title:
Intermediate resolution H-beta spectroscopy and photometric monitoring
  of 3C 390.3 I. Further evidence of a nuclear accretion disk

abstract:
  We have monitored the AGN 3C390.3 between 1995 and 2000.Two large amplitude
outbursts, of different duration, in continuum and H beta light were observed
ie.: in October 1994 a brighter flare that lasted about 1000 days and in July
1997 another one that lasted about 700 days were detected. The flux in the H
beta wings and line core vary simultaneously, a behavior indicative of
predominantly circular motions in the BLR.Important changes of the Hbeta
emission profiles were detected: at times, we found profiles with prominent
asymmetric wings, as those normaly seen in Sy1s, while at other times, we
observe profiles with weak almost symmetrical wings, similar to those seen in
Sy1.8s. We found that the radial velocity difference between the red and blue
bumps is anticorrelated with the light curves of H beta and continuum
radiation.e found that the radial velocity difference between the red and blue
bumps is anticorrelated with the light curves of H-beta and continuum
radiation. Theoretical H-beta profiles were computed for an accretion disk, the
observed profiles are best reproduced by an inclined disk (25 deg) whose region
of maximum emission is located roughly at 200 Rg. The mass of the black hole in
3C 390.3, estimated from the reverberation analysis is Mrev = 2.1 x 10^9 Msun,
ie. 5 times larger than previous estimates


title:
Self-Absorption of Ionizing Radiation and Extended Lyman Alpha Emission
  in High- Redshift QSOs

abstract:
  We calculate the neutral hydrogen column density of self-absorption in QSOs
predicted in a model where the QSOs are located in the same halos that contain
the gas in damped Lya absorption systems. The model is parameterized by the
probability P_0 that any halo has an active QSO. We assume that the QSOs ionize
the gas, but do not expel or heat it. The derived HI column densities produce
negligible Lyman limit absorption, even in the lowest luminosity QSOs, with an
optical depth of only ~ 10% for luminosity L=0.01 L_*, when P_0=10^{-2}. We
also compute the HeII Lyman limit self-absorption, which is slightly higher but
still negligible. The self-absorption can be higher if the gas is highly
clumped; only in this case the overall emissivity from QSOs could be
significantly reduced due to absorption by the known damped Lya systems, to
affect the predicted intensity of the ionizing background or the epoch of HeII
reionization. The presence of the gas associated with damped absorption systems
around QSOs could also be detected from the narrow Lya emission line, which
should have and angular extent of 0.1 to 1'' in typical high-redshift QSOs.


title: Compressible MHD Turbulence in Interstellar Plasmas

abstract:
  Radio-wave scintillation observations reveal a nearly Kolmogorov spectrum of
density fluctuations in the ionized interstellar medium. Although this density
spectrum is suggestive of turbulence, no theory relevant to its interpretation
exists. We calculate the density spectrum in turbulent magnetized plasmas by
extending the theory of incompressible MHD turbulence given by Goldreich &
Sridhar to include the effects of compressibility and particle transport. Our
most important results are as follows. (1) Density fluctuations are due to the
slow mode and the entropy mode. Both modes are passively mixed by the cascade
of shear Alfven waves. Since the shear Alfven waves have a Kolmogorov spectrum,
so do the density fluctuations. (2) Observed density fluctuation amplitudes
imply either that the magnetic and gas pressures are comparable, or that the
outer scale of the turbulence is very small. (3) A high degree of ionization is
required for the cascade to survive damping by neutrals and thereby to extend
to small lengthscales. Regions that are insufficiently ionized produce density
fluctuations only on lengthscales larger than the neutral damping scale. These
regions may account for the excess of power that is found on large scales. (4)
Both the entropy mode and the slow mode are damped on lengthscales below that
at which protons can diffuse across an eddy during the eddy's turnover time.
Consequently, eddies whose extents along the magnetic field are smaller than
the proton collisional mean free path do not contribute to the density
spectrum. However, in MHD turbulence eddies are highly elongated along the
magnetic field. From an observational perspective, the relevant lengthscale is
that transverse to the magnetic field. Thus the cut-off lengthscale for density
fluctuations is significantly smaller than the proton mean free path.


title: Detection of an X-ray jet in 3C 371 with Chandra

abstract:
  We report the detection at X-rays of the radio/optical jet of 3C 371, from a
short (10 ks) Chandra exposure in March 2000. We also present a new MERLIN
observation at 1.4 GHz together with a renalysis of the archival HST WFPC2
F555W image. Despite the limited signal-to-noise ratio of the Chandra data, the
X-ray morphology is clearly different from that of the radio/optical emission,
with the brightest X-ray knot at 1.7" from the nucleus and little X-ray
emission from the brightest radio/optical knot at 3.1". We construct the
spectral energy distributions for the two emission regions at 1.7" and 3.1".
Both show that the X-ray flux is below the extrapolation from the
radio-to-optical continuum, suggesting moderately beamed synchrotron from an
electron population with decreasing high energy cut-off as a plausible emission
mechanism.


title: Making Movies from Radio Astronomical Images with AIPS

abstract:
  We present a detailed recipe for making movies from multi-epoch radio
observations of astronomical sources. Images are interpolated linearly in time
to create a smooth succession of frames so that a continuous movie can be
compiled. Here, we outline the procedure, and draw attention to specific
details necessary for making a successful movie. In particular, we discuss the
issues pertaining specifically to making polarization movies. The procedure
described here has been implemented into scripts in NRAO's AIPS package
(Brandeis AIPS Movie Maker -- BAMM) that are available for public use
(http://www.astro.brandeis.edu).


title: Measuring $\Omega_m$ with the ROSAT Deep Cluster Survey

abstract:
  We analyze the ROSAT Deep Cluster Survey (RDCS) to derive cosmological
constraints from the evolution of the cluster X-ray luminosity distribution.
The sample contains 103 galaxy clusters out to z=0.85 and flux-limit Flim=3
10^{-14} cgs (RDCS-3) in the [0.5-2.0] keV energy band, with a high-z extension
containing four clusters at 0.90<z<1.26 and F>1 10^{-14} cgs (RDCS-1). Model
predictions for the cluster mass function are converted into the X-ray
luminosity function in two steps. First we convert mass into intra-cluster gas
temperature by assuming hydrostatic equilibrium. Then temperature is converted
into X-ray luminosity by using the most recent data on the Lx-T relation for
nearby and distant clusters. These include the Chandra data for seven distant
clusters at 0.57<z<1.27. From RDCS-3 we find \Omega_m=0.35+/-0.12 and
\sigma_8=0.66+/-0.06 for a spatially flat Universe with cosmological constant,
with no significant constraint on \Gamma . Even accounting for theoretical and
observational uncertainties in the mass/X-ray luminosity conversion, an
Einstein-de-Sitter model is always excluded at far more than the 3sigma level.


title: Optical identifications of $\sim 4000$ radio sources at the 1 mJy level

abstract:
  We present an analysis of the properties of optical counterparts of radio
sources down to 1 mJy. Optical identifications have been obtained by matching
together objects from the APM and FIRST surveys over the region
$148.13^\circ\simlt {\rm RA(2000)}\simlt 218.13^\circ$, $-2.77^\circ\simlt {\rm
Dec} \simlt 2.25^\circ$. Selecting radio sources down to 1 mJy, and adopting a
uniform optical limit of $b_J = 21.5$ we find 3176 have a counterpart in the
APM catalogue, corresponding to 13 per cent of the radio sample.
  For $b_J \le 20.5$ we can divide radio sources into resolved radio galaxies
and stellar-like objects (principally QSO). We find the population of radio
galaxies to be mainly made by early-type galaxies with very red colours
($b_J-R$ up to $\sim 4$) and a radio-to-optical ratio $10^2\simlt r\simlt
10^4$. The contribution of starbursting objects is negligible. In general QSO
show $r\simgt 10^4$ and $0\simlt b_J -R \simlt 1$. On the basis of the $R$
magnitudes, we estimate the sample of radio galaxies to be complete up to
$z\simeq 0.3$. We can therefore divide the whole sample of radio sources into a
low-z and high-z population. The low-z one includes the objects identified as
galaxies in the APM survey, the high-z one includes sources either identified
as QSO or with no optical counterpart for $b_J \le 20.5$.
  We find that radio galaxies are strongly clustered and highly biased tracers
of the underlying mass distribution. Models for the angular correlation
function $w(\theta)$ show good agreement with the observations if we assume a
bias factor $b\simeq 2$ at $z\simeq 0.3$.


title:
The 2dF Galaxy Redshift Survey: The population of nearby radio galaxies
  at the 1 mJy level

abstract:
  We use redshift determinations and spectral analysis of galaxies in the 2dF
Galaxy Redshift Survey to study the properties of local radio sources with
$S\ge 1$ mJy. 557 objects drawn from the FIRST survey, corresponding to 2.3 per
cent of the total radio sample, are found in the 2dFGRS cataloge within the
area $9^h 48^m \simlt {\rm RA}({\rm 2000}) \simlt 14^h 32^m$ and $-2.77^\circ
\simlt {\rm dec}({\rm 2000}) \simlt 2.25^\circ$, down to a magnitude limit
$b_J= 19.45$. The excellent quality of 2dF spectra allows us to divide these
sources into classes, according to their optical spectra. Radio galaxies (i.e.
absorption systems, mainly belonging to the class of FR I sources, whose
spectra may or may not show emission lines due to AGN activity) make up 63 per
cent of the spectroscopic sample; they are characterized by relatively high
radio-to-optical ratios, red colours and luminosities $10^{21}\simlt P_{1.4{\rm
GHz}} W Hz^${-1}$ sr$^{-1}$ \simlt 10^{24}$. Actively star-forming galaxies
instead contribute with 30 per cent to the total sample. These objects --
principally found at low redshifts ($z \simlt 0.1$) -- in general show low
radio-to-optical ratios, blue colours and low radio luminosities. We also found
18 Seyfert 2 galaxies and 4 Seyfert 1's. Analysis of the local radio luminosity
function shows that radio galaxies are well described by models that assume
pure luminosity evolution, at least down to radio powers $P_{1.4{\rm
GHz}}\simlt 10^{20.5} W Hz$^{-1}$ sr$^{-1}$ Late-type galaxies, whose relative
contribution to the RLF is found to be lower than was predicted by previous
work, present a luminosity function which is compatible with the IRAS galaxy
LF, and therefore plausibly constitute the radio counterpart of the dusty
spirals and starbursts that dominate the counts at 60 $\mu$m.


title: On the Metallicity of Star-forming Dwarf Galaxies

abstract:
  We construct three extreme different scenarios of the star formation
histories applicable to a sample of dwarf galaxies, based either on their
present metallicity or their luminosity. The three possible scenarios imply
different mechanical energy input rates and these we compare with the
theoretical lower limits established for the ejection of processed matter out
of dwarf galaxies. The comparison strongly points at the existence of extended
gaseous haloes in these galaxies, acting as the barrier that allows galaxies to
retain their metals and enhance their abundance. At the same time our findings
strongly point at a continuous star-forming process, rather than to coeval
bursts, as the main contributors to the overall metallicity in our galaxy
sample.


