title: Supermassive Black Holes in Spiral Galaxies

abstract:
  We have embarked in an HST program to determine the masses of black holes in
spiral galaxies directly by measuring the line emission arising from an
extended accretion disk. For each of the galaxies in our sample we have
measured the rotation curve and determined the mass distribution within the
inner 5-50 pc. We have modeled the stellar mass component using the photometric
data from existing HST images and using both data sets we have derived the
masses of the black holes in each galaxy. These results will be very important
in clarifying the role of the black hole in powering the AGN, will shed light
into the effectiveness of the accretion mechanisms and finally will be
important in addressing the fundamental issue of unification for Seyfert 1 and
Seyfert 2 galaxies.


title: On the iron Kalpha complex in magnetic cataclysmic variables

abstract:
  We present a compilation of spectra of the iron Kalpha region in magnetic
cataclysmic variables, using data from the Chandra-HETG. The H-like, He-like
and fluorescent components are clearly resolved, and there are hints of the
structure within each component. The different shape of the He-like component
in AM Her might be related to greater cyclotron cooling in this star. A
surprising absence of Doppler shifts in the H-like and He-like components
implies that the X-ray emission is predominantly from the denser,
lower-velocity base of the accretion columns. This absence will allow ASTRO-E2
to resolve the structure in each component, leading to temperature diagnostics.
  We do not confirm the report that the H-like and He-like components of AO Psc
are Compton broadened; however we do detect a Compton-downshifted shoulder to
the fluorescent line of GK Per. Further, a Doppler-shifted wing of this line
arises in the high-velocity, pre-shock flow.


title: New insights on unification of radio-loud AGN

abstract:
  The radio-loud AGN unification model associates powerful radio galaxies with
radio-loud quasars and blazars. In analogy with the radio-quiet scheme, the
nuclear regions of objects showing only narrow emission lines in their optical
spectrum are thought to be obscured to our line-of-sight by a geometrically and
optically thick dusty "torus". In objects showing broad emission lines we
directly observe the innermost parsecs around the central black hole, i.e. the
broad line region and the accretion disk. Radiation from the base of the
relativistic jet dominates the overall emission of blazars, that are seen
almost pole-on. Although the broad picture seems to be well established, there
are several fundamental aspects that are still to be understood. HST studies
have recently shed new light on many issues, from the properties of the nuclei
to the structure of the host galaxies.


title: Microquasars and ULXs: Fossils of GRB Sources

abstract:
  Gamma-ray bursts (GRBs) of long duration probably result from the
core-collapse of massive stars in binary systems. After the collapse of the
primary star the binary system may remain bound leaving a microquasar or ULX
source as remnant. In this context, microquasars and ULXs are fossils of GRB
sources and should contain physical and astrophysical clues on GRB-source
progenitors. The identification of the birth place of microquasars and
magnetars can provide constrains on the progenitor stars of the compact
objects, and the runaway velocities can be used to constrain the energy in the
explosion of massive stars that leave neutron stars and black holes. The
observations show that the neutron star binaries LS 5039, LSI +61 303 and the
low-mass black hole in GRO J1655-40 formed in energetic supernova explosions,
whereas the black holes of larger masses (M > 10 Msolar) in Cygnus X-1 and GRS
1915+105 formed promptly or in underluminous supernovae. If the massive star
formation in the parent clusters of the microquasar LSI +61 303 and magnetars
SGR 1806-20 and SGR 1900+14 was coeval, very massive stars (M > 50 Msolar) may
in some cases leave neutron stars rather than black holes. The models of GRB
sources of long duration have the same basic ingredients as microquasars and
ULXs: compact objects with accretion disks and relativistic jets in binary
systems. Therefore, the analogies between microquasars and AGN may be extended
to the sources of GRBs.


title: LMC Self-lensing from a new perspective

abstract:
  We present a new analysis on the issue of the location of the observed
microlensing events in direction of the Large Magellanic Cloud (LMC). This is
carried out starting from a recently drawn coherent picture of the geometrical
structure and dynamics of the LMC disk and by considering different
configurations for the LMC bar. In this framework it clearly emerges that the
spatial distribution of the events observed so far shows a near--far asymmetry.
This turns out to be compatible with the optical depth calculated for the LMC
halo objects. In this perspective, our main conclusion, supported by a
statistical analysis on the outcome of an evaluation of the microlensing rate,
is that self lensing can not account for all the observed events. Finally we
propose a general inequality to calculate quickly an upper limit to the optical
depth along a line of view through the LMC center.


title: Ultra-high energy cosmic rays from a finite number of point sources

abstract:
  We have calculated the probability that the clustering of arrival directions
of ultra-high energy cosmic rays (UHECRs) is consistent with a finite number of
uniformly distributed proton sources. The case of a continuous source
distribution is reached only for an unrealisticly high source density, $n_s\gg
10^{-2}/Mpc^3$. Even for densities as large as $n_s=10^{-3}/Mpc^3$, less than
half of the observed cluster are on average by chance. For the best-fit value
$n_s=(1-3)\times 10^{-5}/Mpc^3$ derived from the AGASA data, the probability
that at least one observed cluster is from a true point source is larger than
99.97%, while on average almost all observed clusters are true. The best-fit
value found is comparable to the density of AGNs and consistent with the recent
HiRes stereo data. In this scenario, the Pierre Auger Observatory will not only
establish the clustering of UHECRs but also determine the density of UHECR
sources within a factor of a few after one year of data taking.


title:
Broadband X-ray spectrum of GRS 1734-292, a luminous Seyfert 1 galaxy
  behind the Galactic Center

abstract:
  Based on a deep survey of the Galactic Center region performed with the
INTEGRAL observatory, we measured for the first time the hard X-ray (20-200
keV) spectrum of the Seyfert 1 galaxy GRS 1734-292 located in the direction of
the Galactic Center. We extended the spectrum to lower energies using archival
GRANAT and ASCA observations. The broadband X-ray spectrum is similar to those
of other nearby luminous AGNs, having a power law shape without cutoff up to at
least 100 keV.


title:
Absolute Proper Motion of the Fornax Dwarf Spheroidal Galaxy from
  Photographic and HST WFPC2 Data

abstract:
  We have measured the absolute proper motion of the Fornax dwarf spheroidal
galaxy from a combination of photographic plate material and HST WFPC2 data
that provide a time baseline of up to 50 years. The extragalactic reference
frame consists of 8 QSO images and 48 galaxies. The absolute proper motion is
mu_alpha cos(delta) = 0.59 +-0.16 mas/yr and mu_delta = -0.15 +- 0.16 mas/yr.
The corresponding orbit of Fornax is polar, with an eccentricity of 0.27, and a
radial period of 4.5 Gyr. Fornax's current location is near pericenter. The
direction of the motion of Fornax supports the notion that Fornax belongs to
the Fornax-LeoI-LeoII-Sculptor-Sextans stream as hypothesized by Lynden-Bell
(1976, 1982) and Majewski (1994).
  According to our orbit determination, Fornax crossed the Magellanic plane
\~190 Myr ago, a time that coincides with the termination of the star-formation
process in Fornax. We propose that ram-pressure stripping due to the passage of
Fornax through a gaseous medium denser than the typical intragalactic medium
left behind from the LMC may have caused the end of star formation in Fornax.
The excess, anomalous clouds within the South Galactic pole region of the
Magellanic Stream whose origin has long been debated in the literature as
constituents of either the Magellanic Stream or of the extragalactic Sculptor
group, are found to lie along the orbit of Fornax. We speculate that these
clouds are stripped material from Fornax as the dwarf crossed the Magellanic
Clouds' orbit.


title: How does clustering depend on environment?

abstract:
  According to the current paradigm, galaxies form and reside in extended cold
dark matter (CDM) halos and in turn are key tracers of cosmological structure.
Understanding how different types of galaxies occupy halos of different masses
is one of the major challenges facing extragalactic astrophysics. The observed
galaxy properties depend on the environment surrounding the galaxy. Within the
framework of most galaxy formation models the environmental dependence of the
galaxy population is mainly due to the change of the halo mass function with
large-scale environment. Such models make precise predictions for how galaxy
clustering should depend on environment. We will illustrate this by presenting
analytical models of dark matter and galaxy clustering along with results
obtained from numerical simulations. With these results we can hope to obtain a
better understanding of the link between galaxies and dark matter and thereby
constrain galaxy formation models.


title: The Physics of Neutron Stars

abstract:
  Neutron stars are some of the densest manifestations of massive objects in
the universe. They are ideal astrophysical laboratories for testing theories of
dense matter physics and provide connections among nuclear physics, particle
physics and astrophysics. Neutron stars may exhibit conditions and phenomena
not observed elsewhere, such as hyperon-dominated matter, deconfined quark
matter, superfluidity and superconductivity with critical temperatures near
${10^{10}}$ kelvin, opaqueness to neutrinos, and magnetic fields in excess of
$10^{13}$ Gauss. Here, we describe the formation, structure, internal
composition and evolution of neutron stars. Observations that include studies
of binary pulsars, thermal emission from isolated neutron stars, glitches from
pulsars and quasi-periodic oscillations from accreting neutron stars provide
information about neutron star masses, radii, temperatures, ages and internal
compositions.


title: Far Ultraviolet Observations of the Dwarf Nova VW Hyi in Quiescence

abstract:
  We present a 904-1183 A spectrum of the dwarf nova VW Hydri taken with the
Far Ultraviolet Spectroscopic Explorer during quiescence, eleven days after a
normal outburst, when the underlying white dwarf accreter is clearly exposed in
the far ultraviolet. However, model fitting show that a uniform temperature
white dwarf does not reproduce the overall spectrum, especially at the shortest
wavelengths. A better approximation to the spectrum is obtained with a model
consisting of a white dwarf and a rapidly rotating ``accretion belt''. The
white dwarf component accounts for 83% of the total flux, has a temperature of
23,000K, a v sin i = 400 km/s, and a low carbon abundance. The best-fit
accretion belt component accounts for 17% of the total flux, has a temperature
of about 48,000-50,000K, and a rotation rate Vrot sin i around 3,000-4,000
km/s. The requirement of two components in the modeling of the spectrum of VW
Hyi in quiescence helps to resolve some of the differences in interpretation of
ultraviolet spectra of VW Hyi in quiescence. However, the physical existence of
a second component (and its exact nature) in VW Hyi itself is still relatively
uncertain, given the lack of better models for spectra of the inner disk in a
quiescent dwarf nova.


title: Theoretical Radii of Transiting Giant Planets: The Case of OGLE-TR-56b

abstract:
  We calculate radius versus age trajectories for the photometrically-selected
transiting extrasolar giant planet, OGLE-TR-56b, and find agreement between
theory and observation, without introducing an ad hoc extra source of heat in
its core. The fact that the radius of HD209458b seems larger than the radii of
the recently discovered OGLE family of extremely close-in transiting planets
suggests that HD209458b is anomalous. Nevertheless, our good fit to OGLE-TR-56b
bolsters the notion that the generic dependence of transit radii on stellar
irradiation, mass, and age is, to within error bars, now quantitatively
understood.


