title: Metals in the Intergalactic Medium

abstract:
  We use high spectral resolution (R=45000) and high signal-to-noise ratio (S/N
\~ 35-70 per pixel) spectra of 19 high-redshift (2.1<z_em<3.2) quasars to
investigate the metal content of the low-density intergalactic medium using
pixel-by-pixel procedures. This high quality homogeneous survey gives the
possibility to statistically search for metals at HI optical depths smaller
than unity. We find that the gas is enriched in carbon and oxygen for neutral
hydrogen optical depths tau(HI)>1. Our observations strongly suggest that the
CIV/HI ratio decreases with decreasing tau(HI) with
log[tau(CIV)]=1.3xlog[tau(HI)]-3.2. We do not detect CIV absorption
statistically associated with gas of tau(HI)<1. However, we observe that a
small fraction of the low density gas is associated with strong metal lines as
a probable consequence of the IGM enrichment being highly inhomogeneous. We
detect the presence of OVI down to tau(HI)~0.2 with log[tau(OVI)/tau(HI)] -2.0.
We show that OVI absorption in the lowest density gas is located within ~300
km/s from strong HI lines. This suggests that this OVI phase may be part of
winds flowing away from overdense regions. This effect is more important at the
largest redshifts (z>2.4). Therefore, at the limit of present surveys, the
presence of metals in the underdense regions of the IGM is still to be
demonstrated.


title: Asymmetries in the CMB anisotropy field

abstract:
  We report on the results from two independent but complementary statistical
analyses of the WMAP first-year data, based on the power spectrum and N-point
correlation functions. We focus on large and intermediate scales (larger than
about 3 degrees) and compare the observed data against Monte Carlo ensembles
with WMAP-like properties. In both analyses, we measure the amplitudes of the
large-scale fluctuations on opposing hemispheres and study the ratio of the two
amplitudes. The power-spectrum analysis shows that this ratio for WMAP, as
measured along the axis of maximum asymmetry, is high at the 95%-99% level
(depending on the particular multipole range included). The axis of maximum
asymmetry of the WMAP data is weakly dependent on the multipole range under
consideration but tends to lie close to the ecliptic axis. In the N-point
correlation function analysis we focus on the northern and southern hemispheres
defined in ecliptic coordinates, and we find that the ratio of the large-scale
fluctuation amplitudes is high at the 98%-99% level. Furthermore, the results
are stable with respect to choice of Galactic cut and also with respect to
frequency band. A similar asymmetry is found in the COBE-DMR map, and the axis
of maximum asymmetry is close to the one found in the WMAP data.


title:
Gamma-Ray Spectra & Variability of the Crab Nebula Emission Observed by
  BATSE

abstract:
  We report ~ 600 days of BATSE earth-occultation observations of the total
gamma-ray (30 keV to 1.7 MeV) emission from the Crab nebula, between 1991 May
24 (TJD 8400) and 1994 October 2 (TJD 9627). Lightcurves from 35-100, 100-200,
200-300, 300-400, 400-700, and 700-1000 keV, show that positive fluxes were
detected by BATSE in each of these six energy bands at significances of
approximately 31, 20, 9.2, 4.5, 2.6, and 1.3 sigma respectively per day. We
also observed significant flux and spectral variations in the 35-300 keV energy
region, with time scales of days to weeks. The spectra below 300 keV, averaged
over typical CGRO viewing periods of 6-13 days, can be well described by a
broken power law with average indices of ~ 2.1 and ~ 2.4 varying around a
spectral break at ~ 100 keV. Above 300 keV, the long-term averaged spectra,
averaged over three 400 d periods (TJD 8400-8800, 8800-9200, and 9200-9628,
respectively) are well represented by the same power law with index of ~ 2.34
up to ~ 670 keV, plus a hard spectral component extending from ~ 670 keV to ~
1.7 MeV, with a spectral index of ~ 1.75. The latter component could be related
to a complex structure observed by COMPTEL in the 0.7-3 MeV range. Above 3 MeV,
the extrapolation of the power-law continuum determined by the low-energy BATSE
spectrum is consistent with fluxes measured by COMPTEL in the 3-25 MeV range,
and by EGRET from 30-50 MeV. We interpret these results as synchrotron emission
produced by the interaction of particles ejected from the pulsar with the field
in different dynamical regions of the nebula system, as observed recently by
HST, XMM-Newton, and Chandra.


title: H_alpha Emission from High-Velocity Clouds and their Distances

abstract:
  We present deep Halpha spectroscopy towards several high-velocity clouds
(HVCs) which vary in structure from compact (CHVCs) to the Magellanic Stream.
The clouds range from being bright (~640 mR) to having upper limits on the
order of 30 to 70 mR. The Halpha measurements are discussed in relation to
their HI properties and distance constraints are given to each of the complexes
based on f_esc = 6% of the ionizing photons escaping normal to the Galactic
disk (f_escs = 1 - 2% when averaged over solid angle). The results suggest that
many HVCs and CHVCs are within a ~40 kpc radius from the Galaxy and are not
members of the Local Group at megaparsec distances. However, the Magellanic
Stream is inconsistent with this model and needs to be explained. It has bright
Halpha emission and little [NII] emission and appears to fall into a different
category than the currently detected HVCs. This may reflect the lower
metallicities of the Magellanic Clouds compared to the Galaxy, but the strength
of the Halpha emission cannot be explained solely by photoionization from the
Galaxy. The interaction of the Stream with halo gas or the presence of yet
unassociated young stars may assist in ionizing the Stream.


title: A Catalog of Young Stellar Groups and Clusters Within 1kpc of the Sun

abstract:
  We present a catalog of near-infrared surveys of young (<= a few 10^6 yr)
stellar groups and clusters within 1 kpc from the Sun, based on an extensive
search of the literature from the past ten years. We find 143 surveys from 69
published articles, covering 73 different regions. The number distribution of
stars in a region has a median of 28 and a mean of 100. About 80% of the stars
are in clusters with at least 100 members. By a rough classification of the
groups and clusters based on the number of their associated stars, we show that
most of the stars form in large clusters. The spatial distribution of cataloged
regions in the Galactic plane shows a relative lack of observed stellar groups
and clusters in the range 270 deg < l < 60 deg of Galactic longitude,
reflecting our location between the Local and Sagittarius arms. This
compilation is intended as a useful resource for future studies of nearby young
regions of multiple star formation.


title:
VLA and BIMA observations toward the exciting source of the massive
  HH~80-81 outflow

abstract:
  We present high angular resolution VLA and BIMA observations of NH$_3$,
HCO$^+$, HCN and SO molecular emission and 1.4, 3.5 and 7 mm continuum emission
toward the exciting source of the HH~80-81 system. This object is one of the
few massive protostars known to be driving a collimated outflow. We report the
first detection of SO 5$_5$--4$_4$ molecular emission toward the exciting
source of HH 80-81, suggesting that this transition may be a good tracer of
molecular gas near massive protostars. We also detected toward this source dust
continuum emission at 1.4 and 3.5 mm. From the SO molecular emission and the
dust emission we roughly estimated that the molecular mass associated with the
circumstellar surroundings of the exciting source of the thermal jet is in the
range 1 -- 3 M$_\odot$. Weak and broad (2,2) ammonia emission was also found in
the direction of the jet suggesting the presence of small amounts of molecular
gas at high temperatures ($>$ 50 K).
  The VLA observations show the presence of three ammonia components toward the
HH 80-81 region. The brightest component peaks at $\sim8^{\prime\prime}$ to the
NE of the thermal jet and is associated with the H$_2$O maser spots in the
region. A second ammonia clump is located about 25$^{\prime\prime}$ to the NE
of the jet and is associated with class I methanol masers. The third ammonia
component is located 1$^\prime$ to the south from the thermal jet and may be a
molecular core yet without stellar formation. The BIMA observations show that
the strongest emission in the HCO$^+$ and HCN lines originate close to the
H$_2$O maser, and cover the same spatial region and velocity range as the
brightest ammonia component.


title:
Survival of Terrestrial Planets in the Presence of Giant Planet
  Migration

abstract:
  The presence of ``Hot Jupiters'', Jovian mass planets with very short orbital
periods orbiting nearby main sequence stars, has been proposed to be primarily
due to the orbital migration of planets formed in orbits initially much further
from the parent star. The migration of giant planets would have profound
effects on the evolution of inner terrestrial planets in these systems, and
previous analyses have assumed that no terrestrial planets survive after
migration has occurred. We present numerical simulations showing that a
significant fraction of terrestrial planets could survive the migration
process, eventually returning to circular orbits relatively close to their
original positions. A fraction of the final orbits are in the Habitable Zone,
suggesting that planetary systems with close-in giant planets are viable
targets for searches for Earth-like habitable planets around other stars.


title: Nonlinear electrodynamics and the surface redshift of pulsars

abstract:
  Currently is argued that the best method of determining the neutron star (NS)
fundamental properties is by measuring the {\it gravitational redshift} ($z$)
of spectral lines produced in the star photosphere. Measurement of $z$ at the
star surface provides a unique insight on the NS mass-to-radius relation and
thus on its equation of state (EoS), which reflects the physics of the strong
interaction between particles making up the star. Evidence for such a
measurement has been provided quite recently by Cottam, Paerels & Mendez
(2002), and also by Sanwal et {\it al.} (2002). Here we argue that although the
quoted observations are undisputed for canonical pulsars, they could be
misidentified if the NS is endowed with a super strong $B$ as in the so-called
magnetars (Duncan & Thompson 1992) and strange quark magnetars (Zhang 2002), as
in the spectral line discovered by Ibrahim et {\it al.} (2002;2003). The source
of this new "confusion" redshift is related to nonlinear electrodynamics
(NLEDs) effects.


title: Cyclical period changes in the dwarf novae V2051 Oph and V4140 Sgr

abstract:
  We report the identification of cyclical changes in the orbital period of the
eclipsing dwarf novae V2051 Ophiuchi and V4140 Sagitarii. We used sets of white
dwarf mid-eclipse timings to construct observed-minus-calculated diagrams
covering, respectively, 25 and 16 years of observations. The V2051 Oph data
present cyclical variations that can be fitted by a linear plus sinusoidal
function with period 22 +/- 2 yr and amplitude 17 +/- 3 s. The statistical
significance of this period by an F-test is larger than 99.9 per cent. The
V4140 Sgr data present cyclical variations of similar amplitude and period 6.9
+/- 0.3 yr which are statistically significant at the 99.7 per cent level. We
derive upper limits for secular period changes of |dP/dt| < 3x10^{-12} and
|dP/dt| < 1.8x10^{-11}, respectively for V2051 Oph and V4140 Sgr. We combined
our results with those in the literature to construct a diagram of the
amplitude versus period of the modulation for a sample of 11 eclipsing
cataclysmic variables (CVs). If the cyclical period changes are the consequence
of a solar-type magnetic activity cycle in the secondary star, then magnetic
activity is a widespread phenomenon in CVs, being equally common among long-
and short-period systems. This gives independent evidence that the magnetic
field (and activity) of the secondary stars of CVs do not disappear when they
become fully convective. We also find that the fractional cycle period changes
of the short-period CVs are systematically smaller than those of the
long-period CVs.


