title:
Towards a refined cosmic concordance model: joint 11-parameter
  constraints from CMB and large-scale structure

abstract:
  We present a method for calculating large numbers of power spectra C_l and
P(k) that accelerates CMBfast by a factor around 10^3 without appreciable loss
of accuracy, then apply it to constrain 11 cosmological parameters from current
Cosmic Microwave Background (CMB) and Large Scale Structure (LSS) data. While
the CMB alone still suffers from several degeneracies, allowing, e.g., closed
models with strong tilt and tensor contributions, the shape of the real space
power spectrum of galaxies from the IRAS Point Source Catalogue Redshift (PSCz)
survey breaks these degeneracies and helps place strong constraints on most
parameters. At 95% confidence, the combined CMB and LSS data imply a baryon
density 0.020 < omega_b < 0.037, dark matter density 0.10 < omega_d < 0.32 with
a neutrino fraction f_nu < 38%, vacuum density Omega_Lambda < 0.76, curvature
-0.19 < Omega_k < 0.10, scalar tilt 0.86 < n_s < 1.16 and reionization optical
depth tau < 0.44. These joint constraints are quite robust, changing little
when we impose priors on the Hubble parameter, tilt, flatness, gravity waves or
reionization. Adding nucleosynthesis and neutrino priors on the other hand
tightens parameters considerably, requiring Omega_Lambda > 0.49 and a red-tilt.
  The analysis allows a number of consistency tests to be made, all of which
pass. At the 95% level, the flat scalar ``concordance model'' with
Omega_Lambda=0.62, omega_d=0.13, omega_b=0.02, f_nu~0, n_s=0.9, tau=0.1, h=0.63
is consistent with external constraints. The inferred PSCz bias b~1.2 agrees
with the value estimated independently from redshift space distortions. The
inferred cosmological constant value agrees with the one independently derived
from SN 1a studies. Cosmology seems to be on the right track.


title:
Evidence for Polarized Synchrotron Components in Radio-Optical Aligned
  Quasars

abstract:
  A tendency for the axes of double-lobed radio quasars to be aligned with the
electric vectors of optical polarization in the active galactic nuclei is
well-known. However, the origin of the polarization and reason behind its
correlation with radio morphology is not yet established. From accurate
spectropolarimetry of 7 quasars which show this alignment effect, we find that
the polarization is universally confined to the continuum, and not shared by
the line emission or 3000A bump. Over the observed region 4000-8000A, the
spectral indices of polarized flux, P x Flambda, are consistent with uniform
polarization applied to the light of the big blue bump or with synchrotron
emission. However, electron scattering from an optically-thick, geometrically-
thin, accretion disk is well-known to give rise to a polarization position
angle that is perpendicular to the disk axis. Optical synchrotron emission akin
to that shown to exist in the miniblazar 3C273 is a more attractive
explanation, and supporting evidence can be found for some of the targets in
the form of polarimetric variability over intervals of years. Properties of the
most strongly-polarized radio-optical aligned quasars can be explained by
misdirected blazar core components that have net polarizations of P~10% and
provide ~10% of the total optical light.


title:
An accelerated Monte Carlo method to solve two-dimensional radiative
  transfer and molecular excitation

abstract:
  We present a numerical method and computer code to calculate the radiative
transfer and excitation of molecular lines. Formulating the Monte Carlo method
from the viewpoint of cells rather than photons allows us to separate local and
external contributions to the radiation field. This separation is critical to
accurate and fast performance at high optical depths (tau>100). The random
nature of the Monte Carlo method serves to verify the independence of the
solution to the angular, spatial, and frequency sampling of the radiation
field. These features allow use of our method in a wide variety of
astrophysical problems without specific adaptations: in any axially symmetric
source model and for all atoms or molecules for which collisional rate
coefficients are available. Continuum emission and absorption by dust is
explicitly taken into account but scattering is neglected. We illustrate these
features in calculations of (i) the HCO+ J=1-0 and 3-2 emission from a
flattened protostellar envelope with infall and rotation, (ii) the CO, HCO+, CN
and HCN emission from a protoplanetary disk and (iii) HCN emission from a
high-mass young stellar object, where infrared pumping is important. The
program can be used for optical depths up to 1000-10,000, depending on source
model. We expect this program to be an important tool in analysing data from
present and future infrared and (sub) millimetre telescopes.


title:
Analysis of Energy Spectra with Low Photon Counts via Bayesian Posterior
  Simulation

abstract:
  Over the past 10 years Bayesian methods have rapidly grown more popular as
several computationally intensive statistical algorithms have become feasible
with increased computer power. In this paper, we begin with a general
description of the Bayesian paradigm for statistical inference and the various
state-of-the-art model fitting techniques that we employ (e.g., Gibbs sampler
and Metropolis- Hastings). These algorithms are very flexible and can be used
to fit models that account for the highly hierarchical structure inherent in
the collection of high-quality spectra and thus can keep pace with the
accelerating progress of new space telescope designs. The methods we develop,
which will soon be available in the CIAO software package, explicitly model
photon arrivals as a Poisson process and, thus, have no difficulty with high
resolution low count X-ray and gamma-ray data. We expect these methods to be
useful not only for the recently launched Chandra X-ray observatory and XMM but
also new generation telescopes such as Constellation X, GLAST, etc. In the
context of two examples (Quasar S5 0014+813 and Hybrid-Chromosphere Supergiant
Star alpha TrA) we illustrate a new highly structured model and how Bayesian
posterior sampling can be used to compute estimates, error bars, and credible
intervals for the various model parameters.


title: The Size Distribution of the Kuiper Belt Objects

abstract:
  The size distribution is determined directly from the current known Kuiper
Belt Objects (KBOs). We found that there is a peak for the size distribution
around 230 km in diameter. For the objects larger than 230 km, the KBOs
populate as $N(s) \propto s^{-4}$ as we see in Jewitt et al. (1998). For the
objects smaller than 230 km, we found $N(s) \propto s^{3}$. This result from
the current observational data is new and very different from the conventional
concept of the KBO size distribution. Though the true size distribution might
change from what we have after more KBOs be discovered, we argue that the
existence of a peak around 150 km to 250 km is likely.


title: The Evolution and Space Density of Damped Lyman-alpha Galaxies

abstract:
  The results of a new spectroscopic survey of 66 $z \simgt 4$ quasars for
Damped Lyman-alpha absorption systems are presented. The search led to the
discovery of 30 new DLA candidates which are analysed in order to compute the
comoving mass density of neutral gas in a non-zero lambda Universe. The
possible sources of uncertainty are discussed and the implications of our
results for the theories of galaxy formation and evolution are emphasized. A
subsequent paper will present details of the calculations summarised here and a
more extensive explanation of the consequences of our observations for the
understanding of the nature of DLAs.


title:
Sub-parsec-scale Accleration of the Radio Jet in the Powerful Radio
  Galaxy NGC 6251

abstract:
  In order to investigate the genesis of powerful radio jet, we have mapped the
central 10 pc region of the nearby radio galaxy NGC 6251 with a 0.2 pc
resolution using Very Long Baseline Interferometer (VLBI) at two radio
frequencies, 5 GHz and 15 GHz, we have found the sub-parsec-scale counterjet
for the first time in this radio galaxy. This discovery allows us to
investigate the jet acceleration based on the relativistic beaming model.


title: The Planetary System of Upsilon Andromedae

abstract:
  The bright F8 V solar-type star upsilon Andromedae has recently been reported
to have a system of three planets of Jovian masses. In order to investigate the
orbital stability and mutual gravitational interactions among these extrasolar
planets, both forward and backward integrations from the latest observed
orbital elements for all three planets' orbits have been performed under the
coplanar assumption. We reconfirm that the middle and the outer planet have
strong interaction leading to large time variations in the eccentricities of
these planets, which was shown by the previous studies. However, we discuss the
validity of the ignorance of the innermost planet. We argue that this planetary
system is likely to be stable and oscillate around current orbital elements
since it was formed.
  We suggest that one possible way to produce these orbital elements: the
innermost planet has very low eccentricity but the outermost planet has high
eccentricity could be the interaction with the protostellar disc.


title:
Feasibility of Reconstructing the Quintessential Potential Using SNIa
  Data

abstract:
  We investigate the feasibility of the method for reconstructing the equation
of state and the effective potential of the quintessence field from SNIa data.
We introduce a useful functional form to fit the luminosity distance with good
accuracy (the relative error is less than 0.1%). We assess the ambiguity in
reconstructing the equation of state and the effective potential which
originates from the uncertainty in $\Omega_M$. We find that the equation of
state is sensitive to the assumed $\Omega_M$, while the shape of the effective
potential is not. We also demonstrate the actual reconstruction procedure using
the data created by Monte-Carlo simulation. Future high precision measurements
of distances to thousands of SNIa could reveal the shape of the quintessential
potential.


title: RXTE observations of XTE J2012+381 during its 1998 outburst

abstract:
  We present an analysis of the RXTE observations of X-ray transient source XTE
J2012+381 during its 1998 outburst. The spectral and timing properties of the
source emission and their evolution during the outburst are very similar to
what of the X-ray Novae.


title: Afterglows from jetted GRB remnants

abstract:
  We have found that the conventional generic dynamical model for gamma-ray
bursts (GRBs) cannot reproduce the Sedov solution in the non-relativistic
limit. Based on our refined generic dynamical model, we investigate afterglows
from jetted GRB remnants numerically. Many new results are reached. For
example, we find no obvious break in the optical light curve during the
relativistic phase itself. But an obvious break does exist at the transition
from the relativistic phase to the non-relativistic phase, which typically
occurs at time 10 to 30 days. It is very interesting that the break is affected
by many parameters, such as the electron energy fraction, $\xi_{\rm e}$, the
magnetic energy fraction, $\xi_{\rm B}^2$, the initial opening angle of the
jet,$\theta_0$, and the medium density, $n$. We also find that afterglows from
jetted GRB remnants are uniformly characterized by a quick decay during the
non-relativistic phase, with power law timing index greater than 2.1 .
Afterglows from GRB 970228, 980326, 980519, 990123, 990510 and 991208 can be
satisfactorily fitted if the corresponding GRB ejecta are highly collimated.


title: Cosmic Shear with the CFHT

abstract:
  We present results of our cosmic shear survey in progress at the Canada-
France-Hawaii Telescope (CFHT). We analysed 1.7 sq. degrees of data, out of
which we measured a significant correlation of galaxy shape-orientation over
several arcmin scale. We present measurements of the variance of the shear
$<\gamma^2>$ and of the correlation functions $<e_r(\theta)e_r(0)>$,
$<e_t(\theta)e_t(0)>$. The signal is consistent with gravitational lensing by
large scale structures predictions. The level of residual systematics after PSF
correction is small compared to our measured signal. We outline several
evolutions of our work by using additional data covering 9 sq. degrees.


