title: The Dark Energy Survey

abstract:
  We describe the Dark Energy Survey (DES), a proposed optical-near infrared
survey of 5000 sq. deg of the South Galactic Cap to ~24th magnitude in SDSS
griz, that would use a new 3 sq. deg CCD camera to be mounted on the Blanco 4-m
telescope at Cerro Telolo Inter-American Observatory (CTIO). The survey data
will allow us to measure the dark energy and dark matter densities and the dark
energy equation of state through four independent methods: galaxy clusters,
weak gravitational lensing tomography, galaxy angular clustering, and supernova
distances. These methods are doubly complementary: they constrain different
combinations of cosmological model parameters and are subject to different
systematic errors. By deriving the four sets of measurements from the same data
set with a common analysis framework, we will obtain important cross checks of
the systematic errors and thereby make a substantial and robust advance in the
precision of dark energy measurements.


title:
Ly-alpha Radiative Transfer in Cosmological Simulations and Application
  to a z~8 Emitter

abstract:
  We develop a Ly-alpha radiative transfer (RT) Monte Carlo code for
cosmological simulations.High resolution,along with appropriately treated
cooling can result in simulated environments with very high optical
depths.Thus,solving the Ly-alpha RT problem in cosmological simulations can
take an unrealistically long time.For this reason,we develop methods to speed
up the Ly-alpha RT.With these accelerating methods,along with the
parallelization of the code,we make the problem of Ly-alpha RT in the complex
environments of cosmological simulations tractable.We test the RT code against
simple Ly-alpha emitter models,and then we apply it to the brightest Ly-alpha
emitter of a gasdynamics+N-body Adaptive Refinement Tree (ART) simulation at
z~8.We find that recombination rather than cooling radiation Ly-alpha photons
is the dominant contribution to the intrinsic Ly-alpha luminosity of the
emitter,which is ~4.8x10e43 ergs/s.The size of the emitter is pretty
small,making it unresolved for currently available instruments.Its spectrum
before adding the Ly-alpha Gunn-Peterson absorption (GP) resembles that of
static media,despite some net inward radial peculiar motion.This is because for
such high optical depths as those in ART simulations,velocities of order some
hundreds km/s are not important.We add the GP in two ways.First we assume no
damping wing,corresponding to the situation where the emitter lies within the
HII region of a very bright quasar,and second we allow for the damping
wing.Including the damping wing leads to a maximum line brightness suppression
by roughly a factor of ~62.The line fluxes,even though quite faint for current
ground-based telescopes,should be within reach for JWST.


title: Cosmological Flashes from Rotating Black Holes

abstract:
  Current phenomenology suggests the presence of a compact baryon-poor energy
source to cosmological gamma-ray bursts reacting to high-density matter. The
association of short and long gamma-ray bursts with hyper- and suspended
accretion onto slowly and rapidly spinning black holes predicts weak X-ray
afterglow emissions from short bursts, as in GRB050509B and GRB050709. Long
gamma-ray bursts are probably the birth place of rapidly spinning high-mass
black holes in core-collapse of massive stars, as in GRB030329 with supernova
SN2003dh. This predicts a long-duration burst of gravitational radiation
powered by the spin-energy of the black hole. In contrast to MeV-neutrino
emissions, as in SN1987A, this can be tested by the advanced detectors LIGO and
Virgo about once per year up to distances of about 100Mpc. Detection of the
expected chirps and long-duration bursts of gravitational waves promises
identification of Kerr black holes as the most luminous objects in the
Universe.


title:
Non-Gaussianity detections in the Bianchi VIIh corrected WMAP 1-year
  data made with directional spherical wavelets

abstract:
  Many of the current anomalies reported in the Wilkinson Microwave Anisotropy
Probe (WMAP) 1-year data disappear after `correcting' for the best-fit embedded
Bianchi type VII_h component (Jaffe et al. 2005), albeit assuming no dark
energy component. We investigate the effect of this Bianchi correction on the
detections of non-Gaussianity in the WMAP data that we previously made using
directional spherical wavelets (McEwen et al. 2005a). As previously discovered
by Jaffe et al. (2005), the deviations from Gaussianity in the kurtosis of
spherical Mexican hat wavelet coefficients are eliminated once the data is
corrected for the Bianchi component. This is due to the reduction of the cold
spot at Galactic coordinates (l,b)=(209^\circ,-57\circ), which Cruz et al.
(2005) claim to be the source of non-Gaussianity introduced in the kurtosis.
Our previous detections of non-Gaussianity observed in the skewness of
spherical wavelet coefficients are not reduced by the Bianchi correction.
Indeed, the most significant detection of non-Gaussianity made with the
spherical real Morlet wavelet at a significant level of 98.4% remains (using a
very conservative method to estimate the significance). We make our code to
simulate Bianchi induced temperature fluctuations publicly available.


title:
Disk and wind interaction in the young stellar object MWC 297 spatially
  resolved with VLTI/AMBER

abstract:
  The young stellar object MWC 297 has been observed with the VLT
interferometer equipped with the AMBER instrument. MWC 297 has been spatially
resolved in the continuum with a visibility of 0.50 as well as in the Br gamma
emission line where the visibility decrease to a lower value of 0.33. This
change in the visibility with the wavelength can be interpreted by the presence
of an optically thick disk responsible for the visibility in the continuum and
of a stellar wind traced by Br gamma and whose apparent size is 40% larger. We
validate this interpretation by building a model of the stellar environment
that combines a geometrically thin, optically thick accretion disk model
consisting of gas and dust, and a latitude-dependent stellar wind outflowing
above the disk surface. The continuum emission and visibilities obtained from
this model are fully consistent with the interferometric AMBER data. They agree
also with existing optical, near-infrared spectra and other broad-band
near-infrared interferometric visibilities. A picture emerges in which MWC 297
is surrounded by an equatorial flat disk that is possibly still accreting and
an outflowing wind which has a much higher velocity in the polar region than at
the equator. [abridged]


title: SHELS: The Hectospec Lensing Survey

abstract:
  The Smithsonian Hectospec Lensing Survey (SHELS) combines a large deep
complete redshift survey with a weak lensing map from the Deep Lens Survey
(Wittman et al. 2002; 2005). We use maps of the velocity dispersion based on
systems identified in the redshift survey to compare the three-dimensional
matter distribution with the two-dimensional projection mapped by weak lensing.
We demonstrate directly that the lensing map images the three-dimensional
matter distribution obtained from the kinematic data.


title: Combined LOPES and KASCADE-Grande Data Analysis

abstract:
  First analyses of coincident data of the LOPES (LOfar PrototypE Station)
radio antennas with the particle air shower experiment KASCADE-Grande show
basic correlations in the observed shower parameters, like the strength of the
radio signal and the particle number, or comparing the estimated shower
directions. In addition, an improvement of the experimental resolution of the
shower parameters reconstructed by KASCADE-Grande can be obtained by including
the data of the radio antennas. This important feature will be shown in this
article explicitely by an example event.


title: Absolute calibration of the LOPES antenna system

abstract:
  Radio emission in extensive air showers arises from an interaction with the
geomagnetic field and is subject of theoretical studies. This radio emission
has advantages for the detection of high energy cosmic rays compared to
secondary particle or fluorescence measurement methods. Radio antennas like the
LOPES30 antenna system are suited to investigate this emission process by
detecting the radio pulses. The characteristic observable parameters like
electric field strength and pulse length require a calibration which was done
with a reference radio source resulting in an amplification factor representing
the system behavior in the environment of the KASCADE-Grande experiment.
Knowing the amplification factor and the gain of the LOPES antennas LOPES30 is
calibrated absolutely for systematic analyses of the radio emission.


title:
The HARPS search for southern extra-solar planets V. A 14 Earth-masses
  planet orbiting HD 4308

abstract:
  We present here the discovery and characterisation of a very light planet
around HD4308. The planet orbits its star in 15.56 days. The circular
radial-velocity variation presents a tiny semi-amplitude of 4.1 m/s that
corresponds to a planetary minimum mass m2sin(i)=14.1 Earth masses. The planet
was unveiled by high-precision radial-velocity measurements obtained with the
HARPS spectrograph on the ESO 3.6-m telescope. The radial-velocity residuals
around the Keplerian solution are 1.3 m/s, demonstrating the very high quality
of the HARPS measurements. Activity and bisector indicators exclude any
significant perturbations of stellar intrinsic origin, which supports the
planetary interpretation. Contrary to most planet-host stars, HD4308 has a
marked sub-solar metallicity ([Fe/H]=-0.31), raising the possibility that very
light planet occurrence might show a different coupling with the parent star's
metallicity than do giant gaseous extra-solar planets. Together with
Neptune-mass planets close to their parent stars, the new planet occupies a
position in the mass-separation parameter space that is constraining for
planet-formation and evolution theories. The question of whether they can be
considered as residuals of evaporated gaseous giant planets, ice giants, or
super-earth planets is discussed in the context of the latest core-accretion
models.


title: CMB Temperature Anisotropy Quadrupole Generated by Tensor Perturbation

abstract: This paper has been withdrawn.


title: The State Equation of the Yang-Mills field Dark Energy Models

abstract:
  In this paper, we study the possibility of building Yang-Mills(YM) field dark
energy models with equation of state (EoS) crossing -1, and find that it can
not be realized by the single YM field models, no matter what kind of
lagrangian or initial condition. But the states of $-1<\omega<0$ and
$\omega<-1$ all can be naturally got in this kind of models. The former is like
a quintessence field, and the latter is like a phantom field. This makes that
one can build a model with two YM fields, in which one with the initial state
of $-1<\omega<0$, and the other with $\omega<-1$. We give an example model of
this kind, and find that its EoS is larger than -1 in the past and less than -1
at the present time. We also find that this change must be from $\omega>-1$ to
$<-1$, and it will go to the critical state of $\omega=-1$ with the expansion
of the Universe, which character is same with the single YM field models, and
the Big Rip is naturally avoided.


title: Cosmology with extended Chaplygin gas media and $w=-1$ crossing

abstract:
  In this paper the accelerating expansion of our universe at the late cosmic
evolution time in a generally modified (extended) \emph{Chaplygin gas} (Dark
Fluid) model is detailed, which is characterized by two parameters ($m$,
$\alpha$). Different choices to the parameters $m$ and $\alpha$ divide this
model into two main kinds of situation by different properties with
cosmological interests. With proper choices of parameters, we find that this
extended model can realize the phantom divide $w=-1$ (Equation Of State
parameter) crossing phenomenon with interesting ranges of the scale factor
value $a(t)$ corresponding to $w=-1$ and present value of state parameter $w$.
  Additionally, through Taylor series expansion of the function $A(a)$ in the
extended Chaplygin gas model, a specific Equation of State is gained. Under the
framework of Friedman-Robertson-Walker cosmic model, it can successfully
explain the accelerating expansion of our universe. However, the value of $w$
in this case is large than -1, that is, indicating it like a quintessence fluid
and no $w=-1$ crossing occurs.


