title: Chaos in the Music of the Spheres

abstract:
  The light curves (time series of the radiated energy) of most large
amplitude, pulsating stars such as the well known Cepheid stars are regular.
However, a smaller group of variable stars that are located next to them in the
Hertzsprung- Russell diagram undergoes irregular light variations and exhibits
irregular radial velocities as well. The mechanism behind this irregular
behavior was a long standing mystery. A flow reconstruction technique based on
the observed lightcurves of six separate stars shows that their underlying
dynamics is chaotic and low dimensional (d=4). Furthermore, we present evidence
that the physical mechanism behind the behavior is the nonlinear interaction of
just two pulsation eigenmodes. In a generalized Shil'nikov scenario, the
pulsation energy alternates continuously, but irregularly between a lower
frequency mode that is linearly unstable and thus growing, and a stable
overtone that gets entrained through a low order resonance (2:1), but that
wants to decay. The flow reconstruction from the stellar light curve thus
yields interesting physical insight into the pulsation mechanism.

categories: astro-ph nlin.CD physics.data-an physics.flu-dyn


title: The K-alpha complex of He-like iron with dielectronic satellites

abstract:
  It is shown that the dielectronic satellites (DES) dominate X-ray spectral
formation in the 6.7 keV K-alpha complex of Fe XXV at temperatures below that
of maximum abundance in collisional ionization equilibrium T_m. Owing to their
extreme temperature sensitivity the DES are excellent spectral diagnostics for
T < T_m in photoionized, colllisional, or hybrid plasmas; whereas the
forbidden, intercombination, and resonance lines of Fe XXV are not. A
diagnostic line ratio GD(T) is defined including the DES and the lines, with
parameters from new relativistic atomic calculations. The DES absorption
resonance strengths may be obtained from differential oscillator strengths to
possibly yield the Fe XXIV/Fe XXV column densities. The DES contribution to
highly ionized Fe should be of interest for models of redward broadening of
K-alpha features, ionized accretion discs, accretion flows, and K-alpha
temporal-temperature variability in AGN.


title:
Radiation in a Closed 3-D Universe Reveals its Present Geometry and its
  Past Evolution

abstract:
  In previous papers, predictions of the new "Spatial Condensation (SC-)"
cosmological model were presented on the (1) foundations, (2) new source of
gravity, and (3) large-scale structure. In this paper predictions will include
new physical features that are due mostly to the postulated geometry of our
closed 3-D universe. Knowledge of the past universe is obtained from its many
types of radiation that travel to our instruments on great circles of our
expanding 3-sphere. Adding the fourth spatial dimension greatly increases our
understanding of the concepts of emission and reception distances of the
sources and 4-D trajectory of the radiation. In a closed expanding 3-D
universe, most of the radiation from a distant bright source at Ze can travel
halfway around the universe and be refocused as a "virtual source" at Zv ~1.5
where some of the re-diverging radiation arrives later to our instruments. With
the added fourth dimension, the SC-model makes some spectacular predictions for
these virtual sources. Indeed, the CBR becomes a re-focused "backside"
microwave radiation with its structure amplified in size and decreased in
luminosity by a factor ~ 1/350. "Viewed" in the optical from a direction
opposite the CBR, the same, but more evolved, structure at "virtual Zsame"
would certainly fix the geometry and size of our universe. Virtual sources are
also added radiation to the diffuse background of X-rays and infrared. The CBR
dipole suggests a preferred reference frame. Reflected light signals in a
non-accelerated frame show, in principle, the moving frame could be brought to
rest in the comoving frame.


title: Mass Spectra from Turbulent Fragmentation

abstract:
  Turbulent fragmentation determines where and when protostellar cores form,
and how they contract and grow in mass from the surrounding cloud material.
Molecular cloud regions without turbulent driving sources, or where turbulence
is driven on large scales, exhibit rapid and efficient star formation in a
clustered mode, whereas interstellar turbulence that carries most energy on
small scales results in isolated star formation with low efficiency. The clump
mass spectrum of shock-generated density fluctuations in pure hydrodynamic,
supersonic turbulence is not well fit by a power law, and it is too steep at
the high-mass end to be in agreement with the observational data. When gravity
is included in the turbulence models, local collapse occurs, and the spectrum
extends towards larger masses as clumps merge together, a power-law description
dN/dM ~ M^nu becomes possible with slope nu = -2. In the case of pure
gravitational contraction the clump mass spectrum is shallower with nu = -3/2.
The mass spectrum of protostellar cores in regions without turbulent support
and where turbulence is replenished on large-scales, however, is well described
by a log-normal or by multiple power laws, similar to the stellar IMF at low
and intermediate masses. In the case of small-scale turbulence, the core mass
spectrum is too flat compared to the IMF for all masses.


title:
The Stellar Winds of Galactic Centre and the Low Accretion Rate of Sgr
  A*

abstract:
  An attempt is made to reconcile the large wind-loss rates of stars in the
Galactic Centre (GC) with the predicted low accretion rate for Sgr A*, the
putative blackhole at the heart of the Milky Way. It is found that, independent
of the details of the accretion, the bound but unaccreted gas has been
accumulating in the potential well of Sgr A* for <1000 yrs and thus is not in
equilibrium. Otherwise, the gas flows of the region would be visible in both
the IR and X-ray. It appears that the blackhole was more active in the recent
past due to the passing of a supernova blast shock but is presently in a
short-lived dormant phase. The extended low frequency radio emission from the
central parsec should visibily increase over the next few decades, as the shock
passes completely in front of the absorbing gas and dust near Sgr A*. The GC
may become more active in < 100,000 yrs due to either another supernova or
sufficient accumulation of stellar winds in the central arcsecond.


title: Radio Spectral Index and Expansion of 3C58

abstract:
  We present new observations of the plerionic supernova remnant 3C58 with the
VLA at 74 and 327 MHz. In addition, we re-reduced earlier observations at 1.4
and 4.9 GHz taken in 1973 and 1984. Comparing these various images, we find
that: 1. the remnant has a flat and relatively uniform spectral index
distribution, 2. any expansion of the remnant with time is significantly less
than that expected for uniform, undecelerated expansion since the generally
accepted explosion date in 1181 A.D., and 3. there is no evidence for a
non-thermal synchrotron emission shell generated by a supernova shock wave,
with any such emission having a surface brightness of <1 x 10^(-21) W / (m^2 Hz
sr) at 327 MHz.


title:
An Atlas of Halpha and R Images and Radial Profiles of 63 Bright Virgo
  Cluster Spiral Galaxies

abstract:
  Narrow-band Halpha and broadband R images and radial profiles are presented
for 63 bright spiral galaxies in the Virgo Cluster. The sample is complete for
Sb-Scd galaxies with B magnitude less than 12 and inclination less than 75
degrees. Isophotal radii, disk scalelengths, concentration parameters, and
integrated fluxes are derived for the sample galaxies.


title: Boyle's law and gravitational instability

abstract:
  We have re-examined the classical problem of the macroscopic equation of
state for a hydrostatic isothermal self-gravitating gas cloud bounded by an
external medium at constant pressure. We have obtained analytical conditions
for its equilibrium and stability without imposing any specific shape and
symmetry to the cloud density distribution. The equilibrium condition can be
stated in the form of an upper limit to the cloud mass; this is found to be
inversely proportional to the power 3/2 of a form factor \mu characterizing the
shape of the cloud. In this respect, the spherical solution, associated with
the maximum value of the form factor, \mu = 1, turns out to correspond to the
shape that is most difficult to realize. Surprisingly, the condition that
defines the onset of the Bonnor instability (or gravothermal catastrophe) can
be cast in the form of an upper limit to the density contrast within the cloud
that is independent of the cloud shape. We have then carried out a similar
analysis in the two-dimensional case of infinite cylinders, without assuming
axisymmetry. The results obtained in this paper generalize well-known results
available for spherical or axisymmetric cylindrical isothermal clouds that have
had wide astrophysical applications, especially in the study of the
interstellar medium.


title: The colour magnitude relation for galaxies in the Coma cluster

abstract:
  We present a new photometric catalogue of the Coma galaxy cluster in the
Johnson U- and V- bands. We cover an area of 3360arcmin2 of sky, to a depth of
V=20 mag in a 13 arcsec diameter aperture, and produce magnitudes for ~1400
extended objects in metric apertures from 8.8 to 26arcsec diameters. The mean
internal RMS scatter in the photometry is 0.014 mag in V, and 0.026 mag in U,
for V13 < 17 mag.
  We place new limits on the levels of scatter in the colour--magnitude
relation (CMR) in the Coma cluster, and investigate how the slope and scatter
of the CMR depends on galaxy morphology, luminosity and position within the
cluster. As expected, the lowest levels of scatter are found in the elliptical
galaxies, while the late type galaxies have the highest numbers of galaxies
bluewards of the CMR. We investigate whether the slope of the CMR is an
artifact of colour gradients within galaxies and, show that it persists when
the colours are measured within a diameter that scales with galaxy size.
Looking at the environmental dependence of the CMR, we find a trend of
systematically bluer galaxy colours with increasing projected cluster-centric
radius which we associate with a gradient in the mean galactic ages.


title:
Trans-Relativistic Supernovae, Circumstellar Gamma-Ray Bursts, and
  Supernova 1998bw

abstract:
  Supernova (SN) 1998bw and gamma-ray burst (GRB) 980425 offer the first direct
evidence that supernovae are the progenitors of some GRBs. However, this burst
was unusually dim, smooth and soft compared to other bursts with known
afterglows. Whether it should be considered a prototype for cosmological GRBs
depends largely on whether the supernova explosion and burst were asymmetrical
or can be modeled as spherical. We address this question by treating the
acceleration of the supernova shock in the outermost layers of the stellar
envelope, the transition to relativistic flow, and the subsequent expansion
(and further acceleration) of the ejecta into the surrounding medium. We find
that GRB 980425 could plausibly have been produced by a collision between the
relativistic ejecta from SN 1998bw and the star's pre-supernova wind; the model
requires no significant asymmetry. This event therefore belongs to a dim
subclass of GRBs and is not a prototype for jet-like cosmological GRBs.


title: The Crab Nebula's Moving Wisps in Radio

abstract:
  We present three high resolution radio images of the Crab nebula, taken in
1998.6, 1998.8 and 2000.1 with the VLA. These are the best radio images of the
Crab to date. We show that, near the pulsar, there are significant changes
between our three observing epochs. These changes have an elliptical geometry
very similar to that of the optical wisps. One radio wisp in particular can be
unambiguously identified between two of our observing epochs, and moves outward
with an apparent velocity of ~0.24. The similarity in both morphology and
behavior of the present radio wisps to the optical wisps suggests that they are
associated. This implies that the radio wisps, like the optical ones, are
likely manifestations of the shock in the Crab pulsar's wind. This suggests
that the radio emitting electrons are accelerated in the same region as the
ones responsible for the optical to X-ray emission, contrary to most current
models.


