title: Cross correlation of Lyman-alpha absorbers with gas-rich galaxies

abstract:
  The HI Parkes All Sky Survey (HIPASS) galaxy catalogue is cross-correlated
with known low redshift, low column density (N_HI <10^15 cm^-2) Lyman-alpha
absorbers from the literature. The redshift-space correlation is found to be
similar in strength to HIPASS galaxy self-clustering (correlation length
s_0,ag=6+/-4 and s_0,gg=3.1+/-0.5 h^-1 Mpc respectively). In real-space the
cross-correlation is stronger than the galaxy auto-correlation (correlation
length r_0,ag=7.2+/-1.4 and r_0,gg=3.5+/-0.7 h^-1 Mpc respectively) on scales
from 1-10 h^-1 Mpc, ruling out the mini-halo model for the confinement
Lyman-alpha absorbers at the 99 percent confidence level. Provided that the
cause of the strong cross-correlation is purely gravitational, the ratio of
correlation lengths suggest that absorbers are embedded in dark matter haloes
with masses log(M/Msun)=14.2 h^-1, similar to those of galaxy groups. The
flattening of the cross-correlation at separations less than ~600 h^-1 kpc
could correspond to the thickness of filaments in which absorbers are embedded.
This work provides indirect statistical evidence for the notion that galaxy
groups and large-scale filaments, particularly those that comprise gas-rich
galaxies, are the dominant environments of low column density Lyman-alpha
absorbers at z=0.


title: Implications of the Early X-Ray Afterglow Light Curves of Swift GRBs

abstract:
  According to current models, gamma-ray bursts (GRBs) are produced when the
energy carried by a relativistic outflow is dissipated and converted into
radiation. The efficiency of this process, $\epsilon_\gamma$, is one of the
critical factors in any GRB model. The X-ray afterglow light curves of Swift
GRBs show an early stage of flat decay. This has been interpreted as reflecting
energy injection. When combined with previous estimates, which have concluded
that the kinetic energy of the late ($\gtrsim 10$ hr) afterglow is comparable
to the energy emitted in gamma-rays, this interpretation implies very high
values of $\epsilon_\gamma \gtrsim 0.9$. Such a high efficiency is hard to
reconcile with most models, including in particular the popular internal-shocks
model. We re-analyze the derivation of the kinetic energy from the afterglow
X-ray flux and re-examine the resulting estimates of the efficiency. We confirm
that, if the flatt decay arises from energy injection and the pre-Swift
broad-band estimates of the kinetic energy are correct, then $\epsilon_\gamma
\gtrsim 0.9$. We point out, however, that another interpretation of the
flattish decay - a variable X-ray afterglow efficiency (e.g., due to a time
dependence of afterglow shock microphysical parameters) - is possible. We also
show that direct estimates of the kinetic energy from the late X-ray afterglow
flux are sensitive to the assumed values of the shock microphysical parameters
and suggest that broad-band afterglow fits might have underestimated the
kinetic energy (e.g., by overestimating the fraction of electrons that are
accelerated to relativistic energies). Either one of these possibilities
implies a lower gamma-ray efficiency, and their joint effect could conceivably
reduce the estimate of the typical $\epsilon_\gamma$ to $\sim 0.1-0.5$.


title: Dissecting the Circumstellar Environment of Gamma-Ray Burst Progenitors

abstract:
  We investigate properties of the interstellar medium (ISM) in galaxies
hosting long-duration gamma-ray bursts (GRBs) from an analysis of atomic
species (MgI, FeI) and excited fine-structure levels of ions (e.g. SiII). Our
analysis is guided primarily by echelle observations of GRB 050730 and GRB
051111. These sightlines exhibit fine-structure transitions of OI, SiII, and
FeII gas that have not yet been detected in intervening quasar absorption line
systems. Our results indicate that the gas with large MgI equivalent width
(e.g. GRB 051111) must occur at distances >~50pc from GRB afterglows to avoid
photoionization. We examine the mechanisms for fine-structure excitation and
find two processes can contribute: (1) indirect UV pumping by the GRB afterglow
provided a far-UV intensity in excess of 10^6 times the Galactic radiation
field; and (2) collisional excitation in gas with electron density n_e>10^4
cm^-3. The observed abundances of excited ions are well explained by UV pumping
with the gas at approximately a few hundred pc from the afterglow for GRB
051111 and r<100pc for GRB 050730, without invoking extreme gas density and
temperature in the ISM. We show that UV pumping alone provides a simple
explanation for all reported detections of excited ions in GRB afterglow
spectra. The presence of strong fine-structure transitions therefore may offer
little constraint for the gas density or temperature. We discuss additional
implications of UV pumping including its impact on chemical abundance
measurements, new prospects for observing line-strength variability, and future
prospects for studying the gas density and temperature. Finally, we list a
series of criteria that can distinguish between the mechanisms of UV pumping
and collisional excitation.


title: The influence of numerical parameters on tidally triggered bar formation

abstract:
  The joint influence of numerical parameters such as the number of particles
N, the gravitational softening length $\epsilon$ and the time-step $\Delta t$
is investigated in the context of galaxy simulations. For isolated galaxy
models we have performed a convergence study and estimated the numerical
parameters ranges for which the relaxed models do not deviate significantly
from its initial configuration. By fixing N, we calculate the range of the mean
interparticle separation $\lambda(r)$ along the disc radius. We have found that
in the simulations with N=1310720 particles $\lambda$ varies by a factor of 6,
and the corresponding final Toomre's parameters Q change by only about 5 per
cent. By decreasing N, the $\lambda$ and Q ranges broaden. Large $\epsilon$ and
small N cause an earlier bar formation. For a given set of parameters the disc
heating is smaller with the Plummer softening than with the spline softening.
For galaxy collision models numerical simulations indicate that the properties
of the formed bars strongly depend upon the selection of N and $\epsilon$.
Large values of the gravitational softening parameter and a small number of
particles results in the rapid formation of a well defined, slowly rotating
bar. On the other hand, small values of $\epsilon$ produce a small, rapidly
rotating disc with tightly wound spiral arms, and subsequently a weak bar
emerges. We have found that by increasing N, the bar properties converge and
the effect of the softening parameter diminishes. Finally, in some cases short
spiral arms are observed at the ends of the bar that change periodically from
trailing to leading and vice-versa - the wiggle.


title:
Suppressing Speckle Noise for Simultaneous Differential Extrasolar
  Planet Imaging (SDI) at the VLT and MMT

abstract:
  We discuss the instrumental and data reduction techniques used to suppress
speckle noise with the Simultaneous Differential Imager (SDI) implemented at
the VLT and the MMT. SDI uses a double Wollaston prism and a quad filter to
take 4 identical images simultaneously at 3 wavelengths surrounding the 1.62 um
methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By
performing a difference of images in these filters, speckle noise from the
primary can be significantly attenuated, resulting in photon noise limited data
past 0.5''. Non-trivial data reduction tools are necessary to pipeline the
simultaneous differential imaging. Here we discuss a custom algorithm
implemented in IDL to perform this reduction. The script performs basic data
reduction tasks but also precisely aligns images taken in each of the filters
using a custom shift and subtract routine. In our survey of nearby young stars
at the VLT and MMT (see Biller et al., this conference), we achieved H band
contrasts >25000 (5 sigma Delta F1(1.575 um) > 10.0 mag, Delta H > 11.5 mag for
a T6 spectral type object) at a separation of 0.5" from the primary star. We
believe that our SDI images are among the highest contrast astronomical images
ever made from ground or space for methane rich companions.


title:
A Census of the Carina Nebula. I: Cumulative Energy Input from Massive
  Stars

abstract:
  (abridged) The Carina Nebula (NGC 3372) is our richest nearby laboratory in
which to study feedback through UV radiation and stellar winds from very
massive stars during the formation of an OB association before supernova
explosions have influenced the environment. This paper takes inventory of the
combined effect from all the known massive stars that power the Carina Nebula.
The present-day total ionizing photon luminosity produced by the 65 O stars and
3 WNL stars in Carina is about 1e51/s, the total bolometric luminosity of all
stars earlier than B2 is 2.5e7 Lsun, and the total mechanical luminosity of
stellar winds is about 1e5 Lsun. The total ionizing flux was about 25 per cent
higher when eta Car was on the main sequence, before it and its companion were
surrounded by its obscuring dust shell, and when the 3 WNL stars were on the
main sequence. For the first 3 Myr, the net ionizing flux of the 70 O-type
stars in Carina was about 150 times greater than in the Orion Nebula. About
400-500 Msun has been contributed to the region by stellar wind mass loss
during the past 3 Myr. The net ionizing flux and mechanical luminosity are also
given for the individual clusters Tr14, 15, and 16, and Bo10 and 11, which are
relevant on smaller spatial scales.


title: Silicate Emission in the Spitzer IRS spectrum of FSC 10214+4724

abstract:
  We present the first MIR spectrum of the z=2.2856 ultraluminous, infrared
galaxy FSC 10214+4724, obtained with the Infrared Spectrograph onboard the
Spitzer Space Telescope. The spectrum spans a rest wavelength range of 2.3-11.5
microns, covering a number of key diagnostic emission and absorption features.
The most prominent feature in the IRS spectrum is the silicate emission at
rest-frame 10 microns. We also detect an unresolved emission line at a rest
wavelength of 7.65 microns which we identify with [NeVI], and a slightly
resolved feature at 5.6 microns identified as a blend of [Mg VII] and [Mg V].
There are no strong PAH emission features in the FSC 10214+4724 spectrum. We
place a limit of 0.1 micron on the equivalent width of 6.2 micron PAH emission
but see no evidence of a corresponding 7.7 micron feature. Semi-empirical fits
to the spectral energy distribution suggest about 45% of the bolometric
luminosity arises from cold 50 K dust, half arises from warm (190 K) dust, and
the remainder, 5%, originates from hot (640 K) dust. The hot dust is required
to fit the blue end of the steep MIR spectrum. The combination of a red
continuum, strong silicate emission, little or no PAH emission, and no silicate
absorption, makes FSC 10214+4724 unlike most other ULIRGs or AGN observed thus
far with IRS. These apparently contradictory properties may be explained by an
AGN which is highly magnified by the lens, masking a (dominant) overlying
starburst with unusually weak PAH emission.


