title:
On the evolution of primordial gravitational waves: a semi-analytic
  detailed approach

abstract:
  A cosmological gravitational wave background resulting from space-time
quantum perturbations at energy scales of $\sim 10^{15}$GeV is expected as a
consequence of the general relativity theory in the context of the standard
cosmological model. Initial conditions %for the problem are determined during
the inflationary (de Sitter) era, at $z \gtrsim 10^{25} $. A semi-analytic
method was developed to evolve the system up to the present with no need of
simplifying approximations as the thin-horizon (super-adiabatic) or the
instantaneous transitions between the successive phases of domain of the
different cosmic fluids. The accuracy of such assumptions, broadly employed in
the literature, is put in check. Since the physical nature of the fluid (known
as dark energy) leading to the accelerated expansion observed in the recent
Universe is still uncertain, four categories of models were analyzed:
cosmological constant, X-fluid (phantom or not), generalized Chaplygin gas and
(a parametric form of) quintessence. The results are conclusive with respect to
the insensitivity of gravitational waves to dark energy, due to the recentness
of its phase of domain ($z \sim 1 $). The empirical counterparts of the
gravitational wave forecasts are still nonexistent for the noise levels and
operational frequencies of the experiments already built are inadequate to
detect those relics. Perspectives are more promising for space detectors
(planned to be sensitive to amplitudes of $\sim 10^{-23}$ at $10^{-3}-1$Hz).
The cosmic microwave background is also discussed as an alternative of indirect
detection and the energy density scale of inflation is constrained to be
smaller than $10^{-10}$ in the analysis here presented.


title:
Gravitational Lensing of Supernovae Type Ia by Pseudo Elliptic NFW
  Haloes

abstract:
  We present the effects of ellipticity of matter distribution in massive halos
on the observation of supernovae. A pseudo elliptical Navarro-Frenk-White (NFW)
mass model is used to calculate the introduced gain factors and observation
rates of type Ia supernovae due to the strong lensing. We investigate how and
to what extent the ellipticity in mass distribution of the deflecting halos can
affect surveys looking for cosmologically distant supernovae. We use halo
masses of $1.0 \times 10^{12} h^{-1} M_{\odot}$ and $1.0 \times 10^{14} h^{-1}
M_{\odot}$ at redshifts $z_{d}=0.2$, $z_{d}=0.5$, and $z_{d}=1.0$, with
ellipticities of up to $\epsilon=0.2$.


title:
An Observational Study of Tidal Synchronization in Solar-Type Binary
  Stars in the Open Clusters M35 and M34

abstract:
  We present rotation periods for the solar-type primary stars in 13 close (a~<
5 AU) single-lined spectroscopic binaries with known orbital periods (P) and
eccentricities (e). All binaries are members of the open clusters M35 (150Myr)
and M34 (250Myr). The binary orbital parameters and the rotation periods of the
primary stars were determined from time-series spectroscopy and time-series
photometry, respectively. Knowledge of the ages, orbital periods, and
eccentricities of these binaries combined with the rotation periods and masses
of their primary stars makes them particularly interesting systems for studying
the rates of tidal circularization and synchronization. Our sample of 13
binaries includes six with orbital periods shortward of 13 days (a ~< 0.12 AU).
The stars in these binaries orbit sufficiently close that their spins and
orbits have evolved toward synchronization and circularization due to tidal
interactions. We investigate the degree of tidal synchronization in each binary
by comparing the angular rotation velocity of the primary stars to the angular
velocity expected if the primary star was synchronized (e=0) or pseudo-
synchronized (e>0) with the orbital motion. Of the six closest binaries two
with circular orbits are not synchronized, one being subsynchronous and one
being supersynchronous, and the primary stars in two binaries with eccentric
orbits are rotating more slowly than pseudosynchronism. The remaining two
binaries have reached the equilibrium state of both a circularized orbit and
synchronized rotation. As a set, the six binaries present a challenging case
study for tidal evolution theory, which in particular does not predict
subsynchronous rotation in such close systems.


title: A Study of Giant Pulses from PSR J1824-2452A

abstract:
  We have searched for microsecond bursts of emission from millisecond pulsars
in the globular cluster M28 using the Parkes radio telescope. We detected a
total of 27 giant pulses from the known emitter PSR J1824-2452A. At wavelengths
around 20 cm the giant pulses are scatter-broadened to widths of around 2
microseconds and follow power-law statistics. The pulses occur in two narrow
phase-windows which correlate in phase with X-ray emission and trail the peaks
of the integrated radio pulse-components. Notably, the integrated radio
emission at these phase windows has a steeper spectral index than other
emission. The giant pulses exhibit a high degree of polarization, with many
being 100% elliptically polarized. Their position angles appear random.
Although the integrated emission of PSR J1824-2452A is relatively stable for
the frequencies and bandwidths observed, the intensities of individual giant
pulses vary considerably across our bands. Two pulses were detected at both
2700 and 3500 MHz. The narrower of the two pulses is 20 ns wide at 3500 MHz. At
2700 MHz this pulse has an inferred brightness temperature at maximum of 5 x
10^37 K. Our observations suggest the giant pulses of PSR J1824-2452A are
generated in the same part of the magnetosphere as X-ray emission through a
different emission process to that of ordinary pulses.


title:
Block Structured Adaptive Mesh and Time Refinement for Hybrid,
  Hyperbolic + N-body Systems

abstract:
  We present a new numerical algorithm for the solution of coupled collisional
and collisionless systems, based on the block structured adaptive mesh and time
refinement strategy (AMR). We describe the issues associated with the
discretization of the system equations and the synchronization of the numerical
solution on the hierarchy of grid levels. We implement a code based on a higher
order, conservative and directionally unsplit Godunov's method for
hydrodynamics; a symmetric, time centered modified symplectic scheme for
collisionless component; and a multilevel, multigrid relaxation algorithm for
the elliptic equation coupling the two components. Numerical results that
illustrate the accuracy of the code and the relative merit of various
implemented schemes are also presented.


title:
Concentration, Spin and Shape of Dark Matter Haloes: Scatter and the
  Dependence on Mass and Environment

abstract:
  We use a series of cosmological N-body simulations for a flat LCDM cosmology
to investigate the properties of dark matter haloes in the mass range
3.0e9-3.0e13 Msun. These properties include the concentration parameter (c),
the spin parameter (lambda) and the mean axis ratio (q). For the
concentration-mass relation we find c~M^(-0.11) in agreement with the model
proposed by Bullock et al. even if we find a lower normalization (15%). The
results for lambda and q are in good agreement with previous studies, while c
and lambda are anti-correlated. In an attempt to remove unrelaxed haloes, we
use the offset parameter (xoff), defined as the distance between the most bound
particle and the center of mass. Removing haloes with large xoff increases the
c by ~10%, lowers the lambda by ~15%, and removes the most prolate haloes. In
addition, it largely removes the anti-correlation between c and lambda though
not entirely. We also investigate the effects of the large-scale environment.
We find that more concentrated haloes live in denser environments. Note,
however, that the trend is weak compared to the scatter. For the spin
parameters we find no environment dependence, while there is a weak indication
that the most spherical haloes reside in denser region. Finally, using a simple
model for disk galaxy formation we show that haloes that host low surface
brightness galaxies are expected to be hosted by a biased sub-set of haloes.
Not only do these haloes have spin parameters that are larger than average,
they also have c that are 15% percent lower than the average at a given halo
mass. We discuss the implications of all these findings for the claimed
disagreement between halo concentrations inferred from LSB rotation curves, and
those expected for a LCDM cosmology. (abridged)


title: Comparison of VSB from BATSE, KONUS and Swift

abstract:
  We show the locations of the SWIFT short hard bursts (SHB) with afterglows on
the Galactic map and compare with the very short bursts (VSB) BATSE events. As
we have pointed out before, there is an excess of events in the Galactic map of
BATSE VSB events. We note, that none of VSB SWIFT era events fall into this
cluster. More SWIFT events are needed to check this claim. We also report a new
study with KONUS data of the VSB sample with an average energy above 90 keV
showing a clear excess of events below 100 ms duration (T_90) that have large
mean energy photons. We suggest that VSB themselves consists of two subclasses:
a fraction of events have peculiar distribution properties and have no
detectable counter parts, as might be expected for exotic sources such as
Primordial Black Holes.


title: Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities

abstract:
  The disruption of binary stars by the tidal field of the black hole in the
Galactic Center can produce the hypervelocity stars observed in the halo. We
use numerical models to simulate the full spectrum of observable velocities of
stars ejected into the halo by this binary disruption process. Our model
includes a range of parameters for binaries with 3-4 M_Solar primaries,
consideration of radial orbits of the ejected stars through an approximate mass
distribution for the Galaxy, and the impact of stellar lifetimes. We calculate
the spectrum of ejection velocities and reproduce previous results for the mean
ejection velocity at the Galactic center. The model predicts that the full
population of ejected stars includes both the hypervelocity stars with
velocities large enough to escape from the Galaxy and a comparable number of
ejected, but bound, stars of the same stellar type. The predicted median speeds
of the population of ejected stars as a function of distance in the halo are
consistent with current observations. Combining the model with the data also
shows that interesting constraints on the properties of binaries in the
Galactic Center and on the mass distribution in the Galaxy can be obtained even
with modest samples of ejected stars.


title: Basic physical parameters of a selected sample of evolved stars

abstract:
  We present the detailed spectroscopic analysis of 72 evolved stars, including
the [Fe/H] determination for the whole sample. These metallicities, together
with the Teff values and the absolute V magnitude derived from Hipparcos
parallaxes, are used to estimate basic stellar parameters (ages, masses, radii,
(B-V)o and log g using theoretical isochrones and a Bayesian estimation method.
The (B-V)o values so estimated turn out to be in excellent agreement with the
observed (B-V), confirming the reliability of the (Teff,(B-V)o) relation used
in the isochrones. The estimated diameters have been compared with limb
darkening-corrected ones measured with independent methods, finding an
agreement better than 0.3 mas within the 1-10 mas interval. We derive the
age-metallicity relation for the solar neighborhood; for the first time such a
relation has been derived from observations of field giants rather than from
open clusters and field dwarfs and subdwarfs. The age-metallicity relation is
characterized by close-to-solar metallicities for stars younger than ~4 Gyr,
and by a large [Fe/H] spread with a trend towards lower metallicities for
higher ages. We find that the [Fe/H] dispersion of young stars (less than 1
Gyr) is comparable to the observational errors, indicating that stars in the
solar neighbourhood are formed from interstellar matter of quite homogeneous
chemical composition. The three giants of our sample which have been proposed
to host planets are not metal rich, what is at odds with those for main
sequence stars. However, two of these stars have masses much larger than a
solar mass so we may be sampling a different stellar population from most
radial velocity searches for extrasolar planets. We also confirm that the
radial velocity variability tends to increase along the RGB.


