title: The Helium-Rich Cataclysmic Variable ES Ceti

abstract:
  We report photometry of the helium-rich cataclysmic variable ES Ceti during
2001-2004. The star is roughly stable at V ~ 17.0 and has a light curve
dominated by a single period of 620 s, which remains measurably constant over
the 3 year baseline. The weight of evidence suggests that this is the true
orbital period of the underlying binary, not a "superhump" as initially
assumed. We report GALEX ultraviolet magnitudes, which establish a very blue
flux distribution (F_nu ~ nu^1.3), and therefore a large bolometric correction.
Other evidence (the very strong He II 4686 emission, and a ROSAT detection in
soft X-rays) also indicates a strong EUV source, and comparison to
helium-atmosphere models suggests a temperature of 130+-10 kK. For a distance
of 350 pc, we estimate a luminosity of (0.8-1.7)x10^34 erg/s, yielding a mass
accretion rate of (2-4)x10^-9 M_sol/yr onto an assumed 0.7 M_sol white dwarf.
This appears to be about as expected for white dwarfs orbiting each other in a
10 minute binary, assuming that mass transfer is powered by gravitational
radiation losses. We estimate mean accretion rates for other helium-rich
cataclysmic variables, and find that they also follow the expected M-dot ~
P_o^-5 relation. There is some evidence (the lack of superhumps, and the small
apparent size of the luminous region) that the mass transfer stream in ES Cet
directly strikes the white dwarf, rather than circularizing to form an
accretion disk.


title: The Fundamental Building Blocks of Galaxies

abstract:
  Most stars form in compact, dense embedded clusters with memberships ranging
from a dozen stars to many millions of stars. Embedded clusters containing more
than a few hundred stars also contain O stars that disrupt the nebula abruptly.
There are observational indications that the expulsion of gas from such
clusters may occur within, or even quicker than, a stellar crossing-time scale.
Because the star-formation efficiency is empirically deduced to be typically
lower than 40 per cent, such clusters are left severely out of dynamical
equilibrium with a super-virial velocity dispersion when they are exposed. As a
consequence, they expand drastically.
  The velocity dispersion of expanding star-burst clusters may achieve values
of a few tens km/s, which would have a significant impact on the stellar
velocity distribution function and therefore the morphology of a galaxy. An
application of these ideas to the vertical structure of the Milky Way (MW) disk
suggests that such popping star clusters may constitute the missing heat source
for understanding the age-velocity-dispersion relation. If the early MW disk
experienced a vigorous epoch of star formation then perhaps even the thick disk
may have formed from popping clusters. Thus we have an alternative hypothesis
to understanding thick disks which does not rely on, or may act in addition to,
sinking galaxy satellites or sinking cosmological sub-structures. The GAIA
mission will test this hypothesis by allowing the kinematical fields around
young clusters to be mapped to exquisite precision.


title:
A Catalog of Northern Stars With Annual Proper Motions Larger Than 0.15
  Seconds of Arc (LSPM catalog - North)

abstract:
  The LSPM-north catalog is a comprehensive list of 61,977 stars north of the
J2000 celestial equator that have proper motions larger than 0.15 seconds of
arc per year (local-background-stars frame). The catalog has been generated
primarily as a result of our systematic search for high proper motion stars in
the Digitized Sky Surveys using our SUPERBLINK software. At brighter
magnitudes, the catalog incorporates stars and data from the Tycho-2 Catalogue
and also, to a lesser extent, from the All-sky Compiled Catalogue of 2.5
million stars. The LSPM catalog expands considerably over the old Luyten (LHS,
NLTT) catalogs, superseding them for northern declinations. Corrections to the
local-background-stars proper motions have been calculated, and absolute proper
motions in the extragalactic frame are given. The catalog is estimated to be
over 99% complete at high Galactic latitudes (|b>15|), and over 90% complete at
low Galactic latitudes (|b<15|), down to a magnitude V=19.0, and has a limiting
magnitude V=21.0. All the northern stars listed in the LHS and NLTT catalogs
have been re-identified, and their positions, proper motions and magnitudes
re-evaluated. The catalog also lists a large number of completely new objects,
which promise to expand very significantly the census of red dwarfs, subdwarfs,
and white dwarfs in the vicinity of the Sun.


title: Nonlinear behavior of a non-helical dynamo

abstract:
  A three-dimensional numerical computation of magnetohydrodynamic dynamo
behavior is described. The dynamo is mechanically forced with a driving term of
the Taylor-Green type. The magnetic field development is followed from
negligibly small levels to saturated values that occur at magnetic energies
comparable to the kinetic energies. Though there is locally a helicity density,
there is no overall integrated helicity in the system. Persistent oscillations
are observed in the saturated state for not-too-large mechanical Reynolds
numbers, oscillations in which the kinetic and magnetic energies vary out of
phase but with no reversal of the magnetic field. The flow pattern exhibits
considerable geometrical structure in this regime. As the Reynolds number is
raised, the oscillations disappear and the energies become more nearly
stationary, but retain some unsystematically fluctuating turbulent time
dependence. The regular geometrical structure of the fields gives way to a more
spatially disordered distribution. The injection and dissipation scales are
identified and the different components of energy transfer in Fourier space are
analyzed, in particular in the context of clarifying the role played by
different flow scales in the amplification of the magnetic field.


title:
Structure and evolution of low-mass W UMa type systems -- II. with
  angular momentum loss

abstract:
  In a preceding paper, using Eggleton's evolution code we have discussed the
structure and evolution of low-mass W UMa type contact binaries without angular
momentum loss (AML). The models exhibit cyclic behavior about a state of
marginal contact on a thermal time-scale. Part of the time of each cycle is
spent in contact and part in a semi-detached state. According to observations,
W UMa systems suffer AML. We present the models of low-mass contact binaries
with AML due to gravitational wave radiation (GR) or magnetic stellar wind
(MSW) are presented. We find that gravitational radiation cannot prevent the
cyclic evolution of W UMa systems, and the effect of gravitational radiation on
the cyclic behavior of contact binary evolution is almost negligible. We also
find that the most likely AML mechanism for W UMa systems is magnetic braking,
and that magnetic braking effects can increase the period of the cyclic
evolution, and shorten the fraction of the time spent in the poor thermal
contact state. If W UMa stars do not undergo cyclic evolution, and their
angular momentum loss is caused simultaneously by MSW of both components, we
find that the value of the parameter, $\lambda$, should be taken a larger value
in comparison with those derived from observations of single stars. This
indicates that the AML efficiency in W UMa systems may be lowered in comparison
with non-contact stars because of the less mass contained in the convective
envelopes of the components in W UMa systems. If W UMa systems lose their
angular momentum at a constant rate. An angular momentum rate of $\frac{{\rm
dln}J}{{\rm d}t}\approx 1.6\times 10^{-9} {\rm yr^{-1}}$ can prevent the cyclic
behaviour of the model, and the model can keep in good contact with an
essentially constant depth of contact.


title:
Collisions among Clouds inside Dusty Torus in Active Galactic Nuclei:
  Observational Consequences

abstract:
  A geometrically thick dusty torus in NGC 1068 has been unambiguously resolved
by an infrared interferometry telescope. This implies clouds composing the
dusty torus are undergoing supersonic collisions with each other. We show that
the collisions form strong non-relativistic shocks, which accelerate
populations of relativistic electrons. Torus reprocesses emission from
accretion disk into infrared band. We show that the energy density of the
infrared photons inside the torus is much higher than that of the magnetic
field in the clouds and the seed photons of inverse Compton scattering are
mainly from the infrared ones. The maximum energy of the relativistic electrons
can reach a Lorentz factor of $10^5$. We calculate the spectrum of the
synchrotron and inverse Compton scattering radiation from the electrons in the
torus. The relativistic electrons in the torus radiate non-thermal emission
from radio to $\gamma$-ray, which isotropically diffuses in the region of the
torus. We find the most prominent character is a peak at $\sim 0.5-1$ GeV. We
apply this model to NGC 1068 and find that the observed radio emission from the
core component $S_1$ can be explained by the synchrotron emission from the
relativistic electrons. We predict that there is a $\gamma$-ray emission with a
luminosity of $10^{40}$ erg/s peaking at $\sim 1$ GeV from the torus, which
could be detected by {\em Gamma-Ray Large-Array Space Telescope} in the future.
This will provide a new clue to understand the physics in the torus. The
non-thermal radiation from dusty torus may explain the radio emission from
Seyfert galaxies. The cosmological implications of the non-thermal emission to
the $\gamma$-ray background radiation have been discussed.


title:
The Connection Between Jets, Accretion Disks, and Black Hole Mass in
  Blazars

abstract:
  The properties of relativistic radio jets are thought to be closely connected
with the properties of accretion disks in active galactic nuclei. We explore
this issue using a sample of 35 blazars with very-long baseline observations,
for which we can estimate the kinetic powers of their relativistic jets, the
bolometric luminosity of their accretion disks, and the masses of their black
holes. Contrary to previous claims, we find that the jet kinetic power is
significantly correlated with the disk luminosity. This supports the notion
that the disk is somehow coupled to the jet, even on parsec scales. Moreover,
we show that the correlation improves by including the black hole mass as a
second parameter. The dominance of the jet, parameterized as the ratio of the
jet kinetic power to the disk luminosity, is largely controlled by and is
inversely correlated with the Eddington ratio of the accretion disk. This
empirical relation should serve as a useful guide for theoretical models for
jet formation.


title:
Narrow Iron K$\alpha$ Lines in Active Galactic Nuclei: Evolving
  Populations?

abstract:
  We assemble a sample consisting of 66 active galactic nuclei (AGNs) from
literature and the {\em XMM-Newton} archive in order to investigate the origin
of the 6.4 keV narrow iron K$\alpha$ line (NIKAL). The X-ray Baldwin effect of
the NIKAL is confirmed in this sample. We find the equivalent width ($EW$) of
the NIKAL is more strongly inversely correlated with Eddington ratio ($\ce$)
than the 2-10 keV X-ray luminosity. Our sample favors the origin from the dusty
torus and the X-ray Baldwin effect is caused by the changing opening angle of
the dusty torus. The relation $EW-\ce$ can be derived from a toy model of the
dusty torus. If the unification scheme is valid in all AGNs, we can derive the
Baldwin effect from the fraction of type {\sc ii} AGNs to the total population
given by {\em Chandra} and {\em Hubble} deep surveys. Thus the evolution of
populations could be reflected by the NIKAL's Baldwin effect.


