title: XMM-Newton study of the lensing cluster of galaxies CL0024+17

abstract:
  We present a detailed gravitational mass measurement based on the XMM-Newton
imaging spectroscopy analysis of the lensing cluster of galaxies CL0024+17 at
z=0.395. The emission appears approximately symmetric. However, on the scale of
r~3.3' some indication of elongation is visible in the northwest-southeast
(NW-SE) direction from the hardness ratio map (HRM). Within 3', we measure a
global gas temperature of 3.52\pm0.17 keV, metallicity of 0.22\pm0.07, and
bolometric luminosity of 2.9\pm0.1 \times 10^{44} h^{-2}_{70} erg/s. We derive
a temperature distribution with an isothermal temperature of 3.9 keV to a
radius of 1.5' and a temperature gradient in the outskirts (1.3<r<3'). Under
the assumption of hydrostatic equilibrium, we measure gravitational mass and
gas mass fraction to be M_{200}=2.0\pm0.3 \times 10^{14} h_{70}^{-1} M_{\odot}
and f_{\rm gas}=0.20\pm0.03 h^{-3/2}_{70} at r_{200}=1.05 h^{-1}_{70} Mpc using
the observed temperature profile. The complex structure in the core region is
the key to explaining the discrepancy in gravitational mass determined from
XMM-Newton X-ray observations and HST optical lensing measurements.


title: Distribution of the extensive Doppler redshift of quasars

abstract:
  We make an analysis of the distribution of the extensive Doppler redshift
defined as $\widetilde{z}_{Dopp}=(z_{abs}-z_{em})/(1+z_{em})$ with a sample of
1317 absorption redshifts available from 401 quasars. The analysis reveals a
bi-peak structure in the distribution, with one component located at
$\widetilde{z}_{Dopp}\simeq 0.00$ and the other at $\widetilde{z}%
_{Dopp}\simeq -0.01$. A study of some possible causes suggests that the
structure can be well interpreted: while the absorbers inside the same cluster
as the quasar concerned could contribute to the first component and the less
populated space between clusters could explain the gap between the two peaks,
the typical distance between clusters could account for the second component.
If the bi-peak structure is true, which needs to be confirmed by complete
samples, one would be able to obtain some useful cosmological information.


title:
Determination of the equation of the state of the Universe using ~ 0.1
  Hz Gravitational Wave Detectors

abstract:
  We show that ten(one) years operation of the ultimate DECIGO (DECihertz
Interferometer Gravitational wave Observatory) can determine the cosmic
equation of the state with such accuracy that 0.06%(3%), 0.08%(4%) and
0.06%(3%) for $\Omega_m$, $\Omega_w$ and $w$, respectively. In more realistic
case of practical DECIGO or BBO (Big Bang Observer), $w$ will be determined
within $\sim 10%$ by ten years observation assuming the flat universe model.
Hence, the DECIGO or BBO will give an independent determination of the cosmic
equation of the state.


title: Weak Lensing by Large-Scale Structure with the FIRST Radio Survey

abstract:
  We present the first measurement of weak lensing by large-scale structure on
1-4 degree scales based on the FIRST Radio Survey, a quarter-sky, 20-cm survey
produced with the NRAO Very Large Array (VLA). The large angular scales provide
an unique measurement in the linear regime of the matter power spectrum. We use
the shapelet method to estimate the shear of radio sources derived directly
from the Fourier(uv) plane. With realistic simulations we verify that the
method yields unbiased shear estimators. We quantify and correct for the
systematic effects which can produce spurious shears, analytically and with
simulations. We measure the shear correlation functions on angular scales of
0.5-40 degrees, and compute the corresponding aperture mass statistics. On 1-4
degrees scales, we find that the B-modes are consistent with zero, and detect a
lensing E-mode signal significant at the 3.0 sigma level. After removing radio
sources with an optical counterpart, the E-mode signal increases by 10-20%, as
expected for a lensing signal derived from more distant sources. We use the
E-mode measurement to constrain the mass power spectrum normalization sigma_8
and the median redshift z_m of the unidentified radio sources. We find
sigma_8*(z_m/2)^(0.6) ~ 1.0 +/- 0.2, where the 1 sigma error bars include
statistical errors, cosmic variance, and systematics. This is consistent with
earlier determinations of sigma_8, and with our current knowledge of the
redshift distribution of radio sources. Taking the prior sigma_8 = 0.9 +/- 0.1
(68%CL) from the WMAP experiment, this corresponds to z_m = 2.2 +/- 0.9 (68%CL)
for radio sources without optical counterparts. Our results offer promising
prospects for precision measurements of cosmic shear with future radio
interferometers such as LOFAR and the SKA.


title:
Evidence for a Geometrically Thick Self-Gravitating Accretion Disk in
  NGC 3079

abstract:
  We have mapped, for the first time, the full velocity extent of the water
maser emission in NGC 3079. The largely north-south distribution of emission,
aligned with a kpc-scale molecular disk, and the segregation of blue- and
red-shifted emission on the sky are suggestive of a nearly edge-on molecular
disk on pc-scales. Positions and line-of-sight velocities of blue- and
red-shifted maser emission are consistent with a central mass of ~2 x 10^6 Msun
enclosed within a radius of ~0.4 pc. The corresponding mean mass density of
10^6.8 Msun pc^-3 is suggestive of a central black hole, which is consistent
with the detection of hard X-ray excess (20-100 keV) and an Fe Kalpha line from
the nucleus. Because the rotation curve traced by the maser emission is flat,
the mass of the pc-scale disk is significant with respect to the central mass.
Since the velocity dispersion of the maser features does not decrease with
radius and constitutes a large fraction of the orbital velocity, the disk is
probably thick and flared. The rotation curve and the physical conditions
necessary to support maser emission imply a Toomre Q-parameter that is << 1.
Thus, the disk is most likely clumpy, and we argue that it is probably forming
stars. Overall, the accretion disk in NGC 3079 stands in contrast to the
compact, thin, warped, differentially rotating disk in the archetypal maser
galaxy NGC 4258 (abridged).


title:
Magnetic field generation in relativistic shocks - An early end of the
  exponential Weibel instability in electron-proton plasmas

abstract:
  We discuss magnetic field generation by the proton Weibel instability in
relativistic shocks, a situation that applies to the external shocks in the
fireball model for Gamma-ray Bursts, and possibly also to internal shocks. Our
analytical estimates show that the linear phase of the instability ends well
before it has converted a significant fraction of the energy in the proton beam
into magnetic energy: the conversion efficiency is much smaller (of order
m_e/m_p) in electron-proton plasmas than in pair plasmas. We find this estimate
by modelling the plasma in the shock transition zone with a waterbag momentum
distribution for the protons and with a background of hot electrons.
  For ultra-relativistic shocks we find that the wavelength of the most
efficient mode for magnetic field generation equals the electron skin depth,
that the relevant nonlinear stabilization mechanism is magnetic trapping, and
that the presence of the hot electrons limits the typical magnetic field
strength generated by this mode so that it does not depend on the energy
content of the protons. We conclude that other processes than the linear Weibel
instability must convert the free energy of the protons into magnetic fields.


title: Large Scale Periodicity in Redshift Distribution

abstract:
  We review the previous studies of galaxies and quasar redshifts
discretisation. We present also the investigations of the large scale
periodicity, detected by pencil--beam observations, which revealed 128 (1/h)
Mpc period, afterwards confirmed with supercluster studies. We present the
theoretical possibility of obtaining such a periodicity using a toy-model. We
solved the Kepler problem, i.e. the equation of motion of a particle with null
energy moving in the uniform, expanding Universe, decribed by FLRW metrics. It
is possible to obtain theoretically the separation between large scale
structures similar to the observed one.


title:
The extragalactic sub-mm population: predictions for the SCUBA
  Half-Degree Extragalactic Survey (SHADES)

abstract:
  We present predictions for the angular correlation function and redshift
distribution for SHADES, the SCUBA HAlf-Degree Extragalactic Survey, which will
yield a sample of around 300 sub-mm sources in the 850 micron waveband in two
separate fields. Complete and unbiased photometric redshift information on
these sub-mm sources will be derived by combining the SCUBA data with i) deep
radio imaging already obtained with the VLA, ii) guaranteed-time Spitzer data
at mid-infrared wavelengths, and iii) far-infrared maps to be produced by
BLAST, the Balloon-borne Large-Aperture Sub-millimeter Telescope. Predictions
for the redshift distribution and clustering properties of the final
anticipated SHADES sample have been computed for a wide variety of models, each
constrained to fit the observed number counts. Since we are dealing with around
150 sources per field, we use the sky-averaged angular correlation function to
produce a more robust fit of a power-law shape w(theta)=(theta/A)^{-delta} to
the model data. Comparing the predicted distributions of redshift and of the
clustering amplitude A and slope delta, we find that models can be constrained
from the combined SHADES data with the expected photometric redshift
information.


title: Constraining jet theories using nova outbursts

abstract:
  It is commonly accepted that jets have not been observed in CVs so far. This
absence was recently explained by their low mass transfer rates compared with
objects with jets. A mass accretion limit for jets in CVs was proposed to be
about 1e-7-1e-6 Mo/yr. There was, however, a report of evidence for jets in
V1494 Aql=Nova Aql 1999/2. We estimate the mass transfer rate of this system
around the reported event and show that it is consistent with the theoretical
limit for jets. We further propose that the X-ray flare that was observed in
this object may be connected with a jet as well. The appearance of jets in
novae is actually expected since during the early decline from outburst some
are alike supersoft X-ray sources, in which jets have been found. The detection
of jets in novae also fits the suggestion that in addition to the presence of
an accretion disk, a hot central source is required for the formation of jets.
The observations of jets during the transition phase in V1494 Aql can be
regarded as evidence for the early existence of the accretion disk in the
system. This conclusion supports our previous suggestion for a link between the
transition phase in novae and the re-establishment of the accretion disk. We
further speculate that jets may be restricted to transient novae. If our ideas
are confirmed, jets should be common in transient novae and may be formed
several times during the transition phase and perhaps even long after it ends.
In classical novae jets may be launched and observed in real time. As binary
systems, these objects are easy to study. Novae may, therefore, be key systems
in understanding the formation and evolution of jets and ideal targets to test
and constrain jet theories.


title:
The Group Evolution Multiwavelength Study (GEMS): bimodal luminosity
  functions in galaxy groups

abstract:
  We present B and R-band luminosity functions (LF) for a sample of 25 nearby
groups of galaxies. We find that the LFs of the groups with low X-ray
luminosity (L_X < 10^{41.7} erg/s) are significantly different from those of
the X-ray brighter groups, showing a prominent dip around M_b = -18. While both
categories show lack of late-type galaxies in their central regions, X-ray dim
groups also show a more marked concentration of optical luminosity towards the
centre. A toy simulation shows that in the low velocity dispersion environment,
as in the X-ray dim group, dynamical friction would facilitate more rapid
merging, thus depleting intermediate-luminosity galaxies to form a few giant
central galaxies, resulting in the prominent dip seen in our LFs. We suggest
that X-ray dim (or low velocity dispersion) groups are the present sites of
rapid dynamical evolution rather than their X-ray bright counterparts, and may
be the modern precursors of fossil groups. We predict that these groups of low
velocity dispersion would harbour younger stellar populations than groups or
clusters with higher velocity dispersion.