title: Stellar Populations in HII Galaxies

abstract:
  We analyse the stellar content of a large number of HII galaxies from the
continua and absorption features of their spectra using population synthesis
methods, in order to gain information about the star formation histories of
these objects.
  We find that all galaxies of our sample contain an old stellar population (>=
1 Gyr) that dominates the stellar mass, and in a majority of these we also
found evidence for an intermediate-age population >= 50 Myr apart from the
presently bursting, ionizing young generation <= 10^7 yrs


title: Direct Detection of Dark Matter with Space-based Laser Interferometers

abstract:
  Dark matter pervades the Solar System, free-streaming at the halo's local
Galactic orbital velocity and density. As these objects pass through the Solar
system, they perturb gravitationally, and thus very weakly, all nearby inertial
masses. Making use of this, we propose an approach to the direct detection of
dark matter at previously inaccessible intermediate masses (1e14 -- 1e20 gm).
Such mass scales are relevant for example for dark matter made of primordial
black holes or clumped matter in a sequestered sector. If such dark matter
exists it will be unambiguously detectable through its inelastic gravitational
interaction with the proposed Laser Interferometer Space Antenna (LISA)
experiment. We demonstrate the efficacy of this approach by studying the dark
matter signal in numerical simulations of the LISA data stream. A more
conservative approach -- to detect dark matter in the differential acceleration
power spectrum -- significantly underestimates the expected rates for LISA.
Interestingly, while the space-density of 1e15 gm DM objects would be
comparable to the space-density of asteroids of similar masses, such ``light
matter'' contaminants are readily detectable in reflected Solar light, allowing
for the elimination of the major background.


title: Could dark energy be vector-like?

abstract:
  In this paper I explore whether a vector field can be the origin of the
present stage of cosmic acceleration. In order to avoid violations of isotropy,
the vector has be part of a ``cosmic triad'', that is, a set of three identical
vectors pointing in mutually orthogonal spatial directions. A triad is indeed
able to drive a stage of late accelerated expansion in the universe, and there
exist tracking attractors that render cosmic evolution insensitive to initial
conditions. However, as in most other models, the onset of cosmic acceleration
is determined by a parameter that has to be tuned to reproduce current
observations. The triad equation of state can be sufficiently close to minus
one today, and for tachyonic models it might be even less than that. I briefly
analyze linear cosmological perturbation theory in the presence of a triad. It
turns out that the existence of non-vanishing spatial vectors invalidates the
decomposition theorem, i.e. scalar, vector and tensor perturbations do not
decouple from each other. In a simplified case it is possible to analytically
study the stability of the triad along the different cosmological attractors.
The triad is classically stable during inflation, radiation and matter
domination, but it is unstable during (late-time) cosmic acceleration. I argue
that this instability is not likely to have a significant impact at present.


title: Large scale systematic signals in weak lensing surveys

abstract:
  We use numerical simulations to model the effect of seeing and extinction
modulations on weak lensing surveys. We find that systematic fluctuations in
the shear amplitude and source depth can give rise to changes in the $E$-mode
signal and to varying amplitudes of large scale $B$-modes. Exquisite control of
such systematics will be required as we approach the era of precision cosmology
with weak lensing.


title:
Isothermal Shock Formation in Non-Equatorial Accretion Flows around Kerr
  Black Holes

abstract:
  We explore isothermal shock formation in non-equatorial, adiabatic accretion
flows onto a rotating black hole, with possible application to some active
galactic nuclei (AGNs). The isothermal shock jump conditions as well as the
regularity condition, previously developed for one-dimensional (1D) flows in
the equatorial plane, are extended to two-dimensional (2D), non-equatorial
flows, to explore possible geometrical effects. The basic hydrodynamic
equations with these conditions are self-consistently solved in the context of
general relativity to explore the formation of stable isothermal shocks. We
find that strong shocks are formed in various locations above the equatorial
plane, especially around a rapidly-rotating black hole with the prograde flows
(rather than a Schwarzschild black hole). The retrograde flows are generally
found to develop weaker shocks. The energy dissipation across the shock in the
hot non-equatorial flows above the cooler accretion disk may offer an
attractive illuminating source for the reprocessed features, such as the iron
fluorescence lines, which are often observed in some AGNs.


title: X-ray constraints on ionizing photons from accreting black holes at Z~6

abstract:
  Using an X-ray stacking procedure, we provide a robust upper limit to the
X-ray luminosity per object of a set of 54 z~5.8 galaxy candidates in the
Hubble Ultra Deep Field, which is within the 1 Ms-exposure Chandra Deep
Field-South (CDF-S). With an effective total exposure of 44 Ms for the stack,
the 3-sigma flux-density limit of 2.1E-17 erg/cm^2/s (soft-band) gives a
3-sigma upper-limit luminosity of L_X = 8E42 erg/s per object at a rest-frame
hard energy range of 3-14 keV at z~5.8 for a photon index of Gamma=2. For an
active accreting black hole (or "mini-quasar") emitting at the Eddington
luminosity, and the Sazonov et al. average-QSO spectral energy distribution, we
calculate an upper limit on the black hole mass, M_bh < 3E6 Msun (3-sigma). The
X-ray limit further implies an upper limit on the rate density of UV ionizing
photons from accreting black holes at that redshift, n-dot (ioniz) < 2E51
/s/Mpc^3 (3-sigma), which is less than 1/10 of the number needed to ionize the
universe. Because the constraint is anchored in the rest-frame hard X-ray
regime, a steeper spectrum for mini-quasars would imply relatively fewer
ionizing UV photons. Unless there are large populations of active black holes
around this mass that are unassociated with luminous galaxies, mini-quasars do
not appear to contribute significantly to the budget of ionizing photons at
z~6.


title:
Constraining the Lifetime of Circumstellar Disks in the Terrestrial
  Planet Zone: A Mid-IR Survey of the 30-Myr-old Tucana-Horologium Association

abstract:
  We have conducted an N-band survey of 14 young stars in the ~30 Myr-old
Tucana-Horologium Association to search for evidence of warm, circumstellar
dust disks. Using the MIRAC-BLINC camera on the Magellan I (Baade) 6.5-m
telescope, we find that none of the stars have a statistically significant
N-band excess compared to the predicted stellar photospheric flux. Using three
different sets of assumptions, this null result rules out the existence of the
following around these post-T Tauri stars: (a) optically-thick disks with inner
hole radii of ~<0.1 AU, (b) optically-thin disks with masses of >10^{-6}
M_Earth (in ~1-micron-sized grains) within ~<10 AU of these stars, (c)
scaled-up analogs of the solar system zodiacal dust cloud with >4000X the
emitting area. Our survey was sensitive to dust disks in the terrestrial planet
zone with fractional luminosity of log(L_{dust}/L_{star}) ~ 10^{-2.9}, yet none
were found. Combined with results from previous surveys, these data suggest
that circumstellar dust disks become so optically-thin as to be undetectable at
N-band before age ~20 Myr. We also present N-band photometry for several
members of other young associations and a subsample of targets that will be
observed with Spitzer Space Telescope by the Formation and Evolution of
Planetary Systems (FEPS) Legacy Science Program. Lastly, we present an absolute
calibration of MIRAC-BLINC for four filters (L, N, 11.6, and Q_s) on the
Cohen-Walker-Witteborn system.


title: Correction for the Flux Measurement Bias in X-ray Source Detection

abstract:
  With a high spatial resolution imaging instrument such as the
  Chandra/ACIS, one can confidently identify an X-ray source with only a few
detected counts. The detection threshold of such sources, however, varies
strongly across the field-of-view of the instrument. Furthermore, the low
detection counting statistics, together with a typical steep source number-flux
relation, causes more intrinsically faint sources to be detected at apparently
higher fluxes than the other way around. We quantify this ``X-ray Eddington
bias'' as well as the detection threshold variation and devise simple
procedures for their corrections. To illustrate our technique, we present
results from our analysis of X-ray sources detected in the fields of the
large-scale hierarchical complex Abell 2125 at $z = 0.247$ and the nearby
galaxy NGC 4594 (Sombrero). We show that the sources detected in the Abell 2125
field, excluding 10 known complex members, have a number-flux relation
consistent with the expected from foreground or background objects. In
contrast, the number-flux relation of the NGC 4594 field is dominated by X-ray
sources associated with the galaxy. This galactic component of the relation is
well characterized by a broken power law.


title: Does Positronium Form in the Universe ?

abstract:
  Positronium (the bound state of electron and positron) has been thought to be
formed after proton decay ($>10^{34}$yr) through collisional recombination and
then decays by pair annihilation, thereby changing the matter content of the
universe. We revisit the issue of the formation of positronium in the long-term
future of the universe in light of recent indication that the universe is
dominated by dark energy and dark matter. We find that if the equation of state
of dark energy $w$ is less than -1/3 (including the cosmological constant
$w=-1$), then the formation of positronium would not be possible, while it is
possible through bound-bound transitions for $-1/3\siml w\siml-0.2$, or through
collisional recombination for $w\simg-0.2$. The radiation from $\epm$ pair
annihilation cannot dominate over $\epm$, while that from proton decay will
dominate over baryon and $\epm$ for a while but not over dark matter.


title: Single pulses as emission from multiple subsources

abstract:
  Single pulses of pulsar radio emission are modeled as superposition of
radiation originating from many small subsources that are randomly distributed
in the emission region. The individual subsources are given an intrinsic finite
angular beaming. This model can produce fluctuations in intensity and pulse
profiles that are similar to the microstructure observed in some pulsars.
Statistics of the phase resolved flux density of a simulated single pulse can
be approximated by a lognormal distribution, which is in good agreement with
observations.


title:
The distribution of cosmic-ray sources in the Galaxy, gamma-rays, and
  the gradient in the CO-to-H2 relation

abstract:
  We present a solution to the apparent discrepancy between the radial gradient
in the diffuse Galactic gamma-ray emissivity and the distribution of supernova
remnants, believed to be the sources of cosmic rays. Recent determinations of
the pulsar distribution have made the discrepancy even more apparent. The
problem is shown to be plausibly solved by a variation in the CO-to-N(H2)
scaling factor. If this factor increases by a factor of 5-10 from the inner to
the outer Galaxy, as expected from the Galactic metallicity gradient, we show
that the source distribution required to match the radial gradient of gamma-ray
can be reconciled with the distribution of supernova remnants as traced by
current studies of pulsars. The resulting model fits the EGRET gamma-ray
profiles extremely well in longitude, and reproduces the mid-latitude inner
Galaxy intensities better than previous models.


