title: Modelling self-pollution of globular clusters from AGB stars

abstract:
  A self-consistent model of the chemical evolution of the globular cluster NGC
6752 is presented to test a popular theory that observed abundance anomalies
are due to ``internal pollution'' from intermediate mass asymptotic giant
branch stars. We simulated the chemical evolution of the intracluster medium
under the assumption that the products of Type II SNe are completely expelled
from the globular cluster, whereas material ejected from stars with m < 7 M_sun
is retained, due to their weak stellar winds. By tracing the chemical evolution
of the intracluster gas, we tested an internal pollution scenario in which the
Na- and Al-enhanced ejecta from intermediate mass stars is either accreted onto
the surfaces of other stars, or goes toward forming new stars. The observed
spread in Na and Al was reproduced, but not the O-Na and Mg-Al
anticorrelations. In particular, neither O nor Mg are sufficiently depleted to
account for the observations. We predict that the Mg content of Na-rich cluster
stars should be overwhelmingly dominated by the 25,26Mg isotopes, whereas the
latest data shows only a mild 26Mg enhancement and no correlation with 25Mg.
Furthermore, stars bearing the imprint of intermediate mass stellar ejecta are
predicted to be strongly enhanced in both C and N, in conflict with the
empirical data. We find that while standard AGB stellar models do show the hot
H burning that seems required to explain the observations, this is accompanied
by He burning, producing primary C, N, Mg and Na (via HBB) which do not match
the observations. (Abridged)


abstract:
  The Fifth Workshop on Galactic Chemodynamics (GCDV) is the pre-eminent
workshop devoted exclusively to observational and theoretical research into the
formation and evolution of galaxies. GCDV brought together 46 researchers from
13 countries for an intensive workshop at Swinburne University in July 2003.
Each of the 28 papers included in the workshop proceedings have been formally
refereed in their entirety, published as a special volume of the Publications
of the Astronomical Society of Australia, and available through NASA's
Astronomical Data System (ADS).


title: Evolution of a neutrino-cooled disc in Gamma-Ray Bursts

abstract:
  Rapid, hyper-Eddington accretion is likely to power the central engines of
gamma-ray bursts (GRBs). In the extreme conditions of densities and
temperatures the accreting torus is cooled by neutrino emission rather than by
radiation. Another important cooling mechanism is the advection of energy into
the central black hole. We compute the time evolution of a neutrino-dominated
disc that proceeds during the burst and investigate the changes in its density
and temperature. The discrimination between short and long bursts is made on
the basis of the different rates of material inflow to the outer parts of the
disc, thus favoring the binary merger scenario for the short GRBs and the
collapsar scenario for the long ones. Within the context of the collapsar
model, we also study the evolution of the photon luminosity of the remnant disc
up to times of the order of 1 day, and discuss its implications for the
production of emission lines in GRB spectra.


title:
The spin periods and magnetic moments of white dwarfs in magnetic
  cataclysmic variables

abstract:
  We have used a model of magnetic accretion to investigate the rotational
equilibria of magnetic cataclysmic variables (mCVs). The results of our
numerical simulations demonstrate that there is a range of parameter space in
the P_spin / P_orb versus mu_1 plane at which rotational equilibrium occurs.
This has allowed us to calculate the theoretical histogram describing the
distribution of magnetic CVs as a function of P_spin / P_orb. We show that this
agrees with the observed distribution assuming that the number of systems as a
function of white dwarf magnetic moment is distributed approximately according
to N(mu_1) d mu_1 proportional to 1/mu_1 d mu_1. The rotational equilibria also
allow us to infer approximate values for the magnetic moments of all known
intermediate polars. We predict that intermediate polars with mu_1 > 5 x 10^33
G cm^3 and P_orb > 3h will evolve into polars, whilst those with mu_1 < 5 x
10^33 G cm^3 and P_orb > 3h will either evolve into low field strength polars
which are (presumably) unobservable, and possibly EUV emitters, or, if their
fields are buried by high accretion rates, evolve into conventional polars once
their magnetic fields re-surface when the mass accretion rate reduces. We
speculate that EX Hya-like systems may have low magnetic field strength
secondaries and so avoid synchronisation. Finally we note that the equilibria
we have investigated correspond to a variety of different types of accretion
flow, including disc-like accretion at small P_spin / P_orb values, stream-like
accretion at intermediate P_spin / P_orb values, and accretion fed from a ring
at the outer edge of the white dwarf Roche lobe at higher P_spin / P_orb
values.


title: Constraints on mode couplings and modulation of the CMB with WMAP data

abstract:
  We investigate a possible asymmetry in the statistical properties of the
cosmic microwave background temperature field and to do so we construct an
estimator aiming at detecting a dipolar modulation. Such a modulation is found
to induce correlations between multipoles with $\Delta\ell=1$. Applying this
estimator, to the V and W bands of the WMAP data, we found a significant
detection in the V band. We argue however that foregrounds and in particular
point sources are the origin of this signal.


title: Clusters of galaxies in the mid-infrared

abstract:
  We describe the results of observations of galaxy clusters conducted with
ISOCAM on-board the Infrared Space Observatory. Our research is aimed at
understanding the processes driving galaxy evolution in dense environments,
free from the bias of dust extinction. The results reveal quite a complex
picture: the star-formation activity of cluster galaxies does not show a simple
evolution with redshift, but also depends on the dynamical status and
evolutionary history of the clusters.


title:
XMM-Newton observations of three poor clusters: Similarity in dark
  matter and entropy profiles down to low mass

abstract:
  (Abridged) We present an analysis of the mass and entropy profiles of three
poor clusters (A1991, A2717 and MKW9) observed with XMM-Newton. The clusters
have similar temperatures (kT=2.65, 2.53 and 2.58 keV), and similar redshifts
(0.04 < z < 0.06). We trace the surface brightness, temperature, entropy and
integrated mass profiles up to 0.5 (0.35 for MKW9) of the virial radius
(r_200). The integrated mass profiles are very similar in physical units and
are reasonably well fitted with the NFW mass model with concentration
parameters of c_200=4-6 and M_200=1.2-1.6 X 10^14 h_70^-1 \msun. The entropy
profiles are similar at large scale, but there is some scatter in the central
region (r<50 kpc). None of the clusters has an isentropic core. Including XMM
data on A1983 (kT=2.2 keV), and A1413 (kT = 6.5 keV), we discuss the structural
and scaling properties of cluster mass and entropy profiles. The scaled mass
profiles display <20% dispersion in the 0.05 - 0.5 r_200 radial range. The
c_200 parameters of these clusters, and other values from the literature, are
fully consistent with the c_200 - M_200 relation derived from simulations. The
dispersion in scaled entropy profiles is small, implying self-similarity down
to low mass (kT ~2 keV), and is reduced by 30-40% (to ~20%) if we use the
empirical relation S \propto T^0.65 instead of the standard self-similar
relation, S \propto T. The mean scaled profile is well fitted by a power law
for 0.05 < r_200 < 0.5, with a slope slightly lower than expected from pure
shock heating (\alpha = 0.94+/-0.14), and a normalisation at 0.1 r_200
consistent with previous studies. The gas history thus likely depends both on
gravitational processes and the interplay between cooling and various galaxy
feedback mechanisms.


title: Multiple merging in the Abell cluster 1367

abstract:
  We present a dynamical analysis of the central ~1.3 square degrees of the
cluster of galaxies Abell 1367, based on 273 redshift measurements (of which
119 are news). From the analysis of the 146 confirmed cluster members we derive
a significantly non-Gaussian velocity distribution, with a mean location C_{BI}
= 6484+/-81 km/s and a scale S_{BI} = 891+/-58 km/s. The cluster appears
elongated from the North-West to the South-East with two main density peaks
associated with two substructures. The North-West subcluster is probably in the
early phase of merging into the South-East substructure (~ 0.2 Gyr before core
crossing). A dynamical study of the two subclouds points out the existence of a
group of star-forming galaxies infalling into the core of the South-East
subcloud and suggests that two other groups are infalling into the NW and SE
subclusters respectively. These three subgroups contain a higher fraction of
star-forming galaxies than the cluster core, as expected during merging events.
Abell 1367 appears as a young cluster currently forming at the intersection of
two filaments.


title: The composite starburst/AGN nature of the superwind galaxy NGC 4666

abstract:
  We report the discovery of a Compton-thick AGN and of intense star-formation
activity in the nucleus and disk, respectively, of the nearly edge-on superwind
galaxy NGC 4666. Spatially unresolved emission is detected by BeppoSAX only at
energies <10 keV, whereas spatially resolved emission from the whole disk is
detected by XMM-Newton. A prominent (EW ~ 1-2 keV) emission line at ~6.4 keV is
detected by both instruments. From the XMM-Newton data alone the line is
spectrally localized at E ~ 6.42 +/- 0.03 keV, and seems to be spatially
concentrated in the nuclear region of NGC 4666. This, together with the
presence of a flat (Gamma ~ 1.3) continuum in the nuclear region, suggests the
existence of a strongly absorbed (i.e., Compton-thick) AGN, whose intrinsic
2-10 keV luminosity is estimated to be L_{2-10} > 2 x 10^{41} erg/s. At
energies <1 keV the integrated (BeppoSAX) spectrum is dominated by a ~0.25 keV
thermal gas component distributed throughout the disk (resolved by XMM-Newton).
At energies ~2-10 keV, the integrated spectrum is dominated by a steep (G > 2)
power-law (PL) component. The latter emission is likely due to unresolved
sources with luminosity L ~ 10^{38} - 10^{39} erg/s that are most likely
accreting binaries (with BH masses <8 M_sun). Such binaries, which are known to
dominate the X-ray point-source luminosity in nearby star-forming galaxies,
have Gamma ~ 2 PL spectra in the relevant energy range. A Gamma ~ 1.8 PL
contribution from Compton scattering of (the radio-emitting) relativistic
electrons by the ambient FIR photons may add a truly diffuse component to the
2-10 keV emission.


title: Bouncing Universes with Varying Constants

abstract:
  We investigate the behaviour of exact closed bouncing Friedmann universes in
theories with varying constants. We show that the simplest BSBM varying-alpha
theory leads to a bouncing universe. The value of alpha increases
monotonically, remaining approximately constant during most of each cycle, but
increasing significantly around each bounce. When dissipation is introduced we
show that in each new cycle the universe expands for longer and to a larger
size. We find a similar effect for closed bouncing universes in Brans-Dicke
theory, where $G$ also varies monotonically in time from cycle to cycle.
Similar behaviour occurs also in varying speed of light theories.


