title:
Constraining cosmological parameters with the clustering properties of
  galaxy clusters in optical and X-ray bands

abstract:
  (abridged) We use a theoretical model to predict the clustering properties of
galaxy clusters. Our technique accounts for past light-cone effects on the
observed clustering and follows the non-linear evolution of the dark matter
correlation function and cluster bias factor. A linear treatment of
redshift-space distortions is also included. We perform a maximum-likelihood
analysis by comparing the theoretical predictions to a set of observational
data, both in the optical (APM and EDCC catalogues) and X-ray band (RASS1
Bright Sample, BCS, XBACs, REFLEX). In the framework of CDM models, we compute
the constraints on cosmological parameters. Our results show that X-ray data
are more powerful than optical ones, allowing smaller regions in the parameter
space. We find that the clustering properties of clusters are almost
independent of the matter density parameter and of the presence of a
cosmological constant, while they appear to be strongly dependent on the shape
parameter. Using the X-ray data only, we obtain Gamma~0.1 and 0.4<sigma_8<1.1
for the Einstein-de Sitter model, while 0.14<Gamma<0.22 and 0.6<sigma_8<1.3 for
open and flat models with Omega_0m=0.3. Finally, we use our model to make
predictions on the correlation length of galaxy clusters expected in future
surveys. In particular, we show the results for an optical catalogue with
characteristics similar to the EIS project and for a very deep X-ray catalogue
with the characteristics of the XMM/LSS survey. We find that clusters at high
redshifts are expected to have larger a correlation length than local ones.


title:
Temperature and Heavy Element Abundance Profiles of Cool Clusters of
  Galaxies from ASCA

abstract:
  We perform a spatially resolved X-ray spectroscopic study of a set of 18
relaxed clusters of galaxies with gas temperatures below 4 keV. Spectral
analysis was done using ASCA/SIS data coupled with the spatial information
contained in ROSAT/PSPC and Einstein/IPC observations. We derive the
temperature profiles using single-temperature fits and also correct for the
presence of cold gas at the cluster centers. For all of the clusters in the
sample, we derive Si and Fe abundance profiles. For a few of the clusters, we
also derive Ne and S abundance profiles. We present a comparison of the
elemental abundances derived at similar overdensities as well as element
mass-to-light ratios. We conclude that the preferential accretion of low
entropy, low abundance gas into the potentials of groups and cold clusters can
explain most of the observed trends in metallicity. In addition, we discuss the
importance of energy input from SNe II on cluster scaling relations and on the
relation between the observed scatter in the retainment of SN Ia products with
differences between the epoch of cluster formation.


title:
A study of the core of the Shapley Concentration: V. The A3528 complex:
  a young merger event?

abstract:
  We present the results of a redshift survey of galaxies in the A3528 complex,
a chain of interacting clusters in the core of the Shapley Concentration. This
complex is characterized in the X-ray band by two pairs of roughly similar
interacting clumps: one pair has been resolved as two optical Abell clusters
(A3530 and A3532), while the two components of the other pair are both
associated to A3528. The optical data show that the distance between the
centers of A3530 and A3532 is smaller than their Abell radii, an indication of
the existence at least of tidal interactions, and that the contours of galaxies
in A3528 appear to be elongated in the North-South direction, pointing towards
the A3530-A3532 pair.
  From our survey we obtained ~600 new radial velocity determinations: using
this sample, we studied the dynamics of the four Abell clusters in this region
(A3528, A3530, A3532 and A3535) and derived their mean velocities and velocity
dispersions. Moreover we performed a substructure analysis, both bi-dimensional
and three-dimensional, of the whole complex.
  All the characteristics of this structure seem to point toward a merging
scenario in an early stage, whose effects on the galaxy population and on the
cluster dynamics are not yet evident, contrary to what happens in the nearby
A3558 complex, where the merging events are in a rather advanced stage and were
already able to induce modifications in the galaxy population.


title: Broad-band diffuse gamma ray emission of the Galactic Disk

abstract:
  The contributions of different radiation mechanisms to the diffuse gamma-ray
emission of the galactic disk are studied in a broad energy region from X-rays
to very high energy gamma rays.


title: Halpha emitting galaxies and the cosmic star formation rate at z = 2.2

abstract:
  About 10 candidate Halpha emitting galaxies at z = 2.2 have been detected in
a 2.1 um narrow band imaging survey covering an area of 100 sq. arcmin
including the WFPC2 and STIS fields in the Hubble Deep Field South. Six of
these have subsequently been confirmed spectroscopically using ISAAC at the ESO
VLT. Star formation rates of the individual galaxies derived from their Halpha
fluxes are 20-35 Msolar/yr, without any correction for extinction, whereas SFRs
derived from their rest frame UV continuum fluxes are up to a factor of 4 lower
- consistent with lower extinction to Halpha. Velocity dispersions are
typically ~ 100km/s and one galaxy, observed under the most favorable
conditions, shows a rotation curve with a terminal velocity ~ 140 km/s at ~
3kpc radius which is within the range observed for nearby spiral galaxies.
These thus appear to be relatively massive systems at high redshift. Comparison
with the HST NICMOS grism Halpha survey of Yan et al. (1999) reveals little or
no evolution in the Halpha luminosity function between z ~ 1.3 and 2.2. The
inferred star formation rate density of 0.12 Msolar/Mpc^3/yr at z = 2.2 is also
equal to that at z ~ 3-4.5 derived by Steidel et al.(1999) from extinction
corrected UV continuum fluxes.


title: Compact High Velocity Clouds

abstract:
  We summarize the observed properties of the CHVC population, which provide
strong evidence for source distances in the range 200-1000 kpc. At these
distances, the population corresponds to strongly dark-matter dominated
sub-dwarf galaxies still accreting onto the more massive Local Group systems.
Recent searches for faint associated stellar populations have revealed
red-giant candidates for which follow-up spectroscopy is scheduled. A sensitive
HI survey for CHVC counterparts in the NGC 628 galaxy group has allowed
tentative detection of 40 candidates, for which confirming observations have
been approved. Many open issues should be resolved by observational programs
within the coming years.


title:
Selection effects in high-redshift submillimeter surveys and pointed
  observations

abstract:
  The results of the first generation of submillimeter-wave surveys have been
published. The opening of this new window on the distant Universe has added
considerably to our understanding of the galaxy formation process, by revealing
a numerous population of very luminous distant galaxies. Most would have been
very difficult to identify using other methods. The potential importance of
selection effects, especially those connected with the spectral energy
distributions of the detected galaxies, for the interpretation of the results
are highlighted.


title:
Wide band observations of the new X-ray burster SAX J1747.0-2853 during
  the March 1998 outburst

abstract:
  We report on our discovery and follow-up observations of the X-ray source SAX
J1747.0-2853 detected in outburst on 1998, March 10 with the BeppoSAX Wide
Field Cameras in the energy range 2-28 keV. The source is located about half
degree off the Galactic Nucleus. A total of 14 type-I X-ray bursts were
detected in Spring 1998, thus identifying the object as a likely low-mass X-ray
binary harboring a weakly magnetized neutron star. Evidence for photospheric
radius expansion is present in at least one of the observed bursts, leading to
an estimate of the source distance of about 9 kpc. We performed a follow-up
target of opportunity observation with the BeppoSAX Narrow Field Instruments on
March 23 for a total elapsed time of 72 ks. The source persistent luminosity
was 2.6x10^36 erg/s in the 2-10 keV energy range. The wide band spectral data
(1-200 keV) are consistent with a remarkable hard X-ray spectrum detected up to
150 keV, highly absorbed at low energies (Nh of the order of 10^23 cm^-2) and
with clear evidence for an absorption edge near 7 keV. A soft thermal component
is also observed, which can be described by single temperature blackbody
emission at about 0.6 keV.


title: HST/STIS Imaging of the Host Galaxy of GRB980425/SN1998bw

abstract:
  We present HST/STIS observations of ESO 184-G82, the host galaxy of the
gamma-ray burst GRB 980425 associated with the peculiar Type Ic supernova
SN1998bw. ESO 184-G82 is found to be an actively star forming SBc sub-luminous
galaxy. We detect an object consistent with being a point source within the
astrometric uncertainty of 0.018 arcseconds of the position of the supernova.
The object is located inside a star-forming region and is at least one
magnitude brighter than expected for the supernova based on a simple
radioactive decay model. This implies either a significant flattening of the
light curve or a contribution from an underlying star cluster.


title: 3D simulations of shear instabilities in magnetized flows

abstract:
  We present results of three-dimensional (3D) simulations of the
magnetohydrodynamic Kelvin-Helmholtz instability in a stratified shear layer.
The magnetic field is taken to be uniform and parallel to the shear flow. We
describe the evolution of the fluid flow and the magnetic field for a range of
initial conditions. In particular, we investigate how the mixing rate of the
fluid depends on the Richardson number and the magnetic field strength. It was
found that the magnetic field can enhance as well as suppress mixing. Moreover,
we have performed two-dimensional (2D) simulations and discuss some interesting
differences between the 2D and 3D results.


title: Redshift space bias and beta from the halo model

abstract:
  We analyze scale dependence of redshift space bias $b$ and $\beta \equiv
\Omega_m^{0.6}/b$ in the context of the halo model. We show that linear bias is
a good approximation only on large scales, for $k<0.1h$Mpc$^{-1}$. On
intermediate scales the virial motions of the galaxies cause a suppression of
the power spectrum relative to the linear one, which differs from the same
effect in dark matter. This suppression can potentially mimic the effect of
massive neutrinos and the degeneracy can only be broken if the power spectrum
is measured for $k \ll 0.1h$Mpc$^{-1}$. Different methods to determine $\beta$
converge for $k<0.1h$Mpc$^{-1}$, but give drastically different results on
smaller scales, which explains some of the trends observed in the real data. We
also asses the level of stochasticity by calculating the cross-correlation
coefficient between the reconstructed velocity field divergence and the
galaxies and show that the two fields decorrelate for $k>0.1h$Mpc$^{-1}$. Most
problematic are galaxies predominantly found in groups and clusters, such as
bright, red or elliptical galaxies, where we find poor convergence to a
constant bias or $\beta$ even on large scales.


title:
The strength and width of Fe Kalpha lines in Seyferts and their
  correlations with the X-ray slope

abstract:
  We study properties of Fe K lines of a large sample of Seyfert 1s observed by
ASCA. Fits with power laws and Gaussian lines yield the average linewidth and
equivalent width of 0.22+-0.03 keV and 0.13+-0.01 keV, respectively. Thus, the
typical lines are weak and narrow. We then obtain the average line profile of
all our spectra, and find it to consist of a narrow core and blue and red
wings, with the red wing being much weaker than that of, e.g., MCG-6-30-15. We
obtain three average spectra of Seyferts grouped according to the hardness, and
find the equivalent width of the core (originating in a remote medium) to be
about 50 eV in all three cases. The wings are well fitted by a broad line from
a disc with strong relativistic effects. Its equivalent width correlates with
the slope, increasing from ~70 eV for the hardest spectrum to ~120 eV for the
softest one. The inner disc radius decreases correspondingly from ~40 to ~10
gravitational radii, and the fitted disc inclination is ~45 degrees. The
obtained correlation between the slope and the strength of the broad Fe K line
is found to be consistent with the previously found correlation of the slope
and Compton reflection.