title: Discovery of a Large-scale Wall in the Direction of Abell 22

abstract:
  We report on the discovery of a large-scale wall in the direction of Abell
22. Using photometric and spectroscopic data from the Las Campanas Observatory
and Anglo-Australian Telescope Rich Cluster Survey, Abell 22 is found to
exhibit a highly unusual and striking redshift distribution. We show that Abell
22 exhibits a foreground wall-like structure by examining the galaxy
distributions in both redshift space and on the colour-magnitude plane. A
search for other galaxies and clusters in the nearby region using the 2dF
Galaxy Redshift Survey database suggests that the wall-like structure is a
significant large-scale, non-virialized filament which runs between two other
Abell clusters either side of Abell 22. The filament stretches over at least
>40 Mpc in length and 10 Mpc in width at the redshift of Abell 22.


title:
Dynamical Evolution and Galaxy Populations in the Cluster ABCG 209 at
  z=0.2

abstract:
  The thesis work is focused on the analysis of the galaxy clusters ABCG 209,
at z~0.2, which is characterized by a strong dynamical evolution. The data
sample used is based mainly on new optical data (EMMI-NTT: B, V and R band
images and MOS spectra), acquired in October 2001 at the European Southern
Observatory in Chile. Archive optical data (CFHR12k: B and R images), and X-ray
(Chandra) and radio (VLA) observations are also analysed. The main goal of the
present analysis is the investigation of the connection between internal
cluster dynamics and star formation history, aimed at understanding the complex
mechanisms of cluster formation and evolution. The analysis of the internal
dynamics of the cluster and the study of the galaxy luminosity function (LF)
suggest an observational scenario in which ABCG 209 is undergoing a strong
dynamical evolution with the merging of two or more subclumps along the SE-NW
direction in a plane which is not parallel to the plane of sky. The effect of
cluster environment on the global properties of the cluster galaxies is
examined through the analysis of the LFs, colour-magnitude relations, and
average colours.Moreover cluster dynamics and large-scale structure have a
strong influence on galaxy evolution, so it is performed a detailed study of
spectroscopic properties of 102 luminous member galaxies. All the results
support an evolutionary scenario in which ABCG 209 is characterized by a sum of
two components: an old galaxy population, formed very earlier (z >~ 3), and a
younger population of infalling galaxies. Moreover this cluster may have
experimented 1 or 2 Gyrs ago a merging with an infalling galaxy group, as
indicated also by the previous dynamical analysis.


title: Dusty plasmas on galactic scales

abstract:
  Interstellar dust is spread in galaxies over large scales, often far beyond
the stellar disks. Several mechanisms can be responsible for carrying the dust
both in the vertical and radial directions, producing in general different
spatial dust distributions. In spite of the small mass fraction dust can be in
some cases dynamically active, and its role in star formation process and
dynamics of shock waves is still not completely understood. In this review I
discuss briefly the issues connected with the large scale distribution of the
interstellar dust, the impact of the dust on star formation and on dynamics of
shock waves.


title: Discovering Interacting Binaries with Halpha Surveys

abstract:
  A deep (R ~ 19.5) photographic Halpha Survey of the southern Galactic Plane
was recently completed using the UK Schmidt Telescope at the AAO. In addition,
we have recently started a similar, CCD-based survey of the northern Galactic
Plane using the Wide Field Camera on the INT. Both surveys aim to provide
information on many types of emission line objects, such as planetary nebulae,
luminous blue variables and interacting binaries.
  Here, we focus specifically on the ability of Halpha emission line surveys to
discover cataclysmic variables (CVs). Follow-up observations have already
begun, and we present initial spectra of a candidate CV discovered by these
surveys. We also present results from analyzing the properties of known CVs in
the Southern Survey. By calculating the recovery rate of these objects, we
estimate the efficiency of Halpha-based searches in finding CVs.


title: LOFAR as a Probe of the Sources of Cosmological Reionisation

abstract:
  We propose use of the thickness of the ionisation front as a discriminant
between alternative modes of reionisation in the early universe, by stars or by
miniquasars. Assuming a photoionisation-recombination balance, we find that for
miniquasar sources the transition from neutral to ionised intergalactic medium
is extended and has two features. The first is a sudden steep increase in the
neutral fraction with a typical width of 5-10 comoving megaparsecs, depending
on the miniquasar power. The second feature is a long wing that represents a
much slower transition from neutral fraction of $\approx 0.8$ to 1. The angular
resolution of LOFAR is expected to resolve these scales and will, therefore,
play an important role in discriminating the hard sources of ionising photons
from the stellar ones.


title:
Extracting stellar parameters from observed spectra: the role of
  cross-correlation and minimum distance methods

abstract:
  One may consider cross-correlation routines applied to stellar spectra as a
way to determine not only the radial velocities but also to assess the
properties of stellar atmospheres. We show that this is not the case. High
value of the cross-correlation coefficient between the observed and a template
spectrum does not mean that the template corresponds to correct values of
stellar temperature, gravity or metallicity. Cross-correlation operates in
normalized space, so it is not sensitive to scaling or shifting of stellar
flux. It is argued that cross-correlation is useful to efficiently determine
the velocity shift between the observed and the template spectrum. But minimal
distance methods need to be used to determine which template gives the best
match to the observed spectrum, and so derive values of physical parameters. To
illustrate the point we use data from the RAVE project which are being obtained
at very similar spectral resolution and wavelength domain as will be the case
for GAIA's RVS.


title: Exploiting the neutronization burst of a galactic supernova

abstract:
  One of the robust features found in simulations of core-collapse supernovae
(SNe) is the prompt neutronization burst, i.e. the first $\sim 25$ milliseconds
after bounce when the SN emits with very high luminosity mainly $\nu_e$
neutrinos. We examine the dependence of this burst on variations in the input
of current SN models and find that recent improvements of the electron capture
rates as well as uncertainties in the nuclear equation of state or a variation
of the progenitor mass have only little effect on the signature of the
neutronization peak in a megaton water Cherenkov detector for different
neutrino mixing schemes. We show that exploiting the time-structure of the
neutronization peak allows one to identify the case of a normal mass hierarchy
and large 13-mixing angle $\theta_{13}$, where the peak is absent. The
robustness of the predicted total event number in the neutronization burst
makes a measurement of the distance to the SN feasible with a precision of
about 5%, even in the likely case that the SN is optically obscured.


title: The Transformation of Cluster Galaxies at Intermeidate Redshift

abstract:
  We combine imaging data from the Advanced Camera for Surveys (ACS) with
VLT/FORS optical spectroscopy to study the properties of star-forming galaxies
in the z=0.837 cluster CL0152-1357. We have morphological information for 24
star-forming cluster galaxies, which range in morphology from late-type and
irregular to compact early-type galaxies. We find that while most star-forming
galaxies have $r_{625}-i_{775}$ colors bluer than 1.0, eight are in the red
cluster sequence. Among the star-forming cluster population we find five
compact early-type galaxies which have properties consistent with their
identification as progenitors of dwarf elliptical galaxies. The spatial
distribution of the star-forming cluster members is nonuniform. We find none
within $R\sim 500$ Mpc of the cluster center, which is highly suggestive of an
intracluster medium interaction. We derive star formation rates from [OII]
$\lambda\lambda 3727$ line fluxes, and use these to compare the global star
formation rate of CL0152-1357 to other clusters at low and intermediate
redshifts. We find a tentative correlation between integrated star formation
rates and $T_{X}$, in the sense that hotter clusters have lower integrated star
formation rates. Additional data from clusters with low X-ray temperatures is
needed to confirm this trend. We do not find a significant correlation with
redshift, suggesting that evolution is either weak or absent between z=0.2-0.8.


title:
A robust sample of submillimetre galaxies: constraints on the prevalence
  of dusty, high-redshift starbursts

abstract:
  We develop and apply a dual-survey extraction technique to published submm
images of the Lockman Hole using the SCUBA and MAMBO bolometer arrays. Cut
above 5 sigma, this catalogue of submm galaxies (SMGs) is significantly more
robust than previous samples, typically selected above 3.0-3.5 sigma, with a
much-reduced likelihood of real, faint SMGs (beneath and around the confusion
limit) entering the catalogue via superposition with noise. Our selection
technique yields 19 SMGs of which we expect at most two to be due to chance
superposition of SCUBA and MAMBO noise peaks. The flux limit of the sample
(~5mJy at 0.85mm), which is sensitive to luminous, dusty galaxies at extreme
redshifts, is optimally matched to a deep 1.4-GHz image (4.6 uJy/beam rms)
which probes starbursts in the z<~4 regime. A high fraction of these robust
SMGs (~80%) have radio counterparts which, given the probable ~10%
contamination by spurious sources, suggests that very distant SMGs (z>~3-4) are
unlikely to make up more than ~10% of the bright SMG population. Finally, the
accurate radio positions are used to test the accuracy of positions determined
in the submm, with important implications for upcoming surveys with SCUBA-2.


title:
Coronal Seismology and the Propagation of Acoustic Waves Along Coronal
  Loops

abstract:
  We use a combination of analytical theory, numerical simulation, and data
analysis to study the propagation of acoustic waves along coronal loops. We
show that the intensity perturbation of a wave depends on a number of factors,
including dissipation of the wave energy, pressure and temperature gradients in
the loop atmosphere, work action between the wave and a flow, and the
sensitivity properties of the observing instrument. In particular, the scale
length of the intensity perturbation varies directly with the dissipation scale
length (i.e., damping length) and the scale lengths of pressure, temperature,
and velocity. We simulate wave propagation in three different equilibrium loop
models and find that dissipation and pressure and temperature stratification
are the most important effects in the low corona where the waves are most
easily detected. Velocity effects are small, and cross-sectional area
variations play no direct role for lines-of-sight that are normal to the loop
axis. The intensity perturbation scale lengths in our simulations agree very
well with the scale lengths we measure in a sample of loops observed by TRACE.
The median observed value is 4.35x10^9 cm. In some cases the intensity
perturbation increases with height, which is likely an indication of a
temperature inversion in the loop (i.e., temperature that decreases with
height). Our most important conclusion is that thermal conduction, the primary
damping mechanism, is accurately described by classical transport theory. There
is no need to invoke anomalous processes to explain the observations.


title: Binary formation within globular clusters : X-ray clues

abstract:
  We have investigated the effect of the number of primordial binaries on the
relationship between the total number of detected binaries within globular
cluster and its collision rate. We have used simulated populations of binary
stars in globular clusters : primordial binaries and binaries formed through
gravitational interactions. We show that the initial number of primordial
binaries influences the relationship between the number of detected sources and
the collision rate, which we find to be a power law. We also show that
observing an incomplete sample provides the same results as those obtained with
a complete sample. We use observations made by XMM-Newton and Chandra to
constrain the formation mechanism of sources with X-ray luminosities larger
than 10^{31} erg/s, and show that some of the cataclysmic variables within
globular clusters should be primordial objects. We point out a possibly hidden
population of neutron stars within high mass globular clusters with a low
collision rate.


