title:
A search for precursors of Ultracompact HII Regions in a sample of
  luminous IRAS sources. III: Circumstellar Dust Properties

abstract:
  The James Clerk Maxwell Telescope has been used to obtain submillimeter and
millimeter continuum photometry of a sample of 30 IRAS sources previously
studied in molecular lines and centimeter radio continuum. All the sources have
IRAS colours typical of very young stellar objects (YSOs) and are associated
with dense gas. In spite of their high luminosities (L>10000 solar units), only
ten of these sources are also associated with a radio counterpart. In 17 cases
we could identify a clear peak of millimeter emission associated with the IRAS
source, while in 9 sources the millimeter emission was extended or faint and a
clear peak could not be identified; upper limits were found in 4 cases only.
  Using simple greybody fitting model to the observed SED, we derive global
properties of the circumstellar dust. The dust temperature varies from 24 K to
45 K, while the exponent of the dust emissivity vs frequency power-law spans a
range 1.56<beta<2.38, characteristic of silicate dust; total circumstellar
masses range up to more than 500 solar masses.
  We find that for sources with comparable luminosities, the total column
densities derived from the dust masses do not distinguish between sources with
and without radio counterpart. We interpret this result as an indication that
dust does not play a dominant role in inhibiting the formation of the HII
region. We examine several scenarios for their origin in terms of newborn ZAMS
stars and although most of these fail to explain the observations, we cannot
exclude that these sources are young stars already on the ZAMS with modest
residual accretion that quenches the expansion of the HII region. Finally, we
consider the possibility that the IRAS sources are high-mass pre-ZAMS (or
pre-H-burning) objects deriving most of the emitted luminosity from accretion.


title: Morphology vs. physical properties: some comments and questions

abstract:
  Some of the correlations between morphological and other physical properties
of planetary nebulae (PNe) are reviewed. In particular, the finding that
bipolar (b) PNe have more massive progenitors than the other morphological
classes is discussed in detail. Earlier results are confirmed; including all
the various sources of uncertainty, the Galactic distribution of objects
indicate that b PNe are formed by stars with initial masses >1.3 solar masses,
while elliptical (e) PNe by progenitors with masses <1.3 solar masses. Recent
results for the chemical abundances of b and e PNe and their orientation within
the Galaxy are also presented. Finally, the key role in the discussion of the
formation of b PNe played by detached binary systems such as symbiotic stars is
briefly discussed.


title: Signatures for a Cosmic Flux of Magnetic Monopoles

abstract:
  Any early universe phase transition occurring after inflation has the
potential to populate the universe with relic magnetic monopoles. Observations
of galactic magnetic fields, as well as observations matched with models for
extragalactic magnetic fields, lead to the conclusion that monopoles of mass
$\lsim 10^{15}$ GeV are accelerated in these fields to relativistic velocities.
We explore the possible signatures of a cosmic flux of relativistic monopoles
impinging on the earth. The electromagnetically-induced signatures of monopoles
are reliable. The hadronically-induced signatures are highly model-dependent.
Among our findings are (i) the electromagnetic energy losses of monopoles
continuously initiate a protracted shower of small intensity; (ii) monopoles
may traverse the earth's diameter, making them a probe of the earth's interior
structure; (iii) in addition to the direct monopole Cherenkov signal presently
employed, a very attractive search strategy for monopoles is detection of their
radio-Cherenkov signal produced by the coherent charge-excess in the $e^+-e^-$
shower - in fact, Cherenkov-detectors have the potential to discover a monopole
flux (or limit it) several orders of magnitude below the theoretical Parker
limit of $10^{-15}/\rm{cm}^2$/s/sr; (iv) it is conceivable (but not compelling)
that bound states of colored monopoles may be the primary particles initiating
the air showers observed above the GZK cutoff.


title: Symbiotic Miras can do it

abstract:
  Symbiotic Miras give a nice practical demonstration of the formation of
bipolar and highly aspherical nebulae as a consequence of interaction in
detached binaries. We believe that these binary systems are among the most
promising candidates for the progenitors of bipolar planetary nebulae. We
present a list of the optically extended nebulae known to date around symbiotic
Miras, and illustrate their properties using recent HST and ESO-NTT [NII]
images of He 2-104 and He 2-147.


title: Abundances in Very Metal-Poor Stars

abstract:
  Metal-poor stars provide information on the characteristics and chemical
evolution of the halo population of the Galaxy, the first epoch of star
formation and Galaxy formation (not just locally but with relevance to
high-redshift objects), and big bang nucleosynthesis. This review looks at
recent developments in this subject.


title: The Galaxy Distribution: Homogeneous, Fractal, or Neither

abstract:
  From the standpoint of theoretical physics we can treat Newtonian cosmology
as a problem in nonlinear dynamics. The attempt to average the density, in
search of a method of making contact between theory and observation, is
replaced by the more systematic idea of coarsegraining. I also explain in this
context why two previous attempts at the construction of hierarchical models of
the universe are not useful in data analysis. The main ideas behind two older
competing data analyses purporting to show evidence from galaxy statistics for
either a homogeneous and isotropic universe in one case, and for a mono-fractal
universe in the other, are presented and discussed. I also present the method
and results of a newer data analysis that shows that visible matter provides no
evidence that would allow us to claim that the cosmological principle holds, or
that the universe is fractal (or multifractal). In other words, observational
data provides us with no evidence that the universe is either homogeneous and
isotropic, or monofractal.


title: A Novel Supernova Detector

abstract:
  We discuss the prospects for detecting nu_{mu,tau} and nu_{tau}neutrinos from
Type II supernovas using the novel detector at the Supernova Burst Observatory
(SNBO) or OMNIS that is being designed for an underground laboratory in the
USA. This detector would collect ~2000 flavor selected events from a Galactic
supernova and could probe neutrino mass down to a few eV, as well as the
dynamics of the supernova process. We believe this is essential to further our
understanding of the neutrino section of elementary particle physics.


title:
CCD photometry in the region of NGC 6994: the remains of an old open
  cluster

abstract:
  We present the results of BV(RI)_KC CCD photometry down to V=21 mag in the
region of NGC 6994. To our knowledge, no photometry has previously been
reported for this object and we find evidences that it is a poor and sparse old
open cluster, with a minimum angular diameter of 9 arcmin, i.e. larger than the
3 arcmin originally assigned to it. We obtain a color excess E(B-V) = 0.07 +/-
0.02 mag by means of the BVI_(C) technique. Based on the theoretical isochrones
from VandenBergh (1985) that are in better agreement with our data, we estimate
for this cluster a distance from the Sun of 620 pc (Vo-Mv = 9 +/- 0.25 mag) and
an age lying within the range of 2 - 3 Gyr, adopting solar metallicity. Thus,
the corresponding cluster's Galactocentric distance is 8.1 kpc and is placed at
about 350 pc below the Galactic plane. According to this results, NGC 6994
belongs to the old open cluster population located in the outer disk and at
large distances from the Galactic plane, and must have suffered significant
individual dynamical evolution, resulting in mass segregation and evaporation
of low mass stars.


title: Modeling the X-ray - UV Correlations in NGC 7469

abstract:
  We model the correlated X-ray - UV observations of NGC 7469, for which well
sampled data in both these bands have been obtained recently in a
multiwavelength monitoring campaign. To this end we derive the transfer
function in wavelength \ls and time lag \t, for reprocessing hard (X-ray)
photons from a point source to softer ones (UV-optical) by an infinite plane
(representing a cool, thin accretion disk) located at a given distance below
the X-ray source, under the assumption that the X-ray flux is absorbed and
emitted locally by the disk as a black body of temperature appropriate to the
incident flux. Using the observed X-ray light curve as input we have computed
the expected continuum UV emission as a function of time at several wavelengths
(\l \l 1315 \AA, \l \l 6962 \AA, \l \l 15000 \AA, \l \l 30000 \AA) assuming
that the X-ray source is located one \sc radius above the disk plane, with the
mass of the black hole $M$ and the latitude angle $\theta$ of the observer
relative to the disk plane as free parameters. We have searched the parameter
space of black hole masses and observer azimuthal angles but we were unable to
reproduce UV light curves which would resemble, even remotely, those observed.
We also explored whether particular combinations of the values of these
parameters could lead to light curves whose statistical properties (i.e. the
autocorrelation and cross correlation functions) would match those
corresponding to the observed UV light curve at \l \l 1315 \AA. Even though we
considered black hole masses as large as $10^9$ M$_{\odot}$ no such match was
possible. Our results indicate that some of the fundamental assumptions of this
model will have to be modified to obtain even approximate agreement between the
observed and model X-ray - UV light curves.


title:
Probing The Gravity Induced Bias with Weak Lensing: Test of Analytical
  results Against Simulations

abstract:
  Future weak lensing surveys will directly probe the density fluctuation in
the universe. Recent studies have shown how the statistics of the weak lensing
convergence field is related to the statistics of collapsed objects. Extending
earlier analytical results on the probability distribution function of the
convergence field we show that the bias associated with the convergence field
can directly be related to the bias associated with the statistics of
underlying over-dense objects. This will provide us a direct method to study
the gravity induced bias in galaxy clustering. Based on our analytical results
which use the hierarchical {\em ansatz} for non-linear clustering, we study how
such a bias depends on the smoothing angle and the source red-shift. We compare
our analytical results against ray tracing experiments through N-body
simulations of four different realistic cosmological scenarios and found a very
good match. Our study shows that the bias in the convergence map strongly
depends on the background geometry and hence can help us in distinguishing
different cosmological models in addition to improving our understanding of the
gravity induced bias in galaxy clustering.


title: Low Mass Density Wide Field Far-IR/Submillimeter Telescope Systems

abstract:
  Fundamentally new technology is described for constructing low areal mass
density (1kg/m^2), high precision (< 10micron RMS) reflectors scalable to large
apertures (10 to 20 meters) for use as the primary element of a telescope
system. A large reduction in mass is achieved by minimizing the mass of the
reflective surface using a high reflectivity metallic membrane. A wide field
diffraction limited telescope system can be constructed using the primary
reflector in conjunction with secondary and tertiary optics.


title: Models of the Time Variability of BHC: Light Curves, PSD, Lags

abstract:
  We present a model for the aperiodic variablity of accreting Black Hole
Candidates (BHC) along with model light curves. According to the model this
variability is the combined outcome of random (Poisson) injection of soft
photons near the center of an extended {\sl inhomogeneous} distribution of hot
electrons (similar to those advocated by the ADAF or ADIOS flows) and the
stochastic nature of Compton scattering which converts these soft photons into
the observed high energy radiation. Thus, the timing properties (PSD, lags,
coherence) of the BHC light curves reflect, to a large extent, the properties
of the scattering medium (which in this approximation acts as a combination of
a {\sl linear} amplifier/filter) and they can be used to probe its structure,
most notably the density profile of the scattering medium. The model accounts
well for the observed PSDs and lags and also the reduction in the RMS
variability and the increase in the characteristic PSD frequencies with
increasing source luminosity. The electron density profiles obtained to date
are consistent mainly with those of ADIOS but also with pure ADAF flows.


