title:
Cross-matching DENIS and 2MASS Point Sources towards the Magellanic
  Clouds

abstract:
  The recent publications of the DENIS Catalogue towards the Magellanic Clouds
(MCs) with more than 1.3 million sources identified in at least two of the
three DENIS filters (I J K_s) and of the incremental releases of the 2MASS
point source catalogues (J H K_s) covering the same region of the sky, provide
an unprecedented wealth of data related to stellar populations in the MCs. In
order to build a reference catalogue of stars towards the Magellanic Clouds, we
have performed a cross-identification of these two catalogues. This implied
developing new tools for cross-identification and data mining.
  This study is partly supported by the Astrovirtel program that aims at
improving access to astronomical archives as virtual telescopes. The main goal
of the present study is to validate new cross-matching procedures for very
large catalogues, and to derive results concerning the astrometric and
photometric accuracy of these catalogues. The cross-matching of large surveys
is an essential tool to improve our understanding of their specific contents.
This approach can be considered as a new step towards a Virtual Observatory.


title:
Burst Oscillation Periods from 4U 1636--53: A Constraint on the Binary
  Doppler Modulation

abstract:
  We present a study of the distribution of asymptotic burst oscillation
periods for a sample of 26 bursts from 4U 1636-53 observed with the Rossi X-ray
Timing Explorer (RXTE). The burst sample includes both archival and proprietary
data and spans more than 4.5 years. We also present new optical light curves of
V801 Arae, the optical counterpart of 4U 1636-53, obtained during 1998-2001. We
use these optical data to refine the binary period measured by Augusteijn et
al. (1998) to 3.7931206(152) hours. We show that a subset of ~70% of the bursts
form a tightly clustered distribution of asymptotic periods consistent with a
period stability of ~ 1/10,000. The tightness of this distribution, made up of
bursts spanning more than 4 years in time, suggests that the underlying period
is highly stable, with a time to change the period of ~30,000 years, comparable
to similar numbers derived for X-ray pulsars. We investigate the period and
orbital phase data for our burst sample and show that it is consistent with
binary motion of the neutron star with v sin i < 55 km/sec at 90% confidence.
We use this limit as well as previous radial velocity data to constrain the
binary geometry and component masses in 4U 1636-53.


title: Near infrared observations of the truncation of stellar disks

abstract:
  We present a first study of truncation of the stellar disks of spiral
galaxies in the near infrared. Observations of NGC4013, NGC4217, NGC6504 and
NGC5981 were made with the CAIN NIR camera on the CST in Tenerife. This
wavelength range provides the best description of the phenomenon, not only
because extinction effects are minimized, but also because the distribution of
the old stellar population is directly obtained. The four galaxies are edge-on
and an inversion method was developed to obtain the deprojected profiles. We
did not assume any model of the different galactic components. The ``truncation
curve'', i.e. T(R)= mu(R)- mu_{D}(R), where mu is the actual surface brightness
in mag/arcsec^2 and mu_{D} the exponential disk surface brightness, has been
obtained with unprecedented precision. It is suggested that T(R) is
proportional to (R_{t}-R)^{-1}, where R_{t} is the truncation radius, i.e. the
radius beyond which no star is observed.


title: Evidence for Ring Caustics in the Milky Way

abstract:
  The late infall of cold dark matter onto our galaxy produces discrete flows
and caustics in its halo. The recently discovered ring of stars near
galactocentric distance 20 kpc and a series of sharp rises in the Milky Way
rotation curve are interpreted as due to the presence of caustic rings of dark
matter in the galactic plane. Their locations are consistent at the 3% level
with the predictions of the self-similar infall model for the caustic ring
radii. Also, a triangular feature in the IRAS map of the galactic plane is
consistent with the imprint of a caustic ring of dark matter upon the baryonic
matter. These observations imply that the dark matter in our neighborhood is
dominated by a single flow whose density and velocity vector are estimated.


title:
H2, HD, and CO at the edge of 30 Dor in the LMC: the line of sight to
  Sk-69 246

abstract:
  FUSE and IUE observations of Sk -69 246, a WN 6 star to the north of 30 Dor,
reveal the existence of LMC interstellar gas in at least 3 velocity
components.In one of these components FUSE spectra show strong absorption by
molecular hydrogen with a column density of log N(H_2)=19.6. We investigate the
physical conditions in this cloud, which is probably located near the H II
region surrounding Sk -69 246. HD and CO with column densities of about 13.9
and 13.0 dex, respectively, are detected. The N(CO)-to-N(H_2) ratio is
consistent with values found in the Galaxy. From the population of the
rotational levels of H_2 we derive a gas temperature of 72 K and a radiation
field U=3*10^-15 erg/(s*cm^3) at 1000 nm. The fractional abundance
f=2N(H_2)/[N(H I)+2N(H_2)] is approximately 0.07, rather high for an
E(B-V)<0.1.


title: Formation and Disruption of Globular Star Clusters

abstract:
  In the first part of this article, we review observations of the mass and
luminosity functions of young and old star cluster systems. We also review some
of the physical processes that may determine the characteristic mass of
globular clusters and the form of their mass function. In the second part of
this article, we summarize our models for the disruption of clusters and the
corresponding evolution of the mass function. Much of our focus here is on
understanding why the mass function of globular clusters has no more than a
weak dependence on radius within their host galaxies.


title:
Bounds on the possible evolution of the Gravitational Constant from
  Cosmological Type-Ia Supernovae

abstract:
  Recent high-redshift Type Ia supernovae results can be used to set new bounds
on a possible variation of the gravitational constant $G$. If the local value
of $G$ at the space-time location of distant supernovae is different, it would
change both the kinetic energy release and the amount of $^{56}$Ni synthesized
in the supernova outburst. Both effects are related to a change in the
Chandrasekhar mass $M_{Ch} \propto G^{-3/2}$. In addition, the integrated
variation of $G$ with time would also affect the cosmic evolution and therefore
the luminosity distance relation. We show that the later effect in the
magnitudes of Type Ia supernovae is typically several times smaller than the
change produced by the corresponding variation of the Chandrasekhar mass. We
investigate in a consistent way how a varying $G$ could modify the Hubble
diagram of Type Ia supernovae and how these results can be used to set upper
bounds to a hypothetical variation of $G$. We find $G/G_0 \la 1.1$ and $G'/G
\la 10^{-11} yr^{-1}$ at redshifts $z\simeq 0.5$. These new bounds extend the
currently available constrains on the evolution of $G$ all the way from solar
and stellar distances to typical scales of Gpc/Gyr, i.e. by more than 15 orders
of magnitudes in time and distance.


title: Local Interstellar Matter: The view from Paris

abstract:
  Observations of interstellar gas and dust towards nearby stars and within the
solar system show that the Sun is embedded in a warm diffuse partially-ionized
cloud. This cloud is the leading edge of a flow of interstellar matter (ISM)
through our Galactic neighborhood. Interstellar matter sets the boundary
conditions of the heliosphere and astrospheres of extra-solar planetary
systems. Moreover, the interplanetary regions in these systems are sensitive to
inflowing ISM.


title: Secular Evolution of Disks

abstract:
  It is found that a previously thought-to-be well established result of
density wave theory, that there is no interaction between a quasi-stationary
spiral density wave and the basic state (i.e. the axisymmetric part) of the
galactic disk, is in fact false. When solved as a nonlinear and globally
self-consistent problem, the presence of non-axisymmetric patterns such as
spirals or bars is shown to lead to significant interaction of the basic state
and the density wave, with the net result being the simultaneous acquirement of
a quasi-steady wave amplitude and the secular redistribution of disk matter.
The secular operation of this dynamical mechanism leads to the evolution of the
Hubble type of a galaxy from late to early.


title:
Chandra Observations of the Stellar Populations and Diffuse Gas in
  Nearby Galaxies

abstract:
  We present Chandra observations of two star-forming galaxies (M82 and the
Antennae) and three starburst/AGN composite galaxies (NGC1808, NGC6240,
NGC7331). In both star-forming galaxies we detect a large number of sources
with diverse properties. Some of them can be identified as X-ray binaries,
based on their variability and spectra. However, there is a significant number
of very soft and/or extended sources which could be supernova remnants.
  These observations confirm previous indications that there is a population of
sources with X-ray luminosities much higher than the Eddington limit for a
neutron star, suggesting that these objects are abundant in star-forming
galaxies. We find the the X-ray luminosity functions of the discrete sources in
these two galaxies are very similar. In the case of the composite galaxies we
find that the AGN does not dominate their X-ray emission. A significant
fraction of the emission from these objects is extended but there are also
X-ray sources associated with circumnuclear star-formation.


title:
The Effect of the Random Magnetic Field Component on the Parker
  Instability

abstract:
  The Parker instability is considered to play important roles in the evolution
of the interstellar medium. Most studies on the development of the instability
so far have been based on an initial equilibrium system with a uniform magnetic
field. However, the Galactic magnetic field possesses a random component in
addition to the mean uniform component, with comparable strength of the two
components. Parker and Jokipii have recently suggested that the random
component can suppress the growth of small wavelength perturbations. Here, we
extend their analysis by including gas pressure which was ignored in their
work, and study the stabilizing effect of the random component in the
interstellar gas with finite pressure. Following Parker and Jokipii, the
magnetic field is modeled as a mean azimuthal component, $B(z)$, plus a random
radial component, $\epsilon(z) B(z)$, where $\epsilon(z)$ is a random function
of height from the equatorial plane. We show that for the observationally
suggested values of $<\epsilon^2>^{1/2}$, the tension due to the random
component becomes important, so that the growth of the instability is either
significantly reduced or completely suppressed. When the instability still
works, the radial wavenumber of the most unstable mode is found to be zero.
That is, the instability is reduced to be effectively two-dimensional. We
discuss briefly the implications of our finding.


title: Irradiation Pressure Effects in Close Binary Systems

abstract:
  We present a method for the calculation of the effects of external
irradiation on the geometrical shape of the secondary in a close binary
containing a compact star, the source of the radiation, and a normal companion
star, where we include the possibility of shadowing by an accretion disc. The
model is based on a simple modification of the standard Roche binary potential
in which the radiation-pressure force is parameterised using the ratio of the
radiation to the gravitational force. We have constructed numerical solutions
of approximate 3-dimensional irradiated equipotential surfaces to demonstrate
the main geometrical effects of external radiation pressure. For systems in
which the inner Lagrangian point is irradiated directly and for sufficiently
high irradiation fluxes, the critical condition for which the secondary fills
its tidal lobe changes from an inner to an outer critical configuration, where
the critical equipotential surface connects to one of the outer rather than the
inner Lagrangian point. Such a situation may apply to evaporating binary pulsar
systems (e.g. PSR 1957+20), stars orbiting supermassive black holes in AGN and
some high-mass X-ray binaries (including Centaurus X-3). For systems containing
an accretion disc, which shadows the inner Lagrangian point from the external
irradiation, the presence of significant radiation pressure causes a
non-axisymmetric deformation of the stellar surface. We have calculated
modified Roche potentials to determine the main effects on the optical
lightcurves and radial velocity curves for typical binary parameters. Compared
to previous studies, the inclusion of irradiation-pressure effects results in
changes in the derived system parameters (e.g. component masses, radial
velocities) that may be as high as 30 per cent.