title:
A Survey of Close, Young Stars with the Simultaneous Differential Imager
  (SDI) at the VLT and MMT

abstract:
  We discuss the preliminary results of a survey of young (<300 Myr), close
(<50 pc) stars with the Simultaneous Differential Extrasolar Planet Imager
(SDI) implemented at the VLT and the MMT. SDI uses a double Wollaston prism and
a quad filter to take 4 identical images simultaneously at 3 wavelengths
surrounding the 1.62 um methane bandhead found in the spectrum of cool brown
dwarfs and gas giants. By performing a difference of images in these filters,
speckle noise from the primary can be significantly attenuated, resulting in
photon noise limited data. In our survey data, we achieved H band contrasts
>25000 (5 sigma Delta F1(1.575 um) > 10 mag, Delta H > 11.5 mag for a T6
spectral type) at a separation of 0.5" from the primary star. With this degree
of attenuation, we should be able to image (5 sigma detection) a 2-4 Jupiter
mass planet at 5 AU around a 30 Myr star at 10 pc. We are currently completing
our survey of young, nearby stars. We have obtained complete datasets for 35
stars in the southern sky (VLT) and 7 stars in the northern sky (MMT). We
believe that our SDI images are the highest contrast astronomical images ever
made from ground or space for methane rich companions.


title: On the origins of part-time radio pulsars

abstract:
  Growing evidence suggests that some radio pulsars only act sporadically.
These "part-time'' pulsars include long-term nulls, quasi-periodic radio flares
in PSR B1931+24, as well as the so-called Rotating RAdio Transients (RRATs).
Based on the assumption that these objects are isolated neutron stars similar
to conventional radio pulsars, we discuss two possible interpretations to the
phenomenon. The first interpretation suggests that these objects are pulsars
slightly below the radio emission "death line'', which become active
occasionally only when the conditions for pair production and coherent emission
are satisfied. The second interpretation invokes a radio emission direction
reversal in conventional pulsars, as has been introduced to interpret the
peculiar mode changing phenomenon in PSR B1822-09. In this picture, our line of
sight misses the main radio emission beam of the pulsar but happens to sweep
the emission beam when the radio emission direction is reversed. These
part-time pulsars are therefore the other half of "nulling'' pulsars. We
suggest that X-ray observations may provide clues to differentiate between
these two possibilities.


title: The true nature of the alleged planetary nebula W16-185

abstract:
  We report the discovery of a small cluster of massive stars embedded in a NIR
nebula in the direction of the IRAS15411-5352 point source, which is related to
the alleged planetary nebula W16-185. The majority of the stars present large
NIR excess characteristic of young stellar objects and have bright counterparts
in the Spitzer IRAC images; the most luminous star (IRS1) is the NIR
counterpart of the IRAS source. We found very strong unresolved Brgamma
emission at the IRS1 position and more diluted and extended emission across the
continuum nebula. From the sizes and electron volume densities we concluded
that they represent ultra-compact and compact HII regions, respectively.
Comparing the Brgamma emission with the 7 mm free-free emission, we estimated
that the visual extinction ranges between 14 and 20 mag. We found that only one
star (IRS1) can provide the number of UV photons necessary to ionize the
nebula.


title:
A Detailed Observation of a LMC Supernova Remnant DEM L241 with
  XMM-Newton

abstract:
  We report on an {\it XMM-Newton} observation of the supernova remnant (SNR)
\object{DEM L241} in the Large Magellanic Cloud. In the soft band image, the
emission shows an elongated structure, like a killifish, with a central compact
source. The compact source is point-like, and named as XMMU J053559.3$-$673509.
The source spectrum is well reproduced with a power-law model with a photon
index of $\Gamma = 1.57$ (1.51--1.62) and the intrinsic luminosity is
$2.2\times 10^{35} \mathrm{ergs s^{-1}}$ in the 0.5--10.0 keV band, with the
assumed distance of 50 kpc. The source has neither significant coherent
pulsations in $2.0\times 10^{-3}$ Hz--8.0 Hz, nor time variabilities. Its
luminosity and spectrum suggest that the source might be a pulsar wind nebula
(PWN) in DEM L241. The spectral feature classifies this source into rather
bright and hard PWN, which is similar to those in Kes 75 and B0540$-$693. The
elongated diffuse structure can be divided into a ``Head'' and ``Tail'', and
both have soft and line-rich spectra. Their spectra are well reproduced by a
plane-parallel shock plasma ({\it vpshock}) model with a temperature of
0.3--0.4 keV and over-abundance in O and Ne and a relative under-abundance in
Fe. Such an abundance pattern and the morphology imply that the emission is
from the ejecta of the SNR, and that the progenitor of DEM L241 is a very
massive star, more than 20 M\sun. This result is also supported by the
existence of the central point source and an OB star association, LH 88. The
total thermal energy and plasma mass are $\sim 4\times 10^{50}$ ergs and $\sim
200$ M\sun, respectively.


title:
Spitzer Imaging of nearby ULIRGs and their Progeny: Fine-Structure
  Elliptical Galaxies

abstract:
  We present results from two mid-infrared imaging programs of ultraluminous
infrared galaxies (ULIRGs) and fine-structure elliptical galaxies. The former
are known to nearly all be recent mergers between two gas-rich spiral galaxies,
while the latter are also believed to be even more aged merger remnants. An
examination of these two classes of objects, which may represent different
stages of the same putative merger sequence, should reveal similarities in the
distribution of their stellar populations and dust content consistent with that
expected for time-evolution of the merger. The data reveal for the first time
extended dust emission in the ULIRG galaxy bodies and along their tidal
features. However, contrary to expectation, we find that the vast majority of
the fine-structure elliptical galaxies lack such structured emission. This
likely results from the optical selection of the elliptical sample, resulting
in a population that reflects the IR-activity (or lack thereof) of optically
selected interacting galaxies. Alternately, this may reflect an evolutionary
process in the distribution of the dust content of the galaxy bodies.


title: Rotation in the ZAMS: Be and Bn stars

abstract:
  We show that Be stars belong to a high velocity tail of a single B-type star
rotational velocity distribution in the MS. This implies that: 1) the number
fraction N(Be)/N(Be+B) is independent of the mass; 2) Bn stars having ZAMS
rotational velocities higher than a given limit might become Be stars.


title: Differential rotation in early type stars

abstract:
  Using 2D models of rotating stars, the interferometric measurements of alpha
Eri and its fundamental parameters corrected for gravitational darkening
effects we infer that the star might have a core rotating 2.7 times faster than
the surface. We explore the consequences on spectral lines produced by surface
differential rotation combined with the effects due to a kind of internal
differential rotation with rotational energies higher than allowed for rigid
rotation which induce geometrical deformations that do not distinguish strongly
from those carried by the rigid rotation.


title: Circumstellar rings, flat and flaring discs

abstract:
  Emission lines formed in the circumstellar envelopes of several type of stars
can be modeled using first principles of line formation. We present simple ways
of calculating line emission profiles formed in circumstellar envelopes having
different geometrical configurations. The fit of the observed line profiles
with the calculated ones may give first order estimates of the physical
parameters characterizing the line formation regions: opacity, size, particle
density distribution, velocity fields, excitation temperature.


title: Evolution of the circumstellar disc of alpha Eri

abstract:
  The Halpha line emission formation region in the circumstellar disc of alpha
Eri is: a) extended with a steep outward matter density decline during low
H$\alpha$ emission phases; b) less extended with rather constant density
distribution during the strong Halpha emission. The long-term variation of the
Halpha emission has a 14-15 year cyclic B-Be phase transition. The disc
formation time scales agree with the viscous decretion model. The time required
for the disc dissipation is longer than expected from the viscous disc model.


title: Metallicity vs. Be phenomenon relation in the solar neighborhood

abstract:
  Fast rotation seems to be the mayor factor to trigger the Be phenomenon.
Surface fast rotation can be favored by initial formation conditions, such as
abundance of metals. We have observed 118 Be stars up to the apparent
magnitudes V=9 mag. Models of fast rotating atmospheres and evolutionary tracks
were used to interpret the stellar spectra and to determine the stellar
fundamental parameters. Since the studied stars are formed in regions that are
separated enough to imply some non negligible gradient of galactic metallicity,
we study the effects of possible incidence of this gradient on the nature as
rotators of the studied stars.


title:
Nonlinear Hydromagnetic Wave Support of a Stratified Molecular Cloud II:
  A Parameter Study

abstract:
  We use numerical simulations to study the effect of nonlinear MHD waves in a
stratified, self-gravitating molecular cloud that is bounded by a hot and
tenuous external medium. In a previous paper, we had shown the details of a
standard model and studied the effect of varying the dimensionless amplitude.
In this paper, we present the results of varying two other important free
parameters: beta_0, the initial ratio of gas to magnetic pressure at the cloud
midplane, and the dimensionless frequency of driving. Furthermore, we present
the case of a temporally random driving force. Our results demonstrate that a
very important consideration for the actual level of turbulent support against
gravity is the ratio of driving wavelength lambda_0 to the the size of the
initial non-turbulent cloud; maximum cloud expansion is achieved when this
ratio is close to unity. The best consistency with the observational
correlation of magnetic field strength, turbulent line width, and density is
achieved by cloud models with beta_0 approx 1. We also calculate the spatial
power spectra of the turbulent clouds, and show that significant power is
developed on scales larger than the scale length H_0 of the initial cloud, even
if the input wavelength of turbulence lambda_0 approx H_0. The cloud
stratification and resulting increase of Alfven speed toward the cloud edge
allows for a transfer of energy to wavelengths significantly larger than
lambda_0. This explains why the relevant time scale for turbulent dissipation
is the crossing time over the cloud scale rather than the crossing time over
the driving scale.


title: Cosmological models with Gurzadyan-Xue dark energy

abstract:
  The formula for dark energy density derived by Gurzadyan and Xue provides a
value of density parameter of dark energy in remarkable agreement with current
cosmological datasets, unlike numerous phenomenological dark energy scenarios
where the corresponding value is postulated. This formula suggests the
possibility of variation of physical constants such as the speed of light and
the gravitational constant. Considering several cosmological models based on
that formula and deriving the cosmological equations for each case, we show
that, in all models source terms appear in the continuity equation. So, one one
hand, GX models make up a rich set covering a lot of currently proposed models
of dark energy, on the other hand, they reveal hidden symmetries, with a
particular role of the separatrix $\Omega_m=2/3$, and link with the issue of
the content of physical constants.


title:
The first 8-13 micron spectra of globular cluster red giants:
  circumstellar silicate dust grains in 47 Tucanae (NGC 104)

abstract:
  We present 8-13 micron spectra of eight red giants in the globular cluster 47
Tucanae (NGC 104), obtained at the European Southern Observatory 3.6m
telescope. These are the first mid-infrared spectra of metal-poor, low-mass
stars. The spectrum of at least one of these, namely the extremely red,
large-amplitude variable V1, shows direct evidence of circumstellar grains made
of amorphous silicate.


title: ASCA Observations of OAO 1657-415 and its Dust-Scattered X-Ray Halo

abstract:
  We report on two ASCA observations of the high-mass X-ray binary pulsar OAO
1657-415. A short observation near mid-eclipse caught the source in a
low-intensity state, with a weak continuum and iron emission dominated by the
6.4-keV fluorescent line. A later, longer observation found the source in a
high-intensity state and covered the uneclipsed through mid-eclipse phases. In
the high-intensity state, the non-eclipse spectrum has an absorbed continuum
component due to scattering by material near the pulsar and 80 per cent of the
fluorescent iron emission comes from less than 19 lt-sec away from the pulsar.
We find a dust-scattered X-ray halo whose intensity decays through the eclipse.
We use this halo to estimate the distance to the source as 7.1 +/- 1.3 kpc.


