title: Cosmology from Cluster SZ and Weak Lensing Data

abstract:
  Weak gravitational lensing and the Sunyaev-Zel'dovich effect provide
complementary information on the composition of clusters of galaxies.
Preliminary results from cluster SZ observations with the Very Small Array are
presented. A Bayesian approach to combining this data with wide field lensing
data is then outlined; this allows the relative probabilities of cluster models
of varying complexity to be computed. A simple simulation is used to
demonstrate the importance of cluster model selection in cosmological parameter
determination.


title:
ECLAIRs: A microsatellite to observe the prompt optical and X-ray
  emission of Gamma-Ray Bursts

abstract:
  ECLAIRs is a French microsatellite devoted to the observation of the prompt
optical and X-ray emission of GRBs. For about 100 GRBs/yr, independent of their
duration, ECLAIRs will provide high time resolution high sensitivity spectral
coverage from a few eV up to ~50 keV and localization to ~5 arcsec in near real
time. This capability is achieved by combining wide field optical and X-ray
cameras sharing a common field of view (~1/6th of the sky) with the coded-mask
imaging telescopes providing the triggers and the coarse localizations of the
bursts. Given the delays to start ground-based observations in response to a
GRB trigger, ECLAIRs is unique in its ability to observe the early phases (the
first ~20 sec) of all GRBs at optical wavelengths. Furthermore, with its mode
of operation, ECLAIRs will enable to search for optical and X-ray precursors
expected from theoretical grounds. Finally ECLAIRs is proposed to operate
simultaneously with GLAST on a synchronous orbit. This combination will ensure
broad band spectral coverage from eV to GeV energies for the GRBs detected by
the two satellites, ECLAIRs further providing their accurate localization to
enable follow-up studies.


title: The complex iron line in NGC 7469 observed by BeppoSAX

abstract:
  In this letter we present analysis of BeppoSAX data from a long look at the
Seyfert 1 galaxy NGC 7469. The presence of a soft excess below 0.8 keV is
confirmed by our analysis and no warm absorber component is required to fit the
spectrum. A complex iron emission line and the Compton reflection hump are
clearly detected. The profile of the line is too broad to associate this
feature with distant matter. In addition, the observed soft excess and the
energy of the iron line E_{Fe}=6.8 keV strongly support a scenario in which the
hard X-rays are reprocessed by a photoionized accretion disc. This hypothesis
was tested fitting the BeppoSAX spectrum with the ionized disc reflection model
of Ross & Fabian. A second narrow line component, in addition to that produced
in the disc, is also required to fit the observed iron line profile. A high
energy cut-off around 150 keV is clearly detected in the spectrum.


title: CH3OH and H2O masers in high-mass star-forming regions

abstract:
  We present a comparison of ClassII CH3OH and H2O masers at high spatial
resolution in a sample of 29 massive star-forming regions. Absolute positions
of both maser types are compared with mm dust continuum, cm continuum and
mid-infrared sources. Spatial correlations of the different tracers and
kinematic signatures are discussed.


title: Parameters of Warm Molecular Clouds from Methyl Acetylene Observations

abstract:
  The results of a survey of 63 galactic star-forming regions in the 6_K-5_K
and 5_K-4_K methyl acetylene lines at 102 and 85 GHz, respectively, are
presented. Fourty-three sources were detected at 102 GHz, and twenty-five at 85
GHz. Emission was detected towards molecular clouds with kinetic temperatures
20-60 K (so-called ``warm clouds''). The CH3CCH abundances in these clouds
appeared to be about several units X 10^(-9). Five mapped sources were analyzed
using the maximum entropy method. The sizes of the mapped clouds fall within
the range between 0.1 and 1.7 pc, virial masses - between 90-6200 Msun, and
densities - between 6 X 10^4 and 6 X 10^5 cm^(-3). The CH3CCH sources spatially
coincide with the CO and CS sources. Chemical evolution simulations showed that
the typical methyl acetylene abundance in the observed clouds corresponds to an
age of ~ 6 X 10^4 years.


title:
Determining the Cosmic Distance Scale from Interferometric Measurements
  of the Sunyaev-Zel'dovich Effect

abstract:
  We determine the distances to 18 galaxy clusters with redshifts ranging from
z~0.14 to z~0.78 from a maximum likelihood joint analysis of 30 GHz
interferometric Sunyaev-Zel'dovich effect (SZE) and X-ray observations. We
model the intracluster medium (ICM) using a spherical isothermal beta model. We
quantify the statistical and systematic uncertainties inherent to these direct
distance measurements, and we determine constraints on the Hubble parameter for
three different cosmologies. These distances imply a Hubble constant of 60 (+4,
-4) (+13, -18) km s-1 Mpc-1 for an Omega_M = 0.3, Omega_Lambda = 0.7 cosmology,
where the uncertainties correspond to statistical followed by systematic at 68%
confidence. With a sample of 18 clusters, systematic uncertainties clearly
dominate. The systematics are observationally approachable and will be
addressed in the coming years through the current generation of X-ray
satellites (Chandra & XMM-Newton) and radio observatories (OVRO, BIMA, & VLA).
Analysis of high redshift clusters detected in future SZE and X-ray surveys
will allow a determination of the geometry of the universe from SZE determined
distances.


title: K-corrections and Extinction Corrections for Type Ia Supernovae

abstract:
  The measurement of the cosmological parameters from Type Ia supernovae hinges
on our ability to compare nearby and distant supernovae accurately. Here we
present an advance on a method for performing generalized K-corrections for
Type Ia supernovae which allows us to compare these objects from the UV to
near-IR over the redshift range 0<z<2. We discuss the errors currently
associated with this method and how future data can improve upon it
significantly. We also examine the effects of reddening on the K-corrections
and the light curves of Type Ia supernovae. Finally, we provide a few examples
of how these techniques affect our current understanding of a sample of both
nearby and distant supernovae.


title: HST STIS observations of four QSO pairs

abstract:
  We present HST STIS observations of four quasar pairs with redshifts
0.84<z_em<1.56 and angular separation 2-3 arcmin corresponding to ~ 1-1.5
h^-1_50 Mpc transverse proper distance at z ~ 0.9. We study the distribution of
velocity differences between nearest neighbor HI Lyman_alpha absorption lines
detected in the spectra of adjacent QSOs in order to search for the possible
correlation caused by the extent or the clustering properties of the structures
traced by the absorption lines over such a scale. The significance of the
correlation signal is determined by comparison with Monte-Carlo simulations of
spectra with randomly distributed absorption lines. We find an excess of lines
with a velocity separation smaller than Delta(V) = 500 km/s significant at the
99.97% level. This clearly shows that the Lyman_alpha forest is correlated on
scales larger than 1 h^-1_50 Mpc at z ~ 1. However, out of the 20 detected
coincidences within this velocity bin, 12 have Delta(V) > 200 km/s. This
probably reflects the fact that the scale probed by our observations is not
related to the real size of individual absorbers but rather to large scale
correlation. Statistics are too small to conclude about any difference between
pairs separated by either 2 or 3 arcmin. A damped Lyman_alpha system is
detected at z_abs = 1.2412 toward LBQS0019-0145A with log[N(HI)] ~ 20.5. From
the absence of ZnII absorption, we derive a metallicity relative to solar
[Zn/H]<-1.75.


title: The Daemon Kernel of the Sun

abstract:
  The daemon-stimulated proton decay is capable of providing an appreciable
part of the Sun luminosity as well as nonelectron flavor component in the solar
neutrino flux. This follows (1) from our experiments on detection of negative
daemons in Earth-crossing orbits, which give ~1 microsec for the decay time of
a daemon-containing proton, and (2) from an estimate of the total number of
daemons which could be captured by the Sun from the Galactic disk (up to
\~2.4E30). Because of their huge mass (~3E-5 g), the captured daemons form in
the Sun's center a kernel a few cm in size. The protons diffuse into the kernel
to decay there with a release of energy. Physically sound estimates of the
parameters of the kernel can be obtained if it consists mainly of negative
daemons. Proton decay maintains a high temperature of the daemon gas (up to
\~1E11-1E12 K), which makes it physically collisionless and prevents kernel
collapse into a black hole.


title: Bar Galaxies and their Environments

abstract:
  The prints of the Palomar Sky Survey, luminosity classificaiton and radial
velocities were used to assign all northern Shapley-Ames galaxies to either (1)
field, (2) group, or (3) cluster environments. This information for 930
galaxies shows no evidence for a dependence of bar frequency on galaxy
environment. This suggests that the formation of a bar in a dish galaxy is
mainly determined by the properties of the parent galaxy, rather than by the
characteristics of its environment.


title:
New abundance measurements in UKS 1927-177, a very metal-poor galaxy in
  the Local Group

abstract:
  We present new results from optical spectroscopy of the brightest Hii region
in the dwarf irregular galaxy UKS 1927-177 in Sagittarius (SagDIG). From high
signal-to-noise spectra, reddening-corrected line flux ratios have been
measured with typical uncertainties of a few percent, from which the oxygen
abundance is rediscussed, and new abundance estimates are derived for N and Ne.
The O abundance in SagDIG, estimated with the empirical abundance indicator R23
and other methods, is in the range 12+log(O/H)=7.26 to 7.50. The fact that
SagDIG is ~10 times closer than IZw18 makes it an ideal target to test the
hypothesis of the existence of young galaxies in the present-day universe.
Indeed, stellar photometry suggests that this galaxy may harbor a stellar
population older than a few Gyr, and possibly an old stellar component as well.
The case of SagDIG therefore supports the view that very low chemical
abundances can be maintained throughout the life of a dwarf stellar system,
even in the presence of multiple star formation episodes.


title:
Toward An Empirical Theory of Pulsar Emission. VII. On the Spectral
  Behavior of Conal Beam Radii and Emission Heights

abstract:
  In this paper we return to the old problem of conal component-pair widths and
profile dimensions. Observationally, we consider a set of 10 pulsars with
prominent conal component pairs, for which well measured profiles exist over
the largest frequency range now possible. Apart from some tendency to narrow at
high frequency, the conal components exhibit almost constant widths. We use all
three profile measures, the component separation as well as the outside
half-power and 10% widths, to determine conal beam radii, which are the focus
of our subsequent analysis. These radii at different frequencies are well
fitted by a relationship introduced by Thorsett (1991), but the resulting
parameters are highly correlated. Three different types of behavior are found:
one group of stars exhibits a continuous variation of beam radius which can be
extrapolated down to the stellar surface along the ``last open field lines''; a
second group exhibits beam radii which asymptotically approach a minimum high
frequency value that is 3--5 times larger; and a third set shows almost no
spectral change in beam radius at all. The first two behaviors are associated
with outer-cone component pairs; whereas the constant separation appears to
reflect inner-cone emission.


