title:
High-Resolution X-ray Spectroscopy of the Interstellar Medium II: Neon
  and Iron Absorption Edges

abstract:
  We present high-resolution spectroscopy of the neon K-shell and iron L-shell
interstellar absorption edges in nine X-ray binaries using the High Energy
Transmission Grating Spectrometer (HETGS) onboard the Chandra X-ray
Observatory. We found that the iron absorption is well fit by an experimental
determination of the cross-section for metallic iron, although with a slight
wavelength shift of ~20 mA. The neon edge region is best fit by a model that
includes the neutral neon edge and three Gaussian absorption lines. We identify
these lines as due to the 1s-2p transitions from Ne II, Ne III, and Ne IX. As
we found in our oxygen edge study, the theoretical predictions for neutral and
low-ionization lines all require shifts of ~20 mA to match our data. Combined
with our earlier oxygen edge study, we find that a best fit O/Ne ratio of
5.4+/-1.6, consistent with standard interstellar abundances. Our best fit Fe/Ne
ratio of 0.20+/-0.03 is significantly lower than the interstellar value. We
attribute this difference to iron depletion into dust grains in the
interstellar medium. We make the first measurement of the neon ionization
fraction in the ISM. We find Ne II/Ne I ~ 0.3 and Ne III/Ne I ~ 0.07. These
values are larger than is expected given the measured ionization of
interstellar helium. For Ne IX, our results confirm the detection of the hot
ionized interstellar medium of the Galaxy.


title:
Can Galactic Cosmic Rays Account for Solar 6Li Without Overproducing
  Gamma Rays?

abstract:
  Cosmic-ray interactions with interstellar gas produces both 6Li, which
accumulates in the interstellar medium (ISM), and $\pi^0$ mesons, which decay
to gamma-rays which propagate throughout the cosmos. Local 6Li abundances and
extragalactic gamma-rays thus have a common origin which tightly links them. We
exploit this connection to use gamma-ray observations to infer the contribution
to 6Li nucleosynthesis by standard Galactic cosmic-ray (GCR) interactions with
the ISM. Our calculation uses a carefully propagated cosmic-ray spectrum and
accounts for 6Li production from both fusion reactions ($\alpha \alpha \to
^6Li$) as well as from spallation channels (${p,\alpha+CNO \to ^6Li$). We find
that although extreme assumptions yield a consistent picture, more realistic
ones indicate that solar 6Li cannot be produced by standard GCRs alone without
overproducing the hadronic gamma rays. Implications for the primordial 6Li
production by decaying dark matter and cosmic rays from cosmological structure
formation are discussed. Upcoming gamma-ray observations by GLAST will be
crucial for determining the resolution of this problem.


title:
Disparate MgII Absorption Statistics towards Quasars and Gamma-Ray
  Bursts : A Possible Explanation

abstract:
  We examine the recent report by Prochter et al. (2006) that gamma-ray burst
(GRB) sight lines have a much higher incidence of strong MgII absorption than
quasar sight lines. We propose that the discrepancy is due to the different
beam sizes of GRBs and quasars, and that the intervening MgII systems are
clumpy with the dense part of each cloudlet of a similar size as the quasars,
i.e. < 10^16 cm, but bigger than GRBs. We also discuss observational
predictions of our proposed model. Most notably, in some cases the intervening
MgII absorbers in GRB spectra should be seen varying, and quasars with smaller
sizes should show an increased rate of strong MgII absorbers. In fact, our
prediction of variable MgII lines in the GRB spectra has been now confirmed by
Hao et al. (2007), who observed intervening FeII and MgII lines at z=1.48 to be
strongly variable in the multi-epoch spectra of z=4.05 GRB060206.


title:
Cosmological and Astrophysical Parameter Measurements with 21-cm
  Anisotropies During the Era of Reionization

abstract:
  We study the prospects for extracting cosmological and astrophysical
parameters from the low radio frequency 21-cm background due to the spin-flip
transition of neutral Hydrogen during and prior to the reionization of the
Universe. We make use of the angular power spectrum of 21-cm anisotropies,
which exists due to inhomogeneities in the neutral Hydrogen density field, the
gas temperature field, the gas velocity field, and the spatial distribution of
the Lyman-$\alpha$ intensity field associated with first luminous sources that
emit UV photons. We extract parameters that describe both the underlying mass
power spectrum and the global cosmology, as well as a set of simplified
astrophysical parameters that connect fluctuations in the dark matter to those
that govern 21-cm fluctuations. We also marginalize over a model for the
foregrounds at low radio frequencies. In this general description, we find
large degeneracies between cosmological parameters and the astrophysical
parameters, though such degeneracies are reduced when strong assumptions are
made with respect to the spin temperature relative to the CMB temperature or
when complicated sources of anisotropy in the brightness temperature are
ignored. Some of the degeneracies between cosmological and astrophysical
parameters are broken when 21-cm anisotropy measurements are combined with
information from the CMB, such as the temperature and the polarization
measurements with Planck. While the overall improvement on the cosmological
parameter estimates is not significant when measurements from first-generation
interferometers are combined with Planck, such a combination can measure
astrophysical parameters such as the ionization fraction in several redshift
bins with reasonable accuracy.


title:
An Observational Determination of the Bolometric Quasar Luminosity
  Function

abstract:
  We combine a large set of quasar luminosity function (QLF) measurements from
the rest-frame optical, soft and hard X-ray, and near- and mid-infrared bands
to determine the bolometric QLF in the redshift interval z=0-6. Accounting for
the observed distributions of quasar column densities and variation of spectral
energy distribution (SED) shapes, and their dependence on luminosity, makes it
possible to integrate the observations in a reliable manner and provides a
baseline in redshift and luminosity larger than that of any individual survey.
We infer the QLF break luminosity and faint-end slope out to z~4.5 and confirm
at high significance (>10sigma) previous claims of a flattening in both the
faint- and bright-end slopes with redshift. With the best-fit estimates of the
column density distribution and quasar SED, which both depend on luminosity, a
single bolometric QLF self-consistently reproduces the observed QLFs in all
bands and at all redshifts for which we compile measurements. Ignoring this
luminosity dependence does not yield a self-consistent bolometric QLF and there
is no evidence for any additional dependence on redshift. We calculate the
expected relic black hole mass function and mass density, cosmic X-ray
background, and ionization rate as a function of redshift and find they are
consistent with existing measurements. The peak in the total quasar luminosity
density is well-constrained at z=2.15+/-0.05. We provide a number of fitting
functions to the bolometric QLF and its manifestations in various bands, and a
script to return the QLF at arbitrary frequency and redshift from these fits,
as the most simple inferences from the QLF measured in a single band can be
misleading.


title:
Curvature and isocurvature perturbations from two-field inflation in a
  slow-roll expansion

abstract:
  We calculate the power spectra of primordial curvature and isocurvature
perturbations from a general two field inflation model at next-to-leading order
correction in a slow-roll expansion. In particular we calculate the spectral
indices to second order in slow-roll parameters. We show that the
cross-correlation of the curvature and isocurvature perturbations at the time
of Hubble-exit during inflation is non-zero at first-order in slow-roll
parameters. We apply our results to different classes of inflation, including
inflaton and curvaton scenarios. The spectrum of primordial gravitational
waves, curvature and isocurvature perturbations obey generalised consistency
relations in two-field inflation models. We give the first two consistency
relations in an infinite hierarchy.


title: The Scattering of Lyman-series Photons in the Intergalactic Medium

abstract:
  We re-examine scattering of photons near the Lyman-alpha resonance in the
intergalactic medium (IGM). We first derive a general integral solution for the
radiation field around resonance when spin diffusivity is ignored. Our solution
shows explicitly that recoil sources an absorption feature, whose magnitude
increases with the relative importance of recoil compared to Doppler
broadening. This spectrum depends on the Lyman-alpha line profile, but
approximating it with the absorption profile appropriate to the Lorentzian
wings of natural broadening accurately reproduces the results for a full Voigt
profile so long as T<1000 K in the IGM. This approximation allows us to obtain
simple analytic formulae for the total scattering rate of Lyman-alpha photons
and the accompanying energy exchange rate. Our power series solutions converge
rapidly for photons that redshift into the Lyman-alpha resonance as well as for
photons injected at line center. We confirm previous calculations showing that
heating through this mechanism is quite slow and probably negligible compared
to other sources. We then show that energy exchange during the scattering of
higher-order Lyman-series photons can be much more important than naively
predicted by recoil arguments. However, the resulting heating is still
completely negligible.


title: The Host Galaxies and Classification of Active Galactic Nuclei

abstract:
  We present an analysis of the host properties of 85224 emission-line galaxies
from the Sloan Digital Sky Survey. We show that Seyferts and LINERs form
clearly separated branches on the standard optical diagnostic diagrams. We
derive a new empirical classification scheme which cleanly separates
star-forming galaxies, composite AGN-HII galaxies, Seyferts and LINERs and we
study the host galaxy properties of these different classes of objects. LINERs
are older, more massive, less dusty and more concentrated, and have higher
velocity dispersions and lower [OIII] luminosities than Seyfert galaxies. We
consider the quantity L[OIII]/sigma^4, which is an indicator of the black hole
accretion rate relative to the Eddington rate. Remarkably, we find that at
fixed L[OIII]/sigma^4, all differences between Seyfert and LINER host
properties disappear. LINERs and Seyferts form a continuous sequence, with
LINERs dominant at low L/L(EDD) and Seyferts dominant at high L/L(EDD). These
results suggest that the majority of LINERs are AGN and that the Seyfert/LINER
dichotomy is analogous to the high/low-state transition for X-ray binary
systems. We apply theoretical photoionization models and show that pure LINERs
require a harder ionizing radiation field with lower ionization parameter than
Seyfert galaxies, consistent with the low and high X-ray binary states.


title: A Universe Dominated by Dilaton Field

abstract:
  Using a single dilaton field, a unified model of the Universe is proposed,
which evolves from the radiation-like dominance in the Big Bang, to the
dark-matter-like dominance in the early Universe, to the coexistence of both
dark-matter-like and dark energy today, and finally to the dark energy
dominance in the infinite future. This model is consistent with current results
on the age of the Universe, the transition redshift from deceleration to
acceleration, BBN and evolution of dark energy. Future higher quality data may
constrain the cosmic evolution of dark matter, dark energy and Hubble constant
more precisely and make critical tests on our model predictions.