title:
Multiband Photometry of the Blazar PKS 0537-441: A Major Active State in
  December 2004 - March 2005

abstract:
  Multiband VRIJHK photometry of the Blazar PKS 0537-441 obtained with the REM
telescope from December 2004 to March 2005 is presented. A major period of
activity is found with more than four magnitudes variability in the V filter in
50 days and of 2.5 in 10 days. In intensity and duration the activity is
similar to that of 1972 reported by Eggen (1973), but it is much better
documented. No clear evidence of variability on time-scale of minutes is found.
The spectral energy distribution is roughly described by a power-law, with the
weaker state being the softer.


title: Relaxing Nucleosynthesis Constraints on Brans-Dicke Theories

abstract:
  We reconsider constraints on Brans-Dicke theories arising from the
requirement of successful Big Bang Nucleosynthesis. Such constraints typically
arise by imposing that the universe be radiation-dominated at early times, and
therefore restricting the contribution that a Brans-Dicke scalar could make to
the energy budget of the universe. However, in this paper we show how the
dynamics of the Brans-Dicke scalar itself can mimic a portion of the radiation
contribution, thereby allowing successful nucleosynthesis with a sizable
contribution to the total cosmic energy density. This possibility significantly
relaxes the existing bounds on Brans-Dicke fields, and opens the door to new
possibilities for early universe cosmology. The necessary fine tunings required
by such an arrangement are identified and discussed.


title: The Disk Mass Project: breaking the disk-halo degeneracy

abstract:
  Little is known about the content and distribution of dark matter in spiral
galaxies. To break the degeneracy in galaxy rotation curve decompositions,
which allows a wide range of dark matter halo density profiles, an independent
measure of the mass surface density of stellar disks is needed. Here, we
present our ongoing Disk Mass project, using two custom-built Integral Field
Units, to measure the vertical velocity dispersion of stars in ~40 spiral
galaxies. This will provide a kinematic measurement of the stellar disk mass
required to break the degeneracy, enabling us to determine the dark matter
properties in spiral galaxies with unprecedented accuracy. Here we present
preliminary results for three galaxies with different central disk surface
brightness levels.


title: Delayed Photoionization Feedback in a Super Star Cluster in SBS0335-052E

abstract:
  SBS0335-052 is a well studied Blue Compact Dwarf galaxy with one of the
lowest metallicities of any known galaxy. It also contains 6 previously
identified Super Star Clusters. We combine archival HST NICMOS images in the Pa
alpha line and the 1.6 micron continuum of the eastern component, SBS0335-052E,
with other space and ground based data to perform a multi-wavelength analysis
of the super star clusters. We concentrate on the southern most clusters,
designated S1 and S2, which appear to be the youngest clusters and are the
strongest emitters of Pa alpha, radio, and x-ray flux. Our analysis leads to a
possible model for S1 and perhaps S2 as a cluster of very young, massive stars
with strong stellar winds. The wind density can be high enough to absorb the
majority of ionizing photons within less than 1000 AU of the stars, creating
very compact HII regions that emit optically thick radiation at radio
wavelengths. These winds would then effectively quench the photoionizing flux
very close to the stars. This can delay the onset of negative feedback by
photoionization and photodissociation on star formation in the clusters. This
is significant since SBS0335-052E resembles the conditions that were probably
common for high redshift star formation in galaxies near the epoch of
reionization.


title:
Late Emission from the Type Ib/c SN 2001em: Overtaking the Hydrogen
  Envelope

abstract:
  The Type Ib/c supernova SN 2001em was observed to have strong radio, X-ray,
and Halpha emission at an age of about 2.5 yr. Although the radio and X-ray
emission have been attributed to an off-axis gamma-ray burst, we model the
emission as the interaction of normal SN Ib/c ejecta with a dense, massive (3
Msun) circumstellar shell at a distance about 7 x 10^{16} cm. We investigate
two models, in which the circumstellar shell has or has not been overtaken by
the forward shock at the time of the X-ray observation. The circumstellar shell
was presumably formed by vigorous mass loss with a rate (2-10) x 10^{-3}
Msun/yr at 1000-2000 yr prior to the supernova explosion. The hydrogen envelope
was completely lost, and subsequently was swept up and accelerated by the fast
wind of the presupernova star up to a velocity of 30-50 km/s. Although
interaction with the shell can explain most of the late emission properties of
SN 2001em, we need to invoke clumping of the gas to explain the low absorption
at X-ray and radio wavelengths.


title:
Multi-wavelength Study of Galaxy Rotation Curves and its Application to
  Cosmology

abstract:
  Rotation information for spiral galaxies can be obtained through the
observation of different spectral lines. While the Halpha(6563 A) line is often
used for galaxies with low to moderate redshifts, it is redshifted into the
near-infrared at z>0.4. This is why most high redshift surveys rely on the
[OII](3727 A) line. Using a sample of 32 spiral galaxies at 0.155 < z < 0.25
observed simultaneously in both Halpha and [OII] with the Hale 200 inch
telescope, the relation between velocity widths extracted from these two
spectral lines is investigated, and we conclude that Halpha derived velocities
can be reliably compared to high z [OII] measurements. The sample of galaxies
is then used along with VIMOS-VLT Deep Survey observations to perform the
angular diameter - redshift test to find constraints on cosmological
parameters. The test makes it possible to discriminate between various
cosmological models, given the upper limit of disc size evolution at the
maximum redshift of the data set, no matter what the evolutionary scenario is.


title: Cosmological Structure Evolution and CMB Anisotropies in DGP Braneworlds

abstract:
  The braneworld model of Dvali, Gabadadze and Porrati (DGP) provides an
intriguing modification of gravity at large distances and late times. By
embedding a three-brane in an uncompactified extra dimension with separate
Einstein-Hilbert terms for both brane and bulk, the DGP model allows for an
accelerating universe at late times even in the absence of an explicit vacuum
energy. We examine the evolution of cosmological perturbations on large scales
in this theory. At late times, perturbations enter a DGP regime in which the
effective value of Newton's constant increases as the background density
diminishes. This leads to a suppression of the integrated Sachs-Wolfe effect,
bringing DGP gravity into slightly better agreement with WMAP data than
conventional LCDM. However, we find that this is not enough to compensate for
the significantly worse fit to supernova data and the distance to the
last-scattering surface in the pure DGP model. LCDM is, therefore, a better
fit.


title: Ages of White Dwarf-Red Subdwarf Systems

abstract:
  We provide the first age estimates for two recently discovered white
dwarf-red subdwarf systems, LHS 193AB and LHS 300AB. These unusual systems
provide a new opportunity for linking the reliable age estimates for the white
dwarfs to the (measurable) metallicities of the red subdwarfs. We have obtained
precise photometry in the $V_{J}R_{KC}I_{KC}JH$ bands and spectroscopy covering
from 6000\AA to 9000\AA for the two new systems, as well as for a comparison
white dwarf-main sequence red dwarf system, GJ 283 AB. Using model grids
available in the literature, we estimate the cooling age as well as
temperature, surface gravity, mass, progenitor mass and {\it total} lifetimes
of the white dwarfs. The results indicate that the two new systems are probably
ancient thick disk objects with ages of at least 6-9 Gyr. We also conduct
searches of red dwarf and white dwarf compendia from SDSS data and the
L{\'e}pine Shara Proper Motion (LSPM) catalog for additional common proper
motion white dwarf-red subdwarf systems. Only seven new candidate systems are
found, which indicates the rarity of these systems.


title:
The Inability of Ambipolar Diffusion to set a Characteristic Mass Scale
  in Molecular Clouds

abstract:
  We investigate the question of whether ambipolar diffusion (ion-neutral
drift) determines the smallest length and mass scale on which structure forms
in a turbulent molecular cloud. We simulate magnetized turbulence in a mostly
neutral, uniformly driven, turbulent medium, using a three-dimensional,
two-fluid, magnetohydrodynamics (MHD) code modified from Zeus-MP. We find that
substantial structure persists below the ambipolar diffusion scale because of
the propagation of compressive slow MHD waves at smaller scales. Contrary to
simple scaling arguments, ambipolar diffusion thus does not suppress structure
below its characteristic dissipation scale as would be expected for a classical
diffusive process. We have found this to be true for the magnetic energy,
velocity, and density. Correspondingly, ambipolar diffusion leaves the clump
mass spectrum unchanged. Ambipolar diffusion appears unable to set a
characteristic scale for gravitational collapse and star formation in turbulent
molecular clouds.


title:
Local Ignition in Carbon/Oxygen White Dwarfs -- I: One-zone Ignition and
  Spherical Shock Ignition of Detonations

abstract:
  The details of ignition of Type Ia supernovae remain fuzzy, despite the
importance of this input for any large-scale model of the final explosion.
Here, we begin a process of understanding the ignition of these hotspots by
examining the burning of one zone of material, and then investigate the
ignition of a detonation due to rapid heating at single point.
  We numerically measure the ignition delay time for onset of burning in
mixtures of degenerate material and provide fitting formula for conditions of
relevance in the Type Ia problem. Using the neon abundance as a proxy for the
white dwarf metallicity, we then find that ignition times can decrease by ~20%
with addition of even 5% of neon by mass. When temperature fluctuations that
successfully kindle a region are very rare, such a reduction in ignition time
can increase the probability of ignition by orders of magnitude. If the neon
comes largely at the expense of carbon, a similar increase in the ignition time
can occur.
  We then consider the ignition of a detonation by an explosive energy input in
one localized zone, eg a Sedov blast wave leading to a shock-ignited
detonation. Building on previous work on curved detonations, we find that
surprisingly large inputs of energy are required to successfully launch a
detonation, leading to required matchheads of ~4500 detonation thicknesses -
tens of centimeters to hundreds of meters - which is orders of magnitude larger
than naive considerations might suggest. This is a very difficult constraint to
meet for some pictures of a deflagration-to-detonation transition, such as a
Zel'dovich gradient mechanism ignition in the distributed burning regime.