title:
Mass and radius determination for the neutron star in X-ray burst source
  4U/MXB 1728-34

abstract:
  We analyzed archival X-ray spectra of MXB 1728-34 obtained in 1996-99 by the
Proportional Counter Array on board of the RXTE satellite. X-ray spectra were
fitted to our extensive grids of model atmosphere spectra to determine the
effective temperature T_eff on the neutron star surface, logarithm of surface
gravity log(g), and the gravitational redshift z simultaneously. We have chosen
fitting by numerical model spectra plus broad Gaussian line, modified by
interstellar absorption and the absorption on dust. We arbitrarily assumed
either hydrogen-helium chemical composition of a model atmosphere, or H-He-Fe
mixture in solar proportion. The statistically best values of log(g), and z
subsequently were used to determine mass and radius of the neutron star. We
obtained the best values of the parameters for the neutron star in X-ray burst
source MXB 1728-34: mass either M=0.40 or 0.63 M_sol (for H-He or H-He-Fe
models, respectively), radius R=4.6 or 5.3 km, log(g)=14.6 or 14.6 and the
gravitational redshift z=0.14 or 0.22. All the above parameters have very wide
1-sigma confidence limits. Their values strongly support the equation of state
for strange matter in MXB 1728-34.


title: Hubble Space Telescope NICMOS Polarization Measurements of OMC-1

abstract:
  We present 2micron polarization measurements of positions in the BN region of
the Orion Molecular Cloud (OMC-1) made with NICMOS Camera 2 (0.2'' resolution)
on HST. Our results are as follows: BN is sim 29% polarized by dichroic
absorption and appears to be the illuminating source for most of the nebulosity
to its north and up to sim 5'' to its south. Although the stars are probably
all polarized by dichroic absorption, there are a number of compact, but
non-point-source, objects that could be polarized by a combination of both
dichroic absorption and local scattering of star light. We identify several
candidate YSOs, including an approximately edge-on bipolar YSO 8.7'' east of
BN, and a deeply-embedded variable star. Additional strongly polarized sources
are IRc2-B, IRc2-D, and IRc7, all of which are obviously self-luminous at
mid-infrared wavelengths and may be YSOs. None of these is a reflection nebula
illuminated by a star located near radio source I, as was previously suggested.
Other IRc sources are clearly reflection nebulae: IRc3 appears to be
illuminated by IRc2-B or a combination of the IRc2 sources, and IRc4 and IRc5
appear to be illuminated by an unseen star in the vicinity of radio source I,
or by Star n or IRc2-A. Trends in the magnetic field direction are inferred
from the polarization of the 26 stars that are bright enough to be seen as
NICMOS point sources. The most polarized star has a polarization position angle
different from its neighbors by sim 40^o, but in agreement with the grain
alignment inferred from millimeter polarization measurements of the cold dust
cloud in the southern part of OMC-1.


title: Ammonia in Infrared Dark Clouds

abstract:
  Infrared Dark Clouds appear to be the long sought population of cold and
dense aggregations with the potential of harbouring the earliest stages of
massive star formation. Up to now there has been no systematic study on the
temperature distribution, velocity fields, chemical and physical state toward
this new cloud population. Knowing these properties is crucial for
understanding the presence, absence and the very potential of star formation.
The present paper aims at addressing these questions. We analyse temperature
structures and velocity fields and gain information on their chemical
evolution. The gas emission is remarkably coextensive with the extinction seen
at infrared wavelengths and with the submillimeter dust emission. Our results
show that IRDCs are on average cold (T < 20 K) and have variations among the
different cores. IRDC cores are in virial equilibrium, are massive (M > 100
M_sun), highly turbulent (1 -- 3 km/s) and exhibit significant velocity
structure (variations around 1 -- 2 km/s over the cloud). We find an increasing
trend in temperature from IRDCs with high ammonia column density to high mass
protostellar objects and hot core/Ultracompact Hii regions stages of early warm
high-mass star formation while linewidths of IRDCs are smaller. On the basis of
this sample, we infer that while active star formation is not yet pervasive in
most IRDCs, local condensations might collapse in the future or have already
begun forming stars.


title: The Most Metal-Rich Intervening Quasar Absorber Known

abstract:
  The metallicity in portions of high-redshift galaxies has been successfully
measured thanks to the gas observed in absorption in the spectra of quasars, in
the Damped Lyman-alpha systems (DLAs). Surprisingly, the global mean
metallicity derived from DLAs is about 1/10th solar at 0<z<4 leading to the
so-called ``missing-metals problem''. In this paper, we present high-resolution
observations of a sub-DLA system at z_abs=0.716 with super-solar metallicity
toward SDSS J1323-0021. This is the highest metallicity intervening quasar
absorber currently known, and is only the second super-solar absorber known to
date. We provide a detailed study of this unique object from VLT/UVES
spectroscopy. We derive [Zn/H]=+0.61, [Fe/H]=-0.51, [Cr/H]=<-0.53, [Mn/H] =
-0.37, and [Ti/H] = -0.61. Observations and photoionisation models using the
CLOUDY software confirm that the gas in this sub-DLA is predominantly neutral
and that the abundance pattern is probably significantly different from a Solar
pattern. Fe/Zn and Ti/Zn vary among the main velocity components by factors of
\~ 3 and ~ 35, respectively, indicating non-uniform dust depletion. Mn/Fe is
super-solar in almost all components, and varies by a factor of ~ 3 among the
dominant components. It would be interesting to observe more sub-DLA systems
and determine whether they might contribute significantly toward the cosmic
budget of metals.


title: A Radio Census of Nuclear Activity in Nearby Galaxies

abstract:
  In order to determine the incidence of black hole accretion-driven nuclear
activity in nearby galaxies, as manifested by their radio emission, we have
carried out a high-resolution Multi-Element Radio-Linked Interferometer Network
(MERLIN) survey of LINERs and composite LINER/H{\sc ii} galaxies from a
complete magnitude-limited sample of bright nearby galaxies (Palomar sample)
with unknown arcsecond-scale radio properties. There are fifteen radio
detections, of which three are new subarcsecond-scale radio core detections,
all being candidate AGN. The detected galaxies supplement the already known
low-luminosity AGN -- low-luminosity Seyferts, LINERs and composite LINER/H{\sc
ii} galaxies -- in the Palomar sample. Combining all radio-detected Seyferts,
LINERs and composite LINER/H{\sc ii} galaxies (LTS sources), we obtain an
overall radio detection rate of 54% (22% of all bright nearby galaxies) and we
estimate that at least $\sim$50% ($\sim$20% of all bright nearby galaxies) are
true AGN. The radio powers of the LTS galaxies allow the construction of a
local radio luminosity function. By comparing the luminosity function with
those of selected moderate-redshift AGN, selected from the 2dF/NVSS survey, we
find that LTS sources naturally extend the RLF of powerful AGN down to powers
of about 10 times that of Sgr A*.


title: The Evolution and Structure of Pulsar Wind Nebulae

abstract:
  Pulsars steadily dissipate their rotational energy via relativistic winds.
Confinement of these outflows generates luminous pulsar wind nebulae, seen
across the electromagnetic spectrum in synchrotron and inverse Compton
emission, and in optical emission lines when they shock the surrounding medium.
These sources act as important probes of relativistic shocks, particle
acceleration and of interstellar gas. We review the many recent advances in the
study of pulsar wind nebulae, with particular focus on the evolutionary stages
through which these objects progress as they expand into their surroundings,
and on morphological structures within these nebulae which directly trace the
physical processes of particle acceleration and outflow. We conclude by
considering some exciting new probes of pulsar wind nebulae, including the
study of TeV gamma-ray emission from these sources, and observations of pulsar
winds in close binary systems.


title:
Desorption rates and sticking coefficients for CO and N2 interstellar
  ices

abstract:
  We present Temperature Programmed Desorption (TPD) experiments of CO and N2
ices in pure, layered and mixed morphologies at various ice "thicknesses" and
abundance ratios as well as simultaneously taken Reflection Absorption Infrared
Spectra (RAIRS) of CO. A kinetic model has been developed to constrain the
binding energies of CO and N2 in both pure and mixed environments and to derive
the kinetics for desorption, mixing and segregation. For mixed ices N2
desorption occurs in a single step whereas for layered ices it proceeds in two
steps, one corresponding to N2 desorption from a pure N2 ice environment and
one corresponding to desorption from a mixed ice environment. The latter is
dominant for astrophysically relevant ice "thicknesses". The ratio of the
binding energies, Rbe, for pure N2 and CO is found to be 0.936 +/- 0.03, and to
be close to 1 for mixed ice fractions. The model is applied to astrophysically
relevant conditions for cold pre-stellar cores and for protostars which start
to heat their surroundings. The importance of treating CO desorption with
zeroth rather than first order kinetics is shown. The experiments also provide
lower limits of 0.87 +/- 0.05 for the sticking probabilities of CO-CO, N2-CO
and N2-N2 ices at 14 K. The combined results from the desorption experiments,
the kinetic model, and the sticking probability data lead to the conclusion
that these solid-state processes of CO and N2 are very similar under
astrophysically relevant conditions. This conclusion affects the explanations
for the observed anti-correlations of gaseous CO and N2H+ in pre-stellar and
protostellar cores.


title: The Initial Mass Functions of Four Embedded Stellar Clusters

abstract:
  We present near-infrared $J$, $H$, and $K$ images of four embedded stellar
clusters in the Galaxy. We find a significant fraction of pre-main-sequence
stars present in at least one of the clusters. For the clusters dominated by
main-sequence stars, we determine the initial mass function (IMF) both by using
the $K$ luminosity function and a global extinction correction and by deriving
individual extinction corrections for each star based on their placement in the
$K$ vs. $H-K$ color-magnitude diagram. Based on our IMFs we find a significant
discrepancy between the mean IMF derived via the different methods, suggesting
that taking individual extinctions into account is necessary to correctly
derive the IMF for an embedded cluster.


title: Stephan's Quintet: A Multi-galaxy Collision

abstract:
  Stephan's Quintet (SQ), discovered more than 100 years ago, is the most
famous and well studied compact galaxy group. It has been observed in almost
all wavebands, with the most advanced instruments including Spitzer, GALEX,
HST, Chandra, VLA, and various large mm/submm telescopes/arrays such as the
IRAM 30m and BIMA. The rich multi-band data reveal one of the most fascinating
pictures in the universe, depicting a very complex web of interactions between
member galaxies and various constituents of the intragroup medium (IGM), which
in turn trigger some spectacular activities such as a 40 kpc large scale shock
and a strong IGM starburst. In this talk I will give a review on these
observations.