title: Interstellar Turbulence Driving by Galactic Spiral Shocks

abstract:
  Spiral shocks are potentially a major source of turbulence in the
interstellar medium. To address this problem quantitatively, we use numerical
simulations to investigate gas flow across spiral arms in vertically
stratified, self-gravitating, magnetized models of galactic disks. Our models
are isothermal, quasi-axisymmetric, and local in the quasi-radial direction
while global in the vertical direction. We find that a stellar spiral potential
perturbation promptly induces a spiral shock in the gas flow. For vertically
stratified gas disks, the shock front in the radial-vertical plane is in
general curved, and never achieves a steady state. This behavior is in sharp
contrast to spiral shocks in two-dimensional (thin) disks, which are generally
stationary. The non-steady motions in our models include large-amplitude
quasi-radial flapping of the shock front. This flapping feeds random gas
motions on the scale of the vertical disk thickness, which then cascades to
smaller scales. The induced gas velocity dispersion in quasi-steady state
exceeds the sonic value for a range of shock strengths, suggesting that spiral
shocks are indeed an important generator of turbulence in disk galaxies.


title: First Evidence of a Precessing Jet Excavating a Protostellar Envelope

abstract:
  We present new, sensitive, near-infrared images of the Class I protostar,
Elias 29, in the Ophiuchus cloud core. To explore the relationship between the
infall envelope and the outflow, narrowband H2 1-0 S(1), Br-gamma, and
narrowband K-continuum filters were used to image the source with the
Wide-Field Infrared Camera on the Hale 5m telescope and with Persson's
Auxiliary Nasmyth Infrared Camera on the Baade 6.5 m telescope. The source
appears as a bipolar, scattered light nebula, with a wide opening angle in all
filters, as is typical for late-stage protostars. However, the pure H2
emission-line images point to the presence of a heretofore undetected
precessing jet. It is argued that high-velocity, narrow, precessing jets
provide the mechanism for creating the observed wide-angled outflow cavity in
this source.


title:
Discovery of Diffuse X-ray Emission in One of the Nearest Massive
  Star-Forming Regions NGC 2024

abstract:
  A deep 75 ks {\it Chandra} ACIS--I data of NGC 2024 was analyzed, aiming at a
search for diffuse X-ray emission in this one of the most nearby (415 pc)
massive star-forming regions. After removing point sources, an extended
emission was detected in the central circular region with a radius of 0.5 pc.
It is spatially associated with the young massive stellar cluster. Its X-ray
spectrum exhibits a very hard continuum ($kT>8$ keV) and a sign of He-like Fe
K$_\alpha$ line with the 0.5--7 keV absorption corrected luminosity of
2$\times10^{31}$ \ergs. Undetected faint point sources, estimated from the
luminosity function of the detected sources, contribute less than 10% to this
emission. Hence the emission is truly diffuse in nature. Because of the
proximity of NGC 2024 and the long exposure, this discovery is one of the most
strong supports for the existence of the diffuse X-ray emission in massive
star-forming regions.


title: Integral/Ibis Census of the Sky Beyond 100 kev

abstract:
  We report on the first census of INTEGRAL/IBIS detections ($\gtrsim 4\sigma$
significance) above 100 keV based on the Core Program and public Open time
observations up to April 2005. There are 49 sources detected in the 100-150 keV
band of which 14 are also seen in the 150-300 keV range. The low energy sample
is dominated by X-ray binary systems of both low and high mass, but also
includes 10 active galaxies. Of the binary systems that are detected above 150
keV, more than 50% are associated with black hole candidates, often reported as
microquasars. The present survey results are then used to construct LogN-LogS
curves for galactic and extragalactic objects in the 100-150 keV band: above a
1 mCrab sensitivity limit we expect that around 200 galactic sources and almost
350 active galaxies populate the sky above 100 keV. While the contribution of
individual point sources to the total Galactic emission has been estimated to
be around 70-80% between 100-300 keV, we find that active galaxies detected
above 1 mCrab account for only about 3% of the cosmic hard X-ray background in
the 100-150 keV band.


title: Two-Field Quintom Models in the w-w' Plane

abstract:
  The w-w' plane, defined by the equation of state parameter for the dark
energy and its derivative with respect to the logarithm of the scale factor, is
useful to the study of classifying the dynamical dark energy models. In this
note, we examine the evolving behavior of the two-field quintom models with w
crossing the w=-1 barrier in the w-w' plane. We find that these models can be
divided into two categories, type A quintom in which w changes from >-1 to <-1
and type B quintom in which w changes from <-1 to >-1 as the universe expands.


title:
Infrared and Optical Observations of GRB 030115 and its Extremely Red
  Host Galaxy: Implications for Dark Bursts

abstract:
  We present near-infrared (nIR) and optical observations of the afterglow of
GRB 030115. Discovered in an infrared search at Kitt Peak 5 hours after the
burst trigger, this afterglow is amongst the faintest observed in the R-band at
an early epoch, and exhibits very red colors, with $R-K\approx 6$. The
magnitude of the optical afterglow of GRB 030115 is fainter than many upper
limits for other bursts, suggesting that without early nIR observations it
would have been classified as a ``dark'' burst. Both the color and optical
magnitude of the afterglow are likely due to dust extinction and indicate that
at least some optical afterglows are very faint due to dust along the line of
sight. Multicolor {\it Hubble Space Telescope} observations were also taken of
the host galaxy and the surrounding field. Photometric redshifts imply that the
host, and a substantial number of faint galaxies in the field are at $z \sim
2.5$. The overdensity of galaxies is sufficiently great that GRB 030115 may
have occurred in a rich high-redshift cluster. The host galaxy shows extremely
red colors (R-K=5) and is the first GRB host to be classified as an Extremely
Red Object (ERO). Some of the galaxies surrounding the host also show very red
colors, while the majority of the cluster are much bluer, indicating ongoing
unobscured star formation. As it is thought that much of high redshift star
formation occurs in highly obscured environments it may be that GRB 030115
represent a transition object, between the relatively unobscured afterglows
seen to date and a population which are very heavily extinguished, even in the
nIR.


title:
The Probability Distribution of the Lya transmitted flux from a sample
  of SDSS quasars

abstract:
  We present a measurement of the probability distribution function (PDF) of
the transmitted flux in the Lya forest from a sample of 3492 quasars included
in the SDSS DR3 data release. Our intention is to investigate the sensitivity
of the Lya flux PDF as measured from low resolution and low signal-to-noise
data to a number of systematic errors such as uncertainties in the mean flux,
continuum and noise estimate. The quasar continuum is described by the
superposition of a power law and emission lines. We perform a power law
continuum fitting on a spectrum-by-spectrum basis, and obtain an average
continuum slope of 0.59 +/- 0.36 in the redshift range 2.5<z<3.5. Taking into
account the variation in the continuum indices increases the mean flux by 3 and
7 per cent at z=3 and 2.4, respectively, as compared to the values inferred
with a single (mean) continuum slope. We compare our measurements to the PDF
obtained with mock lognormal spectra, whose statistical properties have been
constrained to match the observed Lya flux PDF and power spectrum of high
resolution data. Using our power law continuum fitting and the SDSS pipeline
noise estimate yields a poor agreement between the observed and mock PDFs.
Allowing for a break in the continuum slope and, more importantly, for residual
scatter in the continuum level substantially improves the agreement. A decrease
of 10-15 per cent in the mean quasar continuum with a typical rms variance at
the 20 per cent level can account for the data, provided that the noise excess
correction is no larger than 10 per cent.


title: Light superconducting strings in the Galaxy

abstract:
  Observations of the Milky Way by the SPI/INTEGRAL satellite have confirmed
the presence of a strong 511 KeV gamma-ray line emission from the bulge, which
require an intense source of positrons in the galactic center. These
observations are hard to account for by conventional astrophysical scenarios,
whereas other proposals, such as light DM, face stringent constraints from the
diffuse gamma-ray background. Here we suggest that light superconducting
strings could be the source of the observed 511 KeV emission. The associated
particle physics, at the ~ 1 TeV scale, is within reach of planned accelerator
experiments, while the distinguishing spatial distribution, proportional to the
galactic magnetic field, could be mapped by SPI or by future, more sensitive,
satellite missions.


title: Extended Star Formation and Molecular Gas in the Tidal Arms near NGC3077

abstract:
  We report the detection of ongoing star formation in the prominent tidal arms
near NGC 3077 (member of the M 81 triplet). In total, 36 faint compact HII
regions were identified, covering an area of ~4x6 kpc^2. Most of the HII
regions are found at HI column densities above 1x10^21 cm^-2 (on scales of 200
pc), well within the range of threshold columns measured in normal galaxies.
The HII luminosity function resembles the ones derived for other low-mass dwarf
galaxies in the same group; we derive a total star formation rate of 2.6x10^-3
M_sun/yr in the tidal feature. We also present new high-resolution imaging of
the molecular gas distribution in the tidal arm using CO observations obtained
with the OVRO interferometer. We recover about one sixth of the CO flux (or
M_H2~2x10^6 M_sun, assuming a Galactic conversion factor) originally detected
in the IRAM 30m single dish observations, indicating the presence of a diffuse
molecular gas component in the tidal arm. The brightest CO peak in the
interferometer map (comprising half of the detected CO flux) is coincident with
one of the brightest HII regions in the feature. Assuming a constant star
formation rate since the creation of the tidal feature (presumably ~3x10^8
years ago), a total mass of ~7x10^5 M_sun has been transformed from gas into
stars. Over this period, the star formation in the tidal arm has resulted in an
additional enrichment of Delta(Z)>0.002. The reservoir of atomic and molecular
gas in the tidal arm is ~3x10^8 M_sun, allowing star formation to continue at
its present rate for a Hubble time. Such wide-spread, low-level star formation
would be difficult to image around more distant galaxies but may be detectable
through intervening absorption in quasar spectra.


title:
Very low metallicity massive star models: Pre-SN evolution and primary
  nitrogen production

abstract:
  Two series of models were computed. The first series consists of 20 solar
mass models with varying initial metallicity (Z=0.02 down to Z=10^{-8}) and
rotation (V_{ini}=0-600 km/s). The second one consists of models with an
initial metallicity of Z=10^{-8}, masses between 9 and 85 solar masses and fast
initial rotation velocities (V_{ini}=600-800 km/s).
  The most interesting models are the models with Z=10^{-8} ([Fe/H]~-6.6). In
the course of helium burning, carbon and oxygen are mixed into the hydrogen
burning shell. This boosts the importance of the shell and causes a reduction
of the CO core mass. Later in the evolution, the hydrogen shell deepens and
produces large amount of primary nitrogen. For the most massive models (M>~60
solar masses), significant mass loss occurs during the red supergiant stage.
This mass loss is due to the surface enrichment in CNO elements via rotational
and convective mixing. The 85 solar mass model ends up as a WO type Wolf-Rayet
star. Therefore the models predict SNe of type Ic and possibly long and soft
GRBs at very low metallicities.
  The rotating 20 solar mass models can best reproduce the observed CNO
abundances at the surface of extremely metal poor (EMP) stars and the
metallicity trends when their angular momentum content is the same as at solar
metallicity (and therefore have an increasing surface velocity with decreasing
metallicity). The wind of the massive star models can also reproduce the CNO
abundances of the most metal-poor carbon-rich star known to date, HE1327-2326.


