title: Formation of giant planets in disks with different metallicities

abstract:
  We present the first results from simulations of processes leading to planet
formation in protoplanetary disks with different metallicities. For a given
metallicity, we construct a two-dimensional grid of disk models with different
initial masses and radii ($M_0$, $R_0$). For each disk, we follow the evolution
of gas and solids from an early evolutionary stage, when all solids are in the
form of small dust grains, to the stage when most solids have condensed into
planetesimals. Then, based on the core accretion - gas capture scenario, we
estimate the planet-bearing capability of the environment defined by the final
planetesimal swarm and the still evolving gaseous component of the disk. We
define the probability of planet-formation, $P_p$, as the normalized fractional
area in the ($M_0$, $\log R_0$) plane populated by disks that have formed
planets inside 5 AU. With such a definition, and under the assumption that the
population of planets discovered at $R$ $<$ 5 AU is not significantly
contaminated by planets that have migrated from $R$ $>$ 5 AU, our results agree
fairly well with the observed dependence between the probability that a star
harbors a planet and the star's metal content. The agreement holds for the disk
viscosity parameter $\alpha$ ranging from $10^{-3}$ to $10^{-2}$, and it
becomes much poorer when the redistribution of solids relative to the gas is
not allowed for during the evolution of model disks.


title:
Applications to cosmological models of a complex scalar field coupled to
  a U(1) vector gauge field

abstract:
  We consider the Abelian model of a complex scalar field coupled to a gauge
field within the framework of General Relativity and search for cosmological
solutions. For this purpose we assume a homogeneous, isotropic and uncharged
Universe and a homogeneous scalar field. This model may be inserted in several
contexts in which the scalar field might act as inflaton or quintessence,
whereas the gauge field might play the role of radiation or dark matter, for
instance. Particularly, we propose two such models: (i) in the first, the
inflaton field decays to massive vector bosons that we regard as dark-matter;
(ii) in the second, due to its coupling to radiation the scalar field is
displaced from its ground state and drives an accelerated expansion of the
Universe, playing the role of quintessence. We observe that the equations are
quite simplified and easier to be solved if we assume a roughly monochromatic
radiation spectrum.


title:
Galaxy Occupation Statistics of Dark Matter Haloes: Observational
  Results

abstract:
  We study the occupation statistics of galaxies in dark matter haloes using
galaxy groups identified from the 2-degree Field Galaxy Redshift Survey with
the halo-based group finder of Yang et al. The occupation distribution is
considered separately for early and late type galaxies, as well as in terms of
central and satellite galaxies. The mean luminosity of the central galaxies
scales with halo mass approximately as $L_c\propto M^{2/3}$ for haloes with
masses $M<10^{13}h^{-1}\msun$, and as $L_c\propto M^{1/4}$ for more massive
haloes. The characteristic mass of $10^{13} h^{-1} \Msun$ is consistent with
the mass scale where galaxy formation models suggest a transition from
efficient to inefficient cooling. Another characteristic halo mass scale,
$M\sim 10^{11} h^{-1}\msun$, which cannot be probed directly by our groups, is
inferred from the conditional luminosity function (CLF) that matches the
observed galaxy luminosity function and clustering. For a halo of given mass,
the distribution of $L_c$ is rather narrow. The satellite galaxies are found to
follow a Poissonian number distribution. The central galaxies in low-mass
haloes are mostly late type galaxies, while those in massive haloes are almost
all early types. We also measure the CLF of galaxies in haloes of given mass.
Over the mass range that can be reliably probed with the present data ($13.3
\lta {\rm log}[M/(h^{-1}\Msun)] \lta 14.7$), the CLF is reasonably well fit by
a Schechter function. Contrary to recent claims based on semi-analytical models
of galaxy formation, the presence of central galaxies does not show up as a
strong peak at the bright end of the CLF. (Abridged)


title: Cosmic Microwave Background Anisotropies: Beyond Standard Parameters

abstract:
  In the first part of this work, I review the theoretical framework of
cosmological perturbation theory necessary to understand the generation and
evolution of cosmic microwave background (CMB) anisotropies. Using analytical
and numerical techniques, in the second part I describe the impact on the CMB
power spectra of the standard cosmological parameters (such as the
matter-energy budget of the Universe, its curvature, the amplitude and spectral
properties of the primordial fluctuations, etc.). I introduce the most general
type of initial conditions for the primordial perturbations, deriving a new
analytical approximation for the neutrino isocurvature modes.
  In the third part, I discuss the issue of extracting constraints on the
parameters of interest from the recent, high-quality CMB measurements,
presenting the relevant statistical tools and focusing on the Fisher matrix
analysis as a technique to produce reliable forecasts for the performance of
future observations. I then apply those tools to the study of several possible
extensions of the (currently) standard Lambda CDM model: the presence of extra
relativistic particles, possible time variations of the fine structure
constant, and the value of the primordial Helium mass fraction. I also use the
CMB as a tool to study the very early Universe, via its dependence on the type
of initial conditions: I relax the assumption of purely adiabatic initial
conditions and discuss the observational consequences and constraints on the
presence of general isocurvature modes.


title: Black Hole Spin in AGN and GBHCs

abstract:
  We discuss constraints on black hole spin and spin-related astrophysics as
derived from X-ray spectroscopy. After a brief discussion about the robustness
with which X-ray spectroscopy can be used to probe strong gravity, we summarize
how these techniques can constrain black hole spin. In particular, we highlight
XMM-Newton studies of the Seyfert galaxy MCG-6-30-15 and the stellar-mass black
hole GX339-4. The broad X-ray iron line profile, together with reasonable and
general astrophysical assumptions, allow a non-rotating black hole to be
rejected in both of these sources. If we make the stronger assertion of no
emission from within the innermost stable circular orbit, the MCG-6-30-15 data
constrain the dimensionless spin parameter to be a>0.93. Furthermore, these
XMM-Newton data are already providing evidence for exotic spin-related
astrophysics in the central regions of this object. We conclude with a
discussion of the impact that Constellation-X will have on the study of strong
gravity and black hole spin.


title: XMM-Newton survey of M 31

abstract:
  In an analysis of XMM-Newton archival observations of the bright Local Group
spiral galaxy M 31 we study the population of X-ray sources (X-ray binaries,
supernova remnants) down to a 0.2-4.5 keV luminosity of 4.4E34 erg/s. EPIC
hardness ratios and optical and radio information are used to distinguish
between different source classes. The survey detects in an area of 1.24 square
degree 856 sources. We correlate our sources with earlier M 31 X-ray catalogues
and use information from optical, infra-red and radio wavelengths. As M 31
sources we detect 21 supernova remnants (SNR) and 23 SNR candidates, 18
supersoft source (SSS) candidates, 7 X-ray binaries (XRBs) and 9 XRB
candidates, as well as 27 globular cluster sources (GlC) and 10 GlC candidates,
which most likely are low mass XRBs within the GlC. Comparison to earlier X-ray
surveys reveal transients not detected with XMM-Newton, which add to the number
of M 31 XRBs. There are 567 sources classified as hard, which may either be
XRBs or Crab-like SNRs in M 31 or background AGN. The number of 44 SNRs and
candidates more than doubles the X-ray detected SNRs. 22 sources are new SNR
candidates in M 31 based on X-ray selection criteria. Another SNR candidate may
be the first plerion detected outside the Galaxy and the Magellanic Clouds. On
the other hand, six sources are foreground stars and 90 foreground star
candidates, one is a BL Lac type active galactic nucleus (AGN) and 36 are AGN
candidates, one source coincides with the Local Group galaxy M 32, one with a
background galaxy cluster (GCl) and another is a GCl candidate, all sources not
connected to M 31.


title:
Ground based Gamma Ray Studies based on Atmospheric Cherenkov technique
  at high mountain altitude

abstract:
  In this paper we present a new method for ground based gamma ray astronomy
based only on atmospheric Cherenkov light flux analysis. The Cherenkov light
flux densities in extensive air showers (EAS) initiated by different primaries
are simulated, precisely primary protons in the energy range 100 GeV –
100 PeV, primary gamma quanta in the energy range 10 GeV – 10 PeV and
primary iron nuclei in the energy range 10 TeV –100 PeV using the CORSIKA
6 code at high mountain observation level of 536 g/cm2. An approximation of
lateral distribution of Cherenkov light in extensive air showers is obtained.
The obtained approximation is a nonlinear fit such as Breit-Wigner with few
parameters. A detailed study of the energy dependence of the proposed model
function parameters is carried out and the fit of model parameters as a
function of the primary energy is obtained as well. On the basis of the
difference between the model parameters, precisely their behavior as a function
of the energy, the strong no linearity of the model, we propose a method, which
permits to make the distinction between gamma ray primaries from hadronic
primaries. The possible backgrounds for ground based gamma ray astronomy are
studied and the efficiency of the method is calculated. Different detector
displacements are analyzed using the simulation of simplified mass spectrum of
cosmic ray. The detector response is simulated taking into account the physical
fluctuation of the processes, the statistical and possible systematic errors.
The simulated and reconstructed events are compared and the accuracy in energy
and primary mass reconstruction is obtained. Moreover the accuracy in shower
axis determination is studied and criteria in shower axis position estimation
are proposed.


title:
The Blazhko behaviour of RR Geminorum I - CCD photometric results in
  2004

abstract:
  Extended CCD monitoring of RR Gem revealed that it is a Blazhko type RRab
star with the shortest Blazhko period (7.23d) and smallest modulation amplitude
(Delta Mmax<0.1 mag) currently known. The short period of the modulation cycle
enabled us to obtain complete phase coverage of the pulsation at each phase of
the modulation. This is the first multicolour observation of a Blazhko star
which is extended enough to define accurate mean magnitudes and colours of the
variable at different Blazhko phases. Small, but real, changes in the intensity
mean colours at different Blazhko phases have been detected. The Fourier
analysis of the light curves shows that, in spite of the mmag and smaller order
of the amplitudes, the triplet structure is noticeable up to about the 14th
harmonic. The modulation is concentrated to a very narrow, 0.2 phase range of
the pulsation, centred on the supposed onset of the H emission during rising
light. These observational results raise further complications for theoretical
explanation of the long known but poorly understood Blazhko phenomenon.


