title: On the light echo in V838 Mon

abstract:
  After having presented a theoretical outline of the light echo phenomenon and
results of simple numerical simulations we study the available images of the
light echo in V838 Mon obtained with HST. From an analysis of the observed
expansion of the light echo we conclude that the distance to V838 Mon is
greater then $\sim$5 kpc. We also investigate the structure of the dust
distribution in the vicinity of the object. We find no obvious signs of
spherical symmetry in the resultant distribution. Near the central object there
is a strongly asymmetric dust-free region which we interpret as an evidence
that V838 Mon is moving relatively to the dusty medium. From these results we
conclude that dust illuminated by the light echo is of interstellar origin
rather than produced by mass loss from V838 Mon in the past.


title:
The HELLAS2XMM survey: IV. Optical identifications and the evolution of
  the accretion luminosity in the Universe

abstract:
  We present results from the photometric and spectroscopic identification of
122 X-ray sources recently discovered by XMM-Newton in the 2-10 keV band (the
HELLAS2XMM 1dF sample). Their flux cover the range 8E-15-4E-13 cgs and the
total area surveyed is 0.9 deg2. About 20% of the hard X-ray selected sources
have an X-ray to optical flux ratio (X/O) ten times or more higher than that of
optically selected AGN. Unlike the faint sources found in the ultra-deep
Chandra and XMM-Newton surveys, which reach X-ray (and optical) fluxes more
than one order of magnitude lower than the HELLAS2XMM survey sources, many of
the extreme X/O sources in our sample have R<=25 and are therefore accessible
to optical spectroscopy. We report the identification of 13 sources with
X/O>10: 8 are narrow line QSO (i.e. QSO2), four are broad line QSO. We use a
combined sample of 317 hard X-ray selected sources (HELLAS2XMM 1dF, CDFN 1Msec,
SSA13 and Lockman Hole flux limited samples), 221 with measured z, to evaluate
the cosmological evolution of the hard X-ray source's number and luminosity
densities. Looking backward in time, the low luminosity sources (logL(2-10keV)
= 43-44 erg/s) increase in number at a rate different than the high luminosity
sources (logL(2-10keV)>44.5 erg/s), reaching a maximum around z=1 and then
levelling off beyond z=2. This translates into an accretion driven luminosity
density which is dominated by sources with logL(2-10keV) < 44.5 erg/s up to at
least z=1, while the contribution of the same sources and of those with
logL(2-10keV)>44.5 erg/s appear to be comparable between z=2 and 4.


title: A Fast Simulator for the Sky Map Observed by the GLAST Experiment

abstract:
  In this report, the implementation of a program for the simulation of the sky
map, in the gamma rays energy range, observed by the GLAST experiment will be
described. The program generates a list of photons and images of the galactic
and extragalactic background and of the sources, in a selected energy range and
in a given region of the sky.


title:
The spiral galaxy M33 mapped in the FIR by ISOPHOT: A spatially resolved
  study of the warm and cold dust

abstract:
  The Sc galaxy M33 has been mapped with ISOPHOT in the far-infrared, at 60,
100, and 170mue. The spatial resolution of these FIR maps allows the separation
of spiral arms and interarm regions and the isolation of a large number of
star-forming regions. The spectral energy distribution in the FIR indicates a
superposition of two components, a warm one originating from dust at ~45K, and
a cold one, at ~16K. The warm component is concentrated towards the spiral arms
and the star-forming regions, and is likely heated by the UV radiation from OB
stars. The cold component is more smoothly distributed over the disk, and
heated by the diffuse interstellar radiation. For the about 60 star-forming
regions detected the H-alpha/FIR flux ratio increases significantly with the
distance from the galaxy center, probably due to decreasing extinction. An
anti-correlation of F_Ha/F_60 with F_170 suggests the intrinsic extinction to
be related to the cold dust surface brightness according to
A_V/S_170~0.03mag/MJy*sr. For the total galaxy the star formation rate (SFR)
derived from the FIR is in agreement with that derived from the de-extincted
H-alpha emission. For individual star-forming regions, a consistency between
SFRs derived from the optical and from the FIR requires only a fraction of the
UV radiation to be absorbed locally. The individual star-forming regions also
show a local radio-FIR correlation. This local correlation is, however, due to
quite different components than to those that lead to the well-known global
radio-FIR correlation for entire galaxies.


title: High-Resolution Spectroscopy of FUors

abstract:
  High-resolution spectroscopy was obtained of the FUors FU Ori and V1057 Cyg
between 1995 and 2002 with SOFIN at NOT and with HIRES at Keck I. During those
years FU Ori remained about 1 mag. (in B) below its 1938-39 maximum brightness,
but V1057 Cyg (B ~ 10.5 at peak in 1970-71) faded from about 13.5 to 14.9 and
then recovered slightly. Their photospheric spectra resemble a rotating G0 Ib
supergiant, with v_eq sin i = 70 km/s for FU Ori and 55 km/s for V1057 Cyg. As
V1057 Cyg faded, P Cyg structure in Halpha and the IR CaII lines strengthened
and a complex shortward-displaced shell spectrum increased in strength,
disappeared in 1999, and reappeared in 2001. Night-to-night changes in the wind
structure of FU Ori show evidence of sporadic infall. The strength of P Cyg
absorption varied cyclically with a period of 14.8 days, with phase stability
maintained over 3 seasons, and is believed to be the rotation period. The
structure of the photospheric lines also varies cyclically, but with a period
of 3.54 days. A similar variation may be present in V1057 Cyg. As V1057 Cyg has
faded, the emission lines of a pre-existing low-excitation chromosphere have
emerged, so we believe the `line doubling' in V1057 Cyg is produced by these
central emission cores in the absorption lines, not by orbital motion in an
inclined Keplerian disk. No dependence of v_eq sin i on wavelength or
excitation potential was detected in either star, again contrary to expectation
for a self-luminous accretion disk. Nor are critical lines in the near infrared
accounted for by synthetic disk spectra. A rapidly rotating star near the edge
of stability (Larson 1980), can better explain these observations. FUor
eruptions may not be a property of ordinary TTS, but may be confined to a
special subspecies of rapid rotators having powerful quasi-permanent winds.


title: Using spectroscopic data to disentangle stellar population properties

abstract:
  It is well known that, when analyzed at the light of current synthesis model
predictions, variations in the physical properties of single stellar
populations (e.g. age, metallicity, initial mass function, element abundance
ratios) may have a similar effect in their integrated spectral energy
distributions. The confusion is even worsened when more realistic scenarios,
i.e. composite star formation histories, are considered. This is, in fact, one
of the major problems when facing the study of stellar populations in star
clusters and galaxies. Typically, the observational efforts have been aimed to
find the most appropriate spectroscopic indicators in order to avoid, as far as
possible, degeneracies in the parameter space. However, from a practical point
of view, the most suited observables are not, necessarily, those that provide
more orthogonality in that parameter space, but those that give the best
balance between parameter degeneracy and sensitivity to signal-to-noise ratio
per Angstrom, SN_A. In order to achieve the minimum combined total error in the
derived physical parameters, this work discusses how the functional dependence
of typical line-strength indices and colors on SN_A allows to define a
suitability parameter which helps to obtain better realistic combinations of
spectroscopic data. As an example, we discuss in more detail the problem of
breaking the well known age-metallicity degeneracy in relatively old stellar
populations, comparing the suitability of different spectroscopic diagrams for
a simple stellar population of solar metallicity and 12 Gyr old.


title: Neutralino annihilation gamma-rays from clumps and the LMC

abstract:
  We discuss the detectability of dark matter clumps in the Milky Way halo due
to neutralino annihilation. We then focus on a known ``clump'', the Large
Magellanic Cloud.


title:
Deuterium fractionation on interstellar grains studied with the direct
  master equation approach

abstract:
  We have studied deuterium fractionation on interstellar grains with the use
of an exact method known as the direct master equation approach. We consider
conditions pertinent to dense clouds at late times when the hydrogen is mostly
in molecular form and a large portion of the gas-phase carbon has already been
converted to carbon monoxide. Hydrogen, oxygen and deuterium atoms, as well as
CO molecules, are allowed to accrete on to dust particles and react there to
produce various stable molecules. The surface abundances, as well as the
abundance ratios between deuterated and normal isotopomers, are compared with
those calculated with the Monte Carlo approach. We find that the agreement
between the Monte Carlo and the direct master equation methods can be made as
close as desired. Compared with previous examples of the use of the direct
master equation approach, our present method is much more efficient. It should
now be possible to run large-scale gas-grain models in which the diffusive dust
chemistry is handled `exactly'.


title:
An application of the Independent Component Analysis methodology to
  gamma ray astrophysical imaging

abstract:
  Independent Component Analysis (ICA) is a statistical method often used to
decompose a complex dataset in its independent sub-parts. It is a powerful
technique to solve a typical Blind Source Separation problem. A fast
calculation of the gamma ray sky observed by GLAST, assuming the expected
instrumental response, has been implemented. The simulated images were used to
test the capability of the ICA method in identifying the sources.


title:
Gravitational Microlensing: Black Holes, Planets; OGLE, VLTI, HST and
  Space Probes

abstract:
  OGLE and other projects are likely to discover first stellar mass black holes
and the first planets through gravitational lensing in the next year or two. It
is important to have follow-up projects ready, using diverse observing methods.
The best for black hole detection would be a measurement of image splitting
with VLTI, or any other optical interferometer. Alternative approach is to
measure non-linear motion of the light centroid with the HST, or even with a
ground based telescope. Every year OGLE detects several very long duration
microlensing events brighter than I = 16 mag and K = 14 mag. The two images may
be separated by up to 10 mas.
  Ground based detection of strong caustic crossing planetary events will
provide mass ratios and proper motions for the detected systems. For most
events photometric parallax needed for mass determination will require a space
instrument at least as far as the L2 point, to provide long enough baseline.


title: Collimation of a Central Wind by a Disc-Associated Magnetic Field

abstract:
  Studies of jets from young stellar objects (YSO's) suggest that material is
launched from a small central region at wide opening angles and collimated by
an interaction with the surrounding environment. Using time-dependent,
numerical magnetohydrodynamic simulations, we follow the detailed launching of
a central wind via the coupling of a stellar dipole field to the inner edge of
an accretion disc. Our method employs a series of nested computational grids,
which allows the simulations to follow the central wind out to scales of tens
of AU, where it may interact with its surroundings. The coupling between the
stellar magnetosphere and disc inner edge has been known to produce an outflow
containing both a highly collimated jet plus a wide-angle flow. The jet and
wide-angle wind flow at roughly the same speed (100--200 km/s), and most of the
energy and mass is carried off at relatively wide angles. We show that the
addition of a weak disc-associated field (<< 0.1 Gauss) has little effect on
the wind launching, but it collimates the entire flow (jet + wide wind) at a
distance of several AU. The collimation is inevitable, regardless of the
relative polarity of the disc field and stellar dipole, and the result is a
more powerful and physically broader collimated flow than from the star-disc
interaction alone. Within the collimation region, the morphology of the
large-scale flow resembles a pitchfork, in projection. We compare these results
with observations of outflows from YSO's and discuss the possible origin of the
disc-associated field.


