title:
Discovery of absorption features of the ADC and systematic acceleration
  of the X-ray burst rate in XB 1323-619

abstract:
  We present results from analysis of the observation of the dipping,
quasi-periodic bursting LMXB XB 1323-619 made with XMM-Newton in Jan., 2003. A
number of absorption lines were discovered in the spectrum, notably at 6.70 and
6.98 keV which we identify with scattering by ions Fe XXV and Fe XXVI. Such
features have been seen in other dipping sources, but their origin has not been
understood. Curve of growth analysis provided a consistent solution assuming
collisional ionization with kT=45 keV, close to the electron temperature we
previously determined for the ADC in this source. We thus propose that the
absorption lines in the dipping LMXB are produced in the ADC. Spectral
evolution in dipping was well-described by the progressive covering model which
we have previously shown to give very good explanations of many dipping
sources. We discuss the proposal of Boirin et al. (2004b), that spectral
evolution in the dipping LMXB may be explained by subjecting the continuum to a
highly ionized absorber. This would require a decrease in X-ray intensity by a
factor of ~3 in dipping at energies where photoelectric absorption is not
effective (40-100 keV) which previous analysis of BeppoSAX data on several
sources rules out, e.g. in XB 1323-619, any decrease was less than 10+/-10%. We
find a remarkable linear increase in the rate of X-ray bursts with time over
the 14-year period since 1989, and a systematic non-linear increase in source
luminosity (L). The linear variation of burst rate with L shows that the burst
rate is proportional to mass accretion rate, and if continued implies that the
gap between bursts will become zero on January 11, 2008. In reality we expect
the source to undergo a transition from X-ray bursting to X-ray flaring
confirming that flaring is unstable nuclear burning.


title: Tracking pulsar dispersion measures using the GMRT

abstract:
  In this paper, we describe a novel experiment for the accurate estimation of
pulsar dispersion measures using the Giant Metre-wave Radio Telescope. This
experiment was carried out for a sample of twelve pulsars, over a period of
more than one year (January 2001 to May 2002) with observations about once
every fortnight. At each epoch, the pulsar DMs were obtained from simultaneous
dual frequency observations, without requiring any absolute timing information.
The DM estimates were obtained from both the single pulse data streams and from
the average profiles. The accuracy of the DM estimates at each epoch is ~ 1
part in 10^4 or better, making the data set useful for many different kinds of
studies. The time series of DM shows significant variations on time scales of
weeks to months for most of the pulsars. A comparison of the mean DM values
from these data show significant deviations from catalog values (as well as
from other estimates in literature) for some of the pulsars, with PSR B1642-03
showing the most notable changes. From our analysis results it appears that
constancy of pulsar DMs (at the level of 1 in 10^3 or better) can not be taken
for granted. For PSR B2217+47, we see evidence for a large-scale DM gradient
over a one year period, which is modeled as being due to a blob of enhanced
electron density sampled by the line of sight. For some pulsars, including
pulsars with fairly simple profiles like PSR B1642-03, we find evidence for
small changes in DM values for different frequency pairs of measurement, a
result that needs to be investigated in detail. Another interesting result is
that we find significant differences in DM values obtained from average
profiles and single pulse data.


title: New Measurement of the Cosmic-Ray Positron Fraction from 5 to 15 GeV

abstract:
  We present a new measurement of the cosmic-ray positron fraction at energies
between 5 and 15 GeV with the balloon-borne HEAT-pbar instrument in the spring
of 2000. The data presented here are compatible with our previous measurements,
obtained with a different instrument. The combined data from the three HEAT
flights indicate a small positron flux of non-standard origin above 5 GeV. We
compare the new measurement with earlier data obtained with the HEAT-e+-
instrument, during the opposite epoch of the solar cycle, and conclude that our
measurements do not support predictions of charge sign dependent solar
modulation of the positron abundance at 5 GeV.


title: Maxwell's Multipole Vectors and the CMB

abstract:
  The recently re-discovered multipole vector approach to understanding the
harmonic decomposition of the cosmic microwave background traces its roots to
Maxwell's Treatise on Electricity and Magnetism. Taking Maxwell's directional
derivative approach as a starting point, the present article develops a fast
algorithm for computing multipole vectors, with an exposition that is both
simpler and better motivated than in the author's previous work.
  Tests show the resulting algorithm, coded up as a Mathematica notebook, to be
both fast and robust. This article serves to announce the free availability of
the code.
  The algorithm is then applied to the much discussed anomalies in the low-ell
CMB modes, with sobering results. Simulations show the quadrupole-octopole
alignment to be unusual at the 98.7% level, corroborating earlier estimates of
a 1-in-60 alignment while showing recent reports of 1-in-1000 (using
non-unit-length normal vectors) to have unintentionally relied on the near
orthogonality of the quadrupole vectors in one particular data set. The
alignment of the quadrupole and octopole vectors with the ecliptic plane is
confirmed at better than the 2sigma level.


title: Outliers to the Isotropic Energy - Peak Energy Relation in GRBs

abstract:
  The peak energy - isotropic energy (EpEi) relation is among the most
intriguing recent discoveries concerning GRBs. It can have numerous
implications on our understanding of the emission mechanism of the bursts and
on the application of GRBs for cosmological studies. However, this relation was
verified only for a small sample of bursts with measured redshifts. We propose
here a test whether a burst with an unknown redshift can potentially satisfy
the EpEi relation. Applying this test to a large sample of BATSE bursts we find
that a significant fraction of those bursts cannot satisfy this relation. Our
test is sensitive only to dim and hard bursts and therefore this relation might
still hold as an inequality (i.e. there are no intrinsically bright and soft
bursts). We conclude that the observed relation seen in the sample of bursts
with a known redshift might be influenced by observational biases and from the
inability to locate and well localize hard and weak bursts that have only a
small number of photons. In particular we point out that the threshold for
detection, localization and redshift measurement is essentially higher than the
threshold for detection alone. We predict that Swift will detect some hard and
weak bursts that would be outliers to the EpEi relation. However, we cannot
quantify this prediction. We stress the importance of understanding the
detection-localization-redshift threshold for the coming Swift detections.


title:
Temperature and entropy profiles of nearby cooling flow clusters
  observed with XMM-Newton

abstract:
  We investigate temperature and entropy profiles of 13 nearby cooling flow
clusters observed with the EPIC cameras of XMM-Newton. When normalized and
scaled by the virial radius the temperature profiles turn out to be remarkably
similar. At large radii the temperature profiles show a clear decline starting
from a break radius at ~ 0.1 r_vir. The temperature decreases by ~30 % between
0.1 r_vir and 0.5 r_vir. As expected for systems where non-gravitational
processes are of great importance, the scale length characterizing the central
temperature drop is not found to be proportional to the virial radius of the
system. The entropy of the plasma increases monotonically moving outwards
almost proportional to the radius and the central entropy level is tightly
correlated with the core radius of the X-ray emission. The dispersion in the
entropy profiles is smaller if the empirical relation S \propto T^{0.65} is
used instead of the standard self-similar relation S \propto T and, as expected
for cooling flow clusters, no entropy cores are observed.


title: Principal Component Analysis of PSF Variation in Weak Lensing Surveys

abstract:
  We introduce a new algorithm for interpolating measurements of the
point-spread function (PSF) using stars from many exposures. The principal
components of the variation in the PSF pattern from multiple exposures are used
to solve for better fits for each individual exposure. These improved fits are
then used to correct the weak lensing shapes. Since we expect some degree of
correlation in the PSF anisotropy across exposures, using information from
stars in all exposures leads to a significant gain in the accuracy of the
estimated PSF. It means that in general, the accuracy of PSF reconstruction is
limited not by the number density of stars per exposure, but by the stacked
number density across all exposures in a given survey. This technique is
applied to the 75 square degree CTIO lensing survey, and we find that the PSF
variation is well described by a small number of components. There is a
significant improvement in the lensing measurements: the residual stellar PSF
correlations are reduced by several orders of magnitude, and the measured
B-mode in the two-point correlation is consistent with zero down to 1
arcminute. We also discuss the applications of the PCA technique to future
surveys.


title: Cosmic Infrared Background and Early Galaxy Evolution

abstract:
  The Cosmic Infrared Background (CIB) reflects the sum total of galactic
luminosities integrated over the entire age of the universe. From its
measurements one can deduce information about objects at epochs currently
inaccessible to telescopic studies. This review discusses the state of the
current CIB measurements and the (mostly space-based) instruments with which
these measurements have been made, the obstacles (the various foreground
emissions)and the physics behind the CIB and its structure. Theoretical
discussion of the CIB levels can now be normalized to the standard cosmological
model narrowing down theoretical uncertainties. We review the information
behind and theoretical modeling of both the mean (isotropic) levels of the CIB
and their fluctuations. The CIB is divided into three broad bands: near-IR,
mid-IR and far-IR. For each of the bands we review the main contributors to the
CIB flux and the epochs at which the bulk of the flux originates. We also
discuss the data on the various quantities relevant for correct interpretation
of the CIB levels: the star-formation history, the present-day luminosity
function measurements, resolving the various galaxy contributors to the CIB,
etc. The integrated light of all galaxies in the deepest near-IR galaxy counts
to date fails to match the observed mean level of the CIB, probably indicating
a significant high-redshift contribution to the CIB. Additionally, Population
III stars should have left a strong and measurable signature via their
contribution to the cosmic infrared background (CIB) anisotropies for a wide
range of their formation scenarios, and measuring the excess CIB anisotropies
coming from high z would provide direct information on that epoch.


title: Unusual X-ray transients in the Galactic Centre

abstract:
  We report the discovery in the Galactic Centre region of two hard X-ray
sources, designated as XMM J174457-2850.3 and XMM J174544-2913.0, which
exhibited flux variations in the 2--10 keV band in excess of a factor of 100 in
observations spanning roughly a year. In both cases the observed hydrogen
column density is consistent with a location near to the Galactic Centre,
implying peak X-ray luminosities of ~5 x 10^34 erg/s. These objects may
represent a new population of transient source with very different properties
to the much more luminous Galactic Centre transients associated with neutron
star and black-hole binary systems. Spectral analysis shows that XMM
J174457-2850.3 has relatively weak iron-line emission set against a very hard
continuum. XMM J174544-2913.0, on the other hand, has an extremely strong
K-line from helium-like iron with an equivalent width of ~2.4keV. The nature of
the latter source is of particular interest. Does it represent an entirely new
class of object or does it correspond to a known class of source in a very
extreme configuration?


