title:
Bubbles, feedback and the intra-cluster medium: three-dimensional
  hydrodynamic simulations

abstract:
  We use a three dimensional hydrodynamical code to simulate the effect of
energy injection on cooling flows in the intracluster medium. Specifically, we
compare a simulation of a 10$^{15}$ $M_\odot$ cluster with radiative cooling
only, with a second simulation in which thermal energy is injected 31 $\kpc$
off-centre, over 64 kpc$^{3}$ at a rate of $4.9\times 10^{44} \ergs$ for 50
Myr. The heat injection forms a hot, low density bubble which quickly rises,
dragging behind it material from the cluster core. The rising bubble pushes
with it a shell of gas which expands and cools. We find the appearance of the
bubble in X-ray temperature and luminosity to be in good qualitative agreement
with recent {\it Chandra} observations of cluster cores. Toward the end of the
simulation, at 600 Myr, the displaced gas begins to fall back toward the core,
and the subsequent turbulence is very efficient at mixing the low and high
entropy gas. The result is that the cooling flow is disrupted for up to $\sim
50$ Myr after the injection of energy ceases. Thus, this mechanism provides a
very efficient method for regulating cooling flows, if the injection events
occur with a 1:1 duty cycle.


title: Molecular ions in L1544. II. The ionization degree

abstract:
  The maps presented in Paper I are here used to infer the variation of the
column densities of HCO+, DCO+, N2H+, and N2D+ as a function of distance from
the dust peak. These results are interpreted with the aid of a crude chemical
model which predicts the abundances of these species as a function of radius in
a spherically symmetric model with radial density distribution inferred from
the observations of dust emission at millimeter wavelengths and dust absorption
in the infrared. Our main observational finding is that the N(N2D+)/N(N2H+)
column density ratio is of order 0.2 towards the L1544 dust peak as compared to
N(DCO+)/N(HCO+) = 0.04. We conclude that this result as well as the general
finding that N2H+ and N2D+ correlate well with the dust is caused by CO being
depleted to a much higher degree than molecular nitrogen in the high density
core of L1544. Depletion also favors deuterium enhancement and thus N2D+, which
traces the dense and highly CO-depleted core nucleus, is much more enhanced
than DCO+. Our models do not uniquely define the chemistry in the high density
depleted nucleus of L1544 but they do suggest that the ionization degree is a
few times 10^{-9} and that the ambipolar diffusion time scale is locally
similar to the free fall time. It seems likely that the lower limit which one
obtains to ionization degree by summing all observable molecular ions is not a
great underestimate of the true ionization degree. We predict that atomic
oxygen is abundant in the dense core and, if so, H3O+ may be the main ion in
the central highly depleted region of the core.


title: The role of the screen factor in GRBs

abstract:
  We derive the screen factor for the radiation flux from an optically thick
plasma of electron-positron pairs and photons, created by vacuum polarization
process around a black hole endowed with electromagnetic structure.


title: Cosmological implications of galaxy clusters: best-fit models

abstract:
  The galaxy cluster power spectrum and mass/temperature functions are
currently the most precise observational tools for constraining the theory of
the formation of large scale structure (LSS) in the Universe. Complementing
these tests by the observational data at larger (cosmic microwave backgroud
anisortopy (CMBA)) and smaller (distribution of $Ly_\alpha$ clouds) scales
opens the way to a straightforward determination of the cosmological parameters
in simplest dark matter (DM) models. We argue that such a 'minimal data set' is
free from systematic effects and can indicate quite precisely the parameters of
spatially flat mixed DM model with a positive cosmological constant and no
cosmic gravitational waves.


title: Extensive Air Showers from Ultra High Energy Gluinos

abstract:
  We study the proposal that the cosmic ray primaries above the
Greisen-Zatsepin-Kuzmin (GZK) cutoff are gluino-containing hadrons ($\tilde
g$-hadrons). We describe the interaction of $\tilde g$-hadrons with nucleons in
the framework of the Gribov-Regge approach using a modified version of the
hadronic interaction model QGSJET for the generations of Extensive Air Showers
(EAS). There are two mass windows marginally allowed for gluinos: $m_{\tilde
g}\lsim 3$ GeV and $25\lsim m_{\tilde g}\lsim 35$ GeV. Gluino-containing
hadrons corresponding to the second window produce EAS very different from the
observed ones. Light $\tilde g$-hadrons corresponding to the first gluino
window produce EAS similar to those initiated by protons, and only future
detectors can marginally distinguish them. We propose a beam-dump accelerator
experiment to search for $\tilde g$-hadrons in this mass window. We emphasize
the importance of this experiment: it can discover (or exclude) the light
gluino and its role as a cosmic ray primary at ultra high energies.


title: Energy Distribution of Micro-events in the Quiet Solar Corona

abstract:
  Recent imaging observations of EUV line emissions have shown evidence for
frequent flare-like events in a majority of the pixels in quiet regions of the
solar corona. The changes in coronal emission measure indicate impulsive
heating of new material to coronal temperatures. These heating or evaporation
events are candidate signatures of "nanoflares" or "microflares" proposed to
interpret the high temperature and the very existence of the corona. The energy
distribution of these micro-events reported in the literature differ widely,
and so do the estimates of their total energy input into the corona. Here we
analyze the assumptions of the different methods, compare them by using the
same data set and discuss their results.
  We also estimate the different forms of energy input and output, keeping in
mind that the observed brightenings are most likely secondary phenomena. A
rough estimate of the energy input observed by EIT on the SoHO satellite is of
the order of 10% of the total radiative output in the same region. It is
considerably smaller for the two reported TRACE observations. The discrepancy
can be explained partially by different thresholds for flare detection. There
is agreement on the slope and the absolute value of the distribution if the
same method were used and a numerical error corrected. The extrapolation of the
power law to unobserved energies that are many orders of magnitude smaller
remains questionable. Nevertheless, these micro-events and unresolved smaller
events are currently the best source of information on the heating process of
the corona.


title:
Age as the Second Parameter in NGC 288 / NGC 362? I. Turnoff Ages: a
  Purely Differential Comparison

abstract:
  We present deep V,I photometry of the globular clusters NGC 288, NGC 362 and
NGC 1851 obtained during a single observational run under strictly homogeneous
conditions. We use the bimodal horizontal branch (HB) of NGC 1851 as a
``bridge'' to obtain the optimum relative match between the HBs of NGC 288 and
NGC 362. In this way we can effectively remove the uncertainties associated
with distance, reddening and inhomogeneities in the absolute calibration, thus
obtaining a very robust, purely differential estimate of the age difference
between these two clusters. According to the bridge test, NGC 288 is found to
be older than NGC 362 by 2 +- 1 Gyr. This result is fully confirmed also by all
classical differential age diagnostics, either based on the luminosity or color
of the main sequence turnoff point.


title: Disruption of satellites in cosmological haloes

abstract:
  We investigate how the survival of dark matter satellites inside virialized
halos depends on tidal stripping and dynamical friction. We use an analytic
approach and then compare the results with N-Body simulations. Both the
satellites and the primary halos are similar to cosmological haloes and have
NFW density profiles. Satellites can either merge with the primary halo or
continue to move on barely perturbed orbits, eventually being disrupted,
depending on the relative strength of friction and tidal forces. We propose
that their actual fate depends simply on their mass ratio relative to the
primary halo.


title:
A Systematic Study of X-Ray Substructure of Galaxy Clusters Detected in
  the ROSAT All-Sky Survey

abstract:
  Results of a systematic study of substructure in X-ray surface brightness
distributions of a combined sample of 470 REFLEX+BCS clusters of galaxies are
presented. The fully automized morphology analysis is based on data of the 3rd
processing of the ROSAT All-Sky survey (RASS-3). After correction for several
systematic effects, $52\pm 7$ percent of the REFLEX+BCS clusters are found to
be substructured in metric apertures of 1 Mpc radius ($H_0= 50 {\rm km} {\rm
s}^{-1} {\rm Mpc}^{-1}$). Future simulations will show statistically which mass
spectrum of major and minor mergers contributes to this number. Another
important result is the discovery of a substructure-density relation, analogous
to the morphology-density relation for galaxies. Here, clusters with asymmetric
or multi-modal X-ray surface brightness distributions are located
preferentially in regions with higher cluster number densities. The
substructure analyses techniques are used to compare the X-ray morphology of 53
clusters with radio halos and relics, and 22 cooling flow clusters with the
REFLEX+BCS reference sample. After careful equalization of the different
`sensitivities' of the subsamples to substructure detection it is found that
the halo and relic sample tends to show more often multi-modal and elongated
X-ray surface brightness distributions compared to the REFLEX+BCS reference
sample. The cooling flow clusters show more often circular symmetric and
unimodal distributions compared to the REFLEX+BCS and the halo/relic reference
samples. Both findings further support the idea that radio halos and relics are
triggered by merger events, and that pre-existing cooling flows might be
disrupted by recent major mergers.


title: The BeppoSAX 0.1 - 100 keV Spectrum of the X-ray Pulsar 4U 1538-52

abstract:
  We report the results of temporal and spectral analysis performed on the
X-ray pulsar 4U 1538-52 observed by BeppoSAX. We obtained a new estimate of the
spin period of the neutron star P=528.24 \pm 0.01 s (corrected for the orbital
motion of the X-ray source): the source is still in the spin-up state, as since
1988. The pulse profile is double peaked, although significant variations of
the relative intensity of the peaks with energy are present. The broad band
(0.12-100 keV) out-of-eclipse spectrum is well described by an absorbed power
law modified by a high energy cutoff at \sim 16 keV (e-folding energy \sim 10
keV) plus an iron emission line at \sim 6.4 keV. A cyclotron line at \sim 21
keV is present. The width of the line is consistent with thermal Doppler
broadening at the temperature of the exponential cutoff. We searched for the
presence of the second harmonic, previously reported for this source. We found
no evidence of lines at \sim 42 keV, although an absorption feature at 51 keV
seems to be present (at 99% confidence level). A soft excess, modelled by a
blackbody with a temperature of \sim 0.08 keV could be present, probably
emitted by the matter at the magnetosphere. We also performed a spectral
analysis during the X-ray eclipse. The spectral evolution during the eclipse
can be well described by a progressive covering of the primary Comptonization
spectrum that is scattered into the line of sight. During the deep eclipse this
spectrum also softens, suggesting that the dust-scattered component becomes
important. An alternative, more complex model, with an emission iron line and
scattered components (as the one that has been used to fit the eclipse of
Centaurus X-3), also gives a good fit of the deep-eclipse data.


