title: A "Baedecker" for the Dark Matter Annihilation Signal

abstract:
  We provide a ``Baedecker'' or travel guide to the directions on the sky where
the dark matter annihilation signal may be expected. We calculate the flux of
high energy gamma-rays from annihilation of neutralino dark matter in the
centre of the Milky Way and the three nearest dwarf spheroidals (Sagittarius,
Draco and Canis Major), using realistic models of the dark matter distribution.
Other investigators have used cusped dark halo profiles (such as the
Navarro-Frenk-White) to claim a significant signal. This ignores the
substantial astrophysical evidence that the Milky Way is not dark-matter
dominated in the inner regions. We show that the annihilation signal from the
Galactic Centre falls by two orders of magnitude on substituting a cored dark
matter density profile for a cusped one. The present and future generation of
high energy gamma-ray detectors, whether atmospheric Cerenkov telescopes or
space missions like GLAST, lack the sensitivity to detect any of the
monochromatic gamma-ray annihilation lines. The continuum gamma-ray signal
above 1 GeV and above 50 GeV may however be detectable either from the dwarf
spheroidals or from the Milky Way itself. If the density profiles of the dwarf
spheroidals are cusped, then the best prospects are for detecting Sagittarius
and Canis Major. However, if the dwarf spheroidals have milder, cored profiles,
then the annihilation signal is not detectable. For GLAST, an attractive
strategy is to exploit the wide field of view and observe the Milky Way at
medium latitudes, as suggested by Stoehr et al. This is reasonably robust
against changes in the density profile.


title:
Ratio of energies radiated in the universe through accretive processes
  and nucleosynthesis

abstract:
  We present here a new determination of the ratio of energies radiated by
active galactic nuclei and by stars and discuss the reasons for the apparently
conflicting results found in previous studies. We conclude that the energy
radiated by accretion processes onto super massive black holes is about 1 to 5%
of the energy radiated by stars. We also estimate that the total mass accreted
on average by a super massive black hole at the centre of a typical 10^11 Msol
galaxy is of about 7 10^7 Msol.


title:
Detection of hard X-ray emission from the Galactic nuclear region with
  INTEGRAL

abstract:
  This letter presents the first results of an observational campaign to study
the Galactic Centre with INTEGRAL. The mosaicked images obtained with the
IBIS/ISGRI coded aperture instrument in the energy ranges 20-40 and 40-100 keV,
give a yet unseen view of the high-energy sources of this region in hard X- and
gamma-rays with an angular resolution of 12 arcmin (FWHM). We report on the
discovery of a source, IGR J17456-2901, coincident with the Galactic Nucleus
SgrA* to within 0.9 arcmin. Located at R.A.(J2000.0) = 17h45m38.5s,
Dec.(J2000.0) = -29:01:15, the source is visible up to about 100 keV with a
20-100 keV luminosity at 8 kpc of (2.89 +/- 0.41) x 10^35 ergs/s. Although the
new INTEGRAL source cannot unequivocally be associated to the Galactic Nucleus,
this is the first report of significant hard X-ray emission from within the
inner 10 arcmin of the Galaxy and a contribution from the galactic supermassive
black hole itself cannot be excluded.


title: Interacting black holes on the brane: the seeding of binaries

abstract:
  We consider the evolution of sub-horizon-sized black holes which are formed
during the high energy phase of the braneworld scenario. These black holes are
long-lived due to modified evaporation and accretion of radiation during the
radiation dominated era. We argue that an initial mass difference between any
two neighbouring black holes is always amplified because of their exchange of
energy with the surrounding radiation. We present a scheme of binary formation
based on mass differences suggesting that such a scenario could lead to
binaries with observable signatures.


title: The angular momentum of dark halos: merger and accretion effects

abstract:
  We present new results on the angular momentum evolution of dark matter
halos. Halos, from N-body simulations, are classified according to their mass
growth histories into two categories: the accretion category contains halos
whose mass has varied continuously and smoothly, while the merger category
contains halos which have undergone sudden and significant mass variations
(greater than 1/3 of their initial mass per event). We observe for the growth
of angular momentum that it continues well into the nonlinear regime, that it
is correlated with mass growth and that it occurs in two phases: a fast
followed by a slow phase. The spin parameter decreases with time for the
accretion catalog whereas slightly increases for the merger catalog, but does
not change when two catalogs are considered together, and furthermore it does
not depend on halo mass or cosmological model. We also develop a simple model
for the formation of a disk galaxy similar to Milky Way, and conclude that our
own halo must have captured satellites in order to acquire the required angular
momentum and to achieve most of the disk around z ~ 1.6. Angular momentum
distribution indicates that at z ~ 1.6 only 22% of the halos have angular
momentum of magnitude comparable to that of disk galaxies in the mass range of
$(0.1-5)*10^{11}$ of solar mass, clearly insufficient to explain the present
observed abundance of these objects.


title: Possible Evidence for MeV Dark Matter In Dwarf Spheroidals

abstract:
  It has been recently proposed that the observed 511 keV emission from the
Galactic bulge could be the product of very light (1-100 MeV) annihilating dark
matter particles. Other possible explanations for this signal are associated
with stellar objects, such as hypernovae. In order to distinguish between
annihilating light dark matter scenario and more conventional astrophysical
sources for the bulge emission, we here propose the study of dwarf spheroidals
such as Sagittarius. These galaxies have typical luminosities of $10^5 L_\odot$
but mass-to-light ratios of $\sim 100$. As there are comparatively few stars,
the prospects for 511 keV emission from standard astrophysical scenarios are
minimal. The dwarf spheroidals do, however, contain copious amounts of dark
matter. INTEGRAL/SPI has observed the Sagittarius region. Analysis of this data
for 511 keV emission will provide a test of MeV dark matter which can
distinguish between annihilating dark matter and more standard astrophysics.
The observation of such a signal from Sagittarius should be a ``smoking gun''
for MeV dark matter.


title:
Stokes imaging, Doppler mapping and Roche tomography of the AM Her
  system V834 Cen

abstract:
  We report on new simultaneous phase resolved spectroscopic and polarimetric
observations of the polar (AM Herculis star) V834 Cen during a high state of
accretion. Strong emission lines and high levels of variable circular and
linear polarization are observed over the orbital period. The polarization data
is modelled using the Stokes imaging technique of Potter et al. The
spectroscopic emission lines are investigated using the Doppler tomography
technique of Marsh and Horne and the Roche tomography technique of Dhillon and
Watson. Up to now all three techniques have been used separately to investigate
the geometry and accretion dynamics in Cataclysmic Variables. For the first
time, we apply all three techniques to simultaneous data for a single system.
This allows us to compare and test each of the techniques against each other
and hence derive a better understanding of the geometry, dynamics and system
parameters of V834 Cen.


title: "Soft X-ray transient" outbursts which aren't soft

abstract:
  We have accumulated multiwavelength (X-ray, optical, radio) lightcurves for
the eight black hole X-ray binaries which have been observed to enter a
supposed `soft X-ray transient' outburst, but remained in the low/hard state
throughout the outburst. Comparison of the lightcurve morphologies, spectral
behaviour, properties of the quasi-periodic oscillations and the radio jet
provides the first study of such objects as a sub-class of X-ray transients.
However rather than assuming that these hard state X-ray transients are
different from the `canonical' soft X-ray transient, we prefer to consider the
possibility that new analysis of both soft and hard state X-ray transients in a
spectral context will provide a model capable of explaining the outburst
mechanisms of (almost) all black hole X-ray binaries.


title: The Shape of the Big Blue Bump as Revealed by Spectropolarimetry

abstract:
  Thermal models for the quasar Big Blue Bump generally lead to bound-free
continuum features, which may be in absorption or emission. Searches for Lyman
edges attributable to quasar atmospheres (in particular accretion disk
atmospheres) have been ambiguous at best, but various relativistic and non-LTE
effects may make them hard to detect.
  The Balmer edge features tentatively predicted by such models might be easier
to detect since they'd form farther out in the potential wells. These can be
sought in certain cases using spectropolarimetry to remove the effects of
atomic emission (i.e. the Small Blue Bump) from the spectrum. We do find
apparent Balmer edges in absorption in several quasars using this method!
Although the features we see are believable and apparently common, more data
and more modeling are needed to verify that they are best interpreted as
atmospheric Balmer edges.


title: Dust enshrouded star-forming activity in Arp 299

abstract:
  We present mid-infrared spectro-imaging (5 - 16 microns) observations of the
infrared luminous interacting system Arp 299 (=Mrk171 =IC694+NGC3690) obtained
with the ISOCAM instrument aboard ISO. Our observations show that nearly 40% of
the total emission at 7 and 15 microns is diffuse, originating from the
interacting disks of the galaxies. Moreover, they indicate the presence of
large amounts of hot dust in the main infrared sources of the system and large
extinctions toward the nuclei. While the observed spectra have an overall
similar shape, mainly composed of Unidentified Infrared Bands (UIB) in the
short wavelength domain, a strong continuum at ~ 13 microns and a deep silicate
absorption band at 10 microns, their differences reveal the varying physical
conditions of each component. For each source, the spectral energy distribution
(SED) can be reproduced by a linear combination of a UIB "canonical" spectral
template and a hot dust continuum due to a 230-300 K black body, after
independently applying an extinction correction to both of them. We find that
the UIB extinction does not vary much throughout the system (A_V ~ 5 mag)
suggesting that most UIBs originate from less enshrouded regions. IC694 appears
to dominate the infrared emission of the system and our observations support
the interpretation of a deeply embedded nuclear starburst located behind an
absorption of about 40 mag. The central region of NGC3690 displays a hard
radiation field characterized by a [NeIII]/[NeII] ratio > 1.8. It also hosts a
strong continuum from 5 to 16 microns which can be explained as thermal
emission from a deeply embedded (A_V ~ 60 mag) compact source, consistent with
the mid-infrared signature of an active galactic nucleus (AGN), and in
agreement with recent X-ray findings.


title: Discreteness effects in cosmological N-body simulations

abstract:
  An estimate of the convergence radius of a simulated CDM halo is obtained
under the assumption that the peak phase-space density in the system is set by
discreteness effects that operate prior to relaxation. The predicted
convergence radii are approximately a factor 2 larger than those estimated for
numerical convergence studies.
  A toy model is used to study the formation of sheets of the cosmic web, from
which DM haloes form later. This model demonstrates the interplay between phase
mixing and violent relaxation that must also be characteristic of spherical
collapse. In the limit that sheets contain arbitrarily many particles, it seems
that power-law profiles are established in both distance and energy. When only
a finite number of particles is employed, relaxation is prematurely terminated
and the power laws are broken. In a given simulation, the sheets with the
highest peak phase-space densities are those that form from the longest waves.
Hence simulations with little small-scale power are expected to form the
cuspiest haloes.


