens flowing over the neutron star surface (Michel, 1991, Beskin et al.,
1993). It is this force that is responsible for the transfer of angular
momentum of a neutron star to an outgoing magneto-dipole wave. If a pulsar is
surrounded by plasma, and there is no longitudinal current in its
magnetosphere, there is no energy loss (Beskin et al., 1993, Mestel et al.,
1999). It is the longitudinal current closing within the pulsar polar cap that
exerts the retardation torque acting on the neutron star. This torque can be
determined if the structure of longitudinal current is known. Here we remind of
the solution by Beskin, Gurevitch & Istomin (1993) and discuss the validity of
such an assumption. The behavior of the recently observed "part-time job"
pulsar B1931+24 can be naturally explained within the model of current loss
while the magneto-dipole model faces difficulties.


title: Environmental Dependence of Cold Dark Matter Halo Formation

abstract:
  We use a high-resolution $N$-body simulation to study how the formation of
cold dark matter (CDM) halos is affected by their environments, and how such
environmental effects produce the age-dependence of halo clustering observed in
recent $N$-body simulations. We estimate, for each halo selected at redshift
$z=0$, an `initial' mass $M_{\rm i}$ defined to be the mass enclosed by the
largest sphere which contains the initial barycenter of the halo particles and
within which the mean linear density is equal to the critical value for
spherical collapse at $z=0$. For halos of a given final mass, $M_{\rm h}$, the
ratio $M_{\rm i}/M_{\rm h}$ has large scatter, and the scatter is larger for
halos of lower final masses. Halos that form earlier on average have larger
$M_{\rm i}/M_{\rm h}$, and so correspond to higher peaks in the initial density
field than their final masses imply. Old halos are more strongly clustered than
younger ones of the same mass because their initial masses are larger. The
age-dependence of clustering for low-mass halos is entirely due to the
difference in the initial/final mass ratio. Low-mass old halos are almost
always located in the vicinity of big structures, and their old ages are
largely due to the fact that their mass accretions are suppressed by the hot
environments produced by the tidal fields of the larger structure. The
age-dependence of clustering is weaker for more massive halos because the
heating by large-scale tidal fields is less important.


title:
Non-Gaussianity of the density distribution in accelerating universes
  II:N-body simulations

abstract:
  We explore the possibility of putting constraints on dark energy models with
statistical property of large scale structure in the non-linear region. In
particular, we investigate the $w$ dependence of non-Gaussianity of the
smoothed density distribution generated by the nonlinear dynamics. In order to
follow the non-linear evolution of the density fluctuations, we apply N-body
simulations based on $P^3 M$ scheme. We show that the relative difference
between non-Gaussianity of $w=-0.8$ model and that of $w=-1.0$ model is $0.67
%$ (skewness) and $1.2 %$ (kurtosis) for $R=8h^{-1}$ Mpc. We also calculate the
correspondent quantities for $R=2h^{-1}$ Mpc, $3.0 %$ (skewness) and $4.5 %$
(kurtosis), and the difference turn out to be greater, even though
non-linearity in this scale is so strong that the complex physical processes
about galaxy formation affect the galaxy distribution. From this, we can expect
that the difference can be tested by all sky galaxy surveys with the help of
mock catalogs created by selection functions, which suggests that
non-Gaussianity of the density distribution potentially plays an important role
for extracting information on dark energy.


title:
XMM search for $X$-ray emission from the black hole candidate
  MACHO-96-BLG-5

abstract:
  MACHO-96-BLG-5 is a microlensing event observed towards the bulge of the
Galaxy with exceptionally long duration of $\sim 970$ days. The microlensing
parallax fit parameters were used to estimate the lens mass $M=6^{+10}_{-3}$
M$_{\odot}$ and its distance $d$ which results to be in the range 0.5 kpc - 2
kpc. The upper limit on the absolute brightness for main-sequence stars of the
same mass is less than 1 $L_{\odot}$ so that the lens is a good black hole
candidate. If it is so, the black hole would accrete by interstellar medium
thereby emitting in the $X$-ray band. Here, the analysis of an {\it XMM} deep
observation towards MACHO-96-BLG-5 lens position is reported. Only an upper
limit (at 99.8% confidence level) to the $X$-ray flux from the lens position of
$9.10\times 10^{-15}$-- $1.45\times 10^{-14}$ erg cm$^{-2}$ s$^{-1}$ in the
energy band $0.2-10$ keV has been obtained from that deep observation allowing
to constrain the putative black hole accretion parameters.