title: The 3-D clustering of radio galaxies in the TONS survey

abstract:
  We present a clustering analysis of the Texas-Oxford NVSS Structure (TONS)
radio galaxy redshift survey. This complete flux-limited survey consists of 268
radio galaxies with spectroscopic redshifts in three separate regions of the
sky covering a total of 165 deg^2. By going to faint radio flux densities
(s_1.4>3 mJy) but imposing relatively bright optical limits (E R 19.5), the
TONS sample is optimised for looking at the clustering properties of low
luminosity radio galaxies in a region of moderate (0 < z < 0.5) redshifts. We
use the two point correlation function to determine the clustering strength of
the combined TONS08 and TONS12 sub-samples and find a clustering strength of
r_0(z)=8.7+/-1.6 Mpc (h=0.7). If we assume growth of structure by linear theory
and that the median redshift is 0.3, this corresponds to r_0(0)=11.0+/-2.0 Mpc
which is consistent with the clustering strength of the underlying host
galaxies (~ 2.5 Lstar ellipticals) of the TONS radio galaxy population.


title: Probing Primordial and Pre-Galactic Lithium with High Velocity Clouds

abstract:
  The pre-Galactic abundance of lithium offers a unique window into non-thermal
cosmological processes. The primordial Li abundance is guaranteed to be present
and probes big bang nucleosynthesis (BBN), while an additional Li component is
likely to have been produced by cosmic rays accelerated in large scale
structure formation. Pre-Galactic Li currently can only be observed in low
metallicity Galactic halo stars, but abundance measurements are plagued with
systematic uncertainties due to modeling of stellar atmospheres and convection.
We propose a new site for measuring pre-Galactic Li: low-metallicity,
high-velocity clouds (HVCs) which are likely to be extragalactic gas accreted
onto the Milky Way, and which already have been found to have deuterium
abundances consistent with primordial. A Li observation in such an HVC would
provide the first extragalactic Li measurement, and could shed new light on the
apparent discrepancy between BBN predictions and halo star Li abundance
determinations. Furthermore, HVC Li could at the same time test for the
presence of non-primordial Li due to cosmic rays. The observability of
elemental and isotopic Li abundances is discussed, and candidate sites
identified.


title: Magnetic Accretion Onto White Dwarfs

abstract:
  The influence of the magnetic field on process of the accretion onto White
Dwarfs in Cataclysmic Variables (CVs) is discussed. Except for the Polars or AM
Her objects, the strength of magnetic field can not be measured directly in CVs
by modern techniques. But there is growing evidence that most of the types of
Cataclysmic Variables classified on the basis of their observational
characteristics are behaving in one or the other way under the influence of the
magnetic field of the accreting White Dwarf, among other things. Here, we
discuss the bulk of CVs that are traditionally considered as non magnetic and
review the properties that could be best explained by the magnetic governed
accretion process.


title:
Discovery of Two Very Low-Mass Binaries: Final Results of an Adaptive
  Optics Survey of Nearby M6.0-M7.5 Stars

abstract:
  We present updated results of a high-resolution, magnitude limited (Ks<12
mag) imaging survey of nearby low-mass M6.0-M7.5 field stars. The observations
were carried out using adaptive optics at the Gemini North, VLT, Keck II, and
Subaru telescopes. Our sample of 36 stars consists predominantly of nearby (<30
pc) field stars, 5 of which we have resolved as binaries. Two of the binary
systems, 2MASSI J0429184-312356 and 2MASSI J1847034+552243, are presented here
for the first time. All 5 discovered binary systems have separations between
0.08"-0.53" (2-9 AU) with similar mass ratios (q>0.8, delta Ks < 1 mag). This
result supports the hypothesis that wide (a>20 AU) very low-mass (M_tot<0.19
M_sun) binary systems are rare. The projected semimajor axis distribution of
these systems peak at ~ 5 AU and we report a sensitivity-corrected binary
fraction of 9% (-3%, +4%) for stars with primaries of spectral type M6.0-M7.5
with separations >3 AU and mass ratios q>0.6. Within these instrumental
sensitivities, these results support the overall trend that both the semimajor
axis distribution and binary fraction are a function of the mass of the primary
star and decrease with decreasing primary mass. These observations provide
important constraints for low-mass binary star formation theories.


title: Three Components Evolution in a Simple Big Bounce Cosmological Model

abstract:
  We consider a five-dimensional Ricci flat Bouncing cosmology and assume that
the four-dimensional universe is permeated smoothly by three minimally coupled
matter components: CDM+baryons $\rho_{m}$, radiation $\rho_{r}$ and dark energy
$\rho_{x}$. Evolutions of these three components are studied and it is found
that dark energy dominates before the bounce, and pulls the universe
contracting. In this process, dark energy decreases while radiation and the
matter increase. After the bounce, the radiation and matter dominates
alternatively and then decrease with the expansion of the universe. At present,
the dark energy dominates again and pushes the universe accelerating. In this
model, we also obtain that the equation of state (EOS) of dark energy at
present time is $w_{x0}\approx -1.05$ and the redshift of the transition from
decelerated expansion to accelerated expansion is $z_{T}\approx 0.37$, which
are compatible with the current observations.


title:
A Statistical Analysis of Point-like Sources in Chandra Galactic Center
  Survey

abstract: This paper has been withdrawn


title:
Three-dimensional simulations of stellar core collapse in full general
  relativity: Nonaxisymmetric dynamical instabilities

abstract:
  We perform fully general relativistic simulations of rotating stellar core
collapse in three spatial dimension. A parametric equation of state is adopted
following Dimmelmeier et al. The early stage of the collapse is followed by an
axisymmetric code. When the stellar core becomes compact enough, we start a
3-dimensional simulation adding a bar-mode nonaxisymmetric density
perturbation. In the axisymmetric simulations, it is clarified that the maximum
value of $\beta \equiv T/W$ achieved during the stellar collapse and depends
sensitively on the velocity profile and total mass of the initial core, and
equations of state. It is also found that for all the models with high degree
of differential rotation, a funnel structure is formed around the rotational
axis after the formation of neutron stars. For selected models in which the
maximum value of $\beta$ is larger than $\sim 0.27$, 3-dimensional simulations
are performed. It is found that the bar-mode dynamical instability sets in for
the case that the following conditions are satisfied: (i) the progenitor should
be rapidly rotating with the initial value of $0.01 \alt \beta \alt 0.02$, (ii)
the degree of differential rotation of the initial condition should be
sufficiently high, and (iii) a depletion factor of pressure in an early stage
of collapse should be large enough to induce a significant contraction for
which an efficient spin-up can be achieved. As a result of the onset of the
bar-mode dynamical instabilities, the amplitude of gravitational waves can be
by a factor of $\sim 10$ larger than that in the axisymmetric collapse. It is
found that a dynamical instability with the $m=1$ mode is also induced, but the
perturbation does not grow significantly and, hence, it does not contribute to
an outstanding amplification of gravitational waves.


title:
A Statistical Analysis of Intergalactic Medium Transmission Approaching
  Reionization

abstract:
  We use hydrodynamic cosmological simulations in a 9.6 Mpc box to explore the
evolution of the intergalactic medium (IGM) transmissivity from z=2 through the
epoch of reionization. Reionization is achieved through an ultraviolet
background (UVB) that includes evolving stellar and QSO source populations. We
construct and analyze noiseless synthetic HI Lya absorption spectra along lines
of sight through our continuously evolving box and find a smooth evolution of
the effective optical depth under a power law up to the epoch of reionization.
Crossing into the epoch of reionization, both the mean transmitted flux (MTF)
and variance to the mean transmitted flux sharply deviate from a smooth
evolution and hence such observables have large margins of error. Despite the
statistical uncertainty in inferring the reionization profile from spectra, the
end of an opacity phase transition of the IGM correlates well with the redshift
when both the mean and variance of the transmitted flux rapidly deviate from
the post-reionization profile. However, an unobtainable number of lines of
sight is needed to allow an estimate of the MTF with less than 10% relative
margin of error. In addition to optical transmission, we compare the predicted
dark gap length distribution with observations. We show that this statistic is
sensitive to spectral resolution at reionization redshifts, but overall in
agreement with results by Songaila and Cowie (2002). Finally, we derive a
positive correlation between the mean optical depth within a gap and the size
of the gap, in attempt to relate "transmission statistics" to "dark gap
statistics" in high redshift studies of the IGM.


title: Possible TeV Source Candidates In The Unidentified EGRET Sources

abstract:
  We study the $\gamma$-ray emission from the pulsar magnetosphere based on
outer gap models, and the TeV radiation from pulsar wind nebulae (PWNe) through
inverse Compton scattering using a one-zone model. We showed previously that
GeV radiation from the magnetosphere of mature pulsars with ages of $\sim
10^5-10^6$ years old can contribute to the high latitude unidentified EGRET
sources. We carry out Monte Carlo simulations of $\gamma$-ray pulsars in the
Galaxy and the Gould Belt, assuming the pulsar birth rate, initial position,
proper motion velocity, period, and magnetic field distribution and evolution
based on observational statistics. We select from the simulation a sample of
mature pulsars in the Galactic plane ($|b|\leq 5^\circ$) and in the high
latitude ($|b|> 5^\circ$) which could be detected by EGRET. The TeV flux from
the pulsar wind nebulae of our simulated sample through the inverse Compton
scattering by relativistic electrons on the microwave cosmic background and
synchrotron seed photons are calculated. The predicted fluxes are consistent
with the present observational constraints. We suggest that strong EGRET
sources can be potential TeV source candidates for present and future
ground-based TeV telescopes.


title: Starbursts at z >~6: from the present to Herschel and ALMA

abstract:
  The SED of the lensed z=6.56 galaxy HCM6A behind the cluster Abell 370 has
been analysed. We find clear indications for the presence of dust in this
galaxy, and we estimate the properties of its stellar populations (SFR, age,
etc.). From its estimated luminosity, L~(1-4)e.+11 Lsun, this galaxy ranks as a
luminous infrared galaxy. This case is then used to examine the detectability
of high-z galaxies with Herschel and ALMA. It is evident that with the use of
strong gravitational lensing SPIRE/Herschel observations could provide very
interesting information on z > 5 galaxies. Strong synergies between
ground-based near-IR instruments on 8-10m class telescopes and ELTs, Herschel,
the JWST, and ALMA can be expected for the exploration of the first galaxies in
the Universe.


