title: The line-of-sight distribution of water in the SgrB2 complex

abstract:
  We report the detection, with the Caltech Submillimeter Observatory, of the
894-GHz HDO(111-000) transition, observed in absorption against the background
continuum emission of the SgrB2 cores M and N. Radiative transfer modeling of
this feature, together with the published data set of mm and submm HDO and
H2O-18 transitions, suggests that ground-state absorption features from
deuterated and non-deuterated water trace different gas components along the
line of sight. In particular, while the HDO line seems to be produced by the
large column densities of gas located in the SgrB2 warm envelope, the H2O-18
ground-state transition detected by SWAS and KAO at 548 GHz (Neufeld et al.
2000; Zmuidzinas et al. 1995a) is instead a product of the hot, diffuse, thin
gas layer lying in the foreground of the SgrB2 complex.


title:
Fine Scale Temperature Fluctuations in the the Orion Nebula and the t^2
  Problem

abstract:
  We present a high spatial resolution map of the columnar electron temperature
(Tc) of a region to the south west of the Trapezium in the Orion Nebula. This
map was derived from Hubble Space Telescope images that isolated the primary
lines of HI for determination of the local extinction and of the OIII lines for
determination of Tc. Although there is no statistically significant variation
of Tc with distance from the dominant ionizing star theta1-Ori-C, we find small
scale variations in the plane of the sky down to a few arcseconds that are
compatible with the variations inferred from comparing the value of Te derived
from forbidden and recombination lines, commonly known as the t^2 problem. We
present other evidence for fine scale variations in conditions in the nebula,
these being variations in the surface brightness of the the nebula,
fluctuations in radial velocities, and ionization changes. From our Tc map and
other considerations we estimate that t^2=0.028 +-0.006 for the Orion nebula.
Shadowed regions behind clumps close to the ionization front can make a
significant contribution to the observed temperature fluctuations, but they
cannot account for the t^2 values inferred from several methods of temperature
determination. It is shown that an anomalous broadening of nebular emission
lines appears to have the same sense of correlation as the temperature
anomalies, although a causal link is not obvious.


title: Two-Pole Caustic Model for High-Energy Lightcurves of Pulsars

abstract:
  We present a new model of high-energy lightcurves from rotation powered
pulsars. The key ingredient of the model is the gap region (i.e. the region
where particle acceleration is taking place and high-energy photons originate)
which satisfies the following assumptions: i) the gap region extends from each
polar cap to the light cylinder; ii) the gap is thin and confined to the
surface of last open magnetic-field lines; iii) photon emissivity is uniform
within the gap region. The model lightcurves are dominated by strong peaks
(either double or single) of caustic origin. Unlike in other pulsar models with
caustic effects, the double peaks arise due to crossing two caustics, each of
which is associated with a different magnetic pole. The generic features of the
lightcurves are consistent with the observed characteristics of pulsar
lightcurves: 1) the most natural (in terms of probability) shape consists of
two peaks (separated by 0.4 to 0.5 in phase for large viewing angles); 2) the
peaks posess well developed wings; 3) there is a bridge (inter-peak) emission
component; 4) there is a non-vanishing off-pulse emission level; 5) the radio
pulse occurs before the leading high-energy peak. The model is well suited for
four gamma-ray pulsars - Crab, Vela, Geminga and B1951+32 - with double-peak
lightcurves exhibiting the peak separation of 0.4 to 0.5 in phase. Hereby, we
apply the model to the Vela pulsar. Moreover, we indicate the limitation of the
model in accurate reproducing of the lightcurves with single pulses and
narrowly separated (about 0.2 in phase) pulse peaks. We also discuss the
optical polarization properties for the Crab pulsar in the context of the
two-pole caustic model.


title: Sunyaev-Zeldovich Fluctuations from the First Stars?

abstract:
  WMAP's detection of high electron-scattering optical depth suggests
substantial star formation at high redshift z~17 +/- 5. On the other hand, the
recovered sigma_8 ~ 0.84 +/-0.04 disfavors a cluster Sunyaev-Zeldovich (SZ)
origin for the observed small-scale-CMB fluctuation excess, which generally
requires sigma_8 ~ 1.1. Here we consider the effects of high-redshift star
formation on the CMB. We derive a fairly model-independent relation between the
electron scattering optical depth and the number of ionizing photons emitted
per baryon, and use this to calibrate the amount of high-redshift supernova
activity. The resulting supernova remnants Compton cool against the CMB
creating a Compton-y distortion y ~ few x 10^-6, within observational bounds.
However they also create small-scale SZ fluctuations, which could be comparable
with SZ fluctuations from unresolved galaxy clusters. This raises the exciting
possibility that we have already detected signatures of the first stars not
just once, but twice, in the CMB.


title: Multiple Molecular H2 Outflows in AFGL 618

abstract:
  We report high spatial (0.5 arcsec) and high spectral (9 km/s) resolution
spectro-imaging of the 2.12 micron H2 1-0 S(1) line in the proto-planetary
nebula AFGL 618 using BEAR at the CFHT. The observations reveal the presence of
multiple, high-velocity, molecular outflows that align with the remarkable
optical jets seen in HST images. The structure and kinematics of the outflows
show how jets interact with circumstellar gas and shape the environment in
which planetary nebulae form.


title:
Exploring the Expanding Universe and Dark Energy using the Statefinder
  Diagnostic

abstract:
  The coming few years are likely to witness a dramatic increase in high
quality Sn data as current surveys add more high redshift supernovae to their
inventory and as newer and deeper supernova experiments become operational.
Given the current variety in dark energy models and the expected improvement in
observational data, an accurate and versatile diagnostic of dark energy is the
need of the hour. This paper examines the Statefinder diagnostic in the light
of the proposed SNAP satellite which is expected to observe about 2000
supernovae per year. We show that the Statefinder is versatile enough to
differentiate between dark energy models as varied as the cosmological constant
on the one hand, and quintessence, the Chaplygin gas and braneworld models, on
the other. Using SNAP data, the Statefinder can distinguish a cosmological
constant ($w=-1$) from quintessence models with $w \geq -0.9$ and Chaplygin gas
models with $\kappa \leq 15$ at the $3\sigma$ level if the value of $\om$ is
known exactly. The Statefinder gives reasonable results even when the value of
$\om$ is known to only $\sim 20%$ accuracy. In this case, marginalizing over
$\om$ and assuming a fiducial LCDM model allows us to rule out quintessence
with $w \geq -0.85$ and the Chaplygin gas with $\kappa \leq 7$ (both at
$3\sigma$). These constraints can be made even tighter if we use the
Statefinders in conjunction with the deceleration parameter. The Statefinder is
very sensitive to the total pressure exerted by all forms of matter and
radiation in the universe. It can therefore differentiate between dark energy
models at moderately high redshifts of $z \lleq 10$.


title: Planet Migration and Binary Companions: the case of HD 80606b

abstract:
  The exo-solar planet HD 80606b has a highly eccentric (e=0.93) and tight
(a=0.47 AU) orbit. We study how it might arrive at such an orbit and how it has
avoided being tidally circularized until now. The presence of a stellar
companion to the host star suggests the possibility that the Kozai mechanism
and tidal dissipation combined to draw the planet inward well after it formed:
Kozai oscillations produce periods of extreme eccentricity in the planet orbit,
and the tidal dissipation that occurs during these periods of small pericentre
distances leads to gradual orbital decay. We call this migration mechanism the
'Kozai migration'. It requires that the initial planet orbit is highly inclined
relative to the binary orbit. For a companion at 1000 AU and an initial planet
orbit at 5 AU, the minimum relative inclination required is ~ 85. We discuss
the efficiency of tidal dissipation inferred from the observations of
exo-planets. Moreover, we investigate possible explanations for the velocity
residual (after the motion induced by the planet is removed) observed on the
host star: a second planet in the system is excluded over a large extent of
semi-major axis space if Kozai migration is to work, and the tide raised on the
star by HD 80606b is likely too small in amplitude. Lastly, we discuss the
relevance of Kozai migration for other planetary systems.


title: Distances to Local Group Galaxies

abstract:
  Distances to galaxies in the Local Group are reviewed. In particular, the
distance to the Large Magellanic Cloud is found to be $(m-M)_0 = 18.52 \pm
0.10$, corresponding to $50,600 \pm 2,400$ pc. The importance of M31 as an
analog of the galaxies observed at greater distances is stressed, while the
variety of star formation and chemical enrichment histories displayed by Local
Group galaxies allows critical evaluation of the calibrations of the various
distance indicators in a variety of environments.


title:
The Large Synoptic Survey Telescope (LSST) and its Impact on Variable
  Star Research

abstract:
  The Large Synoptic Survey Telescope (LSST) is conceived as an 8.4-m telescope
with CCD or CMOS focal plane covering most of a field 0.6 m in diameter, the
latter exceeding the size of the largest photographic plates ever used in
astronomy. The telescope design is driven by the desire to cover much of the
accessible sky to faint magnitudes on a timescale of $\sim$ one night, with
major science drivers the search for near Earth-orbit asteroids down to a
diameter of 300 m, discovering supernovae to z $\sim 2$, and mass tomography of
the Universe via gravitational weak lensing. Here the suitability of this
facility for more ``traditional'' variable star research is investigated.


title: Galactic archaeology: IMF and depletion in the "thin disk"

abstract:
  We determine the initial mass function (IMF) of the ``thin disk'' by means of
a direct comparison between synthetic stellar samples (for different matching
choices of IMF, star formation rate SFR and depletion) and a complete
(volume-limited) sample of single stars near the galactic plane (|z| < 25pc),
selected from the Hipparcos catalogue (d < 100pc, M_v < +4.0). Our synthetic
samples are computed from first principles: stars are created with a random
distribution of mass M_* and age t_* which follow a given (genuine) IMF and
SFR(t_*). They are then placed in the HR diagram by means of a grid of
empirically well-tested evolution tracks. The quality of the match (synthetic
versus observed sample) is assessed by means of star counts in specific regions
in the HR diagram. 7 regions are located along the MS (main sequence, mass
sensitive), while 4 regions represent different evolved (age-sensitive) stages
of the stars. The counts of evolved stars, in particular, give valuable
evidence of the history of the ``thin disk'' (apparent) star formation and lift
the ambiguities in models restricted to MS star counts.