title:
A Deep Chandra X-ray Observation of the Embedded Young Cluster in NGC
  2024

abstract:
  We present results of a sensitive 76 ksec Chandra observation of the young
stellar cluster in NGC 2024 (d = 415 pc) in the Orion B giant molecular cloud.
Previous infrared observations have shown that this remarkable cluster contains
several hundred embedded young stars, most of which are still surrounded by
circumstellar disks. Thus, it presents a rare opportunity to study X-ray
activity in a large sample of optically invisible protostars and classical T
Tauri stars (cTTS) undergoing accretion. Chandra detected 283 X-ray sources of
which 248 were identified with counterparts at other wavelengths, mostly in the
near-IR. Astrometric registration of Chandra images against 2MASS resulted in
sub-arcsecond positional accuracy and high-confidence identifications of IR
counterparts. The Chandra detections are characterized by hard heavily-
absorbed spectra and spectacular variability. Spectral analysis of >100 sources
gives a mean extinction A_v = 10.5 mag and typical plasma energies E = 3 keV.
The range of variability includes rapid impulsive flares and persistent
low-level fluctuations indicative of strong magnetic activity, as well as slow
rises and falls in count rate whose origin is more obscure. Some outbursts
reached sustained temperatures of kT = 6 - 10 keV. Chandra detected all but one
of a subsample of 27 cTTS identified from previous IR photometry, and their
X-ray and bolometric luminosities are correlated. We also report the X-ray
detection of IRS 2b, which is thought to be a massive embedded late O or early
B star that may be the ionizing source of NGC 2024. Seven millimeter-bright
cores (FIR 1-7) in NGC 2024 that may be protostellar were not detected, with
the possible exception of faint emission near the unusual core FIR-4.


title:
The Optical Gravitational Lensing Experiment. Population II Cepheids in
  the Galactic Bulge

abstract:
  We present I-band light curves of 54 Population II Cepheids identified in the
OGLE-II catalog of variable objects in the Galactic bulge fields. Their periods
range from a fraction of a day to several days. Their light curves show very
close similarity to the light curves of classical Cepheids with periods a few
times longer.
  We analyze location of the newly identified Population II Cepheids in the
color--magnitude diagram. The position of these objects confirms recent
discovery that the interstellar extinction toward the Galactic bulge might be
anomalous. The slope of the reddening line obtained from our sample is in very
good agreement with the earlier one derived with red clump stars and the one
derived with RR~Lyr stars in the Galactic bulge.
  Our Population II Cepheids follow the same period--luminosity (P--L) relation
indicating similar status of these objects. We compare the P--L relation of
these stars with the relation of Population II Cepheid detected by the OGLE-II
survey in the LMC. Deviations from the P--L relation of the Galactic bulge
Cepheids seem to indicate that these objects are located in the Galactic bar
similarly to red clump stars.


title:
Momentum transfer across shear flows in Smoothed Particle Hydrodynamic
  simulations of galaxy formation

abstract:
  We investigate the evolution of angular momentum in SPH simulations of galaxy
formation, paying particular attention to artificial numerical effects. We find
that a cold gas disc forming in an ambient hot gas halo receives a strong
hydrodynamic torque from the hot gas. By splitting the hydrodynamic force into
artificial viscosity and pressure gradients, we find that the angular momentum
transport is caused not by the artificial viscosity but by the pressure
gradients. Using simple test simulations of shear flows, we conclude that the
pressure gradient-based viscosity can be divided into two components: one due
to the noisiness of SPH and the other to ram pressure. The former is
problematic even with very high resolution because increasing resolution does
not reduce the noisiness. On the other hand, the ram pressure effect appears
only when a cold gas disc or sheet does not contain enough particles. In such a
case, holes form in the disc or sheet, and then ram pressure from intra-hole
hot gas, causes significant deceleration. In simulations of galactic disc
formation, star formation usually decreases the number of cold gas particles,
and hole formation leads to the fragmentation of the disc. To circumvent these
problem, we modify the SPH algorithm, decoupling the cold from the hot gas
phases, i.e. inhibiting the hydrodynamic interaction between cold and hot
particles. This, a crude modelling of a multi-phase fluid in SPH cosmological
simulations, leads to the formation of smooth extended cold gas discs and to
better numerical convergence. The decoupling is applicable in so far as the
self-gravitating gas disc with negligible external pressure is a good
approximation for a cold gas disc. (abridged)


title: The spectrum of the cosmic X-ray background observed by RTXE/PCA

abstract:
  We have analyzed a large set of RXTE/PCA scanning and slewing observations
performed between April 1996 and March 1999. We obtained the 3-20 keV spectrum
of the cosmic X-ray background (CXB) by subtracting Earth-occulted observations
from observations of the X-ray sky at high galactic latitude and far away from
sources. The sky coverage is approximately ~22600 sq.deg. The PCA spectrum of
CXB in 3-20 keV energy band is adequately approximated by a single power law
with photon index Gamma~1.4 and normalization at 1 keV ~9.5 phot/s/cm2/keV/sr.
Instrumental background uncertainty precludes accurate RXTE/PCA measurements of
the spectrum of cosmic X-ray background at energies above 15 keV and therefore
we can not detect the high energy cutoff observed by HEAO-1 A2 experiment. Deep
observations of the 6 high latitude points used to model the PCA background
provide a coarse measure of the spatial variation of the CXB. The CXB
variations are consistent with a fixed spectral shape and variable
normalization characterized by a fractional rms amplitude of ~7% on angular
scales of ~1 square deg.


title:
High resolution 21 cm mapping of the Ursa Major Galactic cirrus: power
  spectra of the high-latitude HI gas

abstract:
  We present a power spectrum analysis of interferometric 21 cm observations of
the Ursa Major high-latitude cirrus, obtained with the Dominion Radio
Astrophysical Observatory (DRAO) of Penticton (Canada). These high-resolution
data reveal the intricate structure of the diffuse Galactic HI, at angular
scales from 1 arcminute to 3 degrees. A filtering method based on a wavelet
decomposition was used to enhance the signal-to-noise ratio of the data. The
power spectra of the integrated emission and of the centroid velocity fields
were used to deduce the three-dimensional (3D) spectral index of the density
and velocity fields of the HI cirrus. The spectral index is similar for the 3D
density and velocity fields with a value of -3.6\pm0.2. Using the
Leiden/Dwingeloo observations, this analysis was extended to the whole North
Celestial Loop (which includes the Ursa Major cirrus), showing that the scaling
laws prevail from 0.1 to 25 pc. The centroid velocity and integrated emission
fields show moderate correlation, with a maximum cross-correlation value of
0.44.


title: Two-Mirror Apodization for High-Contrast Imaging

abstract:
  Direct detection of extrasolar planets will require imaging systems capable
of unprecedented contrast. Apodized pupils provide an attractive way to achieve
such contrast but they are difficult, perhaps impossible, to manufacture to the
required tolerance and they absorb about 90% of the light in order to create
the apodization, which of course lengthens the exposure times needed for planet
detection. A recently proposed alternative is to use two mirrors to accomplish
the apodization. With such a system, no light is lost. In this paper, we
provide a careful mathematical analysis, using one dimensional mirrors, of the
on-axis and off-axis performance of such a two-mirror apodization system. There
appear to be advantages and disadvantages to this approach. In addition to not
losing any light, we show that the nonuniformity of the apodization implies an
extra magnification of off-axis sources and thereby makes it possible to build
a real system with about half the aperture that one would otherwise require or,
equivalently, resolve planets at about half the angular separation as one can
achieve with standard apodization. More specifically, ignoring pointing error
and stellar disk size, a planet at $1.7 \lambda/D$ ought to be at the edge of
detectability. However, we show that the non-zero size of a stellar disk pushes
the threshold for high-contrast so that a planet must be at least $2.5
\lambda/D$ from its star to be detectable. The off-axis analysis of
two-dimensional mirrors is left for future study.


title: Constraints on Cold Dark Matter in the Gamma-ray Halo of NGC 253

abstract:
  A gamma-ray halo in a nearby starburst galaxy NGC 253 was found by the
CANGAROO-II Imaging Atmospheric Cherenkov Telescope (IACT). By fitting the
energy spectrum with expected curves from Cold Dark Matter (CDM) annihilations,
we constrain the CDM-annihilation rate in the halo of NGC 253. Upper limits for
the CDM density were obtained in the wide mass range between 0.5 and 50 TeV.
Although these limits are higher than the expected values, it is complementary
important to the other experimental techniques, especially considering the
energy coverage. We also investigate the next astronomical targets to improve
these limits.


title: Radio-Excess IRAS Galaxies: PMN/FSC Sample Selection

abstract:
  A sample of 178 extragalactic objects is defined by correlating the 60 micron
IRAS FSC with the 5 GHz PMN catalog. Of these, 98 objects lie above the
radio/far-infrared relation for radio-quiet objects. These radio-excess
galaxies and quasars have a uniform distribution of radio excesses and appear
to be a new population of active galaxies not present in previous
radio/far-infrared samples. The radio-excess objects extend over the full range
of far-infrared luminosities seen in extragalactic objects. Objects with small
radio excesses are more likely to have far-infrared colors similar to
starbursts, while objects with large radio excesses have far-infrared colors
typical of pure AGN. Some of the most far-infrared luminous radio-excess
objects have the highest far-infrared optical depths. These are good candidates
to search for hidden broad line regions in polarized light or via near-infrared
spectroscopy. Some low far-infrared luminosity radio-excess objects appear to
derive a dominant fraction of their far-infrared emission from star formation,
despite the dominance of the AGN at radio wavelengths. Many of the radio-excess
objects have sizes likely to be smaller than the optical host, but show
optically thin radio emission. We draw parallels between these objects and high
radio luminosity Compact Steep-Spectrum (CSS) and GigaHertz Peaked-Spectrum
(GPS) objects. Radio sources with these characteristics may be young AGN in
which the radio activity has begun only recently. Alternatively, high central
densities in the host galaxies may be confining the radio sources to compact
sizes. We discuss future observations required to distinguish between these
possibilities and determine the nature of radio-excess objects.


title: Electromagnetic Radiation From The Accelerating Universe

abstract:
  The acceleration of the expansion of the universe has been argued for by
several research groups. If the universe is accelerating and if the universe or
some part of the universe has a charge, then there may be electromagnetic
radiation produced from the acceleration of the universe since accelerating
charges produce electromagnetic radiation. This letter does a thought
experiment to ask about the possible characteristics of the radiation from an
accelerating universe. A value for the power, or rate of energy flow, of the
universe's acceleration is calculated in this letter. A value of the power of
the electromagnetic radiation emitted by the universe's acceleration is
calculated to be P = 5.99 x 10 -82 Joule/sec or 5.99 x 10 -82 Watts. This value
for the power assumes only the charge of an electron as the value for the
charge; larger charges would produce much larger rates of energy flow. The
letter then reveals what a characteristic of a charged, accelerating universe
would be.