title: The boundary layer of VW Hyi in quiescence

abstract:
  In this letter, we suggest that the missing boundary layer luminosity of
dwarf novae in quiescence is released mainly in the ultraviolet (UV) as the
second component commonly identified in the far ultraviolet (FUV) as the
"accretion belt".
  We present the well-studied SU UMa-type system VW Hyi in detail as a
prototype for such a scenario. We consider detailed multiwavelength
observations and in particular the recent FUSE observations of VW Hyi which
confirm the presence of a second component (the "accretion belt") in the FUV
spectrum of VW Hyi in quiescence. The temperature (50,000K) and rotational
velocity (> 3,000km/s) of this second FUV component are entirely consistent
with the optically thick region (tau = 1) located just at the outer edge of
optically thin boundary layer in the simulations of Popham (1999).
  This second component contributes 20% of the FUV flux, therefore implying a
boundary layer luminosity: $L_{BL} = 2 \times (0.2 \times L_{UV} + L_{X-ray}) =
0.6 \times L_{disc}$, while the theory (Klu\'zniak 1987) predicts, for the
rotation rate of VW Hyi's WD, $L_{BL} \approx 0.77 L_{disc}$. The remaining
accretion energy ($<0.1 L_{acc}$) is apparently advected into the star as
expected for optically thin advection dominated boundary layers. This scenario
is consistent with the recent simultaneous X-ray and UV observations of VW Hyi
by (Pandel, C\'ordova & Howell 2003), from which we deduced here that the alpha
viscosity parameter in the boundary layer region must be as small as $\alpha
\approx 0.004$.


title:
A "Starless" Core that Isn't: Detection of a Source in the L1014 Dense
  Core with the Spitzer Space Telescope

abstract:
  We present observations of L1014, a dense core in the Cygnus region
previously thought to be starless, but data from the Spitzer Space Telescope
shows the presence of an embedded source. We propose a model for this source
that includes a cold core, heated by the interstellar radiation field, and a
low-luminosity internal source. The low luminosity of the internal source
suggests a substellar object. If L1014 is representative, other "starless"
cores may turn out to harbor central sources.


title: Linear line polarimetry modelling of pre-main sequence stars

abstract:
  We present emission line polarimetry data and modelling relevant to the
circumstellar geometry and kinematics around pre-main sequence stars. For a
sample of both Herbig Ae/Be stars and T Tauri stars, we find that most show
polarization changes across Halpha, implying that flattened structures are
common on the smallest scales -- and over a range of stellar masses. We also
present Monte Carlo calculations of spectral line profiles scattered in
rotating accretion disks. We consider both the case of a central star that
emits line photons uniformly, as well as via hot spots. Intriguingly, the
switch between a uniform point source and a finite-sized star results in a
marked difference in the position angle variation across the line. Our models
demonstrate the diagnostic potential of line polarimetry in determining the
disk inclination and the size of the inner hole -- a spatial scale no other
technique currently accesses.


title:
Automated Nonlinear Stellar Pulsation Calculations: Applications to RR
  Lyrae stars. The Slope of the Fundamental Blue Edge and the First RRd Model
  Survey

abstract:
  We describe a methodology that allows us to follow the pulsational behavior
of an RR Lyrae model consistently and automatically along its evolutionary
track throughout the whole instability strip. It is based on the powerful
amplitude equation formalism, and resorts to a judicious combination of
numerical hydrodynamical simulations, the analytical signal time-series
analysis, and amplitude equations. A large-scale survey of the nonlinear
pulsations in RR Lyr instability strip is then presented, and the mode
selection mechanism is delineated throughout the relevant regions of parameter
space. We obtain and examine two regions with hysteresis, where the pulsational
state depends on the direction of the evolutionary tracks, namely a region with
either fundamental (RRab) or first overtone (RRc) pulsations and a region with
either fundamental (RRab) or double-mode (RRd) pulsations. The regions where
stable double-mode (DM, or RRd) pulsations occur are very narrow and hard to
find in astrophysical parameter (L, M, T_eff, X, Z) space with hydrodynamic
simulations, but our systematic and efficient methodology allows us to
investigate them with unprecedented detail. It is shown that by simultaneously
considering the effects of mode selection and of horizontal branch evolution we
can naturally solve one of the extant puzzles involving the topologies of the
theoretical and observed instability strips, namely the slope of the
fundamental blue edge. The importance of the interplay between mode selection
and stellar evolutionary effects is also demonstrated for the properties of
double-mode RR Lyr. Finally, the Petersen diagram of double-mode RR Lyr models
is discussed for the first time.


title: High Contrast Imaging with Gaussian Aperture Pupil Masks (GAPMs)

abstract:
  Gaussian aperture pupil masks (GAPMs) can in theory achieve the contrast
requisite for directly imaging an extrasolar planet around a nearby solar type
star. We outline the process of designing, fabricating, and testing a GAPM for
use on current telescopes and specifically the Penn State near-IR Imager and
Spectrograph (PIRIS) at the Mt. Wilson 100$^{\prime\prime}$ telescope. We find
that the initial prototype observations are quite successful, achieving a
contrast similar to a traditional Lyot coronagraph without blocking any light
from a central object and useful for finding faint companions to nearby young
solar analogues. In the lab we can reproduce the expected PSF reasonably well
and with a single aperture design which achieves $\sim4 \times 10^{-5}$
contrast at 10$\lambda/D$.
  We find that small inaccuracies in the mask fabrication process and
insufficient correction of the atmosphere contribute the most degradation to
contrast at these levels.


title: How accurately can suborbital experiments measure the CMB?

abstract:
  Great efforts are currently being channeled into ground- and balloon-based
CMB experiments, mainly to explore anisotropy on small angular scales and
polarization. To optimize instrumental design and assess experimental
prospects, it is important to understand in detail the atmosphere-related
systematic errors that limit the science achievable with new suborbital
instruments. For this purpose, we spatially compare the 648 square degree
ground- and balloon-based QMASK map with the atmosphere-free WMAP map, finding
beautiful agreement on all angular scales where both are sensitive. This is a
reassuring quantitative assessment of the power of the state-of-the-art FFT-
and matrix-based mapmaking techniques that have been used for QMASK and
virtually all subsequent experiments.


title: Galaxy-Galaxy Flexion: Weak Lensing to Second Order

abstract:
  In this paper, we develop a new gravitational lensing inversion technique.
While traditional approaches assume that the lensing field varies little across
a galaxy image, we note that this variation in the field can give rise to a
``Flexion'' or bending of a galaxy image, which may then be used to detect a
lensing signal with increased signal to noise. Since the significance of the
Flexion signal increases on small scales, this is ideally suited to
galaxy-galaxy lensing. We develop an inversion technique based on the
``Shapelets'' formalism of Refregier (2003). We then demonstrate the proof of
this concept by measuring a Flexion signal in the Deep Lens Survey. Assuming an
intrinsically isothermal distribution, we find from the Flexion signal alone a
velocity width of v_c=221\pm 12 km/s for lens galaxies of r < 21.5, subject to
uncertainties in the intrinsic Flexion distribution.


title:
Boundary Layer Self-Similar Solution for the Hot Radiative Accretion
  onto a Rapidly Spinning Neutron Star

abstract:
  We consider hot accretion onto a rapidly spinning neutron star (or any other
compact object with a surface). A radiative hot settling flow has been
discovered at low accretion rates in the early work by Medvedev & Narayan
(2001) and analytical solution has been presented. It was shown later that this
flow can match external medium smoothly, thus enforcing its physical
feasibility. Here we complete the study of the global structure of such hot
accretion by presenting the analytical solution for the boundary later, which
forms between the bulk of the flow and the stellar surface. We confirm our
results via full numerical solution of height-integrated two-temperature
hydrodynamic equations.


title:
Far Ultraviolet Observations of Molecular Hydrogen in the Diffuse
  Interstellar Medium of Starburst Galaxies

abstract:
  (Abridged) We have used the Far Ultraviolet Spectroscopic Explorer (FUSE) to
search for H_2 absorption in five starburst galaxies: NGC 1705, NGC 3310, NGC
4214, M83 (NGC 5236), and NGC 5253. We tentatively detect weak absorption by
H_2 in M83 and NGC 5253, and set upper limits on the H_2 column density in the
other galaxies. Conservative upper limits on the mass of molecular gas detected
with FUSE are many orders of magnitude lower than the H_2 mass inferred from CO
emission. This indicates that almost all of the H_2 is in the form of clouds
with N(H_2)>10^20 cm^-2 that are opaque to far-UV light and therefore cannot be
probed with far-UV absorption measurements. The far-UV continuum visible in the
FUSE spectra passes between the dense clouds, which have a covering factor <1.
The complex observational biases related to varying extinction across the
extended UV emission in the FUSE apertures prevent an unambiguous
characterization of the diffuse H_2 in these starbursts. However, the evidence
is suggestive that there is less H_2 in the diffuse interstellar medium between
the dense clouds compared to similarly reddened sight lines in the Milky Way.
This holds with the expectation that the destructive UV radiation field is
stronger in starbursts. However, previous UV observations of these starbursts
have shown that there is reddening caused by the diffuse interstellar medium.
This suggests that while diffuse H_2 may be destroyed in the starburst, dust
still exists.


title: Spatial Distribution of Warm Dust in Early-Type Galaxies

abstract:
  Images taken with the IRAC instrument on the Spitzer Space Telescope show
that the spatial distribution of warm dust emission in lenticular galaxies is
often organized into dynamically-stable structures strongly resembling spiral
arms. These galaxies have bulge-to-disk-ratios and colors for their stellar
content appropriate for their morphological classification. Two of the three
galaxies with warm dust detected at 8.0 um also show far-IR emission expected
from that dust. More importantly, the [5.8]-[8.0] color of the dust emission
matches the colors found for late-type, star-forming galaxies, as well as
theoretical predictions for PAH emission from dust grains. The spatially
resolved dust structures may be powerful indicators of the evolutionary history
of the lenticular class of galaxies, either as a tracer of on-going quiescent
star formation or as a fossil record of a previous episode of more active star
formation.


title:
The HIPASS Catalogue - II. Completeness, Reliability, and Parameter
  Accuracy

abstract:
  The HI Parkes All Sky Survey (HIPASS) is a blind extragalactic HI 21-cm
emission line survey covering the whole southern sky from declination -90 to
+25. The HIPASS catalogue (HICAT), containing 4315 HI-selected galaxies from
the region south of declination +2, is presented in Meyer et al. (2004a, Paper
I). This paper describes in detail the completeness and reliability of HICAT,
which are calculated from the recovery rate of synthetic sources and follow-up
observations, respectively. HICAT is found to be 99 per cent complete at a peak
flux of 84 mJy and an integrated flux of 9.4 Jy km/s. The overall reliability
is 95 per cent, but rises to 99 per cent for sources with peak fluxes >58 mJy
or integrated flux > 8.2 Jy km/s. Expressions are derived for the uncertainties
on the most important HICAT parameters: peak flux, integrated flux, velocity
width, and recessional velocity. The errors on HICAT parameters are dominated
by the noise in the HIPASS data, rather than by the parametrization procedure.