title: The AGB superwind speed at low metallicity

abstract:
  We present the results of a survey for OH maser emission at 1612 MHz from
dust-enshrouded AGB stars and supergiants in the LMC and SMC, with the Parkes
radio telescope, aimed at deriving the speed of the superwind from the
double-peaked OH maser profiles. Out of 8 targets in the LMC we detected 5, of
which 3 are new detections - no maser emission was detected in the two SMC
targets. We detected for the first time the redshifted components of the OH
maser profile in the extreme red supergiant IRAS 04553-6825, confirming the
suspicion that its wind speed had been severely underestimated. Despite a much
improved spectrum for IRAS 04407-7000, which was known to exhibit a
single-peaked OH maser, no complementary peak could be detected. The new
detection in IRAS 05003-6712 was also single-peaked, but for two other new
detections, IRAS 04498-6842 and IRAS 05558-7000, wind speeds could be
determined from their double-peaked maser profiles. The complete sample of
known OH/IR stars in the LMC is compared with a sample of OH/IR stars in the
galactic centre. The LMC sources generally show a pronounced asymmetry between
the bright blueshifted maser emission and weaker redshifted emission, which we
attribute to the greater contribution of amplification of radiation coming
directly from the star itself as the LMC sources are both more luminous and
less dusty than their galactic centre counterparts. We confirm that the OH
maser strength is a measure of the dust (rather than gas) mass-loss rate. At a
given luminosity or pulsation period, the wind speed in LMC sources is lower
than in galactic centre sources, and the observed trends confirm simple
radiation-driven wind theory if the dust-to-gas ratio is approximately
proportional to the metallicity.


title: Structural properties of discs and bulges of early-type galaxies

abstract:
  We have used the EFAR sample of galaxies to study the light distributions of
early-type galaxies. We decompose the 2D light distribution of the galaxies in
a flattened spheroidal component with a Sersic radial light profile and an
inclined disc component with an exponential light profile. We show that the
brightest, bulge dominated elliptical galaxies have a fairly broad distribution
in the Sersic profile shape parameter n_B, with a median of about 3.7 and a
sigma of ~0.9. Other galaxies have smaller n_B values, meaning that spheroids
are in general less concentrated than the n_B=4 de Vaucouleurs-law profile.
  The results of our light decompositions are robust, even though without
kinematic information we cannot prove that the spheroids and discs are really
pressure- and rotation-supported stellar systems. If we assume that the
detected spheroids and discs are indeed separate components, we can draw the
following conclusions: 1) the spheroid and disc scale sizes are correlated; 2)
bulge-to-total luminosity ratios, bulge effective radii, and bulge n_B values
are all positively correlated; 3) the bivariate space density distribution of
elliptical galaxies in the (luminosity, scale size)-plane is well described by
a Schechter luminosity function in and a log-normal scale-size distribution at
a given luminosity; 4) at the brightest luminosities, the scale size
distribution of elliptical galaxies is similar to those of bright spiral
galaxies; at fainter luminosities the elliptical scale size distribution peaks
at distinctly smaller sizes than the spiral galaxy distribution; and 5) bulge
components of early-type galaxies are typically a factor 1.5 to 2.5 smaller
than the disks of spiral galaxies, while disc components of early-type galaxies
are typically twice as large as the discs of spiral galaxies. [abridged]


title: Sterile Neutrinos in astrophysical and cosmological sauce

abstract:
  The study of sterile neutrinos has recently acquired a different flavor:
being now excluded as the dominant solution for the solar or atmospheric
conversions, sterile neutrinos, still attractive for many other reasons, have
thus become even more elusive. The present relevant questions are: which
subdominant role can they have? Where (and how) can they show up? Cosmology and
supernovae turn out to be powerful tools to address these issues. With the most
general mixing scenarios in mind, I present the analysis of many possible
effects on BBN, CMB, LSS, and in SN physics due to sterile neutrinos. I discuss
the computational techniques, present the state-of-the-art bounds, identify the
still allowed regions and study some of the most promising future probes. I
show how the region of the LSND sterile neutrino is excluded by the constraints
of standard cosmology.


title: A New Kind of Nova

abstract:
  We performed extensive, multi-wavelength observations of the prototypical
symbiotic star Z Andromedae between 2000 and 2003, during a large eruption. The
rise to optical maximum occurred in three distinct stages. During the first
stage, the rise was very similar to an earlier, small outburst which we
determined was due to an accretion-disk instability. In the second stage, an
optically thick shell of material was ejected, and in the third stage, the
shell cleared to reveal a white dwarf whose luminosity was roughly 10^4 Lsun.
We suggest that the outburst was powered by an increase in the rate of nuclear
burning on the white-dwarf surface, triggered by a sudden burst of accretion.
This outburst thus combined elements of both dwarf novae and classical novae.


title: Chandra measurement of the X-ray spectrum of a quasar at z=5.99

abstract:
  We report the first measurement of the X-ray spectrum of the z = 5.99 quasar
SDSSp J130608.26+035626.3 from a 120 ks observation by the Chandra ACIS-S
instrument. Between 0.5 and 7 keV, corresponding to 3.5--49 keV in the quasar
rest frame, we find an energy index of 0.86 +/- 0.2, consistent with the
typical indices found for radio quiet quasars at lower redshifts, and
inconsistent with the index required to match the diffuse X-ray background. We
have a weak indication of a redshifted Fe-K line. In comparing the counting
rate between an earlier, short observation and the longer observation reported
here, we find evidence for source variability at the 99.9% confidence level. We
note that other nearby X-ray sources would bias the measured alpha_{ox} = 1.70
by -0.09 if the X-ray flux were determined from within a 60" extraction circle.
Our results for the energy index and the alpha_{ox} are consistent with no
strong evolution in the active galactic nucleus emission mechanism with
redshift out to z ~ 6, and therefore with the picture that massive black holes
have already formed less than 1 Gyr after the big bang.


title:
The Ultraviolet flash accompanying GRBs from neutron-rich internal
  shocks

abstract:
  In the neutron-rich internal shocks model for Gamma-ray Burts (GRBs), the
Lorentz factors (LFs) of ions shells are variable, so are the LFs of
accompanying neutron shells. For slow neutron shells with a typical LF tens,
the typical beta-decay radius reads R_{\beta,s} several 10^{14} cm, which is
much larger than the typical internal shocks radius 10^{13} cm, so their impact
on the internal shocks may be unimportant. However, as GRBs last long enough
(T_{90}>20(1+z) s), one earlier but slower ejected neutron shell will be swept
successively by later ejected ion shells in the range 10^{13}-10^{15} cm, where
slow neutrons have decayed significantly. We show in this work that ion shells
interacting with the beta-decay products of slow neutron shells can power a
ultraviolet (UV) flash bright to 12th magnitude during the prompt gamma-ray
emission phase or slightly delayed, which can be detected by the upcoming
Satellite SWIFT in the near future.


title: A Prototype Si/CdTe Compton Camera and the Polarization Measurement

abstract:
  A Compton camera is the most promising approach for gamma-ray detection in
the energy region from several hundred keV to MeV, especially for application
in high energy astrophysics. In order to obtain good angular resolution,
semiconductor detectors such as silicon, germanium and cadmium telluride(CdTe)
have several advantages over scintillation detectors, which have been used so
far. Based on the recent advances of high resolution CdTe and silicon imaging
detectors, we are working on a Si/CdTe Compton camera. We have developed
64-pixel CdTe detectors with a pixel size of 2mmx2mm and double-sided Si strip
detectors(DSSDs) with a position resolution of 800 micron. As a prototype
Si/CdTe Compton camera, we use a DSSD as a scatterer and two CdTe pixel
detectors as an absorber. In order to verify its performance, we irradiate the
camera with 100% linearly polarised 170keV gamma-rays and demonstrate the
system works properly as a Compton camera. The resolution of the reconstructed
scattering angle is 22 degrees(FWHM). Measurement of polarization is also
reported. The polarimetric modulation factor is obtained to be 43%, which is
consistent with the prediction of Monte Carlo simulations.


title: Luminous Compact Blue Galaxies in the Local Universe

abstract:
  We use the KPNO International Spectroscopic Survey (KISS) for emission-line
galaxies to identify and describe a sample of local analogues to the luminous
compact blue galaxies (LCBGs) that are observed to be abundant at intermediate
and high redshift. The sample is selected using criteria believed effective at
isolating true examples of LCBGs: SB_e(B-band) < 21.0 mag/arcsec^2, M(B) <
-18.5 (for H_o = 75 km/s/Mpc), and B-V < 0.6. Additionally, all LCBG candidates
presented are selected to have star-formation as their dominant form of
activity. We examine the properties of our LCBGs and compare them to those of
other KISS star-forming galaxies of the same absolute magnitude range. We find
that the KISS LCBGs lie on the extreme end of a fairly continuous distribution
of ``normal'' star-forming galaxies in the plane of surface brightness versus
color. This result differs from the results of previous studies that show LCBGs
at higher-z to be more separate from the ``normal'' (usually non-active)
galaxies they are compared against. On average, LCBGs have a higher tendency to
emit detectable flux in the radio continuum, have higher H-alpha luminosities
by a factor of 1.6, indicating strong star-formation activity, and have
slightly lower than expected metal abundances based on the
luminosity-metallicity relation for KISS galaxies. We calculate the volume
density of our low-z (z<0.045) sample to be 5.4 x 10^-4 h_75^3 Mpc^-3,
approximately 4 times lower than the volume density of the LCBGs at 0.4 < z <
0.7 and ~10 times lower than the volume density of the population at 0.7 < z <
1.0.


title: Full radiative coupling in two-phase models for accreting black holes

abstract:
  The emission from galactic black holes and Seyfert galaxies is generally
understood in term of two-phase models (Haardt and Maraschi 1991, 1993). Such
models postulate that a hot plasma coexists with relatively colder material in
the inner part of the accretion flow. We present the first simulated broad-band
spectra produced by such a system and accounting simultaneously for energy
balance and Comptonisation in the hot phase, together with reflection,
reprocessing, ionization and thermal balance in the cold phase. This was made
possible by coupling three radiative transfer codes: a non-linear Monte-Carlo
code (NLMC), a photo-ionization code TITAN and a linear Monte-Carlo code NOAR.
The equilibrium comptonisation spectrum appears to be sensitive to the shape of
the reprocessed spectrum that, in turn, depends on the ionization parameter,
but also on the structure of the irradiated cold material. This is illustrated
by a comparison of simulations assuming constant density or a constant pressure
in the cold phase. We also compare our results with simplified models where
reprocessing is approximated by a blackbody spectrum. Our detailed treatment
leads to noticeably different spectral energy distributions (SEDs)
characterised by harder X-ray spectra. Even at low ionization parameters the
commonly used blackbody approximation is poor, leading to X-ray spectra that
are too soft. The effect, however, seems not to be strong enough to reconcile
the slab corona model with the hardest observed spectra, unless the reflector
has a constant density and the ionization parameter is large.


