title: Energy Extraction From Gravitational Collapse to Static Black Holes

abstract:
  The mass--energy formula of black holes implies that up to 50% of the energy
can be extracted from a static black hole. Such a result is reexamined using
the recently established analytic formulas for the collapse of a shell and
expression for the irreducible mass of a static black hole. It is shown that
the efficiency of energy extraction process during the formation of the black
hole is linked in an essential way to the gravitational binding energy, the
formation of the horizon and the reduction of the kinetic energy of implosion.
Here a maximum efficiency of 50% in the extraction of the mass energy is shown
to be generally attainable in the collapse of a spherically symmetric shell:
surprisingly this result holds as well in the two limiting cases of the
Schwarzschild and extreme Reissner-Nordstr\"{o}m space-times. Moreover, the
analytic expression recently found for the implosion of a spherical shell onto
an already formed black hole leads to a new exact analytic expression for the
energy extraction which results in an efficiency strictly less than 100% for
any physical implementable process. There appears to be no incompatibility
between General Relativity and Thermodynamics at this classical level.


title: 2D Transonic Hydrodynamics in General Relativity

abstract:
  The goal of my lecture is to present the introduction into the hydrodynamical
version of the Grad-Shafranov equation. Although not so well-known as the full
MHD one, it allows us to clarify the nontrivial structure of the Grad-Shafranov
approach as well as to discuss the simplest version of the 3+1-split language
-- the most convenient one for the description of the ideal flows in the
vicinity of a rotating black hole.


title:
Shear and magnification angular power spectra and higher-order moments
  from weak gravitational lensing

abstract:
  We present new results on the gravitational lensing shear and magnification
power spectra obtained from numerical simulations of a flat cosmology with a
cosmological constant. These results are of considerable interest since both
the shear and the magnification are observables. We find that the power
spectrum in the convergence behaves as expected, but the magnification develops
a shot-noise spectrum due to the effects of discrete, massive clusters and
symptomatic of moderate lensing beyond the weak-lensing regime. We find that
this behaviour can be suppressed by "clipping" of the largest projected
clusters. Our results are compared with predictions from a Halo Model-inspired
functional fit for the non-linear evolution of the matter field and show
excellent agreement. We also study the higher-order moments of the convergence
field and find a new scaling relationship with redshift. In particular, the
statistic $S_3$ is found to vary as $z_s^{-2.00\pm 0.08}$ (where $z_s$ is the
source redshift) for the cosmology studied, which makes corrections for
different median redshifts in different observational surveys particularly
simple to apply.


title:
An Intrinsic Baldwin Effect in the H-beta Broad Emission Line in the
  Spectrum of NGC 5548

abstract:
  We investigate the possibility of an intrinsic Baldwin Effect (i.e.,nonlinear
emission-line response to continuum variations) in the broad H-beta emission
line of the active galaxy NGC 5548 using cross-correlation techniques to remove
light travel-time effects from the data. We find a nonlinear relationship
between the H-beta emission line and continuum fluxes that is in good agreement
with theoretical predictions. We suggest that similar analysis of multiple
lines might provide a useful diagnostic of physical conditions in the
broad-line region.


title:
The Formation of a Star Cluster: Predicting the Properties of Stars and
  Brown Dwarfs

abstract:
  We present results from the largest numerical simulation of star formation to
resolve the fragmentation process down to the opacity limit. The simulation
follows the collapse and fragmentation of a large-scale turbulent molecular
cloud to form a stellar cluster and, simultaneously, the formation of
circumstellar discs and binary stars. This large range of scales enables us to
predict a wide variety of stellar properties for comparison with observations.
The calculation clearly demonstrates that star formation is a highly-dynamic
and chaotic process. Star-disc encounters form binaries and truncate discs.
Stellar encounters disrupt bound multiple systems. The cloud produces roughly
equal numbers of stars and brown dwarfs, with masses down to the opacity limit
for fragmentation (~5 Jupiter masses). The initial mass function is consistent
with a Salpeter slope (Gamma=-1.35) above 0.5 Msun, a roughly flat distribution
(Gamma=0) in the range 0.006-0.5 Msun, and a sharp cutoff below ~0.005 Msun.
This is consistent with recent observational surveys. The brown dwarfs form by
the dynamical ejection of low-mass fragments from dynamically unstable multiple
systems before the fragments have been able to accrete to stellar masses. Close
binary systems (with separations <10 AU) are not formed by fragmentation in
situ. Rather, they are produced by hardening of initially wider multiple
systems through a combination of dynamical encounters, gas accretion, and/or
the interaction with circumbinary and circumtriple discs. Finally, we find that
the majority of circumstellar discs have radii less than 20 AU due to
truncation in dynamical encounters. This is consistent with observations of the
Orion Trapezium Cluster and implies that most stars and brown dwarfs do not
form large planetary systems.


title: X-ray Emission Diagnostics from the M87 Jet

abstract:
  We use Chandra, HST and VLA observations of M87 to investigate the physics of
X-ray emission from AGN jets. We find that X-ray hotspots in the M87 jet occur
primarily in regions with hard optical-to-X-ray spectra and lower than average
polarization. Particle injection appears to be required both continuously in
the jet sheath as well as locally at X-ray hotspots.


title:
A Radiative Cycle with Stimulated Emission from Atoms (Ions) in an
  astrophysical Plasma

abstract:
  We propose that a radiative cycle operates in atoms (ions) located in a
rarefied gas in the vicinity of a hot star. Besides spontaneous transitions the
cycle includes a stimulated transition in one very weak intermediate channel.
This radiative "bottle neck" creates a population inversion, which for an
appropriate column density results in amplification and stimulated radiation in
the weak transition. The stimulated emission opens a fast decay channel leading
to a fast radiative cycle in the atom (or ion). We apply this model by
explaining two unusually bright Fe II lines at 250.7 and 250.9 nm in the UV
spectrum of gas blobs close to h Carinae, one of the most massive and luminous
stars in the Galaxy. The gas blobs are spatially resolved from the central star
by the Hubble Space Telescope (HST). We also suggest that in the frame of a
radiative cycle stimulated emission is a key phenomenon behind many spectral
lines showing anomalous intensities in spectra of gas blobs outside eruptive
stars.


title:
Sequential star formation at the periphery of the HII regions Sh 217 and
  Sh 219

abstract:
  The HII regions Sh 217 and Sh 219 are textbook examples of a Stromgren sphere
surrounded by an annular photodissociation region (PDR). The annular PDR is
observed in both the 21 cm atomic hydrogen emission and the dust (PAH) emission
near 8 micron (MSX Survey). An ultracompact radio continuum source is observed
in the direction of the annular PDR, in both Sh 217 and Sh 219. JHKobservations
show the presence of highly reddened stellar clusters (AV ~ 20 mag) in the
directions of these radio sources. These clusters are also IRAS sources, of
luminosities 22700 Lo for Sh 217 and 5900 Lo for Sh 219. Each cluster contains
at least one luminous star with an IR colour excess; the one in the Sh 219
cluster shows H-alpha emission. The cluster associated with Sh 217 is almost
spherical and contains luminous objects at its centre. The cluster associated
with Sh 219 is elongated along the ionization front of this HII region. We
argue that these are `second-generation clusters', which means that the
physical conditions present in the PDRs, close to the ionization fronts, have
favoured the formation of clusters containing massive objects. We discuss the
physical mechanisms which may be at the origin of the observed triggered star
formation.


title: The X-ray/gamma-ray spectrum of XTE J1550--564 in the very high state

abstract:
  We fit the broad-band X/gamma-ray spectrum (0.8-1000 keV) of the accreting
black hole XTE J1550-564 in the very high state. The quasi-simultaneous data
from ASCA, RXTE and OSSE show that the disc is strongly Comptonized, with a
high energy tail extending out to several hundreds keV. However, inverse
Compton scattering by a purely thermal or purely power-law electron
distribution cannot explain the observed spectrum. Instead the data require a
hybrid distribution, with both thermal and non-thermal electrons scattering the
disc photons. This is very similar to the electron distribution inferred for
other high and very high state black hole binaries, showing that it is a
generic feature of high mass accretion rate black holes.


title: Star Formation: 3D Collapse of Turbulent Cloud Cores

abstract:
  We have performed fully 3D simulations of the collapse of molecular cloud
cores which obey the logatropic equation of state. By following the collapse of
these cores from states of near hydrodynamic equilibrium, we are able to
produce accretion histories which closely resemble those of observed cores. The
accretion proceeds in four distinct stages: an initial period of very slow
accretion; a period of vigorous accretion following the development of a
central density singularity, with a mass accretion rate proportional to t^3, as
predicted by self-similar models; a period of relatively stable, vigorous
accretion; and finally a gradual decrease in the accretion rate once about 50%
of the available mass of the molecular cloud core has been accreted. These
results may explain the accretion histories of cores as they pass through the
pre-protostellar, Class 0, and Class I stages.


title:
The Parkes quarter-Jansky flat-spectrum sample 2. New Optical Spectra
  and Redshift Measurements

abstract:
  We present optical spectra and redshift measurements for 178 flat-spectrum
objects from the Parkes quarter-Jansky flat-spectrum sample. These spectra were
obtained in order to compile a complete sample of quasars for use in a study of
quasar evolution. We present a composite optical spectrum made from the subset
of 109 quasars that have flux densities in the range 0.25Jy < S(2.7GHz)< 0.5Jy,
and make a comparison with a composite for radio-quiet QSOs from the Large
Bright Quasar Survey. Our large sample of radio-loud quasars allows us to
strengthen previous reports that the Ly-alpha and CIV emission lines have
larger equivalent width in radio-loud quasars than radio-quiet QSOs to greater
than the 3-sigma level. However we see no significant difference in the
equivalent widths of CIII] or MgII. We also show that the flux decrements
across the Lyman-alpha line (D_A) measured from these spectra show the same
trend with redshift as for optically selected QSOs.


title: Does circular polarisation reveal the rotation of quasar engines?