title: Heating groups and clusters of galaxies: the role of AGN jets

abstract:
  X-Ray observations of groups and clusters of galaxies show that the
Intra-Cluster Medium (ICM) in their cores is hotter than expected from
cosmological numerical simulations of cluster formation which include star
formation, radiative cooling and SN feedback. We investigate the effect of the
injection of supersonic AGN jets into the ICM using axisymmetric hydrodynamical
numerical simulations. A simple model for the ICM, describing the radial
properties of gas and the gravitational potential in cosmological N-Body+SPH
simulations of one cluster and three groups of galaxies at redshift z=0, is
obtained and used to set the environment in which the jets are injected. We
varied the kinetic power of the jet and the emission-weighted X-Ray temperature
of the ICM. The jets transfer their energy to the ICM mainly by the effects of
their terminal shocks. A high fraction of the injected energy can be deposited
through irreversible processes in the cluster gas, up to 75% in our
simulations. We show how one single, powerful jet can reconcile the predicted
X-Ray properties of small groups, e.g. the Lx-Tx relation, with observations.
We argue that the interaction between AGN jets and galaxy groups and cluster
atmospheres is a viable feedback mechanism.


title:
A Chandra Observation of the Diffuse Emission Centered on the Low Mass
  X-ray Binary 4U 1755-33

abstract:
  We present an analysis of a Chandra observation of the field surrounding the
low-mass X-ray binary 4U 1755-33, which has been in quiescence since 1996. In
2003, Angelini and White reported the appearance of a narrow 7 arcmin long
jetlike feature centered on the position of 4U 1755-33 using the XMM-Newton
telescope. Though the source and jet are not visibly apparent in our
Chandra/ACIS-S image, there is a significant excess (4-6 sigma) of counts in a
region that encloses the jet when compared to adjacent regions. We examined a
knot of emission in the jet that was detected by XMM-Newton but not by Chandra
and calculated that if the knot flux observed by XMM-Newton was concentrated in
a point source, Chandra would have easily detected it; we therefore conclude
that this knot of emission is diffuse. In summary, we suggest that the jetlike
feature found previously in the XMM-Newton data is quite diffuse and likely a
true jet, and is not due to a chance alignment of discrete point sources or
point-like regions of emission associated with internal shocks.


title:
K-band Properties of Galaxy Clusters and Groups: Brightest Cluster
  Galaxies and Intracluster Light

abstract:
  We investigate the near-infrared K-band properties of the brightest cluster
galaxies (BCGs) in a sample of 93 galaxy clusters and groups, using data from
the Two Micron All Sky Survey. Our cluster sample spans a factor of 70 in mass,
making it sensitive to cluster mass related trends. We study the correlations
between the BCG luminosity L_b and the mass or luminosity of the host clusters,
finding that BCGs in more massive clusters are more luminous than their
counterparts in less massive systems, and that the BCGs become less important
in the overall cluster light L200 as cluster mass increases. We argue that BCGs
grow in luminosity mainly by merging with other luminous galaxies as the host
clusters grow hierarchically; the decreasing BCG luminosity fraction L_b/L_200
with cluster mass indicates that the rate of luminosity growth in BCGs is slow
compared to the rate at which clusters acquire galaxy light from the field or
other merging clusters.
  We use the observed cluster luminosity-mass relation and a merger tree model
to estimate that the amount of intracluster light (ICL) increases with cluster
mass; calculations suggest that in 10^{15}Mo clusters more than 50% of total
stellar mass is in ICL. The cluster baryon fraction accounting for the ICL is
in good agreement with the CMB constraints. The inclusion of ICL reduces
thediscrepancy between the observed cluster cold baryon fraction and that found
in hydro simulations. Based on the observed Fe abundance in the ICM, we find
that the predicted ICL together with the observed galaxy light, match the Fe
mass-tolight ratio expected from simple stellar population models with a
Salpeter IMF. The ICL also makes it easier to produce the Fe core excess found
in cool-core clusters. (abridged)


title: Non-Fermi Power law Acceleration in Astrophysical Plasma Shocks

abstract:
  Collisionless plasma shock theory, which applies for example to the afterglow
of gamma ray bursts, still contains key issues that are poorly understood. In
this paper we study charged particle dynamics in a highly relativistic
collisionless shock numerically using ~10^9 particles. We find a power law
distribution of accelerated electrons, which upon detailed investigation turns
out to originate from an acceleration mechanism that is decidedly different
from Fermi acceleration.
  Electrons are accelerated by strong filamentation instabilities in the
shocked interpenetrating plasmas and coincide spatially with the power law
distributed current filamentary structures. These structures are an inevitable
consequence of the now well established Weibel-like two-stream instability that
operates in relativistic collisionless shocks.
  The electrons are accelerated and decelerated instantaneously and locally; a
scenery that differs qualitatively from recursive acceleration mechanisms such
as Fermi acceleration.
  The slopes of the electron distribution power laws are in concordance with
the particle power law spectra inferred from observed afterglow synchrotron
radiation in gamma ray bursts, and the mechanism can possibly explain more
generally the origin of non-thermal radiation from shocked inter- and
circum-stellar regions and from relativistic jets.


title:
Anisotropic Distribution of SDSS Satellite Galaxies: Planar (not Polar)
  Alignment

abstract:
  The distribution of satellite galaxies relative to isolated host galaxies in
the Sloan Digital Sky Survey (SDSS) is investigated. Host-satellite systems are
selected using three different methods, yielding samples of ~3300, ~1600, and
\~950 satellites. In the plane of the sky, the distributions of all three
samples show highly significant deviations from circular symmetry (> 99.99%, >
99.99%, and 99.79% confidence levels, respectively), and the degree of
anisotropy is a strong function of the projected radius, r_p, at which the
satellites are found. For r_p < 100 kpc, the SDSS satellites are aligned
preferentially with the major axes of the hosts. This is in stark contrast to
the Holmberg effect, in which satellites are aligned with the minor axes of
host galaxies. The degree of anisotropy in the distribution of the SDSS
satellites decreases with r_p and is consistent with an isotropic distribution
at of order the 1-sigma level for 250 kpc < r_p < 500 kpc.


title: WMAP constraints on the Intra-Cluster Medium

abstract:
  We devise a Monte-Carlo based, optimized filter match method to extract the
thermal Sunyaev-Zel'dovich (SZ) signature of a catalog of 116 low-redshift
X-ray clusters from the first year data release of the Wilkinson Microwave
Anisotropy Probe (WMAP). We detect an over-all amplitude for the SZ signal at
the ~ 8-sigma level, yielding a combined constraint of f_{gas}h = 0.08 +/- 0.01
(ran) +/- 0.01 (sys) on the gas mass fraction of the Intra-Cluster Medium. We
also compile X-ray estimated gas fractions from the literature for our sample,
and find that they are consistent with the SZ estimates at the 2-sigma level,
while both show an increasing trend with X-ray temperature. Nevertheless, our
SZ estimated gas fraction is 30-40% smaller than the concordance LCDM cosmic
average. We also express our observations in terms of the SZ flux-temperature
relation, and compare it with other observations, as well as numerical studies.
  Based on its spectral and spatial signature, we can also extract the
microwave point source signal of the clusters at the 3-sigma level, which puts
the average microwave luminosity (at ~ 41 GHz) of bright cluster members (M_K <
-21) at (2.4 +/- 0.8) x 10^{27} h^{-2} erg/s/Hz. Furthermore, we can constrain
the average dark matter halo concentration parameter to c_{vir}=3.4+0.6-0.9,
for clusters with T_x > 5 kev.
  Our work serves as an example for how correlation of SZ surveys with cluster
surveys in other frequencies can significantly increase our physical
understanding of the intra-cluster medium.


title: The Nature of the Variable Galactic Center Source IRS16SW

abstract:
  We report measurements of the light curve of the variable Galactic Center
source IRS16SW. The light curve is not consistent with an eclipsing binary or
any other obvious variable star. The source may be an example of a high mass
variable predicted theoretically but not observed previously.


title: A microquasar shot out from its birth place

abstract:
  We show that the microquasar LSI+61303 is running away from its birth place
in a young complex of massive stars. The supernova explosion that formed the
compact object shot out the x-ray binary with a linear momentum of 430 +/- 140
Msun km/s, which is comparable to the linear momenta found in solitary runaway
neutron stars and millisecond pulsars. The properties of the binary system and
its runaway motion of 27 +/- 6 km/s imply that the natal supernova was
asymmetric and that the upper limit for the mass that could have been suddenly
ejected in the explosion is ~2 Msun. The initial mass of the progenitor star of
the compact object that is inferred depends on whether the formation of massive
stars in the parent stellar cluster was coeval or a sequential process.


title: Formation Histories of Dwarf Galaxies in the Local Group

abstract:
  We compare the properties of dwarf galaxies in the Local Group with the
simulated galaxies formed before reionization in a cosmological simulation of
unprecedented spatial and mass resolution,including radiative feedback effects.
We find that a subset of the Local Group dwarfs are remarkably similar to the
simulated dwarf galaxies in all their properties already before reionization.
Based on this similarity, we propose the hypothesis that Local Group dwarfs
form in a variety of ways: some of them are ``true fossils'' of the
pre-reionization era, some of them form most of their stars later, after
reionization (we call them ``survivors'' of the reionization era), and the rest
of them form an intermediate group of ``polluted fossils''. We also identify a
simple observational test that is able to falsify our hypothesis.


title:
Theoretical Models of the Halo Occupation Distribution: Separating
  Central and Satellite Galaxies

abstract:
  The halo occupation distribution (HOD) describes the relation between
galaxies and dark matter at the level of individual dark matter halos. The
properties of galaxies residing at the centers of halos differ from those of
satellite galaxies because of differences in their formation histories. Using a
smoothed particle hydrodynamics (SPH) simulation and a semi-analytic (SA)
galaxy formation model, we examine the separate contributions of central and
satellite galaxies to the HOD, more specifically to the probability P(N|M) that
a halo of virial mass M contains N galaxies of a particular class. In agreement
with earlier results for dark matter subhalos, we find that the mean occupation
function <N> for galaxies above a baryonic mass threshold can be approximated
by a step function for central galaxies plus a power law for satellites, and
that the distribution of satellite numbers is close to Poisson at fixed halo
mass. For galaxy samples defined by different baryonic mass thresholds, there
is a nearly linear relation between the minimum halo mass Mmin required to host
a central galaxy and the mass M1 at which an average halo hosts one satellite,
with M1 ~ 14 Mmin (SPH) or M1 ~ 18 Mmin (SA). The mean occupation number of
young galaxies exhibits a local minimum at M ~ 10 Mmin where halos are too
massive to host a young central galaxy but not massive enough to host
satellites. We show that the conditional galaxy mass function at fixed halo
mass cannot be described by a Schechter function because central galaxies
produce a "bump" at high masses. We suggest parameterizations for the HOD and
the conditional luminosity function that can be used to model observed galaxy
clustering. Many of our predictions are in good agreement with recent results
inferred from clustering in the Sloan Digital Sky Survey.


