title:
Cold dust in a selected sample of nearby galaxies. I. The interacting
  galaxy NGC4631

abstract:
  We have observed the continuum emission of the interacting galaxy NGC4631 at
0.87 and 1.23mm using the Heinrich-Hertz-Telescope on Mt. Graham and the IRAM
30-m telescope on Pico Veleta. We have obtained fully sampled maps which cover
the optical emission out to a radius of about 7' at both wavelengths. For a
detailed analysis, we carefully subtracted the line contributions and
synchrotron and free-free emission from the data, which added up to 6% at
1.23mm and 10% at 0.87mm. We combined the flux densities with FIR data to
obtain dust spectra and calculate dust temperatures, absorption cross sections,
and masses. Assuming a ``standard'' dust model, which consists of two
populations of big grains at moderate and warm temperatures, we obtained
temperatures of 18K and 50K for the both components. However, such a model
suffers from an excess of the radiation at 1.23mm, and the dust absorption
cross section seems to be enhanced by a factor 3 compared to previous results
and theoretical expectations. At large galactocentric radii, where the galaxy
shows disturbances as a result of gravitational interaction, this effect seems
to be even stronger. Some possibilities to resolve these problems are
discussed. The data could be explained by a very cold dust component at a
temperature of 4-6K, an increased abundance of very small grains, or a
component of grains with unusual optical properties. We favour the latter
possibility, since the first two lead to inconsistencies.


title: A simple but efficient algorithm for multiple-image deblurring

abstract:
  We consider the simultaneous deblurring of a set of noisy images whose point
spread functions are different but known and spatially invariant, and the noise
is Gaussian. Currently available iterative algorithms that are typically used
for this type of problem are computationally expensive, which makes their
application for very large images impractical. We present a simple extension of
a classical least-squares (LS) method where the multi-image deblurring is
efficiently reduced to a computationally efficient single-image deblurring. In
particular, we show that it is possible to remarkably improve the
ill-conditioning of the LS problem by means of stable operations on the
corresponding normal equations, which in turn speed up the convergence rate of
the iterative algorithms. The performance and limitations of the method are
analyzed through numerical simulations. Its connection with a column weighted
least-squares approach is also considered in an appendix.


title: Sub-mm observations and modelling of Vega type stars

abstract:
  We present new sub-mm observations and modelling of Vega excess stars, using
realistic dust grain models. For resolved disks, we find that different objects
require very different dust grain properties in order to simultaneously fit the
image data and SED. Fomalhaut and Vega require solid dust grains, whilst HR4796
and HD141569 can only be fitted using porous grains. The older stars tend to
have less porous grains than younger stars, which may indicate that collisions
have compacted the dust grains. Eps Eri appears to be deficient in small dust
grains compared to our best fitting model. This may be due to factors which
affect the size distribution of grains close to the radiation pressure blowout
limit. Alternatively, this discrepancy may be due to some external influence on
the disk (e.g. a planet). When the model is applied to unresolved targets, an
estimate of the disk size can be made. However, the large diversity in dust
composition for the resolved disks means that we cannot make a reliable
assumption as to the composition of the grains in an unresolved disk, and there
is corresponding uncertainty in the disk size. In addition, the poor fit for
Eps Eri shows that the model cannot always account for the SED even if the disk
size is known. These two factors mean that it may not be possible to determine
a disk's size without actually resolving it.


title: Evolution of the Dark Matter Distribution at the Galactic Center

abstract:
  Annihilation radiation from neutralino dark matter at the Galactic center
(GC) would be greatly enhanced if the dark matter were strongly clustered
around the supermassive black hole (SBH). The existence of a dark-matter
"spike" is made plausible by the observed, steeply-rising stellar density near
the GC SBH. Here the time-dependent equations describing gravitational
interaction of the dark matter particles with the stars are solved. Scattering
of dark matter particles by stars would substantially lower the dark matter
density near the GC SBH over 10^10 yr, due both to kinetic heating, and to
capture of dark matter particles by the SBH. This result suggests that
enhancements in the dark matter density around a SBH would be modest whether or
not the host galaxy had experienced the scouring effects of a binary SBH.


title: What are S0 (0) Galaxies?

abstract:
  Among early-type galaxies with almost circular isophotes E0 and E1 galaxies
are, at 99.3% significance, more luminous than face-on objects classified as S0
(0) and S(0) (1). This result supports the view that rotation and "diskiness"
are more important in the outer regions of faint-early type galaxies than they
are for more luminous galaxies of very early morphological type.


title: A Medium-Resolution Near-Infrared Spectral Library of Late Type Stars: I

abstract:
  We present an empirical infrared spectral library of medium resolution
(R~2000-3000) H (1.6 micron) and K (2.2 micron) band spectra of 218 red stars,
spanning a range of [Fe/H] from ~-2.2 to ~+0.3. The sample includes Galactic
disk stars, bulge stars from Baade's window, and red giants from Galactic
globular clusters. We report the values of 19 indices covering 12 spectral
features measured from the spectra in the library. Finally, we derive
calibrations to estimate the effective temperature, and diagnostic
relationships to determine the luminosity classes of individual stars from
near-infrared spectra.
  This paper is part of a larger effort aimed at building a near-IR spectral
library to be incorporated in population synthesis models, as well as, at
testing synthetic stellar spectra.


title: Towards a Molecular Inventory of Protostellar Discs

abstract:
  The chemical environment in circumstellar discs is a unique diagnostic of the
thermal, physical and chemical environment. In this paper we examine the
structure of star formation regions giving rise to low mass stars, and the
chemical environment inside them, and the circumstellar discs around the
developing stars.


title: The Subillimeter Properties of Extremely Red Objects in the CUDSS Fields

abstract:
  We discuss the submillimeter properties of Extremely Red Objects (EROs) in
the two Canada-UK Deep Submillimeter Survey (CUDSS) Fields. We measure the mean
submillimeter flux of the ERO population (to K < 20.7) and find 0.4 +/- 0.07
mJy for EROs selected by (I-K) > 4.0 and 0.56 +/- 0.09 mJy for EROs selected by
(R-K) > 5.3 but, these measurements are dominated by discrete, bright
submillimeter sources. We estimate that EROs produce 7-11% of the far-infrared
background at 850um. This is substantially less than a previous measurement by
Wehner, Barger & Kneib (2002) and we discuss possible reasons for this
discrepancy. We show that ERO counterparts to bright submillimeter sources lie
within the starburst region of the near-infrared color-color plot of Pozzetti &
Mannucci (2000). Finally, we claim that pairs or small groups of EROs with
separations of < 10 arcseconds often mark regions of strong submillimeter flux.


title: A Sample of Field Ellipticals

abstract:
  Using well-defined selection criteria applied to the LEDA galaxy catalogue we
have constructed a sample of elliptical galaxies that can be taken to lie in
the field. Such criteria can easily be applied to theoretical simulations for
direct comparison with observations. The variation of the number of `isolated'
ellipticals with selection criteria is also investigated. A preliminary study
of the environment of the field ellipticals shows that, in the mean, they are
surrounded by a population of dwarf galaxies, out to projected radii of at
least 500 kpc, with a radial density profile of $r^{-0.6\pm 0.2}$ and a
luminosity function slope of $\alpha \sim -1.8$. The results are compared and
contrasted to the satellite population around isolated spiral galaxies.


title: The quasar Q0957+561: Lensed CO emission from a disk at z~1.4?

abstract:
  In recent years large efforts have been made to detect molecular gas towards
high redshifted objects. Up to now the literature reports on only two cases of
CO-detection in quasars at a redshift between 1 and 2 - Q0957+561, a
gravitationally lensed system at z=1.41 (Planesas et al. 1999), and HR10 at
z=1.44 (Andreani et al. 2000). According to Planesas et al. (1999), 12CO(2-1)
emission was detected towards both the lensed images of Q0957+561 with the IRAM
Plateau de Bure Interferometer (PdBI). In contrast to the optical spectra of
the two images which support the idea that they are images of one and the same
object, the CO-spectra were surprisingly different: the southern image (named
CO-B) shows a single blueshifted line whereas a double-peaked line profile with
a blue- and a redshifted part appears towards the northern image (CO-A). Based
on the observations and on simulations with a gravitational lens program, we
are tempted to argue that the line profile traces the presence of molecular gas
of a disk in the host galaxy around the quasar. We have now new observations
with the PdBI providing the necessary sensitivity to corroborate our disk
model.


title:
Constraining the origin of TeV photons from gamma-ray bursts with
  delayed MeV-GeV emission formed by interaction with cosmic infrared/microwave
  background photons

abstract:
  It has been suggested that electromagnetic cascade of very high energy
gamma-rays from gamma-ray bursts (GRBs) in the infrared/microwave background
can produce delayed MeV-GeV photons. This delay could be caused by the angular
spreading effect of the scattered microwave photons or deflection of the
secondly pairs due to intergalactic magnetic field. Very high energy TeV
photons of GRBs could be produced by a few mechanisms including the
proton-synchrotron radiation and electron inverse Compton emission from GRB
internal shocks as well as external shocks. We suggest that the information
provided by the delayed emission could give constraints on models for TeV
gamma-rays. A more accurate calculation of the delayed time caused by the
angular spreading effect is presented by considering recent observations of the
extragalactic infrared background and the theoretic high-redshift infrared
background. We also suggest that the dependence of the maximum time delay of
scattered photons on their energies, if determined by future GLAST detector,
could differentiate the two mechanisms causing the time delay.


title: Surface Brightness Fluctuations: A Case for Extremely Large Telescopes

abstract:
  The Surface Brightness Fluctuations (SBF) Method for distance determinations
of elliptical galaxies is been modeled in order to investigate the effect of
the Point Spread Function (PSF). We developed a method to simulate observations
of SBF of galaxies having various properties and located at different
distances. We will use this method in order to test the accuracy on the
estimates of the extra-galactic distances for PSFs representing typical seeing
conditions, Adaptive Optics (AO) systems and for future observations with
Extremely Large Telescopes (ELTs) close to the diffraction limit.


title: Emission line galaxies at z = 6.5

abstract:
  We are carrying out a search for Lyman alpha emitting galaxies at z = 6.5
employing slitless spectroscopy at the VLT. In our 43 square arcminute field we
find three isolated single emission lines with SEDs consistent with line
emitting galaxies at z = 6.5.


title: The Iron Unresolved Transition Array in Active Galactic Nuclei

abstract:
  The unresolved transition array (UTA) of iron M-shell ions is a prominent
absorption feature in the X-ray spectrum of many active galactic nuclei (AGNs).
Modeling photoionized plasmas in attempt to match the observed silicon and
oxygen lines fail to predict the level of ionization of iron as inferred by
this feature. It is suggested that the discrepancy is due to underestimation of
the low-temperature dielectronic recombination rates for iron M-shell ions.
Modified ionization balance calculations, based on new (guessed) atomic data,
support this idea. The results are shown and compared to the global properties
of several observed UTAs. Implications for AGN absorbing gas are discussed
including an analysis of the ionization parameter distribution in such sources.
The need for real calculations of such atomic data is stressed.