title: Cosmic-Ray Detection System using Internet

abstract:
  A cosmic ray detection system, consisting of standardized detector stations
connected through the Internet, is described. The system can be used for
detecting air showers that arrive over a wide area with correlated time. The
data at each site are exchanged in (quasi) real time, which makes the system
suitable for displaying cosmic ray arrivals at museumns and schools.


title: The Deuterium Abundance in the z=0.7 absorber towards QSO PG1718+4807

abstract:
  We report a further analysis of the ratio of deuterium to hydrogen (D/H)
using HST spectra of the z=0.701 Lyman limit system towards the QSO PG1718+481.
Initial analyses of this absorber found it gave a high D/H value, 1.8 - 3.1
\times 10^{-4} (Webb et al. 1998), inconsistent with several higher redshift
measurements. It is thus important to critically examine this measurement. By
analysing the velocity widths of the DI, HI and metal lines present in this
system, Kirkman et al. (2001) report that the additional absorption in the blue
wing of the lya line can not be DI, with a confidence level of 98%. Here we
present a more detailed analysis, taking into account possible wavelength
shifts between the three sets of HST spectra used in the analysis. We find that
the constraints on this system are not as strong as those claimed by Kirkman et
al. The discrepancy between the parameters of the blue wing absorption and the
parameters expected for DI is marginally worse than 1 sigma.
  Tytler et al.(1999) commented on the first analysis of Webb et
al.(1997,1998), reporting the presence of a contaminating lower redshift Lyman
limit system, with log[N(HI)] = 16.7 at z=0.602, which biases the N(HI)
estimate for the main system. Here we show that this absorber actually has
log[N(HI)] < 14.6 and does not impact on the estimate of N(HI) in the system of
interest at z = 0.701.
  The purpose of the present paper is to highlight important aspects of the
analysis which were not explored in previous studies, and hence help refine the
methods used in future analyses of D/H in quasar spectra.


title: Predicting QSO Continua in the Ly Alpha Forest

abstract:
  We present a method to make predictions with sets of correlated data values,
in this case QSO flux spectra. We predict the continuum in the Lyman-Alpha
forest of a QSO, from 1020 -- 1216 A, using the spectrum of that QSO from 1216
-- 1600 A . We find correlations between the unabsorbed flux in these two
wavelengths regions in the HST spectra of 50 QSOs. We use principal component
analysis (PCA) to summarize the variety of these spectra and we relate the
weights of the principal components for 1020 -- 1600 A to the weights for 1216
-- 1600 A, and we apply this relation to make predictions. We test the method
on the HST spectra, and we find an average absolute flux error of 9%, with a
range 3 -- 30%, where individual predictions are systematically too low or too
high. We mention several ways in which the predictions might be improved.


title:
Results from a Near Infrared Search for Emission-line Stars in the Inner
  Galaxy: Spectra of New Wolf-Rayet Stars

abstract:
  We present follow-up spectroscopy of emission line candidates detected on
near-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The
filters are optimized for the detection of Wolf-Rayet stars and other objects
which exhibit emission--lines in the 2 $\mu$m region. Approximately three
square degrees along the Galactic plane have been analyzed in seven
narrow--filters (four emission--lines and three continuum). We have discovered
4 new Wolf-Rayet stars and present coordinates, finding charts, and K-band
spectra.


title: Stability of FRW Cosmology with Generalized Chaplygin Gas

abstract:
  We apply methods of dynamical systems to study the behaviour of universe
dominated by the generalized Chaplygin gas. We reduce the dynamics to a
2-dimensional Hamiltonian system and study its behaviour for various ranges of
parameters. The dynamics is studied on the phase plane by using methods of
qualitative analysis of differential equations. The behaviour of trajectories
at infinity is studied in some convenient coordinates introduced on the phase
plane. Hence we shown that FRW model with the generalized Chaplygin gas is
structurally stable. We clearly find the domains of cosmic acceleration as well
as conditions for which the horizon problem is solved. We also define some
general class of fluids which generalize the Chaplygin gas. The dynamics of
such models in terms of energy conditions is also discussed.


title:
Chandra Analysis and Mass Estimation of the Lensing Cluster of Galaxies
  CL0024+17

abstract:
  We present a detailed analysis of Chandra X-ray observations of the lensing
cluster of galaxies CL0024+17 at z=0.395. We found that the radial temperature
profile is consistent with being isothermal out to ~600 kpc and that the
average X-ray temperature is 4.47 (+0.83, -0.54) keV. The X-ray surface
brightness profile is represented by the sum of extended emission centered at
the central bright elliptical galaxy with a small core of 50 kpc and more
extended emission which can be well described by a spherical beta-model with a
core radius of about 210 kpc. Assuming the X-ray emitting gas to be in
hydrostatic equilibrium, we estimated the X-ray mass within the arc radius and
found it is significantly smaller than the strong lensing mass by a factor of
about 2--3. We detected a strong redshifted iron K line in the X-ray spectrum
from the cluster for the first time and find the metal abundance to be 0.76
(+0.37, -0.31) solar.


title: The 2dF Galaxy Redshift Survey: Final Data Release

abstract:
  The 2dF Galaxy Redshift Survey (2dFGRS) has obtained spectra for 245591
sources, mainly galaxies, brighter than a nominal extinction-corrected
magnitude limit of b_J=19.45. Reliable redshifts were measured for 221414
galaxies. The galaxies are selected from the extended APM Galaxy Survey and
cover an area of approximately 1500 square degrees in three regions: an NGP
strip, an SGP strip and random fields scattered around the SGP strip. This
paper describes the 2dFGRS final data release of 30 June 2003 and complements
Colless et al. (2001), which described the survey and the initial 100k data
release. The 2dFGRS database and full documentation are available on the WWW at
http://www.mso.anu.edu.au/2dFGRS/


title:
Measurement of Cosmic-Ray Proton and Antiproton Spectra at Mountain
  Altitude

abstract:
  Cosmic-ray proton and antiproton spectra were measured at mountain altitude,
2770 m above sea level. We observed more than 2 x 10^5 protons and 10^2
antiprotons in a kinetic energy range between 0.25 and 3.3 GeV. The
zenith-angle dependence of proton flux was obtained. The observed spectra were
compared with theoretical predictions.


title:
Shells of dust around AGB stars: effects on the integrated spectrum of
  Single Stellar Populations

abstract:
  In this paper we present models for SSPs of intermediate and old ages where
dust enshrouded AGB stars are introduced. To this aim, particular care is
devoted to follow the evolution of the AGB stars throughout the quiet and
thermally pulsing regimes, to evaluate the effect of self contamination in the
outermost layers by the third dredge-up mechanism, to follow the transition
from oxygen-rich to carbon-rich objects, and finally to estimate the efficiency
of mass-loss by stellar winds. In addition to this, accurate physical models of
the dusty shells are presented in which the re-processing of radiation from the
central stars is calculated. The resulting spectral energy distribution (SED)
is examined to show how important features evolve with time. The SEDs are then
convolved with the IRAS filters to obtain the flux in various pass-bands for
individual AGB stars of different, mass, chemical composition, and age. The
comparison is made by means of SSPs along which AGB stars of the same age but
different initial masses are located. The theoretical results are compared to
the observational data for selected groups of stars. The same is made for the
J,H,K,L pass-bands of the Johnson system. Finally, from the integrated SEDs of
the SSPs, we derive the integrated Johnson J,H,K,L magnitudes and colors to be
compared to infrared data for star clusters of the Magellanic Clouds.


title: FeII/MgII Emission Line Ratio in High Redshift Quasars

abstract:
  We present results of the analysis of near infrared spectroscopic
observations of 6 high-redshift quasars (z > 4), emphasizing the measurement of
the ultraviolet FeII/MgII emission line strength in order to estimate the
beginning of intense star formation in the early universe. To investigate the
evolution of the FeII/MgII ratio over a wider range in cosmic time, we measured
this ratio for composite quasar spectra which cover a redshift range of 0 < z <
5 with nearly constant luminosity, as well as for those which span ~6 orders of
magnitude in luminosity. A detailed comparison of the high-redshift quasar
spectra with those of low-redshift quasars with comparable luminosity shows
essentially the same FeII/MgII emission ratios and very similar continuum and
line spectral properties, i.e. a lack of evolution of the relative iron to
magnesium abundance of the gas in bright quasars since z=5. Current
nucleosynthesis and stellar evolution models predict that alpha-elements like
magnesium are produced in massive stars ending in type II SNe, while iron is
formed predominantly in SNe of type Ia with intermediate mass progenitors. This
results in an iron enrichment delay of 0.2 to 0.6 Gyr. We conclude that intense
star formation activity in the host galaxies of z>4 quasars must have started
already at an epoch corresponding to z_f = 6 to 9, when the age of the universe
was ~0.5 Gyr (H_o = 72 km/s/Mpc, Omega_M = 0.3, Omega_Lambda = 0.7). This epoch
corresponds well to the re-ionization era of the universe.


title:
The Canada-France deep fields survey-II: Lyman-break galaxies and galaxy
  clustering at z~3

abstract:
  (abridged) We present a large sample of z~3 U- band dropout galaxies
extracted from the Canada-France deep fields survey (CFDF). Our catalogue
covers an effective area of ~1700 arcmin^2 divided between three large,
contiguous fields separated widely on the sky. To IAB=24.5, the survey contains
1294 Lyman-break candidates, in agreement with previous measurements by other
authors. Based on comparisons with spectroscopic observations and simulations,
we estimate that our sample of Lyman-break galaxies is contaminated by stars
and interlopers at no more than ~30%. We find that \omega(\theta) is well
fitted by a power-law of fixed slope, \gamma=1.8, even at small (\theta<10'')
angular separations. In two of our three fields, we are able to fit
simultaneously for both the slope and amplitude and find a slope \gamma ~ 1.81.
Our data marginally indicates in one field (at a 3 \sigma level) that the
Lyman-break correlation length r_0 depends on sample limiting magnitude:
brighter Lyman-break galaxies are more clustered than fainter ones. For the
entire CFDF sample, assuming a fixed slope \gamma = 1.8 we find r_0 =
(5.9\pm0.5)h^{-1} Mpc. Using these clustering measurements and prediction for
the dark matter density field, we derive a linear bias of b = 3.5 +/- 0.3.
Finally we show that the dependence of the correlation length with the surface
density of Lyman-break galaxies is in good agreement with a simple picture
where more luminous galaxies are hosted by more massive dark matter halos with
a simple one-to-one correspondence.


