title: Time variations in the deep underground muon flux measured by MACRO

abstract:
  More than 30 million of high-energy muons collected with the MACRO detector
at the underground Gran Sasso Laboratory have been used to search for flux
variations of different natures. Two kinds of studies were carried out: search
for periodic variations and for the occurrence of clusters of events. Different
analysis methods, including Lomb-Scargle spectral analysis and Scan Test
statistics have been applied to the data.


title:
Reconciling the ultra-high energy cosmic ray spectrum with Fermi shock
  acceleration

abstract:
  The energy spectrum of ultra-high energy cosmic rays (UHECR) is usually
calculated for sources with identical properties. Assuming that all sources can
accelerate UHECR protons to the same extremely high maximal energy E_max >
10^{20} eV and have the steeply falling injection spectrum 1/E^{2.7}, one can
reproduce the measured cosmic ray flux above E > 10^{18} eV. We show that
relaxing the assumption of identical sources and using a power-law distribution
of their maximal energy allows one to explain the observed UHECR spectrum with
the injection 1/E^2 predicted by Fermi shock acceleration.


title: A Soft X-ray Transient in the M31 Bulge

abstract:
  We have examined a probable soft X-ray transient source in the M31 bulge at
R.A.=0:42:41.814 +/- 0.08", Dec. = 41:16:35.86 +/- 0.07". On the three
occasions we observed the source, its spectrum was soft (kT_{in} ~1 keV). The
brightest detection of the source was 2004 July 17 with a 0.3-7 keV luminosity
of ~5 X 10^{37} erg/s. The only previous detection of the source was in 1979 by
the Einstein observatory. The multiple detections over 25 years suggest the
duty cycle of the source is in the range 0.02-0.06. Coordinated HST/ACS imaging
before, during, and after the outburst revealed no variable optical source
within the position errors of the X-ray source. The optical data place a firm
upper limit on the brightness of the counterpart of the X-ray outburst of
B>24.7, suggesting the binary has a period <5.2 days. The X-ray spectrum and
lack of bright stars at the source location indicate the source was a soft
transient event occurring in a low-mass X-ray binary, making this source a good
black hole candidate in M31.


title: Discovery of the short gamma-ray burst GRB 050709

abstract:
  Gamma-Ray Bursts (GRBs) fall into two classes: short-hard and long-soft
bursts. The latter are now known to have X-ray and optical afterglows, to occur
at cosmological distances in star-forming galaxies, and to be associated with
the explosion of massive stars. In contrast, the distance scale, the energy
scale, and the progenitors of short bursts have remained a mystery. Here we
report the discovery of a short-hard burst whose accurate localization has led
to follow-up observations that have identified the X-ray afterglow and (for the
first time) the optical afterglow of a short-hard burst. These, in turn, have
led to identification of the host galaxy of the burst as a late-type galaxy at
z=0.16 showing that at least some short-hard bursts occur at cosmological
distances in the outskirts of galaxies, and are likely to be due to the merging
of compact binaries.


title: Radio Bubbles in Clusters

abstract:
  We extend our earlier work on cluster cores with distinct radio bubbles,
adding more active bubbles, i.e. those with Ghz radio emission, to our sample,
and also investigating ``ghost bubbles,'' i.e. those without GHz radio
emission. We have determined k, which is the ratio of the total particle energy
to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on
the ages of the active bubbles confirm that the ratio of the energy factor, k,
to the volume filling factor, f lies within the range 1 < k/f < 1000. In the
assumption that there is pressure equilibrium between the radio-emitting plasma
and the surrounding thermal X-ray gas, none of the radio lobes has
equipartition between the relativistic particles and the magnetic field. A
Monte-Carlo simulation of the data led to the conclusion that there are not
enough bubbles present in the current sample to be able to determine the shape
of the population. An analysis of the ghost bubbles in our sample showed that
on the whole they have higher upper limits on k/f than the active bubbles,
especially when compared to those in the same cluster. A study of the Brightest
55 cluster sample shows that 17, possibly 20, clusters required some form of
heating as they have a short central cooling time, t_cool < 3 Gyr, and a large
central temperature drop, T_centre/T_outer< 1/2. Of these between 12 (70 per
cent) and 15 (75 per cent), contain bubbles. This indicates that the duty cycle
of bubbles is large in such clusters and that they can play a major role in the
heating process.


title:
X-ray flares following short gamma-ray bursts from shock heating of
  binary stellar companions

abstract:
  The discovery of long-lasting (~100 s) X-ray flares following short gamma-ray
bursts initially called into question whether they were truly classical
short-hard bursts. Opinion over the last few years has coalesced around the
view that the short-hard bursts arise from the merger of pairs of neutron
stars, or a neutron star merging with a stellar-mass black hole. The natural
timescales associated with these processes, however, essentially preclude an
X-ray flare lasting ~100 s. Here we show that an interaction between the GRB
outflow and a non-compact stellar companion at a distance of ~a light-minute
provides a natural explanation for the flares. In the model, the burst is
triggered by the collapse of a neutron star after accreting matter from the
companion. This is reminiscent of type Ia supernovae, where there is a wide
distribution of delay times between formation and explosion, leading to an
association with both star-forming galaxies and old ellipticals.


title: Long Term Variability of Cygnus X-1. IV. Spectral Evolution 1999-2004

abstract:
  (abbreviated abstract) We present the long term spectral evolution of the
Galactic black hole candidate Cygnus X-1 in the X-rays and at 15GHz using ~200
pointed observations taken between early 1999 and late 2004 with RXTE and the
Ryle radio telescope. The X-ray spectra are remarkably well described by a
simple broken power law spectrum with an exponential cutoff. Physically
motivated Comptonization models, e.g., compTT or eqpair, can reproduce this
simplicity. Broken power law models reveal a significant linear correlation
between the photon index of the lower energy power law and the hardening of the
power law at approximately 10keV. Comptonization models show that the
bolometric flux of a soft excess (e.g., disk component) is strongly correlated
with the compactness ratio of the Comptonizing medium. We also find that the
fraction of the time spent in low radio emission/soft X-ray spectral states has
increased from ~10% in 1996-2000 to ~34% since early 2000. Radio flares
typically occur during state transitions and failed state transitions. There is
also a strong correlation between the 10-50keV X-ray flux and the radio
luminosity of the source. We demonstrate that rather than there being
distinctly separated states, in contrast to the timing properties the spectrum
of Cyg X-1 shows variations between extremes of properties, with clear cut
examples of spectra at every intermediate point in the observed spectral
correlations.


title: Dark Energy Studies: Challenges to Computational Cosmology

abstract:
  The ability to test the nature of dark mass-energy components in the universe
through large-scale structure studies hinges on accurate predictions of sky
survey expectations within a given world model. Numerical simulations predict
key survey signatures with varying degrees of confidence, limited mainly by the
complex astrophysics of galaxy formation. As surveys grow in size and scale,
systematic uncertainties in theoretical modeling can become dominant. Dark
energy studies will challenge the computational cosmology community to
critically assess current techniques, develop new approaches to maximize
accuracy, and establish new tools and practices to efficiently employ globally
networked computing resources.