title:
Photometric observations of Southern Abell Cluster Redshifts Survey
  Clusters: Structure of galaxies in the inner region of clusters of galaxies

abstract:
  We analyze photometric properties of 1384 cluster galaxies as a function of
the normalized distance to cluster center. These galaxies were selected in the
central region ($r/r_{200} \leq$ 0.8) of 14 southern Abell clusters chosen from
the Southern Abell Cluster Redshifts Survey (SARS). For 507 of these galaxies
we also obtained their luminosity profiles. We have studied the
morphology-clustercentric distance relation on the basis of the shape parameter
$n$ of the S\'ersic's law. We also have analyzed the presence of a possible
segregation in magnitude for both, the galaxy total luminosity and that of
their components (i.e. the bulge and the disk).
  Results show a marginal ($2\sigma$ level) decrease of the total luminosity as
a function of normalized radius. However, when bulges are analyzed separately,
a significant luminosity segregation is found ($3\sigma$ and $2\sigma$ for
galaxies in projection and member galaxies respectively). The fraction of
bulges brighter than $M_B \leq -22$ is three times larger in the core of
clusters than in the outer region. Our analysis of the disk component suggests
that disks are, on average, less luminous in the cluster core than at
$r/r_{200} \sim 0.8$. In addition, we found that the magnitude-size relation as
a function of $r/r_{200}$ indicates (at $2\sigma$ level) that disks are smaller
and centrally brighter in the core of clusters. However, the Kormendy relation
(the bulge magnitude-size relation) appears to be independent of environment.


title: Bright Side versus Dark Side of Star Formation -- UV and IR Views

abstract:
  This is a review talk on the UV and infrared selected galaxies. The central
question addressed is: do UV and infrared surveys see the 2 sides of star
formation of the same population, or star formation of 2 different populations?
We first review the literature on the UV and IR selected galaxy samples, try to
quantify the difference and overlaps between these two populations of star
forming galaxies. We then present some preliminary results of a GALEX/SWIRE
comparison study for IR and UV selected galaxies at z=0.6, in an attempt to
constrain the evolution of the dust attenuation and of stellar mass of these
galaxies.


title: The young massive stellar cluster associated to RCW121

abstract:
  We report NIR broad and narrow band photometric observations in the direction
of the IRAS17149-3916 source that reveal the presence of a young cluster of
massive stars embedded in an HII region coincident with RCW121. These
observations, together with published radio data, MSX and Spitzer images were
used to determine some of the physical parameters of the region. We found 96
cluster member candidates in an area of about 1.5 x 2.0 square arcmin, 30% of
them showing excess emission in the NIR. IRS 1, the strongest source in the
cluster with an estimated spectral type of O5V-O6V ZAMS based on the
color-magnitude diagram, is probably the main ionizing source of the HII region
detected at radio wavelengths. Using the integrated Brgamma and the 5 GHz flux
densities, we derived a mean visual extinction AV=5.49 magnitudes. From the
observed size of the Brgamma extended emission, we calculated the emission
measure E and the electron density ne, characteristic of compact HII regions.


title: Late Light Curves of Normally-Luminous Type Ia Supernovae

abstract:
  The use of Type Ia supernovae as cosmological tools has reinforced the need
to better understand these objects and their light curves. The light curves of
Type Ia supernovae are powered by the nuclear decay of $^{56}Ni \to ^{56}Co \to
^{56}Fe$. The late time light curves can provide insight into the behavior of
the decay products and their effect of the shape of the curves. We present the
optical light curves of six "normal" Type Ia supernovae, obtained at late times
with template image subtraction, and the fits of these light curves to
supernova energy deposition models.


title: Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey

abstract:
  We present near-infrared observations of 71 newly discovered L and T dwarfs,
selected from imaging data of the Sloan Digital Sky Survey (SDSS) using the
i-dropout technique. Sixty-five of these dwarfs have been classified
spectroscopically according to the near-infrared L dwarf classification scheme
of Geballe et al. and the unified T dwarf classification scheme of Burgasser et
al. The spectral types of these dwarfs range from L3 to T7, and include the
latest types yet found in the SDSS. Six of the newly identified dwarfs are
classified as early- to mid-L dwarfs according to their photometric
near-infrared colors, and two others are classified photometrically as M
dwarfs. We also present new near-infrared spectra for five previously published
SDSS L and T dwarfs, and one L dwarf and one T dwarf discovered by Burgasser et
al. from the Two Micron All Sky Survey. The new SDSS sample includes 27 T
dwarfs and 30 dwarfs with spectral types spanning the complex L-T transition
(L7-T3). We continue to see a large (~0.5 mag) spread in J-H for L3 to T1
types, and a similar spread in H-K for all dwarfs later than L3. This color
dispersion is probably due to a range of grain sedimentation properties,
metallicity, and gravity. We also find L and T dwarfs with unusual colors and
spectral properties that may eventually help to disentangle these effects.


title: Are galaxy properties only determined by the dark matter halo mass?

abstract:
  Conditional luminosity function (CLF) of dark matter halos supersedes simple
models on the number of galaxies as a function of the halo mass, or the
so-called halo occupation number, by assigning a luminosity distribution to
those galaxies. Suggestions have now been made that both the clustering
strength and properties of hosted galaxies of a given dark matter halo depends
also on the age and the environment of that halo in addition to halo mass.
Based on simple CLF models, we find that at least one suggestion that made use
of central galaxy properties may be affected by uncertainties in the group
catalog from which clustering properties were measured to address the age
dependence. Establishing how galaxy properties of fixed mass halos change with
the environment or the age is challenging, if not impossible, given
uncertainties in group and cluster catalogs. It may be possible to address this
issue through statistics based on a combined study of luminosity and color
distributions, and luminosity- and color-dependent galaxy clustering, all of
them as a function of the galaxy overdensity, though no single statistic is
likely to provide the ultimate answer. The suggestion that the age dependence
of the halo bias invalidates the analytical models of the galaxy distribution
is premature given the improvements associated with modeling approaches based
on conditional functions.


title:
A Measurement of Time-Averaged Aerosol Optical Depth using Air-Showers
  Observed in Stereo by HiRes

abstract:
  Air fluorescence measurements of cosmic ray energy must be corrected for
attenuation of the atmosphere. In this paper we show that the air-showers
themselves can yield a measurement of the aerosol attenuation in terms of
optical depth, time-averaged over extended periods. Although the technique
lacks statistical power to make the critical hourly measurements that only
specialized active instruments can achieve, we note the technique does not
depend on absolute calibration of the detector hardware, and requires no
additional equipment beyond the fluorescence detectors that observe the air
showers. This paper describes the technique, and presents results based on
analysis of 1258 air-showers observed in stereo by the High Resolution Fly's
Eye over a four year span.


title:
Resolving the Surfaces of Extrasolar Planets With Secondary Eclipse
  Light Curves

abstract:
  We present a method that employs the secondary eclipse light curves of
transiting extrasolar planets to probe the spatial variation of their thermal
emission. This technique permits an observer to resolve the surface of the
planet without the need to spatially resolve its central star. We evaluate the
feasibility of this technique for the HD 209458 system [..]. We consider two
representations of the planetary thermal emission; a simple model parameterized
by a sinusoidal dependence on longitude and latitude, as well as the results of
a three-dimensional dynamical simulation of the planetary atmosphere previously
published by Cooper & Showman. We find that observations of the secondary
eclipse light curve are most sensitive to a longitudinal offset in the
geometric and photometric centroids of the hemisphere of the planet visible
near opposition. To quantify this signal, we define a new parameter, the
``uniform time offset,'' which measures the time lag between the observed
secondary eclipse and that predicted by a planet with a uniform surface flux
distribution. We compare the predicted amplitude of this parameter for HD
209458 with the precision with which it could be measured with IRAC. We find
that IRAC observations at 3.6um a single secondary eclipse should permit
sufficient precision to confirm or reject the Cooper & Showman model of the
surface flux distribution for this planet. We quantify the signal-to-noise
ratio for this offset in the remaining IRAC bands (4.5um, 5.8um, and 8.0um),
and find that a modest improvement in photometric precision (as might be
realized through observations of several eclipse events) should permit a
similarly robust detection.


title: High Energy Emission from Supernova Remnants

abstract:
  This paper discusses several aspects of current research on high energy
emission from supernova remnants, covering the following main topics: 1) The
recent evidence for magnetic field amplification near supernova remnant shocks,
which makes that cosmic rays are more efficiently accelerated than previously
thought. 2) The evidence that ions and electrons in some remnants have very
different temperatures, and only equilibrate through Coulomb interactions. 3)
The evidence that the explosion that created Cas A was asymmetric, and seems to
have involved a jet/counter jet structure. And finally, 4), I will argue that
the unremarkable properties of supernova remnants associated with magnetars
candidates, suggest that magnetars are not formed from rapidly (P ~ 1 ms)
rotating proto-neutron stars, but that it is more likely that they are formed
from massive progenitors stars with high magnetic fields.


title:
High-Resolution Simulations of a Moon-Forming Impact and Post-Impact
  Evolution

abstract:
  In order to examine the ``giant impact hypothesis'' for the Moon formation,
we run the first grid-based, high-resolution hydrodynamic simulations for an
impact between proto-Earth and a proto-planet. The spatial resolution for the
impact-generated disk is greatly improved from previous particle-based
simulations. This allows us to explore fine structures of a circumterrestrial
debris disk and its long-term evolution. We find that in order to form a debris
disk from which a lunar-sized satellite can be accumulated, the impact must
result in a disk of mostly liquid or solid debris, where pressure is not
effective, well before the accumulation process starts. If the debris is
dominated by vapor gas, strong spiral shocks are generated, and therefore the
circumterrestrial disk cannot survive more than several days. This suggests
that there could be an appropriate mass range for terrestrial planets to harbor
a large moon as a result of giant impacts, since vaporization during an impact
depends on the impact energy.


title:
Searching for CPT Violation with Cosmic Microwave Background Data from
  WMAP and BOOMERANG

abstract:
  We search for signatures of Lorentz and $CPT$ violations in the cosmic
microwave background (CMB) temperature and polarization anisotropies by using
the WMAP and the 2003 flight of BOOMERANG (B03) data. We note that if the
Lorentz and $CPT$ symmetries are broken by a Chern-Simons term in the effective
lagrangian, which couples the dual electromagnetic field strength tensor to an
external four-vector, the polarization vectors of propagating CMB photons will
get rotated. Using the WMAP data alone, one could put an interesting constraint
on the size of such a term. Combined with the B03 data, we found that a nonzero
rotation angle of the photons is mildly favored: $\Delta \alpha=
-6.0^{+4.0}_{-4.0}$ $^{+3.9}_{-3.7}$ deg (1, 2 $\sigma$).