title: NGC 2264 IRS1: The central engine and its cavity

abstract:
  We present a high-resolution study of NGC 2264 IRS1 in CS(2-1) and in the
3-mm continuum using the IRAM Plateau de Bure Interferometer. We complement
these radio data with images taken at 2.2, 4.6, and 11.9 micron. The combined
information allow a new interpretation of the closest environment of NGC 2264
IRS1. No disk around the B-type star IRS1 was found. IRS1 and its low-mass
companions are located in a low-density cavity which is surrounded by the
remaining dense cloud core which has a clumpy shell-like structure. Strong
evidence for induced on-going star formation was found in the surroundings of
IRS1. A deeply embedded very young stellar object 20 arcsec to the north of
IRS1 is powering a highly collimated bipolar outflow. The object 8 in the
closer environment of IRS1 is a binary surrounded by dusty circumbinary
material and powering two bipolar outflows.


title: Nonradial Pulsations in Classical Cepheids of the Magellanic Clouds

abstract:
  We have performed systematic frequency analysis of the LMC Cepheids observed
by OGLE project. Several new types of pulsation behaviour are identified,
including triple-mode and amplitude-modulated double-mode pulsations. In ~10%
of the first overtone Cepheids we find low amplitude secondary periodicities
corresponding to nonradial modes. This is the first evidence for excitation of
nonradial oscillations in Classical Cepheid variables.


title: Far-infrared photometry of deeply embedded outflow sources

abstract:
  We present far-infrared maps and spectroscopy for a number of deeply embedded
protostellar objects (CepE, HH211-MM, IC1396W, L1157, L1211, and RNO15FIR) from
data that we acquired with the ISO instruments PHOT and LWS. Several previously
undetected deeply embedded sources are found in the vicinity of our targets. We
determine temperatures and luminosities of seven objects and locate them on a
Lbol-Tbol diagram - the equivalent to a Hertzsprung-Russell diagram for
protostars. Their masses and ages, according to their location on tracks taken
from our evolutionary model, are derived. L1211 and CepE appear to be
intermediate mass objects which will reach final masses of about 3Mo, while the
other sources are in or below the solar mass range. The derived ages of 15000
to 30000yr are consistent with their current Class0 state. A comparison of the
luminosity of the associated outflows in the 1-0S(1) line of molecular hydrogen
with the source properties (bolometric luminosity, bolometric temperature, and
envelope mass) of 16 Class0 sources shows no statistically significant
correlations. Nevertheless, the data are consistent with a scheme in which the
outflow strength and protostar evolve simultaneously. We show that the
relationship is partially disguised, however, by the local properties of the
surrounding material, the extinction, and short-term flux variability.


title: The Intimate Link Between Accretion and BELR

abstract:
  In this paper I present evidence suggesting that the absence or presence of
Hidden Broad Line Regions (HBLRs) in Seyfert 2 galaxies is regulated by the
rate at which matter accretes onto a central supermassive black hole, in units
of Eddington. I discuss the above findings in the context of a model proposed
by Nicastro (2000), in which the existence of the BLRs is regulated by the disk
accretion rate. For low enough accretion rates, the disk is stable, and the
BLRs do not form.


title: Newtonian Gravity in Theories with Inverse Powers of R

abstract:
  We discuss theories with inverse powers of the Ricci scalar. We find the
exact metric produced by point masses in these theories, and show that the
gravitational force between static objects is consistent with experiments.


title: Month-Timescale Optical Variability in the M87 Jet

abstract:
  A previously inconspicuous knot in the M87 jet has undergone a dramatic
outburst and now exceeds the nucleus in optical and X-ray luminosity.
Monitoring of M87 with the Hubble Space Telescope and Chandra X-ray Observatory
during 2002-2003, has found month-timescale optical variability in both the
nucleus and HST-1, a knot in the jet 0.82'' from the nucleus. We discuss the
behavior of the variability timescales as well as spectral energy distribution
of both components. In the nucleus, we see nearly energy-independent
variability behavior. Knot HST-1, however, displays weak energy dependence in
both X-ray and optical bands, but with nearly comparable rise/decay timescales
at 220 nm and 0.5 keV. The flaring region of HST-1 appears stationary over
eight months of monitoring. We consider various emission models to explain the
variability of both components. The flares we see are similar to those seen in
blazars, albeit on longer timescales, and so could, if viewed at smaller
angles, explain the extreme variability properties of those objects.


title: Chandra and FUSE view of the WHIM: the Local Group and beyond

abstract:
  In this contribution, I review the current observational evidence for the
existence of filaments of Warm-Hot Intergalactic Medium (WHIM). In particular,
I first focus on the controversial issue of the identification of the $z\sim 0$
highly ionized far-ultraviolet (i.e. OVI) and X-ray (i.e. OVII, OVIII and NeIX)
absorbers with either a very tenuous and diffuse WHIM filament, or with much
denser condensations of material at large distances in the Galactic halo. I
then present our recent detection (confidence level $> 3\sigma$) of the OVII
WHIM at $z > 0$ and derive an estimate of the total number of baryons contained
in this hard-to-detect phase of the IGM.


title: Interstellar Ices

abstract:
  Currently ~36 different absorption bands have been detected in the infrared
spectra of cold, dense interstellar and circumstellar environments. These are
attributed to the vibrational transitions of ~17 different molecules frozen on
dust grains. We review identification issues and summarize the techniques
required to extract information on the physical and chemical evolution of these
ices. Both laboratory simulations and line of sight studies are essential.
Examples are given for ice bands observed toward high mass protostars, fields
stars and recent work on ices in disks surrounding low mass protostars. A
number of clear trends have emerged in recent years. One prominent ice
component consists of an intimate mixture between H2O, CH3OH and CO2 molecules.
Apparently a stable balance exists between low temperature hydrogenation and
oxidation reactions on grain surfaces. In contrast, an equally prominent ice
component, consisting almost entirely of CO, must have accreted directly from
the gas phase. Thermal processing, i.e. evaporation and crystallization, proves
to be readily traceable in both these ice components. The spectroscopic
signatures of energetic processing by cosmic rays and high energy photons from
nearby protostars are weaker and not as well understood. A fundamental
limitation in detecting complex, energetically produced (and also some simple)
species is blending of weak features in the spectra of protostars.
Sophisticated techniques are required to extract information from blended
features. We conclude with a summary of key goals for future research and
prospects for observations of ices using future instrumentation, including
SIRTF/IRS.


title:
Numerical simulations of expanding supershells in dwarf irregular
  galaxies. I. Application to Holmberg I

abstract:
  Numerical hydrodynamical modelling of supernova-driven shell formation is
performed with a purpose to reproduce a giant HI ring (diameter 1.7 kpc) in the
dwarf irregular galaxy Holmberg I (Ho I). We find that the contrast in HI
surface density between the central HI depression and the ring is sensitive to
the shape of the gravitational potential. This circumstance can be used to
constrain the total mass (including the dark matter halo) of nearly face-on
dwarf irregulars. We consider two models of Ho I, which differ by an assumed
mass of the dark matter halo M_h. The contrast in HI surface density between
the central HI depression and the ring, as well as the lack of gas expansion in
the central hole, are better reproduced by the model with a massive halo of
M_h=6.0*10^9 M_sun than by that with a small halo of M_h=4.0*10^8 M_sun,
implying that Ho I is halo-dominated. Assuming the halo mass of 6.0*10^9 M_sum,
we determine the mechanical energy required to form the observed ring equal to
(3.0 +- 0.5)*10^53 ergs, equivalent 300+-50 Type II supernovae. The inclination
of Ho I is constrained to 15-20 degrees by comparing the modelled HI spectrum
and channel maps with those observed.


title: An extragalactic supernebula confined by gravity

abstract:
  Little is known about the origins of the giant star clusters known as
globular clusters. How can hundreds of thousands of stars form simultaneously
in a volume only a few light years across the distance of the sun to its
nearest neighbor? Radiation pressure and winds from luminous young stars should
disperse the star-forming gas and disrupt the formation of the cluster.
Globular clusters in our Galaxy cannot provide answers; they are billions of
years old. Here we report the measurement of infrared hydrogen recombination
lines from a young, forming super star cluster in the dwarf galaxy, NGC 5253.
The lines arise in gas heated by a cluster of an estimated million stars, so
young that it is still enshrouded in gas and dust, hidden from optical view. We
verify that the cluster contains 4000-6000 massive, hot "O" stars. Our
discovery that the gases within the cluster are bound by gravity may explain
why these windy and luminous O stars have not yet blown away the gases to allow
the cluster to emerge from its birth cocoon. Young clusters in "starbursting"
galaxies in the local and distant universe may be similarly gravitationally
confined and cloaked from view.


title: The intrinsic intensity modulation of PSR B1937+21 at 1410 MHz

abstract:
  The single-pulse properties of the millisecond radio pulsar PSR B1937+21 are
studied in the 1410 MHz radio band. Aside from occasional ``giant pulses''
occurring in restricted regions of pulse phase, the emission appears to be
remarkably stable, showing no pulse-to-pulse fluctuations other then those
induced by propagation through the interstellar medium. This type of behavior
has not been seen in any other pulsar although it was seen in previous 430 MHz
observations of this source.
  The stability of PSR B1937+21 can be understood in the context of the
sparking gap model of radio pulsar emission. Given the emission properties of
this source at 430 MHz, this model predicts that the emission at all higher
frequencies will be just as stable. Since the stability depends on the outflow
velocity of the emitting plasma, an upper bound may be placed on its Lorentz
factor.


title: Cosmological perturbations from varying masses and couplings

abstract:
  We study the evolution of perturbations during the domination and decay of a
massive particle species whose mass and decay rate are allowed to depend on the
expectation value of a light scalar field. We specialize in the case where the
light field is slow-rolling, showing that during a phase of inhomogeneous
mass-domination and decay the isocurvature perturbation of the light field is
converted into a curvature perturbation with an efficiency which is nine times
larger than when the mass is fixed. We derive a condition on the annihilation
cross section and on the decay rate for the domination of the massive particles
and we show that standard model particles cannot dominate the universe before
nucleosynthesis. We also compare this mechanism with the curvaton model.
Finally, observational signatures are discussed. A cold dark matter
isocurvature mode can be generated if the dark matter is produced out of
equilibrium by both the inflaton and the massive particle species decay.
Non-Gaussianities are present: they are chi-square deviations. However, they
might be too small to be observable.


title: Energy and Angular Momentum Deposition During Common Envelope Evolution

abstract:
  I consider three processes which enhance mass loss rate from a common
envelope of a giant star with a main sequence or a white dwarf companion
spiraling-in inside its envelope. I consider deposition of orbital energy and
orbital angular momentum to the giant's envelope, and in more detail the
formation of jets by an accreting companion and their propagation in the
envelope. I find that in many cases the deposition of orbital angular momentum
to the envelope may be more important to the mass loss process than the
deposition of orbital energy. Jets blown by an accreting companion, in
particular a white dwarf, orbiting inside the outer regions of the giant's
envelope may also dominate over orbital energy deposition at early stage of the
common envelope evolution. These imply that studies which ignore the deposition
of angular momentum to the envelope and the effects of the accreting companion
may reach wrong conclusions.