title:
The ELODIE survey for northern extra-solar planets II. A Jovian planet
  on a long-period orbit around GJ 777 A

abstract:
  We present radial-velocity measurements obtained with the ELODIE and AFOE
spectrographs for GJ 777 A (HD 190360), a metal-rich ([Fe/H]=0.25) nearby
(d=15.9 pc) star in a stellar binary system. A long-period low radial-velocity
amplitude variation is detected revealing the presence of a Jovian planetary
companion. Some of the orbital elements remain weakly constrained because of
the smallness of the signal compared to our instrumental precision. The
detailed orbital shape is therefore not well established. We present our best
fitted orbital solution: an eccentric (e=0.48) 10.7--year orbit. The minimum
mass of the companion is 1.33 M_Jup.


title: The Properties of Galaxies at z>5

abstract:
  In a recent paper Lehnert & Bremer have photometrically selected a sample of
galaxies at z>4.8 from a single VLT/FORS2 pointing and spectroscopically
confirmed half of them to be at 4.8<z<5.8. To study the properties of such
galaxies further, we have photometrically selected a similar sample (V(AB)>28,
i(AB)<26.3, i(AB)-z(AB)>0) from the HST ACS images of the Chandra Deep Field
South. This selection results in a sample of 44 sources from ~150 sq. arcmin.
We find that such galaxies are often barely resolved in the ACS images, having
half-light radii of 0.1-0.3 arcsec (<2 kpc). They show no difference in spatial
clustering from sources selected by i(AB)<26.3, i(AB)-z(AB)>0, which are
generally galaxies of lower redshift. However, their distribution over the
field is not uniform and their surface density varies considerably over areas
comparable to a single 8m or HST pointing. The reliable determination of the
surface and volume densities of such galaxies requires a sky area considerably
larger than the current ACS imaging of this field. No individual z>5 candidate
was detected to a 3-sigma limit of 6 x 10^-17 erg s^-1 cm^-2 at 0.5-5 keV by
Chandra (a limiting luminosity of below 2 x 10^43 erg s^-1 at z~5.3). By
summing over all positions, we find that the mean source must be undetected at
a level at least a factor 4 times fainter than this. This rules out anything
other than a weak AGN contribution to the emission from these objects and thus
luminous AGN made little contribution to the final stages of re-ionization of
the Universe.


title: Constraining the helium abundance with CMB

abstract:
  We consider for the first time the ability of present-day cosmic microwave
background (CMB) anisotropies data to determine the primordial helium mass
fraction, Y_p. We find that CMB data alone gives the confidence interval 0.160
< Y_p < 0.501 (at 68% c.l.). We analyse the impact on the baryon abundance as
measured by CMB and discuss the implications for big bang nucleosynthesis. We
identify and discuss correlations between the helium mass fraction and both the
redshift of reionization and the spectral index. We forecast the precision of
future CMB observations, and find that Planck alone will measure Y_p with
error-bars of 5%. We point out that the uncertainty in the determination of the
helium fraction will have to be taken into account in order to correctly
estimate the baryon density from Planck-quality CMB data.


title:
Development of the Gaseous Antiparticle Spectrometer for Space-based
  Antimatter Detection

abstract:
  We report progress in developing a novel antimatter detection scheme. The
gaseous antiparticle spectrometer (GAPS) identifies antimatter through the
characteristic X-rays emitted by antimatter when it forms exotic atoms in
gases. The approach provides large area and field of view, and excellent
background rejection capability. If the GAPS concept is successfully
demonstrated, then it would be an ideal candidate for space-based, indirect
dark matter searches. GAPS can detect antideuterons produced in neutralino
annihilations. A modest GAPS experiment can detect the neutralino for all
minimal SUSY models in which the neutralino mass is in the 50-350 GeV mass
range. Underground searches, by contrast, are only sensitive to about 1/2 the
SUSY parameter space in this mass range.


title:
The Chemical Composition and Gas-to-Dust Mass Ratio of Nearby
  Interstellar Matter

abstract:
  Recent results on nearby interstellar gas and interstellar byproducts within
the solar system are used to select among the equilibrium radiative transfer
models of the nearest interstellar material of Slavin and Frisch (2002).
Assuming O/H~400 ppm, Models 2 and 8 are found to yield good fits to available
data on local interstellar material, and pickup ions and anomalous cosmic rays
inside of the heliosphere, with the exception of Ne. For these models, the
density of interstellar gas at the entry point to the heliosphere is n(HI)~0.20
/cc and n(e-)~0.1 /cc. These models suggest the chemical composition of the
nearby ISM is ~60--70% subsolar if S is undepleted (where HI and HII must be
included for abundance calculations). Gas-to-dust mass ratios of 178-183 for
solar abundances, or 611-657 for 70% solar abundances are found. The percentage
of the dust mass that is carried by iron is directly correlated with the
gas-to-dust mass ratio implying an Fe-rich grain core remains after grain
destruction.


title:
Line-of-Sight Reddening Predictions: Zero Points, Accuracies, the
  Interstellar Medium, and the Stellar Populations of Elliptical Galaxies

abstract:
  Revised (B-V)_0-Mg_2 data for 402 elliptical galaxies are given to test
reddening predictions which can also tell us both what the intrinsic errors are
in this relationship among gE galaxy stellar populations, as well as details of
nearby structure in the interstellar medium (ISM) of our Galaxy and of the
intrinsic errors in reddening predictions. Using least-squares fits, the
explicit 1-sigma errors in the Burstein-Heiles (BH) and the Schlegel et al.
(IR) predicted reddenings are calculated, as well as the 1-sigma observational
error in the (B-V)_0-Mg_2 for gE galaxies. It is found that, in directions with
E(B-V)<0.100 mag (where most of these galaxies lie), 1-sigma errors in the IR
reddening predictions are 0.006 to 0.009 in E(B-V) mag, those for BH reddening
prediction are 0.011 mag, and the 1-sigma agreement between the two reddening
predictions is 0.007 mag. IR predictions have an accuracy of 0.010-0.011 mag in
directions with E(B-V)>= 0.100 mag, significantly better than those of the BH
predictions (0.024-0.025). Gas-to-dust variations that vary by a factor of 3,
both high and low, exist along many lines-of-sight in our Galaxy. The approx
0.02 higher reddening zero point in E(B-V) previously determined by Schlegel et
al. is confirmed, primarily at the Galactic poles. Despite this, both methods
also predict many directions with E(B-V)<0.015 mag. Independent evidence of
reddening at the North Galactic pole is reviewed, with the conclusion that
there still exists directions at the NGP that have E(B-V)<<0.01. Two lines of
evidence suggest that IR reddenings are overpredicted in directions with high
gas-to-dust ratios. As high gas-to-dust directions in the ISM also include the
Galactic poles, this overprediction is the likely cause of the E(B-V) = 0.02
mag larger IR reddening zero point.


title:
A high spatial resolution X-ray and H-alpha study of hot gas in the
  halos of star-forming disk galaxies. I. Spatial and spectral properties of
  the diffuse X-ray emission

abstract:
  We present arcsecond resolution Chandra X-ray and ground-based optical
H-alpha imaging of a sample of ten edge-on star-forming disk galaxies (seven
starburst and three ``normal'' spiral galaxies), a sample which covers the full
range of star-formation intensity found in disk galaxies. We use the
unprecedented spatial resolution of the Chandra X-ray observatory to robustly
remove point sources, and hence obtain the X-ray properties of the diffuse
thermal emission alone. The X-ray observations are combined with
comparable-resolution H-alpha and R-band imaging, and presented as a mini-atlas
of images on a common spatial and surface brightness scale. The vertical
distribution of the halo-region X-ray surface brightness is best described as
an exponential, with the observed scale heights lying in the range H_eff = 2 --
4 kpc. The ACIS X-ray spectra of extra-planar emission from all these galaxies
can be fit with a common two-temperature spectral model with an enhanced
alpha-to-iron element ratio. This is consistent with the origin of the X-ray
emitting gas being either metal-enriched merged SN ejecta or shock-heated
ambient halo or disk material with moderate levels of metal depletion onto
dust. The thermal X-ray emission observed in the halos of the starburst
galaxies is either this pre-existing halo medium, which has been swept-up and
shock heated by the starburst-driven wind, or wind material compressed near the
walls of the outflow by reverse shocks within the wind. In either case the
X-ray emission provides us with a powerful probe of the properties of gaseous
halos around star-forming disk galaxies.


title: Phase Coherent Timing of RX J0806.3+1527 with ROSAT and CHANDRA

abstract:
  RX J0806.3+1527 is an ultra-compact, double degenerate binary with the
shortest known orbital period (321.5 s). Hakala et al. (2003) have recently
reported new optical measurements of the orbital frequency of the source which
indicate that the frequency has increased over the ~9 years since the earliest
ROSAT observations. They find two candidate solutions for the long term change
in the frequency; df/dt = 3 or 6 x 10E-16 Hz/s. Here we present the results of
a phase coherent timing study of the archival ROSAT and Chandra data for RX
J0806.3+1527 in the light of these new constraints. We find that the ROSAT --
Chandra timing data are consistent with both of the solutions reported by
Hakala et al., but that the higher df/dt = 6.1 x 10E-16 Hz/s solution is
favored at the ~97 % level. Such a large df/dt can be accomodated by an ~1 Msun
detached double degenerate system powered in the X-ray by electrical energy (Wu
et al. 2002). With such a large df/dt the system provides a unique opportunity
to explore the interaction of gravitational radiation and electromagnetic
torques on the evolution of an ultracompact binary.


title: Star Formation History and Other Properties of the Northern HDF

abstract:
  The original analysis of the star formation history in the NICMOS Deep images
of the NHDF is extended to the entire NHDF utilizing NICMOS and WFPC2 archival
data. The roughly constant star formation rate from redshifts 1 to 6 found in
this study is consistent with the original results. Star formation rates from
this study, Lyman break galaxies and sub-mm observations are now in concordance
The spike of star formation at redshift 2 due to 2 ULIRGs in the small Deep
NICMOS field is smoothed out in the larger area results presented here. The
larger source base of this study allows comparison with predictions from
hierarchical galaxy formation models. In general the observation are consistent
with the predictions. The observed luminosity functions at redshifts 1-6 are
presented for future comparisons with theoretical galaxy evolution
calculations. Mid and far infrared properties of the sources are also
calculated and compared with observations. A candidate for the VLA source VLA
3651+1221 is discussed.


title: The Physics of Star Formation

abstract:
  Our current understanding of the physical processes of star formation is
reviewed, with emphasis on processes occurring in molecular clouds like those
observed nearby. The dense cores of these clouds are predicted to undergo
gravitational collapse characterized by the runaway growth of a central density
peak that evolves toward a singularity. As long as collapse can occur, rotation
and magnetic fields do not change this qualitative behavior. The result is that
a very small embryonic star or protostar forms and grows by accretion at a rate
that is initially high but declines with time as the surrounding envelope is
depleted. Rotation causes some of the remaining matter to form a disk around
the protostar, but accretion from protostellar disks is not well understood and
may be variable. Most, and possibly all, stars form in binary or multiple
systems in which gravitational interactions can play a role in redistributing
angular momentum and driving episodes of disk accretion. Variable accretion may
account for some peculiarities of young stars such as flareups and jet
production, and protostellar interactions in forming systems of stars will also
have important implications for planet formation. The most massive stars form
in the densest environments by processes that are not yet well understood but
may include violent interactions and mergers. The formation of the most massive
stars may have similarities to the formation and growth of massive black holes
in very dense environments.