title: Constraints on (Omega_M0, Omega_Lambda) from strong lensing in AC 114

abstract:
  We use a strong lensing inversion in the cluster of galaxies AC 114 to derive
constraints on the cosmological parameters Omega_M0 and Omega_Lambda. If it is
possible to measure spectroscopically the redshifts of many multiple images
then one can in principle constrain (Omega_M0,Omega_Lambda) through ratios of
angular diameter distances, independently of any external assumptions.
Numerical tests on simulated data show rather good constraints from this test.
We also use an analytic ``pseudo-elliptical'' NFW profile in the simulations,
following the general new formalism we present. An application to AC 114 favors
a flat Universe, an EdS model being marginally ruled out.


title:
Terahertz Initiatives at the Antarctic Submillimeter Telescope and
  Remote Observatory (AST/RO)

abstract:
  The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) is a
1.7-meter diameter offset Gregorian instrument located at the NSF
Amundsen-Scott South Pole Station. This site is exceptionally dry and cold,
providing opportunities for Terahertz observations from the ground. Preliminary
analysis of recent site testing results shows that the zenith transparency of
the 1.5 THz atmospheric window at South Pole frequently exceeds 10% during the
Austral winter. Routine observations at 810 GHz have been conducted over the
past two years, resulting in large-scale maps of the Galactic Center region and
measurements of the (13)C line in molecular clouds. During the next two years,
the observatory plans to support two Terahertz instruments: 1) TREND (Terahertz
Receiver with Niobium Nitride Device--K. S. Yngvesson, University of
Massachusetts, P. I.), and 2) SPIFI (South Pole Imaging Fabry-Perot
Interferometer--G. J. Stacey, Cornell University, P. I.). AST/RO could be used
in future as an observational test bed for additional prototype Terahertz
instruments. Observing time on AST/RO is available on a proposal basis (see
http://cfa-www.harvard.edu/~adair/AST_RO).


title:
The Nature of Dark Matter in Elliptical Galaxies: Chandra Observations
  of NGC 4636

abstract:
  We determine the total enclosed mass profile from 0.7 to 35 kpc in the
elliptical galaxy NGC 4636 based on the hot interstellar medium temperature
profile measured using the Chandra X-ray Observatory, and other X-ray and
optical data. The total mass increases as radius to the power 1.2 to a good
approximation over this range in radii, attaining a total mass-to-light ratio
of 40 solar masses per solar visual luminosity at 35 kpc. We find that at least
half, and as much as 80%, of the mass within the optical half-light radius is
non-luminous, implying an exceptionally low baryon fraction in NGC 4636. The
large inferred dark matter concentration and central dark matter density,
consistent with the upper end of the range expected for standard cold dark
matter halos, imply that mechanisms proposed to explain low dark matter
densities in less massive galaxies are not effective in elliptical galaxies.


title: PeV Cosmic Rays: A Window on the Leptonic Era?

abstract:
  It is shown that a variety of characteristic features of the high-energy
hadronic cosmic ray spectra, in particular the abrupt changes in the spectral
index that occur around 3 PeV and 300 PeV, as well as the corresponding changes
in elemental composition that are evident from kinks in the $<X_{\max}>$
distribution, can be explained in great detail from interactions with relic Big
Bang antineutrinos, provided that the latter have a rest mass of $\sim 0.5$
eV/$c^2$.


title: The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda VI

abstract:
  We have surveyed Andromeda VI, a dwarf spheroidal galaxy companion to M31,
for variable stars using F450W and F555W observations obtained with the Hubble
Space Telescope. A total of 118 variables were found, with 111 being RR Lyrae,
6 anomalous Cepheids, and 1 variable we were unable to classify. We find that
the Andromeda VI anomalous Cepheids have properties consistent with those of
anomalous Cepheids in other dwarf spheroidal galaxies. We revise the existing
period-luminosity relations for these variables. Further, using these and other
available data, we show that there is no clear difference between fundamental
and first-overtone anomalous Cepheids in a period-amplitude diagram at shorter
periods, unlike the RR Lyrae. For the Andromeda VI RR Lyrae, we find that they
lie close to the Oosterhoff type I Galactic globular clusters in the
period-amplitude diagram, although the mean period of the RRab stars, <P_ab> =
0.588 d, is slightly longer than the typical Oosterhoff type I cluster. The
mean V magnitude of the RR Lyrae in Andromeda VI is 25.29+/-0.03, resulting in
a distance 815+/-25 kpc on the Lee, Demarque, & Zinn distance scale. This is
consistent with the distance derived from the I magnitude of the tip of the red
giant branch. Similarly, the properties of the RR Lyrae indicate a mean
abundance for Andromeda VI which is consistent with that derived from the mean
red giant branch color.


title:
XMM-Newton and Chandra Observations of the Galaxy Group NGC 5044. I.
  Evidence for Limited Multi-Phase Hot Gas

abstract:
  Using new XMM and Chandra observations we present an analysis of the
temperature structure of the hot gas within a radius of 100 kpc of the bright
nearby galaxy group NGC 5044. A spectral deprojection analysis of data
extracted from circular annuli reveals that a two-temperature model (2T) of the
hot gas is favored over single-phase or cooling flow (M_dot = 4.5 +/- 0.2
M_{sun}/yr) models within the central ~30 kpc. Alternatively, the data can be
fit equally well if the temperature within each spherical shell varies
continuously from ~T_h to T_c ~ T_h/2, but no lower. The high spatial
resolution of the Chandra data allows us to determine that the temperature
excursion T_h --> T_c required in each shell exceeds the temperature range
between the boundaries of the same shell in the best-fitting single-phase
model. This is strong evidence for a multi-phase gas having a limited
temperature range. The cooler component of the 2T model has a temperature (T_c
\~ 0.7 keV) similar to the kinetic temperature of the stars. The hot phase has
a temperature (T_h ~ 1.4 keV) characteristic of the virial temperature of the
\~10^{13} M_{sun} halo expected in the NGC 5044 group. However, in view of the
morphological disturbances and X-ray holes visible in the Chandra image within
R ~10 kpc, bubbles of gas heated to ~T_h in this region may be formed by
intermittent AGN feedback. Some additional heating at larger radii may be
associated with the evolution of the cold front near R ~50 kpc, as suggested by
the sharp edge in the EPIC images.


title:
The Extended Deep Minimum and the Subsequent Brightening of RX And in
  1996-1997

abstract:
  We discovered that RX And, one of prototypical Z Cam-type dwarf novae,
underwent a deep, extended faint state in 1996-1997. Time-resolved photometry
at the bottom of the fading revealed the presence of strong flickering, and the
absence of detectable orbital modulation. This finding indicates that the
mass-transfer remained even at the deepest minimum of the fading, contrary to
what was observed in a deep minimum of a VY Scl-type star, MV Lyr. RX And
subsequently underwent a brightening (outburst) during its recovery stage. The
photometric and spectroscopic characteristics of the brightening significantly
differed from those of ordinary outbursts of RX And, and are considered to
resemble an inside-out type outburst of a long-period dwarf nova. An
examination of historical visual observations revealed the possible presence of
\~10-yr periodicity, which is close to what has been proposed for MV Lyr. The
common observed features between RX And and VY Scl-type stars may suggest a
common underlying mechanism for producing temporary deep fadings. The departure
from the disk instability model, as observed in VY Scl-type stars, was not
apparent in the present fading of RX And. In conjunction with the recently
published Hubble Space Telescope observation during the same fading, we can
conclude that the phenomenological difference from the VY Scl-type fading is
understood as a smaller effect of irradiation on the accretion disk in RX And.


title:
The Formation of Low-Mass Cluster Galaxies and the Universal Initial
  Galaxy Mass Function

abstract:
  Clusters of galaxies have an observed over-density of low-luminosity systems
in comparison to the field, although it is not yet agreed whether this effect
is the result of initial galaxy mass functions that vary with environment or
galaxy evolutionary effects. In this letter we argue that this over-density is
the result of low-mass systems with red colors that are over-populating the
faint-end of the observed luminosity function in the nearby rich cluster Abell
0426. We show that the luminosity function of Abell 0426 becomes steeper, from
the field value alpha = -1.25+/-0.05 to alpha=-1.44+/-0.04, due to a recently
identified population of red low-mass cluster galaxies that are possibly the
remnants of dynamical stripped high-mass systems. We further demonstrate,
through simple models of stripping effects, how cluster luminosity functions
can become artificially steep over time from the production of these low-mass
cluster galaxies.


title:
Pop III Hypernova Nucleosynthesis and Abundances in Very Metal-Poor Halo
  Stars

abstract:
  We calculate evolution and nucleosynthesis in massive Pop III stars with M =
13 ~ 270Msun, and compare the results with abundances of very metal-poor halo
stars. The observed abundances can be explained by the energetic core-collapse
supernovae with M < ~ 130Msun (``hypernovae'') but not by pair-instability
supernovae (PISNe) with M ~ 140-270 Msun. This result constrain the IMF for the
Pop III and very metal-poor Pop II stars.


title:
Dust clouds or magnetic spots? Exploring the atmospheres of L dwarfs
  with time-resolved spectrophotometry

abstract:
  I present the results of a program to spectrophotometrically monitor the L1.5
dwarf 2MASSW J1145572+231730 to identify the cause of photospheric variability
in ultra cool dwarfs. Plausible candidates are magnetically-induced star spots
and inhomogeneous photospheric dust clouds. Based on the atmospheric models and
synthetic spectra of Allard et al. (2001), the expected signatures of these
phenomena in the 0.5-2.5 um wavelength region are presented and discussed. Near
infrared spectra of 2M1145 were obtained along with a nearby reference star
observed simultaneously in the spectrograph slit. No convincing variability
over a 54 hour interval is found in any one of several colour indices designed
to be most sensitive to dust- and spot-related variability. Nonetheless, a
significant correlation between the variability of two colour indices is found.
This is slightly more consistent with the dust-related variability model than
the cool spot one considered. Based on the theoretically predicted signatures
and the median errors in the colour indices (0.03-0.05 magnitudes), upper
limits are placed on the coverage of possible spots and clouds. Assuming the L
dwarf to be best modelled by a dusty atmosphere at 1900K, coherent clear clouds
are limited to a coverage of 10-15% of the projected surface area and 200K
cooler spots to a 20% coverage. A larger coverage of many small features
varying incoherently cannot be ruled out with this method. A lower effective
temperature restricts coherent clear clouds to be much smaller; a higher
temperature allows both clouds and spots to be larger. These upper limits are
consistent with the two separate variability detections in the I-band reported
by Bailer-Jones & Mundt (2001).


title:
First results from the Very Small Array -- IV. Cosmological parameter
  estimation

abstract:
  We investigate the constraints on basic cosmological parameters set by the
first compact-configuration observations of the Very Small Array (VSA), and
other cosmological data sets, in the standard inflationary LambdaCDM model.
Using a weak prior 40 < H_0 < 90 km/s/Mpc and 0 < tau < 0.5 we find that the
VSA and COBE_DMR data alone produce the constraints Omega_tot =
1.03^{+0.12}_{-0.12}, Omega_bh^2 = 0.029^{+0.009}_{-0.009}, Omega_cdm h^2 =
0.13^{+0.08}_{-0.05} and n_s = 1.04^{+0.11}_{-0.08} at the 68 per cent
confidence level. Adding in the type Ia supernovae constraints, we additionally
find Omega_m = 0.32^{+0.09}_{-0.06} and Omega_Lambda = 0.71^{+0.07}_{-0.07}.
These constraints are consistent with those found by the BOOMERanG, DASI and
MAXIMA experiments. We also find that, by combining all the recent CMB
experiments and assuming the HST key project limits for H_0 (for which the
X-ray plus Sunyaev--Zel'dovich route gives a similar result), we obtain the
tight constraints Omega_m=0.28^{+0.14}_{-0.07} and Omega_Lambda=
0.72^{+0.07}_{-0.13}, which are consistent with, but independent of, those
obtained using the supernovae data.