title: The ISM of Low Surface Brightness Galaxies

abstract:
  Using Monte Carlo radiative transfer techniques, we model the dust content of
the edge-on low surface brightness (LSB) galaxy UGC 7321 and explore the
effects of dust on its disk color gradients. Dust alone cannot explain the
large radial disk color gradients observed in this galaxy and we find that a
significant fraction (~50%) of the dust in UGC 7321 appears to be contained in
a clumped medium, indicating that at least some LSB galaxies can support a
modest multi-phase ISM structure. In addition, we report some of the first
direct detections of molecular gas (CO) in LSB galaxies.


title: Stellar models and Hyades: the Hipparcos test

abstract:
  We compare theoretical stellar models for Main Sequence (MS) stars with the
Hipparcos database for the Hyades cluster to give a warning against the
uncritical use of available theoretical scenarios and to show how formal MS
fittings can be fortuitous if not fictitious. Moreover, we find that none of
the current theoretical scenarios appears able to account for an observed
mismatch between theoretical predictions and observations of the coolest Hyades
MS stars. Finally, we show that current theoretical models probably give too
faint He burning luminosities unlike the case of less massive He burning
models, with degenerate progenitors, which have been suggested to suffer the
opposite discrepancy.


title: The Case Against Cosmology

abstract:
  It is argued that some of the recent claims for cosmology are grossly
overblown. Cosmology rests on a very small database: it suffers from many
fundamental difficulties as a science (if it is a science at all) whilst
observations of distant phenomena are difficult to make and harder to
interpret. It is suggested that cosmological inferences should be tentatively
made and sceptically received.


title: A detailed two-dimensional stellar population study of M32

abstract:
  We present Two-Dimensional Spectroscopy of the 9x12 arcsec^2 central region
of M32 obtained with the 2D_FIS fibre spectrograph installed at the William
Herschel Telescope. From these spectra line strength maps have been
reconstructed for about 20 absorption lines, mostly belonging to the Lick
system. We find good agreement with long-slit line strength profiles in the
literature. In contrast with previous studies, indices were azimuthally
averaged along continuum isophotes of M32. A remarkable result is that no
gradients are presented in the spectral indices. So, we have fitted the mean
values of each spectral index and central colours to the models of Vazdekis et
al. (1996) and Worthey (1994), finding that an intermediate age (~4 Gyr) and
metallicity similar to solar (Z=0.02) are the best fitted values for the
innermost region of M32.


title: Viscosity Mechanisms in Accretion Disks

abstract:
  The self-sustained turbulence which develops in magnetized accretion disks is
suppressed in the weakly-ionized, quiescent disks of close binary stars.
Because accretion still proceeds during quiescence, another viscosity mechanism
operates in these systems. An anticorrelation of the recurrence times of SU UMa
dwarf novae with their mass ratio supports spiral waves or shock-waves tidally
induced by the companion star as the main process responsible for accretion in
the quiescent disks. Other weakly-ionized gaseous disks in systems lacking a
massive companion have to rely on yet another transport mechanism or they could
be essentially passive.


title: Imaging the secondary stars in cataclysmic variables

abstract:
  The secondary, Roche-lobe filling stars in cataclysmic variables (CVs) are
key to our understanding of the origin, evolution and behaviour of this class
of interacting binary. We review the basic properties of the secondary stars in
CVs and the observational and analysis methods required to detect them. We then
describe the various astro-tomographic techniques which can be used to map the
surface intensity distribution of the secondary star, culminating in a detailed
explanation of Roche tomography. We conclude with a summary of the most
important results obtained to date and future prospects.


title: A Submillimeter Selected Quasar in the Field of Abell 478

abstract:
  We report the discovery of a z=2.83 quasar in the field of the cooling flow
galaxy cluster Abell 478. This quasar was first detected in a submm survey of
star forming galaxies at high redshifts, as the brightest source. We discuss
the optical spectrum and far-IR spectral energy distribution (SED) of this
object.


title:
VLT spectroscopy of GRB 990510 and GRB 990712; probing the faint and
  bright end of the GRB host galaxy population

abstract:
  We present time-resolved optical spectroscopy of the afterglows of the
gamma-ray bursts GRB 990510 and GRB 990712. Through the identification of
several absorption lines in the first epoch GRB 990510 spectrum, we determine
the redshift for this burst at z >= 1.619. No clear emission lines are
detected. The strength of the MgI feature is indicative of a dense environment,
most likely the host galaxy of GRB 990510. Although the host is extremely faint
(V >~ 28), the GRB afterglow allows us to probe its interstellar medium and -
in principle - to measure its metallicity. The optical spectrum of GRB 990712
(whose host galaxy is the brightest of the known GRB hosts at cosmological
redshifts), shows clear features both in emission and absorption, at a redshift
of z = 0.4331 +/- 0.0004. On the basis of several line emission diagnostic
diagrams, we conclude that the host galaxy of GRB 990712 is most likely an HII
galaxy. We derive a unreddened [OII] star formation rate of 2.7 +/- 0.8
Msun/yr. Correcting for the measured extinction intrinsic to the host galaxy
(A(V) = \gpm{3.4}{2.4}{1.7}), this value increases to \gpm{35}{178}{25}
Msun/yr. The [OII] equivalent width, compared to that of field galaxies at z <=
1, also suggests that the host of GRB 990712 is vigorously forming stars. We
employ the oxygen and Hbeta emission-line intensities to estimate the global
oxygen abundance for the host of GRB 990712: log(O/H) = -3.7 +- 0.4, which is
slightly below the lowest metallicity one finds in nearby spiral galaxies. For
both GRBs we study the time evolution of the absorption lines, whose equivalent
width might be expected to change with time if the burst resides in a dense
compact medium. We find no evidence for a significant change in the MgII width.


title: A Deep, Wide-Field H-alpha Survey of Nearby Clusters of Galaxies

abstract:
  We present a progress report on an ongoing H-alpha imaging survey of nearby
clusters of galaxies. Four clusters have been surveyed to date: A1367, A1656,
A347 and A569. A preliminary comparison of H-alpha luminosity functions
obtained from our imaging survey with those from the prism survey reveals a
significant level of incompleteness in the latter. This in turn is due to a
combination of insensitivity to low-luminosity emission-line galaxies and to
brighter galaxies with weak extended H-alpha emission. The survey has also
revealed a unique population of clustered dwarf emission-line objects which may
be the results of recent tidal encounters between larger gas-rich galaxies.


title: SN 1997bs in M66: Another Extragalactic Eta Carinae Analog?

abstract:
  We report on SN 1997bs in NGC 3627 (M66), the first supernova discovered by
the Lick Observatory Supernova Search using the 0.75-m Katzman Automatic
Imaging Telescope (KAIT). Based on its early-time optical spectrum, SN 1997bs
was classified as Type IIn. However, from the BVRI light curves obtained by
KAIT early in the supernova's evolution, and F555W and F814W light curves
obtained from Hubble Space Telescope archival WFPC2 images at late times, we
question the identification of SN 1997bs as a bona fide supernova. We believe
that it is more likely a super-outburst of a very massive luminous blue
variable star, analogous to Eta Carinae, and similar to SN 1961V in NGC 1058
(Filippenko et al. 1995 [AJ, 110, 2261]) and SN 1954J (``Variable 12'') in NGC
2403 (Humphreys & Davidson 1994 [PASP, 106, 1025]). The progenitor may have
survived the outburst, since the SN is seen in early 1998 at m_F555W=23.4,
about 0.5 mag fainter than the progenitor identified by Van Dyk et al. (1999,
[AJ, 118, 2331]) in a pre-discovery image. Based on analysis of its environment
in the Hubble Space Telescope images, the progenitor was not in an H II region
or association of massive stars. The recent discovery of additional objects
with properties similar to those of SN 1997bs suggests that the heterogeneous
class of Type IIn supernovae consists in part of ``impostors.''


title: Clusters of Galaxies at High Redshift: The LMT/GTM Perspective

abstract:
  The lack of reliable cluster samples at intermediate and high redshift has
motivated many optical/infrared and X-ray cluster searches. The motivation of
such searches is well justified: the abundance of massive collapsed regions
gives a direct constraint on Omega(matter). Alternatively, the
Sunyaev-Zeldovich effect (SZE) offers a robust method for the detection of
clusters which is, almost, independent of redshift. In this paper we comment on
the possibility of mapping the SZE at high resolution in the millimeter regime
using the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT/GTM) and
the bolometer array BOLOCAM. The construction of the LMT/GTM facility is
underway atop Cerro La Negra (latitude=18deg 59min; height=4600 m) in Mexico.


title: Photometric Properties of Low-Redshift Galaxy Clusters (LOCOS)

abstract:
  A comprehensive multicolor survey was undertaken to investigate global
optical properties of Abell clusters of galaxies. This survey was christened
the "Low-Redshift Cluster Optical Survey" (LOCOS). LOCOS was devised to search
for patterns of galaxy evolution induced by the environment. The generated data
base contains accurate deep CCD photometric measurements (Kron-Cousins R,,B and
I) for a sample of 46 low-redshift (0.04 <= z <= 0.18) Abell clusters. This is
one of the few large surveys that included the contribution due to dwarf
galaxies (about 5.5 mag deeper than the R characteristic magnitude (M*); Ho=50
km/s/Mpc, qo=0). Due to space restrictions only the main results concerning the
variations at the bright-end of the luminosity function (LF) are presented
here. Other results are presented elsewhere (Lopez-Cruz & Yee 2000a,b). We have
detected clear variations at both the bright end and the faint end of the LF.
The nature of the variations at the bright end revealed that poor cD clusters
have dimmer M*. We can explain these variations as a result of dynamical
friction. On the other hand, non-cD clusters seem to have unaffected LFs. A
third class termed as binary clusters seems to be a transition class that might
have resulted from cluster-cluster mergers.


title: Dwarf Galaxies in Clusters: the Effects of a Violent Environment

abstract:
  Recent observations suggest that dwarf galaxies pervade the universe, for
they have been encountered in large numbers in all the environments. However,
we present evidence that suggests dwarf galaxies may be subject to strong
dynamical processes in high density environments, the combined effects of
multiple encounters and the tidal effects due to the potential well of rich
clusters could result in the effective disruption of dwarf galaxies in the
clusters' central regions. Alternatively, the lack of dwarf galaxies in rich
environments has been interpreted in terms of a "density-morphology relation":
dwarf galaxies prefer low density environments (Phillipps et al. 1998). We
argue that such an explanation cannot account for the relationship between the
cD halo luminosity and the gas mass in the ICM, whereas the dwarf disruption
scenario proposed by Lopez-Cruz et al. (1997) addresses this naturally.


