title: ISO and the Cosmic Infrared Background

abstract:
  ISO observed, for the first time to such a high sensitivity level, the mid-
and far-infrared universe. A Number of deep surveys were performed to probe the
cosmological evolution of galaxies. In this review, I discuss and summarize
results of mid-infrared ISOCAM and far-infrared ISOPHOT surveys, and show how
our vision of the extragalactic infrared universe has become more accurate. In
particular, ISO allowed us to resolve into sources a significant fraction of
the Cosmic Infrared Background (CIB) in the mid-infrared, and to probe a
fainter population in the far-infrared with the detection of the CIB
fluctuations. Together with other wavelength data sets, the nature of ISO
galaxies is now in the process of being understood. I also show that the high
quality of the ISO data put strong constraints on the scenarios of galaxy
evolution. This induced a burst in the development of models, yielding to a
more coherent picture of galaxy evolution. I finally emphasize the potential of
the ISO data archive in the field of observational cosmology, and describe the
next steps, in particular the forthcoming cosmological surveys to be carried
out by SIRTF.


title: An Ultra-luminous X-Ray Object with a 2 hour period in M51

abstract:
  Ultra-luminous X-Ray Objects are off-nucleus point sources with
$L_X=10^{39}$-$10^{41}$ erg/s but the nature of such systems are largely
unidentified. Here we report a 2.1 hour period observed in a Chandra ACIS
observation for ULX M51 X-7, which is located on the edge of a young star
cluster in the star forming region in a spiral arm. In two ACIS observations
separated by one year, the ULX changed from a high-hard to a low-soft spectral
state, in contrast to most Galactic low mass X-ray binaries. Based on its
period and spectral behaviors, we suggest that this ULX is a low mass X-ray
binary system, with a dwarf companion of 0.2-0.3 $M_\odot$ and a compact
accretor, either a neutron star or a black hole, whose mass is not well
constrained. Relativistic beaming effects are likely involved to produce the
observed high X-ray luminosities given its low accretion rate as inferred from
a sustainable accretion scenario via Roche lobe overflow.


title:
Predictions for Cosmological Infrared Surveys from Space with the
  Multiband Imaging Photometer for SIRTF (MIPS)

abstract:
  We make predictions for the cosmological surveys to be conducted by
MIPS/SIRTF at 24, 70 and 160 microns, for the GTO and the legacy programs,
using the latest knowledge of the instrument. In addition to detector and
cirrus confusion noise, we discuss in detail the derivation of the confusion
noise due to extragalactic sources, that depends strongly on the shape of the
source counts at a given wavelength and on the telescope and detector pixel
sizes. We show that it is wise in general to compare the classical photometric
criterion and the so called source density criterion to predict the confusion
levels. We obtain, using the model of Lagache, Dole, & Puget (2002) limiting
fluxes of 50 microJy, 3.2 mJy and 36 mJy at 24, 70 and 160 microns (resp.). We
compute the redshift distributions of the detected sources at each wavelength,
and show that they extend up to z ~ 2.7 at 24 microns and up to z ~ 2.5 at 70
and 160 microns, leading to resolve at most 69, 54 and 24% of the Cosmic
Infrared Background (CIB) at 24, 70 and 160 microns (resp.). We estimate which
galaxy populations will be used to derive the luminosity function evolution
with redshift. We also give the redshift distributions of the unresolved
sources in the FIR range, that dominates the fluctuations of the CIB, and a
predicted power spectrum showing the feasibility of fluctuations (due to
Poissonian & clustered source distributions) measurements. The main conclusion
is that MIPS (and SIRTF in general) cosmological surveys will greatly improve
our understanding of galaxy evolution by giving data with unprecedented
accuracy in the mid and far infrared range.


title:
The Blue Straggler RS CVn Star S1082 in M67: A Detailed Light Curve and
  the Possibility of a Triple

abstract:
  We present a picture of the very unusual blue straggler S1082 in the old open
cluster M67 whose light is the sum of a close binary (P = 1.0677978 d) and
another cluster member. We provide a complete V-band light curve for the
system, and show a number of unusual features including brightness variations
at the 0.01-0.03 mag level from month to month at all phases, and a narrow
primary and broad secondary eclipses. We use spectra from several sources to
constrain the temperatures of the three known components, the relative flux
contributions, rotational velocities, and radial velocities. The data clearly
show that the brightest star (narrow-line component) seen in the spectrum is on
an orbit with period P = 1189 +/- 7 d and eccentricity e = 0.57 +/- 0.08,
although we cannot prove that there is a dynamical link between it and the
close binary. Our models of the system indicate that the cooler component of
the close binary lies on the main sequence near the cluster turn-off, while the
hotter component lies near an extension of the main sequence blueward of the
turn-off, and thus qualifies as a blue straggler by itself. The reduction of
the masses of the stars in the close binary compared to previous models
indicates that it is possible that the more massive component of the close
binary formed from a merger of just two turnoff-mass stars.(abridged)


title: The optical counterpart of a Ultraluminous X-Ray Object in M81

abstract:
  Ultraluminous X-Ray Objects are off-nucleus point sources with
$L_X=10^{39}$-$10^{41}$ erg/s and are among the most poorly understood X-ray
sources. To help understand their nature, we are trying to identify their
optical counterparts by combining images from the Hubble Space Telescope and
the Chandra Observatory. Here we report an optical counterpart for ULX NGC 3031
X-11, which has average X-ray luminosity of $\sim2\times10^{39}$ erg/s and has
varied by a factor of 40% over the last 20 years. We find a unique optical
counterpart with the magnitude and color of an O8V star and we identify this as
the secondary in a binary system. The primary is believed to be a black hole of
approximately 18 $M_\odot$, based on analyses of ACIS and ASCA spectra. This
binary system probably is powered by mass transfer from the O8V star onto the
black hole, with the Roche Lobe equal to the stellar radius. This model
predicts an orbital period of $\sim1.8$ days, which can be tested by future
observations.


title:
Transfer of Polarized Radiation in Strongly Magnetized Plasmas and
  Thermal Emission from Magnetars: Effect of Vacuum Polarization

abstract:
  We present a theoretical study of radiative transfer in strongly magnetized
electron-ion plasmas, focusing on the effect of vacuum polarization due to
quantum electrodynamics. This study is directly relevant to thermal radiation
from the surfaces of highly magnetized neutron stars, which have been detected
in recent years. Strong-field vacuum polarization modifies the photon
propagation modes in the plasma, and induces a ``vacuum resonance'' at which a
polarized X-ray photon propagating outward in the neutron star atmosphere can
convert from a low-opacity mode to a high-opacity mode and vice versa. The
effectiveness of this mode conversion depends on the photon energy and the
atmosphere density gradient. For a wide range of field strengths, $7\times
10^{13}< B < 10^{16}$ G, the vacuum resonance lies between the photospheres of
the two photon modes, and the emergent radiation spectrum from the neutron star
is significantly modified by the vacuum resonance. (For lower field strengths,
only the polarization spectrum is affected.) Under certain conditions, which
depend on the field strength, photon energy and propagation direction, the
vacuum resonance is accompanied by the phenomenon of mode collapse (at which
the two photon modes become degenerate) and the breakdown of Faraday
depolarization. Thus, the widely used description of radiative transfer based
on photon modes is not adequate to treat the vacuum polarization effect
rigorously. We study the evolution of polarized X-rays across the vacuum
resonance and derive the transfer equation for the photon intensity matrix
(Stokes parameters), taking into account the effect of birefringence of the
plasma-vacuum medium, free-free absorption, and scatterings by electrons and
ions.


title:
Magnetically Driven Warping and Precession of Accretion Disks:
  Implications for "Exotic" Stellar Variabilities

abstract:
  The inner region of the accretion disk around a magnetized star is subjected
to magnetic torques that induce warping and precession of the disk. These
torques arise from interactions between the stellar field and the induced
electric currents in the disk. These novel magnetic effects give rise to some
``exotic'' stellar variabilities, and may play an important role in explaining
a number of puzzling behaviors related to disk accretion onto magnetic stars,
such as mHz QPOs in X-ray pulsars, long-term periodicities of X-ray binaries
(including precession of jets), low-Frequency (10-50 Hz) QPO's in low-mass
X-ray binaries, and photometric variabilities of T Tauri stars.


title: Spectral Energy and Age Distributions for 51 Globular Cluster Candidates

abstract:
  This paper is the fourth in a series presenting spectrophotometry of 51
globular cluster candidates, that were detected by Mochejska et al. in the
nearby galaxy M33 using the data collected by the DIRECT project. The frames of
M33 in this study were taken as part of the BATC Multicolor Sky Survey. We
obtained the spectral energy distributions of these candidates in 13
intermediate-band filters. By comparing the integrated photometric measurements
with theoretical stellar population synthesis models of Bruzual & Charlot, we
estimated their ages. The BC96 models provide the evolution in time of the
spectrophotometric properties of simple stellar populations for a wide range of
stellar metallicity. Our results show that half of the candidates are younger
than 10^8 years, whose age degeneracy is not pronounced. We also find that
globular clusters formed continuously in M33 from ~4*10^6 -- 10^{10} years. Our
results are in agreement with Chandar et al., who estimated ages for 35
globular clusters candidates in common by comparing the photometric
measurements to integrated colors from theoretical models by Bertelli et al.
The Kolmogorov-Smirnov Test shows that the maximum value of the absolute
difference of estimated ages between Chandar et al. and us is 0.48, and the
significance level probability is 100.00 per cent.


title: Radio asymmetry in 3C99

abstract:
  The N-galaxy 3C99, a Compact Steep-spectrum Source showing a triple
asymmetric structure, has been observed with several arrays of radio telescopes
at sub-arcsecond resolution. New images from MERLIN, European VLBI Network and
the Very Long Baseline Array show that the source components detected in the
central region of 3C99 have steep spectral indices, making it difficult to
determine which of them is the core. The asymmetric radio structure of 3C99 is
explained using the Scheuer-Baldwin continuous streaming model with a rather
large difference in the interstellar medium density on the two sides of the
central region. The age of 3C99 has been estimated; the source is found younger
than 10^6 years.


title: Abundance determinations in HII regions: model fitting versus Te-method

abstract:
  The discrepancy between the oxygen abundances in high-metallicity HII regions
determined through the Te-method (and/or through the corresponding "strong
lines - oxygen abundance" calibration) and that determined through the model
fitting (and/or through the corresponding "strong lines - oxygen abundance"
calibration) is discussed. It is suggested to use the interstellar oxygen
abundance in the solar vicinity, derived with very high precision from the
high-resolution observations of the weak interstellar absorption lines towards
the stars, as a "Rosetta stone" to verify the validity of the oxygen abundances
derived in HII regions with the Te-method at high abundances. The agreement
between the value of the oxygen abundance at the solar galactocentric distance
traced by the abundances derived in HII regions through the Te-method and that
derived from the interstellar absorption lines towards the stars is strong
evidence in favor of that i) the two-zone model for Te seems to be a realistic
interpretation of the temperature structure within HII regions, and ii) the
classic Te-method provides accurate oxygen abundances in HII regions. It has
been concluded that the "strong lines - oxygen abundance" calibrations must be
based on the HII regions with the oxygen abundances derived with the Te-method
but not on the existing grids of the models for HII regions.


