title: Extinction Effects in Spiral Galaxy Rotation Curves

abstract:
  Observations show that the slope of the inner part of the H$\alpha$/[NII]
rotation curves of disk galaxies is depressed by extinction: at fixed
luminosity, the observed slope is in fact seen to depend on the disk
inclination to the line of sight. Using a simple extinction model, we are able
to reproduce well the observed trends. The model assumes an exponential
distribution, both in the radial and $z$ directions, identical for
star--forming regions and dust. Fits to the data are optimized by varying the
scale height and scale length of absorbers, as well as the disk's central
optical depth $\tau_\circ$, as seen face--on. The observations indicate that
disk central opacity increases with total luminosity. Model fits for the most
luminous galaxies (brighter than $M-5\log h=-21.4$ in the I band) yield
$\tau_\circ \simeq 3.5^{+4.0}_{-2.0}$, near $\lambda=0.66$ $\mu$m. The large
uncertainty on the inferred value of $\tau_\circ$ is due to the poorly known
characteristics of the distribution of absorbers in the disk, as well as to the
likelihood of strong departures from an exponential radial distribution near
the galaxy centers.


title:
X-ray binaries and ultra-luminous X-ray sources in nearby and distant
  galaxies

abstract:
  We review recent results on populations of compact X-ray sources in normal
galaxies. The luminosity distributions of low and high mass X-ray binaries in
nearby galaxies appear to be described by the respective ``universal''
luminosity functions, whose shapes do not vary significantly from galaxy to
galaxy and the normalizations are proportional to the SFR (HMXBs) and stellar
mass (LMXBs) of the host galaxy. There is a significant qualitative difference
between XLFs of high and low mass X-ray binaries, reflecting the difference in
the accretion regimes in these two types of X-ray binaries.
  The high luminosity cut-off is by an order of magnitude larger for HMXBs --
although bright sources, log(Lx)>39, are observed in both young and old
galaxies, the truly ultraluminous ones, with log(Lx)~40-40.5, are associated
with the regions of intense star formation and have not been detected so far in
old stellar populations of elliptical and S0 galaxies. The Lx-SFR relation for
distant galaxies in the HDF-N indicates that ULXs at redshifts of z~0.2-1.3
were not significantly more luminous than those observed in nearby galaxies.


title: PSR J1829+2456: a relativistic binary pulsar

abstract:
  We report the discovery of a new binary pulsar, PSR J1829+2456, found during
a mid-latitude drift-scan survey with the Arecibo telescope. Our initial timing
observations show the 41-ms pulsar to be in a 28-hr, slightly eccentric, binary
orbit. The advance of periastron, omegadot = 0.28 +/- 0.01 deg/yr is derived
from our timing observations spanning 200 days. Assuming that the advance of
periastron is purely relativistic and a reasonable range of neutron star masses
for PSR J1829+2456 we constrain the companion mass to be between 1.22 Msun and
1.38 Msun, making it likely to be another neutron star. We also place a firm
upper limit on the pulsar mass of 1.38 Msun. The expected coalescence time due
to gravitational-wave emission is long (~60 Gyr) and this system will not
significantly impact upon calculations of merger rates that are relevant to
upcoming instruments such as LIGO.


title: Extreme Physics via X-rays from Black Holes and `Neutron' Stars

abstract:
  A combination of microchannel plate optics and a 32x32 pixel microcalorimeter
would allow the successor to the Rossi XTE to explore new domains of
spectroscopic timing in a MIDEX class mission. With ~10 times the area and ~100
times the spectral resolution of the PCA (and 10 times that of silicon
detectors) such a mission would be able to explore redshifts and plasma
conditions in weak line features over a wide range of celestial sources. This
would allow several tests of basic physics, both QED/QCD and GR.


title:
Reduction of chemical networks. II. Analysis of the fractional
  ionisation in protoplanetary discs

abstract:
  (abridged) We analyse the evolution of the fractional ionisation in a
steady-state protoplanetary disc with a vertical temperature gradient and with
gas-grain chemistry including surface reactions. The ionisation due to stellar
X-rays, stellar and interstellar UV radiation, cosmic rays and radionuclide
decay is taken into account. Using our reduction schemes as a tool for the
analysis, we isolate small sets of chemical reactions that reproduce the
evolution of the ionisation degree at representative disc locations with an
accuracy of 50%-100%. Column densities of key molecules are calculated and
compared to the results of other recent studies and observational data.


title: Galaxy Evolution in the Environment of ABCG 209

abstract:
  We examine the environmental effects on the photometric properties of
galaxies for the rich galaxy cluster ABCG 209 at z=0.209. We use archive CFHT
optical imaging of a 42'x28' field centred on the cluster to produce a galaxy
sample complete to B=25.0 and R=24.5. Both the composite and red sequence
galaxy luminosity functions are found to be dependent on the local galaxy
surface density, their faint-end slopes becoming shallower with increasing
density. We explain this as a combination of the morphology-density relation,
and dwarf galaxies being cannibalised and/or disrupted by the cD galaxy and the
ICM in the cluster core. The B-R colour of the red sequence itself appears
0.02mag redder for the highest-density regions, indicative of their stellar
populations being marginally (<5%) older or (<20%) more metal-rich. This may be
due to the galaxies themselves forming earliest in the rarest overdensities
marked by rich clusters, or their star-formation being suppressed earliest by
the ICM.


title: A CNO Dichotomy among O2 Giant Spectra in the Magellanic Clouds

abstract:
  From a survey of the 3400 A region in the earliest O-type spectra, we have
found that two of the four O2 giants observed in the LMC have the OIV lines
there stronger than the NIV, while the other two have the opposite. A SMC
counterpart also has the NIV stronger than OIV. Inspection of the blue spectra
of these stars shows that the former pair have weaker N lines in all ionization
states (III, IV, V) present as well as lines of CIV lambda 4658, while the
latter three have stronger N lines and greater He/H. Space ultraviolet
observations of two of the N-strong stars show NV wind profiles substantially
stronger than those of CIV, while in the N-weak stars the CIV features are
equal to or stronger than the NV. The N-strong stars are now reclassified as
ON2 III(f*), newly defining that category. These characteristics strongly
suggest a larger fraction of processed material in the atmospheres of the ON2
stars, which we confirm by modeling the optical spectra. In the context of
current models, it is in turn implied that the ON2 stars are in a more advanced
evolutionary state than the others, and/or that they had higher initial
rotational velocities. The recent formulation of the effects of rotation on
massive stellar evolution introduces an additional fundamental parameter, which
the CNO abundances are in principle able to constrain. We present some
illustrative comparisons with current Geneva evolutionary models for rotating
massive stars. It is possible that these very hot, nitrogen-rich objects are
products of homogeneous evolution. Our results will provide motivation for
further physical modeling of the atmospheres and evolutionary histories of the
most massive hot stars.


title:
Qualitative aspects of quasar microlensing with two mass components:
  magnification patterns and probability distributions

abstract:
  It has been conjectured that the distribution of magnifications of a point
source microlensed by a population of intervening point masses is independent
of its mass spectrum. We present gedanken experiments that cast doubt on this
conjecture and numerical simulations that show it to be false.


title:
The Faintness of the 158 um [CII] Transition in the z=6.42 Quasar SDSS
  J1148+5251

abstract:
  We report the non-detection of the [CII] 157.74 um transition in the z=6.42
quasar SDSS J1148+5251 after 37.5 hours of integration with the James Clerk
Maxwell Telescope. This transition is the main cooling line of the star-forming
interstellar medium, and usually the brightest FIR line in galaxies. Our
observed RMS of 1.3 mK in the Ta* scale translates to L([CII])<2.6 x 10^9 Lsun.
Using a recent estimate of the far-infrared continuum of this quasar, we derive
for SDSS J1148+5251 L([CII])/L(FIR)<5 x 10^-4, a ratio similar to that observed
in local ultra-luminous infrared galaxies but considerably smaller than what is
typical in nearby normal and starburst galaxies. This indicates that the small
L([CII])/L(FIR) ratio observed locally in luminous far-infrared objects also
persists at the highest redshifts.


title: Eigenspectra of the SDSS DR1 quasars

abstract:
  We construct eigenspectra from the DR1 quasars in the SDSS using the
Karhunen-Lo\`eve (KL) transform (or Principal Component Analysis, PCA) in
different redshift and luminosity bins. We find that the quasar spectra can be
classified, by the first two eigenspectra, into a continuous sequence in the
variation of the spectral slope. We also find a dependence on redshift and
luminosity in the eigencoefficients. The dominant redshift effect is the
evolution of the blended Fe~II emission (optical) and the Balmer continuum (the
``small-bump'', $\lambda_{rest} \approx 2000-4000$\AA), while the luminosity
effect is related to the Baldwin effect. Correlations among several major broad
emission lines are found, including the well-known ``Eigenvector-1''.


title: On the excess of power in high resolution CMB experiments

abstract:
  We revisit the possibility that an excess in the CMB power spectrum at small
angular scales (CBI, ACBAR) can be due to galaxy clusters (or compact sources
in general). We perform a Gaussian analysis of ACBAR-like simulated data based
on wavelets. We show how models with a significant excess should show a clear
non-Gaussian signal in the wavelet space. In particular, a value of the
normalization sigma_8 = 1 would imply a highly significant skewness and
kurtosis in the wavelet coefficients at scales around 3 arcmin. Models with a
more moderate excess also show a non-Gaussian signal in the simulated data. We
conclude that current data (ACBAR) should show this signature if the excess is
to be due to the SZ effect. Otherwise, the reason for that excess should be
explained by some systematic effect. The significance of the non-Gaussian
signal depends on the cluster model but it grows with the surveyed area.
Non-Gaussianity test performed on incoming data sets should reveal the presence
of a cluster population even for models with moderate-low sigma_8's.


title:
The Broad Emission Line Regions of Quasars - current status and future
  prospects

abstract:
  The spectrum emitted by the Broad Emission Line Regions of Active Galactic
Nuclei can measure the luminosity of the central object and the chemical
composition of the interstellar medium in a very young galaxy, and so constrain
the expansion of the universe and the first stages of the evolution of massive
galaxies. Here I review some recent developments in our understanding of the
nature of the clouds and the interpretation of their spectra.


title:
The Red Giant Branch in the Near-Infrared Colour-Magnitude Diagrams. I:
  The calibration of photometric indices

abstract:
  We present new high-quality near-infrared photometry of 10 Galactic Globular
Clusters spanning a wide metallicity range (-2.12<[Fe/H]<-0.49): five clusters
belong to the Halo (namely, NGC288, NGC362, NGC6752, M15 and M30) and five
(namely, NGC6342, NGC6380, NGC6440, NGC6441 and NGC6624) to the Bulge. By
combining J, H and K observations with optical data, we constructed
Colour-Magnitude Diagrams in various planes (K,J-K), (K,V-K), (H,J-H), and
(H,V-H). A set of photometric indices (colours, magnitudes and slopes)
describing the location and the morphology of the Red Giant Branch (RGB) have
been measured. We have combined this new data set with those already published
by Ferraro et al.(2000) and Valenti et al. (2004), and here we present an
updated calibration of the various RGB indices in the 2MASS photometric system,
in terms of the cluster metallicity.