title:
A log N(HI) = 22.6 DLA in a dark gamma-ray burst: the environment of GRB
  050401

abstract:
  The optical afterglow spectrum of GRB050401 (at z=2.8992+/-0.0004) shows the
presence of a DLA, with log(nHI)=22.6+/-0.3. This is the highest column density
ever observed in a DLA, and is about five times larger than the strongest DLA
detected so far in any QSO spectrum. From the optical spectrum, we also find a
very large Zn column density, allowing us to infer an abundance of
[Zn/H]=-1.0+/-0.4. These large columns are supported by the X-ray spectrum from
Swift-XRT which shows a column density (in excess of Galactic) of
log(nH)=22.21^{+0.06}_{-0.08} assuming solar abundances (at z=2.9). The
comparison of this X-ray column density, which is dominated by absorption due
to alpha-chain elements, and the HI column density derived from the Ly-alpha
absorption line, allows us to derive a metallicity for the absorbing matter of
[alpha/H]=-0.4+/-0.3. The optical spectrum is reddened and can be well
reproduced with a power-law with SMC extinction, where A_V=0.62+/-0.06. But the
total optical extinction can also be constrained in a way which is independent
of the shape of the extinction curve: from the optical-to-X-ray spectral energy
distribution we find, 0.5<~A_V<~4.5. However, even this upper limit,
independent of the shape of the extinction curve, is still well below the dust
column that is inferred from the X-ray column density, i.e.
A_V=9.1^{+1.4}_{-1.5}. This discrepancy might be explained by a small dust
content with high metallicity (low dust-to-metals ratio). `Grey' extinction
cannot explain the discrepancy since we are comparing the metallicity to a
measurement of the total extinction (without reference to the reddening).
Little dust with high metallicity may be produced by sublimation of dust grains
or may naturally exist in systems younger than a few hundred Myr.


title: How Much Mass do Supermassive Black Holes Eat in their Old Age?

abstract:
  We consider the distribution of local supermassive black hole Eddington
ratios and accretion rates, accounting for the dependence of radiative
efficiency and bolometric corrections on the accretion rate. We find that black
hole mass growth, both of the integrated mass density and the masses of most
individual objects, must be dominated by an earlier, radiatively efficient,
high accretion rate stage, and not by the radiatively inefficient low accretion
rate phase in which most local supermassive black holes are currently observed.
This conclusion is particularly true of supermassive black holes in elliptical
host galaxies, as expected if they have undergone merger activity in the past
which would fuel quasar activity and rapid growth. We discuss models of the
time evolution of accretion rates and show that they all predict significant
mass growth in a prior radiatively efficient state. The only way to avoid this
conclusion is through careful fine-tuning of the accretion/quasar timescale to
a value that is inconsistent with observations. Our results agree with a wide
range of observational inferences drawn from the quasar luminosity function and
X-ray background synthesis models, but our approach has the virtue of being
independent of the modeling of source populations. Models in which black holes
spend the great majority of their time in low accretion rate phases are thus
completely consistent both with observations implying mass gain in relatively
short, high accretion rate phases and with the local distribution of accretion
rates.


title:
Globular clusters, satellite galaxies and stellar haloes from early dark
  matter peaks

abstract:
  The Milky Way contains several distinct old stellar components that provide a
fossil record of its formation. We can understand their spatial distribution
and kinematics in a hierarchical formation scenario by associating the
proto-galactic fragments envisaged by Searle and Zinn (1978) with the rare
peaks able to cool gas in the cold dark matter density field collapsing at
redshift z>10. We use hierarchical structure formation simulations to explore
the kinematics and spatial distribution of these early star-forming structures
in galaxy haloes today. Most of the proto-galaxies rapidly merge, their stellar
contents and dark matter becoming smoothly distributed and forming the inner
Galactic halo. The metal-poor globular clusters and old halo stars become
tracers of this early evolutionary phase, centrally biased and naturally
reproducing the observed steep fall off with radius. The most outlying peaks
fall in late and survive to the present day as satellite galaxies. The observed
radial velocity dispersion profile and the local radial velocity anisotropy of
Milky Way halo stars are successfully reproduced in this model. If this epoch
of structure formation coincides with a suppression of further cooling into
lower sigma peaks then we can reproduce the rarity, kinematics and spatial
distribution of satellite galaxies as suggested by Bullock et al. (2000).
Reionisation at z=12+/-2 provides a natural solution to the missing satellites
problem. Measuring the distribution of globular clusters and halo light on
scales from galaxies to clusters could be used to constrain global versus local
reionisation models. If reionisation occurs contemporary, our model predicts a
constant frequency of blue globulars relative to the host halo mass, except for
dwarf galaxies where the average relative frequencies become smaller.


title:
First Measurement of the Clustering Evolution of
  Photometrically-Classified Quasars

abstract:
  We present new measurements of the quasar autocorrelation from a sample of
\~80,000 photometrically-classified quasars taken from SDSS DR1. We find a
best-fit model of $\omega(\theta) =
(0.066\pm^{0.026}_{0.024})\theta^{-(0.98\pm0.15)}$ for the angular
autocorrelation, consistent with estimates from spectroscopic quasar surveys.
We show that only models with little or no evolution in the clustering of
quasars in comoving coordinates since z~1.4 can recover a scale-length
consistent with local galaxies and Active Galactic Nuclei (AGNs). A model with
little evolution of quasar clustering in comoving coordinates is best explained
in the current cosmological paradigm by rapid evolution in quasar bias. We show
that quasar biasing must have changed from b_Q~3 at a (photometric) redshift of
z=2.2 to b_Q~1.2-1.3 by z=0.75. Such a rapid increase with redshift in biasing
implies that quasars at z~2 cannot be the progenitors of modern L* objects,
rather they must now reside in dense environments, such as clusters. Similarly,
the duration of the UVX quasar phase must be short enough to explain why local
UVX quasars reside in essentially unbiased structures. Our estimates of b_Q are
in good agreement with recent spectroscopic results, which demonstrate the
implied evolution in b_Q is consistent with quasars inhabiting halos of similar
mass at every redshift. Treating quasar clustering as a function of both
redshift and luminosity, we find no evidence for luminosity dependence in
quasar clustering, and that redshift evolution thus affects quasar clustering
more than changes in quasars' luminosity. We provide a new method for
quantifying stellar contamination in photometrically-classified quasar catalogs
via the correlation function.


title: On The Assembly History of Dark Matter Haloes

abstract:
  (abridged) We study the mass assembly history (MAH) of dark matter haloes. We
compare MAHs obtained using (i) merger trees constructed with the extended
Press-Schechter (EPS) formalism, (ii) numerical simulations, and (iii) the
Lagrangian perturbation code PINOCCHIO. We show that the PINOCCHIO MAHs are in
excellent agreement with those obtained using numerical simulations. Using a
suite of 55 PINOCCHIO simulations, with 256^3 particles each, we study the MAHs
of 12,924 cold dark matter haloes in a \LambdaCDM concordance cosmology. We
show that haloes less massive than the characteristic non-linear mass scale
establish their potential wells much before they acquire most of their mass.
The time when a halo reaches its maximum virial velocity roughly divides its
mass assembly into two phases, a fast accretion phase which is dominated by
major mergers, and a slow accretion phase dominated by minor mergers. Each halo
experiences about 3 \pm 2 major mergers since its main progenitor had a mass
equal to one percent of the final halo mass. This major merger statistic is
found to be virtually independent of halo mass. However, the average redshift
at which these major mergers occur, is strongly mass dependent, with more
massive haloes experiencing their major mergers later.


title: The Nature of the Density Clump in the Fornax Dwarf Spheroidal Galaxy

abstract:
  We have imaged the recently discovered stellar overdensity located
approximately one core radius from the center of the Fornax dwarf spheroidal
galaxy using the Magellan Clay 6.5m telescope with the Magellan Instant Camera
(MagIC). Superb seeing conditions allowed us to probe the stellar populations
of this overdensity and of a control field within Fornax to a limiting
magnitude of R=26. The color-magnitude diagram of the overdensity field is
virtually identical to that of the control field with the exception of the
presence of a population arising from a very short (less than 300 Myr in
duration) burst of star formation 1.4 Gyr ago. Coleman et al. have argued that
this overdensity might be related to a shell structure in Fornax that was
created when Fornax captured a smaller galaxy. Our results are consistent with
this model, but we argue that the metallicity of this young component favors a
scenario in which the gas was part of Fornax itself.


title:
A Comparison of Halpha and Stellar Scale Lengths in Virgo and Field
  Spirals

abstract:
  The scale lengths of the old stars and ionized gas distributions are compared
for similar samples of Virgo Cluster members and field spiral galaxies via
Halpha and broad R-band surface photometry. While the R-band and Halpha scale
lengths are, on average, comparable for the combined sample, we find
significant differences between the field and cluster samples. While the Halpha
scale lengths of the field galaxies are a factor of 1.14 +- 0.07 longer on
average than their R-band scale lengths, the Halpha scale lengths of Virgo
Cluster members are on average 20% smaller than their R-band scale lengths.
Furthermore, in Virgo, the scale length ratios are correlated with the size of
the star-forming disk: galaxies with smaller overall Halpha extents also show
steeper radial falloff of star formation activity. At the same time, we find no
strong trends in scale length ratio as a function of other galaxy properties
including galaxy luminosity, inclination, morphological type, central R--band
light concentration, or bar type. Our results for Halpha emission are similar
to other results for dust emission, suggesting that Halpha and dust have
similar distributions. The environmental dependence of the Halpha scale length
places additional constraints on the evolutionary process(es) that cause gas
depletion and a suppression of the star formation rate in clusters of galaxies.


title:
Comparison of air fluorescence and ionization measurements of E.M.
  shower depth profiles: test of a UHECR detector technique

abstract:
  Measurements are reported on the fluorescence of air as a function of depth
in electromagnetic showers initiated by bunches of 28.5 GeV electrons. The
light yield is compared with the expected and observed depth profiles of
ionization in the showers. It validates the use of atmospheric fluorescence
profiles in measuring ultra high energy cosmic rays.


title: The Anisotropic Spatial Distribution of CDM Subhalos

abstract:
  I review recent results on the spatial distribution of substructure in CDM
halos. I show that the spatial distribution of subhalos is anisotropic and
generally prolate with a long axis that is closely aligned with the long axis
of the total mass distribution of the host halo. I show that the correlation
between the subhalo distribution and the long axis of the host halo is strong
both in dissipationless and dissipational gasdynamical simulations. More
massive subhalos tend to be more strongly clustered along the major axis of the
host halo reflecting filamentary accretion. The anisotropy of subhalos has
potential implications for the interpretation of several observations in the
Local Group and beyond. For example, I show that while the mean projected mass
fraction in substructure in the central regions of CDM halos is fsub \approx
0.4%, fsub is a strong function of projection angle and is ~ 5 to 6 times
higher for projections that are nearly collinear with the major axis of the
host halo.


title: The solar model problem resurrected

abstract:
  The new solar composition, when applied to compute a model of the Sun, leads
to serious disagreement between the predictions of the model and the
observations obtained by helioseismology. New measurements of the coronal Ne/O
abundance ratio in nearby stars using X-ray spectra typically find high values
of Ne/O=0.4 rather than 0.15 normally adopted for the Sun. Drake & Testa (2005)
suggest that this high Ne/O ratio is appropriate also for the Sun, which would
bring the solar models back in agreement with the helioseismological
observations. Here we present arguments why the high Ne/O ratio is unlikely to
be applicable to the Sun.