title:
Constraining Dark Energy with the Dark Energy Survey: Theoretical
  Challenges

abstract:
  The Dark Energy Survey (DES) will use a new imaging camera on the Blanco 4-m
telescope at CTIO to image 5000 square degrees of sky in the South Galactic Cap
in four optical bands, and to carry out repeat imaging over a smaller area to
identify and measure lightcurves of Type Ia supernovae. The main imaging area
overlaps the planned Sunyaev-Zel'dovich survey of the South Pole Telescope. The
idea behind DES is to use four distinct and largely independent methods to
probe the properties of dark energy: baryon oscillations of the power spectrum,
abundance and spatial distribution of clusters, weak gravitational lensing, and
Type Ia supernovae. This white paper outlines, in broad terms, some of the
theoretical issues associated with the first three of these probes (the issues
for supernovae are mostly different in character), and with the general task of
characterizing dark energy and distinguishing it from alternative explanations
for cosmic acceleration. A companion white paper discusses the kind of
numerical simulations and other theoretical tools that will be needed to
address the these issues and to create mock catalogs that allow end-to-end
tests of analysis procedures. Although we have been thinking about these
problems in the specific context of DES, many of them are also relevant to
other planned dark energy studies.


title: Dark Energy: The Observational Challenge

abstract:
  Nearly all proposed tests for the nature of dark energy measure some
combination of four fundamental observables: the Hubble parameter H(z), the
distance-redshift relation d(z), the age-redshift relation t(z), or the linear
growth factor D_1(z). I discuss the sensitivity of these observables to the
value and redshift history of the equation of state parameter w, emphasizing
where these different observables are and are not complementary. Demonstrating
time-variability of w is difficult in most cases because dark energy is
dynamically insignificant at high redshift. Time-variability in which dark
energy tracks the matter density at high redshift and changes to a cosmological
constant at low redshift is {\it relatively} easy to detect. However, even a
sharp transition of this sort at z_c=1 produces only percent-level differences
in d(z) or D_1(z) over the redshift range 0.4 < z < 1.8$, relative to the
closest constant-w model. Estimates of D_1(z) or H(z) at higher redshift,
potentially achievable with the Ly-alpha forest, galaxy redshift surveys, and
the CMB power spectrum, can add substantial leverage on such models, given
precise distance constraints at z < 2. The most promising routes to obtaining
sub-percent precision on dark energy observables are space-based studies of
Type Ia supernovae, which measure d(z) directly, and of weak gravitational
lensing, which is sensitive to d(z), D_1(z), and H(z).


title: Mapping the Large Scale Structure of the Universe

abstract:
  In a large scale view of the universe, galaxies are the basic unit of
structure. A typical bright galaxy may contain 100 billion stars and span tens
of thousands of light years, but the empty expanses between the galaxies are
much larger still. Galaxies are not randomly distributed in space, but instead
reside in groups and clusters, which are themselves arranged in an intricate
lattice of filaments and walls, threaded by tunnels and pocked with bubbles.
Two ambitious new surveys, the Two-Degree Field Galaxy Redshift Survey (2dFGRS)
and the Sloan Digital Sky Survey (SDSS), have mapped the three-dimensional
distribution of galaxies over an unprecedented range of scales. Astronomers are
using these maps to learn about conditions in the early universe, the matter
and energy contents of the cosmos, and the physics of galaxy formation.


title: On the relation between Hot-Jupiters and the Roche Limit

abstract:
  Many of the known extrasolar planets are ``hot Jupiters,'' giant planets with
orbital periods of just a few days. We use the observed distribution of hot
Jupiters to constrain the location of the ``inner edge'' and planet migration
theory. If we assume the location of the inner edge is proportional to the
Roche limit, then we find that this edge is located near twice the Roche limit,
as expected if the planets were circularized from a highly eccentric orbit. If
confirmed, this result would place significant limits on migration via slow
inspiral. However, if we relax our assumption for the slope of the inner edge,
then the current sample of hot Jupiters is not sufficient to provide a precise
constraint on both the location and power law index of the inner edge.


title: On the dynamics of the ABDoradus system

abstract:
  We present an astrometric analysis of the binary systems ABDorA /ABDorC and
ABDorBa / ABDorBb. These two systems of well-known late-type stars are
gravitationally associated and they constitute the quadruple ABDoradus system.
  From the astrometric data available at different wavelengths, we report: (i)
a determination of the orbit of ABDorC, the very low mass companion to ABDorA,
which confirms the mass estimate of 0.090Msun reported in previous works; (ii)
a measurement of the parallax of ABDorBa, which unambiguously confirms the
long-suspected physical association between this star and ABDorA; and (iii)
evidence of orbital motion of ABDorBa around ABDorA, which places an upper
bound of 0.4Msun on the mass of the pair ABDorBa / ABDorBb (50% probability).
Further astrometric monitoring of the system at all possible wavelengths would
determine with extraordinary precision the dynamical mass of its four
components.


title: The origin of planetary impactors in the inner solar system

abstract:
  New insights into the history of the inner solar system are derived from the
impact cratering record of the Moon, Mars, Venus and Mercury, and from the size
distributions of asteroid populations. Old craters from a unique period of
heavy bombardment that ended $\sim$3.8 billion years ago were made by asteroids
that were dynamically ejected from the main asteroid belt, possibly due to the
orbital migration of the giant planets. The impactors of the past $\sim$3.8
billion years have a size distribution quite different from the main belt
asteroids, but very similar to the population of near-Earth asteroids.


title: The Elongations and Supersonic Motions of Molecular Clouds

abstract:
  New 13CO data from the BU-FCRAO Milky Way Galactic Ring Survey (GRS) are
analyzed to understand the shape and internal motions of molecular clouds. For
a sample of more than five hundred molecular clouds, we find that they are
preferentially elongated along the Galactic plane. On the other hand, their
spin axes are randomly oriented. We therefore conclude that the elongation is
not supported by internal spin but by internal velocity anisotropy. It has been
known that some driving mechanisms are necessary to sustain the supersonic
velocity dispersion within molecular clouds. The mechanism for generating the
velocity dispersion must also account for the preferred elongation. This
excludes some driving mechanisms, such as stellar winds and supernovae, because
they do not produce the systemic elongation along the Galactic plane. Driving
energy is more likely to come from large scale motions, such as the Galactic
rotation.


title:
Bolocam Survey for 1.1 mm Dust Continuum Emission in the c2d Legacy
  Clouds. I. Perseus

abstract:
  We have completed a 1.1 mm continuum survey of 7.5 sq deg of the Perseus
Molecular Cloud using Bolocam at the Caltech Submillimeter Observatory. This
represents the largest millimeter or submillimeter continuum map of Perseus to
date. Our map covers more than 30,000 31" (FWHM) resolution elements to a 1
sigma RMS of 15 mJy/beam. We detect a total of 122 cores above a 5 sigma point
source mass detection limit of 0.18 M_sun, assuming a dust temperature of 10 K,
60 of which are new millimeter or submillimeter detections. The 1.1 mm mass
function is consistent with a broken power law of slope -1.3 (0.5 M_sun<M<2.5
M_sun) and -2.6 (M>2.5 M_sun), similar to the local initial mass function
slope. No more than 5% of the total cloud mass is contained in discrete 1.1 mm
cores, which account for a total mass of 285 M_sun. We suggest an extinction
threshold for millimeter cores of Av~5 mag, based on our calculation of the
probability of finding a 1.1 mm core as a function of Av. Much of the cloud is
devoid of compact millimeter emission; despite the significantly greater area
covered compared to previous surveys, only 5-10 of the newly identified sources
lie outside previously observed areas. The two-point correlation function
confirms that dense cores in the cloud are highly structured, with significant
clustering on scales as large as 2e5 AU. These 1.1 mm results, especially when
combined with recently acquired c2d Spitzer Legacy data, will provide a census
of dense cores and protostars in Perseus and improve our understanding of the
earliest stages of star formation in molecular clouds.