title: Exploring the Lyman Forest with VLT/UVES

abstract:
  A sample of 8 QSOs with 1.7 < z_em < 3.7 has been observed with VLT/UVES at a
typical resolution 45000 and S/N~40-50. Thanks to the two-arm design of the
spectrograph, a remarkable efficiency has been achieved below 400nm and above
800nm, which translates immediately in the possibility of obtaining new
results, especially at z<2.5. We report here new insight gained about the
evolution of the number density of Ly-a lines, their column density
distribution, the ionizing UV background and the cosmic baryon density.


title:
Periodicities in data observed during the minimum and the rising phase
  of solar cycle 23; years 1996 - 1999

abstract:
  Three types of observations: the daily values of the solar radio flux at 7
frequencies, the daily international sunspot number and the daily Stanford mean
solar magnetic field were processed in order to find all the periodicities
hidden in the data. Using a new approach to the radio data, two time series
were obtained for each frequency examined, one more sensitive to spot magnetic
fields, the other to large magnetic structures not connected with sunspots.
Power spectrum analysis of the data was carried out separately for the minimum
(540 days from 1 March 1996 to 22 August 1997) and for the rising phase (708
days from 23 August 1997 to 31 July 1999) of the solar cycle 23. The Scargle
periodograms obtained, normalized for the effect of autocorrelation, show the
majority of known periods and reveal a clear difference between the
periodicities found in the minimum and the rising phase. We determined the
rotation rate of the `active longitudes' in the rising phase as equal to 444.4
$\pm$ 4 nHz ($26\fd0 \pm 0\fd3$). The results indicate that appropriate and
careful analysis of daily radio data at several frequencies allows the
investigation of solar periodicities generated in different layers of the solar
atmosphere by various phenomena related to the periodic emergence of diverse
magnetic structures.


title: Chandra Observations of Embedded Young Stellar Objects

abstract:
  This paper reviews the Chandra deep exposure observations of star forming
regions, rho-Ophiuchi, Orion Molecular Clouds 2 and 3, Sagittarius B2 and
Monoceros R2. The results are; (1) class I protostars are found to exhibit
higher temperature plasma than those of T Tauri stars, (2) heavily absorbed
X-rays are discovered from the candidates of class 0 protostars, (3) hard and
highly variable X-rays are observed from high-mass young stars, and (4) young
brown dwarfs emit X-rays similar to those of low-mass young stars.


title: The evolution of AGNs in the Hard X-Rays and the Infrared

abstract:
  We present the estimate of the evolution of type 1 AGNs in the hard (2-10
keV) X-rays drawn from the HELLAS survey, and in the IR (15um) obtained from
the ELAIS survey. We find that the local luminosity function (LF) of AGN1 in
the 2-10 keV band is fairly well represented by a double-power-law-function.
There is evidence for significant cosmological evolution according to a pure
luminosity evolution model Lx(z)~(1+z)^k, with k=2.12 and k=2.19 in a
(Omega_m,Omega_lambda)=(1.0,0.0) and in a (Omega_m,Omega_lambda)=(0.3,0.7)
cosmology respectively. In a (Omega_m,Omega_lambda)=(1.0,0.0) Universe the data
show an excess of faint high redshift type 1 AGN which is well modeled by a
luminosity dependent density evolution, similarly to what observed in the soft
X-rays. In the IR band, with a (Omega_m,Omega_lambda)=(1.0,0.0) cosmology, the
evolution found is similar to what observed in other wavebands, the LF is a
double-power-law-function with a bright slope 2.9 and a faint slope 1.1,
following a luminosity evolution model L(z)~(1+z)^3.0.


title:
Inference on the Nature and the Mass of Earth's Late Veneer from Noble
  Metals and Gases

abstract:
  Noble metals and gases are very sensitive to the late accretion to the Earth
of asteroids and comets. We present mass balance arguments based on these
elements that indicate that 0.7E22-2.7E22 kg of extraterrestrial bodies struck
the Earth after core formation and that comets comprised less than 1E-5 by mass
of the impacting population. These results imply that the dynamics of asteroids
and comets changed drastically with time and that biogenic elements and
prebiotic molecules were not delivered to the Earth by comets but rather by
carbonaceous asteroids.


title:
Final Calibration of the Berkeley Extreme and Far-Ultraviolet
  Spectrometer on the ORFEUS-SPAS I and II Missions

abstract:
  The Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS) flew as part of
the ORFEUS telescope on the ORFEUS-SPAS I and II space-shuttle missions in 1993
and 1996, respectively. The data obtained by this instrument have now entered
the public domain. To facilitate their use by the astronomical community, we
have re-extracted and re-calibrated both data sets, converted them into a
standard (FITS) format, and placed them in the Multimission Archive at Space
Telescope (MAST). Our final calibration yields improved wavelength scales and
effective-area curves for both data sets.


title: Emission from the secondary star in the old CV WZ Sge

abstract:
  We present the first detection of the mass donor star in the cataclysmic
variable WZ Sge. Phase resolved spectroscopy reveals narrow Balmer emission
components from the irradiated secondary star during the 2001 outburst. Its
radial velocity curve indicates a systemic velocity of -72 +/- 3 km/s and an
apparent velocity amplitude of K_2_app=493 +/- 10 km/s. Doppler tomography
reveals a highly asymmetric accretion disc including a significant bright spot
contribution 20 days into the outburst. We estimate the primary radial velocity
K_1 using a center of symmetry method and find K_1_app=37 +/- 5 km/s.
Accounting for the likely systematic errors affecting both K_1 and K_2
measurements, we conservatively derive 508 < K_2 < 585 km/s and K_1 < 37 km/s.
This implies a massive white dwarf with M_1 > 0.77 M_sun. A non-degenerate mass
donor, implying WZ Sge has not yet evolved through its minimum orbital period,
is not ruled out by our observations. This would require an improved estimate
of K_1. Together with the measured phase offset between bright spot eclipse and
inferior conjuction of the secondary star, we can bracket the allowed mass
ratio (q=M_2/M_1) to lie between 0.040 and 0.073. This provides a firm upper
limit to the mass of the secondary of M_2 < 0.10 M_sun.


title:
Parsec-scale structure in galactic disk and halo, from diffuse radio
  polarization

abstract:
  We present multi-frequency polarization observations of the diffuse radio
synchrotron background modulated by Faraday rotation. No total intensity is
observed, indicating that total intensity does not vary on scales below
approximately a degree. However, polarized intensity and polarization angle
show abundant small-scale structure due to Faraday rotation in the warm ionized
disk on small scales. The distribution of Rotation Measures enables us to
estimate structure in magnetic field, weighted with electron density, in the
warm ionized disk.


title: High-redshift QSOs in the FIRST survey

abstract:
  In a pilot search for high-redshift radio QSOs, we have obtained spectra of
55 FIRST sources (S(1.4GHz) > 1 mJy) with very red (O-E > 3) starlike optical
identifications. 10 of the candidates are QSOs with redshifts 3.6 < z < 4.4 (4
previously known), six with z > 4. The remaining 45 candidates comprise: a z =
2.6 BAL QSO; 3 low-redshift galaxies with narrow emission lines; 18 probable
radio galaxies; and 23 M stars (mainly misidentifications). The success rate
(high-redshift QSOs / spectroscopically-observed candidates) for this search is
1/2 for S(1.4GHz) > 10 mJy, and 1/9 for S(1.4GHz) > 1 mJy. With an effective
search area of 4030 deg^2, the surface density of high-redshift (z > 4) QSOs
discovered with this technique is 0.0015 deg^-2.


title:
Soft X-Ray Absorption by Fe$^{0+}$ to Fe$^{15+}$ in Active Galactic
  Nuclei

abstract:
  A full set of calculations is presented for inner-shell n = 2 to 3
photoexcitation of the 16 iron charge states: Fe I through Fe XVI. The blend of
the numerous absorption lines arising from these excitations (mainly 2p - 3d)
forms an unresolved transition array (UTA), which has been recently identified
as a prominent feature between 16 - 17 \AA in the soft X-ray spectra of active
galactic nuclei (AGN). Despite the blending within charge-states, the ample
separation between the individual-ion features enables precise diagnostics of
the ionization range in the absorbing medium. Column density and turbulent
velocity diagnostics are also possible, albeit to a lesser accuracy. An
abbreviated set of atomic parameters useful for modeling the Fe 2p - 3d UTA is
given. It is shown that the effects of accompanying photoexcitation to higher
levels ($n \ge$ 4), as well as the associated photoionization edges, may also
be relevant to AGN spectra.


title:
The cosmic flow in the Local Supercluster: Tracing PSCz tidal influence
  through optimized Least Action Principle

abstract:
  We assess the extent to which the flux-limited PSCz redshift sample is
capable of accounting for the major share of mass concentrations inducing the
external tidal forces affecting the peculiar velocities within the Local
Supercluster (LS). The investigation is based upon a comparison of the ``true''
velocities in 2 large N-body simulations and their reconstruction from
``observation-mimicking'' mock catalogues. The mildly nonlinear ``mock'' LS and
PSCz velocities are analyzed by means of the Least Action Principle technique
in its highly optimized implementation of Nusser & Branchini's Fast Action
Method (FAM). For both model N-body Universes, we conclude that the dipolar and
quadrupolar force field implied by the PSCz galaxy distribution would indeed be
sufficiently representing the full external tidal force field.


title:
VLA HI Imaging of the brightest spiral galaxies in Coma II. The HI Atlas
  and deep continuum imaging of selected early type galaxies

abstract:
  In the first paper of this series we used HI observations of the 19 brightest
spirals in Coma to analyze the dynamical state of the cluster. In this paper we
present the detailed HI distribution and kinematics of the spirals that were
detected in HI, and radio continuum data for a sample of star forming and post
starburst galaxies in Coma. We discuss the importance of ICM-ISM interactions
to explain the observed HI morphology. A rough comparison of observed HI sizes
with predicted HI sizes from simulations by Abadi et al. (1999) gives
reasonable agreement. We use the results on radio continuum emission to
estimate the star formation rate in the PSB galaxies we pointed at. The radio
continuum emission in the 11 so called post starburst galaxies, identified by
Caldwell et al. (1993) in the cluster, is weak. Eight of the 11 were not
detected down to a 3 sigma upper limit of 0.6 mJy. This sets an upper limit to
the star formation rate in these galaxies of less than 0.2 solar masses per
year. The three detected post starburst galaxies have a star formation rate of
less than one solar mass per year. Thus none of the post starburst galaxies in
Coma are dust enshrouded starbursts.