title: New Physics In Clusters of Galaxy: A New Dark Matter Component ?

abstract:
  The latest cosmological observables analyses seem to converge to a concordant
view of the cosmological model: namely the power law Lambda-CDM. The recent
WMAP results comfort this new standard model. Nevertheless, some degeneracy in
the CMB physics do not allow one to exclude alternative models. A combined
analysis with other cosmological observations is thus needed. An example of
such work is shown here, focusing on the abundance of local clusters. The
latter is a traditional way to derive the amplitude of matter fluctuations, but
which suffers from a lack of accurate knowledge of their masses. Here we show
that the mass temperature relation can be specified for any cosmological model
from consistency arguments, removing most of this uncertainty. This allows to
obtain an estimation of the amplitude of matter fluctuations with an accuracy
of 5%. Quite remarkably, this amplitude can be also tightly constrained from
existing CMB measurements. However, the amplitude inferred in this way in a
concordance model (Lambda-CDM) is significantly larger than the value derived
from x-ray clusters. Such a discrepancy may reveal the existence of a new dark
component in the Universe. It may alternatively reveal a significant depletion
of the gas during the formation of clusters. In all cases, an essential element
of clusters formation history seems to be missing.


title:
GMOS Integral Field Spectroscopy of a Merging System with Enhanced
  Balmer Absorption

abstract:
  In this paper we present the three dimensional dynamics of the galaxy SDSS
J101345.39+011613.66, selected for its unusually strong Balmer absorption lines
(Wo(H-delta)=7.5A). Using the GMOS-South IFU in Nod & Shuffle mode we have
mapped the continuum and optical absorption lines of this z=0.1055 field
galaxy. This galaxy has a disturbed morphology, with a halo of diffuse material
distributed asymmetrically toward the north. Using the [OII] emission line
(Wo([OII])=4.1A) we find that the gas and hot OB stars are offset from the
older stars in the system. The gas also has a spatially extended and elongated
morphology with a velocity gradient of 100+/-20km/s across 6kpc in projection.
Using the strong H-gamma and H-delta absorption lines we find that the A- stars
are widely distributed across the system and are not centrally concentrated
arguing that the A-star population has formed in molecular clouds outside the
nucleus. By cross correlating the spectra from the datacube with an A-star
template we find evidence that the A-star population has a 40km/s shear in the
same direction as the gas. The disturbed morphology, strong colour gradients
and strong H-delta and H-gamma absorption lines in SDSS J101345.39 argue that
this is a recent tidal interaction/merger between a passive elliptical and
star-forming galaxy. Although based on a single object, these results show that
we can spatially resolve and constrain the dynamics of this short lived (yet
important) phase of galaxy formation in which the evolutionary process take
galaxies from star-forming to their quiescent end products.


title: Where Does The Dark Matter Begin?

abstract:
  While there is convincing evidence that the central regions (r<<Re) of
early-type galaxies are dominated by stars and that the outer regions (r>>Re)
are dominated by dark matter, the structure of early-type galaxies in the
transition region (a few effective radii, Re) between the stars and the dark
matter is unclear both locally and in gravitational lenses. Understanding the
structure of galaxies in this transition region is a prerequisite for
understanding dark matter halos and how they relate to the luminous galaxy.
Potentially the best probe of this region is the sample of ~80 strong
gravitational lenses. I review the determination of mass distributions using
gravitational lenses using image positions, statistics, stellar dynamics, time
delays and microlensing. While the present situation is confusing, there is
little doubt that the existing problems can be resolved by further
observations.


title: Light and Motion in the Local Volume

abstract:
  Using high-quality data on 149 galaxies within 10 megaparsecs (Mpc), I find
no correlation between luminosity and peculiar velocity at all. There is no
unequivocal sign on scales of 1-2 Mpc of the expected gravitational effect of
the brightest galaxies, in particular infall toward groups; or of infall toward
the Supergalactic Plane on any scale. Either dark matter is not distributed in
the same way as luminous matter in this region, or peculiar velocities are not
due to fluctuations in mass. The sensitivity of peculiar velocity studies to
the background model is highlighted.


title: Nuclear Input for Core-collapse Models

abstract:
  We review the nuclear physics input necessary for the study of the collapse
of massive stars as precursor to supernova explosions. Recent theoretical
advances for the calculation of the relevant weak-interaction processes and
their influence in the collapse and postbounce dynamics are discussed. Future
improvements are expected to come with the advent of radioactive ion-beam
facilities.


title: No cold dust within the supernova remnant Cassiopeia A

abstract:
  A large amount (about three solar masses) of cold (18 K) dust in the
prototypical type II supernova remnant Cassiopeia A was recently reported. It
was concluded that dust production in type II supernovae can explain how the
large quantities (10^8 solar masses) of dust observed in the most distant
quasars could have been produced within only 700 million years after the Big
Bang. Foreground clouds of interstellar material, however, complicate the
interpretation of the earlier submillimetre observations of Cas A. Here we
report far-infrared and molecular line observations that demonstrate that most
of the detected submillimetre emission originates from interstellar dust in a
molecular cloud complex located in the line of sight between the Earth and Cas
A, and is therefore not associated with the remnant. The argument that type II
supernovae produce copious amounts of dust is not supported by the case of Cas
A, which previously appeared to provide the best evidence for this possibility.


title:
Confirmation of Errors in Hipparcos Parallaxes from HST/FGS Astrometry
  of the Pleiades

abstract:
  We present absolute trigonometric parallaxes and relative proper motions for
three members of the Pleiades star cluster, obtained with HST's Fine Guidance
Sensor 1r, a white-light interferometer. We estimate spectral types and
luminosity classes of the stars comprising the astrometric reference frame from
R \approx 2,000 spectra, VJHK photometry, and reduced proper motions. From
these we derive estimates of absolute parallaxes and introduce them into our
model as observations with error. We constrain the three cluster members to
have a 1 sigma dispersion in distance less than 6.4 pc, and find an average
pi_{abs}=7.43+-0.17+-0.20 milliseconds of arc, where the second error is
systematic due to member placement within the cluster. This parallax
corresponds to a distance of 134.6+-3.1 pc or a distance modulus of
(m-M)=5.65+-0.05 for these three Pleiads, presuming a central location. This
result agrees with three other independent determinations of the Pleiades
distance. Presuming that the cluster depth systematic error can be
significantly reduced because of the random placement of these many members
within the cluster, these four independent measures yield a best-estimate
Pleiades distance of pi_{abs}=7.49+-0.07 milliseconds of arc, corresponding to
a distance of 133.5+-1.2 pc or a distance modulus of (m-M)=5.63+-0.02. This
resolves the dispute between the main sequence fitting and the Hipparcos
distance moduli in favor of main sequence fitting.


title:
A tensor formalism for transfer and Compton scattering of polarized
  light

abstract:
  A novel covariant formalism for the treatment of the transfer and Compton
scattering of partially polarized light is presented. This was initially
developed to aid in the computation of relativistic corrections to the
polarization generated by the Sunyaev-Zeldovich effect (demonstrated in a
companion paper), but it is of more general utility. In this approach, the
polarization state of a light beam is described by a tensor constructed from
the time average of quadratic products of the electric field components in a
local observer frame. This leads naturally to a covariant description which is
ideal for calculations involving the boosting of polarized light beams between
Lorentz frames, and is more flexible than the traditional Stokes parameter
approach in which a separate set of polarization basis vectors is required for
each photon. The covariant kinetic equation for Compton scattering of partially
polarized light by relativistic electrons is obtained in the tensor formalism
by a heuristic semi-classical line of reasoning. The kinetic equation is
derived first in the electron rest frame in the Thomson limit, and then is
generalized to account for electron recoil and allow for scattering from an
arbitrary distribution of electrons.


title: Kinetic theory of polarization in the Sunyaev-Zeldovich effect

abstract:
  We apply the coherency tensor formalism to the calculation of the spectral
distortions imprinted in the intensity and polarization of the cosmic microwave
background radiation due to the kinematic and thermal Sunyaev-Zeldovich effects
(SZE). We obtain the first relativistic corrections to the intensity produced
by the kinematic and thermal SZE, and the first correction to the polarization
magnitude due to electron thermal motion.


title:
How do Uncertainties in the Surface Chemical Abundances of the Sun
  Affect the Predicted Solar Neutrino Fluxes?

abstract:
  We show that uncertainties in the values of the surface heavy element
abundances of the Sun are the largest source of the theoretical uncertainty in
calculating the p-p, pep, 8B, 13N, 15O, and 17F solar neutrino fluxes. We
evaluate for the first time the sensitivity (partial derivative) of each solar
neutrino flux with respect to the surface abundance of each element. We then
calculate the uncertainties in each neutrino flux using `conservative
(preferred)' and `optimistic' estimates for the uncertainties in the element
abundances. The total conservative (optimistic) composition uncertainty in the
predicted 8B neutrino flux is 11.6% (5.0%) when sensitivities to individual
element abundances are used. The traditional method that lumps all abundances
into a single quantity (total heavy element to hydrogen ratio, Z/X) yields a
larger uncertainty, 20%. The uncertainties in the carbon, oxygen, neon,
silicon, sulphur, and iron abundances all make significant contributions to the
uncertainties in calculating solar neutrino fluxes; the uncertainties of
different elements are most important for different neutrino fluxes. The
uncertainty in the iron abundance is the largest source of the estimated
composition uncertainties of the important 7Be and 8B solar neutrinos. Carbon
is the largest contributor to the uncertainty in the calculation of the p-p,
13N, and 15O neutrino fluxes. However, for all neutrino fluxes, several
elements contribute comparable amounts to the total composition uncertainty.