title:
Millihertz Optical/UV Oscillations in 4U 1626-67: Evidence for a Warped
  Accretion Disk

abstract:
  We have detected large-amplitude 0.3-1.2 mHz quasi-periodic oscillations
(QPOs) from the low-mass X-ray binary pulsar 4U 1626-67/KZ TrA, using UV
photometry from HST and ground-based optical photometry. These 1 mHz QPOs,
which have coherence (Nu/DeltaNu)=8, are entirely distinct from the 130 mHz
pulsar spin frequency, a previously known 48 mHz QPO, and the 42 min binary
period (independently confirmed here). Unlike the 48 mHz and 130 mHz
oscillations which are present in both the optical/UV and the X-ray emission,
the 1 mHz QPOs are not detected in simultaneous observations with RXTE. The rms
amplitude of the mHz QPO decreases from 15% in the far UV to 3% in the optical,
while the upper limit on a corresponding X-ray QPO is as low as 0.8%. We
suggest that the mHz oscillations are due to warping of the inner accretion
disk. We also report the detection of coherent upper and lower sidebands of the
130 mHz optical pulsations, with unequal amplitude and a spacing of 1.93 mHz
around the main pulsation. The origin of these sidebands remains unclear.


title: The Brightest AGB Stars in the Inner Bulge of M31

abstract:
  JHK images with angular resolutions approaching the diffraction limit of the
3.6 meter Canada-France-Hawaii Telescope are used to investigate the bright AGB
content of the M31 bulge. The AGB-tip in a field 2.6 arcmin from the galaxy
center occurs at K = 15.6, which is significantly fainter than measured in
previous ground-based studies that sampled similar projected distances from the
center of M31. Within 2.6 arcmin of the center of M31 the number density of
bright AGB stars scales with r-band surface brightness, and the K brightness of
the AGB-tip does not vary measureably with radius. It is concluded that the
infrared bright AGB stars (1) belong to the bulge, and not the disk, and (2)
are well mixed throughout the inner bulge, suggesting that they formed at a
time when the overall structural properties of the M31 bulge were imprinted.
The bolometric luminosity functions of the M31 bulge and Baade's Window are in
excellent agreement, while the brightest AGB stars in the M31 bulge, the
Galactic bulge, and M32 have similar M_K. These data suggest that the brightest
stars in M32 and the bulges of M31 and the Milky-Way belong to an old,
metal-rich population; these stars are bright not because they have a young or
intermediate age, but because they have a high metallicity.


title:
Multi-frequency VLBA Observations of the Compact Double B2 2050+36:
  Constraints on Interstellar Scattering Revisited

abstract:
  We present multi-frequency observations with the Very Long Baseline Array of
the compact double radio source B2 2050+36. Our observations are at 0.33, 0.61,
1.67, 2.3, and 8.4 GHz, with the 0.61 GHz observations forming the third epoch
of observation of this source at that frequency. At 0.61 GHz, the structure of
B2 2050+36 is dominated by two components 56 mas apart. Within the
uncertainties of the various measurements, this separation has remained
unchanged for the past 16 years. Any differential image wander caused by
refractive interstellar scattering is less than 4 mas. Both the lack of
differential image wander and the frequency dependence of the angular diameter
of B2 2050+36 below 1 GHz indicate that the electron density power spectrum
along this line of sight has a spectral index near the Kolmogorov value, with a
value of 4 being highly unlikely. We conclude that diffractive scattering
dominates along this line of sight; results in the literature indicate that
this conclusion also holds true for the line of sight to the pulsar PSR
B2020+28 (8.7 deg. from B2 2050+36). Comparison of our 1.67 GHz observations
with those obtained 21 years previously place a limit on the projected linear
separation velocity of the two components of c.


title: St. Petersburg Conference on Physics of Neutron Stars, 2001

abstract:
  The Programme and Abstracts booklet of the sixth Conference on "Physics of
Neutron Stars" held at the Ioffe Physical Technical Institute, St. Petersburg,
Russia, on June 6 -- 8, 2001 is presented. The abstracts contain references to
the web pages, LANL archive and published articles. More information on the
Conference can be found at http://www.ioffe.rssi.ru/astro/NS2001/index.html


title: Global versus Nuclear Starbursts

abstract:
  The strongest starbursts are observed towards galaxy nuclei, or circumnuclear
regions. However in interacting galaxies, star formation is also triggered in
overlap regions far from nuclei, in spiral arms and sometimes in tidal tails.
What is the relative importance of these starbursts? What kind of starformation
is dominating, as a function of redshift? These different starbursts occur in
different dynamical conditions (global and local): gravitational instabilities,
density waves, radial flows, shear, cloud collisions, density accumulations,
and they have been investigated with the help of numerical simulations.
Gravitational instabilities are necessary to initiate star formation, but they
are not sufficient; galactic disks are self-regulated through these
instabilities to have their Toomre Q parameter of the order of 1, and thus this
criterium is in practice unable to predict the onset of intense star formation.
Super star clusters are a characteristic SF mode in starbursts, and might be
due to the rapid formation of large gas complexes. Star formation can propagate
radially inwards, due to gravity torques and gas inflow, but also outwards, due
to superwinds, and energy outflows: both expanding or collapsing waves are
observed in circumnuclear regions. Mergers are more efficient in forming stars
at high redshift, because of larger gas content, and shorter dynamical times.
The relation between nuclear starbursts and nuclear activity is based on the
same fueling mechanisms, but also on reciprocal triggering and regulations.


title: Scale Dependence of Dark Energy Antigravity

abstract:
  We investigate the effects of negative pressure induced by dark energy
(cosmological constant or quintessence) on the dynamics at various
astrophysical scales. Negative pressure induces a repulsive term (antigravity)
in Newton's law which dominates on large scales. Assuming a value of the
cosmological constant consistent with the recent SnIa data we determine the
critical scale $r_c$ beyond which antigravity dominates the dynamics ($r_c \sim
1Mpc $) and discuss some of the dynamical effects implied. We show that
dynamically induced mass estimates on the scale of the Local Group and beyond
are significantly modified due to negative pressure. We also briefly discuss
possible dynamical tests (eg effects on local Hubble flow) that can be applied
on relatively small scales (a few $Mpc$) to determine the density and equation
of state of dark energy.


title: Catalogue of [Fe/H] determinations for FGK stars : 2001 edition

abstract:
  The catalogue presented here is a compilation of published atmospheric
parameters (Teff, logg, [Fe/H]) obtained from high resolution, high
signal-to-noise spectroscopic observations. This new edition has changed
compared to the five previous versions. It is now restricted to intermediate
and low mass stars (F, G and K stars). It contains 6354 determinations of
(Teff, logg, [Fe/H]) for 3356 stars, including 909 stars in 79 stellar systems.
The literature is complete between January 1980 and December 2000 and includes
378 references. The catalogue is made up of two tables, one for field stars and
one for stars in galactic associations, open and globular clusters and external
galaxies. The catalogue is distributed through the CDS database. Access to the
catalogue with cross-identification to other sets of data is also possible with
VizieR (Ochsenbein et al. 2000).


title: NGC 3310, a galaxy merger?

abstract:
  The HI structure and kinematics of the peculiar starburst galaxy NGC 3310
(Arp 217, UGC 5786) are discussed. New evidence bearing on the origin of the
starburst is presented. The bulk of HI coincides with the bright optical disk
and shows differential rotation. Its velocity dispersion is, however, unusually
large for a spiral galaxy (up to 40 km/s), suggesting that the disk is highly
perturbed as already indicated by optical emission line spectroscopy. There
are, in addition, two prominent HI tails, one extending to the north-west and
the other, somewhat patchy, to the south. These HI tails, the perturbed
kinematics and the peculiar optical morphology strongly suggest a recent merger
between two gas-rich galaxies. This seems to have been a major merger in which
most of the gas in the inner parts has been preserved in neutral atomic form
and either one of the progenitor disks has survived or a new disk has formed.


title:
Periodic variations in the colours of the classical T Tauri star RW Aur
  A

abstract:
  The classical T Tauri star RW Aur A is an irregular variable with a large
amplitude in all photometric bands. In an extended series of photometric data
we found small-amplitude periodic variations in the blue colours of the star,
with a period of 2.64 days. The period was relatively stable over several
years. The amplitude of the periodic signal is 0.21 mag in U-V, 0.07 mag in
B-V, and about 0.02 mag in V-R and V-I. No periodicity was found in the V
magnitude. The relevance of this photometric period to the recently discovered
periodicity in spectral features of the star is discussed, and the hypothesis
of a hot spot is critically considered.


title:
The Lithium Flash - Thermal instabilities generated by lithium burning
  in RGB stars

abstract:
  We present a scenario to explain the lithium-rich phase which occurs on the
red giant branch at the so-called bump in the luminosity function. The high
transport coefficients required to enhance the surface lithium abundance are
obtained in the framework of rotation-induced mixing thanks to the impulse of
the important nuclear energy released in a lithium burning shell. Under certain
conditions a lithium flash is triggered off. The enhanced mass loss rate due to
the temporary increase of the stellar luminosity naturally accounts for a dust
shell formation.


title:
Numerical Simulations of Pinhole and Single Mode Fibre Spatial Filters
  for Optical Interferometers

abstract:
  We use a numerical simulation to investigate the effectiveness of pinhole
spatial filters at optical/IR interferometers and to compare them with
single-mode optical fibre spatial filters and interferometers without spatial
filters. We show that fringe visibility measurements in interferometers
containing spatial filters are much less affected by changing seeing conditions
than equivalent measurements without spatial filters. This reduces visibility
calibration uncertainties, and hence can reduce the need for frequent
observations of separate astronomical sources for calibration of visibility
measurements. We also show that spatial filters can increase the
signal-to-noise ratios of visibility measurements and that pinhole filters give
signal-to-noise ratios within 17% of values obtained with single-mode fibres
for aperture diameters up to 3r_0. Given the simplicity of the use of pinhole
filters we suggest that it represents a competitive, if not optimal, technique
for spatial filtering in many current and next generation interferometers.


title: L-Band Photometry of L and T Dwarfs

abstract:
  We present K- and L-band photometry obtained with the Keck I telescope for a
representative sample of L and T dwarfs. These observations were motivated in
part by the dominant role water and methane play in shaping the flux near 2 and
3 microns and by the potential use of these bands as indicators of spectral
class in the infrared. In addition, these observations aid the determination of
the bolometric luminosity of L and T dwarfs. Here we report the K, L' and Ls
magnitudes of our objects and the trends observed in the (K-L') and (K-Ls)
colors as a function of L- and T-dwarf spectral class. We compare these colors
with theoretical models, derive a relationship between effective temperature
and L-spectral class, and compare our temperature estimates with others.


