title: Nitrogen Abundances in High-z DLAs

abstract:
  Determination of chemical abundances for elements produced mainly by Type I
SNae and intermediate mass stars in high redshift DLAs probes the early
chemical build-up on time-scales comparable with their production. Nitrogen
shows a peculiar behaviour never detected before in any other class of objects.
For [N/H] < -3 there is a plateau with [N/Si]= -1.45(\pm 0.05). We interpret
this as empirical evidence for primary N production by massive stars in young
systems where AGB stars have not yet had time to make their contribution. The
plateau provides the observational integrated yields for N production by
massive stars which are theoretically rather uncertain. High N/Si and solar
[alpha/iron-peak] ratios are observed at high redshift and place at an earlier
epoch the onset of star formation. On the other hand, low N/Si, i.e. young
objects, are observed also at relatively low redshifts. These evidences suggest
that DLAs started to be formed at a very early epoch but their formation has
been extended up to later times.


title:
XMM-Newton observation of the 5.25 ms transient millisecond pulsar XTE
  J1807-294 in outburst

abstract:
  We report on the results obtained for the millisecond transient X-ray pulsar
XTE J1807-294 in a 40 min orbital period system, based on an XMM-Newton ToO
observation carried out during March 2003. The source was found at a luminosity
level of about 2x10^36 erg/s in the 0.5-10 keV range (assuming a distance of 8
kpc). We confirm the presence of the 5.25 ms pulsations (after accounting for
the orbital modulation) and find a pulsed fraction of 5.8% in the 0.3-10 keV
band. The pulse shape in nearly sinusoidal. The spectral continuum of the
source is well fitted by an absorbed Comptonization model plus a soft
component. No emission or absorption lines have been detected in the 0.5-10 keV
range with upper limits of 10-40 eV. The reported analysis represent the first
detailed study of this source, the fourth belonging to the ultra-compact binary
system class hosting an accreting neutron star.


title: Dependence of Dust Obscuration on Star Formation Rates in Galaxies

abstract:
  Many investigations of star formation rates (SFRs) in galaxies have explored
details of dust obscuration, with a number of recent analyses suggesting that
obscuration appears to increase in systems with high rates of star formation.
To date these analyses have been primarily based on nearby (z < 0.03) or UV
selected samples. Using 1.4 GHz imaging and optical spectroscopic data from the
Phoenix Deep Survey, the SFR-dependent obscuration is explored. The use of a
radio selected sample shows that previous studies exploring SFR-dependent
obscurations have been biased against obscured galaxies. The observed relation
between obscuration and SFR is found to be unsuitable to be used as an
obscuration measure for individual galaxies. Nevertheless, it is shown to be
successful as a first order correction for large samples of galaxies where no
other measure of obscuration is available, out to intermediate redshifts (z ~
0.8).


title: Measurement of the Integrated Faraday Rotations of BL Lac Objects

abstract:
  We present the results of multi-frequency polarization VLA observations of
radio sources from the complete sample of northern, radio-bright BL Lac objects
compiled by H. Kuhr and G. Schmidt. These were used to determine the integrated
rotation measures of 18 objects, 15 of which had never been measured
previously, which hindered analysis of the intrinsic polarization properties of
objects in the complete sample. These measurements make it possible to correct
the observed orientations of the linear polarizations of these sources for the
effect of Faraday rotation. The most probable origin for Faraday rotation in
these objects is the Galactic interstellar medium. The results presented
complete measurements of the integrated rotation measures for all 34 sources in
the complete sample of BL Lac objects.


title: Using the Sunyaev-Zel'dovich Effect to Probe the Gas in Clusters

abstract:
  The thermal Sunyaev-Zel'dovich effect is an important probe of clusters of
galaxies, and has the attractive property of being proportional to the thermal
energy content of the intracluster medium. With the assistance of X-ray data,
the effect can be used to measure the number of hot electrons in clusters, and
thus measure cluster baryon contents. Cluster absolute distances and other
structural parameters can also be measured by combining thermal
Sunyaev-Zel'dovich, X-ray, and other data. This review presents an introduction
to the effect, shows some representative results, and sketches imminent
developments.


title:
Chemical Abundances and Rotation Velocities of Blue Horizontal-Branch
  Stars in Six Globular Clusters

abstract:
  High-resolution spectroscopic measurements of blue horizontal-branch stars in
six metal-poor globular clusters -- M3, M13, M15, M68, M92, and NGC 288 --
reveal remarkable variations in photospheric composition and rotation velocity
as a function of a star's position along the horizontal branch. For the cooler
stars (Teff < 11200 K), the derived abundances are in good agreement with the
canonical cluster metallicities, and we find a wide range of v sin i rotation
velocities, some as high as 40 km/s. In the hotter stars, however, most metal
species are strongly enhanced, by as much as 3 dex, relative to the expected
cluster metallicity, while helium is depleted by 2 dex or more. In addition,
the hot stars all rotate slowly, with v sin i < 8 km/s. The anomalous
abundances appear to be due to atomic diffusion mechanisms -- gravitational
settling of helium, and radiative levitation of metals -- in the non-convective
atmospheres of these hot stars. We discuss the influence of these photospheric
metal enhancements on the stars' photometric properties, and explore possible
explanations for the observed distribution of rotation velocities.


title: The X-ray Binary GRS 1741.9-2853 in Outburst and Quiescence

abstract:
  We report Chandra and XMM-Newton observations of the transient neutron star
low-mass X-ray binary GRS 1741.9-2853. Chandra detected the source in outburst
on 2000 October 26 at an X-ray luminosity of ~10^{36} erg/s (2--8 keV; 8 kpc),
and in quiescence on 2001 July 18 at ~10^{32} erg/s. The latter observation is
the first detection of GRS 1741.9-2853 in quiescence. We obtain an accurate
position for the source of 17h 45m 2.33s, -28o 54' 49.7" (J2000), with an
uncertainty of 0.7". GRS 1741.9-2853 was not detected significantly in three
other Chandra observations, nor in three XMM-Newton observations, indicating
that the luminosity of the source in quiescence varies by at least a factor of
5 between (< 0.9 - 5.0) \times 10^{32} erg/s (2--8 keV). A weak X-ray burst
with a peak luminosity of 5 \times 10^{36} erg/s above the persistent level was
observed with Chandra during the outburst on 2000 October 26. The energy of
this burst, 10^{38} erg, is unexpectedly low, and may suggest that the accreted
material is confined to the polar caps of the neutron star. A search of the
literature reveals that GRS 1741.9-2853 was observed in outburst with ASCA in
Fall 1996 as well, when the BeppoSAX WFC detected the three previous X-ray
bursts from this source. The lack of X-ray bursts from GRS 1741.9-2853 at other
epochs suggests that it produces bursts only during transient outbursts when
the accretion rate onto the surface of the neutron star is about 10^{-10}
M_sun/yr. A similar situation may hold for other low-luminosity bursters
recently identified from WFC data.


title: The Seyfert Population in the Local Universe

abstract:
  The magnitude-limited catalog of the Southern Sky Redshift Survey (SSRS2), is
used to characterize the properties of galaxies hosting Active Galactic Nuclei.
Using emission-line ratios, we identify a total of 162 (3%) Seyfert galaxies
out of the parent sample with 5399 galaxies. The sample contains 121 Seyfert 2
galaxies and 41 Seyfert 1. The SSRS2 Seyfert galaxies are predominantly in
spirals of types Sb and earlier, or in galaxies with perturbed appearance as
the result of strong interactions or mergers. Seyfert galaxies in this sample
are twice as common in barred hosts than the non-Seyferts. By assigning
galaxies to groups using a percolation algorithm we find that the Seyfert
galaxies in the SSRS2 are more likely to be found in binary systems, when
compared to galaxies in the SSRS2 parent sample. However, there is no
statistically significant difference between the Seyfert and SSRS2 parent
sample when systems with more than 2 galaxies are considered. The analysis of
the present sample suggests that there is a stronger correlation between the
presence of the AGN phenomenon with internal properties of galaxies
(morphology, presence of bar, luminosity) than with environmental effects
(local galaxy density, group velocity dispersion, nearest neighbor distance).


title: Companions of Bright Barred Shapley Ames Galaxies

abstract:
  Companion galaxy environment for a subset of 78 bright and nearby barred
galaxies from the Shapley Ames Catalog is presented. Among spiral barred
galaxies there are Seyfert galaxies, galaxies with circumnuclear structures,
galaxies not associated with any large scale galaxy cloud structure, galaxies
with peculiar disk morphology (crooked arms) and galaxies with normal disk
morphology; the list includes all Hubble types. The companion galaxy list
includes number of companion galaxies within 20 diameters (D25), their Hubble
type and projected separation distance. Additionally, companion environment was
searched for four known active spiral galaxies, three of them are Seyfert
galaxies, namely, NGC 1068, NGC 1097, NGC 5548 and one is a starburst galaxy,
M82. Among the results obtained it is noted that the only spiral barred galaxy
classified as Sy 1 in our list has no companions within a projected distance of
20 diameters; 6 out of 10 Sy 2 bar galaxies have no companions within 10
diamters, 6 out of 10 Sy 2 galaxies have one or more companions at projected
separation distances between 10 and 20 diameters; 6 out of 12 galaxies with
circumnuclear structures have 2 or more companions within 20 diameters


title: The Homogeneity of Interstellar Krypton in the Galactic Disk

abstract:
  We present an analysis of high resolution HST Space Telescope Imaging
Spectrograph (STIS) observations of Kr I 1236 Angstrom absorption in seven
sight lines that probe a variety of interstellar environments. In combination
with krypton and hydrogen column densities derived from current and archival
STIS and Far-Ultraviolet Spectroscopic Explorer data, the number of sight lines
with reliable Kr/H ISM abundance ratios has been increased by 50% to
26--including paths that sample a range of nearly 5 orders of magnitude in
f(H_2), over 2 orders of magnitude in <n_H>, and extending up to 4.8 kpc in
length. For sight lines contained entirely within the local spiral arm (the
Orion Spur), the spread of Kr/H ratios about the mean of log_10[N(Kr)/N(H)]_ISM
= -9.02+/-0.02 is remarkably tight (0.06 dex), less than the typical datapoint
uncertainty. Intriguingly, the only two sight lines that extend through
neighboring structures, in particular gas associated with the
Carina/Sagittarius Arm, exhibit relatively large, near-solar krypton abundances
(log_10[N(Kr)/N(H)]_combined = -8.75+0.09_-0.11). Although these deviations are
only measured at the 2 sigma level, they suggest the possibility that krypton
abundances beyond the Orion Spur may differ from the local value.