title: Myths and Truths Concerning Estimation of Power Spectra

abstract:
  It is widely believed that maximum likelihood estimators must be used to
provide optimal estimates of power spectra. Since such estimators require
require of order N_d^3 operations they are computationally prohibitive for N_d
greater than a few tens of thousands. Because of this, a large and
inhomogeneous literature exists on approximate methods of power spectrum
estimation. These range from manifestly sub-optimal, but computationally fast
methods, to near optimal but computationally expensive methods. Furthermore,
much of this literature concentrates on the power spectrum estimates rather
than the equally important problem of deriving an accurate covariance matrix.
In this paper, I consider the problem of estimating the power spectrum of
cosmic microwave background (CMB) anisotropies from large data sets. Various
analytic results on power spectrum estimators are derived, or collated from the
literature, and tested against numerical simulations. An unbiased hybrid
estimator is proposed that combines a maximum likelihood estimator at low
multipoles and pseudo-C_\ell estimates at high multipoles. The hybrid estimator
is computationally fast, nearly optimal over the full range of multipoles, and
returns an accurate and nearly diagonal covariance matrix for realistic
experimental configurations (provided certain conditions on the noise
properties of the experiment are satisfied). It is argued that, in practice,
computationally expensive methods that approximate the N_d^3 maximum likelihood
solution are unlikely to improve on the hybrid estimator, and may actually
perform worse. The results presented here can be generalised to CMB
polarization and to power spectrum estimation using other types of data, such
as galaxy clustering and weak gravitational lensing.


title:
Damped Lyman Alpha Gas Metallicities at Redshifts z=0.9-2.0 from SDSS
  Spectra

abstract:
  Using Sloan Digital Sky Survey (SDSS) early data release spectra, we have
identified 370 MgII absorption systems with MgII 2796 rest equivalent widths >=
1A and redshifts z=0.9-2.2. From our previous and ongoing HST UV spectroscopic
studies, we estimate that the mean neutral hydrogen column density of a system
selected in this manner is N(HI) = 3.6 +/- 1.3 x10^(20) atoms cm^(-2), which
corresponds to the damped Ly-alpha (DLA) regime. We have formed high
signal-to-noise ratio composite spectra using 223 of these systems with
z=0.9-2.0 in order to study the strength of the ZnII and CrII absorption lines
corresponding to this mean neutral hydrogen column density. After making a
correction for missed DLAs, overall we find that [Zn/H] = -1.13 +/- 0.19. We
find [Cr/Zn] = -0.45 +/- 0.13, which indicates that approx 65% of the Cr is
depleted on to grains, but this does not correct for the missed DLAs. We have
also derived Zn and Cr abundances in two kinematic regimes, and within each
regime we consider two redshift intervals. We find trends which indicate that
metallicities are higher in the composites where the absorption has larger
velocity spreads as measured by MgII 2796 rest equivalent width. Larger
velocity spreads may correspond to deeper gravitational potential wells which
represent more massive and chemically evolved structures, and/or regions
associated with winds from starbursting galaxies, also leading to kinematically
broad structures of chemically enriched gas. Within the large velocity spread
regime, we find that at lower redshifts the Zn metallicity is larger and more
Cr is depleted on to grains.


title:
Superwind-driven Intense H$_2$ Emission in NGC 6240 II: Detailed
  Comparison of Kinematical and Morphological Structures of the Warm and Cold
  Molecular Gas

abstract:
  We report on our new analysis of the spatial and kinematical distribution of
warm and cold molecular gas in NGC 6240, which was undertaken to explore the
origin of its unusually luminous H$_2$ emission. By comparing three-dimensional
emission-line data (in space and velocity) of CO (J=2-1) in the radio and H$_2$
in the near infrared, we are able to study the H$_2$ emitting efficiency,
defined in terms of the intensity ratio of H$_2$ to CO [$I$(H$_2$)/$I$(CO)], as
a function of velocity. The integrated H$_2$ emitting efficiency is calculated
by integrating the velocity profile of H$_2$ emitting efficiency in blue, red,
and total (blue + red) velocity regions of the profile. We find that (1) both
the total H$_2$ emitting efficiency and the blue-to-red ratio of the efficiency
are larger in regions surrounding the CO and H$_2$ intensity peaks, and (2) the
H$_2$ emitting efficiency and the kinematical conditions in the warm molecular
gas are closely related to each other. A collision between the molecular gas
concentration and the external superwind outflow from the southern nucleus
seems plausible to explain these characteristics, since it can reproduce the
enhanced emitting efficiency of blueshifted H$_2$ around the molecular gas
concentration, if we assume that the superwind blows from the southern nucleus
toward us, hitting the entire gas concentration from behind. In this model,
internal cloud-cloud collisions within the molecular gas concentration are
enhanced by the interaction with the superwind outflow, and efficient and
intense shock-excited H$_2$ emission is expected as a result of the
cloud-crushing mechanism.


title:
Helical Tomography of an Accretion Disk by Superhump Light Curves of the
  2001 Outburst of WZ Sagittae

abstract:
  A new method for analyzing complex superhump light curves for the 2001
outburst of WZ Sagittae is proposed. The complexity arises because
intrinsically time-varying and non-axisymmetric distributions of superhump
light sources are coupled with the aspect effects around the binary orbital
phase because of its high orbital inclination. The new method can disentangle
these complexities by separating the non-axisymmetric spatial distribution in
the disk from the time variation with the superhump period. It may be called a
helical tomography of an accretion disk because it can reconstruct a series of
disk images (i.e., disk's azimuthal structures) at different superhump phases.
The power spectral data of superhump light curves of the 2001 outburst of WZ
Sge by Patterson et al.(2002,PASP,114,721) are now interpreted under a new
light based on the concept of helical tomography, and the azimuthal wave
numbers of various frequency modes are identified. In particular, a frequency
component, $n\omega_0-\Omega$, where $\omega_0$ and $\Omega$ are the orbital
frequency and a low frequency of the apsidal precession of the eccentric disk,
is understood as an $(n-1)$-armed traveling wave in the disk. A vigorous
excitation of a wave component of $\cos(2\Theta-3\omega_0 t)$ in the first week
of the superhump era of WZ Sge, where $\Theta$ is the azimuthal angle, supports
Lubow's (1991) theory of non-linear wave coupling of the eccentric Lindblad
resonance for the superhump phenomenon. This method can in principle be applied
to other SU UMa stars with high orbital inclination if light curves are fully
covered over the beat cycle.


title:
Relativistic Corrections to the Sunyaev-Zeldovich Effect for Clusters of
  Galaxies. V. Numerical Results for High Electron Temperatures

abstract:
  We present an accurate numerical table for the relativistic corrections to
the thermal Sunyaev-Zeldovich effect for clusters of galaxies. The numerical
results for the relativistic corrections have been obtained by numerical
integration of the collision term of the Boltzmann equation. The numerical
table is provided for the ranges 0.002 <= theta_e <= 0.100 and 0 <= X <= 20,
where theta_e = kT_e/mc^2, X = hbar omega/kT_0, T_e is the electron
temperature, omega is the angular frequency of the photon, and T_0 is the
temperature of the cosmic microwave background radiation. We also present an
accurate analytic fitting formula that reproduces the numerical results with
high precision.


title: Supernovae in Galaxy Clusters

abstract:
  We present the results of several surveys for supernovae (SNe) in galaxy
clusters. SNe discovered in deep, archival HST images were used to measure the
cluster SN Ia rate to z=1. A search for SNe in nearby (0.06 < z < 0.2) Abell
galaxy clusters yielded 15 SNe, 12 of which were spectroscopically confirmed.
Of these, 7 are cluster SNe Ia, which we will use to measure the SN Ia rate in
nearby clusters. This search has also discovered the first convincing examples
of intergalactic SNe. We conclude with a brief description of ongoing and
future cluster SN surveys.


title:
Galaxies Under the Cosmic Microscope: A GMOS Study of the Lensed
  Disk-Galaxy #289 in A2218

abstract:
  In this letter, we exploit the gravitational potential of the rich cluster
A2218 as a magnifying glass. We demonstrate that the magnification due to the
cluster allows us to observe distant background galaxies at a comparable level
of detail to galaxies at z~0.1. Using the GMOS Integral Field Unit on Gemini
North we observed the spatially-resolved [OII](3727) emission line spectrum for
a lensed disk-galaxy at z=1.034. Using a detailed model for the cluster mass
distribution, we are able to correct for the lensing by the cluster and
reconstruct the source morphology. We find that the overall magnification is a
factor of 4.92 +/- 0.15, and the rest-frame absolute I-band magnitude is
M_{I}^{rest} = -22.4 +/- 0.2, where the error bars include conservative
estimates of the uncertainty in the source-plane reconstruction. The
inclination-corrected circular velocity is 206 +/- 18km/s. The galaxy lies very
close to the mean Tully-Fisher relation of present-day spirals. Although our
results are based on a single object, they demonstrate that gravitational
lensing can be viably used to make detailed studies of the evolution of the
structure of distant field galaxies.


title:
A possible signature for quark deconfinement in the compact star in 4U
  1728-34

abstract:
  In a very recent paper Shaposhnikov et al. (ApJ 593, 2003, L35) have
extracted very tight constraints on the radius and the mass for the compact
star in the low mass X-ray binary 4U~1728-34, from the analysis of a set of
Type I X-ray bursts from this source. In the present letter, we perform a
systematic comparison between the mass-radius (MR) relation given by
Shaposhnikov et al., with the theoretical determination of MR curves for
compact stars using some of the most recent and realistic models for the
equation of state for stellar dense matter. Our study clearly reveals that the
semi-empirical MR relation for the compact star in 4U~1728-34 is not compatible
with models of neutrons stars composed of nuclear matter or hyperonic matter,
while it is consistent with strange stars or neutron stars with a core of
deconfined quark matter (hybrid neutron stars).


title: GRB021125: the first GRB imaged by INTEGRAL

abstract:
  In the late afternoon of November 25, 2002 a gamma-ray burst (GRB) was
detected in the partially coded field of view (about 7.3 deg from the centre)
of the imager IBIS on board the INTEGRAL satellite. The instruments on-board
INTEGRAL allowed, for the first time, the observation of the prompt gamma-ray
emission over a broad energy band from 15 to 500 keV. GRB021125 lasted ~24 s
with a mean flux of ~5.0 photons/cm^2/s in the 20-500 keV energy band, and a
fluence of 4.8x10^-5 erg/cm^2 in the same energy band. Here we report the
analysis of the data from the imager IBIS and the spectrometer SPI.