title:
A Rigidly Rotating Magnetosphere Model for Circumstellar Emission from
  Magnetic OB Stars

abstract:
  We present a semi-analytical approach for modeling circumstellar emission
from rotating hot stars with a strong dipole magnetic field tilted at an
arbitrary angle to the rotation axis. By assuming the rigid-field limit in
which material driven (e.g., in a wind outflow) from the star is forced to
remain in strict rigid-body co-rotation, we are able to solve for the effective
centrifugal-plus-gravitational potential along each field line, and thereby
identify the location of potential minima where material is prone to
accumulate. Applying basic scalings for the surface mass flux of a radiatively
driven stellar wind, we calculate the circumstellar density distribution that
obtains once ejected plasma settles into hydrostatic stratification along field
lines. The resulting accumulation surface resembles a rigidly rotating, warped
disk, tilted such that its average surface normal lies between the rotation and
magnetic axes. Using a simple model of the plasma emissivity, we calculate
time-resolved synthetic line spectra for the disk. Initial comparisons show an
encouraging level of correspondence with the observed rotational phase
variations of Balmer-line emission profiles from magnetic Bp stars like sigma
Ori E.


title:
Star Formation in the W49A Molecular Cloud: Birth of a Massive Star
  Cluster

abstract:
  The W49A star-forming region is embedded in a 10^6 solar mass molecular
cloud, one of the most massive in our Galaxy. It has been long known as one of
the most luminous radio HII regions, containing 30-40 compact and ultracompact
HII regions and several hot cores. We have detected a previously unknown
massive star cluster (Cluster 1) embedded in the W49 molecular cloud using JHKs
observations with SOFI+NTT. We find that the inferred mass of Cluster 1 is 1-2
x 10^4 solar masses, and is 2 pc in projected distance from the largest
grouping of ultracompact HII regions (including the Welch ring). We use the
extensive line-of-sight extinction to isolate a population of objects
associated with W49A, and use this sample to obtain a mass function. The slope
of the derived mass function for objects associated with W49A, -1.3 \pm 0.3, is
consistent with a Salpeter slope. About 3 pc away from the main star-forming
complexes seen in near-infrared and radio observations is an ~80 solar mass
star ionizing a compact H II region (object CC). We obtained adaptive optics
imaging with NACO on the VLT of the 1.5 pc surrounding this object to search
investigate the stellar initial mass function in the vicinity of a massive
star. On the global molecular cloud scale in W49, massive star formation
apparently did not proceed in a single concentrated burst, but in small groups,
or subclusters.


title:
Accretion relicts in the solar neighbourhood: debris from omegaCen's
  parent galaxy

abstract:
  We use numerical simulations to investigate the orbital characteristics of
tidal debris from satellites whose orbits are dragged into the plane of
galactic disks by dynamical friction before disruption. We find that these
satellites may deposit a significant fraction of their stars into the disk
components of a galaxy, and use our results to motivate the search for
accretion relicts in samples of metal-poor disk stars in the vicinity of the
Sun. Satellites disrupted on very eccentric orbits coplanar with the disk are
expected to shed stars in "trails" of distinct orbital energy and angular
momentum during each pericentric passage. To an observer located between the
pericenter and apocenter of such orbits, these trails would show as distinct
groupings of stars with low vertical velocity and a broad, symmetric, often
double-peaked distribution of Galactocentric radial velocities. One group of
stars with these characteristics stands out in available compilations of nearby
metal-poor stars. These stars have specific angular momenta similar to that of
the globular cluster omegaCen, long hypothesized to be the nucleus of a dwarf
galaxy disrupted by the Milky Way tidal field. In addition to their kindred
kinematics, stars in the omegaCen group share distinct chemical abundance
characteristics, and trace a well-defined track in the [alpha/Fe] versus [Fe/H]
plane, consistent with simple closed-box enrichment models and a protracted
star formation history. The dynamical and chemical coherence of this group
suggests that it consists of stars that once belonged to the dwarf that brought
omegaCen into the Galaxy. The presence of this and other "tidal relicts" in the
solar neighbourhood suggest an extra-Galactic origin for the presence of nearby
stars with odd kinematics and chemistry.


title: Shapelets "multiple multipole" shear measurement methods

abstract:
  The measurement of weak gravitational lensing is currently limited to a
precision of ~10% by instabilities in galaxy shape measurement techniques and
uncertainties in their calibration. The potential of large, on-going and future
cosmic shear surveys will only be realised with the development of more
accurate image analysis methods. We present a description of several possible
shear measurement methods using the linear "shapelets" decomposition. Shapelets
provides a complete reconstruction of any galaxy image, including higher-order
shape moments that can be used to generalise the KSB method to arbitrary order.
Many independent shear estimators can then be formed for each object, using
linear combinations of shapelet coefficients. These estimators can be treated
separately, to improve their overall calibration; or combined in more
sophisticated ways, to eliminate various instabilities and a calibration bias.
We apply several methods to simulated astronomical images containing a known
input shear, and demonstrate the dramatic improvement in shear recovery using
shapelets. A complete IDL software package to perform image analysis and
manipulation in shapelet space can be downloaded from the shapelets web site at
http://www.astro.caltech.edu/~rjm/shapelets/ .


title: The Luminosity and Color Dependence of the Galaxy Correlation Function

abstract:
  We study the luminosity and color dependence of the galaxy 2-point
correlation function in the Sloan Digital Sky Survey, starting from a sample of
200,000 galaxies over 2500 deg^2. We concentrate on the projected correlation
function w(r_p), which is directly related to the real space \xi(r). The
amplitude of w(r_p) grows continuously with luminosity, rising more steeply
above the characteristic luminosity L_*. Redder galaxies exhibit a higher
amplitude and steeper correlation function at all luminosities. The correlation
amplitude of blue galaxies increases continuously with luminosity, but the
luminosity dependence for red galaxies is less regular, with bright red
galaxies more strongly clustered at large scales and faint red galaxies more
strongly clustered at small scales. We interpret these results using halo
occupation distribution (HOD) models assuming concordance cosmological
parameters. For most samples, an HOD model with two adjustable parameters fits
the w(r_p) data better than a power-law, explaining inflections at r_p ~ 1-3
Mpc/h as the transition between the 1-halo and 2-halo regimes of \xi(r). The
implied minimum mass for a halo hosting a central galaxy above a luminosity
threshold L grows as M_min ~ L at low luminosities and more steeply above L_*.
The mass at which an average halo has one satellite galaxy brighter than L is
M_1 ~ 23 M_min(L). These results imply a conditional luminosity function (at
fixed halo mass) in which central galaxies lie far above a Schechter function
extrapolation of the satellite population. HOD models nicely explain the joint
luminosity-color dependence of w(r_p) in terms of the color fractions of
central and satellite populations as a function of halo mass. The inferred HOD
properties are in good qualitative agreement with theoretical predictions.


title:
The self regulating star formation of gas rich dwarf galaxies in
  quiescent phase

abstract:
  The expected episodic or intermittent star formation histories (SFHs) of gas
rich dwarf irregular galaxies (dIrrs) are the longstanding puzzles to
understand their whole evolutional history. Solving this puzzle, we should
grasp what physical mechanism causes the quiescent phase of star formation
under the very gas rich condition after the first starburst phase. We consider
that this quiescent phase is kept by lack of H2, which can be important coolant
to generate the next generation of stars in the low-metal environment like
dIrrs. Furthermore, in dIrrs, H2 formation through gas-phase reactions may
dominate the one on dust-grain surfaces because their interstellar medium (ISM)
are very plentiful and the typical dust-to-gas ratio of dIrrs (D_dIrrs = 1.31 x
10^-2 D_MW, where D_MW is its value for the local ISM) is on the same order
with a critical value D_cr ~ 10^-2 D_MW. We show that the lack of H2 is mainly
led by H- destruction when gas-phase H2 formation dominates since H- is
important intermediary of gas-phase H2 formation. H- is destroyed by the
radiation from all stars born in the previous starburst phase because H-
destroying infrared photon can penetrate the whole ISM of dIrrs. Considering
the physical process which timescale is the longest as main process in
regulating global star formation, we can show this lack of H2 leads the
quiescent phase of star formation. Hence, we can say that the stellar radiation
which destroys H- and leads low H2 abundance should be properly treated in
studying SFHs of dIrrs.


title: Distance of the Hypernova SN 2002ap via the Expanding Photosphere Method

abstract:
  New optical photometric and spectroscopic data of the bright hypernova SN
2002ap are presented. The obtained BVRI light curves as well as the optical
spectra agree well with other published data series. The distance has been
inferred by applying the Expanding Photosphere Method for the data around
maximum. The derived 6.7 Mpc is in good agreement with recent photometric
distances of M74. However, the total (random plus systematic) uncertainty of
the EPM-distance is at least 4.5 Mpc (about 70 %). The physical parameters of
the SN have been determined via simplified analytic models of the light and
velocity curves. It is confirmed that SN 2002ap was a less energetic hypernova,
the kinetic energy was 4 - 8 10^51 erg, and the reddening-free absolute
bolometric magnitude reached -16.63 mag (corresponding to L_bol = 3.47 10^8
L_solar), about 2 magnitude less than the prototype hypernova SN 1998bw.


title:
The Araucaria Project. The Distance to the Local Group Galaxy NGC 6822
  from Cepheid Variables discovered in a Wide-Field Imaging Survey

abstract:
  We have obtained mosaic images of NGC 6822 in V and I bands on 77 nights.
  From these data, we have conducted an extensive search for Cepheid variables
over the entire field of the galaxy, and we have found 116 such variables with
periods ranging from 1.7 to 124 days. We used the long-period ($>$ 5.6 days)
Cepheids to establish the period-luminosity relations in V, I and in the
reddening-independent Wesenheit index, which are all very tightly defined.
Fitting the OGLE LMC slopes in the various bands to our data, we have derived
distance values for NGC 6822 in V, I and ${\rm W}_{\rm I}$ which agree very
well among themselves. Our adopted best distance value from the reddening-free
Wesenheit index is 23.34 $\pm$ 0.04 (statistical) $\pm$ 0.05 (systematic) mag.
This value agrees within the combined 1 sigma uncertainties with a previous
distance value derived for NGC 6822 by McAlary et al. from near-IR photometry
of 9 Cepheids, but our new value is significantly more accurate. We compare the
slopes of the Cepheid PL relation in V and I as determined in the five
best-observed nearby galaxies, which span a metallicity range from -1.0 to -0.3
dex, and find the data consistent with no metallicity dependence of the PL
relation slope in this range. Comparing the magnitudes of 10-day Cepheids with
the I-band magnitudes of the TRGB in the same set of galaxies, there is no
evidence either for a significant variation of the period-luminosity zero
points in V and I. The available data limit such a zero point variation to less
than 0.03 mag, in the considered low-metallicity regime.