title: Stellar populations and Lyman-alpha emission from lensed z > 6 galaxies

abstract:
  We present results from an SED analysis of two lensed high-z objects, the
z=6.56 galaxy HCM6A behind the cluster Abell 370 discovered by Hu et al. (2002)
and the triple arc at z~7 behind Abell 2218 found by Kneib et al. (2004). For
HCM 6A we find indications for the presence of dust in this galaxy, and we
estimate the properties of its stellar populations (SFR, age, etc.), and the
intrinsic Lyman-alpha emission. From the "best fit" reddening (E(B-V)~0.25) its
estimated luminosity is L~(1-4)e.+11 Lsun, in the range of luminous infrared
galaxies. For the arc behind Abell 2218 we find a most likely redshift of
z~6.0-7.2 taking into account both our photometric determination and lensing
considerations. SED fits indicate generally a low extinction but do not
strongly constrain the SF history. Best fits have typical ages of ~3 to 400
Myr. The apparent 4000 Ang break observed recently by Egami et al. (2004) from
combination of IRAC/Spitzer and HST observations can also well be reproduced
with templates of young populations (~15 Myr or even younger) and does not
necessarily imply old ages. Finally, we briefly examine the detectability of
dusty lensed high-z galaxies with Herschel and ALMA.


title:
The Number and Observability of Population III Supernovae at High
  Redshifts

abstract:
  We consider the feasibility of detecting Population III pair-instability
supernovae (PISN) at very high redshifts with the James Webb Space Telescope
(JWST). Four published estimates for the PISNe rate show a rather wide
dispersion, between 50-2200 deg-2 yr-1. Correcting problems with several of
these, we conclude that even a fairly optimistic estimate is probably a further
order of magnitude lower than this range, at a rate of order 4 deg-2 yr-1 at z
\~ 15 and 0.2 deg-2 yr-1 at z ~ 25, both with substantial uncertainty. Although
such supernovae would be bright enough to be readily detectable with the JWST
at any relevant redshift, the lower number densities derived here will likely
require either a dedicated wide-angle search strategy or a serendipitous
search. We expect that typically about 1 deg2 (or 500 JWST NIRCam images) per
detected supernova at 4.5 mm must be imaged to detect one PISN at z ~ 15 and
about 35 deg2 to detect one at z ~ 25. If some Population III star-formation
persists to lower redshifts z ~ 5, then PISNe may also be detectable in
wide-angle ground-based Z-band imaging surveys at ZAB ~ 23, at a density of
order 1 deg-2 of surveyed area. In an Appendix, we consider the possible
effects of intergalactic dust in obscuring high redshift supernovae or other
high redshift sources. We show that the obscuration at a given rest-wavelength
will peak at some maximum redshift and thereafter decline. While it may be a
significant effect in observations of the very high redshift Universe, it is
unlikely, even under rather pessimistic assumptions, to completely obscure
primordial objects.


title: Chandra Observation of the Starburst Galaxy NGC 2146

abstract:
  We present six monitoring observations of the starburst galaxy NGC 2146 using
the Chandra X-ray Observatory. We have detected 67 point sources in the 8'.7 x
8'.7 field of view of the ACIS-S detector. Six of these sources were
Ultra-Luminous X-ray Sources, the brightest of which has a luminosity of 5 x
10^{39} ergs s^{-1}. One of the source, with a luminosity of ~1 x 10^{39} ergs
s^{-1}, is coincident with the dynamical center location, as derived from the
^{12}CO rotation curve. We suggest that this source may be a low-luminosity
active galactic nucleus. We have produced a table where the positions and main
characteristics of the Chandra-detected sources are reported. The comparison
between the positions of the X-ray sources and those of compact sources
detected in NIR or radio does not indicate any definite counterpart. Taking
profit of the relatively large number of sources detected, we have derived a
logN-logS relation and a luminosity function. The former shows a break at
\~10^{-15} ergs cm^{-2} s^{-1}, that we interpret as due to a detection limit.
The latter has a slope above the break of 0.71, which is similar to those found
in the other starburst galaxies. In addition, a diffuse X-ray emission has been
detected in both, soft (0.5--2.0keV) and hard (2.0--10.0keV), energy bands. The
spectra of the diffuse component has been fitted with a two (hard and soft)
components. The hard power-law component, with a luminosity of ~4 x 10^{39}
ergs s^{-1}, is likely originated by unresolved point sources, while the soft
component is better described by a thermal plasma model with a temperature of
0.5keV and high abundances for Mg and Si.


title: Kinematic and chemical evolution of early-type galaxies

abstract:
  We investigate in detail 13 early-type field galaxies with 0.2<z<0.7 drawn
from the FORS Deep Field. Since the majority (9 galaxies) is at z~0.4, we
compare the field galaxies to 22 members of three rich clusters with z=0.37 to
explore possible variations caused by environmental effects. We exploit
VLT/FORS spectra (R~1200) and HST/ACS imaging to determine internal kinematics,
structures and stellar population parameters. From the Faber-Jackson and
Fundamental Plane scaling relations we deduce a modest luminosity evolution in
the B-band of 0.3-0.5mag for both samples. We compare measured Lick absorption
line strengths (Hdelta, Hgamma, Hbeta, Mg_b, & Fe5335) with evolutionary
stellar population models to derive light-averaged ages, metallicities and the
element abundance ratios Mg/Fe. We find that all these three stellar parameters
of the distant galaxies obey a scaling with velocity dispersion (mass) which is
very well consistent with the one of local nearby galaxies. In particular, the
distribution of Mg/Fe ratios of local galaxies is matched by the distant ones,
and their derived mean offset in age corresponds to the average lookback time.
This indicates that there was little chemical enrichment and no significant
star formation within the last ~5Gyr. The calculated luminosity evolution of a
simple stellar population model for the derived galaxy ages and lookback times
is in most cases very consistent with the mild brightening measured by the
scaling relations.


title:
A catalog of bright calibrator stars for 200-meter baseline
  near-infrared stellar interferometry

abstract:
  We present in this paper a catalog of reference stars suitable for
calibrating infrared interferometric observations. In the K band, visibilities
can be calibrated with a precision of 1% on baselines up to 200 meters for the
whole sky, and up to 300 meters for some part of the sky. This work, extending
to longer baselines a previous catalog compiled by Borde et al. (2002), is
particularly well adapted to hectometric-class interferometers such as the Very
Large Telescope Interferometer (VLTI, Glindemann et al. 2003) or the CHARA
array (ten Brummelaar et al. 2003) when observing well resolved, high surface
brightness objects (K<8). We use the absolute spectro-photometric calibration
method introduced by Cohen et al. (1999) to derive the angular diameters of our
new set of 948 G8--M0 calibrator stars extracted from IRAS, 2MASS and MSX
catalogs. Angular stellar diameters range from 0.6 mas to 1.8 mas (median is
1.1 mas) with a median precision of 1.35%. For both the northern and southern
hemispheres, the closest calibrator star is always less than 10 degree away.


title:
An estimate of the time variation of the abundance gradient from
  planetary nebulae II. Comparison with open clusters, cepheids and young
  objects

abstract:
  The temporal behaviour of the radial abundance gradients has important
consequences for models of the chemical evolution of the Galaxy. We present a
comparison of the time variation of the abundance gradients in the Milky Way
disk as determined from a sample of planetary nebulae, open clusters, cepheids
and young objects, such as stars in OB associations and HII regions. We
conclude that the [Fe/H] gradients as measured in open cluster stars strongly
support the time flattening of the abundance gradient as determined from O/H
and S/H measurements in planetary nebulae. This conclusion is also supported by
the cepheid variables, for which very accurate gradients and ages can be
determined, and also by some recent estimates for OB stars and HII regions. It
is estimated that the average flattening rate for the last 8 Gyr is in the
range 0.005-0.010 dex/kpc/Gyr.


title:
Evolution of the Solar Activity over Time and Effects on Planetary
  Atmospheres: I. High-energy Irradiances (1-1700 A)

abstract:
  We report on the results of the Sun in Time multi-wavelength program (X-rays
to the UV) of solar analogs with ages covering ~0.1-7 Gyr. The chief science
goals are to study the solar magnetic dynamo and to determine the radiative and
magnetic properties of the Sun during its evolution across the main sequence.
The present paper focuses on the latter goal, which has the ultimate purpose of
providing the spectral irradiance evolution of solar-type stars to be used in
the study and modeling of planetary atmospheres. The results from the Sun in
Time program suggest that the coronal X-ray-EUV emissions of the young
main-sequence Sun were ~100-1000 times stronger than those of the present Sun.
Similarly, the transition region and chromospheric FUV-UV emissions of the
young Sun are expected to be 20-60 and 10-20 times stronger, respectively, than
at present. When considering the integrated high-energy emission from 1 to 1200
A, the resulting relationship indicates that the solar high-energy flux was
about 2.5 times the present value 2.5 Gyr ago and about 6 times the present
value about 3.5 Gyr ago (when life supposedly arose on Earth). The strong
radiation emissions inferred should have had major influences on the thermal
structure, photochemistry, and photoionization of planetary atmospheres and
also played an important role in the development of primitive life in the Solar
System. Some examples of the application of the Sun in Time results on
exoplanets and on early Solar System planets are discussed.


title:
Thermodynamic evolution of the cosmological baryonic gas : II. Galaxy
  formation

abstract:
  The problem of galaxy formation and its dependence on thermodynamic
properties is addressed by using Eulerian hydrodynamic numerical simulations of
large scale structure formation. Global galaxy properties are explored in
simulations including gravitation, shock heating and cooling processes, and
following self-consistently the chemical evolution of a primordial composition
hydrogen-helium plasma without assuming collisional ionization equilibrium. The
galaxy formation model is mainly based on the identification of converging
dense cold gas regions. We show that the evolution at low redshift of the
observed cosmic star formation rate density is reproduced, and that the
galaxy-like object mass function is dominated by low-mass objects. The galaxy
mass functions are well described by a two power-law Schechter function whose
parameters are in good agreement with observational fits of the galaxy
luminosity function. The high-mass end of the galaxy mass function includes
objects formed at early epochs and residing in high-mass dark matter halos
whereas the low-mass end includes galaxies formed at later epochs and active in
their ``stellar'' mass formation. Finally, the influence of two other physical
processes, photoionization and non-equipartition processes between electrons,
ions and neutrals of the cosmological plasma is discussed and the modifications
on galaxy formation are examined.


title: Neutrinos and Primordial Nucleosynthesis

abstract:
  The importance of the Big Bang Nucleosynthesis (BBN) as a unique tool for
studying neutrino properties is discussed, and the recent steps towards a
self-consistent and robust handling of the weak reaction decoupling from the
thermal bath as well as of the neutrino reheating following the e+e-
annihilation are summarized. We also emphasize the important role of the Cosmic
Microwave Background (CMB) anisotropy in providing an accurate and independent
determination of the baryon density parameter omegab. The BBN is presently a
powerful parameter-free theory that can test the standard scenario of the
neutrino decoupling in the early Universe. Moreover it can constrain new
physics in the neutrino sector. The perspectives for improvements in the next
years are outlined.