title:
The influence of dark matter halo onto the evolution of a supermassive
  black hole

abstract:
  The influence of dark matter (DM) on the growth of supermassive black holes
(SMBHs) in galaxies is studied. It is shown that gravitational scattering of DM
particles on bulge stars leads to diffusion of DM in phase space {m, m_z, I}
('m' denotes the angular momentum and 'I' is the radial action). Appropriate
diffusion coefficients are calculated for different bulge models, and it is
argued that the diffusion along 'm' axis is the most important effect. It is
shown that this process leads to noticeable flow of DM into the black hole
(BH), resulting in its power-law growth: M_{bh} ~ t^{9/16}. Comparison with
observational data shows that, in principle, this effect may explain observed
masses of SMBHs. Special attention is paid to the corrections related to the
innermost region of BH gravitational influence and the diffusion along 'I'
axis. Their influence on the BH growth law is shown to be negligible in most
cases.


title:
Perspective on Afterglows: Numerically Computed Views, Lightcurves and
  the Analysis of Homogeneous and Structured Jets with Lateral Expansion

abstract:
  Herein I present numerical calculations of lightcurves of homogeneous and
structured afterglows with various lateral expansion rates as seen from any
vantage point. Such calculations allow for direct simulation of observable
quantities for complex afterglows with arbitrary energy distributions and
lateral expansion paradigms. A simple, causal model is suggested for lateral
expansion of the jet as it evolves; namely, that the lateral expansion kinetic
energy derives from the forward kinetic energy. As such the homogeneous jet
model shows that lateral expansion is important at all times in the afterglow
evolution and that analytical scaling laws do a poor job at describing the
afterglow decay before and after the break. In particular, I find that lateral
expansion does not cause a break in the lightcurve as had been predicted. A
primary purpose of this paper is to study structured afterglows, which do a
good job of reproducing global relationships and correlations in the data and
thus suggest the possibility of a universal afterglow model. Simulations of
structured jets show a general trend in which jet breaks become more pronounced
with increasing viewing angle with respect to the jet axis. In fact, under
certain conditions a bump can occur in the lightcurve at the jet break time. I
derive scaling relations for this bump and suggest that it may be a source of
some bumps in observed lightcurves such as that of GRB 000301C. A couple of
lateral expansion models are tested over a range of efficiencies and viewing
angles and it is found that lateral expansion can, in some cases, substantially
sharpen the jet break. I show flux surface contour maps and simulated images of
the afterglows which give insight into how they evolve and determine their
lightcurves.


title:
First Results from the IBIS/ISGRI Data Obtained During the Galactic
  Plane Scan. II. The Vela Region

abstract:
  We report on INTEGRAL/IBIS observations of the Vela region during a Galactic
Plane Scan (hereafter GPS) presenting the IBIS in-flight performances during
these operations. Among all the known sources in the field of view we clearly
detect
  4U 0836-429, Vela X-1, Cen X-3, GX 301-2, 1E 1145.1-6141, and H0918-549 in
the 20-40 keV energy range. Only Vela X-1 and GX 301-2 are detected in the
40-80 keV energy range, and no sources are visible above. We present the
results of each individual observation (~2200 s exposure), as well as those
from the mosaic of these scans.


title:
On the origin of HE0107-5240, the most iron deficient star presently
  known

abstract:
  We show that the "puzzling" chemical composition observed in the extremely
metal poor star HE0107-5240 may be naturally explained by the concurrent
pollution of at least two supernovae. In the simplest possible model a
supernova of quite low mass (~15 Msun), underwent a "normal" explosion and
ejected ~0.06 Msun of 56Ni while a second one was massive enough (~35 Msun) to
experience a strong fall back that locked in a compact remnant all the
carbon-oxygen core. In a more general scenario, the pristine gas clouds were
polluted by one or more supernovae of relatively low mass (less than ~25 Msun).
The successive explosion of a quite massive star experiencing an extended fall
back would have largely raised the abundances of the light elements in its
close neighborhood.


title: Sensitivity of the C and O production on the 3-alpha rate

abstract:
  We investigate the dependence of the carbon and oxygen production in stars on
the 3-alpha rate by varying the energy of the 02+-state of 12C and determine
the resulting yields for a selection of low-mass, intermediate-mass, and
massive stars. The yields are obtained using modern stellar evolution codes
that follow the entire evolution of massive stars, including the supernova
explosion, and consider in detail the 3rd dredge-up process during the
thermally pulsating asymptotic giant branch of low-mass and intermediate-mass
stars. Our results show that the C and O production in massive stars depends
strongly on the initial mass, and that it is crucial to follow the entire
evolution. A rather strong C production during the He-shell flashes compared to
quiescent He burning leads to a lower sensitivity of the C and O production in
low-mass and intermediate-mass stars on the 3-alpha-rate than predicted in our
previous work. In particular, the C production of intermediate-mass stars seems
to have a maximum close to the actual value of the 02+ energy level of 12C.


title:
Photometric redshifts in the Hubble Deep Fields: evolution of extinction
  and the star-formation rate

abstract:
  Photometric redshifts are studied with a template approach using data from
HDF-N and -S . The problem of aliasing in photometric redshift estimates is
investigated in some detail and found not to be a significant problem if at
least four photometric bands are available. The performance of the approach
presented here appears to exceed that of others in the literature.
  With reasonable restrictions, it is possible to determine the dust extinction
as well as the photometric redshift, provided five or more photometric bands
are available. An important result is that evolution of <A_V(z)> with redshift
is seen, with higher values than locally at z = 0.5-1.5, and lower values at z
> 2. This is consistent with current models for the star formation history of
the universe.
  Deconvolving the uv-to-ir seds into an old star and young star component
allows determination of M_* and \dot{M}_* for each galaxy, as well as z_{phot}
and A_V, provided that infrared photometric bands are available. The expected
trend of b = M_*/\dot{M}_* t_0 increasing to the past is seen. However there is
a great deal of scatter in the relation between b and sed type, showing that
the recent star-formation history is not very well correlated with the
long-term history of a galaxy.
  The 2800 A luminosity function and star-formation rate are calculated for a
large sample of HDF-N (2490) and HDF-S (28719) galaxies, using photometric
redshifts, for the redshift range 0.2-5. The star-formation rates agree
reasonably well with those from a variety of other uv, $H_{\alpha}$, infrared
and submillimetre estimates, and with star-formation histories used to model
optical, infrared and submillimetre source-counts.


title:
New insights to the photometric structure of Blue Compact Dwarf Galaxies
  from deep Near-Infrared studies I. Observations, surface photometry and
  decomposition of surface brightness profiles

abstract:
  (shortened) We analyze deep Near Infrared (NIR) broad band images for a
sample of Blue Compact Dwarf Galaxies (BCDs), allowing for the quantitative
study of their extended stellar low-surface brightness (LSB) host galaxies. NIR
surface brightness profiles (SBPs) of the LSB hosts agree at large
galactocentric radii with those from optical studies. At small to intermediate
radii, however, the NIR data reveal for more than half of our sample a
significant flattening of the exponential SBP of the LSB host. Such SBPs ("type
V" SBPs, Binggeli & Cameron 1991) have rarely been detected in LSB hosts of
BCDs at optical wavelengths, where the relative flux contribution of the
starburst is stronger than in the NIR and can hide such central intensity
depressions of the LSB host. The structural properties, frequency and physical
origin of type V LSB SBPs in BCDs and other dwarf galaxies have not yet been
systematically studied. Nevertheless, their occurrence in a significant
fraction of BCDs would impose important new constraints to the radial
distribution of their stellar mass, and to the photometric fading of BCDs after
the termination of star-forming activity. Both a modified exponential
(Papaderos et al. 1996a) and the Sersic law give satisfactory empirical
descriptions for type V SBPs. However, we argue that the practical
applicability of Sersic fits to LSB SBPs of BCDs is limited by, e.g., the
extreme sensitivity of the solutions to small SBP uncertainties. Most stellar
LSB host galaxies in the sample show optical-NIR colors indicative of evolved
stellar populations with subsolar metallicity. Unsharp-masked NIR images and
optical-NIR maps reveal numerous morphological details, and cases of
non-uniform dust absorption on spatial scales up to ~1 kpc.


title: Massive Stars in the Local Group: Star Formation and Stellar Evolution

abstract:
  The galaxies of the Local Group that are currently forming stars can serve as
our laboratories for understanding star formation and the evolution of massive
stars. In this talk I will summarize what I think we've learned about these
topics over the past few decades of research, and briefly mention what I think
needs to happen next.


title: Thermal equilibrium under the influence of gravitation

abstract:
  Gas clouds under the influence of gravitation in thermodynamic equilibrium
cannot be isothermal due to the Dufour effect, the energy flux induced by
density gradients. In galaxy clusters this effect may be responsible for most
of the "cooling flows" instead of radiative cooling of the gas.


title: Large scale structure and the generalised Chaplygin gas as dark energy

abstract:
  The growth of large scale structure is studied in a universe containing both
cold dark matter (CDM) and generalized Chaplygin gas (GCg). GCg is assumed to
contribute only to the background evolution of the universe while the CDM
component collapses and forms structures. We present some new analytical as
well as numerical results for linear and non-linear growth in such model. The
model passes the standard cosmological distance test without the need of a
cosmological constant (LCDM). But we find that the scenario is severely
constrained by current observations of large scale structure. Any small
deviations of the GCg parameters away from the standard Lambda dominated
cosmology (LCDM) produces substantial suppression for the growth of structures.


title: A new model for the lower overshoot layer in the Sun

abstract:
  We present a model for the lower overshoot layer of the Sun, based on the
realistic solar stratification, without the use of a "mixing-length" parameter,
by solving the system of Reynolds momentum equations using the closure
formalism of Canuto & Dubovikov (1997, 1998). A fixed value of velocity
anisotropy is assumed, and the local convection model is assumed to be valid
for the convectively unstable layer. In accordance with seismic constraints,
overshoot (defined as the amount by which the convectively mixed zone extends
beyond its boundary in local theory) is found to be as low as about 6 percent
of the pressure scale height, and it is not bounded by a discontinuity from
below.


title:
Multiscale image analysis applied to gamma/hadron discrimination for VHE
  gamma-ray astronomy with ARGO-YBJ

abstract:
  Intrinsic differences in the processes involved in the development of
electromagnetic and hadronic showers in the atmosphere have been evidenced by
means of a careful analysis of the event image given by the ARGO-YBJ detector.
The images have been analyzed at different length scales and their multifractal
nature has been studied. The use of the multiscale approach together with a
properly designed and trained Artificial Neural Network, allowed us to obtain a
good gamma/hadron discrimination power. If confirmed by further studies on
different event cathegories, this result would allow to nearly double the
detector sensitivity to gamma ray sources.


title: Testing General Relativity with Pulsar Timing

abstract:
  Pulsars of very different types - isolated objects, and binaries with short-
and long-period orbits, white-dwarf and neutron-star companions - provide the
means to test both the predictions of general relativity and the viability of
alternate theories of gravity. This article presents an overview of pulsars,
then discusses the current status and future prospects of tests of equivalence
principle violations and strong-field gravitational experiments.