title:
Small-scale CMB polarization anisotropies due to tangled primordial
  magnetic fields

abstract:
  Tangled, primordial cosmic magnetic fields create small rotational velocity
perturbations on the last scattering surface (LSS) of the cosmic microwave
background radiation (CMBR). Such perturbations can contribute significantly to
the CMBR temperature and polarization anisotropies at large l > 1000 or so,
like the excess power detected by the CBI experiment. The magnetic contribution
can be distinguished from most conventional signals, as they lead to CMBR
polarization dominated by the odd parity, B-type signal. Experiments like DASI
and WMAP have detected evidence for CMBR polarization at small l. Many
experiments will also probe the large $l$ regime. We therefore calculate the
polarization signals due to primordial magnetic fields, for different spectra
and different cosmological parameters. A scale-invariant spectrum of tangled
fields which redshifts to a present value B_{0}=3\times 10^{-9} Gauss, produces
B-type polarization anisotropies of order 0.3 - 0.4 micro Kelvin between l of
1000-5000. Larger signals result if the spectral index of magnetic tangles is
steeper, n>-3. The peak of the signal shifts to larger l for a lambda-dominated
universe, or if the baryon density is larger. The signal will also have
non-Gaussian statistics. We also predict the much smaller E-type polarization,
and T-E cross correlations for these models.


title: Hyperdiffusion in non-linear, large and small-scale turbulent dynamos

abstract:
  The generation of large-scale magnetic fields is generically accompanied by
the more rapid growth of small-scale fields. The growing Lorentz force due to
these fields back reacts on the turbulence to saturate the mean-field and
small-scale dynamos. For the mean-field dynamo, in a quasi-linear treatment of
this saturation, it is generally thought that, while the alpha-effect gets
renormalised and suppressed by non-linear effects, the turbulent diffusion is
left unchanged. We show here that this is not true and the effect of the
Lorentz forces, is also to generate additional non-linear hyperdiffusion of the
mean field. A combination of such non-linear hyperdiffusion with diffusion at
small scales, also arises in a similar treatment of small-scale dynamos, and is
crucial to understand its saturation.


title:
Detection of Non-Random Galaxy Orientations in X-ray Subclusters of the
  Coma Cluster

abstract:
  This study on the Coma cluster suggests that there are deviations from a
completely random galaxy orientation on small scales. Since we found a
significant coincidence of hot-gas features identified in the latest X-ray
observations of Coma with these local anisotropies, they may indicate regions
of recent mutual interaction of member galaxies within subclusters which are
currently falling in on the main cluster.


title:
Star Formation at the Twilight of the Dark Ages: Which Stars Reionized
  the Universe?

abstract:
  We calculate the global star formation rate density (SFRD) from z ~ 30-3
using a semi-analytic model incorporating the hierarchical assembly of dark
matter halos, gas cooling via atomic hydrogen, star formation, supernova
feedback, and suppression of gas collapse in small halos due to the presence of
a photoionizing background. We compare the results with the predictions of
simpler models based on the rate of dark matter halo growth and a fixed ratio
of stellar-to-dark mass, and with observational constraints on the SFRD at 3 <
z < 6. We also estimate the star formation rate due to very massive, metal-free
Pop III stars using a simple model based on the halo formation rate, calibrated
against detailed hydrodynamic simulations of Pop III star formation. We find
that the total production rate of hydrogen-ionizing photons during the probable
epoch of reionization (15 < z < 20) is approximately equally divided between
Pop II and Pop III stars, and that if reionization is late (less than about 15,
close to the lower limit of the range allowed by the WMAP results), then Pop II
stars alone may be able to reionize the Universe.


title:
A photometric monitoring of bright high-amplitude delta Scuti stars. II.
  Period updates for seven stars

abstract:
  We present new photometric data for seven high-amplitude delta Scuti stars.
The observations were acquired between 1996 and 2002, mostly in the Johnson
photometric system. For one star (GW UMa), our observations are the first since
the discovery of its pulsational nature from the Hipparcos data.The primary
goal of this project was to update our knowledge on the period variations of
the target stars. For this, we have collected all available photometric
observations from the literature and constructed decades-long O-C diagrams of
the stars. This traditional method is useful because of the single-periodic
nature of the light variations. Text-book examples of slow period evolution (XX
Cyg, DY Her, DY Peg) and cyclic period changes due to light-time effect (LITE)
in a binary system (SZ Lyn) are updated with the new observations. For YZ Boo,
we find a period decrease instead of increase. The previously suggested
LITE-solution of BE Lyn (Kiss & Szatmary 1995) is not supported with the new
O-C diagram. Instead of that, we suspect the presence of transient light curve
shape variations mimicking small period changes.


title: The coronal mass ejection waiting-time distribution

abstract:
  The distribution of times $\Delta t$ between coronal mass ejections (CMEs) in
the Large Angle and Spectrometric Coronagraph (LASCO) CME catalog for the years
1996-2001 is examined. The distribution exhibits a power-law tail $\propto
(\Delta t)^{\gamma}$ with an index $\gamma\approx -2.36\pm 0.11$ for large
waiting times ($\Delta t>10 {\rm hours}$). The power-law index of the
waiting-time distribution varies with the solar cycle: for the years 1996-1998
(a period of low activity), the power-law index is $\gamma\approx-1.86\pm
0.14$, and for the years 1999-2001 (a period of higher activity), the index is
$\gamma\approx-2.98\pm 0.20$. The observed CME waiting-time distribution, and
its variation with the cycle, may be understood in terms of CMEs occurring as a
time-dependent Poisson process. The CME waiting-time distribution is compared
with that for greater than C1 class solar flares in the Geostationary
Operational Environmental Satellite (GOES) catalog for the same years. The
flare and CME waiting-time distributions exhibit power-law tails with very
similar indices and time variation.


title: Genus Topology of the Cosmic Microwave Background from WMAP

abstract:
  We have independently measured the genus topology of the temperature
fluctuations in the cosmic microwave background seen by the Wilkinson Microwave
Anisotropy Probe (WMAP). A genus analysis of the WMAP data indicates
consistency with Gaussian random-phase initial conditions, as predicted by
standard inflation.


title: Constraints on Cardassian Expansion from Distant type Ia Supernovae

abstract:
  The distant type Ia supernovae data compiled by Perlmutter et al. (1999) are
used to analyze the Cardassian expansion scenario, which was recently proposed
by Freese and Lewis (2002) as an alternative to a cosmological constant (or
more generally a dark energy component) in explaining the currently
accelerating universe. We show that the allowed intervals for $n$ and $z_{eq}$,
the two parameters of the Cardassian model, will give rise to a universe with a
very low matter density, which can hardly be reconciled with the current value
derived from the measurements of the cosmic microwave background anisotropy and
galaxy clusters (cluster baryon fraction). As a result, this Cardassian
expansion proposal does not seem to survive the magnitude-redshift test for the
present type Ia supernovae data, unless the universe contains primarily
baryonic matter.


title:
Spectroscopic Observations of Twenty-one Faint Cataclysmic Variables
  Candidates

abstract:
  We provide the first minimum light spectroscopic observations for 21
previously known or suspected faint cataclysmic variable candidates. The
sources were selected from the Downes et al. (2001) living edition catalog and
the identified candidates have minimum light magnitudes of V~18-22. We confirm
15 of the candidates to be cataclysmic variables.


title: The formation and evolution of field massive galaxies

abstract:
  The problem of the formation and evolution of field massive galaxies is
briefly reviewed from an observational perspective. The motivations and the
characteristics of the K20 survey are outlined. The redshift distribution of
Ks<20 galaxies, the evolution of the rest-frame Ks-band luminosity function and
luminosity density to z=1.5, the nature and the role of the red galaxy
population are presented. Such results are compared with the predictions of
models of galaxy evolution.


title:
Probabilistic description of the first-order Fermi acceleration in shock
  waves: Time-dependent solution by single-particle approach

abstract:
  We give a new coherent description of the first-order Fermi acceleration of
particles in shock waves from the point of view of stochastic process of the
individual particles, under the test particle approximation. The time
development of the particle distribution function can be dealt with by this
description, especially for relativistic shocks. We formulate the acceleration
process of a particle as a two-dimensional Markov process in a logarithmic
momentum-time space, and relate the solution of the Markov process with the
particle distribution function at the shock front, for both steady and
time-dependent case. For the case where the probability density function of the
energy gain and cycle-time at each shock crossing of the particles obeys a
scaling law in momentum, which is usually assumed in the literature, it is
confirmed in more general form that the energy distribution of particles has
the power-law feature in steady state. The equation to determine the exact
power-law index which is applicable for any shock speed is derived and it is
shown that the power-law index, in general, depends on the shape of the
probability density function of the energy gain at each shock crossing; in
particular for relativistic shocks, the dispersion of the energy gain can
influence the power-law index. It is also shown that the time-dependent
solution has a self-similarity for the same case.


title:
The Conspicuous Absence of X-ray Emission from Carbon-Enriched
  Wolf-Rayet Stars

abstract:
  The carbon-rich WC5 star WR 114 was not detected during a 15.9 ksec
XMM-Newton observation, implying an upper limit to the X-ray luminosity of Lx <
2.5*10^{30} erg/s and to the X-ray to bolometric luminosity ratio of Lx/Lbol <
4*10^{-9}. This confirms indications from earlier less sensitive measurements
that there has been no convincing X-ray detection of any single WC star. This
lack of detections is reinforced by XMM-Newton and Chandra observations of WC
stars. Thus the conclusion has to be drawn that the stars with
radiatively-driven stellar winds of this particular class are insignificant
X-ray sources. We attribute this to photoelectronic absorption by the stellar
wind. The high opacity of the metal-rich and dense winds from WC stars puts the
radius of optical depth unity at hundreds or thousands of stellar radii for
much of the X-ray band. We believe that the essential absence of hot plasma so
far out in the wind exacerbated by the large distances and correspondingly high
ISM column densities makes the WC stars too faint to be detectable with current
technology. The result also applies to many WC stars in binary systems, of
which only about 20% are identified X-ray sources, presumably due to colliding
winds.


title:
On multicomponent effects in stellar winds of stars at extremely low
  metallicity

abstract:
  We calculate multicomponent line-driven wind models of stars at extremely low
metallicity suitable for massive first generation stars. For most of the models
we find that the multicomponent wind nature is not important for either wind
dynamics or for wind temperature stratification. However, for stars with the
lowest metallicities we find that multicomponent effects influence the wind
structure. These effects range from pure heating to possible fallback of the
nonabsorbing wind component. We present a simple formula for the calculation of
metallicity for which the multicomponent effects become important. We show that
the importance of the multicomponent nature of winds of low metallicity stars
is characterised not only by the low density of driving ions, but also by lower
mass-loss rate.


title:
Secular variability, geodetic precession and moment of inertia of binary
  pulsars

abstract:
  More and more binary pulsars show significant secular variations, in which
the measured projected semi-major axis, $\dot{x}^{obs}$, and the first
derivative of orbital period, $\dot{P}_{b}^{obs}$, are several order of
magnitude larger than the prediction of general relativity (GR). This paper
shows that the geodetic precession induced orbital effects can explain both
$\dot{x}$ and $\dot{P}_{b}$ measured in binary pulsars. Moreover, by this model
we can automatically estimate the magnitude of the spin angular momenta of the
pulsar and its companion star, and therefore the moment of inertia ($10^{44}$g
cm$^2$ to $10^{45}$g cm$^2$) of pulsar of binary pulsar systems, which agrees
well with theoretical predictions. In other words, the contamination (residual
represented by $\dot{x}$ and $\dot{P}_{b}$) in pulsar timing measurements might
be caused by geodetic precession, an interesting gravitational effect we have
been seeking for.


