title: The size evolution of galaxies since z~3: combining SDSS, GEMS and FIRES

abstract:
  We present the evolution of the luminosity-size and stellar mass-size
relations of luminous (L_V>3.4x10^10h_70^-2L_sun) and of massive
(M_*>3x10^10h_70^-2M_sun) galaxies in the last ~11 Gyr. We use very deep
near-infrared images of the Hubble Deep Field-South and the MS1054-03 field in
the J_s, H and K_s bands from FIRES to retrieve the sizes in the optical
rest-frame for galaxies with z>1. We combine our results with those from GEMS
at 0.2<z<1 and SDSS at z~0.1 to achieve a comprehensive picture of the optical
rest-frame size evolution from z=0 to z=3. Galaxies are differentiated
according to their light concentration using the Sersic index n. For less
concentrated objects, the galaxies at a given luminosity were typically ~3+-0.5
(+-2 sigma) times smaller at z~2.5 than those we see today. The stellar
mass-size relation has evolved less: the mean size at a given stellar mass was
\~2+-0.5 times smaller at z~2.5, evolving proportional to (1+z)^{-0.40+-0.06}.
Simple scaling relations between dark matter halos and baryons in a
hierarchical cosmogony predict a stronger (although consistent within the error
bars) than observed evolution of the stellar mass-size relation. The observed
luminosity-size evolution out to z~2.5 matches well recent infall model
predictions for Milky-Way type objects. For low-n galaxies, the evolution of
the stellar mass-size relation would follow naturally if the individual
galaxies grow inside-out. For highly concentrated objects, the situation is as
follows: at a given luminosity, these galaxies were ~2.7+-1.1 times smaller at
z~2.5 (or put differently, were typically ~2.2+-0.7 mag brighter at a given
size than they are today), and at a given stellar mass the size has evolved
proportional to (1+z)^{-0.45+-0.10}.


title: The Dynamics of Brane-World Cosmological Models

abstract:
  Brane-world cosmology is motivated by recent developments in string/M-theory
and offers a new perspective on the hierarchy problem. In the brane-world
scenario, our Universe is a four-dimensional subspace or {\em brane} embedded
in a higher-dimensional {\em bulk} spacetime. Ordinary matter fields are
confined to the brane while the gravitational field can also propagate in the
bulk, leading to modifications of Einstein's theory of general relativity at
high energies. In particular, the Randall-Sundrum-type models are
self-consistent and simple and allow for an investigation of the essential
non-linear gravitational dynamics. The governing field equations induced on the
brane differ from the general relativistic equations in that there are nonlocal
effects from the free gravitational field in the bulk, transmitted via the
projection of the bulk Weyl tensor, and the local quadratic energy-momentum
corrections, which are significant in the high-energy regime close to the
initial singularity. In this review we discuss the asymptotic dynamical
evolution of spatially homogeneous brane-world cosmological models containing
both a perfect fluid and a scalar field close to the initial singularity. Using
dynamical systems techniques it is found that, for models with a physically
relevant equation of state, an isotropic singularity is a past-attractor in all
orthogonal spatially homogeneous models (including Bianchi type IX models). In
addition, we describe the dynamics in a class of inhomogeneous brane-world
models, and show that these models also have an isotropic initial singularity.
These results provide support for the conjecture that typically the initial
cosmological singularity is isotropic in brane-world cosmology.


title:
Three-dimensional MHD simulations of X-ray emitting subcluster plasmas
  in cluster of galaxies

abstract:
  Recent high resolution observations by the {\it Chandra} X-ray satellite
revealed various substructures in hot X-ray emitting plasmas in cluster of
galaxies. For example, {\it Chandra} revealed the existence of sharp
discontinuities in the surface brightness at the leading edge of subclusters in
merging clusters (e.g., Abell 3667), where the temperature drops sharply across
the fronts. These sharp edges are called cold fronts. We present results of
three-dimensional (3D) magnetohydrodynamic simulations of the interaction
between a dense subcluster plasma and ambient magnetized intracluster medium.
Anisotropic heat conduction along magnetic field lines is included. At the
initial state, magnetic fields are assumed to be uniform and transverse to the
motion of the dense subcluster. Since magnetic fields ahead of the subcluster
slip toward the third direction in the 3D case, the strength of magnetic fields
in this region can be reduced compared to that in the 2D case. Nevertheless, a
cold front can be maintained because the magnetic field lines wrapping around
the forehead of the subcluster suppress the heat conduction across them. On the
other hand, when the magnetic field is absent, a cold front cannot be
maintained because isotropic heat conduction from the hot ambient plasma
rapidly heats the cold subcluster plasma.


title:
Anisotropic cosmological models with non-minimally coupled magnetic
  field

abstract:
  Motivated by the structure of one-loop vacuum polarization effects in curved
spacetime we discuss a non-minimal extension of the Einstein-Maxwell equations.
This formalism is applied to Bianchi I models with magnetic field. We obtain
several exact solutions of the non-minimal system including those which
describe an isotropization process. We show that there are inflationary
solutions in which the cosmological constant is determined by the non-minimal
coupling parameters. Furthermore, we find an isotropic de Sitter solution
characterized by a "screening" of the magnetic field as a consequence of the
non-minimal coupling.


title:
Triggering and Feedback: The Relation between the HI Gas and the
  Starburst in the Dwarf Galaxy NGC 1569

abstract:
  As part of our study on the impact of violent star formation on the
interstellar medium (ISM) of dwarf galaxies, we report observations of neutral
atomic hydrogen (HI) in the post-starburst dwarf galaxy NGC 1569.
High-resolution measurements with the VLA (B-, C- and D-array) are aimed at
identifying morphological and kinematical signatures in the HI caused by the
starburst. Our kinematical data suggest a huge hole in the HI distribution,
probably due to the large number of supernovae explosions in the center of the
galaxy over the past 20 Myr. Investigating the large-scale HI structure, we
confirm the existence of a possible HI companion and a so-called HI bridge east
of NGC 1569. Furthermore, we report the detection of additional low-intensity
HI halo emission, which leads us to suggest a revised halo structure. Based on
the new picture, we discuss the origin of the halo gas and possible
implications for the evolution of the starburst in NGC 1569.


title:
Morphologies of Ultracompact HII Regions in W49A and Sgr B2: Prevalence
  of Shells and a Modified Classification Scheme

abstract:
  We have used Very Large Array (VLA) observations of the massive star forming
regions W49A and Sgr B2, obtained with resolutions from 2\farcs0 to 0\farcs04,
to classify the morphologies of nearly 100 ultracompact HII regions. These high
resolution, multi-frequency, multi-configuration VLA observations motivate
several modifications of the existing morphological classification scheme for
UC HII regions. In this work, we describe the modified morphology scheme and
the criteria used in source classification. In particular, we drop the
``core-halo'' classification, add a ``bipolar'' classification, and change the
shell classification to ``shell-like''. We tally the percentage of each
morphology found in the Sgr B2 and W49A regions and find broad agreement with
the Galactic plane surveys in the distribution of morphologies for most types.
However, we find that nearly a third of the sources in these regions are
shell-like, which is a higher percentage by nearly a factor of ten than found
in the surveys of Galactic plane star forming regions by Wood & Churchwell
(1989a) and Kurtz et al. (1994). This difference may be due to physical
differences in the environments of these two extreme star forming regions.
Alternatively, differences in observational technique may be responsible.


title: Observing Near Earth Asteroids with a Small Telescope

abstract:
  Even from a light polluted city it is possible to observe Near Earth
Asteroids (NEAs) at opposition using a small telescope equipped with a CCD
camera. In this paper, we will overview first the major NEA programs,
continuing with planning the observations and the data reduction. Second, we
will present a NEA follow-up program carried out on the 60-cm telescope at York
University Observatory in Toronto, Canada. Part of this program, five NEAs have
been observed during ten nights. Their astrometric and photometric data were
reduced and sent to the Minor Planet Centre, following which an observatory
code was assigned and four batches have been included in the NEODyS database
and MPC Circulars. The results are applicable to any other small facility.


title:
Observations of the binary pulsar system PSR B1718-19 -- The Role of
  Tidal Circularisation

abstract:
  We present optical and infrared observations taken with the Very Large
Telescope of the eclipsing binary pulsar system PSR B1718-19. The candidate
companion of the pulsar, identified earlier in Hubble Space Telescope
observations, has been detected in all three bands, R, I, and J. These
detections allowed us to derive constraints on temperature, radius, and mass,
pointing to a companion that has expanded to a radius between one of a main
sequence star and one at the Roche-limit. We focus on the role of tidal
circularisation in the system, which will have transformed the initially
eccentric orbit expected from formation scenarios into the nearly circular
orbit presently observed. Based on simple energy balance arguments, we are able
to draw a picture of the companion's evolution resulting from the energy
deposition in the star due to circularisation. In this picture, our measurement
of the companion's parameters is consistent with the expected initial
eccentricity. However, with the present understanding of tidal dissipation it
remains difficult to account for the short time in which the system was
circularised.


title:
XMM-Newton Observations of Evolution of Cluster X-Ray Scaling Relations
  at z=0.4-0.7

abstract:
  We present a spatially-resolved analysis of the temperature and gas density
profiles of galaxy clusters at z=0.4-0.7 observed with XMM-Newton. These data
are used to derive the total cluster mass within the radius r_500 without
assuming isothermality, and also to measure the average temperature and total
X-ray luminosity excluding the cooling cores. We derive the high-redshift M-T
and L-T relations and compare them with the local measurements. The
high-redshift L-T relation has low scatter and evolves as L ~ (1+z)^{1.8\pm0.3}
for a fixed T, in good agreement with several previous Chandra and XMM-Newton
studies (Vikhlinin et al., Lumb et al., Maughan et al.). The observed evolution
of the M-T relation follows M_500 = A T^{3/2} E(z)^{-alpha}, where we measure
alpha=0.88\pm0.23. This is in good agreement with predictions of the
self-similar theory, alpha=1.


title: Effects of photon escape on diagnostic diagrams for HII regions

abstract:
  In this article we first outline the mounting evidence that a significant
fraction of the ionizing photons emitted by OB stars within HII regions escape
from their immediate surroundings and explain how an HII region structure
containing high density contrast in homogeneities facilitates this escape. Next
we describe sets of models containing inhomogeneities which are used to predict
tracks in the commonly used diagnostic diagrams (based on ratios of emission
lines) whose only independent variable is the photon escape fraction, xi. We
show that the tracks produced by the models in two of the most cited of these
diagrams conform well to the distribution of observed data points, with the
models containing optically thick inhomogeneities ("CLUMPY" models) yielding
somewhat better agreement than those with optically thin inhomogeneities ("FF"
models). We show how variations in the ionization parameter U, derived from
emission line ratios, could be due to photon escape. Using a rather wide range
of assumptions about the filling factor of dense clumps we find, for a selected
set of regions observed in M51 photon escape fraction ranging between 30% and
50%. We show, using oxygen as the test element, that models with different
assumptions about the gas inhomogeneity will give variations in the abundance
values derived from diagnostic diagrams, but do not claim here to have a fully
developed set of diagnostic tools to improve abundance determinations made in
this way. We finally propose a combination of line ratios with the absolute
Halpha luminosity of a given HII region, which allows us to determine the
photon escape fraction, and hence resolve the degeneracy between U and xi.