title:
Unveiling the AGN powering the "Composite" Seyfert/Star-forming galaxy
  NGC 7679: BeppoSAX and ASCA results

abstract:
  We discuss BeppoSAX observations and archive ASCA data of NGC 7679, a nearby,
nearly face-on SB0 galaxy in which starburst and AGN activities coexist. The
X-ray observations reveal a bright (L_{0.1-50 keV} \sim 2.9 \times 10^{43} erg
s^{-1}) and variable source having a minimum observed doubling/halving time
scale of \sim 10 - 20 ksec. A simple power law with photon index of \Gamma \sim
1.75 and small absorption (N_H < 4\times 10^{20} cm^{-2}) can reproduce the NGC
7679 spectrum from 0.1 up to 50 keV. These X-ray properties are unambiguous
signs of Seyfert 1 activity in the nucleus of NGC 7679. The starburst activity,
revealed by the IR emission, optical spectroscopy and H\alpha imaging, and
dominating in the optical and IR bands, is clearly overwhelmed by the AGN in
the X-ray band. Although, at first glance, this is similar to what is observed
in other starburst-AGN galaxies (e.g. NGC 6240, NGC 4945), most strikingly here
and at odds with the above examples, the X-ray spectrum of NGC 7679 does not
appear to be highly absorbed. The main peculiarity of objects like NGC 7679 is
not the strength of their starburst but the apparent optical weakness of the
Seyfert 1 nucleus when compared with its X-ray luminosity. To date NGC 7679 is
one of the few Seyfert 1/ Starburst composites for which the broad-band X-ray
properties have been investigated in detail. The results presented here imply
that optical and infrared spectroscopy could be highly inefficient in revealing
the presence of an AGN in these kinds of objects, which instead is clearly
revealed from X-ray spectroscopic and variability investigations.


title:
H-atom laser without inversion (LWI) in space: a possible explanation
  for the intense, narrow-band, H(alpha) emission frequently observed in
  reddened early-type stars

abstract:
  A model is suggested to explain the frequently observed presence of intense,
narrow-band, H(alpha) emission lines in the optical spectra of reddened,
early-type stars (e.g. HD 44179, IRAS 18179-1346, IRAS 20298+4011). It is
proposed that hydrogen atoms surrounding compact H II regions enveloping such
stars become coherently phased via a nonlinear photonic mechanism that leads to
`electromagnetically induced transparency (EIT)'. EIT is a powerful technique
that can be used to make a material system transparent to resonant laser
radiation, while still allowing large nonlinear resonant processes to occur
with high probability. In EIT terminology, a `Lambda' configuration, involving
H-atom levels (1s, 3p, and 2s), is here assumed to be operative. The EIT
`coupling beam' is the narrow-band H(alpha) radiation predicted to be
coherently generated via a standard `laser without inversion (LWI)' scenario
when coherently phased atoms are excited to the 3p level by means of a separate
nonlinear excitation process known as resonant hyper-Raman scattering (HRS). In
the unit HRS pumping process, a pair of far-ultraviolet (FUV) photons, with
frequencies lying very close to Ly- beta but offset from it by equal amounts to
high and low energies, are absorbed from the star's blackbody continuum, a
photon at Ly-beta line center is emitted, and an atom is excited to the 3p
level - with all events in this energy conserving process occurring
simultaneously. The EIT `probe beam' is the light predicted to be coherently
generated at Ly-beta line center, which - as a result of the complete linear
transparency afforded at this frequency by the coherently phased H atoms - can
propagate completely unattenuated through the optically thick H-atom cloud
surrounding the star.


title:
Likelihood distribution for models with cosmological constant from COBE
  data

abstract:
  Using COBE-DMR 4-year data, we find a general expression yielding the
likelihood distribution in the 3-dimensional parameter space spanned by the
spectral index $n$, the spectral amplitude $a_{10}$ and the false-vacuum
density parameter $\Omega_\Lambda$. Using such simple expression, the range of
possible normalizations, within a given likelihood interval from top-likelihood
normalization, is readily found, with fair approximation, for any model with
total density parameter $\Omega_o = 1$ and assigned $n$ and $\Omega_\Lambda$.


title: 1999 Quadrantids and the lunar Na atmosphere

abstract:
  Enhancements of the Na emission and temperature from the lunar atmosphere
were reported during the Leonids meteor showers of 1995, 1997 and 1998. Here we
report a search for similar enhancement during the 1999 Quadrantids, which have
the highest mass flux of any of the major streams. No enhancements were
detected. We suggest that different chemical-physical properties of the Leonid
and Quadrantid streams may be responsible for the difference.


title: Confronting atomic data with Fe L-shell spectra of stellar coronae

abstract:
  It is common to suggest the uncertainties in the atomic data for explaining
difficulties that arise in interpreting astrophysical x-ray spectra. The atomic
data for the Fe L-shell ions have, over the years, been considered particularly
suspect. In this paper, we confront Fe-L spectra calculated using the HULLAC
atomic code assuming coronal conditions with recent observations of the stellar
coronae of Capella and HR 1099, obtained with the high-resolution grating
spectrometers on board Chandra and XMM-Newton. We find very good agreement,
which indicates that Fe-L transition rates calculated with state-of-the-art
codes, can generally be trusted in the analysis of x-ray spectra.


title: Comments on "A Supernova Brane Scan"

abstract:
  Recently we proposed that the acceleration of the Universe could be due to
gravity leaking to extra dimensions. This scenario gives an alternative to the
cosmological constant or quintessence. In [astro-ph/0106274] the authors
claimed that this proposal is strongly disfavored if not ruled out by the
existing data on Supernovae, Cosmic Microwave Background and clusters. We show
that the work [astro-ph/0106274] contains incorrect statements in the
theoretical part, and, moreover, we argue that the main conclusions of the work
concerning the comparison with the data are premature.


title:
On time-dependent X-ray reflection by photoionized accretion disks:
  implication for Fe K-alpha line reverberation studies of AGN

abstract:
  We perform a first study of time-dependent X-ray reflection in photo-ionized
accretion disks. We assume a step-functional change in the X-ray flux and use a
simplified prescription to describe the time evolution of the illuminated gas
density profile in response to changes in the flux. We find that the dynamical
time for re-adjustment of the hydrostatic balance is an important relaxation
time scale of the problem since it affects evolution of the ionization state of
the reflector. Because of this the Fe K-alpha line emissivity depends on the
shape and intensity of the illuminating flux in prior times, and hence it is
not a function of the instantaneous illuminating spectrum. Moreover, during the
transition, a prominent Helium-like component of the Fe K-alpha line may
appear. As a result, the line flux may appear to be completely uncorrelated
with X-ray continuum flux on time scales shorter than the dynamical time. In
addition, the time-dependence of the illuminating flux may leave imprints even
on the time-averaged line spectra, which may be used as an additional test of
accretion disk geometry. Our findings appear to be important for the proposed
Fe K-alpha line reverberation studies in lamppost-like geometries for accretion
rates exceeding about $\sim 1%$ of the Eddington value. However, most AGN do
not show Helium-like lines that are prominent in such models, probably
indicating that these models are not applicable to real sources.


title: Making Maps Of The Cosmic Microwave Background: The MAXIMA Example

abstract:
  This work describes Cosmic Microwave Background (CMB) data analysis
algorithms and their implementations, developed to produce a pixelized map of
the sky and a corresponding pixel-pixel noise correlation matrix from time
ordered data for a CMB mapping experiment. We discuss in turn algorithms for
estimating noise properties from the time ordered data, techniques for
manipulating the time ordered data, and a number of variants of the maximum
likelihood map-making procedure. We pay particular attention to issues
pertinent to real CMB data, and present ways of incorporating them within the
framework of maximum likelihood map-making. Making a map of the sky is shown to
be not only an intermediate step rendering an image of the sky, but also an
important diagnostic stage, when tests for and/or removal of systematic effects
can efficiently be performed. The case under study is the MAXIMA data set.
However, the methods discussed are expected to be applicable to the analysis of
other current and forthcoming CMB experiments.


title:
Constraints on the Acceleration of Ultra-High-Energy Cosmic Rays in
  Accretion-Induced Collapse Pulsars

abstract:
  (Abridged) We have recently proposed that the ultra-high energy cosmic rays
(UHECRs) observed above the GZK limit could be mostly protons accelerated in
reconnection sites just above the magnetosphere of newborn millisecond pulsars
originated by accretion induced collapse (AIC-pulsars). Although the expected
rate of AIC sources in our own Galaxy is very small, our estimates have shown
that the observed total flux of UHECRs could be obtained from the integrated
contribution from AIC-pulsars of the whole distribution of galaxies located
within a distance which is unaffected by the GZK cutoff ($\sim 50 $ Mpc). We
presently examine the potential acceleration mechanisms in the magnetic
reconnection site and find that first-order Fermi acceleration cannot provide
sufficient efficiency (due to synchrotron losses). This leaves the one-shot
acceleration via an induced electric field within the reconnection region as
the only viable process for UHECR acceleration. We formulate the constraints on
both the magnetic field topology and strength in order to accelerate the
particles and allow them to freely escape from the system. Under fast
reconnection, we find that AIC-pulsars with surface B-fields $10^{12} $ G $<
B_{\star} \lesssim $ $10^{15}$ G and spin periods 1 ms $\lesssim P_{\star} < $
60 ms, are able to accelerate particles to energies $\geq 10^{20} $ eV, but the
magnetic field just above the Alfv\'en surface must be predominantly toroidal
for the particles to be allowed to escape from the acceleration zone without
being deflected. Synchrotron losses bring potentially important constraints on
the B-field geometry of $any$ UHECR accelerators involving compact sources with
strong magnetic fields.


title: Secular interactions between inclined planets and a gaseous disk

abstract:
  In a planetary system, a secular particle resonance occurs at a location
where the precession rate of a test particle (e.g. an asteroid) matches the
frequency of one of the precessional modes of the planetary system. We
investigate the secular interactions of a system of mutually inclined planets
with a gaseous protostellar disk that may contain a secular nodal particle
resonance. We determine the normal modes of some mutually inclined planet-disk
systems. The planets and disk interact gravitationally, and the disk is
internally subject to the effects of gas pressure, self-gravity, and turbulent
viscosity. The behavior of the disk at a secular resonance is radically
different from that of a particle, owing mainly to the effects of gas pressure.
The resonance is typically broadened by gas pressure to the extent that global
effects, including large-scale warps, dominate. The standard resonant torque
formula is invalid in this regime. Secular interactions cause a decay of the
inclination at a rate that depends on the disk properties, including its mass,
turbulent viscosity, and sound speed. For a Jupiter-mass planet embedded within
a minimum-mass solar nebula having typical parameters, dissipation within the
disk is sufficient to stabilize the system against tilt growth caused by
mean-motion resonances.


