title: The Importance of Dry and Mixed Mergers for Early-Type Galaxy Formation

abstract:
  We use semi-analytical modelling techniques to investigate the progenitor
morphologies of present day ellipticals. We find that, independent of the
environment, the fraction of mergers of bulge dominated galaxies (early-types)
increases with time. The last major merger of bright present day ellipticals
with $M_{B} \lesssim -21$ is preferentially between bulge dominated galaxies,
while those with $ M_{B} \sim -20$ have mainly experienced last major mergers
between a bulge dominated and a disk dominated galaxy.
  Independent of specific model assumptions, more than 50% of present day
elliptical in clusters with $M_B \lesssim -18$ had last major mergers which are
not of spirals as usually expected within the standard merger scenario.


title:
On the origin of the X-ray emission from a narrow-line radioquasar at
  z>1

abstract:
  We present new XMM-Newton X-ray observations of the z=1.246 narrow-line
radioquasar RX J1011.2+5545 serendipitously discovered by ROSAT. The flat X-ray
spectrum previously measured by ROSAT and ASCA is shown to be the result of a
steep Gamma~1.8 power law spectrum seen through a moderate intrinsic absorbing
column NH~4E21 cm^-2. The position of the X-ray source is entirely coincident
with the nucleus of the radio source that we have resolved in new sensitive VLA
observations at 3.6 and 6 cm, implying that scattering in the radio lobes is
not responsible for the bulk of X-ray emission. In the EPIC pn image, a faint
patch of X-ray emission is apparent 14'' to the NE of the main X-ray source.
The former is positionally coincident with an apparently extended optical
object with R~21.9, but there is no associated radio emission, thus ruling out
the possibility that this represents a hotspot in a jet emanating from the
primary X-ray source. No reflection features are detected in the X-ray spectrum
of the narrow-line radioquasar, although an Fe line with equivalent width of up
to 600 eV cannot be ruled out.


title:
The Properties of Spiral Galaxies: Confronting Hierarchical Galaxy
  Formation Models with Observations

abstract:
  We compare the properties of local spiral galaxies with the predictions of
the Cole et al. semi-analytic model of hierarchical galaxy formation, in order
to gain insight into the baryonic processes that were responsible for shaping
these galaxies. On the whole, the models reproduce the properties of
present-day spirals (such as SFRs, SFHs, scale sizes, metallicities, and gas
fractions) rather well. In particular, we find that once the effects of dust
and variations in stellar populations have been taken into account, published
spiral galaxy scale-size distributions derived from optical data (with
logarithmic widths ~0.3) can be reconciled with the width of the stellar mass
scale-size distribution predicted by the semi-analytic model (~0.5). There are
some illuminating discrepancies between the observations and the model
predictions. The model colours of luminous spiral galaxies are somewhat too
blue and those of faint galaxies somewhat too red, most likely indicating
shortcomings in the way that gas is accreted by spiral galaxies. Furthermore,
the model produces too few luminous spiral galaxies. These difficulties could
be resolved by altering the way in which gas cooling is treated or, perhaps, by
adopting a higher baryon fraction and invoking galactic `superwinds.' Secondly,
stellar M/Ls are found to be as high as observations permit. Yet, typically 60%
of the mass in the inner half-light radius of the model galaxies is dark. This
results in an offset between the model and observed spiral galaxy
luminosity-linewidth relation. This could be resolved by substantially reducing
the mass of baryons which make it into a galaxy disc (with an attendant
decrease in stellar M/L), or by modifying the assumed dark matter profile to
include less dark matter in the inner parts. [Abridged]


title:
Turbulent viscosity in clumpy accretion disks II supernova driven
  turbulence in the Galaxy

abstract:
  An analytical model for a turbulent clumpy gas disk is presented where
turbulence is maintained by the energy input due to supernovae. Expressions for
the disk parameters, global filling factors, molecular fractions, and star
formation rates are given as functions of the Toomre parameter $Q$, the ratio
between the cloud size and the turbulent driving length scale $\delta$, the
mass accretion rate within the disk $\dot{M}$, the constant of molecule
formation $\alpha$, the disk radius, the angular velocity, and its radial
derivative. Two different cases are investigated: a dominating stellar disk and
a self-gravitating gas disk in $z$ direction. The turbulent driving wavelength
is determined in a first approach by energy flux conservation, i.e. the
supernovae energy input is transported by turbulence to smaller scales where it
is dissipated. The results are compared to those of a fully gravitational
model. For Q=1 and $\delta=1$ both models are consistent with each other. In a
second approach the driving length scale is directly determined by the size of
supernovae remnants. Both models are applied to the Galaxy and can reproduce
its integrated and local gas properties. The influence of thermal and magnetic
pressure on the disk structure is investigated. We infer $Q \sim 1$ and
$\dot{M} \sim 0.05 - 0.1 M_{\odot} yr ^{-1}$ for the Galaxy.


title: The Evolution of Cluster Radio Galaxies at 0.5<z<1

abstract:
  We are conducting a deep radio survey of a sample of 25 distant ($0.5<z<1$)
clusters of galaxies. Here we present a progress report. So far 17 of 25
clusters have been observed, to varying depths. We have found 33 radio sources
within 0.3 Abell radii of the cluster center, of which 28 are likely associated
with cluster member galaxies. A comparison of the radio luminosity function of
these clusters with the results of two surveys at lower redshift, reveals no
evidence for strong evolution in the population of cluster radio galaxies at $z
\sim 0.65$.


title:
Building the MEGA Image-Subtraction Pipeline in the Era of Virtual
  Observatories

abstract: This paper has been withdrawn.


title:
Studying the Properties of Accretion Disks and Coronae in Black Hole
  X-ray Binaries with Monte-Carlo Simulations

abstract:
  Understanding the properties of the hot corona is important for studying the
accretion disks in black hole X-ray binary systems. Using the Monte-Carlo
technique to simulate the inverse Compton scattering between photons emitted
from the cold disk and electrons in the hot corona, we have produced two table
models in the $XSPEC$ format for the spherical corona case and the disk-like
(slab) corona case. All parameters in our table models are physical properties
of the system and can be derived from data fitting directly. Applying the
models to broad-band spectra of the black hole candidate XTE J2012+381 observed
with BeppoSAX, we estimated the size of the corona and the inner radius of the
disk. The size of the corona in this system is several tens of gravitational
radius, and the substantial increase of the inner disk radius during the
transit from hard-state to soft-state is not found.


title:
Optical and near-infrared observations of the microquasar V4641
  Sagittarii during the 1999 September outburst

abstract:
  We present photometric and spectroscopic optical and near-infrared (NIR)
observations (Based on observations collected at the European Southern
Observatory, Chile (ESO ID 63.H-0493 and 64.H-0382)) taken during the outburst
of the microquasar V4641 Sgr = SAX J1819.3-2525 (in'tzand et al., 2000) in
September 1999. We observed an increase in the J-Ks colour between 5 and 8 days
after the outburst, which we interpret as likely evidence for the presence of
dust around the source. We also observed an extraordinarily strong, broad and
variable H_alpha line, with a velocity width of 4560 km/s suggesting the
presence of a high-velocity outflow component. We constrain the distance of the
system between 3 and 8 kpc, locating it further away than previously derived
from radio observations (Hjellming et al., 2000), but consistent with Orosz et
al. (2001). We then discuss the nature of this system, showing that the
companion star is either a B3-A2 main sequence star, or a B3-A2 sub-giant
crossing the Hertzsprung gap. The system is therefore an Intermediate or High
Mass X-ray Binary System (IMXB or HMXB). The distance derived by these
optical/NIR observations implies that the jets observed by Hjellming et al.
(2000) would then exhibit apparent velocities of ~ 10 c. We finally discuss the
possibility of an interaction between the jets and surroundings of the source,
and also of this source being a ``microblazar''.


title: WZ Sge: FUSE Spectroscopy of the 2001 Outburst

abstract:
  The short-period cataclysmic variable WZ Sge underwent its first dwarf nova
outburst in 23 years in 2001 July. Here we describe 905-1187 Ang. spectra
obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) during the
outburst and within the first few months after the outburst. The first
spectrum, obtained about 7 days after the outburst began and 6.4 days past
optical maximum, is dominated by a broad (50-60 Ang. EW) feature due to O VI
and can be characterized in terms of emission from a highly inclined disk
modulated by the effects of a highly ionized wind. WZ Sge is fainter in later
observations (starting about 45 days after optical maximum) and increasingly
"red" in the far ultraviolet. The spectral shape increasingly resembles that
expected from a metal-enriched white dwarf photosphere, although it seems
likely that some disk contribution remains at least through the second FUSE
observation, when the visible light curve showed the system to be undergoing a
rebrightening event. The absorption lines observed on 29 September and in early
November, when the visible light curve was in a fairly steady decline toward
quiescence, are narrow, with widths (FWHM) of order 0.7-1.3 Ang. (200-400
km/s). The most natural explanation for these spectra is that the continuum
arises from a relatively massive, slowly rotating white dwarf, and that the
lines are created by a combination of metals in the atmosphere and of absorbing
material along the line of sight to the white dwarf. If the white dwarf has
log{g}= 8.5, then the white dwarf cooled from ~25,000 K on 29 September to
23,000 K in early November.


title: WMAP Constraints on the Generalized Chaplygin Gas Model

abstract:
  The generalized Chaplygin gas (GCG) model explains the recent accelerated
expansion of the Universe via an exotic background fluid whose equation of
state is given by p=-A/\rho^\alpha, where A is a positive constant and
0<\alpha\le 1. The model is an interesting alternative to scenarios involving
scalar field potentials, with the ensuing unnatural fine tuning conditions for
the underlying particle physics theories. We derive constraints on the
parameter space of the model from bounds on the location of the first few peaks
and troughs of the the Cosmic Microwave Background Radiation (CMBR) power
spectrum arising from recent WMAP and BOOMERanG data.


title:
The X-ray Afterglows of GRB 020813 and GRB 021004 with Chandra HETGS:
  Possible Evidence for a Supernova Prior to GRB 020813

abstract:
  We report on the detection of an emission line near 1.3 keV, which we
associate with blue-shifted hydrogen-like sulfur (S XVI), in a 76.8 ksec
Chandra HETGS spectrum of the afterglow of GRB 020813. The line is detected at
3.3 sigma significance. We also find marginal evidence for a line possibly due
to hydrogen-like silicon (Si XIV) with the same blue-shift. A line from Fe is
not detected, though a very low significance Ni feature may be present. A
thermal model fits the data adequately, but a reflection model may provide a
better fit. There is marginal evidence that the equivalent width of the S XVI
line decrease as the burst fades. We infer from these results that a supernova
likely occurred >~ 2 months prior to the GRB. We find no discrete or variable
spectral features in the Chandra HETGS spectrum of the GRB 021004 afterglow.