title: A kinematical approach to dark energy studies

abstract:
  We present and employ a new kinematical approach to cosmological `dark
energy' studies. We construct models in terms of the dimensionless second and
third derivatives of the scale factor a(t) with respect to cosmic time t,
namely the present-day value of the deceleration parameter q_0 and the cosmic
jerk parameter, j(t). An elegant feature of this parameterization is that all
LCDM models have j(t)=1 (constant), which facilitates simple tests for
departures from the LCDM paradigm. Applying our model to the three best
available sets of redshift-independent distance measurements, from type Ia
supernovae and X-ray cluster gas mass fraction measurements, we obtain clear
statistical evidence for a late time transition from a decelerating to an
accelerating phase. For a flat model with constant jerk, j(t)=j, we measure
q_0=-0.81+-0.14 and j=2.16+0.81-0.75, results that are consistent with LCDM at
about the 1sigma confidence level. A standard `dynamical' analysis of the same
data, employing the Friedmann equations and modeling the dark energy as a fluid
with an equation of state parameter, w (constant), gives
Omega_m=0.306+0.042-0.040 and w=-1.15+0.14-0.18, also consistent with LCDM at
about the 1sigma level. In comparison to dynamical analyses, the kinematical
approach uses a different model set and employs a minimum of prior information,
being independent of any particular gravity theory. The results obtained with
this new approach therefore provide important additional information and we
argue that both kinematical and dynamical techniques should be employed in
future dark energy studies, where possible. Our results provide further
interesting support for the concordance LCDM paradigm.


title: Gauss-Bonnet braneworld and WMAP three year results

abstract:
  We compare predictions for the spectral index and tensor-scalar ratio in
models of patch inflation with the WMAP three year data. There are three cases
of these models of inflation, which arise in the Gauss-Bonnet braneworld
scenario: Gauss-Bonnet (GB), Randall-Sundrum (RS), and 4D general relativity
(GR). We consider the large-field potential $V \propto \phi^p$ in both
commutative and noncommutative spacetimes, and find that in the cases of the GB
and GR patch cosmologies, the quadratic potential is observationally favored,
while the quartic potential is ruled out in most patches. Strong noncommutative
inflation is excluded in all cases because it leads to a blue-tilted scalar
spectral index.


title: Report on the CoRoT Evolution and Seismic Tools Activity

abstract:
  We present the work undertaken by the Evolution and Seismic Tools Activity
(ESTA) team of the CoRoT Seismology Working Group. We have focused on two main
tasks: Task 1 - now finished - has aimed at testing, comparing and optimising
seven stellar evolution codes which will be used to model the internal
structure and evolution of the CoRoT target stars. Task 2, still underway, aims
at testing, comparing and optimising different seismic codes used to calculate
the oscillations of models for different types of stars. The results already
obtained are quite satisfactory, showing minor differences between the
different numerical tools provided the same assumptions on the physical
parameters are made. This work gives us confidence on the numerical tools that
will be available to interpret the future CoRoT seismic data.


title: The AGN Obscuring Torus -- End of the "Doughnut" Paradigm?

abstract:
  Unified schemes of active galactic nuclei (AGN) require an obscuring dusty
torus around the central engine. The compact sizes (only a few pc) determined
in recent high-resolution observations require that the obscuring matter be
clumpy and located inside the region where the black-hole gravity dominates
over the galactic bulge. This location is in line with the scenario depicting
the torus as the region of the clumpy wind coming off the accretion disk in
which the clouds are dusty and optically thick. We study here the outflow
scenario within the framework of hydromagnetic disk winds, incorporating the
cloud properties determined from detailed modeling of the IR emission from
clumpy tori. We find that torus clouds were likely detected in recent water
maser observations of NGC 3079. In the wind scenario, the AGN main dynamic
channel for release of accreted mass seems to be switching at low luminosities
from torus outflow to radio jets. The torus disappears when the bolometric
luminosity decreases below about \E{42} erg/sec because the accretion onto the
central black hole can no longer sustain the required cloud outflow rate. This
disappearance seems to have been observed in both LINERs and radio galaxies.
With further luminosity decrease, suppression of cloud outflow spreads radially
inward from the disk's dusty, molecular region into its atomic, ionized zone,
resulting in disappearance of the broad emission line region at lower
luminosities, yet to be determined.


title: Asymmetries in the inner regions of LCDM haloes

abstract:
  Many galaxies display warps, lopsided images, asymmetric rotation curves or
other features which suggest that their immediate dynamical environment is
neither static nor in equilibrium. In Cold Dark Matter (CDM) theories, such
non-equilibrium features are expected in the inner regions of many dark haloes
as a result of recent hierarchical growth. We used the excellent statistics
provided by the very large Millennium Simulation to study (i) how the
distribution of position and velocity asymmetries predicted for halo cores by
the concordance LCDM cosmogony depends on halo mass, and (ii) how much of the
dark matter in the inner core has been added at relatively recent times.
Asymmetries are typically larger in more massive haloes. Thus 20% of cluster
halos have density centre separated from barycentre by more than 20% of the
virial radius, while only 7% of Milky Way halos have such large asymmetries.
About 40% of all cluster halos have a mean core velocity which differs from the
barycentre velocity by more than a quarter of the characteristic halo circular
velocity, whereas only 10% of Milky Way halos have such large velocity offsets.
About 25% of all cluster haloes have acquired more than a quarter of the mass
currently in their inner 10kpc through mergers since z=1. The corresponding
percentage of Milky Way haloes is 15%. These numbers seem quite compatible with
the levels of asymmetry seen in the observable regions of galaxies, but
quantitative comparison requires more detailed modelling of the observable
components.


title:
Velocity Curves for Stars in Disk Galaxies: A case for Nearly Newtonian
  Dynamics

abstract:
  The dark matter constraint imposed by the recent WMAP experiment on
gravitational theories is analyzed. Using the non-linearity of the vacuum
Einstein's equations, it is shown that when the slow motion condition is
applied to the geodesic equations, the resulting nearly Newtonian gravitational
field describes nearly flat velocity curves for rotating stars in the vicinity
of thin disk galaxies.


title: The superburst recurrence time in luminous persistent LMXBs

abstract:
  Theory and observations favor stable helium burning as the most important
means to produce fuel for superbursts on neutron star surfaces. However, all
known superbursters exhibit unstable burning as well. This ambiguity prompted
us to search for superbursts in data from the BeppoSAX Wide Field Cameras of
ten luminous LMXBs, most of which do not exhibit normal type-I X-ray bursts. We
found no superbursts and determine a lower limit on the recurrence time which
varies between 30 and 76 days (90% confidence). All recurrence time limits
except one are longer than the observed recurrence time for GX 17+2. This
difference can be understood if the mass accretion rate in GX 17+2 is several
tens of percent higher than in the other sources; alternatively, the accreted
material in GX 17+2 might be hydrogen deficient, leading to larger carbon
yields than in the other sources. We compare our results to the latest models
of superbursts. As our search method is indiscriminate of the burst ignition
scenario, the recurrence time limits may also be applied to other bursts of
similar duration and brightness.


title: Reconstructing the dark energy equation of state with varying couplings

abstract:
  We revisit the idea of using varying couplings to probe the nature of dark
energy, in particular by reconstructing its equation of state. We show that
this method can be far superior to the standard methods (using type Ia
supernovae or weak lensing). We also show that the simultaneous use of
measurements of the fine-structure constant $\alpha$ and the electron-to-proton
mass ratio $\mu$ allows a direct probe of grand unification scenarios. We
present forecasts for the sensitivity of this method, both for the near future
and for the next generation of spectrographs -- for the latter we focus on the
planned CODEX instrument for ESO's Extremely Large Telescope (formerly known as
OWL). A high-accuracy reconstruction of the equation of state may be possible
all the way up to redshift $z\sim4$.


title: The aftermath of the first stars: massive black holes

abstract:
  We investigate the evolution of the primordial gas surrounding the first
massive black holes formed by the collapse of Population III stars at redshifts
z > 20. Carrying out three-dimensional hydrodynamical simulations using GADGET,
we study the dynamical, thermal and chemical evolution of the first relic H II
regions. We also carry out simulations of the mergers of relic H II regions
with neighboring neutral minihaloes, which contain high density primordial gas
that can accrete onto a Pop III remnant black hole. We find that there may have
been a significant time delay, of order ~10^8 yr, between black hole formation
and the onset of efficient accretion. The build-up of supermassive black holes,
believed to power the z > 6 quasars observed in the Sloan Digital Sky Survey,
therefore faces a crucial early bottleneck. More massive seed black holes may
thus be required, such as those formed by the direct collapse of a primordial
gas cloud facilitated by atomic line cooling. The high optical depth to
Lyman-Werner (LW) photons that results from the high fraction of H_2 molecules
that form in relic H II regions, combined with the continued formation of H_2
inside the dynamically expanding relic H II region, leads to shielding of the
molecules inside these regions at least until a critical background LW flux of
\~10^{-24} ergs s^{-1} cm^{-2} Hz^{-1} sr^{-1}, is established. Furthermore, we
find that a high fraction of HD molecules, X_{HD} > 10^{-7}, is formed,
potentially enabling the formation of Pop II.5 stars during later stages of
structure formation when the relic H II region gas is assembled into a
sufficiently deep potential well to gravitationally confine the gas again.


title:
The Evolution of Low Mass Helium Stars towards Supernova Type I
  Explosion

abstract:
  We explore the hypothesis, that helium stars in a certain mass range can
evolve to a carbon core explosion similar to what is widely accepted as an
explanation for the SN I phenomenon. This should happen when their
carbon-oxygen core grows thanks to the helium shell burning above the core. We
found that in the mass range of about 1.7-2.2 Msun, indeed this can happen.
  The main new insight we believe we gained is the crucial importance of an
"early" off-center ignition of carbon, which at a later stage prevents the
carbon which forms below the helium burning shell and ignites, from burning the
carbon all the way to the center. When helium is almost depleted in the
convective envelope by the helium burning shell at its bottom, the now
super-Chandrasekhar mass carbon-oxygen core contracts, and the residual
degenerate carbon at the center is ignited, resulting in a runaway similar to
the classical SN I scenario.
  Since the structure and behavior of the carbon-oxygen core of the helium
stars of our interest is very similar to that of a mass accreting carbon-oxygen
star, we also thoroughly examined the behavior of carbon-oxygen stars. We
discovered that the models which ignite carbon off-center (in the mass range of
about 1.05-1.18 Msun, depending on the carbon mass fraction) present an
interesting SN I progenitor scenario of their own, since whereas in the
standard scenario runaway always takes place at the same density of about 2E9
gr/cm3, in our case, due to the small amount of carbon ignited, we get a whole
range of densities from 1E9 up to 6E9 gr/cm3.