title:
Magnetic Rayleigh-Taylor instability for Pulsar Wind Nebulae in
  expanding Supernova Remnants

abstract:
  We present a numerical investigation of the development of Rayleigh-Taylor
instability at the interface between an expanding Pulsar Wind Nebula and its
surrounding Supernova Remnant. These systems have long been thought to be
naturally subject to this kind of instability, given their expansion behavior
and the density jump at the contact discontinuity. High resolution images of
the Crab Nebula at optical frequencies show the presence of a complex network
of line-emitting filaments protruding inside the synchrotron nebula. These
structures are interpreted as the observational evidence that Rayleigh-Taylor
instability is in fact at work. The development of this instability in the
regime appropriate to describe Supernova Remnant-Pulsar Wind Nebula systems is
non-trivial. The conditions at the interface are likely close to the stability
threshold, and the inclusion of the nebular magnetic field, which might play an
important role in stabilizing the system, is essential to the modeling. If
Rayleigh-Taylor features can grow efficiently a mixing layer in the outer
portion of the nebula might form where most of the supernova material is
confined. When a magnetic field close to equipartition is included we find that
the interface is stable, and that even a weaker magnetic field affects
substantially the growth and shape of the fingers.


title: Serpens X-1 observed by INTEGRAL

abstract:
  Here we report results of an INTEGRAL-AO1 observation of the X-ray burst and
atoll source Ser X-1 performed in May 2003. The object was observed for a total
on-source time of 400 ks but nearly 8 degrees off-axis due to its amalgamation
with an observation of SS 433, the pointing target source. Ser X-1 has been
clearly detected up to 30 keV with unprecedented positional accuracy for
high-energy emission. The 20-30 keV light curve showed substantial variability
during the observation. Comparison with previous observations indicates that
the source was in its high (`banana') state and displayed a soft spectrum
during the INTEGRAL pointing. A (non simultaneous) radio-to-gamma-rays
broad-band spectral energy distribution is also presented for the first time
and discussed.


title:
PFP 1: A Large Annular Planetary Nebula Caught in the First Stages of
  ISM Interaction

abstract:
  This paper presents (H-alpha + [NII]) imaging and spectroscopy of a
previously unknown, highly evolved planetary nebula of low excitation. It was
discovered serendipitously from AAO/UKST H-alpha Survey images as part of a
project to exploit the survey data and has evaded detection by previous surveys
due to very low surface brightness. It is a remarkably annular planetary
nebula, some 19' across, making it one of the largest examples of its type. We
estimate a radius of 1.5 pc and a distance of 550pc as derived from a new
H-alpha surface brightness - radius relation. PFP 1 has near perfect circular
symmetry, broken only at the NW edge which is coupled with significantly
increased (H-alpha + [NII]) intensity. This indicates an early stage of an
interaction with the interstellar medium. A blue central star candidate has
been identified from the SuperCOSMOS Sky Survey data.


title: VLT/ISAAC Spectra of the H-beta Region in Intermediate Redshift Quasars

abstract:
  We present high S/N spectra of the H-beta region in 17 intermediate redshift
(0.85 le z le 2.5) quasars. The spectra represent first results of our campaign
to test the redshift/luminosity robustness of the so-called Eigenvector 1 (E1)
parameter space as developed for low redshift AGN in Sulentic et al. (2000).
The new quasars span the luminosity range -26 ge M_B ge -29 while most of our
low redshift sample (n=215) involve sources in the range -19 ge M_B ge -26. The
high redshift sources show E1 parameter values and domain occupation that are
similar to our low redshift sample supporting earlier findings that E1
parameters are uncorrelated with source luminosity. Elementary accretion theory
can account for a systematic increase of the minimum observed H-beta profile
width with source luminosity. Narrow line Seyfert 1 sources with M_B = -28 show
FWHM(H-beta) as much as 2000 km/s broader than those with M_B = -22. A possible
change in the higher redshift/luminosity sources involves systematically weaker
[OIII]4959,5007 narrow line emission.


title:
First polarimetry results of two candidate high-mass protostellar
  objects

abstract:
  We present 850micron imaging polarimetry of two high-mass star forming
regions - W48 and S152. Within these regions we have identified two candidate
high-mass protostellar objects - W48W and S152SE. The submillimetre continuum
emission from the candidate HMPOs is bright in comparison to the nearby HII
regions. W48W is a cold dense source, with no radio or mid-infrared emission.
S152SE has an IRAS source IRAS 22566+5828 in the Southwestern part of the
region, which appears in the mid-infrared 8.28micron emission, but there is no
radio emission. The 850micron data shows another core within the region, in the
Northeast. The polarimetry is ordered and the degree of polarisation is high
over the candidate HMPOs - ~6% for W48W and ~8% for S152SE. Polarimetry results
of this nature indicate a strong, ordered magnetic field threading the
candidate HMPOs. The magnetic field direction in both S152SE and W48W is
perpendicular to the direction of elongation of the cloud which would imply
collapse along the field lines. Estimates of the magnetic field strength are
derived using the Chandrasekhar & Fermi method. We calculate plane of the sky
field strengths of ~0.7 mG for W48W and ~0.2 mG for S152SE. We discuss the
drawbacks of using the Chandrasekhar & Fermi method with a large beam size.
Mass-to-flux ratios have been calculated and both clouds are found to be
roughly critical.


title:
Are coronae of late type stars made of solar-like structures? The Fx-HR
  diagram and the pressure-temperature correlation

abstract:
  We show that stellar coronae can be composed of X-ray emitting structures
like those in the solar corona, using a large set of ROSAT/PSPC observations of
late-type-stars, and a large set of solar X-ray data collected with Yohkoh/SXT.
We have considered data on the solar corona at various phases of the cycle and
various kinds of X-ray coronal structures, from flares to the background
corona. The surface flux (F_x) vs. spectral hardness ratio (HR) diagram is a
fundamental tool for our study. We find that $F_X$ is strongly correlated to HR
in stellar coronae, in the solar corona at all phases of the cycle, and in the
individual solar coronal structures; all follow the same law. We therefore
claim that coronae of late type stars are formed with X-ray structures very
similar to the solar ones. In this scenario, the fraction of the stellar
surface covered with active regions and with their bright cores increases with
activity; the most active stars are brighter and hotter than if they were
entirely covered with active regions so they can be explained only with the
additional presence of several flares (or flare-like structures) at any time.
Using the F_x vs. HR correlation (F_X ~ T^6) we derive new laws relating the
temperature, pressure, volumetric heating and characteristic loop length of the
coronal plasma, on all the late type stars Individual solar coronal structures
and the whole solar corona, follow the same laws. We claim that the strong
correlation between surface flux and temperature and the laws mentioned above
are just the effect of more fundamental physical mechanisms driving the coronal
structures of all the late-type stars from the emergence of new magnetic
structures to their dissipation.


title: DAMA/NaI results

abstract:
  The DAMA/NaI set-up of the DAMA experiment has been operative during seven
annual cycles and has investigated several rare processes. In particular, it
has been realised in order to investigate the model independent annual
modulation signature for Dark Matter particles in the galactic halo. With the
total exposure collected in the seven annual cycles (107731 kg day) a model
independent evidence for the presence of a Dark Matter particle component in
the galactic halo has been pointed out at 6.3 sigma C.L.. Some of the many
possible corollary model dependent quests for the candidate particle have been
presented as well.


title: Optical studies of companions to millisecond pulsars

abstract:
  Optical observations of the companions of pulsars can help determine the
properties of the binaries, as well as those of their components, and give
clues to the preceding evolution. In this review, we first describe the
different classes of binary pulsars, and present a table with a summary what is
known about their optical counterparts. Next, we focus on the class of pulsars
that have low-mass, helium-core white dwarf companions. We discuss attempts to
determine the masses of both components using optical spectroscopy, and compare
the pulsar spin-down ages with cooling ages of the white dwarfs. We confirm
that for a given age, the lowest-mass white dwarfs are much hotter than the
more massive ones, consistent with recent evolutionary models, although with
one glaring exception. We discuss the case of PSR B0820+02, where the cooling
age indicates a braking index less than 3, and conclude by describing how
cooling ages can be used to test formation scenarios for PSR J1911-5958A, a
pulsar binary in the outskirts of NGC 6752.


title: On the instantaneous spectrum of Gamma-Ray Bursts

abstract:
  A theoretical attempt to identify the physical process responsible for the
afterglow emission of Gamma-Ray Bursts (GRBs) is presented, leading to the
occurrence of thermal emission in the comoving frame of the shock wave giving
rise to the bursts. The determination of the luminosities and spectra involves
integration over an infinite number of Planckian spectra, weighted by
appropriate relativistic transformations, each one corresponding to a different
viewing angle in the past light cone of the observer. The relativistic
transformations have been computed using the equations of motion of GRBs within
our theory, giving special attention to the determination of the equitemporal
surfaces. The only free parameter of the present theory is the ``effective
emitting area'' in the shock wave front. A self consistent model for the
observed hard-to-soft transition in GRBs is also presented. When applied to GRB
991216 a precise fit $(\chi^2\simeq 1.078)$ of the observed luminosity in the
2--10 keV band is obtained. Similarly, detailed estimates of the observed
luminosity in the 50--300 keV and in the 10--50 keV bands are obtained.


title:
XMM-Newton observations of the starburst merger galaxies NGC 3256 & NGC
  3310

abstract:
  We present XMM-Newton EPIC observations of the two nearby starburst merger
galaxies NGC 3256 & NGC 3310. The broad-band (0.3-10 keV) integrated X-ray
emission from both galaxies shows evidence of multi-phase thermal plasmas plus
an underlying hard non-thermal power-law continuum. NGC 3256 is well-fit with a
model comprising two MEKAL components (kT=0.6/0.9 keV) plus a hard power-law
(Gamma=2), while NGC 3310 has cooler MEKAL components (kT=0.3/0.6 keV) and a
harder power-law tail (Gamma=1.8). Chandra observations of these galaxies both
reveal the presence of numerous discrete sources embedded in the diffuse
emission, which dominate the emission above ~2 keV and are likely to be the
source of the power-law emission. The thermal components show a trend of
increasing absorption with higher temperature, suggesting that the hottest
plasmas arise from supernova-heated gas within the disks of the galaxies, while
the cooler components arise from outflowing galactic winds interacting with the
ambient interstellar medium (ISM). We find no strong evidence for an active
galactic nucleus (AGN) in either galaxy.