abstract:
  Many radio sources like quasars, blazars, radio galaxies, and micro-quasars
exhibit circular polarisation (CP) with surprising temporal persistent
handedness. As a possible explanation we propose that the CP is due to Faraday
conversion (FC) of linear polarisation (LP) synchrotron light which propagates
along a line-of-sight (LOS) through twisted magnetic fields. The rotational
nature of accretion flows onto black holes naturally generates the required
magnetic twist in the emission region, independent of whether it is a jet or an
ADAF. The expected twist in both types of flows is of the order of what is
required for optimal CP generation. This scenario requires that Faraday
rotation (FR) is insignificant in the emission region. Although this is an
assumption, it relaxes constraints on the plasma parameters, that were given in
scenarios which rely on FR, since there the strength of FR can not be too far
from the optimum. The proposed mechanism works in electron-positron (e+-) as
well as electron-proton (e/p) plasma. In the latter case, the emission region
should consist of individual flux tubes with independent polarities in order to
suppress too strong FR. The predominant CP is expected to mostly counter-rotate
(rotation is measured here in sky-projection) with respect to the central
engine in all cases (jet or ADAF, e+- or e/p plasma). If the proposed mechanism
is indeed operating, it will allow to measure the sense of rotation of quasar
engines. The engine of SgrA* is then expected to rotate clockwise and therefore
counter-Galactic, as do the young hot stars in its vicinity, which are thought
to feed SgrA* by their winds. Similarly, we expect the microquasars SS 443 and
GRS 1915+105 to rotate clockwise. Generally, sources with Stokes-V<0 (V>0) are
expected to rotate clockwise (counter-clockwise) in this scenario.


title: Positron Fraction in the CMSSM

abstract:
  A fit to the present data on the cosmic ray positron fraction can be
considerably improved,if in addition to the positron production by nuclear
interactions in the universe the possible contribution from supersymmetric dark
matter annihilation is taken into account. We scan over the complete SUSY
parameter space of the Constrained Minimal Supersymmetric Model (CMSSM) and
find that in the acceptable regions the neutralino annihilation into b-bbar
quark pairs is the dominant channel with hard positrons emerging from the
semileptonic decays of the B-mesons.


title:
X-ray Spectroscopy and Variability of AGN Detected in the 2 Ms Chandra
  Deep Field-North Survey

abstract:
  We investigate the nature of the faint X-ray source population through X-ray
spectroscopy and variability analyses of 136 AGN detected in the 2 Ms Chandra
Deep Field-North survey with > 200 background-subtracted 0.5-8.0 keV counts
[F(0.5-8.0 keV)=(1.4-200)e-15 erg cm^{-2} s^{-1}]. Our preliminary spectral
analyses yield median spectral parameters of Gamma=1.61 and intrinsic
N_H=6.2e21 cm^{-2} (z=1 assumed when no redshift available) when the AGN
spectra are fitted with a simple absorbed power-law model. However,
considerable spectral complexity is apparent (e.g., reflection, partial
covering) and must be taken into account to model the data accurately.
Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has
a pronounced effect on the derived N_H distribution and, to a lesser extent,
the X-ray luminosity distribution. Ten of the 136 AGN (~7%) show significant Fe
Kalpha emission-line features with equivalent widths in the range 0.1-1.3 keV.
Two of these emission-line AGN could potentially be Compton thick (i.e., Gamma
< 1.0 and large Fe Kalpha equivalent width). Finally, we find that 81 (~60%) of
the 136 AGN show signs of variability, and that this fraction increases
significantly (~80-90%) when better photon statistics are available.


title: The Dark Matter Distribution in Galaxy Cluster Cores

abstract:
  Determining the structure of galaxy clusters is essential for an
understanding of large scale structure in the universe, and may hold important
clues to the identity and nature of dark matter particles. Moreover, the core
dark matter distribution may offer insight into the structure formation
process. Unfortunately, cluster cores also tend to be the site of complicated
astrophysics. X-ray imaging spectroscopy of relaxed clusters, a standard
technique for mapping their dark matter distributions, is often complicated by
the presence of their putative ``cooling flow'' gas, and the dark matter
profile one derives for a cluster is sensitive to assumptions made about the
distribution of this gas. Here we present a statistical analysis of these
assumptions and their effect on our understanding of dark matter in galaxy
clusters.


title:
Circumnuclear Dust in Nearby Active and Inactive Galaxies. II. Bars,
  Nuclear Spirals, and the Fueling of Active Galactic Nuclei

abstract:
  (Abridged) We present a detailed study of the relation between circumnuclear
dust morphology, host galaxy properties, and nuclear activity in nearby
galaxies. We use our sample of 123 nearby galaxies with visible--near-infrared
colormaps from the Hubble Space Telescope to create well-matched, "paired"
samples of 28 active and 28 inactive galaxies, as well as 19 barred and 19
unbarred galaxies, that have the same host galaxy properties. Comparison of the
barred and unbarred galaxies shows that grand design nuclear dust spirals are
only found in galaxies with a large-scale bar. Tightly wound nuclear dust
spirals, in contrast, show a strong tendency to avoid galaxies with large-scale
bars. Comparison of the AGN and inactive samples shows that nuclear dust
spirals, which may trace shocks and angular momentum dissipation in the ISM,
occur with comparable frequency in both active and inactive galaxies. The only
difference between the active and inactive galaxies is that several inactive
galaxies appear to completely lack dust structure in their circumnuclear
region, while none of the AGN lack this structure. The comparable frequency of
nuclear spirals in active and inactive galaxies, combined with previous work
that finds no significant differences in the frequency of bars or interactions
between well-matched active and inactive galaxies, suggests that no universal
fueling mechanism for low-luminosity AGN operates at spatial scales greater
than ~100 pc radius from the galactic nuclei. The similarities instead suggest
that the lifetime of nuclear activity is less than the characteristic inflow
time from these spatial scales. An order-of-magnitude estimate of this inflow
time is the dynamical timescale. This sets an upper limit of several million
years to the lifetime of an individual episode of nuclear activity.


title:
Extraction of cluster parameters with future Sunyaev-Zel'dovich
  observations

abstract:
  The Sunyaev-Zel'dovich (SZ) effect of galaxy clusters is characterized by
three parameters: Compton parameter, electron temperature and cluster peculiar
velocity. In the present study we consider the problem of extracting these
parameters using multi-frequency SZ observations only. We show that there
exists a parameter degeneracy which can be broken with an appropriate choice of
frequencies. As a result we discuss the optimal choice of observing frequencies
from a theoretical point of view. Finally, we analyze the systematic errors (of
the order micro K) on the SZ measurement introduced by finite bandwidths, and
suggest a possible method of reducing these errors.


title:
Size estimates for intervening C IV absorbers from high resolution
  spectroscopy of APM 0827+5255

abstract:
  A new analysis of Keck/HIRES observations of the broad absorption line QSO
APM 0827+5255 indicates that a number of intervening C IV absorbers give rise
to absorption lines for which the observed optical depths for 1548, 1550 A
doublet components are not in the expected 2:1 ratio. To compensate for the
effect, a local adjustment of the zero-level is required. We model this effect
as coverage of one line of sight to this gravitationally lensed QSO and perform
a set of simulations to select a sample of lines for which our model provides
an explanation for the effect. We use lines in this sample to obtain estimates
for minimum C IV absorber sizes from total coverage and the separations of the
lines of sight for a range of lens redshifts, z_l, and two cosmologies. We also
obtain best estimates for overall sizes from a statistical `hit and miss'
approach. For z_l=0.7 our results set a lower limit to sizes of C IV absorbers
of ~0.3 h_72^{-1} kpc (~0.5 h_72^{-1} kpc) for Omega_M=1, Omega_Lambda=0
(Omega_M=0.3, Omega_Lambda=0.7), in agreement with other results from similar
work but are limited by sample size and the uncertainty in z_l. Our method can
be used to detect lensed QSOs and to probe absorber sizes when separate spectra
cannot be obtained for each line of sight.


title: A Joint Sunyaev-Zel'dovich Effect and X-ray Analysis of Abell 3667

abstract:
  We present a 40GHz (7.5 mm) raster scan image of a 3.6x2 degree region
centered on the low redshift (z=0.055) cluster of galaxies Abell 3667. The
cluster was observed during the Antarctic winter of 1999 using the Corona
instrument (15.7' FWHM beam) on the Viper Telescope at the South Pole. The
Corona image of A3667 is one of the first direct (i.e. rather than
interferometer) thermal Sunyaev-Zel'dovich effect images of a low redshift
cluster. The brightness temperature decrement at the X-ray centroid (20h 12m
28.9s, -56 49 51 J2000) was measured to be $\Delta T_{\rm CMB}=-154\mu K$. We
have used the 40GHz map of A3667 in conjunction with a deep ROSAT PSPC (X-ray)
image of the cluster, to make a measurement of the Hubble Constant. We find
$H_0 = 64^{+96}_{-30}$ km s$^{-1}$ Mpc$^{-1}$ (68% confidence interval). Our
$H_0$ calculation assumes that the cluster can be described using an
isothermal, tri-axial ellipsoidal, $\beta$-model and includes several new
analysis techniques including an automated method to remove point sources from
X-ray images with variable point spread functions, and an efficient method for
determining the errors in multi-parameter maximum likelihood analyzes. The
large errors on the $H_0$ measurement are primarily due to the statistical
noise in the Corona image. We plan to increase the precision of our measurement
by including additional clusters in our analysis and by increasing the
sensitivity of the Viper SZE maps.


title: Lyman Alpha Absorber Correlations and the Bias of the Lyman Alpha Forest

abstract:
  Lyman alpha absorber correlations contain information about the underlying
density distribution associated with a particular class of absorbers. As such,
they provide an opportunity to independently measure the "bias" of the Lyman
alpha forest, i.e. the relationship between HI column density and underlying
dark matter density. In these proceedings we use hydrodynamic simulations to
investigate whether the evolution of this bias is measurable from observable
correlations. Unfortunately, the increasingly complex physics in the IGM at z<1
makes a direct measurement of the bias difficult. Nevertheless, current
simulations do make predictions for HI absorber correlations that are in broad
agreement with observations at both high and low redshift, thus reinforcing the
bias evolution predictions given by these models.


title: Circumnuclear Dust in Nearby Active and Inactive Galaxies. I. Data

abstract:
  The detailed morphology of the interstellar medium (ISM) in the central
kiloparsec of galaxies is controlled by pressure and gravitation. The
combination of these forces shapes both circumnuclear star formation and the
growth of the central, supermassive black hole. We present visible and
near-infrared Hubble Space Telescope images and color maps of 123 nearby
galaxies that show the distribution of the cold ISM, as traced by dust, with
excellent spatial resolution. These observations reveal that nuclear dust
spirals are found in the majority of active and inactive galaxies and they
possess a wide range in coherence, symmetry, and pitch angle. We have used this
large sample to develop a classification system for circumnuclear dust
structures. In spite of the heterogeneous nature of the complete sample, we
only find symmetric, two-arm nuclear dust spirals in galaxies with large scale
bars and these dust lanes clearly connect to dust lanes along the leading edges
of the large scale bars. Not all dust lanes along large scale bars form two arm
spirals, however, and several instead end in nuclear rings. We find that
tightly wound, or low pitch angle, nuclear dust spirals are more common in
unbarred galaxies than barred galaxies. Finally, the extended narrow line
region in several of the active galaxies is well-resolved. The connection
between the ionized gas and circumnuclear dust lanes in four of these galaxies
provides additional evidence that a significant fraction of their extended
narrow line region is ambient gas photoionized in situ by the active nucleus.
In a future paper, we will use our classification system for circumnuclear dust
to identify differences between active and inactive galaxies, as well as barred
and unbarred galaxies, in well-matched subsamples of these data.