title:
Spectroscopic study of blue compact galaxies III. Empirical population
  synthesis

abstract:
  This is the third paper of a series dedicated to the study of the star
formation rates, star formation histories, metallicities and dust contents of a
sample of blue compact galaxies (BCGs). We constrain the stellar contents of 73
blue compact galaxies by analyzing their continuum spectra and the equivalent
widths of strong stellar absorption features using a technique of empirical
population synthesis based on a library of observed star-cluster spectra. Our
results indicate that blue compact galaxies are typically age-composite stellar
systems; in addition to young stars, intermediate-age and old stars contribute
significantly to the 5870 A continuum emission of most galaxies in our sample.
The stellar populations of blue compact galaxies also span a variety of
metallicities. The ongoing episodes of star formation started typically less
than a billion years ago. Some galaxies may be undergoing their first global
episode of star formation, while for most galaxies in our sample, older stars
are found to contribute up to half the optical emission. Our results suggest
that BCGs are primarily old galaxies with discontinuous star formation
histories. The absorption equivalent widths measured in the synthetic spectra
range from typically 1.5 A for Halpha, to 2 -- 5 A for Hbeta, Hgamma, and
Hdelta. The implied accurate measurements of emission-line intensities will be
used in a later study to constrain the star formation rates and gas-phase
chemical element abundances of blue compact galaxies.


title: On the Radii of Extrasolar Giant Planets

abstract:
  We have computed evolutionary models for extrasolar planets which range in
mass from 0.1 to 3.0 Jovian Masses, and which range in equilibrium temperature
from 113 K to 2000 K. We present four sequences of models, designed to show the
structural effects of a solid core and of internal heating due to the
conversion of kinetic to thermal energy at pressures of tens of bars. The model
planetary radii are intended for comparisons with radii derived from
observations of transiting extrasolar planets. To provide such comparisons, we
expect that of order 10 transiting planets with orbital periods less than 200
days can be detected around bright (V<10) main-sequence stars for which
accurate, well-sampled radial velocity measurements can be readily accumulated.
Through these observations, structural properties of the planets will be
derivable, particularly for low-mass, high-temperature planets. Implications
regarding the transiting companion to OGLE-TR-56 recently announced by Konacki
et al. are discussed.
  With regard to the confirmed transiting planet, HD 209458b, we find, in
accordance with other recent calculations, that models without internal heating
predict a radius that is 35 percent smaller than the observed radius. We
explore the possibility that HD 209458b owes its large size to dissipation of
energy arising from ongoing tidal circularization of the orbit. We show that
residual scatter in the current radial velocity data set for HD 209458b is
consistent with the presence of an as-of-yet undetected second companion, and
that further radial velocity monitoring of the star is indicated.


title:
The Extremely Metal-Poor, Neutron-Capture-Rich Star CS 22892-052: A
  Comprehensive Abundance Analysis

abstract:
  High-resolution spectra obtained with three ground-based facilities and the
Hubble Space Telescope (HST) have been combined to produce a new abundance
analysis of CS 22892-052, an extremely metal-poor giant with large relative
enhancements of neutron-capture elements. A revised model stellar atmosphere
has been derived with the aid of a large number of Fe-peak transitions,
including both neutral and ionized species of six elements.Several elements,
including Mo, Lu, Au, Pt and Pb, have been detected for the first time in CS
22892-052, and significant upper limits have been placed on the abundances of
Ga, Ge, Cd, Sn, and U in this star. In total, abundance measurements or upper
limits have been determined for 57 elements, far more than previously possible.
New Be and Li detections in CS 22892-052 indicate that the abundances of both
these elements are significantly depleted compared to unevolved main-sequence
turnoff stars of similar metallicity. Abundance comparisons show an excellent
agreement between the heaviest n-capture elements (Z >= 56) and scaled solar
system r-process abundances, confirming earlier results for CS 22892-052 and
other metal-poor stars. New theoretical r-process calculations also show good
agreement with CS 22892-052 abundances as well as the solar r-process abundance
components.The abundances of lighter elements (40<= Z <= 50), however, deviate
from the same scaled abundance curves that match the heavier elements,
suggesting different synthesis conditions or sites for the low-mass and
high-mass ends of the abundance distribution. The detection of Th and the upper
limit on the U abundance together imply a lower limit of 10.4 Gyr on the age of
CS 22892-052, quite consistent with the Th/Eu age estimate of 12.8 +/- ~= 3
Gyr. An average of several chronometric ratios yields an age 14.2 +/- ~= 3 Gyr.


title: Physical processes behind the morphological Hubble sequence

abstract:
  The study of formation and evolution of galaxies is reviewed, making emphasis
on the physical factors which are important to understand the origin of the
galaxy Hubble sequence. We concentrate on predictions of the hierarchical Cold
Dark Matter (CDM) scenario and the confrontation with observations. The mass
assembling of the CDM halos, the baryonic processes within them, and the
evolution of disks and spheroids are described. The successes and shortcomings
are discussed. Disk evolution seems to be a quiescent and extended process
driven by the cosmological initial conditions, while spheroids are formed
probably in violent events, where several astrophysical processes are
competing.


title: Ultraviolet structure in the lensed QSOs 0957+561

abstract:
  Imaging and spectra of the lensed QSO pair 0957+561 are presented and
discussed. The data are principally those from the STIS NUV MAMA, and cover
rest wavelengths from 850A to 1350A. The QSOs are both extended over about 1
arcsec, with morphology that matches with a small rotation, and includes one
feature aligned with the VLBI radio jets. This is the first evidence of lensed
structure in the host galaxy. The off-nuclear spectra arise from emission line
gas and a young stellar population. The gas has velocity components with radial
velocities at least 1000 km/s with respect to the QSO BLR, and may be related
to the damped Ly alpha absorber in the nuclear spectra.


title: Early-type Galaxies in the Cluster Abell 2390 at z=0.23

abstract:
  To examine the evolution of the early-type galaxy population in the rich
cluster Abell 2390 at z=0.23 we have gained spectroscopic data of 51 elliptical
and lenticular galaxies with MOSCA at the 3.5 m telescope on Calar Alto
Observatory. This investigation spans both a broad range in luminosity
(-19.3>M_B>-22.3) and uses a wide field of view of 10'x10', therefore the
environmental dependence of different formation scenarios can be analysed in
detail as a function of radius from the cluster centre. Here we present results
on the surface brightness modelling of galaxies where morphological and
structural information is available in the F814W filter aboard the Hubble Space
Telescope (HST) and investigate for this subsample the evolution of the
Fundamental Plane.


title: On X-ray variability in narrow line and broad line AGNs

abstract:
  We assembled a sample of broad line and narrow lines AGNs observed by ASCA,
whose excess variances have been determined. The central black hole masses in
this sample can be obtained from the reverberation mapping method and the width
of H$\beta$ emission line. Using the black hole masses and the bolometric
luminosity, the Eddington ratio can also be obtained. We confirmed the strong
anti-correlation between X-ray variability and the central black mass founded
by Lu & Yu. We further found that narrow line Seyfert 1 galaxies (NLS1s) also
follow this relation with a larger scatter and there is only a weak correlation
between the X-ray variability and the Eddington ratio, which suggest that rapid
variability and narrow lines in NLS1s are mainly due to small central black
holes in NLS1s, not the difference of circumnuclear gas around NLS1s. A strong
correlation was found between the hard X-ray photon index and the Eddington
ratio. If the suggestion of two distinct accretion classes, namely ADAF and
thin disk accretion, in AGNs (Lu & Yu) is correct, the strong photon
index-Eddington ration correlation showed that there exists a kind of two zone
accretion disk, in which the outer zone is a thin disk, and the inner zone is
an ADAF disk. Otherwise, the accretion process is the thin disk accretion and
the ADAF accretion is not required.


title: The 2003 eclipse of EE Cep is coming. A review of past eclipses

abstract:
  EE Cep is an eclipsing binary with a period of 5.6 years. The next eclipse
will occur soon, in May-June 2003, and all available past eclipses were
collected and briefly analysed. EE Cep shows very large changes of the shape
and the depth of minima during different eclipses, however it is possible to
single out some persistent features. The analysis suggests that the eclipsing
body should be a long object surrounded by an extended semi-transparent
envelope. As an explanation, a model of a precessing optically thick disc,
inclined to the plane of the binary orbit, is invoked. The changes of its
spatial orientation, which is defined by the inclination of the disc and the
tilt, induced most probably by precession of the disc spin axis with a period
of about 50 years, produce strange photometric behaviour of this star. The
H_alpha emission, and possibly the NaI absorptions, show significant changes
during several months outside of the eclipse phase.


title: Timescales of Soft X-Ray Variability and Physical Constraints in Agns

abstract:
  We present soft X-ray variability time-scales for 65 active galactic nuclei
(AGNs) derived from ROSAT/PSPC pointing data. For these 65 objects with obvious
exponential increasing or decreasing patterns in their light curves, we use the
exponential time-scales and find they are more suitable for analyzing ROSAT
light curve data. We also discuss some physical constraints on the central
engine implied by our results. Assuming that this soft X-ray variability
exponential time-scale is approximately equal to the thermal timescale of the
standard accretion disk, we obtain the accretion rate, the size of soft x-ray
radiation region and the compactness parameter for 37 AGNs, using their
recently estimated central black hole masses. For 12 of these 37 AGNs, the
radii of the gravitational instability in the standard thin accretion disks are
obtained using central black hole masses and the calculated accretion rates.
These are consistent with the results from the reverberation mapping method.
These results provide supporting evidence that such gravitational instabilities
contribute to the formation of the Broad Line Regions (BLRs) in AGNs.


title:
Reanalysis of the OGLE-I observations with the Image Subtraction Method.
  I. Galactic bar fields MM1-A, MM1-B, MM7-A, and MM7-B

abstract:
  As a result of the reanalysis of the OGLE-I observations by means of the
image subtraction method, we present the first part of a catalog, consisting of
the data for variable stars in four Galactic fields observed by the OGLE-I,
viz. MM1-A, MM1-B, MM7-A, and MM7-B. In total, 2016 variable stars have been
found. This increased the number of known variable in these fields stars more
than twofold. We comment on the detectability of the variable stars in previous
studies.
  Some interesting findings are also discussed. Among others, we found 45 Delta
Scuti stars (38 are new) including several multiperiodic objects. Detailed
analysis of the light curves of 47 RR Lyrae stars (24 are new detections)
allowed us to find five stars which exhibit nonradial pulsations and one RRd
star. Three RRab stars are members of the Sagittarius dwarf galaxy (Sgr dSph).
We also find four objects which are probably galactic RV Tauri stars and one W
Virginis star which seems to belong to Sgr dSph. This is the first Population
II Cepheid found in this satellite galaxy and dSph other than the Fornax one.
  For eclipsing EW-type binaries, which are the most abundant variables in our
catalog, we investigate the amplitude and period distributions. A comparison
with the previous OGLE-I catalogs indicates that we found more stars with
smaller amplitudes. Finally, in addition to the two microlensing events
discovered previously in these fields, we find five more.