title: Abundances In Very Metal Poor Dwarf Stars

abstract:
  We discuss the detailed composition of 28 extremely metal-poor dwarfs, 22 of
which are from the Hamburg/ESO Survey, based on Keck Echelle spectra. Our
sample has a median [Fe/H] of -2.7 dex, extends to -3.5 dex, and is somewhat
less metal-poor than was expected from [Fe/H](HK,HES) determined from low
resolution spectra. Our analysis supports the existence of a sharp decline in
the distribution of halo stars with metallicity below [Fe/H] = -3.0 dex. So far
no additional turnoff stars with [Fe/H]}<-3.5 have been identified in our
follow up efforts. For the best observed elements between Mg and Ni, we find
that the abundance ratios appear to have reached a plateau, i.e. [X/Fe] is
approximately constant as a function of [Fe/H], except for Cr, Mn and Co, which
show trends of abundance ratios varying with [Fe/H]. These abundance ratios at
low metallicity correspond approximately to the yield expected from Type II SN
with a narrow range in mass and explosion parameters; high mass Type II SN
progenitors are required. The dispersion of [X/Fe] about this plateau level is
surprisingly small, and is still dominated by measurement errors rather than
intrinsic scatter. The dispersion in neutron-capture elements, and the
abundance trends for Cr, Mn and Co are consistent with previous studies of
evolved EMP stars. Two dwarfs in the sample are carbon stars, while two others
have significant C enhancements, all with C12/C13 ~ 7 and with C/N between 10
and 150. Three of these C-rich stars have large enhancements of the heavy
neutron capture elements, including lead, which implies a strong s-process
contribution, presumably from binary mass transfer; the fourth shows no excess
of Sr or Ba.


title: Pixelized Gas Micro-well Detectors for Advanced Gamma-ray Telescopes

abstract:
  We describe possible applications of pixelized micro-well detectors (PMWDs)
as three-dimensional charged particle trackers in advanced gamma-ray telescope
concepts. A micro-well detector consists of an array of individual
micro-patterned gas proportional counters opposite a planar drift electrode.
When combined with pixelized thin film transistor (TFT) array readouts, large
gas volumes may be imaged with very good spatial and energy resolution at
reasonable cost. The third dimension is determined by timing the drift of the
ionization electrons. The primary advantage of this technique is the very low
scattering that the charged particles experience in a gas tracking volume, and
the very accurate determination of the initial particle momenta that is thus
achieved. We consider two applications of PMWDs to gamma-ray astronomy: 1) A
tracker for an Advanced Compton Telescope (ACT) in which the recoil electron
from the initial Compton scatter may be accurately tracked, greatly reducing
the telescope's point spread function and increasing its polarization
sensitivity; and 2) an Advanced Pair Telescope (APT) whose angular resolution
is limited primarily by the nuclear recoil and which achieves useful
polarization sensitivity near 100 MeV. We have performed Geant4 simulations of
both these concepts to estimate their angular resolution and sensitivity for
reasonable mission designs.


title: Superclusters and Voids in the Sloan DSS

abstract:
  We analyze quasi-2-dimensional slices of the SDSS EDR. Gaussian smoothing
with weighting by the inverse of the selection function provides 2D density
fields across the full survey depth. Superclusters (SC) are characterized by a
percolation algorithm in the large-scale smoothed field. Group candidates are
identified with density maxima in the small-scale smoothed field. The group
mass function depends on the SC environmental density. We derive the
shape-dependent 3-point correlation function and the void size distribution.
These are well reproduced by the galaxies identified in high-resolution
$\Lambda$CDM simulations.


title: Core-Collapse Supernovae: Modeling between Pragmatism and Perfectionism

abstract:
  We briefly summarize recent efforts in Garching for modeling stellar core
collapse and post-bounce evolution in one and two dimensions. The transport of
neutrinos of all flavors is treated by iteratively solving the coupled system
of frequency-dependent moment equations together with a model Boltzmann
equation which provides the closure. A variety of progenitor stars, different
nuclear equations of state, stellar rotation, and global asymmetries due to
large-mode hydrodynamic instabilities have been investigated to ascertain the
road to finally successful, convectively supported neutrino-driven explosions.


title: Shocks and Wind Bubbles Around Energetic Pulsars

abstract:
  The Crab Nebula demonstrates that neutron stars can interact with their
environments in spectacular fashion, their relativistic winds generating
nebulae observable across the electromagnetic spectrum. At many previous
conferences, astronomers have discussed, debated and puzzled over the
complicated structures seen in the Crab, but have been limited to treating most
other pulsar wind nebulae (PWNe) as simple calorimeters for a pulsar's
spin-down energy. However, with the wealth of high-quality data which have now
become available, this situation has changed dramatically. I here review some
of the main observational themes which have emerged from these new
measurements. Highlights include the ubiquity of pulsar termination shocks, the
unambiguous presence of relativistic jets in PWNe, complicated time variability
seen in PWN structures, and the use of bow shocks to probe the interaction of
pulsar winds with the ambient medium.


title:
Search for very high energy gamma-rays from WIMP annihilations near the
  Sun with the Milagro Detector

abstract:
  The neutralino, the lightest stable supersymmetric particle, is a strong
theoretical candidate for the missing astronomical ``dark matter''. A profusion
of such neutralinos can accumulate near the Sun when they lose energy upon
scattering and are gravitationally captured. Pair-annihilations of those
neutralinos may produce very high energy (VHE, above $100 GeV$) gamma-rays.
  Milagro is an air shower array which uses the water Cherenkov technique to
detect extensive air showers and is capable of observing VHE gamma-rays from
the direction of the Sun with an angular resolution of $0.75^{\circ}$. Analysis
of Milagro data with an exposure to the Sun of 1165 hours presents the first
attempt to detect TeV gamma-rays produced by annihilating neutralinos captured
by the Solar system and shows no statistically significant signal. Resulting
limits that can be set on gamma-ray flux due to near-Solar neutralino
annihilations and on neutralino cross-section are presented.


title: First Results from a Multi-wavelength Survey of Quasar Jets

abstract:
  We present results based on the first 20 Chandra images obtained in a survey
of jets in radio selected flat-spectrum quasars (FSRQs), along with new
sub-arcsecond radio maps and optical images. We discover jet X-ray flux in 12
sources despite short exposures, establishing that FSRQ jets are often X-ray
bright. The X-ray morphology typically matches the radio and fades rapidly
after the first sharp radio bend, but there are notable exceptions. Optical
non-detections rule out simple synchrotron models for jet X-ray emission,
implying these systems are dominated by inverse Compton (IC) scattering. Models
of IC scattering of the cosmic microwave background (CMB) constrain the bulk
flow and magnetic field, suggesting the jets are oriented close to our line of
sight, with deprojected lengths often \gg 100 kpc.


title: The cooling flow cluster Abell 2626 and the associated radio emission

abstract:
  We present VLA data at 330 MHz and 1.5 GHz of the radio emission observed in
the cooling flow cluster A2626. By producing images at different resolutions we
found that the radio source consists of different components: an unresolved
core plus a jet-like feature, two elongated parallel features, and an extended
diffuse emission (radio mini-halo). Low resolution images allow us to derive
morphological and spectral information of the diffuse emission: the radio
mini-halo is extended on a scale comparable to that of the cooling flow region
and is characterized by amorphous morphology, lack of polarized flux and very
steep spectrum which steepens with distance from the center. We then applied to
this new mini-halo source a model for particle re-acceleration in cooling flows
(Gitti, Brunetti & Setti 2002). In particular, we found that its main radio
properties (brightness profile, integrated radio spectrum and radial spectral
steepening) can be accounted for by the synchrotron radiation from relic
relativistic electrons in the cluster, which are efficiently re-accelerated by
MHD turbulence amplified by the compression of the cluster magnetic field in
the cooling flow region.


title: A Two-Fluid Thermally-Stable Cooling Flow Model

abstract:
  A new model for cooling flows in X-ray clusters, capable of naturally
explaining salient features observed, is proposed. The only requirement is that
a significant relativistic component, in the form of cosmic rays (CR), be
present in the intra-cluster medium and significantly frozen to the thermal
gas. Such an addition qualitatively alters the conventional isobaric thermal
instability criterion such that a fluid parcel becomes thermally stable when
its thermal pressure drops below a threshold fraction of its CR pressure.
Consequently, the lowest possible temperature at any radius is about one third
of the ambient temperature {\it at that radius}, exactly as observed, In
addition, we suggest that dissipation of internal gravity waves, excited by
radial oscillatory motions of inward drifting cooling clouds about their radial
equilibrium positions, may be responsible for heating up cooling gas. With the
ultimate energy source for powering the cooling X-ray luminosity and heating up
cooling gas being gravitational due to inward drifting cooling clouds as well
as the general inward flow, heating is spatially distributed and energetically
matched with cooling. One desirable property of this heating mechanism is that
heating energy is strongly centrally concentrated, providing the required
heating for emission-line nebulae.


title: AC 114: a cluster with a soft X-ray tail

abstract:
  We present Chandra observations of the galaxy cluster AC114, which shows a
strongly irregular morphology, with signs of multiple merging activity. We
report the discovery of a soft X-ray filament originating close to the core of
the cluster. We confirm that X-ray emission is associated with two of three
mass concentrations identified in previous gravitational lensing studies of
this object. These two mass concentrations are located at opposite ends of the
soft filament, evidence for interaction between them. In the northern part, the
cluster shows two sharp discontinuities, both in surface brightness and in
temperature, evincing another, more recent merger event which took place in, or
close, to the cluster core. In spite of the merger activity, a combined mass
and lensing analysis shows remarkably good agreement between lensing and X-ray
masses. We therefore advocate for the robustness of the X-ray mass estimates,
and conclude that the assumption of hydrostatic equilibrium can yield accurate
mass estimates even in clusters as dynamically active as AC 114, once the gas
density distribution is properly mapped.


title: Physical processes behind the alignment effect

abstract:
  The radio/optical alignment effect for small powerful radio galaxies has been
shown to be produced by shock waves formed by the interaction of the head of
the jet and/or cocoon with clouds embedded in the interstellar/intergalactic
medium. We present here preliminary results of analytical and numerical
solutions that have been made to account for the production of implosive shock
waves induced by embedding cold clouds in the radio lobe of expanding powerful
radio sources.


title: The angular velocity of the apsidal rotation in binary stars

abstract:
  The shape of a rotating star consisting of equilibrium plasma is considered.
The velocity of apsidal rotation of close binary stars (periastron rotation)
which depends on the star shapes is calculated. The obtained estimations are in
a good agreement with the observation data of the apsidal motion in binary
systems.


title:
Ordinary Chondrite Formation from two Components: Implied Connection to
  Planet Mercury

abstract:
  Major element fractionation among chondrites has been discussed for decades
as ratios relative to Si or Mg. Expressing ratios relative to Fe leads to a new
relationship admitting the possibility that ordinary chondrite meteorites are
derived from two components: one is a relatively undifferentiated, primitive
component, oxidized like the CI or C1 chondrites; the other is a somewhat
differentiated, planetary component, with oxidation state like the reduced
enstatite chondrites. Such a picture would seem to explain for the ordinary
chondrites, their major element compositions, their intermediate states of
oxidation, and their ubiquitous deficiencies of refractory siderophile
elements. I suggest that the planetary component of ordinary chondrite
formation consists of planet Mercury's missing complement of elements.


