title:
Temperature Bias in Measurements of The Hubble Constant Using The
  Sunyaev-Zeldovich Effect

abstract:
  Measurements of the Hubble constant to distant galaxy clusters using the
Sunyaev-Zeldovich effect are systematically low in comparison to values
obtained by other means. These measurements usually assume a spherical
isothermal $\beta$ model for the intracluster medium (ICM). We present the
results of a statistical analysis of {\em temperature bias} in $H_0$
determinations in a sample of 27 numerically simulated X-ray clusters drawn
from a $\Lambda$CDM model at z=0.5. We employ adaptive mesh refinement to
provide high resolution (15.6 h$^{-1} kpc$) in cluster cores which dominate the
X-ray and radio signals. Fitting synthetic X-ray and y-parameter maps to the
standard isothermal beta model, we find a broad, skewed distribution in
$f\equiv H_0(SZ)/H_0(actual)$ with a mean, median, and standard deviation of
0.89, 0.83 and 0.32 respectively, where $H_0(SZ)$ is the value of $H_0$ derived
by using Sunyaev-Zeldovich effect method and $H_0(actual)$ is the value used in
the cosmological simulation. We find that the clusters' declining temperature
profiles systematically lower estimates of $H_0$ by 10% to 20%. The declining
temperature profile of our adiabatic system is consistent with the result
including radiative cooling and supernovae feedback (Loken et al. 2002). We
thereby introduce a non-isothermal $\beta$ model as an improvement. Applying
the non-isothermal $\beta$ model to the refined sample with well-fitted
temperature profile, the value of f improves 9% relative to the actual value.
The study of the morphology and the clumping effects conclude that these two
factors combine to induce scatter in f of $\pm$ 30 %.


title: Microlensing of a Ring Model for Quasar Structure

abstract:
  Microlensing observations of the Q0957+561 A,B have consistently shown
evidence for structure in the quasar that has not been evident in available
microlensing models, where the luminous source has been consistently modeled as
a single large round structure. We show that the microlensing features can
easily be reproduced by a luminous quasar model motivated by observations; a
luminous inner accretion disc edge and outer ring-shaped structures where the
emission lines form. Such a model can explain all of the features known from 24
years of Q0957 microlensing observations.


title: Relativistic Hubble's law

abstract:
  Considering the hyperbolic nature of the universe, the Hubble's law and the
inverse square laws such as, the Coulomb's law and Newton's gravitational law,
should be modified in accordance with the special theory of relativity.
Consequently there is no the Hubble's length, which might be the observable
boundary of our universe, does not appear in point of view of the special
theory of relativity, and the Newton's third law still hold in the special
theory of relativity. Recent astronomical observations of type Ia supernovae
support the modified Hubble's law which also leads a view that the cosmic
microwave might come from extra-universes.


title: Vacuum polarization and photon mass in inflation

abstract:
  We give a pedagogical review of a mechanism through which long wave length
photons can become massive during inflation. Our account begins with a
discussion of the period of exponentially rapid expansion known as inflation.
We next describe how, when the universe is not expanding, quantum fluctuations
in charged particle fields cause even empty space to behave as a polarizable
medium. This is the routinely observed phenomenon of vacuum polarization. We
show that the quantum fluctuations of low mass, scalar fields are enormously
amplified during inflation. If one of these fields is charged, the vacuum
polarization effect of flat space is strengthened to the point that long wave
length photons acquire mass. Our result for this mass is shown to agree with a
simple model in which the massive photon electrodynamics of Proca emerges from
applying the Hartree approximation to scalar quantum electrodynamics during
inflation. A huge photon mass is not measured today because the original phase
of inflation ended when the universe was only a tiny fraction of a second old.
However, the zero-point energy left over from the epoch of large photon mass
may have persisted during the post-inflationary universe as very weak, but
cosmological-scale, magnetic fields. It has been suggested that these small
seed fields were amplified by a dynamo mechanism to produce the micro-Gauss
magnetic fields observed in galaxies and galactic clusters.


title:
Uncovering Additional Clues to Galaxy Evolution. II. The Environmental
  Impact of the Virgo Cluster on the Evolution of Dwarf Irregular Galaxies

abstract:
  The impact of the cluster environment on the evolution of dwarf galaxies is
investigated by comparing the properties of a sample of dwarf irregulars (dIs)
in the Virgo Cluster with a control sample of nearby ("field") dIs having
oxygen abundances derived from [O III]4363 measurements and measured distances
from resolved stellar constituents. Spectroscopic data are obtained for H II
regions in 11 Virgo dIs distributed in the central and outer regions of the
cluster. To ensure that oxygen abundances are derived in a homogeneous manner,
oxygen abundances for field and Virgo dIs are computed using the bright-line
method and compared with abundances directly obtained from [O III]4363, where
available. They are found to agree to within about 0.2 dex with no systematic
offset. At a given optical luminosity, there is no systematic difference in
oxygen abundance between the sample of Virgo dIs and the sample of nearby dIs.
However, five of the eleven Virgo dIs exhibit much lower baryonic gas fractions
than field dIs at comparable oxygen abundances. Using field dIs as a reference,
a gas-deficiency index for dIs is constructed, making it possible
quantitatively to identify which galaxies have lost gas. For the Virgo sample,
some of the dwarfs are gas-deficient by a factor of 30. The gas-deficiency
correlates roughly with the X-ray surface brightness of the intracluster gas.
Ram-pressure stripping can best explain the observed gas-poor dIs in the
cluster sample. Together with the lack of significant fading and reddening of
the gas-poor dIs compared to gas-normal dIs, these observations suggest that
the gas-poor dIs in Virgo have recently encountered the intracluster medium for
the first time. Faded remnants of gas-poor dIs in Virgo will resemble bright
dwarf ellipticals presently seen in the cluster core.


title:
Collisionless Shocks -- Magnetic Field Generation and Particle
  Acceleration

abstract:
  We present numerical results from plasma particle simulations of
collisionless shocks and ultra-relativistic counter-streaming plasmas. We
demonstrate how the field-particle interactions lead to particle acceleration
behind the shock-front. Further, we demonstrate how ultra relativistic
counter-streaming plasmas create large scale patchy magnetic field structures
and that these field structures propagate down-stream of the shock front. These
results may help explain the origin of the magnetic fields and accelerated
electrons responsible for afterglow synchrotron radiation from gamma ray
bursts.


title: Relativistic parsec-scale jets: II. Synchrotron emission

abstract:
  We calculate the optically thin synchrotron emission of fast electrons and
positrons in a spiral stationary magnetic field and a radial electric field of
a rotating relativistic strongly magnetized force-free jet consisting of
electron-positron pair plasma. The magnetic field has a helical structure with
a uniform axial component and a toroidal component that is maximal inside the
jet and decreasing to zero towards the boundary of the jet. Doppler boosting
and swing of the polarization angle of synchrotron emission due to the
relativistic motion of the emitting volume are calculated. The distribution of
the plasma velocity in the jet is consistent with the electromagnetic field
structure. Two spatial distributions of fast particles are considered: uniform,
and concentrated in the vicinity of the Alfven resonance surface. The latter
distribution corresponds to the regular acceleration by an electromagnetic wave
in the vicinity of its Alfven resonance surface inside the jet. The
polarization properties of the radiation have been obtained and compared with
the existing VLBI polarization measurements of parsec-scale jets in BL Lac
sources and quasars. Our results give a natural explanation of the observed
bimodality in the alignment between the electric field vector of the polarized
radiation and the projection of the jet axis on the plane of the sky. We
interpret the motion of bright knots as a phase velocity of standing spiral
eigenmodes of electromagnetic perturbations in a cylindrical jet. The degree of
polarization and the velocity of the observed proper motion of bright knots
depend upon the angular rotational velocity of the jet. The observed
polarizations and velocities of knots indicate that the magnetic field lines
are bent in the direction opposite to the direction of the jet rotation.


title:
The Effect of Tidal Inflation Instability on the Mass and Dynamical
  Evolution of Extrasolar Planets with Ultra-Short Periods

abstract:
  We investigate the possibility of substantial inflation of short-period
Jupiter-mass planets, as a result of their internal tidal dissipation
associated with the synchronization and circularization of their orbits. We
employ the simplest prescription based on an equilibrium model with a constant
lag angle for all components of the tide. We show that for young Jupiter-mass
planets, with a period less than 3 days, an initial radius about 2 Jupiter
radii, and an orbital eccentricity greater than 0.2, the energy dissipated
during the circularization of their orbits is sufficiently intense and
protracted to inflate their sizes up to their Roche radii.


title: Measuring Shapes of Galaxy Images I: Ellipticity and Orientation

abstract:
  We suggest a set of morphological measures that we believe can help in
quantifying the shapes of two-dimensional cosmological images such as galaxies,
clusters, and superclusters of galaxies. The method employs non-parametric
morphological descriptors known as the Minkowski functionals in combination
with geometric moments widely used in the image analysis. For the purpose of
visualization of the morphological properties of image contour lines we
introduce three auxiliary ellipses representing the vector and tensor Minkowski
functionals. We study the discreteness, seeing, and noise effects on elliptic
contours as well as their morphological characteristics such as the ellipticity
and orientation. In order to reduce the effect of noise we employ a technique
of contour smoothing. We test the method by studying simulated elliptic
profiles of toy spheroidal galaxies ranging in ellipticity from E0 to E7. We
then apply the method to real galaxies, including eight spheroidals, three disk
spirals and one peculiar galaxy, as imaged in the near-infrared $K_s$-band (2.2
microns) with the Two Micron All Sky Survey (2MASS). The method is numerically
very efficient and can be used in the study of hundreds of thousands images
obtained in modern surveys.


title:
The VLA-VIRMOS Deep Field I. Radio observations probing the microJy
  source population

abstract:
  We have conducted a deep survey (r.m.s noise 17 microJy) with the Very Large
Array (VLA) at 1.4 GHz, with a resolution of 6 arcsec, of a 1 square degree
region included in the VIRMOS VLT Deep Survey. In the same field we already
have multiband photometry down to I(AB)=25, and spectroscopic observations will
be obtained during the VIRMOS VLT survey. The homogeneous sensitivity over the
whole field has allowed to derive a complete sample of 1054 radio sources (5
sigma limit). We give a detailed description of the data reduction and of the
analysis of the radio observations, with particular care to the effects of
clean bias and bandwidth smearing, and of the methods used to obtain the
catalogue of radio sources. To estimate the effect of the resolution bias on
our observations we have modelled the effective angular-size distribution of
the sources in our sample and we have used this distribution to simulate a
sample of radio sources. Finally we present the radio count distribution down
to 0.08 mJy derived from the catalogue. Our counts are in good agreement with
the best fit derived from earlier surveys, and are about 50 % higher than the
counts in the HDF. The radio count distribution clearly shows, with extremely
good statistics, the change in the slope for the sub-mJy radio sources.