title: Optical and near-IR Spectrophotometry of CNSFRs: Preliminary Results

abstract:
  Preliminary results from spectrophotometric observations of Circumnuclear
Star Forming Regions (CNSFRs) in the spiral galaxies NGC 2903, NGC 3351 and NGC
3504 are presented. The analysis is focused both on the determination of
elemental abundances in the gas and the unveiling of the ionising stellar
population responsible of the observed excitation in these regions.


title: NGC 4654: gravitational interaction or ram pressure stripping?

abstract:
  The Virgo cluster spiral galaxy NGC 4654 is supposed to be a good candidate
for ongoing ram pressure stripping based on its very asymmetric HI
distribution. However, this galaxy also shows an asymmetric stellar
distribution. Numerical simulations using ram pressure as the only perturbation
can produce a tail structure of the gas content, but cannot account for its
kinematical structure. It is shown that a strong edge-on stripping event can
produce an asymmetric stellar distribution up to 800 Myr after the stripping
event, i.e. the galaxy's closest passage to the cluster center. Simulations
using a gravitational interaction with the companion galaxy NGC 4639 can
account for the asymmetric stellar distribution of NGC 4654, but cannot
reproduce the observed extended gas tail. Only a mixed interaction,
gravitational and ram pressure, can reproduce all observed properties of NGC
4654. It is concluded that NGC 4654 had a tidal interaction ~500 Myr ago and is
continuing to experience ram pressure.


title:
The nuclear accretion in the FR I radio galaxy IC4296 from CHANDRA and
  VLBA observations

abstract:
  A high angular resolution study of the nucleus of the FR I galaxy IC4296
using Chandra ACIS-S and VLBA observations is presented, with the aim of
studying the nature of the accretion process. Pointlike and hard X-ray emission
is found, well described by a moderately absorbed power law of
Gamma=1.48^{+0.42}_{-0.34}; no iron fluorescence line from cold material is
detected. The 0.3-10 keV luminosity is 2.4\times 10^{41} erg/s, that is \sim
400 times lower than the accretion luminosity resulting from the estimated
Bondi mass accretion rate and a radiative efficiency of 10%. On the parsec
scale a jet and a counter-jet extend out from a central unresolved ``core'' in
the 8.4 GHz image. Their orientation is in good agreement with that of the
large scale jets and their bulk speed is relativistic. The parsec scale
spectrum is convex over 2-22 GHz. The observed nuclear luminosity is not likely
to be reconciled with the accretion luminosity by assuming that Compton thick
material surrounds the nucleus. Low radiative efficiency accretion flow models
(ADAF and its variants) cannot account for the observed emission and spectral
shape of the nucleus in the radio band. The power in the jets accounts for a
sizable fraction (\ga 10%) of the accretion luminosity; therefore the mass
accretion rate needs not to be much different from the estimate obtained using
Bondi's theory. A jet dominated origin also for the observed radiative losses
of the nucleus is suggested. This could also explain the finding that a nuclear
luminosity orders of magnitude lower than that of ``normal'' radio loud AGNs is
accompanied by a relatively higher radio emission.


title: Mass-to-light ratios in early-type galaxies and the dark matter content

abstract:
  The distribution of the radial trends of the mass-to-light ratios (M/L)
within an assorted sample of early-type galaxies is discussed. Three classes of
galaxies are identified according to their M/L gradients. Two such classes are
characterized by the presence or by the absence of a radial gradient of the
dark-matter (DM) distribution. A third class contains objects which are likely
undergoing interaction; they exhibit steep M/L gradients which are possibly the
result of a wrong assumption on their equilibrium conditions. Finally, a
possible correlation between DM content and morphological types is briefly
discussed.


title:
Wavelength and Redshift Dependence of Bulge/Total Light Ratios in
  Galaxies

abstract:
  We present evolutionary synthesis models for both components and add their
spectra in various proportions to obtain the full range of local galaxies'
B-band bulge-to-total light ratios. Bulge star formation is assumed to occur on
a short timescale of $10^9$ yr, disk star formation proceeds at a constant
rate. Models are presented for three scenarios: bulges and disks of equal age,
old bulges and delayed disk star formation, and old disks with subsequent bulge
star formation. We quantitatively show that bulge-to-total ($=$ B/T) light
ratios for local galaxies increase significantly from U through I-bands with
the rate of increase slightly depending on the relative ages of the two
components. Hence, simultaneous decomposition of galaxy profiles in several
bands can give direct information about the relative ages of bulges and disks
and help constrain galaxy formation scenarios. The redshift evolution of
B/T-ratios in various bands U, B, V, I, H is calculated accounting both for
cosmological and evolutionary corrections. I- and H-bands show the smoothest
redshift evolution and, hence, are best suited for a first order comparison of
galaxies over the redshift range from ${\rm z=0}$ to ${\rm z \gta 1}$ but still
are shown to increasingly overestimate B/T ratios at higher redshifts. This is
a robust result irrespective of the respective ages of the bulge and disk
stellar components and implies that the scarcity of bulge-strong systems at
${\rm z \geq 0.8}$ reported for HDF and Hawaiian Deep Field galaxies is further
enhanced.


title: Formation of small-scale structure in SUSY CDM

abstract:
  The lightest supersymmetric particle, most likely the lightest neutralino, is
one of the most prominent particle candidates for cold dark matter (CDM). We
show that the primordial spectrum of density fluctuations in neutralino CDM has
a sharp cut-off, induced by two different damping mechanisms. During the
kinetic decoupling of neutralinos, non-equilibrium processes constitute
viscosity effects, which damp or even absorb density perturbations in CDM.
After the last scattering of neutralinos, free streaming induces neutralino
flows from overdense to underdense regions of space. Both damping mechanisms
together define a minimal mass scale for perturbations in neutralino CDM,
before the inhomogeneities enter the nonlinear epoch of structure formation. We
find that the very first gravitationally bound neutralino clouds ought to have
masses above 10^{-6} solar masses, which is six orders of magnitude above the
mass of possible axion miniclusters.


title:
The dynamics of the nebula M1-67 around the run-away Wolf-Rayet star WR
  124

abstract:
  A new point of view on the dynamics of the circumstellar nebula M1-67 around
the run-away Wolf-Rayet (WR) star WR 124 is presented. We found that it has
been interacting with the surrounding ISM and has formed a bow shock due to its
high velocity of about 180 km/s relative to the local ISM. The star is about
1.3 parsec away from the front of this bow shock. The outbursts that are
responsible for the nebula are assumed to be discrete outbursts that occurred
inside this bow shock. The ejecta collide with this bow shock shortly after the
outburst. After the collision, they are dragged away by the pressure of the
ISM, along the surface of the bow shock. The bow shock is oriented in such way
that we are looking from the rear into this paraboloid, almost along the main
axis. Evidence for this is given firstly by the fact that the far hemisphere is
much brighter than the near hemisphere, secondly by the fact that there is
hardly any emission found with radial velocities higher than the star's radial
velocity, thirdly by the fact that the star looks to be in the centre of the
nebula, as seen from Earth, and finally by the asymmetric overall velocity
distribution of the nebula, which indicates higher radial velocities in the
centre of the nebula, and lower velocities near the edges. We find evidence for
at least two discrete outbursts that occurred inside this bow shock. For these
outbursts, we find expansion velocities of about 150 km/s and dynamical
timescales of about 8 and 20 kyr, which are typical values for LBV outbursts.
We therefore conclude that M1-67 originates from several outbursts that
occurred inside the bow shock around WR 124, during an LBV phase that preceded
the current WR phase of the star.


title: Search for Dark Matter with GLAST

abstract:
  The detection of exotic cosmic rays due to pair annihilation of dark matter
particles in the Milky Way halo is a viable techniques to search for
supersymmetric dark matter candidates. The study of the spectrum of gamma-rays,
antiprotons and positrons offers good possibilities to perform this search in a
significant portion of the Minimal Supersymmetric Standard Model parameter
space. In particular the EGRET team have seen a convincing signal for a strong
excess of emission from the Galactic center that has no simple explanation with
standard processes. We will review the limits achievable with the experiment
GLAST taking into accounts the LEP results and we will compare this method with
the antiproton and positrons experiments.


title:
Vertical distribution of Galactic disk stars : II. The surface mass
  density in the Galactic plane

abstract:
  High resolution spectra data of red clump stars towards the NGP have been
obtained with the high resolution spectrograph Elodie at OHP for Tycho-2
selected stars. Combined with Hipparcos local analogues, we determine both the
gravitational force law perpendicaular to the Galactic plane, and the total
surface mass density and thickness of the Galactic disk. The surface mass
density of the Galactic disk within 800 pc derived from this analysis is
Sigma(|z|<800pc)=76 Msol.pc-2 and, removing the dark halo contribution, the
total disk mass density is Sigma0=67 Msol.pc-2 at solar radius. The thickness
of the total disk mass distribution is dynamicaly measured for the first time
and is found to be 390pc in relative agreement with the old stellar disk scale
height. All dynamical evidences concerning the structure of the disk (its local
volume density -i.e. the Oort limit-, its surface density and its thickness)
are compatible with our knowledge of the corresponding stellar disk properties.


title: The Neutrino Signal in Stellar Core Collapse and Postbounce Evolution

abstract:
  General relativistic multi-group and multi-flavor Boltzmann neutrino
transport in spherical symmetry adds a new level of detail to the numerical
bridge between microscopic nuclear and weak interaction physics and the
macroscopic evolution of the astrophysical object. Although no supernova
explosions are obtained, we investigate the neutrino luminosities in various
phases of the postbounce evolution for a wide range of progenitor stars between
13 and 40 solar masses. The signal probes the dynamics of material layered in
and around the protoneutron star and is, within narrow limits, sensitive to
improvements in the weak interaction physics. Only changes that dramatically
exceed physical limitations allow experiments with exploding models. We discuss
the differences in the neutrino signal and find the electron fraction in the
innermost ejecta to exceed 0.5 as a consequence of thermal balance and weak
equilibrium at the masscut.


