title: Using SKA to observe relativistic jets from X-ray binary systems

abstract:
  I briefly outline our current observational understanding of the relativistic
jets observed from X-ray binary systems, and how their study may shed light on
analogous phenomena in Active Galactic Nuclei and Gamma Ray Bursts. How SKA may
impact on this field is sketched, including the routine tracking of
relativistic ejections to large distances from the binaries, detecting and
monitoring the radio counterparts to 'quiescent' black holes, and detecting the
radio counterparts of the brightest X-ray binaries throughout the Local Group
of galaxies.


title: The initial mass function : from Salpeter 1955 to 2005

abstract:
  Fifty years after Ed Salpeter's seminal paper, tremendous progress both on
the observational and theoretical sides allow a fairly accurate determination
of the Galactic IMF not only down to the hydrogen-burning limit but into the
brown dwarf domain. The present review includes the most recent observations of
low-mass stars and brown dwarfs to determine this IMF and the related Galactic
mass budget. The IMF definitely exhibits a similar behaviour in various
environments, disk, young and globular clusters, spheroid. Small scale
dissipation of large scale compressible MHD turbulence seems to be the
underlying triggering mechanism for star formation. Modern simulations of
compressible MHD turbulence yield an IMF consistent with the one derived from
observations.


title:
Double-peak spectral energy density of GRBs and the true identity of GRB
  031203

abstract:
  A double-peak spectral-energy-density of gamma-rays, similar to that observed
in blazars, is expected in gamma-ray bursts (GRBs) produced in supernova (SN)
explosions. The second peak, which is formed by inverse Compton scattering of
ambient SN light by cosmic ray electrons accelerated by the jets from the SN
explosion, has a much higher peak-energy than the first ordinary peak. However,
in X-ray flashes (XRFs), which in the cannonball (CB) model are normal GRBs
viewed farther off axis, the first peak-energy is shifted to the soft X-ray
region while the second peak-energy moves to the MeV range. In far-off-axis
GRBs, such as GRBs 980425 and 031203, the second peak may have been confused
with the normal GRB peak. In most GRBs, which have been observed so far, the
gamma-ray detectors ran out of statistics far below the second peak. However,
in bright GRBs, the two peaks may be resolved by simultaneous measurements with
SWIFT and GLAST.


title:
High resolution observations of SiO masers: comparing the spatial
  distribution at 43 and 86 GHz

abstract:
  We present sub-milliarcsecond observations of SiO masers in the late-type
stars IRC +10011 and Chi Cyg. We have used the NRAO Very Long Baseline Array
(VLBA) to map the 43 GHz (v=1, 2 J=1-0) and the 86 GHz (v=1, 2 J=2-1) SiO
masers. All the transitions have been imaged except the v=2 J=2-1 in IRC
+10011. We report the first VLBI map of the v=1 J=2-1 28SiO maser in IRC +10011
as well as the first VLBA images of SiO masers in an S-type Mira variable, Chi
Cyg. In this paper we have focused on the study of the relative spatial
distribution of the different observed lines. We have found that in some cases
the observational results are not reproduced by the current theoretical pumping
models, either radiative or collisional. In particular, for IRC +10011, the v=1
J=1-0 and J=2-1 28SiO lines have different spatial distributions and emitting
region sizes, the J=2-1 emission being located in an outer region of the
envelope. For Chi Cyg, the distributions also differ, but the sizes of the
masing regions are comparable. We suggest that the line overlaps between
ro-vibrational transitions of two abundant molecular species, H2O and 28SiO, is
a possible explanation for the discrepancies found between the observations and
the theoretical predictions. We have introduced this overlapping process in the
calculations of the excitation of the SiO molecule. We conclude that the line
overlaps can strongly affect the excitation of SiO and may reproduce the
unexpected observational results for the two sources studied.


title: A Time-Dependent Radiative Model of HD209458b

abstract:
  We present a time-dependent radiative model of the atmosphere of HD209458b
and investigate its thermal structure and chemical composition. In a first
step, the stellar heating profile and radiative timescales were calculated
under planet-averaged insolation conditions. We find that 99.99% of the
incoming stellar flux has been absorbed before reaching the 7 bar level.
Stellar photons cannot therefore penetrate deeply enough to explain the large
radius of the planet. We derive a radiative time constant which increases with
depth and reaches about 8 hr at 0.1 bar and 2.3 days at 1 bar. Time-dependent
temperature profiles were also calculated, in the limit of a zonal wind that is
independent on height (i.e. solid-body rotation) and constant absorption
coefficients. We predict day-night variations of the effective temperature of
\~600 K, for an equatorial rotation rate of 1 km/s, in good agreement with the
predictions by Showman &Guillot (2002). This rotation rate yields day-to-night
temperature variations in excess of 600 K above the 0.1-bar level. These
variations rapidly decrease with depth below the 1-bar level and become
negligible below the ~5--bar level for rotation rates of at least 0.5 km/s. At
high altitudes (mbar pressures or less), the night temperatures are low enough
to allow sodium to condense into Na2S. Synthetic transit spectra of the visible
Na doublet show a much weaker sodium absorption on the morning limb than on the
evening limb. The calculated dimming of the sodium feature during planetary
transites agrees with the value reported by Charbonneau et al. (2002).


title: Far-infrared and sub-mm observations of the Crab nebula

abstract:
  We present FIR and sub-mm images of the Crab nebula, taken with ISOPHOT on
board ISO and with the SCUBA on the JCMT. The ISOPHOT observations were made at
60, 100, 170 micron, with FWHM of equivalent area Gaussian beams of 44, 47 and
93 arcsec, respectively. The 850 micron SCUBA image has a Gaussian FWHM of 17
arcsec. The 60 and 100 micron images show clear excess of emission above that
expected from an extrapolation of the synchrotron spectrum of the Crab nebula
from lower frequencies. The ISOPHOT images reveal that about half this excess
is attributable to two peaks, separated by approximately 80 arcsec. We also
present spectra taken using the LWS on board ISO, which show that the FIR
excess is not due to line emission. The lower resolution 170 micron image does
not show any excess emission. These findings are consistent with a picture in
which the FIR excess is due to emission from a small amount of warm dust which
radiates predominantly at 60 and 100 micron micron but not at 170 micron, and
which is superimposed on a synchrotron spectrum which gradually steepens
towards shorter wavelengths throughout the FIR and MIR spectral range. The dust
geometry is consistent with a torus of diameter approximately 0.8 pc created by
the supernova progenitor, superimposed upon a broadly distributed component
which may be supernova condensates in the filaments. The dust-to-gas ratio in
the filaments is comparable to the interstellar value. To study spectral index
variations in the radio synchrotron emission we compared the 850-micron image
with a 20-cm VLA image. These images are very similar, implying that there is
little variation in spectral index across the face of the remnant between these
wavelengths.


title:
The Pierre Auger Observatory: Science Prospects and Performance at First
  Light

abstract:
  The Pierre Auger Observatory is a major international effort aiming at
high-statistics study of highest energy cosmic rays. A general description of
the experimental set-up and overall performance of the detector at first light
are presented.


title: Satellite measurement of the Hannay angle

abstract:
  The concept of a measurement of the yet unevaluated Hannay angle, by means of
an Earth-bound satellite, adiabatically driven by the Moon, is shown herein.
Numerical estimates are given for the angles, the orbital displacements, the
shortening of the orbital periods, for different altitudes. It is concluded
that the Hannay effect is measurable in high Earth orbits, by means of atomic
clocks, accurate Time & Frequency transfer system and precise positioning.


title: Flare and quiescent X-ray emission from Sigma Geminorum

abstract:
  The X-ray active RS CVn binary system Sigma Geminorum was observed during a
long-duration flare with XMM-Newton. We compare line emission during the flare
with line emission measured from a previous Chandra observation during
quiescence, in a model independent way. We find that in addition to an overall
25% flux increase, which can be ascribed to variations in the system's
quiescence activity over the 15 months that passed between the observations,
there is a hot plasma component of kT_e > 1 keV that arises with the flare. The
hot component is manifested primarily by high charge states of Fe and by a vast
continuum, but with no temperature or abundance effect on the cooler plasma,
except perhaps for Mg that is anomalously enhanced.


title:
Quantifying the uncertainties of chemical evolution studies. I. The
  stellar initial mass function and the stellar lifetimes

abstract:
  The stellar initial mass function and the stellar lifetimes are basic
ingredients of chemical evolution models, for which different recipes can be
found in the literature. In this paper, we quantify the effects on chemical
evolution studies of the uncertainties in these two parameters. We concentrate
on chemical evolution models for the Milky Way, because of the large number of
good observational constraints. Such chemical evolution models have already
ruled out significant temporal variations for the stellar initial mass function
in our own Galaxy, with the exception perhaps of the very early phases of its
evolution. Therefore, here we assume a Galactic initial mass function constant
in time. Through an accurate comparison of model predictions for the Milky Way
with carefully selected data sets, it is shown that specific prescriptions for
the initial mass function in particular mass ranges should be rejected. As far
as the stellar lifetimes are concerned, the major differences among existing
prescriptions are found in the range of very low-mass stars. Because of this,
the model predictions widely differ for those elements which are produced
mostly by very long-lived objects, as for instance 3He and 7Li. However, it is
concluded that model predictions of several important observed quantities,
constraining the plausible Galactic formation scenarios, are fairly robust with
respect to changes in both the stellar mass spectrum and the stellar lifetimes.
For instance, the metallicity distribution of low-mass stars is nearly
unaffected by these changes, since its shape is dictated mostly by the time
scale for thin-disk formation.


title: Initial mass function and galactic chemical evolution models

abstract:
  In this contribution we focus on results from chemical evolution models for
the solar neighbourhood obtained by varying the IMF. Results for galaxies of
different morphological type are discussed as well. They argue against a
universal IMF independent of star forming conditions.


title:
Time Variability of Low Angular Momentum Flows Accreting onto Black
  Holes: A Natural Mechanism For Radiation Flaring

abstract:
  We present results from our magnetohydrodynamical simulations of accretion
flows onto black holes. Our main focus is the interplay between inflows and
related outflows. We consider applications of such flows to the Galatic center
and low luminosity active galactic nuclei.