title:
Light curve solutions for bright detached eclipsing binaries in SMC:
  absolute dimensions and distance indicators

abstract:
  This paper presents a careful and detailed light curve analysis of bright
detached eclipsing binaries (DEB) in the Small Magellanic Cloud, discovered by
OGLE collaboration, on the basis of recently available difference image
analysis (DIA) photometry. The 19 binaries brighter than 16.4 mag in I band and
with the depth of primary and secondary eclipse greater than 0.25 mag were
investigated. The solutions were obtained by a modified version of the
Wilson-Devinney program. The quality of DIA light curves - a good phase
coverage and relatively small scatter - is enough to calculate realistic
estimates for the third light l_3 and the argument of periastron. It was found
that solutions of detached, eccentric systems with flat light curve between
eclipses usually may suffer from indetermination of l_3 in contrast to those of
similar systems having some proximity effects.
  The physical properties of the stars were estimated on the basis of their
photometric elements and indices assuming the distance modulus to SMC ~18.9 and
consistency between an empirical mass-luminosity relation and the flux scaling.
The method was tested on three LMC stars of known absolute dimensions and a
good agreement was found for m-M ~18.5. Such an approach may give fast and
accurate estimates of absolute dimensions for large and homogeneous samples of
eclipsing binaries in the Magellanic Clouds and other close galaxies. Moreover,
this method allows also for independent estimation of E(B-V) in the direction
to a particular binary. The subset of six bright DEB's worth future intensive
investigations as likely distance indicators to SMC, was chosen. They are SC3
139376, SC4 53898, SC5 129441, SC6 67221, SC6 215965 and SC9 175336.


title:
Absolute calibration and beam reconstruction of MITO (a ground-based
  instrument in the millimetric region)

abstract:
  An efficient sky data reconstruction derives from a precise characterization
of the observing instrument. Here we describe the reconstruction of
performances of a single-pixel 4-band photometer installed at MITO (Millimeter
and Infrared Testagrigia Observatory) focal plane. The strategy of differential
sky observations at millimeter wavelengths, by scanning the field of view at
constant elevation wobbling the subreflector, induces a good knowledge of beam
profile and beam-throw amplitude, allowing efficient data recovery. The
problems that arise estimating the detectors throughput by drift scanning on
planets are shown. Atmospheric transmission, monitored by skydip technique, is
considered for deriving final responsivities for the 4 channels using planets
as primary calibrators.


title: The Selection of Tenured Astronomers in France

abstract:
  The organization of the recruitment of tenured astronomers and
astrophysicists in France is presented and compared with the setup in other
countries. The ages for getting tenure have increased from 27-28 in 1980 to 31
today. Foreign scientists constitute at least 11% of the recruits and the delay
in their hiring is quantified. The large reliance on national tenure committees
is justified, while the increased targeting of positions is questioned and a
compromise proposed.


title: Projection effects on the FP thickness: a Monte-Carlo exploration

abstract:
  We study the contribution of projection effects to the intrinsic thickness of
the Fundamental Plane (FP) of elliptical galaxies. The Monte-Carlo mapping
technique between model properties and observed quantities, introduced by
Bertin, Ciotti, and Del Principe (2002), is extended to oblate, two-integrals
galaxy models, with non-homologous density profiles, adjustable flattening,
variable amount of ordered rotational support, and for which all the relevant
projected dynamical quantities can be expressed in fully analytical way. In
agreement with previous works, it is found that projection effects move models
not exactly parallel to the edge-on FP, by an amount that can be as large as
the observed FP thickness. The statistical contribution of projection effects
to the FP thickness is however marginal, and the estimated physical FP rms
thickness is ~90% of the observed one (when corrected for measurement errors).


title: Uncovering High-z Clusters Using Wide-Angle Tailed Radio Sources

abstract:
  The morphologies of wide-angle tailed (WAT) radio sources (edge-darkened,
C-shaped, FR I radio sources) are the result of confinement and distortion of
the radio lobes by the dense X-ray-emitting gas in clusters or groups of
galaxies. These radio sources are easily seen at high redshifts (z~1) in
short-exposure images from the Faint Images of the Radio Sky at Twenty-cm
(FIRST) survey. Using a sample of approximately 400 WAT sources from the FIRST
survey, we have discovered a number of high-z clusters. Here, we present the
highest-z cluster found so far using this method: 1137+3000 at z=0.96. We
include photometric and spectroscopic results. Ten galaxies are confirmed at
the cluster redshift, with a line-of-sight velocity dispersion of 530 +190/-90
km/s, typical of an Abell richness class 0 cluster.


title: Simulating weak lensing by large scale structure

abstract:
  We model weak gravitational lensing of light by large-scale structure using
ray tracing through N-body simulations. The method is described with particular
attention paid to numerical convergence. We investigate some of the key
approximations in the multi-plane ray tracing algorithm. Our simulated shear
and convergence maps are used to explore how well standard assumptions about
weak lensing hold, especially near large peaks in the lensing signal.


title: Search for Relativistic Curvature Effects in Gamma-Ray Burst Pulses

abstract:
  We analyze the time profiles of individual gamma-ray burst (GRB) pulses, that
are longer than 2 s, by modelling them with analytical functions that are based
empirical descriptions of GRB spectral evolution. These analytical profiles are
independent of the emission mechanism and can be used to model both the rise
and decay profiles Using this method, we have studied a sample of 77 individual
GRB pulses, allowing us to examine the fluence, pulse width, asymmetry, and
rise and decay power-law distributions. We find that the rise phase is best
modelled with a power law of average index $r = 1.31 \pm 0.11$ and that the
average decay phase has an index o.f $d = 2.39 \pm 0.12$. We also find that the
ratio between the rise and decay times (the pulse asymmetry) exhibited by the
GRB pulse shape has an average value of 0.47 which varies little from pulse to
pulse and is independent of pulse duration or intensity. We compare these
parameters with those predicted to occur if individual pulse shapes are created
purely by relativistic curvature effects in the context of the fireball model,
a process that makes specific predictions about the shape of GRB pulses. The
decay index distribution obtained from our sample shows that the average GRB
pulse fades faster than the value predicted by curvature effects, with only 39%
of our sample being consistent with the curvature model. We discuss several
refinements of the relativistic curvature scenario that could naturally account
for these observed deviations.


title: Evidence for Planet-induced Chromospheric Activity on HD 179949

abstract:
  We have detected the synchronous enhancement of Ca II H & K emission with the
short-period planetary orbit in HD 179949. High-resolution spectra taken on
three observing runs extending more than a year show the enhancement coincides
with phi ~ 0 (the sub-planetary point) of the 3.093-day orbit with the effect
persisting for more than 100 orbits. The synchronous enhancement is consistent
with planet-induced chromospheric heating by magnetic rather than tidal
interaction. Something which can only be confirmed by further observations.
Independent observations are needed to determine whether the stellar rotation
is sychronous with the planet's orbit. Of the five 51 Peg-type systems
monitored, HD 179949 shows the greatest chromospheric H & K activity. Three
others show significant nightly variations but the lack of any phase coherence
prevents us saying whether the activity is induced by the planet. Our two
standards, tau Ceti and the Sun, show no such nightly variations.


title: Modeling the Void H I Column Density Spectrum

abstract:
  The equivalent width distribution function (EWDF) of \hone absorbers specific
to the void environment has been recently derived (Manning 2002), revealing a
large line density of clouds (dN/dz ~500 per unit z for Log (N_HI)> 12.4). I
show that the void absorbers cannot be diffuse (or so-called filamentary)
clouds, expanding with the Hubble flow, as suggested by N-body/hydro
simulations. Absorbers are here modeled as the baryonic remnants of
sub-galactic perturbations that have expanded away from their dark halos in
response to reionization at z ~ 6.5. A 1-D Lagrangian hydro/gravity code is
used to follow the dynamic evolution and ionization structure of the baryonic
clouds for a range of halo circular velocities. The simulation products at z=0
can be combined according to various models of the halo velocity distribution
function to form a column density spectrum that can be compared with the
observed. I find that such clouds may explain the observed EWDF if the halo
velocity distribution function is as steep as that advanced by Klypin (1999),
and the halo mass distribution is closer to isothermal than to NFW.


title:
Non-LTE Model Atmospheres for Late-Type Stars I. A Collection of Atomic
  Data for Light Neutral and Singly-Ionized Atoms

abstract:
  With the goal of producing a reliable set of model atoms and singly-ionized
ions for use in building NLTE model atmospheres, we have combined measured
energy levels, critically-compiled line transition probabilities, and
resonance-averaged calculations of photoionization cross-sections. A majority
of the elements from Li to Ca are considered, covering most of the important
species in late-type atmospheres. These include elements which contribute free
electrons and/or continuous opacity in the ultraviolet (e.g., Mg, and Si), as
well as trace elements whose abundance determinations rely on ultraviolet lines
(e.g., B from B I lines). The new data complement and, for the species in
common, supersede a previous collection of model atoms originally designed for
use in studies of early-type stars.


title:
Non-LTE Model Atmospheres for Late-Type Stars II. Restricted NLTE
  Calculations for a Solar-Like Atmosphere

abstract:
  We test our knowledge of the atomic opacity in the solar UV spectrum. Using
the atomic data compiled in Paper I from modern, publicly available, databases,
we perform calculations that are confronted with space-based observations of
the Sun. At wavelengths longer than about 260 nm, LTE modeling can reproduce
quite closely the observed fluxes; uncertainties in the atomic line data
account fully for the differences between calculated and observed fluxes. At
shorter wavelengths, departures from LTE appear to be important, as our LTE and
restricted NLTE calculations differ. Analysis of visible-near infrared Na I and
O I lines, two species that produce a negligible absorption in the UV, shows
that observed departures from LTE for theses species can be reproduced very
accurately with restricted (fixed atmospheric structure) NLTE calculations.


title: Model atmospheres and thermal spectra of magnetized neutron stars

abstract:
  Thermal surface radiation has been detected with X-ray instruments for
several neutron stars with high spectral, spatial and timing resolution. These
observations allow for direct study of fundamental properties of the source,
but require model atmospheres and spectra for careful interpretation. We
describe a robust and extensible implementation of complete linearization for
computing the spectra of isolated cooling neutron stars for a broad range of
temperature and magnetic field. Self-consistent spectra are derived for
arbitrary magnetic field geometries at $B \leq 10^{14}$ G.