title: High resolution CO imaging of high redshift QSO host galaxies

abstract:
  We review recent high-resolution CO observations of distant QSOs obtained at
the Very Large Array. The aim of these observations is to resolve the molecular
gas distribution in these extreme objects both spatially and in velocity space.
They provide unique information regarding the small-scale distribution, the
extent, and the brightness temperatures of the molecular gas in these early
systems. E.g., the structure and dynamics of the molecular gas may reveal
whether or not mergers can be the cause of the ongoing starburst activity. The
observations also allow for a first estimate of the dynamical gas mass.
Currently, only the VLA is able to obtain resolutions in CO of up to 0.15"
which is needed to resolve typical galactic structures of sizes ~1 kpc. We
present new high-resolution VLA imaging of high-z QSOs (BRI 1335-0417, APM
08279+5255 and J1148+5251). These observations pave the road to future ALMA
observations where resolutions of order 0.1'' will be obtained routinely.


title: Cosmological evolution of compact AGN at 15 GHz

abstract:
  We study the uniformity of the distribution of compact flat-spectrum AGN on
the sky and the evolution of their relativistic jets with cosmic epoch. A
complete sample of compact extragalactic radio sources at 15 GHz was recently
compiled to conduct the MOJAVE program. The MOJAVE sample comprises 133
radio-loud flat-spectrum AGN with compact relativistic outflows detected at
parsec scales. The source counts of compact AGN shows that the MOJAVE sample
represents a flux-limited complete sample. Analysis of the population of
flat-spectrum quasars of the sample reveals that the pc-scale jets of quasars
have intrinsic luminosities in the range between ~10^24 W/Hz and ~10^27 W/Hz
and Lorentz factors distributed between 3 and 30. We find that the apparent
speed (or Lorentz factor) of jets evolves with redshift, increasing from z~0 to
z~1 and then falling at higher redshifts (z~2.5) by a factor of 2.5. The
evolution of apparent speeds does not affect significantly the evolution of the
beamed luminosity function of quasars, which is most likely to be dependent on
the evolution of radio luminosity. Furthermore, the beamed radio luminosity
function suggests that the intrinsic luminosity function of quasars has a
double power-law form: it is flat at low luminosities and steep at high
luminosities. There is a positive evolution of quasars at low redshifts (z<0.5)
and strong negative evolution at redshifts >1.7 with space density decline up
to z~2.5. This implies that the powerful jets were more populous at redshifts
between 0.5 and 1.7. We show that the evolution of compact quasars is
luminosity dependent and it depends strongly on the speed of the jet suggesting
that there are two distinct populations of quasars with slow and fast jets
which evolve differently with redshift.


title: An X-ray Tour of Massive Star-forming Regions with Chandra

abstract:
  The Chandra X-ray Observatory is providing fascinating new views of massive
star-forming regions, revealing all stages in the life cycles of massive stars
and their effects on their surroundings. I present a Chandra tour of some of
the most famous of these regions: M17, NGC 3576, W3, Tr14 in Carina, and 30
Doradus. Chandra highlights the physical processes that characterize the lives
of these clusters, from the ionizing sources of ultracompact HII regions (W3)
to superbubbles so large that they shape our views of galaxies (30 Dor). X-ray
observations usually reveal hundreds of pre-main sequence (lower-mass) stars
accompanying the OB stars that power these great HII region complexes, although
in one case (W3 North) this population is mysteriously absent. The most massive
stars themselves are often anomalously hard X-ray emitters; this may be a new
indicator of close binarity. These complexes are sometimes suffused by soft
diffuse X-rays (M17, NGC 3576), signatures of multi-million-degree plasmas
created by fast O-star winds. In older regions we see the X-ray remains of the
deaths of massive stars that stayed close to their birthplaces (Tr14, 30 Dor),
exploding as cavity supernovae within the superbubbles that these clusters
created.


title: Fast cosmological parameter estimation using neural networks

abstract:
  We present a method for accelerating the calculation of CMB power spectra,
matter power spectra and likelihood functions for use in cosmological parameter
estimation. The algorithm, called CosmoNet, is based on training a multilayer
perceptron neural network and shares all the advantages of the recently
released Pico algorithm of Fendt & Wandelt, but has several additional benefits
in terms of simplicity, computational speed, memory requirements and ease of
training. We demonstrate the capabilities of CosmoNet by computing CMB power
spectra over a box in the parameter space of flat \Lambda CDM models containing
the 3\sigma WMAP1 confidence region. We also use CosmoNet to compute the WMAP3
likelihood for flat \Lambda CDM models and show that marginalised posteriors on
parameters derived are very similar to those obtained using CAMB and the WMAP3
code. We find that the average error in the power spectra is typically 2-3% of
cosmic variance, and that CosmoNet is \sim 7 \times 10^4 faster than CAMB (for
flat models) and \sim 6 \times 10^6 times faster than the official WMAP3
likelihood code. CosmoNet and an interface to CosmoMC are publically available
at www.mrao.cam.ac.uk/software/cosmonet.


title: Is the dark matter halo of the Milky Way flattened?

abstract:
  We performed an extended analysis of the parameter space for the interaction
of the Magellanic System with the Milky Way (MW). The varied parameters cover
the phase space parameters, the masses, the structure, and the orientation of
both Magellanic Clouds, as well as the flattening of the dark matter halo of
the MW. The analysis was done by a specially adopted optimization code
searching for the best match between numerical models and the detailed HI map
of the Magellanic System by Bruens et al. (2005). The applied search algorithm
is a genetic algorithm combined with a code based on the fast, but
approximative restricted N-body method. By this, we were able to analyze more
than 10^6 models, which makes this study one of the most extended ones for the
Magellanic System. Here we focus on the flattening q of the axially symmetric
MW dark matter halo potential, that is studied within the range 0.74<=q<=1.20.
We show that creation of a trailing tail (Magellanic Stream) and a leading
stream (Leading Arm) is quite a common feature of the Magellanic System-MW
interaction, and such structures were modeled across the entire range of halo
flattening values. However, important differences exist between the models,
concerning density distribution and kinematics of HI, and also the dynamical
evolution of the Magellanic System. Detailed analysis of the overall agreement
between modeled and observed distribution of neutral hydrogen shows that the
models assuming an oblate (q<1.0) dark matter halo of the Galaxy allow for
better satisfaction of HI observations than models with other halo
configurations.


title:
The VIMOS VLT Deep Survey:The ultraviolet galaxy luminosity function and
  luminosity density at 3<z<4

abstract:
  We study the LF of the high-z galaxy population with 3<z<4 using a purely
I-band magnitude-selected spectroscopic sample obtained in the framework of the
VVDS. We determine the LF from the VVDS, taking care to add as few assumptions
and as simple corrections as possible, and compare our results with those
obtained from photometric studies, based on Lyman-break selections or photo-z
measurements. We find that in the range 3<z<4, the VVDS LF is parameterized by
phi*=1.24+-0.50 10-3 mag-1 Mpc-3 and M*=-21.49+-0.19, assuming a slope
alpha=-1.4 consistent with most previous studies. While phi* is comparable to
previously found values, M* is significantly brighter by about 0.5 mag at
least. Using the conservative slope -1.4, we find a LD at 1700A
rho(M<-18.5)=2.4 10 19 W Mpc-3 and rho Tot=3.1 10 19 W Mpc-3, comparable to
that estimated in other studies. The unexpectedly large number of very bright
galaxies found in the VVDS indicates that the color-selection and photo-z
techniques that are generally used to build high-z galaxy samples may be
affected by a significant fraction of color-measurement failures or by
incomplete modelling of the mix of stellar emission, AGN contribution, dust
absorption and intergalactic extinction assumed to identify high-z galaxies,
making pure magnitude selection better able to trace the full population.
Because of the difficulty to identify all low-luminosity galaxies in a
spectroscopic survey, the LD could still be significantly underestimated. We
also find that the relative contribution of the most luminous galaxies compared
to the fainter ones is at least twice as large in the VVDS compared to former
estimates. Therefore, the VVDS paints a quite different picture of the role of
the most actively star-forming galaxies in the history of star formation.


title:
XMM-Newton high-resolution spectroscopy reveals the chemical evolution
  of M 87

abstract:
  We present here a study of chemical abundances in the giant elliptical galaxy
M 87 using high-resolution spectra obtained with the Reflection Grating
Spectrometers during two deep XMM-Newton observations. While we confirm the
two-temperature structure of the inter-stellar medium (ISM) in M 87, we also
show that a continuous temperature distribution describes the data equally
well. The high statistics allows us, for the first time, to determine
relatively accurate abundance values also for carbon and nitrogen. The
comparison of the abundance ratios of C, N, O and Fe in the ISM of M 87 with
those in the stellar population of our Galaxy shows that the relative
contribution of core-collapse supernovae to the enrichment of the ISM in M 87
is significantly less than in the Milky Way and indicates that the enrichment
of the ISM by iron through Type Ia supernovae and by carbon and nitrogen is
occurring in parallel. This suggests that the main source of carbon and
nitrogen in M 87 are the low- and intermediate-mass asymptotic giant branch
stars. From the oxygen to iron abundance ratio in the hot gas we estimate that
the relative number of core collapse and type Ia supernovae contributing to the
enrichment of the ISM in the core of M 87 is ~60% and ~40% respectively. The
spatial distributions of iron and oxygen are different. While the oxygen
abundance distribution is flat the iron abundance peaks in the core and has a
gradient throughout the ~4' wide field of view of the instrument, suggesting an
early enrichment by core-collapse supernovae and a continuous contribution of
type Ia supernovae.


title:
Sources of Stellar Energy, Einstein- Eddington Timescale of
  Gravitational Contraction and Eternally Collapsing Objects

abstract:
  We point out that although conventional stars are primarily fed by burning of
nuclear fuel at their cores, in a strict sense, the process of release of
stored gravitational energy, known as, Kelvin - Helmholtz (KH) process is
either also operational albeit at an arbitrary slow rate, or lying in wait to
take over at the disruption of the nuclear channel. In fact, the latter mode of
energy release is the true feature of any self-gravity bound object including
stars. We also highligh the almost forgotten fact that Eddington was the first
physicist to introduce Special Relativity into the problem and correctly insist
that, actually, total energy stored in a star is not the mere Newtonian energy
but the total mass energy (E = M c^2). Accordingly, Eddington defined an
``Einstein Time Scale'' of Evolution where the maximum age of the Sun turned
out to be t_E = 1.4. 10^{13} yr. We extend this concept by introducing General
Relativity and show that the minimum value of depletion of total mass-energy is
t_E =infty not only for Sun but for and sufficiently massive or dense object.
We propose that this time scale be known in the name of ``Einstein -
Eddington''. We also point out that, recently, it has been shown that as
massive stars undergo continued collapse to become a Black Hole, first they
become extremely relativistic Radiation Pressure Supported Stars. And the life
time of such relativistic radiation pressure supported compact stars is indeed
dictated by this Einstein -Eddington time scale whose concept is formally
developed here. Since this observed time scale of this radiation pressure
supported quasistatic state turns out to be infinite, such objects are called
Magnetospheric Eternally Collapsing Objects (MECO).