title:
The Proper Motion, Parallax, and Origin of the Isolated Neutron Star RX
  J185635-3754

abstract:
  The isolated neutron star RX J185635-3754 is the closest known neutron star
to the Sun. Based on HST WFPC2 obervations over a 3 year baseline, I report its
proper motion (332 +/- 1 mas/yr at a position angle of 100.3 +/- 0.1 degrees)
and parallax (16.5 +/- 2.3 mas; 61 pc). This proper motion brings the neutron
star from the general vicinity of the Sco-Cen OB association. For an assumed
neutron star radial velocity between -55 and -60 km/s, the runaway O star zeta
Oph, the Upper Sco OB association, and the neutron star come into spatial
coincidence between 0.9 and 1.0 million years ago. RX J185635-3754 may be the
remnant of the original primary of the zeta Oph system. If so, the space
velocity suggests that the neutron star received a kick of about 200 km/s at
birth.


title: Scaling properties of the redshift power spectrum: theoretical models

abstract:
  We report the results of an analysis of the redshift power spectrum
$P^S(k,\mu)$ in three typical Cold Dark Matter (CDM) cosmological models, where
$\mu$ is the cosine of the angle between the wave vector and the line-of-sight.
Two distinct biased tracers derived from the primordial density peaks of
Bardeen et al. and the cluster-underweight model of Jing, Mo, & B\"orner are
considered in addition to the pure dark matter models. Based on a large set of
high resolution simulations, we have measured the redshift power spectrum for
the three tracers from the linear to the nonlinear regime. We investigate the
validity of the relation - guessed from linear theory - in the nonlinear regime
$$ P^S(k,\mu)=P^R(k)[1+\beta\mu^2]^2D(k,\mu,\sigma_{12}(k)), $$ where $P^R(k)$
is the real space power spectrum, and $\beta$ equals $\Omega_0^{0.6}/b_l$. The
damping function $D$ which should generally depend on $k$, $\mu$, and
$\sigma_{12}(k)$, is found to be a function of only one variable
$k\mu\sigma_{12}(k)$. This scaling behavior extends into the nonlinear regime,
while $D$ can be accurately expressed as a Lorentz function - well known from
linear theory - for values $D > 0.1$. The difference between $\sigma_{12}(k)$
and the pairwise velocity dispersion defined by the 3-D peculiar velocity of
the simulations (taking $r=1/k$) is about 15%. Therefore $\sigma_{12}(k)$ is a
good indicator of the pairwise velocity dispersion. The exact functional form
of $D$ depends on the cosmological model and on the bias scheme. We have given
an accurate fitting formula for the functional form of $D$ for the models
studied.


title: HST as a powerful astrometric tool for pulsar astronomy

abstract:
  Given their intrinsic faintness, isolated neutron stars represent an elusive
target for optical astronomy. Up to date, an optical counterpart has been
identified only for a very tiny fraction of the overall population of more than
1000 radio pulsars. The HST contributions to the optical studies of isolated
neutron stars have been recently reviewed by Mignani et al. (2000) and by
Caraveo et al. (these proceedings). Here, we review its specific contribution
in the field of pulsar astrometry and kinematics.


title:
HST as a reliable astrometric tool for pulsar astronomy: the cases of
  the Vela and Geminga pulsars

abstract:
  The quest for the distance of the Vela and Geminga pulsars yielded, so far, a
set of four WFPC2 images for each object. The availability of couples of images
taken at the same period of the year, thus affected by the same parallactic
displacement, prompted us to use Vela and Geminga as test cases to assess the
reliability of HST astrometry.


title: SNR0540-69 -the Crab twin- revisited: Chandra vs. HST

abstract:
  High resolution images of the Crab-like SNR SNR0540-69 have been recently
obtained by the HRC, on board the Chandra X-ray Observatory, and by the FORS1
instrument, attached to ESO/VLT1. A detailed comparison of these images with an
archival Planetary Camera one will be presented.


title: Canonical Timing and Spectral Behavior of LMC X-3 in the Low/Hard State

abstract:
  We present results from three observations with the Rossi X-ray Timing
Explorer (RXTE) of LMC X-3, obtained while the source was in an extended
'low/hard' state. The data reveal a hard X-ray spectrum which is well fit by a
pure power law with photon index Gamma=1.69+/-0.02, with a source luminosity at
50 kpc of 5-16x10^{36}erg/s (2--10 keV). Strong broad-band (0.01-100 Hz) time
variability is also observed, with fractional rms amplitude 40+/-4%, plus a
quasi-periodic oscillation (QPO) peak at 0.46+/-0.02 Hz with rms amplitude
\~14%. This is the first reported observation in which the full canonical
low/hard state behavior (pure hard power law spectrum combined with strong
broad-band noise and QPO) for LMC X-3 is seen. We reanalyze several archival
RXTE observations of LMC X-3 and derive consistent spectral and timing
parameters, and determine the overall luminosity variation between high/soft
and low/hard states. The timing and spectral properties of LMC X-3 during the
recurrent low/hard states are quantitatively similar to that typically seen in
the Galactic black hole candidates.


title: Morphological classification of high redshift galaxies

abstract:
  We present GASPHOT, a tool for automated surface photometry and morphological
classification of galaxies in deep and wide fields. The requirements for any
such tool are reviewed, and its use for the classification of high-z galaxies
is presented. In the case if HDF-like images, for galaxies having a magnitude
ranging from 24 to 27.5, the uncertainties on the photometric parameters
derived from GASPHOT are respectively 0.02-0.1 on magnitude, 0.03 on the
logarithm of the scale length, 0.02-0.5 on the Sersic index n used to classify
the surface brightness profile of the galaxies. A comparison with the results
achieved using Sextractor is presented.


title: The Ultra-Luminous IR Galaxy Population

abstract:
  We summarize results from an on-going Hubble Space Telescope (HST) survey of
a large sample of ULIRGs (Ultra-Luminous IR Galaxies). New ground-based
multi-fiber spectroscopic observations are now being obtained to complement the
HST data and to assist in the interpretation of these complex objects.


title:
Southern Hemisphere Observations of a $10^{18}$eV Cosmic Ray Source Near
  the Direction of the Galactic Centre

abstract:
  We report on an analysis of data from the southern hemisphere SUGAR cosmic
ray detector. We confirm the existence of an excess of $10^{18}$eV cosmic rays
from a direction close to the Galactic Centre, first reported by the AGASA
group. We find that the signal is consistent with that from a point source, and
we find no evidence for an excess of cosmic rays coming from the direction of
the Galactic Centre itself.


title: Secondary CMB anisotropies from the kinetic SZ effect

abstract:
  We present an analytic model, based on previous works which tackled the
reionization history of the universe, which allows us to describe the
generation of the secondary CMB anisotropies due to the kinetic SZ effect. We
take into account the "patchy pattern" of reionization (HII bubbles), the
cross-correlations of these ionized regions, the small-scale fluctuations of
the matter density field and the contribution from collapsed objects. For an
open universe, we find that the power-spectrum $l(l+1)C_l/(2\pi)$ exhibits a
plateau of height $10^{-13}$ in the range $10^3 < l < 10^6$. We find that for
large wavenumbers $l > 10^4$ the signal is dominated by the contribution from
collapsed halos while for $l < 10^4$ it is governed by the large-scale
correlations of HII bubbles. This implies that one cannot discriminate
reionization by stars from a quasar-driven scenario since the size of ionized
regions never dominates the behaviour of the anisotropies. Moreover, the
secondary CMB anisotropies arise from a broad range of redshifts (7.5<z<10 for
the IGM and 0<z<7 for galactic halos). The signal expected in our model might
bias the cosmological parameter estimation from CMB experiments such as Planck
and could be detected by future mm-wavelength interferometers (e.g., ALMA).


title: Maximum Galactic Disks vs. Hot Dark Halos

abstract:
  A series of arguments is presented for heavy galaxy disks not only in the
optical regions, but also in the dark matter dominated regions of spirals. We
are testing this possibility with extreme maximum disk N-body models without
any conventional spheroidal dark halo.


title: Constraining our Universe with X-ray & Optical Cluster Data

abstract:
  We have used recent X-ray and optical data in order to impose some
constraints on the cosmology and cluster scaling relations. Generically two
kind of hypotheses define our model. First we consider that the cluster
population is well described by the standard Press-Schechter (PS) formalism,
and second, these clusters are supposed to follow scaling relations with mass:
Temperature-Mass (T-M) and X-ray Luminosity-Mass (L_x - M). As a difference
with many other authors we do not assume specific scaling relations to model
cluster properties such as the usual $T-M$ virial relation or one observational
determination of the $L_x-T$ relation. Instead we consider general free
parameter scaling relations. With the previous model (PS plus scalings) we fit
our free parameters to several X-ray and optical data with the advantage over
many other works that we consider all the data sets at the same time. This
prevents us from being inconsistent with some of the available observations.
Among other interesting conclusions, we find that only low-density universes
are compatible with all the data considered and that the degeneracy between
$\Omega_m$ and $\sigma_8$ is broken. Also we obtain interesting limits on the
parameters characterizing the scaling relations.


title:
Molecular cloud complexes in detail: Interferometric observations of
  GMCs in M31

abstract:
  We have accumulated 12CO(1-0) and (2-1) data of several GMCs in M31 using the
Plateau de Bure Interferometer. The sample covers a range of 5 to 18 kpc
galactocentric distance and various physical conditions. The spatial resolution
attains values down to 3 pc. All GMCs investigated have been resolved into
several components, also seemingly quiescent clouds and not only the cases
where already the survey positions show obvious multiple-peaked spectra. Such
kinematically disjunct emission is however spatially coincident in the small
volume of the interferometer beam in M31, which strongly favours local effects
as the cause of the velocity splitting. This is well consistent with the
observed absence of strong streaming motions in the survey data. The nature of
the sometimes strong separation in velocity space needs further investigation.
The complete data set (i.e. including the large-scale survey) yields a uniquely
complete view of the molecular gas which allows to investigate the conditions
for star formation in detail and helps to establish guide lines for the
derivation of the properties of molecular gas.


title:
Hard X-rays from Type II bursts of the Rapid Burster and its transition
  toward quiescence

abstract:
  We report on 4 BeppoSAX Target Of Opportunity observations of MXB 1730-335,
the Rapid Burster (RB), made during the 1998 February-March outburst. In the
first observation, approximately 20 days after the outburst peak, the X-ray
light curve showed Type II bursts at a rate of 43 per hour. Nine days later,
during the second BeppoSAX pointing, only 5 Type II bursts were detected at the
beginning of the observation. During the third pointing no X-ray bursts were
detected and in the fourth and final observation the RB was not detected at
all. Persistent emission from the RB was detected up to 10 keV during the first
three pointings. The spectra of the persistent and bursting emissions below 10
keV were best fit with a model consisting of two blackbodies. An additional
component (a power law) was needed to describe the 1-100 keV bursting spectrum
when the persistent emission was subtracted. To our knowledge, this is the
first detection of the RB beyond 20 keV. We discuss the evolution of the
spectral parameters for the bursting and persistent emission during the
outburst decay. The light curve, after the second BeppoSAX pointing, showed a
steepening of the previous decay trend, and a sharper decay rate leading to
quiescence was observed with BeppoSAX in the two subsequent observations. We
interpret this behaviour as caused by the onset of the propeller effect.
Finally, we infer a neutron star magnetic field B ~ 4 10^8 Gauss.