title: A comparison of the acceleration mechanisms in YSO and AGN jets

abstract:
  We examine the hypothesis that there exists a simple scaling between the
observed velocities of jets found in Young Stellar Objects (YSOs) and jets
found in Active Galactic Nuclei (AGN). We employ a very simplified physical
model of the jet acceleration process. We use time-dependent, spherically
symmetric wind models in Newtonian and relativistic gravitational fields to ask
whether the energy input rates required to produce the jet velocities observed
in YSOs (of about 2 $\times$ the escape velocity from the central object) can
also produce AGN jet velocities (Lorentz factors of $\gamma \sim$ 10). Such a
scaling would be expected if there is a common production mechanism for such
jets. We demonstrate that such a scaling does exist, provided that the energy
input process takes place sufficiently deep in the gravitational potential
well, enabling physical use to be made of the speed of light as a limiting
velocity, and provided that the energy released in the accretion process is
imparted to a small fraction of the available accreting material.


title:
Simulations of Galaxy Formation in a Lambda CDM Universe I: Dynamical
  and Photometric Properties of a Simulated Disk Galaxy

abstract:
  We analyze the properties of a disk galaxy simulated with unprecedented
numerical resolution in the Lambda CDM cosmogony. The galaxy is assembled
through a number of high-redshift mergers followed by a period of quiescent
accretion after z~1 which lead to the formation of two distinct dynamical
components: a spheroid and a disk. The surface brightness profile is very well
approximated by the superposition of an R^{1/4} spheroid and an exponential
disk. The surface brightness profile is remarkably similar to that of Sab
galaxy UGC615, but the simulated galaxy rotates significantly faster and has a
declining rotation curve dominated by the spheroid near the center. The decline
in circular velocity is at odds with observation and results from the high
concentration of the dark matter and baryonic components, as well as from the
relatively high mass-to-light ratio of the stars in the simulation. The
simulated galaxy lies ~ 1 mag off the I-band Tully-Fisher relation of late-type
spirals, but seems to be in reasonable agreement with Tully-Fisher data on S0
galaxies. The angular momentum of the luminous component is an order of
magnitude lower than that of late-type spirals of similar rotation speed. This
reflects the dominance of the slowly-rotating, dense spheroidal component. The
disk component, on the other hand, has properties rather similar to those of
late-type spirals. This suggests that a different form of feedback than adopted
in this simulation is required to inhibit the efficient collapse and cooling of
gas at high redshift that leads to the formation of the spheroid. Reconciling
the properties of disk galaxies with the early collapse and high merging rates
characteristic of hierarchical scenarios such as Lambda CDM remains a
challenging, yet so far elusive, proposition.


title: Optical Linear Polarimetry of Ultra Cool Dwarfs

abstract:
  Optical linear polarimetry of 8 ultra cool field dwarfs, with spectral types
ranging from M9 to L8, is presented. The linear polarisation, P, of each dwarf
we measured is P < 0.2%. Three dwarfs have polarisations compatible with zero,
two are marginal detections, and three have significant polarisation. Due to
their small distance, an insterstellar origin for the detected polarisation can
be safely ruled out. Our detections confirm that dust is present in the
atmosphere of these brown dwarfs and that the scattering geometry is not
symmetric. Possibilities for asymmetry include the dwarfs rotating rapidly and
being oblate, or the cloud coverage in the atmosphere being inhomogenous.


title:
Matching the Observed Star Formation Intensity Distribution with
  Empirical Laws

abstract:
  This letter matches the shape of the star formation intensity distribution
function to empirical laws such as the Schmidt law. The shape of the
distribution at a redshift of one is reproduced from the empirical Schmidt law
with a critical density, a Schechter distribution of galaxy masses and the
assumption that star formation occurs mainly in exponential disks. The shape of
the distribution depends primarily on two values, the characteristic mass m* in
the Schechter mass distribution and the characteristic radius re in the
exponential disk. As these characteristic values evolve they will affect the
shape of the distribution function. The expected direction of evolution of the
parameters partially cancels each other leaving the distribution shape
relatively invariant.


title: A Population of Intergalactic Supernovae in Galaxy Clusters

abstract:
  We have discovered seven type Ia cluster supernovae (SNe) in the course of
the Wise Observatory Optical Transients Search in the fields of galaxy clusters
with redshifts between z=0.06 and z=0.2. Two of these events, SN 1998fc in
Abell 403 (z=0.10) and SN 2001al in Abell 2122/4 (z = 0.066), have no obvious
hosts. Both events appear projected on the halos of the central cD galaxies,
but have velocity offsets of 750-2000 km/s relative to those galaxies,
suggesting they are not bound to them. We use deep Keck imaging of the
locations of the two SNe to put upper limits on the luminosities of possible
dwarf hosts, M_R > -14 mag for SN 1998fc and M_R > -11.8 mag for SN 2001al. The
fractions of the cluster luminosities in dwarf galaxies fainter than our limits
are less than 3 x 10^-3 and 3 x 10^-4, respectively. Thus, 2/7 of the SNe would
be associated with less than 3 x 10^-3 of the luminosity attributed to
galaxies. We argue, instead, that the progenitors of both events were probably
members of a diffuse population of intergalactic stars, recently detected in
local clusters via planetary nebulae and red giants. Considering the higher
detectability of hostless SNe compared to normal SNe, we estimate that
20^{+12}_{-15} percent of the SN Ia parent stellar population in clusters is
intergalactic. This fraction is consistent with other measurements of the
intergalactic stellar population, and implies that the process that produces
intergalactic stars (e.g., tidal disruption of cluster dwarfs) does not disrupt
or enhance significantly the SN Ia formation mechanism. Hostless SNe are
potentially powerful tracers of the formation of the intergalactic stellar
population out to high redshift.


title:
Constraining the cosmological parameters with the gas mass fraction in
  local and z>0.7 Galaxy Clusters

abstract:
  We present a study of the baryonic fraction in galaxy clusters aimed at
constraining the cosmological parameters Omega_m, Omega_Lambda and the ratio
between the pressure and density of the ``dark'' energy, w. We use results on
the gravitating mass profiles of a sample of nearby galaxy clusters observed
with the BeppoSAX X-ray satellite (Ettori, De Grandi, Molendi 2002) to set
constraints on the dynamical estimate of Omega_m. We then analyze Chandra
observations of a sample of eight distant clusters with redshift in the range
0.72 and 1.27 and evaluate the geometrical limits on the cosmological
parameters Omega_m, Omega_Lambda and w by requiring that the gas fraction
remains constant with respect to the look-back time. By combining these two
independent probability distributions and using a priori distributions on both
Omega_b and H0 peaked around primordial nucleosynthesis and HST-Key Project
results respectively, we obtain that, at 95.4 per cent level of confidence, (i)
w < -0.49, (ii) Omega_m = 0.34^+0.11_-0.05, Omega_Lambda = 1.30^+0.44_-1.09 for
w=-1 (corresponding to the case for a cosmological constant), and (iii) Omega_m
= 1-Omega_Lambda = 0.33^+0.07_-0.05 for a flat Universe. These results are in
excellent agreement with the cosmic concordance scenario which combines
constraints from the power spectrum of the Cosmic Microwave Background, the
galaxy and cluster distribution, the evolution of the X-ray properties of
galaxy clusters and the magnitude-redshift relation for distant type Ia
supernovae. By combining our results with the latter method we further
constrain Omega_Lambda =0.94^+0.28_-0.32 and w < -0.89 at the 2 sigma level.


title:
Investigations of Pointwise Ignition of Helium Deflagrations on Neutron
  Stars

abstract:
  We look at the spreading of localized temperature perturbations in the
accreted fuel layer of a non-rotating neutron star. The pressure at the base of
the accreted fuel layer is large and the material is only partially degenerate.
Any temperature perturbations and resulting pressure gradients will lead to
enormous accelerations (both laterally and vertically) of the material in the
fuel layer. If the burning of this fuel cannot proceed more rapidly than the
spreading of this perturbation, then localized burning cannot take place, and
it is likely that the ignition would have to proceed simultaneously throughout
the envelope. We present some multidimensional simulations of the spreading of
temperature perturbations in a helium atmosphere on a neutron star.


title: Could thermal fluctuations seed cosmic structure?

abstract:
  We examine the possibility that thermal, rather than quantum, fluctuations
are responsible for seeding the structure of our universe. We find that while
the thermalization condition leads to nearly Gaussian statistics, a
Harrisson-Zeldovich spectrum for the primordial fluctuations can only be
achieved in very special circumstances. These depend on whether the universe
gets hotter or colder in time, while the modes are leaving the horizon. In the
latter case we find a no-go theorem which can only be avoided if the
fundamental degrees of freedom are not particle-like, such as in string gases
near the Hagedorn phase transition. The former case is less forbidding, and we
suggest two potentially successful ``warming universe'' scenarios. One makes
use of the Phoenix universe, the other of ``phantom'' matter.


title: Role of Reconnection in AGN Jets

abstract:
  We discuss the possible role of reconnection in electro-magnetically
dominated cores of relativistic AGN jets. We suggest that reconnection may
proceed in a two-fold fashion: initial explosive collapse on the Alfven
time-scale of a current-carrying jet (which is of the order of the light
crossing time) and subsequent slow quasi-steady reconnection. Sites of
explosive collapse are associated with bright knots, while steady-state
reconnection re-energizes particles in the ``bridges'' between the knots.
  Ohmic dissipation in reconnection layers leads to particle acceleration
either by inductive electric fields or by stochastic particle acceleration in
the ensuing electro-magnetic turbulence.


title: Collapse of a Magnetized Star to a Black Hole

abstract:
  We study of the collapse of a magnetized spherical star to a black hole in
general relativity theory. The matter and gravitational fields are described by
the exact Oppenheimer-Snyder solution for the collapse of a spherical,
homogeneous dust ball. We adopt a ``dynamical Cowling approximation'' whereby
the matter and the geometry (metric), while highly dynamical, are unaffected by
the electromagnetic fields. The matter is assumed to be perfectly conducting
and threaded by a dipole magnetic field at the onset of collapse. We determine
the subsequent evolution of the magnetic and electric fields without
approximation; the fields are determined analytically in the matter interior
and numerically in the vacuum exterior. We apply junction conditions to match
the electromagnetic fields across the stellar surface. We use this model to
experiment with several coordinate gauge choices for handling spacetime
evolution characterized by the formation of a black hole and the associated
appearance of singularities. These choices range from ``singularity avoiding''
time coordinates to ``horizon penetrating'' time coordinates accompanied by
black hole excision. The later choice enables us to integrate the
electromagnetic fields arbitrarily far into the future. At late times the
longitudinal magnetic field in the exterior has been transformed into a
transverse electromagnetic wave; part of the electromagnetic radiation is
captured by the hole and the rest propagates outward to large distances. The
solution we present for our simple scenario can be used to test codes designed
to treat more general evolutions of relativistic MHD fluids flowing in strong
gravitational fields in dynamical spacetimes.


title:
General-Relativistic MHD for the Numerical Construction of Dynamical
  Spacetimes

abstract:
  We assemble the equations of general relativistic magnetohydrodynamics (MHD)
in 3+1 form. These consist of the complete coupled set of Maxwell equations for
the electromagnetic field, Einstein's equations for the gravitational field,
and the equations of relativistic MHD for a perfectly conducting ideal gas. The
adopted form of the equations is suitable for evolving numerically a
relativistic MHD fluid in a dynamical spacetime characterized by a strong
gravitational field.