title: Relations between Massive Black Holes in AGN and their Host Galaxies

abstract:
  Massive black holes detected in the centers of many nearby galaxies are
linearly correlated with the luminosity of the host bulge, the black hole mass
being about 0.1% of the bulge mass. An even stronger relation exists between
the BH mass (Mbh) and the stellar velocity dispersion in the host bulge. We
show that massive BHs of AGNs (measured by reverberation mapping) and their
bulge luminosity (measured by using a bulge/disk decomposition) follow the same
relations as ordinary (inactive) galaxies, with the exeption of narrow line AGN
which apparently have significantly lower BH/bulge ratios. Narrow line AGNs
seem to be outstanding also in the Mbh-velocity dispersion relation: the few
Seyfert galaxies with measured velocity dispersion seem to indicate that narrow
line Seyfert 1 galaxies have a smaller BH mass/velocity dispersion ratio than
quiescent galaxies and broad line Syferts. Estimating the velocity dispersion
for from the bulge luminosity with the Faber-Jackson relation more than doubles
the sample and supports these results.


title: High Resolution Spectroscopy of the Pulsating White Dwarf G29-38

abstract:
  We present the analysis of time-resolved, high resolution spectra of the cool
white dwarf pulsator, G29-38. From measuring the Doppler shifts of the H-alpha
core, we detect velocity changes as large as 16.5 km/s and conclude that they
are due to the horizontal motions associated with the g-mode pulsations on the
star. We detect seven pulsation modes from the velocity time-series and
identify the same modes in the flux variations. We discuss the properties of
these modes and use the advantage of having both velocity and flux measurements
of the pulsations to test the convective driving theory proposed for DAV stars.
Our data show limited agreement with the expected relationships between the
amplitude and phases of the velocity and flux modes. Unexpectedly, the velocity
curve shows evidence for harmonic distortion, in the form of a peak in the
Fourier transform whose frequency is the exact sum of the two largest
frequencies. Combination frequencies are a characteristic feature of the
Fourier transforms of light curves of G29-38, but before now have not been
detected in the velocities, nor does published theory predict that they should
exist. We compare our velocity combination frequency to combination frequencies
found in the analysis of light curves of G29-38, and discuss what might account
for the existence of velocity combinations with the properties we observe.
  We also use our high-resolution spectra to determine if either rotation or
pulsation can explain the truncated shape observed for the DAV star's line
core. We are able to eliminate both mechanisms: the average spectrum does not
fit the rotationally broadened model and the time-series of spectra provides
proof that the pulsations do not significantly truncate the line.


title: The Role of Baryons in Unified Dark Matter Models

abstract:
  We discuss the importance of including baryons in analyses of unified dark
matter scenarios, focusing on toy models involving a generalized Chaplygin gas.
We determine observational constraints on this unified dark matter scenario
coming from large scale structure, type Ia Supernovae and CMB data showing how
this component can bring about a different behaviour from classical
$\Lambda$CDM and thus motivate further studies of this type of models. We also
speculate on interesting new features which are likely to be important on
non-linear scales in this context.


title: Evidence for a T Tauri Phase in Young Brown Dwarfs

abstract:
  As part of a multi-faceted program to investigate the origin and early
evolution of sub-stellar objects, we present high-resolution Keck optical
spectra of 14 very low mass sources in the IC 348 young cluster and the Taurus
star-forming cloud. All of our targets, which span a range of spectral types
from M5 to M8, exhibit moderate to very strong H$\alpha$ emission. In half of
the IC 348 objects, the H$\alpha$ profiles are broad and asymmetric, indicative
of on-going accretion. Of these, IC348-355 (M8) is the lowest mass object to
date to show accretion-like H$\alpha$. Three of our ~M6 IC 348 targets with
broad H$\alpha$ also harbor broad OI (8446\AA) and CaII (8662\AA) emission, and
one shows broad HeI (6678\AA) emission; these features are usually seen in
strongly accreting classical T Tauri stars. We find that in very low mass
accretors, the H$\alpha$ profile may be somewhat narrower than that in higher
mass stars. We propose that low accretion rates combined with small infall
velocities at very low masses can conspire to produce this effect. In the
non-accretors in our sample, H$\alpha$ emission is commensurate with, or higher
than, saturated levels in field M dwarfs of similar spectral type. Our results
constitute the most compelling evidence to date that young brown dwarfs undergo
a T Tauri-like accretion phase similar to that in stars. This is consistent
with a common origin for most low-mass stars, brown dwarfs and isolated
planetary mass objects.


title:
Star formation and turbulent dissipation in models of disk galaxy
  evolution

abstract:
  The kinetic energy dissipation rate in the turbulent ISM of disk galaxies is
a key ingredient in galaxy evolution models since it determines the
effectiveness of large-scale star formation (SF) feedback. Using
magneto-hydro-dynamic simulations, we find that the ISM dissipates efficiently
the turbulent kinetic energy injected by sources of stellar nature. Thus, the
SF process may be self-regulated by an energy balance only at the level of the
disk ISM. The use of the self-regulation SF mechanism in galaxy evolutionary
models, where disks form inside growing Cold Dark Matter halos, allows to
predict the SF history of disk galaxies, including the Milky Way and the solar
neighborhood, as well as the contribution of the whole population of disk
galaxies to the cosmic SF history. The results are encouraging.


title: Interaction between the Outflow and the Core in IRAM 04191+1522

abstract:
  We have carried out mapping observations of the molecular core associated
with the young Class 0 protostar, IRAM 04191+1522, in the CH3OH (JK=2K-1K) and
C34S (J=2-1) lines using the 45 m telescope at Nobeyama Radio Observatory. As
well as an elongated envelope associated with the protostellar formation (size
\~0.07 pc x 0.04 pc, mass ~ 2.3 Mo), two compact (~ 0.03 pc) condensations were
found in the CH3OH line at the southern edge of the elongated envelope, where
the blueshifted CO outflow emerging from the protostar is located. In contrast
to the elongated envelope, those compact CH3OH condensations show much larger
line width (up to 2.0 km s-1) with centroid velocities blueshifted by ~ 0.8 km
s-1. The compact condensations have momenta (~ 0.06 Mo km s-1) comparable to
that of the blueshifted molecular outflow. These results suggest that the
compact condensations are probably formed in the course of interaction between
the outflow and the ambient gas surrounding the protostar, and that such
interaction may cause dissipation of a part of the ambient gas. No drastic,
localized enhancement of the CH3OH abundance is, however, observed toward the
compact condensations, implying that there seems to be no significant shock
heating at the compact condensations. This may be because the CO outflow
velocity (< 10 km s-1) is too low to cause effective heating to release CH3OH
on dust grains into gas phase.


title:
Some Properties of an Axisymmetric Pulsar Magnetosphere Constructed by
  Numerical Calculation

abstract:
  We have explored the magnetosphere described by a numerical solution for an
axisymmetric rotating field satisfying the force-free and ideal MHD conditions
everywhere. The electric current distribution is determined by the requirement
of continuity and smoothness of the flux function across the light cylinder.
The overall magnetic field structure is obtained using the numerical result. We
also checked the drift velocity of a charged particle, which is caused by the
resultant electric and magnetic fields. It is found that the velocity exceeds
the light speed beyond a few times the size of the light cylinder. This fact
suggests the breakdown of some underlying assumptions.


title: Optical Spectra of Four Objects Identified with Variable Radio Sources

abstract:
  We obtained optical spectra of four objects identified with variable radio
sources. Three objects (0029+0554, 0400+0550, 2245+0500) were found to be
quasars with redshifts of 1.314, 0.761, and 1.091. One object (2349+0534) has a
continuum spectrum characteristic of BL Lac objects. We analyze spectra of the
radio sources in the range 0.97-21.7 GHz for the epoch 1997 and in the range
3.9-11.1 GHz for the epoch 1990, as well as the pattern of variability of their
flux densities on time scales of 1.5 and 7 years.


title:
Radio and Optical Spectra of Objects from Two Complete Samples of Radio
  Sources

abstract:
  We present optical identifications and radio spectra for ten radio sources
from two flux-density-complete samples. Radio variability characteristics are
presented for four objects. The observations were obtained on the RATAN-600
radio telescope at 0.97-21.7 GHz and the 2.1 m telescope of the Haro
Observatory in Cananea, Mexico at 4200-9000 =C5. Among the ten objects studied,
three are quasars, four are BL Lac objects, two are radio galaxies, and one is
a Sy 1 galaxy. Two of the sources identified with BL Lac objects, 0509 + 0541
and 0527 + 0331, show rapid variability on time scales of 7-50 days.


title: Stellar Tidal Processes Near Massive Black Holes

abstract:
  Close tidal interactions of stars with a central massive black hole (MBH) or
with other stars in the high density cusp around it can affect a significant
fraction of the stellar population within the MBH radius of influence. We
consider three strong processes that have the potential of modifying stellar
structure and evolution there. (1) Tidal spin-up by hyperbolic star-star
encounters. (2) Tidal scattering of stars on the MBH. (3) Tidal heating of
inspiraling stars - "squeezars" - that were tidally captured by the MBH. We
discuss the implications for stellar populations near MBHs and for the growth
of MBHs by tidal disruption of stars, and the possible observational signature
of such processes near the MBH in the Galactic Center. We compare the event
rates of prompt tidal encounters (tidal disruption and tidal scattering) and
slow inspiral events (squeezars / tidal capture), and find that tidal capture
is at least an order of magnitude less efficient than prompt disruption. This
means that past studies, which assigned similar weights to prompt disruption
and tidal capture, over-estimated the contribution of tidal disruption to the
growth of the MBH by at least a factor of two.


title:
Mass function of gravitationally bounded objects in the inhomogeneous
  Universe

abstract:
  We modify the Press-Schechter formalism to calculate the mass function of
gravitationally bounded objects in a local Universe with size $L> 10h^{-1}$Mpc,
i.e. separately in voids ($\Omega_{m,L}<\Omega_m$) and superclusters
($\Omega_{m,L}>\Omega_m$). The dependence of the abundance of gravitationally
bounded objects on local matter density is analyzed.


title:
Evaluating GAIA performances on eclipsing binaries. II. Orbits and
  stellar parameters for V781 Tau, UV Leo and GK Dra

abstract:
  The orbits and physical parameters of three close, double-lined G0 eclipsing
binaries have been derived combining H_P, V_T, B_T photometry from the
Hipparcos/Tycho mission with 8480-8740 \AA ground-based spectroscopy. The setup
is mimicking the photometric and spectroscopic observations that should be
obtained by GAIA. The binaries considered here are all of G0 spectral type, but
each with its own complications: V781 Tau is an overcontact system with
components of unequal temperature, UV Leo shows occasional surface spots and GK
Dra contains a delta-Scuti variable. Such peculiarities will be common among
binaries to be discovered by GAIA. We find that the values of masses, radii and
temperatures for such stars can be derived with a 1-2% accuracy using the
adopted GAIA-like observing mode.


