title:
Reconstructing Cepheid Light Curve with Fourier Techniques I: The
  Fourier Expansion and Interrelations

abstract:
  Fourier decomposition is a well established technique used in stellar
pulsation. However the quality of reconstructed light curves using this method
is reduced when the observed data have uneven phase coverage. We use simulated
annealing techniques together with Fourier decomposition to improve the quality
of the Fourier decomposition for many OGLE LMC fundamental mode Cepheids. This
method restricts the range that Fourier amplitudes can take. The ranges are
specified by well sampled Cepheids in the Galaxy and Magellanic Clouds.
  We also apply this method to reconstructing Cepheid light curves observed by
the HST. These typically consist of 12 V band and 4 I band points. We employ a
direct Fourier fit to the 12 V band points using the simulated annealing method
mentioned above and explicitly derive and use Fourier interrelations to
reconstruct the I band light curve. We discuss advantages and drawbacks of this
method when applied to HST Cepheid data over existing template methods.
Application of this method to reconstruct the light curves of Cepheids observed
in NGC 4258 shows that the derived Cepheid distance ($\mu_0=29.38\pm0.06$,
random error) is consistent with its geometrical distance
($\mu_0=29.28\pm0.09$) derived from observations of water maser.


title:
Radio Galaxies and the Acceleration of the Universe Beyond a Redshift of
  One

abstract:
  Radio galaxies provide a means to determine the coordinate distance,the
luminosity distance, the dimensionless luminosity distance, or the angular size
distance to sources with redshifts as large as two. Dimensionless coodinate
distances for 55 supernovae and 20 radio galaxies are presented and discussed
here. The radio galaxy results are consistent with those obtained using
supernovae, suggesting that neither method is plagued by unknown systematic
errors. The acceleration parameter q(z) and the expansion rate H(z) or
dimensionless expansion rate E(z) can be determined directly from the data
without having to make assumptions regarding the nature or evolution of the
``dark energy.'' The expansion rate E(z) can be determined from the first
derivative of the dimensionless coordinate distance, and the acceleration
parameter can be determined from a combination of the first and second
derivatives of the dimensionless coordinate distance. A model-independent
determination of E(z) will allow the properties and redshift evolution of the
``dark energy'' to be determined, and a model-independent determination of q(z)
will allow the redshift at which the universe transitions from acceleration to
deceleration to be determined directly. Determination of E(z) and q(z) may also
elucidate possible systematic errors in the determinations of the dimensionless
coordinate distances.


title: Cosmological Magnetogenesis driven by Radiation Pressure

abstract:
  The origin of large scale cosmological magnetic fields remains a mystery,
despite the continuous efforts devoted to that problem. We present a new model
of magnetic field generation, based on local charge separation provided by an
anisotropic and inhomogeneous radiation pressure. In the cosmological context,
the processes we explore take place at the epoch of the reionisation of the
Universe. Under simple assumptions, we obtain results (i) in terms of the order
of magnitude of the field generated at large scales and (ii) in terms of its
power spectrum. The amplitudes obtained (B ~ 8.10^(-6) micro-Gauss) are
considerably higher than those obtained in usual magnetogenesis models and
provide suitable seeds for amplification by adiabatic collapse and/or dynamo
during structure formation.


title: ISOCAM view of the starburst galaxies M82, NGC253, and NGC1808

abstract:
  We present results of mid-infrared 5.0-16.5 micron spectrophotometric imaging
of the starburst galaxies M82, NGC253, and NGC1808 from the ISOCAM instrument
on board the Infrared Space Observatory. The mid-infrared spectra of the three
galaxies are very similar in terms of features present. The > 11 micron
continuum attributed to very small dust grains (VSGs) exhibits a large spread
in intensity relative to the short-wavelength emission. We find that the 15
micron dust continuum flux density correlates well with the fine-structure
[ArII] 6.99 micron line flux and thus provides a good quantitative indicator of
the level of star formation activity. By contrast, the 5-11 micron region
dominated by emission from polycyclic aromatic hydrocarbons (PAHs) has a nearly
invariant shape. Variations in the relative intensities of the PAH features are
nevertheless observed, at the 20%-100% level. We illustrate extinction effects
on the shape of the mid-infrared spectrum of obscured starbursts, emphasizing
the differences depending on the applicable extinction law and the consequences
for the interpretation of PAH ratios and extinction estimates. The relative
spatial distributions of the PAH, VSG, and [ArII] 6.99 micron emission between
the three galaxies exhibit remarkable differences. The < 1 kpc size of the
mid-infrared source is much smaller than the optical extent of our sample
galaxies and 70%-100% of the IRAS 12 micron flux is recovered within the ISOCAM
< 1.5 arcmin squared field of view, indicating that the nuclear starburst
dominates the total mid-infrared emission while diffuse light from quiescent
disk star formation contributes little.


title: Do clusters of galaxies rotate?

abstract:
  It is shown that the number of members, $N_A$, and the linear radius of the
Abell clusters at $z<0.18$ increase with redshift. The increase is caused by
observational selection: the number of rich and large clusters is small in the
nearby small volume of space, while poor and small clusters are not detected at
high distances. Besides, the numbers of clusters with different ellipticities
are about the same at all distances, though in the case of cosmological
evolution the number of the more elliptical clusters increases with decrease of
distance. It means that clusters do not evolve dynamically. The dependences of
the X-ray emission detection rate and the temperature of the X-ray emission on
redshift are consequences of the dependence of $N_A$ on redshift. The radial
velocity dispersion of the less elliptical clusters is higher than that of the
elongated ones. This shows that galaxies in a cluster move preferentially along
the large axis of the cluster. The space density is not changing in the
considered range of $z$. Movement of galaxies along the cluster elongation may
be explained by rotation along the large axis of a cluster.


title: Galactic Cosmic Ray Nuclei as a Tool for Astroparticle Physics

abstract:
  Cosmic Ray nuclei in the energy range 100 MeV/nuc - 100 GeV/nuc provide
crucial information about the physical properties of the Galaxy. They can also
be used to answer questions related to astroparticle physics. This paper
reviews the results obtained in this direction, with a strong bias towards the
work done by the authors at {\sc lapth}, {\sc isn} and {\sc iap}. The
propagation of these nuclei is studied quantitatively in the framework of a
semi-analytical two-zone diffusion model taking into account the effect of
galactic wind, diffuse reacceleration and energy losses. The parameters of this
model are severely constrained by an analysis of the observed B/C ratio. These
constraints are then used to study other species such as radioactive species
and light antinuclei. Finally, we focus on the astroparticle subject and we
study the flux of antiprotons and antideuterons that might be due to neutralino
annihilations or primordial black hole evaporation. The question of the spatial
origin of all these species is also addressed.


title:
Spatial Origin of Galactic Cosmic Rays in Diffusion Models: I- Standard
  sources in the Galactic disk

abstract:
  The propagation of Galactic Cosmic Ray nuclei having energies between 100
MeV/nuc and several PeV/nuc is strongly believed to be of diffusive nature. The
particles emitted by a source located in the disk do not pervade the whole
Galaxy, but are rather confined to a smaller region whose spatial extension is
related to the height of the diffusive halo, the Galactic wind and the
spallation rate. Following the pioneering work of Jones (1978), this paper
presents a general study on the spatial origin of cosmic rays, with a
particular attention to the role of spallations and Galactic wind. This
question is different, and to a certain extent disconnected, from that of the
origin of cosmic rays. We find the regions of the disk from which a given
fraction of cosmic rays detected in the Solar neighborhood were emitted
(f-surfaces). After a general study, we apply the results to a realistic source
distribution, with the propagation parameters obtained in our previous
systematic analysis of the observed secondary-to-primary ratios Maurin et al
(2002). The shape and size of these f-surfaces depend on the species as well as
on the values of the propagation parameters. For some of the models preferred
by our previous analysis (i.e. large diffusion slope $\delta$), these
f-surfaces are small and in some extreme cases only a fraction of a percent of
the whole Galactic sources actually contribute to the Solar neighborhood Cosmic
Ray flux. Moreover, a very small number of sources may be responsible for more
than 15 % of the flux detected in the Solar neighborhood. This may point
towards the necessity to go beyond the approximations of both homogeneity and
stationarity. Finally, the observed primary composition is dominated by sources
within a few kpc.


title:
Spatial Origin of Galactic Cosmic Rays in Diffusion Models: II- Exotic
  Primary Cosmic Rays

abstract:
  In a companion paper, we investigated the question of the spatial origin of
the cosmic rays detected in the Solar neighborhood, in the case of standard
sources located in the Galactic disk. There are some reasons to believe that
there may also be a large number of sources located in the halo, for example if
the Galactic dark matter is made of supersymmetric particles or if Primordial
Black Holes are present. These exotic sources could enhance the $\bar{p}$,
$\bar{d}$ or positrons above the standard background, indicating the existence
of new physics. The spatial distribution of these hypothetical sources, though
an important ingredient to evaluate these exotic signals, is poorly known. The
aim of this paper is to point out that this discussion should not be
disconnected from that of the propagation properties in the Galaxy. More
precisely, we determine the regions of the halo from which a significant
fraction f of cosmic rays antiprotons and antideuterons detected in the Solar
neighborhood were emitted (we refer to these regions as f-volumes), for
different sets of propagation parameters consistent with B/C data, as derived
in Maurin et al (2002). It is found that some of them lead to rather small
f-volumes, indicating that the exotic cosmic rays could have a local origin (in
particular for a small halo or a large Galactic convective wind), coming from
the solar neighborhood or the Galactic center region. It is also found that the
dark matter density enhancement (spike) due to the accretion around the central
supermassive black hole gives a negligible contribution to the exotic charged
particle signal on Earth. The case of electrons and positrons is also
discussed.


title: The end of unified dark matter?

abstract:
  Despite the interest in dark matter and dark energy, it has never been shown
that they are in fact two separate substances. We provide the first strong
evidence that they are separate by ruling out a broad class of so-called
unified dark matter models that have attracted much recent interest. We find
that they produce oscillations or exponential blowup of the matter power
spectrum inconsistent with observation. For the particular case of generalized
Chaplygin gas models, 99.999% of the previously allowed parameter space is
excluded, leaving essentially only the standard Lambda-CDM limit allowed.


title: Black Hole Masses in Three Seyfert Galaxies

abstract:
  We analyze published reverberation mapping data for three Seyfert galaxies
(NGC 3227, NGC 3516, and NGC 4593) to refine the mass estimate for the
supermassive black hole in the center of each object. Treatment of the data in
a manner more consistent with other large compilations of such masses allows us
to more securely compare our results to wider samples of data, e.g., in the
investigation of the M_bh-sigma relationship for active and quiescent galaxies.