title: A WIMP Detector with Two-Phase Liquid Xenon

abstract:
  We describe the liquid-xenon dark-matter detector program of the UCLA-Torino
team. A two-phase detector, ZEPLIN II, for the Boulby Mine is a good match for
the current search for WIMP dark matter.


title:
New Models for X-Ray Synchrotron Radiation from the Remnant of Supernova
  1006 AD

abstract:
  Galactic cosmic rays up to energies of around 10^15 eV are assumed to
originate in supernova remnants (SNRs). The shock wave of a young SNR like SN
1006 AD can accelerate electrons to energies greater than 1 TeV, where they can
produce synchrotron radiation in the X-ray band. A new model (SRESC) designed
to model synchrotron X-rays from Type Ia supernovae can constrain values for
the magnetic-field strength and electron scattering properties, with
implications for the acceleration of the unseen ions which dominate the
cosmic-ray energetics. New observations by ASCA, ROSAT, and RXTE have provided
enormously improved data, which now extend to higher X-ray energies. These data
allow much firmer constraints. We will describe model fits to these new data on
SN 1006 AD, emphasizing the physical constraints that can be placed on SNRs and
on the cosmic-ray acceleration process.


title: Probing the Neutron Star Interior with Glitches

abstract:
  With the aim of constraining the structural properties of neutron stars and
the equation of state of dense matter, we study sudden spin-ups, glitches,
occurring in the Vela pulsar and in six other pulsars. We present evidence that
glitches represent a self-regulating instability for which the star prepares
over a waiting time. The angular momentum requirements of glitches in Vela
indicate that at least 1.4% of the star's moment of inertia drives these
events. If glitches originate in the liquid of the inner crust, Vela's
`radiation radius' $R_\infty$ must exceed ~12 km for a mass of 1.4 solar
masses. The isolated neutron star RX J18563-3754 is a promising candidate for a
definitive radius measurement, and offers to further our understanding of dense
matter and the origin of glitches.


title: The Chandrasekhar limit for quark stars

abstract:
  The Chandrasekhar limit for quark stars is evaluated from simple energy
balance relations, as proposed by Landau for white dwarfs or neutron stars. It
has been found that the limit for quark stars depends on, in addition to the
fundamental constants, the Bag constant.


title: Suppressing Linear Power on Dwarf Galaxy Halo Scales

abstract:
  Recently is has been suggested that the dearth of small halos around the
Milky Way arises due to a modification of the primordial power spectrum of
fluctuations from inflation. Such modifications would be expected to alter the
formation of structure from bottom-up to top-down on scales near where the
short-scale power has been suppressed. Using cosmological simulations we study
the effects of such a modification of the initial power spectrum. While the
halo multiplicity function depends primarily on the linear theory power
spectrum, most other probes of power are more sensitive to the non-linear power
spectrum. Collapse of large-scale structures as they go non-linear regenerates
a ``tail'' in the power spectrum, masking small-scale modifications to the
primordial power spectrum except at very high-z. Even the small-scale
(k>2h/Mpc) clustering of the Ly-alpha forest is affected by this process, so
that CDM models with sufficient power suppression to reduce the number of 10^10
Msun halos by a factor of about 5 give similar Ly-alpha forest power spectrum
results. We conclude that other observations that depend more directly on the
number density of collapsed objects, such as the number of damped Ly-alpha
systems, or the redshift of reionization may provide the most sensitive tests
of these models.


title: The Observations of Type Ia Supernovae

abstract:
  The past ten years have seen a tremendous increase in the number of Type Ia
supernovae discovered and in the quality of the basic data presented. The
cosmological results based on distances to Type Ia events have been
spectacular, leading to statistically accurate values of the Hubble constant,
Omega_M, and Omega_Lambda. However, in spite of the recent advances, a number
of mysteries continue to remain in our understanding of these events. In this
short review, I will concentrate on unresolved problems and curious
correlations in the data on Type Ia SNe, whose resolution may lead to a deeper
understanding of the physical mechanism of the Type Ia supernova explosions.


title: A Unified Scaling Law in Spiral Galaxies

abstract:
  We investigate the origin of a unified scaling relation in spiral galaxies.
Observed spiral galaxies are spread on a plane in the
three-dimensionallogarithmic space of luminosity L, radius R and rotation
velocity V. The plane is expressed as $L \propto (V R)^{\alpha}$ in I-passband,
where $\alpha$ is a constant. On the plane, observed galaxies are distributed
in an elongated region which looks like the shape of a surfboard. The
well-known scaling relations, L-V (Tully-Fisher relation), V-R (also the
Tully-Fisher relation) and R-L (Freeman's law), can be understood as oblique
projections of the surfboard-like plane into 2-D spaces. This unified
interpretation of the known scaling relations should be a clue to understand
the physical origin of all the relations consistently. Furthermore, this
interpretation can also explain why previous studies could not find any
correlation between TF residuals and radius.
  In order to clarify the origin of this plane, we simulate formation and
evolution of spiral galaxies with the N-body/SPH method, including cooling,
star formation and stellar feedback. Initial conditions are set to isolated 14
spheres with two free parameters, such as mass and angular momentum. The CDM
(h=0.5, $\Omega_0=1$) cosmology is considered as a test case. The simulations
provide the following two conclusions: (a) The slope of the plane is well
reproduced but the zero-point is not. This zero-point discrepancy could be
solved in a low density ($\Omega_0<1$) and high expansion (h>0.5) cosmology.
(b) The surfboard-shaped plane can be explained by the control of galactic mass
and angular momentum.


title: Extragalactic H2 and its variable relation to CO

abstract:
  A steep metallicity dependence of the CO-to-H2 conversion factor X of the
form log X = 12.2 - 2.5 log[O]/[H], based on a sample of 20 (extra)galactic
determinations, is presented and discussed. The apparently less steep
dependence found from millimeter interferometer observations is explained
within the context of photon-dominated regions.


title:
A problem of hypothetical emerging of cosmic background radiation
  photons on horizon in the standard model of universe

abstract:
  The present temperature of cosmic background radiation and the present number
density of photons of cosmic background radiation in the observed expansive and
isotropic relativistic Universe is in the standard model of universe explained
by the assumption of emergence of the photons of cosmic background radiation on
the horizon (of the most remote visibility). However, the physical analysis
shows unambiguously that this assumption contradicts the special theory of
relativity and the quantum mechanics.


title:
On the numerical analysis of triplet pair production cross-sections and
  the mean energy of produced particles for modelling electron-photon cascade
  in a soft photon field

abstract:
  The double and single differential cross-sections with respect to positron
and electron energies as well as the total cross-section of triplet production
in the laboratory frame are calculated numerically in order to develop a Monte
Carlo code for modelling electron-photon cascades in a soft photon field. To
avoid numerical integration irregularities of the integrands, which are
inherent to problems of this type, we have used suitable substitutions in
combination with a modern powerful program code Mathematica allowing one to
achieve reliable higher-precission results. The results obtained for the total
cross-section closely agree with others estimated analytically or by a
different numerical approach. The results for the double and single
differential cross-sections turn out to be somewhat different from some
reported recently. The mean energy of the produced particles, as a function of
the characteristic collisional parameter (the electron rest frame photon
energy), is calculated and approximated by an analytical expression that
revises other known approximations over a wide range of values of the argument.
The primary-electron energy loss rate due to triplet pair production is shown
to prevail over the inverse Compton scattering loss rate at several ($\sim$2)
orders of magnitude higher interaction energy than that predicted formerly.


title:
The influence of nova nucleosynthesis on the chemical evolution of the
  Galaxy

abstract:
  We adopt up-to-date yields of 7Li, 13C, 15N from classical novae and use a
well tested model for the chemical evolution of the Milky Way in order to
predict the temporal evolution of these elemental species in the solar
neighborhood. In spite of major uncertainties due to our lack of knowledge of
metallicity effects on the final products of explosive nucleosynthesis in nova
outbursts, we find a satisfactory agreement between theoretical predictions and
observations for 7Li and 13C. On the contrary, 15N turns out to be overproduced
by about an order of magnitude.


title: Co Detection of the Extremely Red Galaxy HR10

abstract:
  CO J = 5 - 4 and J = 2 - 1 emission lines were detected towards the extremely
red galaxy (ERG) HR10 (J164502+4626.4) at z=1.44. The CO intensities imply a
molecular gas mass M(H2) of 1.6 x 10^{11} h^{-2}_50 solar masses, and, combined
with the intensity of the dust continuum, a gas-to-dust mass ratio around
200-400 (assuming galactic values for the conversion factors). The peak of the
CO lines are at the same redshift as the [O II]3727 line, but blue- shifted by
430 km s^{-1} from the Halpha line. These CO detections confirm the previous
results that HR10 is a highly obscured object with a large thermal far-infrared
luminosity and a high star-formation rate. The overall properties of HR10 (CO
detection, L_FIR to L'_CO ratio, and FIR to radio flux ratio) clearly favour
the hypothesis that its extreme characteristics are related to star-formation
processes rather than to a hidden AGN.


title: Metric Perturbations and Inflationary Phase Transitions

abstract:
  We study the out of equilibrium dynamics of inflationary phase transitions
and compute the resulting spectrum of metric perturbations relevant to
observation. We show that simple single field models of inflation may produce
an adiabatic perturbation spectrum with a blue spectral tilt and that the
precise spectrum depends on initial conditions at the outset of inflation.


title:
Radio Properties of the Shapley Concentration. III. Merging Clusters in
  the A3558 Complex

abstract:
  We present the results of a 22 cm radio survey carried out with the A3558
complex, a chain formed by the merging ACO clusters A3556-A3558-A3562 and
thetwo groups SC1327-312 and SC1323-313, located in the central region of the
complex, a chain formed by the merging ACO clusters A3556-A3558-A3562 and the
two groups SC1327-312 and SC1323-313, located in the central region of the
Shapley Concentration. The purpose of our survey is to study the effects of
cluster mergers on the statistical properties of radio galaxies and to
investigate the connection between mergers and the presence of radio halos and
relic sources. We found that the radio source counts in the A3558 complex are
consistent with the background source counts. Furthermore, we found that no
correlation exists between the local density and the radio source power, and
that steep spectrum radio galaxies are not segregated in denser optical
regions. The radio luminosity function for elliptical and S0 galaxies is
significantly lower than that for cluster type galaxies and for those not
selected to be in clusters at radio powers logP(1.4) > 22.5, implying that the
probability of a galaxy becoming a radio source above this power limit is lower
in the Shapley Concentration compared with any other environment. The detection
of a head-tail source in the centre of A3562, coupled with careful inspection
of the 20 cm NRAO VLA Sky Survey (NVSS) and of 36 cm MOST observations, allowed
us to spot two extended sources in the region between A3562 and SC1329-313,
i.e. a candidate radio halo at the centre of A3562, and low brightness extended
emission around a 14.96 magnitude Shapley galaxy.