title:
Observational evidence of the formation of cyanopolyynes in CRL618
  through the polimerization of HCN

abstract:
  The abundance ratio of consecutive members of the cyanopolyynes family has
been explored in CRL618 using data acquired in a complete line survey covering
the frequency range 81-356 GHz. The Jup range explored for the different
molecules is the following: 1 to 4 for HCN and HNC, 9 to 39 for HC3N, 31 to 133
for HC5N, and 72 to 85 for HC7N (not detected beyond Jup=85). The lowest
vibrationally excited state of HC7N (nu_15 at 62 cm^-1) has been tentatively
detected. Data analysis has been performed by extending our previous
geometrical and radiative transfer model of the slowly expanding envelope (SEE)
surrounding the compact central continuum source of CRL 618, that was
established from the study of rotational lines in several vibrationally excited
states of HC_3N. The new lines analyzed here require to model the high velocity
wind (HVW) component and the colder circumstellar gas, remnant of the AGB phase
of CRL618. The derived HC3N/HC5N and HC5N/HC7N abundance ratios from this set
of uniformly calibrated lines are between 3 and 6 in the different regions,
similar to standard values in the CSM and ISM, and consistent with previous
estimates obtained from ISO observations and chemical models. However, the
abundance ratios of HC3N, HC5N and HC7N with respect to HCN are at least two
orders of magnitude larger than those typical for AGB C-rich stars, such as
IRC+10216. This fact indicates that, in the short transition toward the
Planetary Nebula phase, HCN is quickly reprocessed into longer cyanopolyyne
chains. A similar behavior was previously found in this object for the
polyacetylenic chains (C(2n)H2).


title: Automated Detection of Classical Novae with Neural Networks

abstract:
  The POINT-AGAPE collaboration surveyed M31 with the primary goal of optical
detection of microlensing events, yet its data catalogue is also a prime source
of lightcurves of variable and transient objects, including classical novae
(CNe). A reliable means of identification, combined with a thorough survey of
the variable objects in M31, provides an excellent opportunity to locate and
study an entire galactic population of CNe. This paper presents a set of 440
neural networks, working in 44 committees, designed specifically to identify
fast CNe. The networks are developed using training sets consisting of
simulated novae and POINT-AGAPE lightcurves, in a novel variation on K-fold
cross-validation. They use the binned, normalised power spectra of the
lightcurves as input units. The networks successfully identify 9 of the 13
previously identified M31 CNe within their optimal working range (and 11 out of
13 if the network error bars are taken into account). They provide a catalogue
of 19 new candidate fast CNe, of which 4 are strongly favoured.


title: X-ray Bright QSO's around NGC 3079

abstract:
  NGC 3079 is a very active, disturbed galaxy which has been observed to have
X-ray and radio ejections from it as well as an optical superbubble along its
minor axis. Here we show that the brightest X-ray sources within about 40
arcmin are in large excess of background values. The X-ray sources are
identified as quasars and AGN's which are aligned and spaced across the Seyfert
nucleus to a degree which is unlikely to be due to chance. The famous double
quasar which has been interpreted as a gravitational lens is discussed in terms
of the the X - ray and ULX sources which appear associated with NGC 3079.


title:
Asteroseismology of the Beta Cephei star Nu Eridani -- IV. The 2003-4
  multisite photometric campaign and the combined 2002-4 data

abstract:
  The second multisite photometric campaign devoted to Nu Eri is reported. For
Nu Eri, analysis of the new data adds four independent frequencies to the nine
derived previously from the 2002-3 data, three in the range from 7.20 to 7.93
c/d, and a low one, equal to 0.614 c/d. Combining the new and the old data
results in two further independent frequencies, equal to 6.7322 and 6.2236 c/d.
Altogether, the oscillation spectrum is shown to consist of 12 high frequencies
and two low ones. The latter have u amplitudes about twice as large as the v
and y amplitudes, a signature of high radial-order g modes. Thus, the
suggestion that Nu Eri is both a Beta Cephei and an SPB star, put forward on
the basis of the first campaign's data, is confirmed.
  Nine of the 12 high frequencies form three triplets, of which two are new.
The triplets represent rotationally split l=1 modes, although in case of the
smallest-amplitude one this may be questioned. Mean separations and asymmetries
of the triplets are derived with accuracy sufficient for meaningful comparison
with models.
  The first comparison star, Mu Eri, is shown to be an SPB variable with an
oscillation spectrum consisting of six frequencies, three of which are
equidistant in period. The star is also found to be an eclipsing variable. The
eclipse is a transit, probably total, the secondary is fainter than the primary
by several magnitudes, and the system is widely detached.
  The second comparison star, Xi Eri, is confirmed to be a Delta Scuti
variable. To the frequency of 10.8742 c/d seen already in the first campaign's
data, another one, equal to 17.2524 c/d, is added.


title: Estimating Dark Matter Distributions

abstract:
  Thanks to instrumental advances, new, very large kinematic datasets for
nearby dwarf spheroidal (dSph) galaxies are on the horizon. A key aim of these
datasets is to help determine the distribution of dark matter in these
galaxies. Past analyses have generally relied on specific dynamical models or
highly restrictive dynamical assumptions. We describe a new, non-parametric
analysis of the kinematics of nearby dSph galaxies designed to take full
advantage of the future large datasets. The method takes as input the projected
positions and radial velocities of stars known to be members of the galaxies,
but does not use any parametric dynamical model, nor the assumption that the
mass distribution follows that of the visible matter. The problem of estimating
the radial mass distribution, M(r) (the mass interior to true radius r), is
converted into a problem of estimating a regression function
non-parametrically. From the Jeans Equation we show that the unknown regression
function is subject to fundamental shape restrictions which we exploit in our
analysis using statistical techniques borrowed from isotonic estimation and
spline smoothing. Simulations indicate that M(r) can be estimated to within a
factor of two or better with samples as small as 1000 stars over almost the
entire radial range sampled by the kinematic data. The technique is applied to
a sample of 181 stars in the Fornax dSph galaxy. We show that the galaxy
contains a significant, extended dark halo some ten times more massive than its
baryonic component. Though applied here to dSph kinematics, this approach can
be used in the analysis of any kinematically hot stellar system in which the
radial velocity field is discretely sampled.


title:
Evidence for Radio Detection of Extensive Air Showers Induced by Ultra
  High Energy Cosmic Rays

abstract:
  Firm evidence for a radio emission counterpart of cosmic ray air showers is
presented. By the use of an antenna array set up in coincidence with ground
particle detectors, we find a collection of events for which both time and
arrival direction coincidences between particle and radio signals are observed.
The counting rate corresponds to shower energies $\gtrsim 5\times 10^{16}$ eV.
These results open overwhelming perspectives to complete existing detection
methods for the observation of ultra high-energy cosmic rays.


title: Direct search for WIMP dark matter

abstract:
  We will review the experimental aspects of the direct search for WIMP dark
matter. In thin search, one looks in a terrestrial target for nuclear recoils
produced by the impacts with WIMPs from the galatic halo. After describing the
different search strategies and review the currently running experiments and
the prospects of future experiments


title:
Constraining the mass transfer in massive binaries through progenitor
  evolution models of Wolf-Rayet+O binaries

abstract:
  Since close WR+O binaries are the result of a strong interaction of both
stars in massive close binary systems, they can be used to constrain the highly
uncertain mass and angular momentum budget during the major mass transfer
phase. We explore the progenitor evolution of the three best suited WR+O
binaries HD 90657, HD 186943 and HD 211853, which are characterized by a WR/O
mass ratio of $\sim$0.5 and periods of 6..10 days. We are doing so at three
different levels of approximation: predicting the massive binary evolution
through simple mass loss and angular momentum loss estimates, through full
binary evolution models with parametrized mass transfer efficiency, and through
binary evolution models including rotation of both components and a physical
model which allows to compute mass and angular momentum loss from the binary
system as function of time during the mass transfer process. All three methods
give consistently the same answers. Our results show that, if these systems
formed through stable mass transfer, their initial periods were smaller than
their current ones, which implies that mass transfer has started during the
core hydrogen burning phase of the initially more massive star. Furthermore,
the mass transfer in all three cases must have been highly non-conservative,
with on average only $\sim$10% of the transferred mass being retained by the
mass receiving star. This result gives support to our system mass and angular
momentum loss model, which predicts that, in the considered systems, about 90%
of the overflowing matter is expelled by the rapid rotation of the mass
receiver close to the $\Omega$-limit, which is reached through the accretion of
the remaining 10%.


title:
Detection of satellite remnants in the Galactic Halo with Gaia - I. The
  effect of the Galactic background, observational errors and sampling

abstract:
  We address the problem of identifying remnants of satellite galaxies in the
halo of our galaxy with Gaia data. The remnants have to be extracted from a
very large data set (of order 10^9 stars) in the presence of observational
errors and against a background population of Galactic stars. We address this
issue through a numerical simulation of the Gaia catalogue with a realistic
number of entries. The Galaxy model includes separate light distributions and
kinematics for the bulge, disc and stellar halo. Our catalogue contains
3.5x10^8 stars. We perform tree code 10^6-body simulations of satellite dwarf
galaxies in orbit around a rigid mass model of the Galaxy. The shrinking
satellite cores and tidal tails are added to the Monte Carlo simulation of the
Gaia catalogue. When combining the Milky Way and dwarf galaxy models we include
the complication that the luminosity function of the satellite is probed at
various depths as a function of position along the tidal tails. The combined
models are converted to a synthetic Gaia catalogue using a detailed model for
the expected astrometric and radial velocity errors, depending on magnitude,
colour and sky position of the stars. We explore the feasibility of detecting
tidal streams in the halo using the energy versus angular momentum plane. A
straightforward search in this plane will be very challenging. The background
population and the observational errors make it difficult to detect tidal
streams as discrete structures in the E-Lz plane. The propagation of
observational errors leads to apparent caustic structures in the integrals of
motion space that may be mistaken for physical entities. Any practical search
strategy will have to use a combination of pre-selection of high-quality data
and complementary searches using the photometric data from Gaia. (abridged)


title: An Atlas of Spectrophotometric Landolt Standard Stars

abstract:
  We present CCD observations of 102 Landolt standard stars obtained with the
R-C spectrograph on the CTIO 1.5 m telescope. Using stellar atmosphere models
we have extended the flux points to our six spectrophotometric secondary
standards, in both the blue and the red, allowing us to produce flux-calibrated
spectra that span a wavelength range from 3050 \AA to 1.1 \micron. Mean
differences between UBVRI spectrophotometry computed using Bessell's standard
passbands and Landolt's published photometry is found to be 1% or less.
Observers in both hemispheres will find these spectra useful for
flux-calibrating spectra and through the use of accurately constructed
instrumental passbands be able to compute accurate corrections to bring
instrumental magnitudes to any desired standard photometric system
(S-corrections). In addition, by combining empirical and modeled spectra of the
Sun, Sirius and Vega, we calculate and compare synthetic photometry to observed
photometry taken from the literature for these three stars.