title: On Non-Primordial Deuterium Production by Accelerated Particles

abstract:
  Deuterium plays a crucial role in cosmology because the primordial D/H
abundance, in the context of big bang nucleosynthesis (BBN) theory, yields a
precise measure of the cosmic baryon content. Observations of D/H can limit or
measure the true primordial abundance because D is thought to be destroyed by
stars and thus D/H monotonically decreases after BBN. Recently, however, Mullan
& Linsky have pointed out that D arises as a secondary product of neutrons in
stellar flares which then capture on protons via n+p \to d + gamma, and that
this could dominate over direct D production in flares. Mullan & Linsky note
that if this process is sufficiently vigorous in flaring dwarf stars, it could
lead to significant non-BBN D production. We have considered the production of
D in stellar flares, both directly and by n capture. We find that for
reasonable flare spectra, n/d < 10 and (n+d)/6Li < 400, both of which indicate
that the n-capture channel does not allow for Galactic D production at a level
which will reverse the monotonic decline of D. We also calculate the 2.22 MeV
gamma-ray line production associated with n capture, and find that existing
COMPTEL limits also rule out significant D production in the Galaxy today.
Thus, we find flares in particular, and neutron captures in general, are not an
important Galactic source of D. On the other hand, we cannot exclude that flare
production might contribute to recent FUSE observations of large variations in
the local interstellar D/H abundance; we do, however, offer important
constraints on this possibility. Finally, since flare stars should inevitably
produce some n-capture events, a search for diffuse 2.22 MeV gamma-rays by
INTEGRAL can further constrain (or measure!) Galactic deuterium production via
n-capture.


title: History of Hydrogen Reionization in the Cold Dark Matter Model

abstract:
  We calculate the reionization history in Cold Dark Matter (CDM) models. The
epoch of the end of reionization and the Thomson scattering optical depth to
the cosmic microwave background depend on the power spectrum amplitude on small
scales and on the ionizing photon emissivity per unit mass in collapsed halos.
We calibrate the emissivity to reproduce the measured ionizing background
intensity at z=4. Models in which all CDM halos have either a constant
emissivity or a constant energy emitted per Hubble time, per unit mass, predict
that reionization ends near z~6 and the optical depth is in the range 0.05 <
tau_e < 0.09, consistent with WMAP results at the 1 to 2 sigma level. If the
optical depth is as high as 0.17 (as suggested by WMAP), halos of velocity
dispersion ~ 3-30 km/s at z>15 must have ionizing emissivities per unit mass
larger by a factor >~ 50 compared to the more massive halos that produce the
ionizing emissivity at z=4. This factor increases to 100 if the CDM power
spectrum amplitude is required to agree with the Croft et al. (2002)
measurement from the Lyman alpha forest. If tau_e >~ 0.17 were confirmed, a
higher ionizing emissivity at z>15 compared to z=4 might arise from an enhanced
star formation rate or quasar abundance per unit mass and an increased escape
fraction for ionizing photons; the end of reionization could have been delayed
to z~6 because of the suppression of gas accretion and star formation in
low-mass halos as the medium was reionized.


title: Observational Bounds on Cosmic Doomsday

abstract:
  Recently it was found, in a broad class of models, that the dark energy
density may change its sign during the evolution of the universe. This may lead
to a global collapse of the universe within the time t_c ~ 10^{10}-10^{11}
years. Our goal is to find what bounds on the future lifetime of the universe
can be placed by the next generation of cosmological observations. As an
example, we investigate the simplest model of dark energy with a linear
potential V(\phi) =V_0(1+\alpha\phi). This model can describe the present stage
of acceleration of the universe if \alpha is small enough. However, eventually
the field \phi rolls down, V(\phi) becomes negative, and the universe
collapses. The existing observational data indicate that the universe described
by this model will collapse not earlier than t_c > 10 billion years from the
present moment. We show that the data from SNAP and Planck satellites may
extend the bound on the "doomsday" time to t_c > 40 billion years at the 95%
confidence level.


title: Radio emission models of Colliding-Wind Binary Systems

abstract:
  We present calculations of the spatial and spectral distribution of the radio
emission from a wide WR+OB colliding-wind binary system based on
high-resolution hydrodynamical simulations and solutions to the radiative
transfer equation. We account for both thermal and synchrotron radio emission,
free-free absorption in both the unshocked stellar wind envelopes and the
shocked gas, synchrotron self-absorption, and the Razin effect. The
applicability of these calculations to modelling radio images and spectra of
colliding-wind systems is demonstrated with models of the radio emission from
the wide WR+OB binary WR147. Its synchrotron spectrum follows a power-law
between 5 and 15 GHz but turns down to below this at lower and higher
frequencies. We find that while free-free opacity from the circum-binary
stellar winds can potentially account for the low-frequency turnover, models
that also include a combination of synchrotron self-absorption and Razin effect
are favoured. We argue that the high-frequency turn down is a consequence of
inverse-Compton cooling. We present our resulting spectra and intensity
distributions, along with simulated MERLIN observations of these intensity
distributions. From these we argue that the inclination of the WR147 system to
the plane of the sky is low. We summarise by considering extensions of the
current model that are important for models of the emission from closer
colliding wind binaries, in particular the dramatically varying radio emission
of WR140.


title:
An Extensive Census of HST Counterparts to Chandra X-ray Sources in the
  Globular Cluster 47 Tucanae. I. Astrometry and Photometry

abstract:
  We report the largest number of optical identifications of X-ray sources yet
obtained in a single globular cluster. Using deep Chandra/ACIS-I imaging and
extensive HST studies with WFPC2, we have detected optical counterparts to at
least 22 cataclysmic variables (CVs) and 29 chromospherically active binaries
(BY Dras and RS CVns) in 47 Tuc. These identifications are all based on tight
astrometric matches between X-ray sources and objects with unusual (non main
sequence) optical colors and/or optical variability. In the U vs U-V color
magnitude diagram (CMD), the CVs all show evidence for blue colors compared to
the main sequence, but most of them fall close to the main sequence in the V vs
V-I CMD, showing that the secondary stars dominate the optical light. The X-ray
detected active binaries have magnitude offsets above the main sequence that
are indistinguishable from those of the much larger sample of optical variables
(eclipsing and contact binaries and BY Dras) detected in the WFPC2 studies of
Albrow et al. (2001). We also present the results of a new, deeper search for
optical companions to MSPs. One possible optical companion to an MSP (47 Tuc T)
was found, adding to the two optical companions already known. Finally, we
study several blue stars with periodic variability from Albrow et al. (2001)
that show little or no evidence for X-ray emission. The optical colors of these
objects differ from those of 47 Tuc (and field) CVs.


title: Variability of EGRET Gamma-Ray Sources

abstract:
  The variability of the high-energy gamma ray sources in the Third EGRET
catalog is analyzed by a new method. We re-analyze the EGRET data to calculate
a likelihood function for the flux of each source in each observation, both for
detections and upper limits. These functions can be combined in a uniform
manner with a simple model of the flux distribution to characterize the flux
variation by a confidence interval for the relative standard deviation of the
flux. The main result is a table of these values for almost all the cataloged
sources. As expected, the identified pulsars are steady emitters and the
blazars are mostly highly variable. The unidentified sources are heterogeneous,
with greater variation at higher Galactic latitude. There is an indication that
pulsar wind nebulae are associated with variable sources. There is a population
of variable sources along the Galactic plane, concentrated in the inner spiral
arms.


title:
An Extensive Census of HST Counterparts to Chandra X-ray Sources in the
  Globular Cluster 47 Tucanae. II. Time Series and Analysis

abstract:
  We report time series and variability information for the optical
identifications of X-ray sources in 47 Tuc reported in Paper I. The eight CVs
with secure orbital periods have fainter accretion disks, in the V band, than
field CVs with similar periods. These faint disks and the faint absolute
magnitudes (Mv) of the 47 Tuc CVs suggests they have low accretion rates. The
median Fx/Fopt value for the 47 Tuc CVs is higher than that of all known
classes of field CV, because of both the faint Mv values and the relatively
high X-ray luminosities (Lx). The latter are only seen in DQ Her systems in the
field, but the 47 Tuc CVs are much fainter optically than most field DQ Hers.
Some combination of magnetic behavior and low accretion rates may be able to
explain our observations, but the results at present are ambiguous, since no
class of field CV has distributions of both Lx and Mv that are consistent with
those of the 47 Tuc CVs. The radial distribution of the X-ray detected active
binaries is indistinguishable from that of the much larger sample of optical
variables detected in previous WFPC2 studies. The X-ray properties of these
objects are consistent with those of active binaries found in field studies.
One reasonable and one marginal candidate for optical identification of a
quiescent LMXB was found (one is already known). Finally, we study the blue
variables showing little or no evidence for X-ray emission. Their generally
long periods and the absence of flickering suggests they are not CVs. At
present we have no satisfactory explanation for these objects, although some
may be detached WD-main sequence star binaries.


title:
The Phase of the Annual Modulation as a Tool for Determining the WIMP
  Mass

abstract:
  The count rate of Weakly Interacting Massive Particle (WIMP) dark matter
candidates in direct detection experiments experiences an annual modulation due
to the Earth's motion around the Sun. In the standard isothermal halo model,
the signal peaks near June 2nd at high recoil energies; however, the signal
experiences a phase reversal and peaks in December at low energy recoils. We
show that this phase reversal may be used to determine the WIMP mass. If an
annual modulation were observed with the usual phase ({\it i.e.}, peaking on
June 2nd) in the lowest accessible energy recoil bins of the DAMA, CDMS-II,
CRESST-II, EDELWEISS-II, GENIUS-TF, ZEPLIN-II, XENON, or ZEPLIN-IV detectors,
one could immediately place upper bounds on the WIMP mass of [103, 48, 6, 97,
10, 52, 29, 29] GeV, respectively. In addition, detectors with adequate energy
resolution and sufficiently low recoil energy thresholds may determine the
crossover recoil energy at which the phase reverses, thereby obtaining an
independent measurement of the WIMP mass. We study the capabilities of various
detectors, and find that CRESST-II, ZEPLIN-II, and GENIUS-TF should be able to
observe the phase reversal in a few years of runtime, and can thus determine
the mass of the WIMP if it is $\mathcal{O}(100$ GeV). Xenon based detectors
with 1000 kg (XENON and ZEPLIN-IV) and with energy recoil thresholds of a few
keV require 25 kg-yr exposure, which will be readily attained in upcoming
experiments.


title: Simulating Voids

abstract:
  We present a novel method for simulation of the interior of large cosmic
voids, suitable for study of the formation and evolution of objects lying
within such regions. Following Birkhoff's theorem, void regions dynamically
evolve as universes with cosmological parameters that depend on the
underdensity of the void. We derive the values of $\Omega_M$,
$\Omega_{\Lambda}$, and $H_0$ that describe this evolution. We examine how the
growth rate of structure and scale factor in a void differ from the background
universe. Together with a prescription for the power spectrum of fluctuations,
these equations provide the initial conditions for running specialized void
simulations. The increased efficiency of such simulations, in comparison with
general-purpose simulations, allows an improvement of upwards of twenty in the
mass resolution. As a sanity check, we run a moderate resolution simulation
($N=128^3$ particles) and confirm that the resulting mass function of void
halos is consistent with other theoretical and numerical models.