title: Gamma-Ray Bursts from Neutron Star Kicks

abstract:
  The idea that gamma-ray bursts might be a kind of phenomena associated with
neutron star kicks was first proposed by Dar & Plaga (1999). Here we study this
mechanism in more detail and point out that the neutron star should be a high
speed one (with proper motion larger than $\sim 1000$ km/s). It is shown that
the model agrees well with observations in many aspects, such as the
energetics, the event rate, the collimation, the bimodal distribution of
durations, the narrowly clustered intrinsic energy, and the association of
gamma-ray bursts with supernovae and star forming regions. We also discuss the
implications of this model on the neutron star kick mechanism, and suggest that
the high kick speed were probably acquired due to the electromagnetic rocket
effect of a millisecond magnetar with an off-centered magnetic dipole.


title: Is B1422+231 a Golden Lens?

abstract:
  B1422+231 is a quadruply-imaged QSO with an exceptionally large lensing
contribution from group galaxies other than the main lensing galaxy. We detect
diffuse X-rays from the galaxy group in archival Chandra observations; the
inferred temperature is consistent with the published velocity dispersion. We
then explore the range of possible mass maps that would be consistent with the
observed image positions, radio fluxes, and ellipticities. Under plausible but
not very restrictive assumptions about the lensing galaxy, predicted time
delays involving the faint fourth image are fairly well constrained around 7/h
days.


title:
XMM-Newton Survey of a Distance-limited Sample of Seyfert Galaxies:
  Preliminary Spectral Results

abstract:
  An unbiased estimate of the average intrinsic X-ray properties and column
density distribution of Seyfert galaxies in the local Universe is crucial to
validate unified models of active galactic nuclei (AGNs) and to synthesis
models for the X-ray background. We present here preliminary results obtained
from an on-going XMM-Newton study (~250 ks awarded in the EPIC GT) on a
well-defined, statistically complete, and significant sample of nearby Seyfert
galaxies.


title: CCD based phase resolved stroboscopic photometry of pulsars

abstract:
  A stroboscope designed to observe pulsars in the optical spectrum is
presented. The absolute phase of the stroboscope is synchronized to better than
2.5 microseconds with the known radio ephemerides for a given pulsar. The
absolute timing is provided by the GPS clock. With such a device phase resolved
photometry of pulsars can be performed. We demonstrate the instrument's
capabilities with the results of a set of observations of the Crab pulsar, the
brightest of the known optical pulsars, with a visual magnitude of 16.5, and a
rotational frequency of ~29Hz.


title: Crab Pulsar Photometry and the Signature of Free Precession

abstract:
  Optical photometry for the pulsar PSR0531+21 has been extended with new
observations that strengthen evidence for a previously observed 60 seconds
periodicity. This period is found to be increasing with time at approximately
the same rate as the rotational period of the pulsar. The observed period and
its time dependence fit a simple free precession model.


title:
External shock model for the large-scale, relativistic X-ray jets from
  the microquasar XTE J1550-564

abstract:
  Large-scale, decelerating, relativistic X-ray jets due to material ejected
from the black-hole candidate X-ray transient and microquasar XTE J1550-564 has
been recently discovered with Chandra by Corbel et al. (2002). We find that the
dynamical evolution of the eastern jet at the late time is consistent with the
well-known Sedov evolutionary phase. A trans-relativistic external shock
dynamic model by analogy with the evolution of gamma-ray burst remnants, is
shown to be able to fit the observation data reasonably well. The inferred
interstellar medium density around the source is well below the canonical value
$n_ISM \sim 1 cm^{-3}$. We find that the emission from the continuously shocked
interstellar medium (forward shock region) decays too slowly to be a viable
mechanism for the eastern X-ray jet. However, the rapidly fading X-ray emission
can be interpreted as synchrotron radiation from the non-thermal electrons in
the adiabatically expanding ejecta. These electrons were accelerated by the
reverse shock (moving back into the ejecta) which becomes important when the
inertia of the swept external matter leads to an appreciable slowing down of
the original ejecta. To ensure the dominance of the emission from the shocked
ejecta over that from the forward shock region during the period of the
observations, the magnetic field and electron energy fractions in the forward
shock region must be far below equipartition. Future continuous, follow-up
multi-wavelength observations of new ejection events from microquasars up to
the significant deceleration phase should provide more valuable insight into
the nature of the interaction between the jets and external medium.


title: MHD simulations of small and large scale dynamos

abstract:
  Isotropic homogeneous hydromagnetic turbulence is studied using numerical
simulations at resolutions of up to 1024^3 meshpoints. It is argued that, in
contrast to the kinematic regime, the nonlinear regime is characterized by a
spectral magnetic power that is decreasing with increasing wavenumber,
regardless of whether or not the turbulence has helicity. This means that the
root-mean-square field strength converges to a limiting value at large magnetic
Reynolds numbers. The total (magnetic and kinetic) energy spectrum tends to be
somewhat shallower than k^{-5/3}, in agreement with the findings of other
groups. In the presence of helicity, an inverse cascade develops, provided the
scale separation between the size of the computational box and the scale of the
energy carrying eddies exceeds a ratio of at least two. Finally, the
constraints imposed by magnetic helicity conservation on mean-field theory are
reviewed and new results of simulations are presented.


title: Is nonhelical hydromagnetic turbulence peaked at small scales?

abstract:
  Nonhelical hydromagnetic turbulence without an imposed magnetic field is
considered in the case where the magnetic Prandtl number is unity. The magnetic
field is entirely due to dynamo action. The magnetic energy spectrum peaks at a
wavenumber of about 5 times the minimum wavenumber in the domain, and not at
the resistive scale, as has previously been argued. Throughout the inertial
range the spectral magnetic energy exceeds the kinetic energy by a factor of
about 2.5, and both spectra are approximately parallel. At first glance, the
total energy spectrum seems to be close to k^{-3/2}, but there is a strong
bottleneck effect and it is suggested that the asymptotic spectrum is k^{-5/3}.
This is supported by the value of the second order structure function exponent
that is found to be \zeta_2=0.70, suggesting a k^{-1.70} spectrum.


title:
2D MHD modelling of compressible and heated coronal loops obtained via
  nonlinear separation of variables and compared to TRACE and SoHO observations

abstract:
  An analytical MHD model of coronal loops with compressible flows and
including heating is compared to observational data. The model is constructed
via a systematic nonlinear separation of the variables method used to calculate
several classes of exact MHD equilibria in Cartesian geometry and uniform
gravity. By choosing a particularly versatile solution class with a large
parameter space we are able to calculate models whose loop length, shape,
plasma density, temperature and velocity profiles are fitted to loops observed
with TRACE, SoHO/CDS and SoHO/SUMER. Synthetic emission profiles are also
calculated and fitted to the observed emission patterns. An analytical
discussion is given of the two-dimenional balance of the Lorentz force and the
gas pressure gradient, gravity and inertial forces acting along and across the
loop. These models are the first to include a fully consistent description of
the magnetic field, 2D geometry, plasma density and temperature, flow velocity
and thermodynamics of loops. The consistently calculated heating profiles which
are largely dominated by radiative losses are influenced by the flow and are
asymmetrical being concentrated at the upflow footpoint.


title: The X-ray Scaling Properties of Virialized Systems

abstract:
  Virialized systems, such as clusters and groups of galaxies, represent an
ideal laboratory for investigating the formation and evolution of structure on
the largest scales. Furthermore, the properties of the gaseous intracluster
medium provide key insights into the influence of important non-gravitational
processes like energy injection and radiative cooling, resulting from feedback
associated with star formation, for example. We have assembled a very large
X-ray sample of virialized systems, spanning over two decades in halo mass.
Each object has high-quality X-ray data available, enabling a full deprojection
analysis to be made; for a subsample we have additionally determined the
deprojected optical light distribution. We find clear evidence of a departure
from the simple expectations of self-similarity. The intracluster medium is
more spatially extended and systematically less dense in smaller haloes, and
there is evidence of an entropy excess in the hot gas. Our results favour a
significant role for both non-gravitational heating and radiative cooling in
modifying the properties of this gas, although we find no clear evidence of
significantly enhanced star formation efficiency in groups.


title: Millisecond pulsars with r-modes as steady gravitational radiators

abstract:
  Millisecond pulsars (MSPs) are generally agreed to originate in low-mass
X-ray binaries (LMXBs), in which mass transfer onto the neutron stars spins
them up to their observed, fast rotation. The lack of MSPs and LMXBs rotating
near break-up and the similar rotation periods of several LMXBs have been
attributed to the accretion torque being balanced, at fast rotation, by
gravitational radiation, perhaps caused by an oscillation mode made unstable
through the so-called Chandrasekhar-Friedman-Schutz mechanism. Recently,
Wagoner has argued that internal dissipation through weak interaction processes
involving $\Lambda^0$ and $\Sigma^-$ hyperons may cause LMXBs to evolve into a
quasi-steady state, in which the neutron star has a nearly constant rotation
rate, temperature, and mode amplitude. We take this hypothesis one step
further, showing that MSPs descending from these LMXBs spend a long time in a
similar state, in which a low-amplitude r-mode turns them into extremely steady
sources of both gravitational waves and thermal X-rays, while they spin down
due to a combination of gravitational radiation and the standard magnetic
torque. Observed MSP braking torques already place meaningful constraints on
the allowed gravitational wave amplitudes and dissipation mechanisms.


title:
The IAU 2000 resolutions for astrometry, celestial mechanics and
  metrology in the relativistic framework: explanatory supplement

abstract:
  This paper discusses the IAU Resolutions B1.3, B1.4, B1.5 and B1.9 (2000)
that were adopted during the 24th General Assembly in Manchester, 2000 and
provides details and explanations for these Resolutions. It is explained why
they present significant progress over the corresponding IAU 1991 Resolutions
and why they are necessary in the light of present accuracies in astrometry,
celestial mechanics and metrology. In fact most of these Resolutions are
consistent with astronomical models and software already in use.
  The metric tensors and gravitational potentials of both the Barycentric
Celestial Reference System and Geocentric Celestial Reference System are
defined and discussed. The necessity and relevance of the two celestial
reference systems are explained. The transformations of coordinates and
gravitational potentials are discussed. Potential coefficients parameterizing
the post-Newtonian gravitational potentials are expounded. Simplified versions
of the time transformations suitable for modern clock accuracies are
elucidated. Various approximations used in the Resolutions are explicated and
justified. Some models (e.g. for higher spin moments) that serve the purpose
for estimating orders of magnitude have actually never been published before.


title:
Earth's rotation in the framework of general relativity: rigid multipole
  moments

abstract:
  A set of equations describing the rotational motion of the Earth relative to
the GCRS is formulated in the approximation of rigidly rotating multipoles. The
external bodies are supposed to be mass monopoles. The derived set of formulas
is supposed to form the theoretical basis for a practical post-Newtonian theory
of Earth precession and nutation.