title: What ignites optical jets?

abstract:
  The properties of radio galaxies and quasars with and without optical or
X-ray jets are compared. The majority of jets from which high-frequency
emission has been detected so far (13 with optical emission, 11 with X-rays, 13
with both) are associated with the most powerful radio sources at any given
redshift. It is found that optical/X-ray jet sources are more strongly beamed
than the average population of extragalactic radio sources. This suggests that
the detection or non-detection of optical emission from jets has so far been
dominated by surface brightness selection effects, not by jet physics. It
implies that optical jets are much more common than is currently appreciated.


title:
Petschek-like Reconnection with Current-driven Anomalous Resistivity and
  its Application to Solar Flares

abstract:
  Recent numerical simulations of magnetic reconnection in two dimensions have
shown that, when the resistivity is strongly localized, the reconnection region
develops a Petschek-like structure, with the width of the inner diffusion
region being of the order of the resistivity localization scale. In this paper,
we combine this fact with a realistic model for locally-enhanced anomalous
resistivity generated by current-driven microturbulence. The result is a
qualitative model of the reconnection layer where the size of Petschek's
diffusion region and, therefore, the final reconnection rate are determined
self-consistently in terms of the main parameters of the functional dependence
of anomalous resistivity on the electric current density. We then consider
anomalous resistivity due to ion-acoustic turbulence as a particular case. This
enables us to express the reconnection region's parameters directly in terms of
the basic parameters of the plasma. Finally, we apply this reconnection model
to solar flares and obtain specific predictions for typical reconnection times,
which are very consistent with observations.


title:
Cosmic Structure Traced by Precision Measurements of the X-Ray Brightest
  Galaxy Clusters in the Sky

abstract:
  The current status of our efforts to trace cosmic structure with 10^6
galaxies (2MASS), 10^3 galaxy clusters (NORAS II cluster survey), and precision
measurements for 10^2 galaxy clusters (HIFLUGCS) is given. The latter is
illustrated in more detail with results on the gas temperature and metal
abundance structure for 10^0 cluster (A1644) obtained with XMM-Newton.


title: Formation of the First Supermassive Black Holes

abstract:
  We consider the physical conditions under which supermassive black holes
could have formed inside the first galaxies. Our SPH simulations indicate that
metal-free galaxies with a virial temperature ~10^4 K and with suppressed H2
formation (due to an intergalactic UV background) tend to form a binary black
hole system which contains a substantial fraction (>10%) of the total baryonic
mass of the host galaxy. Fragmentation into stars is suppressed without
substantial H2 cooling. Our simulations follow the condensation of ~5x10^6
M_sun around the two centers of the binary down to a scale of < 0.1pc. Low-spin
galaxies form a single black hole instead. These early black holes lead to
quasar activity before the epoch of reionization. Primordial black hole
binaries lead to the emission of gravitational radiation at redshifts z>10 that
would be detectable by LISA.


title:
GCD+: A New Chemodynamical Approach to Modeling SNe and Chemical
  Enrichment

abstract:
  We have developed a new galactic chemo-dynamical evolution code, called GCD+,
for studies of galaxy formation and evolution. This code is based on our
original three-dimensional tree N-body/smoothed particle hydrodynamics code
which includes self-gravity, hydrodynamics, radiative cooling, star formation,
supernova feedback, and metal enrichment. GCD+ includes a new Type II (SNe II)
and Ia (SNe Ia) supernovae model taking into account the lifetime of progenitor
stars, and chemical enrichment from intermediate mass stars. We apply GCD+ to
simulations of elliptical galaxy formation, and examine the colour-magnitude
relation (CMR), the Kormendy relation, and the [Mg/Fe]--magnitude relation of
simulation end-products. GCD+ is a useful and unique tool which enables us to
compare simulation results with the observational data directly and
quantitatively. Our simulation confirm the results of Kawata (2001) who uses a
simpler chemo-dynamical evolution code. We newly find that radiative cooling
becomes more efficient and thus the gas infall rate increases, with decreasing
mass of galaxies, which contributes to the slope of the CMR. In addition, the
sophisticated treatments of both SNe II and SNe Ia in GCD+ show that feedback
from SNe Ia plays a crucial role in the evolution of elliptical galaxies. We
conclude that the feedback effect of SNe Ia should not be ignored in studying
the evolution of elliptical galaxies.


title:
Physical and Chemical Structure of the Solar Type Protostar
  NGC1333-IRAS4

abstract:
  Sun like stars are born from the collapse of fragment of molecular clouds.
During the first embedded phase (the so called class 0/1), the protostar is
surrounded by a collapsing envelope, whose physical and chemical structure
would set up the initial conditions of the proto-stellar disk which may
eventually form planets. In this contribution, we show how spectroscopic far
infrared to millimeter observations can be a powerful diagnostic to derive the
chemical and physical structure of the innermost regions of envelopes
collapsing around solar type protostars, where disk are believe to form. Our
claim is based on the simultaneous modeling of the dynamics, chemistry and
radiative transfer in a protostellar envelope. Here we present a study of a
class 0 protostar NGC1333-IRAS4, obtained using ISO-LWS observations of water
far-infrared lines. We show the derived physical and chemical structure of the
protostar, namely the density and temperature profiles, as well as the water
abundance across the envelope. Besides, the mass of the central protostar and
its accretion rate can be constrained by these observations and modeling,
yielding an alternative method to measure these two poorly know parameters.


title:
The Formation of Close Binary Systems by Dynamical Interactions and
  Orbital Decay

abstract:
  We present results from the first hydrodynamical star formation calculation
to demonstrate that close binary stellar systems (separations $\lsim 10$ AU)
need not be formed directly by fragmentation. Instead, a high frequency of
close binaries can be produced through a combination of dynamical interactions
in unstable multiple systems and the orbital decay of initially wider binaries.
Orbital decay may occur due to gas accretion and/or the interaction of a binary
with its circumbinary disc. These three mechanisms avoid the problems
associated with the fragmentation of optically-thick gas to form close systems
directly. They also result in a preference for close binaries to have roughly
equal-mass components because dynamical exchange interactions and the accretion
of gas with high specific angular momentum drive mass ratios towards unity.
Furthermore, due to the importance of dynamical interactions, we find that
stars with greater masses ought to have a higher frequency of close companions,
and that many close binaries ought to have wide companions. These properties
are in good agreement with the results of observational surveys.


title: On the global structure of distant galactic disks

abstract:
  Radial and vertical profiles are determined for a sample of 34 edge-on disk
galaxies in the HDFs, selected for their apparent diameter larger than 1.3
arcsec and their unperturbed morphology. The thickness and flatness of their
galactic disks are determined and discussed with regard to evolution with
redshift. We find that sub-L* spiral galaxies with z \sim 1 have a relative
thickness or flatness (characterized by h_z/h the scaleheight to scalelength
ratio) globally similar to those in the local Universe. A slight trend is
however apparent, with the h_z/h flatness ratio larger by a factor of \sim 1.5
in distant galaxies if compared to local samples. In absolute value, the disks
are smaller than in present-day galaxies. About half of the z \sim 1 spiral
disks show a non-exponential surface brightness distribution.


title:
Luminosity Function of Morphologically Classified Galaxies in the Sloan
  Digital Sky Survey

abstract:
  The morphological dependence of the luminosity function is studied using a
sample containing approximately 1500 bright galaxies classified into Hubble
types by visual inspections for a homogeneous sample obtained from the Sloan
Digital Sky Survey (SDSS) northern equatorial stripes. Early-type galaxies are
shown to have a characteristic magnitude by 0.45 mag brighter than spiral
galaxies in the $r^{\ast}$ band, consistent with the `universal characteristic
luminosity' in the $B$ band. The shape of the luminosity function differs
rather little among different morphological types: we do not see any symptoms
of the sharp decline in the faint end for the luminosity function for
early-type galaxies at least 2 mag fainter than the characteristic magnitude,
although the faint end behaviour shows a slight decline ($\alpha\lsim -1$)
compared with the total sample. We also show that a rather flat faint end slope
for early-type galaxies is not due to an increasing mixture of the dwarf
galaxies which have softer cores. This means that there are numerous faint
early-type galaxies with highly concentrated cores.


title: Elemental abundances of metal poor carbon rich lead star: CS29497-030

abstract:
  We present here the abundance analysis of a metal poor carbon rich lead star,
CS29497-030. High resolution and high signal to noise spectra were obtained
using the UVES spectrograph on the 8.2m VLT-Kueyen telescope. The observations
were made as a part of the Large Programme 165.N-0276, P.I. R. Cayrel.
Abundance analysis was done using the latest version of the MARCS model
atmospheres (Plez et. al. 1992) and the turbospectrum spectrum synthesis code.
We have derived Teff = 6650K from the FeI lines. Visible and infrared broad
band colours using the Alonso et al. (1996) calibration, gives similar
temperatures. A log g value of 3.5 was obtained from the ionisation equilibrium
of FeI and FeII, we remark that this gravity also satisfies the MgI/MgII,
TiI/TiII and MnI/MnII equilibria, within errors. The abundance analysis
indicates a metallicity, [Fe/H] = --2.7. A large overabundance of carbon
([C/Fe]=2.7) was found. We have also found large enhancement in the s-process
elements and in particular lead shows an extremely high abundance of
[Pb/Fe]=3.5, which makes this the star with the highest Pb/Fe ratio, up to
date. The Pb/Ba ratio is found to be high ([Pb/Ba]=1.2) and the same s true for
other second-peak s-process elements(e.g La, Ce, Nd). The star is a known
spectroscopic binary with a period of 346 days (Preston & Sneden 2000). The
abundance pattern suggests that CS 29497-30 has accreted matter from its
companion, when it was in the AGB phase.


title:
Discovery of a High-Redshift (z=0.96) Cluster of Galaxies Using a FIRST
  Wide-Angle Tailed Radio Source

abstract:
  Using a combination of near-infrared and optical photometry, along with
multi-object spectroscopy, we have confirmed the existence of a high-redshift
cluster of galxies at z = 0.96. The cluster was found using a wide-angle tailed
radio source selected from the VLA FIRST survey as a cluster signpost. These
types of radio sources are often found in clusters, and are thought to attain
their C-shaped morphologies from the relative motion between the radio source
host galaxy and the intracluster medium. We present optical/near-infrared
color-magnitude diagrams which show a concentration of cluster galaxies in
color space. We also include spectroscopic results obtained from the Keck II
LRIS. Ten galaxies are confirmed at the cluster redshift, with a line-of-sight
velocity dispersion of 530 +190/-90 km/s, typical of an Abell richness class 0
cluster. Using data from the ROSAT public archive, we limit the X-ray
luminosity for the cluster to less than 3 x 10^{44} erg/s, consistent with the
value expected from the L_X - sigma relation.


