title: New Clues on the Calcium Underabundance in Early-Type Galaxies

abstract:
  We use our new stellar population models, which include effects from variable
element abundance ratios, to model the Ca4227 absorption line indices of
early-type galaxies (Trager et al.), and to derive calcium element abundances.
We find that calcium, although being an alpha-element, is depressed with
respect to the other alpha-elements by up to a factor 2. This confirms
quantitatively earlier speculations that early-type galaxies are calcium
underabundant. We find a clear correlation between alpha/Ca ratio and central
velocity dispersion, which implies that more massive galaxies are more calcium
underabundant. Interestingly this correlation extends down to the dwarf
spheroidal galaxies of the Local Group for which alpha/Ca ratios have been
measured from high-resolution spectroscopy of individual stars (Shetrone et
al.). The increase of the calcium underabundance with galaxy mass balances the
higher total metallicities of more massive galaxies, so that calcium abundance
in early-type galaxies is fairly constant and in particular does not increase
with increasing galaxy mass. This result may be the key to understand why the
CaII triplet absorption of early-type galaxies at 8600 A is constant to within
5 per cent over a large range of velocity dispersions (Saglia et al.; Cenarro
et al.). The origin of the calcium underabundance in early-type galaxies
remains yet to be understood. We argue that formation timescales are
disfavoured to produce calcium underabundance, and that the option of
metallicity dependent supernova yields may be the most promising track to
follow.


title:
GRB 021004: A Possible Shell Nebula around a Wolf-Rayet Star Gamma-Ray
  Burst Progenitor

abstract:
  The rapid localization of GRB 021004 by the HETE-2 satellite allowed nearly
continuous monitoring of its early optical afterglow decay, as well as
high-quality optical spectra that determined a redshift of z3=2.328 for its
host galaxy, an active starburst galaxy with strong Lyman-alpha emission and
several absorption lines. Spectral observations show multiple absorbers at
z3A=2.323, z3B= 2.317, and z3C= 2.293 blueshifted by 450, 990, and 3,155 km/s
respectively relative to the host galaxy Lyman-alpha emission. We argue that
these correspond to a fragmented shell nebula that has been radiatively
accelerated by the gamma-ray burst (GRB) afterglow at a distance greater than
0.3 pc from a Wolf-Rayet star progenitor. The chemical abundance ratios
indicate that the nebula is overabundant in carbon and silicon. The high level
of carbon and silicon is consistent with a swept-up shell nebula gradually
enriched by a WCL progenitor wind over the lifetime of the nebula prior to the
GRB onset. The detection of statistically significant fluctuations and color
changes about the jet-like optical decay further supports this interpretation
since fluctuations must be present at some level due to inhomogeneities in a
clumpy stellar wind medium or if the progenitor has undergone massive ejection
prior to the GRB onset. This evidence suggests that the mass-loss process in a
Wolf-Rayet star might lead naturally to an iron-core collapse with sufficient
angular momentum that could serve as a suitable GRB progenitor.


title: Spectral Energy Distributions of Seyfert Nuclei

abstract:
  We present nuclear spectral energy distributions (SEDs) in the range
0.4-16micron for an expanded CfA sample of Seyfert galaxies. The spectral
indices from 1-16micron range from alpha_IR 0.9 to 3.8. The shapes of the
spectra are correlated with Seyfert type in the sense that steeper nuclear SEDs
(nu*f_nu increasing with increasing wavelength) tend to be found in Seyfert 2s
and flatter SEDs (nu *f_nu constant) in Seyfert 1-1.5s. The galaxies optically
classified as Seyferts 1.8s and 1.9s display values of alpha_IR as in type 1
objects, or values intermediate between those of Seyfert 1s and Seyfert 2s. The
intermediate SEDs of many Seyfert 1.8-1.9s may be consistent with the presence
of a pure Seyfert 1 viewed through a moderate amount (A_V <5mag) of foreground
galaxy extinction. We find, however, that between 10 and 20% of galaxies with
broad optical line components have steep infrared SEDs.
  Torus models usually adopt high equatorial opacities to reproduce the
infrared properties of Seyfert 1s and 2s, resulting in a dichotomy of infrared
SEDs (flat for type 1s, and steep for type 2s). Such a dichotomy, however, is
not observed in our sample. The wide range of spectral indices observed in the
type 2 objects, the lack of extremely steep SEDs, and the large numbers of
objects with intermediate spectral indices cannot be reconciled with
predictions from existing optically thick torus models. We discuss possible
modifications to improve torus models, including low optical depth tori, clumpy
dusty tori, and high-optical-depth tori with an extended optically thin
component.


title:
High Redshift Candidates and the Nature of Small Galaxies in the Hubble
  Deep Field

abstract:
  We present results on two related topics: 1. A discussion of high redshift
candidates (z>4.5), and 2. A study of very small galaxies at intermediate
redshifts, both sets being detected in the region of the northern Hubble Deep
Field covered by deep NICMOS observations at 1.6 and 1.1 microns. The high
redshift candidates are just those with redshift z>4.5 as given in the recent
catalog of Thompson, Weymann and Storrie-Lombardi, while the ``small galaxy''
sample is defined to be those objects with isophotal area <= 0.2 squ. arcsec
and with photometric redshifts 1<z<4.5. Of the 19 possible high redshift
candidates listed in the Thompson et al. catalog, 11 have (nominal) photometric
redshifts less than 5.0. Of these, however, only 4 are ``robust'' in the sense
of yielding high redshifts when the fluxes are randomly perturbed with errors
comparable to the estimated measuring error in each wave band. For the 8 other
objects with nominal photometric redshifts greater than 5.0, one (WFPC2 4--473)
has a published spectroscopic redshift. Of the remaining 7, 4 are robust in the
sense indicated above. Two of these form a close pair (NIC 586 and NIC 107).
The redshift of the object having formally the highest redshift, at 6.56
(NIC118 = WFPC2 4--601), is problematic, since F606W and F814W flux are clearly
present, and the nature of this object poses a dilemma. (abridged)


title:
Simultaneous single-pulse observations of radio pulsars III. The
  behaviour of circular polarization

abstract:
  We investigate circular polarization in pulsar radio emission through
simultaneous observations of PSR B1133+16 at two frequencies. In particular, we
investigate the association of the handedness of circular polarization with the
orthogonal polarization mode phenomenon at two different frequencies. We find
the association to be significant across the pulse for PSR B1133+16, making a
strong case for orthogonal polarization modes determining the observed circular
polarization. The association however is not perfect and decreases with
frequency. Based on these results and assuming emission occurs in superposed
orthogonal polarization modes, we present a technique of mode decomposition
based on single pulses. Average profiles of the polarization of each mode can
then be computed by adding the individual mode-separated single pulses. We show
that decomposing single pulses produces different average profiles for the
orthogonal polarization modes from decomposing average profiles. Finally, we
show sample single pulses and discuss the implications of the frequency
dependence of the correlation of the circular polarization with the orthogonal
polarization mode phenomenon.


title: Stellar Winds of Hot Massive Stars Nearby and Beyond the Local Group

abstract:
  Photospheric radiation momentum is efficiently transferred by absorption
through metal lines to the gaseous matter in the atmospheres of massive stars,
sustaining strong winds and mass loss rates. Not only is this critical for the
evolution of such stars, it also provides us with diagnostic UV/optical
spectral lines for the determination of mass loss rates, chemical abundances
and absolute stellar luminosities. We review the mechanisms which render the
wind parameters sensitive to the chemical composition, through the statistics
of the wind-driving lines. Observational evidence in support of the radiation
driven wind theory is presented, with special regard to the Wind
Momentum-Luminosity Relationship and the blue supergiant work carried out by
our team in galaxies outside of the Local Group.


title:
A Failed Gamma-Ray Burst with Dirty Energetic Jets Spirited Away? New
  Implications for the GRB-SN Connection from Supernova 2002ap

abstract:
  (Abridged) SN 2002ap is an interesting event with broad spectral features
like the famous SN 1998bw / GRB 980425. Here we examine the recently proposed
jet hypothesis from SN 2002ap by a spectropolarimetric observation. We show
that jets should be moving at about 0.23c with a jet kinetic energy of ~5 x
10^{50} erg, a similar energy scale to the GRB jets. The weak radio emission
from SN 2002ap has been used to argue against the jet hypothesis, but we show
that this problem can be avoided. However, the jet cannot be kept ionized
because of adiabatic cooling without external photoionization or heating
source. We found that only the radioactivity of 56Ni is a possible source,
indicating that the jet is formed and ejected from central region of the core
collapse. Then we point out that the jet will eventually sweep up enough
interstellar medium and generate shocks in a few to 10 years, producing strong
radio emission that can be spatially resolved, giving us a clear test for the
jet hypothesis. Discussions are given on possible implications for the GRB-SN
connection in the case that the jet is real. We suggest existence of two
distinct classes of GRBs from similar core-collapse events but by completely
different mechanisms. Cosmologically distant GRBs (~10^{50} erg) are collimated
jets generated by central activity of core collapses. SN 2002ap could be a
failed GRB of this type with a large baryon load. On the other hand, much less
energetic ones like GRB 980425 are rather isotropic, which may be produced by
hydrodynamical shock acceleration at the outer envelope. We propose that the
radioactive ionization for the SN 2002ap jet may give a new explanation also
for the X-ray line features often observed in GRB afterglows.


title:
Early Structure Formation and Reionization in a Warm Dark Matter
  Cosmology

abstract:
  We study first structure formation in Lambda-dominated universes using large
cosmological N-body/SPH simulations. We consider a standard LCDM model and a
LWDM model in which the mass of the dark matter particles is taken to be m_X=10
keV. The linear power spectrum for the LWDM model has a characteristic cut-off
at a wavenumber k=200 /Mpc, suppressing the formation of low mass (< 10^6 Msun)
nonlinear objects early on. The absence of low mass halos in the WDM model
makes the formation of primordial gas clouds with molecular hydrogen very
inefficient at high redshifts. The first star-forming gas clouds form at z~21
in the WDM model, considerably later than in the CDM counterpart, and the
abundance of these gas clouds differs by an order of magnitude between the two
models. We carry out radiative transfer calculations by embedding massive
Population III stars in the gas clouds. We show that the volume fraction of
ionized gas rises up close to 100% by z=18 in the CDM case, whereas that of the
WDM model remains extremely small at a level of a few percent. Thus the WDM
model with m_X=10 keV is strongly inconsistent with the observed high optical
depth by the WMAP satellite.


title: Fred Hoyle: Contributions to the Theory of Galaxy Formation

abstract:
  I review two fundamental contributions that Fred Hoyle made to the theory of
galaxy formation. Hoyle was the first to propose that protogalaxies acquired
their angular momentum via tidal torques from neighbouring perturbations during
a period of gravitational instability. To my knowledge, he was also the first
to suggest that the masses of galaxies could be explained by the requirement
that primordial gas clouds cool radiatively on a suitable timescale. Tidal
torques and cooling arguments play a central role in the modern theory of
galaxy formation. It is a measure of Hoyle's breadth and inventiveness that he
recognised the importance of these processes at such an early stage in the
history of the subject.