title:
Analysis of 6cm VLBI polarization observations of a complete sample of
  northern BL Lacertae Objects

abstract:
  The results of VLBI total intensity (I) and linear polarization (P)
observations at 6cm are presented for ten radio bright BL Lacertae objects.
These images complete first-epoch polarization observations for the 1-Jy sample
of northern BL Lacertae objects defined by Kuhr and Schmidt. Estimates of
superluminal speeds are presented for several sources, bringing the total
number of sources in the sample for which such estimates are available to 16.
Second epoch observations currently being reduced should yield speed estimates
for VLBI features in essentially all the sources in the sample. The jet
magnetic fields of these BL Lacertae objects are usually transverse to the
local jet direction, but a sizeable minority (about 30%) have VLBI jet
components with longitudinal magnetic fields. This may suggest that the
conditions in the VLBI jets of BL Lacertae objects are favorable for the
formation of relativistic shocks; alternatively, it may be that the toroidal
component of the intrinsic jet magnetic field is characteristically dominant in
these sources.


title:
New Astrophysical Tests from the Einstein's Equivalence Principle and
  Gravitational Experiments

abstract:
  The Einstein's equivalence principle and experiments, in which bodies and
observers are in different G potentials, have been used to prove that the chain
of hypothesis coming from assuming the absolute invariability of the bodies,
after a change of G potential, are wrong. The absolute changes of frequencies,
masses and lengths of every well-defined part of the non-local bodies, compared
with the local ones, are linearly related to the differences of G potential
between the non-local bodies and the observer. Such absolute changes are
independent on the forces within the structure of the bodies. Then the increase
of G potential due to universe expansion also expands bodies in same proportion
as distances. Consequently, such uniform expansion cannot change the results of
any measurement of distance or velocity. The cosmological red shifts and the
average universe density cannot change with the time, i.e., the new universe
age is not limited by the Hubble law. The new linear G relationships and the
unlimited age of the universe fix a new astrophysical context that turns out to
be independent on any cosmological hypothesis. Thus the best fit of this new
scenario with astronomical observations has been obtained independently on the
chain of hypotheses that are not simultaneously consistent with all of the
experimental facts.


title:
Determination of the Central Mass in Active Galactic Nuclei Using
  Cross-Correlation Lags and Velocity Dispersions

abstract:
  We here estimate the mass M of the central object in five active galactic
nuclei (AGNs), using the most recent reverberation data obtained by the AGN
Watch Consortium. The cross-correlation function (CCF) centroids of the broad
Ly-alpha 1216 and C IV 1549 lines are used to estimate the size of the
broad-line region (BLR) in these sources. We calculate the velocity dispersions
of these lines in the root mean square (rms) spectra and then use our results
to estimate M. We argue that our technique of calculating the velocity
dispersion should work in the general case of an arbitrary line profile, unlike
methods that depend on the measurement of the full-width at half-maximum (FWHM)
of the broad line. We also show that our results agree with the FWHM method in
the limit of a normal (Gaussian) line profile. The masses calculated here are
considerably smaller than those calculated with the previous generation of
reverberation data.


title:
X-ray Variability of the Magnetic Cataclysmic Variable V1432 Aql and the
  Seyfert Galaxy NGC 6814

abstract:
  V1432 Aquilae (=RX J1940.2-1025) is the X-ray bright, eclipsing magnetic
cataclysmic variable ~37' away from the Seyfert galaxy, NGC 6814. Due to a 0.3%
difference between the orbital (12116.3 s) and the spin (12150 s) periods, the
accretion geometry changes over the ~50 day beat period. Here we report the
results of an RXTE campaign to observe the eclipse 25 times, as well as of
archival observations with ASCA and BeppoSAX. Having confirmed that the eclipse
is indeed caused by the secondary, we use the eclipse timings and profiles to
map the accretion geometry as a function of the beat phase. We find that the
accretion region is compact, and that it moves relative to the center of white
dwarf on the beat period. The amplitude of this movement suggest a low-mass
white dwarf, in contrast to the high mass previously estimated from its X-ray
spectrum. The size of the X-ray emission region appears to be larger than in
other eclipsing magnetic CVs. We also report on the RXTE data as well as the
long-term behavior of NGC 6814, indicating flux variability by a factor of at
least 10 on time scales of years.


title:
On the link between rotation, chromospheric activity and Li abundance in
  subgiant stars

abstract:
  The connection rotation-CaII emission flux-lithium abundance is analyzed for
a sample of bona fide subgiant stars, with evolutionary status determined from
HIPPARCOS trigonometric parallax measurements and from the Toulouse-Geneva
code.


title: Observational constraints for Lithium depletion before the RGB

abstract:
  Precise Li abundances are determined for 54 giant stars mostly evolving
across the Hertzsprung gap. We combine these data with rotational velocity and
with information related to the deepening of the convective zone of the stars
to analyse their link to Li dilution in the referred spectral region. A sudden
decline in Li abundance paralleling the one already established in rotation is
quite clear. Following similar results for other stellar luminosity classes and
spectral regions, there is no linear relation between Li abundance and
rotation, in spite of the fact that most of the fast rotators present high Li
content. The effects of convection in driving the Li dilution is also quite
clear. Stars with high Li content are mostly those with an undeveloped
convective zone, whereas stars with a developed convective zone present clear
sign of Li dilution.


title: The stability of protostellar disks with Hall effect and buoyancy

abstract:
  The stability properties of inviscid protostellar disks are examined taking
into account the Hall effect and buoyancy. Depending on the parameters,
different types of instabilities can exist in different regions of disks. In a
very low ionized region, the instability associated with baroclinic effects of
buoyancy is likely most efficient. The Hall-driven shear instability can lead
to destabilization of regions with a higher ionization. The magnetorotational
instability modified by buoyancy can only be a destabilizing factor in regions
with strong magnetic field or a relatively high conductivity ($\sigma B^2 /
\rho > a_e \Omega$, with $a_e$ the magnetization parameter of electrons).


title:
Individual and collective behavior of dust particles in a protoplanetary
  nebula

abstract:
  We study the interaction between gas and dust particles in a protoplanetary
disk, comparing analytical and numerical results. We first calculate
analytically the trajectories of individual particles undergoing gas drag in
the disk, in the asymptotic cases of very small particles (Epstein regime) and
very large particles (Stokes regime). Using a Boltzmann averaging method, we
then infer their collective behavior. We compare the results of this analytical
formulation against numerical computations of a large number of particles.
Using successive moments of the Boltzmann equation, we derive the equivalent
fluid equations for the average motion of the particles; these are
intrinsically different in the Epstein and Stokes regimes. We are also able to
study analytically the temporal evolution of a collection of particles with a
given initial size-distribution provided collisions are ignored.


title:
The Globular Cluster Systems of NGC 3258 and NGC 3268 in the Antlia
  Cluster

abstract:
  The Antlia galaxy cluster is the third nearest galaxy cluster after Virgo and
Fornax. We used the wide-field MOSAIC camera of the 4-m CTIO telescope to
search in the brightest cluster galaxies for globular cluster systems, which
were detected in the two larger ellipticals -- NGC 3258 and NGC 3268. These
galaxies each contain several thousand clusters; NGC 3258 more than NGC 3268.
The color distributions of the globular cluster systems are clearly bimodal.
The peak colors agree with those of other ellipticals. The radial number
density profiles of the globular cluster systems are indistinguishable for the
two galaxies and no difference in the distribution of red and blue clusters -
as observed in other elliptical galaxies - can be seen. The light profile of
NGC 3268 appears to be similar to that of NGC 1399, the central galaxy of the
Fornax cluster. NGC 3258 has a light profile which is steeper at large radii.
Both galaxies exhibit color gradients, becoming bluer outwards.In NGC 3268, the
color and morphology in the inner 3" indicate the presence of an inner dusty
disk. The globular cluster systems closely trace the galaxy light in the
studied radial regime. The elongation of the cluster systems of both galaxies
is approximately aligned at large radii with the connecting axis of the two
galaxies.We find specific frequencies within a radial range of 4'of
S_N=3.0+-2.0 for NGC 3268 and S_N=6.0+-2.5 for NGC 3258.
  As a byproduct resulting from surveying our wide-field frames, we describe a
strange absorption feature in the Antlia spiral galaxy NGC 3269, which we argue
might be a tiny galactic dust cloud projected onto NGC 3269.


title:
Outflows and accretion in a star--disc system with stellar magnetosphere
  and disc dynamo

abstract:
  The interaction between a protostellar magnetosphere and a surrounding
dynamo-active accretion disc is investigated using an axisymmetric mean-field
model. In all models investigated, the dynamo-generated magnetic field in the
disc arranges itself such that in the corona, the field threading the disc is
anti-aligned with the central dipole so that no X-point forms. When the
magnetospheric field is strong enough (stellar surface field strength around 2
kG or larger), accretion happens in a recurrent fashion with periods of around
15 to 30 days, which is somewhat longer than the stellar rotation period of
around 10 days. In the case of a stellar surface field strength of at least a
few 100 G, the star is being spun up by the magnetic torque exerted on the
star. The stellar accretion rates are always reduced by the presence of a
magnetosphere which tends to divert a much larger fraction of the disc material
into the wind. Both, a pressure-driven stellar wind and a disc wind form. In
all our models with disc dynamo, the disc wind is structured and driven by
magneto-centrifugal as well as pressure forces.


title:
A Physical Model for the Co-evolution of QSOs and of their Spheroidal
  Hosts

abstract:
  We present a physically motivated model for the early co-evolution of massive
spheroidal galaxies and active nuclei at their centers. Within dark matter
halos, forming at the rate predicted by the canonical hierarchical clustering
scenario, the gas evolution is controlled by gravity, radiative cooling, and
heating by feedback from supernovae and from the growing active nucleus.
Supernova heating is increasingly effective with decreasing binding energy in
slowing down the star formation and in driving gas outflows. The more massive
proto-galaxies virializing at earlier times are thus the sites of the faster
star-formation. The correspondingly higher radiation drag fastens the angular
momentum loss by the gas, resulting in a larger accretion rate onto the central
black-hole. In turn, the kinetic energy carried by outflows driven by active
nuclei can unbind the residual gas, thus halting both the star formation and
the black-hole growth, in a time again shorter for larger halos. For the most
massive galaxies the gas unbinding time is short enough for the bulk of the
star-formation to be completed before type Ia supernovae can substantially
increase the $Fe$ abundance of the interstellar medium, thus accounting for the
$\alpha$-enhancement seen in the largest galaxies. The feedback from supernovae
and from the active nucleus also determines the relationship between the
black-hole mass and the mass, or the velocity dispersion, of the host galaxy,
as well as the black-hole mass function. These and other model predictions are
in excellent agreement with observations for a number of observables which
proved to be extremely challenging for all the current semi-analytic models,
including the sub-mm counts and the corresponding redshift distributions, and
the epoch-dependent K-band luminosity function of spheroidal galaxies.