title: Isolated Star Formation: A Compact HII Region in the Virgo Cluster

abstract:
  We report on the discovery of an isolated, compact HII region in the Virgo
cluster. The object is located in the diffuse outer halo of NGC 4388, or could
possibly be in intracluster space. Star formation can thus take place far
outside the main star forming regions of galaxies. This object is powered by a
small starburst with an estimated mass of $\sim 400\msun$ and age of $\sim
3\myr$. From a total sample of 17 HII region candidates, the present rate of
isolated star formation estimated in our Virgo field is small, $\sim 10^{-6}
Msun arcmin}^{-2} yr^{-1}$. However, this mode of star formation might have
been more important at higher redshifts and be responsible for a fraction of
the observed intracluster stars and total cluster metal production. This object
is relevant also for distance determinations with the planetary nebula
luminosity function from emission line surveys, for high-velocity clouds and
the in situ origin of B stars in the Galactic halo, and for local enrichment of
the intracluster gas by Type II supernovae.


title:
Radiative Torques on Interstellar Grains. III. Dynamics with Thermal
  Relaxation

abstract:
  In the previous papers in this series, we found that radiative torques can
play a major role in the alignment of grains with the interstellar magnetic
field. Since the radiative torques can drive the grains to suprathermal
rotational speeds, in previous work we made the simplifying assumption that the
grain principal axis of greatest moment of inertia is always parallel to the
grain angular momentum. This enabled us to describe many of the features of the
grain dynamics. However, this assumption fails when the grains enter periods of
thermal rotation, which occur naturally in the radiative torque alignment
scenario. In the present paper, we relax this assumption and explore the
consequences for the grain dynamics. We develop a treatment to follow the grain
dynamics including thermal fluctuations and ``thermal flipping'', and show
results for one illustrative example. By comparing with a treatment without
thermal fluctuations, we see that inclusion of thermal fluctuations can lead to
qualitative changes in the grain dynamics. In a future installment in this
series, we will use the more complete dynamical treatment developed here to
perform a systematic study of grain alignment by radiative torques.


title:
XMM-Newton View of the Hubble Deep Field-North and Groth-Westphal Strip
  Regions

abstract:
  We report the progress on our analysis of two deep XMM observations in the
areas of Hubble Deep Field-North and the Groth-Westphal Strip field. We present
the source detection method, Monte-Carlo simulation on source detection, and
our preliminary Log N -- Log S relations. Comparing these two fields and other
fields in literature, we find up to 30% variations in number counts near our
flux limits, which is most likely to be due to cosmic variance. This serves as
a pilot study for a more systematic investigation. The nature of the X-ray
sources in the Groth-Westphal field is also discussed in terms of hardness
ratios, morphology and spectroscopic properties.


title: The number and metallicities of the most metal-poor stars

abstract:
  Simple, one-zone models for inhomogeneous chemical evolution of the Galactic
halo are used to predict the number fraction of zero-metallicity, Population
III stars, which currently is empirically estimated at < 4e-4. These analytic
models minimize the number of free parameters, highlighting the most
fundamental constraints on halo evolution. There are disagreements of at least
an order of magnitude between observations and predictions in limiting cases
for both homogeneous Simple Model and Simple Inhomogeneous Model (SIM). Hence,
this demonstrates a quantitative, unambiguous discrepancy in the observed and
expected fraction of Population III stars. We explore how the metallicity
distribution of the parent enrichment events f(z_0) drives the SIM and
predictions for the Population III fraction. The SIM shows that the
previously-identified "high halo" and "low halo" populations are consistent
with a continuous evolutionary progression, and therefore may not necessarily
be physically distinct populations. Possible evolutionary scenarios for halo
evolution are discussed within the SIM's simplistic one-zone paradigm.
  The values of z_0 depend strongly on metal dispersal processes, thus we
investigate interstellar mixing and mass transport, for the first time
explicitly incorporating this into a semi-analytic chemical evolution model.
Diffusion is found to be inefficient for all phases, including the hot phase,
of the interstellar medium (ISM): relevant diffusion lengths are 2 - 4 orders
of magnitude smaller than corresponding length scales for turbulent mixing.
Rough relations for dispersal processes are given for multiphase ISM. These
suggest that the expected low-metallicity threshold above zero is consistent
with the currently observed limit.


title:
Andreev-Bashkin effect and knot solitons in interacting mixture of a
  charged and a neutral superfuids with possible releveance for neutron stars

abstract:
  We discuss a mixture of interacting a neutral and a charged Bose condensates,
which is supposed being realized in interior of neutron stars in form of
coexistent neutron superfluid and protonic superconductor. We show that in this
system, besides ordinary vortices of $S^1\to S^1$ map, the neutron condensate
also allows for (meta)stable finite-length knotted solitons, which are
characterized by a nontrivial Hopf invariant and in some circumsatnces are
stablized by Faddeev-Skyrme term induced by drag effect. We also consider a
helical protonic fluxtube in this system and show that, in contrast, it does
not induce a Faddeev-Skyrme term.


title: Hadronization of the Quark Universe

abstract:
  We explore quantitatively the conditions in which matter (protons, neutrons)
formed in the Early Universe during a period which spanned 10--50mus. We obtain
all chemical potentials implied by the present day baryon-to-photon ratio. The
baryochemical potential reaches its minimal value at the beginning of
hadronization of the quark Universe, where mu_b=1.1 \pm 0.25 eV. In the mixed
hadron-quark phase, a significant hadron sector electric charge distillation is
found.


title: After MAP: Next Generation CMB

abstract:
  We discuss several opportunities involving cosmic microwave background (CMB)
observations during the post-MAP era. The curl-modes of CMB polarization allow
a direct detection of inflationary gravitational waves and a measurement of the
energy scale of inflation. While a significant source of confusion is expected
from cosmic shear conversion of polarization related to density perturbations,
higher resolution observations of CMB anisotropies can be used for a lensing
reconstruction and to separate gravitational-wave polarization signature from
that of lensing. With perfect all-sky maps, separations based on current
lensing reconstruction techniques allow the possibility to probe inflationary
energy scales down to 10^15 GeV, well below that of grand unified theories.
Another aspect of future CMB studies will be related to large scale structure,
such as wide-field imaging of Sunyaev-Zel'dovich (SZ) effect in galaxy
clusters. Here, we comment on a potentially interesting and unique application
of the SZ effect involving a measurement of the absolute temperature of CMB at
high redshifts. Finally, we address cluster polarization signals and the
possibility to directly measure some aspect of the temperature quadrupole
associated with time evolving potentials.


title: Strange quark stars - A review

abstract:
  A pedagogical overview of strange quark matter and strange stars is
presented. After a historical notation of the research and an introduction to
quark matter, a major part is devoted to the physics and astrophysics of
strange stars, with attention being paid to the possible ways by which neutron
stars and strange stars can be distinguished in astrophysics. Recent possible
evidence for bare strange stars is also discussed.


title: Chandra Grating Observations of AGN

abstract:
  The highest spectral resolution data for the Fe-K lines in type I AGN, as
observed with the Chandra High Energy Grating (HEG), reveal a variety of line
shapes. However, the energies of the most prominent peak are all clustered
tightly around 6.4 keV (weighted mean $6.403 \pm 0.062$ keV). If all the peaks
were part of single, relativistically broadened disk line, this would require
unrealistically fine tuning. Thus, some of the cores must originate in distant
matter (e.g. BLR, NLR, torus). On the other hand, in at least two AGN, the
emission at 6.4 keV has been seen to vanish on short timescales, indicating an
origin close to the central engine. For one of these (Mrk 509) this is puzzling
because the HEG and simultaneous RXTE time-averaged spectra indicate only a
narrow line was present at that time. Simultaneous HEG/RXTE observations for
NGC 4593 indicate a broad and narrow Fe-K complex, all originating in neutral
Fe, and for F9 show a narrow, neutral Fe-K component plus a broad, He-like
component. The latter signature has been observed in three other AGN by XMM and
may be quite common.


title: The detection of diffuse emission in HCG 16 with XMM-Newton

abstract:
  We report results obtained from analysis of the XMM-Newton observation of the
compact group of galaxies HCG 16. It is a peculiar system composed of 7
spirals,
  6 of which are active, and its nature as a bound system has been much
debated. The EPIC camera observations give new insights into the X-ray
parameters describing the physical status of the group. We detect diffuse X-ray
emission with a rather elliptical morphology which extends to at least a radius
of 135 h^{-1}_{50} kpc from the group centre. The spectrum within this region
is well modelled by a thermal plasma with a temperature of 0.49+/-0.17 keV, and
a non-zero metallicity. We measure a bolometric X-ray luminosity of 9.6 10{^40}
h^{-2}_{50} erg/s which may be only a small fraction of the total luminosity
because of the limit in spatial detection arising from the high background
level. Despite its low temperature and luminosity, HCG 16 obeys the Lx-T
relation obtained for brighter galaxy groups even if it lies in a very extreme
position. The properties of the diffuse emission confirm the bound nature of
HCG 16 even if the gas trapped in the potential well may not yet be virialized.
This reopens the debate about the real nature of spiral-dominated galaxy
groups, and on their role in a more general cosmological context.


title:
Narrow band imaging in [OIII] and Halpha to search for ICPNe in the
  Virgo cluster

abstract:
  We have identified intracluster planetary nebulae in a Virgo cluster core
field by imaging with the Subaru Suprime-Cam through two narrow band filters
centered at the redshifted wavelengths of the [OIII] $\lambda=5007$ \AA and the
H$\alpha$ $\lambda = 6563$ \AA lines; broad-band images in V and R were
acquired to check for emission in the adjacent continuum. Emission line objects
in Virgo are then selected from the two-color diagram ([OIII] -- Halpha) vs.
([OIII] -- (V+R)), which is calibrated using PNe in M84 (Jacoby et al. 1990).
Using both [OIII] and Halpha allows us to distinguish bona-fide planetary
nebulae from high redshift emission-line galaxies at the bright end of the
[OIII] luminosity function. Spectroscopic observations of a subsample of these
objects were made at the TNG and at the VLT, in a region around M84 and in an
intracluster field respectively. The observations confirm the efficiency of the
combined [OIII]+H$\alpha$ imaging to identify true PNe. We also obtained the
first spectrum of an intracluster PN which shows the [OIII] doublet with S/N >
10 and its Halpha emission. From the results based on the spectroscopic
follow-up, we derive a lower limit to the fraction of the Virgo cluster light
contributed by the intracluster stars at the surveyed position in the cluster
core: it amounts to 10%.