title:
Detecting the Earliest Galaxies Through Two New Sources of 21cm
  Fluctuations

abstract:
  The first galaxies that formed at a redshift ~20-30 emitted continuum photons
with energies between the Lyman-alpha and Lyman limit wavelengths of hydrogen,
to which the neutral universe was transparent except at the Lyman-series
resonances. As these photons redshifted or scattered into the Lyman-alpha
resonance they coupled the spin temperature of the 21cm transition of hydrogen
to the gas temperature, allowing it to deviate from the microwave background
temperature. We show that the fluctuations in the radiation emitted by the
first galaxies produced strong fluctuations in the 21cm flux before the
Lyman-alpha coupling became saturated. The fluctuations were caused by biased
inhomogeneities in the density of galaxies, along with Poisson fluctuations in
the number of galaxies. Observing the power-spectra of these two sources would
probe the number density of the earliest galaxies and the typical mass of their
host dark matter halos. The enhanced amplitude of the 21cm fluctuations from
the era of Lyman-alpha coupling improves considerably the practical prospects
for their detection.


title: Small PAHs in the Red Rectangle

abstract:
  Following our initial discovery of blue luminescence in the spectrum of the
Red Rectangle (RR) and its identification as fluorescence by small three- to
four-ringed polycyclic aromatic hydrocarbon (PAH) molecules, we report on the
spatial correlation between the blue luminescence and the 3.3 micron emission,
commonly attributed to small, neutral PAH molecules, and on the newly-derived
UV/optical attenuation curve for the central source of the RR, HD 44179. Both
results provide strong additional evidence for the presence of small PAH
molecules with masses of less than 250 a.m.u. in the RR, which supports the
attribution of the blue luminescence to fluorescence by the same molecules. We
contrast the excellent spatial correlation of the two former emissions with the
distinctly different spatial distribution of the extended red emission (ERE)
and of the dust-scattered light within the RR. The UV/optical attenuation curve
of the central star is unlike any interstellar extinction curve and is
interpreted as resulting from circumstellar opacity alone. Major contributions
to this opacity are absorptions in broad bands in the mid-UV, contributing to
the electronic excitation of the luminescing PAH molecules, and a sharp
ionization discontinuity near 7.5 eV in the far-UV, which places a sharp upper
limit on the masses of the PAH molecules that are responsible for this
absorption. The strength of the far-UV absorption leads to an abundance of the
PAH molecules of 10^{-5} relative to hydrogen in the RR. Such small PAHs are
perhaps unique to the environment in the RR, where they are shielded from harsh
radiation by the dense circmstellar disk.


title: VLT Spectroscopy of RR Lyrae Stars in the Sagittarius Tidal Stream

abstract:
  Sixteen RR Lyrae variables from the QUEST survey that lie in the leading arm
of the tidal stream from the Sagittarius dSph galaxy have been observed
spectroscopically to measure their radial velocities and metal abundances. The
systemic velocities of 14 stars, which were determined by fitting a standard
velocity curve to the individual measurements, have a sharply peaked
distribution with a mean of 33 km/s and a standard deviation of only 25 km/s.
The [Fe/H] distribution of these stars has a mean of -1.76 and a standard
deviation of 0.22. These measurements are in good agreement with previous ones
from smaller samples of stars. The mean metallicity is consistent with the
age-metallicity relation that is observed in the main body of the Sgr dSph
galaxy.
  The radial velocities and the distances from the Sun of these stars are
compared with recent numerical simulations of the Sgr streams that assume
different shapes for the dark matter halo. Models that assume a oblate halo do
not fit the data as well as ones that assume a spherical or a prolate
distribution. However, none of the fits are completely satisfactory. Every
model fails to reproduce the long extent of the stream in right ascension (36
degr) that is seen in the region covered by the QUEST survey. Further modeling
is required to see if this and the other mismatches between theory and
observation can be removed by judicial choices for the model parameters or
instead rule out a class of models.


title: Very High-Redshift Lensed Galaxies

abstract:
  We review in this paper the main results recently obtained on the
identification and study of very high-z galaxies usinglensing clusters as
natural gravitational telescopes. We present in detail our pilot survey with
ISAAC/VLT, aimed at the detection of z>7 sources. Evolutionary synthesis models
for extremely metal-poor and PopIII starbursts have been used to derive the
observational properties expected for these high-z galaxies, such as expected
magnitudes and colors, line fluxes for the main emission lines, etc. These
models have allowed to define fairly robust selection criteria to find z~7-10
galaxies based on broad-band near-IR photometry in combination with the
traditional Lyman drop-out technique. The first results issued from our
photometric and spectroscopic survey are discussed, in particular the
preliminary confirmation rate, and the global properties of our high-z
candidates, including the latest results on the possible z=10.0 candidate
A1835-1916. The search efficiency should be significantly improved by the
future near-IR multi-object ground-based and space facilities. However, strong
lensing clusters remain a factor of ~5-10 more efficient than blank fields in
this redshift domain, within the FOV of a few arcminutes around the cluster
core, for the typical depth required for this survey project.


title:
A model of inflation independent of the initial conditions, with bounded
  number of e-folds and n_s larger orsmaller than one

abstract:
  We study a supergravity model of inflation essentially depending on one
parameter which can be identified with the slope of the potential at the
origin. In this type of models the inflaton rolls at high energy from negative
values and a positive curvature potential. At some point defined by the
equation $\eta=1$ inflation starts. The potential curvature eventually changes
to negative values and inflation ends when $\eta=-1$. No spontaneous symmetry
breaking type mechanism for inflation of the new type to occur is here
required. The model naturally gives a bounded $\it{total}$ number of e-folds
which is typically close to the required number for observable inflation and it
is independent of the initial conditions for the inflaton. The energy scale
introduced is fixed by the amplitude of the anisotropies and is of the order of
the supersymmetry breaking scale. The model can also accommodate an spectral
index bigger or smaller than one without extreme fine tuning. We show that it
is possible to obtain reasonable numbers for cosmological parameters and, as an
example, we reproduce values obtained recently by Tegmark $\it{et. al.}$, from
WMAP and SDSS data alone.


title:
High-resolution Imaging of the OH Megamaser Emission in IRAS12032+1707
  and IRAS14070+0525

abstract:
  We present results from VLBA observations of the 1667 and 1665 MHz OH lines
in the two OH megamaser galaxies IRAS12032+1707 and IRAS14070+0525. For
IRAS12032+1707 we also present Arecibo HI absorption data. Almost all OH
emission previously detected by single dish observations has been recovered in
IRAS12032+1707 and is found on a compact scale of <100 pc. The emission shows
an ordered velocity field that is consistent with a single disk. However, the
data is also consistent with a scenario including two physically different gas
components. We explore this possibility, in which the two strongest and most
blueshifted maser features are identified as the tangent points of a
circumnuclear torus. The redshifted maser features would be extended in a
direction perpendicular to the torus, which is in the direction of the merger
companion. Thus, redshifted emission could be associated with an inflow
triggered by a tidal interaction. HI absorption covers the velocities of the
redshifted maser emission, suggesting a common origin. In the second source,
IRAS14070+0525, a large fraction of the OH emission is resolved out with the
VLBA. We find no significant evidence of an ordered velocity field in this
source, but these results are inconclusive due to a very low signal-to-noise
ratio.


title: f(R) theories of gravity in Palatini approach matched with observations

abstract:
  We investigate the viability of f(R) theories in the framework of the
Palatini approach as solutions to the problem of the observed accelerated
expansion of the universe. Two physically motivated popular choices for f(R)
are considered: power law, f(R) = \beta R^n, and logarithmic, f(R) = \alpha
\ln{R}. Under the Palatini approach, both Lagrangians give rise to cosmological
models comprising only standard matter and undergoing a present phase of
accelerated expansion. We use the Hubble diagram of type Ia Supernovae and the
data on the gas mass fraction in relaxed galaxy clusters to see whether these
models are able to reproduce what is observed and to constrain their
parameters. It turns out that they are indeed able to fit the data with values
of the Hubble constant and of the matter density parameter in agreement with
some model independent estimates, but the today deceleration parameter is
higher than what is measured in the concordance LambdaCDM model.


title: Chandra Orion Ultradeep Project: Observations and Source Lists

abstract:
  We present a description of the data reduction methods and the derived
catalog of more than 1600 X-ray point sources from the exceptionally deep
January 2003 Chandra X-ray Observatory observation of the Orion Nebula Cluster
and embedded populations around OMC-1. The observation was obtained with
Chandra's Advanced CCD Imaging Spectrometer (ACIS) and has been nicknamed the
Chandra Orion Ultradeep Project (COUP). With an 838 ks exposure made over a
continuous period of 13.2 days, the COUP observation provides the most uniform
and comprehensive dataset on the X-ray emission of normal stars ever obtained
in the history of X-ray astronomy.


title: Clarification of the Nature of the Galaxy CFC97 Cen 05

abstract:
  The galaxy CFC97 Cen 05 has in the past been considered an HI-rich dwarf
galaxy in the nearby Centaurus A group. We have used Australia Telescope
Compact Array observations to show that the HI associated with CFC97 Cen 05 by
Cote et al. (1997) is most likely a Galactic High Velocity Cloud that is
centered ~17' from the optical image of the galaxy. At the optical location of
the galaxy, which is not that tabulated by Banks et al. (1999), there is no
indication of the presence of HI for velocities less than the upper limit of
the HIPASS survey at ~12,500 km/s. In addition, WFPC2 images of CFC97 Cen 05
obtained from the HST Archive reveal that this galaxy is in fact not a dwarf at
all, but rather is a distant background spiral not associated with the
Centaurus A group.


title:
Probing Sub-parsec Structure in the Lyman Alpha Forest with
  Gravitational Microlensing

abstract:
  We present the results of microlens ray-tracing simulations showing the
effect of absorbing material between a source quasar and a lensing galaxy in a
gravitational lens system. We find that, in addition to brightness fluctuations
due to microlensing, the strength of the absorption line relative to the
continuum varies with time, with the properties of the variations depending on
the structure of the absorbing material. We conclude that such variations will
be measurable via UV spectroscopy of image A of the gravitationally lensed
quasar Q2237+0305 if the Lyman Alpha clouds between the quasar and the lensing
galaxy possess structure on scales smaller than $\sim 0.1$ pc. The time scale
for the variations is on the order of order years to decades, although very
short term variability can occur. While the Lyman alpha lines may not be
accessible at all wavelengths, this approach is applicable to any absorption
system, including metal lines.


title: Minimum Length Cutoff in Inflation and Uniqueness of the Action

abstract:
  According to most inflationary models, fluctuations that are of cosmological
size today started out much smaller than any plausible cutoff length such as
the string or Planck lengths. It has been shown that this could open an
experimental window for testing models of the short-scale structure of
space-time. The observability of effects hinges crucially, however, on the
initial conditions imposed on the new comoving modes which are continually
being created at the cutoff length scale. Here, we address this question while
modelling spacetime as obeying the string and quantum gravity inspired minimum
length uncertainty principle. We find that the usual strategy for determining
the initial conditions faces an unexpected difficulty because it involves
reformulating the action and discarding a boundary term: we find that actions
that normally differ merely by a boundary term can differ significantly when
the minimum length is introduced. This is possible because the introduction of
a minimum length comes with an ordering ambiguity much like the ordering
ambiguity that arises with the introduction of hbar in the process of
quantization.