title:
RR Lyrae Stars in the Halo: Tracers of Streams of Debris of Disrupted
  Galaxies

abstract:
  We discuss the first part of a survey for RR Lyrae variables in the galactic
halo that is being made with the 1m Schmidt telescope at the Venezuelan
National Observatory. So far the survey has discovered 497 variables in 380 sq.
degrees, lying from 4 to 60 kpc from the Sun. It has detected three
statistically significant clumps of variables, which shows that outer halo does
not have smooth density contours. One clump is located at 50 kpc from the
galactic center, and it is probably tidal debris from the Sagittarius dwarf
spheroidal galaxy. A second structure, at 17 kpc from the galactic center,
appears to be due to the tidal disruption of the globular cluster Pal 5. The
third group, at 19 kpc, is not related with any known globular cluster or dwarf
galaxy. The little that is known about its properties is consistent with it
being debris from a disrupted galaxy.


title: WFPC2 CTE Characterization

abstract:
  The limiting factor of the accuracy of WFPC2 photometry is the CTE loss,
which has increased to the level of 50% or more for faint stars at the top of
the chips. I describe recent work on characterizing this effect, and provide
improved equations for CTE correction. I also examine issues affecting
background measurement, which if not done correctly can introduce artificial
nonlinearities into photometry.


title: Iron-Rich Ejecta in the Supernova Remnant DEM L71

abstract:
  Chandra X-ray observations of DEM L71, a supernova remnant (SNR) in the Large
Magellanic Cloud (LMC), reveal a clear double shock morphology consisting of an
outer blast wave shock surrounding a central bright region of reverse-shock
heated ejecta. The abundances of the outer shock are consistent with LMC
values, while the ejecta region shows enhanced abundances of Si, Fe, and other
species. However, oxygen is not enhanced in the ejecta; the Fe/O abundance
ratio there is more than 5 times the solar ratio. Based on the relative
positions of the blast wave shock and the contact discontinuity in the context
of SNR evolutionary models, we determine a total ejecta mass of approximately
1.5 solar masses. Ejecta mass estimates based on emission measures derived from
spectral fits are subject to considerable uncertainty due to lack of knowledge
of the true contribution of hydrogen continuum emission. Maximal mass
estimates, i.e., assuming no hydrogen, result in 1.5 solar masses of Fe and
0.24 solar masses of Si. Under the assumption that an equal quantity of
hydrogen has been mixed into the ejecta, we estimate 0.8 solar masses of Fe and
0.12 solar masses of Si. These characteristics support the view that in DEM L71
we see Fe-rich ejecta from a Type Ia SN several thousand years after explosion.


title: Generalized Shock Solutions for Hydrodynamic Black Hole Accretion

abstract:
  For the first time, {\it all} available pseudo-Schwarzschild potentials are
exhaustively used to investigate the possibility of shock formation in
hydrodynamic, invicid, black hole accretion discs. It is shown that a
significant region of parameter space spanned by important accretion parameters
allows shock formation for flow in {\it all} potentials used in this work. This
leads to the conclusion that the standing shocks are essential ingredients in
accretion discs around non-rotating black holes in general. Using a complete
general relativistic framework, equations governing multi-transonic black hole
accretion and wind are also formulated and solved in the Schwarzschild metric.
Shock solutions for accretion flow in various pseudo potentials are then
compared with such general relativistic solutions to identify which potential
is the best approximation of Schwarzschild space-time as far as the question of
shock formation in black hole accretion discs is concerned.


title:
The Spatial, Ionization, and Kinematic Conditions of the z=1.39 Damped
  Ly-alpha Absorber in Q0957+561 A,B

abstract:
  We examined the sizes of the absorption clouds in a z=1.3911 damped Ly-alpha
absorber (DLA) in the double image lensed quasar Q0957+561 A,B (separation 135
pc at the absorber redshift). Using HIRES/Keck spectra, we studied the MgII
2796,2803 doublet, FeII multiplet, and MgI 2853 transition in absorption. We
defined six "clouds" in the system of sightline A and seven clouds in the
system of sightline B. An examination of the N(v) profiles, using the apparent
optical depth method, reveals no clear physical connection between the clouds
in A and those in B. The observed column density ratios of all clouds is
log[N(MgI)/N(FeII)] ~ -2 across the full velocity range in both systems and
also spatially (in both sightlines). This is a remarkable uniformity not seen
in Lyman limit systems. The uniformity of the cloud properties suggests that
the multiple clouds are not part of a "halo". Based upon photoionization
modeling, we constrain the ionization parameters in the range -6.2 < log(U) <
-5.1, where the range brackets known abundance ratio and dust depletion
patterns. The inferred cloud properties are densities of 2 < n_H < 20 cm^-3,
and line of sight sizes of 1 < D < 25 pc. The masses of the clouds in system A
are 10 < M/M_sun < 1000 and in system B are 1 < M/M_sun < 60 for spherical
clouds. For planar clouds, the upper limits are 400 M_sun and 160 M_sun for A
and B, respectively. We favor a model of the absorber in which the DLA region
itself is a single cloud in thiscomplex, which could be a parcel of gas in a
galactic ISM. A spherical cloud of ~10 pc would be limited to one of the
sightlines (A) and imply a covering factor less than 0.1 for the DLA complex.
We infer that the DLA cloud properties are consistent with those of lower
density, cold clouds in the Galactic interstellar medium.


title:
Estimating Star Formation Rates from Infrared and Radio Luminosities:
  The Origin of the Radio-Infrared Correlation

abstract:
  I have assembled a diverse sample of galaxies from the literature with
far-ultraviolet (FUV), optical, infrared (IR) and radio luminosities to explore
the calibration of radio-derived and IR-derived star formation (SF) rates, and
the origin of the radio-IR correlation. By comparing the 8-1000 micron IR,
which samples dust-reprocessed starlight, with direct stellar FUV emission, I
show that the IR traces most of the SF in luminous L* galaxies but traces only
a small fraction of the SF in faint ~0.01 L* galaxies. If radio emission were a
perfect SF rate indicator, this effect would cause easily detectable curvature
in the radio-IR correlation. Yet, the radio-IR correlation is nearly linear.
This implies that the radio flux from low-luminosity galaxies is substantially
suppressed, compared to brighter galaxies. This is naturally interpreted in
terms of a decreasing efficiency of non-thermal radio emission in faint
galaxies. Thus, the linearity of the radio-IR correlation is a conspiracy: both
indicators underestimate the SF rate at low luminosities. SF rate calibrations
which take into account this effect are presented, along with estimates of the
random and systematic error associated with their use.


title: Proper Motions in Compact Symmetric Objects

abstract:
  We discuss recent measurements of proper motions of the hotspots of Compact
Symmetric Objects. Source expansion has been detected in ten CSOs so far and
all these objects are very young (<3000 years). In a few sources ages have also
been estimated from energy supply and spectral ageing arguments and these
estimates are comparable. This argues that these sources are close to
equipartition and that standard spectral ageing models apply. Proper motions
studies are now constraining hotspot accelerations, side-to-side motions and
differences in hotspot advance speeds between the two hotspots within sources.
Although most CSOs are young sources their evolution is unclear. There is
increasing evidence that in some objects the CSO structure represents a new
phase of activity within a recurrent source.


title:
The redshift determination of GRB 990506 and GRB 000418 with the
  Echellete Spectrograph Imager on Keck

abstract:
  Using the Echellete Spectrograph Imager (ESI) on the Keck II 10-m telescope
we have measured the redshifts of the host galaxies of gamma-ray bursts GRB
990506 and GRB 000418, z=1.30658 +/- 0.00004 and 1.1181 +/- 0.0001,
respectively. Thanks to the excellent spectral resolution of ESI we resolved
the [O II] 3727 doublet in both cases. The measured redshift of GRB 990506 is
the highest known for a dark burst GRB, though entirely consistent with the
notion that dark and non-dark bursts have a common progenitor origin. The
relative strengths of the [O II], He I, [Ne III], and H gamma emission lines
suggest that the host of GRB 000418 is a starburst galaxy, rather than a LINER
or Seyfert 2. Since the host of GRB 000418 has been detected at sub-millimeter
wavelengths these spectroscopic observations suggest that the sub-millimeter
emission is due to star-formation (as opposed to AGN) activity. The [O
II]-derived unobscured star-formation rates are 13 and 55 M_solar/yr for the
hosts of GRB 990506 and GRB 000418, respectively. In contrast, the
star-formation rate of the host of GRB 000418 derived from sub-millimeter
observations is twenty times larger.


title: A new aspects of physics of a photon gas

abstract:
  Bose-Einstein condensation (BEC) and evaporation of transverse photons from
the Bose condensate is studied in the case when the density of plasma does not
change. The generation of the longitudinal photons (photonikos) by the
transverse photons (photons) in terms of the Cherenkov type of radiation in a
uniform plasma is demonstrated. The Bogoliubov energy spectrum is derived for
photonikos. A new physical phenomena of the "Compton" scattering type in
nonlinear photon gas is discussed. To this end, a new version of the Pauli
equation in the wavevector representation is derived. The formation of
Bose-Einstein condensate and evaporation of photons from the condensate is
investigated by means of the newly derived Fokker-Planck equation for
photonikos. The relevance of this work to recent discovery of black hole X-ray
jets is pointed out.

categories: astro-ph physics.gen-ph physics.optics physics.plasm-ph


title: The minimum period problem in cataclysmic variables

abstract:
  We investigate if consequential angular momentum losses (CAML) or an
intrinsic deformation of the donor star in CVs could increase the CV bounce
period from the canonical theoretical value ~65 min to the observed value
$P_{min} \approx77$ min, and if a variation of these effects in a CV population
could wash out the theoretically predicted accumulation of systems near the
minimum period (the period spike). We are able to construct suitably mixed CV
model populations that a statisticial test cannot rule out as the parent
population of the observed CV sample. However, the goodness of fit is never
convincing, and always slightly worse than for a simple, flat period
distribution. Generally, the goodness of fit is much improved if all CVs are
assumed to form at long orbital periods. The weighting suggested by King,
Schenker & Hameury (2002) does not constitute an improvment if a realistically
shaped input period distribution is used. Put your abstract here.


title: The Lyalpha Forest Around High Redshift Galaxies

abstract:
  Motivated by the relative lack of neutral hydrogen around Lyman Break
Galaxies deduced from recent observations, we investigate the properties of the
Lyalpha forest around high redshift galaxies. The study is based on improved
numerical SPH simulations implementing, in addition to standard processes, a
new scheme for multiphase and outflow physics description. Although on large
scales our simulations reproduce a number of statistical properties of the IGM
(because of the small filling factor of shock-heated gas), they underpredict
the Lyalpha optical depth decrease inside 1 Mpc/h of the galaxies by a factor
of ~2. We interpret this result as due to the combined effect of infall
occurring along the filaments, which prevents efficient halo gas clearing by
the outflow, and the insufficient increase of (collisional) hydrogen ionization
produced by the temperature increase inside the hot, outflow-carved bubble.
Unless an observational selection bias is present, we speculate that local
photoionization could be the only viable explanation to solve the puzzle.