title:
Candidates for Intracluster Planetary Nebulae in the Virgo Cluster based
  on the Suprime-Cam Narrow-Band Imaging in O[III] and Halpha

abstract:
  We have identified 38 candidates of intracluster planetary nebulae (ICPNe) in
a $34'\times27'$ field in the core of the Virgo cluster based on the
Suprime-Cam imaging through two narrow-band filters centered at the redshifted
wavelengths of the [OIII]$\lambda=5007\AA$ and the Halpha \lambda=6563\AA
lines. Broad-band images in V and R bands are used to check for any emissions
in the adjacent continuum. We describe the method briefly and present the list
of intracluster planetary nebulae candidates, together with their finding
charts. The ICPN candidates show a highly inhomogeneous distribution, which may
suggest an association with the M86-M84 subcluster. Fraction of diffuse
intracluster light with respect to total light in galaxies is estimated to be
about 10%, leading to an estimate of about 20% for the baryon fraction.
Spectroscopic follow up and a wider survey are critical to reveal the nature of
intracluster stellar population.


title: Do sub-mm sources and quasars form an evolutionary sequence?

abstract:
  The high redshift sub-mm sources discovered by SCUBA are widely believed to
represent the dust-enshrouded formation of massive elliptical galaxies. Given
the strong evidence for a link between the formation of the spheroid and the
growth of the central black hole, one might expect to see a luminous quasar at
the nucleus of every SCUBA source. Somewhat surprisingly, however, only a very
small fraction (~5%) are detected by Chandra with quasar luminosities. In this
paper I discuss some of the implications of these results and discuss the
accumulating evidence that sub-mm sources and quasars may represent different
stages in the evolutionary sequence of a massive proto-spheroid.


title: Indirect searches for neutralino dark matter

abstract:
  There is mounting evidence for dark matter in the Universe and one of the
favourite dark matter candidates is the neutralino, which naturally appears as
the lightest supersymmetric particle (LSP) in many supersymmetric extensions of
the standard model. The neutralino has the desired properties to be a good dark
matter candidate and we will here review the different indirect searches for
neutralino dark matter and discuss the implications on these from recent direct
searches.


title: Einstein's coefficients and the nature of thermal blackbody radiation

abstract:
  We show that thermal radio emission has an induced character and argue that
thermal blackbody radiation in other spectral ranges also has an induced
origin. A new theory of thermal radio emission of non-uniform gas basing on the
induced origin of emission and its astrophysical applications are considered.
The nature of emission from various astrophysical objects is discussed.


title:
A FUSE Survey of Molecular Hydrogen in Intermediate-Velocity Clouds in
  the Milky Way Halo

abstract:
  Far Ultraviolet Spectroscopic Explorer (FUSE) data is used to investigate the
molecular hydrogen (H_2) content of intermediate-velocity clouds (IVCs) in the
lower halo of the Milky Way. We analyze interstellar absorption towards 56
(mostly extragalactic) background sources to study H_2 absorption in the Lyman-
and Werner bands in 61 IVC components at H I column densities >10^19 cm^-2. For
data with good S/N (~9 per resolution element and higher), H_2 in IVC gas is
convincingly detected in 14 cases at column densities varying between ~10^14
and ~10^17 cm^-2. We find an additional 17 possible H_2 detections in IVCs in
FUSE spectra with lower S/N. The molecular hydrogen fractions, f, vary between
10^-6 and 10^-3, implying a dense, mostly neutral gas phase that is probably
related to the Cold Neutral Medium (CNM) in these clouds. If the H_2 stays in
formation-dissociation equlibrium, the CNM in these clouds can be characterized
by compact (D~0.1 pc) filaments with volume densities on the order of n_H~30
cm^-3. The relatively high detection rate of H_2 in IVC gas implies that the
CNM in these clouds is ubiquitous. More dense regions with much higher
molecular fractions may exist, but it would be difficult to detect them in
absorption because of their small size.


title: High resolution X-ray observations of pulsar winds

abstract:
  Young pulsars spin incredibly quickly, but are also slowing down at a very
rapid rate. This process carries away enormous amounts of energy from the star
in the form of a relativistic wind. Through the high resolution now offered by
the Chandra X-ray Observatory, a flood of new observations of pulsars and their
winds is demonstrating the diversity and complexity with which pulsars interact
with their surroundings. This paper reviews our basic understanding of pulsar
winds, and briefly summarizes some of the new insights provided by Chandra on
shock structure, particle acceleration and wind composition.


title: Astrophysical sources of high energy neutrinos

abstract:
  Several high energy, >100 GeV, neutrino telescopes are currently operating or
under construction. Their main motivation is the extension of the horizon of
neutrino astronomy to cosmological scales. We show that general, model
independent, arguments imply that ~1 Gton detectors are required to detect
cosmic high energy neutrino sources. Predictions of models of some of the
leading candidate sources, gamma-ray bursts and micro-quasars, are discussed,
and the question of what can be learned from neutrino observations is
addressed.


title:
XMM-Newton observations of PSR B1823-13: An asymmetric synchrotron
  nebula around a Vela-like pulsar

abstract:
  We present a deep observation with the X-ray Multi-Mirror Mission of PSR
B1823-13, a young pulsar with similar properties to the Vela pulsar. We detect
two components to the X-ray emission associated with PSR B1823-13: an elongated
core of extent 30'' immediately surrounding the pulsar, embedded in a fainter,
diffuse component of emission 5' in extent, seen only on the southern side of
the pulsar. The pulsar itself is not detected, either as a point source or
through its pulsations. Both components of the X-ray emission are well fit by a
power law spectrum, with photon index Gamma ~ 1.6 and X-ray luminosity (0.5-10
keV) L_x ~ 9e32 erg/s for the core, and Gamma ~ 2.3 and L_x ~ 3e33 erg/s for
the diffuse emission, for a distance of 4 kpc. We interpret both components of
emission as corresponding to a pulsar wind nebula, which we designate
G18.0-0.7. We argue that the core region represents the wind termination shock
of this nebula, while the diffuse component indicates the shocked downstream
wind. We propose that the asymmetric morphology of the diffuse emission with
respect to the pulsar is the result of a reverse shock from an associated
supernova remnant, which has compressed and distorted the pulsar-powered
nebula. Such an interaction might be typical for pulsars at this stage in their
evolution. The associated supernova remnant is not detected directly, most
likely being too faint to be seen in existing X-ray and radio observations.


title: Acceleration of Cosmic Rays at Large Scale Cosmic Shocks in the Universe

abstract:
  Cosmological hydrodynamic simulations of large scale structure in the
universe have shown that accretion shocks and merger shocks form due to flow
motions associated with the gravitational collapse of nonlinear structures.
Estimated speed and curvature radius of these shocks could be as large as a few
1000 km/s and several Mpc, respectively. According to the diffusive shock
acceleration theory, populations of cosmic-ray particles can be injected and
accelerated to very high energy by astrophysical shocks in tenuous plasmas. In
order to explore the cosmic ray acceleration at the cosmic shocks, we have
performed nonlinear numerical simulations of cosmic ray (CR) modified shocks
with the newly developed CRASH (Cosmic Ray Amr SHock) numerical code. We
adopted the Bohm diffusion model for CRs, based on the hypothesis that strong
Alfv\'en waves are self-generated by streaming CRs. The shock formation
simulation includes a plasma-physics-based ``injection'' model that transfers a
small proportion of the thermal proton flux through the shock into low energy
CRs for acceleration there. We found that, for strong accretion shocks, CRs can
absorb most of shock kinetic energy and the accretion shock speed is reduced up
to 20 %, compared to pure gas dynamic shocks. For merger shocks with small Mach
numbers, however, the energy transfer to CRs is only about 10-20 % with an
associated CR particle fraction of $10^{-3}$. Nonlinear feedback due to the CR
pressure is insignificant in the latter shocks. Although detailed results
depend on models for the particle diffusion and injection, these calculations
show that cosmic shocks in large scale structure could provide acceleration
sites of extragalactic cosmic rays of the highest energy.


title: Ozone Depletion from Nearby Supernovae

abstract:
  Estimates made in the 1970's indicated that a supernova occurring within tens
of parsecs of Earth could have significant effects on the ozone layer. Since
that time, improved tools for detailed modeling of atmospheric chemistry have
been developed to calculate ozone depletion, and advances have been made in
theoretical modeling of supernovae and of the resultant gamma-ray spectra. In
addition, one now has better knowledge of the occurrence rate of supernovae in
the galaxy, and of the spatial distribution of progenitors to core-collapse
supernovae. We report here the results of two-dimensional atmospheric model
calculations that take as input the spectral energy distribution of a
supernova, adopting various distances from Earth and various latitude impact
angles. In separate simulations we calculate the ozone depletion due to both
gamma-rays and cosmic rays. We find that for the combined ozone depletion
roughly to double the ``biologically active'' UV flux received at the surface
of the Earth, the supernova must occur at <8 pc. Based on the latest data, the
time-averaged galactic rate of core-collapse supernovae occurring within 8 pc
is ~1.5/Gyr. In comparing our calculated ozone depletions with those of
previous studies, we find them to be significantly less severe than found by
Ruderman (1974), and consistent with Whitten et al. (1976). In summary, given
the amplitude of the effect, the rate of nearby supernovae, and the ~Gyr time
scale for multicellular organisms on Earth, this particular pathway for mass
extinctions may be less important than previously thought.


title: An outflow from the nebula around the LBV candidate S 119

abstract:
  We present an analysis of the kinematic and morphological structure of the
nebula around the LMC LBV candidate S 119. On HST images, we find a
predominantly spherical nebula which, however, seems to be much better confined
in its eastern hemisphere than in the western one. The filamentary western part
of the nebula is indicative of matter flowing out of the nebula's main body.
This outflow is even more evidenced by our long-slit echelle spectra. They show
that, while most of the nebula has an expansion velocity of 25.5 km/s, the
outflowing material reaches velocities of almost 140 km/s, relative to the
systemic one. A ROSAT HRI image shows no trace of S 119 and thus no indications
of hot or shocked material.