title: SDSS J1335+0118: A New Two-Image Gravitational Lens

abstract:
  We report the discovery of the two-image gravitationally lensed quasar SDSS
J1335+0118. The object was selected as a lens candidate from the Sloan Digital
Sky Survey. The imaging and spectroscopic follow-up observations confirm that
the system exhibits two gravitationally lensed images of a quasar at z=1.57.
The image separation is 1.56''. We also detect an extended component between
the two quasar images, likely the lensing galaxy. Preliminary mass modeling
predicts the differential time delay \Delta t ~ 30 h^{-1} day assuming the
redshift of the lens galaxy is 0.5.


title:
A continuous population of variable stars up to about 1.5 mag above the
  horizontal branch?

abstract:
  Increasing samples of pulsating variable stars populating the classical
instability strip from the horizontal branch to a few magnitudes brighter are
being found in several Local Group galaxies, irrespective of the galaxy
morphological type. We will review the observational scenario focusing in
particular on the Anomalous Cepheids and related objects.


title: Monte Carlo radiative transfer in molecular cloud cores

abstract:
  We present the results of a three-dimensional Monte Carlo radiative transfer
code for starless molecular cloud cores heated by an external isotropic or
non-isotropic interstellar radiation field. The code computes the dust
temperature distribution inside model clouds with specified but arbitrary
density profiles. In particular we examine in detail spherical (Bonnor-Ebert)
clouds, axisymmetric and non-axisymmetric toroids, and clouds heated by an
external stellar source in addition to the general interstellar field. For
these configurations, the code also computes maps of the emergent intensity at
different wavelengths and arbitrary viewing angle, that can be compared
directly with continuum maps of prestellar cores. In the approximation where
the dust temperature is independent of interactions with the gas and where the
gas is heated both by collisions with dust grains and ionization by cosmic
rays, the temperature distribution of the gas is also calculated. For cloud
models with parameters typical of dense cores, the results show that the dust
temperature decreases monotonically from a maximum value near the cloud's edge
(14-15 K) to a minimum value at the cloud's center (6-7 K). Conversely, the gas
temperature varies in a similar range, but, due to efficient dust-gas coupling
in the inner regions and inefficient cosmic-ray heating in the outer regions,
the gradient is non-monotonic and the gas temperature reaches a maximum value
at intermediate radii. The emission computed for these models (at 350 micron
and 1.3 mm) shows that deviations from spherical symmetry in the density and/or
temperature distributions are generally reduced in the simulated intensity maps
(even without beam convolution), especially at the longer wavelengths.


title: The INTEGRAL/IBIS Scientific Data Analysis

abstract:
  The gamma-ray astronomical observatory INTEGRAL, succesfully launched on 17th
October 2002, carries two large gamma-ray telescopes. One of them is the
coded-mask imaging gamma-ray telescope onboard the INTEGRAL satellite (IBIS)
which provides high-resolution (~ 12') sky images of 29deg x 29deg in the
energy range from 15 keV to 10 MeV with typical on-axis sensitivity of ~ 1
mCrab at 100 keV (3 sigma, 10E6 s exposure). We report here the general
description of the IBIS coded-mask imaging system and of the standard IBIS
science data analysis procedures. These procedures reconstruct, clean and
combine IBIS sky images providing at the same time detection, identification
and preliminary analysis of point-like sources present in the field. Spectral
extraction has also been implemented and is based on simultaneous fitting of
source and background shadowgram models to detector images. The procedures are
illustrated using some of the IBIS data collected during the inflight
calibrations and present performance is discussed. The analysis programs
described here have been integrated as instrument specific software in the
Integral Science Data Center (ISDC) analysis software packages currently used
for the Quick Look, Standard and Off-line Scientific Analysis.


title: HE0107-5240, A Chemically Ancient Star.I. A Detailed Abundance Analysis

abstract:
  We report a detailed abundance analysis for HE0107-5240, a halo giant with
[Fe/H]_NLTE=-5.3. This star was discovered in the course of follow-up
medium-resolution spectroscopy of extremely metal-poor candidates selected from
the digitized Hamburg/ESO objective-prism survey. On the basis of
high-resolution VLT/UVES spectra, we derive abundances for 8 elements (C, N,
Na, Mg, Ca, Ti, Fe, and Ni), and upper limits for another 12 elements. A
plane-parallel LTE model atmosphere has been specifically tailored for the
chemical composition of {\he}. Scenarios for the origin of the abundance
pattern observed in the star are discussed. We argue that HE0107-5240 is most
likely not a post-AGB star, and that the extremely low abundances of the
iron-peak, and other elements, are not due to selective dust depletion. The
abundance pattern of HE0107-5240 can be explained by pre-enrichment from a
zero-metallicity type-II supernova of 20-25M_Sun, plus either self-enrichment
with C and N, or production of these elements in the AGB phase of a formerly
more massive companion, which is now a white dwarf. However, significant radial
velocity variations have not been detected within the 52 days covered by our
moderate-and high-resolution spectra. Alternatively, the abundance pattern can
be explained by enrichment of the gas cloud from which HE0107-5240 formed by a
25M_Sun first-generation star exploding as a subluminous SNII, as proposed by
Umeda & Nomoto (2003). We discuss consequences of the existence of HE0107-5240
for low-mass star formation in extremely metal-poor environments, and for
currently ongoing and future searches for the most metal-poor stars in the
Galaxy.


title:
Chandra and XMM-Newton Observations of NGC 4214: The Hot Interstellar
  Medium and the Luminosity Function of Dwarf Starbursts

abstract:
  We present results from Chandra and XMM-Newton X-ray observations of NGC
4214, a nearby dwarf starburst galaxy containing several young regions of very
active star-formation. Starburst regions are known to be associated with
diffuse X-ray emission, and in this case the X-ray emission from the galaxy
shows an interesting morphological structure within the galaxy, clearly
associated with the central regions of active star-formation. Of the two main
regions of star-formation in this galaxy, X-ray emission associated with the
older is identified whereas little is detected from the younger, providing an
insight into the evolutionary process of the formation of superbubbles around
young stellar clusters. The spectra of the diffuse emission from the galaxy can
be fitted with a two temperature component thermal model with kT=0.14keV and
0.52keV, and analysis of this emission suggests that NGC 4214 will suffer a
blow-out in the future.
  The point source population of the galaxy has an X-ray luminosity function
with a slope of -0.76. This result, together with those for other dwarf
starburst galaxies (NGC 4449 and NGC 5253), was added to a sample of luminosity
functions for spiral and starburst galaxies. The slope of the luminosity
function of dwarf starbursts is seen to be similar to that of their larger
counterparts and clearly flatter than those seen in spirals. Further
comparisons between the luminosity functions of starbursts and spiral galaxies
are also made.


title: Linear and non-linear perturbations in dark energy models

abstract:
  I review the linear and second-order perturbation theory in dark energy
models with explicit interaction to matter in view of applications to N-body
simulations and non-linear phenomena. Several new or generalized results are
obtained: the general equations for the linear perturbation growth; an
analytical expression for the bias induced by a species-dependent interaction;
the Yukawa correction to the gravitational potential due to dark energy
interaction; the second-order perturbation equations in coupled dark energy and
their Newtonian limit. I also show that a density-dependent effective dark
energy mass arises if the dark energy coupling is varying.


title:
The INTEGRAL IBIS/ISGRI System Point Spread Function and Source Location
  Accuracy

abstract:
  The imager on board INTEGRAL (IBIS) presently provides the most detailed sky
images ever obtained at energies above 30 keV. The telescope is based on a
coded aperture imaging system which allows to obtain sky images in a large
field of view 29deg x 29deg with an angular resolution of 12'. The System Point
Spread Function of the telescope and its detailed characteristics are here
described along with the specific analysis algorithms used to derive the
accurate point-like source locations. The derived location accuracy is studied
using the first in-flight calibration data on strong sources for the IBIS/ISGRI
system. The dependence of the calibrated location accuracy with the signal to
noise ratio of the sources is presented. These preliminary studies demonstrate
that the IBIS/ISGRI telescope and the standard scientific analysis software
allow source localizations with accuracy at 90% confidence level better than 1'
for sources with signal to noise ratios > 30 over the whole field of view, in
agreement with the expected performances of the instrument.


title:
The Deuterium-to-Hydrogen Ratio in a Low-Metallicity Cloud Falling onto
  the Milky Way

abstract:
  Using Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope
observations of the QSO PG1259+593, we detect D I Lyman-series absorption in
high velocity cloud Complex C, a low-metallicity gas cloud falling onto the
Milky Way. This is the first detection of atomic deuterium in the local
universe in a location other than the nearby regions of the Galactic disk. A
new Westerbork Synthesis Radio Telescope (WSRT) interferometer map of the H I
21 cm emission toward PG1259+593 indicates that the sight line passes through a
compact concentration of neutral gas in Complex C. We find D/H =
(2.2+/-0.7)x10^-5, O/H = (8.0+/-2.5)x10^-5, and D/O = 0.28+/-0.12. The
metallicity of Complex C gas toward PG1259+593 is approximately 1/6 solar, as
inferred from the oxygen abundance [O/H] = -0.79 (+0.12, -0.16). While we
cannot rule out a value of D/H similar to that found for the local ISM, we can
confidently exclude values as low as those determined recently for extended
sight lines in the Galactic disk. Combined with the sub-solar metallicity
estimate and the low nitrogen abundance, this conclusion lends support to the
hypothesis that Complex C is located outside the Milky Way, rather than inside
in material recirculated between the Galactic disk and halo. The value of D/H
for Complex C is consistent with the primordial abundance of deuterium inferred
from recent Wilkinson Microwave Anisotropy Probe observations of the cosmic
microwave background and simple chemical evolution models that predict the
amount of deuterium astration as a function of metallicity. [Abbreviated
abstract]


title: On the Detectability of the SZ Effect of Massive Young Galaxies

abstract:
  The Sunyaev-Zel'dovich (SZ) effect expected to be associated with massive
star-formation activity produced during the formation of the most luminous
bulges of normal galaxies is discussed. Using 1-D chemohydrodynamical models
for spheroidal galaxy evolution we show that during the early epochs of galaxy
evolution the gas in massive events of star formation may reach temperatures
and densities high enough to produce values of the comptonisation parameter "y"
comparable to those present in galaxy clusters. In this scenario, we discuss
the possibility of detection of the SZ signature in high redshift starforming
galaxies with the next generation of mm telescopes capable of arcsecond
resolution and equipped with high sensitivity detectors. We show how millimeter
colour--colour diagrams or diagnostic diagrams could be used to distinguish
between the dust emission and the SZ effect and suggest the use of simultaneous
multifrequency observations to improve the chances of detecting the SZ effect.