title:
Solar quadrupole moment and purely relativistic gravitation
  contributions to Mercury's perihelion Advance

abstract:
  The perihelion advance of the orbit of Mercury has long been one of the
observational cornerstones for testing General Relativity (G.R.).
  The main goal of this paper is to discuss how, presently, observational and
theoretical constraints may challenge Einstein's theory of gravitation
characterized by beta=gamma=1. To achieve this purpose, we will first recall
the experimental constraints upon the Eddington-Robertson parameters gamma,
beta and the observational bounds for the perihelion advance of Mercury. A
second point will address the values given, up to now, to the solar quadrupole
moment by several authors. Then, we will briefly comment why we use a recent
theoretical determination of the solar quadrupole moment, J2=(2.0 +/- 0.4)
10^{-7}, which takes into account both surfacic and internal differential
rotation, in order to compute the solar contribution to Mercury's perihelion
advance. Further on, combining bounds on gamma and J2 contributions, and taking
into account the observational data range for the perihelion shift, we will be
able to give a range of values for beta.
  Alternatively, taking into account the observed value of perihelion shift,
one can deduce a dynamical estimation of J2 in the setting of G.R. This point
is important as it provides a solar model independent estimation that can be
confronted with other determinations of J2 based upon solar theory and solar
observations (oscillation data, oblateness...).
  Finally, a glimpse at future satellite experiments will help us to understand
how stronger constraints upon the parameter space (gamma, beta, J2) as well as
a separation of the two contributions (J2, or purely relativistic) might be
expected in the future.


title: ISO Observations of the dusty quasar BR1202-0725

abstract:
  We present mid- and far-IR photometry of the high-redshift (z=4.69) dusty
quasar BR1202-0725. The quasar was detected in the near-IR, at a flux level
(0.7+/-0.2 mJy) consistent with an average Radio-Quiet Quasar at it's redshift.
Only upper limits for the emission were obtained in the far-IR. These upper
limits, when combined with data from ground-based telescopes, are the first
direct evidence for a turn-over in the far-IR emission and hence confirm that a
black-body dominates the SED at FIR wavelengths. This black-body is most
probably cool dust, constrained to have a temperature below 80K, for a beta of
1.5.


title: The youngest massive star clusters in the Magellanic Clouds

abstract:
  High resolution observations with HST have recently allowed us to resolve and
study several very tight clusters of newly born massive stars in the Magellanic
Clouds. Situated in an extremely rare category of HII regions, being only 5 to
10 arcsecs across and of high excitation and extinction, these stars are just
hatching from their natal molecular clouds. Since the SMC is the most
metal-poor galaxy observable with very high angular resolution, this work may
provide valuable templates for addressing issues of star formation in the very
distant metal-poor galaxies of the early Universe.


title: The Dust Opacity of Star-Forming Galaxies

abstract:
  Presence of dust in galaxies removes half or more of the stellar energy from
the UV-optical budget of the Universe and has profound impact on our
understanding of how galaxies evolve. Measures of opacity in local galaxies are
reviewed together with widely used theoretical and empirical methods for
quantifying its effects. Existing evidence shows that the dust content of
nearby galaxies depends not only on their morphology, but also on their
luminosity and activity level. A digression is devoted to starbursts in view of
their potential relevance for measures of opacity in distant galaxies. Scarcity
of coherent multiwavelength datasets hampers our ability to derive reliable
obscuration estimates in intermediate and high redshift galaxies. This, in
turn, limits the reliability of inferred physical quantities, such as star
formation rates, stellar population ages, galaxy luminosity functions, and
others.


title:
An upper limit on the X-ray luminosity of the black hole - microlens
  OGLE-1999-BUL-32

abstract:
  We present an upper limit on the 3--20 keV X-ray flux from the black hole -
microlens OGLE-1999-BUL-32, based on RXTE/PCA scans over the Galactic Center
region in 1999-2000. It is shown that the X-ray luminosity of the black hole
did not exceed L(3-20 keV)<3e33(d/1kpc)^2 ergs/s (where d is the distance to
the black hole). Near the maximum of the background star amplification by the
microlens (July 6, 1999), the upper limit on the X-ray flux corresponds to an
X-ray luminosity L(3-20 keV)<7e33(d/1kpc)^2 ergs/s.


title: Gamma-Ray Bursts as a Probe of Cosmology

abstract:
  We show that, if the long GRBs are produced by the collapse of massive stars,
GRBs and their afterglows may provide a powerful probe of cosmology and the
early universe.


title:
The Formation and Evolution of Planetary Systems: SIRTF Legacy Science
  in the VLT Era

abstract:
  We will utilize the sensitivity of SIRTF through the Legacy Science Program
to carry out spectrophotometric observations of solar-type stars aimed at (1)
defining the timescales over which terrestrial and gas giant planets are built,
from measurements diagnostic of dust/gas masses and radial distributions; and
(2) establishing the diversity of planetary architectures and the frequency of
planetesimal collisions as a function of time through observations of
circumstellar debris disks. Together, these observations will provide an
astronomical context for understanding whether our solar system - and its
habitable planet - is a common or a rare circumstance. Achieving our science
goals requires measuring precise spectral energy distributions for a
statistically robust sample capable of revealing evolutionary trends and the
diversity of system outcomes. Our targets have been selected from two carefully
assembled databases of solar-like stars: (1) a sample located within 50 pc of
the Sun spanning an age range from 100-3000 Myr for which a rich set of
ancillary measurements (e.g. metallicity, stellar activity, kinematics) are
available; and (2) a selection located between 15 and 180 pc and spanning ages
from 3 to 100 Myr. For stars at these distances SIRTF is capable of detecting
stellar photospheres with SNR >30 at lambda < 24 microns for our entire sample,
as well as achieving SNR >5 at the photospheric limit for over 50% of our
sample at lambda=70 microns. Thus we will provide a complete census of stars
with excess emission down to the level produced by the dust in our present-day
solar system. More information concerning our program can be found at:
http://gould.as.arizona.edu/feps


title: A Spectral Atlas of the Pre-WN Candidate HD 326823

abstract:
  HD 326823 is a peculiar emission line object. In the literature it was
considered as a pre-WN candidate. Based mainly on high resolution data,
obtained with the FEROS spectrograph, we made an atlas covering 3800-9200A
region. This atlas confirms the presence of several strong HeI lines and
numerous N lines. There is also a deficiency of H, indicating that this object
is indeed in an evolved stage. In addition, with low resolution spectra, we
obtained intensities of several lines.


title: Clusters of Galaxies - Keys to Cosmology

abstract:
  Various cosmological applications of galaxy clusters are presented. Clusters
are used to determine the baryon fraction, dark matter distribution and the
matter density of the universe. They also contain a wealth of information about
structure formation and evolution on different scales: large-scale structure,
cluster formation and also galaxy formation via the interaction of cluster
galaxies with the intra-cluster medium. In particular, the X-ray satellites
CHANDRA and XMM yield exciting new results for galaxy cluster physics and
cosmology.


title: An x-ray detector using PIN photodiodes for the axion helioscope

abstract:
  An x-ray detector for a solar axion search was developed. The detector is
operated at 60K in a cryostat of a superconducting magnet. Special care was
paid to microphonic noise immunity and mechanical structure against thermal
contraction. The detector consists of an array of PIN photodiodes and tailor
made preamplifiers. The size of each PIN photodiode is $11\times 11\times 0.5\
{\rm mm^3}$ and 16 pieces are used for the detector. The detector consists of
two parts, the front-end part being operated at a temperature of 60K and the
main part in room temperature. Under these circumstances, the detector achieved
1.0 keV resolution in FWHM, 2.5 keV threshold and 6\times 10^{-5} counts
sec^{-1} keV^{-1} cm^{-2} background level.


title:
Binaries discovered by the SPY project I. HE 1047-0436: a subdwarf B +
  white dwarf system

abstract:
  In the course of our search for double degenerate binaries as potential
progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT
(ESO SN Ia Progenitor surveY - SPY) we discovered that the sdB star HE
1047-0436 is radial velocity variable. The orbital period of 1.213253d, a
semi-amplitude of 94km/s, and a minimum mass of the invisible companion of
0.44Msol are derived from the analysis of the radial velocity curve. We use an
upper limit on the projected rotational velocity of the sdB star to constrain
the system inclination and the companion mass to M>0.71Msol, bringing the total
mass of the system closer to the Chandrasekhar limit. However, the system will
merge due to loss of angular momentum via gravitational wave radiation only
after several Hubble times. Atmospheric parameters and metal abundances are
also derived. The resulting values are typical for sdB stars.


title:
The Effects of Weak Gravitational Lensing on Determinations of the
  Cosmology from Type Ia Supernov\ae

abstract:
  Underlying cosmologies with deceleration parameter,
$q_0=-0.51^{+0.03}_{-0.24},$ may be interpreted as having $q_0=-0.55,$ on the
basis of weak gravitational lensing effects.


title: Follow-up observations from observatories based in Spain

abstract:
  We present a review of the follow-up observations carried out from
observatories located in Spain; Calar-Alto, Izanha and Roque de Los Muchachos.
It summarizes the observations carried out by our group for 27 GRBs occurred in
the period 1999-2000, spanning from GRB 990123 to GRB 001007.


title: Cosmological structure problem of the ekpyrotic scenario

abstract:
  We address the perturbation power spectrum generated in the recently proposed
ekpyrotic scenario by Khoury et al. The issue has been raised recently by Lyth
who used the conventional method based on a conserved variable in the
large-scale limit, and derived different results from Khoury et al. The
calculation is straightforward in the uniform-curvature gauge where the
generated blue spectrum with suppressed amplitude survives as the final
spectrum. Whereas, although the metric fluctuations become unimportant and a
scale-invariant spectrum is generated in the zero-shear gauge the mode does not
survive the bounce, thus with the same final result. Therefore, an exponential
potential leads to a power-law expansion/contraction $a \propto |t|^p$, and the
power $p$ dictates the final power spectra of both the scalar and tensor
structures. If $p \ll 1$ as one realization of the ekpyrotic scenario suggests,
the results are $n_S -1 \simeq 2 \simeq n_T$ and the amplitude of the scalar
perturbation is suppressed relative to the one of the gravitational wave by a
factor $\sqrt{p}/2$. Both results confirm Lyth's. An observation is made on the
constraint on the dynamics of the seed generating stage from the requirement of
scale-invariant spectrum.


title: The large-scale ionised outflow of CH Cygni

abstract:
  HST and ground-based [OII} and [NII] images obtained from 1996 to 1999 reveal
the existence of a ionised optical nebula around the symbiotic binary CH Cyg
extending out to 5000 A.U. from the central stars. The observed velocity range
of the nebula, derived from long-slit echelle spectra, is of 130 km/s. In spite
of its complex appearence, the velocity data show that the basic morphology of
the inner regions of the optical nebula is that of a bipolar (or conical)
outflow extending nearly along the plane of the sky out to some 2000 A.U. from
the centre. Even if the extension of this bipolar outflow and its position
angle are consistent with those of the radio jet produced in 1984 (extrapolated
to the time of our optical imagery), no obvious counterpart is visible of the
original, dense radio bullets ejected by the system. We speculate that the
optical bipolar outflow might be the remannt of the interaction of the bullets
with a relatively dense circumstellar medium.