title: Upper limits of the $^{22}$Na yield from O-Ne nova

abstract:
  The radioactive isotope $^{22}$Na is one of the primary tracer isotopes that
may potentially be detectable by gamma-ray spectroscopy. This isotope is
predicted to be produced in ONe nova explosions, yet no detection of its 1.275
MeV gamma-ray signature has been reported so far. In particular, 6 years of
COMPTEL observations of the galactic bulge, a region that should be
particularily rich in nova explosions, have only led to an upper-limit. In this
paper we will present the implications of the COMPTEL upper flux limit on the
permissible $^{22}$Na yield for ONe novae. We base our analysis on extensive
Monte-Carlo simulations of galactic 1.275 MeV emission that were constrained by
the most recent results of galactic nova rates and distributions. We
demonstrate that the non-detection of the 1.275 MeV line from the galactic
bulge implies a solid upper $^{22}$Na yield limit in agreement with current
theoretical nucleosynthesis calculations.


title: Super Stellar Clusters in HII Galaxies

abstract:
  Stellar Clusters are identified in images and in the spectra of these star
forming dwarf galaxies. These Stellar Clusters have properties similar to those
observed in other violent star forming galaxies and may the elementary entities
of a starburst.


title: Nonlinear Kinetic Sunyaev-Zeldovich Effect

abstract:
  We derive fully nonlinear expressions for temperature fluctuations from the
kinetic Sunyaev-Zeldovich (SZ) effect, the scattering of cosmic microwave
background photons off hot electrons in bulk motion. Our result reproduces the
Ostriker-Vishniac effect to second order in perturbation theory but contains
nonlinear corrections to the electron velocities and densities that were
neglected previously. We use the recently developed halo model for nonlinear
gravitational clustering to compute the nonlinear kinetic SZ power spectrum,
which dominates the primary anisotropy on small angular scales.


title: X-ray Destruction of Dust Along the Line of Sight to Gamma-Ray Bursts

abstract:
  We show that if all gamma-ray bursts emit X-rays in a way similar to those
observed by BeppoSax, much of the extinction along the line of sight in the
host galaxy of the burst can be destroyed. Two mechanisms are principally
responsible for dust destruction: grain heating and grain charging. The latter,
which can lead to electrostatic stresses greater than the tensile strength of
the grains, is often the more important. Grains may regularly be destroyed at
distances as large as 100 parsecs. This dust destruction can permit us to see
the UV/optical afterglow even when the burst is embedded deep within a
highly-obscured region. Because the destruction rate depends on grain
composition and size, it may be possible to observe the amount and
wavelength-dependence of extinction change during the course of the burst and
first few minutes of the afterglow. It may also be possible to detect
interstellar absorption lines in the afterglow spectrum that would not exist
but for the return of heavy elements to the gas phase.


title: Mid-IR Observations of Mira Circumstellar Environment

abstract:
  This paper presents results from high-angular resolution mid-IR imaging of
the Mira AB circumbinary environment using the MIRAC3 camera at the NASA
Infrared Telescope Facility (IRTF). We resolved the dusty circumstellar
envelope at 9.8, 11.7 and 18 micron around Mira A (o Ceti), and measured the
size of the extended emission. Strong deviations from spherical symmetry are
detected in the images of Mira AB system, including possible dust clumps in the
direction of the companion (Mira B). These observations suggest that Mira B
plays an active role in shaping the morphology of the circumstellar environment
of Mira A as it evolves toward the Planetary Nebula phase.


title: Evolution of Globular Clusters Formed in Mergers

abstract:
  Globular clusters formed in galactic mergers (e.g., The Antennae) can now be
studied at different stages of their evolution. In young merger remnants (e.g.,
NGC 7252) these "second-generation" globulars appear by the hundreds as young
halo clusters of roughly solar metallicity. While at first bluer and much more
luminous than old metal-poor globulars, they become redder after 1 - 1.5 Gyr
and can then be observed as still overluminous red clusters of intermediate age
in perturbed-looking E and S0 galaxies (e.g., NGC 1316, NGC 1700, and NGC
3610). There is evidence from the color distributions, projected radial
distributions, and perhaps also luminosity functions that these clusters
eventually assume the properties of red metal-rich globulars observed in many
giant ellipticals. Studies of globular clusters in ongoing mergers and young
remnants suggest that second-generation globulars form from giant molecular
clouds shocked by the rapid pressure increase in the merger-induced starburst.
This pressure-induced formation lends credence to Cen's (2001) argument that
the general pressure increase during cosmological reionization at z ~= 7 - 15
triggered the near-simultaneous formation of the universal population of
first-generation metal-poor globulars observed in galaxies of all types.


title: The CANGAROO-III Project: Status report

abstract:
  We report on the status of the construction of an array of four 10 m
atmospheric Cherenkov telescopes for gamma-ray astronomy, near Woomera, in
South Australia -- the CANGAROO-III project. The first telescope of this array
is the upgraded version of the CANGAROO-II 7 m telescope and has been in
operation since March 2000. The second telescope, an improved version of the
first, is being constructed for installation in late 2001. Stereoscopic
observation of sub TeV gamma-rays with the two 10 m telescopes will begin in
2002 and the full array will be operational in 2004.


title: Cangaroo-II and Cangaroo-III

abstract:
  Preliminary results from CANGAROO-II, a 10 m imaging Cherenkov telescope, in
Woomera, South Australia are presented. They include the confirmation of
detections of TeV gamma-ray sources we have reported using a 3.8 m telescope,
CANGAROO-I. Also the status of the construction of an array of four 10 m
telescopes, called CANGAROO-III, is reported. The first telescope of the array
was upgraded from the 7 m telescope and the second one is being constructed in
this year. The full array will be operating in 2004.


title:
Solving for closure errors due to polarization leakage in radio
  interferometry of unpolarized sources

abstract:
  Mechanical and electronic imperfections can result into polarization leakage
in individual antennas of a radio interferometer. Such leakages manifest
themselves as closure errors even in co-polar visibility measurements of
unpolarized sources. This paper describes and tests a method for the study of
polarization leakage for radio interferometric telescopes using {\it only} the
nominally co-polar visibilities for unpolarized calibrators. Interpretation of
the resulting closure phases on the Poincar\'e sphere is presented. Since
unpolarized sources are used, the actual solutions for leakage parameters is
subject to a degeneracy which is discussed. This however, does not affect the
correction of closure errors in our scheme.


title: Constraints on Cosmic Quintessence and Quintessential Inflation

abstract:
  Recently, attempts have been made to understand the apparent near coincidence
of the present dark energy and matter energy in terms of a dynamical
attractor-like solution for the evolution of a scalar field. In these models
the field couples with the dominant constituent and only acts like a
cosmological constant after the onset of the matter-diminated epoch. A generic
feature of such solutions, however, is the possibility of significant energy
density in the scalar field during the radiation-dominated epoch. This
possibility is even greater if the quintessence field begins in a
kinetic-dominated regime generated at the end of quintessential inflation. As
such, these models can affect and be constrained by primordial nucleosynthesis
and the epoch of of photon decoupling. Here, we analyze one popular form of the
quintessence field (with and without a supergravity correction) and quantify
constraints on the allowed initial conditions and parameters for the effective
potential. We also deduce constraints on the epoch of matter creation at the
end of quintessential inflation.


title: Measurements of the Gravity Waves Velocity

abstract:
  Some results are presented of the Earth's microseismic background. It is
assumed that background peaks should correspond to the resonance gravity-wave
exchange in the system of two gravity-connected bodies. The microseismic
spectrum is compared with the distribution of gravity potential of the nearest
stars. A close peak-to-peak correspondence is found. This correspondence and
resonance condition lead to an evaluation of the gravity-wave velocity. The
resulting value is nine orders of magnitude more than the velocity of light.
Some consequences of such result are discussed.


title:
New statistical goodness of fit techniques in noisy inhomogeneous
  inverse problems - With application to the recovering of the luminosity
  distribution of the Milky Way

abstract:
  The assumption that a parametric class of functions fits the data structure
sufficiently well is common in fitting curves and surfaces to regression data.
One then derives a parameter estimate resulting from a least squares fit, say,
and in a second step various kinds of chi^2 goodness of fit measures, to assess
whether the deviation between data and estimated surface is due to random noise
and not to systematic departures from the model. In this paper we show that
commonly-used chi^2-measures are invalid in regression models, particularly
when inhomogeneous noise is present. Instead we present a bootstrap algorithm
which is applicable in problems described by noisy versions of Fredholm
integral equations. of the first kind. We apply the suggested method to the
problem of recovering the luminosity density in the Milky Way from data of the
DIRBE experiment on board the COBE satellite.


title:
Search for gamma-rays above 10 TeV from Markarian 421 in a high state
  with the CANGAROO-II telescope

abstract:
  A preliminary result from Markarian 421 observations in the energy region
above 10 TeV with the CANGAROO-II 10 m telescope is presented. In January 2001,
the HEGRA group reported that Markarian 421 had become very active, with flux
levels up to 4 times that of the Crab Nebula. As a result, we observed Mkn 421
during six nights from January 24th to February 1st, and four nights from March
1st to 4th. Observations were carried out using the very large zenith angle
technique ($\sim$70 degree) and the energy threshold is estimated from Monte
Carlo simulations to be around 10 TeV. We have detected gamma-ray emission in
this energy range.


title: A Search for Sub-Millisecond Pulsars

abstract:
  We have conducted a search of 19 southern Galactic globular clusters for
sub-millisecond pulsars at 660 MHz with the Parkes 64-m radio telescope. To
minimize dispersion smearing we used the CPSR baseband recorder, which samples
the 20 MHz observing band at the Nyquist rate. By possessing a complete
description of the signal we could synthesize an optimal filterbank in
software, and in the case of globular clusters of known dispersion measure,
much of the dispersion could be removed using coherent techniques. This allowed
for very high time resolution (25.6 us in most cases), making our searches in
general sensitive to sub-millisecond pulsars with flux densities greater than
about 3 mJy at 50 cm. No new pulsars were discovered, placing important
constraints on the proportion of pulsars with very short spin periods in these
clusters.