title:
A Study of the Distribution of Star-Forming Regions in Luminous Infrared
  Galaxies by Means of H$\alpha$ Imaging Observations

abstract:
  We performed H-alpha imaging observations of 22 luminous infrared galaxies to
investigate how the distribution of star-forming regions in these galaxies is
related to galaxy interactions. Based on correlation diagrams between H-alpha
flux and continuum emission for individual galaxies, a sequence for the
distribution of star-forming regions was found: very compact (~100 pc) nuclear
starbursts with almost no star-forming activity in the outer regions (type 1),
dominant nuclear starbursts < 1 kpc in size and a negligible contribution from
the outer regions (type 2), nuclear starbursts > 1 kpc in size and a
significant contribution from the outer regions (type 3), and extended
starbursts with relatively faint nuclei (type 4). These classes of star-forming
region were found to be strongly related to global star-forming properties such
as star-formation efficiency, far-infrared color, and dust extinction. There
was a clear tendency for the objects with more compact distributions of
star-forming regions to show a higher star-formation efficiency and hotter
far-infrared color. An appreciable fraction of the sample objects were
dominated by extended starbursts (type 4), which is unexpected in the standard
scenario of interaction-induced starburst galaxies. We also found that the
distribution of star-forming regions was weakly but clearly related to galaxy
morphology: severely disturbed objects had a more concentrated distribution of
star-forming regions. This suggests that the properties of galaxy interactions,
such as dynamical phase and orbital parameters, play a more important role than
the internal properties of progenitor galaxies, such as dynamical structure or
gas mass fraction. We also discuss the evolution of the distribution of
star-forming regions in interacting galaxies.


title: Curvature radiation and giant subpulses in the Crab pulsar

abstract:
  It is argued that the nanosecond giant subpulses detected recently in the
Crab pulsar are generated by means of the coherent curvature radiation of
charged relativistic solitons associated with sparking discharges of the inner
gap potential drop above the polar cap.


title:
Convection in protoneutron stars and the structure of surface magnetic
  fields in pulsars

abstract:
  We consider generation and evolution of small-scale magnetic fields in
neutron stars. These fields can be generated by small-scale turbulent dynamo
action soon after the collapse when the proto-neutron star is subject to
convective and neutron finger instabilities. After instabilities stop,
small-scale fields should be frozen into the crust that forms initially at high
density about 10^{14} g/cm^{3} and then spreads to the surface. Because of high
crustal conductivity, magnetic fields with the lengthscale about 1-3 km can
survive in the crust as long as 10-100 Myr and form a sunspot-like structure at
the surface of radiopulsars.


title: Quasi-Periodic Changes in the Parsec-Scale Jet of 3C345

abstract:
  We have observed the QSO 3C345 with VSOP at 1.6GHz and 5GHz and with the VLBA
at 22GHz and 43GHz, with 24 epochs in total, from 1997.40 to 1999.69. This
study, combined with previous observations, reveals periodic changes in the
parsec-scale jet. This quasi-periodicity can be found in the initial position
angles, the trajectories and the flux density evolution of the jet components,
with a period of about 9 years. This period should reflect the dynamics of the
material in the central region of 3C345 and it is possibly related to a
putative binary black hole in the center of this object.


title: A double-lined spectroscopic orbit for the young star HD 34700

abstract:
  We report high-resolution spectroscopic observations of the young star HD
34700, which confirm it to be a double-lined spectroscopic binary. We derive an
accurate orbital solution with a period of 23.4877 +/- 0.0013 days and an
eccentricity of e = 0.2501 +/- 0.0068. The stars are found to be of similar
mass (M2/M1 = 0.987 +/- 0.014) and luminosity. We derive also the effective
temperatures (5900 K and 5800 K) and projected rotational velocities (28 km/s
and 22 km/s) of the components. These values of v sin i are much higher than
expected for main-sequence stars of similar spectral type (G0), and are not due
to tidal synchronization. We discuss also the indicators of youth available for
the object. Although there is considerable evidence that the system is young
--strong infrared excess, X-ray emission, Li I 6708 absorption (0.17 Angstroms
equivalent width), H alpha emission (0.6 Angstroms), rapid rotation-- the
precise age cannot yet be established because the distance is unknown.


title: Starbursts and Extra-planar H-alpha from SINGG

abstract:
  The NOAO Survey for Ionization in Neutral Gas Galaxies (SINGG) is the largest
star formation survey of an HI selected sample. Since the selection is made
without regard to optical morphology, it is not biased toward or against
"interesting" types of galaxies; thus SINGG is an ideal sample for studying
galaxy demographics. Of a sample of 90 extra-galactic sources observed in
photometric conditions, all are detected in H-alpha. This indicates that
dormant galaxies, those containing an appreciable ISM but no star formation,
are at best rare. We have made first pass morphological surveys for starbursts,
as judged by H-alpha surface brightness, and outflows as judged by extra-planar
H-alpha. We find that about 15% of the sources contain starbursts, with little
dependence on the neutral hydrogen mass MHI. Nearly one half of a sample ~35
edge-on galaxies show evidence for extra-planar H-alpha having a scale size of
0.5 Kpc or larger, while nearly one quarter have extra-planar H-alpha features
1.0 Kpc in size or larger. There is a hint that high MHI systems preferentially
have displaced outflows (chimneys, or fountains) while central outflows
(galactic winds) preferentially occur in low MHI systems. However, a larger
sample (e.g. the full SINGG survey) is needed to confirm this trend.


title:
Decomposition of the Visible and Dark Matter Mass Profiles in the
  Einstein Ring 0047-2808

abstract:
  Using our semi-linear inversion method, we measure the mass profile of the
lens galaxy in the Einstein ring system 0047-2808. The lens is modelled as a
baryonic component following the observed light, embedded in a dark matter
generalised NFW halo. The semi-linear method makes full use of the information
content in the ring image. We determine an unevolved B-band mass to light ratio
for the baryons of 3.05 +0.45 -0.86 h_65 M_sol/L_sol (95% CL), accounting for
65% of the total projected mass within the radius of 1.16'' traced by the ring.
This result is obtained without need of dynamical measurements. The inner
logarithmic slope of the halo is found to be 0.87 +0.69 -0.61 (95% CL). We find
that the halo is fairly well aligned with the light but has only half the
ellipticity.


title: Watching the Birth of Super Star Clusters

abstract:
  Subarcsecond infrared and radio observations yield important information
about the formation of super star clusters from their surrounding gas. We
discuss the general properties of ionized and molecular gas near young, forming
SSCs, as illustrated by the prototypical young forming super star cluster
nebula in the dwarf galaxy, NGC 5253. This super star cluster appears to have a
gravitationally bound nebula. The lack of molecular gas suggests a very high
star formation efficiency, consistent with the formation of a large, bound star
cluster.


title: Pal 12 As A Part of the Sgr Stream; the Evidence From Abundance Ratios

abstract:
  We present a detailed abundance analysis for 21 elements based on high
dispersion, high spectral resolution Keck spectra for four members of the outer
halo ``young'' Galactic globular cluster Pal 12. All four stars show identical
abundance distributions with no credible indication of any star-to-star
scatter. However, the abundance ratios of the Pal 12 stars are very peculiar.
There is no detected enhancement of the alpha-elements; the mean of [Si/Fe],
[Ca/Fe] and [Ti/Fe] is -0.07\pm0.05 dex, O/Fe is also Solar, while Na is very
deficient. The distribution among the heavy elements shows anomalies as well.
These are inconsistent with those of almost all Galactic globular clusters or
of field stars in the Galaxy. The peculiarities shown by the Pal 12 stars are,
however, in good general agreement with the trends established by by
Smecker-Hane & McWilliam and by Bonifacio et al for stars in the Sgr dSph
galaxy evaluated at the [Fe/H] of Pal 12. This reinforces earlier suggestions
that Pal 12 originally was a cluster in the Sgr dSph galaxy which during the
process of accretion of this galaxy by our own was tidally stripped from the
Sgr galaxy to become part of the extended Sgr stream.


title: The Globular Cluster System of NGC4374

abstract:
  We study the globular cluster system (GCS) of the giant elliptical NGC4374
(M84) in the Virgo cluster using B and R photometry. The colour distribution is
bimodal with peaks at B-R=1.11 and B-R=1.36, fitting well to those found in
other early-type galaxies. The radial profile of the cluster number density is
flatter than the galaxy light. Using the luminosity function we derive a
distance modulus of $\mu=31.61\pm0.2$, which within the uncertainty agrees with
the distance from surface brightness fluctuations. Blue and red clusters show
similar radial concentrations and azimuthal distributions. The total number of
clusters is $N=1775\pm150$, which together with our distance modulus leads to a
specific frequency of $S_{N}=1.6\pm0.3$. This value is surprisingly low for a
giant elliptical, but resembles the case of merger remnants like NGC1316, where
the low specific frequency is probably caused by the luminosity contribution of
an intermediate-age population. A further common property is the high rate of
type Ia supernovae which also may indicate the existence of a younger
population. However, unlike in the case of NGC1316, one cannot find any further
evidence that NGC4374 indeed hosts younger populations. The low specific
frequency would also fit to a S0 galaxy seen face-on.


title: Aberration by gravitational lenses in motion

abstract:
  It is known that a fully relativistic integration of the null geodesics of a
weak perturbation of flat spacetime leads to a correction of order $v/c$ to the
bending angle and time delay due to a gravitational lens in slow motion with
small acceleration. The existence of the $v/c$ correction was verified by the
VLBI experiment of the bending of light by Jupiter on September 8, 2002. Here
the $v/c$ correction is interpreted by means of standard aberration of light in
an optically active medium with an effective index of refraction induced by the
gravitational field of a lens in motion.


title:
Quasi-universal Gaussian jets: a unified picture for gamma-ray bursts
  and X-ray flashes

abstract:
  An observed correlation Ep \propto (E_{iso})^{1/2} extending from Gamma-ray
Bursts (GRBs) to X-ray flashes (XRFs) poses problems both for a power-law
universal jet model where the energy per solid angle decreases as the inverse
square of the angle respect to the jet axis, and for a conical jet model with a
uniform energy density within the jet beam and a sharp energy cut-off at the
jet edge. Here we show that the current GRB-XRF prompt emission/afterglow data
can be understood in terms of a picture in which the GRB-XRF jets are
quasi-universal and structured, with a Gaussian-like or similar structure,
i.e., one where the jet has a characteristic angle, with a mild variation of
energy inside and a rapid (e.g. exponential) decrease of energy outside of it.
A Monte Carlo simulation shows that the current data is compatible with such a
quasi-universal Gaussian jet with a typical opening angle of 5.7(+3.4)(-2.1)
degrees, and with a standard jet energy of about log (E_j/1 erg)= 51.1+-0.3.
According to this model, the true-to-observed number ratio of the whole GRB-XRF
population is about 14 with the current instrumental sensitivity.