title:
On the X-Ray and Mass Distribution in the Merging Galaxy Cluster 1E
  0657-56: Ram Pressure-Stripping in Substructures with an NFW Density Profile

abstract:
  We investigate the X-ray and mass distribution in the merging galaxy cluster
1E 0657-56. We study head-on collisions of two virialized clusters with an NFW
density profile in the $\Lambda$CDM universe using an N-body + hydrodynamical
code. A clear off-set of an X-ray peak from a mass peak, which is like what is
reported in Clow et al. (2004), is first reproduced in the N-body +
hydrodynamical simulations. We estimate the ram pressure-stripping conditions
of the substructure in mergers of two NFW dark halos using a simple analytical
model. We find that the ram pressure dominates the gravity of the substructure
when the smaller cluster's mass is less than approximately one tenth of the
larger cluster's mass. The characteristic X-ray and mass structures found in 1E
0657-56 suggest that neither the ram pressure nor the gravitational bound force
overwhelms the other and that the mass ratio between the progenitors is near
the critical value mentioned above.


title: One-armed oscillations in Be star discs

abstract:
  In this paper we study the effect of the quadrupole-term in the gravitational
potential of a rotationally deformed central Be star on one armed density waves
in the circumstellar disc.
  The aim is to explain the observed long-term violet over red (V/R) intensity
variations of the double peaked Balmer emission-lines, not only in cool Be star
systems, but also in the hot systems like gamma Cas. We have carried out
semi-analytic and numerical studies of low-frequency one armed global
oscillations in near Keplerian discs around Be stars. In these we have
investigated surface density profiles for the circumstellar disc which have
inner narrow low surface density or gap regions, just interior to global maxima
close to the rapidly rotating star, as well as the mode inner boundary
conditions. Our results indicate that it is not necessary to invoke extra
forces such as caused by line absorption from the stellar flux in order to
explain the long-term V/R variations in the discs around massive Be stars. When
there exists a narrow gap between the star and its circumstellar disc, with the
result that the radial velocity perturbation is non-zero at the inner disc
boundary, we find oscillation (and V/R) periods in the observed range for
plausible magnitudes for the rotational quadrupole term.


title:
Self-induced conversion in dense neutrino gases: Pendulum in flavour
  space

abstract:
  Neutrino-neutrino interactions can lead to collective flavour conversion
effects in supernovae and in the early universe. We demonstrate that the case
of "bipolar" oscillations, where a dense gas of neutrinos and antineutrinos in
equal numbers completely converts from one flavour to another even if the
mixing angle is small, is equivalent to a pendulum in flavour space. Bipolar
flavour conversion corresponds to the swinging of the pendulum, which begins in
an unstable upright position (the initial flavour), and passes through
momentarily the vertically downward position (the other flavour) in the course
of its motion. The time scale to complete one cycle of oscillation depends
logarithmically on the vacuum mixing angle. Likewise, the presence of an
ordinary medium can be shown analytically to contribute to a logarithmic
increase in the bipolar conversion period. We further find that a more complex
(and realistic) system of unequal numbers of neutrinos and antineutrinos is
analogous to a spinning top subject to a torque. This analogy easily explains
how such a system can oscillate in both the bipolar and the synchronised mode,
depending on the neutrino density and the size of the neutrino-antineutrino
asymmetry. Our simple model applies strictly only to isotropic neutrino gasses.
In more general cases, and especially for neutrinos streaming from a supernova
core, different modes couple to each other with unequal strength, an effect
that can lead to kinematical decoherence in flavour space rather than
collective oscillations. The exact circumstances under which collective
oscillations occur in non-isotropic media remain to be understood.


title: X-ray emission from the young brown dwarfs of the Taurus Molecular Cloud

abstract:
  The XMM-Newton Extended Survey of the TMC (XEST) is a large program designed
to systematically investigate the X-ray properties of young stellar/substellar
objects in the TMC. In particular, the area surveyed by 15 XMM-Newton pointings
(of which three are archival observations), supplemented with one archival
Chandra observation, allows us to study 17 BDs with M spectral types. Half of
this sample (9 out of 17 BDs) is detected; 7 BDs are detected here for the
first time in X-rays. We observed a flare from one BD. We confirm several
previous findings on BD X-ray activity: a log-log relation between X-ray and
bolometric luminosity for stars (with L*<10 Lsun) and BDs detected in X-rays; a
shallow log-log relation between X-ray fractional luminosity and mass; a
log-log relation between X-ray fractional luminosity and effective temperature;
a log-log relation between X-ray surface flux and effective temperature. We
find no significant log-log correlation between the X-ray fractional luminosity
and EW(Halpha). Accreting and nonaccreting BDs have a similar X-ray fractional
luminosity. The median X-ray fractional luminosity of nonaccreting BDs is about
4 times lower than the mean saturation value for rapidly rotating low-mass
field stars. Our TMC BDs have higher X-ray fractional luminosity than BDs in
the Chandra Orion Ultradeep Project. The X-ray fractional luminosity declines
from low-mass stars to M-type BDs, and as a sample, the BDs are less efficient
X-ray emitters than low-mass stars. We thus conclude that while the BD
atmospheres observed here are mostly warm enough to sustain coronal activity, a
trend is seen that may indicate its gradual decline due to the drop in
photospheric ionization degree (abridged).