title:
Depletion of background galaxies due to the cluster lens CL0024+1654: U
  and R band observations

abstract:
  We have obtained U and R band observations of the depletion of background
galaxies due to the gravitational lensing of the galaxy cluster CL0024+1654
(z=0.39). The radial depletion curves show a significant depletion in both
bands within a radius of 40''-70'' from the cluster center. This is the first
time depletion is detected in the U band. This gives independent evidence for a
break in the slope of the U band luminosity function at faint magnitudes. The
radially averaged R band depletion curve is broader and deeper than in the U
band. The differences can be attributed to the wavelength dependence of the
slope of the luminosity function and to the different redshift distribution of
the objects probed in the two bands. We estimate the Einstein radius of a
singular isothermal sphere lens model using maximum likelihood analysis.
Adopting a slope of the number counts of 0.2 and using the background density
found beyond 150'' from the cluster center we find an Einstein radius of
17''+/-3'' and 25''+/-3'' in the U and R band, respectively. When combined with
the redshift of the single background galaxy at z=1.675 seen as four giant arcs
around 30'' from the cluster center, these values indicate a median redshift in
the range 0.7 to 1.1 for the U_AB > 24 mag and R_AB > 24 mag populations.


title: Using Perturbative Least Action to Reconstruct the Local Group

abstract:
  In this paper, we apply the Perturbative Least Action Method to model the
Local Group of galaxies for various Cosmological models. We show that though
the galaxy masses are theoretically good discriminators of $\Omega_M$ given
some observed MW and M31 separation and radial velocity, current estimates of
the masses are insufficient to make any cosmological claims. We then discuss
additional complications to expand this analysis.


title: Neon abundances in normal late-B and mercury-manganese stars

abstract:
  We make new Non-LTE calculations to deduce abundances of neon from
visible-region echelle spectra of selected Ne I lines in 7 normal stars and 20
HgMn stars. We find that the best strong blend-free Ne line which can be used
at the lower end of the Teff range is 6402 A, although several other
potentially useful Ne I lines are found in the red region of the spectra of
these stars. The mean neon abundance in the normal stars (log A =8.10) is in
excellent agreement with the standard abundance of neon (8.08). However, in
HgMn stars, neon is almost universally underabundant, ranging from marginal
deficits of 0.1-0.3 dex to underabundances of an order of magnitude or more. In
many cases, the lines are so weak that only upper limits can be established.
The most extreme example found is upsilon Her with an underabundance of at
least 1.5 dex. These underabundances are qualitatively expected from radiative
acceleration calculations, which show that Ne has a very small radiative
acceleration in the photosphere and is expected to undergo gravitational
settling if mixing processes are sufficiently weak, and there is no strong
stellar wind. According to the theoretical predictions of Landstreet et al.
(1998), the low Ne abundances place an important constraint on the intensity of
such stellar winds, which must be less than $10^-14 M_sun per yr if they are
non-turbulent.


title: H_0 from gravitational lenses: recent results

abstract:
  The 0th, 1st and 2nd derivatives of a ``Fermat potential'' give the three D's
of gravitational lensing: delay, deflection and distortion. Observations of
these delays, deflections and distortions for doubly and quadruply imaged
quasars give estimates of Hubble's constant, H_0. The single largest
contribution to the uncertainty in H_0 arises from the difficulty in
constraining the degree of central concentration of the lensing potential.
Fortunately, astronomers have spent a good deal of effort over the past quarter
century addressing just this question. If galaxies at z=0.5 are like nearby
galaxies, the associated systematic uncertainty in H_0 is less than 10%. The
expected lens-to-lens scatter is 20%. Results from three particularly well
constrained systems are reported.


title: The Orbital Period of Intermediate Polar 1WGA J1958.2+3232

abstract:
  The detection of the orbital period of 4.36his reported for the new
Intermediate Polar 1 WGA 1958.2+3232. The orbital period was derived from
time-resolved photometric and spectral observations. We also confirmed the 733
sec spin period of the White Dwarf consistent with the X-ray pulsations and
were able to distinguish the beat period in the light curve. Strong modulations
with orbital period are detected in the emission spectral lines from spectral
observations. They show the presence of a bright hot spot on the edge of the
accretion disk.
  The parameters of this recently discovered Intermediate Polar are determined.


title: Do High-Velocity Clouds Really Fuel Galactic Star Formation?

abstract:
  Tantalizing evidence has been presented supporting the suggestion that a
large population of extragalactic gas clouds permeates the Local Group, a
population which has been associated with the Galactic High-Velocity Clouds
(HVCs). We comment on both the strengths and weaknesses of this suggestion,
informally referred to as the Blitz/Spergel picture. Theoretical predictions
for the spatial and kinematic distributions, metallicities, distances, and
emission properties of Blitz/Spergel HVCs will be confronted with extant
observational data.


title: The Distribution of [OII] Equivalent Widths of LCRS Galaxies

abstract:
  We present a simple functional form for the joint distribution of R-band
luminosity and [OII] 3727 emission-line equivalent widths of galaxies, and show
that this form is a good fit to the galaxies in the Las Campanas Redshift
Survey. We find a relationship between [OII] equivalent width W and R-band
luminosity L_R of the approximate form: <W> \approx (10 \AA)
(L_R/L_{R,*})^{-1/2}, where L_{R,*} is the characteristic luminosity in the
Schechter function. Because this joint distribution yields information about
the relationship between stellar mass in a galaxy and its recent star-formation
rate, it can be useful for testing theories of galaxy formation. Furthermore,
understanding this joint distribution locally will make it easier to interpret
the evolution of [OII] emission-line widths to higher redshifts.


title:
Spin induced galaxy alignments and their implications for weak lensing
  measurements

abstract:
  Large scale correlations in the orientations of galaxies can result from
alignments in their angular momentum vectors. These alignments arise from the
tidal torques exerted on neighboring proto-galaxies by the smoothly varying
shear field. We compute the predicted amplitude of such ellipticity
correlations using the Zel'dovich approximation for a realistic distribution of
galaxy shapes. Weak gravitational lensing can also induce ellipticity
correlations since the images of neighboring galaxies will be distorted
coherently. On comparing these two effects that induce shape correlations, we
find that for current weak lensing surveys with a median redshift of z_m = 1,
the intrinsic signal is of order 1 - 10 percent of the measured signal.
However, for shallower surveys with z_m < 0.3, the intrinsic correlations
dominate over the lensing signal. The distortions induced by lensing are
curl-free, whereas those resulting from intrinsic alignments are not. This
difference can be used to disentangle these two sources of ellipticity
correlations.


title: N-body simulations of warped galaxies

abstract:
  Two methods generating warped galaxies with N-body simulations are presented.
One uses an external potential as a disturber while the other is based on
material accretion. The results of both methods are compared. A particular
attention is given on the shape of the line of node (LON).


title:
A radio-continuum and photoionization-model study of the two planetary
  nebulae in the Sagittarius dwarf galaxy

abstract:
  Radio continuum observations at 1.4, 4.8 and 8.6 GHz of the two Planetary
Nebulae (PNe) in the Sagittarius dwarf galaxy reveal the elongated shape of
Wray 16-423 and the extreme compactness of He 2-436. He 2-436 is confirmed as
subject to local dust extinction.
  Photoionization models for both PNe are obtained from two different codes,
allowing theoretical uncertainties to be assessed. Wray 16-423, excited by a
star of Teff 1.07x10^5K, is an ellipsoidal, matter-bounded nebula, except for a
denser sector. He 2-436, excited by a 7x10^4K star, includes two
radiation-bounded shells, with the inner one possibly corresponding to a
transitory event. Both stars are on the same (H-burning) evolutionary track of
initial mass (1.2+/-0.1) Msun and may be twins, with the PN ejection of Wray
16-423 having occured ~1500 years before He 2-436.
  The PN abundances re-inforce the common origin of the parent stars,
indicating almost identical depletions with respect to solar for O, Ne, Mg, S,
Cl, Ar, and K (-0.55+/-0.07 dex), large identical overabundances for He and
strong overabundances for carbon, particularly in He2-436. Excess nitrogen
makes Wray 16-423 nearly a Type I PN. These PNe provide a means to calibrate
both metallicity and age of the Sagittarius stellar population, and they
confirm that the youngest, most metal-rich population has an age of 5Gyr and a
metallicity of [Fe/H]=-0.55, in agreement with the slope of the red giant
branch. (Abridged abstract)


title: Dynamical models for dusty disk galaxies

abstract:
  Disk galaxies contain a large amount of interstellar dust, which affects the
projection of kinematic quantities. We investigate in detail the effects of
dust extinction on the mean projected velocity and the projected velocity
dispersion. We use our results to construct a general strategy to determine the
dynamical structure of disk galaxies, with the aim to constrain their mass
distribution and dynamical history.


title:
The HST snapshot survey of the B2 sample of low luminosity
  radio-galaxies: a picture gallery

abstract:
  A Hubble Space Telescope snapshot survey of the B2 sample of low luminosity
radio galaxies has, at present, produced V and I images of 41 objects. Together
with 16 images of B2 sources taken from the HST archive, there are now high
resolution optical data for 57 % of the sample. All host galaxies are luminous
ellipticals, except one which is a spiral galaxy, while another one turns out
to be a misidentification.
  We present an album of the images of the B2 radio galaxies observed so far,
and give a brief description of the optical morphology of the galaxies. Dust
features (in the form of disks, lanes or irregular patches) are seen in most of
the galaxies of the sample, 58 %. Compact optical cores are also very common
(18/57). A preliminary analysis has revealed the presence of an optical jet in
three objects, indicating they can be detected in a sizeable percentage in
these low luminosity radio sources. Brightness profiles of dust-free galaxies
are well represented by a Nuker law and all shows the existence of a resolved
shallow cusp.