title: Obstacles to the Collisional Growth of Planetesimals

abstract:
  The debate over whether kilometer-sized solids, or planetesimals, assemble by
collision-induced chemical sticking or by gravity-driven unstable modes remains
unsettled. In light of recent work showing that gravitational growth can occur
despite turbulent stirring, we critically evaluate the collisional hypothesis.
Impact speeds in protoplanetary disks reach 50 m/s in a laminar disk and may be
larger in turbulent disks. We consider the role of elastic and plastic
deformations, restructuring of "rubble piles," and sticky organic matter.
Coagulation is possible for dust grains with large surface area-to-volume
ratios. Simple energetic arguments show that bouncing, cratering, and
fragmentation should dominate collisional dynamics between millimeter and
kilometer sizes.


title: VLBA observations of z > 4 radio-loud quasars

abstract:
  We present high resolution (< 20 mas) observations of the radio continuum
emission at 1.4 GHz from three high-redshift quasars: J1053-0016 (z=4.29),
1235-0003 (z=4.69), and J0913+5919 (z=5.11), thereby doubling the number of z >
4 radio-loud quasars that have been imaged at mas resolution. The observations
were carried out with the Very Long Baseline Array (VLBA) of the NRAO. All
three sources are unresolved in these observations, with source size limits of
a few mas. In all cases the flux densities measured by the VLBA are within 10%
of those measured with the VLA, implying that the sources are not highly
variable on yearly timescales. We find no indication for multiple images that
might be produced by strong gravitational lensing on scales from 20 mas (VLBA)
to a few arcseconds (VLA), to dynamic range limits of ~100.


title: Pre-Processing of Galaxies before Entering a Cluster

abstract:
  We consider several mechanisms that possibly affect the evolution of disk
galaxies in clusters using analytical models based on a hierarchical clustering
scenario. We especially focus on the evolution of disk galaxies in subclusters
located around a main cluster. We show that ram-pressure stripping cannot be
always ignored in subclusters, although their masses are much smaller than that
of the main cluster. The star-formation rate of a galaxy may gradually decrease
by the stripping of warm gas (`strangulation') in a main cluster. However, we
find that ram-pressure stripping could start before the strangulation is
completed, if a field galaxy directly falls into the main cluster. Since this
conflicts with some recent observations, many galaxies might have been affected
by some environmental effects when they were in subclusters before they fell
into the main cluster (`pre-processing'). We show that strangulation and
evaporation of the cold gas by the surrounding hot ICM in subclusters are the
possible candidates. We also show that the observed morphological
transformation of disk galaxies at z ~< 1 is not chiefly due to galaxy mergers.


title:
NACO Polarimetric Differential Imaging of TW Hya: A Sharp Look at the
  Closest T Tauri Disk

abstract:
  We present high-contrast imaging data on the disk of the classical T Tauri
star TW Hya. The images were obtained through the polarimetric differential
imaging technique with the adaptive optics system NACO. Our commissioning data
show the presence of polarized disk emission between 0.1" and 1.4" from the
star. We derive the first Ks-band radial polarized intensity distribution. We
show that the polarized intensity compares well to shorter wavelengths surface
brightness observations and confirm the previously reported gradual slope
change around 0.8". These results show the potential of the new polarimetric
differential imaging technique at 8m-class telescopes to map the inner regions
of protoplanetary disks.


title:
Extragalactic Large-Scale Structures behind the Southern Milky Way. IV.
  Redshifts Obtained with MEFOS

abstract:
  Abbreviated: As part of our efforts to unveil extragalactic large-scale
structures behind the southern Milky Way, we here present redshifts for 764
galaxies in the Hydra/Antlia, Crux and Great Attractor region (266deg < l <
338deg, |b| < 10deg), obtained with the Meudon-ESO Fibre Object Spectrograph
(MEFOS) at the 3.6-m telescope of ESO. The observations are part of a redshift
survey of partially obscured galaxies recorded in the course of a deep optical
galaxy search behind the southern Milky Way. A total of 947 galaxies have been
observed, a small percentage of the spectra (N=109, 11.5%) were contaminated by
foreground stars, and 74 galaxies (7.8%) were too faint to allow a reliable
redshift determination. With MEFOS we obtained spectra down to the faintest
galaxies of our optical galaxy survey, and hence probe large-scale structures
out to larger distances (v <~ 30000 km/s) than our other redshift follow-ups.
The most distinct large-scale structures revealed in the southern Zone of
Avoidance are discussed in context to known structures adjacent to the Milky
Way.


title: A Galactic O-Star Catalog

abstract:
  We have produced a catalog of 378 Galactic O stars with accurate spectral
classifications which is complete for V<8 but includes many fainter stars. The
catalog provides cross-identifications with other sources; coordinates
(obtained in most cases from Tycho-2 data); astrometric distances for 24 of the
nearest stars; optical (Tycho-2, Johnson, and Stromgren) and NIR photometry;
group membership, runaway character, and multiplicity information; and a
web-based version with links to online services.


title: Modeling of Dust Scattering in the Coalsack

abstract:
  Murthy et. al.(1994) discovered intense UV (1100 \AA) emission from the
directi on of the Coalsack Nebula. We have used their results in conjunction
with a Mon te Carlo model for the scattering in the region to show that the
scattering is from dust in the foreground of the Coalsack molecular cloud. We
have constrained the albedo of the grains to 0.4 $\pm$ 0.1. This is the first
determination of the albedo of dust in the diffuse ISM in the FUV.


title: Ideal kink instability of a magnetic loop equilibrium

abstract:
  The force-free coronal loop model by Titov & D\'emoulin (1999} is found to be
unstable with respect to the ideal kink mode, which suggests this instability
as a mechanism for the initiation of flares. The long-wavelength ($m=1$) mode
grows for average twists $\Phi\ga3.5\pi$ (at a loop aspect ratio of $\approx$
5). The threshold of instability increases with increasing major loop radius,
primarily because the aspect ratio then also increases. Numerically obtained
equilibria at subcritical twist are very close to the approximate analytical
equilibrium; they do not show indications of sigmoidal shape. The growth of
kink perturbations is eventually slowed down by the surrounding potential
field, which varies only slowly with radius in the model. With this field a
global eruption is not obtained in the ideal MHD limit. Kink perturbations with
a rising loop apex lead to the formation of a vertical current sheet below the
apex, which does not occur in the cylindrical approximation.


title:
Formation of current sheets and sigmoidal structure by the kink
  instability of a magnetic loop

abstract:
  We study dynamical consequences of the kink instability of a twisted coronal
flux rope, using the force-free coronal loop model by Titov & D\'emoulin (1999)
as the initial condition in ideal-MHD simulations. When a critical value of the
twist is exceeded, the long-wavelength ($m=1$) kink mode develops. Analogous to
the well-known cylindrical approximation, a helical current sheet is then
formed at the interface with the surrounding medium. In contrast to the
cylindrical case, upward-kinking loops form a second, vertical current sheet
below the loop apex at the position of the hyperbolic flux tube (generalized X
line) in the model. The current density is steepened in both sheets and
eventually exceeds the current density in the loop (although the kink
perturbation starts to saturate in our simulations without leading to a global
eruption). The projection of the field lines that pass through the vertical
current sheet shows an S shape whose sense agrees with the typical sense of
transient sigmoidal (forward or reverse S-shaped) structures that brighten in
soft X rays prior to coronal eruptions. The upward-kinked loop has the opposite
S shape, leading to the conclusion that such sigmoids do not generally show the
erupting loops themselves but indicate the formation of the vertical current
sheet below them that is the central element of the standard flare model.


title:
The Stellar Content of the Southern Tail of NGC 4038/9 and a Revised
  Distance

abstract:
  We have used the Hubble Space Telescope and Wide Field Planetary Camera 2 to
image the putative tidal dwarf galaxy located at the tip of the Southern tidal
tail of NGC 4038/9, the Antennae. We resolve individual stars, and identify two
stellar populations. Hundreds of massive stars are present, concentrated into
tight OB associations on scales of 200 pc, with ages ranging from 2-100 Myr. An
older stellar population is distributed roughly following the outer contours of
the neutral hydrogen in the tidal tail; we associate these stars with material
ejected from the outer disks of the two spirals. The older stellar population
has a red giant branch tip at I=26.5+/-0.2 from which we derive a distance
modulus (m-M)_0=30.7+/-0.25. The implied distance of 13.8+/-1.7 Mpc is
significantly smaller than commonly quoted distances for NGC 4038/9. In
contrast to the previously studied core of the merger, we find no super star
clusters. One might conclude that SSCs require the higher pressures found in
the central regions in order to form, while spontaneous star formation in the
tail produces the kind of O-B star associations seen in dwarf irregular
galaxies. The youngest population in the putative tidal dwarf has a total
stellar mass of ~2x10^5 Msun, while the old population has a stellar mass of
\~7x10^7 Msun. If our smaller distance modulus is correct, it has far-reaching
consequences for this proto-typical merger. Specifically, the luminous to
dynamical mass limits for the tidal dwarf candidates are significantly less
than 1, the central super star clusters have sizes typical of galactic globular
clusters rather than being 1.5 times as large, and the unusually luminous X-ray
population becomes both less luminous and less populous.


title: Air shower fluorescence light simulations

abstract:
  A new approach to simulate fluorescence photons produced in extensive air
showers is described. A Monte Carlo program based on CORSIKA produces the
fluorescence photons for each charged particle in the development of the
shower. This method results in a full three-dimensional simulation of the
particles in a shower and of the fluorescence light generated in the
atmosphere. The photons produced by this program are tracked down to a
telescope and the simulation of a particular detector is applied. The
differences between this method and one-dimensional approaches are
quantitatively determined as a function of the distance between the telescope
and the shower core. As a particular application, the maximum distance at which
the Auger fluorescence telescope might be able to measure the lateral
distribution of a shower is determined as a function of energy.


title: Anisotropy in the Distribution of Satellite Galaxy Orbits

abstract:
  Nearby clusters such as Virgo and Coma possess galaxy distributions which
tend to be aligned with the principal axis of the cluster itself. This has also
been confirmed by a recent statistical analysis of some 300 Abell clusters
where the effect has been linked to the dynamical state of the cluster.
Moreover, the orbits of satellite galaxies in galactic systems like our own
Milky Way also demonstrate a high degree of anisotropy - the so-called Holmberg
effect, the origin of which has been the subject of debate for more than 30
years. This study presents the analysis of cosmological simulations focusing on
the orbits of satellite galaxies within dark matter halos. The apocentres of
the orbits of these satellites are preferentially found within a cone of
opening angle ~40 around the major axis of the host halo, in accordance with
the observed anisotropy found in galaxy clusters. We do, however, note that a
link to the dynamical age of the cluster is not well established as both our
oldest dark matter halos do show a clear anisotropy signal. Further analysis
connects this distribution to the infall pattern of satellites along the
filaments: the orbits are determined rather by the environment of the host halo
than some "dynamical selection" during their life within the host's virial
radius.