title:
Dark energy and the angular size - redshift diagram for milliarcsecond
  radio sources

abstract:
  We investigate observational constraints on the cosmic equation of state from
measurements of angular size for a large sample of milliarcsecond compact radio
sources. The results are based on a flat Friedmann-Robertson-Walker (FRW) type
models driven by non-relativistic matter plus a smooth dark energy component
parametrized by its equation of state $p_x = \omega \rho_x$ ($-1 \leq \omega <
0$). The allowed intervals for $\omega$ and $\Omega_{\rm{m}}$ are heavily
dependent on the value of the mean projected linear size $l$. For $l \simeq
20h^{-1} - 30h^{-1}$ pc, we find $\Omega_{\rm{m}} \leq 0.62$, $\omega \leq
-0.2$ and $\Omega_{\rm{m}} \leq 0.17$, $\omega \leq -0.65$ (68% c.l.),
respectively. As a general result, this analysis shows that if one minimizes
$\chi^{2}$ for the parameters $l$, $\Omega_{\rm{m}}$ and $\omega$, the
conventional flat $\Lambda$CDM model ($\omega = -1$) with $\Omega_{\rm{m}} =
0.2$ and $l = 22.6 h^{-1}$pc is the best fit for these angular size data.


title:
The Spectral Energy Distribution of HH30 IRS: Constraining The
  Circumstellar Dust Size Distribution

abstract:
  We present spectral energy distribution (SED) models for the edge-on
classical T Tauri star HH30 IRS that indicate dust grains have grown to larger
than 50 microns within its circumstellar disk. The disk geometry and
inclination are known from previous modeling of multiwavelength Hubble Space
Telescope images and we use the SED to constrain the dust size distribution.
Model spectra are shown for different circumstellar dust models: a standard ISM
mixture and larger grain models. As compared to ISM grains, the larger dust
grain models have a shallower wavelength dependent opacity. Models with the
larger dust grains provide a good match to the currently available data, but
mid and far-IR observations are required to more tightly constrain the dust
size distribution. The accretion luminosity in our models is L_acc<0.2 L_star
corresponding to an accretion rate of 4E-9M_sun/yr. Dust size distributions
that are simple power-law extensions (i.e., no exponential cutoff) yield
acceptable fits to the optical/near-IR but too much emission at mm wavelengths
and require larger disk masses. Such a simple size distribution would not be
expected in an environment such as the disk of HH30 IRS, particularly over such
a large range in grain sizes. However, its ability to adequately characterize
the grain populations may be determined from more complete observational
sampling of the SED in the mid to far-IR.


title:
Magnetically Driven Precession of Warped Disks and Milli-Hertz
  Variabilities in Accreting X-Ray Pulsars

abstract:
  The inner region of the accretion disk around a magnetized neutron star is
subjected to magnetic torques that induce warping and precession of the disk.
These torques arise from interactions between the stellar field and the induced
electric currents in the disk. We carry out a global analysis of
warping/precession modes in a viscous accretion disk, and show that under a
wide range of conditions typical of accreting X-ray pulsars, the magnetic
warping torque can overcome viscous damping and make the mode grow. The
warping/precession modes are concentrated near the inner edge of the disk (at
the magnetosphere-disk boundary), and can give rise to variabilities or
quasi-periodic oscillations (QPOs) in the X-ray/UV/optical fluxes from X-ray
pulsars. We examine the observed properties of mHz QPOs in several systems
(such as 4U 1626-67), and suggest that some hitherto unexplained QPOs are the
results of magnetically driven disk warping/precession.


title: Weighing black holes with warm absorbers

abstract:
  We present a new technique for determining an upper limit for the mass of the
black hole in active galactic nuclei showing warm absorption features. The
method relies on the balance of radiative and gravitational forces acting on
outflowing warm absorber clouds. It has been applied to 6 objects: five Seyfert
1 galaxies: IC 4329a, MCG-6-30-15, NGC 3516, NGC 4051 and NGC 5548; and one
radio-quiet quasar: MR 2251-178. We discuss our result in comparison with other
methods. The procedure could also be applied to any other radiatively driven
optically thin outflow in which the spectral band covering the major absorption
is directly observed.


title:
The first million years of the Sun: A calculation of formation and early
  evolution of a solar-mass star

abstract:
  We present the first coherent dynamical study of the cloud
fragmentation-phase, collapse and early stellar evolution of a solar mass star.
We determine young star properties as the consequence of the parent cloud
evolution. Mass, luminosity and effective temperature in the first million
years of the proto-Sun result from gravitational fragmentation of a molecular
cloud region that produces a cluster of prestellar clumps. We calculate the
global dynamical behavior of the cloud using isothermal 3D hydrodynamics and
follow the evolution of individual protostars in detail using a 1D
radiation-fluid-dynamic system of equations that comprises a correct standard
solar model solution, as a limiting case. We calculate the pre-main sequence
(PMS) evolutionary tracks of a solar mass star in a dense stellar cluster
environment and compare it to one that forms in isolation. Up to an age of
950.000 years differences in the accretion history lead to significantly
different temperature and luminosity evolution. As accretion fades and the
stars approach their final masses the two dynamic PMS tracks converge. After
that the contraction of the quasi-hydrostatic stellar interiors dominate the
overall stellar properties and proceed in very similar ways. Hence the position
of a star in the Hertzsprung-Russell diagram becomes a function of age and mass
only. However, our quantitative description of cloud fragmentation, star
formation and early stellar evolution predicts substantial corrections to the
classical, i.e. hydrostatic and initially fully convective models: At an age of
1 million years the proto-Sun is twice as bright and 500 Kelvin hotter than
according to calculations that neglect the star formation process.


title: Extragalactic Star Clusters: Speculations on the Future

abstract:
  We discuss the future possibilities for extragalactic star cluster research
with the expected new ground-based and space-based telescopes and
instrumentation. Significant gains are expected due to improved angular
resolution, sensitivity, and area coverage particularly in the infrared and
radio, accompanied by progress in evolutionary and dynamical modelling.
Improvements in angular resolution are anticipated, especially through new
adaptive optics systems (e.g., Keck, Gemini, VLT), and interferometry (e.g.,
Keck, VLT, LBT, ALMA, SMA, SkA), and space instrumentation (e.g., Chandra,
NGST), enabling studies even of deeply embedded, forming extragalactic star
clusters. Tidal disruption of Galactic clusters becomes observable through
wide-area surveys such as the SDSS, VISTA, PRIME, including proper motion
measurements through high-resolution imaging (e.g., HST, LBT, SIM, GAIA).
Sensitive new optical and infrared spectrographs (e.g., HET, SALT, GranTeCan,
Magellan, Keck, VLT, CELT, OWL, NGST) will push kinematic and abundance studies
to new limits, allowing us detailed comparisons with model predictions. One
important wavelength range for the study of young, massive star clusters, the
far UV, appears to be neglected by future planned instrumentation.


title: Spectral Properties of Short Gamma-Ray Bursts

abstract:
  The distribution of GRB durations is bimodal, but there is little additional
evidence to support the division of GRBs into short and long classes. Based on
simple hardness ratios, several studies have shown a tendency for longer GRBs
to have softer energy spectra. Using a database of standard model fits to BATSE
GRBs, we compare the distributions of spectral parameters for short and long
bursts. Our preliminary results show that the average spectral break energy
differs discontinuously between short and long burst classes, but within each
class shows only a weak dependence on burst duration.


title:
Characterization of extrasolar terrestrial planets from diurnal
  photometric variability

abstract:
  The detection of massive planets orbiting nearby stars has become almost
routine, but current techniques are as yet unable to detect terrestrial planets
with masses comparable to the Earth's. Future space-based observatories to
detect Earth-like planets are being planned. Terrestrial planets orbiting in
the habitable zones of stars-where planetary surface conditions are compatible
with the presence of liquid water-are of enormous interest because they might
have global environments similar to Earth's and even harbor life. The light
scattered by such a planet will vary in intensity and colour as the planet
rotates; the resulting light curve will contain information about the planet's
properties. Here we report a model that predicts features that should be
discernible in light curves obtained by low-precision photometry. For
extrasolar planets similar to Earth we expect daily flux variations up to
hundreds of percent, depending sensitively on ice and cloud cover. Qualitative
changes in surface or climate generate significant changes in the predicted
light curves. This work suggests that the meteorological variability and the
rotation period of an Earth-like planet could be derived from photometric
observations. Other properties such as the composition of the surface (e.g.,
ocean versus land fraction), climate indicators (for example ice and cloud
cover), and perhaps even signatures of Earth-like plant life could be
constrained or possibly, with further study, even uniquely determined.


title:
Optical emission from high velocity clouds and the ionization sources in
  the Galactic halo

abstract:
  Optical emission lines have now been detected from about 20 high velocity
clouds. These emission lines -- primarily H-alpha, secondarily [N II] and [S
II] -- are very faint and diffuse, spread over the surfaces of the clouds. We
compile emission line measurements and present a model in which the H-alpha is
recombination caused by photoionizing radiation escaping the Milky Way. In such
a model, we infer HVC distances of 5--30 kpc. The photoionization model fails
to explain the relatively strong H-alpha emission from the Magellanic Stream,
and the O VI absorption seen by FUSE in HVCs and the MS, which require a second
source of ionization (likely collisional). Regardless of mechanism, the fact
that HVCs are detectable in H-alpha indicates they are not far away enough to
be Local Group objects. Adopting the HVC distances from the model, there appear
to be two classes of HVCs: H-alpha-bright clouds with low velocity deviations
from Galactic rotation, and often strong [N II], which are presumably
affiliated with the Galactic disk; and H-alpha-faint clouds with high velocity
deviations, which are likely to be infalling gas.


title: Viewing the circumnuclear medium "through" the radio absorption

abstract:
  Observations of radio absorption (free-free and 21 cm neutral hydrogen
absorption) can provide important constraints on the interstellar medium
(either ionised or neutral) surrounding AGN. This gas is relevant in the
obscuration of the central regions and, therefore, in producing the
orientation-dependent aspects of the emission from the AGN itself, one of the
key elements of the unified schemes. From these observations we can learn: how
strong is the evidence for circumnuclear tori/disks and how often, instead, is
the interaction between the radio plasma and large-scale ISM playing a role;
are the tori/disks (when observed) thick or thin and how important is this gas
in affecting the characteristics of radio sources, especially in their early
phase. Here, I will summarise the recent results obtained from free-free and HI
absorption observations of Seyfert and radio galaxies, what they can tell us
about these issues, and which questions remain open.