title:
New Period-Luminosity and Period-Color Relations of Classical Cepheids:
  I. Cepheids in the Galaxy

abstract:
  321 Galactic fundamental-mode Cepheids with good B,V,I photometry by
Berdnikov et al. 2000 and with homogenized color excesses E(B-V) based on
Fernie et al. 1995 are used to determine their P-C relation in the range
0.4<log P<1.6. Distances of 25 Cepheids in open clusters (Feast 1999) and of 28
Cepheids with BBW distances (Gieren et al. 1998) are used in a first step to
determine the absorption coefficients R_B=4.17, R_V=3.17, and R_I=1.89. The two
sets define two independent P-L relations which agree very well in slope. They
are therefore combined into a single mean Galactic P-L relation. Galactic
Cepheids are redder in (B-V) than those in LMC and SMC as shown by the over
1000 Cloud Cepheids with good standard B,V,I photometry by Udalski et al 1999.
Also the (B-V), (V-I) two-color diagrams differ between Cepheids in the Galaxy
and the Clouds, attributed both to the effects of metallicity differences, on
the spectral energy distributions of the Cepheids and to a shift in the
effective temperature of the middle of the instability strip for LMC and SMC
relative to the Galaxy by about Delta log Te ~ 0.02 at M_V=-4.0 mag, hotter for
both LMC and SMC. Differences in the P-C relations between the Galaxy and the
Clouds show that there cannot be a universal P-L relation from galaxy-to-galaxy
in any given color. The inferred non-uniqueness of the slope of the P-L
relations in the Galaxy, LMC, and SMC is born out by the observations. The
Cloud Cepheids follow a shallower overall slope of the P-L relations in B,V,I
than the Galactic ones. LMC and SMC Cepheids are brighter in V than in the
Galaxy by up to 0.5 mag at short periods and fainter at long periods.


title:
Discovery of X-Ray Burst Oscillations from a Neutron-Star X-Ray
  Transient in the Globular Cluster NGC 6440

abstract:
  We report the discovery of millisecond oscillations in an X-ray burst from
the X-ray transient SAX J1748.9-2021 in the globular cluster NGC 6440.
Oscillations at a frequency of 409.7 +/- 0.3 Hz were present in one of nine
X-ray bursts observed with the Proportional Counter Array on the Rossi X-ray
Timing Explorer during the outburst which occurred in 2001. The burst was one
of the two dimmest and had the longest duration and decay time. The average
peak luminosity of two bursts showing radius expansion is (3.6 +/- 0.4) x 10^38
erg/s, consistent with the Eddington luminosity for a 1.4 solar mass and 10 km
radius neutron star burning hydrogen-poor matter. We speculate that the
dichotomy observed between sources with burst oscillations at once versus twice
the frequency difference of kHz quasiperiodic oscillations in the persistent
emission may be related to the magnetic field geometry of the neutron stars.


title:
Detection of Pulsed X-ray Emission from XMM-Newton Observations of PSR
  J0538+2817

abstract:
  We report on the XMM-Newton observations of the 143 ms pulsar PSR J0538+2817.
We present evidence for the first detections of pulsed X-rays from the source
at a frequency which is consistent with the predicted radio frequency. The
pulse profile is broad and asymmetric, with a pulse fraction of 18 +/- 3%. We
find that the spectrum of the source is well-fit with a blackbody with
T^{infty} = (2.12^{+0.04}_{-0.03}) x 10^6 K and N_{H} = 2.5 x 10^21 cm^{-2}.
The radius determined from the model fit of 1.68 +/- 0.05 km suggests that the
emission is from a heated polar cap. A fit to the spectrum with an atmospheric
model reduces the inferred temperature and hence increases the radius of the
emitting region, however the pulsar distance determined from the fit is then
smaller than the dispersion distance.


title: Shear-selected clusters from the Deep Lens Survey

abstract:
  Weak gravitational lensing has the potential to select clusters independently
of their baryon content, dynamical state, and star formation history. We
present steps toward the first shear-selected sample of clusters, from the Deep
Lens Survey (DLS), a deep BVRz' imaging survey of 28 square degrees. Cluster
redshifts are determined from photometric redshifts of members and from lensing
tomography, and in some cases have been confirmed spectroscopically. DLS
imaging data are also used to derive mass-to-light ratios, and upcoming Chandra
and XMM time will yield X-ray luminosities and temperatures for a subsample of
12 clusters. Thus we can begin to address any baryon or luminous-matter bias
which may be present in current optical and X-ray samples. When the DLS is
complete, we expect to have a sample of ~ 100 shear-selected clusters from z ~
0.2-1.


title:
The Asiago-ESO/RASS QSO Survey. III. Clustering analysis and its
  theoretical interpretation

abstract:
  This is the third paper of a series describing the Asiago-ESO/RASS QSO survey
(AERQS), a project aimed at the construction of an all-sky statistically
well-defined sample of relatively bright QSOs (B<15) at z<0.3. We present here
the clustering analysis of the full spectroscopically identified database (392
AGN). The clustering signal at 0.02<z<0.22 is detected at a 3-4 sigma level and
its amplitude is measured to be r_0=8.6\pm 2.0 h^{-1} Mpc (in a LambdaCDM
model). The comparison with other classes of objects shows that low-redshift
QSOs are clustered in a similar way to Radio Galaxies, EROs and early-type
galaxies in general, although with a marginally smaller amplitude. The
comparison with recent results from the 2QZ shows that the correlation function
of QSOs is constant in redshift or marginally increasing toward low redshift.
We discuss this behavior with physically motivated models, deriving interesting
constraints on the typical mass of the dark matter halos hosting QSOs, M_DMH=
10^{12.7} h^{-1} M_sun (10^{12.0}-10^{13.5}h^{-1} M_sun at 1 sigma confidence
level). Finally, we use the clustering data to infer the physical properties of
local AGN, obtaining M_BH=2 10^8 h^{-1} M_sun (10^7-3 10^9 h^{-1} M_sun) for
the mass of the active black holes, tau_{AGN}= 8 10^6 yr (2 10^{6}-5 10^{7} yr)
for their life-time and eta = 0.14 for their efficiency (always for a LambdaCDM
model).


title: WMAP constraints on Cardassian model

abstract:
  We have investigated the constraints on the Cardassian model using the recent
results from the Wilkinson Microwave Anisotropy Probe (WMAP) for the locations
of the peaks of the Cosmic Microwave Background
  (CMB) anistropy spectrum. We find that the model is consistent with the
recent observational data for certain range of the model parameter $n$ and the
cosmological parameters. We find that the Cardassian model is favoured compared
to $\Lambda$CDM model, for a higher spectral index ($n_s \approx 1$) together
with lower value of
  Hubble parameter $h$ ($h\leq 0.71$). But for smaller values of $n_s$, both
$\Lambda$CDM and Cardassian are equally favoured. Also, irrespective of
Supernova constraint, CMB data alone predicts current acceleration of the
universe in this model. We have also studied the constraint on the
$\sigma_{8}$, the rms density fluctuations at
  $8h^{-1}$ Mpc scale.


title: Explosive reconnection in magnetars

abstract:
  X-ray activity of Anomalous X-ray Pulsars and Soft Gamma-Ray Repeaters may
result from the heating of their magnetic corona by direct currents dissipated
by magnetic reconnection. We investigate the possibility that X-ray flares and
bursts observed from AXPs and SGRs result from magnetospheric reconnection
events initiated by development of tearing mode in magnetically-dominated
relativistic plasma. We formulate equations of resistive force-free
electrodynamics, discuss its relation to ideal electrodynamics, and give
examples of both ideal and resistive equilibria. Resistive force-free current
layers are unstable toward the development of small-scale current sheets where
resistive effects become important. Thin current sheets are found to be
unstable due to the development of resistive force-free tearing mode. The
growth rate of tearing mode is intermediate between the short \Alfven time
scale $ \tau_A$ and a long resistive time scale $\tau_R$: $\Gamma \sim
1/(\tau_R \tau_A)^{1/2}$, similar to the case of non-relativistic
non-force-free plasma. We propose that growth of tearing mode is related to the
typical rise time of flares, $\sim 10$ msec. Finally, we discuss how
reconnection may explain other magnetar phenomena and ways to test the model.


title:
X-ray imaging and spectroscopy of (radio-quiet) AGN: Highlights from
  Chandra and XMM-Newton

abstract:
  The X-ray observatories XMM-Newton and Chandra provided a wealth of exciting
new results. Chandra delivered X-ray images of outstanding detail, reaching
subarcsecond spatial resolution for the first time in X-ray astronomy.
XMM-Newton provided the highest-signal X-ray spectra ever taken. The imaging
and spectral observations are greatly improving our understanding of the
physical processes in the central region of active galaxies. The increased
sensitivity also allows to peer into the high-redshift universe beyond z=5. I
shall provide a review of recent X-ray highlights on (radio-quiet) AGN from low
to high redshift, and exciting questions still open. I conclude with a glimpse
into the future of X-ray astronomy.


title: Lyman Break Galaxies and Reionization of the Universe

abstract:
  We present the star formation histories, luminosities, colors, mass to light
ratios, and halo masses of "galaxies" formed in a simulation of cosmological
reionization. We compare these galaxies with Lyman Break Galaxies observed at
high redshift. While the simulation is severely limited by the small box size,
the simulated galaxies do appear as fainter cousins of the observed ones. They
have similar colors, and both simulated and observed galaxies can be fitted
with the same luminosity function. This is significant to the process of
reionization since in the simulation the stars alone are responsible for
reionization at a redshift consistent with that of the Gunn-Peterson trough
seen in the absorption spectra of QSO's. The brightest galaxies at z = 4 are
indeed quite young in accord with observational studies. But these brightest
galaxies are free riders - they contributed only about 25% to the reionization
of the universe at z > 6. Instead, the bulk of the work was done by dimmer
galaxies, those that fall within the 28 < I < 30 magnitude range at z = 4.
These dimmer galaxies are not necessarily less massive than the brightest ones.


title:
A Chandra X-ray Study of NGC 1068: II. The Luminous X-ray Source
  Population

abstract:
  We present an analysis of the compact X-ray source population in the
Seyfert~2 galaxy NGC 1068, imaged with Chandra. We find a total of 84 compact
sources, of which 66 are projected onto the galactic disk of NGC 1068. Spectra
of the brightest sources have been modeled with both multi-color disk blackbody
and power-law models. The power-law model provides the better description of
the spectrum for most of these sources. Five sources have 0.4-8 keV intrinsic
luminosities greater than 10^{39} erg/s, assuming that their emission is
isotropic and that they are associated with NGC 1068. We refer to these sources
as Intermediate Luminosity X-ray Objects (IXOs). If these five sources are
X-ray binaries accreting with luminosities that are both sub-Eddington and
isotropic, then the implied source masses are >7 solar masses, and so they are
inferred to be black holes. The brightest source has a much harder spectrum
(Gamma = 0.9\pm0.1) than that found in Galactic black hole candidates and other
IXOs. It also shows large-amplitude variability on both short-term and
long-term timescales. The ratio of the number of sources with luminosities
greater than 2.1 x 10^{38} erg/s in the 0.4-8 keV band to the rate of massive
star formation is the same, to within a factor of two, for NGC 1068, the
Antennae, NGC 5194 (the main galaxy in M51), and the Circinus galaxy. This
suggests that the rate of production of X-ray binaries per massive star is
approximately the same for galaxies with currently active star formation,
including ``starbursts''.