title:
Multiwavelength WHAM Observations of Extra-planar Warm Ionized Gas in
  the Galaxy

abstract:
  We report on observations of several optical emission lines toward a variety
of newly revealed faint, large-scale H-alpha-emitting structures in the warm
ionized medium (WIM) of the Galaxy. The lines include [N II] 6583, [N II] 5755,
[S II] 6716, [O III] 5007, and He I 5876 and were obtained with the Wisconsin
H-Alpha Mapper (WHAM) toward sightlines that probe both large filamentary
features and the more diffuse WIM, from the outer Perseus spiral arm to the
inner Galaxy. These emission lines allow us to explore the temperature and
ionization conditions within the emitting gas and their variations between the
different emission regions. We compare the relative intensities of the emission
lines toward these faint H II structures to brighter, classical O star H II
regions. We find that the line ratios of [N II]/H-alpha and [S II]/H-alpha are
generally high, while [O III]/H-alpha and He I/H-alpha are generally low in the
diffuse WIM and in the faint filamentary structures. This suggests that the gas
is warmer, in a lower ionization state, and ionized by a softer spectrum than
the gas in classical H II regions surrounding O stars, the presumed ionization
source for the WIM. In addition, we find differences in the physical conditions
between the large filamentary structures and the more diffuse WIM, suggesting
that the filaments are regions of higher density, not geometrical projections
of folds in large sheet-like or shell-like structures.


title:
Detection of CO from SMM J16359+6612, The Multiply Imaged Submillimeter
  Galaxy Behind A2218

abstract:
  We report the detection of CO ($J$=3$\to$2) line emission from all three
multiple images (A,B and C) of the intrinsically faint ($\simeq$ 0.8 mJy)
submillimeter-selected galaxy SMM J16359+6612. The brightest source of the
submm continuum emission (B) also corresponds to the brightest CO emission,
which is centered at $z$=2.5168, consistent with the pre-existing redshift
derived from \Ha. The observed CO flux in the A, B and C images is 1.2, 3.5 and
1.6 Jy \kms respectively, with a linewidth of $500\pm 100$ \kms. After
correcting for the lensing amplification, the CO flux corresponds to a
molecular gas mass of $\sim 2\times 10 ^{10} h_{71}^{-2}$ \Msun, while the
extent of the CO emission indicates that the dynamical mass of the system
$\sim9\times10^{10}$ \Msun. Two velocity components are seen in the CO spectra;
these could arise from either a rotating compact ring or disk of gas, or
merging substructure. The star formation rate in this galaxy was previously
derived to be $\sim$100--500 \Msun \yr. If all the CO emission arises from the
inner few kpc of the galaxy and the galactic CO-to-H$_2$ conversion factor
holds, then the gas consumption timescale is a relatively short 40 Myr, and so
the submm emission from SMM J16359+6612 may be produced by a powerful, but
short-lived circumnuclear starburst event in an otherwise normal and
representative high-redshift galaxy.


title: Covariance of Weak Lensing Observables

abstract:
  Analytical expressions for covariances of weak lensing statistics related to
the aperture mass $\Map$ are derived for realistic survey geometries such as
SNAP for a range of smoothing angles and redshift bins. We incorporate the
contributions to the noise due to the intrinsic ellipticity distribution and
the effects of finite size of the catalogue. Extending previous results to the
most general case where the overlap of source populations is included in a
complete analysis of error estimates, we study how various angular scales in
various redshifts are correlated and how the estimation scatter changes with
survey parameters. Dependence on cosmological parameters and source redshift
distributions are studied in detail. Numerical simulations are used to test the
validity of various ingredients to our calculations. Correlation coefficients
are defined in a way that makes them practically independent of cosmology. They
can provide important tools to cross-correlate one or more different surveys,
as well as various redshift bins within the same survey or various angular
scales from same or different surveys. Dependence of these coefficients on
various models of underlying mass correlation hierarchy is also studied.
Generalisations of these coefficients at the level of three-point statistics
have the potential to probe the complete shape dependence of the underlying
bi-spectrum of the matter distribution. A complete error analysis incorporating
all sources of errors suggest encouraging results for studies using future
space based weak lensing surveys such as SNAP.


title: Galaxy Evolution and Cosmology with the Square Kilometre Array

abstract:
  The present-day Universe is seemingly dominated by dark energy and dark
matter, but mapping the normal (baryonic) content remains vital for both
astrophysics - understanding how galaxies form - and astro-particle physics -
inferring properties of the dark components. The Square Kilometre Array (SKA)
will provide the only means of studying the cosmic evolution of neutral
Hydrogen (HI) which, alongside information on star formation from the radio
continuum, is needed to understand how stars formed from gas within dark-matter
over-densities and the roles of gas accretion and galaxy merging. `All
hemisphere' HI redshift surveys to redshift 1.5 are feasible with
wide-field-of-view realizations of the SKA and, by measuring the galaxy power
spectrum in exquisite detail, will allow the first precise studies of the
equation-of-state of dark energy. The SKA will be capable of other uniquely
powerful cosmological studies including the measurement of the dark-matter
power spectrum using weak gravitational lensing, and the precise measurement of
H0 using extragalactic water masers. The SKA is likely to become the premier
dark-energy-measuring machine, bringing breakthroughs in cosmology beyond those
likely to be made possible by combining CMB (e.g. Planck), optical (e.g. LSST,
SNAP) and other early-21st-century datasets.


title:
Type Ia Supernova models arising from different distributions of
  igniting points

abstract:
  In this paper we address the theory of Type Ia supernovae from the moment of
carbon runaway up to several hours after the explosion. We have concentrated on
the boiling-pot model: a deflagration characterized by the (nearly-)
simultaneous ignition of a number of bubbles that pervade the core of the white
dwarf. Thermal fluctuations larger than >1% of the background temperature
(7x10^8 K) on lengthscales of < 1m could be the seeds of the bubbles.
Variations of the homogeneity of the temperature perturbations can lead to two
alternative configurations at carbon runaway: if the thermal gradient is small,
all the bubbles grow to a common characteristic size related to the value of
the thermal gradient, but if the thermal gradient is large enough, the size
spectrum of the bubbles extends over several orders of magnitude. The explosion
phase has been studied with the aid of a smoothed particle hydrodynamics code
suited to simulate thermonuclear supernovae. In spite of important procedural
differences and different physical assumptions, our results converge with the
most recent calculations of 3D deflagrations in white dwarfs carried out in
supernova studies by different groups. For large initial numbers of bubbles
(>3-4 per octant), the explosion produces about 0.45 solar masses of 56Ni, and
the kinetic energy of the ejecta is 0.45x10^{51} ergs. However, all
three-dimensional deflagration models share three main drawbacks: 1) the scarce
synthesis of intermediate-mass elements, 2) the loss of chemical stratification
of the ejecta due to mixing by Rayleigh-Taylor instabilities during the first
second of the explosion, and 3) the presence of big clumps of 56Ni at the
photosphere at the time of maximum brightness.


title: Structure Formation in Inhomogeneous Dark Energy Models

abstract:
  We investigate how inhomogeneous quintessence models may have a specific
signature even in the linear regime of large scale structure formation. The
dynamics of the collapse of a dark matter halo is governed by the value or the
dynamical evolution of the dark energy equation of state, the energy density's
initial conditions and its homogeneity nature in the highly non-linear regime.
These have a direct impact on the redshift of collapse, altering in consequence
the linearly extrapolated density threshold above which structures will end up
collapsing. We compute this quantity for minimally coupled and coupled
quintessence models, examining two extreme scenarios: first, when the
quintessence field does not exhibit fluctuations on cluster scales and below -
homogeneous dark energy; and second, when the field inside the overdensity
collapses along with the dark matter - inhomogeneous dark energy. One shows
that inhomogeneous dark energy models present distinct features which may be
used to confront them with observational data, for instance galaxy number
counting. Fitting formulae for the linearly extrapolated density threshold
above which structures will end up collapsing are provided for models of dark
energy with constant equation of state.


title: Alkali and Halogen Chemistry in Volcanic Gases on Io

abstract:
  We use chemical equilibrium calculations to model the speciation of alkalis
and halogens in volcanic gases emitted on Io. The calculations cover wide
temperature (500-2000 K) and pressure (10^-6 to 10^+1 bars) ranges, which
overlap the nominal conditions at Pele (T = 1760 K, P = 0.01 bars). About 230
compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are
considered. We predict the major alkali and halogen species in a Pele-like
volcanic gas and the major alklai and halogen condensates. We also model
disequilibrium chemistry of the alkalis and halogens in the volcanic plume.
Based on this work and our prior modeling for Na, K, and Cl in a volcanic
plume, we predict the major loss processes for the alkali halide gases are
photolysis and/or condensation onto grains. On the basis of elemental
abundances and photochemical lifetimes, we recommend searching for gaseous KCl,
NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during
eruptions. Based on abundance considerations and observations of brown dwarfs,
we also recommend a search of Io's extended atmosphere and the Io plasma torus
for neutral and ionized Li, Cs, Rb, and F.


title: What are the environments of lens galaxies?

abstract:
  Using measured tangential shear profiles and number counts of massive
elliptical galaxies, the halo occupation distribution of strong lensing
galaxies is constrained. The resulting HOD is then used to populate an N-body
simulation with lens galaxies, in order to assess the importance of environment
for strong lensing systems. Typical estimated values for the convergence and
shear produced by nearby correlated matter are kappa = gamma = 0.03, with much
stronger events occurring relatively infrequently. This implies that estimates
of quantities like the Hubble constant are not expected to be significantly
biased by environmental effects. One puzzle is that predicted values for the
external shear at lens galaxies are far below the values obtained by modeling
of strong lensing data.


title: QSO lensing magnification associated with galaxy groups

abstract:
  We simulated both the matter and light (galaxy) distributions in a wedge of
the universe and calculated the gravitational lensing magnification caused by
the mass along the line of sight of galaxies and galaxy groups identified in
sky surveys. A large volume redshift cone containing cold dark matter particles
mimics the expected cosmological matter distribution in a flat universe with
low matter density and a cosmological constant. We generate a mock galaxy
catalogue from the matter distribution and identify thousands of galaxy groups
in the luminous sky projection. We calculate the expected magnification around
galaxies and galaxy groups and then the induced QSO-lens angular correlation
due to magnification bias. This correlation is an observable and can be used to
estimate the average mass of the lens population and also make cosmological
inferences. We also use analytic calculations and various analysis to compare
the observational results with theoretical expectations for the
cross-correlation between faint QSOs from the 2dF Survey and nearby galaxies
and groups from the APM and SDSS EDR. The observed QSO-lens anti-correlations
are stronger than the predictions for the cosmological model used. This
suggests that there could be unknown systematic errors in the observations and
data reduction, or that the model used is not adequate. If the observed signal
is assumed to be solely due to gravitational lensing then the lensing is
stronger than expected, due to more massive galactic structures or more
efficient lensing than simulated.