title:
The gravitational wave "probability event horizon" for double neutron
  star mergers

abstract:
  Gravitational waves generated by the final merger of double neutron star
(DNS) binary systems are a key target for the gravitational wave (GW)
interferometric detectors, such as LIGO, and the next generation detectors,
Advanced LIGO. The cumulative GW signal from DNS mergers in interferometric
data will manifest as "geometrical noise": a non-continuous stochastic
background with a unique statistical signature dominated by the spatial and
temporal distribution of the sources. Because geometrical noise is highly
non-Gaussian, it could potentially be used to identify the presence of a
stochastic GW background from DNS mergers. We demonstrate this by fitting to a
simulated distribution of transients using a model for the DNS merger rate and
idealized Gaussian detector noise. Using the cosmological "probability event
horizon" concept and recent bounds for the Galactic DNS merger rate, we
calculate the evolution of the detectability of DNS mergers with observation
time. For Advanced LIGO sensitivities and a detection threshold assuming
optimal filtering, there is a 95% probability that a minimum of one DNS merger
signal will be detectable from the ensemble of events comprising the stochastic
background during 12-211 days of observation. For initial LIGO sensitivities,
we identify an interesting regime where there is a 95% probability that at
least one DNS merger with signal-to-noise ratio > unity will occur during 4-68
days of observation. We propose that there exists an intermediate detection
regime with pre-filtered signal-noise-ratio less than unity, where the DNS
merger rate is high enough that the geometrical signature could be identified
in interferometer data.


title: Chandra and XMM Observations of Type II Quasars from the SDSS

abstract:
  We are carrying out sensitive X-ray observations with Chandra and XMM of type
II quasars selected from the Sloan Digital Sky Survey based on their optical
emission line properties. We present observations of four objects at redshifts
0.4 < z < 0.8 and an analysis of the archival data for four additional objects
in the same redshift range. Six of the eight were detected in X-rays; five of
them have sufficient signal to derive spectral information. All of the detected
sources have intrinsic luminosities L(2-10 keV) > 5 x 10^43 erg s^-1. The five
with sufficient counts for spectral fitting show evidence for significant
absorption (N_H >~ a few x 10^22 cm^-2). At least three of the objects likely
have N_H > 10^23 cm^-2; some may be Compton-thick (N_H > 10^{24} cm^-2). In the
five objects for which we could fit spectra, the slopes tend to be
significantly flatter than is typically observed in AGN; it is possible that
this is due either to reprocessing of the nuclear emission or to a line of
sight that passes through patchy absorption.


title: Why the observed black hole candidates do not show spin pulsation

abstract:
  It is shown here that the so-called spinning Black Hole Candidates (BHCs)
cannot be Black Holes (BHs) at all and, on the other hand, must be spinning hot
Eternally Collapsing Objects (ECOs). The question would then arise why the
spinning BHCs do not reveal their spin pulsation unlike the spinning cold
Neutron Stars (NSs). Even for magnetized NSs with ``hard surfaces'', there may
be no observed spin pulsation if the dipole axis and spin direction are exactly
same. However, spinning ECOs do not show spin pulsation because their surface
gravitational red shift is extremely high, z >> 1 and could be in the range of
10^{7-8} for stellar mass range. In contrast NSs have z ~ 0.1 -0.3. The time
profile of periodic signals generated on the surface of a spinning MECO get
extremely distorted due to extreme general relativistic frame dragging effect
as they traverse through extremely steep gravitational field. However, if any
radiation would be formed in the ECO magnetosphere sufficiently away from the
surface like in the pulsar ``outer slots''(which may happen for isolated
spinning ECOs), it might be a pulsed one.


title: Properties of Planetary Caustics in Gravitational Microlensing

abstract:
  Although some of the properties of the caustics in planetary microlensing
have been known, our understanding of them is mostly from scattered information
based on numerical approaches. In this paper, we conduct a comprehensive and
analytic analysis of the properties of the planetary caustics, which are one of
the two sets of caustics in planetary microlensing, those located away from the
central star. Under the perturbative approximation, we derive analytic
expressions for the location, size, and shape of the planetary caustic as a
function of the star-planet separation and the planet/star mass ratio. Based on
these expressions combined with those for the central caustic, which is the
other set of caustics located close to the central star, we compare the
similarities and differences between the planetary and central caustics. We
also present the expressions for the size ratio between the two types of
caustics and for the condition of the merging of the two types of caustics.
These analytic expressions will be useful in understanding the dependence of
the planetary lensing behavior on the planet parameters and thus in
interpreting the planetary lensing signals


title: Dark energy in hybrid inflation

abstract:
  The situation that a scalar field provides the source of the accelerated
expansion of the universe while rolling down its potential is common in both
the simple models of the primordial inflation and the quintessence-based dark
energy models. Motivated by this point, we address the possibility of causing
the current acceleration via the primordial inflation using a simple model
based on hybrid inflation. We trigger the onset of the motion of the
quintessence field via the transition field, and find that the fate of the
universe depends on the true vacuum energy determined by choosing the
parameters. We also briefly discuss the variation of the equation of state and
the possible implementation of our scenario in supersymmetric theories.


title: Testing for w<-1 in the Solar System

abstract:
  In scalar-tensor theories of gravity, the equation of state of dark energy,
w, can become smaller than -1 without violating any energy condition. The value
of w today is tied to the level of deviations from general relativity which, in
turn, is constrained by solar system and pulsars timing experiments. The
conditions on these local constraints for w to be significantly less than -1
are established. It is demonstrated that this requires to consider theories
that differ from the Jordan-Fierz-Brans-Dicke theory and that involve either a
steep coupling function or a steep potential. It is also shown how a robust
measurement of w could probe scalar-tensor theories.


title:
XMM-Newton observations of the sigma Ori cluster. II. Spatial and
  spectral analysis of the full EPIC field

abstract:
  We present the results of an XMM-Newton observation of the young (~2-4 Myr)
cluster around the hot star sigma Orionis. In a previous paper we presented the
analysis of the RGS spectrum of the central hot star; here we discuss the
results of the analysis of the full EPIC field. We have detected 175 X-ray
sources, 88 of which have been identified with cluster members, including very
low-mass stars down to the substellar limit. We detected eleven new possible
candidate members from the 2MASS catalogue. We find that late-type stars have a
median log L_X/L_bol ~ -3.3, i.e. very close to the saturation limit. We
detected significant variability in ~40% of late-type members or candidates,
including 10 flaring sources; rotational modulation is detected in one K-type
star and possibly in another 3 or 4 stars. Spectral analysis of the brightest
sources shows typical quiescent temperatures in the range T_1 ~ 0.3-0.8 keV and
T_2 ~ 1-3 keV, with subsolar abundances Z ~ 0.1-0.3 Z_sun, similar to what is
found in other star-forming regions and associations. We find no significant
difference in the spectral properties of classical and weak-lined T Tauri
stars, although classical T Tauri stars tend to be less X-ray luminous than
weak-lined T Tauri stars.


title:
Large scale correlations in galaxy clustering from the Two degree Field
  Galaxy Redshift Survey

abstract:
  We study galaxy correlations from samples extracted from the 2dFGRS final
release. Statistical properties are characterized by studying the nearest
neighbor probability density, the conditional density and the reduced two-point
correlation function. The result is that the conditional density has a
power-law behavior in redshift space described by an exponent \gamma=0.8 \pm
0.2 in the interval from about 1 Mpc/h, the average distance between nearest
galaxies, up to about 40 Mpc/h, corresponding to radius of the largest sphere
contained in the samples. These results are consistent with other studies of
the conditional density and are useful to clarify the subtle role of
finite-size effects on the determination of the two-point correlation function
in redshift and real space


title: A multi-flow model for microquasars

abstract:
  We present a new picture for the central regions of Black Hole X-ray
Binaries. In our view, these central regions have a multi-flow configuration
which consists in (1) an outer standard accretion disc down to a transition
radius r_J, (2) an inner magnetized accretion disc below r_J driving (3) a non
relativistic self-collimated electron-proton jet surrounding, when adequate
conditions for pair creation are met, (4) a ultra relativistic
electron-positron beam. This accretion-ejection paradigm provides a simple
explanation to the canonical spectral states, from radio to X/gamma-rays, by
varying the transition radius r_J and disc accretion rate independently. Large
values of r_J and low accretion rate correspond to Quiescent and Hard states.
These states are characterized by the presence of a steady electron-proton MHD
jet emitted by the disc below r_J. The hard X-ray component is expect to form
at the jet basis. When r_J becomes smaller than the marginally stable orbit
r_i, the whole disc resembles a standard accretion disc with no jet,
characteristic of the Soft state. Intermediate states correspond to situations
where r_J ~ r_i. At large accretion rate, an unsteady pair cascade process is
triggered within the jet axis, giving birth to flares and ejection of
relativistic pair blobs. This would correspond to the luminous intermediate
state, with its associated superluminal motions.