title: Identification of the Coronal Sources of the Fast Solar Wind

abstract:
  The present spectroscopic study of the ultraviolet coronal emission in a
polar hole, detected on April 6-9, 1996 with the Ultraviolet Coronagraph
Spectrometer aboard the SOHO spacecraft, identifies the inter-plume lanes and
background coronal hole regions as the channels where the fast solar wind is
preferentially accelerated. In inter-plume lanes, at heliocentric distance 1.7
\rsun, the corona expands at a rate between 105 km/s and 150 km/s, that is,
much faster than in plumes where the outflow velocity is between 0 km/s and 65
km/s. The wind velocity is inferred from the Doppler dimming of the O VI
$\lambda\lambda$ 1032, 1037 \AA lines, within a range of values, whose lower
and upper limit corresponds to anisotropic and isotropic velocity distribution
of the oxygen coronal ions, respectively.


title: Probing The Structure of Space-Time with Cosmic Rays

abstract:
  The study of the interactions of Cosmic Rays (CR's) with universal diffuse
background radiation can provide very stringent tests of the validity of
Special Relativity. The interactions we consider are the ones characterized by
well defined energy thresholds whose energy position can be predicted on the
basis of Special Relativity. We argue that the experimental confirmation of the
existence of these thresholds can in principle put very stringent limits on the
scale where Special Relativity and/or continuity of space-time may possibly
break down.


title: Could merged star-clusters build up a small galaxy?

abstract:
  We investigate the behaviour of a cluster of young massive star clusters
(hereafter super-cluster) in the tidal field of a host galaxy with a
high-resolution particle-mesh code, Superbox. Specifically we want to establish
if and how such super star-clusters merge and carry out a detailed study of the
resulting merger-object. This merger-object shows either the properties of a
compact spherical object or the elongated (`fluffy') shape of dSph-galaxies
depending on the initial concentration of the super-cluster.


title:
Evidence for Stellar Streaming in the Cores of Elliptical Galaxies: A
  Kinematic Signature of Mergers?

abstract:
  We present evidence for non-Gaussian velocity fields within the cores of
luminous elliptical galaxies. This evidence is based upon high signal-to-noise,
medium-resolution spectroscopy of the cores of early-type members of the Virgo
and Coma clusters obtained with the WIYN 3.5-m telescope. The Virgo data were
acquired using an integral-field unit (DensePak) allowing the velocity field to
be sampled over a variety of spatial scales. The Coma data were obtained
through single, 2-arcsec diameter fibers. The cross-correlation profiles of
luminous ellipticals show considerable structure, often having several features
with amplitudes as high as 10% that of the cross-correlation peak itself. This
structure is most obvious within a radius of 1.5 arcsec (at Virgo), or < 100
pc, and is nearly undetectable when the data are binned over R < 15 arcsec, or
< 1 kpc. Similar features are found in the single-fiber spectra of the luminous
ellipticals in the Coma Cluster suggesting they are ubiquitous to giant
ellipticals. Interesting, only the most luminous elliptical galaxies show this
phenomena; the central regions of lower luminosity ellipticals have regular,
Gaussian-like profiles. We interpret this kinematic structure as ``stellar
streaming'' and suggest that this phenomena could be a relic signature of the
merger history of luminous elliptical galaxies.


title: Search for Relic Neutrinos and Supernova Bursts

abstract:
  We describe the current situation concerning methods to search for relic
neutrinos from the Big Bang and from all past supernovae (SNs). The most
promising method for Big Bang neutrinos is by the interaction of ultra-high-
energy (UHE) neutrinos. For supernova neutrinos, both Super Kamiokande- and
ICARUS-type detectors will be important to study both nubar_{e} and nu_{e}
fluxes. We also discuss a dedicated supernova burst observatory (OMNIS) being
planned for three sites in the world. We also describe the possible analysis of
the supernova type-II (SNII) neutrinos, including flavor mixing, that might be
carried out in the future.


title:
Electron Firehose instability and acceleration of electrons in solar
  flares

abstract:
  An electron distribution with a temperature anisotropy T_par/T_perp > 1 can
lead to the Electron Firehose instability (Here par and perp denote directions
relative to the background magnetic field B_0). Since possible particle
acceleration mechanisms in solar flares exhibit a preference of energizing
particles in parallel direction, such an anisotropy is expected during the
impulsive phase of a flare. The properties of the excited waves and the
thresholds for instability are investigated by using linearized kinetic theory.
These thresholds were connected to the pre-flare plasma parameters by assuming
an acceleration model acting exclusively in parallel direction. For usually
assumed pre-flare plasma conditions the electrons become unstable during the
acceleration process and lefthand circularly polarized waves with frequencies
of about the proton gyrofrequency are excited at parallel propagation.
Indications have been found, that the largest growth rates occur at oblique
propagation and the according frequencies lie well above the proton
gyrofrequency.


title: Warm Absorbers in Active Galactic Nuclei

abstract:
  We first provide a review of the properties of warm absorbers concentrating
on what we have learned from ROSAT and ASCA. This includes dusty and dust-free
warm absorbers, non-X-ray emission and absorption features of warm absorbers,
and the possible warm absorber interpretation of the peculiar 1.1 keV features.
  We then discuss facets of warm absorbers by a more detailed investigation of
individual objects: In a first part, we discuss several candidates for dusty
warm absorbers. In a second part, we review and extend our earlier study of a
possible relation between warm absorber and CLR in NGC 4051, and confirm that
both components are of different origin (the observed coronal lines are
underpredicted by the models, the warm absorber is too highly ionized). We then
suggest that a potential overprediction of these lines in more lowly ionized
absorbers can be avoided if these warm absorbers are dusty. In a third part, we
present first results of an analysis of a deep ROSAT PSPC observation of the
quasar MR2251-178, the first one discovered to host a warm absorber. Finally,
we summarize our scrutiny under which conditions a warm absorber could account
for the dramatic spectral variability of the Narrow-line Seyfert 1 galaxy
RXJ0134-4258.


title:
The giant X-ray outbursts from nearby, non-active galaxies: tidal
  disruption flares ?

abstract:
  One efficient method to probe the direct vicinity of SMBHs in nearby galaxies
is to make use of the detection of flares from tidally disrupted stars (e.g.,
Lidskii & Ozernoi 1979, Rees 1988). The first few excellent candidates for the
occurrence of this process in non-active galaxies have emerged recently. Here,
we present a review of these observations, compare with variability in AGN, and
discuss theoretical implications. We concentrate on the cases of NGC 5905 and
RXJ1242-1119, and report results from a systematic search for further X-ray
flares from a sample of >100 nearby galaxies.


title: Dynamics of the X-ray clusters Abell 222, Abell 223 and Abell 520

abstract:
  We present the results of a dynamical analysis of three rich, X-ray luminous
galaxy clusters, Abell 222, Abell 223 and Abell 520, that are at intermediate
redshifts. Our study is based on radial velocities for 71 cluster members,
respectively 30 for A222, 20 for A223 and 21 for A520, measured from spectra
obtained at the Canada-France-Hawaii Telescope, the European Southern
Observatory, and the Pic du Midi Observatory, and supplemented with radial
velocities from the literature. A222 galaxies have slightly higher velocities
than those of A223, with bi-weighted mean velocity of V_{bi} = 64242 +/- 194
km/s for A222, and of V_{bi} = 63197 +/- 266 km/s for A223. The velocity
dispersions of the two clusters are about the same: sigma_{bi} = 1013 +/- 150
km/s and sigma_{bi} = 1058 +/- 160 km/s for A222 and A223, respectively. For
A520 we obtain V_{bi} = 60127 +/- 284 km/s with sigma_{bi} = 1250 +/- 189 km/s.
We also give mass and mass-luminosities ratio estimates for each cluster
separately. We argue that these clusters are presently undergoing strong
dynamical evolution and that A222 and A223 will probably merge in the future.
We have applied a Principal Component Analysis to a sample of 51 CFHT spectra
to produce a spectral classification for these galaxies. This classification
has allowed us to show that the morphological and kinematical segregations were
already established in these intermediate redshift clusters.


title:
The red giant branches of Galactic globular clusters in the [(V-I)o,Mv]
  plane: metallicity indices and morphology

abstract:
  The purpose of this study is to carry out a thorough investigation of the
changes in morphology of the red giant branch (RGB) of Galactic globular
clusters (GGC) as a function of metallicity, in the V,I bands. To this aim, two
key points are developed in the course of the analysis.
  (a) Using our photometric V,I database for Galactic globular clusters (the
largest homogeneous data sample to date; Rosenberg et al. 1999) we measure a
complete set of metallicity indices, based on the morphology and position of
the red-giant branch. In particular, we provide here the first calibration of
the S, DV_(1.1) and DV_(1.4) indices in the (V-I,V) plane. We show that our
indices are internally consistent, and we calibrate each index in terms of
metallicity, both on the Zinn & West (1984) and the Carretta & Gratton (1997)
scales. Our new calibrations of the (V-I)o,g, DV_(1.2), (V-I)_(-3.0) and
(V-I)_(-3.5) indices are consistent with existing relations.
  (b) Using a grid of selected RGB fiducial points, we define a function in the
{(V-I)o,Mi,[Fe/H]} space which is able to reproduce the whole set of GGC giant
branches in terms of a single parameter (the metallicity). As a first test, we
show that the function is able to predict the correct trend of our observed
indices with metallicity.
  The usage of this function will improve the current determinations of
metallicity and distances within the Local Group, since it allows to easily map
[(V-I)o,Mi] coordinates into {[Fe/H],Mi} ones. To this aim the ``synthetic''
RGB distribution is generated both for the currently used Lee et al. (1990)
distance scale, and for the most recent results on the RR Lyr distance scale.