title: Understanding the LMXB X2127+119 in M15

abstract:
  We present HST UV observations of the high-inclination low mass X-ray binary
AC211 (X2127+119), which is located in the globular cluster M15 (NGC 7078). We
have discovered a CIV P Cygni profile in this system, which confirms the
existence of an outflow from AC211. The outflow velocity as measured from the P
Cygni profile is 1500km/s. We calculate that the mass lost through this wind is
too small to support a large period derivative as favoured by Homer & Charles
(1998). Using new X-ray observations we have revised the ephemeris for AC211
and we find no evidence in support of a period derivative. The UV spectrum
exhibits several absorption features due to O, Si and C. The very strong HeII
line at 1640A is not seen to modulate strongly with orbital phase, suggesting
its origin lies in the outer parts of the system. In contrast, the eclipse of
the UV continuum is short compared with the X-ray and optical eclipses.


title:
Oxygen isotopic ratios in first dredge-up red giant stars and nuclear
  reaction rate uncertainties revisited

abstract:
  We describe a general yet simple method to analyse the propagation of nuclear
reaction rate uncertainties in a stellar nucleosynthesis and mixing context.
The method combines post-processing nucleosynthesis and mixing calculations
with a Monte Carlo scheme. With this approach we reanalyze the dependence of
theoretical oxygen isotopic ratio predictions in first dredge-up red giant
branch stars in a systematic way. Such predictions are important to the
interpretation of pre-solar Al_2 O_3 grains from meteorites. The reaction rates
with uncertainties were taken from the NACRE compilation (Angulo etal., 1999).
We include seven reaction rates in our systematic analysis of stellar models
with initial masses from 1 to 3 M_sun. We find that the uncertainty of reaction
rate for reaction O18(p,alpha)N15 typically causes an error in the theoretical
O16/O18 ratio of about +20/-5 per cent. The error of the O16/O17 prediction is
+-10 to 40 per cent depending on the stellar mass, and is persistently
dominated by the comparatively small uncertainty of the O16(p,gamma)F17
reaction. With the new estimates on reaction rate uncertainties by the NACRE
compilation, the p-capture reactions O17(p,alpha)N14 and O17(p,gamma)F18 have
virtually no impact on theoretical predictions for stellar mass <= 1.5 M_sun.
However, this is not the case for masses > 1.5 M_sun, where core mixing and
subsequent envelope mixing interact. In these cases where core mixing
complicates post-dredge-up surface abundances, uncertainty in other reactions
have a secondary but noticeable effect on surface abundances.


title: Performance Characteristics of TreePM codes

abstract:
  We present a detailed analysis of the error budget for the TreePM method for
doing cosmological N-Body simulations. It is shown that the choice of filter
for splitting the inverse square force into short and long range components
suggested in Bagla (2002) is close to optimum. We show that the error in the
long range component of the force contributes very little to the total error in
force. Errors introduced by the tree approximation for the short range force
are different from those for the inverse square force, and these errors
dominate the total error in force. We calculate the distribution function for
error in force for clustered and unclustered particle distributions. This gives
an idea of the error in realistic situations for different choices of
parameters of the TreePM algorithm. We test the code by simulating a few power
law models and checking for scale invariance.


title: A parallel implementation of a new fast algorithm for N-body simulations

abstract:
  A new, momentum preserving fast Poisson solver for N-body systems sharing
effective O(N) computational complexity, has been recently developed by Dehnen
(2000, 2002). We have implemented the proposed algorithms in a Fortran-90 code,
and parallelized it by a domain decomposition using the MPI routines. The code
has been applied to intensive numerical investigations of galaxy mergers, in
particular focusing on the possible origin of some of the observed scaling
relations of elliptical galaxies. We found that the Fundamental Plane is
preserved by an equal mass merging hierarchy, while it is not in a scenario
where galaxies grow by accretion of smaller stellar systems. In addition, both
the Faber-Jackson and Kormendy relations are not reproduced by our simulations.


title:
High-resolution re-simulations of massive DM halos and the Fundamental
  Plane of galaxy clusters

abstract:
  Pure N-body high-resolution re-simulations of 13 massive dark matter halos in
a Lambda-CDM cosmology are presented. The resulting sample is used to
investigate the physical origin of the Fundamental Plane, ``Faber-Jackson'',
and ``Kormendy'' relations observed for nearby galaxy clusters. In particular,
we focus on the role of dissipationless hierarchical merging in establishing or
modifying these relations. Contrarily to what found in the case of the
Faber-Jackson and Kormendy relations for galaxies (see Londrillo, Nipoti and
Ciotti, this conference), dissipationless merging on cluster scales produces
scaling relations remarkably similar to the observed ones. This suggests that
gas dissipation plays a minor role in the formation of galaxy clusters, and the
hierarchical merger scenario is not at odd with the observed regularity of
these systems.


title: Swirling astrophysical flows - efficient amplifiers of Alfven waves

abstract:
  We show that a helical shear flow of a magnetized plasma may serve as an
efficient amplifier of Alfven waves. We find that even when the flow is purely
ejectional (i.e., when no rotation is present) Alfven waves are amplified
through the transient, shear-induced, algebraic amplification process. Series
of transient amplifications, taking place sequentially along the flow, may
result in a cascade amplification of these waves. However, when a flow is
swirling or helical (i.e., some rotation is imposed on the plasma motion),
Alfven waves become subject to new, much more powerful shear instabilities. In
this case, depending on the type of differential rotation, both usual and
parametric instabilities may appear. We claim that these phenomena may lead to
the generation of large amplitude Alfven waves and the mechanism may account
for the appearance of such waves in the solar atmosphere, in accretion-ejecion
flows and in accretion columns. These processes may also serve as an important
initial (linear and nonmodal) phase in the ultimate subcritical transition to
MHD Alfvenic turbulence in various kinds of astrophysical shear flows.


title:
Elliptical galaxies interacting with the cluster tidal field: origin of
  the intracluster stellar population

abstract:
  With the aid of simple numerical models, we discuss a particular aspect of
the interaction between stellar orbital periods inside elliptical galaxies (Es)
and the parent cluster tidal field (CTF), i.e., the possibility that
collisionless stellar evaporation from Es is an effective mechanism for the
production of the recently discovered intracluster stellar populations (ISP).
These very preliminary investigations, based on idealized galaxy density
profiles (such as Ferrers density distributions) show that, over an Hubble
time, the amount of stars lost by a representative galaxy may sum up to the 10%
of the initial galaxy mass, a fraction in interesting agreement with
observational data. The effectiveness of this mechanism is due to the fact that
the galaxy oscillation periods near its equilibrium configurations in the CTF
are of the same order of stellar orbital times in the external galaxy regions.


title: The First Compact Objects in the $\Lambda$-dominated Universe

abstract:
  We calculate the evolution of a low-mass ($M \le 10^5 M_{\odot}$) spherically
symmetric density perturbation in the $\Omega_b h^2=0.02$, $\Omega_M =0.35$,
$\Omega_{\Lambda}=0.65$, $h=0.72$ Universe. The results are compared with the
ones that assume no cosmological constant and the flat, dark matter dominated
Universe. We include thermal processes and non-equilibrium chemical evolution
of the collapsing gas. We find that direct formation of bound objects with such
masses by $z=8$ is unlikely so in fact they may form only through fragmentation
of greater objects. This is in stark contrast to the $\Omega=1$ pure CDM
cosmology, where low-mass objects form abundantly at redshits $z>10$.


title:
Helium and Hydrogen Line Ratios and The Stellar Content of Compact HII
  Regions

abstract:
  We present observations and models of the behaviour of the HI and HeI lines
between 1.6 and 2.2um in a small sample of compact HII regions. As in our
previous papers on planetary nebulae, we find that the `pure' 1.7007um
4^3D-3^3P and 2.16475um 7^(3,1)G-4^(3,1)F HeI recombination lines behave
approximately as expected as the effective temperature of the central exciting
star(s) increases. However, the 2.058um 2^1P-2^1S HeI line does not behave as
the model predicts, or as seen in planetary nebulae. Both models and planetary
nebulae showed a decrease in the HeI 2^1P-2^1S/HI Br gamma ratio above an
effective temperature of 40000K. The compact HII regions do not show any such
decrease. The problem with this line ratio is probably due to the fact that the
photoionisation model does not account correctly for the high densities seen in
these HII regions, and that we are therefore seeing more collisional excitation
of the 2^1P level than the model predicts. It may also reflect some deeper
problem in the assumed model stellar atmospheres. In any event, although the
normal HeI recombination lines can be used to place constraints on the
temperature of the hottest star present, the HeI 2^1P-2^1S/HI Br gamma ratio
should not be used for this purpose in either Galactic HII regions or in
starburst galaxies, and conclusions from previous work using this ratio should
be regarded with extreme caution. We also show that the combination of the near
infrared `pure' recombination line ratios with mid-infrared forbidden line data
provides a good discriminant of the form of the far ultraviolet spectral energy
distribution of the exciting star(s). From this we conclude that CoStar models
are a poor match to the available data for our sources, though the more recent
WM-basic models are a better fit.


title: Kinematics of the disk population in the GAIA era

abstract:
  GAIA data will create a precise 3-dimensional map of the Galaxy, providing
positional information, radial velocities, luminosity, temperature and chemical
composition of a representative sample of stars. Here we present a new
implementation of the Padova Galaxy Model, where kinematics simulations are
included. A few examples of application to GAIA science are discussed, in
particular concerning radial velocities determinations of the thin and thick
disk.


title: Influence of internal energy on the stability of relativistic flows

abstract:
  A set of simulations concerning the influence of internal energy on the
stability of relativistic jets is presented. Results show that perturbations
saturate when the amplitude of the velocity perturbation approaches the speed
of light limit. Also, contrary to what predicted by linear stability theory,
jets with higher specific internal energy appear to be more stable.


title: An Automated System to Classify Stellar Spectra I

abstract:
  Analyses of stellar spectra often begin with the determination of a number of
parameters that define a model atmosphere. This work presents a prototype for
an automated spectral classification system that uses a 15 nm-wide region
around Hbeta, and applies to stars of spectral types A to K with normal (scaled
solar) chemical composition. The new tool exploits synthetic spectra based on
plane-parallel flux-constant model atmospheres. The input data are high
signal-to-noise spectra with a resolution greater than about 0.1 nm.
  The output parameters are forced to agree with an external scale of effective
temperatures based on the Infrared Flux Method. The system is fast -- a
spectrum is classified in a few seconds-- and well-suited for implementation on
a web server. We estimate upper limits to the 1-sigma random error in the
retrieved effective temperatures, surface gravities, and metallicities as 100
K, 0.3 dex, and 0.1 dex, respectively.