title: Heating Rate Profiles in Galaxy Clusters

abstract:
  In recent years evidence has accumulated suggesting that the gas in galaxy
clusters is heated by non-gravitational processes. Here we calculate the
heating rates required to maintain a physically motived mass flow rate, in a
sample of seven galaxy clusters. We employ the spectroscopic mass deposition
rates as an observational input along with temperature and density data for
each cluster. On energetic grounds we find that thermal conduction could
provide the necessary heating for A2199, Perseus, A1795 and A478. However, the
suppression factor, of the clasical Spitzer value, is a different function of
radius for each cluster. Based on the observations of plasma bubbles we also
calculate the duty cycles for each AGN, in the absence of thermal conduction,
which can provide the required energy input. With the exception of Hydra-A it
appears that each of the other AGNs in our sample require duty cycles of
roughly $10^{6}-10^{7}$ yrs to provide their steady-state heating requirements.
If these duty cycles are unrealistic, this may imply that many galaxy clusters
must be heated by very powerful Hydra-A type events interspersed between more
frequent smaller-scale outbursts. The suppression factors for the thermal
conductivity required for combined heating by AGN and thermal conduction are
generally acceptable. However, these suppression factors still require
`fine-tuning` of the thermal conductivity as a function of radius. As a
consequence of this work we present the AGN duty cycle as a cooling flow
diagnostic.


title: CO(2-1) large scale mapping of the Perseus cluster core with HERA

abstract:
  Cold molecular gas has recently been found is several cooling flow clusters
cores with single dish telescopes. High spatial resolution imaging of some of
these clusters then revealed the peculiar morphology and dynamics of the CO
emission lines, pointing out a perturbed very cold component in the cluster
centers. We report here the observations of NGC 1275, in the Perseus cluster of
galaxies. This object is the strongest cooling flow emitter in the millimeter.
The 9 dual polarization pixels of the HERA focal plane array, installed on the
30m telescope, enabled to image the large scale emission of the cold molecular
gas which is found to follow the very peculiar Halpha filamentary structure
around the central galaxy. We discuss here this association and the
non-rotating dynamics of the cold gas that argue for a cooling flow origin of
the molecular component.


title: Full polarization study of SiO masers at 86 GHz

abstract:
  We study the polarization of the SiO maser emission in a representative
sample of evolved stars in order to derive an estimate of the strength of the
magnetic field, and thus determine the influence of this magnetic field on
evolved stars. We made simultaneous spectroscopic measurements of the 4 Stokes
parameters, from which we derived the circular and linear polarization levels.
The observations were made with the IF polarimeter installed at the IRAM 30m
telescope. A discussion of the existing SiO maser models is developed in the
light of our observations. Under the Zeeman splitting hypothesis, we derive an
estimate of the strength of the magnetic field. The averaged magnetic field
varies between 0 and 20 Gauss, with a mean value of 3.5 Gauss, and follows a
1/r law throughout the circumstellar envelope. As a consequence, the magnetic
field may play the role of a shaping, or perhaps collimating agent of the
circumstellar envelopes in evolved objects.


title: Revisiting the Constraint on the Helium Abundance from CMB

abstract:
  We revisit the constraint on the primordial helium mass fraction Yp from
observations of cosmic microwave background (CMB) alone. By minimizing chi
square of recent CMB experiments over 6 other cosmological parameters, we
obtained rather weak constraints as 0.17 < Yp < 0.52 at 1 sigma C.L. for a
particular data set. We also study the future constraint on cosmological
parameters when we take account of the prediction of the standard big bang
nucleosynthesis (BBN) theory as a prior on the helium mass fraction where Yp
can be fixed for a given energy density of baryon. We discuss the implications
of the prediction of the standard BBN on the analysis of CMB.


title:
Optical Spectroscopy of X-Mega targets in the Carina Nebula - VI. FO 15:
  a new O-Type double-lined eclipsing binary

abstract:
  We report the discovery of a new O-type double-lined spectroscopic binary
with a short orbital period of 1.4 days. We find the primary component of this
binary, FO 15, to have an approximate spectral type O5.5Vz, i.e. a
Zero-Age-Main-Sequence star. The secondary appears to be of spectral type
O9.5V. We have performed a numerical model fit to the public ASAS photometry,
which shows that FO 15 is also an eclipsing binary. We find an orbital
inclination of ~ 80 deg. From a simultaneous light-curve and radial velocity
solution we find the masses and radii of the two components to be 30 +/- 1 and
16 +/- 1 solar masses and 7.5 +/- 0.5 and 5.3 +/- 0.5 solar radii. These radii,
and hence also the luminosities, are smaller than those of normal O-type stars,
but similar to recently born ZAMS O-type stars. The absolute magnitudes derived
from our analysis locate FO 15 at the same distance as Eta Carinae. From
Chandra and XMM X-ray images we also find that there are two close X-ray
sources, one coincident with FO 15 and another one without optical counterpart.
This latter seems to be a highly variable source, presumably due to a
pre-main-sequence stellar neighbour of FO 15.


title: A Short Hard X-ray Flare from the Blazar NRAO 530 Observed by INTEGRAL

abstract:
  We report about a short flare from the blazar NRAO 530 occurred on 17
February 2004 and detected serendipitously by the IBIS/ISGRI detector on board
INTEGRAL. In the 20-40 keV energy range, the source, that is otherwise below
the detection limit, is detected at a level of ~2 x 10^-10 erg cm^-2 s^-1
during a time interval of less than 2000 s, which is about a factor 2 above the
detection threshold. At other wavelengths, only nearly-simultaneous radio data
are available (1 observation at 2 cm on 11 February 2004), indicating a
moderate increase of the polarization. This appears to be the shortest time
variability episode ever detected in a high luminosity blazar at hard X-rays,
unless the blazar is contaminated by the presence of an unknown unresolved
rapidly varying source.


title: The Discovery of a P Cygni Analog in M31

abstract:
  We present spectroscopy and discuss the photometric history of a previously
obscure star in M31. The spectrum of the star is an extremely close match to
that of P Cygni, one of the archetypes of Luminous Blue Variables (LBVs). The
star has not shown much variability over the past 40 years ($<0.2$ mag),
although small-scale (0.05 mag) variations over a year appear to be real.
Nevertheless, the presence of a sub-arcsecond extension around the star is
indicative of a past outburst, and from the nebula's size (0.5 pc diameter) we
estimate the outburst took place roughly 2000 yrs ago. P Cygni itself exhibits
a similar photometric behavior, and has a similar nebula (0.2 pc diameter). We
argue that this may be more typical behavior for LBVs than commonly assumed.
The star's location in the HR diagram offers substantial support for stellar
evolutionary models that include the effects of rotation, as the star is just
at a juncture in the evolutionary track of a 85Mo star. The star is likely in a
transition from an O star to a late-type WN Wolf-Rayet.


title: The flat synchrotron spectra of partially self-absorbed jets revisited

abstract:
  Flat radio spectra with large brightness temperatures at the core of AGN and
X-ray binaries are usually interpreted as the partially self-absorbed bases of
jet flows emitting synchrotron radiation. Here we extend previous models of
jets propagating at large angles to our line of sight to self-consistently
include the effects of energy losses of the relativistic electrons due to the
synchrotron process itself and the adiabatic expansion of the jet flow. We also
take into account energy gains through self-absorption. Two model classes are
presented. The ballistic jet flows, with the jet material travelling along
straight trajectories, and adiabatic jets. Despite the energy losses, both
scenarios can result in flat emission spectra, however, the adiabatic jets
require a specific geometry. No re-acceleration process along the jet is needed
for the electrons. We apply the models to observational data of the X-ray
binary Cygnus X-1. Both models can be made consistent with the observations.
The resulting ballistic jet is extremely narrow with a jet opening angle of
only 5". Its energy transport rate is small compared to the time-averaged jet
power and therefore suggests the presence of non-radiating protons in the jet
flow. The adiabatic jets require a strong departure from energy equipartition
between the magnetic field and the relativistic electrons. These models also
imply a jet power two orders of magnitude higher than the Eddington limiting
luminosity of a 10 solar mass black hole. The models put strong constraints on
the physical conditions in the jet flows on scales well below achievable
resolution limits.


title:
XMM-Newton and Chandra observations of the ultra-compact binary RX
  J1914+24

abstract:
  The nature of the X-ray source RX J1914+24 has been the subject of much
debate. It shows a prominent period of 569 sec in X-rays and the
optical/infra-red: in most models this has been interpreted as the binary
orbital period. We present our analysis of new XMM-Newton and Chandra data. We
find a longer term trend in the XMM-Newton data and power at 556 and 585 sec in
5 sets of data. It is not clear if they are produced as a result of a beat
between a longer intrinsic period and the 569 sec modulation or if they are due
to secular variations. We obtain a good fit to the XMM-Newton spectrum with a
low temperature thermal plasma model with an edge at 0.83keV. This model
implies an unabsorbed bolometric X-ray luminosity of 1x10^{33} ergs/s (for a
distance of 1kpc) - this is 2 orders of magnitude lower than our previous
estimate (derived using a different model). If the distance is much less, as
the absorption derived from the X-ray fits suggest, then it is even lower at
\~3x10^{31} ergs/s.


title:
A Chandra/ACIS Study of 30 Doradus I. Superbubbles and Supernova
  Remnants

abstract:
  We present an X-ray tour of diffuse emission in the 30 Doradus star-forming
complex in the Large Magellanic Cloud using high-spatial-resolution X-ray
images and spatially-resolved spectra obtained with the Advanced CCD Imaging
Spectrometer aboard the Chandra X-ray Observatory. The dominant X-ray feature
of the 30 Doradus nebula is the intricate network of diffuse emission generated
by interacting stellar winds and supernovae working together to create vast
superbubbles filled with hot plasma. We construct maps of the region showing
variations in plasma temperature (T = 3--9 million degrees), absorption (N_H =
1--6 x 10^{21} cm^{-2}), and absorption-corrected X-ray surface brightness (S_X
= 3--126 x 10^{31} ergs s^{-1} pc^{-2}). Enhanced images reveal the pulsar wind
nebula in the composite supernova remnant N157B and the Chandra data show
spectral evolution from non-thermal synchrotron emission in the N157B core to a
thermal plasma in its outer regions. In a companion paper we show that R136,
the central massive star cluster, is resolved at the arcsecond level into
almost 100 X-ray sources. Through X-ray studies of 30 Doradus the complete life
cycle of such a massive stellar cluster can be revealed.