title:
6-m Telescope Spectroscopic Observations of The Bubble Complex in NGC
  6946

abstract:
  We describe the results of a long-slit spectroscopic study of an unusual star
complex in the nearby spiral galaxy NGC 6946 using the SAO 6-m telescope and
the Keck 10-m telescope. The complex resembles a circular bubble 600 pc in
diameter with a young super star cluster (SSC) near the center. The kinematics
of ionized gas is studied through Ha emission with several slit positions.
Position-velocity diagrams show two distinct features with high speed motions.
One is an irregularly shaped region to the east of the SSC, 270 pc in size, in
which most of the Ha emission is blue shifted by 120 km/s, and another is a 350
pc shell centered on the SSC with positive and negative velocity shifts of 60
km/s. Balmer and HeI absorption lines in the SSC give an age of 12-13 Myr,
which is consistent with the photometric age but significantly older than the
kinematic ages of the high speed regions. The energetics of the SSC and its
interaction with the environment are considered. The expansion energies exceed
10^52 ergs, but the power outputs from winds and supernova in the SSC are large
enough to account for this. The intensities of Balmer, [NII], and [SII]
emission lines within and around the complex indicate that shock excitation
makes a significant contribution to the emission from the most energetic
region.


title: A Possible Aeronomy of Extrasolar Terrestrial Planets

abstract:
  Terrestrial planetary systems may exist around nearby stars as the
Earth-sized counterparts to the many giant planets already discovered within
the solar neighborhood. In this chapter we first discuss the numerous
techniques which have been suggested to search for extrasolar terrestrial
planets. We then focus on the expected results from that technique in which an
orbiting telescope or interferometer is used to obtain a visible or infrared
spectrum of a planet, without contamination from the parent star. We show
examples of such spectra for selected cases: the present Earth, the
Neoproterozoic (snowball) Earth, a methane-rich Earth, and the present Mars and
Venus. We conclude by discussing the implications of such spectra for the
detection of life on an extrasolar terrestrial planet.


title:
Stellar evolution with rotation VIII: Models at Z = 10^{-5} and CNO
  yields for early galactic evolution

abstract:
  We calculate a grid of star models with and without the effects of axial
rotation for stars in the mass range between 2 and 60 M$_{\odot}$ for the
metallicity $Z = 10^{-5}$. Star models with initial masses superior or equal to
9 M$_\odot$ were computed up to the end of the carbon--burning phase. Star
models with masses between 2 and 7 M$_\odot$ were evolved beyond the end of the
He--burning phase through a few thermal pulses during the AGB phase. Compared
to models at $Z=0.02$, the low $Z$ models show faster rotating cores and
stronger internal $\Omega$--gradients, which favour an important mixing of the
chemical elements. In very low $Z$ models, primary nitrogen is produced during
the He--burning phase by rotational diffusion of $^{12}$C into the H--burning
shell. The intermediate mass stars of very low $Z$ are the main producers of
primary $^{14}$N, but massive stars also contribute to this production; no
significant primary nitrogen is made in models at metallicity $Z$=0.004 or
above. We calculate the chemical yields in He, C, N, O and heavy elements and
discuss the chemical evolution of the CNO elements at very low Z. Remarkably,
the C/O vs O/H diagram is mainly sensitive to the interval of stellar masses,
while the N/O vs O/H diagram is mainly sensitive to the average rotation of the
stars contributing to the element synthesis. The presently available
observations in these diagrams seem to favour contributions either from stars
down to about 2 M$_{\odot}$ with normal rotation velocities or from stars above
8 M$_{\odot}$ but with very fast rotation.


title:
High Mass X-ray Binaries as a Star Formation Rate Indicator in Distant
  Galaxies

abstract:
  Based on CHANDRA observations of nearby starburst galaxies and RXTE/ASM, ASCA
and MIR-KVANT/TTM studies of high mass X-ray binary (HMXB) populations in the
Milky Way and Magellanic Clouds, we propose that the number and/or the
collective X-ray luminosity of HMXBs can be used to measure the star formation
rate (SFR) of a galaxy. We show that, within the accuracy of the presently
available data, a linear relation between HMXB number and the star formation
rate exists. The relation between SFR and collective luminosity of HMXBs is
non-linear in the low SFR regime, $L_X\propto \SFR^{\approx 1.7}$, and becomes
linear only for sufficiently high star formation rate, when the total number of
HMXB sources becomes sufficiently large. Such behaviour is caused by the fact,
that we measure collective luminosity of a population of the discrete sources.
Although more subtle SFR dependent effects are likely to exist, the data are
broadly consistent with the existence of a universal luminosity function of
HMXBs which can be roughly described as a power law with a differential slope
of $\sim 1.6$, a cutoff at $L_X \sim few \times 10^{40}$ erg/sec and a
normalisation proportional to the star formation rate.
  We apply our results to (spatially unresolved) starburst galaxies observed by
CHANDRA at redshifts up to $z\sim 1$ in the Hubble Deep Field North and show
that the calibration of the collective luminosity of HMXBs as a SFR indicator
based on the local sample agrees well with the SFR estimates obtained for these
distant galaxies with conventional methods.


title: O/Fe in metal-poor main sequence and subgiant stars

abstract:
  A study of the O/Fe ratio in metal-poor main sequence and subgiant stars is
presented using the [OI] 6300A line, the OI 7774A triplet, and a selection of
weak FeII lines observed on high-resolution spectra acquired with the VLT UVES
spectrograph. The [OI] line is detected in the spectra of 18 stars with -0.5 <
[Fe/H] < -2.4, and the triplet is observed for 15 stars with [Fe/H] ranging
from -1.0 to -2.7. The abundance analysis was made first using standard model
atmospheres taking into account non-LTE effects on the triplet: the [OI] line
and the triplet give consistent results with [O/Fe] increasing quasi-linearly
with decreasing [Fe/H] reaching [O/Fe] ~ +0.7 at [Fe/H] = -2.5. When
hydrodynamical model atmospheres representing stellar granulation in dwarf and
subgiant stars replace standard models, the [O/Fe] from the [OI] and FeII lines
is decreased by an amount which increases with decreasing [Fe/H]. The [O/Fe] vs
[Fe/H] relation remains quasi-linear extending to [O/Fe] ~ +0.5 at [Fe/H] =
-2.5, but with a tendency of a plateau with [O/Fe] ~ +0.3 for -2.0 < [Fe/H] <
-1.0, and a hint of cosmic scatter in [O/Fe] at [Fe/H] ~ -1.0. Use of the
hydrodynamical models disturbs the broad agreement between the oxygen
abundances from the [OI], OI, and OH lines, but 3D non-LTE effects may serve to
erase these differences.


title: X-ray Emission from the Type Ic Supernova 1994I Observed with Chandra

abstract:
  We present two high-resolution Chandra X-ray observations of supernova (SN)
1994I which show, for the first time, that the interaction of the blast wave
from a Type Ic SN with its surrounding circumstellar material (CSM) can give
rise to soft X-ray emission. Given a 0.3-2 keV band X-ray luminosity of L_x ~ 1
x 10^{37} ergs/s between six and seven years after the outburst of SN 1994I,
and assuming the X-ray emission arises from the shock-heated CSM, we derive a
pre-SN mass-loss rate of \dot{M} ~ 1 x 10^{-5} M_sun/yr (v_w/10 km/s).
Combining the results with earlier ROSAT observations, we construct the X-ray
lightcurve of SN 1994I. A best-fit X-ray rate of decline of L_x \propto t^{-s}
with index s~1 and a CSM density profile of rho_csm \propto r^{-1.9\pm0.1} are
inferred, consistent with what is expected for a constant mass-loss rate and
constant wind velocity profile for the SN progenitor (rho_csm \propto r^{-2}).


title:
Chandra Observations of Abell 2029: No Cooling Flow and a Steep
  Abundance Gradient

abstract:
  We have obtained high spatial resolution temperature and abundance profiles
for the galaxy cluster Abell 2029 with the Chandra ACIS-S instrument. Our
observations reveal that the spectra are well-fit by a single-phase gas in each
annulus. While the temperature of the intracluster medium drops from ~9 keV at
3 arcmin (260 kpc) to 3 keV in the central 5 arcsec (5 kpc) of the cluster,
there is no evidence for gas emitting at temperatures below 3 keV. The addition
of a cooling flow component does not improve the fits, despite previous claims
for a massive cooling flow. There is also no evidence for excess absorption
above the Galactic N_H value. We also observe a steep Fe abundance gradient,
such that Z_Fe >= 2 Z_solar (assuming meteoritic solar Fe abundance) in the
core, consistent with significant enrichment from Fe-rich Type Ia supernovae in
the cD galaxy. The Fe abundance drops to ~0.5 Z_solar at 3 arcmin (260 kpc), in
good agreement with previous BeppoSAX measurements. The high resolution image
reveals neither a strong central point source, nor any filamentary structure
related to a cooling flow or a merger. The absence of a strong merger signature
argues against the creation of the wide-angle-tail radio source morphology in a
merger event. (modified for astro-ph).


title: Gamma-ray emission from Wolf-Rayet binaries

abstract:
  In the colliding wind region of early-type binaries, electrons can be
accelerated up to relativistic energies displaying power-law spectra, as
demonstrated by the detection of non-thermal radio emission from several WR+OB
systems. The particle acceleration region, located between the stars, is
exposed to strong photon fields in such a way that inverse Compton cooling of
the electrons could result in a substantial high-energy non-thermal flux. In
particular cases, the ratio of the energy densities of magnetic to photon
fields in the colliding wind region will determine whether a given source can
produce or not significant gamma-ray emission. We present here a study of the
binaries WR 140, WR 146, and WR 147 in the light of recent radio and gamma-ray
observations. We show that with reasonable assumptions for the magnetic field
strength WR 140 can produce the gamma-ray flux from the EGRET source 3EG
J2022+4317. WR 146 and WR 147 are below the detection threshold, but
forthcoming instruments like INTEGRAL and GLAST could detect non-thermal
emission from them.