title: Hard X-ray and radio observations of Abell 754

abstract:
  We present a long BeppoSAX observation of Abell 754 that reports a nonthermal
excess with respect to the thermal emission at energies greater than ~45 keV. A
VLA radio observation at 1.4 GHz definitely confirms the existence of diffuse
radio emission in the central region of the cluster, previously suggested by
images at 74 and 330 MHz (Kassim et al 2001), and reports additional features.
Besides, our observation determines a steeper radio halo spectrum in the
330-1400 MHz frequency range with respect to the spectrum detected at lower
frequencies, indicating the presence of a spectral cutoff. The presence of a
radio halo in A754, considered the prototype of a merging cluster, reinforces
the link between formation of Mpc-scale radio regions and very recent or
current merger processes. The radio results combined with the hard X-ray excess
detected by BeppoSAX give information on the origin of the electron population
responsible for nonthermal phenomena in galaxy clusters. We discuss also the
possibility that 26W20, a tailed radio galaxy with BL Lac characteristics
located in the field of view of the PDS, could be responsible for the observed
nonthermal hard X-ray emission.


title:
Chandra Observations of the Luminous, O-Rich SNR in the Irregular Galaxy
  NGC 4449

abstract:
  An analysis of a 29 ksec Chandra ACIS-S observation of the young,
Cassiopeia-A like supernova remnant in the irregular galaxy NGC 4449 is
presented. The observed 0.5-2.1 keV spectrum reveals the likely presence of
several emission lines including O VIII at 0.65 keV and 0.77 keV, Ne X at 1.05
keV, Mg XI at 1.5 keV, and Si XIII at 1.85 keV. From the observed spectrum, we
derive an N_H = 10^21 cm^-2 and an X-ray temperature of T = 9 * 10^6 K. A
non-equilibrium ionization fit to the spectrum suggests an overabundance of
oxygen around 20 times solar, consistent with the remnant's UV and optical
emission-line properties. We discuss tht remnant's approximate X-ray derived
elemental abundances and compare its X-ray spectrum and luminosity to other
oxygen-rich remnants.


title:
The Optical Gravitational Lensing Experiment. Catalog of RR Lyrae Stars
  from the Small Magellanic Cloud

abstract:
  We present the catalog of RR Lyrae stars from 2.4 square degrees of central
parts of the Small Magellanic Cloud (SMC). The photometric data were collected
during four years of the OGLE-II microlensing survey. Photometry of each star
was obtained using the Difference Image Analysis (DIA) method. The catalog
contains 571 objects, including 458 RRab, 56 RRc variables, and 57 double mode
RR Lyr stars (RRd). Additionally we attach a list of variables with periods
between 0.18-0.26 days, which are probably delta Sct stars. Period, BVI
photometry, astrometry, amplitude, and parameters of the Fourier decomposition
of the I-band light curve are provided for each object. We also present the
Petersen diagram for double mode pulsators.
  We found that the SMC RR Lyr stars are fairly uniformly distributed over the
studied area, with no clear correlation to any location. The most preferred
periods for RRab and RRc stars are 0.589 and 0.357 days, respectively. We
noticed significant excess of stars with periods of about 0.29 days, which
might be second-overtone RR Lyr stars (RRe). The mean extinction free
magnitudes derived for RRab stars are 18.97, 19.45 and 19.73 mag for the I, V
and B-band, respectively.
  All presented data, including individual BVI observations, are available from
the OGLE Internet archive.


title:
Unveiling the hidden AGN in the merging starburst system ARP 299 (IC694
  + NGC 3690)

abstract:
  As part of a research of elusive AGN in a well defined sample of infrared
selected galaxies (using BeppoSAX, Chandra, XMM-Newton and INTEGRAL data) we
have observed with BeppoSAX the merging starburst system Arp 299. The
broad-band (0.1-40 keV) coverage of this observation clearly reveals, for the
first time in this system, the presence of a deeply buried AGN having an
intrinsic luminosity of L(0.5-100 keV) = 1.9E43 cgs.


title: Chandra Observations of the Anomalous X-ray Pulsar 4U 0142+61

abstract:
  We present X-ray imaging, timing, and phase resolved spectroscopy of the
anomalous X-ray pulsar 4U 0142+61 using the Chandra X-ray Observatory. The
spectrum is well described by a power law plus blackbody model with power law
index = 3.35(2), kT_BB=0.458(3) keV, and N_H=0.91(2) x 10^{22} cm^{-2}$; we
find no significant evidence for spectral features (0.5-7.0 keV). Time resolved
X-ray spectroscopy shows evidence for evolution in phase in either index, or
KT_BB, or some combination thereof as a function of pulse phase. We derive a
precise X-ray position for the source and determine its spin period,
P=8.68866(30) s. We have detected emission beyond 4 arcsec from the central
source and extending beyond 100 arcsec, likely due to dust scattering in the
interstellar medium.


title: Predictive Mining of Time Series Data in Astronomy

abstract:
  We discuss the development of a Java toolbox for astronomical time series
data. Rather than using methods conventional in astronomy (e.g., power spectrum
and cross-correlation analysis) we employ rule discovery techniques commonly
used in analyzing stock-market data. By clustering patterns found within the
data, rule discovery allows one to build predictive models, allowing one to
forecast when a given event might occur or whether the occurrence of one event
will trigger a second. We have tested the toolbox and accompanying display tool
on datasets (representing several classes of objects) from the RXTE All Sky
Monitor. We use these datasets to illustrate the methods and functionality of
the toolbox. We also discuss issues that can come up in data analysis as well
as the possible future development of the package.


title: Unified Model for Dark Energy

abstract:
  A new model for the universe filled with a generalized Chaplygin fluid is
considered which unitarily describes as a single vacuum entity both a
quintessence scalar field and a cosmological constant, so unifying the notion
of dark energy. While the evolution of the universe filled with such a fluid
does not obviously contradict the present cosmic acceleration, the introduced
single dark-energy component, for equations of state with characteristic
parameter $\omega\geq -1$, behaves like an usual quintessence fluid with
constant equation of state at early high densities, and like a pure
cosmological constant at late cosmological times.


title:
Radio-selected Galaxies in Very Rich Clusters at z < 0.25: I.
  Multi-wavelength Observations and Data Reduction Techniques

abstract:
  Radio observations were used to detect the `active' galaxy population within
rich clusters of galaxies in a non-biased manner that is not plagued by dust
extinction or the K-correction. We present wide-field radio, optical (imaging
and spectroscopy), and ROSAT All-Sky Survey (RASS) X-ray data for a sample of
30 very rich Abell (R > 2) cluster with z < 0.25. The VLA radio data samples
the ultra-faint radio (L(1.4 GHz) > 2E22 W/Hz) galaxy population within these
extremely rich clusters for galaxies with M_R < -21. This is the largest sample
of low luminosity 20 cm radio galaxies within rich Abell clusters collected to
date. The radio-selected galaxy sample represents the starburst (Star formation
rate > 5 M_sun/yr) and active galactic nuclei (AGN) populations contained
within each cluster. Archival and newly acquired redshifts were used to verify
cluster membership for most (~95%) of the optical identifications. Thus we can
identify all the starbursting galaxies within these clusters, regardless of the
level of dust obscuration that would affect these galaxies being identified
from their optical signature. Cluster sample selection, observations, and data
reduction techniques for all wavelengths are discussed.


title: The Hubble Deep Field South Flanking Fields

abstract:
  As part of the Hubble Deep Field South program, a set of shorter 2-orbit
observations were obtained of the area adjacent to the deep fields. The WFPC2
flanking fields cover a contiguous solid angle of 48 square arcminutes.
Parallel observations with the STIS and NICMOS instruments produce a patchwork
of additional fields with optical and near-infrared (1.6 micron) response.
Deeper parallel exposures with WFPC2 and NICMOS were obtained when STIS
observed the NICMOS deep field. These deeper fields are offset from the rest,
and an extended low surface brightness object is visible in the deeper WFPC2
flanking field. In this data paper, which serves as an archival record of the
project, we discuss the observations and data reduction, and present SExtractor
source catalogs and number counts derived from the data. Number counts are
broadly consistent with previous surveys from both ground and space. Among
other things, these flanking field observations are useful for defining slit
masks for spectroscopic follow-up over a wider area around the deep fields, for
studying large-scale structure that extends beyond the deep fields, for future
supernova searches, and for number counts and morphological studies, but their
ultimate utility will be defined by the astronomical community.


title:
The last stand before MAP: cosmological parameters from lensing, CMB and
  galaxy clustering

abstract:
  Cosmic shear measurements have now improved to the point where they deserve
to be treated on par with CMB and galaxy clustering data for cosmological
parameter analysis, using the full measured aperture mass variance curve rather
than a mere phenomenological parametrization thereof. We perform a detailed
9-parameter analysis of recent lensing (RCS), CMB (up to Archeops) and galaxy
clustering (2dF) data, both separately and jointly. CMB and 2dF data are
consistent with a simple flat adiabatic scale-invariant model with
Omega_Lambda=0.72+/-0.09, omega_cdm=0.115+/- 0.013, omega_b=0.024+/-0.003, and
a hint of reionization around z~8. Lensing helps further tighten these
constraints, but reveals tension regarding the power spectrum normalization:
including the RCS survey results raises sigma8 significantly and forces other
parameters to uncomfortable values. Indeed, sigma8 is emerging as the currently
most controversial cosmological parameter, and we discuss possible resolutions
of this sigma8 problem. We also comment on the disturbing fact that many recent
analyses (including this one) obtain error bars smaller than the Fisher matrix
bound. We produce a CMB power spectrum combining all existing experiments, and
using it for a "MAP versus world" comparison next month will provide a powerful
test of how realistic the error estimates have been in the cosmology community.


title: HI Absorption in GPS/CSS Sources

abstract:
  Combining our own observations with data from the literature, we consider the
incidence of HI absorption in Gigahertz Peaked Spectrum (GPS) and Compact Steep
Spectrum (CSS) sources. Here we present our preliminary results, where we find
that the smaller GPS sources (<1 kpc) on average have larger HI column
densities than the larger CSS sources (>1 kpc). Both a spherical and an
axi-symmetric gas distribution, with a radial power law density profile, can be
used to explain this anti-correlation between projected linear size and HI
column density. Since most detections occur in galaxy classified objects, we
argue that if the unified schemes apply to the GPS/CSSs, a disk distribution
for the HI is more likely.