title: Interpolation of Stellar Model Grids and Application to the NEMO Grid

abstract:
  NEMO.2003 (vienna NEw MOdel grid of stellar atmospheres) is a DVD with 91,520
stellar model atmospheres representing a 5D grid of modified ATLAS9
atmospheres; the purpose of the modifications was to include different
treatments of convection and higher vertical resolution. In addition, for every
model fluxes are provided and color indices for 14 different photometric
systems. Because the model grid contained gaps due to non-converging models, we
developed and applied a set of 4D interpolation routines to complete the grid.
  All the data, which will continuously be updated, can be found on the NEMO
homepage (http://ams.astro.univie.ac.at/nemo/) and are available via DVD.


title: On the propagation of non stationary pressure waves in stellar interiors

abstract:
  An analysis of the propagation of non stationary waves in the adiabatic
region of stellar interior is presented. An equation of motion with an
effective potential is derived, similar to the Zerilli equation known in the
propagation of gravitational waves. The Huyghens principle is violated in this
case and the energy diffusion outward null cones is expected. Numerical
calculations demonstrate that the diffusion is weak for the case of standard
Solar model; thus no significant effect corresponding to quasinormal modes can
be expected. The likely reason for the absence of stronger features is the
restriction of our analysis to adiabatic regions only, where the breakdown of
the Huyghens principle is insignificant.


title:
The Circumstellar Environment of the Early B Protostar G192.16-3.84 and
  the Discovery of a Low-Mass, Protostellar Core

abstract:
  We have observed the massive star forming region associated with the early B
protostar G192.16-3.84 in NH3(1,1), 22.2 GHz water masers, 1.3 cm continuum
emission, and at 850 microns. The dense gas associated with G192.16 is clumpy,
optically thin, and has a mass of 0.9 Msun. The ammonia core is gravitationally
unstable which may signal that the outflow phase of this system is coming to an
end. Water masers trace an ionized jet 0.8" (1600 AU at a distance of 2 kpc)
north of G192.16. Masers are also located within 500 AU of G192.16, their
velocity distribution is consistent with but does not strongly support the
interpretation that the maser emission arises in a 1000 AU rotating disk
centered on G192.16. Roughly 30" south of G192.16 (0.3 pc) is a compact,
optically thick (optical depth = 1.2) ammonia core (called G192 S3) with an
estimated mass of 2.6 Msun. Based on the presence of 850 micron and 1.2 mm
continuum emission, G192 S3 probably harbors a very young, low-mass protostar
or proto-cluster. The dense gas in the G192 S3 core is likely to be
gravitationally bound and may represent the next site of star formation in this
region.


title: The HIPASS Catalogue - I. Data Presentation

abstract:
  The HI Parkes All-Sky Survey (HIPASS) Catalogue forms the largest uniform
catalogue of HI sources compiled to date, with 4,315 sources identified purely
by their HI content. The catalogue data comprise the southern region
declination <+2 deg of HIPASS, the first blind HI survey to cover the entire
southern sky. RMS noise for this survey is 13 mJy/beam and the velocity range
is -1,280 to 12,700 km/s. Data search, verification and parametrization methods
are discussed along with a description of measured quantities. Full catalogue
data are made available to the astronomical community including positions,
velocities, velocity widths, integrated fluxes and peak flux densities. Also
available are on-sky moment maps, position-velocity moment maps and spectra of
catalogue sources. A number of local large-scale features are observed in the
space distribution of sources including the Super-Galactic plane and the Local
Void. Notably, large-scale structure is seen at low Galactic latitudes, a
region normally obscured at optical wavelengths.


title: The Homogeneity of Interstellar Oxygen in the Galactic Disk

abstract:
  We present an analysis of high resolution HST Space Telescope Imaging
Spectrograph (STIS) observations of O I 1356 and H I Lyman-alpha absorption in
36 sight lines that probe a variety of Galactic disk environments and include
paths that range over nearly 4 orders of magnitude in f(H_2), over 2 orders of
magnitude in mean sight line density, and that extend up to 6.5 kpc in length.
Consequently, we have undertaken the study of gas-phase O/H abundance ratio
homogeneity using the current sample and previously published Goddard
High-Resolution Spectrograph (GHRS) results. Two distinct trends are identified
in the 56 sight line sample: an apparent decrease in gas-phase oxygen abundance
with increasing mean sight line density and a gap between the mean O/H ratio
for sight lines shorter and longer than about 800 pc. The first effect is a
smooth transition between two depletion levels associated with large mean
density intervals; it is centered near a density of 1.5 cm^-3 and is similar to
trends evident in gas-phase abundances of other elements. Paths less dense than
the central value exhibit a mean O/H ratio of log_10 (O/H) = -3.41+/-0.01 (or
390+/-10 ppm), which is consistent with averages determined for several long,
low-density paths observed by STIS (Andre et al. 2003) and short low-density
paths observed by FUSE (Moos et al. 2002). Sight lines of higher mean density
exhibit an average O/H value of log_10 (O/H) = -3.55+/-0.02 (284+/-12 ppm). The
datapoints for low-density paths are scattered more widely than those for
denser sight lines, due to O/H ratios for paths shorter than 800 pc that are
generally about 0.10 dex lower than the values for longer ones.


title:
The Nature of Faint 24 micron Sources Seen in Spitzer Observations of
  ELAIS-N1

abstract:
  The Spitzer Space Telescope has undertaken the deepest ever observations of
the 24 micron sky in the ELAIS-N1 field as part of GOODS Science Verification
observations. We present the shape of the 24 micron source counts in the flux
range 20-1000 microJy, discuss the redshift distribution and nature of these
sources with particular emphasis on their near-infrared counterparts.


title: Test of patch cosmology with WMAP

abstract:
  We calculate the power spectrum, spectral index, and running spectral index
for inflationary patch cosmology arisen from Gauss-Bonnet braneworld scenario
using the Mukhanov equation. This patch cosmology consists of Gauss-Bonnet(GB),
Randall-Sundrum (RS-II), and four dimensional (4D) cosmological models. There
exist several modifications in higher order calculations. However, taking the
power-law inflation by choosing different potentials depending on the model,
there exist minor changes up to second order corrections. Since second order
corrections are rather small in the slow-roll limit, we could not choose a
desired power-law model which explains the WMAP data. Finally we discuss the
reliability of high order calculations based on the Mukhanov equation by
comparing the perturbed equation including 5D metric perturbations. It turns
out that first order corrections are reliable, while second order corrections
are not proved to be reliable.


title:
Effect of clustering on extragalactic source counts with low-resolution
  instruments

abstract:
  In the presence of strong clustering, low-resolution surveys measure the
summed contributions of groups of sources within the beam. The counts of bright
intensity peaks are therefore shifted to higher flux levels compared to the
counts of individual sources detected with high-resolution instruments. If the
beam-width corresponds a sizable fraction of the clustering size, as in the
case of Planck/HFI, one actually detects the fluxes of clumps of sources. We
argue that the distribution of clump luminosities can be modelled in terms of
the two- and three-point correlation functions, and apply our formalism to the
Planck/HFI 850 micron surveys. The effect on counts is found to be large and
sensitive also to the evolution of the three-point correlation function; in the
extreme case that the latter function is redshift-independent, the source
confusion due to clustering keeps being important above the canonical 5*sigma
detection limit. Detailed simulations confirm the reliability of our approach.
As the ratio of the beam-width to the clustering angular size decreases, the
observed fluxes approach those of the brightest sources in the beam and the
clump formalism no longer applies. However, simulations show that also in the
case of the Herschel/SPIRE 500 micron survey the enhancement of the bright
source counts due to clustering is important.


title: The emissivity of dust grains in spiral galaxies

abstract:
  We use the radiation transfer simulation of Xilouris et al. (1999) to
constrain the quantity of dust in three nearby spiral galaxies (NGC 4013, NGC
5907 and NGC 4565). The predicted visual optical depth from the model is
compared with the thermal continuum radiation detected from NGC 4013 and NGC
5907 at 850 microns and from NGC 4565 at 1.2 mm. The former is based on SCUBA
images of NGC 4013 and NGC 5907, reduced and presented for the first time in
this work. The comparison of visual optical depth and 850 microns (1.2 mm)
emission yields the emissivity of dust grains in the submillimeter (millimeter)
waveband. We infer a value of 1.2x10^{4} for the emissivity at 850 microns
which is a factor 4 higher than the benchmark, semi-empirical model of Draine &
Lee (1984). At 1.2 mm our values are a factor 1.5 higher than this model. Our
estimates are more closely aligned with recent measurements carried out in the
laboratory on amorphous carbon and silicate particulates. A comparison between
the distribution of 850 microns (1.2 mm) surface brightness and the intensity
levels in the ^{12}CO(1-0) and 21 cm lines underlines the spatial association
between dust detected in the submillimeter/millimeter waveband and molecular
gas clouds. We suggest that the relatively high emissivity values that we
derive may be attributable to amorphous, fluffy grains situated in denser gas
environments.


title: Phase light curves for extrasolar Jupiters and Saturns

abstract:
  We predict how a remote observer would see the brightness variations of giant
planets similar to Jupiter and Saturn as they orbit their central stars. We
model the geometry of Jupiter, Saturn and Saturn's rings for varying orbital
and viewing parameters. Scattering properties for the planets and rings at
wavelenghts 0.6-0.7 microns follow Pioneer and Voyager observations, namely,
planets are forward scattering and rings are backward scattering. Images of the
planet with or without rings are simulated and used to calculate the
disk-averaged luminosity varying along the orbit, that is, a light curve is
generated. We find that the different scattering properties of Jupiter and
Saturn (without rings) make a substantial difference in the shape of their
light curves. Saturn-size rings increase the apparent luminosity of the planet
by a factor of 2-3 for a wide range of geometries. Rings produce asymmetric
light curves that are distinct from the light curve of the planet without
rings. If radial velocity data are available for the planet, the effect of the
ring on the light curve can be distinguished from effects due to orbital
eccentricity. Non-ringed planets on eccentric orbits produce light curves with
maxima shifted relative to the position of the maximum planet's phase. Given
radial velocity data, the amount of the shift restricts the planet's unknown
orbital inclination and therefore its mass. Combination of radial velocity data
and a light curve for a non-ringed planet on an eccentric orbit can also be
used to constrain the surface scattering properties of the planet. To summarize
our results for the detectability of exoplanets in reflected light, we present
a chart of light curve amplitudes of non-ringed planets for different
eccentricities, inclinations, and the viewing azimuthal angles of the observer.