title: Strong Gravitational Lenses in a Cold Dark Matter Universe

abstract:
  We present theoretical and observational studies of strong gravitational
lenses produced by clusters of galaxies. Our purpose is to test the Cold Dark
Matter (CDM) model at small and highly non-linear scales where it has been
claimed that the CDM model may confront several difficulties. We concentrate
our attention on the statistics of strong gravitational lenses. We use two
complementary statistics, lensed arcs and quasars, to probe the mass
distributions. First, we construct a triaxial lens model, and develop a new
method to include triaxiality of dark halos in the lens statistics. We find
that the effect of triaxiality is significant; it enhances lensing
probabilities by a factors of a few to ten, assuming the degree of triaxiality
predicted in the CDM model. In particular, we argue that both central
concentration and large triaxiality of dark halos are required to reproduce the
observed number of arcs in clusters; thus the result can be interpreted as a
strong evidence for the cold and collisionless dark matter. One of the most
notable advantages of the triaxial modeling is that the triaxial modeling
allows us to predict image multiplicities. We find that the CDM halos predict
significant fraction (more than 20%) of naked cusp lenses. In addition, we
point out the image multiplicities depend strongly on the central concentration
of dark halos. Therefore we propose image multiplicities as a new powerful test
of the CDM model. Finally we searched for large-separation lensed quasars from
the data of the Sloan Digital Sky Survey, and succeeded in discovering the
first large-separation lensed quasar SDSS J1004+4112. We find that the
discovery of the large-separation quadruple lens SDSS J1004+4112 is quite
consistent with the theoretical predictions based on the CDM model. (Abridged)


title:
Probing the embedded YSOs of the R CrA region through VLT-ISAAC
  spectroscopy

abstract:
  Near IR spectra obtained with ISAAC at VLT, have been used to pose
constraints on the evolutionary state and accretion properties of a sample of
five embedded YSOs located in the R CrA core. This sample includes three Class
I sources (HH100 IR, IRS2 and IRS5), and two sources with NIR excesses (IRS6
and IRS3). Absorption lines have been detected in the medium resolution spectra
of all the observed targets, together with emission lines likely originating in
the disk-star-wind connected regions. We derived spectral types, veiling and
stellar luminosity of the five observed sources, which in turn have been used
to infer their mass and age adopting pre-main sequence evolutionary tracks. We
find that in HH100 IR and IRS2 most of the bolometric luminosity is due to
accretion, while the other three investigated sources, including the Class I
object IRS5a, present a low accretion activity (L_{acc}/L_{bol} < 0.2). We
observe a general correlation between the accretion luminosity, the IR veiling
and the emission line activity of the sources. A correlation between the
accretion activity and the spectral energy distribution slope is recognizable
but with the notable exception of IRS5a. Our analysis therefore shows how the
definition of the evolutionary stage of deeply embedded YSOs by means of IR
colors needs to be more carefully refined.


title: A-Stars and the Virtual Observatory

abstract:
  The Virtual Observatory (VO) will revolutionise the way we do Astronomy, by
allowing easy access to all astronomical data and by making the handling and
analysis of datasets at various locations across the globe much simpler and
faster. I report here on the need for the VO and its status in Europe,
including the first ever VO-based astronomical paper, and then give two
specific applications of VO tools to open problems of A-stars research.


title: Simulations of the Population of Centaurs II: Individual Objects

abstract:
  Detailed orbit integrations of clones of five Centaurs -- namely, 1996 AR20,
2060 Chiron, 1995 SN55, 2000 FZ53 and 2002 FY36 -- for durations of 3 Myr are
presented. One of our Centaur sample starts with perihelion initially under the
control of Jupiter (1996 AR20), two start under the control of Saturn (Chiron
and 1995 SN55) and one each starts under the control of Uranus (2000 FZ53) and
Neptune (2002 FY36) respectively. A variety of interesting pathways are
illustrated with detailed examples including: capture into the Jovian Trojans,
repeated bursts of short-period comet behaviour, capture into mean-motion
resonances with the giant planets and into Kozai resonances, as well as
traversals of the entire Solar system. For each of the Centaurs, we provide
statistics on the numbers (i) ejected, (ii) showing short-period comet
behaviour and (iii) becoming Earth and Mars crossing. For example, Chiron has
over 60 % of its clones becoming short-period objects, whilst 1995 SN55 has
over 35 %. Clones of these two Centaurs typically make numerous close
approaches to Jupiter. At the other extreme, 2000 FZ53 has roughly 2 % of its
clones becoming short-period objects. In our simulations, typically 20 % of the
clones which become short-period comets subsequently evolve into
Earth-crossers.


title: Brans-Dicke Theory as a Unified Model for Dark Matter - Dark Energy

abstract:
  The Brans-Dicke (BD) theory of gravity is taken as a possible theory of
k-essence coupled to gravity. It then has been realized that the BD scalar
field does indeed play a role of a k-essence, but in a very unique way which
distinguishes it from other k-essence fields studied in the literature. That
is, first in the BD scalar field-dominated era when the contribution from this
k-essence overwhelms those from other types of matter, the BD theory predicts
the emergence of a yet-unknown {\it zero acceleration} epoch which is an
intermediate stage acting as a ``crossing bridge'' between the decelerating
matter-dominated era and the accelerating phase. Upon realizing this, next,
closer study of the effects of this k-essence on the evolutionary behavior of
the matter-dominated and the accelerating eras has been performed. The result
of the study indicates that the BD scalar field appears to interpolate {\it
smoothly} between these two late-time stages by speeding up the expansion rate
of the matter-dominated era somewhat while slowing down that of the
accelerating phase to some degree. Thus with the newly found BD scalar
field-dominated era in between these two, the late-time of the universe
evolution appears to be mixed sequence of the three stages.


title:
Spectral Classification of Quasars in the Sloan Digital Sky Survey:
  Eigenspectra; Redshift and Luminosity Effects

abstract:
  We study 16,707 quasar spectra from the SDSS using the Karhunen-Lo\`eve (KL)
transform (or Principal Component Analysis, PCA). The quasar eigenspectra of
the full catalog reveal the following: 1st order - the mean spectrum; 2nd order
- a host-galaxy component; 3rd order - the UV-optical continuum slope; 4th
order - the correlations of Balmer emission lines. We find that the spectral
classification of quasars is redshift and luminosity dependent, as such there
does not exist a compact set (< 10 modes) of eigenspectra (covering 900 to 8000
angstrom) which can describe most variations (> 95%) of the entire catalog. We
therefore construct several sets of eigenspectra in different redshift and
luminosity bins. From these eigenspectra we find that quasar spectra can be
classified (by the first two eigenspectra) into a sequence that is defined by a
simple progression in the steepness of the slope of the continuum. We also find
a dependence on redshift and luminosity in the eigencoefficients. The dominant
redshift effect is a result of the evolution of the blended FeII emission
(optical) and the Balmer continuum (the ``small bump''). A luminosity
dependence is also present in the eigencoefficients and is related to the
Baldwin effect. The eigenspectra constructed from the wavelength-selected SDSS
spectra are found to agree with the principal components by Francis et al.
(1992) and the well-known ``Eigenvector-1'' (Boroson and Green 1992).
(Abridged)


title: Charged Particle Dynamics in the Field of a Slowly Rotating Compact Star

abstract:
  We study the dynamics of a charged particle in the field of a slowly rotating
compact star in the gravitoelectromagnetic approximation to the geodesic
equation . The star is assumed to be surrounded by an ideal, highly conducting
plasma (taken as a magnetohydrodynamic fluid) with a stationary, axially
symmetric electromagnetic field. The general relativistic Maxwell equations are
solved to obtain the effects of the background spacetime on the electromagnetic
field in the linearized Kerr spacetime. The equations of motion are then set up
and solved numerically to incorporate the gravitational as well as the
electromagnetic effects. The analysis shows that in the slow rotation
approximation the frame dragging effects on the electromagnetic field are
absent. However the particle is directly effected by the rotating gravitational
source such that close to the star the gravitational and electromagnetic field
produce contrary effects on the particle's trajectory.


title: INTEGRAL observations of the field of the BL Lacertae object S5~0716+714

abstract:
  We have performed observations of the blazar S5 0716+714 with INTEGRAL on 2-6
April 2004. In the first months of 2004, the source had increased steadily in
optical brightness and had undergone two outbursts. During the latter, occurred
in March, it reached the extreme level of R = 12.1 mag, which triggered our
INTEGRAL program. The target has been detected with IBIS/ISGRI up to 60 keV,
with a flux of ~3 x 10e-11 erg/s/cm2 in the 30-60 keV interval, a factor of ~2
higher than observed by the BeppoSAX PDS in October 2000. In the field of S5
0716+714 we have also detected the Flat Spectrum Radio Quasar S5 0836+710 and
the two Seyfert galaxies Mkn 3 and Mkn 6. Their IBIS/ISGRI spectra are rather
flat, albeit consistent with those measured by BeppoSAX. In the spectrum of Mkn
3 we find some evidence of a break between ~60 and ~100 keV, reminiscent of the
high energy cut-offs observed in other Seyfert galaxies. This is the first
report of INTEGRAL spectra of weak Active Galactic Nuclei.


title:
Absolute kinematics of radio source components in the complete S5 polar
  cap sample

abstract:
  We observed the thirteen extragalactic radio sources of the complete S5 polar
cap sample at 15.4 GHz with the Very Long Baseline Array, on 27 July 1999
(1999.57) and 15 June 2000 (2000.46). We present the maps from those two
epochs, along with maps obtained from observations of the 2 cm VLBA survey for
some of the sources of the sample, making a total of 40 maps. We discuss the
apparent morphological changes displayed by the radio sources between the
observing epochs. Our VLBA observations correspond to the first two epochs at
15.4 GHz of a program to study the absolute kinematics of the radio source
components of the members of the sample, by means of phase delay astrometry at
8.4 GHz, 15.4 GHz, and 43 GHz.
  Our 15.4 GHz VLBA imaging allowed us to disentangle the inner milliarcsecond
structure of some of the sources, thus resolving components that appeared
blended at 8.4 GHz. For most of the sources, we identified the brightest
feature in each radio source with the core. These identifications are supported
by the spectral index estimates for those brightest features, which are in
general flat, or even inverted. Most of the sources display core-dominance in
the overall emission. We find that three of the sources have their most
inverted spectrum component shifted with respect to the origin in the map,
which approximately coincides with the peak-of-brightness at both 15.4 GHz and
8.4 GHz.