title: On the future of Gamma-Ray Burst Cosmology

abstract:
  With the understanding that the enigmatic Gamma-Ray Burts (GRBs) are beamed
explosions, and with the recently discovered ``Ghirlanda-relation'', the dream
of using GRBs as cosmological yardsticks may have come a few steps closer to
reality. Assuming the Ghirlanda-relation is real, we have investigated possible
constraints on cosmological parameters using a simulated future sample of a
large number of GRBs inspired by the ongoing SWIFT mission. Comparing with
constraints from a future sample of Type Ia supernovae, we find that GRBs are
not efficient in constraining the amount of dark energy or its equation of
state. The main reason for this is that very few bursts are available at low
redshifts.


title: Phase-space mixing and the merging of cusps

abstract:
  Collisionless stellar systems are driven towards equilibrium by mixing of
phase-space elements. I show that the excess-mass function D(f)= int_{F(x,v)>f}
(F(x,v)-f) d^3x d^3v (with F(x,v) the coarse-grained distribution function)
always decreases on mixing. D(f) gives the excess mass from values of
F(x,v))>f. This novel form of the mixing theorem extends the maximum
phase-space density argument to all values of f. The excess-mass function can
be computed from N-body simulations and is additive: the excess mass of a
combination of non-overlapping systems is the sum of their individual D(f). I
propose a novel interpretation for the coarse-grained distribution function,
which avoids conceptual problems with the mixing theorem.
  As an example application, I show that for self-gravitating cusps (rho propto
r^{-gamma} as r->0) the excess mass D propto f^{-2(3-gamma)/(6-gamma)} as
f->oo, i.e. steeper cusps are less mixed than shallower ones, independent of
the shape of surfaces of constant density or details of the distribution
function (e.g. anisotropy). This property, together with the additivity of D(f)
and the mixing theorem, implies that a merger remnant cannot have a cusp
steeper than the steepest of its progenitors. Furthermore, I argue that the
remnant's cusp should not be shallower either, implying that the steepest cusp
always survives.


title:
Overview of the ISM Phases: Evolution of Large and Small Scale
  Structures in 3D high resolution HD and MHD simulations

abstract:
  We review recent 3D high resolution numerical HD and MHD studies of a
multi-component and multi-phase ISM. The computational grid was chosen large
enough in the disk to represent typical ISM gas patterns, and in the halo to
include the full extent of the Galactic fountain. The evolution of the ISM is
driven by supernovae of all types and followed for 400 Myrs, long enough to get
rid of memory effects of the initial distributions. The results are
substantially different from previous classical analytical models and entail:
(i) a very inhomogeneous distribution of ISM gas, (ii) a high level of
supernova driven turbulence, (iii) an active Galactic fountain flow, reaching
out to about 5 kpc on either side of the disk, (iv) a low volume filling factor
for the hot gas of about 20%, (v) a very weak correlation between magnetic
field and gas density, n, for n < 100 cm^-3, and, (vi) about 50% of the gas
disk mass with n < 100 cm^-3, residing in classically thermally unstable
temperature regimes.


title:
The K20 survey. VII. The spectroscopic catalogue: spectral properties
  and evolution of the galaxy population

abstract:
  The K20 survey is a near infrared-selected, deep (Ks < 20) redshift survey
targeting galaxies in two independent regions of the sky, the CDFS and the
q0055-2659 field. The total Ks-selected sample includes 545 objects. Optical
spectra for 525 of them have been obtained, providing 501 spectroscopic
identifications (including 12 type-1 AGN and 45 stars). This paper describes
the final K20 spectroscopic catalogue, along with the technique used to
determine redshifts, measure the spectral features and characterize the
spectra. The classification of the galaxy spectra has been performed according
to a simple parametric recipe that uses the equivalent widths of the two main
emission lines (O[II] and Halpha+[N II]) and two continuum indices (the 4000A
break index, and a near-UV color index, C(28-39)). We defined three main
spectroscopic classes: red early-type galaxies, blue emission-line galaxies and
the intermediate galaxies, which show emission lines but a red continuum. More
than 95% of the examined galaxies is included in one of these spectral types
and a composite spectrum is built for each of the three galaxy classes. The
blue emission-line and the early-type galaxies have been divided in redshift
bins, and the corresponding composite spectra have been built, in order to
investigate the evolution of the spectral properties of the K20 galaxies with
redshift.


title:
Lorentz-violation and cosmological perturbations: a toy brane-world
  model

abstract:
  We study possible effects of Lorentz-violation on the generation of
cosmological perturbations at inflation by introducing a simple inflating
five-dimensional brane-world setup with violation of four-dimensional
Lorentz-invariance at an energy scale $k$. We consider massless scalar field,
meant to mimic perturbations of inflaton and/or gravitational field, in this
background. At three-momenta below $k$, there exists a zero mode localized on
the brane, whose behaviour coincides with that in four-dimensional theory. On
the contrary, at three-momenta above $k$, the localized mode is absent and
physics is entirely five-dimensional. As three-momenta get redshifted, more
modes get localized on the brane, the phenomenon analogous to ``mode
generation''. We find that for $k\gg H$, where $H$ is the inflationary Hubble
scale, the spectrum of perturbations coincides with that in four-dimensional
theory. For $k < H$ and time-dependent bulk parameters, the spectrum deviates,
possibly strongly, from the flat spectrum even for pure de Sitter inflation.


title:
Chemical Abundances in the Secondary Star of the Neutron Star Binary
  Centaurus X-4

abstract:
  Using a high resolution spectrum of the secondary star in the neutron star
binary {Cen X-4}, we have derived the stellar parameters and veiling caused by
the accretion disk in a consistent way. We have used a $\chi^{2}$ minimization
procedure to explore a grid of 1 500 000 LTE synthetic spectra computed for a
plausible range of both stellar and veiling parameters. Adopting the best model
parameters found, we have determined atmospheric abundances of Fe, Ca, Ti, Ni
and Al. These element abundances are super solar ($\mathrm{[Fe/H]}=0.23 \pm
0.10$), but only the abundance of Ti and Ni appear to be moderately enhanced
($\ge1\sigma$) as compared with the average values of stars of similar iron
content. These element abundances can be explained if the secondary star
captured a significant amount of matter ejected from a spherically symmetric
supernova explosion of a 4 {$M_\odot$} He core progenitor and assuming solar
abundances as primordial abundances in the secondary star. The kinematic
properties of the system indicate that the neutron star received a natal kick
velocity through an aspherical SN and/or an asymmetric neutrino emission. The
former scenario might be ruled out since our model computations cannot produce
acceptable fits to the observed abundances. We have also examined whether this
system could have formed in the Galactic halo, and our simulations show that
this possibility seems unlikely. We also report a new determination of the Li
abundance consistent with previous studies that is unusually high and close to
the cosmic Li abundance in the Galactic disk.


title: GCRT J1745-3009: A precessing radio pulsar?

abstract:
  A unique transient bursting radio source, GCRT J1745-3009, has been
discovered (Hyman et al. 2005a) near the direction of the Galactic center. It
is still an open question to explain this phenomenon, although some efforts to
understand its nature have been made. This paper shows that most of the
observed features can be reproduced by our proposed precessing pulsar model. It
is found that the precession angle of the pulsar should be larger ($\ga 15^{\rm
o}$) than that of previously known precessing pulsars, which have a precession
angle $\la 10^{\rm o}$, if the beam width of the pulsar is larger than 10
degree. The pulsar could be a nulling (or even extremely) radio pulsars to
account for the transient nature of the source. This model can be confirmed if
a pulsar is detected at the position of the source. The pulsar could hardly be
a normal neutron star (but probably a solid quark star) if the spin period of
the pulsar is detected to be $\ga 10$ ms in the future.


title:
Luminosity-Dependent Quasar Lifetimes: A New Interpretation of the
  Quasar Luminosity Function

abstract:
  We propose a new interpretation of the quasar luminosity function (LF),
derived from physically motivated models of quasar lifetimes and light curves.
In our picture, quasars evolve rapidly and their lifetime depends on both their
instantaneous and peak luminosities. We study this model using simulations of
galaxy mergers that successfully reproduce a wide range of observed quasar
phenomena. With lifetimes inferred from the simulations, we deconvolve the
observed quasar LF from the distribution of peak luminosities, and show that
they differ qualitatively, unlike for the simple models of quasar lifetimes
used previously. We find that the bright end of the LF traces the intrinsic
peak quasar activity, but that the faint end consists of quasars which are
either undergoing exponential growth to much larger masses and higher
luminosities, or are in sub-Eddington quiescent states going into or coming out
of a period of peak activity. The 'break' in the LF corresponds directly to the
maximum in the intrinsic distribution of peak luminosities, which falls off at
both brighter and fainter luminosities. Our interpretation of the quasar LF
provides a physical basis for the nature and slope of the faint-end
distribution, as well as the location of the break luminosity.


title:
Luminosity-Dependent Quasar Lifetimes: Reconciling the Optical and X-ray
  Quasar Luminosity Functions

abstract:
  We consider implications of our new model of quasar lifetimes and light
curves for the quasar luminosity function (LF) at different frequencies and
redshifts. In our picture, quasars evolve rapidly and the lifetime depends on
both their instantaneous and peak luminosities. The bright end of the LF traces
the peak intrinsic quasar activity, but the faint end consists of quasars which
are either undergoing exponential growth to much larger masses and
luminosities, or are in sub-Eddington quiescent states going into or coming out
of a period of peak activity. The 'break' in the observed LF corresponds
directly to the maximum in the intrinsic distribution of peak luminosities,
which falls off at both brighter and fainter luminosities. We study this model
using simulations of galaxy mergers which successfully reproduce a wide range
of observed quasar phenomena, including the observed column density
distribution. By combining quasar lifetimes and the distribution of maximum
quasar luminosities determined from the observed hard X-ray LF with the
corresponding luminosity and host-system dependent column densities, we produce
the expected soft X-ray and B-band LFs. Our predictions agree exceptionally
well with the observed LFs at all observed luminosities, over the redshift
range considered (z < 1), without invoking any ad hoc assumptions about an
obscured population of sources. Our results also suggest that observed
correlations in hard X-ray samples between the obscured fraction of quasars and
luminosity can be explained in the context of our model by the expulsion of
surrounding gas due to heating from accretion feedback energy as a quasar nears
its peak luminosity and final black hole mass.