title:
How particle collisions increase the rate of accretion from the
  cosmological background onto primordial black holes in braneworld cosmology

abstract:
  It is shown that, contrary to the widespread opinion, particle collisions
considerably increase accretion rate from the cosmological background onto 5D
primordial black holes formed during the high-energy phase of the
Randall-Sundrum Type II braneworld scenario. Increase of accretion rate leads
to much tighter constraints on initial primordial black hole mass fraction
imposed by the critical density limit and measurements of high-energy diffuse
photon background and antiproton excess.


title:
New soft gamma-ray bursts in the BATSE records and spectral properties
  of X-ray rich bursts

abstract:
  A population of X-ray dominated gamma-ray bursts (GRBs) observed by Ginga,
BeppoSax and Hete-2 should be represented in the BATSE data as presumably soft
bursts. We have performed a search for soft GRBs in the BATSE records in the
25--100 keV energy band. A softness of a burst spectrum can be a reason why it
has been missed by the on-board procedure and previous searches for untriggered
GRBs tuned to 50--300 keV range. We have found a surprisingly small number
(~20/yr down to 0.1 ph cm$^{-2}$ s$^{-1}$) of soft GRBs where the count rate is
dominated by 25--50 keV energy channel. This fact as well as the analysis of
HETE-2 and common BeppoSAX/BATSE GRBs indicates that the majority of GRBs with
a low Epeak has a relatively hard tail with the high-energy power-law photon
index >-3. An exponential cutoff in GRB spectra below 20 keV may be a
distinguishing feature separating non-GRB events.


title:
Comparison of dynamical model atmospheres of Mira variables with
  mid-infrared interferometric and spectroscopic observations

abstract:
  We present a comparison of dynamical model atmospheres with mid-infrared (~11
micron) interferometric and spectroscopic observations of the Mira variable o
Cet. The dynamical model atmospheres of Mira variables pulsating in the
fundamental mode can fairly explain, without assuming ad-hoc components, the
seemingly contradictory mid-infrared spectroscopic and interferometric
observations of o Cet: the 11 micron sizes measured in the bandpass without any
salient spectral features are about twice as large as those measured in the
near-infrared. Our calculations of synthetic spectra show that the strong
absorption due to a number of optically thick H2O lines is filled in by the
emission of these H2O lines originating in the geometrically extended layers,
providing a possible physical explanation for the picture proposed by Ohnaka
(2004a) based on a semi-empirical modeling. This filling-in effect results in
rather featureless, continuum-like spectra in rough agreement with the observed
high-resolution 11 micron spectra, although the models still predict the H2O
lines to be more pronounced than the observations. The inverse P-Cyg profiles
of some strong H2O lines observed in the 11 micron spectra can also be
reasonably reproduced by our dynamical model atmospheres. The presence of the
extended H2O layers manifests itself as mid-infrared angular diameters much
larger than the continuum diameter. The 11 micron uniform-disk diameters
predicted by our dynamical model atmospheres are in fair agreement with those
observed with the Infrared Spatial Interferometer (ISI), but still somewhat
smaller than the observed diameters. We discuss possible reasons for this
discrepancy and problems with the current dynamical model atmospheres of Mira
variables.


title: The transmission spectrum of Earth-size transiting planets

abstract:
  A variety of terrestrial planets with different physical parameters and
exotic atmospheres might plausibly exist outside our Solar System, waiting to
be detected by the next generation of space-exploration missions. Some of these
planets might transit their parent star. We present here the first study of
atmospheric signatures of transiting Earth-size exoplanets. We focus on a
limited number of significant examples, for which we discuss the detectability
of some of the possible molecules present in their atmospheres, such as water,
carbon dioxide, ozone or molecular oxygen. To this purpose, we developed a
model to simulate transmission spectra of Earth-size exoplanets from the
ultraviolet to the near infrared. According to our calculations, the signatures
of planetary atmospheres represent an absorption of a few parts-per-million
(ppm) in the stellar flux. The atmospheres of a few Earth-like planets can be
detected with a 30-40m telescope. The detection of the extensive atmospheres of
tens of small satellites of giant exoplanets and hundreds of hypothetical
ocean-planets can be achieved with 20-30m and 10-20m instruments, respectively,
provided all these planets are frequent and they are efficiently surveyed. We
also found that planets around K stars are favored, mainly because these stars
are more numerous and they are smaller compared to G or F stars. While not
addressed in this study, limitations might come from the stellar photometric
micro-variability.


title: Dust obscuration of DLA galaxies

abstract:
  We show that the extinction of quasar absorbers increases exponentially with
the logarithmic column density of any volatile metal (e.g. zinc), with a
charateristic turning point above which the quasars are severely dimmed. We
derive the relation between extinction, HI column density, metallicity and
fraction of iron in dust in Damped Lyman alpha (DLA) systems. We use this
relation to estimate the effect of dust obscuration on the statistical
distributions of N(HI) and metallicity measured in magnitude-limited surveys of
DLAs. In the redshift range where the measurements of zinc column densities
have sufficient statistics (1.8 </= z </= 3) we find that the obscuration bias
affects the shapes of the observed distributions. The metallicity distribution
is particularly affected by the bias, which hampers the detection of DLA
galaxies with near solar metallicity. Our results perfectly reproduce, without
tuning the dust parameters, the DLA observational threshold log N(ZnII) </~
13.15 found by Boisse' and collaborators in 1998, in terms of a rapid rise of
the obscuration. Our predictions of the effects of the bias on the statistics
of DLAs are consistent with observational results obtained from unbiased
surveys of radio-selected quasars.


title: Chandra observations of the globular cluster M54

abstract:
  We have carried out a Chandra observation of the globular cluster M54. We
detected 7 sources located within the half-mass radius of M54, at a flux limit
of 1.5x10^-15 erg/s/cm in the 0.3-8 keV energy band. The spatial distribution
and the colour/spectral properties of the 7 sources suggest that they are
likely to be cataclysmic variables or LMXBs in the globular cluster. M54 shows
the largest number of X-ray sources with luminosities greater than 10^32 ergs/s
compared to other globular clusters observed using Chandra and XMM-Newton. We
searched for a correlation between the number of sources above this luminosity
level with globular cluster parameters. We found evidence that the number of
sources peaks at a King concentration parameter c~1.7-1.9, with globular
clusters which are core-collapsed or have low-c values having a smaller number
of sources. We speculate on possible reasons for this.