title:
An ISOCAM survey through gravitationally lensing galaxy clusters. II.
  The properties of infrared galaxies in the A2218 field

abstract:
  We observed the cluster Abell 2218 (z=0.175), with ISOCAM on board the
Infrared Space Observatory, using two filters with reference wavelengths of 6.7
and 14.3 microns. We detected 67 extragalactic mid-infrared sources. Using the
``GRASIL'' models of Silva et al. (1998) we have obtained acceptable and well
constrained fits to the observed spectral energy distributions (SEDs) of 41 of
these sources, for which additional optical/near-infrared magnitudes, and, in
some cases, redshifts, were available. We have then determined the total
infrared luminosities and star formation rates (SFRs) of these 41 sources, of
which 27 are cluster members and 14 are field galaxies at a median redshift
z~0.6.
  The SEDs of most of the ISOCAM cluster members are best fit by models with
negligible star formation in the last ~1 Gyr. The 7 faintest cluster members
have a slightly higher, but still very mild, star-formation activity. The
ISOCAM-selected cluster galaxies appear to be an unbiased subsample of the
overall cluster population. If A2218 is undergoing a merger, as suggested by
some optical and X-ray analyses, then this merger does not seem to affect the
mid-infrared properties of its galaxies.
  The SEDs of most ISOCAM-selected field sources are best fit by models with
significant ongoing (and recent) star formation, resembling those of massive
star-forming spirals or (post)starburst galaxies. Their median SFR is 22 solar
masses per year. Eight of the 14 field sources are Luminous IR Galaxies.
(Abridged)


title:
Smoothed particle hydrodynamics with radiative transfer in the
  flux-limited diffusion approximation

abstract:
  We describe the implementation and testing of a smoothed particle
hydrodynamics (SPH) code that solves the equations of radiation hydrodynamics
in the flux-limited diffusion (FLD) approximation. The SPH equations of
radiation hydrodynamics for an explicit integration scheme are derived and
tested. We also discuss the implementation of an implicit numerical scheme for
solving the radiation equations that allows the system to be evolved using
timesteps much longer than the explicit radiation timestep. The code is tested
on a variety of one-dimensional radiation hydrodynamics problems including
radiation propagating in an optically thin medium, optically thick and thin
shocks, subcritical and supercritical radiating shocks, and a radiation
dominated shock. Many of the tests were also performed by Turner and Stone
(2001) to test their implementation of a FLD module for the ZEUS-2D code. The
SPH code performs at least as well as the ZEUS-2D code in these tests.


title: Testing the isotropy of the Cosmic Microwave Backround

abstract:
  There have recently been several claims of an asymmetric distribution of
large scale fluctuations in the WMAP data. I review some recent results from a
test of isotropy of the power spectrum at all scales and show how the power is
asymmetrically distributed for the multipole range l=5-40 in three WMAP
frequency channels. I compare this to a recent detection of a non-Gaussian
signal in one part of the sky using the local curvature properties of the
cosmic microwave background fluctuation field. I find that there may be a
common origin of these two findings due to a similar direction and frequency
independence of the results.


title:
Probing the primordial power spectrum with the VSA (and other CMB
  experiments)

abstract:
  We present estimates of parameters which model the primordial density
fluctuations using CMB data from the VSA, 1st year WMAP, CBI and ACBAR along
with external priors from 2dF and the HST. Taken at face value there is
significant evidence for a running spectral index when only scalar fluctuations
are considered. The significance of this result is increased by the inclusion
of tensors and, although the result is weakened by the inclusion of `running of
the running', the basic trend toward significantly negative running remains. We
discuss the implications of this result and how it might be strengthened by
future observations.


title:
Time-resolved photometry and spectroscopy of the new deeply-eclipsing SW
  Sextantis star HS 0728+6738

abstract:
  We present time-resolved optical spectroscopy and photometry, and
far-ultraviolet spectroscopy of HS 0728+6738, a cataclysmic variable discovered
in the Hamburg Quasar Survey. We show that the system is a new eclipsing member
of the SW Sex class of CVs with an orbital period of 3.21 hours. We derive an
orbital inclination of ~85 +- 4 degrees from the average eclipse profile,
making HS 0728+6738 the highest inclination SW Sex star known. The optical and
far-ultraviolet emission lines are not or only weakly occulted during the
eclipse, indicating the presence of line-emission sites either far outside the
Roche lobe of the primary or, more likely, above the orbital plane of the
binary. The photometric light curves exhibit fast variability with a period of
\~7 min, which might be related to the spin of the white dwarf.


title:
Velocity trends in the debris of Sagittarius and the shape of the
  dark-matter halo of the Galaxy

abstract:
  Recently, radial velocities have been measured for a large sample of M giants
from the 2MASS catalog, selected to be part of the Sgr dwarf leading and
trailing streams. Here we present a comparison of their kinematics to models of
the Sgr dwarf debris orbiting Galactic potentials, with halo components of
varying degrees of flattening and elongation. This comparison shows that the
portion of the trailing stream mapped so far is dynamically young and hence
does not provide very stringent constraints on the shape of the Galactic
dark-matter halo. The leading stream, however, contains slightly older debris,
and its kinematics provide for the first time direct evidence that the
dark-matter halo of the Galaxy has a prolate shape with an average density axis
ratio within the orbit of Sgr close to 5/3.


title: Improved Baade-Wesselink surface-brightness relations

abstract:
  Recent, and older accurate, data on (limb-darkened) angular diameters is
compiled for 221 stars, as well as BVRIJK[12][25] magnitudes for those objects,
when available. Nine stars (all M-giants or supergiants) showing excess in the
[12-25] colour are excluded in the analysis as this may indicate the present of
dust influencing the optical and near-infrared colours as well. Based on this
large sample, Baade-Wesselink surface-brightness (SB) relations are presented
for dwarfs, giants, supergiants and dwarfs in the optical and near-infrared.
M-giants are found to follow different SB-relations from non-M giants, in
particular in V-(V-R). The preferred relation for non-M giants are compared to
earlier relation by Fouque & Gieren (1997, based on 10 stars) and Nordgren et
al. (2002, based on 57 stars). Increasing the sample size does not lead to a
lower rms value. It is shown that the residuals do not correlate with
metallicity at a significant level. The finally adopted observed angular
diameters are compared to those predicted by Cohen et al. (1999) for 45 stars
in common, and there is reasonable overall, to good agreement when \theta <6
mas. Finally, I comment on the common practice in the literature to average,
and then fix, the zero point of the V-(V-K), V-(V-R) and K-(J-K) relations, and
then re-derive the slopes. Such a common zero point at zero colour is not
expected from model atmospheres for the (V-R) colour and depends on gravity.
Relations derived in this way may be biased.


title: Non-Gaussianity from Inflation: Theory and Observations

abstract:
  This is a review of models of inflation and of their predictions for the
primordial non-Gaussianity in the density perturbations which are thought to be
at the origin of structures in the Universe. Non-Gaussianity emerges as a key
observable to discriminate among competing scenarios for the generation of
cosmological perturbations and is one of the primary targets of present and
future Cosmic Microwave Background satellite missions. We give a detailed
presentation of the state-of-the-art of the subject of non-Gaussianity, both
from the theoretical and the observational point of view, and provide all the
tools necessary to compute at second order in perturbation theory the level of
non-Gaussianity in any model of cosmological perturbations. We discuss the new
wave of models of inflation, which are firmly rooted in modern particle physics
theory and predict a significant amount of non-Gaussianity. The review is
addressed to both astrophysicists and particle physicists and contains useful
tables which summarize the theoretical and observational results regarding
non-Gaussianity.


title: INTEGRAL monitoring of the Black Hole candidate 1E 1740.7-2942

abstract:
  The brightest persistent Galactic black hole candidate close to the Galactic
Centre, 1E 1740.7-2942, has long been observed with INTEGRAL. In this paper, we
report on the long-term hard X-ray monitoring obtained during the first year of
observations as part of the Galactic Centre Deep Exposure. We discuss the
temporal and spectral behaviours in different energy bands up to 250 keV, as
well as the hardness-flux correlations.


title: Theoretical Modeling of Weakly Lensed Polarized Radio Sources

abstract:
  In this paper we present the theoretical basis for the modeling of weakly
gravitationally lensed extended sources that are polarized. This technique has
been used in the past to constrain the mass profiles of galaxies projected
against the jet of the quasar 3C9. Since then, work has been done to improve
both the measurement and theoretical modeling of the lensing signal, which
manifests itself as an alignment breaking between the morphology and the
polarization, parametrized as eta-g. To this end, we present the mathematical
derivation of the theoretical value of eta-g as well as numerical simulations
of expected signals in polarized radio jets. We use the radio jet sources 3C9
and 1253+104 as illustrative examples of the measurement and modeling of the
eta-g signal. For 3C9, we present constraints on the parameters of the two
intervening lenses and quantify their confidence intervals. One lens has no
measured redshift and in this case, we show the dependence of mass and
mass-to-light ratio on assumed redshift.


title: Radiation Transfer of Emission Lines in Curved Space-Time

abstract:
  We present a general formulation for ray-tracing calculations in curved
space-time. The formulation takes full account of relativistic effects in the
photon transport and the relative motions of the emitters and the
light-of-sight absorbing material. We apply the formulation to calculate the
emission from accretion disks and tori around rotating black holes.


title: Molecular Hydrogen and [FeII] in Active Galactic Nuclei

abstract:
  (Abridge) Near-infrared spectroscopy is used to study the kinematics and
excitation mechanisms of the H2 and [FeII] gas in a sample of AGN. The H2 lines
are unresolved in all objects in which they were detected while the [FeII]
lines have widths implying gas velocities of up to 650 km/s. This suggests
that, very likely, the H2 and [FeII] emission does not originate from the same
parcel of gas. Molecular H2 were detected in 90% of the sample, including PG
objects, indicating detectavel amounts of molecular material even in objects
with low levels of circumnuclear starburst activity. The data favors thermal
excitation for the H2 lines. Indeed, in NGC3227, Mrk766, NGC4051 and NGC4151,
the molecular emission is found to be purely thermal. This result is also
confirmed by the rather similar vibrational and rotational temperatures in the
objects for which they were derived. [FeII] lines are detected in all of the
AGN. The [FeII] 1.254mu/Pa-beta ratio is compatible with excitation of the
[FeII] by the active nucleus, but in Mrk 766 it implies a stellar origin. A
correlation between H2/Br-gamma and [FeII]/Pa-beta is found. We confirm that it
is a useful diagnostic tool in the NIR to separate emitting line objects by
their level of nuclear activity. X-ray excitation models are able to explain
the observed H2 and part of the [FeII] emission. Most likely, a combination of
X-ray heating, shocks driven by the radio jet, and circumnuclear star formation
contributes, in different proportions, to the H2 and [FeII] emission. In most
of our spectra, the [FeII] 1.257mu/1.644mu ratio is found to be 30% lower than
the intrinsic value based on current atomic data. This implies either than the
extinction towards the [FeII] emitting clouds is very similar in most objects
or there are possible inaccuracies in the A-values in the [FeII] transitions.