title: Map of the Galaxy in the 6.7 keV emission line

abstract:
  We study the two dimensional surface brightness distribution of the Galactic
X-ray background emission outside the central degree around Sgr A* in the 6.7
keV line as measured by the PCA spectrometer of the RXTE observatory. The use
of the emission line instead of continuum (3-20 keV) radiation and application
of time variability filtering to the long data set allows us to strongly
suppress the contamination of the GRXE map by bright point sources. The surface
brightness in the 6.7 keV line demonstrates very good correspondence with the
near-infrared surface brightness over the whole Galaxy, supporting the notion
that the GRXE consists mostly of integrated emission from weak Galactic X-ray
sources. We find compatible linear correlations between near-infrared and 6.7
keV surface brightness for the bulge and disk of the Galaxy. This indicates
that the populations of weak X-ray sources making up the GRXE in the disk and
bulge are not significantly different.


title: Analysis to the entangled states from an extended Chaplygin gas model

abstract:
  With considerations of the recently released WMAP year three and supernova
legacy survey (SNLS) data set analysis that favors models similar to the $%
\Lambda CDM$ model by possibly mild fluctuations around the vacuum energy or
the cosmological constant, we extend the original Chaplygin Gas model (ECG) via
modifying the Chaplygin Gas equation of state by two parameters to describe an
entangled mixture state from an available matter and the rest component (which
can take the cosmological constant or dark energy as in the current cosmic
stage, or `curvature-like' term, or radiation component in the early epoch, as
various phases) coexistence. At low redshifts, the connection of the ECG model
and the Born-infeld field is set up. As paradigms, we use the data coming from
the recently released SNLS for the first year and also the famous 157 type Ia
supernova (Ia SNe) gold dataset to constrain the model parameters. The
restricted results demonstrate clearly how large the entangled degree or the
ratio between the energy density parameters of the two entangled phases being.
The fact that the ECG models are consistent with the observations of Ia SNe is
obtained through the redshift-luminosity distance diagram, hence the ECG can be
regarded possible candidates for mimicking the current speed-up expansion of
our universe.


title:
On the relation between electron temperatures in the O+ and O++ zones in
  high-metallicity HII regions

abstract:
  We suggest a new way to establish the relation between the electron
temperature t3 within the [OIII] zone and the electron temperature t2 within
the [OII] zone in high-metallicity (12+log(O/H) > 8.25) HII regions. The t2 -
t3 diagram is constructed by applying our method to a sample of 372 HII
regions. We find that the correlation between t2 and t3 is tight and can be
approximated by a linear expression. The new t2 - t3 relation can be used to
determine t2 and accurate abundances in high-metallicity HII regions with a
measured t3. It can also be used in conjunction with the ff relation for the
determination of t3 and t2 and oxygen abundances in high-metallicity HII
regions where the [OIII]4363 auroral line is not detected. The derived t2 - t3
relation is independent of photoionization models of HII regions.


title: Cosmic tomographies: baryon acoustic oscillations and weak lensing

abstract:
  We explore the complementarity between two tomographic probes of the
universe: baryon acoustic oscillations (BAOs) and weak lensing (WL). We find
that photometric measurements of BAOs alone do not provide very tight
constraints on the dark energy equation of state parameters, partially due to
our uncertain knowledge of the galaxy bias. WL, on the other hand, is adversely
impacted by the uncertainties of the probability distribution of photometric
redshift (photo-z) errors. A joint analysis of the two, however, is more robust
to these uncertainties and leads to a remarkable improvement over the results
of either probe alone.
  Forecasts of cosmological constraints are provided for various BAO and WL
surveys in combination with CMB measurements from Planck. In particular, we
find that the joint analysis of BAO and WL power spectra with the Large
Synoptic Survey Telescope can tighten the errors of the dark energy equation of
state (at a = 0.63) and its rate of change, respectively, to 0.016 and 0.16
(marginalized over 131 other parameters). With supernovae and cluster counting
as well as higher-order statistics of the same galaxy and shear data, one can
further improve the constraints.


title: A Cosmological Mass Function with Broken Hierarchy

abstract:
  We construct an analytic formalism for the mass function of cold dark matter
halos, assuming that there is a break in the hierarchical merging process.
According to this {\it broken-hierarchy} scenario, due to the inherent nature
of the gravitational tidal field the formation of massive pancakes precedes
that of dark halos of low-mass. In the framework of the Zel'dovich
approximation which generically predicts the presence of pancakes, we first
derive analytically the conditional probability that a low-mass halo observed
at present epoch was embedded in an isolated pancake at some earlier epoch.
Then, we follow the standard Press-Schechter approach to count analytically the
number density of low-mass halos that formed through anti-hierarchical
fragmentation of the massive pancakes. Our mass function is well approximated
by a power-law dN/dM = M^{-l} in the mass range 10^{6}M_{sun}/h < M <
10^{10}M_{sun}/h with the slope l=1.86 shallower than that of the currently
popular Sheth-Tormen mass function l = 2.1. It is expected that our mass
function will provide a useful analytic tool for investigating the effect of
broken hierarchy on the structure formation.


title: Forming a constant density medium close to long gamma-ray bursts

abstract:
  The progenitor stars of long Gamma-Ray Bursts (GRBs) are thought to be
Wolf-Rayet stars, which generate a massive and energetic wind. Nevertheless,
about 25 percent of all GRB afterglows light curves indicate a constant density
medium close to the exploding star. We explore various ways to produce this, by
creating situations where the wind termination shock arrives very close to the
star, as the shocked wind material has a nearly constant density. Typically,
the distance between a Wolf-Rayet star and the wind termination shock is too
large to allow afterglow formation in the shocked wind material. Here, we
investigate possible causes allowing for a smaller distance: A high density or
a high pressure in the surrounding interstellar medium (ISM), a weak Wolf-Rayet
star wind, the presence of a binary companion, and fast motion of the
Wolf-Rayet star relative to the ISM. We find that all four scenarios are
possible in a limited parameter space, but that none of them is by itself
likely to explain the large fraction of constant density afterglows. A low GRB
progenitor metallicity, and a high GRB energy make the occurrence of a GRB
afterglow in a constant density medium more likely. This may be consistent with
constant densities beingpreferentially found for energetic, high redshift GRBs.


title:
The Millennium Galaxy Catalogue: Bulge/Disc Decomposition of 10095
  Nearby Galaxies

abstract:
  We have modelled the light distribution in 10095 galaxies from the Millennium
Galaxy Catalogue (MGC), providing publically available structural catalogues
for a large, representative sample of galaxies in the local Universe. Three
different models were used: (1) a single Sersic function for the whole galaxy,
(2) a bulge-disc decomposition model using a de Vaucouleurs (R^{1/4}) bulge
plus exponential disc, (3) a bulge-disc decomposition model using a Sersic
(R^{1/n}) bulge plus exponential disc. Repeat observations for 700 galaxies
demonstrate that stable measurements can be obtained for object components with
a half-light radius comparable to, or larger than, the seeing half-width at
half maximum. We show that with careful quality control, robust measurements
can be obtained for large samples such as the MGC. We use the catalogues to
show that the galaxy colour bimodality is due to the two-component nature of
galaxies (i.e. bulges and discs) and not to two distinct galaxy populations. We
conclude that understanding galaxy evolution demands the routine bulge-disc
decomposition of the giant galaxy population at all redshifts.


title:
SN 2005cs in M51 I. The first month of evolution of a subluminous SN II
  plateau

abstract:
  Early time optical observations of supernova (SN) 2005cs in the Whirlpool
Galaxy (M51), are reported. Photometric data suggest that SN 2005cs is a
moderately under-luminous Type II plateau supernova (SN IIP). The SN was
unusually blue at early epochs (U-B ~ -0.9 about three days after explosion)
which indicates very high continuum temperatures. The spectra show relatively
narrow P-Cygni features, suggesting ejecta velocities lower than observed in
more typical SNe IIP. The earliest spectra show weak absorption features in the
blue wing of the He I 5876A absorption component and, less clearly, of H$\beta$
and H$\alpha$. Based on spectral modelling, two different interpretations can
be proposed: these features may either be due to high-velocity H and He I
components, or (more likely) be produced by different ions (N II, Si II).
Analogies with the low-luminosity, $^{56}$Ni-poor, low-velocity SNe IIP are
also discussed.
  While a more extended spectral coverage is necessary in order to determine
accurately the properties of the progenitor star, published estimates of the
progenitor mass seem not to be consistent with stellar evolution models.


title: Observational constraints on phantom-like braneworld cosmologies

abstract:
  We investigate a simple braneworld model in which the universe contains only
cold dark matter and a cosmological constant, but the effective dark energy is
phantom-like because of extra-dimensional gravity effects. Modified gravity
screens the cosmological constant Lambda, allowing for a larger Lambda. In
practice, observations do not favour any significant screening. We use
supernova data, the cosmic microwave background shift parameter, and the baryon
oscillation peak in the galaxy distribution to constrain the model. We find the
mean value of Omega_m with 68% confidence limits, and an upper limit on
Omega_Lambda at the 68% confidence level. The best-fit model is very close to a
standard LCDM model, but the LCDM model provides a better fit since it has one
less parameter.


title:
Molecular Gas Dynamics in NGC 6946: a Bar-driven Nuclear Starburst
  "Caught in the Act"

abstract:
  We present high angular resolution ~1" and 0.6" mm-interferometric
observations of the 12CO(1-0) and 12CO(2-1) line emission in the central 300pc
of the late-type spiral galaxy NGC6946. The data, obtained with the IRAM
Plateau de Bure Interferometer (PdBI), allow the first detection of a molecular
gas spiral in the inner ~10" (270pc) with a large concentration of molecular
gas (M(H_2) ~1.6x10^7M_sun) within the inner 60pc. This nuclear clump shows
evidence for a ring-like geometry with a radius of ~10pc as inferred from the
p-v diagrams. Both the distribution of the molecular gas as well as its
kinematics can be well explained by the influence of an inner stellar bar of
about 400pc length. A qualitative model of the expected gas flow shows that
streaming motions along the leading sides of this bar are a plausible
explanation for the high nuclear gas density. Thus, NGC6946 is a prime example
of molecular gas kinematics being driven by a small-scale, secondary stellar
bar.