title:
A near-infrared survey of the N49 region around the Soft Gamma-Ray
  Repeater 0526-66

abstract:
  We report the results of a deep near-infrared survey with VLT/ISAAC of the
environment of the supernova remnant N49 in the Large Magellanic Cloud, which
contains the soft gamma-ray repeater SGR 0526-66. Two of the four confirmed
SGRs are potentially associated with compact stellar clusters. We thus searched
for a similar association of SGR 0526-66, and imaged a young stellar cluster at
a projected distance of ~30 pc from the SGR. This constitutes the third
cluster-SGR link, and lends support to scenarios in which SGR progenitors
originate in young, dusty clusters. If confirmed, the cluster-SGR association
constrains the age and thus the initial mass of SGR progenitors.


title: The Angular Size and Proper Motion of the Afterglow of GRB 030329

abstract:
  The bright, nearby (z=0.1685) gamma-ray burst of 29 March 2003 has presented
us with the first opportunity to directly image the expansion of a GRB. This
burst reached flux density levels at centimeter wavelengths more than 50 times
brighter than any previously studied event. Here we present the results of a
VLBI campaign using the VLBA, VLA, Green Bank, Effelsberg, Arecibo, and
Westerbork telescopes that resolves the radio afterglow of GRB 030329 and
constrains its rate of expansion. The size of the afterglow is found to be
\~0.07 mas (0.2 pc) 25 days after the burst, and 0.17 mas (0.5 pc) 83 days
after the burst, indicating an average velocity of 3-5 c. This expansion is
consistent with expectations of the standard fireball model. We measure the
projected proper motion of GRB 030329 in the sky to <0.3 mas in the 80 days
following the burst. In observations taken 52 days after the burst we detect an
additional compact component at a distance from the main component of 0.28 +/-
0.05 mas (0.80 pc). The presence of this component is not expected from the
standard model.


title:
Asymmetric Surface Brightness Distribution of Altair Observed with the
  Navy Prototype Optical Interferometer

abstract:
  An asymmetric surface brightness distribution of the rapidly rotating A7IV-V
star, Altair, has been measured by the Navy Prototype Optical Interferometer
(NPOI). The observations were recorded simultaneously using a triangle of three
long baselines of 30m, 37m, and 64m, on 19 spectral channels, covering the
wavelength range of 520nm to 850nm. The outstanding characteristics of these
observations are (a) high resolution with the minimum fringe spacing of 1.7mas,
easily resolving the 3-milliarcsecond (mas) stellar disk, and (b) the
measurement of closure phase which is a sensitive indicator to the asymmetry of
the brightness distribution of the source. Uniform disk diameters fit to the
measured squared visibility amplitudes confirms the Altair's oblate shape due
to its rapid rotation. The measured observables of Altair showed two features
which are inconsistent with both the uniform-disk and limb-darkened disk
models, while the measured observable of the comparison star, Vega, are
consistent with the limb-darkened disk model. The first feature is that
measured squared visibility amplitudes at the first minimum do not reach 0.0
but rather remain at about 0.02, indicating the existence of a small bright
region on the stellar disk. The other is that the measured closure phases show
non-zero/180 degrees at all spectral channels, which requires an asymmetric
surface brightness distribution. We fitted the measured observables to a model
with a bright spot on a limb-darkened disk and found the observations are well
reproduced by a bright spot, which has relative intensity of 4.7%, on a 3.38
mas limb-darkened stellar disk. Rapid rotation of Altair indicates that this
bright region is a pole, which is brighter than other part of the star owing to
gravity darkening.


title:
Luminous infrared galaxies as plausible gamma-ray sources for GLAST and
  IACTs

abstract:
  We argue that luminous infrared galaxies (LIGs) may constitute a newly
detectable population of gamma-ray sources for the next generation of ground
and space-based high energy telescopes. Additionally, we report for the first
time upper limits on their fluxes using data obtained with the EGRET telescope.


title: Morphological Statistics of the Cosmic Web

abstract:
  We report the {\em first} systematic study of the supercluster-void network
in the $\Lambda$CDM concordance cosmology treating voids and superclusters on
an equal footing. We study the dark matter density field in real space smoothed
with the $L_s = 5$ \hm1 Mpc Gaussian window. Superclusters and voids are
defined as individual members of over-dense and under-dense excursion sets
respectively. We determine the morphological properties of the cosmic web at a
large number of dark matter density levels by computing Minkowski functionals
for every supercluster and void. At the adopted smoothing scale individual
superclusters totally occupy no more than about 5% of the total volume and
contain no more than 20% of mass if the largest supercluster is excluded.
Likewise, individual voids totally occupy no more than 14% of volume and
contain no more than 4% of mass if the largest void is excluded.
  The genus of individual superclusters can be $\sim 5$ while the genus of
individual voids reaches $\sim 55$, implying significant amount of substructure
in superclusters and especially in voids. Large voids are typically distinctly
non-spherical.


title: The abundance of Lyman-(\alpha) emitters in hierarchical models

abstract:
  We present predictions for the abundance of Ly-$\alpha$ emitters in
hierarchical structure formation models. We use the {\tt GALFORM}
semi-analytical model to explore the impact on the predicted counts of varying
assumptions about the escape fraction of Ly-$\alpha$ photons, the redshift at
which the universe reionised and the cosmological density parameter. A model
with a fixed escape fraction gives a remarkably good match to the observed
counts over a wide redshift interval. We present predictions for the expected
counts in a typical observation with the Multi Unit Spectroscopic Explorer
instrument proposed for the Very Large Telescope.


title:
First detection of a lithium rich carbon star in the Draco dwarf galaxy:
  evidence for a young stellar population

abstract:
  We present a spectroscopic study of D461, a giant star belonging to Draco
dwarf spheroidal galaxy. From spectral synthesis in LTE we derive a lithium
abundance of log e(Li)=3.5+/-0.4 and a C/O ratio between 3 and 5. This is the
first detection of a lithium rich C-star in a dwarf spheroidal galaxy. Basing
on stellar models of appropriate chemical composition, we show that a similar C
enrichment is compatible with that expectedfor a low mass low metallicity
thermally pulsing AGB star, undergoing few third dredge up episodes. The
position in the log g-log Teff diagram of D461 is also compatible with this
theoretical scenario. In particular, the low effective temperature, lower than
that expected for a low metallicity giant star, is a consequence of the huge
increase of the envelope opacity occurring after the carbon dredge up. The Li
enrichment may be explained if a deep circulation would take place during the
interpulse period, the so called cool bottom process. In spite of the low
resolution of our spectra, we derive a lower limit for the carbon isotopic
ratio, namely 12C/13C>40, and a constraint for the Ba abundance, namely
0.5<[Ba/Fe]< 2. The proposed scenario also fits these further constraints.
Then, we estimate that the mass of D461 ranges between 1.2 and 2 $M_\odot$,
which corresponds to an age ranging between 1 and 3 Gyr. We conclude that this
star is more massive and younger than the typical stellar population of Draco.


title: The Emergence of the Thick Disk in a CDM Universe

abstract:
  The disk galaxy simulated using our chemo-dynamical galaxy formation code,
GCD+, is shown to have a thick disk component. This is evidenced by the
velocity dispersion versus age relation for solar neighbourhood stars, which
clearly shows an abrupt increase in velocity dispersion at lookback time of
approximately 8 Gyrs, and is in excellent agreement with observation. These
thick disk stars are formed from gas which is accreted to the galaxy during a
chaotic period of hierarchical clustering at high redshift. This formation
scenario is shown to be consistent with observations of both the Milky Way and
extragalactic thick disks.


title: X-ray spectroscopy on Abell 478 with XMM-Newton

abstract:
  We report the results from a spatially resolved spectroscopy study with
XMM-Newton on the relaxed cluster of galaxies Abell 478. From the EPIC data we
extract a temperature profile and radial abundance profiles for Ne, Mg, Si, S,
Ca, Fe and Ni. The abundance profiles follow the same trends as observed in
other clusters. The spectra of the core of the cluster can be best fitted with
a multi-temperature model. We argue that this multi-temperature behavior is
mostly due to projection effects, because of the strong temperature gradient in
the core. Contributions from other effects, for example, intrinsic temperature
stratification cannot be fully excluded. For the first time we measure an
underabundance of oxygen in the Galactic absorption component toward a cluster.
The measured oxygen abundance in this absorber is about 0.5 times the solar
oxygen abundance as determined by Anders & Grevesse (1989).


title: Discovery of kilogauss magnetic fields in three DA white dwarfs

abstract:
  We have detected longitudinal magnetic fields between 2 and 4 kG in three (WD
0446$-$790, WD 1105$-$048, WD 2359$-$434) out of a sample of 12 normal DA white
dwarfs by using optical spectropolarimetry done with the VLT Antu 8 m telescope
equipped with FORS1. With the exception of 40 Eri B (4 kG) these are the first
positive detections of magnetic fields in white dwarfs below 30 kG. Although
suspected, it was not clear whether a significant fraction of white dwarfs
contain magnetic fields at this level. These fields may be explained as fossil
relics from magnetic fields in the main-sequence progenitors considerably
enhanced by magnetic flux conservation during the shrinkage of the core. A
detection rate of 25 % (3/12) may indicate now for the first time that a
substantial fraction of white dwarfs have a weak magnetic field. This result,
if confirmed by future observations, would form a cornerstone for our
understanding on the evolution of stellar magnetic fields.
  Keywords: stars: white dwarfs - stars: magnetic fields - stars: individual:
WD0446-790, WD1105-048, WD2359-434


title:
On-axis spectroscopy of the z=0.144 radio-loud quasar HE 1434-1600: an
  elliptical host with a highly ionized ISM

abstract:
  VLT on-axis optical spectroscopy of the z=0.144 radio-loud quasar HE
1434-1600 is presented. The spatially resolved spectra of the host galaxy are
deconvolved and separated from those of the central quasar in order to study
the dynamics of the stars and gas as well as the physical conditions of the
ISM. We find that the host of HE 1434-1600 is an elliptical galaxy that resides
in a group of at least 5 member galaxies, and that most likely experienced a
recent collision with its nearest companion. Compared with other quasar host
galaxies, HE 1434-1600 has a highly ionized ISM. The ionization state
corresponds to that of typical Seyferts, but the ionized regions are not
distributed in a homogeneous way around the QSO, and are located preferentially
several kiloparsecs away from it. While the stellar absorption lines do not
show any significant velocity field, the gas emission lines do. The observed
gas velocity field is hard to reconcile with dynamical models involving
rotating disk, modified Hubble laws or power laws, that all require extreme
central masses (M > 10^9 M_sun) to provide only poor fit to the data. Power law
models, which best fit the data, provide a total mass of M(< 10 kpc)=9.2 10^10
M_sun. We conclude that the recent interaction between HE 1434-1600 and its
closest companion has strongly affected the gas velocity and ionization state,
from the center of the galaxy to its most external parts.