title: Ar I as a tracer of ionization evolution

abstract:
  We present a study of Ar abundances in 15 damped Ly alpha systems (DLAs) in
the redshift interval from 2.3 to 3.4. The sample includes 4 new UVES/VLT
measurements of Ar I column densities. The majority of DLAs show significant
underabundances of Ar relative to other alpha-capture elements with common
nucleosynthetic origin. We show that neither dust depletion nor intervening HII
regions inside DLAs offer a viable justification to these underabundances. A
natural explanation is found in the framework of photoionization models of HI
regions embedded in an ionizing continuum with varying spectral distribution.
At z ~ 2.5 the observed Ar deficiencies are large, [Ar/alpha] ~ -0.6/-0.8 dex,
suggestive of a hard, QSO-dominated spectrum. At z >~ 3 the deficiencies are
instead small, suggestive of a soft, stellar-type spectrum, though more data
are needed to generalize this high-z result. We argue that the change of Ar
abundances is induced by the evolution of the UV metagalactic continuum, in
which case the UV emission internal to DLAs must be small (i.e. DLAs should
have modest star formation rates) and the external background must become
softer at z > 3. The former requirement is consistent with the modest evolution
of DLAs abundances and the lack of Ly_alpha and H_alpha emissions associated
with DLAs. The latter requirement is consistent with the observed evolution of
SiIV/CIV ratios in the IGM, the claims of high escape fraction of UV photons
from Ly-break galaxies at z >~ 3, and the recent finding that the HeII
re-ionization seems to occur between z ~ 3.4 and z ~ 3. From the comparison
with local interstellar studies, we predict a rise of Ar abundances in the
redshift range from z ~ 2.3 to z=0, at the epoch at which the metagalactic
field of galaxies overcomes that of quasars.


title: Identification of the ionizing source of NGC 2024

abstract:
  We propose the late-O, early-B star IRS2b as the ionizing source of the Flame
Nebula (NGC 2024). It has been clear that such a hot, massive star must be
present in this heavily obscured region, and now it has been identified. New
near-infrared photometry shows that IRS2b is the most luminous and hottest star
in the young star cluster embedded in the center of NGC 2024. The near-infrared
observations (5' x 5') cover ~90 % of the HII region detected in radio
continuum radiation, making the probability very low that the ionizing star is
not present in the field. A K-band spectrum of IRS2b obtained with ISAAC on the
Very Large Telescope indicates that the spectral type of IRS2b is in the range
O8V - B2V. Additional arguments indicate that its spectral type is likely
closer to O8 than to B2. The corresponding amount of ionizing radiation is
consistent with published radio continuum and recombination line observations.


title:
Modeling of multicomponent radiatively driven stellar winds using a
  Newton-Raphson method

abstract:
  We present a simple method for the solution of one-component and
multicomponent hydrodynamic equations based on the Newton-Raphson method. We
show that this method can be used for the solution of stationary hydrodynamic
equations. This method has been used for the calculation of the low density
stellar wind models for which the multicomponent nature of the wind influences
the overall wind structure.


title: Full Sky Study of Diffuse Galactic Emission at Decimeter Wavelengths

abstract:
  A detailed knowledge of the Galactic radio continuum is of high interest for
studies of the dynamics and structure of the Galaxy as well as for the problem
of foreground removal in Cosmic Microwave Background measurements. In this work
we present a full-sky study of the diffuse Galactic emission at frequencies of
few GHz, where synchrotron radiation is by far the dominant component. We
perform a detailed combined analysis of the extended surveys at 408, 1420 and
2326 MHz (by Haslam et al. 1982, Reich 1982, Reich & Reich, 1986 and Jonas et
al. 1998, respectively). Using the technique applied by Schlegel et al. (1998)
to the IRAS data, we produce destriped versions of the three maps. This allows
us to construct a nearly-full-sky map of the spectral index and of the
normalization factor with sub-degree angular resolution. The resulting
distribution of the spectral indices has an average of beta = 2.695 and
dispersion sigma_{beta} = 0.120. This is representative for the Galactic
diffuse synchrotron emission, with only minor effects from free-free emission
and point sources.


title: Selection criteria for targets of asteroseismic campaigns

abstract:
  Various dedicated satellite projects are underway or in advanced stages of
planning to perform high-precision, long duration time series photometry of
stars, with the purpose of using the frequencies of stellar oscillations to put
new constraints on the internal structure of stars. It is known (cf. Brown, et
al. 1994) that the effectiveness of oscillation frequencies in constraining
stellar model parameters is significantly higher if classical parameters such
as effective temperature, and luminosity are known with high precision. In
order to optimize asteroseismic campaigns it is therefore useful to select
targets from among candidates for which good spectroscopic and astrometric data
already exists. This paper presents selection criteria, as well as
redeterminations of stellar luminosity and reddening for stars satisfying these
criteria.


title:
An XMM-Newton-based X-ray survey of pre-main sequence stellar emission
  in the L1551 star-forming complex

abstract:
  We present a study of the X-ray sources present in the nearby L1551 star
forming region, based on a deep XMM observation complemented with Chandra data
for the brightest sources. All the known pre-main sequence stars in the region
have been detected, most of them with sufficient statistics to allow a detailed
study of the temporal and spectral characteristics of their X-ray emission.
Significant temporal (and spectral) variability on both short and long time
scales is visible for most of the stars. In particular XZ Tau shows
large-amplitude variations on time scales of several hours with large changes
in the intervening absorption, suggestive of the X-ray emission being eclipsed
by the accretion stream (and thus of the X-ray emission being partly or totally
accretion-induced). The coronal metal abundance of the WTTS sources is
clustered around Z = 0.2, while the CTTS sources span almost two orders of
magnitudes in coronal Z, even though the photospheric abundance of all stars in
the L1551 is likely to be very similar. Some individual elements (notably Ne)
appear to be systematically enhanced with respect to Fe in the WTTS stars. The
significant differences between the spectral and temporal characteristics of
the CTTS and WTTS populations suggest that a different emission mechanism is
(at least partly) responsible for the X-ray emission of the two types of stars.


title: A Consistent One-Dimensional Model for the Turbulent Tachocline

abstract:
  The first consistent model for the turbulent tachocline is presented, with
the turbulent diffusivity computed within the model instead of being specified
arbitrarily. For the origin of the 3D turbulence a new mechanism is proposed.
Owing to the strongly stable stratification, the mean radial shear is stable,
while the horizontal shear is expected to drive predominantly horizontal,
quasi-2D motions in thin slabs. Here I suggest that a major source of 3D
overturning turbulent motions in the tachocline is the secondary shear
instability due to the strong, random vertical shear arising between the
uncorrelated horizontal flows in neighbouring slabs. A formula for the vertical
diffusivity due to this turbulence, equation (9), is derived and applied in a
simplified 1D model of the tachocline. It is found that Maxwell stresses due to
an oscillatory poloidal magnetic field of a few hundred gauss are able to
confine the tachocline to a thickness below 5 Mm. The integral scale of the 3D
overturning turbulence is the buoyancy scale, on the order of 10 km and its
velocity amplitude is a few m/s, yielding a vertical turbulent diffusivity on
the order of 10^8 cm^2/s.


title:
Population II standard candle calibration of the Fundamental Plane of
  groups and clusters of galaxies and the Hubble Constant

abstract: This paper has been withdrawn by the author.


title:
Measurements of Attenuation and Absorption Lengths with the KASCADE
  Experiment

abstract:
  The attenuation of the electron shower size beyond the shower maximum is
studied with the KASCADE extensive air shower experiment in the primary energy
range of about $10^{14}-10^{16}$ eV. Attenuation and absorption lengths are
determined by applying different approaches, including the method of constant
intensity, the decrease of the flux of extensive air showers with increasing
zenith angle, and its variation with ground pressure. We observe a significant
dependence of the results on the applied method. The determined values of the
attenuation length ranges from 175 to 196 g/cm$^2$ and of the absorption length
from 100 to 120 g/cm$^2$. The origin of these differences is discussed
emphasizing the influence of intrinsic shower fluctuations.


title: Luminous quasars and their hosts: Accretion at the limit?

abstract:
  We present the results of our recent Hubble Space Telescope imaging study, in
which we have successfully deconvolved host and nuclear flux for the some of
the most luminous quasars in the Universe. Host morphologies have been
recovered for each of our 17-strong sample. From these fits, we have estimated
Black Hole masses through extrapolation of the Black Hole - Spheroid mass
relation and begun to address the complicated issue of fuelling vs black hole
mass in determining quasar luminosity: We find that the order-of-magnitude
increase in luminosity is due to increased black hole size, and to increased
fuelling efficiency, in roughly equal measure. The brightest objects are found
to radiate at or near the Eddington limit.


title:
Secrets of Magnetohydrodynamic Hell: The Solar Circulation Paradox and
  the Geodynamo

abstract:
  Differential rotation is widely supposed to be essential for the dynamo
effects that sustain solar and planetary magnetic fields, but dynamo effects
tend to oppose the flows that drive them, and it is uncertain what drives
differential rotation. The relative sign of the differential rotation and
meridional circulation is not consistent with simple convection modified by
Coriolis forces. We investigate dynamo mechanisms consistent with the observed
solar circulation, and discuss how reactive JxB forces would affect such flows.
We formulate scaling rules that relate the magnetic field strength to mean
rotation and convective heat transport.


title: White Dwarf Asteroseismology and the ^12C(alpha,gamma)^16O Rate

abstract:
  Due to a new global analysis method, it is now possible to measure the
internal composition of pulsating white dwarf stars, even with relatively
simple theoretical models. The precise internal mixture of carbon and oxygen is
the largest single source of uncertainty in ages derived from white dwarf
cosmochronometry, and contains information about the rate of the
astrophysically important, but experimentally uncertain, ^12C(alpha,gamma)^16O
nuclear reaction. Recent determinations of the internal composition and
structure of two helium-atmosphere variable (DBV) white dwarf stars, GD 358 and
CBS 114, initially led to conflicting implied rates for the
^12C(alpha,gamma)^16O reaction. If both stars were formed through single-star
evolution, then the initial analyses of their pulsation frequencies must have
differed in some systematic way. I present improved fits to the two sets of
pulsation data, resolving the tension between the initial results and leading
to a value for the ^12C(alpha,gamma)^16O reaction rate that is consistent with
recent laboratory measurements.