title: Cosmic Shear with the VLT

abstract:
  We report on the detection of cosmic shear on angular scales of 1.3-6.5
arcmin using 45 independent empty fields observed with the Very Large Telescope
(VLT). This result confirms previous measurements obtained with the CFH
Telescope at the same angular scales. We present the data analysis and the
first preliminary results.


title: A Numerical Study of Cosmic Shear Statistics

abstract:
  We explore the stability of the variance and skewness of the cosmic
gravitational convergence field, using two different approaches: first we
simulate a whole MEGACAM survey (100 sq. degrees). The reconstructed mass map,
obtained from a shear map, shows that the state-of-the-art data analysis
methods can measure weak-lensing statistics at angular scales ranging from 2.5'
to 25'. We looked also at the influence of a varying signal-to-noise ratio over
the shear map (due to local variations of source density) on the mass
reconstruction, by means of Monte-Carlo simulation. The effect at small scales
can easily be corrected-for in most of the relevant cases. These results
enhance the confidence in the capability of future large surveys to measure
accurately cosmologically interesting quantities.


title: Hot dust in two hard Chandra X-ray sources

abstract:
  The two brightest hard X-ray sources discovered serendipitously by Chandra in
the field of the lensing cluster A2390 are found to have ISOCAM counterparts at
6.7 and 15 micron. We use this fact, together with their non-detection by SCUBA
at 850 micron, as the basis for DUSTY radiative transfer modelling of their
infrared spectral energy distributions. For the best-fitting models, we find
that the dust which reprocesses the optical--UV light in these Compton-thin AGN
is heated to near its sublimation temperature (above 1000K), with an inner
radius within a parsec of the nucleus. Some warm dust models with inner
temperatures of 200K are also formally acceptable. These findings strongly
support the obscured AGN hypothesis for the new hard X-ray Chandra sources,
which lack both strong emission lines and 850 micron SCUBA detections.


title:
Chandra observations of NGC 253: New insights into the nature of
  starburst-driven superwinds

abstract:
  Arcsecond-resolution X-ray imaging of the nucleus of the nearby starburst
galaxy NGC 253 with Chandra reveals a well-collimated, strongly
limb-brightened, kiloparsec-scale conical outflow from the central starburst
region. The outflow is very similar in morphology to the known H-alpha outflow
cone, on scales down to <= 20 pc. This provides, for the first time, robust
evidence that both X-ray and H-alpha emission come from low volume filling
factor regions of interaction between the fast energetic wind of SN-ejecta and
the denser ambient interstellar medium (ISM), and not from the wind fluid
itself. We provide estimates of the (observationally and theoretically
important) filling factor of the X-ray emitting gas, of between 4 and 40 per
cent, consistent with an upper limit of ~40 per cent based directly on the
observed limb-brightened morphology of the outflow. Only <= 20 per cent of the
observed X-ray emission can come from the volume-filling, metal-enriched, wind
fluid itself. Spatially-resolved spectroscopy of the soft diffuse thermal X-ray
emission reveals that the predominant source of spectral variation along the
outflow cones is due to strong variation in the absorption, on scales of < 60
pc, there being little change in the characteristic temperature of the
emission. We show that these observations are easily explained by, and fully
consistent with, the standard model of a superwind driven by a starburst of NGC
253's observed power. If these results are typical of all starburst-driven
winds, then we do not directly see all the energy and gas (in particular the
hot metal-enriched gas) transported out of galaxies by superwinds, even in
X-ray emission.


title: New theoretical Mass-loss rates of O and B Stars

abstract:
  We have calculated mass-loss rates for a grid of wind models covering a wide
range of stellar parameters and have derived a mass-loss recipe for two ranges
of effective temperature at either side of the bi-stability jump around
spectral type B1.
  For a large sample of O stars, it is shown that there is now good agreement
between these new theoretical mass-loss rates that take multiple scattering
into account and observations.
  Agreement between the observed and new theoretical wind momenta increases
confidence in the possibility to derive distances to luminous stars in distant
stellar systems using the Wind momentum Luminosity Relation.
  For the winds of the B stars there is an inconsistency in the literature
between various mass-loss rate determinations from observations by different
methods. One group of the determinations for B stars does follow the new
theoretical relation, while another group does not. The lack of agreement
between the observed mass-loss rates derived by different methods may point to
systematic errors in mass-loss determinations from observations for B stars.
  We show that our theoretical mass-loss recipe is reliable and recommend it be
used in evolutionary calculations.


title:
The Edinburgh/Durham Southern Galaxy Catalogue - IX. The Galaxy
  Catalogue

abstract:
  We announce here the public availability of the Edinburgh/Durham Southern
Galaxy Catalogue (EDSGC, http://www.edsgc.org). This objective galaxy catalogue
was constructed using the COSMOS micro-densitometer at the Royal Observatory
Edinburgh and constitutes one of the largest digitized galaxy surveys currently
in existence. The EDSGC contains a total of 1,495,877 galaxies (each with 27
image parameters) covering an contiguous area of 1182 sq deg centered on the
South Galactic Pole. The data consists of photographic bj magnitudes calibrated
via CCD sequences which provide a plate-to-plate accuracy of bj~0.1. Extensive
external checks have demonstrated that the global EDSGC photometry is free of
large-scale systematic gradients and is therefore, ideal for studying the
distribution of galaxies on large angular scales. Independent spectroscopy of
EDSGC galaxies has shown that the accuracy of the star-galaxy separation is
consistent with earlier visual checks and that only 12% of EDSGC galaxies are
potentially mis-classified. This paper is intended to provide a summary of the
essential details of the catalogue's design and construction as well as provide
a brief summary of the main scientific achievements using the EDSGC over the
last ten years.


title: The Age of the Galaxy from Thorium Cosmochronometry

abstract:
  The long-lived radioactive element thorium can potentially provide a simple
and direct clock to determine the age of our Galaxy. Spectroscopic
investigations of thorium in metal-poor stars have yielded some promising
initial results. We discuss the major observational and theoretical limitations
in thorium cosmochronometry, and point out the ways in which the implied
Galactic ages from thorium abundances can be made more accurate.


title: Visualization of Large Multi-Dimensional Datasets

abstract:
  Visualization techniques are well developed for many problem domains, but
these systems break down for datasets which are very large or multidimensional.
Techniques for data which is discrete rather than continuous are also less well
studied. Astronomy datasets like the Sloan Digital Sky Survey are very much in
this category. We propose the extension of information visualization techniques
to these very large record-oriented datasets. Specifically, we describe the
possible adaptation of the ``Visage'' information visualization tool to
terabyte astronomy datasets.


title:
Fast Algorithms and Efficient Statistics: Density Estimation in Large
  Astronomical Datasets

abstract:
  In this paper, we outline the use of Mixture Models in density estimation of
large astronomical databases. This method of density estimation has been known
in Statistics for some time but has not been implemented because of the large
computational cost. Herein, we detail an implementation of the Mixture Model
density estimation based on multi-resolutional KD-trees which makes this
statistical technique into a computationally tractable problem. We provide the
theoretical and experimental background for using a mixture model of Gaussians
based on the Expectation Maximization (EM) Algorithm. Applying these analyses
to simulated data sets we show that the EM algorithm - using the AIC penalized
likelihood to score the fit - out-performs the best kernel density estimate of
the distribution while requiring no ``fine--tuning'' of the input algorithm
parameters. We find that EM can accurately recover the underlying density
distribution from point processes thus providing an efficient adaptive
smoothing method for astronomical source catalogs. To demonstrate the general
application of this statistic to astrophysical problems we consider two cases
of density estimation: the clustering of galaxies in redshift space and the
clustering of stars in color space. From these data we show that EM provides an
adaptive smoothing of the distribution of galaxies in redshift space
(describing accurately both the small and large-scale features within the data)
and a means of identifying outliers in multi-dimensional color-color space
(e.g. for the identification of high redshift QSOs). Automated tools such as
those based on the EM algorithm will be needed in the analysis of the next
generation of astronomical catalogs (2MASS, FIRST, PLANCK, SDSS) and ultimately
in in the development of the National Virtual Observatory.


title: BOOMERanG Data Suggest a Purely Baryonic Universe

abstract:
  The amplitudes of peaks in the angular power spectrum of anisotropies in the
microwave background radiation depend on the mass content of the universe. The
second peak should be prominent when cold dark matter is dominant, but is
depressed when baryons dominate. Recent microwave background data are
consistent with a purely baryonic universe with Omega(matter) = Omega(baryon) ~
0.03 and Omega(Lambda) ~ 1.


title:
On a Probable Contribution of the Einstein-Podolsky-Rosen Effect to
  Solving the Problem of Homogeneity of the Universe

abstract:
  Evading formation of the domain walls in cosmological phase transitions is
one of key problems to be solved for explanation of the observed large-scale
homogeneity of the Universe. The previous attempts to get around this obstacle
led to imposing severe observational constraints on the parameters of the
fields involved. Aim of the present report is to show that yet another way to
overcome the above problem is accounting for Einstein-Podolsky-Rosen (EPR)
effect. Namely, if the scalar (Higgs) field was presented by a single coherent
quantum state at the initial instant of time, then its reduction during a phase
transition at some later instant should be correlated even at distances
exceeding the local cosmological horizon. Consideration of a simplest
one-dimensional cosmological model with Z_2 Higgs field demonstrates that EPR
correlations can substantially reduce the probability of spontaneous creation
of the domain walls, and such effect seems to be even more promising in the
cases of two- and three-dimensional geometry.


title:
Influence of Cooled Interstellar Gas on the Fundamental Plane for
  Elliptical Galaxies

abstract:
  We explore the possibly important influence of cooled interstellar gas on the
fundamental plane of elliptical galaxies. Interstellar cooling is described by
a parameterized sink term in the equation of continuity. Parameters that give
the best fits to the X-ray observations of NGC 4472 are used as a template for
the radial distribution of interstellar cooling in structurally homologous
elliptical galaxies of lower mass. Gas that cools within an effective radius
can contribute an additional 10 - 30 percent to the mass of the old stellar
population. If the cooled gas forms into stars of very low mass, $\ll
M_{\odot}$, as is commonly assumed, the cooled mass is optically dark. As a
result, the mass to light ratios determined from stellar velocities
systematically overestimate that of the old stellar population. Moreover, the
total mass and spatial distribution of the optically dark young stellar
population does not scale homologously with galactic luminosity or radius and
the total stellar mass to light ratio varies with galactic radius. We
investigate the non-homologous perturbations of cooled gas on the mass to light
ratio for several idealized homologous elliptical galaxies and show that they
appear to be incompatible with the observed thinness of the fundamental plane.
If optically luminous young stars formed from the cooled gas, the disturbance
of the fundamental plane would be lessened.