title:
Methanol masers : Reliable tracers of the early stages of high-mass star
  formation

abstract:
  The GLIMPSE and MSX surveys have been used to examine the mid-infrared
properties of a statistically complete sample of 6.7 GHz methanol masers. The
GLIMPSE point sources associated with methanol masers are clearly distinguished
from the majority, typically having extremely red mid-infrared colors, similar
to those expected of low-mass class 0 young stellar objects. The intensity of
the GLIMPSE sources associated with methanol masers is typically 4 magnitudes
brighter at 8.0 micron than at 3.6 micron. Targeted searches towards GLIMPSE
point sources with [3.6]-[4.5] > 1.3 and an 8.0 micron magnitude less than 10
will detect more than 80% of class II methanol masers. Many of the methanol
masers are associated with sources within infrared dark clouds (IRDC) which are
believed to mark regions where high-mass star formation is in its very early
stages. The presence of class II methanol masers in a significant fraction of
IRDC suggests that high-mass star formation is common in these regions.
Different maser species are thought to trace different evolutionary phases of
the high-mass star formation process. Comparison of the properties of the
GLIMPSE sources associated with class II methanol masers and other maser
species shows interesting trends, consistent with class I methanol masers
tracing a generally earlier evolutionary phase and OH masers tracing a later
evolutionary phase.


title:
Internal kinematics and stellar populations of early-type galaxies in
  the Fornax cluster

abstract:
  We present a study of the internal kinematics and stellar populations of
early-type galaxies in the Fornax cluster based on integral-field spectroscopic
observations with Gemini South GMOS and VLT-VIMOS. Seven galaxies in a
luminosity range of -21.3 < M_B < -17.7 have been observed with these integral
field units (IFU). As first results, velocity and line strength maps are
presented for NGC 1427 and NGC 1419.


title: High-resolution proper motions in a sunspot penumbra

abstract:
  Local correlation tracking techniques are used to measure proper motions in a
series of high angular resolution (~0.1 arcsec) penumbra images. If these
motions trace true plasma motions, then we have detected converging flows that
arrange the plasma in long narrow filaments co-spatial with dark penumbral
filaments. Assuming that these flows are stationary, the vertical
stratification of the atmosphere and the conservation of mass suggest downflows
in the filaments of the order of 200 m/s. The association between downflows and
dark features may be a sign of convection, as it happens with the non-magnetic
granulation. Insufficient spatial resolution may explain why the estimated
vertical velocities are not fast enough to supply the radiative losses of
penumbrae.


title: The Fundamental Manifold of Spheroids

abstract:
  We present a unifying empirical description of the structural and kinematic
properties of all spheroids embedded in dark matter halos. We find that the
stellar spheroidal components of galaxy clusters, which we call cluster
spheroids (CSphs) and which are typically one hundred times the size of normal
elliptical galaxies, lie on a "fundamental plane" as tight as that defined by
ellipticals (rms in effective radius of ~0.07), but that has a different slope.
The slope, as measured by the coefficient of the log(sigma) term, declines
significantly and systematically between the fundamental planes of ellipticals,
brightest cluster galaxies (BCGs), and CSphs.We attribute this decline
primarily to a continuous change in M_e/L_e, the mass-to-light ratio within the
effective radius r_e, with spheroid scale. The magnitude of the slope change
requires that it arises principally from differences in the relative
distributions of luminous and dark matter, rather than from stellar population
differences such as in age and metallicity. By expressing the M_e/L_e term as a
function of sigma in the simple derivation of the fundamental plane and
requiring the behavior of that term to mimic the observed nonlinear
relationship between log(M_e/L_e) and log(sigma), we simultaneously fit a 2-D
manifold to the measured properties of dwarf ellipticals, ellipticals, BCGs,
and CSphs. The combined data have an rms scatter in log(r_e) of 0.114 (0.099
for the combination of Es, BCGs, and CSphs), which is modestly larger than each
fundamental plane has alone, but which includes the scatter introduced by
merging different studies done in different filters by different investigators.
This ``fundamental manifold'' fits the structural and kinematic properties of
spheroids that span a factor of 100 in sigma and 1000 in r_e. (ABRIDGED)


title: Forming supermassive black holes by accreting dark and baryon matter

abstract:
  Given a large-scale mixture of self-interacting dark matter (SIDM) particles
and baryon matter distributed in the early Universe, we advance here a
two-phase accretion scenario for forming supermassive black holes (SMBHs) with
masses around $\sim 10^9 M_{\odot}$ at high redshifts $z (\gsim 6)$. The first
phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi
accretion of mainly SIDM particles embedded with baryon matter onto seed black
holes (BHs) created at redshifts $z\lsim 30$ by the first generation of massive
Population III stars; this earlier phase rapidly gives birth to significantly
enlarged seed BH masses of $M_{\hbox{\tiny BH},t_1}\backsimeq 1.4\times 10^6\
M_\odot \sigma_0/(1\hbox{cm}^2\hbox{g}^{-1})(C_s/30\hbox{km s}^{-1})^4$ during
$z\sim 20-15$, where $\sigma_0$ is the cross section per unit mass of SIDM
particles and $C_s$ is the velocity dispersion in the SIDM halo referred to as
an effective "sound speed". The second phase of BH mass growth is envisaged to
proceed primarily via baryon accretion, eventually leading to SMBH masses of
$M_{\hbox{\tiny BH}}\sim 10^9 M_\odot$; such SMBHs may form either by $z\sim 6$
for a sustained accretion at the Eddington limit or later at lower $z$ for
sub-Eddington mean accretion rates. We intend to account for the reported
detections of a few SMBHs at early epochs, e.g., SDSS 1148+5251 and so forth,
without necessarily resorting to either super-Eddington baryon accretion or
very frequent BH merging processes. Only extremely massive dark SIDM halos
associated with rare peaks of density fluctuations in the early Universe may
harbour such early SMBHs or quasars. Observational consequences are discussed.


title: ESO Imaging Survey: Optical follow-up of 12 selected XMM-Newton fields

abstract:
  (Abridged) This paper presents the data recently released for the
XMM-Newton/WFI survey carried out as part of the ESO Imaging Survey (EIS)
project. The aim of this survey is to provide optical imaging follow-up data in
BVRI for identification of serendipitously detected X-ray sources in selected
XMM-Newton fields. In this paper, fully calibrated individual and stacked
images of 12 fields as well as science-grade catalogs for the 8 fields located
at high-galactic latitude are presented. The data covers an area of \sim 3
square degrees for each of the four passbands. The median limiting magnitudes
(AB system, 2" aperture, 5\sigma detection limit) are 25.20, 24.92, 24.66, and
24.39 mag for B-, V-, R-, and I-band, respectively. These survey products,
together with their logs, are available to the community for science
exploitation in conjunction with their X-ray counterparts. Preliminary results
from the X-ray/optical cross-correlation analysis show that about 61% of the
detected X-ray point sources in deep XMM-Newton exposures have at least one
optical counterpart within 2" radius down to R \simeq 25 mag, 50% of which are
so faint as to require VLT observations thereby meeting one of the top
requirements of the survey, namely to produce large samples for spectroscopic
follow-up with the VLT, whereas only 15% of the objects have counterparts down
to the DSS limiting magnitude.


title: Biosignatures from Earth-Like Planets Around M Dwarfs

abstract:
  Coupled one-dimensional photochemical-climate calculations have been
performed for hypothetical Earth-like planets around M dwarfs. Visible,
near-infrared and thermal-infrared synthetic spectra of these planets were
generated to determine which biosignature gases might be observed by a future,
space-based telescope. Our star sample included two observed active M dwarfs,
AD Leo and GJ 643, and three quiescent model stars. The spectral distribution
of these stars in the ultraviolet generates a different photochemistry on these
planets. As a result, the biogenic gases CH4, N2O, and CH3Cl have substantially
longer lifetimes and higher mixing ratios than on Earth, making them
potentially observable by space-based telescopes. On the active M-star planets,
an ozone layer similar to Earth's was developed that resulted in a
spectroscopic signature comparable to the terrestrial one. The simultaneous
detection of O2 (or O3) and a reduced gas in a planet's atmosphere has been
suggested as strong evidence for life. Planets circling M stars may be good
locations to search for such evidence.