title: Cosmological parameters from complementary observations of the Universe

abstract:
  We use observational data on the large scale structure (LSS) of the Universe
measured over a wide range of scales from sub-galactic up to horizon scale and
on the cosmic microwave background anisotropies to determine cosmological
parameters within the class of adiabatic inflationary models. We show that a
mixed dark matter model with cosmological constant ($\Lambda$MDM model) and
parameters $\Omega_m=0.37^{+0.25}_{-0.15}$,
$\Omega_{\Lambda}=0.69^{+0.15}_{-0.20}$, $\Omega_{\nu}=0.03^{+0.07}_{-0.03}$,
$N_{\nu}=1$, $\Omega_b=0.037^{+0.033}_{-0.018}$, $n_s=1.02^{+0.09}_{-0.10}$,
$h=0.71^{+0.22}_{-0.19}$, $b_{cl}=2.4^{+0.7}_{-0.7}$ (1$\sigma$ confidence
limits) matches observational data on LSS, the nucleosynthesis constraint,
direct measurements of Hubble constant, the high redshift supernova type Ia
results and the recent measurements of the location and amplitude of the first
acoustic peak in the CMB anisotropy power spectrum. The best model is $\Lambda$
dominated (65% of the total energy density) and has slightly positive
curvature, $\Omega=1.06$. The clustered matter consists in 8% massive
neutrinos, 10% baryons and 82% cold dark matter (CDM). The upper 2$\sigma$
limit on the neutrino content can be expressed in the form
$\Omega_{\nu}h^2/N_{\nu}^{0.64}\le0.042$ or, via the neutrino mass,
$m_{\nu}\le4.0$eV. The upper 1(2)$\sigma$ limit for the contribution of a
tensor mode to the COBE DMR data is T/S$<1(1.5)$. Furthermore, it is shown that
the LSS observations together with the Boomerang (+MAXIMA-1) data on the first
acoustic peak rule out zero-$\Lambda$ models at more than $2\sigma$ confidence
limit.


title: Search for High Proper Motion White Dwarfs

abstract:
  Recent results of microlensing surveys, show that 10-20% of the dark halo
mass of the Milky Way consists of compact objects. The masses of these compact
objects range from 0.1 to 1 solar mass. New theoretical cooling models for
white dwarfs, and the detection of faint blue high proper motion objects, imply
that ancient white dwarfs might make up part of this population. In this pilot
project, using data from the C and D patches of the ESO Imaging Survey and data
obtained at CTIO, we attempted to find such halo white dwarfs in the solar
neighbourhood. With a time baseline of approximately one year between data sets
and a limiting I-band magnitude of 23, we can find these high proper motion
objects up to distances of 85 parsecs. In the 2.5 square degrees studied so far
we have found three high proper motion candidates.


title: The evolution of the Milky Way monitored in the solar neighbourhood

abstract:
  In this review we concentrate on the dynamical evolution of the Milky Way as
monitored in the solar neighbourhood. The relevant data sets are presented and
discussed in detail. In the second part we review various mechanisms, which
drive the dynamical evolution.


title:
A relativistic calculation of super-Hubble suppression of inflation with
  thermal dissipation

abstract:
  We investigated the evolution of the primordial density perturbations
produced by inflation with thermal dissipation. A full relativistic analysis on
the evolution of initial perturbations from the warm inflation era to a
radiation-dominated universe has been developed. The emphasis is on tracking
the ratio between the adiabatic and the isocurvature mode of the initial
perturbations. This result is employed to calculate a testable factor: the
super-Hubble suppression of the power spectrum of the primordial perturbations.
We show that based on the warm inflation scenario, the super-Hubble suppression
factor, $s$, for an inflation with thermal dissipation is at least 0.5. This
prediction does not depend on the details of the model parameters. If $s$ is
larger than 0.5, it implies that the friction parameter $\Gamma$ is larger than
the Hubble expansion parameter $H$ during the inflation era.


title: Magnetic Fields in the Early Universe

abstract:
  This review concerns the origin and the possible effects of magnetic fields
in the early Universe. We start by providing to the reader with a short
overview of the current state of art of observations of cosmic magnetic fields.
We then illustrate the arguments in favour of a primordial origin of magnetic
fields in the galaxies and in the clusters of galaxies. We argue that the most
promising way to test this hypothesis is to look for possible imprints of
magnetic fields on the temperature and polarization anisotropies of the cosmic
microwave background radiation (CMBR). With this purpose in mind, we provide a
review of the most relevant effects of magnetic fields on the CMBR. A long
chapter of this review is dedicated to particle physics inspired models which
predict the generation of magnetic fields during the early Universe evolution.
Although it is still unclear if any of these models can really explain the
origin of galactic and intergalactic magnetic fields, we show that interesting
effects may arise anyhow. Among these effects, we discuss the consequences of
strong magnetic fields on the big-bang nucleosynthesis, on the masses and
couplings of the matter constituents, on the electroweak phase transition, and
on the baryon and lepton number violating sphaleron processes. Several
intriguing common aspects, and possible interplay, of magnetogenesis and
baryogenesis are also dicussed.


title: The minimum orbital period in thermal-timescale mass transfer

abstract:
  We show that the usual picture of supersoft X-ray binary evolution as driven
by conservative thermal-timescale mass transfer cannot explain the short
orbital periods of RX J0537.7-7034 (3.5 hr) and 1E 0035.4-7230 (4.1 hr).
Non-conservative evolution may produce such periods, but requires very
significant mass loss, and is highly constrained.


title:
Dynamical and content evolution of a sample of clusters from z~0 to
  z~0.5

abstract:
  In this paper, we present an analysis of the dynamics and segregation of
galaxies in rich clusters from z~0.32 to z~0.48 taken from the CFHT Optical
PDCS (COP) survey and from the CNOC survey (Carlberg et al. 1997). Our results
from the COP survey are based upon the recent observational work of Adami et
al. (2000) and Holden et al. (2000) and use new spectroscopic and photometric
data on six clusters selected from the Palomar Distant Cluster Survey (PDCS;
Postman et al. 1996). We have compared the COP and CNOC samples to the ESO
Nearby Abell Cluster Survey (ENACS: z~0.07). Our sample shows that the z<0.4
clusters have the same velocity dispersion versus magnitude, morphological type
and radius relationships as nearby Abell clusters. The z~0.48 clusters exhibit,
however, departures from these relations. Furthermore, there appears to be a
higher fraction of late-type (or bluer, e.g. Butcher and Oemler, 1984) galaxies
in the distant clusters compared to the nearby ones. The classical scenario in
which massive galaxies virialize before they evolve from late into early type
explain our observations. In such a scenario, the clusters of our sample began
to form before a redshift of ~0.8 and the late-type galaxy population had a
continuous infall into the clusters.


title: Optical photometry of the PSR B0656+14 and its neighborhood

abstract:
  We present the results of the broad-band photometry of the nearby middle-aged
radio pulsar PSR B0656+14 and its neighborhood obtained with the 6-meter
telescope of the SAO RAS and with the Hubble Space Telescope. The broad-band
spectral flux $F_\nu$ of the pulsar decreases with increasing frequency in the
near-IR range and increases with frequency in the near-UV range. The increase
towards UV can be naturally interpreted as the Rayleigh-Jeans tail of the soft
thermal component of the X-ray spectrum emitted from the surface of the cooling
neutron star. Continuation of the power-law component, which dominates in the
high-energy tail of the X-ray spectrum, to the IR-optical-UV frequencies is
consistent with the observed fluxes. This suggests that the non-thermal pulsar
radiation may be of the same origin in a broad frequency range from IR to hard
X-rays. We also studied 4 objects detected in the pulsar's 5" neighborhood.


title: The template type Ia supernova 1996X

abstract:
  UBVRIJ photometry and optical spectra of the Type Ia SN 1996X obtained at ESO
during a one-year-long observational campaign are presented, and supplemented
by late time HST photometry. Spectroscopically, SN 1996X appears to be a
`normal' SN Ia. The apparent magnitude at maximum was B=13.24 +/- 0.02, and the
colour B-V=0.00 +/- 0.03. The luminosity decline rate, Delta m_B(15) = 1.31 +/-
0.08, is close to average for a SN Ia. The best estimate of the galactic
extinction is A_B=0.30 +/- 0.05, and there is evidence that reddening within
the parent galaxy is negligible. Detailed comparison of the light and colour
curves of various `normal' SNe Ia shows that the assumption that multicolour
light curves can be described simply as a one-parameter family is not perfect.
Together with problems in the calibration of the templates, this may explain
the discrepancies in the distance modulus derived adopting different
calibrations of the absolute magnitude vs. light curve shape relations. Indeed
we found that M_B ranges from -19.08 to -19.48 and M-m range from 32.02 to
32.48 depending on the method used (Hamuy et al. 1996a,Phillips et al. 1999,
Riess et al. 1998a). Computations of model light curve and synthetic spectra
for both early- and late-times, confirm that 1996X is a normal Type Ia SN and
that a satisfactory fit can be obtained using a W7 progenitor structure only if
we adopt the short distance. A larger distance would imply a too large Ni mass
for this fainter than average SNIa.


title: Searching for Tidal Tails in Galactic Dwarf Spheroidal Satellites

abstract:
  We present preliminary results of a long-term project to investigate the
process of accretion and tidal disruption of dSph satellites in the Galactic
halo and, in particular, to search for new tidal tails in a sample of nearby
dSph satellites of the Milky Way. Here we present our finding of extra-tidal
debris in the Ursa Minor dS ph and discuss the detection by the Sloan Digitized
Sky Survey team of what could be a tidal stream associated to the Sagittarius
dSph.


title:
Submillimetre sources in rich cluster fields - source counts, redshift
  estimates, and cooling flow limits

abstract:
  Recent submillimetre surveys have revealed a population of dusty, high
redshift sources of great cosmological significance for understanding
dust-enshrouded star formation in distant galaxies, and for determining the
origin of the far-IR background. In this paper, we analyze nine rich cluster
fields mapped at 850 and 450 microns with the SCUBA array on the James Clerk
Maxwell telescope. Lensing models of the clusters are developed in order to
derive accurate source counts for our sample. VLA maps of the same clusters are
used to help constrain the redshift distribution of our SCUBA detections.
Implications for high redshift galaxies and for the far-IR background are
discussed. We also provide limits on distributed dust produced by cooling flows
in these clusters.


title: Gravitational Lensing by Galaxy Groups in the Hubble Deep Field

abstract:
  We investigate strong lensing of galaxies in the Hubble Deep Field by
foreground groups and clusters of galaxies with masses from $10^{13}$ to
$10^{15} \MSun$. Over this mass range, groups with the profile of Navarro,
Frenk, & White (1995) are less efficient than singular isothermal spheres at
producing multiple images of galaxies, by factors of $5 \times 10^{- 2}$ to
$10^{- 3}$. This difference highlights the sensitivity of the lensing cross
section to the central density profile. Nonetheless, with either profile we
find that the expected number of galaxies lensed by groups in the Hubble Deep
Field is at most $\lesssim 1$, consistent with the lack of clearly identified
group lens systems.


title: Star Formation and the ISM in Dwarf Galaxies

abstract:
  High spatial and spectral resolution observations of the atomic interstellar
medium in nearby dwarf galaxies reveal evidence for warm and cold neutral gas,
just like the phases in our own Galaxy. The cold or quiescent phase (about 20%
of the HI in the galaxies studied, except for LGS 3) seems to be associated
with star formation activity--- it may mark the regions where the conditions
are right for star formation. These results help to explain the patterns of
star formation activity which are seen in color-magnitude data for the dwarf
irregulars.