title: Young massive star clusters in M51

abstract:
  A search for young massive star clusters (YMCs) in the nearby face-on spiral
galaxy M51 (NGC 5194) has been carried out using UBV CCD images from the prime
focus camera on the Lick 3 meter Shane telescope. The YMC population is found
to be quite rich with a specific U-band luminosity T_L(U) = 1.4, consistent
with the high current star formation rate of this galaxy. The brightest
clusters have M_V about -12.5, far brighter than any young clusters currently
known in the Milky Way and even surpassing the luminosity of the R136 cluster
in the 30 Dor complex in the Large Magellanic Cloud. A few of the YMCs are
examined on archive HST/WFPC2 images, confirming their cluster nature and
providing estimates of their effective radii of 2-3 pc. The number of YMCs in
M51 is compatible with extrapolation of a power-law luminosity function with
exponent roughly equal to -2 from a Milky Way-like population of open clusters.
Both the SFR and T_L(U) of M51 are similar to those of other cluster-rich
spiral galaxies like NGC 1313 and M83.


title:
The Giant Radio Galaxy MRC B0319-454: Circumnuclear Structure of the
  Host Galaxy ESO248-G10

abstract:
  We present optical and near-infrared images and spectra of ESO248-G10, the
host of giant radio galaxy MRC B0319-454. From near-infrared colours, the
active nucleus is shown to be reddened by hot dust emission or dust extinction.
Star forming regions are identified beyond a radius of 5" (8.1 kpc) where hot
gas is prevalent. The optical spectrum shows gas rotation at speeds of up to
350km/s out to >=32kpc along the radio axis. A model is proposed in which the
giant elliptical is triaxial with the radio axis along the short axis, and the
figure rotation is around the long axis. From the model, the angles of the
principal axes are psi=34 degrees, theta=65 degrees, and phi=19 degrees with
axis ratios of B/A=0.75 and C/A=0.69. A second velocity feature from 5" to 15"
to the north-east of the nucleus is proposed to be a merging gas-rich galaxy
inducing star formation while settling into an orbit about the figure rotation
axis.


title: Linear Coasting in Cosmology and SNe Ia

abstract:
  A strictly linear evolution of the cosmological expansion scale factor is a
characteristic feature in several classes of alternative gravity theories as
also in the standard (big-bang) model with specially chosen equations of state
of matter. Such an evolution has no free parameters as far as the classical
cosmological tests are concerned and should therefore be easily falsifiable. In
this article we demonstrate how such models present very good fits to the
current supernovae 1a data. We discuss the overall viability of such models.


title:
Are X-ray properties of loose groups different from those of compact
  groups?

abstract:
  We compare the X-ray properties of loose and compact galaxy groups, using a
combined sample of 42 groups. We find that we are unable to separate loose and
compact groups on the luminosity-temperature relation, the luminosity-velocity
dispersion relation or the velocity dispersion-temperature relation using
equally weighted errors. This suggests that the distinction between compact and
loose groups is not a fundamental one, and we argue that a more useful
distinction is that between X-ray bright and X-ray faint systems. Given their
similarity in X-ray properties, we combine the loose and compact subsamples to
derive relations based on the full sample. This provides the highest
statistical quality results to date on the way in which the correlations in
X-ray properties of low mass systems depart from those seen in rich clusters.


title: Evolution of Galaxy morphologies in Clusters

abstract:
  We have studied the evolution of galaxian morphologies from ground-based,
good-seeing images of 9 clusters at z=0.09-0.25. The comparison of our data
with those relative to higher redshift clusters (Dressler et al. 1997) allowed
us to trace for the first time the evolution of the morphological mix at a
look-back time of 2-4 Gyr, finding a dependence of the observed evolutionary
trends on the cluster properties.


title:
Detection of a Compact X-ray Source in the Supernova Remnant G29.6+0.1:
  A Variable Anomalous X-ray Pulsar?

abstract:
  We present follow-up observations of the serendipitously discovered 7-s X-ray
pulsar AX J1845-0258, which displays characteristics similar to those observed
in the anomalous X-ray pulsars (AXPs). We find a dramatic reduction in its 3-10
keV flux in both new ASCA and RXTE datasets. Within the pulsar's position-error
locus, we detect a faint point source, AX J184453-025640, surrounded by an arc
of diffuse X-ray emission. This arc is coincident with the South-East quadrant
of the radio shell of the newly discovered supernova remnant G29.6+0.1,
reported in our companion paper (Gaensler et al. 1999). Lack of sufficient flux
from the source prevents us from confirming the 7-s pulsed emission observed in
the bright state; hence, at present we cannot definitively resolve whether AX
J1845-0258 and AX J184453-025640 are one and the same. If they are the same,
then the peak-to-peak luminosity changes recorded for AX J1845-0258 may be
larger than seen in other AXPs; closer monitoring of this pulsar might lead to
a resolution on the mechanism that drives AXPs.


title: The Current Status of CLASS

abstract:
  I give a brief overview of the current status of some aspects of the Cosmic
Lens All-Sky Survey (CLASS): description of the survey, current list of lens
systems, cosmological parameters from lensing statistics, H_0 from time delays,
dark lenses, wide-separation lenses.


title: The Lens-Redshift Test Revisited

abstract:
  Kochanek (1992) suggested that the redshifts of gravitational lens galaxies
rule out a large cosmological constant. This result was questioned by Helbig &
Kayser (1996), who pointed out that selection effects related to the brightness
of the lens can bias the results of this test against a high lambda value;
however, we did not claim that the observations favoured a high lambda value,
merely that current observational data were not sufficient to say either way,
using the test as proposed by Kochanek (1992) but corrected for selection
effects. Kochanek (1996) pointed out that additional information (fraction of
measured lens redshifts) provides additional information which restores the
sensitivity of the test to the cosmological model, at least somewhat. Here, I
consider three aspects. First, I examine the accuracy of the correction to the
test proposed by Kochanek (1996). Second, I compare the slightly different
statistical methods which have been used in connection with this test. Third, I
discuss what results can be obtained today now that more and better-defined
observations are available.


title: Isolated Neutron Stars in the Galaxy

abstract:
  In this article we briefly review our recent results on evolution and
properties of isolated neutron stars (INSs) in the Galaxy.
  As the first step we calculate a {\it census} of INSs in our Galaxy.
  We infer a lower bound for the mean kick velocity of NSs, $ <V> \sim
$(200-300) ${\rm km s^{-1}}$. The same conclusion is reached for both a
constant magnetic field ($B\sim 10^{12}$ G) and for a magnetic field decaying
exponentially with a timescale $\sim 10^9$ yr. These results, moreover,
constrain the fraction of low velocity stars, which could have escaped pulsar
statistics, to $\sim$few percents.
  Then we show that the range of minimum value of magnetic moment, $\mu_b$:
$\sim 10^{29.5}\ge \mu_b \ge 10^{28} {\rm G} {\rm cm}^3$, and the
characteristic decay time, $t_d$: $\sim 10^8\ge t_d \ge 10^7 {\rm yrs}$, can be
excluded assuming the standard initial magnetic momentum, $\mu_0=10^{30} {\rm
G} {\rm cm}^3$, if accreting INSs are observed. For these parameters an INS
would never reach the stage of accretion from the interstellar medium even for
a low space velocity of the star and high density of the ambient plasma. The
range of excluded parameters increases for lower values of $\mu_0$.
  It is shown that old accreting INSs become more abundant than young cooling
INSs at X-ray fluxes below $\sim 10^{-13}$ erg cm$^{-2}$ s$^{-1}$. We can
predict that about one accreting INS per square degree should be observed at
the {\it Chandra} and {\it Newton} flux limits of $\sim 10^{-16}$ erg cm$^{-2}$
s$^{-1}.$ The weak {\it ROSAT} sources, associated with INSs, can be young
cooling objects, if the NSs birth rate in the solar vicinity during the last
$\sim 10^6$ yr was much higher than inferred from radiopulsar observations.


title: Deep Halpha imagery of the Eridanus shells

abstract:
  A deep \ha image of interlocking filamentary arcs of nebulosity has been
obtained with a wide-field ($\approx$ 30\degree diameter) narrow-band filter
camera combined with a CCD as a detector. The resultant mosaic of images,
extending to a galactic latitude of 65$^{o}$, has been corrected for field
distortions and had galactic coordinates superimposed on it to permit accurate
correlations with the most recent H{\sc i} (21 cm), X-ray (0.75 kev) and FIR
(IRAS 100 $\mu$m) maps.
  Furthermore, an upper limit of 0.13 arcsec/yr to the expansion proper motion
of the primary 25\degree long nebulous arc has been obtained by comparing a
recent \ha image obtained with the San Pedro Martir telescope of its
filamentary edge with that on a POSS E plate obtained in 1951.
  It is concluded that these filamentary arcs are the superimposed images of
separate shells (driven by supernova explosions and/or stellar winds) rather
than the edges of a single `superbubble' stretching from Barnard's Arc (and the
Orion Nebula) to these high galactic latitudes. The proper motion measurement
argues against the primary \ha emitting arc being associated with the giant
radio loop (Loop 2) except in extraordinary circumstances.


title: Galaxy Groups at Intermediate Redshift

abstract:
  Galaxy groups likely to be virialized are identified within the CNOC2
intermediate redshift galaxy survey using an iterative method. The
number-velocity dispersion relation is in agreement with the low-mass
extrapolation of the cluster normalized Press-Schechter function. The two-point
group-group correlation function has r_0=6.8+/- 0.3 Mpc, which is larger than
the correlations of individual galaxies at the level predicted from n-body
calibrated halo clustering.
  The groups are stacked in velocity and position to create a sample large
enough for measurement of a density and velocity dispersion profile. The
stacked mean galaxy density profile falls nearly as a power law with r^{-2.5}
and has no well-defined core. The projected velocity dispersion is examined for
a variety of samples with different methods and found to be either flat or
slowly rising outwards. The combination of a steeper-than-isothermal density
profile and the outward rising velocity dispersion implies that the
mass-to-light ratio of groups rises with radius. The M/L can be kept nearly
constant if the galaxy orbits are nearly circular, although such strong
tangential anisotropy is not supported by other evidence. The segregation of
mass and light is not dependent on galaxy luminosity but is far more prominent
in the red galaxies than the blue. The M/L gradient could arise from orbital
``sloshing'' of the galaxies in the group halos, dynamical friction acting on
the galaxies in a background of ``classical'' collisionless dark matter, or,
more speculatively, the dark matter may have a true core.


title:
Infrared Helium-Hydrogen Line Ratios as a Measure of Stellar Effective
  Temperature

abstract:
  We have observed a large sample of compact planetary nebulae in the
near-infrared to determine how the 2^1P-2^1S HeI line at 2.058um varies as a
function of stellar effective temperature, Teff. The ratio of this line with HI
Br g at 2.166um has often been used as a measure of the highest Teff present in
a stellar cluster, and hence on whether there is a cut-off in the stellar
initial mass function at high masses. However, recent photoionisation modelling
has revealed that the behaviour of this line is more complex than previously
anticipated. Our work shows that in most aspects the photoionisation models are
correct. In particular, we confirm the weakening of the 2^1P-2^1S as Teff
increases beyond 40000K. However, in many cases the model underpredicts the
observed ratio when we consider the detailed physical conditions in the
individual planetary nebulae. Furthermore, there is evidence that there is
still significant 2^1P-2^1S HeI line emission even in the planetary nebulae
with very hot (Teff>100000K) central stars. It is clear from our work that this
ratio cannot be considered as a reliable measure of effective temperature on
its own.


