title:
How to Avoid the Ambiguity in Applying the Copernican Principle for
  Cosmic Topology: Take the Observational Approach

abstract:
  It is often stated that homogeneity and isotropy of the Universe are
assumptions of the almost Friedmann-Lema^itre (FL) model (the hot big bang
model), inspired from the Copernican Principle. However, only local homogeneity
and isotropy are required by the model: multiply connected almost FL models are
locally homogeneous and isotropic, but they can be globally anisotropic and/or
globally inhomogeneous. Toy models are used here to show how global anisotropy
and/or global inhomogeneity of an almost FL model could be shown directly in
observations. This approach may avoid having to make any assumptions regarding
global anisotropy and inhomogeneity.


title:
Optical studies of two LMC X-ray transients : RX J0544.1-7100 and RX
  J0520.5-6932

abstract:
  We report observations which confirm the identities of the optical
counterpart to the transient sources RX J0544.1-7100 and RX J0520.5-6932. The
counterparts are suggested to be a B-type stars. Optical data from the
observations carried out at ESO and SAAO, together with results from the OGLE
data base, are presented. In addition, X-ray data from the RXTE all-sky monitor
are investigated for long term periodicities. A strong suggestion for a binary
period of 24.4d is seen in RX J0520.5-6932 from the OGLE data.


title: On the dynamics of superfluid neutron star cores

abstract:
  We discuss the nature of the various modes of pulsation of superfluid neutron
stars using comparatively simple Newtonian models. The matter in these stars is
described in terms of a two-fluid model, where one fluid is the neutron
superfluid, which is believed to exist in the core and inner crust of mature
neutron stars, and the other fluid represents a conglomerate of all other
constituents (crust nuclei, protons, electrons, etc.). In our model, we
incorporate the non-dissipative interaction due to the so-called entrainment
effect, whereby the momentum of one constituent (e.g. the neutrons) carries
along part of the mass of the other constituent. We show that there is no
independent set of propagating g-modes in a superfluid neutron star core. We
also approach the toroidal pulsation modes of a slowly rotating superfluid
star. We show that the superfluid equations support a new class of r-modes.
Finally, the role of the entrainment effect on the superfluid mode frequencies
is shown explicitly via solutions to local dispersion relations.


title: Cusp Disruption in Minor Mergers

abstract:
  We present 0.55 x 10^6 particle simulations of the accretion of high-density
dwarf galaxies by low-density giant galaxies, using models that contain both
power-law central density cusps and point masses representing supermassive
black holes. The cusp of the dwarf galaxy is disrupted during the merger,
producing a remnant with a central density that is only slightly higher than
that of the giant galaxy initially. Removing the black hole from the giant
galaxy allows the dwarf galaxy to remain intact and leads to a remnant with a
high central density, contrary to what is observed. Our results support the
hypothesis that the persistence of low-density cores in giant galaxies is a
consequence of supermassive black holes.


title: Neutron Diffusion and Nucleosynthesis in an Inhomogeneous Big Bang Model

abstract:
  This article describes the production of primordial He4 nuclei in an
inhomogeneous universe. The baryon distribution is spherically symmetric and
consists of a high density inner region and a low density outer region. As the
temperature decreases neutrons diffuse to the outer region until they are
homogeneously distributed, and protons may be redistributed depending on how
fast diffusion occurs. Nucleosynthesis occurs earlier in the inner region and
neutrons diffuse back to that region. The rapidity of diffusion determines how
much He4 is ultimately produced.


title: The Merger History of Supermassive Black Holes in Galaxies

abstract:
  The ubiquity of supermassive black holes (SMBHs) at the centers of nearby
luminous galaxies can arise from the multiple mergers experienced by dark
matter halos in hierarchical structure formation models, even if only a small
fraction of these galaxies harbor SMBHs at high redshifts. We illustrate this
possibility using cosmological Monte Carlo simulations of the merger history of
dark matter halos and their associated SMBHs. In our most extreme models, in
order to populate nearly every bright galaxy with a SMBH at z=0, only a few
percent of the halos with virial temperatures above 10^4 K are required to
harbor a SMBH at high redshift. This possibility must be included in studies of
the luminosity function and the clustering properties of quasars. We predict
the number of SMBH merger events that are detectable by the gravitational wave
experiment LISA, as a function of redshift, out to z=5. Although the event
rates can be significantly reduced in scenarios with rare SMBHs, a minimum of
\~10 detectable merger events per year is predicted if SMBH binaries coalesce
efficiently. The observed distribution of events with redshift could yield
valuable information on the SMBH formation process. If SMBH binaries do not
coalesce, we find that at least several SMBH slingshot ejections probably
occurred from z=5 to the present in each galaxy more massive than ~10^11 Msun
at z=0. Although our results are sensitive to the minimum cooling mass assumed
for the formation of SMBHs, we expect the qualitative predictions of our models
to be robust.


title:
Synchronized Formation of Sub-Galactic Systems at Cosmological
  Reionization: Origin of Halo Globular Clusters

abstract:
  Gas rich sub-galactic halos with mass Mt <= 10^7.5 Msun, while incapable of
forming stars due to lack of adequate coolants, contain a large fraction of
baryonic mass at cosmological reionization. We show that the reionization of
the universe at z=10-20 has an interesting physical effect on these halos. The
external radiation field causes a synchronous inward propagation of an
ionization front towards each halo, resulting in an inward, convergent shock.
The resident gas of mass Mb~10^4-10^7 Msun in low spin (initial dimensionless
spin parameter lambda <= 0.01) halos with a velocity dispersion sigmav <=
11km/s would be compressed by a factor of ~100 in radius and form self
-gravitating baryonic systems. Under the assumption that such compressed
gaseous systems fragment to form stars, the final stellar systems will have a
size 2-40pc, velocity dispersion 1-10km/s and a total stellar mass of M*
10^3-10^6 Msun. The characteristics of these proposed systems seem to match the
observed properties of halo globular clusters. The expected number density is
consistent with the observed number density of halo globular clusters. The
observed mass function of slope ~-2 at the high mass end is predicted by the
model. Strong correlation between velocity dispersion and luminosity (or
surface brightness) and lack of correlation between velocity dispersion and
size, in agreement with observations, are expected. Metallicity is, on average,
expected to be low and should not correlate with any other quantities of
globular clusters, except that a larger dispersion of metallicity among
globular clusters is expected for larger galaxies. The observed trend of
specific frequency with galaxy type may be produced in the model. We suggest
that these stellar systems are seen as halo globular clusters today.


title: The supernova remnants G67.7+1.8, G31.5-0.6 and G49.2-0.7

abstract:
  Wide field CCD observations of three, less known, supernova remnants.
Filamentary and diffuse emission is discovered from the supernova remnant
G67.7+1.8. Emission can also be seen in the ROSAT All Sky Survey data which
indicate an extended hard X-ray source. The optical radiation from the
G31.5-0.6 area shows weak sulfur emission and is probably not related to the
remnant. Weak sulfur emission is also observed from W51C or G49.2-0.7. However,
a small patch of emission in the south-east seems to emit strong sulfur
emission. Results from long slit spectra are also presented.


title: The peculiar supernova remnant CTB 80

abstract:
  Deep CCD exposures of the peculiar supernova remnant CTB 80 in the light of
major optical lines have been obtained. These images reveal significant shock
heated emission in the area of the remnant. The sulfur line image shows
emission in the north along the outer boundary of the IRAS and HI shells. The
comparison between the [OIII] and [OII] line images further suggest the
presence of significant inhomogeneities in the interstellar medium. The flux
calibrated images do not indicate the presence of incomplete recombination
zones, and we estimate that the densities of the preshock clouds should not
exceed a few atoms per cm^3. The area covered by the optical radiation along
with the radio emission at 1410 MHz suggest that CTB 80 occupies a larger
angular extent than was previously known.


title:
The Proper Motion of the Globular Cluster NGC 6553 and of Bulge Stars
  with HST

abstract:
  WFPC2 images obtained with the Hubble Space telescope 4.16 years apart have
allowed us to measure the proper motion of the metal rich globular cluster NGC
6553 with respect to the background bulge stars. With a space velocity of
(${\Pi}, {\Theta}, W$) = (-3.5, 230, -3) km s$^{-1}$, NGC 6553 follows the mean
rotation of both disk and bulge stars at a Galactocentric distance of 2.7 kpc.
While the kinematics of the cluster is consistent with either a bulge or a disk
membership, the virtual identity of its stellar population with that of the
bulge cluster NGC6528 makes its bulge membership more likely. The astrometric
accuracy is high enough for providing a measure of the bulge proper motion
dispersion and confirming its rotation. A selection of stars based on the
proper motions produced an extremely well defined cluster color-magnitude
diagram (CMD), essencially free of bulge stars. The improved turnoff definition
in the decontaminated CMD confirms an old age for the cluster (~13 Gyr)
indicating that the bulge underwent a rapid chemical enrichment while being
built up at in the early Universe. An additional interesting feature of the
cluster color-magnitude diagram is a significant number of blue stragglers
stars, whose membership in the cluster is firmly established from their proper
motions.


title: High-Speed Energy-Resolved STJ Photometry of the Eclipsing Binary UZ For

abstract:
  We present high time-resolution optical photometry of the eclipsing binary UZ
For using a superconducting tunnel junction (STJ) device, a photon-counting
array detector with intrinsic energy resolution. Three eclipses of the $\sim$18
mag 126.5 min orbital binary were observed using a $6\times6$ array of Tantalum
STJs at the 4.2-m William Herschel Telescope on La Palma. The detector
presently provides individual photon arrival time accuracy to about 5 $\mu$s,
and a wavelength resolution of about 60 nm at 500 nm, with each array element
capable of counting up to $\sim$5000 photons s$^{-1}$. The data allow us to
place accurate constraints on the accretion geometry from our time- and
spectrally-resolved monitoring, especially of the eclipse ingress and egress.
We find that there are two small accretion regions, located close to the poles
of the white dwarf. The positions of these are accurately constrained, and show
little movement from eclipse to eclipse, even over a number of years. The
colour of the emission from the two regions appears similar, although their
X-ray properties are known to be significantly different: we argue that the
usual accretion shock may be absent at the non-X-ray emitting region, and
instead the flow here interacts directly with the white dwarf surface;
alternatively, a special grazing occultation of this region is required. There
is no evidence for any quasi-periodic oscillations on time-scales of the order
of seconds, consistent with relatively stable cyclotron cooling in each
accretion region.


title: Radio Plasma as a Cosmological Probe

abstract:
  Plasma containing relativistic particles appears in various forms in the
inter galactic medium (IGM): As radio plasma released by active radio galaxies,
as fossil radio plasma from former radio galaxies - so called `radio ghosts',
as `cluster radio relics' in some clusters of galaxies, and as `cluster radio
halos'. The impact of the different forms of radio plasma on the IGM and their
use as diagnostic tools are briefly discussed.