title: GAIA Spectroscopy and Radial Velocities

abstract:
  GAIA spectroscopic and radial velocity performancies are reviewed on the base
of ground-based test observations and simulations. The prospects for accurate
analysis of stellar atmospheres (temperature, gravity, chemical abundances,
rotation, peculiarities) and precise radial velocities (single stars, binaries,
pulsating stars) are colorful provided the spectral dispersion is high enough.
A higher dispersions also favors a given precision of radial velocities to be
reached at fainter magnitudes: for example, with current parameters for GAIA
spectrograph, a 1 km/sec accuracy on epoch RVs of a K0 star is reached at
V~13.0 mag with 0.25 Ang/pix dispersion spectra, at V~10.3 mag for 0.5 Ang/pix,
and V~6.7 mag for 1 Ang/pix. GAIA radial velocities for single stars can match
the ~0.5 km/sec mean accuracy of tangential motions at V=15 mag, provided the
observations are performed at a dispersion not less than 0.5 Ang/pix.


title:
Energy deposition due to neutrino pair annhilation near rotating neutron
  stars

abstract:
  General relativistic effects have been shown to increase the energy
deposition rate due to the process $\nu \bar{\nu} \to e^{+}e^{-}$ in supernovae
and neutron stars. In this paper we study the effect of inclusion of the
rotation of the star in the general relativistic treatment. We show that
inclusion of rotation results in a reduction in the heating rate as compared to
the no rotation case.


title:
Color--Magnitude Diagram and Luminosity Function of M4 Near the
  Hydrogen-Burning Limit

abstract:
  A proper-motion separation of M4 members from field stars, using deep HST
observations separated by a time base-line of 5 years, allows us to study a
pure sample of cluster main-sequence stars almost to the minimum mass for
hydrogen burning. High-precision photometry shows how badly current theoretical
models fail to reproduce the color-magnitude diagram of low-mass stars of
moderate metallicity ([M/H] ~ -1). This inability of theory to reproduce the
luminosity-radius relation casts doubt on the theoretical mass-luminosity
relation, which is needed to convert the observed luminosity function (LF) into
a mass function (MF), as well as to convert our locally determined LF into a
global MF. To the extent that we trust theoretical M-L relations for such
transformations, we obtain a flat MF from the LF, and some indication that
theoretical masses might be too low at a given luminosity, near the H-burning
limit.


title: MIFS: A Mega Integral Field Spectrograph for the VLT

abstract:
  We describe MIFS, a second generation integral-field spectrograph for the
VLT, operating in the visible wavelength range. It combines a 1'x1' field of
view with the improved spatial resolution provided by multi-conjugate adaptive
optics and covers a large simultaneous spectral range (0.6-1.0 microns). A
separate mode exploits the highest spatial resolution provided by adaptive
optics. With this unique combination of capabilities, MIFS has a wide domain of
application and a large discovery potential.
  The MIFS low-spatial resolution mode (sampled at 0.2") combined with the
initial MCAO capabilities planned for the VLT will provide ultra-deep fields
with a limiting magnitude for spectroscopy of R~28. MIFS will improve the
present day detection limit of Lyman alpha emitters by a factor of 100, and
will detect low-mass star-forming galaxies to z~7. The MIFS high-spatial
resolution mode (3"x3" field sampled at 0.01") is optimized for the next step
in (MC)AO. It will probe, e.g., the relationship between supermassive central
black holes and their host galaxy and the physics of winds from accretion disks
in young stellar objects at unprecedented spatial resolution.
  MIFS will extend Europe's lead in integral-field spectroscopy. It capitalizes
on new developments in adaptive optics, and is a key step towards
instrumentation for OWL.


title: A close look into an intermediate redshift galaxy using STIS

abstract:
  We present a detailed view of a galaxy at z=0.4 which is part of a large
database of intermediate redshifts using high resolution images. We used the
STIS parallel images and spectra to identify the object and obtain the
redshift. The high resolution STIS image (0.05'') enabled us to analyse the
internal structures of this galaxy. A bar along the major axis and hot-spots of
star formation separated by 0.37'' (1.6 kpc) are found along the inner region
of the galaxy. The analysis of the morphology of faint galaxies like this one
is an important step towards estimating the epoch of formation of the Hubble
classification sequence.


title:
Dynamical evolution of rotating stellar systems - II. Post-collapse,
  equal mass system

abstract:
  We present the first post core collapse models of initially rotating star
clusters, using the numerical solution of an orbit-averaged 2D Fokker-Planck
equation. Based on the code developed by Einsel & Spurzem (1999), we have
improved the speed and the stability and included the steady three-body binary
heating source. We have confirmed that rotating clusters, whether they are in a
tidal field or not, evolve significantly faster than non-rotating ones.
Consequences for observed shapes, density distribution, and kinematic
properties of young and old star clusters are discussed. The results are
compared with gaseous and 1D Fokker-Planck models in the non-rotating case.


title: Intrinsic Galaxy Alignments and Weak Gravitational Lensing

abstract:
  Gravitational lensing causes background galaxy images to become aligned, and
the statistical characteristics of the image alignments can then be used to
constrain the power spectrum of mass fluctuations. Analyses of gravitational
lensing assume that intrinsic galaxy alignments are negligible, but if this
assumption does not hold, then the interpretation of image alignments will be
in error. As gravitational lensing experiments become more ambitious and seek
very low-level alignments arising from lensing by large-scale structure, it
becomes more important to estimate the level of intrinsic alignment in the
galaxy population. In this article, I review the cluster of independent
theoretical studies of this issue, as well as the current observational status.
Theoretically, the calculation of intrinsic alignments is by no means
straightforward, but some consensus has emerged from the existing works,
despite each making very different assumptions. This consensus is that a)
intrinsic alignments are a small but non-negligible (< 10%) contaminant of the
lensing ellipticity correlation function, for samples with a median redshift z
= 1; b) intrinsic alignments dominate the signal for low-redshift samples (z =
0.1), as expected in the SuperCOSMOS lensing survey and the Sloan Digital Sky
Survey


title:
On the role of the UV and X-ray radiation in driving a disk wind in
  X-ray binaries

abstract:
  X-ray heating of the photosphere of an accretion disk is a possible mechanism
to produce strong, broad UV emission lines in low mass X-ray binaries (LMXBs).
However, detailed photoionization calculations show that this mechanism fails
to produce sufficient emission measure. We present the results of
hydrodynamical calculations of the disk photosphere irradiated by strong
X-rays. We attempt to determine whether LMXBs can harbor significant UV-driven
disk winds despite the effects of X-ray ionization. Such winds would be a
likely candidate for the site of emission of UV lines and may better explain
the observations than the X-ray heated disk photosphere. We find that the local
disk radiation cannot launch a wind from the disk because of strong ionizing
radiation from the central object. Unphysically high X-ray opacities would be
required to shield the UV emitting disk and allow the line force to drive a
disk wind. However the same X-ray radiation that inhibits line driving heats
the disk and can produce a hot bipolar wind or corona above the disk. To assess
the impact of X-ray heating upon driving of a disk wind by the line force in
any system with an accretion disk we derive analytic formulae. In particular,
we compare results of line-driven disk wind models for accretion disks in LMXBs
and active galactic nuclei. The latter show spectral features associated with a
strong and fast disk wind. The key parameter determining the role of the line
force is not merely the presence of the luminous UV zone in the disk and the
presence of the X-rays, but also the distance of this UV zone from the center.


title:
Limits on the early afterglow phase of gamma-ray burst sources from
  TAROT-1

abstract:
  The T\'elescope \`a Action Rapide pour les Objets Transitoires (TAROT-1) has
as prime objective the observation of the prompt and delayed emission of cosmic
gamma-ray bursts (GRBs). We have performed a search for optical emission from 6
GRBs detected by BATSE. The positioning error circle was fully covered within
typically thirty minutes after the trigger. No detection of the early afterglow
phase was made, and magnitude limits in the range of $ \mathrm{m}_{\mathrm{R}}
= 13-15 $ were estimated using 20s exposures. These limits are compared to
optical afterglow data obtained in later phases and the results are interpreted
in terms of source distances. They correspond to a median redshift of z = 0.5.
With HETE-2 and the planned instrument upgrade, TAROT-1 will be able to detect
the early optical emission of GRBs up to a redshift of the order of 5.


title: Nova Sco 2001 (V1178 Sco)

abstract:
  We present intermediate resolution spectroscopy and near infrared photometry
of NOVA Sco 2001 (V1178 Sco), which was first detected May 13th 2001 and
reported June 21th 2001, and obtained by us the same day. We also retrieved
very accurate astrometry of the target in this very crowded field. This is
needed to be able to do follow up observations of the postnova during the next
years. The spectrum shows an overall expansion of 2100 km/s and has clearly
complex, and most likely nonsymmetric, outflow substructures. We clearly
identify this object as classical nova, "Fe II" subclass.


title: The effects of seeing on Sersic profiles. II. The Moffat PSF

abstract:
  The effects of seeing on Sersic r^{1/n} profile parameters are extensively
studied using a Moffat function. This analytical approximation to the point
spread function (PSF) is shown to provide the best fit to the PSF predicted
from atmospheric turbulence theory when beta=4.765. The Moffat PSF is
additionally shown to contain the Gaussian PSF as a limiting case
beta->infinity. The Moffat function is also shown to be numerically well
behaved when modelling narrow PSFs in HST images. Seeing effects are computed
for elliptically symmetric surface brightness distributions. The widely used
assumption of circular symmetry when studying the effects of seeing on
intrinsically elliptical sources is shown to produce significant discrepancies
with respect to the true effects of seeing on these sources. A prescription to
correct raw (observed) central intensities, effective radii, index n and mean
effective surface brightness is given.


title: Spectroscopic Analysis of Two Carbon Rich Post-AGB Stars

abstract:
  The chemical compositions of the C-rich pAGB stars IRAS 05113+1347 and IRAS
22272+5424 are determined from high-resolution optical spectra using standard
LTE model atmosphere-based techniques. The stars are C, N, and $s$-process
enriched suggesting efficient operation of the third-dredge up in the AGB star
following a first dredge-up that increased the N abundance. Lithium is present
with an abundance requiring Li manufacture. With this pair, abundance analyses
are now available for 11 C-rich pAGBs. A common history is indicated and, in
particular, the $s$-abundances, especially the relative abundances of light to
heavy $s$-process elements, follow recent predictions for the third dredge-up
in AGB stars.