title: The Cool ISM in Elliptical Galaxies. I. A Survey of Molecular Gas

abstract:
  We present preliminary results from a survey of CO emission from members of a
volume-limited sample of non-cluster elliptical galaxies. Our intent is to
compare the gas properties of these ellipticals to a sample of lenticulars
selected using similar criteria. The data, although still sparse, suggest that
the cool gas in ellipticals shows the same puzzling upper mass cutoff found in
the lenticular galaxies. We find, however, significantly lower detection rates
and possibly much lower H2/HI mass ratios in the ellipticals. The detection
rate is higher among the lower-mass galaxies, as has been found previously.
This seems puzzling given that the deeper potential wells of the larger
galaxies ought to make gas retention easier, but perhaps that effect is
overwhelmed by feedback from the central suppermassive black hole. As we have
observed ~40 percent of our sample, the conclusions are necessarily tentative
at this time.


title:
Photometry of comet 9P/Tempel 1 during the 2004/2005 approach and the
  Deep Impact module impact

abstract:
  The results of the 9P/Tempel 1 CARA (Cometary Archive for Amateur
Astronomers) observing campaign is presented. The main goal was to perform an
extended survey of the comet as a support to the Deep Impact (DI) Mission. CCD
R, I and narrowband aperture photometries were used to monitor the $Af\rho$
quantity. The observed behaviour showed a peak of 310 cm 83 days before
perihelion, but we argue that it could be distorted by the phase effect, too.
The phase effect is roughly estimated around 0.0275 mag/degree, but we had no
chance for direct determination because of the very similar geometry of the
observed apparitions. The log-slope of $Af\rho$ was around -0.5 between about
180--100 days before the impact but evolved near the steady-state like 0 value
by the impact time. The DI module impact caused an about 60%{} increase in the
value of $Af\rho$ and a cloud feature in the coma profile which was observed
just after the event. The expansion of the ejecta cloud was consistent with a
fountain model with initial projected velocity of 0.2 km/s and $\beta$=0.73.
Referring to a 25~000 km radius area centered on the nucleus, the total cross
section of the ejected dust was 8.2/$A$ km$^2$ 0.06 days after the impact, and
1.2/$A$ km$^2$ 1.93 days after the impact ($A$ is the dust albedo). 5 days
after the event no signs of the impact were detected nor deviations from the
expected activity referring both to the average pre-impact behaviour and to the
previous apparitions ones.


title: Time-Dependent Ionization in Radiatively Cooling Gas

abstract:
  We present new computations of the equilibrium and non-equilibrium cooling
efficiencies and ionization states for low-density radiatively cooling gas
containing cosmic abundances of the elements H, He, C, N, O, Ne, Mg, Si, S, and
Fe. We present results for gas temperatures between 1e4 and 1e8 K, assuming
dust-free and optically thin conditions, and no external radiation. For
non-equilibrium cooling we solve the coupled time-dependent ionization and
energy loss equations for a radiating gas cooling from an initially hot, >5e6K
equilibrium state, down to 1e4K. We present results for heavy element
compositions ranging from 1e-3 to 2 times the elemental abundances in the Sun.
We consider gas cooling at constant density (isochoric) and at constant
pressure (isobaric). We calculate the critical column densities and
temperatures at which radiatively cooling clouds make the dynamical transition
from isobaric to isochoric evolution. We construct ion ratio diagnostics for
the temperature and metallicity in radiatively cooling gas. We provide
numerical estimates for the maximal cloud column densities for which the gas
remains optically thin to the cooling radiation. We present our computational
results in convenient on-line figures and tables (see
http://wise-obs.tau.ac.il/~orlyg/cooling/).


title: Analytical Study of Diffusive Relativistic Shock Acceleration

abstract:
  Particle acceleration in relativistic shocks is studied analytically in the
test-particle, small-angle scattering limit, for an arbitrary velocity-angle
diffusion function D. Accurate analytic expressions for the spectral index s
are derived using few (2-6) low-order moments of the shock-frame angular
distribution. For isotropic diffusion, previous results are reproduced and
justified. For anisotropic diffusion, s is shown to be sensitive to D,
particularly downstream and at certain angles, and a wide range of s values is
attainable. The analysis, confirmed numerically, can be used to test
collisionless shock models and to observationally constrain D. For example,
strongly forward- or backward-enhanced diffusion downstream is ruled out by GRB
afterglow observations.


title:
Multi-Wavelength Observations of GRB 050820A: An Exceptionally Energetic
  Event Followed from Start to Finish

abstract:
  We present observations of the unusually bright and long gamma-ray burst GRB
050820A, one of the best-sampled broadband data sets in the Swift era. The
gamma-ray light curve is marked by a soft precursor pulse some 200 s before the
main event; the lack of any intervening emission suggests that it is due to a
physical mechanism distinct from the GRB itself. The large time lag between the
precursor and the main emission enabled simultaneous observations in the
gamma-ray, X-ray, and optical band-passes, something only achieved for a
handful of events to date. While the contemporaneous X-rays are the low-energy
tail of the prompt emission, the optical does not directly track the gamma-ray
flux. Instead, the early-time optical data appear mostly consistent with the
forward shock synchrotron peak passing through the optical, and are therefore
likely the beginning of the afterglow. On hour time scales after the burst, the
X-ray and optical light curves are inconsistent with an adiabatic expansion of
the shock into the surrounding region, but rather indicate that there is a
period of energy injection. Observations at late times allow us to constrain
the collimation angle of the relativistic outflow to theta = 6.8 - 9.3 degrees.
Our estimates of both the kinetic energy of the afterglow and the prompt
gamma-ray energy release make GRB 050820A one of the most energetic events for
which such values could be determined.


title: Cosmological model selection

abstract:
  Model selection aims to determine which theoretical models are most plausible
given some data, without necessarily asking about the preferred values of the
model parameters. A common model selection question is to ask when new data
require introduction of an additional parameter, describing a newly-discovered
physical effect. We review several model selection statistics, and then focus
on use of the Bayesian evidence, which implements the usual Bayesian analysis
framework at the level of models rather than parameters. We describe our
CosmoNest code, which is the first computationally-efficient implementation of
Bayesian model selection in a cosmological context. We apply it to recent WMAP
satellite data, examining the need for a perturbation spectral index differing
from the scale-invariant (Harrison-Zel'dovich) case.


title: Requirements for Cosmological 21-cm Masers

abstract:
  We perform Monte-Carlo calculations of the radiative transfer of Lyman Alpha
(hereafter Lya) photons emitted by a source embedded in a neutral collapsing
gas cloud. This represents a young galaxy or quasar during the early stages of
the epoch of reionisation (EoR). After computing the Lya spectrum as function
of radius and time, we find that the Lya color temperature may be negative in
large volumes surrounding the central source. Motivated by this result, we
explore the prospects for a population inversion in the hyperfine levels of
atomic hydrogen via the Wouthuysen-Field (WF) effect. The reason for this
exploration is clear: if 21-cm masers exist during the EoR, they could greatly
boost the expected 21-cm flux from this epoch. We find that population
inversion is unlikely to occur for several reasons: (1) the required Lya
luminosities of the central source exceed ~10e45 erg/s. The radiation pressure
exerted by such a large Lya flux likely halts the collapse of the cloud; (2)
When quantum corrections to the WF-coupling strength are applied, the required
Lya luminosities are (even) larger by orders of magnitude; (3) A relatively low
flux of Lya photons that is produced via other channels (x-ray heating,
collisional excitation of hydrogen) prevents the Lya color temperature from
becoming negative.


title: Nflation: non-gaussianity in the horizon-crossing approximation

abstract:
  We analyze the cosmic non-gaussianity produced in inflation models with
multiple uncoupled fields with monomial potentials, such as Nflation. Using the
horizon-crossing approximation to compute the non-gaussianity, we show that
when each field has the same form of potential, the prediction is independent
the number of fields, their initial conditions, and the spectrum of
masses/couplings. It depends only on the number of e-foldings after the horizon
crossing of observable perturbations. We also provide a further generalization
to the case where the fields can have monomial potentials with different
powers. Unless the horizon-crossing approximation is substantially violated,
the predicted non-gaussianity is too small to ever be observed.


title: Long-term evolution of accretion discs in Be/X-ray binaries

abstract:
  We numerically study the long-term evolution of the accretion disc around the
neutron star in a coplanar Be/X-ray binary with a short period and a moderate
eccentricity. From three dimensional Smoothed Particle Hydrodynamics
simulations, we find that the disc evolves through three distinct phases, each
characterized by different mass accretion patterns. In the first "developing
phase", the disc is formed and develops towards a nearly Keplerian disc. It has
a relatively large, double-peaked mass-accretion rate with the higher peak by
the direct accretion at periastron, which is followed by the lower peak by the
accretion induced by a one-armed spiral wave. In the second "transition phase",
the disc is approximately Keplerian and grows with time. The mass-accretion
rate increases as the disc grows. In the second phase, there is a transition in
the mass accretion rate from a double peaked to a single peaked pattern. In the
final quasi-steady state, the mass-accretion rate is on average balanced with
the mass-transfer rate from the Be disc and exhibits a regular orbital
modulation. In the quasi-steady state, the mass-accretion rate has a single
peak by the wave-induced accretion as in a later stage of the transition phase.
The orbital modulation of X-ray maxima could provide not only a circumstantial
evidence for the persistent disc but also an observational diagnosis of the
disc evolutionary state.


title:
Comparison of Magnetic Field Structures on Different Scales in and
  around the Filamentary Dark Cloud GF 9

abstract:
  New visible polarization data combined with existing IR and FIR polarization
data are used to study how the magnetic field threading the filamentary
molecular cloud GF 9 connects to larger structures in its general environment.
We find that when both visible and NIR polarization data are plotted as a
function of extinction, there is no evidence for a plateau or a saturation
effect in the polarization at Av ~ 1.3 as seen in dark clouds in Taurus. This
lack of saturation effect suggests that even in the denser parts of GF 9 we are
still probing the magnetic field. The visible polarization is smooth and has a
well-defined orientation. The IR data are also well defined but with a
different direction, and the FIR data in the core region are well defined and
with yet another direction, but are randomly distributed in the filament
region. On the scale of a few times the mean radial dimension of the molecular
cloud, it is as if the magnetic field were `blind' to the spatial distribution
of the filaments while on smaller scales within the cloud, in the core region
near the IRAS point source PSC 20503+6006, polarimetry shows a rotation of the
magnetic field lines in these denser phases. Hence, in spite of the fact that
the spatial resolution is not the same in the visible/NIR and in the FIR data,
all the data put together indicate that the field direction changes with the
spatial scale. Finally, the Chandrasekhar and Fermi method is used to evaluate
the magnetic field strength, indicating that the core region is approximately
magnetically critical. A global interpretation of the results is that in the
core region an original poloidal field could have been twisted by a rotating
elongated (core+envelope) structure. There is no evidence for turbulence and
ambipolar diffusion does not seem to be effective at the present time.