title:
A correlation between light profile and [Mg/Fe] abundance ratio in
  early-type galaxies

abstract:
  We explore possible correlations between light profile shapes, as
parameterized by the Sersic index or the concentration index C_re(1/3), and
relevant stellar population parameters in early-type galaxies. Mean luminosity
weighted ages, metallicities and abundance ratios were obtained from spectra of
very high signal-to-noise and stellar population models that synthesize galaxy
spectra at the resolution given by their velocity dispersions, in combination
with an age indicator that is virtually free of the effects of metallicity. We
do not find any significant correlation between the Sersic index (or C_re(1/3))
and mean age or metallicity, but a strong positive correlation of the shape
parameters with [Mg/Fe] abundance ratio. This dependence is as strong as the
[Mg/Fe] vs. velocity dispersion and C_re(1/3) vs. velocity dispersion
relations. We speculate that early-type galaxies settle up their structure on
time-scales in agreement with those imposed by their [Mg/Fe] ratios. This
suggest that the global structure of larger galaxies, with larger [Mg/Fe]
ratios and shorter time-scales, was already at place at high z, without
experiencing a significant time evolution.


title: FU Orionis: A Binary Star?

abstract:
  By using the ALFA adaptive optics system at the 3.6m telescope of the Calar
Alto Observatory we detected a faint red star in the apparent vicinity of FU
Ori, the prototype of the FUor outburst stars. Independent confirmation of the
detection is obtained from archival PUEO/CFHT images. The separation between
the companion candidate and FU Ori is 0."50 and their brightness contrast is
around 4 magnitudes. We discuss the possible nature of the newly detected star
based on near-infrared photometry and its proper motion relative to FU Ori. The
photometric data are consistent with a nearby late-type main sequence star, a
background giant star, and a pre-main sequence star. On the basis of the proper
motion and the stellar surface density in the direction towards FU Ori, we
argue that the probabilities of the first two options are very low.


title:
Toward a detailed view on the kinematics of intermediate luminosity
  early-type galaxies no dark matter candidates

abstract:
  In several nearby intermediate luminosity early-type galaxies, recent
observations at large radii have shown a indications of a lack of dark matter,
substantially at odds with the prediction from the CDM hierarchical merger
models. Here we discuss a pilot observational project for the study of the
internal kinematical and dynamical properties of this remarkable sample of
galaxies. Using the VIMOS-IFU in its high spectral resolution mode, it would be
possible to investigate the regions up to about 1.2 effective radii, taking
advantage of the much larger field of view and telescope diameter. This will
allow to disclose the presence of any kinematical substructures which could
affect the conclusion on the mass modeling and definitely clarify the inner
structure of this particular class of early-type galaxies.


title: Spectroscopy of Molecular Hydrogen Emission from KH 15D

abstract:
  We report infrared spectroscopy of the unusual eclipsing pre-main sequence
object KH 15D, obtained using NIRSPEC on Keck II. During eclipse, observations
using low spectral resolution (1000) reveal the presence of prominent molecular
hydrogen emission in 5 lines near 2 microns. The relative line strengths are
consistent with thermal excitation at T = 2800 +/-300K. Observations out of
eclipse, at both low and high spectral resolution (20,000), show reduced
contrast with the stellar continuum. The change in contrast for the strongest
line, 1-0 S(1), is consistent with an approximately constant emission line
superposed on a variable stellar continuum. Emission in the 1-0 S(1) line is
observed to extend by more than 4 arc-sec both east and west of the stellar
point spread function (more than 3000 AU). Observed at high spectral
resolution, the velocity and intensity structure of the 1-0 S(1) profile are
both asymmetric. East of the stellar PSF (by 1.1 - 2.3 arc-sec) the emission is
blueshifted (-63 km/sec), and has significantly greater intensity than the
marginally redshifted component (+2 km/sec, consistent with zero) which
dominates west of the stellar PSF. The spatial extent of the emission, and the
excitation temperature, suggest shock-excitation of ambient gas by a bipolar
outflow from the star and/or disk. However, it is difficult to account for the
observed radial velocity unless the outflow axis is inclined significantly to
the plane of the sky.


title:
The XMM-Newton/2dF survey - II. The nature of X-ray faint optically
  bright X-ray sources

abstract:
  In this paper we investigate the properties of low X-ray-to-optical flux
ratio sources detected in a wide area (2.5deg^2) shallow
(f(0.5-8keV)~10e-14cgs) XMM-Newton survey. We find a total of 26 sources (5% of
the total X-ray selected population) with log f_X/f_{opt}<-0.9 to the above
flux limit. Optical spectroscopy is available for 20 of these low
X-ray-to-optical flux ratio objects. Most of them are found to be associated
with Galactic stars (total of 8) and broad line AGNs (total of 8).We also find
two sources with optical spectra showing absorption and/or narrow emission
lines and X-ray/optical properties suggesting AGN activity. Another two sources
are found to be associated with low redshift galaxies with narrow emission line
optical spectra, X-ray luminosities L_X(0.5-8keV)~10e41cgs and logf_X/f_opt ~
-2 suggesting `normal' star-forming galaxies. Despite the small number
statistics the sky density of `normal' X-ray selected star-forming galaxies at
the flux limit of the present sample is low consistent with previous ROSAT HRI
deep surveys. Also, the number density estimated here is in good agreement with
both the logN-logS of `normal' galaxies in the Chandra Deep Field North
(extrapolated to bright fluxes) and model predictions based on the X-ray
luminosity function of local star-forming galaxies.


title: A Systematic Analysis of Supernova Light in Gamma-Ray Burst Afterglows

abstract:
  We systematically reanalyzed all Gamma-Ray Burst (GRB) afterglow data
published through the end of 2002, in an attempt to detect the predicted
supernova light component and to gain statistical insight on its
phenomenological properties. We fit the observed photometric light curves as
the sum of an afterglow, an underlying host galaxy, and a supernova component.
The latter is modeled using published multi-color light curves of SN 1998bw as
a template. The total sample of afterglows with established redshifts contains
21 bursts (GRB 970228 - GRB 021211). For nine of these GRBs a weak supernova
excess (scaled to SN 1998bw) was found, what makes this to one of the first
samples of high-z core collapse supernovae. Among this sample are all bursts
with redshifts less than ~0.7. These results strongly support the notion that
in fact all afterglows of long-duration GRBs contain light from an associated
supernova. A statistics of the physical parameters of these GRB-supernovae
shows that SN 1998bw was at the bright end of its class, while it was not
special with respect to its light curve shape. Finally, we have searched for a
potential correlation of the supernova luminosities with the properties of the
corresponding bursts and optical afterglows, but we have not found such a
relation.


title: Observations of gas and dust at the Galactic Centre

abstract:
  The Infrared Space Observatory Long wavelength Spectrometerhas been used to
map distribution of the emission from a sample of 22 atomic, molecular and
ionised lines toward the Circumnuclear Disk at the Galactic Centre. The CND
disc is clearly seen in the maps of molecular lines such as CO and OH, whilst
the central region dominates in other atomic and ionised lines. The spectrum
toward Sgr A star is best represented by the sum of a 58 K blackbody,
superposed with 22 identifiable emission or absorption features, including four
lines each attributed to CO and OH, two broad features that may be indicative
of a complex of solid state features, two H2O lines, and the rest being various
atomic or ionised atomic lines.


title: Proper Motion and Kinematics of the Ansae in NGC7009

abstract:
  We have measured the proper motion (PM) and kinematics of the ansae in NGC
7009 using high dispersion echelle spectra and archive narrow band HST images.
Assuming that the ansae are moving at equal and opposite velocities from the
central star we obtain a system radial velocity of -53+-2km/s, the eastern ansa
approaching and the western ansa receding at Vr=5.3+-1km/s with respect to this
value. The PM of the eastern ansa is 28+-8mas/yr, which with our weighted
distance to NGC 7009 of 0.86+-0.34kpc gives Vexp=112+-32km/s. The electron
temperature and density in both ansae were determined to be Te=9000+-400K and
Ne=2300+-400/cc. The dynamic age of the ansae is 925+-260yrs.and the implied PM
of the central star is 1+-0.5mas/yr. This is in qualitative but not
quantitative agreement with previous work.


title: Extended tachyon field, Chaplygin gas and solvable k-essence cosmologies

abstract:
  We investigate a flat Friedmann-Robertson-Walker spacetime filled with
k-essence and find the set of functions F which generate three different
families of extended tachyon fields and Chaplygin gases. They lead to
accelerated and superaccelerated expanding scenarios.
  For any function F, we find the first integral of the k-field equation when
the k-field is driven by an inverse square potential or by a constant one. In
the former, we obtain the general solution of the coupled Einstein-k-field
equations for a linear function F. This model shares the same kinematics of the
background geometry with the ordinary scalar field one driven by an exponential
potential. However, they are dynamically different. For a constant potential,
we introduce a k-field model that exhibits a transition from a power-law phase
to a de Sitter stage, inducing a modified Chaplygin gas.


title: Satellite galaxies in cosmological dark matter halos

abstract:
  We present preliminary results from a series of high-resolution N-body
simulations that focus on 8 dark matter halos each of order a million particles
within the virial radius. We follow the time evolution of hundreds of
individually tracked satellite galaxies and relate their physical properties to
the differing halo environmental conditions. Our main science driver is to
understand how satellite galaxies lose their mass and react to tidal stripping.
Unlike previous work our results are performed in a fully self-consistent
cosmological context. The preliminary results demonstrate that while
environment may vary considerably with respects to formation time and richness
of substructure, the satellites evolve similarly.


title: Spectropolarimetry of Compton-thin Seyfert 2s

abstract:
  We present new spectropolarimetry of a sample of nearby Compton-thin Seyfert
2 galaxies (ie those with N_H<10^23 cm^-2). We show that the detection rate of
scattered broad Halpha in this sample is considerably higher than in Seyfert 2
galaxies as a whole. Our results also show that in this low obscuration set it
is possible to find scattered broad Halpha even when the global properties of
the galaxy are largely dominated by the host galaxy and not the active galactic
nucleus. These results argue against the existence of a population of `pure'
Seyfert 2 galaxies.


title:
Long slit spectroscopy of a sample of isolated spirals with and without
  an AGN

abstract:
  We present the kinematical data obtained for a sample of active (Seyfert) and
non active isolated spiral galaxies, based on long slit spectra along several
position angles in the Halpha line region and, in some cases, in the Ca triplet
region as well. Gas velocity distributions are presented, together with a
simple circular rotation model that allows to determine the kinematical major
axes. Stellar velocity distributions are also shown. The main result is that
active and control galaxies seem to be equivalent in all kinematical aspects.
For both subsamples, the departure from pure circular rotation in some galaxies
can be explained by the presence of a bar and/or of a spiral arm. They also
present the same kind of peculiarities, in particular, S-shape structures are
quite common near the nuclear regions. They define very similar Tully-Fisher
relations. Emission line ratios are given for all the detected HII regions; the
analysis of the [NII]/Halpha metallicity indicator shows that active and
non-active galaxies have indistinguishable disk metallicities. These results
argue in favour of active and non-active isolated spiral galaxies having
essentially the same properties, in agreement with our previous results based
on the analysis of near infrared images. It appears now necessary to confirm
these results on a larger sample.