title: Stability of the viscously spreading ring

abstract:
  We study analytically and numerically the stability of the pressure-less,
viscously spreading accretion ring. We show that the ring is unstable to small
non-axisymmetric perturbations. To perform the perturbation analysis of the
ring we use a stretching transformation of the time coordinate. We find that to
1st order, one-armed spiral structures, and to 2nd order additionally two-armed
spiral features may appear. Furthermore, we identify a dispersion relation
determining the instability of the ring. The theoretical results are confirmed
in several simulations, using two different numerical methods. These
computations prove independently the existence of a secular spiral instability
driven by viscosity, which evolves into persisting leading and trailing spiral
waves. Our results settle the question whether the spiral structures found in
earlier simulations of the spreading ring are numerical artifacts or genuine
instabilities.


title: Core-Collapse Supernovae and Neutron Star Kicks

abstract:
  Recent observations have revealed many new puzzles related to core-collapse
supernovae, including the formation of magnetars and black holes and their
possible GRB connections. We review our current understanding of the origin of
pulsar kicks and supernova asymmetry. It is argued that neutron star kicks are
intimately connected to the other fundamental parameters of young neutron
stars, such as the initial spin and magnetic field strength.


title:
On second-order superhorizon perturbations in multifield inflationary
  models

abstract:
  We present a method for the study of second-order superhorizon perturbations
in multi field inflationary models with non trivial kinetic terms. We utilise a
change of coordinates in field space to separate isocurvature and adiabatic
perturbations generalizing previous results. We also construct second order
gauge invariant variables related to them. It is found that with an arbitrary
metric in field space the isocurvature perturbation sources the gravitational
potential on long wavelengths even for ``straight'' trajectories. The potential
decouples from the isocurvature perturbations if the background fields'
trajectory is a geodesic in field space. Taking nonlinear effects into account
shows that, in general, the two types of perturbations couple to each other.
This is an outline of a possible procedure to study nonlinear and non-Gaussian
effects during multifield inflation.


title:
The [FeII]1.644micron emission in M82 and NGC253: Is it a measure of the
  supernova rate?

abstract:
  We present HST/NICMOS [FeII]1.644micron, Pa-alpha (1.87micron) and continuum
images of the starburst galaxies M82 and NGC253 at an unprecedented spatial
resolution. In both galaxies we detect [FeII] compact sources superimposed on a
diffuse background in the disk of the galaxies together with a component above
and below the plane of the galaxy. The radio and [FeII] emissions perpendicular
to the disk of M82 show a remarkable similarity to each other, suggesting that
both emissions originate in shocks from supernova explosions. We find a spatial
correspondence between bright compact [FeII] emitting regions and the location
of radio supernova remnants (SNR) for approximately 30-50% of radio SNRs in M82
and NGC253. This lack of a one-to-one correspondence, more than being
indicative of a different origin for the radio and [FeII] emission in
starbursts, suggests two populations of SNRs: an older population(<10^4yr)
traced by the [FeII] emission and a younger population (a few hundred years
old) traced by the radio SNRs. We therefore conclude that the [FeII] emission
in starburst galaxies provides a good estimate of the supernova activity. Using
our newly determined [FeII] luminosities (corrected for extinction) of M82 and
NGC253, we reevaluate the calibration of the supernova rate in terms of the
[FeII] luminosity for starburst galaxies.


title: Four Partially Baked Results

abstract:
  D Whysong and I have been carrying out a mid-IR survey of 3C radio galaxies
to see which have IR-excesses, interpretable as hidden Type-1 AGN. Mostly due
to relentless bad weather, we have a modest collections of observations so far.
However, we can say with confidence that some radio galaxies are true kinetic,
nonthermal emitters, with negligible energetic contributifrom a visible or
hidden Big Blue Bump. To make up for the modest collection of mid-IR
observations so far, we also present a new spectropolarimetric discovery
regarding the underlying shape of the quasar Big Blue Bump in the Balmer Edge
region, a fairly radical view of quasar reddening, and a bit of Keck adaptive
optics data on Cygnus A and the ultraluminous infrared galaxy NGC6240.


title: Massive Variability Search and Monitoring by OGLE and ASAS

abstract:
  OGLE and ASAS are long term observing projects operated by the Warsaw
University Observatory at the Las Campanas site in Chile. OGLE is currently
monitoring almost 200 million stars in the Galactic Bulge and the Magellanic
Clouds, and has detected so far almost 1,000 events of gravitational
microlensing with the dedicated 1.3-meter telescope. ASAS uses several very
small instruments to monitor all southern sky for variability down to
approximately 14 magnitude. A total of almost 300 thousand variable stars were
discovered so far by the two projects, and all photometric data is available on
the WWW. Both projects aim at real time recognition and verification of all new
phenomena in the sky. OGLE is likely to discover planets by 2003 and stellar
mass black holes by 2004-2005. All OGLE and ASAS data is made public domain as
soon as possible, and may be used by a Virtual Observatory.


title: The Equivalence between Different Dark (Matter) Energy Scenarios

abstract:
  We have shown that the phenomenological models with a cosmological constant
of the type $\Lambda=\beta(\frac{\ddot R}{R})$ and $\Lambda=3\alpha H^2$, where
$R$ is the scale factor of the universe and $H$ is the Hubble constant, are
equivalent to a quintessence model with a scalar ($\phi$) potential of the form
$V\propto \phi^{-n}, n$ = constant. The equation of state of the cosmic fluid
is described by these parameters ($\alpha, \beta, n$) only. The equation of
state of the cosmic fluid (dark energy) can be determined by any of these
parameters. The actual amount of dark energy will define the equation of state
of the cosmic fluid. All of the three forms can give rise to cosmic
acceleration depending the amount of dark energy in the universe.


title: Dependence of the Inner DM Profile on the Halo Mass

abstract:
  I compare the density profile of dark matter (DM) halos in cold dark matter
(CDM) N-body simulations with 1 Mpc, 32 Mpc, 256 Mpc and 1024 Mpc box sizes. In
dimensionless units the simulations differ only for the initial power spectrum
of density perturbations. I compare the profiles when the most massive halos
are composed of about 10^5 DM particles. The DM density profiles of the halos
in the 1 Mpc box show systematically shallower cores with respect to the
corresponding halos in the 32 Mpc simulation that have masses, M_{dm}, typical
of the Milky Way and are fitted by a NFW profile. The DM density profiles of
the halos in the 256 Mpc box are consistent with having steeper cores than the
corresponding halos in the 32 Mpc simulation, but higher mass resolution
simulations are needed to strengthen this result. Combined, these results
indicate that the density profile of DM halos is not universal, presenting
shallower cores in dwarf galaxies and steeper cores in clusters. Physically the
result sustains the hypothesis that the mass function of the accreting
satellites determines the inner slope of the DM profile. In comoving
coordinates, r, the profile \rho_{dm} \propto 1/(X^\alpha(1+X)^{3-\alpha}),
with X=c_\Delta r/r_\Delta, r_\Delta is the virial radius and \alpha
=\alpha(M_{dm}), provides a good fit to all the DM halos from dwarf galaxies to
clusters at any redshift with the same concentration parameter c_\Delta ~ 7.
The slope, \gamma, of the outer parts of the halo appears to depend on the
acceleration of the universe: when the scale parameter is a=(1+z)^{-1} < 1, the
slope is \gamma ~ 3 as in the NFW profile, but \gamma ~ 4 at a > 1 when
\Omega_\Lambda ~ 1 and the universe is inflating.[abridged]


title:
The Las Campanas Infrared Survey. IV. The Photometric Redshift Survey
  and the Rest-frame R-band Galaxy Luminosity Function at 0.5 <= z <= 1.5

abstract:
  (Abridged) We present rest-frame R-band galaxy luminosity function
measurements for three different redshift ranges: 0.5<=z<=0.75, 0.75<=z<=1.0,
and 1.0<=z<=1.5. Our measurements are based on photometric redshifts for ~3000
H-band selected galaxies with apparent magnitudes 17<=H<=20 from the Las
Campanas Infrared Survey. We show that our photometric redshifts are accurate
with an RMS dispersion between the photometric and spectroscopic redshifts of
\sigma_z/(1+z)~0.08. Using galaxies identified in the Hubble Deep Field South
and Chandra Deep Field South regions, we find, respectively, that (7.3\pm 0.2)
% and (16.7\pm 0.4)% of the H<=20 galaxies are at z>=1. We first demonstrate
that the systematic uncertainty inherent in the luminosity function
measurements due to uncertainties in photometric redshifts is non-negligible
and therefore must be accounted for. We then develop a technique to correct for
this systematic error by incorporating the redshift error functions of
individual galaxies in the luminosity function analysis. The redshift error
functions account for the non-gaussian characteristics of photometric redshift
uncertainties. They are the products of a convolution between the corresponding
redshift likelihood functions of individual galaxies and a Gaussian
distribution function that characterizes template-mismatch variance. We
demonstrate, based on a Monte Carlo simulation, that we are able to completely
recover the bright end of the intrinsic galaxy luminosity function using this
technique. Finally, we calculate the luminosity function separately for the
total H-band selected sample and for a sub-sample of early-type galaxies that
have a best-fit spectral type of E/S0 or Sab from the photometric redshift
analysis.


title: Cosmology for Scalar Fields with Negative Potentials and w <-1

abstract:
  We study the cosmology of canonically normalized scalar fields that lead to
an equation of state parameter of w_\phi=p_\phi/\rho_\phi<-1 without violating
the weak energy condition: rho=\Sigma_i\rho_i \geq 0 and \rho_i+p_i\geq 0. This
kind of behavior requires a negative scalar potential V, widely predicted in
particle physics. We show that the energy density \rho_\phi=E_k+V takes
negative values with an equation of state with w_\phi < -1. However, the net
effect of the $\phi$ field on the scale factor is to decelerate it giving a
total equation of state parameter w=p/\rho> w_b=p_b/\rho_b, where \rho_b stands
for any kind of energy density with -1\leq w_b \leq 1. The fact that
\rho_\phi<0 allows, at least in principle, to have a small cosmological
constant or quintessence today as the cancellation of high energy scales such
as the electroweak or susy breaking scale. While V is negative |\rho_\phi| is
smaller than the sum of all other energy densities regardless of the functional
form of the potential V. We show that the existence of a negative potential
leads, inevitable, to a collapsing universe, i.e. to a would be "big crunch".
In this picture we would still be living in the expanding universe.


