title: Cosmic Rays in Clusters of Galaxies

abstract:
  We argue that clusters of galaxies have an intergalactic medium, which is
permeated by strong magnetic fields and also has a contribution of pressure
from cosmic rays. These two components of total pressure are probably highly
time dependent, and range probably between 1/10 of the gas pressure up to
equipartition between gas pressure and the sum of the two other components.
Radio galaxies are likely to provide the main source for both magnetic fields
and cosmic rays. In this concept it becomes easy to understand the occasional
mismatch between the total mass inferred from the assumption of hydrostatic
equilibrium derived purely from gas, and the total mass derived from lensing
data. We also suggest that the structure and topology of the magnetic field may
be highly inhomogeneous - at least over a certain range of scales, and may
contain long twisted filaments of strong magnetic fields, as on the Sun. The
analogy with the interstellar medium may be fruitful to explore further, where
we do not know where magnetic fields come from, but suspect that the cosmic
rays derive from supernova explosions. In such an analogy it becomes useful to
refer to "radio galaxy explosions" in clusters of galaxies. A full scale
exploration of all the implications, especially of the notion that occasionally
complete equipartition may be reached, is a task for the future.


title: The Relativistic Binary Pulsar B1913+16

abstract:
  We describe the results of a relativistic analysis of our observations of
binary pulsar B1913+16, up to the latest measurements in 2001 August.


title:
Photometric Properties of Galaxy Population in the Cluster EIS 0048-2942
  at z~0.64

abstract:
  ~Deep photometric data in the V-, R-, I-, z- and K-bands for the cluster of
galaxies EIS 0048-2942 are used to investigate the properties of the galaxy
populations at z~0.64 in a field of 2.5x2.5 Mpc^2. The sample of candidate
cluster members (N = 171) is selected by the photometric redshift technique and
is complete up to I=22.5. Galaxies were classified as spheroids and disks
according to the shape of the light profile in the I-band, as parametrized by
the Sersic index. In both optical and NIR, spheroids define a sharp
colour-magnitude sequence, whose slope and zero points are consistent with a
high formation redshift (z_f > 2). The disk population occupies a different
region in the colour-magnitude diagram, having bluer colours with respect to
the red sequence. Interestingly, we find some level of mixing between the
properties of the two classes: some disks lie on the colour-magnitude sequence
or are redder, while some spheroids turn out to be bluer. The spatial
distribution of cluster galaxies show a clumpy structure, with a main
over-density of radius ~0.5 Mpc, and at least two other clumps distant ~1 Mpc
from the center. The various sub-structures are mostly populated by the red
galaxies, while the blue population has an almost uniform distribution. The
fraction of blue galaxies in EIS 0048-2942 is f_B=0.11 +/-0.07. This is much
lower than what expected on the basis of the Butcher-Oemler effect at lower
redshifts.


title: Variety in Supernovae

abstract:
  Detailed observations of a growing number of supernovae have determined a
bloom of new peculiar events. In this paper we take a short tour through the SN
diversity and discuss some important, physical issues related to it. Because of
the role of SN Ia in determining the cosmological parameters, it is crucial to
understand the physical origin of even subtle, observed differences. An
important issue is also the reddening correction. We belive that the measure of
interstellar lines on medium resolution spectra of SNe can be used to derive
lower limits on the interstellar extinction. A few physical parameters of the
progenitor, namely radius, mass, density structure and angular momentum, may
explain most of the diversity of core-collapse events. In addition, if the
ejecta expand into a dense circumstellar medium the ejecta-CSM interaction may
dominate the observed outcome and provide a mean to probe the mass loss history
of the SN progenitor in the last stages of its evolution.


title:
The radiation properties of an accretion disk with a non-zero torque on
  its inner edge

abstract:
  The structure of the inner edge of the accretion disk around a black hole can
be altered, if the matter inside the marginally stable orbit is magnetically
connected to the disk. In this case, a non-zero torque is exerted on its inner
edge, and the accretion efficiency $\epsilon$ can be much higher than that in
the standard accretion disk model. We explore the radiation properties of an
accretion disk at its sonic point around a black hole with a time-steady torque
exerted on the inner edge of the disk. The local structure of the accretion
flow at the sonic point is investigated in the frame of general relativity. It
is found that the accretion flow will be optically thin at its sonic point for
most cases, if the additional accretion efficiency $\delta\epsilon$ caused by
the torque is as high as $\sim$10 %. The results imply that the variable torque
may trigger transitions of the flow between different accretion types.


title: Continued Radio Monitoring of the Gamma Ray Burst 991208

abstract:
  We present radio observations of the afterglow of the bright gamma-ray burst
GRB 991208 at frequencies of 1.4, 4.9 and 8.5 GHz, taken between two weeks and
300 days after the burst. The well-sampled radio light curve at 8.5 GHz shows
that the peak flux density peaked about 10 days after the burst and decayed
thereafter as a power-law t^-1.07. This decay rate is more shallow than the
optical afterglow with t^-2.2, which was measured during the first week. These
late-time data are combined with extensive optical, millimeter and centimeter
measurements and fitted to the standard relativistic blast wave model. In
agreement with previous findings, we find that an isotropic explosion in a
constant density or wind-blown medium cannot explain these broadband data
without modifying the assumption of a single power-law slope for the electron
energy distribution. A jet-like expansion provides a reasonable fit to the
data. In this case, the flatter radio light curve compared to the optical may
be due to emission from an underlying host galaxy, or due to the blastwave
making a transition to non-relativistic expansion. The model that best
represents the data is a free-form model in which it is assumed that the
broadband emission originates from a synchrotron spectrum, while the
time-evolution of the break frequencies and peak flux density are solved for
explicitly. Although the decay indices for most of the synchrotron parameters
are similar to the jet model, the evolution of the cooling break is unusually
rapid, and therefore requires some non-standard evolution in the shock.
(abridged)


title:
Cluster-Cluster Microlensing as a Probe of Intracluster Stars, MACHOs,
  and Remnants of the First Generation Stars

abstract:
  The galaxy cluster Abell 2152 is recently found to be forming a
cluster-cluster system with another, more distant cluster whose core is almost
perfectly aligned to that of A2152. We discuss the detectability of
microlensing events where a single star in the source cluster behind A2152 is
extremely magnified by an intracluster compact object in A2152. We show that a
search with an 8m-class telescope with a wide field of view, such as the
Subaru/Suprime-Cam, can probe intracluster compact objects with a wide mass
range of m_{co} ~ 10^{-5}-10^{10} M_sun, including ranges that have not yet
been constrained by any past observations. We expect that the event rate is
biased for the background cluster than the foreground cluster (A2152), which
would be a unique signature of microlensing, making this experiment
particularly powerful. The sensitivity of this experiment for the mass fraction
of compact objects would be 1-10% in the total dark matter of the cluster,
which is roughly constant against m_{co}, with a reasonable telescope time for
large telescopes (~10 nights). Therefore any compact objects in this mass range
can be detected or rejected as the dominant component of the dark matter. About
10 events are expected if 20% of the cluster mass is in a form of compact
objects with M ~ 1 M_sun, as claimed by the MACHO collaboration for the Milky
Way halo. Other possibly detectable targets include intracluster stars stripped
by galaxy interactions, and hypothetical very massive black holes (M >~ 100
M_sun) produced as remnants of the first generation stars, which might be
responsible for the recently reported excess of the cosmic infrared background
radiation that seems impossible to explain by normal galactic light.


title: Cosmology with Galaxy Clusters through the Sunyaev-Zel'dovich effect

abstract:
  Future Sunyaev-Zel'dovich effect (SZE) surveys will detect thousands of
clusters, many of them at high redshift. We show how the SZE number counts as a
function of flux can be used as a useful way of constraining the cosmological
model. The constraints can be dramatically improved if redshift information is
provided for a small subsample of the observed clusters. In this work we
present the constraints in Omega_m and Sigma_8 expected for a combined
mm-optical survey. The mm survey (Planck) providing the cluster number counts
as a function of flux and the optical survey (GTC) the redshift estimation of a
small subsample of the cluster catalogue. We also show how it is possible to
get an accurate estimate of the cluster flux using a non-parametric component
separation algorithm and how using morphological redshifts it is possible to
make a high-z preselection of the small subsample to be observed in the
optical.


title: Is the afterglow of Gamma Ray Burst 021004 unusual?

abstract:
  The bumpy light-curve of the bright optical afterglow (AG) of gamma ray burst
(GRB) 021004, its spectral evolution and its radio emission have been claimed
to be unusual. In the Cannonball Model of GRBs that is not the case. The very
early AG's shape is, as for GRB 990123, a direct tracer of the expected
circumburst density profile. The unprecedented precision of the data allows for
the ``resolution'' of two cannonballs (CBs) in the AG. These two CBs correspond
to the two pulses in the GRB and to the two wide humps in the AG light curve.
The smaller wiggles in the AG are, as for GRBs 000301c and 970508, to be
expected: they trace moderate deviations from a constant density interstellar
medium. The observed evolution of the optical spectrum is that predicted in the
CB model. The X-ray and radio emissions of GRB 021004 are also normal.


title: Uncertainties in Spiral Galaxy Projection Parameters

abstract:
  We investigate the impact of nonaxisymmetric structure on estimates of galaxy
inclinations and position angles. A new minimization technique is used to
obtain estimates of inclination and position angle from a global fit to either
photometric or kinematic data. We discuss possible systematic uncertainties
which are much larger than statistical uncertainties. Our investigation reveals
that systematic uncertainties associated with fitting photometric data dominate
the formal statistical uncertainties. For our sample of inclined galaxies, we
estimate that nonaxisymmetric features introduce inclination and position angle
uncertainties of approximately 5 degrees, on average. The magnitudes of these
uncertainties weaken the arguments for intrinsically elliptical galaxy disks.


title:
Discovery of water vapor megamaser emission from Mrk1419 (NGC 2690): An
  analogue of NGC 4258?

abstract:
  Water vapor emission at 22 GHz is reported from the nucleus of the LINER
galaxy Mrk 1419 (NGC 2960). Single-dish spectra of the maser source show
properties that are similar to those seen in NGC 4258, namely (1) a cluster of
systemic H2O features, (2) two additional H2O clusters, one red- and one
blue-shifted by about 475 km/s, (3) a likely acceleration of the systemic
features, and (4) no detectable velocity drifts in the red- and blue-shifted
features. Interpreting the data in terms of the paradigm established for NGC
4258, i.e. assuming the presence of an edge-on Keplerian circumnuclear annulus
with the systemic emission arising from the near side of its inner edge, the
following parameters are derived: Rotational velocity: 330-600 km/s; radius:
0.13-0.43 pc; binding mass: about 10 million solar masses. With the galaxy
being approximately ten times farther away than NGC 4258, a comparison of
linear and angular scales (the latter via Very Long Baseline Interferometry)
may provide an accurate geometric distance to Mrk 1419 that could be used to
calibrate the cosmic distance scale.