title: A quantitative analysis of OCN- formation in interstellar ice analogs

abstract:
  The 4.62 micron absorption band, observed along the line-of-sight towards
various young stellar objects, is generally used as a qualitative indicator for
energetic processing of interstellar ice mantles. This interpretation is based
on the excellent fit with OCN-, which is readily formed by ultraviolet (UV) or
ion-irradiation of ices containing H2O, CO and NH3. However, the assignment
requires both qualitative and quantitative agreement in terms of the efficiency
of formation as well as the formation of additional products. Here, we present
the first quantitative results on the efficiency of laboratory formation of
OCN- from ices composed of different combinations of H2O, CO, CH3OH, HNCO and
NH3 by UV- and thermally-mediated solid state chemistry. Our results show large
implications for the use of the 4.62 micron feature as a diagnostic for
energetic ice-processing. UV-mediated formation of OCN- from H2O/CO/NH3 ice
matrices falls short in reproducing the highest observed interstellar
abundances. In this case, at most 2.7% OCN- is formed with respect to H2O under
conditions that no longer apply to a molecular cloud environment. On the other
hand, photoprocessing and in particular thermal processing of solid HNCO in the
presence of NH3 are very efficient OCN- formation mechanisms, converting
60%--85% and ~100%, respectively of the original HNCO. We propose that OCN- is
most likely formed thermally from HNCO given the ease and efficiency of this
mechanism. Upper limits on solid HNCO and the inferred interstellar ice
temperatures are in agreement with this scenario.


title:
The runaway instability of thick discs around black holes. II. Non
  constant angular momentum discs

abstract:
  We present results from a comprehensive number of relativistic,
time-dependent, axisymmetric simulations of the runaway instability of
non-constant angular momentum thick discs around black holes. This second paper
extends earlier results where only constant angular momentum discs were
considered. All relevant aspects of the theory of stationary thick discs around
rotating black holes, necessary to build the initial state in our simulations,
are presented in great detail. The angular momentum of the discs is assumed to
increase outwards with the radial distance according to a power law. The main
simplifying assumptions of our approach are not to include magnetic fields and
self-gravity in the discs. Furthermore, the dynamics of the spacetime is
accounted for by computing the transfer of mass and angular momentum from the
disc to the black hole through the event horizon : the evolution of the central
black hole is assumed to follow a sequence of Kerr black holes of increasing
mass and spin. In agreement with previous results based on stationary models we
find that by allowing the mass and the spin of the black hole to grow, constant
angular momentum discs rapidly become unstable on a dynamical timescale. The
comparison with the results of paper I shows that the effect of the angular
momentum transfer from the torus to the black hole is to make constant angular
momentum discs less unstable, increasing the timescale of the instability.
However, we find that non-constant angular momentum discs are dramatically
stabilized for very small values of the angular momentum slope. Our
time-dependent simulations confirm, thus, the predictions of stationary studies
concerning the stabilizing effect of non-constant angular momentum
distributions.


title:
Local Supermassive Black Holes, Relics of Active Galactic Nuclei and the
  X-ray Background

abstract:
  We quantify the importance of mass accretion during AGN phases in the growth
of supermassive black holes (BH) by comparing the mass function of black holes
in the local universe with that expected from AGN relics, which are black holes
grown entirely with mass accretion during AGN phases. The local BH mass
function (BHMF) is estimated by applying the well-known correlations between BH
mass, bulge luminosity and stellar velocity dispersion to galaxy luminosity and
velocity functions. The density of BH's in the local universe is 4.6 (-1.4;
+1.9) (h/0.7)^2 10^5 Msun Mpc^-3. The relic BHMF is derived from the continuity
equation with the only assumption that AGN activity is due to accretion onto
massive BH's and that merging is not important. We find that the relic BHMF at
z=0 is generated mainly at z<3. Moreover, the BH growth is anti-hierarchical in
the sense that smaller BH's (MBH< 10^7 Msun) grow at lower redshifts (z<1) with
respect to more massive one's (z~1-3). Unlike previous work, we find that the
BHMF of AGN relics is perfectly consistent with the local BHMF indicating the
local BH's were mainly grown during AGN activity. This agreement is obtained
while satisfying, at the same time, the constraints imposed from the X-ray
background. The comparison with the local BHMF also suggests that the merging
process is not important in shaping the relic BHMF, at least at low redshifts
(z<3). Our analysis thus suggests the following scenario: local black holes
grew during AGN phases in which accreting matter was converted into radiation
with efficiencies epsilon = 0.04-0.16 and emitted at a fraction lambda =
0.1-1.7 of the Eddington luminosity. The average total lifetime of these active
phases ranges from ~4.5 10^8 yr for MBH< 10^8 Msun to ~1.5 10^8 yr for MBH>
10^9 Msun. (abridged)


title:
CMB Observations and the Production of Chemical Elements at the End of
  the Dark Ages

abstract:
  The metallicity evolution and ionization history of the universe must leave
its imprint on the Cosmic Microwave Background through resonant scattering of
CMB photons by atoms, ions and molecules. These transitions partially erase
original temperature anisotropies of the CMB, and also generate new
fluctuations. In this paper we propose a method to determine the abundance of
these heavy species in low density (over-densities less than $10^4-10^5$)
optically thin regions of the universe by using the unprecedented sensitivity
of current and future CMB experiments. In particular, we focus our analysis on
the sensitivity of the PLANCK HFI detectors in four spectral bands. We also
present results for l=220 and 810 which are of interest for balloon and
ground-based instruments, like ACT, APEX and SPT. We use the fine-structure
transitions of atoms and ions as a source of frequency dependent optical depth
($\tau_{\nu}$). These transitions give different contributions to the power
spectrum of CMB in different observing channels. By comparing results from
those channels, it is possible to {\it avoid} the limit imposed by the cosmic
variance and to extract information about the abundance of corresponding
species at the redshift of scattering. For PLANCK HFI we will be able to get
strong constraints ($10^{-4}-10^{-2}$ solar fraction) on the abundances of
neutral atoms like C, O, Si, S, and Fe in the redshift range 1-50.
Fine-structure transitions of ions like CII, NII or OIII set similar limits in
the very important redshift range 3-25 and can be used to probe the ionization
history of the universe. Foregrounds and other frequency dependent contaminants
may set a serious limitation for this method.


title: Theory of magnetized accretion discs driving jets

abstract:
  In this lecture I review the theory of magnetized accretion discs driving
jets, with a focus on Young Stellar Objects (YSOs). I first introduce
observational and theoretical arguments in favor of the ``disc wind'' paradigm.
There, accretion and ejection are interdependent, requiring therefore to
revisit the standard picture of accretion discs. A simple magnetostatic
approach is shown to already provide some insights of the basic phenomena. The
magnetohydrodynamic equations as well as all usual assumptions are then clearly
listed. The relevant physical mechanisms of steady-state accretion and ejection
from Keplerian discs are explained in a model independent way. The results of
self-similar calculations are shown and critically discussed, for both cold and
warm jet configurations. I finally provide observational predictions and the
physical conditions required in YSOs discs. The necessity of introducing a
magnetospheric interaction between the disc and the protostar is briefly
discussed.


title:
Cosmological parameters from supernova observations: A critical
  comparison of three data sets

abstract:
  We extend our previous analysis of cosmological supernova data (Padmanabhan &
Choudhury 2003) to include three recent compilation of data sets. Our analysis
ignores systematic effects in the data and concentrates on some key theoretical
issues. The first data set consists of 194 points while the second discards
some of the points from the first one because of large uncertainties and thus
consists of 142 points. The third data set is obtained from the second by
adding the latest 14 points observed through HST. A careful comparison of these
different data sets help us to draw the following conclusions: (i) All the data
sets strongly rule out non-accelerating models. Interestingly, the first and
the second sets favour a closed universe; i.e., the probability P(Omega_{tot} >
1) \gtrsim 0.97. Hence these sets are in mild disagreement with the
``concordance'' flat model. However, this disagreement is reduced
[P(Omega_{tot} > 1) \approx 0.9] for the third data set, which includes the
points observed by HST around 1 < z < 1.6. (ii) When the first data set is
divided into two separate subsets consisting of low (z < 0.34) and high (z >
0.34) redshift supernova, it turns out that these two subsets, individually,
admit non-accelerating models. However, these models seem to be ruled out using
only the low redshift data for the other two data sets, which have less
uncertainties. (iii) It is quite difficult to measure the evolution of the dark
energy equation of state w_X though its present value can be constrained quite
well. The best-fit value seems to mildly favour a dark energy component with
current equation of state w_X < -1, thus opening the possibility of existence
of more exotic forms of matter. However, the data is still consistent with the
the standard cosmological constant at 99% confidence level (abridged).


title: Accretion--ejection phenomena from young stars

abstract:
  In the current paradigm of star formation magnetic fields play a very central
role. Indeed, they probably help or even channel the initial gravitational
collapse of the parent molecular cloud. But their most spectacular effect is
certainly the production of ubiquitous, powerful, bipolar self-collimated jets.
Also, in the last decade, evidence has come that in such systems a
magnetosphere links the protostar to its surrounding accretion disc.
  I will first briefly review the magnetohydrodynamic models of jets from young
stars. Then, I will discuss some constraints on the magnetospheric interaction
since accretion must proceed despite strong stellar magnetic fields. Finally, I
will introduce the "Reconnection X-wind" scenario that leads to episodic jet
formation with efficient removal of protostellar angular momentum.


title: A search for evolved dust in Herbig Ae stars

abstract:
  We present observations of six isolated, pre-main-sequence, intermediate mass
stars selected for shallow spectra at submillimeter wavelengths at 1.3, 2.6,
7.0, and 36 millimeters from the IRAM PdBI and the VLA. We analyze the new
observations of these stars (HD34282, HD35187, HD142666, HD143006, HD150193,
HD163296) together with similar observations of three additional stars from the
literature (CQ Tau, UX Ori, TW Hya), in the context of self-consistent
irradiated disk models. Our aim is to constrain the wavelength dependence of
the dust opacity and the total dust mass in the disks. The shallow wavelength
dependence of the opacity is confirmed and for a few stars extended to
significantly longer wavelengths. For any plausible dust properties, this
requires grain growth from interstellar sizes to maximum sizes of at least a
few millimeters, and very likely to several centimeters or more. For four of
the stars (HD34282, HD163296, CQ Tau, TW Hya), the millimeter emission has been
spatially resolved, and the large disk radii ($>100$ AU) rule out that high
optical depths play a role. The mass of dust that has been processed into large
grains is substantial, and in some cases implies a disk mass comparable to the
mass of the central star.