title: The Evolution of Field Spiral Galaxies over the Past 8 Gyr

abstract:
  We have performed a large observing campaign of intermediate-redshift disk
galaxies including spectroscopy with the FORS instruments of the VLT and
imaging with the Advanced Camera for Surveys onboard the HST. Our data set
comprises 113 late-type galaxies in the redshift range 0.1<z<1.0 and thereby
probes galaxy evolution over more than half the age of the universe. Spatially
resolved rotation curves have been extracted and fitted with synthetic velocity
fields that account for geometric distortions and blurring effects. With these
models, the intrinsic maximum rotation velocity Vmax was derived for 73
spirals. By comparing our sample to the Tully-Fisher Relation of local spiral
galaxies, we find evidence for a differential luminosity evolution: the massive
distant galaxies are of comparable luminosity as their present-day
counterparts, while the distant low-mass spirals are brighter than locally by
up to >2mag in rest-frame B. This evolution would be at variance with the
predictions from numerical simulations. On the other hand, the disks of the
distant galaxies are, for a given Vmax, slightly smaller than those of their
local counterparts, as expected for a hierarchical structure growth. Hence, the
discrepancy between the observations and theoretical predictions would be
limited to the properties of the stellar populations. A possible explanation
could be the suppression of star formation in low-mass disks which is not yet
properly implemented in models of galaxy evolution. (abridged)


title: Galaxy Groups in the SDSS-DR3

abstract:
  We present a new sample of galaxy groups identified in the Sloan Digital Sky
Survey Data Release 3. Following previous works we use the well tested
friend-of-friend algorithm developed by Huchra & Geller which take into account
the number density variation due to the apparent magnitude limit of the galaxy
catalog. To improve the identification we implement a procedure to avoid the
artificial merging of small systems in high density regions and then apply an
iterative method to recompute the group centers position. As a result we obtain
a new catalog with 10864 galaxy groups with at least four members. The final
group sample has a mean redshift of 0.1 and a median velocity dispersion of
$230 km s^{-1}$.


title: Fluorine in extremely hot post-AGB stars

abstract:
  We have discovered lines of highly ionized fluorine (Fv and Fvi) in the
far-UV spectra of extremely hot (Teff=85,000--150,000 K) post-AGB stars. Our
sample comprises H-rich central stars of planetary nebulae as well as
H-deficient PG1159 stars. We performed non-LTE calculations and find strong F
overabundances (up to 10**-4 by mass, i.e., 250 times solar) in a number of
PG1159 stars, while F is essentially solar in the H-rich stars. Since PG1159
stars are believed to exhibit intershell matter of the preceding AGB phase on
their surface, their chemical analyses allow for a direct insight into
nucleosynthesis processes during the AGB phase. The high F abundances in PG1159
stars confirm the conclusion from abundance determinations in giants, that F is
synthesized in AGB stars and that the F enrichment in the intershell must be
very high.


title:
Blue and IR Light Curves of the Mysterious Pre-Main Sequence Star V582
  Mon (KH 15D) from 1955 to 1970

abstract:
  In recent years, an increasing number of publications have been addressed to
the peculiar and mysterious pre-main sequence star V582 Mon, also known as KH
15D. This extraordinary T Tauri star, located in the young star cluster NGC
2264, appears as to be an eclipsing variable. In the present paper, we report a
unique and self-consistent set of light curves in the blue and near-infrared
bands, spanning a 15-year interval (epoch 1955-1970). Our photometric data show
clearly the beginning of the eclipse stage occurred in early 1958 in the blue,
and perhaps around four years later in the infrared. The light curve period
turns out to be the same reported by recent observations (about 48.3 days), so
that no evidence for a period change results. On the other hand, in our data
the light curve shape appears as sinusoidal and is therefore different from the
one displayed today. The photometric behaviour, determined with time-series and
colour-index analysis, suggests that V582 Mon (KH 15D) could be initially
surrounded by an accretion disk/torus seen edge-on, with subsequent thin dust
formation at the beginning of the blue radiation absorption. The dust could
then aggregate into larger particles providing the transition between selective
and total absorption, accompanied with eclipsing variability in the infrared.
The minima of the periodic light curve become deeper due to the increasing
dimension and number of dust grains, and then flattens due to a contraction in
the disk.


title: Variable stars as standard candles and stellar tracers

abstract:
  We review the current status of classical Cepheid and RR Lyrae distance
scales. We discuss the most recent theoretical and empirical findings together
with pros and cons of different methods. The use of Cepheids and RR Lyrae stars
as stellar tracers are also discussed. Preliminary findings concerning the
impact that GAIA will have on the calibration of distance determinations and
astrophysical parameters are also presented.


title:
Nobeyama Millimeter Array Observations of GRB 030329: a Decay of
  Afterglow with Bumps and Molecular Gas in the Host Galaxy

abstract:
  Nobeyama Millimeter Array was used to observe millimeter-wave afterglow of
GRB 030329 at 93 GHz and 141 GHz from 2003 April 6 to 2003 May 30. A sensitive
search for CO(J=1-0) emission/absorption from the host galaxy of GRB 030329 was
also carried out. Unresolved millimeter continuum emission at the position of
GRB 030329 was detected until 2003 April 21. We found a steep decline of
continuum flux (\propto t^{-2.0}) during this period, in accord with a previous
report. Moreover, our data implies that the decay was accompanied by possible
plateaus phases, or bumps, on a time scale of several days. From an integrated
spectrum, produced by summing up the data from 2003 April 10 to 2003 May 30, we
found a possible emission feature, which could be a redshifted CO(J=1-0) line.
Its position and redshift coincide well with those of GRB 030329, though
further observations are required to confirm the detection. If the emission
feature is real, the observed CO flux is 1.4 +/- 0.52 Jy km/s, corresponding to
a large molecular gas mass of M(H_2) > 10^9 Mo. This implies that the host
galaxy, which is optically faint, is highly obscured due to a rich interstellar
medium.


title: Stellar model atmospheres with magnetic line blanketing

abstract:
  Model atmospheres of A and B stars are computed taking into account magnetic
line blanketing. These calculations are based on the new stellar model
atmosphere code LLModels which implements direct treatment of the opacities due
to the bound-bound transitions and ensures an accurate and detailed description
of the line absorption. The anomalous Zeeman effect was calculated for the
field strengths between 1 and 40 kG and a field vector perpendicular to the
line of sight. The model structure, high-resolution energy distribution,
photometric colors, metallic line spectra and the hydrogen Balmer line profiles
are computed for magnetic stars with different metallicities and are discussed
with respect to those of non-magnetic reference models. The magnetically
enhanced line blanketing changes the atmospheric structure and leads to a
redistribution of energy in the stellar spectrum. The most noticeable feature
in the optical region is the appearance of the 5200 A depression. However, this
effect is prominent only in cool A stars and disappears for higher effective
temperatures. The presence of a magnetic field produces opposite variation of
the flux distribution in the optical and UV region. A deficiency of the UV flux
is found for the whole range of considered effective temperatures, whereas the
``null wavelength'' where flux remains unchanged shifts towards the shorter
wavelengths for higher temperatures.


title: Discovery of two M32 twins in Abell 1689

abstract:
  The M31 satellite galaxy M32 has long been considered an object of unique
properties, being the most extreme example of the very rare compact elliptical
galaxy class. Here we present the spectroscopic discovery of two M32 twins in
the massive galaxy cluster Abell 1689. As these objects are so rare, this is an
important step towards a better understanding of the nature of compact
galaxies. The two M32 twins had first been detected within our photometric
search for ultra compact dwarf galaxy (UCDs) candidates in A1689 (Mieske et al.
2004) with the Advanced Camera for Surveys (ACS). Their luminosities (M_V ~ -17
mag) are very similar to M32 and their surface brightness profiles are
consistent with that of M32 projected to A1689's distance. From our ACS imaging
we detect several fainter compact galaxy candidates with luminosities
intermediate between M32 and the Fornax UCDs. If spectroscopically confirmed as
cluster members, this would almost close the gap in the magnitude-surface
brightness plane between the region of UCDs and the compact ellipticals,
implying a sequence of faint compact galaxies well separated from that of dwarf
ellipticals.


title: Detection of the N2+ First Negative System in a Bright Leonid Fireball

abstract:
  An ultraviolet-visible spectrum between 300 and 450 nm of a cometary
meteoroid that originated from 55P/Tempel-Tuttle was investigated, and its new
molecules, induced by atmospheric interaction, were discovered. The
spectroscopy was carried out using an intensified high-definition TV camera
with a slitless reflection grating during the 2001 Leonid meteor shower over
Japan. A best-fit calculation mixed with atoms and molecules confirmed the
first discovery of N2+ (B-X) bands in the UV meteor spectrum. The N2+
temperature was estimated to be 10,000 K with a low number density of 1.55 x
10^5 cm-3. Such unexpectedly strong ultraviolet emission, in particular for
N2+(1,0) at 353.4 nm, is supposed to be formed through the wide dimensions of
high-temperature regions caused by a large meteoroid. Spectroscopic
observations of reentry capsules will provide us with good opportunities for
confirming the discovered N2+.


title:
Planets and IR Excesses: Preliminary Results from a Spitzer/MIPS Survey
  of Solar-Type Stars

abstract:
  As part of a large Spitzer/MIPS GTO program, we have searched for infrared
excesses due to debris disks toward 26 FGK field stars known from radial
velocity (RV) studies to have one or more planets. While none of these stars
show excesses at 24um, we have detected 70um excesses around 6 stars at the
3-sigma confidence level. The excesses are produced by cool material (< 100 K)
located beyond 10 AU, well outside the "habitable zones" of these systems and
consistent with the presence of Kuiper Belt analogues with ~100 times more
emitting surface area than in our own planetary system.
  These planet-bearing stars are, by selection for RV studies, typically older
than 1 Gyr, and the stars identified here with excesses have a median age of 4
Gyr. We find a preliminary correlation of both the frequency and the magnitude
of dust emission with the presence of known planets. These are the first stars
outside the solar system identified as having both well-confirmed planetary
systems and well-confirmed IR excesses.


title:
The unresolved hard X-ray background: the missing source population
  implied by the Chandra and XMM-Newton deep fields

abstract:
  We extend our earlier work on X-ray source stacking in the deep XMM-Newton
observation of the Lockman Hole, to the 2 Ms Chandra Deep Field North and the 1
Ms Chandra Deep Field South. The XMM-Newton work showed the resolved fraction
of the X-ray background to be ~80-100 per cent at <2 keV but this decreased to
only ~50 per cent above ~8 keV. The CDF-N and CDF-S probe deeper, and are able
to fill-in some of the missing fraction in the 4-6 keV range, but the resolved
fraction in the 6-8 keV band remains only ~60 per cent, confirming the trend
seen with XMM-Newton. The missing X-ray background component has a spectral
shape that is consistent with a population of highly obscured AGN at redshifts
\~0.5-1.5 and with absorption column densities of ~10^23 - 10^24 cm^-2.