title: The Isotopic Mixture of Barium in the Metal-poor Subgiant HD 140283

abstract:
  Analyses of the abundances of neutron-capture elements have led to the belief
that these elements in metal-poor stars are r-process products with relative
abundances closely resembling those found in the solar system. This picture was
challenged by Magain (1995), who found that a pure r-process mix of the barium
isotopes was inconsistent with the mix of odd to even barium isotopes derived
from analysis of the Ba II line at 4554 A in the spectrum of the metal-poor
subgiant HD 140283. In this paper, we address Magain's challenge using new high
resolution high signal-to-noise spectra of HD 140283, and find, in contrast to
his result, that a solar-like r-process isotopic mixture provides a fair fit to
the observed 4554 A profile.


title:
Dynamics and Structure of Three-Dimensional Trans-Alfvenic Jets. II. The
  Effect of Density and Winds

abstract:
  Two three-dimensional magnetohydrodynamical simulations of strongly
magnetized conical jets, one with a poloidal and one with a helical magnetic
field, have been performed. In the poloidal simulation a significant sheath
(wind) of magnetized moving material developed and partially stabilized the jet
to helical twisting. The fundamental pinch mode was not similarly affected and
emission knots developed in the poloidal simulation. Thus, astrophysical jets
surrounded by outflowing winds could develop knotty structures along a straight
jet triggered by pinching. Where helical twisting dominated the dynamics,
magnetic field orientation along the line-of-sight could be organized by the
toroidal flow field accompanying helical twisting. On astrophysical jets such
structure could lead to a reversal of the direction of Faraday rotation in
adjacent zones along a jet. Theoretical analysis showed that the different
dynamical behavior of the two simulations could be entirely understood as a
result of dependence on the velocity shear between jet and wind which must
exceed a surface Alfven speed before the jet becomes unstable to helical and
higher order modes of jet distortion.


title: First results from the Very Small Array -- I. Observational methods

abstract:
  The Very Small Array (VSA) is a synthesis telescope designed to image faint
structures in the cosmic microwave background on degree and sub-degree angular
scales. The VSA has key differences from other CMB interferometers with the
result that different systematic errors are expected. We have tested the
operation of the VSA with a variety of blank-field and calibrator observations
and cross-checked its calibration scale against independent measurements. We
find that systematic effects can be suppressed below the thermal noise level in
long observations; the overall calibration accuracy of the flux density scale
is 3.5 percent and is limited by the external absolute calibration scale.


title:
An alternative theoretical approach to describe planetary systems
  through a Schrodinger-type diffusion equation

abstract:
  In the present work we show that planetary mean distances can be calculated
with the help of a Schrodinger-type diffusion equation. The obtained results
are shown to agree with the observed orbits of all the planets and of the
asteroid belt in the solar system, with only three empty states. Furthermore,
the equation solutions predict a fundamental orbit at 0.05 AU from solar-type
stars, a result confirmed by recent discoveries. In contrast to other similar
approaches previously presented in the literature, we take into account the
flatness of the solar system, by considering the flat solutions of the
Schrodinger-type equation. The model has just one input parameter, given by the
mean distance of Mercury.


title: First results from the Very Small Array -- III. The CMB power spectrum

abstract:
  We present the power spectrum of the fluctuations in the cosmic microwave
background detected by the Very Small Array (VSA) in its first season of
observations in its compact configuration. We find clear detections of first
and second acoustic peaks at l~200 and l~550, plus detection of power on scales
up to l=800. The VSA power spectrum is in very good agreement with the results
of the Boomerang, Dasi and Maxima telescopes despite the differing potential
systematic errors.


title: First results from the Very Small Array -- II. Observations of the CMB

abstract:
  We have observed the cosmic microwave background temperature fluctuations in
eight fields covering three separated areas of sky with the Very Small Array at
34 GHz. A total area of 101 square degrees has been imaged, with sensitivity on
angular scales 3.6 - 0.4 degrees (equivalent to angular multipoles l=150-900).
We describe the field selection and observing strategy for these observations.
In the full-resolution images (with synthesised beam of FWHM ~ 17 arcmin) the
thermal noise is typically 45 microK and the CMB signal typically 55 microK.
The noise levels in each field agree well with the expected thermal noise level
of the telescope, and there is no evidence of any residual systematic features.
The same CMB features are detected in separate, overlapping observations.
Discrete radio sources have been detected using a separate 15 GHz survey and
their effects removed using pointed follow-up observations at 34 GHz. We
estimate that the residual confusion noise due to unsubtracted radio sources is
less than 14 mJy/beam (15 microK in the full-resolution images), which added in
quadrature to the thermal noise increases the noise level by 6 %. We estimate
that the rms contribution to the images from diffuse Galactic emission is less
than 6 microK. We also present images which are convolved to maximise the
signal-to-noise of the CMB features and are co-added in overlapping areas, in
which the signal-to-noise of some individual CMB features exceeds 8.


title:
The 2dF Galaxy Redshift Survey: Cosmological Parameters and Galaxy
  Biasing

abstract:
  The 2dF Galaxy Redshift Survey (2dFGRS) has already measured over 220,000
redshifts of nearby (z ~0.1) galaxies. It allows us to estimate fundamental
cosmological parameters and to subdivide the survey into subsets according to
the galaxy intrinsic properties. The large-scale structure analysis of the
survey has already yielded several significant results: (i) the shape of the
power spectrum of fluctuations is consistent with the Lambda - Cold Dark Matter
concordance model; (ii) from joint analysis of the 2dFGRS data with the Cosmic
Microwave Background anisotropies the linear-theory rms mass fluctuations is
sigma_8m ~ 0.73, lower than the COBE-alone normalization and previous estimates
from cluster abundance and cosmic shear; (iii) The biasing parameter of bright
galaxies on scales > 10 Mpc/h is nearly unity; and (iv) on scales smaller than
< 10 Mpc/h red galaxies are more strongly clustered than blue galaxies.


title:
The Effect of the Hall Term on the Nonlinear Evolution of the
  Magnetorotational Instability: II. Saturation Level and Critical Magnetic
  Reynolds Number

abstract:
  The nonlinear evolution of the magnetorotational instability (MRI) in weakly
ionized accretion disks, including the effect of the Hall term and ohmic
dissipation, is investigated using local three-dimensional MHD simulations and
various initial magnetic field geometries. When the magnetic Reynolds number,
Re_M \equiv v_A^2 / \eta \Omega (where v_A is the Alfven speed, \eta the
magnetic diffusivity, and \Omega the angular frequency), is initially larger
than a critical value Re_{M, crit}, the MRI evolves into MHD turbulence in
which angular momentum is transported efficiently by the Maxwell stress. If
Re_M < Re_{M, crit}, however, ohmic dissipation suppresses the MRI, and the
stress is reduced by several orders of magnitude. The critical value is in the
range of 1 - 30 depending on the initial field configuration. The Hall effect
does not modify the critical magnetic Reynolds number by much, but enhances the
saturation level of the Maxwell stress by a factor of a few. We show that the
saturation level of the MRI is characterized by v_{Az}^2 / \eta \Omega, where
v_{Az} is the Alfven speed in the nonlinear regime along the vertical component
of the field. The condition for turbulence and significant transport is given
by v_{Az}^2 / \eta \Omega \gtrsim 1, and this critical value is independent of
the strength and geometry of the magnetic field or the size of the Hall term.
If the magnetic field strength in an accretion disk can be estimated
observationally, and the magnetic Reynolds number v_A^2 / \eta \Omega is larger
than about 30, this would imply the MRI is operating in the disk.


title:
The Anisotropy of the Microwave Background to l = 3500: Deep Field
  Observations with the Cosmic Background Imager

abstract:
  We report measurements of anisotropy in the cosmic microwave background
radiation over the multipole range l ~ 200 - 3500 with the Cosmic Background
Imager based on deep observations of three fields. These results confirm the
drop in power with increasing l first reported in earlier measurements with
this instrument, and extend the observations of this decline in power out to l
\~ 2000. The decline in power is consistent with the predicted damping of
primary anisotropies. At larger multipoles, l = 2000 - 3500, the power is 3.1
sigma greater than standard models for intrinsic microwave background
anisotropy in this multipole range, and 3.5 sigma greater than zero. This
excess power is not consistent with expected levels of residual radio source
contamination but, for sigma_8 >~ 1, is consistent with predicted levels due to
a secondary Sunyaev-Zeldovich anisotropy. Further observations are necessary to
confirm the level of this excess and, if confirmed, determine its origin.


title:
A Fast Gridded Method for the Estimation of the Power Spectrum of the
  CMB from Interferometer Data with Application to the Cosmic Background Imager

abstract:
  We describe an algorithm for the extraction of the angular power spectrum of
an intensity field, such as the cosmic microwave background (CMB), from
interferometer data. This new method, based on the gridding of interferometer
visibilities in the aperture plane followed by a maximum likelihood solution
for bandpowers, is much faster than direct likelihood analysis of the
visibilities, and deals with foreground radio sources, multiple pointings, and
differencing. The gridded aperture-plane estimators are also used to construct
Wiener-filtered images using the signal and noise covariance matrices used in
the likelihood analysis. Results are shown for simulated data. The method has
been used to determine the power spectrum of the cosmic microwave background
from observations with the Cosmic Background Imager, and the results are given
in companion papers.


title:
The Sunyaev-Zeldovich effect in CMB-calibrated theories applied to the
  Cosmic Background Imager anisotropy power at l > 2000

abstract:
  We discuss the nature of the possible high-l excess in the Cosmic Microwave
Background (CMB) anisotropy power spectrum observed by the Cosmic Background
Imager (CBI). We probe the angular structure of the excess in the CBI deep
fields and investigate whether it could be due to the scattering of CMB photons
by hot electrons within clusters, the Sunyaev-Zeldovich (SZ) effect. We
estimate the density fluctuation parameters for amplitude, sigma_8, and shape,
Gamma, from CMB primary anisotropy data and other cosmological data. We use the
results of two separate hydrodynamical codes for Lambda-CDM cosmologies,
consistent with the allowed sigma_8 and Gamma values, to quantify the expected
contribution from the SZ effect to the bandpowers of the CBI experiment and
pass simulated SZ effect maps through our CBI analysis pipeline. The result is
very sensitive to the value of sigma_8, and is roughly consistent with the
observed power if sigma_8 ~ 1. We conclude that the CBI anomaly could be a
result of the SZ effect for the class of Lambda-CDM concordance models if
sigma_8 is in the upper range of values allowed by current CMB and Large Scale
Structure (LSS) data.


title:
Cosmological Parameters from Cosmic Background Imager Observations and
  Comparisons with BOOMERANG, DASI, and MAXIMA

abstract:
  We report on the cosmological parameters derived from observations with the
Cosmic Background Imager (CBI), covering 40 square degrees and the multipole
range 300 < l < 3500. The angular scales probed by the CBI correspond to
structures which cover the mass range from 10^14 to 10^17 M_sun, and the
observations reveal, for the first time, the seeds that gave rise to clusters
of galaxies. These unique, high-resolution observations also show damping in
the power spectrum to l ~ 2000, which we interpret as due to the finite width
of the photon-baryon decoupling region and the viscosity operating at
decoupling. Because the observations extend to much higher l the CBI results
provide information complementary to that probed by the Boomerang, DASI,
Maxima, and VSA experiments. As the observations are pushed to higher
multipoles no anomalies relative to standard models appear, and extremely good
consistency is found between the cosmological parameters derived for the CBI
observations over the range 610 < l < 2000 and observations at lower l
[abridged].