title:
Determining Tangential Peculiar Velocities of Clusters of Galaxies using
  Gravitational Lensing

abstract:
  We propose two new methods for measuring tangential peculiar velocities of
rich clusters of galaxies. Our first method is based on weak gravitational
lensing and takes advantage of the differing images of background galaxies
caused by moving and stationary gravitational potentials. Our second method is
based on measuring relative frequency shifts between multiple images of a
single strongly lensed background galaxy. We illustrate this method using the
example of galaxy cluster CL 0024+1654.


title: The AGN Paradigm: Radio-Quiet Objects

abstract:
  The current paradigm for radio-quiet AGNs is reviewed, taking into account
new results from recent large-scale surveys carried out from the ground and
from space. Topics include structure of the central engine, AGN demography,
fueling/triggering processes, and connection between the supermassive black
hole, host galaxy, circumnuclear starburst and AGN. Dependences on AGN power
and lookback time are pointed out in the discussion. Suggestions for future
avenues of research are mentioned in the last section.


title: The Evolution of a Mass-Selected Sample of Early-Type Field Galaxies

abstract:
  We investigate the evolution of mass-selected early-type field galaxies using
a sample of 28 gravitational lenses spanning the redshift range 0 < z < 1.
Based on the redshift-dependent intercept of the fundamental plane in the rest
frame B band, we measure an evolution rate of d log (M/L)_B / dz = -0.56 +/-
0.04 (all errors are 1 sigma unless noted) if we directly compare to the local
intercept measured from the Coma cluster. Re-fitting the local intercept helps
minimize potential systematic errors, and yields an evolution rate of d log
(M/L)_B / dz = -0.54 +/- 0.09. An evolution analysis of properly-corrected
aperture mass-to-light ratios (defined by the lensed image separations) is
closely related to the Faber-Jackson relation. In rest frame B band we find an
evolution rate of d log (M/L)_B / dz = -0.41 +/- 0.21, a present-day
characteristic magnitude of M_{*0} = -19.70 + 5 log h +/- 0.29 (assuming a
characteristic velocity dispersion of sigma_{DM*} = 225 km/s), and a
Faber-Jackson slope of gamma_{FJ} = 3.29 +/- 0.58. The measured evolution rates
favor old stellar populations (mean formation redshift z_f > 1.8 at 2 sigma
confidence for a Salpeter initial mass function and a flat Omega_m =0.3
cosmology) among early-type field galaxies, and argue against significant
episodes of star formation at z < 1.


title: BeppoSAX observation of the cluster Abell 970

abstract:
  We report new results on the cluster of galaxies Abell 970 obtained from
X-ray observation with BeppoSAX. Our analysis of the BeppoSAX MECS and LECS
data in the range [0.15-10] keV reveals a mean cluster gas temperature of kT =
4.46_{-0.15}^{+0.14}, a metallicity of Z = 0.31_{-0.04}^{+0.05} Z_\odot, and an
interstellar hydrogen absorption density column of N_H = 6.05_{-0.97}^{+1.29}
10^20 cm^-2. Moreover, we obtained azimuthally averaged radial profiles of
these quantities. Our results are consistent with the hypothesis that Abell 970
has been disturbed by a past merger or by the ongoing merger process of a
substructure, that put the cluster out of equilibrium. This is also
demonstrated by the offset between the gas and galaxy distributions. Combining
the X-ray data with a recently published analysis of new galaxy radial
velocities, we conclude that a subcluster 8 arcmin to the NW is falling into
Abell 970 and will merge in a few Gigayears, thus disturbing Abell 970's newly
acquired equilibrium. The high alpha-elements/iron ratio that we derive for
this cluster supports the hypothesis of early intracluster medium enrichment by
Type II supernovae.


title:
Damped Lyman alpha systems and galaxy formation models - II. High ions
  and Lyman limit systems

abstract:
  We investigate a model for the high-ionization state gas associated with
observed damped Lyman-alpha systems, based on a semi-analytic model of galaxy
formation set within the paradigm of hierarchical structure formation. In our
model, the hot gas in halos and sub-halos gives rise to CIV absorption, while
the low-ionization state gas is associated with the cold gas in galaxies. The
model matches the distribution of CIV column densities and leads naturally to
kinematic properties that are in good agreement with the data.
  We examine the contribution of both hot and cold gas to sub-damped systems
and suggest that the properties of these systems can be used as an important
test of the model. We expect that sub-DLA systems will generally be composed of
a single gas disk and thus predict that they should have markedly different
kinematics than the damped systems.
  Finally, we find that hot halo gas produces less than one third of Lyman
limit systems at redshift three. We model the contribution of mini-halos (halos
with virial velocities < 35 km/s) to Lyman limit systems and find that they may
contain as much gas as is observed in these systems. However, if we adopt
realistic models of the gas density distribution we find that these systems are
not a significant source of Lyman limit absorption. Instead we suggest that
uncollapsed gas outside of virialized halos is responsible for most of the
Lyman limit systems at high redshift.


title:
Extended X-ray emission around four 3C quasars at 0.55<z<0.75 observed
  with Chandra

abstract:
  We report on the detection of a soft spatially-extended component of X-ray
emission around four intermediate-redshift 3C quasars observed with Chandra:
3C254, 3C263, 3C275.1 and 3C281. The bolometric luminosity of this emission
ranges over 0.3-1.6 times 10^{44}erg/s, and extends to lengthscales of over 350
kpc at the redshift of the quasar. The X-rays are most likely thermal emission
from the intracluster medium of a cluster of galaxies around each quasar, which
provides the working surface for the powerful radio lobes. Some X-ray emission
is also seen to be associated with the radio plasma.


title: Stationary models of relativistic magnetohydrodynamic jets

abstract:
  Highly relativistic jets are most probably driven by strong magnetic fields
and are launched from the accretion disk surrounding a central black hole. In
this paper we review some of our recent results considering the two-dimensional
magnetic field structure and the dynamics of collimating relativistic jets.
Applying the stationarity assumption enables us to calculate global solutions
of the relevant MHD equations. We discuss solutions of the Grad-Shafranov
equation obtained in a general relativistic context applying the 3+1 formalism
for Kerr geometry. These solutions extend from the inner light surface around
the Kerr black hole to the asymptotic regime of a cylindrically collimated jet
with a finite radius. In a further step, we include differential rotation of
the foot points of the field lines. Considering the general relativistic MHD
wind equation, we investigate the dynamics of the collimating jet, in
particular the effects of Kerr metric on the acceleration. Temperature and
density follow a power law. Having at hand a relativistic MHD jet solution, we
calculate the thermal optically thin X-ray spectrum for the innermost hot part
of the jet. Doppler shift and boosting is taken into account. For microquasars
we obtain a jet X-ray luminosity 10^33 erg/s. Iron emission lines are clearly
visible.


title:
The Correlation between X-ray spectral slope and FeKalpha line energy in
  radio-quiet active galactic nuclei

abstract:
  A significant correlation between FeKalpha line energy and X-ray spectral
slope has been discovered among radio-quiet active galactic nuclei. The
ionization stage of the bulk of the FeKalpha emitting material is not the same
in all active galactic nuclei and is related to the shape of the X-ray
continua. Active galactic nuclei with a steep X-ray spectrum tend to have a
fluorescence FeKalpha line from highly ionized material. In the narrow-line
Seyfert 1 galaxies with steeper X-ray spectrum (Gamma_X > 2.1), the FeKalpha
line originates from highly ionized material. In the Seyfert 1 galaxies and
quasars with flatter X-ray spectrum (Gamma_X < 2.1), bulk of the FeKalpha
emission arises from near neutral or weakly ionized material. The correlation
is an important observational characteristic related to the accretion process
in radio quiet active galactic nuclei and is driven by a fundamental physical
parameter which is likely to be the accretion rate relative to the Eddington
rate.


title:
Time-Dependent Photoionization in a Dusty Medium II: Evolution of Dust
  Distributions and Optical Opacities

abstract:
  The interaction of a radiation field with a dusty medium is a relevant issue
in several astrophysical contexts. We use the time-dependent photoionization
code in a dusty medium developed by Perna & Lazzati (2002), to study the
modifications in the dust distribution and the relative optical opacities when
a strong X-ray UV radiation flux propagates into a medium. We find that
silicates are preferentially destroyed with respect to graphite, and the
extinction curve becomes significantly flatter (hence implying less reddening),
with the characteristic bump at lambda 2175 A highly suppressed, due to the
destruction of the small graphite grains. This could explain the observational
lack of such a feature in GRB afterglow and AGN spectra. For a very intense and
highly variable source irradiating a compact and dense region, time variability
in the optical opacity resulting from dust destruction can be observed on a
relatively short timescale. We show that, under these circumstances, monitoring
the time variability of the opacity can yield powerful clues on the properties
of dust in the environment of the source. In particular, it allows to break the
observational degeneracy as to whether a grey extinction is the result of a low
dust-to-gas ratio or of a dust grain distribution that is skewed towards large
grains.


title: Line Profiles from Different Accretion Engine Geometries

abstract:
  Line profiles represent an important probe of the geometry and dynamics of
the central accretion engines in AGN. Although a flat disk illuminated from
above can explain the relativistic Fe K alpha line profile in some cases,
current data, plausible disk physics, and future comparison to the iron and
other AGN lines invite some consideration of other geometries. General features
of line profiles calculated fom concave discs, warped discs, thick clumpy
(inflow/outflow) discs, and disks with spiral structure, are briefly
summarized.


title:
XMM-Newton observations of ULIRGs I: A Compton-thick AGN in
  IRAS19254-7245

abstract:
  We present the XMM-Newton observation of the merging system IRAS 19254-7245,
also known as The Superantennae, whose southern nucleus is classified as a
Seyfert 2 galaxy. The XMM-Newton data have allowed us to perform a detailed
X-ray imaging and spectral analysis of this system. We clearly detect, for the
first time in this system, a strong EW ~ 1.4 keV Fe emission line at 6.49+/-0.1
keV (rest-frame). The X-ray spectrum requires a soft thermal component (kT~0.9
keV; L(0.5-2) ~ 4E41 cgs), likely associated with the starburst, and a hard
power-law continuum above 2 keV (observed L(2-10) ~ 4E42 cgs). We confirm the
flatness of this latter component, already noted in previous ASCA data. This
flatness, together with the detection of the strong Fe-Kalpha line and other
broad band indicators, suggest the presence of a Compton-thick AGN with
intrinsic luminosity > 1E44 cgs. We show that a Compton-thick model can
perfectly reproduce the X-ray spectral properties of this object.