title: r-Process Abundance Signatures

abstract:
  Abundance observations indicate the presence of rapid-neutron capture (i.e.,
r-process) elements in old Galactic halo and globular cluster stars. These
observations demonstrate that the earliest generations of stars in the Galaxy,
responsible for neutron-capture synthesis and the progenitors of the halo
stars, were rapidly evolving. Abundance comparisons among large numbers of
stars provide clues about the nature of neutron-capture element synthesis both
during the earliest times and throughout the history of the Galaxy. In
particular, these comparisons suggest differences in the way the heavier
(including Ba and above) and lighter neutron capture elements are synthesized
in nature. Understanding these differences will help to identify the
astrophysical site (or sites) of and conditions in the r-process. The abundance
comparisons also demonstrate a large star-to-star scatter in the
neutron-capture/iron ratios at low metallicities- which disappears with
increasing [Fe/H]- and suggests an early, chemically unmixed and inhomogeneous
Galaxy. The very recent neutron-capture element observations indicate that the
early phases of Galactic nucleosynthesis, and the associated chemical
evolution, are quite complex, with the yields from different (progenitor)
mass-range stars contributing to different chemical mixes. Stellar abundance
comparisons suggest a change from the r-process to the slow neutron capture
(i.e., s-) process at higher metallicities (and later times) in the Galaxy.
Finally, the detection of thorium and uranium in halo and globular cluster
stars offers a promising, independent age-dating technique that can put lower
limits on the age of the Galaxy and thus the Universe.


title: Cosmic Shear Review

abstract:
  We present an overview of the cosmic shear results obtained so far. We focus
on the 2-point statistics only. Evidences supporting the cosmological origin of
the measured signal are reviewed, and issues related to various systematics are
discussed.


title:
A 6.3-h superhump in the cataclysmic variable TV Columbae: the longest
  yet seen

abstract:
  We present results from a two week multi-longitude photometric campaign on TV
Col held in 2001 January. The data confirm the presence of a permanent positive
superhump found in re-examination of extensive archive photometric data of TV
Col. The 6.3-h period is 15 per cent longer than the orbital period and obeys
the well known relation between superhump period excess and binary period. At
5.5-h, TV Col has an orbital period longer than any known superhumping
cataclysmic variable and, therefore, a mass ratio which might be outside the
range at which superhumps can occur according to the current theory. We suggest
several solutions for this problem.


title: An Inside Out View of Bubbles

abstract:
  Fast stellar winds can sweep up ambient media and form bubbles. The evolution
of a bubble is largely controlled by the content and physical conditions of the
shocked fast wind in its interior. This hot gas was not clearly observed until
the recent advent of Chandra and XMM-Newton X-ray observatories. To date,
diffuse X-ray emission has been unambiguously detected from two circumstellar
bubbles blown by WR stars, four planetary nebulae, and two superbubbles blown
by young clusters. Model fits to the X-ray spectra show that the circumstellar
bubbles are dominated by hot gas with low temperatures (<= 3x10^6 K), while the
interstellar bubbles contain significant fractions of hotter gas (>= 5x10^6 K).
In all cases, large discrepancies in the X-ray luminosity are found between
observations and conventional models of bubbles. Future theoretical models of
bubbles need to re-examine the validity of heat conduction and take into
account realistic microscopic processes such as mass loading from dense
clumps/knots and turbulent mixing. Chandra ACIS-S observation of NGC 6888 will
shed light on these astrophysical processes.


title: HST/WFPC2 Morphologies of K-selected Extremely Red Galaxies

abstract:
  We selected 115 extremely red objects (EROs) from deep HST WFPC2 archive data
combined with ground-based K-band images, with (F814W - Ks) >= 4mag, K-band SNR
>= 5, and a median limiting Ks magnitude of 18.7mag, over a corresponding area
of 228 sq. arcminutes, for a morphological study of the ERO galaxy population.
The survey covered a total of 409 sq. arcminutes over 77 separate WFPC2 fields.
This is the first complete sample of bright EROs with high resolution HST
morphologies. From a visual morphological classification, we find that 30+/-5%
of our EROs have morphologies consistent with a pure bulge or bulge-dominated
galaxy (equivalent to E/S0), while disks comprise 64+/-$7% of the sample. Only
6% of the EROs remained unclassifiable. Mergers or strongly interacting
systems, which includes sources from both classes, make up 17+/-4% of the full
sample. The quantitative MDS profile fitting is consistent with these results.
These results highlight the complex nature of optical/near-IR color selected
EROs. The dominant component of our sample is comprised of disks, not spheroids
or strongly interacting systems like HR10. Using Bruzual & Charlot SED models,
we investigated population differences in EROs selected by their (I-K) vs.
(R-K) colors and found that I-band based surveys preferentially select systems
with prolonged star formation. Real differences in the surface densities of
EROs in R-band and I-band based surveys may reflect this color selection
effect, complicating the comparisons between and interpretations on the nature
of the ERO population. <Abstract truncated>


title: PKS B1400-33: an unusual radio relic in a poor cluster

abstract:
  We present new arcminute resolution radio images of the low surface
brightness radio source PKS B1400-33 that is located in the poor cluster Abell
S753. The observations consist of 330 MHz VLA, 843 MHz MOST and 1398 and 2378
MHz ATCA data. These new images, with higher surface brightness sensitivity
than previous observations, reveal that the large scale structure consists of
extended filamentary emission bounded by edge-brightened rims. The source is
offset on one side of symmetrically distributed X-ray emission that is centered
on the dominant cluster galaxy NGC 5419. PKS B1400-33 is a rare example of a
relic in a poor cluster with radio properties unlike those of most relics and
halos observed in cluster environments.
  The diffuse source appears to have had an unusual origin and we discuss
possible mechanisms. We examine whether the source could be re-energized relic
radio plasma or a buoyant synchrotron bubble that is a relic of activity in NGC
5419. The more exciting prospect is that the source is relic plasma preserved
in the cluster gaseous environment following the chance injection of a radio
lobe into the ICM as a result of activity in a galaxy at the periphery of the
cluster.


title: Compressible MHD Turbulence: Mode Coupling, Anisotropies and Scalings

abstract:
  Compressible turbulence, especially the magnetized version of it,
traditionally has a bad reputation with researchers. However, recent progress
in theoretical understanding of incompressible MHD as well as that in
computational capabilities enabled researchers to obtain scaling relations for
compressible MHD turbulence. We discuss scalings of Alfven, fast, and slow
modes in both magnetically dominated (low $\beta$) and gas pressure dominated
(high $\beta$) plasmas. We also show that the new regime of MHD turbulence
below viscous cutoff reported earlier for incompressible flows persists for
compressible turbulence. Our recent results show that this leads to density
fluctuations. New understanding of MHD turbulence is likely to influence many
key astrophysical problems.


title:
On the Formation of Accretion-powered Galactic and Extra-galactic
  Outflows

abstract:
  Though widely observed to be emanating from a variety of astrophysical
sources, the underlying physical mechanism behind the formation of galactic and
extragalactic outflows is still enshrouded in a veil of mystery. In addition,
it has not been possible to calculate accurately the amount of matter expelled
in these events. In this article we present a {\em non-self-similar analytical
model}, which, for the first time, we believe is able to explain the outflow
formation phenomenon as well as compute the mass outflow rate by simultaneously
solving the equations governing the exact transonic accretion and outflow. Our
model predicts the dependence of this rate on various flow parameters as well
as the {\em exact} location from where the outflows are launched.


title: Casimir energy in finite expanding universes: a prelude

abstract:
  We present the Green's functions that are the solutions of the massive
Klein-Gordon equation for a scalar field with non-minimal coupling to
gravitation for several static and expanding cosmological models. An important
feature of such functions is that they can be used to study the appearence of a
Casimir energy in models of the universe with compact spatial sections.


title:
Constraint on intergalactic dust from thermal history of intergalactic
  medium

abstract:
  This Letter investigates the amount of dust in the intergalactic medium
(IGM). The dust photoelectric heating can be the most efficient heating
mechanism in the IGM where the density is very small and there are a lot of
hard ultraviolet photons. Comparing the observational thermal history of IGM
with a theoretical one taking into account the dust photoelectric heating, we
can put an upper limit on the dust-to-gas ratio, ${\cal D}$, in the IGM. Since
the rate of the dust photoelectric heating depends on the size of dust, we find
the following results: If the grain size is $\ga 100$ \AA, ${\cal D}$ at $z
\sim 3$ is $\la 1/100$ Galactic value corresponding to $\Omega_{\rm dust}^{\rm
IGM}\la 10^{-5}$. On the other hand, if the grain size is as small as $\sim 10$
\AA, ${\cal D}$ is $\la 1/1000$ Galactic value corresponding to $\Omega_{\rm
dust}^{\rm IGM}\la 10^{-6}$.


title:
Absorption Line Survey of H3+ toward the Galactic Center Sources I. GCS
  3-2 and GC IRS3

abstract:
  We present high-resolution (R = 20000) spectroscopy of H3+ absorption toward
the luminous Galactic center sources GCS 3-2 and GC IRS 3. With the efficient
wavelength coverage afforded by Subaru IRCS, six absorption lines of H3+ have
been detected in each source from 3.5 to 4.0 um, three of which are new. In
particular the 3.543 um absorption line of the R(3, 3)^l transition arising
from the metastable (J, K) = (3, 3) state has been tentatively detected for the
first time in the interstellar medium, where previous observations of H3+ had
been limited to absorption lines from the lowest levels: (J, K) = (1, 0) of
ortho-H3+ and (1, 1) of para-H3+. The H3+ absorption toward the Galactic center
takes place in dense and diffuse clouds along the line of sight as well as the
molecular complex close to the Galactic nucleus. At least four kinematic
components are found in the H3+ absorption lines. We suggest identifications of
the velocity components with those of HI, CO, and H2CO previously reported from
radio and infrared observations. H3+ components with velocities that match
those of weak and sharp CO and H2CO lines are attributed to diffuse clouds. Our
observation has revealed a striking difference between the absorption profiles
of H3+ and CO, demonstrating that the spectroscopy of H3+ provides information
complementary to that obtained from CO spectroscopy. The tentative detection of
the R(3, 3)^l line and the non-detection of spectral lines from other J > 1
levels provide observational evidence for the metastability of the (3, 3)
level, which is theoretically expected. This suggests that other metastable J =
K levels with higher J may also be populated.


title: Clustering around radio galaxies at z~1.5

abstract:
  The importance of studying old elliptical galaxies at redshift z ~ 1.5 is
reviewed, considering both what can be learned by extending studies of the
evolution of cluster galaxy scaling relations to earlier cosmic epochs, and the
age-dating of old elliptical galaxies at high redshifts. Following this, the
first results are provided of an on-going project to find such distant
elliptical galaxies, through an investigation of the cluster environments of
powerful radio sources with redshifts 1.44 < z < 1.7. These studies show a
considerable excess of red galaxies in the radio sources fields, with the
magnitudes (K >~ 17.5) and colours (R-K > 4) expected of old passively evolving
galaxies at the radio source redshift. The red galaxy overdensities are found
on two different scales around the radio sources; a pronounced small-scale peak
at radial distances of <~ 150 kpc, and a weaker large-scale excess extending
out to 1 - 1.5 Mpc. The presence and richness of these red galaxy excesses
varies considerably from source to source. An interpretation of these results
is provided.