title: Molecular Gas in Elliptical Galaxies

abstract:
  The distribution and kinematics of the molecular gas in elliptical galaxies
give information on the origin and history of the gas and the rate of star
formation activity in ellipticals. I describe some preliminary results of a
survey which will more than double the number of elliptical galaxies with
resolved molecular distributions.


title: A simple model of the hierarchical formation of galaxies

abstract:
  We develop a simple, fast and predictive model of the hierarchical formation
of galaxies which is in quantitative agreement with observations. Comparing
simulations with observations we place constraints on the density of the
universe and on the power spectrum of density fluctuations.


title: A vorton gun

abstract:
  In about half of all near-cusp events in superconducting cosmic strings with
chiral currents (and probably with general currents as well), the string
intersects itself near the cusp. Intercommutation causes the conversion of the
string near the cusp into a vorton (in the chiral case) with very high Lorentz
boost. We demonstrate how to analyze the cusp shape in a Lorentz frame that
makes the motion simple, by the use of a 5-dimensional procedure, and analyze
the resulting production of vortons.


title: Star Formation in Galaxies between 0.7 < z < 1.8

abstract:
  We present an analysis of the star formation rate in galaxies between
0.7<z<1.8 using Near Infrared Camera and Multi-Object Spectrograph (NICMOS)
grism spectral observations. We detect 163 galaxies in an area of ~4.4 square
arcminutes, 37 of which show possible H-alpha emission. We extend the observed
H-alpha luminosity function (LF) in this redshift range to luminosities a
factor of two fainter than earlier work, and are consistent in the region of
overlap. Using the H-alpha LF, we estimate a star formation rate (SFR) density
in this redshift range of 0.166 M_sun/yr/Mpc^3 (H0=75 km/s/Mpc), consistent
with other estimates based on emission lines, and supporting the order of
magnitude increase in SFR density between z=0 and z=1. Our measurement of SFR
density is a factor of ~2-3 greater than that estimated from UV data,
comparable to the factor observed locally, implying little evolution in the
relative extinctions between UV and H-alpha out to z~1.3.


title: Does Dark Matter Exist?

abstract:
  The success of the Lambda-CDM model on large scales does not extend down to
galaxy scales. We list a dozen problems of the dark matter hypothesis, some of
which arise in specific models for the formation of structure in the universe,
while others are generic and require fine tuning in any dark matter theory.
Modifications to the theory, such as adding properties to the DM particles
beyond gravitational interactions, or simply a better understanding of the
physics of galaxy formation, may resolve some problems, but a number of
conspiracies and correlations are unlikely to yield to this approach. The
alternative is that mass discrepancies result from of a non-Newtonian law of
gravity, a hypothesis which avoids many of the more intractable problems of
dark matter. A modified law of gravity is not without formidable difficulties
of its own, but it is no longer obvious that they are any more daunting than
those facing DM.


title: Galactic Superwinds at Low and High Redshift

abstract:
  In this contribution I summarize our current knowledge of the nature and
significance of starburst-driven galactic superwinds. These flows are driven
primarily by the kinetic energy supplied by supernovae. Superwinds are complex,
multiphase phenomena requiring a panchromatic observational approach. They are
ubiquitous in galaxies in which the global star-formation rate per unit area
exceeds roughly 10$^{-1}$ M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$ (a condition
satisfied by local starbursts and high-z Lyman Break galaxies). Data on X-ray
emission, optical line-emission, and optical/UV interstellar absorption-lines
together imply that the mass outflow rates are comparable to the
star-formation-rates and that the conversion of kinetic energy from supernovae
to superwind is quite efficient ($\sim$ 30 to 100%). Measured/inferred outflow
speeds range from a few $\times 10^2$ to 10$^3$ km/s and appear to be
independent of the rotation speed of the ``host'' galaxy. The outflows are
dusty (dust/gas ratios of $\sim$ 1% by mass). These properties imply that
superwinds may have established the mass-metallicity relation in elliptical and
bulges, polluted the inter-galactic medium to a metallicity of $\sim$ 10 to 30%
solar, heated the inter-galactic medium by up to $\sim$1 kev per baryon, and
ejected enough dust into the inter-galactic medium to have potentially
observable consequences.


title: Black Hole Demographics from the M(BH)-sigma Relation

abstract:
  We analyze a sample of 32 galaxies for which a dynamical estimate of the mass
of the hot stellar component, M_bulge, is available. For each of these
galaxies, we calculate the mass of the central black hole, M_BH, using the
tight empirical correlation between M_BH and the bulge stellar velocity
dispersion. The frequency function N(log M_BH/M_bulge) is reasonably well
described as a Gaussian with <log M_BH/M_bulge> ~ -2.90 and standard deviation
0.45; the implied mean ratio of black hole to bulge mass is a factor 5 smaller
than generally quoted in the literature. We present marginal evidence for a
lower, average black-hole mass fraction in more massive galaxies. The total
mass density in black holes in the local Universe is estimated to be 5 x 10^5
solar masses per cubic megaparsec, consistent with that inferred from high
redshift (z ~ 2) AGNs.


title:
Orbital solution for the MACHO*05:34:41.3 -69:31:39 O3 If*+O6:V
  eclipsing binary system in the LMC

abstract:
  An orbital solution to the MACHO*05:34:41.3 -69:31:39 eclipsing binary system
is presented, based on the published light curve and spectral data obtained
with the 2.15-m telescope at CASLEO. Based on these spectroscopic observations,
this system's binary components were classified as O3 If* and O6:V
respectively. The radial velocity data alongwith the published light curve were
analysed with the Wilson-Devinney code to derive the following masses and radii
for the components of this system: M1 = 41 +- 1.2, R1 = 9.6 +- 0.02, M2 = 27 +-
1.2 and R2 = 8.0 +- 0.05, in solar units. The solution shows that the system is
in over-contact as one would expect from the derived masses and the very short
orbital period (~1.4 days).


title: High Spatial Resolution Imaging of NGC 1068 in the Mid Infrared

abstract:
  Mid-infrared observations of the central source of NGC 1068 have been
obtained with a spatial resolution in the deconvolved image of 0.1" (~ 7pc).
The central source is extended by ~1" in the north-south direction but appears
unresolved in the east-west direction over most of its length. About two-thirds
of its flux can be ascribed to a core structure which is itself elongated
north-south and does not show a distinct unresolved compact source. The source
is strongly asymmetric, extending significantly further to the north than to
the south. The morphology of the mid-infrared emission appears similar to that
of the radio jet, and has features which correlate with the images in [O III].
Its 12.5-24.5 micron color temperature ranges from 215 to 260 K and does not
decrease smoothly with distance from the core. Silicate absorption is strongest
in the core and to the south and is small in the north.
  The core, apparently containing two-thirds of the bolometric luminosity of
the inner 4" diameter area, may be explained by a thick, dusty torus near the
central AGN viewed at an angle of ~65 deg to its plane. There are, however,
detailed difficulties with existing models, especially the narrow east-west
width of the thin extended mid-infrared "tongue" to the north of the core. We
interpret the tongue as re-processed visual and ultraviolet radiation that is
strongly beamed and that originates in the AGN.


title:
Constraints on the Inner Mass Profiles of Lensing Galaxies from Missing
  Odd Images

abstract:
  Most gravitational lens systems consist of two or four observable images. The
absence of detectable odd images allows us to place a lower limit on the
power-law slope of the inner mass profile of lensing galaxies. Using a sample
of six two-image radio-loud lens systems and assuming a singular power-law
surface density (Sigma proportional to r^{-beta}) for the inner several kpc of
the mass distribution, we find that there is less than a 10% probability that
the data are consistent with profile slopes beta < 0.80. Furthermore,
individual mass modeling yields beta > 0.85 for B0739+366 and beta > 0.91 for
B1030+074. Modeling central black holes as additional point masses changes the
constraints in these systems to beta > 0.84 and beta > 0.83, respectively. The
inner mass profiles of lensing galaxies are therefore not much shallower than
isothermal.


title: NVO and the LSB Universe

abstract:
  There is tremendous scientific potential in a National Virtual Observatory,
particularly for projects that need to mine large databases for rare or unusual
objects. However, the NVO will also make an impact on any project, large or
small, the requires a mixture of datasets to explore a wide range of
astrophysical phenomenon. In this article I discuss the influence of the NVO on
research into the formation and evolution of low surface brightness (LSB)
galaxies. In particular, I present the preliminary results from an NVO-style
project that combines the DPOSS and 2MASS datasets to search for giant disk
galaxies.


title:
Ionized Gas in Damped Lyman Alpha Protogalaxies: I. Model-Independent
  Inferences From Kinematic Data

abstract:
  We investigate the kinematics of ionized and neutral gas in a sample of 35
damped Lyman alpha protogalaxies (DLAs) with HIRES on the Keck I 10 m
telescope. Velocity profiles with resolution of ~ 8 km/s are obtained for high
ions such as C IV and Si IV, and for intermediate ions such as Al III.
Combining these profiles with accurate low-ion (e.g., Fe II) profiles, we
investigate the kinematic state of DLAs in the redshift range 1.8 < z < 4.4 by
comparisons between data for various ion pairs.
  We find the DLAs comprise distinct kinematic subsystems: a low ion subsystem
in which the low ions are physically associated with intermediate ions, and a
high subsystem containing neither low nor intermediate ions. The evidence for
two subsystems stems from (a) differences between the widths of the velocity
profiles, (b) misalignment in velocity space between the narrow components
comprising the profiles in each subsystem, and (c) significant dissimilarities
between the mean velocities of the high ion and low ion velocity profiles. In
every case we find that test statistics such as velocity width and various
asymmetry parameters distribute differently for low ions than for high ions.
  Despite misalignment in velocity space, the low and high ion kinematic
subsystems are interrelated. This is indicated by detection of a statistically
significant C IV versus low-ion cross correlation function, and by a systematic
effect where the C IV velocity widths are greater than or equal to the low ion
velocity widths in 29 out of 32 systems. These phenomena are consistent with
the location of the two subsystems in the same potential well.