title: Detection of a warm molecular wind in DG Tauri

abstract:
  We detect near-infrared H2 emission in DG Tau using the Infrared Camera and
Spectrograph (IRCS) on the 8.2-m SUBARU telescope. The spectra obtained along
the jet axis show that the centroidal position of the 1-0 S(1) emission is
offset by 0.2" from the star towards the jet, while those obtained
perpendicular to the jet axis show a marginal extension, indicating that the
emission line region has a typical width of ~0.6". Their line profiles show a
peak velocity of ~15 km s^-1 blueshifted from the systemic velocity. These
results indicate that the emission originates from a warm molecular wind with a
flow length and width of ~40 and ~80 AU, respectively. The line flux ratios
I_{1-0 S(0)}/I_{1-0 S(1)} and an upper limit for I_{2-1 S(1)}/I_{1-0 S(1)})
suggest that the flow is thermalized at a temperature of ~2000 K, and is likely
heated by shocks or ambipolar diffusion. The observed velocity and spatial
extension suggest that the H2 and forbidden line emission originate from
different components of the same flow, i.e., a fast and partially ionised
component near the axis and a slow molecular component surrounding it. Such a
flow geometry agrees with model predictions of magneto-centrifugal driven
winds.


title:
XMM-Omega project : cosmological implication from the high-z L-T
  relation of X-ray clusters

abstract:
  The evolution of the temperature distribution function (TDF) of X-ray
clusters is kn own to be a powerful cosmological test of the density parameter
of the Universe. Recent XMM observations allows us to measure accurately the L
- T relation of high redshift X-ray clusters. In order to investigate
cosmological implication of this recent results, we have derived theoretical
number counts for different X-ray clusters samp les, namely the RDCS, EMSS,
SHARC, 160 deg^2 and MACS at z > 0.3 in different fl at models. We show that a
standard hierarchical modeling of cluster distribution in a flat low density
universe, normalized to the local abundance, overproduces cluster abundance at
high redshift (z>0.5) by an order of magnitude. We conclude that presently
existing data on X-ray clusters at high redshift strongly favor a universe with
a high density of matter, insensitively to the details of the modeli ng.


title:
Age determination of the nuclear stellar population of Active Galactic
  Nuclei using Locally Weighted Regression

abstract:
  We present a new technique to segregate old and young stellar populations in
galactic spectra using machine learning methods. We used an ensemble of
classifiers, each classifier in the ensemble specializes in young or old
populations and was trained with locally weighted regression and tested using
ten-fold cross-validation. Since the relevant information concentrates in
certain regions of the spectra we used the method of sequential floating
backward selection offline for feature selection.
  The application to Seyfert galaxies proved that this technique is very
insensitive to the dilution by the Active Galactic Nucleus (AGN) continuum.
Comparing with exhaustive search we concluded that both methods are similar in
terms of accuracy but the machine learning method is faster by about two orders
of magnitude.


title: Evolution of the ISM of Starburst galaxies: the SN heating efficiency

abstract:
  The interstellar medium heated by SN explosions may acquire an expansion
velocity larger than the escape velocity and leave the galaxy through a
supersonic wind. SN ejecta are transported out of the galaxies by such winds
which thus affect the chemical evolution of the galaxies. The effectiveness of
the processes mentioned above depends on the heating efficiency (HE) of the
SNe, that is a matter of debate. We have constructed a simple semi-analytic
model, considering the essential ingredients of a SB environment which is able
to qualitatively trace the thermalisation history of the ISM in a SB region and
determine the HE evolution. We find that, as long as the mass-loss rate of the
clouds remains larger than the rate at which the SNRs interact one with each
other, the SN heating efficiency remains very small, as radiative cooling of
the gas dominates. We conclude that the HE value has a time-dependent trend
that is sensitive to the initial conditions of the system.


title: Other Kuiper Belts

abstract:
  When a main sequence star evolves into a red giant and its Kuiper Belt
Object's (KBO's) reach a temperature of about 170 K, the dust released during
the rapid ice-sublimation of these cometary bodies may lead to a detectable
infrared excess at 25 microns, depending upon the mass of the KBO's. Analysis
of IRAS data for 66 first ascent red giants with 200 L(Sun) < L < 300 L(Sun)
within 150 pc of the Sun provides an upper limit to the mass in KBO's at 45 AU
orbital radius that is usually less than about 0.1 M(Earth). With improved
infrared data, we may detect systems of KBO's around first ascent red giants
that are analogs to our Solar System's KBO's.


title: Spectral analysis of 50 GRBs detected by HETE-2

abstract:
  FREGATE, the gamma-ray detector of HETE-2 is entirely dedicated to the study
of GRBs. Its main characteristic is its broad energy range, from 7 keV to 400
keV. This energy range can be further extended down to 2 keV using the data
from the WXM, the X-ray detector of HETE-2. Such a large energy range allows to
study in details the prompt emission of GRBs, determining with a high precision
their spectral parameters. Moreover, because this energy range extends at low
energies, the sample of GRBs detected by both FREGATE and WXM contains a
significant fraction of X-Ray Rich GRBs and X-Ray Flashes.
  We present here the distributions of the spectral parameters mesured for the
time integrated spectra of 50 GRBs. We put emphasis on the distribution of the
low energy spectral index alpha. Because FREGATE and WXM detected all classes
of GRBs, we also discuss the connection between GRBs, X-Ray Rich GRBs and X-Ray
Flashes.


title: The Satellite-substructure Connection

abstract:
  We describe our recent attempts to model substructure in dark matter halos
down to very small masses, using a semi-analytic model of halo formation. The
results suggest that numerical simulations of halo formation may still be
missing substructure in the central regions of halos due to purely numerical
effects. If confirmed, this central 'overmerging' problem will have important
consequences for the interpretation of lensing measurements of substructure. We
also show that the spatial distribution of subhalos relative to the satellite
companions of the Milky Way rules out at least one simple model of how dwarf
galaxies form in low-mass halos.


title:
A bias in optical observations of high redshift luminous infrared
  galaxies

abstract:
  We present evidence for the dramatically different morphology between the
rest frame UV and 7micron mid-IR emission of VV114 and Arp299, two nearby (z~0)
violently interacting infrared luminous galaxies (LIRGs). Nearly all LIRGs are
interacting systems and it is currently accepted that they dominate the IR
emission at z>1. Luminous IR galaxies located at z=1-2 could easily be detected
as unresolved sources in deep optical/near-IR ground based surveys, as well as
in upcoming 24micron surveys with the Space Infrared Telescope Facility. We
demonstrate that the spatial resolution of these surveys will result in
blending of the emission from unresolved interacting components. An increased
scatter will thus be introduced in the observed optical to mid-IR colors of
these galaxies, leading to a systematic underestimation of their dust content.


title: Ongoing Mass Transfer in the Interacting Galaxy Pair NGC 1409/10

abstract:
  I present two-band HST STIS imaging, and WIYN spectral mapping, of ongoing
mass transfer in the interacting galaxy pair NGC 1409/10 (where NGC 1410 is the
Seyfert galaxy also catalogued as III Zw 55). Archival snapshot WFPC2 imaging
from the survey by Malkan et al. showed a dust feature stretching between the
galaxies, apparently being captured by NGC 1409. The new images allow estimates
of the mass being transferred and rate of transfer. An absorption lane
typically 0.25" (100 pc) wide with a representative optical depth tau_B = 0.2
cuts across the spiral structure of NGC 1410, crosses the 7-kpc projected space
between the nuclei, wraps in front of and, at the limits of detection, behind
NGC 1409, and becomes a denser (tau_B = 0.4) polar feature around the core of
NGC 1409. Combination of extinction data in two passbands allows a crude
three-dimensional recovery of the dust structure, supporting the front/back
geometry derived from colors and extinction estimates. The whole feature
contains of order $10^6$ solar masses in dust, implying about 2x10^7 solar
masses of gas, requiring a mass transfer rate averaging ~1 solar mass per year
unless we are particularly unlucky in viewing angle. Curiously, this
demonstrable case of mass transfer seems to be independent of the occurrence of
a Seyfert nucleus, since the Seyfert galaxy in this pair is the donor of the
material. Likewise, the recipient shows no signs of recent star formation from
incoming gas, although NGC 1410 has numerous luminous young star clusters and
widespread H-alpha emission.


title:
The Gravitational Suppression Hypothesis: Dynamical Analysis in the
  Small Velocity Regime

abstract:
  In a previous paper we have proposed a non--Newtonian, phenomenological
description of the effective gravitational force acting between exotic dark
matter and baryons, which was shown to fit well the kinematics in the inner
regions of low surface brightness, gas--rich galaxies. The Gravitational
Suppression (GraS) scheme is, admittedly, an ad-hoc model; it does however
successfully address interesting cosmological issues. Here, we test the
potential generality of the GraS concept. GraS predictions on motions on scales
measurable in dwarf spheroidal galaxies and in the solar neighborhood show
significant departures from those of Newtonian mechanics. By analyzing such
systems, we find that the paradigm of a universal GraS potential cannot be
rejected. Indeed, compared to Newtonian predictions, GraS provides a better
description of data, when realistic dark matter density profiles are
considered.


title: Investigating the Origins of Dark Matter Halo Density Profiles

abstract:
  Although high-resolution N-body simulations make robust empirical predictions
for the density distribution within cold dark matter halos, these studies have
yielded little physical insight into the origins of the distribution. We
investigate the problem using analytic and semi-analytic approaches. Simple
analytic considerations suggest that the inner slope of dark matter halos
cannot be steeper than alpha=2 (rho ~ r^-alpha), with alpha=1.5-1.7 being a
more realistic upper limit. Our analysis suggests that any number of effects,
both real (angular momentum from tidal torques, secondary perturbations) and
artificial (two-body interactions, the accuracy of the numerical integrator,
round-off errors), will result in shallower slopes. We also find that the halos
should exhibit a well-defined relation between r_peri/r_apo and j_theta/j_r. We
derive this relation analytically and speculate that it may be "universal".
Using a semi-analytic scheme based on Ryden & Gunn (1987), we further explore
the relationship between the specific angular momentum distribution in a halo
and its density profile. For now we restrict ourselves to halos that form
primarily via nearly-smooth accretion of matter, and only consider the specific
angular momentum generated by secondary perturbations associated with the cold
dark matter spectrum of density fluctuations. Compared to those formed in
N-body simulations, our ``semi-analytic'' halos are more extended, have flatter
rotation curves and have higher specific angular momentum, even though we have
not yet taken into account the effects of tidal torques. Whether the density
profiles of numerical halos is indeed the result of loss in angular momentum
outside the central region, and whether this loss is a feature of hierarchical
merging and major mergers in particular, is under investigation.


title:
Radio observations of HD 93129A: The earliest O star with the highest
  mass loss ?