title:
DarkSUSY - A numerical package for supersymmetric dark matter
  calculations

abstract:
  The question of the nature of dark matter in the Universe remains one of the
most outstanding unsolved problems in basic science. One of the best motivated
particle physics candidates is the lightest supersymmetric particle, assumed to
be the lightest neutralino. We here describe DarkSUSY, an advanced numerical
FORTRAN package for supersymmetric dark matter calculations. With DarkSUSY one
can: (i) compute masses and compositions of various supersymmetric particles;
(ii) compute the relic density of the lightest neutralino, using accurate
methods which include the effects of resonances, pair production thresholds and
coannihilations; (iii) check accelerator bounds to identify allowed
supersymmetric models; and (iv) obtain neutralino detection rates for a variety
of detection methods, including direct detection and indirect detection through
antiprotons, gamma-rays and positrons from the Galactic halo or neutrinos from
the center of the Earth or the Sun.


title: The positron excess and supersymmetric dark matter

abstract:
  Using a new instrument, the HEAT collaboration has confirmed the excess of
cosmic ray positrons that they first detected in 1994. We explore the
possibility that this excess is due to the annihilation of neutralino dark
matter in the galactic halo. We confirm that neutralino annihilation can
produce enough positrons to make up the measured excess only if there is an
additional enhancement to the signal. We quantify the `boost factor' that is
required in the signal for various models in the Minimal Supersymmetric
Standard Model parameter space, and find that a boost factor >30 provides good
fits to the HEAT data. Such an enhancement in the signal could arise if we live
in a clumpy halo.


title:
Global Three-Dimensional Simulations of Black Hole Accretion Disks:
  X-ray Flares in the Plunging Region

abstract:
  We present the results of three-dimensional global resistive
magnetohydrodynamic (MHD) simulations of black hole accretion flows. General
relativistic effects are simulated by using the pseudo-Newtonian potential.
Initial state is an equilibrium model of a torus threaded by weak toroidal
magnetic fields. As the magnetorotational instability (MRI) grows in the torus,
mass accretes to the black hole by losing the angular momentum. We found that
in the innermost plunging region, non-axisymmetric accretion flow creates
bisymmetric spiral magnetic fields and current sheets. Mass accretion along the
spiral channel creates one armed spiral density distribution. Since the
accreting matter carries in magnetic fields which subsequently are stretched
and amplified due to differential rotation, current density increases inside
the channel. Magnetic reconnection taking place in the current sheet produces
slow mode shock waves which propagate away from the reconnection site. Magnetic
energy release in the innermost plunging region can be the origin of X-ray
shots observed in black hole candidates. Numerical simulations reproduced soft
X-ray excess preceding the peak of the shots, X-ray hardening at the peak of
the shot, and hard X-ray time lags.


title: CI Aquilae: a recurrent nova with an unusually long plateau phase

abstract:
  We present the results of optical photometry of the recurrent nova CI Aql in
later phase of the outburst which occurred in 2000. Our observation revealed
that the object reached the quiescent level between 2001 December and 2002
April and therefore that CI Aql is a unique recurrent nova characterized by an
extremely long (1.4--1.7 yr) plateau phase. The light curve obtained in the
outburst suggests that the object is the first example of an intermediate
between classical novae and recurrent novae. In comparison with estimation
given in published theoretical calculations, the long duration of the plateau
phase supports a higher hydrogen content of the white-dwarf envelope, while
such an abundance of hydrogen requires a later cessation of the wind which is
in disagreement with the sudden fading observed in late November of 2000. The
light curve obtained in later phase of the outburst indicates that the object
was fainter and the gradual decline was steeper than predicted. These
discrepancies between the observation and theoretical prediction require
drastic modification of the present model of CI Aql.


title: Influence of geometry in the delayed detonation model of SNIa

abstract:
  We present several hydrodynamical simulations of thermonuclear supernovae
dealing with multiple delayed detonations. The calculations were carried out in
three dimensions, making possible to study the influence of geometry of the
flame front in two aspects. First, the evolution of its fractal dimension
during the deflagration phase has been followed until a critical value is
reached such that the deflagration may turn into a detonation. Second, as the
resulting detonation could probably be scattered through the flame, the effect
of its initial location on the detonation propagation, final energetics and
nucleosynthesis has been explored.


title: The Vertical Structure of the Halo Rotation

abstract:
  New GSC-II proper motions of RR Lyrae and Blue Horizontal Branch (BHB) stars
near the North Galactic Pole are used to show that the Galactic Halo 5 kpc
above the Plane has a significantly retrograde galactic rotation.


title:
The Cosmic Lens All-Sky Survey: statistical strong lensing, cosmological
  parameters, and global properties of galaxy populations

abstract:
  Extensive analyses of statistical strong gravitational lensing are performed
based on the final Cosmic Lens All Sky Survey (CLASS) well-defined statistical
sample of flat spectrum radio sources and current estimates of galaxy
luminosity functions per morphological type. The analyses are done under the
assumption that galactic lenses are well-approximated by singular isothermal
ellipsoids and early-type galaxies evolved passively since redshift $z \sim 1$.
Depending on how the late-type galaxy population is treated (i.e., whether its
characteristic velocity dispersion is constrained or not), we find for a flat
universe with a cosmological constant that the present matter fraction of the
present critical density $\Omega_{\rm m} = 0.31^{+0.27}_{-0.14}$ (68%) for the
unconstrained case or $0.40^{+0.28}_{-0.16}$ (68%) for the constrained case,
with an additional systematic uncertainty of $\approx 0.11$ arising from the
present uncertainty in the distribution of CLASS sources in redshift and flux
density. For a flat universe with a constant equation of state for dark energy
w = $p_x$(pressure)/$\rho_x$(energy density), we find that $w <
-0.55^{+0.18}_{-0.11}$ (68%) for the unconstrained case or $w <
-0.41^{+0.28}_{-0.16}$ (68%) for the constrained case. For the equal
frequencies of oblates and prolates, we find that $\sigma_{*}^{(e)} =
198^{+22}_{-18}$ km s$^{-1}$ (68%) for a `steep' $\alpha^{(e)}=-1$ or
$\sigma_{*}^{(e)} = 181^{+18}_{-15}$ km s$^{-1}$ (68%) for a `shallow'
$\alpha^{(e)}=-0.54$. Finally, from the relative frequencies of doubly-imaged
sources and quadruply-imaged sources, we find that a mean projected mass
ellipticity of early-type galaxies $\bar{\epsilon}_{\rm mass} = 0.42$ with a
68% lower limit of 0.28. (Abridged)


title: Polarization Evolution of the GRB 020405 Afterglow

abstract:
  Polarization measurements for the optical counterpart to GRB 020405 are
presented and discussed. Our observations were performed with the VLT-UT3
(Melipal) during the second and third night after the gamma-ray burst
discovery. The polarization degree (and the position angle) appears to be
constant between our two observations at a level around (1.5 - 2)%. The
polarization can be intrinsic but it is not possible to unambiguously exclude
that a substantial fraction of it is induced by dust in the host galaxy.


title:
A search for the radio counterpart of the unidentified gamma-ray source
  3EG J1410-6147

abstract:
  We have made radio continuum, HI and X-ray observations in the direction of
the unidentified EGRET source 3EG J1410-6147, using the Australia Telescope
Compact Array and the Chandra X-ray Observatory. The observations encompass the
supernova remnant (SNR) G312.4-0.4 and the two young pulsars PSRs J1412-6145
and J1413-6141.
  We derive a lower distance limit of 6 kpc to the SNR, although interpretation
of positive velocity features in the HI spectrum may imply the SNR is more
distant than 14 kpc. PSR J1412-6145, with an age of 50 kyr, is the pulsar most
likely associated with SNR G312.4-0.4. X-rays are not detected from either
pulsar and diffuse X-ray emission near the bright western edge of the SNR is
weak. Although there is circumstantial evidence that this western region is a
pulsar wind nebula (PWN), the embedded pulsar PSR J1412-6145 is apparently not
sufficiently powerful to explain the radio enhancement. The origin of the
electron acceleration in this region and of the gamma-rays remain unidentified,
unless the distance to PSR J1413-6141 is at least a factor of 3 lower than its
dispersion measure distance.


title: H-band observations of the Chandra Deep Field South

abstract:
  We report preliminary results of our H-band survey of the Chandra Deep Field
South (CDFS). The observations were made using SofI on the NTT, and cover 0.027
square degrees with a 50% completeness limit of H = 20.5, and 0.17 square
degrees with a 50% completeness limit of H =19.8. We used SExtractor to extract
sources from our fields. In total we have detected 4819 objects. Star-galaxy
separation was performed using the SExtractor parameter ``stellarity index''.
All objects with an index of 0.5 or lower were classified as galaxies.
According to this criterion, 80 % of our detections are galaxies. We then
compare our results with previous observations of the CDFS. Our astrometric
solutions are in good agreement with the Las Campanas Infrared Survey (LCIRS),
the COMBO-17 and the ESO-EIS surveys. The photometry of our catalog compares
satisfactorily with the results of the LCIRS, as well as with the GOODS data.
Galaxy number counts are presented and compared with the LCIRS results. The
present data are intended to complement the recent and future multi-wavelenghth
observations of the CDFS and will be used, in conjuction with additional
multiband photometry, to find counterparts of the upcoming mid-infrared surveys
with SIRTF.


title:
Semi-Analytic Estimates of Lyapunov Exponents in Lower-Dimensional
  Systems

abstract:
  Recent work has shown that statistical arguments, seemingly well-justified in
higher dimensions, can also be used to derive reasonable, albeit less accurate,
estimates of the largest Lyapunov exponent ${\chi}$ in lower-dimensional
Hamiltonian systems. This letter explores the detailed assumptions incorporated
into these arguments. The predicted values of ${\chi}$ are insensitive to most
of these details, which can in any event be relaxed straightforwardly, but {\em
can} depend sensitively on the nongeneric form of the auto-correlation function
characterising the time-dependence of an orbit. This dependence on dynamics
implies a fundamental limitation to the application of thermodynamic arguments
to such lower-dimensional systems.


title: Weak CSS Sources from FIRST Survey

abstract:
  We report early results of an observational campaign targeted on a sample of
compact steep spectrum sources selected from the FIRST survey which are
significantly weaker than those investigated before. The selection criteria and
procedure are given in detail. We present here an assortment of MERLIN and VLBI
observations and make some general comments based on the morphologies of the
sources presented.