title:
Afterglow Light Curves from Impulsive Relativistic Jets with an
  Unconventional Structure

abstract:
  The jet structure in gamma-ray burst (GRB) sources is still largely an open
question. The leading models invoke either (i) a roughly uniform jet with sharp
edges, or (ii) a jet with a narrow core and wide wings where the energy per
solid angle drops as a power law with the angle $\theta$ from the jet symmetry
axis. Recently, a two component jet model has also been considered, with a
narrow uniform jet of initial Lorentz factor $\Gamma_0 \gtrsim 100$ surrounded
by a wider uniform jet with $\Gamma_0 \sim 10-30$. Some models predict more
exotic jet profiles, such as a thin uniform ring (i.e. the outflow is bounded
by two concentric cones of half opening angle $\theta_c$ and $\theta_c +
\Delta\theta$, with $\Delta\theta \ll \theta_c$) or a fan (a thin outflow with
$\Delta\theta \ll 1$ along the rotational equator, $\theta_c = \pi/2 +
\Delta\theta/2$). In this paper we calculate the expected afterglow light
curves from such jet structures, using a simple formalism that is developed
here for this purpose, and could also have other applications. These light
curves are qualitatively compared to observations of GRB afterglows. It is
shown that the two component jet model cannot produce sharp features in the
afterglow model due to the deceleration of the wide jet or the narrow jet
becoming visible at lines of sight outside of it. We find that a "ring" shaped
jet or a "fan" shaped jet produce a jet break in the afterglow light curve that
is too shallow compared to observations, where the change in the temporal decay
index across the jet break is about half of that for a uniform conical jet. For
a "ring" jet, the jet break is divided into two distinct and smaller breaks,
the first occurring when $\gamma\Delta\theta \sim 1-2$ and the second when
$\gamma\theta_c \sim 1/2$.


title: An X-ray Transient and Optical Counterpart in the M31 Bulge

abstract:
  We have obtained snapshot images of a transient X-ray source in M31 from
Chandra ACIS-I and the Hubble Space Telescope (HST) Advanced Camera for Surveys
(ACS). The Chandra position of the X-ray nova was R.A.=00:42:56.038 +/-0.08'',
Dec.=+41:12:18.50 +/-0.07''. The transient was active for at least 6 months.
Previous observations set an upper limit before the X-ray outburst,
demonstrating variability by a factor of >100 and confirming the transient
nature of the source. For the first 6 months after the initial detection, the
X-ray luminosity was ~6 X 10$^{37}$ erg/s; it then decayed to <5 X 10$^{36}$
erg/s over the following 2 months. An HST observation 29 days after the initial
X-ray detection revealed a source at R.A.=00:42:56.042, Dec.=+41:12:18.45 that
was B=24.52 +/- 0.07. This optical source faded to B=24.95 +/- 0.08$ in 9
months. The HST identification of an optical source at the same position as the
X-ray source, fading in concert with the X-ray source, indicates that this
optical source is the counterpart of the X-ray transient. The lack of high-mass
stars in the region suggests this source is a low-mass X-ray binary, and the
X-ray and optical luminosities provide a rough orbital period estimate of
8$^{+12}_{-5}$ days for the system.


title: The Birth of Massive Stars and Star Clusters

abstract:
  In the present-day universe, it appears that most, and perhaps all, massive
stars are born in star clusters. It also appears that all star clusters contain
stars drawn from an approximately universal initial mass function, so that
almost all rich young star clusters contain massive stars. In this review I
discuss the physical processes associated with both massive star formation and
with star cluster formation. First I summarize the observed properties of
star-forming gas clumps, then address the following questions. How do these
clumps emerge from giant molecular clouds? In these clustered environments, how
do individual stars form and gain mass? Can a forming star cluster be treated
as an equilibrium system or is this process too rapid for equilibrium to be
established? How does feedback affect the formation process?


title: Supernovae and Gamma-Ray Bursts Powered by Hot Neutrino-Cooled Coronae

abstract:
  Cosmological explosions such as core-collapse supernovae (SNe) and gamma-ray
bursts (GRBs) are thought to be powered by the rapid conversion of roughly a
solar mass' worth of gravitational binding energy into a comparatively small
amount of outgoing observable kinetic energy. A fractional absorption of the
emitted neutrinos, the particles which carry away the binding energy, by the
expelled matter is a widely discussed mechanism for powering such explosions.
Previous work addressing neutrino emission from core-collapse like environments
assumes that the outgoing neutrino spectrum closely resembles a black body
whose effective temperature is determined by both the rate of energy release
and the surface area of the entire body. Unfortunately, this assumption
minimizes the net efficiency for both neutrino-driven explosion mechanisms.
Motivated by this fact, we qualitatively outline a scenario where a hot corona
deforms the neutrino spectrum away from that of a cool thermal emitter. Our
primary result is that in principle, a coronal-driven explosion mechanism can
enhance the net efficiency of neutrino-driven SNe and GRBs by more than an
order of magnitude.


title:
Line Polarization of Molecular Lines at Radio Frequencies: The case of
  DR21(OH)

abstract:
  We present polarization observations in DR21(OH) from thermal dust emission
at 3 mm and from CO J=1-0 line emission. The observations were obtained using
the Berkeley-Illinois-Maryland Association array. Previous observations of this
region at 1.3 mm for the polarized continuum emission, and also the CO J=2-1
polarized emission have been made before. Our continuum polarization results
are consistent with those results. However, the direction of the linear
polarization for the J=1-0 is perpendicular to that of the CO J=2-1
polarization. This unexpected result was explored by obtaining numerical
solutions to the multilevel, radiative transfer equations for a gas with
anisotropic optical depths. We find that in addition to the anisotropic optical
depths, anisotropic excitation due to a source of radiation that is external to
the CO is needed to understand the orthogonality in the directions of
polarization. The continuum emission by dust grains at the core of DR21(OH) is
sufficient to provide this external radiation. The CO polarization must arise
in relatively low density (nH2 ~ 100 [cm^-3]) envelope gas. We infer B ~ 10
[micro Gauss] in this gas, which implies that the envelope is subcritical.


title: Complex Topology of the Magnetic Field in Strong Flares

abstract:
  We report the "5+1" dynamical classification of the most frequently observed
topologies of the magnetic field in sunspot groups associated with powerful
flares.


title: Gravitational Microlensing and the Structure of Quasar Outflows

abstract:
  We show that invaluable information on the structure of quasar outflows can
be obtained by considering microlensing (ML) induced variability of absorption
line troughs in lensed quasars. Depending on the structure and geometry of the
outflowing gas, such extrinsic line variability can be manifested as changes to
the equivalent width of the line as well as line profile distortions. Here we
consider several physically distinct outflow models, having very similar
spectral predictions, and show how ML induced absorption line variability can
be used to distinguish between them. The merits of future systematic studies of
these effects are exemplified.


title: Energy-dependent variability from accretion flows

abstract:
  We develop a formalism to calculate energy-dependent fractional variability
(rms) in accretion flows. We consider rms spectra resulting from radial
dependencies of the level of local variability (as expected from propagation of
disturbances in accretion flows) assuming the constant shape of the spectrum
emitted at a given radius. We consider the cases when the variability of the
flow is either coherent or incoherent between different radial zones. As
example local emission, we consider blackbody, Wien and thermal Comptonization
spectra. In addition to numerical results, we present a number of analytical
formulae for the resulting rms. We also find an analytical formula for the disc
Wien spectrum, which we find to be a very good approximation to the disc
blackbody. We compare our results to the rms spectrum observed in an ultrasoft
state of GRS 1915+105.


title: The temperature structure in the core of Sersic 159-03

abstract:
  We present results from a new 120 ks XMM-Newton observation of the cluster of
galaxies Sersic 159-03. In this paper we focus on the high-resolution X-ray
spectra obtained with the Reflection Grating Spectrometer (RGS). The spectra
allow us to constrain the temperature structure in the core of the cluster and
determine the emission measure distribution as a function of temperature. We
also fit the line widths of mainly oxygen and iron lines.


title:
Discovery of 10 micron silicate emission in quasars. Evidence of the AGN
  unification scheme

abstract:
  According to the unified scheme, AGN are surrounded by a dust-torus, and the
observed diversity of AGN properties results from the different orientations
relative to our line of sight. The strong resonance of silicate dust at 10
micron is therefore, as expected, seen in absorption towards many type-2 AGN.
In type-1 AGN, it should be seen in emission because the hot inner surface of
the dust torus becomes visible. However, this has not been observed so far,
thus challenging the unification scheme or leading to exotic modifications of
the dust-torus model. Here we report the discovery of the 10 micron silicate
feature in emission in two luminous quasars with the Infrared Spectrograph of
the Spitzer Space Telescope.


title:
The Structure and Star Formation History of Early-Type Galaxies in the
  UDF/GRAPES Survey

abstract:
  We present a two-pronged approach to the formation of early-type galaxies,
using a sample of 18 galaxies at 0.5 < z < 1 from the HST/ACS Ultra Deep Field
and GRAPES surveys: 1) We combine slitless low resolution spectroscopy from the
GRAPES dataset with simple models of galaxy formation to explore their star
formation histories. 2) We also perform an analysis of their surface brightness
distribution with the unprecedented details provided by the ACS superb angular
resolution and photometric depth. Our spectroscopic analysis reveals that their
stellar populations are rather homogeneous in age and metallicity and formed at
redshifts z ~ 2-5. Evolving them passively, they become practically
indistinguishable from ellipticals at z = 0. Also, their isophotal shapes
appear very similar to those observed for nearby ellipticals, in that the
percentages of disky and boxy galaxies at z ~ 1 are close to the values
measured at z = 0. Moreover,we find that the isophotal structure of z ~ 1
early-type galaxies obeys the correlations already observed among nearby
ellipticals, i.e. disky ellipticals have generally higher characteristic
ellipticities, and boxy ellipticals have larger half-light radii and are
brighter in the restframe B band. In this respect then, no significant
structural differences are seen for ellipticals between z = 0 and 1.