title:
Black Hole Mass and Eddington Ratio as Drivers for the Observable
  Properties of Radio-Loud and Radio-Quiet QSOs

abstract:
  Recent studies of black holes in the nuclei of both active and normal
galaxies have yielded relationships that permit a physical interpretation of
the principal components of the spectra of QSOs. It is shown that principal
component (or eigenvector) 1 (PC1) is driven predominantly by L/L{Edd}, and
principal component 2 (PC2) is driven by luminosity or accretion rate. This
results in a PC2 vs. PC1 diagram in which lines of constant black hole mass are
diagonal. Using a sample consisting of the low-redshift PG objects supplemented
by 46 radio-loud QSOs, it is shown that such a diagram effectively
distinguishes radio-loud from radio-quiet as well as demonstrating that both
narrow-line Seyfert 1s and broad absorption-line QSOs (BALQSOs) lie at the high
L/LEdd} extreme, though these two types of objects are well separated in the
PC2 direction. The very few radio-loud BALQSOs known fall in the region
expected to be populated by such objects. Finally, a simple picture that ties
together physical parameters and classification of AGN is presented.


title: The cosmic ray positron excess and neutralino 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 study the dependence on various parameters.
We find models with a boost factor greater than 30. Such an enhancement in the
signal could arise if we live in a clumpy halo. We discuss what part of
supersymmetric parameter space is favored (in that it gives the largest
positron signal), and the consequences for other direct and indirect searches
of supersymmetric dark matter.


title: Advanced Exposure-Time Calculations

abstract:
  The familiar tools of Fourier analysis and Fisher matrices are applied to
derive the uncertainties on photometric, astrometric, and weak-lensing
measurements of stars and galaxies in real astronomical images. Many effects or
functions that are ignored in basic exposure-time calculators can be included
in this framework: pixels of size comparable to the stellar image; undersampled
and dithered exposures; cosmic-ray hits; intrapixel sensitivity variations;
positional and ellipticity errors as well as photometric errors. I present a
formalism and a C++ implementation of these methods. As examples of their use,
I answer some commonly arising questions about imaging strategies: What amount
of dithering is ideal? What pixel size optimizes the productivity of a camera?
Which is more efficient---space-based or ground-based observing?


title: Two New Low Redshift 21cm Absorbers

abstract:
  As part of a larger program to identify low redshift radio analogues of the
damped Lyman-alpha (DLA) absorbers seen in the spectra of high redshift
quasars, Westerbork Synthesis Radio Telescope (WSRT) observations have
discovered two new HI 21cm absorption lines at z=0.394 and z=0.437 in the
spectra of the radio sources B 0248+430 and B 1243-072 respectively. These
sightlines and redshifts were selected for study on the basis of the previously
known low ionization absorption lines of MgII, and neither has been observed in
the Lyman-alpha line. The 21cm line observations provide information on column
densities, temperatures and kinematics of the thickest cold neutral clouds in
the absorbers.


title:
Determination of cosmology and evolution from K-band magnitude-redshift
  and number count observations

abstract:
  We determine cosmological and evolutionary parameters from the 3CR K-band
Hubble diagram and K-band number counts, assuming that the galaxies in question
undergo pure luminosity evolution. Separately the two data sets are highly
degenerate with respect to choice of cosmological and evolutionary parameters,
but in combination the degeneracy is resolved. Of models which are either flat
or have $\Omega_\Lambda=0$, the preferred ones are close to the canonical case
$\Omega_\CdM=1$, $\Omega_\Lambda=0$, with luminosity evolution amounting to one
magnitude brighter at z=1.


title:
Predicting the number, spatial distribution and merging history of dark
  matter haloes

abstract:
  We present a new algorithm (PINOCCHIO, PINpointing Orbit-Crossing Collapsed
HIerarchical objects) to predict accurately the formation and evolution of
individual dark matter haloes in a given realization of an initial linear
density field. Compared with the halo population formed in a large (360^3
particles) collisionless simulation of a CDM universe, our method is able to
predict to better than 10 per cent statistical quantities such as the mass
function, two-point correlation function and progenitor mass function of the
haloes. Masses of individual haloes are estimated accurately as well, with
errors typically of order 30 per cent in the mass range well resolved by the
numerical simulation. These results show that the hierarchical formation of
dark matter haloes can be accurately predicted using local approximations to
the dynamics when the correlations in the initial density field are properly
taken into account. The approach allows one to automatically generate a large
ensemble of accurate merging histories of haloes with complete knowledge of
their spatial distribution. The construction of the full merger tree for a
256^3 realisation requires a few hours of CPU-time on a personal computer,
orders of magnitude faster than the corresponding N-body simulation would take,
and without needing any extensive post-processing. The technique can be
efficiently used, for instance, for generating the input for galaxy formation
modeling.


title:
PINOCCHIO: pinpointing orbit-crossing collapsed hierarchical objects in
  a linear density field

abstract:
  PINOCCHIO (PINpointing Orbit-Crossing Collapsed Hierarchical Objects) is a
new algorithm for identifying dark matter halos in a given numerical
realisation of the linear density field in a hierarchical universe (Monaco et
al. 2001). It is shown that Lagrangian perturbation theory, and in particular
its ellipsoidal truncation, is able to predict accurately the collapse, in the
orbit-crossing sense, of generic mass elements. Some points that have undergone
orbit crossing are assigned to the network of filaments and sheets that
connects the halos; it is demonstrated that this network resembles closely that
found in N-body simulations. The code generates a catalogue of dark matter
halos with known mass, position, velocity, merging history and angular
momentum. It is shown that the predictions of the code are very accurate when
compared with the results of large N-body simulations that cover a range of
cosmological models, box sizes and numerical resolutions. The mass function is
recovered with an accuracy of better than 10 per cent in number density for
halos with at least 30-50 particles. A similar accuracy is reached in the
estimate of the correlation length r_0. The good agreement is still valid on
the object-by-object level, with 70-100 per cent of the objects with more than
50 particles in the simulations also identified by our algorithm. For these
objects the masses are recovered with an error of 20-40 per cent, and positions
and velocities with a root mean square error of ~1-2 Mpc (0.5-2 grid lengths)
and ~100 km/s, respectively. The recovery of the angular momentum of halos is
considerably noisier and accuracy at the statistical level is achieved only by
introducing free parameters. The algorithm requires negligible computer time as
compared with performing a numerical $N$-body simulation.


title: PINOCCHIO and the hierarchical build-up of dark matter haloes

abstract:
  We study the ability of PINOCCHIO (PINpointing Orbit-Crossing Collapsed
HIerarchical Objects) to predict the merging histories of dark matter (DM)
haloes, comparing the PINOCCHIO predictions with the results of two large
N-body simulations run from the same set of initial conditions. We focus our
attention on quantities most relevant to galaxy formation and large-scale
structure studies. PINOCCHIO is able to predict the statistics of merger trees
with a typical accuracy of 20 per cent. Its validity extends to higher-order
moments of the distribution of progenitors. The agreement is valid also at the
object-by-object level, with 70-90 per cent of the progenitors cleanly
recognised when the parent halo is cleanly recognised itself. Predictions are
presented also for quantities that are usually not reproduced by semi-analytic
codes, such as the two-point correlation function of the progenitors of massive
haloes and the distribution of initial orbital parameters of merging haloes.
For the accuracy of the prediction and for the facility with which merger
histories are produced, PINOCCHIO provides a means to generate catalogues of DM
haloes which is extremely competitive to large-scale N-body simulations, making
it a suitable tool for galaxy formation and large-scale structure studies.


title: Supermassive Black Holes and Galaxy Formation

abstract:
  The formation of supermassive black holes (SMBH) is intimately related to
galaxy formation, although precisely how remains a mystery. I speculate that
formation of, and feedback from, SMBH may alleviate problems that have arisen
in our understanding of the cores of dark halos of galaxies.


title:
Solar-cycle variation of the sound-speed asphericity from GONG and MDI
  data 1995-2000

abstract:
  We study the variation of the frequency splitting coefficients describing the
solar asphericity in both GONG and MDI data, and use these data to investigate
temporal sound-speed variations as a function of both depth and latitude during
the period from 1995-2000 and a little beyond. The temporal variations in even
splitting coefficients are found to be correlated to the corresponding
component of magnetic flux at the solar surface. We confirm that the
sound-speed variations associated with the surface magnetic field are
superficial. Temporally averaged results show a significant excess in sound
speed around 0.92 solar radii and latitude of 60 degrees.


title:
Visual binaries among high-mass stars - An adaptive optics survey of OB
  stars in the NGC 6611 cluster

abstract:
  We have searched for visual binaries with projected separations in the range
200-3000 AU (0.1"-1.5") among a sample of 96 stars in the massive young NGC
6611 cluster, 60 of them being subsequently identified as high probability
cluster members of mainly OB spectral type. This is the first visual binary
survey among such a large and homogeneous sample of high-mass stars. We find an
uncorrected binary frequency of 18+/-6% over the surveyed separation range.
Considering only binaries with mass ratios q>0.1, we find that OB stars in NGC
6611 host more companions than solar-type field stars. We derive mass ratios
for the detected binaries from their near-infrared flux ratios and conclude
that about half of the detected binaries have q<0.2, which does not contradict
the assumption that companion masses are randomly drawn from the initial mass
function. There is no evidence in our sample that wide-binary properties depend
upon the mass of the primary star. The high frequency of massive binaries in a
cluster as rich as NGC 6611 and the lack of a strong mass dependence of their
properties are difficult to reconcile with the scenario whereby massive stars
form as the result of mergers of smaller stars. The canonical protostellar
accretion scenario together with cloud fragmentation, on the other hand, can
naturally explain most of the observed binary properties, although the very
high stellar density in the protocluster is likely to require significant
modification to that picture as well.