title:
Limits on the evolution of galaxies from the statistics of gravitational
  lenses

abstract:
  We use gravitational lenses from the Cosmic Lens All-Sky Survey (CLASS) to
constrain the evolution of galaxies since redshift $z \sim 1$ in the current
$\LCDM$ cosmology. This constraint is unique as it is based on a mass-selected
lens sample of galaxies. Our method of statistical analysis is the same as in
Chae (2003). We parametrise the early-type number density evolution in the form
of $(1+z)^{\nu_n}$ and the velocity dispersion as $(1+z)^{\nu_v}$. We find that
$\nu_n=-0.11^{+0.82}_{-0.89}$ ($1\sigma$) if we assume $\nu_v =0$, implying
that the number density of early-type galaxies is within 50% to 164% of the
present-day value at redshift $z=1$. Allowing the velocity dispersion to
evolve, we find that $\nu_v=-0.4^{+0.5}_{-0.4}$ ($1\sigma$), indicating that
the velocity dispersion must be within 57% and 107% of the present-day value at
$z=1$. These results are consistent with the early formation and passive
evolution of early-type galaxies. More stringent limits from lensing can be
obtained from future large lens surveys and by using very high-redshift quasars
($z \ga 5$) such as those found from the Sloan Digital Sky Survey.


title:
OASIS High-Resolution Integral Field Spectroscopy of the SAURON
  Ellipticals and Lenticulars

abstract:
  We present a summary of high-spatial resolution follow-up observations of the
elliptical (E) and lenticular (S0) galaxies in the SAURON survey using the
OASIS integral field spectrograph. The OASIS observations explore the central
8x10" regions of these galaxies using a spatial sampling four times higher than
SAURON, often revealing previously undiscovered features. Around 75% (31/48) of
the SAURON E/S0s with central velocity dispersion >= 120 km/s were observed
with OASIS, covering well the original SAURON representative sample. We present
here an overview of this follow-up survey, and some preliminary results on
individual objects, including a previously unreported counter-rotating core in
NGC 4382; the decoupled stellar and gas velocity fields of NGC 2768; and the
strong age gradient towards the centre of NGC 3489.


title: A unique small-scale gravitational arc in Abell 1201

abstract:
  We present a snapshot Hubble Space Telescope (HST) image of the galaxy
cluster A1201 (z=0.169), revealing a tangential arc 2arcsec from the brightest
cluster galaxy (BCG). Keck-ESI spectroscopy confirms that the arc is
gravitational in nature and that the source galaxy lies at z=0.451. We
construct a model of the gravitational potential of the cluster that faithfully
reproduces the observed arc morphology. Despite the relaxed appearance of the
cluster in the HST frame, the best fit ellipticity of the total matter
distribution is epsilon_total>0.5, in contrast to the light distribution of the
BCG epsilon_BCG=0.23+/-0.03 on 2'' scales. Further deep optical observations
and pointed X-ray spectro-imaging observations with Chandra are required to
determine whether this elongation is due to a single elongated dark matter
halo, or a more complex distribution of matter in the cluster core. We compare
the arc with a sample drawn from the published literature, and confirm that it
is unique among tangential systems in the small physical scales that it probes
(6kpc). In anticipation of a more thorough investigation of this cluster across
a broad range of physical scales, we use our fiducial lens model to estimate
the projected mass and mass-to-light ratio of the cluster within a radius of
6kpc, obtaining: M=(5.9^+0.9_-0.7)x10^11 M_o, M/L_V=9.4^+2.4_-2.1(M/L)_o.
Overall our results confirm the importance of HST snapshot surveys for
identifying rare lensing constraints on cluster mass distributions. In
combination with follow--up optical and X-ray observations, the arc in A1201
should help to increase our understanding of the physics of cluster cores.


title:
The Spectral Energy Distribution and Emission-Line properties of the
  NLS1 Galaxy Arakelian 564

abstract:
  We present the intrinsic spectral energy distribution (SED) of the NLS1
Arakelian 564, constructed with contemporaneous data obtained during a
multi-wavelength, multi-satellite observing campaign in 2000 and 2001. We
compare it with that of the NLS1 Ton S180 and with those obtained for BLS1s to
infer how the relative accretion rates vary among the Sy1 population. Although
the peak of the SED is not well constrained, most of the energy is emitted in
the 10-100 eV regime, constituting roughly half of the emitted energy in the
optical/X-ray ranges. This is consistent with a primary spectral component
peaking in the extreme UV/soft X-ray band, and disk-corona models, hence high
accretion rates. Indeed, we estimate that \dot{m}~1. We examine the emission
lines in its spectrum, and we constrain the physical properties of the
line-emitting gas through photoionization modeling. The line-emitting gas is
characterized by log n~11 and log U~0, and is stratified around log U~0. Our
estimate of the radius of the H\beta-emitting region ~10 \pm 2 lt-days is
consistent with the radius-luminosity relationships found for Sy1 galaxies. We
also find evidence for super-solar metallicity in this NLS1. We show that the
emission lines are not good diagnostics for the underlying SEDs and that the
absorption line studies offer a far more powerful tool to determine the
ionizing continuum of AGNs, especially if comparing the lower- and
higher-ionization lines.


title: The MAGIC Cherenkov Telescope for gamma ray astronomy

abstract:
  The Major Atmospheric Gamma ray Imaging Cherenkov Telescope (MAGIC) is in
commissioning phase and will start to become fully operative by the end of
2003. Located at El Roque de los Muchachos in La Palma (Canary Islands, Spain),
it has the largest reflector area (17 m diameter) of all the existing Cherenkov
telescopes. New technologies have been used to reduce the energy threshold for
gamma-ray detection to about 30 GeV. Due to its characteristics, the catalog of
very high energy sources will considerably increase with the MAGIC
observations, anticipating exciting results for the near future. An overview of
the telescope, its current status and first results, together with a highlight
of the scientific research is presented.


title: Integral field spectroscopy of QSO host galaxies

abstract:
  We describe a project to study the state of the ISM in ~20 low redshift
(z<0.3) QSO host galaxies observed with the PMAS integral field spectrograph.
We describe method developement to access the stellar and gas component of the
spectrum without the strong nuclear emission to access the host galaxy
properties also in the central region. It shows that integral field
spectroscopy promises to be very efficient to study the gas distribution and
its velocity field, and also spatially resolved stellar population in the host
galaxies also of luminous AGN.


title: Galactic winds and the Lya forest

abstract:
  We study the effect of galactic outflows on the Lya forest. The winds are
modelled as fully ionised spherical bubbles centered around galactic haloes.
The observed flux probability distribution and flux power spectrum limit the
volume filling factor of bubbles to be less than 10%. We have compared the mean
flux as a function of distance from haloes with the Adelberger etal (ASSP)
measurement. A model with bubbles of constant radius of 1.5Mpc/h surrounding
the most massive haloes matches the high transmissivity at separations
<0.5Mpc/h, but the increase of the transmissivity at small scales is more
gradual than observed. At separations <0.5Mpc/h, our estimate of the cosmic
variance error is $\Delta F\sim 0.3$, 30% higher than that of ASSP. The
difficulty in matching the rise in the transmissivity at small separations is
caused by residual absorption of neutral hydrogen lying physically outside the
bubbles but having a redshift position similar to the haloes. The flux level is
thus sensitive to the amplitude of the coherent velocity shear near haloes
which increases with halo mass in the simulation. A model where LBGs are
starbursts in small mass haloes matches the observations with smaller bubble
size than one where more massive haloes host the LBGs. A starburst model with a
bubble radius of 1Mpc/h and a volume filling factor of 2% is consistent with
the ASSP measurements at the 1-1.5$\sigma$ level. If this model is correct the
sharp rise of the transmissivity at small separation in the ASSP sample is due
to cosmic variance and is expected to become more moderate for a larger sample.


title: An Extremely Young Massive Stellar Object near IRAS 07029-1215

abstract:
  In the course of a comprehensive mm/submm survey of massive star-forming
regions, the vicinities of a sample of 47 luminous IRAS sources were closely
investigated with SCUBA and IRAM bolometers in order to search for massive
protostellar candidates. A particularly interesting object has been found in
the surroundings of the bright FIR source IRAS 07029-1215. Follow-up line
observations show that the object is cold, that it has a massive envelope, and
that it is associated with an energetic molecular outflow. No infrared point
source has been detected at its position. Therefore, it is a very good
candidate for a member of the long searched-for group of massive protostars.


title: Constraints on Cardassian Expansion

abstract:
  High redshift supernovae and Cosmic Microwave Background data are used to
constrain the Cardassian expansion model (Freese & Lewis 2002), a cosmology in
which a modification to the Friedmann equation gives rise to a flat,
matter-dominated Universe which is currently undergoing a phase of accelerated
expansion. In particular, the precision of the positions of the Doppler peaks
in the CMB angular power spectrum provided by WMAP tightly constrains the
cosmology. The available parameter space is further constrained by various high
redshift supernova datasets taken from Tonry et al. (2003), a sample of 230
supernovae collated from the literature, in which fits to the distance and
extinction have been recomputed where possible and a consistent zero-point has
been applied. In addition, the Cardassian model can also be loosely constrained
by inferred upper limits on the epoch at which the Cardassian term in the
modified Friedmann equation begins to dominate the expansion (z_eq). Using
these methods, a Cardassian cosmology is constrained at the 2 sigma level to
0.19<Omega_m<0.26, 0.01<n<0.24 for the Cardassian expansion parameter, n, and
0.42<z_eq<0.89, in contradiction to the previous constraints of Sen & Sen
(2003). There is also a large discrepancy between the 1 sigma confidence
regions defined by the CMB and tightest supernova constraints, with the CMB
data favouring a low-Omega_m, high-n Cardassian cosmology and z_eq>1, as
opposed to the supernova data which supports a high-Omega_m, low-n cosmology.


title: Emission processes in quiescent neutron star transients

abstract:
  We review the observational properties of transient systems made by a neutron
star primary and a late dwarf companion (known also as Soft X-ray Transients)
during their quiescent state. We focus on the several emission mechanisms
proposed and try to compare them with observations. Finally, we review new
tools to improve our comprehension of the physics of the emission processes.