title: Constraining the dark energy with galaxy clusters X-ray data

abstract:
  The equation of state characterizing the dark energy component is constrained
by combining Chandra observations of the X-ray luminosity of galaxy clusters
with independent measurements of the baryonic matter density and the latest
measurements of the Hubble parameter as given by the HST key project. By
assuming a spatially flat scenario driven by a "quintessence" component with an
equation of state $p_x = \omega \rho_x$ we place the following limits on the
cosmological parameters $\omega$ and $\Omega_{\rm{m}}$: (i) $-1 \leq \omega
\leq -0.55$ and $\Omega_{\rm m} = 0.32^{+0.027}_{-0.014}$ (1$\sigma$) if the
equation of state of the dark energy is restricted to the interval $-1 \leq
\omega < 0$ (\emph{usual} quintessence) and (ii) $\omega =
-1.29^{+0.686}_{-0.792}$ and $\Omega_{\rm{m}} = 0.31^{+0.037}_{-0.034}$
($1\sigma$) if $\omega$ violates the null energy condition and assume values $<
-1$ (\emph{extended} quintessence or ``phantom'' energy). These results are in
good agreement with independent studies based on supernovae observations,
large-scale structure and the anisotropies of the cosmic background radiation.


title:
Angular Momentum Evolution of Young Stars: Toward a Synthesis of
  Observations, Theory, and Modeling

abstract:
  The aim of this AAS Topical Session was to update the community on the
current state of knowledge about the angular momentum evolution of young stars.
For newcomers to the subject, the session was intended to provide an
introduction and general overview and to highlight emerging issues. For
experienced workers in this field, the session provided an opportunity for
synthesizing recent developments in observations, theory, and modeling of
rotation of young stars and for identifying promising new research directions.


title: The Fundamental Properties of Dwarf Elliptical Galaxies in Clusters

abstract:
  We present preliminary results of an extensive study of the fundamental
properties of dwarf elliptical galaxies (dEs) in the Coma cluster. Our study
will combine HST surface photometry with ground-based UBRIJK photometry and
optical spectroscopy. The combined data set will be used to investigate the
intrinsic correlations among global parameters in cluster dEs, including the
Fundamental Plane, the color-magnitude relation, the Faber-Jackson and Kormendy
relation, and velocity dispersion versus line strength indices. These empirical
correlations have provided important constraints to theoretical models of
galaxy formation and evolution for "normal" elliptical galaxies. Although dEs
are the most abundant galaxy population in clusters their properties remain,
however, largely unknown. Our study aims to provide an essential reference for
testing current theories on the formation and evolution of dEs in clusters, and
understanding their relation to more massive elliptical galaxies.


title:
HST photometry of dwarf elliptical galaxies in Coma, and an explanation
  for the alleged structural dichotomy between dwarf and bright elliptical
  galaxies

abstract:
  We have analyzed archival HST F606W images of 18 dwarf elliptical (dE) galaxy
candidates in the Coma Cluster. We model the full radial extent of their
light-profiles by simultaneously fitting a PSF-convolved Sersic R^(1/n) model
and, when necessary, either a central point-source or a central PSF-convolved
Gaussian. The luminosities of the central component L_nuc scale with the host
galaxy luminosity L_gal such that L_nuc = 10^(4.76 +/- 0.10)*(L_gal/10^7)^(0.87
+/- 0.26). The underlying host galaxies display systematic departures from an
exponential model that are correlated with the model-independent host galaxy
luminosity and are not due to biasing from the nuclear component. The Pearson
correlation coefficient between log(n) and central galaxy surface brightness
mu_0 (excluding the flux from extraneous central components) is -0.83 at a
significance level of 99.99%. The Pearson correlation coefficient between the
logarithm of the Sersic index `n' and the host galaxy magnitude is -0.77 at a
significance of 99.9%. We explain the observed relationship between dE galaxy
luminosity and inner logarithmic profile slope (gamma-prime) as a by-product of
the correlation between luminosity and Sersic index n. Including, from the
literature, an additional 232 dE and E galaxies spanning 10 mag in absolute
magnitude (M), the dE galaxies are shown to display a continuous sequence with
the brighter E galaxies such that mu_0 brightens linearly with M until core
formation causes the most luminous (M_B < -20.5 mag) E galaxies to deviate from
this relation. The different behavior of dE and E galaxies in the M-mu_e (and
M-<mu>_e) diagram, and the <mu>_e-log(R_e) diagram have nothing to do with core
formation, and are in fact expected from the continuous and linear relation
between M and mu_0 and M and log(n).


title: H-alpha Spectroscopy of Galaxies at z>2: Kinematics and Star Formation

abstract:
  We present near-infrared spectroscopy of H-alpha emission lines in a sample
of 16 star-forming galaxies at redshifts 2.0<z<2.6. Our targets are drawn from
a large sample of galaxies photometrically selected and spectroscopically
confirmed to lie in this redshift range. Six of the galaxies exhibit spatially
extended, tilted H-alpha emission lines; rotation curves for these objects
reach mean velocities of ~150 km/s at radii of ~6 kpc, without corrections for
any observational effects. The velocities and radii give a mean dynamical mass
of M>4e10 M_sun. One-dimensional velocity dispersions for the 16 galaxies range
from ~50 to ~260 km/s, and in cases where we have both virial masses implied by
the velocity dispersions and dynamical masses derived from the spatially
extended emission lines, they are in rough agreement. We compare our kinematic
results to similar measurements made at z~3, and find that both the observed
rotational velocities and velocity dispersions tend to be larger at z~2 than at
z~3. We find a mean SFR_H-alpha of 16 M_sun/yr and an average
SFR_H-alpha/SFR_UV ratio of 2.4, without correcting for extinction. We see
moderate evidence for an inverse correlation between the UV continuum
luminosity and the ratio SFR_H-alpha/SFR_UV, such as might be observed if the
UV-faint galaxies suffered greater extinction. We discuss the effects of dust
and star formation history on the SFRs, and conclude that extinction is the
most likely explanation for the discrepancy between the two SFRs.


title: Star Formation in Cluster-Cluster Mergers

abstract:
  Radio continuum emission at 1.4 GHz was used to identify active galaxies in a
sample of 20 nearby Abell clusters. The radio emission indicates either an
active galactic nucleus or current star formation, and optical spectroscopy was
used to evaluate which of these dominates for each of the radio-selected
galaxies. In an analysis which parallels the blue fractions of Butcher-Oemler
studies, we calculated radio galaxy fractions for the clusters. One cluster in
particular shows a dramatic increase in activity relative to the others: the
cluster-cluster merger Abell 2255. We compare the results for Abell 2255 with
those for Abell 2256 to assess the role of cluster-cluster mergers on the star
formation activity of member galaxies. From these clusters, as well as several
identified in other studies, a picture emerges in which substructure and
cluster dynamical activity are of great importance in understanding
evolutionary phenomenon such as the Butcher-Oemler Effect. Increased fractions
of active galaxies (be they the blue galaxies of Butcher-Oemler studies or
radio galaxies as discussed here) naturally result as clusters are built
through mergers of smaller groups in hierarchical formation scenarios. The
observed spread in fractions of active galaxies at any given redshift reflects
the spread in cluster dynamical state.


title:
Nearly 5000 Distant Early-Type Galaxies in COMBO-17: a Red Sequence and
  its Evolution since z~1

abstract:
  We present the rest-frame colors and luminosities of ~25000 m_R<24 galaxies
in the redshift range 0.2<z<1.1, drawn from 0.78 square degrees of the COMBO-17
survey. We find that the rest-frame color distribution of these galaxies is
bimodal at all redshifts out to z~1. This bimodality permits a
model-independent definition of red, early-type galaxies and blue, late-type
galaxies at any given redshift. The colors of the blue peak become redder
towards the present day, and the number density of blue luminous galaxies has
dropped strongly since z~1. Focusing on the red galaxies, we find that they
populate a color-magnitude relation. Such red sequences have been identified in
galaxy cluster environments, but our data show that such a sequence exists over
this redshift range even when averaging over all environments. The mean color
of the red galaxy sequence evolves with redshift in a way that is consistent
with the aging of an ancient stellar population. The rest-frame B-band
luminosity density in red galaxies evolves only mildly with redshift in a
Lambda-dominated cold dark matter universe. Accounting for the change in
stellar mass-to-light ratio implied by the redshift evolution in red galaxy
colors, the COMBO-17 data indicate an increase in stellar mass on the red
sequence by a factor of two since z~1. The largest source of uncertainty is
large-scale structure, implying that considerably larger surveys are necessary
to further refine this result. We explore mechanisms that may drive this
evolution in the red galaxy population, finding that both galaxy merging and
truncation of star formation in some fraction of the blue, star-forming
population are required to fully explain the properties of these galaxies.


title:
The Spin-Kinetic Temperature Coupling and the Heating Rate due to Lyman
  Alpha Scattering before Reionization: Predictions for 21cm Emission and
  Absorption

abstract:
  We investigate the interaction of Lyman alpha photons produced by the first
stars in the universe with the intergalactic medium (IGM) prior to
reionization. The background Lyman alpha spectral profile is obtained by
solving a Fokker-Planck equation. Accurate values of the heating and scattering
rates, and the spin-kinetic temperature coupling coefficient, are presented. We
show that the heating rate induced by the Lyman alpha scatterings is much lower
than found previously, and is basically negligible. The dominant heating source
is most likely the X-rays from the first ionizing sources, which are able to
penetrate into the atomic medium. The scattering of Lyman alpha photons couples
the hydrogen spin temperature to the kinetic temperature. If the first ionizing
sources in the universe did not emit significant X-rays, the spin temperature
would be rapidly brought down to the very low gas kinetic temperature, and a
21cm absorption signal against the CMB larger than 100 mK would be predicted.
However, we argue that sufficient X-rays are likely to have been emitted by the
first stellar population, implying that the gas kinetic temperature should
rapidly increase, turning a reduced and brief absorption signal into emission,
with a smaller amplitude of about 10 mK. The detection of the 21cm absorption
and emission feature would be a hallmark in unravelling the history of the
``dark age'' before reionization.