title:
The Wavelength Dependence of Interstellar Extinction from 1.25 to 8.0
  microns Using GLIMPSE Data

abstract:
  We determine and tabulate A(lambda)/A(K), the wavelength dependence of
interstellar extinction, in the Galactic plane for 1.25um<lambda<8.0um along
two lines of sight: l~42 and l~284. The first is a relatively quiescent and
unremarkable region; the second contains the giant HII region RCW 49 as well as
a ``field'' region unrelated to the cluster and nebulosity. Areas near these
Galactic longitudes were imaged at J, H, and K bands by 2MASS and at 3--8um by
Spitzer for the GLIMPSE Legacy program. We measure the mean values of the color
excess ratios (A(lambda)-A(K))/(A(J)-A(K)) directly from the color
distributions of observed stars. The extinction ratio between two of the
filters, e.g. A(J)/A(K), is required to calculate A(lambda)/A(K) from those
measured ratios. We use the apparent JHK magnitudes of giant stars along our
two sightlines, and fit the reddening as a function of magnitude (distance) to
determine A(J)/kpc, A(K)/kpc, and A(J)/A(K). Our values of A(lambda)/A(K) show
a flattening across the 3--8um wavelength range, roughly consistent with the
Lutz 1996 extinction measurements derived for the sightline toward the Galactic
center.


title: Power Law Stellar Distributions

abstract:
  The density profiles and other quantities of physical interest for
spherically symmetric systems are computed by assuming that a collisionless
stellar gas may relax to the non-Gaussian power law distribution suggested by
the nonextensive kinetic theory. There are two different classes of solutions.
The first class behaves like a subset of the polytropic Lane-Emden spheres,
whereas the second one corresponds to a transition between two different
polytropic indices. Unlike the isothermal Maxwellian sphere, the total mass and
sizes of both classes are finite for a large range of the nonextensive
q-parameter.


title:
Poynting Flux Dominated Jets in Decreasing Density Atmospheres. I. The
  Non-relativistic Current-driven Kink Instability and the Formation of
  "Wiggled" Structures

abstract:
  Non-relativistic three-dimensional magnetohydrodynamical (MHD) simulations of
Poynting flux dominated (PFD) jets are presented. Our study focuses on the
propagation of strongly magnetized hypersonic, but sub-Alfv\'enic ($C^{2}_{\rm
s} \ll V^{2}_{\rm jet} < V^{2}_{\rm A}$) flow and on the subsequent development
of a current-driven (CD) kink instability. This instability may be responsible
for the ``wiggled'' structures seen in sub-parsec scale (VLBI) jets. In the
present paper, we investigate the nonlinear behavior of PFD jets in a variety
of external ambient magnetized gas distributions, including those with density,
pressure, and temperature gradients. Our numerical results show that the jets
can develop CD distortions in the trans-Alfv\'enic flow case, even when the
flow itself is still strongly magnetically dominated. An internal
non-axisymmetric body mode grows on time scales of order of the Alfv\'en
crossing time and distorts the structure and magnetic configuration of the jet.
The kink ($m=1$) mode of the CD instability, driven by the radial component of
the Lorentz force, grows faster than other higher order modes ($m>1$). In the
jet frame the mode grows locally and expands radially at each axial position
where the jet is unstable: the instability, therefore, does not propagate as a
wave along the jet length. A naturally-occurring, external helically magnetized
wind, which is (quasi-) axially current-free, surrounds the well-collimated
current-carrying jet and reduces velocity shear between the jet and external
medium. This stabilizes the growth of MHD Kelvin-Helmholtz surface modes in the
inner jet flow.


title: Thermal-IR Detection of Optical Outflow Sources in OMC1 South

abstract:
  We present the first thermal-infrared imaging photometry for several embedded
sources in the OMC1 South cloud core in the Orion nebula, and propose that some
of these drive optical Herbig-Haro jets emerging from the region.
Thermal-infrared images at 8.8 and 11.7 micron obtained at Gemini South show a
handful of sources in OMC1-S with no visual-wavelength counterparts, although a
few can be seen in recent near-infrared data. For the three brightest
mid-infrared sources, we also present 18.75 micron photometry obtained with the
Keck telescope. The most prominent blueshifted outflows in the Orion nebula at
visual wavelengths such as HH202, HH203/204, HH529, and HH269 all originate
from OMC1-S. The brightest infrared source in OMC1-S at 11.7 micron is located
at the base of the prominent jet that powers HH202 and is likely to be the
sought-after driver of this outflow. The second brightest infrared source is
located at the base of the HH529 jet. We consider the possibility that
HH203/204 and HH269 trace parts of a single bent outflow from the
third-brightest infrared source. While there may be some lingering ambiguity
about which infrared stars drive specific jets, there is now a sufficient
number of embedded sources to plausibly account for the multiple outflows from
OMC1-S.


title: Geometrical Constraints on Dark Energy

abstract:
  We explore the recently introduced statefinder parameters. After reviewing
their basic properties, we calculate the statefinder parameters for a variety
of cosmological models, and investigate their usefulness as a means of
theoretical classification of dark energy models. We then go on to consider
their use in obtaining constraints on dark energy from present and future
supernovae type Ia data sets. Provided that the statefinder parameters can be
extracted unambiguously from the data, they give a good visual impression of
where the correct model should lie. However, it is non-trivial to extract the
statefinders from the data in a model-independent way, and one of our results
indicates that an expansion of the dark energy density to second order in the
redshift is inadequate. Hence, while a useful theoretical and visual tool,
applying the statefinders to observations is not straightforward.


title: The Purple Haze of Eta Carinae: Binary-Induced Variability?

abstract:
  Asymmetric variability in ultraviolet images of the Homunculus obtained with
the Advanced Camera for Surveys/High Resolution Camera on the Hubble Space
Telescope suggests that Eta Carinae is indeed a binary system. Images obtained
before, during, and after the recent ``spectroscopic event'' in 2003.5 show
alternating patterns of bright spots and shadows on opposite sides of the star
before and after the event, providing a strong geometric argument for an
azimuthally-evolving, asymmetric UV radiation field as one might predict in
some binary models. The simplest interpretation of these UV images, where
excess UV escapes from the secondary star in the direction away from the
primary, places the major axis of the eccentric orbit roughly perpendicular to
our line of sight, sharing the same equatorial plane as the Homunculus, and
with apastron for the hot secondary star oriented toward the southwest of the
primary. However, other orbital orientations may be allowed with more
complicated geometries. Selective UV illumination of the wind and ejecta may be
partly responsible for line profile variations seen in spectra. The brightness
asymmetries cannot be explained plausibly with delays due to light travel time
alone, so a single-star model would require a seriously asymmetric shell
ejection.


title: A 2dF survey of the Small Magellanic Cloud

abstract:
  We present a catalogue of new spectral types for hot, luminous stars in the
Small Magellanic Cloud. The catalogue contains 4161 objects, giving an order of
magnitude increase in the number of SMC stars with published spectroscopic
classifications. The targets are primarily B- and A-type stars (2862 and 853
objects respectively), with 1 Wolf-Rayet, 139 O-type, and 306 FG stars,
sampling the main sequence to ~mid-B. The selection and classification criteria
are described, and objects of particular interest are discussed, including
UV-selected targets from the Ultraviolet Imaging Telescope (UIT) experiment, Be
and B[e] stars, `anomalous A supergiants', and composite-spectrum systems. We
examine the incidence of Balmer-line emission, and the relationship between
H-gamma equivalent width and absolute magnitude for BA stars.


title:
The Light Curve of Supernova 1987A: The Structure of the Presupernova
  and Radioactive Nickel Mixing

abstract:
  We have studied the influence of the presupernova structure and the degree of
Ni-56 mixing on the bolometric light curve of SN 1987A in terms of radiation
hydrodynamics in the one-group approximation by abandoning LTE and by taking
into account nonthermal ionization and the contribution of spectral lines to
opacity. Our study shows that moderate Ni-56 mixing at velocities of < 2500
km/s can explain the observed light curve if the density of the outer layers of
the presupernova exceeds the value obtained in the evolutionary model of a
single nonrotating star severalfold. Abandoning LTE and allowing for nonthermal
ionization when solving the equation of state and calculating the mean
opacities and the thermal emission coefficient leads to a significant
difference between the gas temperature and the radiation temperature in the
optically thin layers of the supernova envelope. We demonstrate the fundamental
role of the contribution of spectral lines to the opacity in an expanding
envelope and of the accurate description of radiative transfer in reproducing
the observed shape of the bolometric light curve. We have found that
disregarding the contribution of spectral lines to the opacity introduces an
error of 20% into the explosion energy, and that a similar error is possible
when determining the mass of the ejected matter. The resonant scattering of
radiation in numerous lines accelerates the outer layers to velocities of 36
000 km/s; this additional acceleration affects the outer layers with a mass of
10^{-6} Msun. Proper calculations of the supernova luminosity require that not
only the delay effects, but also the limb-darkening effects be taken into
account.


title:
The Most Massive Stars in the Local Group: Measuring Accurate Masses of
  Stars in Eclipsing Binaries

abstract:
  Accurate masses and, in general, all fundamental parameters of distant stars
can only be measured in eclipsing binaries. Several massive star candidates
with masses near 200 Mo exist, however they have large uncertainties associated
with them. The most massive binary ever measured accurately is WR 20a, for
which we present the light curve. Measuring the period and inclination, we
derive masses greater than 80 Mo for each component. Massive binaries are bound
to exist in Local Group galaxies, such as M31 and M33. These can be selected
from their light curves, obtained by variability studies, such as the DIRECT
project. We present photometry and spectroscopy of the detached system M33A,
for which we are obtaining a direct distance determination. The DIRECT project
has detected several candidate massive binaries which are brighter but
non-detached systems, perhaps similar to WR 20a. We plan to obtain spectra for
them and measure their masses.


title: On the Rotation of Post-T Tauri Stars in Associations

abstract:
  Nearby associations are excellent objects for the study of the initial spin
up phase during the PMS evolution. An empirical approach is adopted here to
infer their rotations properties and relations to X-ray emission. Three nearby
associations are considered. The TW Hya association with an age of 8 Myr, the
Beta Pictoris moving group with 12 Myr and a combination of Tucana and
Horologium associations (30 Myr). Two low and high rotation modes are
considered for each association with stellar masses less than 1.5M and greater
than 1.5M respectively. We infer representative equatorial rotation velocities
Vo from the observed distribution of projected rotational velocities vsini. A
spin up is found for the high rotation mode, whereas in the low rotation mode
the Vo do not increase significantly. This insufficient increase of Vo is
probably the cause of a decrease of the total mean specific angular momentum
for the low mass stars between 8 and 30 Myr. However, for the high mass stars,
where a sufficient spin up is present, the specific angular momentum is
practically conserved in this same time interval. By supposing that the
distribution of masses of these three associations follows a universal mass
function, we estimate the number of members of these associations that remain
to be detected. The analysis of rotation and stellar masses using luminosity
X-rays indicators present similar properties, as the dependence on stellar mass
and rotation, at least for the younger associations, to those obtained for T
Tauri stars in the ONC. A strong desaturation effect appears at 30 Myr. This
effect seems to be provoked by the minimum configuration of the stellar
convection layers, attained for the first time for the higher mass stars at 30
Myr. The desaturation appears to be independent of rotation at this stage.