title:
Dynamical friction for dark halo satellites: effects of tidal massloss
  and growing host potential

abstract:
  How fast a satellite decays its orbit depends on how slowly its mass is lost
by tide. Motivated by inner halo satellite remnants like the Sgr and Omega Cen,
we develop fully analytical models to study the orbital decay and tidal
massloss of satellites. The orbital decay rate is often severely overestimated
if applying the ChandraSekhar's formula without correcting for (a) the
evaporation and tidal loss of the satellite and (b) the contraction of
satellite orbits due to adiabatic growth of the host galaxy potential over the
Hubble time. As a satellite migrates inwards, the increasing halo density
affects the dynamical friction in two opposite ways:(1) it boosts the number of
halo particles swept in the satellite's gravitational "wake", hence increasing
the drag on the satellite, and (2) it boosts the tide which "peels off" the
satellite, and reduces the amplitude of the wake. These competing processes can
be modeled analytically for a satellite with the help of an empirical formula
for the massloss history. The analytical model agrees with more numerical
simulations of tidal massloss and dynamical friction. Rapid massloss due to
increasing tides at ever smaller radius makes it less likely for streams or
remnants of infalling satellites to intrude the inner halo (as the Sgr stream
and oCen) than to stay in the outer halo (Magellanic stream), hence any
intermediate-mass central black holes of the satellites are also likely "hung
up" at large distances as well. To avoid "hung-up" the satellites might start
with (i) pericenters much smaller than the typical distances to present-day
observed satellites and with (ii) central density much higher than in the often
seen finite density cores of observed satellites.


title: A Cosmological Modification to Energy from Mach-Hamilton Consistency

abstract:
  If Mach's Principle explains the Newtonian inertial reaction to acceleration
then the role of the 'fixed stars' should also be manifest through Hamilton's
formulation of mechanics. This consistency may be achieved if the expression
for relativistic energy contains a cosmological coefficient that is (currently)
equal to one. The presence of the required cosmological term exactly identifies
the rest energy of a body as its gravitational potential energy due to the mass
of the Universe.


title: Luminosity limits on white dwarfs in a Galactic shroud

abstract:
  We place observational constraints on a recently proposed Galactic
population, dubbed the shroud (Gyuk & Gates 1999, Gates & Gyuk 2001). The
shroud would be a very thick Galactic disk of low luminosity objects, most
likely old white dwarfs, proposed to explain the optical depth seen in
microlensing surveys towards the Magellanic clouds. The shroud is a simple
alternative to the lenses being distributed in a classical, near-spherical dark
halo; the advantage of the shroud is that it would compose only a fraction of a
dark halo's total mass.
  In this paper, we argue that stars of the Galactic shroud would be detectable
in the recent proper motion survey of Oppenheimer et al. (2001) if their
absolute luminosities were brighter than M_R_59F = 19.4 or approximately M_V =
18.6. We adopt a range of simple models of the shroud's kinematics and
morphology, and the colours and luminosities of its white dwarfs; via
Monte-Carlo simulations, we predict the numbers expected in the Oppenheimer et
al. survey, which would be clearly separated from the numbers produced by white
dwarfs of the disk, thick disk and halo.
  The number of white dwarf detections in the proper motion survey (98) is
found to be well explained by the disk, thick disk and halo. With the most
conservative kinematic and density parameters for the shroud, and an absolute
luminosity of the white dwarfs of M_R_59F = 17.6, we find that the proper
motion survey would detect over 100 WDs, just from the shroud. For a M_R_59F =
19.4 shroud, the survey would find 5 +/- 2 peculiar objects, whereas only two
white dwarfs with such characteristics are found in the original data. M_R_59F
= 19.4 corresponds to M_V = 18.6 for WDs with V - I = -1.030.


title:
On the band-to-continuum intensity ratio in the infrared spectra of
  interstellar carbonaceous dust

abstract:
  Published interpretations of the relative intensity variations of the
Unidentified Infrared Bands (UIBs) and their underlying continuum are
discussed. An alternative model is proposed, in which a single carrier for both
emits a) mostly a continuum when it is electronically excited by photons
(visible or UV), or b) exclusively the UIBs, when only chemical energy is
deposited by H capture on its surface, inducing only nuclear vibrations. The
bands will dominate in atomic H regions but will be overcome by thermal
continuum radiation when the ambient field is strong but lacks dissociating
photons (900-1100 Angstroms). The model applies to PDRs as well as to limbs of
molecular clouds in the ISM and agrees quantitatively with recent satellite
observations. It gives indications on atomic H density and UIB intensity
provided the ambient radiation field is known. It invokes no chemical,
electronic, structural or size change in order to interpret the observed
intensity variations.


title: On the Pulsar Emission Mechanism

abstract:
  We discuss a general mechanism which allows to explain naturally both radio
and high energy emission by pulsars. We also discuss the plasma distribution in
the region surrounding the pulsar, the pulsar wind and the formation of jet
along the magnetic axis. We suggest a plausible mechanism to generate pulsar
proper motion velocities.


title:
Timing Analysis of Light Curves in the Tartarus Active Galactic Nuclei
  Database

abstract:
  The Tartarus database contains products for 529 ASCA observations of active
galactic nuclei. We have been updating Tartarus to include observing sequences
conducted after 1999 January. The revised database will contain products for
375 objects, with a total of 614 observing sequences. We have begun a
systematic timing analysis of the Tartarus light curves. We present here some
preliminary results of an investigation into the relation between excess
variance and black-hole mass. Having optimised our analysis to minimize the
scatter in the variance measurements, we find that the narrow-line active
galactic nuclei follow roughly the same relation as the broad-line objects.


title: Does the butterfly diagram indicate asolar flux-transport dynamo?

abstract:
  We address the question whether the properties of the observed latitude-time
diagram of sunspot occurence (the butterfly diagram) provide evidence for the
operation of a flux-transport dynamo, which explains the migration of the
sunspot zones and the period of the solar cycle in terms of a deep equatorward
meridional flow. We show that the properties of the butterfly diagram are
equally well reproduced by a conventional dynamo model with migrating dynamo
waves, but without transport of magnetic flux by a flow. These properties seem
to be generic for an oscillatory and migratory field of dipole parity and thus
do not permit an observational distinction between different dynamo approaches.


title: Bose Einstein Condensation as Dark Energy and Dark Matter

abstract:
  We study a cosmological model in which the boson dark matter gradually
condensates into dark energy. Negative pressure associated with the condensate
yields the accelerated expansion of the Universe and the rapid collapse of the
smallest scale fluctuations into many black holes, which become the seeds of
the first galaxies. The cycle of gradual sedimentation and rapid collapse of
condensate repeats many times and self-regularizes the ratio of dark energy and
dark matter to be order one.


title: Eclipsing binaries in open clusters. II. V453 Cyg in NGC 6871

abstract:
  We derive absolute dimensions of the early B-type detached eclipsing binary
V453 Cygni (B0.4 IV + B0.7 IV, P=3.89d), a member of the open cluster NGC 6871.
  From the analysis of new, high-resolution, spectroscopy and the UBV light
curves of Cohen (1974) we find the masses to be 14.36 +/- 0.20 and 11.11 +/-
0.13 Msun, the radii to be 8.55 +/- 0.06 and 5.49 +/- 0.06 Rsun, and the
effective temperatures to be 26600 +/- 500 and 25 500 +/- 800 K for the primary
and secondary stars, respectively. The surface gravities of 3.731 +/- 0.012 and
4.005 +/- 0.015 indicate that V453 Cyg is reaching the end of its main sequence
lifetime. We have determined the apsidal motion period of the system to be 66.4
+/- 1.8 yr using the technique of Lacy (1992) extended to include spectroscopic
data as well as times of minimum light, giving a density concentration
coefficient of log(k_2) = -2.226 +/- 0.024. Contaminating (third) light has
been detected for the first time in the light curve of V453 Cyg; previous
analyses without this effect systematically underestimate the ratio of the
radii of the two stars. The absolute dimensions of the system have been
compared to the stellar evolution models of the Granada, Geneva, Padova and
Cambridge groups. All model sets fit the data on V453 Cyg for solar helium and
metal abundances and an age of 10.0 +/- 0.2 Myr. The Granada models also agree
fully with the observed log(k_2) once general relativistic effects have been
accounted for. The Cambridge models with convective core overshooting fit V453
Cyg better than those without. Given this success of the theoretical
predictions, we briefly discuss which eclipsing binaries should be studied in
order to further challenge the models.


title: Dynamic model atmospheres of cool giants

abstract:
  Cool giant stars are highly dynamical objects, and complex micro-physical
processes play an important role in their extended atmospheres and winds. The
interpretation of observations, and in particular of high-resolution IR
spectra, requires realistic self-consistent model atmospheres. Current
dynamical models include rather detailed micro-physics, and the resulting
synthetic spectra compare reasonably well with observations. A transition from
qualitative to quantitative modelling is taking place at present. We give an
overview of existing dynamical model atmospheres for AGB stars, discussing
recent advances and current trends in modelling, including 3D 'star-in-a-box'
models. When comparing synthetic spectra and other observable properties
resulting from dynamical models with observations we focus on the near- and
mid-IR wavelength range.


title: Migration and giant planet formation

abstract:
  We extend the core-accretion model of giant gaseous planets by Pollack et al.
(\cite{P96}) to include migration, disc evolution and gap formation. Starting
with a core of a fraction of an Earth's mass located at 8 AU, we end our
simulation with the onset of runaway gas accretion when the planet is at 5.5 AU
1 Myr later. This timescale is about a factor ten shorter than the one found by
Pollack et al. (\cite{P96}) even though the disc was less massive initially and
viscously evolving. Other initial conditions can lead to even shorter
timescales. The reason for this speed-up is found to result from the fact that
a moving planet does not deplete its feeding zone to the extend of a static
planet. Thus, the uncomfortably long formation timescale associated with the
core-accretion scenario can be considerably reduced and brought in much better
agreement with the typical disc lifetimes inferred from observations of young
circumstellar discs.


title: BL Lac X-ray Spectra: simpler than we thought

abstract:
  We report results from {\it XMM-Newton} observations of thirteen X-ray bright
BL Lacertae objects, selected from the {\it Einstein} Slew Survey sample. The
spectra are generally well fit by power-law models, with four objects having
hard ($\alpha<1; F_\nu \propto \nu^{-\alpha}$) spectra that indicates
synchrotron peaks at $>5$ keV. None of our spectra show line features,
indicating that soft X-ray absorption ``notches'' must be rare amongst BL Lacs,
rather than common or ubiquitous as had previously been asserted. We find
significant curvature in most of the spectra. This curvature is almost
certainly intrinsic, as it appears nearly constant from 0.5 to 6 keV, an
observation which is inconsistent with the small columns seen in these sources.