title:
An 850-micron SCUBA map of the Groth Strip and reliable source
  extraction

abstract:
  We present an 850-micron map and list of candidate sources in a 70 arcmin^2
sub-area of the Groth Strip observed using SCUBA. We initially detect 7
candidate sources with signal-to-noise ratios (SNRs) between 3.0 and 3.5 and 4
candidate sources with SNR > 3.5. Simulations suggest that on average in a map
this size one expects 1.6 false positive sources for SNR > 3.5 and 4.5 for 3 <
SNR < 3.5. Flux boosting in maps is a well known effect and we have developed a
simple Bayesian prescription for estimating the unboosted flux distribution and
used this method to determine the best flux estimates of our sources. This
method is easily adapted for any other modest signal-to-noise survey in which
there is prior knowledge of the source counts. We performed follow-up
photometry in an attempt to confirm or reject 5 of our source candidates. We
confirm the reality of 2 of the SCUBA sources, although at lower levels than
suggested in the map and we find that the photometry results are consistent
with and confirm the de-boosted map fluxes. Our final candidate source list
contains 3 sources, including the 2 confirmed detections and 1 further
candidate source with SNR > 3.5 which has a reasonable chance of being real.


title: Faraday Rotation Observations of Magnetic Fields in galaxy Clusters

abstract:
  The presence of magnetic fields in the intracluster medium in clusters of
galaxies has been revealed through several different observational techniques.
These fields may be dynamically important in clusters as they will provide
additional pressure support to the intracluster medium as well as inhibit
transport mechanisms such as thermal conduction. Here, we review the current
observational state of Faraday rotation measure studies of the cluster fields.
The fields are generally found to be a few to 10 microG in non-cooling core
clusters and ordered on scales of 10-20 kpc. Studies of sources at large impact
parameters show that the magnetic fields extend from cluster cores to radii of
at least 500 kpc. In central regions of cooling core systems the field
strengths are often somewhat higher (10-40 microG) and appear to be ordered on
smaller scales of a few to 10 kpc. We also review some of the recent work on
interpreting Faraday rotation measure observations through theory and numerical
simulations. These techniques allow us to build up a much more detailed view of
the strength and topology of the fields.


title: Constraints on the redshift dependence of the dark energy potential

abstract:
  We develop a formalism to characterize the redshift evolution of the dark
energy potential. Our formalism makes use of quantities similar to the
Horizon-flow parameters in inflation and is general enough that can deal with
multiscalar quintessence scenarios, exotic matter components, and higher order
curvature corrections to General Relativity. We show how the shape of the dark
energy potential can be recovered non parametrically using this formalism and
we present approximations analogous to the ones relevant to slow-roll
inflation. Since presently available data do not allow a non-parametric and
exact reconstruction of the potential, we consider a general parametric
description. This reconstruction can also be used in other approaches followed
in the literature (e.g., the reconstruction of the redshift evolution of the
dark energy equation of state w(z)). Using observations of passively evolving
galaxies and supernova data we derive constraints on the dark energy potential
shape in the redshift range 0.1 < z < 1.8. Our findings show that at the 1sigma
level the potential is consistent with being constant, although at the same
level of confidence variations cannot be excluded with current data. We
forecast constraints achievable with future data from the Atacama Cosmology
Telescope.


title: Dead Zones and the Origin of Planetary Masses

abstract:
  Protoplanets accrete material from their natal protostellar disks until they
are sufficiently massive to open a gap in the face of the disk's viscosity that
arises from the magneto-rotational instability (MRI). By computing the
ionization structure within observationally well-constrained disk models, we
demonstrate that poorly ionized, low viscosity "dead zones" stretch out to 12
AU within typical disks. We find that planets of terrestrial mass robustly form
within the dead zones while massive Jovian planets form beyond. Dead zones will
also halt the rapid migration of planets into their central stars. Finally, we
argue that the gravitational scattering of low mass planets formed in the dead
zone, to larger radii by a rapidly accreting Jupiter beyond, can explain the
distribution of planetary masses in our solar system.


title: Modeling Cloud Formation: Source Code

abstract:
  We have posted the source code for our cloud model for public use as a tool
for the intercomparison of planetary radiation transport models attempting to
incorporate the physics of cloud condensation.


title: The Outburst of V1647 Ori Revealed by Spitzer

abstract:
  We present Spitzer Space Telescope observations of V1647 Ori, the outbursting
source lighting McNeil's nebula, taken near the optical peak of the outburst in
early March 2004. The source is easily detected in all Spitzer imaging bands
from 3.6 - 70 microns. The fluxes at all wavelengths are roughly a factor of 15
brighter than pre-outburst levels; we measure a bolometric luminosity of 44
Lsun. We posit that this event is due to an increase in the accretion
luminosity of the source. Simple models of an accretion disk plus tenuous
envelope can qualitatively explain the observed pre- and post-outburst spectral
energy distributions. The accretion activity implied by our results indicates
that the outburst may be intermediate between FUor and EXor-type events. We
also report the discovery of a previously unknown mid-infrared counterpart to
the nearby Herbig-Haro object HH 22.


title: MIMAC-He3: a new detector for non-baryonic dark matter search

abstract:
  The project of a micro-TPC matrix of cells of 3He for direct detection of
non-baryonic dark matter is presented. The privileged properties of 3He for
this detection are highlighted. The double detection: ionization-projection of
tracks is explained and its rejection evaluated. The specific capabilities of
this project with respect to other experiments are mentioned and its
complementarities concerning the supersymmetric phenomenology explicitly
showed.


title: Starbursting Nuclear CO Disks of Early-type Spiral Galaxies

abstract:
  We have initiated the first CO interferometer survey of early-type spiral
galaxies (S0-Sab). We observed five early-type spiral galaxies with HII nuclei
(indicating circumnuclear starburst activities). These observations indicate
gas masses for the central kiloparsec of \sim 1-5% of the dynamical masses.
Such low gas mass fractions suggest that large-scale gravitational instability
in the gas is unlikely to be the driving cause for the starburst activities.
The Toomre Q values were >1 (mostly >3) within the central kiloparsec,
indicating that the gas disks are globally gravitationally stable. The area
filling factor of the gas disks is estimated to be about 0.05. This small value
indicates the existence of lumpy structure, i.e. molecular clouds, in the
globally-gravitationally stable disks. The typical surface density of the
molecular clouds is as high as \sim 3000 Msun pc^{-2}. We reconsider the nature
of the Toomre Q criterion, and conclude that the Q derived from CO observations
indicates neither star formation nor molecular cloud formation. This argument
should be valid not only for the circumnuclear disks but also for any region in
galactic disks. We tentatively explore an alternative model, i.e. cloud-cloud
collisions, as an initiating mechanism of star formation.


title: Average magnification effect of clumping of matter

abstract:
  The aim of this paper is to re-examine the question of the average
magnification in a universe with some inhomogeneously distributed matter. We
present an analytic proof, valid under rather general conditions, including
clumps of any shape and size, and strong lensing, that so long as the clumps
are uncorrelated the average \emph{reciprocal} magnification (in one of several
possible senses) is precisely the same as in a homogeneous universe with equal
mean density. From this result, we also show that a similar statement can be
made about one definition of average \emph{direct} magnification. We discuss,
in the context of observations of discrete and extended sources, the physical
significance of the various different measures of magnification and the
circumstances in which they are appropriate.


title:
On the absence of gravitational lensing of the cosmic microwave
  background

abstract:
  The magnification of distant sources by mass clumps at lower ($z \leq 1$)
redshifts is calculated analytically. The clumps are initially assumed to be
galaxy group isothermal spheres with properties inferred from an extensive
survey. The average effect, which includes strong lensing, is exactly
counteracted by the beam divergence in between clumps (more precisely, the
average reciprocal magnification cancels the inverse Dyer-Roeder
demagnification). This conclusion is in fact independent of the matter density
function within each clump, and remains valid for arbitrary densities of matter
and dark energy. When tested against the CMB, a rather large lensing induced
{\it dispersion} in the angular size of the primary acoustic peaks of the TT
power spectrum is inconsistent with WMAP observations. The situation is
unchanged by the use of NFW profiles for the density distribution of groups.
Finally, our formulae are applied to an ensemble of NFW mass clumps or
isothermal spheres having the parameters of galaxy {\it clusters}. The acoustic
peak size dispersion remains unobservably large, and is also excluded by WMAP.
For galaxy groups, two possible ways of reconciling with the data are proposed,
both exploiting maximally the uncertainties in our knowledge of group
properties. The same escape routes are not available in the case of clusters,
however, because their properties are well understood. Here we have a more
robust conclusion: neither of the widely accepted models are good description
of clusters, or important elements of physics responsible for shaping zero
curvature space are missing from the standard cosmological model. When all the
effects are accrued, it is difficult to understand how WMAP could reveal no
evidence whatsoever of lensing by groups and clusters.


title: Stochastic Gravitational Wave Background from Cosmological Supernovae

abstract:
  Based on new developments in the understanding of supernovae (SNe) as
gravitational-wave (GW) sources we estimate the GW background from all cosmic
SNe. For a broad range of frequencies around 1 Hz, this background is crudely
comparable to the GW background expected from standard inflationary models.
While our estimate remains uncertain within several orders of magnitude, the SN
GW background may become detectable by second-generation space-based
interferometers such as the proposed Big-Bang Observatory (BBO). By the same
token, the SN GWs may become a foreground for searches of the inflationary GWs,
in particular for sub-Hz frequencies where the SN background is Gaussian and
where the BBO will be most sensitive. SN simulations lasting far beyond the
usual cutoff of about 1 second are needed for more robust predictions in the
sub-Hz frequency band. An even larger GW background can arise from a
hypothetical early population of massive stars, although their GW source
strength as well as their abundance are currently poorly understood.


title: Pulsar Physics at Low Frequencies

abstract:
  Recent work has made it clear that the ``standard model'' of pulsar radio
emission cannot be the full answer. Some fundamental assumptions about the
magnetic field and plasma flow in the radio-loud region have been called into
question by recent observational and theoretical work, but the solutions to the
problems posed are far from clear. It is time to formulate and carry out new
observational campaigns designed to address these problems; sensitive
low-frequency observations will an important part of such a campaign. Because
pulsars are strong at low frequencies, we believe there will be a good number
of candidates even for high-time-resolution single pulse work, as well as mean
profile and integrated spectrum measurements. Such data can push the envelope
of current models, test competing theories of the radio loud region, and
possibly provide direct measures of the state of the emitting plasma.