title: VLT and HST Observations of the Host Galaxy of GRB990705

abstract:
  We present VLT spectroscopic observations of Gamma-Ray Burst (GRB) 990705
host galaxy and highlight the benefits provided by the prompt-phase features of
GRBs to derive the redshifts of the latter. In the host spectrum, we indeed
detect an emission feature which we attribute to the [OII] 3726/3729 Angstrom
doublet and derive an unambiguous redshift z=0.8424+/-0.0002 for this galaxy.
This is in full agreement with the value z~0.86+/-0.17 previously derived using
a transient absorption edge discovered in the X-ray spectrum of GRB990705. This
burst is therefore the first GRB for which a reliable redshift was derived from
the prompt phase emission itself, as opposed to redshift determinations
performed using putative host galaxy emission lines or intestellar absorption
lines in the GRB afterglows. Deep and high resolution images of the host of
GRB990705 with the HST/STIS camera reveal that the burst occured in a nearly
face-on Sc spiral galaxy typical of disk-dominated systems at 0.75<z<1.
Assuming a cosmology with Ho=65km/s/Mpc, Omega_m=0.3 and Omega_lambda=0.7, we
derive an absolute B magnitude M_B=-21.75 for this galaxy and a star formation
rate SFR ~ 5-8~Msol/yr. Finally, we discuss the implications of using X-ray
transient features to derive GRB redshifts with larger burst samples, and
especially examine the case of short and dark-long GRBs.


title:
"Fundamental-Plane"-Like Relations From Collisionless Stellar Dynamics:
  A Comparison of Mergers and Collapses

abstract:
  We present a new set of dissipationless N-body simulations aiming to better
understand the pure dynamical aspects of the ``Fundamental Plane'' (FP) of
elliptical galaxies. We have extended our previous hierarchical merger scheme
by considering the Hernquist profile for the initial galaxy model.
Two-component Hernquist galaxy models were also used to study the effect of
massive dark halos on the end-products characteristics. We have also performed
new collapse simulations including initial spin. We found that the
one-component Hernquist mergers give results similar to those found for the
one-component King models, namely both were able to build-up small scatter
FP-like correlations with slopes consistent with what is found for the
near-infrared FP of nearby galaxies. The two-component models also reproduce a
FP-like correlation, but with a significantly steeper slope. This is in
agreement with what has been found for elliptical galaxies at higher redshift
(0.1 $<$ z $<$ 0.6). We discuss some structural properties of the simulated
galaxies and their ability to build-up FP-like correlations. We confirm that
collapses generally do not follow a FP-like correlation regardless of the
initial spin. We suggest that the evolution of gradients in the gravitational
field of the merging galaxies may be the main ingredient dictating the final
non-homology property of the end products.


title: The blue colors of Gamma-ray burst host galaxies

abstract:
  There is now an increasing number of evidence supporting the idea that the
cosmic Gamma-ray Bursts (GRBs) originate from the collapse of massive stars in
distant star-forming galaxies. Because GRBs are likely detectable up to very
high redshift, and because the gamma-rays are not attenuated by intervening
columns of gas and dust, these phenomena thus offer a unique perspective to
probe the star formation in the early Universe independently of the biases
associated with dust extinction. We report on the R-K colors of the GRB host
galaxies. We find that they are very blue sources, with colors comparable to
those of the faint blue star-forming galaxies at high redshift.


title: Location of Weak CSS Sources on the Evolutionary Path of Radio-loud AGN

abstract:
  According to the currently accepted paradigm compact steep spectrum (CSS)
sources are precursors of larger/older objects and gigahertz peaked spectrum
(GPS) sources may be earlier stages of CSS sources. In this paper we confront
this paradigm with the outcome of recent observations of CSS sources that are
significantly weaker than those known before. In particular we claim that not
all CSS sources must end up as large scale objects; if the activity phase of an
AGN's central engine is shorter than the lifetime of a large scale radio source
(up to ~10^8 years) the radio source associated with such an AGN decays
earlier, e.g. at the CSS stage. We point out that a theory of thermal-viscous
instabilities in the accretion disks of AGN may explain many features of radio
sources at all stages of their evolution.


title:
Deriving the redshift of distant galaxies with Gamma-Ray Burst transient
  edges

abstract:
  Cosmological Gamma-Ray Bursts (GRBs) offer a unique perspective to probe the
evolution of distant galaxies. We discuss one of the multiple benefits of this
approach, i.e. the detection of transient edges in the GRB prompt phase
emission. These absorption features can be used to directly derive the redshift
of GRBs and their host galaxies without the need of any optical spectroscopic
follow-up.


title: A Method of Correcting Near-Infrared Spectra for Telluric Absorption

abstract:
  We present a method for correcting near-infrared medium-resolution spectra
for telluric absorption. The method makes use of a spectrum of an A0V star,
observed near in time and close in airmass to the target object, and a
high-resolution model of Vega, to construct a telluric correction spectrum that
is free of stellar absorption features. The technique was designed specifically
to perform telluric corrections on spectra obtained with SpeX, a 0.8-5.5
micron, medium-resolution cross-dispersed spectrograph at the NASA Infrared
Telescope Facility, and uses the fact that for medium resolutions there exist
spectral regions uncontaminated by atmospheric absorption lines. However, it is
also applicable (in a somewhat modified form) to spectra obtained with other
near-infrared spectrographs. An IDL-based code that carries out the procedures
is available for downloading via the World Wide Web from the IRTF website.


title: Broadband Modeling of GRB 021004

abstract:
  We present a broadband modeling of the afterglow of GRB 021004. The optical
transient of this burst has been detected very early and densely sampled in
several bands. Its light curve shows significant deviations from a simple power
law. We use the data from the X-ray to the $I-$band gathered in the first month
of observations, and examine three models. Two involve variations in the energy
of the shock. The first (energy injection) allows only increases to the shock
energy, while the second (patchy shell) allows the energy to increase or
decrease. In the final model (clumpy medium) the energy of the shock is
constant while the density varies. While all three models reproduce well the
optical bands, the variable density model can best account for the X-ray data,
and the energy-injection model has the poorest fit. None of the models can
account for the modest color variations observed during the first few days of
the burst.


title:
A Search for H2 Outflow Signatures from Massive Star Formation Regions
  Containing Linearly Distributed Methanol Masers

abstract:
  I present here the summary of results from a survey by De Buizer (2003)
searching for outflows using near-infrared imaging. Targets were massive young
stellar objects associated with methanol masers in linear distributions.
Presently, it is a widely held belief that these methanol masers are found in
(and delineate) circumstellar accretion disks around massive stars. A way to
test the disk hypothesis is to search for outflow signatures perpendicular to
the methanol maser distributions. The main objective of the survey was to
obtain wide-field near-infrared images of the sites of linearly distributed
methanol masers using a narrow-band 2.12 micron filter which is centered on the
H2 v=1-0 S(1) line. This line is a shock diagnostic that has been shown to
successfully trace CO outflows from young stellar objects. Twenty-eight sources
in total were imaged with eighteen sources displaying H2 emission. Of these,
only TWO sources showed emission found to be dominantly perpendicular to the
methanol maser distribution. These results seriously question the hypothesis
that methanol masers exist in circumstellar disks.


title: Updated Nucleosynthesis Constraints on Unstable Relic Particles

abstract:
  We revisit the upper limits on the abundance of unstable massive relic
particles provided by the success of Big-Bang Nucleosynthesis calculations. We
use the cosmic microwave background data to constrain the baryon-to-photon
ratio, and incorporate an extensively updated compilation of cross sections
into a new calculation of the network of reactions induced by electromagnetic
showers that create and destroy the light elements deuterium, he3, he4, li6 and
li7. We derive analytic approximations that complement and check the full
numerical calculations. Considerations of the abundances of he4 and li6 exclude
exceptional regions of parameter space that would otherwise have been permitted
by deuterium alone. We illustrate our results by applying them to massive
gravitinos. If they weigh ~100 GeV, their primordial abundance should have been
below about 10^{-13} of the total entropy. This would imply an upper limit on
the reheating temperature of a few times 10^7 GeV, which could be a potential
difficulty for some models of inflation. We discuss possible ways of evading
this problem.


title:
A hidden population of Wolf-Rayet stars in the massive galactic cluster
  Westerlund 1

abstract:
  We report the discovery of a hitherto undetected population of Wolf-Rayet
stars in the young galactic open cluster Westerlund 1. Optical spectroscopy of
the cluster identified 11 such objects; provisional classification suggests
that 6 are nitrogen rich (WN) and 5 carbon rich (WC). Including the previously
identified Blue, Yellow and Red Super- & Hypergiants, Westerlund 1 clearly has
a very rich population of massive post-Main Sequence objects. To date, the
post-MS population of Westerlund 1 is significantly larger than that of any
other galactic young open cluster - with the possible exception of the Arches -
implying that it is potentially amongst the most massive young clusters yet
identified in the Local Group.


title: Internal structure of a thin transonic disk

abstract:
  The internal structure of the thin transonic disk accreting onto a
nonrotating black hole inside the last stable orbit ($r < 3r_{\rm g}$) is
considered within the hydrodynamical version of the Grad-Shafranov equation. It
is shown that in the vicinity of the sonic surface takes place a sharp
diminishing of the disk thickness. As a result, in the vertical balance
equation the dynamical forces $\rho[({\bf v}\nabla){\bf v}]_{\theta}$ become
important, these on the sonic surface being of the same order as the pressure
gradient $\nabla_{\theta} P$. In the supersonic region the thickness of the
disk is determined by the form of ballistic trajectories rather than by the
pressure gradient.


title: New Pulsars from Arecibo Drift-Scan Searches

abstract:
  We report new pulsars discovered in drift-scan data taken by two
collaborations (Berkeley/Cornell and STScI/NAIC) during the latter stages of
the Arecibo upgrade period. The data were taken with the Penn State Pulsar
Machine and are being processed on the COBRA cluster at Jodrell Bank.
Processing is roughly 70% complete and has resulted in the detection of 10 new
and 31 known pulsars, in addition to a number of pulsar candidates. The 10 new
pulsars include one pulsar with a spin-period of 55 ms and another with a spin
period of 5.8 ms. At the completion of the processing, we expect to have
discovered roughly 20 new pulsars. All new pulsars are being subjected to a
program of followup observations at Arecibo to determine spin and astrometric
parameters.


title:
Estimates of Stellar Weak Interaction Rates for Nuclei in the Mass Range
  A=65-80

abstract:
  We estimate lepton capture and emission rates, as well as neutrino energy
loss rates, for nuclei in the mass range A=65-80. These rates are calculated on
a temperature/density grid appropriate for a wide range of astrophysical
applications including simulations of late time stellar evolution and x-ray
bursts. The basic inputs in our single particle and empirically inspired model
are i) experimentally measured level and weak decay information, ii) estimates
of matrix elements for allowed experimentally-unmeasured transitions based on
the systematics of experimentally observed allowed transitions, and iii)
estimates of the centroids of the GT resonances motivated by shell model
calculations in the fp shell as well as by (n,p) and (p,n) experiments.
Transitions involving Fermi resonances (isobaric analog states) are also
included and dominate the rates for many interesting proton rich nuclei for
which an experimentally-determined ground state lifetime is unavailable. To
compare our results with more detailed shell model based calculations we also
calculate weak rates for nuclei in the mass range A=60-65 for which Langanke
and Martinez-Pinedo have provided rates. The typical deviation in the electron
capture and B- decay rates for these ~30 nuclei is less than a factor of two or
three for a wide range of temperature and density appropriate for pre-supernova
stellar evolution. We also discuss some subtleties associated with the
partition functions used in calculations of stellar weak rates and show that
the proper treatment of the partition functions is essential for estimating
high temperature beta decay rates. Partition functions based on un-converged
Lanczos calculations can result in estimates of high temperature beta decay
rates that are systematically low.