title:
The Anisotropic Transfer of Resonance Photons in Hot Plasmas on
  Magnetized White Dwarfs

abstract:
  In order to confirm the anisotropic effect of resonance photons in hot
accretion columns on white dwarfs in magnetic cataclysmic variables, proposed
by Terada etal (2001), systematic studies with ASCA of 7 polars and 12
intermediate polars are performed. The equivalent widths of He-like Fe
K$_\alpha$ line of polars are found to be systematically modulated at their
spin periods in such a way that it increases at the pole-on phase. This implies
that the anisotropic mechanism is commonly operating among polars. On the other
hand, those of intermediate polars are statistically consistent with being
unmodulated with an upper limit of 1.5 times modulation. This may be due to a
different accretion manner like aurora curtain (Rosen etal 1988) so that the
plasma becomes optically thin along the horizontal axis also for the resonance
lines, or because of larger optical depths for Compton scattering if the
emission regions have the same coin-like shapes as polars.


title: First Simultaneous NIR/X-ray Detection of a Flare from SgrA*

abstract:
  We report on the first simultaneous near-infrared/X-ray detection of the Sgr
A* counterpart which is associated with the massive black hole at the center of
the Milky Way. The observations have been carried out using the NACO adaptive
optics (AO) instrument at the European Southern Observatory's Very Large
Telescope and the ACIS-I instrument aboard the Chandra X-ray Observatory. We
also report on quasi-simultaneous observations at a wavelength of 3.4 mm using
the Berkeley-Illinois-Maryland Association (BIMA) array. A flare was detected
in the X-domain with an excess 2-8 keV luminosity of about 6$\times10^{33}$
erg/s. A fading flare of Sgr A* with $>$2 times the interim-quiescent flux was
also detected at the beginning of the NIR observations, that overlapped with
the fading part of the X-ray flare. Compared to 8-9 hours before the NIR/X-ray
flare we detected a marginally significant increase in the millimeter flux
density of Sgr A* during measurements about 7-9 hours afterwards. We find that
the flaring state can be conveniently explained with a synchrotron self-Compton
model involving up-scattered sub-millimeter photons from a compact source
component, possibly with modest bulk relativistic motion. The size of that
component is assumed to be of the order of a few times the Schwarzschild
radius. The overall spectral indices $\alpha_{NIR/X-ray}$
($S_{\nu}$$\propto$$\nu^{-\alpha}$) of both states are quite comparable with a
value of $\sim$1.3. Since the interim-quiescent X-ray emission is spatially
extended, the spectral index for the interim-quiescent state is probably only a
lower limit for the compact source Sgr A*. A conservative estimate of the upper
limit of the time lag between the ends of the NIR and X-ray flare is of the
order of 15 minutes.


title:
Radio and X-ray observations during the outburst decay of the Black Hole
  Candidate XTE J1908+094

abstract:
  Obtaining simultaneous radio and X-ray data during the outburst decay of soft
X-ray transients is a potentially important tool to study the disc - jet
connection. Here we report results of the analysis of (nearly) simultaneous
radio (VLA or WSRT) and Chandra X-ray observations of XTE J1908+094 during the
last part of the decay of the source after an outburst. The limit on the index
of a radio - X-ray correlation we find is consistent with the value of 0.7
which was found for other black hole candidates in the low/hard state.
Interestingly, the limit we find seems more consistent with a value of 1.4
which was recently shown to be typical for radiatively efficient accretion flow
models. We further show that when the correlation-index is the same for two
sources one can use the differences in normalisation in the radio - X-ray flux
correlation to estimate the distance towards the sources if the distance of one
of them is accurately known (assuming black hole spin and mass and jet Lorentz
factor differences are unimportant or minimal). Finally, we observed a strong
increase in the rate of decay of the X-ray flux. Between March 23, 2003 and
April 19, 2003 the X-ray flux decayed with a factor ~5 whereas between April
19, 2003 and May 13, 2003, the X-ray flux decreased by a factor ~750. The
source (0.5-10 keV) luminosity at the last Chandra observation was L~3x10^32
(d/8.5 kpc)^2 erg s^-1.


title: Cosmology of Brane-worlds

abstract:
  This talk presents an overview of the brane cosmology scenario, based on the
idea that our Universe is a 3-brane embedded in a five-dimensional anti-de
Sitter bulk space-time. Special emphasis is put on the novel features of this
scenario: an unconventional cosmological evolution at high energy densities,
i.e. in the early universe, and dark radiation, that embodies the gravitational
effects of the bulk onto the brane, and which is shown to be generated during
the high energy era by the production of bulk gravitons.


title: On shear-induced turbulence in rotating stars

abstract:
  We review various prescriptions which have been proposed for the turbulent
transport of matter and angular momentum in differentially rotating stellar
radiation zones. A new prescription is presented for the horizontal transport
associated with the anisotropic shear turbulence which is produced by the
differential rotation in latitude; this `beta-viscosity' is drawn from torque
measurements in the classical Couette-Taylor experiment (Richard & Zahn 1999).
Its implementation in a stellar evolution code leads to enhanced mixing, as
illustrated by models of a rotating main-sequence star of 1.5 solar mass.


title:
Modelling the Spectral Energy Distribution of Compact Luminous Infrared
  Galaxies: Constraints from High Frequency Radio Data

abstract:
  We have performed 23 GHz VLA observations of 7 compact, luminous infrared
galaxies, selected to have evidence of starburst activity. New and published
multi-frequency data are combined to obtain the spectral energy distributions
of all 7 galaxies from the near-infrared to the radio (at 1.4 GHz). These SEDs
are compared with new models, for dust enshrouded galaxies, which account for
both starburst and AGN components. In all 7 galaxies the starburst provides the
dominant contribution to the infrared luminosity; in 4 sources no contribution
from an AGN is required. Although AGN may contribute up to 50 percent of the
total far--infrared emission, the starbursts always dominate in the radio. The
SEDs of most of our sources are best fit with a very high optical depth of
(>=50) at 1 micron. The scatter in the far-infrared/radio correlation, found
among luminous IRAS sources, is due mainly to the different evolutionary status
of their starburst components. The short time-scale of the star formation
process amplifies the delay between the far-infrared and radio emission. This
becomes more evident at low radio frequencies (below about 1 GHz) where
synchrotron radiation is the dominant process. In the far-infrared (at
wavelengths shorter than 100 micron) an additional source of scatter is
provided by AGN, where present. AGN may be detected in the near-infrared by the
absence of the knee, typical of stellar photospheres. However, near-infrared
data alone cannot constrain the level at which AGN contribute because the
interpretation of their observed properties, in this wave-band, depends
strongly on model parameters.


title:
Synthetic infrared images and spectral energy distributions of a young
  low-mass stellar cluster

abstract:
  We present three-dimensional Monte Carlo radiative transfer models of a very
young (<10^5 years old) low mass (50 Msun) stellar cluster containing 23 stars
and 27 brown dwarfs. The models use the density and the stellar mass
distributions from the large-scale smoothed particle hydrodynamics (SPH)
simulation of the formation of a low-mass stellar cluster by Bate, Bonnell and
Bromm. We compute the spectral energy distributions of the whole cluster and
the individual objects, simulated far-infrared Spitzer Space Telescope (SST)
images and construct colour-colour diagrams (near-infrared HKL and SST
mid-infrared bands). The presence of accretion discs around the light sources
influences the morphology of the dust temperature structure on a large scale
(up to a several 10^4 au). A considerable fraction of the interstellar dust is
underheated compared to a model without the accretion discs because the
radiation from the light sources is blocked/shadowed by the discs. The spectral
energy distribution (SED) of the model cluster with accretion discs shows
excess emission at lambda = 3-30 micron and lambda > 500 micron compared to
that without accretion discs. Our model with accretion discs around each object
shows a similar distribution of spectral index (2.2-20 micron) values (i.e.
Class 0--III sources) as seen in the Rho Ophiuchus cloud. We confirm that the
best diagnostics for identifying objects with accretion discs are mid-infrared
(lambda = 3-10 micron) colours (e.g. SST IRAC bands) rather than HKL colours.


title: Observable primordial vector modes

abstract:
  Primordial vector modes describe vortical fluid perturbations in the early
universe. A regular solution exists with constant non-zero radiation
vorticities on super-horizon scales. Baryons are tightly coupled to the
photons, and the baryon velocity only decays by an order unity factor by
recombination, leading to an observable CMB anisotropy signature via the
Doppler effect. There is also a large B-mode CMB polarization signal, with
significant power on scales larger than l~2000. This B-mode signature is
distinct from that expected from tensor modes or gravitational lensing, and
makes a primordial vector to scalar mode power ratio ~10^(-6) detectable.
Future observations aimed at detecting large scale B-modes from gravitational
waves will also be sensitive to regular vector modes at around this level.


title: Multiwavelength study of the very long GRB 020410

abstract:
  GRB 020410 is by far the longest gamma-ray burst (with a duration of about
1600 s) to have been followed up from the X-ray through the radio regime.
Afterglow emission was detected in X-rays and at optical wavelengths while no
emission was detected at 8 GHz brighter than 120 microJy. The decaying X-ray
afterglow, back extrapolated to 11 hr after the burst, had a flux of 7.9 10^-12
cgs (2-10 keV); the brightest detected so far. No direct redshift determination
is available yet for this GRB, but according to the empirical relationship
between the peak energy in the \nu F_\nu spectrum and the isotropic energy
output, z is constrained in the range 0.9-1.5. The reconstructed optical
afterglow light curve implies at least two breaks in the simple power-law
decay. This may be related to emergence of a SN, or refreshment of the external
shock by a variation in the circumstellar medium. By comparing the backward
extrapolation of the 2-10 keV afterglow decay it is shown that the long
duration of the prompt emission is not related to an early onset of afterglow
emission, but must be related to prolonged activity of the ``central engine''.


title:
Near-Infrared Properties of I-Drop Galaxies in the Hubble Ultra Deep
  Field

abstract:
  We analyse near-infrared HST/NICMOS F110W (J) and F160W (H) band photometry
of a sample of 27 i'-drop candidate z~6 galaxies in the central region of the
HST/ACS Ultra Deep Field (HUDF). The infrared colours of the 20 objects not
affected by near neighbours are consistent with a high redshift interpretation.
This suggests that the low redshift contamination of this i'-drop sample is
smaller than that observed at brighter magnitudes where values of 10-40% have
been reported. The J-H colours are consistent with a slope flat in f_nu (f_lam
\propto lam^{-2}), as would be expected for an unreddened starburst. There is,
however, evidence for a marginally bluer spectral slope (f_lam propto
lam^{-2.2) which is perhaps indicative of an extremely young starburst (~10 Myr
old) or a top heavy initial mass function and little dust. The low levels of
contamination, median photometric redshift of z~6.0 and blue spectral slope,
inferred using the near-infrared data, supports the validity of the assumptions
in our earlier work in estimating the star formation rates and, that the
majority of the i-drop candidates galaxies lie at z~6.