title: Nonparametric Inference for the Cosmic Microwave Background

abstract:
  The Cosmic Microwave Background (CMB), which permeates the entire Universe,
is the radiation left over from just 380,000 years after the Big Bang. On very
large scales, the CMB radiation field is smooth and isotropic, but the
existence of structure in the Universe - stars, galaxies, clusters of galaxies
- suggests that the field should fluctuate on smaller scales. Recent
observations, from the Cosmic Microwave Background Explorer to the Wilkinson
Microwave Anisotropy Project, have strikingly confirmed this prediction. CMB
fluctuations provide clues to the Universe's structure and composition shortly
after the Big Bang that are critical for testing cosmological models. For
example, CMB data can be used to determine what portion of the Universe is
composed of ordinary matter versus the mysterious dark matter and dark energy.
To this end, cosmologists usually summarize the fluctuations by the power
spectrum, which gives the variance as a function of angular frequency. The
spectrum's shape, and in particular the location and height of its peaks,
relates directly to the parameters in the cosmological models. Thus, a critical
statistical question is how accurately can these peaks be estimated. We use
recently developed techniques to construct a nonparametric confidence set for
the unknown CMB spectrum. Our estimated spectrum, based on minimal assumptions,
closely matches the model-based estimates used by cosmologists, but we can make
a wide range of additional inferences. We apply these techniques to test
various models and to extract confidence intervals on cosmological parameters
of interest. Our analysis shows that, even without parametric assumptions, the
first peak is resolved accurately with current data but that the second and
third peaks are not.


title: The Pre--Main-Sequence of A-type stars

abstract:
  Young A-type stars in the pre--main-sequence (PMS) evolutionary phase are
particularly interesting objects since they cover the mass range (1.5-4 solar
ma sses) which is most sensitive to the internal conditions inherited during
the protostellar phase. In particular, they undergo a process of thermal
relaxation from which they emerge as fully radiative objects contracting
towards the main sequence. A-type stars also show intense surface activity
(including winds, accretion, pulsations) whose origin is still not completely
understood, and infrared excesses related to the presence of circumstellar
disks and envelopes. Disks display significant evolution in the dust
properties, likely signalling the occurrence of protoplanetary growth. Finally,
A-type stars are generally found in multiple systems and small aggregates of
lower mass companions.


title:
Constraining the Primordial Magnetic Field from Cosmic Microwave
  Background Anisotropies at Higher Multipoles

abstract:
  The cosmological magnetic field is one of the important physical quantities
which affect strongly the cosmic microwave background (CMB) power spectrum.
Recent CMB observations have been extended to higher multipoles $l\gtrsim$1000,
and they resultantly exhibit an excess power than the standard model prediction
in cosmological theory which best fits the Wilkinson Microwave Anisotropy Probe
(WMAP) data at lower multipoles $l\lesssim$900. We calculate the CMB
temperature anisotropies generated by the power-law magnetic field at the last
scattering surface (LSS) in order to remove the tension between theory and
observation at higher multipoles and also place an upper limit on primordial
magnetic field. In our present calculation we take account of the effect of
ionization ratio exactly without approximation. This effect is very crucial to
precisely estimate the effect of the magnetic field on CMB power spectrum. We
consider both effects of the scalar and vector modes of magnetic field on the
CMB anisotropies, where current data are known to be insensitive to the tensor
mode which we ignore in the present study. In order to constrain the primordial
magnetic field, we evaluate likelihood function of the WMAP data in a wide
range of parameters of the magnetic field strength $|\mathbf{B}|_\lambda$ and
the power-law spectral index $n$, along with six cosmological parameters in
flat Universe models, using the technique of the Markov Chain Monte Carlo(MCMC)
method. We find that the upper limit at $2\sigma$ C.L. turns out to be
$|\mathbf{B}_\lambda|\lesssim 3.9 $nG at 1 Mpc for any $n_B$ values, which is
obtained by comparing the calculated result including the Sunyaev-Zeldovich(SZ)
effect with recent WMAP data of the CMB anisotropies.


title: Outbursts of WZ Sagittae

abstract:
  The outbursts of the dwarf nova WZ Sagittae occur on timescales which are
much longer than expected from the standard thermal viscous disc instability
model, which correctly reproduces the outburst behaviour of many other dwarf
novae. In addition short `echo' outbursts have sometimes been observed after
the main outburst. The increased timescales could be explained by a magnetic
propeller, anchored to the primary star, which clears the inner disc . We argue
that the propeller, combined with the resonances of the binary orbit, may also
be the cause of the echo outbursts. We present numerical models which reproduce
the echo outbursts.


title: The Structure and Origin of Magnetic Fields on Accreting White Dwarfs

abstract:
  We have started a systematic study of the field topologies of magnetic single
and accreting white dwarfs using Zeeman tomography. Here we report on our
analysis of phase-resolved flux and circular polarization spectra of the
magnetic cataclysmic variables BL Hyi and MR Ser obtained with FORS1 at the ESO
VLT. For both systems we find that the field topologies are more complex than a
dipole or an offset dipole and require at least multipole expansions up to
order l = 3 to adequately describe the observed Zeeman features and their
variations with rotational phase. Overall our model fits are in excellent
agreement with observations. Remaining residuals indicate that the field
topologies might even be more complex. It is, however, assuring that the global
characteristics of our solutions are consistent with the average effective
field strengths and the halo field strengths derived from intensity spectra in
the past.


title: An Analytic Model of Superclusters

abstract:
  We construct an analytic model for the mass distributions of superclusters
and clusters in each supercluster. Our model is a modification of the
Press-Schechter theory, and defines superclusters as the regions that have some
overdensity smaller than those for usual virialized objects. We compare the
mass functions with a catalog of superclusters in the Sloan Digital Sky Survey
Early Data Release and found that they are in reasonable agreement with each
other.


title:
Submillimetre continuum emission from Class 0 sources: Theory,
  Observations, and Modelling

abstract:
  We report on a study of the thermal dust emission of the circumstellar
envelopes of a sample of Class 0 sources. The physical structure (geometry,
radial intensity profile, spatial temperature and spectral energy distribution)
and properties (mass, size, bolometric luminosity (L_bol) and temperature (T_
bol), and age) of Class 0 sources are derived here in an evolutionary context.
This is done by combining SCUBA imaging at 450 and 850 microm of the thermal
dust emission of envelopes of Class 0 sources in the Perseus and Orion
molecular cloud complexes with a model of the envelope, with the implementation
of techniques like the blackbody fitting and radiative transfer calculations of
dusty envelopes, and with the Smith evolutionary model for protostars. The
modelling results obtained here confirm the validity of a simple spherical
symmetric model envelope, and the assumptions about density and dust
distributions following the standard envelope model. The spherically model
reproduces reasonably well the observed SEDs and the radial profiles of the
sources. The implications of the derived properties for protostellar evolution
are illustrated by analysis of the L_bol, the T_bol, and the power-law index p
of the density distribution for a sample of Class 0 sources.


title:
The Self-Gravitating Gas in the Presence of Dark Energy: Monte-Carlo
  Simulations and Stability Analysis

abstract:
  The self-gravitating gas in the presence of a positive cosmological constant
Lambda is studied in thermal equilibrium by Monte Carlo simulations and by the
mean field approach. We find excellent agreement between both approaches
already for N = 1000 particles on a volume V [The mean field is exact in the
infinite N limit]. The domain of stability of the gas is found to increase when
the cosmological constant increases. The particle density is shown to be an
increasing (decreasing) function of the distance when the dark energy dominates
over self-gravity (and vice-versa).We confirm the validity of the thermodynamic
limit: N, V -> infty with N/V^{1/3} and Lambda V^{2/3} fixed. In such dilute
limit extensive thermodynamic quantities like energy, free energy, entropy turn
to be proportional to N. We find that the gas is stable till the isothermal
compressibility diverges. Beyond this point the gas becomes a extremely dense
object whose properties are studied by Monte Carlo.

categories: astro-ph cond-mat.stat-mech gr-qc hep-th


title:
Golden Binary Gravitational-Wave Sources: Robust Probes of Strong-Field
  Gravity

abstract:
  Space-born gravitational-wave interferometers such as {\it LISA} will detect
the gravitational wave (GW) signal from the inspiral, plunge and ringdown
phases of massive black hole binary mergers at cosmological distances. From the
inspiral waves, we will be able to measure the masses of the binaries' members;
from the ringdown waves, we will be able to measure the mass of the final
merged remnant. A subset of detected events allow the identification of both
the inspiral and the ringdown waveforms in a given source, and thus allow a
measurement of the total mass-energy lost to GWs over the coalescence, $M_{\rm
GW}$. We define ``golden'' binary mergers to be those with measurement errors
likely to be small enough for a physically useful determination of $M_{\rm
GW}$. A detailed sensitivity study, combined with simple black hole population
models, suggests that a few golden binary mergers may be detected during a
3-year {\it LISA} mission lifetime. Any such mass deficit measurement would
constitute a robust and valuable observational test of strong-field
relativistic gravity. An extension of this concept to include spin measurements
may allow a direct empirical test of the black hole area theorem.


title: A deep Chandra observation of the Groth Strip. I. The X-ray data

abstract:
  We present the results of a 200 ks Chandra observation of part of the Groth
Strip region, using the ACIS-I instrument. We present a relatively simple
method for the detection of point-sources and calculation of limiting
sensitivities, which we argue is at least as sensitive and more self-consistent
than previous methods presented in the literature. 158 distinct X-ray sources
are included in our point-source catalogue in the ACIS-I area. The number
counts show a relative dearth of X-ray sources in this region. For example at a
flux limit of 1E-15 (cgs) around 20 per cent more soft band sources are
detected in the HDF-N and almost 50 per cent more in the ELAIS-N1 field, which
we have analysed by the same method for comparison. We find, however, that
these differences are consistent with Poisson variations at 2 sigma
significance, and therefore there is no evidence for cosmic variance based on
these number counts alone. We determine the average spectra of the objects and
find a marked difference between the soft-band selected sources, which have
Gamma=1.9 typical of unobscured AGN, and the hard-band selected sources, which
have Gamma=1.0. Reassuringly, the sample as a whole has a mean spectrum of
Gamma=1.4\pm 0.1, the same as the X-ray background. Nonetheless, our results
imply that the fraction of sources with significant obscuration is only ~25 per
cent, much less than predicted by standard AGN population synthesis models.
This is confirmed by direct spectral fitting, with only a handful of objects
showing evidence for absorption. After accounting for absorption, all objects
are consistent with mean intrinsic spectrum of Gamma=1.76 \pm 0.08, very
similar to local Seyferts (abridged).