title: Extragalactic Synchrotron Sources at Low Frequencies

abstract:
  The LWA will be well suited to address many important questions about the
physics and astrophysics of extragalactic synchrotron sources. Good
low-frequency data will enable major steps forward in our understanding of
radio galaxy physics, of the plasma in clusters of galaxies, and of active
objects in the high-redshift universe. Such data will also be important in
answering some basic questions about the physics of synchrotron-emitting
plasmas.


title: Photon emissivity of the electrosphere of bare strange stars

abstract:
  We consider the spectrum, emissivity and flux of the electromagnetic
radiation emitted by the thin electron layer (the electrosphere) at the surface
of a bare strange star. In particular, we carefully consider the effect of the
multiple and uncorrelated scattering on the radiation spectrum (the
Landau-Pomeranchuk-Migdal effect), together with the effect of the strong
electric field at the surface of the star. The presence of the electric field
strongly influences the radiation spectrum emitted by the electrosphere. All
the radiation properties of the electrons in the electrosphere essentially
depend on the value of the electric potential at the quark star surface. The
effect of the multiple scattering, which strongly suppresses radiation
emission, is important only for the dense layer of the electrosphere situated
near the star's surface and only for high values of the surface electric
potential of the star. Hence a typical bremsstrahlung radiation spectrum, which
could extend to very low frequencies, could be one of the main observational
signatures even for low temperature quark stars.


title: X-ray Chemistry in the Envelopes around Young Stellar Objects

abstract:
  We have studied the influence of X-rays from a massive young stellar object
(YSO) on the chemistry of its own envelope by extending the models of Doty et
al. (2002) and Staeuber et al. (2004). The models are applied to the massive
star-forming region AFGL 2591 for different X-ray luminosities and plasma
temperatures. Enhanced column densities for several species are predicted. In
addition we present first detections of CO+ and SO+ toward AFGL 2591. These
molecular ions are believed to be high-energy tracers. Herschel-HIFI will be
able to observe other tracers like CH and CH+ whereas ALMA is well suited to
measure the size and geometry of the emitting region.


title: Low-Mass Star Formation, Triggered by Supernova in Primordial Clouds

abstract:
  The evolution of a gas shell, swept by the supernova remnant of a massive
first generation star, is studied with H_2 and HD chemistry taken into account.
When a first-generation star explodes as a supernova, H_2 and HD molecules are
formed in the swept gas shell and effectively cool the gas shell to
temperatures of 32 K - 154 K. If the supernova remnant can sweep to gather the
ambient gas, the gas shell comes to be dominated by its self-gravity, and
hence, is expected to fragment. Our result shows that for a reasonable range of
temperatures (200 K - 1000 K) of interstellar gas, the formation of
second-generation stars can be triggered by a single supernova or hypernova.


title: Molecular hydrogen beyond the optical edge of an isolated spiral galaxy

abstract:
  We know little about the outermost portions of galaxies because there is
little light coming from them. We do know that in many cases atomic hydrogen
(HI) extends well beyond the optical radius \cite{Casertano91}. In the centers
of galaxies, however, molecular hydrogen (H2) usually dominates by a large
factor, raising the question of whether H2 is abundant also in the outer
regions but hitherto unseen.Here we report the detection of emission from
carbon monoxide (CO), the most abundant tracer of H2, beyond the optical radius
of the nearby galaxy NGC 4414. The molecular clouds probably formed in the
regions of relatively high HI column density and in the absence of spiral
density waves. The relative strength of the lines from the two lowest
rotational levels indicates that both the temperature and density of the H2 are
quite low compared to conditions closer to the center. The inferred surface
density of the molecular material continues the monotonic decrease from the
inner regions. We conclude that while molecular clouds can form in the outer
region of this galaxy, there is little mass associated with them.


title: XMM-Newton observations of the ultra-compact binary RX J1914+24

abstract:
  We present XMM-Newton observations of the 569 sec period system RX J1914+24
(V407 Vul). This period is believed to represent the binary orbital period
making it an ultra-compact binary system. By comparing the phase of the rise to
maximum X-ray flux at various epochs (this includes observations made using
ROSAT, ASCA and Chandra) we find that the system is spinning up at a rate of
3.17+/-0.07x10^{-12} s/s. We find that the spectra softens as the X-ray flux
declines towards the off-phase of the 569 sec period. Further, the spectra are
best fitted by an absorbed blackbody component together with a broad emission
feature around 0.59keV. This emission feature is most prominent at the peak of
the on-phase. We speculate on its origin.


title:
Investigating the EGRET-radio galaxies link with INTEGRAL: the case of
  3EG J1621+8203 and NGC 6251

abstract:
  The analysis of an INTEGRAL AO2 observation of the error contours of the
EGRET source 3EG J1621+8203 is presented. The only source found inside the
error contours for energies between 20 and 30 keV at 5 sigma detection
significance is the FR I radio galaxy NGC 6251. This supports the
identification of NGC 6251 with 3EG J1621+8203. The observed flux is higher and
softer than observed in the past, but consistent with a variable blazar-like
spectral energy distribution.


title: XMM-Newton Observations of Extra-planar Gas in Nearby Starburst Galaxies

abstract:
  We report on first results of XMM-Newton observations of nearby starburst
galaxies that form part of a multi-wavelength study of gaseous halos around
late-type spiral galaxies and their dependence on the level of star formation
activity in the underlying disks. XMM-Newton, with its extraordinary
sensitivity for faint extended X-ray emission, is used to derive spatial and
spectral properties of the very hot extraplanar/halo gas. For example, spectral
models can be tested and hot gas properties like density, mass and energy can
be estimated. Comparing the distribution of the halo X-ray emission with
optical filaments and/or observed magnetic field structures uncovers
interesting correlations on which work just has started. Our study aims - in
general - at assessing the importance of galactic halos as repositories of a
metal-enriched hot medium and their significance in terms of galactic chemical
evolution and possible metal enrichment of the intergalactic medium.


title: BS Indi: An enigmatic object

abstract:
  BS Ind is a young K0V star in the Tucana association. Photometric
observations with the Hipparcos satellite show an eclipse-like light-curve with
primary and secondary eclipse. The eclipsing binary has a period of 0.435338
days and a circular orbit. Our spectroscopic observations however show that the
K0V primary is a single-line spectroscopic binary with a period of 3.3 years.
The minimum mass of the invisible component is about 0.9 Mo which means that
the mass of the companion is about the same as that of the primary. The first
inspection of our FEROS spectra, as well as a CES spectrum shows no obvious
companion. However, when the FEROS spectra are cross-correlated with an M-star,
a secondary becomes visible as a broad peak in the cross-correlation function.
The width and the position of this broad peak is variable on a short
time-scale. When phased to a period of 0.435338 days, the radial velocity
variations of the broad peak show the characteristic sine-wave of a
spectroscopic binary in a circular orbit. The best interpretation of this data
is that the broad peak in the cross-correlation function is caused by an
eclipsing binary consisting of two late-K, or early-M stars with an orbital
period of 0.435338 days. This is the eclipsing system. These two stars then
orbit the K0V-primary with a period of 3.3 years. The assumption that BS Ind is
a triple system consisting of a K0V star and two late-K, or early-M stars also
explains the unusual brightness of the object and the near infrared excess.
Thus, BS Ind is unique, as it contains by far the shortest-period young binary
star, and these stars are eclipsing.


title: The global properties of all variety of AGN

abstract:
  Active Galactic Nuclei (AGN) have been a challenging field of research for
the past six decades. Nevertheless, many questions still remain unanswered
today, regardless of the tremendous theoretical and technological advances. In
this brief review I propose to take a step back from the usual discussion of
AGN properties and draw attention to some topics that I believe are important
to keep in mind as we strive forward in our pursuit of knowledge about these
sources.


title: An Approach Detecting the Event Horizon of SgrA*

abstract:
  Imaging the vicinity of black hole is one of the ultimate goals of VLBI
astronomy. The closest massive black hole, SgrA*, located at Galactic center is
the leading candidate for such observations. Combined with recent VLBI
recording technique and sub-mm radio engineering, we now have the sufficient
sensitivity for the observations. We here show performance simulations of
sub-mm VLBI arrays for imaging SgrA*. An excellent image is obtained from a
sub-mm VLBI array in the Southern hemisphere like the configuration of VLBA. We
also note that even with a small array, we can estimate the shadow size and
then the mass of black hole from visibility analysis. Now, if only constructing
a sub-mm VLBI array in Southern hemisphere, we can unveil the black hole
environments of SgrA*.


title:
Optical and Radio emission from BL Lac objects: long-term trends and
  structural changes

abstract:
  Optical light curves of bright BL Lac objects, in particular those having the
SED synchrotron peak at frequencies lower than 10E14 Hz, are characterized by
long-term trends with time scales of a few decades. These variations are
probabily not related to fast perturbations moving down the jet, which have a
much faster evolution, but more likely to slow changes of other physical or
geometrical parameters, for example the jet direction. In these cases we can
expect changes of the inner jet structure detectable with VLBI imaging. Recent
literature results are reviewed and discussed in this context.


title:
The chemistry of transient microstructure in the diffuse interstellar
  medium

abstract:
  Transient microstructure in the diffuse interstellar medium has been observed
towards galactic and extragalactic sources for decades, usually in lines of
atoms and ions, and, more recently, in molecular lines. Evidently, there is a
molecular component to the transient microstructure. In this paper we explore
the chemistry that may arise in such microstructure. We use a PDR code to model
the conditions of relatively high density, low temperature, very low visual
extinction and very short elapsed time that are appropriate for these objects.
We find that there is a well defined region of parameter space where detectable
abundances of molecular species might be found. The best matching models are
those where the interstellar microstructure is young (<100 yr), small (~100
AU), and dense (>10^4 cm^-3).


title: High output data rates with PCInt on the EVN MkIV data processor

abstract:
  The EVN MkIV data processor is being equipped with a high data output
capability, called PCInt. In its next phase it will allow very high data output
rates, up to 160 Mb/s. This functionality is required for the high spectral
resolution that will be offered with recirculation. Moreover, VLBI observations
traditionally focus on a small patch of sky and image typically a few 100 mas
around a bright source. High spectral and time resolution is needed to image a
larger area of the sky, up to the primary beam of the individual telescopes.
After the upgrade such high resolution data will become the standard product.
  From the archive of high resolution data it will be possible to image many
sources in each field of view around the original targets.