title: The large-scale polarization of the microwave background and foreground

abstract:
  The DASI discovery of CMB polarization has opened a new chapter in cosmology.
Most of the useful information about inflationary gravitational waves and
reionization is on large angular scales where Galactic foreground contamination
is the worst, so a key challenge is to model, quantify and remove polarized
foregrounds. We use the POLAR experiment, COBE/DMR and radio surveys to provide
the strongest limits to date on the TE cross power spectrum of the CMB on large
angular scales and to quantify the polarized synchrotron radiation, which is
likely to be the most challenging polarized contaminant for the MAP satellite.
We find that the synchrotron E- and B-contributions are equal to within 10%
from 408-820 MHz with a hint of E-domination at higher frequencies. We quantify
Faraday Rotation and Depolarization effects in the two-dimensional (l,nu)-plane
and show that they cause the synchrotron polarization percentage to drop both
towards lower frequencies and towards lower multipoles.


title:
Radio-selected Galaxies in Very Rich Clusters at z < 0.25: II. Radio
  Properties and Analysis

abstract:
  (Abridged) We report on the properties of radio-selected galaxies within 30
very-rich Abell clusters with z < 0.25. These radio data sample the ultra-faint
(L(1.4) > 2E22 W/Hz) radio galaxy population with M_R < -21 using the
well-known FIR/radio correlation to link the radio with ongoing star formation
within individual cluster galaxies. These radio-selected galaxies reveal the
`active' galaxy population (starburst and active galactic nuclei) within these
rich cluster environments that can be identified regardless of their level of
dust obscuration. For all clusters in our sample, we are sensitive to star
formation rates (M > 5 M_sun) > 5 M_sun/yr. We have found that the excess
number of low-luminosity `starburst' radio-selected galaxies (SBRG) found by
Owen et. al. 1999 in Abell 2125 is not indicative of other rich clusters in our
sample. The average fraction of SBRG is <f(SBRG)> = 0.022+/-0.003. The A2125
fraction is f(SBRG) = 0.09+/-10.03 which is significantly different from the
sample average at a >99.99% confidence level. The bimodal structure of both the
x-ray brightness distribution and optical adaptively smoothed images of A1278
and A2125 suggests that ongoing cluster-cluster mergers may be enhancing this
SBRG population. There is a significant spatial distribution difference between
the low and high-luminosity (HLRG) radio-selected populations. The HLRGs seem
to be a subclass of the cluster's massive red elliptical population, while the
SBRGs have a projected radial distribution more like the blue spiral
population. Our results indicate that most of the SBRGs are probably gas-rich
disk galaxies undergoing > 5 M_sun/yr of star-formation.


title:
Semianalytic Models of Two-Phase Disk Winds in Active Galactic Nuclei
  with Combined Hydromagnetic and Radiative Driving

abstract:
  (abridged) We present a semianalytic model of steady-state magnetically and
radiatively driven disk outflows in Active Galactic Nuclei (AGNs) consisting of
a continuous wind with embedded clouds. The continuous outflow is launched from
the disk surface as a centrifugally driven wind, whereas the clouds are
uplifted from the disk by the ram pressure of the continuous outflow. In
addition, the continuous wind and clouds are subject to both line and continuum
radiative acceleration. We describe this model in detail, outline the tests
used to verify its accuracy, and compare it to other outflow models, showing
possible difficulties with some past line-driven models. We then perform a
comprehensive parameter study to explore the dependence of the continuous wind
on the relevant physical parameters. We find that clouds have a significant
impact on the geometry, density, and velocity in the continuous wind, changing
the terminal velocity by up to 50%. Furthermore, line driving is the dominant
acceleration mechanism for clouds; continuum driving can also become important
for dusty clouds. We find that radiative acceleration can have a significant
impact on the velocities in the continuous wind and note that the radiative
acceleration comes largely from continuum opacities, not from line driving as
in some previous models. When the continuous winds are dusty, their terminal
velocities change by approximately 20% to 30% (depending on the type of dust).


title: X-ray Spectral Properties of Low-Mass X-ray Binaries in Nearby Galaxies

abstract:
  We investigated the X-ray spectral properties of a collection of low-mass
X-ray binaries (LMXBs) within a sample of 15 nearby early-type galaxies
observed with Chandra. We find that the spectrum of the sum of the sources in a
given galaxy is remarkably similar from galaxy to galaxy when only sources with
X-ray luminosities less than 10^39 ergs/s (0.3-10 keV) are considered. Fitting
these lower luminosity sources in all galaxies simultaneously yielded a
best-fit power law exponent of Gamma = 1.56 +/- 0.02 (or kT_brem = 7.3 +/- 0.3
keV). This is the tightest constraint to date on the spectral properties of
LMXBs in external galaxies. There is no apparent difference in the spectral
properties of LMXBs that reside inside and outside globular clusters. We
demonstrate how the uniformity of the spectral properties of LMXBs can lead to
more accurate determinations of the temperature and metallicity of the hot gas
in galaxies. Although few in number in any given galaxy, sources with
luminosities of 1-2 x 10^39 ergs/s are present in 10 of the galaxies. The
spectra of these luminous sources are softer than the spectra of the rest of
the sources, and are consistent with the spectra of Galactic black hole X-ray
binary candidates when they are in their very high state. The spectra of these
sources are very different than those of ultraluminous X-ray sources (ULXs)
found within spiral galaxies, suggesting that the two populations of X-ray
luminous objects have different formation mechanisms. The number of sources
with apparent luminosities above 2 x 10^39 ergs/s is equal to the number of
expected background AGN and thus appear to not be associated with the galaxy,
indicating that very luminous sources are absent or very rare in early-type
galaxies. (Abridged)


title:
Investigation of the possible third image and mass models of the
  gravitational lens PMN J1632-0033

abstract:
  We present multi-frequency VLBA observations of PMN J1632-0033, one of the
few gravitationally lensed quasars suspected of having a central ``odd'' image.
The central component has a different spectral index than the two bright quasar
images. Therefore, either the central component is not a third image, and is
instead the active nucleus of the lens galaxy, or else it is a third image
whose spectrum is inverted by free-free absorption in the lens galaxy. In
either case, we have more constraints on mass models than are usually available
for a two-image lens, especially when combined with the observed orientations
of the radio jets of the two bright quasars. If there is no third quasar image,
the simplest permitted model is a singular isothermal sphere in an external
shear field: beta=2.05^{+0.23}_{-0.10}, where rho(r) \propto r^{-beta}. If the
central component is a third image, a hypothesis which can be tested with
future high-frequency observations, then the density distribution is only
slightly shallower than isothermal: beta=1.91 +/- 0.02. We also derive limits
on the size of a constant-density core, and the break radius and exponent of an
inner density cusp.


title: Automatic abundance analysis of high resolution spectra

abstract:
  We describe an automatic procedure for determining abundances from high
resolution spectra. Such procedures are becoming increasingly important as
large amounts of data are delivered from 8m telescopes and their
high-multiplexing fiber facilities, such as FLAMES on ESO-VLT. The present
procedure is specifically targeted for the analysis of spectra of giants in the
Sgr dSph; however, the procedure may be, in principle, tailored to analyse
stars of any type. Emphasis is placed on the algorithms and on the stability of
the method; the external accuracy rests, ultimately, on the reliability of the
theoretical models (model-atmospheres, synthetic spectra) used to interpret the
data. Comparison of the results of the procedure with the results of a
traditional analysis for 12 Sgr giants shows that abundances accurate at the
level of 0.2 dex, comparable with that of traditional analysis of the same
spectra, may be derived in a fast and efficient way. Such automatic procedures
are not meant to replace the traditional abundance analysis, but as an aid to
extract rapidly a good deal of the information contained in the spectra.


title:
CMB Polarization at Large Angular Scales: Data Analysis of the POLAR
  Experiment

abstract:
  The coming flood of CMB polarization experiments, spurred by the recent
detection of CMB polarization by DASI and WMAP, will be confronted by many new
analysis tasks specific to polarization. For the analysis of CMB polarization
data sets, the devil is truly in the details. With this in mind, we present the
details of the data analysis for the POLAR experiment, which recently led to
the tightest upper limits on the polarization of the Cosmic Microwave
Background Radiation at large angular scales. We discuss the data selection
process, mapmaking algorithms, offset removal, and the likelihood analysis
which were used to find upper limits on the polarization. Stated using the
modern convention for reporting CMB Stokes parameters, these limits are 5.0 \uK
on both E-type and B-type polarization at 95% confidence. Finally, we discuss
simulations used to test our analysis techniques and to probe the fundamental
limitations of the experiment.


title:
Near-IR line-strengths in elliptical galaxies: evidence for IMF
  variations?

abstract:
  We present new relations between recently defined line-strength indices in
the near-IR (CaT*, CaT, PaT, MgI, and sTiO) and central velocity dispersion
(sigma_0) for a sample of 35 early-type galaxies, showing evidence for
significant anti-correlations between CaII triplet indices (CaT* and CaT) and
log(sigma_0). These relations are interpreted in the light of our recent
evolutionary synthesis model predictions, suggesting the existence of important
Ca underabundances with respect to Fe and/or an increase of the dwarf to giant
stars ratio along the mass sequence of elliptical galaxies.


title:
Structural Evidence for Environment-Driven Transformation of the Blue
  Galaxies in Local Abell Clusters - A85, A496, and A754

abstract:
  We compare V-band structural properties of cluster and field galaxies, to
test whether much of the current cluster membership resulted from the
transformation of infalling spirals into red early types. We use 140 galaxies
from 3 z<0.6 Abell clusters (A85,A496,A754 - spectroscopic membership) with
blue colors, and compare them to 80 field galaxies with similar colors and
luminosities. Our previous work (McIntosh et al. 2004, ApJ submitted) shows
that the blue galaxies in these local clusters are a recently infalling
population that has yet to encounter the dense core. We quantify galaxy
internal structure from 2D B/D decompositions using GIM2D. We observe
structural differences between blue galaxies in clusters, compared to the
field. Most blue cluster members are physically smaller and fainter than their
field counterparts. At a matched size and luminosity, recent arrivals are
smoother in appearance, yet their total light is as disk-dominated as in normal
field spirals. Moreover, 50% of blue cluster galaxies have blue cores or
globally blue color profiles, in contrast with field spirals that have
typically red color gradients. Without environment dependent evolution outside
of cluster cores, we expect blue disk galaxies in clusters and the field to
have similar morphologies, sizes, and color gradients. We show conclusively
that galaxy properties do reflect the environment in which the galaxy is found.
The data show that the transformation of accreted galaxies is not confined to
the dense cluster core. The overall properties of bluer cluster galaxies are
best explained by environment-driven transformation of accreted field spirals,
and our results suggest that the processes that govern color and morphological
evolution occur separately. (abridged)


title:
The Infocus Hard X-ray Telescope: Pixellated CZT Detector/Shield
  Performance and Flight Results

abstract:
  The CZT detector on the Infocus hard X-ray telescope is a pixellated
solid-state device capable of imaging spectroscopy by measuring the position
and energy of each incoming photon. The detector sits at the focal point of an
8m focal length multilayered grazing incidence X-ray mirror which has
significant effective area between 20--40 keV. The detector has an energy
resolution of 4.0keV at 32keV, and the Infocus telescope has an angular
resolution of 2.2 arcminute and a field of view of about 10 arcminutes. Infocus
flew on a balloon mission in July 2001 and observed Cygnus X-1. We present
results from laboratory testing of the detector to measure the uniformity of
response across the detector, to determine the spectral resolution, and to
perform a simple noise decomposition. We also present a hard X-ray spectrum and
image of Cygnus X-1, and measurements of the hard X-ray CZT background obtained
with the SWIN detector on Infocus.