title: The Effect of Pre-Main Sequence Stars on Star Cluster Dynamics

abstract:
  We investigate the effects of the addition of pre-main sequence evolution to
star cluster simulations. We allowed stars to follow pre-main sequence tracks
that begin at the deuterium burning birthline and end at the zero age main
sequence. We compared our simulations to ones in which the stars began their
lives at the zero age main sequence, and also investigated the effects of
particular choices for initial binary orbital parameters. We find that the
inclusion of the pre-main sequence phase results in a slightly higher core
concentration, lower binary fraction, and fewer hard binary systems. In
general, the global properties of star clusters remain almost unchanged, but
the properties of the binary star population in the cluster can be dramatically
modified by the correct treatment of the pre-main sequence stage.


title: Relativistic effects on the imaging by a rotating optical system

abstract:
  Context. High accuracy astrometric instruments like Gaia aiming at an
accuracy of 1 microarcsecond cannot be considered as point-like observers in
the framework of relativistic modelling of observable quantities.
  Aims. Special-relativistic effects on the imaging by a non-point-like
arbitrarily moving optical instrument are discussed.
  Methods. A special-relativistic reflection law for a mirror of arbitrary
shape and motion is derived in the limit of geometrical optics. The aberration
patterns are computed with ray tracing using a full pecial-relativistic model
for two simple rotating optical instrument.
  Results. It was found that the effect of special-relativistic reflection law
on the photocenters of aberration patterns of an optical system rotating with a
moderate angular velocity of $60 \arcsec/{\rm s}$ may be at the level of 1
microarcsecond if the system involves mirrors significantly inclined relative
to the optical axis.
  Conclusions. Special-relativistic optical modelling of the future astrometric
instrument is generally speaking indispensable if a level of a few
microarcseconds is envisaged.


title:
An Initial Look at the Far Infrared-Radio Correlation within Nearby
  Star-forming Galaxies using the Spitzer Space Telescope

abstract:
  (Abridged) We present an initial look at the far infrared-radio correlation
within the star-forming disks of four nearby, nearly face-on galaxies (NGC
2403, NGC 3031, NGC 5194, and NGC 6946). Using Spitzer MIPS imaging and WSRT
radio continuum data, observed as part of the Spitzer Infrared Nearby Galaxies
Survey (SINGS), we are able to probe variations in the logarithmic 24mu/22cm
(q_24) and 70mu/22cm (q_70) surface brightness ratios across each disk at
sub-kpc scales. We find general trends of decreasing q_24 and q_70 with
declining surface brightness and with increasing radius. The residual
dispersion around the trend of q_24 and q_70 versus surface brightness is
smaller than the residual dispersion around the trend of q_24 and q_70 versus
radius, on average by ~0.1 dex, indicating that the distribution of star
formation sites is more important in determining the infrared/radio disk
appearance than the exponential profiles of disks. We have also performed
preliminary phenomenological modeling of cosmic ray electron (CRe^-) diffusion
using an image-smearing technique, and find that smoothing the infrared maps
improves their correlation with the radio maps. Exponential kernels tend to
work better than Gaussian kernels which suggests that additional processes
besides simple random-walk diffusion in three dimensions must affect the
evolution of CRe^-s. The best fit smoothing kernels for the two less active
star-forming galaxies (NGC 2403 and NGC 3031) have much larger scale-lengths
than those of the more active star-forming galaxies (NGC 5194 and NGC 6946).
This difference may be due to the relative deficit of recent CRe^- injection
into the interstellar medium (ISM) for the galaxies having largely quiescent
disks.


title: Superlong GRBs

abstract:
  We searched for anomalously long GRBs (GRBs) in the archival records of the
Burst and Transient Sources Experiment (BATSE). Ten obvious superlong (>500 s)
GRBs with almost continuous emission episodes were found. Nine of these events
are known from the BATSE catalog, but five have no duration estimates; we found
one burst for the first time. We also detected events with emission episodes
separated by a long period of silence (up to 1000 s) with a total duration of
1000--2000 s. In the latter case, we cannot reach an unequivocal conclusion
about a common origin of the episodes due to the BATSE poor angular resolution.
However, for most of these pairs, the probability of a coincidence of
independent GRBs is much lower than unity, and the probability that all of
these are coincidences is 10E-8. All of the events have a hardness ratio (the
ratio of the count rates in different energy channels) typical of GRBs, and
their unique duration is unlikely to be related to their high redshifts.
Superlong bursts do not differ in their properties from typical long (>2 s)
GRBs. We estimated the fraction of superlong GRBs (>500 s) among the long GRBs
in the BATSE sample with fluxes up to 0.1 ph cm^{-2} s^{-1} to be between 0.3
and 0.5%, which is higher than the estimate based on the BATSE catalog.


title:
Multi-Dimensional Radiation/Hydrodynamic Simulations of Protoneutron
  Star Convection

abstract:
  Based on multi-dimensional, multi-group, flux-limited-diffusion hydrodynamic
simulations of core-collapse supernovae with the VULCAN/2D code, we study the
physical conditions within and in the vicinity of the nascent protoneutron star
(PNS). Our numerical study follows the evolution of the collapsing envelope of
the 11-Msun model of Woosley & Weaver, from ~200 ms before bounce to ~300ms
after bounce, on a spatial grid that switches from Cartesian at the PNS center
to spherical above a 10km radius.
  As has been shown previously, we do not see any large-scale overturn of the
inner PNS material. Convection, directly connected to the PNS, is found to
occur in two distinct regions: between 10 and 20km, coincident with the region
of negative lepton gradient, and exterior to the PNS above 50km. Separating
these two regions, an interface, with no sizable outward or inward motion, is
the site of gravity waves, emerging at ~200-300ms after core bounce, excited by
the convection in the outer convective zone.
  In the PNS, convection is always confined within the neutrinospheric radii
for all neutrino energies above just a few MeV. We find that such convective
motions do not appreciably enhance the nu_e neutrino luminosity, and that they
enhance the anti-nu_e and "nu_mu" luminosities modestly, by ~15% and ~30%,
respectively, during the first post-bounce 100--200ms. Moreover, we see no
evidence of doubly-diffusive instabilities in the PNS, expected to operate on
diffusion timescales of at least a second, much longer than the millisecond
timescale associated with PNS convection.
  PNS convection is thus found to be a secondary feature of the core-collapse
phenomenon, rather than a decisive ingredient for a successful explosion.


title: Neon Lights Up a Controversy: the Solar Ne/O Abundance

abstract:
  The standard solar model was so reliable that it could predict the existence
of the massive neutrino. Helioseismology measurements were so precise that they
could determine the depth of the convection zone. This agreement between theory
and observation was the envy of all astrophysics -- until recently when
sophisticated three-dimensional hydrodynamic calculations of the solar
atmosphere reduced the metal content by a factor of almost two. Antia & Basu
(2005) suggested that a higher value of the solar neon abundance, Ne/O = 0.52,
would resolve this controversy. Drake & Testa (2005) presented strong evidence
in favor of this idea from a sample of 21 Chandra stars with enhanced values of
the neon abundance, Ne/O = 0.41. In this paper, we have analyzed solar active
region spectra from the archive of the Flat Crystal Spectrometer on Solar
Maximum Mission, a NASA mission from the 1980s, as well as full-Sun spectra
from the pioneering days of X-ray astronomy in the 1960s. These data seem
consistent with the standard neon-to-oxygen abundance value, Ne/O = 0.15
(Grevesse & Sauval 1998). If these results prove to be correct, than the
enhanced-neon hypothesis will not resolve the current controversy.


