title: Evolution of the Universe with Flat Extra Dimensions

abstract:
  Evolution of a universe with homogeneous extra dimensions is studied with the
benefit of a well-chosen parameter space that provides a systematic, useful,
and convenient way for analysis. In this model we find a natural evolution
pattern that entails not only stable extra dimensions in the
radiation-dominated era, thereby preserving essential predictions in the
standard cosmology, but also the present accelerating expansion while
satisfying the limit on the variation of Newtonian gravitational constant. In
this natural evolution pattern the extra dimensions tend to be stabilized
automatically without resorting to artificial mechanisms in both the
radiation-dominated and the matter-dominated era, as a wonderful feature for
building models with extra dimensions. In addition, the naturalness of this
evolution pattern that guarantees the late-time accelerating expansion of a
matter-dominated universe presents a solution to the coincidence problem: why
the accelerating phase starts at the present epoch. The feasibility of this
evolution pattern for describing our universe is discussed.


title: 21st Century VLBI: Deep Wide-Field Surveys

abstract:
  A 20-hour VLBI observation with the NRAO VLBA and GBT in the NOAO Bootes
field reaches an rms noise of 9 microJy per beam at 1.4 GHz. Three sources were
detected at 10-milliarcsecond resolution within the GBT primary beam of FWHM
8.6', including the 20-milliJy calibrator and two sub-milliJy sources. By
tapering the visibility data, portions of the VLBA primary beam of FWHM 29'
were imaged at poorer sensitivity and resolution to yield five further
detections. New developments at JIVE will permit deeper and wider VLBI surveys
at full sensitivity and resolution, enabling new types of survey science.


title:
Active Galaxies at Milliarcsecond Resolution in the NOAO Deep Wide-Field
  Survey

abstract:
  We are using the NRAO VLBA at 5.0 GHz to image about 200 FIRST sources
stronger than 10 mJy at 1.4 GHz in the NDWFS.


title:
On the Rate of Detectability of Intermediate-Mass Black-Hole Binaries
  using LISA

abstract:
  We estimate the rate at which the proposed space gravitational-wave
interferometer LISA could detect intermediate-mass black-hole binaries, that
is, binaries containing a black hole in the mass range 10 -- 100 Msun orbiting
a black hole in the mass range 100 -- 1000 Msun. For one-year integrations
leading up to the innermost stable orbit, and a signal-to-noise ratio of 10, we
estimate a detection rate of only 1 per million years for 10 Msun/100 Msun
binaries. The estimate uses the method of parameter estimation via matched
filtering, incorporates a noise curve for LISA established by the LISA Science
Team that is available online, and employs an IMBH formation rate model used by
Miller (2002). We find that the detectable distance is relatively insensitive
to LISA arm lengths or acceleration noise, but is roughly inversely
proportional to LISA position errors, and varies roughly as T^(1/2), where T is
the integration time in years. We also show that, while all IMBH systems in
this mass range may be detected in the Virgo cluster up to 40 years before
merger, none can be detected there earlier than 400 years before merger. An
extended LISA mission that enabled 10-year integrations could detect IMBH
systems at the Virgo cluster 1000 years before merger, and systems in galactic
globular clusters a million years before merger. We compare and contrast these
estimates with earlier estimates by Miller (2002).


title: Colors of AGN host galaxies at 0.5<z<1.1 from GEMS

abstract:
  We present the results from a study of the host galaxies of 15 optically
selected AGNs with 0.5<z<1.1 from GEMS. GEMS is a Hubble Space Telescope
imaging survey of a ~28"x28" contiguous field centered on the Chandra Deep
Field South in the F606W and F850LP filter bands. It incorporates the SEDs and
redshifts of ~10000 objects, obtained by the COMBO-17 project. We have detected
the host galaxies of all 15 AGNs in the F850LP-band (and 13/15 in the
F606W-band), recovering their fluxes, morphologies and structural parameters.
We find that 80% of the host galaxies have early-type (bulge-dominated)
morphologies, while the rest have structures characteristic of late-type
(disk-dominated) galaxies. We find that 25% of the early types, and 30% of the
late types, exhibit disturbances consistent with galaxy interactions. The hosts
show a wide range of colors, from those of red-sequence galaxies to blue colors
consistent with ongoing star formation. Roughly 70% of the morphologically
early-type hosts have rest-frame blue colors, a much larger fraction than those
typical of non-active morphologically early-type galaxies in this redshift and
luminosity range. Yet, we find that the early-type hosts are structurally
similar to red-sequence ellipticals, inasmuch as they follow an absolute
magnitude versus half-light size correlation that are consistent with the mean
relation for early-type galaxies at similar redshifts.


title: X-ray Survey Results on Active Galaxy Physics and Evolution

abstract:
  This "pedagogical" review describes the key Chandra and XMM-Newton
extragalactic surveys to date and details some of their implications for AGN
physics and evolution. We additionally highlight two topics of current
widespread interest: (1) X-ray constraints on the AGN content of luminous
submillimeter galaxies, and (2) the demography and physics of high-redshift (z
> 4) AGN as revealed by X-ray observations. Finally, we discuss prospects for
future X-ray surveys with Chandra, XMM-Newton, and upcoming missions.


title: In-orbit Vignetting Calibrations of XMM-Newton Telescopes

abstract:
  We describe measurements of the mirror vignetting in the XMM-Newton
Observatory made in-orbit, using observations of SNR G21.5-09 and SNR
  3C58 with the EPIC imaging cameras. The instrument features that complicate
these measurements are briefly described. We show the spatial and energy
dependences of measured vignetting, outlining assumptions made in deriving the
eventual agreement between simulation and measurement. Alternate methods to
confirm these are described, including an assessment of source elongation with
off-axis angle, the surface brightness distribution of the diffuse X-ray
background, and the consistency of Coma cluster emission at different position
angles. A synthesis of these measurements leads to a change in the XMM
calibration data base, for the optical axis of two of the three telescopes, by
in excess of 1 arcminute. This has a small but measureable effect on the
assumed spectral responses of the cameras for on-axis targets.


title: The X-ray afterglow of GRB030329 at early and late times

abstract:
  Thanks to its extraordinary brightness, the X-ray afterglow of GRB030329
could be studied by XMM-Newton up to two months after the prompt Gamma-ray
emission.
  We present the results of two XMM-Newton observations performed on May 5 and
29, as well as an analysis of the Rossi-XTE data of the early part of the
afterglow, discussing in particular the stability of the X-ray spectrum and
presenting upper limits on the presence of X-ray emission lines.


title: Low-rate accretion onto isolated stellar mass black holes

abstract:
  Magnetic field behaviour in a spherically-symmetric accretion flow for
parameters typical of single black holes in the Galaxy is discussed. It is
shown that in the majority of Galaxy volume, accretion onto single stellar-mass
black holes will be spherical and have a low accretion rate ($10^{-6} -
10^{-9}$ of the Eddington rate). An analysis of plasma internal energy growth
during the infall is performed. Adiabatic heating of collisionless accretion
flow due to magnetic adiabatic invariant conservation is 25% more efficient
than in the standard non-magnetized gas case. It is shown that magnetic field
line reconnections in discrete current sheets lead to significant nonthermal
electron component formation. In a framework of quasi-diffusion acceleration,
the "energy-radius" electron distribution is computed and the function
describing the shape of synchrotron radiation spectrum is constructed. It is
shown that nonthermal electron emission leads to formation of a hard (UV,
X-ray, up to gamma), highly variable spectral component in addition to the
standard synchrotron optical component first derived by Shvartsman generated by
thermal electrons in the magnetic field of accretion flow. For typical
interstellar medium parameters, a black hole at 100 pc distance will be a
16-25$^{\rm m}$ optical source coinciding with the highly variable bright X-ray
counterpart, while the variable component of optical emission will be about
18-27$^{\rm m}$. The typical time scale of the variability is $10^{-4}$ sec,
with relative flare amplitudes of 0.2-6% in various spectral bands. Possible
applications of these results to the problem of search for single black holes
are discussed.


title: Wide-field spectroscopy of A1689 and A1835 with VIMOS: First results

abstract:
  We are using VIMOS to conduct a wide-field spectroscopic survey covering
fields of 0.5 x 0.5 sqdeg around the X-ray luminous clusters of galaxies Abell
1689 (z = 0.185) and Abell 1835 (z = 0.25). Here we describe the observations
and first results on the redshift distribution of subsamples of cluster
galaxies to R~22 for which we at present have obtained secure redshifts. These
subsamples constitute ~40% of the total spectroscopic sample and contain 525
and 630 cluster members in Abell 1689 and Abell 1835, respectively, placing
them amongst the largest redshift samples available for any cluster of
galaxies.


title: The X-ray properties of the PG QSO sample observed with XMM-Newton

abstract:
  We present preliminary results of a systematic analysis of the XMM-Newton
spectra of nearby optically-bright QSOs. The objects have been optically
selected from the Bright Quasar Survey sample. The goal of this project is to
characterise the X-ray spectral properties of optically selected QSOs in the
0.3-12 keV energy band. A power law component accounts the hard band spectra
with a average photon index of 2.0+/-0.2. No single model is able to account
for the ubiquitous soft excess. We discuss several possibilities such single
and multi-temperature black-body, power law and bremsstrahlung. We observed a
X-ray Baldwin effect in our sample.


title:
Star formation activity of intermediate redshift cluster galaxies out to
  the infall regions

abstract:
  We present a spectroscopic analysis of two galaxy clusters out to ~4Mpc at
z~0.2. The two clusters VMF73 and VMF74 identified by Vikhlinin et al. (1998)
were observed with MOSCA at the Calar Alto 3.5m telescope. Both clusters lie in
the ROSAT PSPC field R285 and were selected from the X-ray Dark Cluster Survey
(Gilbank et al. 2004) that provides optical V- and I-band data. VMF73 and VMF74
are located at respective redshifts of z=0.25 and z=0.18 with velocity
dispersions of 671 km/s and 442 km/s, respectively. The spectroscopic
observations reach out to ~2.5 virial radii. Line strength measurements of the
emission lines H_alpha and [OII]3727 are used to assess the star formation
activity of cluster galaxies which show radial and density dependences. The
mean and median of both line strength distributions as well as the fraction of
star forming galaxies increase with increasing clustercentric distance and
decreasing local galaxy density. Except for two galaxies with strong H_alpha
and [OII] emission, all of the cluster galaxies are normal star forming or
passive galaxies. Our results are consistent with other studies that show the
truncation in star formation occurs far from the cluster centre.


title: Extreme Superluminal Motion in the Curved Jet of PKS 1502+106

abstract:
  In this paper we present a multifrequency and multiepoch study of \object{PKS
1502+106} at radio frequencies. The analysis is based on an EVN (European VLBI
Network) dataset at 5 GHz and archive VLBA (Very Long Baseline Array) datasets
at 2.3, 8.3, 24.4 and 43.1 GHz over a period of 8 years. The source is
characterized by a multi--component one--sided jet at all epochs. The
high--resolution images at 5, 8.3, 24.4 and 43.1 GHz show a curved jet
morphology in the source. The radio core brightness temperature approaches the
equipartition limit. Superluminal motions of $37.3\pm9.3 c$, $22.0\pm15.5 c$,
$10.5\pm2.6 c$ and $27.9\pm7.0 c$ are measured in four distinct components of
the jet. Our analysis supports the idea that the relativistic jet in
\object{PKS 1502+106} is characterised by extreme beaming and that its radio
properties are similar to those of $\gamma$--ray loud sources.