title:
Spitzer SAGE survey of the Large Magellanic Cloud II: Evolved Stars and
  Infrared Color Magnitude Diagrams

abstract:
  Color-magnitude diagrams (CMDs) are presented for the Spitzer SAGE (Surveying
the Agents of a Galaxy's Evolution) survey of the Large Magellanic Cloud (LMC).
IRAC and MIPS 24 um epoch one data are presented. These data represent the
deepest, widest mid-infrared CMDs of their kind ever produced in the LMC.
Combined with the 2MASS survey, the diagrams are used to delineate the evolved
stellar populations in the Large Magellanic Cloud as well as Galactic
foreground and extragalactic background populations. Some 32000 evolved stars
brighter than the tip of the red giant branch are identified. Of these,
approximately 17500 are classified as oxygen-rich, 7000 carbon-rich, and
another 1200 as ``extreme'' asymptotic giant branch (AGB) stars. Brighter
members of the latter group have been called ``obscured'' AGB stars in the
literature owing to their dusty circumstellar envelopes. A large number (1200)
of luminous oxygen--rich AGB stars/M supergiants are also identified. Finally,
there is strong evidence from the 24 um MIPS channel that previously
unexplored, lower luminosity oxygen-rich AGB stars contribute significantly to
the mass loss budget of the LMC (1200 such sources are identified).


title: Formation of z ~ 6 quasars from hierarchical galaxy mergers

abstract:
  The discovery of luminous quasars at redshift z ~ 6 indicates the presence of
supermassive black holes (SMBHs) of mass ~10^9 Msun when the Universe was less
than one billion years old. This finding presents several challenges for
theoretical models. Here, we present the first multi-scale simulations that,
together with a self-regulated model for the SMBH growth, produce a luminous
quasar at z ~ 6.5 in the LCDM paradigm. We follow the hierarchical assembly
history of the most massive halo in a ~ 3 Gpc^3 volume, and find that this halo
of ~ 8x 10^{12} Msun forming at z ~ 6.5 after several major mergers is able to
reproduce a number of observed properties of SDSS J1148+5251, the most distant
quasar detected at z =6.42 (Fan et al. 2003). Moreover, the SMBHs grow through
gas accretion below the Eddington limit in a self-regulated manner owing to
feedback. We find that the progenitors experience significant star formation
(up to 10^4 Msun/yr) preceding the major quasar phase such that the stellar
mass of the quasar host reaches 10^{12} Msun at z ~ 6.5, consistent with
observations of significant metal enrichment in SDSS J1148+5251. Our results
provide a viable formation mechanism for z ~ 6 quasars in the standard LCDM
cosmology, and demonstrate a common, merger-driven origin for the rarest
quasars and the fundamental SMBH-host correlation in a hierarchical
Universe.(Abridged)


title:
Discovery of a Compact X-ray Source in the LMC Supernova Remnant N23
  with Chandra

abstract:
  An X-ray compact source was discovered with Chandra in a supernova remnant
(SNR) N23, located in the Large Magellanic Cloud. The compact source (CXOU
J050552.3-680141) is seen in only the hard band (> 2 keV) image of N23, while
the soft band image (< 2 keV) shows diffuse emission of the SNR, with an extent
of ~60 arcsec times ~80 arcsec. The compact source is located at almost the
center of N23, and there is no identifiable object for the source from previous
observations at any other wavelength. The source spectrum is best explained by
a power-law model with a photon index of 2.2 (1.9-2.7) and an
absorption-corrected luminosity of 1.0 x 10^34 ergs s^-1 in the 0.5--10 keV
band for a distance of 50 kpc. Neither pulsation nor time variability of the
source was detected with this observation with a time resolution of 3.2 sec.
These results correspond with those of Hughes et al. (2006) who carried out
analysis independently around the same time as our work. Based on information
from the best-fit power-law model, we suggest that the source emission is most
likely from a rotation-powered pulsar and/or a pulsar wind nebula. It is
generally inferred that the progenitor of N23 is a core-collapsed massive star.
  Based on information from the best-fit power-law model, we suggest that the
source emission is most likely from a rotation-powered pulsar and/or a pulsar
wind nebula. It is generally inferred that the progenitor of N23 is a
core-collapsed massive star.


title: The giant arc statistics in the three year WMAP cosmological model

abstract:
  We use high-resolution $N$-body simulations to investigate the optical depth
of giant arcs with length-to-width ratio larger than 7.5 and 10 in the
`standard' $\LCDM$ model with $\sigma_8=0.9$ and $\Omega_{\rm m,0}=0.3$ and a
model based on three-year Wilkinson Microwave Anisotropy Probe (WMAP) data. We
find that, in dark-matter only simulations, the lensing probability in the
three-year WMAP model (with $\sigma_8=0.74$ and $\Omega_{\rm m,0}=0.238)$
decreases by a factor of $\sim 6$ compared with that in the `standard' $\LCDM$
model. The effects of baryonic cooling, star formation and feedbacks are
uncertain, but we argue that baryons will only increase the the lensing
cross-section by a moderate factor, $\sim 2$. We conclude that the low central
value of $\sigma_8$ and $\Omega_{\rm m,0}$ preferred by the WMAP three-year
data may be too low to be compatible with observations if conventional
assumptions of the background source population are correct.


title:
On the mass-to-light ratio of the local Galactic disc and the optical
  luminosity of the Galaxy

abstract:
  We measure the volume luminosity density and surface luminosity density
generated by the Galactic disc, using accurate data on the local luminosity
function and the disc's vertical structure. From the well measured volume mass
density and surface mass density, we derive local volume and surface
mass-to-light ratios for the Galactic disc, in the bands B, V and I. We obtain
mass-to-light ratios for the local column of stellar matter of (M/L)_B = 1.4
+/- 0.2, (M/L)_V = 1.5 +/- 0.2 and (M/L)_I = 1.2 +/- 0.2. The dominant
contributors to the surface luminosity in these bands are main sequence
turn-off stars and giants. Our results on the colours and mass-to-light ratios
for the ``Solar cylinder'' well agree with population synthesis predictions
using Initial Mass Functions typical of the Solar Neighbourhood. Finally we
infer the global luminosity of the Milky Way, which appears to be
under-luminous by about 1-sigma with respect to the main locus of the
Tully-Fisher relation, as observed for external galaxies.


title: Algorithm of Ensemble Pulsar Time

abstract:
  An algorithm of the ensemble pulsar time based on the Wiener filtration
method has been constructed. This algorithm has allowed the separation of the
contributions of an atomic clock and a pulsar itself to the post-fit pulsar
timing residuals. The method has been applied to the timing data of the
millisecond pulsars PSR B1855+09 and PSR B1937+21 and allowed the filtering out
of the atomic scale component from the pulsar phase variations. Direct
comparison of the terrestrial time TT(BIPM96) and the ensemble pulsar time
PT$_{\rm ens}$ has displayed that the difference TT(BIPM96) -- PT$_{\rm ens}$
is within $\pm0.4 \mu$s range. A new limit of gravitational wave background
based on the difference TT(BIPM96) -- PT$_{\rm ens}$ was established to be
$\Omega_g {\rm h}^2\sim 10^{-10}$.


title:
Structured Red Giant Winds with Magnetized Hot Bubbles and the
  Corona/Cool Wind Dividing Line

abstract:
  By performing MHD simulations, we investigate the mass loss of intermediate-
and low-mass stars from main sequence (MS) to red giant branch (RGB) phases.
Alfven waves, which are excited by the surface convections travel outwardly and
dissipate by nonlinear processes to accelerate and heat the stellar winds. We
dynamically treat these processes in open magnetic field regions from the
photospheres to 25 stellar radii. When the stars evolve to slightly blueward
positions of the dividing line (Linsky & Haisch), the steady hot corona with
temperature, ~ 1MK, suddenly disappears. Instead, many hot (~1MK) and warm
(~10^5K) bubbles are formed in cool (T<~2x10^4K) chromospheric winds because of
thermal instability; the red giant wind is not a steady stream but structured
outflow. As a result, the mass loss rates, \dot{M}, largely vary in time by 3-4
orders or magnitude in the RGB stars. Supported by magnetic pressure, the
density of hot bubbles can be kept low to reduce the radiative cooling and to
maintain the high temperature long time. Even in the stars redward of the
dividing line, hot bubbles intermittently exist, and they can be sources of
UV/soft X-ray emissions from hybrid stars. Nearly static regions are formed
above the photospheres of the RGB stars, and the stellar winds are effectively
accelerated from several stellar radii. Then, the wind velocity is much smaller
than the surface escape speed, because it is regulated by the slower escape
speed at that location. We finally derive an equation that determines \dot{M}
from the energetics of the simulated wave-driven winds in a forward manner. The
relation explains \dot{M} from MS to RGB, and it can play a complementary role
to the Reimers' formula, which is mainly for more luminous stars.


title: An evolutionary disc model of the edge-on galaxy NGC 5907

abstract:
  We present a physical model that explains the two disparate observational
facts: 1) the exponential vertical disc structure in the optical and NIR of the
non-obscured part of the stellar disc and 2) the enhanced FIR/submm luminosity
by about a factor of four near the obscured mid-plane, which requires
additional dust and also stellar light to heat the dust component. We use
multi-band photometry in U, B, V, R, and I- band combined with radiative
transfer through a dust component to fit simultaneously the vertical
surface-brightness and colour index profiles in all bands adopting a reasonable
star formation history and dynamical heating function. The final disc model
reproduces the surface-brightness profiles in all bands with a moderately
declining star formation rate and a slowly starting heating function for young
stars. The total dust mass is 57 million solar masses as required from the
FIR/submm measurements. Without a recent star burst we find in the midplane an
excess of 5.2-, 4.0-, and 3.0-times more stellar light in the U-, B-, and
V-band, respectively. The corresponding stellar mass-to-light ratios are 0.91
in V- and 1.0 in R-band. The central face-on optical depth in V-band is 0.81
and the radial scale length of the dust is 40% larger than that of the stellar
disc. Evolutionary disc models are a powerful method to understand the vertical
structure of edge-on galaxies. Insights to the star formation history and the
dynamical evolution of stellar discs can be gained. FIR/submm observations are
necessary to restrict the parameter space for the models.