title:
A Chandra/ACIS Study of 30 Doradus II. X-ray Point Sources in the
  Massive Star Cluster R136 and Beyond

abstract:
  We have studied the X-ray point source population of the 30 Doradus
star-forming complex in the Large Magellanic Cloud using
high-spatial-resolution X-ray images and spatially-resolved spectra obtained
with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray
Observatory. Here we describe the X-ray sources in a 17' x 17' field centered
on R136, the massive star cluster at the center of the main 30 Dor nebula. We
detect 20 of the 32 Wolf-Rayet stars in the ACIS field. R136 is resolved at the
subarcsecond level into almost 100 X-ray sources, including many typical O3--O5
stars as well as a few bright X-ray sources previously reported. Over two
orders of magnitude of scatter in L_X is seen among R136 O stars, suggesting
that X-ray emission in the most massive stars depends critically on the details
of wind properties and binarity of each system, rather than reflecting the
widely-reported characteristic value L_X/L_bol ~ 10^{-7}. Such a canonical
ratio may exist for single massive stars in R136, but our data are too shallow
to confirm this relationship. Through this and future X-ray studies of 30
Doradus, the complete life cycle of a massive stellar cluster can be revealed.


title: Hybrid Estimation of CMB Polarization Power Spectra

abstract:
  This paper generalises the hybrid power spectrum estimator developed in
Efstathiou (2004a) to the estimation of polarization power spectra of the
cosmic microwave background radiation. The hybrid power spectrum estimator is
unbiased and we show that it is close to optimal at all multipoles, provided
the pixel noise satisfies certain reasonable constraints. Furthermore, the
hybrid estimator is computationally fast and can easily be incorporated in a
Monte-Carlo chain for Planck-sized data sets. Simple formulae are given for the
covariance matrices, including instrumental noise, and these are tested
extensively against numerical simulations. We compare the behaviour of simple
pseudo-Cell estimates with maximum likelihood estimates at low multipoles. For
realistic sky cuts, maximum likelihood estimates reduce very significantly the
mixing of E and B modes. To achieve limits on the scalar-tensor ratio of r<<0.1
from sky maps with realistic sky cuts, maximum likelihood methods, or
pseudo-Cell estimators based on unambiguous E and B modes, will be essential.


title: Environmental Effects on Late-Type Galaxies in Nearby Clusters

abstract:
  The transformations taking place in late-type galaxies in the environment of
rich clusters of galaxies at z=0 are reviewed. From the handful of late-type
galaxies that inhabit local clusters, whether they were formed in-situ and
survived as such, avoiding transformation or even destruction or if they are
newcomers that recently infall from outside, we can learn an important lesson
on the latest stages of galaxy evolution. We start by reviewing the
observational scenario, covering the broadest possible stretch of the
electromagnetic spectrum, from the gas tracers, the star formation tracers, the
old star tracers and the dust. Strong emphasis is given to the three nearby,
well studied clusters Virgo, A1367 and Coma, representative of different
evolutionary stages, from unrelaxed, spiral rich (Virgo) to relaxed, spiral
poor clusters (Coma). We continue by providing a review of models of galaxy
interactions relevant to clusters of galaxies. Prototypes of various mechanisms
and processes are discussed and their typical time-scales are given in an
Appendix. Observations indicate the presence of healthy late-type galaxies
falling into nearby clusters individually or belonging to massive groups. More
rare are infalling galaxies belonging to compact groups where significant
pre-processing might take place. Once entered the cluster, they loose their gas
and quench their star formation activity, becoming anemics. Observations and
theory agree in indicating that the interaction with the intergalactic medium
is responsible for the gas depletion. This process, however, cannot be at the
origin of the cluster lenticular galaxy population. Physical and statistical
properties of S0 in nearby clusters and at higher redshift, indicate that they
originate from spiral galaxies transformed by gravitational interactions.


title:
Are non-magnetic mechanisms such as temporal solar diameter variations
  conceivable for an irradiance variability?

abstract:
  Irradiance variability has been monitored from space for more than two
decades. Even if data are coming from different sources, it is well established
that a temporal variability exists which can be set to as approximately 0.1%,
in phase with the solar cycle. Today, one of the best explanation for such an
irradiance variability is provided by the evolution of the solar surface
magnetic fields. But if some 90 to 95% can be reproduced, what would be the
origin of the 10 to 5% left? Non magnetic effects are conceivable. In this
paper we will consider temporal variations of the diameter of the Sun as a
possible contributor for the remaining part. Such an approach imposes strong
constraints on the solar radius variability. We will show that over a solar
cycle, variations of no more than 20 mas of amplitude can be considered. Such a
variability (far from what is reported by observers conducting measurements by
means of ground-based solar astrolabes) may explain a little part of the
irradiance changes not explained by magnetic features. Further requirements are
needed that may help to reach a conclusion. Dedicated space missions are
necessary (for example PICARD, GOLF-NG or SDO, scheduled for a launch around
2008); it is also proposed to reactivate SDS flights for such a purpose.


title:
From Canonical to Enhanced Extra Mixing in Low-Mass Red Giants: Tidally
  Locked Binaries

abstract:
  Stellar models which incorporate simple diffusion or shear induced mixing are
used to describe canonical extra mixing in low mass red giants of low and solar
metallicity. These models are able to simultaneously explain the observed Li
and CN abundance changes along upper red giant branch (RGB) in field
low-metallicity stars and match photometry, rotation and carbon isotopic ratios
for stars in the old open cluster M67. The shear mixing model requires that
main sequence (MS) progenitors of upper RGB stars possessed rapidly rotating
radiative cores and that specific angular momentum was conserved in each of
their mass shells during their evolution. We surmise that solar-type stars will
not experience canonical extra mixing on the RGB because their more efficient
MS spin-down resulted in solid-body rotation, as revealed by helioseismological
data for the Sun. Thus, RGB stars in the old, high metallicity cluster NGC 6791
should show no evidence for mixing in their carbon isotopic ratios.
  We develop the idea that canonical extra mixing in a giant component of a
binary system may be switched to its enhanced mode with much faster and
somewhat deeper mixing as a result of the giant's tidal spin-up. This scenario
can explain photometric and composition peculiarities of RS CVn binaries. The
tidally enforced enhanced extra mixing might contribute to the star-to-star
abundance variations of O, Na and Al in globular clusters. This idea may be
tested with observations of carbon isotopic ratios and CN abundances in RS CVn
binaries.


title: Explosive Nucleosynthesis in GRB Jets Accompanied by Hypernovae

abstract:
  Two-dimensional hydrodynamic simulations are performed to investigate
explosive nucleosynthesis in a collapsar using the model of MacFadyen and
Woosley (1999). It is shown that 56Ni is not produced in the jet of the
collapsar sufficiently to explain the observed amount of a hypernova when the
duration of the explosion is \sim 10 sec, which is considered to be the typical
timescale of explosion in the collapsar model. Even though a considerable
amount of 56Ni is synthesized if all explosion energy is deposited initially,
the opening angles of the jets become too wide to realize highly relativistic
outflows and gamma-ray bursts in such a case. From these results, it is
concluded that the origin of 56Ni in hypernovae associated with GRBs is not the
explosive nucleosynthesis in the jet. We consider that the idea that the origin
is the explosive nucleosynthesis in the accretion disk is more promising. We
also show that the explosion becomes bi-polar naturally due to the effect of
the deformed progenitor. This fact suggests that the 56Ni synthesized in the
accretion disk and conveyed as outflows are blown along to the rotation axis,
which will explain the line features of SN 1998bw and double peaked line
features of SN 2003jd. Some fraction of the gamma-ray lines from 56Ni decays in
the jet will appear without losing their energies because the jet becomes
optically thin before a considerable amount of 56Ni decays as long as the jet
is a relativistic flow. We show that abundance of nuclei whose mass number \sim
40 in the ejecta depends sensitively on the energy deposition rate. So it may
be determined by observations of chemical composition in metal poor stars which
model is the proper one as a model of a gamma-ray burst accompanied by a
hypernova.


title: AAT Imaging and Microslit Spectroscopy in the Southern Hubble Deep Field

abstract:
  We present a deep photometric (B- and R-band) catalog and an associated
spectroscopic redshift survey conducted in the vicinity of the Hubble Deep
Field South. The spectroscopy yields 53 extragalactic redshifts in the range
0<z<1.4 substantially increasing the body of spectroscopic work in this field
to over 200 objects. The targets are selected from deep AAT prime focus images
complete to R<24 and spectroscopy is 50% complete at R=23. There is now strong
evidence for a rich cluster at z\simeq 0.58 flanking the WFPC2 field which is
consistent with a known absorber of the bright QSO in this field. We find that
photometric redshifts of z<1 galaxies in this field based on HST data are
accurate to \sigma_z/(1+z)=0.03 (albeit with small number statistics). The
observations were carried out as a community service for Hubble Deep Field
science, to demonstrate the first use of the `nod & shuffle' technique with a
classical multi-object spectrograph and to test the use of `microslits' for
ultra-high multiplex observations along with a new VPH grism and deep-depletion
CCD. The reduction of this new type of data is also described.


title:
The Space Density and Colors of Massive Galaxies at 2<z<3: the
  Predominance of Distant Red Galaxies

abstract:
  Using the deep multi-wavelength MUSYC, GOODS, and FIRES surveys we construct
a stellar mass-limited sample of galaxies at 2<z<3. The sample comprises 294
galaxies with M>10^11 Solar masses distributed over four independent fields
with a total area of almost 400 sq arcmin. The mean number density of massive
galaxies in this redshift range is (2.2+-0.6) x 10^-4 Mpc^-3. We present median
values and 25th and 75th percentiles for the distributions of observed R mags,
observed J-K colors, and rest-frame UV continuum slopes, M/L(V) ratios, and U-V
colors. The galaxies show a large range in all these properties. The ``median
galaxy'' is faint in the observer's optical (R=25.9), red in the observed
near-IR (J-K=2.48), has a rest-frame UV spectrum which is relatively flat
(beta=-0.4), and rest-frame optical colors resembling those of nearby spiral
galaxies (U-V=0.62). We determine which galaxies would be selected as Lyman
break galaxies (LBGs) or Distant Red Galaxies (DRGs, having J-K>2.3) in this
mass-limited sample. By number DRGs make up 69% of the sample and LBGs 20%,
with a small amount of overlap. By mass DRGs make up 77% and LBGs 17%. Neither
technique provides a representative sample of massive galaxies at 2<z<3 as they
only sample the extremes of the population. As we show here, multi-wavelength
surveys with high quality photometry are essential for an unbiased census of
massive galaxies in the early Universe. The main uncertainty in this analysis
is our reliance on photometric redshifts; confirmation of the results presented
here requires extensive near-infrared spectroscopy of optically-faint samples.