title: Accretion and emission processes in AGN

abstract:
  The UV-X continuum, the X-ray spectral features, and the variability in these
bands provide powerful tools for studying the innermost regions of AGNs from
which we gain an insight into the accretion process. In this chapter the
discussion focusses on luminous AGN, i.e. Seyfert galaxies and quasars. The
standard accretion disk model (a stationary geometrically thin disk) is
described, and vertically averaged solutions for the radial structure are
given. The emission of the standard disk is discussed using different
approximations, and it is compared to the observations. This leads to the
conclusion that more complex models are required, such as the irradiated disk
and the disk-corona models. The advantage of this last model is that it
explains the overall UV-X spectral distribution. In the framework of these disk
models, the profile, intensity, and variability properties of the X-ray iron
line can be explained by reprocessing at the surface of the cold disk very
close to the black hole (the "relativistic disk model"). An alternative
possibility is discussed, where the UV-X continuum is produced by a
quasi-spherical distribution of dense clouds surrounded by (or embedded in) a
hot medium. In such a model the iron line profile could be due to
Comptonization instead of relativistic effects.


title: Dark Matter Search in the Edelweiss Experiment

abstract:
  Preliminary results obtained with 320g bolometers with simultaneous
ionization and heat measurements are described. After a few weeks of data
taking, data accumulated with one of these detectors are beginning to exclude
the upper part of the DAMA region. Prospects for the present run and the second
stage of the experiment, EDELWEISS-II, using an innovative reversed cryostat
allowing data taking with 100 detectors, are briefly described.


title: The Annulus-Filtered E and B Modes in CMBR Polarization

abstract:
  Although it has previously been recognized that the CMB polarization
measurement on a sky ring is able to separate the B and E-mode patterns, we
show that the rotational symmetry of the CMB polarization measurement is indeed
unique, in that it enables the B and E modes to be separately measured in a
simple and clean manner. The separation of B and E modes can in principle be
achieved even with a single-polarization detector of arbitrary beam pattern.
Based on this premise, a specific observing strategy is suggested, where the
telescope scans along a sky circle with the polarimeter axis always oriented to
a fixed direction with respect to the radial direction of the sky circle. The
observational strategy for B-mode measurements can further be refined by
choosing appropriate beam sizes to suppress the accidental E-mode leakage. We
present the expected variances of the measured E and B-mode surface-brightness
fluctuations as functions of the sky annulus radius and beam size. The measured
peak power is expected to be up to 10% of the total power contained in the CMB
polarization fluctuations for both B and E modes. The temperature-polarization,
or T-E, correlation can be measured by the present method as well. By adopting
this strategy, the AMiBA experiment is expected to detect, in a single sky
annulus, a 1\sigma$ B-mode signal in 340 hours.


title: Early Chandra X-ray Observations of Eta Carinae

abstract:
  Sub-arcsecond resolution Chandra observations of Eta Carinae reveal a 40
arcsec X 70 arcsec ring or partial shell of X-ray emission surrounding an
unresolved, bright, central source. The spectrum of the central source is
strongly absorbed and can be fit with a high-temperature thermal continuum and
emission lines. The surrounding shell is well outside the optical/IR bipolar
nebula and is coincident with the Outer Shell of Eta Carinae. The X-ray
spectrum of the Shell is much softer than that of the central source. The X-ray
Shell is irregular and only correlates well with optical features where a
bright X-ray knot coincides with a bright feature of the Outer Shell.
Implications for the binary model of the central source are discussed.


title: Evolution from OB Associations and Moving Groups to the Field Population

abstract:
  If we want to understand the evolution from star clusters to the Galactic
field star population, the Solar neighbourhood is an ideal place to start. It
contains objects from dense, very young clusters to old and almost dissolved
moving groups. I describe the observational evidence for the ongoing
dissolution of OB associations and open clusters. Subsequently, the
interpretation of the local phase space distribution of stars in terms of old
moving groups is discussed, emphasising the present limitations. Finally, I
discuss future observational requirements and the possibilities offered by
upcoming astrometric space missions.


title: The Be/X-ray transient 4U 0115+63/V635 Cas: II. Outburst mechanisms

abstract:
  We present multi-wavelength long-term monitoring observations of V635 Cas,
the optical counterpart to the transient X-ray pulsar 4U0115+63. The evolution
of emission lines and photometric magnitudes indicates that the Be star
undergoes relatively fast (~ 3-5 yr) quasi-cyclic activity, losing and
reforming its circumstellar disc. We show that the general optical, infrared
and X-ray behaviour can be explained by the dynamical evolution of the viscous
circumstellar disc around the Be star. After each disc-loss episode, the disc
starts reforming and grows until it reaches the radius at which the resonant
interaction of the neutron star truncates it. At some point, the disc becomes
unstable to (presumably radiative) warping and then tilts and starts
precessing. The tilting is very large and disc precession leads to a succession
of single-peaked and shell profiles in the emission lines. Type II X-ray
outbursts take place after the disc has been strongly disturbed and we
speculate that the distortion of the disc leads to interaction with the
orbiting neutron star.
  We discuss the implications of these correlated optical/X-ray variations for
the different models proposed to explain the occurrence of X-ray outbursts in
Be/X-ray binaries. We show that the hypothesis of mass ejection events as the
cause of the spectacular variability and X-ray outbursts is unlikely to be
meaningful for any Be/X-ray binary.


title: Non LTE radiation processes: application to the solar corona

abstract:
  These lectures are intended to present a simple but relatively complete
description of the theory needed to understand the formation of lines in
non-local thermodynamical equilibrium (NLTE), without appealing to any previous
knowledge except a few basics of physics and spectroscopy. After recalling
elementary notions of radiation transfer, the chapter is focussed on the
computation of the level populations, the source function, the ionization
state, and finally the line intensity. An application is made to forbidden
coronal lines which were observed during eclipses since decades.


title: A new test for the stable clustering hypothesis

abstract:
  The stable clustering hypothesis is a fundamental assumption about the
nonlinear clustering of matter in cosmology. It states that the mean physical
separation of particles is a constant on sufficiently small scales. While many
authors have attempted to test the hypothesis with cosmological N-body
simulations, no consensus has been reached on whether and where the hypothesis
is valid, because of the limited dynamical range this type of simulations can
achieve. In this Letter, we propose to test the hypothesis with high resolution
halo simulations, since the individual halo simulations can resolve much better
the fine structures of the halos and since almost all pairs of particles with
small separations are presumed to be inside virialized halos. We calculated the
mean pair velocity for 14 high resolution halos of $\sim 1$ million particles
in a low-density flat cold dark matter model. The result agrees very well with
the stable clustering prediction within the measurement uncertainty $\sim 30%$
over a large range of scales where the overdensity is $10^3$ to $10^6$. The
accuracy of the test can be improved to $\sim 10%$ if some 100 halos with a
similar resolution are analyzed.


title:
The Scaling of the Redshift Power Spectrum: Observations from the Las
  Campanas Redshift Survey

abstract:
  In a recent paper we have studied the redshift power spectrum $P^S(k,\mu)$ in
three CDM models with the help of high resolution simulations. Here we apply
the method to the largest available redshift survey, the Las Campanas Redshift
Survey (LCRS). The basic model is to express $P^S(k,\mu)$ as a product of three
factors P^S(k,\mu)=P^R(k)(1+\beta\mu^2)^2 D(k,\mu). Here $\mu$ is the cosine of
the angle between the wave vector and the line of sight. The damping function
$D$ for the range of scales accessible to an accurate analysis of the LCRS is
well approximated by the Lorentz factor D=[1+{1\over
2}(k\mu\sigma_{12})^2]^{-1}. We have investigated different values for $\beta$
($\beta=0.4$, 0.5, 0.6), and measured $P^R(k)$ and $\sigma_{12}(k)$ from
$P^S(k,\mu)$ for different values of $\mu$. The velocity dispersion
$\sigma_{12}(k)$ is nearly a constant from $k=0.5$ to 3 $\mpci$. The average
value for this range is $510\pm 70 \kms$. The power spectrum $P^R(k)$ decreases
with $k$ approximately with $k^{-1.7}$ for $k$ between 0.1 and 4 $\mpci$. The
statistical significance of the results, and the error bars, are found with the
help of mock samples constructed from a large set of high resolution
simulations. A flat, low-density ($\Omega_0=0.2$) CDM model can give a good fit
to the data, if a scale-dependent special bias scheme is used which we have
called the cluster-under-weighted bias (Jing et al.).


title:
Cosmological Evolution of the Universe Neutral Gas Mass Measured by
  Quasar Absorption Systems

abstract:
  The cosmological evolution of neutral hydrogen is an efficient way of tracing
structure formation with redshift. It indicates the rate of evolution of gas
into stars and hence the gas consumption and rate star formation history of the
Universe. In measuring HI, quasar absorbers have proven to be an ideal tool and
we use observations from a recent survey for high-redshift quasar absorption
systems together with data gathered from the literature to measure the
cosmological comoving mass density of neutral gas. This paper assumes
Omega_M=0.3, Omega_lambda=0.7 and h=0.65.


title: Detection of Cosmic Shear with the HST Survey Strip

abstract:
  Weak lensing by large-scale structure provides a unique method to directly
measure matter fluctuations in the universe, and has recently been detected
from the ground. Here, we report the first detection of this `cosmic shear'
based on space-based images. The detection was derived from the Hubble Space
Telescope (HST) Survey Strip (or Groth Strip), a 4' by 42' set of 28 contiguous
WFPC2 pointings with I<27. The small size of the HST Point-Spread Function
(PSF) affords both a lower statistical noise, and a much weaker sensitivity to
systematic effects, a crucial limiting factor of cosmic shear measurements. Our
method and treatment of systematic effects were discussed in an earlier paper
(Rhodes, Refregier & Groth 2000). We measure an rms shear of 1.8% on the WFPC2
chip scale (1.27'), in agreement with the predictions of cluster-normalized CDM
models. Using a Maximum Likelihood (ML) analysis, we show that our detection is
significant at the 99.5% confidence level (CL), and measure the normalization
of the matter power spectrum to be sigma8*Omega_m^(0.48) = 0.51 (+0.14,-0.17),
in a LambdaCDM universe. These 68% CL errors include (Gaussian) cosmic
variance, systematic effects and the uncertainty in the redshift distribution
of the background galaxies. Our result is consistent with earlier lensing
measurements from the ground, and with the normalization derived from cluster
abundance. We discuss how our measurement can be improved with the analysis of
a large number of independent WFPC2 fields.