title: Gemini H-band imaging of the field of a z=10 candidate

abstract:
  We present a deep H-band image of the field of a candidate z=10 galaxy
magnified by the foreground (z=0.25) cluster A1835. The image was obtained with
NIRI on Gemini North to better constrain the photometry and investigate the
morphology of the source. The image is approximately one magnitude deeper and
has better spatial resolution (seeing was 0.4-0.5 arcsec) than the existing
H-band image obtained with ISAAC on the VLT by Pello' et al. 2004. The object
is not detected in our new data. Given the published photometry (H(AB)=25.0),
we would have expected it to have been detected at more than ~7 sigma in a 1.4
arcsec diameter aperture. We obtain a limit of H(AB)>26.0 (3 sigma) for the
object. A major part of the evidence that this object is at z=10 was the
presence of a strong continuum break between the J and H band, attributed to
absorption of all continuum shortward of 1216 Ang in the rest-frame of the
object. Our H-band non-detection substantially reduces the magnitude of any
break and therefore weakens the case that this object is at z=10. Without a
clear continuum break, the identification of an emission line at 1.33745um as
Ly-alpha at z~10 is less likely. We show that the width and flux of this line
are consistent with an alternative emission line such as [OIII]5007 from an
intermediate redshift HII/dwarf galaxy.


title: CO in the Bipolar-Radio-Continuum Galaxy NGC 3367

abstract:
  CO emission has been imaged at 2" resolution in the central 10 kpc of the
barred spiral galaxy NGC 3367. This galaxy has bipolar synchrotron lobes out to
a radii of 6 kpc, straddling the compact nucleus. The peak molecular emission
is in a source of radius 2" (425 pc) centered on the galaxy nucleus. The
molecular mass is about 3 times 10**8 Msun in this peak an about 5.9 times
10**8 Msun within a radius of 4".5 (950 pc). The very large gas masses in the
central source imply extinctions sufficiently high to completely obscure
optical emission lines (e.g.BLR) associated with the nuclear radio source. The
observed Balmer lines probably originate in the narrow line region few hundred
pc from the nucleus. The CO emission in the central region is elongated NE-SW,
very similar to the PA of the large scale synchrotron lobes. This elongation is
likely due to non-axisymmetric gravitational potential of the stellar bar. We
infer that the NE radio continuum lobe is on the far side of the galaxy and the
SW lobe is on the near side. The central mass of molecular gas is sufficient
mass to power the AGN accretion luminosity for over 10**8 yrs at 3 Msun per yr.


title:
Physical Conditions in the Narrow-Line Region of Markarian 3. I.
  Observational Results

abstract:
  We use Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS)
longslit low-resolution spectroscopy from 1150A to 10,300A to study the
physical conditions in the narrow-line region (NLR) of the Seyfert 2 galaxy
Markarian 3. We find from the HeII 1640/4686 line ratio and the Balmer
decrement that the extinction within Markarian 3 along the line-of-sight to the
NLR is best characterized by a Large Magellanic Cloud (LMC) type extinction
curve. We observe an extinction gradient increasing from west to east along the
STIS slit in both line and continuum emission. We infer from this gradient that
the host galaxy disk is tilted towards the observer in the east: the
line-of-sight to the eastern emission-line cone intersects more dust in the
plane of the galaxy than that to the western cone. We model the observed
continuum as a combination of reddened host galaxy light from an old stellar
population, reddened H+ and He++ recombination continua, and less reddened
scattered light from the central engine with spectral index alpha=1 (L(nu)
proportional to nu^(-alpha)). The host galaxy to scattered-light ratio is
estimated to be 3:1 at 8125 A in 0.1 X 1.8 square-arcsecond aperture. We
estimate that the amount of intrinsic non-ionizing UV continuum scattered into
our line-of-sight is 0.04%. This is consistent with our estimate of the
scattering fraction for broad CIV 1548,1551 emission.


title: Galaxies at z~7-8: z-dropouts in the Hubble Ultra Deep Field

abstract:
  We have detected likely z~7-8 galaxies in the 144"x144" NICMOS observations
of the Hubble Ultra Deep Field. Objects are required to be >3 sigma detections
in both NICMOS bands, J and H. The selection criteria for this sample are
(z-J)>0.8, (z-J) > 0.66 (J-H)+0.8, (J-H)<1.2, and no detection at <8500
Angstroms. The 5 selected sources have total magnitudes H~27. Four of the five
sources are quite blue compared to typical lower-redshift dropout galaxies and
are clustered within a 1 arcmin**2 region. Because all 5 sources are near the
limit of the NICMOS data, we have carefully evaluated their reality. Each of
the candidates is visible in different splits of the data and a median stack.
We analyzed several noise images and estimate the number of spurious sources to
be 1+/-1. A search using an independent reduction of this same data set clearly
revealed 3 of the 5 candidates and weakly detected a 4th candidate, suggesting
the contamination could be higher. For comparison with predictions from lower
redshift samples we take a conservative approach and adopt four z~7-8 galaxies
as our sample. With the same detection criteria on simulated datasets, assuming
no-evolution from z~3.8, we predict 10 sources at z~7-8, or 14 if we use a more
realistic (1+z)^{-1} size scaling. We estimate that the rest-frame continuum UV
(~1800 Angstroms) luminosity density at z~7.5 (integrated down to 0.3L*) is
just 0.20_{-0.08}^{+0.12}x that found at z~3.8. Effectively this sets an upper
limit on the luminosity density down to 0.3 L*. This result is consistent with
significant evolution at the bright end of the luminosity function from z~7.5
to z~3.8. Even with the lower UV luminosity density at z~7.5, it appears that
galaxies could still play an important role in reionization at these redshifts,
though definitive measurements remain to be made. [abridged]


title: Magnetic fields in GRBs

abstract:
  We discuss the dynamical role of magnetic fields in GRB explosions in the
framework of the fireball and electromagnetic models. We contrast the
observational predictions of the two models and argue that only the very early
afterglow observations, almost coincident with the prompt phase, can be used as
decisive tests of the ejecta content.


title:
The Ionized Nuclear Environment in NGC 985 as seen by Chandra and
  BeppoSAX

abstract:
  (Abridged) We investigate the ionized environment of the Seyfert 1 galaxy NGC
985 with a new Chandra-HETGS observation and an archival BeppoSAX observation.
Two absorption components are clearly required to fit absorption features
observed in the Chandra spectrum. The components have a difference of 29 in
ionization parameter and 3 in column density. The presence of the low
ionization component is evidenced by an Fe M-shell unresolved transition array
(UTA) produced by charge states VII to XIII. The high ionization phase is
required by the presence of broad absorption features arising from several
blends of Fe L-shell transitions (Fe XVII-XXII). A third highly ionized
component might also be present, but the data does not allow to constrain its
properties. An X-ray luminosity variation by a factor 2.3 is observed between
the BeppoSAX and Chandra observations (separated by almost 3 years).
Variability in the opacity of the absorbers is detected in response to the
continuum variation, but while the colder component is consistent with a simple
picture of photoionization equilibrium, the ionization state of the hotter
component seems to increase while the continuum flux drops. The most striking
result in our analysis is that during both the Chandra and the BeppoSAX
observations, the two absorbing components appear to have the same pressure.
Thus, we suggest that the absorption arises from a multi-phase wind. Such
scenario can explain the change in opacity of both absorption components during
the observations, but requires that a third hotter component is
pressure-confining the two phases. Hence, our analysis points to a 3-phase
medium similar to the wind found in NGC 3783, and further suggests that such a
wind might be a common characteristic in AGN.


title: The main frequencies of solar core natural oscillations

abstract:
  The oscillations of a spherical body consisting of hot electron-nuclear
plasma are considered. It is shown that there are two basic modes of
oscillations. The estimation of the main frequencies of the solar core
oscillation gives a satisfactory fit of the calculated spectrum and the
measurement data.


title: Reddening map of the Large Magellanic Cloud bar region

abstract:
  E(V$-$I) reddening values for 1123 locations in the bar region of the Large
Magellanic Cloud are presented. V, I photometry of red clump stars identified
in the Optical Gravitational Lensing Experiment II catalogue of LMC were used
to estimate reddening. E(V$-$I) values were estimated as the difference between
observed and the characteristic values of (V$-$I) for the red clump population
in a given region. It is found that most of the regions in the bar have
reddening values less than 0.1 mag with only a few locations having values more
than 0.2 mag. Eastern side of the bar is found to be more reddened when
compared to the western side, with similar and relatively small values for
differential reddening as in most parts of the bar. Increased reddening in the
eastern end of the bar could be caused by a small fraction of the H I clouds in
the line of sight. A high density of HI clouds located in the eastern end of
the bar should have caused very high reddening in these regions, whereas only a
relatively small increase in the reddening is estimated. This indicates that
most of the H I clouds in this direction are likely to be located behind the
bar.


title:
Apparent Stellar Wobble by a Planet in a Circumstellar Disk: Limitations
  on Planet Detection by Astrometry

abstract:
  Astrometric detection of a stellar wobble on the plane of the sky will
provide us a next breakthrough in searching extrasolar planets. The Space
Interferometry Mission (SIM) is expected to achieve a high-precision astrometry
as accurate as 1 micro-as, which is precise enough to discover a new-born
Jupiter mass planet around a pre-main-sequence (PMS) star in the Taurus-Auriga
star forming region. PMS stars, however, have circum-stellar disks that may be
obstacles to the precise measurement of the stellar position. We present
results on disk influences to the stellar wobble. The density waves excited by
a planet move both of the disk's mass center and the photo-center. The motion
of the disk mass center induces an additional wobble of the stellar position,
and the motion of the disk photo-center causes a contamination in the
measurement of the stellar position. We show that the additional stellar motion
dynamically caused by the disk's gravity is always negligible, but that the
contamination of the disk light can interfere with the precise measurement of
the stellar position, if the planet's mass is smaller than ~10 Jupiter mass.
The motion of the disk photo-center is sensitive to a slight change in the wave
pattern and the disk properties. Measurements by interferometers are generally
insensitive to extended sources such as disks. Because of this property SIM
will not suffer significant contaminations of the disk light, even if the
planet's mass is as small as 1 Jupiter mass.


title: Type Ia supernova SN 2003du: optical observations

abstract:
  UBVRI photometry and optical spectra of type Ia supernova SN 2003du obtained
at the Indian Astronomical Observatory for nearly a year since discovery are
presented.
  The apparent magnitude at maximum was B=13.53 +/- 0.02 mag, and the colour
(B-V) = -0.08 +/- 0.03 mag. The luminosity decline rate, Delta(m_{15}(B)) =
1.04 +/- 0.04 mag indicates an absolute B magnitude at maximum of M_B = -19.34
+/- 0.3 mag and the distance modulus to the parent galaxy as mu=32.89 +/-
0.4.The light curve shapes are similar, though not identical, to those of SNe
1998bu and 1990N, both of which had luminosity decline rates similar to that of
SN 2003du and occurred in spiral galaxies. The peak bolometric luminosity
indicates that 0.9 Msun mass of 56Ni was ejected by the supernova. The spectral
evolution and the evolution of the Si II and Ca II absorption velocities
closely follows that of SN 1998bu, and in general, is within the scatter of the
velocities observed in normal type Ia supernovae.
  The spectroscopic and photometric behaviour of SN 2003du is quite typical for
SNe Ia in spirals.
  A high velocity absorption component in the Ca II (H & K) and IR-triplet
features, with absorption velocities of ~20,000 km/s and ~22,000 km/s
respectively, is detected in the pre-maximum spectra of days -11 and -7.