title:
A Far Ultraviolet Spectroscopic Explorer Survey of Coronal Forbidden
  Lines in Late-Type Stars

abstract:
  We present a survey of coronal forbidden lines detected in Far Ultraviolet
Spectroscopic Explorer (FUSE) spectra of nearby stars. Two strong coronal
features, Fe XVIII 974 A and Fe XIX 1118 A, are observed in 10 of the 26 stars
in our sample. Various other coronal forbidden lines, observed in solar flares,
also were sought but not detected. The Fe XVIII feature, formed at log T (K) =
6.8, appears to be free of blends, whereas the Fe XIX line can be corrupted by
a C I multiplet. FUSE observations of these forbidden iron lines at spectral
resolution R ~ 15,000 provides the opportunity to study dynamics of hot coronal
plasmas. We find that the velocity centroid of the Fe XVIII feature deviates
little from the stellar rest frame, confirming that the hot coronal plasma is
confined. The observed line widths generally are consistent with thermal
broadening at the high temperatures of formation and show little indication of
additional turbulent broadening. The fastest rotating stars, 31 Com, alpha Aur
Ab, and AB Dor, show evidence for excess broadening beyond the thermal
component and the photospheric v sin i. The anomalously large widths in these
fast rotating targets may be evidence for enhanced rotational broadening
consistent with emission from coronal regions extending an additional delta R ~
0.4-1.3 R_star above the stellar photosphere or represent the turbulent
broadening caused by flows along magnetic loop structures. For the stars in
which Fe XVIII is detected, there is an excellent correlation between the
observed Rontgensatellit} (ROSAT) 0.2-2.0 keV soft X-ray flux and the coronal
forbidden line flux. As a result, Fe XVIII is a powerful new diagnostic of
coronal thermal conditions and dynamics that can be utilized to study high
temperature plasma processes in late-type stars.


title:
The feedback of massive stars on the ISM: XMM-Newton view of the LMC
  superbubble N51D

abstract:
  N51D (= DEM L 192) appears at first glance as a nearly circular, 120pc
diameter bubble of ionized gas around the LMC OB association LH 54. A deeper
look reveals a complex web of filaments and deviations from radial expansion.
Using a deep XMM-Newton X-ray pointing centered on N51D we find that diffuse
soft X-ray emitting gas fills the whole superbubble as delineated by the
H-alpha filaments. Contrary to recent findings for galactic winds, the
correlation between H-alpha and X-ray surface brightness is not good. The X-ray
spectrum of this diffuse gas cannot be fitted with the LMC abundance pattern,
but implies an overabundance of at least oxygen and neon, consistent with
recent enrichment from supernovae type II. Some indications for enhanced mixing
at the brightest region of the H-alpha shell and for a beginning outflow of the
hot gas were also detected.


title: Clusters of Galaxies: Shock Waves and Cosmic Rays

abstract:
  Recent observations of galaxy clusters in radio and X-ray indicate that
cosmic rays and magnetic fields may be energetically important in the
intracluster medium. According to the estimates based on theses observational
studies, the combined pressure of these two components of the intracluster
medium may range between $10% \sim 100 %$ of gas pressure, although their total
energy is probably time dependent. Hence, these non-thermal components may have
influenced the formation and evolution of cosmic structures, and may provide
unique and vital diagnostic information through various radiations emitted via
their interactions with surrounding matter and cosmic background photons. We
suggest that shock waves associated with cosmic structures, along with
individual sources such as active galactic nuclei and radio galaxies, supply
the cosmic rays and magnetic fields to the intracluster medium and to
surrounding large scale structures. In order to study 1) the properties of
cosmic shock waves emerging during the large scale structure formation of the
universe, and 2) the dynamical influence of cosmic rays, which were ejected by
AGN-like sources into the intracluster medium, on structure formation, we have
performed two sets of N-body/hydrodynamic simulations of cosmic structure
formation. In this contribution, we report the preliminary results of these
simulations.


title: Chandra Observations of Three SDSS Quasars at z~6

abstract:
  Chandra snapshot observations of the three most distant quasars then known,
at redshifts 5.82, 5.99, and 6.28, gave signficant detections even in the
short, 6 -- 8 ks, observations. The X-ray to optical luminosity ratios indicate
that quasars will be detectable in X-rays if they exist at even larger
redshifts. The present observations hint at two exciting discoveries. An
extended X-ray source 23 arcsec from SDSS1306+0356 may be a jet emitting
inverse Compton radiation from the Cosmic Microwave Background. SDSS 1030+0524
does not appear to be a point source, and may be a gravitationally lensed
system, or contain a small scale X-ray jet.


title: On the escape of cosmic rays from radio galaxy cocoons

abstract:
  (Abridged) A model for the escape of CR particles from radio galaxy cocoons
is presented here. It is assumed that the radio cocoon is poorly magnetically
connected to the environment. An extreme case of this kind is an insulating
boundary layer of magnetic fields, which can efficiently suppress particle
escape. More likely, magnetic field lines are less organised and allow the
transport of CR particles from the source interior to the surface region. For
such a scenario two transport regimes are analysed: diffusion of particles
along inter-phase magnetic flux tubes (leaving the cocoon) and cross field
transport of particles in flux tubes touching the cocoon surface. The cross
field diffusion is likely the dominate escape path, unless a significant
fraction of the surface is magnetically connected to the environment. Major
cluster merger should strongly enhance the particle escape by two complementary
mechanisms. i) The merger shock waves shred radio cocoons into filamentary
structures, allowing the CRs to easily reach the radio cocoon boundary due to
the changed morphology. ii) Also efficient particle losses can be expected for
radio cocoons not compressed in shock waves. There, for a short period after
the sudden injection of large scale turbulence, the (anomalous) cross field
diffusion can be enhanced by several orders of magnitude. This lasts until the
turbulent energy cascade has reached the microscopic scales, which determine
the value of the microscopic diffusion coefficients.


title: Physics Fundamentals of Luminous Accretion Disks Around Black Holes

abstract:
  These lectures provide an overview of the theory of accretion disks with
application to bright sources containing black holes. I focus on the
fundamental physics of these flows, stressing modern developments and
outstanding questions wherever possible. After a review of standard
Shakura-Sunyaev based models and their problems and uncertainties, I describe
the basic principles that determine the overall spectral energy distribution
produced by the flow. I then describe the physics of angular momentum transport
in black hole accretion disks, stressing the important role of magnetic fields.
Finally, I discuss the physics of radiation magnetohydrodynamics and how it
might affect the overall flow structure in the innermost regions near the black
hole.


title:
Gas-phase recombination, grain neutralization and cosmic-ray ionization
  in diffuse gas

abstract:
  Atomic ions are mostly neutralized by small grains (or PAH molecules) in
current theories of heating and cooling in cool diffuse clouds; in the main
they do not recombine with free electrons. This alters the ionization balance
by depressing n(H+) and n(He+) while carbon generally remains nearly fully
once-ionized: charge exchange with atomic oxygen and formation of H2 and OH
also depress n(H+) in partly molecular gas. Seemingly restrictive empirical
limits on the cosmic ray ionization rate of hydrogen ($\zeta_H$) are relaxed
and faster rates are favored in a wide range of circumstances, when grain
neutralization is recognized. Maintenance of the proton density at levels
needed to reproduce observations of HD requires $\zeta_H$ at least 2x10^{-16}
s^{-1}, but such models naturally explain the presence of both HD and H3^+ in
relatively tenuous H I clouds. In dense gas, a higher ionization rate can
account for high observed fractions of atomic hydrogen, and recognition of the
effects of grain neutralization can resolve a major paradox in the formation of
sulfur-bearing compounds.


title:
Comparing Young Stellar Populations Across Active Regions in the M31
  Disk

abstract:
  I present preliminary BV resolved stellar photometry of the M31 disk measured
from the data set of the NOAO/CTIO Local Group Survey. I have performed
detailed analyses of the star formation histories in and around three currently
active regions in the M31 disk: OB 78, OB 102 and the northeast spiral arm. The
results suggest that low H$\alpha$ emission from OB 78 compared to other active
regions is directly related to the details of the recent star formation
histories of the regions. In addition, while every active region I analyzed
shows a recent increase in star formation activity, some active regions also
contain overdensities of stars with ages <~100 Myr compared to adjacent
regions. The adjacent regions show a relatively constant, low star formation
rate over the past 100 Myr. There is no significant difference between the
stellar populations on either side of the active regions. This symmetry
provides no obvious signature of recent propagation of star formation near
these currently active regions of the M31 disk.


title:
Advanced Camera for Surveys Observations of Young Star Clusters in the
  Interacting Galaxy UGC 10214

abstract:
  We present the first Advanced Camera for Surveys (ACS) observations of young
star clusters in the colliding/merging galaxy UGC 10214. The observations were
made as part of the Early Release Observation (ERO) program for the newly
installed ACS during service mission SM3B for the Hubble Space Telescope (HST).
Many young star clusters can be identified in the tails of UGC 10214, with ages
ranging from ~3 Myr to 10 Myr. The extreme blue V-I (F606W-F814W) colors of the
star clusters found in the tail of UGC 10214 can only be explained if strong
emission lines are included with a young stellar population. This has been
confirmed by our Keck spectroscopy of some of these bright blue stellar knots.
The most luminous and largest of these blue knots has an absolute magnitude of
M_V = -14.45, with a half-light radius of 161 pc, and if it is a single star
cluster, would qualify as a super star cluster (SSC). Alternatively, it could
be a superposition of multiple scaled OB associations or clusters. With an
estimated age of ~ 4-5 Myr, its derived mass is < 1.3 x 10^6 solar masses. Thus
the young stellar knot is unbound and will not evolve into a normal globular
cluster. The bright blue clusters and associations are much younger than the
dynamical age of the tail, providing strong evidence that star formation occurs
in the tail long after it was ejected. UGC 10214 provides a nearby example of
processes that contributed to the formation of halos and intra-cluster media in
the distant and younger Universe.


title:
Does the Narrow [O III] 5007 Line Reflect the Stellar Velocity
  Dispersion in AGN?

abstract:
  It has been proposed that the width of the narrow [O III] 5007 emission line
can be used as a surrogate for the stellar velocity dispersion in active
galaxies. This proposition is tested using the SDSS EDR spectra of 107
low-redshift radio-quiet QSOs and Seyfert 1 galaxies by investigating the
correlation between black hole mass, as determined from H-beta FWHM and optical
luminosity, and [O III] FWHM. The correlation is real, but the scatter is
large. Without additional information or selection criteria, the [O III] width
can predict the black hole mass to a factor of 5.


title: Results from a Complete Chandra Survey of Radio Jets

abstract:
  We report preliminary results from the first targets observed as part of a
program to image the X-ray jets in a complete sample of radio selected jets. We
have acquired Australian Telescope Compact Array and Very Large Array data with
resolution 1", matching the Chandra resolution. PKS 1202-262 and PKS 0208-512
show dramatic coincidence with the initial radio jet, with the X-ray emission
dropping off at the large angle radio bends, similar to the structure of PKS
0637-752.


title: The effect of HII regions on rotation measure of pulsars

abstract:
  We have obtained new rotation measure for 11 pulsars observed with the
Effelsberg 100-m radio telescope, in the direction of the Perseus arm. Using a
combination of 34 published and the 11 newly measured pulsar rotation measures
we study the magnetic field structure towards the Perseus arm. We find that two
pulsars towards l$\sim$ 149$^{\circ}$ (Region 1) and four pulsars towards
l$\sim113^{\circ}$ (Region 2) lie behind HII regions which seriously affects
the pulsar rotation measures. The rotation measure of PSR J2337+6151 seem to be
affected by its passage through the supernova remnant G114.3+0.3. For Region 1,
we are able to constrain the random component of the magnetic field to
$5.7\mu$G. For the large-scale component of the Galactic magnetic field we
determine a field strength of $1.7\pm1.0\mu$G. This average field is constant
on Galactic scales lying within the Galactic longitude range of $85^{\circ} <$
l $ < 240^{\circ}$ and we find no evidence for large scale field reversal upto
5-6 kpc. We highlight the great importance to include the effects of foreground
emission in any systematic study.


