title:
The dependence on environment of the color-magnitude relation of
  galaxies

abstract:
  The distribution in color and absolute magnitude is presented for 55,158
galaxies taken from the Sloan Digital Sky Survey in the redshift range
$0.08<z<0.12$, as a function of galaxy number overdensity in a line-of-sight
cylinder of transverse radius $1 h^{-1} \mathrm{Mpc}$. In all environments,
bulge-dominated galaxies (defined to be those with radial profiles best fit
with large S\'ersic indices) form a narrow, well defined color--magnitude
relation. Although the most luminous galaxies reside preferentially in the
highest density regions, there is only a barely detectable variation in the
color (zero-point) or slope of the color--magnitude relation ($<0.02
\mathrm{mag}$ in $^{0.1}[g-r]$ or $[B-V]$). These results constrain variations
with environmental density in the ages or metallicities of typical
bulge-dominated galaxies to be under 20 percent.


title: White Dwarfs Near Black Holes: A New Paradigm for Type I Supernovae

abstract:
  We present calculations indicating the possibility of a new class of Type I
supernovae. In this new paradigm relativistic terms enhance the self gravity of
a carbon-oxygen white dwarf as it passes or orbits near a black hole. This
relativistic compression can cause the central density to exceed the threshold
for pycnonuclear reactions so that athermonuclear runaway ensues. We consider
three possible environments: 1) white dwarfs orbiting a low-mass black hole; 2)
white dwarfs encountering a massive black hole in a dense globular cluster; and
3) white dwarfs passing a supermassive black hole in a dense galactic core. We
estimate the rate at which such events could occur out to a redshift of z = 1.
Event rates are estimated to be significantly less than the rate of normal Type
Ia supernovae for all three classes. Nevertheless, such events may be frequent
enough to warrant a search for this new class of supernova. We propose several
observable signatures which might be used to identify this type of event and
speculate that such an event might have produced the observed
"mixed-morphology" Sgr A East supernova remnant in the Galactic core.


title: 1/R gravity and Scalar-Tensor Gravity

abstract:
  We point out that extended gravity theories, the Lagrangian of which is an
arbitrary function of scalar curvature $R$, are equivalent to a class of the
scalar tensor theories of gravity. The corresponding gravity theory is
$\omega=0$ Brans-Dicke gravity with a potential for the Brans-Dicke scalar
field, which is not compatible with solar system experiments if the field is
very light: the case when such modifications are important recently.


title:
A Young White Dwarf Companion to Pulsar 1620-26: Evidence for Early
  Planet Formation

abstract:
  The pulsar B1620-26 has two companions, one of stellar mass and one of
planetary mass. We detected the stellar companion using Hubble Space Telescope
observations. The color and magnitude of the stellar companion indicate that it
is an undermassive white dwarf ($0.34 \pm 0.04 M_{\odot}$) of age $480\pm 140$
Myr. This places a constraint on the recent history of this triple system and
supports a scenario in which the current configuration arose through a
dynamical exchange interaction in the cluster core. This implies that planets
may be relatively common in low-metallicity globular clusters and that planet
formation is more widespread and happened earlier than previously believed.


title:
Optical identification of the companion to PSR J1911-5958A, the pulsar
  binary in the outskirts of NGC 6752

abstract:
  We report on the identification of the optical counterpart of the binary
millisecond pulsar PSR J1911-5958A, located in the outskirts of the globular
cluster NGC 6752. At the position of the pulsar we find an object with V=22.08,
B-V=0.38, U-B=-0.49. The object is blue with respect to the cluster main
sequence by 0.8 magnitudes in B-V. We argue that the object is the white dwarf
companion of the pulsar. Comparison with white dwarf cooling models shows that
this magnitude and colors are consistent with a low-mass white dwarf at the
distance of NGC 6752. If associated with NGC 6752, the white dwarf is
relatively young, <2 Gyr, which sets constraints on the formation of the binary
and its ejection from the core of the globular cluster.


title: KH15D: a star eclipsed by a large scale dusty vortex?

abstract:
  We propose that the large photometric variations of KH15D are due to an
eclipsing swarm of solid particles trapped in giant gaseous vortex rotating at
\~0.2 AU from the star. The efficiency of the capture-in-vortex mechanism
easily explains the observed large optical depth. The weaker opacity at
mid-eclipse is consistent with a size segregation of the particles toward the
center of the vortex. This dusty structure must extend over ~1/3 of an orbit to
account for the long eclipse duration. The estimated size of the trapped
particles is found to range from 1 to 10cm, consistent with the gray extinction
of the star. The observations of KH15D support the idea that giant vortices can
grow in circumstellar disks and play a central role in planet formation.


title: XMM-Newton observation of the interacting cluster Abell 3528

abstract:
  We analyze the XMM dataset of the interacting cluster of galaxies Abell 3528
located westward in the core of the Shapley Supercluster, the largest
concentration of mass in the nearby Universe. A3528 is formed by two
interacting clumps (A3528-N at North and A3528-S at South) separated by 0.9
$h_{70}^{-1}$ Mpc at redshift 0.053. XMM data describe these clumps as relaxed
structure with an overall temperature of $4.14 \pm 0.09$ and $4.29 \pm 0.07$
keV in A3528-N and A3528-S, respectively, and a core cooler by a factor
1.4--1.5 and super-solar metal abundance in the inner 30 arcsec. These clumps
are connected by a X-ray soft, bridge-like emission and present asymmetric
surface brightness with significant excess in the North--West region of A3528-N
and in the North--East area of A3528-S. However, we do not observe any evidence
of shock heated gas, both in the surface brightness and in the temperature map.
Considering also that the optical light distribution is more concentrated
around A3528-N and makes A3528-S barely detectable, we do not find support to
the originally suggested head-on pre-merging scenario and conclude that A3528
is in a off-axis post-merging phase, where the closest cores encounter happened
about 1--2 Gyrs ago.


title: Radial Velocity Variations in Pulsating Ap Stars. II. 33 Librae

abstract:
  We present precise relative radial velocity (RV) measurements for the rapidly
oscillating Ap (roAp) star 33 Librae measured from high resolution data
spanning the wavelength interval 5000--6200 A. We find that pulsational radial
velocity amplitude determined over a broad wavelength range (~100 A) depends on
the spectral region that is examined and can be as high as 60 m/s at 5600 A and
as low as 7 m/s in the 5900 A region. RV measurements of individual spectral
lines can show even higher RV amplitudes. The acoustic cross-sections of the
atmosphere, i.e. the phase and amplitude of the pulsations, as a function of
optical depth is found for spectral lines of Ca, Cr, Fe, La, Ce, Gd, Er and Nd.
This analysis shows that pulsation phase is variable through the atmosphere and
that Nd III lines pulsate almost 180 degrees out-of-phase with those of Nd II
features and are formed significantly higher in the stellar atmosphere. This
conclusively establishes the presence of at least one radial node to the
pulsations in the upper stellar atmosphere. The histogram of pulsational phases
for all individual spectral feature shows a bi-modal Gaussian distribution with
17% of the lines having a pulsational phase approximatels 165 degrees
out-of-phase with most other spectral lines. This is also consistent with the
presence of a radial node in the stellar atmosphere. The accumulation of phase
due to a running wave component can explain the 165 degree phase difference as
well as the broader width (by a factor of two) of one of the Gaussian
components of the phase distribution.


title:
On the Enhanced X-ray Emission from SGR 1900+14 after the August 27
  Giant Flare

abstract:
  We show that the giant flares of soft-gamma ray repeaters (E~10^44 ergs) can
push the inner regions of a fall-back disk out to larger radii by radiation
pressure, while matter remains bound to the system for plausible parameters.
The subsequent relaxation of this pushed-back matter can account for the
observed enhanced X-ray emission after the August 27 giant flare of SGR
1900+14. Based on the results of our models, we estimate that the ratio of the
fluences of the enhanced X-ray emissions to that of the preceding bursts
remains constant for a particular SGR with similar preburst inner disk
conditions, which is consistent with the four different burst observations of
SGR 1900+14.


title:
A quadruply imaged quasar with an optical Einstein ring candidate: 1RXS
  J113155.4-123155

abstract:
  We report the discovery of a new quadruply imaged quasar surrounded by an
optical Einstein ring candidate. Spectra of the different components of 1RXS
J113155.4-123155 reveal a source at z=0.658. Up to now, this object is the
closest known gravitationally lensed quasar. The lensing galaxy is clearly
detected. Its redshift is measured to be z=0.295. Additionally, the total V
magnitude of the system has varied by 0.3 mag between two epochs separated by
33 weeks. The measured relative astrometry of the lensed images is best fitted
with an SIS model plus shear. This modeling suggests very high magnification of
the source (up to 50 for the total magnification) and predicts flux ratios
between the lensed images significantly different from what is actually
observed. This suggests that the lensed images may be affected by a combination
of micro or milli-lensing and dust extinction effects.


title:
Model-independent dark energy test with sigma_8 using results from the
  Wilkinson Microwave Anisotropy Probe

abstract:
  By combining the recent WMAP measurements of the cosmic microwave background
anisotropies and the results of the recent luminosity distance measurements to
type-Ia supernovae, we find that the normalization of the matter power spectrum
on cluster scales, sigma_8, can be used to discriminate between dynamical
models of dark energy (quintessence models) and a conventional cosmological
constant model (LCDM).


title: Primordial bubbles of colour superconducting quark matter

abstract:
  We analyze the possibility that bubbles of quark matter surviving the
confinement phase transition might have become colour superconducting due to
the enormous compression suffered by them.
  Because of the relatively high temperature of the process we compare the
initially unpaired quark matter with the colour-flavour locked alternative when
the extremely large chemical potential could have increased the critical
temperature sufficiently and find that this latter phase would be more stable
before the bubble compression stops.
  If other physical effects have not affected completely their stability, these
bubbles might still exist today and perhaps be observed as strangelets.


title: Rebrightening in GRBs by Precessing Jet

abstract:
  A clear gamma polarization in the gamma signals from GRB021206 probes the
presence of a very thin collimated jet (opening angle Delta\theta < 0.6^o,
(Delta\Omega)\Omega< 2.5 10^-5) in Gamma Ray Burst, GRBs. The last and well
proved GRB030329/SN2003dh time and space coincidence confirms definitively the
earliest GRB980425/SN1998bw connection among GRB and Supernova. The apparent
extreme GRBs luminosity is just the extreme beamed blazing gamma Jet observed
in axis during a Supernova birth. The late relic GRBs sources may be found in
compact SNRs core, as NS or BH jets; at much later epoch, their lower power
gamma jets may be within detectability only from nearby galactic distances, as
Soft Gamma Repeaters (SGRs) or anomalous X-ray Pulsars, AXPs. This common Jet
nature explain some connection between GRBs and SGRs spectra. The geometrical
multi-precessing beaming and their reappearance to the observer may explain the
puzzling presence of X-Ray precursors in GRBs as well as in SGRs. A mysterious
re-brightening afterglows observed in early and late GRB 030329 optical
transient, like in the 27 August 1998 and 18 April 2001 SGR 1900+14 events,
might be understood as the damped oscillatory imprint left by such a
multi-precessing gamma-X-Optical and Radio Jet.