title:
Detection of absorption features in the X-ray spectrum of the
  narrow-line Quasar PG 1404+226 : Possible evidence for accretion disk winds

abstract:
  We present the results of an analysis of data from XMM-Newton and CHANDRA
observations of the high luminosity narrow-line quasar PG 1404+226. We confirm
a strong soft X-ray excess in the X-ray spectrum and we find rapid variability
(a factor of two in about 5000 s). When the X-ray spectrum is fit with a two
component model which includes a power-law and a blackbody component, we find
that low energy absorption lines are required to fit the data. If we interpret
these lines as due to highly ionized species of heavy elements in an outflowing
accretion disk wind, an outflow velocity of about 26000 km/s could be derived.
One interesting feature of the present observation is the possible detection of
variability in the absorption features: the absorption lines are visible only
when the source is bright. From the upper limits of the equivalent widths (EW)
of the absorption lines during the low flux states and also from the model
independent pulse height ratios, we argue that the strength of absorption is
lower during the low flux states. This constraints the physical size of the
absorbing medium within 100 Schwartzschild radius (Rg) of the putative
supermassive black hole. We also find a marginal evidence for a correlation
between the strength of the absorption line and the X-ray luminosity.


title: Microlensing towards LMC and M31

abstract:
  (Short version) The nature and the location of the lenses discovered in the
microlensing surveys done so far towards the LMC remain unclear. This
contribution is comprised of two distinct parts. In the first part, motivated
by these questions, we compute the optical depth for the different intervening
populations an the number of expected events for self-lensing, using a recently
drawn coherent picture of the geometrical structure and dynamics of the LMC
disk. In the second part (section 5), a preliminary account of the final
results from the EROS-2 programme is presented. Based on the analysis of 33
million LMC and SMC stars followed during 6.7 years, strict limits on the macho
content of the galactic halo are presented; they cover the range of macho
masses between 0.0001 and 100 solar mass. The limits are better than 20% (resp.
5%) of the standard halo for masses between 0.0002 and 10 (resp. 0.001 to 0.1)
solar mass. This is presently the data set with the largest sensitivity to halo
machos.


title: A nonextensive entropy approach to solar wind intermittency

abstract:
  The probability distributions (PDFs) of the differences of any physical
variable in the intermittent, turbulent interplanetary medium are scale
dependent. Strong non-Gaussianity of solar wind fluctuations applies for short
time-lag spacecraft observations, corresponding to small-scale spatial
separations, whereas for large scales the differences turn into a Gaussian
normal distribution. These characteristics were hitherto described in the
context of the log-normal, the Castaing distribution or the shell model. On the
other hand, a possible explanation for nonlocality in turbulence is offered
within the context of nonextensive entropy generalization by a recently
introduced bi-kappa distribution, generating through a convolution of a
negative-kappa core and positive-kappa halo pronounced non-Gaussian structures.
The PDFs of solar wind scalar field differences are computed from WIND and ACE
data for different time lags and compared with the characteristics of the
theoretical bi-kappa functional, well representing the overall scale dependence
of the spatial solar wind intermittency. The observed PDF characteristics for
increased spatial scales are manifest in the theoretical distribution
functional by enhancing the only tuning parameter $\kappa$, measuring the
degree of nonextensivity where the large-scale Gaussian is approached for
$\kappa \to \infty$. The nonextensive approach assures for experimental studies
of solar wind intermittency independence from influence of a priori model
assumptions. It is argued that the intermittency of the turbulent fluctuations
should be related physically to the nonextensive character of the
interplanetary medium counting for nonlocal interactions via the entropy
generalization.


title:
The local sub-mm luminosity functions and predictions from Spitzer to
  Herschel

abstract:
  We present new determinations of the local sub-mm luminosity functions,
solving the ``sub-mm Olbers' Paradox.'' We also present predictions of source
counts and luminosity functions in current and future far-infrared to sub-mm
surveys. Using the sub-mm colour temperature relations from the SCUBA Local
Universe Galaxy Survey, and the discovery of excess 450 micron excess emission
in these galaxies, we interpolate and extrapolate the IRAS detections to make
predictions of the SEDs of all 15411 PSC-z galaxies from 50-1300 microns.
Despite the long extrapolations we find excellent agreement with (a) the 90
micron luminosity function of Serjeant et al. (2001), (b) the 850 micron
luminosity function of Dunne et al. (2000), (c) the mm-wave photometry of
Andreani & Franceschini (1996); (d) the asymptotic differential and integral
source count predictions at 50-1300 microns by Rowan-Robinson (2001). We find
the local 850 micron sub-mm luminosity density converges to (7.3+/-0.2)x10^{19}
h_{65} W/Hz/Mpc^3. Remarkably, the local spectral luminosity density and the
extragalactic background light together strongly constrain the cosmic star
formation history for a wide class of evolutionary assumptions. We find that
the extragalactic background light, the 850 micron 8mJy source counts, and the
Omega_* constraints all independently point to a decline in the comoving star
formation rate at z>1. In order to reconcile this with direct determinations,
we suggest either there is a top-heavy initial mass function at high redshifts,
and/or there is stronger evolution in the more luminous far-infrared galaxies
than seen in the population as a whole.


title: Lambda Orionis: A 0.02-50 Msun Initial Mass Function

abstract:
  The Lambda Orionis Star Forming Region is dominated by the O8 III star
lambda^1 Ori. Among other structures, it includes a CO and a dust ring whose
diameter is about nine deg, the S264 HII region, a large number of IRAS
sources, the Barnard 30 and 35 dark clouds and a cluster associated with the
central star, the Lambda Ori cluster (Collinder 69). We derive the initial mass
function for this cluster (~5 Myr), covering several orders of magnitude in
mass (50 - 0.02 Msun).


title:
Anomalous HI kinematics in Centaurus A: evidence for jet-induced star
  formation

abstract:
  We present new 21-cm HI observations performed with ATCA of the large HI
filament located about 15 kpc NE from the centre of Centaurus A and discovered
by Schiminovich et al.(1994). This HI cloud is situated (in projection) near
the radio jet of Centaurus A, as well as near a large filament of ionised gas
of high excitation and turbulent velocities and near regions with young stars.
The higher velocity and spatial resolution of the new data reveals that, apart
from the smooth velocity gradient corresponding to the overall rotation of the
cloud around Centaurus A, HI with anomalous velocities of about 100 km/s is
present at the southern tip of this cloud. This is interpreted as evidence for
an ongoing interaction between the radio jet and the HI cloud. Gas stripped
from the HI cloud gives rise to the large filament of ionised gas and the star
formation regions that are found downstream from the location of the
interaction. The implied flow velocities are very similar to the observed
anomalous HI velocities. Given the amount of HI with anomalous kinematics and
the current star formation rate, the efficiency of jet-induced star formation
is at most of the order of a percent.


title:
Disks, Tori, and Cocoons: Emission and Absorption Diagnostics of AGN
  Environments

abstract:
  One of the most important problems in the study of active galaxies is
understanding the detailed geometry, physics, and evolution of the central
engines and their environments. The leading models involve an accretion disk
and torus structure around a central dense object, thought to be a supermassive
black hole. Gas found in the environment of AGN is associated with different
structures: molecular accretion disks, larger scale atomic tori, ionized and
neutral "cocoons" in which the nuclear regions can be embedded. All of them can
be studied at radio wavelengths by various means. Here, we summarize the work
that has been done to date in the radio band to characterize these structures.
Much has been learned about the central few parsecs of AGN in the last few
decades with contemporary instruments but the picture remains incomplete. In
order to be able to define a more accurate model of this region, significant
advances in sensitivity, spectral and angular resolution, and bandpass
stability are required. The necessary advances will only be provided by the
Square Kilometer Array and we discuss the possibilities that these dramatic
improvements will open for the study of the gas in the central region of AGN.


title:
Molecular Gas in a z~2.5 Triply-Imaged, sub-mJy Submillimetre Galaxy
  Typical of the Cosmic Far-Infrared Background

abstract:
  We present the results of observations from the IRAM array of the submm
galaxy SMMJ16359+6612 lying at z=2.516 behind the massive cluster A2218. The
foreground gravitational lens produces 3 images with a total mag. of 45 of this
faint submm galaxy, which has an intrinsic submm flux of f_850mic=0.8mJy
placing it below the confusion limit of blank-field surveys. The substantial
magnification provides a rare opportunity to probe the nature of a distant
sub-mJy submm-selected galaxy, part of the population which produces the bulk
of the submm cosmic far-infrared background. Our observations detect the
CO(3-2) line in all 3 images, as well as the CO(7-6) line and the dust
continuum at 1.3mm for the brightest image. The CO(3-2) velocity profile
displays a double-peak profile which is well fit by two Gaussians with FWHM of
220km/s and separated by 280km/s. We estimate the dynamical mass of the system
to be ~1.5 10^10 M_sun and an H2 gas mass of 2.6 10^9 M_sun. We identify a
spatial offset of ~1'' between the two CO(3-2) velocity components, modeling of
which indicates that the offset corresponds to just ~3kpc in projection at
z=2.5. The spatial and velocity properties of these two components are closely
related to features detected in previously published Halpha spectroscopy. We
conclude that this source is likely to be a compact merger of 2 fairly typical
Ly-break galaxies with a maximal separation between the two nuclei of ~3kpc.
This system is much less luminous and massive than other high-z submm galaxies
studied to date, but it bears a close similarity to similarly luminous, dusty
starburst resulting from lower-mass mergers in the local Universe.


title:
Bar-induced perturbation strengths of the galaxies in the Ohio State
  University Bright Galaxy Survey (OSUBGS) I

abstract:
  This paper presents bar strength measurements for a sample of 180 galaxies,
based on the H-band images of the Ohio State University Bright Galaxy Survey
(Eskridge et al. 2002, ApJS, 143, 73). We use a gravitational bar torque
method, where the ratio of the maximum tangential force to the mean
axisymmetric radial force is used as a quantitative measure of the bar
strength. Based on our Fourier analysis we found that nearly 70 % of the
galaxies classified as SAB-types in the near-IR might actually be non-barred
systems. We also found that ovals are capable of inducing tangential forces at
some level. The measurements of this study are used by Buta et al. (AJ, 127,
279) for the analysis of the distribution of bar strengths in spiral galaxies,
and by Laurikainen et al. (ApJ, 607, 103) to study the connection between bar
strength and nuclear activity.