title: Gas and Galaxy Evolution in Poor Groups of Galaxies

abstract:
  Poor groups of galaxies are the repositories of most of the baryons in the
local Universe and are environments in which galaxy evolution is likely to be
both more recent and simpler than in the cores of rich clusters. Yet we know
little about groups outside of our own Local Group. We discuss recent results
from optical, X-ray, and radio observations of nearby poor groups that focus on
the evolution of gas and galaxies in these common environments.


title: The Galactic Bulge: The Stellar and Planetary Nebulae Populations

abstract:
  We compare abundances patterns in the Bulge for elements observed in stars
and in planetary nebulae. Some alpha elements, like Mg and Ti, are overabundant
respect to Fe, and others are not, like He, O, Si, S, Ar, Ca. The first ones
favor a quick evolution of the Galactic Bulge, and the seconds a much slower
one.


title: Neutrinos from propagation of ultra-high energy protons

abstract:
  We present a calculation of the production of neutrinos during propagation of
ultra-high energy cosmic rays from their astrophysical sources to us.
Photoproduction interactions are modeled with the event generator SOPHIA that
represents very well the experimentally measured particle production cross
sections at accelerator energies. We give the fluxes expected from different
assumptions on cosmic ray source distributions, cosmic ray injection spectra,
cosmological evolution of the sources and different cosmologies, and compare
them to the Waxman-Bahcall limit on source neutrinos. We estimate rates for
detection of neutrino induced showers in a km3 water detector. The ratio of the
local high energy neutrino flux to the ultra-high energy cosmic ray flux is a
crucial parameter in distinguishing between astrophysical and cosmological
(top-down) scenarios of the ultra-high energy cosmic ray origin.


title:
Astrometric imaging of crowded stellar fields with only two SIM
  pointings

abstract:
  The Space Interferometry Mission (SIM) will observe sources in crowded
fields. Recent work has shown that source crowding can induce significant
positional errors in SIM's astrometric measurements, even for targets many
magnitudes brighter than all other crowding sources. Here we investigate
whether the spectral decomposition of the fringe pattern may be used to
disentangle the overlapping fringes from multiple blended sources, effectively
by performing synthesis imaging with two baselines. We find that spectrally
dispersed fringes enable SIM to identify and localize a limited number of field
sources quite robustly, thereby removing their effect from SIM astrometry and
reducing astrometry errors to near photon noise levels. We simulate SIM
measurements of the LMC, and show that (a) SIM astrometry will not be corrupted
by blending and (b) extremely precise imaging of mildly crowded fields may be
performed using only two orthogonal baseline orientations, allowing
microarcsecond positional measurements. We lastly illustrate the method's
potential with the example of astrometric microlensing, showing that SIM's mass
and distance measurements of lenses will be untainted by crowding.


title: Measuring Feedback in Damped Lyman Alpha Systems

abstract:
  We measure feedback (heating rates) in damped Lyman alpha systems from the
cooling rate of the neutral gas. Since cooling occurs through [C II] 158 micron
emission, we infer cooling from C II^{*} 1335.7 absorption lines detected with
HIRES on the Keck I telescope. The inferred heating rates are about 30 times
lower than for the Galaxy ISM. At z = 2.8, the implied star formation rate per
unit area is 10^{-2.4+-0.3} solar masses per kpc^{2} per year, and the the star
formation rate per unit comoving volume is 10^{-0.8+-0.2} solar masses per
Mpc^{3} per year. This is the first measurement of star formation rates in
objects likely to be the progenitors of current galaxies.


title:
Testing Comptonization models using BeppoSAX observations of Seyfert 1
  galaxies

abstract:
  We used high quality BeppoSAX data of 6 Seyfert galaxies to test realistic
thermal Comptonization models. Our main effort was to adopt a Comptonization
model taking into account the anisotropy of the soft photon field. The best fit
parameter values of the temperature and optical depth of the corona and of the
reflection normalization obtained fitting this class of models to the data are
substantially different from those derived fitting the same data with the power
law + cut--off model commonly used. The two models also provide different
trends and correlation between the physical parameters, which has major
consequences for the physical interpretation of the data


title:
Pair Creation at Shocks: Application to the High Energy Emission of
  Compact objects

abstract:
  We investigate the effect of pair creation on a shock structure. Actually,
particles accelerated by a shock can be sufficiently energetic to boost, via
Inverse Compton (IC) process for example, surrounding soft photons above the
rest mass electron energy and thus to trigger the pair creation process. The
increase of the associated pair pressure is thus able to disrupt the plasma
flow and possibly, for too high pressure, to smooth it completely. Reversely,
significant changes of the flow velocity profile may modify the distribution
function of the accelerated particles, modifying consequently the pair creation
rate. Stationary states are then obtained by solving self-consistently for the
particle distribution function and the flow velocity profile. We discuss our
results and the application of these processes to the high energy emission and
variability of compact objects.


title:
Constraints on the High Energy Continuum of Seyfert galaxies from RXTE
  Color-Color and Color-Flux Diagrams

abstract:
  We report on some results from a three-year program of RXTE observations of 4
Seyfert galaxies: NGC 4051, NGC 5548, MCG-6-30-15 and NGC 5506. We focus here
on color-color and color-flux diagrams obtained using the count-rates of the
PCA instrument in different energy ranges: 3--5, 5--7 and 7--10 keV. The data
of the different sources show interesting trends in the different color-color
and color-flux planes. These trends are quite similar from one source to the
other, even in the case of the narrow line Seyfert 1 NGC 4051 which exhibits
strong flux and spectral variability. We discuss these results in term of a
simple spectral model: a power law with high energy cut-off + reflection + Iron
line, with the scope of understanding the relations between the observed
variations of different components and the physical causes of the variability.


title:
Damping time and stability of density fermion perturbations in the
  expanding universe

abstract:
  The classic problem of the growth of density perturbations in an expanding
Newtonian universe is revisited following the work of Bisnovatyi-Kogan and
Zel'dovich. We propose a more general analytical approach: a system of free
particles satisfying semi-degenerate Fermi-Dirac statistics on the background
of an exact expanding solution is examined in the linear approximation. This
differs from the corresponding work of Bisnovatyi-Kogan and Zel'dovich where
classical particles fulfilling Maxwell-Boltzmann statistics were considered.
The solutions of the Boltzmann equation are obtained by the method of
characteristics. An expression for the damping time of a decaying solution is
discussed and a zone in which free streaming is hampered is found,
corresponding to wavelengths less than the Jeans one. In the evolution of the
system, due to the decrease of the Jeans length, those perturbations may lead
to gravitational collapse. At variance with current opinions, we deduce that
perturbations with lambda >=lambda_(J Max)/1.48 are able to generate structures
and the lower limit for substructures mass is M = M_(J max)/(1.48)^3 ~ M_(J
max)/3, where M_(J max) is the maximum value of the Jeans mass.


title: Massive Black Holes as Population III Remnants

abstract:
  Recent numerical simulations of the fragmentation of primordial molecular
clouds in hierarchical cosmogonies have suggested that the very first stars
(the so-called Population III) may have been rather massive. Here we point out
that a numerous population of massive black holes (MBHs) -- with masses
intermediate between those of stellar and supermassive holes -- may be the
endproduct of such an episode of pregalactic star formation. If only one MBH
with m > 150 msun formed in each of the `minihalos' collapsing at z=20 from
3-sigma fluctuations, then the mass density of Pop III MBHs would be comparable
to that of the supermassive variety observed in the nuclei of galaxies. Since
they form in high-sigma rare density peaks, relic MBHs are predicted to cluster
in the bulges of present-day galaxies as they become incorporated through a
series of mergers into larger and larger systems. Dynamical friction would
cause more than 50 (m/150 msun)^{1/2} such objects to sink towards the center.
The presence of a small cluster of MBHs in galaxy nuclei may have several
interesting consequences associated with tidal captures of ordinary stars
(likely followed by disruption), MBH capture by the central supermassive black
hole, gravitational wave radiation from such coalescences. Accreting
pregalactic MBHs may be detectable as ultra-luminous, off-nuclear X-ray
sources.


title: Spatio-Temporal Scaling of Solar Surface Flows

abstract:
  The Sun provides an excellent natural laboratory for nonlinear phenomena. We
use motions of magnetic bright points on the solar surface, at the smallest
scales yet observed, to study the small scale dynamics of the photospheric
plasma. The paths of the bright points are analyzed within a continuous time
random walk framework. Their spatial and temporal scaling suggest that the
observed motions are the walks of imperfectly correlated tracers on a turbulent
fluid flow in the lanes between granular convection cells.


title:
The Density Perturbation Power Spectrum to Second-Order Corrections in
  the Slow-Roll Expansion

abstract:
  We set up a formalism that can be used to calculate the power spectrum of the
curvature perturbations produced during inflation up to arbitrary order in the
slow-roll expansion, and explicitly calculate the power spectrum and spectral
index up to second-order corrections.


title: Candidate tidal dwarf galaxies associated with the Stephan's Quintet

abstract:
  We present kinematic and photometric evidence for the presence of seven
candidate tidal dwarf galaxies in Stephan's quintet. The central regions of the
two most probable parent galaxies, N7319 and N7318B, contain little or no gas
whereas the intragroup medium, and particularly the optical tails that seem to
be associated with N7318B are rich in cold and ionized gas.
  Two tidal-dwarf candidates may be located at the edge of a tidal tail, one
within a tail and for four others there is no obvious stellar/gaseous bridge
between them and the parent galaxy. Two of the candidates are associated with
HI clouds, one of which is, in addition, associated with a CO cloud. All seven
regions have low continuum fluxes and high H$\alpha$ luminosity densities
(F(H$\alpha$) = 1 -- 60 $\times$ 10$^{-14}$ erg s$^{-1}$ cm$^{-2}$). Their
magnitudes (M$_B =$ --16.1 to --12.6), sizes ($\sim$ 3.5 h$_{75}^{-1}$ kpc),
colors (typically $B-R = 0.7$) and gas velocity gradients ($\sim$ 8 -- 26
h$_{75}$ km s$^{-1}$ kpc$^{-1}$) are typical for tidal dwarf galaxies. In
addition the ratios between their star formation rates determined from
H$\alpha$ and from the B band luminosity are typical of other tidal dwarf
galaxies. The masses of the tidal dwarf galaxies in Stephan's quintet range
from $\sim$ 2 $\times$ 10$^8$ to 10$^{10}$ M$_\odot$ and the median value for
their inferred mass-to-light ratios is 7 M$_\odot$/L$_\odot$.