title:
Absorption-Line Systems and Galaxies in Front of the Second Brightest
  Quasar, PHL 1811

abstract:
  The extraordinarily bright quasar PHL 1811 at a redshift z = 0.192 provides
an attractive opportunity to use ultraviolet absorption-line spectroscopy to
study the properties of gas systems in the local universe. An R = 20,000 far-UV
spectrum recorded by FUSE revealed 7 extragalactic absorption systems, one of
which is a Lyman limit system at z = 0.08093 accompanied by three systems
having redshifts which differ from it by less than 0.008. The abundance of O
with respect to Fe in the Lyman limit system is not much different from the
solar abundance ratio. Supplementary low resolution spectra recorded by STIS
(on HST) at longer wavelengths helped to substantiate our identifications of
systems in the FUSE spectrum and suggested the presence of an additional 4
systems that could be detected only through their Ly-alpha features.
Spectroscopy at visible wavelengths of 7 galaxies within approximately 2' of
PHL 1811 indicated that 2 of them are near the redshift of the quasar and 4
have redshifts within 850 km/s of the extragalactic absorption systems. The
Lyman limit system is likely associated with an L* galaxy lying 23" from the
sightline. Finally, in addition to prominent features at very low velocities
arising from the disk of our Galaxy, the strong resonance transitions of C II
and Mg II show evidence for material at v = -200 km/s; the column densities of
these two species suggest that 17.7 < log N(H I) < 18.1 if the material has a
solar composition.


title:
Spectropolarimetry of SN 2001el in NGC 1448: Asphericity of a Normal
  Type Ia Supernova

abstract:
  High-quality spectropolarimetry (range 417-860 nm; spectral resolution 1.27
nm and 0.265 nm/pixel) of the SN Ia 2001el were obtained with the ESO Very
Large Telescope Melipal (+ FORS1) at 5 epochs. The spectra a week before
maximum and around maximum indicate photospheric expansion velocities of about
10,000 km s$^{-1}$. Prior to optical maximum, the linear polarization of the
continuum was $\approx 0.2 - 0.3 %$ with a constant position angle, showing
that SN 2001el has a well-defined axis of symmetry. The polarization was nearly
undetectable a week after optical maximum. The spectra are similar to those of
the normally-bright SN 1994D with the exception of a strong double-troughed
absorption feature seen around 800 nm (FWHM about 22 nm). This feature could be
an important clue to the binary nature of SN Ia, perhaps associated with an
accretion disk, or to the nature of the thermonuclear burning. If modeled in
terms of an oblate spheroid, the continuum polarization implies a minor to
major axis ratio of around 0.9 if seen equator-on; this level of asymmetry
would produce an absolute luminosity dispersion of about 0.1 mag when viewed at
different viewing angles. If typical for SNe Ia, this would create an RMS
scatter of several hundredths of a magnitude around the mean brightness-decline
relation.


title: Migration of Asteroidal Dust

abstract:
  We numerically investigate the migration of dust particles with initial
orbits close to those of the numbered asteroids. The fraction of silicate
particles that collided with the Earth during their lifetimes varied from 0.2%
for 40 micron particles to 0.008% for 1 micron particles. Almost all particles
with diameter d>4 microns collided with the Sun. The peaks in the migrating
asteroidal dust particles' semi-major axis distribution at the n/(n+1)
resonances with Earth and Venus and the gaps associated with the 1:1 resonances
with these planets are more pronounced for larger particles.


title: The First Measurement of Cassiopeia A's Forward Shock Expansion Rate

abstract:
  We have obtained a second epoch observation of the Cassiopeia A supernova
remnant (SNR) with the Chandra X-ray Observatory to measure detailed X-ray
proper motions for the first time. Both epoch observations are 50 ks exposures
of the ACIS-S3 chip and they are separated by 2 years. Measurements of the thin
X-ray continuum dominated filaments located around the edge of the remnant
(that are identified with the forward shock) show expansion rates from 0.02%/yr
to 0.33%/yr. Many of these filaments are therefore significantly decelerated.
Their median value of 0.21%/yr is equal to the median expansion of the bright
ring (0.21%/yr) as measured with Einstein and ROSAT. This presents a conundrum
if the motion of the bright ring is indicative of the reverse shock speed. We
have also re-evaluated the motion of the radio bright ring with emphasis on
angle-averaged emissivity profiles. Our new measurement of the expansion of the
angle-averaged radio bright ring is 0.07 plus or minus 0.03%/yr, somewhat
slower than the previous radio measurements of 0.11%/yr which were sensitive to
the motions of small-scale features. We propose that the expansion of the
small-scale bright ring features in the optical, X-ray, and radio do not
represent the expansion of the reverse shock, but rather represent a
brightness-weighted average of ejecta passing through and being decelerated by
the reverse shock. The motion of the reverse shock, itself, is then represented
by the motion of the angle-averaged emissivity profile of the radio bright
ring.


title: Model-Independent Reionization Observables in the CMB

abstract:
  We represent the reionization history of the universe as a free function in
redshift and study the potential for its extraction from CMB polarization
spectra. From a principal component analysis, we show that the ionization
history information is contained in 5 modes, resembling low-order Fourier modes
in redshift space. The amplitude of these modes represent a compact description
of the observable properties of reionization in the CMB, easily predicted given
a model for the ionization fraction. Measurement of these modes can ultimately
constrain the total optical depth, or equivalently the initial amplitude of
fluctuations to the 1% level regardless of the true model for reionization.


title:
A 13CO and C18O Survey of the Molecular Gas Around Young Stellar
  Clusters Within 1kpc of the Sun

abstract:
  As the first step of a multi-wavelength investigation into the relationship
between young stellar clusters and their environment we present fully-sampled
maps in the J=1--0 lines of 13CO and C18O and the J=2--1 line of C18O for a
selected group of thirty young stellar groups and clusters within 1kpc of the
Sun. This is the first systematic survey of these regions to date. The clusters
range in size from several stars to a few hundred stars. Thirty fields ranging
in size from 8'x 8' to 60'x 30' were mapped with 47'' resolution simultaneously
in the J=1-0 lines with Five College Radio Observatory. Seventeen sources were
mapped over fields ranging in size from 3'x 3' to 13'x 13' in the J=2--1 line
with 35'' resolution with the Heinrich Hertz Telescope. We compare the cloud
properties derived from each of the three tracers in order to better understand
systematic uncertainties in determing masses and linewidths. Cloud masses are
determined independently using the 13CO and C18O transitions, these masses
range from 30 to 4000 M_sun. Finally, we present a simple morphological
classification scheme which may serve as a rough indicator of cloud evolution.


title: Long-term X-ray Variability of Circinus X-1

abstract:
  We present an analysis of long term X-ray monitoring observations of Circinus
X-1 (Cir X-1) made with four different instruments: Vela 5B, Ariel V ASM, Ginga
ASM, and RXTE ASM, over the course of more than 30 years. We use Lomb-Scargle
periodograms to search for the ~16.5 day orbital period of Cir X-1 in each of
these data sets and from this derive a new orbital ephemeris based solely on
X-ray measurements, which we compare to the previous ephemerides obtained from
radio observations. We also use the Phase Dispersion Minimization (PDM)
technique, as well as FFT analysis, to verify the periods obtained from
periodograms. we obtain dynamic periodograms (both Lomb-Scargle and PDM) of Cir
X-1 during the RXTE era, showing the period evolution of Cir X-1, and also
displaying some unexplained discrete jumps in the location of the peak power.


title: The New Transiting Planet OGLE-TR-56b: Orbit and Atmosphere

abstract:
  Motivated by the identification of the very close-in extrasolar giant planet
OGLE-TR-56b, we explore the implications of its existence on problems of tidal
dissipation, planet migration, and atmospheric stability. The small orbit of
OGLE-TR-56b makes the planet an interesting test particle case for tidal
dissipation in stellar convection zones. We show that it favors prescriptions
of suppressed convective eddy viscosity. Precise timing of the transits of
OGLE-TR-56b might place interesting constraints on stellar convection theory,
if orbital period change is detected in the near future.


title: Acceleration of Cosmic Rays at Cosmic Shocks

abstract:
  Nonthermal particles can be produced due to incomplete thermalization at
collisionless shocks and further accelerated to very high energies via
diffusive shock acceleration. In a previous study we explored the cosmic ray
(CR) acceleration at cosmic shocks through numerical simulations of CR
modified, quasi-parallel shocks in 1D plane-parallel geometry with the physical
parameters relevant for the shocks emerging in the large scale structure
formation of the universe (Kang & Jones 2002). In order to consider the CR
acceleration at shocks with a broader range of physical properties, in this
contribution we present additional simulations. For a given Mach number, shocks
with higher speeds accelerate CRs faster with a greater number of particles.
However, two shocks with a same Mach number but with different shock speeds
evolve qualitatively similarly when the results are presented in terms of
diffusion length and time scales. Therefore, the time asymptotic value for the
fraction of shock kinetic energy transferred to CRs is mainly controlled by
shock Mach number rather than shock speed. We present the ``CR energy ratio''
for a wide range of shock parameters and for $\epsilon=0.2-0.3$ at terminal
time of our simulations. We suggest that these values can be considered as
time-asymptotic values for the CR acceleration efficiency, since the
time-dependent evolution of CR modified shocks has become approximately
self-similar before the terminal time.


title: Variable Yellow and Red Stragglers in the Old Open Cluster NGC 6791

abstract:
  Two sets of archive time series observations of an old open cluster NGC 6791
were re-analysed using an image subtraction technique. We report identification
of four new variables. Proper motion data are available for three of them and
indicate that they are likely cluster members. Photometry of these stars is
discussed along with the data for two earlier identified variables. The sample
analysed includes one yellow and three red stragglers. An eclipsing red
straggler V9 is of particular interest. Cluster membership of this RS Cvn type
binary would imply that its cooler component is in a stage of thermal
inequilibrium. One of variables is a K type red giant showing low-amplitude
variability with a period of about 0.33 d.


title: Tachyon Field in Cosmology

abstract:
  We study cosmological effects of homogeneous tachyon field as dark energy. We
concentrate on two different scalar field potentials, the inverse square
potential and the exponential potential. These models have a unique feature
that the matter density parameter and the density parameter for tachyons remain
comparable for a large range in redshift. It is shown that there exists a range
of parameters for which the universe undergoes an accelerated expansion and the
evolution is consistent with structure formation requirements. For a viable
model we require fine tuning of parameters comparable to that in LCDM or in
quintessence models. For the exponential potential, the accelerated phase is
followed by a phase with a(t)~ t^{2/3} thus eliminating a future horizon.


title: Mimicking transPlanckian effects in the CMB with conventional physics

abstract:
  We investigate the possibility that fields coupled to the inflaton can
influence the primordial spectrum of density perturbations through their
coherent motion. For example, the second field in hybrid inflation might be
oscillating at the beginning of inflation rather than at the minimum of its
potential. Although this effect is washed out if inflation lasts long enough,
we note that there can be up to 30 e-foldings of inflation prior to horizon
crossing of COBE fluctuations while still giving a potentially visible
distortion. Such pumping of the inflaton fluctuations by purely conventional
physics can resemble transPlanckian effects which have been widely discussed.
The distortions which they make to the CMB could leave a distinctive signature
which differs from generic effects like tilting of the spectrum.