title: Coronal heating through braiding of magnetic field lines

abstract:
  Cool stars like our Sun are surrounded by a million degree hot outer
atmosphere, the corona. Since more than 60 years the physical nature of the
processes heating the corona to temperatures well in excess of those on the
stellar surface remain puzzling. Recent progress in observational techniques
and numerical modeling now opens a new window to approach this problem. We
present the first coronal emission line spectra synthesized from
three-dimensional numerical models describing the evolution of the dynamics and
energetics as well as of the magnetic field in the corona. In these models the
corona is heated through motions on the stellar surface that lead to a braiding
of magnetic field lines inducing currents which are finally dissipated. These
forward models enable us to synthesize observed properties like (average)
emission line Doppler shifts or emission measures in the outer atmosphere,
which until now have not been understood theoretically, even though many
suggestions have been made in the past. As our model passes these observational
tests, we conclude that the flux braiding mechanism is a prime candidate for
being the dominant heating process of the magnetically closed corona of the Sun
and solar-like stars.


title:
The Solar Neighborhood XII: Discovery of New High Proper Motion Stars
  with 1.0"/yr > mu >= 0.4"/yr between Declinations -90 degrees and -47 degrees

abstract:
  We report the discovery of 141 new high proper motion systems (1.0"/yr > mu
>= 0.4"/yr) in the southern sky (Declination = -90 degrees to -47 degrees)
brighter than UKST plate R_{59F} = 16.5 via our SuperCOSMOS-RECONS (SCR)
search. When combined with the nine systems having mu >= 1.0"/yr and/or late
spectral type from the initial phases of this effort (Hambly et al. 2004, Henry
et al. 2004), we find that 73 of the 150 total systems are moving faster than
0.5"/yr, and are therefore new members of the classic "LHS" (Luyten Half
Second) sample. These constitute a 21% increase in the sample of stars with mu
>= 0.5"/yr in the declination region searched, thereby comprising an important
addition to this long-neglected region of the sky.
  Distance estimates are provided for the entire sample, based upon a
combination of photographic plate magnitudes and 2MASS photometry, using the
relations presented in Hambly et al. (2004) for the presumed main sequence
stars. Three systems are anticipated to be within 10 pc, and an additional 15
are within 25 pc. Eight of these 18 nearby systems have proper motions falling
between 0.4"/yr and 0.6"/yr, hinting at a large population of nearby stars with
fast, but not extremely high, proper motions that have not been thoroughly
investigated.


title: Transit Detectability of Ring Systems Around Extrasolar Giant Planets

abstract:
  We investigate whether rings around extrasolar planets could be detected from
those planets' transit lightcurves. To this end we develop a basic theoretical
framework for calculating and interpreting the lightcurves of ringed planet
transits based on the existing framework used for stellar occultations, a
technique which has been effective for discovering and probing ring systems in
the solar system. We find that the detectability of large, Saturn-like ring
systems is largest during ingress and egress, and that reasonable photometric
precisions of $\sim 1-3 \times 10^{-4}$ with 15-minute time resolution should
be sufficient to discover such ring systems. For some ring particle sizes,
diffraction around individual particles leads to a detectable level of
forward-scattering that can be used to measure modal ring particle diameters.
An initial census of large ring systems can be carried out using high-precision
follow-up observations of detected transits and by the upcoming NASA
\emph{Kepler} mission. The distribution of ring systems as a function of
stellar age and as a function of planetary semimajor axis will provide
empirical evidence to help constrain how rings form and how long rings last.


title:
Eclipsing binaries as standard candles: HD 23642 and the distance to the
  Pleiades

abstract:
  We present a reanalysis of the light curves of HD 23642, a detached eclipsing
binary star in the Pleiades open cluster, with emphasis on a detailed error
analysis. We compare the masses and radii of the two stars to predictions of
stellar evolutionary models and find that the metal and helium abundances of
the Pleiades are approximately solar. We present a new method for finding
distances to eclipsing binaries, of spectral types A to M, using the empirical
calibrations of effective temperature versus surface brightness given by
Kervella et al. (2004). We use the calibration for K-filter surface brightness
to determine a distance of 139.1 +/- 3.5 pc to HD 23642 and the Pleiades. This
distance is in excellent agreement with distances found from the use of
theoretical and empirical bolometric corrections. We show that the
determination of distance, both from the use of surface brightness relations
and from the use of bolometric corrections, is more accurate and precise at
infrared wavelengths than at optical wavelengths. The distance to HD 23642 is
consistent with that derived from photometric methods and Hubble Space
Telecscope parallaxes, but is inconsistent with the distance measured using
Hipparcos parallaxes of HD 23642 and of other Pleiades stars.


title: Effects of Rotation on Presupernovae Models

abstract:
  We show that rotation strongly affects the nature of the supernova progenitor
(blue/red supergiant or Wolf--Rayet star), and thus the supernova types. In
particular our models well reproduce the variations of the number ratio SNIb/Ic
to SNII with metallicity. Rotation also produces envelope enrichments of the
N/C ratio, and increases the size of the CO cores. We show the evolution of the
specific angular momentum up to the preSN stage and make comparison with
neutron stars. We suggest that the rare WO stars, preferentially formed at low
metallicity, are the progenitors of GRB.


title:
Total to Selective Extinction Ratios and Visual Extinctions from
  Ultraviolet Data

abstract:
  We present determinations of the total to selective extinction ratio R_V and
visual extinction A_V values for Milky Way stars using ultraviolet color
excesses. We extend the analysis of Gnacinski and Sikorski (1999) by using
non-equal weights derived from observational errors. We present a detailed
discussion of various statistical errors. In addition, we estimate the level of
systematic errors by considering different normalization of the extinction
curve adopted by Wegner (2002). Our catalog of 782 R_V and A_V values and their
errors is available in the electronic form on the World Wide Web.


title: A search for late-type supergiants in the inner regions of the Milky Way

abstract:
  We present the results of a narrow-band infrared imaging survey of a narrow
strip (12' wide) around the galactic equator between 6 deg and 21 deg of
galactic longitude aimed at detecting field stars with strong CO absorption,
mainly late-type giants and supergiants. Our observations include follow-up low
resolution spectroscopy (R = 980) of 191 selected candidates in the H and K
bands. Most of these objects have photometric and spectroscopic characteristics
consistent with them being red giants, and some display broad, strong
absorption wings due to water vapor absorption between the H and K bands. We
also identify in our sample 18 good supergiant candidates characterized by
their lack of noticeable water absorption, strong CO bands in the H and K
windows, and HK_S photometry suggestive of high intrinsic luminosity and
extinctions reaching up to A_V ~40 mag. Another 9 additional candidates share
the same features except for weak H2O absorption, which is also observed among
some M supergiants in the solar neighbourhood. Interesting differences are
noticed when comparing our stars to a local sample of late-type giants and
supergiants, as well as to a sample of red giants in globular clusters of
moderately subsolar metallicity and to a sample of bulge stars. (...) We
propose that the systematic spectroscopic differences of our inner Galaxy stars
are due to their higher metallicities that cause deeper mixing in their
mantles, resulting in lower surface abundances of C and O and higher abundances
of CN, which contribute to the strength of the CaI and NaI features at low
resolution. Our results stress the limitations of using local stars as
templates for the study of composite cool stellar populations such as central
starbursts in galaxies (Abridged).


title:
A submillimeter exponential disk in M~51: evidence for an extended cold
  dust disk

abstract:
  A 850 micron map of the interacting spiral galaxy M51 shows well-defined
spiral arms, closely resembling the structures seen in CO and HI emission.
However, most of the 850 micron emission originates in an underlying
exponential disk, a component that has not been observed before in a face-on
galaxy at these wavelengths. The scale-length of this disk is 5.45 kpc, which
is somewhat larger than the scale-length of the stellar disk, but somewhat
smaller than that of atomic hydrogen. Its profile can not be explained solely
by a radial disk temperature gradient but requires the underlying dust to have
an exponential distribution as well. This reinforces the view that the submm
emission from spiral galaxy disks traces total hydrogen column density, i.e.the
sum of H2 and HI. A canonical gas-to-dust ratio of 100+/-26 is obtained for
kappa(850)=1.2 g**-1 cm**2, where kappa(850) is the dust opacity at 850 micron.


title: Polarimetric line profiles for scattering off rotating disks

abstract:
  We predict polarimetric line profiles for scattering off rotating disks using
a Monte Carlo technique. We have discovered that there is a marked difference
between scattering of line emission by a disk that reaches the stellar surface,
and a disk with an inner hole. For the case with an inner hole, we find single
position-angle rotations, similar to those predicted by analytic models. For
the case of an undisrupted disk, we find double rotations in the position angle
-- an effect not reported before. We show that this new effect is due to the
finite-sized star interacting with the disk's rotational velocity field. Since
a gradual increase of the hole size transforms the double rotations smoothly
back into single ones -- as the line emission object approaches that of a point
source -- our models demonstrate the diagnostic potential of line polarimetry
in determining not only the disk inclination, but also the size of the disk
inner hole. Our models are generic, and relevant to any line emitting object
that is embedded in a rotating disk. Examples are: Herbig Ae stars, T Tauri
stars, other young stars, early-type stars with disks, post-AGB stars,
cataclysmic variables and other binary systems, as well as extra-galactic
objects, such as the disks around super-massive black holes.


title:
HEALPix -- a Framework for High Resolution Discretization, and Fast
  Analysis of Data Distributed on the Sphere

abstract:
  HEALPix -- the Hierarchical Equal Area iso-Latitude Pixelization -- is a
versatile data structure with an associated library of computational algorithms
and visualization software that supports fast scientific applications
executable directly on very large volumes of astronomical data and large area
surveys in the form of discretized spherical maps. Originally developed to
address the data processing and analysis needs of the present generation of
cosmic microwave background (CMB) experiments (e.g. BOOMERanG, WMAP), HEALPix
can be expanded to meet many of the profound challenges that will arise in
confrontation with the observational output of future missions and experiments,
including e.g. Planck, Herschel, SAFIR, and the Beyond Einstein CMB
polarization probe. In this paper we consider the requirements and constraints
to be met in order to implement a sufficient framework for the efficient
discretization and fast analysis/synthesis of functions defined on the sphere,
and summarise how they are satisfied by HEALPix.