title:
Entropy amplification from energy feedback in simulated galaxy groups
  and clusters

abstract:
  We use hydrodynamical simulations of galaxy clusters and groups to study the
effect of pre-heating on the entropy structure of the ICM. Our simulations
account for non-gravitational heating of the gas either by imposing a minimum
entropy floor at redshift z=3, or by considering feedback by galactic winds
powered by supernova (SN) energy. In the adiabatic simulations we find that the
entropy is increased out to the external regions as a consequence of the
transition from clumpy to smooth accretion induced by extra heating. This
result is in line with the predictions of the semi-analytical model by Voit et
al. However, the introduction of radiative cooling substantially reduces this
entropy amplification effect. While galactic winds of increasing strength are
effective in regulating star formation, they have a negligible effect on the
entropy profile of cluster-sized halos. Only in models where the action of the
winds is complemented with diffuse heating corresponding to a pre-collapse
entropy do we find a sizable entropy amplification out to the virial radius of
the groups. Observational evidence for entropy amplification in the outskirts
of galaxy clusters and groups therefore favours a scenario for feedback that
distributes heating energy in a more diffuse way than predicted by the model
for galactic winds from SN explosions explored here.


title: Scattering properties and composition of cometary dust

abstract:
  Composition of Comet dust obtained by the dust impact analyser on the Halley
probes indicated that the comet dust is a mixure of silicate and carbonaceous
material. The collected interplanetary dust particles (IDP's) are fluffy and
composite having grains of several different types stuck together. Using
Discrete Dipole Approximation (DDA) we study the scattering properties of
composite grains. In particular, we study the angular distribution of the
scattered intensity and linear polarization of composite grains. We assume that
the composite grains are made up of host silicate sphere/spheroid with the
inclusions of graphite. Results of our calculations on the composite grains
show that the angle of maximum polarization shifts, and the degree of
polarizaion varies with the volume fraction of inclusions. We use these results
on the composite grains to interpret the observed scattering in the cometary
dust.


title:
Two-temperature accretion flows in magnetic cataclysmic variables:
  Structures of post-shock emission regions and X-ray spectroscopy

abstract:
  We use a two-temperature hydrodynamical formulation to determine the
temperature and density structures of the post-shock accretion flows in
magnetic cataclysmic variables (mCVs) and calculate the corresponding X-ray
spectra. The effects of two-temperature flows are significant for systems with
a massive white dwarf and a strong white-dwarf magnetic field. Our calculations
show that two-temperature flows predict harder keV spectra than one-temperature
flows for the same white-dwarf mass and magnetic field. This result is
insensitive to whether the electrons and ions have equal temperature at the
shock but depends on the electron-ion exchange rate, relative to the rate of
radiative loss along the flow. White-dwarf masses obtained by fitting the X-ray
spectra of mCVs using hydrodynamic models including the two-temperature effects
will be lower than those obtained using single-temperature models. The bias is
more severe for systems with a massive white dwarf.


title: ASCA and XMM-Newton Observations of A2029

abstract:
  The X-ray data of A2029 obtained with XMM-Newton show no evidence of an
embedded AGN in the central region of this cluster, which was suggested from
the analysis of restored ASCA image data, although some hot spots are seen
within or around the central cD galaxy. The absence of AGN at the cluster
center is consistentent with the result of Chandra observations. Radial
profiles of the iron abundance and the 2D (surface) temperature obtained from
the XMM-Newton data are in good agreement with the Chandra data as a whole.


title: Air Cherenkov Methods in Cosmic Rays: A Review and Some History

abstract:
  The history of application of the Cherenkov light emission in the atmosphere
to cosmic ray and gamma-ray astronomy studies is briefly outlined with an
emphasis on the pioneering activity of A.E. Chudakov. The present-day situation
and some new ideas are also discussed.


title: The HI content of Fornax dwarf elliptical galaxies: FCC032 and FCC336

abstract:
  We present HI 21cm line observations, obtained with the Australia Telescope
Compact Array, of two dwarf elliptical galaxies (dEs) in the Fornax cluster:
FCC032 and FCC336. The optical positions and velocities of these galaxies place
them well within the Fornax cluster. FCC032 was detected at the 3sigma
significance level with a total HI flux density of 0.66+-0.22 Jy km s^-1 or an
HI mass of 5.0+-1.7 10^7 h_75^-2 M_sun. Based on our deep Halpha+[NII]
narrow-band images, obtained with FORS2 mounted on the VLT, this dE was already
known to contain 600-1800 h_75^-2 M_sun of ionised Hydrogen (depending on the
relative strengths of the Halpha and [NII] emission lines). Hence, this is the
first study of the complex, multi-phase interstellar medium of a dE outside the
Local Group. FCC336 was detected at the same significance level: 0.37+-0.10 Jy
km s^-1 or a total HI mass of 2.8+-0.7 10^7 h_75^-2,M_sun. Using a compilation
of HI data of dwarf galaxies, we find that the observed high HI-mass boundary
of the distribution of dIrrs, BCDs, and dEs in a log(L_B) versus log (M_HI)
diagram is in good agreement with a simple chemical evolution model with
continuous star formation. The existence of many gas-poor dEs (undetected at
21cm) suggest that the environment (or more particularly, a galaxy's orbit
within a cluster) also plays a crucial role in determining the amount of gas in
present-day dEs. E.g., FCC032 and FCC336 are located in the sparsely populated
outskirts of the Fornax cluster. This is in agreement with HI surveys of dEs in
the Virgo Cluster and an Halpha survey of the Fornax Cluster, which also tend
to place gas-rich dwarf galaxies in the cluster periphery.


title:
Organic Molecules in the Hot Corinos and Circumstellar Disks of IRAS
  16293-2422

abstract:
  Using the recently-commissioned Submillimeter Array (SMA), we have detected
several complex organic molecules, including (CH3)2O, C2H5OH, C2H5CN, and
tentatively CH2CDCN, toward the protostellar hot cores of IRAS 16293-2422 at
arcsecond-resolution (~< 400 AU in radius). Vibrationally excited transitions
of SO, SO2 and HCN with energy levels up to 1800 K were also observed. In
addition to the other organic molecules (HC3N, CH2CO, CH3OH, CH2CHCN and
HCOOCH3) previously reported by us (Kuan et al. 2004), these results clearly
indicate the existence of a rich organic chemistry in low-mass `hot corinos'.
  From the observation of optically thin HC15N emission, we conclude I16293A is
a rotating circumstellar disk lying along the north-south direction ~10 deg to
the east and with an inclination ~30 deg to the sky. We suggest that the
observed vibrational SO and SO2 emission may originate from shock waves near or
in the circumstellar disks. Between the two cores, we find a strong
anticorrelation in emission from C2H5OH and C2H5CN. The relative contribution
of gas phase and grain-surface chemistries to the production of the observed
complex molecules is discussed. We point out the shortcomings underlying recent
claims that all the O-bearing organics are formed on grains.
  The presence of so many well-known interstellar molecules in solar-type hot
corinos strengthens the link between molecular cloud chemistry, the starting
materials of protoplanetary disks such as the protosolar nebula, and the
composition of comets. Establishing the fine details of this connection is
crucial in answering fundamental questions concerning the importance of
galactic astrochemistry for astrobiology.


title:
Low energy conversion electron detection in superfluid He3 at ultra-low
  temperature

abstract:
  We report on the first results of the MACHe3 (MAtrix of Cells of Helium 3)
prototype experiment concerning the measurement of low energy conversion
electrons at ultra-low temperature. For the first time, the feasibility of the
detection of low energy electrons is demonstrated in superfluid He3-B cooled
down to 100 microK. Low energy electrons at 7.3 keV coming from the K shell
conversion of the 14.4 keV nuclear transition of a low activity Co57 source are
detected, opening the possibility to use a He3-based detector for the detection
of Weakly Interacting Massive Particles (WIMPs) which are expected to release
an amount of energy higher-bounded by 5.6 keV.


title: MHD Interaction of Pulsar Wind Nebulae with SNRs and the ISM

abstract:
  In the late 1960s the discovery of the Crab pulsar in its associated
supernova remnant, launched a new field in supernova remnant research: the
study of pulsar-driven or plerionic supernova remnants. In these type of
remnants, the relativistic wind emitted by the pulsar, blows a pulsar wind
nebula into the interior of its supernova remnant. Now, more then forty years
after the discovery of the Crab pulsar, there are more then fifty plerionic
supernova remnants known, due to the ever-increasing capacity of observational
facilities. I will review our current understanding of the different
evolutionary stages of a pulsar wind nebula as it is interacting with its
associated supernova remnant.Therefore I will discuss both analytical and more
recent numerical (M)HD models.The four main stages of a pulsar wind nebula are:
the supersonic expansion stage, the reverse shock interaction stage, the
subsonic expansion stage and ultimatelythe stage when the head of the bubble is
bounded by a bow shock, due to the supersonic motion of the pulsar. Ultimately
this pulsar wind nebula bow shock will break through its associated remnant,
after which the pulsar-powered bow shock will interact directly with the
interstellar medium. I will discuss recent numerical models from these type of
pulsar wind nebulae and their morphology.


title: Constrained Cluster Parameters from Sunyaev-Zel'dovich Observations

abstract:
  Near-future SZ surveys such as ACT, SPT, APEX, and Planck will find thousands
of galaxy clusters. Multi-frequency arcminute-resolution SZ observations can,
in principle, determine each cluster's gas temperature (T_e), bulk velocity
(v_pec), and optical depth (tau). However, the frequency bands and detector
sensitivity employed by upcoming surveys will generally not be sufficient to
disentangle the degeneracy between these three cluster parameters, even in the
absence of SZ signal contamination from point sources and imperfect primary
microwave background subtraction. Assuming contaminants can be removed, we find
that near-future SZ surveys will be able to constrain well two cluster gas
parameters that are linear combinations of tau*T_e, tau*v_z, and tau*T_e^2.
Because the SZ intensity shift is nearly a linear function of tau*T_e, tau*v_z,
and tau*T_e^2, a correspondence exists between the two effective gas parameters
that SZ surveys can constrain and simple line-of-sight integrals through the
three dimensional cluster. We illustrate the parameter constraints and
correspondence to line-of-sight integrals using 3D Nbody + hydro cluster
simulations and a Markov chain Monte Carlo method. We show that adding an
independent T_e measurement to upcoming SZ data breaks the parameter
degeneracy. The cluster effective velocity thus constrained is approximately
the optical-depth-weighted velocity integrated along the cluster line of sight.
A temperature prior with an error as large as 2 keV still gives bulk velocity
errors < 100 km/sec, even for a more typical cluster with an electron
temperature of 3 keV, for ACT-like SZ observations in the absence of signal
contamination. The Markov chain constraints on v_pec and tau are more
encouraging and likely more accurate than those obtained from Fisher matrices.