title: Noise power spectrum estimation and fast map making for CMB experiments

abstract:
  We present a method designed to estimate the noise power spectrum in the time
domain for CMB experiments. The noise power spectrum is extracted from the time
ordered data avoiding the contamination coming from sky signal and accounting
the pixellisation of the signal and the projection of the noise when making
intermediate sky projections. This method is simple to implement and relies on
Monte-Carlo simulations, it runs on a simple desk computer. We also propose a
trick for filtering data before making coadded maps in order to avoid ringing
due to the presence of signal in the timelines. These algorithms were
succesfully tested on Archeops data.


title:
Stellar black hole mass function: determination and possible
  implications for fundamental gravity

abstract:
  We discuss masses of stellar black holes found in binary systems and errors
in their determination. The observed mass distribution has a broad shape within
the range $4-16 M_\odot$ without visible concentration to some preferred value.
On the other hand, the black hole mass funciton as inferred from observations
of luminous X-ray sources in other galaxies exhibits a power-law form. We show
that both dynamically obtained black hole mass function and derived from X-ray
observations can be made consistent in the frame of the hypothesis of enhanced
black hole evaporation on a RSII brane for reasonable values of the warp-factor
of the Anti-de-Sitter bulk space.


title: Radio spectra of the WMAP catalog sources

abstract:
  Compiled radio spectra are presented for 208 extragalactic sources from the
catalog created from the WMAP satellite all-sky survey data in a range of 23-94
GHz taken during the first year of its operation in orbit. 205 out of 208 WMAP
sources are reliably identified with radio sources from other catalogs,
including also four out of five sources unidentified by the WMAP survey
authors. We have found 203 WMAP sources to have optical identification: 141
quasars, 29 galaxies, 19 active galactic nuclei, 19 BL Lac-type objects and one
planetary nebula, IC418. Simultaneous measurements of flux densities for 26
sources at five frequencies, 2.3, 3.9, 7.7, 11.2 and 21.7 GHz, were made with
the radio telescope RATAN-600 in 2003 March. 25 sources were detected at all
the frequencies, and only one, WMAP0517-0546, unidentified in other catalogs
was not detected in our observations and is likely to be spurious. Using the
database CATS we found a large number of identifications in different radio
catalogs and in several long-term monitoring programs (GBI, UMRAO, SEST, IRAM,
and others). The total number of flux density measurements that we collected in
the frequency range from 10 MHz to 245 GHz for the identified WMAP sources is
over 206,000, varying from 10-20 points for some southern sources to a few
thousand points for sources from long-term monitorings. A considerable number
of WMAP sources are variable on time scales from hours to dozens of years,
nevertheless, the obtained integral spectra, including measurements in
different years, may be of particular interest because these bright sources
have been studied for more than forty years. The general character of the
spectrum (power, flat, with a turnovers at low or high frequencies) of the WMAP
sources remains unchanged.


title: Gravitational Effects on Particle Dark Matter and Indirect Detection

abstract:
  The annihilation signal of particle dark matter can be strongly enhanced in
over-dense regions such as close to the Galactic centre. We summarize some of
our recent results on fluxes of gamma-rays, neutrinos and radio waves under
different assumptions for the largely uncertain dark matter profile which close
to the Galactic centre is strongly influenced by the super-massive black hole.
We apply this to two particle dark matter scenarios, namely the case of
neutralinos in supersymmetric scenarios and the lowest Kaluza-Klein excitation
of the hyper-charge gauge boson in scenarios where the Standard Model fields
propagate in one microscopic extra dimension.


title:
Properties of host haloes of Lyman-break galaxies and Lyman-alpha
  Emitters from their number densities and angular clustering

abstract:
  We explore empirical relations between three different populations of
high-redshift galaxies and their hosting dark halos employing the halo model
approach. Specifically we consider Lyman-break galaxies at z\sim4 and at
z\sim5, and Lyman-Alpha emitters at z\simeq 4.86. We adopt a halo occupation
function prescription to parameterize the properties of their hosting halos and
the efficiency of halo-dependent star formation. We find that the two LBG
samples are well described by the halo model with an appropriate HOF. We obtain
constraints on properties of their hosting halos. A typical mass of hosting
halos for LBGs is 5\times10^{11}h^{-1}M_\odot and the expected number of LBGs
per halo is \sim0.5, therefore there is an approximate one-to-one
correspondence between halos and LBGs. We also find a sign of the minimum mass
of LBG hosting halos decreasing with time. We discuss implications of these
findings on the star formation history of LBGs. On the other hand, for LAEs,
our simple HOF prescription fails to reproduce simultaneously the observed
angular correlation function and the number density. This might imply either
that the distribution of LAEs within hosting halos differs from that of dark
matter, or that the strong large-scale correlation is due to the existence of
an unusual, large overdense region, and so the survey region is not a
representative of the z\sim5 universe, the definite answer should wait for a
much wider survey of LAEs at high redshifts.


title: Cosmological dynamics of the tachyon with an inverse power-law potential

abstract:
  We investigate tachyon dynamics with an inverse power-law potential $V(\phi)
\propto \phi^{-\alpha}$. We find global attractors of the dynamics leading to a
dust behaviour for $\alpha > 2$ and to an accelerating universe for $0 < \alpha
\le 2$. We study linear cosmological perturbations and we show that metric
fluctuations are constant on large scales in both cases. In presence of an
additional perfect fluid, the tachyon with this potential behaves as dust or
dark energy.


title: On Dark Matter Annihilation in the Local Group

abstract:
  Under the hypothesis of a Dark Matter composed by supersymmetric particles
like neutralinos, we investigate the possibility that their annihilation in the
haloes of nearby galaxies could produce detectable fluxes of $\gamma$-photons.
Expected fluxes depend on several, poorly known quantities such as the density
profiles of Dark Matter haloes, the existence and prominence of central density
cusps and the presence of a population of sub-haloes. We find that, for all
reasonable choices of Dark Matter halo models, the intensity of the
$\gamma$-ray flux from some of the nearest extragalactic objects, like M31, is
comparable or higher than the diffuse Galactic foreground. We show that next
generation ground-based experiments could have the sensitivity to reveal such
fluxes which could help us unveiling the nature of Dark Matter particles.


title: Polar Fields for AB Dor

abstract:
  Polar spots are often observed on rapidly-rotating cool stars, but the nature
of the magnetic field in these spots is as yet unknown. While Zeeman-Doppler
imaging can provide surface magnetic field maps over much of the observed
stellar surface, the Zeeman signature is suppressed in the dark polar regions.
We have determined the effect on the global coronal structure of three current
models for this polar field: that it is composed (a) of unipolar field, (b) of
bipolar regions or (c) of nested rings of opposite polarity. We take as an
example the young, rapid rotator AB Dor (rotation period = 0.514 days). By
adding these model polar fields into the surface field maps determined from
Zeeman-Doppler imaging, we have compared the resulting coronal structure with
the observable properties of the corona - the magnitude and rotational
modulation of the X-ray emission measure and the presence of slingshot
prominences trapped in the corona around the Keplerian co-rotation radius. We
find that only the presence of a unipolar spot has any significant effect on
the overall coronal structure, forcing much of the polar field to be open.


title: Charged Domain Walls

abstract:
  In this paper we investigate Charged Domain Walls (CDW's), topological
defects that acquire surface charge density $Q$ induced by fermion states
localized on the walls. The presence of an electric and magnetic field on the
walls is also discussed. We find a relation in which the value of the surface
charge density $Q$ is connected with the existence of such topological defects.


title: Weak Gravitational Lensing by Large-Scale Structure

abstract:
  Weak gravitational lensing provides a unique method to map directly the
distribution of dark matter in the universe and to measure cosmological
parameters. This cosmic-shear technique is based on the measurement of the weak
distortions that lensing induces in the shape of background galaxies as photons
travel through large-scale structures. This technique is now widely used to
measure the mass distribution of galaxy clusters and has recently been detected
in random regions of the sky. In this review, we present the theory and
observational status of cosmic shear. We describe the principles of weak
lensing and the predictions for the shear statistics in favored cosmological
models. Next, we review the current measurements of cosmic shear and show how
they constrain cosmological parameters. We then describe the prospects offered
by upcoming and future cosmic-shear surveys as well as the technical challenges
that have to be met for the promises of cosmic shear to be fully realized.


title:
Present status of primordial nucleosynthesis after WMAP: results from a
  new BBN code

abstract:
  We report on the status of primordial nucleosynthesis in light of recent
results on CMB anisotropies from WMAP experiment. Theoretical estimates for
nuclei abundances, along with the corresponding uncertainties, are evaluated
using a new numerical code, where all nuclear rates usually considered have
been updated using the most recent available data. Moreover, additional
processes, neglected in previous calculations, have been included. The combined
analysis of CMB and primordial nucleosynthesis prediction for Deuterium gives
an effective number of relativistic degrees of freedom in good agreement with
the simplest scenario of three non degenerate neutrinos. Our findings seem to
point out possible systematics affecting 4He mass fraction measurements, or the
effect of exotic physics, like a slightly degenerate relic neutrino background.


title:
Nonlinear evolution of dark matter and dark energy in the Chaplygin-gas
  cosmology

abstract:
  The hypothesis that dark matter and dark energy are unified through the
Chaplygin gas is reexamined. Using generalizations of the spherical model which
incorporate effects of the acoustic horizon we show that an initially
perturbative Chaplygin gas evolves into a mixed system containing cold dark
matter-like gravitational condensate.


title:
The Bursting Behavior of 4U 1728-34: Parameters of a Neutron Star and
  Geometry of a NS-disk system

abstract:
  We analyze a set of Type I X-ray bursts from the low mass X-ray binary 4U
1728 -34, observed with Rossi X-ray Timing Explorer (RXTE). and we implement an
analytical model of X-ray spectral formation in the neutron star (NS)
atmosphere during a burst. We infer the dependence of the neutron star mass and
radius with respect to the assumed distance to the system using an analytical
model of X-ray burst spectral formation. The model behavior clearly indicates
that the burster atmosphere is helium-dominated. Our results strongly favor the
soft equation of state (EOS) of NS for 4U 1728-34. We find that distance to the
source should be within 4.5-5.0 kpc range. We obtain rather narrow constrains
for the NS radius in 8.7-9.7 km range and interval 1.2-1.6 solar masses for NS
mass for this particular distance range.
  We uncover a temporal behavior of red-shift corrected burst flux for the
radial expansion episodes and we put forth a dynamical evolution scenario for
the NS--accretion disk geometry during which an expanded envelope affects the
accretion disk and increases the area of the neutron star exposed to the Earth
observer. Our scenario enables us to explain the timing characteristics and
peak flux variation observed during the burst expansion stage, which is now
believed to be common phenomenon. In the framework of this scenario we provide
a new method for the estimation of the inclination angle which leads to the
value of 50 degrees for 4U 1728-34 .