title: The first second of the Universe

abstract:
  The history of the Universe after its first second is now tested by high
quality observations of light element abundances and temperature anisotropies
of the cosmic microwave background. The epoch of the first second itself has
not been tested directly yet; however, it is constrained by experiments at
particle and heavy ion accelerators. Here I attempt to describe the epoch
between the electroweak transition and the primordial nucleosynthesis.
  The most dramatic event in that era is the quark--hadron transition at 10
$\mu$s. Quarks and gluons condense to form a gas of nucleons and light mesons,
the latter decay subsequently. At the end of the first second, neutrinos and
neutrons decouple from the radiation fluid. The quark--hadron transition and
dissipative processes during the first second prepare the initial conditions
for the synthesis of the first nuclei.
  As for the cold dark matter (CDM), WIMPs (weakly interacting massive
particles) -- the most popular candidates for the CDM -- decouple from the
presently known forms of matter, chemically (freeze-out) at 10 ns and
kinetically at 1 ms. The chemical decoupling fixes their present abundances and
dissipative processes during and after thermal decoupling set the scale for the
very first WIMP clouds.


title:
Multi-frequency polarimetry of the Galactic radio background around 350
  MHz: I. A region in Auriga around l = 161, b = 16

abstract:
  With the Westerbork Synthesis Radio Telescope (WSRT), multi-frequency
polarimetric images were taken of the diffuse radio synchrotron background in a
region centered on (l,b) = (161,16). The observations were done simultaneously
in 5 frequency bands from 341 MHz to 375 MHz, with 5 arcmin resolution.
Ubiquitous structure on arcminute and degree scales in the polarized intensity
and polarization angle, combined with no observed structure in total intensity,
indicates that the structure in the polarized radiation must be due to Faraday
rotation and depolarization mostly in the warm nearby Galactic interstellar
medium (ISM). Beam depolarization most likely creates "depolarization canals"
of one beam wide, while depth depolarization is responsible for creating most
of the structure on scales larger than a beam width. Rotation measures RM are
in the range -17 < RM < 10 rad/m2 with a non-zero average of about -3.4 rad/m2.
The gradient and average RM are consistent with a regular magnetic field of
about 1 uG which has a pitch angle of p = -14 degrees. 13 Extragalactic sources
in the field have |RM| < 13 rad/m2, with an estimated intrinsic source
contribution of 3.6 rad/m2. The RMs of the extragalactic sources show a
gradient (with a sign reversal) that is about 3 times larger than the gradient
in the RMs of the diffuse emission, and that is approximately in Galactic
latitude. This difference is ascribed to a vastly different effective length of
the line of sight. The observations are interpreted in terms of a
single-cell-size model of the warm ISM which contains gas and magnetic fields,
with a polarized background.


title:
Dust Temperatures in the Infrared Space Observatory Atlas of Bright
  Spiral Galaxies

abstract:
  We examine far-infrared and submillimeter spectral energy distributions for
galaxies in the Infrared Space Observatory Atlas of Bright Spiral Galaxies. For
the 71 galaxies where we had complete 60-180 micron data, we fit blackbodies
with lambda^-1 emissivities and average temperatures of 31 K or lambda^-2
emissivities and average temperatures of 22 K. Except for high temperatures
determined in some early-type galaxies, the temperatures show no dependence on
any galaxy characteristic. For the 60-850 micron range in eight galaxies, we
fit blackbodies with lambda^-1, lambda-2, and lambda^-beta (with beta variable)
emissivities to the data. The best results were with the lambda^-beta
emissivities, where the temperatures were ~30 K and the emissivity coefficient
beta ranged from 0.9 to 1.9. These results produced gas to dust ratios that
ranged from 150 to 580, which were consistent with the ratio for the Milky Way
and which exhibited relatively little dispersion compared to fits with fixed
emissivities.


title:
Potential of the Surface Brightness Fluctuations method to measure
  distances to dwarf elliptical galaxies in nearby clusters

abstract:
  The potential of the Surface Brightness Fluctuations (SBF) method to
determine the membership of dwarf elliptical galaxies (dEs) in nearby galaxy
clusters is investigated. Extensive simulations for SBF measurements on dEs in
the I-band for various combinations of distance modulus, seeing and integration
time are presented, based on average VLT FORS1 and FORS2 zero points. These
show that for distances up to 20 Mpc (Fornax or Virgo cluster distance),
reliable membership determination of dEs can be obtained down to very faint
magnitudes -10<M_V<-12 mag (25 mag / arcsec^2) within integration times of the
order of 1 hour and with good seeing. Comparing the limiting magnitudes of the
method for the different simulated observing conditions we derive some simple
rules to calculate integration time and seeing needed to reach a determined
limiting magnitude at a given distance modulus for observing conditions
different to the ones adopted in the simulations. Our simulations show a small
offset of the order of 0.15 mag towards measuring too faint SBF. It is shown
that this is due to loss of fluctuation signal when recovering pixel-to-pixel
fluctuations from a seeing convolved image. To check whether our simulations
represent well the behaviour of real data, SBF measurements for a real and
simulated sample of bright Centaurus Cluster dEs are presented. They show that
our simulations are in good agreement with the achievable S/N of SBF
measurements on real galaxies.


title: Radial evolution of solar wind intermittency in the inner heliosphere

abstract:
  We analyzed intermittency in the solar wind, as observed on the ecliptic
plane, looking at magnetic field and velocity fluctuations between 0.3 and 1
AU, for both fast and slow wind and for compressive and directional
fluctuations. Our analysis focused on the property that probability
distribution functions of a fluctuating field affected by intermittency become
more and more peaked at smaller and smaller scales. Since the peakedness of a
distribution is measured by its flatness factor we studied the behavior of this
parameter for different scales to estimate the degree of intermittency of our
time series. We confirmed that both magnetic field and velocity fluctuations
are rather intermittent and that compressive magnetic fluctuations are
generally more intermittent than the corresponding velocity fluctuations. In
addition, we observed that compressive fluctuations are always more
intermittent than directional fluctuations and that while slow wind
intermittency does not depend on the radial distance from the sun, fast wind
intermittency of both magnetic field and velocity fluctuations clearly
increases with the heliocentric distance....


title:
Relativistic particle transport in extragalactic jets: I. Coupling MHD
  and kinetic theory

abstract:
  Multidimensional magneto-hydrodynamical (MHD) simulations coupled with
stochastic differential equations (SDEs) adapted to test particle acceleration
and transport in complex astrophysical flows are presented. The numerical
scheme allows the investigation of shock acceleration, adiabatic and radiative
losses as well as diffusive spatial transport in various diffusion regimes. The
applicability of SDEs to astrophysics is first discussed in regards to the
different regimes and the MHD code spatial resolution. The procedure is then
applied to 2.5D MHD-SDE simulations of kilo-parsec scale extragalactic jets.
The ability of SDE to reproduce analytical solutions of the
diffusion-convection equation for electrons is tested through the incorporation
of an increasing number of effects: shock acceleration, spatially dependent
diffusion coefficients and synchrotron losses. The SDEs prove to be efficient
in various shock configuration occurring in the inner jet during the
development of the Kelvin-Helmholtz instability. The particle acceleration in
snapshots of strong single and multiple shock acceleration including realistic
spatial transport is treated. In chaotic magnetic diffusion regime, turbulence
levels $\eta_T=<\delta B^2>/(B^2+<\delta B^2>)$ around $0.2-0.3$ are found to
be the most efficient to enable particles to reach the highest energies. The
spectrum, extending from 100 MeV to few TeV (or even 100 TeV for fast flows),
does not exhibit a power-law shape due to transverse momentum dependent
escapes. Out of this range, the confinement is not so efficient and the
spectrum cut-off above few hundreds of GeV, questioning the Chandra
observations of X-ray knots as being synchrotron radiation. The extension to
full time dependent simulations to X-ray extragalactic jets is discussed.


title:
Cosmic microwave background constraints on multi-connected spherical
  spaces

abstract:
  This article describes the Cosmic Microwave Background anisotropies expected
in a closed universe with the topology of a lens space L(p,q) and with density
parameter Omega_0 close to 1. It provides the first simulated maps for such
spaces along with their corresponding power spectra. In spite of our initial
expectations that increasing p (and thus decreasing the size of the fundamental
domain) should suppress the quadrupole, we found just the opposite: increasing
p elevates the relative power of the low multipoles, for reasons that have
since become clear. For Omega_0 = 1.02, an informal ``by eye'' examination of
the simulated power spectra suggests that $p$ must be less than 15 for
consistency with WMAP's data, while geometric considerations imply that
matching circles will exist (potentially revealing the multi-connected
topology) only if p > 7. These bounds become less stringent for values of
Omega_0 closer to 1.


title: Star Formation in Active Galaxies: A Spectroscopic Perspective

abstract:
  I review the relationship between star formation and black hole building,
based on spectroscopic observations of the stellar population in active
galactic nuclei (AGNs) and their host galaxies. My emphasis is on large,
well-defined local samples of AGNs, whose optical continua are dominated by
starlight. I summarize the spectroscopic tools used to characterize their
stellar content. Surveys of the nuclei of the nearest galaxies show that the
stellar population in most low-power AGNs is predominantly old. In contrast,
young ($< 1$ Gyr) stars are detected in about half of the powerful type 2
Seyfert nuclei. I summarize Sloan Digital Sky Survey spectroscopy of the host
galaxies of 22,000 AGNs. The AGN phenomenon is commonplace only in galaxies
with high mass, high velocity dispersion, and high stellar surface mass
density. Most normal galaxies with these properties have old stellar
populations. However, the hosts of powerful AGNs (Seyfert 2s) have young
stellar populations. The fraction of AGN hosts that have recently undergone a
major starburst also increases with AGN luminosity. A powerful AGN presumably
requires a massive black hole (host with a substantial bulge) plus an abundant
fuel supply (a star-forming ISM). This combination is rare today, but would
have been far more common at early epochs.


title: Characterization of the Crab Pulsar's Timing Noise

abstract:
  We present a power spectral analysis of the Crab pulsar's timing noise,
mainly using radio measurements from Jodrell Bank taken over the period
1982-1989. The power spectral analysis is complicated by nonuniform data
sampling and the presence of a steep red power spectrum that can distort power
spectra measurement by causing severe power ``leakage''. We develop a simple
windowing method for computing red noise power spectra of uniformly sampled
data sets and test it on Monte Carlo generated sample realizations of red
power-law noise. We generalize time-domain methods of generating power-law red
noise with even integer spectral indices to the case of noninteger spectral
indices. The Jodrell Bank pulse phase residuals are dense and smooth enough
that an interpolation onto a uniform time series is possible. A windowed power
spectrum is computed revealing a periodic or nearly periodic component with a
period of about 568 days and a 1/f^3 power-law noise component with a noise
strength of 1.24 +/- 0.067 10^{-16} cycles^2/sec^2 over the analysis frequency
range 0.003 - 0.1 cycles/day. This result deviates from past analyses which
characterized the pulse phase timing residuals as either 1/f^4 power-law noise
or a quasiperiodic process. The analysis was checked using the Deeter
polynomial method of power spectrum estimation that was developed for the case
of nonuniform sampling, but has lower spectral resolution. The timing noise is
consistent with a torque noise spectrum rising with analysis frequency as f
implying blue torque noise, a result not predicted by current models of pulsar
timing noise. If the periodic or nearly periodic component is due to a binary
companion, we find a companion mass > 3.2 Earth masses.