title: The GZK cutoff behind a Magnetized Universe

abstract:
  We study the effect of random extra-galactic magnetic fields on the
propagation of protons of energy larger than $10^{19}$ eV. We show that for
reasonable field values (in the 100 nG range) the transition between diffusive
and ballistic regimes occurs in the same energy range as the GZK cutoff (a few
$10^{19}$ eV). The usual interpretation of the flux reduction above the GZK
energy in terms of a sudden reduction of the visible horizon is modified.
Moreover, since the size of the diffusion sphere of a continuous source of
cosmic rays is of the order of 10 Mpc, the local structure of the Universe and
therefore of potential local astrophysical sources plays a dominant role in the
expected spectrum. Under reasonable assumptions on the sources configurations
the expected GZK cutoff is reduced.


title: QSOs Associated with Messier 82

abstract:
  The starburst / AGN galaxy M82 was studied by Dahlem, Weaver and Heckman
using X-ray data from ROSAT and ASCA, as part of their X-ray survey of edge-on
starburst galaxies. They found seventeen unresolved hard-X-ray sources around
M82, in addition to its strong nuclear source, and other X-rays within the main
body of M82. We have measured optical point sources at these positions, and
have obtained redshifts of six candidates at the Keck I 10-m telescope, using
the low-resolution imaging spectrograph (LRIS). All six are highly compact
optical and X-ray objects with redshifts ranging from 0.111 to 1.086. They all
show emission lines. The three with the highest redshifts are clearly QSOs. The
others with lower redshifts may either be QSOs or compact emission-line
galaxies. In addition to these six there are nine QSOs lying very close to M82
which were discovered many years ago. There is no difference between optical
spectra of these latter QSOs, only two of which are known to be X-ray sources,
and the X-ray emitting QSOs. The redshifts of all fifteen range between 0.111
and 2.05. The large number of QSOs and their apparent association with ejected
matter from M82 suggest that they are physically associated with the galaxy,
and have large intrinsic redshift components. If this is correct, the absolute
magnitudes lie in the range -8 < M_v < -10. Also we speculate that the luminous
variable X-ray source which has been detected by Chandra in the main body of
M82 some 9 arcseconds from the center is another QSO in the process of ejection
from the nucleus, and propose some observational tests of this hypothesis.


title:
The properties of the absorbing and line emitting material in IGR
  J16318-4848

abstract:
  We have performed a detailed analysis of the XMM-Newton observation of IGR
J16318-4848, to study the properties of the matter responsible for the
obscuration and for the emission of Fe and Ni lines. Even if the line of sight
material has a column density of about 2x10^24 cm^-2, from the Fe Kalpha line
EW and Compton Shoulder we argue that the matter should have an average column
density of a few x10^23 cm^-2, along with a covering factor of about 0.1-0.2.
The iron Kalpha line varies on time scales as short as 1000 s, implying a size
of the emitting region smaller than about 3x10^13 cm. The flux of the line
roughly follows the variations of the continuum, but not exactly, suggesting a
variation of the geometrical properties of the emitting region on similar time
scales.


title: Detectibility of Mixed Unburnt C+O in Type Ia Supernova Spectra

abstract:
  Motivated by recent 3-D calculations of the explosion of Type Ia supernova
via a pure deflagration we calculate the observed spectra at 15-25 days past
maximum light of a parameterized model which has a considerable fraction of
unburnt C+O in the central regions. Rather than attempting a self consistent
3-D calculation, which is beyond the scope of current computer codes, we modify
the composition structure of the 1-D deflagration model W7. In our exploratory
parameterized calculations, we find that a central concentration of C+O is not
ruled out by observations for the epochs we study. We briefly examine whether
nebular phase spectra could be incompatible with observations.


title:
Observational evidence for a connection between supermassive black holes
  and dark matter haloes

abstract:
  We present new velocity dispersion measurements of sample of 12 spiral
galaxies for which extended rotation curves are available. These data are used
to refine a recently discovered correlation between the circular velocity and
the central velocity dispersion of spiral galaxies. We find a slightly steeper
slope for our larger sample, we confirm the negligible intrinsic scatter on
this correlation, and we find a striking agreement with a corresponding
relation for elliptical galaxies. We combine this correlation with the
well-known MBH-sigma relation to obtain a tight correlation between the
circular velocities of galaxies and the masses of the supermassive black holes
they host. This correlation is the observational evidence for an intimate link
between dark matter haloes and supermassive black holes. Apart from being an
important ingredient for theoretical models of galaxy formation and evolution,
the relation between MBH and circular velocity can serve as a practical tool to
estimate black hole masses in spiral galaxies.


title:
Exact solution for the Green's function describing time-dependent
  thermal Comptonization

abstract:
  We obtain an exact, closed-form expression for the time-dependent Green's
function solution to the Kompaneets equation. The result, which is expressed as
the integral of a product of two Whittaker functions, describes the evolution
in energy space of a photon distribution that is initially monoenergetic.
Effects of spatial transport within a homogeneous scattering cloud are also
included within the formalism. The Kompaneets equation that we solve includes
both the recoil and energy diffusion terms, and therefore our solution for the
Green's function approaches the Wien spectrum at large times. We show that the
Green's function can be used to generate all of the previously known
steady-state and time-dependent solutions to the Kompaneets equation. The new
solution allows the direct determination of the spectrum, without the need to
numerically solve the partial differential equation. Based upon the Green's
function, we obtain a new time-dependent solution for the photon distribution
resulting from the reprocessing of an optically thin bremsstrahlung initial
spectrum with a low-energy cutoff. The new bremsstrahlung solution possesses a
finite photon number density, and therefore it displays proper equilibration to
a Wien spectrum at large times. The relevance of our results for the
interpretation of emission from variable X-ray sources is discussed, with
particular attention to the production of hard X-ray time lags, and the Compton
broadening of narrow features such as iron lines.


title: Where is the second planet in the HD 160691 planetary system?

abstract:
  The set of radial velocity measurements of the HD 160691 has been recently
published by Jones et.al 2002 (MNRAS). It reveals a linear trend that indicates
a presence of the second planet in this system. The preliminary
double-Keplerian orbital fit to the observations, announced by the discovery
team, describes a highly unstable, self-disrupting configuration. Because the
observational window of the HD 160691 system is narrow, the orbital parameters
of the hypothetical second companion are unconstrained. In this paper we try to
find out whether a second giant planet can exist up to the distance of Jupiter
and search for the dynamical constraints on its orbital parameters. Our
analysis employs a combination of fitting algorithms and simultaneous
examination of the dynamical stability of the obtained orbital fits. It reveals
that if the semi-major axis of the second planet is smaller than $\simeq 5.2$
AU, the observations are consistent with quasi-periodic, regular motions of the
system confined to the islands of various low-order mean motion resonances,
e.g., 3:1, 7:2, 4:1, 5:1, or to their vicinity. In such cases the second planet
has smaller eccentricity $\simeq 0.2-0.5$ than estimated in the previous works.
We show that the currently available Doppler data rather preclude the 2:1 mean
motion resonance expected by some authors to be present in the HD 160691
planetary system. We also demonstrate that the MEGNO-penalty method, developed
in this paper, which is a combination of the genetic minimization algorithm and
the MEGNO analysis, can be efficiently used for predicting stable planetary
configurations when only a limited number of observations is given or the data
do not provide tight constraints on the orbital elements.


title:
On the rotational evolution of solar- and late-type stars, its magnetic
  origins, and the possibility of stellar gyrochronology

abstract:
  We propose a simple interpretation of the rotation period data for solar- and
late-type stars. The open cluster and Mt. Wilson star observations suggest that
rotating stars lie primarily on two sequences, initially called I and C. Some
stars lie in the intervening gap. These sequences, and the fractional numbers
of stars on each sequence evolve systematically with cluster age, enabling us
to construct crude rotational isochrones allowing `stellar gyrochronology', a
procedure, upon improvement, likely to yield ages for individual field stars.
The age and color dependences of the sequences allow the identification of the
underlying mechanism, which appears to be primarily magnetic. The majority of
solar- and late-type stars possess a dominant Sun-like, or Interface magnetic
field, which connects the convective envelope both to the radiative interior of
the star and to the exterior where winds can drain off angular momentum. These
stars spin down Skumanich-style. An age-decreasing fraction of young G, K, and
M stars, which are rapid rotators, possess only a Convective field which is not
only inefficient in depleting angular momentum, but also incapable of coupling
the surface convection zone to the inner radiative zone, so that only the outer
zone is spun down, and on an exponential timescale. These stars do not yet
possess large-scale dynamos. The large-scale magnetic field associated with the
dynamo, apparently created by the shear between the decoupled radiative and
convective zones, (re)couples the convective and radiative zones and drives a
star from the Convective to the Interface sequence through the gap on a
timescale that increases as stellar mass decreases. (Abstract is truncated
here.)


title:
A connection between the morphology of the X-ray emission and rotation
  for solar-type stars in open clusters

abstract:
  It is suggested that the three-segmented morphology of the soft X-ray
emission from cluster and field stars may be understood in terms of the recent
classification of rotating stars into three kinds: those lying on the
convective sequence, on the interface sequence, or in the gap between them.


title:
Galaxies Inside Stromgren Spheres of Luminous Quasars at z>6: Detection
  of The First Galaxies

abstract:
  The intrinsic Lyman-alpha emission lines of normal galaxies before
reionization are much absorbed by the damping wing of the Gunn-Peterson trough,
rendering their direct detection nearly impossible, if their intrinsic line
widths are less than ~100km/s. High redshift luminous quasars prior to the
completion of cosmological reionization at z~6, on the other hand, are capable
of producing large HII regions around them (Stromgren spheres) to allow their
intrinsic Lyman-alpha emission lines to be transmitted without overwhelming
absorption (Cen & Haiman 2000). We suggest that targeted observations at the
Stromgren spheres of known luminous quasars at z >= 6 would be able to detect
Lyman-alpha emission lines of galaxies inside the Stromgren spheres largely
unattenuated. A tunable, very narrowband filter of \Delta\lambda\over \lambda ~
0.1% or a narrowband filter of \Delta\lambda\over \lambda ~1% with follow-up
spectroscopic identifications will be required. Such observations could
directly observe the sources of cosmological reionization including possibly
the Pop III galaxies at z=6-20 by JWST. Possible applications include
determinations of the ionization state of the intergalactic medium, the sizes
of the Stromgren spheres, the ages of the quasars, the luminosity function of
high redshift galaxies and its evolution, the spatial distribution of galaxies
and its evolution, the biased distribution of galaxies around quasars and the
anisotropy of quasar emission. Observations using Keck-class telescopes may
already be made to enable a differentiation between a fully neutral and a 10%
neutral intergalactic medium at z>6.