title:
The shape of "dark matter" halos in disc galaxies according to the
  modified dynamics

abstract:
  Analyses of halo shapes for disc galaxies are said to give incongruous
results. I point out that the modified dynamics (MOND) predicts for disc
galaxies a distribution of fictitious dark matter that comprises two
components: a pure disc and a rounder halo. The former dominates the true disc
in regions of small accelerations, where it controls the z-dynamics in the disc
(disc flaring etc.); it has a finite total mass. It also dominates the round
component near the centre where the geometry is nearly planar. The second
component controls motions far from the plane, has a total enclosed mass that
diverges linearly with radius, and determines the rotation curve at large
radii. Its ellipticity may be appreciable at small radii but vanishes
asymptotically. This prediction of MOND differs from what one expects from
galaxy-formation scenarios with dark matter.
  Analyses to date, which, as they do, assume one component--usually with a
constant ellipticity, perforce give conflicting results for the best-value
ellipticity, depending on whether they probe the disc or the sphere, small
radii or large ones.


title: Using Gravitational Lensing to study HI clouds at high redshift

abstract:
  We investigate the possibility of detecting HI emission from gravitationally
lensed HI clouds (akin to damped Lyman-$\alpha$ clouds) at high redshift by
carrying out deep radio observations in the fields of known cluster lenses.
Such observations will be possible with present radio telescopes only if the
lens substantially magnifies the flux of the HI emission. While at present this
holds the only possibility of detecting the HI emission from such clouds, it
has the disadvantage of being restricted to clouds that lie very close to the
caustics of the lens. We find that observations at a detection threshold of 50
micro Jy at 320 MHz (possible with the GMRT) have a greater than 20%
probability of detecting an HI cloud in the field of a cluster, provided the
clouds have HI masses in the range 5 X 10^8 M_{\odot} < M_{HI} < 2.5 X 10^{10}
M_{\odot}. The probability of detecting a cloud increases if they have larger
HI masses, except in the cases where the number of HI clouds in the cluster
field becomes very small. The probability of a detection at 610 MHz and 233 MHz
is comparable to that at 320 MHz, though a definitive statement is difficult
owing to uncertainties in the HI content at the redshifts corresponding to
these frequencies. Observations at a detection threshold of 2 micro Jy
(possible in the future with the SKA) are expected to detect a few HI clouds in
the field of every cluster provided the clouds have HI masses in the range 2 X
10^7 M_{\odot} < M_{HI} < 10^9 M_{\odot}. Even if such observations do not
result in the detection of HI clouds, they will be able to put useful
constraints on the HI content of the clouds.


title: The spectrum of V4334 Sgr (Sakurai's object) in August, 1998

abstract:
  Theoretical spectral energy distributions are computed for a grid of
hydrogen-deficient and carbon-rich model atmospheres with a range in T(eff) of
4000 - 5500 K and log g of 1.0 - 0.0, using the technique of opacity sampling,
and taking into account continuous, atomic line and molecular band absorption.
The energy distributions are compared with the spectrum of V4334 Sgr (Sakurai's
object) of August 12, 1998 in the wavelength interval 300-1000 nm. This
comparison yields an effective temperature of V4334 Sgr of T(eff) = 5250+/-200
K, and a value for the interstellar plus circumstellar reddening of E(B-V) =
1.3+/-0.1.


title: A Survey for Large Separation Lensed FIRST Quasars

abstract:
  Little is known about the statistics of gravitationally lensed quasars at
large (7''-30'') image separations, which probe masses on the scale of galaxy
clusters. We have carried out a survey for gravitationally-lensed objects,
among sources in the FIRST 20cm radio survey that have unresolved optical
counterparts in the digitizations of the Palomar Observatory Sky Survey. From
the statistics of ongoing surveys that search for quasars among FIRST sources,
we estimate that there are about 9100 quasars in this source sample, making
this one of the largest lensing surveys to date. Using broad-band imaging, we
have isolated all objects with double radio components separated by 5''-30'',
that have unresolved optical counterparts with similar BVI colours. Our
criteria for similar colours conservatively allow for observational error and
for colour variations due to time delays between lensed images. Spectroscopy of
these candidates shows that none of the pairs are lensed quasars. This sets an
upper limit (95% confidence) on the lensing fraction in this survey of
3.3x10^-4, assuming 9100 quasars. Although the source redshift distribution is
poorly known, a rough calculation of the expected lensing frequency and the
detection efficiencies and biases suggests that simple theoretical expectations
are of the same order of magnitude as our observational upper limit. Our
procedure is novel in that our exhaustive search for lensed objects does not
require prior identification of the quasars in the sample as such.
Characterization of the FIRST-selected quasar population will enable using our
result to constrain quantitatively the mass properties of clusters.


title:
Cosmic Rays below Z=30 in a diffusion model: new constraints on
  propagation parameters

abstract:
  Cosmic ray nuclei fluxes are expected to be measured with high precision in
the near future. For instance, high quality data on the antiproton component
could give important clues about the nature of the astronomical dark matter. A
very good understanding of the different aspects of cosmic ray propagation is
therefore necessary. In this paper, we use cosmic ray nuclei data to give
constraints on the diffusion parameters. Propagation is studied with
semi-analytical solutions of a diffusion model, and we give new analytical
solutions for radioactively produced species. Our model includes convection and
reacceleration as well as the standard energy losses. We perform a $\chi^2$
analysis over B/C data for a large number of configurations obtained by varying
the relevant parameters of the diffusion model. A very good agreement with B/C
data arises for a number of configurations, all of which are compatible with
sub-Fe/Fe data. Different source spectra $Q(E)$ and diffusion coefficients
$K(E)$ have been tried, but for both parameters only one form gives a good fit.
Another important result is that models without convection or without
reacceleration are excluded. We find that the various parameters, i.e. the
diffusion coefficient normalisation $K_0$ and spectral index $\delta$, the halo
thickness $L$, the Alfv\'en velocity $V_a$, and the convection velocity $V_c$
are strongly correlated. We obtain limits on the spectral index $\delta$ of
thediffusion coefficient, and in particular we exclude a Kolmogorov spectrum
($\delta = 1/3$).


title:
Scintillation measurements of the millisecond pulsar PSR J0030+0451 and
  pulsar space velocities

abstract:
  Scintillation observations of the nearby single millisecond pulsar (MSP) PSR
J0030+0451 were carried out with the Parkes 64m radiotelescope at three
different epochs in 1999. From analysis of the dynamic spectrum we obtained the
amplitude of the electron density power spectrum log C_N^2 ~= -3.33$ and a
scintillation velocity V_iss <~ 15 km s^-1. This result shows that the
Shklovskii effect on the spin-down rate \dot P is negligible. We also performed
a correlation analysis between pulsar proper motions (V_pm) and scintillation
velocities (V_iss) using updated measurements for a sample of 77 objects, 17 of
which are MSPs. The full sample shows a correlation coefficient r_s ~= 80% at
an extremely high significance level, while for the MSP sub-sample (excluding 2
outliers) we obtain r_s ~= 90%.


title: Microquasars: hard X-ray/gamma-ray emission

abstract:
  I review some of the basic observational details of jets from X-ray binaries,
or `microquasars'. It is shown that in both (Z and Atoll) NS and BHC systems
radio emission, and therefore jet formation, is correlated with the presence of
hard (30-500 keV) X-ray emission. At gamma-ray (> 500 keV) energies, the
relation is not so clear. Possible physical connections between the presence of
a jet, with a population of relativistic electrons, and the emission of hard
X-rays, are briefly discussed.


title: Chromatic Signatures in the Microlensing of GRB Afterglows

abstract:
  We calculate the radial surface brightness profile of the image of a
Gamma-Ray-Burst (GRB) afterglow. The afterglow spectrum consists of several
power-law segments separated by breaks. The image profile changes considerably
across each of the spectral breaks. It also depends on the density profile of
the ambient medium into which the GRB fireball propagates. Gravitational
microlensing by an intervening star can resolve the afterglow image. We
calculate the predicted magnification history of GRB afterglows as a function
of observed frequency and ambient medium properties. We find that intensive
monitoring of a microlensed afterglow lightcurve can be used to reconstruct the
parameters of the fireball and its environment, and provide constraints on
particle acceleration and magnetic field amplification in relativistic blast
waves.


title: GAIA: Composition, Formation and Evolution of the Galaxy

abstract:
  The GAIA astrometric mission has recently been approved as one of the next
two `cornerstones' of ESA's science programme, with a launch date target of not
later than mid-2012. GAIA will provide positional and radial velocity
measurements with the accuracies needed to produce a stereoscopic and kinematic
census of about one billion stars throughout our Galaxy (and into the Local
Group), amounting to about 1 per cent of the Galactic stellar population.
GAIA's main scientific goal is to clarify the origin and history of our Galaxy,
from a quantitative census of the stellar populations. It will advance
questions such as when the stars in our Galaxy formed, when and how it was
assembled, and its distribution of dark matter. The survey aims for
completeness to V=20 mag, with accuracies of about 10 microarcsec at 15 mag.
Combined with astrophysical information for each star, provided by on-board
multi-colour photometry and (limited) spectroscopy, these data will have the
precision necessary to quantify the early formation, and subsequent dynamical,
chemical and star formation evolution of our Galaxy. Additional products
include detection and orbital classification of tens of thousands of
extra-Solar planetary systems, and a comprehensive survey of some 10^5-10^6
minor bodies in our Solar System, through galaxies in the nearby Universe, to
some 500,000 distant quasars. It will provide a number of stringent new tests
of general relativity and cosmology. The complete satellite system was
evaluated as part of a detailed technology study, including a detailed payload
design, corresponding accuracy assesments, and results from a prototype data
reduction development.


title:
Determination of Omega_b From Big Bang Nucleosynthesis in the Presence
  of Regions of Antimatter

abstract:
  Production of regions of antimatter in the early universe is predicted in
many baryogenesis models. Small scale antimatter regions would annihilate
during or soon after nucleosynthesis, affecting the abundances of the light
elements. In this paper we study how the acceptable range in Omega_b changes in
the presence of antimatter regions, as compared to the standard big bang
nucleosynthesis. It turns out that it is possible to produce at the same time
both a low 4He value (Y_p < 0.240) and a low D/H value (D/H < 4e-5), but
overproduction of 7Li is unavoidable at large Omega_b.


title: The Effects of Magnetic Fields on Radiative Cooling Jets

abstract:
  We here review the results of recent studies of magnetic field effects on the
structure and evolution of overdense, radiative cooling, steady and pulsed jets
which were carried out with the help of fully three-dimensional MHD
simulations. Three initial magnetic field topologies are considered: (i) a
helical and (ii) a longitudinal field, both of which permeate the jet and the
ambient medium, and (iii) a pure toroidal field in the jet. Using a set of
parameters which is particularly suitable for protostellar jets, we examine the
emission structure of the internal knots and the leading working surface and
compare with a nonmagnetic baseline and also with 2-D MHD calculations.