title:
High spatial resolution mid-infrared spectroscopy of NGC 5253: The
  stellar content of the embedded super-star cluster

abstract:
  We present the N-band (8-13 micron) spectrum of the hidden compact radio
super-star cluster in NGC 5253, C2, obtained with TIMMI2 on the ESO 3.6m
telescope. The spectrum is characterised by a rising continuum due to warm
dust, a silicate absorption and a strong [SIV] line at 10.5 micron. Weaker
lines of [ArIII] at 9.0 micron and [NeII] at 12.8 micron are also present. The
continuum can be modeled by an optically thick emission from hot dust emission
extinguished by a cold foreground dust screen and a silicate absorption feature
with A_sil = 0.73+/-0.05 mag. We show how the spatial scale of the observations
greatly determine the mid-IR appearance of NGC 5253 and the important
implications that this has on the interpretation of line fluxes in terms of the
properties (age, IMF, etc.) of the embedded cluster. We have modeled the
observed line fluxes towards C2 using photoionisation models with the most
recent spectral energy distributions available to describe the integrated
properties of the stellar cluster. Strong constraints on the geometry based on
high spatial resolution observations at different wavelengths -- near-IR (HST
and Keck), mid-IR (TIMMI2) and radio (VLA) -- allows us to restrain the
ionisation parameters to values logU >= -0.5 dex. This constraint on U lead to
two possible solutions for the age and upper mass cutoff of C2: 1) a young (< 4
Myr) cluster with a "non-standard" IMF with a low upper mass cutoff Mup < 50
Msun, and 2) a cluster of ~5-6 Myr with a standard high upper mass cutoff (Mup
\~ 100 Msun). Arguments in favour and against these two scenarios are
presented. The origin of the [OIV] 25.9 micron emission measured by ISO and the
possible presence of an intermediate mass black hole inside C2 are also
addressed.


title: Mapping the Cosmic Web with the Sloan Digital Sky Survey

abstract:
  Wide-angle, moderately deep redshift surveys such as that conducted as part
of the Sloan Digital Sky Survey (SDSS) allow study of the relationship between
the structural elements of the large-scale distribution of galaxies --
including groups, cluster, superclusters, and voids -- and the dependence of
galaxy formation and evolution on these enviroments. We present a progress
report on mapping efforts with the SDSS and discuss recently constructed
catalogs of clusters, voids, and void galaxies, and evidence for a 420Mpc/h
supercluster or ``Great Wall.'' Analysis of multi-band photometry and
moderate-resolution spectroscopy from the SDSS reveals environmental dependence
of the star formation history of galaxies that extends over more than a factor
of 100 in density, from clusters all the way to the deep interiors of voids. On
average, galaxies in the rarified environments of voids exhibit bluer colors,
higher specific star formation rates, lower dust content, and more disk-like
morphology than objects in denser regions. This trend persists in comparisons
of samples in low vs. high-density regions with similar luminosity and
morphology, thus this dependence is not simply an extension of the
morphology-density relation. Large-scale modulation of the halo mass function
and the temperature of the intergalactic medium might explain this dependence
of galaxy evolution on the large-scale environment.


title:
Indirect evidence for an active radio pulsar in the quiescent state of
  the transient ms pulsar SAX J1808.4-3658

abstract:
  Millisecond radio pulsars are neutron stars that have been spun-up by the
transfer of angular momentum during the low-mass X-ray binary phase. The
transition from an accretion-powered to a rotation-powered pulsar takes place
on evolutionary timescales at the end of the accretion process, however it may
also occur sporadically in systems undergoing transient X-ray activity. We have
obtained the first optical spectrum of the low mass transient X-ray pulsar SAX
J1808.4-3658 in quiescence. Similar to the black widow millisecond pulsar
B1957+20, this X-ray pulsar shows a large optical modulation at the orbital
period due to an irradiated companion star. Using the brightness of the
companion star as a bolometer, we conclude that a very high irradiating
luminosity, a factor of ~100 larger than directly observed, must be present in
the system. This most likely derives from a rotation-powered neutron star that
resumes activity during quiescence.


title:
Detection of a NEPTUNE-mass planet in the $\rho^{1}$ Cancri system using
  the Hobby-Eberly Telescope

abstract:
  We report the detection of the lowest mass extra-solar planet yet found
around a Sun-like star - a planet with an \msini of only 14.21 $\pm$ 2.91 Earth
masses in an extremely short period orbit (P=2.808 days) around $\rho^{1}$
Cancri, a planetary system which already has three known planets. Velocities
taken from late 2003-2004 at McDonald Observatory with the Hobby-Eberly
Telescope (HET) revealed this inner planet at 0.04 AU. We estimate an
inclination of the outer planet $\rho^{1}$ Cancri d, based upon {\it Hubble
Space Telescope} Fine Guidance Sensor (FGS) measurements. This inclination
suggests an inner planet of only 17.7 $\pm$ 5.57 Earth masses, if coplanarity
is assumed for the system.


title:
Tunable-filter imaging of quasar fields at z ~ 1. II. The star-forming
  galaxy environments of radio-loud quasars

abstract:
  We have scanned the fields of six radio-loud quasars using the Taurus Tunable
Filter to detect redshifted [OII] 3727 line-emitting galaxies at redshifts 0.8
< z < 1.3. Forty-seven new emission-line galaxy (ELG) candidates are found.
This number corresponds to an average space density about 100 times that found
locally and, at L([OII]) < 10^{42} erg s^{-1} cm^{-2}, is 2 - 5 times greater
than the field ELG density at similar redshifts, implying that radio-loud
quasars inhabit sites of above-average star formation activity. The implied
star-formation rates are consistent with surveys of field galaxies at z ~ 1.
However, the variation in candidate density between fields is large and
indicative of a range of environments, from the field to rich clusters. The ELG
candidates also cluster -- both spatially and in terms of velocity -- about the
radio sources. In fields known to contain rich galaxy clusters, the ELGs lie at
the edges and outside the concentrated cores of red, evolved galaxies,
consistent with the morphology-density relation seen in low-redshift clusters.
This work, combined with other studies, suggests that the ELG environments of
powerful AGN look very much the same from moderate to high redshifts, i.e. 0.8
< z < 4.


title: A Neptune-Mass Planet Orbiting the Nearby M Dwarf GJ 436

abstract:
  We report precise Doppler measurements of GJ 436 (M2.5V) obtained at Keck
Observatory. The velocities reveal a planetary companion with orbital period of
2.644 d, eccentricity of 0.12 (consistent with zero) and velocity
semi-amplitude of $K =18.1$ \ms. The minimum mass (\msini) for the planet is
0.067 \mjup = 1.2 M$_{\rm NEP}$ = 21 M$_{\rm EARTH}$, making it the lowest mass
exoplanet yet found around a main sequence star and the first candidate in the
Neptune mass domain. GJ 436 (Mass = 0.41 \msune) is only the second M dwarf
found to harbor a planet, joining the two--planet system around GJ 876. The low
mass of the planet raises questions about its constitution, with possible
compositions of primarily H and He gas, ice/rock, or rock--dominated. The
implied semi--major axis is $a$ = 0.028 AU = 14 stellar radii, raising issues
of planet formation, migration, and tidal coupling with the star. GJ 436 is
$>3$ Gyr old, based on both kinematic and chromospheric diagnostics. The star
exhibits no photometric variability on the 2.644-day Doppler period to a
limiting amplitude of 0.0004 mag, supporting the planetary interpretation of
the Doppler periodicity. Photometric transits of the planet across the star are
ruled out for gas giant compositions and are also unlikely for solid
compositions. As the third closest known planetary system, GJ 436 warrants
follow--up observations by high resolution optical and IR


title: Numerical Modeling of Eta Carinae Bipolar Outflows

abstract:
  In this paper, we present two-dimensional gas dynamic simulations of the
formation and evolution of the eta-Car bipolar outflows. Adopting the
interacting nonspherical winds model, we have carried out high-resolution
numerical simulations, which include explicitly computed time-dependent
radiative cooling, for different possible scenarios of the colliding winds. In
our simulations, we consider different degrees of non-spherical symmetry for
the pre-outburst wind and the great eruption of the 1840s presented by the
eta-Car wind. From these models, we obtain important differences in the shape
and kinematical properties of the Homunculus structure. In particular, we find
an appropriate combination of the wind parameters (that control the degree of
non-spherical symmetry) and obtain numerical experiments that best match both
the observed morphology and the expansion velocity of the eta-Car bipolar
shell. In addition, our numerical simulations show the formation of a bipolar
nebula embedded within the Homunculus (the little Homunculus) developed from a
secondary eruptive event suffered by the star in the 1890s, and also the
development of tenuous, high velocity ejections in the equatorial region that
result from the impact of the eruptive wind of the 1840s with the pre-outburst
wind and that could explain some of the high speed features observed in the
equatorial ejecta. The models were, however, unable to produce equatorial
ejections associated to the second eruptive event.


title:
An All-Sky Survey for the Detection of Transiting Extrasolar Planets and
  for Permanent Variable Star Tracking

abstract:
  An overview is given of the Permanent All Sky Survey (PASS) project. The
primary goal of PASS is the detection of all transiting giant planets in the
entire sky, complete for stellar systems of magnitudes ~ 5.5-10.5. Since the
sample stars are fairly bright and relatively close, planets detected by PASS
would be ideally suited for any follow-up study with ground- or space-based
instrumentation. The survey would also allow the pursuit of a variety of work
on temporal astronomical phenomena of any kind, and is intended to lead to a
permanent all-sky tracking of variable stars with high temporal resolution. The
instrument consists of arrays of CCD cameras with wide-field optics that cover
the entire sky visible from their observing locations. Calculations of the
instrument's noise sources and subsequent simulations indicate that the
proposed design is able to achieve the prime objective of a full-sky survey for
transits. An equation for the signal-to-noise ratio from photometry of unguided
stellar images is given in the appendix, together with equations for the
detection probability of planetary transits based on the observational coverage
and the instrument's duty cycle.