title: Star formation and the environment of nearby field galaxies

abstract:
  We investigate the environmental dependence of galaxies with star formation
from a volume-limited sample of 4782 nearby field galaxy spectra extracted from
the 2dF Galaxy Redshift Survey final data release. The environment is
characterized by the local spatial density of galaxies, estimated from the
distance to the 5th nearest neighbour. Extensive simulations have been made to
estimate correction factors for the local density due to sample incompleteness.
We discriminate the galaxies in distinct spectral classes -- passive,
star-forming, and short starburst galaxies -- by the use of the equivalent
widths of [{\sc O ii}]$\lambda$3727 and H$\delta$. The frequency of galaxies of
different classes are then evaluated as a function of the environment. We show
that the fraction of star-forming galaxies decreases with increasing density,
whereas passive galaxies present the opposite behaviour. The fraction of short
starburst galaxies -- that suffered a starburst at $\sim$ 200 Myr ago -- do not
present strong environmental dependence. The fraction of this class of galaxies
is also approximately constant with galaxy luminosity, except for the faintest
bins in the sample, where their fraction seems to increase. We find that the
star-formation properties are affected in all range of densities present in our
sample (that excludes clusters), what supports the idea that star-formation in
galaxies is affected by the environment everywhere. We suggest that mechanisms
like tidal interactions, which act in all environments, do play a relevant role
on the star-formation in galaxies.


title: Cosmological constraints on a dark matter -- dark energy interaction

abstract:
  It is generally assumed that the two dark components of the energy density of
the universe, a smooth component called dark energy and a fluid of
nonrelativistic weakly interacting particles called dark matter, are
independent of each other and interact only through gravity. In this paper, we
consider a class of models in which the dark matter and dark energy interact
directly. The dark matter particle mass is proportional to the value of a
scalar field, and the energy density of this scalar field comprises the dark
energy. We study the phenomenology of these models and calculate the luminosity
distance as a function of redshift and the CMB anisotropy spectrum for several
cases. We find that the phenomenology of these models can differ significantly
from the standard case, and current observations can already rule out the
simplest models.


title:
Space Telescope Imaging Spectrograph slitless observations of Small
  Magellanic Cloud Planetary Nebulae: a study on morphology, emission line
  intensity, and evolution

abstract:
  A sample of 27 Planetary Nebulae (PNs) in the Small Magellanic Clouds (SMC)
have been observed with the Hubble Space Telescope Imaging Spectrograph
(HST/STIS) to determine their morphology, size, and the spatial variation of
the ratios of bright emission lines. The morphologies of SMC PNs are similar to
those of LMC and Galactic PNs. However, only a third of the resolved SMC PNs
are asymmetric, compared to half in the LMC. The low metallicity environment of
the SMC seems to discourage the onset of bipolarity in PNs. We measured the
line intensity, average surface brightness (SB), and photometric radius of each
nebula in halpha, hbeta, [O III] lambda4959 and 5007, [NII] 6548 and 6584, [S
II] lambda6716 and 5731, He I 6678, and [OI] 6300 and 6363. We show that the
surface brightness to radius relationship is the same as in LMC PNs, indicating
its possible use as a distance scale indicator for Galactic PNs. We determine
the electron densities and the ionized masses of the nebulae where the [S II]
lines were measured accurately, and we find that the SMC PNs are denser than
the LMC PNs by a factor of 1.5. The average ionized mass of the SMC PNs is 0.3
Msun. We also found that the median [O III]/hbeta intensity ratio in the SMC is
about half than the corresponding LMC median. We use Cloudy to model the
dependence of the [O III]/hbeta ratio on the oxygen abundance. Our models
encompass very well the average observed physical quantities. We suggest that
the SMC PNs are principally cooled by the carbon lines, making it hard to study
their excitation based on the optical lines at our disposal.


title: Pulsar Recoil by Large-Scale Anisotropies in Supernova Explosions

abstract:
  Assuming that the neutrino luminosity from the neutron star core is
sufficiently high to drive supernova explosions by the neutrino-heating
mechanism, we show that low-mode (l = 1, 2) convection can develop from random
seed perturbations behind the shock. A slow onset of the explosion is crucial,
requiring the core luminosity to vary slowly with time, in contrast to the
burst-like exponential decay assumed in previous work. Gravitational and
hydrodynamic forces by the globally asymmetric supernova ejecta were found to
accelerate the remnant neutron star on a timescale of more than a second to
velocities above 500 km/s, in agreement with observed pulsar proper motions.


title:
Statistics of the Chi-Square Type, with Application to the Analysis of
  Multiple Time-Series Power Spectra

abstract:
  It is often necessary to compare the power spectra of two or more time
series: one may, for instance, wish to estimate what the power spectrum of the
combined data sets might have been, or one may wish to estimate the
significance of a particular peak that shows up in two or more power spectra.
Also, one may occasionally need to search for a complex of peaks in a single
power spectrum, such as a fundamental and one or more harmonics, or a
fundamental plus sidebands, etc. Visual inspection can be revealing, but it can
also be misleading. This leads one to look for one or more ways of forming
statistics, which readily lend themselves to significance estimation, from two
or more power spectra. The familiar chi-square statistic provides a convenient
mechanism for combining variables drawn from normal distributions, and one may
generalize the chi-square statistic to be any function of any number of
variables with arbitrary distributions. In dealing with power spectra, we are
interested mainly in exponential distributions. One well-known statistic,
formed from the sum of two or more variables with exponential distributions,
satisfies the gamma distribution. We show that a transformation of this
statistic has the convenient property that it has an exponential distribution.
We introduce two additional statistics formed from two or more variables with
exponential distributions. For certain investigations, we may wish to study the
minimum power (as a function of frequency) drawn from two or more power
spectra. In other investigations, it may be helpful to study the product of the
powers. We give numerical examples and an example drawn from our solar-neutrino
research.


title: Modified Friedmann Equations in R$^{-1}$-Modified Gravity

abstract:
  Recently, corrections to Einstein-Hilbert action that become important at
small curvature are proposed. We discuss the first order and second order
approximations to the field equations derived by the Palatini variational
principle. We work out the first and second order Modified Friedmann equations
and present the upper redshift bounds when these approximations are valid. We
show that the second order effects can be neglected on the cosmological
predictions involving only the Hubble parameter itself, e.g. the various
cosmological distances, but the second order effects can not be neglected in
the predictions involving the derivatives of the Hubble parameter. Furthermore,
the Modified Friedmann equations fit the SN Ia data at an acceptable level.


title:
Near-Infrared, Adaptive Optics Observations of the T Tauri Multiple-Star
  System

abstract:
  With high-angular-resolution, near-infrared observations of the young stellar
object T Tauri at the end of 2002, we show that, contrary to previous reports,
none of the three infrared components of T Tau coincide with the compact radio
source that has apparently been ejected recently from the system (Loinard,
Rodriguez, and Rodriguez 2003). The compact radio source and one of the three
infrared objects, T Tau Sb, have distinct paths that depart from orbital or
uniform motion between 1997 and 2000, perhaps indicating that their interaction
led to the ejection of the radio source. The path that T Tau Sb took between
1997 and 2003 may indicate that this star is still bound to the presumably more
massive southern component, T Tau Sa. The radio source is absent from our
near-infrared images and must therefore be fainter than K = 10.2 (if located
within 100 mas of T Tau Sb, as the radio data would imply), still consistent
with an identity as a low-mass star or substellar object.


title:
Catalogue of averaged stellar effective magnetic fields. I. Chemically
  peculiar A and B type stars

abstract:
  This paper presents the catalogue and the method of determination of averaged
quadratic effective magnetic fields B_e for 596 main sequence and giant stars.
the catalogue is based on measurements of the stellar effective (or mean
longitudinal) magnetic field strengths B_e, which were compiled from the
existing literature. We analysed the properties of 352 chemically peculiar A
and B stars in the catalogue, including Am, ApSi, He-weak, He-rich, HgMn,
ApSrCrEu, and all ApSr type stars. We have found, that the number distribution
of all chemically peculiar (CP) stars vs. averaged magnetic field strength is
described by a decreasing exponential function. Relations of this type hold
also for stars of all the analysed subclasses of chemical peculiarity. The
exponential form of the above distribution function can break down below about
100 Gs, the latter value representing approximately the resolution of our
analysis for A type stars.


title: Double-Peaked Low-Ionization Emission Lines in Active Galactic Nuclei

abstract:
  We present a new sample of 116 double-peaked Balmer line Active Galactic
Nuclei (AGN) selected from the Sloan Digital Sky Survey. Double-peaked emission
lines are believed to originate in the accretion disks of AGN, a few hundred
gravitational radii (Rg) from the supermassive black hole. We investigate the
properties of the candidate disk emitters with respect to the full sample of
AGN over the same redshifts, focusing on optical, radio and X-ray flux, broad
line shapes and narrow line equivalent widths and line flux-ratios. We find
that the disk-emitters have medium luminosities (~10^44erg/s) and FWHM on
average six times broader than the AGN in the parent sample. The double-peaked
AGN are 1.6 times more likely to be radio-sources and are predominantly (76%)
radio quiet, with about 12% of the objects classified as LINERs. Statistical
comparison of the observed double-peaked line profiles with those produced by
axisymmetric and non-axisymmetric accretion disk models allows us to impose
constraints on accretion disk parameters. The observed Halpha line profiles are
consistent with accretion disks with inclinations smaller than 50 deg, surface
emissivity slopes of 1.0-2.5, outer radii larger than ~2000 Rg, inner radii
between 200-800Rg, and local turbulent broadening of 780-1800 km/s. The
comparison suggests that 60% of accretion disks require some form of asymmetry
(e.g., elliptical disks, warps, spiral shocks or hot spots).


title: A generic problem with purely metric formulations of MOND

abstract:
  We give a simple argument to show that no purely metric-based, relativistic
formulation of Milgrom's Modified Newtonian Dynamics (MOND) whose energy
functional is stable (in the sense of being quadratic in perturbations) can be
consistent with the observed amount of gravitational lensing from galaxies. An
important part of the argument is the fact that reproducing the MOND force law
requires any completely stable, metric-based theory of gravity to become
conformally invariant in the weak field limit. We discuss the prospects for a
formulation with a very weak instability.