title: Weak lensing in generalized gravity theories

abstract:
  We extend the theory of weak gravitational lensing to cosmologies with
generalized gravity, described in the Lagrangian by a generic function
depending on the Ricci scalar and a non-minimal coupled scalar field. We work
out the generalized Poisson equations relating the dynamics of the fluctuating
components to the two gauge invariant scalar gravitational potentials, fixing
the new contributions from the modified background expansion and fluctuations.
We show how the lensing equation gets modified by the cosmic expansion as well
as by the presence of the anisotropic stress, which is non-null at the linear
level both in scalar-tensor gravity and in theories where the gravitational
Lagrangian term features a non-minimal dependence on the Ricci scalar. Starting
from the geodesic deviation, we derive the generalized expressions for the
shear tensor and projected lensing potential, encoding the spacetime variation
of the effective gravitational constant and isolating the contribution of the
anisotropic stress, which introduces a correction due to the spatial
correlation between the gravitational potentials. Finally, we work out the
expressions of the lensing convergence power spectrum as well as the
correlation between the lensing potential and the Integrated Sachs-Wolfe effect
affecting Cosmic Microwave Background total intensity and polarization
anisotropies. To illustrate phenomenologically the new effects, we work out
approximate expressions for the quantities above in Extended Quintessence
scenarios where the scalar field coupled to gravity plays the role of the dark
energy.


title:
Magnetic Fields and Ionized Gas in the inner Galaxy: An Outer Scale for
  Turbulence and the Possible Role of HII Regions

abstract:
  We present an analysis of rotation measure (RM) fluctuations from the Test
Region of the Southern Galactic Plane Survey (SGPS), along with emission
measure (EM) fluctuations in the same field taken from the Southern H-Alpha Sky
Survey Atlas. The structure function of RM fluctuations shows a relatively
steep slope at small scales (1-5 arcmin), a break in slope to a flatter
structure function at intermediate scales (5-60 arcmin), and a systematic
variation of the strength of fluctuations as a function of position angle on
the sky at the largest scales (60-200 arcmin). The structure function of EM
fluctuations shows similar behavior, although the lower resolution of the data
prevents detection of a possible break in the spectrum. We interpret the
anisotropy in RM/EM structure on large scales as resulting from a large-scale
gradient in electron density (and possibly magnetic field) across the region.
The break in the slope of the RM structure function at scales of about 5 arcmin
can be explained by contributions from two spatially distinct magneto-ionized
screens, most likely in the Local and Carina spiral arms. The observed
structure function then implies that the outer scale of RM fluctuations in
these screens is about 2 pc. We conclude that we have identified an additional
source of enhanced turbulence, injected on scales of a few pc, possibly seen
only in the Galactic plane. The most likely source of such turbulence is
individual HII regions from relatively low-mass stars, whose characteristic
scale size is similar to the outer scale of turbulence inferred here. These
sources may be the dominant source of density and velocity fluctuations in warm
ionized gas in the Galactic plane.


title: Weak lensing evidence for a filament between A222/A223

abstract:
  We present a weak lensing analysis and comparison to optical and X-ray maps
of the close pair of massive clusters A222/223. Indications for a filamentary
connection between the clusters are found and discussed.


title: Minimal Cooling of Neutron Stars: A New Paradigm

abstract:
  A new classification of neutron star cooling scenarios, involving either
``minimal'' cooling or ``enhanced'' cooling is proposed. The minimal cooling
scenario replaces and extends the so-called standard cooling scenario to
include neutrino emission from the Cooper pair breaking and formation process.
This emission dominates that due to the modified Urca process for temperatures
close to the critical temperature for superfluid pairing. Minimal cooling is
distinguished from enhanced cooling by the absence of neutrino emission from
any direct Urca process, due either to nucleons or to exotica. Within the
minimal cooling scenario, theoretical cooling models can be considered to be a
four parameter family involving the equation of state of dense matter,
superfluid properties of dense matter, the composition of the neutron star
envelope, and the mass of the neutron star. Consequences of minimal cooling are
explored through extensive variations of these parameters. Results are compared
with the inferred properties of thermally-emitting neutron stars in order to
ascertain if enhanced cooling occurs in any of them. All stars for which
thermal emissions have been clearly detected are at least marginally consistent
with the lack of enhanced cooling. The two pulsars PSR 0833-45 (Vela) and PSR
1706-44 would require enhanced cooling in case their ages and/or temperatures
are on the lower side of their estimated values whereas the four stars PSR
0656+14, PSR 1055-52, Geminga, and RX J0720.4-3125 may require some source of
internal heating in case their age and/or luminosity are on the upper side of
their estimated values. The new upper limits on the thermal luminosity of PSR
J0205+6449 and RX J0007.0+7302 are indicative of the occurrence of some
enhanced neutrino emission beyond the minimal scenario.


title:
Spatial Locality of Galaxy Correlation Function in Phase Space: Samples
  from the 2MASS Extended Source Catalog

abstract:
  We analyze the statistical properties and dynamical implications of galaxy
distributions in phase space for samples selected from the 2MASS Extended
Source Catalog. The galaxy distribution is decomposed into modes $\delta({\bf
k, x})$ which describe the number density perturbations of galaxies in phase
space cell given by scale band $\bf k$ to ${\bf k}+\Delta {\bf k}$ and spatial
range $\bf x$ to ${\bf x}+\Delta {\bf x}$. In the nonlinear regime,
$\delta({\bf k, x})$ is highly non-Gaussian. We find, however, that the
correlations between $\delta({\bf k, x})$ and $\delta({\bf k', x'})$ are always
very weak if the spatial ranges (${\bf x}$, ${\bf x}+\Delta {\bf x}$) and
(${\bf x'}$, ${\bf x'}+\Delta {\bf x'}$) don't overlap. This feature is due to
the fact that the spatial locality of the initial perturbations is memorized
during hierarchical clustering. The highly spatial locality of the 2MASS galaxy
correlations is a strong evidence for the initial perturbations of the cosmic
mass field being spatially localized, and therefore, consistent with a Gaussian
initial perturbations on scales as small as about 0.1 h$^{-1}$ Mpc. Moreover,
the 2MASS galaxy spatial locality indicates that the relationship between
density perturbations of galaxies and the underlying dark matter should be
localized in phase space. That is, for a structure consisting of perturbations
on scales from $k$ to $ k+\Delta {k}$, the nonlocal range in the relation
between galaxies and dark matter should {\it not} be larger than $|{\Delta {\bf
x}}|=2\pi/|\Delta {\bf k}|$. The stochasticity and nonlocality of the bias
relation between galaxies and dark matter fields should be no more than the
allowed range given by the uncertainty relation $|{\Delta {\bf x}|| \Delta{\bf
k}}|=2\pi$.


title: Evidence for a New Elliptical-Galaxy Paradigm: Sersic and Core Galaxies

abstract:
  We fit the surface-brightness profiles of 21 elliptical galaxies using both
the Sersic function and a new empirical model which combines an inner power law
with an outer Sersic function. The profiles are combinations of deconvolved HST
profiles from the literature and ellipse fits to the full WFPC2 mosaic images,
and thus span a radial range from ~ 0.02 arcsec to ~ twice the half-light
radius. We are able to accurately fit the entire profiles using either the
Sersic function or our new model. In doing so, we demonstrate that most, if not
all, so-called ``power-law'' galaxies are better described as ``Sersic
galaxies'' -- they are well modeled by the three-parameter Sersic profile into
the limits of HST resolution -- and that ``core'' galaxies are best understood
as consisting of an outer Sersic profile with an inner power-law cusp, which is
a downward deviation from the inward extrapolation of the Sersic profile. This
definition of cores resolves ambiguities that result when the popular ``Nuker
law'' is fitted to the profiles of ellipticals and bulges, particularly at
lower luminosities. We also find that using the Nuker law to model core-galaxy
nuclear profiles systematically overestimates the core radii by factors of
1.5--4.5 and underestimates the inner power-law slope by ~ 20--40% or more.


title:
Generation of Magnetic Fields in the Multi-phase ISM with
  Supernova-Driven Turbulence

abstract:
  Several lines of evidence suggest that protogalactic and galactic
environments manage to grow magnetic field very rapidly. This makes the
theoretical problem of achieving rapid growth of magnetic fields in such
environments difficult. Following Balsara, Benjamin and Cox (2001), we show
that a multiphase ISM that is dominated by realistic energy inputs via
supernova explosions will naturally become a strongly turbulent medium with
large positive and negative values of the fluid helicity. The resultant
interstellar turbulence seems to have some of the essential characteristics of
a fast dynamo. Magnetic field growth in such a turbulent dynamo is studied in
this paper. It is shown that the field undergoes a linear phase of evolution
where it has a time of growth that is comparable to the eddy turn-over time.
Energetics, power spectra, statistics and structures of the turbulent dynamo
are studied here. It is shown that despite the fact that the ISM is driven by
compressive motions, the kinetic energy in this high Mach number flow is mainly
concentrated in solenoidal motions rather than compressive motions.


title: Sources of Cosmic Rays and Galactic Diffuse Gamma Radiation

abstract:
  The diffuse galactic gamma-ray spectrum measured by the EGRET experiment
\citep{Hunter:1997} are interpreted within a scenario in which cosmic rays
(CRs) are injected by three different kind of sources, (i) supernovae (SN)
which explode into the interstellar medium (ISM), (ii) Red Supergiants (RSG),
and (iii) Wolf-Rayet stars (WR), where the two latter explode into their pre-SN
winds (Biermann et al. 2001; Sina et al. 2001).


title: A Composite Extreme Ultraviolet QSO Spectrum from FUSE

abstract:
  The Far Ultraviolet Spectroscopic Explorer (FUSE) has surveyed a large sample
(> 100) of active galactic nuclei in the low redshift universe (z < 1). Its
response at short wavelengths makes it possible to measure directly the EUV
spectral shape of QSOs and Seyfert 1 galaxies at z < 0.3. Using archival FUSE
spectra, we form a composite extreme ultraviolet (EUV) spectrum of QSOs at z <
1 and compare it to UV/optical composite spectra of QSOs at higher redshift,
particularly the composite spectrum from archival Hubble Space Telescope
spectra.