title:
The Anisotropy of the Microwave Background to l = 3500: Mosaic
  Observations with the Cosmic Background Imager

abstract:
  Using the Cosmic Background Imager, a 13-element interferometer array
operating in the 26-36 GHz frequency band, we have observed 40 sq deg of sky in
three pairs of fields, each ~ 145 x 165 arcmin, using overlapping pointings
(mosaicing). We present images and power spectra of the cosmic microwave
background radiation in these mosaic fields. We remove ground radiation and
other low-level contaminating signals by differencing matched observations of
the fields in each pair. The primary foreground contamination is due to point
sources (radio galaxies and quasars). We have subtracted the strongest sources
from the data using higher-resolution measurements, and we have projected out
the response to other sources of known position in the power-spectrum analysis.
The images show features on scales ~ 6 - 15 arcmin, corresponding to masses ~
(5 - 80)*10^{14} Msun at the surface of last scattering, which are likely to be
the seeds of clusters of galaxies. The power spectrum estimates have a
resolution Delta-l = 200 and are consistent with earlier results in the
multipole range l <~ 1000. The power spectrum is detected with high
signal-to-noise ratio in the range 300 <~ l <~ 1700. For 1700 <~ l <~ 3000 the
observations are consistent with the results from more sensitive CBI deep-field
observations. The results agree with the extrapolation of cosmological models
fitted to observations at lower l, and show the predicted drop at high l (the
"damping tail").


title:
Variable UV Absorption in the Seyfert 1.5 Galaxy NGC 3516: The Case for
  Associated UV and X-ray Absorption

abstract:
  We present observations of the UV absorption lines in the Seyfert 1 galaxy
NGC 3516, obtained at a resolution of $\lambda$/$\Delta\lambda$ $\approx$
40,000 with the Space Telescope Imaging Spectrograph (STIS) on 2000 October 1.
The UV continuum was $\sim$4 times lower than that observed during 1995 with
the Goddard High Resolution Spectrograph (GHRS), and the X-ray flux from a
contemporaneous {\it Chandra X-ray Observatory (CXO)} observation was a factor
of $\sim$8 below that observed with {\it ASCA}. The STIS spectra show kinematic
components of absorption in Ly$\alpha$, C IV, and N V at radial velocities of
-376, -183, and -36 km s$^{-1}$ (components 1, 2, and 3+4, respectively), which
were detected in the earlier GHRS spectra; the last of these is a blend of two
GHRS components that have increased greatly in column density. Four additional
absorption components have appeared in the STIS spectra at radial velocities of
-692, -837, -994, and -1372 km s$^{-1}$ (components 5 through 8); these may
also have been present in earlier low-flux states observed by the {\it
International Ultraviolet Explorer (IUE)}. Based on photoionization models, we
suggest that the components are arranged in increasing radial distance in the
order, 3+4, 2, 1, followed by components 5 -- 8. We have achieved an acceptable
fit to the X-ray data using the combined X-ray opacity of the UV components 1,
2 and 3+4. By increasing the UV and X-ray fluxes of these models to match the
previous high states, we are able to match the GHRS C IV column densities,
absence of detectable C IV absorption in components 5 through 8, and the 1994
{\it ASCA} spectrum. We conclude that variability of the UV and X-ray
absorption in NGC 3516 is primarily due to changes in the ionizing flux.


title:
Connection between supernova shocks, flavor transformation, and the
  neutrino signal

abstract:
  We show that the supernova neutrino signal in terrestrial detectors could
give characteristic signatures as the shock propagates through the regions
where matter-enhanced neutrino flavor transformation takes place. This effect
could allow existing and proposed supernova neutrino detectors to provide new
insights into the problem of shock re-generation and propagation.
Alternatively, such observations could allow unique insights into the neutrino
mass and mixing matrix.


title: Status of Cold Dark Matter Cosmology

abstract:
  Cold Dark Matter (CDM) has become the standard modern theory of cosmological
structure formation. Its predictions appear to be in good agreement with data
on large scales, and it naturally accounts for many properties of galaxies. But
despite its many successes, there has been concern about CDM on small scales
because of the possible contradiction between the linearly rising rotation
curves observed in some dark-matter-dominated galaxies vs. the $1/r$ density
cusps at the centers of simulated CDM halos. Other CDM issues on small scales
include the very large number of small satellite halos in simulations, far more
than the number of small galaxies observed locally, and problems concerning the
angular momentum of the baryons in dark matter halos. The latest data and
simulations have lessened, although not entirely resolved, these concerns.
Meanwhile, the main alternatives to CDM that have been considered to solve
these problems, self-interacting dark matter (SIDM) and warm dark matter (WDM),
have been found to have serious drawbacks.


title:
Time-Resolved Photometry of Kuiper Belt Objects: Rotations, Shapes and
  Phase Functions

abstract:
  We present a systematic investigation of the rotational lightcurves of
trans-Neptunian objects based on extensive optical data from Mauna Kea. Four of
13 objects (corresponding to 31%) in our sample ((33128) 1998 BU48, 2000 GN171,
(20000) Varuna and 1999 KR16) were found to exhibit lightcurves with
peak-to-peak range > 0.15 magnitude. In a larger sample obtained by combining
our data with reliably determined lightcurves from the literature, 7 of 22
objects (32%) display significant (> 0.15 magnitude range) lightcurves. About
23% of the sampled objects have lightcurve ranges > 0.4 magnitudes. Curiously,
the objects are very large (> 250 km diameter, assuming an albedo of 0.04) and,
in the absence of rotation, should be near spherical due to self compression.
We propose that the large amplitude, short period objects are rotationally
distorted, low density rubble piles. Statistically, the trans-Neptunian objects
are less spherical than their main-belt asteroid counterparts, indicating a
higher specific angular momentum perhaps resulting from the formation epoch. In
addition to the rotational lightcurves, we measured phase darkening for 7
Kuiper Belt objects in the 0 to 2 degree phase angle range. Unlike Pluto, the
measured values show steep slopes and moderate opposition surge indicating
backscatter from low albedo porous surface materials.


title:
Chemical Abundances Of Three Metal-Poor Globular Clusters (NGC 6287, NGC
  6293, And NGC 6541) In The Inner Halo

abstract:
  We present a chemical abundance study of three inner old halo clusters NGC
6287, NGC 6293, and NGC 6541, finding [Fe/H] = -2.01 +/- 0.05, -1.99 +/- 0.02,
and -1.76 +/- 0.02, respectively, and our metallicity measurements are in good
agreement with previous estimates. The mean alpha-element abundances of our
program clusters are in good agreement with other globular clusters, confirming
previous results. However, the individual alpha-elements appear to follow
different trends. The silicon abundances of the inner halo clusters appear to
be enhanced and the titanium abundances appear to be depleted compared to the
intermediate halo clusters. Our results also appear to oppose to those of
metal-rich bulge giants studied by McWilliam and Rich, who found that bulge
giants are titanium enhanced and silicon deficient. In particular, [Si/Ti]
ratios appear to be related to Galactocentric distances,in the sense that
[Si/Ti] ratios decrease with Galactocentric distance. We propose that
contributions from different masses of the SNe II progenitors that enriched
proto-globular cluster clouds' elemental abundances and the different initial
physical environments surrounding the proto-globular clusters clouds are
responsible for this gradient in [Si/Ti] ratios versus Galactocentric distances
of the "old halo" globular clusters. On the other hand, our program clusters'
enhanced s-process elemental abundances suggest that the formation timescale of
our program clusters might be as short as a few times 10^8 yr after the star
formation is initiated in the Galaxy's central regions, if the s-process site
is intermediate mass AGB stars.


title: How large is our universe?

abstract:
  We reexamine constraints on the spatial size of closed toroidal models with
cold dark matter and the cosmological constant from cosmic microwave
background. We carry out Bayesian analyses using the Cosmic Background Explorer
(COBE) data properly taking into account the statistically anisotropic
correlation, i.e., off-diagonal elements in the covariance. We find that the
COBE constraint becomes more stringent in comparison with that using only the
angular power spectrum, if the likelihood is marginalized over the orientation
of the observer. For some limited choices of orientations, the fit to the COBE
data is considerably better than that of the infinite counterpart. The best-fit
matter normalization is increased because of large-angle suppression in the
power and the global anisotropy of the temperature fluctuations. We also study
several deformed closed toroidal models in which the fundamental cell is
described by a rectangular box. In contrast to the cubic models, the
large-angle power can be enhanced in comparison with the infinite counterparts
if the cell is sufficiently squashed in a certain direction. It turns out that
constraints on some slightly deformed models are less stringent. We comment on
how these results affect our understanding of the global topology of our
universe.


title: Fundamental Approach to the Cosmological Constant Issue

abstract:
  The issue of the cosmological constant is discussed in details and a solution
to the problem is suggested.


title: Accelerating Universe: Theory versus Experiment

abstract:
  We present gravitation as a theory in which the coordinates are distances and
velocities between galaxies. We show that there are three possibilities for the
Universe to expand: decelerating, constant and accelerating, and it is shown
that the Universe is now in the latter phase. Assuming "Omega"_m=0.245, the
time at which the Universe goes over from a decelerating to an accelerating
expansion, occurs at 8.5 Gyr ago, at which time the cosmic radiation
temperature was 146K. The theory predicts also that now there is a positive
pressure, p=0.034g/cm^2, in the Universe. Although the theory has no
cosmological constant, we extract from it its equivalence and show that
"Lambda"=1.934x10^{-35}s^{-2}, which is in excellent agreement with
measurements. It is also shown that the three-dimensional space of the Universe
is Euclidean. Comparison with general relativity theory is finally made and it
is shown that the classical experiments as well as the gravitational radiation
prediction follow from the present theory, too.


title: The Brightest AGB Stars in the Leo I Dwarf Spheroidal Galaxy

abstract:
  The first results of a study of the the dwarf spheroidal galaxy, Leo I, using
the new Japanese-South African Infrared Survey Facility (IRSF) are presented.
J,H,K_{s} observations show that most, if not all, of at least the top one
magnitude of the AGB is populated by carbon stars. These objects form a tight
sequence in the K_{s} - (J-K_{s}) plane. In addition there are five very red
objects which are believed to be dust enshrouded AGB stars. They have Mbol near
-5.0 and are at the AGB tip. Comparison with carbon Miras in Magellanic Cloud
clusters and taking into account other evidence on the ages and metallicities
of Leo I populations suggests that these obscured stars belong to the youngest
significant population of Leo I and have ages of ~2 Gyr. Some of them can be
shown to be variable.