title: A Note on the Robustness of Pair Separations Methods in Cosmic Topology

abstract:
  The pair separations statistical methods devised to detect the topology of
the universe rely on the accurate knowledge of the three-dimensional positions
of the cosmic sources. The determination of these positions, however, involves
inevitable observational uncertainties. The only significant (measurable) sign
of a nontrivial topology in PSH's was shown to be spikes. We briefly report our
results concerning the sensitivity of the topological spikes in the presence of
the uncertainties in the positions of the cosmic sources, which arise from
uncertainties in the values of the density parameters.


title: Interpretation of parabolic arcs in pulsar secondary spectra

abstract:
  Pulsar dynamic spectra sometimes show organised interference patterns; these
patterns have been shown to have power spectra which often take the form of
parabolic arcs, or sequences of inverted parabolic arclets whose apexes
themselves follow a parabolic locus. Here we consider the interpretation of
these arc and arclet features. We give a statistical formulation for the
appearance of the power spectra, based on the stationary phase approximation to
the Fresnel-Kirchoff integral. We present a simple analytic result for the
power-spectrum expected in the case of highly elongated images, and a
single-integral analytic formulation appropriate to the case of axisymmetric
images. Our results are illustrated in both the ensemble-average and snapshot
regimes. Highly anisotropic scattering appears to be an important ingredient in
the formation of the observed arclets.


title:
A Hubble Space Telescope Lensing Survey of X-ray Luminous Galaxy
  Clusters: IV. Mass, Structure and Thermodynamics of Cluster Cores at z=0.2

abstract:
  We present a comprehensive space-based study of ten X-ray luminous galaxy
clusters (L_X>=8e44erg/s[0.1-2.4keV]) at z=0.2. Hubble Space Telescope
observations reveal numerous gravitationally-lensed arcs for which we present
four new spectroscopic redshifts, bringing the total to thirteen confirmed arcs
in this cluster sample. We combine the multiple-image systems with the
weakly-sheared background galaxies to model the total mass distribution in the
cluster cores (R<=500kpc). These models are complemented by high-resolution
X-ray data from Chandra and used to develop quantitative criteria to classify
the clusters as relaxed or unrelaxed. Formally, (30+/-20)% of the clusters form
a homogeneous sub-sample of relaxed clusters; the remaining (70+/-20)% are
unrelaxed and are a much more diverse population. Most of the clusters
therefore appear to be experiencing a cluster-cluster merger, or relaxing after
such an event. We also study the normalization and scatter of scaling relations
between cluster mass, luminosity and temperature. The scatter in these
relations is dominated by the unrelaxed clusters and is typically sigma~0.4.
Most notably, we detect 2-3 times more scatter in the mass-temperature relation
than theoretical simulations and models predict. The observed scatter is also
asymmetric - the unrelaxed systems are systematically 40% hotter than the
relaxed clusters at 2.5 sigma significance. This structural segregation should
be a major concern for experiments designed to constrain cosmological
parameters using galaxy clusters. Overall our results are consistent with a
scenario of cluster-cluster merger induced boosts to cluster X-ray luminosities
and temperatures. [Abridged]


title:
Detection of two-armed spiral shocks on the accretion disk of the
  eclipsing fast nova V1494 Aquilae

abstract:
  We have modeled the unusual orbital light curve of V1494 Aquilae (Nova
Aquilae 1999 No.2) and found that such an unusual orbital light curve can be
reproduced when there exist two-armed, spiral shocks on the accretion disk.
V1494 Aql is a fast classical nova and found to be an eclipsing system with the
orbital period of 0.1346138 days in the late phase of the nova outburst. Its
orbital light curve shows a small bump at orbital phase 0.2, a small dip at
0.3, sometimes a small bump at 0.4, and a large bump at 0.6-0.7 outside
eclipse. Such a double- or triple-wave pattern outside eclipse has never been
observed even though overall patterns look like some supersoft X-ray sources or
eclipsing polars. We have calculated orbital light curves including the
irradiation effects of the accretion disk and the companion by the hot white
dwarf. These unusual patterns can be reproduced when we assume two-armed spiral
shocks on the accretion disk. Especially, triple-wave patterns are naturally
obtained. This result strongly suggests the existence of two-armed spiral
shocks on the accretion disk in the late phase of the nova outburst.


title: Supernova Constraints on a holographic dark energy model

abstract:
  In this paper, we use the type Ia supernova data to constrain the model of
holographic dark energy. For $d=1$, the best fit result is $\Omega^0_m = 0.25$,
the equation of the state of the holographic dark energy $w^0_\d = -0.91$ and
the transition between the decelerating expansion and the accelerating
expansion happened when the cosmological red-shift was $z_T=0.72$. If we set
$d$ as a free parameter, the best fit results are $d=0.21$, $\Omega_m^0=0.46$,
$w_\d^0=-2.67$, which sounds like a phantom today, and the transition redshift
is $z_T=0.28$.


title: A possible age-metallicity relation in the Galactic thick disk?

abstract:
  A sample of 229 nearby thick disk stars has been used to investigate the
existence of an age-metallicity relation (AMR) in the Galactic thick disk. The
results indicate that that there is indeed an age-metallicity relation present
in the thick disk. By dividing the stellar sample into sub-groups, separated by
0.1 dex in metallicity, we show that the median age decreases by about 5-7 Gyr
when going from [Fe/H]=-0.8 to [Fe/H]=-0.1. Combining our results with our
newly published alpha-element trends for a local sample of thick disk stars,
that show signatures from supernovae type Ia (SNIa), we can here draw the
conclusion that the time-scale for the peak of the SNIa rate is of the order
3-4 Gyr in the thick disk. The tentative evidence for a thick disk AMR that we
present here also has implications for the thick disk formation scenario;
star-formation must have been an ongoing process for several billion years.
This is further discussed here and appear to strengthen the hypothesis that the
thick disk originates from a merger event with a companion galaxy that puffed
up a pre-existing thin disk.


title:
Detection of Sub-TeV Gamma-Rays from the Galactic Center Direction by
  CANGAROO-II

abstract:
  We have detected sub-TeV gamma-ray emission from the direction of the
Galactic Center (GC) using the CANGAROO-II Imaging Atmospheric Cherenkov
Telescope (IACT). We detected a statistically signicant excess at energies
greater than 250GeV. The flux was one order of magnitude lower than that of
Crab at 1 TeV with a soft spectrum E^{-4.6+-0.5}. The signal centroid is
consistent with the GC direction and the observed prole is consistent with a
point-like source. Our data suggests that the GeV source 3EG J1746-2851 is
identical with this TeV source and we study the combined spectra to determine
the possible origin of the gamma-ray emission. We also obtain an upper limit on
the cold dark-matter density in the Galactic halo.


title:
Evolution of the Cosmological Density Distribution Function: A New
  Analytical Model

abstract:
  The one-point probability distribution function (pdf) of the large-scale
density field is an important tool to follow the evolution of cosmological
structures. In this paper we present a new model for this pdf for all regimes
and all densities, that is from linear to highly non-linear scales and from
rare voids up to rare high densities. This is probably the simplest model one
can build which is consistent with normalization constraints and known rigorous
results (the quasi-linear regime and the rare void limit). It is fully
parameterized by the non-linear variance and skewness. We obtain a good
agreement with N-body data from realistic cosmological simulations of the VIRGO
consortium and we find that it works significantly better than previous models
such as the lognormal model or the Extended Perturbation Theory (EPT). We
explain this success as a result of the tight constraints onto the pdf provided
by these consistency conditions. We also point out that while the Lagrangian
dynamics of typical fluctuations is quite complex the statistical outcome seems
rather simple. This simple model should be useful for studies which require a
realistic and convenient description of this pdf.


title:
Evidence for a deficit of young and old stars in the Milky Way inner
  in-plane disc

abstract:
  We give independent proof of the deficit of stars in the in-plane central
disc with respect to the predictions of a pure exponential density
distribution. We use three different methods: 1) the inversion of the red clump
giant distribution in near-infrared colour-magnitude diagrams to obtain the
star density along the line of sight; 2) the determination of the density
distribution of 1612 MHz sources by means of the distance determination of
OH/IR sources from their kinematical information; 3) an analysis of near and
mid-infrared star counts and comparison with models. All the tests give the
same result: a defect of stars in the inner disc with respect to an exponential
disc (either with constant scaleheight or extrapolated from the outer disc),
but only in near plane regions. This deficit might be interpreted as a flare in
the vertical distribution. The in-plane density is almost independent of R and
not an exponential law. Further away from the plane, however, the density
increases towards the centre due to the increase of the scaleheight. Tests also
show that this result cannot be due to extinction. The deficit affects both the
young and the old populations, so it is probably a rather stable feature of the
disc, and might be due to the existence of an in-plane bar sweeping the
near-plane stars.


title: Double degenerates and progenitors of supernovae type Ia

abstract:
  We report on systematic radial velocity surveys for white dwarf - white dwarf
binaries (double degenerates - DDs) including SPY (ESO Supernovae Ia progenitor
survey) recently carried out at the VLT. A large sample of DD will allow us to
put strong constrains on the phases of close binary evolution of the progenitor
systems and to perform an observational test of the DD scenario for supernovae
of type Ia. We explain how parameters of the binaries can be derived from
various methods. Results for a sample of DDs are presented and discussed.


title:
XMM-Newton observation of the relaxed cluster A478: gas and dark matter
  distribution from 0.01 R_200 to 0.5 R_200

abstract:
  We present an \xmm mosaic observation of the hot ($kT\sim6.5$ keV) and nearby
($z=0.0881$) relaxed cluster of galaxies A478. We derive precise gas density,
gas temperature, gas mass and total mass profiles up to $12\arcmin$ (about half
of the virial radius $R_{200}$). The gas density profile is highly peaked
towards the center and the surface brightness profile is well fitted by a sum
of three $\beta$--models. The derived gas density profile is in excellent
agreement, both in shape and in normalization, with the published Chandra
density profile (measured within $5\arcmin$ of the center). Projection and PSF
effects on the temperature profile determination are thoroughly investigated.
The derived radial temperature structure is as expected for a cluster hosting a
cooling core, with a strong negative gradient at the cluster center. The
temperature rises from $\sim2$ keV up to a plateau of $\sim6.5$ keV beyond 2'
(i.e. $r>208\rm{kpc}=0.1 R_{200}$, $R_{200}=2.08$ Mpc being the virial radius).
  From the temperature profile and the density profile and under the hypothesis
of hydrostatic equilibrium, we derived the total mass profile of A478 down to
0.01 and up to 0.5 the virial radius. We tested different dark matter models
against the observed mass profile. The Navarro, Frenk & White
(\cite{navarro97}) model is significantly preferred to other models. It leads
to a total mass of $M_{200}=1.1\times 10^{15}$ M$_\odot$ for a concentration
parameter of $c=4.2\pm0.4$. The gas mass fraction slightly increases with
radius. The gas mass fraction at a density contrast of $\delta=2500$ is
$\fgas=0.13\pm0.02$, consistent with previous results on similar hot and
massive clusters. We confirm the excess of absorption in the direction of
A478.[abridged]


title: Hyperbolic Universes with a Horned Topology and the CMB Anisotropy

abstract:
  We analyse the anisotropy of the cosmic microwave background (CMB) in
hyperbolic universes possessing a non-trivial topology with a fundamental cell
having an infinitely long horn. The aim of this paper is twofold. On the one
hand, we show that the horned topology does not lead to a flat spot in the CMB
sky maps in the direction of the horn as stated in the literature. On the other
hand, we demonstrate that a horned topology having a finite volume could
explain the suppression of the lower multipoles in the CMB anisotropy as
observed by COBE and WMAP.