title:
Supersoft X-ray sources in M31: II. ROSAT-detected supersoft sources in
  the ROSAT, Chandra and XMM eras

abstract:
  We have performed Chandra observations during the past 3 years of 5 of the
M31 supersoft X-ray sources (SSS) discovered with ROSAT. Surprisingly, only one
of these sources has been detected, despite a predicted detection of about
20-80 counts. This has motivated a thorough check of the ROSAT M31 survey I
data, including a relaxation of the hardness ratio requirement used to select
SSS. This increases the number of SSS identified in survey I by 7. We then
carried out a comparison with the ROSAT M31 survey II dataset which had
hitherto not been explicitly investigated for SSS. We find that most of the
ROSAT survey I sources are not detected, and only two new SSS are identified.
The low detection rate in the ROSAT survey II and our Chandra observations
implies that the variability time scale of SSS is a few months. If the majority
of these sources are close-binary SSS with shell hydrogen burning, it further
implies that half of these sources predominantly experience large mass transfer
rates.


title:
Direct Determination of the Kinematics of the Universe and Properties of
  the Dark Energy as Functions of Redshift

abstract:
  Understanding of the nature of dark energy, which appears to drive the
expansion of the universe, is one of the central problems of physical cosmology
today. In an earlier paper [Daly & Djorgovski (2003)] we proposed a novel
method to determine the expansion rate and the deceleration parameter in a
largely model-independent way, directly from the data on coordinate distances.
Here we expand this methodology to include measurements of the pressure of dark
energy, its normalized energy density, and the equation of state parameter as
functions of redshift. We then apply this methodology to a new, combined data
set of distances to supernovae and radio galaxies.


title:
The Radial Velocity and Mass of the White Dwarf of EX Hydrae Measured
  with Chandra

abstract:
  We present the first detection of orbital motion in the cataclysmic variable
EX Hydrae based on X-ray data from the Chandra X-ray Observatory. The large
collecting area of the telescope and the high resolution of the HETG
spectrometers allow for an unprecedented velocity accuracy of ~15 km/s in the
X-ray wavelength regime. We find an emission line velocity amplitude of
58.2+-3.7 km/s and infer a white dwarf mass of 0.49+-0.13 M_sun, in good
agreement with previous studies using optical, ultraviolet, and far ultraviolet
data.


title:
A catalogue of the Chandra Deep Field South with multi-colour
  classification and photometric redshifts from COMBO-17

abstract:
  We present the COMBO-17 object catalogue of the Chandra Deep Field South for
public use, covering a field which is 31.5' x 30' in size. This catalogue lists
astrometry, photometry in 17 passbands from 350 to 930 nm, and ground-based
morphological data for 63,501 objects. The catalogue also contains multi-colour
classification into the categories 'Star', 'Galaxy' and 'Quasar' as well as
photometric redshifts. We include restframe luminosities in Johnson, SDSS and
Bessell passbands and estimated errors. The redshifts are most reliable at
R<24, where the sample contains approximately 100 quasars, 1000 stars and 10000
galaxies. We use nearly 1000 spectroscopically identified objects in
conjunction with detailed simulations to characterize the performance of
COMBO-17. We show that the selection of quasars, more generally type-1 AGN, is
nearly complete and minimally contaminated at z=[0.5,5] for luminosities above
M_B=-21.7. Their photometric redshifts are accurate to roughly 5000 km/sec.
Galaxy redshifts are accurate to 1% in dz/(1+z) at R<21. They degrade in
quality for progressively fainter galaxies, reaching accuracies of 2% for
galaxies with R~222 and of 10% for galaxies with R>24. The selection of stars
is complete to R~23, and deeper for M stars. We also present an updated
discussion of our classification technique with maps of survey completeness,
and discuss possible failures of the statistical classification in the faint
regime at R>24.


title: IRAS 05436-0007 and the Emergence of McNeil's Nebula

abstract:
  We present a study of McNeil's Nebula, a newly appeared reflection nebula in
the L1630 cloud, together with photometry and spectroscopy of its source. New
IR photometry compared to earlier 2MASS data shows that the star has brightened
by about 3 magnitudes in the near-infrared, changing its location in a J-H/H-K
diagram precisely along a reddening vector. A Gemini NIRI K-band spectrum shows
strong CO-bandhead emission and Br-gamma is in emission, indicative of strong
accretion. A Gemini GMOS optical spectrum shows only a red, heavily veiled
continuum, with H-alpha strongly in emission and displaying a pronounced P
Cygni profile, with an absorption trough reaching velocities up to 600 km s-1.
This implies significant mass loss in a powerful wind. However, no evidence is
found for any shocks, as commonly seen in collimated outflows from young stars.
Apparently the eruption has dispersed a layer of extinction and this, together
with the intrinsic brightening of the IRAS source, has allowed an earlier
outflow cavity to be flooded with light, thus creating McNeil's Nebula.


title:
Condition for Primordial Black Hole Formation in Randall-Sundrum
  Cosmology

abstract:
  We consider spherical collapse in the Randall-Sundrum type II model and
estimate the critical over density for black hole formation in the radiation
dominated era. It is found that when (density)$^{2}$-term is dominant in the
modified Friedmann equation the critical density is smaller than in the
standard cosmology, which implies that PBHs are more easily produced in the
Randall-Sundrum model.


title:
Chandra & XMM-Newton Observations of NGC5253. Analysis of the X-ray
  Emission from a Dwarf Starburst Galaxy

abstract:
  We present Chandra and XMM-Newton X-ray data of NGC5253, a local starbursting
dwarf elliptical galaxy, in the early stages of a starburst episode.
Contributions to the X-ray emission come from discrete point sources and
extended diffuse emission, in the form of what appear to be multiple
superbubbles, and smaller bubbles probably associated with individual star
clusters. Chandra detects 17 sources within the optical extent of NGC5253 down
to a completeness level corresponding to a luminosity of 1.5E37 erg/s.The slope
of the point source X-ray luminosity function is -0.54, similar to that of
other nearby dwarf starburst galaxies. Several different types of source are
detected within the galaxy, including X-ray binaries and the emission
associated with star-clusters.
  Comparison of the diffuse X-ray emission with the observed Halpha emission
shows similarities in their extent. The best spectral fit to the diffuse
emission is obtained with an absorbed, two temperature model giving
temperatures for the two gas components of ~0.24keV and ~0.75keV.The derived
parameters of the diffuse X-ray emitting gas are as follows: a total mass of
\~1.4E6 f^{1/2} Msun, where f is the volume filling factor of the X-ray
emitting gas, and a total thermal energy content for the hot X-ray emitting gas
of \~3.4E54 f^{1/2} erg. The pressure in the diffuse gas is P/k ~
1E6f^{-1/2}K/cm3. We find that these values are broadly commensurate with the
mass and energy injection from the starburst population. Analysis of the
kinematics of the starburst region suggest that the stellar ejecta contained
within it can escape the gravitational potential well of the galaxy, and
pollute the surrounding IGM.


title:
Modeling non-linear effects in the redshift space two-point correlation
  function and its implications for the pairwise velocity dispersion

abstract:
  The anisotropies in the galaxy two-point correlation function measured from
redshift surveys exhibits deviations from the predictions of the linear theory
of redshift space distortion on scales as large 20 Mpc/h where we expect linear
theory to hold in real space. Any attempt at analyzing the anisotropies in the
redshift correlation function and determining the linear distortion parameter
\beta requires these deviations to be correctly modeled and taken into account.
These deviations are usually attributed to galaxy random motions and these are
incorporated in the analysis through a phenomenological model where the linear
redshift correlation is convolved with the random pairwise velocity
distribution function along the line of sight. We show that a substantial part
of the deviations arise from non-linear effects in the mapping from real to
redshift space caused by the coherent flows. Models which incorporate this
effect provide a better fit to N-body results as compared to the
phenomenological model which has only the effect of random motions. We find
that the pairwise velocity dispersion predicted by all the models that we have
considered are in excess of the values determined directly from the N-body
simulations. This indicates a shortcoming in our understanding of the
statistical properties of peculiar velocities and their relation to redshift
distortion.


title:
The Primordial Perturbation Spectrum from Various Expanding and
  Contracting Phases

abstract:
  In this paper, focusing on the case of single scalar field, we discuss
various expanding and contracting phases generating primordial perturbations,
and study the relation between the primordial perturbation spectrum from these
phases and the parameter w of state equation in details. Furthermore, we offer
an interesting classification for the primordial perturbation spectrum from
various phases, which may have important implications for building an early
universe scenario embedded in possible high energy theories.


title: Linear spectropolarimetry of young and other emission line stars

abstract:
  The aim of this article is to demonstrate the useful role that can be played
by spectropolarimetric observations of young and evolved emission line stars
that analyse the linearly polarized component in their spectra. At the time of
writing, this demonstration has to be made on the basis of optical data since
there is no common-user infrared facility, in operation, that offers the
desired combination of spectral resolution and sensitivity. Here we focus on
what can be learned from linear spectropolarimetry alone at reasonably high
spectral resolution and at $10^3 < $S/N$ < 10^4$. And we remind that the near
infrared (1--2 micron) has the potential to out-perform the optical as a domain
to work in because of the greatly reduced interstellar obscuration at these
wavelengths. This point has been reached at a time when theory, exploiting
flexible Monte Carlo methods, is fast becoming a powerful tool. In short we
have the complex phenomena, and the rise of the modelling capability to match
-- good data are the missing link.


title: XMM-Newton observations of the binary cluster system Abell 399/401

abstract:
  Abell 399 and Abell 401 are both rich clusters of galaxies, at temperatures
7.2keV and 8.5keV respectively. They lie at a projected separation of ~3Mpc,
forming a close pair. We have observed the system with the XMM-Newton
satellite. The data of each cluster show significant departures from our
idealised picture of relaxed rich clusters. There is also evidence for enhanced
X-ray flux in the region between the two, where the temperature is higher than
our expectations.
  Although tidal or compression effects might affect the large scale structure
of the two clusters, we show that these cannot account for the distortions seen
in the inner regions. We argue that the reasonably relaxed morphology of the
clusters, and the absence of major temperature anomalies, argues against models
in which the two have already experienced a close encounter. The properties of
the intermediate region suggests that they are at an early stage of merging,
and are currently interacting mildly, because their separation is still too
large for more dramatic effects. The substructure we find in their inner
regions seems to point to their individual merging histories. It seems likely
that in the Abell 399/401 system, we are witnessing two merger remnants, just
before they merge together to form a single rich cluster. This picture is
consistent with recent numerical simulations of cluster formation. (abridged)


title: Why a Single-Star Model Cannot Explain the Bipolar Nebula of Eta Carinae

abstract:
  I examine the angular momentum evolution during the 1837-1856 Great Eruption
of the massive star Eta Carinae. I find that the new estimate of the mass blown
during that eruption implies that the envelope of Eta Car substantially
spun-down during the 20 years eruption. Single-star models, most of which
require the envelope to rotate close to the break-up velocity, cannot account
for the bipolar nebula (the Homunculus) formed from matter expelled in that
eruption. The kinetic energy and momentum of the Homunculus further constrains
single-star models. I discuss how Eta Car can fit into a unified model for the
formation of bipolar lobes where two oppositely ejected jets inflate two lobes
(or bubbles). These jets are blown by an accretion disk, which requires stellar
companions in the case of bipolar nebulae around stellar objects.