title: Emission-Line Properties of z > 4 Quasars

abstract:
  We present results of a program of high signal-to-noise spectroscopy for 44
QSOs at redshifts > 4 using the MMT and Keck observatories. The quasar spectra
cover 1100 -- 1700 A in the rest frame for sources spanning a luminosity range
of approximately 2 orders of magnitude. Comparisons between these data and
spectra of lower redshift quasars reveal a high degree of similarity, although
differences are present in the profiles and the strengths of some emission
features. An examination of the luminosity dependence of the emission lines
reveals evidence for a weak or absent Baldwin effect among z > 4 QSOs. We
compare measurements for objects in our sample with results from other high
redshift surveys characterized by different selection techniques. Distributions
of equivalent widths for these different ensembles are consistent with a common
parent population, suggesting that our sample is not strongly biased, or in any
case, subject to selection effects that are not significantly different from
other surveys, including the Sloan Digital Sky Survey. Based on this
comparison, we tentatively conclude that the trends identified here are
representative of high z QSOs. In particular, the data bolster indications of
supersolar metallicities in these luminous, high-z sources, which support
scenarios that assume substantial star formation at epochs preceding or
concurrent with the QSO phenomena.


title:
Physical Implications of the X-ray Properties of Galaxy Groups and
  Clusters

abstract:
  Within the standard framework of structure formation, where clusters and
groups of galaxies are built up from the merging of smaller systems, the
physical properties of the intracluster medium, such as the gas temperature and
the total X-ray luminosity, are predicted to possess well defined self-similar
scaling relations. Observed clusters and groups, however, show strong
deviations from these predicted relations. We argue that these deviations are
unlikely to be entirely due to observational biasses; we assume they are
physically based, due to the presence of excess entropy in the intracluster
medium in addition to that generated by accretion shocks during the formation
of the cluster. Several mechanisms have been suggested as a means of generating
this entropy. Focussing on those mechanisms that preheat the gas before it
becomes a constituent of the virialized cluster environment, we present a
simple, intuitive, physically motivated, analytic model that successfully
captures the important physics associated with the accretion of high entropy
gas onto group and cluster-scale systems. We use the model to derive the new
relationships between the observable properties of clusters and groups of
galaxies, as well as the evolution of these relations. These include the
luminosity-temperature and luminosity-$\sigma$ relations, as well as the
temperature distribution function and X-ray luminosity function. These
properties are found to be a more accurate description of the observations than
those predicted from the standard framework. Future observations will that
further test the efficacy of the preheated gas scenario are also discussed.


title:
Simulating the Performance of Large-Format Submillimetre Focal-Plane
  Arrays

abstract:
  A robust measurement of the clustering amplitude of the sub-mm population of
starburst galaxies requires large-area surveys (>> 1 deg^2). The largest-format
arrays subtend only 10 arcmin^2 on the sky and hence scan-mapping is a
necessary observing mode. Providing realistic representations of the
extragalactic sky and atmosphere, as the input to a detailed simulator of the
telescope and instrument performance, allows important decisions to be made
about the design of large-area fully-sampled surveys and observing strategies.
In this paper we present preliminary simulations that include detector noise,
time-constants and array geometry, telescope pointing errors, scan speeds and
scanning angles, sky noise and sky rotation.


title: Infrared Classification of L and T Dwarfs

abstract:
  We use new and published medium resolution 0.6--2.5 $\mu$m spectra of L and T
dwarfs to develop a unified classification system for both of these new
spectral classes. Two indices of the system at 1.2 $\mu$m and 1.5 $\mu$m are
based on nearby absorption bands of water vapor and two are associated with
methane bands near 1.6 $\mu$m and 2.2 $\mu$m. The 1.5 $\mu$m index is monotonic
through the L and T sequences, and forms the backbone of the system; the
indices for the other bands provide extensive, but only partial, coverage. We
correlate the 1.5 $\mu$m index with continuum indices shortward of 1 $\mu$m
devised by others for classifying L dwarfs, in order to obtain a tight link
between optical and infrared classifications. Our proposed system defines ten
spectral subclasses for L (L0--L9) and nine for T (T0--T8). The boundary
between L and T is defined to be the onset of absorption by methane in the H
band. Methane absorption in the K band near 2.2 $\mu$m is found to begin
approximately at L8.


title: Reconnection in pulsar winds

abstract:
  The spin-down power of a pulsar is thought to be carried away in an MHD wind
in which, at least close to the star, the energy transport is dominated by
Poynting flux. The pulsar drives a low-frequency wave in this wind, consisting
of stripes of toroidal magnetic field of alternating polarity, propagating in a
region around the equatorial plane. The current implied by this configuration
falls off more slowly with radius than the number of charged particles
available to carry it, so that the MHD picture must, at some point, fail.
Recently, magnetic reconnection in such a structure has been shown to
accelerate the wind significantly. This reduces the magnetic field in the
comoving frame and, consequently, the required current, enabling the solution
to extend to much larger radius. This scenario is discussed and, for the Crab
Nebula, the range of validity of the MHD solution is compared with the radius
at which the flow appears to terminate. For sufficiently high particle
densities, it is shown that a low frequency entropy wave can propagate out to
the termination point. In this case, the "termination shock" itself must be
responsible for dissipating the wave.


title:
Supernova SN1987A Revisited as a Major Production Site for r-Process
  Elements

abstract:
  The origin of nucleosynthesis products of rapid neutron capture reactions
(the r-process) is a longstanding astrophysical problem. Recent analyses of
elemental abundances for extremely metal-poor stars shed light on the elemental
abundances of individual supernovae. Comparison of the abundance distributions
of some extremely metal-poor stars with those of the best-observed supernova SN
1987A clearly indicates that the overabundances of barium and strontium found
in SN 1987A that have been ascribed to the slow neutron capture process must be
results of r-process nucleosynthesis. The mass of freshly synthesized barium in
SN 1987A is estimated to be 6x10^-6 solar mass based on the observed surface
abundance and detailed hydrodynamical models for this supernova. These new
findings lead to the conclusion that 20 solar mass stars, one of which is the
progenitor star of SN 1987A, are the predominant production sites for r-process
elements in the Galaxy and the r-process element donors for notable
neutron-capture-rich giant stars, CS22892-052 and CS31082-001.


title: Chemical Evolution of Odd Elements in an Inhomogeneous Early Galaxy

abstract:
  We investigate the chemical evolution of odd-numbered elements such as sodium
(Na) and aluminum (Al) during the early epochs of the Galactic halo with the
use of a model that reproduces the observed box-shaped distribution of
extremely metal-poor stars in the [Na, Al/Mg] versus [Mg/H] plane. Our model is
constructed under the assumptions that those stars retain the elemental
abundance patterns produced by individual Type II supernovae (SNe), and that
the yields of the odd elements depend on the initial metallicity, z, of their
SN progenitors. As a result, recent abundance determinations that clarify how
the [Na, Al/Mg] ratios of field stars have evolved to the solar values enable
us to deduce how the yields of these odd elements depend on z. The observed
trends in these abundances, in particular the very large scatter (over 1 dex in
[Al/Mg]) requires that the Al yield scales as m_Al proportional to z^0.6 for
[Mg/H]<-1.8, while the observed [Na/Mg] trend requires that the Na yield scales
as m_Na proportional to z^-0.4 for [Mg/H]<-1.8 and m_Na proportional to z^0.4
for [Mg/H]>-1.8. It is found that the predicted frequency distribution of stars
in the [Na/Mg] versus [Mg/H] diagram is very sensitive to the assumed form of
the primordial IMF, and that its slope is steeper than the Salpeter IMF. The
necessity to match the observed abundance patterns of odd elements and the
frequency distribution of extremely metal-poor stars should provide useful
constraints on nucleosynthesis calculations of metal-free massive stars as well
as on theories of their formation.


title: The gaseous content of the Blue Compact Galaxy Mrk 59

abstract:
  FUSE far-UV spectroscopy of the nearby metal-deficient (Zo/8) cometary Blue
Compact Dwarf galaxy Mrk59 have been used to investigate element abundances in
its interstellar medium. The lack of diffuse H2 (N(H2)<10e15 cm-2) is due to
the combined effect of a strong UV radiation field and a low metallicity. By
fitting the line profiles with multiple components having b=7kms-1 and spanning
a radial velocity range of 100 kms-1, we derive heavy element abundances in the
neutral gas. We find log N(OI)/N(HI)=-5.0+/-0.3, about a factor of 10 below the
oxygen abundance of the supergiant HII region.


title:
Spatially-resolved X-ray spectroscopy of the core of the Centaurus
  cluster

abstract:
  We present Chandra data from a 31.7 ks observation of the Centaurus cluster,
using the ACIS-S detector. Images of the X-ray emission show a plume-like
feature at the centre of the cluster, of extent 60 arcsec (20 kpc in
projection). The feature has the same metallicity as gas at a similar radius,
but is cooler. Using adaptive binning, we generate temperature, abundance and
absorption maps of the cluster core. The radial abundance profile shows that
the previously known, steep abundance gradient peaks with a metallicity of
1.3-1.8 Zsolar at a radius of about 45 arcsec (15 kpc), before falling back to
0.4 Zsolar at the centre of the cluster. A radial temperature profile shows
that the temperature decreases inwards. We determine the spatial distributions
of each of two temperature components, where applicable. The radiative cooling
time of the cooler component within the inner 10 arcsec (3 kpc) is less than
2x10^7 yr. X-ray holes in the image coincident with the radio lobes are seen,
as well as two outer sharp temperature drops, or cold fronts. The origin of the
plume is unclear. The existence of the strong abundance gradient is a strong
constraint on extensive convection or gas motion driven by a central radio
source.


title: Magnetic fields in the Centaurus cluster

abstract:
  We present multi-frequency VLA observations of the radio galaxy PKS 1246-410
at the center of the Centaurus Cluster, and compare these results to recent
Chandra observations. The unusual radio morphology of PKS 1246-410 probably
results from interactions with the hot, X-ray emitting gas. This gas, along
with cluster magnetic fields, also produces substantial Faraday Rotation
Measures towards PKS 1246-410. We discuss these observations in the context of
a sample of 14 luminous X-ray clusters with embedded radio galaxies and
possible cooling flows. A correlation is found between the cooling flow rate
and the maximum Faraday Rotation Measures. Magnetic fields of strength 10-40 uG
are found to be common to the centers of clusters with strong cooling flows,
and somewhat lower field strengths of 2-10 uG are found in the non cooling-flow
clusters.


title: Observations and Simulations of Relativistic Jets

abstract:
  The recent improvement in VLBI arrays is providing information of the
emission and magnetic field structure of relativistic jets, both extragalactic
and galactic (microquasars), with unprecedented spatial and temporal
resolution. These observations are revealing the importance of the
hydrodynamical processes that govern the jet evolution, which can be studied by
the recently developed time-dependent relativistic hydrodynamical models.
Computation of the non-thermal emission from these hydrodynamical models, and
its comparison with actual sources, is proving as one of the most powerful
tools in the understanding of the physical processes taking place in these
jets. This paper reviews some of the recent observational results, as well as
the numerical models used to interpret them.