title: Star Formation and X-ray Emission in Distant Star Forming Galaxies

abstract:
  About 45% of the point sources detected in the 2 Ms Chandra exposure of the
HDF-N can be matched with moderately bright galaxies with z<1.4 that have been
studied by the Caltech Faint Galaxy Redshift Survey. Although the optical
spectra of these galaxies appear normal, based on their X-ray properties ~20%
of them appear to contain weak AGNs. More than 90% of the X-ray photons
detected by Chandra from galaxies within the redshift regime 0.4 < z < 1.1 are
powered by accretion onto massive black holes. For the sample of galaxies in
common, we use their emitted luminosity in the 3727 A line of [OII] to estimate
their star formation rate (SFR). The X-ray emitting galaxies are not those with
the highest rest frame equivalent width in this emission line, but rather are
among those with the highest SFR. With SFR corrected for inclination effects,
the distant galaxies show a L(X) -- SFR relationship that is comparable to that
of local galaxies. The HDF sample has a significantly higher median SFR and
median SFR/galaxy stellar mass than does a sample of local star forming
galaxies. We demonstrate that the observed SFR for most of the galaxies at z~1
in the HDF sample, if maintained as constant over their ages, suffices to
produce the stellar mass observed in these galaxies. A rise in SFR at still
earlier times is not required. We provide further evidence to support the
conclusion that, once AGNs are eliminated, X-ray emission in these distantstar
forming galaxies is related to the SFR through the same physical mechanisms
that prevail locally.


title: Applications of High Resolution High Sensitivity Observations of the CMB

abstract:
  With WMAP putting the phenomenological standard model of cosmology on a
strong footing, one can look forward to mining the cosmic microwave background
(CMB) for fundamental physics with higher sensitivity and on smaller scales.
Future CMB observations have the potential to measure absolute neutrino masses,
test for cosmic acceleration independent of supernova Ia observations, probe
for the presence of dark energy at redshifts of 2 and larger, illuminate the
end of the dark ages, measure the scale--dependence of the primordial power
spectrum and detect gravitational waves generated by inflation.


title: Simulated Versus Observed Cluster Eccentricity Evolution

abstract:
  The rate of galaxy cluster eccentricity evolution is useful in understanding
large scale structure. Rapid evolution for $z < $ 0.13 has been found in two
different observed cluster samples. We present an analysis of projections of 41
clusters produced in hydrodynamic simulations augmented with radiative cooling
and 43 clusters from adiabatic simulations. This new, larger set of simulated
clusters strengthens the claims of previous eccentricity studies. We find very
slow evolution in simulated clusters, significantly different from the reported
rates of observational eccentricity evolution. We estimate the rate of change
of eccentricity with redshift and compare the rates between simulated and
observed clusters. We also use a variable aperture radius to compute the
eccentricity, r$_{200}$. This method is much more robust than the fixed
aperture radius used in previous studies. Apparently radiative cooling does not
change cluster morphology on scales large enough to alter eccentricity. The
discrepancy between simulated and observed cluster eccentricity remains.
Observational bias or incomplete physics in simulations must be present to
produce halos that evolve so differently.


title:
A Study of Cyg OB2: Pointing the Way Towards Finding Our Galaxy's Super
  Star Clusters

abstract:
  New optical MK classification spectra have been obtained for 14 OB star
candidates identified by Comeron et al. (2002) and presumed to be possible
members of the Cyg OB2 cluster. All 14 candidate OB stars observed are indeed
early-type stars, strongly suggesting the remaining 31 candidates identified by
Comeron et al. are also early-type stars. However, as many as half of the new
stars appear to be significantly older than the previously studied optical
cluster, making their membership in Cyg OB2 suspect. Despite this, the
recognition of Cyg OB2 being a more massive and extensive star cluster than
previously realized, along with the recently recognized candidate super star
cluster Westerlund 1 only a few kpc away (Clark & Negueruela 2002), reminds us
that we are woefully under-informed about the massive cluster population in our
Galaxy. Extrapolations of the locally derived cluster luminosity function
indicate 10s to perhaps 100 of these very massive open clusters (Mcl ~ 10^4
M_sun, Mv ~ -11) should exist within our galaxy. Radio surveys will not detect
these massive clusters if they are more than a few million years old. Our best
hope for remedying this shortfall is through deep infrared searches and follow
up near-infrared spectroscopic observations, as was used by Comeron et al. to
locate candidate members of the Cyg OB2 association.


title:
Apparent Sizes and Spectral Line Profiles for Spherical and Disk Masers:
  Solutions to the Full Equations

abstract:
  Calculations are performed for the spectral line profiles and images of
astrophysical maser radiation that emerges from isolated spheres and thin disks
viewed edge-on. In contrast to previous investigations where various
approximations are made, the full equations are solved here for the
frequency-dependent radiative transport that includes the thermal motion of the
molecules. The spectral line profiles for spheres and disks are found to
rebroaden to the full thermal Doppler breadth with increasing saturation in
essentially the same way as is well known to occur for a linear maser. The
variation with frequency in the apparent angular sizes of masing spheres and
thin disks is found to be negligible at frequencies within the spectral line
where the flux is significant. Calculations also are performed for spherical
and disk masers that are not isolated, but for which the seed radiation for the
masers is incident from one side as would occur when a strong continuum source
is on the far side of the masers. Again, the spectral line profiles are found
to rebroaden to the full thermal breadths with increasing saturation and there
are no significant variations in the apparent angular sizes with frequency.
However, the full rebroadening does occur at somewhat higher saturation and the
variation of the apparent angular sizes as a function of the degree of
saturation is quite different from that of the isolated masers. Spheres and
disks have served as idealized geometries with which to examine possible
deviations from the linear approximation for astrophysical masers.


title: The Peculiar X-ray Transient IGR 16358-4726

abstract:
  The new transient IGR 16358-4726 was discovered on 2003 March 19 with
INTEGRAL. We detected the source serendipitously during our 2003 March 24
observation of SGR 1627-41 with the Chandra X-ray Observatory at the 1.7 x
10^{-10} ergs s^{-1} cm^{-2} flux level (2-10 keV) with a very high absorption
column (N_H=3.3(1) x 10^{23} cm^{-2}) and a hard power law spectrum of index
0.5(1). We discovered a very strong flux modulation with a period of 5880(50) s
and peak-to-peak pulse fraction of 70(6)% (2-10 keV), clearly visible in the
x-ray data. The nature of IGR 16358-4726 remains unresolved. The only neutron
star systems known with similar spin periods are low luminosity persistent
wind-fed pulsars; if this is a spin period, this transient is a new kind of
object. If this is an orbital period, then the system could be a compact Low
Mass X-ray Binary (LMXB).


title:
Importance of Biologically Active Aurora-like Ultraviolet Emission:
  Stochastic Irradiation of Earth and Mars by Flares and Explosions

abstract:
  (Abridged) We show that sizeable fractions of incident ionizing radiation
from stochastic astrophysical sources can be redistributed to biologically and
chemically important UV wavelengths, a significant fraction of which can reach
the surface. This redistribution is mediated by secondary electrons, resulting
from Compton scattering and X-ray photoabsorption, with energies low enough to
excite atmospheric molecules and atoms, resulting in a rich aurora-like
spectrum. We calculate the fraction of energy redistributed into biologically
and chemically important wavelength regions for spectra characteristic of
stellar flares and supernovae using a Monte-Carlo transport code written for
this problem and then estimate the fraction of this energy that is transmitted
from the atmospheric altitudes of redistribution to the surface for a few
illustrative cases. Redistributed fractions are found to be of order 1%, even
in the presence of an ozone shield. This result implies that planetary
organisms will be subject to mutationally significant, if intermittent,
fluences of UV-B and harder radiation even in the presence of a narrow-band UV
shield like ozone. We also calculate the surficial transmitted fraction of
ionizing radiation and redistributed ultraviolet radiation for two illustrative
evolving Mars atmospheres whose initial surface pressures were 1 bar. Our
results suggest that coding organisms on planets orbiting low-mass stars (and
on the early Earth) may evolve very differently than on contemporary Earth,
with diversity and evolutionary rate controlled by a stochastically varying
mutation rate and frequent hypermutation episodes.


title: Optical Pulse-Phased Photopolarimetry of PSR B0656+14

abstract:
  We have observed the optical pulse profile of PSR B0656+14 in 10 phase bins
at a high signal-to-noise ratio, and have measured the linear polarization
profile over 30% of the pulsar period with some significance. The pulse profile
is double-peaked, with a bridge of emission between the two peaks, similar to
gamma-ray profiles observed in other pulsars. There is no detectable unpulsed
flux, to a 1-sigma limit of 16% of the pulse-averaged flux. The emission in the
bridge is highly (~ 100%) polarized, with a position angle sweep in excellent
agreement with the prediction of the Rotating Vector Model as determined from
radio polarization observations. We are able to account for the gross features
of the optical light curve (i.e., the phase separation of the peaks) using both
polar cap and outer gap models. Using the polar cap model, we are also able to
estimate the height of the optical emission regions.


title: The K-selected Butcher-Oemler Effect

abstract:
  [abridged] We investigate the Butcher-Oemler effect in a sample of K-selected
galaxies in 33 clusters at 0.15 < z < 0.92. We attempt to duplicate the
original Butcher-Oemler analysis as closely as possible given the
characteristics of our data. We find that the infrared selected blue fractions
are lower than those measured in the optical and that the trend with redshift
is much weaker. Comparison with optical data in clusters in common with Butcher
& Oemler (1984) shows that infrared selection is the primary difference between
our study and optically selected samples. We suggest that the Butcher-Oemler
effect is in large part due to a population of star-forming low mass galaxies
which will evolve into dwarf galaxies. These early results point to the need
for larger and deeper infrared samples of cluster galaxies to address this
issue


title: Neutrino Nucleosynthesis

abstract:
  We study neutrino process nucleosynthesis in massive stars using newly
calculated cross sections, an expanded reaction network, and complete and
self-consistent models of the progenitor star. We reevaluate the production of
light isotopes from abundant progenitors as well as that of rare, heavy,
proton-rich isotopes. In particular, new results are given for B11, F19, La138,
and Ta180. The production of these isotopes places limits on neutrino spectrum
and oscialltions.


title: Globular Clusters in the Sgr Stream and other structures

abstract:
  The possible association of Galactic globular clusters with the Sgr Stream is
shortly reviewed at the light of the most recent observations of the Stream. >=
20 % of the Galactic globular clusters with R_{GC}>= 10 Kpc are found to lie
within or very nearby to the Sgr Stream as traced over the whole sky by the M
giants from the 2MASS catalogue, in agreement with the results by Bellazzini,
Ferraro and Ibata (2003a). Another possible association of outer halo globulars
(NGC 1904, NGC 1851, NGC 2808, and NGC 2298) is also noted and briefly
discussed.