title:
Near-infrared observations of galaxies in Pisces-Perseus. V. On the
  origin of bulges

abstract:
  We investigate the scaling relations of bulge and disk structural parameters
for a sample of 108 disk galaxies.Structural parameters are obtained from 2D
bulge/disk decomposition of H-band images.Bulges are modelled with a
generalized exponential (Sersic) with variable shape index n. We find that
bulge effective scalelength and luminosity increase with increasing n, but disk
properties are independent of bulge shape. As Hubble type T increases, bulges
become less luminous and their mean effective surface brightness gets fainter;
disks shows a similar, but much weaker, trend. When bulge parameters are
compared with disk ones, they are tightly correlated for n=1 bulges. The
correlations gradually worsen with increasing n such that n=4 bulges appear
virtually independent of their disks. The Kormendy relation, surf. brightness
vs. effect. radius, is shown to depend on bulge shape; the two parameters are
tightly correlated in n=4 bulges, and increasingly less so as n decreases;
disks are well correlated .Bulge-to-disk size ratios are independent of Hubble
type, but smaller for exponential bulges. Strongly barred SB galaxies with
exponential bulges are more luminous than their unbarred counterparts.
Exponential bulges appear to be closely related to their underlying disks,
while bulges with higher n values are less so. We interpret our results as
being most consistent with a secular evolutionary scenario, in which
dissipative processes in the disk are responsible for building up the bulges in
most spirals.


title: GRB afterglows in the deep Newtonian phase

abstract:
  In many GRBs, afterglows have been observed for months or even years. It
deserves noting that at such late stages, the remnants should have entered the
deep Newtonian phase, during which the majority of shock-accelerated electrons
will no longer be highly relativistic. However, a small portion of electrons
are still ultra-relativistic and capable of emitting synchrotron radiation.
Under the assumption that the electrons obey a power-law distribution according
to their kinetic energy (not simply the Lorentz factor), we calculate optical
afterglows from both isotropic fireballs and beamed ejecta, paying special
attention to the late stages. In the beamed cases, it is found that the light
curves are universally characterized by a flattening during the deep Newtonian
phase. Implication of our results on orphan afterglows is also addressed.


title:
Spectroscopic Analyses of the Blue Hook Stars in NGC 2808: A More
  Stringent Test of the Late Hot Flasher Scenario

abstract:
  Recent UV observations of the globular cluster NGC2808 (Brown et al. 2001)
show a significant population of hot stars fainter than the zero-age horizontal
branch (``blue hook'' stars), which cannot be explained by canonical stellar
evolution. Their results suggest that stars which experience unusually large
mass loss on the red giant branch and which subsequently undergo the helium
core flash while descending the white dwarf cooling curve could populate this
region. Theory predicts that these ``late hot flashers'' should show higher
temperatures than the hottest canonical horizontal branch (HB) stars and should
have He- and C-rich atmospheres. As a test of this late hot flasher scenario,
we have obtained and analysed medium resolution spectra of a sample of blue
hook stars in NGC2808 to derive their atmospheric parameters. Using the same
procedures, we have also re-analyzed our earlier spectra of the blue hook stars
in omega Cen (Moehler et al. 2002) for comparison with the present results for
NGC2808. The blue hook stars in these two clusters are both hotter (Teff >
35,000 K) and more helium-rich than canonical extreme HB stars in agreement
with the late hot flasher scenario. Moreover, we find indications for C
enhancement in the three most He-enriched stars in NGC2808. However, the blue
hook stars still show some H in their atmospheres, perhaps indicating that some
residual H survives a late hot flash and then later diffuses to the surface
during the HB phase. We note that the presence of blue hook stars apparently
depends mostly on the total mass of the globular cluster and not so much on its
HB morphology.


title: Astrochemistry and Observations

abstract:
  A major limitation and a continuing source of confusion in the interpretation
of molecular line observations has been the large degree of chemical complexity
that is observed in star-forming molecular cores. The past decade has seen
dramatic improvements in our ability to extract chemical information from
molecular line observations. These advances have been driven by new
observational platforms and techniques that use combined studies of molecular
emission and dust emission/absorption to derive chemical abundances. I will
outline the various methods and uncertainties in computing chemical information
from observations and discuss these new techniques that allow for the
estimation of line of sight structure in molecular abundance in both quiescent
and active star forming regions. I will show how improved chemical knowledge
can be used to place stronger constraints on theoretical astrochemical models,
but also open new avenues in the use of molecular emission to examine the
physics of molecular clouds and star formation. Thus, we can begin the process
of unraveling the chemical complexities and more fully realize the
long-standing promise of molecular line observations.


title: The Hydrogen Clouds in the Galactic Halo

abstract:
  New 21cm observations with the Green Bank Telescope show that a significant
fraction of the HI in the inner Galaxy's halo 1 kpc from the midplane exists in
the form of discrete clouds. Some look very much like a Spitzer ``standard''
diffuse cloud but with their HI in two phases. They mark the transition between
the neutral disk and the highly ionized halo. The dominant motion of the clouds
is Galactic rotation, but some have random velocities of as much as 50 km/s.
They are part of the Galaxy and are not related to high-velocity clouds, yet
their origin is obscure.


title: Line shape diagnostics of Galactic 26Al

abstract:
  The shape of the gamma-ray line from radioactive 26Al, at 1808.7 keV energy
in the frame of the decaying isotope, is determined by its kinematics when it
decays, typically 10^6 y after its ejection into the interstellar medium from
its nucleosynthesis source. Three measurements of the line width exist:
HEAO-C's 1982 value of (0+3) keV FWHM, the GRIS 1996 value of (5.4 +/- 1.3) keV
FWHM, and the recent RHESSI value of (2.0 +/- 0.8) keV FWHM, suggesting either
"cold", "hot", or "warm" 26Al in the ISM. We model the line width as expected
from Galactic rotation, expanding supernova ejecta, and/or Wolf-Rayet winds,
and predict a value below 1 keV (FWHM) with plausible assumptions about 26Al
initial velocities and expansion history. Even though the recent RHESSI
measurement reduces the need to explain a broad line corresponding to 540 km/s
mean 26Al velocity through extreme assumptions about grain transport of 26Al or
huge interstellar cavities, our results suggest that standard 26Al ejection
models produce a line on the narrow side of what is observed by RHESSI and
INTEGRAL. Improved INTEGRAL and RHESSI spatially-resolved line width
measurements should help to disentangle the effects of Galactic rotation from
the ISM trajectories of 26Al.


title:
Protostellar collapse induced by compression. II: rotation and
  fragmentation

abstract:
  We investigate numerically and semi-analytically the collapse of low-mass,
rotating prestellar cores. Initially, the cores are in approximate equilibrium
with low rotation (the initial ratio of thermal to gravitational energy is
$\alpha_0 \simeq 0.5$, and the initial ratio of rotational to gravitational
energy is $\beta_0 = 0.02 {\rm to} 0.05$). They are then subjected to a steady
increase in external pressure. Fragmentation is promoted -- in the sense that
more protostars are formed -- both by more rapid compression, and by higher
rotation (larger $\beta_0$). In general, the large-scale collapse is
non-homologous, and follows the pattern described in Paper I for non-rotating
clouds, viz. a compression wave is driven into the cloud, thereby increasing
the density and the inflow velocity. The effects of rotation become important
at the centre, where the material with low angular momentum forms a central
primary protostar (CPP), whilst the material with higher angular momentum forms
an accretion disc around the CPP. More rapid compression drives a stronger
compression wave and delivers material more rapidly into the outer parts of the
disc.


title:
Combined Long and Short Timescale X-ray Variability of NGC4051 with RXTE
  and XMM-Newton

abstract:
  We present over 6.5 years of frequent X-ray observations of the NLS1 galaxy
NGC4051 by RXTE together with a >100ks observation by XMM-Newton and so derive
a 2-10 keV PSD covering an unprecedent frequency range of over 6.5 decades from
<10^-8 to >10^-2 Hz. This PSD is a very good match to the PSD of the galactic
black hole binary system (GBH) Cyg X-1 when in a `high', rather than `low',
state providing the first definite confirmation of an AGN in a `high' state. A
bending, rather than sharply broken, powerlaw is a better description of the
PSDs of Cyg X-1 in the high state and of NGC4051. At low frequencies the PSD of
NGC4051 has a slope of -1.1 bending, at nu_B = 8 x 10^-4 Hz, to a slope of
alpha_H ~ -2 (steeper at lower energies). If nu_B scales with mass, we imply a
black hole mass of 3 x 10^5 Msolar in NGC4051, consistent with the 5 x 10^5
Msolar reverberation value. Hence NGC4051 is emitting at ~30% L_Edd.
  NGC4051 follows the same rms-flux relationship as GBHs. Phase lags and
coherence between bands are also the same as in GBHs. The lag of soft by hard
photons increases, and coherence decreases, as band separation increases. The
lag, and coherence, are greater for variations of longer Fourier period. This
behaviour suggests that higher photon energies and shorter variability
timescales are associated with smaller radii. Using also data from the
literature, we cannot fit all AGN to the same linear scaling of break timescale
with black hole mass. However broad line AGN are consistent with a linear
scaling from Cyg X-1 in its low state and NLS1 galaxies scale better with Cyg
X-1 in its high state. We suggest that the relationship between black hole mass
and break timescale is a function of at least one other underlying parameter,
which may be accretion rate or black hole spin.


title: Semi-analytical homologous solutions of the gravo-magnetic contraction

abstract:
  We propose an extension of the semi-analytical solutions derived by Lin et
al. (1965) describing the two-dimensional homologous collapse of a
self-gravitating rotating cloud having uniform density and spheroidal shape,
which includes magnetic field (with important restrictions) and thermal
pressure. The evolution of the cloud is reduced to three time dependent
ordinary equations allowing to conduct a quick and preliminary investigation of
the cloud dynamics during the precollapse phase, for a wide range of
parameters. We apply our model to the collapse of a rotating and magnetized
oblate and prolate isothermal core. Hydrodynamical numerical simulations are
performed and comparison with the semi-analytical solutions is discussed. Under
the assumption that all cores are similar, an apparent cloud axis ratio
distribution is calculated from the sequence of successive evolutionary states
for each of a large set of initial conditions. The comparison with the
observational distribution of the starless dense cores belonging to the catalog
of Jijina et al. (1999) shows a good agreement for the rotating and initially
prolate cores (aspect ratio $\simeq 0.5$) permeated by an helical magnetic
field ($\simeq 17-20 \mu$G for a density of $\simeq 10^4$ cm$^{-3}$).


title: Stellar populations in local star-forming galaxies

abstract:
  The main goal of this thesis work is studying the main properties of the
stellar populations embedded in a statistically complete sample of local active
star-forming galaxies: the Universidad Complutense de Madrid (UCM) Survey of
emission-line galaxies. This sample contains 191 local star-forming galaxies at
an average redshift of 0.026. The survey was carried out using an
objective-prism technique centered at the wavelength of the Halpha nebular
emission-line (a common tracer of recent star formation). (continues)


title: Time Structure of Muonic Showers

abstract:
  An analytical description of the time structure of the pulses induced by
muons in air showers at ground level is deduced assuming the production
distance distribution for the muons can be obtained elsewhere. The results of
this description are compared against those obtained from simulated showers
using AIRES. Major contributions to muon time delays are identified and a
relation between the time structure and the depth distribution is unveiled.