title: Quantitative Morphology of Galaxies Observed in the Ultraviolet

abstract:
  We present a quantitative study of the far-ultraviolet (FUV) and optical
morphology in 32 nearby galaxies and estimate the ``morphological
k-correction'' expected if these objects were observed unevolved at high
redshift. Using the common indices of central concentration (C) and rotational
asymmetry (A) to quantify morphology, we consider independently two phenomena
that give rise to this k-correction. Bandshifting, the decrease in rest-frame
wavelength of light observed through optical filters, is explored by measuring
these indices in several passbands for each galaxy, and it is found to be the
primary driver of changes in C and A. In general, the optical trend found for
decreasing C and increasing A when going to shorter wavelengths extends to the
FUV. However, the patchy nature of recent star-formation in late-type galaxies,
which is accentuated in the FUV, results in poor quantitative correspondence
between morphologies determined in the optical and FUV. We then artificially
redshift our FUV images into the Hubble Deep Field (HDF) filters to simulate
various cosmological distance effects such as surface brightness dimming and
loss of spatial resolution. Hubble types of many galaxies in our sample are not
readily identifiable at redshifts beyond z ~ 1, and the galaxies themselves are
difficult to detect beyond z ~ 3. Only features of the highest surface
brightness remain visible at cosmological distances. Our simulations suggest
that k-corrections alone are indeed capable of producing the peculiar
morphologies observed at high redshift.


title: Cosmological Studies with Gamma-Ray Bursts

abstract:
  Gamma-Ray Burst (GRB) explosions from the first generation of stars offer an
exciting opportunity to probe the epoch of reionization. Clues about how and
when the intergalactic medium was ionized can be read off their UV emission
spectrum. Roughly a percent of all GRBs should be strongly gravitationally
lensed by intervening stars. A microlensed lightcurve can be inverted to
reconstruct the surface brightness profile of the GRB image on the sky, with
micro-arcsecond resolution.


title:
Competition between shocks and entropy floor : unifying groups and
  clusters of galaxies

abstract:
  Semi-analytic models of X-ray clusters and groups of galaxies, relying on the
idea that there was a non-gravitational energy injection in these systems, are
able to reproduce many observed correlations, in particular the L_X-T relation
and the ``central entropy floor'' in groups. Limiting models exist which
describe the behaviour of clusters and groups separately, but no analytic
modeling has yet been found to unify both mass ranges. {\it It is the aim of
this paper to provide such an analytic model.} Our description relies on a now
standard description of the shock thought to occur in these systems near the
virial radius (Cavaliere et al., 98), the isothermality and spherical symmetry
of the intracluster medium, as well as the reinterpretation of observed
quantities (like the X-ray luminosity, the gas mass M_{ICM} and the central SZ
effect y_0) in terms of the specific entropy. This allows the derivation of
analytic expressions for several observed correlations (L_X-T, M_{ICM}-T,
y_0-T,...) and their normalisation encompassing \emph{both the group and the
cluster regimes}. The analytic predictions compare very well with observations,
as well as with more elaborated semi-analytic schemes. This agreement allows a
reinterpretation of the L_X-T relation (via the quantity L_X/T^{7/2}) and the
y_0-T relation (via y_0/T^{5/2}) as indirect measures of the non-gravitational
entropy content of groups and clusters of galaxies. Finally, we emphasize the
need for shock heating, even in the group mass range : \emph{shocks can not be
completely supressed in groups} (and thus groups can not be entirely
isentropic) unless an unacceptably high entropy floor is needed in order to
break the self-similarity in the L_X-T relation.


title:
Globular Cluster Subpopulations in Early-Type Galaxies: Insights into
  Galaxy Formation

abstract:
  New and archival HST images of the globular cluster systems of 17 relatively
nearby galaxies and 6 more distant galaxies have been used to establish the
characteristics of GC subpopulations over a range of host galaxy morphological
type from E5 to Sa. GC color/metallicity, size and luminosity distributions
have been examined in the nearby galaxies and color distributions have been
determined for the more distant sample. Correlations with parent galaxy
properties and trends with galactocentric radius have been explored.
Supplemented with Keck spectroscopy, our results are best explained by an in
situ formation scenario in which both GC subpopulations formed at early times
within the potential well of the protogalaxy, in multiple episodes of star
formation. We have also discovered a third population of clusters,
fundamentally distinct from the compact red and blue clusters common in early
type galaxies.


title:
Constraints on the Interaction between Dark Matter and Baryons from
  Cooling Flow Clusters

abstract:
  Other nongravitational heating processes are needed to resolve the
disagreement between the absence of cool gas components in the centers of
galaxy clusters revealed recently by Chandra and XMM observations and the
expectations of conventional radiative cooling models. Here we propose that the
interaction between dark matter particles and ordinary baryonic matter may act
as an alternative for the reheating of intracluster medium (ICM) in the inner
regions of clusters, in which kinetic energy of dark matter is transported to
ICM to balance the radiative cooling. Using the Chandra and XMM data of typical
clusters, we set a useful constraint on the dark matter-baryon cross-section:
$\sigma_{xp}/m_x \sim 1 \times 10^{-25}$ cm$^2$GeV$^{-1}$, where $m_x$ is the
mass of dark matter particles.


title: Bulge Globular Clusters in Spiral Galaxies

abstract:
  There is now strong evidence that the metal-rich globular clusters (GC) near
the center of our Galaxy are associated with the Galactic bulge rather than the
disk as previously thought. Here we extend the concept of bulge GCs to the GC
systems of nearby spiral galaxies. In particular, the kinematic and metallicity
properties of the GC systems favor a bulge rather than a disk origin. The
number of metal-rich GCs normalized by the bulge luminosity is roughly constant
(i.e. bulge S_N ~ 1) in nearby spirals, and this value is similar to that for
field ellipticals when only the red (metal--rich) GCs are considered. We argue
that the metallicity distributions of GCs in spiral and elliptical galaxies are
remarkably similar, and that they obey the same correlation of mean GC
metallicity with host galaxy mass. We further suggest that the metal-rich GCs
in spirals are the direct analogs of the red GCs seen in ellipticals. The
formation of a bulge/spheroidal stellar system is accompanied by the formation
of metal-rich GCs. The similarities between GC systems in spiral and elliptical
galaxies appear to be greater than the differences.


title: ASTRO-F Survey as Input Catalogues for FIRST

abstract:
  ASTRO-F is the second Japanese space mission for infrared astronomy and is
scheduled to be launched into a sun-synchronous polar orbit by the Japanese M-V
rocket in February 2004. ASTRO-F has a cooled 67 cm telescope with two focal
plane instruments: one is the Far-Infrared Surveyor (FIS) and the other is the
Infrared Camera (IRC). The main purpose of FIS is to perform the all-sky survey
with four photometric bands in the wavelength range of 50 - 200 $\mu$m. The
advantages of the FIS survey over the IRAS survey are (1) higher spatial
resolution ($30''$ at 50-110 $\mu$m and $50''$ at 110-200 $\mu$m) and (2)
better sensitivity by one to two orders of magnitude. The FIS survey will
provide the next generation far-infrared survey catalogs, which will be ideal
inputs for observations by FIRST. The other instrument, IRC, will make deep
imaging and low-resolution spectroscopic observations in the spectral range of
$1.8-26 \mu$m. The IRC will make large-area surveys with its wide field of view
($10' \times 10'$), and will be complementary with the FIRST observations at
longer wavelengths.


title:
Age Dating of Globular Clusters Using UBV(RI) Main-sequence Photometry
  in the Two-color Diagram: Age of NGC 6397

abstract:
  I propose and apply a method for deriving ages of the metal-poor globular
clusters (GCs) in a distance-independent way, which is based on age indicator
related to the main sequence in the two-color diagrams with U-B index. Age of
the metal-poor GC NGC 6397 has been estimated, using Yale isochrones of
Demarque et al. (1996), to be close to 16 Gyr provided the cluster metallicity
is near [Fe/H]=-2.0.


title:
Including star formation and supernova feedback within cosmological
  simulations of galaxy formation

abstract:
  We investigate phenomenological models of star formation and supernova
feedback in N-body/SPH simulations of galaxy formation. First, we compare
different prescriptions in the literature for turning cold gas into stars
neglecting feedback effects. We find that most prescriptions give broadly
similar results: the ratio of cold gas to stars in the final galaxies is
primarily controlled by the range of gas densities where star formation is
allowed to proceed efficiently. In the absence of feedback, the fraction of gas
that cools is much too high resulting, for example, in a K-band luminosity
function that is much brighter than observed. This problem is ameliorated by
including a feedback model which either imparts radial kinetic perturbations to
galactic gas or directly reheats such material and prevents it from cooling for
a certain period of time. In both these models, a significant fraction of cold
gas is heated and expelled from haloes with an efficiency that varies inversely
with with halo circular velocity. Increasing the resolution of a simulation
allows a wider dynamic range in mass to be followed, but the average properties
of the resolved galaxy population remain largely unaffected. However, as the
resolution is increased, more and more gas is reheated by small galaxies; our
results suggest that convergence requires the full mass range of galaxies to be
resolved.


title: The low mass white dwarf companion to Beta Crateris

abstract:
  We present FUSE H Lyman series spectroscopy of the hot white dwarf companion
to the 4th magnitude A1III star Beta Crateris, which shows that is has an
unusually low mass, 0.43Msun, and has almost certainly evolved through binary
interaction. This system could be a long-sought remnant of Algol-type
evolution, although radial velocity measurements appear to show that the pair
are not close. Instead, micro-variations in Beta Crt's proper motion as
measured by Hipparcos suggests that the period could be as high as 10 years.
However, a low mass white dwarf in a system with a period >3 years is difficult
to explain by conventional models for binary evolution. We speculate on
alternative models for the evolution of this system which involve an eccentric
binary or multiple components.


title: On the state of low luminous accreting neutron stars

abstract:
  Observational appearance of a neutron star in the subsonic propeller state
which is a companion of a wind-fed mass-exchange close binary system is
discussed. During the subsonic propeller state the neutron star magnetosphere
is surrounded by a spherical quasi-static plasma envelope, which is extended
from the magnetospheric boundary up to the star accretion radius. The energy
input to the envelope due to the propeller action by the neutron star exceeds
the radiative losses and the plasma temperature in the envelope is of the order
of the free-fall temperature. Under this condition the magnetospheric boundary
is interchange stable. Nevertheless, I find that the rate of plasma penetration
from the envelope into the magnetic field of the neutron star due to diffusion
and magnetic field line reconnection processes is large enough for the
accretion power to dominate the spindown power. I show that the accretion
luminosity of the neutron star in the subsonic propeller state is 5*10**{30} -
10**{33} (dM/dt)_{15} erg/s, where dM/dt is the strength of the normal
companion stellar wind which is parametrized in terms of the maximum possible
mass accretion rate onto the neutron star magnetosphere. On this basis I
suggest that neutron stars in the subsonic propeller state are expected to be
observed as low luminous accretion-powered pulsars. The magnetospheric radius
of the neutron star in this state is determined by the strength of the stellar
wind, (dM/dt)_c, while the accretion luminosity is determined by the rate of
plasma penetration into the star magnetosphere, (dM/dt)_a, which is (dM/dt)_a
<< (dM/dt)_c. That is why the classification of the neutron star state in these
objects using the steady accretion model (i.e. setting (dM/dt)_a = (dM/dt)_c)
can lead to a mistaken conclusion.