title: Stars in the Hubble Ultra Deep Field

abstract:
  We identified 46 unresolved source candidates in the Hubble Ultra Deep Field,
down to i775 = 29.5. Unresolved objects were identified using a parameter S,
which measures the deviation from the curve-of-growth of a point source.
Extensive testing of this parameter was carried out, including the effects of
decreasing signal-to-noise and of the apparent motions of stars, which
demonstrated that stars brighter than i775 = 27.0 could be robustly identified.
Low resolution grism spectra of the 28 objects brighter than i775 = 27.0
identify 18 M and later stellar type dwarfs, 2 candidate L-dwarfs, 2 QSOs, and
4 white dwarfs. Using the observed population of dwarfs with spectral type M4
or later, we derive a Galactic disk scale height of 400 \pm 100 pc for M and L
stars. The local white dwarf density is computed to be as high as (1.1 \pm 0.3)
x10^(-2) stars/pc^3. Based on observations taken 73 days apart, we determined
that no object in the field has a proper motion larger than 0.027"/year (3
sigma detection limit). No high velocity white dwarfs were identified in the
HUDF, and all four candidates appear more likely to be part of the Galactic
thick disk. The lack of detected halo white dwarfs implies that, if the dark
matter halo is 12 Gyr old, white dwarfs account for less than 10% of the dark
matter halo mass.


title: UVES observations of the Canis Major overdensity

abstract:
  We present the first detailed chemical abundances for three giant stars which
are candidate members of the Canis Major overdensity, obtained by using
FLAMES-UVES at VLT. The stars, in the background of the open cluster NGC 2477,
have radial velocities compatible with a membership to this structure. However,
due to Galactic disc contamination, radial velocity by itself is unable to
firmly establish membership. The metallicities span the range -0.5 < [Fe/H] <
+0.1. Assuming that at least one of the three stars is indeed a member of CMa
implies that this structure has undergone a high level of chemical processing,
comparable to that of the Galactic disc. The most metal-rich star of the
sample, EIS 6631, displays several abundance ratios which are remarkably
different from those of Galactic stars: [alpha/Fe] ~-0.2, [Cu/Fe] ~+0.25,
[La/Fe]~+0.6, [Ce/Fe]~+0.8 and [Nd/Fe]~+0.6. These ratios make it likely that
this star was formed in an external galaxy.


title: Recombination Line vs. Forbidden Line Abundances in Planetary Nebulae

abstract:
  Recombination lines (RLs) of C II, N II, and O II in planetary nebulae (PNs)
have been found to give abundances that are much larger in some cases than
abundances from collisionally-excited forbidden lines (CELs). The origins of
this abundance discrepancy are highly debated. We present new spectroscopic
observations of O II and C II recombination lines for six planetary nebulae.
With these data we compare the abundances derived from the optical
recombination lines with those determined from collisionally-excited lines.
Combining our new data with published results on RLs in other PNs, we examine
the discrepancy in abundances derived from RLs and CELs. We find that there is
a wide range in the measured abundance discrepancy Delta(O+2) = log O+2(RL) -
log O+2(CEL), ranging from approximately 0.1 dex up to 1.4 dex. Most RLs yield
similar abundances, with the notable exception of O II multiplet V15, known to
arise primarily from dielectronic recombination, which gives abundances
averaging 0.6 dex higher than other O II RLs. We compare Delta(O+2) against a
variety of physical properties of the PNs to look for clues as to the mechanism
responsible for the abundance discrepancy. The strongest correlations are found
with the nebula diameter and the Balmer surface brightness. An inverse
correlation of Delta(O+2) with nebular density is also seen. Similar results
are found for carbon in comparing C II RL abundances with ultraviolet
measurements of C III].


title: Variations of the Mid-IR Emission Spectrum in Reflection Nebulae

abstract:
  Using spatial-spectral data cubes of reflection nebulae obtained by ISOCAM,
we have observed a shift in the central wavelength of the 7.7 um band within
several reflection nebulae. This band, composed of components at 7.85 um and
7.65 um, shows a centroid shift from 7.75 um near the edge of the nebulae to
7.65 um towards the center of the nebulae as the shorter wavelength component
becomes relatively stronger. The behavior of the 7.7 um band center can be
explained either by assuming that anions are the origin of the 7.85 um band and
cations the 7.65 um band, or that the band center wavelength depends on the
chemical nature of the PAHs. The ratio of the 11.3/7.7 um bands also changes
with distance from the central star, first rising from the center towards the
edge of the nebula, then falling at the largest distances from the star,
consistent with the 11.3/7.7 um band ratio being controlled by the PAH
ionization state.


title: Black Hole Paradoxes

abstract:
  The Black Hole enigma has produced many paradoxes. A consensus regarding the
resolution of some conundrums such as the Naked Singularity Paradox and the
Black Hole Lost Information Paradox (LIP) has still not been achieved. Black
hole complementarity as related to the LIP and the LIP itself are challenged by
gravitational tunneling radiation. Where possible, the paradoxes will be
presented in historical context presenting the interplay of competing
perspectives such as those of Bekenstein, Belinski, Chandrasekar, Finkelstein,
Hawking, Maldacena, Page, Penrose, Preskill, Susskind, 't Hooft, Veneziano,
Wald, Winterberg, Yilmaz, and others. The simplest possible equation is
obtained for Hawking radiation. The average kinetic energy of emitted particles
may have a feature in common with thermionic emission. A broad range of topics
will be covered including: Why can or can't the formation of a black hole be
observed? Can one observe a naked singularity like the one clothed by a black
hole? What can come out of, or seem to come out of, a black hole? What happens
to the information that falls into a black hole? Doesn't the resolution of the
original black hole entropy paradox introduce an equally challenging puzzle?
Related anomalies in the speed of light, the speed of gravity, the speed of
inflation, and Mach's principle are considered. Black hole entropy violation of
the Nernst heat theorem is virtual As we shall see, these paradoxes have served
as an incentive for research to sharpen our thinking, and even to promote the
development of new theoretical and experimental physics. A reasonable number of
paradoxes are a good thing. But too many paradoxes requiring manifold patchwork
fixes may augur basic flaws/inconsistencies that signal the need for a paradigm
shift.


title: The Ages of Elliptical Galaxies from Mid-Infrared Emission

abstract:
  The mid-infrared (10-20 um) luminosity of elliptical galaxies is dominated by
the integrated emission from circumstellar dust in red giant stars. As a single
stellar population evolves, the rate of dusty mass loss from red giant stars
decreases with time, so the mid-infrared luminosity should also decline with
stellar age. To seek such a correlation, we have used archival ISO observations
to determine surface brightness profiles and central fluxes at 15 um in 17
early-type galaxies for which stellar ages have been determined from optical
spectral indices. The radial surface brightness distributions at 15 um
generally follow the stellar de Vaucouleurs profile as expected. We find that
the surface brightness ratio mu_{15um}/mu_{I-band} is systematically higher in
elliptical galaxies with ages < 5 Gyrs and in galaxies that exhibit evidence of
recent mergers. Within the accuracy of our observations, mu_{15um}/mu_{I-band}
shows no age dependence for ages > 5 Gyrs. The corresponding flux ratios
F_{15um}/F_{I-band} within apertures scaled to the effective radius (R_e/8) are
proportional to the mu_{15um}/mu_{I-band} ratios at larger galactic radii,
indicating that no 15 um emission is detected from central dust clouds visible
in optical images in some of our sample galaxies. Emission at 15 um is observed
in non-central massive clouds of dust and cold gas in NGC1316, an elliptical
galaxy that is thought to have had a recent merger. Recent {\it Spitzer Space
Telescope} data also indicate the presence of PAH emission at 8 um. Several
ellipticals have extended regions of 15 um emission that have no obvious
counterparts at other frequencies.


title:
Direct and Indirect Searches for Dark Matter in the Form of Weakly
  Interacting Massive Particles (WIMPs)

abstract:
  Numerous lines of evidence indicate that the matter content of the Universe
is dominated by some unseen component. Determining the nature of this Dark
Matter is one of the most important problems in cosmology. Weakly Interacting
Massive Particles (WIMPs) are widely considered to be one of the best
candidates which may comprise the Dark Matter. A brief overview of the
different methods being used to search for WIMP Dark Matter is given, focusing
on the technologies of several benchmark experiments.


title:
Stellar Evolution with Enriched Surface Convection Zones I. General
  Effects of Planet Consumption

abstract:
  Abundance analyses of stars with planets have revealed that their
metallicities are enhanced relative to field stars. Such a trend was originally
suggested to be due to accretion of iron-rich planetary material. Based on this
assumption, we have developed a stellar evolution code to model stars with
non-uniform metallicity distributions. We have calculated ``polluted'' stellar
evolution tracks for stars with M=0.9-1.2 M_sun. Our models encompass a range
of initial metal content from Z=0.01 to 0.03, and include metallicity
enhancements within the stellar convection zone corresponding to
Delta-Z=0.005-0.03. We find that the primary effects of metal enhancement on
stellar structure and evolution are expansion of the convection zone and
downward shift of effective temperature. In addition, we have computed the
surface metallicities expected for stars of different mass for fixed quantities
of pollution; there appears to be no correlation with present observational
data on the metallicities of stars known to harbor planets.


title: Early optical afterglow lightcurves of neutron-fed Gamma-ray bursts

abstract:
  In this paper, within the popular internal shock scenario of GRBs, we
calculate the early optical afterglow lightcurves of a neutron-fed GRB fireball
for different assumed neutron fractions in the fireball and for both ISM- and
wind-interaction models. The cases for both long and short GRBs are considered.
We show that as long as the neutron fraction is significant (e.g. the number of
neutrons is comparable to that of protons), rich afterglow signatures would
show up. For a constant density (ISM) model, a neutron-rich early afterglow is
characterized by a slowly rising lightcurve followed by a sharp re-brightening
bump caused by collision between the leading neutron decay trail ejecta and the
trailing ion ejecta. For a massive star stellar-wind model, the neutron-rich
early afterglow shows an extended plateau lasting for about 100 seconds before
the lightcurve starts to decay. The plateau is mainly attributed to the
emission from the unshocked neutron decay trail. When the overlapping of the
initial prompt $\gamma-$rays with the shocks and the trail is important, as is
common for the wind model and is also possible in the ISM model under some
conditions, the IC cooling effect suppresses the very early optical afterglow
significantly, making the neutron-fed signature dimmer. For short GRBs powered
by compact star mergers, a neutron-decay-induced step-like re-brightening is
predicted, although the amplitude is not large. All these neutron-fed
signatures are likely detectable by the Ultraviolet Optical Telescope (UVOT) on
board the {\em Swift} observatory if GRB fireballs are indeed baryonic and
neutron-rich. Close monitoring of early afterglows from 10s to 1000s of
seconds, when combined with detailed theoretical modeling, could be used to
potentially diagnose the existence of the neutron component in GRB fireballs.