title: The Properties of Galaxies in Voids

abstract:
  We present a comparison of the properties of galaxies in the most underdense
regions of the Universe, where the galaxy number density is less than 10% of
the mean density, with galaxies from more typical regions. We have compiled a
sample of galaxies in 46 large nearby voids that were identified using the
Sloan Digital Sky Survey DR4, which provides the largest coverage of the sky.
We study the u-r color distribution, morphology, specific star formation rate,
and radial number density profiles for a total of 495 galaxies fainter than
M_r=-20.4 +5logh located inside the voids and compare these properties with a
control sample of field galaxies. We show that there is an excess of blue
galaxies inside the voids. However, inspecting the properties of blue and red
galaxies separately, we find that galaxy properties such as color distribution,
bulge-to-total ratios, and concentrations are remarkably similar between the
void and overall sample. The void galaxies also show the same specific star
formation rate at fixed color as the control galaxies. We compare our results
with the predictions of cosmological simulations of galaxy formation using the
Millennium Run semi-analytic galaxy catalog. We show that the properties of the
simulated galaxies in large voids are in reasonably good agreement with those
found in similar environments in the real Universe. To summarize, in spite of
the fact that galaxies in voids live in the least dense large-scale
environment, this environment makes very little impact on properties of
galaxies.


title: On the Rees-Sciama effect: maps and statistics

abstract:
  Small maps of the Rees-Sciama (RS) effect are simulated by using an
appropriate N-body code and a certain ray-tracing procedure. A method designed
for the statistical analysis of cosmic microwave background (CMB) maps is
applied to study the resulting simulations. These techniques, recently proposed
--by our team-- to consider lens deformations of the CMB, are adapted to deal
with the RS effect. This effect and the deviations from Gaussianity associated
to it seem to be too small to be detected in the near future. This conclusion
follows from our estimation of both the RS angular power spectrum and the RS
reduced n-direction correlation functions for n<7.


title: An Orphan in the "Field of Streams"

abstract:
  We use Sloan Digital Sky Survey Data Release 5 photometry and spectroscopy to
study a tidal stream that extends over 50 degrees in the North Galactic Cap.
  From the analysis of the path of the stream and the colors and magnitudes of
its stars, the stream is about 20 kpc away at its nearest detection (the
celestial equator). We detect a distance gradient -- the stream is farther away
from us at higher declination. The contents of the stream are made up from a
predominantly old and metal-poor population that is similar to the globular
clusters M13 and M92. The integrated absolute magnitude of the stream stars is
estimated to be M_r = -7.5. There istentative evidence for a velocity
signature, with the stream moving at -40 km/s at low declinations and +100 km/s
at high declinations. The stream lies on the same great circle as Complex A, a
roughly linear association of HI high velocity clouds stretching over 30
degrees on the sky, and as Ursa Major II, a recently discovered dwarf
spheroidal galaxy. Lying close to the same great circle are a number of
anomalous, young and metal-poor globular clusters, including Palomar 1 and
Ruprecht 106.


title: Can sterile neutrinos be ruled out as warm dark matter candidates?

abstract:
  We present constraints on the mass of warm dark matter (WDM) particles from a
combined analysis of the matter power spectrum inferred from the Sloan Digital
Sky Survey \lya flux power spectrum at 2.2<z<4.2, cosmic microwave background
data, and the galaxy power spectrum. We obtain a lower limit of m~10 keV (2
sigma) if the WDM consists of sterile neutrinos and m~2 keV (2 sigma) for early
decoupled thermal relics. If we combine this bound with the constraint derived
from x-ray flux observations in the Coma cluster, we find that the allowed
sterile neutrino mass is ~10 keV (in the standard production scenario). Adding
constraints based on x-ray fluxes from the Andromeda galaxy, we find that dark
matter particles cannot be sterile neutrinos, unless they are produced by a
nonstandard mechanism (resonant oscillations, coupling with the inflaton) or
get diluted by some large entropy release.


title: The Discovery of Cepheids and a Distance to NGC 5128

abstract:
  We discuss a new distance to NGC 5128 (Centaurus A) based on Cepheid
variables observed with the Hubble Space Telescope. Twelve F555W (V) and six
F814W (I) epochs of cosmic-ray-split Wide Field Planetary Camera 2 observations
were obtained. A total of 56 bona-fide Cepheids were discovered, with periods
ranging from 5 to ~50 days; five of these are likely Population II Cepheids of
the W Virginis class, associated with the bulge or halo of NGC 5128. Based on
the period and V and I-band luminosities of a sub-sample of 42 classical (Pop
I) Cepheids, and adopting a Large Magellanic Cloud distance modulus and
extinction of 18.50 +/- 0.10 mag and E(B-V)=0.10 mag, respectively, the true
reddening-corrected distance modulus to NGC 5128 is mu_0 = 27.67 +/- 0.12
(random)+/- 0.16 (systematic) mag, corresponding to a distance of 3.42 +/- 0.18
(random) +/- 0.25 (systematic) Mpc. The random uncertainty in the distance is
dominated by the error on the assumed value for the ratio of total to selective
absorption, R_V, in NGC 5128, and by the possible metallicity dependence of the
Cepheid Period-Luminosity relation at V and I. This represent the first
determination of a Cepheid distance to an early-type galaxy.


title: No Detectable H3+ Emission from the Atmospheres of Hot Jupiters

abstract:
  H$_3^+$ emission is the dominant cooling mechanism in Jupiter's thermosphere
and a useful probe of temperature and ion densities. The H$_3^+$ ion is
predicted to form in the thermospheres of close-in `hot Jupiters' where its
emission would be a significant factor in the thermal energy budget, affecting
temperature and the rate of hydrogen escape from the exosphere. Hot Jupiters
are predicted to have up to 10$^5$ times Jupiter's H$_3^+$ emission because
they experience extreme stellar irradiation and enhanced interactions may occur
between the planetary magnetosphere and the stellar wind. Direct (but
unresolved) detection of an extrasolar planet, or the establishment of useful
upper limits, may be possible because a small but significant fraction of the
total energy received by the planet is re-radiated in a few narrow lines of
H$_3^+$ within which the flux from the star is limited.
  We present the observing strategy and results of our search for emission from
the Q(1,0) transition of H$_3^+$ (3.953~$\mu$m) from extrasolar planets
orbiting six late-type dwarfs using CSHELL, the high-resolution echelle
spectrograph on NASA's Infrared Telescope Facility (IRTF). We exploited the
time-dependent Doppler shift of the planet, which can be as large as 150 km
s$^{-1}$, by differencing spectra between nights, thereby removing the stellar
photospheric signal and telluric lines. We set limits on the H$_3^+$ emission
from each of these systems and compare them with models in the literature.
Ideal candidates for future searches are intrinsically faint stars, such as M
dwarfs, at very close distances.


title: How Many Universes Do There Need To Be?

abstract:
  In the simplest cosmological models consistent with General Relativity, the
total volume of the Universe is either finite or infinite, depending on whether
or not the spatial curvature is positive. Current data suggest that the
curvature is very close to flat, implying that one can place a lower limit on
the total volume. In a Universe of finite age, the "particle horizon" defines
the patch of the Universe which is observable to us. Based on today's best-fit
cosmological parameters it is possible to constrain the number of observable
Universe sized patches, N_U. Specifically, using the new WMAP data, we can say
that there are at least 21 patches out there the same volume as ours, at 95%
confidence. Moreover, even if the precision of our cosmological measurements
continues to increase, density perturbations at the particle horizon size limit
us to never knowing that there are more than about 10^5 patches out there.


title:
High Redshift Intergalactic C IV Abundance Measurements from the
  Near-Infrared Spectra of Two z~6 QSOs

abstract:
  New measurements of the z~6 intergalactic CIV abundance are presented, using
moderate resolution IR spectra of two QSOs taken with GNIRS on Gemini South.
These data were systematically searched for high redshift CIV absorption lines,
using objective selection criteria. Comprehensive tests were performed to
quantify sample incompleteness, as well as the rate of false positive CIV
identifications. The trend of constant $\Omega_{CIV}(z)$ observed at z~2-5
appears to continue to z~6, the highest observed redshift. The CIV sample is
also consistent with the redshift-invariant form of the CIV column density
distribution reported by Songaila (2001) at lower redshift, although with
fairly large uncertainties due to a smaller sample size and noisier infrared
data. The constant value of $\Omega_{CIV}$ does not necessarily imply that the
IGM was infused with an early metallicity ``floor,'' but the presence of early
CIV does indicate that heavy-element enrichment began < 1 Gyr after the Big
Bang. The lack of a decline in $\Omega_{CIV}$ at high redshift may indicate
that integrated CIV measurements are sensitive to the instantaneous rate of
feedback from galaxy formation at each epoch. Alternatively, it could result
from a balance in the evolution of the intergalactic gas density, ionization
conditions, and heavy-element abundance over time.


title:
What measurable zero point fluctuations can(not) tell us about dark
  energy

abstract:
  We show that laboratory experiments cannot measure the absolute value of dark
energy. All known experiments rely on electromagnetic interactions. They are
thus insensitive to particles and fields that interact only weakly with
ordinary matter. In addition, Josephson junction experiments only measure
differences in vacuum energy similar to Casimir force measurements. Gravity,
however, couples to the absolute value. Finally we note that Casimir force
measurements have tested zero point fluctuations up to energies of ~10 eV, well
above the dark energy scale of ~0.01 eV. Hence, the proposed cut-off in the
fluctuation spectrum is ruled out experimentally.


title:
Statistical Study of the Reconnection Rate in Solar Flares Observed with
  YOHKOH/SXT

abstract:
  We report a statistical study of flares observed with the Soft X-ray
Telescope (SXT) onboard Yohkoh in the year of 2000. We measure physical
parameters of 77 flares, such as the temporal scale, the size, and the magnetic
flux density and find that the sizes of flares tend to be distributed more
broadly as the GOES class becomes weaker and that there is a lower limit of
magnetic flux density that depends on the GOES class. We also examine the
relationship between these parameters and find weak correlation between
temporal and spatial scales of flares. We estimate reconnection inflow
velocity, coronal Alfven velocity, and reconnection rate using above observed
values. The inflow velocities are distributed from a few km/s to several tens
km/s and the Alfven velocities in the corona are in the range from 10^3 to 10^4
km/s. Hence the reconnection rate is 10^-3 - 10^-2. We find that the
reconnection rate in a flare tends to decrease as the GOES class of the flare
increases. This value is within one order of magnitude from the theoretical
maximum value predicted by the Petschek model, although the dependence of the
reconnection rate on the magnetic Reynolds number tends to be stronger than
that in the Petschek model.


title: The high velocity outflow in NGC6334I

abstract:
  We observed the high velocity outflow originating from NGC6334I in several CO
transitions with the APEX telescope, with the goal of deriving the physical
parameters of the gas. Using an LVG analysis, we studied line ratios between
the CO(3-2), CO(4-3), and CO(7-6) data as a function of the density and of the
kinetic temperature of the gas. An upper limit on the CO column density is
derived by comparison with 13CO data. We constrained the temperature to be
higher than 50 K and the H_2 density to values higher than n~10^4 cm^{-3}
towards the peak position in the red lobe, while T>15 K and n>10^3 cm^{-3} are
derived towards the peak position in the blue lobe. The physical parameters of
the outflow, its mass and its energetics, have been computed using the
temperatures derived from this analysis. We conclude that high kinetic
temperatures are present in the outflow and traced by high excitation CO lines.
Observations of high-J CO lines are thus needed to infer reliable values of the
kinetic temperatures and of the other physical parameters in outflows.