title: Evolutionary processes in clusters

abstract:
  Are the morphologies of galaxies imprinted during an early and rapid
formation epoch or are they due to environmental processes that subsequently
transform galaxies between morphological classes? Recent numerical simulations
demonstrate that the cluster environment can change the morphology of galaxies,
even at a couple of cluster virial radii. The gravitational and hydrodynamical
mechanisms that could perform such transformations were proposed in the 1970's,
before the key observational evidence for environmental dependencies - the
morphology-density relation and the Butcher-Oemler effect.


title:
Can Cosmic Shear Shed Light on Low Cosmic Microwave Background
  Multipoles?

abstract:
  The lowest multipole moments of the cosmic microwave background (CMB) are
smaller than expected for a scale-invariant power spectrum. One possible
explanation is a cutoff in the primordial power spectrum below a comoving scale
of $k_c \simeq 5.0 \times 10^{-4}$ Mpc$^{-1}$. This would affect not only the
CMB but also the cosmic-shear (CS) distortion of the CMB. Such a cutoff
increases significantly the cross-correlation between the large-angle CMB and
cosmic-shear patterns. The cross-correlation may be detectable at $> 2\sigma$
which, when combined with the low CMB moments, may tilt the balance between a
$2\sigma$ result and a firm detection of a large-scale power-spectrum cutoff.
As an aside, we also note that the cutoff increases the large-angle
cross-correlation between the CMB and low-redshift tracers of the mass
distribution.


title:
A high spatial resolution X-ray and H-alpha study of hot gas in the
  halos of star-forming disk galaxies. II. Quantifying supernova feedback

abstract:
  We investigate how the empirical properties of hot X-ray-emitting gas in a
sample of seven starburst and three normal edge-on spiral galaxies (a sample
which covers the full range of star-formation intensity found in disk galaxies)
correlate with the size, mass, star formation rate and star formation intensity
in the host galaxies. Intriguingly, the diffuse X-ray properties of the normal
spirals (both in their disks and halos) fall where extrapolation of the trends
from the starburst galaxies with superwinds would predict. We demonstrate that
the luminosity of diffuse X-ray emission in both disk and halo is directly
proportional to the rate of mechanical energy feedback from massive stars.
Nevertheless, with only three non-starburst normal spiral galaxies it is hard
to exclude an accretion-based origin for extra-planar diffuse X-ray emission
around normal star-forming galaxies. Larger galaxies have more extended
X-ray-emitting halos, but galaxy mass appears to play no role in determining
the properties of the disk or extra-planar X-ray emitting plasma. The
combination of these luminosity and size correlations leads to a correlation
between the surface brightness of the diffuse X-ray emission and the mean star
formation rate per unit area in the disk (L_FIR/D_25^2). We argue that the
crucial spatial region around a galaxy that controls whether gas in
starburst-driven superwinds will escape into the IGM is not the outer halo ~100
kpc from the host galaxy, but the inner few halo scale heights, within ~20 kpc
of the galaxy plane. Given the properties of the gaseous halos we observe,
superwind outflows from disk galaxies of mass M ~ 10^10 -- 10^11 Msun should
still eject some fraction of their material into the IGM. (abstract abridged)


title:
Shadowing of the Nascent Jet in NGC 4261 by a Line-Emitting Supersonic
  Accretion Disk

abstract:
  NGC 4261 (3C 270) is a low-luminosity radio galaxy with two symmetric
kiloparsec-scale jets. Earlier Hubble Space Telescope observations indicated
the presence of a hundred-parsec scale disk of cool dust and gas surrounding a
central, supermassive ($\sim 4.9\times 10^8\msun$) black hole. The recent
detection of free-free radio absorption by a small, geometrically-thin disk,
combined with earlier studies of the disk's large scale properties, provide the
strictest constraints to date on the nature of the accretion process in this
system. We show here that a supersonic disk, illuminated by the active galactic
nucleus (AGN), can not only account for the observed radio shadowing, but can
also produce the optical broad lines emitted from this region. Beyond a
critical radius $r_c$, line cooling dominates over gravitational dissipation
and the gas is effectively cooled down to temperatures below $10^4$ K. Within
$r_c$, however, heating due to the release of gravitational energy overwhelms
line cooling and the plasma is heated very quickly to a temperature close to
its virial value as it falls toward the central engine. The disk is
optically-thin to UV and X-ray radiation within $r_c$, so the ionizing
radiation from the AGN is preferentially absorbed near $r_c$, affecting the
disk structure significantly. To include the ensuing photoionization effect, we
have used the algorithm Cloudy with additional heating introduced by
gravitational dissipation to calculate the temperature profile and line
emission from the disk in a self-consistent manner. The results of our model
calculation are consistent with current multiwavelength observations of the
disk in this source.


title:
Constraints on the Origin of Manganese from the Composition of the
  Sagittarius Dwarf Spheroidal Galaxy and the Galactic Bulge

abstract:
  The trend of [Mn/Fe] in the Galactic bulge follows the solar-neighborhood
relation, but most stars in the Sagittarius dwarf spheroidal galaxy show
[Mn/Fe] deficient by approximately 0.2 dex. This leads us to conclude that the
Mn yields from both type Ia and type II SNe are metallicity-dependent. Our
observations militate against the idea, suggested by Gratton, that Mn is
over-produced by type Ia SNe, relative to type II SNe. We predict Mn/Fe ratios,
lower than the solar neighborhood relation, for the younger populations of
nearly all dwarf galaxies, and that Mn/Fe ratios may be useful for tracing the
accretion of low-mass satellites into the Milky Way.


title: Dispersing the Gaseous Protoplanetary Disc and Halting Type II Migration

abstract:
  More than 30 extra-solar Jupiter-like planets have shorter periods than the
planet Mercury. It is generally accepted that they formed further out, and
migrated inwards. In order to be driven by tidal torques from the gaseous disc,
the disc exterior to the planet had to contain about a planetary mass. The fact
that the planets stopped migrating means that their outer disc was removed. We
suggest that the outer disc was accreted by the planet. In this scenario, the
endgame is a race. The planet survives if it accretes its outer disc before
being accreted by the star. The winner is determined solely by the ratio of the
mass of the outer disc to the local surface density of the disc.


title: General plane wave mode functions for scalar-driven cosmology

abstract:
  We give a solution for plane wave scalar, vector and tensor mode functions in
the presence of any homogeneous, isotropic and spatially flat cosmology which
is driven by a single, minimally coupled scalar. The solution is obtained by
rescaling the various mode functions so that they reduce, with a suitable scale
factor and a suitable time variable, to those of a massless, minimally coupled
scalar. We then express the general solution in terms of co-moving time and the
original scale factor.


title: Outflows from dynamo-active protostellar accretion discs

abstract:
  An axisymmetric model of a cool, dynamo-active accretion disc is applied to
protostellar discs. Thermally and magnetically driven outflows develop that are
not collimated within 0.1 AU. In the presence of a central magnetic field from
the protostar, accretion onto the protostar is highly episodic, which is in
agreement with earlier work.


title: The interferometric diameter and internal structure of Sirius A

abstract:
  The interferometric observations of dwarf stars in the solar neighbourhood,
combined with Hipparcos parallaxes provide very precise values of their linear
diameters. In this paper, we report the direct measurement of the angular
diameter of the bright star Sirius A with the VINCI/VLTI instrument. We obtain
a uniform disk angular diameter of UD = 5.936 +/- 0.016 mas in the K band and a
limb darkened value of LD = 6.039 +/- 0.019 mas. In combination with the
Hipparcos parallax of 379.22 +/- 1.58 mas, this translates into a linear
diameter of 1.711 +/- 0.013 Dsun. Using the VINCI/VLTI interferometric diameter
and the published properties of Sirius A, we derive internal structure models
corresponding to ages between 200 and 250 +/- 12 Myr. This range is defined
mainly by the hypothesis on the mass of the star, the overshoot and the
metallicity.


title: The Dual Origin of the Terrestrial Atmosphere

abstract:
  The origin of the terrestrial atmosphere is one of the most puzzling enigmas
in the planetary sciences. It is suggested here that two sources contributed to
its formation, fractionated nebular gases and accreted cometary volatiles.
During terrestrial growth, a transient gas envelope was fractionated from
nebular composition. This transient atmosphere was mixed with cometary
material. The fractionation stage resulted in a high Xe/Kr ratio, with xenon
being more isotopically fractionated than krypton. Comets delivered volatiles
having low Xe/Kr ratios and solar isotopic compositions. The resulting
atmosphere had a near-solar Xe/Kr ratio, almost unfractionated krypton
delivered by comets, and fractionated xenon inherited from the fractionation
episode. The dual origin therefore provides an elegant solution to the
long-standing "missing xenon" paradox. It is demonstrated that such a model
could explain the isotopic and elemental abundances of Ne, Ar, Kr, and Xe in
the terrestrial atmosphere.


title: Photometry of SN 2002bo with template image subtraction

abstract:
  VRI photometry of the type Ia supernova 2002bo is presented. This SN exploded
in a dusty region of the host galaxy NGC 3190, thus, subtraction of a template
frame was necessary to obtain reliable photometry. We used a template frame of
NGC 3190 taken during the course of our galaxy imaging project, fortunately,
just a few days before SN 2002bo was discovered. The aim of this project is to
collect template frames of nearby galaxies that are potential hosts of bright
SNe. Subtraction of pre-SN images helped us to exclude the background light
contamination of the host galaxy. The maximum occurred at JD 2452346, with
maximal V brightness of 13.58. MLCS analysis led to T0(B)=JD 2452346.1 pm 0.8
(fiducial B-maximum), E(B-V)=0.24 pm 0.02, mu0=32.46 pm 0.06, Delta=-0.14 pm
0.04. E(B-V)=0.24(2) indicates a significant extinction in the host galaxy as
the galactic reddening is negligible toward NGC 3190. The accepted value of
Delta indicates that SN 2002bo was a slightly overluminous SN by about 0.14
relative to fiducial SN Type Ia. The distance turned out to be 31.0 pm 3 Mpc.
In addition, the heavily obscured SN 2002cv was also detected on the I frame
taken on JD 2452434 (June 8, 2002), and a variable star is found in the field,
very close to the host galaxy.


title:
Analytical approximation for the structure of differentially rotating
  barotropes

abstract:
  Approximate analytical formula for density distribution in differentially
rotating stars is derived. Any barotropic EOS and conservative rotation law can
be handled with use of this method for wide range of differential rotation
strength. Results are in good qualitative agreement with comparison to the
other methods. Some applications are suggested and possible improvements of the
formula are discussed.