title: Dark Energy - Dark Matter Unification: Generalized Chaplygin Gas Model

abstract:
  We review the main features of the generalized Chaplygin gas (GCG) proposal
for unification of dark energy and dark matter and discuss how it admits an
unique decomposition into dark energy and dark matter components once
phantom-like dark energy is excluded. In the context of this approach we
consider structure formation and show that unphysical oscillations or blow-up
in the matter power spectrum are not present. Moreover, we demonstrate that the
dominance of dark energy occurs about the time when energy density fluctuations
start evolving away from the linear regime.


title:
IRS 16SW - A New Comoving Group of Young Stars in the Central Parsec of
  the Milky Way

abstract:
  One of the most perplexing problems associated with the supermassive black
hole at the center of our Galaxy is the origin of the young stars in its close
vicinity. Using proper motion measurements and stellar number density counts
based on 9 years of diffraction-limited K(2.2 micron)-band speckle imaging at
the W. M. Keck 10-meter telescopes, we have identified a new comoving group of
stars, which we call the IRS 16SW comoving group, located 1.9" (0.08 pc, in
projection) from the central black hole. Four of the five members of this
comoving group have been spectroscopically identified as massive young stars,
specifically He I emission-line stars and OBN stars. This is the second young
comoving group within the central parsec of the Milky Way to be recognized and
is the closest, by a factor of 2, in projection to the central black hole.
These comoving groups may be the surviving cores of massive infalling star
clusters that are undergoing disruption in the strong tidal field of the
central supermassive black hole.


title:
Simultaneous ram pressure and tidal stripping; how dwarf spheroidals
  lost their gas

abstract:
  We perform high-resolution N-Body+SPH simulations of gas-rich dwarf galaxy
satellites orbiting within a Milky Way-sized halo and study for the first time
the combined effects of tides and ram pressure. The structure of the galaxy
models and the orbital configurations are chosen in accordance to those
expected in a LCDM Universe.While tidal stirring of disky dwarfs produces
objects whose stellar structure and kinematics resembles that of dwarf
spheroidals after a few orbits, ram pressure stripping is needed to entirely
remove their gas component. Gravitational tides can aid ram pressure stripping
by diminishing the overall potential of the dwarf, but tides also induce bar
formation which funnels gas inwards making subsequent stripping more difficult.
This inflow is particularly effective when the gas can cool radiatively.
Assuming a low density of the hot Galactic corona consistent with observational
constraints, dwarfs with V_{peak} < 30 km/s can be completely stripped of their
gas content on orbits with pericenters of 50 kpc or less. Instead, dwarfs with
more massive dark haloes and V_{peak} > 30 km/s lose most or all of their gas
content only if a heating source keeps the gas extended, partially
counteracting the bar-driven inflow. We show that the ionizing radiation from
the cosmic UV background at z > 2 can provide the required heating. In these
objects most of the gas is removed or becomes ionized at the first pericenter
passage,explaining the early truncation of the star formation observed in Draco
and Ursa Minor. The stripped gas breaks up into individual clouds pressure
confined by the outer gaseous medium that have masses, sizes and densities
comparable to the HI clouds recently discovered around M31.(abridged)


title: On the Exotic Hard X-ray Source Populations in the Hellas2XMM survey

abstract:
  Recent hard X-ray surveys have proven to be effective in discovering large
numbers of X-ray sources that, despite the likely association with active
nuclei, appear to be characterized by "peculiar" properties. Among these
"exotic" source populations, we will focus on the nature of two classes of hard
X-ray sources: those characterized by high X-ray-to-optical flux ratios -- a
fraction of these are associated with the rather elusive Type 2 quasars -- and
the X-ray bright optically normal galaxies, also known as XBONGs.


title: Type 2 counterparts of narrow-line Seyfert 1 galaxies

abstract:
  Unified models of Seyfert galaxies, based on viewing angles, successfully
explain the observed differences between type 1 and 2 Seyferts. The existence
of a range in accretion rates relative to the Eddington rate (from broad-line
Seyfert 1s to narrow-line Seyfert 1s or NLS1s) and the unification of Seyfert
galaxies imply that there must be type 2 counterparts of NLS1 galaxies i.e.,
Seyfert 2s with high accretion rate or small black hole mass. One such Seyfert
2, NGC5506, has already been unmasked based on near infra-red spectroscopy.
Here we confirm the above result, and present evidence for two additional type
2 counterparts of NLS1s based on XMM-Newton observations. The three AGNs
NGC7314, NGC7582 and NGC5506, with a type 1.9/2 optical spectrum, show
extremely rapid variability by factors >2.4, 1.3, and 1.7 in 200s, 350s and
300s, respectively, and steep 2-12 keV spectrum in their intrinsic X-ray
emission, characteristic of NLS1 galaxies. These observations establish the
obscured NLS1 galaxies as a subclass of Seyfert 2 galaxies.


title:
Near Infrared Surface Properties of the Two Intrinsically Brightest
  Minor Planets (90377) Sedna and (90482) Orcus

abstract:
  We present low resolution K band spectra taken at the Gemini 8 meter
telescope of (90377) Sedna and (90482) Orcus (provisional designations 2003
VB12 and 2004 DW, respectively), currently the two minor planets with the
greatest absolute magnitudes (i.e. the two most reflective minor planets). We
place crude limits on the surface composition of these two bodies using a Hapke
model for a wide variety of assumed albedos. The unusual minor planet (90377)
Sedna was discovered on November 14, 2003 UT at roughly 90 AU with 1.6 times
the heliocentric distance and perihelion distance of any other bound minor
planet. It is the first solar system object discovered between the Kuiper Belt
and the Oort Cloud, and may represent a transition population between the two.
The reflectance spectrum of (90377) Sedna appears largely featureless at the
current signal-to-noise ratio, suggesting a surface likely to be highly
processed by cosmic rays. For large grain models (100 micron to 1 cm) we find
that (90377) Sedna must have less than 70% surface fraction of water ice and
less than 60% surface fraction of methane ice to 3 sigma confidence. Minor
planet (90482) Orcus shows strong water ice absorption corresponding to less
than 50% surface fraction for grain models 25 micron and larger. Orcus cannot
have more than 30% of its surface covered by large (100 mm to 1 cm) methane
grains to 3 sigma confidence.


title: The Complex Star Formation History of NGC 1569

abstract:
  We present new results on the star formation history of the dwarf irregular
galaxy NGC 1569. The data were obtained with Hubble Space Telescope's
NICMOS/NIC2 in the F110W (J) and F160W (H) near-infrared (NIR) filters and
interpreted with the synthetic color-magnitude diagram method. The galaxy
experienced a complex star formation (SF) activity. The best fit to the data is
found by assuming three episodes of activity in the last 1-2 Gyr. The most
recent and strong episode constrained by these NIR data started ~37 Myr ago and
ended ~13 Myr ago, although we cannot exclude the possibility that up to three
SF episodes occurred in this time interval. The average star-formation rate
(SFR) of the episode is 3.2 Msun yr-1 kpc-2, in agreement with literature data.
A previous episode produced stars between 150 Myr and 40 Myr ago, with a mean
SFR about 2/3 lower than the mean SFR of the youngest episode. An older SF
episode occurred about 1 Gyr ago. All these SFRs are 2-3 orders of magnitude
higher than those derived for late-type dwarfs of the Local Group. In all cases
an initial mass function similar to Salpeter's allows for a good reproduction
of the data, but we cannot exclude flatter mass functions. These results have
been obtained adopting a distance of 2.2 Mpc and a reddening E(B-V)=0.56. A
larger distance would require younger episodes and higher SFRs. We have
explored some possible scenarios using the astrated mass in the best fit model,
in order to constrain the past star formation history. We cannot rule out a low
rate in the past SF but we can safely conclude that the last 1-2 Gyr have been
peculiar.


title:
Metal abundances in extremely distant Galactic old open clusters. II.
  Berkeley 22 and Berkeley 66

abstract:
  We report on high resolution spectroscopy of four giant stars in the Galactic
old open clusters Berkeley~22 and Berkeley~66 obtained with HIRES at the Keck
telescope. We find that $[Fe/H]=-0.32\pm0.19$ and $[Fe/H]=-0.48\pm0.24$ for
Berkeley~22 and Berkeley~66, respectively. Based on these data, we first revise
the fundamental parameters of the clusters, and then discuss them in the
context of the Galactic disk radial abundance gradient. We found that both
clusters nicely obey the most updated estimate of the slope of the gradient
from \citet{fri02} and are genuine Galactic disk objects.


title: Abundances in giant stars of the globular cluster NGC 6752

abstract:
  Recent theoretical yields and chemical evolution models demonstrate that
intermediate-mass AGB stars cannot reproduce the observed abundance
distributions of O, Na, Mg, and Al. As a further observational test of this
finding, we present elemental abundance ratios [X/Fe] for 20 elements in 38
bright giants of the globular cluster NGC 6752. Our mean abundance ratios
[X/Fe] are in good agreement with previous studies of this cluster and are also
consistent with other globular clusters and field stars at the same
metallicity. The mean abundance ratios [Ba/Eu] and [La/Eu] exhibit values, in
agreement with field stars at the same metallicity, that lie approximately
midway between the pure r-process and the solar (s-process + r-process) mix,
indicating that AGB stars have played a role in the chemical evolution of the
proto-cluster gas.
  For the first time, we find possible evidence for an abundance variation for
elements heavier than Al in this cluster. We find a correlation between [Si/Fe]
and [Al/Fe] which is consistent with the abundance anomalies being synthesized
via proton captures at high temperatures. Leakage from the Mg-Al chain into
28Si may explain the Si excess in stars with the highest [Al/Fe]. We identify
correlations between [Y/Fe] and [Al/Fe], [Zr/Fe] and [Al/Fe], and [Ba/Fe] and
[Al/Fe] suggesting that Y, Zr, and Ba abundances may increase by about 0.1 dex
as Al increases by about 1.3 dex. While the correlations are statistically
significant, the amplitudes of the variations are small. If the small
variations in Y, Zr, and Ba are indeed real, then the synthesis of the Al
anomalies must have taken place within an unknown class of stars that also ran
the s-process. [Abridged]


title: Chandra Observations of the Interacting Galaxies NGC 3395/3396 (Arp 270)

abstract:
  In this paper we present the results of a 20 ks high resolution Chandra X-ray
observation of the peculiar galaxy pair NGC 3395/3396, a system at a very early
stage of merging, and less evolved than the famous Antennae and Mice merging
systems. Previously unpublished ROSAT HRI data are also presented. The point
source population and the hot diffuse gas in this system are investigated, and
compared with other merging galaxy pairs. 16 X-ray point sources are detected
in Arp 270, 7 of which are classified as ULXs (Lx > 10^39 erg/s). From spectral
fits and the age of the system it seems likely that these are predominantly
high mass X-ray binaries. The diffuse gas emits at a global temperature of ~0.5
keV, consistent with temperatures observed in other interacting systems, and we
see no evidence of the starburst-driven hot gaseous outflows seen in more
evolved systems such as The Mice and The Antennae. It is likely that these
features are absent from Arp 270 as the gas has had insufficient time to break
out of the galaxy disks. 32% of the luminosity of Arp 270 arises from the
diffuse gas in the system, this is low when compared to later stage merging
systems and gives further credence that this is an early stage merger.
Comparing the ULX population of Arp 270 to other merging systems, we derive a
relationship between the star formation rate of the system, indicated by Lfir,
and the number (N(ULX)) and luminosity (Lulx) of its ULX population. We find
Nulx proportional to Lfir^0.18 and Lulx proportional to Lfir^0.54. These
relationships, coupled with the relation of the point source X-ray luminosity
(Lxp) to Lk and Lfir+uv (Colbert et al. 2003), indicate that the ULX sources in
an interacting system have contributions from both the old and young stellar
populations.