title: Two populations among the metal-poor field RR Lyrae stars

abstract:
  We compute the spatial velocity components and the galactic orbital elements
for 209 metal-poor $([Fe/H] < -1.0)$ RRLyrae (ab) variable stars in the solar
neighborhood using proper motions, radial velocities, and photometric distances
available in the literature. We observe abrupt changes in the stellar spatial
and kinematical characteristics when the peculiar velocities relative to the
local standard of rest cross the threshold value, $V_{\rm pec}\approx 280$
\mbox{km s$^{-1}$}. This provides evidence that the general population of
metal-poor RRLyrae stars is not uniform, and includes two spherical subsystems
occupying different volumes in the Galaxy. Based on the agreement between
typical parameters of corresponding subsystems of field RRLyrae stars and of
the globular clusters, studied by us earlier, we conclude that metal-poor stars
and globular clusters can be subdivided into two populations, but using
different criteria for stars and clusters. We suppose that field stars with
fast motion and clusters with redder horizontal branches constitute the
spheroidal subsystem of the accreted outer halo, with is approximately two
times larger in size than the first subsystem. It has absolutely no metallicity
gradients, most of its stars have eccentric orbits, many stars display
retrograde motion in the Galaxy, and their ages are comparatively low,
supporting the hypothesis that the objects in this subsystem have an
extragalactic origin.


title: Results from the Antarctic Muon and Neutrino Detector Array (AMANDA)

abstract:
  We show new results from both the older and newer incarnations of AMANDA
(AMANDA-B10 and AMANDA-II, respectively). These results demonstrate that AMANDA
is a functioning, multipurpose detector with significant physics and
astrophysics reach. They include a new higher-statistics measurement of the
atmospheric muon neutrino flux and preliminary results from searches for a
variety of sources of ultrahigh energy neutrinos: generic point sources,
gamma-ray bursters and diffuse sources producing muons in the detector, and
diffuse sources producing electromagnetic or hadronic showers in or near the
detector.


title:
Pearson-Readhead Survey Sources II: The Longterm Centimeter-band Total
  Flux and Linear Polarization Properties of a Complete Radio Sample

abstract:
  Using UMRAO centimeter-band total flux density and linear polarization
monitoring observations of the complete Pearson-Readhead extragalactic source
sample obtained between August 1984 and March 2001, we identify the range of
variability in extragalactic objects as functions of optical and radio
morphological classification, and relate total flux density variations to
structural changes in published coeval VLBI maps in selected objects. We have
identified preferred orientations of the electric vector of the polarized
emission at 14.5 and 4.8 GHz in roughly half of the objects, and compared these
with orientations of the flow direction indicated by VLBI morphology. When
comparing the distributions of the orientation offsets for the BL Lacs and for
the QSOs, we find differences in both range and mean value, in support of
intrinsic class differences. In the shock-in-jet scenario, we attribute this to
the allowed range of obliquities of shocks developing in the flow relative to
the flow direction. The fact that we find longterm stability in EVPA over many
events implies that a dominant magnetic field orientation persists; in the
core-dominated objects, with small contribution from the underlying quiescent
jet, this plausibly suggests that the magnetic field has a longterm memory,
with subsequent shock events exhibiting similar EVPA orientation, or,
alternatively, the presence of a standing shock in the core. We have looked for
systematic, monotonic changes in EVPA which might be expected in the emission
from a precessing jet, a model currently invoked for some AGNs; none were
identified. Further, we carried out a Scargle periodogram analysis of the total
flux density observations, but found no strong evidence for periodicity in any
of the sample sources.


title:
Determining the spectroscopic mass ratio in interacting binaries:
  Application to X-Ray Nova Sco 1994

abstract:
  We present a model for determining the mass ratio in interacting binaries by
directly fitting the observed spectrum with synthetic spectra. We make direct
use of NextGen model atmospheres intensities which are the most comprehensive
and detailed models available for cool stars. We fully take into account the
varying temperature and gravity across the secondary star's photosphere, by
incorporating the synthetic spectra into the secondary star's Roche geometry.
As a result, we determine the exact rotationally broadened spectrum of the
secondary star and so eliminate the need for a limb-darkening law, and the
uncertainties associated with it. As an example we determine the mass ratio for
the well studied soft X-ray transient Nova Sco 1994. In order to obtain a more
accurate determination of the mass ratio, which does not depend on assumptions
about the rotation profile and limb-darkening coefficients, we use our model to
compute the exact rotationally broadened model spectrum, which we compare
directly with the observed intermediate resolution spectrum of Nova Sco 1994.
We determine the mass ratio of Nova Sco 1994 to be 0.419+/-0.028 (90 percent
confidence), which is the most accurate determination of the binary mass ratio
in an X-ray binary. This result combined with the binary mass function and
inclination angle gives a refined black hole mass of 5.99+\-0.42 Mo (90 percent
confidence). We also perform simulations which show that, for an F-type
secondary star, the standard rotation profile with zero and continuum value for
the line limb-darkening coefficient gives a value for q that brackets the value
found using the full geometrical treatment.


title:
The Chandra Deep Field-North Survey. XIV. X-ray detected Obscured AGNs
  and Starburst Galaxies in the Bright Submm Source Population

abstract:
  We provide X-ray constraints and perform the first X-ray spectral analyses
for bright (f_850>=5mJy; S/N>=4) SCUBA sources in an 8.4'x8.4' area of the 2 Ms
Chandra Deep Field-North survey containing the Hubble Deep Field-North. X-ray
emission is detected from 7 of the 10 bright submm sources in this region,
corresponding to an X-ray detected submm source density of ~360 deg^-2 (>~36%
of the bright submm source population). Two of the X-ray detected sources have
nearby (within 3") X-ray companions, suggesting merging/interacting sources or
gravitational lensing effects, and 3 lie within the approximate extent of a
proto-cluster candidate. Five of the X-ray detected sources have flat X-ray
spectral slopes, suggesting obscured AGN activity. X-ray spectral analyses
suggest that one of these AGNs may be a Compton-thick source; of the other 4
AGNs, 3 appear to be Compton-thin sources and one has poor constraints. The
rest-frame unabsorbed X-ray luminosities of these AGNs are more consistent with
those of Seyfert galaxies than QSOs. Thus, the low X-ray detection rate of
bright submm sources by moderately deep X-ray surveys appears to be due to the
relatively low luminosities of the AGNs rather than Compton-thick absorption. A
comparison of these sources to the well-studied heavily obscured AGN NGC6240
shows that the average AGN contribution is negligible at submm wavelengths. The
X-ray properties of the other 2 X-ray detected sources are consistent with
those expected from luminous star formation; however, we cannot rule out the
possibility that low-luminosity AGNs are present. The 3 X-ray undetected
sources appear to lie at high redshift (z>4) and could be either AGNs or
starbust galaxies.


title: Fireball Models for Flares in AE Aquarii

abstract:
  We examine the flaring behaviour of the cataclysmic variable AE~Aqr in the
context of the `magnetic propeller' model for this system. The flares are
thought to arise from collisions between high density regions in the material
expelled from the system after interaction with the rapidly rotating
magnetosphere of the white dwarf. We calculate the first quantitative models
for the flaring and calculate the time-dependent emergent optical spectra from
the resulting hot, expanding ball of gas. We compare the results under
different assumptions to observations and derive values for the mass,
lengthscale and temperature of the material involved in the flare. We see that
the fits suggest that the secondary star in this system has Population II
composition.


title: Physics and Operation of the AMANDA-II High Energy Neutrino Telescope

abstract:
  This paper briefly describes the principle of operation and science goals of
the AMANDA high energy neutrino telescope located at the South Pole,
Antarctica. Results from an earlier phase of the telescope, called AMANDA-B10,
demonstrate both reliable operation and the broad astrophysical reach of this
device, which includes searches for a variety of sources of ultrahigh energy
neutrinos: generic point sources, Gamma-Ray Bursts and diffuse sources. The
predicted sensitivity and angular resolution of the telescope were confirmed by
studies of atmospheric muon and neutrino backgrounds. We also report on the
status of the analysis from AMANDA-II, a larger version with far greater
capabilities. At this stage of analysis, details of the ice properties and
other systematic uncertainties of the AMANDA-II telescope are under study, but
we have made progress toward critical science objectives. In particular, we
present the first preliminary flux limits from AMANDA-II on the search for
continuous emission from astrophysical point sources, and report on the search
for correlated neutrino emission from Gamma Ray Bursts detected by BATSE before
decommissioning in May 2000. During the next two years, we expect to exploit
the full potential of AMANDA-II with the installation of a new data acquisition
system that records full waveforms from the in-ice optical sensors.


title:
Radio sources in the 2dF Galaxy Redshift Survey: AGN, starburst galaxies
  and their cosmic evolution

abstract:
  Radio continuum surveys can detect galaxies over a very wide range in
redshift, making them powerful tools for studying the distant universe. Until
recently, though, identifying the optical counterparts of faint radio sources
and measuring their redshifts was a slow and laborious process which could only
be carried out for relatively small samples of galaxies.
  Combining data from all-sky radio continuum surveys with optical spectra from
the new large-area redshift surveys now makes it possible to measure redshifts
for tens of thousands of radio-emitting galaxies, as well as determining
unambiguously whether the radio emission in each galaxy arises mainly from an
active nucleus (AGN) or from processes related to star formation. Here we
present some results from a recent study of radio-source populations in the 2dF
Galaxy Redshift Survey, including a new derivation of the local star-formation
density, and discuss the prospects for future studies of galaxy evolution using
both radio and optical data.