title: Reflection at large distance from the central engine in Seyferts

abstract:
  We consider the possibility that most of the reflection component, observed
in the hard X-ray spectra of Seyfert galaxies, could be formed on an extended
medium, at large distance from the central source of primary radiation (e.g. on
a torus). Then, the reflector cannot respond to the rapid fluctuations of the
primary source. The observed reflected flux is controlled by the time-averaged
primary spectrum rather than the instantaneous (observed) one. We show that
this effect strongly influence the spectral fits parameters derived under the
assumption of a reflection component consistent with the primary radiation. We
find that a pivoting primary power-law spectrum with a nearly constant
Comptonised luminosity may account for the reported correlation between the
reflection amplitude $R$ and the spectral index $\Gamma$.


title: Interpreting the Behavior of Time Resolved Gamma-Ray Burst Spectra

abstract:
  In this paper, we explore time resolved Gamma-Ray Burst (GRB) spectra in the
context of the synchrotron emission model presented in Lloyd and Petrosian
(2000; LP00). First, we show that our model - which involves three distinct
emission regimes - can provide excellent fits to the time resolved spectra of
GRBs, and we present these results for a few bursts. We then describe how the
phenomenological Band spectrum (Band et al., 1993) can be interpreted in the
context of our models based on the value of the low energy photon index
$\alpha$. We discuss the types of correlations one would expect to observe
among the Band parameters if these models are correct. We then compare these
predictions to the existing data, combining a sample of 2,026 time resolved
spectra (from approximately 80 bursts). We show that the correlations found in
the data are consistent with the models, and discuss the constraints they place
on the emission physics. In particular, we find a 4-sigma negative correlation
between the peak of the nu-Fnu spectrum, Ep, and the low energy photon index
$\alpha$ for bursts with $-2/3 < \alpha < 0$, in contrast to what is predicted
by the instrumental effect discussed in LP00. We suggest that this correlation
is simply due to the mechanism responsible for producing $\alpha$'s above the
value of -2/3 - namely, a decreasing mean pitch angle of the electrons. We also
show that Ep is correlated with the photon flux, and interpret this as a result
of changing magnetic field or characteristic electron energy between emission
episodes. Finally, we discuss the implications our results have on particle
acceleration in GRBs, and prospects for further testing these models with the
anticipated data from HETE-2, Swift and GLAST.


title: Gravitational tidal effects on galactic open clusters

abstract:
  We have investigated the 2-D stellar distribution in the outer parts of three
nearby open clusters: NGC 2287 (=M41), NGC 2516, and NGC 2548 (=M48).
Wide-field star counts have been performed in two colours on pairs of digitized
ESO and SRC Schmidt plates, allowing us to select likely cluster members in the
colour-magnitude diagrams. Cluster tidal extensions were emphasized using a
wavelet transform. Taking into account observational biases, namely the galaxy
clustering and differential extinction in the Galaxy, we have associated these
stellar overdensities with real open cluster structures stretched by the
galactic gravitational field. As predicted by theory and simulations, and
despite observational limitations, we detected a general elongated (prolate)
shape in a direction parallel to the galactic Plane, combined with tidal tails
extended perpendicularly to it. This geometry is due both to the static
galactic tidal field and the heating up of the stellar system when crossing the
Disk. The time varying tidal field will deeply affect the cluster dynamical
evolution, and we emphasize the importance of adiabatic heating during the
Disk-shocking. In the case of NGC 2548, our dating of the last shocking with
the Plane (based on a tidal clump) is consistent with its velocity. During the
10-20 Z-oscillations experienced by a cluster before its dissolution in the
Galaxy, crossings through the galactic Disk contribute to at least 15% of the
total mass loss. Using recent age estimations published for open clusters, we
find a destruction time-scale of about 600 Myr for clusters in the solar
neighbourhood.


title:
Deep ROSAT-HRI observations of the NGC 1399/NGC 1404 region: morphology
  and structure of the X-ray halo

abstract:
  We present the analysis of a deep (167 ks) ROSAT HRI observation of the cD
galaxy NGC 1399 in the Fornax cluster. Using both HRI and, at larger radii,
archival PSPC data, we find that the radial behavior of the X-ray surface
brightness profile is not consistent with a simple Beta model and suggests
instead three distinct components. We use a multi-component bidimensional model
to study in detail these three components that we identify respectively with
the cooling flow region, the galactic and the cluster halo. From these data we
derive a binding mass distribution in agreement with that suggested by optical
dynamical indicators, with an inner core dominated by luminous matter and an
extended dark halo differently distributed on galactic and cluster scales. The
HRI data and a preliminary analysis of Chandra public data, allow us to detect
significant density fluctuations in the halo. We discuss possible
non-equilibrium scenarios to explain the hot halo structure, including tidal
interactions with neighboring galaxies, ram stripping from the intra-cluster
medium and merging events. In the innermost region of NGC 1399, the comparison
between the X-ray and radio emission suggests that the radio emitting plasma is
displacing and producing shocks in the hot X-ray emitting gas. We found that
the NGC 1404 halo is well represented by a single symmetric Beta model and
follows the stellar light profile within the inner 8 kpc. The mass distribution
is similar to the `central' component of the NGC 1399 halo. At larger radii ram
pressure stripping from the intra-cluster medium produces strong asymmetries in
the gas distribution. Finally we discuss the properties of the point source
population finding evidence of correlation between the source excess and NGC
1399.


title: The Very Small Array

abstract:
  The Very Small Array (VSA) is a fourteen-element interferometer designed to
study the cosmic microwave background on angular scales of 2.4 to 0.2 degrees
(angular multipoles l = 150 to 1800). It operates at frequencies between 26 and
36 GHz, with a bandwidth of 1.5 GHz, and is situated at the Teide Observatory,
Tenerife. The instrument also incorporates a single-baseline interferometer,
with larger collecting area, operating simultaneously with and at the same
frequency as the VSA main array. This provides accurate flux measurements of
contaminating radio sources in the VSA observations. Since September 2000, the
VSA has been making observations of primordial CMB fluctuations. We describe
the instrument, observing strategy and current status of the first year of
observations.


title:
Changes in solar oscillation frequencies during the current activity
  maximum: analysis and interpretation

abstract:
  We describe systematic changes in the centroid frequencies and the splitting
coefficients as found using data from MDI on board SOHO, covering cycle 23. The
data allow us to construct a seismic map of the evolving solar activity --
covering all latitudes. At lower latitudes, the temporal evolution closely
tracks that of {\it butterfly diagram}. The additional information from higher
latitudes in the map is of a significant activity in the polar region, peaking
at activity minimum in 1996. The most plausible source of solar oscillation
frequency changes over the solar cycle is the evolution of the radial component
of the small-scale magnetic field. The amplitude of the required mean field
changes is about 100 G at the photosphere, and increasing going inward.


title:
Contemporary interstellar meteoroids in the solar system - in situ
  measurements and clues on composition

abstract:
  Meteoroids originating from the local interstellar medium, traverse the solar
system. This has been proven by in situ measurements by interplanetary
spacecraft as well as highly sensitive radar measurements. Early attempts to
detect interstellar meteoroids using the instruments on board the Pioneer 8 and
9 spacecraft failed. More sensitive detectors on board the joint ESA/NASA
mission Ulysses as well as on board the NASA spacecraft Galileo, however,
unambiguously detected meteoroids of interstellar origin. This discovery has
started efforts to compare the results from the in situ measurements with
highly sophisticated models of interstellar dust properties derived from
astronomical absorption and extinction measurements. It was found that, at
least locally, is more mass locked up in meteoroids than expected from the
astronomical measurements. So far the in situ measurements only allow to derive
composition information indirectly via the meteoroid's dynamics.


title:
An XMM-Newton observation of the extreme Narrow Line Seyfert 1 Galaxy,
  Mrk 359

abstract:
  We present XMM-Newton observations of Mrk 359, the first Narrow Line Seyfert
1 galaxy discovered. Even among NLS1s, Mrk 359 is an extreme case with
extraordinarily narrow optical emission lines. The XMM-Newton data show that
Mrk 359 has a significant soft X-ray excess which displays only weak absorption
and emission features. The (2-10) keV continuum, including reflection, is
flatter than the typical NLS1, with Gamma approximately 1.84. A strong emission
line of equivalent width approximately 200 eV is also observed, centred near
6.4 keV. We fit this emission with two line components of approximately equal
strength: a broad iron-line from an accretion disc and a narrow, unresolved
core. The unresolved line core has an equivalent width of approximately 120 eV
and is consistent with fluorescence from neutral iron in distant reprocessing
gas, possibly in the form of a `molecular torus'. Comparison of the narrow-line
strengths in Mrk 359 and other low-moderate luminosity Seyfert 1 galaxies with
those in QSOs suggests that the solid angle subtended by the distant
reprocessing gas decreases with increasing AGN luminosity.


title:
The Dark Galaxy Problem and the Effects of Substructure on Gravitational
  Lenses

abstract:
  I argue that the cold dark matter (CDM) model requires that even within a few
kpc of the center of a galactic halo a significant fraction (greater than a few
percent) of the surface density is contained in substructures with masses >
10^3 solar masses. These structures should be light enough to avoid dynamical
friction and dense enough to avoid tidal disruption. I then show using the
results of numerical simulations that this substructure will significantly
alter the flux ratios of multiply imaged quasars (QSOs) without changing the
image positions. The degree to which this occurs will depend on the angular
size of the QSO and thus the wavelength of the observations.


title: A new wide pair of cool white dwarfs in the Solar neighbourhood

abstract:
  We report the discovery of a wide pair (93 arcsec angular separation) of
extremely cool ($T_{eff}<4000$ K) white dwarfs with a very large common proper
motion ($\sim1.9$ arcsec/yr). The objects were discovered in a high proper
motion survey in the poorly investigated southern sky region with
$\delta<-60^{\circ}$ using SuperCOSMOS Sky Survey (SSS) data. Both objects,
SSSPM J2231-7514 and SSSPM J2231-7515, show featureless optical spectra. Fits
of black-body models to the spectra yield effective temperatures of 3810 K and
3600 K, respectively for the bright (V=16.60) and faint (V=16.87) component.
Both degenerates are much brighter than other recent discoveries of cool white
dwarfs with comparable effective temperatures and/or $B_J-R$ colours.
Therefore, they should be relatively nearby objects. The comparison with other
cool white dwarfs and a photometric distance determination yield distance
estimates between 9 pc and 14 pc. The latter seems to be more realistic, since
the good agreement of the proper motion of both components within the errors of
about 8 mas/yr and the angular separation between the two stars support a
distance of about 15 pc with relatively small masses of the components. With
smaller distance we should be able to measure a differential proper motion due
to orbital motion if the orbital plane is not strongly inclined and the present
orbital velocity vector is not close to the line of sight. The space velocity
based on that distance and assumptions on radial velocity makes the new pair of
extremely cool white dwarfs some of the probably oldest members of the Galactic
disk population, although the possibility that these objects are part of a
Galactic halo dark matter component can also not yet be ruled out.