title: A New X-Ray Flare from the Galactic Nucleus Detected with the XMM-Newton

abstract:
  The compact radio source Sgr A*, believed to be the counterpart of the
massive black hole at the Galactic nucleus, was observed to undergo rapid and
intense flaring activity in X-rays with Chandra in October 2000. We report here
the detection with XMM-Newton EPIC cameras of the early phase of a similar
X-ray flare from this source, which occurred on 2001 September 4. The source
2-10 keV luminosity increased by a factor ~ 20 to reach a level of 4 10$^{34}$
erg s$^{-1}$ in a time interval of about 900 s, just before the end of the
observation. The data indicate that the source spectrum was hard during the
flare and can be described by simple power law of slope ~ 0.7. This XMM-Newton
observation confirms the results obtained by Chandra, suggests that, in Sgr A*,
rapid and intense X-ray flaring is not a rare event and therefore sets some
constraints on the emission mechanism models proposed for this source.


title: The Dawn of Galaxies

abstract:
  The development of primordial inhomogeneities into the non-linear regime and
the formation of the first astrophysical objects within dark matter halos mark
the transition from a simple, neutral, cooling universe -- described by just a
few parameters -- to a messy ionized one -- the realm of radiative,
hydrodynamic, and star formation processes. The recent measurement by the WMAP
satellite of a large optical depth to electron scattering implies that this
transition must have begun very early, and that the universe was reionized at
redshift z_ion=17\pm 5. It is an early generation of extremely metal-poor
massive stars and/or `seed' accreting black holes in subgalactic halos that may
have generated the ultraviolet radiation and mechanical energy that reheated
and reionized most of the hydrogen in the cosmos. The detailed thermal,
ionization, and chemical enrichment history of the universe during the crucial
formative stages around z=10-20 depends on the power-spectrum of density
fluctuations on small scales, the stellar initial mass function and star
formation efficiency, a complex network of poorly understood `feedback'
mechanisms, and remains one of the crucial missing links in galaxy formation
and evolution studies.


title: Energy and time-lag spectra of black-hole systems in the low state

abstract:
  Most, probably all, accreting binaries that are believed to contain a
black-hole emit radio waves when they are in the low/hard state. Whenever this
radio emission has been resolved, a jet-like structure has become apparent. We
propose that Compton upscattering of low-energy photons in the jet can explain
both the energy spectra and the time lags versus Fourier frequency observed in
the low/hard state of black-hole systems. The soft photons originate in the
inner part of the accretion disk. We have performed Monte Carlo simulations of
Compton upscattering in a jet and have found that for a rather wide range of
values of the parameters we can obtain power-law high-energy X-ray spectra with
photon-number index in the range 1.5 - 2 and power-law time lags versus Fourier
frequency with index ~ 0.7. The black-hole source Cyg X-1 in the low/hard state
is well described by our model.


title: Oxygen Gas Phase Abundance Revisited

abstract:
  We present new measurements of the interstellar gas-phase oxygen abundance
along the sight lines towards 19 early-type galactic stars at an average
distance of 2.6 kpc. We derive O {\small I} column densities from {\it
HST}/STIS observations of the weak 1355 \AA intersystem transition. We derive
total hydrogen column densities [N(H {\small I})+2N(H$_2$)] using {\it
HST}/STIS observations of \lya and {\it FUSE} observations of molecular
hydrogen. The molecular hydrogen content of these sight lines ranges from
f(H$_2$) = 2N(H$_2$)/[N(H {\small I})+2N(H$_2$)] = 0.03 to 0.47. The average
$<H_{tot}/E_{B-V}>$ of 6.3$\times10^{21}$ cm$^{-2}$ mag$^{-1}$ with a standard
deviation of 15% is consistent with previous surveys. The mean oxygen abundance
along these sight lines, which probe a wide range of galactic environments in
the distant ISM, is 10$^6$ \oh = $408 \pm 13$ (1 $\sigma$ in the mean). %$({\rm
O/H})_{gas} = 408 \pm 14$(1 $\sigma$). We see no evidence for decreasing
gas-phase oxygen abundance with increasing molecular hydrogen fraction and the
relative constancy of \oh suggests that the component of dust containing the
oxygen is not readily destroyed. We estimate that, if 60% of the dust grains
are resilient against destruction by shocks, the distant interstellar total
oxygen abundance can be reconciliated with the solar value derived from the
most recent measurements %by Holweger and by Allende Prieto, Lambert & Asplund:
of 10$^6$ \oh$_\odot$ = 517 $\pm$ 58 (1 $\sigma$). We note that the smaller
oxygen abundances derived for the interstellar gas within 500 pc %by Meyer,
Cardelli & Jura or from nearby B star surveys are consistent with a local
elemental deficit.


title:
Triple Experiment Spectrum of the Sunyaev-Zeldovich Effect in the Coma
  Cluster: H_0

abstract:
  The Sunyaev-Zeldovich (SZ) effect was previously measured in the Coma cluster
by the Owens Valley Radio Observatory and Millimeter and IR Testa Grigia
Observatory experiments and recently also with the Wilkinson Microwave
Anisotropy Probe satellite. We assess the consistency of these results and
their implications on the feasibility of high-frequency SZ work with
ground-based telescopes. The unique data set from the combined measurements at
six frequency bands is jointly analyzed, resulting in a best-fit value for the
Thomson optical depth at the cluster center, tau_{0}=(5.35 \pm 0.67) 10^{-3}.
The combined X-ray and SZ determined properties of the gas are used to
determine the Hubble constant. For isothermal gas with a \beta density profile
we derive H_0 = 84 \pm 26 km/(s\cdot Mpc); the (1\sigma) error includes only
observational SZ and X-ray uncertainties.


title:
Limits on charge non-conservation from possible seasonal variations of
  the solar neutrino experiments

abstract:
  Variable speed of light (VSL) theories generically lead to large violations
of charge conservation that can be written in terms of a dimensionless
parameter $\lambda$. It is shown that the motion of the Earth with respect to
the Sun could lead to a seasonal variation for the SAGE and GALLEX-GNO
experiments and analyzing the reported counting rates for these experiments, a
very stringent bound $\lambda \le 2 \times 10^{-19} $ is obtained, some $10^9$
times smaller than previous ones. Furthermore, a bound on the lifetime of the
$\null^{71}{\rm Ga} \to \null^{71} {\rm Ge}$ charge-nonconserving decay in VSL
theories is found as: $ \tau_{\rm CNC} \ge 1.4 \times 10^{27} {\rm years}$.
Similarly a new upper limit for the ratio of the charge-nonconserving to the
normal weak decay of the neutron in VSL theories is obtained: $\Gamma(n \to p +
\nu_e + \bar{\nu}_e) /\Gamma(n \to p + e + \bar{\nu}_e) \le 2 \times 10^{-27}$.


title: LBQS 1429-0053: a binary quasar rather than a lensed quasar

abstract:
  Very deep ESO/VLT FORS1 and ISAAC images, as well as HST NICMOS2 data are
used to infer the nature of the quasar pair LBQS 1429-0053 A and B, either a
binary quasar or a doubly-imaged lensed quasar. Direct search of a putative
lensing galaxy is unsuccessful . Moreover, no galaxy overdensity close to the
quasar pair is found. A weak shear analysis of the field also fails at
detecting any concentration of dark matter and weakens the hypothesis of a dark
lens. The only sign of a possible lens consists in a group of 5 objects at z~1,
within a radius of 5'', from the quasar pair. Considering this group as the
lensing potential does not allow to reproduce the image position and flux ratio
of the quasars. Our deep R-band image shows a blue, extended object at the
position of quasar A, which is consistent with either being the lensed quasar A
host, or being an intervening galaxy at lower redshift. Unless future very deep
optical images demonstrate that this object is actually the lensed host of LBQS
1429-0053, we conclude that there is very little evidence for this quasar being
lensed. Therefore, we are led to declare LBQS 1429-0053 A and B a genuine
binary quasar.


title: Dust and the Infrared Kinematic Properties of Early-Type Galaxies

abstract:
  We have obtained spectra and measured the stellar kinematics in a sample of
25 nearby early-type galaxies (with velocity dispersions from less than 100
km/s to over 300 km/s) using the near-infrared CO absorption bandhead at 2.29
microns. Our median uncertainty for the dispersions is ~10%. We examine the
effects of dust on existing optical kinematic measurements. We find that the
near-infrared velocity dispersions are in general smaller than optical velocity
dispersions, with differences as large as 30%. The median difference is 11%
smaller, and the effect is of greater magnitude for higher dispersion galaxies.
The lenticular galaxies (18 out of 25) appear to be causing the shift to lower
dispersions while the classical ellipticals (7 out of 25) are consistent
between the two wavelength regimes. If uniformly distributed dust causes these
differences, we would expect to find a correlation between the relative amount
of dust in a galaxy and the fractional change in dispersion, but we do not find
such a correlation. We do see correlations both between velocity dispersion and
CO bandhead equivalent width, and velocity dispersion and Mg2 index. The
differences in dispersion are not well explained by current models of dust
absorption. The lack of correlation between the relative amount of dust and
shift in dispersion possibly suggets that dust does not have a similar
distribution from galaxy to galaxy. The CO equivalent widths of these galaxies
are quite high (>10 angstroms for almost all), requiring the light at these
wavelengths to be dominated by very cool stars.


title: A new mechanism for generating density perturbations from inflation

abstract:
  We propose a new mechanism to generate density perturbations in inflationary
models. Spatial fluctuations in the decay rate of the inflaton field to
ordinary matter lead to fluctuations in the reheating temperature. We argue
that in most realistic models of inflation the coupling of the inflaton to
normal matter is determined by the vacuum expectation values of fields in the
theory. If those fields are light during inflation (this is a generic situation
in the minimal models of supersymmetric inflation) they will fluctuate leading
to density perturbations through the proposed mechanism. We show that these
fluctuations could easily dominate over the ones generated through the standard
mechanism. The new scenario has several consequences for inflation model
building and observations. The proposed mechanism allows to generate the
observed level of density perturbations with a much lower scale of inflation
and thus generically predicts a smaller level of gravitational waves. The
relation between the slope of the spectrum of the produced density
perturbations and the potential of the inflaton field is different from the
standard relations obtained in the context of slow roll inflation. Because the
field responsible for the fluctuations is not the inflaton, it can have
significantly larger self couplings and thus density perturbations could be
non-Gaussian. The non-Gaussianity can be large enough to be detectable by CMB
and Large Scale Structure observations.