title:
The Structure and Emission of the Accretion Shock in T Tauri Stars II:
  the Ultraviolet Continuum Emission

abstract:
  We compare accretion shock models with optical and ultraviolet spectra of
pre-main sequence stars to (1) make the first determinations of accretion rates
in intermediate mass T Tauri stars from continuum emission, and (2) derive
improved estimates of accretion rates and extinctions for continuum T Tauri
stars. Our method extends the shock models developed by Calvet and Gullbring to
enable comparisons with optical and archival International Ultraviolet Explorer
ultraviolet spectra. We find good agreement between the observations and the
model predictions, supporting the basic model of magnetospheric accretion
shocks as well as previous determinations of accretion rates and interstellar
reddening for the low mass T Tauri stars. The accretion rates determined for
the intermediate-mass T Tauri stars agree well with values obtained through
other methods that use near-infrared hydrogen line strengths (Muzerolle et al.
1998).


title:
The Disk and Dark Halo Mass of the Barred Galaxy NGC 4123. I.
  Observations

abstract:
  The non-circular streaming motions in barred galaxies are sensitive to the
mass of the bar and can be used to lift the degeneracy between disk and dark
matter halo encountered when fitting axisymmetric rotation curves of disk
galaxies. In this paper, we present photometric and kinematic observations of
NGC 4123, a barred galaxy of modest size (V_rot = 130 km/sec, L = 0.7 L_*),
which reveal strong non-circular motions. The bar has straight dust lanes and
an inner Lindblad resonance. The disk of NGC 4123 has no sign of truncation out
to 10 scale lengths, and star-forming regions are found well outside R_25. A
Fabry-Perot H-alpha velocity field shows velocity jumps of >100 km/sec at the
location of the dust lanes within the bar, indicating shocks in the gas flow.
VLA observations yield the velocity field of the H I disk. Axisymmetric mass
models yield good fits to the rotation curve outside the bar regionfor disk
I-band M/L of 2.25 or less, and dark halos with either isothermal or power-law
profiles can fit the data well. In a companion paper, we model the full 2-D
velocity field, including non-circular motions, to determine the stellar M/L
and the mass of the dark halo.


title:
The Disk and Dark Halo Mass of the Barred Galaxy NGC 4123. II.
  Fluid-Dynamical Models

abstract:
  We report a dynamical determination of the separate contributions of disk and
dark halo masses to the rotation curve of a spiral galaxy. We use
fluid-dynamical models of gas flow in the barred galaxy NGC 4123 to constrain
the dynamical properties of the galaxy: disk M/L, bar pattern speed, and the
central density and scale radius of the dark halo. We derive a realistic barred
potential directly from the light distribution. For each model we assume a
value of the stellar M/L and a bar pattern speed Omega_p and add a dark halo to
fit the rotation curve. We then compute the gas flow velocities with a 2-D gas
dynamical code, and compare the model flow patterns to a 2-D velocity field
derived from Fabry-Perot observations. The strong shocks and non-circular
motions in the observed gas flow require a high stellar M/L and a fast-rotating
bar. Models with I-band disk M/L of 2.0 -- 2.5 h_75, or 80 -- 100% of the
maximum disk value, are highly favored. The corotation radius of the bar must
be <= 1.5 times the bar semi-major axis. These results contradict some recent
claimed ``universal'' galaxy disk/halo relations, since NGC 4123 is of modest
size (rotation curve maximum 145 km/sec, and V_flat = 130 km/sec) yet is quite
disk-dominated. The dark halo of NGC 4123 is less concentrated than favored by
current models of dark halos based on cosmological simulations. Since some 30%
of bright disk galaxies are strongly barred and have dust lanes indicating
shock morphology similar to that of NGC 4123, it is likely that they also have
high stellar M/L and low density halos. We suggest that luminous matter
dominates inside the optical radius R_25 of high surface brightness disk
galaxies.


title:
A Measurement of the Average Longitudinal Development Profile of Cosmic
  Ray Air Showers Between 10^{17}eV and 10^{18}eV

abstract:
  The average extensive air shower longitudinal development profile as a
function of shower age in the energy range from 10$^{17}$ to 10$^{18}$eV is
measured using data from the hybrid HiRes/MIA experiment. An angular bin signal
based Cerenkov light component subtraction method and a shower maximum fitting
method using a local parabolic function are used to correct and normalize the
data. The Gaisser-Hillas and Greisen functions work equally well for describing
the shower profile. The Gaussian function is a poor fit. A simple scale-free
function is proposed and fits the data equally well. The best-fit parameters
for the above functions are determined.


title: Structured Mixed Phase is Favored in Neutron Stars

abstract:
  We give a general thermodynamical argument showing that in neutron stars, the
Coulomb structured mixed phase is always favored for any first order phase
transition involving systems in equilibrium with baryon number and electric
charge as the two independent components. This finding is likely to have
important consequences for many neutron star properties, e.g., glitch
phenomena, transport and superfluid properties, r-mode instabilities, and the
braking index.


title:
Emergence of power-law correlation in 1-dimensional self-gravitating
  system

abstract:
  A new phase of temporal evolution of the one-dimensional self-gravitating
system is numerically discovered. Fractal structure is dynamically created from
non-fractal initial conditions. Implication to astrophysics and mathematical
physics is discussed.


title:
Acceleration of Particles by Oblique Shocks and Cosmic Ray Spectra
  around the Knee Region

abstract:
  We examine the first order Fermi acceleration on the presumption that
supernova remnant shocks cross ambient magnetic fields with various angles.
These oblique shocks accelerate particles more efficiently than the parallel
shocks and elevate the maximum energies achievable by the particles. The
primary cosmic ray spectrum is strongly dependent upon these energies. We also
consider the dependence of the injection efficiency and of spectral indices on
obliquity. When indices and absolute fluxes at $10^{12}$ eV are given for six
nuclear groups from balloon-borne data, each energy spectrum develops a smooth
rigidity dependent knee structure. The resultant total spectrum also behaves
similarly and fits well with ground-based experimental data up to several
$10^{17}$ eV. It is shown as well that the chemical composition changes
significantly from lighter to heavier nuclei as the energies of particles
exceed the knee region. Other predicted curves are compared with the
experimental data which they reproduce rather well.


title: Interpretation of Extreme Scattering Events

abstract:
  Extreme Scattering Events are sometimes manifest in the light-curves of
compact radio-quasars at frequencies of a few GHz. These events are not
understood. The model which appears to offer the best explanation requires a
new population of AU-sized, neutral gas clouds; these clouds would then make up
a large fraction of the Galaxy's dark matter. Independent of the question of
which theoretical model is correct, if we extrapolate the observed behaviour to
low radio-frequencies, we expect that the sky should be criss-crossed by a
network of narrow caustics, at frequencies below about 700 MHz. Consequently at
these frequencies sources should typically manifest additional, faint images
which are substantially delayed with respect to the primary image. Although
some examples of this type of behaviour are already known, it is expected that
these are just the tip of the iceberg, with strong selection biases having been
imposed by the instrumentation employed to date.


title:
The TeV Energy Spectrum of Mkn 501 Measured with the Stereoscopic
  Telescope System of HEGRA during 1998 and 1999

abstract:
  During 1997, the BL Lac object Mkn 501 went into an extraordinary state of
high X-ray and TeV gamma-ray activity, lasting more than 6 months. In this
paper we report on the TeV emission characteristics of the source in the
subsequent years of 1998 and 1999 as measured with the Stereoscopic Cherenkov
Telescope System of HEGRA (La Palma, Canary Islands). Our observations reveal a
1998-1999 mean emission level at 1 TeV of 1/3 of the flux of the Crab Nebula, a
factor of 10 lower than during the year of 1997. A dataset of 122 observations
hours with the HEGRA telescope system makes it possible to assess for the first
time the Mkn 501 TeV energy spectrum for a mean flux level substantially below
that of the Crab Nebula with reasonable statistical accuracy. Excluding the
data of a strong flare, we find evidence that the 1998--1999 low-flux spectrum
is substantially softer (by 0.44+-0.1(stat) in spectral index) than the 1997
time averaged spectrum. The 500 GeV to 10 TeV energy spectrum can well be
described by a power law model with exponential cutoff: dN/dE ~ E^(-alpha)
exp(-E/E0) with alpha=2.31+-0.22(stat), and E0=5.1 (-2.3+7.8)(stat) TeV. Within
statistical accuracy, also a pure power law model gives an acceptable fit to
the data: dN/dE ~ E^(-Gamma) with Gamma=2.76+-0.08(stat). After presenting the
1998-1999 TeV characteristics of the source we discuss the implications of the
results.


title:
Vortex solitons - Mass, Energy and Angular momentum bunching in
  relativistic electron-positron plasmas

abstract:
  It is shown that the interaction of large amplitude electromagnetic waves
with a hot electron-positron (e-p) plasma (a principal constituent of the
universe in the MeV epoch) leads to a bunching of mass, energy, and angular
momentum in stable, long-lived structures. Electromagnetism in the MeV epoch,
then, could provide a possible route for seeding the observed large-scale
structure of the universe.


title:
CO band emission from MWC349: I. First overtone bands from a disk or
  from a wind?

abstract:
  We observed the near infrared emission in the wavelength range 2.28-2.50
micron from the peculiar B[e]-star MWC349. The spectra contain besides the
strong IR continuum the first overtone CO bands and most of the hydrogen
recombination lines of the Pfund series, both in emission. We also modeled the
spectra. The Pfund lines have a gaussian profile with a FWHM of ~100 km/s, and
it turned out that their emission is in LTE and optically thin. To explain the
CO bands, several scenarios were investigated. We found that the CO band heads
are formed under LTE and that the gas must have a temperature of 3500 to 4000
K. The width of the 2 -> 0 band head indicates kinematical broadening of 50 to
60 km/s. We can obtain fits to the measured spectra assuming that the CO gas
has a column density of 5 10^{20} cm^{-2} and is located either at the inner
edge of the rotating circumstellar disk. In this case, the disk must have a
bulge which partly blocks the radiation so that the observer sees only a sector
on the far side where the radial velocities are small. Or the CO emission
originates in a wind with gaussian line profiles. Both fits are of equal
quality and satisfactory. In a third alternative where the fit is less
convincing, the CO emission is optically thin and comes from an extended
Keplerian disk.