title: The Enigma of AA Dor

abstract:
  AA Dor (LB 3459) is an eclipsing, close binary (P = 0.26d) consisting of a
sdOB primary star and an unseen secondary with an extraordinary small mass. The
secondary is possibly a former planet which may have survived a common-envelope
phase and has even gained mass.
  In order to investigate on an existing discrepancy between the components'
mass derived from NLTE spectral analysis and subsequent comparison to
evolutionary tracks and masses derived from radial-velocity and the eclipse
curves, we performed phase-resolved high-resolution and high-SN spectroscopy
with the UVES attached to the ESO VLT. From the obtained spectra, we have
determined AA Dor's orbital parameters (P = 22600.702 +/- 0.005 sec, A = 39.19
+/- 0.05 km/sec, T0 = 2451917.152690) and the rotational velocity (v = 47 +/- 5
km/sec) of the primary.


title: The black hole mass of low redshift radiogalaxies

abstract:
  We make use of two empirical relations between the black hole mass and the
global properties (bulge luminosity and stellar velocity dispersion) of nearby
elliptical galaxies, to infer the mass of the central black hole (M_BH) in low
redshift radiogalaxies. Using the most recent determinations of black hole
masses for inactive early type galaxies we show that the bulge luminosity and
the central velocity dispersion are almost equally correlated (similar scatter)
with the central black-hole mass. Applying these relations to two large and
homogeneous datasets of radiogalaxies we find that they host black-holes whose
mass ranges between ~5x10^7 to ~6x10^9 M_sun (average <LogM_BH> ~8.9). M_BH is
found to be proportional to the mass of the bulge (M_bulge). The distribution
of the ratio M_BH/M_bulge has a mean value of 8x10^{-4} and shows a scatter
that is consistent with that expected from the associated errors. At variance
with previous claims no significant correlation is instead found between M_BH
(or M_bulge) and the radio power at 5GHz.


title: The Rotational Velocity of Helium-rich Pre-White Dwarfs

abstract:
  Previous investigations on hydrogen-rich white dwarfs generally yield only
very small rotational velocities (v_rot sin i). We have analyzed line profiles
in high-resolution optical spectra of eight hydrogen-deficient (pre-) white
dwarfs and find deviations from the dominant Stark line broadening in five
cases which, interpreted as an effect of stellar rotation, indicate projected
rotational velocities of 40 - 70 km/sec. For the three least luminous stars
upper limits of v_rot sin i = 15 - 25 km/sec could be derived only. The
resulting velocities correlate with luminosity and mass. However, since the
mass-loss rate is correlated to the luminosity of a star, the observed line
profiles may be affected by a stellar wind as well. In the case of RX
J2117.1+3412, this would solve discrepancies to results of pulsational modeling
(v_rot sin i ~ 0).


title: The host galaxy - AGN connection at low and high redshift

abstract:
  The properties of radio loud active galaxies (radiogalaxies, BL Lac objects
and radio loud quasar) at low and high redshift are briefly reviewed and
compared. The recently derived empirical relations between central black hole
mass and host properties allow one to explore the demographics of massive black
hole in active galaxies. It is shown that all classes of active galaxies
considered exhibit very similar host properties and, consequently, have central
black holes of comparable mass. The future observing capabilities would allow
the investigation of the evolution of the host galaxy properties up to z $\sim$
3, and will give insight into the joint formation of black holes and massive
spheroids.


title: PG 1613+426: a new sdB pulsator

abstract:
  We report the detection of short period oscillations in the hot subdwarf B
(sdB) star PG 1613+426 from time-series photometry carried out with the 91-cm
Cassegrain telescope of the Catania Astrophysical Observatory. This star, which
is brighter than the average of the presently known sdB pulsators, with B =
14.14 mag, has $T_{\rm eff}=34 400 {\rm K}$ and $\log g = 5.97$, its position
is near the hot end of the sdB instability strip, and it is a pulsator with a
well observed peak in the power spectrum at $144.18\pm 0.06 \rm s$. This star
seems to be well suited for high precision measurements, which could detect a
possible multi-mode pulsation behaviour


title: Gas Phase Processes Affecting Galactic Evolution

abstract:
  Gas processes affecting star formation are reviewed with an emphasis on
gravitational and magnetic instabilities as a source of turbulence.
Gravitational instabilities are pervasive in a multi-phase medium, even for
sub-threshold column densities, suggesting that only an ISM with a pure-warm
phase can stop star formation. The instabilities generate turbulence, and this
turbulence influences the structure and timing of star formation through its
effect on the gas distribution and density. The final trigger for star
formation is usually direct compression by another star or cluster. The star
formation rate is apparently independent of the detailed mechanisms for star
formation, and determined primarily by the total mass of gas in a dense form.
If the density distribution function is a log-normal, as suggested by
turbulence simulations, then this dense gas mass can be calculated and the star
formation rate determined from first principles. The results suggest that only
10**(-4) of the ISM mass actively participates in the star formation process
and that this fraction does so because its density is larger than 10**5 cm-3,
at which point several key processes affecting dynamical equilibrium begin to
break down.


title:
X-ray and weak lensing measurements of the mass profile of
  MS1008.1-1224: Chandra and VLT data

abstract:
  We analyse the Chandra dataset of the galaxy cluster MS1008.1-1224 to recover
an estimate of the gravitating mass as function of the radius and compare these
results with the weak lensing reconstruction of the mass distribution obtained
from deep FORS1-VLT multicolor imaging. Even though the X-ray morphology is
disturbed with a significant excess in the northern direction suggesting that
the cluster is not in a relaxed state, we are able to match the two mass
profiles both in absolute value and in shape within 1 sigma uncertainty and up
to 1100 h50^-1 kpc. The recovered X-ray mass estimate does not change by using
either the azimuthally averaged gas density and temperature profiles or the
results obtained in the northern sector alone where the signal-to-noise ratio
is higher.


title:
Possible new gamma-ray pulsar detections for AGILE and GLAST missions:
  The outer gap model look at the Parkes pulsar Catalog

abstract:
  The predictive power of the outer gap model of high energy emission from
pulsars is used to analyze the Parkes Multibeam pulsar survey. We find that
most of the radio pulsars of the Parkes catalog are not $\gamma$-ray emitters
according to the outer gap model. The sample of possible new $\gamma$-ray
pulsar detections for AGILE and GLAST is given. That includes thirteen new
excellent candidates. Four new positional coincidences between EGRET detections
and Parkes pulsars are found, but for which we discard a physical association.
The consequences of applying a new electron density model in assigning the
pulsar distances are explored. The new model systematically reduce the
distances to the pulsars, corrections can be as large as 90%, increasing their
fluxes and affecting the detection prospects.


title:
Constraints on dark energy and quintessence with a comoving standard
  ruler applied to 2dF quasars

abstract:
  Structures on very large scales (> 100 Mpc) have negligible peculiar motions,
and are thus roughly fixed in comoving space. We looked for significant peaks
at very large separation in the two-point correlation function -- corrected for
redshift selection effects -- of a well convered subsample of 2378 quasars of
the recently released 10k sample of the 2dF quasar survey. Dividing our sample
in three redshift intervals, we find a peak at 244/h Mpc, which is perfectly
comoving for a restricted set of cosmological parameters, namely Omega_m =
0.25+/-0.15 and Omega_Lambda=0.65+/-0.35 (both at 95% confidence). Assuming a
flat Universe, we constrain the quintessence parameter w_Q < -0.35 (95%
confidence). We discuss the compatibility of our analysis with possible peaks
in the power spectrum.


title:
Detection of TeV Gamma Rays from the BL Lac Object 1ES1959+650 with the
  Whipple 10m Telescope

abstract:
  We present the first strong detection of very high energy gamma-rays from the
close (z=0.048) X-ray selected BL Lacertae object 1ES1959+650. Observations
were made with the Whipple 10m telescope on Mt. Hopkins, Arizona, using the
atmospheric Cherenkov imaging technique. The flux between May and July 2002 was
highly variable, with a mean of 0.64 +/- 0.03 times the steady flux from the
Crab Nebula and reaching a maximum of five Crab, with variability on timescales
as short as seven hours.


title:
Non-LTE Abundances of Magnesium, Aluminum and Sulfur in OB Stars Near
  the Solar Circle

abstract:
  Non-LTE abundances of magnesium, aluminum and sulfur are derived for a sample
of 23 low-v \sin i stars belonging to six northern OB associations of the
Galactic disk within 1 kpc of the Sun. The abundances are obtained from the
fitting of synthetic line profiles to high resolution spectra. A comparison of
our results with HII region abundances indicates good agreement for sulfur
while the cepheid abundances are higher. The derived abundances of Mg show good
overlap with the cepheid results. The aluminum abundances for OB stars are
significantly below the cepheid values. But, the OB star results show a
dependence with effective temperature and need further investigation. The high
Al abundances in the cepheids could be the result of mixing. A discussion of
the oxygen abundance in objects near the solar circle suggests that the current
mean galactic oxygen abundance in this region is 8.6-8.7 and in agreement with
the recently revised oxygen abundance in the solar photosphere. Meaningful
comparisons of the absolute S, Al and Mg abundances in OB stars with the Sun
must await a reinvestigation of these elements, as well as the meteoritic
reference element Si, with 3D hydrodynamical model atmospheres for the Sun. No
abundance gradients are found within the limited range in galactocentric
distances in the present study. Such variations would be expected only if there
were large metallicity gradients in the disk.


title:
Interactions between a Bright YSO and the MSX Infrared-Dark Cloud
  G79.3+0.3: An Early Stage of Triggered Star Formation?

abstract:
  Millimeter and mid-infrared observations have been made of the dense clumps
of dust and gas and of young stellar objects (YSOs) associated with the bright,
compact submillimeter source G79.3+0.3 P1 in the relatively nearby MSX
infrared-dark cloud G79.3+0.3. The Gemini mid-infrared observations reported
here indicate the presence of three YSOs within the cloud. BIMA 3 mm continuum
observations show that the brightest of the YSOs is likely to be a Herbig Ae/Be
star. High-angular-resolution molecular-line observations suggest that a wind
from this star may be triggering collapse in the adjacent molecular cloud. The
submillimeter source G79.3+0.3 P1 itself does not contain infrared sources and
may represent an earlier stage of star formation.


title: An XMM-Newton observation of the globular cluster Omega Centauri

abstract:
  We report on a deep XMM-Newton EPIC observation of the globular cluster Omega
Cen performed on August 13th, 2001. We have detected 11 and 27 faint X-ray
sources in the core and half mass radii, searching down to a luminosity of 1.3
x 10^{31} erg s^{-1} in the 0.5-5 keV range. Most sources have bolometric X-ray
luminosities between ~ 10^{31}-10^{32} erg s^{-1}. We present the color-color
and hardness-intensity diagrams of the source sample, as well as high-quality
EPIC spectra of the brightest objects of the field; including the two candidate
Cataclysmic Variables (CVs) in the core and the quiescent neutron star low-mass
X-ray binary candidate. The spectra of the latter objects fully support their
previous classification. We show that the bulk of sources are hard and
spectrally similar to CVs. The lack of soft faint sources might be related to
the absence of millisecond pulsars in the cluster. The XMM-Newton observations
reveal the presence of an excess of sources well outside the core of the
cluster where several RS CVn binaries have already been found. We have also
analyzed a publicly available Chandra ACIS-I observation performed on January
24-25th, 2000, to improve the XMM-Newton source positions and to search for
source intensity variations between the two data sets. 63 XMM-Newton sources
have a Chandra counterpart, and 15 sources within the half-mass radius have
shown time variability. Overall, the general properties of the faint X-ray
sources in Omega Cen suggest that they are predominantly CVs and active
binaries (RS CVn or BY Dra).