title: The braking indices in pulsar emission models

abstract:
  Using the method proposed in a previous paper, we calculate pulsar braking
indices in the models with torque contributions from both inner and outer
accelerating regions, assuming that the interaction between them is negligible.
We suggest that it is likely that the inverse Compton scattering induced polar
vacuum gap and the outer gap coexist in the pulsar magnetosphere. We include
the new near threshold vacuum gap models with curvature-radiation and inverse
Compton scattering induced cascades, respectively; and find that these models
can well reproduce the measured values of the braking indices.


title:
Disentangling discrepancies between stellar evolution theory and
  sub-solar mass stars. The influence of the mixing length parameter for the UV
  Psc binary

abstract:
  Serious discrepancies have recently been observed between predictions of
stellar evolution models in the 0.7-1.1 M_sun mass range and accurately
measured properties of binary stars with components in this mass range. We
study one of these objects, the eclipsing binary UV Piscium, which is
particularly interesting because Popper (1997) derived age estimates for each
component which differed by more than a factor of two. In an attempt to solve
this significant discrepancy (a difference in age of 11 Gyr), we compute a
large grid of stellar evolution models with the CESAM code for each component.
By fixing the masses to their accurately determined values (relative error
smaller than 1% for both stars), we consider a wide range of possible
metallicities Z (0.01 to 0.05), and Helium content Y (0.25 to 0.34)
uncorrelated to Z. In addition, the mixing length parameter alpha_MLT is left
as another free parameter. We obtain a best fit in the T_eff-radius diagram for
a common chemical composition (Z, Y)=(0.012, 0.31), but a different MLT
parameter alpha_MLT_A = 0.95+-0.12(statistical)+0.30(systematic) and
alpha_MLT_B = 0.65+-0.07(stat)+0.10(syst). The apparent age discrepancy found
by Popper (1997) disappears with this solution, the components being coeval to
within 1%. This suggests that fixing alpha_MLT to its solar value (~1.6), a
common hypothesis assumed in most stellar evolutionary models, may not be
correct. Secondly, since alpha_MLT is smaller for the less massive component,
this suggests that the MLT parameter may decrease with stellar mass, showing
yet another shortcoming of the mixing length theory to explain stellar
convection. This trend needs further confirmation with other binary stars with
accurate data.


title: Supermassive Stars in Quasar Disks

abstract:
  We propose that supermassive stars may form in quasar accretion disks, and we
discuss possible observational consequences. The structure and stability of
very massive stars are reviewed. Because of high accretion rates, quasar disks
are massive and the fringes of their optically luminous parts are prone to
fragmentation. Starting from a few hundred solar masses, a dominant fragment
will grow to the isolation mass, which is a significant fraction of the disk
mass, more quickly than the fragment contracts onto the stellar main sequence.
A gap will form in the disk and the star will migrate inward on the accretion
timescale, which is comparable to the star's main sequence lifetime. By
interrupting the gas supply to the inner disk, the gap may temporarily dim and
redden the quasar. The final stages of stellar migration will be a strong
source of low-frequency gravitational waves.


title:
Galaxies and Overmerging: What Does it Take to Destroy a Satellite
  Galaxy?

abstract:
  The Ultra Compact Dwarf (UCD) galaxies recently discovered in the Fornax and
Virgo clusters exhibit structural similarity to the dense nuclei of nucleated
dEs indicating that the progenitor galaxy and its halo have been entirely
tidally disrupted. Using high resolution $N$-body simulations with up to ten
million particles we investigate the evolution and tidal stripping of
substructure halos orbiting within a host potential. We find that complete
disruption of satellite halos modeled following the NFW density profile occurs
only for very low values of concentration in disagreement with the theoretical
predictions of CDM models. This discrepancy is further exacerbated when we
include the effect of baryons since disk formation increases the central
density.


title: Polarization observations in a low synchrotron emission field at 1.4 GHz

abstract:
  We present the first observation of the diffuse polarized synchrotron
radiation of a patch ($\sim 3^\circ \times 3^\circ$) in the BOOMERanG field,
one of the areas with the lowest CMB foreground emission. The work has been
carried out with the Australia Telescope Compact Array at 1.4 GHz with 3.4
arcmin resolution and sensitivity of $\sim 0.18$ mJy beam$^{-1}$. The mean
polarized signal has been found to be $P_{rms} = \sqrt{(Q_{rms}^2 + U_{rms}^2)}
= 11.6 \pm 0.6$ mK, nearly one order of magnitude below than in the Galactic
Plane.
  Extrapolations to frequencies of interest for cosmological investigations
suggest that polarized synchrotron foreground noise should allow the detection
of the CMB Polarization $E$--mode already at 32 GHz and make us confident that,
at 90 GHz, it is accessible with no relevant foreground contamination. Last but
not least, even the $B$--mode detection for $T/S > 0.01$ is not ruled out in
such a low emission patch.


title: The obscured QSO 1SAX J1218.9+2958

abstract:
  We present results from XMM-Newton observations of the obscured QSO 1SAX
J1218.9+2958. We find that the previously reported optical and soft X-ray
counterpart positions are incorrect. However we confirm the spectroscopic
redshift of 0.176. The optical counterpart has a K magnitude of 13.5 and an R-K
colour of 5.0 and is therefore a bright extremely red object (ERO). The X-ray
spectrum is well described by a power-law ($\Gamma=2.0\pm0.2$) absorbed by an
intrinsic neutral column density of $8.2^{+1.1}_{-0.7}\times 10^{22} cm^{-2}$.
We find that any scattered emission contributes at most 0.5 percent to the
total X-ray flux. From the optical/near-IR colour we estimate that the active
nucleus must contribute at least 50 percent of the total flux in the K band and
that the ratio of extinction to X-ray absorption is 0.1-0.7 times that expected
from a Galactic dust-gas ratio and extinction curve. If 1SAX J1218.9+2958 were
100 times less luminous it would be indistinguishable from the population
responsible for most of the 2-10 keV X-ray background. This has important
implications for the optical/IR properties of faint absorbed X-ray sources.


title:
MSX Mid infrared imaging of massive star birth environments. II: Giant
  HII regions

abstract:
  We conduct a Galactic census of Giant HII regions, based on the all sky 6cm
dataset of Kuchar & Clark, plus the kinematic distances obtained by Russeil.
  From an inspection of mid-IR Mid-course Space Experiment (MSX) and far-IR
IRAS Sky Survey Atlas images we identify a total of 56 GHII regions in the
Milky Way, of which 15% (65%) can be seen at optical (near-IR) wavelengths.The
mid to far-IR fluxes from each GH {\sc ii} region are measured, and sample the
thermal emission from the ubiquitous dust present within the exciting clusters
of OB stars, arising from the integrated luminosity of the hot stars heating
the cluster dust, for which we obtain log L(IR)=5.5-7.3 L_sun. The mid-IR
21micron spatial morphology is presented for each GHII region, and often
indicates multiple emission sources, suggesting complicated cluster formation.
IR colour-colour diagrams are presented, providing information about the
temperature distribution and optical depth of the dust. For the clusters of our
study, the dust is not optically thick to all the stellar radiation, thus the
measured infra-red luminosity is lower than the L(bol). As the dust environment
of a cluster begins to dissipate, the thermal emission and its optical depth
ought to decrease even before the stars appreciably evolve. We see evidence of
this in our empirical relationship between the integrated IR and Lyman
continuum luminosities.


title: Period-magnitude relations for M giants in Baade's Window NGC6522

abstract:
  A large and complete sample of stars with K < 9.75 in the NGC6522 Baade's
Window is examined using light curves from MACHO and IJK from DENIS. All 4 of
the sequences ABCD in the K vs logP diagram of the LMC are seen in the Bulge.
The Bulge sequences however show some differences from the Magellanic Clouds.
The sequences may be useful as distance indicators. A new diagram of the
frequency of late-type variables is presented. The catalogued SR variables of
the solar nbd are found to be a subset of the total of SRs, biased towards
large amplitude.


title:
Searching For the Physical Drivers of Eigenvector 1: Influence of Black
  Hole Mass and Eddington Ratio

abstract:
  [Abridged] We compute the virial mass of the central black hole (M) and the
luminosity-to-mass (L/M) ratio of ~ 300 low-z quasars and luminous Seyfert 1
nuclei. We analyze: (1) whether radio-quiet and radio-loud objects show
systematic differences in terms of M and L/M; (2) the influence of M and L/M on
the shape of the H-beta broad component line profile; (3) the significance of
the so-called "blue outliers" i.e., sources showing a significant blueshift of
the [OIII] 4959, 5007 lines with respect to the narrow component of H-beta
which is used as an estimator of the quasar reference frame. We show that M and
L/M distributions for RQ and RL sources are likely different for samples
matched in luminosity and redshift. Line profile comparisons for median spectra
computed over narrow ranges of M and L/M indicate that a Lorentz function
provides a better fit for higher L/M sources and a double Gaussian for lower
L/M values. A second (redshifted) Gaussian component at low L/M appears as a
red asymmetry frequently observed in radio-loud and radio-quiet sources with
broader (FWHM > 4000 km/s) H-beta broad component profiles. This component
becomes stronger in larger mass and lower L/M sources. No specific influence of
radio loudness on the H-beta broad component profile is detected, although
equivalent widths of H-beta broad component and especially of [OIII] 4959,5007
are larger for radio-loud sources. We identify five more "blue outlier"
sources. Since these sources are, on average, one magnitude brighter than other
AGNs with similar mass, they are accreting at an Eddington ratio that is 2-3
times higher. We hint at evolutionary effects that explain some of these
results and reinforce the "Eigenvector 1" correlations.


title:
The Hellas2XMM survey: III. Multiwavelength observations of hard X-ray
  selected sources in the PKS 0312-77 field

abstract:
  We present extensive optical, radio and infrared follow-up observations of a
sample of 35 hard X-ray (2-10 keV) selected sources discovered serendipitously
in the PV XMM-Newton observation of the radio-loud quasar PKS 0312-77 field,
for which also an archival Chandra observation is available. The observations
have been carried out as part of the HELLAS2XMM survey, a program aimed to
understand the nature of the sources responsible for the bulk of the hard X-ray
Background (XRB). The identification of the optical counterparts greatly
benefits from the positional accuracy obtained from Chandra and radio
observations. As a consequence, the spectroscopic completeness of the present
sample (80%) is limited only by the faintness of the optical counterparts. The
multiwavelength coverage of our survey allows us to unveil a large spread in
the overall properties of hard X-ray selected sources. At low redshift (z<1),
the source breakdown includes Broad Line AGN, Narrow Emission-Line Galaxies,
and optically ``normal'' galaxies. All the ten sources at z>1 are
spectroscopically classified as Broad Line AGNs. A few of them show significant
intrinsic X-ray absorption (N(H)>10^22 cm^-2), further supporting previous
evidence of a decoupling between optical and X-ray properties at high
luminosities and redshifts. Finally, a non negligible fraction (15%) of the
hard X-ray sources are not detected down to the limiting magnitude of the
optical images. The corresponding high X-ray to optical flux ratio, X-ray and
optical-infrared colors strongly suggest that they are high redshift, obscured
AGN.