title: Gamma-rays and cosmic-rays from a pulsar in Cygnus OB2

abstract:
  We argue that gamma-rays sources observed in the direction of the Cyg OB2
association in the GeV and TeV energy range are due to a pulsar which was
created by a supernova a few tens of thousands years ago. The excess of cosmic
rays at 10^18 eV can be also related to the appearance of this pulsar.


title: Properties of discrete X-ray sources in the starburst spiral galaxy M83

abstract:
  We have identified 127 discrete sources in a Chandra observation of M83, with
a detection limit of ~ 3 x 10^{36} erg/s in the 0.3-8.0 keV band. We discuss
the individual properties of about 20 bright sources with L_x >~ 10^{38} erg/s,
and the statistical properties of the whole sample. About 1/3 of the bright
sources show X-ray spectra with a bb component at kT <~ 1 keV, plus a p-law
component with Gamma ~ 2.5, typical of X-ray binaries (XRBs) in a soft state;
another third have p-law spectra with Gamma ~ 1.5, consistent with XRBs in a
hard state. Two bright sources show emission lines on a hard p-law continuum,
and are probably XRBs surrounded by a photo-ionized nebula or stellar wind.
Among the other bright sources, we also identified two SNR candidates, with
optically-thin thermal plasma spectra at kT ~ 0.5 keV. The two brightest
supersoft sources have T_bb ~ 70 eV and L_x ~ 10^{38} erg/s. Two candidate
X-ray pulsars are detected with periods ~ 200 s. Another source corresponds to
the core of a background FRII radio galaxy. The discrete sources can be divided
into three groups, based on their spatial, color and luminosity distributions.
The first group comprises supersoft sources with no detected emission above 1
keV. The second group consists of soft sources with little or no detected
emission above 2 keV. They are strongly correlated with H-alpha emission in the
spiral arms and starburst nucleus, tracing a young population. Their relative
abundance depends on the current level of star-formation. Most of them are
likely to be SNRs. The sources in the third group are mostly XRBs (in a soft or
hard state), reaching higher X-ray luminosities than sources in the other two
groups. Being a mixture of old low-mass and young high-mass systems, the whole
group appears to be of intermediate age when correlated with H-alpha.


title:
The evolution of the high energy tail in the quiescent spectrum of the
  soft X-ray transient Aql X-1

abstract:
  A moderate level of variability has been detected in the quiescent luminosity
of several neutron star soft X-ray transients. Spectral variability was first
revealed by Chandra observations of Aql X-1 in the four months that followed
the 2000 X-ray outburst. By adopting the canonical model for quiescent spectrum
of soft X-ray transients, i.e. an absorbed neutron star atmosphere model plus a
power law tail, Rutledge et al. (2002a) concluded that the observed spectral
variations can be ascribed to temperature variations of the neutron star
atmosphere. These results can hardly be reconciled with the neutron star
cooling that is expected to take place in between outbursts (after deep crustal
heating in the accretion phase). Here we reanalyse the Chandra spectra of Aql
X-1, together with a long BeppoSAX observation in the same period, and propose
a different interpretation of the spectral variability: that this is due to
correlated variations of the power law component and the column density (>5, a
part of which might be intrinsic to the source), while the temperature and flux
of the neutron star atmospheric component remained unchanged. This lends
support to the idea that the power law component arises from emission at the
shock between a radio pulsar wind and inflowing matter from the companion star.


title:
An improved Markov-chain Monte Carlo sampler for the estimation of
  cosmological parameters from CMB data

abstract:
  Markov-chain Monte Carlo sampling has become a standard technique for
exploring the posterior distribution of cosmological parameters constrained by
observations of CMB anisotropies. Given an infinite amount of time, any MCMC
sampler will eventually converge such that its stationary distribution is the
posterior of interest. In practice, however, naive samplers require a
considerable amount of time to explore the posterior distribution fully. In the
best case, this results only in wasted CPU time, but in the worse case can lead
to underestimated confidence limits on the values of cosmological parameters.
Even for the current CMB data set, the sampler employed in the widely-used
cosmomc package does not sample very efficiently. This difficulty is yet more
pronounced for data sets of the quality anticipated for the Planck mission. We
thus propose a new MCMC sampler for analysing total intensity CMB observations,
which can be easily incorporated into the cosmomc software, but has rapid
convergence and produces reliable confidence limits. This is achieved by using
dynamic widths for proposal distributions, dynamic covariance matrix sampling,
and a dedicated proposal distribution for moving along well-known degeneracy
directions.


title: First results from the INTEGRAL Galactic plane scans

abstract:
  Scans of the Galactic plane performed at regular intervals constitute a key
element of the guaranteed time observations of the INTEGRAL observing
programme. These scans are done for two reasons: frequent monitoring of the
Galactic plane in order to detect transient sources, and time resolved mapping
of the Galactic plane in continuum and diffuse line emission. This paper
describes first results obtained from the Galactic plane scans executed so far
during the early phase (Dec 2002 - May 2003) of the nominal mission.


title: First detection of doubly deuterated hydrogen sulfide

abstract:
  This work was carried out with using the Caltech Submillimeter Observatory
and presents the observational study of HDS and D2S towards a sample of Class 0
sources, and dense cores. We report the first detection of doubly deuterated
hydrogen sulfide (D2S) in two dense cores and analyze the chemistry of these
molecules aiming to help understand the deuteration processes in the
interstellar medium. The observed values of the D2S/HDS ratio, and upper
limits, require an atomic D/H ratio in the accreting gas of 0.1-1. The study
presented in this Letter supports the hypothesis that formaldehyde, methanol
and hydrogen sulfide are formed on the grain surfaces, during the cold
pre-stellar core phase, where the CO depleted gas has large atomic D/H ratios.
The high values for the D/H ratios are consistent with the predictions of a
recent gas-phase chemical model that includes H3+ and its deuterated
isotopomers, H2D+, D2H+ and D3+ (Roberts et al. 2003).


title: The afterglow and the host galaxy of GRB 011211

abstract:
  We present optical, near-infrared, and X-ray observations of the optical
afterglow (OA) of the X-ray rich, long-duration gamma-ray burst GRB 011211.
Hubble Space Telescope (HST) data obtained 14, 26, 32, and 59 days after the
burst, show the host galaxy to have a morphology that is fairly typical of blue
galaxies at high redshift. We measure its magnitude to be R = 24.95 +/- 0.11.
We detect a break in the OA R-band light curve which is naturally accounted for
by a collimated outflow geometry. By fitting a broken power-law to the data we
find a best fit with a break 1.56 +/- 0.02 days after the burst, a pre-break
slope of alpha_1 = -0.95 +/- 0.02, and a post-break slope of alpha_2 = -2.11
+/- 0.07. The UV-optical spectral energy distribution (SED) around 14 hours
after the burst is best fit with a power-law with index beta = -0.56 +/- 0.19
reddened by an SMC-like extinction law with a modest A_V = 0.08 +/- 0.08 mag.
By comparison, from the XMM-Newton X-ray data at around the same time, we find
a decay index of alpha_X = -1.62 +/- 0.36 and a spectral index of beta_X =
-1.21 +0.10/-0.15. Interpolating between the UV-optical and X-ray implies that
the cooling frequency is located close to ~10^16 Hz in the observer frame at
the time of the observations. We argue, using the various temporal and spectral
indices above, that the most likely afterglow model is that of a jet expanding
into an external environment that has a constant mean density rather than a
wind-fed density structure. We estimate the electron energy index for this
burst to be p ~ 2.3.


title:
A Cluster of Galaxies hiding behind M31: XMM-Newton observations of RX
  J0046.4+4204

abstract:
  We report on our serendipitous discovery with the XMM-Newton Observatory of a
luminous X-ray emitting cluster of galaxies that is located behind the
Andromeda galaxy (M31). X-ray emission from the cluster was detected previously
by ROSAT, and cataloged as RX J0046.4+4204, but it was not recognized as a
galaxy cluster. The much greater sensitivity of our XMM-Newton observations
revealed diffuse x-ray emission that extends at least 5 arcmin and has a
surface brightness profile that is well fit by the alpha-beta model with beta =
0.70 +/- 0.08, a core radius r_c = 56 arcsec +/- 16, and alpha = 1.54 +/- 0.25.
A joint global spectral fit of the EPIC/MOS1, MOS2, and PN observations with
Mewe-Kaastra-Liedahl plasma emission model gives a cluster temperature of 5.5
+/- 0.5 keV. The observed spectra also show high significance iron emission
lines that yield a measured cluster redshift of z = 0.290 with a 2% accuracy.
For a cosmological model with H_0 = 71 km s^{-1} Mpc^{-1}, Omega_M = 0.3 and
Omega_{Lambda} = 0.7 we derive a bolometric luminosity of L_x=(8.4 +/-
0.5)*10^{44}$ erg/s. This discovery of a cluster behind M31 demonstrates the
utility of x-ray surveys for finding rich clusters of galaxies, even in
directions of heavy optical extinction.


title:
Overdensities of Extremely Red Objects in the Fields of High-Redshift
  Radio-Loud Quasars

abstract:
  We have examined the occurrence of Extremely Red Objects (EROs) in the fields
of 13 luminous quasars (11 radio-loud and two radio-quiet) at 1.8 < z < 3.0.
The average surface density of K_s<=19 mag EROs is two-three times higher than
in large, random-field surveys, and the excess is significant at the $\approx
3$ sigma level even after taking into account that the ERO distribution is
highly inhomogeneous. This is the first systematic investigation of the surface
density of EROs in the fields of radio-loud quasars above z=2, and shows that a
large number of the fields contain clumps of EROs, similar to what is seen only
in the densest areas in random-field surveys. The high surface densities and
angular distribution of EROs suggest that the excess originates in high-z
galaxy concentrations, possibly young clusters of galaxies. The fainter EROs at
K_s>19 mag show some evidence of being more clustered in the immediate 20
arcsec region around the quasars, suggesting an association with the
quasars.Comparing with predictions from spectral synthesis models, we find that
if the $K_s\approx19$ mag ERO excess is associated with the quasars at
$z\approx2$, their magnitudes are typical of >~ L* passively evolving galaxies
formed at z~3.5 (Omega_m=0.3, Omega_l=0.7, and H0=70 km/s/Mpc). Another
interpretation of our results is that the excess originates in concentrations
of galaxies at $z\approx1$ lying along the line of sight to the quasars. If
this is the case, the EROs may be tracing massive structures responsible for a
magnification bias of the quasars.