title:
Post-Newtonian treatment of bar mode instability in rigidly rotating
  equilibrium configurations for polytropic stars

abstract:
  We determine the onset point of secular instability for the nonaxisymmetric
bar mode in rigidly rotating equilibrium configurations in the Post-Newtonian
approximation, in order to apply it to neutron stars. The treatment is based on
a precedent Newtonian analytic energy variational method which we have extended
to the Post-Newtonian case. This method, based upon Landau's theory of
second-order phase transitions, provides the critical value of the ellipsoid
polar eccentricity e at the onset of viscosity-driven instability and it is
valid for any equation of state. The extension of this method to Post-Newtonian
fluid configurations has been accomplished by combining two earlier orthogonal
works, specialized respectively to slow rotating configurations but with
arbitrary density profile and to constant mass density but arbitrarily fast
rotating ellipsoids. We also determine the explicit expressions for the density
functionals which allow the generalization of the physical quantities involved
in our treatment from the constant mass density to an arbitrary density profile
form. We find that, considering homogeneous ellipsoids, the value of the
critical eccentricity increases as the stars become more relativistic, in
qualitatively agreement with previous investigations but with a less relevant
amount of such an increase. Studying then the dependence of this critical value
on the configuration equation of state, we find that for polytropic matter
distributions the increase of the critical eccentricity with the star
compactness is confirmed for softer equations of state (with respect to the
incompressible case). The amount of this stabilizing effect is nearly
independent of the polytropic index.


title: A Large Brightness Enhancement of the QSO 0957+561 A Component

abstract:
  We report an increase of more than 0.2 mag in the optical brightness of the
leading image (A) of the gravitational lens Q0957+561, detected during the
09/2000 -- 06/2001 monitoring campaign (2001 observing season). The brightening
is similar to or even greater than the largest change ever detected during the
20 years of monitoring of this system. We discuss two different provisional
explanations to this event: intrinsic source variability or microlensing
(either short timescale microlensing or cessation of the historical
microlensing). An exhaustive photometric monitoring of Q0957+561 is needed
until summer of 2002 and during 2003 to discriminate between these
possibilities.


title: The rich 6 to 9 um spectrum of interstellar PAHs

abstract:
  Here, we present 6-9 um spectra of a sample of RNe, HII regions, YSOs,
evolved stars and galaxies that show strong unidentified infrared bands,
obtained with the ISO-SWS. The IR emission features show pronounced variations.
1) The 6.2 um feature shifts and clearly shows profile variations. 2) The 7.7
um complex is comprised of at least two subpeaks peaking at 7.6 and one
longwards of 7.7 um. In some cases the main peak can apparently shift up to 8
um. Two sources do not exhibit a 7.7 um complex but instead show a broad
emission feature at 8.22 um. 3) The 8.6 um feature has a symmetric profile in
all sources and some sources exhibit this band at slightly longer wavelengths.
For the 6.2, 7.7 and 8.6 um features, the sources have been classified
independently based on their profile and peak position. The classes derived for
these features are directly linked with each other. Furthermore, the observed
6--9 um spectrum depends on the type of object. We attribute the observed 6.2
um profile and peak position to the combined effect of a PAH family and
anharmonicity with pure PAHs representing the 6.3 um component and
substituted/complexed PAHs representing the 6.2 um component. The 7.6 um
component is well reproduced by both pure and substituted/complexed PAHs but
the 7.8 um component remains an enigma. In addition, the exact identification
of the 8.22 um feature remains unknown. The observed variations in the
characteristics of the IR emission bands are linked to the local physical
conditions. Possible formation and evolution processes that may influence the
interstellar PAH class are highlighted.


title: Extended mid-infrared emission from VV 114: probing the birth of a ULIRG

abstract:
  We present our 5-16 micron spectro-imaging observations of VV114, an infrared
luminous early-stage merger, taken with the ISOCAM camera on-board ISO. We find
that only 40% of the mid-infrared (MIR) flux is associated with a compact
nuclear region, while the rest of the emission originates from a rather diffuse
component extended over several kpc. This is in stark contrast with the very
compact MIR starbursts usually seen in luminous infrared galaxies. A secondary
peak of MIR emission is associated with an extra-nuclear star forming region
which displays the largest Halpha equivalent width in the whole system.
Comparing our data with the distribution of the molecular gas and cold dust, as
well as with radio observations, it becomes evident that the conversion of
molecular gas into stars can be triggered over large areas at the very first
stages of an interaction. The presence of a very strong continuum at 5 microns
in one of the sources indicates that an enshrouded active galactic nucleus may
contribute to 40% of its MIR flux. We finally note that the relative variations
in the UV to radio spectral properties between the merging galaxies provide
evidence that the extinction-corrected star formation rate of similar objects
at high z, such as those detected in optical deep surveys, can not be
accurately derived from their rest-frame UV properties.


title: Near-infrared synchrotron emission from the compact jet of GX339-4

abstract:
  We have compiled contemporaneous broadband observations of the black hole
candidate X-ray binary GX 339-4 when in the low/hard X-ray state in 1981 and
1997. The data clearly reveal the presence of two spectral components, with
thermal and non-thermal spectra, overlapping in the optical -- near-infrared
bands. The non-thermal component lies on an extrapolation of the radio spectrum
of the source, and we interpret it as optically thin synchrotron emission from
the powerful, compact jet in the system. Detection of this break from
self-absorbed to optically thin synchrotron emission from the jet allows us to
place a firm lower limit on the ratio of jet (synchrotron) to X-ray
luminosities of $\geq 5$%. We further note that extrapolation of the optically
thin synchrotron component from the near-infrared to higher frequencies
coincides with the observed X-ray spectrum, supporting models in which the
X-rays could originate via optically thin synchrotron emission from the jet
(possibly instead of Comptonisation).


title:
Abundances and Physical Conditions in the Interstellar Gas toward HD 192
  639

abstract:
  We present a study of the abundances and physical conditions in the
interstellar gas toward the heavily reddened star HD 192639 [E_(B-V) = 0.64],
based on analysis of FUSE and HST/STIS spectra covering the range from 912 to
1361 A. This work constitutes a survey of the analyses that can be performed to
study the interstellar gas when combining data from different instruments.
Low-velocity (-18 to -8 km/s) components are seen primarily for various neutral
and singly ionized species such as C I, O I, S I, Mg II, Cl I, Cl II, Mn II, Fe
II and Cu II. Numerous lines of H2 are present in the FUSE spectra, with a
kinetic temperature for the lowest rotational levels T_(01) = (90 +/- 10) K.
Analysis of the C I fine-structure excitation implies an average local density
of hydrogen n_H = (16 +/- 3) cm^-3. The average electron density, derived from
five neutral/first ion pairs under the assumption of photoionization
equilibrium, is n_e = (0.11 +/- 0.02) cm^-3. The relatively complex component
structure seen in high-resolution spectra of K I and Na I, the relatively low
average density, and the measured depletions all suggest that the line of sight
contains a number of diffuse clouds, rather than a single dense, translucent
cloud. Comparisons of the fractions of Cl in Cl I and of hydrogen in molecular
form suggest a higher molecular fraction, in the region(s) where H2 is present,
than that derived considering the average line of sight. In general, such
comparisons may allow the identification and characterization of translucent
portions of such complex lines of sight. The combined data also show
high-velocity components near -80 km/s for various species which appear to be
predominantly ionized, and may be due to a radiative shock. A brief overview of
the conditions in this gas will be given.


title: High Velocity Cloud Edges and Mini-HVCs

abstract:
  Arecibo mapping is reported of the neutral hydrogen distribution along
selected directions out from the centers of two small High Velocity Clouds
(HVC), W486 and W491. Both HVCs have a small inner region where the neutral
hydrogen column density N_HI decreases slowly and a larger outer region where
N_HI declines more rapidly, smoothly and exponentially from ~ 2 X 10^19 atoms
cm^-2 down to < 10^18 atoms cm^-2. Line widths, and presumably temperature and
turbulence, do not increase in the outermost regions. Therefore pressure
decreases smoothly, making confinement by dark matter gravity more likely than
confinement by external pressure.
  The more extended HVC, W491, has a superimposed small cloud (which we dub a
``mini-HVC''), offset by 66 km s^-1 in velocity along the line of sight with
peak column density about 5 X 10^18 atoms cm^-2. Preliminary data toward future
mapping of two more HVCs reveals two more mini-HVCs of similarly small size and
central column density a bit less than 1 X 10^19 atoms cm^-2. We suggest that
these three mini-HVCs are not physically associated with the HVCs on which they
are superimposed, but are either very small outlyers of the extended Magellanic
Stream HVC complex or more distant and/or smaller isolated CHVCs.
  The value of N_HI at the point where the neutral and ionized column densities
are equal is ~ 2 X 10^19 atoms cm^-2 for the two mapped HVCs. Therefore the
angular scalelength of the total hydrogen is appreciably larger than the
observed HI scalelength. Previous distance estimates, related to absolute size
and mass of the total hydrogen cloud, may have to be scaled down because of the
undetected, more extended ionized hydrogen.


title:
A SSC model for the spectral variability of the intermediate blazar ON
  231

abstract:
  In April-May 1998 the blazar ON 231 (W Com, B2 1219+28) showed an
extraordinary optical outburst alerted by the Perugia Astronomical Observatory.
The source reached the most luminous state, observed at least since the
beginning of the previous century. BeppoSAX observed ON 231 in the band from
0.1 up to 100 keV, detecting an X-ray spectrum with a peculiar concave profile,
that could be considered as a signature of the intermediate blazar subclass.
The spectral energy distributions (SED) of blazars were studied with a time
dependent synchrotron self-Compton (SSC)model, tested here on this object. Even
with the preliminary ``toy'' model of a single flaring region, emitting by
means of mere SSC process, the X-ray spectrum is reasonably reproduced. The SED
was calculated with a hard spectrum of the injected electrons and with other
physical parameters comparable to previous works, validating a base consistence
of the method.


title:
Constraining the strength of Dark Matter Interactions from Structure
  Formation

abstract:
  We discuss the damping of primordial dark matter fluctuations, taking into
account explicitly the interactions of dark matter - whatever their intensity -
both with itself and with other particle species. Relying on a general
classification of dark matter particle candidates, our analysis provides, from
structure formation, a new set of constraints on the dark matter particle mass
and interaction rates (in particular with photons and neutrinos).
  This determines up to which cross sections the dark matter interactions may
effectively be disregarded, and when they start playing an essential role,
either through collisional damping or through an enhancement of the
free-streaming scale. It leads us to extend the notions of Cold, Warm and Hot
Dark Matter scenarios when dark matter interactions are no longer taken to be
negligible. It also suggests the possibility of new scenarios of Collisional
Warm Dark Matter, with moderate damping induced by dark matter interactions.


title:
The Influence of Gravitational Microlensing on the Broad Emission Lines
  of Quasars

abstract:
  We discuss the effects of microlensing on the broad emission lines (BELs) of
QSOs in the light of recent determinations of the size of the broad line region
(BLR) and its scaling with QSO luminosity. Microlensing by star-sized objects
can produce significant amplifications in the BEL of some multiple-imaged QSOs,
and could be very relevant for high-ionization lines. We have identified a
group of ten gravitational lens systems (30% of the selected sample) in which
microlensing could be observed. Using standard kinematic models for AGNs, we
have studied the changes induced in the line profile by a microlens located at
different positions with respect to the center of the BLR. We found that
microlensing could produce important effects such as the relative enhancement
of different parts of the line profile or the displacement of the peak of the
line. The study of BEL profiles of different ionization in a microlensed QSO
image could be an alternative method for probing the BLR structure and size.