title: The Burst and Transient Source Experiment Earth Occultation Technique

abstract:
  An Earth orbiting detector sensitive to gamma ray photons will see step-like
occultation features in its counting rate when a gamma ray point source crosses
the Earth's limb. This is due to the change in atmospheric attenuation of the
gamma rays along the line of sight. In an uncollimated detector, these
occultation features can be used to locate and monitor astrophysical sources
provided their signals can be individually separated from the detector
background. We show that the Earth occultation technique applied to the Burst
and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory
(CGRO) is a viable and flexible all-sky monitor in the low energy gamma ray and
hard X-ray energy range (20 keV - 1 MeV). The method is an alternative to more
sophisticated photon imaging devices for astronomy, and can serve well as a
cost-effective science capability for monitoring the high energy sky.
  Here we describe the Earth occultation technique for locating new sources and
for measuring source intensity and spectra without the use of complex
background models. Examples of transform imaging, step searches, spectra, and
light curves are presented. Systematic uncertainties due to source confusion,
detector response, and contamination from rapid background fluctuations are
discussed and analyzed for their effect on intensity measurements. A sky
location-dependent average systematic error is derived as a function of
galactic coordinates. The sensitivity of the technique is derived as a function
of incident photon energy and also as a function of angle between the source
and the normal to the detector entrance window. Occultations of the Crab Nebula
by the Moon are used to calibrate Earth occultation flux measurements
independent of possible atmospheric scattering effects.


title:
Coping with Type Ia Supernova "Evolution" When Probing the Nature of the
  Dark Energy

abstract:
  Observations of high-redshift Type Ia supernovae (SNe Ia) have provided
strong evidence that the dark energy is real, and making further accurate
observations of high-redshift SNe Ia is the most promising way to probe the
nature of the dark energy. We discuss one of the concerns about such a project
- that of coping with SN Ia evolution. We emphasize that SN Ia evolution
differs in an important respect from the kind of evolution that has foiled some
past projects in observational cosmology, and we outline empirical strategies
that will take it into account. The supporting role of physical models of SNe
Ia also is discussed. Our conclusion is that systematic errors due to SN Ia
evolution will be small.


title:
The Evolution of Helium and Hydrogen Ionization Corrections as HII
  Regions Age

abstract:
  Helium and hydrogen recombination lines observed in low-metallicity,
extragalactic, HII regions provide the data used to infer the primordial helium
mass fraction, Y_P. In deriving abundances from observations, the correction
for unseen neutral helium or hydrogen is usually assumed to be absent; i.e.,
the ionization correction factor is taken to be unity (icf = 1). In a previous
paper (VGS), we revisited the question of the icf, confirming a "reverse"
ionization correction: icf < 1. In VGS the icf was calculated using more nearly
realistic models of inhomogeneous HII regions, suggesting that the published
values of Y_P needed to be reduced by an amount of order 0.003. As star
clusters age, their stellar spectra evolve and so, too, will their icfs. Here
the evolution of the icf is studied, along with that of two, alternate,
measures of the "hardness" of the radiation spectrum. The differences between
the icf for radiation-bounded and matter-bounded models are also explored,
along with the effect on the icf of the He/H ratio (since He and H compete for
some of the same ionizing photons). Particular attention is paid to the amount
of doubly-ionized helium predicted, leading us to suggest that observations of,
or bounds to, He++ may help to discriminate among models of HII regions ionized
by starbursts of different ages and spectra. We apply our analysis to the
Izotov & Thuan (IT) data set utilizing the radiation softness parameter, the
[OIII]/[OI] ratio, and the presence or absence of He++ to find 0.95 < icf <
0.99. This suggests that the IT estimate of the primordial helium abundance
should be reduced by Delta-Y = 0.006 +- 0.002, from 0.244 +- 0.002 to 0.238 +-
0.003.


title: The Heating of the ICM: Energy Crisis and viable solutions

abstract:
  X-ray observations indicate that non-gravitational processes play a key role
in the thermodynamics of the Intra Cluster Medium (ICM). The effect of
non-gravitational processes is imprinted in the ICM as an entropy minimum,
whose effects are visible in the Luminosity-Temperature relation and in the
Entropy-Temperature relation. However, the X-ray emission alone cannot
discriminate between different mechanisms and sources of heating. There are no
answers at present to the following questions: how much non-gravitational
energy per baryons is present in the ICM? When was this energy injected? Which
are the sources of heating? The embarrassment in front of these questions is
amplified by the fact that the most viable sources of heating, SNae and stellar
winds, seem to be inefficient in bringing the ICM to the observed entropy
level. We may call it the energy crisis. Here we review the main aspects of
this crisis, listing possible solutions, including other sources, like AGNs and
Radio Galaxies, or other mechanisms, like large scale shocks and selective
cooling.


title:
Age as the Second Parameter in NGC 288/NGC 362? II. The Horizontal
  Branch Revisited

abstract:
  We revisit the "second parameter" pair of globular clusters NGC 288/NGC 362
on the basis of theoretical models for red giant branch (RGB) and horizontal
branch (HB) stars. The results of the most extensive set of RGB/HB simulations
computed so far for these clusters are presented for two different
metallicities. Using several different analytical mass loss formulae for RGB
stars, we derive relative "HB morphology ages." We compare them with the
relative main-sequence turnoff ages derived by application of the "bridge test"
by Bellazzini et al. (2001), who found that NGC 288 is 2+/-1 Gyr older than NGC
362. We find that adoption of a higher metallicity ([Fe/H] ~ -1.2), as favored
by the Carretta & Gratton metallicity scale, makes age a much more plausible
second parameter candidate for this pair than is the case when a lower
metallicity ([Fe/H] ~ -1.5), closer to the Zinn & West scale, is adopted.
However, while the different HB morphology of these two clusters can be
reproduced by canonical HB models with [Fe/H] ~ -1.2 and an age difference of 2
Gyr, this explanation is not without difficulty. In particular, we confirm
previous suggestions that canonical models are unable to reproduce the detailed
HB morphology of NGC 288 at its red end, for as yet unknown reasons. Finally,
we show that the mass dispersion on the HB of NGC 362 is substantially larger
than for NGC 288, and suggest that there is a correlation between the mass
dispersion on the HB phase and the central density of globular clusters. This
is presumably related to the way environmental effects affect RGB mass loss.
[Abridged]


title:
First Results from SPARO: Evidence for Large-Scale Toroidal Magnetic
  Fields in the Galactic Center

abstract:
  We have observed the linear polarization of 450 micron continuum emission
from the Galactic center, using a new polarimetric detector system that is
operated on a 2 m telescope at the South Pole. The resulting polarization map
extends ~ 170 pc along the Galactic plane and ~ 30 pc in Galactic latitude, and
thus covers a significant fraction of the central molecular zone. Our map shows
that this region is permeated by large-scale toroidal magnetic fields. We
consider our results together with radio observations that show evidence for
poloidal fields in the Galactic center, and with Faraday rotation observations.
We compare all of these observations with the predictions of a magnetodynamic
model for the Galactic center that was proposed in order to explain the
Galactic Center Radio Lobe as a magnetically driven gas outflow. We conclude
that the observations are basically consistent with the model.


title:
Detection, photometry and slitless radial velocities of 535 planetary
  nebulae in the flattened elliptical galaxy NGC 4697

abstract:
  We have detected 535 planetary nebulae (PNs) in NGC 4697, using the classic
on-band, off-band filter technique with the Focal Reducer and Spectrograph
(FORS) at the Cassegrain focus of the first 8-meter telescope unit of the ESO
Very Large Telescope. From our photometry we have built the [O III] 5007
planetary nebula luminosity function (PNLF) of NGC 4697. It indicates a
distance of 10.5 Mpc, substantially smaller than a previous estimate of 24 Mpc
used in earlier dynamical studies. The PNLF also provides an estimate of the
specific PN formation rate. Combining the information from on-band images with
PN positions on dispersed, slitless grism images, we have obtained radial
velocities for 531 of the 535 PNs. They provide kinematic information up to a
distance of almost three effective radii from the nucleus. Some rotation is
detected in the outer regions, but the rotation curve of this galaxy appears to
drop beyond one effective radius. Assuming an isotropic velocity distribution,
the velocity dispersion profile is consistent with no dark matter within three
effective radii of the nucleus (however, some dark matter can be present if the
velocity distribution is anisotropic). We obtain a blue mass-to-light ratio of
11. Earlier M/L ratios for NGC 4697 were too small, because of the too large
distance used for their derivation.


title: Young Clusters in the Nuclear Starburst of M 83

abstract:
  We present a photometric catalog of 45 massive star clusters in the nuclear
starburst of M 83 (NGC 5236), observed with the Hubble Space Telescope WFPC2,
in both broad-band (F300W, F547M, and F814W) and narrow-band (F656N and F487N)
filters. By comparing the photometry to theoretical population synthesis
models, we estimate the age and mass of each cluster. We find that over 75% of
the star clusters more massive than 2*10^4 Msun in the central 300 pc of M 83
are less than 10 Myr old. Among the clusters younger than 10 Myr and more
massive than 5*10^3 Msun, 70% are between 5 and 7 Myr old. We list an
additional 330 clusters that are detected in our F300W images, but not in the
shallower F547M and F814W images. The clusters are distributed throughout a
semicircular annulus that identifies the active region in the galaxy core,
between 50 and 130 pc from the optical center of M 83. Clusters younger than 5
Myr are preferentially found along the perimeter of the semicircular annulus.
We suggest that the 5-7 Myr population has evacuated much of the interstellar
material from the active ringlet region, and that star formation is continuing
along the edges of the region.


title:
Constrained Simulations of the Real Universe: II. Observational
  Signatures of Intergalactic Gas in the Local Supercluster Region

abstract:
  We present results of gasdynamics+N-body constrained cosmological simulations
of the Local Supercluster region (LSC; about 30/h Mpc around the Virgo
cluster), which closely mimic the real Universe within 100 Mpc by imposing
constraints from Mark III catalog of galaxy peculiar velocities. The
simulations are used to study the properties and possible observational
signatures of intergalactic medium in the LSC region. We find that, in
agreement with previous unconstrained simulations, about 30% of the gas in this
region is in the warm/hot phase at T~10^5-10^7 K, and about 40% in the diffuse
phase at T<10^5 K in low-density regions. The best prospects for detection of
the warm/hot intergalactic medium of the LSC located in filaments and in the
vicinity of virialized regions of groups and clusters are through absorption in
resonant lines of OVII and OVIII in soft X-rays and in the OVI doublet in UV.
If intergalactic gas in filaments (rho/<rho>~ 1-10) is enriched to typical
metallicities of >0.05, the column densities of OVI, OVII, and OVIII along a
random line of sight near the North Galactic Pole, especially near the
supergalactic plane, have a significant probability to be in the range
detectable by the current (FUSE,XMM) and future (Constellation-X) instruments.
(Abridged)


title: Inclusion of turbulence in solar modeling

abstract:
  The general consensus is that in order to reproduce the observed solar p-mode
oscillation frequencies, turbulence should be included in solar models.
However, until now there has not been any well-tested efficient method to
incorporate turbulence into solar modeling. We present here two methods to
include turbulence in solar modeling within the framework of the mixing length
theory, using the turbulent velocity obtained from numerical simulations of the
highly superadiabatic layer of the sun at three stages of its evolution. The
first approach is to include the turbulent pressure alone, and the second is to
include both the turbulent pressure and the turbulent kinetic energy. The
latter is achieved by introducing two variables: the turbulent kinetic energy
per unit mass, and the effective ratio of specific heats due to the turbulent
perturbation. These are treated as additions to the standard thermodynamic
coordinates (e.g. pressure and temperature). We investigate the effects of both
treatments of turbulence on the structure variables, the adiabatic sound speed,
the structure of the highly superadiabatic layer, and the p-mode frequencies.
We find that the second method reproduces the SAL structure obtained in 3D
simulations, and produces a p-mode frequency correction an order of magnitude
better than the first method.