title:
Coordinated Multiwavelength Observations and Spectral Variability
  Modeling of Gamma-Ray Blazars

abstract:
  Our recent progress on time-dependent modeling of the multiwavelength spectra
and variability of blazars with leptonic and hadronic jet models is reviewed.
Special emphasis is placed on X-ray spectral variability of low-frequency
peaked (LBLs) and intermediate BL Lac objects (IBLs). As an example, recent
observational and modeling results of an extensive multiwavelength campaign of
BL Lacertae in 2000 are presented. It is demonstrated how combined spectral and
variability modeling of LBLs and IBLs can significantly constrain emission
models and potential variability scenarios. In the case of BL Lacertae, the
variability appears to be driven primarily by fluctuations in the spectral
index of the non-thermal, ultrarelativistic electron population in the jet.
Such constraints allow us to refine predictions of the intrinsic GeV gamma-ray
emission and the dominant electron cooling mechanism in these objects.


title:
Dynamical effects of the radial galactic tide on an Oort cloud of comets
  for stars with different masses and varying distances from the galactic
  center

abstract:
  We show that the effects of radial galactic tides alone can change the
dynamics of an Oort cloud of comets around a star in a highly sensitive manner.
The Oort cloud dynamics depends primarily from the star's position in the
Galaxy and its mass. The dynamical variation is characterized by a dramatic
change of comet perihelia, many of which are shifted towards the inner
planetary system if the star's position goes towards the galactic center or if
its mass is set to be smaller. These preliminary result suggested us a possible
future line of research which aims to a better dynamical generalization of
comet orbits around extrasolar systems that might be tested through numerical
simulations of an Oort cloud of comets around non solar type stars and in
different galactic or extragalactic environments.


title: The Initial Helium Abundance of the Galactic Globular Cluster System

abstract:
  We estimate the initial He content in about 30% of the Galactic globular
clusters (GGCs) from new star counts we have performed on the recently
published HST snapshot database of Colour Magnitude Diagrams (Piotto et al.
2002). More in detail, we use the so-called $R$-parameter and estimate the He
content from a calibration based on a recently updated set of stellar models.
We performed an accurate statistical analysis in order to assess whether GGCs
show a statistically significant spread in their initial He abundances, and
whether there is a correlation with the metallicity. We do not find any
significant dependence of the He abundance on the GC metallicity; this provides
an important constraint for models of Galaxy formation and evolution. Apart
from GGCs with the bluest HB morphology, the observed spread in the individual
He abundances is statistically compatible with the individual errors. This
means that either there is no intrinsic He spread among the GGCs, or that this
is masked by the errors. In the latter case we have estimated a firm 1$\sigma$
upper limit of 0.019 to the possible intrinsic spread. In case of the GGCs with
the bluest HB morphology we detect a significant spread towards higher
abundances inconsistent with the individual errors. In the hypothesis that the
intrinsic dispersion on the individual He abundances is zero, taking into
account the errors on the individual R-parameter estimates, as well as the
uncertainties on the GGC [M/H] scale and theoretical calibration, we have
determined an initial He abundance Y(GGC)=0.250\pm0.006 a value in perfect
agreement with current estimates based on CMB radiation analyses and
cosmological nucleosynthesis computations.


title:
XMM-Newton observations of GB B1428+4217: confirmation of intrinsic soft
  X-ray absorption

abstract:
  We report the results of XMM-Newton observations of the X-ray bright,
radio-loud blazar GB B1428+4217 at a redshift of z=4.72. We confirm the
presence of soft X-ray spectral flattening at energies <0.7 keV as reported in
previous ROSAT and BeppoSAX observations. At hard X-ray energies the spectrum
is consistent with a power-law although we find the spectral slope varied
between both XMM-Newton observations and is also significantly different from
that reported previously. Whilst we cannot rule-out intrinsic cold absorption
to explain the spectral depression, we favour a dust-free warm absorber. Cold
absorption requires a column density ~1.4-1.6 x 10^22 cm^-2 whilst a warm
absorber could have up to ~10^23 cm^-2 and an ionization parameter ~10^2. The
spectrum of GB B1428+4217 shows remarkable parallels with that of the z=4.4
blazar PMN J0525-3343, in which the available evidence is also most consistent
with a warm absorber model.


title:
The Predicted Metallicity Distribution of Stars in Dwarf Spheroidal
  Galaxies

abstract:
  We predict the metallicity distribution of stars and the age-metallicity
relation for 6 Dwarf Spheroidal (dSph) galaxies of the Local Group by means of
a chemical evolution model which is able to reproduce several observed
abundance ratios and the present day total mass and gas content of these
galaxies. The model adopts up to date nucleosynthesis and takes into account
the role played by supernovae of different types (II, Ia) allowing us to follow
in detail the evolution of several chemical elements (H, D, He, C, N, O, Mg,
Si, S, Ca, and Fe). Each galaxy model is specified by the prescriptions of the
star formation rate and by the galactic wind efficiency chosen to reproduce the
main features of these galaxies. These quantities are constrained by the star
formation histories of the galaxies as inferred by the observed color-magnitude
diagrams (CMD). The main conclusions are: i) 5 of the 6 dSphs galaxies are
characterized by very low star formation efficiencies ($\nu = 0.005 - 0.5 Gyr
^{-1}$) with only Sagittarius having a higher one ($\nu = 1.0 - 5.0 Gyr
^{-1}$); ii) the wind efficiency is high for all galaxies, in the range $w_i$ =
6 - 15; iii) a high wind efficiency is required in order to reproduce the
abundance ratios and the present day gas mass of the galaxies; iv) the
predicted age-metallicity relation implies that the stars of the dSphs reach
solar metallicities in a time-scale of the order of 2 - 6 Gyr; v) the
metallicity distributions of stars in dSphs exhibit a peak around [Fe/H] $\sim$
-1.8 to -1.5 dex, with the exception of Sagittarius ([Fe/H] $\sim$ -0.8 dex);
iv) the predicted metallicity distributions of stars suggest that the majority
of stars in dSphs are formed in a range of metallicity in agreement with the
one of the observed stars.


title: Ion-by-Ion DEM Determination: I. Method

abstract:
  We describe a technique to derive constraints on the differential emission
measure (DEM) distribution, a measure of the temperature distribution, of
collisionally ionized hot plasmas from their X-ray emission line spectra. This
technique involves fitting spectra using a number of components, each of which
is the entire X-ray line emission spectrum for a single ion. It is applicable
to high-resolution X-ray spectra of any collisionally ionized plasma and
particularly useful for spectra in which the emission lines are broadened and
blended such as those of the winds of hot stars. This method does not require
that any explicit assumptions about the form of the DEM distribution be made
and is easily automated.


title: How Accurately Can We Calculate the Depth of the Solar Convective Zone?

abstract:
  We evaluate the logarithmic derivative of the depth of the solar convective
zone with respect to the logarithm of the radiative opacity. We use this
expression to show that the radiative opacity near the base of the solar
convective zone (CZ) must be known to an accuracy of +- 1% in order to
calculate the CZ depth to the accuracy of the helioseismological measurement,
R(CZ) = (0.713 +- 0.001)R(Sun). The radiative opacity near the base of the CZ
that is obtained from OPAL tables must be increased by about 21% in the
Bahcall-Pinsonneault (2004) solar model if one wants to invoke opacity errors
in order to reconcile recent solar heavy abundance determinations with the
helioseismological measurement of R(CZ). We show that the radiative opacity
near the base of the convective zone depends sensitively upon the assumed heavy
element mass fraction, Z. The uncertainty in the measured value of Z is
currently the limiting factor in our ability to calculate the depth of the CZ.
Different state-of-the-art interpolation schemes using the existing OPAL tables
yield opacity values that differ by 4% . We describe the finer grid spacings
that are necessary to interpolate the radiative opacity to 1%. Uncertainties
due to the equation of state do not significantly affect the calculated depth
of the convective zone.


title: Mechanical and Thermal Tests of the Containers of Liquid Mirrors

abstract:
  We give a generic description of a liquid mirror system and summarize some
practical information useful to making them. We compare laboratory measurements
of deformations, due to the weight of mercury on the container of a 3.7-m
mirror and to temperature changes on a 1-m container, to finite element
computer simulations. We find that the measurements agree reasonably well with
the numerical simulations. The measurements on the 1-m container show no
evidence of fatigue after a few thermal cycles. These results validate the
computer models of containers described in a companion article.


title: Two New Low Galactic D/H Measurements from FUSE

abstract:
  We analyze interstellar absorption observed towards two subdwarf O stars, JL
9 and LSS 1274, using spectra taken by the Far Ultraviolet Spectroscopic
Explorer (FUSE). Column densities are measured for many atomic and molecular
species (H I, D I, C I, N I, O I, P II, Ar I, Fe II, and H2), but our main
focus is on measuring the D/H ratios for these extended lines of sight, as D/H
is an important diagnostic for both cosmology and Galactic chemical evolution.
We find D/H=(1.00+/-0.37)e-5 towards JL 9, and D/H=(0.76+/-0.36)e-5 towards LSS
1274 (2 sigma uncertainties). With distances of 590+/-160 pc and 580+/-100 pc,
respectively, these two lines of sight are currently among the longest Galactic
lines of sight with measured D/H. With the addition of these measurements, we
see a significant tendency for longer Galactic lines of sight to yield low D/H
values, consistent with previous inferences about the deuterium abundance from
D/O and D/N measurements. Short lines of sight with H I column densities of log
N(H I)<19.2 suggest that the gas-phase D/H value within the Local Bubble is
(D/H)_LBg=(1.56+/-0.04)e-5. However, the four longest Galactic lines of sight
with measured D/H, which have d>500 pc and log N(H I)>20.5, suggest a
significantly lower value for the true local-disk gas-phase D/H value,
(D/H)_LDg=(0.85+/-0.09)e-5. One interpretation of these results is that D is
preferentially depleted onto dust grains relative to H and that longer lines of
sight that extend beyond the Local Bubble sample more depleted material. In
this scenario, the higher Local Bubble D/H ratio is actually a better estimate
than (D/H)_LDg for the true local-disk D/H, D/H)_LD. However, if (D/H)_LDg is
different from (D/H)_LBg simply because of variable astration and incomplete
ISM mixing, then (D/H)_LD=(D/H)_LDg.