title:
Cool Companions to White Dwarfs from the 2MASS Second Incremental Data
  Release

abstract:
  We present near-infrared magnitudes for all white dwarfs (selected from the
catalog of McCook & Sion) contained in the 2 Micron All Sky Survey Second
Incremental Data Release(2MASS 2IDR). We show that the near-IR color-color
diagram is an effective means of identifying candidate binary stars containing
a WD and a low mass main sequence star. The loci of single WDs and WD + red
dwarf binaries occupy distinct regions of the near-IR color-color diagram. We
recovered all known unresolved WD + red dwarf binaries located in the 2IDR sky
coverage, and also identified as many new candidate binaries (47 new candidates
out of 95 total). Using observational near-IR data for WDs and M-L dwarfs, we
have compared a sample of simulated WD + red dwarf binaries with our 2MASS
data. The colors of the simulated binaries are dominated by the low mass
companion through the late-M to early-L spectral types. As the spectral type of
the companion becomes progressively later, however, the colors of unresolved
binaries become progressively bluer. Binaries containing the lowest mass
companions will be difficult to distinguish from single WDs solely on the basis
of their near-IR colors.


title:
Near-Infrared Observations of Powerful High-Redshift Radio Galaxies: 4C
  40.36 and 4C 39.37

abstract:
  We present near-infrared imaging and spectroscopic observations of two FR II
high-redshift radio galaxies (HzRGs), 4C 40.36 (z=2.3) and 4C 39.37 (z=3.2),
obtained with the Hubble, Keck, and Hale Telescopes. High resolution images
were taken with filters both in and out of strong emission lines, and together
with the spectroscopic data, the properties of the line and continuum emissions
were carefully analyzed. Our analysis of 4C 40.36 and 4C 39.37 shows that
strong emission lines (e.g., [O III] 5007 A and H alpha+[N II]) contribute to
the broad-band fluxes much more significantly than previously estimated (80%
vs. 20-40%), and that when the continuum sources are imaged through line-free
filters, they show an extremely compact morphology with a high surface
brightness. If we use the R^1/4-law parametrization, their effective radii
(r(e)) are only 2-3 kpc while their restframe B-band surface brightnesses at
r(e) are I(B) ~ 18 mag/arcsec^2. Compared with z ~ 1 3CR radio galaxies, the
former is x3-5 smaller, while the latter is 1-1.5 mag brighter than what is
predicted from the I(B)-r(e) correlation. Although exponential profiles produce
equally good fits for 4C 40.36 and 4C 39.37, this clearly indicates that with
respect to the z~1 3CR radio galaxies, the light distribution of these two
HzRGs is much more centrally concentrated. Spectroscopically, 4C 40.36 shows a
flat (fnu=const) continuum while 4C 39.37 shows a spectrum as red as that of a
local giant elliptical galaxy. Although this difference may be explained in
terms of a varying degree of star formation, the similarities of their surface
brightness profiles and the submillimeter detection of 4C 39.37 might suggest
that the intrinsic spectra is equally blue (young stars or an AGN), and that
the difference is the amount of reddening.


title: Limits on Galactic Dark Matter with 5 Years of EROS SMC Data

abstract:
  Five years of EROS data towards the Small Magellanic Cloud have been searched
for gravitational microlensing events, using a new, more accurate method to
assess the impact of stellar blending on the efficiency. Four long-duration
candidates have been found which, if they are microlensing events, hint at a
non-halo population of lenses. Combined with results from other EROS
observation programs, this analysis yields strong limits on the amount of
Galactic dark matter made of compact objects. Less than 25% of a standard halo
can be composed of objects with a mass between 2 10^-7 Msol and 1 Msol at the
95% C.L.


title: Comet and Asteroid Hazard to the Terrestrial Planets

abstract:
  We estimated the rate of comet and asteroid collisions with the terrestrial
planets by calculating the orbits of 13000 Jupiter-crossing objects (JCOs) and
1300 resonant asteroids and computing the probabilities of collisions based on
random-phase approximations and the orbital elements sampled with a 500 yr
step. The Bulirsh-Stoer and a symplectic orbit integrator gave similar results
for orbital evolution, but may give different collision probabilities with the
Sun. A small fraction of former JCOs reached orbits with aphelia inside
Jupiter's orbit, and some reached Apollo orbits with semi-major axes less than
2 AU, Aten orbits, and inner-Earth orbits (with aphelia less than 0.983 AU) and
remained there for millions of years. Though less than 0.1% of the total, these
objects were responsible for most of the collision probability of former JCOs
with Earth and Venus. We conclude that a significant fraction of near-Earth
objects could be extinct comets that came from the trans-Neptunian region.


title: Chemistry and Dynamics in Pre-Protostellar Cores

abstract:
  We have compared the intensity distribution of molecular line emission with
that of dust continuum emission, and modeled molecular line profiles in three
different preprotostellar cores in order to test how dynamical evolution is
related to chemical evolution, and whether we can use different chemical
tracers to identify specific dynamical evolutionary stages. We used dust
continuum emission to obtain the input density and temperature structures by
calculating radiative transfer of dust emission. Our results show that chemical
evolution is dependent on dynamical processes, which can give different
evolutionary timescales, as well as the density structure of the core.


title:
Searching for z ~ 6 Objects with the HST Advanced Camera for Surveys:
  Preliminary Analysis of a Deep Parallel Field

abstract:
  Recent results suggest that z ~ 6 marks the end of the reionization era. A
large sample of objects at z ~ 6, therefore, will be of enormous importance, as
it will enable us to observationally determine the exact epoch of the
reionization and the sources that are responsible for it. With the HST Advanced
Camera for Surveys (ACS) coming on line, we now have an unique opportunity to
discover a significant number of objects at z ~ 6. The pure parallel mode
implemented for the Wide Field Camera (WFC) has greatly enhanced this ability.
We present our preliminary analysis of a deep ACS/WFC parallel field at
|b|=74.4^o. We find 30 plausible z ~ 6 candidates, all of which have S/N > 7 in
the F850LP-band. The major source of contamination could be faint Galactic cool
dwarfs, and we estimated that they would contribute at most 4 objects to our
candidate list. We derived the cumulative number density of galaxies at 6.0 <=
z <= 6.5 as 2.3 arcmin^{-2} to a limit of 28.0 mag in the F850LP-band, which is
slightly higher than our prediction. If this is not due to an underestimated
contamination rate, it could possibly imply that the faint-end slope of the z ~
6 luminosity function is steeper than alpha=-1.6. At the very least, our result
suggests that galaxies with L<L^* do exist in significant number at z ~ 6 and
they could be the major sources that contributed to the reionizing photons.


title: Improved Bounds on Violation of the Strong Equivalence Principle

abstract:
  I describe a unique, 20-year-long timing program for the binary pulsar
B0655+64, the stalwart control experiment for measurements of gravitational
radiation damping in relativistic neutron-star binaries. Observed limits on
evolution of the B0655+64 orbit provide new bounds on the existence of dipolar
gravitational radiation, and hence on violation of the Strong Equivalence
Principle.


title:
Prospects for the Determination of H_0 through Observation of Multiply
  Imaged Supernovae in Galaxy Cluster Fields

abstract:
  We assess the possibility of determining the Hubble constant H_0 by measuring
time delays between multiple images of supernovae gravitationally lensed by
rich clusters of galaxies and combining these delay measurements with detailed
cluster-potential models based on other lensing constraints. Such a lensing
determination of H_0 would be complementary to those obtained from galaxy-QSO
lensing studies, and could potentially be better calibrated. We show that
relatively low-redshift (z approximately 0.2), significantly elliptical
clusters have appreciable lensing cross sections for observable image pairings
with tractable time delays on the order of a few years despite large lensing
mass scales. We find that a targeted search for such image pairs would be a
significant undertaking for current observatories, but that it would be
appropriate for a facility such as the proposed Large-aperture Synoptic Survey
Telescope.


title: Thermal Bremsstrahlung Radiation in a Two-Temperature Plasma

abstract:
  In the normal one-temperature plasma the motion of ions is usually neglected
when calculating the Bremsstrahlung radiation of the plasma. Here we calculate
the Bremsstrahlung radiation of a two-temperature plasma by taking into account
of the motion of ions. Our results show that the total radiation power is
always lower if the motion of ions is considered. We also apply the
two-temperature Bremsstrahlung radiation mechanism for an analytical
Advection-Dominated Accretion Flow (ADAF) model; we find the two-temperature
correction to the total Bremsstrahlung radiation for ADAF is negligible.


title: Variable stars in Stellar Systems

abstract:
  We discuss in detail the pulsation properties of variable stars in globular
clusters (GCs) and in Local Group (LG) dwarf galaxies. Data available in the
literature strongly support the evidence that we still lack a complete census
of variable stars in these stellar systems. This selection bias is even more
severe for small-amplitude variables such as Oscillating Blue Stragglers (OBSs)
and new exotic groups of variable stars located in crowded cluster regions. The
same outcome applies to large-amplitude, long-period variables as well as to RR
Lyrae and Anomalous Cepheids in dwarf galaxies.


title:
Galactic bulges from Hubble Space Telescope NICMOS observations: the
  lack of r^{1/4} bulges

abstract:
  We use HST near-infrared imaging to explore the shapes of the surface
brightness profiles of bulges of S0-Sbc galaxies at high resolution. Modeling
extends to the outer bulge via bulge-disk decompositions of combined HST -
ground based profiles. Compact, central unresolved components similar to those
reported by others are found in ~84% of the sample. We also detect a moderate
frequency (~34%) of nuclear components with exponential profiles which may be
disks or bars. Adopting the S\'ersic r^{1/n} functional form for the bulge,
none of the bulges have an r^{1/4} behaviour; derived S\'ersic shape-indices
are <n> = 1.7 \pm 0.7. For the same sample, fits to NIR ground-based profiles
yield S\'ersic indices up to n = 4-6. The high-$n$ of ground-based profiles are
a result of nuclear point sources blending with the bulge extended light due to
seeing. The low S\'ersic indices are not expected from merger violent
relaxation, and argue against significant merger growth for most bulges.