title: Long-Lived Double-Barred Galaxies: Critical Mass and Length Scales

abstract:
  A substantial fraction of disk galaxies is double-barred. We analyze the
dynamical stability of such nested bar systems by means of Liapunov
exponents,by fixing a generic model and varying the inner (secondary) bar mass.
We show that there exists a critical mass below which the secondary bar cannot
sustain its own orbital structure, and above which it progressively destroys
the outer (primary) bar-supporting orbits. In this critical state, a large
fraction of the trajectories (regular and chaotic) are aligned with either bar,
suggesting the plausibility of long-lived dynamical states when
secondary-to-primary bar mass ratio is of the order of a few percent.
Qualitatively similar results are obtained by varying the size of the secondary
bar, within certain limits, while keeping its mass constant. In both cases, an
important role appears to be played by chaotic trajectories which are trapped
around (especially) the primary bar for long periods of time.


title: Chandra Observations of Point Sources in Abell 2255

abstract:
  In our search for ``hidden'' AGN we present results from a Chandra
observation of the nearby cluster Abell 2255. Eight cluster galaxies are
associated with point-like X-ray emission, and we classify these galaxies based
on their X-ray, radio, and optical properties. At least three are associated
with active galactic nuclei (AGN) with no optical signatures of nuclear
activity, with a further two being potential AGN. Of the potential AGN, one
corresponds to a galaxy with a post-starburst optical spectrum. The remaining
three X-ray detected cluster galaxies consist of two starbursts and an
elliptical with luminous hot gas. Of the eight cluster galaxies five are
associated with luminous (massive) galaxies and the remaining three lie in much
lower luminosity systems. We note that the use of X-ray to optical flux ratios
for classification of X-ray sources is often misleading, and strengthen the
claim that the fraction of cluster galaxies hosting an AGN based on optical
data is signficantly lower than the fraction based on X-ray and radio data.


title: SDSS J0903+5028: A New Gravitational Lens

abstract:
  We report the discovery of a new gravitationally lensed quasar from the Sloan
Digital Sky Survey, SDSS J090334.92+502819.2. This object was targeted for SDSS
spectroscopy as a Luminous Red Galaxy (LRG), but manual examination of the
spectrum showed the presence of a quasar at z= 3.6 in addition to a red galaxy
at z=0.388, and the SDSS image showed a second possible quasar image nearby.
Follow-up imaging and spectroscopy confirmed the lensing hypothesis. In images
taken at the ARC 3.5-meter telescope, two quasars are separated by 2.8
arc-seconds; the lensing galaxy is clearly seen and is blended with one of the
quasar images. Spectroscopy taken at the Keck II telescope shows that the
quasars have identical redshifts of z=3.6 and both show the presence of the
same broad absorption line-like troughs. We present simple lens models which
account for the geometry and magnifications. The lens galaxy lies near two
groups of galaxies and may be a part of them. The models suggest that the
groups may contribute considerable shear and may have a strong effect on the
lens configuration.


title: Signs of Planetary Microlensing Signals

abstract:
  An extrasolar planet can be detected via microlensing from the perturbation
it makes in the smooth lensing light curve of the primary. In addition to the
conventional photometric microlensing, astrometric observation of the
center-of-light motion of the source star image provides a new channel of
detecting and characterizing extrasolar planets. It was known that the
planet-induced astrometric signals tend to be positive while the photometric
signals can be either positive or negative. In this paper, we analytically show
the reason for these tendencies of microlensing planetary signals.


title: Correlated Optical and X-ray Variability in LMC X-2

abstract:
  We have obtained high time resolution (seconds) photometry of LMC X-2 in
December 1997, simultaneously with the Rossi X-ray Timing Explorer (RXTE), in
order to search for correlated X-ray and optical variability on timescales from
seconds to hours. We find that the optical and X-ray data are correlated only
when the source is in a high, active X-ray state. Our analysis shows evidence
for the X-ray emission leading the optical with a mean delay of <20s. The
timescale for the lag can be reconciled with disc reprocessing, driven by the
higher energy X-rays, only by considering the lower limit for the delay. The
results are compared with a similar analysis of archival data of Sco X-1.


title:
The 2MASS Wide-Field T Dwarf Search. II. Discovery of Three T Dwarfs in
  the Southern Hemisphere

abstract:
  We present the discovery of three new Southern Hemisphere T dwarfs identified
in the Two Micron All Sky Survey. These objects, 2MASS 0348-6022, 2MASS
0516-0445, and 2MASS 2228-4310, have classifications T7, T5.5, and T6.5,
respectively. Using linear absolute magnitude/spectral type relations derived
from T dwarfs with measured parallaxes, we estimate spectrophotometric
distances for these discoveries; the closest, 2MASS 0348-6022, is likely within
10 pc of the Sun. Proper motions and estimated tangential velocities are
consistent with membership in the Galactic disk population. We also list
Southern Hemisphere T dwarf candidates that were either not found in subsequent
near-infrared imaging observations and are most likely uncatalogued minor
planets, or have near-infrared spectra consistent with background stars.


title:
Gamma-ray and synchrotron emission from neutralino annihilation in the
  Large Magellanic Cloud

abstract:
  We calculate the expected flux of gamma-ray and radio emission from the LMC
due to neutralino annihilation. Using rotation curve data to probe the density
profile and assuming a minimum disk, we describe the dark matter halo of the
LMC using models predicted by N-body simulations. We consider a range of
density profiles including the NFW profile, a modified NFW profile proposed by
Hayashi et al.(2003) to account for the effects of tidal stripping, and an
isothermal sphere with a core. We find that the gamma-ray flux expected from
these models may be detectable by GLAST for a significant part of the
neutralino parameter space. The prospects for existing and upcoming Atmospheric
Cherenkov Telescopes are less optimistic, as unrealistically long exposures are
required for detection. However, the effects of adiabatic compression due to
the baryonic component may improve the chances for detection by ACTs. The
maximum flux we predict is well below EGRET's measurements and thus EGRET does
not constrain the parameter space. The expected synchrotron emission generally
lies below the observed radio emission from the LMC in the frequency range of
19.7 to 8550 MHz. As long as <sigma v> <2x 10^-26 cm^3 s^-1 for a neutralino
mass of 50 GeV, the observed radio emission is not primarily due to neutralinos
and is consistent with the assumption that the main source is cosmic rays. We
find that the predicted fluxes, obtained by integrating over the entire LMC,
are not very strongly dependent on the inner slope of the halo profile, varying
by less than an order of magnitude for the range of profiles we considered.


title:
Adaptive Optics Imaging and Spectroscopy of Cygnus A: I. Evidence for a
  Minor Merger

abstract:
  We present Keck II adaptive optics near infrared imaging and spectroscopic
observations of the central regions of the powerful radio galaxy Cygnus A. The
0.05" resolution images clearly show an unresolved nucleus between two
spectacular ionization/scattering cones. We report the discovery of a
relatively bright (K'~19) secondary point source 0.4" or 400 pc in projection
southwest of the radio nucleus. The object is also visible in archival Hubble
Space Telescope optical images, although it is easily confused with the
underlying structure of the host. Although the near infrared colors of this
secondary point source are roughly consistent with those of an L-dwarf, its
spectrum and optical-to-infrared spectral energy distribution (SED) virtually
rule out the possibility that it may be any foreground projected object. We
conclude that the secondary point source is likely to be an extragalactic
object associated with Cygnus A. We consider several interpretations of the
nature of this object, including: a young star cluster peering through the dust
at the edge of one of the ionization cones; an older, large globular cluster; a
compact cloud of dust or electrons that is acting as a mirror of the hidden
active nucleus; and the dense core of a gas stripped satellite galaxy that is
merging with the giant elliptical host. The data presented here are most
consistent with the minor merger scenario. The spectra and SED of the object
suggest that it may be a densely packed conglomeration of older stars heavily
extincted by dust, and its high luminosity and compact nature are consistent
with those of a satellite that has been stripped to its tidal radius. Further
spectroscopic observations are nevertheless necessary to confirm this
possibility.


title: The Phoenix Deep Survey: X-ray properties of faint radio sources

abstract:
  In this paper we use a 50ks XMM-Newton pointing overlapping with the Phoenix
Deep Survey, a homogeneous radio survey reaching muJy sensitivities, to explore
the X-ray properties and the evolution of star-forming galaxies. UV, optical
and NIR photometry is available and is used to estimate photometric redshifts
and spectral types for radio sources brighter than R=21.5mag (total of 82).
Sources with R<21.5mag and spiral galaxy SEDs (34) are grouped into two
redshift bins with a median of z=0.240 and 0.455 respectively. Stacking
analysis for both the 0.5-2 and 2-8keV bands is performed on these subsamples.
A high confidence level signal (>3.5sigma) is detected in the 0.5-2keV band
corresponding to a mean flux of ~3e-16cgs for both subsamples. This flux
translates to mean luminosities of ~5e40 and 1.5e41cgs for the z=0.240 and
0.455 subsamples respectively. Only a marginally significant signal (2.6sigma)
is detected in the 2-8keV band for the z=0.455 subsample. We argue that the
stacked signal above is dominated by star-formation. The mean L_X/L_B ratio and
the mean L_X of the two subsamples are found to be higher than optically
selected spirals and similar to starbursts. We also find that the mean L_X and
L_1.4 of the faint radio sources studied here are consistent with the L_X-L_1.4
correlation of local star-forming galaxies. Moreover, the X-ray emissivity of
sub-mJy sources to z~0.3 is found to be elevated compared to local HII
galaxies. The observed increase is consistent with L_X evolution of the form
(1+z)^3. Assuming that our sample is indeed dominated by starbursts this is
direct evidence for evolution of such systems at X-ray wavelengths. Using an
empirical L_X to SFR conversion we estimate a global SFR density at z~0.3 of
\~0.029M_o/yr/Mpc in agreement with previous studies.


title: Joint Formation of Supermassive Black Holes and Galaxies

abstract:
  The tight correlation between black hole mass and velocity dispersion of
galactic bulges is strong evidence that the formation of galaxies and
supermassive black holes are closely linked. I review the modeling of the joint
formation of galaxies and their central supermassive black holes in the context
of the hierarchical structure formation paradigm.