title: Diffuse elliptical galaxies, the first 3D spectroscopic observations

abstract:
  Diffuse elliptical galaxies (or dwarfs) are the numerically dominant
population in clusters like Virgo and Fornax. They carry only a few percent of
the baryonic mass but are very sensitive to the environment; so they keep a
fossil record of the environmental conditions over the life of the cluster.
  Recent observations of their kinematics and stellar populations cast new
insights to their evolutionary history. The most promising constraints come
from integral field spectroscopy. We present for the first time 3D observations
of a dwarf elliptical galaxy, IC 3653. These good signal to noise data (S/N=30)
obtained with the Russian 6 meters telescope reveal a complex kinematics
reminiscent of that commonly observed in elliptical galaxies. The disk-like
feature has no morphological counterpart in ACS data.
  Kinematical evidences for thin stellar disks confirm and enforce the earlier
imagery observations and strengthen the connection with disk galaxies. We
suggest that dE galaxies formed from small units, developing a disk. This disk
was heated or destroyed by the winds induced by the star formation, and the
galaxy was later depleted from the remaining gas by ram-pressure stripping when
crossing the cluster.


title: A Review of VLBI Instrumentation

abstract:
  The history of VLBI is summarized with emphasis on the technical aspects. A
summary of VLBI systems which are in use is given, and an outlook to the future
of VLBI instrumentation.


title: Circumstellar masers

abstract:
  Circumstellar masers are unique tools for probing the envelopes around low
mass dying stars using VLBI. In this contribution I briefly review the status
of our knowledge on these emissions, especially focusing on the latest results
obtained by means of VLBI observations.I also outline some of the new windows
that will open for VLBI maser research thanks to the upcoming new
instrumentation.


title: Intermediate Scale Structures in BL Lac objects

abstract:
  The parsec-scale total intensity structures of BL Lac objects share many
characteristics with quasars: e.g. well-collimated jets and superluminal
motion. However, the jets of BL Lac objects appear to fade much more quickly
than those in quasars and on VLA scales many BL Lacs have structures comparable
to those of low luminosity (FR I) radio galaxies, in which kpc-scale flow
speeds are non-relativistic.
  The region between parsec and kiloparsec scales is therefore one of
transition in BL Lac objects. We have carried out VLBI observations of a small
sample of BL Lac objects at frequencies between 2.3 GHz and 327 MHz in order to
investigate this transition region. Preliminary results for two of these
sources are presented here.
  Coherent structures are detected in these sources out to a distance of
several tens of parsecs. We find evidence for significant changes in jet
structure on scales of a few tens of milliarcseconds, both in terms of the
orientation and collimation of the jets.


title: Dark Matter and Galaxy Formation: Challenges for the Next Decade

abstract:
  The origin of the galaxies represents an important focus of current
cosmological research, both observational and theoretical. Its resolution
involves a comprehensive understanding of star formation, galaxy dynamics, the
cosmology of the very early universe, and the nature of the dark matter. In
this review, I will focus on those aspects of dark matter that are relevant for
understanding galaxy formation, and describe the outlook for detecting the most
elusive component, non-baryonic dark matter.


title:
Radio Luminosity Function, Importance of Jet Power, and Radio Properties
  of Nearby Low-Luminosity Active Galactic Nuclei

abstract:
  We present the completed results of a high resolution radio imaging survey of
all (around 200) low-luminosity active galactic nuclei (LLAGNs) in the Palomar
spectroscopic Sample of all (around 470) nearby bright northern galaxies. The
high incidence of pc-scale radio nuclei, with implied brightness temperatures
of the order of 10E7 K, and sub-parsec jets argue for accreting black holes in
50% of all LLAGNs; there is no evidence against all LLAGNs being mini-AGNs.The
detected parsec-scale radio nuclei are preferentially found in massive
ellipticals and in type 1 nuclei (i.e. nuclei with broad Halpha emission). The
radio luminosity function (RLF) of Palomar Sample LLAGNs extends three orders
of magnitude below, and is continuous with, that of "classical" AGNs.We find
marginal evidence for a low-power turnover in the RLF; nevertheless LLAGNs are
responsible for a significant fraction of accretion in the local universe. The
accretion energy output in LLAGNs is dominated by the energy in the observed
jets rather than the radiated bolometric luminosity. The Palomar LLAGNs follow
the same scaling between jet power and narrow line region (NLR) luminosity as
the parsec to kilo-parsec jets in powerful radio galaxies. Low accretion rates
(of 10E-2 to 10E-6 of the Eddington rate) are impliedin both advection- and
jet-type models, with evidence for increasing "radio-loudness" with decreasing
Eddington fraction. The jets are energetically more significant than supernovae
in the LLAGN host galaxies, and are potentially able to dump sufficient energy
into the innermost parsecs to significantly slow the accretion inflow. Detailed
results can be found in Nagar et al. (2002a) and Nagar et al. (2004, to appear
in Astronomy & Astrophysics).


title: Polarization in CSS/GPS radio sources

abstract:
  The polarisation properties of the intrinsically small (< 20 kpc) radio
sources are briefly discussed. At centimetric and decimetric wavelengths,
substantial polarised emission is often detected in quasars and, at a lower
level, in radio sources identified with galaxies with projected linear sizes in
excess of a few kpc. The projected linear size at which some polarised emission
is detected decreases with observing frequency.
  High Rotation Measures are commonly found in these sources, implying high
electron/ion densities and/or strong interstellar magnetic fields. For the
objects found unpolarized at resolutions of the order of a few pc, either the
source magnetic field is highly disordered or the scale of ambient magnetic
field cells is not resolved.


title: Galaxy Bimodality due to Cold Flows and Shock Heating

abstract:
  We address the origin of the robust bi-modality observed in galaxy properties
about a characteristic stellar mass ~3x10^{10}Msun. Less massive galaxies tend
to be ungrouped blue star-forming discs, while more massive galaxies are
typically grouped red old-star spheroids. Colour-magnitude data show a gap
between the red and blue sequences, extremely red luminous galaxies already at
z~1, a truncation of today's blue sequence above L_*, and massive starbursts at
z~2-4. We propose that these features are driven by the thermal properties of
the inflowing gas and their interplay with the clustering and feedback
processes, all functions of the dark-matter halo mass and associated with a
similar characteristic scale. In haloes below a critical shock-heating mass
M_shock~10^{12}Msun, discs are built by cold streams, not heated by a virial
shock, yielding efficient early star formation. It is regulated by supernova
feedback into a long sequence of bursts in blue galaxies constrained to a
"fundamental line". Cold streams penetrating through hot media in M>M_shock
haloes preferentially at z>2 lead to massive starbursts in L>L_* galaxies. At
z<2, in M>M_shock haloes hosting groups, the gas is heated by a virial shock,
and being dilute it becomes vulnerable to feedback from energetic sources such
as AGNs. This shuts off gas supply and prevents further star formation, leading
by passive evolution to "red-and-dead" massive spheroids starting at z~1. A
minimum in feedback efficiency near M_shock explains the observed minimum in
M/L and the qualitative features of the star-formation history. The cold flows
provide a hint for solving the angular-momentum problem. When these processes
are incorporated in simulations they recover the main bi-modality features and
solve other open puzzles.


title: Carbon stars in the IRTS survey

abstract:
  We have identified 139 cool carbon stars in the near-infrared
spectro-photometric survey of the InfraRed Telescope in Space (IRTS) from the
conspicuous presence of molecular absorption bands at 1.8, 3.1 and 3.8 microns.
Among them 14 are new, bright (K ~ 4.0-7.0), carbon stars. We find a trend
relating the 3.1 microns band strength to the K-L' color index, which is known
to correlate with mass-loss rate. This could be an effect of a relation between
the depth of the 3.1 microns feature and the degree of development of the
extended stellar atmosphere where dust starts to form.


title:
A systematic analysis of X-ray afterglows of gamma-ray burst observed by
  XMM-Newton

abstract:
  This work is part of a systematic re-analysis program of all the data of
Gamma-Ray Burst (GRB) X-ray afterglows observed so far, in order to constrain
the GRB models. We present here a systematic analysis of those afterglows
observed by XMM-Newton between January 2000 and March 2004. This dataset
includes GRB 011211 and GRB 030329. We have obtained spectra, light curves and
colors for these afterglows. In this paper we focus on the continuum spectral
and temporal behavior. We compare these values with the theoretical ones
expected from the fireball model. We derive constraints about the burst
environment (absorption, density profile) and put constraints on their beaming
angle.


title: Dark Energy and Large-Scale Structure of the Universe

abstract:
  The evolution of matter density perturbations in two-component model of the
Universe consisting of dark energy (DE) and dust-like matter (M) is considered.
We have analyzed it for two kinds of DE with $\omega\ne -1$: a) unperturbed
energy density and b) perturbed one (uncoupled with matter). For these cases
the linear equations for evolution of the gauge-invariant amplitudes of matter
density perturbations are presented. It is shown that in the case of
unperturbed energy density of DE the amplitude of matter density perturbations
grow slightly faster than in the second case.


title: Intensity of the cosmic X-ray backgound from HEAO1/A2 experiment

abstract:
  We reanalyze data of HEAO1/A2 -- Cosmic X-ray Experiment -- in order to
repeat the measurements of the cosmic X-ray background (CXB) intensity and
accurately compare this value with other measurements of the CXB. We used the
data of MED, HED1 and HED3 detectors in scan mode, that allowed us to measure
effective solid angles and effective areas of detectors self consistently, in
the same mode as the CXB intensity was measured. We obtained the average value
of the CXB intensity is 1.96+/-0.10 x10^{-11} erg/s/cm2/deg2 in the energy band
2-10 keV, or 9.7+/-0.5 phot/s/cm2/sr at 1 keV assuming the power law spectral
shape with photon index Gamma=1.4 in this energy band. We compare the obtained
measurements with those obtained by different instruments over last decades.


title: Cosmological Origin of Small-Scale Clumps and DM Annihilation Signal

abstract:
  We study the cosmological origin of small-scale DM clumps in the hierarchical
scenario with the most conservative assumption of adiabatic Gaussian
fluctuations. The mass spectrum of small-scale clumps with M<10^3Msun is
calculated with tidal destruction of the clumps taken into account within the
hierarchical model of clump structure. Only 0.1-0.5% of small clumps survive
the stage of tidal destruction in each logarithmic mass interval. The mass
distribution of clumps has a cutoff at Mmin due to diffusion of DM particles
out of a fluctuation and free streaming at later stage. Mmin is a model
dependent quantity. In the case the neutralino DM, considered as a pure bino,
Mmin~10^-8 Msun. The evolution of density profile in a DM clump does not result
in the singularity because of formation of the core under influence of tidal
interaction. The radius of the core is ~0.1R, where R is radius of the clump.
The applications for annihilation of DM particles in the Galactic halo are
studied. The number density of clumps as a function of their mass, radius and
distance to the Galactic center is presented. The enhancement of annihilation
signal due to clumpiness, valid for arbitrary DM particles, is calculated. In
spite of small survival probability, the global annihilation signal in most
cases is dominated by clumps, with major contribution given by small clumps.
The enhancement due to large clumps with M>10^6 Msun is very small.