title:
Altitude Effect in Cherenkov Light Flashes of Low Energy
  Gamma-ray-induced Atmospheric Showers

abstract:
  At present the ground-based Very High Energy (VHE) gamma-ray astronomy is
racing to complete construction of a number of modern gamma-ray detectors, i.e.
CANGAROO III, MAGIC, H.E.S.S., and VERITAS. They should be fully operational in
a year's time. After much debate, the further development of this gamma-ray
astronomy in the foreseeable future must be widely anticipated to proceed with
the designing and building of a new instrumentation, which is primarily
intended for the further drastic reduction of the energy threshold in gamma-ray
observations down to about 10 GeV. On the ground one can hardly reach such low
energy thresholds without considerably larger, up to 30 m diameter, optical
telescopes, which might be able to collect sufficient amount of Cherenkov light
from the atmospheric gamma-ray showers of that low energy. If not taken off the
ground entirely (like GLAST), then it seems to be profitable to mount future
low energy Cherenkov telescopes at higher altitudes in the atmosphere in order
that they will be able to detect substantially more unabsorbed Cherenkov light
from a shower. There are a few sites up on the high mountains of roughly 5 km
height worldwide, which can be used for such a venture. However, one has to
remember that actual time profile, and in particular a two-dimensional
distribution (image) of Cherenkov light flash from atmospheric gamma-ray
showers, undergo a rapid change after an increase in the observational level.
This paper briefly describes the results of a topological analysis of Cherenkov
light images calculated at both conventional and desirable altitudes of 2.2 and
5 km above the sea, respectively. A discussion on major upgrades of image
topology at high altitude is also given.


title: The star formation rate history in the FORS Deep and GOODS South Fields

abstract:
  We measure the star formation rate (SFR) as a function of redshift z up to z
\~4.5, based on B, I and (I+B) selected galaxy catalogues from the FORS Deep
Field (FDF) and the K-selected catalogue from the GOODS-South field. Distances
are computed from spectroscopically calibrated photometric redshifts accurate
to (Delta_z / (z_spec+1)) ~0.03 for the FDF and ~0.056 for the GOODS-South
field. The SFRs are derived from the luminosities at 1500 Angstroem. We find
that the total SFR estimates derived from B, I and I+B catalogues agree very
well ($\lsim 0.1$ dex) while the SFR from the K catalogue is lower by ~0.2 dex.
We show that the latter is solely due to the lower star-forming activity of
K-selected intermediate and low luminosity (L<L_*) galaxies. The SFR of bright
(L>L_*) galaxies is independent of the selection band, i.e. the same for B, I,
(I+B), and K-selected galaxy samples. At all redshifts, luminous galaxies
(L>L_*) contribute only ~1/3 to the total SFR. There is no evidence for
significant cosmic variance between the SFRs in the FDF and GOODs-South field,
  ~0.1 dex, consistent with theoretical expectations. The SFRs derived here are
in excellent agreement with previous measurements provided we assume the same
faint-end slope of the luminosity function as previous works (alpha ~ -1.6).
However, our deep FDF data indicate a shallower slope of alpha=-1.07, implying
a SFR lower by ~0.3 dex. We find the SFR to be roughly constant up to z ~4 and
then to decline slowly beyond, if dust extinctions are assumed to be constant
with redshift.


title: On Detecting the X-ray Silhouette of a Damped Lyman alpha System

abstract:
  We explore the possibility of resolving an image of a damped Lyman alpha
(DLA) system in absorption against an extended, diffuse background X-ray
source. Typical columns of neutral hydrogen in DLAs are high enough to block
out up to ~30% of the soft X-ray flux at an observed photon energy of 0.5 keV,
and we find that ~ 1% of the area of extended X-ray sources at z > 1 have their
0.5 keV flux reduced by at least 20%. We discuss the observability of such
absorption and find that < 2 arcsecond resolution, and > 300 photons per
angular resolution element are required in the 0.3-8 keV band for its
detection, and in order to distinguish it from intrinsic surface brightness
fluctuations. For the surface brightness of the currently known high-redshift
extended X-ray sources, this requires an integration time of a few Msec on
Chandra. The detection will be within the reach of a routine observation with a
next generation X-ray telescope such as XEUS or Generation X.


title: Non-thermal X-ray Emission from Supernova Remnants

abstract:
  Recent studies of narrow, X-ray synchrotron radiating filaments surrounding
young supernova remnants indicate that magnetic fields strengths are relatively
high, B ~ 0.1 mG, or even higher, and that diffusion is close to the Bohm
limit. I illustrate this using Cas A as an example. Also older remnants such as
RCW 86 appear to emit X-ray synchrotron radiation, but the emission is more
diffuse, and not always confined to a region close to the shock front. I argue
that for RCW 86 the magnetic field is likely to be low (B ~ 17 microGauss), and
at the location where the shell emits X-ray synchrotron radiation the shock
velocity is much higher than the average shock velocity of ~600 km/s.


title: Spectropolarimetry of Core-Collapse Supernovae

abstract:
  We briefly review the young field of spectropolarimetry of core-collapse
supernovae (SNe). Spectropolarimetry provides the only direct known probe of
early-time supernova (SN) geometry. The fundamental result is that asphericity
is a ubiquitous feature of young core-collapse SNe. However, the nature and
degree of the asphericity vary considerably. The best predictor of
core-collapse SN polarization seems to be the mass of the hydrogen envelope
that is intact at the time of the explosion: those SNe that arise from
progenitors with large, intact envelopes (e.g., Type II-plateau) have very low
polarization, while those that result from progenitors that have lost part (SN
IIb, SN IIn) or all (SN Ib) of their hydrogen (or even helium; SN Ic) layers
prior to the explosion tend to show substantial polarization. Thus, the deeper
we probe into core-collapse events, the greater the asphericity seems to be,
suggesting a fundamentally asymmetric explosion with the asymmetry damped by
the addition of envelope material.


title:
X-rays of Stellar Coronae with Chandra and XMM-Newton: Flares and
  Elemental Composition in Stellar Atmospheres (Invited review)

abstract:
  Observations of magnetically active stars with Chandra and XMM-Newton have
deepened our knowledge of the physics of the atmospheres in late-type stars. In
this review paper, I discuss two topics that have profited significantly from
Chandra and XMM-Newton. Of particular interest, studies of the elemental
composition of stellar coronae have taken advantage of the high spectral
resolution available with the grating instruments on board these satellites. I
summarize the status of our knowledge and discuss the elemental composition in
a variety of stellar coronae. I also focus on the topic of flares in stellar
coronae, and review the contributions made by XMM-Newton and Chandra to X-ray
and multi-wavelength studies.


title: A Multiwavelength Study of RZ Cassiopeiae: The XMM-Newton/VLA Campaign

abstract:
  XMM-Newton and the VLA simultaneously observed the eclipsing Algol-type
binary RZ Cassiopeiae in August 2003. The secondary eclipse (K3 IV companion
behind the A3 V primary) was placed at the center of the 15-hour radio
campaign, while the X-ray satellite monitored a full 1.2-day orbital period. We
present results of the X-ray and radio campaigns. The X-ray light curve shows
significant modulation probably related to rotational modulation and active
region evolution, and even small flares. However, the X-ray eclipse is not
deep, implying that the coronal X-ray emitting material is spatially extended.
The Reflection Grating Spectrometer (RGS) spectrum shows a variety of bright
emission lines from Fe, Ne, O, N. A strong [C/N] depletion probably reflects
the surface composition of the secondary which fills its Roche lobe and loses
material onto the primary. The O~\textsc{vii} He-like triplet reflects a low
forbidden-to-intercombination ratio; while it generally suggests high electron
densities, the ratio is here modified by photoexcitation by the strong UV flux
of the primary A3 V star. The radio light curve shows no similarity to the
X-ray light curve. The eclipse timings are different, and the radio flux
increased while the X-ray flux decreased. The radio spectral slope is shallow
($\alpha = 0 - 1$).


title: Pulsar kicks from neutrino oscillations

abstract:
  Neutrino oscillations in a core-collapse supernova may be responsible for the
observed rapid motions of pulsars. Given the present bounds on the neutrino
masses, the pulsar kicks require a sterile neutrino with mass 2-20 keV and a
small mixing with active neutrinos. The same particle can be the cosmological
dark matter. Its existence can be confirmed the by the X-ray telescopes if they
detect a 1-10 keV photon line from the decays of the relic sterile neutrinos.
In addition, one may be able to detect gravity waves from a pulsar being
accelerated by neutrinos in the event of a nearby supernova.


title: A Survey for Outer Satellites of Mars: Limits to Completeness

abstract:
  We surveyed the Hill sphere of Mars for irregular satellites. Our search
covered nearly the entire Hill Sphere, but scattered light from Mars excluded
the inner few arcminutes where the satellites Phobos and Deimos reside. No new
satellites were found to an apparent limiting red magnitude of 23.5, which
corresponds to radii of about 0.09 km using an albedo of 0.07.


title: A Realistic Particle Physics Dark Energy Model

abstract:
  We present a realistic dark energy model derived from particle physics. Our
model has essentially no free parameters and has an equivalent fit to the
observational data (CMB, SN1a and LSS) as LCDM and a better fit than the best
effective $w(z)$ model. With the lack of a clear determination of the
cosmological parameters theoretical considerations should be taken seriously to
distinguish between dark energy models.


title: A Physical Bias in Cosmological Simulations

abstract:
  Numerical simulation plays an important role in the study of structure
formation of the universe. However, the mass resolution in current simulations
is still poor. Due to technical difficulties, it is necessary to use both
greatly reduced number density of particles and greatly raised unit particle
mass. Consequently, the particle masses used in cosmological simulations are
about $10^{70}$ times larger than the $Gev$ candidates in particle physics.
This is a huge physical bias that cannot be neglected when interpreting the
results of the simulations. Here we discuss how such a bias affects Cold Dark
Matter (CDM) cosmological simulations. We find that the small scale properties
of the CDM particle system are changed in two aspects. 1) An upper limit is
imposed on the spatial resolution of the simulation results. 2) Most
importantly, an unexpected short mean free path is produced, and the
corresponding two body scattering cross section is close to the value expected
in the Self-Interaction Dark Matter(SIDM) model. Since the mean free path of
real CDM particle systems is much longer than that in the simulations, our
results imply 1) that there is probably no 'cusp problem' in real CDM halos,
and 2) that a much longer time is needed to form new virialized halos in real
CDM particle systems than in the simulations. This last result can help us
understand the 'substructure problem'. Our discussion can also explain why the
massive halos in the simulations may have smaller concentration coefficients.