title:
Possible High-energy neutrinos from the cosmic accelerator
  RXJ1713.7-3946

abstract:
  The observation of TeV-gamma rays of neutral pion origin from the supernova
remnant RX J1713.7-3946 might have revealed the first specific site where
protons are accelerated to energies typical of the main component of the cosmic
rays. In this letter we calculate the high-energy neutrino flux associated with
this source to be at least 40 muon-type neutrinos per kilometer-squared per
year. We perform the same calculations for other known sources of TeV-gamma
rays and show how neutrino observations can establish whether the TeV-gamma
rays emitted by blazars and supernova remnants are the decay products of
neutral pions and thus unequivocally establish the sources as cosmic
accelerators.


title: The environment of active objects in the nearby universe

abstract:
  We study the galaxy environment of active galaxies, radio-loud and
radio-quiet quasars in the redshift range $0.1\leq z\leq0.25$. We use APM
galaxies in order to explore the local galaxy overdensity and the $b_J-R$
colour distribution of neighbouring galaxies of these target samples. For
comparison, we perform similar analysis on samples of Abell clusters with X-ray
emission, and samples of Abell clusters with richness R=1 and R=0. The
projected cross-correlations show that the samples of quasars and active
galaxies reside in regions of galaxy density enhancements lower than those
typical of R=0 clusters. We also find that in the nearby universe the local
galaxy overdensity of radio-loud and radio-quiet quasars are comparable. The
analysis of the distribution of $b_J-R$ galaxy colour indexes suggests that the
environment of quasars is not strongly dominated by a population of red
galaxies, characteristic of rich Abell cluster, an effect that is more clearly
appreciated for our sample of radio-loud quasars.


title:
The Detectability of High Redshift Lyman Alpha Emission Lines Prior to
  the Reionization of the Universe

abstract:
  For a source of Ly alpha radiation embedded in a neutral intergalactic medium
(IGM) prior to the reionization epoch, the emission line is strongly suppressed
by the intervening IGM. The damping wing of the so-called Gunn-Peterson trough
can extend to the red side of the emission line, and erase a significant
fraction of the total line flux. However, the transmitted fraction increases
with the size of the local cosmological HII region surrounding the source, and
therefore with the ionizing luminosity and age of the source. Motivated by the
recent discovery of a Ly alpha emitting galaxy at a redshift z=6.56 (Hu et al.
2002), possibly prior to the reionization of the IGM, we revisit the effects of
a neutral IGM on the Ly alpha emission line. We show that even for faint
sources with little ionizing continuum, the emission line can remain
observable. In particular, the line detected by Hu et al. is consistent with a
source embedded in a neutral IGM. We provide characterizations of the asymmetry
and total transmitted flux of the Ly alpha line as functions of the ionizing
emissivity of its source. A statistical sample of Ly alpha emitters extending
beyond the reionization redshift can be a useful probe of reionization.


title:
The Complex Chemical Abundances and Evolution of the Sagittarius Dwarf
  Spheroidal Galaxy

abstract:
  We report on the chemical abundances derived from high-dispersion spectra of
14 red giant stars in the Sagittarius dwarf spheroidal (Sgr dSph) galaxy. The
stars span a wide range of metallicities, -1.6 < [Fe/H] < -0.1 dex, and exhibit
very unusual abundance variations. For metal-poor stars with [Fe/H] < -1,
[alpha/Fe] \approx +0.3 similar to Galactic halo stars, but for more metal-rich
stars the relationship of [alpha/Fe] as a function of [Fe/H] is lower than that
of the Galactic disk by 0.1 dex. The light elements [Al/Fe] and [Na/Fe] are
sub-solar by an even larger amount, 0.4 dex. The pattern of neutron-capture
heavy elements, as indicated by [La/Fe] and [La/Eu], shows an increasing
s-process component with increasing [Fe/H], up to [La/Fe] \sim +0.7 dex for the
most metal-rich Sgr dSph stars. The large [La/Y] ratios show that the s-process
enrichments came from the metal-poor population. We can best understand the
observed abundances with a model in which the Sgr dSph formed stars over a many
Gyr and lost a significant fraction of its gas during its evolution. Low-mass,
metal-poor AGB stars polluted the more metal-rich stars with s-process
elements, and type Ia SNe from low-mass progenitors enriched the ISM with
iron-peak metals. The type II/type Ia SNe ratio was smaller than in the
Galactic disk, presumably due to a slower star formation rate; this resulted in
the observed low [alpha/Fe], [Al/Fe] and [Na/Fe] ratios. The fact that Sgr
stars span such a wide range in metallicity leads us to conclude that their age
spread is even larger than previously inferred. We derive ages using the Padova
models (Girardi et al. 2000) that span \sim 0.5 to 13 Gyr, implying a very long
duration of star formation in the central regions of the Sgr dSph.


title: Three-Dimensional Mapping of the Dark Matter

abstract:
  We study the prospects for three-dimensional mapping of the dark matter to
high redshift through the shearing of faint galaxies images at multiple
distances by gravitational lensing. Such maps could provide invaluable
information on the nature of the dark energy and dark matter. While in
principle well-posed, mapping by direct inversion introduces exceedingly large,
but usefully correlated noise into the reconstruction. By carefully propagating
the noise covariance, we show that lensing contains substantial information,
both direct and statistical, on the large-scale radial evolution of the density
field. This information can be efficiently distilled into low-order
signal-to-noise eigenmodes which may be used to compress the data by over an
order of magnitude. Such compression will be useful for the statistical
analysis of future large data sets. The reconstructed map also contains useful
information on the localization of individual massive dark matter halos, and
hence the dark energy from halo number counts, but its extraction depends
strongly on prior assumptions. We outline a procedure for maximum entropy and
point-source regularization of the maps that can identify alternate
reconstructions.


title:
Composite Luminosity Functions Based on the Sloan Digital Sky Survey
  "Cut & Enhance" Galaxy Cluster Catalog

abstract:
  We present here results on the composite luminosity functions of galaxies in
the clusters of galaxies selected from the SDSS Cut and Enhance cluster catalog
(CE; Goto et al. 2001). We construct the composite luminosity function in the
five SDSS bands, u,g,r,i and z, using 204 CE clusters ranging from z=0.02 to
z=0.25. We use photometric redshifts to construct composite luminosity
functions. The robustness of the weighting scheme was tested using Monte Carlo
simulation. We find the slope of composite LFs become flatter toward redder
color band. Comparing with field LFs of SDSS (Blanton et al. 2001), cluster LFs
have brighter characteristic magnitude and flatter slopes in g, r, i and z
bands. These results are consistent with the hypothesis that the cluster LF has
two distinct underlying populations i.e. the bright end of the LF is dominated
by bright early types that follow a gaussian--like luminosity distribution,
while the faint--end of the cluster LF is a steep power--law like function
dominated by star--forming (bluer) galaxies. We also study the composite
luminosity functions for early--type and late--type galaxies using profile
fits, a concentration parameter and u-r color to classify galaxy morphology.
The strong dependence of LF on galaxy morphology is found.The faint end slope
of the LF is always flatter for early--type galaxies than late--type regardless
of passband and methodology. These results are consistent with the hypothesis
that the cluster region are dominated by bright elliptical galaxies.


title:
Optical Spectropolarimetry of SN 2002ap: High Velocity Asymmetric
  Explosion

abstract:
  We present spectropolarimetry of the Type Ic supernova SN 2002ap and give a
preliminary analysis: the data were taken at two epochs, close to and one month
later than the visual maximum (2002 February 8). In addition we present June 9
spectropolarimetry without analysis. The data show the development of linear
polarization. Distinct polarization profiles were seen only in the O I \lambda
7773 multiplet/Ca II IR triplet absorption trough at maximum light and in the
Ca II IR triplet absorption trough a month later, with the latter showing a
peak polarization as high as ~2 %. The intrinsic polarization shows three clear
position angles: 80 degs for the February continuum, 120 degs for the February
line feature, and 150 degs for the March data. We conclude that there are
multiple asymmetric components in the ejecta. We suggest that the supernova has
a bulk asymmetry with an axial ratio projected on the sky that is different
from 1 by of order 10 %. Furthermore, we suggest very speculatively that a high
velocity ejecta component moving faster than ~0.115c (e.g., a jet) contributes
to polarization in the February epoch.


title: A FUSE Survey of Interstellar Molecular Hydrogen in Translucent Clouds

abstract:
  We report the first ensemble results from the FUSE survey of molecular
hydrogen in lines of sight with A_V $\gtrsim$ 1 mag. We have developed
techniques for fitting computed profiles to the low-J lines of H2, and thus
determining column densities for J = 0 and J = 1, which contain $\gtrsim$99% of
the total H2. From these column densities and ancillary data we have derived
the total H2 column densities, hydrogen molecular fractions, and kinetic
temperatures for 23 lines of sight. This is the first significant sample of
molecular hydrogen column densities of 10^21 cm^-2, measured through UV
absorption bands. We have also compiled a set of extinction data for these
lines of sight, which sample a wide range of environments. We have searched for
correlations of our H2-related quantities with previously published column
densities of other molecules and extinction parameters. We find strong
correlations between H2 and molecules such as CH, CN, and CO, in general
agreement with predictions of chemical models. We also find the expected
correlations between hydrogen molecular fraction and various density indicators
such as kinetic temperature, CN abundance, the steepness of the far-UV
extinction rise, and the width of the 2175A bump. Despite the relatively large
molecular fractions, we do not see the values greater than 0.8 expected in
translucent clouds. With the exception of a few lines of sight, we see little
evidence for the presence of individual translucent clouds in our sample. We
conclude that most of the lines of sight are actually composed of two or more
diffuse clouds similar to those found toward targets like zeta Oph. We suggest
a modification in terminology to distinguish between a "translucent line of
sight" and a "translucent cloud."


title:
Spatially resolved STIS spectra of the gravitationally lensed BAL quasar
  APM08279+5255: the nature of component C and evidence for microlensing

abstract:
  While gravitationally lensed quasars are expected to display an odd number of
images, invariably systems are observed with an even number of quasars. For
this, lensing galaxies must have very small core radii; this provides strong
demagnification of one of the images. High resolution imaging of the
gravitationally lensed BAL quasar, APM08279+5255, reveals three point-like
images. As these images possess similar colours, it has been suggested that
each represents a lensed image. Here, spatially resolved spectra of the
individual components, obtained with STIS on the HST, are presented, clearly
revealing that each is an image of the quasar. This confirms that APM08279+5255
represents the first example of an odd-image gravitationally lensed system. The
implications for the properties of the lensing galaxy are discussed. It is also
found that the individual images possess spectral differences indicative of the
influence of gravitational microlensing in this system.