title: CHANDRA Observations of V407 Vul: Confirmation of the Spin-up

abstract:
  V407 Vul is a candidate double-degenerate binary with a putative 1.756 mHz
(9.5 min) orbital frequency. In a previous timing study using archival ROSAT
and ASCA data we reported evidence for an increase of this frequency at a rate
consistent with expectations for gravitational radiation from a detached
ultracompact binary system. Here we report the results of new CHANDRA timing
observations which confirm the previous indications of spin-up of the X-ray
frequency, and provide much tighter constraints on the frequency derivative. We
obtained with CHANDRA a total of 90 ksec of exposure in two epochs separated in
time by 11.5 months. The total time span of the archival ROSAT, ASCA and new
CHANDRA data is now 10.5 years. This more than doubles the interval spanned by
the ROSAT and ASCA data alone, providing much greater sensitivity to a
frequency derivative. With the addition of the CHANDRA data an increasing
frequency is unavoidable, with a value df/dt = 7.0 x 10-18 Hz/s. Although a
long-term spin-up trend is confirmed, there is excess variance in the phase
timing residuals, perhaps indicative of shorter timescale torque fluctuations
or phase instability associated with the source of the X-ray flux. Power
spectral searches for periods longward of the 9.5 minute period do not find any
significant modulations, however, the sensitivity of searches in this frequency
range are somewhat compromised by the dithering of the Chandra attitude. The
observed spin-up is of a magnitude consistent with that expected from
gravitational radiation decay, however, the factor of 3 variations in flux
combined with the timing noise could conceivably result from accretion-induced
spin-up of a white dwarf. Continued monitoring to explore correlations of
torque with X-ray flux could provide a further test of this hypothesis.


title:
Study of Unidentified EGRET sources with INTEGRAL: first results and
  future prospects

abstract:
  The primary objective of the study of unidentified EGRET sources with
INTEGRAL is to locate with a few arcminute accuracy the hard X-ray / soft
gamma-ray counterparts within the EGRET error circle or to determine upper
limits on their emission in the INTEGRAL energy range. The INTEGRAL Galactic
Plane Scan (GPS) and Galactic Centre Deep Exposure (GCDE) data have been
analysed and cross-correlated with the EGRET 3^rd Catalogue to search for
counterparts of EGRET sources. The IBIS detection of a source within the EGRET
error circle of 3EG J1736-2908 is presented and its possible identification
with the active galaxy GRS 1734-292 is discussed. Finally, preliminary results
on the cross-correlation between EGRET unidentified sources and the first data
from the IBIS survey of the Galactic Centre are presented.


title:
The Peak Energy Distribution of the nu F_nu Spectra and the Implications
  for the Jet Structure Models of Gamma-Ray Bursts

abstract:
  We study the peak energy ($E_{\rm{p}}$) distribution of the $\nu F_{\nu}$
spectra of gamma-ray bursts (GRBs) and X-ray flashes (XRFs) with a sample of 57
bursts observed by {\em High Energy Transient Explorer 2} ({\em HETE-2}) French
Gamma Telescope and discuss its implications for the jet structure models.
Combining the observed $E_{\rm{p}}$ distribution of {\em HETE--2} GRBs/XRFs
with that of BATSE GRBs, we find that the observed $E_{\rm{p}}$ distribution of
GRBs/XRFs is a bimodal one with peaks of $\lesssim 30$ keV and $\sim 160-250$
keV. According to the recently-discovered equivalent-isotropic
energy-$E_{\rm{p}}$ relationship, such a bimodal distribution implies a
two-component structure of GRB/XRF jets. A simple simulation analysis shows
that this structured jet model does roughly reproduce a bimodal distribution
with peaks of $\sim 15$ and $\sim 200$ keV. We argue that future observations
of the peak of $\sim 15$ keV in the $E_{\rm{p}}$ distribution would be evidence
supporting this model. {\em Swift}, which covers an energy band of 0.2--150
keV, is expected to provide a key test for our results.


title: Viscous Shear Instability in Weakly Magnetized, Dilute Plasmas

abstract:
  When the ion mean free path much exceeds the Larmor radius in a plasma, the
viscous stress tensor is altered dramatically, and depends only upon quantities
measured along the field lines. This regime corresponds to typical interstellar
medium conditions in galaxies and protogalaxies, even if the magnetic field is
extremely weak, with a negligible Lorentz force on all scales of interest. In
this work, the only role of the magnetic field is to channel angular momentum
transport along its lines of force. We show that differential rotation in such
a gas is highly unstable, with a maximum growth rate exceeding that of the
magnetorotational instability. The regime of interest has been treated
previously by plasma kinetic methods. Where there is overlap, our work appears
to be in agreement with the kinetic results. The nonlinear outcome of this
instability is likely to be a turbulent process, significantly augmenting the
magnetorotational instability, and important to the initial phases of the
amplification of small galactic magnetic fields.


title: The Search for AGN in Distant Galaxy Clusters

abstract:
  We are undertaking the first systematic study of the prevalence of AGN
activity in a large sample of high redshift galaxy clusters. Local clusters
contain mainly red elliptical galaxies, and have little or no luminous AGN
activity. However, recent studies of some moderate to high redshift clusters
have revealed significant numbers of luminous AGN within the cluster. This
effect may parallel the Butcher-Oemler effect - the increase in the fraction of
blue galaxies in distant clusters compared to local clusters. Our aim is to
verify and quantify recent evidence that AGN activity in dense environments
increases with redshift, and to evaluate the significance of this effect. As
cluster AGN are far less prevalent than field sources, a large sample of over
120 cluster fields at z > 0.1 has been selected from the Chandra archives and
is being analysed for excess point sources. The size of the excess, the radial
distribution and flux of the sources and the dependence of these on cluster
redshift and luminosity will reveal important information about the triggering
and fueling of AGN.


title: Weak lensing of the high redshift SNIa sample

abstract:
  The current sample of high-redshift Supernova Type Ia, which combines results
from two teams, High-z Supernova Search Team and Supernova Cosmology Project,
is analyzed for the effects of weak lensing. After correcting SNe magnitudes
for cosmological distances, assuming recently published, homogeneous distance
and error estimates, we find that brighter SNe are preferentially found behind
regions (5-15 arcmin radius) which are overdense in foreground, z~0.1 galaxies.
This is consistent with the interpretation that SNe fluxes are magnified by
foreground galaxy excess, and demagnified by foreground galaxy deficit,
compared to a smooth Universe case. The difference between most magnified and
most demagnified SNe is about 0.3-0.4 mag. The effect is significant at >99%
level. Simple modeling reveals that the slope of the relation between SN
magnitude and foreground galaxy density depends on the amount and distribution
of matter along the line of sight to the sources, but does not depend on the
specifics of the galaxy biasing scheme.


title:
Canals beyond Mars: Beam depolarization in radio continuum maps of the
  warm ISM

abstract:
  Multi-frequency radio polarimetric observations of the diffuse Galactic
synchrotron background enable us to study the structure of the diffuse ionized
gas via rotation measure maps. However, depolarization will introduce artifacts
in the resulting rotation measure, most notably in the form of narrow,
elongated ``depolarization canals''. We use numerical models of a non-emitting
Faraday rotating medium to study the RM distribution needed to create
depolarization canals by depolarization due to a finite beam width, and to
estimate the influence of this depolarization mechanism on the determination of
RM. We argue that the depolarization canals indeed can be caused by beam
depolarization, which in turn is a natural consequence when observing a
turbulent medium with limited resolution. Furthermore, we estimate that beam
depolarization can induce an additional error of about 20% in RM
determinations, and considerably less in regions that are not affected by
depolarization canals.


title: A Far-Ultraviolet Spectroscopic Survey of Low-Redshift AGN

abstract:
  Using the Far Ultraviolet Spectroscopic Explorer (FUSE) we have obtained 87
spectra of 57 low-redshift (z<0.15) active galactic nuclei (AGN). This sample
comprises 53 Type 1 AGN and 4 Type 2. All the Type 1 objects show broad O VI
1034 emission; two of the Type 2s show narrow O VI emission. In addition to O
VI, we also identify emission lines due to C III 977, N III 991, S IV
1062,1072, and He II 1085 in many of the Type-1 AGN. Of the Type 1 objects, 30
show intrinsic absorption by the O VI 1032,1038 doublet. Most of these
intrinsic absorption systems show multiple components with intrinsic widths of
100 km/s spread over a blue-shifted velocity range of less than 1000 km/s.
Galaxies in our sample with existing X-ray or longer wavelength UV observations
also show C IV absorption and evidence of a soft X-ray warm absorber. In some
cases, a UV absorption component has physical properties similar to the X-ray
absorbing gas, but in others there is no clear physical correspondence between
the UV and X-ray absorbing components. Models in which a thermally driven wind
evaporates material from the obscuring torus naturally produce such
inhomogeneous flows.


title:
Radiative Processes, Spectral States and Variability of Black-Hole
  Binaries

abstract:
  We review radiative processes responsible for X-ray emission in hard (low)
and soft (high) spectral states of black-hole binaries. The main process in the
hard state appears to be scattering of blackbody photons from a cold disk by
thermal electrons in a hot inner flow, and any contribution from nonthermal
synchrotron emission is at most small. In the soft states, blackbody disk
emission dominates energetically, and its high-energy tail is due to scattering
by hybrid, thermal/nonthermal electrons, probably in active regions above the
disk surface. State transitions appear to correspond to a variable inner radius
of the cold disk driven by changes of the accretion rate. The existence of two
accretion solutions, hot and cold, in a range of the accretion rate leads to
hysteresis in low-mass X-ray binaries.


title:
Spectroscopy of Candidate Members of the Eta Cha and MBM12 Young
  Associations

abstract:
  We present an analysis of candidate members of the Eta Cha and MBM 12A young
associations. For an area of 0.7 deg^2 toward Eta Cha, we have performed a
search for members of the association by combining JHK_s photometry from 2MASS
and i photometry from DENIS with followup optical spectroscopy at Magellan
Observatory. We report the discovery of three new members with spectral types
of M5.25-M5.75, corresponding to masses of 0.13-0.08 M_sun by theoretical
evolutionary models. Two and three of these members were found independently by
Lyo and coworkers and Song and coworkers, respectively. Meanwhile, no brown
dwarfs were detected in Eta Cha down to the completeness limit of 0.015 M_sun.
For MBM 12A, we have obtained spectra of three of the remaining candidate
members that lacked spectroscopy at the end of the survey by Luhman, all of
which are found to be field M dwarfs. Ogura and coworkers have recently
presented four "probable" members of MBM 12A. However, two of these objects
were previously classified as field dwarfs by the spectroscopy of Luhman. In
this work, we find that the other two objects are field dwarfs as well.