title: Design of 2-m to 6-m Liquid Mirror Containers

abstract:
  A new design is proposed for large (up to 6-m) liquid mirror containers. The
design uses Kevlar, foam and aluminum, as in previous designs, but with a
different configuration that makes the container lighter, stronger and more
rigid. The results of finite element analysis are presented, consisting in the
deformations due to temperature changes and to weight, and in the security
factor for each material when maximum constraints are applied. Tilt rigidity is
also analyzed. They show that the composite material construction technique
gives a good performance up to 6 meter diameters. The figures and tables
contained in this paper can be used as recipes to build containers having
diameters between 2 and 6 meters.


title: The J-band Light Curve of SN 2003lw, Associated with GRB 031203

abstract:
  At z=0.1055, the gamma-ray burst GRB 031203 is one of the two nearest GRBs
known. Using observations from the Very Large Array (VLA) and Chandra X-ray
Observatory, we derive sub-arcsecond localizations of the radio and X-ray
afterglow of this GRB. We present near-infrared observations of the supernova
SN 2003lw, which exploded in the host galaxy of the GRB 031203. Our deep, high
resolution Magellan/PANIC data establish that this SN is spatially coincident
with the radio and X-ray localizations of the afterglow of GRB 031203 to
sub-arcsecond precision, and is thus firmly associated with the GRB. We use
image differencing to subtract the bright emission from the host galaxy, and
measure the time evolution of the SN between ~5 and ~50 days after the GRB. The
resulting light curve has a shape which is quite different from that of the two
SNe previously associated with GRBs, SN 1998bw and SN 2003dh. With SN 2003lw
securely associated with this burst, we confirm that all three GRBs with
redshifts z<0.3 were accompanied by SN explosions.


title: The absence of crystalline silicates in the diffuse interstellar medium

abstract:
  We have studied the dust along the line-of-sight towards the Galactic Center
using Short Wavelength Spectrometer (SWS) data obtained with the Infrared Space
Observatory (ISO). We focussed on the wavelength region from 8-13 micron which
is dominated by the strong silicate absorption feature. Using the absorption
profiles observed towards Galactic Center Sources (GCS) 3 and 4, which are
C-rich Wolf-Rayet Stars, as reference objects, we are able to disentangle the
interstellar silicate absorption and the silicate emission intrinsic to the
source, toward Sgr A* and derive a very accurate profile for the intrinsic 9.7
micron band. The interstellar absorption band is smooth and featureless and is
well reproduced using a mixture of 15.1% amorphous pyroxene and 84.9% of
amorphous olivine by mass, all in spherical sub-micron-sized grains. There is
no direct evidence for substructure due to interstellar crystalline silicates.
We are able to determine an upper limit to the degree of crystallinity of
silicates in the diffuse interstellar medium (ISM), and conclude that the
crystalline fraction of the interstellar silicates is 0.2% (+/- 0.2%) by mass.
This is much lower than the degree of crystallinity observed in silicates in
the circumstellar environment of evolved stars, the main contributors of dust
to the ISM. There are two possible explanations for this discrepancy. First, an
amorphization process occurs in the ISM on a time scale significantly shorter
than the destruction time scale, possibly caused by particle bombardment by
heavyweight ions. Second, we consider the possibility that the crystalline
silicates in stellar ejecta are diluted by an additional source of amorphous
silicates, in particular supernovae.


title:
The Mass Discrepancy-Acceleration Relation: Disk Mass and the Dark
  Matter Distribution

abstract:
  The mass discrepancy in disk galaxies is shown to be well correlated with
acceleration, increasing systematically with decreasing acceleration below a
critical scale a0 = 3700 km^2/s^2/kpc = 1.2E-10 m/s/s. For each galaxy, there
is an optimal choice of stellar mass-to-light ratio which minimizes the scatter
in this mass discrepancy-acceleration relation. The same mass-to-light ratios
also minimize the scatter in the baryonic Tully-Fisher relation and are in
excellent agreement with the expectations of stellar population synthesis. Once
the disk mass is determined in this fashion, the dark matter distribution is
specified. The circular velocity attributable to the dark matter can be
expressed as a simple equation which depends only on the observed distribution
of baryonic mass. It is a challenge to understand how this very fine-tuned
coupling between mass and light comes about.


title: Proper Motion Objects in the Hubble Deep Field

abstract:
  Using the deepest and finest resolution images of the Universe acquired with
the Hubble Space Telescope and a similar image taken 7 years later for the
Great Observatories Origins Deep Survey, we have derived proper motions for the
point sources in the Hubble Deep Field--North. Two faint blue objects,HDF2234
and HDF3072, are found to display significant proper motion, 10.0 $\pm$ 2.5 and
15.5 $\pm$ 3.8 mas yr$^{-1}$. Photometric distances and tangential velocities
for these stars are consistent with disk white dwarfs located at $\sim$ 500 pc.
The faint blue objects analyzed by Ibata et al. (1999) and Mendez & Minniti
(2000) do not show any significant proper motion; they are not halo white
dwarfs and they do not contribute to the Galactic dark matter. These objects
are likely to be distant AGN.


title: 13 Years of Timing of PSR B1259-63

abstract:
  This paper summarizes the results of 13 years of timing observations of a
unique binary pulsar, PSR B1259$-$63, which has a massive B2e star companion.
The data span encompasses four complete orbits and includes the periastron
passages in 1990, 1994, 1997 and 2000. Changes in dispersion measure occurring
around the 1994, 1997 and 2000 periastrons are measured and accounted for in
the timing analysis. There is good evidence for a small glitch in the pulsar
period in 1997 August, not long after the 1997 periastron, and a significant
frequency second derivative indicating timing noise. We find that spin-orbit
coupling with secular changes in periastron longitude and projected semi-major
axis ($x$) cannot account for the observed period variations over the whole
data set. While fitting the data fairly well, changes in pulsar period
parameters at each periastron seem ruled out both by X-ray observations and by
the large apparent changes in pulsar frequency derivative. Essentially all of
the systematic period variations are accounted for by a model consisting of the
1997 August glitch and step changes in $x$ at each periastron. These changes
must be due to changes in the orbit inclination, but we can find no plausible
mechanism to account for them. It is possible that timing noise may mask the
actual changes in orbital parameters at each periastron, but the good fit to
the data of the $x$ step-change model suggests that short-term timing noise is
not significant.


title: A Bayesian Approach to Solar Flare Prediction

abstract:
  A number of methods of flare prediction rely on classification of physical
characteristics of an active region, in particular optical classification of
sunspots, and historical rates of flaring for a given classification. However
these methods largely ignore the number of flares the active region has already
produced, in particular the number of small events. The past history of
occurrence of flares (of all sizes) is an important indicator to future flare
production. We present a Bayesian approach to flare prediction, which uses the
flaring record of an active region together with phenomenological rules of
flare statistics to refine an initial prediction for the occurrence of a big
flare during a subsequent period of time. The initial prediction is assumed to
come from one of the extant methods of flare prediction. The theory of the
method is outlined, and simulations are presented to show how the refinement
step of the method works in practice.


title: Dark Matter Relic Abundance and Scalar-Tensor Dark Energy

abstract:
  Scalar-tensor theories of gravity provide a consistent framework to
accommodate an ultra-light quintessence scalar field. While the equivalence
principle is respected by construction, deviations from General Relativity and
standard cosmology may show up at nucleosynthesis, CMB, and solar system tests
of gravity. After imposing all the bounds coming from these observations, we
consider the expansion rate of the universe at WIMP decoupling, showing that it
can lead to an enhancement of the dark matter relic density up to few orders of
magnitude with respect to the standard case. This effect can have an impact on
supersymmetric candidates for dark matter.


title: Principal Component Analysis of AGN Spectra

abstract:
  We discuss spectral principal component analysis (SPCA) and show examples of
its application in analyzing AGN spectra in both small and large samples. It
can be used to identify peculiar spectra and classify AGN spectra. Its
application to correlation studies of AGN spectral properties and spectral
measurements for large samples is promising.


title:
Constraints on the cosmic equation of state: age conflict versus phantom
  energy. Age-redshift relations in an accelerated universe

abstract:
  The currently available values and confidence limits for Omega_m0, H_0 and
globular cluster ages still indicate that the dark energy that dominates the
Universe could also be a form of quintessence or phantom energy. In fact,
current cosmological values favor phantom energy. To increase the likelihood of
a cosmological constant as dark energy instead of phantom energy, the
possibilities seem to lie in reducing globular cluster ages, the Hubble
constant, or both, and possibly advancing the epoch of globular cluster
formation. For a set of possible dark energy equations of state that includes
the cosmological constant, quintessence or phantom energy, age-redshift
analytical expressions for null curvature universes that include ordinary
matter are derived together with the corresponding ages for these universes.


title:
Detection and high-resolution spectroscopy of a huge flare on the old M9
  dwarf DENIS 104814.7-395606.1

abstract:
  We report a flare on the M9 dwarf DENIS 104814.7-395606.1, whose mass places
it directly at the hydrogen burning limit. The event was observed in a spectral
sequence during 1.3 hours. Line shifts to bluer wavelengths were detected in H
alpha, H beta, and in the Na D lines, indicating mass motions. In addition we
detect a flux enhancement on the blue side of the two Balmer lines in the last
spectrum of our series. We interpret this as rising gas cloud with a projected
velocity of about 100 km/s which may lead to mass ejection. The higher Balmer
lines H gamma to H 8 are not seen due to our instrumental setup, but in the
last spectrum there is strong evidence for H 9 being in emission.


title: A panchromatic view of AGN

abstract:
  We review the continuum emission of Active Galactic Nuclei (AGN) over the
entire electromagnetic spectrum. After a brief historical introduction, we
describe the main spectral properties of unobscured AGN, discussing the
selection biases which prevent us from having a complete view of the AGN
population in the universe, and trying to build an updated spectral energy
distribution of optically selected quasars. In the second part of the review,
we describe the spectral properties of obscured AGN. Finally, we discuss the
main observational methods in the different wavelength bands for disentangling
AGN and stellar emission, and the ability of these methods to find new (mainly
obscured) AGN, a significant fraction of which are probably still missing in
current surveys.


title:
Gravitational microlensing and dark matter problem in our Galaxy: 10
  years later

abstract:
  Foundations of standard theory of microlensing are described, namely we
consider microlensing stars in Galactic bulge, the Magellanic Clouds or other
nearby galaxies. We suppose that gravitational microlenses lie between an Earth
observer and these stars. Criteria of an identification of microlensing events
are discussed. We also consider such microlensing events which do not satisfy
these criteria (non-symmetrical light curves, chromatic effects, polarization
effects). We describe results of MACHO collaboration observations towards the
Large Magellanic Cloud (LMC) and the Galactic bulge. Results of EROS
observations towards the LMC and OGLE observations towards the Galactic bulge
are also presented. Future microlensing searches are discussed.