title: U, B and r band luminosity functions of galaxies in the Coma cluster

abstract:
  We present a deep multi-colour CCD mosaic of the Coma cluster (Abell 1656),
covering 5.2 deg^2 in the B and r bands, and 1.3 deg^2 in the U band. This
large, homogeneous data set provides a valuable low redshift comparison sample
for studies of galaxies in distant clusters. In this paper we present our
survey, and study the dependence of the galaxy luminosity function (LF) on
passband and radial distance from the cluster centre. The U, B and r band LFs
of the complete sample cannot be represented by single Schechter functions. For
the central area, r<245 h_{100}^{-1} kpc, we find best-fitting Schechter
parameters of M^{*}_U=-18.60^{+0.13}_{-0.18} and
\alpha_U=-1.32^{+0.018}_{-0.028}, M^{*}_B=-19.79^{+0.18}_{-0.17} and
\alpha_B=-1.37^{+0.024}_{-0.016} and M^{*}_r=-20.87^{+0.12}_{-0.17} and
\alpha_r=-1.16^{+0.012}_{-0.019}. The LF becomes steeper at larger radial
distance from the cluster centre. The effect is most pronounced in the U band.
This result is consistent with the presence of a star forming dwarf population
at large distance from the cluster centre, which may be in the process of being
accreted by the cluster. The shapes of the LFs of the NGC 4839 group support a
scenario in which the group has already passed through the centre.


title: The X-ray background from groups and clusters of galaxies

abstract:
  We present an estimate of the X-ray background (XRB) spectrum from the
warm-hot intergalactic medium (IGM) associated with groups and clusters of
galaxies, using purely the observationally determined X-ray luminosity function
(XLF) and X-ray luminosity (Lx) - temperature (T) relations for groups and
clusters. As compared with previous semi-analytic models based on the
Press-Schechter mass function, our approach provides a much simpler and more
realistic way to evaluate the XRB from groups and clusters in the sense that we
make no assumption about the dynamical and heating properties of the IGM, and
the intrinsic dispersion in the Lx-T relations due to different physical
mechanisms among different groups and clusters can be also included. It shows
that the resulting 0.1-10 keV XRB spectrum by summing up the X-ray emission
from all groups and clusters is consistent with current upper limits placed on
the contribution from diffuse gas to the XRB. This may have profound
implications for our understanding of the missing baryons in the universe.


title: The Imprint of Presupernova Evolution on Supernovae Remnants

abstract:
  The evolution of type Ia supernova binary system progenitors is highly
uncertain. Several evolutionary models predict that the accretion of mass onto
the white dwarf is accompanied by mass ejection from the binary in the form of
a powerful wind, but very few observations have been made during the initial
phase of formation of supernovae remnants, when the interaction of supernova
ejecta with presupernova wind could be tested. Here we present hydrodynamical
simulations of supernova ejecta interaction with an ambient medium modified by
presupernova wind. The structure of the ambient medium when the supernova
explodes is very sensitive to the details of wind history, and the evolution of
the supernova remnant can be affected during several thousand years. We have
found that the forward shock expansion parameter is a good tool for
discriminating between several wind models. The evolution of the supernova
remnant in the presence of an ambient medium modified by interaction with
pre-supernova wind cannot be described by a similarity solution. We also rule
out simple models based on a circumstellar medium that merges smoothly with a
uniform density ambient medium.


title: K-band spectroscopy of the intermediate polar XY Ari

abstract:
  We present the K-band infrared spectrum of the intermediate polar XY Ari. The
spectrum confirms the cataclysmic binary nature of XY Ari, showing emission
lines of HeI (2.0587 microns) and the Brackett and Paschen series of HI. The
broad nature of these lines suggest an origin in an accretion disc. The
spectrum is strongly reddened by absorption within the molecular cloud Lynds
1457 and shows prominent absorption features from the secondary star, from
which we determine a spectral type for the secondary of M0V. The secondary
contributes 80 +/- 6% of the K-band light. We derive a visual extinction to XY
Ari of Av = 11.5 +/- 0.3 and a distance of d=270 +/- 100 pc, placing XY Ari
behind the molecular cloud.


title: Galactic Mergers with Supermassive Black Holes

abstract:
  We present the results of N-body simulations of the accretion of high-density
dwarf galaxies by low-density giant galaxies. Both galaxies contain power-law
central density cusps and point masses representing supermassive black holes;
the ratio of galaxy masses is 3:1. The cusp of the dwarf galaxy is always
disrupted during the merger, leading to a remnant with a weak power law in the
intrinsic density and a ``core'' in the projected density. Removing both black
holes from the giant and dwarf galaxies allows the dwarf galaxy to remain
intact and leads to a remnant with a high central density, contrary to what is
observed. Our results support the hypothesis than the persistence of
low-density cores in giant galaxies following mergers is a consequence of the
existence of supermassive central black holes.


title: The Interstellar Environment of our Galaxy

abstract:
  We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.


title: The 'Forbidden' Abundance of Oxygen in the Sun

abstract:
  We reexamine closely the solar photospheric line at 6300 A, which is
attributed to a forbidden line of neutral oxygen, and is widely used in
analyses of other late-type stars.
  We use a three-dimensional time-dependent hydrodynamical model solar
atmosphere which has been tested successfully against observed granulation
patterns and an array of absorption lines. We show that the solar line is a
blend with a Ni I line, as previously suggested but oftentimes neglected.
Thanks to accurate atomic data on the [O I] and Ni I lines we are able to
derive an accurate oxygen abundance for the Sun: log epsilon (O) = 8.69 +/-
0.05 dex, a value at the lower end of the distribution of previously published
abundances, but in good agreement with estimates for the local interstellar
medium and hot stars in the solar neighborhood. We conclude by discussing the
implication of the Ni I blend on oxygen abundances derived from the [O I] 6300
A line in disk and halo stars.


title:
A multivariate statistical analysis of spiral galaxy luminosities. I.
  Data and results

abstract:
  We have performed a multiparametric analysis of luminosity data for a sample
of 234 normal spiral and irregular galaxies observed in X-rays with the {\it
Einstein Observatory}. This sample is representative of S and Irr galaxies,
with a good coverage of morphological types and absolute magnitudes. In
addition to X-ray and optical da ta, we have compiled H-band magnitudes, IRAS
near- and far-infrared, and 6cm radio co ntinuum observations for the sample
from the literature. We have also performed a carefu l compilation of distance
estimates. We have explored the effect of morphology by dividing the sample
into early (S0/a-Sab), intermediate (Sb-Sbc), and late-type (Sc-Irr)
subsamples. The data were analysed with bivariate and multiv ariate survival
analysis techniques that make full use of all the information available in both
detections and limits.


title:
The SCUBA Local Universe Galaxy Survey II. 450 micron data - evidence
  for cold dust in bright IRAS Galaxies

abstract:
  This is the second in a series of papers presenting results from the SCUBA
Local Universe Galaxy Survey. In our first paper we provided 850 micron flux
densities for 104 galaxies selected from the IRAS Bright Galaxy Sample and we
found that the 60, 100 micron (IRAS) and 850 micron (SCUBA) fluxes could be
adequately fitted by emission from dust at a single temperature. In this paper
we present 450 micron data for the galaxies. With the new data, the spectral
energy distributions of the galaxies can no longer be fitted with an isothermal
dust model - two temperature components are now required. Using our 450 micron
data and fluxes from the literature, we find that the 450/850 micron flux ratio
for the galaxies is remarkably constant and this holds from objects in which
the star formation rate is similar to our own Galaxy, to ultraluminous infrared
galaxies (ULIRGS) such as Arp 220. The only possible explanation for this is if
the dust emissivity index for all of the galaxies is ~2 and the cold dust
component has a similar temperature in all galaxies (20-21 K). The dust masses
estimated using the new temperatures are higher by a factor ~2 than those
determined previously using a single temperature. This brings the gas-to-dust
ratios of the IRAS galaxies into agreement with those of the Milky Way and
other spiral galaxies which have been intensively studied in the submm.


title: Mean Square Radius of EAS Electrons

abstract:
  Detailed theoretical study of the mean square radius of extensive air shower
electrons has been made in connection with further development of scaling
formalism for electron lateral distribution function. A very simple
approximation formula, which allows joint description of all our results
obtained in wide primary energy range and for different observation depths is
presented. The sensitivity of the mean square radius to variations of basic
parameters of hadronic interaction model is discussed.


title: Theoretical Estimates of Intrinsic Galaxy Alignment

abstract:
  It has recently been argued that the observed ellipticities of galaxies may
be determined at least in part by the primordial tidal gravitational field in
which the galaxy formed. Long-range correlations in the tidal field could thus
lead to an ellipticity-ellipticity correlation for widely separated galaxies.
We present a new model relating ellipticity to angular momentum, which can be
calculated in linear theory. We use this model to calculate the angular power
spectrum of intrinsic galaxy shape correlations. We show that for low redshift
galaxy surveys, our model predicts that intrinsic correlations will dominate
correlations induced by weak lensing, in good agreement with previous
theoretical work and observations. We find that our model produces `E-mode'
correlations enhanced by a factor of 3.5 over B-modes on small scales, making
it harder to disentangle intrinsic correlations from those induced by weak
gravitational lensing.


title:
The Shape of EAS Lateral Distribution and Primary Composition of the UHE
  Cosmic Rays

abstract:
  Theoretical predictions for lateral distribution function of electrons in
extensive air showers based on scaling formalism are presented. Our results are
tested by comparison with AGASA experimental data taking into account the
contribution of low-energy muons and simultaneously the effect of scintillation
detectors response, according to recent simulation results. The possibility for
ultrahigh energy cosmic ray primary composition deduction from the shape of LDF
is discussed in detail.


title: Neutron-Capture Element Abundances and Cosmochronometry

abstract:
  Abundance ratios of radioactive to stable neutron-capture elements in very
metal-poor stars may be used to estimate the age of our Galaxy. But extracting
accurate ages from these data requires continuing work on many fronts: a)
identification of more low metallicity stars with neutron-capture element
excesses; b) acquisition of the best high resolution stellar spectra; c)
improvement in neutron-capture element transition probabilities; d) calculation
of more realistic nuclear models for, and interactions among the heaviest
elements; and e) and more self-consistent production predictions for these
elements in supernovae. This review discusses several of these areas and makes
suggestions about how to improve the accuracy of Galactic cosmochronometry.


title: Direct Analysis of Spectra of Type Ib Supernovae

abstract:
  Synthetic spectra generated with the parameterized supernova
synthetic-spectrum code SYNOW are compared to photospheric-phase spectra of
Type Ib supernovae (SNe Ib). Although the synthetic spectra are based on many
simplifying approximations, including spherical symmetry, they account well for
the observed spectra. Our sample of SNe Ib obeys a tight relation between the
velocity at the photosphere, as determined from the Fe II features, and the
time relative to that of maximum light. From this we infer that the masses and
the kinetic energies of the events in this sample were similar. After maximum
light the minimum velocity at which the He I features form usually is higher
than the velocity at the photosphere, but the minimum velocity of the ejected
helium is at least as low as 7000 kms. Previously unpublished spectra of SN
2000H reveal the presence of hydrogen absorption features, and we conclude that
hydrogen lines also were present in SNe 1999di and 1954A. Hydrogen appears to
be present in SNe Ib in general, although in most events it becomes too weak to
identify soon after maximum light. The hydrogen-line optical depths that we use
to fit the spectra of SNe 2000H, 1999di, and 1954A are not high, so only a mild
reduction in the hydrogen optical depths would be required to make these events
look like typical SNe Ib. Similarly, the He I line optical depths are not very
high, so a moderate reduction would make SNe Ib look like SNe Ic.