title: APEX 1 mm line survey of the Orion Bar

abstract:
  Unbiased molecular line surveys are a powerful tool for analyzing the
physical and chemical parameters of astronomical objects and are the only means
for obtaining a complete view of the molecular inventory for a given source.
The present work stands for the first such investigation of a photon-dominated
region. The first results of an ongoing millimeter-wave survey obtained towards
the Orion Bar are reported. The APEX telescope in combination with the APEX-2A
facility receiver was employed in this investigation. We derived the physical
parameters of the gas through LVG analyses of the methanol and formaldehyde
data. Information on the sulfur and deuterium chemistry of photon-dominated
regions is obtained from detections of several sulfur-bearing molecules and
DCN.


title: A quantum-mechanical study of rotational transitions in H2 induced by H

abstract:
  Cross sections have been computed for rotational transitions of H2, induced
by collisions with H atoms, using a recent H - H2 potential calculated by
Mielke et al. [1]. These results are compared with those obtained with earlier
potentials. Significant discrepancies are found with results deriving from the
potential of Boothroyd et al. [3] in the low collision energy regime. We
compare also cross sections derived using different levels of approximation to
the vibrational motion.


title: Low sulfur depletion in the Horsehead PDR

abstract:
  We present 3.65''x3.34'' angular-resolution IRAM PdBI observations of the CS
J=2-1 line toward the Horsehead Photodissociation Region (PDR), complemented
with IRAM-30m single-dish observations of several rotational lines of CS, C34S
and HCS+. We analyse the CS and HCS+ photochemistry, excitation and radiative
transfer to obtain their abundances and the physical conditions prevailing in
the cloud edge. Since the CS abundance scales to that of sulfur, we determine
the gas phase sulfur abundance in the PDR, an interesting intermediate medium
between translucent clouds (where sulfur remains in the gas phase) and dark
clouds (where large depletions have been invoked). A nonlocal non-LTE radiative
transfer code including dust and cosmic background illumination adapted to the
Horsehead geometry has been developed to carefuly analyse the CS, C34S, HCS+
and C18O rotational line emission. We use this model to consistently link the
line observations with photochemical models to determine the CS/HCS+/S/S+
structure of the PDR. The combination of CS, C34S and HCS+ observations
together with the inclusion of the most recent CS collisional and chemical
rates in our models implies that sulfur depletion invoked to account for CS and
HCS+ abundances is much smaller than in previous studies.


title: Are Short GRBs Really Hard?

abstract:
  Thanks to the rapid position notice and response by HETE-2 and Swift, the
X-ray afterglow emissions have been found for four recent short gamma-ray
bursts (GRBs; GRB 050509b, GRB 050709, GRB 050724, and GRB 050813). The
positions of three out of four short GRBs are coincident with galaxies with no
current or recent star formation. This discovery tightens the case for a
different origin for short and long GRBs. On the other hand, from the prompt
emission point of view, a short GRB shows a harder spectrum comparing to that
of the long duration GRBs according to the BATSE observations. We investigate
the prompt emission properties of four short GRBs observed by Swift/BAT. We
found that the hardness of all four BAT short GRBs is in between the BATSE
range for short and long GRBs. We will discuss the spectral properties of short
GRBs including the short GRB sample of Konus-Wind and HETE-2 to understand the
hard nature of the BATSE short GRBs.


title:
An updated survey of globular clusters in M 31. I. Classification and
  radial velocity for 76 candidate clusters

abstract:
  Aims - We present the first results of a large spectroscopic survey of
globular clusters and candidate globular clusters in the nearby M~31 galaxy.
The survey is aimed at the classification of known candidate M~31 clusters and
at the study of their kinematic properties. Methods - We obtained
low-resolution spectroscopy (lambda/Dlambda~800-1300) for 133 targets,
including 76 yet-to-confirm candidate clusters (i.e. with no previous
spectroscopic information), 55 already-confirmed genuine M31 clusters, and 2
uncertain candidates. Our observations allowed a reliable estimate of the
target radial velocity, within a typical accuracy of ~+-20km/s. The observed
candidates have been robustly classified according to their radial velocity and
shape parameters that allowed us to confidently discriminate between point
sources and extended objects even from low-spatial-resolution imagery. Results
- In our set of 76 candidates clusters we found: 42 newly-confirmed bona-fide
M~31 clusters, 12 background galaxies, 17 foreground Galactic stars, 2 HII
regions belonging to M31 and 3 unclassified (possibly M31 clusters or
foreground stars) objects. The classification of a few other candidates not
included in our survey has been also reassessed on various observational bases.
All the sources of radial velocity estimates for M31 known globular clusters
available in the literature have been compared and checked, and a homogeneous
general list has been obtained for 349 confirmed clusters with radial velocity.
Conclusions - Our results suggest that a significant number of genuine clusters
(~> 100) is still hidden among the plethora of known candidates proposed by
various authors. Hence our knowledge of the globular cluster system of the M31
galaxy is still far from complete even in terms of simple membership.


title:
Deep Underground Science and Engineering Lab: S1 Dark Matter Working
  Group

abstract:
  A study of the current status of WIMP dark matter searches has been made in
the context of scientific and technical planning for a Deep Underground Science
and Engineering Laboratory (DUSEL) in the U.S. The table of contents follows:
  1. Overview
  2. WIMP Dark Matter: Cosmology, Astrophysics, and Particle Physics
  3. Direct Detection of WIMPs
  4. Indirect Detection of WIMPs
  5. Dark Matter Candidates and New Physics in the Laboratory
  6. Synergies with Other Sub-Fields
  7. Direct Detection Experiments: Status and Future Prospects
  8. Infrastructure
  9. International Context
  10. Summary and Outlook
  11. Acknowledgments


title: Adiabatic scaling relations of galaxy clusters

abstract:
  The aim of the present work is to show that, contrary to popular belief,
galaxy clusters are **not** expected to be self-similar, even when the only
energy sources available are gravity and shock-wave heating. In particular, we
investigate the scaling relations between mass, luminosity and temperature of
galaxy groups and clusters in the absence of radiative processes. Theoretical
expectations are derived from a polytropic model of the intracluster medium and
compared with the results of high-resolution adiabatic gasdynamical
simulations. It is shown that, in addition to the well-known relation between
the mass and concentration of the dark matter halo, the effective polytropic
index of the gas also varies systematically with cluster mass, and therefore
neither the dark matter nor the gas profiles are exactly self-similar. It is
remarkable, though, that the effects of concentration and polytropic index tend
to cancel each other, leading to scaling relations whose logarithmic slopes
roughly match the predictions of the most basic self-similar models. We provide
a phenomenological fit to the relation between polytropic index and
concentration, as well as a self-consistent scheme to derive the non-linear
scaling relations expected for any cosmology and the best-fit normalizations of
the M-T, L-T and F-T relations appropriate for a Lambda-CDM universe. The
predicted scaling relations reproduce observational data reasonably well for
massive clusters, where the effects of cooling and star formation are expected
to play a minor role.


title:
Absorption of Nuclear Gamma-rays on the Starlight Radiation in FR I
  Sources: the Case of Centaurus A

abstract:
  Several BL Lac objects are confirmed sources of variable and strongly
Doppler-boosted TeV emission produced in the nuclear portions of their
relativistic jets. It is more than probable, that also many of the FR I radio
galaxies, believed to be the parent population of BL Lacs, are TeV sources, for
which Doppler-hidden nuclear gamma-ray radiation may be only too weak to be
directly observed. Here we show, however, that about one percent of the total
time-averaged TeV radiation produced by the active nuclei of low-power FR I
radio sources is inevitably absorbed and re-processed by photon-photon
annihilation on the starlight photon field, and the following emission of the
created and quickly isotropized electron-positron pairs. In the case of the
radio galaxy Centaurus A, we found that the discussed mechanism can give a
distinctive observable feature in the form of an isotropic gamma-ray halo. It
results from the electron-positron pairs injected to the interstellar medium of
the inner parts of the elliptical host by the absorption process, and
upscattering starlight radiation via the inverse-Compton process mainly to the
GeV-TeV photon energy range. Such a galactic gamma-ray halo is expected to
possess a characteristic spectrum peaking at ~0.1 TeV photon energies, and the
photon flux strong enough to be detected by modern Cherenkov Telescopes and, in
the future, by GLAST. These findings should apply as well to the other nearby
FR I sources.


title: Ultra-compact (X-ray) binaries

abstract:
  A short review of ultra-compact binaries, focused on ultra-compact X-ray
binaries, is followed by a discussion of recent results of our VLT campaign to
obtain optical spectra of (candidate) ultra-compact X-ray binaries. We find
evidence for carbon/oxygen as well as helium/nitrogen discs and no evidence for
(traces) of hydrogen. This suggests that the donors in the observed systems are
white dwarfs. However, we also find large differences between the two C/O discs
of which we have good spectra, which highlights the need for a better
understanding of the optical spectra.


title:
Accretion onto the Companion of Eta Carinae During the Spectroscopic
  Event: III. the He II 4686 Line

abstract:
  We continue to explore the accretion model of the massive binary system eta
Carinae by studying the anomalously high He II 4686 line. The line appears just
before periastron and disappears immediately thereafter. Based on the He II
4686 line emission from O-stars and their modeling in the literature, we
postulate that the He II 4686 line comes from the acceleration zone of the
secondary stellar wind. We attribute the large increase in the line intensity
to a slight increase in the density of the secondary stellar wind in its
acceleration zone. The increase in density could be due to the ionization and
subsequent deceleration of the wind by the enhanced X-ray emission arising from
the shocked secondary wind further downstream or to accretion of the primary
stellar wind. Accretion around the secondary equatorial plane gives rise to
collimation of the secondary wind, which increases its density, hence enhancing
the He II 4686 emission line. In contrast with previous explanations, the
presently proposed model does not require a prohibitively high X-ray flux to
directly photoionize the He.


title: Compact stars made of fermionic dark matter

abstract:
  Compact stars consisting of fermions with arbitrary masses and interaction
strengths are studied by solving the structure equation of general relativity,
the Tolman-Oppenheimer-Volkoff equations. Scaling solutions are derived for a
free and an interacting Fermi gas and tested by numerical calculations. We
demonstrate that there is a unique mass-radius relation for compact stars made
of free fermions which is independent of the fermion mass. For sufficiently
strong interactions, the maximum stable mass of compact stars and its radius
are controlled by the parameter of the interaction, both increasing linearly
with the interaction strength. The mass-radius relation for compact stars made
of strongly interacting fermions shows that the radius remains approximately
constant for a wide range of compact star masses.