title: PSF Anisotropy and Systematic Errors in Weak Lensing Surveys

abstract:
  Given the basic parameters of a cosmic shear weak lensing survey, how well
can systematic errors due to anisotropy in the point spread function (PSF) be
corrected? The largest source of error in this correction to date has been the
interpolation of the PSF to the locations of the galaxies. To address this
error, we separate the PSF patterns into components that recur in multiple
exposures/pointings and those that vary randomly between different exposures
(such as those due to the atmosphere). In an earlier study we developed a
principal component approach to correct the recurring PSF patterns (Jarvis and
Jain 2004). In this paper we show how randomly varying PSF patterns can also be
circumvented in the measurement of shear correlations. For the two-point
correlation function this is done by simply using pairs of galaxy shapes
measured in different exposures. Combining the two techniques allows us to
tackle generic combinations of PSF anisotropy patterns. The second goal of this
paper is to give a formalism for quantifying residual systematic errors due to
PSF patterns. We show how the main PSF corrections improve with increasing
survey area (and thus can stay below the reduced statistical errors), and we
identify the residual errors which do not scale with survey area. Our formalism
can be applied both to planned lensing surveys to optimize instrumental and
survey parameters and to actual lensing data to quantify residual errors.


title:
Multipole Models of Four-Image Gravitational Lenses with Anomalous Flux
  Ratios

abstract:
  Anomalous radio flux ratios in four-image gravitational lens systems can be
explained by adding a clumpy cold dark matter (CDM) component to the potential
of the lens galaxy. Evans & Witt (2003) recently suggested that smooth
multipole perturbations can provide a reasonable alternative to CDM
substructure in some but not all cases. We generalize their method in two ways
so as to determine whether multipole models can explain highly anomalous
systems. We carry the multipole expansion to higher order, and also include
external tidal shear as a free parameter. Fitting for the shear proves crucial
to finding a physical (positive-definite density) model. For B1422+231, working
to order k = 5 (and including shear) yields a model that is physical but
implausible. Going to higher order (k >~ 9) reduces global departures from
ellipticity at the cost of introducing small scale wiggles near the bright
images. These localized undulations are more pronounced in B2045+265, where k ~
17 multipoles are required to smooth out large scale deviations from elliptical
symmetry. Such modes surely cannot be taken at face value; they must indicate
that the models are trying to reproduce some other sort of structure. Our
formalism naturally finds models that fit the data exactly, but we use
B0712+472 to show that measurement uncertainties have little effect on our
results. Finally, we consider the system B1933+503, where two sources are
lensed by the same foreground galaxy. The additional constraints provided by
the images of the second source render the multipole model unphysical. We
conclude that external shear must be taken into account to obtain plausible
models, and that a purely smooth angular structure for the lens galaxy does not
provide a viable alternative to the prevailing CDM clump hypothesis.


title: Flattening Scientific CCD Imaging Data with a Dome Flat Field System

abstract:
  We describe the flattening of scientific CCD imaging data using a dome flat
field system. The system uses light emitting diodes (LEDs) to illuminate a
carefully constructed dome flat field screen. LEDs have several advantages over
more traditional illumination sources: they are available in a wide range of
output wavelengths, are inexpensive, have a very long source lifetime, and are
straightforward to control digitally. The circular dome screen is made of a
material with Lambertian scattering properties that efficiently reflects light
of a wide range of wavelengths and incident angles. We compare flat fields
obtained using this new system with two types of traditionally-constructed flat
fields: twilight sky flats and nighttime sky flats. Using photometric standard
stars as illumination sources, we test the quality of each flat field by
applying it to a set of standard star observations. We find that the dome flat
field system produces flat fields that are superior to twilight or nighttime
sky flats, particularly for photometric calibration. We note that a ratio of
the twilight sky flat to the nighttime sky flat is flat to within the expected
uncertainty; but since both of these flat fields are inferior to the dome flat,
this common test is not an appropriate metric for testing a flat field. Rather,
the only feasible and correct method for determining the appropriateness of a
flat field is to use standard stars to measure the reproducibility of known
magnitudes across the detector.


title:
Precessing jets from a moving source and bright X-ray filaments in
  galaxy clusters

abstract:
  We present hydrodynamical calculations carried out with the 3D yguazu-a code
of a precessing jet model, which interacts with a plane parallel wind. This
scenario describes an extragalactic jet, in which the jet source is in motion
with respect to the surrounding intra-cluster medium. From the numerical
results, synthetic emission maps and spectra in X-ray band were obtained. We
compare these predictions with observations of the radio jets emanating from
the radio-galaxy 4C 26.42 (in the Abell 1795 galaxy cluster). We find that the
general morphology of the radio jets can be described by a point-symmetric
precessing jet system interacting with a plane parallel wind (i.e., the
intra-cluster medium flowing past the galaxy). We also find that our synthetic
X-ray emission maps reproduce the observed large scale structures (with sizes
of the order of tens of kpc).


title: Planets Rapidly Create Holes in Young Circumstellar Discs

abstract:
  Recent spectral observations by the Spitzer Space Telescope (SST) reveal that
some discs around young ($\sim {\rm few} \times 10^6$ yr old) stars have
remarkably sharp transitions to a low density inner region in which much of the
material has been cleared away. It has been recognized that the most plausible
mechanism for the sharp transition at a specific radius is the gravitational
influence of a massive planet. This raises the question of whether the planet
can also account for the hole extending all the way to the star. Using high
resolution numerical simulations, we show that Jupiter-mass planets drive
spiral waves which create holes on time scales $\sim 10$ times shorter than
viscous or planet migration times. We find that the theory of spiral-wave
driven accretion in viscous flows by Takeuchi et al. (1996) can be used to
provide a consistent interpretation of the simulations. In addition, although
the hole surface densities are low, they are finite, allowing mass accretion
toward the star. Our results therefore imply that massive planets can form
extended, sharply bounded spectral holes which can still accommodate
substantial mass accretion rates. The results also imply that holes are more
likely than gaps for Jupiter mass planets around solar mass stars.


title:
Detection of Large Grains in the Coma of Comet C/2001 A2 (LINEAR) from
  Arecibo Radar Observations

abstract:
  Arecibo S-band (lambda=13cm) radar observations of Comet C/2001 A2 (LINEAR)
on 2001 July 7-9 showed a strong echo from large coma grains. This echo was
significantly depolarized. This is the first firm detection of depolarization
in a grain-coma radar echo and indicates that the largest grains are at least
lambda / 2 or 2 cm in radius. The grains are moving at tens of m/s with respect
to the nucleus. The non-detection of the nucleus places an upper limit of 3 km
on its diameter. The broad, asymmetric echo power spectrum suggests a fan of
grains that have a steep (differential number ~ a^-4) size distribution at
cm-scales, though the observed fragmentation of this comet complicates that
picture.


title:
The N2K Consortium. IV. New temperatures and metallicities for 100,000+
  FGK dwarfs

abstract:
  We have created a framework to facilitate the construction of specialized
target lists for radial velocity surveys that are biased toward stars that (1)
possess planets and (2) are easiest to observe with current detection
techniques. We use a procedure that uniformly estimates fundamental stellar
properties of Tycho 2 stars, with errors, using spline functions of broadband
photometry and proper motion found in Hipparcos/Tycho 2 and 2MASS. We provide
estimates of temperature and distance for 2.4 million Tycho 2 stars that lack
trigonometric distances. For stars that appear to be FGK dwarfs according to
estimated temperature and absolute magnitude, we also derive [Fe/H] and
identify unresolved binary systems with mass ratios between 1.25 and 3. Our
spline function models are trained on the unique Valenti & Fischer (2005) set,
composed of 1000 dwarfs with precise stellar parameters estimated from HIRES
spectroscopy. For FGK dwarfs with V photometric error less than 0.05
magnitudes, or V < 9, our temperature model gives a one-sigma error of
+58.7/-65.9 K and our metallicity model gives a one-sigma error of +0.13/-0.14
dex. Our estimates of distance and spectral type enable us to isolate 354,822
Tycho 2 dwarfs, 321,996 of which are absent from Hipparcos, with giant and
subgiant contamination at 2.6% and 7.2%, respectively. 2,500 of these FGK
dwarfs are bright (V < 9.0) and metal-rich ([Fe/H] > 0.2). Our metallicity
estimates have been used to identify targets for N2K (Fischer et al. 2005), a
large-scale radial velocity search for Hot Jupiters, which has published the
detection of 4 Hot Jupiters with one transit. The broadband filtering outlined
here is the first screening tier for N2K; the second tier is a low-resolution
spectroscopy program headed by S.E. Robinson (astro-ph/0510150).