title: Spectroscopy and near-infrared photometry of the helium nova V445 Puppis

abstract:
  Nova Puppis 2000 (V445 Pup) has been proposed as the first example of a
helium nova. Recent optical spectroscopy of V445 Pup at V=19.91 mag obtained
with IMACS on the 6.5-m Magellan telescope, shows that the spectrum consists of
HeI, [OI], [OII] and [OIII] emission lines and no hydrogen is present. The
spectroscopy shows an expanding nova shell with blue- and redshifted velocity
components around +/- 850 km/s and +/- 1600 km/s. Images taken with Magellan
under very good seeing conditions (FWHM ~ 0.6") shows V445 Pup to be extended
(full width at zero intensity ~ 1.9") and elongated (position angle ~ 150deg).
We have followed the secular evolution of V445 Pup since the decline from
(optical) maximum, at near-infrared wavelengths (J, H and Ks) using the
Infrared Survey Facility (IRSF) at the Sutherland site of the South African
Astronomical Observatory. We find that V445 Pup is still covered by a dense
dust shell more than three years after its outburst.


title:
A Robust Method for the Analysis of Integrated Spectra from Globular
  Clusters using Lick Indices

abstract:
  We define a method for analysis of the integrated spectra of extra-galactic
globular clusters that provides more reliable measures of age, metallicity and
alpha-element abundance ratio than have so far been achieved. The method
involves the simultaneous fitting of up to 25 Lick indices in a
chi-squared-fitting technique that maximises the use of the available data.
Here we compare three sets of single stellar population (SSP) models of Lick
indices to the high signal-to-noise, integrated spectra of 20 Galactic globular
clusters. The ages, [Fe/H] and alpha-element abundance ratios derived from the
SSP models are compared to the results of resolved stellar population studies
from the literature. We find good consistency with the published values, with
an agreement of better than 0.1 dex in all three derived parameters. The
technique allows identification of abundance ratio anomalies, such as the known
nitrogen over-abundance in Galactic globular clusters, and the presence of
anomalous horizontal-branch morphologies. It also minimises the impact on the
derived parameters of imperfect calibration to the Lick system, and reduction
errors in general. The method defined in this work is therefore robust with
respect to many of the difficulties that plague the application of SSP models
in general, and is, consequently, well suited to the study of extra-galactic
globular cluster systems.


title: Relativistic Gravitational mass in Tolman-VI type solution

abstract:
  Some known solutions for static charged fluid spheres of Tolman-VI type in
general relativity are reexamined. The gravitational mass that appears in the
Pant and Sah \cite{pan79} and Tikekar \cite{tik84} solutions is shown to be of
electromagnetic origin in the sense that the gravitational mass, along with all
other physical quantities, depends on the electromagnetic field alone. The
energy condition, singularity and stability problems of the models are
discussed thoroughly.


title: Chemical Abundances and Yields from Massive Stars

abstract:
  Stellar rotation produces an internal mixing of the elements due to shear
instability and meridional circulation. This leads to observable $N/C$
enhancements in massive stars above about 7--9 $M_{\odot}$. Rotation also
favours mass loss by stellar winds. Mass loss effects dominate for masses above
30 $M_{\odot}$, while mixing dominates below that limit.
  The effects of mixing are also much larger at lower metallicity $Z$, because
the internal $\Omega$--gradients are steeper. This appears to be in agreement
with observations in the SMC.
  At very low $Z$ and Z=0, mixing between the He--burning core and the
H--burning shell leads to the production of primary N in intermediate mass
stars.
  Such enrichments increase the metallicity of the rotating star, also massive
Z=0 stars with moderate initial velocities currently reach break--up velocity
during a fraction of the MS phase. Both effects favour mass loss in Z=0 stars,
which have ejecta with abundance anomalies very similar to those of C--rich
very metal poor stars.


title:
Probing the evolutionary status of starless cores through N2H+ and N2D+
  observations

abstract:
  We have undertaken a survey of N2H+ and N2D+ towards 31 low-mass starless
cores using the IRAM 30m telescope. Our main objective has been to determine
the abundance ratio of N2D+ and N2H+ towards the nuclei of these cores and thus
to obtain estimates of the degree of deuterium enrichment, a symptom of
advanced chemical evolution according to current models. We find that the
N(N2D+)/N(N2H+) ratio is larger in more "centrally concentrated cores" with
larger peak H2 and N2H+ column density than the sample mean. The deuterium
enrichment in starless cores is presently ascribed to depletion of CO in the
high density (> 3*10^4 cm-3) core nucleus. To substantiate this picture, we
compare our results with observations in dust emission at 1.2 mm and in two
transitions of C18O. We find a good correlation between deuterium fractionation
and N(C18O)/N(H2) for the nuclei of 14 starless cores. We, thus, identified a
set of properties that characterize the most evolved, or "pre-stellar",
starless cores. These are: higher N2H+ and N2D+ column densities, higher
N(N2D+)/N(N2H+), more pronounced CO depletion, broader N2H+ lines with infall
asymmetry, higher central H2 column densities and a more compact density
profile than in the average core. We conclude that this combination of
properties gives a reliable indication of the evolutionary state of the core.
Seven cores in our sample (L1521F, OphD, L429, L694, L183, L1544 and TMC2) show
the majority of these features and thus are believed to be closer to forming a
protostar than are the other members of our sample. Finally, we note that the
subsample of Taurus cores behaves more homogeneously than the total sample, an
indication that the external environment could play an important role in the
core evolution.


title: Dark Energy and the Dark Matter relic abundance

abstract:
  Two mechanisms by which the Quintessence scalar could enhance the relic
abundance of dark matter particles are discussed. This effect can have an
impact on supersymmetric candidates for dark matter.


title:
Microarcsecond astrometry with Gaia: the solar system, the Galaxy and
  beyond

abstract:
  Gaia is an all sky, high precision astrometric and photometric satellite of
the European Space Agency (ESA) due for launch in 2010-2011. Its primary
mission is to study the composition, formation and evolution of our Galaxy.
Gaia will measure parallaxes and proper motions of every object in the sky
brighter than V=20, amounting to a billion stars, galaxies, quasars and solar
system objects. It will achieve an astrometric accuracy of 10muas at V=15 -
corresponding to a distance accuracy of 1% at 1kpc. With Gaia, tens of millions
of stars will have their distances measured to a few percent or better. This is
an improvement over Hipparcos by several orders of magnitude in the number of
objects, accuracy and limiting magnitude. Gaia will also measure radial
velocities for source brighter than V~17. To characterize the objects, each
object is observed in 15 medium and broad photometric bands with an onboard CCD
camera. With these capabilities, Gaia will make significant advances in a wide
range of astrophysical topics. These include a detailed kinematical map of
stellar populations, stellar structure and evolution, the discovery and
characterization of thousands of exoplanetary systems and General Relativity on
large scales. I give an overview of the mission, its operating principles and
its expected scientific contributions. For the latter I provide a quick look in
five areas on increasing scale size in the universe: the solar system, exosolar
planets, stellar clusters and associations, Galactic structure and
extragalactic astronomy.


title:
The populations of planetary nebulae in the direction of the Galactic
  bulge

abstract:
  We have observed 44 planetary nebulae (PNe) in the direction of the Galactic
bulge, and merged our data with published ones. We have distinguished, in the
merged sample of 164 PNe, those PNe most likely to prtain physically to the
Galactic bulge and those most likely to belong to the Galactic disk. We have
determined the chemical composition of all the 164 objects in a coherent way.
We looked for stellar emission features and discovered 14 new [WR] stars and 15
new weak emission line central stars.
  The analyzed data led us to the following conclusions: (1) The spectral type
distribution of [WR] stars is very different in the bulge and in the disk of
the Galaxy. However, the observed distributions are strongly dependent on
selection effects. (2) The proportion of [WR] PNe is significantly larger in
the bulge than in the disk. (3) The oxygen abundances in [WR] stars do no
appear to be significantly affected by nucleosynthesis and mixing in the
progenitors. (4) The O/H gradient of the Galactic disk PNe population flattens
in the most internal parts of the Galaxy. (5) The median oxygen abundance in
the bulge PN population is larger by 0.2 dex than in the disk population seen
in the direction of the bulge. (6) Bulge PNe with smaller O/H tend to have
smaller radial velocities. (7) The oxygen abundance distribution of bulge PNe
is similar in shape to that of the metallicity distribution of bulge giants,
but significantly narrower. (8) The location of SB 32 (PN G 349.7-09.1) in the
(V_lsr, l_II) diagram and its low oxygen abundance argues that it probably
belongs to the halo population.


title:
A Solution to the Isolatitude, Equi-area, Hierarchical Pixel-Coordinate
  System

abstract:
  Gorski et al (1999b) have earlier presented the outline of a
pixelisation-to-spherical-coordinate transformation scheme which simultaneously
satisfies three properties which are especially useful for rapid analyses of
maps on a sphere: (i) equal spacing of pixels along lines of constant latitude,
(ii) equal pixel `areas' (solid angles) and (iii) hierarchical scaling with
increasing numbers of pixels. Their outline is based on the division of the
sphere into twelve regions covering equal solid angles, which are
hierarchically subdivided in a way compatible with these three criteria. In
this paper, a complete derivation of this scheme is presented, including, in
particular, (1) the angle theta^* defining the limit between polar and
equatorial regions, and (2) the transformations from the unit interval [0,1]
\wedge [0,1] to spherical coordinates in a polar region.


title:
Is 3C111, an apparently normal radio galaxy, the counterpart of 3EG
  J0416+3650?

abstract:
  The Third EGRET Catalog (3EG) lists 66 high-confidence identifications of
sources with Active Galactic Nuclei (AGN). All are classified as belonging to
the blazar class, with the only exception of the nearby radio galaxy Centaurus
A. We report and strengthen the association of another radio galaxy, 3C111,
with the EGRET source 3EG J0416+3650. At the time of the compilation of the 3EG
catalogue, 3C111 has been considered as a low-confidence counterpart of
3EGJ0416+3650, being located outside the 99% gamma-ray probability contour.
Since this first suggestion, no other counterparts have been reported nor the
EGRET error box has been searched for likely candidates. 3C111 has never been
considerated or cited in literature as a radiogalaxy counterpart of an EGRET
source. We report a detailed multiwavelength study of the EGRET error box as
well as for the first time the overall spectral energy distribution of 3C111,
which appears to be intriguingly similar to those of blazars, suggesting that
the radiogalaxy 3C111 is the likely counterpart of 3EG J0416+3650.