title: Variations in D/H and D/O from New FUSE Observations

abstract:
  We use data obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE)
to determine the interstellar abundances of DI, NI, OI, FeII, and H2 along the
sigh tlines to WD1034+001, BD+393226, and TD132709. Our main focus is on
determining the D/H, N/H, O/H, and D/O ratios along these sightlines, with log
N(H) > 20.0, that probe gas well outside of the Local Bubble. Hubble Space
Telescope (HST) and International Ultraviolet Explorer (IUE) archival data are
used to determine the HI column densities along the WD1034+001 and TD132709
sightlines, respectively. For BD+393226, a previously published N(HI) is used.
We find (D/H)x10^5 = 2.14 + 0.53 - 0.45, 1.17 + 0.31 - 0.25, and 1.86 + 0.53 -
0.43, and (D/O)x10^2 = 6.31 + 1.79 - 1.38, 5.62 + 1.61 - 1.31, and 7.59 + 2.17
- 1.76, for the WD1034+001, BD+393226, and TD132709 sightlines, respectively
(all 1 si gma). The scatter in these three D/H ratios exemplifies the scatter
that has been found by other authors for sightlines with column densities in
the range 19.2 < log N(H) < 20.7. The D/H ratio toward WD1034+001 and all the
D/O ratios derived here are inconsistent with the Local Bubble value and are
some of the highest in the literature. We discuss the implications of our
measurements for the determination of the present-epoch abundance of deuterium,
and for the different scenarios that try to explain the D/H variations. We
present a study of D/H as a function of the average sightline gas density,
using the ratios derived in this work as well as ratios from the literature,
which suggests that D/H decreases with increasing gas volume density. Similar
behaviors by other elements such Fe and Si have been interpreted as the result
of depletion into dust grains.


title:
Angular momentum transport and disk morphology in SPH simulations of
  galaxy formation

abstract:
  We perform controlled N-Body/SPH simulations of disk galaxy formation by
cooling a rotating gaseous mass distribution inside equilibrium cuspy spherical
and triaxial dark matter halos. We systematically study the angular momentum
transport and the disk morphology as we increase the number of dark matter and
gas particles from 10^4 to 10^6, and decrease the gravitational softening from
2 kpc to 50 parsecs. The angular momentum transport, disk morphology and radial
profiles depend sensitively on force and mass resolution. At low resolution,
similar to that used in most current cosmological simulations, the cold gas
component has lost half of its initial angular momentum via different
mechanisms. The angular momentum is transferred primarily to the hot halo
component, by resolution-dependent hydrodynamical and gravitational torques,
the latter arising from asymmetries in the mass distribution. In addition,
disk-particles can lose angular momentum while they are still in the hot phase
by artificial viscosity. In the central disk, particles can transfer away over
99% of their initial angular momentum due to spiral structure and/or the
presence of a central bar. The strength of this transport also depends on force
and mass resolution - large softening will suppress the bar instability, low
mass resolution enhances the spiral structure. This complex interplay between
resolution and angular momentum transfer highlights the complexity of
simulations of galaxy formation even in isolated haloes. With 10^6 gas and dark
matter particles, disk particles lose only 10-20% of their original angular
momentum, yet we are unable to produce pure exponential profiles.


title: M33's Variable A -- A Hypergiant Star More Than 35 Years in Eruption

abstract:
  Variable A in M33 is a member of a rare class of highly luminous, evolved
stars near the upper luminosity boundary that show sudden and dramatic shifts
in apparent temperature due to the formation of optically thick winds in high
mass loss episodes. Recent optical and infrared spectroscopy and imaging reveal
that its ``eruption'' begun in $\sim$1950 has ended, {\it lasting $\approx$ 45
yrs}. Our current observations show major changes in its wind from a cool,
dense envelope to a much warmer state surrounded by low density gas with rare
emission lines of Ca II, [Ca II] and K I. Its spectral energy distribution has
unexpectedly changed, especially at the long wavelengths, with a significant
decrease in its apparent flux, while the star remains optically obscured. We
conclude that much of its radiation is now escaping out of our line of sight.
We attribute this to the changing structure and distribution of its
circumstellar ejecta corresponding to the altered state of its wind as the star
recovers from a high mass loss event.


title: The Local Interstellar Medium

abstract:
  The Local Interstellar Medium (LISM) is a unique environment that presents an
opportunity to study general interstellar phenomena in great detail and in
three dimensions. In particular, high resolution optical and ultraviolet
spectroscopy have proven to be powerful tools for addressing fundamental
questions concerning the physical conditions and three-dimensional (3D)
morphology of this local material. After reviewing our current understanding of
the structure of gas in the solar neighborhood, I will discuss the influence
that the LISM can have on stellar and planetary systems, including LISM dust
deposition onto planetary atmospheres and the modulation of galactic cosmic
rays through the astrosphere - the balancing interface between the outward
pressure of the magnetized stellar wind and the inward pressure of the
surrounding interstellar medium. On Earth, galactic cosmic rays may play a role
as contributors to ozone layer chemistry, planetary electrical discharge
frequency, biological mutation rates, and climate. Since the LISM shares the
same volume as practically all known extrasolar planets, the prototypical
debris disks systems, and nearby low-mass star-formation sites, it will be
important to understand the structures of the LISM and how they may influence
planetary atmospheres.


title: AMIGA: Very low environment galaxies in the local Universe

abstract:
  The evolutionary history of galaxies is thought to be strongly conditioned by
the environment. In order to quantify and set limits on the role of nurture one
must identify and study an isolated sample of galaxies. But it is not enough to
identify a small number of the "most isolated" galaxies. We begin with 950
galaxies from the Catalogue of Isolated Galaxies (Karachentseva 1973) and
reevaluate isolation using an automated star-galaxy classification procedure on
large digitised POSS-I fields. We define, compare and discuss various criteria
to quantify the degree of isolation for these galaxies: Karachentseva's revised
criterion, local surface density computations and an estimation of the external
tidal force affecting each isolated galaxy. Comparison of multi-wavelength ISM
properties, in particular the H$\alpha$ emission line, will allow us to
separate the influence of the environment from the one due to the initial
conditions at formation.


title: Speed of Sound in the Mass Varying Neutrinos Scenario

abstract:
  We discuss about the speed of sound squared in the Mass Varying Neutrinos
scenario (MaVaNs). Recently, it was argued that the MaVaNs has a catastrophic
instability which is the emergence of an imaginary speed of sound at the
non-relativistic limit of neutrinos. As the result of this instability, the
neutrino-acceleron fluid cannot act as the dark energy. However, it is found
that the speed of sound squared in the neutrino-acceleron fluid could be
positive in our model. We examine the speed of sound in two cases of the scalar
potential. One is the small fractional power-law potential and another is the
logarithmic one. The power-law potential model with the right-handed neutrinos
gives a stable one.


title: The Dependence of the Occupation of Galaxies on the Halo Formation Time

abstract:
  We study the dependence of the galaxy contents within halos on the halo
formation time using two galaxy formation models, one being a semianalytic
model utilizing the halo assembly history from a high resolution N-body
simulation and the other being a smoothed particle hydrodynamics simulation
including radiative cooling, star formation, and energy feedback from galactic
winds. We confirm the finding by Gao et al. that at fixed mass, the clustering
of halos depends on the halo formation time, especially for low-mass halos.
This age dependence of halo clustering makes it desirable to study the
correlation between the occupation of galaxies within halos and the halo age.
We find that, in halos of fixed mass, the number of satellite galaxies has a
strong dependence on halo age, with fewer satellites in older halos. The
youngest one-third of the halos can have an order of magnitude more satellites
than the oldest one-third. For central galaxies, in halos that form earlier,
they tend to have more stars and thus appear to be more luminous, and the
dependence of their luminosity on halo age is not as strong as that of stellar
mass. The results can be understood through the star formation history in halos
and the merging of satellites onto central galaxies. The age dependence of the
galaxy contents within halos would constitute an important ingredient in a more
accurate halo-based model of galaxy clustering.


title: Resolving the Stellar Outskirts of M31 and M33

abstract:
  Many clues about the galaxy assembly process lurk in the faint outer regions
of galaxies. The low surface brightnesses of these parts pose a significant
challenge for studies of diffuse light, and few robust constraints on galaxy
formation models have been derived to date from this technique. Our group has
pioneered the use of extremely wide-area star counts to quantitatively address
the large-scale structure and stellar content of external galaxies at very
faint light levels. We highlight here some results from our imaging and
spectroscopic surveys of M31 and M33.


title: Oxygen abundances in the most oxygen-rich spiral galaxies

abstract:
  Oxygen abundances in the spiral galaxies expected to be richest in oxygen are
estimated. The new abundance determinations are based on the recently
discovered ff-relation between auroral and nebular oxygen line fluxes in HII
regions. We find that the maximum gas-phase oxygen abundance in the central
regions of spiral galaxies is 12+log(O/H)~8.75. This value is significantly
lower than the previously accepted value. The central oxygen abundance in the
Milky Way is similar to that in other large spirals.


title:
Ultraviolet-to-Far Infrared Properties of Lyman Break Galaxies and
  Luminous Infrared Galaxies at z ~ 1

abstract:
  We present the first large, unbiased sample of Lyman Break Galaxies (LBGs) at
z ~ 1. Far ultraviolet-dropout (1530 A) galaxies in the Chandra Deep Field
South have been selected using GALEX data. This first large sample in the z ~ 1
universe provides us with a high quality reference sample of LBGs. We analyzed
the sample from the UV to the IR using GALEX, SPITZER, ESO and HST data. The
morphology (obtained from GOODS data) of 75 % of our LBGs is consistent with a
disk. The vast majority of LBGs with an IR detection are also Luminous Infrared
Galaxies (LIRGs). As a class, the galaxies not detected at 24 microns are an
order of magnitude fainter relative to the UV compared with those detected
individually, suggesting that there may be two types of behavior within the
sample. For the IR-bright galaxies, there is an apparent upper limit for the UV
dust attenuation and this upper limit is anti-correlated with the observed UV
luminosity. Previous estimates of dust attenuations based on the ultraviolet
slope are compared to new ones based on the FIR/UV ratio (for LBGs detected at
24 microns), which is usually a more reliable estimator. Depending on the
calibration we use to estimate the total IR luminosity, beta-based attenuations
A_{FUV} are larger by 0.2 to 0.6 mag. than the ones estimated from FIR/UV
ratio. Finally, for IR-bright LBGs, median estimated beta-based SFRs are 2-3
times larger than the total SFRs estimated as SFR_{TOT} = SFR_{UV} + SFR_{IR}
while IR-based SFRs provide values below SFR_{TOT} by 15 - 20 %. We use a
stacking method to statistically constrain the 24 microns flux of LBGs non
individually detected. The results suggest that these LBGs do not contain large
amounts of dust.