title:
Pulse Profile Change Possibly Associated with a Glitch in an Anomalous
  X-Ray Pulsar 4U 0142+61

abstract:
  We report a glitch-like pulse frequency deviation from the simple spin-down
law in an anomalous X-ray pulsar (AXP) 4U 0142+61 detected by ASCA
observations. We also found a significant pulse profile change after the
putative glitch. The glitch parameters resemble those found in another AXP 1RXS
J170849.0$-$400910, in the Vela pulsar, and in other radio pulsars. This
suggests that the radio pulsars and AXPs have the same internal structure and
glitch mechanism. It must be noted, however, that the pulse frequency anomaly
can also be explained by a gradual change of the spin-down rate ($\dot{P}$)
without invoking a glitch.


title:
The Shapes of Atomic Lines from the Surfaces of Weakly Magnetic Rotating
  Neutron Stars and Their Implications

abstract:
  Motivated by the report by Cottam et al. (2002) of iron resonance scattering
lines in the spectra of thermonuclear bursts from EXO 0748-676, we have
investigated the information about neutron star structure and the geometry of
the emission region that can be obtained by analyzing the profiles of atomic
lines formed at the surface of the star. We have calculated the detailed
profiles of such lines, taking into account the star's spin and the full
effects of special and general relativity, including light-bending and
frame-dragging. We discuss the line shapes produced by rotational Doppler
broadening and magnetic splitting of atomic lines, for the spin rates and
magnetic fields expected in neutron stars in low-mass X-ray binary systems. We
show that narrow lines are possible even for rapidly spinning stars, if the
emission region or the line of sight are close to the spin axis. For most
neutron stars in low-mass systems, magnetic splitting is too small to obscure
the effects of special and general relativity. We show that the ratio of the
star's mass to its equatorial radius can be determined to within 5% using
atomic line profiles, even if the lines are broad and skewed. This is the
precision required to constrain strongly the equation of state of neutron star
matter. We show further that if the radius and latitude of emission are known
to ~ 5-10% accuracy, then frame-dragging has a potentially detectable effect on
the profiles of atomic lines formed at the stellar surface.


title: On gravito-magnetic time delay by extended lenses

abstract:
  Gravitational lensing by rotating extended deflectors is discussed. Due to
spin, corrections on image positions, caustics and critical curves can be
significant. In order to obtain realistic quantitative estimates, the lens is
modeled as a singular isothermal sphere. Gravito-magnetic time delays of nearly
0.2 days between different images of background sources can occur.


title: Photodisintegration of Ultra-High-Energy Cosmic Rays revisited

abstract:
  Recent microscopic and phenomenological calculations of giant dipole
resonances for A <= 56 nuclei are presented. The derived photodisintegration
cross sections are exhaustively compared to the photonuclear data available to
date. An accurate description of the data is found. Our new calculations are
also compared with the previous and widely-used estimates of Puget, Stecker and
Bredekamp. The present calculations also include all the possible paths down
the nuclear chart. The impact on the photodisintegration of ultra-high-energy
cosmic rays (UHECR) is illustrated for a Fe source with typical energies of
10^{20-21} eV. At energies around 10^20 eV, the new cross sections are found to
modify the UHECR photodisintegration rates. At energies around 10^21 eV, it is
recommended to solve a full reaction network to estimate the
photodisintegration rate of the UHECR.


title: Metal-poor Field Blue Stragglers: More Evidence for Mass Transfer

abstract:
  We report radial velocity studies of five candidate metal-poor field blue
stragglers, all known to be deficient in lithium. Four of the five stars are
single-lined spectroscopic binaries, with periods ranging from 302 to 840 days,
and low orbital eccentricities, in agreement with similar behavior found for
other blue straggler candidates by Preston & Sneden (2000) and Carney et al.
(2001). The limited data available for lithium abundances indicate that all
blue straggler candidates have depleted lithium abundances. Our results show
higher values of v(rot) sin i for the binary stars than comparable temperature
constant-velocity stars. The orbital periods are too long for tidal effects to
now be important, implying that spin-up during mass transfer when the orbital
separations and periods were smaller is that cause of the enhanced rotation.


title:
A Survey of Proper Motion Stars. XVII. A Deficiency of Binary Stars on
  Retrograde Galactic Orbits and the Possibility that omega Centauri is Related
  to the Effect

abstract:
  We find a deficiency of binary stars moving on strongly retrograde Galactic
orbits. No binary deficiencies are seen for U or W velocities, however. From
theoretical analyses, we rule out preferential disruption of pre-existing
binary stars due to encounters with massive perturbers. We also rule out
globular clusters as the source of the effect since prograde motions are more
likely to create such an effect. We search for star streams and find one
possible candidate, but it is not on a retrograde orbit and probably represents
the remains of a cluster that has passed too near the Galactic center. Based on
a very small number of stars, we find that about the right fraction of stars on
retrograde Galactic orbits share some chemical similarities to the cluster
omega Cen, suggesting that its parent galaxy could be the explanation.


title: Simulations of Dust in Interacting Galaxies

abstract:
  A new Monte-Carlo radiative-transfer code, Sunrise, is used to study the
effects of dust in N-body/hydrodynamic simulations of interacting galaxies.
Dust has a profound effect on the appearance of the simulated galaxies. At peak
luminosities, about 90% of the bolometric luminosity is absorbed, and the dust
obscuration scales with luminosity in such a way that the brightness at
UV/visual wavelengths remains roughly constant. A general relationship between
the fraction of energy absorbed and the ratio of bolometric luminosity to
baryonic mass is found. Comparing to observations, the simulations are found to
follow a relation similar to the observed IRX-Beta relation found by Meurer et
al (1999) when similar luminosity objects are considered. The
highest-luminosity simulated galaxies depart from this relation and occupy the
region where local (U)LIRGs are found. This agreement is contingent on the
presence of Milky-Way-like dust, while SMC-like dust results in far too red a
UV continuum slope to match observations. The simulations are used to study the
performance of star-formation indicators in the presence of dust. The
far-infrared luminosity is found to be reliable. In contrast, the H-alpha and
far-UV luminosity suffer severely from dust attenuation, and dust corrections
can only partially remedy the situation.


title: Patchy He II reionization and the physical state of the IGM

abstract:
  We present a Monte-Carlo model of He II reionization by QSOs and its effect
on the thermal state of the clumpy intergalactic medium (IGM). The model
assumes that patchy reionization develops as a result of the discrete
distribution of QSOs. It includes various recipes for the propagation of the
ionizing photons, and treats photo-heating self-consistently. The model
provides the fraction of He III, the mean temperature in the IGM, and the He II
mean optical depth -- all as a function of redshift. It also predicts the
evolution of the local temperature versus density relation during reionization.
Our findings are as follows: The fraction of He III increases gradually until
it becomes close to unity at $z\sim 2.8-3.0$. The He II mean optical depth
decreases from $\tau\sim 10$ at $z\geq 3.5$ to $\tau\leq 0.5$ at $z\leq 2.5$.
The mean temperature rises gradually between $z\sim 4$ and $z\sim 3$ and
declines slowly at lower redshifts. The model predicts a flattening of the
temperature-density relation with significant increase in the scatter during
reionization at $z\sim 3$. Towards the end of reionization the scatter is
reduced and a tight relation is re-established. This scatter should be
incorporated in the analysis of the Ly$\alpha$ forest at $z\leq 3$. Comparison
with observational results of the optical depth and the mean temperature at
moderate redshifts constrains several key physical parameters.


title: IMF variations and their implications for Supernovae numbers

abstract:
  The stellar initial mass function (IMF) integrated over an entire galaxy is
an integral over all separate star-formation events. Since most stars form in
star clusters with different masses the integrated IMF becomes an integral of
the (universal or invariant) canonical stellar IMF over the star-cluster mass
function. This integrated IMF is steeper (contains fewer massive stars per
G-type star) than the canonical stellar IMF. Furthermore, observations indicate
a relation between the star-formation rate of a galaxy and the most luminous
stellar cluster in it. This empirical relation can be transformed into one
between the star-formation rate of a galaxy and a maximum cluster mass. The
assumption that this cluster mass marks the upper end of a young-cluster mass
function leads to a connection of the star-formation rate and the slope of
integrated IMF for massive stars. This integrated IMF varies with the
star-formation history of a galaxy. Notably, large variations of the integrated
IMF are evident for dwarf galaxies. One important result is that the number of
type II supernovae per star is supressed relative to that expected for a
canonical IMF, and that dwarf galaxies have a supressed number of supernovae
per star relative to massive galaxies. For dwarf galaxies the number of
supernovae per star also varies substantially depending on the galaxy assembly
history.


title: Optical spectroscopy of (candidate) ultra-compact X-ray binaries

abstract:
  We present (preliminary) results of our systematic spectroscopic study of
(candidate) ultra-compact X-ray binaries. Most candidates are confirmed and we
found the first optical spectra of (pure) carbon-oxygen accretion discs.


title:
Discovery of a bright X-ray transient in the Galactic Center with
  XMM-Newton

abstract:
  We report the discovery of a bright X-ray transient object, XMMU
J174554.4-285456, observed in outburst with XMM-Newton on October 3, 2002,and
located at 6.3' from SgrA*, the supermassive black hole at the Galactic
center.This object exhibits a very large X-ray luminosity variability of a
factor of about 1300 between two X-ray observations separated by four months.
The X-ray spectrum is best fitted by a power-law with a photon index of
1.6+/-0.2 and absorption column density of 14.1 (+1.6,-1.4) x 10^22 cm^-2. This
large absorption suggests this source is located at the distance of the
Galactic center, i.e., 8 kpc. The 2-10 keV luminosity is about 1.0 x
10^35(d/8kpc)^2 erg/s. A pulsation period of about 172 s is hinted by the
timing analysis. The X-ray properties strongly suggest a binary system with
either a black hole or a neutron star for the compact object.


title:
Dust coagulation in protoplanetary disks: a rapid depletion of small
  grains

abstract:
  We model the process of dust coagulation in protoplanetary disks and
calculate how it affects their observational appearance. Our model involves the
detailed solution of the coagulation equation at every location in the disk. At
regular time intervals we feed the resulting 3-D dust distribution functions
into a continuum radiative transfer code to obtain spectral energy
distributions. We find that, even if only the very basic -- and well understood
-- coagulation mechanisms are included, the process of grain growth is much too
quick to be consistent with infrared observations of T Tauri disks. Small
grains are removed so efficiently that, long before the disk reaches an age of
1E6 years typical of T Tauri stars, the SED shows only very weak infrared
excess. This is inconsistent with observed SEDs of most classical T Tauri
stars. Small grains somehow need to be replenished, for instance by aggregate
fragmentation through high-speed collisions. A very simplified calculation
shows that when aggregate fragmentation is included, a quasi-stationary grain
size distribution is obtained in which growth and fragmentation are in
equilibrium. This quasi-stationary state may last 1E6 years or even longer,
dependent on the circumstances in the disk, and may bring the time scales into
the right regime. We conclude that a simple evolutionary scenario in which
grains slowly grow from pristine 0.1 micron grains to larger grains over a
period of a few Myr is most likely incorrect.