title:
PAMELA - A Payload for Antimatter Matter Exploration and Light-nuclei
  Astrophysics

abstract:
  The PAMELA experiment is a satellite-borne apparatus designed to study
charged particles in the cosmic radiation with a particular focus on
antiparticles. PAMELA is mounted on the Resurs DK1 satellite that was launched
from the Baikonur cosmodrome on June 15th 2006. The PAMELA apparatus comprises
a time-of-flight system, a magnetic spectrometer, a silicon-tungsten
electromagnetic calorimeter, an anticoincidence system, a shower tail catcher
scintillator and a neutron detector. The combination of these devices allows
antiparticles to be reliably identified from a large background of other
charged particles. This paper reviews the design, space qualification and
on-ground performance of PAMELA. The in-orbit performance will be discussed in
future publications.


title: Spectral Synthesis of Massive Stars in Clusters

abstract:
  Stellar clusters are thought to be the simplest stellar systems and the
closest observational counterparts to theoretical models for single stellar
populations. Progress in our understanding of the atmospheres and evolution of
massive stars has led to generally reliable synthesis models. The future
release of new evolution models with rotation, however, will require
non-trivial updates to previously published synthesis models, in particular for
all Wolf-Rayet and red supergiant related quantities. Cluster synthesis work is
currently progressing from a purely stellar approach to a more comprehensive
stellar+cluster perspective. The photometric evolution of stars and the
dynamical evolution of clusters are delicately interwoven. Recent work attempts
to combine these seemingly related fields.


title:
Assessing The Starburst Contribution to the Gamma-Ray and Neutrino
  Backgrounds

abstract:
  If cosmic ray protons interact with gas at roughly the mean density of the
interstellar medium in starburst galaxies, then pion decay in starbursts is
likely to contribute significantly to the diffuse extra-galactic background in
both gamma-rays and high energy neutrinos. We describe the assumptions that
lead to this conclusion and clarify the difference between our estimates and
those of Stecker (2006). Detection of a single starburst by GLAST would confirm
the significant contribution of starburst galaxies to the extra-galactic
neutrino and gamma-ray backgrounds.


title:
An improved deprojection and PSF-deconvolution technique for
  galaxy-cluster X-ray surface-brightness profiles

abstract:
  We have developed a regularisation procedure for the direct deprojection and
PSF-deconvolution of X-ray surface brightness profiles of clusters of galaxies.
This procedure allows us to obtain accurate density profiles in a
straightforward manner from X-ray observations (in particular data from
XMM-Newton, where the PSF correction is important), while retaining information
about substructure in the gas distribution, in contrast to analytic modelling
of the profiles. In addition to describing our procedure, we present here a
detailed investigation of the accuracy of the method and its error calculations
over a wide range of input profile characteristics and data quality using Monte
Carlo simulations. We also make comparisons with gas density profiles obtained
from Chandra observations, where the PSF correction is small, and with profiles
obtained using analytic modelling, which demonstrate that our procedure is a
useful improvement over standard techniques. This type of method will be
especially valuable in the ongoing analysis of unbiased and complete samples of
X-ray clusters, both local and distant, helping to improve the quality of their
results.


title: The Cosmic Battery Revisited

abstract:
  We reinvestigate the generation and accumulation of magnetic flux in
optically thin accretion flows around active gravitating objects. The source of
the magnetic field is the azimuthal electric current associated with the
Poynting-Robertson drag on the electrons of the accreting plasma. This current
generates magnetic field loops which open up because of the differential
rotation of the flow. We show through simple numerical simulations that what
regulates the generation and accumulation of magnetic flux near the center is
the value of the plasma conductivity. Although the conductivity is usually
considered to be effectively infinite for the fully ionized plasmas expected
near the inner edge of accretion disks, the turbulence of those plasmas may
actually render them much less conducting due to the presence of anomalous
resistivity. We have discovered that if the resistivity is sufficiently high
throughout the turbulent disk while it is suppressed interior to its inner
edge, an interesting steady-state process is established: accretion carries and
accumulates magnetic flux of one polarity inside the inner edge of the disk,
whereas magnetic diffusion releases magnetic flux of the opposite polarity to
large distances. In this scenario, magnetic flux of one polarity grows and
accumulates at a steady rate in the region inside the inner edge and up to the
point of equipartition when it becomes dynamically important. We argue that
this inward growth and outward expulsion of oppositely-directed magnetic fields
that we propose may account for the ~30 min cyclic variability observed in the
galactic microquasar GRS1915+105.