title: Sunyaev-Zel'dovich Surveys: Analytic treatment of cluster detection

abstract:
  Thanks to advances in detector technology and observing techniques, true
Sunyaev-Zel'dovich (SZ) surveys will soon become a reality. This opens up a new
window into the Universe, in many ways analogous to the X-ray band and
inherently well-adapted to reaching high redshifts. I discuss the nature,
abundance and redshift distributions of objects detectable in ground-based
searches with state-of-the-art technology. An advantage of the SZ approach is
that the total SZ flux density depends only on the thermal energy of the
intracluster gas and not on its spatial or temperature structure, in contrast
to the X-ray luminosity. Because ground-based surveys will be characterized by
arcminute angular resolution, they will resolve a large fraction of the cluster
population. I quantify the resulting consequences for the cluster selection
function; these include less efficient cluster detection compared to idealized
point sources and corresponding steeper integrated source counts. This implies,
contrary to expectations based on a point source approximation, that deep
surveys are better than wide ones in terms of maximizing the number of detected
objects. At a given flux density sensitivity and angular resolution, searches
at millimeter wavelengths (bolometers) are more efficient than centimeter
searches (radio), due to the form of the SZ spectrum. Possible ground-based
surveys could discover up to $\sim 100$ clusters per square degree at a
wavelength of 2 mm and $\sim 10$/sq. deg. at 1 cm, modeling clusters as a
simple self-similar population.


title: High Resolution Simulation of Galaxy Formation with Feedback

abstract:
  We present results from a Smoothed Particle Hydrodynamic (SPH) simulation of
galaxy formation that exceeds the minimum resolution requirement suggested by
Steinmetz & Muller (1993) of 3*10^4 SPH particles per galaxy. Using the
multiple mass technique an effective resolution of a little over one billion
particles is attained within a 48 Mpc cube. We find that even with an SPH mass
resolution of 1.5*10^6 solar masses and a plausible feedback algorithm, the
cooling catastrophe continues to be a problem for Einstein-de Sitter CDM
cosmologies. Increasing resolution also appears to exacerbate the core-halo
angular momentum transport problem.


title:
Chandra Observation of Abell 2142: Survival of Dense Subcluster Cores in
  a Merger

abstract:
  We use Chandra data to map the gas temperature in the central region of the
merging cluster A2142. The cluster is markedly nonisothermal; it appears that
the central cooling flow has been disturbed but not destroyed by a merger. The
X-ray image exhibits two sharp, bow-shaped, shock-like surface brightness edges
or gas density discontinuities. However, temperature and pressure profiles
across these edges indicate that these are not shock fronts. The pressure is
reasonably continuous across these edges, while the entropy jumps in the
opposite sense to that in a shock (i.e. the denser side of the edge has lower
temperature, and hence lower entropy). Most plausibly, these edges delineate
the dense subcluster cores that have survived a merger and ram pressure
stripping by the surrounding shock-heated gas.


title: Helium Emission in the Type Ic SN 1999cq

abstract:
  We present the first unambiguous detection of helium emission lines in
spectra of Type Ic supernovae (SNe Ic). The presence of He I lines, with full
width at half maximum ~ 2000 km/s, and the distinct absence of any other
intermediate-width emission (e.g., Halpha), implies that the ejecta of SN Ic
1999cq are interacting with dense circumstellar material composed of almost
pure helium. This strengthens the argument that the progenitors of SNe Ic are
core-collapse events in stars that have lost both their hydrogen and helium
envelopes, either through a dense wind or mass-transfer to a companion. In this
way, SN 1999cq is similar to supernovae such as SN 1987K and SN 1993J that
helped firmly establish a physical connection between Type Ib and Type II
supernovae. The light curve of SN 1999cq is very fast, with an extremely rapid
rise followed by a quick decline. SN 1999cq is also found to exhibit a high
level of emission at blue wavelengths (< 5500 A), likely resulting from either
an unusually large amount of iron and iron-group element emission or
uncharacteristically low reddening compared with other SNe Ic.


title: Probing the Cosmic Dark Age in X-rays

abstract:
  Empirical studies of the first generation of stars and quasars will likely
become feasible within the next decade in several different wavelength bands.
Microwave anisotropy experiments, such as MAP or Planck, will set constraints
on the ionization history of the intergalactic medium due to these sources. In
the infrared, the Next Generation Space Telescope (NGST) will be able to
directly detect sub-galactic objects at redshifts z>10. In the optical, data
from the Hubble Deep Field already places a constraint on the abundance of
high-redshift quasars. However, the epoch of the first quasars might be first
probed in X-ray bands, by instruments such as the Chandra X-ray Observatory
(CXO) and the X-ray Multi-mirror Mission (XMM). In a 500 Ksec integration, CXO
reaches a sensitivity of 2x10-16 erg/s cm^2. Based on simple hierarchical CDM
models, we find that at this flux threshold approx. 100 quasars might be
detectable from redshifts z>5, and approx. 1 quasar at z=10, in each 17x17
arcmin field. Measurement of the power spectrum of the unresolved soft X-ray
background will further constrain models of faint, high-redshift quasars.


title:
The MACHO Project: Microlensing Results from 5.7 Years of LMC
  Observations

abstract:
  We report on our search for microlensing towards the Large Magellanic Cloud
(LMC). Analysis of 5.7 years of photometry on 11.9 million stars in the LMC
reveals 13 - 17 microlensing events. This is significantly more than the $\sim$
2 to 4 events expected from lensing by known stellar populations. The
timescales ($\that$) of the events range from 34 to 230 days. We estimate the
microlensing optical depth towards the LMC from events with $2 < \that < 400$
days to be 1.2 ^{+0.4}_ {-0.3} \ten{-7}$, with an additional 20% to 30% of
systematic error. The spatial distribution of events is mildly inconsistent
with LMC/LMC disk self-lensing, but is consistent with an extended lens
distribution such as a Milky Way or LMC halo. Interpreted in the context of a
Galactic dark matter halo, consisting partially of compact objects, a maximum
likelihood analysis gives a MACHO halo fraction of 20% for a typical halo model
with a 95% confidence interval of 8% to 50%. A 100% MACHO halo is ruled out at
the 95% C.L. for all except our most extreme halo model. Interpreted as a
Galactic halo population, the most likely MACHO mass is between $ 0.15 \msun$
and $ 0.9 \msun$, depending on the halo model, and the total mass in MACHOs out
to 50 kpc is found to be 9+4-3 10^{10} msun, independent of the halo model.
These results are marginally consistent with our previous results, but are
lower by about a factor of two. Besides a larger data set, this work also
includes an improved efficiency determination, improved likelihood analysis,
and more thorough testing of systematic errors, especially with respect to the
treatment of potential backgrounds to microlensing, such as supernovae in
galaxies behind the LMC. [Abridged]


title: Thermodynamic properties of nuclear "pasta" in neutron star crusts

abstract:
  Equilibrium phase diagrams for neutron star matter at subnuclear densities
are obtained at zero temperature. Spherical, rod-like and slab-like nuclei as
well as spherical and rod-like nuclear bubbles are taken into account by using
a compressible liquid-drop model. This model is designed to incorporate
uncertainties in the nuclear surface tension and in the proton chemical
potential in a gas of dripped neutrons. The resultant phase diagrams show that
for typical values of these quantities, the phases with rod-like nuclei and
with slab-like nuclei occur in the form of Coulomb lattice at densities below a
point where the system becomes uniform. Thermal fluctuations leading to
displacements of such nuclei from their equilibrium positions are considered
through explicit evaluations of their elastic constants; these fluctuations can
be effective at destroying the layered lattice of slab-like nuclei in the
temperature region typical of matter in the neutron star crust.


title:
Neutrino decay and the thermochemical equilibrium of the interstellar
  medium

abstract:
  We calculate the thermochemical equilibrium of the diffuse interstellar
medium, including ionization by a photon flux F_{nu} from neutrino decay. The
main heating mechanism considered is photoelectrons from grains and PAHs. For
the studied range of F_{nu} values, there always exists two regions of
stability (a warm and a cold phase) that can coexist in equilibrium if the
thermal interstellar pressure is between a maximum value P_{max} and a minimum
value P_{min}. High F_{nu} values (~10^4-10^5 cm^{-2} s^{-1}) can be consistent
with observed interstellar pressures only if more efficient sources are heating
the gas. It is shown that a neutrino flux increase (due, for example, to an
increase in the supernova explosion rate) may stimulate the condensation of
cold gas by decreasing P_{max} below the interstellar pressure value.


title: Dust in the 55 Cancri planetary system

abstract:
  The presence of debris disks around $\sim$ 1-Gyr-old main sequence stars
suggests that an appreciable amount of dust may persist even in mature
planetary systems. Here we report the detection of dust emission from 55
Cancri, a star with one, or possibly two, planetary companions detected through
radial velocity measurements. Our observations at 850$\mu$m and 450$\mu$m imply
a dust mass of 0.0008-0.005 Earth masses, somewhat higher than that in the the
Kuiper Belt of our solar system. The estimated temperature of the dust grains
and a simple model fit both indicate a central disk hole of at least 10 AU in
radius. Thus, the region where the planets are detected is likely to be
significantly depleted of dust. Our results suggest that far-infrared and
sub-millimeter observations are powerful tools for probing the outer regions of
extrasolar planetary systems.


title:
Implementing Feedback in Simulations of Galaxy Formation: A Survey of
  Methods

abstract:
  We present a detailed investigation of different approaches to modeling
feedback in simulations of galaxy formation. Gas-dynamic forces are evaluated
using Smoothed Particle Hydrodynamics (SPH) while star formation and supernova
feedback are included using a three parameter model which determines the star
formation rate normalization, feedback energy and lifetime of feedback regions.
The star formation rate is calculated using a Lagrangian Schmidt Law for all
gas particles which satisfy temperature, density and convergent flow criteria.
Feedback is incorporated as thermal heating of the ISM. We compare the effects
of distributing this energy over the smoothing scale or depositing it on a
single particle. Radiative losses are prevented from heated particles by
adjusting the density used in radiative cooling. We test the models on the
formation of galaxies from cosmological initial conditions and also on isolated
Milky Way and dwarf galaxies. Extremely violent feedback is necessary to
produce a gas disk with angular momentum remotely close to that of observed
disk galaxies. This is a result of the extreme central concentration of the
dark halos in the sCDM model, and the pervasiveness of the core-halo angular
momentum transport mechanism. We emphasize that the disks formed in
hierarchical simulations are partially a numerical artifact produced by the
minimum mass scale of the simulation acting as a highly efficient `support'
mechanism. Disk formation is strongly affected by the treatment of dense
regions in SPH, which along with the difficulty of representing the
hierarchical formation process, means that realistic simulations of galaxy
formation require far higher resolution than currently used.


title: High Resolution Rotation Curves of Low Surface Brightness Galaxies

abstract:
  High resolution Halpha rotation curves are presented for five low surface
brightness galaxies. These Halpha rotation curves have shapes different from
those previously derived from HI observations, probably because of the higher
spatial resolution of the Halpha observations. The Halpha rotation curves rise
more steeply in the inner parts than the HI rotation curves and reach a flat
part beyond about two disk scale lengths. With radii expressed in optical disk
scale lengths, the rotation curves of the low surface brightness galaxies
presented here and those of HSB galaxies have almost identical shapes. Mass
modeling shows that the contribution of the stellar component to the rotation
curves may be scaled to explain most of the inner parts of the rotation curves,
albeit with high stellar mass-to-light ratios. On the other hand, well fitting
mass models can also be obtained with lower contributions of the stellar disk.
These observations suggest that the luminous mass density and the total mass
density are coupled in the inner parts of these galaxies.