title:
Nucleosynthesis Yields of Core-Collapse Supernovae and Hypernovae, and
  Galactic Chemical Evolution

abstract:
  We present new nucleosynthesis yields as functions of the stellar mass,
metallicity, and explosion energy (corresponding to normal supernovae and
Hypernovae). We apply the results to the chemical evolution of the solar
neighborhood. Our new yields are based on the new developments in the
observational/theoretical studies of supernovae (SNe) and extremely metal-poor
(EMP) stars in the halo, which have provided excellent opportunities to test
the explosion models and their nucleosynthesis. We use the light curve and
spectra fitting of individual SN to estimate the mass of the progenitor,
explosion energy, and produced 56Ni mass. Comparison with the abundance
patterns of EMP stars has made it possible to determine the model parameters of
core-collapse SNe, such as mixing-fallback parameters.
  More specifically, we take into account the two distinct new classes of
massive SNe: 1) very energetic Hypernovae, whose kinetic energy (KE) is more
than 10 times the KE of normal core-collapse SNe, and 2) very faint and low
energy SNe (Faint SNe). These two new classes of SNe are likely to be
``black-hole-forming'' SNe with rotating or non-rotating black holes.
Nucleosynthesis in Hypernovae is characterized by larger abundance ratios
(Zn,Co,V,Ti)/Fe and smaller (Mn,Cr)/Fe than normal SNe, which can explain the
observed trends of these ratios in EMP stars. Nucleosynthesis in Faint SNe is
characterized by a large amount of fall-back, which explains the abundance
pattern of the most Fe-poor stars. These comparisons suggest that
black-hole-forming SNe made important contributions to the early Galactic (and
cosmic) chemical evolution.


title:
The Interplanetary Network Supplement to the BATSE 5B Catalog of Cosmic
  Gamma-Ray Bursts

abstract:
  We present Interplanetary Network (IPN) localization information for 343
gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE)
between the end of the 4th BATSE catalog and the end of the Compton Gamma-Ray
Observatory (CGRO) mission, obtained by analyzing the arrival times of these
bursts at the Ulysses, Near Earth Asteroid Rendezvous (NEAR), and CGRO
spacecraft. For any given burst observed by CGRO and one other spacecraft,
arrival time analysis (or "triangulation") results in an annulus of possible
arrival directions whose half-width varies between 11 arcseconds and 21
degrees, depending on the intensity, time history, and arrival direction of the
burst,as well as the distance between the spacecraft. This annulus generally
intersects the BATSE error circle, resulting in an average reduction of the
area of a factor of 20. When all three spacecraft observe a burst, the result
is an error box whose area varies between 1 and 48000 square arcminutes,
resulting in an average reduction of the BATSE error circle area of a factor of
87.


title: GEMINI spectroscopy of the ultra-compact binary candidate V407 Vul

abstract:
  We present time-resolved spectroscopy of the optical counterpart to the
proposed ultra-compact binary system V407 Vul (=RX J1914.4+2456). Our Gemini
spectra resolve the 9.48 minute periodicity that has previously been reported
for this source. We find that the optical counterpart is dominated by a
reddened late-type spectrum of type G9V and contains solely unresolved
absorption features. No radial velocity signatures exceeding 10 km/s could be
detected on periods from minutes to hours. Using interstellar extinction
estimates, we derive a distance to the G9 star of 1.1-3.5 kpc. In addition to
this stellar spectrum, we detect a blue component that modulates solely on the
9.48 minute period, and peaks ~0.15 in phase ahead of the X-ray peak. This blue
component which contributes up to 40% of the light shows no evidence for
emission line features that are the usual hallmarks of an interacting binary.
Good seeing images obtained with the Magellan telescopes indicate that the
variable and the G-star are aligned to better than 0.1". Despite the low
probability of a chance alignment of a field star along the line of sight, the
G9 light cannot be directly associated with the 9.48 minute variable that
powers the luminous (~10^35 ergs/s) and highly variable X-ray source. The
outlook for the detection of conclusive radial velocity measurements will
remain challenging due to the extinction along the line of sight in conjunction
with the contaminating effect of the G9V star.


title: The Spiral Structure of the Outer Milky Way in Hydrogen

abstract:
  We produce a detailed map of the perturbed surface density of neutral
hydrogen in the outer Milky Way disk demonstrating that the Galaxy is a
non-axisymmetric multi-armed spiral. Spiral structure in the southern half of
the Galaxy can be traced out to at least 25 kpc, implying a minimum radius for
the gas disk. Overdensities in the surface density are coincident with regions
of reduced gas thickness. The ratio of the surface density to the local median
surface density is relatively constant along an arm. Logarithmic spirals can be
fit to the arms with pitch angles of 20-25 degrees.


title:
BUCS: An Engine For Generating Realistic Imaging Data for Deep Galaxy
  Fields

abstract:
  Today's deep high resolution multiwavelength surveys contain a wealth of
information about galaxies at different epochs. To fully exploit this
information, it is useful to be able to produce highly realistic simulations to
compare with the observations. Here, we describe one such simulator for
producing imaging data for deep galaxy fields. Based upon a pixel-by-pixel
modelling of object SEDs and their selection volumes, this simulator allows
users to make realistic multicolor simulations of galaxy fields from galaxy
samples at all redshifts. Input samples for this simulator range from z~0
samples selected from the Sloan Digital Sky Survey to z~1-6 samples selected
from the Great Observatories Origins Deep Survey. Users can specify the
passbands, noise, and PSFs, or equivalently the exposure times on well-known
instruments like HST or ground-based telescopes.


title: QSO Absorption Lines from QSOs

abstract:
  We present the results of a search for metal absorption lines in the spectra
of background QSOs whose sightlines pass close to foreground QSOs. We detect
MgII(2796,2803) absorption in Sloan Digital Sky Survey (SDSS) spectra of four
z>1.5 QSOs whose lines of sight pass within 26-98 kpc of lower redshift
(z~0.5-1.5) QSOs. The 100% [4/4 pairs] detection of MgII in the background QSOs
is clearly at odds with the incidence of associated (z_abs ~ z_em) systems --
absorbers which exist towards only a few percent of QSOs. Although the quality
of our foreground QSO spectra is not as high as the SDSS data, absorption seen
towards one of the background QSOs clearly does not show up at the same
strength in the spectrum of the corresponding foreground QSO. This implies that
the absorbing gas is distributed inhomogeneously around the QSO, presumably as
a direct consequence of the anisotropic emission from the central AGN. We
discuss possible origins for the MgII lines, including: absorption by gas from
the foreground QSO host galaxy; companion galaxies fuelling the QSO through
gravitational interactions; and tidal debris left by galaxy mergers or
interactions which initiated the QSO activity. No single explanation is
entirely satisfactory, and we may well be seeing a mixture of phenomena.


title: Spitzer Spectra of Magellanic Cloud PNe

abstract:
  Planetary nebulae (PNe) in the Magellanic Clouds (LMC, SMC) offer a unique
opportunity to study both the population and evolution of low- and
intermediate-mass stars in an environment which is free of the distance scale
bias that hinder Galactic PN studies. The emission shown by PNe in the 5-40
$\mu$m range is characterized by the presence of a combination of solid state
features (from the dust grains) and nebular emission lines over-imposed on a
strong dust continuum. We acquired low resolution IRS spectroscopy of a
selected sample of LMC and SMC PNe whose morphology, size, central star
brightness, and chemical composition are known. The data have been acquired and
reduced, and the IRS spectra show outstanding quality as well as very
interesting features. The preliminary analysis presented here allows to
determine strong correlations between gas and dust composition, and nebular
morphology. More detailed analysis in the future will deepen our knowledge of
mass-loss mechanism, its efficiency, and its relation to PN morphology.


title: Observing IMBH-IMBH Binary Coalescences via Gravitational Radiation

abstract:
  Recent numerical simulations have suggested the possibility of forming double
intermediate mass black holes (IMBHs) via the collisional runaway scenario in
young dense star clusters. The two IMBHs formed would exchange into a common
binary shortly after their birth, and quickly inspiral and merge. Since
space-borne gravitational wave (GW) observatories such as LISA will be able to
see the late phases of their inspiral out to several Gpc, and LIGO will be able
to see the merger and ringdown out to similar distances, they represent
potentially significant GW sources. In this Letter we estimate the rate at
which LISA and LIGO will see their inspiral and merger in young star clusters,
and discuss the information that can be extracted from the observations. We
find that LISA will likely see tens of IMBH--IMBH inspirals per year, while
advanced LIGO could see ~10 merger and ringdown events per year, with both
rates strongly dependent on the distribution of cluster masses and densities.


title:
Temperature inversion on the surface of externally heated optically
  thick multigrain dust clouds

abstract:
  It was recently discovered that the temperature in the surface layer of
externally heated optically thick gray dust clouds increases with the optical
depth for some distance from the surface, as opposed to the normal decrease in
temperature with distance in the rest of the cloud. This temperature inversion
is a result of efficient absorption of diffuse flux from the cloud interior by
the surface dust exposed to the external radiation. A micron or bigger size
grains experience this effect when the external flux is of stellar spectrum. We
explore what happens to the effect when dust is a mixture of grain sizes
(multigrain). Two possible boundary conditions are considered: i) a constant
external flux without constrains on the dust temperature, and ii) the maximum
dust temperature set to the sublimation temperature. We find that the first
condition allows small grains to completely suppress the temperature inversion
of big grains if the overall opacity is dominated by small grains. The second
condition enables big grains to maintain the inversion even when they are a
minor contributor to the opacity. In reality, the choice of boundary condition
depends on the dust dynamics. When applied to the physics of protoplanetary
disks, the temperature inversion leads to a previously unrecognized disk
structure where optically thin dust can exist inside the dust destruction
radius of an optically thick disk. We conclude that the transition between the
dusty disk and the gaseous inner clearing is not a sharp edge, but rather a
large optically thin region.


title: The Particle Content of Extragalactic Jets

abstract:
  Recent x-ray and radio data from radio sources in galaxy clusters are used to
show that the pdV work required to inflate the radio lobes exceeds all other
energy estimates deduced from the radio emission. If the required jet energy
density has an isotropic pressure, then in almost all cases the jet cannot be
confined by an external medium. This problem can be resolved with jets
dominated by cold protons, but even here the accompanying energy density in
relativistic electons can cause decollimation. Electron-positron jets cannot
solve this problem unless they are highly beamed with unusual energy
distributions. Poynting flux jets may be a viable alternative.