abstract:
  We present the results of radio continuum observations towards the open
cluster Tr 14, where our main targets are the early-type O stars HD 93129A/B
and HD 93128. The observations were carried out at 3 cm (8.64 GHz) and 6 cm
(4.80 GHz) with the Australia Telescope Compact Array. Only HD 93129A (type O2
If*) was detected; we measure flux densities of S_(3cm) = 2.0 +- 0.2 mJy and
S_(6cm) = 4.1 +- 0.4 mJy. The resulting spectral index of alpha = -1.2 +- 0.3
(S_(nu) = k . nu^alpha) indicates predominantly non-thermal emission,
suggesting HD 93129A may be a binary system. We propose that the observed 3 cm
radio emission is mostly coming from the non-thermal wind collision region of a
binary, and, to a lesser extent, from the thermal winds of the primary and
secondary stars in HD 93129A. At a stellar distance of 2.8 kpc, we derive a
mass-loss rate M_dot = 5.1 x 10^(-5) M_sun/yr, assuming the thermal fraction of
the 3 cm emission is about 0.5.


title: A Chandra HETGS observation of the Narrow-line Seyfert 1 galaxy Ark 564

abstract:
  We present results from a 50 ks observation of the narrow-line Seyfert 1
galaxy Ark 564 with the Chandra HETGS. The spectra above 2 keV are modeled by a
power-law with a photon-index of 2.56+/-0.06. We confirm the presence of the
soft excess below about 1.5 keV. If we fit the excess with blackbody model, the
best-fit temperature is 0.124 keV. Ark 564 has been reported to show a peculiar
emission line-like feature at 1 keV in various observations using lower
resolution detectors, and the Chandra grating spectroscopy rules out an origin
of blends of several narrow emission lines. We detect an edge-like feature at
0.712 keV in the source rest frame. The preferred interpretation of this
feature is combination of the O VII K-edge and a number of L-absorption lines
from slightly ionized iron, which suggests a warm absorber with ionization
parameter xi~1 and N_H ~ 10^21 cm^-2. These properties are roughly consistent
with those of the UV absorber. We also detect narrow absorption lines of O VII,
O VIII, Ne IX, Ne X, and Mg XI at the systemic velocity. From these lines, a
second warm absorber having log xi ~ 2 and N_H ~ 10^21 cm^-2 is required.


title:
Redshifted 21 cm Emission From the Pre-Reionization Era I. Mean Signal
  and Linear Fluctuations

abstract:
  We use cosmological simulations of reionization to predict the possible
signal from the redshifted 21 cm line of neutral hydrogen in the
pre-reionization era and to investigate the observability of this signal. We
show that the separation of the mean (global) signal over the whole sky from
the known foreground contamination may be feasible, but very challenging. In
agreement with previous studies, we demonstrate that measuring angular
fluctuations in the HI signal is likely to be extremely difficult if not
impossible because of the overwhelming contamination from the galactic and
extragalactic foregrounds. However,we show that the sharp HI fluctuations in
the frequency domain should be easily separable from the relatively smooth
spectra of the foregrounds, and that these fluctuations should be detectable
even at moderate angular resolution (10-20 arcmin).


title:
Stationary electromagnetic fields in the exterior of a slowly rotating
  relativistic star: a description beyond the low-frequency approximation

abstract:
  We investigate the electromagnetic fields in the vacuum exterior of a
rotating relativistic star endowed with a magnetic dipole moment, and with the
stellar surface behaving as a perfect conductor. While the stellar rotation is
treated in the slow-approximation of general relativity, we do not restrict our
attention to slowly rotating electromagnetic fields, and take our analysis
beyond the low-frequency approximation considered so far. When the dipole
moment is misaligned with the rotational axis, our approach does not yield
analytic solutions as in Rezzolla et al. (2001a, b), but determines the
properties of the electromagnetic fields approximately and semi-analytically,
by computing the coefficients of simple expressions for the fields through the
numerical solution of two partial differential equations. Because our approach
provides a solution which is in principle valid throughout space, we can
evaluate the accuracy and/or invalidity of previously known analytic
expressions at different distances from the stellar surface. Overall, the
solutions found in this way represent an efficient way of bridging in a single
semi-analytic formalism the strongly relativistic (Rezzolla et al. 2001a, b)
and the asymptotic regimes (Deutsch 1955) for which analytic solutions have
been found.


title:
The Stellar Content and Star Formation History of the late-type spiral
  galaxy NGC 300 from Hubble Space Telescope observations

abstract:
  We present the first WFPC2 V, I photometry for the Sculptor Group galaxy NGC
300 in four fields ranging from the centre to the outer edge. We have made the
first measurement of the star formation histories in two disk fields: the
oldest stars were born at similar epochs and formation activity increased but
at different mean rates. The main disk stellar population is predominantly old,
consisting of RGB and AGB stars, based on a synthetic colour magnitude diagram
analysis. Z is found to have been more metal poor than 0.006 (or 0.33Zsolar)
with no evidence for significant change in the mean Z value over time in both
disk fields. In the central region, we find a dearth of bright stars with
respect to the two disk fields that cannot be explained by observational
effects. Taken at face value, this finding would agree with the Davidge (1998)
report of suppressed star formation there during the past 1Gyr with respect to
his disk fields at larger radii; but the possibility of significant central
extinction affecting our finding remains. We have also determined the first
distance modulus estimate based on the tip of the red giant branch method: on
the Cepheid distance scale of Ferrarese et al. (2000) we find (m-M)o =
26.56+/-0.07 (+/-0.13) mag; and a similar value from the Cepheid-independent
empirical method by Lee et al. (1993), both in good agreement with the Cepheid
distance determined by Freedman et al. (2001). A discrepancy between this and
the theoretical calibration of the red giant branch tip magnitude method
remains. Finally, we report a newly detected young (up to about 10Myr) stellar
association of about average size (~140pc) in one of the disk fields.


title:
Optical spectra of the carbon-oxygen accretion discs in the
  ultra-compact X-ray binaries 4U 0614+09, 4U 1543-624 and 2S 0918-549

abstract:
  We present optical spectra in the range 4600 -- 8600 A for three low-mass
X-ray binaries which have been suggested to belong to the class of
ultra-compact X-ray binaries based on their X-ray spectra. Our spectra show no
evidence for hydrogen or helium emission lines, as are seen in classical X-ray
binaries. The spectrum of 4U~0614+09 does show emission lines which we identify
with carbon and oxygen lines of CII, CIII, OII and OIII. While the spectra of
4U 1543-624 and 2S 0918-549 have a lower signal-to-noise ratio, and thus are
more difficult to interpret, some of the characteristic features of 4U 0614+09
are present in these spectra too, although sometimes they are clearly weaker.
We conclude that the optical spectra give further evidence for the
ultra-compact nature of these X-ray binaries and for their donor stars being
carbon-oxygen white dwarfs.


title: Bulk Viscosity in Hybrid Stars

abstract:
  We compute the bulk viscosity of a mixed quark-hadron phase. In the first
scenario to be discussed, the mixed phase occurs at large densities and we
assume that it is composed of a mixing of hyperonic matter and quarks in the
Color Flavor Locked phase. In a second scenario, the mixed phase occurs at
lower densities and it is composed of a mixing of nucleons and unpaired quark
matter. We have also investigated the effect of a non-vanishing surface tension
at the interface between hadronic and quark matter. In both scenarios, the bulk
viscosity is large when the surface tension is absent, while the value of the
viscosity reduces in the second scenario when a finite value for the surface
tension is taken into account. In all cases, the r-mode instabilities of the
corresponding hybrid star are suppressed.


title:
Outer-magnetospheric model for Vela-like pulsars:formation of sub-GeV
  spectrum

abstract:
  We investigate the $\gamma$-ray emission from a outer-gap accelerator, which
is located in the outer-magnetosphere of a pulsar. The charge depletion from
the Goldreich-Julian density causes a large electric field along the magnetic
field lines. The electric field accelerates electrons and positrons to high
energies. We solve the formation of the electric field self-consistently with
the radiation and the pair-creation processes in one-dimensional geometry along
the magnetic field lines, and calculate curvature spectrum to compare with the
observations. We find that because the particles escape from the accelerating
region with large Lorentz factors as $10^{7.5}$, curvature radiation from the
outside of the gap, in which there is no electric field, still has a important
contribution to the spectrum. Including the outside emission, the model spectra
are improved between 100 MeV and 1 GeV for the Vela-type pulsars. Since the
field line curvature close to the light cylinder affects the spectrum in
several hundred MeV, there is a possibility to diagnose the field structure by
using the spectrum in these bands. The difference found in the $\gamma$-ray
spectra of the twin pulsars, PSR B0833-45 (Vela) and B1706-44, is deduced from
the dimensionless electric current running through the gap. The extension to
the three-dimensional modeling with self-consistent electrodynamics is
necessary to understand the difference in the observed flux between the twin
pulsars.


title: Do arcs require flat halo cusps?

abstract:
  It was recently claimed that several galaxy clusters containing radial and
tangential gravitational arcs and having a measured velocity-dispersion profile
for the brightest cluster galaxy had to have central density profiles
considerably flatter than those found in CDM cluster simulations. Using a
simple analytic mass model, we confirm this result_for axially symmetric_ mass
distributions, but show that steep density profiles are well in agreement with
the cluster requiring the flattest axially symmetric profile once even small
deviations from axial symmetry are introduced.


title: The Infrared Counterpart of the X-Ray Nova XTE J1720-318

abstract:
  We report on the discovery of an infrared counterpart to the X-ray transient
XTE J1720-318 on 2003 January 18, nine days after an X-ray outburst, and the
infrared light curve during the first 130 days after the outburst. The infrared
light curve shows a decline of about 1.2 mag from the peak magnitude of Ks
about 15.3 over the observation period, and a secondary maximum, about 40 days
after the outburst. Another small increase in the flux was also recorded about
20 days after the outburst. These increases were also detected in the X-ray
light curve. The J H Ks colors are consistent with an X-ray irradiated
accretion disk suffering an extinction of Av about 8, which is also inferred
from its X-ray spectrum and the extinction map constructed from far-infrared
dust emission of this line of sight. These J, H, and Ks observations
demonstrate that useful data can be obtained even for such an object, which
suffers heavy optical extinction, possibly located beyond the Galactic center.


title: Gravitational Thomas Precession - A Gravitomagnetic Effect ?

abstract:
  Gravitational Thomas Precession (GTP) is the name given to the Thomas
Precession when the acceleration is caused by a gravitational force field. In
continuation of our discussion on the idea of a GTP, in this note by way of
considering the motion of a planet around the Sun, the GTP is shown to be a
gravitomagnetic effect that a planet might experience while moving through a
gravitational field (say that of the Sun). The contribution of the GTP to the
perihelion advance of Mercury is again estimated at 21.49 arc-seconds per
century confirming and clarifying our earlier results.