title:
The Distribution of Ly-alpha-Emitting Galaxies at z=2.38: Paper 2,
  Spectroscopy

abstract:
  In Paper 1 of this series we identified an 80 co-moving Mpc filament of
candidate Lyman-alpha emitting galaxies at redshift 2.38. In this paper we
present spectroscopy of the 37 galaxy candidates. Our spectroscopy reached a
surface brightness limit of 5.0E-17 erg/cm^2/s/arcsec^2. Of the 14 candidates
down to this limit, 12 were confirmed to be Lyman-alpha emitting galaxies at
the filament redshift. We also obtained spectral confirmation for six of the
lower surface brightness candidates, all of which also lay at the filament
redshift. In addition, we identify a foreground cluster of QSOs at z=1.65.


title:
On the constraining observations of the dark GRB 001109 and the
  properties of a z = 0.398 radio selected starburst galaxy contained in its
  error box

abstract:
  We present optical and NIR (near infrared) follow up observations of the GRB
001109 from 1 to 300 days after the burst. No transient emission was found at
these wavelengths within this GRB's (Gamma Ray Burst) 50" radius BeppoSAX error
box. Strong limits (3 sigma) are set with: R >~ 21, 10.2 hr after the GRB; I >~
23, 11.4 hr after the GRB; H >~ 20.7, 9.9 hr after the GRB; and Ks >~ 20, 9.6
hours after the GRB. We discuss whether the radio source found in the GRB's
error box (Taylor et al. 2000) might be related to the afterglow. We also
present a multiwavelength study of a reddened starburst galaxy, found
coincident with the potential radio and the X ray afterglow. We show that our
strong I band upper limit makes of the GRB 001109 the darkest one localised by
the BeppoSAX's NFI (Narrow Field Instrument), and it is one of the most
constraining upper limits on GRB afterglows to date. Further to it, the
implications of these observations in the context of dark GRBs are considered.


title:
Black hole mass and accretion rate of active galactic nuclei with
  double-peaked broad emission lines

abstract:
  (Abridged) Using an empirical relation between the broad line region size and
optical continuum luminosity, we estimated the black hole mass and accretion
rate for 135 AGNs with double-peaked broad emission lines in two samples. With
black hole masses from $3\times 10^7M_\odot$ to $5\times 10^9M_\odot$, these
AGNs have the dimensionless accretion rates (Eddington ratios) between 0.001
and 0.1, and the bolometric luminosity between $10^{43}erg/s$ and
$10^{46}erg/s$, both being significantly larger than those of several
previously known low-luminosity double-peaked AGNs. The optical-X-ray spectra
indices, $\alpha_{OX}$, of these high-luminosity double-peaked AGNs is between
1 and 1.9. Modest correlations of the $\alpha_{OX}$ value with the Eddington
ratio and bolometric luminosity indicate that double-peaked AGNs with higher
Eddington ratio or higher luminosity tend to have larger $\alpha_{OX}$ value.
Therefore we suggested that the accretion process in some high-luminosity
double-peaked AGNs is probably different from that of low-luminosity objects
where an ADAF-like accretion flow was thought to exist. This is also supported
by the presence of possible big blue bumps in the spectra of some double-peaked
AGNs with higher Eddington ratios. We noticed that the prototype double-peaked
emission line AGN, Arp 102B, may be an ``intermediate'' object between the high
and low luminosity double-peaked AGNs. In addition, we found an apparent strong
anti-correlation between the peak separation of double-peaked profile and
Eddington ratio. If it is real, it may provide us a clue to understand why
double-peaked broad emission lines were hardly found in luminous AGNs with
Eddington ratio larger than 0.1.


title: The Shape of the Milky Way Halo and the Satellite Tidal Tails

abstract:
  The dwarf galaxies orbiting a main galaxy suffer strong tidal forces produced
by its dark halo. As a consequence, substructures and tidal tails could appear
in the satellites. These structures could give us information about the dark
matter content of the main and the dwarf galaxies. The Milky Way satellites,
because of their proximity, are a good sample to study the effects of the tidal
forces. The shape of the Milky Way potential could be inferred from the
observational data of the tidal tails of its satellites. The Sagittarius dwarf
is one of the most interesting satellites as it presents a long tidal tail that
covers a wide angle on the sky with a large variation of heliocentric distance
along the stream.


title:
Searches of stellar mass dark matter from an analysis of variabilities
  of high red-shifted QSOs

abstract:
  We consider a contribution of microlensing to the X-ray variability of
high-redshifted QSOs. Such an effect could be caused by stellar mass objects
(SMO) located in a bulge or/and in a halo of this quasar as well as at
cosmological distances between an observer and a quasar. Cosmologically
distributed gravitational microlenses could be localized in galaxies (or even
in bulge or halo of gravitational macrolenses) or could be distributed in a
uniform way. We have analyzed both cases of such distributions. As a result of
our analysis, we obtained that the optical depth for microlensing caused by
stellar mass objects is usually small for quasar bulge and quasar halo
gravitational microlens distributions. On the other hand, the optical depth for
gravitational microlensing caused by cosmologically distributed deflectors
could be significant and could reach 0.01 - 0.1 at z ~ 2. This means that
cosmologically distributed deflectors may contribute significantlly to the
X-ray variability of high-redshifted QSOs (z > 2). Considering that the upper
limit of the optical depth (~ 0.1) corresponds to the case where dark matter
forms cosmologically distributed deflectors, observations of the X-ray
variations of unlensed QSOs can be used for the estimation of the dark matter
fraction of microlenses.


title:
Transport and mixing in the radiation zones of rotating stars:
  I-Hydrodynamical processes

abstract:
  The purpose of this paper is to improve the modelization of the rotational
mixing which occurs in stellar radiation zones, through the combined action of
the thermally driven meridional circulation and of the turbulence generated by
the shear of differential rotation. The turbulence is assumed to be
anisotropic, due to the stratification, with stronger transport in the
horizontal directions than in the vertical. The main difference with the former
treatments by Zahn (1992) and Maeder & Zahn (1998) is that we expand here the
departures from spherical symmetry to higher order, and include explicitly the
differential rotation in latitude, to first order. This allows us to treat
simultaneously the bulk of a radiation zone and its tachocline(s). Moreover, we
take fully into account the non-stationarity of the problem, which will enable
us to tackle the rapid phases of evolution. The system of partial differential
equations, which govern the transport of angular momentum, heat and chemical
elements, is written in a form which makes it ready to implement in a stellar
evolution code. Here the effect of a magnetic field is deliberately ignored; it
will be included in forthcoming papers.


title: Galaxy dynamics with the Planetary Nebula Spectrograph

abstract:
  The Planetary Nebula Spectrograph is a dedicated instrument for measuring
radial velocity of individual Planetary Nebulae (PNe) in galaxies. This new
instrument is providing crucial data with which to probe the structure of dark
halos in the outskirts of elliptical galaxies in particular, which are
traditionally lacking of easy interpretable kinematical tracers at large
distance from the center. Preliminary results on a sample of intermediate
luminosity galaxies have shown little dark matter within 5 ~ R_eff implying
halos either not as massive or not as centrally concentrated as CDM predicts
(Romanowsky et al. 2003). We briefly discuss whether this is consistent with a
systematic trend of the dark matter content with the luminosity as observed in
an extended sample of early-type galaxies.


title: Long Term Behavior of X-ray Pulsars in the Small Magellanic Cloud

abstract:
  Results of a 4 year monitoring campaign of the SMC using the Rossi X-ray
timing Explorer (RXTE) are presented. This large dataset makes possible
detailed investigation of a significant sample of SMC X-ray binaries. 8 new
X-ray pulsars were discovered and a total of 20 different systems were
detected. Spectral and timing parameters were obtained for 18. In the case of
10 pulsars, repeated outbursts were observed, allowing determination of
candidate orbital periods for these systems. We also discuss the spatial and
pulse period distributions of the SMC pulsars.


title: A Supernova Factory in the Merger System Arp 299

abstract:
  We have imaged the nearby galaxy merger Arp 299 at arcsecond and
milliarcsecond resolution, using both the Very Large Array and the Very Long
Baseline Array. The large-scale radio emission from the merger contains 5
bright, compact radio sources embedded in diffuse emission, with diameters less
than 200 pc. Supernova rates of 0.1 to 1 per year are required to produce the
VLA-detected radio emission in these sources. Two of the compact VLA radio
sources, designated Source A and Source D, also have been detected and imaged
at milliarcsecond scales. Source A, which is associated with the nucleus of one
of the merging galaxies, contains five milliarcsecond-scale sources, each with
a radio power between 100 and 1000 times that of the Galactic supernova remnant
Cassiopeia A. Four of these have flat or inverted spectra and appear to be
young supernovae. Three of the VLBI-scale sources are located within 10 pc
(projected) of one another, and two are separated by less than 3 pc, indicating
that they all may be within the same super starcluster or complex of such
clusters. The brightest VLBI-scale source, A0, has an extremely inverted
pectrum, with alpha larger than +2 at gigahertz frequencies. It seems to be the
youngest supernova, which has not yet broken out of its circumstellar shell.
The milliarcsecond radio sources within Source A appear to constitute a
upernova factory, confirming the presence of an extreme starburst that peaked
at least a few million years ago.


title:
Far Ultraviolet Observations of the Dwarf Novae SS Aur and RU Peg in
  Quiescence

abstract:
  We have analyzed the Far Ultraviolet Spectrocopic Explorer (FUSE) spectra of
two U Gem-Type dwarf novae, SS Aur and RU Peg, observed 28 days and 60 days
(respectively) after their last outburst. In both systems the FUSE spectra (905
- 1182 A) reveal evidence of the underlying accreting white dwarf exposed in
the far UV. Our grid of theoretical models yielded a best-fitting photosphere
to the FUSE spectra with Teff=31,000K for SS Aur and Teff=49,000K for RU Peg.
This work provides two more dwarf nova systems with known white dwarf
temperatures above the period gap where few are known. The absence of CIII
(1175 A) absorption in SS Aur and the elevation of N above solar suggests the
possibility that SS Aur represents an additional accreting white dwarf where
the surface C/N ratio derives from CNO processing. For RU Peg, the modeling
uncertainties prevent any reliable conclusions about the surface abundances and
rotational velocity.


title: Modeling the Circumstellar Disk of $\zeta$ Tauri

abstract:
  We present a model for the disk of the classical Be star $\zeta$ Tauri. The
model consists of a Keplerian rotating disk with a power-law surface density
and a vertical density distribution that follows from the balance between the
thermal gas pressure and the z-component of the stellar gravitation. The
opening angle of such a disk is not a fixed value but increases with the
distance to the star (flared disk). We use a Monte Carlo code that solves
simultaneously the thermal equilibrium, the statistical equilibrium and the
hydrostatic equilibrium equations. The result is a self-consistent solution for
the electron temperature, level populations and gas density distribution. It
follows from this model that the only free parameter is the disk density. All
other parameters (e.g. shape of the disk surface) are self-consistently
calculated given the disk density. In this paper we present a successful fit
for $\zeta$ Tauri data using this model.