title:
Relativistic Accretion Disk Models of High State Black Hole X-ray Binary
  Spectra

abstract:
  We present calculations of non-LTE, relativistic accretion disk models
applicable to the high/soft state of black hole X-ray binaries. We include the
effects of thermal Comptonization and bound-free and free-free opacities of all
abundant ion species. We present spectra calculated for a variety of accretion
rates, black hole spin parameters, disk inclinations, and stress prescriptions.
We also consider nonzero inner torques on the disk, and explore different
vertical dissipation profiles, including some which are motivated by recent
radiation MHD simulations of magnetorotational turbulence. Bound-free metal
opacity generally produces significantly less spectral hardening than previous
models which only considered Compton scattering and free-free opacity. It also
tends to keep the effective photosphere near the surface, resulting in spectra
which are remarkably independent of the stress prescription and vertical
dissipation profile, provided little dissipation occurs above the effective
photosphere. We provide detailed comparisons between our models and the widely
used multicolor disk model. Frequency dependent discrepancies exist that may
affect the parameters of other spectral components when this simpler disk model
is used to fit modern X-ray data. For a given source, our models predict that
the luminosity in the high/soft state should approximately scale with the
fourth power of the empirically inferred maximum temperature, but with a slight
hardening at high luminosities. This is in good agreement with observations.
(abridged)


title:
The small Blue Straggler star population in the dense Galactic Globular
  Cluster NGC 6752

abstract:
  We have used high resolution WFPC2-HST and wide field ground-based
observations to construct a catalog of blue straggler stars (BSS) which spans
the entire radial extent of the globular cluster NGC 6752. The BSS sample is
the most extensive ever obtained for this cluster. Though NGC 6752 is a high
density cluster with a large binary population, we found that its BSS content
is surprisingly low: the specific number of BSS is among the lowest ever
measured in a cluster. The BSS distribution is highly peaked in the cluster
center, shows a rapid decrease at intermediate radii, and finally rises again
at larger distances. This distribution closely resembles those observed in M3
and 47Tuc by Ferraro et al. (1993), Ferraro et al. (2003c). To date, BSS
surveys covering the central regions with HST and the outer regions with wide
field CCD ground-based observations have been performed for only these three
clusters. Despite the different dynamical properties, a bimodal radial
distribution has been found in each. A detailed comparison of observed BSS
luminosity and temperature distributions with theoretical models reveals a
population of luminous, hot BSS which is not easily interpreted.


title:
Laboratory coded aperture imaging experiments: radial hole coded masks
  and depth-sensitive CZT detectors

abstract:
  The proposed black-hole finder mission EXIST will consist of multiple
wide-field hard X-ray coded-aperture telescopes. The high science goals set for
the mission require innovations in telescope design. In particular, wide energy
band coverage and fine angular resolution require relatively thick coded masks
and thick detectors compared to their pixel size, which may introduce mask
self-collimation and depth-induced image blurring with conventional design
approaches. Previously we proposed relatively simple solutions to these
potential problems: radial hole for mask selfcollimation and cathode depth
sensing detector for image blurring. We have now performed laboratory
experiments to explore the potential of these two techniques. The experimental
results show that the radial hole mask greatly alleviates mask self-collimation
and a ~1 mm resolution depth-sensitive detector scheme can be relatively easily
achieved for the large scale required for EXIST.


title:
Evidence for new unidentified TeV gamma-ray sources from
  angularly-correlated hot-spots observed by independent TeV gamma-ray sky
  surveys

abstract:
  We have examined the directional cross-correlation of statistical `hot-spots'
between a Northern Sky TeV Gamma Ray Survey by the Milagro Observatory and a
similar survey by the Tibet Array. We find the directions of these hot-spots
are angularly uncorrelated between the two surveys for large angular
separations (Delta theta > 4 degrees), but there appears to be a statistically
significant correlation between hot-spot directions for Delta theta < 1.5
degrees. Independent simulations indicate the chance probability for the
occurrence of this correlation is approximately 10^-4, implying the existence
of one or more previously unobserved TeV gamma-ray sources in these directions.
The data sets are consistent with both point-like sources or diffuse sources
with extent of 1 - 2 degrees.


title: A Substantial Amount of Hidden Magnetic Energy in the Quiet Sun

abstract:
  Deciphering and understanding the small-scale magnetic activity of the quiet
solar photosphere should help to solve many of the key problems of solar and
stellar physics, such as the magnetic coupling to the outer atmosphere and the
coronal heating. At present, we can see only ${\sim}1%$ of the complex
magnetism of the quiet Sun, which highlights the need to develop a reliable way
to investigate the remaining 99%. Here we report three-dimensional radiative
tranfer modelling of scattering polarization in atomic and molecular lines that
indicates the presence of hidden, mixed-polarity fields on subresolution
scales. Combining this modelling with recent observational data we find a
ubiquitous tangled magnetic field with an average strength of ${\sim}130$ G,
which is much stronger in the intergranular regions of solar surface convection
than in the granular regions. So the average magnetic energy density in the
quiet solar photosphere is at least two orders of magnitude greater than that
derived from simplistic one-dimensional investigations, and sufficient to
balance radiative energy losses from the solar chromosphere.


title:
Signatures of Incomplete Paschen-Back Splitting in the Polarization
  Profiles of the He I 10830 multiplet

abstract:
  We investigate the formation of polarization profiles induced by a magnetic
field in the He I multiplet at 1083,0 nm . Our analysis considers the Zeeman
splitting in the incomplete Paschen-Back regime. The effects turn out to be
important and produce measurable signatures on the profiles, even for fields
significantly weaker than the level-crossing field ($\sim$400 G). When compared
to profiles calculated with the usual linear Zeeman effect, the incomplete
Paschen-Back profiles exhibit the following conspicuous differences: a) a
non-Doppler blueshift of the Stokes V zero-crossing wavelength of the blue
component; b) area and peak asymmetries, even in the absence of velocity and
magnetic gradients; c) a $\sim$25% reduction in the amplitude of the red
component. These features do not vanish in the weak field limit. The spectral
signatures that we analyze in this paper may be found in previous observations
published in the literature.


title: The Fundamental Plane Evolution of Active Galactic Nucleus Host Galaxies

abstract:
  We measured the stellar velocity dispersions of 15 active galactic nucleus
(AGN) host galaxies at redshifts as high as $\sim 0.34$. Combining these with
published velocity dispersion measurements from the literature, we study the
Fundamental Plane of AGN host galaxies and its evolution. BL Lac hosts and
radio galaxies seem to lie on the same Fundamental Plane as normal early-type
galaxies. The evolution of the mass-to-light ratio of AGN host galaxies shows a
similar trend to that observed in normal early-type galaxies, consistent with
single-burst passive evolution models with formation redshifts $z \gtrsim 1$.
The lack of a significant difference between normal and AGN host galaxies in
the Fundamental plane supports the "Grand Unification" picture wherein AGNs are
a transient phase in the evolution of normal galaxies. The black hole masses of
BL Lac objects and radio galaxies, derived using the mass -- dispersion
relation, are similar. The black hole mass is independent of BL Lac type. The
local black hole mass -- host galaxy luminosity relation of our sub-sample at
$z < 0.1$ is similar to that of local normal and radio galaxies, but is less
well defined at higher redshift due to the luminosity evolution of the host
galaxies.


title:
Full-sky correlation functions for CMB experiments with asymmetric
  window functions

abstract:
  We discuss full-sky convolution of the instrumental beam with the CMB sky
signal in CMB single-dish and interferometry experiments, using the method
(Challinor et al. 2000) that the measured temperature and polarization
anisotropies are defined globally on the group manifold of the
three-dimensional rotation by means of Wigner D-functions. We re-derive the
anisotropy and polarization correlation functions incorporated with asymmetric
window functions, which are then explicitly calculated for a single-dish
elliptical Gaussian beam and an interferometric Gaussian beam.


title: Magnetospheres and Disk Accretion in Herbig Ae/Be Stars

abstract:
  We present evidence of magnetically-mediated disk accretion in Herbig Ae/Be
stars. Magnetospheric accretion models of Balmer and sodium profiles calculated
with appropriate stellar and rotational parameters are in qualitative agreement
with the observed profiles of the Herbig Ae star UX Ori, and yield a mass
accretion rate of ~ 10^{-8} Msun/yr. If more recent indications of an extremely
large rotation rate for this object are correct, the magnetic field geometry
must deviate from that of a standard dipole in order to produce line emission
consistent with observed flux levels. Models of the associated accretion shock
qualitatively explain the observed distribution of excess fluxes in the Balmer
discontinuity for a large ensemble of Herbig Ae/Be stars, and imply typically
small mass accretion rates, < 10^{-7} Msun/yr. In order for accretion to
proceed onto the star, significant amounts of gas must exist inside the dust
destruction radius, which is potentially problematic for recently advocated
scenarios of "puffed" inner dust wall geometries. However, our models of the
inner gas disk show that for the typical accretion rates we have derived, the
gas should be generally optically thin, thus allowing direct stellar
irradiation of the inner dust edge of the disk.


title: QSO-Galaxy Association and Gravitational Lensing

abstract:
  The amplification caused by gravitational light bending by compact objects in
a foreground galaxy can affect the apparent number density of background QSOs,
as well as their distribution in the fields of galactic halos. In this work we
investigate the number enhancement of QSOs in the fields of galactic halos
caused by point mass lensing effect and singular isothermal lensing effect, and
apply the microlensing effect due to dark compact objects in the halo to NGC
3628. NGC 3628 is a well-studied nearby edge-on Sbc peculiar galaxy, where QSOs
are shown to be concentrated around the galaxy with a density much higher than
background. We show that if present understanding of the luminosity function of
QSOs is right, such concentration could not be caused by gravitational lensing.


title:
Probing Warm-Hot Intergalactic Medium Associated with the Virgo Cluster
  using an Oxygen Absorption Line

abstract:
  To detect a warm-hot intergalactic medium associated with the large-scale
structure of the universe, we observed a quasar behind the Virgo cluster with
XMM-Newton. With a net exposure time of 54 ks, we marginally detected an OVIII
K alpha absorption line at 650.9 +0.8/-1.9 eV in the RGS spectra, with a
statistical confidence of 96.4 %. The observed line center energy is consistent
with the redshift of M87, and hence the absorber is associated with the Virgo
cluster. From the curve of growth, the OVIII column density was estimated to be
> 7 x 10^16 cm^-2. In the EPIC spectra, excess emission was found after
evaluating the hot intracluster medium in the Virgo cluster and various
background components. We inspected the ROSAT All-Sky Survey map of the diffuse
soft X-ray background, and confirmed that the level of the north and west
regions just outside of the Virgo cluster is consistent with the background
model that we used, while that of the east side is significantly higher and the
enhancement is comparable with the excess emission found in the EPIC data. We
consider a significant portion of the excess emission to be associated with the
Virgo cluster, although a possible contribution from the North Polar Spur
cannot be excluded. Using the column density and the emission measure and
assuming an oxygen abundance of 0.1 and an ionization fraction of 0.4, we
estimate that the mean electron density and the line-of-sight distance of the
warm-hot gas are < 6 x 10^-5 cm^-3 and > 9 Mpc, respectively. These numbers
strongly suggest that we have detected a warm-hot intergalactic medium in a
filament associated with the Virgo cluster.