title:
Planck-scale structure of spacetime and some implications for
  astrophysics and cosmology

abstract:
  I briefly review some scenarios for the role of the Planck length in quantum
gravity. In particular, I examine the differences between the schemes in which
quantum gravity is expected to introduce a maximum acceleration and the schemes
in which the Planck length sets the minimum value of wavelengths (maximum value
of momentum). I also comment on some pictures for the structure of spacetime at
the Planck scale, such as spacetime discretization and spacetime
noncommutativity. I stress that some of these proposals can have significant
implications in astrophysics and cosmology.


title: On the formation of cold fronts in massive mergers

abstract:
  Using adiabatic hydrodynamical simulations, we follow the evolution of two
symmetric cold fronts developing in the remnant of a violent z=0.3 massive
cluster merger. The structure and location of the simulated cold fronts are
very similar to those recently found in X-ray cluster observations, supporting
the merger hypothesis for the origin of at least some of the cold fronts. The
cold fronts are preceded by an almost spherical bow shock which originates at
the core and disappears after 1.6 Gyr. The cold fronts last longer and survive
until z=0. We trace back the gas mass constituting the fronts and find it
initially associated with the two dense cores of the merging clusters.
Conversely, we follow how the energy of the gas of the initial merging cores
evolves until z=0 from the merging and show that a fraction of this gas can
escape from the local potential well of the sub-clumps. This release occurs as
the sub-clumps reach their apocentre in an eccentric orbit and is due to
decoupling between the dark matter and part of the gas in the sub-clump because
of, first, heating of the gas at first close core passage and of, second, the
effect of the global cluster pressure which peaks as the centrifugal
acceleration of the sub-clump is maximal. The fraction of the gas of the
sub-clump liberated in the outbound direction then cools as it expands
adiabatically and constitutes the cold fronts.


title: New limits on the generation of magnetic field

abstract:
  Magnetic fields are generated in ionized objects rotating with respect to a
radiation background. Based on conservation of canonical ion momentum, it has
been previously suggested that even if the radiation intensity is unrestricted
the maximum field strength generated this way is ~(10^{-4}\Omega) Gauss, where
\Omega is the initial angular velocity of the object. We show that this limit
is valid only for an object made of fully ionized and optically thin plasma.
The limit can be relaxed by orders of magnitude in the presence of a high
neutral fraction or if the plasma is coupled to other forms of matter such as
stars or compact clouds.


title:
The Asymmetric Thick Disk: A Star Count and Kinematic Analysis. II The
  Kinematics

abstract:
  We report a kinematic signature associated with the observed asymmetry in the
distribution of thick disk/inner halo stars interior to the Solar circle
described in Paper I. In that paper we found a statistically significant excess
(20% to 25 %) of stars in quadrant I (l ~ 20 deg to 55 deg) both above and
below the plane (b ~ +/- 25 deg to +/- 45 deg) compared to the complementary
region in quadrant IV. We have measured Doppler velocities for 741 stars,
selected according to the same magnitude and color criteria, in the direction
of the asymmetry and in the corresponding fields in quadrant IV. We have also
determined spectral types and metallicities measured from the same spectra. We
not only find an asymmetric distribution in the V_LSR velocities for the stars
in the two regions, but the angular rate of rotation, w, for the stars in
quadrant I reveals a slower effective rotation rate compared to the
corresponding quadrant IV stars. We use our [Fe/H] measurements to separate the
stars into the three primary population groups, halo, thick disk, and disk, and
conclude that it is primarily the thick disk stars that show the slower
rotation in quadrant I. A solution for the radial, tangential and vertical
components of the V_LSR velocities, reveals a significant lag of ~ 80 to 90
km/s in the direction of Galactic rotation for the thick disk stars in quadrant
I, while in quadrant IV, the same population has only a ~ 20 km/s lag. The
results reported here support a rotational lag among the thick disk stars due
to a gravitational interaction with the bar as the most likely explanation for
the asymmetry in both the star counts and the kinematics. The affected thick
disk stars, however, may be associated with the recently discovered Canis Major
debris stream or a similar merger event (abridged).


title:
Finding structures in photometric redshift galaxy surveys: An extended
  friends-of-friends algorithm

abstract:
  We present a modified version of the friends-of-friends (FOF) structure
finding algorithm, designed specifically to locate groups or clusters of
galaxies in photometric redshift datasets. The main objective of this paper is
to show that this extended friends-of-friends (hereafter EXT-FOF) algorithm
yields results almost identical to the original FOF, if applied to a
spectroscopic redshift dataset, and a rather conservative catalogue of
structures, in case of a dataset with simulated photometric redshifts.
Therefore, we create group catalogues for the first Center for Astrophysics
Redshift Survey (CFA1), as well as for the Las Campanas Redshift Survey (LCRS),
both of which being spectroscopic surveys, using FOF-algorithms. We then apply
our new algorithm to said surveys and compare the resulting structure
catalogue. Furthermore, we bestow simulated photometric redshifts on the LCRS
galaxies, and use the EXT-FOF to detect structures, that we compare in size and
composition to the ones found in the original, spectroscopic dataset. We will
show that the properties of this modified algorithm are well understood and
that it is suited for finding structures in photometric datasets.
  This is the first paper in a series of papers, dealing with the application
of our new cluster finding algorithm to various photometric redshift galaxy
surveys.


title: The Shape of Poor Groups of Galaxies

abstract:
  We estimate the distribution of intrinsic shapes of UZC-SSRS2 groups of
galaxies from the distribution of their apparent shapes. We measure the
projected group axial ratio using the moments of their discrete galaxy
distribution. Then using the non-parametric kernel method to estimate the
smooth apparent axial ratio distribution we numerically invert a set of
integral equations to recover the corresponding intrinsic distribution under
the assumption that groups are either oblate or prolate spheroids. We find that
the prolate spheroidal model fits very well the UZC-SSRS2 group distribution
with a true mean axial ratio <\beta>~0.3 and \sigma ~0.15. This shows that
groups of galaxies are significantly more elongated, both on the plane of the
sky and in 3 dimensions, than clusters of galaxies. The poorest groups that we
consider, those with 4 members, are even more elongated than the overall
population with 85% of the groups having \beta < 0.4.


title: Local redshift surveys and galaxy evolution

abstract:
  We present observations of galaxy environmental dependencies using data from
the 2dF Galaxy Redshift Survey. From a combined analysis of the luminosity
function, Butcher-Oemler effect and trends in H$\alpha$ line strengths we find
support for a model where galaxy properties are mainly set by initial
conditions at the time of their formation.


title: Anomalous radio emission from dust in the Helix

abstract:
  A byproduct of experiments designed to map the CMB is the recent detection of
a new component of foreground Galactic emission. The anomalous foreground at ~
10--30 GHz, unexplained by traditional emission mechanisms, correlates with
100um dust emission. We report that in the Helix the emission at 31 GHz and
100um are well correlated, and exhibit similar features on sky images, which
are absent in H\beta. Upper limits on the 250 GHz continuum emission in the
Helix rule out cold grains as candidates for the 31 GHz emission, and provide
spectroscopic evidence for an excess at 31 GHz over bremsstrahlung. We estimate
that the 100um-correlated radio emission, presumably due to dust, accounts for
at least 20% of the 31 GHz emission in the Helix. This result strengthens
previous tentative interpretations of diffuse ISM spectra involving a new dust
emission mechanism at radio frequencies. Very small grains have not been
detected in the Helix, which hampers interpreting the new component in terms of
spinning dust. The observed iron depletion in the Helix favors considering the
identity of this new component to be magnetic dipole emission from hot
ferromagnetic grains. The reduced level of free-free continuum we report also
implies an electronic temperature of Te=4600\pm1200K for the free-free emitting
material, which is significantly lower than the temperature of 9500\pm500K
inferred from collisionally-excited lines (abridged).


title:
Constraints on Cardassian Scenario from the Expansion Turnaround
  Redshift and the Sunyaev-Zeldovich/X-ray Data

abstract:
  Cosmic acceleration is one of the most remarkable cosmological findings of
recent years. Although a dark energy component has usually been invoked as the
mechanism for the acceleration, A modification of Friedmann equation from
various higher dimensional models provides a feasible alternative. Cardassian
expansion is one of these scenarios. In this work, we first consider the
constraints on the parameter space from the turnaround redshift, z_{q=0}, at
which the universe switches from deceleration to acceleration. We show that,
for every Omega_m, there exist a unique n_{peak} (Omega_m), which makes z_{q=0}
reach its maximum value, [z_{q=0}]_{max} = exp[1/ (2-3n_{peak})] -1, which is
unlinearly inverse to Omega_m. If the acceleration happans earlier than z_{q=0}
= 0.6, suggested by Type Ia supernovae measurements, we have Omega_m < 0.328 no
matter what the power index is, and moreover, for reasonable matter density,
Omega_m ~ 0.3, it is found n ~ (-0.45,0.25). We next test this scenario using
the Sunyaev-Zeldovich/X-ray data of a sample of 18 galaxy clusters with 0.14 <
z < 0.83 compiled by Reese et al. (2002). The constraints from the current
SZ/X-ray data is weak, though a model with lower matter density is prefered. A
certain range of the model parameters is also consistent with the data.


title: Stellar Halo Constraints on Simulated Late Type Galaxies

abstract:
  How do late type spiral galaxies form within the context of a CDM cosmology?
We contrast N-body, smoothed particle hydrodynamical simulations of galaxy
formation which employ two different supernova feedback mechanisms. Observed
mass and metallicity distributions of the stellar halos of the Milky Way and
M31 provide constraints on these models. A strong feedback model, incorporating
an adiabatic phase in star burst regions, better reproduces these observational
properties than our comparative thermal feedback model. This demonstrates the
importance of energy feedback in regulating star formation in small systems,
which collapse at early epochs, in the evolution of late type disk galaxies.


title: Rhombic cell analysis II. Application to the IRAS/PSCz Catalogue

abstract:
  Rhombic cell analysis as outlined in the first paper of the present series is
applied to samples of varying depths and liming luminosities of the IRAS/PSCz
Catalogue. Numerical indices are introduced to summarize essential information.
Because of the discrete nature of the anlaysis and of the space distribution of
galaxies, the indices for a given sample must be regarded as each having an
irreducible scatter. Despite the scatter, the mean indices show remarkable
variations across the samples. The underlying factor for the variations is
shown to be the limiting luminosity rather than the sampling depth. As samples
of more and more luminous galaxies are considered over a range of some 2
magnitudes (a factor of some 50 in space density), the morpholgy of the filled
and empty regions the galaxies define degrades steadily towards insignificance,
and the degrading is faster for the filled than the empty region.