title: The optical-ultraviolet continuum of Seyfert 2 galaxies

abstract:
  This paper aims to understand the continuum of Seyfert 2 galaxies. By fitting
the single galaxies in the sample of Heckman et al. (1995) with composite
models (shock+ photoionization from the active center), we show that five main
components characterize the SED of the continuum. Shocks play an important role
since they produce a high temperature zone where soft X-rays are emitted.
  We show that in the optical-UV range, the slope of the NLR emission
reproduces the observed values, and may be the main component of the
featureless continuum. The presence of star forming regions cannot be excluded
in the circumnuclear region of various Seyfert galaxies. An attempt is made to
find their fingerprints in the observed AGN spectra. Finally, it is
demonstrated that multi-cloud models are necessary to interpret the spectra of
single objects, even in the global investigation of a sample of galaxies.


title: The Fractional Kinetic Equation and Thermonuclear Functions

abstract:
  The paper discusses the solution of a simple kinetic equation of the type
used for the computation of the change of the chemical composition in stars
like the Sun. Starting from the standard form of the kinetic equation it is
generalized to a fractional kinetic equation and its solutions in terms of
H-functions are obtained. The role of thermonuclear functions, which are also
represented in terms of G- and H-functions, in such a fractional kinetic
equation is emphasized. Results contained in this paper are related to recent
investigations of possible astrophysical solutions of the solar neutrino
problem.


title: Analytical Study of Thermonuclear Reaction Probability Integrals

abstract:
  An analytic study of the reaction probability integrals corresponding to the
various forms of the slowly varying cross-section factor $S(E)$ is attempted.
Exact expressions for reaction probability integrals are expressed in terms of
the extended gamma functions.


title: Solar-Like Cycle in Asymptotic Giant Branch Stars

abstract:
  I propose that the mechanism behind the formation of concentric semi-periodic
shells found in several planetary nebulae (PNs) and proto-PNs, and around one
asymptotic giant branch (AGB) star, is a solar-like magnetic activity cycle in
the progenitor AGB stars. The time intervals between consecutive ejection
events is about 200-1,000 years, which is assumed to be the cycle period (the
full magnetic cycle can be twice as long, as is the 22-year period in the sun).
The magnetic field has no dynamical effects; it regulates the mass loss rate by
the formation of magnetic cool spots. The enhanced magnetic activity at the
cycle maximum results in more magnetic cool spots, which facilitate the
formation of dust, hence increasing the mass loss rate. The strong magnetic
activity implies that the AGB star is spun up by a companion, via a tidal or
common envelope interaction. The strong interaction with a stellar companion
explains the observations that the concentric semi-periodic shells are found
mainly in bipolar PNs.


title:
Analysis of The Hipparcos Measurements of HD10697 - A Mass Determination
  of a Brown-Dwarf Secondary

abstract:
  HD10697 is a nearby main-sequence star around which a planet candidate has
recently been discovered by means of radial-velocity measurements (Vogt et al.
1999, submitted to ApJ). The stellar orbit has a period of about three years,
the secondary minimum mass is 6.35 Jupiter masses and the minimum semi-major
axis is 0.36 milli-arc-sec (mas). Using the Hipparcos data of HD10697 together
with the spectroscopic elements of Vogt et al. (1999) we found a semi-major
axis of 2.1 +/- 0.7 mas, implying a mass of 38 +/- 13 Jupiter masses for the
unseen companion. We therefore suggest that the secondary of HD10697 is
probably a brown dwarf, orbiting around its parent star at a distance of 2 AU.


title:
Induction of supernova-like explosions by gamma-ray bursts in close
  binary systems

abstract:
  We propose that a gamma-ray burst in one member of a binary may induce a
supernova-like explosion of a close, white-dwarf companion. Such an explosion
might be brought about in rather light companions, which cannot undergo the
standard accretion-induced explosion. This would give some GRB-associated
supernova an appearance rather unlike that of the typical Type I. GRB 980425,
if indeed associated with SN 1998bw, is too weak to have produced it through
our proposed mechanism.


title: The Spectroscopic Orbit of the Planetary Companion Transiting HD209458

abstract:
  We report a spectroscopic orbit with period P = 3.52433 +/- 0.00027 days for
the planetary companion that transits the solar-type star HD209458. For the
metallicity, mass, and radius of the star we derive [Fe/H] = 0.00 +/- 0.02, M =
1.1 +/- 0.1 solar masses, and R = 1.3 +/- 0.1 solar radii. This is based on a
new analysis of the iron lines in our HIRES template spectrum, and also on the
absolute magnitude and color of the star, and uses isochrones from four
different sets of stellar evolution models. Using these values for the stellar
parameters we reanalyze the transit data and derive an orbital inclination of i
= 85.2 +/- 1.4 degrees. For the planet we derive a mass of Mp = 0.69 +/- 0.05
Jupiter masses, a radius of Rp = 1.54 +/- 0.18 Jupiter radii, and a density of
0.23 +/- 0.08 grams per cubic cm.


title: The INT Wide Field Imaging Survey(WFS)

abstract:
  The 2.5m Isaac Newton Telescope(INT) is currently being used to carry out a
major multi-colour, multi-epoch, CCD based wide field survey over an area of
100 square degrees. The survey parameters have been chosen to maximise
scientific return over a wide range of scientific areas and to complement other
surveys being carried out elsewhere. Unique aspects of the survey is that it
concentrates on regions of sky that are easily accessible from telescopes in
both Northern and Southern terrestrial hemispheres and that it the first public
survey to use filters similar to that being used by the Sloan Digital Sky
Survey. A major aim of the the INT Wide Field Survey program is to bridge the
gap between the all-sky photographic 2 and 3 band surveys such as the Palomar
and UK Schmidt sky surveys and the ultra-deep keyhole surveys such as the
Hubble Deep Field.


title:
Starbursts in barred spiral galaxies IV: On young bars and the formation
  of abundance gradients

abstract:
  The oxygen (O/H) and N/O abundance ratios along the bar of 16 barred spiral
starburst galaxies are determined using long-slit spectroscopy. The abundance
gradients and the spatial distribution of the ionized gas along the bar are
used to understand the role of bars in starburst galaxies.
  The oxygen abundance gradients are steeper than in normal barred galaxies,
while the intersects are low. This excludes the possibility that these are
chemically evolved galaxies rejuvenated by the effect of a bar. The
nitrogen-to-oxygen abundance gradients are flatter than the oxygen ones. But
N/O intersects are high, which rules out the possibility that a large quantity
of gas was recently funneled by a bar toward the center of a young galaxy.
Bars, therefore, cannot be at the origin of the bursts in the nuclei of our
sample galaxies.
  The oxygen and N/O abundance gradients are generally stronger in the bar than
in the disk and are linked together by a linear relation. This can be fully
explained in terms of star formation history: the gradients build up from the
inside out, becoming stronger as the oxygen and N/O abundances increase in the
bulge while staying low in the disk.
  In many of the sample galaxies, star formation occurs at one or both ends of
the bar. The low level of chemical enrichment in these regions suggests that
they recently experienced bar-triggered star formation: this is the only
visible effect of bars. Our analysis shows that bars probably appeared very
recently (a few 10^7 years) in the starburst galaxies, which are relatively
"young" galaxies still in the process of formation.(Abridged)


title: The formation of bars and disks in Markarian starburst galaxies

abstract:
  We have proposed in a companion paper (Considere et al. 2000) that bars
appeared recently in massive starburst nucleus galaxies. We now test this
hypothesis on an extended sample of barred and unbarred Markarian starburst
galaxies, using several samples of normal galaxies as control samples.
  In support of this hypothesis, we show that the proportion of barred galaxies
is much lower in Markarian starburst galaxies than in normal galaxies. In
addition to this deficiency of bars, we find that Markarian starburst galaxies
have smaller disks than normal galaxies, and that the disks of unbarred
starburst galaxies are smaller, on average, than barred ones. Finally, we show
that the Markarian starburst galaxies do not seem to follow the local
Tully--Fisher relation.
  Various alternatives are examined to explain the deficiency of bars and the
small disk dimensions in Markarian starburst galaxies. One possibility, which
is in agreement with the young bar hypothesis, is that the formation of disks
happens after the formation of bulges and that bars appear only later, when
enough gas has been accreted in the disk.


title: Dark Matter Halos Simulated with Million Particles

abstract:
  We report a series of high-resolution N-body simulations designed to examine
the internal physical properties of dark matter halos. A total of fifteen
halos, each represented by $\sim 1$ million particles within the virial radius,
have been simulated covering the mass range of $2\times10^{12}\sim
5\times10^{14} h^{-1}{\rm M_\odot}$. As the first application of these
simulations, we have examined the density profiles of the halos. We found a
clear systematic correlation between the halo mass and the slope of the density
profile at one percent of the virial radius, in addition to the variations of
the slope among halos of the similar mass. More specifically, the slope is
$\sim - 1.5$, -1.3, and -1.1 for galaxy, group, and cluster mass halos,
respectively. Thus we conclude that the dark matter density profiles,
especially in the inner region, are not universal.


title: Optical Identification of the ASCA Large Sky Survey

abstract:
  We present results of optical identification of the X-ray sources detected in
the ASCA Large Sky Survey. Optical spectroscopic observations were done for 34
X-ray sources which were detected with the SIS in the 2-7 keV band above 3.5
sigma. The sources are identified with 30 AGNs, 2 clusters of galaxies, and 1
galactic star. Only 1 source is still unidentified. The flux limit of the
sample corresponds to 1 x 10^{-13} erg s^{-1} cm^{-2} in the 2-10 keV band.
  Based on the sample, the paper discusses optical and X-ray spectral
properties of the AGNs, contribution of the sources to the Cosmic X-ray
Background, and redshift and luminosity distributions of the AGNs. An
interesting result is that the redshift distribution of the AGNs suggests a
deficiency of high-redshift (0.5 < z < 2) and luminous (Lx(2-10 keV) > 10^{44}
erg s^{-1}) absorbed narrow-line AGNs (so called type 2 QSOs).


title:
Combined color indexes and photometric structure of galaxies NGC 834 and
  NGC 1134

abstract:
  We present the results of BVRI photometry of two galaxies with active star
formation: NGC 834 and NGC 1134. Combined color index Q_{BVI} was used to
investigate the photometrical structure of the galaxies. Index Q_{BVI} is not
affected by internal extinction and is sensitive to the presence of blue stars.
  Ring-like region with active star formation at 15" from the center reveals
itself in the Q_{BVI} map of NGC 834. Three-arm spiral structure is well-seen
on the Q_{BVI} map of NGC 1134.
  We propose to use the combined indexes Q_{BVI} and similarly defined indices
as a tracers of Star Formation activity and structure of dusty galaxies.