title: HST observations of NGC 6240

abstract:
  WFPC2 images and STIS spectroscopic observations are presented of the double
nucleus in the merger system NGC 6240. We find that: (a) the kinematics of the
ionized gas is similar to that of the molecular gas, despite a different
morphology; (b) the gaseous and stellar kinematics are quite different,
suggesting an early merger stage; (c) neither the gaseous nor the stellar
kinematics show an obvious sign of the supermassive black hole believed to be
responsible for the X-ray emission of NGC 6240; and (d) the steep off-nuclear
velocity gradient is not due to a 10E11 solar mass black hole, in contrast to
earlier suggestions.


title: Microwave plasma emission of a flare on AD Leo

abstract:
  An intense radio flare on the dMe star AD Leo, observed with the Effelsberg
radio telescope and spectrally resolved in a band of 480 MHz centred at 4.85
GHz is analysed. A lower limit of the brightness temperature of the totally
right handed polarized emission is estimated as T_b ~ 5x10^10 K (with values
T_b > ~3x10^13 K considered to be more probable), which requires a coherent
radio emission process. In the interpretation we favour fundamental plasma
radiation by mildly relativistic electrons trapped in a hot and dense coronal
loop above electron cyclotron maser emission. This leads to densities and
magnetic field strengths in the radio source of n ~ 2x10^11 cm^-3 and B ~ 800
G. Quasi-periodic pulsations during the decay phase of the event suggest a loop
radius of r ~ 7x10^8 cm. A filamentary corona is implied in which the dense
radio source is embedded in hot thin plasma with temperature T >= 2x10^7 K and
density n_ext <= 10^-2 n. Runaway acceleration by sub-Dreicer electric fields
in a magnetic loop is found to supply a sufficient number of energetic
electrons.


title: Rejection of the C7- Diffuse Interstellar Band Hypothesis

abstract:
  Using the new high resolution (~ 8 km/s) echelle spectrograph on the 3.5-m
telescope at the Apache Point Observatory, we have begun a high sensitivity
survey of the diffuse interstellar bands in a large sample of reddened stars.
Now that we are two years into this long-term survey, our sample includes over
20 reddened stars which show at least one of the DIBs that had been suggested
to be caused by C7-, based on the gas phase measurement of the C7- spectrum by
J. P. Maier's group.
  The high quality astronomical data from this larger sample of stars, along
with the spectroscopic constants from the new laboratory work recently reported
by Maier's group, have enabled us to examine more carefully the agreement
between C7- and the DIBs. We find that none of the C7- bands matches the DIBs
in wavelength or expected profile. One of the DIBs (lambda5748) attributed to
C7- is actually a stellar line. The two strongest DIBs attributed to C7-
(lambda 6270 and lambda4964) do not vary together in strength, indicating that
they do not share the same carrier.
  On the whole, we find no evidence supporting the hypothesis that C7- is a
carrier of the diffuse interstellar bands.


title: PSR J1740+1000: A Young Pulsar Well Out Of The Galactic Plane

abstract:
  We discuss PSR J1740+1000, one of five pulsars recently discovered in a
search of 470 square degrees at 430 MHz during the upgrade of the 305-m Arecibo
telescope. The period of 154 ms and period derivative of 2.1 x 10^-14 s/s imply
a spin-down age of 114 kyr that is smaller than 95% of all known pulsars. The
youth and proximity of this pulsar make it a good candidate for detection at
X-ray and gamma-ray energies. Its high Galactic latitude of 20.4 degrees
suggests a very high velocity if the pulsar was born in the midplane of the
Galaxy and if its kinematic age equals its spindown age. Interstellar
scintillations, however, suggest a much lower velocity. We discuss possible
explanations for this discrepancy, taking into account (a) possible birth sites
away from the midplane; (b) contributions from the unmeasured radial velocity;
(c) a kinematic age different from the spin-down age; and (d) biasing of the
scintillation velocity by enhanced scattering from the North Polar Spur.


title: Relativistic photoionization cross sections for C II

abstract:
  High resolution measurements of photoionization cross sections for atomic
ions are now being made on synchrotron radiation sources. The recent
measurements by Kjeldsen etal. (1999) showed good agreement between the
observed resonance features and the the theoretical calculations in the close
coupling approximation (Nahar 1995). However, there were several observed
resonances that were missing in the theoretical predictions. The earlier
theoretical calculation was carried out in LS coupling where the relativistic
effects were not included. Present work reports photoionization cross sections
including the relativistic effects in Breit-Pauli R-matrix (BPRM)
approximation. The configuration interaction eigenfunction expansion for the
core ion C III consists of 20 fine structure levels dominated by the
configurations from 1s^22s^2 to 1s^22s3d. Detailed features in the calculated
cross sections exhibit the missing resonances due to fine structure. The
results benchmark the accuracy of BPRM photoionization cross sections as needed
for recent and ongoing experiments.


title: Star Formation Modes in Low-Mass Disk Galaxies

abstract:
  Low-mass disk galaxies with well-organized structures are relatively common
in low density regions of the nearby Universe. They display a wide range in
levels of star formation activity, extending from sluggishly evolving
`superthin' disk systems to nearby starbursts. Investigations of this class of
galaxy therefore provides opportunities to test and define models of galactic
star formation processes. In this paper we briefly explore characteristics of
examples of quiescent and starbursting low-mass disk galaxies.


title: Public Release of 2dF data from the Fornax Cluster Spectroscopic Survey

abstract:
  Thanks to the 2dF spectrograph on the Anglo-Australian Telescope, we have
recently completed the first stage of a complete spectroscopic survey more than
one order of magnitude larger than any previous study, measuring 7000 spectra
in a 6 sq.deg. area as part of our study of the Fornax Cluster. In this article
we describe the public release of 3600 spectra from our first field. We hope
that this public release will encourage colleagues making surveys for rare
objects to choose these fields, as much of the follow-up spectroscopy that
might be required is available from our data.


title:
Ultra-compact dwarf galaxies: a new class of compact stellar system
  discovered in the Fornax Cluster

abstract:
  We have used the 2dF spectrograph on the Anglo-Australian Telescope to obtain
a complete spectroscopic sample of all objects in the magnitude range, Bj= 16.5
to 19.8, regardless of morphology, in an area centred on the Fornax Cluster of
galaxies. Among the unresolved targets are five objects which are members of
the Fornax Cluster. They are extremely compact stellar systems with scale
lengths less than 40 parsecs. These ultra-compact dwarfs are unlike any known
type of stellar system, being more compact and significantly less luminous than
other compact dwarf galaxies, yet much brighter than any globular cluster.


title: The evolution and star formation of dwarf galaxies in the Fornax Cluster

abstract:
  We present the results of a spectroscopic survey of 675 bright (16.5<Bj<18)
galaxies in a 6 degree field centred on the Fornax cluster with the FLAIR-II
spectrograph on the UK Schmidt Telescope. We measured redshifts for 516
galaxies of which 108 were members of the Fornax Cluster. Nine of these are new
cluster members previously misidentified as background galaxies. The cluster
dynamics show that the dwarf galaxies are still falling into the cluster
whereas the giants are virialised. Our spectral data reveal a higher rate of
star formation among the dwarf galaxies than suggested by morphological
classification: 35 per cent have H-alpha emission indicative of star formation
but only 19 per cent were morphologically classified as late-types. The
distribution of scale sizes is consistent with evolutionary processes which
transform late-type dwarfs to early-type dwarfs. The fraction of dwarfs with
active star formation drops rapidly towards the cluster centre. The
star-forming dwarfs are concentrated in the outer regions of the cluster, the
most extreme in an infalling subcluster. We estimate gas depletion time scales
for 5 dwarfs with detected HI emission: these are long (of order 10 Gyr),
indicating that active gas removal must be involved if they are transformed
into gas-poor dwarfs as they fall further into the cluster. In agreement with
our previous results, we find no compact dwarf elliptical (M32-like) galaxies
in the Fornax Cluster.


title: Ultra-Compact Dwarf Galaxies in the Fornax Cluster

abstract:
  By utilising the large multi-plexing advantage of the 2dF spectrograph on the
Anglo-Australian Telescope, we have been able to obtain a complete
spectroscopic sample of all objects in a predefined magnitude range,
16.5<Bj<19.7, regardless of morphology, in an area towards the centre of the
Fornax Cluster of galaxies. Among the unresolved or marginally resolved targets
we have found five objects which are actually at the redshift of the Fornax
Cluster, i.e. they are extremely compact dwarf galaxies or extremely large star
clusters. All five have absorption line spectra. With intrinsic sizes less than
1.1 arc second HWHM (corresponding to approximately 100 pc at the distance of
the cluster), they are more compact and significantly less luminous than other
known compact dwarf galaxies, yet much brighter than any globular cluster. In
this letter we present new ground based optical observations of these enigmatic
objects. In addition to having extremely high central surface brightnesses,
these objects show no evidence of any surrounding low surface brightness
envelopes down to much fainter limits than is the case for, e.g., nucleated
dwarf ellipticals. Thus, if they are not merely the stripped remains of some
other type of galaxy, then they appear to have properties unlike any previously
known type of stellar system.


title: Shocking Clouds in the Cygnus Loop

abstract:
  With Hubble Space Telescope Wide-Field Planetary Camera 2 observations of the
Cygnus Loop supernova remnant, we examine the interaction of an interstellar
cloud with the blast wave on physical scales of 10^15 cm. The shock front is
distorted, revealing both edge-on and face-on views of filaments and diffuse
emission, similar to those observed on larger scales at lower resolution. We
identify individual shocks in the cloud of density n~15 cm^-3 having velocity
v_s~170 km/s. We also find the morphologically unusual diffuse Balmer-dominated
emission of faster shocks in a lower-density region. The obstacle diffracts
these shocks, so they propagate at oblique angles with respect to the primary
blast wave. The intricate network of diffuse and filamentary H alpha emission
arises during the early stage of interaction between the cloud and blast wave,
demonstrating that complex shock propagation and emission morphology occur
before the onset of instabilities that destroy clouds completely.