title:
The diameters of Alpha Centauri A and B - A comparison of the
  asteroseismic and VINCI/VLTI views

abstract:
  We compare the first direct angular diameter measurements obtained on our
closest stellar neighbour, Alpha Centauri, to recent model diameters
constrained by asteroseismic observations. Using the VINCI instrument installed
at ESO's VLT Interferometer (VLTI), the angular diameters of the two main
components of the system, Alpha Cen A and B, were measured with a relative
precision of 0.2% and 0.6%, respectively. Particular care has been taken in the
calibration of these measurements, considering that VINCI is estimating the
fringe visibility using a broadband K filter. We obtain uniform disk angular
diameters for Alpha Cen A and B of UD[A] = 8.314 +/- 0.016 mas and UD[B] =
5.856 +/- 0.027 mas, and limb darkened angular diameters of LD[A] = 8.511 +/-
0.020 mas and LD[B] = 6.001 +/- 0.034 mas. Combining these values with the
parallax from Soderhjelm (1999), we derive linear diameters of D[A] = 1.224 +/-
0.003 Dsun and D[B] = 0.863 +/- 0.005 Dsun. These values are compatible with
the masses published by Thevenin et al.(2002) for both stars.


title: An investigation into the prominence of spiral galaxy bulges: The Data

abstract:
  The best-fitting B, R, I and K-band (Sersic R^(1/n) bulge + exponential disk)
model parameters for the de Jong & van der Kruit (1994) sample of 86 spiral
galaxies are made electronically available. This sample covers all spiral
galaxy types and provides the largest homogeneous set of structural parameters
for spiral galaxies modeled with an R^(1/n) bulge.


title: Suppressing the lower Multipoles in the CMB Anisotropies

abstract:
  The Cosmic Microwave Background (CMB) anisotropy power on the largest angular
scales observed both by WMAP and COBE DMR appears to be lower than the one
predicted by the standard model of cosmology with almost scale free primordial
perturbations arising from a period of inflation
\cite{cobe,Bennett:2003bz,Spergel,Peiris}. One can either interpret this as a
manifestation of cosmic variance or as a physical effect that requires an
explanation. We discuss various mechanisms that could be responsible for the
suppression of such low $\ell$ multipoles. Features in the late time evolution
of metric fluctuations may do this via the integral Sachs-Wolfe effect. Another
possibility is a suppression of power at large scales in the primordial
spectrum induced by a fast rolling stage in the evolution of the inflaton field
at the beginning of the last 65 e-folds of inflation. We illustrate this effect
in a simple model of inflation and fit the resulting CMB spectrum to the
observed temperature-temperature (TT) power spectrum. We find that the WMAP
observations suggest a cutoff at $k_c=4.9^{+1.3}_{-1.6}\times
10^{-4}$Mpc$^{-1}$ at 68% confidence, while only an upper limit of $k_c <
7.4\times 10^{-4}$Mpc$^{-1}$ at 95%. Thus, although it improves the fit of the
data, the presence of a cutoff in power spectrum is only required at a level
close to $2\sigma$. This is obtained with a prior which corresponds to equal
distribution wrt $k_c$. We discuss how other choices (such as an equal
distribution wrt $\ln k_c$ which is natural in the context of inflation) can
affect the statistical interpretation.


title: Giant Lya nebulae associated with high redshift radio galaxies

abstract:
  We report deep Keck narrow-band Lya images of the luminous z > 3 radio
galaxies 4C 41.17, 4C 60.07, and B2 0902+34. The images show giant, 100-200 kpc
scale emission line nebulae, centered on these galaxies, which exhibit a wealth
of morphological structure, including extended low surface brightness emission
in the outer regions, radially directed filaments, cone-shaped structures and
(indirect) evidence for extended Lya absorption. We discuss these features
within a general scenario where the nebular gas cools gravitationally in large
Cold Dark Matter (CDM) halos, forming stars and multiple stellar systems.
Merging of these ``building'' blocks triggers large scale starbursts, forming
the stellar bulges of massive radio galaxy hosts, and feeds super-massive black
holes which produce the powerful radio jets and lobes. The radio sources,
starburst superwinds and AGN radiation then disrupt the accretion process
limiting galaxy and black hole growth, and imprint the observed filamentary and
cone-shaped structures of the Lya nebulae.


title:
High-Precicison Limb-Darkening Measurement of a K3 Giant Using
  Microlensing

abstract:
  We obtain high-precision limb-darkening measurements in five bands (V, V_E,
I_E, I, and H) for the K3 III (Teff=4200 K, [Fe/H]=+0.3, log(g)=2.3) source of
the Galactic bulge microlensing event EROS BLG-2000-5. These measurements are
inconsistent with the predictions of atmospheric models at >10 sigma. While the
disagreement is present in all bands, it is most apparent in I, I_E and V_E, in
part because the data are better and in part because the intrinsic disagreement
is stronger. We find that when limb-darkening profiles are normalized to have
unit total flux, the I-band models for a broad range of temperatures all cross
each other at a common point. The solar profile also passes through this point.
However, the profile as measured by microlensing does not. We conjecture that
the models have incorporated some aspect of solar physics that is not shared by
giant atmospheres.


title: Supermassive black holes may be limited by the Holographic Bound

abstract:
  Supermassive Black Holes are the most entropic objects found in the universe.
The Holographic Bound (HB) to the entropy is used to constrain their formation
time with initial masses $\sim{10}^{6-8}M_{\odot}$, as inferred from
observations. We find that the entropy considerations are more limiting than
causality for this "direct" formation. Later we analyze the possibility of
SMBHs growing from seed black holes. The growth of the initial mass is studied
in the case of accretion of pure radiation and quintessence fields, and we find
that there is a class of models that may allow this metamorphosis. Our analysis
generalizes recent work for some models of quintessence capable of producing a
substantial growth in a short time, while simultaneously obeying the causal and
Holographic Bound limits.


title:
Envelope Emission in Young Stellar Systems: A Sub-Arcsecond Survey of
  Circumstellar Structure

abstract:
  We present modeling results for six of the eleven deeply embedded systems
from our sub-arcsecond 2.7 mm wavelength continuum interferometric survey. The
modeling, performed in the uv plane, assumes dust properties, allows for a
power-law density profile, uses a self-consistent, luminosity conserving
temperature profile, and has an embedded point source to represent a
circumstellar disk. Even though we have the highest spatial resolution to date
at these wavelengths, only the highest signal-to-noise systems can adequately
constrain the simple self-similar collapse models. Of the six sources modeled,
all six were fit with a density power-law index of 2.0; however, in half of the
systems, those with the highest signal-to-noise, a density power-law index of
1.5 can be rejected at the 95% confidence level. Further, we modeled the
systems using the pure Larson-Penston (LP) and Shu solutions with only age and
sound speed as parameters. Overall, the LP solution provides a better fit to
the data, both in likelihood and providing the observed luminosity, but the age
of the systems required by the fits are surprising low (1000-2000 yrs). We
suggest that either there is some overall time scaling of the self-similar
solutions that invalidate the age estimates, or more likely we are at the limit
of the usefulness of these models. With our observations we have begun to reach
the stage where models need to incorporate more of the fundamental physics of
the collapse process, probably including magnetic fields and/or turbulence. In
addition to constraining collapse solutions, our modeling allows the separation
of large-scale emission from compact emission, enabling the probing of the
circumstellar disk component embedded within the protostellar envelope.


title: Search for Antimatter with the AMS Cosmic Ray Detector

abstract:
  Antimatter search results of the Alpha Magnetic Spectrometer (AMS) detector
are presented. About 100 million triggers were collected in the 1998 precursor
flight onboard space shuttle Discovery. This ten day mission exposed the
detector on a 51.7 degrees orbit at an altitude around 350 km. Identification
of charged cosmic rays is achieved by multiple energy loss and time-of-flight
measurements. Bending inside the 0.15 T magnetic volume yields a measurement of
the absolute value of the particle's rigidity. The supplemental knowledge of
the sense of traversal identifies the sign of the charge. In the rigidity range
1 < R < 140 GV no antinucleus at any rigidity was detected, while 2.86 million
helium and 165 thousand heavy nuclei were precisely measured. Hence, upper
limits on the flux ratio antinuclei-to-nuclei are given. Different prior
assumptions on the antimatter spectrum are considered and corresponding limits
are given.


title: The Physical and Chemical Status of Pre-protostellar Core B68

abstract:
  We have investigated the physical and chemical status of the pre-protostellar
core B68. A previous extinction study suggested that the density profile of B68
is remarkably consistent with a Bonnor-Ebert sphere with 2.1 $M_{\odot}$ at 16
K. We mapped B68 in C3H2, CCS, and NH3 with the Deep Space Network (DSN) 70m
telescope at Goldstone. Our results show that the B68 chemical structure is
consistent with that seen in other pre-protostellar cores (L1498, L1544) and is
explained by time dependent chemical models that include depletion. We measured
a kinetic temperature of 11K with NH3 (1,1) and (2,2) spectra. We also show
that B68 is thermally dominated with little contribution from turbulence
support (< 10%). We consider a modified Bonnor-Ebert sphere to include effects
of turbulence and magnetic fields and use it to constrain the uncertainties in
its distance determination. We conclude that the distance to B68 is $\sim$ 95pc
with a corresponding mass of $\sim$ 1.0 $M_{\odot}$. If some magnetic field is
present it can be further away (beyond $\sim$ 100pc) and still satisfy the
density structure of a Bonnor-Ebert sphere. Our observations do not preclude
any instability such as the onset of collapse, or slow contraction, occurring
in the center of the core, which cannot be resolved with our beam size (45").


title: Non-Gaussianity of the derived maps from the first-year WMAP data

abstract:
  We present non-Gaussianity testing on recently-released derived maps from the
first-year WMAP data by Tegmark, de Oliveria-Costa and Hamilton. Our test is
based on a phase mapping technique which has the advantage of testing
non-Gaussianity at separate multipole bands. We show that their
foreground-cleaned map is against the random-phase hypothesis at all 4
multipole bands centered around l = 150, 290, 400 and 500. Their
Wiener-filtered map, on the other hand, is Gaussian for l < 250, and marginally
Gaussian for 224 < l < 350. However, we see the evidence of non-Gaussianity for
l > 350 as we detect certain degrees of phase coupling, hence against the
random-phase hypothesis. Our phase mapping technique is particularly useful for
testing the accuracy of component separation methods.