title:
Cool bottom processes on the thermally-pulsing AGB and the isotopic
  composition of circumstellar dust grains

abstract:
  (Abridged) We examine the effects of cool bottom processing (CBP) on several
isotopic ratios in the convective envelope during the TP-AGB phase of evolution
in a 1.5 M_sun initial-mass star of solar initial composition. We use a
parametric model which treats extra mixing by introducing mass flow between the
convective envelope and the underlying radiative zone. The parameters of this
model are the mass circulation rate (Mdot) and the maximum temperature (T_P)
experienced by the circulating material. The effects of nuclear reactions in
the flowing matter were calculated using a set of structures of the radiative
zone selected from a complete stellar evolution calculation. The compositions
of the flowing material were obtained and the resulting changes in the envelope
determined. Abundant ^26Al was produced by CBP for log T_P > 7.65. While
^26Al/^27Al depends on T_P, the isotopic ratios in CNO elements depend
dominantly on the circulation rate. The correspondence is shown between models
of CBP as parameterized by a diffusion formalism within the stellar evolution
model and those using the mass-flow formalism employed here. The isotopic
ratios are compared with the data on circumstellar dust grains. It is found
that the ratios ^{18}O/^{16}O, ^{17}O/^{16}O, and ^26Al/^27Al observed for
oxide grains formed at C/O < 1 are reasonably well-understood. However, the
^15N/^14N, ^12C/^13C, and ^26Al/^27Al in carbide grains (C/O > 1) require many
stellar sources with ^14N/^15N at least a factor of 4 below solar. The rare
grains with ^12C/^13C < 10 cannot be produced by any red-giant or AGB source.


title: Quantum Effects and Cluster Formation

abstract:
  The causal interpretation of quantum mechanics is applied to the universe as
a whole and the problem of cluster formation is studied in this framework. It
is shown that the quantum effects be the source of the cluster formation.


title: Synchrotron Radiation at Radio Frequencies from Cosmic Ray Air Showers

abstract:
  We review some of the properties of extensive cosmic ray air showers and
describe a simple model of the radio-frequency radiation generated by shower
electrons and positrons as they bend in the Earth's magnetic field. We perform
simulations by calculating the trajectory and radiation of a few thousand
charged shower particles. The results are then transformed to predict the
strength and polarization of the electromagnetic radiation emitted by the whole
shower.


title: A stellar relic from the early Milky Way

abstract:
  The chemical composition of the most metal-deficient stars reflects the
composition of the gas from which they formed. These old stars provide crucial
clues to the star formation history and the synthesis of chemical elements in
the early Universe. They are the local relics of epochs otherwise observable
only at very high redshifts; if totally metal-free (``population III'') stars
could be found, this would allow the direct study of the pristine gas from the
Big Bang. Earlier searches for such stars found none with an iron abundance
less than 1/10,000 that of the Sun, leading to the suggestion that low-mass
stars could only form from clouds above a critical iron abundance. Here we
report the discovery of a low-mass star with an iron abundance as low as
1/200,000 of the solar value. This discovery suggests that population III stars
could still exist, that is, that the first generation of stars also contained
long-lived low-mass objects. The previous failure to find them may be an
observational selection effect.


title:
Freshly ionized matter around the final Helium shell flash object V4334
  Sgr (Sakurai's object)

abstract:
  We report on the discovery of recently ionized hydrogen-deficient gas in the
immediate circumstellar environment of the final helium shell flash star V4334
Sgr (Sakurai's object). On spectra obtained with FORS2 multi-object
spectroscopy we have found spatially extended (about 2") emission from [N II],
[O I], [O II] and very faint Halpha and [S II]. In the [N II] (ll6548,83) lines
we have identified two components located at velocities -350 +/-50 and +200
+/-50 km/s, relative to V4334 Sgr itself. The full width of the [N II] l6583
feature at zero intensity corresponds to a velocity spread of about 1500 km/s.
Based on the available data it is not possible to conclusively determine the
mechanism of ionization. Both photo-ionization, from a rapidly evolving central
star, and shock excitation, as the result of the collision of the fast ouflows
with slower circumstellar matter, could account for the observed lines. The
central star is still hidden behind strong dust absorption, since only a faint
highly reddened continuum is apparent in the spectra. Theory states that it
will become hotter and will retrace its post-asymptotic giant branch evolution
towards the planetary nebula domain. Our detection of the ionized ejecta from
the very late helium shell flash marks the beginning of a new phase in this
star's amazingly rapid evolution.


title:
Adiabatic and Isocurvature Perturbations for Multifield Generalized
  Einstein Models

abstract:
  Low energy effective field theories motivated by string theory will likely
contain several scalar moduli fields which will be relevant to early Universe
cosmology. Some of these fields are expected to couple with non-standard
kinetic terms to gravity. In this paper, we study the splitting into adiabatic
and isocurvature perturbations for a model with two scalar fields, one of which
has a non-standard kinetic term in the Einstein-frame action. Such actions can
arise, e.g., in the Pre-Big-Bang and Ekpyrotic scenarios. The presence of a
non-standard kinetic term induces a new coupling between adiabatic and
isocurvature perturbations which is non-vanishing when the potential for the
matter fields is nonzero. This coupling is un-suppressed in the long wavelength
limit and thus can lead to an important transfer of power from the entropy to
the adiabatic mode on super-Hubble scales. We apply the formalism to the case
of a previously found exact solution with an exponential potential and study
the resulting mixing of adiabatic and isocurvature fluctuations in this
example. We also discuss the possible relevance of the extra coupling in the
perturbation equations for the process of generating an adiabatic component of
the fluctuations spectrum from isocurvature perturbations without considering a
later decay of the isocurvature component.


title: Thermonuclear Supernovae: Is Deflagration Triggered by Floating Bubbles?

abstract:
  In recent years, it has become clear from multidimensional simulations that
the outcome of deflagrations depends strongly on the initial configuration of
the flame. We have studied under which conditions this configuration could
consist of a number of scattered, isolated, hot bubbles. Afterwards, we have
calculated the evolution of deflagrations starting from different numbers of
bubbles. We have found that starting from 30 bubbles a mild explosion is
produced M(Ni56)=0.56 solar masses, while starting from 10 bubbles the star
becomes only marginally unbound (K = 0.05 foes).


title: Molecular Gas Reservoir in low-z Powerful Radio Galaxies

abstract:
  We report a survey for molecular gas in 3C radio galaxies at redshifts z <
0.031. Four of the twenty-three galaxies observed were detected with molecular
gas masses in the range 10^7--10^9 Msun. The remainder had typical upper limits
in molecular gas masses of ~10^8 Msun.


title: Molecular Gas in nearby Early-Type Powerful Classical Radio Galaxies

abstract:
  We report a survey for molecular gas in nearby powerful radio galaxies. Eight
of the eighteen radio galaxies observed were detected with molecular masses in
the range 10^7--10^9 Msun, similar to the same survey we performed towards 3C
radio galaxies. The upper limits of molecular gas in the remainder are
typically of 10^8 Msun, indicating that very few radiogalaxies have molecular
gas reservoir with more than 10^9 Msun.


title: Molecular outflow in the composite galaxy NGC6764

abstract:
  NGC 6764 is a composite galaxy exhibiting central activity (LINER) and recent
massive star formation (Wolf-Rayet galaxy). We report new high-resolution
interferometric data of the CO(1--0) and CO(2--1) emission in the central part
of the galaxy together with high resolution VLA data of the radio continuum
emission. The bulk of molecular gas (few times 10^8 Msun) is located in the
central part. A molecular outflow (~1.7 x 10^7 Msun) out-of the plane is
associated with the starburst-driven outflow radiocontinuum emission.


title:
Polar Ring Galaxies and the Tully Fisher relation: implications for the
  dark halo shape

abstract:
  We have investigated the Tully-Fisher relation for Polar Ring Galaxies
(PRGs), based on near infrared, optical and HI data available for a sample of
these peculiar objects. The total K-band luminosity, which mainly comes from
the central host galaxy, and the measured HI linewidth at 20% of the peak line
flux density, which traces the potential in the polar plane, place most polar
rings of the sample far from the Tully-Fisher relation defined for spiral
galaxies, with many PRGs showing larger HI linewidths than expected for the
observed K band luminosity. This result is confirmed by a larger sample of
objects, based on B-band data. This observational evidence may be related to
the dark halo shape and orientation in these systems, which we study by
numerical modeling of PRG formation and dynamics: the larger rotation
velocities observed in PRGs can be explained by a flattened polar halo, aligned
with the polar ring.


title: Properties of the Brightest Cluster Galaxy and Its Host Cluster

abstract:
  We investigate the relation between the properties of Brightest Cluster
Galaxies (BCGs) and those of their host clusters. To quantify the properties of
cluster hot gas, we employ the parameter $Z$ of the fundamental plane of X-ray
clusters. It is found that the offset of the BCG from the peak of cluster X-ray
emission is larger for smaller $Z$ clusters. The parameter $Z$ (not the
redshift {\it z}), which mainly depends on virial density $\rho_{\rm {vir}}$,
is considered to represent the formation epoch of a cluster. We thus consider
that the offset of the BCG is correlated with the dynamical equilibrium state
of its host cluster. On the contrary, no significant correlation is found
between the absolute optical magnitude of the BCG and the parameter $Z$. If the
extreme brightness of the BCG is mainly acquired in the course of cluster
evolution by environmental effect, BCGs are expected to be brighter in large
$Z$ clusters. Our result is not consistent with this simplified view. On the
contrary, it is possible that the extreme brightness of the BCG is likely to be
determined in the early history of cluster collapse.


title:
Three-component modeling of C-rich AGB star winds I. Method and first
  results

abstract:
  Radiative acceleration of newly-formed dust grains and transfer of momentum
from the dust to the gas plays an important role for driving winds of AGB
stars. Therefore a detailed description of the interaction of gas and dust is a
prerequisite for realistic models of such winds. In this paper we present the
method and first results of a three-component time-dependent model of
dust-driven AGB star winds. With the model we plan to study the role and
effects of the gas-dust interaction on the mass loss and wind formation. The
wind model includes separate conservation laws for each of the three components
of gas, dust and the radiation field and is developed from an existing model
which assumes position coupling between the gas and the dust. As a new feature
we introduce a separate equation of motion for the dust component in order to
fully separate the dust phase from the gas phase. The transfer of mass, energy
and momentum between the phases is treated by interaction terms. We also carry
out a detailed study of the physical form and influence of the momentum
transfer term (the drag force) and three approximations to it. In the present
study we are interested mainly in the effect of the new treatment of the dust
velocity on dust-induced instabilities in the wind. As we want to study the
consequences of the additional freedom of the dust velocity on the model we
calculate winds both with and without the separate dust equation of motion. The
wind models are calculated for several sets of stellar parameters. We find that
there is a higher threshold in the carbon/oxygen abundance ratio at which winds
form in the new model. The winds of the new models, which include drift, differ
from the previously stationary winds, and the winds with the lowest mass loss
rates no longer form.


title: The He-shell flash in action: T Ursae Minoris revisited

abstract:
  We present an updated and improved description of the light curve behaviour
of T Ursae Minoris, which is a Mira star with the strongest period change (the
present rate is an amazing -3.8+/-0.4 days/year corresponding to a relative
decrease of about 1% per cycle). Ninety years of visual data were collected
from all available databases and the resulting, almost uninterrupted light
curve was analysed with the O-C diagram, Fourier analysis and various
time-frequency methods. The Choi-Williams and Zhao-Atlas-Marks distributions
gave the clearest image of frequency and light curve shape variations. A
decrease of the intensity average of the light curve was also found, which is
in accordance with a period-luminosity relation for Mira stars. We predict the
star will finish its period decrease in the meaningfully near future (c.c. 5 to
30 years) and strongly suggest to closely follow the star's variations
(photometric, as well as spectroscopic) during this period.