title:
The Initial Conditions to Star Formation: Low Mass Stars at Low
  Metallicity

abstract:
  We have measured the present accretion rate of roughly 800 low-mass (~1-1.4
Mo) pre-Main Sequence stars in the field of SN 1987A in the Large Magellanic
Cloud. The stars with statistically significant Balmer continuum and Halpha
excesses are measured to have accretion rates larger than about 1.5x10^{-8}
Mo/yr at an age of 12-16 Myrs. For comparison, the time scale for disk
dissipation observed in the Galaxy is of the order of 6 Myrs.


title:
The radial velocity of the companion star in the low-mass X-ray binary
  2S 0921-630: limits on the mass of the compact object

abstract:
  In this Paper we report on optical spectroscopic observations of the low-mass
X-ray binary 2S 0921-630 obtained with the Very Large Telescope. We found
sinusoidal radial velocity variations of the companion star with a
semi-amplitude of 99.1+-3.1 km s^-1 modulated on a period of 9.006+-0.007 days,
consistent with the orbital period found before for this source, and a systemic
velocity of 44.4+-2.4 km s^-1. Due to X-ray irradiation the centre-of-light
measured by the absorption lines from the companion star is likely shifted with
respect to the centre-of-mass. We try to correct for this using the so-called
K-correction. Conservatively applying the maximum correction possible and using
the previously measured rotational velocity of the companion star, we find a
lower limit to the mass of the compact object in 2S 0921-630 of M_X sin^3 i >
1.90+-0.25 Msun (1 sigma errors). The inclination in this system is well
constrained since partial eclipses have been observed in X-rays and optical
bands. For inclinations between 60< i<90 degrees we find
1.90+-0.25<M_X<2.9+-0.4 Msun. However, using this maximum K-correction we find
that the ratio between the mass of the companion star and that of the compact
object, q, is 1.32+-0.37 implying super-Eddington mass transfer rates; however,
evidence for that has not been found in 2S 0921-630. We conclude that the
compact object in 2S 0921-630 is either a (massive) neutron star or a low-mass
black hole.


title: Radiation efficiencies of the pulsars detected in the optical range

abstract:
  Using available multiwavelength data for the pulsars of different ages
detected in the optical range, we analyze the efficiencies of the conversion of
the pulsar spindown power \dot{E} into the observed non-thermal luminosity L in
different spectral domains. We find that these pulsars show significantly
non-monotonic dependencies of the optical and X-ray efficiencies (\eta =
L/\dot{E}) versus pulsar age with a pronounced minimum at the beginning of the
middle-age epoch and comparably higher efficiencies of younger and older
pulsars. In addition, we find a strong correlation between the optical and
2--10 keV X-ray luminosities of these pulsars that implies the same origin of
their nonthermal emission in both spectral domains.


title: Type IIP Supernovae as Cosmological Probes: A SEAM Distance to SN 1999em

abstract:
  Due to their intrinsic brightness, supernovae make excellent cosmological
probes. We describe the SEAM method for obtaining distances to Type IIP
supernovae (SNe IIP) and present a distance to SN 1999em for which a Cepheid
distance exists. Our models give results consistent with the Cepheid distance,
even though we have not attempted to tune the underlying hydrodynamical model,
we have simply chosen the best fits. This is in contradistinction to the
expanding photosphere method (EPM) which yields a distance to SN 1999em that is
50% smaller than the Cepheid distance. We emphasize the differences between
SEAM and EPM. We show that the dilution factors used in the EPM analysis were
systematically too small at later epochs. We also show that the EPM blackbody
assumption is suspect.
  Since SNe IIP are visible to redshifts as high as z less than about 6, with
the JWST, SEAM may be a valuable probe of the early universe.


title: The Galaxy Cluster Abell 3581 as seen by Chandra

abstract:
  We present results from an analysis of a Chandra observation of the cluster
of galaxies Abell 3581. We discover the presence of a point-source in the
central dominant galaxy which is coincident with the core of the radio source
PKS 1404-267. The emission from the intracluster medium is analysed, both as
seen in projection on the sky, and after correcting for projection effects, to
determine the spatial distribution of gas temperature, density and metallicity.
We find that the cluster, despite hosting a moderately powerful radio source,
shows a temperature decline to around 0.4Tmax within the central 5 kpc. The
cluster is notable for the low entropy within its core. We test and validate
the xspec projct model for determining the intrinsic cluster gas properties.


title:
The Stellar Populations of Low Luminosity Active Galactic Nuclei. III:
  Spatially Resolved Spectral Properties

abstract:
  In a recent survey of the stellar populations of LINERS and LINER/HII
Transition Objects (TOs) we identified a numerous class of nuclei which stand
out because of their conspicuous 10^8-9 yr populations. These objects were
called ``Young-TOs'', since they all have TO-like emission line ratios. In this
paper we investigate the radial variations of spectral properties in Low
Luminosity AGN. Our analysis is based on high S/N, 3500-5500 A, long-slit
spectra for 47 galaxies. The data probe distances of typically up to 850 pc
from the nucleus with a resolution of ~ 100 pc and S/N ~ 30. Stellar population
gradients are mapped by the radial profiles of absorption line equivalent
widths and colours along the slit. These variations are further analyzed by
means of a decomposition of each spectrum in terms of template galaxies
representative of very young (<= 10^7 yr), intermediate age (10^8-9 yr) and old
(10^10 yr) populations.
  Our main findings are: (1) Significant stellar population gradients are found
almost exclusively in Young-TOs. (2) The intermediate age population of
Young-TOs, although heavily concentrated in the nucleus, reaches distances of
up to a few hundred pc. (3) Objects with predominantly old populations present
spatially homogeneous spectra, be they LINERs or TOs. (4) Young-TOs have much
more dust in their central regions than other LLAGN. (5) The B-band
luminosities of the central <~ 1 Gyr population in Young-TOs are within an
order of magnitude of M_B = -15, implying masses of order ~ 10^7-10^8 Mo. This
population was 10-100 times more luminous in its formation epoch, at which time
young massive stars would have completely outshone any active nucleus, unless
the AGN too was brighter in the past. (abridged)


title:
Intra-night Optical Variability of BL Lacs, Radio-Quiet Quasars and
  Radio-Loud Quasars

abstract:
  We report optical monitoring observations of 20 high-luminosity AGN, 12 of
which are radio-quiet quasars (RQQs). Intra-night optical variability (INOV)
was detected for 13 of the 20 objects, including 5 RQQs. The variations are
distinctly stronger and more frequent for blazars than for the other AGN
classes. By combining these data with results obtained earlier in our program,
we have formed an enlarged sample consisting of 9 BL Lacs, 19 RQQs and 11
lobe-dominated radio-loud quasars. The moderate level of rapid optical
variability found for both RQQs and radio lobe-dominated quasars argues against
a direct link between INOV and radio-loudness. We supplemented the present
observations of 3 BL Lacs with additional data from the literature. In this
extended sample of 12 well observed BL Lacs, stronger INOV is found for the
EGRET detected BL Lacs.


title:
Testing blend scenarios for extrasolar transiting planet candidates. II.
  -- OGLE-TR-56

abstract:
  We re-examine the photometric and spectroscopic evidence available for the
star OGLE-TR-56, recently discovered to harbor a giant planet presenting
transits and orbiting with a period of 1.21 days. We investigate the
possibility that the observational signatures reported might be the result of
"blending" with the light of an eclipsing binary along the same line of sight.
Using techniques developed earlier we perform fits to the light curve under a
variety of blend configurations, subject to all observational constraints, and
we infer further properties of these possible blends. We then carry out
realistic end-to-end simulations based on those properties in order to quantify
the spectral line asymmetries and radial velocity variations expected from such
scenarios. We confront these calculations with the observations. The results
from these models are clearly inconsistent with the measured radial velocity
and bisector span variations, ruling out blends and confirming the planetary
nature of the companion. The example of OGLE-TR-56 serves to illustrate the
sort of tests that can and should be performed on transiting planet candidates
to eliminate the possibility of "false positives", and in particular,
line-of-sight contamination from eclipsing binaries.


title: A Photometric Technique to Search for Be Stars in Open Clusters

abstract:
  We describe a technique to identify Be stars in open clusters using Stromgren
b, y, and narrow-band Halpha photometry. We first identify the B-type stars of
the cluster using a theoretical isochrone fit to the (b-y, y) color-magnitude
diagram. The strongest Be stars are easily identified in a (b-y, y-Halpha)
color-color diagram, but those with weaker Halpha emission (classified as
possible Be star detections) may be confused with evolved or foreground stars.
Here we present such photometry plus Halpha spectroscopy of members of the
cluster NGC 3766 to demonstrate the accuracy of our technique. Statistical
results on the relative numbers of Be and B-type stars in additional clusters
will be presented in a future paper.


title: HST spectral mapping of V2051 Ophiuchi in a low state

abstract:
  V2051 Oph is an eclipsing dwarf novae with an orbital period of 90 min. This
system belongs to a small group of ultrashort period eclipsing dwarf nova
together with Z Cha, OY Car and HT Cas. We report a study of the spectra and
structure of the accretion disc of the V2051 Oph while the star was in an
unusual, faint brightness state during 1996. The analysis is based on
high-speed ultraviolet and optical spectroscopy secured with the Hubble Space
Telescope.


title: News from a Multi-Wavelength Monitoring Campaign on Mrk 421

abstract:
  We conducted a daily monitoring campaign on Mrk 421 in 2003 and 2004 with the
Whipple 10 m telescope and the large-area instruments aboard RXTE,
simultaneously covering TeV and X-ray energies. Supporting observations at
optical and radio wavelengths were also frequently carried out. Mrk 421 was
observed over a wide range of fluxes (with a dynamic range of ~30 both at TeV
and X-ray energies). The source was relatively quiet in 2003 but became
unusually active in 2004, with flares reaching peak fluxes of ~80 mCrab in
X-rays and >3 Crab at TeV energies! We will describe the multiwavelength
campaign and present some preliminary results. We will also discuss the
implications of the results on the proposed emission models for TeV blazars.


title: Extra-planar H I in the Inner Milky Way

abstract:
  The extra-planar H I in the inner parts of the Milky Way has been discovered
to contain numerous cloud-like structures when observed in the 21cm line with
the Green Bank Telescope (GBT). These halo clouds have motions consistent with
Galactic rotation and do not seem to be related to the classic high-velocity
clouds. They are found to distances >1 kpc from the plane and can contain
hundreds of solar masses of H I. Spectra of many of the halo clouds show
evidence of coexisting cool and warm H I phases. A preliminary high-resolution
study of one of the clouds suggests that it consists of a diffuse envelope and
a few dense cores, with a peak H I column density reaching 4 x 10^20 cm^-2. The
clouds are often organized into larger structures, one example of which was
discovered near 35 degrees Galactic longitude rising higher than 2 kpc above
the Galactic plane. New observations should answer some fundamental questions
about the nature of these clouds.