title:
Hierarchical build-up of galactic bulges and the merging rate of
  supermassive binary black holes

abstract:
  The hierarchical build-up of galactic bulges should lead to the build-up of
present-day supermassive black holes by a mixture of gas accretion and merging
of supermassive black holes. The tight relation between black hole mass and
stellar velocity dispersion is thereby a strong argument that the supermassive
black holes in merging galactic bulges do indeed merge. Otherwise the ejection
of supermassive black holes by gravitational slingshot would lead to excessive
scatter in this relation. At high redshift the coalescence of massive black
hole binaries is likely to be driven by the accretion of gas in the major
mergers signposted by optically bright QSO activity. If massive black holes
only form efficiently by direct collapse of gas in deep galactic potential
wells with v_c > 100 km/s as postulated in the model of Kauffmann & Haehnelt
(2000) LISA expects to see event rates from the merging of massive binary black
holes of about 0.1-1 yr^{-1} spread over the redshift range 0 < z < 5. If,
however, the hierarchical build-up of supermassive black holes extends to
pre-galactic structures with significantly shallower potential wells event
rates may be as high as 10-100 yr^{-1} and will be dominated by events from
redshift z > 5.


title: Elusive Active Galactic Nuclei

abstract:
  A fraction of active galactic nuclei do not show the classical Seyfert-type
signatures in their optical spectra, i.e. they are optically "elusive". X-ray
observations are an optimal tool to identify this class of objects. We combine
new Chandra observations with archival X-ray data in order to obtain a first
estimate of the fraction of elusive AGN in local galaxies and to constrain
their nature. Our results suggest that elusive AGN have a local density
comparable to or even higher than optically classified Seyfert nuclei. Most
elusive AGN are heavily absorbed in the X-rays, with gas column densities
exceeding 10^24 cm^-2, suggesting that their peculiar nature is associated with
obscuration. It is likely that in elusive AGN, the nuclear UV source is
completely embedded and the ionizing photons cannot escape, which prevents the
formation of a classical Narrow Line Region. Elusive AGN may contribute
significantly to the 30 keV bump of the X-ray background.


title: A weak lensing analysis of a STIS dark-lens candidate

abstract:
  We perform a weak lensing analysis on a previously reported dark-lens
candidate on STIS Parallel data (Miralles et al. 2002). New VLT-data indicate
that the reported signal originates from a small number of galaxies
tangentially aligned towards the center of the STIS field but no signature for
an extended mass distribution is found. We argue that we should be able to
detect a massive cluster ($M\geq 3.2\times 10^{14}M_{\odot}$) through its
lensing signal up to a redshift of $z\approx 0.6$ with our data. Also the
double image hypothesis of two galaxies with very similar morphologies in the
STIS data is ruled out with colour information.


title: SN 1993J VLBI (III): The Evolution of the Radio Shell

abstract:
  We present two sequences of VLBI images of SN1993J in M81, with 24 images at
8.4 GHz and 19 images at 5.0 GHz, These sequences, from 50 d to ~9 yr after
shock breakout, show the evolution of the expanding radio shell of an exploded
star in detail. The images are all phase-referenced to the stable reference
point of the core of M81, allowing us to display them relative to the supernova
explosion center. At 50 d, SN1993J is almost unresolved with a radius of 520
AU. The shell structure becomes discernible at 175 d. The brightness of the
ridge of the projected shell is not uniform, but rather varies by a factor of
two, having a distinct maximum to the south-east and a minimum to the west.
Over the next ~350 d, this pattern appears to rotate counter-clockwise. After
two years, the structure becomes more complex with hot spots developing in the
east, south, and west. The pattern of modulation continues to change, and after
five years the three hot spots have shifted somewhat. After nine years, the
radio shell has expanded to a radius of 19,000 AU. The brightness in the center
of the images is lower than expected for an optically thin, spherical shell.
Absorption in the center is favored over a thinner shell in the back and/or
front. Allowing for absorption, we find that the thickness of the shell is
(25+/-3)% of its outer radius. We find no compact source in the central region
and conclude that any pulsar nebula in the center of SN 1993J is either much
fainter than the Crab or affected by remaining significant internal radio
absorption.


title:
From Globular Clusters to Tidal Dwarfs: Structure Formation in the Tidal
  Tails of Merging Galaxies

abstract:
  Using V and I images obtained with WFPC2/HST, we investigate compact stellar
structures within tidal tails. Six regions of tidal debris in the four classic
``Toomre Sequence'' mergers: NGC 4038/39 (``Antennae''), NGC 3256, NGC 3921,
and NGC 7252 (``Atoms for Peace'') have been studied in order to explore how
the star formation depends upon the local and global physical conditions. These
mergers sample a range of stages in the evolutionary sequence and tails with
and without embedded tidal dwarf galaxies. The six tails are found to contain a
variety of stellar structures, with sizes ranging from those of globular
clusters up to those of dwarf galaxies. From V and I WFPC2 images, we measure
the luminosities and colors of the star clusters. NGC 3256 is found to have a
large population of blue clusters (0.2 < V-I < 0.9), particularly in its
Western tail, similar to those found in the inner region of the merger. In
contrast, NGC 4038/39 has no clusters in the observed region of the tail, only
less luminous point sources likely to be individual stars. A significant
cluster population is clearly associated with the prominent tidal dwarf
candidates in the eastern and western tails of NGC 7252. The cluster-rich
Western tail of NGC 3256 is not distinguished from the others by its dynamical
age or by its total HI mass. However, the mergers that have few clusters in the
tail all have tidal dwarf galaxies, while NGC 3256 does not have prominent
tidal dwarfs. We speculate that star formation in tidal tails may manifest
itself either in small structures like clusters along the tail or in large
structures such as dwarf galaxies, but not in both. Also, NGC 3256 has the
highest star formation rate of the four mergers studied, which may contribute
to the high number of star clusters in its tidal tails.


title:
Measurements of anisotropic scintillation efficiency for carbon recoils
  in a stilbene crystal for dark matter detection

abstract:
  It is known that scintillation efficiency of organic single crystals depends
on the direction of nuclear recoils relative to crystallographic axes. This
property could be applied to the directional WIMP dark matter detector.
  The scintillation efficiency of carbon recoils in a stilbene crystal was
measured for recoil energies of 30 keV to 1 MeV using neutrons from
$^7$Li(p,n)$^7$Be and $^{252}$Cf. Anisotropic response was confirmed in low
energy regions. The variation of the scintillation efficiency was about 7 %,
that could detect the possible dark matter signal.


title:
Disappearance of Hard X-ray Emission in the Last BeppoSAX Observation of
  the Z Source GX 349+2

abstract:
  We report on the results from two BeppoSAX observations of the Z source GX
349+2 performed in February 2001 and covering the broad energy range 0.12-200
keV. The light curve obtained from these observations shows a large flaring
activity, the count rate varying from ~130 to ~260 counts/s, indicating that
the source was in the flaring branch during these observations. The average
spectrum is well described by a soft blackbody and a Comptonized component. To
well fit the energy spectrum three gaussian lines are needed at 1.2 keV, 2.6
keV, and 6.7 keV with corresponding equivalent widths of 13 eV, 10 eV, and 39
eV, probably associated to L-shell emission of Fe XXIV, Ly-alpha S XVI, and Fe
XXV, respectively. These lines may be produced at different distances from the
neutron star, which increase when the count rate of the source increases. An
absorption edge is also needed at 9 keV with an optical depth of ~3 10^{-2}.
  From the Color-Color Diagram (CD) we selected five zones from which we
extracted the corresponding energy spectra. The temperatures of the blackbody
and of the Comptonized component tend to increase when the intensity of the
source increases. We discuss our results comparing them to those obtained from
a previous BeppoSAX observation, performed in March 2000, during which the
source was a similar position of its Z-track. In particular we find that,
although the source showed similar spectral states in the 2000 and the 2001
observations, a hard tail, that was significantly detected in March 2000, is
not observed in these recent observations.


title: How many active galaxies and QSOs will future Space Missions detect?

abstract:
  Averaged spectral energy distributions (SEDs) of active and starburst
galaxies from the 12 micron sample in the Local Universe and Quasars, from an
optically selected sample at a mean redshift <z>=0.7, are built from
optical/near-IR/far-IR (IRAS & ISO) photometric observations. These SEDs are
then used to predict at various redshifts the number of Seyfert type 1 and type
2, starburst, normal galaxies, and quasars, that will be detected by future
Space Missions dedicated to far-infrared and submillimeter astronomy, like
SIRTF and Herschel. These predictions are then compared with the expected
capabilities and detection limits of future deep far-IR surveys. Possible ways
to identify AGN candidates on far-IR colour-colour plots for follow-up
observations are then explored.


title: Defect formation in the early universe

abstract:
  Topological defects are common in many everyday systems. In general, they
appear if a symmetry is broken at a rapid phase transition. In this article, I
explain why it is believed that they should have also been formed in the early
universe and how that would have happened. If topological defects are found,
this will provide a way to study observationally the first fractions of a
second after the Big Bang, but their apparent absence can also tell us many
things about the early universe.


title: Temporal variability in early afterglows of short gamma-ray bursts

abstract:
  The shock model has successfully explained the observed behaviors of
afterglows from long gamma-ray bursts (GRBs). Here we use it to investigate the
so-called early afterglows from short GRBs, which arises from blast waves that
are not decelerated considerably by their surrounding medium. We consider a
nearby medium loaded with $e^{\pm}$ pairs (Beloborodov 2002). The temporal
behaviors show first a soft-to-hard spectral evolution, from the optical to
hard X-ray, and then a usual hard-to-soft evolution after the blast waves begin
to decelerate. The light curves show variability, and consist of two peaks. The
first peak, due to the pair effect, can be observed in the X-ray, though too
faint and too short in the optical. The second peak will be easily detected by
{\it Swift}. We show that detections of the double-peak structure in the light
curves of early afterglows are very helpful to determine all the shock
parameters of short GRBs, including both the parameters of the relativistic
source and the surroundings. Besides, from the requirement that the
forward-shock emission in short GRBs should be below the BATSE detection
threshold, we give a strong constraint on the shock model parameters. In
particular, the initial Lorentz factor of the source is limited to be no more
than $\sim 10^3$, and the ambient medium density is inferred to be low, $n\la
10^{-1}$ cm$^{-3}$.


title: The puzzle about the radial cut-off in galactic disks

abstract:
  The stellar disk in a spiral galaxy is believed to be truncated physically
because the disk surface brightness is observed to fall faster than that for an
exponential in the outer, faint regions. We review the literature associated
with this phenomenon and find that a number of recent observations contradict
the truncation picture. Hence we question the very existence of a physical
outer cut-off in stellar disks. We show, in this paper, that the observed drop
in the surface brightness profiles in fact corresponds to a negligible decrease
in intensity, and that this minor change at the faint end appears to be
exaggerated on a log-normal plot. Since minor deviations from a perfect
exponential are common throughout the disk, we suggest that such a deviation at
the faint end could easily give rise to the observed sharp drop.