title:
A Two-Phase Chemical Enrichment Model for the Milky Way Globular Cluster
  System

abstract:
  Many globular cluster systems have a distinct bimodal metallicity
distribution function (MDF) which has strikingly similar features in many large
galaxies of all types. By using the Milky Way cluster system as a typical
example, we show that bimodal MDFs can be very well matched with a double
``accreting-box'' chemical enrichment model in which both the halo (metal-poor)
and bulge (metal-rich) clusters form during an early phase of gas inflow
simultaneously with star formation. However, differences in effective yield
between the two phases are not enough by themselves to reproduce the observed
MDF shape: gas infall is required for both phases, and either the initial gas
or the infalling gas must have very different metallicities in the two separate
phases.


title: Accretion disc formation around the neutron star in Be/X-ray binaries

abstract:
  We study the accretion on to the neutron star in Be/X-ray binaries, using a
3D SPH code and the data imported from a simulation by \citet{oka2} for a
coplanar system with a short period ($P_{\rm orb}=24.3 \rm{d}$) and a moderate
eccentricity $(e=0.34)$, which targeted the Be/X-ray binary 4U 0115+63. For
simplicity, we adopt the polytropic equation of state. We find that a
time-dependent accretion disc is formed around the neutron star regardless of
the simulation parameters. In the long term, the disc evolves via a two-stage
process, which consists of the initial developing stage and the later developed
stage. The developed disc is nearly Keplerian. In the short term, the disc
structure modulates with the orbital phase. The disc shrinks at the periastron
passage of the Be star and restores its radius afterwards. The accretion rate
on to the neutron star is also phase dependent, but its peak is broader and
much lower than that of the mass-transfer rate from the Be disc, unless the
polytropic exponent is as large as 5/3. Our simulations show that the truncated
Be disk model for Be/X-ray binaries is consistent with the observed X-ray
behaviour of 4U 0115+63.


title: The Molecular Gas Distribution and Schmidt Law in M33

abstract:
  The relationship between the star formation rate and surface density of
neutral gas within the disk of M33 is examined with new imaging observations of
CO J=1-0 emission gathered with the FCRAO 14m telescope and IRAS HiRes images
of the 60 micron and 100 micron emission. The Schmidt law, Sigma_SFR ~
Sigma_gas^n, is constructed using radial profiles of the HI 21cm, CO, and far
infrared emission. A strong correlation is identified between the star
formation rate and molecular gas surface density. This suggests that the
condensation of giant molecular clouds is the limiting step to star formation
within the M33 disk. The corresponding molecular Schmidt index, n_{mol}, is
1.36 +/- 0.08. The star formation rate has a steep dependence on total mass gas
surface density, (Sigma_{HI}+Sigma_{H_2}), owing to the shallow radial profile
of the atomic gas which dominates the total gas surface density for most radii.
The disk pressure of the gas is shown to play a prominent role in regulating
the molecular gas fraction in M33.


title: Mass Outflows from Accretion Disks: Old and New Challenges

abstract:
  We summarize recent developments in modeling of mass outflows from accretion
disks in AGN. We illustrate how the hydrodynamical and magnetohydrodynamical
wind structures revealed in numerical simulations relate to observations.
Important results from the numerical simulations include: no shielding from
X-rays is needed to radiatively launch a wind from the inner disk; shielding is
needed to accelerate the wind to high velocities. Disk winds launched
magnetically seem to be too dense to be accelerated by line driving. It appears
that we have an all or nothing situation for radiation-driving: radiation
driving has to be responsible for both launching and accelerating the wind or a
wind launched by some other mechanism must have a very finely tuned density in
order to be accelerated by radiation driving to velocities as high as measured
in BAL QSOs.


title: Implications of Low Energy X-ray Emission from Millisecond Radio Pulsars

abstract:
  Low energy X-ray emission (0.1-10 keV) from all six millisecond radio pulsars
(MSPs) for which such emission has been reported support a proposed pulsar
magnetic field evolution previously compared only to radiopulse data: old, very
strongly spun-up neutron stars become mainly orthogonal rotators (magnetic
dipole moment perpendicular to stellar spin) or aligned rotators. The neutron
star properties which lead to such evolution are reviewed. Special
consideration is given to agreement between predictions and observed X-ray
emission for the aligned MSP candidate PSR J0437-4715.


title: JHK Magnitudes for L and T Dwarfs and Infrared Photometric Systems

abstract:
  L and T dwarfs emit most of their radiation in the near infrared and their
spectral energy distributions are dominated by strong molecular absorption
bands. These highly structured energy distributions lead to JHK magnitudes that
are extremely sensitive to the exact filter bandpass used. In the case of the T
dwarfs, the differences between commonly used photometric systems can be as
large as 0.4 mag at J and 0.5 mag at J-K. To address this problem, we have
synthesized J,H and K magnitudes for some of the common photometric systems and
present transformation equations. If the spectral type of the dwarf is known,
our transformations allow data to be converted between systems to 0.01 mag,
which is better than the typical measurement uncertainty. Transforming on the
basis of color alone is more difficult because of the degeneracy and intrinsic
scatter in near-infrared colors of L and T dwarfs; in this case J magnitudes
can only be transformed to < 0.05 mag and H and K to < 0.02 mag.


title: Mock Catalogs for the DEEP2 redshift survey

abstract:
  We present a set of mock redshift catalogs, constructed from N-body
simulations, designed to mimic the DEEP2 survey. Galaxies with a range of
luminosities are placed within virialized halos in the simulation using a
variant of the halo model. The halo model parameters are chosen to reproduce
local clustering and abundance data and assumed to be independent of redshift.
This allows us to predict the luminosity function, two-point correlation
function, luminosity- and scale-dependent bias, redshift space distortions etc.
of our galaxies at higher redshifts. We show that the low order clustering
properties are consistent with preliminary DEEP2 data. The catalogs can be used
to evaluate the selection effects of the survey and to test new algorithms and
statistics that are to be used in the analysis of DEEP2 data.


title:
The Inner Structure of LambdaCDM Halos III: Universality and Asymptotic
  Slopes

abstract:
  We investigate the mass profile of LambdaCDM halos using a suite of numerical
simulations spanning five decades in halo mass, from dwarf galaxies to rich
galaxy clusters. Our analysis confirms the proposal of Navarro, Frenk & White
(NFW) that the shape of LambdaCDM halo mass profiles differs strongly from a
power law and depends little on mass. The logarithmic slope of the
spherically-averaged density profile, as measured by beta=-dln(rho)/dln(r),
decreases monotonically towards the center and becomes shallower than
isothermal (beta<2) inside a characteristic radius, r_{-2}. Although the
fitting formula proposed by NFW provides a reasonably good approximation to the
density and circular velocity profiles of individual halos, systematic
deviations from the best NFW fits are also noticeable. Inside r_{-2}, the
profile of simulated halos gets shallower with radius more gradually than
predicted and, as a result, NFW fits tend to underestimate the dark matter
density in these regions. This discrepancy has been interpreted as indicating a
steeply divergent cusp, but our results suggest a different interpretation. We
use the density and enclosed mass at our innermost resolved radii to place
strong constraints on beta_{0}: density cusps as steep as r^{-1.5} are
inconsistent with most of our simulations, although beta_{0}=1 is still
consistent with our data. Our density profiles show no sign of converging to a
well-defined asymptotic inner power law. We propose a simple formula that
reproduces the radial dependence of the slope better than the NFW profile, and
so may minimize errors when extrapolating our results inward to radii not yet
reliably probed by numerical simulations.


title:
The dynamical mass of the young cluster W3 in NGC 7252: Heavy-Weight
  globular cluster or ultra compact dwarf galaxy ?

abstract:
  We have determined the dynamical mass of the most luminous stellar cluster
known to date, i.e. object W3 in the merger remnant galaxy NGC 7252. The
dynamical mass is estimated from the velocity dispersion measured with the
high-resolution spectrograph UVES on VLT. Our result is the astonishingly high
velocity dispersion of sigma=45 +- 5 km/s. Combined with the large cluster size
R_eff=17.5 +-1.8 pc, this translates into a dynamical virial mass for W3 of 8
+- 2 x 10^7 Msun. This mass is in excellent agreement with the value 7.2 x 10^7
Msun we previously estimated from the cluster luminosity M_V=-16.2 by means of
stellar M/L ratios predicted by Simple Stellar Population models (with a
Salpeter IMF) and confirms the heavy-weight nature of this object. This results
points out that the NGC 7252-type of mergers are able to form stellar systems
with masses up to ~ 10^8 Msun. We find that W3, when evolved to ~ 10 Gyr, lies
far from the typical Milky Way globular clusters, but appears to be also
separated from omegaCen in the Milky Way and G1 in M31, the most massive old
stellar clusters of the Local Group, because it is too extended for a given
mass, and from dwarf elliptical galaxies because it is much more compact for
its mass. Instead the aged W3 is amazingly close to the compact objects named
ultracompact dwarf galaxies (UCDGs) found in the Fornax cluster (Hilker et al.
1999; Drinkwater et al. 2000), and to a miniature version of the compact
elliptical M32. These objects start populating a previously deserted region of
the fundamental plane.


title:
ADEMIS: A Library of Evolutionary Models for Emission-Line Galaxies: I-
  Dustfree Models

abstract:
  We present an extensive set of stellar population synthesis models, which
self-consistently include the (optical--far-UV) continuum emission from stars
as well as the resulting emission-line spectrum from photoionized gas
surrounding massive stars during their main sequence life-time. The models are
presented as a compiled library, ADEMIS, available electronically. ADEMIS
contains the equivalent widths and the intensities of the lines [OII]3727,
Hbeta, [OIII]5007, Halpha, [NII]6584, which were calculated assuming a
metallicity of 0.2, 0.4, 1.0, and 1.5 Zo and a wide range of ionization
parameters. We investigate the regime of continuous star formation, assuming a
Salpeter initial mass function, whose upper mass limit is an input parameter.
The calculated equivalent width models, which are function of the burst age,
are compared with the Jansen et al. atlas of integrated spectra for nearby
galaxies. We reproduce the observed properties of galaxies along the full
Hubble sequence and suggest how the metallicity and age of such galaxies might
be be roughly estimated.


title: Quiescent Magnetar Emission: Resonant Compton Upscattering

abstract:
  A principal candidate for quiescent non-thermal gamma-ray emission from
magnetars is resonant inverse Compton scattering in the strong fields of their
magnetospheres. This paper outlines expectations for such emission, formed from
non-thermal electrons accelerated in a pulsar-like polar cap potential
upscattering thermal X-rays from the hot stellar surface. The resultant spectra
are found to be strikingly flat, with fluxes and strong pulsation that could be
detectable by GLAST.