title: Cosmic rays from Galactic pulsars

abstract:
  We calculate energy spectra and mass composition of cosmic rays accelerated
by the galactic population of pulsars during their radio and gamma-ray phase.
Several models proposed for the distribution of the initial parameters of the
galactic pulsar population are considered. The best description of the observed
cosmic ray spectrum and mass composition between 10^15 eV and 10^18 eV is
obtained for the model B of Lorimer et al. (1993) in which the logs of initial
pulsar periods and surface magnetic fields are given by the Gaussian
distributions with the average values of log P[ms] = 2.6 and log B[G] = 12.3,
respectively.


title: Global Anisotropies in Supernova Explosions and Pulsar Recoil

abstract:
  We show by two-dimensional and first three-dimensional simulations of
neutrino-driven supernova explosions that low (l=1,2) modes can dominate the
flow pattern in the convective postshock region on timescales of hundreds of
milliseconds after core bounce. This can lead to large global anisotropy of the
supernova explosion and pulsar kicks in excess of 500 km/s.


title:
Chemical abundances in spiral and irregular galaxies. O and N abundances
  derived from global emission--line spectra

abstract:
  The validity of oxygen and nitrogen abundances derived from the global
emission-line spectra of galaxies via the P-method has been investigated using
a collection of published spectra of individual HII regions in irregular and
spiral galaxies. The conclusions of Kobulnicky, Kennicutt & Pizagno (1999) that
global emission-line spectra can reliably indicate the chemical properties of
galaxies has been confirmed. It has been shown that the comparison of the
global spectrum of a galaxy with a collection of spectra of individual HII
regions can be used to distinguish high and low metallicity objects and to
estimate accurate chemical abundances in a galaxy. The oxygen and nitrogen
abundances in samples of UV-selected and normal nearby galaxies have been
determined. It has been found that the UV-selected galaxies occupy the same
area in the N/O -- O/H diagram as individual HII regions in nearby galaxies.
Finally, we show that intermediate-redshift galaxies systematically deviate
from the metallicity -- luminosity trend of local galaxies.


title: Full-Fledged Dwarf Irregular Galaxy Leo A

abstract:
  We have studied Leo A - the isolated and extremely gas rich dwarf irregular
galaxy of very low stellar mass and metallicity. Ages of the stellar
populations in Leo A are ranging from ~10 Myr to ~10 Gyr. Here we report the
discovery of an old stellar halo and a sharp stellar edge. Also we find the
distribution of stars extending beyond the gaseous envelope of the galaxy.
Therefore, Leo A by its structure as well as stellar and gaseous content is
found to resemble massive disk galaxies. This implies that galaxies of very low
stellar mass are also able to develop complex structures, challenging
contemporary understanding of galaxy evolution.


title:
Influence of interstellar and atmospheric extinction on light curves of
  eclipsing binaries

abstract:
  Interstellar and atmospheric extinctions redden the observational photometric
data and they should be handled rigorously. This paper simulates the effect of
reddening for the modest case of two main sequence T1 = 6500K and T2 = 5500K
components of a detached eclipsing binary system. It is shown that simply
subtracting a constant from measured magnitudes (the approach often used in the
field of eclipsing binaries) to account for reddening should be avoided.
Simplified treatment of the reddening introduces systematics that reaches
\~0.01mag for the simulated case, but can be as high as ~0.2mag for e.g.
B8V--K4III systems. With rigorous treatment, it is possible to uniquely
determine the color excess value E(B-V) from multi-color photometric light
curves of eclipsing binaries.


title:
A pseudo-planar, periodic-box formalism for modelling the outer
  evolution of structure in spherically expanding stellar winds

abstract:
  We present an efficient technique to study the 1D evolution of
instability-generated structure in winds of hot stars out to very large
distances (more than 1000 stellar radii). This technique makes use of our
previous finding that external forces play little role in the outer evolution
of structure. Rather than evolving the entire wind, as is traditionally done,
the technique focuses on a representative portion of the structure and follows
it as it moves out with the flow. This requires the problem to be formulated in
a moving reference frame. The lack of Galilean invariance of the spherical
equations of hydrodynamics is circumvented by recasting them in a pseudo-planar
form. By applying the technique to a number of problems we show that it is fast
and accurate, and has considerable conceptual advantages. It is particularly
useful to test the dependence of solutions on the Galilean frame in which they
were obtained. As an illustration, we show that, in a one-dimensional
approximation, the wind can remain structured out to distances of more than
1300 stellar radii from the central star.


title: Polarimetric observations of OH masers in proto-planetary nebulae

abstract:
  The 1612 and 1667 MHz OH maser lines have been measured in all four Stokes
parameters in 47 proto-planetary nebula (PPN) candidates. Out of 42 objects
detected, 40 and 34 are 1612 and 1667 MHz emitters, respectively. The spectral
extent of the 1667 MHz line overshoots that of the 1612 MHz line in about 80%
of the targets. 52% and 26% of the 1612 and 1667 MHz sources, respectively,
show linear polarization in at least some features. Circular polarization is
more frequent, occurring in 78% and 32% of sources of the respective OH lines.
The percentage polarization is usually small (<15%) reaching up to 50-80% in a
few sources. Features of linearly polarized emission are usually weak (0.5-4Jy)
and narrow (0.3-0.5kms^{-1}). The strength of magnetic field inferred from
likely Zeeman pairs in two sources of a few mG is consistent with values
reported elsewhere for those classes of objects. An upper limit of the electron
density in the envelope of OH17.7-2.0 derived from the difference in the
position angle of polarization vectors for the two OH lines is about 1cm^{-3}.
Distinct profiles of polarization position angle at 1612 and 1667 MHz are seen
in about one third of the sources and strongly suggest that the envelopes are
permeated with structured magnetic fields. The geometry of the magnetic field
is implicated as an important cause of the depolarization found in some PPN
candidates. For the subset of targets which show axisymmetric shells in the
optical or radio images we found a dominance of magnetic field components which
are orthogonal to the long axis of the nebulae. This finding supports the
hypothesis that such bipolar lobes are shaped by the magnetic field.


title: A possible radio supernova in the outer part of NGC 3310

abstract:
  As part of an on-going radio supernova monitoring program, we have discovered
a variable, compact steep spectrum radio source ~65 arcsec (~4 kpc) from the
centre of the starburst galaxy NGC 3310. If the source is at the distance of
NGC 3310, then its 5 GHz luminosity is ~3 x 10^{19} WHz^-1. The source
luminosity, together with its variability characteristics, compact structure
(<17 mas) and its association with a group of HII regions, leads us to propose
that it is a previously uncatalogued type II radio supernova. A search of
archival data also shows an associated X-ray source with a luminosity similar
to known radio supernova.


title: Intrinsic spectra and energetics of cosmological Gamma-Ray Bursts

abstract:
  We extend a previous work on the intrinsic spectral properties and energetics
of GRBs with known redshift based on 12 BeppoSAX events by including in the
sample a total of 10 more events detected either by BATSE, BeppoSAX or HETE-2.
An indication of a trend of the total isotropic equivalent radiated energy,
E_rad, with redshift is found and, remarkably, the previously found
relationship between the peak energy of the rest-frame nuFnu spectrum, E_p,rest
, and E_rad is confirmed and its significance increased. The implications of
these results are briefly discussed in the framework of standard models for the
prompt emission of GRBs.


title: Limits on the Optical Brightness of the Epsilon Eridani Dust Ring

abstract:
  The STIS/CCD camera on the {\em Hubble Space Telescope (HST)} was used to
take deep optical images near the K2V main-sequence star $\epsilon$ Eridani in
an attempt to find an optical counterpart of the dust ring previously imaged by
sub-mm observations. Upper limits for the optical brightness of the dust ring
are determined and discussed in the context of the scattered starlight expected
from plausible dust models. We find that, even if the dust is smoothly
distributed in symmetrical rings, the optical surface brightness of the dust,
as measured with the {\em HST}/STIS CCD clear aperture at 55 AU from the star,
cannot be brighter than about 25 STMAG/"$^2$. This upper limit excludes some
solid grain models for the dust ring that can fit the IR and sub-mm data.
Magnitudes and positions for $\approx $59 discrete objects between 12.5" to 58"
from $\epsilon$ Eri are reported. Most if not all of these objects are likely
to be background stars and galaxies.


title: The BeppoSAX revolution in Gamma-Ray Burst science

abstract:
  We review the BeppoSAX discoveries and studies in the field of Gamma-Ray
Bursts, which allowed a huge step forward in the understanding of these still
mysterious and highly interesting astrophysical sources.


title:
GIRAFFE multiple integral field units at VLT: a unique tool to recover
  velocity fields of distant galaxies

abstract:
  The GIRAFFE spectrograph is unique in providing the integral field
spectroscopy of fifteen distant galaxies at the same time. It has been
successfully implemented at the second VLT unit within the FLAMES facility. We
present GIRAFFE observations acquired during the Guaranteed Time Observation of
the Paris Observatory, using total exposure times ranging from 6 to 12 hours.
The reduced 3D cube of each galaxy has been deconvolved using our new package
DisGal3D. This software has been written using the only assumption that UV
light traces the emission line regions. The comparison between GIRAFFE spectra
and HST imagery allows us to recover details on velocity fields as small as
0.3-0.4 arcsec. It has been successfully tested using Fabry Perot observations
of nearby galaxies purposely redshifted to large distances. We present here
preliminary results for three distant galaxies at 0.45< z < 0.65, whose
velocity fields have been derived with exquisite spectral (R=10000) and spatial
resolutions. Observed velocity fields range from disturbed fields expected in
major merger events to those of regular spiral with minor perturbations. For
the latter, one could accurately derive the dynamical major axis and the
maximal rotational velocity. We conclude that dynamical properties of a large
number of distant galaxies can be routinely derived at VLT. This opens a new
avenue towards the understanding of the galaxy formation and evolution during
the last 8 Gyr.


title:
Present-day scaling relations of submm galaxies: origin of spheroidal
  sytems

abstract:
  We analyse the spectral energy distributions (SEDs) of 23 submm galaxies and
3 ISO-detected EROs, all of which have the spectroscopic redshifts, by using an
evolutionary SED model of starbursts. This SED model allows us to investigate
intrinsic properties of starbursts, such as the starburst age and the mean
stellar metallicity, as it takes into account the chemical evolution. Also, the
intrinsic size of the starburst region is estimated from observed SEDs. Using
this SED model, we predict colour, magnitude, and size of present-day
descendants of submm galaxies, and derive scaling relations, such as the
present-day colour-magnitude and size-magnitude relations. We argue that submm
galaxies are the progenitors of present-day elliptical galaxies, provided that
the initial mass function (IMF) of submm galaxies is slightly flatter than the
Salpeter IMF. In this case, we find that 1) the mean present-day magnitude of
submm galaxies is similar to that of L* elliptical galaxies, 2) the present-day
colour-magnitude relation is consistent with that of elliptical galaxies, 3)
the present-day size-magnitude relation of elliptical galaxies can be
reproduced if massive submm galaxies consist of multiple starburst regions. We
estimate the effect of feedback in submm galaxies as a function of starburst
age. It is found that starburst regions in submm galaxies are likely to be
self-regulated; i.e. the effect of feedback is nearly balanced with the
self-gravity of starburst regions.