title: Photometric Identification of Cool White Dwarfs

abstract:
  We investigate the use of a narrow-band DDO51 filter for photometric
identification of cool white dwarfs. We report photometric observations of 30
known cool white dwarfs with temperatures ranging from 10,000 K down to very
cool temperatures (<3500 K). Follow-up spectroscopic observations of a sample
of objects selected using this filter and our photometric observations show
that DDO51 filter photometry can help select cool white dwarf candidates for
follow-up multi--object spectroscopy by rejecting 65% of main sequence stars
with the same broad--band colors as the cool white dwarfs. This technique is
not selective enough to efficiently feed single--object spectrographs. We
present the white dwarf cooling sequence using this filter. Our observations
show that very cool white dwarfs form a sequence in the r-DDO vs. r-z
color--color diagram and demonstrate that significant improvements are needed
in white dwarf model atmospheres.


title: Analysis of the Spatial Distribution of Galaxies by Multiscale Methods

abstract:
  Galaxies are arranged in interconnected walls and filaments forming a cosmic
web encompassing huge, nearly empty, regions between the structures. Many
statistical methods have been proposed in the past in order to describe the
galaxy distribution and discriminate the different cosmological models. We
present in this paper results relative to the use of new statistical tools
using the 3D isotropic undecimated wavelet transform, the 3D ridgelet transform
and the 3D beamlet transform. We show that such multiscale methods produce a
new way to measure in a coherent and statistically reliable way the degree of
clustering, filamentarity, sheetedness, and voidedness of a dataset


title:
Pattern Speeds of BIMA-SONG Galaxies with Molecule-Dominated ISMs Using
  the Tremaine-Weinberg Method

abstract:
  We apply the Tremaine-Weinberg method of pattern speed determination to data
cubes of CO emission in six spiral galaxies from the BIMA SONG survey each with
an ISM dominated by molecular gas. We compare derived pattern speeds with
estimates based on other methods, usually involving the identification of a
predicted behavior at one or more resonances of the pattern(s). In two cases
(NGC 1068 and NGC 4736) we find evidence for a central bar pattern speed that
is greater than that of the surrounding spiral and roughly consistent with
previous estimates. However, the spiral pattern speed in both cases is much
larger than previous determinations. For the barred spirals NGC 3627 and NGC
4321, the method is insensitive to the bar pattern speed (the bar in each is
nearly parallel to the major axis; in this case the method will not work), but
for the former galaxy the spiral pattern speed found agrees with previous
estimates of the bar pattern speed, suggesting that these two structures are
part of a single pattern. For the latter, the spiral pattern speed found is in
agreement with several previous determinations. For the flocculent spiral NGC
4414 and the ``Evil Eye'' galaxy NGC 4826, the method does not support the
presence of a large-scale coherent pattern. We also apply the method to a
simulated barred galaxy in order to demonstrate its validity and to understand
its sensitivity to various observational parameters. In addition, we study the
results of applying the method to a simulated, clumpy axisymmetric disk with no
wave present. The TW method in this case may falsely indicate a well-defined
pattern.


title: The far-infrared spectrum of Arp 220

abstract:
  ISO/LWS grating observations of the ultraluminous infrared galaxy Arp 220
shows absorption in molecular lines of OH, H$_2$O, CH, NH, and NH$_3$, as well
as in the [O I] 63 $\mu$m line and emission in the [C II] 158 $\mu$m line. We
have modeled the continuum and the emission/absorption of all observed features
by means of a non-local radiative transfer code. The continuum from 25 to 1300
$\mu$m is modeled as a warm (106 K) nuclear region that is optically thick in
the far-infrared, attenuated by an extended region (size 2$''$) that is heated
mainly through absorption of nuclear infrared radiation. The molecular
absorption in the nuclear region is characterized by high excitation due to the
high infrared radiation density. The OH column densities are high toward the
nucleus and the extended region. The H$_2$O column density is also high toward
the nucleus and lower in the extended region. The column densities in a halo
are similar to what are found in the diffuse clouds toward Sgr B2 near the
Galactic Center. Most notable are the high column densities found for NH and
NH$_3$ toward the nucleus, with values of $\sim1.5\times10^{16}$ cm$^{-2}$ and
$\sim3\times10^{16}$ cm$^{-2}$, respectively. A combination of PDRs in the
extended region and hot cores with enhanced \hdo photodissociation and a
possible shock contribution in the nuclei may explain the relative column
densities of OH and \hdo, whereas the nitrogen chemistry may be strongly
affected by cosmic ray ionization. The [C II] 158 $\mu$m line is well
reproduced by our models and its ``deficit'' relative to the CII/FIR ratio in
normal and starburst galaxies is suggested to be mainly a consequence of the
dominant non-PDR component of far-infrared radiation, although our models alone
cannot rule out extinction effects in the nuclei.


title: The Effect of Hot Gas in WMAP's First Year Data

abstract:
  By cross-correlating templates constructed from the 2 Micron All Sky Survey
(2MASS) Extended Source (XSC) catalogue with WMAP's first year data, we search
for the thermal Sunyaev-Zel'dovich signature induced by hot gas in the local
Universe. Assuming that galaxies trace the distribution of hot gas, we select
regions on the sky with the largest projected density of galaxies. Under
conservative assumptions on the amplitude of foreground residuals, we find a
temperature decrement of -35 $\pm$ 7 $\mu$K ($\sim 5\sigma$ detection level,
the highest reported so far) in the $\sim$ 26 square degrees of the sky
containing the largest number of galaxies per solid angle. We show that most of
the reported signal is caused by known galaxy clusters which, when convolved
with the average beam of the WMAP W band channel, subtend a typical angular
size of 20--30 arcmins. Finally, after removing from our analyses all pixels
associated with known optical and X-ray galaxy clusters, we still find a tSZ
decrement of -96 $\pm$ 37 $\mu$K in pixels subtending about $\sim$ 0.8 square
degrees on the sky. Most of this signal is coming from five different cluster
candidates in the Zone of Avoidance (ZoA), present in the Clusters In the ZoA
(CIZA) catalogue. We found no evidence that structures less bound than clusters
contribute to the tSZ signal present in the WMAP data.


title: On the Stability of Test Particles in Extrasolar Multiple Planet Systems

abstract:
  We present results of extensive numerical studies of the stability of
non-interacting particles in the planetary systems of stars Upsilon Andromedae,
GJ 876, 47 UMa, and 55 Cancri. We discuss the possibility of the existence of
islands of stability and/or instability at different regions in these
multi-body systems, and their probable correspondence to certain mean-motion
resonances. The results of our study may be applied to questions concerning the
stability of terrestrial planets in these systems and also the trapping of
particles in resonances with the planets.


title: Dust Depletion and Extinction in a Gamma-Ray Burst Afterglow

abstract:
  We put stringent constraints for the first time on the dust properties in the
circumburst medium of a gamma-ray burst (GRB) afterglow. This is based on the
optical spectrum of GRB 020813 (z=1.255), obtained with Keck I LRIS 4.65 h
after the burst. From the absorption lines in the spectrum, we derive very high
column densities for six heavy elements with different refractory properties.
The relative abundances resemble the dust depletion patterns in the Milky Way,
from which we infer a visual extinction of A_V=0.4 and A_V>0.3 at 95%
confidence level. However, the high columns of metals and dust contrast with an
observed UV continuum spectrum that is remarkably close to a power law of the
form F_nu \propto nu^{-0.9}, with no sign of curvature, or a 2200 A extinction
feature, suggesting low reddening. The Milky Way or Magellanic Cloud reddenings
are possible only for very low visual extinctions (A_V<0.08 or A_V<0.2,
respectively at 95% confidence), inconsistent with the A_V values inferred from
the depletion analysis. If we assume a GRB intrinsic spectrum and an extinction
law of the forms F_lambda^i = F_V (5500/lambda)^alpha and A_lambda= A_V
(5500/lambda)^gamma, we obtain (for A_V=0.4) the constraints from continuum
spectrum: gamma<0.85 and alpha<1.72.


title: The masses of the cataclysmic variables AC Cancri and V363 Aurigae

abstract:
  We present time-resolved spectroscopy and photometry of the double-lined
eclipsing cataclysmic variables AC Cnc and V363 Aur (= Lanning 10). There is
evidence of irradiation on the inner hemisphere of the secondary star in both
systems, which we correct for using a model that reproduces the observations
remarkably well. We find the radial velocity of the secondary star in AC Cnc to
be K_R = 176 \pm 3 km/s and its rotational velocity to be v sin i = 135 \pm 3
km/s. From these parameters we obtain masses of M_1 = 0.76 \pm 0.03 M_sun for
the white dwarf primary and M_2 = 0.77 \pm 0.05 M_sun for the K2 \pm 1V
secondary star, giving a mass ratio of q = 1.02 \pm 0.04. We measure the radial
and rotational velocites of the G7 \pm 2V secondary star in V363 Aur to be K_R
= 168 \pm 5 km/s and v sin i = 143 \pm 5 km/s respectively. The component
masses of V363 Aur are M_1 = 0.90 \pm 0.06 M_sun and M_2 = 1.06 \pm 0.11 M_sun,
giving a mass ratio of q = 1.17 \pm 0.07. The mass ratios for AC Cnc and V363
Aur fall within the theoretical limits for dynamically and thermally stable
mass transfer. Both systems are similar to the SW Sex stars, exhibiting
single-peaked emission lines with transient absorption features, high-velocity
S-wave components and phase-offsets in their radial velocity curves. The Balmer
lines in V363 Aur show a rapid increase in flux around phase 0 followed by a
rapid decrease, which we attribute to the eclipse of an optically thick region
at the centre of the disc. This model could also account for the behaviour of
other SW Sex stars where the Balmer lines show only a shallow eclipse compared
to the continuum.


title: Search for Cosmic Strings in CMB Anisotropies

abstract:
  We have searched the 1st-year WMAP W-Band CMB anisotropy map for evidence of
cosmic strings. We have set a limit of $\delta = 8 \pi G \mu / c^2 < 8.2 \times
10^{-6}$ at 95% CL for statistical search for a significant number of strings
in the map. We also have set a limit using the uniform distribution of strings
model in the WMAP data with $\delta = 8 \pi G \mu / c^2 < 7.34 \times 10^{-5}$
at 95% CL. And the pattern search technique we developed here set a limit
$\delta = 8 \pi G \mu / c^2 < 1.54 \times 10^{-5}$ at 95% CL.