title: UV and X-ray Observations of Mass Outflows in AGN

abstract:
  More than half of all low-redshift AGN exhibit UV and X-ray absorption by
highly ionized gas. The observed UV and X-ray absorption lines are almost
always blue-shifted at velocities of hundreds of km/s, indicating that the
absorbing gas is outflowing from the active nucleus. In some cases the inferred
mass flux rivals the Eddington limit of the central black hole, an indication
that these outflows are intimately related to the mass accretion and energy
generation mechanism in AGN. The ejected material can also have an affect on
the interstellar medium of the host galaxy and the surrounding intergalactic
medium. Over the past several years, coordinated UV and X-ray observations of
several bright AGN at high spectral resolution using HST, FUSE, Chandra, and
XMM-Newton have contributed greatly to our understanding of these outflows. I
will give an overview of these recent observations, summarize our {\it FUSE}
survey of low-redshift AGN, and interpret the results in the context of models
of winds from accretion disks and thermally driven winds from the obscuring
torus.


title:
Separated at Birth: The origin of the pulsars B2020+28 and B2021+51 in
  the Cygnus Superbubble

abstract:
  High precision astrometric data have enabled us to determine the trajectories
through the Galactic potential for a growing number of pulsars. This has
resulted in the discovery of a pulsar pair (B2020+28 and B2021+51) that has a
common origin in the Cygnus Superbubble or in one of its related OB
associations at an epoch which is comparable with the spin-down ages of the
pulsars. Analysis of the Galactic orbits indicates that the progenitors of the
pulsars had similar masses and were in a binary system, which was disrupted
after the second supernova explosion. The implied pulsar birth velocities are
consistent with the high velocities of neutron stars in general. The initial
spin period of the pulsar that was formed in the second supernova explosion was
approximately 200 ms. A further increase in astrometric accuracy will allow us
to more tightly constrain the birth velocities and the kick velocities that
were imparted by the two respective supernova explosions. Two additional
pulsars in the sample of 24 with parallax measurements may also have originated
in the Cygnus Superbubble.


title: The case for dynamical dark energy revisited

abstract:
  We investigate the behaviour of dark energy using the recently released
supernova data of Riess et al ~(2004) and a model independent parameterization
for dark energy (DE). We find that, if no priors are imposed on $\Omega_{0m}$
and $h$, DE which evolves with time provides a better fit to the SNe data than
$\Lambda$CDM. This is also true if we include results from the WMAP CMB data.
  From a joint analysis of SNe+CMB, the best-fit DE model has $w_0 < -1$ at the
present epoch and the transition from deceleration to acceleration occurs at
$z_T = 0.39 \pm 0.03$. However, DE evolution becomes weaker if the $\Lambda$CDM
based CMB results $\Omega_{0m} = 0.27 \pm 0.04$, $h = 0.71 \pm 0.06$ are
incorporated in the analysis. In this case, $z_T = 0.57 \pm 0.07$. Our results
also show that the extent of DE evolution is sensitive to the manner in which
the supernova data is sampled.


title:
Cosmological parameters sigma_8, the baryon density, and the UV
  background intensity from a calibrated measurement of H I Lyman-alpha
  absorption at z = 1.9

abstract:
  We identify a concordant model for the intergalactic medium (IGM) at redshift
z=1.9 that uses popular values for cosmological and astrophysical parameters
and accounts for all baryons with an uncertainty of 6%. We have measured the
amount of absorption, DA, in the Ly-alpha forest at redshift 1.9 in spectra of
77 QSO from the Kast spectrograph. We calibrated the continuum fits with
realistic artificial spectra, and we found that averaged over all 77 QSOs the
mean continuum level is within 1-2% of the correct value. Absorption from all
lines in the Ly-alpha forest at z=1.9 removes DA=15.1 +/- 0.7% of the flux
between 1070 and 1170 (rest) Angstroms. This is the first measurement using
many QSOs at this z, and the first calibrated measurement at any redshift.
Metal lines absorb 2.3 +/- 0.5%, and LLS absorb 1.0 +/- 0.4% leaving 11.8 +/-
1.0% from the lower density bulk of the IGM. Averaging over Delta z=0.1 or 154
Mpc, the dispersion is 6.1 +/- 0.3% including LLS and metal lines, or 3.9
(+0.5, -0.7)% for the lower density IGM alone, consistent with the usual
description of large scale structure. LLS and metal lines are major
contributors to the variation in the mean flux, and they make the flux field
significantly non-Gaussian. We find that a hydrodynamic simulation on a 1024
cubed grid in a 75.7 Mpc box reproduces the observed DA from the low density
IGM with parameters values H_o=71 km/s/Mpc, Omega_Lambda=0.73, Omega_m=0.27,
Omega_b=0.044, sigma_8=0.9 and a UV background that has an ionization rate that
is 1.08 +/- 0.08 times the prediction by Madau, Haardt & Rees (1999).


title:
Free-Free Spectral Energy Distributions of Hierarchically Clumped HII
  Regions

abstract:
  In an effort to understand unusual power-law spectral slopes observed in some
hypercompact HII regions, we consider the radio continuum energy distribution
from an ensemble of spherical clumps. An analytic expression for the free-free
emission from a single spherical clump is derived. The radio continuum slope
(with F_\nu \nu^\alpha) is governed by the population of clump optical depths
N(tau), such that (a) at frequencies where all clumps are thick, a continuum
slope of +2 is found, (b) at frequencies where all clumps are optically thin, a
flattened slope of -0.11 is found, and (c) at intermediate frequencies, a
power-law segment of significant bandwidth with slopes between these two
limiting values can result. For the ensemble distribution, we adopt a power-law
distribution N(tau) tau^{-\gamma}, and find that significant power-law segments
in the SED with slopes from +2 to -0.11 result only for a relatively restricted
range of $\gamma$ values of 1 to 2. Further, a greater range of clump optical
depths for this distribution leads to a wider bandwidth over which the
intermediate power-law segment exists. The model is applied to the source
W49N-B2 with an observed slope of \alphab +0.9, but that may be turning over to
become optically thin around 2 mm. An adequate fit is found in which most
clumps are optically thin and there is little shadowing of rearward clumps by
foreground clumps (i.e., the geometrical covering factor C<<1). The primary
insight gained from our study is that in the Rayleigh-Jeans limit for the
Planck function that applies for the radio band, it is the distribution in
optical depth of the clump population that is solely responsible for setting
the continuum shape, with variations in the size and temperature of clumps
serving to modulate the level of free-free emission.


title: 3D simulations of viscous dissipation in the intracluster medium

abstract:
  We present three-dimensional simulations of viscous dissipation of AGN
induced gas motions and waves in clusters of galaxies. These simulations are
motivated by recent detections of ripples in the Perseus and Virgo clusters.
Although the sound waves generated by buoyant bubbles decay with distance from
the cluster center, we show that these waves can contribute substantially to
offsetting the radiative cooling at distances significantly exceeding the
bubble size. The energy flux of the waves declines more steeply with radius
than the inverse-square law predicted by energy conservation, implying that
dissipation plays an important role in tapping the wave energy. We show that
such dispersing sound waves/weak shocks are detectable as ripples on
unsharp-masked X-ray cluster maps, and point out that the interfaces between
the intracluster medium and old bubbles are also clearly detectable in
unsharp-masked X-ray maps. This opens up the possibility of detecting fossil
bubbles that are difficult to detect in radio emission. This mode of heating is
consistent with other observational constraints, such as the presence of cool
rims around the bubbles and the absence of strong shocks. Thus, the mechanism
offers a way of heating clusters in a spatially distributed and gentle fashion.
We also discuss the energy transfer between the central AGN and the surrounding
medium. In our numerical experiments, we find that roughly 65 per cent of the
energy injected by the AGN is transferred to the intracluster medium and
approximately 25 percent of the injected energy is dissipated by viscous
effects and contributes to heating of the gas. The overall transfer of heat
from the AGN to the gas is comparable to the radiative cooling losses. The
simulations were performed with the FLASH adaptive mesh refinement code.


title: Chandra Low Energy Transmission Grating Spectrum of SS Cygni in Outburst

abstract:
  We have fitted the Chandra Low Energy Transmission Grating spectrum of SS
Cygni in outburst with a single temperature blackbody suffering the
photoelectric opacity of a neutral column density and the scattering opacity of
an outflowing wind. We find that this simple model is capable of reproducing
the essential features of the observed spectrum with the blackbody temperature
T_bl = 250+/-50 kK, hydrogen column density N_H = 5.0^{+2.9}_{-1.5} x 10^{19}
cm^{-2}, fractional emitting area f = 5.6^{+60}_{-4.5} x 10^{-3}, boundary
layer luminosity L_bl = 5^{+18}_{-3} x 10^{33} erg/s, wind velocity v ~ 2500
km/s, wind mass-loss rate Mdot_w ~ 1.1 x 10^{16} g/s, and arbitrary values of
the wind ionization fractions of 20 ions of O, Ne, Mg, Si, S, and Fe. Given
that in outburst the accretion disk luminosity L_disk ~ 1 x 10^{35} erg/s,
L_bl/L_disk ~ 0.05^{+0.18}_{-0.03}, which can be explained if the white dwarf
(or an equatorial belt thereon) is rotating with an angular velocity Omega_wd ~
0.7^{+0.1}_{-0.2} Hz, hence V_rot sin i ~ 2300 km/s.


title:
Blazar Counterparts for 3EG Sources at -40 < decl. < 0: Pushing South
  Through the Bulge

abstract:
  Supplementing existing survey data with VLA observations, we have extended
$\gamma-$ray counterpart identifications down to decl. = -40$^\circ$ using our
Figure of Merit approach. We find blazar counterparts for $\sim$ 70% of EGRET
sources above decl. = -40$^\circ$ away from the Galaxy. Spectroscopic
confirmation is in progress, and spectra for $\sim$ two dozen sources are
presented here. We find evidence that increased exposure in the bulge region
allowed EGRET to detect relatively faint blazars; a clear excess of non-blazar
objects in this region however argues for an additional (new) source class.


title: Compton Thick AGN: the dark side of the X-ray background

abstract:
  The spectrum of the hard X-ray background records the history of accretion
processes integrated over the cosmic time. Several pieces of observational and
theoretical evidence indicate that a significant fraction of the energy density
is obscured by large columns of gas and dust. The absorbing matter is often
very thick, with column densities exceeding N_H > 1.5 10^24 cm-2, the value
corresponding to unity optical depth for Compton scattering. These sources are
called ``Compton thick'' and appear to be very numerous, at least in the nearby
universe. Although Compton thick Active Galactic Nuclei (AGN) are thought to
provide an important contribution to the overall cosmic energy budget, their
space density and cosmological evolution are poorly known. The properties of
Compton thick AGN are reviewed here, with particular emphasis on their
contributions to the extragalactic background light in the hard X-ray and
infrared bands.