title: Morphological fluctuations of large-scale structure: the PSCz survey

abstract:
  In a follow-up study to a previous analysis of the IRAS 1.2Jy catalogue, we
quantify the morphological fluctuations in the PSCz survey. We use a variety of
measures, among them the family of scalar Minkowski functionals. We confirm the
existence of significant fluctuations that are discernible in volume-limited
samples out to 200Mpc/h. In contrast to earlier findings, comparisons with
cosmological N-body simulations reveal that the observed fluctuations roughly
agree with the cosmic variance found in corresponding mock samples. While
two-point measures, e.g. the variance of count-in-cells, fluctuate only mildly,
the fluctuations in the morphology on large scales indicate the presence of
coherent structures that are at least as large as the sample.


title:
Very Red and Extremely Red Galaxies in the Fields of z ~ 1.5 Radio-Loud
  Quasars

abstract:
  We previously identified an excess of mostly red galaxies around 31 RLQs at
z=1-2. These fields have an ERO (extremely red object, R-K>6) density 2.7 times
higher than the field. Assuming the EROs are passively evolved galaxies at the
quasar redshifts, they have characteristic luminosities of only ~L^*. We also
present new observations of four z~1.54 RLQ fields: (1) Wide-field J & Ks data
confirm an Abell richness ~2 excess within 140" of Q0835+580 but an excess only
within 50" of Q1126+101. (2) In 3 fields we present deep narrow-band redshifted
H-alpha observations. We detect five candidate galaxies at the quasar
redshifts, a surface density 2.5x higher than the field. (3) SCUBA sub-mm
observations of 3 fields detect 2 quasars and 2 galaxies with SEDs best fit as
highly reddened galaxies at the quasar z. (4) H-band adaptive optics (AO)
imaging is used to estimate redshifts for 2 red, bulge-dominated galaxies using
the Kormendy relation. Both have structural redshifts foreground to the quasar,
but these are not confirmed by photometric redshifts, possibly because their
optical photometry is corrupted by scattered light from the AO guidestar. (5)
We use quantitative SED fits to constrain the photometric redshifts z_ph for
some galaxies. Most galaxies near Q0835+580 are consistent with being at its
redshift, including a candidate very old passively evolving galaxy. Many very &
extremely red objects have z_ph z_q, and dust reddening is required to fit most
of them, including many objects whose fits also require relatively old stellar
populations. Large reddenings of E(B-V)~0.6 are required to fit four J-K
selected EROs, though all but one of them have best-fit z_ph>z_q. These objects
may represent a population of dusty high-z galaxies underrepresented in
optically selected samples. (Abridged)


title: A Chandra detection of the radio hotspot of 3C123

abstract:
  Chandra X-ray Observatory observations of the powerful, peculiar radio galaxy
3C123 have resulted in an X-ray detection of the bright eastern hotspot, with a
1-keV flux density of ~ 5 nJy. The X-ray flux and spectrum of the hotspot are
consistent with the X-rays being inverse-Compton scattering of radio
synchrotron photons by the population of electrons responsible for the radio
emission (`synchrotron self-Compton emission') if the magnetic fields in the
hotspot are close to their equipartition values. 3C123 is thus the third radio
galaxy to show X-ray emission from a hotspot which is consistent with being in
equipartition. Chandra also detects emission from a moderately rich cluster
surrounding 3C123, with Lx (2-10 keV) = 2 x 10^44 ergs/s and kT ~ 5 keV, and
absorbed emission from the active nucleus, with an inferred intrinsic column
density of 1.7 x 10^22 cm^-2 and an intrinsic 2-10 keV luminosity of 10^44
ergs/s.


title: Detection of Earth-like Planets Using Apodized Telescopes

abstract:
  The mission of NASA's Terrestrial Planet Finder (TPF) is to find Earth-like
planets orbiting other stars and characterize the atmospheres of these planets
using spectroscopy. Because of the enormous brightness ratio between the star
and the reflected light from the planet, techniques must be found to reduce the
brightness of the star. The current favorite approach to doing this is with
interferometry: interfering the light from two or more separated telescopes
with a $\pi$ phase shift, nulling out the starlight. While this technique can,
in principle, achieve the required dynamic range, building a space
interferometer that has the necessary characteristics poses immense technical
difficulties. In this paper, we suggest a much simpler approach to achieving
the required dynamic range. By simply adjusting the transmissive shape of a
telescope aperture, the intensity in large regions around the stellar image can
be reduced nearly to zero. This approach could lead to construction of a TPF
using conventional technologies, requiring space optics on a much smaller scale
than the current TPF approach.


title: T Dwarf Discoveries by 2MASS

abstract:
  Over a dozen T dwarfs, brown dwarfs that exhibit methane absorption features
at 1.6 and 2.2 $\micron$, have been discovered by the 2MASS survey. We discuss
how the search for these objects has been made, point out some of the
limitations of using near-infrared data to find the warmest T dwarfs, and
highlight a few of the more interesting T dwarfs that have been identified in
2MASS data.


title: The Classification of T Dwarfs

abstract:
  We discuss methods for classifying T dwarfs based on spectral morphological
features and indices. T dwarfs are brown dwarfs which exhibit methane
absorption bands at 1.6 and 2.2 ${\mu}m$. Spectra at red optical (6300--10100
{\AA}) and near-infrared (1--2.5 ${\mu}m$) wavelengths are presented, and
differences between objects are noted and discussed. Spectral indices useful
for classification schemes are presented. We conclude that near-infrared
spectral classification is generally preferable for these cool objects, with
data sufficient to resolve the 1.17 and 1.25 ${\mu}m$ K I doublets lines being
most valuable. Spectral features sensitive to gravity are discussed, with the
strength of the K-band peak used as an example. Such features may be used to
derive a two-dimensional scheme based on temperature and mass, in analogy to
the MK temperature and luminosity classes.


title: Optical Spectroscopy of T Dwarfs

abstract:
  Optical spectra are presented for a sample of T dwarfs, obtained using the
Keck 10m Low Resolution Imaging Spectrograph. Dominant features are discussed,
including possible temperature diagnostics.


title:
Particle Energy And Acceleration Efficiencies In Highly Relativistic
  Shocks

abstract:
  In this paper we present an investigation of numerical Monte Carlo
simulations of the diffusive shock acceleration in the test particle limit.
Very high gamma flow astrophysical plasmas, have been used, from $\gamma_{up}$
$\sim50$ up to $\gamma_{up}$ $\sim1000$, which could be relevant to the
suggested models of AGNs Jets and their Central Engines as well as the
ultra-relativistic shock particle acceleration in Gamma Ray Burst (GRB)
fireballs. Particularly the energy gain per shock crossing and the time
constant for the above high relativistic processes is numerically calculated.
We explicitly find a considerable $\gamma^{2}$ energy boosting in the first
shock cycle, and in all subsequent shock cycles the particle energy is
multiplied by a large factor. Also a noted acceleration speed-up for the same
acceleration process has been observed. Both of those results are connected
with theoretical suggestions that a significant enhancement of the acceleration
process is possible due to relativistic effects not present at lower plasma
flow speeds. The acceleration speed-up and the mean energy-gain per shock cycle
found could efficiently justify the theory of the origin of Ultra High Energy
Cosmic Rays (UHECR) from the sites of GRBs.


title: Particle Spectra Of Ultra-Relativistic Shock Waves

abstract:
  Numerical Monte Carlo simulations of the diffusive shock acceleration in the
test particle limit are investigated. We simulate high relativistic flow
astrophysical plasmas for upstream $\gamma$ $\sim5$ and up to $\gamma$
$\sim1000$. These gamma values are relevant to the diffusive shock acceleration
models of Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRBs). The
spectral shape for the above high relativistic processes will be calculated.
This work presents distinctive spectral shapes with plateau-like
characteristics due to the relativistic effects and the spectral indexes are
found to be as flat as the flow becomes relativistic; the latter is in a very
good agreement with previous theoretical and numerical works concerning
relativistic plasma flows.


title:
Numerical Simulations Of Particle Acceleration In Relativistic Shocks
  With Application To AGN Central Engines

abstract:
  Numerical modelling is performed for extreme relativistic parallel shocks
with upstream Lorentz factor $\Gamma=50$. Assuming the scattering is either
large angle or over pitch angles $\sim \Gamma^{-1}$, spectral flattening and
shock aaceleration speed-up is found. The energy gain for the first shock cycle
is $\sim \Gamma^{2}$. The likely output from relativistic shocks due to the
infall from the accretion disk to the AGN black hole is computed. Neutrinos
from proton-gamma interactions may be detectable with planned neutrino
telescopes.


title:
The Duality of Spiral Structure, and a Quantitative Dust Penetrated
  Morphological Tuning Fork at Low and High Redshift

abstract:
  In the near-infrared, the morphology of older star-dominated disks indicates
a simple classification scheme (1) H$m$ where $m$ is the dominant harmonic, (2)
a pitch angle (derived from the Fourier spectra) associated with the rate of
shear A/$\omega$ in the stellar disk and (3) a `bar strength' parameter,
robustly derived from the gravitational potential or torque of the bar. A
spiral galaxy may present two radically different morphologies in the optical
and near-infrared regime; there is no correlation between our quantitative dust
penetrated tuning fork and that of Hubble. Applications of our $z\sim$0 Fourier
template to the HDF are discussed using $L$ and $M$ band simulations from an
8-m NGST; the rest-wavelength IR morphology of high-$z$ galaxies should
probably be a key factor in deciding the final choice of instruments for the
NGST.


title: Issues in Blazar Research

abstract:
  As an overview of blazar research, we briefly discuss some of the themes of
this conference, including the various types of blazars, blazar samples and
selection effects, unified schemes, evolution, and jet physics.


title: Population gradients in nearby dwarf galaxies

abstract:
  Recent results on the detection of substructure in dwarf spheroidal galaxies
are discussed. In most cases they show that, when a galaxy experiences multiple
SF episodes, the intermediate age population is more centrally concentrated
than the old population, and that the recent SF is even more concentrated
towards the central regions. Moreover, it appears that the spatial distribution
of stars becomes more and more irregular as younger and younger subpopulations
are considered. We illustrate how wide-area observations, allowing a
substantial coverage of dwarf spheroidals (in particular the satellites of the
Milky Way), has provided evidence for cosmologically old populations in every
dSph galaxy. All these results are placed in the broader scenario of population
gradients in nearby dwarf galaxies of different morphological types.