title: The Payload Data Handling and Telemetry Systems of Gaia

abstract:
  The Payload Data Handling System (PDHS) of Gaia is a technological challenge,
since it will have to process a huge amount of data with limited resources. Its
main tasks include the optimal codification of science data, its packetisation
and its compression, before being stored on-board ready to be transmitted. Here
we describe a set of proposals for its design, as well as some simulators
developed to optimise and test these proposals.


title:
Supernova Blastwaves in Low-density Hot Media: a Mechanism for Spatially
  Distributed Heating

abstract:
  Most supernovae are expected to explode in low-density hot media,
particularly in galactic bulges and elliptical galaxies. The remnants of such
supernovae, though difficult to detect individually, can be profoundly
important in heating the media on large scales. We characterize the evolution
of this kind of supernova remnants, based on analytical approximations and
hydrodynamic simulations. We generalize the standard Sedov solution to account
for both temperature and density effects of the ambient media. Although cooling
can be neglected, the expansion of such a remnant deviates quickly from the
standard Sedov solution and asymptotically approaches the ambient sound speed
as the swept-up thermal energy becomes important. The relatively steady and
fast expansion of the remnants over large volumes provides an ideal mechanism
for spatially distributed heating, which may help to alleviate the over-cooling
problem of hot gas in groups and clusters of galaxies as well as in galaxies
themselves. The simulations were performed with the FLASH code.


title:
Total Galaxy Magnitudes and Effective Radii from Petrosian Magnitudes
  and Radii

abstract:
  Petrosian magnitudes were designed to help with the difficult task of
determining a galaxy's total light. Although these magnitudes (taken here as
the flux within 2R_P, with the inverted Petrosian index 1/eta(R_P)=0.2) can
represent most of an object's flux, they do of course miss the light outside of
the Petrosian aperture (2R_P). The size of this flux deficit varies
monotonically with the shape of a galaxy's light-profile, i.e., its
concentration. In the case of a de Vaucouleurs R^{1/4} profile, the deficit is
0.20 mag; for an R^{1/8} profile this figure rises to 0.50 mag. Here we provide
a simple method for recovering total (Sersic) magnitudes from Petrosian
magnitudes using only the galaxy concentration (R_90/R_50 or R_80/R_20) within
the Petrosian aperture. The corrections hold to the extent that Sersic's model
provides a good description of a galaxy's luminosity profile. We show how the
concentration can also be used to convert Petrosian radii into effective
half-light radii, enabling a robust measure of the mean effective surface
brightness. Our technique is applied to the SDSS DR2 Petrosian parameters,
yielding good agreement with the total magnitudes, effective radii, and mean
effective surface brightnesses obtained from the NYU--VAGC Sersic R^{1/n} fits
by Blanton et al. (2005). Although the corrective procedure described here is
specifically applicable to the SDSS DR2 and DR3, it is generally applicable to
all imaging data where any Petrosian index and concentration can be
constructed.


title: Parameter Study of Star-Discs Encounters

abstract:
  Interactions between disc-surrounded stars might play a vital role in the
formation of planetary systems. Here a first parameter study of the effects of
encounters on low-mass discs is presented. The dependence of the mass and
angular momentum transport on the periastron distance, the relative mass of the
encountering stars and eccentricity of the encounter is investigated in detail.
This is done for prograde and retrograde coplanar encounters as well as
non-coplanar encounters. For distant coplanar encounters our simulation results
agree with the analytical approximation of the angular momentum loss by
Ostriker(1994). However, for close or high-mass encounters, significant
differences to this approximation are found. This is especially so in the case
of retrograde encounters, where the analytical result predict no angular
momentum loss regardless of the periastron distance whereas the simulations
find up to ~ 20% loss for close encounters. For the non-coplanar case a more
complex dependency on the inclination between orbital path and disc plane is
found than for distant encounters. For the coplanar prograde case new fitting
formulae for the mass and angular momentum loss are obtained, which cover the
whole range from grazing to distant encounters. In addition, the final disc
size and the mass exchange between discs is examined, demonstrating that for
equal mass stars in encounters as close as 1.5 the disc radius, the disc size
only is reduced by approximately 10%.


title: The Origin of UCDs in the Virgo Cluster

abstract:
  We present the internal velocity dispersions and spectral line indices for
six Virgo ultra-compact dwarf (UCD) galaxies obtained from spectroscopy with
the Keck II 10-m telescope. We use these results: 1) to compare the Virgo UCDs
with the Fornax UCD population; 2) to compare UCDs with globular clusters (GCs)
to determine if UCDs and the most luminous GCs are the same or distinct
systems; 3) to further test the nucleated dwarf elliptical (dE,N) stripping
hypothesis for UCD formation.


title:
An indirect limit on the amplitude of primordial Gravitational Wave
  Background from CMB-Galaxy Cross Correlation

abstract:
  While large scale cosmic microwave background (CMB) anisotropies involve a
combination of the scalar and tensor fluctuations, the scalar amplitude can be
independently determined through the CMB-galaxy cross-correlation. Using
recently measured cross-correlation amplitudes, arising from the
cross-correlation between galaxies and the Integrated Sachs Wolfe effect in CMB
anisotropies, we obtain a constraint r < 0.5 at 68% confidence level on the
tensor-to-scalar fluctuation amplitude ratio. The data also allow us to exclude
gravity waves at a level of a few percent, relative to the density field, in a
low - Lambda dominated universe(Omega_Lambda~0.5). In future, joining
cross-correlation ISW measurements, which captures cosmological parameter
information, with independent determinations of the matter density and CMB
anisotropy power spectrum, may constrain the tensor-to-scalar ratio to a level
above 0.05. This value is the ultimate limit on tensor-to-scalar ratio from
temperature anisotropy maps when all other cosmological parameters except for
the tensor amplitude are known and the combination with CMB-galaxy correlation
allows this limit to be reached easily by accounting for degeneracies in
certain cosmological parameters.


title: On ion-ion correlation effects during stellar core collapse

abstract:
  The role of ion-ion correlations in suppressing neutrino-nucleus elastic
scattering during stellar core collapse is reinvestigated, using two different
equations of state. We test the improved description by Itoh et al. against the
treatment suggested by Horowitz and find that the stronger cross section
reduction for small momentum transfer in the former case does not lead to
noticeable changes of the core deleptonization and entropy increase during
collapse, because the improvements are relevant below neutrino trapping
conditions only for very low neutrino energies, corresponding to a very small
phase space volume. Treating screening effects for ionic mixtures by the linear
mixing rule, applied to the collection of representative heavy nucleus, alpha
particles, and free nucleons, which is assumed to characterize the composition
in nuclear statistical equilibrium, we cannot determine mentionable differences
during stellar collapse, because alpha particles are not sufficiently abundant
and their coherent scattering opacity is too small.


title: Strange stars and superbursts at near-Eddington mass accretion rates

abstract:
  Careful assessment of four good superburst candidates for GX 17+2 reveals
that superburst is possible at near Eddington mass accretion rates. For the
other seven stars, where superburst is found, there is the standard model of
burning accumulated carbon from normal type I bursts of the accreting stars.
However, there is the need for carbon, nitrogen and oxygen mass fraction
(Z_{CNO}) which must be larger than Z_{CNO,\odot}, where the latter refers to
the standard value found in the sun. Also it is very difficult to incorporate
GX 17+2 into the standard picture of superbursts. In case of superbursts from
strange stars, arising from broken quark pairs going over to diquarks at the
surface of the star, these problems do not arise. Furthermore there is a
natural explanation for the large value of ~ 1000 for \alpha which is defined
in the literature as the ratio of energy released between normal bursts to the
energy released during the normal burst. In the scenario for superbursts in
strange stars it may be argued that the relatively smaller value of \alpha of ~
440 indicates frequent recurrence of superbursts which is reflected in 4U
1636-53.


abstract:
  We present spatially resolved X-ray spectroscopy of PSR B1951+32 and its
pulsar wind nebula (PWN) in supernova remnant (SNR) CTB 80 using a {\sl
Chandra} observation. The {\sl Chandra} X-ray map reveals clearly various
components of a ram-pressure confined PWN embedded in the SNR ejecta: a point
source representing the pulsar, X-ray emission from the bow shock, a luminous
X-ray tail, a 30$\arcsec$ diameter plateau whose northwestern part is absent,
and the outside more diffuse X-ray emission. The plateau is just surrounded by
the radio, [O III], [S II], and [N II] shells, and the outside diffuse emission
is mostly within the H${\alpha}$ shells. While the spectra of all the features
are well fitted with power law models, a power law plus blackbody model can fit
the spectrum of the pulsar significantly better than using a power law model
alone. Generally the spectra of these components obey the trend of steepening
from the inside to the outside. However, the edge of the plateau probably has a
harder spectrum than that of the central region of the plateau. The cause of
the apparent hard spectrum of the plateau edge is unclear, and we speculate
that it might be due to a shock between the PWN and the SNR ejecta. The
possible blackbody radiation component from the pulsar has a temperature of
0.13$\pm0.02$ keV and an equivalent emitting radius of 2.2$^{+1.4}_{-0.8}$ (d/2
kpc) km, and is thus probably from the hot spots on the pulsar. We also show in
this paper that the blackbody temperature of the entire surface of PSR B1951+32
is much lower than those predicted by the standard neutron star cooling models.