title: An X-ray view of WLRGs/LINERs

abstract:
  We present X-ray observations of nine Weak-Line Radio Galaxies (WLRGs),
optically classified as confirmed or possible Low Ionization Nuclear
Emission-line Regions (LINERs). The data were taken from the Chandra, XMM, and
BeppoSax archives. The Chandra images typically show complex X-ray
morphologies, with hard (2-10 keV) point sources embedded in diffuse soft
(0.3-2.0 keV) emission in all cases except 1246-41 (NGC 4696), where only
diffuse emission is detected on the scale of the cluster, and 0334-01 (3C 15),
where only a point source is detected. The nuclear X-ray spectra are well
fitted at hard energies by an absorbed powerlaw, with a wide range of photon
indices, Gamma=1.5-2.7. Excess absorption over the Galactic value is detected
in 6/9 sources, with column densities NH approximately 10^21-22 cm^-2. A
thermal component is required at softer energies, in agreement with the results
of the spatial analysis. We find that there is no correlation between the core
X-ray luminosity and the radio core dominance parameter, suggesting that the
bulk of the core X-ray emission is not beamed, but rather is isotropic and thus
likely related to the accretion flow. In an attempt to constrain the nature of
the accretion flow, we calculate the ratios of bolometric to Eddington
luminosities L_bol/L_Edd, and the radiative efficiency eta based on the Bondi
accretion rates. We find that L_bol/L_Edd ~10^-4 - 10^-6 and eta ~10^-2 - 10^-6
for all the objects in our sample, suggesting radiatively inefficient accretion
flows.


title: The Radio and X-ray Luminous Type Ibc Supernova 2003L

abstract:
  We present extensive radio observations of SN 2003L, the most luminous and
energetic Type Ibc radio supernova with the exception of SN 1998bw (associated
with GRB 980425). Observations from the Very Large Array are well described by
a fitting a synchrotron self-absorption model to the emission spectrum. This
model implies a sub-relativistic ejecta velocity, v ~ 0.2c, and a size of r ~
4.3 x 10^{15} cm at t ~ 10 days. The circumstellar density is suitably fit with
a stellar wind profile, n_e ~ r^{-2} and a constant mass loss rate of M_dot ~
7.5 x 10^{-6} M_{solar}/year. Moreover, the magnetic field follows B ~ r^{-1}
and the kinetic energy of the radio bright ejecta is roughly E ~ 10^{48} erg
assuming equipartition of energy between relativistic electrons and magnetic
fields. Furthermore, we show that free-free absorption does not contribute
significantly to the radio spectrum, since it implies ejecta velocities which
are inconsistent with size constraints derived from Very Long Baseline Array
observations. In conclusion, we find that although SN 2003L has a radio
luminosity comparable to that seen in SN 1998bw, it shows no evidence for a
significant amount of energy coupled to relativistic ejecta. Using SN 2003L as
an example, we comment briefly on the coupling of ejecta velocity and energy in
Type Ibc supernovae.


title:
The properties and luminosity function of extremely low luminosity
  galaxies

abstract:
  We examine a sample of low redshift (10 < d < 150 Mpc) galaxies including
galaxies with r-band absolute magnitudes as faint as -12.5 (for h=1), selected
from the Sloan Digital Sky Survey Data Release 2 (SDSS). The sample is unique
in containing galaxies of extremely low luminosities in a wide range of
environments, selected with uniform and well-understood criteria. We present
the luminosity function as well as the broad-band properties of low luminosity
galaxies in this sample. A Schechter function is an insufficient
parameterization of the r-band luminosity function; there is an upturn in the
slope at low luminosities. The resulting slope at low luminosities in this
sample is around -1.3. However, we almost certainly miss a large number of
galaxies at very low luminosities due to low surface brightness selection
effects, and we estimate that the true low luminosity slope may be as steep or
steeper than -1.5. The results here are consistent with previous SDSS results
and, in the g-band, roughly consistent with the results of the Two degree Field
Galaxy Redshift Survey. Extremely low luminosity galaxies are predominantly
blue, low surface brightness, exponential disks.


title: The Spatial Clustering of Star-forming Galaxies at Redshifts 1.4<z<3.5

abstract:
  We analyzed the spatial distribution of 28500 photometrically selected
galaxies with AB magnitude 23.5<R<25.5 and redshift 1.4<z<3.5 in 21 fields with
a total area of 0.81 square degrees. The galaxies were divided into three
subsamples, with mean redshifts z=1.7, 2.2, 2.9, according to the UGR selection
criteria of Adelberger et al. (2004) and Steidel et al. (2003). Combining the
galaxies' measured angular clustering with redshift distributions inferred from
1600 spectroscopic redshifts, we find comoving correlation lengths at the three
redshifts of r_0 = 4.5+-0.6, 4.2+-0.5, and 4.0+-0.6 h^-1 Mpc, respectively, and
infer a roughly constant correlation function slope of gamma=1.6+-0.1. We
derive similar numbers from the 1600 object spectroscopic sample itself with a
new statistic, K, that is insensitive to many possible systematics. Galaxies
that are bright in R (lambda_rest ~ 1500-2500A) cluster more strongly than
fainter galaxies at z=2.9 and z=2.2 but not, apparently, at z=1.7. Comparison
to a numerical simulation that is consistent with recent WMAP observations
suggests that galaxies in our samples are associated with dark matter halos of
mass ~ 10^12, and that a small fraction of the halos contain more than one
galaxy that satisfies our selection criteria. Adding recent observations of
galaxy clustering at z~0 and z~1 to the simulation results, we conclude that
the typical object in our samples will evolve into an elliptical galaxy by
redshift z=0 and will already have an early-type spectrum by redshift z=1. We
comment briefly on the implied relationship between galaxies in our survey and
those selected with other techniques. (slightly abridged)


title: NYU-VAGC: a galaxy catalog based on new public surveys

abstract:
  Here we present the New York University Value-Added Galaxy Catalog
(NYU-VAGC), a catalog of local galaxies (mostly below a redshift of about 0.3)
based on a set of publicly-released surveys (including the 2dFGRS, 2MASS, PSCz,
FIRST, and RC3) matched to the Sloan Digital Sky Survey (SDSS) Data Release 2.
Excluding areas masked by bright stars, the photometric sample covers 3514
square degrees and the spectroscopic sample covers 2627 square degrees (with
about 85% completeness). Earlier, proprietary versions of this catalog have
formed the basis of many SDSS investigations of the power spectrum, correlation
function, and luminosity function of galaxies. We calculate and compile derived
quantities (for example, K-corrections and structural parameters for galaxies).
The SDSS catalog presented here is photometrically recalibrated, reducing
systematic calibration errors across the sky from about 2% to about 1%. We
include an explicit description of the geometry of the catalog, including all
imaging and targeting information as a function of sky position. Finally, we
have performed eyeball quality checks on a large number of objects in the
catalog in order to flag deblending and other errors. This catalog is
complementary to the SDSS Archive Servers, in that NYU-VAGC's calibration,
geometrical description, and conveniently small size are specifically designed
for studying galaxy properties and large-scale structure statistics using the
SDSS spectroscopic catalog.


title:
Chandra X-ray Observations of Newly Discovered, z ~ 1 Clusters from the
  Red-Sequence Cluster Survey

abstract:
  Observational studies of cluster evolution over moderate redshift ranges (to
z ~ 1) are a powerful tool for constraining cosmological parameters, yet a
comprehensive knowledge of the properties of these clusters has been hitherto
unattained. Using a highly efficient optical selection technique, the
Red-Sequence Cluster Survey (RCS) has unearthed a large sample of high redshift
cluster candidates. All six of the clusters from this sample which have been
observed with the Chandra X-Ray Observatory were detected in the X-ray. These
Chandra follow-up observations (0.64 < z < 1.0) indicate that the clusters are
systematically less luminous than their similarly rich, X-ray selected
counterparts at lower redshifts, though they are consistent with standard Lx-Tx
relationships. Comparisons with X-ray selected samples suggest that the
discrepancy may be due in part to systematic differences in the spatial
structure of the X-ray emitting gas. Our initial results from Chandra follow-up
observations of six RCS clusters are presented, including beta model parameters
and spectral information.


title:
The Need to Measure Low Energy Anti-Neutrinos (E < 0.782MeV) from the
  Sun

abstract:
  Measurements are needed of low energy, anti-neutrinos generated by possible
neutron decay at the core of the Sun. The measurement will test the validity of
a proposal that solar luminosity, neutrinos, and the solar wind are products of
a chain of reactions triggered by neutron emission from the solar core. Inverse
beta-decay of 87-day S-35, induced by capture of low-energy anti-neutrinos on
Cl-35, is a likely candidate for this measurement.


title:
Chandra discovery of activity in the quiescent nuclear black hole of
  NGC821

abstract:
  We report the results of the Chandra ACIS-S observations of the elliptical
galaxy NGC 821, which harbors a supermassive nuclear black hole (of 3.5x10^7
solar masses), but does not show sign of AGN activity. A small, 8.5" long (~1
kpc at the galaxy's distance of 23 Mpc), S-shaped, jet-like feature centered on
the nucleus is detected in the 38 ksec ACIS-S integrated exposure of this
region. The luminosity of this feature is L_X ~ 2.6 x 10^39 erg/s (0.3-10 keV),
and its spectrum is hard (described by a power-law of Gamma =
1.8^{+0.7}_{-0.6}; or by thermal emission with kT > 2 keV). We discuss two
possibilities for the origin of this feature: (1) a low-luminosity X-ray jet,
or (2) a hot shocked gas. In either case, it is a clear indication of nuclear
activity, detectable only in the X-ray band. Steady spherical accretion of the
mass losses from the central stellar cusp within the accretion radius, when
coupled to a high radiative efficiency, already provides a power source
exceeding the observed radiative losses from the nuclear region.


title:
New Silhouette Disks with Reflection Nebulae and Outflows in the Orion
  Nebula and M43

abstract:
  We report the detection of several new circumstellar disks seen in silhouette
in the outskirts of the Orion nebula and M43, detected as part of our Halpha
survey of Orion with the HST/ACS. Several of the disks show bipolar reflection
nebulae, microjets, or temporal variability. Two disks in our sample are large
and particularly noteworthy: A nearly edge-on disk, d216-0939, is located
several arcminutes northwest of M43 and resembles the famous HH30 disk/jet
system in Taurus. It drives the 0.15 pc long bipolar outflow HH667, and
exhibits a remarkable asymmetric reflection nebula. With a diameter of 1200 AU,
it is as large as the giant edge-on silhouette disk d114-426 in the core of the
Orion Nebula. The large disk d253-1536 is located in a binary system embedded
within an externally-ionized giant proplyd in M43. The disk exhibits
distortions which we attribute to tidal interactions with a companion. The
bipolar jet HH668 emerges orthogonal to the disk, and a bow shock lies 54''
south of this binary system along the outflow axis. Proper motions over 1.4 yr
confirm that these emission knots are moving away from d253-1536, with speeds
as high as 330 km/s in the HH668 microjet, and slower motion farther from the
star.