title:
CADIS deep star counts: Galactic structure and the stellar luminosity
  function

abstract:
  In this paper we present the first results of deep star counts carried out
within the Calar Alto Deep Imaging Survey, CADIS (Meisenheimer 1998). Although
CADIS was designed as an extragalactic survey, it also attempts to identify the
stars in the fields in order to avoid confusion with quasars and compact
galaxies. We have identified a sample of about 300 faint stars 15.5< R < 23),
which are well suited to study the structure of the Galaxy. The stars lie in
two fields, hereafter 16h and 9h field, respectively. The stars have been
separated from galaxies by a classification scheme based on photometric spectra
and morphological criteria. Distances were derived by photometric parallaxes.
We are able to find stars up to distances of approximately 25 kpc above the
Galactic plane. The vertical density distribution of the stars shows the
contribution of the thin disk, the stellar halo and the ``thick disk'' of the
Galaxy. We give quantitative descriptions of the components in terms of
exponential disks and a de Vaucouleurs spheroid. For the disk stars we derive
the luminosity function. It is equal within the errors to the local luminosity
function and continues to rise out to at least M_V = 13. Implications for the
mass function are briefly discussed.


title: VSL theories and the Doppler peak

abstract:
  We discuss constraints on so-called `varying speed of light theories' coming
from the physics of the early universe. Specifically, we consider the position
of the first acoustic peak of the CMB angular power spectrum, showing that the
recent determination of its position by various CMB experiments, in particular
BOOMERanG/NA, can be used to constrain the value of the speed of light $c$
after the epoch of last scattering. Specifically, we find that for a flat
universe and a standard density of baryonic matter a variation in $c$ of up to
4% is consistent with the current observations. The position of the Doppler
peak is fairly sensitive to changes in $c$, and future observations should
dramatically improve this bound. On the other hand, we also find that the
maximum baryonic density allowed in VSL theories is about $\Omega_B h^2\sim
0.06\Omega_0$. We comment on the significance of these results.


title: Solar cycle variation in solar f-mode frequencies and radius

abstract:
  Using data from the Global Oscillation Network Group (GONG) covering the
period from 1995 to 1998, we study the change with solar activity in solar
f-mode frequencies. The results are compared with similar changes detected from
the Michelson Doppler Imager (MDI) data. We find variations in f-mode
frequencies which are correlated with solar activity indices. If these changes
are due to variation in solar radius then the implications are that the solar
radius decreases by about 5 km from minimum to maximum activity.


title: Solar cycle variations of large scale flows in the Sun

abstract:
  Using data from the Michelson Doppler Imager (MDI) instrument on board the
Solar and Heliospheric Observatory (SOHO), we study the large-scale velocity
fields in the outer part of the solar convection zone using the ring diagram
technique. We use observations from four different times to study possible
temporal variations in flow velocity. We find definite changes in both the
zonal and meridional components of the flows. The amplitude of the zonal flow
appears to increase with solar activity and the flow pattern also shifts
towards lower latitude with time.


title:
Comprehensive analytic formulae for stellar evolution as a function of
  mass and metallicity

abstract:
  We present analytic formulae that approximate the evolution of stars for a
wide range of mass and metallicity. Stellar luminosity, radius and core mass
are given as a function of age, M and Z, for all phases from the zero-age
main-sequence up to, and including, the remnant stages. For the most part we
find continuous formulae accurate to within 5% of detailed models. These
formulae are useful for purposes such as population synthesis that require very
rapid but accurate evaluation of stellar properties, and in particular for use
in combination with N-body codes. We describe a mass loss prescription that can
be used with these formulae and investigate the resulting stellar remnant
distribution.


title:
H2 emission as a diagnostic of physical processes in starforming
  galaxies

abstract:
  Observations and interpretation of extragalactic rotational and rovibrational
H2 emission are reviewed. Direct observations of H2 lines do not trace bulk H2
mass, but excitation rate. As such, the H2 lines are unique diagnostics, if the
excitation mechanism can be determined, which generally requires high-quality
spectroscopy and suitable additional data. The diagnostic power of the H2 lines
is illustrated by two cases studies: H2 purely rotational line emission from
the disk of the nearby spiral galaxy NGC891 and high resolution imaging and
spectroscopy of H2 vibrational line emision from the luminous merger NGC6240.


title: Are HVCs Produced in Galactic Fountains?

abstract:
  Three-dimensional simulations of the disk-halo interaction show the formation
of a thick HI and HII gas disk with different scale heights. The thick HI disk
prevents the disk gas from expanding freely upwards, unless some highly
energetic event such as chimneys occurs, whereas the thick HII disk acts as a
disk-halo interaction region from where the hot ionized gas flows freely into
the halo.
  The upflowing gas reaches the maximum height at $z\sim 9.3\pm 1$ kpc becoming
thermally unstable due to radiative losses, and condenses into HI clouds.
Because the major fraction of the gas is gravitationally bound to the Galaxy,
the cold gas returns to the disk. The descending clouds will have at some
height high velocities. In a period of 200 Myr of fountain evolution, some 10
percent of the total number of clouds are HVCs.


title: Direct Distance Measurements to Superluminal Radio Sources

abstract:
  We present a new technique for directly measuring the distances to
superluminal radio sources. By comparing the observed proper motions of
components in a parsec scale radio jet to their measured Doppler factors, we
can deduce the distance to the radio source independent of the standard rungs
in the cosmological distance ladder. This technique requires that the jet angle
to the line of sight and the ratio of pattern to flow velocities are
sufficiently constrained. We evaluate a number of possibilities for
constraining these parameters and demonstrate the technique on a well defined
component in the parsec scale jet of the quasar 3C279 (z = 0.536). We find an
angular size distance to 3C279 of greater than 1.8 (+0.5,-0.3) n^{1/8} Gpc,
where n is the ratio of the energy density in the magnetic field to the energy
density in the radiating particles in that jet component. For an Einstein-de
Sitter Universe, this measurement would constrain the Hubble constant to be H <
65 n^{-1/8} km/s/Mpc at the two sigma level. Similar measurements on higher
redshift sources may help discriminate between cosmological models.


title: The X-ray Properties of z>4 Quasars

abstract:
  We report on a search for X-ray emission from quasars with redshifts greater
than four using the ROSAT public database. Our search has doubled the number of
z>4 quasars detected in X-rays from 6 to 12. Most of those known prior to this
work were radio-loud and X-ray selected sources; our study increases the number
of X-ray detected, optically selected z>4 quasars from one to seven. We present
their basic X-ray properties and compare these to those of lower redshift
quasars. We do not find any evidence for strong broad-band spectral differences
between optically selected z>4 quasars and those at lower redshifts.


title: The Unique Potential of SKA Radio Observations of Gamma-Ray Bursts

abstract:
  Radio observations with the Square Kilometer Array (SKA) provide the agility,
sensitivity, and spectral coverage to trace the evolution of the size, shape
and spectra of gamma-ray burst (GRB) remnants from the earliest moments on. In
the first hours to days after the burst a major, and unique tool, will be
provided through the study of dynamically evolving radio spectra, caused by
diffractive and refractive scintillation in the local ISM. Simultaneous
observations from optically thin to optically thick frequencies will provide
strong constraints on any model for the GRB remnant. SKA will also allow for
extremely rapid (within minutes, if not seconds) follow-up observations by
electronic steering of the array. SKA observations have the sensitivity to
detect GRB afterglows out to redshifts of 10 or greater. They therefore allow
studies of the high redshift universe, and measure the massive star formation
(and massive star death rate!) history of the universe, unbiased by optical
obscuration. Wide field surveys may detect thousands of GRBs within a few days
of observing (depending on the amount of collimation, the width of the GRB
luminosity function, the number of GRBs like GRB 980425/SN 1998bw). There would
be new ones, but many more would be old, fading afterglows, allowing the
determination of the multi-variate GRB-optical-radio luminosity function of
GRBs. This should elucidate the relation of the `faint' ones, like GRB 980425,
to the luminous ones like GRB 970508. Such surveys will also tell us whether
GRB fireballs (and which ones) are collimated into jets.


title: HEGRA Observations of Galactic Sources

abstract:
  In this talk I will first give a summary of the observations of expected
Galactic TeV gamma-ray sources with the HEGRA CT-Sytem since the Kruger Park
Workshop in 1997. Then I will go into some detail regarding the observations of
Supernova Remnants (SNRs), especially those of Tycho's SNR and of Cas A. The
emphasis will not be on all aspects of these published data. I will rather
review the selection of these observational targets, and discuss some of the
physical implications of the results.


title: A continuous low star formation rate in IZw 18 ?

abstract:
  Deep long-slit spectroscopic observations of the blue compact galaxy IZw 18
obtained with the CFH 3.6 m Telescope are presented. The very low value of
oxygen abundance previously reported is confirmed and a very homogeneous
abundance distribution is found (no variation larger than 0.05 dex) over the
whole ionized region. We concur with Tenorio-Tagle (1996) and Devost et al.
(1997) that the observed abundance level cannot result from the material
ejected by the stars formed in the current burst, and propose that the observed
metals were formed in a previous star formation episode. Metals ejected in the
current burst of star formation remain most probably hidden in a hot phase and
are undetectable using optical spectroscopy. We discuss different scenarios of
star formation in IZw 18. Combining various observational facts, for instance
the faint star formation rate observed in low surface brightness galaxies van
Zee et al. (1997), it is proposed that a low and continuous rate of star
formation occurring during quiescent phases between bursts could be a
significant source of metal enrichment of the interstellar medium.


title: Weak Lensing of the CMB: A Harmonic Approach

abstract:
  Weak lensing of CMB anisotropies and polarization for the power spectra and
higher order statistics can be handled directly in harmonic-space without
recourse to real-space correlation functions. For the power spectra, this
approach not only simplifies the calculations but is also readily generalized
from the usual flat-sky approximation to the exact all-sky form by replacing
Fourier harmonics with spherical harmonics. Counterintuitively, due to the
nonlinear nature of the effect, errors in the flat-sky approximation do not
improve on smaller scales. They remain at the 10% level through the acoustic
regime and are sufficiently large to merit adoption of the all-sky formalism.
For the bispectra, a cosmic variance limited detection of the correlation with
secondary anisotropies has an order of magnitude greater signal-to-noise for
combinations involving magnetic parity polarization than those involving the
temperature alone. Detection of these bispectra will however be severely noise
and foreground limited even with the Planck satellite, leaving room for
improvement with higher sensitivity experiments. We also provide a general
study of the correspondence between flat and all sky potentials, deflection
angles, convergence and shear for the power spectra and bispectra.