title:
The Clustering Dipole of the Local Universe from the Two Micron All Sky
  Survey

abstract:
  The unprecedented sky coverage and photometric uniformity of the Two Micron
All Sky Survey (2MASS) provides a rich resource for investigating the galaxies
populating the local Universe. A full characterization of the large-scale
clustering distribution is important for theoretical studies of structure
formation. 2MASS offers an all-sky view of the local galaxy population at 2.15
micron, unbiased by young stellar light and minimally affected by dust. We use
2MASS to map the local distribution of galaxies, identifying the largest
structures in the nearby universe. The inhomogeneity of these structures causes
an acceleration on the Local Group of galaxies, which can be seen in the dipole
of the Cosmic Microwave Background (CMB). We find that the direction of the
2MASS clustering dipole is 11 degrees from the CMB dipole, confirming that the
local galaxy distribution accelerates the Local Group. From the magnitude of
the dipole we find a value of the linear bias parameter b=1.37 +/- 0.3 in the
K_s-band. The 2MASS clustering dipole is 19 degrees from the latest measurement
of the dipole using galaxies detected by the Infrared Astronomical Satellite
(IRAS) suggesting that bias may be non-linear in some wavebands.


title: Numerical Modeling of Gamma Radiation from Galaxy Clusters

abstract:
  We investigate the spatial and spectral properties of non-thermal emission
from clusters of galaxies at gamma-ray energies between 10 keV and 10 TeV due
to inverse-Compton (IC) emission, pion-decay and non-thermal bremsstrahlung
(NTB) from cosmic-ray(CR) ions and electrons accelerated at cosmic shock and
secondary e+- from inelastic p-p collisions. We identify two main emission
region, namely the core (also bright in thermal X-ray) and the outskirts region
where accretion shocks occur. IC emission from shock accelerated CR electrons
dominate the emission in the outer regions of galaxy clusters, provided that at
least a fraction of a percent of the shock ram pressure is converted into CR
electrons. A clear detection of this component and of its spatial distribution
will allow us direct probing of cosmic accretion shocks. In the cluster core,
gamma-ray emission above 100 MeV is dominated by pion-decay mechanism and, at
lower energies, by IC emission from secondary e+-. However, IC emission from
shock accelerated electrons projected onto the cluster core will not be
negligible. We emphasize the importance of separating these emission components
for a correct interpretation of the experimental data and outline a strategy
for that purpose. Failure in addressing this issue will produce unsound
estimates of the intra-cluster magnetic field strength and CR ion content.
According to our estimate future space borne and ground based gamma-ray
facilities should be able to measure the whole nonthermal spectrum both in the
cluster core and at its outskirts. The importance of such measurements in
advancing our understanding of non-thermal processes in the intra-cluster
medium is discussed.


title: The general relativistic geometry of the Navarro-Frenk-White model

abstract:
  We derive the space time geometry associated with the Navarro Frenk White
dark matter galactic halo model. We discuss several properties of such a
spacetime, with particular attention to the corresponding Newtonian limit,
stressing the qualitative and quantitative nature of the differences between
the relativistic and the Newtonian description. We also discuss on the
characteristics of the possible stress energy tensors which could produce such
a geometry, via the Einstein's equations.


title: A Search for Close Binaries in the Rho Ophiuchus Star-Forming Region

abstract:
  We have carried out a new, near-infrared speckle imaging survey of 19 members
of the young stellar population in the nearby (d=140 pc), Rho Ophiuchi cloud
core. Results for four binary and one newly discovered triple system are
reported. Data for all known multiple systems among the pre-main-sequence
population of Rho Oph are tabulated. We define a "restricted binary fraction",
Fbr, and a "restricted companion fraction", Fcr, as counting only those systems
most detectable in the present and previous high-resolution near-infrared
imaging surveys, having separations between 0.1-1.1 arcsec and K-band magnitude
differences, Delta K < 3. Analysis of all the available multiplicity data
results in updated values of Fbr=Fcr=24%+/-11% for the Ophiuchus
pre-main-sequence population. These values are consistent with the values in
the Taurus star-forming region, and Fcr is in excess by a factor of 2 relative
to the Main Sequence at the 1-sigma level.


title:
Polarized X-Ray Emission from Magnetized Neutron Stars: Signature of
  Strong-Field Vacuum Polarization

abstract:
  In the atmospheric plasma of a strongly magnetized neutron star, vacuum
polarization can induce a Mikheyev-Smirnov-Wolfenstein like resonance across
which a X-ray photon may (depending on its energy) convert from one mode into
the other, with significant changes in opacities and polarizations. We show
that this vacuum resonance effect gives rise to an unique energy-dependent
polarization signature in the surface emission from neutron stars. The
detection of polarized X-rays from neutron stars can provide a direct probe of
strong-field quantum electrodynamics and constrain the neutron star magnetic
field and geometry.


title: Chandra Observation of the Anomalous X-ray Pulsar 1E 1841-045

abstract:
  We present the results from the {\it Chandra} ACIS CC mode observation of an
anomalous X-ray pulsar (AXP) 1E 1841-045. This is the first observation in
which the pulsar spectrum in wide energy range is spatially discriminated from
the surrounding SNR, Kes 73. Like other AXPs, the phase-integrated spectrum is
fitted well with power-law plus blackbody model. The spectral parameters are
$\Gamma = 2.0 \pm 0.3$, $kT_{\rm BB} = 0.44 \pm 0.02$ keV, and $N_H =
2.54^{+0.15}_{-0.13} \times 10^{22} {\rm cm}^{-2}$. This photon index is
significantly flatter than the other AXPs, and resemble to soft gamma-ray
repeaters (SGRs) in the quiescent state. The pulse profile is double-peaked,
and we found that the second peak has significantly hard spectrum. The spectra
of all phases are consistent with power-law plus blackbody model with constant
temperature and photon index. When fitted with two blackbody model, we obtained
similarly good fit. These results can be interpreted that there are two
emission regions with different energy spectra.


title:
Optical Luminosity Functions of the Abell Galaxy Cluster ABCG 209 at
  z=0.21

abstract:
  We derive the luminosity functions in three bands (BVR) for the rich galaxy
cluster ABCG 209 at z=0.21. The data cover an area of ~78 arcmin^2 in the B and
R bands, while a mosaic of three pointings was obtained in the V band, covering
an area of approximately 160 arcmin^2. The galaxy sample is complete to B =
22.8 (N_gal = 339), V = 22.5 (N_gal = 1078) and R = 22.0 (N_gal = 679).
Although the fit of a single Schechter function cannot be rejected in any band,
the luminosity functions are better described by a sum of two Schechter
functions for bright and faint galaxies, respectively. There is an indication
for a presence of a dip in the luminosity functions in the range V = 20.5--21.5
and R = 20.0--21.0. We find a marked luminosity segregation, in the sense that
the number ratio of bright--to--faint galaxies decreases by a factor 4 from the
center to outer regions. Our analysis supports the idea that ABCG 209 is an
evolved cluster, resulting from the merger of two or more sub--clusters.


title:
The origin of IRS 16: dynamically driven inspiral of a dense star
  cluster to the Galactic center?

abstract:
  We use direct N-body simulations to study the inspiral and internal evolution
of dense star clusters near the Galactic center. These clusters sink toward the
center due to dynamical friction with the stellar background, and may go into
core collapse before being disrupted by the Galactic tidal field. If a cluster
reaches core collapse before disruption, its dense core, which has become rich
in massive stars, survives to reach close to the Galactic center. When it
eventually dissolves, the cluster deposits a disproportionate number of massive
stars in the innermost parsec of the Galactic nucleus. Comparing the spatial
distribution and kinematics of the massive stars with observations of IRS 16, a
group of young He I stars near the Galactic center, we argue that this
association may have formed in this way.


title:
Brown dwarfs and low-mass stars in the Pleiades and Praesepe:-
  Membership and binarity

abstract:
  We present near infrared J-, H- and K-band photometry and optical
spectroscopy of low-mass star and brown dwarf (BD) candidates in the Pleiades
and Praesepe open clusters. We find that Pleiades stars with K=10.5--13 are
rather redder than the NextGen isochrones. We also identify this effect amongst
alphaPer sources from the literature, but find no evidence of it for field
stars from the literature. It is possible that the I-K colour of youthful stars
is affected by the presence of magnetic activity. In the 2-colour diagram we
find no colour change across the "M dwarf gap" (which would be indicative of
dust formation). For Teff=2800--3150K, the colours of Praesepe and Pleiades
sources differ, which may result from gravity sensitive molecular opacities.
Praesepe sources cooler than 2500K agree with the dusty models, but Pleiades
sources agree with the NextGen models down to 2000K. It is possible that dust
formation does not begin until lower Teffs in sources with lower surface
gravities. We also identify unresolved binaries in both clusters, and estimate
mass ratios (q) for Pleiades BDs. Most of these have q>0.7, however, 3/18
appear to have lower q values. We determine the binary fraction (BF) for
numerous mass ranges in each cluster, and find that it is generally rising
towards lower masses. We find a BD BF of 50(+11/-10)%. We also find some
evidence suggesting that the BF-q distribution is flat for 0.5-0.35Mo, in
contrast to solar type stars.


title:
A near-infrared spectroscopic screening of the red giant populations in
  omega Centauri

abstract:
  Near-infrared spectra of 21 giants in omega Centauri, spanning the whole
range of metallicities observed in this cluster, are presented. This work is
part of a coordinated photometric and spectroscopic campaign in the optical and
in the infrared, aimed at studying the complex stellar population of omega
Centauri and understanding its formation and chemical evolution. By analyzing
the several CO and OH molecular bands and atomic lines in the spectra of the
selected giants, metal abundances and abundance ratios have been obtained. The
existence of three major metallicity regimes at [Fe/H]=-1.6, -1.2 and
[Fe/H]<-0.5 has been confirmed. The most metal-rich stars in our sample show a
lower (if any) alpha-enhancement when compared to the more metal-poor
components, suggesting that they should have formed in a medium significantly
polluted by type Ia supernova ejecta. Isotopic carbon abundances have been also
inferred, providing an average 13C/12C=4, which clearly indicates that
extra-mixing processes occurred in the stellar interiors during the ascent on
the Red Giant Branch.


title: Centrifugally driven relativistic dynamics on curved trajectories

abstract:
  Motion of test particles along rotating curved trajectories is considered.
The problem is studied both in the laboratory and the rotating frames of
reference. It is assumed that the system rotates with the constant angular
velocity $\omega = const$. The solutions are found and analyzed for the case
when the form of the trajectory is given by an Archimedes spiral. It is found
that particles can reach infinity while they move along these trajectories and
the physical interpretation of their behaviour is given. The analogy of this
idealized study with the motion of particles along the curved rotating magnetic
field lines in the pulsar magnetosphere is pointed out. We discuss further
physical development (the conserved total energy case, when $\omega \ne const$)
and astrophysical applications (the acceleration of particles in active
galactic nuclei) of this theory.