title:
Massive core parameters from spatially unresolved multi-line
  observations

abstract:
  We present observations of 15 massive cores in three different CS transitions
from the FCRAO 14m and the KOSMA 3m telescope. We derive physical parameters of
these cores using different approaches to the line radiative transfer problem.
The local radiative transfer approximations fail to provide reliable values
except for the column densities. A self-consistent explanation of the observed
line profiles is only possible when taking density gradients and an internal
turbulent structure of the cores into account. The observational data can be
fitted by a spherically symmetric radiative transfer model including such
gradients and a turbulent clumping. We find that the observed massive cores are
approximately virialised with a clumpy density profile that decays with a
radial exponent of about -1.6 down to a relatively sharp outer boundary.
  We show that a careful analysis of spatially unresolved multi-line
observations using a physical radiative transfer model can provide values for
physical parameters that could be obtained otherwise only by direct
observations with much higher spatial resolution. This applies to all
quantities directly affecting the line excitation, like the mass and size of
dense cores. Information on the exact location or number of clumps, of course,
always has to rely on high-resolution observations e.g. from interferometers.


title: Arguments for a Hubble Constant near $H_0$ = 55

abstract:
  Recent analyses of Cepheid distances to spiral galaxies have led to an
announcement of a Hubble constant of $H_0 = 72 \pm 8$ km/sec/Mpc. The new
Cepheid distances, however, show that there are numerous redshift distances
with large excesses which cannot be due to peculiar velocities. Ignoring these
discordant redshifts, if the Hubble constant is calibrated with Cepheid
distances of low redshift spirals a value near $H_0$ = 55 is obtained. Use of
independent distance criteria such as Tully-Fisher and group membership
verifies this value and leads to three conclusions: 1) The peculiar velocities
of galaxies in space are characteristically small. 2) Sc companions to normal
Sb's tend to be less luminous, with younger stellar populations and small
amounts non velocity redshift. 3) ScI and other purportedly over luminous
spirals have large amounts of intrinsic redshift.


title: A critical appraisal of ATLAS9 and NextGen 5 model atmospheres

abstract:
  The fitting atmosphere parameters (Teff, g, and [Fe/H]) for over 300 stars in
the Gunn & Striker and Jacoby et al. catalogs have been obtained relying on the
Kurucz (1992) ATLAS9 and Hauschildt et al (1999) NextGen5 synthesis models. The
output results are compared, and a critical appraisal of both theoretical codes
is performed.


title:
Cosmology with Self-Adjusting Vacuum Energy Density from a
  Renormalization Group Fixed Point

abstract:
  Cosmologies with a time dependent Newton constant and cosmological constant
are investigated. The scale dependence of $G$ and $\Lambda$ is governed by a
set of renormalization group equations which is coupled to Einstein's equation
in a consistent way. The existence of an infrared attractive renormalization
group fixed point is postulated, and the cosmological implications of this
assumption are explored. It turns out that in the late Universe the vacuum
energy density is automatically adjusted so as to equal precisely the matter
energy density, and that the deceleration parameter approaches $q = -1/4$. This
scenario might explain the data from recent observations of high redshift type
Ia Supernovae and the cosmic microwave background radiation without introducing
a quintessence field.


title: The Evolution of Circumstellar Disks: Lessons from the VLT and ISO

abstract:
  There is strong evidence that the planets in the solar system evolved from a
disk-shaped solar nebula ~4.56 Gyr ago. By studying young stars in various
evolutionary stages, one aims at tracing back the early history of the solar
system, in particular the timescales for disk dissipation and for the formation
of planetary systems. We used the VLT & ISAAC, and ESA's Infrared Space
Observatory & ISOCAM to study the circumstellar environment of young low-mass
stars.


title: Passive irradiated circumstellar disks with an inner hole

abstract:
  A model for irradiated dust disks around Herbig Ae stars is proposed. The
model is based on the flaring disk model of Chiang & Goldreich (1997), but with
the central regions of the disk removed. The inner rim of the disk is puffed up
and is much hotter than the rest of the disk, because it is directly exposed to
the stellar flux. If located at the dust evaporation radius, its reemitted flux
produces a conspicuous bump in the SED which peaks at 2-3 micron. We propose
that this emission is the explanation for the near-infrared bump observed in
the SEDs of Herbig Ae stars. We study for which stellar parameters this bump
would be observable, and find that it is the case for Herbig Ae stellar
parameters but not for T-Tauri stars, confirming what is found from the
observations. We also study the effects of the shadow cast by the inner rim
over the rest of the flaring disk. The shadowed region can be quite large, and
under some circumstances the entire disk may lie in the shadow. This shadowed
region will be much cooler than an unshadowed flaring disk, since its only
heating sources are radial radiative diffusion and possible indirect sources of
irradiation. Under certain special circumstances the shadowing effect can
suppress, or even completely eliminate, the 10 micron emission feature from the
spectrum, which might explain the anomalous SEDs of some isolated Herbig Ae
stars in the sample of Meeus et al. (2001). At much larger radii the disk
emerges from the shadow, and continues as a flaring disk towards the outer
edge. The complete model, including structure of the inner edge, shadowed
region and the flared outer part, is described in detail in this paper, and we
show examples of the general behavior of the model for varying parameters.


title:
Summary: Clusters of Galaxies and the High Redshift Universe Observed in
  X-Rays

abstract:
  This Meeting featured the recent advancements in our understanding of galaxy
clusters and the distant Universe, achieved by the past and new generation of
X-ray satellites. I summarize here the main themes that have been discussed:
(a) Clusters of galaxies as probes of cosmological models; (b) The physics of
cosmic baryons trapped within the potential wells of galaxy clusters; (c) The
origin of the cosmic X-ray background and the nature of the contributing
sources.


title: Violation of Lorentz Invariance and neutral component of UHECR

abstract:
  The observed clustering of ultra-high energy cosmic rays suggests the
existence of a neutral component. The models with violation of Lorentz
invariance may explain this component by neutrons becoming stable above some
threshold energy E_0. The protons, in turn, may become unstable above some
energy E_1>E_0. We calculate the dependence of the threshold energies E_0 and
E_1 on the parameters of the model and find E_1/E_0\gsim 1.5. We argue that the
characteristic threshold behavior of charged and neutral components may be used
as the specific signature of models with violation of Lorentz invariance. The
existence of the neutron stability threshold E_0 can be investigated with
already existing data.


title: On the redshift cut-off for steep-spectrum radio sources

abstract:
  We use three samples (3CRR, 6CE and 6C*) selected at low radio frequency to
constrain the cosmic evolution in the radio luminosity function (RLF) for the
`most luminous' steep-spectrum radio sources. Although intrinsically rare, such
sources give the largest possible baseline in redshift for the complete
flux-density-limited samples currently available. Using parametric models to
describe the RLF which incorporate distributions in radio spectral shape and
linear size as well as the usual luminosity and redshift, we find that the data
are consistent with a constant comoving space density between z~2.5 and z~4.5.
We find this model is favoured over a model with similar evolutionary behaviour
to that of optically-selected quasars (i.e. a roughly Gaussian distribution in
redshift) with a probability ratio of ~25:1 and ~100:1 for spatially-flat
cosmologies with Omega_Lambda = 0 and Omega_Lambda = 0.7 respectively. Within
the uncertainties, this evolutionary behaviour may be reconciled with the
shallow decline preferred for the comoving space density of flat-spectrum
sources by Dunlop & Peacock (1990) and Jarvis & Rawlings (2000), in line with
the expectations of Unified Schemes.


title:
Difference Image Analysis of the OGLE-II bulge data. II. Microlensing
  events

abstract:
  We present a sample of microlensing events discovered in the Difference Image
Analysis (DIA) of the OGLE-II images collected during 3 observing seasons,
1997--1999. 4424 light curves pass our criteria on the presence of a
brightening episode on top of a constant baseline. Among those, 512 candidate
microlensing events were selected visually. We designed an automated procedure,
which unambiguously selects up to 237 best events. Including 8 candidate events
recovered by other means, a total of 520 light curves are presented in this
work.
  In addition to microlensing events, the larger sample contains certain types
of transients, but is also strongly contaminated by artifacts. All 4424 light
curves in the weakly filtered group are available electronically, with the
intent of showing the gray zone between microlensing events and variable stars,
as well as artifacts, to some extent inevitable in massive data reductions. We
welcome suggestions for improving the selection process before the full
analysis of complete 4 seasons of the OGLE-II bulge data. Selection criteria
for binary events can also be investigated with our extended sample.


title: The Energetics and Mass-loss of Mrk33

abstract:
  We present ROSAT HRI X-ray data and optical imaging of the important dwarf
starburst Markarian 33. We find an extended, complex, shell-like morphology in
the X-ray emission, with an extent of 2.3 x 1.9kpc, coincident with the bright
star-forming regions at the centre of the galaxy. The physical extent of this
X-ray emission from Mrk 33 is very similar to the observed Halpha emission, and
suggests that the bulk of the X-ray emission is coming from an expanding
superbubble.
  We estimate the age and mass of Mrk 33's starburst to be 5.8 Myr and 6.9 x
10^{6} Msolar respectively with the energy injection rate in the central
regions of the galaxy being 10^{41} erg/s, while the associated mass-loss rate
from the star-forming regions is estimated to be 0.2 Msolar/yr. We suggest that
the X-ray emission is predominantly powered by starburst type activity and
argue that a blowout in the form of a galactic wind is the most likely fate for
Mrk 33 resulting in the loss of most of the galaxy's metal-enriched material
and a small fraction (<1 per cent) of the ISM.