title:
Caltech Faint Galaxy Redshift Survey XIII: Spectral Energy Distributions
  for Galaxies in the Region of the Hubble Deep Field North

abstract:
  We introduce a new empirical function for modeling the spectral energy
distributions of galaxies. We apply it to a sample of 590 galaxies in the
region of the HDF with $z < 1.5$ using multi-color photometry with wide
wavelength coverage combined with spectroscopic redshifts from our 93% complete
R-selected redshift survey there. We find the following: As expected, galaxies
with strong signs of recent star formation (i.e. those which show emission
lines) have bluer continua in both the rest frame UV and the
optical/near-infrared. The redder galaxies tend to be more luminous. The SEDs
of actively star forming galaxies become bluer in the mean in the rest-frame UV
at higher redshift, which trend might arise from SED modeling errors. Aside
from this, we discern no change with redshift in the relationship between SED
characteristics and galaxy spectral type based on the strength of narrow
emission and absorption features. There is no evidence in our R-selected sample
that supports the existence of a substantial population of very dusty star
forming galaxies at z < 1.5. The overall pattern of the L(K) - z relationship
suggests that passive evolution at constant stellar mass is a good
approximation to the actual behavior of at least the most luminous galaxies in
this large sample of galaxies in the region of the HDF out to z \sim 1.5.
(abridged)


title: A Map-Making Algorithm for the Planck Surveyor

abstract:
  We present a parallel implementation of a map-making algorithm for CMB
anisotropy experiments which is both fast and efficient. We show for the first
time a Maximum Likelihood, minimum variance map obtained by processing the
entire data stream expected from the Planck Surveyor, under the assumption of a
symmetric beam profile. Here we restrict ourselves to the case of the 30 GHz
channel of the Planck Low Frequency Instrument. The extension to Planck higher
frequency channels is straightforward. If the satellite pointing periodicity is
good enough to average data that belong to the same sky circle, then the code
runs very efficiently on workstations. The serial version of our code also runs
on very competitive time-scales the map-making pipeline for current and
forthcoming balloon borne experiments.


title: Episodic accretion in magnetically layered protoplanetary discs

abstract:
  We study protoplanetary disc evolution assuming that angular momentum
transport is driven by gravitational instability at large radii, and
magnetohydrodynamic (MHD) turbulence in the hot inner regions. At radii of the
order of 1 AU such discs develop a magnetically layered structure, with
accretion occurring in an ionized surface layer overlying quiescent gas that is
too cool to sustain MHD turbulence. We show that layered discs are subject to a
limit cycle instability, in which accretion onto the protostar occurs in bursts
with an accretion rate of 10^{-5} solar masses / yr, separated by quiescent
intervals where the accretion rate is 10^{-8} solar masses / yr. Such bursts
could lead to repeated episodes of strong mass outflow in Young Stellar
Objects. The transition to this episodic mode of accretion occurs at an early
epoch (t < 1 Myr), and the model therefore predicts that many young
pre-main-sequence stars should have low rates of accretion through the inner
disc. At ages of a few Myr, the discs are up to an order of magnitude more
massive than the minimum mass solar nebula, with most of the mass locked up in
the quiescent layer of the disc at around 1 AU. The predicted rate of low mass
planetary migration is reduced at the outer edge of the layered disc, which
could lead to an enhanced probability of giant planet formation at radii of 1-3
AU.


title: Deep Observations of Lyman Break Galaxies

abstract:
  We summarise the main results of recent work on the Lyman break galaxy
population which takes advantage of newly commissioned instrumentation on the
VLT and Keck telescopes to push the detection of these objects to new
wavelengths and more sensitive limits. We focus in particular on near-infrared
observations targeted at detecting emission lines of [O II], [O III], and
H-beta and on the first tentative detection of Lyman continuum emission from
star forming galaxies at z = 3.


title: The Milky Way as a Key to Structural Evolution in Galaxies

abstract:
  Much of our effort in understanding the long-term evolution and morphology of
the Milky Way and other galaxies has focused on the equilibrium of its luminous
disk. However, the interplay between all components, seen and unseen, is a
major cause of observed features and drives evolution. I will review the key
underlying dynamics, and in a number of examples, show how this leads to
lopsidedness and offset nuclei, may trigger bars and cause warps. Indeed, the
Milky Way like most spiral galaxies show exhibit many of these features. In
addition, the mechanisms suggest that observed morphology depends on the
properties of the galaxy and only weakly on any particular disturbance. Because
of this convergence, understanding a galaxy's history will be subtle and
require the level of detail that study of the Milky Way can provide.


title: Crystallinity versus mass-loss rate in Asymptotic Giant Branch stars

abstract:
  Infrared Space Observatory (ISO) observations have shown that O-rich
Asymptotic Giant Branch (AGB) stars exhibit crystalline silicate features in
their spectra only if their mass-loss rate is higher than a certain threshold
value. Usually, this is interpreted as evidence that crystalline silicates are
not present in the dust shells of low mass-loss rate objects. In this study,
radiative transfer calculations have been performed to search for an
alternative explanation to the lack of crystalline silicate features in the
spectrum of low mass-loss rate AGB stars. It is shown that due to a temperature
difference between amorphous and crystalline silicates it is possible to
include up to 40% of crystalline silicate material in the circumstellar dust
shell, without the spectra showing the characteristic spectral features. Since
this implies that low mass-loss rate AGB stars might also form crystalline
silicates and deposit them into the Interstellar Medium (ISM), the described
observational selection effect may put the process of dust formation around AGB
stars and the composition of the predominantly amorphous dust in the
Interstellar Medium in a different light. Our model calculations result in a
diagnostic tool to determine the crystallinity of an AGB star with a known
mass-loss rate.


title: Relativistic superfluid models for rotating neutron stars

abstract:
  This article starts by providing an introductory overview of the theoretical
mechanics of rotating neutron stars as developped to account for the frequency
variations, and particularly the discontinuous glitches, observed in pulsars.
The theory suggests, and the observations seem to confirm, that an essential
role is played by the interaction between the solid crust and inner layers
whose superfluid nature allows them to rotate independently. However many
significant details remain to be clarified, even in much studied cases such as
the Crab and Vela. The second part of this article is more technical,
concentrating on just one of the many physical aspects that needs further
development, namely the provision of a satisfactorily relativistic (local but
not microscopic) treatment of the effects of the neutron superfluidity that is
involved.


title: Observations of Ultracool White Dwarfs

abstract:
  We present new spectroscopic and photometric measurements of the white dwarfs
LHS 3250 and WD 0346+246. Along with F351-50, these white dwarfs are the
coolest ones known, all with effective temperatures below 4000 K. Their
membership in the Galactic halo population is discussed, and detailed
comparisons of all three objects with new atmosphere models are presented. The
new models consider the effects of mixed H/He atmospheres and indicate that WD
0346+246 and F351-50 have predominantly helium atmospheres with only traces of
hydrogen. LHS 3250 may be a double degenerate whose average radiative
temperature is between 2000 and 4000 K, but the new models fail to explain this
object.


title: Three Dimensional Structure of the Milky Way Disk

abstract:
  We present a three dimensional model for the Milky Way fit to the
far-infrared (FIR) and near-infrared (NIR) data from the COBE/DIRBE instrument
for Galactic latitudes |b| < 30 degrees and to within 20 degrees of the
Galactic center. Because of the low optical depth at 240 microns, the FIR
emission traces the distribution of galactic dust in the Galaxy. We model the
dust distribution as due to three components: a warped exponential disk with
scale length 0.28 R_sun and a flaring scale height, a spiral arm component with
four arms as traced by Galactic HII regions, and the local (Orion) arm which
produces prominent emission features at galactic longitude l approx. 80 and
-100 degrees. A Cosmic Infrared Background of 1.07 MJy/sr is recovered,
consistent with previous determinations. The dust distribution is then used to
calculate absorption in J and K, and the stellar emission in these wavebands is
modeled with two components: a warped exponential disk with a scale length of
0.28 R_sun and a spiral arm component dominated by two arms. This small scale
length is consistent with a maximal disk model for our Galaxy, which is
inconsistent with the cuspy dark matter halos predicted in CDM models. We find
different amplitudes for the warp in the stars and dust, which starts within
the Solar Circle.


title:
A representative sample of Be stars IV: Infrared Photometry and the
  Continuum Excess

abstract:
  We present infra-red (JHK) photometry of 52 isolated Be stars of spectral
types O9--B9 and luminosity classes III--V. We describe a new method of
reduction, enabling separation of interstellar reddening and circumstellar
excess. Using this technique we find that the disc emission makes a maximum
contribution to the optical (B-V) colour of a few tenths of a magnitude. We
find strong correlations between a range of emission lines (H\alpha, Br\gamma,
Br11, and Br18) from the Be stars' discs, and the circumstellar continuum
excesses. We also find that stellar rotation and disc excess are correlated.


title: Estimate of the primordial magnetic field helicity

abstract:
  Electroweak baryogenesis proceeds via changes in the non-Abelian Chern-Simons
number. It is argued that these changes generate a primordial magnetic field
with left-handed helicity. The helicity density of the primordial magnetic
field today is then estimated to be given by $\sim 10^2 n_b$ where $n_b\sim
10^{-6}$ /cm$^3$ is the present cosmological baryon number density. With
certain assumptions about the inverse cascade we find that the field strength
at recombination is $\sim 10^{-13}$ G on a comoving coherence scale $\sim 0.1$
pc.


title: Deep HST imaging surveys and the formation of spheroidal galaxies

abstract:
  We have extended our previous analysis of morphologically selected elliptical
and S0 galaxies in the Hubble Deep Field (HDF) North to include HST data in the
HDF South and the HDFS-NICMOS areas. Our final sample amounts to 69 E/S0
galaxies with $K<20.15$ over an area of 11 square arcmins. Although a
moderately small number over a modest sky area, this sample benefits of the
best imaging and photometric data available on high-redshift galaxies.
Multi-waveband photometry allows us to estimate with good accuracy the
redshifts for the majority of these galaxies which lack a spectroscopic
measure. We confirm our previous findings that massive E/S0s tend to disappear
from flux-limited samples at $z>1.4$. This adds to the evidence that the
rest-frame colours and SEDs of the numerous objects found at $0.8<z<1.2$ are
inconsistent with a very high redshift of formation for the bulk of stars,
while they are better consistent with protracted (either continuous or
episodic) star-formation down to $z \le 1$. These results based on high-quality
imaging on a small field can be complemented with data from colour-selected
EROs on much larger sky areas: our claimed demise of E/S0s going from $z=1$ to
$z=1.5$ is paralleled by a similarly fast decrease in the areal density of EROs
when the colour limit is changed from $(R-K)=5$ to $(R-K)=6$ (corresponding to
$z\simeq 1$ and $z\simeq 1.3$ respectively). Altogether, the redshift interval
from 1 to 2 seems to correspond to a very active phase for the assembly of
massive E/S0 galaxies in the field, and also probably one where a substantial
fraction of their stars are formed.