title: Supermassive black holes (SMBH) and formation of galaxies

abstract:
  The recently confirmed correlation between the mass of SMBH and bulges of
galaxies (and their central velocity dispersion), suggest a common formation
scenario for galaxies and their central black holes. Common fueling can be
invoked through internal dynamical processes, external accretion, and
hierarchical merging of structures. The success of recent theories is reviewed,
as the self-regulated growth of both bulges and SMBHs, the predicted AGN
statistics, when activity is triggered by accretion and mergers, the predicted
frequency of binary SMBH and consequences. In particular, the SMBH growth
problem can now be revised, invoking intermediate-mass black holes (IMBH) as BH
seeds in the early universe. As a by-product, the merger of binary SMBHs help
to heat and destroy central stellar cusps. Remaining problems are mentioned.


title: Measuring CMB polarisation with the Planck mission

abstract:
  In this paper, we discuss why and how the Planck mission, originally designed
and proposed for mapping CMB intensity fluctuations, has been revised for
polarisation measurement capability as well.


title: An update on Archeops: flights and data products

abstract:
  Archeops is a balloon-borne instrument dedicated to measuring CMB temperature
anisotropies at high resolution over a large fraction of sky. We present the
Archeops flights and data products, Archeops results, and the future use of
Archeops data for multi-experiment data analysis.


title:
The Ultra Luminous Infrared Galaxy MKN 231: New clues from BeppoSAX and
  XMM-Newton

abstract:
  We present BeppoSAX and XMM-Newton observations of MKN 231. These
observations and in particular the BeppoSAX PDS data allowed us to unveil, for
the first time, the highly absorbed (N$_H\sim 2\times10^{24}$ cm$^{-2}$) AGN
component. We find that: a) the AGN powering MKN231 has an intrinsic 2-10 keV
luminosity of $1^{+1}_{-0.5}\times 10^{44}$ erg/s; b) the strong starburst
activity contributes significantly in the 0.1-10 keV energy range. We propose
that the starburst activity strongly contributes to the far infrared luminosity
of MKN 231; this is also suggested by the multiwavelength properties of MKN
231.


title:
ISO spectroscopy of star formation and active nuclei in the luminous
  infrared galaxy NGC 6240

abstract:
  We present Infrared Space Observatory mid- and far-infrared spectroscopy of
the merging galaxy NGC 6240, an object presenting many aspects of importance
for the role of star formation and AGN activity in [ultra]luminous infrared
galaxies. The mid-infrared spectrum shows starburst indicators in the form of
low excitation fine-structure line emission and aromatic `PAH' features. A
strong high excitation [OIV] line is observed which most likely originates in
the Narrow Line Region of an optically obscured AGN. NGC 6240 shows extremely
powerful emission in the pure rotational lines of molecular hydrogen. We argue
that this emission is mainly due to shocks in its turbulent central gas
component and its starburst superwind. The total shock cooling in infrared
emission lines accounts for ~0.6% of the bolometric luminosity, mainly through
rotational H_2 emission and the [OI] 63micron line. We analyse several ways of
estimating the luminosities of the starburst and the AGN in NGC 6240 and
suggest that the contributions to its bolometric luminosity are most likely in
the range 50-75% starburst and 25-50% AGN.


title:
On the collisional depolarization and transfer rates of spectral lines
  by atomic hydrogen. III: application to $f$-states of neutral atoms

abstract:
  The theory of collisional depolarization of spectral lines by atomic hydrogen
(Derouich et al. 2003a; Derouich et al. 2003b) is extended to $f$-atomic levels
$(l$=3). Depolarization rates, polarization and population transfer rates are
calculated and results are given. Each cross section as a function of the
effective quantum number for a relative velocity of 10 $\textrm{km s}^{-1}$ is
given together with an exponent $\lambda$, if it exists, on the assumption that
the cross section varies with velocity as $v^{-\lambda}$. A general trends of
depolarization rates, of polarization transfer rates and of population transfer
rates are given. A discussion of our results is achieved.


title:
The Distances to Open Clusters from Main-Sequence Fitting. I. New Models
  and a Comparison to the Properties of the Hyades Eclipsing Binary vB 22

abstract:
  In the first of a new series of papers on open cluster distances, we use
updated stellar evolution models to construct an isochrone appropriate for the
Hyades, and compare it with the Hyades eclipsing binary system vB 22. We find
that the absolute and relative luminosities of the two stars are in good
agreement with the model, but the radii do not match the values inferred from
eclipse data. We present evidence that there is a consistency problem with the
flux ratios and the inferred radii, and discuss possible theoretical effects
that could be responsible for the mismatch in the radii. We derive a helium
abundance for the Hyades of Y = 0.271 \pm 0.006, which is equal within the
errors to the Sun's initial helium abundance even though the Hyades is
considerably more metal-rich.


title: The First Deep ACS Lyman alpha Images of Local Starburst Galaxies

abstract:
  We report the first results from a deep Lya imaging program of local
starburst galaxies with the Advanced Camera for Surveys (ACS) of the Hubble
Space Telescope. The two observed galaxies ESO 350-IG038 and SBS 0335-052 have
luminosities similar to those of the Magellanic Clouds but differ in their
chemical composition. ESO 350-IG038 has an oxygen abundance of 1/8 solar,
whereas SBS 0335-052 is known to have one of the lowest abundances among blue
galaxies (~1/30). The ACS imaging reveals a complex Lya morphology, with
sometimes strong offsets between the emission of Lya and the location of
stellar light, ionized gas traced by Halpha, and the neutral gas. Overall, more
Lya photons escape from the more metal- and dust-rich galaxy ESO 350-IG038. The
absence of clear SBS 0335-052 Lya emission over all observed knots, whatever
their dust content or/and color indices, contradicts model expectations of a
lower escape fraction from dust-rich gas due to destruction of Lya photons by
dust grains. Rather, the results are in qualitative agreement with models
suggesting the kinematic properties of the gas as the dominant Lya escape
regulator. If the properties of the two observed galaxies are representative
for starburst galaxies in general, Lya will be difficult to interpret as a
star-formation indicator, in particular if based on Lya imaging at low spatial
resolution.


title:
Starburst in HS 0822+3542 induced by the very blue LSB dwarf SAO
  0822+3545

abstract:
  (Abridged). One of the most metal-deficient blue compact galaxies (BCGs) HS
0822+3542 (Z=1/34 Zsun), is also one of the nearest such objects. A trigger
mechanism for its current SF burst has remained unclear. We report the
discovery of a very blue ((B-V)tot=0.08 and (V-R)tot=0.14) LSB (mu_B^0 > 23.4
arcsec^-2) dwarf irregular (dIrr) galaxy, named SAO 0822+3545. Its small
relative velocity and projected distance of ~11 kpc from the BCG imply their
physical association. For this LSB galaxy, we present spectroscopic results,
total B,V,R magnitudes, the effective radii and surface brightness (SB), and we
describe its morphological properties. We compare the very blue colours of this
dwarf with PEGASE.2 models of the colour evolution of a Z=1/20 Zsun stellar
population, and combine this analysis with the data on the LSBD EW(Ha) values.
The models best describing all available observational data depend on the
relative fraction of massive stars in the IMF used. For a Salpeter IMF with Mup
= 120 Msun, the best model includes a "young" single stellar population (SSP)
with an age of ~10 Myr and an "old" SSP with the age of ~0.2--10 Gyr. The mass
ratio of the old to young components should be in the range of 10 to 30. The
role of interaction in triggering the galaxies major SF episodes during the
last ~100-200 Myr is discussed. For the BCG, based on the spectroscopy with the
6m telescope, we estimate the physical parameters of its SF region and present
the first evidence of an ionized gas supershell. This pair of dwarfs lies deep
within the nearby Lynx-Cancer void, with the nearest bright (L > L*) galaxies
at distances > 3 Mpc. This is probably one of the main factors responsible for
the unevolved state of HS 0822+3542.


title:
Properties of QSO Metal Line Absorption Systems at High Redshifts:
  Nature and Evolution of the Absorbers and the Ionizing Radiation Background

abstract:
  In Keck HIRES spectra of 9 QSOs we identify a sample of 908 CIV absorber
components in 188 systems outside the Lyman forest in the redshift range 1.6 <
z < 4.4, with related lines of SiIV, CII, SiII and NV. The properties of the
CIV absorbers are almost constant with z. We find a mild increase in Omega(CIV)
with decreasing z with a mean = (3.8+/-0.7)*10^(-8) (spatially flat LCDM
cosmology and h = 0.71). Using Omega(b) from the CMB and ionization fractions
from our data we obtain [C/H]_(z = 4.0) >/= -3.11(+0.14/-0.19) and [C/H]_(z =
2.1) >/= -2.64(+0.15/-0.22), suggesting a rise by about a factor 3. Relating
Omega(H) more directly to regions containing the absorbers our values become >~
-2.2 and >~ -2.0, respectively. CIV components exhibit strong clustering at
Delta(v) < 300 km/s but there is no clustering on any scale between systems. We
argue that for our sample the CIV clustering is entirely due to the peculiar
velocities of gas present in the outer extensions of galaxies. We find no
change with z in the median column density ratio SiIV/CIV, contrary to previous
observations; other ionic ratios vary continuously with redshift. We show that
these are only partial indicators of ionization state and remedy this by use of
specific pairs of ratios. We demonstrate that the majority of absorbers are
photoionized and find that at z < 2.65 QSOs dominate the ionization whereas at
z > 3.4 an additional, dominant contribution from galaxies with specific
spectral characteristics and high radiative escape fraction in the range 1-4
Ryd is required. These results also indicate that [Si/C] = 0.0-0.4 fits the
data well. We conclude that the heavy element absorbers at z > 3.4 are located
close to galaxies and irradiated dominantly by them, consistent with our
independent conclusion from clustering properties.


title: Offset balancing in pseudo-correlation radiometers for CMB measurements

abstract:
  Radiometeric CMB measurements need to be highly stable and this stability is
best obtained with differential receivers. The residual 1/f noise in the
differential output is strongly dependent on the radiometer input offset which
can be cancelled using various balancing strategies. In this paper we discuss a
software method implemented in the Planck-LFI pseudo-correlation receivers
which uses a tunable "gain modulation factor, r, in the sky-load difference.
Numerical simulations and experimental data show how proper tuning of the
parameter r ensures a very stable differential output with knee frequencies of
the order of few mHz. Various approaches to calculate r using the radiometer
total power data are discussed with some examples relevant to Planck-LFI.
Although the paper focuses on pseudo-correlation receivers and the examples are
relative to Planck-LFI, the proposed method and its analysis is general and can
be applied to a large class of differential radiometric receivers.