title: Relativistic gravitation theory for the MOND paradigm

abstract:
  The modified newtonian dynamics (MOND) paradigm of Milgrom can boast of a
number of successful predictions regarding galactic dynamics; these are made
without the assumption that dark matter plays a significant role. MOND requires
gravitation to depart from Newtonian theory in the extragalactic regime where
dynamical accelerations are small. So far relativistic gravitation theories
proposed to underpin MOND have either clashed with the post-Newtonian tests of
general relativity, or failed to provide significant gravitational lensing, or
violated hallowed principles by exhibiting superluminal scalar waves or an
\textit{a priori} vector field. We develop a relativistic MOND inspired theory
which resolves these problems. In it gravitation is mediated by metric, a
scalar field and a 4-vector field, all three dynamical. For a simple choice of
its free function, the theory has a Newtonian limit for nonrelativistic
dynamics with significant acceleration, but a MOND limit when accelerations are
small. We calculate the $\beta$ and $\gamma$ PPN coefficients showing them to
agree with solar system measurements. The gravitational light deflection by
nonrelativistic systems is governed by the same potential responsible for
dynamics of particles. To the extent that MOND successfully describes dynamics
of a system, the new theory's predictions for lensing by that system's visible
matter will agree as well with observations as general relativity's predictions
made with a dynamically successful dark halo model. Cosmological models based
on the theory are quite similar to those based on general relativity; they
predict slow evolution of the scalar field. For a range of initial conditions,
this last result makes it easy to rule out superluminal propagation of metric,
scalar and vector waves.


title: Looking for Cosmological Alfven Waves in WMAP Data

abstract:
  A primordial cosmological magnetic field induces and supports vorticity or
Alfven waves, which in turn generate cosmic microwave background (CMB)
anisotropies. A homogeneous primordial magnetic field with fixed direction
induces correlations between the $a_{l-1,m}$ and $a_{l+1,m}$ multipole
coefficients of the CMB temperature anisotropy field. We discuss the
constraints that can be placed on the strength of such a primordial magnetic
field using CMB anisotropy data from the WMAP experiment. We place 3 $\sigma$
upper limits on the strength of the magnetic field of $B < 15$ nG for vector
perturbation spectral index $n=-5$ and $B<1.7$ nG for $n=-7$.


title: Dynamical-Friction Galaxy-Gas Coupling and Cluster Cooling Flows

abstract:
  We revisit the notion that galaxy motions can efficiently heat intergalactic
gas in the central regions of clusters through dynamical friction. For
plausible values of the galaxy mass-to-light ratio, the heating rate is
comparable to the cooling rate due to X-ray emission. Heating occurs only for
supersonic galaxy motions, so the mechanism is self-regulating: it becomes
efficient only when the gas sound speed is smaller than the galaxy velocity
dispersion. We illustrate with the Perseus cluster, assuming a stellar
mass-to-light ratio for galaxies in the very central region with the
dark-matter contribution becoming comparable to this at some radius $r_s$. For
$r_s \la 400 {\rm kpc} \sim 3 r_{\rm cool}$--corresponding to an average
mass-to-light ratio of $\sim10$ inside that radius--the dynamical-friction
coupling is strong enough to provide the required rate of gas heating. The
measured sound speed is smaller than the galaxy velocity dispersion, as
required by this mechanism. With this smaller gas temperature and the observed
distribution of galaxies and gas, the energy reservoir in galactic motions is
sufficient to sustain the required heating rate for the lifetime of the
cluster. The galaxies also lose a smaller amount of energy through dynamical
friction to the dark matter implying that non--cooling-flow clusters should
have flat-cored dark-matter density distributions.


title: The Growth of HII Regions During Reionization

abstract:
  Recently, there has been a great deal of interest in understanding the
reionization of hydrogen in the intergalactic medium (IGM). One of the major
outstanding questions is how this event proceeds on large scales. Motivated by
numerical simulations, we develop a model for the growth of HII regions during
the reionization era. We associate ionized regions with large-scale density
fluctuations and use the excursion set formalism to model the resulting size
distribution. We then consider ways in which to characterize the morphology of
ionized regions. We show how to construct the power spectrum of fluctuations in
the neutral hydrogen field. The power spectrum contains definite features from
the HII regions that should be observable with the next generation of
low-frequency radio telescopes through surveys of redshifted 21 cm emission
from the reionization era. Finally, we also consider statistical descriptions
beyond the power spectrum and show that our model of reionization qualitatively
changes the distribution of neutral gas in the IGM.


title: Large scale bias and stochasticity of halos and dark matter

abstract:
  On large scales galaxies and their halos are usually assumed to trace the
dark matter with a constant bias and dark matter is assumed to trace the linear
density field. We test these assumption using several large N-body simulations
with 384^3-1024^3 particles and box sizes between 100-1000h/Mpc, which can both
resolve the small galactic size halos and sample the large scale fluctuations.
We explore the average halo bias relation as a function of halo mass and show
that existing fitting formulae overestimate the halo bias by up to 20% in the
regime just below the nonlinear mass. We propose a new expression that fits our
simulations well. We find that the halo bias is nearly constant, b~0.65-0.7,
for masses below one tenth of the nonlinear mass. We explore next the relation
between the initial and final dark matter in individual Fourier modes and show
that there are significant fluctuations in their ratio, ranging from 10% rms at
k~0.03h/Mpc to 50% rms at k~0.1h/Mpc. We argue that these large fluctuations
are caused by perturbative effects beyond the linear theory, which are
dominated by long wavelength modes with large random fluctuations. Similar or
larger fluctuations exist between halos and dark matter and between halos of
different mass. While these fluctuations are small compared to the sampling
variance, they are significant for attempts to determine the bias by relating
directly the maps of galaxies and dark matter or the maps of different galaxy
populations, which would otherwise be immune to sampling variance.


title: Reionization, SLOAN, and WMAP: is the Picture Consistent?

abstract:
  I show that advanced simulations of cosmological reionization are able to fit
the observed data on the mean transmitted flux in the hydrogen Lyman-alpha line
at z~6. At the same time, posteriori models can be constructed that also
produce a large value (20%) for the Thompson scattering optical depth,
consistent with the WMAP measurements. Thus, it appears that a consistent
picture emerges in which early reionization (as suggested by WMAP) is complete
by z~6 in accord with the SLOAN data.


title: Galaxy Genesis -- unravelling the epoch of dissipation in the early disk

abstract:
  So how did the Galactic disk form and can the sequence of events ever be
unravelled from the vast stellar inventory? This will require that some of the
residual inhomogeneities from prehistory escaped the dissipative process at an
early stage. Fossil hunting to date has concentrated mostly on the stellar
halo, but a key source of information will be the thick disk. This is believed
to be a 'snap frozen' relic which formed during or shortly after the last major
epoch of dissipation, or it may have formed from infalling systems early in the
life of the Galaxy. As part of the KAOS Galaxy Genesis project, we explore the
early history of the halo and the thick disk by looking for discrete
substructures, either due to infall or in situ star formation, through chemical
tagging. This will require high signal to noise, echelle spectroscopy of up to
a million stars throughout the disk. Our program has a short-term and a
long-term goal.


title:
A Two Micron All-Sky Survey View of the Sagittarius Dwarf Galaxy: II.
  Swope Telescope Spectroscopy of M Giant Stars in the Dynamically Cold
  Sagittarius Tidal Stream

abstract:
  We present moderate resolution (~6 km/s) spectroscopy of 284 M giant
candidates selected from the Two Micron All Sky Survey photometry. Radial
velocities (RVs) are presented for stars mainly in the south, with a number
having positions consistent with association to the trailing tidal tail of the
Sagittarius (Sgr) dwarf galaxy. The latter show a clear RV trend with orbital
longitude, as expected from models of the orbit and destruction of Sgr. A
minimum 8 kpc width of the trailing stream about the Sgr orbital midplane is
implied by verified RV members. The coldness of this stream (dispersion ~10
km/s) provides upper limits on the combined contributions of stream heating by
a lumpy Galactic halo and the intrinsic dispersion of released stars, which is
a function of the Sgr core mass. The Sgr trailing arm is consistent with a
Galactic halo containing one dominant, LMC-like lump, however some lumpier
halos are not ruled out. An upper limit to the total M/L of the Sgr core is 21
in solar units. A second structure that roughly mimics expectations for
wrapped, leading Sgr arm debris crosses the trailing arm in the Southern
Hemisphere; however, this may also be an unrelated tidal feature. Among the <13
kpc M giants toward the South Galactic Pole are some with large RVs that
identify them as halo stars, perhaps part of the Sgr leading arm near the Sun.
The positions and RVs of Southern Hemisphere M giants are compared with those
of southern globular clusters potentially stripped from the Sgr system and
support for association of Pal 2 and Pal 12 with Sgr debris is found. Our
discussion includes description of a masked-filtered cross-correlation
methodology that achieves better than 1/20 of a resolution element RVs in
moderate resolution spectra.


title:
Gradient measure and extended self-similarity of the cosmic microwave
  background anisotropy

abstract:
  Using the WMAP cosmic microwave background data it is shown that collisions
between Alfven wave packets and the cascades generated by these collisions (the
Iroshnikov model) can determine the photon temperature fluctuations for
arcminute scales on the last scattering surface.


title:
Run-away formation of intermediate-mass black holes in dense star
  clusters

abstract:
  We consider spherical stellar clusters with a broad mass function and a
relaxation time short enough so that the segregation of massive stars toward
the centre occurs before they have time to evolve off the main sequence. The
relaxational and collisional dynamics of model clusters is followed with a
high-resolution Monte Carlo code. Stellar collisions are treated in a realistic
way, through the use of a outcome of a very large set of SPH simulations. We
find that, even in proto-galactic nuclei models with high velocity dispersions,
run-away growth of a very massive star (VMS, M>100 M_sun) occurs in all cases
when the core collapse time is shorter than the MS life time of massive stars,
i.e. 3 Myrs. The VMS is a likely progenitor for an intermediate-mass or massive
black hole (IMBH/MBH).


title:
Measurements of Primary and Atmospheric Cosmic-Ray Spectra with the
  BESS-TeV Spectrometer

abstract:
  Primary and atmospheric cosmic-ray spectra were precisely measured with the
BESS-TeV spectrometer. The spectrometer was upgraded from BESS-98 to achieve
seven times higher resolution in momentum measurement. We report absolute
fluxes of primary protons and helium nuclei in the energy ranges, 1-540 GeV and
1-250 GeV/n, respectively, and absolute flux of atmospheric muons in the
momentum range 0.6-400 GeV/c.


title: X-ray and optical coverage of 3EG J0616-3310 and 3EG J1249-8330

abstract:
  The limited angular resolution of gamma-ray telescopes prevents the straight
identification of the majority of the sources detected so far. This is
particularly true for the low latitude, probably galactic ones, only 10 % of
which has been identified. Most of the counterparts are Isolated Neutron Stars,
both radio-loud and radio-quiet, characterised by an extremely high value of
X-ray-to-optical flux ratio. The best way to search for INSs in the error boxes
of unidentified EGRET sources is to perform the X-ray coverage of the gamma-ray
field, followed by the optical characterization of each X-ray source. We
applied this procedure to two EGRET sources, which could belong to a local
galactic population: 3EG J0616-3310 and 3EG J1249-8330. Here we report on the
analysis of about 300 X-ray objects, as well as on their optical study.