title:
Radio source contamination of the Sunyaev-Zeldovich effect in galaxy
  clusters

abstract:
  By cross-correlating the 1.4 GHz FIRST catalog of radio sources with the
Abell cluster catalog we have found an excess surface density by a factor ~5 of
radio sources within a projected distance, r_p, of 0.1 Mpc (for h=0.65) from
the cluster center. The profile of the excess density can be described, for r_p
> 0.1 Mpc, by a beta-model with a core radius of ~0.70 Mpc and beta=1.65. The
luminosity function of cluster sources does not show hints of cosmological
evolution over the redshift range (z>~0.4) covered by our cluster sample. The
mean luminosity function is in excellent agreement with the recent
determination by Reddy & Yun (2004) for 7 nearby clusters and extends it by two
orders of magnitude to higher luminosities. Its shape is very similar to that
of the local luminosity function of field galaxies, but the space density is
about 3000 times higher. When extrapolated to 30 GHz, our luminosity function
compares very favourably with an estimate obtained directly from the 30 GHz
observations by Cooray et al. (1998). The antenna temperature contributed by
radio sources within the nominal cluster radius of 1.7 Mpc is estimated to be
\~13.5 microK at 30 GHz for clusters at z~0 and decreases to ~3.4 microK at
z~0.5, in the absence of cosmological evolution; it increases by a factor of
\~1.5 within 0.25 Mpc from the cluster center. If the pure luminosity evolution
models by Dunlop & Peacock (1990) are adopted, the radio source antenna
temperature turns out to be essentially independent of redshift.


title:
A giant molecular cloud falling through the heart of Cygnus A: clues to
  the triggering of the activity

abstract:
  We present intermediate resolution near-IR long-slit spectroscopic data for
the nearby radio galaxy Cygnus A (3C 405) (obtained with the NIRSPEC
spectrograph on the Keck II telescope). The data reveal considerable complexity
in the near-IR emission line kinematics, including line splittings of 200-350
km/s and a mixture of narrow (FWHM ~200 km/s) and broad (FWHM ~700 km/s)
components to the emission lines. It is notable that the Pa alpha and H2
emission lines show markedly different kinematics, both on- and off-nucleus.
Overall, the data provide evidence for the presence of a giant molecular cloud
falling through the heart of the Cygnus A host galaxy, the motion of which is
not driven by the AGN itself. We suggest that this cloud may be connected to
the triggering of the activity in this highly powerful AGN. We also detect
split H2 components on the nucleus that are likely to originate in the
circum-nuclear torus.


title: A transient high-coherence oscillation in 4U 1820-30

abstract:
  We re-analyzed two Rossi X-Ray Timing Explorer archival observations of the
atoll source 4U 1820-30 in order to investigate the detailed time-frequency
properties of the source during the intervals when a ~7 Hz QPO was detected by
Wijnands et al. (1999, ApJ, 512, L39). We find that in both observations, in
addition to a QPO signal lasting a couple of minutes as previously reported,
there is a much narrower transient oscillation with a life time of only a few
seconds. Within this time, the oscillation is consistent with being coherent.
Its integrated fractional rms is around 10% and its frequency 7.3 Hz and 5.7 Hz
in the two observations. We discuss the possible association of this QPO with
other oscillations known both in Neutron-Star and Black-Hole systems,
concentrating on the similarities with the narrow 5-7 Hz oscillations observed
at high flux in Black-Hole Candidates.


title:
Internal Color Properties of Resolved Spheroids in the Deep HST/ACS
  field of UGC 10214

abstract:
  (Abridged) We study the internal color properties of a morphologically
selected sample of spheroidal galaxies taken from HST/ACS ERO program of UGC
10214 (``The Tadpole''). By taking advantage of the unprecedented high
resolution of the ACS in this very deep dataset we are able to characterize
spheroids at sub-arcseconds scales. Using the V_606W and I_814W bands, we
construct V-I color maps and extract color gradients for a sample of spheroids
at I_814W < 24 mag. We investigate the existence of a population of
morphologically classified spheroids which show extreme variation in their
internal color properties similar to the ones reported in the HDFs. These are
displayed as blue cores and inverse color gradients with respect to those
accounted from metallicity variations. Following the same analysis we find a
similar fraction of early-type systems (~30%-40%) that show non-homologous
internal colors, suggestive of recent star formation activity. We present two
statistics to quantify the internal color variation in galaxies and for tracing
blue cores, from which we estimate the fraction of non-homogeneous to
homogeneous internal colors as a function of redshift up to z<1.2. We find that
it can be described as about constant as a function of redshift, with a small
increase with redshift for the fraction of spheroids that present strong color
dispersions. The implications of a constant fraction at all redshifts suggests
the existence of a relatively permanent population of evolving spheroids up to
z~1. We discuss the implications of this in the context of spheroidal
formation.


title:
Organic matter in Seyfert2 nuclei : comparison with our Galactic center
  lines of sight

abstract:
  We present ESO - Very Large Telescope and ESA - Infrared Space Observatory 3
to 4 $\mu$m spectra of Seyfert 2 nuclei as compared to our galactic center
lines of sight. The diffuse interstellar medium probed in both environments
displays the characteristic 3.4 $\mu$m aliphatic CH stretch absorptions of
refractory carbonaceous material. The profile of this absorption feature is
similar in all sources, indicating the CH$_2$/CH$_3$ ratios of the carbon
chains present in the refractory components of the grains are the same in
Seyfert 2 inner regions. At longer wavelengths the circumstellar contamination
of most of the galactic lines of sight precludes the identification of other
absorption bands arising from the groups constitutive of the aliphatics seen at
3.4 $\mu$m. The clearer continuum produced by the Seyfert 2 nuclei represents
promising lines of sight to constrain the existence or absence of strongly
infrared active chemical groups such as the carbonyl one, important to
understand the role of oxygen insertion in interstellar grains. The Spitzer
Space Telescope spectrometer will soon allow one to investigate the importance
of aliphatics on a much larger extragalactic sample.


title: Circular polarimetry of magnetic cataclysmic variables

abstract:
  Magnetic cataclysmic variables are complex accreting binary systems with
short orbital periods. Here we present circular polarimetry of five magnetic
cataclysmic variable candidates. 1RXS J161008.0+035222, V1432 Aql, and 1RXS
J231603.9-052713 have cyclotron emission, which confirms them as AM Her
systems. Our data are consistent with zero values for the circular polarization
of 1RXS J042555.8-194534 and FIRST J102347.6+003841 imposing some constraints
to the polar classification of these objects.


title: Molecular Cloud Formation Behind Shock Waves

abstract:
  We examine the formation of molecular gas behind shocks in atomic gas using a
chemical/dynamical model, particular emphasis is given to constraints the
chemistry places on the dynamical evolution. The most important result of this
study is to stress the importance of shielding the molecular gas from the
destructive effects of UV radiation. For shock ram pressures comparable to or
exceeding typical local ISM pressures, self-shielding controls the formation
time of H2 but CO formation requires shielding of the interstellar radiation
field by dust grains. We find that the molecular hydrogen fractional abundance
can become significant well before CO forms. The timescale for (CO) molecular
cloud formation is not set by H2 formation, but rather by the timescale for
accumulating a sufficient column density or extinction, A_V > 0.7. The local
ratio of atomic to molecular gas (4:1), coupled with short estimates for cloud
lifetimes (3-5 Myr), suggests that the timescales for accumulating molecular
clouds from atomic material typically must be no longer than about 12-20 Myr.
Based on the shielding requirement, this implies that the typical product of
pre-shock density and velocity must be n*v > 20 cm^-3 km s^-1. Based on these
results we find that flow-driven formation of molecular clouds in the local
interstellar medium can occur sufficiently rapidly to account for observations.
We also provide detailed predictions of atomic and molecular emission and
absorption that track molecular cloud formation, with a view toward helping to
verify cloud formation by shock waves. Finally, we provide an analytic solution
for time-dependent H2 formation which may be of use in numerical hydrodynamic
calculations.


title:
Gas Density, Stability, and Starbursts Near the Inner Lindblad Resonance
  of the Milky Way

abstract:
  A key project of the Antarctic Submillimeter Telescope and Remote Observatory
(AST/RO) reported by Martin et al. (2004) is the mapping of CO J=4-3 and J=7-6
emission from the inner Milky Way, allowing determination of gas density and
temperature. Galactic center gas that Binney et al. (1991) identify as being on
x_2 orbits has a density near 10^3.5 cm ^-3, which renders it only marginally
stable against gravitational coagulation into a few Giant Molecular Clouds, as
discussed by Elmegreen (1994). This suggests a relaxation oscillator mechanism
for starbursts in the Milky Way, where inflowing gas accumulates in a ring at
150 pc radius for approximately 20 million years, until the critical density is
reached, and the resulting instability leads to the sudden formation of giant
clouds and the deposition of 4 x 10^7 solar masses of gas onto the Galactic
center.


title: Are galactic disks dynamically influenced by dust?

abstract:
  Dynamically cold components are well known to destabilize hotter, even much
more massive components. In this paper we studied the dynamical influence of a
cold dust component on the gaseous phase in the central regions of galactic
disks. We performed two-dimensional hydrodynamical simulations for flat
multi-component disks embedded in a combined static stellar and dark matter
potential. The pressure-free dust component is coupled to the gas by a drag
force depending on their velocity difference.
  It turned out that the most unstable regions are those with either a low or
near to minimum Toomre parameter or with rigid rotation, i.e. the central area.
In that regions the dust-free disks become most unstable for high azimuthal
modes (m~8), whereas in dusty disks all modes have a similar amplitude
resulting in a patchy appearance. The structures in the dust have a larger
contrast between arm and inter-arm regions than those of the gas. The dust
peaks are frequently correlated with peaks of the gas distribution, but they do
not necessarily coincide with them. Therefore, a large scatter in the
dust-to-gas ratios is expected. The appearance of the dust is more cellular
(i.e. sometimes connecting different spiral features), whereas the gas is
organized in a multi-armed spiral structure.
  An admixture of 2% dust destabilizes gaseous disks substantially, whereas
dust-to-gas ratios below 1% have no influence on the evolution of the gaseous
disk. For a high dust-to-gas ratio of 10% the instabilities reach a saturation
level already after 30 Myr.