title:
Propagation of non-linear circularly polarised Alfven waves in a
  homogeneous medium

abstract:
  We study the evolution of non-linear circularly polarised Alfven waves by
solving numerically the time-dependent equations of magnetohydrodynamics (MHD)
in one dimension. We examine the behaviour of the waves and find that different
physical mechanisms are relevant in different ranges of beta. In a low beta
plasma the wave may undergo a parametric decay. This is because the wave
excites a density enhancement that travels slower than the wave itself and thus
interacts with the wave. When beta is greater or equal to one the density
enhancement does not interact with the wave and no decay takes place, instead
the Alfven wave is reflected against the density enhancement. The reflection
zone propagates with the speed 1/n of the Alfven speed. Because of that the
magnetic flux is conserved which results in an amplification of the oscillating
magnetic field by a factor 1/n. We find that n depends on beta, and that in
particular it is less or equal to one for values of beta ~ 1 and is greater or
equal to one for beta >> 1. We discuss the relevance of these mechanisms to the
acceleration of the solar wind, and the triggering of MHD turbulence in the
polar wind region. In particular these simulations can explain the presence of
inward propagating Alfven waves in the solar corona.


title: Chandra Detections of SCUBA Galaxies around High-z Radio Sources

abstract:
  The most massive galaxies in the present day universe are the giant
ellipticals found in the centers of rich clusters. These have old, coeval
stellar populations, suggesting they formed at high redshift, and are expected
to host supermassive black holes (SMBHs). The recent detection of several
high-redshift radio galaxies (HzRGs) at submm wavelengths confirms that indeed
some massive galaxies may have formed the bulk of their stellar populations in
spectacular dust-enshrouded starbursts at high-z. In this letter we compare
sensitive Chandra X-ray images - which identify actively-fueled SMBHs - and
submm observations - capable of detecting obscured activity in luminous
galaxies at high redshift - of the environments of three HzRGs. These
observations exhibit overdensities of X-ray sources in all 3 fields and a close
correspondence between the Chandra and SCUBA populations. This suggests that
both substantial star formation and nuclear activity may be occuring in these
regions. We identify possible pairs of Chandra sources with each of 2 SCUBA
sources, suggesting that their ultraluminous activity may be triggered by the
interaction of two massive galaxies, each of which hosts an accreting SMBH. The
presence of two SMBHs in the resulting remanent is predicted to produce a
flattened stellar core in the galaxy, a morphological signature frequently seen
in luminous cluster ellipticals. Hence the confirmation of pairs of Chandra
sources within individual, luminous SCUBA galaxies would provide additional
evidence that these galaxies at z~2-4 are the progenitors of the giant
elliptical galaxies found in clusters at the present-day.


title:
The X-ray, optical and radio evolution of the GRB030329 afterglow and
  the associated SN2003dh

abstract:
  Extensive X-ray, optical and radio observations of the bright afterglow of
the Gamma Ray Burst GRB 030329 are used to construct the multi-frequency
evolution of the event. The data are fitted using the standard fireball shock
model to provide estimates of the initial energy, epsilon = 6.8 x 10^52 ergs
sr^-1, the density of the ambient medium, n_0 = 1 cm^-3, the electron and
magnetic energy density fractions, epsilon_e = 0.24 & epsilon_B = 0.0017, the
power law index of the relativistic electron spectrum, p = 2.25, and the
opening angle of the jet, theta_j = 3 degrees. Deviations from the standard
model seen in the optical and radio are most likely attributable to the
concurrent hypernova SN2003dh. Peaks at 0.23 and 1.7 days in the R-band are
much brighter than expected from a standard SN, and there is a large radio
excess over the expected afterglow flux for t>2 days. No deviation from the
best-fit afterglow model is seen in the X-ray decline, indicating that the
excess optical and radio flux from 1-5 days arises from a later injection of
slower electrons by the central engine.


title:
Probing Interstellar Dust Models Through SAXS (Small Angle X-Ray
  Scattering)

abstract:
  A viable interstellar dust model - characterized by the composition,
morphology, and size distribution of the dust grains and by the abundance of
the different elements locked up in the dust - should fit all observational
constraints arising primarily from the interactions of the dust with incident
radiation or the ambient gas. In spite of the many different manifestations of
these interactions, we still lack a comprehensive dust model that is consistent
with {\it all} the observational constraints.
  An important advance towards the construction of such a model was recently
made by Zubko, Dwek, and Arendt (2003, ZDA03) who, for the first time, included
the average interstellar extinction, the diffuse infrared emission, {\it and}
the interstellar abundances as explicit constraints in the construction of
models consisting of astrophysical dust particles without any predetermined
functional form for their grain size distribution. The results showed the
existence of many distinct dust models that satisfy a basic set of
observational constraints.
  X-ray halos, produced primarily by small angle scattering off large dust
particles along the line of sight to bright X-ray sources, probe dust
properties largely inaccessible at other wavelengths. In this contribution we
briefly review the microscopic physics and the macroscopic effects that
determine the intensity and spatial profile of X-ray halos. Focusing on the
X-ray halo around the bright source GX~13+1, we show that halo observations can
be used to discriminate between the different, currently viable, ZDA03 dust
models. X-ray halos may therefore be an essential constraint that need to be
explicitly included in all future dust models.


title:
The Transverse Proximity Effect: A Probe to the Environment, Anisotropy,
  and Megayear Variability of QSOs

abstract:
  The transverse proximity effect is the expected decrease in the strength of
the Lya forest absorption in a QSO spectrum when another QSO lying close to the
line of sight enhances the photoionization rate above that due to the average
cosmic ionizing background. We select three QSOs from the Early Data Release of
the Sloan Digital Sky Survey that have nearby foreground QSOs, with proper line
of sight tangential separations of 0.50, 0.82, and 1.10 h^{-1} Mpc. We estimate
that the ionizing flux from the foreground QSO should increase the
photoionization rate by a factor (94, 13, 13) in these three cases, which would
be clearly detectable in the first QSO and marginally so in the other two. We
do not detect the transverse proximity effect. Three possible explanations are
provided: an increase of the gas density in the vicinity of QSOs, time
variability, and anisotropy of the QSO emission. We find that the increase of
gas density near QSOs can be important if they are located in the most massive
halos present at high redshift, but is not enough to fully explain the absence
of the transverse proximity effect. Anisotropy requires an unrealistically
small opening angle of the QSO emission. Variability demands that the
luminosity of the QSO with the largest predicted effect was much lower 10^6
years ago, whereas the transverse proximity effect observed in the HeII Lya
absorption in QSO 0302-003 by Jakobsen et al. (2003) implies a lifetime longer
than 10^7 years. A combination of all three effects may better explain the lack
of Lya absorption reduction. A larger sample of QSO pairs may be used to
diagnose the environment, anisotropy and lifetime distribution of QSOs.


title: Ancient Origins of a Modern Anthropic Cosmological Argument

abstract:
  Ancient origins of a modern anthropic argument against cosmologies involving
infinite series of past events are considered. It is shown that this argument -
which in modern times has been put forward by distinguished cosmologists like
Paul C. W. Davies and Frank J. Tipler - originates in pre-Socratic times and is
implicitly present in the cyclical cosmology of Empedocles. There are traces of
the same line of reasoning throughout the ancient history of ideas, and the
case of a provocative statement of Thucydides is briefly analyzed. Moreover,
the anthropic argument has been fully formulated in the epic of Lucretius,
confirming it as the summit of ancient cosmology. This is not only of
historical significance but presents an important topic for the philosophy of
cosmology provided some of the contemporary inflationary models, particularly
Linde's chaotic inflation, turn out to be correct.


title: Carbon Ignition in Type Ia Supernovae: An Analytic Model

abstract:
  The observable properties of a Type Ia supernova are sensitive to how the
nuclear runaway ignites in a Chandrasekhar mass white dwarf - at a single point
at its center, off-center, or at multiple points and times. We present a simple
analytic model for the runaway based upon a combination of stellar
mixing-length theory and recent advances in understanding Rayleigh-Benard
convection. The convective flow just prior to runaway is likely to have a
strong dipolar component, though higher multipoles may contribute appreciably
at the very high Rayleigh number (10$^{25}$) appropriate to the white dwarf
core. A likely outcome is multi-point ignition with an exponentially increasing
number of ignition points during the few tenths of a second that it takes the
runaway to develop. The first sparks ignite approximately 150 - 200 km off
center, followed by ignition at smaller radii. Rotation may be important to
break the dipole asymmetry of the ignition and give a healthy explosion.


title: Optical spectra of selected Chamaeleon I young stellar objects

abstract:
  We present optical spectra of eight candidate brown dwarfs and a previously
known T Tauri star (Sz 33) of the Chamaeleon I dark cloud. We derived spectral
types based on the strength of the TiO or VO absorption bands present in the
spectra of these objects as well as on the PC3 index of Martin et al. (1999).
Photometric data from the literature are used to estimate the bolometric
luminosities for these sources. We apply D'Antona & Mazzitelli (1997) pre-main
sequence evolutionary tracks and isochrones to derive masses and ages. Based on
the presence of Halpha in emission, we confirm that most of the candidates are
young objects. Our sample however includes two sources for which we can only
provide upper limits for the emission in Halpha; whereas these two objects are
most likely foreground/background stars, higher resolution spectra are required
to confirm their true nature. Among the likely cloud members, we detect one new
sub-stellar object and three transition stellar/sub-stellar sources.


title: Measuring Statistical isotropy of the CMB anisotropy

abstract:
  The statistical expectation values of the temperature fluctuations of cosmic
microwave background (CMB) are assumed to be preserved under rotations of the
sky. This assumption of {\em statistical isotropy} (SI) of the CMB anisotropy
should be observationally verified since detection of violation of SI could
have profound implications for cosmology. We propose a set of measures,
$\kappa_\ell$ ($\ell=1,2,3, ...$) for detecting violation of statistical
isotropy in an observed CMB anisotropy sky map indicated by non zero
$\kappa_\ell$. We define an estimator for the $\kappa_\ell$ spectrum and
analytically compute its cosmic bias and cosmic variance. The results match
those obtained by measuring $\kappa_\ell$ using simulated sky maps. Non-zero
(bias corrected) $\kappa_\ell$ larger than the SI cosmic variance will imply
violation of SI. The SI measure proposed in this paper is an appropriate
statistics to investigate preliminary indication of SI violation in the
recently released WMAP data.


title: Statistical isotropy of the Cosmic Microwave Background

abstract:
  The breakdown of statistical homogeneity and isotropy of cosmic perturbations
is a generic feature of ultra large scale structure of the cosmos, in
particular, of non trivial cosmic topology. The statistical isotropy (SI) of
the Cosmic Microwave Background temperature fluctuations (CMB anisotropy) is
sensitive to this breakdown on the largest scales comparable to, and even
beyond the cosmic horizon. We propose a set of measures, $\kappa_\ell$
($\ell=1,2,3, ...$) which for non-zero values indicate and quantify statistical
isotropy violations in a CMB map. We numerically compute the predicted
$\kappa_\ell$ spectra for CMB anisotropy in flat torus universe models.
Characteristic signature of different models in the $\kappa_\ell$ spectrum are
noted.