title:
Chandra temperature profiles for a sample of nearby relaxed galaxy
  clusters

abstract:
  We present Chandra gas temperature profiles at large radii for a sample of 13
nearby, relaxed galaxy clusters and groups, which includes A133, A262, A383,
A478, A907, A1413, A1795, A1991, A2029, A2390, MKW4, RXJ1159+5531, and USGC
S152. The sample covers a range of average temperatures from 1 to 10 keV. The
clusters are selected from the archive or observed by us to have sufficient
exposures and off-center area coverage to enable accurate background
subtraction and reach the temperature accuracy of better than 20-30% at least
to r=0.4-0.5 r_180, and for the three best clusters, to 0.6-0.7 r_180. For all
clusters, we find cool gas in the cores, outside of which the temperature
reaches a peak at r =~ 0.15 r_180 and then declines to ~0.5 of its peak value
at r =~ 0.5 r_180. When the profiles are scaled by the cluster average
temperature (excluding cool cores) and the estimated virial radius, they show
large scatter at small radii, but remarkable similarity at r>0.1-0.2 r_180 for
all but one cluster (A2390). Our results are in good agreement with previous
measurements from ASCA by Markevitch et al. and from Beppo-SAX by DeGrandi &
Molendi. Four clusters have recent XMM-Newton temperature profiles, two of
which agree with our results, and we discuss reasons for disagreement for the
other two. The overall shape of temperature profiles at large radii is
reproduced in recent cosmological simulations.


title: From the Tully-Fisher relation to the Fundamental Plane through Mergers

abstract:
  We set up a series of self-consistent N-body simulations to investigate the
fundamental plane of merger remnants of spiral galaxies. These last ones are
obtained from a theoretical Tully-Fisher relation at z=1, assuming a constant
mass-to-light ratio within the LambdaCDM cosmogony. Using a Sersic growth curve
and an orthogonal fitting method, we found that the fundamental plane of our
merger remnants is described by the relation Re ~ sigma^{1.48} Ie^{-0.75} which
is in good agreement with that reported from the Sloan Digital Sky Survey Re ~
sigma^{1.49} Ie^{-0.75}. However, the R^{1/4}-profile leads to a fundamental
plane given by Re ~ sigma^{1.79} Ie^{-0.60}. In general, the correlation found
in our merger remnants arises from homology breaking (V^2 ~ sigma^nu, Rg ~
Re^eta) in combination with a mass scaling relation between the total and
luminous mass, $M ~ ML^gamma. Considering an orthogonal fitting method, it is
found that 1.74<nu<1.79, 0.21<eta<0.52 and 0.80<gamma<0.90 depending on the
adopted profile (Sersic or R^{1/4}).


title:
Constraints on linear-negative potentials in quintessence and phantom
  models from recent supernova data

abstract:
  We study quintessence and phantom field theory models based on
linear-negative potentials of the form $V(\phi)=s \phi$. We investigate the
predicted redshift dependence of the equation of state parameter $w(z$ for a
wide range of slopes $s$ in both quintessence and phantom models. We use the
gold dataset of 157 SnIa and place constraints on the allowed range of slopes
$s$. We find $s=0\pm 1.6$ for quintessence and $s=\pm 0.7\pm 1$ for phantom
models (the range is at the $2\sigma$ level and the units of $s$ are in
$\sqrt{3}M_p H_0^2\simeq 10^{-38}eV^3$ where $M_p$ is the Planck mass). In both
cases the best fit is very close to $s\simeq 0$ corresponding to a cosmological
constant. We also show that specific model independent parametrizations of
$w(z)$ which allow crossing of the phantom divide line $w=-1$ (hereafter PDL)
provide significantly better fits to the data. Unfortunately such crossings are
not allowed in any phantom or quintessence single field model minimally coupled
to gravity. Mixed models (coupled phantom-quintessence fields) can in principle
lead to a $w(z)$ crossing the PDL but a preliminary investigation indicates
that this does not happen for natural initial conditions.


title: Radio Flares and the Magnetic Field Structure in GRB Outflows

abstract:
  The magnetic field structure in GRB outflows is of great interest as it can
provide valuable clues that can help pin down the mechanism responsible for the
acceleration and collimation of GRB jets. The most promising way of probing it
is through polarization measurements of the synchrotron emission from the GRB
ejecta, which includes the gamma-ray emission and the reverse shock emission.
Measuring polarization in gamma-rays with current instruments is extremely
difficult: so far there is only one claim of detection (in GRB 021206) which
despite the favorable conditions remains very controversial. The emission from
the reverse shock that propagates into the ejecta as it is decelerated by the
ambient medium peaks in the optical after tens of seconds (the `optical flash')
and dominates the optical emission up to about ten minutes after the GRB.
Unfortunately, no polarization measurements of this optical emission have been
made to date. However, after the reverse shock finishes crossing the shell of
GRB ejecta, the shocked ejecta cools adiabatically and radiates at lower and
lower frequencies, peaking in the radio after $\sim 1$ day (the `radio flare').
We use VLA data of radio flares from GRBs to constrain the polarization of this
emission. We find only upper limits for both linear and circular polarization.
Our best limits are for GRB 991216, for which we find $3\sigma$ upper limits on
the linear and circular polarization of 7% and 9%, respectively. These limits
provide interesting constraints on existing GRB models. Specifically, our
results are hard to reconcile with a predominantly ordered toroidal magnetic
field in the GRB outflow together with a `structured' jet, where the energy per
solid angle drops as the inverse square of the angle from the jet axis, that is
expected in models where the outflow is Poynting flux dominated.


title:
Radiative Effects on Particle Acceleration in Electromagnetic Dominated
  Outflows

abstract:
  Plasma outflows from gamma-ray bursts (GRB), pulsar winds, relativistic jets,
and ultra-intense laser targets radiate high energy photons. However, radiation
damping is ignored in conventional PIC simulations. In this letter, we study
the radiation damping effect on particle acceleration via Poynting fluxes in
two-and-half-dimensional particle-in-cell (PIC) plasma simulation of
electron-positron plasmas. Radiation damping force is self-consistently
calculated for each particle and reduces the net acceleration force. The
emitted radiation is peaked within a few degrees from the direction of Poynting
flux and strongly linear-polarized.


title:
Secular stability and instability in stellar systems surrounding massive
  objects

abstract:
  We examine the stability of a low-mass stellar system surrounding a massive
central object. Examples of such systems include the centers of galaxies or
star clusters containing a massive black hole, and the Oort comet cloud. If the
self-gravity of the stellar system is the dominant non-Keplerian force, such
systems may be subject to slowly growing (secular) lopsided instabilities.
Stability to secular modes is largely determined by the dependence of the
distribution function F on angular momentum J. If dF/dJ < 0 at constant energy,
all spherical systems are secularly stable. If dF/dJ > 0, as is expected if
there is a loss cone at low angular momentum, all spherical systems in which
F=0 at J=0 (an empty loss cone) are only neutrally stable, and flattened,
non-rotating systems are generally unstable. These results suggest that secular
instabilities may dominate the structure and evolution of the stellar systems
in the centers of galaxies.


title:
The gravitational and hydrodynamical interaction between the LMC and the
  Galaxy

abstract:
  We use high resolution N-Body/SPH simulations to study the hydrodynamical and
gravitational interaction between the Large Magellanic Cloud and the Milky Way.
We model the dark and hot extended halo components as well as the
stellar/gaseous disks of the two galaxies. Both galaxies are embedded in
extended cuspy LCDM dark matter halos. We follow the previous four Gyrs of the
LMC's orbit such that it ends up with the correct location and orientation on
the sky. Tidal forces elongate the LMC's disk, forcing a bar and creating a
strong warp and diffuse stellar halo, although very few stars become unbound.
The stellar halo may account for some of the microlensing events. Ram-pressure
from a low density ionised halo is then sufficient to remove 1.4e8 Msolar of
gas from the LMC's disk forming a great circle trailing stream around the
Galaxy. The column density of stripped gas falls by two orders of magnitude 100
degrees from LMC. The LMC does not induce any response in the Milky Way disk.
On the contrary, the tides raised by the Milky Way determine the truncation of
the satellite at about 11 kpc. After several Gyrs of interaction the gas disk
of the LMC is smaller than the stellar disk due to ram pressure and its size
compares well with the observational data.


title: An Infrared Spectroscopic Sequence of M, L and T Dwarfs

abstract:
  We present a 0.6-4.1 micron spectroscopic sequence of M, L, and T dwarfs. The
spectra have R~2000 from 0.9 to 2.4 microns and R=2500-200 from 2.9 to 4.1
microns. These new data nearly double the number of L and T dwarfs that have
reported L-band spectra. The near-infrared spectra are combined with previously
published red-optical spectra to extend the wavelength coverage to ~0.6
microns. Prominent atomic and molecular absorption features are identified
including neutral lines of Al, Fe, Mg, Ca, Ti, Na, and K and 19 new weak CH_4
absorption features in the H-band spectra of mid- to late-type T dwarfs. In
addition, we detect for the first time the 0-0 band of the A ^4\Pi - X
^4\Sigma^- transition of VO at ~1.06 microns in the spectra of L dwarfs and the
P and R branches of the \nu_3 band of CH_4 in the spectrum of a T dwarf. The
equivalent widths of the refractory atomic features all decrease with
increasing spectral type and are absent by a spectral type of ~L0, except for
the 1.189 micron Fe I line which persists to at least ~L3. We compute the
bolometric luminosities of the dwarfs in our sample with measured parallaxes
and find good agreement with previously published results that use L'-band
photometry to account for the flux emitted from 2.5 to 3.6 microns. Finally,
2MASS J2224381-0158521 (L4.5) has an anomalously red spectrum and the strongest
\Delta \nu=+2 CO bands in our sample. This may be indicative of unusually thick
condensate clouds and/or low surface gravity.


title:
Fluctuation Properties and Polar Emission Mapping of Pulsar B0834+06 at
  Decameter Wavelengths

abstract:
  Recent results regarding subpulse-drift in pulsar B0943+10 have led to the
identification of a stable system of sub-beams circulating around the magnetic
axis of the star. Here, we present single-pulse analysis of pulsar B0834+06 at
35 MHz, using observations from the Gauribidanur Radio Telescope. Certain
signatures in the fluctuation spectra and correlations allow estimation of the
circulation time and drift direction of the underlying emission pattern
responsible for the observed modulation. We use the `cartographic transform'
mapping technique to study the properties of the polar emission pattern. These
properties are compared with those for the other known case of B0943+10, and
the implications are discussed.