title: Accelerated Expansion: Theory and Observations

abstract:
  The present paradigm in cosmology is the usual Big-Bang Cosmology in which
two stages of accelerated expansion are incorporated: the inflationary phase in
the very early universe which produces the classical inhomogeneities observed
in the universe, and a second stage of acceleration at the present time as the
latest Supernovae observations seem to imply. Both stages could be produced by
a scalar field and observations will strongly constrain the microscopic
lagrangian of any proposed model.


title: A Model of Varying Fine Structure Constant and Varying Speed of Light

abstract:
  The recent evidence for a cosmological evolution of the fine structure
constant \alpha=e^2/\hbar c found from an analysis of absorption systems in the
spectra of distant quasars, is modelled by a cosmological scenario in which it
is assumed that only the speed of light varies. The model fits the spectral
line data and can also lead to a solution of the initial value problems in
cosmology.


title: SZ surveys with the Arcminute MicroKelvin Imager

abstract:
  The Arcminute MicroKelvin Imager (AMI) is an instrument currently under
construction in Cambridge designed to produce a survey of galaxy clusters via
the Sunyaev-Zel'dovich effect. It consists of two interferometric arrays, both
operating at 12-18 GHz; one of ten 3.7-m antennas to provide good temperature
sensitivity to arcminute-scale structures, and one of eight 13-m antennas (the
present Ryle Telescope) to provide flux sensitivity for removing contaminating
radio sources. The telescope is due to be observing by 2003, and will produce a
public survey of galaxy clusters, as well as being available to guest
observers.


title: Numerical evolutions of nonlinear r-modes in neutron stars

abstract:
  Nonlinear evolution of the gravitational radiation (GR) driven instability in
the r-modes of neutron stars is studied by full numerical 3D hydrodynamical
simulations. The growth of the r-mode instability is found to be limited by the
formation of shocks and breaking waves when the dimensionless amplitude of the
mode grows to about three in value. This maximum mode amplitude is shown by
numerical tests to be rather insensitive to the strength of the GR driving
force. Upper limits on the strengths of possible nonlinear mode--mode coupling
are inferred. Previously unpublished details of the numerical techniques used
are presented, and the results of numerous calibration runs are discussed.


title:
Pulsar Spin-Down Induced Phenomena: Heating; Magnetic Field Evolution;
  Glitches; Pulse-Period Modulations

abstract:
  Modeling the dynamics of the quantum fluids within a spinning-down neutron
star gives a description consistent with observed pulsar magnetic field
evolution and spin-period "glitches." The long-standing problem of large
predicted excesses in spin-down sustained pulsar heating from such models now
see ms resolvable. However, the origin of some pulsar spin-period and
pulse-shape modulations which have been interpreted as manifestations of very
long period (~year) stellar precession is a crucial challenge to canonical
neutron star models.


title: Scale Dependent Spectral Index in Slow Roll Inflation

abstract:
  Recent observations suggest that the spectral index of the primordial
perturbations is very close to unity, as expected in models of slow roll
inflation. It is still possible for such models to produce spectra which are
scale dependent. We present a formula for the spectrum produced by an arbitrary
inflaton potential (within the context of slow roll models); this formula
explicitly illustrates and accounts for the possiblity of scale dependence. A
class of examples are studied and comparisons made with the standard slow roll
formula.


title:
Tree-Structured Grid Model of Line and Polarization Variability from
  Massive Binaries

abstract:
  We have developed a 3-D Monte Carlo radiative transfer model which computes
line and continuum polarization variability for a binary system with an
optically thick non-axisymmetric envelope. This allows us to investigate the
complex (phase-locked) line and continuum polarization variability features
displayed by many massive binaries: W-R+O, O+O, etc. An 8-way tree data
structure constructed via a ``cell-splitting'' method allows for high precision
with efficient use of computer resources. The model is not restricted to binary
systems; it can easily be adapted to a system with an arbitrary density
distribution and large density gradients. As an application to a real system,
the phase dependent Stokes parameters (I, Q, U) and the phase dependent He I
(5876) profiles of the massive binary system V444 Cyg (WN5+O6 III-V) are
computed.


title:
Rate Coefficients for D(1s) + H^+ <--> D^+ + H(1s) Charge Transfer and
  Some Astrophysical Implications

abstract:
  We have calculated the rate coefficients for D(1s) + H^+ <--> D^+ + H(1s)
using recently published theoretical cross sections. We present results for
temperatures T from 1 K to 2x10^5 K and provide fits to our data for use in
plasma modeling. Our calculations are in good agreement with previously
published rate coefficients for 25 <= T <= 300 K, which covers most of the
limited range for which those results were given. Our new rate coefficients for
T >~ 100 K are significantly larger than the values most commonly used for
modeling the chemistry of the early universe and of molecular clouds. This may
have important implications for the predicted HD abundance in these
environments. Using our results, we have modeled the ionization balance in high
redshift QSO absorbers. We find that the new rate coefficients decrease the
inferred D/H ratio by <~ 0.4%. This is a factor of >~ 25 smaller than the
current >~ 10% uncertainties in QSO absorber D/H measurements.


title: Voids in the PSCz Survey and the Updated Zwicky Catalog

abstract:
  We describe an algorithm to detect voids in galaxy redshift surveys. The
method is based on the void finder algorithm of El-Ad & Piran. We apply a
series of tests to determine how accurately we are able to recover the volumes
of voids using our detection method. We simulate voids of different ellipticity
and find that if voids are approximately spherical, our algorithm will recover
100% of the volume of the void. The more elliptical the void, the smaller the
fraction of the volume we can recover. We insist that voids lie completely
within the survey. Voids close to the edge of the survey will therefore be
underestimated in volume. By considering a deeper sample, we estimate the
maximal sphere diameters are correct to within 30%.
  We apply the algorithm to the Point Source Catalogue Survey (PSCz) and the
Updated Zwicky Catalog (UZC). The PSCz survey is an almost all-sky survey with
objects selected from the IRAS catalog. The UZC covers a smaller area of sky
but is optically selected and samples the structures more densely. We detect 35
voids in the PSCz and 19 voids in the UZC with diameter larger than
20h^{-1}Mpc. Using this minimum size threshold, voids have an average effective
diameter of 29.8+-3.5 h^{-1}Mpc (PSCz) and 29.2+-2.7 h^{-1}Mpc (UZC) and that
they are underdense regions with delta rho /rho values of -0.92+-0.03 (PSCz)
and -0.96+-0.01(UZC) respectively. Using this quite stringent threshold for
void definition, voids fill up to 40% of the volume of the universe.


title: The Morphological Evolution of Galaxies

abstract:
  Many galaxies appear to have taken on their familiar appearance relatively
recently. In the distant Universe, galaxy morphology started to deviate
significantly (and systematically) from that of nearby galaxies at redshifts,
z, as low as z = 0.3. This corresponds to a time ~3.5 Gyr in the past, which is
only ~25% of the present age of the Universe. Beyond z = 0.5 (5 Gyr in the
past) spiral arms are less well-developed and more chaotic, and barred spiral
galaxies may become rarer. By z = 1, around 30% of the galaxy population is
sufficiently peculiar that classification on Hubble's traditional tuning fork
system is meaningless. On the other hand, some characteristics of galaxies do
not seem to have changed much over time. The co-moving space density of
luminous disk galaxies has not changed significantly since z = 1, indicating
that while the general appearance of these objects has continuously changed
with cosmic epoch, their overall numbers have been conserved. Attempts to
explain these results with hierarchical models for the formation of galaxies
have met with mixed success.


title:
The Discovery of a Second Luminous Low Mass X-ray Binary in the Globular
  Cluster M15

abstract:
  We report an observation by the Chandra X-ray Observatory of 4U2127+119, the
X-ray source identified with the globular cluster M15. The Chandra observation
reveals that 4U2127+119 is in fact two bright sources, separated by 2.7". One
source is associated with AC211, the previously identified optical counterpart
to 4U2127+119, a low mass X-ray binary (LMXB). The second source, M15-X2, is
coincident with a 19th U magnitude blue star that is 3.3" from the cluster
core. The Chandra count rate of M15-X2 is 2.5 times higher than that of AC211.
Prior to the 0.5" imaging capability of Chandra the presence of two so closely
separated bright sources would not have been resolved. The optical counterpart,
X-ray luminosity and spectrum of M15-X2 are consistent with it also being an
LMXB system. This is the first time that two LMXBs have been seen to be
simultaneously active in a globular cluster. The discovery of a second active
LMXB in M15 solves a long standing puzzle where the properties of AC211 appear
consistent with it being dominated by an extended accretion disk corona, and
yet 4U2127+119 also shows luminous X-ray bursts requiring that the neutron star
be directly visible. The resolution of 4U2127+119 into two sources suggests
that the X-ray bursts did not come from AC211, but rather from M15-X2. We
discuss the implications of this discovery for understanding the origin and
evolution of LMXBs in GCs as well as X-ray observations of globular clusters in
nearby galaxies.


title: Infrared Colors of L and T Dwarfs

abstract:
  We discuss the behaviour of the JHKL'M' colors of L and T dwarfs, based on
photometric and spectroscopic data obtained at the United Kingdom Infrared
Telescope in Hawaii. We have measured the first accurate M' photometry for L
and T dwarfs. The K-M' colors of T dwarfs are much bluer than predicted by
published models, suggesting that CO may be more abundant than expected, as has
been found spectroscopically for the T6 dwarf Gl 229B. We also find that K-L'
increases monotonically through most of the M, L, and T subclasses, but it is
approximately constant between types L6 and T5, due to the onset of methane
absorption at the blue edge of the L' bandpass. The JHK colors of L dwarfs show
significant scatter, suggesting variations in the amount and properties of
photospheric dust, and indicating that it may not be possible to associate a
unique effective temperature with a given L spectral type. The H-K colors of
the later T dwarfs also show some scatter which we suggest is due to variations
in pressure-induced molecular hydrogen opacity, which is sensitive to gravity
(or age for a brown dwarf) and metallicity.