title: Evolution of Lithium in the Milky Way

abstract:
  We adopt up-to-date 7Li yields from asymptotic giant branch stars in order to
study the temporal evolution of this element in the solar neighbourhood.
Several lithium stellar sources are considered besides the AGBs: Type II
supernovae, novae, low-mass giants. Galactic cosmic ray nucleosynthesis is
taken into account as well. We conclude that AGB stars do not substantially
contribute to 7Li enrichment on a Galactic scale. Therefore, a significant 7Li
production from novae and low-mass stars is needed to explain the late, steep
rise of the 7Li abundance in disk stars and the meteoritic 7Li abundance.


title: Fragmentation in Kinematically Cold Disks

abstract:
  Gravity is scale free. Thus gravity may form similar structures in
self-gravitating systems on different scales. Indeed, observations of the
interstellar medium, spiral disks and cosmic structures, reveal similar
characteristics. The structures in these systems are very lumpy and
inhomogeneous. Moreover some of these structures do not seem to be of random
nature, but obey certain power laws.
  Models of slightly dissipative self-gravitating disks show how such
inhomogeneous structures can be maintained on the kpc-scale. The basic physical
processes in these models are self-gravity, dissipation and differential
rotation. In order to explore the structures resulting from these processes,
local simulations of self-gravitating disks are performed in 2D and 3D. We
observe persistent patterns, formed by transient structures, whose intensity
and morphological characteristic depend on the dissipation rate.


title: N-Body Simulations of Open, Self-Gravitating Systems

abstract:
  Astrophysical systems differ often in two points from classical
thermodynamical systems: 1.) They are open and 2.) gravity is a dominant
factor. Both modifies the homogeneous equilibrium structure, known from
classical thermodynamics. In order to study the consequence for structure
formation in astrophysical systems, we carry out N-body simulations of
self-gravitating systems, subjected to an energy-flow. The simulations show
that physically realistic, time-dependent boundary conditions can maintain a
molecular cloud in a statistically steady state, out of thermodynamic
equilibrium.
  Moreover we perform some simple "gravo-thermal" N-body experiments and
compare them with theoretical results. We find negative specific heat in an
energy range predicted by Follana and Laliena (1999).


title: Why AGN Studies Need Higher Resolution

abstract:
  The need for high angular resolution is emphasised, especially in the context
of programs to understand massive black holes and the processes in their
environment.


title: Strange quark stars within the Nambu-Jona-Lasinio model

abstract:
  We investigate the properties of charge-neutral $\beta$-equilibrium cold
quark matter within the Nambu-Jona-Lasinio model. The calculations are carried
out for different ratios of coupling constants characterizing the vector and
scalar 4-fermion interaction, $\xi\equiv G_V/G_S$. It is shown that for $\xi <
0.4$ matter is self-bound and for $\xi < 0.65$ it has a first order phase
transition of the liquid-gas type. The Gibbs conditions in the mixed phase are
applied for the case of two chemical potentials associated with the baryon
number and electric charge. The characteristics of the quark stars are
calculated for $\xi = 0, 0.5$ and 1. It is found that the phase transition
leads to a strong density variation at the surface of these stars. For $\xi =
1$ the properties of quark stars show behaviors typical for neutron stars. At
$\xi\goo 0.4$ the stars near to the maximum mass have a large admixture of
strange quarks in their interiors.


title: Concluding Perspective

abstract:
  This contribution to the concluding session at IAU Symposium 205 offered
comments on some current controversies, including the scientific status of the
''multiverse'' concept and on the prospects for cosmology in the coming decade.


title: The Calar Alto Deep Imaging Survey: K-band Galaxy Number Counts

abstract:
  We present K-band number counts for the faint galaxies in the Calar Alto Deep
Imaging Survey (CADIS). We covered 4 CADIS fields, a total area of 0.2deg^2, in
the broad band filters B, R and K. We detect about 4000 galaxies in the K-band
images, with a completeness limit of K=19.75mag, and derive the K-band galaxy
number counts in the range of 14.25 < K < 19.75mag. This is the largest medium
deep K-band survey to date in this magnitude range. The B- and R-band number
counts are also derived, down to completeness limits of B=24.75mag and
R=23.25mag. The K-selected galaxies in this magnitude range are of particular
interest, since some medium deep near-infrared surveys have identified breaks
of both the slope of the K-band number counts and the mean B-K color at
K=17\sim18mag. There is, however, a significant disagreement in the K-band
number counts among the existing surveys. Our large near-infrared selected
galaxy sample allows us to establish the presence of a clear break in the slope
at K=17.0mag from dlogN/dm = 0.64 at brighter magnitudes to dlogN/dm = 0.36 at
the fainter end. We construct no-evolution and passive evolution models, and
find that the passive evolution model can simultaneously fit the B-, R- and
K-band number counts well. The B-K colors show a clear trend to bluer colors
for K > 18mag. We also find that most of the K=18-20mag galaxies have a B-K
color bluer than the prediction of a no-evolution model for an L_* Sbc galaxy,
implying either significant evolution, even for massive galaxies, or the
existence of an extra population of small galaxies.


title: Quasars in the 2MASS Second Incremental Data Release

abstract:
  Using the 2MASS Second Incremental Data Release, we have searched for near
infrared counterparts to 13214 quasars from the Veron-Cetty & Veron(2000)
catalog. We have detected counterparts within 4 arcsec for 2277 of the
approximately 6320 quasars within the area covered by the 2MASS Second
Incremental Data Release. Only 1.6% of these are expected to be chance
coincidences. Though this sample is heterogeneous, we find that known
radio-loud quasars are more likely to have large near-infrared-to-optical
luminosity ratios than radio-quiet quasars are, at a statistically significant
level. This is consistent with dust-reddened quasars being more common in
radio-selected samples than in optically-selected samples, due to stronger
selection effects against dust-reddened quasars in the latter. We also find a
statistically significant dearth of optically luminous quasars with large
near-infrared-to-optical luminosity ratios. This can be explained in a dust
obscuration model but not in a model where synchrotron emission extends from
the radio into the near-infrared and creates such large ratios. We also find
that selection of quasar candidates from the B-J/J-K color-color diagram,
modelled on the V-J/J-K selection method of Warren, Hewett & Foltz (2000), is
likely to be more sensitive to dust-obscured quasars than selection using only
infrared-infrared colors.


title: The X-ray Emission in Post-Merger Ellipticals

abstract:
  The evolution in X-ray properties of early-type galaxies is largely
unconstrained. In particular, little is known about how, and if, remnants of
mergers generate hot gas halos. Here we examine the relationship between X-ray
luminosity and galaxy age for a sample of early-type galaxies. Comparing
normalized X-ray luminosity to three different age indicators we find that
L_X/L_B increases with age, suggesting an increase in X-ray halo mass with time
after a galaxy's last major star-formation episode. The long-term nature of
this trend, which appears to continue across the full age range of our sample,
poses a challenge for many models of hot halo formation. We conclude that
models involving a declining rate of type Ia supernovae, and a transition from
outflow to inflow of the gas originally lost by galactic stars, offers the most
promising explanation for the observed evolution in X-ray luminosity.


title:
CO (J = 4-3) and [C I] Observations of the Carina Molecular Cloud
  Complex

abstract:
  We present large area, fully-sampled maps of the Carina molecular cloud
complex in the CO (J = 4 - 3) and neutral carbon [CI] 3P1 - 3P0 transitions.
These data were obtained using the 1.7 meter diameter Antarctic Submillimeter
Telescope and Remote Observatory (AST/RO). The maps cover an area of
approximately 3 square degrees with a uniform 1' spatial sampling. Analysis of
these data, in conjunction with CO (J = 1 - 0) data from the Columbia CO survey
and the IRAS HIRES continuum maps for the same region, suggests that the spiral
density wave shock associated with the Carina spiral arm may be playing an
important role in the formation and dissociation of the cloud complex, as well
as in maintaining the internal energy balance of the clouds in this region.
Massive stars form at the densest regions of the molecular cloud complex. The
winds and outflows associated with these stars have a disrupting effect on the
complex and inject mechanical energy into the parent clouds, while the UV
radiation from the young stars also heat the parent clouds. The present set of
data suggests, however, that massive stars alone may not account for the
energetics of the clouds in the Carina region. The details of the data and the
correlation among the various data sets hint at the possible role that the
spiral density wave shock plays in feeding interstellar turbulence and in
heating molecular clouds.


title: Calibrating nebular diagnostics of T_* and abundance

abstract:
  We obtained nebular spectroscopy of LMC HII regions having classified stellar
populations, thereby strongly constraining the ionization input parameters.
Using photoionization models, we then evaluate the performance of nebular
diagnostics of T_* and abundance. We introduce [Ne III]/H-beta as a nebular
diagnostic of the ionizing stellar T_*. In contrast to the widely-used
\eta-prime parameter, [Ne III]/H-beta has greater sensitivity to mid and early
O-stars, and is robust to nebular morphology and the presence of shocks. We
present a preliminary calibration of both T_* diagnostics for LMC metallicity.
We also introduce S234 = ([S II] + [S III] + [S IV])/H-beta as a diagnostic of
S abundance. S234 is much less sensitive to the nebular ionization parameter
than is S23 or R23. The intensity of [S IV]10.5 microns is easily estimated
from the optical and near-IR line ratios. We present calibrations of S23 and
S234 that are reliable at metallicities Z < 0.5 Z_sol.


title: A New ASCA and ROSAT Study of the Supernova Remnant: G272.2-3.2

abstract:
  G272.2-3.2 is a supernova remnant (SNR) characterized by an apparent
centrally brightened X-ray morphology and thermally dominated X-ray emission.
Because of this combination of Sedov-type (thermal emission) and non-Sedov type
(non-shell like morphology) features, the remnant is classified as a ``thermal
composite'' SNR. This class of remnant is still poorly understood due in part
to the difficulties in modeling accurately all the physical conditions which
shape the emission morphology. In this paper we present a combined analysis of
data from the ASCA and ROSAT satellites coupled with previous results at other
wavelengths. We find that the X-ray emission from G272.2-3.2 is best described
by a non-equilibrium ionization (NEI) model with a temperature around 0.70 keV,
an ionization timescale of 3200 cm^-3 yr and a relatively high column density
(NH about 10^22 atoms/cm^2). We look into the possible explanations for the
apparent morphology of G272.2-3.2 using several models (among which both cloud
evaporation and thermal conduction models). For each of the models considered
we examine all the implications on the evolution of G272.2-3.2.