title: Inward Bound: Studying the Galactic Centre with NAOS/CONICA

abstract:
  We report on the first results obtained using adaptive optics measurements of
the Galactic Centre done with NAOS/CONICA.


title:
Possible contribution of olefins and heteroatoms to the Unidentified
  Infrared Bands

abstract:
  The current assignments of the 11.3 feature are shown to be incompatible with
observations. An unbiased survey of correlation charts suggests that the
olefinic group R2=CH2 is a good alternative candidate. For the 12.7 feature,
the best fits are provided by nitrites, R-O-N=O, and amines, R-N=H2. Sulfones,
SO2, exhibit strong features near 7.7 and 8.6 microns, which may contribute to
the UIBs. These additional functional groups are likely to be attached to the
main hydrocarbon dust skeleton previously hypothesized in the coal/kerogen
model. They provide further leeway in modelling the large variety of relative
band intensities observed in the sky.


title: What can biologists say about galaxy evolution ?

abstract:
  It is possible to borrow from a topic of biology called phylogenetic
systematics, concepts and tools for a logical and objective classification of
galaxies. It is based on observable properties of objects - characters - either
qualitative (like morphology) or quantitative (like luminosity, mass or
spectrum). Distance analysis can readily be performed using a method called
phenetics and based on characters. But the most promising approach is
cladistics. It makes use of characters that can exist in at least two states,
one being ancestral and the other one derived. Objects are gathered depending
on the derived states they share. We illustrate a first application of this
method to astrophysics, that we name astrocladistics, with dwarf galaxies from
the Local Group.


title:
Explosion Energies, Nickel Masses, and Distances of Supernovae of Type
  IIP

abstract:
  The hydrodynamical modelling of Type II plateau supernova light curves
predicts a correlation between three observable parameters (the plateau
duration, the absolute magnitude and photospheric velocity at the middle of the
plateau) on the one side and three physical parameters (the explosion energy E,
the mass of the envelope expelled M, and the presupernova radius R) on the
other side. The correlation is used, together with adopted EPM distances, to
estimate E, M, and R for a dozen of well-observed SNe IIP. For this set of
supernovae, the resulting value of E varies within a factor of 6 [0.5< E/(10^51
erg)<3], whereas the envelope mass remains within the limits 10< M/M_sun <30.
The presupernova radius is typically (200-600)R_sun, but can exceed 1000R_sun
for the brightest supernovae (e.g., SN 1992am).
  A new method of determining the distance of SNe IIP is proposed. It is based
on the assumption of a correlation between the explosion energy E and the Ni56
mass required to power the post-plateau light curve tail through Co56 decay.
The method is useful for SNe IIP with well-observed bolometric light curves
both during the plateau and radioactive tail phases. The resulting distances
and future improvements are discussed.


title: Nonlinear self-interaction of plane gravitational waves

abstract:
  Recently Mendonca and Cardoso [Phys. Rev. D, vol. 66, 104009 (2002)]
considered nonlinear gravitational wave packets propagating in flat space-time.
They concluded that the evolution equation - to third order in amplitude -
takes a similar form to what arises in nonlinear optics. Based on this
equation, the authors found that nonlinear gravitational waves exhibit
self-phase modulation and high harmonic generation leading to frequency
up-shifting and spectral energy dilution of the gravitational wave energy. In
this Brief Report we point out the fact - a possibility that seems to have been
overlooked by Mendonca and Cardoso - that the nonlinear terms in the evolution
equation cancels and, hence, that there is no amplitude evolution of the pulse.
Finally we discuss scenarios where these nonlinearities may play a role.


title: Parallelization of a treecode

abstract:
  I describe here the performance of a parallel treecode with individual
particle timesteps. The code is based on the Barnes-Hut algorithm and runs
cosmological N-body simulations on parallel machines with a distributed memory
architecture using the MPI message-passing library. For a configuration with a
constant number of particles per processor the scalability of the code was
tested up to P=128 processors on an IBM SP4 machine. In the large $P$ limit the
average CPU time per processor necessary for solving the gravitational
interactions is $\sim 10 %$ higher than that expected from the ideal scaling
relation. The processor domains are determined every large timestep according
to a recursive orthogonal bisection, using a weighting scheme which takes into
account the total particle computational load within the timestep. The results
of the numerical tests show that the load balancing efficiency $L$ of the code
is high ($>=90%$) up to P=32, and decreases to $L\sim 80%$ when P=128. In the
latter case it is found that some aspects of the code performance are affected
by machine hardware, while the proposed weighting scheme can achieve a load
balance as high as $L\sim 90%$ even in the large $P$ limit.


title:
Fast estimation of polarization power spectra using correlation
  functions

abstract:
  We present a fast method for estimating the cosmic microwave background
polarization power spectra using unbiased estimates of heuristically-weighted
correlation functions. This extends the O(N_pix^(3/2)) method of Szapudi et al.
(2001) to polarized data. If the sky coverage allows the correlation functions
to be estimated over the full range of angular separations, they can be
inverted directly with integral transforms and clean separation of the electric
(E) and magnetic (B) modes of polarization is obtained exactly in the mean. We
assess the level of E-B mixing that arises from apodized integral transforms
when the correlation function can only be estimated for a subset of angular
scales, and show that it is significant for small-area observations. We
introduce new estimators to deal with this case on the spherical sky that
preserve E-B separation; their construction requires an additional integration
of the correlation functions but the computational cost is negligible. We
illustrate our methods with application to a large-area survey with parameters
similar to PLANCK, and the small-area Background Imaging of Cosmic
Extragalactic Polarization experiment. In both cases we show that the errors on
the recovered power spectra are close to theoretical expectations.


title:
Long-term Evolution of Stellar Self-Gravitating System away from the
  Thermal Equilibrium: connection with non-extensive statistics

abstract:
  With particular attention to the recently postulated introduction of a
non-extensive generalization of Boltzmann-Gibbs statistics, we study the
long-term stellar dynamical evolution of self-gravitating systems on timescales
much longer than the two-body relaxation time. In a self-gravitating N-body
system confined in an adiabatic wall, we show that the quasi-equilibrium
sequence arising from the Tsallis entropy, so-called stellar polytropes, plays
an important role in characterizing the transient states away from the
Boltzmann-Gibbs equilibrium state.


title: The origin of cores and density profiles of gaseous baryonic structures

abstract:
  We study the origin of cores and density profiles of gaseous baryonic
structures in cosmology. By treating the baryons as a viscous gas, we find that
both spheres and disks are possible solutions. We find analytically that the
density profiles have inner and outer solutions, which in general are
different. For disks we identify a central core, with density profile rho_d =
constant, and the outer profile rho_d ~ r^{-3}. For spherical structures we
find the profile rho_s ~ r^{-6}. In the presence of a dominating central black
hole we find the inner profile rho ~ r^{-3/2}. When the mass is dominated by a
dark matter component then the baryonic density profile will depend on the dark
matter profile, and we point out how one can use this connection to infer the
DM profile directly by observing the baryonic density profile.


title: Internal Kinematics of Spiral Galaxies in Distant Clusters

abstract:
  We present first results from our project to examine the internal kinematics
of disk galaxies in 7 rich clusters with 0.3<=z<0.6. Spatially resolved MOS
spectra have been obtained with FORS at the VLT. We concentrate here on the
clusters MS1008.1-1224 at z=0.30 and Cl0413-6559 (F1557.19TC) at z=0.51. Out of
22 cluster members, 12 galaxies exhibit a rotation curve of the universal form
rising in the inner region and passing over into a flat part. The other members
have intrinsically peculiar kinematics. The 12 cluster galaxies for which a
maximum rotation velocity could be derived are distributed in the Tully-Fisher
diagram very similar to field galaxies from the FORS Deep Field with
corresponding redshifts. The same is true for 6 galaxies observed in the
cluster fields that turned out not to be members. In particular, these cluster
spirals do not show any significant luminosity evolution as might be expected
from certain clusterspecific phenomena. Contrary to that, the other half of the
cluster sample with disturbed kinematics also shows a higher degree of
structural assymetries on average indicating ongoing or recent interaction
processes.


title: A softer look at MCG--6-30-15 with XMM-Newton

abstract:
  We present analysis and results from the Reflection Grating Spectrometer
during the 320 ks XMM observation of the Seyfert 1 galaxy MCG-6-30-15. The
spectrum is marked by a sharp drop in flux at 0.7 keV which has been
interpreted by Branduardi-Raymont et al. as the blue wing of a relativistic
OVIII emission line and by Lee at al. as a dusty warm absorber. We find that
the drop is well explained by the FeI L2,3 absorption edges and obtain
reasonable fits over the 0.32-1.7 keV band using a multizone, dusty warm
absorber model. Some residuals remain which could be due to emission from a
relativistic disc, but at a much weaker level than from any model relying on
relativistic emission lines alone. A model based on such emission lines can be
made to fit if sufficient (warm) absorption is added, although the line
strengths exceed those expected. The EPIC pn difference spectrum between the
highest and lowest flux states of the source indicates that this is a power-law
in the 3-10 keV band which, if extrapolated to lower energies, reveals the
absorption function acting on the intrinsic spectrum, provided that any
emission lines do not scale exactly with the continuum. We find that this
function matches our dusty warm absorber model well. The soft X-ray spectrum is
therefore dominated by absorption structures, with the equivalent width of any
individual emission lines in the residuals being below about 30 eV. (abridged)


title:
The Low Frequency Radio Counterpart of the XMM Large Scale Structure
  Survey

abstract:
  The XMM Large Scale Structure Survey (XMM-LSS) is a major project to map the
large scale structure of the universe out to cosmological distances. An 8
degree by 8 degree region will be surveyed by XMM with planned optical
follow-up to produce a three-dimensional map of many hundreds of clusters out
to a redshift of z = 1. To explore the relation of the large scale structure to
the location and properties of extragalactic radio sources, the XMM-LSS project
also includes a low frequency radio survey of this region. This combination
will provide unprecedented insight into how the radio source formation and
evolution are affected by the local environment. Here, we present preliminary
results from our 325 MHz and 74 MHz surveys in this region. At 325 MHz, we have
a flux limit of 4 mJy/beam, a resolution of 6.3", and a total of 256 source
detections over 5.6 square degrees. At 74 MHz, we have a flux limit of 275
mJy/beam, a resolution of 30", and a total of 211 source detections over 110
square degrees. We describe these results and explore what they tell us about
the population of extra-galactic low frequency radio sources. The 74 MHz survey
represents the first presentation of a deep, sub-arcminute resolution survey at
such a low frequency. This was made possible by recent advances in both
hardware and data reduction algorithms which we describe in detail.