title: The w-mode instability of ultracompact relativistic stars

abstract:
  In this article we show that the, mainly spacetime, w-modes may become
unstable in a rotating ultracompact ($R<3M$) relativistic star. We provide
results for the axial modes of a rotating star in the slow rotation
approximation, and demonstrate that an instability may become active in stars
with an ergosphere. These results suggest that the so-called ``ergoregion
instability'' discussed by other authors is, in fact, associated with the
w-modes of the star. The unstable modes are found to grow on a timescale of
seconds to minutes. We discuss briefly whether the instability is likely to
have any astrophysical relevance.


title:
A VLBA Search for a Stimulated Recombination Line from the Accretion
  Region in NGC1275

abstract:
  The radio source 3C84, in NGC1275, has a two sided structure on parsec
scales. The northern feature, presumed to be associated with a jet moving away
from the Earth, shows strong evidence for free-free absorption. The ionized gas
responsible for that absorption would be a source of detectable stimulated
recombination line emission for a wide range of physical conditions. The VLBA
has been used to search for the H65$\alpha$ hydrogen recombination line. The
line is only expected to be seen against the northern feature which contains a
small fraction of the total radio flux density. This spatial discrimination
significantly aids the search for a weak line. No line was seen, with upper
limits of roughly 15% of the continuum over a velocity range of 1486 km/s with
resolutions up to 6.6 km/s. In the absence of a strong radiation field, this
would imply that the free-free absorbing gas has a wide velocity width, is
moving rapidly relative to the systemic velocity, or is concentrated in a thin,
high density structure. All of these possibilities are reasonably likely close
to an AGN. However, in the intense radiation environment of the AGN, even
considering only the radiation we actually observe passing through the
free-free absorbing gas, the non-detection is probably assured by a combination
of saturation and radiation damping.


title: Luminous Lyman Break Galaxies at z>5 and the Source of Reionization

abstract:
  We have discovered six galaxies with spectroscopically confirmed redshifts of
4.8<z<5.8 in a single 44 square arcminute field imaged deeply in R, I and
z-bands. All the spectra show an emission-line in the region around 7000-8400
angstroms with a spectroscopically-detected faint continuum break across the
line. These six were drawn from 13 sources with I_AB<26.2 and R_AB-I_AB>1.5 in
the field, this photometric cut designed to select galaxies at z>4.8. The line
fluxes range between 0.2 to 2.5 x 10^-17 ergs cm^-2 s^-1 indicating
luminosities of around 10^42-43 ergs s^-1 for Ly-alpha and their high emission
line equivalent widths suggest very young ages (<10^8 yrs). A further
line-emitting object with no detectable continuum was serendipitously detected
by spectroscopy. If this line is Ly-alpha then it is from a source at z=6.6,
making this the most distant galaxy known. However, the redshift cannot be
considered secure as it is based on a single line. No broad emission line
objects (quasars) were detected. The 13 sources at I_AB<26.2 are less than that
expected if the luminosity function of dropout galaxies remained unchanged
between z=3 and z=6, although the deficit is not highly significant given
possible cosmic variance. The UV luminosity density from galaxies brighter than
our flux limit is considerably less than that necessary to keep the volume
probed by our field at <z>~5.3 ionized. These galaxies are observed within
several hundred Myr of the end of the epoch of reionization (z=6-7), with
little time for the luminosity function to evolve. This, and the lack of
detected quasars, imply that the bulk of the UV flux that reionized the
universe came from faint galaxies with M_(1700 ang)>-21.


title: The dynamical state of the Coma cluster with XMM-Newton

abstract:
  We present in this paper a substructure and spectroimaging study of the Coma
cluster of galaxies based on XMM-Newton data. XMM-Newton performed a mosaic of
observations of Coma to ensure a large coverage of the cluster. We add the
different pointings together and fit elliptical beta-models to the data. We
subtract the cluster models from the data and look for residuals, which can be
interpreted as substructure. We find several significant structures: the
well-known subgroup connected to NGC4839 in the South-West of the cluster, and
another substructure located between NGC 4839 and the centre of the Coma
cluster. Constructing a hardness ratio image, which can be used as a
temperature map we see that in front of this new structure the temperature is
significantly increased (higher or equal 10 keV). We interpret this temperature
enhancement as the result of heating as this structure falls onto the Coma
cluster. We furthermore reconfirm the filament-like structure South-East of the
cluster centre. This region is significantly cooler than the mean cluster
temperature. We estimate the temperature of this structure to be equal or below
1keV. A possible scenario to explain the observed features is stripping caused
by the infall of a small group of galaxies located around the two galaxies
NGC4921 and NGC4911 into the Coma cluster with a non-zero impact parameter. We
also see significant X-ray depressions North and South-East of NGC4921, which
might either be linked to tidal forces due to the merger with the Western
structure or connected to an older cluster merger.


title: A Wave-Mechanical Approach to Cosmic Structure Formation

abstract:
  The dynamical equations describing the evolution of a self-gravitating fluid
can be rewritten in the form of a Schrodinger equation coupled to a Poisson
equation determining the gravitational potential. This wave-mechanical
representation allows an approach to cosmological gravitational instability
that has numerous advantages over standard fluid-based methods. We explore the
usefulness of the Schrodinger approach by applying it to a number of simple
examples of self-gravitating systems in the weakly non-linear regime. We show
that consistent description of a cold self-gravitating fluid requires an extra
"quantum pressure" term to be added to the usual Schrodinger equation and we
give examples of the effect of this term on the development of gravitational
instability. We also show how the simple wave equation can be modified by the
addition of a non-linear term to incorporate the effects of gas pressure
described by a polytropic equation-of-state.


title: X-ray halos in galaxies

abstract:
  A hot phase of the interstellar medium has now been detected and studied in
several objects through its X-ray emission. A proper assessment of its
characteristics is relevant for our understanding of several aspects of galaxy
properties, from the large scale distribution of matter to the stellar and
galaxian evolution, to the dynamics of systems and to the feeding of a central
black hole. I will briefly summarize our current understanding of some of the
main issues related to the hot gaseous component in galaxies that are fast
evolving given the ever more striking and interesting details provided by the
X-ray satellites currently operating. I hope to convince you that the X-ray
characteristics of the hot gas are quite complex, both in morphology and
spectra, in a wide range of objects, which should promote greater efforts in
understanding the role played by this component in all galaxies.


title:
Optical polarization and near IR photometry of the proto-planetary
  nebula Hen 3-1475

abstract:
  We present BVRI CCD aperture polarization and near-infrared photometry of the
proto-planetary nebula Hen 3-1475. Its intrinsic polarization is high and shows
a strong spectral dependence. The position angles in all bands are
perpendicular to the axis of the observed bipolar structure. A Monte Carlo code
is used to model the intrinsic polarization of \hhe. Using disk dimensions and
other constraints suggested by previous works, we are able to reproduce the
observations with an optically thick disk composed by grains with a power-law
size distribution ranging from 0.06 to 0.22 um. We also reliably estimate the
foreground polarization from hundreds of stars contained in the CCD images. It
is parallel to the intrinsic polarization of Hen 3-1475. Possible implications
of this result are discussed. From IR observations, we estimate a interstellar
reddening, A(V), of about 3.2.


title:
Analysis of the XMM-Newton EPIC Background: Production of Background
  Maps and Event Files

abstract:
  XMM-Newton background maps for the 3 EPIC instruments in their different
instrument/mode/filter combinations and in several energy bands have been
constructed using a superposition of many pointed observations. Event datasets
for the different instrument/mode/filter combinations have also been
constructed, with longer exposure times than previously created files. This
document describes the construction of the background maps and event files, and
their usage. Further details on how to obtain these background products,
together with related software and these explanatory notes can be found at
http://www.sr.bham.ac.uk/xmm3/BGproducts.html


title: The Time-Variable Ultra-Luminous X-ray Sources of "The Antennae"

abstract:
  We report the first results of the Chandra temporal monitoring of the
ultra-luminous X-ray sources (ULXs) in the Antennae galaxies (NGC 4038/39).
Observations at four different epochs, covering time scales of 2 years to 2
months, show variability in seven out of nine ULXs, confirming that they are
likely to be accreting compact X-ray binaries (XRBs). The seven variable ULXs
exhibit a variety of temporal and spectral behaviors: one has harder X-ray
colors with decreasing luminosity, similar to the black hole binary Cyg X-1,
but four other ULXs show the opposite behavior. We suggest that the latter may
be black-hole binaries accreting at very high rates.


title: The Status of Core-collapse Supernova Simulations

abstract:
  Core-collapse supernovae can be used to place limits on dark matter candidate
particles, but the strength of these limits depends on the depth of our
theoretical understanding of these astrophysical events. To date, limitations
on computing power have prevented inclusion of all the physics that would
constitute a realistic simulation. The TeraScale Supernova Initiative (TSI)
will overcome these obstacles in the next few years, elucidating the explosion
mechanism and other phenomena closely associated with the core collapse of
massive stars.


title: The Fizeau Interferometer Testbed

abstract:
  The Fizeau Interferometer Testbed (FIT) is a collaborative effort between
NASA's Goddard Space Flight Center, the Naval Research Laboratory, Sigma Space
Corporation, and the University of Maryland. The testbed will be used to
explore the principles of and the requirements for the full, as well as the
pathfinder, Stellar Imager mission concept. It has a long term goal of
demonstrating closed-loop control of a sparse array of numerous articulated
mirrors to keep optical beams in phase and optimize interferometric synthesis
imaging. In this paper we present the optical and data acquisition system
design of the testbed, and discuss the wavefront sensing and control algorithms
to be used. Currently we have completed the initial design and hardware
procurement for the FIT. The assembly and testing of the Testbed will be
underway at Goddard's Instrument Development Lab in the coming months.