title: H_alpha emission line morphologies of Markarian starburst galaxies

abstract:
  We present broad band R and narrow band H_alpha emission line images of a
sample of optically selected starburst galaxies from the Markarian lists. The
emission line morphology is studied and global properties like luminosities,
equivalent widths and star formation rates are derived. The radial distribution
of H_alpha flux and the EW are determined using concentric aperture photometry
on the emission line and the continuum images. H_alpha flux is generally found
to peak in the nuclear region and fall off outwards. The EW is found to peak
off-center in most of the cases implying that though the intensity of emission
is maximum at the nucleus, the star formation activity relative to the
underlying continuum often peaks away from the center in Markarian starburst
galaxies.


title:
Kinematics of the local universe IX. The Perseus-Pisces supercluster and
  the Tolman-Bondi model

abstract:
  We study the mass distribution and the infall pattern of the Perseus-Pisces
(PP) supercluster. First we calculate the mass of the central part of PP, a
sphere with a radius of 15/h Mpc centered at (l,b)=(140.2\deg ,-22.0\deg),
d=50/h Mpc, using the virial and other estimators. We get M_{PP} = 4 -- 7 /h
10^{15} M_{sun}, giving mass-to-light ratio 200 -- 600 h M_{sun} / L_{sun}, and
overdensity \delta \approx 4.
  The radially averaged smoothed density distribution around the PP is inputted
to the Tolman-Bondi (TB) equations, calculated for different cosmologies:
\Omega_0 = [0.1,1], \Omega_{\Lambda} = 1-\Omega_0 or 0. As a result we get the
infall velocities towards the PP center. Comparing the TB results to the
peculiar velocities measured for the Kinematics of the Local Universe (KLUN)
Tully-Fisher data set we get the best fit for the conditions \Omega_0 = 0.2 --
0.4 and v_{inf} < 100 km/s for the Local Group infall towards the center of PP.
The applicability of the TB method in a complex environment, such as PP, is
tested on an N-body simulation.


title: The Nature of the 10 Kilosecond X-ray Flare in Sgr A*

abstract:
  The X-ray mission Chandra has observed a dramatic X-ray flare -- a
brightening by a factor of 50 for only three hours -- from Sgr A*, the Galactic
Center supermassive black hole. Sgr A* has never shown variability of this
amplitude in the radio and we therefore argue that a jump of this order in the
accretion rate does not seem the likely cause. Based on our model for
jet-dominated emission in the quiescent state of Sgr A*, we suggest that the
flare is a consequence of extra electron heating near the black hole. This can
either lead to direct heating of thermal electrons to T_e~6*10^11 K and
significantly increased synchrotron-self Compton emission, or result from
non-thermal particle acceleration with increased synchrotron radiation and
electron Lorentz factors up to gamma_e>10^5. While the former scenario is
currently favored by the data, simultaneous VLBI, submm, mid-infrared and X-ray
observations should ultimately be able to distinguish between the two cases.


title: 3D Spatial Distribution of the Intergalactic Medium

abstract:
  Very recently a new inversion method has been developped to analyze the
intergalactic medium seen in absorption in quasar spectra (the so-called
Lyman-alpha forest). This method is applied to recover the temperature of the
gas and the underlying density field. Using constraints from the Lyman-beta
forest, it is possible to recover this field up to over-densities delta=10. By
inverting the HI and CIV absorptions together it has been shown that the CIV/HI
ratio varies through the profile of strong lines, beeing larger in the wings.
The method can be applied to reconstruct the 3D density field from multiple
lines of sight and is shown to give good results up to mean separations of 3
arcmin. Results from a survey of QSO pairs performed with HST/STIS and
VLT/UVES-FORS are summarized.


title:
On the relation between the IR continuum and the active galactic nucleus
  in Seyfert galaxies

abstract:
  A sample of the brightest known Seyfert galaxies from the CfA sample is
analyzed on the basis of ISO photometric and spectroscopic data.
  Regardless of the Seyfert type, the mid-IR continuum emission from these
galaxies is found to be correlated with the coronal line emission arising in
the nuclear active region. Conversely, the correlation degrades progressively
when moving from the mid- to the far-IR emission, where it ends to vanish. It
is concluded that the mid-IR emission is largely dominated by dust heated by
processes associated with the active nucleus whereas the far-IR is a different
component most probably unrelated with the active region. We suggest that the
far-IR component is due to dust heated by the stellar population in the disks
of these galaxies.


title:
The contribution of primordial globular clusters to the central galactic
  activity

abstract:
  Globular clusters in galaxies have a mutual feedback with the environment,
which is tuned by their dynamical evolution. This feedback may be the
explanation of various features of both the globular cluster system and the
host galaxy. Relevant examples of these are the radial distribution of
globulars and the violent initial activity of galaxies as AGN.


title: Kinemetry: quantifying kinematic maps

abstract:
  We describe a new technique, kinemetry, to quantify kinematic maps of
early-type galaxies in an efficient way. We present the first applications to
velocity fields obtained with the integral-field spectrograph SAURON.


title: A blind HI survey of the M81 group

abstract:
  Results are presented of the first blind HI survey of the M81 group of
galaxies. The data were taken as part of the HI Jodrell All Sky Survey
(HIJASS). The survey reveals several new aspects to the complex morphology of
the HI distribution in the group. All four of the known dwarf irregular (dIrr)
galaxies close to M81 can be unambiguously seen in the HIJASS data. Each forms
part of the complex tidal structure in the area. We suggest that at least three
of these galaxies may have formed recently from the tidal debris in which they
are embedded. The structure connecting M81 to NGC2976 is revealed as a single
tidal bridge of mass approx. 2.1 x 10^8 Msol and projected spatial extent
approx. 80 kpc. Two `spurs' of HI projecting from the M81 complex to lower
declinations are traced over a considerably larger spatial and velocity extent
than by previous surveys. The dwarf elliptical (dE) galaxies BK5N and Kar 64
lie at the spatial extremity of one of these features and appear to be
associated with it. We suggest that these may be the remnants of dIrrs which
has been stripped of gas and transmuted into dEs by close gravitational
encounters with NGC3077. The nucleated dE galaxy Kar 61 is unambiguously
detected in HI for the first time and has an HI mass of approx.10^8 Msol,
further confirming it as a dE/dIrr transitional object. HIJASS has revealed one
new possible group member, HIJASS J1021+6842. This object contains approx. 2 x
10^7 Msol of HI and lies approx.105arcmin from IC2574. It has no optical
counterpart on the Digital Sky Survey.


title: Gas Rich Galaxies and the HI Mass Function

abstract:
  We have developed an automated cross-correlation technique to detect 21cm
emission in sample spectra obtained from the HI Parkes All Sky Survey.
  The initial sample selection was the nearest spectra to 2435 low surface
brightness galaxies in the catalogue of Morshidi-Esslinger et al. (1999).
  The galaxies were originally selected to have properties similar to Fornax
cluster dE galaxies. As dE galaxies are generally gas poor it is not surprising
that there were only 26 secure detections. All of the detected galaxies have
very high values of $(M_{H}/L_{B})_{\odot}$. Thus the HI selection of faint
optical sources leads to the detection of predominately gas rich galaxies. The
gas rich galaxies tend to reside on the outskirts of the large scale structure
delineated by optically selected galaxies, but they do appear to be associated
with it. These objects appear to have similar relative dark matter content to
optically selected galaxies. The HI column densities are lower than the
'critical density' necessary for sustainable star formation and they appear,
relatively, rather isolated from companion galaxies. These two factors may
explain their high relative gas content. We have considered the HI mass
function by looking at the distribution of velocities of HI detections in
random spectra on the sky.
  The inferred HI mass function is steep though confirmation of this results
awaits a detailed study of the noise characteristics of the HI survey.


title: Where May Ultra-Fast Rotating Neutron Stars Be Hidden?

abstract:
  The existence of ultra-fast rotating neutron stars (spin period P < 1 ms) is
expected on the basis of current models for the secular evolution of
interacting binaries, though they have not been detected yet. Their formation
depends on the quantity of matter accreted by the neutron star which, in turn,
is limited by the mechanism of mass ejection from the binary. An efficient mass
ejection can avoid the formation of ultra-fast pulsars or their accretion
induced collapse to a black hole. We propose that significant reductions of the
mass-transfer rate may cause the switch-on of a radio pulsar phase, whose
radiation pressure may be capable of ejecting out of the system most of the
matter transferred by the companion. This can prevent, for long orbital periods
and if a sufficiently fast spin has been reached, any further accretion, even
if the original transfer rate is restored, thus limiting the minimum spin
period attainable by the neutron star. We show that close systems (orbital
periods P_orb \sim 1 hr are the only possible hosts for ultra-fast spinning
neutron stars. This could explain why ultra-fast radio pulsars have not been
detected so far, as the detection of pulsars with very short spin periods in
close systems is hampered, in current radio surveys, by strong Doppler
modulation and computational limitations.


title:
Supernovae in Deep Hubble Space Telescope Galaxy Cluster Fields: Cluster
  Rates and Field Counts

abstract:
  We have searched for high-redshift supernova (SN) candidates in multiple deep
Hubble Space Telescope (HST) archival images of nine galaxy-cluster fields. We
detect six apparent SNe, with I814 between 21.6 and 28.4 mag. There is roughly
1 SN per deep (flux limit I814 > 26 mag), doubly-imaged, WFPC2 cluster field.
Two SNe are associated with cluster galaxies (at redshifts z=0.18 and z=0.83),
three are probably in galaxies not in the clusters (at z=0.49, z=0.60, and
z=0.98), and one is at unknown z. After accounting for observational
efficiencies and uncertainties (statistical and systematic) we derive the rate
of type-Ia SNe within the projected central 500 kpc of rich clusters:
R=0.20(+0.84)(-0.19) SNu in clusters at z=0.18 to 0.37, and
R=0.41(+1.23)(-0.39) SNu in clusters at z=0.83 to 1.27 (95 per cent confidence
interval; H_0=50; 1 SNu = 1 SN per century per 10^10 L_B_sun). Combining the
two redshift bins, the SN rate at a mean redshift of z=0.41 is R(z=0.41) =
0.30(+0.58)(-0.28) SNu. The upper bounds argue against SNe-Ia being the
dominant source of the large iron mass observed in the intra-cluster medium. We
also compare our observed counts of field SNe (i.e., non-cluster SNe of all
types) to recent model predictions. The observed field count is zero or one SN
with I814 < 26 mag, and 1 to 3 SNe with I814 < 27 mag. These counts are about
two times lower than some of the predictions. Since the counts at these
magnitudes are likely dominated by type-II SNe, our observations may suggest
obscuration of distant SNe-II, or a SN-II luminosity distribution devoid of a
large high-luminosity tail.