title: Nucleosynthesis of 26Al in rotating Wolf-Rayet stars

abstract:
  The 26Al radionuclide can be detected through its decay emission line at
1.809 MeV, as was first observed by Mahoney et al. (1982). Since then, COMPTEL
on board of the CGRO satellite, performed a sky survey in this energy range,
and provided maps of the 26Al distribution in the Galaxy. These results
revealed that the main contributors to the synthesis of 26Al are most likely
the massive stars, which contribute through their winds (Wolf-Rayet stars) and
through their supernova explosion. Comparison between these observations (in
particular observations in localized regions such as the Vela region and the
Cygnus region) and the models available at that moment, showed however the need
for improvements from both theoretical and observational points of view, in
order to improve our understanding of the 26Al galactic distribution as well as
that of its synthesis. With the launch of the INTEGRAL satellite in October
2002, the observational part will hopefully be improved, and the construction
of better resolution maps at 1.809 MeV is one of the main aims of the mission.
  From a theoretical point of view, we need the most up-to-date predictions in
order to be able to interpret the forthcoming data. In this paper, we address
this latter part, and present new results for 26Al production by rotating
Wolf-Rayet stars and their contribution to the total amount observed in the
Galaxy.


title: X-ray emission lines from inhomogeneous stellar winds

abstract:
  It is commonly adopted that X-rays from O stars are produced deep inside the
stellar wind, and transported outwards through the bulk of the expanding matter
which attenuates the radiation and affects the shape of emission line profiles.
None of the existing models was able to fit the observationed lines
consistently. The possible caveat of these models was the assumption of a
smooth stellar wind. Motivated by the various evidences that the stellar winds
are in fact structured, we present a 2-D numerical model of a stochastic,
inhomogeneous wind. Small parcels of hot, X-ray emitting gas are permeated with
cool, absorbing wind material which is compressed into thin shell fragments.
Wind fragmentation alters the radiative transfer drastically, compared to
homogeneous models of the same mass-loss rate. X-rays produced deep inside the
wind, which would be totally absorbed in a homogeneous flow, can effectively
escape from a fragmented wind. The wind absorption becomes wavelength
independent if the individual fragments are optically thick. The X-ray line
profiles are flat-topped in the blue part and decline steeply in the red part
for the winds with short acceleration zone. For the winds where the
acceleration extends over significant distances, the lines can appear nearly
symmetric and only slightly blueshifted, in contrast to the skewed, triangular
line profiles typically obtained from homogeneous wind models of high optical
depth. We show that profiles from a fragmented wind model can reproduce the
observed line profiles from zeta Orionis.


title:
TIMMI2 and VLT-ISAAC Spectroscopy of Circumstellar Dust Disks - A
  Spatially Resolved 3.3 micron PAH Feature Around HD 100546

abstract:
  We present preliminary results of spectroscopic data obtained with the La
Silla 3.6m TIMMI2 and the VLT-ISAAC instruments. We have obtained 23 TIMMI2
N-band and 18 Q-band spectra for our total sample of 36 stars in March 2003 to
investigate the evolution of the grain properties in circumstellar disks. Our
sample consists of Herbig stars, T Tauri stars and Vega-like stars, some of
which have recently been identified to be members of nearby (<100 pc) stellar
associations. Silicate and Polycyclic Aromatic Hydrocarbon (PAH) emission
features are detected and the spatial resolution of TIMMI2 allowed to place
upper limits on the spatial extent of the emission. We also obtained ISAAC
L-band spectra of 4 well-studied disks. For the Herbig Be star HD 100546, we
detect spatially extended PAH emission at 3.3 micron which corresponds to a
source with radius 11 +/- 3 AU in this line.


title: Survival Rates and Consequences

abstract:
  To first order, the initial cluster luminosity function appears to be
universal. This means that the brightest young cluster in a galaxy can be
predicted from the total number of young clusters based purely on statistics.
This suggests that the physical processes responsible for the formation of
clusters are similar in a wide variety of galaxies, from mergers to quiescent
spirals. One possibility is that conditions for making young massive clusters
are globally present in mergers while only locally present in spirals (i.e., in
the spiral arms). However, understanding the destruction of clusters and the
accompanying survival rates is more important for understanding cluster
demographics than understanding their formation. This is because only about 1
in 1,000 clusters with mass greater than 10^4 M_odot will survive to become an
old globular cluster. In this paper we briefly review this basic framework and
then develop a toy model that allows us to begin to address several fundamental
questions. In particular, we demonstrate that young clusters in the Antennae
Galaxies have a high ``infant mortality'' rate, with roughly 90% of the
clusters being destroyed each decade of log(time). We also advocate the use of
an objective classification system for clusters, with the three parameters
being mass, age, and size.


title: On the mechanism of low-mass compact object formation

abstract:
  We suggest that low-mass compact objects (hadron stars, quark stars) with
$M<1 M_{\odot}$ can appear only due to fragmentation of rapidly rotating
proto-neutron stars. Such low-mass stars receive large kicks due to an
explosion of a lighter companion in a pair of fragments, or due to dynamical
ejection of one of the lighter components in the case when three bodies are
formed.
  As far as low-mass compact objects are expected to be slowly cooling in all
popular models of thermal evolution possible candidates are expected to be
found among hot high velocity sources.


title:
Two-dimensional structure of thin transonic discs: observational
  manifestations

abstract:
  We study the two-dimensional structure of thin transonic accretion discs in
the vicinity of a non-spinning black hole within the framework of
hydrodynamical version of the Grad-Shafranov equation. Our analysis focuses on
the region inside the marginally stable orbit (MSO), r < r_{ms}. We show that
all components of the dynamical force in the disc become significant near the
sonic surface and (especially) in the supersonic region. Under certain
conditions, the disc structure can be far from radial, and we review the
affected disc properties, in particular the role of the critical condition at
the sonic surface. Finally, we present a simple model aimed at explaining
quasi-periodical oscillations that have been observed in the infra-red and
X-ray radiation of the Galactic Centre.


title: HST Absolute Spectrophotometry of Vega from the Far-UV to the IR

abstract:
  The Space Telescope Imaging Spectrograph has measured the absolute flux for
Vega from 0.17-1.01 microns on the HST White Dwarf flux scale. These data are
saturated by up to a factor of 80 overexposure but retain linearity to a
precision of 0.2%, because the charge bleeds along the columns and is recovered
during readout of the CCD. The S/N per pixel exceeds 1000, and the resolution R
is about 500. A V magnitude of 0.026 +/- 0.008 is established for Vega; and the
absolute flux level is 3.46 x 10^{-9} erg cm^{-2} s^{-1} at 5556 A. In the
regions of Balmer and Paschen lines, the STIS equivalent widths differ from the
pioneering work of Hayes in 1985 but do agree with predictions of a Kurucz
model atmosphere, so that the STIS flux distribution is preferred to that of
Hayes. Over the full wavelength range, the model atmosphere calculation shows
excellent agreement with the STIS flux distribution and is used to extrapolate
predicted fluxes into the IR region. However, the IR fluxes are 2% low with
respect to the standard Vega model of Cohen. IUE data provide the extension of
the measured STIS flux distribution from 0.17 down to 0.12 microns. The STIS
relative flux calibration is based on model atmosphere calculations of pure
hydrogen WDs, while the Hayes flux calibration is based on the physics of
laboratory lamps and black body ovens. The agreement to 1% of these two
independent methods for determining the relative stellar flux distributions
suggests that both methods may be correct from 0.5-0.8 microns and adds
confidence to claims that the fluxes relative to 5500 A are determined to
better than 4% by the pure hydrogen WD models from 0.12 to 3 microns.


title: Ambient Interstellar Pressure and Superbubble Evolution

abstract:
  High ambient interstellar pressure is suggested as a possible factor to
explain the ubiquitous observed growth-rate discrepancy for supernova-driven
superbubbles and stellar wind bubbles. Pressures of P/k ~ 1e5 cm-3 K are
plausible for regions with high star formation rates, and these values are
intermediate between the estimated Galactic mid-plane pressure and those
observed in starburst galaxies. High-pressure components also are commonly seen
in Galactic ISM localizations. We demonstrate the sensitivity of shell growth
to the ambient pressure, and suggest that superbubbles ultimately might serve
as ISM barometers.


title:
Calibrating the Galaxy Halo - Black Hole Relation Based on the
  Clustering of Quasars

abstract:
  The observed number counts of quasars may be explained either by long-lived
activity within rare massive hosts, or by short-lived activity within smaller,
more common hosts. It has been argued that quasar lifetimes may therefore be
inferred from their clustering length, which determines the typical mass of the
quasar host. Here we point out that the relationship between the mass of the
black-hole and the circular velocity of its host dark-matter halo is more
fundamental to the determination of the clustering length. In particular, the
clustering length observed in the 2dF quasar redshift survey is consistent with
the galactic halo - black-hole relation observed in local galaxies, provided
that quasars shine at ~10-100% of their Eddington luminosity. The slow
evolution of the clustering length with redshift inferred in the 2dF quasar
survey favors a black-hole mass whose redshift-independent scaling is with halo
circular velocity, rather than halo mass. These results are independent from
observations of the number counts of bright quasars which may be used to
determine the quasar lifetime and its dependence on redshift. We show that if
quasar activity results from galaxy mergers, then the number counts of quasars
imply an episodic quasar lifetime that is set by the dynamical time of the host
galaxy rather than by the Salpeter time. Our results imply that as the redshift
increases, the central black-holes comprise a larger fraction of their host
galaxy mass and the quasar lifetime gets shorter.


title: Spectroscopic Confirmation of the Cl 1604 Supercluster at z~0.9

abstract:
  We present spectroscopic confirmation of the Cl 1604 supercluster at z~0.9.
Originally detected as two individual clusters, Cl 1604+4304 at z = 0.90 and Cl
1604+4321 at z = 0.92, which are closely separated in both redshift and sky
position, subsequent imaging revealed a complex of red galaxies bridging the
two clusters, suggesting that the region contained a large scale structure. We
have carried out extensive multi-object spectroscopy, which, combined with
previous measurements, provides ~600 redshifts in this area, including 230
confirmed supercluster members. We detect two additional clusters that are part
of this structure, Cl 1604+4314 at z = 0.87 and Cl 1604+4316 at z = 0.94. All
four have properties typical of local clusters, with line-of-sight velocity
dispersions between 489 and 962 km/s. The structure is significantly extended
in redshift space, which, if interpreted as a true elongation in real space,
implies a depth of 93 Mpc. We examine the spatial and redshift distribution of
the supercluster members.


title:
Variable Stars in the Archival HST Data of Globular Clusters M13, M30
  and NGC 6712

abstract:
  We have analyzed archival HST/WFPC2 time-series data of the central parts of
globular clusters M13, M30 and NGC 6712 in search of variable objects. Among a
total of 21 identified variables there are 15 new discoveries. The sample
includes nine RR Lyr stars, two SX Phe stars and seven W UMa-type contact
binaries. One object is preliminarily classified as a detached eclipsing binary
and another as an ellipsoidal variable.