title:
The Chemical Abundances of the Stellar Populations in the Leo I and Leo
  II dSph Galaxies

abstract:
  We have obtained spectra of 102 red giant branch (RGB) stars in the Leo I
dwarf spheroidal galaxy (dSph) and 74 RGB stars in the Leo II dSph using LRIS
on the Keck I 10-meter Telescope. We report on the calcium abundances [Ca/H]
derived from the strengths of the Ca II triplet absorption lines at 8498, 8542,
8662 angstroms in the stellar spectra using a new Ca II triplet calibration to
[Ca/H]. The two galaxies have different average [Ca/H] values of -1.34 +/- 0.02
for Leo I and -1.65 +/- 0.02 for LeoII with intrinsic abundance dispersions of
1.2 and 1.0 dex, respectively. The typical random and total errors in derived
abundances are 0.10 and 0.17 dex per star. For comparison to existing
literature, we also converted our Ca II measurements to [Fe/H] on the scale of
Carretta and Gratton (1997) though we discuss why this may not be the best
determinant of metallicity; Leo I has a mean [Fe/H] = -1.34 and Leo II has a
mean [Fe/H] = -1.59. The metallicity distribution function of Leo I is
approximately Gaussian in shape with an excess at the metal-rich end, while
that of Leo II shows an abrupt cutoff at the metal-rich end. The lower mean
metallicity of Leo II is consistent with the fact that it has a lower
luminosity, hence lower total mass, than Leo I; thus the evolution of Leo II
may have been affected more by mass lost in galactic winds. We compare our
observed metallicity distribution functions to those inferred by Dolphin (2002)
from modelling of deep CMDs obtained with the Hubble Space Telescope. The
models predict a median metallicity that is systematically more metal-rich than
observed, by 0.36 dex in the Leo I dSph, and by 0.49 dex in the Leo II dSph. We
show that differences this large are not likely caused by non-solar [Ca/Fe] in
the dSph stars.


title:
M-lines characterization of selenide and telluride waveguides for
  mid-infrared interferometry

abstract:
  Nulling interferometry is an astronomical technique that combines equal
wavefronts to achieve a deep rejection ratio of an on-axis star, and that could
permit to detect Earth-like planets in the mid-infrared band 5 -- 20 microns.
Similarly to what is done in the near-infrared, high frequencies spatial
filtering of the incoming beams can be achieved using single-mode waveguides
operating in the mid-infrared. An appreciable reduction of the instrumental
complexity is also possible using integrated optics (IO) devices in this
spectral range. The relative lack of single-mode guided optics in the
mid-infrared has motivated the present technological study to demonstrate the
feasibility of dielectric waveguides functioning at longer wavelengths. We
propose to use selenide and telluride components to pursue the development of
more complex IO functions.


title: Angular power spectrum of CMB anisotropy from WMAP

abstract:
  The remarkable improvement in the estimates of different cosmological
parameters in recent years has been largely spearheaded by accurate
measurements of the angular power spectrum of Cosmic Microwave Background (CMB)
radiation. This has required removal of foreground contamination as well as
detector noise bias with reliability and precision. Recently, a novel
model-independent method for the estimation of CMB angular power spectrum from
multi-frequency observations has been proposed and implemented on the first
year WMAP (WMAP-1) data by Saha et al.~2006. We review the results from WMAP-1
and also present the new angular power spectrum based on three years of the
WMAP data (WMAP-3). Previous estimates have depended on foreground templates
built using extraneous observational input to remove foreground contamination.
This is the first demonstration that the CMB angular spectrum can be reliably
estimated with precision from a self contained analysis of the WMAP data. The
primary product of WMAP are the observations of CMB in 10 independent
difference assemblies (DA) distributed over 5 frequency bands that have
uncorrelated noise. Our method utilizes maximum information available within
WMAP data by linearly combining DA maps from different frequencies to remove
foregrounds and estimating the power spectrum from the 24 cross power spectra
of clean maps that have independent noise. An important merit of the method is
that the expected residual power from unresolved point sources is significantly
tempered to a constant offset at large multipoles (in contrast to the ~l^2
contribution expected from a Poisson distribution) leading to a small
correction at large multipoles. Hence, the power spectrum estimates are less
susceptible to uncertainties in the model of point sources.


title: Chemically peculiar stars in the Large Magellanic Cloud

abstract:
  The detection of magnetic chemically peculiar (CP2) stars in open clusters of
extragalactic systems can give observational answers to many unsolved
questions. The mean percentage of CP2 stars in the Milky Way is of the order of
5% for the spectral range from early B- to F-type, luminosity class V objects.
The origin of the CP2 phenomenon seems to be closely connected to the overall
metallicity and global magnetic field environment. The theoretical models are
still only tested by observations in the Milky Way. It is therefore essential
to provide high quality observations in rather different global environments.
The young clusters NGC 2136/7 were observed in the Delta a photometric system.
This intermediate band photometric system samples the depth of the 520nm flux
depression by comparing the flux at the center with the adjacent regions with
bandwidths of 11nm to 23nm. The Delta a photometric system is most suitable for
detecting CP2 stars with high efficiency, but is also capable of detecting a
small percentage of non-magnetic CP objects. We present high precision
photometric Delta a observations of 417 objects in NGC 2136/7 and its
surrounding field, of which five turned out to be bona fide magnetic CP stars.
In addition, we discovered two Be/Ae stars. From our investigations of NGC
1711, NGC 1866, NGC 2136/7, their surroundings, and one independent field of
the LMC population, we derive an occurrence of classical chemically peculiar
stars of 2.2(6)% in the LMC, which is only half the value found in the Milky
Way. The mass and age distribution of the photometrically detected CP stars is
not different from that of similar objects in galactic open clusters.


title: A probable stellar solution to the cosmological lithium discrepancy

abstract:
  The measurement of the cosmic microwave background has strongly constrained
the cosmological parameters of the Universe. When the measured density of
baryons (ordinary matter) is combined with standard Big Bang nucleosynthesis
calculations, the amounts of hydrogen, helium and lithium produced shortly
after the Big Bang can be predicted with unprecedented precision. The predicted
primordial lithium abundance is a factor of two to three higher than the value
measured in the atmospheres of old stars. With estimated errors of 10 to 25%,
this cosmological lithium discrepancy seriously challenges our understanding of
stellar physics, Big Bang nucleosynthesis or both. Certain modifications to
nucleosynthesis have been proposed, but found experimentally not to be viable.
Diffusion theory, however, predicts atmospheric abundances of stars to vary
with time, which offers a possible explanation of the discrepancy. Here we
report spectroscopic observations of stars in the metalpoor globular cluster
NGC 6397 that reveal trends of atmospheric abundance with evolutionary stage
for various elements. These element-specific trends are reproduced by
stellar-evolution models with diffusion and turbulent mixing. We thus conclude
that diffusion is predominantly responsible for the low apparent stellar
lithium abundance in the atmospheres of old stars by transporting the lithium
deep into the star.


title:
The Cosmological History of Accretion onto Dark Halos and Supermassive
  Black Holes

abstract:
  Aims: We investigate the cosmological growth of dark halos and follow the
consequences of coeval growth for the accretion history of associated
supermassive black holes. Methods: The Press-Schechter approximation is used to
obtain an analytic expression for the mean rate of growth of dark matter halos.
Dark halo accretion rates are compared with numerical work and the consequences
for understanding AGN evolution are described. Results: The mean accretion rate
onto dark matter halos is shown to have a simple analytic form that agrees with
previous numerical work and that may easily be calculated for a wide range of
halo mass, redshift and cosmological parameters. The result offers a
significant improvement over published fitting formulae deduced from merger
trees. We then consider the growth of associated supermassive black holes, and
make a basic test of the simple hypothesis of `Pure Coeval Evolution' (PCE) in
which, on average, black hole growth tracks dark halo growth. We demonstrate
that both the absolute value of the integrated AGN bolometric luminosity
density and its cosmological evolution derived from hard X-ray surveys are
well-reproduced by PCE. Excellent agreement is found at z >~ 0.5, although the
observed luminosity density drops by a factor 2 compared with PCE by z=0: black
hole growth appears to decouple from halo growth at low redshifts, and this may
be related to the phenomenon of `cosmic downsizing'. Overall, AGN evolution
appears either to be caused by or to be closely linked to the slow-down in the
growth of cosmic structure. We also discuss the mean Eddington ratio averaged
over all galaxies, which is predicted to show strong evolution to higher values
with redshift.


title:
VLT/GIRAFFE spectroscopic observations of the metal-poor blue compact
  dwarf galaxy SBS 0335-052E

abstract:
  We present two-dimensional spectroscopy of the extremely metal-deficient blue
compact dwarf (BCD) galaxy SBS 0335-052E aiming to studyphysical conditions,
element abundances and kinematical properties of the ionised gas in this
galaxy. Observations were obtained in the spectral range 3620-9400A with the
imaging spectrograph GIRAFFE installed on the UT2 of the Very Large Telescope
(VLT). These observations are the first ones carried out so far with GIRAFFE in
the ARGUS mode which allows to obtain simultaneously 308 spectra covering a
11.4"x7.3" region. We produced images of SBS 0335-052E in the continuum and in
emission lines of different stages of excitation. We find that while the
maximum of emission in the majority of lines, including the strong lines Hbeta
4861A, Halpha 6563A, [OIII] 4363,5007A, [OII] 3726,3729A, coincides with the
youngest south-eastern star clusters 1 and 2, the emission of HeII 4686A line
is offset to the more evolved north-west clusters 4,5. This suggests that hard
ionising radiation responsible for the HeII 4686A emission is not related to
the most massive youngest stars, but rather is connected with fast radiative
shocks. This conclusion is supported by the kinematical properties of the
ionised gas from the different emission lines as the velocity dispersion in the
HeII 4686A line is systematically higher, by ~50%-100%, than that in other
lines. The variations of the emission line profiles suggest the presence of an
ionised gas outflow in the direction perpendicular to the galaxy disk.
(abridged)


title:
Local helioseismology and correlation tracking analysis of surface
  structures in realistic simulations of solar convection

abstract:
  We apply time-distance helioseismology, local correlation tracking and
Fourier spatial-temporal filtering methods to realistic supergranule scale
simulations of solar convection and compare the results with high-resolution
observations from the SOHO Michelson Doppler Imager (MDI). Our objective is to
investigate the surface and sub-surface convective structures and test
helioseismic measurements. The size and grid of the computational domain are
sufficient to resolve various convective scales from granulation to
supergranulation. The spatial velocity spectrum is approximately a power law
for scales larger than granules, with a continuous decrease in velocity
amplitude with increasing size. Aside from granulation no special scales exist,
although a small enhancement in power at supergranulation scales can be seen.
We calculate the time-distance diagram for f- and p-modes and show that it is
consistent with the SOHO/MDI observations. From the simulation data we
calculate travel time maps for surface gravity waves (f-mode). We also apply
correlation tracking to the simulated vertical velocity in the photosphere to
calculate the corresponding horizontal flows. We compare both of these to the
actual large-scale (filtered) simulation velocities. All three methods reveal
similar large scale convective patterns and provide an initial test of
time-distance methods.