title:
An Accurate, Easy to Use Abundace Scale for Globular Clusters Based on
  2.2um Spectra of Giant Stars

abstract:
  We present a new method for the determination of [Fe/H] for globular
clusters. This new method is based on moderate resolution (R~1500) near-IR
spectroscopy in the K-band of 6 to 10 of the brightest giants in a cluster. Our
calibration is derived from spectra of 105 stars in 15 globular clusters. From
measurements of the equivalent widths of three features in these spectra, Na,
Ca, and CO, we are able to reproduce the Zinn & West (1984) abundance scale as
updated by Harris (1996) to better than 0.10 dex for clusters with near solar
[Fe/H] down to an [Fe/H] of -1.8. Three advantages of this method are that it
can be used for metal rich, heavily reddened globulars in crowded fields, it
does not require any knowledge of any other cluster or stellar parameters such
as reddening, distance, or luminosity, and it requires only minimal telescope
time. If stellar (J-K)0 and MK values are available as well, the accuracy of
the [Fe/H] estimate is further improved. Observations of as few as three stars
per cluster still gives an [Fe/H] estimate wich is nearly as reliable as that
based on two to three times as many stars.
  The accuracy of an [Fe/H] value based on observations of CO absorption alone
is significantly less than that which results from the three spectroscopic
indices. However, we predict that space-based observations of this feature in
the integrated light of stellar systems will prove to be of great value for
abundance determinations at distances as far as the Coma cluster of galaxies.


title:
The z=0 Galaxy Luminosity Function: I. Techniques for Identification of
  Dwarf Galaxies at ~10 Mpc

abstract:
  We present a program to study the galaxy luminosity function (GLF) of the Leo
I and Coma I Groups at ~10 Mpc. We have surveyed over seven square degrees in
Leo I and ~11 square degrees in Coma I. In this paper, we detail the method we
have developed and implemented for identifying on morphological grounds
low-surface-brightness, M_R < -10 dwarf galaxies at a distance of 10 Mpc. We
also describe extensive Montecarlo simulations of artificial galaxies which we
use to tune our detection algorithms and evaluate our detection efficiency and
parameter recovery as a function of mu_R(0) and R_T. We find for a sub-set of
our Leo I data that at the 90% completeness level we can detect dwarfs
comparable to Antlia and Sculptor. Finally, we describe preliminary follow-up
observations which confirm we are detecting dwarf spheroidals in Leo I at 10
Mpc.


title:
The Formation of Stellar Clusters: Time Varying Protostellar Accretion
  Rates

abstract:
  Identifying the processes that determine strength, duration and variability
of protostellar mass growth is a fundamental ingredient of any theory of star
formation. I discuss protostellar mass accretion rates dM/dt from numerical
models which follow molecular cloud evolution from turbulent fragmentation
towards the formation of stellar clusters. In a dense cluster environment,
dM/dt is strongly time varying and influenced by the mutual interaction of
protostellar cores and their competition for accretion from the common cluster
gas reservoir. Even for protostars with similar final mass, the accretion
histories may differ dramatically. High-mass stars build up in the central
parts of dense, cluster-forming cloud regions. They begin to form in the early
phases of cluster evolution, and continue to grow at a high rate until the
available gas is exhausted or expelled by feedback. Lower-mass stars tend to
form at later phases, and dM/dt declines rapidly after a short initial phase of
strong growth. I present a simple fit formula for the time evolution of the
average dM/dt for protostars of different masses in a dense cluster
environment.


title: Measuring the Distribution of Galaxies Between Halos

abstract:
  We develop a method to measure the probability, P(N;M), of finding N galaxies
in a dark-matter halo of mass M from the theoretically determined clustering
properties of dark-matter halos and the observationally measured clustering
properties of galaxies. Knowledge of this function and the distribution of the
dark matter completely specifies all clustering properties of galaxies on
scales larger than the size of dark-matter halos. Furthermore, P(N;M) provides
strong constraints on models of galaxy formation, since it depends upon the
merger history of dark-matter halos and the galaxy-galaxy merger rate within
halos. We show that measurements from a combination of the 2MASS and SDSS or
2dFGRS datasets will allow P(N;M) averaged over halos occupied by bright
galaxies to be accurately measured for N=0-2.


title:
Soft X-ray AGN Luminosity Function from ROSAT Surveys II. Table of the
  binned Soft X-ray Luminosity Function

abstract:
  This is the second paper of our investigation of the 0.5-2 keV soft X-ray
luminosity function (SXLF) of active galactic nuclei (AGN) using results from
ROSAT surveys of various depth. The large dynamic range of the combined sample,
from shallow large-area ROSAT All-Sky Survey (RASS)-based samples to the
satellite's deepest pointed observation on the Lockman Hole, enabled us to
trace the behavior of the SXLF. While the first paper (Miyaji, Hasinger,
Schmidt 2000, hereafter paper I) emphasized the global behavior of the SXLF,
cosmological evolution and contribution to the soft X-ray background, this
paper presents actual numerical values for practical use of our results.
  To present the binned SXLF, we have used an improved estimator, which is free
from biases associated with the conventional 1/Va estimator.


title:
Dynamically tuning away the cosmological constant in effective scalar
  tensor theories

abstract:
  It is known that the cosmological constant can be dynamically tuned to an
arbitrary small value in classes of scalar tensor theories. The trouble with
such schemes is that effective gravity itself vanishes. We explore the
possibility of avoiding this ``no-go'' with a spatially varying effective
gravity. We demonstrate this in principle with the non-minimally coupled scalar
field having an additional coupling to a fermionic field. The expectation value
of the scalar field gets anchored to a non-trivial value inside compact
domains. But for the non-minimal coupling to the scalar curvature, these
configurations are analogous to the non-topological solutions suggested by Lee
and Wick. With non-minimal coupling, this leads to a peculiar spatial variation
of effective gravity. As before, one can dynamically have the long distance
(global) gravitational constant $G$ and ${\Lambda}$, the cosmological constant,
tending to zero. However, inside compact domains, $G$ can be held to a
universal (non-vanishing) value. Long distance gravitational effects turn out
to be indistinguishable from those expected of general theory of relativity
(GTR). There are two ways in which the ensuing theory may lead to a viable
effective gravity theory: (a) the compact domains could be of microscopic
(sub-nuclear) size, or (b) the domains could be large enough to accommodate
structures as large as a typical galaxy. Aspects of effective gravity and
cosmology that follow are described. A toy Freidman - Robertson - Walker (FRW)
model free from several standard model pathologies and characteristic features
emerges.


title: The X-Ray Structure of the Supernova Remnant 3C 400.2

abstract:
  We present here the results of an X-ray study of the supernova remnant 3C
400.2 (G53.6-2.2) using the ASCA data. 3C 400.2 has an unusual morphology at
radio wavelengths, suggesting two SNRs superposed along the same line of sight,
whereas its X-ray emission is known to be centrally peaked. We investigated the
X-ray spectral variation across the remnant using the ASCA GIS and the ROSAT
PSPC data. The X-ray spectra can be well fitted by thin thermal plasma models.
However, there is no significant variation in the temperature and the
ionization parameter across the remnant. We conclude that it is a single SNR
rather than two overlapping SNRs. The centrally peaked X-ray morphology and the
thin thermal emission with nearly cosmic abundances indicate that 3C 400.2
belongs to a class of ``mixed-morphology SNRs''. We found that the physical
parameters of 3C 400.2 are similar to those of other mixed-morphology SNRs. The
morphology of 3C 400.2 can be explained by a supernova explosion occurring near
to the edge of an interstellar cloud.


title: Evidence for Free Precession in the Pulsar B1642-03

abstract:
  We present an analysis of the timing data of the pulsar B1642-03, collected
over a span of 30 years between 1969 and 1999. During this interval, the timing
residuals exhibit cyclical changes with amplitude varying from 15 ms to 80 ms
and spacing of maxima varying from 3 years to 7 years. Interpretation of these
observed cyclical changes in terms of free precession suggests a wobble angle
of about 0.8 degrees.


title:
Methods of Determination of the Energy and Mass of Primary Cosmic Ray
  Particles at Extensive Air Shower Energies

abstract:
  Measurements of cosmic ray particles at energies above E = 5 x 10^{14} eV are
performed by large area ground based air shower experiments. Only they provide
the collection power required for obtaining sufficient statistics at the low
flux levels involved. In this review we briefly outline the physics and
astrophysics interests of such measurements and discuss in more detail various
experimental techniques applied for reconstructing the energy and mass of the
primary particles. These include surface arrays of particle detectors as well
as observations of Cherenkov- and of fluorescence light. A large variety of air
shower observables is then reconstructed from such data and used to infer the
properties of the primary particles via comparisons to air shower simulations.
Advantages, limitations, and systematic uncertainties of different approaches
will be critically discussed.


title: Galactic Winds in Irregular Starburst Galaxies

abstract:
  In this paper we present some results concerning the study of the development
of galactic winds in blue compact galaxies. In particular, we model a situation
very similar to that of the galaxy IZw18, the most metal poor and unevolved
galaxy known locally. To do that we compute the chemo-dynamical evolution of a
galaxy in the case of one istantaneous isolated starburst as well as in the
case of two successive instantaneous starbursts. We show that in both cases a
metal enriched wind develops and that the metals produced by the type Ia SNe
are lost more efficiently than those produced by type II SNe. We also find that
one single burst is able to enrich chemically the surrounding region in few
Myr. Both these results are the effect of the assumed efficiency of energy
transfer from SNe to ISM and to the consideration of type Ia SNe in this kind
of problem. The comparison with observed abundances of IZw18 suggests that this
galaxy is likely to have suffered two bursts in its life, with the previous
being less intense than the last one.


title: Circumnuclear kinematics in NGC 5248: the origin of nuclear spiral arms

abstract:
  We present for the first time a two-dimensional velocity field of the central
region of the grand-design spiral galaxy NGC 5248, at 0.9 arcsec spatial
resolution. The H-alpha velocity field is dominated by circular rotation. While
no systematic streaming motions are seen in the area of the nuclear
grand-design spiral or the circumnuclear ring, the amplitude of residual
velocities, after subtracting a model circular velocity field, reaches 20 km/s
in projection. The rotation curve levels out at around 140 km/s, after a
well-resolved and rather shallow rise. We have generated an analytical model
for the nuclear spiral and fitted it to our observations to obtain estimates of
the pattern speed of the spiral and the sound speed in the central region of
NGC 5248. Our results are consistent with a low pattern speed, suggesting that
the nuclear spiral rotates with the same rate as the main spiral structure in
NGC 5248, and thus that the spiral structure is coupled from scales of a few
hundred parsecs to several kiloparsecs. We have also compared the observed
structure and kinematics between the nuclear regions of NGC 5248 and M100.
Several similarities and differences are discussed, including the location of
the peak emission regions on major and minor axes, and the spiral arm streaming
motions. We find no kinematic evidence for a presence of a nuclear bar in NGC
5248.


title: Big-bang nucleosynthesis with the NACRE compilation

abstract:
  We update the Big Bang Nucleosynthesis (BBN) calculations on the basis of the
recent NACRE compilation of reaction rates. In particular, we calculate the
uncertainties related to the nuclear reaction rates on the abundances of 7Li
and compare our results with an other recent analysis.