title: And Don't Forget The Black Holes

abstract:
  The discovery of the highly relativistic neutron star (NS) binary (in which
both NS's are pulsars) not only increases the estimated merging rate for the
two NS's by a large factor, but also adds the missing link in the double helium
star model of binary NS evolution. This model gives $\sim 20$ times more
gravitational merging of low-mass black-hole (LMBH), NS binaries than binary
NS's, whatever the rate for the latter is.


title: Evolution and Merging of Binaries with Compact Objects

abstract:
  In the light of recent observations in which short gamma-ray bursts are
interpreted as arising from black-hole(BH), neutron-star(NS) or NS-NS mergings
we would like to review our research on the evolution of compact binaries,
especially those containing NS's. These were carried out with predictions for
LIGO in mind, but are directly applicable to short gamma-ray bursts in the
interpretation above.
  Most important in our review is that we show that the standard scenario for
evolving NS-NS binaries always ends up with a low-mass BH (LMBH), NS binary.
Bethe and Brown (1998) showed that this fate could be avoided if the two giants
in the progenitor binary burned He at the same time, and that in this way the
binary could avoid the common envelope evolution of the NS with red giant
companion which sends the first born NS into a BH in the standard scenario. The
burning of He at the same time requires, for the more massive giants such as
the progenitors of the Hulse-Taylor binary NS that the two giants be within 4%
of each other in ZAMS mass. Applying this criterion to all binaries results in
a factor 5 of LMBH-NS binaries as compared with NS-NS binaries.
  Our scenario of NS-NS binaries as having been preceded by a double He-star
binary is collecting observational support in terms of the nearly equal NS
masses within a given close binary.


title: Double Neutron Star Binaries: Implications for LIGO

abstract:
  Double neutrons are especially important because they give most accurate
informations on the masses of neutron stars. Observations on double neutron
stars show that all masses of the neutron stars are below 1.5$\msun$.
Furthermore, two neutron stars in a given double pulsar are nearly equal in
mass. With hypercritical accretion, we found that the probability of having
companion mass $>1.5\msun$ is larger than 90%, while there is no observations
on such systems. We believe that those companions with masses higher than
$1.5\msun$ went into black holes, which is consistent with our preferred
maximum neutron star mass $M_{NS}^{max} \approx 1.5\msun$ due to the kaon
condensation. In this work, we point out that the black-hole neutron star
binaries are 10 times more dominant than double neutron star binaries. As a
result, black-hole, neutron star binaries can increase the LIGO detection rate
by a factor 20.


title:
Detection of a very bright optical flare from a gamma-ray burst at
  redshift 6.29

abstract:
  In this letter we discuss the flux and the behavior of the bright optical
flare emission detected by the 25 cm TAROT robotic telescope during the prompt
high-energy emission and the early afterglow. We combine our data with
simultaneous observations performed in X-rays and we analyze the broad-band
spectrum. These observations lead us to emphasize the similarity of GRB 050904
with GRB 990123, a remarkable gamma-ray burst whose optical emission reached
9th magnitude. While GRB 990123 was, until now, considered as a unique event,
this observation suggests the existence of a population of GRBs which have very
large isotropic equivalent energies and extremely bright optical counterparts.
The luminosity of these GRBs is such that they are easily detectable through
the entire universe. Since we can detect them to very high redshift even with
small aperture telescopes like TAROT, they will constitute powerful tools for
the exploration of the high-redshift Universe and might be used to probe the
first generation of stars.


title: The distance scale and Eddington efficiency of luminous quasars

abstract:
  The relation between the central mass and quasar luminosity (M_BH \propto
L^{\alpha}FHWM^2) links a given Eddington ratio with a value of H_0, within a
cosmology with fixed (\Omega_m,\Omega_{\Lambda}). We point out that because the
relation is calibrated at low z using distance independent reverberation
mapping to get the BLR size, the derived M_BH interestingly does not depend on
H_0, while L/L_Edd is sensitive to H_0, but rather robust to changes of
\Omega_{\Lambda} in the standard flat model. This means, e.g., that enough of
extragalactic objects radiating at the Eddington limit could be used to study
the global Hubble constant in a new way, bypassing the local distance ladder.
The method could become practical when systematic errors in derived M_BH are
understood and objects with L /leq L_Edd can be independently identified. As an
illustration, if we take a sample of tranquil very luminous quasars in the
redshift range 0.5 < z < 1.6, and assume that they are radiating with L_bol
\leq L_Edd, then the usual numeric factors used for calculating M_BH and L_bol
would lead to the result that the Hubble constant must be larger than 45
km/s/Mpc.


title:
High resolution imaging with Fresnel interferometric arrays: suitability
  for exoplanet detection

abstract:
  We propose a new kind of interferometric array that yields images of high
dynamic range and large field. The numerous individual apertures in this array
form a pattern related to a Fresnel zone plate. This array can be used for
astrophysical imaging over a broad spectral bandwidth spanning from the U.V.
(50 nanometers) to the I.R. (20 microns). Due to the long focal lengths
involved, this instrument requires formation-flying of two space borne vessels.
We present the concept and study the S/N ratio in different situations, then
apply these results to probe the suitability of this concept to detect
exoplanets.


title:
Near-UV to near-IR disk-averaged Earth's spectra from Moon's Earthshine
  observations

abstract:
  We discuss a series of Earthshine spectra obtained with the NTT/EMMI
instrument between 320nm and 1020nm with a resolution of R~450 in the blue and
R~250 in the red. These ascending and descending Moon's Earthshine spectra
taken from Chile give disk-averaged spectra for two different Earth's phases.
The spectra show the ozone (Huggins and Chappuis bands), oxygen and water
vapour absorption bands, and also the stronger Rayleigh scattering in the blue.
Removing the known telluric absorptions reveals a spectral feature around 700nm
which is attributed to the vegetation stronger reflectivity in the near-IR,
so-called vegetation red-edge.


title: The Evolution of the Broad-Line Region among SDSS Quasars

abstract:
  Based on 5344 quasar spectra taken from the SDSS Data Release 2, the
dependences of various emission-line flux ratios on redshift and quasar
luminosity are investigated in the ranges 2.0 < z < 4.5 and -24.5 > M_B >
-29.5$. We show that the emission lines in the composite spectra are fitted
better with power-law profiles than with double Gaussian or modified Lorentzian
profiles, and in particular we show that the power-law profiles are more
appropriate to measure broad emission-line fluxes than other methods. The
composite spectra show that there are statistically significant correlations
between quasar luminosity and various emission-line flux ratios, such as NV/CIV
and NV/HeII, while there are only marginal correlations between quasar redshift
and emission-line flux ratios. We obtain detailed photoionization models to
interpret the observed line ratios. The correlation of line ratios with
luminosity is interpreted in terms of higher gas metallicity in more luminous
quasars. For a given quasar luminosity, there is no metallicity evolution for
the redshift range 2.0 < z < 4.5. The typical metallicity of BLR gas clouds is
estimated to be Z ~ 5 Z_sun, although the inferred metallicity depends on the
assumed BLR cloud properties, such as their density distribution function and
their radial distribution. The absence of a metallicity evolution up to z ~ 4.5
implies that the active star-formation epoch of quasar host galaxies occurred
at z > 7.


title:
Lorentz Invariance Breakdown and Constraints from Big-Bang
  Nucleosynthesis

abstract:
  The Standard Model Extension formulated by Colladay and Kosteleck\'y is
reviewed in the framework of the $^4He$ primordial abundance. Upper bounds on
coefficients for the Lorentz violation are derived using the present
observational data.


title:
Comments on the paper "The initial conditions of isolated star formation
  - VI. SCUBA mapping of prestellar cores" (Kirk et al. 2005)

abstract:
  In their survey paper of prestellar cores with SCUBA, Kirk et al. (2005) have
discarded two of our papers on L183 (Pagani et al. 2003, 2004). However these
papers bring two important pieces of information that they cannot ignore.
Namely, the real structure of L183 and the very poor correlation between
submillimeter and far infrared (FIR) dust emission beyond \Avb $\approx$ 15
mag. Making the erroneous assumption that it is the same dust that we are
seeing in emission at both 200 and 850 $\mu$m, they derive constant
temperatures which are only approximate, and column densities which are too
low. In fact dust temperatures do decrease inside dark clouds and the FIR
emission is only tracing the outer parts of the dark clouds (Pagani et al.
2004)


title: The statistics of Sco X-1 kHZ QPOs

abstract:
  Recently an additional technique was applied to investigate the properties of
kHz QPOS, i.e. the analysis of the distribution of frequency ratios or
frequencies themselves. I review the results of such work on the data from
ScoX-1: Abramowicz et al. (2003), which was later criticized by Belloni et
al.(2005). I conclude that the findings of the latter paper are consistent with
results presented earlier: kHz QPOs cluster around the value corresponding to
the frequency ratio of 2/3. I also discuss the random walk model of kHz QPOs
and possible future observations needed to verify it.


title: Can WNM survive inside Molecular Clouds ?

abstract:
  Recent high resolution numerical simulations have suggested that the
interstellar atomic hydrogen clouds have a complex two-phase structure. Since
molecular clouds form through the contraction of HI gas, the question arises as
to whether this structure is maintained in the molecular phase or not. Here we
investigate whether the warm neutral atomic hydrogen (WNM) can exist in
molecular clouds. We calculate how far a piece of WNM which is not heated by
the UV photons could penetrate into the cloud, and find that in the absence of
any heating it is unlikely that large fraction of WNM survives inside high
pressure molecular clouds. We then consider two possible heating mechanisms,
namely dissipation of turbulent energy and dissipation of MHD waves propagating
in the WNM inside the cloud. We find that the second one is sufficient to allow
the existence of WNM inside a molecular cloud of size $\simeq$ 1 pc having
pressure equal to $\simeq 10 \times P_{\rm ISM}$. This result suggests the
possibility that channels of magnetised WMN may provide efficient energy
injection for sustaining internal turbulence which otherwise decays in a
crossing time.


title:
Dark matter search experiment with CaF2(Eu) scintillator at Kamioka
  Observatory

abstract:
  We report recent results of a WIMP dark matter search experiment using 310g
of CaF2(Eu) scintillator at Kamioka Observatory. We chose a highly radio-pure
crystal, PMTs and radiation shields, so that the background rate decreased
considerably. We derived limits on the spin dependent WIMP-proton and
WIMP-neutron coupling coefficients, a_p and a_n. The limits excluded a part of
the parameter space allowed by the annual modulation observation of the DAMA
NaI experiment.