title:
Deci hertz Laser Interferometer can determine the position of the
  Coalescing Binary Neutron Stars within an arc minute a week before the final
  merging event to Black Hole

abstract:
  It may be possible to construct a laser interferometer gravitational wave
antenna in space with $h_{rms}\sim 10^{-23}$ at $ f\sim 0.1{\rm Hz}$ in $\sim
2020$. This deci hertz antenna may be called DECIGO/BBO,which stand for DECi
hertz Interferometer Gravitational wave Observatory and Big Bang Observer,
respectively. The analysis of 1-10 years observational data of the coalescing
binary neutron stars or black holes at the distance of $\sim$ 300Mpc will give
us the spatial position within $\sim$ an arc minute and the time of the
coalescence within $\sim 0.1$ sec beforehand. With the knowledge of the
accurate position and the time of final merging event, the follow up
simultaneous observation using high frequency ($ f\sim 100{\rm Hz}$)
gravitational wave antennae as well as electro-magnetic wave antennae from the
radio frequency to the ultra high energy gamma ray will reveal the physics in
the enigmatic event of the coalescence and the formation of the black hole.


title:
Sensitivity of Gamma Astroparticle Experiments to the Detection of
  Photon Oscillations

abstract:
  The mixing of the photon with a hypothetical sterile paraphotonic state would
have consequences on the cosmological propagation of photons. Observations of
gamma-rays from active galactic nuclei in GLAST and MAGIC will open a new
domain in the search for such a phenomenon.


title:
Accretion Disk Spectra of the Ultra-luminous X-ray Sources in Nearby
  Spiral Galaxies and Galactic Superluminal Jet Sources

abstract:
  Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and
Galactic superluminal jet sources share the common spectral characteristic that
they have unusually high disk temperatures which cannot be explained in the
framework of the standard optically thick accretion disk in the Schwarzschild
metric. On the other hand, the standard accretion disk around the Kerr black
hole might explain the observed high disk temperature, as the inner radius of
the Kerr disk gets smaller and the disk temperature can be consequently higher.
However, we point out that the observable Kerr disk spectra becomes
significantly harder than Schwarzschild disk spectra only when the disk is
highly inclined. This is because the emission from the innermost part of the
accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen
for a face-on disk. The Galactic superluminal jet sources are known to be
highly inclined systems, thus their energy spectra may be explained with the
standard Kerr disk with known black hole masses. For ULXs, on the other hand,
the standard Kerr disk model seems implausible, since it is highly unlikely
that their accretion disks are preferentially inclined, and, if edge-on Kerr
disk model is applied, the black hole mass becomes unreasonably large (> 300
M_solar). Instead, the slim disk (advection dominated optically thick disk)
model is likely to explain the observed super-Eddington luminosities, hard
energy spectra, and spectral variations of ULXs. We suggest that ULXs are
accreting black holes with a few tens of solar mass, which is not unexpected
from the standard stellar evolution scenario, and that their X-ray emission is
from the slim disk shining at super-Eddington luminosities.


title: The Skewness of the Aperture Mass Statistic

abstract:
  We present simple formulae for calculating the skewness and kurtosis of the
aperture mass statistic for weak lensing surveys which is insensitive to
masking effects of survey geometry or variable survey depth. The calculation is
the higher order analog of the formula given by Schneider et al (2002) which
has been used to compute the variance of the aperture mass from several lensing
surveys. As our formula requires the three-point shear correlation function, we
also present an efficient tree-based algorithm for measuring it. We show how
our algorithm would scale in computing time and memory usage for future lensing
surveys. Finally, we apply the procedure to our CTIO survey data, originally
described in Jarvis et al (2003). We find that the skewness is positive
(inconsistent with zero) at the 2 sigma level. However, the signal is too noisy
from this data to usefully constrain cosmology.


title:
Chandra/HETGS Spectroscopy of the Galactic Black Hole GX 339-4: A
  Relativistic Iron Line and Evidence for a Seyfert-like Warm Absorber

abstract:
  We observed the Galactic black hole GX 339-4 with the Chandra High Energy
Transmission Grating Spectrometer (HETGS) for 75 ksec during the decline of its
2002-2003 outburst. The sensitivity of this observation provides an
unprecedented glimpse of a Galactic black hole at about a tenth of the
luminosity of the outburst peak. The continuum spectrum is well described by a
model consisting of multicolor disk blackbody (kT = 0.6 keV) and power-law
(Gamma = 2.5) components. X-ray reflection models yield improved fits. A
strong, relativistic Fe K-alpha emission line is revealed, indicating that the
inner disk extends to the innermost stable circular orbit. The breadth of the
line is sufficient to suggest that GX 339-4 may harbor a black hole with
significant angular momentum. Absorption lines from H-like and He-like O, and
He-like Ne and Mg are detected, as well as lines which are likely due to Ne II
and Ne III. The measured line properties make it difficult to associate the
absorption with the coronal phase of the interstellar medium. A scenario
wherein the absorption lines are due to an intrinsic AGN-like warm-absorber
geometry -- perhaps produced by a disk wind in an extended disk-dominated state
-- may be more viable. We compare our results to Chandra observations of the
Galactic black hole candidate XTE J1650-500, and discuss our findings in terms
of prominent models for Galactic black hole accretion flows and connections to
supermassive black holes.


title:
Morphological Classification of Galaxies by Shapelet Decomposition in
  the Sloan Digital Sky Survey

abstract:
  We describe application of the `shapelet' linear decomposition of galaxy
images to morphological classification using images of $\sim$ 3000 galaxies
from the Sloan Digital Sky Survey. After decomposing the galaxies we perform a
principal component analysis to reduce the number of dimensions of the shapelet
space to nine. We find that each of these nine principal components contains
unique morphological information, and give a description of each principal
component's contribution to a galaxy's morphology. We find that galaxies of
differing Hubble type separate cleanly in the shapelet space. We apply a
Gaussian mixture model to the 9-dimensional space spanned by the principal
components and use the results as a basis for classification. Using the mixture
model, we separate galaxies into seven classes and give a description of each
class's physical and morphological properties. We find that several of the
mixture model classes correlate well with the traditional Hubble types both in
their morphology and their physical parameters (e.g., color, velocity
dispersions, etc.). In addition, we find an additional class of late-type
morphology but with high velocity dispersions and very blue color; most of
these galaxies exhibit post-starburst activity. This method provides an
objective and quantitative alternative to traditional and subjective visual
classification.


title: The Dark Age of the Universe

abstract:
  The Dark Age is the period between the time when the cosmic microwave
background was emitted and the time when the evolution of structure in the
universe led to the gravitational collapse of objects in which the first stars
were formed. The period of reionization started with the ionizing light from
the first stars, and it ended when all the atoms in the intergalactic medium
had been reionized. The most distant sources of light known at present are
galaxies and quasars at redshift z ~ 6, and their spectra indicate that the end
of reionization was occurring just at that time. The Cold Dark Matter theory
for structure formation predicts that the first sources formed much earlier.


title: Chandra Observation of 3C 212: a New Look at the X-ray and UV Absorbers

abstract:
  The red quasar 3C 212 (z=1.049) is one of the most distant and most luminous
AGN which has shown evidence of an X-ray warm absorber. In order to further
investigate this unusual quasar, we used Chandra/ACIS-S to observe 3C 212 for
19.5 ksec, resulting in a net detection of ~4000 counts. The Chandra data
confirm the presence of an excess absorbing column N_H ~ 4 x 10^21 cm^-2 at the
quasar redshift, but we find no compelling evidence for a warm absorber. Using
both the Chandra and archival ROSAT PSPC data, we obtain very good fits for
both a partially covered neutral absorber and a low-ionization (U = 0.03)
photo-ionized absorber. In the ultraviolet, 3C 212 shows a strong associated
MgII absorber. Based on a moderate resolution (80 km/s) MMT spectrum we show
that the absorber is highly saturated and has a covering fraction less than
60%, implying that the absorber is truly intrinsic to the quasar.
Photo-ionization modeling of the MgII absorber yields a constraint on the
ionization parameter of U < 0.03, inconsistent with a warm UV/X-ray absorber.
In addition to our spectral analysis, we find evidence in the ACIS image data
for weak extended emission surrounding the quasar as well as emission
corresponding to the radio lobes at a distance of 5 arcsec from 3C 212. The
statistical significance of these features is low, but we briefly explore the
implications if the detections are valid.


title:
A Survey of 10-Micron Silicate Emission from Dust around Young Sun-Like
  Stars

abstract:
  We obtained low resolution (R = 100) mid-infrared (8-13 micron wavelengths)
spectra of 8 nearby young main sequence stars with the Keck 1 telescope and
Long-Wavelength Spectrometer (LWS) to search for 10 micron silicate (Si-O
stretch) emission from circumstellar dust. No stars exhibited readily apparent
emission: Spectra were then analyzed by least-squares fitting of a template
based on a spectrum of Comet Hale-Bopp. Using this technique, we were able to
constrain the level of silicate emission to a threshold ten times below what
was previously possible from space. We found one star, HD 17925, with a
spectrum statistically different from its calibrator and consistent with a
silicate emission peak of 7% of the photosphere at a wavelength of 10 microns.
Excess emission at 60 microns from this star has already been reported.


title:
Sensitive VLBI Continuum and H I Absorption Observations of NGC 7674:
  First Scientific Observations with the Combined Array VLBA, VLA & Arecibo

abstract:
  We present phase-referenced VLBI observations of the radio continuum emission
from, and the H I 21 cm absorption toward, the Luminous Infrared Galaxy NGC
7674. The observations were carried out at 1380 MHz using the VLBA, the phased
VLA, and theArecibo radio telescope. These observations constitute the first
scientific use of the Arecibo telescope in a VLBI observation with the VLBA.
The high- and low-resolution radio continuum images reveal several new
continuum structures in the nuclear region of this galaxy. At ~100 mas
resolution, we distinguish six continuum structures extending over 1.4 arcsec,
with a total flux density of 138 mJy. Only three of these structures were known
previously. All these structures seem to be related to AGN activity. At the
full resolution of the array, we only detect two of the six continuum
structures. Both are composed of several compact components with brightness
temperatures on the order of $10^{7}$ K. While it is possible that one of these
compact structures could host an AGN, they could also be shock-like features
formed by the interaction of the jet with compact interstellar clouds in the
nuclear region of this galaxy. Complex H I absorption is detected with our VLBI
array at both high and low angular resolution. Assuming that the widest H I
feature is associated with a rotating H I disk or torus feeding a central AGN,
we estimate an enclosed dynamical mass of ~7 x 10^7 M_sun, comparable to the
value derived from the hidden broad H$\beta$ emission in this galaxy. The
narrower H I lines could represent clumpy neutral hydrogen structures in the H
I torus. The detection of H I absorption toward some of the continuum
components, and its absence toward others, suggest an inclined H I disk or
torus in the central region of NGC 7674.