title:
NTT infrared imaging of star cluster candidates towards the central
  parts of the Galaxy

abstract:
  We address the issue whether the central parts of the Galaxy harbour young
clusters other than Arches, Quintuplet and the Nuclear Young Cluster. A large
sample of centrally projected cluster candidates has been recently identified
from the 2MASS J, H and Ks Atlas. We provide a catalogue of higher angular
resolution and deeper images for 57 2MASS cluster candidates, obtained with the
near-IR camera SOFI at the ESO NTT telescope. We classify 10 objects as star
clusters, some of them deeply embedded in gas and/or dust clouds. Three other
objects are probably star clusters, although the presence of dust in the field
does not exclude the possibility of their being field stars seen through
low-absorption regions. Eleven objects are concentrations of stars in areas of
little or no gas, and are classified as dissolving cluster candidates. Finally,
31 objects turned out to be the blend of a few bright stars, not resolved as
such in the low resolution 2MASS images. By combining the above results with
other known objects we provide an updated sample of 42 embedded clusters and
candidates projected within 7 degrees. As a first step we study Object 11 of
Dutra & Bica (2000) projected at approximately 1 degree from the nucleus. We
present H and Ks photometry and study the colour-magnitude diagram and
luminosity function. Object 11 appears to be a less massive cluster than Arches
or Quintuplet, and it is located at a distance from the Sun d=8 kpc, with a
visual absorption Av=15.


title: On the calibration of the COBE/IRAS dust emission reddening maps

abstract:
  In this work we study the spectral properties (3600 - 6800 A) of the nuclear
region of early-type galaxies at low (|b|<25, intermediate (including
surroundings of the Magellanic Clouds) and high (South Polar Cap) Galactic
latitudes. We determine the E(B-V) reddening values of the galaxies by matching
their continuum distribution with respect to those of reddening-free spectral
galaxy templates with similar stellar populations. We also compare the
spectroscopic reddening value of each galaxy with that derived from 100 micron
dust emission (E(B-V)_{FIR}) in its line of sight, and we find that there is
agreement up to E(B-V)=0.25. Beyond this limit E(B-V)_{FIR} values are higher.
Taking into account the data up to E(B-V) \approx 0.7, we derive a calibration
factor of 0.016 between the spectroscopic E(B-V) values and Schlegel et al.'s
(1998) opacities. By combining this result with an A_K extinction map built
within ten degrees of the Galactic centre using Bulge giants as probes (Dutra
et al. 2003), we extended the calibration of dust emission reddening maps to
low Galactic latitudes down to |b|=4 and E(B-V)= 1.6 (A_V \approx 5). According
to this new calibration, a multiplicative factor of approximately 0.75 must be
applied to the COBE/IRAS dust emission reddening maps.


title:
The Serendipitous Extragalactic X-Ray Source Identification (SEXSI)
  Program: I. Characteristics of the Hard X-Ray Sample

abstract:
  The Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program
is designed to extend greatly the sample of identified extragalactic hard X-ray
2-10 keV sources at intermediate fluxes ($\sim 10^{-13} - 10^{-15} erg/cm2/s$).
SEXSI, which studies sources selected from more than 2 deg$^2$, provides an
essential complement to the {\em Chandra} Deep Fields, which reach depths of $5
\times 10^{-16} erg/cm2/s$ (\hardrange) but over a total area of $< 0.2$
deg$^2$. In this paper we describe the characteristics of the survey and our
X-ray data analysis methodology. We present the cumulative flux distribution
for the X-ray sample of 1034 hard sources, and discuss the distribution of
spectral hardness ratios. Our lognlogs in this intermediate flux range connects
to those found in the deep fields, and by combining the data sets, we constrain
the hard X-ray population over the flux range where the differential number
counts change slope, and from which the bulk of the 2 -- 10 keV X-ray
background arises. We further investigate the lognlogs distribution separately
for soft and hard sources in our sample, finding that while a clear change in
slope is seen for the softer sample, the hardest sources are well-described by
a single power-law down to the faintest fluxes, consistent with the notion that
they lie at lower average redshift.


title:
A flat space-time relativistic explanation for the perihelion advance of
  Mercury

abstract:
  Starting with the flat space-time relativistic versions of
Maxwell-Heaviside's toy model vector theory of gravity and introducing the
gravitational analogues for the electromagnetic Lienard-Wiechert potentials
together with the notion of a gravitational Thomas Precession; the observed
anomalous perihelion advance of Mercury's orbit is here explained as a
relativistic effect in flat (Minkowski) space-time, unlike Einstein's curved
space-time relativistic explanation. In this new explanation for the old
paradoxical observation of Mercury's perihelion shift, the predicted value of
the effect happens to coincide with Einstein's predicted value in General
relativity.


title:
A Possible Correlation between Mass Ratio and Period Ratio in Multiple
  Planetary Systems

abstract:
  We report on a possible correlation between the mass ratio and period ratio
of pairs of adjacent planets in extra-solar planetary systems. Monte-Carlo
simulations show that the effect is significant to level of 0.7%, as long as we
exclude two pairs of planets whose periods are at the 1:2 resonance. Only the
next few multiple systems can tell if the correlation is real.


title: Boundary Conditions of the Heliosphere

abstract:
  Radiative transfer equilibrium models of nearby interstellar matter (ISM)
yield the boundary conditions of the heliosphere when constrained with
observations of ISM inside and outside of the heliosphere. Filtration factors
for interstellar neutrals crossing the heliosheath region, from charge exchange
with interstellar plasma, are given for H, He, N, O, Ar, and Ne. The best
models predict n(HI)~0.2 /cc, n(e)~0.1 /cc, however if the isotropic 2 kHz
emission observed by Voyager (Kurth & Gurnett 2003) is formed in the
surrounding ISM, an alternate model with lower electron densities is indicated.
Observations of nearby ISM, the radiative transfer models, and historical 10Be
records provide information on past variations in the galactic environment of
the Sun.


title:
Jet-dominated states: an alternative to advection across black hole
  event horizons in `quiescent' X-ray binaries

abstract:
  We demonstrate that at relatively low mass accretion rates, black hole
candidate (BHC) X-ray binaries (XRBs) should enter `jet-dominated' states, in
which the majority of the liberated accretion power is in the form of a
(radiatively inefficient) jet and not dissipated as X-rays in the accretion
flow. This result follows from the empirically established non-linear relation
between radio and X-ray power from low/hard state BHC XRBs, which we assume
also to hold for neutron star (NS) XRBs. Conservative estimates of the jet
power indicate that all BHC XRBs in `quiescence' should be in this
jet-dominated regime. In combination with an additional empirical result,
namely that BHC XRBs are more `radio loud' than NS XRBs, we find that in
quiescence NS XRBs should be up to two orders of magnitude more luminous in
X-rays than BHC XRBs, without requiring any significant advection of energy
into a black hole. This ratio is as observed, and such observations should
therefore no longer be considered as direct evidence for the existence of black
hole event horizons. Furthermore, even if BHCs do contain black holes with
event horizons, this work demonstrates that there is no requirement for the
advection of significant amounts of accretion energy across the horizon.


title: An Off-Axis Jet Model For GRB980425 and Low Energy Gamma-Ray Bursts

abstract:
  Using a simple off-axis jet model of GRBs, we can reproduce the observed
unusual properties of the prompt emission of GRB980425, such as the extremely
low isotropic equivalent gamma-ray energy, the low peak energy, the high
fluence ratio, and the long spectral lag when the jet with the standard energy
of ~10^{51}ergs and the opening half-angle of \Delta\theta=~10-30 degree is
seen from the off-axis viewing angle ~\Delta\theta+10/\gamma, where \gamma is a
Lorentz factor of the jet. For our adopted fiducial parameters, if the jet that
caused GRB980425 is viewed from the on-axis direction, the intrinsic peak
energy Ep(1+z) is ~2.0-4.0 MeV, which corresponds to those of GRB990123 and
GRB021004. We also discuss the connection of GRB980425 in our model with the
X-ray flash, and the origin of a class of GRBs with small E_gamma.


title: Pairs of Bubbles in Planetary Nebulae and Clusters of Galaxies

abstract:
  I point to an interesting similarity in the morphology and some
non-dimensional quantities between pairs of X-ray-deficient bubbles in clusters
of galaxies and pairs of optical-deficient bubbles in planetary nebulae (PNs).
This similarity leads me to postulate a similar formation mechanism. This
postulate is used to strengthen models for PN shaping by jets (or collimated
fast winds: CFW). The presence of dense material in the equatorial plane
observed in the two classes of bubbles constrains the jets and CFW activity in
PNs to occur while the AGB star still blows its dense wind, or very shortly
after. I argue that only a stellar companion can account for such jets and CFW.


title:
Optical Spectroscopy of BL Lac Objects:new redshifts and mis-identified
  sources

abstract:
  We are carrying out a multi-purpose program of high signal to noise optical
spectroscopy at medium resolution of 30 BL Lac objects. Here we report the
detection of three new redshifts, and the discovery of three misclassified
sources. The new redshifts refer to PKS0754+100 (z=0.266), H-1914-194 (z=0.137)
and
  1ES0715-259, for which we derive a redshift of z=0.465 and also a ``new''
classification a Steep Spectrum Radio Quasar. In two cases (UM493 and 1620+103)
stellar spectra indicate a wrong classification. The three sources with new
redshift measurement show strong [OIII] emission in their spectra and their
host galaxy properties are known.
  The central black hole masses derived using the M_{BH}-L_{bulge} and the
M_{BH}-\sigma([OIII]) relations are compared.


title:
Soft X-Ray Sources at the Centers of the Elliptical Galaxies NGC 4472
  and NGC 4649

abstract:
  Analysis of recent Chandra observations of the elliptical galaxies NGC 4472
and NGC 4649 has revealed faint soft X-ray sources at their centers. The
sources are located to within 1'' of the optical centers of the galaxies. They
are most likely associated with the central supermassive black holes. Interest
in these and several other similar objects stems from the unusually low
luminosity of the supermassive black holes embedded in dense interstellar
medium. Our Chandra sources have very soft spectra. They are detectable only
below ~0.6 keV and have luminosities in the 0.2-2.5 keV energy band of ~ 6 *
10^{37} erg/s and ~1.7 * 10^{38} erg/s in NGC 4649 and NGC 4472, respectively.