title:
3D-radiation hydro simulations of disk-planet interactions: I. Numerical
  algorithm and test cases

abstract:
  We study the evolution of an embedded protoplanet in a circumstellar disk
using the 3D-Radiation Hydro code TRAMP, and treat the thermodynamics of the
gas properly in three dimensions. The primary interest of this work lies in the
demonstration and testing of the numerical method. We show how far numerical
parameters can influence the simulations of gap opening. We study a standard
reference model under various numerical approximations. Then we compare the
commonly used locally isothermal approximation to the radiation hydro
simulation using an equation for the internal energy. Models with different
treatments of the mass accretion process are compared. Often mass accumulates
in the Roche lobe of the planet creating a hydrostatic atmosphere around the
planet. The gravitational torques induced by the spiral pattern of the disk
onto the planet are not strongly affected in the average magnitude, but the
short time scale fluctuations are stronger in the radiation hydro models.
  An interesting result of this work lies in the analysis of the temperature
structure around the planet. The most striking effect of treating the
thermodynamics properly is the formation of a hot pressure--supported bubble
around the planet with a pressure scale height of H/R ~ 0.5 rather than a thin
Keplerian circumplanetary accretion disk. We also observe an outflow of gas
above and below the planet during the gap opening phase.


title: Large-scale magnetized outflows from the Virgo Cluster spiral NGC4569

abstract:
  Using the Effelsberg radio telescope at 4.85GHz and 8.35 GHz we discovered
large symmetric lobes of polarized radio emission around the strongly HI
deficient Virgo cluster spiral galaxy NGC4569. These lobes extend up to 24 kpc
from the galactic disk. Our observations were complemented by 1.4 GHz continuum
emission from existing HI observations. This is the first time that such huge
radio continuum lobes are observed in a cluster spiral galaxy. The eastern lobe
seems detached and has a flat spectrum typical for in-situ cosmic ray electron
acceleration. The western lobe is diffuse and possesses vertical magnetic
fields over its whole volume. The lobes are not powered by an AGN, but probably
by a nuclear starburst producing >10^5 supernovae which occurred ~30 Myr ago.
Since the radio lobes are symmetric, they resist ram pressure due to the
galaxy's rapid motion within the intracluster medium.


title: Disk eccentricity and embedded planets

abstract:
  We investigate the response of an accretion disk to the presence of a
perturbing protoplanet embedded in the disk through time dependent
hydrodynamical simulations. The disk is treated as a two-dimensional viscous
fluid and the planet is kept on a fixed orbit. We run a set of simulations
varying the planet mass, and the viscosity and temperature of the disk. All
runs are followed until they reach a quasi-equilibrium state.
  We find that for planetary masses above a certain minimum mass, already 3
M_Jup for a viscosity of nu = 10^{-5}, the disk makes a transition from a
nearly circular state into an eccentric state. Increasing the planetary mass
leads to a saturation of disk eccentricity with a maximum value of around 0.25.
The transition to the eccentric state is driven by the excitation of an m=2
spiral wave at the outer 1:3 Lindblad resonance. The effect occurs only if the
planetary masses are large enough to clear a sufficiently wide and deep gap to
reduce the damping effect of the outer 1:2 Lindblad resonance. An increase in
viscosity and temperature in the disk, which both tend to close the gap, have
an adverse influence on the disk eccentricity.
  In the eccentric state the mass accretion rate onto the planet is greatly
enhanced, an effect that may ease the formation of massive planets beyond about
5 M_Jup that are otherwise difficult to reach.


title:
A possible association of the new VHE gamma-ray source HESS J1825--137
  with the pulsar wind nebula G18.0--0.7

abstract:
  We report on a possible association of the recently discovered very
high-energy $\gamma$-ray source HESS J1825--137 with the pulsar wind nebula
(commonly referred to as G 18.0--0.7) of the $2.1\times 10^{4}$ year old
Vela-like pulsar PSR B1823--13. HESS J1825--137 was detected with a
significance of 8.1 $\sigma$ in the Galactic Plane survey conducted with the
H.E.S.S. instrument in 2004. The centroid position of HESS J1825--137 is offset
by 11\arcmin south of the pulsar position. \emph{XMM-Newton} observations have
revealed X-ray synchrotron emission of an asymmetric pulsar wind nebula
extending to the south of the pulsar. We argue that the observed morphology and
TeV spectral index suggest that HESS J1825--137 and G 18.0--0.7 may be
associated: the lifetime of TeV emitting electrons is expected to be longer
compared to the {\it XMM-Newton} X-ray emitting electrons, resulting in
electrons from earlier epochs (when the spin-down power was larger)
contributing to the present TeV flux. These electrons are expected to be
synchrotron cooled, which explains the observed photon index of $\sim 2.4$, and
the longer lifetime of TeV emitting electrons naturally explains why the TeV
nebula is larger than the X-ray size. Finally, supernova remnant expansion into
an inhomogeneous medium is expected to create reverse shocks interacting at
different times with the pulsar wind nebula, resulting in the offset X-ray and
TeV $\gamma$-ray morphology.


title:
Discovery of a strong magnetic field on the O star HD 191612: new clues
  to the future of theta1 Orionis C?

abstract:
  From observations made with the ESPaDOnS spectropolarimeter, recently
installed on the 3.6-m Canada--France--Hawaii Telescope, we report the
discovery of a strong magnetic field in the Of?p spectrum variable HD 191612 --
only the second known magnetic O star (following theta1 Ori C). The stability
of the observed Zeeman signature over four nights of observation, together with
the non-rotational shape of line profiles, argue that the rotation period of HD
191612 is significantly longer than the 9-d value previously proposed. We
suggest that the recently identified 538-d spectral-variability period is the
rotation period, in which case the observed line-of-sight magnetic field of
-220+-38 G implies a large-scale field (assumed dipolar) with a polar strength
of about -1.5 kG. If confirmed, this scenario suggests that HD 191612 is,
essentially, an evolved version of the near-ZAMS magnetic O star theta1 Ori C,
but with an even stronger field (about 15 kG at an age similar to that of
theta1Ori C). We suggest that the rotation rate of HD 191612, which is
exceptionally slow by accepted O-star standards, could be due to
angular-momentum dissipation through a magnetically confined wind.


title: Type II superconductivity and magnetic flux transport in neutrons stars

abstract:
  The transition to a type II proton superconductor which is believed to occur
in a cooling neutron star is accompanied by changes in the equation of
hydrostatic equilibrium and by the formation of proton vortices with quantized
magnetic flux. Analysis of the electron Boltzmann equation for this system and
of the proton supercurrent distribution formed at the transition leads to the
derivation of a simple expression for the transport velocity of magnetic flux
in the liquid interior of a neutron star. This shows that flux moves easily as
a consequence of the interaction between neutron and proton superfluid vortices
during intervals of spin-down or spin-up in binary systems. The differences
between the present analysis and those of previous workers are reviewed and an
error in the paper of Jones (1991) is corrected.


title: The H.E.S.S. survey of the Inner Galaxy in very high-energy gamma-rays

abstract:
  We report on a survey of the inner part of the Galactic Plane in very high
energy gamma-rays, with the H.E.S.S. Cherenkov telescope system. The Galactic
Plane between +-30deg in longitude and +-3deg in latitude relative to the
Galactic Centre was observed in 500 pointings for a total of 230 hours,
reaching an average flux sensitivity of 2% of the Crab Nebula at energies above
200 GeV. Fourteen previously unknown sources were detected at a significance
level greater than 4 sigma after accounting for all trials involved in the
search. Initial results on the eight most significant of these sources were
already reported elsewhere. Here we present detailed spectral and morphological
information for all the new sources, along with a discussion on possible
counterparts in other wavelength bands. The distribution in Galactic latitude
of the detected sources appears to be consistent with a scale height in the
Galactic disk for the parent population smaller than 100 pc, consistent with
expectations for supernova remnants and/or pulsar wind nebulae.


title:
Internal kinematics and stellar populations of dE galaxies: Clues to
  their formation/evolution

abstract:
  What is the origin of the numerous population of diffuse elliptical galaxies
(dE) in clusters? These galaxies formed their stars several billion years ago
and lost their gas. Though the stellar winds resulting from star formation and
the interactions with the environment undoubedtly play a role, their respective
role and details of the mechanism of this evolution is still debated.
  In this presentation we will review the first 3D spectroscopic observations
of a handful of dE galaxies. These data reveal complex kinematical structures,
with embedded discs and counter rotating cores, and they open extremely
promising perspectives for studying the history of the stellar population
throughout these various features.
  The presence of disks, which was already known from detailed image analysis,
and of complex kinematics and the new constraints on the stellar population
enforce the hypothesis of the evolutionary connection between dEs and disk
galaxies.


title: Wolf-Rayet Mass-Loss Limits Due to Frequency Redistribution

abstract:
  The hypothesis that CAK-type line driving is responsible for the large
observed Wolf-Rayet (W-R) mass-loss rates has been called into question in
recent theoretical studies. The purpose of this paper is to reconsider the
plausibility of line driving of W-R winds within the standard approach using
the Sobolev approximation while advancing the conceptual understanding of this
topic. Due to the multiple scattering required in this context, of particular
importance is the role of photon frequency redistribution into spectral gaps,
which in the extreme limit yields the statistical Sobolev-Rosseland (SSR) mean
approximation. Interesting limits to constrain are the extremes of no frequency
redistribution, wherein the small radii and corresponding high W-R surface
temperature induces up to twice the mass-loss rate relative to cooler stars,
and the SSR limit, whereby the reduced efficiency of the driving drops the mass
flux by as much as an order of magnitude whenever there exist significant gaps
in the spectral line distribution. To see how this efficiency drop might be
sufficiently avoided to permit high W-R mass loss, we explore the suggestion
that ionization stratification may serve to fill the gaps globally over the
wind. We find that global ionization changes can only fill the gaps
sufficiently to cause about a 25% increase in the mass-loss rate over the local
SSR limit. Higher temperatures and more ionization states (especially of iron)
may be needed to achieve optically thick W-R winds, unless strong clumping
corrections eliminate the need for such winds.


title:
Multiwavelength monitoring of BD+53 2790, the optical counterpart to
  4U~2206+54

abstract:
  We present the results of our long-term monitoring of BD+53 2790, the optical
counterpart to the X-ray source 4U~2206+54. Unlike previous studies that
classify the source as a Be/X-ray binary, we find that its optical and infrared
properties differ from those of typical Be stars: the variability of the V/R
ratio is not cyclical; there are variations in the shape and strength of the
H$\alpha$ emission line on timescales less than 1 day; and no correlation
between the EW and the IR magnitudes or colors is seen. Our observations
suggest that BD+53 2790 is very likely a peculiar O9.5V star. In spite of
exhaustive searches we cannot find any significant modulation in any emission
line parameter or optical/infrared magnitudes. Spectroscopy of the source
extending from the optical to the K-band confirms the peculiarity of the
spectrum: not only are the He lines stronger than expected for an O9.5V star
but also there is no clear pattern of variability. The possibility that BD+53
2790 is an early-type analogue to He-strong stars (like theta^1 Ori C) is
discussed.