title:
Mass Loss and Magnetospheres: X-rays from Hot Stars and Young Stellar
  Objects

abstract:
  High-resolution X-ray spectra of high-mass stars and low-mass T-Tauri stars
obtained during the first year of the Chandra mission are providing important
clues about the mechanisms which produce X-rays on very young stars. For zeta
Puppis (O4 If) and zeta Ori (O9.5 I), the broad, blue-shifted line profiles,
line ratios, and derived temperature distribution suggest that the X-rays are
produced throughout the wind via instability-driven wind shocks. For some less
luminous OB stars, like theta^1 Ori C (O7 V) and tau Sco (B0 V), the line
profiles are symmetric and narrower. The presence of time-variable emission and
very high-temperature lines in theta^1 Ori C and tau Sco suggest that
magnetically confined wind shocks may be at work. The grating spectrum of the
classical T-Tauri star TW Hya is remarkable because the forbidden-line emission
of He-like Ne IX and O VII is very weak, implying that the X-ray emitting
region is very dense, n = 6E+12 cgs, or that the X-rays are produced very close
to the ultraviolet hotspot at the base of an accretion funnel. ACIS light
curves and spectra of flares and low-mass and high-mass young stellar objects
in Orion and rho Ophiuchus further suggest that extreme magnetic activity is a
general property of many very young stars.


title: Nucleosynthesis of s-elements in zero-metal AGB stars

abstract:
  Contrary to previous expectations, recent evolutionary models of
zero-metallicity stars show that the development of mixing episodes at the
beginning of the AGB phase allows low- and intermediate-mass stars to
experience thermal pulses. If these stars, like their metal-rich counterparts,
also experience partial mixing of protons from the H-rich envelope into the
C-rich layers at the time of the third dredge-up, an extensive neutron capture
nucleosynthesis leads to the production of s-process nuclei up to Pb and Bi.
Nucleosynthesis calculations based on stellar AGB models are performed assuming
a parameterized H-abundance profile below the convective envelope at the time
of the third dredge-up. Despite the absence of Fe-group elements, the large
neutron flux resulting from the 13C(alpha,n)16O reaction leads to an efficient
production of s-process elements starting from the neutron captures on the C-Ne
isotopes. Provided partial mixing of protons takes place, it is shown that
population III AGB stars should be enriched in s-process elementsand overall in
Pb and Bi.


title: Dynamics of line-driven disk winds

abstract:
  I review the main results from recent 2-D, time-dependent hydrodynamic models
of radiation-driven winds from accretion disks in AGN. I also discuss the
physical conditions needed for a disk wind to be shielded from the strong
X-rays and to be accelerated to hypersonic velocities. I conclude with a few
remarks on winds in hot stars, low mass young stellar objects, cataclysmic
variables, low mass X-ray binaries, and galactic black holes and future work.


title: Gamma-ray signatures of classical novae

abstract:
  The role of classical novae as potential gamma-ray emitters is reviewed, on
the basis of theoretical models of the gamma-ray emission from different nova
types. The interpretation of the up to now negative results of the gamma-ray
observations of novae, as well as the prospects for detectability with future
instruments (specially onboard INTEGRAL) are also discussed.


title:
Near Infrared Observations of the Giant HII Region W49A: A Starbirth
  Cluster

abstract:
  W49A is one of the most luminous giant H II (GH II) regions in our Galaxy.
This star forming complex contains numerous compact and ultra-compact (UC) H II
regions, extending over an area of 15 pc. It emits about 10^{51} Lyman
continuum photons per second, equivalent to the presence of about 100 O stars,
but it is completely obscured in optical wavelengths by intervening
interstellar dust. The center holds a ``cluster'' of about 30 O stars, each
within an individual UCHII region emitting free-free emission at cm
wavelengths. Our deep K-band (2.2 um) image toward the W49A cluster reveals
just two of the individual exciting stars, each associated with a point--like
radio source, but the rest are invisible. These O stars are so recently born as
to not yet have emerged from their natal dust cocoons, in contrast to other
Galactic clusters embedded in GH II regions in which many of the individual
massive stars are already revealed. Plausibility arguments are made which
suggest that a stellar disc might be common during the entire UCH II phase of
massive star birth, as it persists after accretion ceases in some stars.
Nebular emission (e.g., from Br gamma) is visible around the periphery of the
central region of W49A, along with candidate exciting stars. Star formation
there may have preceeded that in the center, or its lower density environment
may have speeded up the dispersal of the natal dust cocoons. The W49A cluster
can serve as a template for the more luminous buried star clusters now being
found in normal galaxies and starbursts.


title: High-Resolution Mid-Infrared Imaging of G339.88-1.26

abstract:
  G339.88-1.26 is considered to be a good candidate for a massive star with a
circumstellar disk. This has been supported by the observations of linearly
distributed methanol maser spots believed to delineate this disk, and
mid-infrared observations that have discovered a source at this location that
is elongated at the same position angle as the methanol maser distribution. We
used the mid-infrared imager/spectrometer OSCIR at Keck to make high-resolution
images of G339.88-1.26. We resolve the mid-infrared emission into 3 sources
within 1.5 arcsec of the location of the masers. We determine that the methanol
masers are most likely not located in a circumstellar disk. Furthermore we find
that the observed radio continuum emission most likely comes from two sources
in close proximity to each other. One source is an unobscured massive star with
an extended HII region that is responsible for the peak in the radio continuum
emission. A second source is embedded and centered on the elongation in the
radio continuum emission that is believed to be tracing an outflow in this
region.


title:
The environment of FS Tau observed with HST WFPC2 in narrow-band
  emission line filters

abstract:
  We present the results of HST WFPC2 observations of FS Tau and its
environment obtained in the narrow-band emission line filters H alpha and [S
II] (lambda = 6716,6731 Angstrom). Based on these data the morphology of line
emission within this region can be studied on a size scale of 0.1" for the
first time. Despite the fact that FS Tau A has strong forbidden emission lines,
there is no evidence for extended emission at these wavelengths beyond 0.5"
from the components of this close T Tauri binary system. In the FS Tau B
outflow interesting morphological properties can be studied at high spatial
resolution. In this jet we find a structure where circular or elliptical jet
knots are correlated with minima of the jet width. The overall width of this
jet decreases with distance from the source. The FS Tau B jet is thus a rare
example of a jet which may be recollimated far away from its source. The jet is
much more prominent in H alpha than in [S II], while the counterjet shows the
opposite behaviour. The line ratio H alpha/[S II] increases with lateral
distance from the jet axis which is indicative of entrainment of ambient
material.


title:
Constraints on flat cosmologies with tracking Quintessence from Cosmic
  Microwave Background observations

abstract:
  We constrain cosmological parameters in flat cosmologies with tracking dark
energy (or Quintessence) using the existing data on Cosmic Microwave Background
(CMB) anisotropies. We perform a maximum likelihood analysis using combined
data from COBE/DMR, BOOMERanG, DASI and MAXIMA, obtaining estimates for the
dark energy density $\Omega_{Q}$ and equation of state $w_{Q}$, the physical
baryon density $\Omega_{b}h^{2}$, the scalar perturbation spectral index
$n_{S}$, the ratio $R$ between the tensor and scalar perturbation amplitude (or
the tensor spectral index $n_{T}$). Dark energy is found to be the dominant
cosmological component $\Omega_{Q}=0.71^{+0.05}_{-0.04}$, with equation of
state $w_{Q}=-0.82^{+0.14}_{-0.11}$ (68% C.L.). Our best fit value of the
physical baryon density is in good agreement with the primordial
nucleosynthesis bound. We find no significant evidence for deviations from
scale-invariance, although a scalar spectral index slightly smaller than unity
is marginally preferred. Finally, we find that the contribution of cosmological
gravitational waves is negligible. These results confirm that Quintessence is
slightly preferred with respect to ordinary cosmological constant by the
present CMB data.


title:
A high-velocity black hole on a Galactic-halo orbit in the solar
  neighborhood

abstract:
  Only a few of the dozen or so stellar-mass black holes have been observed
away from the plane of the Galaxy$^1$. Those few could have been ejected from
the plane as a result of a ``kick'' received during a supernova explosion, or
they could be remnants of the population of massive stars formed in the early
stages of evolution of the Galaxy. Determining their orbital motion should help
to distinguish between these options. Here we report the transverse motion (in
the plane of the sky) for the black hole X-ray nova XTE J1118+480 (refs 2-5),
from which we derive a large space velocity. This X-ray binary has an eccentric
orbit around the Galactic Centre, like most objects in the halo of the Galaxy,
such as ancient stars and globular clusters. The properties of the system
suggest that its age is comparable to or greater than the age of the Galactic
disk. Only an extraordinary ``kick'' from a supernova could have launched the
black hole into an orbit like this from a birth place in the disk of the
Galaxy.


title: Low Mass Stars and Brown Dwarfs around Sigma Orionis

abstract:
  We present optical spectroscopy of 71 photometric candidate low-mass members
of the cluster associated with Sigma Orionis. Thirty-five of these are found to
pass the lithium test and hence are confirmed as true cluster members, covering
a mass range of <0.055-0.3M_{sun}, assuming a mean cluster age of <5 Myr. We
find evidence for an age spread on the (I, I-J) colour magnitude diagram,
members appearing to lie in the range 1-7 Myr. There are, however, a
significant fraction of candidates that are non-members, including some
previously identified as members based on photometry alone. We see some
evidence that the ratio of spectroscopically confirmed members to photometric
candidates decreases with brightness and mass. This highlights the importance
of spectroscopy in determining the true initial mass-function.


title: HST/STIS Spectroscopy of 3C 273

abstract:
  We present preliminary results on the low-redshift Lyman alpha forest as
based on STIS spectra of 3C 273. A total of 121 intergalactic Lyman
alpha-absorbing systems were detected, of which 60 are above the 3.5 sigma
completness limit, log N(HI)~12.3. The median Doppler parameter, b=27 km/s, is
similar to that seen at high redshift. However the distribution of HI column
densities (dN/dN(HI) propto N(HI)^-beta) has a steeper slope, beta = 2.02 +-
0.21, than is seen at high redshift. Overall, the observed N(HI)-b distribution
is consistent with that derived from a Lambda CDM hydrodynamic simulation.