title: A Second Glitch from the "Anomalous" X-ray Pulsar 1RXS J170849.0-4000910

abstract:
  We report on 5.4 yr of phase-coherent timing, using the Rossi X-ray Timing
Explorer, of the X-ray pulsar 1RXS 1708-4009, a member of the class known as
``anomalous X-ray pulsars.'' This object exhibited a rotational glitch in 1999.
Here we report a second much larger rotational glitch which occured ~1.5 yr
after the first. We show that the recoveries from the two glitches are
different, with the first showing only a possible slow, approximately linear
recovery, while the second showed a nearly complete recovery on a time scale of
\~50 days. The approximately exponential recovery time scale of the second
glitch is similar to that seen recently in 1E 2259+586 at the time of a major
outburst. This suggests 1RXS 1708-4009 undergoes similar bursting behavior,
although with our sparse observations we have detected no other evidence for
bursts from this source.


title: On The Progenitor of the Type II-Plateau Supernova 2003gd in Messier 74

abstract:
  HST WFPC2 archival F606W and F300W images obtained within one year prior to
the explosion of the nearby Type II supernova (SN) 2003gd in Messier 74 (NGC
628) have been analyzed to isolate the progenitor star. The SN site was located
using precise astrometry applied to the HST images. Two plausible candidates
are identified within 0.6" of the SN position in the F606W image. Neither
candidate was detected in the F300W image. SN 2003gd appears to be of Type
II-plateau (II-P), with age ~87 d on June 17 UT and with low reddening [E(B-V)
= 0.13 mag]. The most likely of the two progenitor candidates has M_V_0 ~ -3.5
mag (for an extinction-corrected distance modulus of 29.3 mag) and, based on
additional color information derived from a high-quality, archival ground-based
I-band image, we estimate that this star was a red supergiant with initial mass
M_ZAMS ~ 8 -- 9 Msun. This mass estimate is somewhat lower than, but relatively
consistent with, recent limits placed on the progenitor masses of other SNe
II-P, using HST data. Future HST imaging with the Advanced Camera for Surveys,
when the SN has faded considerably, will be extremely useful in pinpointing the
exact SN location and securing identification of the progenitor. If our
proposed candidate is confirmed, it will be only the sixth SN progenitor ever
directly identified.


title: Mapping the Dark Energy with Varying Alpha

abstract:
  Cosmological dark energy is a natural source of variation of the fine
structure constant. Using a model-independent approach we show that once
general assumptions about the alpha-varying interactions are made, astronomical
probes of its variation constrain the dark energy equation of state today to
satisfy -1 < w_f < -0.96 at 3-sigma and significantly disfavour late-time
changes in the equation of state. We show how dark-energy-induced spatial
perturbations of alpha are linked to violations of the Equivalence Principle
and are thus negligible at low-redshift, in stark contrast to the BSBM
theories. This provides a new test of dark energy as the source of alpha
variation.


title:
A Radio Survey of Type Ib and Ic Supernovae: Searching for Engine Driven
  Supernovae

abstract:
  The association of gamma-ray bursts (GRBs) and core-collapse supernovae (SNe)
of Type Ib and Ic was motivated by the detection of SN 1998bw in the error box
of GRB 980425 and the now-secure identification of a SN 1998bw-like event in
the cosmological GRB 030329. The bright radio emission from SN 1998bw indicated
that it possessed some of the unique attributes expected of GRBs, namely a
large reservoir of energy in (mildly) relativistic ejecta and variable energy
input. The two popular scenarios for the origin of SN 1998bw are a typical
cosmological burst observed off-axis or a member of a new distinct class of
supernova explosions (gSNe). In the former, about 0.5% of local Type Ib/c SNe
are expected to be similar to SN1998bw; for the latter no such constraint
exists. Motivated thus, we began a systematic program of radio observations of
most reported Type Ib/c SNe accessible to the Very Large Array. Of the 33 SNe
observed from late 1999 to the end of 2002 at most one is as bright as SN
1998bw. From this we conclude that the incidence of such events is <3%.
Furthermore, analysis of the radio emission indicates that none of the observed
SNe exhibit clear engine signatures. Finally, a comparison of the SN radio
emission to that of GRB afterglows indicates that none of the SNe could have
resulted from a typical GRB, independent of the initial jet orientation. Thus,
while the nature of SN 1998bw remains an open question, there appears to be a
clear dichotomy between the majority of hydrodynamic and engine-driven
explosions.


title:
On the universal outcome of star-formation: Is there a link between
  stars and brown-dwarfs?

abstract:
  (abridged) The recent evidence obtained by Briceno et al. that star-formation
in Taurus-Auriga (TA) may be producing significantly fewer brown dwarfs (BDs)
per star than the ONC is investigated by setting up a realistic model stellar
plus BD population and explicitly taking into account a high binary proportion
and dynamical evolution in the TA groups and the ONC. The Briceno result is
reproduced almost exactly despite an identical IMF in both systems because many
BD-BD and star-BD binaries are disrupted in the ONC thus freeing BDs, while the
TA groups remain unevolved dynamically. However, the resulting populations do
not have the correct star-star, star-BD and expecially BD-BD binary properties,
even if a variable BD IMF is allowed for. The conclusion is therefore that BDs
need to be added as a separate population which has its own binary properties.
Such an extra population can have various origins which are briefly discussed
in this contribution but more fully in an associated paper.


title:
HII regions in spiral galaxies: Size distribution, luminosity function,
  and new isochrone diagnostics of density wave kinematics

abstract:
  We investigate the relationship of the HII region luminosity function (HII
LF) to the HII region size distribution and density wave triggering in
grand-design spiral galaxies. We suggest that the differential nebular size
distribution is described by a power law of slope ~ -4, with flattening at
radii below ~ 130 pc. This contrasts with the conventional exponential
description, but it is physically and quantitatively consistent with the
typical observed value of -2 for the HII LF slope.
  We have developed an interactive code that computes spatial isochrones for
the evolving loci of spiral density waves in disk galaxies. This allows
comparison of the nebular spatial distribution with the spatial isochrones for
simple rotation curve parameters. Our comparisons for four grand-design
galaxies suggest that the corotation radius r_co coincides with the outer ends
of the star-forming arms. This value for r_co yields the best spatial
correspondence between the HII regions and the isochrones, and also appears to
yield a coincidence between the Inner Lindblad Resonance with the radial onset
of star formation in the arms. Thus, we suggest that isochrones offer a new,
simple, and effective technique for determining r_co, and thus the spiral
pattern speed. However, application of the isochrones also demonstrates that
evolution of the nebular population is difficult to spatially isolate in these
galaxies.


title: Observing the First Stars, One Star at a Time

abstract:
  Gamma-Ray Bursts (GRBs) are believed to originate in compact remnants (black
holes or neutron stars) of massive stars. Their high luminosities make them
detectable out to the edge of the visible universe. We describe the many
advantages of GRB afterglows relative to quasars as probes of the intergalactic
medium during the epoch of reionization. The Swift satellite, planned for
launch by the end of 2003, will likely open a new era in observations of the
high redshift universe.


title: Rotation Velocities of Red and Blue Field Horizontal-Branch Stars

abstract:
  We present measurements of the projected stellar rotation velocities (v sin
i) of a sample of 45 candidate field horizontal-branch (HB) stars spanning a
wide range of effective temperature, from red HB stars with Teff ~ 5000 K to
blue HB stars with Teff of 17000 K. Among the cooler blue HB stars (Teff =
7500-11500 K), we confirm prior studies showing that although a majority of
stars rotate at v sin i < 15 km/s, there exists a subset of "fast rotators"
with v sin i as high as 30-35 km/s. All but one of the red HB stars in our
sample have v sin i < 10 km/s, and no analogous rotation bimodality is evident.
We also identify a narrow-lined hot star (Teff ~ 16000 K) with enhanced
photospheric metal abundances and helium depletion, similar to the abundance
patterns found among hot BHB stars in globular clusters, and four other stars
that may also belong in this category. We discuss details of the spectral line
fitting procedure that we use to deduce v sin i, and explore how measurements
of field HB star rotation may shed light on the issue of HB star rotation in
globular clusters.


title: Large Scale Structure in the SDSS DR1 Galaxy Survey

abstract:
  The Large Scale Structure in the galaxy distribution is investigated using
The First Data Release of the Sloan Digital Sky Survey. Using the Minimal
Spanning Tree technique we have extracted sets of filaments, of wall--like
structures, of galaxy groups, and of rich clusters from this unique sample. The
physical properties of these structures were then measured and compared with
the statistical expectations based on the Zel'dovich' theory.
  The measured characteristics of galaxy walls were found to be consistent with
those for a spatially flat $\Lambda$CDM cosmological model with
$\Omega_m\approx$ 0.3 and $\Omega_\Lambda \approx$ 0.7, and for Gaussian
initial perturbations with a Harrison -- Zel'dovich power spectrum.
Furthermore, we found that the mass functions of groups and of unrelaxed
structure elements generally fit well with the expectations from Zel'dovich'
theory. We also note that both groups and rich clusters tend to prefer the
environments of walls, which tend to be of higher density, rather than the
environments of filaments, which tend to be of lower density.


title: Ionized gas kinematics and massive star formation in NGC 1530

abstract:
  We present emission line mapping of the strongly barred galaxy NGC 1530
obtained from Fabry-Perot interferometry in Halpha, at significantly enhanced
angular resolution compared with published studies. The main point of the work
is to examine in detail the non-circular components of the velocity field of
the gas, presumably induced by the strongly non-axisymmetric gravitational
potential of the bar. These reveal quasi-elliptical motions with speeds of
order 100 km/s aligned with the bar. It also shows how these flows swing in
towards and around the nucleus as they cross a circumnuclear resonance, from
the dominant "x1 orbits" outside the resonance to "x2 orbits" within it.
Comparing cross-sections of the residual velocity map along and across the bar
with the Halpha intensity map indicates a systematic offset between regions of
high non-circular velocity and massive star formation. To investigate further
we produce velocity gradient maps along and across the bar. These illustrate
very nicely the shear compression of the gas, revealed by the location of the
dust lanes along loci of maximum velocity gradient perpendicular to the bar.
They also show clearly how shear acts to inhibit massive star formation,
whereas shocks act to enhance it. Although the inhibiting effect of gas shear
flow on star formation has long been predicted, this is the clearest
observational illustration so far of the effect. It is also the clearest
evidence that dust picks out shock-induced inflow along bars. These
observations should be of considerable interest to those modelling massive star
formation in general.