title:
Galaxy clustering in the Sloan Digital Sky Survey (SDSS) : A first
  comparison with the APM Galaxy Catalogue

abstract:
  We compare the large scale galaxy clustering in the new SDSS early data
release (EDR) with the clustering in the APM Galaxy Survey. We cut out pixel
maps (identical in size and shape) from the SDSS and APM data to allow a direct
comparison of the clustering. Here we concentrate our analysis on an equatorial
SDSS strip in the South Galactic Cap (EDR/SGC) with 166 deg^2, 2.5 wide and 65
degrees long. Only galaxies with Petrosian magnitudes 16.8 <g'<19.8 are
included to match the surface density of the 17< b_J<20 APM pixel maps (median
depth of 400 Mpc/h). Both the amplitude and shape of the angular 2-point
function and variance turn out to be in very good agreement with the APM on
scales smaller than 2 degrees (ie 15 Mpc/h). The 3-point function and skewness
are also in excellent agreement within a 90% confidence level. On one hand
these results illustrate that the EDR data and SDSS software pipelines, work
well and are suitable to do analysis of large scale clustering. On the other
hand it confirms that large scale clustering analysis is becoming "repeatable"
and therefore that our conclusions for structure formation models seem to stand
on solid scientific grounds.


title: Shapes of dark matter halos

abstract:
  I present an analysis of the density shapes of dark matter halos in LCDM and
LWDM cosmologies. The main results are derived from a statistical sample of
galaxy-mass halos drawn from a high resolution LCDM N-body simulation. Halo
shapes show significant trends with mass and redshift: low-mass halos are
rounder than high mass halos, and, for a fixed mass, halos are rounder at low
z. Contrary to previous expectations, which were based on cluster-mass halos
and non-COBE normalized simulations, LCDM galaxy-mass halos at z=0 are not
strongly flattened, with short to long axis ratios of s = 0.70 +/- 0.17. I go
on to study how the shapes of individual halos change when going from a LCDM
simulation to a simulation with a warm dark matter power spectrum (LWDM). Four
halos were compared, and, on average, the WDM halos are more spherical than
their CDM counterparts (s =0.77 compared to s = 0.71). A larger sample of
objects will be needed to test whether the trend is significant.


title: A Hidden Nucleus in Cygnus A, but Not in M87

abstract:
  Historically the narrow line radio galaxies were thought to be intrinsically
nonthermal, and without significant accretion. When the Unified Model came
along the compelling observational motivation for this lost some force: some
are found to be hidden broad line objects, and in principle that could be the
case with all of them.
  The clear sign of a hidden quasar is a normal quasar spectrum in polarized
(scattered) light. However that test requires a suitably placed "mirror." A
more robust test is the high predicted mid-IR core luminosity reradiating from
the obscuring matter. Cygnus A has this component, but M87 does not.


title: Sensitivity of the Astrometric Technique in Detecting Outer Planets

abstract:
  With the advent of optical interferometers that will be coming online in the
next decade, radial velocity searches for extra-solar planets will be
complemented by high angular resolution astrometric measurements. In this
paper, we explore the sensitivity of the astrometric technique, and develop an
analytical understanding of the sensitivity in the regime where the orbital
period is longer than the time-baseline of the survey. As in an earlier paper
that dealt with the radial velocity technique, our analysis of the astrometric
technique utilizes both the orbital amplitude and phase.


title:
Time-resolved spectroscopy and photometry of the dwarf nova FS Aurigae
  in quiescence

abstract:
  We present results of non-simultaneous time-resolved photometric and
spectroscopic observations of the little-studied dwarf nova FS Aur in
quiescence. The spectrum of FS Aur shows strong and broad emission lines of
hydrogen and HeI, and of weaker HeII 4686 and CIII/NIII blend, similar to other
quiescent dwarf novae. All emission lines are single-peaked, however their form
varies with orbital phase. Absorption lines from a late-type secondary are not
detected. From the radial velocity measurements of the hydrogen lines H$_\beta$
and H$_\gamma$ we determined a most probable orbital period P=0.059+-0.002.
This period agrees well with the 0.0595+-0.0001 estimate by Thorstensen et al.
(1996). On the other hand, the period of photometric modulations is longer than
the spectroscopic period and can be estimated as 3 hours. Longer time coverage
during a single night is needed to resolve this problem. Using the
semi-amplitude of the radial velocities, obtained from measurements of hydrogen
and helium lines, and some empirical and theoretical relations we limited the
basic parameters of the system: a mass ratio q>=0.22, a primary mass M_1=0.34 -
0.46 M_sun, a secondary mass M_2<= 0.1M_sun, and an inclination angle
i=51^{\circ} - 65^{\circ}. Doppler tomography has shown at least two bright
regions in the accretion disk of FS Aur. The first, brighter spot is located at
phase about 0.6. The second spot is located opposite the first one and occupies
an extensive area at phases about 0.85 - 1.15.


title: Internal and external shock fronts in He2-104

abstract:
  The spectra of both the inner and outer nebulae in He2-104 are modelled by
composite models which accounts consistently for photoionisation and shocks.
The temperature of the hot star results Ts = 130 000 K. We suggest that the
characteristic "crab legs" in He2-104 are produced by R-T instability at the
shock front. The calculated X-ray flux is below the detection limit of ROSAT.


title: Statistical properties of circumnuclear HII regions in nearby galaxies

abstract:
  We analyze the statistical properties of the circumnuclear HII regions of a
sample of 52 nearby galaxies ($v < 1000km/s) from archival HST/NICMOS H-band
and Pa alpha (1.87micron) observations at unprecedented spatial resolutions of
between 1 and 30pc. We find HII regions in the central regions of most
galaxies, and more than a hundred in 8 galaxies. In contrast to disk HII
regions, the physical properties (luminosity and size) of individual
circumnuclear HII regions do not vary strongly with the morphological type of
the host galaxy, nor does the number of circumnuclear HII regions per unit
area. The H alpha luminosity within the central kpc, as derived from HII region
emission, is significantly enhanced in early-type (S0/a-Sb) galaxies. We find
evidence that bars increase the circumnuclear star formation, presumably by
funneling gas from the disk towards the nucleus. Barred galaxies exhibit
enhanced luminosities of the brightest HII region, the central kpc H alpha
luminosities (an effect mostly due to the early type galaxies in our sample),
and the star formation rates per unit stellar mass (which could also be
understood as the integral equivalent widths of Pa alpha) over the central kpc
with respect to non-barred galaxies.
  We fit the luminosity functions and diameter distributions of the
circumnuclear HII regions in 8 galaxies where we can catalog enough HII regions
to do so in a meaningful way. We use power laws and find that the fitted slopes
of the HII region LF are exactly in the previously found ranges, and even
confirm a trend with steeper slopes in galaxies of earlier morphological type.
This implies that the physical processes giving rise to enhanced star formation
in the circumnuclear regions of galaxies must be similar to those in disks.


title: Pulsars Born in Open Stellar Clusters

abstract:
  For two nearby pulsars, formed close to the galactic plane, their host open
stellar clusters have been found.


title: The Fate of the Accelerating Universe

abstract:
  The presently accelerating universe may keep accelerating forever, eventually
run into the event horizon problem, and thus be in conflict with the
superstring idea. In the other way around, the current accelerating phase as
well as the fate of the universe may be swayed by a negative cosmological
constant, which dictates a big crunch. Based on the current observational data,
in this paper we investigate how large the magnitude of a negative cosmological
constant is allowed to be. In addition, for distinguishing the sign of the
cosmological constant via observations, we point out that a measure of the
evolution of the dark energy equation of state may be a good discriminator.
Hopefully future observations will provide much more detailed information about
dark energy and thereby indicates the sign of the cosmological constant as well
as the fate of the presently accelerating universe.


title: First weak lensing results from the Red-Sequence Cluster Survey

abstract:
  The Red-Sequence Cluster Survey (RCS) is a 100 square degree galaxy cluster
survey designed to provide a large sample of optically selected clusters of
galaxies with redshifts 0.1<z<1.4. The survey data are also useful for a
variety of lensing studies. Several strong lensing clusters have been
discovered so far, and follow up observations are underway. In these
proceedings we present some of the first results of a weak lensing analysis
based on 24 deg^2 of data. We have detected the lensing signal induced by large
scale structure (cosmic shear) at high significance, and find
sigma_8=0.79+-0.08 (for a CDM cosmology with Omega_m=0.3,\Omega_\Lambda=0.7,
h=0.7). Another application of these data is the study of the average
properties of dark matter halos surrounding galaxies. We study the lensing
signal from intermediate redshift galaxies with 19.5<R_C<21 using a
parameterised mass model for the galaxy mass distribution. The analysis yields
a mass weighted velocity dispersion of <sigma^2>^{1/2}= 111+-5 km/s. In
addition we have constrained for the first time the extent of dark matter
halos, and find a robust upper limit for the truncation parameter s<470 h^{-1}
kpc (99.7% confidence). A preliminary analysis also excludes a simple
``prediction'' of lensing according to Modified Newtonian Dynamics (MOND) at
high confidence.


title: M31 globular cluster metallicities and ages

abstract:
  Globular cluster ages are more than just lower limits to the age of the
universe; the distribution of ages constraints the timescales for galaxy
formation and chemical evolution. Globular cluster populations with different
metallicities have now been detected in many galaxies, and understanding how
these populations formed requires knowing their relative ages. We examined the
relative ages of the two M31 globular cluster populations using their color and
luminosity distributions and found that the metal-rich clusters could be up to
50% younger than the metal-poor clusters. While a small delay in the formation
of metal-rich clusters might be imposed by chemical enrichment timescales, a
large age gap demands a more detailed explanation. I outline several
possibilities and their promises and problems.


title:
Light Isotope Abundances in Solar Energetic Particles measured by the
  Space Instrument NINA

abstract:
  This article reports nine Solar Energetic Particle events detected by the
instrument NINA between October 1998 and April 1999. NINA is a silicon-based
particle detector mounted on-board the Russian satellite Resurs-01-N4, which
has flown at an altitude of about 800 km in polar inclination since July 1998.
For every solar event the power-law He4 spectrum across the energy interval
10--50 MeV/n was reconstructed, and spectral indexes, gamma, from 1.8 to 6.8
extracted. Data of He3 and He4 were used to determine the He3/He4 ratio, that
for some SEP events indicated an enrichment in He3. For the 1998 November 7
event the ratio reached a maximum value of 0.33+- 0.06, with spectral indexes
of gamma = 2.5 +- 0.6 and gamma = 3.7 +- 0.3 for He3 and He4, respectively. The
He3/He4 ratio averaged over the remaining events was 0.011 +- 0.004. For all
events the deuterium-to-proton ratio was determined. The average value over all
events was (3.9+-1.4) 10^{-5} across the energy interval 9--12 MeV/n. For one
event (1998 November 24) this ratio yielded approximately 10 times higher than
normal coronal values. Upper limits on the H3/H1 counting ratio for all events
were determined. For the 1998 November 14 SEP event the high flux of heavy
particles detected made it possible to reconstruct the carbon and oxygen flux.