title: Large grains in the disk of CQ Tau

abstract:
  We present 7mm observations of the dusty disk surrounding the 10 Myr old 1.5
Msun pre-main-sequence star CQ Tauri obtained at the Very Large Array with 0.8
arcsecond resolution and 0.1 mJy rms sensitivity. These observations resolve
the 7mm emission in approximately the north-south direction, confirming
previous results obtained with lower resolution. We use a two-layer flared disk
model to interpret the observed fluxes from 7mm to 1.3mm together with the
resolved 7mm structure. We find that the disk radius is constrained to the
range 100 to 300 AU, depending on the steepness of the disk surface density
distribution. The power law index of the dust opacity coefficient, beta, is
constrained to be 0.5 to 0.7. Since the models indicate that the disk is
optically thin at millimeter wavelengths for radii greater than 8 AU, the
contribution of an optically thick region to the emission is less than 10%.
This implies that high optical depth or complex disk geometry cannot be the
cause of the observed shallow millimeter spectral index. Instead, the new
analysis supports the earlier suggestion that dust particles in the disk have
grown to sizes as large as a few centimeters. The dust in the CQ Tauri system
appears to be evolved much like that in the TW Hydra system, a well-studied
pre-main-sequence star of similar age and lower mass. The survival of gas-rich
disks with incomplete grain evolution at such old ages deserves further
investigations.


title: Relativistic Astrophysics Explorer

abstract:
  The great success of the Rossi X-Ray Timing Explorer (RXTE) has shown that
X-ray timing is an excellent tool for the study of strong gravitational fields
and the measurement of fundamental physical properties of black holes and
neutron stars. Here, we describe a next-generation X-ray timing mission, the
Relativistic Astrophysics Explorer (RAE), designed to fit within the envelope
of a medium-sized mission. The instruments will be a narrow-field X-ray
detector array with an area of 6 m^2 equal to ten times that of RXTE and a
wide-field X-ray monitor. We describe the science made possible with this
mission, the design of the instruments, and results on prototype large-area
X-ray detectors.


title: Dark Matter as Dark Energy

abstract:
  Velocity-dependent interactions in a fundamental-string dominated universe
lead quite naturally, with reasonable assumptions on initial conditions, to an
accelerating expanding universe without assuming the existence of a
cosmological constant. This result also holds generically for a universe
dominated by moving extremal black holes, owing to a repulsive velocity-
dependent force. This interaction, however, does not preclude structure
formation. Here we discuss a toy model including both ordinary and extremal
matter, in which the latter accounts for dark matter while simultaneously
acting as effective dark energy. Eternal acceleration is once more seen to
arise in this case.


title: The Flaring H2O Megamaser and Compact Radio Source in Mrk 348

abstract:
  We report on single-dish monitoring and extremely high angular resolution
observations of the flaring H2O megamaser in the Seyfert 2 galaxy Mrk 348. The
H2O line is redshifted by ~130 km/s with respect to the systemic velocity, is
very broad, with a FWHM of 130 km/s, and has no detectable high velocity
components within 1500 km/s on either side of the strong line. Monitoring
observations made with the Effelsberg 100m telescope show that the maser varies
significantly on timescales as short as one day and that the integrated line
flux is loosely correlated with the continuum flux. VLBA observations indicate
that the maser emission arises entirely from a region less than 0.25 pc in
extent, located toward a continuum component thought to be associated with the
receding jet. We also report on integrated flux monitoring with the VLA between
1.4 and 43 GHz, and VLBA continuum observations of the milliarcsecond scale
jets at 1.7, 8, 15, and 22 GHz. These observations have allowed us to
tentatively pinpoint the location of the core, and also show the ejection of a
new jet component during the current radio "flare."


title: Iron Emission in z~6 QSOs

abstract:
  We have obtained low-resolution near infrared spectra of three QSOs at 5.7 <
z < 6.3 using the NICMOS instrument of the Hubble Space Telescope. The spectra
cover the rest-frame ultraviolet emission of the objects between lambda_rest ~
1600A - 2800A. The Fe II emission-line complex at 2500A is clearly detected in
two of the objects, and possibly detected in the third. The strength of this
complex and the ratio of its integrated flux to that of Mg II lambda 2800 are
comparable to values measured for QSOs at lower redshifts, and are consistent
with Fe/Mg abundance ratios near or above the solar value. There thus appears
to be no evolution of QSO metallicity to z~6. Our results suggest that massive,
chemically enriched galaxies formed within 1 Gyr of the Big Bang. If this
chemical enrichment was produced by Type Ia supernovae, then the progenitor
stars formed at z ~ 20 +/- 10, in agreement with recent estimates based on the
cosmic microwave background. These results also support models of an
evolutionary link between star formation, the growth of supermassive black
holes and nuclear activity.


title:
Contrasting the UV and X-ray O VI Column Density Inferred for the
  Outflow in NGC 5548

abstract:
  We compare X-ray and UV spectroscopic observations of NGC 5548. Both data
sets show O VI absorption troughs associated with the AGN outflow from this
galaxy. We find that the robust lower limit on the column density of the O VI
X-ray trough is seven times larger than the column density found in a study of
the O VI UV troughs. This discrepancy suggests that column densities inferred
for UV troughs of Seyfert outflows are often severely underestimated. We
identify the physical limitations of the UV Gaussian modeling as the probable
explanation of the O VI column density discrepancy. Specifically, Gaussian
modeling cannot account for a velocity dependent covering fraction, and it is a
poor representation for absorption associated with a dynamical outflow.
Analysis techniques that use a single covering fraction value for each
absorption component suffer from similar limitations. We conclude by suggesting
ways to improve the UV analysis.


title:
Cross-Correlation and Maximum Likelihood Analysis: A New Approach to
  Combine Cross-Correlation Functions

abstract:
  This paper presents a new approach to combine cross-correlation functions.
The combination is based on a maximum-likelihood approach and uses a non-linear
combination scheme. It can be effective for radial-velocity analysis of
multi-order spectra, or for analysis of multiple exposures of the same object.
Simulations are presented to show the potential of the suggested combination
scheme. The technique has already been used to detect a very faint companion of
HD41004.


title: Shocks, Outflows and Bubbles: New Views on Pulsars and their Winds

abstract:
  A typical young pulsar slows down at an imperceptible rate, its spin period
increasing by less than 10 microseconds over the course of a year. However, the
inertia of a pulsar is so extreme that to effect this tiny change in rotation
rate, the star must dissipate about 10^46 ergs of kinetic energy. Observations
of pulsars and their surroundings demonstrate that this ``spin-down energy'' is
expelled into the pulsar's surroundings in spectacular fashion, in the form of
a relativistic wind of charged particles and magnetic fields. In this review I
highlight some recent observational results on pulsar winds at radio, X-ray and
optical wavelengths, and explain what we can learn from these data about shock
structure, particle acceleration and the interstellar medium.


title: Measuring Cosmology with Supernovae

abstract:
  Over the past decade, supernovae have emerged as some of the most powerful
tools for measuring extragalactic distances. A well developed physical
understanding of type II supernovae allow them to be used to measure distances
independent of the extragalactic distance scale. Type Ia supernovae are
empirical tools whose precision and intrinsic brightness make them sensitive
probes of the cosmological expansion. Both types of supernovae are consistent
with a Hubble Constant within ~10% of H_0 = 70 km/s/Mpc. Two teams have used
type Ia supernovae to trace the expansion of the Universe to a look-back time
more than 60% of the age of the Universe. These observations show an
accelerating Universe which is currently best explained by a cosmological
constant or other form of dark energy with an equation of state near w = p/rho
= -1. While there are many possible remaining systematic effects, none appears
large enough to challenge these current results. Future experiments are planned
to better characterize the equation of state of the dark energy leading to the
observed acceleration by observing hundreds or even thousands of objects. These
experiments will need to carefully control systematic errors to ensure future
conclusions are not dominated by effects unrelated to cosmology.


title: A Low-Mass Central Black Hole in the Bulgeless Seyfert 1 Galaxy NGC 4395

abstract:
  NGC 4395 is one of the least luminous and nearest known type 1 Seyfert
galaxies, and it also lacks a bulge. We present an HST I-band image of its
nuclear region and Keck high-resolution (8 km/s) echelle spectra containing the
Ca II near-infrared triplet. In addition to the unresolved point source, there
is a nuclear star cluster of size r ~ 3.9 pc; the upper limit on its velocity
dispersion is only 30 km/s. We thus derive an upper limit of 6.2x10^6 solar
masses for the mass of the compact nucleus. Based on the amount of spatially
resolved light in the HST image, a sizable fraction of this is likely to reside
in stars. Hence, this estimate sets a stringent upper limit on the mass of the
central black hole. We argue, from other lines of evidence, that the true mass
of the black hole is likely to be 10^4-10^5 solar masses. Although the black
hole is much less massive than those thought to exist in classical active
galactic nuclei, its accretion rate of L_bol/L_Edd ~ 2x10^-2 to 2x10^-3 is
consistent with the mass-luminosity relation obeyed by classical AGNs. This may
explain why NGC 4395 has a high-excitation (Seyfert) emission-line spectrum;
active galaxies having low-ionization spectra seem to accrete at significantly
lower rates. NGC 4395, a pure disk galaxy, demonstrates that supermassive black
holes are not associated exclusively with bulges.


title: Physical Parameters of the Old Open Cluster Trumpler 5

abstract:
  We present a study of the old open cluster Trumpler 5 (Tr 5), based on the
CDS archival data. From the color-magnitude diagrams of Tr 5, we have found the
positions of main-sequence turn-off (MSTO) and red giant clump (RGC) stars.
Using the mean magnitude of the RGC stars, we have estimated the reddening
toward Tr 5, E(B-V) = 0.60 +/- 0.10. Using the stars common in two data sets
and the theoretical isochrones of Padova group, we have estimated the distance
modulus V_0-M_V=12.64 +/- 0.20 (d = 3.4 +/- 0.3 kpc), the metallicity [Fe/H] =
-0.30 +/- 0.10, and the age of 2.4 +/- 0.2 Gyr (log t=9.38). These metallicity
and distance values are consistent with the relation between the metallicity
and the Galactocentric distance of other old open clusters, for which we obtain
the slope of Delta_[Fe/H]/R_gc= -0.064 +/- 0.010 dex/kpc.


title: Distribution of dark and baryonic matter in clusters of galaxies

abstract:
  We present the analysis of baryonic and non-baryonic matter distribution in a
sample of ten nearby clusters (0.03<z<0.09) with temperatures between 4.7 and
9.4 keV. These galaxy clusters are studied in detail using X-ray data and
global physical properties are determined. Correlations between these
quantities are analysed and compared with the results for distant clusters. We
find an interesting correlation between the extent of the intra-cluster gas
relative to the dark matter distribution. The extent of the gas relative to the
extent of the dark matter tends to be larger in less massive clusters. This
correlation might give us some hints on non-gravitational processes in
clusters. We do not see evolution in the gas mass fraction out to a redshift of
unity. Within r_{500}, the mean gas mass fraction obtained is 0.16\pm0.02
h_{50}^{-3/2}.


title:
The Leo I Cloud: Secular nuclear evolution of NGC 3379, NGC 3384, and
  NGC 3368?