title:
AGB Stars as Tracers of Star Formation Histories: Implications for GAIA
  Photometry and Spectroscopy

abstract:
  We argue that tracing star formation histories with ESA's space mission GAIA
using main sequence turn-off (MSTO) point dating will mainly be effective in
cases of mild interstellar extinction (E(B-V)<0.5). For higher reddenings the
MSTO approach will be severely limited both in terms of traceable ages (t<0.5
Gyr at 8 kpc; E(B-V)=1.0) and/or distances (d<2 kpc for t=15 Gyr; E(B-V)=1.0),
since the MSTO will be located at magnitudes too faint for GAIA. AGB stars may
alternatively provide precise population ages with GAIA for a wide range of
ages and metallicities, with traceable distances of up to 250 kpc at E(B-V)=0
(d=15 kpc if E(B-V)=2.0). It is essential however that effective temperatures
precise to 0.01 dex, metallicities to 0.2 dex, and E(B-V) to 0.03 are derived
for individual stars, in order to obtain their ages precise to 0.2 dex. This
task is quite challenging for GAIA photometry and spectroscopy, though
preliminary tests show that comparable precisions may be achieved with GAIA
medium band photometry.


title:
Stability of accretion disk around rotating black holes: a
  pseudo-general-relativistic fluid dynamical study

abstract:
  We discuss the solution of accretion disk when the black hole is chosen to be
rotating. We study, how the fluid properties get affected for different
rotation parameters of the black hole. We know that no cosmic object is static
in Universe. Here the effect of the rotation of the black hole to the
space-time is considered following an earlier work of the author, where the
pseudo-Newtonian potential was prescribed for the Kerr geometry. We show that,
with the inclusion of rotation of the black hole, the valid disk parameter
region dramatically changes and disk becomes unstable. Also we discuss about
the possibility of shock in accretion disk around rotating black holes. When
the black hole is chosen to be rotating, the sonic locations of the accretion
disk get shifted or disappear, making the disk unstable. To bring it in the
stable situation, the angular momentum of the accreting matter has to be
reduced/enhanced (for co/counter-rotating disk) by means of some physical
process.


title: Energy exchange inside SN ejecta and light curves of SNe Ia

abstract:
  A treatment of line opacity in expanding medium is most crucial for the light
curve (LC) modeling of Type Ia supernovae (SNe Ia). Spectral lines are the main
source of opacity inside SN Ia ejecta from ultraviolet through infrared range.
Here we focus on the mean opacity for the energy equation. We solve the
Boltzmann equation for photons in the comoving frame for a
spherically-symmetrical flow. For rectangle line profiles we find an analytical
expression for frequency averaged intensity and absorptive opacity. The results
differ from previously known heuristic solutions. The LCs in the I-band are in
better agreement with observations.


title: X-ray emission of young SN Ia remnants as a probe for an explosion model

abstract:
  We present results of hydrodynamical simulations of young supernova remnants.
To model the ejecta, we use several models (discussed in literature) of type Ia
supernova explosions with different abundances. Our hydro models are
one-dimensional and spherically symmetrical, but they take into account
ionization kinetics with all important processes. We include detailed
calculations for the X-ray emission, allowing for time-dependent ionization and
recombination. In particular, we compare the computed X-ray spectra with recent
XMM-Newton observations of the Tycho SN remnant. Our goal is to find the most
viable thermonuclear SN model that gives good fits to both these X-ray
observations and typical SN Ia light curves.


title:
Ferrofluid Based Deformable Mirrors - a New Approach to Adaptive Optics
  Using Liquid Mirrors

abstract:
  The trend towards ever larger telescopes and more advanced adaptive optics
systems is driving the need for deformable mirrors with a large number of low
cost actuators. Liquid mirrors have long been recognized a potential low cost
alternative to conventional solid mirrors. By using a water or oil based
ferrofluid we are able to benefit from a stronger magnetic response than is
found in magnetic liquid metal amalgams and avoid the difficulty of passing a
uniform current through a liquid. Depositing a thin silver colloid known as a
metal liquid-like film (MELLF) on the ferrofluid surface solves the problem of
low reflectivity of pure ferrofluids. This combination provides a liquid
optical surface that can be precisely shaped in a magnetic field. We present
experimental results obtained with a prototype deformable liquid mirror based
on this combination.


title:
Lorentz violation and Crab synchrotron emission: a new constraint far
  beyond the Planck scale

abstract:
  Special relativity asserts that physical phenomena appear the same for all
inertially moving observers. This symmetry, called Lorentz symmetry, relates
long wavelengths to short ones: if the symmetry is exact it implies that
spacetime must look the same at all length scales. Several approaches to
quantum gravity, however, suggest that there may be a Lorentz violating
microscopic structure of spacetime, for example discreteness,
non-commutativity, or extra dimensions. Here we determine a very strong
constraint on a type of Lorentz violation that produces a maximum electron
speed less than the speed of light. We use the observation of 100 MeV
synchrotron radiation from the Crab nebula to improve the previous limits by a
factor of 40 million, ruling out this type of Lorentz violation, and thereby
providing an important constraint on theories of quantum gravity.


title:
Special Purpose Pulsar Telescope for the Detection of Cosmic
  Gravitational Waves

abstract:
  Pulsars can be used to search for stochastic backgrounds of gravitational
waves of cosmological origin within the very low frequency band (VLF),
$10^{-7}$ to $10^{-9}$ Hz. We propose to construct a special 50 m radio
telescope. Regular timing measurements of about 10 strong millisecond pulsars
will perhaps allow the detection of gravitational waves within VLF or at least
will give a more stringent upper limits.


title:
Cardassian Expansion: Constraints from Compact Radio Source Angular Size
  versus Redshift Data

abstract:
  The ``Cardassian Expansion Scenario'' was recently proposed by Freese and
Lewis (2002) as an alternative to a cosmological constant in explaining the
current accelerating universe. In this paper we investigate observational
constraints on this scenario from recent measurements of the angular size of
high-$z$ compact radio sources compiled by Gurvits et al. (1999). We show that
the allowed intervals for $n$ and $z_{eq}$, the two parameters of the
Cardassian model, are heavily dependent on the value of the mean projected
linear size $l$. However, the best fit to the current angular size data prefers
the conventional flat $\Lambda$CDM model to this Cardassian expansion proposal,
though the latter is cosmologically credible and compatible with the $\Theta -
z$ diagram for some values of $l$.


title:
Subtracting the photon noise bias from single-mode optical
  interferometer visibilities

abstract:
  I present in this paper a method to subtract the bias due to source photon
noise from visibilities measured with a single-mode optical interferometer.
Properties of the processed noise are demonstrated and examples of subtraction
on real data are presented.


title:
A simultaneous solution scheme for coupled transonic accretion-wind
  systems

abstract:
  We discuss a {\it non-self-similar analytical model} capable of explaining
the formation of accretion-powered galactic and extra-galactic jets.


title: Shock propagation and neutrino oscillation in supernova

abstract:
  The effect of the shock propagation on neutrino oscillation in supernova is
studied paying attention to evolution of average energy of $\nu_{e}$ and
$\bar{\nu}_{e}$. We show that the effect appears as a decrease in average
$\nu_{e}$ (in case of inverted mass hierarchy, $\bar{\nu}_{e}$) energy at
stellar surface as the shock propagates. It is found that the effect is
significant 2 seconds after bounce if $3 \times 10^{-5} < \sin^{2}{\theta_{13}}
< 10^{-2}$.


title:
Highly-Ionized Gas in the Galactic Halo: A FUSE Survey of O VI
  Absorption toward 22 Halo Stars

abstract:
  Far Ultraviolet Spectroscopic Explorer spectra of 22 Galactic halo stars are
studied to determine the amount of O VI in the Galactic halo between ~0.3 and
\~10 kpc from the Galactic mid-plane. Strong O VI 1031.93 A absorption was
detected toward 21 stars, and a reliable 3 sigma upper limit was obtained
toward HD 97991. The weaker member of the O VI doublet at 1037.62 A could be
studied toward only six stars. The observed columns are reasonably consistent
with a patchy exponential O VI distribution with a mid-plane density of
1.7x10^(-8) cm^(-3) and scale height between 2.3 and 4 kpc. We do not see clear
signs of strong high-velocity components in O VI absorption along the Galactic
sight lines, which indicates the general absence of high velocity O VI within
2-5 kpc of the Galactic mid-plane. The correlation between the H I and O VI
intermediate velocity absorption is also poor. The O VI velocity dispersions
are much larger than the value of ~18 km/s expected from thermal broadening for
gas at T~300,000 K, the temperature at which O VI is expected to reach its peak
abundance in collisional ionization equilibrium. Turbulence, inflow, and
outflow must have an effect on the shape of the O VI profiles. Kinematical
comparisons of O VI with Ar I suggest the presence of two different types of O
VI-bearing environments toward the Galactic sight lines. Comparison of O VI
with other highly-ionized species suggests that the high ions are produced
primarily by cooling hot gas in the Galactic fountain flow, and that turbulent
mixing also has a significant contribution. The role of turbulent mixing is
most important toward sight lines that sample supernova remnants like Loop I
and IV.


title:
An X-ray investigation of the NGC 346 field in the SMC (2) : the field
  population

abstract:
  We present results from a Chandra observation of the NGC346 cluster, which is
the ionizing source of N66, the most luminous HII region and the largest star
formation region in the SMC. In the first part of this investigation, we have
analysed the X-ray properties of the cluster itself and the remarkable star HD
5980. But the field contains additional objects of interest. In total, 75 X-ray
point sources were detected in the Chandra observation: this is five times the
number of sources detected by previous X-ray surveys. We investigate here their
characteristics in detail. Due to high foreground absorption, the sources
possess rather high hardness ratios. Their cumulative luminosity function
appears generally steeper than that for the rest of the SMC at higher
luminosities. Their absorption columns suggest that most of the sources belong
to NGC 346. Using DSS data and new UBVRI imaging with the ESO 2.2m telescope,
we also discovered possible counterparts for 32 of these X-ray sources and
estimated a B spectral type for a large number of these counterparts. This
tends to suggest that most of the X-ray sources in the field are in fact X-ray
binaries. Finally, some objects show X-ray and/or optical variability, with a
need for further monitoring.


title: Cosmology with tachyon field as dark energy

abstract:
  We present a detailed study of cosmological effects of homogeneous tachyon
matter coexisting with non-relativistic matter and radiation, concentrating on
the inverse square potential and the exponential potential for the tachyonic
scalar field. A distinguishing feature of these models (compared to other
cosmological models) is that the matter density parameter and the density
parameter for tachyons remain comparable even in the matter dominated phase.
For the exponential potential, the solutions have an accelerating phase,
followed by a phase with a(t) ~ t^{2/3} as t goes to infinity. This eliminates
the future event horizon present in LCDM models and is an attractive feature
from the string theory perspective. A comparison with supernova Ia data shows
that for both the potentials there exists a range of models in which the
universe undergoes an accelerated expansion at low redshifts and are also
consistent with requirements of structure formation. They do require fine
tuning of parameters but not any more than in the case of LCDM or quintessence
models.