title:
Tracing the star formation history of cluster galaxies using the
  Halpha/UV flux ratio

abstract:
  Since the Halpha and UV fluxes from galaxies are sensitive to stellar
populations of ages < 10^7 and ~ 10^8 yr respectively, their ratio
f(Halpha)/f(UV) provides us with a tool to study the recent t < 10^8 yr star
formation history of galaxies, an exercise that we present here applied to 98
galaxies in 4 nearby clusters (Virgo, Coma, Abell 1367 and Cancer). The
observed f(Halpha)/f(UV) ratio is ~ a factor of two smaller than the expected
one as determined from population synthesis models assuming a realistic
delayed, exponentially declining star formation history. We discuss various
mechanisms that may have affected the observed f(Halpha)/f(UV) ratio and we
propose that the above discrepancy arises from either the absorption of Lyman
continuum photons by dust within the star formation regions or from the
occurrence of star formation episodes. After splitting our sample into
different subsamples according to evolutionary criteria we find that our
reference sample of galaxies unaffected by the cluster environment show an
average value of f(Halpha)/f(UV) two times lower than the expected one. We
argue that this difference must be mostly due to absorption of ~ 45% of the
Lyman continuum photons within star forming regions. Galaxies with clear signs
of an ongoing interaction show average values of f(Halpha)/f(UV) slightly
higher than the reference value, as expected if those objects had SFR increased
by a factor of ~ 4. The accuracy of the current UV and Halpha photometry is not
yet sufficient to clearly disentangle the effect of interactions on the
f(Halpha)/f(UV) ratio, but significant observational improvements are shortly
expected to result from the GALEX mission.


title:
A comprehensive set of simulations of high-velocity collisions between
  main sequence stars

abstract:
  We report on a very large set of simulations of collisions between two main
sequence (MS) stars. These computations were done with the ``Smoothed Particle
Hydrodynamics'' method. Realistic stellar structure models for evolved MS stars
were used. In order to sample an extended domain of initial parameters space
(masses of the stars, relative velocity and impact parameter), more than 15000
simulations were carried out. We considered stellar masses ranging between 0.1
and 75 Msun and relative velocities up to a few thousands km/s. To limit the
computational burden, a resolution of 2000-30000 particles per star was used.
The primary goal of this study was to build a complete database from which the
result of any collision can be interpolated. This allows us to incorporate the
effects of stellar collisions with an unprecedented level of realism into
dynamical simulations of galactic nuclei and other dense stellar clusters. We
make the data describing the initial condition and outcome (mass and energy
loss, angle of deflection) of all our simulations freely available on the
Internet. We find that the outcome of collisions depends sensitively on the
stellar structure and that, in most cases, using polytropic models is
inappropriate. Published fitting formulas for the collision outcomes,
established from a limited set of collisions, prove of limited use because they
do not allow robust extrapolation to other stellar structures or relative
velocities.


title: Gravity assisted dark energy dominance and cosmic acceleration

abstract:
  It is proposed that dark energy may become dominant over standard matter due
to universe expansion (curvature decrease). Two models: non-linear
gravity-matter system and modified gravity may provide the effective phantom or
effective quintessence dark energy which complies with the conjecture. It is
interesting that future of such universe is not necessary finite time
singularity (Big Rip). The effective quintessence naturally describes current
cosmic speed-up.


title: CENSORS: The VLT/VLA mJy source survey for high redshift AGN evolution

abstract:
  The Combined EIS-NVSS Survey Of Radio Sources (CENSORS) has been produced
with the primary goal of investigating the cosmological evolution of the radio
luminosity function. This 1.4GHz sample, complete to the 7.2 mJy level,
contains 150 radio sources. Host galaxies are almost entirely identified in
optical and near-IR bands and the sample is now approaching 70% spectroscopic
completeness. We show preliminary results demonstrating how CENSORS will
improve upon previous work and how it is applicable to other projects.


title:
Using the X-ray Emission Lines of Seyfert 2 AGN to Measure Abundance
  Ratios

abstract:
  We measure the metal abundance ratios in the X-ray photoionized gas located
near the narrow line region of a sample of Seyfert 2 AGN. The high-resolution
X-ray spectra observed with the Chandra high- and low-energy transmission
grating spectrometers are compared with models of the resonant scattering and
recombination emission from a plasma in thermal balance, and with multiple
temperature zones. The abundance ratios in the sample are close to the Solar
values, with slight over-abundances of N in NGC 1068, and of Ne in NGC 4151.
Our X-ray spectral models use fewer degrees of freedom than previous works.


title: Fine-tuning the accretion disk clock in Hercules X-1

abstract:
  RXTE ASM count rates from the X-ray pulsar Her X-1 began falling consistently
during the late months of 2003. The source is undergoing another state
transition similar to the anomalous low state of 1999. This new event has
triggered observations from both space- and ground-based observatories. In
order to aid data interpretation and telescope scheduling, and to facilitate
the phase-connection of cycles before and after the state transition, we have
re-calculated the precession ephemeris using cycles over the last 3.5 years. We
report that the source has displayed a different precession period since the
last anomalous event. Additional archival data from CGRO suggests that each low
state is accompanied by a change in precession period and that the subsequent
period is correlated with accretion flux. Consequently our analysis reveals
long-term accretion disk behaviour which is predicted by theoretical models of
radiation-driven warping.


title: Stellar populations associated with the LMC Papillon Nebula

abstract:
  We study the Large Magellanic Cloud Papillon Nebula (N159-5), a conspicuous
High Excitation Blob (HEB) lying in the star forming complex N159. Using JHK
near-infrared photometry obtained at the ESO VLT with the ISAAC camera, we
examine the stellar populations associated with the Papillon, tracing their
history using stellar evolution models. Two populations are revealed: one
composed of young, massive stars with an age ~ 3 Myr, and a second consisting
of older lower mass stars of age spreading between 1 and 10 Gyr. We analyze the
properties of those populations and discuss their significance in the context
of N159. We also estimate that if the star at the center of the Papillon is
single its initial mass is ~ 50 solar masses and it is affected by an
extinction Av ~ 7 mag.


title:
Modeling the Multiwavelength Spectra and Variability of BL Lacertae in
  2000

abstract:
  BL Lacertae was the target of an extensive multiwavelength monitoring
campaign in the second half of 2000. In this paper, we are using leptonic and
hadronic jet models to fit the observed broadband spectra and spectral
variability patterns. We start out with global spectral models. Subsequently,
we investigate various flaring scenarios for comparison with the observed
short-term variability. For our leptonic jet model, we find that the short-term
variability, in particular the optical and X-ray spectral variability, can be
best represented with a flaring scenario dominated by a spectral-index change
of the spectrum of ultrarelativistic electrons injected into the jet. Based on
this result, a detailed model simulation, reproducing the observed optical and
X-ray spectral variability and broadband SED of BL Lacertae simultaneously, is
presented. Our leptonic modeling results are compared to fits using the
hadronic synchrotron-proton blazar (SPB) model. That model can reproduce the
observed SEDs of BL Lacertae in a scenario with muon-synchrotron dominated
high-energy emission. It requires a significantly higher magnetic field than
the leptonic model (~ 40 G vs. ~ 2 G in the leptonic model) and a lower Doppler
factor associated with the bulk motion of the emission region (D ~ 8 vs. D ~ 18
in the leptonic model). The hadronic model predicts a significantly larger >
100 GeV flux than the leptonic models, well within the anticipated capabilities
of VERITAS and MAGIC.


title:
The VIMOS VLT Deep Survey: Public release of 1599 redshifts to IAB<=24
  across the Chandra Deep Field South

abstract:
  {This paper presents the VIMOS VLT Deep Survey around the Chandra Deep Field
South (CDFS). We have measured 1599 new redshifts with VIMOS on the European
Observatory Very Large Telescope - UT3, in an area 21x21.6 arcmin^2, including
784 redshifts in the Hubble Space Telescope - Advanced Camera for Surveys GOODS
area. 30% of all objects with I_AB=24 have been observed independently of
magnitude, indicating that the sample is purely magnitude limited. We have
reached an unprecedented completeness level of 88% in terms of the ratio of
secure measurements vs. observed objects, while 95% of all objects have a
redshift measurement. A total of 1452 galaxies, 139 stars, 8 QSOs have a
redshift identification, 141 of these being unsecure measurements. The redshift
distribution down to I_AB=24 is peaked at a median redshift z=0.73, with a
significant high redshift tail extending up to ~4. Several high density peaks
in the distribution of galaxies are identified. In particular, the strong peak
at z=0.735 contains more than 130 galaxies in a velocity range +/-2000 km/s
distributed all across the transverse ~20 h^-1 Mpc of the survey. We are
releasing all redshifts to the community, along with the cross identification
with HST-ACS GOODS sources on the CENCOS database environment
http://cencosw.oamp.fr.


title:
Ellipticals at $z=0$ from Self-Consistent Hydrodynamical Simulations:
  Comparison with SDSS Structural and Kinematical Data

abstract:
  We present results of an analysis of the structural and kinematical
properties of a sample of elliptical-like objects (ELOs) identified in four
hydrodynamical, self-consistent simulations run with the DEVA code (Serna et
al. 2003). Star formation has been implemented in the code through a simple
phenomenological parameterization, that takes into account stellar physics
processes only implicitly through the values of a threshold gas density,
$\rho_{\rm g,thres}$, and an efficiency parameter, $c_*$. The four simulations
operate in the context of a $\Lambda$CDM cosmological model consistent with
observations, resolve ELO mass assembly at scales up to $\simeq$ 2 kpc, and
differ in the values of their star formation parameters. Stellar masses,
projected half-mass radii and central l.o.s. velocity dispersions, $\sigma_{\rm
los, 0}$, have been measured on the ELO sample and their values compared with
data from the Sloan digital sky survey. For the first time in self-consistent
simulations, a good degree of agreement has been shown, including the
Faber-Jackson and the $D_n - \sigma_{\rm los, 0}$ relations, among others, but
only when particular values of the $\rho_{\rm g,thres}$ and $c_*$ parameters
are used. This demostrates the effect that the star formation parameterization
has on the ELO mass distribution. Additionally, our results suggest that it is
not strictly necessary, at the scales resolved in this work, to appeal to
energy sources other than gravitational (as for example supernovae feedback
effects) to account for the structure and kinematics of large ellipticals.


title: A three-dimensional calculation of atmospheric neutrinos

abstract:
  A Monte-Carlo calculation of the atmospheric neutrino fluxes [1,2] has been
extended to take account of the three-dimensional (3D) nature of the problem,
including the bending of secondary particles in the geomagnetic field. Emphasis
has been placed on minimizing the approximations when introducing the 3D
considerations. In this paper, we describe the techniques used and quantify the
effects of the small approximations which remain. We compare 3D and 1D
calculations using the same physics input in order to evaluate the conditions
under which the 3D calculation is required and when the considerably simpler 1D
calculation is adequate. We find that the 1D and 3D results are essentially
identical for neutrino energy greater than 5 GeV except for small effects in
the azimuthal distributions due to bending of the secondary muon by the
geomagnetic field during their propagation in the atmosphere.