abstract:
  The central regions of the three brightest members of the Leo I galaxy group
-- NGC 3368, NGC 3379, and NGC 3384 -- are investigated by means of 2D
spectroscopy. In all three galaxies we have found separate circumnuclear
stellar and gaseous subsystems -- more probably, disks -- whose spatial
orientations and spins are connected to the spatial orientation of the
supergiant intergalactic HI ring reported previously by Schneider et al. (1983)
and Schneider (1985, 1989). In NGC 3368 the global gaseous disk seems also to
be inclined to the symmetry plane of the stellar body, being probably of
external origin. Although the rather young mean stellar age and spatial
orientations of the circumnuclear disks in NGC 3379, NGC 3384, and NGC 3368
could imply their recent formation from material of the intergalactic HI cloud,
the time scale of these secondary formation events, of order 3 Gyr, does not
support the collision scenario of Rood & Williams (1985), but is rather in line
with the ideas of Schneider (1985, 1989) regarding tidal interactions of the
galaxies with the HI cloud on timescales of the intergroup orbital motions.


title: The low surface brightness dwarf members of nearby groups of galaxies

abstract:
  We present the photometric and spectroscopic results of a survey done in a
wide-field area of nearby groups and poor clusters. The main goals are
identifying and characterizing the properties of low-surface-brightness dwarf
galaxies and determining the galaxy luminosity function for Mv>-13. We surveyed
areas (typically 0.1--1.0 square degrees) of the groups NGC 6868 (Telescopium),
NGC 5846, HCG 42, Hydra I, Dorado and the poor clusters IC 4765 in V and I. In
this work we present the results and the analysis of the photometry and
spectroscopy done in four groups: HCG 42, NGC 6868, NGC 5846 and IC4765. In
these groups, we detected hundreds of new low surface brightness dwarf
galaxies. The analysis of their spatial distributions, colors, galaxy
luminosity function and other propierties are presented.


title: GAIA Photometric Performances

abstract:
  GAIA present day (end-2002) photometric performances, estimated basing on the
stellar populations crucial for understanding the formation and evolution of
the Galaxy, are discussed. Performance of the GAIA photometric systems (PSs) is
evaluated taking into account their ability to simultaneously determine the
main stellar parameters: T_eff, log g, [M/H], and E(B-V), for a large variety
of stars down to V ~ 20. A sample of the stars (Photometric System Test
Targets, PSTTs) applicable for evaluation of the GAIA photometric systems is
presented. Definitions of the 1X PS and its accuracies of stellar
parameterization are given. We conclude that there is still no photometric
system, which would allow to achieve the scientific objectives of the GAIA
mission at the limiting magnitude V=20, proposed to date.


title: Absorption spectra of Fe L-lines in Seyfert 1 galaxies

abstract:
  Absorption L-lines of iron ions are observed, in absorption, in spectra of
Seyfert 1 galaxies by the new generation of X-ray satellites: Chandra (NASA)
and XMM-Newton (ESA). Lines associated to Fe23+ to Fe17+ are well resolved.
Whereas, those corresponding to Fe16+ to Fe6+ are unresolved. Forbidden
transitions of the Fe16+ to Fe6+ ions were previously observed, for the same
objects, in the visible and infra-red regions, showing that the plasma had a
low density. To interpret X-ray, visible and infra-red data, astrophysical
models assume an extended absorbing medium of very low density surrounding an
intense X-ray source. We have calculated atomic data (wavelengths, radiative
and autoionization rates) for n=2 to n'=3-4 transitions and used them to
construct refined synthetic spectra of the unresolved part of the L-line
spectra.


title:
Stellar disk in the galactic center -- a remnant of a dense accretion
  disk?

abstract:
  Observations of the galactic center revealed a population of young massive
stars within 0.4 pc from Sgr A* -- the presumed location of a supermassive
black hole. The origin of these stars is a puzzle as their formation in citu
should be suppressed by the black hole's tidal field. We find that out of 13
stars whose 3-dimensional velocities have been measured by Genzel et. al.
(2000), 10 lie in a thin disk. The half-opening angle of the disk is consistent
with zero within the measurement errors, and does not exceed 10 degrees. We
propose that a recent burst of star formation has occurred in a dense gaseous
disk around Sgr A*. Such a disk is no longer present because, most likely, it
has been accreted by the central black hole. The three-dimensional orbit of S2,
the young star closest to Sgr A*, has been recently mapped out with high
precision. It is inclined to the stellar disk by 75 degrees. We find that the
orbit should undergo Lense-Thirring precession with the period of (5/a) Myr,
where a<1 is the dimensionless spin of the black hole. Therefore it is possible
that originally S2 orbit lay in the disk plane. If so, we can constrain the
black hole spin $a$ be greater than 0.2(t_{S2}/5 Myr), where t_{S2} is the age
of S2.


title:
STIS Spectral Imagery of the OB Stars in NGC 604: Describing the
  Extraction Technique for a Crowded Stellar Field

abstract:
  We have developed a data reduction procedure to extract multiple spectra from
a single two-dimensional Space Telescope Imaging Spectrograph (STIS) image of a
crowded stellar field. This paper provides a description of our new technique,
utilizing a STIS ultraviolet spectral image, acquired with the G140L grating
and the 52 arcsec x 2 arcsec aperture, sampling a concentration of O and B
stars in the central region of the NGC 604 starburst in M33. The software
routines can disentangle and produce reliable ultraviolet spectra of stars with
angular separations as small as 0.055 arcsec. Use of the extraction slit, based
upon our model of the spectral cross dispersion profile, generates spectra with
slightly higher resolution than the STScI standard processing. Our results
clearly show that the spectral imaging capability of STIS represents a powerful
tool for studying luminous stars in the star-forming regions of the Local
Group.


title: The 160 Square Degree ROSAT Survey - Revised Catalog & Cluster Evolution

abstract:
  We have constructed a large, statistically complete sample of galaxy clusters
serendipitously detected as extended X-ray sources in 647 ROSAT PSPC pointed
observations. The survey covers 158 square degrees with a median sample flux
limit of 1.2 x 10^-13 erg cm^-2 s^-1 (0.5-2.0 keV). Our sample consists of 201
clusters of galaxies characterized by a median redshift of z=0.25 and a maximum
of z=1.26. With 22 clusters at z > 0.5, the 160 Square Degree ROSAT Survey is
the largest high-redshift sample of X-ray-selected clusters published to date.
Here we describe the revised sample which features spectroscopic redshifts for
99.5% of the clusters and discuss the implications for evolution in the cluster
abundance.


title:
Temperature and cooling age of the white dwarf companion of PSR
  J0218+4232

abstract:
  We report on Keck optical BVRI images and spectroscopy of the companion of
the binary millisecond pulsar PSR J0218+4232. A faint bluish (V=24.2, B-V=0.25)
counterpart is observed at the pulsar location. Spectra of this counterpart
reveal Balmer lines which confirm that the companion is a Helium-core white
dwarf. We find that the white dwarf has a temperature of Teff=8060+-150 K.
Unfortunately, the spectra are of insufficient quality to put a strong
constraint on the surface gravity, although the best fit is for low log g and
hence low mass (~0.2 Msun), as expected. We compare predicted white dwarf
cooling ages with the characteristic age of the pulsar and find similar values
for white dwarf masses of 0.19 to 0.3 Msun. These masses would imply a distance
of 2.5 to 4 kpc to the system. The spectroscopic observations also enable us to
estimate the mass ratio between the white dwarf and the pulsar. We find
q=7.5+-2.4, which is consistent with the current knowledge of white dwarf
companions to millisecond pulsars.


title: Newtonian Collapse of Scalar Field Dark Matter

abstract:
  In this letter, we develop a Newtonian approach to the collapse of galaxy
fluctuations of scalar field dark matter under initial conditions inferred from
simple assumptions. The full relativistic system, the so called
Einstein-Klein-Gordon, is reduced to the Schr\"odinger-Newton one in the weak
field limit. The scaling symmetries of the SN equations are exploited to track
the non-linear collapse of single scalar matter fluctuations. The results can
be applied to both real and complex scalar fields.


title:
Distinct Abundance Patterns in Multiple Damped Ly-alpha Galaxies:
  Evidence for Truncated Star Formation?

abstract:
  (abridged) Following our previous work on metal abundances of a double damped
Ly-alpha system with a line-of-sight separation ~2000 km/s (Ellison & Lopez
2001), we present VLT UVES abundances of 3 new systems spanning a total of
\~6000 km/s at z~2.5 toward the southern QSO CTQ247. These abundances are
supplemented with echelle observations of another `double' damped Ly-alpha
system in the literature. We propose a definition in terms of velocity shift of
the sub-class 'multiple damped Ly-alpha system', which is motivated by its
possible connection with large-scale structure. We find that the abundance
ratio alpha/Fe is systematically low in multiple systems compared with single
systems, and with a small scatter. The same behavior is found in 2 more single
DLA systems taken from the literature that show evidence of belonging to a
galaxy group. After a careful investigation of possible sources of systematic
errors, we conclude that the low alpha/Fe ratios in multiple DLAs have a
nucleosynthetic origin. We suggest that they could be explained by reduced star
formation in multiple damped Ly-alpha systems, possibly due to environmental
effects.


title:
STIS Spectral Imagery of the OB Stars in NGC 604: The Most Luminous
  Stars

abstract:
  We present results using 2-D spectral imagery and photometry obtained with
the Hubble Space Telescope (HST) for the starburst H II region, NGC 604, in
nearby galaxy M33. The spectral imagery was acquired with the Space Telescope
Imaging Spectrograph (STIS) using the MAMA/G140L configuration, spanning
1170-1730 A. From a single 1720 sec STIS exposure, we extracted spectra for 49
stars and derived individual UV spectral types for 40 stars in the crowded
25"x2" stellar field. These stars represent a significant fraction of the
young, luminous O and B stars. Three objects have pronounced He II 1640
emission, the signature of W-R or luminous Of stars. By combining UV fluxes
with WFPC and WFPC2 visual photometry, we derive the extinction curve for NGC
604. We use this curve, the distance for M33, derived UV spectral types, and
HST photometry, to determine positions of these stars in the upper H-R diagram.
The revised O star effective temperature scale (Martins et al.) is essential in
obtaining reliable positions in the log(L*)-log(T(eff)) plane. These stars are
quite young with an age of ~3 Myr. The spectra and photometry indicate three
exceedingly luminous objects. Their inferred locations in the H-R diagram
indicate stellar masses > 120 solar masses. High spatial resolution HST imagery
provides no evidence of multiple stars composing these objects. Still we cannot
eliminate the possibility that they are unresolved multiple stars of lower
mass, possibly W-R stars. Tests demonstrate that the ten most luminous stars
predominantly determine the UV spectral features seen in the total light of NGC
604. We conclude that interpretation of spectral fitting of more distant
starburst galaxies, where individual stars are not resolved, must be done with
extreme care.