title:
Pixel correlation searches for OVI in the Lyman alpha forest and the
  volume filling factor of metals in the Intergalactic Medium at z ~ 2-3.5

abstract:
  Artificial absorption spectra are used to test a variety of instrumental and
physical effects on the pixel correlation technique for the detection of weak
OVI absorption. At HI optical depths <= 0.3-1, the apparent OVI detections are
spurious coincidences due to HI absorption at other redshifts. In this range,
the apparent OVI optical depth is independent of HI optical depth. At larger HI
optical depths, apparent OVI optical depth and HI optical depth are correlated.
Detailed modelling is required in order to interpret the significance of this
relation. High-resolution spectra of four QSOs together with a large suit of
synthetic spectra are used to show that the detection of OVI in individual
spectra is only statistically significant for overdensities >= 5. These
overdensities are larger than would be naively inferred from the onset of the
correlation and a tight optical depth-density relation. The lower limit for the
volume filling factor of regions which are enriched by OVI is 4% at 95%
confidence. This is no larger than the observed volume filling factor of the
winds from Lyman break galaxies. Previous claims that the observed OVI
absorption extends to underdense regions and requires a universal metal
enrichment with large volume filling factor, as may be expected from population
III star formation at very high redshift, appear not to be warranted.


title: Neutrinos and Nucleosynthesis in Gamma-Ray Burst Accretion Disks

abstract:
  We calculate the nuclear composition of matter in accretion disks surrounding
stellar mass black holes as are thought to accompany gamma-ray bursts (GRBs).
We follow a mass element in the accretion disk starting at the point of nuclear
dissociation and calculate the evolution of the electron fraction due to
electron, positron, electron neutrino and electron antineutrino captures. We
find that the neutronization of the disk material by electron capture can be
reversed by neutrino interactions in the inner regions of disks with accretion
rates of 1 M_solar/s and higher. For these cases the inner disk regions are
optically thick to neutrinos, and so to estimate the emitted neutrino fluxes we
find the surface of last scattering for the neutrinos (the equivalent of the
proto-neutron star neutrinosphere) for each optically thick disk model. We also
estimate the influence of neutrino interactions on the neutron-to-proton ratio
in outflows from GRB accretion disks, and find it can be significant even when
the disk is optically thin to neutrinos.


title: Iron Emission in the z=6.4 Quasar SDSS J114816.64+525150.3

abstract:
  We present near-infrared J and K-band spectra of the z = 6.4 quasar SDSS
J114816.64+525150.3 obtained with the NIRSPEC spectrograph at the Keck-II
telescope, covering the rest-frame spectral regions surrounding the C IV 1549
and Mg II 2800 emission lines. The iron emission blend at rest wavelength
2900-3000 A is clearly detected and its strength appears nearly
indistinguishable from that of typical quasars at lower redshifts. The Fe II /
Mg II ratio is also similar to values found for lower-redshift quasars,
demonstrating that there is no strong evolution in Fe/alpha broad-line emission
ratios even out to z=6.4. In the context of current models for iron enrichment
from Type Ia supernovae, this implies that the SN Ia progenitor stars formed at
z > 10. We apply the scaling relations of Vestergaard and of McLure & Jarvis to
estimate the black hole mass from the widths of the C IV and Mg II emission
lines and the ultraviolet continuum luminosity. The derived mass is in the
range (2-6)x10^9 solar masses, with an additional uncertainty of a factor of 3
due to the intrinsic scatter in the scaling relations. This result is in
agreement with the previous mass estimate of 3x10^9 solar masses by Willott,
McLure, & Jarvis, and supports their conclusion that the quasar is radiating
close to its Eddington luminosity.


title: Cool Gas in Clusters of Galaxies

abstract:
  Early X-ray observations suggested that the intracluster medium cools and
condenses at the centers of clusters, leading to a cooling flow of plasma in
the cluster core. The increased incidence of emission-line nebulosity, excess
blue light, AGN activity, and molecular gas in the cores of clusters with short
central cooling times seemed to support this idea. However, high-resolution
spectroscopic observations from XMM-Newton and Chandra have conclusively ruled
out simple, steady cooling flow models. We review the history of this subject,
the current status of X-ray observations, and some recent models that have been
proposed to explain why the core gas does not simply cool and condense.


title:
Observations of cluster substructure using weakly lensed sextupole
  moments

abstract:
  Since dark matter clusters and groups may have substructure, we have examined
the sextupole content of Hubble images looking for a curvature signature in
background galaxies that would arise from galaxy-galaxy lensing. We describe
techniques for extracting and analyzing sextupole and higher weakly lensed
moments. Indications of substructure, via spatial clumping of curved background
galaxies, were observed in the image of CL0024 and then surprisingly in both
Hubble deep fields. We estimate the dark cluster masses in the deep field.
Alternatives to a lensing hypothesis appear improbable, but better statistics
will be required to exclude them conclusively. Observation of sextupole moments
would then provide a means to measure dark matter structure on smaller length
scales than heretofore.


title:
The Origin of the Galactic Center Nonthermal Radio Filaments: Young
  Stellar Clusters

abstract:
  The unusual class of magnetized nonthermal radio filaments (NTF), threads and
streaks with their unique physical characteristics are found only within the
inner couple of degrees of the Galactic center. Also, a number of young,
mass-losing and rare stellar clusters are recognized to lie in the Galactic
center region. The latter characteristic of the Galactic center region is used
to explain the origin of the nonthermal radio filaments. We consider a
mechanism in which the collective winds of massive WR and OB stars within a
dense stellar environment produce shock waves that can accelerate particles to
relativistic energies. This mechanism is an extension of a model originally
proposed by Rosner and Bodo (1996), who suggested that energetic nonthermal
particles are produced in a terminal shock of mass-losing stars. The
large-scale distribution of the magnetic field in the context of this model is
argued to have neither poloidal geometry nor pervasive throughout the Galactic
center region.


title:
Tracing out the Northern Tidal Stream of the Sagittarius Dwarf
  Spheoridal Galaxy

abstract:
  The main aim of this paper is to report two new detections of tidal debris in
the northern stream of the Sagittarius dwarf galaxy located at 45 arcdeg and 55
arcdeg from the center of galaxy. Our observational approach is based on deep
color-magnitude diagrams, that provides accurate distances, surface brightness
and the properties of stellar population of the studied region of this tidal
stream. The derived distances for these tidal debris wraps are 45 kpc and 54
kpc respectively.We also confirm these detections with numerical simulations of
the Sagittarius dwarf plus the Milky Way. The model reproduces the present
position and velocity of the Sagittarius main body and presents a long tidal
stream formed by tidal interaction with the Milky Way potential. This model is
also in good agreement with the available observations of the Sagittarius tidal
stream. We also present a method for estimating the shape of the Milky Way halo
potential using numerical simulations. From our simulations we obtain an
oblateness of the Milky Way dark halo potential of 0.85, using the current
database of distances and radial velocities of the Sagittarius tidal stream.
The color-magnitude diagram of the apocenter of Sagittarius shows that this
region of the stream shares the complex star formation history observed in the
main body of the galaxy. We present the first evidence for a gradient in the
stellar population along the stream, possibly correlated with its different
pericenter passages. (abridged)


title: Time, Distance, Velocity, Redshift: a personal guided tour

abstract:
  An attempt to answer the question 'Can we observe galaxies that recede faster
than light ?' led to a re-examination of the notions of time, distance,
velocity and redshift as they occur in newtonian physics, special relativity,
general relativity and cosmology. A number of misconceptions were uncovered. It
was found that, once freed of special relativity preconceptions, the above
question is easily and unequivocally answered


title: CN Variations in NGC 7006

abstract:
  Rotationally induced mixing with subsequent dredge-up of nucleosynthesized
material is discussed as a second parameter of the horizontal branch morphology
in globular clusters. CNO abundances have been proposed as tracers of the
dredge up of processed material. \ngc is a prominent example of a second
parameter GC: Its HB morphology is too red for its metallicity. We present
spectroscopic measurements of CN molecular band strengths S(3839) and CH band
CH(4300) strengths for 12 giants in \ngc to test rotationally-driven mixing as
a second parameter in this cluster. Our observations reveal (i) a scatter in
star-to-star CN absorption strengths with the same amplitude as seen in other
GCs of the same metallicity, but different HB morphologies; (ii) a possible
continuous distribution of CN absorption strength with a preference for
CN-enriched stars, and (iii) a possible weak radial gradient in the number
ratio of CN-strong and CN-weak stars. We argue against the hypothesis that
CN-variations are directly correlated with the second parameter effect of the
HB morphology. However, the small sample of stars measured in \ngc prevents us
from drawing firm conclusions. Finally, we identify one star of our sample as a
foreground dwarf carbon star.


title: Dynamical Creation of Channels for Particle Escape in the Solar Corona

abstract:
  It is shown that the connection of sufficiently fast flows with dynamical
channels for particle escape in the Solar Corona is rather direct: it depends
on their ability to deform (in specific cases to distort) the ambient magnetic
field lines to temporarily stretch (shrink, destroy) the closed field lines so
that the flow can escape the local region. Using a dissipative two--fluid code
in which the flows are treated at par with the currents, we have demonstrated
channel creation in a variety of closed--field line structures. This
self--induced transparency constitutes the active mode for the formation of the
solar wind.


title: In-flight calibrations of IBIS/PICsIT

abstract:
  PICsIT (Pixellated Imaging CaeSium Iodide Telescope) is the high energy
detector of the IBIS telescope on-board the INTEGRAL satellite. It consists of
4096 independent detection units, ~0.7 cm^2 in cross-section, operating in the
energy range between 175 keV and 10 MeV. The intrinsically low signal to noise
ratio in the gamma-ray astronomy domain implies very long observations, lasting
10^5-10^6 s. Moreover, the image formation principle on which PICsIT works is
that of coded imaging in which the entire detection plane contributes to each
decoded sky pixel. For these two main reasons, the monitoring, and possible
correction, of the spatial and temporal non-uniformity of pixel performances,
expecially in terms of gain and energy resolution, is of paramount importance.
The IBIS on-board 22Na calibration source allows the calibration of each pixel
at an accuracy of <0.5% by integrating the data from a few revolutions at
constant temperature. The two calibration lines, at 511 and 1275 keV, allow
also the measurement and monitoring of the PICsIT energy resolution which
proves to be very stable at ~19% and ~9% (FWHM) respectively, and consistent
with the values expected analytical predictions checked against pre-launch
tests.