title:
Optical Counterparts of X-Ray Point Sources Observed by CHANDRA in
  NGC5128: 20 New Globular Cluster X-Ray Sources

abstract:
  VLT images in $BVI$ are used to identify the optical counterparts to bright
CHANDRA X-ray points sources discovered by Kraft et al. (2001, ApJ, 560, 675)
in NGC5128. Of a total of 111 X-ray point sources with L_X>2*10^{36} ergs/s
present in a 56 arcmin^2 field centered on this galaxy, 58 have optical
counterparts. Based on the sizes, optical magnitudes and colors, 20 new
globular cluster counterparts of X-ray sources are identified, plus 3
identified based on their sizes. This brings the total number of globular
cluster X-ray sources in this galaxy to 33, and establishes that 30% of the
X-ray point sources in NGC5128 are associated with globular clusters. These
X-ray globular clusters occupy the brightest end of the globular cluster
luminosity function, indicating that bright low-mass X-ray binaries are
preferentially found in massive clusters. Most of the globular clusters with
X-ray sources have red colors, with 1.0<V-I<1.5, indicating that low-mass X-ray
binaries are preferentially formed in metal-rich clusters. The NGC5128 X-ray
globular cluster sources are brighter in comparison with the Milky Way sources:
there are 24 globular clusters with X-ray sources of L_x>10^{37} erg/sec. There
is, however, no globular cluster X-ray source in NGC5128 as bright as expected
for an accreting black hole. In addition, 31 optical counterparts of X-ray
point sources that are not associated with globular clusters are identified.
Finally, 53 X-ray point sources (48% of the population), do not have any
optical counterparts down to the faintest magnitude limits (B=25).


title:
The Separate Universe Approach and the Evolution of Nonlinear
  Superhorizon Cosmological Perturbations

abstract:
  In this letter we review the separate universe approach for cosmological
perturbations and point out that it is essentially the lowest order
approximation to a gradient expansion. Using this approach, one can study the
nonlinear evolution of inhomogeneous spacetimes and find the conditions under
which the long wavlength curvature perturbation can vary with time. When there
is one degree of freedom or a well-defined equation of state the nonlinear long
wavelength curvature perturbation remains constant. With more degrees of
freedom it can vary and this variation is determined by the non-adiabatic
pressure perturbation, exactly as in linear theory. We identify combinations of
spatial vectors characterizing the curvature perturbation which are invariant
under a change of time hypersurfaces.


title: Star formation rate indicators in the Sloan Digital Sky Survey

abstract:
  The Sloan Digital Sky Survey (SDSS) first data release provides a database of
106000 unique galaxies in the main galaxy sample with measured spectra. A
sample of star-forming (SF) galaxies are identified from among the 3079 of
these having 1.4 GHz luminosities from FIRST, by using optical spectral
diagnostics. Using 1.4 GHz luminosities as a reference star formation rate
(SFR) estimator insensitive to obscuration effects, the SFRs derived from the
measured SDSS Halpha, [OII] and u-band luminosities, as well as far-infrared
luminosities from IRAS, are compared. It is established that straightforward
corrections for obscuration and aperture effects reliably bring the SDSS
emission line and photometric SFR estimates into agreement with those at 1.4
GHz, although considerable scatter (~60%) remains in the relations. It thus
appears feasible to perform detailed investigations of star formation for large
and varied samples of SF galaxies through the available spectroscopic and
photometric measurements from the SDSS. We provide herein exact prescriptions
for determining the SFR for SDSS galaxies. The expected strong correlation
between [OII] and Halpha line fluxes for SF galaxies is seen, but with a median
line flux ratio F_[OII]/F_Halpha=0.23, about a factor of two smaller than that
found in the sample of Kennicutt (1992). This correlation, used in deriving the
[OII] SFRs, is consistent with the luminosity-dependent relation found by
Jansen et al. (2001). The median obscuration for the SDSS SF systems is found
to be A_Halpha=1.2 mag, while for the radio detected sample the median
obscuration is notably higher, 1.6 mag, and with a broader distribution.


title:
Chandra and RXTE studies of the X-ray/gamma-ray millisecond pulsar PSR
  J0218+4232

abstract:
  We report on high-resolution spatial and timing observations of the
millisecond pulsar PSR J0218+4232 performed with the Chandra X-ray Observatory
(CXO) and the Rossi X-ray Timing Explorer (RXTE). With these observations we
were able to study a) the possible spatial extent at X-ray energies of the DC
source coincident with PSR J0218+4232 in detail (CXO), b) the relative phasing
between the X-ray, radio and gamma-ray profiles (CXO and RXTE) and c) the
spectral properties at energies beyond 10 keV (RXTE). We found no indications
for extended emission at X-ray energies down to ~ 1 arcsec scales and confirmed
the presence of a point-like DC-component. The 2 non-thermal pulses in the
X-ray profile are found to be aligned with 2 of the 3 pulses visible at
radio-frequencies and more importantly with the two gamma-ray pulses seen in
the EGRET 100-1000 MeV pulse profile. The latter reduces now the random
occurrence probability for the detected gamma-ray signal to ~ 1.E-6, which
corresponds to a 4.9 sigma detection significance.


title:
Stellar density distribution in the NIR on the Galactic plane at
  longitudes 15-27 deg. Clues for the Galactic bar ?

abstract:
  Garzon et al. (1997), Lopez-Corredoira et al. (1999) and Hammersley et al.
(2000) have identified in TMGS and DENIS data a large excess of stars at l=27
deg and b=0 deg which might correspond to an in-plane bar. We compared near
infrared CAIN star counts and simulations from the Besancon Model of Galaxy on
15 fields between 15 deg and 45 deg in longitude and -2 deg and 2 deg in
latitude. Comparisons confirm the existence of an overdensity at longitudes
lower than 27 deg which is inhomogeneous and decreases very steeply off the
Galactic plane. The observed excess in the star distribution over the predicted
density is even higher than 100%. Its distance from the sun is estimated to be
lower than 6 kpc. If this overdensity corresponds to the stellar population of
the bar, we estimate its half-length to 3.9 +/ -0.4 kpc and its angle from the
Sun-center direction to 45 +/- 9 degrees.


title: High accuracy proper motions in crowded fields

abstract:
  The image subtraction method is a powerful tool to analyze the light
variations in crowded fields. This method is able to achieve a nearly optimal
differential photometry, even in very dense regions. However, image subtraction
is not limited to photometry, and it is shown in this paper that the method can
be generalized to the measurement of the differential proper motions. It is
important to emphasize that image subtraction can re-construct an un-biased
frame to frame astrometric transform. A nearly optimal determination of this
astrometric transform can be performed by expanding the spatial variations of
the kernel using the derivatives of the constant kernel solution. It is
demonstrated that an expansion using first and second derivatives is optimal.
Differential refraction can be corrected easily using an artificial image and
the first derivatives of the kernel. To illustrate the ability of the method to
measure proper motions, a small sub-area near the center of a Galactic Bulge
field covered 265 times by the OGLE II experiment has been selected. The
resulting astrometric accuracy is very close to the photon noise for the faint
objects, while for the brighter ones it approaches closely the limit set by the
residual seeing fluctuations on the smaller scales. The accuracy obtained with
this new method is compared to the accuracy achieved using classical methods.
The improvement obtained varies from a factor of $\simeq$ 2 for the brighter
objects, to more than a factor of 3 for the fainter ones. This improvement is
typical of the improvement that was obtained for the measurement of the
photometric variations.


title:
The evolution of the galaxy luminosity function in the rest frame blue
  band up to z=3.5

abstract:
  We present an estimate of the cosmological evolution of the field galaxy
luminosity function (LF) in the rest frame 4400 Angstrom B -band up to redshift
z=3.5. To this purpose, we use a composite sample of 1541 I--selected galaxies
selected down to I_(AB)=27.2 and 138 galaxies selected down to K_(AB)=25 from
ground-based and HST multicolor surveys, most notably the new deep JHK images
in the Hubble Deep Field South (HDF-S) taken with the ISAAC instrument at the
ESO-VLT telescope. About 21% of the sample has spectroscopic redshifts, and the
remaining fraction well calibrated photometric redshifts. The resulting blue LF
shows little density evolution at the faint end with respect to the local
values, while at the bright end (M_B(AB)<-20) a brightening increasing with
redshift is apparent with respect to the local LF. Hierarchical CDM models
overpredict the number of faint galaxies by about a factor 3 at z=1. At the
bright end the predicted LFs are in reasonable agreement only at low and
intermediate redshifts (z=1), but fail to reproduce the pronounced brightening
observed in the high redshift (z=2-3) LF. This brightening could mark the epoch
where a major star formation activity is present in the galaxy evolution.


title:
The remarkable rapid X-ray, ultraviolet, optical, and IR variability in
  the black hole XTE J1118+480

abstract:
  The transient black hole binary XTE J1118+480 exhibited dramatic rapid
variability at all wavelengths which were suitably observed during its 2000
April-July outburst. We examine time-resolved X-ray, ultraviolet, optical, and
infrared data spanning the plateau phase of the outburst. We find that both
X-ray and infrared bands show large amplitude variability. The ultraviolet and
optical variability is more subdued, but clearly correlated with that seen in
the X-rays. The ultraviolet, at least, appears to be dominated by the
continuum, although the lines are also variable. Using the X-ray variations as
a reference point, we find that the UV variability at long wavelengths occurs
later than that at short wavelengths. Uncertainty in HST timing prohibits a
determination of the absolute lag with respect to the X-rays, however. The
transfer function is clearly not a delta-function, exhibiting significant
repeatable structure. For the main signal we can rule out an origin in
reprocessing on the companion star - the lack of variation in the lags is not
consistent with this given a relatively high orbital inclination. Weak
reprocessing from the disc and/or companion star may be present, but is not
required, and another component must dominate the variability. This could be
variable synchrotron emission correlated with X-ray variability, consistent
with our earlier interpretation of the IR flux as due to synchrotron emission
rather than thermal disc emission. In fact the broad-band energy distribution
of the variability from IR to X-rays is consistent with expectations of
optically thin synchrotron emission. We also follow the evolution of the
low-frequency quasi-periodic oscillation in X-rays, UV, and optical. Its
properties at all wavelengths are similar indicating a common origin.


title:
Cold dust and its relation to molecular gas in the dwarf irregular
  galaxy NGC 4449

abstract:
  We present observations of the dwarf irregular galaxy NGC 4449 at 850 $\mu$m
and 450 $\mu$m obtained with SCUBA at the JCMT. The distribution of the cold
dust agrees well with that of the CO and H$\alpha$ emission. To explain the
integrated mm- through far-infrared continuum spectrum three dust components
are required, with temperatures of 16 K, 39 K and 168 K, respectively. The dust
mass is dominated by the cold dust component; we derive a total dust mass of
\~3.8 x10^6 Msun, and with the local gas-to-dust ratio of ~130 a total gas mass
of M(HI+H_2}~4.9 x 10^8 Msun. Comparison with the HI mass leads to a total
molecular gas mass of ~3.4 x 10^8 Msun. We derive a conversion factor of the CO
line intensity to molecular hydrogen column density XCO = N(H_2)/I(CO) which is
at least 11 times larger than the Galactic value. These values are in accord
with the lower metallicity of NGC 4449.