title:
The amplitude of mass fluctuations and mass density of the Universe
  constrained by strong gravitational lensing

abstract:
  We investigate the linear amplitude of mass fluctuations in the universe,
$\sigma_8$, and the present mass density parameter of the Universe,
$\Omega_\mathrm{m}$, from the statistical strong gravitational lensing. We use
the two populations of lens halos model with fixed cooling mass scale
$M_\mathrm{c}=3\times 10^{13}h^{-1}M_{\sun}$ to match the observed lensing
probabilities, and leave $\sigma_8$ or $\Omega_\mathrm{m}$ as a free parameter
to be constrained by data. Another varying parameter is the equation of state
of dark energy $\omega$, and its typical values of -1, -2/3, -1/2 and -1/3 are
investigated. We find that $\sigma_8$ is degenerate with $\Omega_\mathrm{m}$ in
a way similar to that suggested by present day cluster abundance as well as
cosmic shear lensing measurements: $\sigma_8\Omega_\mathrm{m}^{0.6}\approx
0.33$ (Bahcall & Bode\cite{bahcall03a} and references therein). However, both
$\sigma_8\leq 0.7$ and $\Omega_\mathrm{m}\leq 0.2$ can be safely ruled out, the
best value is when $\sigma_8=1.0$, $\Omega_\mathrm{m}=0.3$ and $\omega=-1$.
This result is different from that obtained by Bahcall & Bode
(\cite{bahcall03a}), who gives $\sigma_8 =0.98\pm 0.1$ and $\Omega_m =0.17\pm
0.05$. For $\sigma_8=1.0$, higher value of $\Omega_\mathrm{m}=0.35$ requires
$\omega=-2/3$ and $\Omega_\mathrm{m}=0.40$ requires $\omega=-1/2$.


title: The brown dwarf population in the Chamaeleon I cloud

abstract:
  We present the results of a multiband survey for brown dwarfs in the
Chamaeleon I dark cloud with the Wide Field Imager (WFI) camera at the ESO/MPG
2.2-m telescope on La Silla (Chile). The survey has revealed a substantial
population of brown dwarfs in this southern star forming region. Candidates
were selected from R, I and H-alpha imaging observations. We also observed in
two medium-band filters, M855 and M915, for the purpose of spectral type
determination. The former filter covers a wavelength range containing spectral
features characteristic of M-dwarfs, while the latter lies in a relatively
featureless wavelength region for these late-type objects. A correlation was
found between spectral type and (M855-M915) colour index for mid- to late
M-type objects and early L-type dwarfs. With this method, we identify most of
our object candidates as being of spectral type M5 or later. Our results show
that there is no strong drop in the number of objects for the latest spectral
types, hence brown dwarfs may be as abundant as low-mass stars in this region.
Also, both kind of objects have a similar spatial distribution. We derive an
index $\alpha = 0.6 \pm 0.1$ of the mass function in this region of dispersed
star formation, in good agreement with the values obtained in other star
forming regions and young clusters. Some of the brown dwarfs have strong
H-alpha emission, suggesting mass accretion. For objects with published
infrared photometry, we find that strong H-alpha emission is related to a
mid-infrared excess, indicative of the existence of a circumstellar disk.


title:
On Sensitivity of Cherenkov Radiation to the Dynamics of High Energy
  Cosmic Ray Interactions

abstract:
  A simulation study of the effects resulting from creation of quark--gluon
plasma in high energy collisions of cosmic iron nuclei with the air has been
carried out. The Cherenkov light emission has been found to reveal some
features of the dynamics of high energy hadronic interactions.


title:
Predictions of mixed non-Gaussian cosmological density fields for the
  cosmic microwave background radiation

abstract:
  We present simulations of the Cosmic Microwave Background Radiation (CMBR)
power spectrum for a class of mixed, non-Gaussian, primordial random fields. We
assume a skew positive mixed model with adiabatic inflation perturbations plus
additional isocurvature perturbations possibly produced by topological defects.
The joint probability distribution used in this context is a weighted
combination of Gaussian and non-Gaussian random fields, such as: P(delta) =
(1-alpha)f_{1}(delta) + alpha*f_{2}(delta), where f_{1}(delta) is a Gaussian
distribution, f_{2}(delta) is a non-Gaussian general distribution, and alpha is
a scale dependent mixture parameter. Results from simulations of CMBR
temperature and polarisation power spectra show a distinct signature for very
small deviations (~ 0.1%) from a pure Gaussian field. We discuss the main
properties of such mixed models as well, their predictions and suggestions on
how to apply them to small scale CMBR observations. A reduced chi^2 test shows
that the contribution of an isocurvature fluctuation field is not ruled out in
actual CMB observations, even in WMAP first-year sky map.


title: Dust emission in early-type galaxies: The mid-infrared view

abstract:
  We present mid-infrared (MIR) maps for a sample of 18 early-type galaxies
observed at 4.5, 6.7 and 15 microns with the ISOCAM instrument on board the ISO
satellite with a 6'' spatial resolution. We model the Spectral Energy
Distribution (SED) of these galaxies using the stellar evolutionary synthesis
model PEGASE and we derive the MIR excess over the stellar component. We then
explore the nature of this excess in terms of dust and Polycyclic Aromatic
Hydrocarbon molecules (PAHs). We find that out of 18 galaxies, 10 show excess
at 6.7 microns (due to the presence of PAH features) and 14 show excess at 15
microns (due to the presence of warm dust). In two galaxies, where a more
complete wavelength coverage exists, an excess around 9.7 microns is seen
(presumably due to silicate dust emission), while two other galaxies are
totally devoid of dust. We also examine the morphology of the galaxies in these
wavelengths by plotting the azimuthally averaged radial profiles as well as the
MIR color profiles. We find that for the majority of the galaxies the 4.5
micron emission is well described by a de Vaucouleurs profile. The 6.7 and 15
micron emission is smoothly distributed throughout the galaxy while only a few
galaxies show MIR emission which is more concentrated close to the center. Two
dwarf galaxies in our sample show patchy distributions of the MIR emission
while two other galaxies show edge-on disks. With color-color diagrams we
delineate the regions occupied by late-type and early-type galaxies. Finally we
show that the MIR excess found in strong radio galaxies like NGC 4486 (M87) can
be explained by synchrotron emission.


title: CERN Axion Solar Telescope as a probe of large extra dimensions

abstract:
  We explore the potential of the CERN Axion Solar Telescope (CAST) for testing
the presence of large extra dimensions. The CAST experiment has originally been
proposed to search for solar axions with a sensitivity supposed to provide a
limit on the axion-photon coupling g_{a\gamma\gamma}<5x10^{-11} GeV^{-1} or
even lower. The expected bound on the coupling constant is by a factor of ten
more stringent than the current experimental results. This bound extends for
the first time beyond the limit dictated by astrophysical considerations. As a
tuning experiment planning to explore the axion mass region up to about 1 eV,
CAST would also be sensitive to the existence of Kaluza-Klein massive states.
Therefore, the detection of X-rays at least at two pressures may be the
signature of large extra dimensions. From this requirement we find that CAST
may test (two) large extra dimensions with a (common) compactification radius R
down to around 250 nm if m_{PQ}<1/(2R), and down to around 370 nm if
1/(2R)<m_{PQ}, where m_{PQ} is the Peccei-Quinn mass.


title: Photo-Ionization Induced Rapid Grain Growth in Novae

abstract:
  An elementary model is developed for grain growth during the expansion stage
of nova ejecta. Rather than suppressing grain formation, we argue that
agglomeration of atoms by dust nuclei proceeds kinetically through induced
dipole reactions in a partially ionized medium. Ionization of a cluster
increases once the ejecta become transparent in the ultraviolet which triggers
runaway grain growth. This mechanism may also be important in other
dust-forming hot stars such as Luminous Blue Variables and Wolf-Rayet systems.


title: Active star-forming galaxies in pairs in the 2dF

abstract:
  We explore the close environment of active star-forming galaxies (ASF) in the
2dF. We find ASF galaxies to be the most likely population to inhabit extremely
close pairs located in low density regions. In addition, we find that ASF
galaxies in these pairs are almost entirely concentrated in the -20 < M_B < -19
magnitude range.


title:
Evidence for Black Hole Spin in GX 339-4: XMM-Newton EPIC-pn and RXTE
  Spectroscopy of the Very High State

abstract:
  We have analyzed spectra of the Galactic black hole GX 339-4 obtained through
simultaneous 76 ksec XMM-Newton/EPIC-pn and 10 ksec RXTE observations during a
bright phase of its 2002-2003 outburst. An extremely skewed, relativistic Fe
K-alpha emission line and ionized disk reflection spectrum are revealed in
these spectra. Self-consistent models for the Fe K-alpha emission line profile
and disk reflection spectrum rule-out an inner disk radius compatible with a
Schwarzschild black hole at more than the 8 sigma level of confidence. The
best-fit inner disk radius of 2-3 r_g suggests that GX 339-4 harbors a black
hole with a ~ 0.8-0.9 (where r_g = GM/c^2 and a=cJ/GM^2, and assuming that
reflection in the plunging region is relatively small). This confirms
indications for black hole spin based on a Chandra spectrum obtained later in
the outburst. The emission line and reflection spectrum also rule-out a
standard power-law disk emissivity in GX 339-4; a broken power-law form with
enhanced emissivity inside ~6 r_{g} gives improved fits at more than the 8
sigma level of confidence. The extreme red wing of the line and steep
emissivity require a centrally--concentrated source of hard X-rays which can
strongly illuminate the inner disk. Hard X-ray emission from the base of a jet
- enhanced by gravitational light bending effects - could create the
concentrated hard X-ray emission; this process may be related to magnetic
connections between the black hole and the inner disk. We discuss these results
within the context of recent results from analyses of XTE J1650-500 and
MCG-6-30-15, and models for the inner accretion flow environment around black
holes.


title: X-ray Pulsars in the Small Magellanic Cloud

abstract:
  XMM-Newton archival data for the Small Magellanic Cloud have been examined
for the presence of previously undetected X-ray pulsars. One such pulsar, with
a period of 202 s, is detected. Its position is consistent with an early B star
in the SMC and we identify it as a high mass X-ray binary (HMXB). In the course
of this study we determined the pulse period of the possible AXP CXOU
J010043.1-721134 to be 8.0 s, correcting an earlier report (Lamb et al 2002b)
of a 5.4 s period for this object. Pulse profiles and spectra for each of these
objects are presented as well as for a recently discovered (Haberl & Pietsch
2004) 263 s X-ray pulsar. Properties of an ensemble of 24 optically identified
HMXB pulsars from the SMC are investigated. The locations of the pulsars and an
additional 22 X-ray pulsars not yet identified as having high mass companions
are located predominately in the young (ages $\le 3 \times 10^{7}$ years) star
forming regions of the SMC as expected on the basis of binary evolution models.
We find no significant difference between the distribution of spin periods for
the HMXB pulsars of the SMC compared with that of the Milky Way. For those HMXB
pulsars which have Be companions we note an inverse correlation between spin
period and maximum X-ray flux density. (This anti-correlation has been
previously noted for all X-ray binary pulsars by Stella, White & Rosner 1986).
The anti-correlation for the Be binaries may be a reflection of the fact that
the spin periods and orbital periods of Be HMXBs are correlated. We note a
similar correlation between X-ray luminosity and spin period for the Be HMXB
pulsars of the Milky Way and speculate that exploitation of the correlation
could serve as a distance indicator.