title:
Ionized Gas in Damped Lyman Alpha Protogalaxies: II. Comparison Between
  Models and the Kinematic Data

abstract:
  We test semi-analytic models for galaxy formation with accurate kinematic
data of damped Lyman alpha protogalaxies (DLAs) presented in the companion
paper I. The models envisage centrifugally supported exponential disks at the
centers of dark matter halos which are filled with ionized gas undergoing
radial infall to the disks. The halo masses are drawn from cross-section
weighted mass distributions predicted by CDM cosmogonies, or by the null
hypothesis (TF model) that the dark matter mass distribution has not evolved
since z ~ 3. In our models, C IV absorption lines detected in DLAs arise in
infalling ionized clouds while the low-ion absorption lines arise from neutral
gas in the disks. Using Monte Carlo methods we find: (a) The CDM models are
incompatible with the low-ion statistics at more than 99% confidence whereas
some TF models cannot be excluded at more than 88% confidence. (b) Both CDM and
TF models agree with the observed distribution of C IV velocity widths. (c) The
CDM models generate differences between the mean velocities of C IV and low ion
profiles in agreement with the data, while the TF model produces differences in
the means that are too large. (d) Both CDM and TF models produce ratios of C IV
to low-ion velocity widths that are too large. (e) Both CDM and TF models
generate C IV versus low-ion cross-correlation functions incompatible with the
data.
  While it is possible to select model parameters resulting in consistency with
the data, the disk-halo configuration assumed in both cosmogonies still does
not produce significant overlap in velocity space between C IV low-ion velocity
profiles. We conjecture that including angular momentum of the infalling clouds
will increase the overlap between C IV and low-ion profiles.


title:
Red Quasars and Quasar Evolution: the Case of BALQSO FIRST
  J155633.8+351758

abstract:
  We present the first near-IR spectroscopy of the z=1.5 radio-loud BALQSO
FIRST J155633.8+351758. Both the Balmer decrement and the slope of the
rest-frame UV-optical continuum independently suggest a modest amount of
extinction along the line of sight to the BLR (E(B-V)~0.5 for SMC-type screen
extinction at the QSO redshift). The implied gas column density along the line
of sight is much less than is implied by the weak X-ray flux of the object,
suggesting that either the BLR and BAL region have a low dust-to-gas ratio, or
that the rest-frame optical light encounters significantly lower mean column
density lines of sight than the X-ray emission. From the rest-frame UV-optical
spectrum, we are able to constrain the stellar mass content of the system.
Comparing the maximal stellar mass with the black hole mass estimated from the
bolometric luminosity of the QSO, we find that the ratio of the black hole to
stellar mass may be comparable to the Magorrian value, which would imply that
the Magorrian relation is already in place at z=1.5. However, multiple factors
favor a much larger black hole to stellar mass ratio. This would imply that if
the Magorrian relation characterizes the late history of QSOs, and the
situation observed for F1556+3517 is typical of the early evolutionary history
of QSOs, central black hole masses develop more rapidly than bulge masses.
[ABRIDGED]


title:
A grid of composite models for the simulation of the emission-line
  spectra from the NLR of active galaxies

abstract:
  A grid of composite models for the narrow line region of active galaxies,
which consistently account for both the effect of a photoionizing radiation
from the active center and of a shock front, is presented. Theoretical results,
calculated with the SUMA code, are given for different values of shock
velocities, preshock densities, geometrical thickness of the clouds, and,
particularly, for the ionizing radiation intensity in a large range. The input
parameters are chosen within the ranges indicated by previous fits of several
observed emission-line and continuum spectra from active galaxies. Shock
velocities from 100 \kms ~to 1500 \kms ~and preshock densities from 100 \cm3 to
1000 \cm3 are considered. The line intensities of the most important
ultraviolet, optical and infrared transitions are obtained and are listed in
several tables.


title: On the Gas Surrounding High Redshift Galaxy Clusters

abstract:
  Francis & Hewett (1993) identified two 10-Mpc scale regions of the high
redshift universe that were seemingly very overdense in neutral hydrogen.
Subsequent observations showed that at least one of these gas-rich regions
enveloped a cluster of galaxies at redshift 2.38. We present improved
observations of the three background QSOs with sightlines passing within a few
Mpc of this cluster of galaxies. All three QSOs show strong neutral hydrogen
absorption at the cluster redshift, suggesting that this cluster (and perhaps
all high redshift clusters) may be surrounded by a ~5 Mpc scale region
containing ~ 10^12 solar masses of neutral gas.
  If most high redshift clusters are surrounded by such regions, we show that
the gas must be in the form of many small (< 1 kpc), dense (> 0.03 cm^-3)
clouds, each of mass < 10^6 solar masses. These clouds are themselves probably
gathered into > 20 kpc sized clumps, which may be galaxy halos or
protogalaxies.
  If this gas exists, it will be partially photoionised by the UV background.
We predict the diffuse Ly-alpha flux from this photoionisation, and place
observational limits on its intensity.


title: The Maximum Effect of Thermal Instability on Galactic Outflows

abstract:
  We have investigated steady, radial gas outflows (or winds) from galaxies and
the development of thermal instability in the hot gas. In order to see the
maximum influence of the instability on the global structure of the galactic
outflows, we study inhomogeneous comoving flows and the non-linear fate of the
fluctuations in the flows. We compare the results with solutions for
homogeneous flows. In the case of supersonic flows, the global structure of
inhomogeneous flows is not much different from that of homogeneous flows.
However, detailed investigation shows that the average density of inhomogeneous
flows decreases faster than that of homogeneous flows, because local thermal
instability removes overdense regions in the inhomogeneous flows and reduces
the mass flux. We also find that when the gravity of a galaxy is strong, the
cold clouds formed from the removed gas are distributed in the galactic halo.
In the case of subsonic flows, the form of inhomogeneous flows is different
from that of homogeneous flows near the regions where the flows terminate. The
density rise appearing near the regions where the homogeneous flows terminate
is not seen in the inhomogeneous flows because the local thermal instability
decreases the mass flux. The cold clouds formed through thermal instability in
the inhomogeneous flow almost all coast to the same maximum radius.


title:
Magnetospheric Accretion and Winds on the T Tauri Star SU Aurigae:
  Multi-Spectral Line Variability and Cross-Correlation Analysis

abstract:
  SU Aurigae is a T Tauri star that was well monitored during the MUSICOS 96
multi-site campaign. We present the results of the spectroscopic analysis of
the circumstellar environment of this star, particularly of the Halpha, Hbeta,
Na I D and He I D3 line profiles. The signatures of modulated outflows and mass
accretion events are analysed, as well as transient spectral features. We
compute the cross-correlation function (CCF) of several pairs of (velocity bins
in) spectral lines to better investigate the profiles' temporal variability. We
found increasing time lags between the variability of He I D3, Na I D and
Hbeta. We propose this may be understood in terms of azimuthal distortion of
the magnetic field lines due to the different rotation rates of the star and
the disk. We find the slightly blueshifted absorption features in Halpha, Hbeta
and Na I D to be anti-correlated with the accretion flow signatures. We propose
that the transient absorption features in the blue wings of Halpha, Hbeta and
Na I D (signatures of mass outflows), and flare brightenings are related to the
disruption of distorted magnetospheric field lines.


title:
Two-Dimensional MHD Numerical Simulations of Magnetic Reconnection
  Triggered by A Supernova Shock in Interstellar Medium, Generation of X-Ray
  Gas in Galaxy

abstract:
  We examine the magnetic reconnection triggered by a supernova (or a point
explosion) in interstellar medium, by performing two-dimensional resistive
magnetohydrodynamic (MHD) numerical simulations with high spatial resolution.
We found that the magnetic reconnection starts long after a supernova shock
(fast-mode MHD shock) passes a current sheet. The current sheet evolves as
follows: (i) Tearing-mode instability is excited by the supernova shock, and
the current sheet becomes thin in its nonlinear stage. (ii) The current-sheet
thinning is saturated when the current-sheet thickness becomes comparable to
that of Sweet-Parker current sheet. After that, Sweet-Parker type reconnection
starts, and the current-sheet length increases. (iii) ``Secondary tearing-mode
instability'' occurs in the thin Sweet-Parker current sheet. (iv) As a result,
further current-sheet thinning occurs and anomalous resistivity sets in,
because gas density decreases in the current sheet. Petschek type reconnection
starts and heats interstellar gas. Magnetic energy is released quickly while
magnetic islands are moving in the current sheet during Petschek type
reconnection. The released magnetic energy is determined by the interstellar
magnetic field strength, not energy of initial explosion nor distance to
explosion. We suggest that magnetic reconnection is a possible mechanism to
generate X-ray gas in Galaxy.


title:
On the matter entrainment by stellar jets and the acceleration of
  molecular outflows

abstract:
  We study, by numerical simulations, the entrainment process in a supersonic,
radiative jet flow, during the evolution of Kelvin-Helmholtz instabilities, in
the context of the the acceleration problem of molecular bipolar outflows,
observed in Giant Molecular Clouds. Our results show that a large fraction of
the initial jet momentum can be transferred to the ambient medium by this
process. We therefore analyze in detail the instability evolution and compare
some of the main observational properties of molecular outflows with those of
the entrained material that we observe in our simulations. In particular, we
find a good agreement for the mass vs. velocity distribution and for the
outflow collimation structure, especially when a light jet is moving into a
denser ambient medium. This is probably the case for (obscured) optical jets
driving powerful molecular outflows in the denser environment of the inner
regions of molecular clouds.


title:
The `Second Parameter': A Memory from the Globular Cluster Formation
  Epoch

abstract:
  We study the correlations between the distribution of stars on the horizontal
branch (HB), the HB morphology, with some other properties of globular clusters
(GCs) in a large sample of GCs. We strengthen previous results that a general
correlation exists only between HB morphology and metallicity. Correlations
with other properties, e.g., central density and core radius, exist only for
GCs within a narrow metallicity range. We conjecture that the lack of
correlations with present properties of GCs (besides metallicity), is because
the variation of the HB morphologies between GCs having similar metallicities
is caused by a process, or processes, whose effect was determined at the
formation time of GCs. This process (or processes) is historically termed the
`second parameter', metallicity being the `first parameter'. We then argue that
the `planet second parameter' model, where the presence of planets and to a
lesser degree brown dwarfs and low mass main sequence stars is the `second
parameter', fits this conjecture.


title:
Neutral and ionized gas distribution in and around the radio galaxy Coma
  A

abstract:
  HI absorption has been detected with the WSRT against both lobes of the radio
galaxy Coma A. This radio galaxy could be expanding in a particularly gas rich
environment, perhaps the result from interactions/mergers between the dominant
giant galaxy (associated with the radio galaxy) and less massive galaxies in
the same group.


title:
Evolution of the X-ray luminosity and metallicity of starburst blown
  superbubbles

abstract:
  We calculate the time-dependent metal production expected from starbursts and
use them as boundary conditions in our 2D simulations of evolving superbubbles.
We assume that the produced metals (oxygen and iron) thoroughly mix with the
ejected stellar envelopes, and/or with the matter thermally evaporated from the
superbubble cold outer shell. The metal production process determines the
time-dependent metallicity in hot superbubble interiors, and leads to values of
Z greater or equal than solar, when oxygen is used as tracer, and under-solar
when the metallicity is measured with respect to iron. In either case, the
enhanced metallicity boosts the X-ray emissivity of superbubbles, bringing
theory and observations closer together.