title:
Direct Measurement of Neutron-Star Recoil in the Oxygen-Rich Supernova
  Remnant Puppis A

abstract:
  A sequence of three Chandra X-ray Observatory High Resolution Camera images
taken over a span of five years reveals arc-second-scale displacement of RX
J0822-4300, the stellar remnant (presumably a neutron star) near the center of
the Puppis A supernova remnant. We measure its proper motion to be
0.165+/-0.025 arcsec/yr toward the west-southwest. At a distance of 2 kpc, this
corresponds to a transverse space velocity of ~1600 km/s. The space velocity is
consistent with the explosion center inferred from proper motions of the
oxygen-rich optical filaments, and confirms the idea that Puppis A resulted
from an asymmetric explosion accompanied by a kick that imparted roughly
3*10^49 ergs of kinetic energy (some 3 percent of the kinetic energy for a
typical supernova) to the stellar remnant. We discuss constraints on
core-collapse supernova models that have been proposed to explain neutron star
kick velocities.


title:
Sterile neutrinos, lepton asymmetries, primordial elements: how much of
  each?

abstract:
  We investigate quantitatively the extent to which having a primordial
leptonic asymmetry (n_nu \neq n_nubar) relaxes the bounds on light sterile
neutrinos imposed by BBN and LSS. We adopt a few assumptions that allow us to
solve the neutrino evolution equations over a broad range of mixing parameters
and asymmetries. For the general cases of sterile mixing with the electron or
muon neutrino, we identify the regions that can be reopened. For the particular
case of a LSND-like sterile neutrino, soon to be rejected or confirmed by
MiniBooNE, we find that an asymmetry of the order of 10^-4 is needed to lift
the conflicts with cosmology.


title:
Star formation triggered by SN explosions: an application to the stellar
  association of $\beta$ Pictoris

abstract:
  In the present study, considering the physical conditions that are relevant
in interactions between supernova remnants (SNRs) and dense molecular clouds
for triggering star formation we have built a diagram of SNR radius versus
cloud density in which the constraints above delineate a shaded zone where star
formation is allowed. We have also performed fully 3-D radiatively cooling
numerical simulations of the impact between SNRs and clouds under different
initial conditions in order to follow the initial steps of these interactions.
We determine the conditions that may lead either to cloud collapse and star
formation or to complete cloud destruction and find that the numerical results
are consistent with those of the SNR-cloud density diagram. Finally, we have
applied the results above to the $\beta-$Pictoris stellar association which is
composed of low mass Post-T Tauri stars with an age of 11 Myr. It has been
recently suggested that its formation could have been triggered by the shock
wave produced by a SN explosion localized at a distance of about 62 pc that may
have occurred either in the Lower Centaurus Crux (LCC) or in the Upper
Centaurus Lupus (UCL) which are both nearby older subgroups of that association
(Ortega and co-workers). Using the results of the analysis above we have shown
that the suggested origin for the young association at the proposed distance is
plausible only for a very restricted range of initial conditions for the parent
molecular cloud, i.e., a cloud with a radius of the order of 10 pc and density
of the order of 20 cm$^{-3}$ and a temperature of the order of 50$-$100 K.


title:
Extremal free energy in a simple Mean Field Theory for a Coupled
  Barotropic fluid - Rotating Sphere System

abstract:
  A family of spin-lattice models are derived as convergent finite dimensional
approximations to the rest frame kinetic energy of a barotropic fluid coupled
to a massive rotating sphere. In not fixing the angular momentum of the fluid
component, there is no Hamiltonian equations of motion of the fluid component
of the coupled system. This family is used to formulate a statistical
equilibrium model for the energy - relative enstrophy theory of the coupled
barotropic fluid - rotating sphere system, known as the spherical model, which
because of its microcanonical constraint on relative enstrophy, does not have
the low temperature defect of the classical energy - enstrophy theory. This
approach differs from previous works and through the quantum - classical
mapping between quantum field theory in spatial dimension $d$ and classical
statistical mechanics in dimension $d+1,$ provides a new example of Feynman's
generalization of the Least Action Principle to problems that do not have a
standard Lagrangian or Hamiltonian. A simple mean field theory for this
statistical equlibrium model is formulated and solved, providing precise
conditions on the planetary spin and relative enstrophy in order for phase
transitions to occur at positive and negative critical temperatures, $T_{+}$
and $T_{-}.$


title: On the Size of HII Regions around High Redshift Quasars

abstract:
  We investigate the possibility of constraining the ionization state of the
intergalactic medium (IGM) close to the end of reionization (z ~ 6) by
measuring the size of the HII regions in high-z quasars spectra. We perform a
combination of multiphase smoothed particle hydrodynamics (SPH) and 3D
radiative transfer (RT) simulations to reliably predict the properties of
typical high-z quasar HII regions, embedded in a partly neutral IGM (x_HI=0.1).
In this work we assume a fixed configuration for the quasar lifetime and
luminosity, i.e. t_Q=10^7 yr and N_gamma=5.2 10^56 s-1. From the analysis of
mock spectra along lines of sight through the simulated QSO environment, we
find that the HII region size derived from quasar spectra is on average 30 per
cent smaller than the physical one. Additional maximum likelihood analysis
shows that this offset induces an overestimate of the neutral hydrogen
fraction, x_HI, by a factor of 3. By applying the same statistical method to a
sample of observed QSOs our study favors a mostly ionized (x_HI < 0.06)
universe at z=6.1.


title: Studying Millisecond Pulsars in X-rays

abstract:
  Millisecond pulsars represent an evolutionarily distinct group among
rotation-powered pulsars. Outside the radio band, the soft X-ray range ($\sim
0.1$--10 keV) is most suitable for studying radiative mechanisms operating in
these fascinating objects. X-ray observations revealed diverse properties of
emission from millisecond pulsars. For the most of them, the bulk of radiation
is of a thermal origin, emitted from small spots (polar caps) on the neutron
star surface heated by relativistic particles produced in pulsar acceleration
zones. On the other hand, a few other very fast rotating pulsars exhibit almost
pure nonthermal emission generated, most probably, in pulsar magnetospheres.
There are also examples of nonthermal emission detected from X-ray nebulae
powered by millisecond pulsars, as well as from pulsar winds shocked in binary
systems with millisecond pulsars as companions. These and other most important
results obtained from X-ray observations of millisecond pulsars are reviewed in
this paper, as well as results from the search for millisecond pulsations in
  X-ray flux of the radio-quite neutron star RX J1856.5-3754.


title:
A new Cepheid distance to the maser-host galaxy NGC 4258 and its
  implications for the Hubble Constant

abstract:
  We present initial results from a time-series BVI survey of two fields in NGC
4258 using the Advanced Camera for Surveys onboard the Hubble Space Telescope.
This galaxy was selected because of its accurate maser-based distance, which is
anticipated to have a total uncertainty of ~3%. The goal of the HST
observations is to provide an absolute calibration of the Cepheid Distance
Scale and to measure its dependence on chemical abundance (the so-called
"metallicity effect").
  We carried out observations of two fields at different galactocentric
distances with a mean abundance difference of 0.5 dex. We discovered a total of
281 Cepheids with periods ranging from 4 to 45 days (the duration of our
observing window). We determine a Cepheid distance modulus for NGC 4258
(relative to the LMC) of 10.88 +- 0.04 (random) +- 0.05 (systematic) mag. Given
the published maser distance to the galaxy, this implies \mu (LMC)=18.41 +-
0.10 (r) +- 0.13 (s) mag or D(LMC)= 48.1 +- 2.3 (r) +- 2.9 (s) kpc. We measure
a metallicity effect of \gamma=-0.29 +- 0.09 (r) +- 0.05 (s) mag/dex. We see no
evidence for a variation in the slope of the Period-Luminosity relation as a
function of abundance.
  We estimate a Hubble Constant of H_0= 74 +- 3 (r) +- 6 (s) km/s Mpc using a
recent sample of 4 well-observed type Ia SNe and our new calibration of the
Cepheid Distance Scale. It may soon be possible to measure the value of H_0
with a total uncertainty of 5%, with consequent improvement in the
determination of the equation of state of dark energy.


title: Star formation and figure rotation in the early-type galaxy NGC2974

abstract:
  We present Galaxy Evolution Explorer (GALEX) far (FUV) and near (NUV)
ultraviolet imaging of the nearby early-type galaxy NGC2974, along with
complementary ground-based optical imaging. In the ultraviolet, the galaxy
reveals a central spheroid-like component and a newly discovered complete outer
ring of radius 6.2kpc, with suggestions of another partial ring at an even
larger radius. Blue FUV-NUV and UV-optical colours are observed in the centre
of the galaxy and from the outer ring outward, suggesting young stellar
populations (< 1Gyr) and recent star formation in both locations. This is
supported by a simple stellar population model which assumes two bursts of star
formation, allowing us to constrain the age, mass fraction and surface mass
density of the young component pixel by pixel. Overall, the mass fraction of
the young component appears to be just under 1per cent (lower limit,
uncorrected for dust extinction). The additional presence of a nuclear and an
inner ring (radii 1.4 and 2.9kpc, respectively), as traced by [OIII] emission,
suggests ring formation through resonances. All three rings are consistent with
a single pattern speed of $78\pm6$ km/s/kpc, typical of S0 galaxies and only
marginally slower than expected for a fast bar if traced by a small observed
surface brightness plateau. This thus suggests that star formation and
morphological evolution in NGC2974 at the present epoch are primarily driven by
a rotating asymmetry (probably a large-scale bar), despite the standard
classification of NGC2974 as an E4 elliptical.


title: Infall, Fragmentation and Outflow in Sgr B2

abstract:
  Observations of H$_{2}$CO lines and continuum at 1.3 mm towards Sgr B2(N) and
Sgr B2(M) cores were carried out with the SMA. We imaged H$_{2}$CO line
absorption against the continuum cores and the surrounding line emission
clumps. The results show that the majority of the dense gas is falling into the
major cores where massive stars have been formed. The filaments and clumps of
the continuum and gas are detected outside of Sgr B2(N) and Sgr B2(M) cores.
Both the spectra and moment analysis show the presence of outflows from Sgr
B2(M) cores. The H$_{2}$CO gas in the red-shifted outflow of Sgr B2(M) appears
to be excited by a non-LTE process which might be related to the shocks in the
outflow.