title: The glitches of the Anomalous X-ray Pulsar 1RXS J170849.0--400910

abstract:
  We report on a timing analysis of archival observations of the Anomalous
X-ray Pulsar 1RXSJ170849.0-400910 made with the RXTE Proportional Counter
Array. We detect a new large glitch (Delta nu / nu ~ 3 x 10^-6) which occurred
between 2001 March 27 and 2001 May 6, with an associated large increase in the
spin-down rate (Delta nudot/nudot ~ 0.3). The short time (1.5 yrs) elapsed from
the previously detected glitch and the large amplitude of the new spin-up place
this source among the most frequent glitchers, with large average glitch
amplitudes, similar to those of the Vela pulsar. The source shows different
recoveries after the glitches: in the first one it is well described by a long
term linear trend similar to those seen in Vela-like glitches; in the second
case the recovery is considerably faster and is better described by an
exponential plus a fractional change in the long-term spin-down rate of the
order of 1%. No recovery of the latter is detected but additional observations
are necessary to confirm this result. Observed glitch properties are compared
to those of radio pulsar glitches; current models are discussed in light of our
results. It appears that glitches may represent yet another peculiarity of
AXPs. Starquake-based models appear to be prefered on qualitative grounds.
Alternative models can be applied to individual glitches but fail in explaining
both. Thus the two events may as well arise from two different mechanisms.


title: High-energy Emission from Pulsar Outer Magnetospheres

abstract:
  We investigate a stationary pair production cascade in the outer
magnetosphere of an isolated, spinning neutron star. The charge depletion due
to global flows of charged particles, causes a large electric field along the
magnetic field lines. Migratory electrons and/or positrons are accelerated by
this field to radiate gamma-rays via curvature and inverse-Compton processes.
Some of such gamma-rays collide with the X-rays to materialize as pairs in the
gap. The replenished charges partially screen the electric field, which is
self-consistently solved together with the energy distribution of particles and
gamma-rays at each point along the field lines. By solving the set of Maxwell
and Boltzmann equations, we demonstrate that an external injection of charged
particles at nearly Goldreich-Julian rate does not quench the gap but shifts
its position and that the particle energy distribution cannot be described by a
power-law. The injected particles are accelerated in the gap and escape from it
with large Lorentz factors. We show that such escaping particles migrating
outside of the gap contribute significantly to the gamma-ray luminosity for
young pulsars and that the soft gamma-ray spectrum between 100 MeV and 3 GeV
observed for the Vela pulsar can be explained by this component. We also
discuss that the luminosity of the gamma-rays emitted by the escaping particles
is naturally proportional to the square root of the spin-down luminosity.


title:
Astrophysical significance of detection of coalescing binaries with
  gravitational waves

abstract:
  We use the StarTrack stellar population synthesis code to analyze properties
of double compact object binaries as sources of gravitational waves. Since the
distribution of lifetimes of these objects extends up to the Hubble time we
conclude that a proper calculation of the expected rate must include a full
cosmological model. We present such model, calculate the expected coalescence
rates, and analyze the intrinsic sensitivity of these rates to the model
assumptions. We find that the rate alone is a very poor estimator of the
underlying stellar evolution model. However we show that the distribution of
observed chirp masses is very sensitive to the underlying stellar evolution
model, while it is very insensitive to the underlying cosmology, star formation
rate history and variation of detector sensitivity.


title:
First-order Fermi Particle Acceleration at Relativistic Shock Waves with
  a 'Realistic' Magnetic Field Turbulence Model

abstract:
  First-order Fermi acceleration process at a relativistic shock wave is
investigated by means of Monte Carlo simulations involving numerical
integration of particle equations of motion in a turbulent magnetic field near
the shock. In comparison to earlier studies a few 'realistic' features of the
magnetic field structure are included. The upstream field consists of a mean
field component inclined at some angle to the shock normal and finite-amplitude
perturbations imposed upon it. The perturbations are assumed to be static in
the local plasma rest frame. We apply an analytic model for the turbulence with
a flat or a Kolmogorov spectrum within a finite (wide) wave vector range. The
magnetic field is continuous across the shock -- the downstream field structure
is derived from the upstream one from the hydrodynamical shock jump conditions.
We present and discuss the obtained particle spectra and angular distributions
at mildly relativistic sub- and superluminal shocks. We show that particle
spectra diverge from a simple power-law, an exact shape of the spectrum depends
on both an amplitude of the magnetic field perturbations and the considered
wave power spectrum.


title:
Cosmic ray acceleration at parallel relativistic shocks in the presence
  of finite-amplitude magnetic field perturbations

abstract:
  We study the first-order Fermi acceleration process at parallel shock waves
by means of Monte Carlo simulations. A 'realistic' model of the magnetic field
turbulence is applied involving sinusoidal waves imposed on the background mean
field parallel to the shock normal. The finite-amplitude magnetic field
perturbations lead to locally oblique field configurations at the shock and the
respective magnetic field compression. It results in modification of the
particle acceleration process introducing some features observed in oblique
shocks, e.g. particle reflections from the shock. For the parallel mildly
relativistic shocks we demonstrate for the first time a (non-monotonic)
variation of the accelerated particle spectral index with the turbulence
amplitude.


title:
LOFAR: A new radio telescope for low frequency radio observations:
  Science and project status

abstract:
  LOFAR, the Low Frequency Array, is a large radio telescope consisting about
100 soccer field sized antenna stations spread over a region of 400 km in
diameter. It will operate in the frequency range from ~10 to 240 MHz, with a
resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will
allow for a broad range of astrophysical studies. In this contribution we first
discuss four major areas of astrophysical research in which LOFAR will
undoubtedly make important contributions: reionisation, distant galaxies and
AGNs, transient radio sources and cosmic rays. Subsequently, we will discuss
the technical concept of the instrument and the status of the LOFAR project


title: Fast outflow of neutral hydrogen in the radio galaxy 3C293

abstract:
  We report the detection of very broad HI absorption against the central
regions of the radio galaxy 3C293. The absorption profile, obtained with the
Westerbork Synthesis Radio Telescope, has a full width at zero intensity of
about 1400 km/s and most of this broad absorption (~1000 km/s) is blueshifted
relative to the systemic velocity. This absorption represents a fast outflow of
neutral gas from the central regions of this AGN. Possible causes for such an
outflow are discussed. We favour the idea that the interaction between the
radio jet and the rich ISM produces this outflow. Some of the implications of
this scenario are considered.


title:
The DEEP Groth Strip Survey IX: Evolution of the Fundamental Plane of
  Field Galaxies

abstract:
  Fundamental Plane studies provide an excellent means of understanding the
evolutionary history of early-type galaxies. Using the Low Resolution Imaging
Spectrograph on the Keck telescope, we obtained internal stellar kinematic
information for 36 field galaxies in the Groth Strip--21 early-type and 15 disk
galaxies. Their redshifts range from 0.3--1.0, with a median redshift 0.8. The
slope of the relation shows no difference compared with the local slope.
However, there is significant evolution in the zero-point offset; an offset due
to evolution in magnitude requires a 2.4 magnitude luminosity brightening at
z=1. We see little differences of the offset with bulge fraction, which is a
good surrogate for galaxy type. Correcting for the luminosity evolution reduces
the orthogonal scatter in the Fundamental Plane to 8%, consistent with the
local scatter. This scatter is measured for our sample, and does not include
results from other studies which may have different selection effects. The
difference in the degree of evolution between our field sample and published
cluster galaxies suggests a more recent formation epoch--around z=1.5 for field
galaxies compared to z>2.0 for cluster galaxies. The magnitude difference
implies that the field early-type galaxies are about 2 Gyr younger than the
cluster ellipticals using standard single-burst models. However, the same
models imply a significant change in the rest-frame U-B color from then to
present, which is not seen in our sample. Continuous low-level star formation,
however, would serve to explain the constant colors over this large magnitude
change. A consistent model has 7% of the stellar mass created after the initial
burst, using an exponentially decaying star formation rate with an e-folding
time of 5 Gyr.


title: Gravitational lensing by stars with angular momentum

abstract:
  Gravitational lensing by spinning stars, approximated as homogeneous spheres,
is discussed in the weak field limit. Dragging of inertial frames, induced by
angular momentum of the deflector, breaks spherical symmetry. I examine how the
gravito-magnetic field affects image positions, caustics and critical curves.
Distortion in microlensing-induced light curves is also considered.


title: Big Bang Nucleosynthesis: Probing the First 20 Minutes

abstract:
  Within the first 20 minutes of the evolution of the hot, dense, early
Universe, astrophysically interesting abundances of deuterium, helium-3,
helium-4, and lithium-7 were synthesized by the cosmic nuclear reactor. The
primordial abundances of these light nuclides produced during Big Bang
Nucleosynthesis (BBN) are sensitive to the universal density of baryons and to
the early-Universe expansion rate which at early epochs is governed by the
energy density in relativistic particles (``radiation'') such as photons and
neutrinos. Some 380 kyr later, when the cosmic background radiation (CBR)
radiation was freed from the embrace of the ionized plasma of protons and
electrons, the spectrum of temperature fluctuations imprinted on the CBR also
depended on the baryon and radiation densities. The comparison between the
constraints imposed by BBN and those from the CBR reveals a remarkably
consistent picture of the Universe at two widely separated epochs in its
evolution. Combining these two probes leads to new and tighter constraints on
the baryon density at present, on possible new physics beyond the standard
model of particle physics, as well as identifying some challenges to astronomy
and astrophysics. In this review the current status of BBN will be presented
along with the associated estimates of the baryon density and of the energy
density in radiation.


title:
Observability of Scattered-Light Echoes Around Variable Stars and
  Cataclysmic Events

abstract:
  Scattered light echoes from variable and cataclysmic stars offer one of the
most effective means to probe the structure and composition of circumtellar and
interstellar media. I build a simple model of light-echo surface brightness by
considering the source spectrum, and the dust density, geometry, and scattering
efficiency. I use this model to investigate whether echoes should be observable
around short and long-period giants, cataclysmic variables, and supernovae.
Only supernovae are expected to illuminate material on both circumstellar and
interstellar scales. Giant and post-AGB stars (e.g. Cepheids and Miras) with
high mass-loss rates can produce observable echoes within their circumstellar
envelopes. Echoes from novae and dwarf novae are probably detectable only from
nearby material, and only in unusually dense gas. I present characteristic
exposure times to image such echoes over a wide range of wavelengths for
ground-based and {\em Hubble Space Telescope} observations. I apply these
results to analyze the dust properties of the recently-reported echoes around
SN 1993J, finding the dust in M81 to have a grain-size distribution and
chemical composition consistent with Galactic dust. Optimal observing
strategies for echo detection are also discussed.