title: Post-T Tauri Stars in the Nearest OB Association

abstract:
  We present results of a spectroscopic survey of X-ray- and proper
motion-selected samples of late-type stars in the Lower Cen-Cru (LCC) and Upper
Cen-Lup (UCL) subgroups of the nearest OB association: Sco-Cen. The primary
goals of the survey are to determine the star-formation history of the OB
subgroups, and to assess the frequency of accreting stars in a sample dominated
by ``post-T Tauri'' pre-MS stars. We investigate two samples: (1) ACT and TRC
proper motion candidates with X-ray counterparts in the ROSAT All-Sky Survey
BSC, and (2) G and K-type Hipparcos candidate members (de Zeeuw et al. 1999).
We obtained optical spectra of 130 candidates with the MSSSO 2.3-m DBS. Pre-MS
stars were identified by (1) strong Li 6707A absorption, (2) subgiant surface
gravities, (3) proper motions consistent with Sco-Cen membership, and (4) HRD
positions consistent with being pre-MS. We demonstrate that measuring the
gravity-sensitive band-ratio of Sr II 4077A to Fe I 4071A is a valuable means
of discriminating pre-MS and ZAMS stars. Depending on the choice of
evolutionary tracks, we find the mean pre-MS ages to range between 17-23 Myr
(LCC), and 15-22 Myr (UCL). Accounting for observational uncertainties, it
appears that 95% of the low-mass star-formation in each subgroup occurred in
less than 8 Myr (LCC) and 12 Myr (UCL). We find main sequence turn-off ages for
Hipparcos B-type members to be 16+-1 Myr (LCC) and 17+-1 Myr (UCL). Contrary to
previous findings, it appears that LCC is coeval with, or slightly older than,
UCL. Only 1 out of 110 (0.9^+2.1_-0.8 %) pre-MS solar-type stars in the sample
with ages of 13+-1 (s.e.)+-6 (1sigma) Myr and masses of 1.3+-0.2 Msun shows
both enhanced Halpha emission and a K-band excess indicative of accretion from
a truncated circumstellar disk. (abridged)


title:
The relativistic Iron K-alpha line from an accretion disc onto a static
  non-baryonic compact object

abstract:
  This paper continues the study of the properties of an accretion disc
rotating around a non-baryonic (assumed super-massive) compact object. This
kind of objects, generically known as boson stars, were earlier proposed as a
possible alternative scenario to the existence of super-masive black holes in
the center of every galaxy. A dilute boson star has also been proposed as a
large part of the non-baryonic dark matter, flattening galactic rotational
velocities curves. In this contribution, we compute the profile of the emission
lines of Iron; its shape has been for long known as a useful diagnosis of the
space-time geometry. We compare with the case of a Schwarzschild black hole,
concluding that the differences are observationally distinguishable.


title:
Analytical Approach to the Mass Distribution Function of Subhalos and
  Cold Fronts in Galaxy Clusters

abstract:
  We construct an analytical model of the mass distribution function of
subhalos in a galaxy cluster in the context of the cold dark matter (CDM)
theory. Our model takes account of two important effects; the high density of
the precluster region and the spatial correlation of initial density
fluctuations. For subhalos with small masses, the mass distribution function
that our model predicts is intermediate between the Press-Schechter (PS) mass
distribution function and a conditional mass distribution function as an
extension of the PS formalism. We compare the results of our model with those
of numerical simulations. We find that our model predictions are consistent
with the mass and velocity distribution functions of subhalos in a cluster
obtained by numerical simulations. We estimate the probability of finding large
X-ray subhalos that often have ``cold fronts''. The observed large X-ray
subhalos and cold fronts may not always be the result of cluster mergers, but
instead may be internal structures in clusters.


title: Warm Dark Matter versus Bumpy Power Spectra

abstract:
  In this paper we are exploring the differences between a Warm Dark Matter
model and a CDM model where the power on a certain scale is reduced by
introducing a narrow negative feature ("dip"). This dip is placed in a way so
as to mimic the loss of power in the WDM model: both models have the same
integrated power out to the scale where the power of the Dip model rises to the
level of the unperturbed CDM spectrum again.
  Using N-body simulations we show that some of the large-scale clustering
patterns of this new model follow more closely the usual CDM scenario while
simultaneously suppressing small scale structures (within galactic halos) even
more efficiently than WDM. The analysis in the paper shows that the new Dip
model appears to be a viable alternative to WDM but it is based on different
physics. Where WDM requires the introduction of a new particle species the Dip
model is based on a non-standard inflationary period. If we are looking for an
alternative to the currently challenged standard LCDM structure formation
scenario, neither the LWDM nor the new Dip model can be ruled out based on the
analysis presented in this paper. They both make very similar predictions and
the degeneracy between them can only be broken with observations yet to come.


title: Nonradial pulsation of the $\delta$ Scuti star UV Trianguli

abstract:
  We present the results of a three-year photometric study of the $\delta$
Scuti star UV Trianguli. Our data sets consist of 9378 differential
measurements in Johnson V together with a few data collected into the
Str\"{o}mgren {\em uvby$\beta$} system. UV Tri is at least a biperiodic
variable. The two best-fitting frequencies, $f_1$=9.3298 d$^{-1}$ and
$f_2$=10.8513 d$^{-1}$, are still not the complete set of pulsation frequencies
representing the star's light variations. A suspected third frequency might
present in the star. Several ``anomalous cycles'' are observed in the light
curves. They seem real, but are aperiodic. We derive the colour indices and
physical parameters for the variable and conclude that it is a Population I
$\delta$ Sct star with normal metal abundance ([Me/H]=0.0$\pm$n0.1 dex)
evolving on its main sequence stage at an early evolutionary phase before the
turn-off point. Finally, we compare the observed oscillation frequencies with
theoretical models. The two pulsation modes of UV Tri are likely nonradial to
be gravity modes.


title: Sub-millimetre observations of hyperluminous infrared galaxies

abstract:
  We present sub-mm photometry for 11 Hyperluminous Infrared Galaxies (HLIRGs)
and use radiative transfer models for starbursts and AGN to investigate the IR
emission. In all sources both a starburst and AGN are required to explain the
IR emission. The mean starburst fraction is 35%, with a range spanning 80%
starburst dominated to 80% AGN dominated. In all cases the starburst dominates
at rest-frame wavelengths >50 microns, with star formation rates >500 solar
masses per year. The trend of increasing AGN fraction with increasing IR
luminosity seen in IRAS galaxies peaks in HLIRGs, and is not higher than the
fraction seen in bright ULIRGs. The AGN and starburst luminosities correlate,
suggesting that a common physical factor, plausibly the dust masses, governs
their luminosities. Our results suggest that the HLIRG population is comprised
both of ULIRG-like galaxy mergers, and of young galaxies going through their
maximal star formation periods whilst harbouring an AGN. The coeval AGN and
starburst activity in our sources implies that starburst and AGN activity, and
the peak starburst and AGN luminosities, can be coeval in active galaxies
generally. When extrapolated to high-z our sources have comparable sub-mm
fluxes to sub-mm survey sources. At least some sub-mm survey sources are
therefore likely to be comprised of similar galaxy populations to those found
in the HLIRG population. It is also plausible from these results that high-z
sub-mm sources harbour heavily obscured AGN. The differences in X-ray and
sub-mm properties between HLIRGs at z~1 and sub-mm sources at z~3 implies
evolution between the two epochs. Either the mean AGN obscuration level is
greater at z~3 than at z~1, or the fraction of IR-luminous sources at z~3 that
contain AGN is smaller than that at z~1.


title: Massive (?) starburst hosts of blue compact galaxies (BCGs)

abstract:
  We present optical spectroscopy and deep optical/near-IR photometry of 4
luminous metal-poor blue compact galaxies (BCGs) and two of their companions.
With the aid of spectral evolutionary models (SEMs) and structural parameters
derived from the surface photometry we discuss the properties of the central
starbursts and the halo populations of the galaxies. Special attention is paid
to the effects of dust, chemical inhomogeneities and contamination of nebular
emission to the halo light. The optical/near-IR colour index profiles show a
sharp distinction between the starburst and the host. The hosts have luminosity
profiles characteristic of massive ellipticals and remarkably red colours,
typical of a relatively {\it metal-rich} stellar population of {\it old age}.
These properties are in conflict with the relatively low luminosities. The
situation can best be explained if the hosts have an unusually large amount of
dark matter that can hinder the outflow of metals from the system. The
indicated difference in metallicity between the halo and the young starburst
disproves the recurrent burst scenario and supports different origins of the
two populations. We conclude that these BCGs are undergoing mergers between
early type galaxies/thick disks and gas-rich galaxies or intergalactic HI
clouds, in many respects reminiscent of a retarded formation of massive
ellipticals.


title:
Bias and consistency in time delay estimation methods: case of the
  double quasar HE 1104-1805

abstract:
  We present a short re-evaluation of a recently published time delay estimate
for the gravitational lens system HE 1104-1805 with emphasis on important
methodological aspects: bias of the statistics, inconsistency of the methods
and use of the purposeful selection of data points(or so-called "cleaning") at
the preprocessing stage. We show how the inadequate use of simple analysis
methods can lead to too strong conclusions. Our analysis shows that there are
indications for the time delay in HE 1104-1805 to be between -0.9 and -0.7
years, but still with a large uncertainty.


title:
Constraints on (Omega_m,Omega_Lambda) using distributions of inclination
  angles for high redshift filaments

abstract:
  In this paper we present a scale free method to determine the cosmological
parameters (Omega_m, Omega_Lambda). The method is based on the requirement of
isotropy of the distribution of orientations of cosmological filaments. The
current structure formation paradigm predicts that the first structures to form
are voids and filaments, causing a web-like structure of the matter
distribution at high redshifts. Recent observational evidence suggests that the
threads, or filaments, of the cosmic web most easily are mapped in Ly-alpha
emission. We describe how such a 3D map can be used to constrain the
cosmological parameters in a way which, contrary to most other cosmological
tests, does not require the use of a standard rod or a standard candle. We
perform detailed simulations in order to define the optimal survey parameters
for the definition of an observing programme aimed to address this test, and to
investigate how statistical and observational errors will influence the
results. We conclude that observations should target filaments of comoving size
15-50 Mpc in the redshift range 2-4, and that each filament must be defined by
at least four Ly-alpha emitters. Detection of 20 filaments will be sufficient
to obtain a result, while 50 filaments will make it possible to place
significant new constraints on the values of Omega_m and Omega_Lambda permitted
by the current supernova observations. In a future paper we study how robust
these conclusions are to systematic velocities in the survey box.


title: The self-gravitating Fermi gas

abstract:
  We discuss the nature of phase transitions in the self-gravitating Fermi gas
at non-zero temperature. This study can be relevant for massive neutrinos in
Dark Matter models and for collisionless self-gravitating systems experiencing
a ``violent relaxation''. Below a critical energy (in the microcanonical
ensemble) or below a critical temperature (in the canonical ensemble), the
system undergoes a gravitational collapse leading to a compact object with a
massive degenerate nucleus (fermion ball).