title: Implications of Abundance Gradients in Intracluster Gas

abstract:
  Analysis of spatially resolved ASCA spectra of the intracluster gas in Abell
496 confirms that metal abundances increase toward the center. We also find
spatial gradients in several abundance ratios, indicating that the fraction of
iron from SN Ia increases toward the cluster center. The dominant metal
enrichment mechanism near the cluster center must therefore be different than
in the outer parts. We show that ram pressure stripping of gas from cluster
galaxies cannot account for the central abundance enhancement. We suggest that
two successive stages of galactic winds contaminate intracluster gas:
protogalactic winds driven by SN II, followed by less energetic winds driven by
SN Ia, which have longer lived progenitors than SN II. The less energetic
secondary wind from a cD galaxy may be suppressed, due to its location at the
cluster center, leading to the observed central enhancement of SN Ia ejecta.


title: Glimpses of a strange star

abstract:
  There are about 2000 gamma ray burst (GRB) events known to us with data
pouring in at the rate of one per day. While the afterglows of GRBs in radio,
optical and X-ray bands are successfully explained by the fireball model, a
significant difficulty with the proposed mechanisms for GRBs is that a small
amount ($\le 10^{-6} M_{\odot}$) of baryons in the ejecta can be involved.
There are very few models that fulfill this criteria together with other
observational features, among which are the differentially rotating collapsed
object model and the "supernova" model. These models generally invoke rapidly
rotating neutron stars, and may be subject to uncertainties in the formation
mechanisms and the equations of state of neutron stars. According to Spruit,
the problem of making a GRB from an X-ray binary is reduced to finding a
plausible way to make the star rotate differentially. We suggest that a model
of strange star (SS) can naturally explain many of these bursts with not only
their low baryon content, but the differential rotation which leads to an
enhanced magnetic field that surfaces up and is responsible for GRBs.


title: Predicting caustic crossing high magnification events in Q2237+0305

abstract:
  The central regions of the gravitationally lensed quasar Q2237+0305 can be
indirectly resolved on nano-arcsecond scales if viewed spectrophotometricly
during a microlensing high magnification event (HME). Q2237+0305 is currently
being monitored from the ground (eg. OGLE collaboration, Apache Point
Observatory), with the goal, among others, of triggering ground and spacecraft
based target of opportunity (TOO) observations of an HME. In this work we
investigate the rate of change (trigger) in image brightness that signals an
imminent HME and importantly, the separation between the trigger and the event
peak. In addition, we produce colour dependent model light-curves by combining
high-resolution microlensing simulations with a realistic model for a thermal
accretion disc source. We make hypothetical target of opportunity spectroscopic
observations using our determination of the appropriate trigger as a guide. We
find that if the source spectrum varies with source radius, a 3 observation TOO
program should be able to observe a microlensing change in the continuum slope
following a light-curve trigger with a success rate of >80%.


title: Interpretation of the OGLE Q2237+0305 microlensing light-curve

abstract:
  The four bright images of the gravitationally lensed quasar Q2237+0305 are
being monitored from the ground (eg. OGLE collaboration, Apache Point
Observatory) in the hope of observing a high magnification event (HME). Over
the past three seasons (1997-1999) the OGLE collaboration has produced
microlensing light-curves with unprecedented coverage. These demonstrate
smooth, independent (therefore microlensing) variability between the images
(Wozniak et al. 2000a,b; OGLE web page). We have retrospectively compared
probability functions for high-magnification event parameters with several
observed light-curve features. We conclude that the 1999 image C peak was due
to the source having passed outside of a cusp rather than to a caustic
crossing. In addition, we find that the image C light-curve shows evidence for
a caustic crossing between the 1997 and 1998 observing seasons involving the
appearance of new critical images. Our models predict that the next image C
event is most likely to arrive 500 days following the 1999 peak, but with a
large uncertainty (100-2000 days). Finally, given the image A light-curve
derivative at the end of the 1999 observing season, our modelling suggests that
a caustic crossing will occur between the 1999 and 2000 observing seasons,
implying a minimum for the image A light-curve ~1-1.5 magnitudes fainter than
the November 1999 level.


title:
The infrared side of galaxy formation. I. The local universe in the
  semi-analytical framework

abstract:
  We present a new evolutionary model for the far-UV to sub-mm properties of
the galaxy population. This combines a semi-analytic galaxy formation model
based on hierarchical clustering (GALFORM) with a spectro-photometric code
which includes dust reprocessing (GRASIL). The former provides the star
formation and metal enrichment histories, together with the gas mass and
various geometrical parameters, for a representative sample of galaxies formed
in different density environments. These quantities allow us to model the SEDs
of galaxies, taking into account stellar emission and also dust extinction and
re-emission. Two phases are considered for the dust: molecular cloud complexes,
where stars are assumed to be born, and the diffuse interstellar medium. The
model includes both galaxies forming stars quiescently in disks, and starbursts
triggered by galaxy mergers. We test our models against the observed
spectro-photometric properties of galaxies in the local Universe. The models
reproduce fairly well the SEDs of normal spirals and starbursts, and their
internal extinction properties. The starbursts follow the observed relationship
between the FIR to UV luminosity ratio and the slope of the UV continuum. They
also reproduce the observed starburst attenuation law (Calzetti et al 99). This
result is remarkable, because we use a dust mixture which reproduces the Milky
Way extinction law. It suggests that the observed attenuation law is related to
the geometry of the stars and dust. We compute galaxy luminosity functions over
our wide range of wavelengths, which turn out to be in good agreement with
observational data. The UV continuum turns out to be a poor star formation
indicator for our models, whilst the infrared luminosity is much more reliable.


title: Weak lensing observations of the "dark" cluster MG2016+112

abstract:
  We investigate the possible existence of a high-redshift (z=1) cluster of
galaxies associated with the QSO lens system MG2016+112. From an ultra-deep R-
and less deep V- and I-band Keck images and a K-band mosaic from UKIRT, we
detect ten galaxies with colors consistent with the lensing galaxy within
225h^{-1} kpc of the z=1.01 lensing galaxy. This represents an overdensity of
more than ten times the number density of galaxies with similar colors in the
rest of the image. We also find a group of seven much fainter objects closely
packed in a group only 27h^{-1} kpc north-west of the lensing galaxy. We
perform a weak lensing analysis on faint galaxies in the R-band image and
detect a mass peak of a size similar to the mass inferred from X-ray
observations of the field, but located 64" northwest of the lensing galaxy.
  From the weak lensing data we rule out a similar sized mass peak centered on
the lensing galaxy at the 2 sigma level.


title:
Detection of an X-Ray Hot Region in the Virgo Cluster of Galaxies with
  ASCA

abstract:
  Based on mapping observations with ASCA, an unusual hot region with a spatial
extent of 1 square degree was discovered between M87 and M49 at a center
coordinate of R. A. = 12h 27m 36s and Dec. = $9^\circ18'$ (J2000). The X-ray
emission from the region has a 2-10 keV flux of $1 \times 10^{-11}$ ergs
s$^{-1}$ cm$^{-2}$ and a temperature of $kT \gtrsim 4$ keV, which is
significantly higher than that in the surrounding medium of $\sim 2$ keV. The
internal thermal energy in the hot region is estimated to be $V n k T \sim
10^{60}$ ergs with a gas density of $\sim 10^{-4}$ cm$^{-3}$. A power-law
spectrum with a photon index $1.7-2.3$ is also allowed by the data. The hot
region suggests there is an energy input due to a shock which is probably
caused by the motion of the gas associated with M49, infalling toward the M87
cluster with a velocity $\gtrsim 1000$ km s$^{-1}$.


title: Supermassive Black Holes Can Hardly Be "Silent"

abstract:
  There is now ample evidence that most - perhaps all - galactic spheroids host
a supermassive BH at their center. This has been assessed using a variety of
observational techniques, from stellar and/or gas dynamics to megamasers. Yet
another promising technique is offered by the case of the Virgo elliptical NGC
4552, in which early HST/FOC observations revealed a central low-luminosity
flare. Subsequent HST/FOS observations with a 0.21 arcsec aperture have
revealed a rich emission-line spectrum with broad and narrow components with
FWHM of 3000 and 700 km/s, respectively. This variable, mini-AGN at the center
of NGC 4552 is most naturally the result of a sporadic accretion event on a
central BH. It has a H$\alpha$ luminosity of only $\sim 10,000 \lsun$, making
it the likely, intrinsically faintest AGN known today. Only thanks to the
superior resolution of HST such a faint object has been discovered and studied
in detail, but adaptive optics systems on large ground-based telescopes may
reveal in the future that a low level of accretion onto central massive BHs is
an ubiquitous phenomenon among galactic spheroids. FOC/FOS observations of a
central spike in NGC 2681 reveal several analogies with the case of NGC 4552,
while yet another example is offered by a recent exciting finding with STIS by
R.W. O'Connell in NGC 1399, the third galaxy in our original program.
garchingbh


title:
WWhat Heavy Elements in Clusters of Galaxies Tell About Clusters and
  Galaxies

abstract:
  Clusters of galaxies allow a direct estimate of the metallicity and metal
production yield on the largest scale so far. The ratio of the total iron mass
in the ICM to the total optical luminosity of the cluster (the iron
mass-to-light-ratio) is the same for all clusters which ICM is hotter than
$\sim 2$ keV, and the elemental proportions (i.e. the [$\alpha$/Fe] ratio)
appear to be solar. The simplest interpretation of these evidences is that both
the IMF as well the relative contributions of SN types are universal. Currently
available abundances in cooler clusters and groups are much more uncertain,
possibly due to insufficiently accurate atomic physics data for multi-electron
ions, or to the ICM being multi-phase, or to a combination thereof. This
uncertainty automatically extends to the reality of radial abundance gradients
so far reported in cool clusters. It is emphasized that most metals reside in
the ICM rather than in galaxies, which demonstrates that energetic winds
operated early in the evolution of massive galaxies, the likely producers of
most metals now in the ICM. The ICM metallicity is also used to set a
semiempirical constraint of $\sim 0.1$ keV per particle to the ICM {\it
preheating} due to supernova driven galactic winds. A lower limit of the
universe global metallicity at $z=3$ is also mentioned.


title: Metallicity in damped Lyman-alpha systems: evolution or bias?

abstract:
  Assuming that damped Lyman-alpha(DLA) systems are galactic discs, we
calculate the corresponding evolution of metal abundances. We use detailed
multi-zone models of galactic chemical evolution (reproducing successfully the
observed properties of disc galaxies) and appropriate statistics (including
geometrical propability factors) to calculate the average metallicity as a
function of redshift. The results are compatible with available observations,
provided that observational biases are taken into account, as suggested by
Boisse et al. (1998). In particular, high column density and high metallicity
systems are not detected because the light of backround quasars is severely
extinguished, while low column density and low metallicity systems are not
detectable through their absorption lines by current surveys. We show that
these observational constraints lead to a ``no-evolution'' picture for the DLA
metallicity, which does not allow to draw strong conclusions about the nature
of those systems or about their role in ``cosmic chemical evolution''.