title: Large Torque Variations in Two Soft Gamma Repeaters

abstract:
  We have monitored the pulse frequencies of the two soft gamma repeaters SGR
1806-20 and SGR 1900+14 through the beginning of year 2001 using primarily
Rossi X-ray Timing Explorer Proportional Counter Array observations. In both
sources, we observe large changes in the spin-down torque up to a factor of ~4,
which persist for several months. Using long baseline phase-connected timing
solutions as well as the overall frequency histories, we construct torque noise
power spectra for each SGR. The power spectrum of each source is very red
(power-law slope ~-3.5). The torque noise power levels are consistent with some
accreting systems on time scales of ~1 year, yet the full power spectrum is
much steeper in frequency than any known accreting source. To the best of our
knowledge, torque noise power spectra with a comparably steep frequency
dependence have only been seen in young, glitching radio pulsars (e.g. Vela).
The observed changes in spin-down rate do not correlate with burst activity,
therefore, the physical mechanisms behind each phenomenon are also likely
unrelated. Within the context of the magnetar model, seismic activity cannot
account for both the bursts and the long-term torque changes unless the
seismically active regions are decoupled from one another.


title: The Distribution of Thermal Pressures in the Interstellar Medium

abstract:
  It is generally recognized that the interstellar medium has a vast range of
densities and temperatures. While these two properties are usually
anticorrelated with each other, there are nevertheless variations in their
product, i.e., the thermal gas pressure divided by the Boltzmann constant k. In
neutral gas, the relative populations of neutral carbon atoms in the excited
fine-structure states can give a direct measure of a local thermal pressure. A
picture of the distribution function for thermal pressures in H I regions is
now arising from a survey of interstellar C I absorption features in the UV
spectra of 21 early-type stars, observed with a wavelength resolving power of
200,000 by the STIS instrument on the Hubble Space Telescope. Most of the gas
is within the range 1000 < p/k < 10,000 cm^{-3}K, but there is also evidence
for some of the material being at much higher pressures, i.e., p/k > 10^5
cm^{-3}K. While the fraction of gas at these elevated pressures is quite small,
it seems nearly ubiquitous. This phenomenon may arise from small-scale,
short-lived density enhancements that are produced by converging flows of
material in supersonic turbulence.


title: The Hot Phase in the Galactic Disk

abstract:
  Spectra of about 150 early-type stars in the disk of the Milky Way recorded
by the Far Ultraviolet Spectroscopic Explorer (FUSE) reveal absorption features
from interstellar O VI, a tracer of collisionally ionized gases at temperatures
near 300,000 K. (Hotter material is better sensed by its diffuse x-ray
emission.) The FUSE survey indicates that hot gas in the plane of the Galaxy
yields an average density n(O VI) = 1.7 X 10^{-8} cm^{-3}, a value consistent
with earlier results from the Copernicus satellite, but at great distances
there is a large dispersion in the measurements from one line of sight to
another. This dispersion indicates that O VI absorbing regions probably have a
broad distribution of sizes, perhaps giving a power-law behavior for column
densities. Comparisons of O VI with other Li-like ions should give some
guidance on the nature and origin of the O VI-absorbing regions, but poor
correspondences in the velocity profile shapes will complicate the
interpretations.


title:
Population Synthesis in the Blue I. Synthesis of the Integrated Spectrum
  of 47 Tucanae from its Color-Magnitude Diagram

abstract:
  We perform an empirical synthesis of the blue integrated spectrum of the
metal-rich globular cluster 47 Tucanae, based directly on the color-magnitude
diagram of the cluster coupled to a moderately high-resolution spectral
library. Freed from any significant dependence on theory, we are able to
perform a fundamental test of the adequacy of the spectral library and its
associated stellar parameters. Excellent fits are achieved for almost all
absorption-line indices studied, provided the computations are corrected for
two limitations of the spectral library, namely, the lack of a representative
set of metal-poor giants and the absence of CN-strong stars. The latter effect
is corrected by means of spectrum synthesis from model photospheres,
considering the abundance pattern of CN-strong and CN-normal stars. We also
need to perform a slight correction of the metallicity of the cluster (by
--0.05 dex in relation to the standard value [Fe/H]=-0.7) in order to match the
metal-line index measurements in the cluster spectrum. After these relatively
small adjustments, the overall spectral agreement is good. Good fits are
achieved for Hbeta, Hgamma, Mgb, <Fe>, Ca4227 and Fe4383, and only Hdelta_F is
overpredicted. Thus, ages inferred from Hdelta_F are slightly older than the
ages based on the other Balmer lines, by ~ 3 Gyrs. The success of this exercise
suggests that previous failures to synthesize the spectrum of 47 Tuc must have
arisen from inadequacies in the theoretical evolutionary isochrones and/or
luminosity functions. Such a possibility is considered in a companion paper.


title: Population Synthesis in the Blue II. The Spectroscopic Age of 47 Tucanae

abstract:
  We develop a new set of models for intermediate-metallicity single stellar
populations in the blue/optical region and use those models to determine the
spectroscopic age of 47 Tuc. The models are based on a moderately
high-resolution (1.8 A FWHM) empirical spectral library, state-of-the-art
theoretical isochrones from M. Salaris and the most recent set from the Padova
group, and new semi-empirical calibrations between fundamental stellar
parameters and observables. We highlight the importance of correctly modeling
the luminosity function (LF) of the cluster at the level of the giant branch,
in order to achieve a good reproduction of the integrated spectrum; agreement
between the spectroscopic age and the age based on the cluster's
color-magnitude diagram (CMD) is achieved only if the observed LF is used
rather than the theoretical ones, which either do not include AGB stars
(Salaris) or underpredict the total number counts of bright giants in the
cluster by a factor of two(Padova). After all corrections are made, the CMD and
the spectroscopic ages (from Hgamma and Hbeta) are in close agreement: 11--12
Gyrs for Salaris isochrones and about 13 Gyrs for Padova. The difference
between the model ages is due to the inclusion of atomic diffusion in the
Salaris models. Previously older spectroscopic ages were due to the
underestimate of the number of red giants and/or the use of isochrones that
neglected the effects of He-diffusion and alpha-enhancement. A similar
underestimate in the bright giant LF, if it exists in current super-solar
metallicity models, would cause spectroscopic ages of elliptical galaxies
inferred from such models to be too high by approximately 30%.


title: Antibias in Clusters: The Dependence of M/L on Cluster Temperature

abstract:
  We show that the observed mass-to-light ratio of galaxy clusters increases
with cluster temperature as expected from cosmological simulations. Contrary to
previous observational suggestions, we find a mild but robust increase of M/L
from poor (T = 1 - 2 keV) to rich (T = 12 keV) clusters; over this range, the
mean M/L_V increases by a factor of about 2. The best fit relation satisfies
M/L_V = (170 +- 30) T(keV)^(0.3 +- 0.1) h at z=0, with a large scatter. This
trend confirms predictions from cosmological simulations which show that the
richest clusters are antibiased, with a higher ratio of mass per unit light
than average. The antibias increases with cluster temperature. The effect is
caused by the relatively older age of the high-density clusters, where light
has declined more significantly than average since their earlier formation
time. Combining the current observations with simulations, we find a global
value of M/L_V = 240 +- 50 h, and a corresponding mass density of the universe
of Omega_m = 0.17 +- 0.05.


title:
Rapid X-ray flaring from the direction of the supermassive black hole at
  the Galactic Centre

abstract:
  Most galactic nuclei are now believed to harbour supermassive black holes.
Studies of stellar motions in the central few light-years of our Milky Way
Galaxy indicate the presence of a dark object with a mass of about 2.6 million
solar masses. This object is spatially coincident with Sagittarius A* (Sgr A*),
the unique compact radio source located at the dynamical centre of our Galaxy.
By analogy with distant quasars and nearby active galactic nuclei (AGN), Sgr A*
is thought to be powered by the gravitational potential energy released by
matter as it accretes onto a supermassive black hole. However, Sgr A* is much
fainter than expected in all wavebands, especially in X-rays, casting some
doubt on this model. Recently, we reported the first strong evidence of X-ray
emission from Sgr A*. Here we report the discovery of rapid X-ray flaring from
the direction of Sgr A*. These data provide compelling evidence that the X-ray
emission is coming from accretion onto a supermassive black hole at the
Galactic Centre, and the nature of the variations provides strong constraints
on the astrophysical processes near the event horizon of the black hole.


title:
The CFHT Open Star Cluster Survey. III. The White Dwarf Cooling Age of
  the Rich Open Star Cluster NGC 2099 (M37)

abstract:
  We present deep CCD photometry of the very rich, intermediate aged (similar
to the Hyades) open star cluster NGC 2099 (M37). The V, B-V color-magnitude
diagram (CMD) for the cluster shows an extremely well populated and very
tightly constrained main-sequence extending over 12 magnitudes from the
turn-off. The CFH12K photometry for this cluster is faint enough (V ~ 24.5) to
detect the remnants of the most massive progenitor cluster stars under the Type
I SNe limit. Therefore, the CMD of the cluster also exhibits a well defined
white dwarf `clump' caused by the decreased rate of cooling of these stars as
they age, and a subsequent gap with very few objects. The termination point (Mv
= 11.95 +/- 0.30) of the white dwarf luminosity function gives a white dwarf
cooling age of 566 +/- 154/176 Myrs which is in excellent agreement with the
main-sequence turn-off isochrone age (520 Myrs). By carefully accounting for
errors, we show that the cooling age confirms that models including convective
core overshooting are preferred for young-intermediate aged clusters. We also
derive the reddening (E(B-V) = 0.21 +/- 0.03) and distance ((m-M)v = 11.55 +/-
0.13) to NGC 2099 by matching main-sequence features in the cluster to a new
fiducial main-sequence for the Hyades. As a continuing part of the goals of the
CFHT Open Star Cluster Survey to better understand dynamical processes of open
clusters, we also fit a King model to the cluster density distribution and
investigate the cluster main-sequence luminosity and mass functions in
increasing concentric annuli. We find some evidence for mass segregation within
the boundary of NGC 2099 as expected given the cluster's age relative to the
dynamical age. The present global mass function for the cluster is found to be
shallower than a Salpeter IMF.


title:
Properties of the Outer Halos of Galaxies from the Study of Globular
  Clusters

abstract:
  This paper reviews some recent work on the properties of the outer halos of
galaxies. I particularly focus on recent and upcoming advances made with the
study of globular clusters. Globular clusters can be observed out to ~100 kpc
from the centers of galaxies, allowing the study of galactic halos well beyond
the regions probed by many other techniques such as observations of the
integrated light of galaxies. In the few well-studied cases to date, the study
of globular cluster systems has provided dynamical evidence for dark matter
halos around elliptical galaxies, and demonstrated kinematic differences
between different globular cluster populations that shed light on the formation
history of their host galaxies.