title: AGN Feedback Mechanisms

abstract:
  Accreting black holes can release enormous amounts of energy to their
surroundings, in various forms. Such feedback may profoundly influence a black
hole's environment. After briefly reviewing the possible types of feedback, I
focus on the injection of kinetic energy through jets and powerful winds. The
effects of these outflows may be especially apparent in the heating of the
X-ray--emitting atmospheres that pervade clusters of galaxies. Analogous
heating effects, during the epoch of galaxy formation, could regulate the
growth of supermassive black holes.


title: Quintessence without scalar fields

abstract:
  The issues of quintessence and cosmic acceleration can be discussed in the
framework of theories which do not include necessarily scalar fields. It is
possible to define pressure and energy density for new components considering
effective theories derived from fundamental physics like the extended theories
of gravity or simply generalizing the state equation of matter. Exact
accelerated expanding solutions can be achieved in several schemes: either in
models containing higher order curvature and torsion terms or in models where
the state equation of matter is corrected by a second order Van der Waals
terms. In this review, we present such new approaches and compare them with
observations.


title: Some Global Characteristics of the Galactic Globular Cluster System

abstract:
  The relations between the luminosities $M_{V}$, the metallicities $[Fe/H]$,
the Galactocentric radii $R$, and the central concentration indices $c$ of
Galactic globular clusters are discussed. It is found that the most luminous
clusters rarely have collapsed cores. The reason for this might be that the
core collapse time scales for such populous clusters are greater than the age
of the Galaxy. Among those clusters, for which the structure has not been
modified by core collapse, there is a correlation between central concentration
and integrated luminosity, in the sense that the most luminous clusters have
the strongest central concentration. The outermost region of the Galaxy with
$R>10$ kpc was apparently not able to form metal-rich $([Fe/H]>-1.0)$ globular
clusters, whereas such clusters (of which Ter 7 is the prototype) were able to
form in some nearby dwarf spheroidal galaxies. It is not yet clear how the
popular hypothesis that globular clusters were initially formed with a single
power law mass spectrum can be reconciled with the observation that both (1)
Galactic globular clusters with $R>80$ kpc, and (2) the globulars associated
with the Sagittarius dwarf, appear to have bi-modal luminosity functions.


title:
Lack of observational evidence for quantum structure of space-time at
  Plank scales

abstract:
  It has been noted (Lieu & Hillmann, 2002) that the cumulative affect of
Planck-scale phenomenology, or the structure of space-time at extremely small
scales, can be lead to the loss of phase of radiation emitted at large
distances from the observer. We elaborate on such an approach and demonstrate
that such an effect would lead to an apparent blurring of distant
point-sources. Evidence of the diffraction pattern from the HST observations of
SN 1994D and the unresolved appearance of a Hubble Deep Field galaxy at z=5.34
lead us to put stringent limits on the effects of Planck-scale phenomenology.


title:
Submillimeter Wave Astronomy Satellite mapping observations of water
  vapor around Sagittarius B2

abstract:
  Observations of the 1(10)-1(01) 556.936 GHz transition of ortho-water with
the Submillimeter Wave Astronomy Satellite (SWAS) have revealed the presence of
widespread emission and absorption by water vapor around the strong
submillimeter continuum source Sagittarius B2. An incompletely-sampled spectral
line map of a region of size 26 x 19 arcmin around Sgr B2 reveals three
noteworthy features. First, absorption by foreground water vapor is detectable
at local standard-of-rest (LSR) velocities in the range -100 to 0 km/s at
almost every observed position. Second, spatially-extended emission by water is
detectable at LSR velocities in the range 80 to 120 km/s at almost every
observed position. This emission is attributable to the 180-pc molecular ring
identified from previous observations of CO. The typical peak antenna
temperature of 0.075 K for this component implies a typical water abundance of
1.2E-6 to 8E-6 relative to H2. Third, strong absorption by water is observed
within 5 arcmin of Sgr B2 at LSR velocities in the range 60 to 82 km/s. An
analysis of this absorption yields a H2O abundance ~ 2E-7 to 4E-7 relative to
H2 if the absorbing water vapor is located within the core of Sgr B2 itself;
or, alternatively, a water column density ~ 2.5E+16 to 4E+16 per cm2 if the
water absorption originates in the warm, foreground layer of gas proposed
previously as the origin of ammonia absorption observed toward Sgr B2.


title: High-redshift radio galaxies: at the crossroads

abstract:
  The next generation of surveys of extragalactic radio sources will be
dominated by different types of objects than the jetted-AGN that dominate
surveys like 3C, 6C and 7C. Before radio astronomy becomes concentrated on the
new types of object, it is vital that we understand the cosmological importance
of the jetted-AGN that have been studied for many years. I argue that, as
observational manifestations of Eddington-tuned outflow events, these objects
may have more significance for galaxy/cluster formation and evolution than is
typically appreciated. Outstanding problems in galaxy formation may be solved
by cosmological simulations in which this type of outflow, as well as other
types associated with weaker jets, are properly taken into account. I will
highlight areas of ignorance which are currently hindering attempts to do this.


title: Nonlinear Properties of the Semiregular Variable Stars

abstract:
  We demonstrate how, with a purely empirical analysis of the irregular
lightcurve data, one can extract a great deal of information about the stellar
pulsation mechanism. An application to R Sct thus shows that the irregular
lightcurve is the result of the nonlinear interaction of two highly
nonadiabatic pulsation modes, namely a linearly unstable, low frequency mode,
and the second mode that, although linearly stable, gets entrained through a
2:1 resonance. In the parlance of nonlinear dynamics the pulsation is the
result of a 4 dimensional chaotic dynamics.


title: Speed of Light in Gravitational Fields

abstract:
  A spherically symmetric and static metric that describes physical coordinates
is introduced. It is defined to be a metric that gives coordinate independent
results for physically observable quantities without a further coordinate
transformation. The suggested metric also makes a prediction for the second
order gravitational red shift effect that can be utilized for a precision
experimental test in the future. A possible new experimental test would be
provided by a modern Michelson Morley experiment on the earth with the two arms
in vertical and horizontal directions to see the validity of isotropy or
anisotropy for the speed of light. The possibility of using pulsars and GPS
(Global Positioning System) for a general relativity test is discussed.


title: A Preposterous Universe

abstract:
  Recent announcements that the Cosmic Microwave Background (CMB) - the faint
remnant of the Big Bang - is polarized have caused a stir among cosmologists.
Such polarization has long been predicted but could not be detected, until the
recent DASI and WMAP detections. The polarization is a signature of the motion
of the primordial seeds that led to the galaxies and large-scale structure of
the Universe observed today. Earlier measurements of tiny temperature
fluctuations in the CMB have been used to infer the sizes of the primordial
seeds. The polarization signature should help to determine the fundamental
parameters of cosmology and to explain how large-scale structure arose
[Highwire abstract].

categories: astro-ph gr-qc hep-ph hep-th physics.pop-ph


title: Spiderweb Masks for High-Contrast Imaging

abstract:
  Motivated by the desire to image exosolar planets, recent work by us and
others has shown that high-contrast imaging can be achieved using specially
shaped pupil masks. To date, the masks we have designed have been symmetric
with respect to a cartesian coordinate system but were not rotationally
invariant, thus requiring that one take multiple images at different angles of
rotation about the central point in order to obtain high-contrast in all
directions. In this paper, we present a new class of masks that have rotational
symmetry and provide high-contrast in all directions with just one image. These
masks provide the required 10^{-10} level of contrast to within 4 lambda/D, and
in some cases 3 lambda/D, of the central point, which is deemed necessary for
exosolar planet finding/imaging. They are also well-suited for use on
ground-based telescopes, and perhaps NGST too, since they can accommodate
central obstructions and associated support spiders.


title: Transfer of energy and angular momentum in magnetic coupling process

abstract:
  The transfer of energy and angular momentum in the magnetic coupling (MC) of
a rotating black hole (BH) with its surrounding accretion disc is discussed
based on a mapping relation derived by considering the conservation of magnetic
flux with two basic assumptions: (i)the magnetic field on the horizon is
constant, (ii) the magnetic field on the disc surface varies as a power law
with the radial coordinate of the disc. The following results are obtained: (i)
the transfer direction of energy and angular momentum between the BH and the
disc depends on the position of a co-rotation radius relative to the MC region
on the disc, which is eventually determined by the BH spin; (ii) the evolution
characteristics of a rotating BH in the MC process without disc accretion are
depicted in a parameter space, and a series of values of the BH spin are given
to indicate the evolution characteristics; (iii) the efficiency of converting
accreted mass into radiation energy of a BH-disc system is discussed by
considering coexistence of disc accretion and the MC process; (iv) the MC
effects on disc radiation and emissivity index are discussed and it is
concluded that they are consistent with the recent XMM-Newton observation of
the nearby bright Seyfert 1 galaxy MCG-6-30-15 with reference to a variety of
parameters of the BH-disc system.


title: Slow Temperature Equilibration Behind the Shock Front of SN 1006

abstract:
  We report on the observation of OVII Doppler line broadening in a compact
knot at the edge of SN 1006 detected with the Reflective Grating Spectrometer
on board XMM-Newton. The observed line width of sigma = 3.4+/-0.5 eV at a line
energy of 574 eV indicates an oxygen temperature of kT = 528+/-150 keV.
Combined with the observed electron temperature of 1.5 keV the observed
broadening is direct evidence for temperature non-equilibration in high Mach
number shocks, and slow subsequent equilibration. The OVII line emission allows
an accurate determination of the ionization state of the plasma, which is
characterized by a relatively high forbidden line contribution, indicating
log(n_e t) ~ 9.2.


title: The Kinematics in the Core of the Low Surface Brightness Galaxy DDO 39

abstract:
  We present a high resolution, SparsePak two-dimensional velocity field for
the center of the low surface brightness (LSB) galaxy DDO 39. These data are a
significant improvement on previous HI or Halpha long slit data, yet the inner
rotation curve is still uncertain due to significant noncircular and random
motions. These intrinsic uncertainties, probably present in other LSB galaxies
too, result in a wide range of inner slopes being consistent with the data,
including those expected in cold dark matter (CDM) simulations. The halo
concentration parameter provides a more useful test of cosmological models than
the inner slope as it is more tightly constrained by observations. DDO 39's
concentration parameter is consistent with, but on the low end of the
distribution predicted by CDM.