title: Can brane cosmology with a vanishing \Lambda explain the observations?

abstract:
  A plethora of models of the universe have been proposed in recent years
claiming that the present universe is accelerating, being driven by some
hypothetical source with negative pressure collectively known as {\it dark
energy} which though do not appear to resemble any known form of matter tested
in the laboratory. These models are motivated by the high redshift supernovae
Ia observations. Though low density models, without dark energy, also appear to
fit the SN Ia data reasonably well, however, they are ruled out by the CMB
observations.
  In this paper, we present a warped brane model with an additional surface
term of brane curvature scalar in the action. This results in shifting the {\it
dynamical curvature} of the model from its {\it geometrical} counterpart, which
creates profound consequences. Even for \Lambda=0, the low energy decelerating
model successfully explains the observed locations of the peaks in the angular
power spectrum of CMB. This model also fits the high redshift supernovae Ia
observations, taken together with the recently observed SN 1997ff at z~1.7,
very well. Additionally, it also fits the data on the angular size and redshift
of the compact radio sources very well.


title: Antimatter research in Space

abstract:
  Two of the most compelling issues facing astrophysics and cosmology today are
to understand the nature of the dark matter that pervades the universe and to
understand the apparent absence of cosmological antimatter. For both issues,
sensitive measurements of cosmic-ray antiprotons and positrons, in a wide
energy range, are crucial. Many different mechanisms can contribute to
antiprotons and positrons production, ranging from conventional reactions up to
exotic processes like neutralino annihilation. The open problems are so
fundamental (i.e.: is the universe symmetric in matter and antimatter ?) that
experiments in this field will probably be of the greatest interest in the next
years. Here we will summarize the present situation, showing the different
hypothesis and models and the experimental measurements needed to lead to a
more established scenario.


title: DUET - The Dark Universe Exploration Telescope

abstract:
  DUET, a proposed NASA Midex class mission, will produce a catalog of ~20,000
X-ray selected clusters and groups of galaxies suitable for detailed
cosmological investigations. We present the cosmological constraints achievable
by DUET, the functional requirements of the survey, and briefly describe an
instrument/mission design capable of achieving these requirements. The
advantages of an X-ray survey for constraining the nature and amount of dark
energy and dark matter are emphasized. Constraints on cosmological parameters
are precise and complementary to other approaches. The density of dark energy,
dark matter, and neutrinos will be measured with a statistical uncertainty of
0.5%, 0.5%, and 0.2% of the critical density and the dark energy equation of
state can be measured to +/- 0.2 if dark energy and dark matter contribute ~2/3
and ~1/3 of the critical density as currently believed. DUET is a
multi-national collaboration led by GSFC with substantial contributions from
groups in the US, Europe, and Japan.


title: Where has all the neutral hydrogen gone?

abstract:
  Our extremely deep survey for extragalactic HI (HIDEEP) finds no
intergalactic gas clouds, and no galaxies with HI at inferred global
column-densities below 10^20 cm^-2 when we could have detected such objects
down to a completeness limit of 4 x 10^18 cm^-2. We speculate that low
surface-density hydrogen is either ionised or locked up in ``frozen discs'',
i.e. structures where the local Ly-alpha is insufficient to excite the 21-cm
transition to a spin-temperature above the cosmic background. Such ``frozen
discs'' might be responsible for many QSOALSs.


title: Planets in habitable zones: A study of the binary Gamma Cephei

abstract:
  The recently discovered planetary system in the binary GamCep was studied
concerning its dynamical evolution. We confirm that the orbital parameters
found by the observers are in a stable configuration. The primary aim of this
study was to find stable planetary orbits in a habitable region in this system,
which consists of a double star (a=21.36 AU) and a relatively close (a=2.15 AU)
massive (1.7 Mjup sin i) planet. We did straightforward numerical integrations
of the equations of motion in different dynamical models and determined the
stability regions for a fictitious massless planet in the interval of the
semimajor axis 0.5 AU < a < 1.85 AU around the more massive primary. To confirm
the results we used the Fast Lyapunov Indicators (FLI) in separate
computations, which are a common tool for determining the chaoticity of an
orbit. Both results are in good agreement and unveiled a small island of stable
motions close to 1 AU up to an inclination of about 15 deg (which corresponds
to the 3:1 mean motion resonance between the two planets). Additionally we
computed the orbits of earthlike planets (up to 90 earthmasses) in the small
stable island and found out, that there exists a small window of stable orbits
on the inner edge of the habitable zone in GamCep even for massive planets.


title: Empirical diagnostics of HII regions based on sulphur emission lines

abstract:
  Spectrophotometry constitutes a unique way to obtain the whole diagnostics
(density, temperature, ionic abundances) of ionized gas nebulae, thus providing
invaluable information about the objects where they reside. If such nebulae are
in the low excitation regime, the diagnostics have to relie on the observation
of the more intense emission lines. We have compiled data for a sample of HII
regions, GEHR and HII galaxies and compared them with results derived from
photoionizacion models whose parameters cover the physical conditions of the
nebulae. Our results confirm a lower uncertainty for the diagnostics when using
empirical methods based on the strong lines of [SII] and [SIII] replacing and
complementing those based on the [OII] and [OIII] lines.


title:
The chemical evolution of the Galaxy: the importance of stars with an
  initial mass larger than 40Mo

abstract:
  In the present paper we investigate in how far stars with an initial mass
larger than 40Mo affect the chemical enrichment of the Galaxy. We illustrate
the importance for chemical yields of a most up to date treatment of the
various stellar wind mass loss episodes in stellar evolutionary codes and we
discuss the effects of a possible supernova-like outburst prior to massive
black hole formation.


title:
Magnetic Fields in Clusters of Galaxies Obtained Through the Study of
  Faraday Rotation Measures

abstract:
  We are developing a new approach to investigate cluster magnetic field
strengths and structures. It is based on the comparison of simulated Rotation
Measure and radio halo images, obtained from 3-dimensional multi-scale cluster
magnetic fields models, with observations. This approach is applied to A2255 in
which wide diffuse radio emissions and Rotation Measure images show the
evidence of cluster magnetic fields on both large and small scales.


title:
Strong MgII Absorption Systems in QSOs from the Sloan Digital Sky Survey
  Early Data Release

abstract:
  We have constructed samples of low-ionization metal absorption-line systems
selected for the strength of their MgII lambda2796 lines from the SDSS EDR.
There are 640 absorption systems in our unbiased sample with lambda2796 REW >
1.0 A detected at 5 sigma and with redshifts 0.37 < z < 2.27. This sample is an
order of magnitude larger than previous similarly selected samples. In this
contribution, we present preliminary results on the statistical properties of
the sample.


title:
MACHe3: A new generation detector for non-baryonic dark matter direct
  detection

abstract:
  MACHe3 (MAtrix of Cells of superfluid He3) is a project of a new detector for
direct Dark Matter (DM) search, using superfluid as a sensitive medium. An
experiment on a prototype cell has been performed and the first results
reported here are encouraging to develop of a multicell prototype. In order to
investigate the discovery potential of MACHe3, and its complementarity with
other DM detectors, a phenomenological study done with the DarkSUSY code is
shown.


title:
Strong Absorption-line Systems at Low Redshift: MgII and Damped Lyman
  Alpha

abstract:
  We detail a powerful indirect method for the study of damped Lyman alpha
systems (DLAs) at low redshift. We increase the probability of finding a
low-redshift DLA to nearly 50% by targeting QSOs that are known to have strong
low-redshift MgII and FeII absorption lines in their spectra. We are using
Sloan Digital Sky Survey QSO spectra complemented by a survey we are conducting
at the MMT to study the metal-line systems. The Hubble Space Telescope is being
used to confirm low-redshift DLAs. In addition, we are imaging low-redshift DLA
galaxies with several ground-based telescopes to directly study their
environments.


title:
Fourier decomposition and frequency analysis of the pulsating stars with
  P < 1day in the OGLE database. II. Multiperiodic RR Lyrae variables in the
  Galactic Bulge

abstract:
  We present the results of a systematic search for multiperiodic pulsators
among the Galactic Bulge RR Lyrae stars of the OGLE-1 sample. We identify one
"canonical" double-mode variable (RRd star) pulsating in two radial modes. In
38 stars we detect secondary periodicities very close to the primary pulsation
frequency. This type of multiperiodic variables constitute ~23% of RRab and ~5%
of RRc population of the Bulge. With the observed period ratios of 0.95-1.02
the secondary periods must correspond to nonradial modes of oscillation. Their
beating with the primary (radial) pulsation leads to a long-term amplitude and
phase modulation, known as the Blazhko effect. The Blazhko RRab variables occur
more frequently in the Galactic Bulge than in the LMC. The opposite tendency is
seen in case of the RRd stars. The differences of incidence rates are most
likely caused by different metallicity of the two populations. We discuss
pulsation properties of the OGLE-1 Blazhko stars and compare them with
predictions of theoretical models. We argue, that the oblique magnetic pulsator
model of Shibahashi (2000) cannot account for the observations and should be
ruled out.