title: A Resolution of the Vacuum Energy Problem

abstract:
  A new vision of the beginning and expansion of our universe has produced a
solution to the vacuum energy problem (also known as "cosmological constant
problem"). A new dynamic of cellular spaces and a discrete time has space being
produced by a process called spatial condensation (SC). With generic energy
defined as Planck's constant times the rate of cellular space production, both
the vacuum energy and mass energy contents contribute to the expansion in the
ratio 10^123/1, the same ratio of predicted densities by quantum theory and our
astronomers. However, unlike mass energy, vacuum energy, like Casimir vacuum
energy, does not carry the attribute of mass and so does not gravitate. A
geometric derivation of the vacuum energy expansion rate was followed by a
second derivation in terms of the evolution of the contents, from radiation to
matter to dark mass (not matter). With a new definition of cosmic time, the
second derivation was shown to produce exactly the same expansion rate. Free of
singularities and inflation, both derivations also produced reasonable values
of the cosmological parameters and the second derivation produced a good fit to
the supernova Ia data with no acceleration of the expansion rate.


title: Multi-object spectroscopy of low redshift EIS clusters. II

abstract:
  We present the results of carrying out multi-object spectroscopy in 10 EIS
cluster fields. Based on the list of 345 galaxy redshifts we identify
significant 3D-density enhancements. For 9 of the EIS clusters we identify
significant 3D-concentrations corresponding to the originally detected cluster
candidate. We find redshifts in the range 0.097<=z<=0.257 which is in good
agreement with the matched filter estimate of z_MF=0.2. We estimate velocity
dispersions in the range 219-1160 km/s for the confirmed clusters.


title:
Finding the Most Metal-poor Stars of the Galactic Halo with the
  Hamburg/ESO Objective-Prism Survey

abstract:
  I review the status of the search for extremely metal-poor halo stars with
the Hamburg/ESO objective-prism survey (HES). 2194 candidate metal-poor
turn-off stars and 6133 giants in the magnitude range 14 < B < 17.5 have been
selected from 329 (out of 380) HES fields, covering an effective area of 6400
square degrees in the southern extragalactic sky. Moderate-resolution follow-up
observations for 3200 candidates have been obtained so far, and ~200 new stars
with [Fe/H] <- 3.0 have been found, which trebles the total number of such
extremely low-metallicity stars identified by all previous surveys.
  We use VLT-UT2/UVES, Keck/HIRES, Subaru/HDS, TNG/SARG, and Magellan/MIKE for
high-resolution spectroscopy of HES metal-poor stars. I provide an overview of
the scientific aims of these programs, and highlight several recent results.


title:
A Chandra LETGS observation of V4743 Sagittarius: A Super Soft X-ray
  Source and a Violently Variable Light Curve

abstract:
  V4743 Sgr (Nova Sgr 2002 No. 3) was discovered on 20 September 2002. We
obtained a 5ks ACIS-S spectrum in November 2002 and found that the nova was
faint in X-rays. We then obtained a 25ks CHANDRA LETGS observation on 19 March
2003. By this time, it had evolved into the Super Soft X-ray phase exhibiting a
continuous spectrum with deep absorption features. The light curve from the
observation showed large amplitude oscillations with a period of 1325s (22min)
followed by a decline in total count rate after ~13ks of observations. The
count rate dropped from ~40cts/s to practically zero within ~6ks and stayed low
for the rest of the observation (~6ks). The spectral hardness ratio changed
from maxima to minima in correlation with the oscillations, and then became
significantly softer during the decay. Strong H-like and He-like lines of
oxygen, nitrogen, and carbon were found in absorption during the bright phase,
indicating temperatures between 1-2MK, but they were shifted in wavelength
corresponding to a Doppler velocity of -2400km/s. The spectrum obtained after
the decline in count rate showed emission lines of CVI, NVI, and NVII
suggesting that we were seeing expanding gas ejected during the outburst,
probably originating from CNO-cycled material. An XMM-Newton ToO observation,
obtained on 4 April 2003 and a later LETGS observation from 18 July 2003 also
showed oscillations, but with smaller amplitudes.


title: Have the Elusive Progenitors of Supernovae Type Ia Been Discovered?

abstract:
  The recent detection of H-alpha emission in the supernova Type Ia SN 2002ic
could be taken to mean that the elusive progenitor systems of Type Ia
supernovae have finally been identified. At first glance, the observation
appears to support a single-degenerate scenario, in which the white dwarf
accretes from a normal companion. In this Letter we show that the opposite may
be true, and the observations may support the merger of two white dwarfs as the
cause for Type Ia supernovae.


title:
The MACHO Project Large Magellanic Cloud variable star inventory. XI.
  Frequency analysis of the fundamental mode RR Lyrae stars

abstract:
  We have frequency analyzed 6391 variables classified earlier as fundamental
mode RR Lyrae (RR0) stars in the MACHO database on the Large Magellanic Cloud
(LMC). The overwhelming majority of these variables have been proved to be
indeed RR0 stars, whereas the remaining ones have fallen in one of the
following categories: single- and double-mode Cepheids, binaries, first
overtone and double-mode RR Lyrae stars and non-classified variables. Special
attention has been paid to the Blazhko stars. We found altogether 731 Blazhko
variables showing either a doublet or an equidistant triplet pattern at the
main pulsation component in their frequency spectra. The incidence rate of the
Blazhko variables among the RR0 stars in the LMC is 11.9%, which is three times
higher than their rate among the first overtone RR Lyrae stars. From the
frequency spectra we found that variables with larger modulation amplitudes at
the higher frequency side of the main pulsation component are three times more
frequent than the ones showing the opposite amplitude pattern. A search made
for a modulation component with the Blazhko period in the average brightness of
the individual variables showed the existence of such a modulation with an
overall amplitude of ~0.006 mag. On the other hand, a similar search for
quadruple modulation patterns around the main pulsation component have failed
to clearly detect such components at the ~0.004 mag level. This means that the
amplitudes of the quadruple components should be, on the average, at least ten
times smaller than those of the triplet components. This finding and the
existence of Blazhko variables with highly asymmetric modulation amplitudes not
only question the validity of the magnetic oblique rotator model, but also puts
stringent constraints on models based on mode coupling theories.


title: Optical, ultraviolet and infrared observations of X-ray binaries

abstract:
  This chapter for the new CUP book "Compact Stellar Sources" reviews the state
of work on multi-wavelength observations of high mass and low mass X-ray
binaries. Both neutron star and black hole systems are considered for this
work.


title: Planetary migration in evolving planetesimals discs

abstract:
  In the current paper, we further improved the model for the migration of
planets introduced in Del Popolo et al. (2001) and extended to time-dependent
planetesimal accretion disks in Del Popolo and Eksi (2002). In the current
study, the assumption of Del Popolo and Eksi (2002), that the surface density
in planetesimals is proportional to that of gas, is released. In order to
obtain the evolution of planetesimal density, we use a method developed in
Stepinski and Valageas (1997) which is able to simultaneously follow the
evolution of gas and solid particles for up to 10^7 yrs. Then, the disk model
is coupled to migration model introduced in Del Popolo et al. (2001) in order
to obtain the migration rate of the planet in the planetesimal. We find that
the properties of solids known to exist in protoplanetary systems, together
with reasonable density profiles for the disk, lead to a characteristic radius
in the range 0.03-0.2 AU for the final semi-major axis of the giant planet.


title: Molecular gas and AGN fueling

abstract:
  CO emission, tracing the molecular content and distribution in galaxies, is a
privileged tool to trace gas towards the nucleus, since the HI tracer is in
general depleted there. A review is done of recent CO line observations, with
sufficient spatial resolution to indicate the morphology and kinematics of the
gas near the nucleus. The puzzling result that nuclei presently observed in an
active phase have little sign of fueling, is discussed.


title: Nuclear and Particle Astrophysics at CIPANP 2003

abstract:
  In the nuclear and particle astrophysics session of CIPANP 2003 we heard
talks on a number of topics, focused for the most part into four broad areas.
Here we outline the discussions of the standard cosmological model, dark matter
searches, cosmic rays, and neutrino astrophysics. The robustness of theoretical
and experimental programs in all of these areas is very encouraging, and we
expect to have many questions answered, and new ones asked, in time for CIPANP
2006.


title:
The Mass, Baryonic Fraction, and X-ray Temperature of the Luminous, High
  Redshift Cluster of Galaxies, MS0451.6-0305

abstract:
  We present new Chandra X-ray observations of the luminous X-ray cluster,
MS0451.6-0305, at z=0.5386. Spectral imaging data for the cluster are
consistent with an isothermal cluster of 10.0 - 10.6 +/-1.6 keV and an Fe
abundance of 0.32-0.40 +/-0.13 solar. The systematic uncertainties, arising
from calibration and model uncertainties, of the temperature determination are
nearly the same size as the statistical uncertainties. We discuss the effects
of the ACIS absorption correction on the spectral fitting. The effects of
statistics and fitting assumptions of 2-D models for the X-ray surface
brightness are thoroughly explored. This cluster appears to be elongated and so
we quantify the effects of assuming an ellipsoidal gas distribution on the gas
mass and the total gravitating mass estimates. These data are also jointly fit
with previous S-Z observations to obtain an estimate of the cluster's distance
assuming spherical symmetry. If we, instead, assume a Hubble constant, the
X-ray and S-Z data are used together to test the consistency of an ellipsoidal
gas distribution and to weakly constrain the intrinsic axis ratio. The mass
derived from the X-ray data is consistent with the weak lensing and optical
masses. We confirm that this cluster is very hot and massive, further
supporting the conclusion of previous analyses that the universe has a low
matter density and that cluster properties, including iron abundances, have not
evolved much since z~0.5. We discuss the possible detection of a faint, soft,
extended component that may be the by-product of hierarchical structure
formation.


title: Constraining the Cosmic Background Light with four BL Lac TeV spectra

abstract:
  The intrinsic BL Lac spectra above few hundreds GeV can be very different
from the observed ones due to the absorption effects by the diffuse
Extragalactic Background Light (EBL), at present poorly known. With the recent
results, there are now 4 sources with good spectral information: Mkn 421
(z=0.031), Mkn 501 (z=0.034), 1ES 1426+428 (z=0.129) and 1ES 1959+650
(z=0.047). Making simple assumptions on the shape of the intrinsic spectra
(according to the present blazar knowledge), we have considered the effects of
different EBL spectral energy distributions (SED) for the first time on all 4
objects together, deriving constraints for the EBL fluxes. These resulted
significantly lower than many direct estimates.


title:
A brief (blazar oriented) overview on topics for multi-wavelength
  observations with TeV photons

abstract:
  Multi-wavelength observations with TeV photons are an essential diagnostic
tool to study the physics of TeV sources. The complex variability of blazars,
however (timescales from years down to minutes, with different patterns and SED
behaviours), requires a great effort on simultaneous campaigns, which should be
performed possibly over several days. Spectral information is essential, and
now with the new TeV and X-ray telescopes it can be obtained on timescales less
than one hour. The insights from such observations can be tremendous, since
recent results have shown that the X-ray and TeV emissions do not always follow
the same behaviour, and flares can have different relations between rise and
decay times. Unfortunately, the strong pointing constraints of XMM do not allow
the full use of this satellite simultaneously with ground telescopes.