title: Carbon Abundances in the Small Magellanic Cloud Planetary Nebulae

abstract:
  As an ongoing study of Magellanic Cloud PNe we have obtained UV spectra of 9
PNe in the SMC to measure their carbon abundances. The spectra have been
acquired with ACS HRC/PR200L and SBC/PR130L. The ACS prisms give a reasonable
resolution in the range of 1200 -- 2500 A to detect the C IV, C III], and C II]
nebular emission, essential for chemical studies of the PNe. The carbon
abundances of SMC PNe, together with those of the LMC previously determined
with STIS spectroscopy, will allow a comparative study of nebular enrichment
and provide the basis for comparison with stellar evolution models at various
metallicity.


title:
Scientific Results from High-precision Astrometry at the Palomar Testbed
  Interferometer

abstract:
  A new observing mode for the Palomar Testbed Interferometer was developed
in2002-2003 which enables differential astrometry at the level of 20
micro-arcseconds for binary systems with separations of several hundred
milli-arcseconds (mas). This phase-referenced mode is the basis of the Palomar
High-precision Astrometric Search for Exoplanet Systems (PHASES), a search for
giant planets orbiting either the primary or secondary star in fifty binary
systems. We present the first science results from the PHASES search. The
properties of the stars comprising binary systems are determined to high
precision. The mutual inclinations of several hierarchical triple star systems
have been determined. We will present upper limits constraining the the
existence of giant planets in a few of the target systems.


title: A Photonic mm-Wave Local Oscillator

abstract:
  A photonic millimeter wave local oscillator capable of producing two
microwatts of radiated power at 224 GHz has been developed. The device was
tested in one antenna of Smithsonian Institution's Submillimeter Array (SMA)
and was found to produce stable phase on multiple baselines. Graphical data is
presented of correlator output phase and amplitude stability. A description of
the system is given in both open and closed loop modes. A model is given which
is used to predict the operational behavior. A novel method is presented to
determine the safe operating point of the automated system.


title:
The RMS Survey: Radio observations of candidate massive YSOs in the
  southern hemisphere

abstract:
  The Red MSX Source (RMS) survey is a multi-wavelength program of follow-up
observations designed to distinguish between genuine massive young stellar
objects (MYSOs) and other embedded or dusty objects, such as ultra compact (UC)
HII regions, evolved stars and planetary nebulae (PNe). We have identified
nearly 2000 massive YSOs candidates by comparing the colours of MSX and 2MASS
point sources to those of known MYSOs. Unfortunately, there are several other
types of embedded or dust enshrouded objects that have similar colours as MYSOs
and contaminate our sample. Two sources of contamination are from UCHII regions
and PNe, both of which can be identified from the radio emission emitted by
their ionised nebulae. In order to identify UCHII regions and PNe that
contaminate our sample we have conducted high resolution radio continuum
observations at 3.6 and 6 cm of all southern MYSOs candidates ($235< l < 350$)
using the Australia Telescope Compact Array (ATCA). These observations have a
spatial resolution of $\sim$1--2\arcsec and typical image rms noise values of
$\sim$0.3 mJy -- sensitive enough to detect a B0.5 star at the far side of the
Galaxy. Of the 826 RMS sources observed we found 199 to be associated with
radio emission, $\sim$25% of the sample. More significant than those sources
associated with radio emission are the 627 RMS sources for which no radio
emission was detected as these sources are still potential MYSOs. The Galactic
distribution, morphologies and spectral indices of the radio sources associated
with the RMS sources are consistent with these sources being UCHII regions. In
addition to the 826 RMS sources observed we present observations of a further
190 fields. These observations were made towards MSX sources that passed cuts
in earlier versions of the survey, but were later excluded.


title: Constraining Torus Models for AGNs Using X-Ray Observations

abstract:
  In Unification Models, Active Galactic Nuclei (AGN) are believed to be
surrounded by an axisymmetric structure of dust and gas, which greatly
influences their observed properties according to the direction from which they
are observed. The main aim of this work is to constrain the properties of this
obscuring material using X-Ray observations. The distribution of column
densities observed by Chandra in the Chandra Deep Field South is used to
determine geometrical constraints for already proposed torus models. It is
found that the best torus model is given by a classical `donut shape' with an
exponential angular dependency of the density profile. The opening angle is
strongly constrained by the observed column densities. Other proposed torus
models are clearly rejected by the X-Ray observations.


title:
Spatial and Velocity clumping in an SDSS blue horizontal branch star
  catalogue

abstract:
  We present evidence for eight new clumps of blue horizontal branch (BHB)
stars discovered in a catalogue of these stars compiled from the Sloan Digital
Sky Survey (SDSS) by Sirko et al. published in 2004. Clumps are identified by
selecting pairs of stars separated by distances <= 2 kpc and with differences
in galactocentric radial velocities < 25 km/s. Each clump contains four or more
stars. Four of the clumps have supporting evidence: two of them also contain
overdensities of RR Lyrae stars which makes their reality very likely. At least
one of the clumps is likely to be associated with the tidal debris of the
Sagittarius dwarf spheroidal galaxy. We emphasize that more accurate
observations of the radial velocities or proper motions of the stars in the
clumps as well as the identification of other halo stars in these regions are
required to establish the reality of the remaining clumps.


title: Strong magnetic field in W75N OH maser flare

abstract:
  A flare of OH maser emission was discovered in W75N in 2000. Its location was
determined with the VLBA to be within 110 au from one of the ultracompact H II
regions, VLA2. The flare consisted of several maser spots. Four of the spots
were found to form Zeeman pairs, all of them with a magnetic field strength of
about 40 mG. This is the highest ever magnetic field strength found in OH
masers, an order of magnitude higher than in typical OH masers. Three possible
sources for the enhanced magnetic field are discussed: (i) the magnetic field
of the exciting star dragged out by the stellar wind; (ii) the general
interstellar field in the gas compressed by the MHD shock; and (iii) the
magnetic field of planets which orbit the exciting star and produce maser
emission in gaseous envelopes.


title:
Weighing neutrinos in the presence of a running primordial spectral
  index

abstract:
  The three-year WMAP(WMAP3), combined with other cosmological observations
from galaxy clustering and Type Ia Supernova (SNIa), prefers a non-vanishing
running of the primordial spectral index independent of the low CMB multipoles.
Motivated by this feature we study cosmological constraint on the neutrino
mass, which severely depends on what prior we adopt for the spectral shape of
primordial fluctuations, taking possible running into account. As a result we
find a more stringent constraint on the sum of the three neutrino masses, m_\nu
< 0.76eV (2 \sigma), compared with m_\nu < 0.90eV (2 \sigma) for the case where
power-law prior is adopted to the primordial spectral shape.


title: Superhumps: Confronting Theory with Observation

abstract:
  We review the theory and observations related to the ``superhump'' precession
of eccentric accretion discs in close binary sytems. We agree with earlier
work, although for different reasons, that the discrepancy between observation
and dynamical theory implies that the effect of pressure in the disc cannot be
neglected. We extend earlier work that investigates this effect to include the
correct expression for the radius at which resonant orbits occur. Using
analytic expressions for the accretion disc structure, we derive a relationship
between the period excess and mass-ratio with the pressure effects included.
This is compared to the observed data, recently derived results for detailed
integration of the disc equations and the equivalent empirically derived
relations and used to predict values for the mass ratio based on measured
values of the period excess for 88 systems.


title: Accretion Disks in Large-scale Magnetic Fields

abstract:
  This paper presents a survey of a set of simulations of accretion disks
orbiting a rapidly rotating Kerr black hole and embedded in a large-scale
initial magnetic field. Each simulation uses a common state for the initial
torus, including an MRI seed-field consisting of poloidal loops along
isodensity contours, and differ only in the strength of the initial large-scale
magnetic field in relation to these poloidal loops. Simulations with a weak
large-scale initial field differ little from simulations that evolve from only
the poloidal field. Simulations where the large-scale initial field distorts or
completely overwhelms the poloidal loops show more extensive regions of
turbulence, due to the action of the MRI on the large-scale field. However, the
overall structure of the late-time state of the simulations remains
qualitatively unchanged, that is each simulation sees the emergence of a
turbulent accretion disk, axial jets, a funnel-wall outflow and an extensive
corona.


title:
The Diverse Solar Phase Curves of Distant Icy Bodies. Part I:
  Photometric Observations of 18 Trans-Neptunian Objects, 7 Centaurs, and
  Nereid

abstract:
  We have measured the solar phase curves in B, V, and I for 18 Trans-Neptunian
Objects, 7 Centaurs, and Nereid and determined the rotation curves for 10 of
these targets. For each body, we have made ~100 observations uniformly spread
over the entire visible range. We find that all the targets except Nereid have
linear phase curves at small phase angles (< 2 deg) with widely varying phase
coefficients (0.0 to 0.4 mag/deg). At phase angles > 3 deg, the Centaurs
(54598) Bienor and (32532) Thereus have phase curves that flatten. The recently
discovered Pluto-scale bodies (2003 UB313, 2005 FY9, and 2003 EL61), like
Pluto, have neutral colors compared to most TNOs and small phase coefficients
(< 0.1 mag/deg). Together these two properties are a likely indication for
large TNOs of high-albedo, freshly coated icy surfaces. We find several bodies
with significantly wavelength-dependent phase curves. The TNOs (50000) Quaoar,
(120348) 2004 TY364 (47932), and 2000 GN171 have unusually high I-band phase
coefficients (0.290+/-0.038, 0.413+/-0.064, 0.281+/-0.033 mag/deg,
respectively) and much lower coefficients in the B and V bands. Their phase
coefficients increase in proportion to wavelength by 0.5 - 0.8 mag/deg/um. The
phase curves for TNOs with small B-band phase coefficients (< 0.1 mag/deg) have
a similar but weaker wavelength dependence. Coherent backscatter is the likely
cause for the wavelength dependence for all these bodies. We see no such
dependence for the Centaurs, which have visual albedos ~0.05.