title: Particle-Mesh Simulations of the Lyman-Alpha Forest

abstract:
  Numerical hydrodynamical simulations have proven a successful means of
reproducing many of the statistical properties of the Lyman-Alpha forest as
measured in high redshift quasar spectra. Pseudo-hydrodynamical methods based
only on simulating the dark matter component have been claimed to yield a
comparable level of success. We investigate the degree to which two
pseudo-methods, with and without allowing for a pseudo-gas pressure, are able
to match the predictions of fully hydrodynamical plus dark matter simulations.
We also address the requirements for convergence to the statistics of the
spectra and the inferred properties of the Lyman-Alpha forest as a function of
resolution and box size. Generally we find it is possible to reach agreement
with full hydrodynamic simulations at the 10% level in the cumulative
distributions of the flux and absorption line parameter statistics for readily
achievable particle and grid numbers, but difficult to do much better.


title: Evolution of Buoyant Bubbles in M87

abstract:
  The morphology of the X-ray and radio emitting features in the central $\sim$
50 kpc region around the galaxy M87 strongly suggests that buoyant bubbles of
cosmic rays (inflated by an earlier nuclear active phase of the galaxy) rise
through the cooling gas at roughly half the sound speed. In the absence of
strong surface tension, initially spherical bubbles will transform into tori as
they rise through an external medium. Such structures can be identified in the
radio images of the halo of M87. During their rise, bubbles will uplift
relatively cool X-ray emitting gas from the central regions of the cooling flow
to larger distances. This gas is colder than the ambient gas and has a higher
volume emissivity. As a result, rising ``radio'' bubbles may be trailed by
elongated X-ray features as indeed is observed in M87. We performed simple
hydrodynamic simulations to qualitatively illustrate the evolution of buoyant
bubbles in the M87 environment.


title: Modelling the Extinction Properties of Galaxies

abstract:
  Recently (Granato, Lacey, Silva et al. 2000, astro-ph/0001308) we have
combined our spectrophotometric galaxy evolution code which includes dust
reprocessing (GRASIL, Silva et al. 1998) with semi-analytical galaxy formation
models (GALFORM, Cole et al. 1999). One of the most characteristic features of
the former is that the dust is divided in two main phases: molecular cloud
complexes, where stars are assumed to be born, and the diffuse interstellar
medium. As a consequence, stellar populations of different ages have different
geometrical relationships with the two phases, which is essential in
understanding several observed properties of galaxies, in particular those
undergoing major episodes of star formation at any redshift. Indeed, our merged
GRASIL+GALFORM model reproduces fairly well the SEDs of normal spirals and
starbursts from the far-UV to the sub-mm and their internal extinction
properties. In particular in the model the observed starburst attenuation law
(Calzetti 1999) is accounted for as an effect of geometry of stars and dust,
and has nothing to do with the optical properties of dust grains.


title: Self-similar spherical collapse with non-radial motions

abstract:
  We derive the asymptotic mass profile near the collapse center of an initial
spherical density perturbation, $\delta \propto M^{-\epsilon}$, of
collision-less particles with non-radial motions. We show that angular momenta
introduced at the initial time do not affect the mass profile. Alternatively,
we consider a scheme in which a particle moves on a radial orbit until it
reaches its turnaround radius, r_*. At turnaround the particle acquires an
angular momentum $L={\cal L} \sqrt{GM_* r_*}$ per unit mass, where M_* is the
mass interior to r_*. In this scheme, the mass profile is $M\propto
r^{3/(1+3\epsilon)}$ for all $\epsilon >0$, in the region $r/r_t\ll {\cal L}$,
where r_t is the current turnaround radius. If ${\cal L} \ll 1$ then the
profile in the region ${\cal L} \ll r/r_t \ll$ is $M\propto r$ for $\epsilon
<2/3$. The derivation relies on a general property of non-radial orbits which
is that ratio of the pericenter to apocenter is constant in a force field k(t)
r^{n} with k(t) varying adiabatically.


title:
Stellar Populations and Surface Brightness Fluctuations: New
  Observations and Models

abstract:
  We examine the use of surface brightness fluctuations (SBF) for both stellar
population and distance studies. New V-band SBF data are reported for five
Fornax cluster galaxies and combined with literature data to define a new
V-band SBF distance indicator. We use new stellar population models, based on
the latest Padua isochrones transformed empirically to the observational plane,
to predict SBF magnitudes and integrated colours for a wide range of population
ages and metallicities. We examine the sensitivity of the predictions to
changes in the isochrones, transformations, and IMF. The new models reproduce
the SBF data for globular clusters fairly well, especially if higher
metallicity globulars are younger. The models also give a good match to the
"fluctuation colors" of elliptical galaxies. In order to obtain theoretical
calibrations of the SBF distance indicators, we combine our single-burst models
into composite population models. These models reproduce the observed behavior
of the SBF magnitudes as a function of stellar population parameters, including
the steep colour dependence found for HST/WFPC2 F814W SBF data. Because the
theoretical SBF calibrations are fairly sensitive to uncertain details of
stellar evolution, the empirical calibrations are more secure. However, the
sensitivity of SBF to these finer details potentially makes it a powerful
constraint for stellar evolution and population synthesis. [abbridged]


title:
RXTE observations of the Seyfert galaxy NGC 5506: evidence for
  reflection from disk and torus

abstract:
  We report on observations of the narrow line Seyfert galaxy NGC 5506 with the
Rossi X-ray TIming Explorer. The observations cover a time interval of ~1000
days during which the source showed strong flux and spectral variability. The
spectrum clearly shows iron fluorescence emission at 6.4 keV and significant
reflection features. Both the equivalent width of the iron line and the
relative strength of the reflected continuum are higher during low flux states.
The variability of the reflection features can be explained by the presence of
two reflected components: one that responds rapidly to flux changes of the
primary continuum and a second, slowly variable, component originating from a
distant reflector, e.g. a molecular torus.


title: On the large-scale structure of galactic disks

abstract:
  The disk positions for galaxies of various morphological and nuclear-activity
types (normal galaxies, QSO, Sy, E/S0, low-surface brightness galaxies, etc.)
on the "central surface brightness - exponential scalelength" plane are
considered. The stellar disks are shown to form a single sequence on this plane
over a wide range of surface brightnesses (\mu_0(I)=12-25) and sizes (h=10 pc -
100 kpc). The existence of this observed sequence can probably be explaned by a
combination of three factors: a disk-stability requirement, a limited total
disk luminosity, and observational selection. The model by Mo et al. (1998) for
disk formation in the CDM hierarchical-clustering scenario is shown to
satisfactorily reproduce the salient features of the galaxy disk distribution
on the "\mu_0 - h" plane.


title:
Physical parameters of erupting Luminous Blue Variables: NGC 2363-V1
  caught in the act

abstract:
  A quantitative study of the Luminous Blue Variable NGC 2363-V1 in the
Magellanic galaxy NGC 2366 (D = 3.44 Mpc) is presented, based on ultraviolet
and optical HST/STIS spectroscopy. Contemporary WFPC2 and WHT imaging reveals a
modest V-band brightness increase of ~ 0.2 mag per year between 1996 January
and 1997 November, reaching V=17.4 mag, corresponding to Mv=-10.4 mag.
Subsequently, V1 underwent a similar decrease in V-band brightness, together
with a UV brightening of 0.35 mag from 1997 November to 1999 November.
  The optical spectrum of V1 is dominated by H emission lines, with Fe II, He I
and Na I also detected. In the ultraviolet, a forest of Fe absorption features
and numerous absorption lines typical of mid-B supergiants are observed. From a
spectral analysis with the non-LTE, line-blanketed code of Hillier & Miller
(1998), we derive stellar parameters of T*=11kK, R*=420Ro, log(L/Lo)=6.35
during 1997 November, and T*=13kK, R*=315Ro, log(L/Lo)=6.4 for 1999 July. The
wind properties of V1 are also exceptional, with Mdot ~ 4.4 x 10e-4 Mo/yr and
$v_{\infty} ~ $300 km/s, allowing for a clumped wind (filling factor = 0.3),
and assuming H/He ~ 4 by number.
  The presence of Fe lines in the UV and optical spectrum of V1 permits an
estimate of the heavy elemental abundance of NGC 2363 from our spectral
synthesis. Although some deficiencies remain, allowance for charge exchange
reactions in our calculations supports a SMC-like metallicity, that has
previously been determined for NGC 2363 from nebular oxygen diagnostics.
  Considering a variety of possible progenitor stars, V1 has definitely
undergone a giant eruption, with a substantial increase in stellar luminosity,
radius, and almost certainly mass-loss rate.


title: Relativistic Viscous Fluid Description of Microscopic Black Hole Wind

abstract:
  Microscopic black holes explode with their temperature varying inversely as
their mass. Such explosions would lead to the highest temperatures in the
present universe, all the way to the Planck energy. Whether or not a
quasi-stationary shell of matter undergoing radial hydrodynamic expansion
surrounds such black holes is been controversial. In this paper relativistic
viscous fluid equations are applied to the problem. It is shown that a
self-consistent picture emerges of a fluid just marginally kept in local
thermal equilibrium; viscosity is a crucial element of the dynamics.


title: Mining the Metal-Rich Stars for Planets

abstract:
  We examine the correlation between stellar metallicity and short period
planets. It appears that approximately 1% of dwarf stars in the solar
neighborhood harbor short-period planets characterized by near-circular orbits
and orbital periods P<20 days. However, among the most metal-rich stars
(defined as having [Fe/H]>0.2 dex), it appears that the fraction increases to
10%. Using the Hipparcos database and the Hauck & Mermilliod (1998) compilation
of Stromgren uvby photometry, we identify a sample of 206 metal-rich stars of
spectral type K, G, and F which have an enhanced probability of harboring
short-period planets. Many of these stars would be excellent candidates for
addition to radial velocity surveys. We have searched the Hipparcos epoch
photometry for transiting planets within our 206 star catalog. We find that the
quality of the Hipparcos data is not high enough to permit unambiguous transit
detections. It is, however, possible to identify candidate transit periods. We
then discuss various ramifications of the stellar metallicity - planet
connection. First, we show that there is preliminary evidence for increasing
metallicity with increasing stellar mass among known planet-bearing stars. This
trend can be explained by a scenario in which planet-bearing stars accrete an
average of 30 Earth Masses of rocky material after the gaseous protoplanetary
disk phase has ended. We present dynamical calculation which suggest that a
survey of metallicities of spectroscopic binary stars can be used to understand
the root cause of the stellar metallicity - planet connection.


title: Cosmic Statistics of Statistics: N-point Correlations

abstract:
  The fully general calculation of the cosmic error on N-point correlation
functions and related quantities is presented. More precisely, the variance
caused by the finite volume, discreteness, and edge effects is determined for
{\em any} estimator which is based on a general function of N-tuples, such as
multi-point correlation functions and multi-spectra. The results are printed
explicitly for the two-point correlation function (or power-spectrum), and for
the three-point correlation (or bispectrum). These are the most popular
statistics in the study of large scale structure, yet, the a general
calculation of their variance has not been performed until now.