title:
ADAS analysis of the differential emission measure structure of the
  inner solar corona. II. A study of the `quiet Sun' inhomogeneities from SOHO
  CDS-NIS spectra

abstract:
  We present a study of the differential emission measure (DEM) of a `quiet
Sun' area observed in the extreme ultraviolet at normal incidence by the
Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft. The data used for
this work were taken using the NISAT_S observing sequence. This takes the full
wavelength ranges from both the NIS channels (308-381 Angtr. and 513-633
Angst.) with the 2 arcsec by 240 arcsec slit, which is the narrowest slit
available, yielding the best spectral resolution. In this work we contrast the
DEM from subregions of 2 by 80 arcsec$^2$ with that obtained from the mean
spectrum of the whole raster (20 by 240 arcsec$^2$). We find that the DEM
maintains essentially the same shape in the subregions, differing by a constant
factor between 0.5 and 2 from the mean DEM, except in areas were the electron
density is below $2 \times 10^7$ cm$^{-3}$ and downflow velocities of 50 km/s
are found in the transition region. Such areas are likely to contain plasma
departing from ionisation equilibrium, violating the basic assumptions
underlying the DEM method. The comparison between lines of Li-like and Be-like
ions may provide further evidence of departure from ionisation equilibrium. We
find also that line intensities tend to be lower where velocities of the order
of 30 km/s or higher are measured in transition region lines. The DEM analysis
is also exploited to improve the line identification performed by Brooks et al
(1999) and to investigate possible elemental abundance variations from region
to region. We find that the plasma has composition close to photospheric in all
the subregions examined.


title: The starburst phenomenon from the optical/near-IR perspective

abstract:
  The optical/near-IR stellar continuum carries unique information about the
stellar population in a galaxy, its mass function and star-formation history.
Star-forming regions display rich emission-line spectra from which we can
derive the dust and gas distribution, map velocity fields, metallicities and
young massive stars and locate shocks and stellar winds. All this information
is very useful in the dissection of the starburst phenomenon. We discuss a few
of the advantages and limitations of observations in the optical/near-IR region
and focus on some results. Special attention is given to the role of
interactions and mergers and observations of the relatively dust-free starburst
dwarfs. In the future we expect new and refined diagnostic tools to provide us
with more detailed information about the IMF, strength and duration of the
burst and its triggering mechanisms.


title: Weak lensing in scalar-tensor theories of gravity

abstract:
  This article investigates the signatures of various models of dark energy on
weak gravitational lensing, including the complementarity of the linear and
non-linear regimes. It investigates quintessence models and their extension to
scalar-tensor gravity. The various effects induced by this simplest extension
of general relativity are discussed. It is shown that, given the constraints in
the Solar System, models such as a quadratic nonminimal coupling do not leave
any signatures that can be detected while other models, such as a runaway
dilaton, which include attraction toward general relativity can let an imprint
of about 10%.


title: Disk galaxy evolution up to redshift z=1

abstract:
  We have performed intermediate-resolution VLT/FORS spectroscopy and HST/ACS
imaging of 129 field spiral galaxies within the FORS Deep Field. The galaxies
cover the redshift range 0.1 < z < 1.0 and comprise all types from Sa to
Sdm/Im. Spatially resolved rotation curves were extracted and fitted with
synthetic velocity fields that take into account all geometric (e.g.,
inclination and misalignment) and observational effects (in particular,
blurring due to optical beam smearing and seeing). Using these fits, the
maximum rotation velocity Vmax could be determined for 73 objects. The
Tully-Fisher relation of this sample at a mean look-back time of ~5Gyr shows a
luminosity evolution which amounts to ~2mag in rest-frame B for low-mass
spirals (Vmax~100km/s) but is negligible for high-mass spirals (Vmax~300km/s).
This confirms our previous analysis which was limited to ground-based imaging.
The observed overluminosity of low-mass galaxies is at variance with
predictions from simulations. On the other hand, at given Vmax, we find
slightly smaller disk sizes towards higher redshifts, in compliance with the
CDM hierarchical model. The observed mass-dependent luminosity evolution might
therefore point towards the need for a more realistic modelling of the stellar
(i.e. baryonic) component in N-body codes.


title: Beyond the sphericity assumption in dynamical HI models

abstract:
  It is generally agreed that the rotational velocities of spiral galaxies
indicate that a lot of matter is unseen. Hitherto, the majority of these mass
models are all based on spherical symmetry, although this assumption is
obviously not the one that is closest to reality. We present a new method to
derive dynamical mass models from HI-data based on an axisymmetric geometry. To
validate our method, we started a project with the aim to create such models
from a combined sample of late-type Low Surface Brightness galaxies and
early-type High Surface Brightness spiral galaxies. The whole sample spans a
wide range of bulge-to-disk ratios and will ultimately allow us to investigate
the orbital distribution as a function of morphology.


title: Dynamical models linking BH masses and DM content

abstract:
  We investigate the relation between the dark matter distribution of galaxies
and their central supermassive black holes which is suggested by the v_c-sigma
relation. Since early-type galaxies appear to have larger black holes than
late-type ones, we look for an equivalent pattern in the dark matter
distribution as a function of Hubble type. To achieve our goal we use a
state-of-the-art modelling code that allows a variety of geometries to be
fitted to a combination of radio and optical observations of galaxies with
different morphology.


title: The Galaxy Luminosity Function from M_R = -25 to M_R = -9

abstract:
  Redshift surveys like the Sloan Digital Sky Survey (SDSS) have given a very
precise measurement of the galaxy luminosity function down to about M_R = -17
(~ M_B = -16). Fainter absolute magnitudes cannot be probed because of the flux
limit required for spectroscopy. Wide-field surveys of nearby groups using
mosaic CCDs on large telescopes are able to reach much fainter absolute
magnitudes, about M_R = -10. These diffuse, spiral-rich groups are thought to
be typical environments for galaxies so their luminosity functions should be
the same as the field luminosity function. The luminosity function of the
groups at the bright end (M_R < -17) is limited by Poisson statistics and is
far less precise than that derived from redshift surveys. Here we combine the
results of the SDSS and the surveys of nearby groups and supplement the results
with studies of Local Group galaxies in order to determine the galaxy
luminosity function over the entire range -25 <M_R < -9. The average
logarithmic slope of the field luminosity function between M_R = -19 and M_R =
-9 is alpha = -1.26, although a single power law is a poor fit to the data over
the entire magnitude range. We also determine the luminosity function of galaxy
clusters and demonstrate that it is different from the field luminosity
function at a high level of significance: there are many more dwarf galaxies in
clusters than in the field, due to a rise in the cluster luminosity function of
alpha ~ -1.6 between M_R = -17 and M_R = -14.


title: Star formation in RCW 108: triggered or spontaneous?

abstract:
  We present visible, near IR, and mm-wave observations of RCW 108, a molecular
cloud complex in the AraOB1 association that is being eroded by the energetic
radiation of two O-type stars in the nearby cluster NGC 6193. The western part
of the RCW108 cloud contains an embedded compact HII region, IRAS 16362-4845,
ionized by an aggregate of early-type stars. We notice a lack of stars later
than A0 in the aggregate and speculate that this might be a consequence of its
extreme youth. We examine the distribution of stars displaying IR excesses
projected across the molecular cloud. While many of them are located in the
densest area of the molecular cloud near IRAS16362-4845, we also find a group
concentrating towards the edge of the cloud that faces NGC 6193, as well as
some other stars beyond the edge of the molecular cloud. The intense ionizing
radiation field by the O stars in NGC6193 is a clear candidate trigger of star
formation in the molecular cloud, and we suggest that the existence and
arrangement of stars in this region of the cloud supports a scenario in which
their formation may be a consequence of this. However, IR excess stars are also
present in some areas of the opposite side of the cloud, where no obvious
candidate external trigger is identified. The existence of such tracers of
recent star formation scattered across the more massive molecular cloud
associated with IRAS 16362-4845, and the low star formation efficiency that we
derive, indicate that it is in a state to still form stars. This is in contrast
to the less massive cloud close to NGC 6193, which seems to be more evolved and
mostly already recycled into stars, and whose internal kinematics show hints of
having been perturbed by the presence of the massive stars formed out of it.


title:
Transmission of light in deep sea water at the site of the Antares
  neutrino telescope

abstract:
  The ANTARES neutrino telescope is a large photomultiplier array designed to
detect neutrino-induced upward-going muons by their Cherenkov radiation.
Understanding the absorption and scattering of light in the deep Mediterranean
is fundamental to optimising the design and performance of the detector. This
paper presents measurements of blue and UV light transmission at the ANTARES
site taken between 1997 and 2000. The derived values for the scattering length
and the angular distribution of particulate scattering were found to be highly
correlated, and results are therefore presented in terms of an absorption
length lambda_abs and an effective scattering length lambda_sct^eff. The values
for blue (UV) light are found to be lambda_abs ~ 60(26) m, lambda_sct^eff ~
265(122) m, with significant (15%) time variability. Finally, the results of
ANTARES simulations showing the effect of these water properties on the
anticipated performance of the detector are presented.


title:
Southern Infrared Proper Motion Survey I: Discovery of New High Proper
  Motion Stars From First Full Hemisphere Scan

abstract:
  We present the first results from the Southern Infrared Proper Motion Survey.
Using 2 Micron All Sky Survey data along with that of the SuperCOSMOS sky
survey we have been able to produce the first widefield infrared proper motion
survey. Having targeted the survey to identify nearby M, L and T dwarfs we have
discovered 72 such new objects with proper motions greater than 0.5''/yr with
10 of these having proper motions in excess of 1''/yr. The most interesting of
these objects is SIPS1259-4336 a late M dwarf. We have calculated a
trigonometric parallax for this object of $\pi = 276 \pm 41$ milliarcseconds
yielding a distance of $3.62\pm0.54$pc. We have also discovered a common proper
motion triple system and an object with a common proper motion with LHS 128.
The survey completeness is limited by the small epoch differences between many
2MASS and UKI observations. Hence we only recover 22% of Luyten objects with
favourable photometry. However the Luyten study is itself unquantifiably
incomplete. We discuss the prospect of enhancing the survey volume by reducing
the lower proper motion limit.