title: Redshifts for 2410 Galaxies in the Century Survey Region

abstract:
  The `Century Survey' strip covers 102 square degrees within the limits 8.5h
\leq \alpha_{1950} \leq 16.5h, 29.0 degrees \leq \delta_{1950} \leq 30.0
degrees. The strip passes through the Corona Borealis supercluster and the
outer region of the Coma cluster.
  Within the Century Survey region, we have measured 2410 redshifts which
constitute four overlapping complete redshift surveys: (1) 1728 galaxies with
Kron-Cousins R_{phot} \leq 16.13 covering the entire strip, (2) 507 galaxies
with R_{phot} \leq 16.4 in the right ascension range 8h 32m \leq \alpha_{1950}
\leq 10h 45m, (3) 1251 galaxies with absorption- and K-corrected R_{CCD, corr}
\leq 16.2 covering the right ascension range 8.5h \leq \alpha_{1950} \leq 13.5h
and (4) 1255 galaxies with absorption- and K-corrected V_{CCD, corr} \leq 16.7
also covering the right ascension range 8.5h \leq \alpha_{1950} \leq 13.5h. All
of these redshift samples are more than 98 % complete to the specified
magnitude limit.


title:
Observations of the Extended Distribution of Ionized Hydrogen in the
  Plane of M31

abstract:
  We have used the Wisconsin H-Alpha Mapper (WHAM) to observe the spatially
extended distribution of ionized hydrogen in M31 beyond the stellar disk. We
obtained five sets of observations, centered near the photometric major axis of
M31, that extend from the center of the galaxy to just off the edge of the
southwestern HI disk. Beyond the bright stellar disk, but within the HI disk,
weak H-alpha is detected with an intensity I(H-alpha) = 0.05 (+0.01 / -0.02)
Rayleighs. Since M31 is inclined 77 degrees with respect to the line of sight,
this implies that the ambient intergalactic ionizing flux onto each side of M31
is Phi_0 <= 1.6 x 10^4 photons cm^-2 s^-1. Just beyond the outer boundary of
the HI disk we find no significant detection of H-alpha and place an upper
limit I(H-alpha) <= 0.019 Rayleighs.


title: Multiplicity of X-Ray Selected T Tauri Stars in Chamaeleon

abstract:
  We report on a multiplicity survey of a sample of X-ray selected young stars
in the Chamaeleon association. We used speckle-interferometry and direct
imaging to find companions in the separation range 0.13" to 6". After
correction for chance alignment with background stars, we find a multiplicity
(number of binaries or multiples divided by number of systems) of (14.0+-4.3)%
and a companion star frequency (number of companions divided by number of
systems) of (14.7+-5.1)%. Compared to solar-type main-sequence stars, the
companion star frequency is lower by a factor of 0.61+-0.27. This is remarkably
different from the high multiplicity found in the Taurus-Auriga star-forming
region and for T Tauri stars in Chamaeleon known before ROSAT. We find only a
few binaries with projected separations of more than 70 AU, also in contrast to
the results for stars known before ROSAT. This indicates that the X-ray
selected stars belong to a different population than the stars known before
ROSAT, a hypothesis further supported by their Hipparcos distances and proper
motions.


title: The Lyman Break Galaxies: their Progenitors and Descendants

abstract:
  We study the evolution of Lyman Break Galaxies (LBGs) from z=5 to z=0 by
tracing the merger trees of galaxies in a large-scale hydrodynamic simulation
based on a Lambda cold dark matter model. In particular, we emphasize on the
range of properties of the sample selected by the rest-frame V band luminosity,
in accordance with recent near-IR observations. The predicted rest-frame V band
luminosity function agrees well with the observed one when dust extinction is
taken into account. The stellar content and the star formation histories of
LBGs are also studied. We find that the LBGs intrinsically brighter than
Mv=-21.0 at z=3 have stellar masses of at least 10^9\Msun, with a median of
10^{10}h^{-1}\Msun. The brightest LBGs (Mv<-23) at z=3 merge into
clusters/groups of galaxies at z=0, as suggested from clustering studies of
LBGs. Roughly one half of the galaxies with -23<Mv<-22 at z=3 fall into
groups/clusters, and the other half become typical L* galaxies at z=0 with
stellar mass of ~10^{11}\Msun. Descendants of LBGs at the present epoch have
formed roughly 30% of their stellar mass by z=3, and the half of their current
stellar population is 10 Gyr old, favoring the scenario that LBGs are the
precursors of the present day spheroids. We find that the most luminous LBGs
have experienced a starburst within 500 Myr prior to z=3, but also have formed
stars continuously over a period of 1 Gyr prior to z=3 when all the star
formation in progenitors is coadded. We also study the evolution of the mean
stellar metallicity distribution of galaxies, and find that the entire
distribution shifts to lower metallicity at higher redshift. The observed
sub-solar metallicity of LBGs at z=3 is naturally predicted in our simulation.


title:
Overproduction of primordial helium-4 in the presence of neutrino
  oscillations

abstract:
  The maximum overproduction of helium-4 in cosmological nucleosynthesis with
active--sterile neutrino oscillations, nu_e -> nu_s, efficient after decoupling
of electron neutrino, is analyzed. The kinetic effects on primordial
nucleosynthesis due to neutrino spectrum distortion, caused by oscillations,
are precisely taken into account.
  The maximum overproduction of primordial He-4 as a function of oscillation
parameters is obtained from the analysis of the kinetics of the nucleons and
the oscillating neutrinos, for the full range of parameters of the discussed
oscillation model. A maximum relative increase of He-4, up to 14% for
non-resonant oscillations and up to 32% for resonant ones is registered.
Cosmological constraints on oscillation parameters are also discussed.


title:
S 111 and the polarization of the B[e] supergiants in the Magellanic
  Clouds

abstract:
  We have obtained linear polarization measurements of the Large Magellanic
Cloud B[e] supergiant S 111 using optical imaging polarimetry. The intrinsic
polarization found is consistent with the presence of an axisymmetric
circumstellar envelope. We have additionally estimated the electron density for
S 111 using data from the literature and revisited the correlation between
polarization and envelope parameters of the B[e] supergiant stars using more
recent IR calibration color data. The data suggest that the polarization can be
indeed explained by electron scattering. We have used Monte Carlo codes to
model the continuum polarization of the Magellanic B[e] supergiants. The
results indicate that the electron density distribution in their envelopes is
closer to a homogeneous distribution rather than an r$^{-2}$ dependence. At the
same time, the data are best fitted by a spherical distribution with density
contrast than a cylindrical distribution. The data and the model results
support the idea of the presence of an equatorial disk and of the two-component
wind model for the envelopes of the B[e] supergiants. Spectropolarimetry would
help further our knowledge of these envelopes.


title:
Short Distance Physics and the Consistency Relation for Scalar and
  Tensor Fluctuations in the Inflationary Universe

abstract:
  Recent discussions suggest the possibility that short distance physics can
significantly modify the behavior of quantum fluctuations in the inflationary
universe, and alter the standard large scale structure predictions. Such
modifications can be viewed as due to a different choice of the vacuum state.
We show that such changes generally lead to violations of the well-known
consistency relation between the scalar to tensor ratio and the tensor spectral
index. Vacuum effects can introduce an observable modulation to the usual
predictions for the scalar and tensor power spectra.


title: Hydrogen 21-Centimeter Emission from a Galaxy at Cosmological Distance

abstract:
  We have detected the neutral atomic hydrogen (HI) emission line at a
cosmologically significant distance (z=0.18) in the rich galaxy cluster Abell
2218 with the Westerbork Synthesis Radio Telescope. The HI emission originates
in a spiral galaxy 2.0 megaparsecs from the cluster core. No other significant
detections have been made in the cluster, suggesting that the mechanisms that
remove neutral gas from cluster galaxies are efficient. We infer that fewer
than three gas-rich galaxies were accreted by Abell 2218 over the past 10^9
years. This low accretion rate is qualitatively consistent with low-density
cosmological models in which clusters are largely assembled at z>1.


title: Axisymmetric Galaxy Distribution and the Center of the Universe

abstract:
  The validity of Hubble's law defies the determination of the center of the
big bang expansion, even if it exists. Every point in the expanding universe
looks like the center from which the rest of the universe flies away. In this
article, the author shows that the distribution of apparently circular galaxies
is not uniform in the sky and that there exists a special direction in the
universe in our neighborhood. The data is consistent with the assumption that
the tidal force due to the mass distribution around the universe center causes
the deformation of galactic shapes depending on its orientation and location
relative to the center and our galaxy. The location of the center is estimated
to be at a distance ~0.88/h Gpc in the direction of l=135 +/- 30 degrrs and b =
-35 +/- 20 degrees in galactic coordinates (alpha = 01h 36m, delta = +26d 50m
in equatorial J2000.0 or in the direction of the Constellation Pisces). Further
study of the deformation of galaxies such as triaxial galaxies and
non-axisymmetric spiral galaxies can be utilized for a more accurate
determination of the universe center.


title:
The Static Universe Hypothesis: Theoretical Basis and Observational
  Tests of the Hypothesis

abstract:
  From the axiom of the unrestricted repeatability of all experiments, Bondi
and Gold argued that the universe is in a stable, self-perpetuating equilibrium
state. This concept generalizes the usual cosmological principle to the perfect
cosmological principle in which the universe looks the same from any location
at any time. Consequently, I hypothesize that the universe is static and in an
equilibrium state (non-evolving).
  New physics is proposed based on the concept that the universe is a pure wave
system. Based on the new physics and assuming a static universe, processes are
derived for the Hubble redshift and the cosmic background radiation field.
  Then, following the scientific method, I test deductions of the static
universe hypothesis using precise observational data primarily from the Hubble
Space Telescope. Applying four different global tests of the space-time metric,
I find that the observational data consistently fits the static universe model.
The observational data also show that the average absolute magnitudes and
physical radii of first-rank elliptical galaxies have not changed over the last
5 to 15 billion years.
  Because the static universe hypothesis is a logical deduction from the
perfect cosmological principle and the hypothesis is confirmed by the
observational data, I conclude that the universe is static and in an
equilibrium state.


title:
Cosmological Hydrogen Reionization with Three Dimensional Radiative
  Transfer

abstract:
  We present new calculations of the inhomogeneous process of cosmological
reionization by carefully following the radiative transfer in pre-computed
hydrodynamical simulations of galaxy formation. These new computations
represent an important step on the way towards fully self-consistent and
adaptive calculations which will eventually cover the enormous range of scales
from the sizes of individual mini-halos to the mean free path of ionizing
photons in the post-overlap Universe. The goal of such simulations is to
include enough realistic physics to accurately model the formation of early
structures and the end of the `dark ages'. Our new calculations demonstrate
that the process by which the ionized regions percolate the Universe is
complex, and that the idea of voids being ionized before overdense regions is
perhaps too simplistic. It seems that observational information pertaining to
the reionization epoch may now be in our grasp, through the detection of
Gunn-Peterson troughs at z~6. If so, then the comparison of information from
many lines of sight with simulations such as ours may allow us to disentangle
details of the ionization history and trace the early formation of structure.