title:
A New Underground Laboratory in the USA for a Neutrino Factory Detector
  and Other Scientific Projects

abstract:
  A neutrino factory storage ring can provide beams to various locations. We
discuss the ICANOE detector (at LNGS) at one such site. We then describe the
prospects for the use of the underground location at Carlsbad, NM for a
neutrino factory detector. A brief discussion is given of a simple magnetized
Fe detector of 10 50 kT for this site.


title: Stellar Collisions and Pulsar Planets

abstract:
  I describe models for the formation of planetary systems surrounding the
remnants of stellar mergers and collisions. I focus primarily on models for the
viscous evolution of disks suitable for the formation of the planets
surrounding the pulsar B1257+12. I show that the adaptation of models for
traditional protoplanetary disks which invoke quiescent or `dead' zones are
quite successful in producing disks appropriate for the formation of the pulsar
planets. I also briefly describe some even more exotic possibilities that may
arise from compact object mergers.


title: Fast Convolution on the Sphere

abstract:
  We propose fast, exact and efficient algorithms for the convolution of two
arbitrary functions on the sphere which speed up computations by a factor
\order{\sqrt{N}} compared to present methods where $N$ is the number of pixels.
No simplifying assumptions are made other than bandlimitation. This reduces
typical computation times for convolving the full sky with the asymmetric beam
pattern of a megapixel Cosmic Microwave Background (CMB) mission from months to
minutes. Our methods enable realistic simulation and careful analysis of data
from such missions, taking into account the effects of asymmetric ``point
spread functions'' and far side lobes of the physical beam. While motivated by
CMB studies, our methods are general and hence applicable to the convolution or
filtering of any scalar field on the sphere with an arbitrary, asymmetric
kernel. We show in an appendix that the same ideas can be applied to the
inverse problems of map-making and beam reconstruction by similarly
accelerating the {\em transpose convolution} which is needed for the iterative
solution of the normal equations.


title: All-sky convolution for polarimetry experiments

abstract:
  We discuss all-sky convolution of the instrument beam with the sky signal in
polarimetry experiments, such as the Planck mission which will map the
temperature anisotropy and polarization of the cosmic microwave background
(CMB). To account properly for stray light (from e.g. the galaxy, sun, and
planets) in the far side-lobes of such an experiment, it is necessary to
perform the beam convolution over the full sky. We discuss this process in
multipole space for an arbitrary beam response, fully including the effects of
beam asymmetry and cross-polarization. The form of the convolution in multipole
space is such that the Wandelt-Gorski fast technique for all-sky convolution of
scalar signals (e.g. temperature) can be applied with little modification. We
further show that for the special case of a pure co-polarized, axisymmetric
beam the effect of the convolution can be described by spin-weighted window
functions. In the limits of a small angle beam and large Legendre multipoles,
the spin-weight 2 window function for the linear polarization reduces to the
usual scalar window function used in previous analyses of beam effects in CMB
polarimetry experiments. While we focus on the example of polarimetry
experiments in the context of CMB studies, we emphasise that the formalism we
develop is applicable to anisotropic filtering of arbitrary tensor fields on
the sphere.


title:
[Ne II] 12.8 Micron Images of Four Galactic Ultracompact H II Regions:
  Ionized Neon Abundance as a Tracer of the Ionizing Stars

abstract:
  We present the results of ground-based imaging spectroscopy of the [Ne II]
12.8 micron line emitted from the ultracompact (UC) H II regions; W51d,
G45.12+0.13, G35.20-1.74 and Monoceros R2, with 2arcsec spatial resolution. We
found that the overall distribution of the [Ne II] emission is generally in
good agreement with the radio (5 or 15 GHz) VLA distribution for each source.
The Ne+ abundance ([Ne+/H+]) distributions are also derived from the [Ne II]
and the radio maps. As for G45.12+0.13 and W51d, the Ne+ abundance decreases
steeply from the outer part of the map toward the radio peak. On the other
hand, the Ne+ abundance distributions of G35.20-1.74 and Mon R2 appear rather
uniform. These results can be interpreted by the variation of ionizing
structures of neon, which is primarily determined by the spectral type of the
ionizing stars. We have evaluated the effective temperature of the ionizing
star by comparing the Ne+ abundance averaged over the whole observed region
with that calculated by H II region models based on recent non-LTE stellar
atmosphere models: 39,100 (+1100, -500) K (O7.5V-O8V) for W51d, 37,200 (+1000,
-700) K (O8V-O8.5V) for G45.12+0.13, 35,000-37,600 (+1500, -600) K (O8V-O9V)
for G35.20-1.74, and < 34,000 K (< B0V) for Mon R2. These effective
temperatures are consistent with those inferred from the observed Ne+ abundance
distributions.


title: The Dynamics of the Formation of Degenerate Heavy Neutrino Stars

abstract:
  Through reformulating the cold, self-gravitating fermion gas as a Bose
condensate by identifying their mutual Thomas-Fermi limits, the dissipationless
formation of a heavy neutrino star in gravitational collapse is numerically
demonstrated. Such stars offer an alternative to supermassive black holes for
the compact dark objects at the centers of galaxies.


title: Is the deficit of z > 1 field ellipticals real ?

abstract:
  The results of a 700 arcmin^2 survey for EROs are presented. The sky
distribution of EROs is very inhomogeneous and their two point correlation
function shows a very high amplitude, a factor of 10 larger than that of the
field galaxy population. Such a clustering can explain the strong variance
found in previous works, and provides evidence that ERO are mostly made of
high-z ellipticals. The surface density of EROs found in our large survey is in
good agreement with that expected for passively evolving ellipticals formed at
high redshift (z\simgt2.5).


title: CMB anisotropies from pre-big bang cosmology

abstract:
  We present an alternative scenario for cosmic structure formation where
initial fluctuations are due to Kalb-Ramond axions produced during a pre-big
bang phase of inflation. We investigate whether this scenario, where the
fluctuations are induced by seeds and therefore are of isocurvature nature, can
be brought in agreement with present observations by a suitable choice of
cosmological parameters. We also discuss several observational signatures which
can distinguish axion seeds from standard inflationary models. We finally
discuss the gravitational wave background induced in this model and we show
that it may be well within the range of future observations.


title: Complex molecular gas structure in the Medusa merger

abstract:
  High resolution OVRO aperture synthesis maps of the 12CO 1-0 emission in the
`Medusa' galaxy merger (NGC4194) reveal the molecular emission being
surprisingly extended. It is distributed on a total scale of 25$''$ (4.7 kpc) -
despite the apparent advanced stage of the merger. The complex, striking CO
morphology occupies mainly the center and the north-eastern part of the main
optical body. The extended 12CO flux is tracing two prominent dust lanes: one
which is crossing the central region at right angle and a second which curves
to the north-east and then into the beginning of the northern tidal tail. The
bulk of the 12CO emission (67%) can be found in a complex starburst region
encompassing the central 2kpc. The molecular gas is distributed in five major
emission regions of typical size 300pc. About 15% of the total 12CO flux is
found in a bright region 1.5'' south of the radio continuum nucleus. We suggest
that this region together with the kpc sized central starburst is being fueled
by gas flows along the central dust lane. We discuss the merger history of
NGC4194 and suggest that it may be the result of an early-type/spiral merger
with a shell emerging to the south of the center. The total molecular mass in
the system is estimated to be at most 2 X 10^9 M_sun (depending on the CO - H_2
conversion factor). The high 12CO/13CO 1-0 intensity ratio, ~20, indicates
highly excited physical conditions in the interstellar medium showing that the
starburst has a big impact on its surrounding ISM. At the current rate of star
formation, the gas will be consumed within 40 million years.


title: Bi-metric Gravity and "Dark Matter"

abstract:
  We present a bi-metric theory of gravity containing a length scale of
galactic size. For distances less than this scale the theory satisfies the
standard tests of General Relativity. For distances greater than this scale the
theory yields an effective gravitational constant much larger than the locally
observed value of Newton's constant. The transition from one regime to the
other through the galactic scale can explain the observed rotation curves of
galaxies and hence the effects normally attributed to the presence of dark
matter. Phenomena on an extragalactic scale such as galactic clusters and the
expansion of the universe are controlled by the enhanced gravitational
coupling. This provides an explanation of the missing matter normally invoked
to account for the observed value of Hubble's constant in relation to observed
matter.


title: Mira's wind explored in scattering infrared CO lines

abstract:
  We have observed the intermediate regions of the circumstellar envelope of
Mira (o Ceti) in photospheric light scattered by three vibration-rotation
transitions of the fundamental band of CO, from low-excited rotational levels
of the ground vibrational state, at an angular distance of beta = 2"-7" away
from the star. The data were obtained with the Phoenix spectrometer mounted on
the 4 m Mayall telescope at Kitt Peak. The spatial resolution is approximately
0.5" and seeing limited. Our observations provide absolute fluxes, leading to
an independent new estimate of the mass-loss rate of approximately 3e-7
Msun/yr, as derived from a simple analytic wind model. We find that the
scattered intensity from the wind of Mira for 2" < beta < 7" decreases as
beta^-3, which suggests a time constant mass-loss rate, when averaged over 100
years, over the past 1200 years.


title: On the stability of the Kerr metric

abstract:
  The reduced (in the angular coordinate $\phi$) wave equation and Klein-Gordon
equation are considered on a Kerr background and in the framework of
$C^{0}$-semigroup theory. Each equation is shown to have a well-posed initial
value problem,i.e., to have a unique solution depending continuously on the
data. Further, it is shown that the spectrum of the semigroup's generator
coincides with the spectrum of an operator polynomial whose coefficients can be
read off from the equation. In this way the problem of deciding stability is
reduced to a spectral problem and a mathematical basis is provided for mode
considerations. For the wave equation it is shown that the resolvent of the
semigroup's generator and the corresponding Green's functions can be computed
using spheroidal functions. It is to be expected that, analogous to the case of
a Schwarzschild background, the quasinormal frequencies of the Kerr black hole
appear as {\it resonances}, i.e., poles of the analytic continuation of this
resolvent. Finally, stability of the background with respect to reduced massive
perturbations is proven for large enough masses.


title: The Nature of Faint Submillimeter Galaxies

abstract:
  We summarise the main results on the faint submillimeter (submm) galaxy
population which have come from the SCUBA Cluster Lens Survey. We detail our
current understanding of the characteristics of these submm-selected galaxies
across wavebands from X-rays to radio. After presenting the main observational
properties of this population we conclude by discussing the nature of these
distant, ultraluminous infrared galaxies and their relationship to other
high-redshift populations.


title: A near-IR [Fe II] line imaging survey of supernova remnants in M33

abstract:
  We report on the first near-IR [Fe II] line imaging survey of extragalactic
  SNRs.
  Observations of a sample of 42 objects drawn from an optically-selected
catalogue of SNRs in M33 provide evidence for a wide range in the [Fe II] 1.644
microns luminosities. This can be understood as being primarily due to
variations in the chemical abundances and density of the local ISM, although
shock conditions may also play a significant role. We briefly discuss how these
results may be used to better calibrate the supernova rate of star-forming
galaxies.