title: Galaxy Clustering in Early SDSS Redshift Data

abstract:
  We present the first measurements of clustering in the Sloan Digital Sky
Survey (SDSS) galaxy redshift survey. Our sample consists of 29,300 galaxies
with redshifts 5,700 km/s < cz < 39,000 km/s, distributed in several long but
narrow (2.5-5 degree) segments, covering 690 square degrees. For the full,
flux-limited sample, the redshift-space correlation length is approximately 8
Mpc/h. The two-dimensional correlation function \xi(r_p,\pi) shows clear
signatures of both the small-scale, ``fingers-of-God'' distortion caused by
velocity dispersions in collapsed objects and the large-scale compression
caused by coherent flows, though the latter cannot be measured with high
precision in the present sample. The inferred real-space correlation function
is well described by a power law, \xi(r)=(r/6.1+/-0.2 Mpc/h)^{-1.75+/-0.03},
for 0.1 Mpc/h < r < 16 Mpc/h. The galaxy pairwise velocity dispersion is
\sigma_{12} ~ 600+/-100 km/s for projected separations 0.15 Mpc/h < r_p < 5
Mpc/h. When we divide the sample by color, the red galaxies exhibit a stronger
and steeper real-space correlation function and a higher pairwise velocity
dispersion than do the blue galaxies. The relative behavior of subsamples
defined by high/low profile concentration or high/low surface brightness is
qualitatively similar to that of the red/blue subsamples. Our most striking
result is a clear measurement of scale-independent luminosity bias at r < 10
Mpc/h: subsamples with absolute magnitude ranges centered on M_*-1.5, M_*, and
M_*+1.5 have real-space correlation functions that are parallel power laws of
slope ~ -1.8 with correlation lengths of approximately 7.4 Mpc/h, 6.3 Mpc/h,
and 4.7 Mpc/h, respectively.


title: Keck Measurement of the XTE J2123-058 Radial Velocity Curve

abstract:
  We measured the radial velocity curve of the companion of the neutron star
X-ray transient XTE J2123-058. Its semi-amplitude (K_2) of 298.5 +/- 6.9 km/s
is the highest value that has been measured for any neutron star LMXB. The high
value for K_2 is, in part, due to the high binary inclination of the system but
may also indicate a high neutron star mass. The mass function (f_2) of 0.684
+/- 0.047 solar masses, along with our constraints on the companion's spectral
type (K5V-K9V) and previous constraints on the inclination, gives a likely
range of neutron star masses from 1.2 to 1.8 solar masses. We also derive a
source distance of 8.5 +/- 2.5 kpc, indicating that XTE J2123-058 is unusually
far, 5.0 +/- 1.5 kpc, from the Galactic plane. Our measurement of the systemic
radial velocity is -94.5 +/- 5.5 km/s, which is significantly different from
what would be observed if this object corotates with the disk of the Galaxy.


title:
Collisional Plasma Models with APEC/APED: Emission Line Diagnostics of
  Hydrogen-like and Helium-like Ions

abstract:
  New X-ray observatories (Chandra and XMM-Newton) are providing a wealth of
high-resolution X-ray spectra in which hydrogen- and helium-like ions are
usually strong features. We present results from a new collisional-radiative
plasma code, the Astrophysical Plasma Emission Code (APEC), which uses atomic
data in the companion Astrophysical Plasma Emission Database (APED) to
calculate spectral models for hot plasmas. APED contains the requisite atomic
data such as collisional and radiative rates, recombination cross sections,
dielectronic recombination rates, and satellite line wavelengths. We compare
the APEC results to other plasma codes for hydrogen- and helium-like
diagnostics, and test the sensitivity of our results to the number of levels
included in the models. We find that dielectronic recombination with
hydrogen-like ions into high (n=6-10) principal quantum numbers affects some
helium-like line ratios from low-lying (n=2) transitions.


title: Keck adaptive optics observations of TW Hydrae Association members

abstract:
  Adaptive optics (AO) on 8-10 m telescopes is an enormously powerful tool for
studying young nearby stars. It is especially useful for searching for
companions. Using AO on the 10-m W.M. Keck II telescope we have measured the
position of the brown dwarf companion to TWA5 and resolved the primary into an
0.055 arcsecond double. Over the next several years follow-up astrometry should
permit an accurate determination of the masses of these young stars. We have
also re-observed the candidate extrasolar planet TWA6B, but measurements of its
motion relative to TWA6A are inconclusive. We are carrying out a search for new
planetary or brown dwarf companions to TWA stars and, if current giant planet
models are correct, are currently capable of detecting a 1 Jupiter-mass
companion at ~1 arcsecond and a 5 Jupiter-mass companion at ~0.5 arcsecon
around a typical TWA member.


title: On the direct detection of extragalactic WIMPs

abstract:
  We consider the direct detection of WIMPs reaching the Earth from outside the
Milky Way. If these WIMPs form a distinct population they will, although of
much lower flux than typical galactic halo WIMPs, have a number of features
which might aid in their ultimate detectability: a high and essentially unique
velocity ($\sim 600$ km/s in the galactic rest frame) due to their acceleration
in entering the Milky Way, and most likely one or two unique flight directions
at the Earth. This high velocity may be experimentally advantageous in direct
detection experiments, since it gives a recoil signal at relatively high energy
where background is generally much reduced. For a density of extragalactic
WIMPs comparable to the critical density of the universe the count rate
expected is very roughly the same as that of fast galactic WIMPs. If there is
an increased density relative to critical associated with the Local Group of
galaxies, say 10-30 times the critical density, there is a corresponding
increase in rate and the extragalactic WIMPs would show up as a high energy
shoulder in the recoil energy distribution. Evidence of such WIMPs as a
separate population with these distinct properties would offer interesting
information on the formation and prehistory of the galaxy.


title: Massive Datasets in Astronomy

abstract:
  Astronomy has a long history of acquiring, systematizing, and interpreting
large quantities of data. Starting from the earliest sky atlases through the
first major photographic sky surveys of the 20th century, this tradition is
continuing today, and at an ever increasing rate.
  Like many other fields, astronomy has become a very data-rich science, driven
by the advances in telescope, detector, and computer technology. Numerous large
digital sky surveys and archives already exist, with information content
measured in multiple Terabytes, and even larger, multi-Petabyte data sets are
on the horizon. Systematic observations of the sky, over a range of
wavelengths, are becoming the primary source of astronomical data. Numerical
simulations are also producing comparable volumes of information. Data mining
promises to both make the scientific utilization of these data sets more
effective and more complete, and to open completely new avenues of astronomical
research.
  Technological problems range from the issues of database design and
federation, to data mining and advanced visualization, leading to a new toolkit
for astronomical research. This is similar to challenges encountered in other
data-intensive fields today.
  These advances are now being organized through a concept of the Virtual
Observatories, federations of data archives and services representing a new
information infrastructure for astronomy of the 21st century. In this article,
we provide an overview of some of the major datasets in astronomy, discuss
different techniques used for archiving data, and conclude with a discussion of
the future of massive datasets in astronomy.


title: Merging Binary Clusters

abstract:
  We study three prominent bi-modal X-ray clusters: A3528, A1750 and A3395.
Using observations taken with ROSAT and ASCA, we analyze the temperature and
surface brightness distributions. We also analyze the velocity distributions of
the three clusters using new measurements supplemented with previously
published data. We examine both the overall cluster properties, as well as the
two sub-cluster elements in each. These results are then applied to the
determination of the overall cluster masses, and demonstrate excellent
consistency between the various methods used. While the characteristic
parameters of the sub-clusters are typical of isolated objects, our temperature
results for the regions between the two sub-clusters clearly confirm the
presence of merger activity. These three clusters represent a progression of
equal-sized sub-cluster mergers, starting from initial contact to immediately
before first core passage.


title: Dust penetrated morphology in the high redshift Universe

abstract:
  Images from the Hubble Deep Field (HDF) North and South show a large
percentage of dusty, high redshift galaxies whose appearance falls outside
traditional classification systems. The nature of these objects is not yet
fully understood. Since the HDF preferentially samples restframe UV light, HDF
morphologies are not dust or `mask' penetrated. The appearance of high redshift
galaxies at near-infrared restframes remains a challenge for the New
Millennium. The Next Generation Space Telescope (NGST) could routinely provide
us with such images. In this contribution, we quantitatively determine the
dust-penetrated structures of high redshift galaxies such as NGC 922 in their
near-infrared restframes. We show that such optically peculiar objects may
readily be classified using the dust penetrated z ~ 0 templates of Block and
Puerari (1999) and Buta and Block (2001).


title: Super Star Clusters in M82

abstract:
  M82 is the nearest starburst galaxy. It contains two large systems of super
star clusters, one being spawned today in the active starforming core, and one
produced by an earlier starburst event which coincided with the last orbital
passage of its neighbor, M81. The proximity of M82 makes it uniquely valuable
for a wide range of studies of massive young clusters and their environments.


title:
Far Infrared Spectroscopy of Normal Galaxies: Physical Conditions in the
  Interstellar Medium

abstract:
  The most important cooling lines of the neutral interstellar medium (ISM) lie
in the far-infrared (FIR). We present measurements by the Infrared Space
Observatory Long Wavelength Spectrometer of seven lines from neutral and
ionized ISM of 60 normal, star-forming galaxies. The galaxy sample spans a
range in properties such as morphology, FIR colors (indicating dust
temperature), and FIR/Blue ratios (indicating star-formation activity and
optical depth). In two-thirds of the galaxies in this sample, the [CII] line is
proportional to FIR dust continuum. The other one-third show a smooth decline
in [CII]/FIR with increasing F60/F100 and FIR/B, spanning a range of a factor
of more than 50. Two galaxies, at the warm and active extreme of the range have
[CII]/FIR < 2 \times 10^{-4} (3-sigma upper limit). This is due to increased
positive grain charge in the warmer and more active galaxies, which leads to
less efficient heating by photoelectrons from dust grains. The ratio of the two
principal photodissociation region (PDR) cooling lines [CII]/[OI] shows a tight
correlation with F60/F100, indicating that both gas and dust temperatures
increase together. We derive a theoretical scaling between [NII] and [CII] from
ionized gas and use it to separate [CII] emission from neutral PDRs and ionized
gas. Comparison of PDR models of Kaufman et al. (1999) with observed ratios of
(a) [OI]/[CII] and ([CII]+[OI])/FIR and (b) [OI]/FIR and F60/F100 yields far-UV
flux G0 and gas density n. The derived G0 scales as n to the power 1.4. We
interpret this correlation as arising from Stromgren sphere scalings if much of
the line and continuum luminosity arises near star-forming regions. The
differences in G0 and n may be due to differences in the physical properties of
the star-forming clouds.(Short abstract)


title: Chandra observations of the pulsar wind nebula in SNR G0.9+0.1

abstract:
  We present observations with the Chandra X-ray Observatory of the pulsar wind
nebula (PWN) within the supernova remnant G0.9+0.1. At Chandra's high
resolution, the PWN has a clear axial symmetry; a faint X-ray point source
lying along the symmetry axis possibly corresponds to the pulsar itself. We
argue that the nebular morphology can be explained in terms of a torus of
emission in the pulsar's equatorial plane and a jet directed along the pulsar
spin axis, as is seen in the X-ray nebulae powered by other young pulsars. A
bright clump of emission within the PWN breaks the axisymmetry and may
correspond to an intermediate-latitude feature in the pulsar wind.