title:
Characteristics of the structure in the Galactic polarized radio
  background at 350 MHz

abstract:
  Angular power spectra and structure functions of the Stokes parameters Q and
U and polarized intensity P are derived from three sets of radio polarimetric
observations. Two of the observed fields have been studied at multiple
frequencies, allowing determination of power spectra and structure functions of
rotation measure RM as well. The third field extends over a large part of the
northern sky, so that the variation of the power spectra over Galactic latitude
and longitude can be studied. The power spectra of Q and U are steeper than
those of P, probably because a foreground Faraday screen creates extra
structure in Q and U, but not in P. The extra structure in Q and U occurs on
large scales, and therefore causes a steeper spectrum. The derived slope of the
power spectrum of P is the multipole spectral index, and is consistent with
earlier estimates. The multipole spectral index decreases with Galactic
latitude (i.e. the spectrum becomes flatter), but is consistent with a constant
value over Galactic longitude. Power spectra of the rotation measure RM show a
spectral index of about 1, while the structure function of RM is approximately
flat. The structure function is flatter than earlier estimates from polarized
extragalactic sources, which could be due to the fact that extragalactic source
RM probes the complete line of sight through the Galaxy, whereas as a result of
depolarization diffuse radio polarization only probes the nearby ISM.


title:
Trade-off between angular resolution and straylight contamination in CMB
  anisotropy experiments. II. Straylight evaluation

abstract:
  Satellite CMB anisotropy missions and new generation of balloon-borne and
ground experiments, make use of complex multi-frequency instruments at the
focus of a meter class telescope. Between 70 GHz and 300 GHz, where foreground
contamination is minimum, it is extremely important to reach the best trade-off
between the improvement of the angular resolution and the minimization of the
straylight contamination mainly due to the Galactic emission. We focus here, as
a working case, on the 30 and 100 GHz channels of the Planck Low Frequency
Instrument (LFI). We evaluate the GSC introduced by the most relevant Galactic
foreground components for a reference set of optical configurations. We show
that it is possible to improve the angular resolution of 5-7% by keeping the
overall GSC below the level of few microKelvin. A comparison between the level
of straylight introduced by the different Galactic components for different
beam regions is presented. Simple approximate relations giving the rms and
peak-to-peak levels of the GSC are provided. We compare the results obtained at
100 GHz with those at 30 GHz, where GSC is more critical. Finally, we compare
the results based on Galactic foreground templates derived from radio and IR
surveys with those based on WMAP maps including CMB and extragalactic source
fluctuations.


title: Discovery of a z = 6.17 galaxy from CFHT and VLT observations

abstract:
  We report the discovery of a galaxy at a redshift z = 6.17 identified from
deep narrow band imaging and spectroscopic follow-up in one of the CFHT-VIRMOS
deep survey fields at 0226-04. In addition to the existing deep BVRI images of
this field, we obtained a very deep narrow band image at 920 nm with the aim of
detecting Lyalpha emission at redshift ~ 6.5. Spectroscopic follow-up of some
of the candidates selected on the basis of their excess flux in the NB920
filter was performed at the VLT-UT4 with the FORS2 instrument. For one object a
strong and asymmetric emission line associated with a strong break in continuum
emission is identified as Lyalpha at z = 6.17. This galaxy was selected from
its continuum emission in the 920 nm filter rather than for its Lyalpha
emission, in effect performing a Lyman Break detection at z = 6.17. We estimate
a star formation rate of several tens of M/yr for this object, with a velocity
dispersion 400 km/s. The spectroscopic follow-up of other high $z$ galaxy
candidates is on-going.


title:
Discovery and photometry of the binary-lensing caustic-crossing event
  EROS-BLG-2000-5

abstract:
  The EROS collaboration has developed a real time alert system, which was
operational in 1999 and 2000. A very long binary-lensing caustic crossing
event, EROS-BLG-2000-5, was found in the 2000 season and monitored by EROS.
EROS photometric data for this event are presented. The data are well fitted by
the model of An et al. 2002 based on a completely different dataset.
  However, parameters of the model such as the mass ratio or the binary
rotation rate are not very well constrained by EROS data.


title: No Fossil Disk in the T Tauri Multiple System V773 Tau

abstract:
  We present new multi-epoch near-infrared and optical high-angular images of
the V773 Tau pre-main sequence triple system, a weak-line T Tauri (WTTS) system
in which the presence of an evolved, ``fossil'' protoplanetary disk has been
inferred on the basis of a significant infrared excess. Our images reveal a
fourth object bound to the system, V773 Tau D. While it is much fainter than
all other components at 2 micron, it is the brightest source in the system at
4.7 micron. We also present medium-resolution K band adaptive optics
spectroscopy of this object, which is featureless with the exception of a weak
Br gamma emission line. Based on this spectrum and on the spectral energy
distribution of the system, we show that V773 Tau D is another member of the
small class of ``infrared companions'' (IRCs) to T Tauri stars. It is the least
luminous, and probably the least massive, component of the system, as opposed
to most other IRCs, which suggests that numerous low-luminosity IRCs such as
V773 Tau D may still remain to be discovered. Furthermore, it is the source of
the strong IR excess in the system. We therefore reject the interpretation of
this excess as the signature of a fossil (or ``passive'') disk and further
suggest that these systems may be much less frequent than previously thought.
  We further show that V773 Tau C is a variable classical T Tauri star (CTTS)
and that its motion provides a well constrained orbital model. We show that
V773 Tau D can be dynamically stable within this quadruple system if its orbit
is highly inclined. Finally, V773 Tau is the first multiple system to display
such a variety of evolutionary states (WTTS, CTTS, IRC), which may be the
consequence of the strong star-star interactions in this compact quadruple
system.


title:
Power spectrum and intermittency of the transmitted flux of QSOs
  Ly-alpha absorption spectra

abstract:
  Using a set of 28 high resolution, high signal to noise ratio (S/N) QSO
Ly-alpha absorption spectra, we investigate the non-Gaussian features of the
transmitted flux fluctuations, and their effect upon the power spectrum of this
field. We find that the spatial distribution of the local power of the
transmitted flux on scales k >= 0.05 s/km is highly spiky or intermittent. The
probability distribution functions (PDFs) of the local power are long-tailed.
The power on small scales is dominated by small probability events, and
consequently, the uncertainty in the power spectrum of the transmitted flux
field is generally large. This uncertainty arises due to the slow convergence
of an intermittent field to a Gaussian limit required by the central limit
theorem (CLT). To reduce this uncertainty, it is common to estimate the error
of the power spectrum by selecting subsamples with an "optimal" size. We show
that this conventional method actually does not calculate the variance of the
original intermittent field but of a Gaussian field. Based on the analysis of
intermittency, we propose an algorithm to calculate the error. It is based on a
bootstrap re-sampling among all independent local power modes. This estimation
doesn't require any extra parameter like the size of the subsamples, and is
sensitive to the intermittency of the fields. This method effectively reduces
the uncertainty in the power spectrum when the number of independent modes
matches the condition of the CLT convergence.


title:
Wind-Interaction Models for the Early Afterglows of Gamma-Ray Bursts:
  The Case of GRB 021004

abstract:
  Wind-interaction models for gamma-ray burst afterglows predict that the
optical emission from the reverse shock drops below that from the forward shock
within 100s of seconds of the burst. The typical frequency $\nu_m$ of the
synchrotron emission from the forward shock passes through the optical band
typically on a timescale of minutes to hours. Before the passage of $\nu_m$,
the optical flux evolves as $t^{-1/4}$ and after the passage, the decay
steepens to $t^{-(3p-2)/4}$, where $p$ is the exponent for the assumed
power-law energy distribution of nonthermal electrons and is typically $\sim
2$. The steepening in the slope of temporal decay should be readily
identifiable in the early afterglow light curves. We propose that such a
steepening was observed in the R-band light curve of GRB 021004 around day 0.1.
Available data at several radio frequencies are consistent with this
interpretation, as are the X-ray observations around day~1. The early evolution
of GRB 021004 contrasts with that of GRB 990123, which can be described by
emission from interaction with a constant density medium.


title:
The G11.11-0.12 Infrared-Dark Cloud: Anomalous Dust and a Non-Magnetic
  Isothermal Model

abstract:
  The G11.11-0.12 Infrared-Dark Cloud has a filamentary appearance, both in
absorption against the diffuse 8micron Galactic background, and in emission
from cold dust at 850micron. Detailed comparison of the dust properties at
these two wavelengths reveals that standard models for the diffuse interstellar
dust in the Galaxy are not consistent with the observations. The ratio of
absorption coefficients within the cloud is kappa_8/kappa_850 <= 1010, which is
well below that expected for the diffuse ISM where kappa_8/kappa_850 ~ 1700.
This may be due to the formation of ice mantles on the dust and grain
coagulation, both of which are expected within dense regions of molecular
clouds. The 850micron emission probes the underlying radial structure of the
filament. The profile is well represented by a marginally resolved central
region and a steeply falling envelope, with Sigma(r) proportional to r^(-a),
where a <= 3, indicating that G11.11-0.12 is the first observed filament with a
profile similar to that of a non-magnetic isothermal cylinder.


title: Magnetic field evolution in Bok globules

abstract:
  Using the Submillimeter Common-User Bolometer Array (SCUBA) at the James
Clerk Maxwell Telescope (JCMT), we obtained submillimeter polarization maps of
the Bok globules B335, CB230, and CB244 at 850micron.
  We find strongly aligned polarization vectors in the case of B335 and CB230,
indicating a strong coupling of the magnetic field to the dust grains. Based on
the distribution of the orientation and strength of the linear polarization we
derive the magnetic field strengths in the envelopes of the globules. In
agreement with previous submillimeter polarization measurements of Bok globules
we find polarization degrees of several percent decreasing towards the centers
of the cores.
  Furthermore, we compare the magnetic field topology with the spatial
structure of the globules, in particular with the orientation of the outflows
and the orientation of the nonspherical globule cores. In case of the globules
B335 and CB230, the outflows are oriented almost perpendicular to the symmetry
axis of the globule cores. The magnetic field, however, is aligned with the
symmetry axis of the prolate cores in the case of the Bok globules B335 and
CB230, while it is slightly aligned with the outflow axis in the case of the
Bok globules CB26 and CB54. We discuss the possibility that the different
orientations of the magnetic field relative to the outflow directions reflect
different evolutionary stages of the single globules.
  The complete version of this article (containing all figures) can be
downloaded from
http://spider.ipac.caltech.edu/staff/swolf/homepage/public/preprints/mfe.ps.gz


title: Abundances for metal-poor stars with accurate parallaxes I. Basic data

abstract:
  We present element-to-element abundance ratios measured from high dispersion
spectra for 150 field subdwarfs and early subgiants with accurate Hipparcos
parallaxes (errors <20%). For 50 stars new spectra were obtained with the UVES
on Kueyen (VLT UT2), the McDonald 2.7m telescope, and SARG at TNG.
Additionally, literature equivalent widths were taken from the works by Nissen
& Schuster, Fulbright, and Prochaska et al. to complement our data. The whole
sample includes both thick disk and halo stars (and a few thin disk stars);
most stars have metallicities in the range -2<[Fe/H]<-0.6. We found our data,
that of Nissen & Schuster, and that of Prochaska to be of comparable quality;
results from Fulbright scatter a bit more, but they are still of very good
quality and are extremely useful due to the large size of his sample. The
results of the present analysis will be used in forthcoming papers to discuss
the chemical properties of the dissipational collapse and accretion components
of our Galaxy.