title: Spatial and Dynamical Biases in Velocity Statistics of Galaxies

abstract:
  We present velocity statistics of galaxies and their biases inferred from the
statistics of the underlying dark matter using a cosmological hydrodynamic
simulation of galaxy formation in low-density and spatially flat cold dark
matter cosmogony. We find that the pairwise velocity dispersion (PVD) of all
galaxies is significantly lower than that of the dark matter particles, and
that the PVD of the young galaxies is lower than that of the old types, and
even of all galaxies together, especially at small separations. These results
are in reasonable agreement with the recent measurements of PVDs in the Las
Campanas redshift survey, the PSCz catalogue and the SDSS data. We also find
that the low PVD of young galaxies is due to the effects of dynamical friction
as well as the different spatial distribution. We also consider the mean infall
velocity and the POTENT density reconstruction that are often used to measure
the cosmological parameters, and investigate the effects of spatial bias and
dynamical friction. In our simulation, the mean infall velocity of young
galaxies is significantly lower than that of all the galaxies or of the old
galaxies, and the dynamical bias becomes important on scales less than 3Mpc/h.
The mass density field reconstructed from the velocity field of young galaxies
using the POTENT-style method suffers in accuracy both from the spatial bias
and the dynamical friction on the smoothing scale of R_s=8Mpc/h. On the other
hand, in the case of R_s=12Mpc/h, which is typically adopted in the actual
POTENT analysis, the density reconstruction based on various tracers of
galaxies is reasonably accurate.


title:
XMM-Newton and Chandra Observations of the Galaxy Group NGC 5044. II.
  Metal Abundances and Supernova Fraction

abstract:
  Using new XMM and Chandra observations we present an analysis of the metal
abundances of the hot gas within a radius of 100 kpc of the bright nearby
galaxy group NGC 5044. Motivated by the inconsistent abundance and temperature
determinations obtained by different observers for X-ray groups, we provide a
detailed investigation of the systematic errors on the derived abundances
considering the effects of the temperature distribution, calibration, plasma
codes, bandwidth, Galactic Nh, and background rate. The iron abundance (Fe)
drops from Fe ~1 solar within R ~50 kpc to Fe ~0.4 solar near R=100 kpc. This
radial decline in Fe is highly significant: Fe=1.09 +/- 0.04 solar (stat) +/-
0.05 solar + 0.18 solar (sys) within R=48 kpc (5') compared to Fe=0.44 +/- 0.02
solar (stat) +/- 0.10 solar + 0.13 solar (sys) over R=48-96 kpc (5'-10'). The
data rule out with high confidence a very sub-solar value for Fe within R=48
kpc confirming that previous claims of very sub-solar central Fe values in NGC
5044 were primarily the result of the Fe Bias: i.e., the incorrect assumption
of spatially isothermal and single-phase gas when in fact temperature
variations exist. Within R=48 kpc we obtain Si/Fe = 0.83 +/- 0.02 (stat) +/-
0.02 + 0.07 (sys) and S/Fe = 0.54 +/- 0.02 (stat) +/- 0.01 + 0.01 (sys) in
solar units. These ratios are consistent with their values at larger radii and
imply that SNIa have contributed ~80% of the iron mass within a 100 kpc radius
of NGC 5044. This SNIa fraction is similar to the Sun and suggests an IMF
similar to that of the Milky Way. At the very center (R ~2 kpc) the XMM and
Chandra CCDs and the XMM RGS show that the Fe drops to ~50% of its value at
immediately larger radius analogously to that seen in some galaxy clusters.
(Abridged)


title:
Multi-order TODCOR: application to observations taken with the CORALIE
  echelle spectrograph

abstract:
  This paper presents an application of the TwO-Dimensional CORrelation
(TODCOR) algorithm to multi-order spectra. The combination of many orders
enables the detection and measurement of the radial velocities of very faint
companions. The technique is first applied here to the case of HD41004, where
the secondary is 3.68 magnitudes fainter than the primary in the V band. When
applied to CORALIE spectra of this system, the technique measures the secondary
velocities with a precision of 0.6 km/s and facilitates an orbital solution of
the HD41004B subsystem. The orbit of HD41004B is nearly circular, with a
companion of a 19 Jupiter masses (minimum mass). The precision achieved for the
primary is 10 m/s, allowing the measurement of a long-term trend in the
velocities of HD41004A.


title: Physical Structure of Planetary Nebulae. I. The Owl Nebula

abstract:
  The Owl Nebula is a triple-shell planetary nebula with the outermost shell
being a faint bow-shaped halo. We have obtained deep narrow-band images and
high-dispersion echelle spectra in the H-alpha, [O III], and [N II] emission
lines to determine the physical structure of each shell in the nebula. These
spatio-kinematic data allow us to rule out hydrodynamic models that can
reproduce only the nebular morphology. Our analysis shows that the inner shell
of the main nebula is slightly elongated with a bipolar cavity along its major
axis, the outer nebula is a filled envelope co-expanding with the inner shell
at 40 km/s, and the halo has been braked by the interstellar medium as the Owl
Nebula moves through it. To explain the morphology and kinematics of the Owl
Nebula, we suggest the following scenario for its formation and evolution. The
early mass loss at the TP-AGB phase forms the halo, and the superwind at the
end of the AGB phase forms the main nebula. The subsequent fast stellar wind
compressed the superwind to form the inner shell and excavated an elongated
cavity at the center, but has ceased in the past. At the current old age, the
inner shell is backfilling the central cavity.


title: Mg isotopic ratios in giant stars of the globular cluster NGC 6752

abstract:
  Mg isotopic abundance ratios are measured in 20 bright red giants in globular
cluster NGC 6752 based on very high-resolution, high signal-to-noise spectra
obtained with UVES on the VLT. There is a considerable spread in the ratio
24Mg:25Mg:26Mg with values ranging from 53:9:39 to 83:10:7. We measured the
abundances of O, Na, Mg, Al, and Fe combining our sample with 21 RGB bump stars
(Grundahl et al. 2002). The abundances of the samples are consistent and
exhibit the usual anticorrelations between O-Na and Mg-Al. A positive
correlation is found between 26Mg and Al, a mild anticorrelation is found
between 24Mg and Al, while no correlation is found between 25Mg and Al. None of
the elemental or isotopic abundances show a dependence on evolutionary status
and, as shown by Gratton et al. (2001), the abundance variations exist even in
main sequence stars. This strongly suggests that the star-to-star abundance
variations are a result of varying degrees of pollution with intermediate mass
AGB stars being likely polluters. Even for the least polluted stars, the
abundances of 25Mg and 26Mg relative to 24Mg are considerably higher than
predicted for ejecta from Z=0 supernovae. Zero metallicity AGB stars may be
responsible for these higher abundances. Our measured Mg isotopic ratios reveal
another layer to the globular cluster star-to-star abundance variations that
demands extensions of our present theoretical knowledge of stellar
nucleosynthesis by giant stars.


title: The Formation and Evolution of Self-Interacting Dark Matter Halos

abstract:
  We study the formation and evolution of self-interacting dark matter (SIDM)
halos. We find analytical, fully cosmological similarity solutions for their
dynamics, which take proper account of the collisional interaction of SIDM
particles, based on a fluid approximation derived from the Boltzmann equation.
These similarity solutions are relevant to galactic and cluster halo formation
in the cold dark matter (CDM) model. Different solutions arise for different
values of the dimensionless collisionality parameter, Q=sigma*rho_b*r_s, where
sigma is the SIDM particle scattering cross section per unit mass, rho_b is the
cosmic mean density, and r_s is the shock radius. For all solutions, a
flat-density, isothermal core is present which grows in size as a fixed
fraction of r_s, pumped by cosmological infall. Accordingly, core collapse must
in general be delayed until infall becomes negligible, contrary to previous
analyses based on isolated halos, which predict core collapse in a Hubble time.
Our solutions agree with N-body simulations, which match observed galactic
rotation curves if sigma=[0.56 - 5.6]cm^2/g, implying Q=[6.2e-7 - 3.6e-5].
Similar profiles also arise for Q=[1.37e-2 - 1.7e-1], or sigma=[1.2e4 -
2.7e4]cm^2/g, a regime not previously simulated.


title: The Central Engines of Low-Luminosity AGNs

abstract:
  I summarize the main characteristics of AGNs in nearby galaxies and present a
physical picture of their central engines.


title: Detection of the "Active" Nucleus of M32

abstract:
  M32 hosts a 2.5x10^6 solar mass central black hole, but signs of nuclear
activity in this galaxy have long eluded detection. We report the first
conclusive detection of the nucleus of M32 in X-rays, based on high-resolution,
sensitive observations made with Chandra. The 2-10 keV luminosity is merely
9.4x10^35 erg/s, 3x10^-9 of the Eddington luminosity of the black hole. Weak
diffuse emission, consistent with thermal gas at a temperature of 0.37 keV, is
seen in an annular region ~100 pc from the center. We also present a deep,
moderately high-resolution (0.9"), radio continuum observation obtained with
the Very Large Array, which places a tight upper bound on the nuclear radio
power at 8.4 GHz. We combine these new measurements with upper limits at other
wavelengths to discuss implications for the nature of accretion onto the
central black hole.


title:
A Stringent Limit on the Accretion Luminosity of the Possible Central
  Black Hole in the Globular Cluster M15

abstract:
  The globular cluster M15 has recently been found to host a possible central
black hole with a mass of ~2000 solar masses. A deep, high-resolution Chandra
image failed to detect the "nucleus" of the cluster in X-rays. The upper limit
on the X-ray luminosity (L_x < 5.6x10^32 erg/s) corresponds to a bolometric
Eddington ratio of L_bol/L_Edd < (2-4)x10^-8. Combining this limit with an
estimate of the electron density of the intracluster ionized plasma derived
from pulsar dispersion measures, we show that the radiative efficiency of the
accretion flow, if it accretes at the Bondi rate, must be much lower than that
of a standard optically thick, geometrically thin disk.


title: A 3x10^9 solar mass black hole in the quasar SDSS J1148+5251 at z=6.41

abstract:
  We present near-infrared H and K-band spectra of the z=6.41 quasar SDSS
J114816.64+525150.3. The spectrum reveals a broad MgII 2799 emission line with
a full-width half-maximium of 6000 km/s. From the peak wavelength of this
emission line we obtain a more accurate redshift than is possible from the
published optical spectrum and determine a redshift of z=6.41+/-0.01. If the
true peak of the Lyman alpha emission is at the same redshift, then a large
fraction of the flux blueward of the peak is absorbed. The equivalent width of
the MgII emission line is similar to that of lower redshift quasars, suggesting
that the UV continuum is not dominated by a beamed component. Making basic
assumptions about the line-emitting gas we derive an estimate for the central
black hole in this quasar of 3x10^9 solar masses. The very high luminosity of
the quasar shows that it is accreting at the maximal allowable rate for a black
hole of this mass adopting the Eddington limit criterion.