title: Radio astronomical imaging in the presence of strong radio interference

abstract:
  Radio-astronomical observations are increasingly contaminated by
interference, and suppression techniques become essential. A powerful candidate
for interference mitigation is adaptive spatial filtering. We study the effect
of spatial filtering techniques on radio astronomical imaging. Current
deconvolution procedures such as CLEAN are shown to be unsuitable to spatially
filtered data, and the necessary corrections are derived. To that end, we
reformulate the imaging (deconvolution/calibration) process as a sequential
estimation of the locations of astronomical sources. This not only leads to an
extended CLEAN algorithm, the formulation also allows to insert other array
signal processing techniques for direction finding, and gives estimates of the
expected image quality and the amount of interference suppression that can be
achieved. Finally, a maximum likelihood procedure for the imaging is derived,
and an approximate ML image formation technique is proposed to overcome the
computational burden involved. Some of the effects of the new algorithms are
shown in simulated images. Keywords: Radio astronomy, synthesis imaging,
parametric imaging, interference mitigation, spatial filtering, maximum
likelihood, minimum variance, CLEAN.


title:
Large-scale Cosmic Homogeneity from a Multifractal Analysis of the PSCz
  Catalogue

abstract:
  We investigate the behaviour of galaxy clustering on large scales using the
PSCz catalogue. In particular, we ask whether there is any evidence of
large-scale fractal behaviour in this catalogue. We find the correlation
dimension in this survey varies with scale, consistent with other analyses. For
example, our results on small and intermediate scales are consistent those
obtained from the QDOT sample, but the larger PSCz sample allows us to extend
the analysis out to much larger scales. We find firm evidence that the sample
becomes homogeneous at large scales; the correlation dimension of the sample is
D_2=2.992(3) for r>30 h^{-1} Mpc. This provides strong evidence in favour of a
Universe which obeys the Cosmological Principle.


title: On the 21Na(p,gamma)22Mg thermonuclear rate for 22Na production in novae

abstract:
  Classical novae are potential sources of gamma-rays, like the 1.275 MeV gamma
emission following 22Na beta decay, that could be detected by appropriate
instruments on board of future satellites like INTEGRAL. It has been shown that
the production of 22Na by novae is affected by the uncertainty on the
21Na(p,gamma)22Mg rate and in particular by the unknown partial widths of the
Ex = 5.714 MeV, J^pi = 2^+, 22Mg level. To reduce these uncertainties, we
performed shell model calculations with the OXBASH code, compared the results
with available spectroscopic data and calculated the missing partial widths.
Finally, we discuss the influence of these results on the 21Na(p,gamma)22Mg
reaction rate and 22Na synthesis.


title:
Near-Infrared Spectroscopy of Two Galaxies at z=2.3 and z=2.9: New
  Probes of Chemical and Dynamical Evolution at High Redshift

abstract:
  This study presents Keck optical and infrared spectroscopy of the rest-frame
ultraviolet and optical emission lines in two Lyman alpha emitting galaxies at
z>2. These data provide insight on the evolution of fundamental galaxy scaling
relations at early epochs, especially the luminosity-velocity and
luminosity-metallicity relations. Lynx 2-9691 exhibits extended [O III]
emission over a diameter of >28 kpc, reminiscent of the Lyman alpha nebulae
discovered near Lyman-drop galaxies [Steidel et al 2000]. The ratios of strong
nebular emission lines indicate sub-solar oxygen abundances in the range
8.2<12+log(O/H)<8.8 (Z = 0.25-0.95 Z_sun). Interestingly, Galactic metal-rich
globular clusters have similar metallicities, consistent with the idea that we
could be seeing the formation of galaxies like the Milky Way at $z\sim3$. The
measured gas phase oxygen abundances are >4-10 times higher than the Z < 0.1
Z_sun metallicities found in damped Lyman alpha (DLA) absorbers at similar
redshifts, indicating that DLA systems trace different environments than the
vigorously star-forming objects observed here. Star-forming galaxies at
$z\sim3$ are 2-4 magnitudes more luminous than local spiral galaxies of similar
metallicity, and thus, are offset from the local luminosity-metallicity
relation. Their kinematic linewidths are sigma_v=65-130 km/s, making this
sample 1-3 magnitudes more luminous than local galaxies of similar linewidth
and mass. [Abridged]


title: Magnetic Fields and the Triaxiality of Molecular Cloud Cores

abstract:
  We make the hypothesis that molecular cloud fragments are triaxial bodies
with a large scale magnetic field oriented along the short axis. While
consistent with theoretical expectations, this idea is supported by magnetic
field strength data, which show strong evidence for flattening along the
direction of the mean magnetic field. It is also consistent with early
submillimeter polarization data, which show that the projected direction of the
magnetic field is often slightly misaligned with the projected minor axis of a
molecular cloud core, i.e., the offset angle $\Psi$ is nonzero. We calculate
distributions of $\Psi$ for various triaxial bodies, when viewed from a random
set of viewing angles. The highest viewing probability always corresponds to
$\Psi=0^{\circ}$, but there is a finite probability of viewing all nonzero
$\Psi$, including even $\Psi =90^{\circ}$; the average offset typically falls
in the range $10^{\circ}-30^{\circ}$ for triaxial bodies most likely to satisfy
observational and theoretical constraints.


title:
Magnetized accretion-ejection structures V. Effects of entropy
  generation inside the disc

abstract:
  In this paper, steady-state MHD calculations of non-relativistic magnetized
accretion discs driving jets are presented. For the first time, an energy
equation describing the effects of entropy generation along streamlines is
included. Using a simplified approach, we showed that thermal effects have a
tremendous influence on the disc capability to feed jets with mass.
  The disc ejection efficiency is measured by the parameter $\xi= d \ln
\dot{M}_{a}/d \ln{r}$, where $ \dot{M}_{a}(r)$ is the local disc accretion
rate. While previous self-similar solutions were only able to produce jets with
$\xi \sim 0.01$, solutions with a coronal heating display huge efficiencies up
to $\xi \sim 0.5$. Moreover, taking thermal effects into account allows to
obtain both fast and slow magnetic rotators.
  Since most of the jet properties (like asymptotic velocity or degree of
collimation) depend on the mass load, it arises from this study that any
quantitative result requires a detailled analysis of the disc energetics.


title:
The ROSAT-ESO Flux Limited X-ray (REFLEX) Galaxy Cluster Survey II: The
  Spatial Correlation Function

abstract:
  We report the results of the spatial two-point correlation function xi(r) for
the new X-ray galaxy cluster survey REFLEX, which comprises of 452 X-ray
selected clusters (449 with redshifts) detected by the ROSAT satellite during
the ROSAT All-Sky-Survey. The REFLEX cluster sample is flux limited to
3x10^{-12} erg s^{-1} cm^{-2} in the ROSAT energy band (0.1-2.4 keV) and spans
3 decades in X-ray luminosity (10^{42} - 10^{45} h^{-2} erg s^{-1}), containing
galaxy groups and rich clusters out to a redshift z~0.3. Covering a contiguous
area of 4.24 sr REFLEX is the largest X-ray cluster sample to date for which
spatial clustering has been analysed. Correlation studies using clusters
selected on the basis of their X-ray emission are particularly interesting as
they are largely free from the projection biases inherent to optical studies.
For the entire flux-limited sample we find that the correlation length (the
scale at which the correlation amplitude passes through unity) r_0~20
h^{-1}Mpc. For example, if a power-law fit is made to xi(r) over the range 4-40
h^{-1} Mpc then r_0=18.8+-0.9. An indication of the robustness of this result
comes from the high degree of isotropy seen in the clustering pattern on scales
close to the correlation length. On larger scales xi(r) deviates from a
power-law, crossing zero at ~45h^{-1} Mpc. From an examination of 5
volume-limited cluster sub-samples we find no significant trend of r_0 with
limiting X-ray luminosity. A comparison with recent model predictions for the
clustering properties of X-ray flux-limited samples, indicates that Cold Dark
Matter models with the matter density Omega_m=1 fail to produce sufficient
clustering to account for the data, while Omega_m~0.3 models provide an
excellent fit.


title:
A new sample of giant radio galaxies from the WENSS survey II - A
  multi-frequency radio study of a complete sample: Properties of the radio
  lobes and their environment

abstract:
  We have formed a complete sample of 26 low redshift (z < 0.3) giant radio
galaxies (GRGs) from the WENSS survey, selected at flux densities above 1 Jy at
325 MHz. We present 10.5-GHz observations with the 100-m Effelsberg telescope
of 18 sources in this sample. These observations, together with similar data of
the remaining eight sources, are combined with data from the WENSS, NVSS and
GB6 surveys to study the radio properties of the lobes of these sources at
arcminute resolution. We investigate radio source asymmetries, equipartition
energy densities in the lobes, the presence of lobe pressure evolution with
redshift, the spectral age and the density of the environments of these
sources. We find that the armlength asymmetries of GRGs are slightly larger
than those of smaller sized 3CR radio galaxies and that these are difficult to
explain as arising from orientation effects only. We also find indications that
the lobes of the GRGs, despite their large sizes, are still overpressured with
respect to their environment. Further, we argue that any evolution of lobe
pressure with redshift in these large sources is due to selection effects. A
spectral ageing analysis suggests that the GRGs in our sample are the oldest
members of the group of relatively high power radio sources whose radio powers
have evolved to their currently observed lower values.


title:
Ultraviolet Galaxy Counts from STIS Observations of the Hubble Deep
  Fields

abstract:
  We present galaxy counts in the near-ultraviolet (NUV; 2365\AA) and
far-ultraviolet (FUV; 1595\AA) obtained from Space Telescope Imaging
Spectrograph (STIS) observations of portions of the Hubble Deep Field North
(HDFN), the Hubble Deep Field South (HDFS), and a parallel field near the HDFN.
All three fields have deep (AB$>$29) optical imaging, and we determine
magnitudes by taking the ultraviolet flux detected within the limiting optical
isophote. An analysis of the UV-optical colors of detected objects, combined
with a visual inspection of the UV images, indicates that there are no
detectable objects in the UV images that are not also detected in the optical.
We determine our detection area and completeness as a function of magnitude
with a simulated distribution of galaxies based on the HDFN Wide Field
Planetary Camera 2 (WFPC2) V+I image. The galaxy counts reach to $NUV_{AB}=29$
and $FUV_{AB}=30$, which is 1 magnitude fainter than the HDFN WFPC2/F300W
counts, and 7 magnitudes fainter than balloon-based counts. We integrate our
measurements to present the extragalactic background radiation coming from
resolved objects. The NUV galaxy counts show a flattening or turnover beginning
at about $NUV_{AB}=26.0$, which is not predicted either by no-evolution models
based upon a local luminosity function with a steep faint end slope, nor by a
semi-analytic model in which starbursts are caused by major mergers. The FUV
counts also show a flat slope. We argue that the flat slopes could be caused by
a short duty cycle for star formation, additional starbursts triggered by minor
mergers, and an extended quiescent phase between starburst episodes.