title:
Searching for massive pre--stellar cores through observations of N2H+
  and N2D+

abstract:
  We have measured the deuterium fractionation (through the column density
ratio N(N2D+)/N(N2H+)) and the CO depletion factor (ratio between expected and
observed CO abundance) in a sample of 10 high-mass protostellar candidates, in
order to understand whether the earliest evolutionary stages of high-mass stars
have chemical characteristics similar to those of low-mass ones. The
observations were carried out with the IRAM-30m telescope and the JCMT. We have
detected N2D+ emission in 7 of the 10 sources of our sample, and found an
average value N(N2D+)/N(N2H+)~0.015. This value is 3 orders of magnitude larger
than the interstellar D/H ratio, indicating the presence of cold and dense gas,
in which the physical-chemical conditions are similar to those observed in
low-mass pre-stellar cores. Also, the integrated CO depletion factors show that
in the majority of the sources the expected CO abundances are larger than the
observed values, with a median ratio of 3.2. In principle, the cold gas that
gives origin to the N2D+ emission can be the remnant of the massive molecular
core in which the high-mass (proto-)star was born, not yet heated up by the
central object. If so, our results indicate that the chemical properties of the
clouds in which high-mass stars are born are similar to their low-mass
counterparts. Alternatively, this cold gas can be located into one (or more)
starless core (cores) near the protostellar object. Due to the poor angular
resolution of our data, we cannot decide which is the correct scenario.


title:
Nonlinear simulations of magnetic Taylor-Couette flow with current-free
  helical magnetic fields

abstract:
  The magnetorotational instability (MRI) in cylindrical Taylor-Couette flow
with external helical magnetic field is simulated for infinite and finite
aspect ratios. We solve the MHD equations in their small Prandtl number limit
and confirm with time-dependent nonlinear simulations that the additional
toroidal component of the magnetic field reduces the critical Reynolds number
from $O(10^6)$ (axial field only) to $O(10^3)$ for liquid metals with their
small magnetic Prandtl number. Computing the saturated state we obtain velocity
amplitudes which help designing proper experimental setups. Experiments with
liquid gallium require axial field $\sim 50$ Gauss and axial current $\sim 4$
kA for the toroidal field. It is sufficient that the vertical velocity $u_z$ of
the flow can be measured with a precision of 0.1mm/s.
  We also show that the endplates enclosing the cylinders do not destroy the
traveling wave instability which can be observed as presented in earlier
studies. For TC containers without and with endplates the angular momentum
transport of the MRI instability is shown as to be outwards.


title: K-band spectroscopy of deeply embedded, young OB stars

abstract:
  We have obtained high resolution (R = 10,000) K-band spectra of candidate
young massive stars deeply embedded in high-mass star-forming regions. These
objects were selected from a near-infrared survey of 44 regions of high-mass
star-formation (Kaper et al, 2006). In these clusters, 38 OB stars are
identified whose K-band spectra are dominated by photospheric emission. In
almost all those stars, the K-band spectra are indistinguishable from field
stars. However, in some stars the profile of the Bracket gamma line is
different (less deep, or absent) from those of the O field stars. One of the
explanations of these profiles might be an enhanced mass-loss.


title:
The population in the background of open clusters: Tracer of the
  Norma-Cygnus arm

abstract:
  We present colour-magnitude diagrams of open clusters, located in the range
$112^\circ < l < 252^\circ$, manifesting stellar populations in the background
of clusters. Some of the populations are found to be located beyond the Perseus
arm and may be the part of Norma-Cygnus (outer) arm. The outer arm seems to be
continued from $l\sim120^\circ$ to $l\sim235^\circ$. The background populations
follow the downward warp of the Galactic plane around $l\sim240^\circ$.


title: Dark Matter: the Connection with Gamma-Ray Astrophysics

abstract:
  We review the status of indirect Dark Matter searches, focusing in particular
on the connection with gamma-ray Astrophysics, and on the prospects for
detection with the upcoming space telescope GLAST and Air Cherenkov Telescopes
such as CANGAROO, HESS, MAGIC and VERITAS. After a brief introduction where we
review the fundamental motivations for indirect searches, we tackle the
question of whether it is possible to obtain strong enough evidence from
astrophysical observations, to claim discovery of Dark Matter particles. To
this purpose, we discuss some recent conflicting claims that have generated
some confusion in the field, and present new strategies that may provide the
long-awaited smoking-gun for Dark Matter.