title: On Jupiter's inertial mode oscillations

abstract:
  Properties of inertial modes of Jupiter are investigated for an n=1
polytropic description of the planet interior. We use the anelastic
approximation to overcome the usual handicap of a severe spherical harmonics
truncation. A powerful iterative solver then allows us to compute the
frequencies of the most promising low-order modes using as many spherical
harmonics as necessary. The induced O(1%) errors of our model are now within
observational limits. A plausible seismological model of Jupiter might thus be
at hand provided the use of a more realistic description of the planet
interior.


title: White Dwarfs: Contributors and Tracers of the Galactic Dark-Matter Halo

abstract:
  We examine the claim by Oppenheimer et al. (2001) that the local halo density
of white dwarfs is an order of magnitude higher than previously thought. As it
stands, the observational data support the presence of a kinematically distinct
population of halo white dwarfs at the >99% confidence level. A
maximum-likelihood analysis gives a radial velocity dispersion of
sigma^h_U=150(+80/-40) km/s and an asymmetric drift of v_a^h=176(+102/-80)
km/s, for a Schwarzschild velocity distribution function with
sigma_U:sigma_V:sigma_W=1:2/3:1/2. Halo white dwarfs have a local number
density of 1.1(+2.1/-0.7)x10^-4 pc-3, which amounts to 0.8(+1.6/-0.5) per cent
of the nominal local dark-matter halo density and is 5.0(+9.5/-3.2) times
higher and thus only marginally in agreement with previous estimates (all
errors indicate the 90% C.L.). We discuss several direct consequences of this
white-dwarf population (e.g. microlensing) and postulate a potential mechanism
to eject young white dwarfs from the disc to the halo, through the orbital
instabilities in triple or multiple stellar systems.


title:
The Gas Content and Kinematics of Nearby Blue Compact Galaxies:
  Implications for Studies at Intermediate and High Redshift

abstract:
  We present Arecibo 21 cm spectroscopy, Keck HIRES Hb spectroscopy, and WIYN
R-band images of 11 nearby blue compact galaxies selected to be similar to blue
compact star-forming galaxies at intermediate redshifts (0.1<z<1). We detect HI
in 10 of 11 sample galaxies, yielding HI masses of 0.3-4x10^9 M_odot, HI
linewidths, W_20, of 133-249 km/s, dynamical masses of 0.5-5x10^10 M_odot, gas
depletion timescales, tau_gas, of 0.3-7 Gyr, HI mass fractions of 0.01-0.58,
and mass-to-light ratios of 0.1-0.8. These values span the range typical of
nearby HII galaxies, irregulars and spirals. Despite the restricted
morphological selection, our sample is quite heterogeneous in HI content,
dynamical mass, and gas depletion timescale. Therefore, these galaxies should
look very different from each other in 5 Gyr. Fading of intermediate-z luminous
blue compact galaxies into NGC-type spheroidals is a viable evolutionary
scenario for the least massive, most gas-poor objects. The most consistent
characteristic of our sample is that the ratio, R, of HII linewidth to HI 21 cm
linewidth (W_20) are systematically less than unity. The simplest explanation
is that the ionized gas is more centrally concentrated than the neutral gas
within the gravitational potential. On average R=0.66 +/- 0.16, similar to
findings for local HII galaxies. We find R is also a function of linewidth;
smaller linewidth galaxies have smaller values of R. Correcting optical
linewidths by this factor raises derived masses and places these galaxies on
the local luminosity--linewidth (Tully-Fisher) relation. If this ratio applies
to intermediate-redshift galaxies, then the proposed luminosity evolution of
the Tully-Fisher relation is much smaller and more gradual than suggested by
studies using optical emission-linewidth measurements.


title:
Magnetic Fields in Star-Forming Molecular Clouds II. The Depolarization
  Effect in the OMC-3 Filament of Orion A

abstract:
  Polarized 850 micron thermal emission data of the region OMC-3 in the Orion A
molecular cloud are presented. These data, taken in 1998 with the SCUBA
polarimeter mounted on the James Clerk Maxwell Telescope, have been re-reduced
using improved software. The polarization pattern is not suggestive of a
uniform field structure local to OMC-3, nor does the orientation of the vectors
align with existing polarimetry maps of the OMC-1 core 20' to the south. The
depolarization toward high intensity regions cannot be explained by uniform
field geometry except in the presence of changing grain structure, which is
most likely to occur in regions of high density or temperature (i.e. the
embedded cores). The depolarization in fact occurs along the length of the
filamentary structure of OMC-3 and is not limited to the vicinity of the bright
cores. Such a polarization pattern is predicted by helical field models for
filamentary clouds. We present three scenarios to explain the observed
polarization pattern of OMC-3 in terms of a helical field geometry. Qualitative
models incorporating a helical field geometry are presented for two cases.


title: An evolutionary scenario for blazar unification

abstract:
  Blazar subclasses ranging from flat-spectrum radio quasars (FSRQs) through
low-frequency-peaked BL Lac objects (LBLs) to high-frequency-peaked BL Lac
objects (HBLs) exhibit a sequence of increasing spectral hardness with
decreasing luminosity that cannot be explained solely by orientation effects.
Using an analytic model for the synchrotron, synchrotron-self-Compton, and
Compton-scattered external radiation from blazar jets, we propose an
evolutionary scenario that links these blazar subclasses in terms of a
reduction of the black-hole accretion power with time. As the circumnuclear
material accretes to fuel the central engine, less gas and dust is left to
scatter accretion-disk radiation and produce an external Compton-scattered
component in blazar spectra. This evolutionary trend produces the sequence FSRQ
-> LBL -> HBL. Such a scenario may also link radio-loud AGNs with ultraluminous
infrared galaxies and optical QSOs, if the latter constitute the high
Eddington-ratio epoch of supermassive black hole growth, as suggested by the
observed anti-correlation between radio and soft X-ray activity in some
Galactic black-hole candidates.


title:
HST Observations of the Nuclear Regions of the Toomre Sequence of
  Merging Galaxies

abstract:
  We present first results from an HST WFPC2 imaging and STIS spectroscopy
program to investigate the structural and star forming properties in the
nuclear regions of the Toomre Sequence of merging galaxies. Here we discuss
V-band, I-band and H-alpha images of the nuclei. We comment briefly on the
connection between the nuclear morphology of the ionized gas and the merger
stage.


title:
STIS spectroscopy of gas disks in the nuclei of nearby, radio-loud,
  early-type galaxies

abstract:
  We present initial results of our analysis of line emission produced in gas
disks found at the centers of a sample of nearby, radio galaxies with radio
jets. We obtained data using STIS (The Space Telescope Imaging Spectrograph) at
three parallel slit positions on the nucleus of each galaxy. This allows us to
map the H$\alpha$ + [NII] flux, the gas radial velocity and the velocity
dispersion. We find evidence of rotating disks in 11 of the sample galaxies and
we can not currently rule out a rotating disk model for the remaining eight.
For rotating systems, we find that the minimum central enclosed mass is greater
than or similar to the predicted black hole mass based on ground-based stellar
velocity dispersions. By modeling the gas dynamics we will go on to constrain
the masses of the black holes. We will also investigate the properties of the
gas disks themselves, giving us an insight into fueling, ionization mechanisms
and the structure of the central regions.


title:
A physically consistent model for X-ray emission by Seyfert 2 galaxies
  demonstrated on NGC 1068

abstract:
  Preliminary analysis of the X-ray spectrum of NGC 1068 obtained by the RGS
spectrometer on board XMM-Newton is presented. A physically consistent model is
developed in order to quantitatively describe the reprocessing of the central
AGN continuum source into the discrete X-ray emission observed in Seyfert 2
galaxies. All the important atomic processes are taken into account, including
photoexcitation, which has been neglected in some previous models. The model
fits the high resolution NGC 1068 data very well, which implies that the
contribution of hot collisional gas to the X-ray spectrum of NGC 1068 is
negligible.


title: Weak Lensing and Dark Energy

abstract:
  We study the power of upcoming weak lensing surveys to probe dark energy.
Dark energy modifies the distance-redshift relation as well as the matter power
spectrum, both of which affect the weak lensing convergence power spectrum.
Some dark-energy models predict additional clustering on very large scales, but
this probably cannot be detected by weak lensing alone due to cosmic variance.
With reasonable prior information on other cosmological parameters, we find
that a survey covering 1000 sq. deg. down to a limiting magnitude of R=27 can
impose constraints comparable to those expected from upcoming type Ia supernova
and number-count surveys. This result, however, is contingent on the control of
both observational and theoretical systematics. Concentrating on the latter, we
find that the {\it nonlinear} power spectrum of matter perturbations and the
redshift distribution of source galaxies both need to be determined accurately
in order for weak lensing to achieve its full potential. Finally, we discuss
the sensitivity of the three-point statistics to dark energy.


title:
Detection of Coronal Mass Ejections in V471 Tauri with the Hubble Space
  Telescope

abstract:
  V471 Tauri, an eclipsing system consisting of a hot DA white dwarf (WD) and a
dK2 companion in a 12.5-hour orbit, is the prototype of the pre-cataclysmic
binaries. The late-type component is magnetically active, due to its being
constrained to rotate synchronously with the short orbital period. During a
program of UV spectroscopy of V471 Tau, carried out with the Goddard High
Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope, we
serendipitously detected two episodes in which transient absorptions in the Si
III 1206 A resonance line appeared suddenly, on a timescale of <2 min. The
observations were taken in a narrow spectral region around Ly-alpha, and were
all obtained near the two quadratures of the binary orbit, i.e., at maximum
projected separation (~3.3 Rsun) of the WD and K star.
  We suggest that these transient features arise when coronal mass ejections
(CME's) from the K2 dwarf pass across the line of sight to the WD. Estimates of
the velocities, densities, and masses of the events in V471 Tau are generally
consistent with the properties of solar CME's. Given our detection of 2 events
during 6.8 hr of GHRS observing, along with a consideration of the restricted
range of latitudes and longitudes on the K star's surface that can give rise to
trajectories passing in front of the WD as seen from Earth, we estimate that
the active V471 Tau dK star emits some 100-500 CME's per day, as compared to
1-3 per day for the Sun. The K dwarf's mass-loss rate associated with CME's is
at least (5-25) x 10^{-14} Msun/yr, but it may well be orders of magnitude
higher if most of the silicon is in ionization states other than Si III.