title: Dark energy constraints from lensing-detected galaxy clusters

abstract:
  We study the ability of weak lensing surveys to detect galaxy clusters and
constrain cosmological parameters, in particular the equation of state of dark
energy. There are two major sources of noise for weak lensing cluster
measurements: the ``shape noise'' from the intrinsic ellipticities of galaxies;
and the large scale projection noise. We produce a filter for the shear field
which optimizes the signal-to-noise of shape-noise-dominated shear
measurements. Our Fisher-matrix analysis of this projected-mass observable
makes use of the shape of this mass function, and takes into account the
Poisson variance, sample variance, shape noise, and projected-mass noise, and
also the fact that the conversion of the shear signal into mass is
cosmology-dependent. The Fisher analysis is applied to both a nominal 15,000
square degree ground-based survey and a 1000 square degree space-based survey.
Assuming a detection threshold of S/N=5, we find both experiments detect
\~20,000 clusters, and yield 1-sigma constraints of ~0.07 for w0 and ~0.2 for
wa when combined with CMB data (for flat universe). The projection noise
exceeds the shape noise only for clusters at z<=0.1 and has little effect on
the derived dark-energy constraints. Sample variance does not significantly
affect either survey. Finally, we note that all these results are extremely
sensitive to the noise levels and detection thresholds that we impose. They can
be significantly improved if we combine ground and space surveys as independent
experiments and add their corresponding Fisher matrices.


title:
Fe emission and ionized excess absorption in the luminous quasar 3C109
  with XMM-Newton

abstract:
  We report results from an XMM-Newton observation of the broad-line radio
galaxy 3C109 (z=0.3056). Confirming previous results, an Fe emission line is
detected, possibly comprising a broad component. However, the data cannot
distinguish between an untruncated accretion disc and a case in which the
innermost 20-30 gravitational radii are missing. In fact, a partial-covering
plus narrow Fe line scenario is not ruled out statistically. However, the
absorber would have to comprise hundreds/thousands very compact clouds close to
the X-ray source, which seems rather extreme a requirement. The 2-10 keV
intrinsic luminosity of 3C109 is of the order of 2-3x10^45 erg/s which,
combined with a recent black hole mass estimate of ~2x10^8 M_sun, implies an
Eddington ratio greater than unity. If partial covering is excluded, the
observed reflection fraction (of the order of unity), steep photon index
(1.86), and Fe line equivalent width (about 100 eV) all suggest to exclude that
the X-ray continuum is strongly beamed, indicating that the large Eddington
ratio is associated with a radiatively efficient accretion process. We also
confirm previous findings on the detection of low energy absorption in excess
of the Galactic value. The better quality of the XMM-Newton data enables us to
attribute the excess absorption to slightly ionized gas in the line of sight,
located at the redshift of 3C109. [abriged]


title:
Precision Measurements of Higher-Order Angular Galaxy Correlations Using
  11 Million SDSS Galaxies

abstract:
  We present estimates of the N-point galaxy area-averaged angular correlation
functions wN for N = 2,...,7 from the third data release of the Sloan Digital
Sky Survey (SDSS). The sample was selected from galaxies with 18 < r < 21, and
is the largest ever used to study higher-order correlations. The measured wN
are used to calculate the projected, sN, and real space, SN, hierarchical
amplitudes. This produces highly-precise measurements over 0.2 to 10 h-1 Mpc,
which are consistent with Gaussian primordial density fluctuations. The
measurements suggest that higher-order galaxy bias is non-negligible, as
defining b1 = 1 yields c2 = -0.24 +/- 0.08. We report the first SDSS
measurement of marginally significant third-order bias, c3 = 0.98 +/- 0.89,
which suggests that bias terms may be significant to even higher order.
Previous measurements of c2 have yielded inconsistent results. Inconsistencies
would be expected if different data sets sample different galaxy types,
especially if different galaxy types exhibit different higher-order bias. We
find early-type galaxies exhibit significantly different behavior than
late-types at both small and large scales. At large scales (r > 1 h-1 Mpc), we
find the SN for late-type galaxies are lower than for early-types, implying a
significant difference between their higher-order bias. We find b1,early = 1.36
+/- 0.04, c2,early = 0.30 +/- 0.10, b1,late = 0.81 +/- 0.03, and c2,late =
-0.70 +/- 0.08. Our results are robust against the systematic effects of
reddening and seeing. The latter introduces minor structure in wN.


title: The CFHTLS Real Time Analysis System "Optically Selected GRB Afterglows"

abstract:
  We describe a wide and deep search for optical GRB afterglows on images taken
with MegaCAM at the Canada France Hawaii Telescope, within the framework of the
CFHT Legacy Survey. This search is performed in near real-time thanks to a Real
Time Analysis System called "Optically Selected GRB Afterglows", which has been
completely realized and installed on a dedicated computer in Hawaii. This
pipeline automatically and quickly analyzes Megacam images and extracts from
them a list of astrometrically and photometrically variable objects which are
displayed on a web page for validation by a member of the collaboration. In
this paper, we comprehensively describe the RTAS process. We also present
statistical results based on nearly one full year of operation, showing the
quality of the images and the performance of the RTAS. Finally, we compare the
efficiency of this study with similar searches, propose an ideal observational
strategy using simulations, and discuss general considerations on the searches
for GRB afterglows independently of the prompt emission. This is the first of a
series of two papers. A second paper will discuss the characterization of
variable objects we have found, as well as the GRB afterglow candidates and
their nature. We will also estimate or at least constrain the collimation
factor of GRB using the totality of the Very Wide Survey observations.


title:
Accretion, feedback and galaxy bimodality: a comparison of the GalICS
  semi-analytic model and cosmological SPH simulations

abstract:
  We compare the galaxy population of an SPH simulation to those predicted by
the GalICS semi-analytic model and a stripped down version without supernova
and AGN feedback. The SPH simulation and the no-feedback GalICS model make
similar predictions for the baryonic mass functions of galaxies and for the
dependence of these mass functions on environment and redshift. The two methods
also make similar predictions for the galaxy content of dark matter haloes as a
function of halo mass and for the gas accretion history of galaxies. Both the
SPH and no-feedback GalICS models predict a bimodal galaxy population at z=0.
The "red'' sequence of gas poor, old galaxies is populated mainly by satellite
systems while, contrary to observations, the central galaxies of massive haloes
lie on the "blue'' star-forming sequence as a result of continuing hot gas
accretion at late times. Furthermore, both models overpredict the observed
baryonic mass function, especially at the high mass end. In the full GalICS
model, supernova-driven outflows reduce the masses of low and intermediate mass
galaxies by about a factor of two. AGN feedback suppresses gas cooling in large
haloes, producing a sharp cut-off in the baryonic mass function and moving the
central galaxies of these massive haloes to the red sequence. Our results imply
that the observational failings of the SPH simulation and the no-feedback
GalICS model are a consequence of missing input physics rather than
computational inaccuracies, that truncating gas accretion by satellite galaxies
automatically produces a bimodal galaxy distribution with a red sequence, but
that explaining the red colours of the most massive galaxies requires a
mechanism like AGN feedback that suppresses the accretion onto central galaxies
in large haloes.


title:
A correlation between the heavy element content of transiting extrasolar
  planets and the metallicity of their parent stars

abstract:
  Nine extrasolar planets with masses between 110 and 430M are known to transit
their star. The knowledge of their masses and radii allows an estimate of their
composition, but uncertainties on equations of state, opacities and possible
missing energy sources imply that only inaccurate constraints can be derived
when considering each planet separately. Aims: We seek to better understand the
composition of transiting extrasolar planets by considering them as an
ensemble, and by comparing the obtained planetary properties to that of the
parent stars. Methods: We use evolution models and constraints on the stellar
ages to derive the mass of heavy elements present in the planets. Possible
additional energy sources like tidal dissipation due to an inclined orbit or to
downward kinetic energy transport are considered. Results: We show that the
nine transiting planets discovered so far belong to a quite homogeneous
ensemble that is characterized by a mass of heavy elements that is a relatively
steep function of the stellar metallicity, from less than 20 earth masses of
heavy elements around solar composition stars, to up to 100M for three times
the solar metallicity (the precise values being model-dependant). The
correlation is still to be ascertained however. Statistical tests imply a
worst-case 1/3 probability of a false positive. Conclusions: Together with the
observed lack of giant planets in close orbits around metal-poor stars, these
results appear to imply that heavy elements play a key role in the formation of
close-in giant planets. The large masses of heavy elements inferred for planets
orbiting metal rich stars was not anticipated by planet formation models and
shows the need for alternative theories including migration and subsequent
collection of planetesimals.


title:
The Chandra View of the Supernova Remnant 0506-68.0 in the Large
  Magellanic Cloud

abstract:
  A new Chandra observation of SNR 0506-68.0 (also called N23) reveals a
complex, highly structured morphology in the low energy X-ray band and an
isolated compact central object in the high energy band. Spectral analysis
indicates that the X-ray emission overall is dominated by thermal gas whose
composition is consistent with swept-up ambient material. There is a strong
gradient in ambient density across the diameter of the remnant. Toward the
southeast, near a prominent star cluster, the emitting density is 10 - 23
cm^{-3} while toward the northwest it has dropped to a value of only 1 cm^{-3}.
The total extent of the X-ray remnant is 100" by 120" (24 pc x 29 pc for a
distance of 50 kpc), somewhat larger than previously known. The remnant's age
is estimated to be ~4600 yr. One part of the remnant shows evidence for
enhanced O, Ne, and perhaps Mg abundances, which is interpreted as evidence for
ejecta from a massive star core collapse supernova. The compact central object
has a luminosity of a few times 10^{33} ergs/s and no obvious radio or optical
counterpart. It does not show an extended nebula or pulsed emission as expected
from a young energetic pulsar, but resembles the compact central objects seen
in other core collapse SNe, such as Cas A.


title:
A comparison of hydrodynamics techniques for modelling collisions
  between main sequence stars

abstract:
  An Eulerian TVD code and a Lagrangian SPH code are used to simulate the
off-axis collision of equal-mass main sequence stars in order to address the
question of whether stellar mergers can produce a remnant star where the
interior has been replenished with hydrogen due to significant mixing. Each
parent main sequence star is chosen to be found near the turnoff, with hydrogen
depleted in the core, and is modelled with a M=0.8 solar mass realistic stellar
model and as a n=3 polytrope. An ideal fluid description with adiabatic index
gamma=5/3 is used for all hydrodynamic calculations. We found good agreement
between the simulations for the polytropic case, with the remnant showing
strong, non-local mixing throughout. In the interior quarter of the mass, ~35%
is mixed in from larger radii and on average the remnant is ~50% fully mixed.
For the realistic model, we found less mixing, particularly in the interior and
in the SPH simulation. In the inner quarter, ~20% of the contained mass in the
TVD case, but only ~3% in the SPH one is mixed in from outside. The simulations
give consistent results for the overall profile of the merger remnant and the
amount of mass loss, but the differences in mixing suggests that the intrinsic
difference between grid and particle based schemes remains a possible artifact.
We conclude that both the TVD and SPH schemes can be used equally well for
problems that are best suited to their strengths and that care should be taken
in interpreting results about fluid mixing.