title: Hubble Space Telescope Imaging of the Outburst Site of M31 RV

abstract:
  M31 RV is a luminous red variable star that appeared for several months in
the bulge of M31 during 1988. Unlike classical novae, M31 RV was cool
throughout its outburst. Interest in this object has revived recently because
of its strong resemblance to V838 Mon, a luminous Galactic variable star that
appeared in 2002 and is illuminating a spectacular light echo, and has evolved
to ever-cooler surface temperatures. V4332 Sgr is a third object which was also
a red supergiant throughout its eruption.
  We have examined archival Hubble Space Telescope (HST) images of the site of
M31 RV, obtained fortuitously in 1999 with the WFPC2 camera in parallel mode
during spectroscopic observations of the nucleus of M31. We located the site of
M31 RV in the HST frames precisely through astrometric registration with
ground-based CCD images, including several taken during the outburst. No light
echo is seen at the M31 RV site, implying that M31 RV is not surrounded by
circumstellar (or interstellar) dust similar to that around V838 Mon, or that
its extent is less than ~1.7 pc.
  The stellar population at the outburst site consists purely of old red
giants; there is no young population, such as seen around V838 Mon. There are
no stars of unusual color at the site, suggesting that M31 RV had faded below
HST detectability in the 11 years since outburst, that it is an unresolved
companion of one of the red giants in the field, or that it is one of the red
giants. We suggest future observations that may help decide among these
possibilities.


title: Variability in the Lambda Orionis cluster substellar domain

abstract:
  We present the first results on variability of very low mass stars and brown
dwarfs belonging to the 5 Myr Lambda Orionis cluster (Collinder 69). We have
monitored almost continuously in the J filter a small area of the cluster which
includes 12 possible members of the cluster during one night. Some members have
turned to be short-term variable. One of them, LOri167, has a mass close to the
planetary mass limit and its variability might be due to instabilities produced
by the deuterium burning, although other mechanism cannot be ruled out.


title:
XMM-Newton observation of the long-period polar V1309 Ori: The case for
  pure blobby accretion

abstract:
  Using XMM-Newton we have obtained the first X-ray observation covering a
complete orbit of the longest period polar, V1309 Ori. The X-ray light curve is
dominated by a short, bright phase interval with EPIC pn count rates reaching
up to 15 cts/sec per 30 sec resolution bin. The bright phase emission is well
described by a single blackbody component with kT_bb = (45 +- 3) eV. The
absence of a bremsstrahlung component at photon energies above 1 keV yields a
flux ratio F_bb/F_br > 6700. This represents the most extreme case of a soft
X-ray excess yet observed in an AM Herculis star. The bright, soft X-ray
emission is subdivided into a series of individual flare events supporting the
hypothesis that the soft X-ray excess in V1309 is caused by accretion of dense
blobs. In addition to the bright phase emission, a faint, hard X-ray component
is visible throughout the binary orbit with an almost constant count rate of
0.01 cts/sec. Spectral modelling indicates that this emission originates from a
complex multi-temperature plasma. At least three components of an optically
thin plasma with temperatures kT= 0.065, 0.7, and 2.9 keV are required to fit
the observed flux distribution. The faint phase emission is occulted during the
optical eclipse. Eclipse ingress lasts about 15--20 min and is substantially
prolonged beyond nominal ingress of the white dwarf. This and the comparatively
low plasma temperature provide strong evidence that the faint-phase emission is
not thermal bremsstrahlung from a post-shock accretion column above the white
dwarf. A large fraction of the softer faint-phase emission could be explained
by scattering of photons from the blackbody component in the infalling material
above the accretion region. The remaining hard X-ray flux could be produced in
the coupling region, so far unseen in other polars.


title: Low-resolution VLT spectroscopy of GRBs 991216, 011211 and 021211

abstract:
  We present low-resolution VLT spectroscopy of the afterglow of the gamma-ray
bursts (GRBs) 991216, 011211 and 021211. Our spectrum of GRB991216 is the only
optical spectrum for this afterglow. It shows two probable absorption systems
at z=0.80 and z=1.02, where the highest redshift most likely reflects the
distance to the host galaxy. A third system may be detected at z=0.77. HST
imaging of the field, obtained 4 months after the burst, has resulted in the
detection of two amorphous regions of emission, one at the projected afterglow
position, and the other 0.6" away. The spectrum shows a depression in flux in
between 4000 A and 5500 A. This could be the result of a 2175 A-type extinction
feature in the host of GRB991216, but at a rather red wavelength of 2360 A. If
this interpretation is correct, it is the first time the extinction feature is
seen in a GRB afterglow spectrum. It is centered at a wavelength similar to
that of the ultra-violet (UV) bumps inferred from observations of a few
UV-strong, hydrogen-poor stars in the Galaxy. All significant absorption lines
(except for one) detected in the spectrum of GRB011211 are identified with
lines originating in a single absorption system at z=2.142+/-0.002, the
redshift of the GRB011211 host galaxy. We also detect the Lyman alpha
absorption line in the host, to which we fit a neutral hydrogen column density
of log N(HI)=20.4+/-0.2, which indicates that it is a damped Lyman alpha
system. Using a curve-of-growth analysis, we estimate the Si, Fe and Al
metallicity at the GRB011211 redshift. For GRB021211, we detect a single
emission line in a spectrum obtained tens of days after the burst, which we
identify as [OII] 3727 at z=1.006. The corresponding unobscured [OII]
star-formation rate is 1.4 Msun/yr.


title:
Gas Infall and Stochastic Star Formation in Galaxies in the Local
  Universe

abstract:
  We study the recent star formation histories of local galaxies by analyzing
the scatter in their colours and spectral properties. We present evidence that
the distribution of star formation histories changes qualitatively above a
characteristic stellar surface mass density of 3x10^8 M_sol kpc^-2,
corresponding to the transition between disk-dominated and bulge-dominated
galaxies. When we average over subpopulations of galaxies with densities below
this value, we find that subpopulations of all masses form their stars at the
same average rate per unit stellar mass. However, the scatter in galaxy colours
and emission line strengths is larger for more compact galaxies of a given
mass. This suggests that star formation occurs in shorter, higher amplitude
events in galaxies with smaller sizes. Above the characteristic density, galaxy
growth through star formation shuts down. We propose that star formation events
are triggered when cold gas is accreted onto a galaxy. We have used the new
high resolution Millennium Simulation of structure formation in a concordance
LCDM Universe to quantify the incidence of these accretion events and we show
that the observational data are well fit by a model in which the consumption
time of accreted gas decreases with the surface density of the galaxy as t_cons
\propto mu*^-1. The dark matter halos hosting massive galaxies with high
densities are also expected to grow through accretion, but the observations
indicate that star formation in bulge- dominated galaxies is no longer coupled
to the hierarchical build-up of their surrounding dark matter halos.


title:
Examining the Effect of the Map-Making Algorithm on Observed Power
  Asymmetry in WMAP Data

abstract:
  We analyze first-year data of WMAP to determine the significance of asymmetry
in summed power between arbitrarily defined opposite hemispheres, using maps
that we create ourselves with software developed independently of the WMAP
team. We find that over the multipole range l=[2,64], the significance of
asymmetry is ~ 10^-4, a value insensitive to both frequency and power spectrum.
We determine the smallest multipole ranges exhibiting significant asymmetry,
and find twelve, including l=[2,3] and [6,7], for which the significance -> 0.
In these ranges there is an improbable association between the direction of
maximum significance and the ecliptic plane (p ~ 0.01). Also, contours of least
significance follow great circles inclined relative to the ecliptic at the
largest scales. The great circle for l=[2,3] passes over previously reported
preferred axes and is insensitive to frequency, while the great circle for
l=[6,7] is aligned with the ecliptic poles. We examine how changing map-making
parameters affects asymmetry, and find that at large scales, it is rendered
insignificant if the magnitude of the WMAP dipole vector is increased by
approximately 1-3 sigma (or 2-6 km/s). While confirmation of this result would
require data recalibration, such a systematic change would be consistent with
observations of frequency-independent asymmetry. We conclude that the use of an
incorrect dipole vector, in combination with a systematic or foreground process
associated with the ecliptic, may help to explain the observed asymmetry.


title:
Lyman Alpha Radiation From Collapsing Protogalaxies I: Characteristics
  of the Emergent Spectrum

abstract:
  We present Monte Carlo calculations of Lyman alpha (Lya) radiative transfer
through collapsing gas clouds, representing proto-galaxies that are caught in
the process of their assembly. Such galaxies produce Lya flux over an extended
solid angle from a spatially extended Lya emissivity and/or from scattering
effects. We study the effect of the gas distribution and kinematics, and of the
Lya emissivity profile, on the emergent spectrum and surface brightness
distribution. The emergent Lya spectrum is typically double-peaked and
asymmetric. In practice, the blue peak is significantly enhanced and the red
peak, in most cases, will be undetectable. The resulting effective blueshift,
combined with scattering in the intergalactic medium, will render extended Lya
emission from collapsing protogalaxies difficult to detect beyond redshift z=4.
The surface brightness distribution is typically flat, and a strong wavelength
dependence of its slope (with preferential flattening at the red side of the
line) would be a robust indication that Lya photons are being generated (rather
than just scattered) in a spatially extended region around the galaxy. We also
find that for self-ionized clouds whose effective Lya optical depth is less
than 10^3, infall and outflow models can produce nearly identical spectra and
surface brightness distributions, and are difficult to distinguish from one
another. The presence of deuterium with a cosmic abundance may produce a narrow
but detectable dip in the spectra of systems with moderate hydrogen column
densities, in the range 10^18-10^20 cm^-2. Finally, we present a new analytic
solution for the emerging Lya spectrum in the limiting case of a static uniform
sphere, extending previous solutions for static plane-parallel slabs.