title: Detection of Cosmic Shear with the William Herschel Telescope

abstract:
  Gravitational lensing by large-scale structure induces weak coherent
alignments in the shapes of background galaxies. Here we present evidence for
the detection of this `cosmic shear' at the 3.4 sigma significance level with
the William Herschel Telescope. Analysis and removal of notable systematic
effects, such as shear induced by telescope optics and smearing by tracking and
seeing, are conducted in order to recover the physical weak shear signal.
Positive results for shear recovery on realistic simulated data are presented,
enhancing confidence in the measurement method. The detection of cosmic shear
is statistically characterised, and its cosmological significance is discussed.


title: The Local Group

abstract:
  Local Group galaxies such as the Milky Way, the Magellanic Clouds, and M31
are being used by a number of international collaborations to search for
microlensing events. Type and number of detections place constraints on dark
matter and the stellar populations within and along the line of sight to these
galaxies. In this review I briefly discuss the stellar populations,
evolutionary histories, and other properties of different types of Local Group
galaxies as well as constraints on the dark matter content of these galaxies.
Particular emphasis is placed on the dwarf companions of the spiral galaxies in
the Local Group.


title: Comparing Ultraviolet and H alpha Star Formation Rates

abstract:
  We have used a sample of 43 star-forming galaxies imaged in the
far-ultraviolet (FUV) by the UIT supplemented with 33 galaxies observed by
FAUST, to explore the consistency of UV and H alpha derived star formation
rates (SFRs). We find, even before correction for dust, that UV and H alpha
SFRs are quantitatively consistent for low-luminosity galaxies, and that higher
luminosity galaxies have H alpha SFRs a factor of 1.5 higher than their UV
SFRs: this reflects the influence of dust. Our results are consistent with a
scenario where the UV dust extinction is a factor of less than 2 larger than
the H alpha dust extinction in a given galaxy, and that there is over a 4
magnitude range of H alpha dust extinctions which correlate loosely with galaxy
luminosity such that low luminosity galaxies tend to have lower extinctions
than their higher luminosity counterparts.


title: Radio Jet-blown Neutral Hydrogen Supershells in Spiral Galaxies?

abstract:
  Taking a clue from the pair of HI supershells found in the Scd galaxy NGC
3556 (M 108), we propose a new mechanism for the origin of HI supershells in
gas-rich massive galaxies. In this scenario, the two supershells were inflated
out of the neutral hydrogen disk due to the localised flaring of a pair of
radio lobes formed by the jets ejected from the nucleus during an active phase
about 10^7 years ago, but have faded away by now. It is shown that the salient
features of this supershell pair, such as their symmetrical locations about the
galactic centre, the anomalously large energy requirements, the large
galactocentric distances, as well as the Z-symmetric hemispherical shapes, find
a more natural explanation in terms of this scenario, as compared to the
standard models which postulate either a massive starburst, or the infall of
external gas clouds. Other possible implications of this hypothesis are briefly
discussed.


title:
The Properties of Spiral Galaxies in Semi-Analytic Galaxy Formation
  Models

abstract:
  We examine the present-day galaxy disk colors and star formation rates (SFRs)
in the semi-analytic model of Cole et al. (2000). We find that the fiducial
model is a good match to Kennicutt's (1998) observed global star formation law,
the color-based metallicity-magnitude correlation and the colors of
low-luminosity galaxies. The main limitation of the model, from the point of
view of present-day spirals, is that the optical colors of the disks of very
luminous spiral galaxies are too blue, even after accounting for the effects of
dust.


title: The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO)

abstract:
  AST/RO, a 1.7 m diameter telescope for astronomy and aeronomy studies at
wavelengths between 200 and 2000 microns, was installed at the South Pole
during the 1994-1995 Austral summer. The telescope operates continuously
through the Austral winter, and is being used primarily for spectroscopic
studies of neutral atomic carbon and carbon monoxide in the interstellar medium
of the Milky Way and the Magellanic Clouds. The South Pole environment is
unique among observatory sites for unusually low wind speeds, low absolute
humidity, and the consistent clarity of the submillimeter sky. Four heterodyne
receivers, an array receiver, three acousto-optical spectrometers, and an array
spectrometer are installed. A Fabry-Perot spectrometer using a bolometric array
and a Terahertz receiver are in development. Telescope pointing, focus, and
calibration methods as well as the unique working environment and logistical
requirements of the South Pole are described.


title:
Evolution of Stellar Collision Products in Globular Clusters - II.
  Off-axis Collision

abstract:
  We continue our exploration of collisionally merged stars in the blue
straggler region of the color-magnitude diagram. We report the results of new
SPH calculations of parabolic collisions between two main-sequence stars, with
the initial structure and composition profiles of the parent stars having been
determined from stellar evolution calculations. Parallelization of the SPH code
has permitted much higher numerical resolution of the hydrodynamics. We also
present evolutionary tracks for the resulting collision products, which emerge
as rapidly rotating blue stragglers. The rotating collision products are
brighter, bluer and remain on the main sequence longer than their non-rotating
counterparts. In addition, they retain their rapid rotation rates throughout
their main sequence lifetime. Rotationally-induced mixing strongly affects the
evolution of the collision products, although it is not sufficient to mix the
entire star. We discuss the implications of these results for studies of blue
straggler populations in clusters. This work shows that off-axis collision
products cannot become blue stragglers unless they lose a large fraction of
their initial angular momentum. The mechanism for this loss is not apparent,
although some possibilities are discussed.


title:
Search for High Energy Neutrino Emission from Gamma-Ray Bursts with the
  A ntarctic Muon and Neutrino Detector Array (AMANDA)

abstract:
  The photo-meson production of pions by shock-accelerated protons could
generate a burst of ~10^14 eV neutrinos from gamma-ray bursts (GRBs) observable
in the Antarctic Muon and Neutrino Detector Array (AMANDA) or its larger
successors. Measurement of this flux can test the hypothesis that GRBs are the
sources of the highest-energy cosmic rays, and GRB neutrinos could permit
high-precision experiments in neutrino limiting speed, neutrino oscillations,
and the weak equivalence principle. Neutrino emission can be expected primarily
during the prompt gamma-ray flash and satellite coincidence provides a
well-defined window in position and time that can be searched for an excess of
upgoing muon events in AMANDA from bursts in the Northern Hemisphere. Using an
event quality analysis to further reduce background in a sample of 78 GRBs from
the 1997 AMANDA-B10 data set, I find a fluence limit of (E_nu)^2
(dN_nu)/(dE_nu)<3.8*10^-4 min(1,E_nu/E_break) [TeV cm^-2] per average burst,
which is orders of magnitude more stringent than in similar previous searches.


title: The 1997 periastron passage of the binary pulsar PSR B1259-63

abstract:
  We report here on multifrequency radio observations of the pulsed emission
from PSR B1259-63 around the time of the closest approach to its B2e companion
star. There was a general increase in the pulsar's dispersion measure and
scatter broadening, and a decrease in the flux density towards periastron
although changes in these parameters were seen on timescales as short as
minutes. The pulsed emission disappeared 16 days prior to periastron and
remained undetectable until 16 days after periastron.
  The observations are used to determine the parameters of the wind from the Be
star. We show that a simple model, in which the wind density varies with radius
as r^-2, provides a good fit to the data. The wind is clumpy with size scales
<= 10^10 cm, densities of 10^6 cm^-3 and a velocity of 2000 km/s at a distance
of 20 - 50 stellar radii. We find a correlation between dispersion measure
variations and the pulse scattering times, suggesting that the same electrons
are responsible for both effects.


title:
HI line measurements of pulsars towards the Galactic Centre and the
  electron density in the inner Galaxy

abstract:
  We have measured 21-cm absorption and emission spectra in the direction of a
further 7 southern pulsars with the Parkes telescope to derive their kinematic
distances and to study the interstellar medium. For the first time we have
successfully obtained HI absorption measurements for PSRs J1602-5100,
J1740-3015 and J1745-3040. We have also significantly improved the sensitivity
and resolution on PSRs J1600-5044, J1752-2806, and J1825-0935, whose spectra
have previously been measured, and have corrected an error in the published
distance to PSR J1824-1945.
  Since the Frail & Weisberg summary of pulsar distances in 1990, a further 23
pulsars now have measured HI distances, mainly through the efforts of the
current group. We discuss the Taylor & Cordes electron density model in light
of these new measurements and find that, although the model towards the
Galactic Centre appears good, the line of sight through the Carina spiral arm
is poorly fit by the model.


title:
QSO 2359-1241: A Bright, Highly Polarized, Radio-Moderate, Reddened,
  Low-Ionization Broad Absorption Line Quasar

abstract:
  We report the discovery of a bright quasar (E=15.8, z=0.868) associated with
the flat spectrum radio source NVSS J235953-124148. This quasar we designate
QSO 2359-1241 possesses a rare combination of extreme properties that make it
of special interest. These properties include: intrinsic high-velocity outflow
seen in absorption for both high and low-ionization species, high optical
polarization (about 5%), significant radio emission, and dust reddening. The
dereddened absolute magnitude of QSO 2359-1241 places it among the three most
optically luminous quasars known at z<1. High-resolution spectroscopy and a
detailed analysis of the optical/ultraviolet absorption features will be given
in a companion paper (Arav et al 2000).


title: The Intrinsic Absorber in QSO 2359-1241: Keck and HST Observations

abstract:
  We present detailed analyses of the absorption spectrum seen in QSO 2359-1241
(NVSS J235953-124148). Keck HIRES data reveal absorption from twenty
transitions arising from: He I, Mg I, Mg II, Ca II, and Fe II. HST data show
broad absorption lines (BALs) from Al III 1857, C IV 1549, Si IV 1397, and N V
1240. Absorption from excited Fe II states constrains the temperature of the
absorber to 2000K < T < 10,000K and puts a lower limit of 10^5 cm^{-3} on the
electron number density. Saturation diagnostics show that the real column
densities of He I and Fe II can be determined, allowing to derive meaningful
constraints on the ionization equilibrium and abundances in the flow. The
ionization parameter is constrained by the iron, helium and magnesium data to
-3.0 < log(U) < -2.5 and the observed column densities can be reproduced
without assuming departure from solar abundances. From comparison of the He I
and Fe II absorption features we infer that the outflow seen in QSO 2359-1241
is not shielded by a hydrogen ionization front and therefore that the existence
of low-ionization species in the outflow (e.g., Mg II, Al III, Fe II) does not
necessitate the existence of such a front. We find that the velocity width of
the absorption systematically increases as a function of ionization and to a
lesser extent with abundance. Complementary analyses of the radio and
polarization properties of the object are discussed in a companion paper
(Brotherton et al. 2000).