title: The ACS Virgo Cluster Survey II. Data Reduction Procedures

abstract:
  The ACS Virgo Cluster Survey is a large program to carry out multi-color
imaging of 100 early-type members of the Virgo Cluster using the Advanced
Camera for Surveys (ACS) on the Hubble Space Telescope. Deep F475W and F850LP
images (~ SDSS g and z) are being used to study the central regions of the
program galaxies, their globular cluster systems, and the three-dimensional
structure of Virgo itself. In this paper, we describe in detail the data
reduction procedures used for the survey, including image registration,
drizzling strategies, the computation of weight images, object detection, the
identification of globular cluster candidates, and the measurement of their
photometric and structural parameters.


title:
Anomalous Fluctuations in Observations of Q0957+561 A,B: Smoking Gun of
  a Cosmic String?

abstract:
  We report the detection of anomalous brightness fluctuations in the multiple
image Q0957+561 A,B gravitational lens system, and consider whether such
anomalies have a plausible interpretation within the framework of cosmic string
theory. We study a simple model of gravitational lensing by an asymmetrical
rotating string. An explicit form of the lens equation is obtained and
approximate relations for magnification are derived. We show that such a model
with typical parameters of the GUT string can quantitatively reproduce the
observed pattern of brightness fluctuations. On the other hand, explanation
involving a binary star system as an alternative cause requires an unacceptably
large massive object at a small distance. We also discuss possible
observational manifestations of cosmic strings within our lens model.


title:
Physics and evolution of obscured X-ray sources: a multiwavelength
  approach

abstract:
  Observations at high energies yield important information on the structure
and nature of AGN; when coupled with deep optical and near-infrared
(photometric and spectroscopic) follow-up, they provide constraints on the mass
of the growing black holes and, therefore, are essential to better understand
the nature of the various components of the X-ray background light and can be
used as test for the accretion paradigm. Conversely, optical and near-infrared
surveys of galaxies are crucial to discriminate between different cosmological
scenarios (e.g. hierarchical or monolithic growth of the structures) and, thus,
to recover the galaxy evolution path.
  In this framework, in the first part of the thesis, I will discuss the main
results from an extensive program of multiwavelength observations of hard X-ray
selected sources serendipitously discovered in XMM-Newton fields over ~1 deg^2
(the HELLAS2XMM survey). With a complementary approach to that of hard X-ray
surveys, in order to investigate the link between nuclear activity and the
galaxy formation, in the second part of the thesis I will present XMM-Newton
and Chandra observations of photometric and spectroscopically selected
Extremely Red Objects (EROs).


title:
Spectroscopy of Very Low Mass Stars and Brown Dwarfs in IC2391: Lithium
  depletion and Halpha emission

abstract:
  We have obtained intermediate-resolution optical spectroscopy of 44 candidate
very low mass members of the nearby young open cluster IC2391. Of these, 26
spectra are totally new, 14 were already analyzed in a previous paper and
another four are in common.
  These spectra, taken at the Cerro Tololo 4-meter and Magellan I and II
telescopes, allow us to confirm 33 of them as likely cluster members, based on
their spectral types, presence of Li, and Halpha emission. Among these new
cluster members is CTIO-160 (M7), the first IC2391 candidate to satisfy all
criteria for being a substellar member of the cluster, including detection of
the Li 6708A doublet. With the enlarged membership, we are able to locate the
lithium depletion boundary of the cluster more reliably than in the past. Based
on comparison to several theoretical models, we derive an age of 50+-5 Myr for
IC2391. We also estimate new ages for the Alpha Per and Pleiades clusters; our
ages are 85+-10 Myr and 130+-20 Myr, respectively. We derive an estimate of the
initial mass function of IC2391 that extends to below the substellar limit, and
compare it to those of other well-studied young open clusters. The index of the
power law mass function for IC2391 is alpha=0.96+-0.12, valid in the range 0.5
to 0.072 M(sun).


title: Plasma Redshift, Time Dilation, and Supernovas Ia

abstract:
  The measurements of the absolute magnitudes and redshifts of supernovas Ia
show that conventional physics, which includes plasma redshift, fully explains
the observed magnitude-redshift relation of the supernovas. The only parameter
that is required is the Hubble constant, which in principle can be measured
independently. The contemporary theory of the expansion of the universe (Big
Bang) requires in addition to the Hubble constant several adjustable
parameters, such as an initial explosion, the dark matter parameter, and a time
adjustable dark energy parameter for explaining the supernova Ia data. The
contemporary Big Bang theory also requires time dilation of distant events as
an inherent premise. The contention is usually that the light curves of distant
supernovas show or even prove the time dilation. In the present article, we
challenge this assertion. We document and show that the previously reported
data in fact indicate that there is no time dilation. The data reported by
Riess et al. in the Astrophysical Journal in June 2004 confirm the plasma
redshift, the absence of time dilation, dark matter, and dark energy.


title:
ISO Observations of the 53W002 Group at 6.7 microns: In Search of the
  Oldest Stellar Populations at z=2.4

abstract:
  We present a deep ISO observation at 6.7 microns of the 53W002 group of
galaxies and AGN at z=2.4. This approximately samples the emitted K band. The
faint, blue star-forming objects are not detected, as expected from their very
blue color across the emitted optical and UV. However, 53W002 itself is
detected at the 3-sigma level, with an emitted V-K color appropriate for a
population formed starting at z=3.6-7.0 with most likely value z=4.7. This fits
with shorter-wavelength data suggesting that the more massive members of this
group, which may all host AGN, began star formation earlier in deeper potential
wells than the compact Lyman-alpha emission objects. Two foreground galaxies
are detected, as well as several stars. One additional 6.7-micron source
closely coincides with an optically faint galaxy, potentially at z=2-3. The
overall source counts are consistent with other ISO deep fields.


title: ANIS: High Energy Neutrino Generator for Neutrino Telescopes

abstract:
  We present the high-energy neutrino Monte Carlo event generator ANIS (All
Neutrino Interaction Simulation). The program provides a detailed and flexible
neutrino event simulation for high-energy neutrino detectors, such as AMANDA,
ANTARES or ICECUBE. It generates neutrinos of any flavor according to a
specified flux and propagates them through the Earth. In a final step neutrino
interactions are simulated within a specified volume. All relevant standard
model processes are implemented. We discuss strengths and limitations of the
program.


title:
A Simple Bipolar Jet Model for the Polarization of Core-Collapse
  Supernovae

abstract:
  We propose a bipolar jet model for supernova polarization. Light from the
main component of the supernova (which we call the bulk supernova for short)
scatters off electrons in the jets and is polarized: this polarized light is
added to the direct emission from the bulk supernova and causes the overall
supernova emission to be polarized. The motivation for the bipolar jet model is
to resolve the potential paradox set by an analysis which suggests strong
spherical symmetry for Type Ib supernovae and the expectation that Type Ib
supernovae should be highly polarized in the continuum up to perhaps about 4 %.
For the model we have derived simple, non-relativistic, approximate analytic
formulae for relative amount of scattered flux and polarization. The
polarization formula qualitatively reproduces two main features observed for at
least some supernovae: (1) the rise to a polarization maximum and then decline
with time; (2) the inverted P Cygni polarization profiles of lines. The model
is strictly axisymmetric and predicts a constant position angle of intrinsic
polarization. Since position angle variation of intrinsic polarization is
observed, the model cannot account for all the polarization of all supernovae.


title: The Stability Analysis of the Extrasolar Planetary Systems

abstract:
  To date, more than 100 giant Jupiter-like planets have been discovered in
Doppler surveys of solar-type stars. In this paper, we perform simulations to
investigate three systems: GJ 876, HD 82943 and 55 Cnc. The former two systems
both have a pair of planets in the 2:1 Mean Motion Resonance (MMR), while the
inner two companions of the later is close to 3:1 MMR. By integrating hundreds
of the planetary orbits of three systems for million years, we find that for GJ
876 and HD 82943, the critical argument $\lambda_{1} - 2\lambda_{2} +
\varpi_{1}$ and $\lambda_{1} - 2\lambda_{2} + \varpi_{2}$ librate about
$0^{\circ}$ or $180^{\circ}$, indicating 2:1 MMR can play an important role in
stabilizing the motion of the planets so that they are protected from frequent
close encounters. As for 55 Cnc, we further show the three resonant arguments
for 3:1 MMR execute librations for millions of years respectively, which
reveals the evidence of the resonance for this system. Additionally, we should
emphasize another vital mechanism is the apsidal phase-locking between a couple
of planets for a certain system. For GJ 876 and HD 82943, we discover the
relative apsidal longitudes $\varpi_{1} - \varpi_{2}$ move about $0^{\circ}$ or
$180^{\circ}$, respectively; but for 55 Cnc, we find that there exists an
asymmetric apsidal libration between two inner planets. Finally, we made a
brief discussion about the Habitable Zones in the exoplanetary systems.


title: Cluster cannibalism and scaling relations of galactic stellar nuclei

abstract:
  Recently, very massive compact stellar systems have been discovered in the
intracluster regions of galaxy clusters and in the nuclear regions of late-type
disk galaxies. It is unclear how these compact stellar systems -- known as
``ultra-compact dwarf'' (UCD) galaxies or ``nuclear clusters'' (NCs) -- form
and evolve. By adopting a formation scenario where these stellar systems are
the product of multiple merging of star clusters in the central regions of
galaxies, we investigate, numerically, their physical properties. We find that
physical correlations between velocity dispersion, luminosity, effective
radius, and average surface brightness in the stellar merger remnants are quite
different from those observed in globular clusters. We also find that the
remnants have triaxial shapes with or without figure rotation, and these shapes
and their kinematics depend strongly on the initial number and distribution of
the progenitor clusters. These specific predictions can be compared with the
corresponding results of ongoing and future observations of UCDs and NCs,
thereby providing a better understanding of the origin of these enigmatic
objects.


title:
Explaining the mysterious age gap of globular clusters in the Large
  Magellanic Cloud

abstract:
  The Large Magellanic Cloud (LMC) has a unique cluster formation history in
that nearly all of its globular clusters were formed either $\sim$ 13 Gyr ago
or less than $\sim$ 3 Gyr ago. It is not clear what physical mechanism is
responsible for the most recent cluster formation episode and thus the
mysterious age gap between the LMC clusters. We first present results of gas
dynamical N-body simulations of the evolution of the LMC in the context of its
Galactic orbit and interactions with the SMC, paying special attention to the
effect of tidal forces. We find that the first close encounter between the LMC
and the Small Magellanic Cloud (SMC) about 4 Gyr ago was the beginning of a
period of strong tidal interaction which likely induced dramatic gas cloud
collisions, leading to an enhancement of the formation of globular clusters
which has been sustained by strong tidal interactions to the present day. The
tidal interaction results in the formation of a barred, elliptical, thick disk
in the LMC. The model also predicts the presence of a large, diffuse stellar
stream circling the Galaxy, which originated from the LMC.