title:
Abundances of Baade's Window Giants from Keck/HIRES Spectra: I. Stellar
  Parameters and [Fe/H] Values

abstract:
  We present the first results of a new abundance survey of the Milky Way bulge
based on Keck/HIRES spectra of 27 K-giants in the Baade's Window ($l = 1$, $b =
-4$) field. The spectral data used in this study are of much higher resolution
and signal-to-noise than previous optical studies of Galactic bulge stars. The
[Fe/H] values of our stars, which range between -1.29 and $+0.51$, were used to
recalibrate large low resolution surveys of bulge stars. Our best value for the
mean [Fe/H] of the bulge is $-0.10 \pm 0.04$. This mean value is similar to the
mean metallicity of the local disk and indicates that there cannot be a strong
metallicity gradient inside the solar circle. The metallicity distribution of
stars confirms that the bulge does not suffer from the so-called ``G-dwarf''
problem. This paper also details the new abundance techniques necessary to
analyze very metal-rich K-giants, including a new Fe line list and regions of
low blanketing for continuum identification.


title:
Lyman Alpha Radiation From Collapsing Protogalaxies II: Observational
  Evidence for Gas Infall

abstract:
  We model the spectra and surface brightness distributions for the Lyman alpha
(Lya) radiation expected from protogalaxies that are caught in the early stages
of their assembly. We use the results of a companion paper to characterize the
radiation emerging from spherically collapsing gas clouds. We then modify the
intrinsic spectra to incorporate the effect of subsequent resonant scattering
in the intergalactic medium (IGM). Using these models, we interpret a number of
recent observations of extended Lya blobs (LABs) at high redshift. We suggest,
based on the angular size, energetics, as well as the relatively shallow
surface brightness profiles, and double-peaked spectra, that several of these
LABs may be associated with collapsing protogalaxies. We suggest two follow-up
observations to diagnose the presence of gas infall. High S/N spectra of LABs
should reveal a preferential flattening of the surface brightness profile at
the red side of the line. Complementary imaging of the blobs at redshifted
Balmer alpha wavelengths should reveal the intrinsic Lya emissivity and allow
its separation from radiative transfer effects. We show that Lya scattering by
infalling gas can reproduce the observed spectrum of Steidel et al's LAB2 as
accurately as a recently proposed outflow model. Finally, we find similar
evidence for infall in the spectra of point-like Lyman alpha emitters. The
presence of scattering by the infalling gas implies that the intrinsic Lya
luminosities, and derived quantities, such as the star-formation rate, in these
objects may have been underestimated by about an order of magnitude.


title: Bondi-Hoyle Accretion in a Turbulent Medium

abstract:
  The Bondi-Hoyle formula gives the approximate accretion rate onto a point
particle accreting from a uniform medium. However, in many situations accretion
onto point particles occurs from media that are turbulent rather than uniform.
In this paper, we give an approximate solution to the problem of a point
particle accreting from an ambient medium of supersonically turbulent gas.
Accretion in such media is bimodal, at some points resembling classical
Bondi-Hoyle flow, and in other cases being closer to the vorticity-dominated
accretion flows recently studied by Krumholz, McKee, & Klein. Based on this
observation, we develop a theoretical prediction for the accretion rate, and
confirm that our predictions are highly consistent with the results of
numerical simulations. The distribution of accretion rates is lognormal, and
the mean accretion rate in supersonically turbulent gas can be substantially
enhanced above the value that would be predicted by a naive application of the
Bondi-Hoyle formula. However, it can also be suppressed by the vorticity, just
as Krumholz, McKee, & Klein found for non-supersonic vorticity-dominated flows.
Magnetic fields, which we have not included in these models, may further
inhibit accretion. Our results have significant implications for a number
astrophysical problems, ranging from star formation to the black holes in
galactic centers. In particular, there are likely to be significant errors in
results that assume that accretion from turbulent media occurs at the
unmodified Bondi-Hoyle rate, or that are based on simulations that do not
resolve the Bondi-Hoyle radius of accreting objects.


title:
Revisiting and assessing uncertainties in stellar populations synthesis
  models

abstract:
  In this review we address the uncertainties implicit in evolutionary
synthesis model computations. After describing the general structure of
synthesis codes, we discuss several source of uncertainties that may affect
their results. In particular, we discuss the uncertainties arising in the
computation of isochrones from evolutionary tracks; those related to atmosphere
models; those that are a consequence of the incompleteness of the input
ingredients; and those associated with the computational aspect used in
synthesis codes. We also discuss the issue of the inclusion of distributed
properties in synthesis models; as a paradigm of this case, we illustrate the
difficulties implied by the inclusion of tracks with rotation in synthesis
models. Finally, we describe several examples of the statistical approach to
population synthesis. We report on the failure of the fuel consumption theorem
(FCT) and the isochrone synthesis code to produce mutually consistent results.
However, we argue that FCT and isochrone synthesis results are reliable for
application to real systems in the wavelength range where they coincide. On the
constructive side, we derive several useful survival strategies to bypass
uncertainties. We show that single stellar populations at the turn-off ages of
the tabulated tracks can be safely compared, as they are scarcely affected by
the interpolation scheme used to compute isochrones. Finally, we suggest to use
derivative quantities, such as the SN-rate, as bug detectors. On the
recommendation side, we advocate for greater transparency and more
documentation in synthesis modeling. We also ask stellar model makers to think
of us and include more mass values in the tracks.


title: Stars Form By Gravitational Collapse, Not Competitive Accretion

abstract:
  There are now two dominant models of how stars form: gravitational collapse
theory holds that star-forming molecular clumps, typically hundreds to
thousands of solar masses in mass, fragment into gaseous cores that
subsequently collapse to make individual stars or small multiple systems. In
contrast, competitive accretion theory suggests that at birth all stars are
much smaller than the typical stellar mass (~0.5 solar masses), and that final
stellar masses are determined by the subsequent accretion of unbound gas from
the clump. Competitive accretion models explain brown dwarfs and free-floating
planets as protostars ejected from star-forming clumps before accreting much
mass, predicting that they should lack disks, have high velocity dispersions,
and form more frequently in denser clumps. They also predict that mean stellar
mass should vary within the Galaxy. Here we derive a simple estimate for the
rate of competitive accretion as a function of the star-forming environment,
based partly on simulations, and determine in what types of environments
competitive accretion can occur. We show that no observed star-forming region
produces significant competitive accretion, and that simulations that show
competitive accretion do so because their properties differ from those
determined by observation. Our result shows that stars form by gravitational
collapse, and explains why observations have failed to confirm predictions of
the competitive accretion scenario.


title: Hot Populations in M87 Globular Clusters

abstract:
  We have obtained HST/STIS far- and near-UV photometry of globular clusters in
four fields in the gE galaxy M87. To a limit of m(FUV) = 25 we detect a total
of 66 globular clusters (GCs) in common with the deep HST optical-band study of
Kundu et al. (1999). Despite strong overlap in V- and I-band properties, the
M87 GCs have UV/optical properties that are distinct from clusters in the Milky
Way and in M31. M87 clusters, especially metal-poor ones, produce larger hot HB
populations than do Milky Way analogues. Cluster mass is probably not a factor
in these distinctions. The most metal-rich M87 GCs in our sample are near Z_sun
and overlap the local E galaxy sample in estimated Mg_2 line indices.
Nonetheless, the clusters produce much more UV light at a given Mg_2, being up
to 1 mag bluer than any gE galaxy in (FUV-V) color. The M87 GCs do not appear
to represent a transition between Milky Way-type clusters and E galaxies. The
differences are in the correct sense if the clusters are significantly older
than the E galaxies. Comparisons with Galactic open clusters indicate that the
hot stars lie on the extreme horizontal branch, rather than being blue
stragglers, and that the EHB becomes well populated for ages > 5 Gyr. We find
that 43 of our UV detections have no optical-band counterparts. Most appear to
be UV-bright background galaxies, seen through M87. Eleven NUV variable sources
detected at only one epoch in the central field are probably classical novae.
[Abridged]


title:
Gravitational Lensing and Structural Stability of Dark Matter Caustic
  Rings

abstract:
  Gravitational lensing by the dual cusp catastrophes of the cold dark matter
(CDM) caustic rings at cosmological distances may provide the tantalizing
opportunity to detect CDM indirectly, and discriminate between axions and
weakly interacting massive particles (WIMPs). Caustics are places where the CDM
particles are naturally focussed. Our focus is upon the caustic rings which are
closed tubes whose cross-section is an elliptic umbilic catastrophe with three
dual cusps. A caustic ring has a specific density profile, a specific geometry
and, therefore, precisely calculable gravitational lensing signatures. The
magnification monotonically increases as the line of sight approaches to the
cusps where it diverges in the limit of zero velocity dispersion. In this
limit, we find 37% magnification at a sample point near the outer cusps of the
CDM caustic rings at cosmological distances. In the presence of finite velocity
dispersion, the lower and upper bounds of the effective velocity dispersions of
the axion and WIMP flows in galactic halos may be used to constrain the lensing
effects at the cusps. For a cosmological axion caustic ring, we find that the
magnification may range between 3% and 2800% at the outer cusp, and between 2%
and 46% at the non-planer cusps. For a cosmological WIMP caustic ring, on the
other hand, we constrain the magnification between 3% and 28% at the outer
cusp, and between 2% and 5% at the non-planer cusps. The images of extended
sources may also show distortions that can be unambiguously attributed to
lensing by dark matter caustics. Finally, we derive the Catastrophe Function of
the triaxial caustic rings. We obtain the flow equations as the equilibrium
points of this Catastrophe Function. The analysis of the Stability (Hessian)
Matrix show that the caustic rings are structurally stable.


title: A proposed origin for chondrule-forming shocks in the solar nebula

abstract:
  We propose that the nebular shocks currently favored as a model to form
chondrules and other annealed silicates in the solar nebula originate in the
dynamical activity present in the envelope of forming Jovian planets. In
contrast to the classic `core accretion model', our 3D hydrodynamic simulations
show that this envelope is not a 1D hydrostatic structure but is instead
vigorously active and contains densities and temperatures that appear similar
in magnitude and spatial extent to those thought to be responsible for the
production of chondrules.


title: Observing solar-like oscillations: recent results

abstract:
  We review recent progress in observations of ground-based oscillations.
Excellent observations now exist for a few stars (alpha Cen A and B, mu Ara),
while there is some controversy over others (Procyon, eta Boo). We have reached
the stage where single-site observations are of limited value and where careful
planning is needed to ensure the future of asteroseismology.


title: Galaxy Groups: Proceedings from a Swinburne University Workshop

abstract:
  We present the proceedings from a 2-day workshop held at Swinburne University
on the 24th-25th of May 2005. The workshop participants highlighted current
Australian research on both theoretical and observational aspects of galaxy
groups. These proceedings include short 1-page summaries of a number of the
talks presented at the workshop. The talks presented ranged from reconciling
N-body simulations with observations, to the HI content of galaxies in groups
and the existence of ``dark galaxies''. The formation and existence of
ultra-compact dwarfs in groups, and a new supergroup in Eridanus were also
discussed.