title:
The Scaleheight of Giant Molecular Clouds is Less than that of Smaller
  Clouds

abstract:
  We have used an antenna temperature thresholding algorithm on the Bell
Laboratories 13CO Milky Way Survey to create a catalog of 1,400 molecular
clouds. Of these, 281 clouds were selected for having well-determined kinematic
distances. The scaleheight, luminosity, internal velocity dispersion, and size
of the cloud sample are analyzed to show that clouds smaller than ~200,000
solar masses have a scaleheight which is about 35 pc, roughly independent of
cloud mass, while larger clouds, the Giant Molecular Clouds, have a reduced
scaleheight which declines with increasing cloud mass.


title:
Observations of PSR J2021+3651 and its X-ray Pulsar Wind Nebula
  G75.2+0.1

abstract:
  We present results from X-ray and radio observations of the recently
discovered young Vela-like pulsar PSR J2021+3651, which is coincident with the
EGRET gamma-ray source GeV 2020+3658. A 19.0-ks Chandra ACIS-S observation has
revealed a ~20'' x 10'' pulsar wind nebula that is reminiscent of the
equatorial tori seen around some young pulsars, along with thermal emission
from an embedded point source (kT = 0.15 +/- 0.02 keV). We name the nebula
G75.2+0.1. Its spectrum is well fit by an absorbed power-law model with photon
index 1.7 +/- 0.3, hydrogen column density nH = 7.8 +/- 1.7 x 10^21 cm^-2, and
an unabsorbed 0.3-10.0 keV flux of 1.9 +/- 0.3 x 10^-12 erg cm^-2 s^-1. We have
spatially fit G75.2+0.1 with a model that assumes a toroidal morphology, and
from this we infer that the torus is highly inclined 83 deg +/- 1 deg to the
line of sight. A 20.8-ks Chandra observation in continuous-clocking mode
reveals a possible pulse detection, with a pulsed fraction of ~37% and an
H-test probability of occuring by chance of 1.2 x 10^-4. Timing observations
with the Arecibo radio telescope spanning two years show that PSR J2021+3651
glitched sometime between MJDs 52616 and 52645 with parameters delta(v)/v =
(2.587 +/- 0.002) x 10^-6 and delta(dot(v))/v = (6.2 +/- 0.3) x 10^-3, similar
to those of the largest glitches observed in the Vela pulsar. PSR J2021+3651 is
heavily scattered (T_sc = 17.7 ms +/- 0.9 ms at 1 GHz) and exhibits a
significant amount of timing noise.


title:
Effects of Triaxiality on the Statistics of Large-Separation
  Gravitational Lenses

abstract:
  We study the statistics of large-separation gravitational lens systems
produced by non-spherical halos in the Cold Dark Matter (CDM) model.
Specifically, we examine how the triaxiality of CDM halos affects the overall
lensing probabilities and the relative numbers of different image
configurations (double, quadruple, and naked cusp lenses). We find that
triaxiality significantly enhances lensing probabilities by a factor of ~2-4,
so it cannot be ignored. If CDM halos have central density slopes alpha<~1.5,
we predict that a significant fraction (>~20%) of large-separation lenses
should have naked cusp image configurations; this contrasts with lensing by
isothermal (\alpha~2) galaxies where naked cusp configurations are rare. The
image multiplicities depend strongly on the inner density slope \alpha: for
\alpha=1, the naked cusp fraction is >~60%; while for \alpha=1.5, quadruple
lenses are actually the most probable. Thus, the image multiplicities in
large-separation lenses offer a simple new probe of the inner density profiles
of dark matter halos. We also compute the expected probabilities and image
multiplicities for lensed quasars in the Sloan Digital Sky Survey, and argue
that the recent discovery of the large-separation quadruple lens SDSS
J1004+4112 is consistent with expectations for CDM.


title: Identification of the Mass Donor Star's Spectrum in SS 433

abstract:
  We present spectroscopy of the microquasar SS 433 obtained near primary
eclipse and disk precessional phase Psi = 0.0, when the accretion disk is
expected to be most ``face-on''. The likelihood of observing the spectrum of
the mass donor is maximized at this combination of orbital and precessional
phases since the donor is in the foreground and above the extended disk
believed to be present in the system. The spectra were obtained over four
different runs centered on these special phases. The blue spectra show clear
evidence of absorption features consistent with a classification of A3-7 I. The
behavior of the observed lines indicates an origin in the mass donor. The
observed radial velocity variations are in anti-phase to the disk, the
absorption lines strengthen at mid-eclipse when the donor star is expected to
contribute its maximum percentage of the total flux, and the line widths are
consistent with lines created in an A supergiant photosphere. We discuss and
cast doubt on the possibility that these lines represent a shell spectrum
rather than the mass donor itself. We re-evaluate the mass ratio of the system
and derive masses of 10.9 +/- 3.1 Msun and 2.9 +/- 0.7 Msun for the mass donor
and compact object plus disk, respectively. We suggest that the compact object
is a low mass black hole.
  In addition, we review the behavior of the observed emission lines from both
the disk/wind and high velocity jets.


title: Does Disk Locking Solve the Stellar Angular Momentum Problem?

abstract:
  We critically examine the theory of disk locking, which assumes that the
angular momentum deposited on an accreting protostar is exactly removed by
torques carried along magnetic field lines connecting the star to the disk. In
this letter, we consider that the differential rotation between the star and
disk naturally leads to an opening (i.e., disconnecting) of the magnetic field
between the two. We find that this significantly reduces the spin-down torque
on the star by the disk. Thus, disk-locking cannot account for the slow
rotation ($\sim$10% of breakup speed) observed in several systems and for which
the model was originally developed.


title:
An exceptional population of late-type WC stars in the metal-rich spiral
  galaxy

abstract:
  We have surveyed the metal-rich spiral galaxy M83 (NGC5236) for its
Wolf-Rayet population using VLT-FORS2 narrow-band imaging and follow-up
spectroscopy. From a total of 280 candidates identified using HeII 4686
imaging, Multi Object Spectroscopy of 198 sources was carried out, revealing
132 objects containing bona-fide Wolf-Rayet features. From this sample, an
exceptional W-R content of 1030 is inferred, with N(WC)/N(WN)=1.3, continuing
the trend to larger values at higher metallicity amongst Local Group galaxies.
More dramatic is the dominance of late-type WC stars in M83 with
N(WC8-9)/N(WC4-7)=9 which we attribute to the sensitivity of the classification
line CIII 5696 to mass-loss, providing the strength of WC winds scale with
metallicity. One young massive compact cluster, #74 in our catalogue, hosts 20%
of the entire galactic population, namely 180 late WC stars and 50 late WN
stars.


title:
uvby(-$\beta$) photometry of high-velocity and metal-poor stars X. Stars
  of very low metal abundance: observations, reddenings, metallicities,
  classifications, distances, and relative ages

abstract:
  uvby(--$\beta$) photometry has been obtained for an additional 411 very
metal-poor stars selected from the HK survey, and used to derive basic
parameters such as interstellar reddenings, metallicities, photometric
classifications, distances, and relative ages... These very metal-poor stars
are compared to M92 in the c_0,(b-y)_0 diagram, and evidence is seen for field
stars 1-3 Gyrs younger than this globular cluster. The significance of these
younger very metal-poor stars is discussed in the context of Galactic
evolution, mentioning such possibilities as hierarchical
star-formation/mass-infall of very metal-poor material and/or accretion events
whereby this material has been acquired from other (dwarf) galaxies with
different formation and chemical-enrichment histories


title:
Three-point Correlation Functions of SDSS Galaxies in Redshift Space:
  Morphology, Color, and Luminosity Dependence

abstract:
  We present measurements of the redshift--space three-point correlation
function of galaxies in the Sloan Digital Sky Survey (SDSS). For the first
time, we analyze the dependence of this statistic on galaxy morphology, color
and luminosity. In order to control systematics due to selection effects, we
used $r$--band, volume-limited samples of galaxies, constructed from the
magnitude-limited SDSS data ($14.5<r<17.5$), and further divided the samples
into two morphological types (early and late) or two color populations (red and
blue). The three-point correlation function of SDSS galaxies follow the
hierarchical relation well and the reduced three-point amplitudes in
redshift--space are almost scale-independent ($Q_z=0.5\sim1.0$). In addition,
their dependence on the morphology, color and luminosity is not statistically
significant. Given the robust morphological, color and luminosity dependences
of the two-point correlation function, this implies that galaxy biasing is
complex on weakly non-linear to non-linear scales. We show that simple
deterministic linear relation with the underlying mass could not explain our
measurements on these scales.


title:
Near IR Spectroscopic monitoring of WR 140 during the 2001 periastron
  passage

abstract:
  We present new spectra of WR 140 (HD 193793) in the JHK bands with some
covering the 1.083-micron He I emission line at higher resolution, observed
between 2000 October and 2003 May to cover its 2001 periastron passage. The WC7
+ O4-5 spectroscopic binary WR 140 is the prototype of colliding-wind, episodic
dust-making Wolf-Rayet systems which also show strong variations in radio and
X-ray emission. The JHK spectra showed changes in continuum and in the
equivalent widths of the WC emission lines, consistent with formation of dust
starting between 2001 January 3 and March 26 (orbital phases 0.989 and 0.017)
and its subsequent fading and cooling. The 1.083-micron He I line has a P-Cygni
profile which showed variations in both absorption and emission components as
WR 140 went through periastron passage. The variation of the absorption
component yielded tight constraints on the geometry of the wind-collision
region, giving theta = 50 +/- 8 degrees for the opening semi-angle of the
interaction `cone', indicating a wind-momentum ratio of the O to the WR
star=0.1, about three times larger than previously believed. As the system
approached periastron, the emission component showed the appearance of a
significant sub-peak, movement of which across the profile was seen to be
consistent with its formation in wind material flowing along the contact
discontinuity between the two stellar winds and the changing orientation of the
colliding wind region. The flux carried in the sub-peak exceeded the X-ray
fluxes measured at previous periastron passages. This additional source of
radiative cooling of the shock-heated gas probably causes it to depart from
being adiabatic around periastron passage, thereby accounting for the departure
of the X-ray flux from its previously expected $1/d$-dependency.


title: Cosmic rays acceleration at ultrarelativistic subshocks

abstract:
  We present the model of cosmic rays acceleration at ultrarelativistic
subshocks and confront it with the observations of gamma-ray bursts and
blazars. We investigate cosmic rays acceleration in shocks with Lorentz factors
in the range 3 - 40. We show that fluctuations of the magnetic field downstream
of the shock do not play an important role in the acceleration process. Results
of numerical simulations for shocks with considered Lorentz factors and
perpendicular magnetic field inclinations are presented. We fit the derived
particle energy spectral index dependence on fluctuations of the magnetic field
upstream and Lorentz factor of the shock with a function.