title: Extended Emission from Cygnus X-3 Detected with Chandra

abstract:
  We have discovered extended X-ray emission from the microquasar Cyg X-3 in
archival Chandra X-ray Observatory observations. A 5" wide structure lies
approximately 16" to the NE from the core point source and may be extended in
that direction. This angular scale corresponds to a physical extent of roughly
0.8 lyr, at a distance of 2.5 lyr from Cyg X-3 (assuming a 10 kpc distance).
The flux varied by a factor of 2.5 during the four months separating two of the
observations, indicating significant substructure. The peak 2-10 keV luminosity
was about 5e34 ergs/s. There may also be weaker, extended emission of similar
scale oppositely directed from the core, suggesting a bipolar outflow. This
structure is not part of the dust scattering halo, nor is it caused by the
Chandra point spread function. In this Letter we describe the observations and
discuss possible origins of the extension.


title: The Mid-Infrared Emitting Dust Around AB Aur

abstract:
  Using the Keck I telescope, we have obtained 11.7 micron and 18.7 micron
images of the circumstellar dust emission from AB Aur, a Herbig Ae star. We
find that AB Aur is probably resolved at 18.7 micron with an angular diameter
of 1.2" at a surface brightness of 3.5 Jy/arcsec^2. Most of the dust mass
detected at millimeter wavelengths does not contribute to the 18.7 micron
emission, which is plausibly explained if the system possesses a relatively
cold, massive disk. We find that models with an optically thick, geometrically
thin disk, surrounded by an optically thin spherical envelope fit the data
somewhat better than flared disk models.


title:
The Relationship Between Stellar Light Distributions of Galaxies and
  their Formation Histories

abstract:
  A major problem in extragalactic astronomy is the inability to distinguish in
a robust, physical, and model independent way how galaxy populations are
related to each other and to their formation histories. A similar, but
distinct, and also long standing question is whether the structural appearances
of galaxies, as seen through their stellar light distributions, contain enough
physical information to offer this classification. We argue through the use of
240 images of nearby galaxies that three model independent parameters measured
on a single galaxy image reveal its major ongoing and past formation modes, and
can be used as a robust classification system. These parameters quantitatively
measure: the concentration (C), asymmetry (A) and clumpiness (S) of a galaxy's
stellar light distribution. When combined into a three dimensional `CAS' volume
all major classes of galaxies in various phases of evolution are cleanly
distinguished. We argue that these three parameters correlate with important
modes of galaxy evolution: star formation and major merging activity. This is
argued through the strong correlation of Halpha equivalent width and broad band
colors with the clumpiness parameter, the uniquely large asymmetries of 66
galaxies undergoing mergers, and the correlation of bulge to total light
ratios, and stellar masses, with the concentration index. As an obvious goal is
to use this system at high redshifts to trace evolution, we demonstrate that
these parameters can be measured, within a reasonable and quantifiable
uncertainty, with available data out to z ~ 3 using the Hubble Space Telescope
GOODS ACS and Hubble Deep Field images.


title: The galaxy population of the z=1 cluster of galaxies MG2016+112

abstract:
  A photometric redshift analysis of galaxies in the field of the
wide-separation gravitational lens MG2016+112 reveals a population of 69
galaxies with photometric redshifts consistent with being in a cluster at the
redshift of the giant elliptical lensing galaxy, z=1.00. The Ks-band luminosity
function of the cluster galaxies is well represented by the Schechter function
with a characteristic magnitude Ks*=18.90 (-0.57/+0.45) and faint-end slope
alpha=-0.60 (-0.33/+0.39), consistent with what is expected for a passively
evolving population of galaxies formed at high redshift, zf>2. From the total
Ks-band flux of the cluster galaxies and a dynamical estimate of the total mass
of the cluster, the restframe Ks-band mass-to-light ratio of the cluster is
derived to be M/L=27(-17/+64)(h_50)(M/L)_{sun}, in agreement with the upper
limit derived earlier from Chandra X-ray observations and the value derived
locally in the Coma cluster. The cluster galaxies span a red sequence with a
considerable scatter in the colour-magnitude diagrams, suggesting that they
contain young stellar populations in addition to the old populations of
main-sequence stars that dominate the Ks-band luminosity function. This is in
agreement with spectroscopic observations which show that 5 out of the 6
galaxies in the field confirmed to be at the redshift of the lensing galaxy
have emission lines. The projected spatial distribution of the cluster galaxies
is filamentary-like rather than centrally concentrated around the lensing
galaxy, and show no apparent luminosity segregation. A handful of the cluster
galaxies show evidence of merging/interaction. The results presented in this
paper suggest that a young cluster of galaxies is assembling around MG2016+112.


title: The VSNG Project: variable stars in nearby galaxies

abstract:
  We describe the VSNG Project, a collaboration between researchers of Bologna,
Padova, Napoli and Merate Observatories, to study variable stars in a number of
galaxies in the Local Group. We briefly review results obtained for the
galaxies analyzed so far.


title: High Energy Neutrino Astronomy: The Experimental Road

abstract:
  The next ten years promise to be a particularly exciting decade for high
energy neutrino astrophysics. The frontier of TeV and PeV energy is presently
being tackled by large, expandable arrays constructed in open water or ice.
Detectors tailored to record acoustic, radio, fluorescence or air shower
signatures from neutrino interactions at PeV-EeV energy are being designed in
parallel. During the next decade, the sensitivity to neutrinos from TeV to EeV
energies may improve by 2 to 3 orders of magnitude. This talk reviews methods,
status and prospects of detectors and sketches a scenario for the experimental
progress.


title:
The Physics of Supernova Remnant Blast Waves. II. Electron-Ion
  Equilibration in DEM L71 in the Large Magellanic Cloud

abstract:
  We present analysis and modeling of X-ray spectra from the blast wave shock
of DEM L71. We have used both Chandra ACIS-S data and optical Fabry-Perot
spectra of the blast wave to measure the electron and proton temperatures,
respectively. In principle, when combined, these measurements can determine the
degree of electron-ion temperature equilibration (g_0 = T_e/T_p) immediately
behind the shock front. In our X-ray analysis we fit Chandra spectra of three
nested regions behind the blast wave under three different scenarios: (1) a
planar, initially unequilibrated shock (g_0 = m_e/m_p), where the downstream
electron and proton temperatures equilibrate through Coulomb collisions, (2) a
planar, immediately equilibrated shock (g_0 = 1) and (3) a spherical,
equilibrated shock under Sedov evolution. Using independent measurements of T_e
and T_p we find that the X-ray spectra from the fastest blast wave locations
(V_s~700-1000 km/s) are consistent with little or no equilibration at the shock
front and are inconsistent with full equilibration. In contrast, spectra from
regions showing slower blast wave speeds (V_s~400-600 km/s) allow full
equilibration but exclude zero equilibration. In order to directly constrain
the initial equilibration, we incorporated our knowledge of the proton
temperatures into our X-ray models to build planar shock models that allowed
for a variable g_0. This model confirmed and strengthened the above results.
Specifically, we found that X-ray spectra from an intermediate velocity shock
(V_s~800 km/s) were consistent with intermediate equilibration, excluding both
g_0 = m_e/m_p and g_0 = 1 at greater than 1 sigma. Overall, our results support
the picture of decreasing electron-ion equilibration with increasing shock
speed.


title: Preparation of enriched cosmic ray mass groups with KASCADE

abstract:
  The KASCADE experiment measures a high number of EAS observables with a large
degree of sampling of the electron-photon, muon, and hadron components. It
provides accurate data for an event-by-event analysis of the primary cosmic ray
flux in the energy range around the knee. The possibility of selecting samples
of enriched proton and iron induced extensive air showers by applying the
statistical techniques of multivariate analyses is scrutinized using detailed
Monte Carlo simulations of three different primaries. The purity and efficiency
of the proton and iron classified events is investigated. After obtaining
enriched samples from the measured data by application of the procedures the
reconstructed number of hadrons, hadronic energy and other parameters are
investigated in the primary energy range 1-10 PeV. By comparing these shower
parameters for purified proton and iron events, respectively, with simulated
distributions an attempt is made to check the validity of strong interaction
models at high energies.


title: Density Estimators in Particle Hydrodynamics: DTFE versus regular SPH

abstract:
  We present the results of a study confronting density maps reconstructed by
the Delaunay Tessellation Field Estimator (DTFE) and by regular SPH
kernel-based techniques. The comparison between the two methods clearly
demonstrates the superior performance of the DTFE with respect to conventional
SPH methods, in particular at locations where SPH appears to fail. The DTFE is
a fully self-adaptive technique for reconstructing continuous density fields
from discrete particle distributions, and is based upon the corresponding
Delaunay tessellation. Its principal asset is its complete independence of
arbitrary smoothing functions and parameters specifying the properties of
these. As a result it manages to faithfully reproduce the anisotropies of the
local particle distribution and through its adaptive and local nature proves to
be optimally suited for uncovering the full structural richness in the density
distribution. Through the improvement in local density estimates, calculations
invoking the DTFE will yield a much better representation of physical processes
which depend on density. The presented results form an encouraging step towards
the application and insertion of the DTFE in astrophysical hydrocodes. We
describe an outline for the construction of a particle hydrodynamics code in
which the DTFE replaces kernel-based methods. Further discussion addresses the
issue and possibilities for a moving grid based hydrocode invoking the DTFE,
and Delaunay tessellations, in an attempt to combine the virtues of the
Eulerian and Lagrangian approaches.


title: CMB-slow, or How to Estimate Cosmological Parameters by Hand

abstract:
  I derive analytically the spectrum of the CMB fluctuations. The final result
for C_l is presented in terms of elementary functions with an explicit
dependence on the basic cosmological parameters. This result is in a rather
good agreement with CMBFAST for a wide range of parameters around concordance
model. This allows us to understand the physical reasons for dependence of the
particular features of the CMB spectrum on the basic cosmological parameters
and to estimate the possible accuracy of their determination. I also analyse
the degeneracy of the spectrum with respect to certain combinations of the
cosmological parameters.


title: Nucleosynthesis Without a Computer

abstract:
  I derive completely analytically the time evolution and final abundances of
the light elements (up to Be-7) formed in the big-bang nucleosynthesis.This
highlights an interesting physics taking place during the formation of light
elements in the early universe.


title:
A search for high redshift molecular absorption lines toward
  millimetre-loud, optically faint quasars

abstract:
  We describe initial results of a search for redshifted molecular absorption
toward four millimetre-loud, optically faint quasars. A wide frequency
bandwidth of up to 23 GHz per quasar was scanned using the Swedish-ESO
Sub-millimetre Telescope at La Silla. Using a search list of commonly detected
molecules, we obtained nearly complete redshift coverage up to z_abs=5. The
sensitivity of our data is adequate to have revealed absorption systems with
characteristics similar to those seen in the four known redshifted
millimetre-band absorption systems, but none were found. Our frequency-scan
technique nevertheless demonstrates the value of wide-band correlator
instruments for searches such as these. We suggest that a somewhat larger
sample of similar observations should lead to the discovery of new
millimetre-band absorption systems.