title:
Least-squares methods with Poissonian noise: an analysis and a
  comparison with the Richardson-Lucy algorithm

abstract:
  It is well-known that the noise associated with the collection of an
astronomical image by a CCD camera is, in large part, Poissonian. One would
expect, therefore, that computational approaches that incorporate this a priori
information will be more effective than those that do not. The Richardson-Lucy
(RL) algorithm, for example, can be viewed as a maximum-likelihood (ML) method
for image deblurring when the data noise is assumed to be Poissonian.
Least-squares (LS) approaches, on the other hand, arises from the assumption
that the noise is Gaussian with fixed variance across pixels, which is rarely
accurate. Given this, it is surprising that in many cases results obtained
using LS techniques are relatively insensitive to whether the noise is
Poissonian or Gaussian. Furthermore, in the presence of Poisson noise, results
obtained using LS techniques are often comparable with those obtained by the RL
algorithm. We seek an explanation of these phenomena via an examination of the
regularization properties of particular LS algorithms. In addition, a careful
analysis of the RL algorithm yields an explanation as to why it is more
effective than LS approaches for star-like objects, and why it provides similar
reconstructions for extended objects. We finish with a convergence analysis of
the RL algorithm. Numerical results are presented throughout the paper. It is
important to stress that the subject treated in this paper is not academic. In
fact, in comparison with many ML algorithms, the LS algorithms are much easier
to use and to implement, often provide faster convergence rates, and are much
more flexible regarding the incorporation of constraints on the solution.
Consequently, if little to no improvement is gained in the use of an ML
approach over an LS algorithm, the latter will often be the preferred approach.


title:
First stars VI - Abundances of C, N, O, Li, and mixing in extremely
  metal-poor giants. Galactic evolution of the light elements

abstract:
  We have investigated the poorly-understood origin of nitrogen in the early
Galaxy by determining N abundances in 35 extremely metal-poor halo giants (22
stars have [Fe/H]<-3.0) using the C and O abundances determined in Paper V.
Because any dredge-up of CNO processed material to the surface may complicate
the interpretation of CNO abundances in giants, we have also measured the
surface abundance of lithium. Our sample shows a clear dichotomy between two
groups of stars. The first group shows evidence of C to N conversion through CN
cycling and strong Li dilution, a signature of mixing. The second group shows
no evidence for C to N conversion, and Li is only moderately diluted, and we
conclude that their C and N abundances are very close to those of the gas from
which they formed in the early Galaxy. These "unmixed" stars reflect the
abundances in the early Galaxy: the [C/Fe] ratio is constant (about +0.2 dex)
and the [C/Mg] ratio is close to solar at low metallicity, favouring a high C
production by massive zero-metal supernovae. The [N/Fe] and [N/Mg] ratios
scatter widely. The larger values of these ratios define a flat upper plateau
([N/Mg]= 0.0, [N/Fe]= +0.1), which could reflect higher values within a wide
range of yields of zero-metal Sne II. Alternatively, by analogy with the DLA's,
the lower abundances ([N/Mg]= -1.1, [N/Fe]= -0.7) could reflect generally low
yields from the first Sne II, the other stars being N enhanced by winds of
massive Asymptotic Giant Branch (AGB) stars. At present it cannot be decided
whether primary N is produced primarily in SNe II or in massive AGB stars, or
in both. The stellar N abundances and [N/O] ratios are compatible with those
found in Damped Lyman-alpha (DLA) systems.


title:
Phase mixing of shear Alfven waves as a new mechanism for electron
  acceleration in collisionless, kinetic plasmas

abstract:
  Particle-In-Cell (kinetic) simulations of shear Alfv\'en wave interaction
with one dimensional, across the uniform magnetic field, density inhomogeneity
(phase mixing) in collisionless plasma were performed for the first time. As a
result a new electron acceleration mechanism is discovered. Progressive
distortion of Alfv\'en wave front, due to the differences in local Alfv\'en
speed, generates nearly parallel to the magnetic field electrostatic fields,
which accelerate electrons via Landau damping. Surprisingly, amplitude decay
law in the inhomogeneous regions, in the kinetic regime, is the same as in the
MHD approximation described by Heyvaerts and Priest (1983).


title: Low-Mass Quark Stars or Quark White Dwarfs

abstract:
  An equation of state is considered that, in superdense nuclear matter,
results in a phase transition of the first kind from the nucleon state to the
quark state with a transition parameter Lambda> 3/2. A calculation of the
integrated parameters of superdense stars on the basis of this equation of
state shows that on the stable branch of the dependence of stellar mass on
central pressure (dM/dPc> 0), in the low-mass range, following the formation of
a tooth-shaped break (M = 0.08Msun, R = 200 km) due to quark formation, a new
local maximum with Mmax = 0.082Msun and R = 1251 km is also formed. The mass
and radius of the quark core of such a star turn out to be Mcore = 0.005Msun
and Rcore = 1.7 km, respectively. Mass accretion in this model can result in
two successive transitions to a neutron star with a quark core, with energy
release like supernova outbursts.


title:
Time dependent numerical model for the emission of radiation from
  relativistic plasma

abstract:
  We describe a numerical model constructed for the study of the emission of
radiation from relativistic plasma under conditions characteristic, e.g., to
gamma-ray bursts (GRB's) and active galactic nuclei (AGN's). The model solves
self consistently the kinetic equations for e^\pm and photons, describing
cyclo-synchrotron emission, direct Compton and inverse Compton scattering, pair
production and annihilation, including the evolution of high energy
electromagnetic cascades. The code allows calculations over a wide range of
particle energies, spanning more than 15 orders of magnitude in energy and time
scales. Our unique algorithm, which enables to follow the particle
distributions over a wide energy range, allows to accurately derive spectra at
high energies, >100 \TeV. We present the kinetic equations that are being
solved, detailed description of the equations describing the various physical
processes, the solution method, and several examples of numerical results.
Excellent agreement with analytical results of the synchrotron-SSC model is
found for parameter space regions in which this approximation is valid, and
several examples are presented of calculations for parameter space regions
where analytic results are not available.


title: Galaxy Formation and the Cosmological Angular Momentum Problem

abstract:
  The importance of angular momentum in regulating the sizes of galactic disks
and by this their star formation history is highlighted. Tidal torques and
accretion of satellites in principle provide enough angular momentum to form
disks with sizes that are in agreement with observations. However three major
problems have been identified that challenge cold dark matter theory and affect
models of galaxy evolution: (1) too much angular momentum is transferred from
the gas to the dark halos during infall, leading to disks with scale lengths
that are too small, (2) bulgeless disks require more specific angular momentum
than is generated cosmologically even if gas would not lose angular momentum
during infall, (3) gravitational torques and hierarchical merging produce a
specific angular momentum distribution that does not match the distribution
required to form exponential disks naturally; some gas has exceptionally high
angular momentum, leading to extended outer disks while another large gas
fraction will contain very little specific angular momentum and is expected to
fall into the galactic center, forming a massive and dominant bulge component.
Any self-consistent theory of galaxy formation will require to provide
solutions to these questions. Selective mass loss of low-angular-momentum gas
in an early phase of galaxy evolution currently seems to be the most promising
scenario. Such a process would have a strong affect on the early protogalactic
evolution phase, the origin and evolution of galactic morphologies and link
central properties of galaxies like the origin of central massive black holes
with their global structure.


title:
Self-gravitating accretion disk in Sgr A* few million years ago: was Sgr
  A* a failed quasar?

abstract:
  Sgr A* is extra-ordinarily dim in all wavelengths requiring a very low
accretion rate at the present time. However, at a radial distance of a fraction
of a parsec from Sgr A*, two rings populated by young massive stars suggest a
recent burst of star formation in a rather hostile environment. Here we explore
two ways of creating such young stellar rings with a gaseous accretion disk: by
self-gravity in a massive disk, and by capturing "old" low mass stars and
growing them via gas accretion in a disk. The minimum disk mass is above 10^4
Msun for the first mechanism and is few tens times larger for the second one.
The observed relatively small velocity dispersion of the stars rules out disks
more massive than around 10^5 Msun: heavier stellar or gas disks would warp
each other by orbital precession in an axisymmetric potential too strongly. The
capture of "old" stars by a disk is thus unlikely as the origin of the young
stellar disks. The absence of a massive nuclear gas disk in Sgr A* now implies
that the disk was either accreted by the SMBH, which would then imply almost a
quasar-like luminosity for Sgr A*, or was consumed in the star formation
episode. The latter possibility appears to be more likely on theoretical
grounds. We also consider whether accretion disk plane changes, expected to
occur due to fluctuations in the angular momentum of gas infalling into the
central parsec of a galaxy, would dislodge the embedded stars from the disk
midplane. We find that the stars leave the disk midplane only if the disk
orientation changes on time scales much shorter than the disk viscous time.


title: Local Supermassive Black Holes and Relics of Active Galactic Nuclei

abstract:
  We summarize a study where we test the hypothesis that local black holes (BH)
are relics of AGN activity. We compare the mass function of BHs in the local
universe with that expected from AGN relics, which are BHs grown entirely with
mass accretion during AGN phases. The local BH mass function (BHMF) is
estimated by applying the well-known correlations between BH mass, bulge
luminosity and stellar velocity dispersion to galaxy luminosity and velocity
functions. The density of BHs in the local universe is 4.6 (-1.4;+1.9) 10^5
Msun Mpc-3. The relic BHMF is derived from the continuity equation with the
only assumption that AGN activity is due to accretion onto massive BHs and that
merging is not important. We find that the relic BHMF at z=0 is generated
mainly at z<3. Moreover, the BH growth is anti-hierarchical in the sense that
smaller BHs (MBH<10^7 Msun) grow at lower redshifts (z<1) with respect to more
massive ones (z~1-3). Unlike previous work, we find that the BHMF of AGN relics
is perfectly consistent with the local BHMF indicating the local BHs were
mainly grown during AGN activity. This agreement is obtained while satisfying,
at the same time, the constraints imposed by the X-ray background. The
comparison with the local BHMF also suggests that the merging process is not
important in shaping the relic BHMF, at least at low redshifts (z<3). Our
analysis thus suggests the following scenario: local BHs grew during AGN phases
in which accreting matter was converted into radiation with efficiencies
eff=0.04-0.16 and emitted at a fraction lambda=0.1-1.7 of the Eddington
luminosity. The average total lifetime of these active phases ranges from ~4.5
10^8 yr for MBH<10^7 Msun to ~1.5 10^8 yr for MBH>10^9 Msun.


title: Kinematics of Diffuse Ionized Gas Halos

abstract:
  Existing long-slit spectral data for edge-on spiral galaxies suggesting that
their Diffuse Ionized Gas (DIG) halos rotate slower than their underlying disks
are summarized. An attempt to characterize lagging halos using a model of
purely ballistic disk-halo flow is discussed, with the result that the model
fails badly for the lagging halo of NGC 891, but is somewhat more successful
for NGC 5775. New two-dimensional kinematic data on the DIG halo of NGC 4302
are presented, along with a preliminary analysis of its rotation.
Two-dimensional data on NGC 5775 and a preliminary analysis of its halo
rotation is discussed by Heald et al. (this volume). The halo of NGC 4302 shows
clear signs of lagging on its approaching side, but also strong indications of
peculiar kinematics. The kinematics of the receding side are more complex.