title:
Accelerator Measurements of the Askaryan effect in Rock Salt: A Roadmap
  Toward Teraton Underground Neutrino Detectors

abstract:
  We report on further SLAC measurements of the Askaryan effect: coherent radio
emission from charge asymmetry in electromagnetic cascades. We used synthetic
rock salt as the dielectric medium, with cascades produced by GeV
bremsstrahlung photons at the Final Focus Test Beam. We extend our prior
discovery measurements to a wider range of parameter space and explore the
effect in a dielectric medium of great potential interest to large scale
ultra-high energy neutrino detectors: rock salt (halite), which occurs
naturally in high purity formations containing in many cases hundreds of cubic
km of water-equivalent mass. We observed strong coherent pulsed radio emission
over a frequency band from 0.2-15 GHz. A grid of embedded dual-polarization
antennas was used to confirm the high degree of linear polarization and track
the change of direction of the electric-field vector with azimuth around the
shower. Coherence was observed over 4 orders of magnitude of shower energy. The
frequency dependence of the radiation was tested over two orders of magnitude
of UHF and microwave frequencies. We have also made the first observations of
coherent transition radiation from the Askaryan charge excess, and the result
agrees well with theoretical predictions. Based on these results we have
performed a detailed and conservative simulation of a realistic GZK neutrino
telescope array within a salt-dome, and we find it capable of detecting 10 or
more contained events per year from even the most conservative GZK neutrino
models.

categories: astro-ph hep-ex physics.acc-ph physics.ins-det


title: Gamma-Ray Bursts and Afterglow Polarisation

abstract:
  Polarimetry of Gamma-Ray Burst (GRB) afterglows in the last few years has
been considered one of the most effective tool to probe the geometry,
energetic, dynamics and the environment of GRBs. We report some of the most
recent results and discuss their implications and future perspectives.


title: The properties of ultra-compact dwarf galaxies and their possible origin

abstract:
  In this contribution the discovery and properties of ultra-compact dwarf
galaxies are presented, and their possible origin is discussed. This new type
of galaxy resides in the cores of galaxy clusters. In the fundamental plane
diagram of stellar systems, the luminosity and kinematical and structural
properties of ultra-compact dwarfs locate them inbetween globular clusters and
small compact ellipticals (like M32). This regime would also be occupied by
nuclei of dwarf ellipticals if they were isolated from their galactic envelope
or by the merger product of super star-cluster complexes as they are found in
strongly interacting galaxies. Future investigations of ultra-compact dwarfs in
different environments have to show which of these formation scenarios is to be
favoured.


title: Faint radio-loud quasars: clues to their evolution

abstract:
  The quasar sample selected by cross-correlating the FIRST and the 2dF Quasar
Redshift Surveys allows us to explore, for the first time, the faint end of the
radio and optical luminosity functions up to z = 2.2. We find indications (~3
\sigma) of a negative evolution for these faint sources at z > 1.8, both in
radio and optical bands. This corresponds to a decrement in the space density
of faint quasars of about a factor 2 at z=2.2 and confirms the presence of a
differential evolution for the population of radio-active quasars. The faint
end of both luminosity functions flattens and the comparison with the (optical)
number density of the whole quasar population supports a dependence of the
fraction of radio detected quasars on the optical luminosity. A progressive
decrease in the fraction of quasars in the whole radio source population can be
consistently accounted for within the `receding torus' scenario. The population
of low luminosity quasars, which the FIRST-2dF detects, appears to depart from
the `classical' scheme for radio-loud quasars.


title:
alpha-, r-, and s-process element trends in the Galactic thin and thick
  disks

abstract:
  From a detailed elemental abundance analysis of 102 F and G dwarf stars we
present abundance trends in the Galactic thin and thick disks for 14 elements
(O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, Ba, and Eu). Stellar parameters
and elemental abundances (except for Y, Ba and Eu) for 66 of the 102 stars were
presented in our previous studies (Bensby et al. 2003, 2004a). The 36 stars
that are new in this study extend and confirm our previous results and allow us
to draw further conclusions regarding abundance trends. The s-process elements
Y and Ba, and the r-element Eu have also been considered here for the whole
sample for the first time. With this new larger sample we now have the
following results: 1) Smooth and distinct trends that for the thin and thick
disks are clearly separated; 2) The alpha-element trends for the thick disk
show typical signatures from the enrichment of SNIa; 3) The thick disk stellar
sample is in the mean older than the thin disk stellar sample; 4) The thick
disk abundance trends are invariant with galactocentric radii (R_m); 5) The
thick disk abundance trends appear to be invariant with vertical distance
(Z_max) from the Galactic plane. Adding further evidence from the literaure we
argue that a merger/interacting scenario with a companion galaxy to produce a
kinematical heating of the stars (that make up today's thick disk) in a
pre-existing old thin disk is the most likely formation scenario for the
Galactic thick disk.


title: Searching for the Missing Baryons in the Warm-hot Intergalactic Medium

abstract:
  We discuss physical properties and the baryonic content of the Warm-hot
Intergalactic Medium (WHIM) at low redshifts. Cosmological simulations predict
that the WHIM contains a large fraction of the baryons at z=0 in the form of
highly-ionized gas at temperatures between 10^5 and 10^7 K. Using
high-resolution ultraviolet spectra obtained with the Space Telescope Imaging
Spectrograph (STIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE) we
have studied the WHIM at low redshifts by searching for intervening OVI and
thermally broadened Lyman alpha (BL) absorption toward a number of quasars and
active galactic nuclei (AGNs). Our measurements imply cosmological mass
densities of Omega_b(OVI)~0.0027/h_75 and Omega_b(BL)~0.0058/h_75. Our results
suggest that the WHIM at low z contains more baryonic mass than stars and gas
in galaxies.


title: Upper limits on the size of a primordial black hole

abstract:
  We provide precise constraints on the size of any black holes forming in the
early Universe for a variety of formation scenarios. In particular, we prove
that the size of the apparent horizon of a primordial black hole formed by
causal processes in a flat Friedmann universe is considerably smaller than the
cosmological apparent horizon size for an equation of state $p=k\rho$
($1/3<k<1$). This also applies for a stiff equation of state ($k=1$) or for a
massless scalar field. The apparent horizon of a primordial black hole formed
through hydrodynamical processes is also considerably smaller than the
cosmological apparent horizon for $0<k\le 1$. We derive an expression for the
maximum size which an overdense region can have without being a separate closed
universe rather than part of our own. Newtonian argument shows that a black
hole smaller than the cosmological horizon can never accrete much.


title:
Growth of primordial black holes in a universe containing a massless
  scalar field

abstract:
  The evolution of primordial black holes in a flat Friedmann universe with a
massless scalar field is investigated in fully general relativistic numerical
relativity. A primordial black hole is expected to form with a scale comparable
to the cosmological apparent horizon, in which case it may go through an
initial phase with significant accretion. However, if it is very close to the
cosmological apparent horizon size, the accretion is suppressed due to general
relativistic effects. In any case, it soon gets smaller than the cosmological
horizon and thereafter it can be approximated as an isolated vacuum solution
with decaying mass accretion. In this situation the dynamical and inhomogeneous
scalar field is typically equivalent to a perfect fluid with a stiff equation
of state $p=\rho$. The black hole mass never increases by more than a factor of
two, despite recent claims that primordial black holes might grow substantially
through accreting quintessence. It is found that the gravitational memory
scenario, proposed for primordial black holes in Brans-Dicke and scalar-tensor
theories of gravity, is highly unphysical.


title:
Wavelet analysis of millisecond variability of Cygnus X-1 during its
  failed state transition

abstract:
  Application of multi-resolution analysis adopting wavelets in order to
investigate millisecond aperiodic X-ray variability of Cyg X-1 is presented.
This relatively new approach in a time-series analysis allows us to study both
the significance of any flux oscillations localized in time-frequency space, as
well as the stability of its period. Using the observations of the RXTE/PCA we
analyze archival data from Cyg X-1 during its failed state transition. The
power spectrum of such a state is strongly dominated by a single Lorentzian
peak corresponding to a damped oscillator. Our wavelet analysis presented in
this paper shows the existence of short lasting oscillations without an obvious
trend in the frequency domain. Based on this result, we suggest the
interpretation of the dominant components of Cyg X-1 power spectrum in all
spectral states: (i) a power law component dominating a soft state is due to
accretion rate fluctuations related to MRI instability in the cold disk, (ii)
the low frequency Lorentzian is related to the same fluctuations but in the
inner ion torus, and (iii) the high frequency Lorentzian (dominating the power
spectrum during the failed state transition) is due to the dynamical pulsations
of the inner ion torus.
  The usage of the wavelet analysis as a potential and attractive tool in order
to spot the semi-direct evidences of accretion process onto black-holes is
proposed.


title:
Three Additional Quiescent Low-Mass X-ray Binary Candidates in 47
  Tucanae

abstract:
  We identify through their X-ray spectra one certain (W37) and two probable
(W17 and X4) quiescent low-mass X-ray binaries (qLMXBs) containing neutron
stars in a long Chandra X-ray exposure of the globular cluster 47 Tucanae, in
addition to the two previously known qLMXBs. W37's spectrum is dominated by a
blackbody-like component consistent with radiation from the hydrogen atmosphere
of a 10 km neutron star. W37's lightcurve shows strong X-ray variability which
we attribute to variations in its absorbing column depth, and eclipses with a
probable 3.087 hour period. For most of our exposures, W37's blackbody-like
emission (assumed to be from the neutron star surface) is almost completely
obscured, yet some soft X-rays (of uncertain origin) remain. Two additional
candidates, W17 and X4, present X-ray spectra dominated by a harder component,
fit by a power-law of photon index ~1.6-3. An additional soft component is
required for both W17 and X4, which can be fit with a 10 km hydrogen-atmosphere
neutron star model. X4 shows significant variability, which may arise from
either its power-law or hydrogen-atmosphere spectral component. Both W17 and X4
show rather low X-ray luminosities, Lx(0.5-10 keV)~5*10^{31} ergs/s. All three
candidate qLMXBs would be difficult to identify in other globular clusters,
suggesting an additional reservoir of fainter qLMXBs in globular clusters that
may be of similar numbers as the group of previously identified objects. The
number of millisecond pulsars inferred to exist in 47 Tuc is less than 10 times
larger than the number of qLMXBs in 47 Tuc, indicating that for typical
inferred lifetimes of 10 and 1 Gyr respectively, their birthrates are
comparable.