title:
First whole atmosphere night-time seeing measurements at Dome C,
  Antarctica

abstract:
  We report site testing results obtained in night-time during the polar autumn
and winter at Dome C. These results were collected during the first Concordia
winterover by A. Agabi. They are based upon seeing and isoplanatic angle
monitoring, as well as in-situ balloon measurements 2 of the refractive index
structure constant profiles Cn (h). Atmosphere is divided into two regions: (i)
a 36 m high surface layer responsible of 87% of the turbulence and (ii) a very
stable free atmosphere above with a median seeing of 0.36+-0.19 arcsec at an
elevation of h = 30 m. The median seeing measured with a DIMM placed on top of
a 8.5 m high tower is 1.3+-0.8 arcsec.


title: Resonance conditions

abstract:
  Non-linear parametric resonances occur frequently in nature. Here we
summarize how they can be studied by means of perturbative methods. We show in
particular how resonances can affect the motion of a test particle orbiting in
the vicinity of a compact object. These mathematical toy-models find
application in explaining the structure of the observed kHz Quasi-Periodic
Oscillations: we discuss which aspects of the reality naturally enter in the
theory, and which one still remain a puzzle.


title: For whom the disc tolls

abstract: Report on the Nordita Workdays on Quasi-Peridic Oscillations (QPOs).


title:
Detecting Reionization in the Star Formation Histories of High-Redshift
  Galaxies

abstract:
  The reionization of cosmic hydrogen, left over from the big bang, increased
its temperature to >~ 1.e4 K. This photo-heating resulted in an increase of the
minimum mass of galaxies and hence a suppression of the cosmic star formation
rate. The affected population of dwarf galaxies included the progenitors of
massive galaxies that formed later. We show that a massive galaxy at a redshift
z >~ 6 should show a double-peaked star formation history marked by a clear
break. This break reflects the suppression signature from reionization of the
region in which the galaxy was assembled. Since massive galaxies originate in
overdense regions where cosmic evolution is accelerated, their environment
reionizes earlier than the rest of the universe. For a galaxy of ~ 1.e12
M_solar in stars at a redshift of z ~ 6.5, the star formation rate should
typically be suppressed at a redshift z >~ 10 since the rest of the universe is
known to have reionized by z >~ 6.5. Indeed, this is inferred to be the case
for HUDF-JD2, a massive galaxy which is potentially at z ~ 6.5 but is inferred
to have formed the bulk of its 3.e11 M_solar in stars at z >~ 9.


title:
Search for massive protostar candidates in the southern hemisphere: II.
  Dust continuum emission

abstract:
  In an ongoing effort to identify and study high-mass protostellar candidates
we have observed in various tracers a sample of 235 sources selected from the
IRAS Point Source Catalog, mostly with dec < -30 deg, with the SEST antenna at
millimeter wavelengths. The sample contains 142 Low sources and 93 High, which
are believed to be in different evolutionary stages. Both sub-samples have been
studied in detail by comparing their physical properties and morphologies.
Massive dust clumps have been detected in all but 8 regions, with usually more
than one clump per region. The dust emission shows a variety of complex
morphologies, sometimes with multiple clumps forming filaments or clusters. The
mean clump has a linear size of ~0.5 pc, a mass of ~320 Msolar for a dust
temperature Td=30 K, an H_2 density of 9.5E5 cm-3, and a surface density of 0.4
g cm-2. The median values are 0.4 pc, 102 Msolar, 4E4 cm-3, and 0.14 g cm-2,
respectively. The mean value of the luminosity-to-mass ratio, L/M ~99
Lsolar/Msolar, suggests that the sources are in a young, pre-ultracompact HII
phase. We have compared the millimeter continuum maps with images of the mid-IR
MSX emission, and have discovered 95 massive millimeter clumps non-MSX
emitters, either diffuse or point-like, that are potential prestellar or
precluster cores. The physical properties of these clumps are similar to those
of the others, apart from the mass that is ~3 times lower than for clumps with
MSX counterpart. Such a difference could be due to the potential prestellar
clumps having a lower dust temperature. The mass spectrum of the clumps with
masses above M ~100 Msolar is best fitted with a power-law dN/dM proportional
to M-alpha with alpha=2.1, consistent with the Salpeter (1955) stellar IMF,
with alpha=2.35.


title:
Charting the New Frontier of the Cosmic Microwave Background
  Polarization

abstract:
  The anisotropies of the cosmic microwave background are a gold mine for
cosmology and fundamental physics. ESA's Planck satellite should soon extract
all information from the temperature vein but will be limited concerning the
measurement of the degree of polarization of the anisotropies. This
polarization information allows new independent tests of the standard
cosmological paradigm, improves knowledge of cosmological parameters and last
but not least is the best window available for constraining the physics of the
very early universe, particularly the expected background of primordial
gravitational waves. But exploiting this vein will be a challenge, since the
sensitivity required is {\em at least} 10 times better than what Planck might
achieve at best, with the necessary matching level of control of all
systematics effects, both instrumental and astrophysical (foregrounds). We here
recall the cosmological context and the case for CMB polarization studies. We
also briefly introduce the SAMPAN project, a design study at CNES that aims at
detecting the primoridal gravitational wave background for a tensor to scalar
ratio T/S as small as 0.001.


title:
Extrasolar planets and brown dwarfs around A-F type stars III.
  Beta-Pictoris : looking for planets, finding pulsations

abstract:
  In the frame of the search for extrasolar planets and brown dwarfs around
early-type stars, we present the results obtained on Beta-Pictoris, which is
surrounded by a circumstellar disk that is warped by the presence of a planet.
We used 97 spectra acquired with CORALIE and 230 spectra acquired with HARPS to
characterize the radial velocity behavior of Beta-Pictoris and to infer
constraints on the presence of a planet close to this star. With these data, we
were able to exclude the presence of an inner giant planet (2 MJup at a
distance to the star of 0.05 AU, 9 MJup at 1 AU). We also discuss the origin of
the observed radial velocity variations in terms of Delta-Scuti type
pulsations.


title:
Influence of Alfven waves on the Thermal Instability in the Interstellar
  Medium

abstract:
  The effect of Alfv\'en waves on the thermal instability of the Interstellar
Medium (ISM) is investigated both analytically and numerically. A stability
analysis of a finite amplitude circularly polarized Alfv\'en wave propagating
parallel to an ambient magnetic field in a thermally unstable gas at thermal
equilibrium is performed, leading to a dispersion relation which depends on 3
parameters, namely the square ratio of the sonic and Alfv\'en velocities
($\beta$), the wave amplitude and the ratio between the wave temporal period
and the cooling time. Depending on the values of these 3 parameters, the
Alfv\'en waves can stabilize the large-scale perturbations, destabilize those
whose wavelength is a few times the Alfv\'en wavelength $\lambda_{AW}$ or leave
the growth rate of the short scales unchanged. In order to investigate the
non-linear regime, two different numerical experiments are performed in a slab
geometry. (TBC)


title: Nonlinear stability of relativistic sheared planar jets

abstract:
  The linear and non-linear stability of sheared, relativistic planar jets is
studied by means of linear stability analysis and numerical hydrodynamical
simulations. Our results extend the previous Kelvin-Hemlholtz stability studies
for relativistic, planar jets in the vortex sheet approximation performed by
Perucho et al. (2004a,b) by including a shear layer between the jet and the
external medium and more general perturbations. The models considered span a
wide range of Lorentz factors ($2.5-20$) and internal energies ($0.08 c^2-60
c^2$) and are classified into three classes according to the main
characteristics of their long-term, non-linear evolution. We observe a clear
separation of these three groups in a relativistic Mach-number Lorentz-factor
plane. Jets with a low Lorentz factor and small relativistic Mach number are
disrupted after saturation. Those with a large Lorentz factor and large
relativistic Mach number are the stablest, due to the appearance of short
wavelength resonant modes which generate local mixing and heating in the shear
layer around a fast, unmixed core, giving a plausible solution for the problem
of the long-term stability of relativistic jets. A third group is present
between them, including jets with intermediate values of Lorentz factor and
relativistic Mach number, which are disrupted by a slow process of mixing
favored by an efficient and continuous conversion of kinetic into internal
energy. In the long term, all the models develop a distinct transversal
structure (shear/transition layers) as a consequence of KH perturbation growth,
depending on the class they belong to. The properties of these shear layers are
analyzed in connection with the parameters of the original jet models.


title: Thermonuclear supernova simulations with stochastic ignition

abstract:
  We apply an ad hoc model for dynamical ignition in three-dimensional
numerical simulations of thermonuclear supernovae assuming pure deflagrations.
The model makes use of the statistical description of temperature fluctuations
in the pre-supernova core proposed by Wunsch & Woosley (2004). Randomness in
time is implemented by means of a Poisson process. We are able to vary the
explosion energy and nucleosynthesis depending on the free parameter of the
model which controls the rapidity of the ignition process. However, beyond a
certain threshold, the strength of the explosion saturates and the outcome
appears to be robust with respect to number of ignitions. In the most energetic
explosions, we find about 0.75 solar masses of iron group elements. Other than
in simulations with simultaneous multi-spot ignition, the amount of unburned
carbon and oxygen at radial velocities of a few 1000 km/s tends to be reduced
for an ever increasing number of ignition events and, accordingly, more
pronounced layering results.


title: Slitless grism spectroscopy with the HST Advanced Camera for Surveys

abstract:
  The Advanced Camera for Surveys on-board HST is equipped with a set of one
grism and three prisms for low-resolution, slitless spectroscopy in the range
1150 Ang. to 10500 Ang. The G800L grism provides optical spectroscopy between
5500 Ang. and 1 micron with a mean dispersion of 39 Ang./pix and 24 Ang./pix
(in the first spectral order) when coupled with the Wide Field and the High
Resolution Channels, respectively. Given the lack of any on-board calibration
lamps for wavelength and narrow band flat-fielding, the G800L grism can only be
calibrated using astronomical targets. In this paper, we describe the strategy
used to calibrate the grism in orbit, with special attention to the treatment
of the field dependence of the grism flat-field, wavelength solution and
sensitivity in both Channels.


title: Gamma-Ray Pulsar Visibility

abstract:
  PSR J0437-4715 is a millisecond pulsar (MSP) thought to be ``pair formation
starved'' (having limited pair cascades due to magnetic photon absorption).
Fortunately the general relativistic (GR) electrodynamical model under
consideration applicable to this pulsar have few free parameters. We model PSR
J0437-4715's visibility, using a 3D model which incorporates the variation of
the GR E-field over the polar cap (PC), taking different observer and
inclination angles into account. Using this pulsar as a case study, one may
generalize to conducting a pulsar population visibility study. We lastly
comment on the role of the proposed South African SKA (Square Kilometre Array)
prototype, KAT (Karoo Array Telescope), for GLAST gamma-ray pulsar
identification.