title:
Tidal truncation of gas replenishment and global suppression of galactic
  star formation in distant clusters

abstract:
  Recent spectroscopic observations of galaxies in distant clusters have
revealed that the rate of star formation in star-forming galaxies is
significantly suppressed with respect to their counterparts in the field at a
similar redshift. It is, however, highly uncertain which physical processes are
responsible for this suppression. We present the results of a numerical
investigation of how the global tidal field of a cluster dynamically influences
the reservoir of halo gas surrounding a disk galaxy as it falls into the
cluster from the surrounding field. We find that the tidal field of the cluster
efficiently removes the halo gas from the galaxy, thereby halting its accretion
onto the disk, and thus the fueling of star formation within. This effectively
truncates the galaxy's star formation. We also find that this tidal truncation
does not depend very strongly on the orbit of the disk with respect to the
center of the cluster.
  These results suggest that the global tidal field of clusters is capable of
causing a widespread and uniform suppression of star formation in galaxies
accreted by the cluster. In light of these results, we discuss the importance
of this tidal truncation of the gas supply in the formation of S0 galaxies in
clusters.


title: Galaxy threshing and the formation of ultra-compact dwarf galaxies

abstract:
  Recent spectroscopic and morphological observational studies of galaxies
around NGC 1399 in the Fornax Cluster (Drinkwater et al. 2000b) have discovered
several `ultra-compact dwarf' galaxies with intrinsic sizes of $\sim$ 100 pc
and absolute $B$ band magnitudes ranging from -13 to -11 mag. In order to
elucidate the origin of these enigmatic objects, we perform numerical
simulations on the dynamical evolution of nucleated dwarf galaxies orbiting NGC
1399 and suffering from its strong tidal gravitational field. Adopting a
plausible scaling relation for dwarf galaxies, we find that the outer stellar
components of a nucleated dwarf are totally removed. This is due to them being
tidally stripped over the course of several passages past the central region of
NGC 1399. The nucleus, however, manages to survive. We also find that the size
and luminosity of the remnant are similar to those observed for ultra-compact
dwarf galaxies, if the simulated precursor nucleated dwarf has a mass of $\sim$
$10^8$ $M_{\odot}$. These results suggest that ultra-compact dwarf galaxies
could have previously been more luminous dwarf spheroidal or elliptical
galaxies with rather compact nuclei.


title: Spectroscopic evolution of dusty starburst galaxies

abstract:
  By using a one-zone chemical and spectrophotometric evolution model of a disk
galaxy undergoing a dusty starburst, we investigate, numerically, the optical
spectroscopic properties in order to explore galaxy evolution in distant
clusters. We adopt an assumption that the degree of dust extinction
(represented by $A_V$) depends on the ages of starburst populations in such a
way that younger stars have larger $A_V$ (originally referred to as selective
dust extinction by Poggianti & Wu 2000). In particular, we investigate how the
time evolution of the equivalent widths of [OII]$\lambda$3727 and H$\delta$ is
controlled by the adopted age dependence. This leads to three main results: (1)
If a young stellar population (with the age of $\sim$ $10^6$ yr) is more
heavily obscured by dust than an old one ($>$ $10^8$ yr), the galaxy can show
an ``e(a)'' spectrum characterized by strong H$\delta$ absorption and
relatively modest [OII] emission. (2) A dusty starburst galaxy with an e(a)
spectrum can evolve into a poststarburst galaxy with an a+k (or k+a) spectrum
0.2 Gyr after the starburst and then into a passive one with a k-type spectrum
1 Gyr after the starburst. This result clearly demonstrates an evolutionary
link between galaxies with different spectral classes (i.e., e(b), e(a), a+k,
k+a, and k). (3) A dusty starburst galaxy can show an a+k or k+a spectrum even
in the dusty starburst phase if the age-dependence of dust extinction is rather
weak, i.e., if young starburst populations with different ages ($\le$ $10^7$
yr) are uniformly obscured by dust.


title: Spectrum Analysis of Type IIb Supernova 1996cb

abstract:
  We analyze a time series of optical spectra of SN 1993J-like supernova
1996cb, from 14 days before maximum to 86 days after that, with a parameterized
supernova synthetic-spectrum code SYNOW. Detailed line identification are made
through fitting the synthetic spectra to observed ones. The derived
photospheric velocity, decreasing from 11,000 km/s to 3,000 km/s, gives a rough
estimate of the ratio of explosion kinetic energy to ejecta mass, i.e. E/M_ej
\sim 0.2-0.5 \times 10^51 ergs / M_ej(M_\sun). We find that the minimum
velocity of hydrogen is about 10,000 km/s, which suggests a small hydrogen
envelope mass of \sim 0.02-0.1 M_ej, or 0.1-0.2 M_\sun if E is assumed 1 \times
10^51 ergs. A possible Ni II absorption feature near 4000 \AA is identified
throughout the epochs studied here and is most likely produced by primordial
nickel. Unambiguous Co II features emerge from 16 days after maximum onward,
which suggests that freshly synthesized radioactive material has been mixed
outward to a velocity of at least 7,000 km/s as a result of hydrodynamical
instabilities. Although our synthetic spectra show that the bulk of the
blueshift of [O I] 5577 net emission, as large as \sim 70 \AA at 9 days after
maximum, is attributed to line blending, a still considerable residual \sim 20
\AA remains till the late phase. It may be evidence of clumpy or large-scale
asymmetric nature of oxygen emission region.


title: A Two-Field Quintessence Model

abstract:
  We study the dynamics of a quintessence model based on two interacting scalar
fields. The model can account for the (recent) accelerated expansion of the
Universe suggested by astronomical observations. Acceleration can be permanent
or temporary and, for both scenarios, it is possible to obtain suitable values
for the cosmological parameters while satisfying the nucleosynthesis constraint
on the quintessence energy density. We argue that the model dynamics can be
made consistent with a stable zero-energy relaxing supersymmetric vacuum.


title:
A third family of super dense stars in the presence of antikaon
  condensates

abstract:
  The formation of $K^-$ and $\bar K^0$ condensation in $\beta$-equilibrated
hyperonic matter is investigated within a relativistic mean field model. In
this model, baryon-baryon and (anti)kaon-baryon interactions are mediated by
the exchange of mesons. It is found that antikaon condensation is not only
sensitive to the equation of state but also to antikaon optical potential
depth. For large values of antikaon optical potential depth, $K^-$ condensation
sets in before the appearance of negatively charged hyperons. We treat $K^-$
condensation as a first order phase transition. The Gibbs criteria and global
charge conservation laws are used to describe the mixed phase. Nucleons and
$\Lambda$ hyperons behave dynamically in the mixed phase. A second order phase
transition to $\bar K^0$ condensation occurs in the pure $K^-$ condensed phase.
Along with $K^-$ condensation, $\bar K^0$ condensation makes the equation of
state softer thus resulting in smaller maximum mass stars compared with the
case without any condensate. This equation of state also leads to a stable
sequence of compact stars called the third family branch, beyond the neutron
star branch. The compact stars in the third family branch have different
compositions and smaller radii than that of the neutron star branch.


title: r-Process in Prompt Supernova Explosions Revisited

abstract:
  We reanalyze $r$-process nucleosynthesis in the neutron-rich ejecta from a
prompt supernova explosion of a low-mass (11 M$_\odot$) progenitor. A pompt
explosion is not yet ruled out as a possibility for low-mass supernova
progenitors. Moreover, there is mounting evidence that a new $r$-process site
may be required. Hence, we assume that a prompt explosion can occur and make a
study of r-process nucleosynthesis in the supernova ejecta. To achieve a prompt
explosion we have performed a general relativistic hydrodynamic simulation of
adiabatic collapse and bounce using a relativistic nuclear-matter equation of
state. The electron fraction $Y_e$ during the collapse was fixed at the
initial-model value. The size of the inner collapsing core was then large
enough to enable a prompt explosion to occur. Adopting the calculated
trajectories of promptly ejected material, we explicitly computed the burst of
neutronization due to electron captures on free protons in the photodissociated
ejecta after the passage of the shock. The thermal and compositional evolution
of the resulting neutron-rich ejecta originating from near the surface of
proto-neutron star was obtained. These were used in nuclear reaction network
calculations to evaluate the products of $r$-process nucleosynthesis. We find
that, unlike earlier studies, the amount of $r$-process material ejected per
supernova is quite consistent with observed galactic $r$-process abundances.
Furthermore, the computed $r$-process abundances are in good agreement with
Solar abundances of $r$-process elements for A$> 100$. This suggests that
prompt supernovae are still a viable $r$-process site. Such events may be
responsible for the abundances of the heaviest $r$-process nuclei.


title: Radio Observations of Infrared Luminous High Redshift QSOs

abstract:
  We present Very Large Array (VLA) observations at 1.4 GHz and 5 GHz of a
sample of 12 Quasi-stellar Objects (QSOs) at z = 3.99 to 4.46. The sources were
selected as the brightest sources at 250 GHz from the recent survey of Omont et
al. (2001). We detect seven sources at 1.4 GHz with flux densities, S_{1.4} >
50 microJy. These centimeter (cm) wavelength observations imply that the
millimeter (mm) emission is most likely thermal dust emission. The
radio-through-optical spectral energy distributions for these sources are
within the broad range defined by lower redshift, lower optical luminosity
QSOs. For two sources the radio continuum luminosities and morphologies
indicate steep spectrum, radio loud emission from a jet-driven radio source.
For the remaining 10 sources the 1.4 GHz flux densities, or limits, are
consistent with those expected for active star forming galaxies. If the radio
emission is powered by star formation in these systems, then the implied star
formation rates are of order 1e3 M_solar/year. We discuss the angular sizes and
spatial distributions of the radio emitting regions, and we consider briefly
these results in the context of co-eval black hole and stellar bulge formation
in galaxies.


title: On the double-mode RR Lyrae variables of the Sculptor dwarf galaxy

abstract:
  Frequency analysis of more than 300 stars of the OGLE database on Sculptor
galaxy has led to the discovery of 18 double-mode RR Lyrae (RRd) variables.
This yields a 20% incidence rate for double-mode pulsation among the variables
previously classified as first overtone RR Lyrae stars in this galaxy. Most of
the RRd stars cover the period range of 0.47d < P_0 < 0.49d but there are two
stars with longer periods of ~0.54d. All variables fit well in the pattern of
the P_0 --> P_1/P_0 diagram, spanned by the RRd stars of the Galactic globular
clusters and those of the Large Magellanic Cloud (LMC). It follows from our
previous investigations that the luminosities and masses of the RRd stars in
Galactic globular clusters and in the LMC are almost independent of
metallicity. By assuming that the Sculptor RRd variables also obey this rule,
with the aid of the pulsation equations we estimate their metallicities. For
most of the stars we get [Fe/H]~ -1.5, which is the same value as that obtained
from a semi-empirical method for the average metallicity of the fundamental
mode (RRab) stars. Two RRd stars have considerably lower metallicities, but
even those are within the range corresponding to the RRab stars. The narrower
metallicity range of the RRd stars is in agreement with their observed
luminosity range, which is about three times smaller than that of the RRab
stars.