title:
The Large-Scale Extinction Map of the Galactic Bulge from the MACHO
  Project Photometry

abstract:
  We present a (V-R)-based reddening map of about 43 square degrees of the
Galactic bulge/bar. The map is constructed using template image photometry from
the MACHO microlensing survey, contains 9717 resolution elements, and is based
on (V-R)-color averages of the entire color-magnitude diagrams (CMDs) in 4 by 4
arc-minute tiles. The conversion from the observed color to the reddening
follows from an assumption that CMDs of all bulge fields would look similar in
the absence of extinction. Consequently, the difference in observed color
between various fields originates from varying contribution of the disk
extinction summed along different lines of sight. We check that our (V-R)
colors correlate very well with infrared and optical reddening maps. We show
that a dusty disk obeying a cosec|b| extinction law, E(V-R) = 0.0274 cosec|b|,
provides a good approximation to the extinction toward the MACHO bulge/bar
fields. The large-scale (V-R)-color and visual extinction map presented here is
publicly available in the electronic edition of the Journal and on the World
Wide Web.


title: Neutrino masses and the number of neutrino species from WMAP and 2dFGRS

abstract:
  We have performed a thorough analysis of the constraints which can be put on
neutrino parameters from cosmological observations, most notably those from the
WMAP satellite and the 2dF galaxy survey. For this data we find an upper limit
on the sum of active neutrino mass eigenstates of \sum m_nu < 1.0 eV (95%
conf.), but this limit is dependent on priors. We find that the WMAP and 2dF
data alone cannot rule out the evidence from neutrinoless double beta decay
reported by the Heidelberg-Moscow experiment. In terms of the relativistic
energy density in neutrinos or other weakly interacting species we find, in
units of the equivalent number of neutrino species, N_nu, that N_nu =
4.0+3.0-2.1 (95% conf.). When BBN constraints are added, the bound on N_\nu is
2.6+0.4-0.3 (95% conf.), suggesting that N_nu could possibly be lower than the
standard model value of 3. This can for instance be the case in models with
very low reheating temperature and incomplete neutrino thermalization.
Conversely, if N_nu is fixed to 3 then the data from WMAP and 2dFGRS predicts
that 0.2458 < Y_P < 0.2471, which is significantly higher than the
observationally measured value. The limit on relativistic energy density
changes when a small $\nu_e$ chemical potential is present during BBN. In this
case the upper bound on N_nu from WMAP, 2dFGRS and BBN is N_nu < 6.5. Finally,
we find that a non-zero \sum m_nu can be compensated by an increase in N_nu.
One result of this is that the LSND result is not yet ruled out by cosmological
observations.


title: CMB, Quantum Fluctuations and the Predictive Power of Inflation

abstract: I comment on the predictive power of inflation and recent CMB measurements.


title: Energetic Particles in Clusters of Galaxies and Starburst Galaxies

abstract:
  The nonthermal characteristics of starburst galaxies and galaxy clusters are
reviewed and the perspectives for their observation in high energy gamma rays
discussed. It is argued that starburst galaxies should have physically similar
and even simpler nonthermal properties as our Galaxy, the particle transport
being convective in their strong galactic winds. They should be measurable in
TeV gamma rays by large detectors, and in fact the recent detection of NGC 253
is a first demonstration. Galaxy clusters are equally expected to produce a
nonthermal energetic nuclear particle component that gives unambiguous
information about the entropy production history in clusters. Both types of
objects should be main sources of and at the same time also major visible
representatives for the ubiquitous nonthermal component of matter in the
Universe.


title: Quark-Diquark Equations of State Models: The Role of Interactions

abstract:
  Recent observational data suggests a high compacticity (the quotient M/R) of
some "neutron" stars. Motivated by these works we revisit models based on
quark-diquark degrees of freedom and address the question of whether that
matter is stable against diquark disassembling and hadronization within the
different models. We find that equations of state modeled as effective $\lambda
\phi^{4}$ theories do not generally produce stable self-bound matter and are
not suitable for constructing very compact star models, that is the matter
would decay into neutron matter. We also discuss some insights obtained by
including hard sphere terms in the equation of state to model repulsive
interactions. We finally compare the resulting equations of state with previous
models and emphasize the role of the boundary conditions at the surface of
compact self-bound stars, features of a possible normal crust of the latter and
related topics.


title: Chandra observations of X-ray weak Quasars

abstract:
  We present Chandra observations of 18 spectroscopically selected quasars,
already known to be X-ray weak from previous ROSAT observations. All the
sources but one are detected by Chandra, and spectral analysis suggests that
most of them are intrinsically underluminous in the X-rays (by a factor from 3
to >100). These objects could represent a large population of quasars with a
Spectral Energy Distribution different from that of standard blue quasars. We
discuss the possibility that a significant fraction of the obscured AGN needed
in Synthesis models of the X-ray background could be instead optically
broad-line, X-ray weak quasars.


title: Constraining photon-axion oscillations using quasar spectra

abstract:
  Using quasar spectra from the SDSS survey, we constrain the possibility of
photon-axion oscillations as a source of dimming of high redshift objects. Such
a process has been suggested as an explanation of the apparent faintness of
distant Type Ia supernovae. For most combinations of magnetic field strengths
and plasma densities along the line of sight, large beam attenuations in broad
band filters would also lead to significant differential attenuation, not
observed in the quasar sample. However, this conservative study does not
exclude the possibility of 0.1 mag dimming of Type Ia supernovae for average
plasma densities n_e = 10^(-8) cm^(-3). NIR and MIR spectroscopic studies of
high-z sources may be used put further constrains or provide indirect evidence
for the existence of a very light axion.


title:
Radio Polarization of the Young High-Magnetic-Field Pulsar PSR
  J1119-6127

abstract:
  We have investigated the radio polarization properties of PSR J1119-6127, a
recently discovered young radio pulsar with a large magnetic field. Using
pulsar-gated radio imaging data taken at a center frequency of 2496 MHz with
the Australia Telescope Compact Array, we have determined a rotation measure
for the pulsar of +842 +/- 23 rad m^-2. These data, combined with archival
polarimetry data taken at a center frequency of 1366 MHz with the Parkes
telescope, were used to determine the polarization characteristics of PSR
J1119-6127 at both frequencies. The pulsar has a fractional linear polarization
of ~75% and ~55% at 1366 and 2496 MHz, respectively, and the profile consists
of a single, wide component. This pulse morphology and high degree of linear
polarization are in agreement with previously noticed trends for young pulsars
(e.g., PSR J1513-5908). A rotating-vector (RV) model fit of the position angle
(PA) of linear polarization over pulse phase using the Parkes data suggests
that the radio emission comes from the leading edge of a conal beam. We discuss
PSR J1119-6127 in the context of a recent theoretical model of pulsar spin-down
which can in principle be tested with polarization and timing data from this
pulsar. Geometric constraints from the RV fit are currently insufficient to
test this model with statistical significance, but additional data may allow
such a test in the future.


title: The lithium depletion boundary and the age of NGC 2547

abstract:
  We present the results of a photometric and spectroscopic survey of cool M
dwarf candidates in the young open cluster NGC 2547. Using the 2dF fiber
spectrograph, we have searched for the luminosity at which lithium remains
unburned in an attempt to constrain the cluster age. The lack of a population
of individual lithium-rich objects towards the faint end of our sample places a
very strong lower limit to the cluster age of 35 Myr. However, the detection of
lithium in the averaged spectra of our faintest targets suggests that the
lithium depletion boundary lies at 9.5 < M(I) < 10.0 and that the cluster age
is < 54 Myr. The age of NGC 2547 judged from fitting isochrones to low-mass
pre-main-sequence stars in colour-magnitude diagrams is 20-35 Myr using the
same evolutionary models. The sense and size of the discrepancy in age
determined by these two techniques is similar to that found in another young
cluster, IC 2391, and in the low-mass pre main-sequence binary system, GJ
871.1AB. We suggest that the inclusion of rotation or dynamo-generated magnetic
fields in the evolutionary models could reconcile the two age determinations,
but only at the expense of increasing the cluster ages beyond that currently
indicated by the lithium depletion. Alternatively, some mechanism is required
that increases the rate of lithium depletion in young, very low-mass fully
convective stars.


title:
On the Nature of the X-ray Emission from the Accreting Millisecond
  Pulsar SAX J1808.4-3658

abstract:
  The pulse profiles of the accreting X-ray millisecond pulsar SAX J1808.4-3658
at different energies are studied. The two main emission component, the black
body and the Comptonized tail that are clearly identified in the time-averaged
spectrum, show strong variability with the first component lagging the second
one. The observed variability can be explained if the emission is produced by
Comptonization in a hot slab (radiative shock) of Thomson optical depth ~0.3-1
at the neutron star surface. The emission patterns of the black body and the
Comptonized radiation are different: a "knife"- and a "fan"-like, respectively.
We construct a detailed model of the X-ray production accounting for the
Doppler boosting, relativistic aberration and gravitational light bending in
the Schwarzschild spacetime. We present also accurate analytical formulae for
computations of the light curves from rapidly rotating neutron stars using
formalism recently developed by Beloborodov (2002). Our model reproduces well
the pulse profiles at different energies simultaneously, corresponding phase
lags, as well as the time-averaged spectrum. We constrain the compact star mass
to be bounded between 1.2 and 1.6 solar masses. By fitting the observed
profiles, we determine the radius of the compact object to be R~11 km if M=1.6
M_sun, while for M=1.2 M_sun the best-fitting radius is ~6.5 km, indicating
that the compact object in SAX J1808.4-3658 can be a strange star. We obtain a
lower limit on the inclination of the system of 65 degrees.


title:
The intrinsic emission of Seyfert galaxies observed with BeppoSAX/PDS I.
  Comparison of the average spectra of the three classes of Seyfert Galaxies

abstract:
  We present a study of the hard X-ray spectrum (>15 keV) of different classes
of Seyfert galaxies observed with BeppoSAX/PDS. Using hard X-ray data, we avoid
absorption effects modifying the Seyfert emission and have direct access to the
central engine of these sources. The aim of this study is first to characterize
the general properties of the hard X-ray spectrum of Seyfert 1, 1.5 and 2
galaxies and secondly to compare their intrinsic emission to test unified
models according to which all the classes have the same nucleus. We compute the
average spectrum of 14 Sy 1, 9 Sy 1.5 and 22 Sy 2 galaxies observed by the PDS
(15-136 keV). The average spectrum of Sy 1 differs from that of Sy 2, the first
requiring the presence of a high energy cutoff which is absent in the second.
We also show that the reflection component is possibly more important in the Sy
2 emission. The nature of Sy 1.5 galaxies is ambiguous as they have a
negligible reflection component (like Sy 1) and do not require a cutoff (like
Sy 2)


title: Gamma-ray bursts: a Centauro's cry?