title: 3D Simulations of Galactic Winds in Dwarf Galaxies

abstract:
  We present 3D hydrodynamical simulations of galactic winds in dwarf, gas-rich
galaxies. The galaxy is moving through the ICM of a small galaxy group at v=200
km/s. The ram pressure removes the galactic gas at large radii, but does not
strongly influence the ISM near the center. A starburst generates a galactic
wind. The newly produced metals are expelled in the ICM and carried to large
distance from the galaxy by the ram pressure. 500 Myr after the starburst only
a few percent of the heavy elements produced are present in the central region
of the dwarf galaxy. A large collection of ram pressure + wind models will be
presented in a forthcoming paper.


title: The Nature of the Low-Metallicity ISM in the Dwarf Galaxy NGC 1569

abstract:
  We are modeling the spectra of dwarf galaxies from infrared to submillimeter
wavelengths to understand the nature of the various dust components in
low-metallicity environments, which may be comparable to the ISM of galaxies in
their early evolutionary state. The overall nature of the dust in these
environments appears to differ from those of higher metallicity starbursting
systems. Here, we present a study of one of our sample of dwarf galaxies, NGC
1569, which is a nearby, well-studied starbursting dwarf. Using ISOCAM, IRAS,
ISOPHOT and SCUBA data with the Desert et al. (1990) model, we find consistency
with little contribution from PAHs and Very Small Grains and a relative
abundance of bigger colder grains, which dominate the FIR and submillimeter
wavelengths. We are compelled to use 4 dust components, adding a very cold dust
component, to reproduce the submillimetre excess of our observations.


title: On the dynamics of magnetorotational turbulent stresses

abstract:
  [Abridged] The turbulent stresses that lead to angular momentum transport in
accretion discs have often been treated as resulting from an isotropic
effective viscosity, related to the pressure through the alpha parametrization
of Shakura & Sunyaev. This simple approach may be adequate for the simplest
aspects of accretion disc theory, and was necessitated historically by an
incomplete understanding of the origin of the turbulence. More recently, Balbus
& Hawley have shown that the magnetorotational instability provides a robust
mechanism of generating turbulent Reynolds and Maxwell stresses in sufficiently
ionized discs. The alpha viscosity model fails to describe numerous aspects of
this process. This paper introduces a new analytical model that aims to
represent more faithfully the dynamics of magnetorotational turbulent stresses
and bridge the gap between analytical studies and numerical simulations.
Covariant evolutionary equations for the mean Reynolds and Maxwell tensors are
presented, which correctly include the linear interaction with the mean flow.
Non-linear and dissipative effects, in the absence of an imposed magnetic flux
and in the limit of large Reynolds number and magnetic Reynolds number, are
modelled through five non-linear terms that represent known physical processes
and are strongly constrained by symmetry properties and dimensional
considerations. The resulting model should be particularly useful in
understanding the dynamics of warped, eccentric and tidally distorted discs,
non-Keplerian accretion flows close to black holes, and a variety of
time-dependent accretion phenomena.


title:
On the relation between viscoelastic and magnetohydrodynamic flows and
  their instabilities

abstract:
  We demonstrate a close analogy between a viscoelastic medium and an
electrically conducting fluid containing a magnetic field. Specifically, the
dynamics of the Oldroyd-B fluid in the limit of large Deborah number
corresponds to that of a magnetohydrodynamic (MHD) fluid in the limit of large
magnetic Reynolds number. As a definite example of this analogy, we compare the
stability properties of differentially rotating viscoelastic and MHD flows. We
show that there is an instability of the Oldroyd-B fluid that is physically
distinct from both the inertial and elastic instabilities described previously
in the literature, but is directly equivalent to the magnetorotational
instability in MHD. It occurs even when the specific angular momentum increases
outwards, provided that the angular velocity decreases outwards; it derives
from the kinetic energy of the shear flow and does not depend on the curvature
of the streamlines. However, we argue that the elastic instability of
viscoelastic Couette flow has no direct equivalent in MHD.


title:
A simplified numerical model of coronal energy dissipation based on
  reduced MHD

abstract:
  A 3D model intermediate between cellular automata (CA) models and the reduced
magnetohydrodynamic (RMHD) equations is presented to simulate solar impulsive
events generated along a coronal magnetic loop. The model consists of a set of
planes distributed along a magnetic loop between which the information
propagates through Alfven waves. Statistical properties in terms of power-laws
for energies and durations of dissipative events are obtained, and their
agreement with X-ray and UV flares observations is discussed. The existence of
observational biases is also discussed.


title: Gamma-Ray Burst Hubble Diagram to z=4.5

abstract:
  Gamma-ray bursts (GRBs) are tremendous explosions visible across most of the
Universe, certainly out to redshifts of z=4.5 and likely out to z~10. Recently,
GRBs have been found to have a roughly constant explosive energy as well as to
have two luminosity indicators (the spectral lag time and the variability) that
can be used to derive the burst's luminosity distance from the gamma-ray light
curve alone. There currently exists enough information to calibrate luminosity
distances and independent redshifts for nine bursts. From these, a GRB Hubble
diagram can be constructed, where the observed shape of the curve provides a
record of the expansion history of our Universe. The current nine burst diagram
is sparse, yet formal limits can be placed on the mass density of a flat
Universe. This first GRB Hubble diagram provides a proof of concept for a new
technique in cosmology at very high redshifts. With the launch of the SWIFT
satellite in 2003, we should get ~120 bursts to produce a Hubble diagram
impervious to all effects of dust extinction and out to redshifts impossible to
reach by any other method.


title: Deep XMM-Newton survey of M33

abstract:
  In an XMM-Newton raster observation of the bright local group spiral galaxy
M33 we study the population of X-ray sources (X-ray binaries, supernova
remnants, super-shells) down to a 0.5-10 keV luminosity of 10^35 erg s^-1 --
more than a factor of 10 deeper than earlier ROSAT observations. EPIC spectra
and hardness ratios are used to distinguish between different source classes.
We confirmed the 3.45 d orbital light curve of the X-ray binary M33 X7,
detected a transient super-soft source in M33, and searched for short term
variability of the brighter sources. We characterize the diffuse X-ray
component that is correlated with the inner disk and spiral arms. We will
compare the results with other nearby galaxies.


title:
Photometric and Spectroscopic Monitoring of the sdBV star PG 1605+072:
  The Multi-Site Spectroscopic Telescope (MSST) Project

abstract:
  A small fraction of subluminous B stars show short-period, multiperiodic
light variations and form the new class of pulsating star known as EC 14026
variables, after the prototype. The Multi-Site Spectroscopic Telescope (MSST)
is a virtual instrument and is also the name of a collaboration that aims to
open up a new observational window to provide access to a mode identification
for and an asteroseismological analysis of the pulsating sdB star PG 1605+072.
Although the primary aim is to obtain time resolved spectroscopy it also
includes the most extended photometric monitoring campaign for PG 1605+072.


title:
Cosmic Ray Production of $^6$Li by Structure Formation Shocks in the
  Early Galaxy

abstract:
  We discuss the production of the element $^6$Li in the early Galaxy by cosmic
rays accelerated at structure formation shocks, driven by the hierarchical
merging of sub-Galactic halos during Galaxy formation. The salient features of
this scenario are discussed and compared with observations of $^6$Li in
metal-poor halo stars, including a recent Subaru HDS result on the star
HD140283. Some unique predictions of the model are clearly testable by future
observations and may also provide important insight into how the Galaxy formed.


title:
The phase-diagram of the IGM and the entropy floor of groups and
  clusters: are clusters born warm?

abstract:
  We point out that two problems of observational cosmology, the facts i) that
> 60% of the baryonic content of the universe is not observed at z=0 and ii)
that the properties of small clusters do not agree with simple expectations,
could be closely related. As shown by recent studies, the shock-heating
associated with the formation of large-scale structures heats the intergalactic
medium (IGM) and leads to a ``warm IGM'' component for the gas. In the same
spirit, we suggest the intracluster medium (ICM) to be a mixture of
galaxy-recycled, metal enriched gas and intergalactic gas, shock-heated by the
collapsing much larger scales. This could be obtained through two processes: 1)
the late infalling gas from the external warm IGM is efficiently mixed within
the halo and brings some additional entropy, or 2) the shocks generated by
larger non-linear scales are also present within clusters and can heat the ICM.
We show that if assumption (1) holds, the entropy brought by the warm IGM is
sufficient to explain the observed properties of clusters, in particular the
entropy floor and the LX-T relation. On the other hand, we briefly note that
the scenario (2) would require a stronger shock-heating because of the larger
density of the ICM as compared with filaments. Our scenario of clusters being
"born warm" can be checked through the predicted redshift evolution of the
entropy floor.


title: Reproducing the entropy structure in galaxy groups

abstract:
  We carry out a comparison between observations and hydrodynamic simulations
of entropy profiles of groups and clusters of galaxies. We use the Tree+SPH
GADGET code to simulate four halos of sizes in the M_500 = 1.0 - 16.e13 h^-1
Msun range, corresponding to poor groups up to Virgo-like clusters. We
concentrate on the effect of introducing radiative cooling, star formation, and
a variety of non-gravitational heating schemes on the entropy structure and the
stellar fraction. We show that all the simulations result in a correct entropy
profile for the Virgo-like cluster. With the heating energy budget of ~0.7
keV/particle injected at z_h=3, we are also able to reproduce the entropy
profiles of groups. We obtain the flat entropy cores as a combined effect of
preheating and cooling, while we achieve the high entropy at outskirts by
preheating. The resulting baryon fraction locked into stars is in the 25-30%
range, compared to 35-40% in the case of no preheating. Heating at higher
redshift, z_h=9, strongly delays the star-formation, but fails to produce a
sufficiently high specific entropy.


title: NUGA: the IRAM survey of AGN spiral hosts

abstract:
  The NUclei of GAlaxies (NUGA) project is a combined effort to carry out a
high-resolution (<1'') interferometer CO survey of a sample of 12 nearby AGN
spiral hosts, using the IRAM array. We map the distribution and dynamics of
molecular gas in the inner 1 kpc of the nuclei with resolutions of 10-50 pc,
and study the mechanisms for gas fueling of the different low-luminosity AGN.
First results show evidence for the occurrence of strong m=1 gas instabilities
in Seyferts. NUGA maps allow us to address the origin/nature of m=1 modes and
their link with m=2 modes and acoustic instabilities, present in other targets.