title:
Gravitational waves, inflation and the cosmic microwave background:
  towards testing the slow-roll paradigm

abstract:
  One of the fundamental and yet untested predictions of inflationary models is
the generation of a very weak cosmic background of gravitational radiation. We
investigate the sensitivity required for a space-based gravitational wave laser
interferometer with peak sensitivity at $\sim 1$ Hz to observe such signal as a
function of the model parameters and compare it with indirect limits that can
be set with data from present and future cosmic microwave background missions.
We concentrate on signals predicted by slow-roll single field inflationary
models and instrumental configurations such as those proposed for the LISA
follow-on mission: Big Bang Observer.


title: The creation of the Helix planetary nebula (NGC 7293) by multiple events

abstract:
  A deep, continuum-subtracted, image of NGC 7293 has been obtained in the
light of the Halpha+[N II] emission lines. New images of two filamentary halo
stuctures have been obtained and the possible detection of a collimated outflow
made. Spatially resolved, longslit profiles of the Halpha+[N II] lines have
been observed across several of these features with the MES combined with the
SPM 2.1m telescope; these are compared with the [N II]6584, [O III]5007, HeII
6560 and Halpha profiles obtained over the nebular core. The central HeII
emission is originating in a ~0.34pc diameter spherical volume expanding at
<=12km/s which is surrounded, and partially coincident with an [O III] emitting
inner shell expanding at 12km/s. The bright helical structure surrounding this
inner region is modelled as a bi-polar nebula with lobe expansions of 25km/s
whose axis is tilted at 37deg to the sight line but with a toroidal waist
itself expanding at 14 km/s. These observations are compared with the
expectations of the interacting two winds model for the formation of PNe. Only
after the fast wind has switched off could this global velocity structure be
generated. Ablated flows must complicate any interpretation. It is suggested
that the clumpy nature of much of the material could play a part in creating
the radial `spokes' shown here to be apparently present close to the central
star. These `spokes' could in fact be the persistant tails of cometary globules
whose heads have now photo-evaporated completely. A halo arc projecting from
the north-east of the bright core has a conterpart to the south-east. Anomolies
in the position-velocity arrays of line profiles could suggest that these are
part of an expanding disc not aligned with the central helical structure though
expanding bi-polar lobes along a tilted axis are not ruled out.


title:
Chandra HETGS Multi-Phase Spectroscopy of the Young Magnetic O Star
  theta^1 Orionis C

abstract:
  We report on four Chandra grating observations of the oblique magnetic
rotator theta^1 Ori C (O5.5 V) covering a wide range of viewing angles with
respect to the star's 1060 G dipole magnetic field. We employ line-width and
centroid analyses to study the dynamics of the X-ray emitting plasma in the
circumstellar environment, as well as line-ratio diagnostics to constrain the
spatial location, and global spectral modeling to constrain the temperature
distribution and abundances of the very hot plasma. We investigate these
diagnostics as a function of viewing angle and analyze them in conjunction with
new MHD simulations of the magnetically channeled wind shock mechanism on
theta^1 Ori C. This model fits all the data surprisingly well, predicting the
temperature, luminosity, and occultation of the X-ray emitting plasma with
rotation phase.


title:
Radio-Detection Signature of High Energy Cosmic Rays by the CODALEMA
  Experiment

abstract:
  Taking advantage of recent technical progress which has overcome some of the
difficulties encountered in the 1960's in the radio detection of extensive air
showers induced by ultra high energy cosmic rays (UHECR), a new experimental
apparatus (CODALEMA) has been built and operated. We will present the
characteristics of this device and the analysis techniques that have been
developed for observing electrical transients associated with cosmic rays.
  We find a collection of events for which both time and arrival direction
coincidences between particle and radio signals are observed. The counting rate
corresponds to shower energies $\geq 5\times 10^{16}$ eV. The performance level
which has been reached considerably enlarges the perspectives for studying
UHECR events using radio detection.


title: Chemical processes in star forming regions

abstract:
  This paper will review the basic concepts of gas-phase and grain surface
chemistry of dense molecular clouds, where low mass and high mass stars form.
The chemistry of cold pre-stellar cloud cores, where molecular freeze-out and
deuterium fractionation dominate, will be presented. Then, following cloud
evolution after protostellar birth, hot core and shock chemistry will be
discussed in view of recent observations. A brief summary of the chemistry in
protoplanetary disks will also be furnished. The aim is to identify important
gas tracers in the various steps of the star formation process, pointing out
the main problems still open in the field of astrochemistry.


title:
On the Sensitivity of Deflagrations in Chandrasekhar Mass White Dwarf to
  Initial Conditions

abstract:
  We analyze the sensitivity of the flame propagation in a Chandrasekhar mass
white dwarf to initial conditions during the subsonic burning phase, using 2D
simulations of the full WD. Results are presented for a wide variety of initial
flame distributions including central and off-center single point and
multi-point, simultaneous and non-simultaneous, ignitions. We also examine the
effects of convective velocity field which should exist at the core before the
thermo-nuclear runaway. Our main conclusion suggests that the amounts of
burning products and their distributions through the deflagration phase are
extremely sensitive to initial conditions, much more sensitive than presented
in previous studies. In particular, we find that more complex configurations
such as even slight off-center ignitions, non-simultaneous multi-point
ignitions and velocity fields tend to favor solutions in which individual
plumes rise faster than the bulk of a typical Rayleigh-Taylor driven, unstable
burning front. The difference to previous calculations for an octant of a WD
may be understood as a consequence of the suppression of l=1,2 modes. Our
results are consistent with full star calculations by the Chicago group.
Moreover, the total amount of nuclear burning during the phase of subsonic
burning depends sensitively on the initial conditions and may cause the WD to
pulsate or to become unbound. We discuss the implications of the results on
current models for Type Ia SNe, limitations imposed by the 2-D nature of our
study, and suggest directions for further study.


title:
The 2dF-SDSS LRG and QSO Survey: The z<2.1 Quasar Luminosity Function
  from 5645 Quasars to g=21.85

abstract:
  We have used the 2dF instrument on the AAT to obtain redshifts of a sample of
z<3, 18.0<g<21.85 quasars selected from SDSS imaging. These data are part of a
larger joint programme: the 2dF-SDSS LRG and QSO Survey (2SLAQ). We describe
the quasar selection algorithm and present the resulting luminosity function of
5645 quasars in 105.7 deg^2. The bright end number counts and luminosity
function agree well with determinations from the 2dF QSO Redshift Survey (2QZ)
data to g\sim20.2. However, at the faint end the 2SLAQ number counts and
luminosity function are steeper than the final 2QZ results from Croom et al.
(2004), but are consistent with the preliminary 2QZ results from Boyle et al.
(2000). Using the functional form adopted for the 2QZ analysis, we find a faint
end slope of beta=-1.78+/-0.03 if we allow all of the parameters to vary and
beta=-1.45+/-0.03 if we allow only the faint end slope and normalization to
vary. Our maximum likelihood fit to the data yields 32% more quasars than the
final 2QZ parameterization, but is not inconsistent with other g>21 deep
surveys. The 2SLAQ data exhibit no well defined ``break'' but do clearly
flatten with increasing magnitude. The shape of the quasar luminosity function
derived from 2SLAQ is in good agreement with that derived from type I quasars
found in hard X-ray surveys. [Abridged]


title:
Using the photons from the Crab Nebula seen by GLAST to calibrate MAGIC
  and the Imaging Air Cherenkov Telescopes

abstract:
  In this article we discuss the possibility of using the observations by GLAST
of standard gamma sources, as the Crab Nebula, to calibrate Imaging Air
Cherenkov detectors, MAGIC in particular, and optimise their energy resolution.
We show that at around 100 GeV the absolute energy calibration uncertainty of
Cherenkov telescopes can be reduced to <10% by means of such cross-calibration
procedure.


title: Radio Spectral Index Variations of the SNR HB3

abstract:
  We present images of the SNR HB3 at both 408 MHz and 1420 MHz from the
Canadian Galactic Plane Survey mainly based on data from the Synthesis
Telescope of the Dominion Radio Astrophysical Observatory. We reproduce the
100m-Effelsberg HB3 image at 2695 MHz at large scale, and find that there
exists a background emission gradient across the HB3 area. Based on our
analysis of background emission and the boundary between W3 and HB3, we give
HB3's flux density as 68.6 +/- 11.5 Jy at 408 MHz and 44.8 +/- 12.0 Jy at 1420
MHz, after subtracting flux from compact sources within HB3. The integrated
flux-density-based spectral index between 408 MHz and 1420 MHz is 0.34 +/-
0.15. The averaged T-T plot spectral index using all subareas is 0.36. Our
measurement values are less than a previously published value of 0.6. The
408-1420 MHz spectral index varies spatially in HB3 in the range 0.1 to 0.7. We
investigate the data used by previous authors, and consider more data at 232
MHz, 3650 MHz and 3900 MHz which are not included in previous calculations.
There is evidence for two spectral indices for HB3 in the radio band, i.e.,
0.63 (38 - 610 MHz) and 0.32 (408 - 3900 MHz). This is consistent with the
spatial variations: the low frequency data mainly reflects the steeper indices
and the high frequency data mainly reflects the flatter indices.


title:
Implications of Halo Inside-out Growth on the X-Ray Properties of Nearby
  Galaxy Systems within the Preheating Scenario

abstract:
  We present an entirely analytic model for a preheated, polytropic
intergalactic medium in hydrostatic equilibrium within a NFW dark halo
potential in which the evolution of the halo structure between major merger
events proceeds inside-out by accretion. This model is used to explain, within
a standard $\Lambda$CDM cosmogony, the observed X-ray properties of nearby
relaxed, non-cooling flow groups and clusters of galaxies. We find that our
preferred solution to the equilibrium equations produces scaling relations in
excellent agreement with observations, while simultaneously accounting for the
typical structural characteristics of the distribution of the diffuse baryons.
In the class of preheating models, ours stands out because it offers a unified
description of the intrahalo medium for galaxy systems with total masses above
$\sm 2\times 10^{13}$\msun, does not produce baryonic configurations with large
isentropic cores, and reproduces faithfully the observed behavior of the gas
entropy at large radii. All this is achieved with a moderate level of energy
injection of about half a keV, which can be easily accommodated within the
limits of the total energy released by the most commonly invoked feedback
mechanisms, as well as with a polytropic index of 1.2, consistent with both
many observational determinations and predictions from high-resolution
gas-dynamical simulations of non-cooling flow clusters. More interestingly, our
scheme offers a physical motivation for the adoption of this specific value of
the polytropic index, as it is the one that best ensures the conservation after
halo virialization of the balance between the total specific energies of the
gas and dark matter components for the full range of masses investigated.