abstract:
  A new candidate for the gamma-ray bursts central engine is proposed: if in
some energetic cosmic event a macroscopic amount of bubbles of the disoriented
chiral condensate can be formed, then their subsequent decays will produce a
relativistic fireball without the baryon loading problem. The neutron star to
strange star transition is considered as a candidate example of such cosmic
event.


title: Faraday ghosts: depolarization canals in the Galactic radio emission

abstract:
  Narrow, elongated regions of very low polarized intensity -- so-called canals
-- have recently been observed by several authors at decimeter wavelengths in
various directions in the Milky Way, but their origin remains enigmatic. We
show that the canals arise from depolarization by differential Faraday rotation
in the interstellar medium and that they represent level lines of Faraday
rotation measure RM, a random function of position in the sky. Statistical
properties of the separation of canals depend on the autocorrelation function
of RM, and so provide a useful tool for studies of interstellar turbulence.


title: Luminosity and Stellar Mass Functions of Local Star-Forming Galaxies

abstract:
  We present the optical and near-infrared luminosity and mass functions of the
local star-forming galaxies in the Universidad Complutense de Madrid Survey. A
bivariate method which explicitly deals with the Halpha selection of the survey
is used when estimating these functions. Total stellar masses have been
calculated on a galaxy-by-galaxy basis taking into account differences in star
formation histories. The main difference between the luminosity distributions
of the UCM sample and the luminosity functions of the local galaxy population
is a lower normalization (phi^*), indicating a lower global volume density of
UCM galaxies. The typical near-infrared luminosity (L^*) of local star-forming
galaxies is fainter than that of normal galaxies. This is a direct consequence
of the lower stellar masses of our objects. However, at optical wavelengths (B
and r) the luminosity enhancement arising from the young stars leads to M^*
values that are similar to those of normal galaxies. The fraction of the total
optical and near infrared luminosity density in the local Universe associated
with star-forming galaxies is 10-20%. Fitting the total stellar mass function
using a Schechter parametrization we obtain alpha=-1.15+/-0.15,
log({M}^*)=10.82+/-0.17 Msun and log(phi^*)=-3.04+/-0.20 Mpc^{-3}. This gives
an integrated total stellar mass density of 10^{7.83+/-0.07} Msun Mpc^{-3} in
local star-forming galaxies (H_0=70 km s^{-1} Mpc^{-1}, Omega_M=0.3,
Lambda=0.7). The volume-averaged burst strength of the UCM galaxies is
b=0.04+/-0.01, defined as the ratio of the mass density of stars formed in
recent bursts (age<10 Myr) to the total stellar mass density in UCM galaxies.
Finally, we derive that, in the local Universe, (13+/-3)% of the total baryon
mass density in the form of stars is associated with star-forming galaxies.


title:
Upper limits on neutrino masses from the 2dFGRS and WMAP: the role of
  priors

abstract:
  Solar, atmospheric, and reactor neutrino experiments have confirmed neutrino
oscillations, implying that neutrinos have non-zero mass, but without pinning
down their absolute masses. While it is established that the effect of
neutrinos on the evolution of cosmic structure is small, the upper limits
derived from large-scale structure data could help significantly to constrain
the absolute scale of the neutrino masses. In a recent paper the 2dF Galaxy
Redshift Survey (2dFGRS) team provided an upper limit m_nu,tot < 2.2 eV, i.e.
approximately 0.7 eV for each of the three neutrino flavours, or phrased in
terms of their contributioin to the matter density, Omega_nu/Omega_m < 0.16.
Here we discuss this analysis in greater detail, considering issues of assumed
'priors' like the matter density Omega_m and the bias of the galaxy
distribution with respect the dark matter distribution. As the suppression of
the power spectrum depends on the ratio Omega_nu/Omega_m, we find that the
out-of- fashion Mixed Dark Matter Model, with Omega_nu=0.2, Omega_m=1 and no
cosmological constant, fits the 2dFGRS power spectrum and the CMB data
reasonably well, but only for a Hubble constant H_0<50 km/s/Mpc. As a
consequence, excluding low values of the Hubble constant, e.g. with the HST Key
Project is important in order to get a strong constraint on the neutrino
masses. We also comment on the improved limit by the WMAP team, and point out
that the main neutrino signature comes from the 2dFGRS and the Lyman alpha
forest.


title: The surface density of Extremely Red Objects in high-z quasar fields

abstract:
  We report on a study of the surface density of Extremely Red Objects (EROs)
in the fields of 13 radio-loud quasars at 1.8 < z < 3.0 covering a total area
of 61.7 sqr arcmin. There is a large variation in the ERO surface density from
field to field, and as many as 30--40 % of the fields have roughly 4--5 times
more EROs than what is expected from a random distribution. The average surface
density exceeds the value found in large random-field surveys by a factor of
2--3, a result which is significant at the >3 sigma level. Hence, it appears
that the quasar lines of sight are biassed towards regions of high ERO density.
This might be caused by clusters or groups of galaxies physically associated
with the quasars. However, an equally likely possibility is that the observed
ERO excess is part of overdensities in the ERO population along the line of
sight to the quasars. In this case, the non-randomness of quasar fields with
respect to EROs may be explained in terms of gravitational lensing.


title:
The Physics of Supernova Remnant Blast Waves. I. Kinematics of DEM L71
  in the Large Magellanic Cloud

abstract:
  We present the results from Fabry-Perot imaging spectroscopy of the
Balmer-dominated supernova remnant DEM L71 (0505-67.9) in the LMC. Spectra
extracted from the entire circumference of the blast wave reveal the broad and
narrow component H-alpha line emission characteristic of non-radiative shocks
in partially neutral gas. The new spectra of DEM L71 include portions of the
rim that have not been previously observed. We find that the broad component
width varies azimuthally along the edge of DEM L71, ranging from 450+/-60 km/s
along the eastern edge to values as high as 985 (+210)(-165) km/s along the
faint western edge. In part of the faint northern rim the broad component is
not detected, possibly indicating a lower density in these regions and/or a
broad component width in excess of 1000 km/s. Between the limits of zero and
full electron-ion temperature equilibration at the shock front, the allowed
range of shock velocities is 430-560 km/s along the east rim and 700-1250 km/s
along other parts of the blast wave. The H-alpha broad-to-narrow flux ratios
vary considerably around the remnant, ranging from 0.4 to 0.8. These ratios lie
below the values predicted by our shock models. We find that narrow component
H-alpha emission from a cosmic ray precursor may be the cause of the
discrepancy. The least decelerated portions of the blast wave (i.e., regions
excluding the brightest filaments) are well characterized by Sedov models with
a kinetic energy E_51= (0.37+/-0.06)*D_50**(5/2), where D_50 is the LMC
distance in units of 50 kpc. The corresponding age for DEM L71 is
(4360+/-290)*D_50 yr. This is the first time that velocity information from the
entire blast wave has been utilized to study the global kinematics of a
non-radiative SNR at a known distance.


title: The velocity dispersion function of early-type galaxies

abstract:
  The distribution of early-type galaxy velocity dispersions, phi(sigma), is
measured using a sample drawn from the SDSS database. Its shape differs
significantly from that which one obtains by simply using the mean correlation
between luminosity, L, and velocity dispersion, sigma, to transform the
luminosity function into a velocity function: ignoring the scatter around the
mean sigma-L relation is a bad approximation. An estimate of the contribution
from late-type galaxies is also made, which suggests that phi(sigma) is
dominated by early-type galaxies at velocities larger than ~ 200 km/s.


title:
Accretion of low angular momentum material onto black holes: 2D
  magnetohydrodynamical case

abstract:
  We report on the second phase of our study of slightly rotating accretion
flows onto black holes. We consider magnetohydrodynamical (MHD) accretion flows
with a spherically symmetric density distribution at the outer boundary, but
with spherical symmetry broken by the introduction of a small,
latitude-dependent angular momentum and a weak radial magnetic field. We study
accretion flows by means of numerical 2D, axisymmetric, MHD simulations with
and without resistive heating. Our main result is that the properties of the
accretion flow depend mostly on an equatorial accretion torus which is made of
the material that has too much angular momentum to be accreted directly. The
torus accretes, however, because of the transport of angular momentum due to
the magnetorotational instability (MRI). Initially, accretion is dominated by
the polar funnel, as in the hydrodynamic inviscid case, where material has zero
or very low angular momentum. At the later phase of the evolution, the torus
thickens towards the poles and develops a corona or an outflow or both.
Consequently, the mass accretion through the funnel is stopped. The accretion
of rotating gas through the torus is significantly reduced compared to the
accretion of non-rotating gas (i.e., the Bondi rate). It is also much smaller
than the accretion rate in the inviscid, weakly rotating case.Our results do
not change if we switch on or off resistive heating. Overall our simulations
are very similar to those presented by Stone, Pringle, Hawley and Balbus
despite different initial and outer boundary conditions. Thus, we confirm that
MRI is very robust and controls the nature of radiatively inefficient accretion
flows.


title: NGC6822: detection of variable stars with ISIS2.1

abstract:
  Preliminary results on the detection of a conspicuous number of variable
stars in the dwarf irregular galaxy NGC 6822 are presented. We stress the need
for packages specifically designed to the search of variables in distant
galaxies and/or when data are affected by a high level of crowding.


title: Variable Stars in the LMC: the Photometric Catalogue

abstract:
  New B, V, I photometry was obtained for a sample of 152 variables (125 RR
Lyrae's, 4 anomalous Cepheids, 11 classical Cepheids, 11 eclipsing binaries and
a delta Scuti star) in two regions near the bar of the Large Magellanic Cloud
(LMC). We derived complete and well sampled B and V light curves, very accurate
periods, epochs of maximum light, amplitudes, intensity- and magnitude-averaged
apparent luminosities for about 95% of the RR Lyrae stars. All these
informations are contained in the photometric catalogue. Metallicities from the
Fourier decomposition of the V light curves were derived for 29 of the ab type
RR Lyrae's and are compared with the DeltaS metal abundances from low
resolution spectra obtained with the Very Large Telescope (VLT).


title: Cosmology at Low Redshifts

abstract:
  It is argued that it is far more cost effective to carry out some projects
with medium-sized dedicated zenith telescopes rather than large steerable
telescopes, freeing the later to carry out projects that truly need them. I
show that the large number of objects observed with a surveying 4-m zenith
telescope allows one to carry out cosmological projects at low redshifts.
Examining two case studies, I show first that a variability survey would obtain
light curves for several thousands of type Ia supernovae per year up to z=1 and
easily discriminate among competing cosmological models. Finally, I discuss a
second case study, consisting of a spectrophotometric survey carried out with
interference filters, showing its power to discriminate among cosmological
models and to study the large-scale distribution of galaxies in the Universe.