title: Astrometric Calibration of the Sloan Digital Sky Survey

abstract:
  The astrometric calibration of the Sloan Digital Sky Survey is described. For
point sources brighter than r ~ 20 the astrometric accuracy is 45
milliarcseconds (mas) rms per coordinate when reduced against the USNO CCD
Astrograph Catalog, and 75 mas rms when reduced against Tycho-2, with an
additional 20 - 30 mas systematic error in both cases. The rms errors are
dominated by anomalous refraction and random errors in the primary reference
catalogs. The relative astrometric accuracy between the r filter and each of
the other filters (u g i z) is 25 - 35 mas rms. At the survey limit (r ~ 22),
the astrometric accuracy is limited by photon statistics to approximately 100
mas rms for typical seeing. Anomalous refraction is shown to contain components
correlated over two or more degrees on the sky.


title: Astrophysics of Young Star Binaries

abstract:
  This paper describes our study of the astrophysics of individual components
in close pre-main-sequence binaries. We observed both stars in 17 systems,
located in 4 nearby star forming regions, using low-resolution (R=760),
infrared spectroscopy and photometry. For 29 components we detected
photospheric absorption lines and were able to determine spectral type,
extinction, K-band excess, and luminosity. The other 5 objects displayed
featureless or pure emission line spectra. In ~50 % of the systems, the
extinction and K-band excess of the primary stars dominate those of the
secondaries. Masses and ages were determined for these 29 objects by placing
them on the H-R diagram, overlaid with theoretical pre-main-sequence tracks.
Most of the binaries appear to be coeval. The ages span 5x10^5 to 1x10^7 years.
The derived masses range from the substellar, 0.06 M_sun, to 2.5 M_sun, and the
mass ratios from M_2/M_1=0.04 to 1.0. Fourteen stars show evidence of
circumstellar disks. The K-band excess is well correlated with the K-L color
for stars with circumstellar material.


title: Bounds on the Magnetic Fields in the Radiative Zone of the Sun

abstract:
  We discuss bounds on the strength of the magnetic fields that could be buried
in the radiative zone of the Sun. The field profiles and decay times are
computed for all axisymmetric toroidal Ohmic decay eigenmodes with lifetimes
exceeding the age of the Sun. The measurements of the solar oblateness yield a
bound <~ 7 MG on the strength of the field. A comparable bound is expected to
come from the analysis of the splitting of the solar oscillation frequencies.
The theoretical analysis of the double diffusive instability also yields a
similar bound. The oblateness measurements at their present level of
sensitivity are therefore not expected to measure a toroidal field
contribution.


title: Detection of Far-Infrared Features in Star-Forming Regions

abstract:
  We report the detection of a feature at 65um and a broad feature around 100um
in the far-infrared spectra of the diffuse emission from two active
star-forming regions, the Carina nebula and Sharpless 171. The features are
seen in the spectra over a wide area of the observed regions, indicating that
the carriers are fairly ubiquitous species in the interstellar medium. A
similar 65um feature has been detected in evolved stars and attributed to
diopside, a Ca-bearing crystalline silicate. The present observations indicate
the first detection of a crystalline silicate in the interstellar medium if
this identification holds true also for the interstellar feature. A similar
broad feature around 90um reported in the spectra of evolved stars has been
attributed to calcite, a Ca-bearing carbonate mineral. The interstellar feature
seems to be shifted to longer wavelengths and have a broader width although the
precise estimate of the feature profile is difficult. As a carrier for the
interstellar 100um feature, we investigate the possibility that the feature
originates from carbon onions, grains consisting of curved graphitic shells.
Because of the curved graphitic sheet structure, the optical properties in the
direction parallel to the graphitic plane interacts with those in the vertical
direction in carbon onion grains. This effect enhances the interband transition
feature in the direction parallel to the graphitic plane in carbon onions,
which is suppressed in graphite particles. Simple calculations suggest that
carbon onion grains are a likely candidate for the observed 100um feature
carrier, but the appearance of the feature is sensitive to the assumed optical
properties.


title:
Time variation of the fine structure constant and mass-energy
  conservation

abstract:
  A brief note on the time variation of the fine structure constant
$\alpha_{em}$; it is shown that such a variation should violate mass-energy
conservation in the absence of proton decay.


title: Peculiar outburst of the newly revealed variable star V838 Mon

abstract:
  We present photometric and high- and low-resolution spectroscopic
observations of the unusual outburst of V838 Mon. The data were collected at
the NAO Rozhen, Bulgaria and at the Torun Observatory, Poland. Analysis of the
peculiar behavior of the spectrum of the star is given. The star's radial
velocity of +60 km/s is derived. A brief discussion concerning the nature of
the object is also given.


title: XMM-Newton Observations of AGN Iron Line Profiles

abstract:
  XMM-Newton observations of type I AGN are presented. The properties of the
iron K emission line are reviewed, the majority of AGN observed by XMM-Newton
show narrow, unresolved (by XMM) iron lines at 6.4 keV from cold matter that
must originate far from the inner accretion disc, perhaps in the putative torus
or outer broad line region. The strength of this narrow line appears to
decrease with luminosity, implying a reduction in the covering fraction of this
material in the more luminous quasars. Few examples of the broad, relativistic
iron line profile have been found by XMM-Newton, although in MCG -6-30-15, the
extreme breadth of the broad line component may imply a Kerr metric for the
central black hole. Generally, relativistic Fe K line profiles are not required
in a number of other Seyfert 1 X-ray spectra.


title: Time-dependent thermal X-ray afterglows from GRBs

abstract:
  Time-dependent thermal X-ray spectra are calculated from physically plausible
conditions around GRB. It is shown that account for time-dependent ionization
processes strongly affects the observed spectra of hot rarefied plasma. These
calculations may provide an alternative explanation to the observed X-ray lines
of early GRBs afterglows (such as GRB 011211). Our technique will allow one to
obtain independent constraints on the GRB collimation angle and on the
clumpiness of circumstellar matter.


title:
Aspherical galaxy clusters: effects on cluster masses and gas mass
  fractions

abstract:
  We present an investigation of the effects of asphericity on the estimates of
total mass and gas mass fraction in galaxy clusters from X-ray observations. We
model the aspherical shape of galaxy clusters by a triaxial model and compare
the true total mass and the true total gas mass fraction with the corresponding
quantities obtained with the assumption of spherical symmetry. In the triaxial
model we allow the extent along the line of sight to vary in order to describe
elongated and compressed cluster shapes. Using a sample of 10 ROSAT clusters
and a recent CHANDRA observation we find the following results. For prolate or
oblate shapes the difference between triaxial and spherical model both in the
mass and in the gas mass fraction are negligible (less than 3 %). For more
aspherical shapes the total mass is underestimated (overestimated) in the
centre, if the cluster is compressed (elongated). The gas mass fraction is
overestimated for compressed clusters and slightly underestimated for elongated
clusters. Comparing X-ray masses with gravitational lensing estimates, we find
that elongations along the line of sight can resolve discrepancies of masses
determined by the two different methods of up to ~30 %. The combination of
Sunyaev-Zel'dovich and X-ray observations is useful to measure the elongation
of the cluster along the line of sight. As an application, we estimate the
elongation of the cluster CL0016+16 with two different approaches,
Sunyaev-Zel'dovich measurements and comparison of weak lensing and X-ray
masses, and find reasonable agreement.


title: New Chandra/HST-STIS results on Seyfert I AGN: Photoionized Outflows

abstract:
  We present soft X-ray results from observations with the Chandra HETGS of the
Seyfert I AGN NGC 4593 and Mrk 509. We discuss the photoionized outflows
associated with Seyfert I AGN in terms of their absorption spectral signatures
and discuss their kinematics, column density and ionization state. We discuss
the link between UV and X-ray absorbers in Mrk 509 (which was simultaneously
observed with Chandra and HST/STIS. We also briefly discuss the possibility of
absorption due to neutral Fe embedded in the warm absorber of NGC 4593 versus
an interpretation of the data in terms soft X-ray relativistic emission lines.
We conclude with a summary of what is being learnt about warm absorbers in type
I AGN from high resolution spectroscopy.


title:
Quasar Parallax: a Method for Determining Direct Geometrical Distances
  to Quasars

abstract:
  We describe a novel method to determine direct geometrical distances to
quasars that can measure the cosmological constant, Lambda, with minimal
assumptions. This method is equivalent to geometric parallax, with the
`standard length' being the size of the quasar broad emission line region
(BELR) as determined from the light travel time measurements of reverberation
mapping. The effect of non-zero Lambda on angular diameter is large, 40% at
z=2, so mapping angular diameter distances vs. redshift will give Lambda with
(relative) ease. In principle these measurements could be made in the UV,
optical, near infrared or even X-ray bands. Interferometers with a resolution
of 0.01mas are needed to measure the size of the BELR in z=2 quasars, which
appear plausible given reasonable short term extrapolations of current
technology.


title: New {\it Chandra} Results on Seyfert I galaxies: Fe-K lines

abstract:
  We present measurements of the Fe-K line for nine Seyfert I galaxies using
Chandra High Energy Transmission Grating Spectrometer (HETGS) data. The
centroid energies are narrowly dispersed (6.403 +/- 0.062 keV) and indicate an
origin of the line cores in cold matter. If {\it all} the lines in this sample
were the peaks of a relativistically broadened disk line, it would require
unrealistically fine tuning. However, at least three of the nine AGN clearly
show a complex Fe-K line with an underlying broad component, possibly from a
disk. In the others, an apparently narrow Fe-K line (even if it is resolved by
Chandra) may still be due to the peak of a disk line. To distinguish this
scenario from an origin in distant matter requires variability information.


title: A 22GHz search for molecular absorption at z~3 with the upgraded ATCA

abstract:
  We report a lambda > 1cm search for rotational molecular absorption towards
quasars, now possible with the upgraded Australia Telescope Compact Array
(ATCA). The targets were PKS 0201+113, PKS 0336-017 and Q 0537-286, where known
damped Lyman-alpha absorption systems (DLAs) could cause redshifted molecular
absorption in the 12mm band of the telescope. We place 3-sigma upper limits on
any HCO+ 0-1 absorption features of < 30mJy per 3.4km/s channel. The
non-detections could be attributed to the inherent low metallicities in DLAs
leading to generally low H_2, and thus HCO+, column densities. In general, the
detection of molecular rotational transitions in DLAs could be further hindered
by a lower than expected CO-to-H_2 conversion ratio, whether due either to
photoionization of carbon or its relative under-abundance at high redshift.