title:
Confirmation of the effectiveness of sub-mm source redshift estimation
  based on rest-frame radio to FIR photometry

abstract:
  We present a comparison between the published optical, IR and CO
spectroscopic redshifts of 15 (sub-)mm galaxies and their photometric redshifts
as derived from long-wavelength (radio-mm-FIR) photometric data. The redshift
accuracy measured for 12 sub-mm galaxies with at least one robustly-determined
colour in the radio-mm-FIR regime is dz=0.30 (r.m.s.). Despite the wide range
of spectral energy distributions in the local galaxies that are used in an
un-biased manner as templates, this analysis demonstrates that photometric
redshifts can be efficiently derived for sub-mm galaxies with a precision of dz
< 0.5 using only the rest-frame FIR to radio wavelength data.


title:
The Serendipitous Extragalactic X-Ray Source Identification (SEXSI)
  Program: II. Optical Imaging

abstract:
  The Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program
is designed to expand significantly the sample of identified extragalactic hard
X-ray sources at intermediate fluxes, 1e-13 erg/cm2/s < S_(2-10 keV) < 1e-15
erg/cm2/s. SEXSI, which includes sources derived from more than 2 sq deg of
Chandra images, provides the largest hard X-ray-selected sample yet studied,
offering an essential complement to the Chandra Deep Fields (total area ~0.2 sq
deg). In this paper we describe R-band optical imaging of the SEXSI fields from
the Palomar, MDM, and Keck observatories. We have identified counterparts, or
derived flux limits for nearly 1000 hard X-ray sources. Using the optical
images, we derive accurate source positions. We investigate correlations
between optical and X-ray flux, and optical flux and X-ray hardness ratio. We
also study the density of optical sources surrounding X-ray counterparts, as
well as the properties of optically-faint, hard X-ray sources.


title: Young core collapse supernova remnants and their supernovae

abstract:
  Massive star supernovae can be divided into four categories depending on the
amount of mass loss from the progenitor star and the star's radius: red
supergiant stars with most of the H envelope intact (SN IIP), stars with some H
but most lost (IIL, IIb), stars with all H lost (Ib, Ic), and blue supergiant
stars with a massive H envelope (SN 1987A-like). Various aspects of the
immediate aftermath of the supernova are expected to develop in different ways
depending on the supernova category: mixing in the supernova, fallback on the
central compact object, expansion of any pulsar wind nebula, interaction with
circumstellar matter, and photoionization by shock breakout radiation. The
observed properties of young supernova remnants allow many of them to be placed
in one of the supernova categories; all the categories are represented except
for the SN 1987A-like type. Of the remnants with central pulsars, the pulsar
properties do not appear to be related to the supernova category. There is no
evidence that the supernova categories form a mass sequence, as would be
expected in a single star scenario for the evolution. Models for young pulsar
wind nebulae expanding into supernova ejecta indicate initial pulsar periods of
10-100 ms and approximate equipartition between particle and magnetic energies.
Ages are obtained for pulsar nebulae, including an age of 2400 pm 500 yr for
3C58, which is not consistent with an origin in SN 1181. There is no evidence
that mass fallback plays a role in neutron star properties.


title:
An optical absorption study of the Helix Planetary Nebula: NaI and CaII
  lines, and a search for diffuse bands

abstract:
  We present the results of an optical absorption study of NGC 7293, the Helix
planetary nebula (PN), designed to search for diffuse band (DIB) absorptions
perhaps arising in the carbon-rich circumstellar matter of the PN. We made high
resolution spectra of 8 stars located close to and behind the Helix. Through a
detailed analysis of the NaI and CaII lines, we find that two lines of sight
situated close to the PN as mapped in CO and HI exhibit very strong NaI
absorption. This absorption is due to the PN neutral or molecular material. No
corresponding CaII line is observed in agreement with the very high Ca
depletion often observed in PNs. No trace of any DIB features was found in
these two circumstellar lines of sight (shortened abstract).


title: The variable cyclotron line in GX 301-2

abstract:
  We present pulse phase resolved spectra of the hypergiant high mass X-ray
binary GX 301-2. We observed the source in 2001 October with RXTE continuously
for a total on-source time of almost 200ksec. We model the continuum with both,
a heavily absorbed partial covering model and a reflection model. In either
case we find that the well known cyclotron resonant scattering feature (CRSF)
at 35keV is - although present at all pulse phases - strongly variable over the
pulse: the line position varies by 25% from 30keV in the fall of the secondary
pulse to 38keV in the fall of the main pulse where it is deepest. The line
variability implies that we are seeing regions of magnetic field strength
varying between 3.4 10^12G and 4.2 10^12G.


title: On the mass of the gravitational lenses in LMC

abstract:
  In the self--lensing framework, we estimate the modal values of the mass of
the gravitational lenses found by the MACHO collaboration towards the Large
Magellanic Cloud (LMC). Our results suggest that only the events located near
the center can be identified as a low mass star population belonging to the LMC
disk or bar components.


title: Pumping of a Planetesimal Disc by a Rapidly Migrating Planet

abstract:
  We examine the effect of a rapidly migrating protoplanet on a ring of
planetesimals. The eccentricities of the planetesimals are usually increased by
$\Delta e \in (0.01, 0.1)$, with the exact increase being proportional to the
protoplanet's mass, and inversely proportional to its migration rate. The
eccentricity distribution is also substantially changed from a Rayleigh
distribution. We discuss the possible implications for further planet
formation, and suggest that the rapid passage of a protoplanet may not prevent
the planetesimal disc from forming further planets.


title: The First Cosmic Structures and their Effects

abstract:
  Despite much recent theoretical and observational progress in our knowledge
of the early universe, many fundamental questions remain only partially
answered. Here, we review the latest achievements and persisting problems in
the understanding of first cosmic structure formation.


title:
Equilibrium properties of self-interacting neutrinos in the
  quasi-particle approach

abstract:
  In this work a neutrino gas in equilibrium is studied both at T=0 and at
finite temperature. Neutrinos are treated as massive Dirac quasi-particles with
two generations. We include self-interactions among the neutrinos via neutral
currents, as well as the interaction with a background of matter. To obtain the
equilibrium properties we use Wigner function techniques. To account for
corrections beyond the Hartree approximation, we also introduce correlation
functions. We prove that, under the quasi-particle approximation, these
correlation functions can be expressed as products of Wigner functions. We
analyze the main properties of the neutrino eigenmodes in the medium, such as
effective masses and mixing angle. We show that the formulae describing these
quantities will differ with respect to the case with no self-interactions.


title:
Fundamental Physics with the SKA:Strong-Field Tests of Gravity Using
  Pulsars and Black Holes

abstract:
  The Square-Kilometre-Array (SKA) will be a radio telescope with a collecting
area that will exceed that of existing telescopes by a factor of a hundred or
so. This contribution summarises one of the key-science projects selected for
the SKA.
  The sensitivity of the SKA allows us to perform a Galactic Census of pulsars
which will discover a large fraction of active pulsars beamed to us, including
the long-sought for pulsar-black hole systems. These systems are unique in
their capability to probe the ultra-strong field limit of relativistic gravity.
By using pulsar timing we can determine the properties of stellar and massive
black holes, thereby testing the Cosmic Censorship Conjecture and the No-Hair
theorem. The large number of millisecond pulsars discovered with the SKA will
also provide us with a dense array of precision clocks on the sky. These clocks
will act as the multiple arms of a huge gravitational wave detector, which can
be used to detect and measure the stochastic cosmological gravitational wave
background that is expected from a number of sources.


title:
e-VLBI... a Wide-field Imaging Instrument with milliarcsecond Resolution
  & microJy Sensitivity

abstract:
  The European VLBI Network (EVN) is in the process of establishing an e-VLBI
array in which the radio telescopes and the EVN correlator at JIVE are
connected in real-time, via high-speed national fibre optic networks and the
pan-European research network, GEANT. This paper reports on recent test
results, including the production of the first real-time e-VLBI astronomical
image. In a parallel and related development, the field-of-view of VLBI is also
expanding by many orders of magnitude, and the first results of deep,
wide-field surveys capable of detecting many sources simultaneously are
summarised. The detection of sources as faint as 10 microJy should soon be
possible in the era of ``Mk5'' and e-VLBI.


title:
Gamma rays precursors and afterglows surrounding UHECR events: Z-burst
  model is still alive

abstract:
  The Z-burst model and the direct propagation of UHE proton in negligible
extragalactic magnetic fields produce gamma-rays afterglows and precursors
halos, respectively at GeVs and TeV energy band a few degree around the UHECR
arrival direction. The possible correlation of UHECR clusters (doublet,
triplet) with nearby BL Lac sources at E_p = 4*10^19 eV offer a test for this
necessary Gamma-UHECR trace. We estimate the secondary gamma energy and spectra
and we suggest how to disentangle between the different scenarios. We show why
Z-Burst model is still the most realistic model to explain UHECR behaviour and
their correlation to known BL Lac sources.


title:
Surface Brightness and Stellar Populations at the Outer Edge of the
  Large Magellanic Cloud: No Stellar Halo Yet

abstract:
  We present a high quality CMD for a 36'x 36' field located 8 degrees (7 kpc)
from the LMC center, as well as a precise determination of the LMC surface
brightness derived from the resolved stellar population out to this large
galactocentric radius. This deep CMD shows for the first time the detailed age
distribution at this position, where the surface brightness is V=26.5 mag/sq".
At a radius R=474' the main sequence is well populated from the oldest turnoff
at I=21.5 to the 2.5 Gyr turnoff at I=19.5. Beyond this radius, a relatively
strong gradient in the density of stars with ages in the 2.5-4 Gyr range is
apparent. There are some stars brighter and bluer than the main population,
quite uniformly distributed over the whole area surveyed, which are well
matched by a 1.5 Gyr isochrone and may be indicative of a relatively recent
star formation, or merger, event. The surface brightness profile of the LMC
remains exponential to this large galactocentric radius and shows no evidence
of disk truncation. Combining the information on surface brightness and stellar
population we conclude that the LMC disk extends (and dominates over a possible
stellar halo) out to a distance of at least 7 kpc. These results confirm that
the absence of blue stars in the relatively shallow off-center CMDs of dIrr
galaxies is not necessarily evidence for an exclusively old stellar population
resembling the halo of the Milky Way.


title: Y2 Isochrones with an Improved Core Overshoot

abstract:
  Convective core overshoot affects stellar evolution rates and the dating of
stellar populations. In this paper, we provide a patch to the $Y^2$ isochrones
with an improved treatment of convective core overshoot. The new tracks cover
the transition mass range from no convective core to a fully developed
convective core. We compare the improved isochrones to CMDs of a few well
observed open star clusters in the Galaxy and the Large Magellanic Cloud.
Finally we discuss future prospects for improving the treatment of core
overshoot with the help of asteroseismology.