title: Modeling Helical Structures in Relativistic Jets

abstract:
  Many jets exhibit twisted helical structures. Where superluminal motions are
detected, jet orientation and pattern/flow speed are considerably constrained.
In this case modeling efforts can place strong limits on conditions in the jet
and in the external environment. This can be done by modeling the spatial
development of helical structures which are sensitively dependent on these
conditions. Along an expanding jet this sensitivity manifests itself in
predictable changes in pattern speed and observed wavelength. In general,
twists of low frequency relative to the local resonant frequency are advected
along the expanding jet into a region in which the twist frequency is high
relative to the local resonant frequency. The wave speed can be very different
in these two frequency regimes. Potential effects include helical twists with a
nearly constant apparent wavelength, an apparent wavelength scaling
approximately with the jet radius for up to two orders of magnitude of jet
expansion, or multiple twist wavelengths with vastly different intrinsic scale
and vastly different wave speeds that give rise to similar observed twist
wavelengths but with very different observed motion. In this paper I illustrate
the basic intrinsic and observed behavior of these structures and show how to
place constraints on jet conditions in superluminal jets using the apparent
structures and motions in the inner 3C 120 jet.


title:
Discovery of Eight New Extremely Metal--Poor Galaxies in the Sloan
  Digital Sky Survey

abstract:
  We report the discovery of eight new extremely metal-poor galaxies (XMPGs;
12+log(O/H) < 7.65) and the recovery of four previously known or suspected
XMPGs (IZw18, HS0822+3542, HS0837+4717 and A1116+517) using Sloan Digital Sky
Survey (SDSS) spectroscopy. These new objects were identified after an analysis
of 250,000 galaxy spectra within an area of ~3000 deg^2 on the sky. Our oxygen
abundance determinations have an accuracy of $\le$ 0.1 dex and are based on the
temperature-sensitive [O {\sc iii}] $\lambda$4363 \AA line and on the direct
calculation of the electron temperature. We briefly discuss a new method of
oxygen abundance determinations using the [O {\sc ii}] $\lambda$7319,7330 \AA\
lines, which is particularly useful for SDSS emission-line spectra with
redshifts $\le$~0.024 since the [O {\sc ii}] $\lambda$3727 \AA emission line
falls outside of the SDSS wavelength range. We detect XMPGs with redshifts
ranging from 0.0005 to 0.0443 and $M_g$ luminosities from $-$12\fm4 to
$-$18\fm6. Our eight new XMPGs increase the number of known metal-deficient
galaxies by approximately one quarter. The estimated surface density of XMPGs
is 0.004 deg$^{-2}$ for $r$ $\le$ 17\fm77.


title:
Forsterite Amorphisation by Ion Irradiation: Monitoring by Infrared
  Spectroscopy

abstract:
  We present experimental results on crystal--amorphous transition of
forsterite (Mg2SiO4) silicate under ion irradiation. The aim of this work is to
study the structural evolution of one of the most abundant crystalline
silicates observed in space driven by ion irradiation. To this aim, forsterite
films have been sythesised in laboratory and irradiated with low energy (30--60
keV) ion beams. Structural changes during irradiation with H+, He+, C+, and
Ar++ have been observed and monitored by infrared spectroscopy. The fraction of
crystalline forsterite converted into amorphous is a function of the energy
deposited by nuclear collision by ions in the target.
  Laboratory results indicate that ion irradiation is a mechanism potentially
active in space for the amorphisation of silicates. Physical properties
obtained in this work can be used to model the evolution of silicate grains
during their life cycle from evolved stars, through different interstellar
environments and up to be incorporated in Solar System objects.


title: Dark Matter search

abstract:
  Main arguments on the Dark Matter particle direct detection approach are
addressed on the basis of the work and of the results of the about 100 kg
highly radiopure NaI(Tl) DAMA experiment (DAMA/NaI), which has been operative
at the Gran Sasso National Laboratory of the I.N.F.N. for more than one decade,
including the preparation. The effectiveness of the WIMP model independent
annual modulation signature is pointed out by discussing the results obtained
over 7 annual cycles (107731 kg day total exposure); the WIMP presence in the
galactic halo is strongly supported at 6.3 standard deviation C.L. The
complexity of the corollary model dependent quests for a candidate particle is
also addressed and several of the many possible scenarios are examined.


title:
Decelerating Flows in TeV Blazars: A Resolution to the BL Lac -- FR I
  Unification Problem

abstract:
  TeV emission from BL Lacertae (BL) objects is commonly modeled as
Synchrotron-Self Compton (SSC) radiation from relativistically moving
homogeneous plasma blobs. In the context of these models, the blob Lorentz
factors needed to reproduce the corrected for absorption by the diffuse IR
background (DIRB) TeV emission are large ($\delta \gtrsim 50$). The main reason
for this is that stronger beaming eases the problem of the lack of $\sim$ IR-UV
synchrotron seed photons needed to produce the de-absorbed $\sim $ few TeV peak
of the spectral energy distribution (SED). However, such high Doppler factors
are in strong disagreement with the unified scheme, according to which BLs are
FR I radio galaxies with their jets closely aligned to the line of sight. Here,
motivated by the detection of sub-luminal velocities in the sub-pc scale jets
of the best studied TeV blazars, MKN 421 and MKN 501, we examine the
possibility that the relativistic flows in the TeV BLs decelerate. In this
case, the problem of the missing seed photons is solved because of Upstream
Compton (UC) scattering, a process in which the upstream energetic electrons
from the fast base of the flow `see' the synchrotron seed photons produced in
the slow part of the flow relativistically beamed. Modest Lorentz factors
($\Gamma \sim 15$), decelerating down to values compatible with the recent
radio interferometric observations, reproduce the $\sim $ few TeV peak energy
of these sources. Furthermore, such decelerating flows are shown to be in
agreement with the BL - FR I unification, naturally reproducing the observed
BL/FR I broad band luminosity ratios.


title: Molecular Hydrogen Excitation in Ultraluminous Infrared Galaxies

abstract:
  We report medium resolution VLT ISAAC K-band spectroscopy of the nuclei of
seven ultraluminous infrared galaxies. After accounting for stellar absorption
features, we have detected several molecular hydrogen (H_2) v=1-0, 2-1, and 3-2
vibrational emission lines, as well as the HI Br\gamma and HeI 2^1P-2^1S
recombination lines. The relative H_2 line intensities show little variation
between the objects, suggesting that the H_2 excitation mechanisms in the
nuclei are similar in all the objects. The 1-0 emissions appear thermalised at
temperatures T\sim1000K. However, the 2-1 and 3-2 emissions show evidence of
being radiatively excited by far-ultraviolet (FUV) photons, suggesting that the
H_2 excitation in the ULIRGs may arise in dense photon dominated regions
(PDRs). We show that the line ratios in the nuclei are consistent with PDRs
with cloud densities between 10^4 to 10^5cm^{-3}, exposed to far ultraviolet
(FUV) radiation fields at least 10^3 times more intense than the ambient FUV
intensity in the local interstellar medium. We have constructed starburst
models for the ULIRGs based on their H_2 properties, as well as on the
intensities of the recombination lines. Our models provide a consistent picture
of young 1-5Myr star clusters surrounded by relatively dense PDRs which are
irradiated by intense FUV fluxes. Comparison to the inner few hundred parsecs
of the Milky Way indicates that the star formation efficiency in ULIRGs is
10--100 times higher than in the Galactic Center.


title: Observation of GRB 030131 with the INTEGRAL satellite

abstract:
  A long Gamma-Ray Burst (GRB) was detected with the instruments on board the
INTEGRAL satellite on January 31 2003. Although most of the GRB, which lasted
$\sim$150 seconds, occurred during a satellite slew, the automatic software of
the INTEGRAL Burst Alert System was able to detect it in near-real time. Here
we report the results obtained with the IBIS instrument, which detected GRB
030131 in the 15 keV - 200 keV energy range, and ESO/VLT observations of its
optical transient. The burst displays a complex time profile with numerous
peaks. The peak spectrum can be described by a single power law with photon
index $\Gamma\simeq$1.7 and has a flux of $\sim$2 photons cm$^{-2}$ s$^{-1}$ in
the 20-200 keV energy band. The high sensitivity of IBIS has made it possible
for the first time to perform detailed time-resolved spectroscopy of a GRB with
a fluence of 7$\times10^{-6}$ erg cm$^{-2}$ (20-200 keV).


title:
Hot Stars Mass-loss studied with Spectro-Polarimetric INterferometry
  (SPIN)

abstract:
  We present a prospective work undertaken on Spectro-Polarimetric
INterferometry (SPIN). Our theoretical studies suggest that SPIN is a powerful
tool for studying the mass loss from early type stars. Based on Monte Carlo
simulations, we computed the expected SPIN signal for numerous hot star
spectral types covering a broad range of geometries and optical depths. The
SPIN technique is based on the detection and comparison of the fringe
characteristics (complex visibility) between two perpendicular directions of
polarization. In particular, we demonstrate that the SPIN technique is very
sensitive to the beta parameter from the so-called 'beta velocity law' for
optically thin winds. Moreover, the location where the bulk of polarization is
generated can be defined accurately. The required sensitivity for studying main
sequence OB star winds is still very demanding (inferior to 0.5%), but the
signal expected from denser winds or extended atmospheres is well within the
capabilities of existing interferometers. The visibility curves obtained in two
perpendicular polarizations for LBVs or WR stars can differ by more than 15%,
and their corresponding limb-darkened radii obtained by the fit of these curves
by more than 35%. The signal expected from the extended circumstellar
environment of Be stars and B[e] appears also to be easy to detect, relaxing
the required instrumental accuracy to 1%. For these spectral types, the SPIN
technique provide a good tool to extract the highly polarized and spatially
confined envelope contribution from the bright star emission.


title: High-excitation CO in a quasar host galaxy at z=6.42

abstract:
  We report the detection of high excitation CO emission from the most distant
quasar currently known, SDSS J114816.64+525150.3 (hereafter J1148+5251), at a
redshift z=6.419. The CO (J=6-5) and (J=7-6) lines were detected using the IRAM
Plateau de Bure interferometer, showing a width of ~280 km/s. An upper flux
limit for the CO (J=1-0) line was obtained from observations with the
Effelsberg 100-meter telescope. Assuming no gravitational magnification, we
estimate a molecular gas mass of ~2x10^10 M_sun. Using the CO (3-2)
observations by Walter et al. (2003), a comparison of the line flux ratios with
predictions from a large velocity gradient model suggests that the gas is
likely of high excitation, at densities ~10^5 cm^-3 and a temperature ~100 K.
Since in this case the CO lines appear to have moderate optical depths, the gas
must be extended over a few kpc. The gas mass detected in J1148+5251 can fuel
star formation at the rate implied by the far-infrared luminosity for less than
10 million years, a time comparable to the dynamical time of the region. The
gas must therefore be replenished quickly, and metal and dust enrichment must
occur fast. The strong dust emission and massive, dense gas reservoir at z~6.4
provide further evidence that vigorous star formation is co-eval with the rapid
growth of massive black holes at these early epochs of the Universe.