title:
Theory of "Jitter" Radiation from Small-Scale Random Magnetic Fields and
  Prompt Emission from Gamma-Ray Burst Shocks

abstract:
  Abridged.-- We demonstrate that the radiation emitted by ultrarelativistic
electrons in highly nonuniform, small-scale magnetic fields is different from
synchrotron radiation if the electron's transverse deflections in these fields
are much smaller than the beaming angle. A quantitative analytical theory of
this radiation, which we refer to as jitter radiation, is developed. It is
shown that the emergent spectrum is determined by statistical properties of the
magnetic field. As an example,we then use the model of a magnetic field in
internal shocks of GRBs. The spectral power distribution of radiation produced
by the power-law electrons is well described by a sharply broken power-law with
indices 1 and -(p-1)/2 and the jitter break frequency is independent of the
field strength but depends on the electron density in the ejecta. Since
large-scale fields may also be present in the ejecta, we construct a
two-component, jitter+synchrotron spectral model of the prompt $\gamma$-ray
emission. Quite surprisingly, this model seems to be readily capable of
explaining several properties of time-resolved spectra of some GRBs, such as
(i) the violation of the constraint on the low-energy spectral index called the
synchrotron ``line of death'', (ii) the sharp spectral break at the peak
frequency, inconsistent with the broad synchrotron bump, (iii) the evidence for
two spectral sub-components, and (iv) possible existence of emission features
called ``GRB lines''. We believe these facts strongly support both the
existence of small-scale magnetic fields and the proposed radiation mechanism
from GRB shocks. As an example, we use the composite model to analyze GRB
910503 which has two spectral peaks.


title:
Disk-Halo Interaction - I. Three-Dimensional Evolution of the Galactic
  Disk

abstract:
  The results of a three-dimensional model for disk-halo interaction are
presented here. The model considers explicitly the input of energy and mass by
isolated a nd correlated supernovae in the disk. Once disrupted by the
explosions, the disk never returns to its initial state. Instead it approaches
a state where a thin HI disk is formed in the Galactic plane overlayed by thick
HI and HII gas disk w ith scale heights of 500 pc and of 1 to 1.5 kpc,
respectively. The upper parts o f the thick HII disk (the diffuse ionized
medium) act as a disk-halo interface a nd its formation and stability are
directly correlated to the supernova rate per unit area in the simulated disk.


title:
Four Cometary Belts Associated with the Orbits of Giant Planets: A New
  View of the Outer Solar System's Structure Emerges from Numerical Simulations

abstract:
  Using numerical simulations, we examine the structure of a cometary
population near a massive planet, such as a giant planet of the Solar system,
starting with one-planet approximation (the Sun plus one planet). By studying
the distributions of comets in semimajor axis, eccentricity, pericenter, and
apocenter distances, we have revealed several interesting features in these
distributions. The most remarkable ones include (i) spatial accumulation of
comets near the planetary orbit (which we call the `cometary belt') and (ii)
avoidance of resonant orbits by comets. Then we abandon one-planet
approximation and examine as to how a cometary belt is modified when the
influence of all four giant planets is taken into consideration. To this end,
we simulate a stationary distribution of comets, which results from the
gravitational scattering of the Kuiper belt objects on the four giant planets
and accounts for the effects of mean motion resonances. Accounting for the
influence of four giant planets makes the cometary belts overlapping, but
nevertheless keeping almost all their basic features found in one-planet
approximation. In particular, the belts maintain the gaps in the (a,e)- and
(a,i)-space similar to the Kirkwood gaps in the main asteroid belt. We conclude
that the large-scale structure of the Solar system is featured by the four
cometary belts expected to contain 20-30 millions of scattered comets, and only
a tiny fraction of them is currently visible as Jupiter-, Saturn-, etc. family
comets.


title:
Statistics of clustering of ultra-high energy cosmic rays and the number
  of their sources

abstract:
  Observation of clustering of ultra-high energy cosmic rays (UHECR) suggests
that they are emitted by compact sources. Assuming small deflection of UHECR
during the propagation, the statistical analysis of clustering allows to
estimate the spatial density of the sources, h, including those which have not
yet been observed directly. When applied to astrophysical models involving
extra-galactic sources, the estimate based on 14 events with energy E>10^{20}
eV gives h ~ 6 X 10^{-3} Mps^{-3}. With increasing statistics, this estimate
may lead to exclusion of the models which associate the production of UHECR
with exceptional galaxies such as AGN, powerful radio-galaxies, dead quasars,
and models based on gamma ray bursts.


title: Review of Big Bang Nucleosynthesis and Primordial Abundances

abstract:
  Big Bang Nucleosynthesis (BBN) is the synthesis of the light nuclei,
Deuterium, He3, He4 and Li7, during the first few minutes of the universe. This
review concentrates on recent improvements in the measurement of the primordial
(after BBN, and prior to modification) abundances of these nuclei. We mention
improvement in the standard theory, and the non-standard extensions which are
limited by the data. (abridged)


title:
Closing the gap: an X-ray selected sample of clusters of galaxies behind
  the Galactic plane

abstract:
  We discuss the design and current status of the CIZA survey, the first
systematic X-ray search for clusters of galaxies in the Galactic plane region.
So far, we have compiled a sample of more than 70 X-ray selected clusters at
|b|<20 deg, 80% of which were previously unknown. Upon its completion the CIZA
cluster catalogue will complement the existing galaxy surveys in the Galactic
plane region and allow a fresh look at large-scale structure and local
streaming motions.


title: MACS: The evolution and properties of massive clusters of galaxies

abstract:
  We present first results from the MAssive Cluster Survey (MACS), a new
large-scale X-ray survey designed to find and characterize very massive,
distant clusters of galaxies. Based on X-ray detections in the ROSAT All-Sky
Survey, MACS aims to compile a sample of more than 200 X-ray luminous clusters
at z>0.3, about 50 times the number of EMSS clusters in the same redshift and
luminosity range. The MACS sample is uniquely suited to investigate cluster
evolution at redshifts and luminosities poorly sampled by all existing surveys.
  At the time of writing the MACS sample comprises 41 clusters with measured
redshifts of 0.3<z<0.56 and X-ray luminosities in excess of 6 10^44 erg/s
(0.1-2.4 keV). This early sample is thus already twice as large as the high-z,
high-luminosity subsets of the EMSS, BCS, and REFLEX cluster samples taken
together. An additional 85 MACS clusters with photometric redshifts z>0.3 are
scheduled for spectroscopic observation.
  From a preliminary analysis of a statistically well defined subsample of the
25 X-ray brightest MACS clusters we conclude tentatively that negative
evolution is not significant at the highest X-ray luminosities (Lx>10^45 erg/s)
out to redshifts of z~0.4. Our findings thus extend the no-evolution result
obtained by many serendipitous ROSAT cluster surveys at lower luminosities.


title:
The 9.7 Micron Silicate Dust Absorption Toward the Cygnus A Nucleus and
  the Inferred Location of the Obscuring Dust

abstract:
  We report the detection of a 9.7 $\mu$m silicate dust absorption feature
toward the Cygnus A nucleus. Its optical depth is, however, significantly
smaller than that expected from the dust extinction toward the background
$L$-band emission region ($A_{\rm V}$ $\sim$ 150 mag). We argue that the most
likely explanation for the small optical depth is that the obscuring dust
exists so close to the central engine that a temperature gradient occurs. Our
calculation confirms that the small optical depth and the spectral energy
distribution at 3--30 $\mu$m can be quantitatively reproduced by this
explanation. Combining this picture with the huge AGN luminosity, the emission
properties of Cygnus A are consistent with those of a type 2 quasar, that is, a
highly luminous AGN that is highly obscured ($A_{\rm V}$ $>$ 50 mag) by a dusty
torus with an inner radius of $<$10 pc, and not by $>$ a few 100 pc scale dust
in the host galaxy.


title: Profiles of Strong Permitted Lines in Classical T Tauri Stars

abstract:
  We present a spectral analysis of 30 T Tauri stars observed with the Hamilton
echelle spectrograph over more than a decade. One goal is to test
magnetospheric accretion model predictions. Observational evidence previously
published supporting the model, such as emission line asymmetry and a high
frequency of redshifted absorption components, are considered. We also discuss
the relation between different line forming regions and search for good
accretion rate indicators.
  In this work we confirm several important points of the models, such as the
correlation between accretion and outflow, broad emission components that are
mostly central or slightly blueshifted and only the occasional presence of
redshifted absorption. We also show, however, that the broad emission
components supposedly formed in the magnetospheric accretion flow only
partially support the models. Unlike the predictions, they are sometimes
redshifted, and are mostly found to be symmetric. The published theoretical
profiles do not have a strong resemblance to our observed ones. We emphasize
the need for accretion models to include a strong turbulent component before
their profiles will match the observations. The effects of rotation, and the
outflow components, will also be needed to complete the picture.


title: Constraining SN Ia Models Using X-ray Spectra of Clusters of Galaxies

abstract:
  We present constraints on theoretical models of Type Ia SNe using spatially
resolved ASCA X-ray spectroscopy of four galaxy clusters: Abell 496, Abell
2199, Abell 3571 & Perseus. All four clusters have central Fe abundance
enhancements and an ensemble of abundance ratios are used to show that most of
the Fe in the central regions of the clusters comes from SN Ia. At the center
of each cluster, simultaneous analysis of spectra from all ASCA instruments
shows that the Ni to Fe abundance ratio (normalized by the solar ratio) is ~ 4.
We use the Ni/Fe ratio as a discriminator between SN Ia explosion models: the
Ni/Fe ratio of ejecta from the "Convective Deflagration" model W7 is consistent
with the observations, while those of "delayed detonation" models are not
consistent at the 90% confidence level.


title: Observing the effects of strong gravity with future X-ray missions

abstract:
  Spectroscopy of the broad iron iron with ASCA and BeppoSAX has up opened the
innermost regions of accreting black hole systems to detailed study. In this
contribution, I discuss how observations with future X-ray missions will extend
these studies and all us to observationally address issues which are currently
only in the realm of the theorists. In particular, high-throughput spectroscopy
with XMM and, eventually, Constellation-X will allow the full diagnostic power
of iron line variability to be realized. Instabilities of the inner accretion
flow, the geometry of the variable X-ray source, and the black hole mass and
spin will all be open to study. Eventually, X-ray interferometry will allow
direct imaging of the black hole region in nearby active galaxies, thereby
providing the ultimate probe of black hole astrophysics.