title: SED, Age and Metallicity of Star Clusters in M33

abstract:
  In this paper we present CCD spectrophotometry of the star clusters that were
detected by Chandar, Bianchi, & Ford in the nearby spiral galaxy M33, using the
images obtained with the Beijing Astronomical Observatory 60/90 cm Schmidt
Telescope in 13 intermediate-band filters from 3800 to 10000{\AA}. The
observations cover the whole area of M33 with a total integration of 32.75
hours from September 23, 1995 to August 28, 2000. This provides a multi-color
map of M33 in pixels of $1.7'' \times 1.7''$. By aperture photometry, we obtain
the spetral energy distributions (SEDs) of these star clusters. Using
theoretical stellar population synthesis models, we also obtain the
distributions of age and metallicity of of these star clusters. These clusters
formed continuously from $\sim 3\times10^6$ -- $10^{10}$ years, and have a
large span of metallicity from ${\rm {Z}=0.0004}$ to ${\rm {Z}=0.05}$.


title: Globular Cluster Systems in the Hydra I Galaxy Cluster

abstract:
  In this contribution, first results of deep VLT photometry (V,I) in the
central region of the Hydra I galaxy cluster are presented. Many star clusters
have been identified not only around several early-type galaxies, but also in
the intra-cluster field, as far as 250 kpc from the cluster center. Outside the
bulges of the central galaxies NGC 3311 and NGC 3309, the intra-cluster
globular cluster system is dominated by blue clusters whose spatial
distribution is similar to that of the (newly discovered) dwarf galaxies in
Hydra I. The color distributions of globular clusters around NGC 3311 and NGC
3309 are multimodal, with a sharp blue peak and a slightly broader distribution
of the red cluster population.


title: Apparent magnitudes in an inhomogeneous universe: the global viewpoint

abstract:
  Apparent magnitudes are important for high precision cosmology. It is
generally accepted that weak gravitational lensing does not affect the
relationship between apparent magnitude and redshift. By considering metric
perturbations it is shown that objects observed in an inhomogeneous universe
have, on average, higher apparent magnitudes than those observed at the same
redshift in a homogeneous universe.


title:
HST images of B2 radio galaxies: the link between circum-nuclear dust
  and radio properties

abstract:
  We discuss HST images in V and I of radio galaxies selected from the B2
sample of low luminosity radio galaxies. Absorption maps were constructed which
highlight the presence of circumnuclear dust on scales of typically few kpc or
less.


title: The Size and Shape of Local Voids

abstract:
  We study the size and shape of low density regions in the local universe
which we identify in the smoothed density field of the PSCz flux limited IRAS
galaxy catalogue. After quantifying the systematic biases that enter in the
detection of voids using our data set and method, we identify, using a
smoothing length of 5 $h^{-1}$ Mpc, 14 voids within 80 $h^{-1}$ Mpc and using a
smoothing length of 10 $h^{-1}$ Mpc, 8 voids within 130 $h^{-1}$ Mpc. We study
the void size distribution and morphologies and find that there is roughly an
equal number of prolate and oblate-like spheroidal voids. We compare the
measured PSCz void shape and size distributions with those expected in six
different CDM models and find that only the size distribution can discriminate
between models. The models preferred by the PSCz data are those with
intermediate values of $\sigma_{8} (\simeq 0.83)$, independent of cosmology.


title:
Spectroscopic Observations of the Delta Scorpii Binary during Its Recent
  Periastron Passage

abstract:
  The bright star delta Sco has been considered a typical B0-type object for
many years. Spectra of the star published prior to 1990 showed no evidence of
emission, but only of short-term line profile variations attributed to
nonradial pulsations. Speckle interferometric observations show that delta Sco
is a binary system with a highly-eccentric orbit and a period of 10.6 years.
Weak emission in the H-alpha line was detected in its spectrum for the first
time during a periastron passage in 1990. Shortly before the next periastron
passage in the summer of 2000, the binary entered a strong H-alpha emission and
enhanced mass loss phase. We monitored the spectroscopic development of the Be
outburst from July 2000 through March 2001. In this paper we present results
from our spectroscopy, refine elements of the binary orbit, and discuss
possible mechanisms for the mass loss.


title:
The formation and evolution of binary systems. III. Low-mass binaries in
  the Praesepe cluster

abstract:
  With the aim of investigating the binary population of the 700 Myr old
Praesepe cluster, we have observed 149 G and K-type cluster members using
adaptive optics. We detected 26 binary systems with an angular separation
ranging from less than 0.08 to 3.3 arcsec (15-600 AU). After correcting for
detection biases, we derive a binary frequency (BF) in the logP (days) range
from 4.4 to 6.9 of 25.3 +/- 5.4%, which is similar to that of field G-type
dwarfs (23.8%, Duquennoy & Mayor 1991). This result, complemented by similar
ones obtained for the 2 Myr old star forming cluster IC 348 (Paper II) and the
120 Myr old Pleiades open cluster (Paper I), indicates that the fraction of
long-period binaries does not significantly evolve over the lifetime of
galactic open clusters. We compare the distribution of cluster binaries to the
binary populations of star forming regions, most notably Orion and Taurus, to
critically review current ideas regarding the binary formation process. We
conclude that it is still unclear whether the lower binary fraction observed in
young clusters compared to T associations is purely the result of the early
dynamical disruption of primordial binaries in dense clusters or whether it
reflects intrinsically different modes of star formation in clusters and
associations. We also note that if Taurus binaries result from the dynamical
decay of small-N protostellar aggregates, one would predict the existence of a
yet to be found dispersed population of mostly single substellar objects in the
Taurus cloud.


title:
Test of Hadronic Interaction Models in the Forward Region with KASCADE
  Event Rates

abstract:
  An analysis of muon and hadron rates observed in the central detector of the
KASCADE experiment has been carried out. The data are compared to CORSIKA
simulations employing the high-energy hadronic interaction models QGSJET,
DPMJET, HDPM, SIBYLL, and VENUS. In addition, first results with the new
hadronic interaction model neXus 2 are discussed. Differences of the model
predictions, both among each other and when confronted with measurements, are
observed. The hadron rates mainly depend on the inelastic cross-section and on
the contribution of diffraction dissociation. The discrepancy between
simulations and measurements at low primary energies around 5 TeV can be
reduced by increasing the non-diffractive part of the inelastic cross-section
of nucleon-air interactions. Examination of hadron multiplicities points
towards harder spectra of secondary pions and kaons needed in the calculations.


title: Mass Follows Light

abstract:
  We use comparisons between the shapes of gravitational lens galaxies and
models for their mass distributions to derive statistical constraints on the
alignment of the mass distribution relative to the observed lens galaxy and on
the strength of tidal shear perturbations. The mass distributions are aligned
with the luminous galaxies, with a 10 degree upper limit on the rms dispersion
in the angle between the major axes. Statistical constraints, such as our bound
on the misalignment between mass and light, are an important new approach to
reducing the uncertainties in individual lens models, particularly for lenses
used to estimate the Hubble constant.


title: 2 um Narrow-band Adaptive Optics Imaging in the Arches Cluster

abstract:
  Canada-France-Hawaii-Telescope adaptive optics bonnette images through
narrow-band filters in the $K-$band are presented for the Arches cluster.
Continuum fluxes, line fluxes, and equivalent widths are derived from high
angular resolution images, some near diffraction limited, for the well known
massive stars in the Arches cluster. Images were obtained in the lines of
\ion{He}{1} 2.06 \mic, \ion{H}{1} Br$\gamma$ (2.17 \mic), and \ion{He}{2} 2.19
\mic as well as continuum positions at 2.03 \mic, 2.14 \mic, and 2.26 \mic. In
addition, fluxes are presented for \ion{H}{1} P$\alpha$ (1.87 \mic) and a
nearby continuum position (1.90 \mic) from Hubble Space Telescope archival
data. The 2 \mic and P$\alpha$ data reveal two new emission-line stars and
three fainter candidate emission-line objects. Indications for a spectral
change of one object between earlier observations in 1992/1993 and our data
from 1999 are found. The ratio of \ion{He}{2} 2.19 \mic to Br$\gamma$ emission
exhibits a narrow distribution among the stars, suggesting a narrow
evolutionary spread centered predominantly on spectral types O4 If or
Wolf-Rayet stars of the WN7 sub-type. From the approximate spectral types of
the identified emission-line stars and comparisons with evolutionary models we
infer a cluster age between $\sim$ 2 and 4.5 Myr.


title: Deuterium at high redshift: primordial or evolved ?

abstract:
  On the basis of arguments from galactic chemical evolution we suggest that
the recent observations of D/H vs. metallicity in several high redshift
absorbers are best understood if the primordial D value is in the range 2-3
10$^{-5}$. This range points to a rather high baryonic density
($\Omega_Bh^2$=0.019-0.026) compatible to the one obtained by recent estimates
based on the Cosmic Microwave Background (CMB) anisotropy measurements.
Slightly higher values (D/H=4 10$^{-5}$) are found in Lyman limit systems. Such
values are still compatible with CMB estimates but, if taken at face value,
they suggest a trend of decreasing D abundance with metallicity. We argue that
special assumptions, like differential enrichment, are required to explain the
data in that case. A clear test of such a differential enrichment would be an
excess of products of low mass stars like C and/or N in those systems, but
currently available data of N/Si in DLAs do not favour such a ``non-standard''
senario.


title: The 2dF Galaxy Redshift Survey: Spectra and redshifts

abstract:
  The 2dF Galaxy Redshift Survey (2dFGRS) is designed to measure redshifts for
approximately 250000 galaxies. This paper describes the survey design, the
spectroscopic observations, the redshift measurements and the survey database.
The 2dFGRS uses the 2dF multi-fibre spectrograph on the Anglo-Australian
Telescope, which is capable of observing 400 objects simultaneously over a
2-degree diameter field. The source catalogue for the survey is a revised and
extended version of the APM galaxy catalogue, and the targets are galaxies with
extinction-corrected magnitudes brighter than b_J=19.45. The main survey
regions are two declination strips, one in the southern Galactic hemisphere
spanning 80deg x 15deg around the SGP, and the other in the northern Galactic
hemisphere spanning 75deg x 10deg along the celestial equator; in addition,
there are 99 fields spread over the southern Galactic cap. The survey covers
2000 sq.deg and has a median depth of z=0.11. Adaptive tiling is used to give a
highly uniform sampling rate of 93% over the whole survey region. Redshifts are
measured from spectra covering 3600A-8000A at a two-pixel resolution of 9.0A
and a median S/N of 13 per pixel. All redshift identifications are visually
checked and assigned a quality parameter Q in the range 1-5; Q>=3 redshifts are
98.4% reliable and have an rms uncertainty of 85 km/s. The overall redshift
completeness for Q>=3 redshifts is 91.8%, but this varies with magnitude from
99% for the brightest galaxies to 90% for objects at the survey limit. The
2dFGRS database is available on the WWW at http://www.mso.anu.edu.au/2dFGRS


title:
Lithium as a passive tracer probing the rotating solar tachocline
  turbulence

abstract:
  The rotational influence on the eddy-diffusivity tensor D_ij for anisotropic
turbulence fields is considered in order to explain the lithium decay law
during the spin-down process of solar-type stars. Rotation proves to be highly
effective in the transfer of chemicals through the solar tachocline (beneath
the convection zone) which is assumed to contain only turbulence with
horizontal motions. The effect is so strong that the tachocline turbulence must
not exceed a limit of ~10^-(3...4) of the rms velocity in the convection zone
in order to let the lithium survive after Gigayears. Such long depletion times
can also be explained by a very small rotational influence upon the
eddy-diffusion tensor if it is realized with correlation times shorter than 15
min. It is argued that such slow and/or short-living turbulence beneath the
convection zone could hardly drive the solar dynamo. In our theory the
diffusion remains small for rapid rotation due to the rotational quenching of
the turbulence. In young stellar clusters like Pleiades, there should be a
(positive) correlation between rotation rate and lithium abundance, where the
fastest stars should have maximal lithium. First inspections of the data seem
to confirm this finding.