title: Polarimetry in the Visible and Infrared: Application to CMB Polarimetry

abstract:
  Interstellar polarization from aligned dust grains can be measured both in
transmission at visible and near-infrared wavelengths and in emission at
far-infrared and sub-mm wavelengths. These observations can help predict the
behavior of foreground contamination of CMB polarimetry by dust in the Milky
Way. Fractional polarization in emission from aligned dust grains will be at
the higher range of currently observed values of 4-10%. Away from the galactic
plane, fluctuations in Q and U will be dominated by fluctuations in intensity,
and less influenced by fluctuations in fractional polarization and position
angle.


title: Molecular Gas in the Host Galaxy of a Quasar at Redshift z=6.42

abstract:
  Observations of the molecular gas phase in quasar host galaxies provide
fundamental constraints on galaxy evolution at the highest redshifts. Molecular
gas is the material out of which stars form; it can be traced by spectral line
emission of carbon--monoxide (CO). To date, CO emission has been detected in
more than a dozen quasar host galaxies with redshifts (z) larger 2, the record
holder being at z=4.69. At these distances the CO lines are shifted to longer
wavelengths, enabling their observation with sensitive radio and millimetre
interferometers. Here we present the discovery of CO emission toward the quasar
SDSS J114816.64+525150.3 (hereafter J1148+5251) at a redshift of z=6.42, when
the universe was only 1/16 of its present age. This is the first detection of
molecular gas at the end of cosmic reionization. The presence of large amounts
of molecular gas (M(H_2)=2.2e10 M_sun) in an object at this time demonstrates
that heavy element enriched molecular gas can be generated rapidly in the
earliest galaxies.


title: Dusty Molecular Cloud Collapse in the Presence of Alfv\'en Waves

abstract:
  It has been shown that magnetic fields play an important role in the
stability of molecular clouds, mainly perpendicularly to the field direction.
However, in the parallel direction the stability is a serious problem still to
be explained. Interstellar turbulence may allow the generation of Alfv\'en
waves that propagate through the clouds in the magnetic field direction. These
regions also present great amounts of dust particles which can give rise to new
wave modes, or modify the pre-existing ones. The dust-cyclotron damping affects
the Alfv\'en wave propagation near the dust- cyclotron frequency. On the other
hand, the clouds present different grain sizes, which carry different charges.
In this sense, a dust particle distribution has several dust-cyclotron
frequencies and it will affect a broad band of wave frequencies. In this case,
the energy transfer to the gas is more efficient than in the case where the
ion-cyclotron damping is considered alone. This effect becomes more important
if a power law spectrum is considered for the wave energy flux, since the major
part of the energy is concentrated in low-frequency waves. In this work we
calculate the dust- cyclotron damping in a dusty and magnetized dwarf molecular
cloud, as well as determine the changes in the Alfv\'en wave flux. Then, we use
these results to study the gravitational stability of the cloud. We show that,
considering the presence of charged dust particles, the wave flux is rapidly
damped due to dust-cyclotron damping. Then the wave pressure acts in a small
length scale, and cannot explain the observable cloud sizes, but can explain
the existence of small and dense cores.


title: Eccentric-disk models for the nucleus of M31

abstract:
  We construct dynamical models of the ``double'' nucleus of M31 in which the
nucleus consists of an eccentric disk of stars orbiting a central black hole.
The principal approximation in these models is that the disk stars travel in a
Kepler potential, i.e., we neglect the mass of the disk relative to the black
hole. We consider both ``aligned'' models, in which the eccentric disk lies in
the plane of the large-scale M31 disk, and ``non-aligned'' models, in which the
orientation of the eccentric disk is fitted to the data. Both types of model
can reproduce the double structure and overall morphology seen in Hubble Space
Telescope photometry. In comparison with the best available ground-based
spectroscopy, the models reproduce the asymmetric rotation curve, the peak
height of the dispersion profile, and the qualitative behavior of the
Gauss-Hermite coefficients h_3 and h_4. Aligned models fail to reproduce the
observation that the surface brightness at P1 is higher than at P2 and yield
significantly poorer fits to the kinematics; thus we favor non-aligned models.
Eccentric-disk models fitted to ground-based spectroscopy are used to predict
the kinematics observed at much higher resolution by the STIS instrument on the
Hubble Space Telescope (Bender et al. 2003), and we find generally satisfactory
agreement.


title: Ultra High Energy Cosmic Rays and de Sitter Vacua

abstract:
  The production of ultra high-energy cosmic rays in de Sitter invariant vacuum
states is considered. Assuming the present-day universe is asymptoting toward a
future de Sitter phase, we argue the observed flux of cosmic rays places a
bound on the parameter $\alpha$ that characterizes these de Sitter invariant
vacuum states, generalizing earlier work of Starobinsky and Tkachev. If this
bound is saturated, we obtain a new top-down scenario for the production of
super-GZK cosmic rays. The observable predictions bear many similarities to the
previously studied scenario where super-GZK events are produced by decay of
galactic halo super-heavy dark matter particles.


title:
The Formation of the First Stars I. Mass Infall Rates, Accretion Disk
  Structure and Protostellar Evolution

abstract:
  We present a theoretical model for primordial star formation. First we
describe the structure of the initial gas cores as virialized,
quasi-hydrostatic objects in accord with recent high resolution numerical
studies. The accretion rate can then be related to characteristic densities and
temperatures that are set by the cooling properties of molecular hydrogen. We
allow for rotation of the gas core, assuming angular momentum conservation
inside the sonic point of the flow. In the typical case, most mass then reaches
the star via an accretion disk. The structure of the inner region of this disk
is described with the standard theory of viscous disks, but with allowance for
the substantial energies absorbed in ionizing and dissociating the gas. The
size of the protostar and its luminosity depend upon the accretion rate, the
energetics of the accreting gas, and the ability of the radiation to escape
from the stellar accretion shock. We combine these models for the infall rate,
inner disk structure, and protostellar evolution to predict the radiation field
that is the basis for radiative feedback processes acting against infall (Paper
II). For realistic initial angular momenta, the photosphere of the protostar is
much smaller and hotter than in the spherical case, leading to stronger
radiative feedback at earlier stages in the evolution. In particular, once the
star is older than its Kelvin-Helmholtz time, contraction towards the main
sequence causes a rapid increase in ionizing and far-ultraviolet luminosity at
masses ~30Msun in the fiducial case. Since the cores out of which the first
stars formed were much more massive than 30Msun and since feedback is
dynamically unimportant at lower masses, we conclude that the first stars
should have had masses >~30Msun.


title:
Reduced convergence and the local smoothness parameter: bridging two
  different descriptions of weak lensing amplification

abstract:
  Weak gravitational lensing due to the inhomogeneous matter distribution in
the universe is an important systematic uncertainty in the use of standard
candles in cosmology. There are two different descriptions of weak lensing
amplification, one uses a local smoothness parameter $\tilde{\alpha}$, the
other uses reduced convergence $\eta= 1+ \kappa/|\kappa_{min}|$ (where $\kappa$
is convergence). The $\tilde{\alpha}$ description involves Dyer-Roeder distance
$D_A(\tilde{\alpha}|z)$ ($\tilde{\alpha}=1$ corresponds to a smooth universe);
it is simple and convenient, and has been used by the community to illustrate
the effect of weak lensing on point sources such as type Ia supernovae. Wang
(1999) has shown that the $\tilde{\alpha}$ description can be made realistic by
allowing $\tilde{\alpha}$ to be a local variable, the local smoothness
parameter. The $\eta$ description has been used by Wang, Holz, & Munshi (2002)
to derive a universal probability distribution (UPDF) for weak lensing
amplification. In this paper, we bridge the two different descriptions of weak
lensing amplification by relating the reduced convergence $\eta$ and the local
smoothness parameter $\tilde{\alpha}$. We give the variance of $\tilde{\alpha}$
in terms of the matter power spectrum, thus providing a quantitative guidance
to the use of Dyer-Roeder distances in illustrating the effect of weak lensing.
The by-products of this work include a corrected definition of the reduced
convergence, and simple and accurate analytical expressions for
$D_A(\tilde{\alpha}|z)$. Our results should be very useful in studying the weak
lensing of standard candles.


title:
Spatial Separation of the 3.29 micron Emission Feature and Associated 2
  micron Continuum in NGC 7023

abstract:
  We present a new 0.9" resolution 3.29 micron narrowband image of the
reflection nebula NGC 7023. We find that the 3.29 micron IEF in NGC 7023 is
brightest in narrow filaments NW of the illuminating star. These filaments have
been seen in images of K', molecular hydrogen emission lines, the 6.2 and 11.3
micron IEFs, and HCO+. We also detect 3.29 micron emission faintly but
distinctly between the filaments and the star. The 3.29 micron image is in
contrast to narrowband images at 2.09, 2.14, and 2.18 micron, which show an
extended emission peak midway between the filaments and the star, and much
fainter emission near the filaments. The [2.18]-[3.29] color shows a wide
variation, ranging from 3.4-3.6 mag at the 2 micron continuum peak to 5.5 mag
in the filaments. We observe [2.18]-[3.29] to increase smoothly with increasing
distance from the star, up until the filament, suggesting that the main
difference between the spatial distributions of the 2 micron continuum and the
the 3.29 micron emission is related to the incident stellar flux. Our result
suggests that the 3.29 micron IEF carriers are likely to be distinct from, but
related to, the 2 micron continuum emitters. Our finding also imply that, in
NGC 7023, the 2 micron continuum emitters are mainly associated with HI, while
the 3.29 micron IEF carriers are primarily found in warm molecular hydrogen,
but that both can survive in HI or molecular hydrogen. (abridged)


title: UBRI Photometry of Globular Clusters in the Leo Group Galaxy NGC 3379

abstract:
  We present wide area UBRI photometry for globular clusters around the Leo
group galaxy NGC 3379. Globular cluster candidates are selected from their
B-band magnitudes and their (U-B)o vs (B-I)o colours. A colour-colour selection
region was defined from photometry of the Milky Way and M31 globular cluster
systems. We detect 133 globular cluster candidates which, supports previous
claims of a low specific frequency for NGC 3379. The Milky Way and M31 reveal
blue and red subpopulations, with (U-B)o and (B-I)o colours indicating mean
metallicities similar to those expected based on previous spectroscopic work.
The stellar population models of Maraston (2003) and Brocato etal (2000) are
consistent with both subpopulations being old, and with metallicities of [Fe/H]
\~ -1.5 and -0.6 for the blue and red subpopulations respectively. The models
of Worthey (1994) do not reproduce the (U-B)o colours of the red (metal-rich)
subpopulation for any modelled age. For NGC 3379 we detect a blue subpopulation
with similar colours and presumably age/metallicity, to that of the Milky Way
and M31 globular cluster systems. The red subpopulation is less well defined,
perhaps due to increased photometric errors, but indicates a mean metallicity
of [Fe/H] ~ -0.6.