title: The Phoenix Deep Survey: Evolution of Star Forming Galaxies

abstract:
  The Phoenix Deep Survey (PDS) is a multiwavelength survey based on deep 1.4
GHz radio observations used to identify a large sample of star forming galaxies
to z=1. Photometric redshifts are estimated for the optical counterparts to the
radio-detected galaxies, and their uncertainties quantified by comparison with
spectroscopic redshift measurements. The photometric redshift estimates and
associated best-fitting spectral energy distributions are used in a stacking
analysis exploring the mean radio properties of U-band selected galaxies.
Average flux densities of a few microJy are measured.


title:
The Galaxy-mass Correlation Function Measured from Weak Lensing in the
  SDSS

abstract:
  We present galaxy-galaxy lensing measurements over scales 0.025 to 10 Mpc/h
in the Sloan Digital Sky Survey. Using a flux-limited sample of 127,001 lens
galaxies with spectroscopic redshifts and mean luminosity <L> = L_* and
9,020,388 source galaxies with photometric redshifts, we invert the lensing
signal to obtain the galaxy-mass correlation function xi_{gm}. We find xi_{gm}
is consistent with a power-law, xi_{gm} = (r/r_0)^{-gamma}, with best-fit
parameters gamma = 1.79 +/- 0.06 and r_0 = (5.4+/-0.7)(0.27/Omega_m)^{1/gamma}
Mpc/h. At fixed separation, the ratio xi_{gg}/xi_{gm} = b/r where b is the bias
and r is the correlation coefficient. Comparing to the galaxy auto-correlation
function for a similarly selected sample of SDSS galaxies, we find that b/r is
approximately scale independent over scales 0.2-6.7 Mpc/h, with mean <b/r> =
(1.3+/-0.2)(Omega_m/0.27). We also find no scale dependence in b/r for a volume
limited sample of luminous galaxies (-23.0 < M_r < -21.5). The mean b/r for
this sample is <b/r>_{Vlim} = (2.0+/-0.7)(Omega_m/0.27). We split the lens
galaxy sample into subsets based on luminosity, color, spectral type, and
velocity dispersion, and see clear trends of the lensing signal with each of
these parameters. The amplitude and logarithmic slope of xi_{gm} increases with
galaxy luminosity. For high luminosities (L ~5 L_*), xi_{gm} deviates
significantly from a power law. These trends with luminosity also appear in the
subsample of red galaxies, which are more strongly clustered than blue
galaxies.


title:
Accretion and Outflow in the Substellar Domain: Magellan Spectroscopy of
  LS-RCrA 1

abstract:
  We present low-, medium-, and high-resolution optical spectra of LS-RCrA~1.
We confirm both pre-main sequence status and membership, through the detection
of lithium, presence of narrow potassium indicative of low gravity, and
measurement of radial velocity. The Halpha emission profile is very broad, with
a 10% full width of 316 km/s, implying the presence of ongoing accretion. Our
spectra also exhibit many forbidden emission lines indicative of mass outflow.
Using new 2MASS near-infrared photometry, no significant NIR excess is found.
Our optical veiling measurements yield a mass accretion rate of 10^-10 /
10^{-9} M(sun)/yr. Through comparison with the latest synthetic spectra, we
infer Teff~2700+-100K. Theoretical tracks imply an age of ~20 Myr (as derived
from luminosity) or ~8 Myr (Teff vs. gravity) for LS-RCrA~1. Therefore,
LS-RCrA~1 indeed appears sub-luminous relative to expectations for an R~CrA
member. By comparing its position on the H-R diagram with that of other
similarly accreting low-mass objects, we show that accretion-induced effects
are unlikely to account for its faintness. We suggest instead that LS-RCrA~1
posesses a nearly edge-on disk and its photosphere is seen predominantly in
scattered light, making it appear much fainter (and older) than it really is.
Finally, the surface gravity and Teff estimates, combined with the latest
evolutionary tracks, indicate a mass of ~0.07 or 0.035+-0.010 M(sun) (depending
on the Teff scale).


title: Magnetic Braking in Differentially Rotating, Relativistic Stars

abstract:
  We study the magnetic braking and viscous damping of differential rotation in
incompressible, uniform density stars in general relativity. Differentially
rotating stars can support significantly more mass in equilibrium than
nonrotating or uniformly rotating stars. The remnant of a binary neutron star
merger or supernova core collapse may produce such a "hypermassive" neutron
star. Although a hypermassive neutron star may be stable on a dynamical
timescale, magnetic braking and viscous damping of differential rotation will
ultimately alter the equilibrium structure, possibly leading to delayed
catastrophic collapse. Here we consider the slow-rotation, weak-magnetic field
limit in which E_rot << E_mag << W, where E_rot is the rotational kinetic
energy, E_mag is the magnetic energy, and W is the gravitational binding energy
of the star. We assume the system to be axisymmetric and solve the MHD
equations in both Newtonian gravitation and general relativity. Toroidal
magnetic fields are generated whenever the angular velocity varies along the
initial poloidal field lines. We find that the toroidal fields and angular
velocities oscillate independently along each poloidal field line, which
enables us to transform the original 2+1 equations into 1+1 form and solve them
along each field line independently. The incoherent oscillations on different
field lines stir up turbulent-like motion in tens of Alfven timescales ("phase
mixing"). In the presence of viscosity, the stars eventually are driven to
uniform rotation, with the energy contained in the initial differential
rotation going into heat. Our evolution calculations serve as qualitative
guides and benchmarks for future, more realistic MHD simulations in full 3+1
general relativity.


title: The Quest for Microwave Foreground X

abstract:
  The WMAP team has produced a foreground map that can account for most of the
low-frequency Galactic microwave emission in the WMAP maps, tentatively
interpreting it as synchrotron emission. Finkbeiner and collaborators have
challenged these conclusions, arguing that the WMAP team "synchrotron" template
is in fact not dominated by synchrotron radiation, but by some dust-related
Galactic emission process, perhaps spinning dust grains, making dramatically
different predictions for its behavior at lower frequencies. By
cross-correlating this "synchrotron" template with 10 and 15 GHz CMB
observations, we find that its spectrum turns over in a manner consistent with
spinning dust emission, falling about an order of magnitude below what the
synchrotron interpretation would predict.


title:
Evolution of the Colour--Radius Relation and the Morphology--Radius
  Relation in the SDSS Galaxy Clusters

abstract:
  We have investigated the redshift evolution of the
colour--cluster-centric-radius relation and the
morphology--cluster-centric-radius relation in three redshift bins,
  $0.02\leq z\leq 0.14$, $0.14< z\leq 0.20$, and $0.20< z\leq 0.30$ using a
homogeneous sample of 736 galaxy clusters selected from the Sloan
  Digital Sky Survey. Both the relations are well-defined in all the redshift
bins; the fraction of blue/late-type galaxies increases toward outside of
clusters.Blue/late-type galaxy fractions are found to decrease with decreasing
redshift at any cluster-centric radius. The trend is consistent with the
Butcher-Oemler effect and the morphological Butcher-Oemlereffect. In addition,
we find that colour (spectral) evolution is almost completed by $z\sim0.2$,
whereas morphological evolution continues to the present day. The colour-radius
relation is smooth inall the redshift bins, while the morphology--radius
relation has a break only in the highest redshift bin. It is also found
thatfractions of blue-late type galaxies decreases mostly between the highest
and the intermediate redshift bins, while fractions of red-late type galaxies
continuously decreases with decreasing redshift through all the redshift bins.
  These results are consistent with the interpretation that the timescale of
the colour (spectral) evolution is shorter than that of the morphological
evolution. It is suggested that red-late type galaxies in the middle of the
transformation are observed as passive spiral galaxies.


title: The faint end of the QSO luminosity function at z=3

abstract:
  We present the first measurement of the faint end of the QSO luminosity
function at z=3. The QSOs, which range from M_1450 = -21 to M_1450 = -27, were
discovered in 17 fields totaling 0.43 deg^2 using multicolor selection criteria
(the Lyman break technique) and spectroscopic followup. We find that the
faint-end slope of the luminosity function is beta_l=1.24 +/- 0.07, flatter
than the value of beta_l=1.64 +/- 0.18 measured at lower redshift. The
integrated rest 1450 A UV luminosity of z=3 QSOs is only 50% of most previous
estimates, and is only ~8% of that produced by Lyman break galaxies at the same
redshifts. Assuming that ionizing photons from faint QSOs are as successful in
escaping their host galaxies as bright QSOs, we estimate the total contribution
of QSOs to the ionizing flux J_912 at z=3, J_912=2.4*10^-22 ergs/s/cm^2/Hz.
This estimate, which we regard as an upper limit, remains consistent with rough
estimates of J_912 based on the Lyman-alpha forest "proximity effect."


title: The Environmental Effects on Galaxy Evolution Based on the SDSS Data

abstract:
  By constructing a large, uniform galaxy cluster catalog from the SDSS data,
we have found that cluster galaxies evolve both spectrally and morphologically.
By studying the morphology--cluster-centric-radius relation, we have found two
characteristic environments where galaxy morphologies change dramatically. We
found passive spiral galaxies in the infalling region of clusters. They are
likely to be a galaxy population in transition due to the cluster environment.
We also studied E+A galaxies, which have also been thought to be cluster
originated. We found that E+As live in all environments including the field
region.


title: The Morphology-Density Relation in the Sloan Digital Sky Survey

abstract:
  We have studied the morphology-density relation and
morphology--cluster-centric-radius relation using a volume limited sample
(0.05$<z<$0.1, $Mr^*<-$20.5) of the Sloan Digital Sky Survey (SDSS) data.
  We found there are two characteristic changes in both the morphology-density
and the morphology-radius relations, suggesting two different mechanisms are
responsible for the relations.
  In the sparsest regions (below 1 Mpc$^{-2}$ or outside of 1 virial radius),
both relations become less noticeable, suggesting the responsible physical
mechanisms for galaxy morphological change require denser environment.
  In the intermediate density regions (density between 1 and 6 Mpc$^{-2}$ or
virial radius between 0.3 and 1), intermediate-type fractions increase toward
denser regions, whereas late-disc fractions decrease.
  In the densest regions (above 6 Mpc$^{-2}$ or inside of 0.3 virial radius),
intermediate-type fractions decrease radically and early-type fractions
increase in turn. This is a contrasting result to that in intermediate regions
and it suggests that yet another mechanism is more responsible for the
morphological change in these regions.
  We also compared the morphology-density relation from the SDSS
(0.01$<z<$0.054) with that of the MORPHS data ($z\sim$0.5). Two relations lie
on top of each other, suggesting that the morphology-density relation was
already established at $z\sim$0.5 as is in the present universe.