title: Comparison of the Gamma-Ray Burst Sensitivity of Different Detectors

abstract:
  Gamma-ray burst detectors are sensitive at different energies, complicating
the comparison of the burst populations that they detect. The instrument teams
often report their detector sensitivities in their instruments' energy band. I
propose that sensitivities be reported as the threshold peak photon flux F_T
over the 1-1000 keV energy band for a specific spectral shape. The primary
spectral parameter is E_p, the energy of the maximum E^2 N_E propto nu f_nu.
Thus F_T vs. E_p is a useful description of a detector's sensitivity. I find
that Swift will be marginally more sensitive than BATSE for E_p>100 keV, but
significantly more sensitive for E_p<100 keV. Because of its low energy
sensitivity, the FREGATE on HETE-2 is surprisingly sensitive below E_p=100 keV.
Both the WFC on BeppoSAX and the WXM on HETE-2 are/were sensitive for low E_p.
As expected, the GBM on GLAST will be less sensitive than BATSE, while EXIST
will be significantly more sensitive than Swift. The BeppoSAX GRBM was less
sensitive that the WFC, particularly at low E_p.


title: Explaining the Gamma-Ray Burst E_peak Distribution

abstract:
  The characteristic photon energy for Gamma Ray Bursts, E_peak, has a
remarkably narrow distribution for bursts of similar peak flux, with values
between 150 and 600 keV for most faint bursts. This result is surprising within
the framework of internal shock models, since spectral shifts associated with
the jet's blue shift (by a Lorentz factor of Gamma) and the cosmological red
shift (by a factor of 1+z) should cause substantial smearing in the
distribution of the spectral peak in the jet's co-moving frame, E_rest. For the
general case where the luminosity (L) varies as Gamma^N and E_rest varies as
Gamma^M, then the observed E_peak will vary as L^{(M+1)/N}(1+z)^{-1}. For two
independent set of 20 and 84 bursts, E_peak(1+z) varies as a power law of the
luminosity with an index of (M+1)/N=0.36+-0.03. With this measured value, the
above functional dependence of E_peak on L and z results in E_peak being
roughly constant for bursts of similar peak flux, P_256. Thus, the kinematic
smearing will be small, hence allowing the E_peak distribution to be narrow.
This model also predicts that bright bursts will have high E_peak values
because they all have some combination of high luminosity (and hence a large
blue shift Gamma) and a nearby distance (and hence a small cosmological red
shift). Quantitatively, E_peak should vary roughly as P_256^0.36, and this
model prediction is strikingly confirmed with BATSE data by Mallozzi et al. A
prediction of this model is that GRBs at very high red shift z~10 should all
appear with E_peak at ~200 keV. A further prediction of this model is that
normal bursts with P_256 below the BATSE trigger threshold will appear as x-ray
flashes with E_peak~70 keV; just as is reported by Kippen et al. and Heise et
al.


title:
Orbits of Hyades Multiple-Lined Spectroscopic Binaries. Paper 2: The
  Double-Lined System HD 27149

abstract:
  A new determination of the orbit of the Hyades double-lined spectroscopic
binary HD 27149 is presented. The well-defined orbit provides the spectroscopic
basis for an extremely accurate orbital parallax for the system -- in
particular, the size of the relative orbit ($a\sin i = (a_1 + a_2)\sin i =
(67.075 \pm 0.045) \times 10^6$ km) is accurate to $\pm 0.07$ %. The minimum
masses for the primary and secondary -- $m_1\sin ^3i = 1.096 \pm 0.002 M_\odot$
and $m_2\sin ^3i = 1.010 \pm 0.002 M_\odot$ -- are unexpectedly large for the
spectral types thus suggesting the possibility of eclipses. Although the
probability of eclipses is not large, the system being composed of G3V and G6V
stars in a 75-day orbit, the possibility is of great interest. A rediscussion
of a search for eclipses made by J{\o}rgensen & Olsen$^1$ in 1972 shows that
central eclipses can be excluded, but that shorter duration off-centre eclipses
cannot be ruled out. Ephemerides for possible primary and secondary eclipses
are given.


title:
Galaxy groups in the 2dF galaxy redshift survey: A Compactness Analysis
  of Groups

abstract:
  A comprehensive study on compactness has been carried out on the 2dF Galaxy
Group Catalogue constructed by Merch\'an & Zandivarez. The compactness indexes
defined in this work take into account different geometrical constraints in
order to explore a wide range of possibilities. Our results show that there is
no clear distinction between groups with high and low level of compactness when
considering particular properties as the radial velocity dispersion, the
relative fraction of galaxies per spectral type and luminosity functions of
their galaxy members.
  Studying the trend of the fraction of galaxies per spectral type as a
function of the dimensionless crossing time some signs of dynamical evolution
are observed. From the comparison with previous works on compactness we realize
that special care should be taken into account for some compactness criteria
definitions in order to avoid possible biases in the identification.


title: Evolution of Magnetic Fields around a Kerr Black Hole

abstract:
  The evolution of magnetic fields frozen to a perfectly conducting plasma
fluid around a Kerr black hole is investigated. We focus on the plunging region
between the black hole horizon and the marginally stable circular orbit in the
equatorial plane. Adopting the kinematic approximation where the dynamical
effects of magnetic fields are ignored, we exactly solve Maxwell's equations
with the assumptions that the geodesic motion of the fluid is stationary and
axisymmetric, the magnetic field has only radial and azimuthal components and
depends only on time and radial coordinates. We show that the stationary state
of the magnetic field in the plunging region is uniquely determined by the
boundary conditions at the marginally stable circular orbit. If the magnetic
field at the marginally stable circular orbit is in a stationary state, the
magnetic field in the plunging region will quickly settle into a stationary
state if it is not so initially, in a time determined by the dynamical time
scale. The radial component of the magnetic field at the marginally stable
circular orbit is more important than the toroidal component in determining the
structure and evolution of the magnetic field in the plunging region. Even if
at the marginally stable circular orbit the toroidal component is zero, in the
plunging region a toroidal component is quickly generated from the radial
component by the shear motion of the fluid. Finally, we show that the dynamical
effects of magnetic fields are unimportant in the plunging region if they are
negligible on the marginally stable circular orbit. This supports the
``no-torque inner boundary condition'' of thin disks, contrary to the claim in
the recent literature.


title: Numerical Simulations of High Redshift Star Formation in Dwarf Galaxies

abstract:
  We present first results from three-dimensional hydrodynamic simulations of
the high redshift formation of dwarf galaxies. The simulations use an Eulerian
adaptive mesh refinement technique to follow the non-equilibrium chemistry of
hydrogen and helium with cosmological initial conditions drawn from a popular
Lambda-dominated CDM model. We include the effects of reionization using a
uniform radiation field, a phenomenological description of the effect of star
formation and, in a separate simulation, the effects of stellar feedback. The
results highlight the effects of stellar feedback and photoionization on the
baryon content and star formation of galaxies with virial temperatures of
approximately 10^4K. Dwarf sized dark matter halos that assemble prior to
reionization are able to form stars. Most halos of similar mass that assemble
after reionization do not form stars by redshift of three. Dwarf galaxies that
form stars show large variations in their gas content because of stellar
feedback and photoionization effects. Baryon-to-dark matter mass ratios are
found to lie below the cosmic mean as a result of stellar feedback. The
supposed substructure problem of CDM is critically assessed on the basis of
these results. The star formation histories modulated by radiative and stellar
feedbacks are discussed. In addition, metallicities of individual objects are
shown to be naturally correlated with their mass-to-light ratios as is also
evident in the properties of local dwarf galaxies.


title: A Model For Infall Around Virialized Halos

abstract:
  Motivated by the recent direct detection of cosmological gas infall, we
develop an analytical model for calculating the mean density profile around an
initial overdensity that later forms a dark matter halo. We account for the
problem of peaks within peaks; when considering a halo of a given mass we
ensure that this halo is not a part of a larger virialized halo. For halos that
represent high-sigma fluctuations we recover the usual result that such halos
preferentially lie within highly overdense regions; in the limit of very
low-sigma fluctuations, on the other hand, we show that halos tend to lie
within voids. Combined with spherical collapse, our results yield the typical
density and velocity profiles of the gas and dark matter that surround
virialized halos.


title: Long Term Evolution of Massive Black Hole Binaries

abstract:
  The long-term evolution of massive black hole binaries at the centers of
galaxies is studied in a variety of physical regimes, with the aim of resolving
the ``final parsec problem,'' i.e., how black hole binaries manage to shrink to
separations at which emission of gravity waves becomes efficient. A binary
ejects stars by the gravitational slingshot and carves out a loss cone in the
host galaxy. Continued decay of the binary requires a refilling of the loss
cone. We show that the standard treatment of loss cone refilling, derived for
collisionally relaxed systems like globular clusters, can substantially
underestimate the refilling rates in galactic nuclei. We derive expressions for
non-equilibrium loss-cone dynamics and calculate time scales for the decay of
massive black hole binaries following galaxy mergers, obtaining significantly
higher decay rates than heretofore. Even in the absence of two-body relaxation,
decay of binaries can persist due to repeated ejection of stars returning to
the nucleus on eccentric orbits. We show that this recycling of stars leads to
a gradual, approximately logarithmic dependence of the binary binding energy on
time. We derive an expression for the loss cone refilling induced by the
Brownian motion of a black hole binary. We also show that numerical N-body
experiments are not well suited to probe these mechanisms over long times due
to spurious relaxation.


title: Conservative formulations of general relativistic kinetic theory

abstract:
  Experience with core-collapse supernova simulations shows that accurate
accounting of total particle number and 4-momentum can be a challenge for
computational radiative transfer. This accurate accounting would be facilitated
by the use of particle number and 4-momentum transport equations that allow
transparent conversion between volume and surface integrals in both
configuration and momentum space. Such conservative formulations of general
relativistic kinetic theory in multiple spatial dimensions are presented in
this paper, and their relevance to core-collapse supernova simulations is
described.


title: Nonthermal Particles and Radiation Produced by Cluster Merger Shocks

abstract:
  We have developed a numerical model for the temporal evolution of particle
and photon spectra resulting from nonthermal processes at the shock fronts
formed in merging clusters of galaxies. Fermi acceleration is approximated by
injecting power-law distributions of particles during a merger event, subject
to constraints on maximum particle energies. We consider synchrotron,
bremsstrahlung, Compton, and Coulomb processes for the electrons, nuclear,
photomeson, and Coulomb processes for the protons, and knock-on electron
production. Broadband radio through gamma-ray light curves radiated by
nonthermal protons and primary and secondary electrons are calculated both
during and after the merger event. Using ROSAT observations to establish
typical parameters for the matter density profile of clusters of galaxies, we
find that merger shocks are weak and accelerate particles with relatively soft
spectra. Our results suggest that only a minor contribution to the diffuse
extragalactic gamma-ray background can originate from cluster merger shocks.