title: Evolution of planetesimal discs and planets migration

abstract:
  In this paper, we further develop the model for the migration of planets
introduced in Del Popolo, Gambera and Ercan, and extended to time-dependent
planetesimal accretion disks in Del Popolo and Eksi. More precisely, the
assumption of Del Popolo and Eksi that the surface density in planetesimals is
proportional to that of gas is released. Indeed, the evolution of the radial
distribution of solids is governed by many processes: gas-solid coupling,
coagulation, sedimentation, evaporation/condensation, so that the distribution
of planetesimals emerging from a turbulent disk does not necessarily reflect
that of gas. In order to describe this evolution we use a method developed in
Stepinski and Valageas which, using a series of simplifying assumptions, is
able to simultaneously follow the evolution of gas and solid particles for up
to $10^7 {\rm yr}$. Then, the distribution of planetesimals obtained after
$10^7 {\rm yr}$ is used to study the migration rate of a giant planet through
the migration model introduced in \cite{DP1}. This allows us to investigate the
dependence of the migration rate on the disk mass, on its time evolution and on
the value of the dimensionless viscosity parameter alpha. We find that in the
case of disks having a total mass of $10^{-3}-10^{-1} M_{\odot}$, and
$10^{-4}<\alpha<10^{-1}$, planets can migrate inward over a large distance
while if $M_{\rm d}<10^{-3} M_{\odot}$ the planets remain almost at their
initial position for $\alpha>10^{-3}$ and only in the case $\alpha<10^{-3}$ the
planets move to a minimum value of orbital radius of $\simeq 2 {\rm AU}$.
Moreover, the observed distribution of planets in the period range 0-20 days
can be easily obtained from our model.


title:
Diffusive grain-surface chemistry involving the atoms and diatomic
  molecules of two elements

abstract:
  A model of the grain surface chemistry involving the accretion of atoms of
two different elements, X and Y, and their reactions to form species X_2, XY,
and Y_2 was examined for a wide range of choices for the values of its three
free parameters - the accretion rate of X and Y, the desorption rate of X and
the grain surface sweeping time of Y, all considered relative to the grain
surface sweeping rate of X. Relative production rates of the diatomics were
calculated with five methods involving, respectively, a high-order truncation
of the master equation, a low-order truncation of the master equation, the
standard deterministic rate equation approach, a modified rate equation
approach and a set of approximations which are in some cases appropriate for
accretion dominated chemistry. The accuracies of the relative production rates
calculated with the different methods were assessed for the wide range of model
parameters. The more accurate of the low-truncation master equation
calculations and the standard deterministic rate equation approach gives
results which are in most cases within ten or twenty per cent of the results
given by the high-truncation master equation calculations. For many cases, the
more accurate of the low order truncation and the standard deterministic rate
equation approaches is indicated by a consideration of the average number of
atoms of the two species on the grain's surface.


title: A Bayesian Analysis of the Cepheid Distance Scale

abstract:
  We develop and describe a Bayesian statistical analysis to solve the surface
brightness equations for Cepheid distances and stellar properties. Our analysis
provides a mathematically rigorous and objective solution to the problem,
including immunity from Lutz-Kelker bias. We discuss the choice of priors, show
the construction of the likelihood distribution, and give sampling algorithms
in a Markov Chain Monte Carlo approach for efficiently and completely sampling
the posterior probability distribution. Our analysis averages over the
probabilities associated with several models rather than attempting to pick the
`best model' from several possible models. Using a sample of thirteen Cepheids
we demonstrate the method. We discuss diagnostics of the analysis and the
effects of the astrophysical choices going into the model. We show that we can
objectively model the order of Fourier polynomial fits to the light and
velocity data. By comparison with theoretical models of Bono et al. (2001) we
find that EU Tau and SZ Tau are overtone pulsators, most likely without
convective overshoot. The period-radius and period-luminosity relations we
obtain are shown to be compatible with those in the recent literature.


title: Astrophysical components separation of COBE-DMR 4yr data with FastICA

abstract:
  We present an application of the fast Independent Component Analysis method
to the COBE-DMR 4yr data. Although the signal-to-noise ratio in the COBE-DMR
data is typically $\sim 1$, the approach is able to extract the CMB signal with
high confidence when working at high galactic latitudes. The reconstructed CMB
map shows the expected frequency scaling of the CMB. We fit the resulting CMB
component for the rms quadrupole normalisation Qrms and primordial spectral
index n and find results in excellent agreement with those derived from the
minimum-noise combination of the 90 and 53 GHz DMR channels without galactic
emission correction. Including additional channels (priors) such as the Haslam
map of radio emission at 408 MHz and the DIRBE 140um map of galactic infra-red
emission, the FastICA algorithm is able to both detect galactic foreground
emission and separate it from the dominant CMB signal. Fitting the resulting
CMB component for Qrms and n we find good agreement with the results from
Gorski et al.(1996) in which the galactic emission has been taken into account
by subtracting that part of the DMR signal observed to be correlated with these
galactic template maps. We further investigate the ability of FastICA to
evaluate the extent of foreground contamination in the COBE-DMR data. We
include an all-sky Halpha survey (Dickinson, Davies & Davis 2003) to determine
a reliable free-free template. In particular we find that, after subtraction of
the thermal dust emission predicted by the Finkbeiner, Davis & Schlegel (1999)
model 7, this component is the dominant foreground emission at 31.5 GHz. This
indicates the presence of an anomalous dust correlated component which is well
fitted by a power law spectral shape $\nu^{-\beta}$ with $\beta \sim 2.5$ in
agreement with Banday et al. (2003).


title: About EAS inverse approach

abstract:
  It is shown that using the observed extensive air shower (EAS) electron and
truncated muon size spectra at sea level one can solve the EAS inverse problem
- reconstruction of primary energy spectra and elemental composition, for not
more than 2 kinds of primary nuclei.


title: Gravitational radiation from chiral string cusps

abstract:
  We calculate the gravitational radiation from a cusp of the chiral cosmic
strings as a function of the current on the string in the limit of small values
of the current. The smoothing of the cosmic string cusp due to the presence of
the superconducting current on the string leads to the different behavior of
the gravitational radiation from the cusp as compared with the
non-superconducting (ordinary) string. The difference between the gravitational
energy radiation from the chiral cusp and the ordinary one is proportional to
the value of the current on the string. It is shown that there is a
high-frequency cutoff in the spectrum of the gravitational radiation from the
chiral string. The frequency cutoff depends on the value of the string current.
This effect is crucial for the detection of gravitation wave bursts from cosmic
strings: the rather large current on the string would lower the amplitude of
the incoming signal.


title:
On the Evolution and Appearance of a Surviving Companion after a Type Ia
  Supernova Explosion

abstract:
  One promising method to test progenitor models for Type Ia supernovae is to
identify surviving companion stars in historical supernova remnants. A
surviving companion will have been strongly affected by its interaction with
the supernova ejecta. Here we systematically explore the evolution and
appearance of a typical companion star that has been stripped and heated by the
supernova interaction during the post-impact re-equilibration phase. We show
that, depending on the amount of heating and the amount of mass stripped by the
impact or the previous binary mass transfer, such a star may be significantly
overluminous or underluminous 10^3 - 10^4 yr after the supernova relative to
its pre-supernova luminosity (by up to two orders of magnitude) and discuss the
implications of these results for the strategies to be employed in searches for
such companions.


title:
Interaction of a magnetized pulsar wind with its surroundings. MHD
  simulations of Pulsar Wind Nebulae

abstract:
  Magnetohydrodynamical simulations are presented of a magnetized pulsar wind
interacting directly with the interstellar medium, or, in the case of a
surrounding supernova remnant, with the associated freely expanding ejecta of
the progenitor star. In both cases the simulations show that the pulsar wind
nebula will be elongated due to the dynamical influence of the toroidal
magnetic fields, which confirm predictions from a semi-analytical model
presented by Begelman & Li. The simulations follow the expansion of the pulsar
wind nebula when the latter is bounded by a strong shock and show that the
expansion can be modeled with a standard power-law expansion rate. By
performing different simulations with different magnetization parameters, I
show that the latter weakly correlates with the elongation of the pulsar wind
nebula. The results from the simulations are applied to determine the nature of
the expansion rate of the pulsar wind nebula 3C58. It is shown that there is
both observational and theoretical evidence which supports the scenario in
which the pulsar wind nebula 3C58 has caught up with the reverse shock of the
associated (but undetected) supernova remnant.


title: Intermediate age open clusters: Collinder 110

abstract:
  We present CCD BV photometry of the intermediate age open cluster Collinder
110, a nearby, scarcely populated, and poorly studied system. There is no
literature information on the metallicity, so we tested several possibilities,
and found a slight evidence of sub-solar abundances. Using the synthetic Colour
- Magnitude Diagrams technique we estimate the following parameters: age
between 1.1 and 1.5 Gyr, reddening 0.38 <~ E(B-V) <~ 0.45, distance modulus
(m-M)o between 11.45 and 11.7 if the cluster metallicity is sub-solar.


title:
Discovery of an overdensity of faint red galaxies in the vicinity of the
  z=1.786 radio galaxy 3C 294

abstract:
  We report the discovery of an overdensity of faint red galaxies in the
vicinity of the z=1.786 radio galaxy 3C 294. The overdensity, discovered in a
84 min Ks-band ISAAC/VLT image is significant at the 2.4 sigma level (compared
to the local field density), and overlaps with the extended X-ray emission
around 3C 294 detected with the Chandra X-ray Observatory. The near-infrared
colours of the galaxies making up the overdensity show a large scatter and the
galaxies do not follow a red sequence in the colour magnitude diagram. If the
galaxies are in a cluster at z=1.786 they must be dominated by young stellar
populations with different star-formation histories.


title:
Evidence for local mass accretion rate variations in the disc of GRS
  1915+105

abstract:
  We have analysed 16 observations of class beta of GRS 1915+105 performed with
the Rossi X-ray Timing Explorer. We show the time-resolved evolution (every 16
seconds) of the X-ray spectral parameters during these observations. The three
model independent states (A, B, C) identified in the color-color diagrams are
described here in terms of the more physical (and model dependent) quantities
of the disc and power law components. As in the color analysis, we observe
specific and time-asymmetric transitions between states. Within a single
observation, we identified a loop-like cycle of the power law spectral index
that starts and ends with the ending of state C. There is evidence of local
mass accretion rate variations and mass loss during the long instability
intervals (long state C). This is consistent with simultaneous radio and X-ray
observations that show a one-to-one relation between the long state C and the
radio flares, that occur shortly after it: a loss of disc mass is followed by
an ejection of matter in the jet.