title:
Low-Redshift Damped Lyman Alpha Galaxies Toward the Quasars B2 0827+243,
  PKS 0952+179, PKS 1127-145, and PKS 1629+120

abstract:
  We present optical and near-infrared ground-based imaging results on four
low-redshift damped Ly-alpha (DLA) galaxies. The corresponding DLA systems were
discovered in our HST spectroscopic surveys for DLA lines in known strong MgII
absorption-line systems toward the quasars B2 0827+243 (z{DLA}=0.525), PKS
0952+179 (z{DLA}=0.239), PKS 1127-145 (z{DLA}=0.313), and PKS 1629+120
(z{DLA}=0.532). The DLA galaxies span a mixture of morphological types from
patchy, irregular, and low surface brightness to spiral galaxies. The
luminosities range from 0.02L_K* to 1.2L_K*. We also discovered several
extremely red objects (EROs) in two of these fields and discuss the possibility
that they are associated with the DLA galaxies. These observations add to the
small but growing list of DLA galaxies at low redshift. At the present time, 14
DLA galaxies in the redshift range 0.05 < z <1 have been studied. The
distributions of DLA galaxy properties for these 14 cases are discussed and
some important trends emerge. Low-luminosity dwarf galaxies with small impact
parameters dominate this small sample. Also, four of the five highest column
density systems, which dominate in the determination of the cosmological
neutral gas mass density, arise in low surface brightness dwarf galaxies. Zwaan
et al. have shown that only 15% of the neutral gas at the present epoch is
contained in low surface brightness galaxies. Thus, if the low-redshift DLA
galaxy trends hold up with larger samples, it would indicate that a different
population of objects is responsible for the bulk of the neutral hydrogen gas
in the universe at z approx 0.5. (Abridged)


title: Fitting Together the HI Absorption and Emission in the SGPS

abstract:
  In this paper we study 21-cm absorption spectra and the corresponding
emission spectra toward bright continuum sources in the test region (326deg< l
< 333 deg) of the Southern Galactic Plane Survey. This survey combines the high
resolution of the Australia Telescope Compact Array with the full brightness
temperature information of the Parkes single dish telescope. In particular, we
focus on the abundance and temperature of the cool atomic clouds in the inner
galaxy. The resulting mean opacity of the HI, <kappa>, is measured as a
function of Galactic radius; it increases going in from the solar circle, to a
peak in the molecular ring of about four times its local value. This suggests
that the cool phase is more abundant there, and colder, than it is locally.
  The distribution of cool phase temperatures is derived in three different
ways. The naive, ``spin temperature'' technique overestimates the cloud
temperatures, as expected. Using two alternative approaches we get good
agreement on a histogram of the cloud temperatures, T(cool), corrected for
blending with warm phase gas. The median temperature is about 65 K, but there
is a long tail reaching down to temperatures below 20 K. Clouds with
temperatures below 40 K are common, though not as common as warmer clouds (40
to 100 K).
  Using these results we discuss two related quantities, the peak brightness
temperature seen in emission surveys, and the incidence of clouds seen in HI
self-absorption. Both phenomena match what would be expected based on our
measurements of <kappa> and T(cool).


title: The dusty environment of Quasars. Far-IR properties of Optical Quasars

abstract:
  We present the ISO far-IR photometry of a complete sub-sample of optically
selected bright quasars belonging to two complete surveys selected through
multicolour (U,B,V,R,I) techniques. The ISOPHOT camera on board of the ISO
Satellite was used to target these quasars at wavelengths of 7.3, 11.5, 60, 100
and 160 micron. Almost two thirds of the objects were detected at least in one
ISOPHOT band. The detection rate is independent of the source redshift, very
likely due to the negative K-correction of the far-IR thermal emission. More
than a half of the optically selected QSOs show significant emission between 4
and 100 micron in the quasar rest-frame. These fluxes have a very likely
thermal origin, although in a few objects an additional contribution from a
non-thermal component is plausible in the long wavelength bands. In a
colour-colour diagram these objects span a wide range of properties from
AGN-dominated to ULIRG-like. The far-IR composite spectrum of the quasar
population presents a broad far-IR bump between 10 and 30 micron and a sharp
drop at wavelengths greater than 100 micron in the quasar restframe. The amount
of energy emitted in the far-IR, is on average a few times larger than that
emitted in the blue and the ratio L(FIR)/L(B) increases with the bolometric
luminosity. Objects with fainter blue magnitudes have larger ratios between the
far-IR (wavelengths > 60 micron) fluxes and the blue band flux, which is
attributed to extinction by dust around the central source. No relation between
the blue absolute magnitude and the dust colour temperature is seen, suggesting
that the dominant source of FIR energy could be linked to a concurrent
starburst rather than to gravitational energy produced by the central engine.


title:
Supranova Model for the Delayed Reddened Optical Excesses Detected in
  Several GRBs

abstract:
  Excess reddened optical emission has been measured in the power-law decay
afterglow light curves of several GRBs some tens of days after the GRB events.
This emission is claimed to be a signature of a supernova (SN) taking place at
the same time as the GRB event, in support of the collapsar scenario.
Observations of features in prompt and afterglow X-ray spectra of GRBs require
high density, high metallicity material near GRB sources, supporting the
supranova (SA) scenario. These conflicting lines of evidence are resolved in
likely regimes of parameter space if the supernova remnant (SNR) shell is
illuminated and heated by a pulsar wind (PW), and cools following the GRB
event. The heating of the SNR shell by the PW is parameterized, and simplified
expressions for the synchrotron, synchrotron self-Compton, and thermal
radiation fields within the SNR shell and pulsar wind bubble are derived for
monoenergetic injection of wind electrons. A cooling SNR shell could produce
the excess emission detected from GRB 970228, GRB 980326, and GRB 011121. X-ray
synchrotron radiation from the PW electrons provides an important source of
ionizing radiation.


title:
Unification Model of Seyfert Galaxies: Are All Seyfert 2 Galaxies
  Created Equal?

abstract:
  Based on the analysis of a large spectropolarimetric survey of Seyfert 2
galaxies (S2s) from the CfA and 12-micron samples conducted mostly at Lick and
Palomar Observatories, it is shown that S2s with hidden BLR (HBLRs) are
intrinsically more powerful than non-HBLR S2s. The positive detection of BLR in
HBLR S2s appears to be due largely to the intrinsic strength of the hidden AGN
nucleus rather than the lower level of nuclear obscuration or reduced dominance
of circumnuclear starburst. The HBLR S2s, on average, share many similar
large-scale characteristics with Seyfert 1 galaxies (S1s), as would be expected
if the unified model is correct, while the non-HBLR S2s generally do not. These
results strongly suggest that not all S2s are intrinsically similar in nature,
and the HBLR S2s may be the only true counterparts to normal S1s.


title: Dogs that Don't Bark (The Tale of Baryonic Dark Matter in Galaxies)

abstract:
  Fifteen years or so ago, it was commonly argued; ``If we want to believe the
observations rather than our prejudice, we should take as our best bet that
dark haloes are baryonic.'' Such a viewpoint is not often heard today. This
change-of-mind has been enforced upon us largely by the microlensing
experiments. Particle dark matter differs from (most types of) baryonic dark
matter in that it does not produce microlensing events. The familiar parade of
baryonic candidates has now been whittled down, and perhaps only one remains as
a possible substantial contributor to the dark matter in the Galaxy's halo.
This review assesses the distribution of missing matter in the Galaxy, the
likely baryonic dark matter suspects, the evidence from microlensing and from
the halo white dwarf searches.


title: Condensate cosmology -- dark energy from dark matter

abstract:
  Imagine a scenario in which the dark energy forms via the condensation of
dark matter at some low redshift. The Compton wavelength therefore changes from
small to very large at the transition, unlike quintessence or metamorphosis. We
study CMB, large scale structure, supernova and radio galaxy constraints on
condensation by performing a 4 parameter likelihood analysis over the Hubble
constant and the three parameters associated with Q, the condensate field:
Omega_Q, w_f and z_t (energy density and equation of state today, and redshift
of transition). Condensation roughly interpolates between Lambda CDM (for large
z_t) and sCDM (low z_t) and provides a slightly better fit to the data than
Lambda CDM. We confirm that there is no degeneracy in the CMB between H and z_t
and discuss the implications of late-time transitions for the Lyman-alpha
forest. Finally we discuss the nonlinear phase of both condensation and
metamorphosis, which is much more interesting than in standard quintessence
models.


title: The 2-10 keV luminosity as a Star Formation Rate indicator

abstract:
  Radio and far infrared luminosities of star-forming galaxies follow a tight
linear relation. Making use of ASCA and BeppoSAX observations of a well-defined
sample of nearby star-forming galaxies, we argue that tight linear relations
hold between the X-ray, radio and far infrared luminosities. The effect of
intrinsic absorption is investigated taking NGC3256 as a test case. It is
suggested that the hard X-ray emission is directly related to the Star
Formation Rate. Star formation processes may also account for most of the 2-10
keV emission from LLAGNs of lower X-ray luminosities (for the same FIR and
radio luminosity). Deep Chandra observations of a sample of radio-selected
star-forming galaxies in the Hubble Deep Field North show that the same
relation holds also at high (0.2< z< 1.3) redshift. The X-ray/radio relations
also allow a derivation of X-ray number counts up to very faint fluxes from the
radio Log N-Log S, which is consistent with current limits and models. Thus the
contribution of star-forming galaxies to the X-ray background can be estimated.


title: Extremely Red Objects: an X-ray dichotomy

abstract:
  We analyze the X-ray properties of a near-infrared selected (Ks < 20) sample
of spectroscopically identified Extremely Red Objects (R-Ks>5) in a region of
the Chandra Deep Field-South using the public 1 Ms observation. The 21 objects
were classified, on the basis of deep VLT spectra, in two categories: 13 dusty
star-forming galaxies showing [OII] emission, and 8 early-type galaxies with
absorption features in their optical spectra. Only one emission line object has
been individually detected; its very hard X-ray spectrum and the high intrinsic
X-ray luminosity unambiguously reveal the presence of an obscured AGN. Stacking
analysis of the remainder 12 emission line objects shows a significant
detection with an average luminosity L(X)~8x10^{40} erg/s in the rest-frame
2-10 keV band. The stacked counts of the 8 passive galaxies do not provide a
positive detection. We briefly discuss the implications of the present results
for the estimate of the Star Formation Rate (SFR) in emission line EROs.


title: Unconventional AGN in hard X-ray surveys

abstract:
  Extensive programs of follow-up observations of hard X-ray selected sources
have unambiguosly revealed that the sources of the X-ray background are
characterized by an extremely large dispersion in their optical magnitude and
spectroscopic classification. Here we present the results of an attempt to
understand the nature of the observed variety using a simple prescription for
their optical to X-ray energy distribution.


title: Hard X-ray observations of Extremely Red Objects

abstract:
  Extremely Red Objects (EROs, R-K>5) constitute a heterogenous class of
extragalactic sources including high redshift elliptical galaxies, dusty
star-forming systems and heavily obscured AGNs. Hard X-ray observations provide
an unique and powerful tool to uncover obscured nuclear or star-forming
activity. We present the results of XMM-Newton observations of the largest
sample of EROs available to date (about 450 objects over a contiguous area of
700 arcmin^2). Five of the 46 hard X-ray selected sources brighter than
3x10^{-15} cgs in the 2-10 keV band, are associated with EROs. All of the X-ray
detected EROs show rather extreme X-ray-to-optical flux ratios, suggesting the
presence of highly obscured AGN activity. We also report on the X-ray stacking
analysis of spectroscopically identified EROs in the Chandra Deep Field South.


title: The faintest star forming galaxies

abstract:
  I briefly report on the X-ray detection of 10 radio sub-mJy sources in the 2
Ms Chandra observation of the Hubble Deep Field North region. These sources
follow the same radio/X-ray luminosities relation which holds for nearby
galaxies. Making use of this relation, X-ray number counts from star forming
galaxies are predicted from the deep radio Log N-Log S's.


title: Beyond the X-ray background with XEUS

abstract:
  We briefly discuss the perspectives of sensitive hard X-ray observations with
the large collecting area X-ray telescopes of XEUS.