title: Proper motion, age and initial spin period of PSR J0538+2817 in S147

abstract:
  We present results of timing observations of the 143-ms pulsar J0538+2817
that provide a proper motion measurement which clearly associates the pulsar
with the supernova remnant S147. We measure a proper motion of 67$_{-22}^{+48}$
mas yr$^{-1}$, implying a transverse velocity of $v= 385^{+260}_{-130}$ km
s$^{-1}$. We derive an age of the pulsar and S147 of only $30\pm4$ kyr which is
a factor of 20 times less than the pulsar's characteristic age of $\tau_c =
620$ kyr. This age implies an initial spin period of $P_0=139$ ms, close to the
present pulse period and a factor of several larger than what is usually
inferred for birth periods. Implications for recent X-ray detections of this
pulsar are discussed.


title: Theoretical Light Curves of Type II-P SNe and Applications to Cosmology

abstract:
  Based on an extensive grid of stellar models between 13 and 25 Mo and a wide
range of metallicities, we have studied the light curves of core collapse
supernovae, their application to cosmology and evolutionary effects with
redshift. The direct link between the hydro and radiation transport allows to
calculate monochromatic light curves.
  With decreasing metallicity Z and increasing mass, progenitors tend to
explode as compact Blue Supergiants and produce sub-luminous supernovae that
are about 1.5 mag dimmer compared to "normal" SNe II with Red
  Supergiant progenitors (RSGs). Progenitors with small masses tend to explode
as RSGs even at low Z. The consequences are obvious for probing the chemical
evolution, namely, a strong bias when using the statistics of core collapse
supernovae to probe the history of star formation.
  Our study is limited in scope with respect to the explosion energies and the
production of radioactive Ni. Within the class of "extreme SNe II-P"
supernovae, the light curves are rather insensitive with respect to the
progenitor mass and explosion energy compared to analytic models which are
based on parameterized stellar structures. We expect a wider range of
brightness due to variations in Ni56 because radioactive energy is a main
source of luminosity.
  However, the overall insensitivity of LCs may allow their use as
quasi-standard candles for distance determination.


title: 1/R Curvature Corrections as the Source of the Cosmological Acceleration

abstract:
  Corrections to Einstein's equations that become important at small curvatures
are considered. The field equations are derived using a Palatini variation in
which the connection and metric are varied independently. In contrast to the
Einstein-Hilbert variation, which yields fourth order equations, the Palatini
approach produces second order equations in the metric. The Lagrangian
$L(R)=R-\alpha^2/R$ is examined and it is shown that it leads to equations
whose solutions approach a de Sitter universe at late times. Thus, the
inclusion of 1/R curvature terms in the gravitational action offers an
alternative explanation for the cosmological acceleration.


title: Using Narrow Band Photometry to Detect Young Brown Dwarfs in IC348

abstract:
  We report the discovery of a population of young brown dwarf candidates in
the open star cluster IC348 and the development of a new spectroscopic
classification technique using narrow band photometry. Observations were made
using FLITECAM, the First Light Camera for SOFIA, at the 3-m Shane Telescope at
Lick Observatory. FLITECAM is a new 1-5 micron camera with an 8 arcmin field of
view. Custom narrow band filters were developed to detect absorption features
of water vapor (at 1.495 microns) and methane (at 1.66 microns) characteristic
of brown dwarfs. These filters enable spectral classification of stars and
brown dwarfs without spectroscopy. FLITECAM's narrow and broadband photometry
was verified by examining the color-color and color-magnitude characteristics
of stars whose spectral type and reddening was known from previous surveys.
Using our narrow band filter photometry method, it was possible to identify an
object measured with a signal-to-noise ratio of 20 or better to within +/-3
spectral class subtypes for late-type stars. With this technique, very deep
images of the central region of IC348 (H ~ 20.0) have identified 18 sources as
possible L or T dwarf candidates. Out of these 18, we expect that between 3 - 6
of these objects are statistically likely to be background stars, with the
remainder being true low-mass members of the cluster. If confirmed as cluster
members then these are very low-mass objects (~5 Mjupiter). We also describe
how two additional narrow band filters can improve the contrast between M, L,
and T dwarfs as well as provide a means to determine the reddening of an
individual object.


title:
Rigidity dependent knee and cosmic ray induced high energy neutrino
  fluxes

abstract:
  Scenarios in which the knee of the cosmic ray spectrum depends on the
particle rigidities usually predict that the cosmic ray composition becomes
heavier above the knee and have associated a change in the spectral slope of
each individual nuclear component which is steeper than the change
($\Delta\alpha\simeq 0.3$) observed in the total spectrum. We show that this
implies that the very high energy ($E_\nu>10^{14}$ eV) diffuse neutrino fluxes
produced by cosmic rays hitting the atmosphere or colliding with the
interstellar medium in the Galaxy will be significantly suppressed, making
their detection harder but also reducing the background for the search of other
(more challenging) astrophysical neutrino sources.


title: PSR B1849+00 probes the tiny-scale molecular gas?

abstract:
  In this paper we present and discuss the great difference in OH absorption
spectra against PSR B1849+00 and SNR G33.6+0.1 along the same line-of-sight.
This finding is important as it clearly demonstrates that statistics of
absorbing molecular gas depends on the size of the background source.


title:
The tiny-scale atomic structure: gas cloudlets or scintillation
  phenomenon ?

abstract:
  We present preliminary results from the recent multi-epoch HI absorption
measurements toward several pulsars using the Arecibo telescope. We do not find
significant variations in optical depth profiles over periods of 4 months and 9
years. The upper limits on the optical depth variations in directions of
B0823+26 and B1133+16 are similar on scales of 10--20, 350 and 500 AU. The
large number of non detections of the tiny scale atomic structure suggests that
the AU-sized structure is not ubiquitous in the interstellar medium.


title: Skeleton as a probe of the cosmic web: the 2D case

abstract:
  We discuss the skeleton as a probe of the filamentary structures of a 2D
random field. It can be defined for a smooth field as the ensemble of pairs of
field lines departing from saddle points, initially aligned with the major axis
of local curvature and connecting them to local maxima. This definition is thus
non local and makes analytical predictions difficult, so we propose a local
approximation: the local skeleton is given by the set of points where the
gradient is aligned with the local curvature major axis and where the second
component of the local curvature is negative.
  We perform a statistical analysis of the length of the total local skeleton,
chosen for simplicity as the set of all points of space where the gradient is
either parallel or orthogonal to the main curvature axis. In all our numerical
experiments, which include Gaussian and various non Gaussian realizations such
as \chi^2 fields and Zel'dovich maps, the differential length is found within a
normalization factor to be very close to the probability distribution function
of the smoothed field. This is in fact explicitly demonstrated in the Gaussian
case.
  This result might be discouraging for using the skeleton as a probe of non
Gausiannity, but our analyses assume that the total length of the skeleton is a
free, adjustable parameter. This total length could in fact be used to
constrain cosmological models, in CMB maps but also in 3D galaxy catalogs,
where it estimates the total length of filaments in the Universe. Making the
link with other works, we also show how the skeleton can be used to study the
dynamics of large scale structure.


title: The Multiphase Intergalactic Medium towards PKS 2155-304

abstract:
  We study the cluster of H I and O VI absorption systems and the claimed
detection of O VIII absorption from the intergalactic medium at z ~ 0.0567,
associated with a group of galaxies toward the BL Lac object PKS 2155-304. As
measured by spectrographs on the Hubble Space Telescope, Far Ultraviolet
Spectroscopic Explorer, and Chandra, this system appears to contain gas at a
variety of temperatures. We analyze this multi-phase gas in a clumpy-infall
model. From the absence of C IV and Si III absorption in the Ly-alpha clouds,
we infer metallicities less than 2.5-10% of solar values. The only metals are
detected in two O VI absorption components, offset by +/- 400 km/s from the
group barycenter (cz ~ 16,600 km/s). The O VI components may signify "nearside"
and "backside" infall into the group potential well, which coincides with the
claimed O VIII absorption. If the claimed O VIII detection is real, our
analysis suggests that clusters of strong Ly-alpha and O VI absorbers,
associated with groups of galaxies, may be the "signposts" of shock-heated,
metal-enriched baryons. Through combined UV and X-ray spectra of H I and O VI,
O VII, and O VIII, one may be able to clarify the heating mechanism of this
multiphase gas.


title:
The energy scale of inflation: is the hunt for the primordial B-mode a
  waste of time?

abstract:
  Recent theoretical results indicate that the detection of primordial gravity
waves from inflation may be a hopeless task. First, foregrounds from lensing
put a strict lower limit on the detectability of the B-mode polarization signal
in the Cosmic Microwave Background, the ``smoking gun'' for tensor (gravity
wave) fluctuations. Meanwhile, widely accepted theoretical arguments indicate
that the amplitude of gravity waves produced in inflation will be below this
limit. I argue that failure is not inevitable, and that the effort to detect
the primordial signal in the B-mode, whether it succeeds or fails, will yield
crucial information about the nature of inflation.


title:
Asymmetric neutrino emission due to neutrino-nucleon scatterings in
  supernova magnetic fields

abstract:
  We derive the cross section of neutrino-nucleon scatterings in supernova
magnetic fields, including weak-magnetism and recoil corrections. Since the
weak interaction violates the parity, the scattering cross section
asymmetrically depends on the directions of the neutrino momenta to the
magnetic field; the origin of pulsar kicks may be explained by the mechanism.
An asymmetric neutrino emission (a drift flux) due to neutrino-nucleon
scatterings is absent at the leading level of $\mathcal O(\mu_BB/T)$, where
$\mu_B$ is the nucleon magneton, $B$ is the magnetic field strength, and $T$ is
the matter temperature at a neutrinosphere. This is because at this level the
drift flux of the neutrinos are exactly canceled by that of the antineutrinos.
Hence, the relevant asymmetry in the neutrino emission is suppressed by much
smaller coefficient of $\mathcal O(\mu_BB/m)$, where $m$ is the nucleon mass;
detailed form of the relevant drift flux is also derived from the scattering
cross section, using a simple diffusion approximation. It appears that the
asymmetric neutrino emission is too small to induce the observed pulsar kicks.
However, we note the fact that the drift flux is proportional to the deviation
of the neutrino distribution function from the value of thermal equilibrium at
neutrinosphere. Since the deviation can be large for non-electron neutrinos, it
is expected that there occurs cancellation between the deviation and the small
suppression factor of $\mathcal O(\mu_BB/m)$. Using a simple parameterization,
we show that the drift flux due to neutrino-nucleon scatterings may be
comparable to the leading term due to beta processes with nucleons, which has
been estimated to give a relevant kick velocity when the magnetic field is
sufficiently strong as $10^{15}$--$10^{16}$ G.


title: A survey of Probable Open Cluster Remnants in the Galactic Disk

abstract:
  We present preliminary results of an ongoing survey to probe the physical
nature of a sample of open clusters (POCRs, Bica et al. 2001) believed to be in
an advanced stage of dynamical evolution. This kind of object is very important
to constrain dynamical $N$-body models of clusters evolution and dissolution,
and to understand the formation of the Galactic field stars population.
Moreover they might represent what remains of much larger old clusters, which
are of paramount importance to probe the early stages of the Galactic disk
evolution. In this paper we present our results for NGC 1901.