title:
Polarimetric variations of binary stars. VI. Orbit-induced variations in
  the pre-main-sequence binary AK Sco

abstract:
  We present simultaneous UBV polarimetric and photometric observations of the
pre-main-sequence binary AK Sco, obtained over 12 nights, slightly less than
the orbital period of 13.6 days. The polarization is a sum of interstellar and
intrinsic polarization, with a significant intrinsic polarization of 1% at
5250A, indicating the presence of circumstellar matter distributed in an
asymmetric geometry. The polarization and its position angle are clearly
variable on time scales of hours and nights, in all 3 wavelengths, with a
behavior related to the orbital motion. The variations have the highest
amplitudes seen so far for pre-main-sequence binaries (~1%, ~30deg) and are
sinusoidal with periods similar to the orbital period and half of it. The
polarization variations are generally correlated with the photometric ones:
when the star gets fainter, it also gets redder and its polarization increases.
The color-magnitude diagram B-V, V exhibits a ratio of total to selective
absorption R=4.3 higher than in normal interstellar clouds (R=3.1). The
interpretation of the simultaneous photometric and polarimetric observations is
that a cloud of circumstellar matter passes in front of the star, decreasing
the amount of direct, unpolarized light, and hence increasing the contribution
of scattered (blue) light. We show that the large amplitude of the polarization
variations can not be reproduced with a single scattering model and axially
symmetric circumbinary or circumstellar disks.


title: A Catalog of Very Isolated Galaxies from the SDSS Data Release 1

abstract:
  We present a new catalog of isolated galaxies obtained through an automated
systematic search. These 2980 isolated galaxies were found in approximately
2099 sq deg of sky in the Sloan Digital Sky Survey Data Release 1 (SDSS DR1)
photometry. The selection algorithm, implementing a variation on the criteria
developed by Karachentseva in 1973, proved to be very efficient and fast. This
catalog will be useful for studies of the general galaxy characteristics. Here
we report on our results.


title: Tracing cosmic evolution with clusters of galaxies

abstract:
  The most successful cosmological models to date envision structure formation
as a hierarchical process in which gravity is constantly drawing lumps of
matter together to form increasingly larger structures. Clusters of galaxies
currently sit atop this hierarchy as the largest objects that have had time to
collapse under the influence of their own gravity. Thus, their appearance on
the cosmic scene is also relatively recent. Two features of clusters make them
uniquely useful tracers of cosmic evolution. First, clusters are the biggest
things whose masses we can reliably measure because they are the largest
objects to have undergone gravitational relaxation and entered into virial
equilibrium. Mass measurements of nearby clusters can therefore be used to
determine the amount of structure in the universe on scales of 10^14 to 10^15
solar masses, and comparisons of the present-day cluster mass distribution with
the mass distribution at earlier times can be used to measure the rate of
structure formation, placing important constraints on cosmological models.
Second, clusters are essentially ``closed boxes'' that retain all their gaseous
matter, despite the enormous energy input associated with supernovae and active
galactic nuclei, because the gravitational potential wells of clusters are so
deep. The baryonic component of clusters therefore contains a wealth of
information about the processes associated with galaxy formation, including the
efficiency with which baryons are converted into stars and the effects of the
resulting feedback processes on galaxy formation. This article reviews our
theoretical understanding of both the dark-matter component and the baryonic
component of clusters. (Abridged)


title: MRC B1221-423: a compact steep-spectrum radio source in a merging galaxy

abstract:
  We present BVRIK images and spectroscopic observations of the z=0.17 host
galaxy of the compact steep-spectrum radio source MRC B1221-423. This is a
young (~1e5 yr) radio source with double lobes lying well within the visible
galaxy. The host galaxy is undergoing tidal interaction with a nearby
companion, with shells, tidal tails, and knotty star-forming regions all
visible. We analyse the images of the galaxy and its companion pixel-by-pixel,
first using colour-magnitude diagrams, and then fitting stellar population
models to the spectral energy distributions of each pixel. The pixels separate
cleanly in colour-magnitude diagrams, with pixels of different colours
occupying distinct regions of the host galaxy and its companion. We find three
distinct groups of ages: an old population in the outskirts of the host galaxy;
an intermediate-age population around the nucleus and tidal tail, and a young
population in the nucleus and blue "knots".
  The correlation of age with position suggests the two most recent episodes
were triggered by tidal interactions with the companion galaxy. The evidence
points to the AGN in the centre of B1221-423 having been "caught in the act" of
ignition. However, none of the components we have identified is as young as the
radio source, implying that the delay between the interaction and the
triggering of the AGN is at least 300 My.


title:
Cosmological Lepton Asymmetry, Primordial Nucleosynthesis, and Sterile
  Neutrinos

abstract:
  We study post weak decoupling coherent active-sterile and active-active
matter-enhanced neutrino flavor transformation in the early universe. We show
that flavor conversion efficiency at Mikheyev-Smirnov-Wolfenstein resonances is
likely to be high (adiabatic evolution) for relevant neutrino parameters and
energies. However, we point out that these resonances cannot sweep smoothly and
continuously with the expansion of the universe. We show how neutrino flavor
conversion in this way can leave both the active and sterile neutrinos with
non-thermal energy spectra, and how, in turn, these distorted energy spectra
can affect the neutron-to-proton ratio, primordial nucleosynthesis, and
cosmological mass/closure constraints on sterile neutrinos. We demonstrate that
the existence of a light sterile neutrino which mixes with active neutrinos can
change fundamentally the relationship between the cosmological lepton numbers
and the primordial nucleosynthesis He-4 yield.


title: Deep VLBI Imaging of Faint Radio Sources in the NOAO Bootes Field

abstract:
  We have conducted a deep, very long baseline interferometry (VLBI)
observation at 1.4 GHz of an area of sky located within the NOAO Bootes field,
using the NRAO VLBA and 100-m Green Bank Telescope. Applying wide-field VLBI
techniques, a total of 61 sources, selected from a WSRT image, were surveyed
simultaneously with a range of different sensitivities and resolutions. The
inner 0-2', of the field reached an unprecedented 1-sigma rms noise level ~ 9
uJy/beam and yielded 2 detections. A further 7 sources were detected in the
rest of the field. All of the sources have a brightness temperature in excess
of 10^5 K; suggesting they are AGN. Optical identifications are available for 8
of the 9 VLBI detections - only VLBI J142906.6095 remains unidentified (I >
25.6m). Two sources are not detected in K-band (K > 18.5m) suggesting that some
significant fraction of these compact radio sources may be located at z > 1.
The VLBI detection rate for sub-mJy radio sources is 8^{+4}_{-5} %. The VLBI
detection rate for mJy sources is higher, 29^{+11}_{-12}%. This trend is
expected if the radio emission associated with fainter sub-mJy and microJy
sources increasingly arises from extended regions of star formation. The 9 VLBI
detections pin-point the precise location of AGN or candidate AGN, and their
VLBI positions can help to anchor the NOAO Bootes field to the ICRF. The
simultaneous detection of several sub-mJy and mJy radio sources, in a single
observation, suggest that their combined response may be used to self-calibrate
wide-field VLBI data. Future VLBI observations of faint sub-mJy and microJy
radio sources can take full advantage of this "full-beam" calibration
technique.


title:
Multi-wavelength observations of an unusual impulsive flare associated
  with CME

abstract:
  We present the results of a detailed analysis of multi-wavelength
observations of a very impulsive solar flare 1B/M6.7, which occurred on 10
March, 2001 in NOAA AR 9368 (N27 W42). The observations show that the flare is
very impulsive with very hard spectrum in HXR that reveal non-thermal emission
was most dominant. On the other hand this flare also produced type II radio
burst and coronal mass ejections (CME), which are not general characteristics
for impulsive flares. In H$\alpha$ we observed the bright mass ejecta (BME)
followed by drak mass ejecta (DME). Based on the consistence of the onset times
and direction of BME and CME, we conclude that these two phenomena are closely
associated. It is inferred that the energy build-up took place due to
photospheric reconnection between emerging positive parasitic polarity and
predominant negative polarity, which resulted as a consequence of flux
cancellation. The shear increased to $>80^o$ due to further emergence of
positive parasitic polarity causing strongly enhanced cancellation of flux. It
appears that such enhanced magnetic flux cancellation in a strongly sheared
region triggered the impulsive flare.


title:
Near-infrared identification of the counterpart to X1908+075: a new
  OB-supergiant X-ray binary

abstract:
  We report the near-infrared (IR) identification of the likely counterpart to
X1908+075, a highly-absorbed Galactic X-ray source recently suspected to belong
to the rare class of OB supergiant-neutron star binary systems. Our JHKs-band
imaging of the field reveals the existence within the X-ray error boxes of a
near-IR source consistent with an early-type star lying at d=7 kpc and
suffering A(V)=16 mag of extinction, the latter value being in good agreement
with the hydrogen column density derived from a modelling of the X-ray
spectrum. Our follow-up, near-IR spectroscopic observations confirm the nature
of this candidate and lead to a late O-type supergiant classification, thereby
supporting the identification of a new Galactic OB-supergiant X-ray binary.


title: A new method for the UHECR mass composition studies

abstract:
  The detemination of the primary cosmic ray mass composition from the
longitudinal development of atmospheric cascades is still an open problem. In
this work we propose a new method of the multiparametric topological analysis
and show that if both X$_{max}$ - the depth of shower maximum and N$_{max}$ -
the number of charged particles in the shower maximum are used, reliable
results can be obtained.


title:
Mg abundances in metal-poor halo stars as a tracer of early Galactic
  mixing

abstract:
  We present results of a detailed chemical analysis performed on 23
main-sequence turnoff stars having -3.4<=[Fe/H]<=-2.2, a sample selected to be
highly homogeneous in T_eff and log(g). We investigate the efficiency of mixing
in the early Galaxy by means of the [Mg/Fe] ratio, and find that all values lie
within a total range of 0.2 dex, with a standard deviation about the mean of
0.06 dex, consistent with measurement errors. This implies there is "little or
no intrinsic scatter" in the early ISM, as suggested also by the most recent
results from high-quality VLT observations. These results are in contrast with
inhomogeneous Galactic chemical evolution (iGCE) models adopting present
supernova (SN) II yields, which predict a peak-to-peak scatter in [Mg/Fe] as
high as 1 dex at very low metallicity, with a corresponding standard deviation
of about 0.4 dex. We propose that cooling and mixing timescales should be
investigated in iGCE models to account for the apparent disagreement with
present observations. The contrast between the constancy and small dispersion
of [Mg/Fe] reported here and the quite different behaviour of [Ba/Fe]
indicates, according to this interpretation, that Mg and Ba are predominantly
synthesised in different progenitor mass ranges.