title:
Discovery of X-ray QPOs from an Ultra-luminous X-ray Source in M82:
  Evidence Against Beaming

abstract:
  We report the discovery with the EPIC CCD cameras onboard XMM-Newton of a 54
mHz quasiperiodic oscillation (QPO) in the > 2 keV X-ray flux from an
ultraluminous X-ray source (ULX) in the starburst galaxy M82. This is the first
detection of a QPO in the X-ray flux from an extra-Galactic ULX, and confirms
that the source is a compact object. Based on the QPO strength and previous
Chandra observations it appears likely that the QPO is associated with the most
luminous object in the central region of M82, CXOM82 J095550.2+694047, however,
XMM imaging alone is not sufficient to unambiguously confirm this. The other
plausible candidate is CXOM82 J095551.1+694045, however, the QPO luminosity is
comparable to the peak luminosity of this object in Chandra observations, which
argues against it being the source of the QPO. The QPO had a centroid frequency
of 54.3 +- 0.9 mHz, a coherence of 5, and an amplitude (rms) in the 2 - 10 keV
band of 8.5%. Below 0.2 Hz the power spectrum can be described by a power-law
with index ~1, and amplitude (rms) of 13.5%. The X-ray spectrum requires a
curving continuum, with a disk-blackbody (diskbb) at T = 3.1 keV providing an
acceptable fit. A broad Fe line centered at 6.55 keV is required in all fits,
but the equivalent width (EW) is sensitive to the continuum model. There is no
evidence of a reflection component. The implied bolometric luminosity is 4 - 5
x 10^{40} ergs/sec. Archival Rossi X-ray Timing Explorer (RXTE) pointings at
M82 also show evidence for QPOs in the 50 - 100 mHz frequency range. We discuss
the implications of our findings for models of ULXs.


title:
Distance scale and variable stars in Local Group Galaxies: LMC and
  Fornax

abstract:
  We briefly review our photometric and spectroscopic study of RR Lyrae
variable stars in the bar of the Large Magellanic Cloud (LMC), that allowed us
to reconcile the so-called "short" and "long" distance moduli of the LMC on the
value mod_LMC=18.51 +/- 0.085 mag. Then we present preliminary results from the
photometric study of a 33' x 34' area in the Fornax dwarf spheroidal galaxy
containing the stellar clusters Fornax 3 (NGC 1049) and 6. We identified about
1000 candidate variables in this field of Fornax, and report the first
detection and measure of about 60 RR Lyrae variable stars in the globular
cluster Fornax 3.


title: Minor axis kinematics of 19 S0-Sbc bulges

abstract:
  We present minor axis kinematic profiles for a well-studied sample of 19
early- to intermediate-type disk galaxies. We introduce, for the first time,
the use of single-burst stellar population (SSP) models to obtain stellar
velocities, velocity dispersions and higher order Gauss-Hermite moments (h3,h4)
from galaxy spectra in the near-infrared Ca II triplet region. SSP models,
which employs the synthetic spectra of Vazdekis et al. 2003, provide a means to
address the template-mismatch problem, and are shown to provide as good or
better fits as traditional stellar templates. We anticipate the technique to be
of particular use for high-redshift galaxy kinematics. We give the measurement
of a recently defined CaT* index Cenarro et al. 2001a, and describe the global
properties of the bulge kinematics as derived from the kinematic profiles. We
detect small-amplitude minor-axis rotation, generally due to inner isophotal
twists as a result of slightly triaxial bulges or misaligned inner disks; such
inner features do not show peculiar colors or distinct CaT* index values.
Velocity dispersion profiles, which extend well into the disk region, show a
wide range of slopes. Flattened bulges tend to have shallower velocity
dispersion profiles. The inferred similarity of bulge and disk radial velocity
dispersions supports the interpretation of these bulges as thickened disks.


title: The 2dF Galaxy Redshift Survey: galaxy clustering per spectral type

abstract:
  We have calculated the two-point correlation functions in redshift space,
xi(sigma,pi), for galaxies of different spectral types in the 2dF Galaxy
Redshift Survey. Using these correlation functions we are able to estimate
values of the linear redshift-space distortion parameter, beta = Omega_m^0.6/b,
the pairwise velocity dispersion, a, and the real-space correlation function,
xi(r), for galaxies with both relatively low star-formation rates (for which
the present rate of star formation is less than 10% of its past averaged value)
and galaxies with higher current star-formation activity. At small separations,
the real-space clustering of passive galaxies is very much stronger than that
of the more actively star-forming galaxies; the correlation-function slopes are
respectively 1.93 and 1.50, and the relative bias between the two classes is a
declining function of radius. On scales larger than 10 h^-1 Mpc there is
evidence that the relative bias tends to a constant, b(passive)/b(active) ~ 1.
This result is consistent with the similar degrees of redshift-space
distortions seen in the correlation functions of the two classes -- the
contours of xi(sigma,pi) require beta(active)=0.49+/-0.13, and
beta(passive)=0.48+/-0.14. The pairwise velocity dispersion is highly
correlated with beta. However, despite this a significant difference is seen
between the two classes. Over the range 8-20 h^-1 Mpc, the pairwise velocity
dispersion has mean values 416+/-76 km/s and 612+/-92 km/s for the active and
passive galaxy samples respectively. This is consistent with the expectation
from morphological segregation, in which passively evolving galaxies
preferentially inhabit the cores of high-mass virialised regions.


title:
On the tidal interaction of massive extra-solar planets on highly
  eccentric orbit

abstract:
  In this paper we develop a theory of disturbances induced by the stellar
tidal field in a fully convective slowly rotating planet orbiting on a highly
eccentric orbit around a central star. We show that there are two contributions
to the mode energy and angular momentum gain due to impulsive tidal
interaction: a) 'the quasi-static' contribution which requires dissipative
processes operating in the planet; b) the dynamical contribution associated
with excitation of modes of oscillation. These contributions are obtained
self-consistently from a single set of the governing equations. We calculate a
critical 'equilibrium' value of angular velocity of the planet \Omega_{crit}
determined by the condition that action of the dynamical tides does not alter
the angular velocity at that rotation rate. We show that this can be much
larger than the corresponding rate associated with quasi-static tides and that
at this angular velocity, the rate of energy exchange is minimised. We also
investigate the conditions for the stochastic increase in oscillation energy
that may occur if many periastron passages are considered. We make some simple
estimates of time scale of circularization of initially eccentric orbit due to
tides, using a realistic model of the planet, for orbits withperiods after
circularization typical of those observed for extra-solar planets P_{obs} >
3days. We find that dynamic tides could have produced a very large decrease of
the semi-major axis of a planet with mass of the order of the Jupiter mass
M_{J} and final periods P_{obs} < 4.5days on a time-scale < a few Gyrs. We also
discuss several unresolved issues in the context of the scenario of the orbit
circularization due to dynamic tides.


title: Baryon Oscillations as a Cosmological Probe

abstract:
  Mapping the expansion of the universe gives clues to the underlying physics
causing the recently discovered acceleration of the expansion, and enables
discrimination among cosmological models. We examine the utility of measuring
the rate of expansion, H(z), at various epochs, both alone and in combination
with distance measurements. Due to parameter degeneracies, it proves most
useful as a complement to precision distance-redshift data. Using the baryon
oscillations in the matter power spectrum as a standard rod allows
determination of H(z)/\sqrt{\Omega_mh^2} free of most major systematics, and
thus provides a window on dark energy properties. We discuss the addition of
this data from a next generation galaxy redshift survey such as KAOS to
precision distance information from a next generation supernova survey such as
SNAP. This can provide useful crosschecks as well as lead to improvement on
estimation of a time variation in the dark energy equation of state by factors
ranging from 15-50%.


title: High-speed photometry of the Recurrent Nova IM Normae

abstract:
  The recurrent nova IM Nor is found to have an orbital period of 2.462 h,
shown by periodic dips in brightness. This is only the second recurrent nova
known to have such a short period. We interpret the light curve as largely
produced by a reflection effect from the heated face of the secondary star,
probably with addition of a partial eclipse of the accretion disc.


title: The Halo Distribution of 2dF Galaxies

abstract:
  We use the clustering results obtained by Madgwick et al. (2003) for a sample
of 96,791 2dF galaxies with redshift 0.01 \lt z \lt 0.15 to study the
distribution of late-type and early-type galaxies within dark matter haloes of
different mass. Within the framework of our models, galaxies of both classes
are found to be as spatially concentrated as the dark matter within haloes even
though, while the distribution of star-forming galaxies can also allow for some
steeper profiles, this is drastically ruled out in the case of early-type
galaxies. We also find evidence for morphological segregation, as late-type
galaxies appear to be distributed within haloes of mass scales corresponding to
groups and clusters up to about two virial radii, while passive objects show a
preference to reside closer to the halo centre. If we assume a broken power-law
of the form <N_{gal}(m)>=(m/m_0)^{alpha_1} for m_{cut}\le m<m_0 and
<N_{gal}(m)>=(m/m_0)^{alpha_2} at higher masses to describe the dependence of
the average number of galaxies within haloes on the halo mass, fits to the data
show that star-forming galaxies start appearing in haloes of masses
m_{cut}~10^{11}m_{sun}, much smaller than what is obtained for early-type
galaxies (m_{cut}~10^{12.6}m_{sun}). In the high-mass regime m\ge m_0,
<N_{gal}>$ increases with halo mass more slowly (alpha_2~0.7) in the case of
late-type galaxies than for passive objects which present alpha_2~1.1. We
stress that there is no degeneracy in the determination of the best functional
forms for rho(r) and <N_{gal}>, as they affect the behaviour of the
galaxy-galaxy correlation function on different scales.


title:
Formation of Supermassive Black Holes in Galactic Bulges: A Rotating
  Collapse Model Consistent with the $\mbh-\sigma$ Relation

abstract:
  Motivated by the observed correlation between black hole masses $\mbh$ and
the velocity dispersion $\sigma$ of host galaxies, we develop a theoretical
model of black hole formation in galactic bulges (this paper generalizes an
earlier ApJ Letter). The model assumes an initial state specified by a a
uniform rotation rate $\Omega$ and a density distribution of the form $\rho =
\aeff^2 / 2 \pi G r^2$ (so that $\aeff$ is an effective transport speed). The
black hole mass is determined when the centrifugal radius of the collapse flow
exceeds the capture radius of the central black hole (for Schwarzschild
geometry). This model reproduces the observed correlation between the estimated
black hole masses and the velocity dispersions of galactic bulges, i.e., $\mbh
\approx 10^8 M_\odot (\sigma/200 {\rm km s^{-1}})^4$, where $\sigma = \sqrt{2}
\aeff$. To obtain this normalization, the rotation rate $\Omega \approx 2
\times 10^{15}$ rad/s. The model also defines a bulge mass scale $M_B$. If we
identify the scale $M_B$ with the bulge mass, the model determines the ratio
$\mrat$ of black hole mass to the host mass: $\mrat$ $\approx$ 0.0024
$(\sigma/200 {\rm km s^{-1}})$, again in reasonable agreement with observed
values. In this scenario, supermassive black holes form quickly (in $\sim10^5$
yr) and are born rapidly rotating (with $a/M \sim 0.9$). This paper also shows
how these results depend on the assumed initial conditions; the most important
quantity is the initial distribution of specific angular momentum in the
pre-collapse state.