title: The Imprint of Nova Nucleosynthesis in Presolar Grains

abstract:
  Infrared and ultraviolet observations of nova light curves have confirmed
grain formation in their expanding shells that are ejected into the
interstellar medium by a thermonuclear runaway. In this paper, we present
isotopic ratios of intermediate-mass elements up to silicon for the ejecta of
CO and ONe novae, based on 20 hydrodynamic models of nova explosions. These
theoretical estimates will help to properly identify nova grains in primitive
meteorites. In addition, equilibrium condensation calculations are used to
predict the types of grains that can be expected in the nova ejecta, providing
some hints on the puzzling formation of C-rich dust in O>C environments. These
results show that SiC grains can condense in ONe novae, in concert with an
inferred (ONe) nova origin for several presolar SiC grains.


title: Bigger Rip with No Dark Energy

abstract:
  By studying a modified Friedmann equation which arises in an extension of
general relativity which accommodates a time-dependent fundamental length
$L(t)$, we consider cosmological models where the scale factor diverges with an
essential singularity at a finite future time. Such models have no dark energy
in the conventional sense of energy possessing a truly simple pressure-energy
relationship. Data on supernovae restrict the time from the present until the
Rip to be generically longer than the current age of the Universe.


title: The Mass Budget of Merging Quasars

abstract:
  Two spectacular results emerging from recent studies of nearby dead quasars
and distant active quasars are (i) the existence of tight relations between the
masses of black holes (BHs) and the properties of their host galaxies (spheroid
luminosity or velocity dispersion, galaxy mass), and (ii) a consistency between
the local mass density in BHs and that expected by summing up the light
received from distant active quasars. These results are partly shaped by
successive galactic mergers and BH coalescences, since mergers redistribute the
population of BHs in galaxies and BH binary coalescences reduce the mass
density in BHs through losses to gravitational waves. Here, we isolate and
quantify these effects by following the cosmological merger history of a
population of massive BHs representing the quasar population between z = 3 and
z =0. Our results suggest that the relation between BH mass and host galaxy
properties, and inferences on the global efficiency of BH accretion during
active quasar phases, could be influenced by the cumulative effect of repeated
mergers.


title: On The Dark Side of Quasar Evolution

abstract:
  Recent improved determinations of the mass density rho_BH of supermassive
black holes (SMBHs) in the local universe have allowed accurate comparisons of
rho_BH with the amount of light received from past quasar activity. These
comparisons support the notion that local SMBHs are ``dead quasars'' and yield
a value epsilon >~ 0.1 for the average radiative efficiency of cosmic SMBH
accretion. BH coalescences may represent an important component of the quasar
mass assembly and yet not produce any observable electromagnetic signature.
Therefore, ignoring gravitational wave (GW) emission during such coalescences,
which reduces the amount of mass locked into remnant BHs, results in an
overestimate of epsilon. Here, we put constraints on the magnitude of this
bias. We calculate the cumulative mass loss to GWs experienced by a
representative population of BHs during repeated cosmological mergers, using
loss prescriptions based on detailed general relativistic calculations. Despite
the possibly large number of mergers in the assembly history of each individual
SMBH, we find that near--equal mass mergers are rare, and therefore the
cumulative loss is likely to be modest, amounting at most to an increase by 20
percent of the inferred epsilon value. Thus, recent estimates of epsilon >~ 0.1
appear robust. The space interferometer LISA should provide empirical
constraints on the dark side of quasar evolution, by measuring the masses and
rates of coalescence of massive BHs to cosmological distances.


title: A Chandra X-ray Observation of Abell 1991: The Late Stages of Infall?

abstract:
  We present results from a 38 ks Chandra X-ray observation of the z=0.059
galaxy cluster A1991. The cluster has a bright X-ray core and a central
temperature gradient that declines inward from 2.7 keV at 130 kpc to
approximately 1.6 keV at the cluster center. The radiative cooling time of the
gas in the inner 10 kpc is about 0.5 Gyr, and rises to 1 Gyr at a radius of 20
kpc. The cooling rate of the gas within the latter radius is less than about 25
solar mass/yr. The Chandra ACIS-S3 image shows that the intracluster medium has
an asymmetric surface brightness distribution with respect to the central
galaxy. Bright knots of soft X-ray emission embedded in a cometary structure
are located approximately 10 arcsec north of the optical center of the cD
galaxy. Unlike the structures seen in other cooling flow clusters, the knots
have no obvious association with the radio source. The structure's temperature
of 0.83 keV makes it nearly 1 keV cooler than its surroundings, and its mass is
3.4E+09 solar masses. Based on its bow-shaped appearance and modest
overpressure with respect to its surroundings, we interpret the structure as a
cool mass concentration that is breaking apart as it travels northward through
the center of the cluster.


title:
Iron K-alpha Fluorescent Line Profiles from Spiral Accretion Flows in
  AGNs

abstract:
  We present 6.4 keV iron K-alpha fluorescent line profiles predicted for a
relativistic black hole accretion disk in the presence of a spiral motion in
Kerr geometry, the work extended from an earlier literature motivated by recent
magnetohydrodynamic (MHD) simulations. The velocity field of the spiral motion,
superposed on the background Keplerian flow, results in a complicated redshift
distribution in the accretion disk. An X-ray source attributed to a localized
flaring region on the black hole symmetry axis illuminates the iron in the
disk. The emissivity form becomes very steep because of the light bending
effect from the primary X-ray source to the disk. The predicted line profile is
calculated for various spiral waves, and we found, regardless of the source
height, that: (i) a multiple-peak along with a classical double-peak structure
generally appears, (ii) such a multiple-peak can be categorized into two types,
sharp sub-peaks and periodic spiky peaks, (iii) a tightly-packed spiral wave
tends to produce more spiky multiple peaks, whereas (iv) a spiral wave with a
larger amplitude seems to generate more sharp sub-peaks, (v) the effect seems
to be less significant when the spiral wave is centrally concentrated, (vi) the
line shape may show a drastic change (forming a double-peak, triple-peak or
multiple-peak feature) as the spiral wave rotates with the disk. Our results
emphasize that around a rapidly-rotating black hole an extremely redshifted
iron line profile with a noticeable spike-like feature can be realized in the
presence of the spiral wave. Future X-ray observations, from {\it Astro-E2} for
example, will have sufficient spectral resolution for testing our spiral wave
model which exhibits unique spike-like features.


title:
WR 20a is an Eclipsing Binary: Accurate Determination of Parameters for
  an Extremely Massive Wolf-Rayet System

abstract:
  We present a high-precision I-band light curve for the Wolf-Rayet binary WR
20a, obtained as a sub-project of the Optical Gravitational Lensing Experiment.
Rauw et al. have recently presented spectroscopy for this system, strongly
suggesting extremely large minimum masses of 70.7 +/- 4.0 Mo and 68.8 +/- 3.8
Mo for the component stars of the system, with the exact values depending
strongly on the period of the system. We detect deep eclipses of about 0.4 mag
in the light curve of WR 20a, confirming and refining the suspected period of
P=3.686 days and deriving an inclination angle of i=74.5 +/- 2 deg. Using these
photometric data and the radial velocity data of Rauw et al., we derive the
masses for the two components of WR 20a to be 83.0 +/- 5.0 Mo and 82.0 +/- 5.0
Mo. Therefore, WR 20a is confirmed to consist of two extremely massive stars
and to be the most massive binary known with an accurate mass determination.


title:
A multi-wavelength study of the proto-cluster surrounding the z=4.1
  radio galaxy TN J1338-1942

abstract:
  We present a 1.2 mm (250 GHz) map obtained with MAMBO on the IRAM 30m
telescope of the central 25 arcmin^2 of the proto-cluster surrounding the z=4.1
radio galaxy TN J1338-1942. The map reaches a 1sigma sensitivity of 0.6 mJy in
the central area, increasing to 1.2 mJy at the edges. We detect 10 candidate mm
sources, of which 8 are also detected in a deep VLA 1.4 GHz map and/or a VLT
R-band image. Three sources have a flux density S_{1.2 mm}>4.0 mJy,
representing a 7sigma overdensity compared to random field surveys, which
predict only 1 such source in our map area. We obtained SCUBA/JCMT 850 um and
450 um photometry of six radio/optically identified MAMBO sources, confirming 5
of them with S/N>4. Radio-to-mm and mm-to-submm redshift estimators cannot put
strong constraints on the redshifts of these MAMBO sources, but 9 of them are
consistent within the uncertainties (mean Delta z=+2.6) with z=4.1. One faint
MAMBO source is possibly identified with an extremely red object (R-K=6.1) at a
likely spectroscopic redshift z=1.18. The four brightest MAMBO sources are all
located north of the radio galaxy, while the densest area of companion Ly-alpha
excess and Lyman break galaxies is to the southeast. None of the 14
spectroscopically confirmed Ly-alpha emitters in the MAMBO field are detected
at 1.2 mm; their average 1.2 mm flux density is <S_{\rm 1.2mm}>=0.25+-0.24 mJy.
If the mm sources lie at z=4.1, none of them show excess Ly-alpha emission in
our narrow-band images. Both populations thus show no apparent overlap,
possibly due to dust quenching the Ly-alpha emission. If the mm sources are
part of the proto-cluster, our results suggest that galaxies with star
formation rates of a few 1000 M_{Sun} yr^{-1} could be spread throughout the
proto-cluster over projected scales of at least 2 Mpc.


title:
Constraints on dark energy from Chandra observations of the largest
  relaxed galaxy clusters

abstract:
  We present constraints on the mean dark energy density, Omega_X and dark
energy equation of state parameter, w_X, based on Chandra measurements of the
X-ray gas mass fraction in 26 X-ray luminous, dynamically relaxed galaxy
clusters spanning the redshift range 0.07<z<0.9. Under the assumption that the
X-ray gas mass fraction measured within r_2500 is constant with redshift and
using only weak priors on the Hubble constant and mean baryon density of the
Universe, we obtain a clear detection of the effects of dark energy on the
distances to the clusters, confirming (at comparable significance) previous
results from Type Ia supernovae studies. For a standard LambdaCDM cosmology
with the curvature Omega_K included as a free parameter, we find
Omega_Lambda=0.94^{+0.21}_{-0.23} (68 per cent confidence limits). We also
examine extended XCDM dark energy models. Combining the Chandra data with
independent constraints from cosmic microwave background experiments, we find
Omega_X=0.75\pm0.04, Omega_m=0.26^{+0.06}_{-0.04} and w_X=-1.26\pm0.24.
Imposing the prior constraint w_X>-1, the same data require w_X<-0.7 at 95 per
cent confidence. Similar results on the mean matter density and dark energy
equation of state parameter, Omega_m=0.24\pm0.04 and w_X=-1.20^{+0.24}_{-0.28},
are obtained by replacing the CMB data with standard priors on the Hubble
constant and mean baryon density and assuming a flat geometry.