title:
Distances of Quasars and Quasar-Like Galaxies: Further Evidence that
  QSOs may be Ejected from Active Galaxies

abstract:
  If high-redshift QSOs are ejected from the nuclei of low-redshift galaxies,
as some have claimed, a large portion of their redshift must be intrinsic
(non-Doppler). If these intrinsic components have preferred values, redshifts
will tend to cluster around these preferred values and produce peaks in the
redshift distribution. Doppler ejection and Hubble flow components will broaden
each peak. Because ejection velocities are randomly directed and Hubble flow
components are always positive, in this model all peaks are expected to show an
asymmetry, extending further out in the red wing. If peaks are present showing
this predicted asymmetry, it can lead directly to an estimate of quasar
distances. Using two quasar samples, one with high redshifts and one with low,
it is shown here that not only do all peaks in these two redshift distributions
occur at previously predicted preferred values, they also all show the
predicted extra extension in the red wing. For the low and high redshift
samples the mean cosmological components are found to be z$_{c} \sim 0.024$ and
$\sim 0.066$, respectively. The difference can be explained by the improved
detection limit of the high redshift sample. These results offer further
evidence in favor of the model proposing that QSOs are ejected from active
galaxies.


title:
Rapid Oscillations in Cataclysmic Variables, and a Comparison with X-Ray
  Binaries

abstract:
  We compare some of the properties of rapid oscillations in cataclysmic
variables and X-Ray binaries. In addition to the earlier recognition that both
types possess the same correlation between high and low frequency
quasi-periodic oscillations, we have now found that the dwarf nova VW Hyi in
its late stages of outburst shows the 1:2:3 oscillations harmonics that are
seen in some neutron star and black hole X-Ray binaries. We point out that the
behaviour of the dwarf nova WZ Sge has some similarities to those of accreting
millisecond pulsars.


title:
WMAP Microwave Emission Interpreted as Dark Matter Annihilation in the
  Inner Galaxy

abstract:
  Excess microwave emission observed in the inner Galaxy (inner ~1 kpc) is
consistent with synchrotron emission from highly relativistic electron-positron
pairs produced by dark matter particle annihilation. More conventional sources
for this emission, such as free-free (thermal bremsstrahlung), thermal dust,
spinning dust, and the softer Galactic synchrotron traced by low-frequency
surveys, have been ruled out. The total power observed in the range 23 < nu <
61 GHz is between 10^{36} and 5x10^{36} erg/s, depending on the method of
extrapolation to the Galactic center, where bright foreground emission obscures
the signal. The inferred electron energy distribution is diffusion hardened,
and is in qualitative agreement with the energy distribution required to
explain the gamma ray excess in the inner Galaxy at 1-30 GeV as inverse-Compton
scattered starlight. We investigate the possibility that this population of
electrons is produced by dark matter annihilation of 100 GeV particles, with
cross section <sigma v>=2x10^{-26} cm^3/s, and an 1/r dark matter mass profile
truncated in the inner Galaxy, and find this scenario to be consistent with
current data.


title: Noise in strong lensing cosmography

abstract:
  Giant arcs in strong lensing galaxy clusters can provide a purely geometric
determination of cosmological parameters, such as the dark energy density and
equation of state. We investigate sources of noise in cosmography with giant
arcs, focusing in particular on errors induced by density fluctuations along
the line-of-sight, and errors caused by modeling uncertainties. We estimate
parameter errors in two independent ways, first by developing a Fisher matrix
formalism for strong lensing parameters, and next by directly ray-tracing
through N-body simulations using a multi-plane lensing code. We show that for
reasonable power spectra, density fluctuations from large-scale structure
produce > 100% errors in cosmological parameters derived from any single
sightline, precluding the use of individual clusters or golden lenses to derive
accurate cosmological constraints. Modeling uncertainties similarly can lead to
large errors, and we show that the use of parametrized mass models in fitting
strong lensing clusters can significantly bias the inferred cosmological
parameters. We lastly speculate on means by which these errors may be
corrected.


title:
Constraints on the role of synchrotron X-rays from jets of accreting
  black holes

abstract:
  We present an extension of the scale invariance formalism by Heinz & Sunyaev
(2003) which includes the effects of radiative cooling on the X-ray synchrotron
emission from core dominated jets and outflows. We derive the scaling relations
between the radio luminosity L_r, the synchrotron X-ray luminosity L_x, the
mass M, and the accretion rate of an accreting black hole. We argue that the
inclusion of synchrotron losses into the scaling relations is required by the
data used in Merloni, Heinz, & DiMatteo (2003) to define the "fundamental
plane'' correlation between L_r, L_x, and M in AGNs and Galactic X-ray
binaries. We then fit the new scaling relations to the "fundamental plane"
correlation. This allows us to derive statistical constraints on the
contribution from jet synchrotron emission to the X-rays from black holes, or,
alternatively, on the particle acceleration scheme at work in these jets. We
find that, in order for jet synchrotron X-rays to be consistent with the
observed "fundamental plane" correlation, the global particle spectrum must be
both steep: f(gamma) ~ gamma^(-(3.4 (+0.6-0.5)), and unbroken down to energies
well below the radio synchrotron regime. Such a steep particle distribution
would imply steeper X-ray spectra than observed in most sources contributing to
the correlation with avalailable X-ray spectral index measurements. We suggest
that, unless some assumptions of the scale invariance hypothesis are broken,
another emission mechanism (likely either disk radiation and/or inverse Compton
scattering in the jet) contributes significantly to the X-rays of a sizeable
fraction of the sources.


title:
Constraints on Dark Energy Models from Galaxy Clusters with Multiple
  Arcs

abstract:
  We make an exploratory study of how well dark energy models can be
constrained using lensed arcs at different redshifts behind cluster lenses.
Arcs trace the critical curves of clusters, and the growth of critical curves
with source redshift is sensitive to the dark-energy equation of state. Using
analytical models and numerically simulated clusters, we explore the key
factors involved in using cluster arcs as a probe of dark energy. We quantify
the sensitivity to lens mass, concentration and ellipticity with analytical
models that include the effects of dark energy on halo structure. We show with
simple examples how degeneracies between mass models and cosmography may be
broken using arcs at multiple redshifts or additional constraints on the lens
density profile. However we conclude that the requirements on the data are so
stringent that it is very unlikely that robust constraints can be obtained from
individual clusters. We argue that surveys of clusters, analyzed in conjunction
with numerical simulations, are a more promising prospect for arc-cosmography.
  We use such numerically simulated clusters to estimate how large a sample of
clusters/arcs could provide interesting constraints on dark energy models. We
focus on the scatter produced by differences in the mass distribution of
individual clusters. We find from our sample of simulated clusters that at
least 1000 pairs of arcs are needed to obtain constraints if the mass
distribution of individual clusters is taken to be undetermined. We discuss
several unsolved problems that need study to fully develop this method for
precision studies with future surveys.


title:
Structure and star formation in disk galaxies III. Nuclear and
  circumnuclear H alpha emission

abstract:
  From H alpha images of a carefully selected sample of 57 relatively large,
Northern spiral galaxies with low inclination, we study the distribution of the
H alpha emission in the circumnuclear and nuclear regions. At a resolution of
around 100 parsec, we find that the nuclear H alpha emission in the sample
galaxies is often peaked, and significantly more often so among AGN host
galaxies. The circumnuclear H alpha emission, within a radius of two kpc, is
often patchy in late-type, and absent or in the form of a nuclear ring in
early-type galaxies. There is no clear correlation of nuclear or circumnuclear
H alpha morphology with the presence or absence of a bar in the host galaxy,
except for the nuclear rings which occur in barred hosts. The presence or
absence of close bright companion galaxies does not affect the circumnuclear H
alpha morphology, but their presence does correlate with a higher fraction of
nuclear H alpha peaks. Nuclear rings occur in at least 21% (+-5%) of spiral
galaxies, and occur predominantly in galaxies also hosting an AGN. Only two of
our 12 nuclear rings occur in a galaxy which is neither an AGN nor a starburst
host. We confirm that weaker bars host larger nuclear rings. The implications
of these results on our understanding of the occurrence and morphology of
massive star formation, as well as non-stellar activity, in the central regions
of galaxies are discussed.


title: Superburst Ignition and Implications for Neutron Star Interiors

abstract:
  Superbursts are thought to be powered by the unstable ignition of a
carbon-enriched layer formed from the burning of accreted hydrogen and helium.
As shown by Cumming & Bildsten, the short recurrence time hinges on the crust
being sufficiently hot at densities > 1.0e9 g/cc. In this Letter, we
self-consistently solve for the flux coming from the deep crust and core. The
temperature where the carbon unstably ignites is only weakly sensitive to the
composition of the ashes of H/He burning, but does depend on the thermal
conductivity of the inner crust and the neutrino emissivity of the core. The
observed superburst recurrence times and energetics suggest that the crust
thermal conductivity is low, as if the crust were amorphous instead of
crystalline. If the conductivity is higher, such as from a lattice with
impurities, then matching the superburst properties require that the neutrino
emissivity be not stronger than modified Urca. Observations of
superbursts-energetics, recurrence times, and cooling times-therefore
complement observations of isolated cooling neutron stars and soft X-ray
transients in constraining properties of dense matter. Perhaps the most
interesting object in this regard is KS 1731-260, which produced a superburst
during its protracted accretion outburst but had a rapidly declining quiescent
luminosity.


title: On the Accelerated Expansion of the Universe

abstract:
  The Universe is filled with relic neutrinos, remnants from the Leptonic Era.
Since the formation of galaxies started, gravitation has modified the
Fermi-Dirac momentum distribution of these otherwise decoupled particles.
Decelerated neutrinos moving toward the field-free regions between galaxies
could violate the Pauli principle. The fermion degeneracy pressure resulting
from this leads to an accelerated motion of galaxies away from one another. We
show that this model not only offers a natural explanation for the accelerated
expansion of the Universe, but also allows a straightforward calculation of the
Hubble constant and the time-evolution of this constant. Moreover, it sets a
lower limit for the (average) neutrino mass. For the latter, we find $m_\nu >
0.25$ eV/$c^2$ (95% C.L).


title: High energy neutrinos from radio-quiet AGNs

abstract:
  Most active galactic nuclei (AGN) lack prominent jets, and show modest radio
emission and significant X-ray emission which arises mainly from the galactic
core, very near from the central black hole. We use a quantitative scenario of
such core-dominated radio-quiet AGN, which attributes a substantial fraction of
the X-ray emission to the presence of abortive jets involving the collision of
gas blobs in the core. Here we investigate the consequences of the acceleration
of protons in the shocks from such collisions. We find that protons will be
accelerated up to energies above the pion photoproduction threshold on both the
X-rays and the UV photons from the accretion disk. The secondary charged pions
decay, producing neutrinos. We predict significant fluxes of TeV-PeV neutrinos,
and show that the AMANDA II detector is already constraining several important
astrophysical parameters of these sources. Larger cubic kilometer detectors
such as IceCube will be able to detect such neutrinos in less than one year of
operation, or otherwise rule out this scenario.