title:
A Preliminary Observational Search for Circumbinary Disks Around
  Cataclysmic Variables

abstract:
  Circumbinary (CB) disks have been proposed as a mechanism to extract orbital
angular momentum from cataclysmic variables (CVs) during their evolution. As
proposed by Taam & Spruit, these disks extend outwards to several a.u. and
should be detected observationally via their infrared flux or by absorption
lines in the ultraviolet spectra of the CV. We have made use of archival
HST/STIS spectra as well as our own near-IR imaging to search for observational
evidence of such CB disks in seven CVs. Based on the null result, we place an
upper limit on the column density of the disk of N_H~10^17 cm^-2.


title:
Detection of the Intrinsic Size of Sagittarius A* through Closure
  Amplitude Imaging (includes Online Supporting Material)

abstract:
  We have detected the intrinsic size of Sagittarius A*, the Galactic Center
radio source associated with a supermassive black hole, showing that the
short-wavelength radio emission arises from very near the event horizon of the
black hole. Radio observations with the Very Long Baseline Array show that the
source has a size of $24 \pm 2$ Schwarzschild radii at 7 mm wavelength. In one
of eight 7-mm epochs we also detect an increase in the intrinsic size of
$60^{+25}_{-17}$%. These observations place a lower limit to the mass density
of Sgr A* of $1.4\times10^{4}$ solar masses per cubic astronomical unit.


title: Enhanced cooling of neutron stars via Cooper-pairing neutrino emission

abstract:
  We simulate cooling of superfluid neutron stars with nucleon cores where
direct Urca process is forbidden. We adopt density dependent critical
temperatures $T_{cp}(\rho)$ and $T_{cn}(\rho)$ of singlet-state proton and
triplet-state neutron pairing in a stellar core and consider a strong proton
pairing (with maximum $T_{cp}^{max} \ga 5 \times 10^9$ K) and a moderate
neutron pairing ($T_{cn}^{max} \sim 6 \times 10^8$ K). When the internal
stellar temperature $T$ falls below $T_{cn}^{max}$, the neutrino luminosity
$L_{CP}$ due to Cooper pairing of neutrons behaves $\propto T^8$, just as that
produced by modified Urca process (in a non-superfluid star) but is higher by
about two orders of magnitude. In this case the Cooper-pairing neutrino
emission acts like an enhanced cooling agent. By tuning the density dependence
$T_{cn}(\rho)$ we can explain observations of cooling isolated neutron stars in
the scenario in which direct Urca process or similar process in kaon/pion
condensed or quark matter are absent.


title: A Population of Massive Globular Clusters in NGC 5128

abstract:
  We present velocity dispersion measurements of 14 globular clusters in NGC
5128 (Centarus A) obtained with the MIKE echelle spectrograph on the 6.5m
Magellan Clay telescope. These clusters are among the most luminous globular
clusters in NGC 5128 and have velocity dispersions comparable to the most
massive clusters known in the Local Group, ranging from 10 - 30 km/s. We
describe in detail our cross-correlation measurements, as well as simulations
to quantify the uncertainties. These 14 globular clusters are the brightest NGC
5128 globular clusters with surface photometry and structural parameters
measured from the Hubble Space Telescope. We have used these measurements to
derive masses and mass-to-light ratios for all of these clusters and establish
that the fundamental plane relations for globular clusters extend to an order
of magnitude higher mass than in the Local Group. The mean mass-to-light ratio
for the NGC 5128 clusters is ~3+/-1, higher than measurements for all but the
most massive Local Group clusters. These massive clusters begin to bridge the
mass gap between the most massive star clusters and the lowest-mass galaxies.
We find that the properties of NGC 5128 globular clusters overlap quite well
with the central properties of nucleated dwarf galaxies and ultracompact dwarf
galaxies. As six of these clusters also show evidence for extratidal light, we
hypothesize that at least some of these massive clusters are the nuclei of
tidally stripped dwarfs.


title: Photon Bubbles in Young Massive Stars

abstract:
  Spectroscopic studies indicate that gas in the photospheres of young O stars
moves at speeds up to the sound speed. We show, using two-dimensional radiation
MHD calculations and results from a local linear analysis, that the motions may
be due to photon bubble instability if young O stars have magnetic fields.


title:
Cold Neutral Gas in a z=4.2 Damped Lyman-alpha System: The Fuel for Star
  Formation

abstract:
  We discuss interstellar temperature determinations using the excitation
equilibrium of the ^2P levels of Si II and C II. We show how observations of
the ^2P_3/2 fine structure levels of Si II and C II (which have significantly
different excitation energies, corresponding to ~413 and 92 K, respectively)
can be used to limit gas kinetic temperatures. We apply this method to the
z=4.224 damped Lyman-alpha system toward the quasar PSS1443+27. The lack of
significant absorption out of the SiII ^2P_3/2 level and the presence of very
strong C II ^2P_3/2 provides an upper limit to the temperature of the C
II*-bearing gas in this system. Assuming a solar Si/C ratio, the observations
imply a 2-sigma limit T<954 K for this absorber; a super-solar Si/C ratio gives
stricter limits, T<524 K. The observations suggest the presence of a cold
neutral medium; such cold gas may serve as the fuel for star formation in this
young galaxy.


title: Action Model of Infall into the Virgo Cluster

abstract:
  The observed infall of galaxies into the Virgo Cluster puts strong
constraints on the mass of the cluster. A non-parametric fully non-linear
description of the infall can be made with orbit reconstructions based on
Numerical Action Methods. The mass of the cluster is determined to be $1.2
\times 10^{15} M_{\odot}$. The mass-to-light ratio for the cluster is found to
be seven times higher than the mean ratio found across the region within V=3000
km/s.


title:
VLBA Astrometry of Compact Radio Sources in the Spitzer First-Look
  Survey

abstract:
  The NRAO Very Long Baseline Array (VLBA) was used at 1.4 GHz to image 20
compact sources in the inner 1-degree radius of the Spitzer VLA First-Look
Survey. Twelve sources were detected with the VLBA, with peak flux densities
above 2 mJy at 9-mas resolution. The positions of these VLBA detections have
been measured in the International Celestial Reference Frame (ICRF) to 1-sigma
accuracies of 8 mas East-West and 4 mas North-South. These positions can help
anchor ancillary data for the First-Look Survey to the ICRF and are being
reported quickly to the community.


title:
Formation and Collapse of Nonaxisymmetric Protostellar Cores in Planar
  Magnetic Molecular Clouds

abstract:
  We extend our earlier work on ambipolar diffusion induced formation of
protostellar cores in isothermal sheet-like magnetic interstellar clouds, by
studying nonaxisymmetric collapse for the physically interesting regime of
magnetically critical and supercritical model clouds ($\mui \geq 1$, where
$\mui$ is the initial mass-to-magnetic flux ratio in units of the critical
value for gravitational collapse). Cores that form in model simulations are
effectively triaxial, with shapes that are typically closer to being oblate,
rather than prolate. Infall velocities in the critical model ($\mui = 1$) are
subsonic; in contrast, a supercritical model ($\mui = 2$) has extended
supersonic infall that may be excluded by observations. For the magnetically
critical model, ambipolar diffusion forms cores that are supercritical ($\muc >
1$) and embedded within subcritical envelopes ($\muenv < 1$). Cores in our
models have density profiles that eventually merge into a near-uniform
background, which is suggestive of observed properties of cloud cores.


title:
Measuring the Slope of the Dust Extinction Law and the Power Spectrum of
  Dust Clouds Using Differentially-Reddened Globular Clusters

abstract:
  We present 3 methods for measuring the Galactic dust extinction law slope R_V
and a method for quantifying fine structure in dust clouds in the direction of
differentially-reddened globular clusters. We apply these methods to the low-
latitude globular cluster NGC4833 which displays variable extinction/reddening
about a mean <A_V> ~ 1. A set of Monte Carlo simulations is used to
characterize the efficacy of the methods. The essence of the first 2 methods is
to determine, for an assumed value of R_V, the relative visual extinction
delta(A_V) of each cluster horizontal branch (HB) star with respect to an
empirical HB locus; the locus is derived from the CMD of a subset of stars near
the cluster center in which differential reddening is small. A star-by-star
comparison of delta(A_V) from the (B-V,V) CMD with that from the (V-I,V) CMD is
used to find the optimal R_V. In the third method, R_V is determined by
minimizing the scatter in the HB in the (B-V, V) CMD after correcting the
photometry for extinction and reddening using the Schlegel et al. (1998) dust
maps. The weighted average of the results from 3 methods gives R_V = 3.0 +/-
0.4 for the dust towards NGC4833. The dust fine structure is quantified via the
difference, Delta(A_V)_ij = [delta(A_V)]_i - [delta(A_V)]_j, between pairs of
cluster HB stars (i,j) as a function of their angular separation r_ij. The
variance of Delta(A_V)_ij is found to have a power- law dependence on angular
scale: var(r) \propto r^(+0.9 +/- 0.1). This translates into an angular power
spectrum P(kappa) \propto kappa^(-1.9 +/- 0.1) for r ~ 1' - 5', where kappa =
1/r. The dust angular power spectrum on small scales (from optical data)
matches smoothly onto the larger-scale power spectrum derived from Schlegel et
al.'s far-infrared map of the dust thermal emission.


title:
A library of high resolution Kurucz spectra in the wavelength range 3000
  - 10000 AA

abstract:
  We present a library of 6410 synthetic spectra with resolution Lambda/dLambda
= 250,000 based on the revised Kurucz 1993 model atmospheres. The library
covers the wavelength range 3000 - 10,000 AA with 54 values of effective
temperature in the range 5250 - 50,000 K, 11 values of log surface gravity
between 0.0 and 5.0 and 19 metallicities in the range -5.0 to 1.0. We find
that, with a few caveats, the library compares well with both the original 20
AA Kurucz spectra and also with observed spectra. The library is intended for
use in population synthesis and physical parameterisation of stellar spectra.
We assess the suitability of the library for these tasks.


title:
Performance of a Low Noise Front-end ASIC for Si/CdTe Detectors in
  Compton Gamma-ray Telescope

abstract:
  Compton telescopes based on semiconductor technologies are being developed to
explore the gamma-ray universe in an energy band 0.1--20 MeV, which is not well
covered by the present or near-future gamma-ray telescopes. The key feature of
such Compton telescopes is the high energy resolution that is crucial for high
angular resolution and high background rejection capability. The energy
resolution around 1 keV is required to approach physical limit of the angular
resolution due to Doppler broadening. We have developed a low noise front-end
ASIC (Application-Specific Integrated Circuit), VA32TA, to realize this goal
for the readout of Double-sided Silicon Strip Detector (DSSD) and Cadmium
Telluride (CdTe) pixel detector which are essential elements of the
semiconductor Compton telescope. We report on the design and test results of
the VA32TA. We have reached an energy resolution of 1.3 keV (FWHM) for 60 keV
and 122 keV at 0 degree C with a DSSD and 1.7 keV (FWHM) with a CdTe detector.