title: Do Globular Clusters Harbor Black Holes?

abstract:
  It has been firmly established that there exists a tight correlation between
the central black hole mass and velocity dispersion (or luminosity) of
elliptical galaxies, ``pseudobulges'' and bulges of galaxies, although the
nature of this correlation still remains unclear. In this letter, we explore
the possibility of extrapolating such a correlation to less massive, spherical
systems like globular clusters. In particular, motivated by the apparent
success in globular cluster M15, we present an estimate of the central black
hole mass for a number of globular clusters with available velocity dispersion
in the literature.


title: The Central kpc of Galaxy Bulges

abstract:
  We study the innermost regions of bulges with surface brightness data derived
from combined HST/NICMOS and ground-based NIR profiles. Bulge profiles to 1-2
kpc may be fit with Sersic laws, and show a trend with bulge-to-disk ratio:
low-B/D bulges are roughly exponential, whereas higher-B/D bulges show
increasing Sersic shape index $n$, indicating higher peak central densities and
more extended brightness tails. N-body models of accretion of satellites onto
disk-bulge-halo galaxies show that satellite accretion contributes to the
increase of the shape index $n$ as the bulge grows by accretion. The N-body
results demonstrate that exponential profiles are fragile to merging, hence
bulges with exponential surface brightness profiles cannot have experienced
significant growth by accretion of dense satellites.


title: Fitting Zodiacal Models

abstract:
  Models of the zodiacal light are necessary to convert measured data taken
from low Earth orbit into the radiation field outside the solar system. The
uncertainty in these models dominates the overall uncertainty in determining
the extragalactic background light for wavelengths < 100 microns.


title: Nuclear Components in the Bulges of Disk Galaxies

abstract:
  By combining surface brightness profiles from images taken in the HST/NICMOS
F160W and ground-based (GB) $K$ bands, we have obtained NIR profiles for a well
studied sample of inclined disk galaxies, spanning radial ranges from 20 pc to
a few kpc. We fit PSF-convolved Sersic-plus-exponential laws to the profiles,
and compare the results with the fits to the ground-based data alone. HST
profiles show light excesses over the best-fit Sersic law in the inner ~1
arcsec. This is often as a result of inner power-law cusps similar to the inner
profiles of intermediate-luminosity elliptical galaxies.


title: Observations of galaxies with future X-ray observatories

abstract:
  Normal galaxies are faint and complex X-ray sources that provide very
powerful probes for fundamental astrophysical questions. Examples include: the
study of populations of X-ray emitting sources; the study of the entire
spectrum of black-hole phenomena; and galaxy formation and evolution in
interaction with the surrounding environment. While exciting, all these fields
{\bf require} Chandra sub-arcsecond resolution, and at least comparable
spectral capabilities. They also require much large collecting areas. I argue
that this is the direction we must plan for future X-ray observatories.


title: The Thermal X-ray Emitting Shell of LMC Supernova Remnant 0540-693

abstract:
  We use data from the Advanced CCD Imaging Spectrometer (ACIS) on the Chandra
X-ray Observatory to image the shell surrounding the pulsar B0540-69, and to
measure its spectral properties. Weak emission line features, notably of Fe, Mg
and Si, indicate that the shell is composed primarily of ambient material
heated by the blast wave. The shell emission in the east is faint and circular
in appearance, with a temperature and ionization age of approximately 5 keV and
10^10 cm^-3 s, respectively. The emission in the west is brighter and has a
more complex, distorted morphology, and is fitted with significantly lower
average temperatures and higher ionization ages. An image with photon energies
above 2 keV shows two hard arcs of emission located diametrically opposite each
other at the outer boundary of the remnant shell; the spectra from these
regions could include a substantial nonthermal component.


title: Building dwarf galaxies out of merged young star clusters

abstract:
  Young star clusters in interacting galaxies are often found in groups or
clusters of star clusters containing up to 100 single clusters. In our project
we study the future fate of these clusters of star clusters. We find that the
star clusters merge on time scales of a few dynamical crossing times of the
super-cluster. The resulting merger object has similarities with observed dwarf
ellipticals (dE). Furthermore, if destructive processes like tidal heating,
dynamical friction or interaction with disc or bulge of the parent galaxy are
taken into account our merger objects may evolve into objects resembling dwarf
spheroidal galaxies (dSph), without the need of a high dark matter content.


title: The plerion nebula in IC 443: the XMM-Newton view

abstract:
  \xmm ~observations of the X-ray feature 1SAX J0617.1+2221 in the IC443
supernova remnant are reported.We resolve the structure of the nebula into a
compact core with a hard spectrum of photon index $\gamma=
1.63^{+0.11}_{-0.10}$ in the 2--10 keV energy range. The nebula also has an
extended ($\sim 8\arcmin \times 5\arcmin$) X-ray halo, much larger than the
radio emission extension. The photon index softens, following a linear scaling
with distance from the centroid, similar to other known X-ray plerions. The
index range is compatible with synchrotron burn-off models. All the
observational evidence points toward a confirmation of the plerionic nature of
the nebula, as recently suggested by a \ch observation, but with
characteristics more similar to "non Crab-like" plerions. We discuss the
implications on the synchrotron nebula magnetic field if the $>100$ MeV
emission reported by {\it CGRO EGRET} is produced by the synchrotron emission.
We also constrain the thermal emission of the central object, arguing that the
surface temperature should be around 0.1 keV, although other possible fits
cannot be excluded on the base of the \xmm data


title:
Synthesis of intermediate-mass elements in classical novae: from Si to
  Ca

abstract:
  Thermonuclear runaways driven by accretion into degenerate white dwarf cores
are the source that power classical nova outbursts.
  In this paper, we identify the dominant nuclear paths involved in the
synthesis of intermediate-mass elements, from Si to Ca, during such violent
events.
  New evolutionary sequences of 1.35 Mo ONe novae have been computed, using
updated nuclear reaction rates.
  The main nuclear activity in this region is powered by the leakage from the
NeNa-MgAl region, where the activity is confined during the early stages of the
explosion. We discuss the critical role played by 30P(p,gamma) in the synthesis
of nuclear species beyond sulfur and point out the large uncertainty that
affects its rate, which has dramatic consequences for studies of nova
nucleosynthesis in the Si-Ca mass region.


title:
Binary black holes and tori in AGN I. Ejection of stars and merging of
  the binary

abstract:
  Most galaxies have central massive black holes (BH), and merge with others
during their evolution, as strongly suggested by recent observations.
Consequently a black hole binary (BHB) emerges. Considering the evolution of
the binary when it has become hard, at a separation of the BHs of about 1 pc,
we propose to solve two basic questions in our understanding of the central
activity of galaxies: (1) Do the BHs actually merge? (2) And does the effect of
the torque of the BHB on the surrounding stellar distribution help to explain
the presence of the ubiquitous torus of molecular material surrounding
apparently all active galactic nuclei? While the second question is the topic
of a subsequent paper we try to solve the first in this article. Simulating the
evolution of a stellar cluster in the potential of such a binary by solving the
equations of the restricted three body problem, we obtained the following
results: If the cluster is about as massive as the BHB, the two BHs coalesce
after about 10^7 yr due to ejection of stars with low angular momentum and
finally via emission of gravitational radiation. In a sequence of models where
the mass of the secondary BH increases while M_1 is fixed, a bigger fraction of
stars is ejected. For a more massive cluster the merger then proceeds on
smaller time scales. The cluster is depleted in the central region and the
final distribution of stars assumes a torus-like structure, peaking at three
times the initial distance of the two black holes.


title: The Formation of Molecular Clouds

abstract:
  In a recent paper, Elmegreen (2000) has made a cogent case, from an
observational point of view, that the lifetimes of molecular clouds are
comparable to their dynamical timescales. If so, this has important
implications for the mechanisms by which molecular clouds form. In particular
we consider the hypothesis that molecular clouds may form not by {\it in situ}
cooling of atomic gas, but rather by the agglomeration of the dense phase of
the interstellar medium (ISM), much, if not most, of which is already in
molecular form.


title: Classical and quantum quintessence cosmology

abstract:
  This paper implements the idea of considering the instantonic creation of
brane worlds whose five-dimensional bulk contains a negative cosmological
constant and a scalar quintessence field with time-dependent equation of state,
restricting to the case that the quintessence field couples minimally to
Hilbert-Einstein gravity. We construct an Euclidean formalism, both for the
four- and five-dimensional cases, singling out a Hamiltonian constraint that
depends on the parameter defining the quintessence state equation. Specializing
at several particular values of that parameter, we obtain solutions to the
constraint equation and analyse them both classically and quantum mechanically.
It is found that these solutions can represent either asymptotically anti-de
Sitter wormholes or pure anti-de Sitter spaces whose quantum states are
obtained by means of the Wheeler de Witt equation. Starting with the different
five-dimensional solutions, an instantonic procedure is applied to describe the
creation of geometrically equivalent inflating de Sitter branes whose quantum
states are also evaluated in some cases. We thus consider the quantum state of
the universe to be contributed by all the instantonic paths that correspond to
these particular brane worlds.


title:
X-ray outbursts from nearby `normal' and active galaxies. A review, new
  radio observations, and an X-ray search for further tidal disruption flares

abstract:
  In the last few years, giant-amplitude, non-recurrent X-ray flares have been
observed from several non-active galaxies (NGC 5905, RXJ1242-11, RXJ1624+75,
RXJ1420+53, RXJ1331-32). All of them share similar properties, namely: extreme
X-ray softness in outburst, huge peak luminosity (up to ~10^{44} erg/s), and
the absence of optical signs of Seyfert activity. Tidal disruption of a star by
a supermassive black hole is the favored explanation of these unusual events.
  We present a review of the previous results, a search for radio emission from
all outbursters, based on the NVSS database, and dedicated radio observations
of NGC 5905 carried out with the VLA. These provide important constraints on
the presence of an (obscured) active nucleus (AGN) at the center of each
flaring galaxy. We rigorously explore AGN scenarios to account for the unusual
X-ray outbursts from the optically `normal' galaxies and find AGN-related
models highly unlikely. We conclude that the previously favored scenario -
tidal disruption of a star by a supermassive black hole at the center of each
of the outbursters - provides the best explanation for the X-ray observations.
  Finally, we present results from our on-going search for further X-ray flares
from a sample of ~140 nearby active and non-active galaxies, using the ROSAT
data base. While we do not find another X-ray flaring normal galaxy among this
sample - entirely consistent with the predictions of the tidal disruption
scenario - several highly variable active galaxies are detected. Their
variability is not linked to tidal disruption, but best explained in terms of
absorption or accretion-disk-related models.