title:
The Galaxy Angular Correlation Functions and Power Spectrum from the Two
  Micron All Sky Survey

abstract:
  We calculate the angular correlation function of galaxies in the Two Micron
All Sky Survey. We minimize the possible contamination by stars, dust, seeing
and sky brightness by studying their cross correlation with galaxy density, and
limiting the galaxy sample accordingly. We measure the correlation function at
scales between 1-18 arcdegs using a half million galaxies. We find a best fit
power law to the correlation function has a slope of 0.76 and an amplitude of
0.11. However, there are statistically significant oscillations around this
power law. The largest oscillation occurs at about 0.8 degrees, corresponding
to 2.8 h^{-1} Mpc at the median redshift of our survey, as expected in halo
occupation distribution descriptions of galaxy clustering.
  We invert the angular correlation function using Singular Value Decomposition
to measure the three-dimensional power spectrum and find that it too is in good
agreement with previous measurements. A dip seen in the power spectrum at small
wavenumber k is statistically consistent with CDM-type power spectra. A fit of
CDM-type power spectra to k < 0.2 h Mpc^{-1} give constraints of
\Gamma_{eff}=0.116 and \sigma_8=0.96. This suggest a K_s-band linear bias of
1.1+/-0.2. This \Gamma_{eff} is different from the WMAP CMB derived value. On
small scales the power-law shape of our power spectrum is shallower than that
derived for the SDSS. These facts together imply a biasing of these different
galaxies that might be nonlinear, that might be either waveband or luminosity
dependent, and that might have a nonlocal origin.


title:
On the Speed of Gravity and the $v/c$ Corrections to the Shapiro Time
  Delay

abstract:
  Using a relatively simple method, I compute the v/c correction to the
gravitational time delay for light passing by a massive object moving with
speed v. It turns out that the v/c effects are too small to have been measured
in the recent experiment involving Jupiter and quasar J0842+1845 that was used
to measure the speed of gravity.


title: Statistics of Velocity from Spectral Data: Modified Velocity Centroids

abstract:
  We address the problem of studying interstellar turbulence using spectral
line data. We find a criterion when the velocity centroids may provide
trustworthy velocity statistics. To enhance the scope of centroids
applications, we construct a measure that we term ``modified velocity
centroids'' (MVCs) and derive an analytical solution that relates the 2D
spectra of the modified centroids with the underlying 3D velocity spectrum. We
test our results using synthetic maps constructed with data obtained through
simulations of compressible magnetohydrodynamical (MHD) turbulence. We show
that the modified velocity centroids (MVCs) are complementary to the the
Velocity Channel Analysis (VCA) technique. Employed together, they make
determining of the velocity spectral index more reliable and for wider variety
of astrophysical situations.


title: Dynamic cores in hydrostatic disguise

abstract:
  (Abrigded) We discuss the column density profiles of "cores" in 3D SPH
numerical simulations of turbulent molecular clouds. The SPH scheme allows us
to perform a high spatial resolution analysis of the density maxima (cores) at
scales between ~0.003 and 0.3pc. We analyze simulations in three different
physical conditions: large scale driving, small scale driving, and random
Gaussian initial conditions without driving; each one at two different
timesteps: just before self-gravity is turned-on, and when gravity has been
operating such that 5% of the total mass in the box has been accretted into
cores. For this dataset, we perform Bonnor-Ebert fits to the column density
profiles of cores. We find that 65% of the cores can be matched to Bonnor-Ebert
profiles, and of these, 47% correspond to stable equilibrium configurations
with xi_max < 6.5, even though the cores analyzed in the simulations are not in
equilibrium, but instead are dynamically evolving. We also find in some cases
substantial superposition effects when we analyze the projection of the density
structures. As a consequence, different projections of the same core may give
very different values of the BE fits. Finally, we briefly discuss recent
results claiming that Bok globule B68 is in hydrostatic equilibrium, stressing
that they imply that this core is unstable by a wide margin. We conclude that
fitting BE profiles to observed cores is not an unambiguous test of hydrostatic
equilibrium, and that fit-estimated parameters of the BE sphere may differ
significantly from the actual values in the cores.


title: QSO Lifetimes

abstract:
  The QSO lifetime t_Q is one of the most fundamental quantities for
understanding black hole and QSO evolution, yet it remains uncertain by several
orders of magnitude. If t_Q is long, then only a small fraction of galaxies
went through a luminous QSO phase. In contrast, a short lifetime would require
most galaxies today to have undergone a QSO phase in their youth. The current
best estimates or constraints on t_Q from black hole demographics and the
radiative properties of QSOs vary from at least 10^6 to 10^8 years. This broad
range still allows both possibilities: that QSOs were either a rare or a common
stage of galaxy evolution. These constraints also do not rule out the
possibility that QSO activity is episodic, with individual active periods much
shorter than the total active lifetime.
  In the next few years a variety of additional observational constraints on
the lifetimes of QSOs will become available, including clustering measurements
and the proximity effect. These new constraints can potentially determine t_Q
to within a factor of 3 and therefore answer one of the most fundamental
questions in black hole evolution: Do they shine as they grow? This precision
will also test the viability of our current model for accretion physics,
specifically the radiative efficiency and need for super-Eddington luminosities
to explain the black hole population.


title:
The Optical/Near-Infrared Light Curves of SN 2002ap for the First 140
  Days after Discovery

abstract:
  Supernova (SN) 2002ap in M74 was observed in the $UBVRIJHK$ bands for the
first 40 days following its discovery (2002 January 29) until it disappeared
because of solar conjunction, and then in June after it reappeared. The
magnitudes and dates of peak brightness in each band were determined. While the
rate of increase of the brightness before the peak is almost independent of
wavelength, the subsequent rate of decrease becomes smaller with wavelength
from the $U$ to the $R$ band, and is constant at wavelengths beyond $I$. The
photometric evolution is faster than in the well-known ``hypernovae''
SNe~1998bw and 1997ef, indicating that SN 2002ap ejected less mass. The
bolometric light curve of SN 2002ap for the full period of observations was
constructed. The absolute magnitude is found to be much fainter than that of SN
1998bw, but is similar to that of SN 1997ef, which lies at the faint end of the
hypernova population. The bolometric light curve at the early epochs was best
reproduced with the explosion of a C+O star that ejects $2.5~M_\sun$ with
kinetic energy $E_{\rm K}=4\times 10^{51}~{\rm ergs}$. A comparison of the
predicted brightness of SN 2002ap with that observed after solar conjunction
may imply that $\gamma$-ray deposition at the later epochs was more efficient
than in the model. This may be due to an asymmetric explosion.


title: Optical spectrum of the planetary nebula M 2-24

abstract:
  We have obtained medium-resolution, deep optical long-slit spectra of the
bulge planetary nebula (PN) M 2-24. The spectrum covers the wavelength range
from 3610--7330 A. Over two hundred emission lines have been detected. The
spectra show a variety of optical recombination lines (ORLs) from C, N, O and
Ne ions. The diagnostic diagram shows significant density and temperature
variations across the nebula. Our analysis suggests that the nebula has a dense
central emission core. The nebula was thus studied by dividing it into two
regions: 1) an high ionization region characterized by an electron temperature
of T_e=16,300K and a density of logN_e(cm^{-3})=6.3; and 2) a low ionization
region represented by T_e=11,400K and logN_e(cm^{-3})=3.7. A large number of
ORLs from C, N, O and Ne ions have been used to determine the abundances of
these elements relative to hydrogen. In general, the resultant abundances are
found to be higher than the corresponding values deduced from collisionally
excited lines (CELs). This bulge PN is found to have large enhancements in two
{alpha}-elements, magnesium and neon.


title:
Continuous Limit of Multiple Gravitational Lens Effect and Average
  Magnification Factor

abstract:
  We show that the gravitational magnification factor averaged over all
configurations of lenses in a locally inhomogeneous universe satisfy a second
order differential equation with redshift $z$ by taking the continuous limit of
multi-plane gravitational lens equation (the number $N$ of lenses $\to\infty$)
and that the gravitationally magnified Dyer-Roeder distance in a clumpy
universe becomes to that of the Friedmann-Lema\^{\i}tre universe for arbitrary
values of the density parameter $\Omega_{0}$ and of a mass fraction
$\bar{\alpha}$ (smoothness parameter).


title:
Neutrino condensates at center of galaxies as background for the MSW
  mechanism

abstract:
  The possibility is explored that neutrino condensates, possible candidates
for the explanation of very massive objects in galactic centers, could act as
background for the Mikheyev-Smirnov-Wolfeinstein mechanism responsible of
neutrino oscillations. Assuming a simple neutrino star model with constant
density, the lower limit of the mass squared difference of neutrino
oscillations is inferred. Consequences on neutrino asymmetry are discussed.


title: Photoionized OVI absorbers toward the bright QSO HE 0515-4414

abstract:
  We report on detailed Monte Carlo inversion analysis of five OVI systems from
the spectrum of the bright quasar HE 0515-4414 (z_e = 1.71). The associated
system at z_a = 1.697 with the neutral hydrogen column density N(HI)= 4.4
10^{13} cm^{-2} shows pronounced absorption from highly ionized transitions of
CIII, CIV, NV, OVI, SiIV, and probably SVI. We found that only a power law type
ionizing spectrum (J_nu propto nu^{-1.5}) is consistent with the observed
sample of the line profiles, i.e. the system is definitely intrinsic. The
relative metal abundances give almost the solar pattern and the metallicity of
about 5 times solar. The system originates in a thin shell of the line-of-sight
thickness L <= 16 pc. Two OVI systems at z_a = 1.674 ([C/H] = -1.6) and 1.602
([O/H] = -1.1), arising in intervening halos, have linear sizes of L = 3-14 kpc
and 17 kpc, respectively. Absorption systems at z_a = 1.385 ([C/H] = -0.3, L =
1.7-2.5 kpc) and z_a = 1.667 ([C/H] = -0.5, L = 1 kpc) exhibit characteristics
very similar to that observed in metal-enriched high velocity clouds in the
Milky Way.These systems are probably embedded in extremely metal-poor halos
with [C/H] < -2.4 (z_a = 1.667) and [C/H] < -3.7 (z_a = 1.385). We also found
two additional extremely metal-poor Ly-alpha systems at z_a = 1.500 and 1.681
with, respectively, N(HI) = 1.7 10^{15} and 1.8 10^{15} cm^{-2} and [C/H] <
-4.0 and <-3.0, - an indication that the distribution of metals in the
metagalactic medium is utterly patchy. Our results show that the ionization
states in the analyzed OVI absorbers, ranging from z = 1.4 to 1.7, can be
maintained by photoionization only and that the fraction of the shock-heated
hot gas with temperature T > 10^5 K is negligible in these systems.