title:
Outflows Near An Accreting Black Hole: Ionization and Temperature
  Structure

abstract:
  We calculate the temperature and ionization balance in an outflow from an
accreting black hole under illumination by hard radiation from the central
object. Electron scattering of the Fe K_alpha photons within the highly ionized
expanding flow leads to a decrease of their energy (redshift) which is first
order in v/c, when v is the outflow velocity and v is much less than the speed
of light c. This photon redshift is an intrinsic property of any outflow for
which divergence is positive. We also find that the equivalent widths of
red-skewed K_alpha originated in the wind is of order of keV. We conclude that
redshifted lines are intrinsic properties of the powerful outflows that are
observed in many compact objects. Downscattering of the primary line photons
generated in the outflow (a more natural and probable mechanism than the
general relativistic effects in the innermost part of the accretion flow) leads
to the formation of red-skewed lines.


title: Magnetic Field in Clusters of Galaxies

abstract:
  The existence of magnetic fields associated with the intracluster medium in
clusters of galaxies is now well established through different methods of
analysis. Magnetic fields are investigated in the radio band from studies of
the rotation measure of polarized radio galaxies and the synchrotron emission
of cluster-wide diffuse sources. Other techniques include X-ray studies of the
inverse Compton emission and of cold fronts and magneto hydrodynamic
simulations. We review the main issues that have led to our knowledge on
magnetic fields in clusters of galaxies. Observations show that cluster fields
are at the $\mu$G level, with values up to tens of $\mu$G at the center of
cooling core clusters. Estimates obtained from different observational
approaches may differ by about an order of magnitude. However, the discrepancy
may be alleviated by considering that the magnetic field is not constant
through the cluster, and shows a complex structure. In particular, the magnetic
field intensity declines with the cluster radius with a rough dependence on the
thermal gas density. Moreover, cluster magnetic fields are likely to fluctuate
over a wide range of spatial scales with values from a few kpc up to hundreds
kpc. Important information on the cluster field are obtained by comparing the
observational results with the prediction from numerical simulations. The
origin of cluster magnetic fields is still debated. They might originate in the
early Universe, either before or after the recombination, or they could have
been deposited in the intracluster medium by normal galaxies, starburst
galaxies, or AGN. In either case, magnetic fields undergo significant
amplification during the cluster merger processes.


title: Velocity Effects on the Deflection of Light by Gravitational Microlenses

abstract:
  We study the influence of general lens and source velocities on the
gravitational deflection of light by single and two-point-mass microlenses with
general axis orientation. We demonstrate that in all cases the lens equation
preserves its form exactly. However, its parameters -- the Einstein radius and
the binary-lens separation -- are influenced by the lens velocity. In Galactic
microlensing settings the velocity mainly affects the inferred separation for
wide binary-star or star+planet microlenses oriented close to the line of
sight. We briefly discuss the case of lenses moving with highly relativistic
velocities.


title:
A new multiparametric topological method for determining the primary
  cosmic ray mass composition in the knee energy region

abstract:
  The determination of the primary cosmic ray mass composition from the
characteristics of extensive air showers (EAS), obtained at an observation
level in the lower half of the atmosphere, is still an open problem. In this
work we propose a new method of the Multiparametric Topological Analysis and
show its applicability for the determination of the mass composition of the
primary cosmic rays at the PeV energy region.


title: G287.84--0.82: An Infrared Star Cluster in the Carina Nebula

abstract:
  We have studied the properties of an infrared cluster embedded in the gas and
dust of the southern part of the Carina Nebula (NGC 3372), where the probable
existence of current star formation has already been predicted. We used
mid-infrared (A & C bands) and near-infrared (J H K$_{\rm s}$) images from the
MSX and the 2MASS surveys respectively, combined with an optical H$_\alpha$
narrow-band filter image obtained at the CTIO. The infrared star cluster has at
least 17 members, and its parameters, radius and stellar density are in very
good agreement with high- to intermediate-mass star formation scenarios. The
detected IR sources have roughly the same intrinsic infrared excess determined
from their position in colour-colour and colour-magnitude diagrams, suggesting
that these objects could be related to pre-main sequence stars of high to
intermediate mass. Furthermore, we present a low-dispersion spectrum of LS 1883
(O9.5 V) star located near the centre of the IR cluster. The position of this
object in the colour-colour and colour-magnitude IR diagrams lies close to the
reddening vector of an ZAMS O9 V spectral type star, and it seems to be the
first star of this cluster to emerge. All these facts are consistent with the
current star-forming scenarios associated with highly embedded star clusters.


title: Gamma-ray burst interaction with dense interstellar medium

abstract:
  Interaction of cosmological gamma ray burst radiation with the dense
interstellar medium of host galaxy is considered. Gas dynamical motion of
interstellar medium driven by gamma ray burst is investigated in 2D
approximation for different initial density distributions of host galaxy matter
and different total energy of gamma ray burst. The maximum velocity of motion
of interstellar medium is $1.8\cdot10^4$ km/s. Light curves of gamma ray burst
afterglow are calculated for set of non homogeneous density, distribution gamma
ray burst total energy, and different viewing angles. Spectra of gamma ray
burst afterglow are modeled taking into account conversion of hard photons
(soft X-ray, hard UV) to soft UV and optics photons.


title:
The Impact of Supernovae of Type Ia on Large Scales through the Secular
  Evolution of their Rate

abstract:
  A straightforward formalism to evaluate the impact of Type Ia Supernovae on
large scale astrophysical issues is presented, together with analytical
formulations for the SNIa rate following an instantaneous burst of Star
Formation, for both single and double degenrates SNIa progenitors' models. Some
applications of the parametrized formalism are illustrated. In particular, it
is shown that the current SNIa rates measured in early and late type galaxies,
as well as the Fe Mass-to-Light ratio in clusters of galaxies, favour the
double degenerate model.


title: On the geometrical origin of periodicity in blazar-type sources

abstract:
  Periodicities in blazar light curves may be related to helical trajectories
in extragalactic radio jets by differential Doppler boosting effects. We
consider ballistic and non-ballistic (i.e., radial) trajectories and discuss
three possible periodic driving mechanisms for the origin of helical jet paths,
namely, orbital motion in a binary black hole system (BBHS), jet precession,
and intrinsic jet rotation. It is shown that precessional-driven ballistic
motion is unlikely to result in observable periods of less than several tens of
years. We demonstrate that for non-ballistic helical motion the observed period
is generally strongly shortened relative to the real physical driving period
because of light-travel time effects. Internal jet rotation may thus account
for observed periods $P_{\rm obs} \leq 10$ days. Periodicity due to
orbital-driven (non-ballistic) helical motion, on the other hand, is usually
constrained to periods of $P_{\rm obs} \geq 10$ days, while Newtonian-driven
precession is unlikely to be responsible for periodicity on a timescale $P_{\rm
obs} \leq 100$ days but may well be associated with periods of $P_{\rm obs}
\geq 1$ yr.


title: He II Reionization and Sources of Metagalactic Ionization

abstract:
  Intergalactic Ly-alpha opacity suggests that H I was reionized at z ~ 6,
while He II reionization was delayed to z ~ 3. Both epochs are in conflict with
inferences from CMB optical depth (WMAP) which suggest early reionization at z
= 10-20. One of the major contributions of FUSE to cosmological studies has
been the detection of He II Ly-alpha (Gunn-Peterson) absorption in the spectra
of AGN at redshifts z > 2.03. Spectra of He II absorbers, taken in concert with
corresponding H I (Ly-alpha) lines, allow us to fix the epoch of helium
reionization at z(HeII) ~ 2.8 +/- 0.2. Here, I review FUSE observations of He
II absorption, together with their implications for the sources and transport
of ionizing radiation over 30-50 Mpc distances through the IGM. FUSE
observations of He II absorption toward HE 2347-4342, combined with Keck and
VLT observations of H I, are consistent with photoionization by QSOs, with a
wide range of intrinsic spectral indices, and modified by filtering and
reprocessing in the IGM. The He II/H I ratio (eta) exhibits variations over 1
Mpc distance scales (Delta z ~ 0.001). Intriguingly, this eta-ratio is also
correlated with Ly-alpha filaments and voids. The ionizing radiation field
appears to be softer (higher He II/H I) in the voids. These void regions may be
ionized by local soft sources (dwarf starburst galaxies), or the QSO radiation
may softened by escape from AGN cores and transport through denser regions in
the cosmic web. The differences in ionizing spectra may explain the 1.4 Gyr lag
between H I and He II reionization epochs.


title: Stochastic Quintessence

abstract:
  The behavior of the quintessence field is studied during inflation. In order
to have a satisfactory model of dark energy, the quintessence field value today
should be as insensible to the initial conditions as possible. Usually, only
the dependence on the initial conditions specified at the end of inflation or,
equivalently, at the beginning of the radiation dominated era, is considered.
Provided the quintessence field is initially within a large but, crucially,
finite interval, its present value becomes independent of the initial value it
started from. The question as to whether inflation naturally drives the
quintessence field to the above-mentioned interval is addressed. Since the
quantum effects turn out to be important, the formalism of stochastic inflation
is used in order to calculate the evolution of the quintessence field.
Moreover, the quantum effects originating from the inflaton field are also
taken into account and are proved to be sub-dominant in most cases. Finally,
the requirement that the quintessence field is on tracks today is shown to
imply quite tight constraints on the initial values of the quintessence and
inflaton fields at the beginning of inflation. In particular, the initial value
of the inflaton field cannot be too large which indicates that the
quintessential scenario seems to be compatible with inflation only if the total
number of e-folds is quite small.


title: OH rotational lines as a diagnostic of the warm neutral gas in galaxies

abstract:
  We present Infrared Space Observatory (ISO) observations of several OH, CH
and H2O rotational lines toward the bright infrared galaxies NGC253 and
NGC1068. As found in the Galactic clouds in SgrB2 and Orion, the extragalactic
far-IR OH lines change from absorption to emission depending on the physical
conditions and distribution of gas and dust along the line of sight. As a
result, most of the OH rotational lines that appear in absorption toward NGC253
are observed in emission toward NGC1068. We show that the far-IR spectrum of OH
can be used as a powerful diagnostic to derive the physical conditions of
extragalactic neutral gas. In particular, we find that a warm (Tk~150 K, n(H2)<
5 10^4 cm^-3) component of molecular gas with an OH abundance of 10^{-7} from
the inner <15'' can qualitatively reproduce the OH lines toward NGC253. Similar
temperatures but higher densities (5 10^5 cm^-3) are required to explain the OH
emission in NGC1068.