title:
Continuum and CO/HCO+ Emission from the Disk Around the T Tauri Star
  LkCa 15

abstract:
  We present OVRO Millimeter Array lambda = 3.4 - 1.2 mm dust continuum and
spectral line observations of the accretion disk encircling the T Tauri star
LkCa 15. The 1.2 mm dust continuum emission is resolved, and gives a minimum
diameter of 190 AU and an inclination angle of 57+/-5 degrees. There is a
noticeable, but at present poorly constrained, decrease in the continuum
spectral slope with frequency that may result from the coupled processes of
grain growth and dust settling. Imaging of the fairly intense emission from the
lowest rotational transitions of CO, 13CO and HCO+ reveals a rotating disk and
emission extends to 750 AU and the characteristic radius of the disk is
determined to be around 425 AU (HWHM) based on model fits to the CO velocity
field. The disk mass derived from the CO isotopologues with ``typical'' dense
cloud abundances is still nearly two orders of magnitude less than that
inferred from the dust emission, which is probably due to extensive molecular
depletion in the cold, dense disk midplane. N2H+ 1-0 emission has also been
detected which, along with HCO+, sets a lower limit to the fractional
ionization of 10^{-8} in the near-surface regions of protoplanetary disks. This
first detection of N2H+ in circumstellar disks has also made possible a
determination of the N2/CO ratio (~2) that is at least an order of magnitude
larger than those in the envelopes of young stellar objects and dense clouds.
The large N2/CO ratio indicates that our observations probe disk layers in
which CO is depleted but some N2 remains in the gas phase. Such differential
depletion can lead to large variations in the fractional ionization with height
in the outer reaches of circumstellar disks, and may help to explain the
relative nitrogen deficiency observed in comets.


title: A Relation Between Supermassive Black Hole Mass and Quasar Metallicity?

abstract:
  We analyze spectra for a large sample of 578 Active Galactic Nuclei to
examine the relationships between broad emission line properties and central
supermassive black hole (SMBH) mass. We estimate SMBH masses by applying the
virial theorem to the C IV lambda 1549 broad emission line. Although the FWHMs
of C IV and H beta appear nearly unrelated in individual objects, these FWHMs
are well correlated when averaged over sub-samples in our database. Therefore,
the lines are equally valid indicators of the average SMBH mass in quasar
samples. Our sample spans five orders of magnitude in SMBH mass, six orders of
magnitude in luminosity, and a redshift range from 0 <= z <= 5. Most lines
diminish in equivalent width with increasing black hole mass (the usual
"Baldwin Effect") and there are no trends with redshift. Recent studies
indicate that there is a relationship between SMBH mass and the overall
bulge/spheroidal component mass of the surrounding galaxy. This relation,
together with the well-known mass-metallicity relationship among galaxies,
predicts a relationship between SMBH mass and quasar metallicity. We estimate
the metallicity in the broad emission line region by comparing several line
ratios involving nitrogen to theoretical predictions. We find that the data are
consistent with a trend between SMBH mass and metallicity, with some line
ratios indicating a very strong trend, but the uncertainties in several other
important line ratios are too large to confirm or test this correlation.


title: Constraining evolution in the Halo Model using galaxy redshift surveys

abstract:
  We use the latest observations from the 2dF Galaxy Redshift Survey to fit the
conditional luminosity function (CLF) formulation of the halo-model for
galaxies at z=0. This fit is then used to test the extent of evolution in the
halo occupation distribution (HOD) to z=0.8, by comparing the predicted
clustering from this CLF to preliminary results from the DEEP2 Redshift Survey.
We show that the current observations from the DEEP2 Redshift Survey are
remarkably consistent with no evolution in the CLF from z=0 to z=0.8. This
result is surprising, in that it suggests that there has been very little
change in the way galaxies occupy their host dark matter halos over half the
age of the Universe. We discuss in detail the observational constraints we have
adopted and also the various different selection effects in each survey and how
these impact on the galaxy populations encountered in each survey.


title: Detection of the ISW and SZ effects from the CMB-Galaxy correlation

abstract:
  We present a cross-correlation analysis of the WMAP cosmic microwave
background (CMB) temperature anisotropies and the SDSS galaxy density
fluctuations. We find significant detections of the angular CMB-galaxy
correlation for both the flux limited galaxy sample (z~0.3) and the high
redshift (z ~ 0.5) color selected sample. The signal is compatible with that
expected from the integrated Sachs-Wolfe (ISW) effect at large angles (\theta >
3deg) and the Sunyaev-Zeldovich (SZ) effect at small scales (\theta < 1 deg).
The detected correlation at low-z is in good agreement with a previous analysis
using the APM survey (z~0.15). The combined analysis of all 3 samples yields a
total significance better than 3 sigma for ISW and about 2.7 \sigma for SZ,
with a Compton parameter y~10^(-6). For a given flat LCDM model, the ISW effect
depends both on the value of \Omega_\Lambda and the galaxy bias b. To break
this degeneracy, we estimate the bias using the ratio between the galaxy and
mass auto-correlation functions in each sample. With our bias estimation, all
samples consistently favor a best fit dark-energy dominated model:
\Omega_\Lambda ~ 0.8, with a 2 \sigma error \Omega_\Lambda=0.69-0.86.


title:
Post-AGB Evolution in the Large Magellanic Cloud. A Study of the Central
  Stars of Planetary Nebulae

abstract:
  We present medium- and broad-band Hubble Space Telescope (HST) photometry of
a sample of 35 central stars (CSs) of Planetary Nebulae (PNs) in the Large
Magellanic Cloud (LMC). The observations were made with the WFPC2 and STIS
instruments on board the HST. By observing LMC objects, our sample is free of
the distance uncertainty that is the dominate source of error in the
determination of CS luminosities in Galactic PNs. By observing with the HST, we
resolve the nebula and therefore we often detect the CSs unambiguously. We
obtain core masses of 16 of the objects by comparing their positions on the HR
diagram to theoretical evolutionary tracks, once we determine the stellar
effective temperature through Zanstra analysis. This sample of CS masses is the
largest and most reliable set obtained in an extra-Galactic environment. We
find an average mass of 0.65 Msun, though a few of the objects have very high
mass. This average value is consistent with the average mass of the white dwarf
population in the Galaxy. As the immediate precursors of white dwarfs, the
study of the mass distribution of PN CSs should help to constrain the
initial-to-final mass relation within environments of differing metallicity.
Finally, by exploring the physical connections between the star and the nebula,
we establish the importance of the study of PNs in the LMC to constrain the
energy input from the wind during the post-AGB phase.


title:
On the methods of determining the radio emission geometry in pulsar
  magnetospheres

abstract:
  We present a modification of the relativistic phase shift method of
determining the radio emission geometry from pulsar magnetospheres proposed by
Gangadhara & Gupta (2001). Our modification provides a method of determining
radio emission altitudes which does not depend on the viewing geometry and does
not require polarization measurements. We suggest application of the method to
the outer edges of averaged radio pulse profiles to identify magnetic field
lines associated with the edges of the pulse and, thereby, to test the
geometric method based on the measurement of the pulse width at the lowest
intensity level. We show that another relativistic method proposed by
Blaskiewicz et al. (1991) provides upper limits for emission altitudes
associated with the outer edges of pulse profiles. A comparison of these limits
with the altitudes determined with the geometric method may be used to probe
the importance of rotational distortions of magnetic field and refraction
effects in the pulsar magnetosphere. We provide a comprehensive discussion of
the assumptions used in the relativistic methods.


title: Probing AGB nucleosynthesis via accurate Planetary Nebula abundances

abstract:
  The elemental abundances of ten planetary nebulae, derived with high accuracy
including ISO and IUE spectra, are analysed with the aid of synthetic
evolutionary models for the TP-AGB phase. Model prescriptions are varied until
we achieve the simultaneous reproduction of all elemental features, which
allows placing important constraints on the characteristic masses and
nucleosynthetic processes experienced by the stellar progenitors. First of all,
it is possible to separate the sample into two groups of PNe, one indicating
the occurrence of only the third dredge-up during the TP-AGB phase, and the
other showing also the chemical signature of hot-bottom burning. The former
group is reproduced by stellar models with variable molecular opacities (see
Marigo 2002), adopting initial solar metallicity, and typical efficiency of the
third dredge-up 0.3-0.4. The latter group of PNe, with extremely high He
content 0.15<=He/H<=0.20 and marked oxygen deficiency, is consistent with
original sub-solar metallicity (i.e. LMC composition). Moreover, we are able to
explain quantitatively both the N/H-He/H correlation and the N/H-C/H
anti-correlation, thus solving the discrepancy pointed out long ago by Becker &
Iben (1980). This is obtained only under the hypothesis that intermediate-mass
TP-AGB progenitors (M > 4.5-5.0 Mo) with LMC composition have suffered a number
of very efficient, carbon-poor, dredge-up events. Finally, the neon abundances
of the He-rich PNe can be recovered by invoking a significant production of
22Ne during thermal pulses, which would imply a reduced role of the
22Ne(alpha,n)25Mg reaction as neutron source to the s-process nucleosynthesis
in these stars.


title: Supergalactic winds driven by multiple superstar clusters

abstract:
  We present two dimensional hydrodynamic calculations of free expanding
supergalactic winds, taking into consideration strong radiative cooling. Our
main premise is that supergalactic winds are powered by collections of
superstar clusters. Every individual superstar cluster is a source of a high
metallicity radiative supersonic outflow (paper I, 2003, ApJ, 590, 791). The
interaction of winds from neighboring knots of star formation is shown to lead
to a collection of stationary oblique shocks and crossing shocks, able to
structure the general outflow into a network of dense and cold, kpc long
filaments that originate near the base of the outflow. The shocks also lead to
extended regions of diffuse soft X-ray emission and furthermore, to channel the
outflow with a high degree of collimation into the intergalactic medium.


title:
A Hubble Space Telescope Survey of Extended [OIII]5007A Emission in a
  Far-Infrared Selected Sample of Seyfert Galaxies: Observations

abstract:
  We present a Hubble Space Telescope (HST) survey of extended [OIII] emission
for a sample of 60 Seyfert galaxies (22 Seyfert 1's and 38 Seyfert 2's),
selected based on their far infrared properties. The observations for 42 of
these galaxies were done in a snapshot survey with WFPC2. The remaining 18 were
obtained from the HST archive, most of which were observed with the same
configuration. These observations cover 68% of the objects in the sample
defined by Kinney et al. (2000), and create a valuable dataset for the study of
the Narrow Line Region (NLR) properties of Seyfert galaxies. In this paper, we
present the details of the observations, reductions, and measurements. We also
discuss the extended structure of individual sources, and the relation of this
emission to the radio and host galaxy morphology. We also address how
representative the subsample of [O III]-imaged galaxies is of the entire
sample, and possible selection effects that may affect this comparison of the
properties of Seyfert 1 and Seyfert 2 galaxies.