title:
SDSSp J104433.04$-$012502.2 at $z=5.74$ is Gravitationally Magnified by
  an Intervening Galaxy

abstract:
  During the course of our optical deep survey program on L$\alpha$ emitters at
$z \approx 5.7$ in the sky area surrounding the quasar SDSSp
J104433.04$-$012502.2 at $z=5.74$, we found that a faint galaxy with $m_B$(AB)
$\approx 25$ is located at \timeform{1".9} southwest of the quasar. Its
broad-band color properties from $B$ to $z^\prime$ suggest that the galaxy is
located at a redshift of $z \sim 1.5$ -- 2.5. This is consistent with no strong
emission line in our optical spectroscopy. Since the counter image of the
quasar cannot be seen in our deep optical images, the magnification factor
seems not to be very high. Our modest estimate is that this quasar is
gravitationally magnified by a factor of 2.


title:
Images for an Isothermal Ellipsoidal Gravitational Lens from a Single
  Real Algebraic Equation

abstract:
  We present explicit expressions for the lens equation for a cored isothermal
ellipsoidal gravitational lens as a single real sixth-order algebraic equation
in two approaches; 2-dimensional Cartesian coordinates and 3-dimensional polar
ones. We find a condition for physical solutions which correspond to at most
five images. For a singular isothermal ellipsoid, the sixth-order equation is
reduced to fourth-order one for which analytic solutions are well-known.
Furthermore, we derive analytic criteria for determining the number of images
for the singular lens, which give us simple expressions for the caustics and
critical curves. The present formulation offers a useful way for studying
galaxy lenses frequently modeled as isothermal ellipsoids.


title:
Algebraic Properties of the Real Quintic Equation for a Binary
  Gravitational Lens

abstract:
  It has been recently shown that the lens equation for a binary gravitational
lens, which is apparently a coupled system, can be reduced to a real
fifth-order (quintic) algebraic equation. Some algebraic properties of the real
quintic equation are revealed. We find that the number of images on each side
of the separation axis is independent of the mass ratio and separation unless
the source crosses the caustics. Furthermore, the discriminant of the quintic
equation enables us to study changes in the number of solutions, namely in the
number of images. It is shown that this discriminant can be factorized into two
parts: One represents the condition that the lens equation can be reduced to a
single quintic equation, while the other corresponds to the caustics.


title: ATCA HI Observations of the Peculiar Galaxy IC2554

abstract:
  ATCA HI and radio continuum observations of the peculiar southern galaxy
IC2554 and its surroundings reveal typical signatures of an interacting galaxy
group. We detected a large HI cloud between IC2554 and the elliptical galaxy
NGC3136B. The gas dynamics in IC2554 itself, which is sometimes described as a
colliding pair, are surprisingly regular, whereas NGC3136B was not detected.
The HI cloud, which emerges from IC2554 as a large arc-shaped plume, has a size
of about 30 kpc, larger than that of IC2554. The total HI mass of the IC2554
system is about 2 x 10^9 Msun, a third of which resides in the HI cloud. It is
possible that tidal interaction between IC2554 and NGC3136B caused this
spectacular HI cloud, but the possibility of IC2554 being a merger remnant is
also discussed. We also detected HI gas in the nearby galaxies ESO092-G009 and
RKK1959 as well as an associated HI cloud, ATCA J1006-6710. Together they have
an HI mass of about 4.6 x 10^8 Msun. Another new HI source, ATCA J1007-6659,
with an HI mass of only about 2.2 x 10^7 Msun was detected roughly between
IC2554 and ESO092-G009 and corresponds to a face-on low surface brightness
dwarf galaxy. Star formation is evident only in the galaxy IC2554 with a rate
of about 4 Msun/yr.


title:
On mass and velocity distributions in members of star clusters : An
  analytical approach

abstract:
  Dynamical evolution of stellar mass distribution in star clusters is analysed
by considering simultaneously the effects of dynamical friction, stochastic
heating and the gravitational potential due to mass distribution in the
clusters. A simple expression is suggested for the dynamical friction which
adequately describes it in both high and low velocity ranges and the effect of
mass distribution in the cluster on the dynamics of a test mass can be
described by an anharmonic potential. With the help of energy considerations we
describe the dispersions in position and in velocity for stars of different
masses showing how the slowing down and mass segregation of stars evolve in the
cluster. Results are presented with the parameters for the star clusters of our
Galaxy.


title: Possible flakes of molecular hydrogen in the early Universe

abstract:
  The thermochemistry of H2 and HD in non-collapsed, non-reionized primordial
gas up to the end of the dark age is investigated with recent radiation-matter
and chemical reaction rates taking into account the efficient coolant HD, and
the possibility of a gas-solid phase transition of H2. In the standard big-bang
model we find that these molecules can freeze out and lead to the growth of
flakes of solid molecular hydrogen at redshifts z ~ 6-12 in the unperturbed
medium and under-dense regions. While this freezing caused by the mere
adiabatic cooling of the expanding matter is less likely to occur in collapsed
regions due to their higher than radiation background temperature, on the other
hand the super-adiabatic expansion in voids strongly favors it. Later
reionization (at z ~ 5-6) eventually destroys all these H2 flakes. The possible
occurrence of H2 flakes is important for the degree of coupling between matter
and radiation, as well as for the existence of a gas-grain chemistry at the end
of the dark age.


title: Massive z ~ 1.3 evolved galaxies revealed

abstract:
  We present the results of TNG near-IR low resolution spectroscopy of two
(S7F5-254 and S7F5-45) sources belonging to a complete sample of 15 EROs with
K'<18 and R-K'>5 selected from the MUNICS Survey. Both the spectra show a sharp
drop in the continuum which can be ascribed only to the Balmer break. This
places them at 1.2<z<1.5. Their rest-frame z=1.2 K-band absolute magnitude is
M_K ~ -26.6 (L ~ 7L*). The comparison of the spectra and the photometric data
with a grid of synthetic template spectra provides a redshift z=1.22 for
S7F5-254 and z=1.46 for S7F5-45. The resulting lower limits to their stellar
mass are M_{stars}=6x10^{11} M_{sun} and M_{stars}=4x10^{11} M_{sun}. The
minimum age of the last burst of star formation in S7F5-254 is 3.5 Gyr while it
is 0.5 Gyr in S7F5-45 implying a minimum formation redshift z_f>3.5 and z_f>2
for the two EROs respectively.


title:
A photometric mode identification method, including an improved
  non-adiabatic treatment of the atmosphere

abstract:
  We present an improved version of the method of photometric mode
identification of Heynderickx et al. (1994). Our new version is based on the
inclusion of precise non-adiabatic eigenfunctions determined in the outer
stellar atmosphere according to the formalism recently proposed by Dupret et
al.(2002). Our improved photometric mode identification technique is therefore
no longer dependent on ad hoc parameters for the non-adiabatic effects. It
contains the complete physical conditions of the outer atmosphere of the star,
provided that rotation does not play a key role. We apply our improved method
to the two slowly pulsating B stars HD 74560 and HD 138764 and to the beta
Cephei star EN (16) Lac. Besides identifying the degree l of the pulsating
stars, our method is also a tool for improving the knowledge of stellar
interiors and atmospheres, by imposing constraints on parameters such as the
metallicity and the mixing-length parameter alpha (a procedure we label
non-adiabatic asteroseismology).


title:
Surface Brightness Profiles and Structural Parameters for Globular
  Clusters in the Fornax and Sagittarius Dwarf Spheroidal Galaxies

abstract:
  We present radial surface brightness profiles for all five globular clusters
in the Fornax dwarf spheroidal galaxy, and for the four present members of the
Sagittarius dwarf spheroidal galaxy. These profiles are derived from archival
Hubble Space Telescope observations, and have been calculated using the same
techniques with which we measured profiles in our previous studies of LMC and
SMC clusters (astro-ph/0209031 and astro-ph/0209046 respectively), apart from
some small modifications. From the surface brightness profiles, we have
determined structural parameters for each cluster, including core radii and
luminosity and mass estimates. We also provide a brief summary of literature
measurements of other parameters for these clusters, including their ages,
metallicities and distances. Our core radius measurements are mostly in good
agreement with those from previous lower resolution studies, although for
several clusters our new values are significantly different. The profile for
Fornax cluster 5 does not appear to be well fit by a King-type model and we
suggest that it is a post core-collapse candidate. We examine the distribution
of cluster core radii in each of the two dwarf galaxy systems, and compare
these with the distribution of core radii for old LMC clusters. The three
distributions match within the limits of measurement errors and the small
sample sizes. We discuss the implications of this in the context of the
radius-age trend we have previously highlighted for the Magellanic Cloud
clusters.


title: Possible mechanism of electrical field origin around celestial bodies

abstract:
  Slow magnetic field variations in stars and planets create a quasistationary
electrical field which may be observed. It is supposed that the electrical
field near the Earth surface may be partially connected with variation of the
Earth magnetic field. Two examples of the electrical field distribution around
the infinite cylinder, and the circular loop with a lineary growing with time
electrical currents are given.


title: Superluminal Motion and Relativistic Beaming in Blazar Jets

abstract:
  High resolution radio observations remain the most direct way to study the
formation and evolution of radio jets associated with the accretion onto
massive black holes. We report preliminary results of our seven year VLBA
observational program to understand the nature of relativistic beaming in
blazars and the surrounding environment of massive black holes.
  Most blazars show an apparent outward flow away from an active core. However,
in a few sources the motion appears inward, most likely the result of
projection of a curved trajectory which bends back toward along the line of
sight. The apparent motion of jet features is not always oriented along the
direction separating the feature from the core, and in a few cases we have
observed a clear change in the direction and velocity of a feature as it flows
along the jet. In other sources, the motion appears to follow a simple
ballistic trajectory. We find no simple relation between the time scales of
flux density changes and apparent component velocities.


title:
COBE-DMR constraints on the nonlinear coupling parameter: a wavelet
  based method

abstract:
  Nonlinearity introduced in slow-roll inflation will produce weakly
non-Gaussian CMB temperature fluctuations. We have simulated non-Gaussian large
scale CMB maps (including COBE-DMR constraints) introducing an additional
quadratic term in the gravitational potential.The amount of nonlinearity being
controlled by the so called nonlinear coupling parameter f_{nl}. An analysis
based on the Spherical Mexican Hat wavelet was applied to these and to the
COBE-DMR maps. Skewness values obtained at several scales were combined into a
Fisher discriminant. Comparison of the Fisher discriminant distributions
obtained for different nonlinear coupling parameters with the COBE-DMR values,
sets a constraint of abs(f_{nl})<1100 at the 68% confidence level. This new
constraint being tighter than the one previously obtained by using the
bispectrum by Komatsu et al. (2002).