title:
Image-Processing Techniques for the Creation of Presentation-Quality
  Astronomical Images

abstract:
  The quality of modern astronomical data, the power of modern computers and
the agility of current image-processing software enable the creation of
high-quality images in a purely digital form. The combination of these
technological advancements has created a new ability to make color astronomical
images. And in many ways it has led to a new philosophy towards how to create
them. A practical guide is presented on how to generate astronomical images
from research data with powerful image-processing programs. These programs use
a layering metaphor that allows for an unlimited number of astronomical
datasets to be combined in any desired color scheme, creating an immense
parameter space to be explored using an iterative approach. Several examples of
image creation are presented.
  A philosophy is also presented on how to use color and composition to create
images that simultaneously highlight scientific detail and are aesthetically
appealing. This philosophy is necessary because most datasets do not correspond
to the wavelength range of sensitivity of the human eye. The use of visual
grammar, defined as the elements which affect the interpretation of an image,
can maximize the richness and detail in an image while maintaining scientific
accuracy. By properly using visual grammar, one can imply qualities that a
two-dimensional image intrinsically cannot show, such as depth, motion and
energy. In addition, composition can be used to engage viewers and keep them
interested for a longer period of time. The use of these techniques can result
in a striking image that will effectively convey the science within the image,
to scientists and to the public.


title: The galaxy-dark matter bias in the Garching-Bonn Deep Survey

abstract:
  We measured the bias and correlation factor of galaxies with respect to the
dark matter using the aperture statistics including the aperture mass from weak
gravitational lensing. The analysis was performed for three galaxy samples
selected by R-band magnitudes; the median redshifts of the samples were
$\ave{z}=0.34,0.49$ and 0.65, respectively. The brightest sample has the
strongest peak in redshift and can therefore be most accurately represented by
a single redshift. The data used is the GaBoDS, and the COMBO-17 survey for an
accurate estimate of the redshift distribution of the galaxies. Assuming the
currently favoured $\Lambda\rm CDM$ model as cosmology, we obtained values for
the linear stochastic galaxy-dark matter bias on angular scales
$1^\prime\le\theta\le20^\prime$. Averaging the measurements for the bias over
the range $4^\prime\le \theta_{\rm ap}\le 18^\prime$, weighting with the cosmic
variance error, yields $b=0.89(5), 0.79(5), 0.89(5)$, respectively ($1\sigma$).
As for the correlation factor $r$ we see, as Hoekstra et al. (2002), a slight
increase to $r=1$ in the last angular bin from an almost constant value on
smaller scales; the weighted average here over the same range as before is
$r=0.8(1), 0.8(1), 0.5(1)$, respectively (abridged).


title:
Sgr A* in context: daily flares as a probe of the fundamental X-ray
  emission process in accreting black holes

abstract:
  Our central Galactic supermassive black hole, Sgr A*, exists mostly in a very
stable, extremely low-luminosity (~10^{-9} L_Edd), thermal quiescent state,
which is interrupted roughly daily by a brief, nonthermal X-ray flare. Because
they are not accompanied by significant changes in the radio wavelengths, the
flares make Sgr A* unusual in the context of black holes accreting at slightly
higher rates. Those sources display a radio/X-ray luminosity correlation whose
normalization scales with central mass, and that holds over orders of magnitude
in accretion power. There is significant scatter in this correlation, due in
part to measurement uncertainties and intrinsic variability. By studying the
correlation in sources bracketing Sgr A* in radio luminosity and whose physical
parameters are well measured, we can derive a statistical measure of this local
scatter. We find that Sgr A* in quiescence and the lower intensity flares fall
well below the correlation in X-ray luminosity. The brightest flares are
consistent within the scatter, which may indicate an upper bound on the X-ray
luminosity. This trend is suggestive of a state transition at the extreme low
end of accretion activity, only above which the radio/X-ray correlation is
tracked. This scenario is easily testable because it must fulfill three unique
observational predictions: 1) As long as Sgr A* remains at its current radio
luminosity, no X-ray flare will be seen which statistically exceeds the
prediction of the correlation, 2) no source already on the correlation will be
seen to flare in the X-rays similar to Sgr A* (i.e., without corresponding
increases in the radio luminosity), and 3) sources below a critical accretion
rate or luminosity will show similar flares as Sgr A*, on timescales
appropriate to their masses.


title:
Exploring the Jet/Accretion Flow Relationship in Low Disk Luminosity
  Sources

abstract:
  Astrophysical jets seem to gain strength disproportionate to the power of
their associated accretion flow, making low-luminosity sources ideal targets
for studies of the role of outflows. Radio/X-ray correlations have supported
the case for a strong relationship between the jets and the hard X-ray emitting
regions, and here we explore the strongest scenario where the base of the jets
subsumes the role of the corona. The properties of coronae, as inferred from
spectral models, are very similar to what is empirically required at jet bases
assuming conservation laws hold. We present a few preliminary fits to
simultaneous radio and X-ray data sets from our GX 339-4 and Cyg X-1 campaigns.
The fits are performed in detector space, and include a jet plus thermal disk
continuum model, with added Gaussian line and non-relativistic reflection
features similar to the approach of other X-ray models. We find that we can fit
the entire radio through X-ray spectrum quite well, with any deviation
occurring in the line/reflection region. The results suggest that a jet/corona
unification can provide a reasonable description of the data. Future work will
benefit from a more complex approach to the disk feedback features.


title:
Calibrating the Nonlinear Matter Power Spectrum: Requirements for Future
  Weak Lensing Surveys

abstract:
  Uncertainties in predicting the nonlinear clustering of matter are among the
most serious theoretical systematics facing the upcoming wide-field weak
gravitational lensing surveys. We estimate the accuracy with which the matter
power spectrum will need to be calibrated in order not to contribute
appreciably to the error budget for future weak lensing surveys. We consider
the random statistical errors and the systematic biases in P(k), as well as
some estimates based on current N-body simulations. While the power spectrum on
relevant scales (0.1 < k/h Mpc^{-1} < 10) is currently calibrated with N-body
simulations to about 5-10%, in the future it will have to be calibrated to
about 1-2% accuracy, depending on the specifications of the survey.
Encouragingly, we find that even the worst-case error that mimics the effect of
cosmological parameters needs to be calibrated to no better than about 0.5-1%.
These goals require a suite of high resolution N-body simulations on a
relatively fine grid in cosmological parameter space, and should be achievable
in the near future.


title:
Adaptive Optics Imaging of the AU Microscopii Circumstellar Disk:
  Evidence for Dynamical Evolution

abstract:
  We present an H-band image of the light scattered from circumstellar dust
around the nearby (10 pc) young M star AU Microscopii (AU Mic, GJ 803, HD
197481), obtained with the Keck adaptive optics system. We resolve the disk
both vertically and radially, tracing it over 17-60 AU from the star. Our AU
Mic observations thus offer the possibility to probe at high spatial resolution
(0.04" or 0.4 AU per resolution element) for morphological signatures of the
debris disk on Solar-System scales. Various sub-structures (dust clumps and
gaps) in the AU Mic disk may point to the existence of orbiting planets. No
planets are seen in our H-band image down to a limiting mass of 1 M_Jup at >20
AU, although the existence of smaller planets can not be excluded from the
current data. Modeling of the disk surface brightness distribution at H-band
and R-band, in conjunction with the optical to sub-millimeter spectral energy
distribution, allows us to constrain the disk geometry and the dust grain
properties. We confirm the nearly edge-on orientation of the disk inferred from
previous observations, and deduce an inner clearing radius <=10 AU. We find
evidence for a lack of small grains in the inner (<60 AU) disk, either as a
result of primordial disk evolution, or because of destruction by
Poynting-Robertson and/or corpuscular drag. A change in the power-law index of
the surface brightness profile is observed near 33 AU, similar to a feature
known in the profile of the beta Pic circumstellar debris disk. By comparing
the time scales for inter-particle collisions and Poynting-Robertson drag
between the two systems, we argue that the breaks are linked to one of these
two processes.


title: The Neutrino Bubble Instability: A Mechanism for Generating Pulsar Kicks

abstract:
  An explanation for the large random velocities of pulsars is presented. Like
many other models, we propose that the momentum imparted to the star is given
at birth. The ultimate source of energy is provided by the intense optically
thick neutrino flux that is responsible for radiating the proto-neutron star's
gravitational binding energy during the Kelvin-Helmholtz phase. The central
feature of the kick mechanism is a radiative-driven magnetoacoustic
instability, which we refer to as ``neutrino bubbles.'' Identical in nature to
the photon bubble instability, the neutrino bubble instability requires the
presence of an equilibrium radiative flux as well as a coherent steady
background magnetic field. Over regions of large magnetic flux densities, the
neutrino bubble instability is allowed to grow on dynamical timescales ~ 1ms,
potentially leading to large luminosity enhancements and density fluctuations.
Local luminosity enhancements, which preferentially occur over regions of
strong magnetic field, lead to a net global asymmetry in the neutrino emission
and the young neutron star is propelled in the direction opposite to these
regions. For favorable values of magnetic field structure, size, and strength
as well as neutrino bubble saturation amplitude, momentum kicks in excess of
1000 km/s can be achieved. Since the neutrino-powered kick is delivered over
the duration of the Kelvin-Helmholtz time ~ a few seconds, one expects
spin-kick alignment from this neutrino bubble powered model.


title: An Off-Axis Model for GRB 031203

abstract:
  The low luminosity radio emission of the unusually faint GRB 031203 has been
argued to support the idea of a class of intrinsically sub-energetic gamma-ray
bursts (GRBs), currently comprising two members. While low energy GRBs probably
exist, we show that the collective prompt and multiwavelength observations of
the afterglow of GRB 031203 do not necessarily require a sub-energetic nature
for that event. In fact, the data are more consistent with a typical, powerful
GRB seen at an angle of about twice the opening angle of the central jet. The
(redshift corrected) peak energy, E_p, of GRB 031203 then becomes ~ 2 MeV,
similar to many other GRBs.


title: Extended emission associated with young HII regions

abstract:
  We have used the Australia Telescope Compact Array (ATCA) to make
observations of a sample of eight young ultra-compact HII regions, selected on
the basis that they have associated class II methanol maser emission. We have
made observations sensitive to both compact and extended structures and find
both to be present in most sources. The scale of the extended emission in our
sample is in general less than that observed towards samples based on IRAS
properties, or large single-dish flux densities. Our observations are
consistent with a scenario where extended and compact radio continuum emission
coexists within HII regions for a significant period of time.
  We suggest that these observations are consistent with a model where HII
evolution takes place within hierarchically structured molecular clouds. This
model is the subject of a companion paper (Shabala et al. 2005) and addresses
both the association between compact and extended emission and UCHII region
lifetime problem.