title: H and K Band Methane Features in an L Dwarf, 2MASS 0920+35

abstract:
  We have obtained near-infrared spectra of three L dwarfs discovered by 2MASS,
1506+13 (L3), 1507-16 (L5), and 0920+35 (L6.5). From the comparison of the H
and K band spectra of these L dwarfs, we have found the presence of methane
absorption in 0920+35. This implies that detectable methane absorption in the H
and K bands, usually considered the signature of a T dwarf, can be present in
objects classified optically as late L. Methane detection in L dwarfs is
consistent with the presence of a dust layer deep in the atmosphere as the
unified model of Tsuji suggests.


title:
Hands-On TAROT: Intercontinental use of the TAROT for Education and
  Public Outreach

abstract:
  The TAROT telescope has for primary goal the search for the prompt optical
counterpart of Cosmic Gamma-Ray Bursts. It is a completely autonomous 25cm
telescope installed near Nice (France), able to point any location of the sky
within 1-2 seconds. The control, scheduling, and data processing activities are
completely automated, so the instrument is completely autonomous. In addition
to its un-manned modes, we added recently the possibility to remotely control
the telescope, as a request of the "Hands-On Universe" (HOU) program for
exchange of time within automatic telescopes for the education and public
outreach. To this purpose we developed a simple control interface. A webcam was
installed to visualize the telescope. Access to the data is possible through a
web interface. The images can be processed by the HOU software, a program
specially suited for use within the classroom. We experienced these feature
during the open days of the University of California Berkeley and the Astronomy
Festival of Fleurance (France). We plan a regular use for an astronomy course
of the Museum of Tokyo, as well as for French schools. Not only does Hands-On
TAROT gives the general public an access to professional astronomy, but it is
also a more general tool to demonstrate the use of a complex automated system,
the techniques of data processing and automation. Last but not least, through
the use of telescopes located in many countries over the globe, a form of
powerful and genuine cooperation between teachers and children from various
countries is promoted, with a clear educational goal.


title:
Hands-On Universe: A Global Program for Education and Public Outreach in
  Astronomy

abstract:
  Hands-On Universe (HOU) is an educational program that enables students to
investigate the Universe while applying tools and concepts from science, math,
and technology. Using the Internet, HOU participants around the world request
observations from an automated telescope, download images from a large image
archive, and analyze them with the aid of user-friendly image processing
software. This program is developing now in many countries, including the USA,
France, Germany, Sweden, Japan, Australia, and others. A network of telescopes
has been established among these countries, many of them remotely operated, as
shown in the accompanying demo. Using this feature, students in the classroom
are able to make night observations during the day, using a telescope placed in
another country. An archive of images taken on large telescopes is also
accessible, as well as resources for teachers. Students are also dealing with
real research projects, e.g. the search for asteroids, which resulted in the
discovery of a Kuiper Belt object by high-school students. Not only Hands-On
Universe gives the general public an access to professional astronomy, but it
is also a more general tool to demonstrate the use of a complex automated
system, the techniques of data processing and automation. Last but not least,
through the use of telescopes located in many countries over the globe, a form
of powerful and genuine cooperation between teachers and children from various
countries is promoted, with a clear educational goal.


title: Coincidences of high density peaks in UVES spectra of QSO pairs

abstract:
  We present preliminary results of an investigation of the clustering
properties of high matter density peaks between redshift ~2 and ~3, as traced
by Lyman limit and Damped Ly-alpha systems in spectra of close QSO pairs and
groups.


title:
The Chandra LETGS high resolution X-ray spectrum of the isolated neutron
  star RX J1856.5-3754

abstract:
  We present the Chandra LETGS X-ray spectrum of the nearby (~60 pc) neutron
star RX J1856.5-3754. Detailed spectral analysis of the combined X-ray and
optical data rules out the nonmagnetic neutron star atmosphere models with
hydrogen, helium, iron and solar compositions. We also conclude that strongly
magnetized atmosphere models are unable to represent the data. The data can be
explained with a two-component blackbody model. The harder component with
temperature of kT_bb~63 eV and a radius R_bb~2.2 km of the emitting region well
fits the X-ray data and can be interpreted as radiation from a hot region on
the star's surface.


title:
In-orbit performance of the XMM-Newton X-ray telescopes: images and
  spectra

abstract:
  The performance of the three X-ray telescopes on-board of XMM-Newton is
evaluated addressing imaging characteristics and effective collecting area. The
agreement with ground calibration data is excellent. The analysis of images and
spectra of cosmic X-ray sources, emphazising supernova and supernova remnants,
prooves that the telescopes are even better than originally required.


title: The cosmic shear STIS parallel program - First results

abstract:
  Since the Universe is inhomogeneous on scales well below the Hubble radius,
light bundles from distant galaxies are deflected and distorted by the tidal
gravitational field of the large-scale matter distribution as they propagate
through the Universe. Two-point statistical measures of the observed
ellipticities, like the dispersion within a finite aperture or the ellipticity
cross-correlation, can be related to the power spectrum of the large-scale
structure. The measurement of cosmic shear (especially on small angular scales)
can thus be used to constrain cosmological parameters and to test cosmological
structure formation in the non-linear regime, without any assumptions about the
relation between luminous and dark matter. In this paper we will present
preliminary cosmic shear measurements on sub-arcminute scales, obtained from
archival STIS parallel data. The high angular resolution of HST, together with
the sensitivity and PSF-stability of STIS, allows us to measure cosmic shear
along many independent lines-of-sight. Ongoing STIS parallel observations,
currently being carried out in the frame of a big GO program (8562+9248), will
greatly increase the number of available useful fields and will enable us to
measure cosmic shear with higher accuracy on sub-arcminute scales.


title:
Star clusters in the Carina complex: UBVRI photometry of NGC3114,
  Collinder228 and vdB-Hagen99

abstract:
  In this paper we present and analyze CCD $UBVRI$ photometry in the region of
the three young open clusters NGC 3114, Collinder~228, and vdB-Hagen~99,


title: Testing the Modified Press-Schechter Model against N-Body Simulations

abstract:
  A modified version of the extended Press-Schechter model for the growth of
dark-matter haloes was introduced in two previous papers with the aim at
explaining the mass-density relation shown by haloes in high-resolution
cosmological simulations. In this model major mergers are well separated from
accretion, thereby allowing a natural definition of halo formation and
destruction. This makes it possible to derive analytic expressions for halo
formation and destruction rates, the mass accretion rate, and the probability
distribution functions of halo formation times and progenitor masses. The
stochastic merger histories of haloes can be readily derived and easily
incorporated into semi-analytical models of galaxy formation, thus avoiding the
usual problems encountered in the construction of Monte Carlo merger trees from
the original extended Press-Schechter formalism. Here we show that the
predictions of the modified Press-Schechter model are in good agreement with
the results of N-body simulations for several scale-free cosmologies.


title: Decelerating universes older than their Hubble times

abstract:
  Recent observations suggest that Hubble's constant is large, and hence that
the Universe appears to be younger than some of its constituents. The
traditional escape route, which assumes that the expansion is accelerating,
appears to be blocked by observations of Type 1a supernovae, which suggest(ed)
that the Universe is decelerating. These observations are reconciled in a model
in which the Universe has experienced an inflationary phase in the recent past,
driven by an ultra-light inflaton whose Compton wavelength is of the same order
as the Hubble radius.


title: Apocalypse soon

abstract:
  Based upon a simple vacuum Lagrangian, comprising cosmological and quadratic
scalar field terms, a cosmological model is presented whose history is
indistinguishable from that of an innocuous low-density cold dark matter (CDM)
universe, but whose future is very much shorter. For sensible values of the
deceleration parameter (0<q_0<1), its age is greater than 85% of the Hubble
time, thus resolving the current version of the age crisis, which appears
(appeared) to be that t_0 ~ H_0 while q_0 is significantly positive.


title: On the Formation of Massive Primordial Stars

abstract:
  We investigate the formation by accretion of massive primordial protostars in
the range 10 to 300 Msun. The high accretion rate used in the models (4.4 x
10^{-3} Msun/yr) causes the structure and evolution to differ significantly
from those of both present-day protostars and primordial zero-age main sequence
stars. After an initial expansion of the radius (for < 12 Msun), the protostar
undergoes an extended phase of contraction (up to 60 Msun). The stellar surface
is not visible throughout most of the main accretion phase, since a photosphere
is formed in the infalling envelope. Also, significant nuclear burning does not
take place until a protostellar mass of about 80 Msun. As the interior
luminosity approaches the Eddington luminosity, the protostellar radius rapidly
expands, reaching a maximum around 100 Msun. Changes in the ionization of the
surface layers induce a secondary phase of contraction, followed by a final
swelling due to radiation pressure when the stellar mass reaches about 300
Msun. This expansion is likely to signal the end of the main accretion phase,
thus setting an upper limit to the protostellar mass formed in these
conditions.


title: Narrow CIV lambda 1549A Absorption Lines in Moderate-Redshift Quasars

abstract:
  A large, high-quality spectral data base of well-selected, moderate-redshift
radio-loud and radio-quiet quasars is used to characterize the incidence of
narrow associated CIV lambda 1549 absorption, and how this may depend on some
quasar properties, including radio-type. Preliminary results of this study are
presented.


title: Cosmological Parameters and Quintessence From Radio Galaxies

abstract:
  FRIIb radio galaxies provide a tool to determine the coordinate distance to
sources out to redshifts of two. The coordinate distance depends on the present
values of global cosmological parameters, quintessence, and the equation of
state of quintessence, and provides one of the cleanest determinations of
global cosmological parameters because it does not depend on the clustering
properties of any mass-energy components. The modified standard candle method
(using type Ia supernove) of determining the coordinate distance is compared in
detail with the modified standard yardstick method (using FRIIb radio
galaxies); the methods are found to be complementary. The most significant
difference between the methods is that the radio galaxy method is completely
independent of the local distance scale and the properties of local sources,
while the supernovae method is very closely tied to the local distance scale
and the properties of local sources. FRIIb radio galaxies provide one of the
very few reliable probes of the coordinate distance to sources with redshifts
out to two. The method indicates that the current value of the density
parameter in non-relativistic matter must be low irrespective of whether the
universe is spatially flat, and of whether a significant cosmological constant
or quintessence pervades the universe at the present epoch. FRIIb radio
galaxies indicate that the universe is currently accelerating in its expansion
if the primary components of the universe at the present epoch are
non-relativistic matter and quintessence, and the universe is spatially flat.