title:
An S2 Fluorescence Model for Interpreting High-Resolution Cometary
  Spectra. I. Model Description and Initial Results

abstract:
  A new versatile model providing S2 fluorescence spectrum as a function of
time is developed with the aim of interpreting high resolution cometary
spectra. For the S2 molecule, it is important to take into account both
chemical and dynamic processes because S2 has a short lifetime and is confined
in the inner coma where these processes are most important. The combination of
the fluorescence model with a global coma model allows for the comparison with
observations of column densities taken through an aperture and for the analysis
of S2 fluorescence in different parts of the coma. Moreover, the model includes
the rotational structure of the molecule. Such a model is needed for
interpreting recent high spectral resolution observations of cometary S2. A
systematic study of the vibrational-rotational spectrum of S2 is undertaken,
including relevant effects, such as non-equilibrium state superposition and the
number density profile within the coma due to dynamics and chemistry, to
investigate the importance of the above effects on the scale length and
abundance of S2 in comets.


title: SMAUG: a new technique for the deprojection of galaxy clusters

abstract:
  This paper presents a new technique for reconstructing the spatial
distributions of hydrogen, temperature and metal abundance of a galaxy cluster.
These quantities are worked out from the X-ray spectrum, modeled starting from
few analytical functions describing their spatial distributions. These
functions depend upon some parameters, determined by fitting the model to the
observed spectrum. We have implemented this technique as a new model in the
XSPEC software analysis package. We describe the details of the method, and
apply it to work out the structure of the cluster A1795. We combine the
observation of three satellites, exploiting the high spatial resolution of
Chandra for the cluster core, the wide collecting area of XMM-Newton for the
intermediate regions and the large field of view of Beppo-SAX for the outer
regions. We also test the validity and precision of our method by i) comparing
its results with those from a geometrical deprojection, ii) examining the
spectral residuals at different radii of the cluster and iii) reprojecting the
unfolded profiles and comparing them directly to the measured quantities. Our
analytical method yields the parameters defining the spatial functions directly
from the spectra. Their explicit knowledge allows a straightforward derivation
of other indirect physical quantities like the gravitating mass, as well as a
fast and easy estimate of the profiles uncertainties.


title:
Entropy scaling in galaxy clusters: insights from an XMM-Newton
  observation of the poor cluster A1983

abstract:
  An XMM-Newton observation of the cool (kT=2.1 keV) cluster A1983, at z=0.044,
is presented. Gas density and temperature profiles are calculated for the inner
500 h_{50}^{-1} kpc (~0.35 r_200). The outer regions of the surface brightness
profile are well described with a beta model with beta=0.74, but the central
regions require the introduction of a second component. The temperature profile
is flat at the exterior with a slight dip towards the centre. The total mass
profile, calculated assuming hydrostatic equilibrium, is consistent with an NFW
profile, but with a low concentration parameter c=3.75 +/- 0.74. The M/L_B
ratio profile shows that, at large scale, light traces mass to a reasonable
extent, and the M/L_B ratio at 0.35 r_200 is consistent with the trends with
mass observed in the optical. The M_Fe/L_B ratio is about two times less than
that observed for a cluster at 5 keV. The gas mass fraction rises rapidly to
level off at ~200 kpc; the value at 0.35 r_200 is ~8%. The scaling properties
of the emission measure profile are consistent with the empirical relation
\mgas \propto \Tx^{1.94}, and not with the self-similar relation \mgas \propto
\Tx^{1.5}. Comparison of the entropy profile of A1983 with that of the hot
cluster A1413 shows that the profiles are well scaled using the empirically
determined relation S \propto \Tx^{0.65}, suggesting that the slope of the S-T
relation is shallower than in the self-similar model. The form of the entropy
profiles is remarkably similar, and there is no sign of a larger isentropic
core in the cooler cluster. These data provide powerful agruments against
preheating models. In turn, there is now increasing observational support for a
trend of f_gas with system mass, which may go some way towards explaining the
observed scaling behaviour. (Abridged.)


title: A multi-wavelength test of the FR~I - BL Lac unifying model

abstract:
  We collect multi-wavelength measurements of the nuclear emission of 20 low
luminosity FR I radio-galaxies to test the viability of the FR I - BL Lac
unifying model. Although poorly sampled, the Spectral Energy Distributions
(SED) of FR Is are consistent with the double peaked shape characteristic of BL
Lacs. Furthermore while the distribution of the FR Is in the broad-band
spectral index planes shows essentially no overlap with the regions where HBL
and LBL are located, this can be simply due to the effects of relativistic
beaming. More quantitatively, deriving the beaming Doppler factor of a given
radio-galaxy from its X-ray luminosity ratio with respect to BL Lacs with
similar extended radio luminosity, we find that i) the luminosity in all bands,
ii) the value of the spectral indices, iii) the slope of the X-ray spectrum,
iv) the overall SED shape, may be all simultaneously reproduced. However, the
corresponding jet bulk Lorentz factors are significantly smaller than those
derived for BL Lacs from other observational and theoretical considerations.
This suggests to consider a simple variant of the unification scheme that
allows for the presence of a velocity structure in the jet.


title:
OB Stellar Associations in the Large Magellanic Cloud: Survey of young
  stellar systems

abstract:
  The method developed by Gouliermis et al. (2000, Paper I), for the detection
and classification of stellar systems in the LMC, was used for the
identification of stellar associations and open clusters in the central area of
the LMC. This method was applied on the stellar catalog produced from a scanned
1.2m UK Schmidt Telescope Plate in U with a field of view almost 6.5 deg x 6.5
deg, centered on the Bar of this galaxy. The survey of the identified systems
is presented here followed by the results of the investigation on their spatial
distribution and their structural parameters, as were estimated according to
our proposed methodology in Paper I. The detected open clusters and stellar
associations show to form large filamentary structures, which are often
connected with the loci of HI shells. The derived mean size of the stellar
associations in this survey was found to agree with the average size found
previously by other authors, for stellar associations in different galaxies.
This common size of about 80 pc might represent a universal scale for the star
formation process, whereas the parameter correlations of the detected loose
systems support the distinction between open clusters and stellar associations.


title: X-rays from Clusters of Galaxies

abstract:
  The X-ray emission from clusters of galaxies enables them to be used as good
cosmological probes and as an example for massive galaxy formation. The gas
mass fraction in clusters should be a universal standard which by means of
Chandra observations enables Omega_m to be determined to better than 15 per
cent accuracy. Future observations of its apparent variation with redshift will
enable Omega_Lambda to be measured. The interplay of radiative cooling and
heating in cluster cores may reveal the dominant processes acting during the
formation of the baryonic part of massive galaxies.


title: The First CO Map of a Low Surface Brightness Galaxy

abstract:
  Using the Owens Valley Radio Observatory Millimeter-Wavelength Array (OVRO)
we have obtained the first CO map of a low surface brightness (LSB) galaxy. The
studied galaxy, UGC 01922, was chosen for these observations because both of
its previous CO detection with the IRAM 30m telescope and its classification as
a Malin 1 `cousin' - an LSB galaxy with M_HI > 10^10 Msol. The OVRO map
detected approximately 65% of the CO(1-0) flux found earlier with the single
dish measurements, giving a detected gas mass equivalent to M_H2 = 1.1X10^9
Msol. The integrated gas peak lies at the center of the galaxy and coincides
with both the optical and 1.4 GHz continuum emission peaks. The molecular gas
extends well beyond the OVRO beam size (~4'' or 3 kpc), covering ~25% of the
optical bulge. In all, perhaps the most remarkable aspect of this map is its
unexceptional appearance. Given that it took over ten years to successfully
detect molecular gas in any low surface brightness system, it is surprising
that the appearance and distribution of UGC 01922's CO is similar to what would
be expected for a high surface brightness galaxy in the same morphological
class.


title:
The fate of star clusters near the Galactic center I: Analytic
  considerations

abstract:
  A star cluster in a galactic nucleus sinks toward the galactic center due to
dynamical friction. As it spirals inward, the cluster loses mass due to stellar
evolution, relaxation driven evaporation, and tidal stripping, eventually
dissolving in the galactic tidal field. We model the inspiral of dense young
star clusters near the center of our Galaxy to study the extent of the region
of parameter space in which the cluster can reach the inner parsec of the
Galaxy within a few million years. Since we neglect changes in cluster
structure due to internal evolution, the present study is most applicable to
star clusters less than about one initial relaxation time old. We find that
only star clusters with initial masses $\apgt 10^5$ {\msun} can reach the
Galactic center from an initial distance of $\apgt 60$ pc within one initial
relaxation time or a few million years, whichever is smaller.


title:
Decaying neutron propagation in the Galaxy and the Cosmic Ray anisotropy
  at 1 EeV

abstract:
  We study the cosmic ray arrival distribution expected from a source of
neutrons in the galactic center at energies around 1 EeV and compare it with
the anisotropy detected by AGASA and SUGAR. Besides the point-like signal in
the source direction produced by the direct neutrons, an extended signal due to
the protons produced in neutron decays is expected. This associated proton
signal also leads to an excess in the direction of the spiral arm. For
realistic models of the regular and random galactic magnetic fields, the
resulting anisotropy as a function of the energy is obtained. We find that for
the anisotropy to become sufficiently suppressed below E\sim 10^{17.9}eV, a
significant random magnetic field component is required, while on the other
hand, this also tends to increase the angular spread of the associated proton
signal and to reduce the excess in the spiral arm direction. The source
luminosity required in order that the right ascension anisotropy be 4% for the
AGASA angular exposure corresponds to a prediction for the point-like flux from
direct neutrons compatible with the flux detected by SUGAR. We also analyse the
distinguishing features predicted for a large statistics southern observatory.


title:
Chandra reveals a black-hole X-ray binary within the ultraluminous
  supernova remnant MF 16

abstract:
  We present evidence, based on Chandra ACIS-S observations of the nearby
spiral galaxy NGC 6946, that the extraodinary X-ray luminosity of the MF 16
supernova remnant actually arises in a black-hole X-ray binary. This conclusion
is drawn from the point-like nature of the X-ray source, its X-ray spectrum
closely resembling the spectrum of other ultraluminous X-ray sources thought to
be black-hole X-ray binary systems, and the detection of rapid hard X-ray
variability from the source. We briefly discuss the nature of the hard X-ray
variability, and the origin of the extreme radio and optical luminosity of MF
16 in light of this identification.