title: Medium Effects in Neutrino Cooling of Neutron Stars

abstract:
  This review demonstrates that neutrino emission from dense hadronic component
in neutron stars is subject of strong modifications due to collective effects
in the nuclear matter. With the most important in-medium processes incorporated
in the cooling code an overall agreement with available soft $X$ ray data can
be easily achieved. With these findings so called "standard" and "non-standard"
cooling scenarios are replaced by one general "nuclear medium cooling scenario"
which relates slow and rapid neutron star coolings to the star masses (interior
densities). In-medium effects take important part also at early hot stage of
neutron star evolution decreasing the neutrino opacity for less massive and
increasing for more massive neutron stars. A formalism for calculation of
neutrino radiation from nuclear matter is presented that treats on equal
footing one-nucleon and multiple-nucleon processes as well as reactions with
resonance bosons and condensates.


title: Shocks and Nonthermal Processes in Clusters

abstract:
  Clusters of galaxies generally form by the gravitational merger of smaller
clusters and groups. Major cluster mergers are the most energetic events in the
Universe since the Big Bang. Mergers drive shocks into the intracluster gas,
and these shocks heat the intracluster gas, and should also accelerate
nonthermal relativistic particles. The X-ray signatures of the thermal effects
of merger shocks will be discussed. X-ray observations of shocks can be used to
determine the geometry and kinematics of the merger. As a result of particle
acceleration in shocks, clusters of galaxies should contain very large
populations of relativistic electrons and ions. Electrons with Lorentz factors
gamma~300 (energies E = gamma m_e c^2 ~ 150 MeV) are expected to be
particularly common. Observations and models for the radio, extreme
ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles
accelerated in these shocks will also be described. The predicted gamma-ray
fluxes of clusters should make them easily observable with GLAST.


title:
The Formation of Supermassive Black Holes and the Evolution of
  Supermassive Stars

abstract:
  The existence of supermassive black holes is supported by a growing body of
observations. Supermassive black holes and their formation events are likely
candidates for detection by proposed long-wavelength, space-based gravitational
wave interferometers like LISA. However, the nature of the progenitors of
supermassive black holes is rather uncertain. Supermassive black hole formation
scenarios that involve either the stellar dynamical evolution of dense clusters
or the hydrodynamical evolution of supermassive stars have been proposed. Each
of these formation scenarios is reviewed and the evolution of supermassive
stars is then examined in some detail. Supermassive stars that rotate uniformly
during their secular cooling phase will spin up to the mass-shedding limit and
eventually contract to the point of relativistic collapse. Supermassive stars
that rotate differentially as they cool will likely encounter the dynamical bar
mode instability prior to the onset of relativistic collapse. A supermassive
star that undergoes this bar distortion, prior to or during collapse, may be a
strong source of quasiperiodic, long-wavelength gravitational radiation.


title: Damped Lyman-Alpha Galaxies

abstract:
  Some results from an imaging program to identify low-redshift (0.09<z<1.63)
damped Lyman-alpha (DLA) galaxies are presented. The standard paradigm that was
widely accepted a decade ago, that DLA galaxies are the progenitors of luminous
disk galaxies, is now being seriously challenged. The indisputable conclusion
from imaging studies at low redshift is that the morphological types of DLA
galaxies are mixed and that they span a range in luminosities and surface
brightnesses.


title: The effects of seeing on Sersic profiles

abstract:
  The effects of seeing on the parameters of the S\`ersic profile are studied
in an analytical form using a Gaussian point spread function. The surface
brightness of S\`ersic profiles is proportional (in magnitudes) to $r^{1/n}$.
The parameter $n$ serves to classify the type of profile and is related to the
central luminosity concentration. It is the parameter most affected by seeing;
furthermore, the value of $n$ that can be measured is always smaller than the
real one. It is shown that the luminosity density of the S\`ersic profile with
$n$ less than 0.5 has a central depression, which is physically unlikely. Also,
the intrinsic ellipticity of the sources has been taken into account and we
show that the parameters are dependent when the effects of seeing are
non-negligible. Finally, a prescription for correcting raw effective radii,
central intensities and $n$ parameters is given.


title: The Cosmological Evolution of Quasar Damped Lyman-Alpha Systems

abstract:
  We present results from an efficient, non-traditional survey to discover
damped Lyman-alpha (DLA) absorption-line systems with neutral hydrogen column
densities N(HI)>2x10^{20} atoms cm^{-2} and redshifts z<1.65. Contrary to
previous studies at higher redshift that showed a decrease in the cosmological
mass density of neutral gas in DLA absorbers, Omega_{DLA}, with time, our
results indicate that Omega_{DLA} is consistent with remaining constant from
redshifts z \approx 4 to z \approx 0.5. There is no evidence that Omega_{DLA}
is approaching the value at z=0. Other interesting results from the survey are
also presented.


title: Do mergers make (normal) ellipticals?

abstract:
  Under the merger hypothesis, elliptical galaxies are built through mergers of
gas-rich spirals. However, the relative paucity of HI in most normal
ellipticals demands significant processing of atomic gas into other forms if
this process is to be viable. Here I present a few qualitative remarks on how
the properties of merger-spawned ellipticals might depend on the (evolving) gas
content of the progenitor disks, then turn to a more quantitative study of the
constraints provided by the nuclear properties of ellipticals and merger
remnants.


title: The Impact of External Tidal Fields on the ISM of Dwarf Spheroidals

abstract:
  It was found that for three dwarf spheroidal galaxies - Sculptor, Tucana, and
Cetus - there is a correspondence between the distribution of associated HI gas
and the projected tidal axis direction. Numerical hydrodynamical simulations
confirmed the following scenario: SN Ia explosions remove most of the
interstellar medium beyond the tidal radius of the dwarf galaxy, with most of
the mass being in clouds moving along the principal tidal axis.


title: MACS: A quest for the most massive galaxy clusters in the universe

abstract:
  We describe the design and current status of a new X-ray cluster survey aimed
at the compilation of a statistically complete sample of very X-ray luminous
(and thus, by inference, massive), distant clusters of galaxies. The primary
goal of the MAssive Cluster Survey (MACS) is to increase the number of known
massive clusters at z>0.3 from a handful to hundreds. Upon completion of the
survey, the MACS cluster sample will greatly improve our ability to study
quantitatively the physical and cosmological parameters driving cluster
evolution at redshifts and luminosities poorly sampled by all existing surveys.
  To achieve these goals we apply an X-ray flux and X-ray hardness-ratio cut to
select distant cluster candidates from the ROSAT Bright Source Catalogue.
Starting from a list of more than 5,000 X-ray sources within the survey area of
22,735 square degrees we use positional cross-correlations with public
catalogues of Galactic and extragalactic objects, reference to APM colours,
visual inspection of Digitized Sky Survey images, extensive CCD imaging, and
finally spectroscopic observations with the University of Hawaii's 2.2m and the
Keck 10m telescopes to compile the final cluster sample.
  We discuss in detail the X-ray selection procedure and the resulting
selection function, and present model predictions for the number of distant
clusters expected to emerge from MACS. At the time of this writing the MACS
cluster sample comprises 101 spectroscopically confirmed clusters at 0.3<z<0.6;
more than two thirds of these are new discoveries. Our preliminary sample is
already 15 times larger than that of the EMSS in the same redshift and X-ray
luminosity range.


title: Optical Spectra of Type Ia Supernovae at z=0.46 and z=1.2

abstract:
  We present optical spectra, obtained with the Keck 10-m telescope, of two
high-redshift type Ia supernovae (SNe Ia) discovered by the High-z Supernova
Search Team: SN 1999ff at z=0.455 and SN 1999fv at z~1.2, the highest-redshift
published SN Ia spectrum. Both SNe were at maximum light when the spectra were
taken. We compare our high-z spectra with low-z normal and peculiar SNe Ia as
well as with SNe Ic, Ib, and II. There are no significant differences between
SN 1999ff and normal SNe Ia at low redshift. SN 1999fv appears to be a SN Ia
and does not resemble the most peculiar nearby SNe Ia.


title: Cerenkov Line-like Radiation, The Extended and Improved Formulae System

abstract:
  You & Cheng (1980) argued that, for relativistic electrons moving through a
dense gas, the Cerenkov effect will produce peculiar atomic and/or molecular
emission lines--Cerenkov lines. They presented a series of formulae to describe
the new line-mechanism. Elegant experimental confirmation has been obtained by
Xu. et al. in the laboratory which definitely verified the existence of
Cerenkov lines. Owing to the potential importance in high energy astrophysics,
in this paper we give a more detailed physical discussion of the emission
mechanisms and improve the previous formulae system into a form which is more
convenient for astrophysical application. Specifically, the extended formulae
in this paper can be applied to other species of atoms and/or ions rather than
hydrogen as in the previous paper, and also to X-ray astronomy. They can also
be used for the calculation of a nonuniform plane-parallel slab of the emissive
gas.


title:
Discovery of 172-s Pulsations from a Be/X-ray Binary Candidate AX
  J0051.6-7311 in the SMC with ASCA

abstract:
  The results from three ASCA observations of AX J0051.6-7311 = RX J0051.9-7311
are reported. Coherent pulsations with a barycentric period of 172.40 +/- 0.03
s were discovered in the third observation, with an exceptionally long exposure
time of ~177 ks. The X-ray spectrum was found to remain unchanged through these
observations, with a photon index of ~0.9. Energy-resolved pulse profiles in
the third observation reveal that the pulsations are mostly due to photons with
an energy above ~2 keV. Archival data of ROSAT and Einstein indicate that AX
J0051.6-7311 exhibits a flux variation having a factor ~> 20.


title:
Accretion Disk Instabilities, CDM models and their role in Quasar
  Evolution

abstract:
  We have developed a consistent analytical model to describe the observed
evolution of the quasar luminosity function. Our model combines black hole mass
distributions based on the Press - Schechter theory of the structure formation
in the Universe with quasar luminosity functions resulting from a physics-based
emission model that takes into account the time-dependent phenomena occurring
in the accretion disks. Quasar evolution and CDM models are mutually
constraining, therefore our model gives an estimation of the exponent, n, of
the power spectrum, P(k), which is found to be -1.8 < n < -1.6. We were able to
reject a generally assumed hypothesis of a constant ratio between Dark Matter
Halo and the Black Hole mass, since the observed data could not be fitted under
this assumption. We found that the relation between the Dark Matter Halos and
Black Hole masses is better described by M_{BH}=M_{DMH}^{0.668}. This model
provides a reasonable fit to the observed quasar luminosity function at
redshifts higher than ~2.0. We suggest that the disagreement at lower redshift
is due to mergers. Based on the agreement at high redshift, we estimated the
merger rate at lower redshift, and argue that this rate should depend on the
redshift, like (1+z)^3.


title: Atmospheric Secondary Particles In Near Earth Space

abstract:
  The Alpha Magnetic Spectrometer detects a large amount of particles below
rigidity cutoff. Those high energy particles create questions related to
radiation belts and atmospheric neutrinos. To understand the origin of these
particles, we use a trajectory tracing program to simulate particle
trajectories in realistic geomagnetic field. The complex behaviors and large
e^+/e^- are explained here.