title:
A high velocity ionised outflow and XUV photosphere in the narrow
  emission line quasar PG1211+143

abstract:
  We report on the analysis of a ~60 ksec XMM observation of the bright, narrow
emission line quasar PG 1211+143. Absorption lines are seen in both EPIC and
RGS spectra corresponding to H- and He-like ions of Fe, S, Mg, Ne, O, N and C.
The observed line energies indicate an ionised outflow velocity of ~24000 km
s^-1. The highest energy lines require a column density of N_H ~ 5 x 10^23
cm^-2, at an ionisation parameter of log(xi) ~ 3.4. If the origin of this high
velocity outflow lies in matter being driven from the inner disc, then the flow
is likely to be optically thick within a radius ~130 Schwarzschild radii,
providing a natural explanation for the Big Blue Bump (and strong soft X-ray)
emission in PG 1211+143.


title: Amplification of MHD waves in swirling astrophysical flows

abstract:
  Recently it was found that helical magnetized flows efficiently amplify
Alfv\'en waves (Rogava et al. 2003, A&A, v.399, p.421). This robust and
manifold nonmodal effect was found to involve regimes of transient algebraic
growth (for purely ejectional flows), and exponential instabilities of both
usual and parametric nature. However the study was made in the incompressible
limit and an important question remained open - whether this amplification is
inherent to swirling MHD flows per se and what is the degree of its dependence
on the incompressibility condition. In this paper, in order to clear up this
important question, we consider full compressible spectrum of MHD modes:
Alfv\'en waves (AW), slow magnetosonic waves (SMW) and fast magnetosonic waves
(FMW). We find that helical flows inseparably blend these waves with each other
and make them unstable, creating the efficient energy transfer from the mean
flow to the waves. The possible role of these instabilities for the onset of
the MHD turbulence, self-heating of the flow and the overall dynamics of
astrophysical flows are discussed.


title:
HST/ACS Coronagraphic Imaging of the Circumstellar Disk around
  HD1415659A

abstract:
  Multicolor coronagraphic images of the circumstellar disk around HD141569A
have been obtained with the Hubble Space Telescope (HST) Advanced Camera for
Surveys. B, V, and I images show that the disk's previously-described
multiple-ring structure is actually a continuous distribution of dust with a
tightly-wound spiral structure. Two, more open spiral arms extend from the
disk, one of which appears to reach the nearby binary star HD141569BC. Diffuse
dust is seen up to 1200AU from HD141569A. Although planets may exist in the
inner region of the disk, tidal interaction with HD141569BC seems more likely
to be the cause of these phenomena. The disk appears redder than the star (B-V
= 0.21 and V-I = 0.25), and its color is spatially uniform. A scattering
asymmetry factor of g = 0.25-0.35 is derived. The azimuthal density
distribution is asymmetric, varying by a factor of ~3 at some radii.


title: Coupling Between Periodic and Aperiodic Variability in SAX J1808.4-3658

abstract:
  We detect a significant broadening in the wings of the 401 Hz peak in the
power spectrum of the accreting millisecond binary pulsar SAX J1808.4-3658.
This feature is consistent with the convolution of the red noise present in the
power spectrum with the harmonic line. We conclude that the flux modulated by
the spin period shows aperiodic variability similar to the red noise in the
overall flux, suggesting such variability also originates at the magnetic caps
close to the neutron star surface. This is analogous to the results found in
some longer period, higher magnetic field pulsators in high mass X-ray
binaries.


title: Near-IR spectra of ISOGAL sources in the Inner Galactic Bulge

abstract:
  In this work we present near-IR spectra (HK-band) of a sample of 107 sources
with mid-IR excesses at 7 and 15 $\rm \mu$m detected during the ISOGAL survey.
Making use of the DENIS interstellar extinction map from Schultheis et al.
(1999) we derive luminosities and find that the $\rm M_{bol}$ vs.~$\rm ^{12}CO$
and $\rm M_{bol} vs. H_{2}O$ diagrams are powerful tools for identifying
supergiants, AGB stars, giants and young stellar objects. The majority of our
sample are AGB stars (~ 80%) while we find four good supergiant candidates,
nine young stellar objects and 12 RGB candidates. We have used the most recent
$\rm K_{0}-[15]$ relation by Jeong et al. (2002) based on recent theoretical
modeling of dust formation of AGB stars to determine mass-loss rates. However,
the uncertainties in the mass-loss rates are rather large. The mass-loss rates
of the supergiants are comparable with those in the solar neighbourhood while
the long-period Variables cover a mass-loss range from $\rm -5 < log
\dot{\it{M}} < -7$. The red giant candidateslie at the lower end of the
mass-loss rate range between $\rm -6.5 < log \dot{{\it{M}}} < -9$. We used the
equivalent width of the CO bandhead at 2.3 $\rm \mu m$, the NaI doublet and the
CaI triplet to estimate metallicities using the relation by Ram\'{\i}rez et al.
(\cite{Ramirez2000}). The metallicity distribution of the ISOGAL objects shows
a mean [Fe/H] $\sim$ -0.25 dex with a dispersion of $\rm \pm 0.40 dex$ which is
in agreement with the values of Ram\'{i}rez et al. (\cite{Ramirez2000}) for
Galactic Bulge fields between $\rm b = -4^{o}$ and $\rm b = -1.3^{o}$. A
comparison with the solar neighbourhood sample of Lan\c{c}on & Wood (LW) shows
that our sample is ~ 0.5 dex more metal-rich on average.


title: Conditions for fast magnetic reconnection in astrophysical plasmas

abstract:
  We investigate favourable circumstances for fast magnetic reconnection in
astrophysical plasmas based on recent results by Rogers et al. (2001). Given
that a critical magnetic field structure with antiparallel field lines exists,
our analysis demonstrates that a sufficient condition for fast reconnection is
that the ratio of the thermal pressure to the magnetic field pressure $\beta$
should be significantly larger than $ 2 m_e/m_p$ (twice the ratio of electron
mass to proton mass). Using several examples (like the different components of
the interstellar medium, the intergalactic medium, active galactic nuclei and
jets) we show that in almost all astrophysical plasmas, magnetic reconnection
proceeds fast i.e. independent of the resistivity, with a few percent of the
Alfv{\'e}n speed. Only for special cases like neutron stars and white dwarfs is
$\beta$ smaller than $2 m_e/ m_p$.


title: Clusters of galaxies: a fundamental pillar of cosmology

abstract:
  Clusters of galaxies are used in a variety of ways to do cosmology. Some of
them are presented here. Their X-ray emitting gas allows us to determine the
baryon fraction, dark matter distribution and the matter density $\Omega_{m}$
of the universe. Another interesting component is relativistic particles whose
radio emission provide the measure of the magnetic fields ($\approx \mu G$) in
the intra-cluster medium (ICM). The observation of distant clusters of galaxies
is also important for cosmology. In particular the new X-ray satellites CHANDRA
and XMM yield exciting new results for galaxy cluster physics and cosmology.


title: Clusters of Galaxies in X-rays: Dark Matter

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 have been studied in detail using X-ray data and
global physical properties have been determined. Correlations between these
quantities have been analysed and compared with the results for distant
clusters. We found an interesting dependence between the relative gas extent
(expressed as the ratio of gas mass fractions at $r_{500}$ and $0.5\times
r_{500}$) and the total cluster mass. The extent of the gas relative to the
extent of the dark matter tends to be larger in less massive clusters. This
dependence might give us some hints about non-gravitational processes in
clusters. The new X-ray satellites Chandra and XMM yield exciting new results
for galaxy cluster physics and cosmology. We show the interesting X-ray
observations of two intermediate redshift clusters, RBS797 ($z=0.35$) and CL
0939+4713 ($z=0.41$) taken with Chandra and XMM respectively.


title: The AGN-Disk Dynamics Connection

abstract:
  Any connection between central activity and the large-scale dynamics of disk
galaxies requires an efficient mechanism to remove angular momentum from the
orbiting material. The only viable means of achieving inflow from kiloparsec
scales is through gravitational stresses created by bars and/or mergers. The
inflow of gas in bars today appears to stall at a radius of few hundred parsec,
however, forming a nuclear ring. Here we suggest that bars in the early
Universe may have avoided this problem, and propose that the progenitors of
central supermassive black holes (SMBHs) are created by gas that is driven deep
into the centers of galaxies by bars in the early stages of disk formation. The
coincidence of the QSO epoch with galaxy formation, the short lifetimes of
QSOs, and the existence of SMBHs in the centers of most bright galaxies are all
naturally accounted for by disk dynamics in this model. The progenitor SMBHs
are the seeds for brighter QSO flares during galaxy mergers. We present a new
study of bar weakening by central mass concentrations, which shows that bars
are less easily destroyed than previously thought. An extremely massive and
compact central mass can, however, dissolve the bar, which creates a
pseudo-bulge component in the center of the disk.


title:
A Fluorescent Aerogel for Capture and Identification of Interplanetary
  and Interstellar Dust

abstract:
  Contemporary interstellar dust has never been analyzed in the laboratory,
despite its obvious astronomical importance and its potential as a probe of
stellar nucleosynthesis and galactic chemical evolution. Here we report the
discovery of a novel fluorescent aerogel which is capable of capturing
hypervelocity dust grains and passively recording their kinetic energies. An
array of these "calorimetric" aerogel collectors in low earth orbit would lead
to the capture and identification of large numbers of interstellar dust grains.


title:
Structure and star formation in disk galaxies I. Sample selection and
  near infrared imaging

abstract:
  We present near-infrared imaging of a sample of 57 relatively large, Northern
spiral galaxies with low inclination. After describing the selection criteria
and some of the basic properties of the sample, we give a detailed description
of the data collection and reduction procedures. The K_s lambda=2.2 micron
images cover most of the disk for all galaxies, with a field of view of at
least 4.2 arcmin. The spatial resolution is better than an arcsec for most
images. We fit bulge and exponential disk components to radial profiles of the
light distribution. We then derive the basic parameters of these components, as
well as the bulge/disk ratio, and explore correlations of these parameters with
several galaxy parameters.


title: Probing String Theory with Modulated Cosmological Fluctuations

abstract:
  Superstring theory, models with extra dimensions and other SUSY models
generically predict that the coupling constants are in fact vacuum expectation
values of fields like the dilaton, moduli etc. Assuming some of these fields
are light during inflation, we get generation of small classical
inhomogeneities in these fields from inflation. Consequently, coupling
constants inherit small inhomogeneities at scales much larger than the causal
horizon in the early universe. After the moduli get pinned down to their
minima, the spatial variations of coupling constants in the late time universe
will be erased. However, inhomogeneities in coupling constants in the very
early universe would generate modulated large scale fluctuations in all relic
species that are produced due to interactions and freezing out. Moreover
(p)reheating of the inflaton field results in modulated curvature fluctuations.
Even if the standard inflaton fluctuations are suppressed, in this picture we
may have pure curvature cosmological fluctuations entirely generated by the
modulated spatial variations of the coupling constants during preheating.