title: The Morphological Evolution of Merger Remnants

abstract:
  Elliptical galaxies formed in a major merger tend to become more nearly
spherical with time, thanks to the gravitational effect of their central black
hole (or black holes). Observational results indicate that elliptical galaxies
with older stellar populations (t > 7.5 Gyr) have rounder central isophotes
than ellipticals with younger stellar populations. In addition, older
ellipticals tend to have core profiles, while younger ellipticals tend to have
power-law profiles. Numerical simulations of galaxy mergers indicate that if
one or both of the progenitors have a central black hole with a mass around 0.2
percent of the mass in stars, then the effect of the black hole(s) is to make
the central regions of the remnant rounder, with a characteristic time of a few
gigayears.


title: The Mysterious Ultrahigh Energy Cosmic Ray Clustering

abstract:
  We examine the correlation between compact radio quasars (redshifts in the
range $z = 0.3 - 2.2$) and the arrival direction of ultrahigh energy cosmic
rays forming clusters. Our Monte Carlo simulation reveals a statistically
significant correlation on the AGASA sample: the chance probability of this
effect being less than 1%. The implications of this result on the origin of
ultrahigh energy cosmic rays are discussed.


title: New calculation of radioactive secondaries in cosmic rays

abstract:
  We use a new version of our numerical model for particle propagation in the
Galaxy to study radioactive secondaries. For evaluation of the production cross
sections we use the Los Alamos compilation of all available experimental cross
sections together with calculations using the improved Cascade-Exciton Model
code CEM2k. Using the radioactive secondary ratios 26Al/27Al, 36Cl/Cl, 54Mn/Mn,
we show how the improved cross-section calculations together with the new
propagation code allow us to better constrain the size of the CR halo.


title: Secondary Antiprotons in Cosmic Rays

abstract:
  High energy collisions of cosmic ray (CR) nuclei with interstellar gas are
believed to be the mechanism producing the majority of CR antiprotons. The
distinguishing spectral shape with a maximum at 2 GeV and a sharp decrease
towards lower energies makes antiprotons a unique probe of the models of
particle propagation in the Galaxy and modulation in the heliosphere. Besides,
accurate calculation of the secondary antiproton flux provides a ``background''
for searches for exotic signals from the annihilation of supersymmetric
particles and primordial black hole evaporation. Recently new data with large
statistics on the antiproton flux have become available which allow for such
tests to be performed. We use our 3D Galactic cosmic ray propagation code
GALPROP to calculate interstellar propagation in several models. For our best
model we make predictions of proton and antiproton fluxes near the Earth for
different modulation levels and polarity using a steady-state drift model for
heliospheric modulation.


title: New developments in the GALPROP CR propagation model

abstract:
  The GALPROP cosmic-ray (CR) propagation model has been extended to three
dimensions including the effects of stochastic SNR sources, a comprehensive
cross-section database, and nuclear reaction networks. A brief description of
the new code is given and some illustrative results for the distribution of CR
protons presented. Results for electrons and gamma rays are given in an
accompanying paper.


title: A 3D time-dependent model for Galactic cosmic rays and gamma rays

abstract:
  In studies of cosmic-ray (CR) propagation and diffuse continuum gamma-ray
emission from the Galaxy it has usually been assumed that the source function
can be taken as smooth and time-independent. However, especially for electrons
at high energies where energy losses are rapid, the effect of the stochastic
nature of the sources becomes apparent and indeed has been invoked to explain
the GeV excess in the diffuse emission observed by EGRET. In order to address
this problem in detail a model with explicit time-dependence and a stochastic
SNR population has been developed, which follows the propagation in three
dimensions. The results indicate that although the inhomogeneities are large
they are insufficient to easily explain the GeV excess. However the
fluctuations should show up in the gamma-ray distribution at high energies and
this should be observable with GLAST. Estimates of the TeV continuum emission
from the plane are consistent with the Whipple upper limit.


title:
Environment and Galaxy Evolution at Intermediate Redshift in the CNOC2
  Survey

abstract:
  (abridged) The systematic variation of galaxy colors and types with
clustering environment could either be the result of local conditions at
formation or subsequent environmental effects as larger scale structures draw
together galaxies whose stellar mass is largely in place. At z~0.4 the
co-moving galaxy correlation length, r_0, measured in the CNOC2 sample is
strongly color dependent, rising from 2/h Mpc to nearly 10/h Mpc as the
volume-limited subsamples range from blue to red. The luminosity dependence of
r_0 at z~0.4 is weak below L_ast although there is an upturn at high luminosity
where its interpretation depends on separating it from the r_0-color relation.
The dominant effect of the group environment on star formation is seen in the
radial gradient of the mean galaxy colors which on the average become redder
than the field toward the group centers. The redder-than-field trend applies to
groups with a line-of-sight velocity dispersion, sigma_1>150 kms. There is an
indication, somewhat statistically insecure, that the high luminosity galaxies
in groups with sigma_1<125 kms become bluer toward the group center. We
conclude that the higher velocity dispersion groups largely act to suppress
star formation relative to the less clustered field, leading to ``embalmed''
galaxies. The tidal fields within the groups appear to be a strong candidate
for the physical source of the reduction of star formation in group galaxies
relative to field. Tides operate effectively at all velocity dispersions to
remove gas rich companions and low density gas in galactic halos. Given that
much of the field population is in groups we suggest that this suppression may
be the dominant galaxy evolution force at low redshift.


title: Far-infrared dust opacity and visible extinction in the Polaris Flare

abstract:
  We present an extinction map of the Polaris molecular cirrus cloud derived
from star counts and compare it with the Schlegel et al. (1998) extinction map
derived from the far--infrared dust opacity. We find that, within the Polaris
cloud, the Schlegel et al. Av values are a factor 2 to 3 higher than the star
count values. We propose that this discrepancy results from a difference in
$\tau_{FIR}/ A_V$ between the diffuse atomic medium and the Polaris cloud. We
use the difference in spectral energy distribution, warm for the diffuse atomic
medium, cold for the Polaris cloud, to separate their respective contribution
to the line of sight integrated infrared emission and find that the
$\tau_{FIR}/ A_V$ of cold dust in Polaris is on average 4 times higher than the
Schlegel et al. value for dust in atomic cirrus. This change in dust property
could be interpreted by a growth of fluffy particles within low opacity
molecular cirrus clouds such as Polaris. Our work suggests that variations in
dust emissivity must be taken into account to estimate Av from dust emission
wherever cold infrared emission is present (i.e. molecular clouds).


title: Highlights of RXTE Studies of Compact Objects after ~5 Years

abstract:
  Observations with the Rossi X-ray Timing Explorer (RXTE) have led to
fundamental progress in the study of compact objects, in particular neutron
stars and black holes. In this paper we present briefly some highlights from ~5
years of RXTE operations.


title: The Distribution of Pressures in a Supernova-Driven Interstellar Medium

abstract:
  Observations have suggested substantial departures from pressure equilibrium
in the interstellar medium (ISM) in the plane of the Galaxy, even on scales
under 50 pc. Nevertheless, multi-phase models of the ISM assume at least
locally isobaric gas. The pressure then determines the density reached by gas
cooling to stable thermal equilibrium. We use two different sets of numerical
models of the ISM to examine the consequences of supernova driving for
interstellar pressures. The first set of models is hydrodynamical, and uses
adaptive mesh refinement to allow computation of a 1 x 1 x 20 kpc section of a
stratified galactic disk. The second set of models is magnetohydrodynamical,
using an independent code framework, and examines a 200 pc cubed periodic
domain threaded by magnetic fields. Both of these models show broad pressure
distributions with roughly log-normal functional forms produced by both shocks
and rarefaction waves, rather than the power-law distributions predicted by
previous work, with rather sharp thermal pressure gradients. The width of the
distribution of the logs of pressure in gas with log T < 3.9 is proportional to
the rms Mach number in that gas, while the distribution in hotter gas is
broader, but not so broad as would be predicted by the Mach numbers in that
gas. Individual parcels of gas reach widely varying points on the thermal
equilibrium curve: no unique set of phases is found, but rather a
dynamically-determined continuum of densities and temperatures. Furthermore, a
substantial fraction of the gas remains entirely out of thermal equilibrium.
Our results appear consistent with observations of interstellar pressures, and
suggest that the pressures observed in molecular clouds may be due to ram
pressure rather than gravitational confinement.


title:
An Empirical Ultraviolet Iron Spectrum Template Applicable to Active
  Galaxies

abstract:
  Iron emission is often a severe contaminant in optical-ultraviolet spectra of
active galaxies. Its presence complicates emission line studies. A viable
solution, already successfully applied at optical wavelengths, is to use an
empirical iron emission template. We have generated FeII and FeIII templates
for ultraviolet active galaxy spectra based on HST archival 1100 - 3100 A
spectra of IZw1. Their application allows fitting and subtraction of the iron
emission in active galaxy spectra. This work has shown that in particular CIII]
lambda 1909 can be heavily contaminated by other line emission, including iron
transitions. Details of the data processing, generation, and use of the
templates, are given by Vestergaard & Wilkes (2001).


title: A photometricity and extinction monitor at the Apache Point Observatory

abstract:
  An unsupervised software ``robot'' that automatically and robustly reduces
and analyzes CCD observations of photometric standard stars is described. The
robot measures extinction coefficients and other photometric parameters in real
time and, more carefully, on the next day. It also reduces and analyzes data
from an all-sky $10 \mu m$ camera to detect clouds; photometric data taken
during cloudy periods are automatically rejected. The robot reports its
findings back to observers and data analysts via the World-Wide Web. It can be
used to assess photometricity, and to build data on site conditions. The
robot's automated and uniform site monitoring represents a minimum standard for
any observing site with queue scheduling, a public data archive, or likely
participation in any future National Virtual Observatory.