title:
A genetic algorithm for the non-parametric inversion of strong lensing
  systems

abstract:
  We present a non-parametric technique to infer the projected-mass
distribution of a gravitational lens system with multiple strong-lensed images.
The technique involves a dynamic grid in the lens plane on which the mass
distribution of the lens is approximated by a sum of basis functions, one per
grid cell. We used the projected mass densities of Plummer spheres as basis
functions. A genetic algorithm then determines the mass distribution of the
lens by forcing images of a single source, projected back onto the source
plane, to coincide as well as possible. Averaging several tens of solutions
removes the random fluctuations that are introduced by the reproduction process
of genomes in the genetic algorithm and highlights those features common to all
solutions. Given the positions of the images and the redshifts of the sources
and the lens, we show that the mass of a gravitational lens can be retrieved
with an accuracy of a few percent and that, if the sources sufficiently cover
the caustics, the mass distribution of the gravitational lens can also be
reliably retrieved. A major advantage of the algorithm is that it makes full
use of the information contained in the radial images, unlike methods that
minimise the residuals of the lens equation, and is thus able to accurately
reconstruct also the inner parts of the lens.


title: The early X-ray emission from GRBs

abstract:
  We present observations of the early X-ray emission for a sample of 40
gamma-ray bursts (GRBs) obtained using the Swift satellite for which the
narrow-field instruments were pointed at the burst within 10 minutes of the
trigger. Using data from the Burst Alert and X-Ray Telescopes, we show that the
X-ray light curve can be well described by an exponential that relaxes into a
power law, often with flares superimposed. The transition time between the
exponential and the power law provides a physically defined timescale for the
burst duration. In most bursts the power law breaks to a shallower decay within
the first hour, and a late emission "hump" is observed which can last for many
hours. In other GRBs the hump is weak or absent. The observed variety in the
shape of the early X-ray light curve can be explained as a combination of three
components: prompt emission from the central engine; afterglow; and the late
hump. In this scenario, afterglow emission begins during or soon after the
burst and the observed shape of the X-ray light curve depends on the relative
strengths of the emission due to the central engine and that of the afterglow.
There is a strong correlation such that those GRBs with stronger afterglow
components have brighter early optical emission. The late emission hump can
have a total fluence equivalent to that of the prompt phase. GRBs with the
strongest late humps have weak or no X-ray flares.


title:
Three dimensional SPH simulations of radiation-driven warped accretion
  discs

abstract:
  We present three dimensional smoothed particle hydrodynamics (SPH)
calculations of warped accretion discs in X-ray binary systems. Geometrically
thin, optically thick accretion discs are illuminated by a central radiation
source. This illumination exerts a non-axisymmetric radiation pressure on the
surface of the disc resulting in a torque that acts on the disc to induce a
twist or warp. Initially planar discs are unstable to warping driven by the
radiation torque and in general the warps also precess in a retrograde
direction relative to the orbital flow. We simulate a number of X-ray binary
systems which have different mass ratios using a number of different
luminosities for each. Radiation-driven warping occurs for all systems
simulated. For mass ratios q ~ 0.1 a moderate warp occurs in the inner disc
while the outer disc remains in the orbital plane (c.f. X 1916-053). For less
extreme mass ratios the entire disc tilts out of the orbital plane (c.f. Her
X-1). For discs that are tilted out of the orbital plane in which the outer
edge material of the disc is precessing in a prograde direction we obtain both
positive and negative superhumps simultaneously in the dissipation light curve
(c.f. V603 Aql).


title:
Optically Selected GRB Afterglows, a Real Time Analysis System at the
  CFHT

abstract:
  We attempt to detect optical GRB afterglows on images taken by the Canada
France Hawaii Telescope for the Very Wide survey, component of the Legacy
Survey. To do so, a Real Time Analysis System called "Optically Selected GRB
Afterglows" has been installed on a dedicated computer in Hawaii. This pipeline
automatically and quickly analyzes Megacam images and extracts from them a list
of variable objects which is displayed on a web page for validation by a member
of the collaboration. The Very Wide survey covers 1200 square degrees down to
i'=23.5. This paper briefly explain the RTAS process.


title:
Eclipsing binaries in extrasolar planet transit surveys: the case of
  SuperWASP

abstract:
  Using a comprehensive binary population synthesis scheme, we investigate the
statistical properties of a sample of eclipsing binaries that is detectable by
an idealised extrasolar planet transit survey with specifications broadly
similar to those of the SuperWASP (Wide Angle Search for Planets) project. In
this idealised survey the total number of detectable single stars in the
Galactic disc is of the order of 10^6-10^7, while, for a flat initial mass
ratio distribution, the total number of detectable eclipsing binaries is of the
order of 10^4-10^5. The majority of the population of detectable single stars
is made up of main-sequence stars (60%), horizontal-branch stars (20%), and
giant-branch stars (10%). The largest contributions to the population of
detectable eclipsing binaries stem from detached double main-sequence star
binaries (60%), detached giant-branch main-sequence star binaries (20%), and
detached horizontal-branch main-sequence star binaries (10%). The ratio of the
number of eclipsing binaries to the number of single stars detectable by the
idealised SuperWASP survey varies by less than a factor of 2.5 across the sky,
and decreases with increasing Galactic latitude. It is found to be largest in
the direction of the Galactic longitude l=-7.5deg and the Galactic latitude
b=-22.5deg. We also show that the fractions of systems in different subgroups
of eclipsing binaries are sensitive to the adopted initial mass ratio
distribution, which is one of the poorest constrained input parameters in
present-day binary population synthesis calculations. This suggests that once
statistically meaningful results from transit surveys are available, they will
be able to significantly improve the predictive power of population synthesis
studies of interacting binaries and related objects. (abridged)


title: NLTE models of line-driven stellar winds II. O stars in SMC

abstract:
  We calculate NLTE line-driven wind models of selected O stars in the spectral
range of O4 to O9 in the Small Magellanic Cloud (SMC). We compare predicted
basic wind properties, i.e. the terminal velocity and the mass-loss rate with
values derived from observation. We found relatively good agreement between
theoretical and observed terminal velocities. On the other hand, predicted
mass-loss rates and mass-loss rates derived from observation are in a good
agreement only for higher mass-loss rates. Theoretical mass-loss rates lower
than approximately 10^{-7} M_o/year are significantly higher than those derived
from observation. These results confirm the previously reported problem of weak
winds, since our calculated mass-loss rates are in a fair agreement with
predictions of Vink et al. (2001). We study multicomponent models for these
winds. For this purpose we develop a more detailed description of wind
decoupling. We show that the instability connected with the decoupling of
individual wind elements may occur for low-density winds. In the case of winds
with very low observed mass-loss rate the multicomponent effects are important
for the wind structure, however this is not able to consistently explain the
difference between predicted mass-loss rate and mass-loss rate derived from
observation for these stars. Similar to previous studies, we found the
dependence of wind parameters on the metallicity. We conclude that the wind
mass-loss rate significantly increases with metallicity as dM/dt ~ Z^0.67,
whereas the wind terminal velocity on average depends on metallicity only
slightly, namely v_infty ~ Z^0.06 (for studied stars).


title:
The origin and chemical evolution of carbon in the Galactic thin and
  thick disks

abstract:
  [ABRIDGED] In order to trace the origin and evolution of carbon in the
Galactic disk we have determined carbon abundances in 51 nearby F and G dwarf
stars. The sample is divided into two kinematically distinct subsamples with 35
and 16 stars that are representative of the Galactic thin and thick disks,
respectively. The analysis is based on spectral synthesis of the forbidden [C
I] line at 872.7 nm using spectra of very high resolution (R~220000)and high
signal-to-noise (S/N>300) that were obtained with the CES spectrograph on the
ESO 3.6-m telescope on La Silla in Chile. We find that [C/Fe] versus [Fe/H]
trends for the thin and thick disks are totally merged and flat for sub-solar
metallicities. The thin disk that extends to higher metallicities than the
thick disk,shows a shallow decline in [C/Fe] from [Fe/H]=0 and up to
[Fe/H]=+0.4. The [C/O] versus [O/H] trends are well separated between the two
disks (due to differences in the oxygen abundances)and bear a great resemblance
to the [Fe/O] versus [O/H] trends. Our interpretation of our abundance trends
is that the sources that are responsible for the carbon enrichment in the
Galactic thin and thick disks have operated on a time-scale very similar to
those that are responsible for the Fe and Y enrichment (i.e., SNIa and AGB
stars, respectively)...... For the Galaxy we hence conclude that the carbon
enrichment at metallicities typical of the disk is mainly due to low and
intermediate mass stars, while massive stars are still the main carbon
contributor at low metallicities (halo and metal-poor thick disk).


title: X-ray High Resolution and Imaging Spectroscopy of Supernova Remnants

abstract:
  The launch of Chandra and XMM-Newton has led to important new findings
concerning the X-ray emission from supernova remnants. These findings are a
result of the high spatial resolution with which imaging spectroscopy is now
possible, but also some useful results have come out of the grating
spectrometers of both X-ray observatories, despite the extended nature of
supernova remnants. The findings discussed here are the evidence for slow
equilibration of electron and ion temperatures near fast supernova remnant
shocks, the magnetic field amplification near remnant shocks due to cosmic ray
acceleration, a result that has come out of studying narrow filaments of X-ray
synchrotron emission, and finally the recent findings concerning Fe-rich ejecta
in Type Ia remnants and the presence of a jet/counter jet system in the Type Ib
supernova remnant Cas A.


title:
Clarifying Slow Roll Inflation and the Quantum Corrections to the
  Observable Power Spectra

abstract:
  Slow-roll inflation can be studied as an effective field theory. The form of
the inflaton potential consistent with the data is V(phi) = N M^4
w(phi/[sqrt{N} M_{Pl}]) where phi is the inflaton field, M is the inflation
energy scale, and N ~ 50 the number of efolds. The dimensionless function
w(chi) and field chi are O(1). This form of the potential encodes the slow-roll
expansion as an expansion in 1/N.A The Hubble parameter, inflaton mass and
non-linear couplings are of the see-saw form in terms of M/M_{Pl}. The quartic
coupling is lambda~1/N (M/M_{Pl})^4. The smallness of the non-linear couplings
is not a result of fine tuning but a natural consequence of the validity of the
effective field theory and slow roll approximation. Quantum corrections to slow
roll inflation are computed and turn to be an expansion in powers (H/M_{Pl})^2.
The corrections to the inflaton effective potential and its equation of motion
are computed, as well as the quantum corrections to the observable power
spectra. The near scale invariance of the fluctuations introduces a strong
infrared behavior naturally regularized by Delta=(n_s -1)/2+r/8. We consider
scalar curvature and tensor perturbations as well as light scalars and Dirac
fermions coupled to the inflaton.The subhorizon part is completely specified by
the trace anomaly of the fields with different spins and is solely determined
by the space-time geometry. This inflationary effective potential is strikingly
different from the usual Minkowski space-time result.Quantum corrections to the
power spectra are expressed in terms of the CMB observables. Trace anomalies
(especially the graviton part) dominate these quantum corrections in a definite
direction: they enhance the scalar curvature fluctuations and reduce the tensor
fluctuations.