title:
The Nitrogen-to-Oxygen evolution in galaxies: the role of the star
  formation rate

abstract:
  The main objective of the present work is to ckeck if the star formation
efficiency plays a relevant role in the evolution of the relative abundance
N/O. We analyze the evolution of the nitrogen-to-oxygen ratio as predicted by a
set of computed theoretical models of simulated galaxies with different total
masses which are evolved assuming different collapse time scales and different
star formation efficiencies, thus producing different star formation histories.
The stellar yield set we use for all of them (Gavil\'{a}n et al. 2005) have an
important contribution of primary nitrogen proceeding from low and intermediate
mass stars. It allows to obtain a dispersion of results in the N/O-O/H plane,
when star formation efficiencies vary, in general agreement with observations.
The model results for the N/O abundance ratio are in good agreement with most
observational data trends: the extragalactic H{\sc ii} regions is well
reproduced with present time resulting abundances and the low N/O values
estimated for high-redshift objects, as well as the higher and constant values
of N/O observed for irregular and dwarf galaxies or halo stars, can be
simultaneously obtained with our models at the same low oxygen abundances. We
conclude that differences in the star formation history of galaxies and regions
within them are a key factor to explain the data in the N/O-O/H plane.


title: GCIRS16SW: a massive eclipsing binary in the Galactic Center

abstract:
  We report on the spectroscopic monitoring of GCIRS16SW, an Ofpe/WN9 star and
LBV candidate in the central parsec of the Galaxy. SINFONI observations show
strong daily spectroscopic changes in the K band. Radial velocities are derived
from the HeI 2.112 um line complex and vary regularly with a period of 19.45
days, indicating that the star is most likely an eclipsing binary. Under
various assumptions, we are able to derive a mass of ~ 50 Msun for each
component.


title: Triggered Star Formation on the Border of the Orion-Eridanus Superbubble

abstract:
  A census of classical T Tauri stars and Herbig Ae/Be stars has been performed
around the Orion-Eridanus Superbubble which is ionized and created by the Ori
OB1 association. This sample is used to study the spatial distribution of
newborn stars, hence the recent star formation sequence, in the region that
includes two giant molecular clouds (Orion A and B) and additional smaller
clouds (NGC 2149, GN 05.51.4, VdB 64, the Crossbones, the Northern Filament,
LDN 1551, LDN 1558, and LDN 1563). Most of the molecular clouds are located on
the border of the Superbubble, and associated with H-alpha filaments and star
formation activity, except the Northern Filament which is probably located
outside the Superbubble. This suggests that while star formation progresses
from the oldest Ori OB1a subgroup to 1b, 1c and 1d, the Superbubble compresses
and initiates starbirth in clouds such as NGC 2149, GN 05.51.4, VdB 64, and the
Crossbones, which are located more than one hundred pc away from the center of
the Superbubble, and even in clouds some two hundred pc away, i.e., in LDN
1551, LDN 1558, and LDN 1563. A superbubble appears to have potentially a
long-range influence in triggering next-generation star formation in an OB
association.


title:
The 1 um discontinuity in the Extragalactic Background Light spectrum:
  an artefact of foreground subtraction

abstract:
  Several recent papers claim the detection of a near infrared Extragalactic
Background Light (EBL) intensity at 1.25 - 4 um that exceeds the integrated
light of galaxies by factors of >3. When combined with a claimed optical
detection of the EBL at 0.80 um the EBL excess emission spectrum has a
discontinuity at ~1 um. This discontinuity has given rise to an interpretation
in terms of ultraviolet radiation emanating from the first generation of
massive stars at redshifts of 7 - 20 (so called Population III stars). The
interpretation of the NIR excess emission as being of extragalactic origin
depends crucially on the model used in the subtraction of the Zodiacal Light,
the dominant foreground contaminant. We estimate the Zodiacal Light at 0.80 um
using on the one hand the measurement by Bernstein et al.,2002, ApJ, 571,85),
with corrections for some omitted effects of atmospheric scattering and
calibration, and on the other hand the model of Kelsall et al.,1998, ApJ,
508,44). There is in neither case any evidence for a step in the EBL at ~1 um.
We emphasize that in order to avoid systematic effects it is essential to use
the same Zodiacal Light model (Kelsall et al. 1998) for both the NIR (1.25 - 4
um) and optical (0.80 um) data. We emphasize, however, that our analysis does
not allow a statement on the overall level of the NIR EBL. The contribution of
the Diffuse Galactic Light to the ``EBL excess'' emission is estimated. It is
found to be significant at 3 - 4 um and should be carefully evaluated in future
measurements which aim at detecting an EBL signal at the level of ~10 nW m^-2
sr^-1, i.e. at the level of the integrated light of (known) galaxies.


title:
Plateau de Bure Interferometer Observations of the Disk and Outflow of
  HH30

abstract:
  HH30 is a well-known Pre-Main-Sequence star in Taurus. HST observations have
revealed a flared, edge-on disk driving a highly-collimated optical jet, making
this object a case study for the disk-jet-outflow paradigm. We obtained high
angular resolution (about 1") observations of the dust continuum at 2.7 and 1.3
mm, and of the 12CO(2-1), 13CO(2-1) & (1-0), C18O(1-0) emissions around HH30. A
standard disk model is used to fit the 13CO(2-1) uv-plane visibilities and
derive the disk properties, and the stellar mass. It results that HH30 is a low
mass TTauri of spectral type around M1 and age 1 to 4 Myrs, surrounded by a
medium size Keplerian disk, of mass around 4e-3 Msun and outer radius 420 AU.
The disk rotation vector points toward the North-Eastern jet. Using a distance
of 140 pc, we deduce a stellar mass of 0.45 Msun. A highly asymmetric outflow
originates from the inner parts of the disk. It presents to first order a
conical morphology with a 30 degree half opening angle and a constant (12 km/s)
radial velocity field. Outflow rotation was searched for but not found. These
observations do not enable to assign the origin of the molecular outflow to
entrainment by the optical jet or to a disk wind. In the latter case, the upper
limit of the outflow rotation velocity implies an origin in the inner 15 AU of
the disk.


title:
A dip in the UHECR spectrum and the transition from galactic to
  extragalactic cosmic rays

abstract:
  The dip is a feature in the diffuse spectrum of ultra-high energy (UHE)
protons caused by electron-positron pair production on the cosmic microwave
background (CMB) radiation. For a power-law generation spectrum $E^{-2.7}$, the
calculated position and shape of the dip is confirmed with high accuracy by the
spectra observed by the Akeno-AGASA, HiRes, Yakutsk and Fly's Eye detectors.
When the particle energies, measured in these detectors, are calibrated by the
dip, their fluxes agree with a remarkable accuracy. The predicted shape of the
dip is quite robust. The dip is only modified strongly when the fraction of
nuclei heavier than protons is high at injection, which imposes some
restrictions on the mechanisms of acceleration operating in UHECR sources. The
existence of the dip, confirmed by observations, implies that the transition
from galactic to extragalactic cosmic rays occurs at $E \lsim 1\times 10^{18}$
eV. We show that at energies lower than a characteristic value $E_{\rm
cr}\approx 1\times 10^{18}$ eV, the spectrum of extragalactic cosmic rays
flattens in all cases of interest, and it provides a natural transition to a
steeper galactic cosmic ray spectrum. This transition occurs at some energy
below $E_{\rm cr}$, corresponding to the position of the so-called second knee.
We discuss extensively the constraints on this model imposed by current
knowledge of acceleration processes and sources of UHECR and compare it with
the traditional model of transition at the ankle.


title: A Young Open Cluster Surrounding V838 Monocerotis

abstract:
  During a program of spectroscopic monitoring of V838 Mon, we serendipitously
discovered that a neighboring 16th-mag star is of type B. We then carried out a
spectroscopic survey of other stars in the vicinity, revealing two more B-type
stars, all within 45" of V838 Mon. We have determined the distance to this
sparse, young cluster, based on spectral classification and photometric
main-sequence fitting of the three B stars. The distance is found to be
6.2+-1.2 kpc, in excellent agreement with the geometric distance to V838 Mon of
5.9 kpc obtained from Hubble Space Telescope polarimetry of the light echoes.
The cluster's age is less than 25 Myr.
  The absolute luminosity of V838 Mon during its outburst, based on our
distance measurement, was very similar to that of M31 RV, an object in the
bulge of M31 that was also a cool supergiant throughout its eruption in 1988.
However, there is no young population at the site of M31 RV.
  It does not appear possible to form a nova-like cataclysmic binary system
within the young age of the V838 Mon cluster, and the lack of a young
population surrounding M31 RV suggests that the outburst mechanism does not
require a massive progenitor. These considerations appear to leave
stellar-collision or merger scenarios as one of the remaining viable
explanations for the outbursts of V838 Mon and M31 RV.


title:
Effect of motions in prominences on the helium resonance lines in the
  extreme ultraviolet

abstract:
  We aim at studying the effect of radial motions on the spectrum emitted by
moving prominences in the helium resonance lines and at facilitating the
interpretation of observations, in order to improve our understanding of these
dynamic structures. We develop our non-local thermodynamic equilibrium
radiative transfer code formerly used for the study of quiescent prominences.
The new numerical code is now able to solve the statistical equilibrium and
radiative transfer equations in the non-static case by using velocity-dependent
boundary conditions for the solution of the radiative transfer problem. This
first study investigates the effects of different physical conditions
(temperature, pressure, geometrical thickness) on the emergent helium
radiation. The motion of the prominence plasma induces a Doppler dimming effect
on the resonance lines of He I and He II. The velocity effects are particularly
important for the He II 304 A line as it is mostly formed by resonant diffusion
of incident radiation under prominence conditions. The He I resonance lines at
584 and 537 A also show some sensitivity to the motion of the plasma, all the
more when thermal emission is not too important in these lines. We also show
that it is necessary to consider partial redistribution in frequency for the
scattering of the incident radiation. This set of helium lines offers strong
diagnostic possibilities that can be exploited with the SOHO spectrometers and
with the EIS spectrometer on board the Hinode satellite. The addition of other
helium lines and of lines from other elements (in particular hydrogen) in the
diagnostics will further enhance the strength of the method.


title:
Hubble Space Telescope Observations of the Light Echo around V838
  Monocerotis

abstract:
  The outburst of V838 Monocerotis in early 2002, and the subsequent appearance
of its light echoes, occurred just before the installation of the Advanced
Camera for Surveys into the Hubble Space Telescope (HST). This fortunate
sequence of events has allowed us to obtain spectacular HST images of the
echoes, yielding not only pictures of extraordinary beauty, but also providing
unique scientific information. Our team has used the HST images to provide a
direct geometrical distance to V838 Mon, based on polarimetric imaging, and
limits on the distance based on the apparent angular expansion rates. Several
morphological features seen in the HST images strongly suggest that the
illuminated dust was ejected from the star in a previous outburst, similar to
the current one. In particular, a "double-helix" feature points exactly back to
the star. Moreover, three-dimensional mapping of the outer edges of the dust
suggests an overall ellipsoidal shape, centered on V838 Mon itself. And the
appearance of the light echo in the most recent Hubble images is remarkably
similar to that of a well-known planetary nebula, M27. Future work on the HST
images will include an analysis of interstellar-dust physics, in a situation
where the scattering angle and illumination are unambiguously known, and
visualization of a fully three-dimensional map of the dust distribution.