title:
Physical implication of the Kocevski Ryde Liang pulse function of gamma
  ray bursts

abstract:
  In this paper, we contrast an empirical pulse function of gamma-ray bursts
with a theoretical model in order to provide a physical explanation to the
parameters of the KRL function and directly relate parameters in both models.
We find the ratio of the rise index r to the decay index d, derived when fitted
by the KRL function, increases quickly first and then remains nearly invariant
with the relative width of local pulses when the width exceeds 2. The rise and
decay times of pulses are found to be related to the Lorentz factor by a power
law, where the power law index associated with the rise time is less than that
of the decay time, and both are close to -2. In addition, the mean asymmetry
shows a slight trend of decreasing with Lorentz factors. In plots of decay
indices versus asymmetry, there is a descending phase and after this phase
there is a rising portion. We find that these long bursts of the KRL sample are
mainly associated with those light curves arising from co-moving pulses with
the relative width being larger than 0.1. We show that the effect of the
co-moving pulse shape on the KRL function parameters of the resulting pulses is
considerable and can be distinguished by the decay index d when the relative
co-moving pulse width is less than 2.


title: Universal fitting formulae for baryon oscillation surveys

abstract:
  The next generation of galaxy surveys will attempt to measure the baryon
oscillations in the clustering power spectrum with high accuracy. These
oscillations encode a preferred scale which may be used as a standard ruler to
constrain cosmological parameters and dark energy models. In this paper we
present simple analytical fitting formulae for the accuracy with which the
preferred scale may be determined in the tangential and radial directions by
future spectroscopic and photometric galaxy redshift surveys. We express these
accuracies as a function of survey parameters such as the central redshift,
volume, galaxy number density and (where applicable) photometric redshift
error. These fitting formulae should greatly increase the efficiency of
optimizing future surveys, which requires analysis of a potentially vast number
of survey configurations and cosmological models. The formulae are calibrated
using a grid of Monte Carlo simulations, which are analyzed by dividing out the
overall shape of the power spectrum before fitting a simple decaying sinusoid
to the oscillations. The fitting formulae reproduce the simulation results with
a fractional scatter of 7% (10%) in the tangential (radial) directions over a
wide range of input parameters. We also indicate how sparse-sampling strategies
may enhance the effective survey area if the sampling scale is much smaller
than the projected baryon oscillation scale.


title: Centimeter Emission in the UY Aur System

abstract:
  We report 3.6 cm continuum observations taken with the Very Large Array (VLA)
of the young binary system UY Aur. The binary consists of a T Tauri star, UY
Aur A, and a so-called ``infrared companion'' (IRC), UY Aur B, separated by
0.''89. UY Aur is an interesting system because it shows observational features
whose origin is not well understood. One of them is the unusual low spectral
index found in the millimeter region. In our VLA study, we have detected
centimeter continuum radiation that coincides with the reported positions at
1.3 and 2.7 mm and is consistent with the optical position of UY Aur. We
conclude that the 3.6 cm emission is associated with the binary system.
Furthermore, we suggest that the centimeter emission might be related to a
previously reported bipolar outflow.


title: The jet power, radio loudness and black hole mass in radio loud AGNs

abstract:
  The jet formation is thought to be closely connected with the mass of central
supermassive black hole in Active Galactic Nuclei. The radio luminosity
commonly used in investigating this issue is merely an indirect measure of the
energy transported through the jets from the central engine, and severely
Doppler boosted in core-dominated radio quasars. In this work, we investigate
the relationship between the jet power and black hole mass, by estimating the
jet power using extrapolated extended 151 MHz flux density from the VLA 5 GHz
extended radio emission, for a sample of 146 radio loud quasars complied from
literature. After removing the effect of relativistic beaming in the radio and
optical emission, we find a significant intrinsic correlation between the jet
power and black hole mass. It strongly implies that the jet power, so as jet
formation, is closely connected with the black hole mass.To eliminate the
beaming effect in the conventional radio loudness, we define a new radio
loudness as the ratio of the radio extended luminosity to the optical
luminosity estimated from the broad line luminosity.In a tentatively combined
sample of radio quiet with our radio loud quasars, the apparent gap around the
conventional radio loudness R=10 is not prominent for the new-defined radio
loudness. In this combined sample, we find a significant correlation between
the black hole mass and new-defined radio loudness.


title: Possible Origin of Clusters in Ultra-High-Energy Cosmic rays

abstract:
  We estimate the detection rate of ultrahigh-energy cosmic rays on ground
based arrays by assuming that the cosmic ray sources are active galactic
nuclei. We analyse the cases of detection of clusters, several particles that
arrived, within the error limits, from the same area of the sky. The adopted
model is shown to explain the detection rate of clusters on the AGASA array.


title: Polar Outflows in Six Broad Absorption Line Quasars

abstract:
  Using the radio observations by FIRST and NVSS, we build a sample of 151
radio variable quasars selected from the Sloan Digital Sky Survey Data Release
3 (SDSS DR3). Six (probably another two) among them are classified as broad
absorption line (BAL) quasars, with radio flux variations of a few 10 percent
within 1.5-5 years. Such large amplitudes of the variations imply brightness
temperatures much higher than the inverse Compton limits (10$^{12}$ K) in all
the BAL quasars, suggesting the presence of relativistic jets beaming toward
the observer. The angle between the outflow and the jet is constrained to be
less than $\sim 20^{\circ}$. Such BAL quasars with polar outflows are beyond
the simple unification models of BAL quasars and non-BAL quasars, which
hypothesize that BAL quasars are normal quasars seen nearly edge-on.


title: On the Origin of Exponential Disks at High Redshift

abstract:
  The major axis and ellipse-fit intensity profiles of spiral galaxies larger
than 0.3'' in the Hubble Space Telescope Ultra Deep Field (UDF) are generally
exponential, whereas the major axis profiles in irregular disk galaxies, called
clump-clusters in our previous studies, are clearly not. Here we show that the
deprojected positions of star-forming clumps in both galaxy types are
exponential, as are the deprojected luminosity profiles of the total emissions
from these clumps. These exponentials are the same for both types when
normalized to the outer isophotal radii. The results imply that clumps form or
accrete in exponential radial distributions, and when they disperse they form
smooth exponential disks. The exponential scale lengths for UDF spirals average
1.5 kpc for a standard cosmology. This length is smaller than the average for
local spirals by a factor of 2. Selection effects that may account for this
size difference among spirals are discussed. Regardless of these effects, the
mere existence of small UDF galaxies with grand-design spiral arms differs
significantly from the situation in local fields, where equally small disks are
usually dwarf Irregulars that rarely have spiral arms. Spiral arms require a
disk mass comparable to the halo mass in the visible region -- something local
spirals have but local dwarfs Irregulars do not. Our UDF result then implies
that galaxy disks grow from the inside out, starting with a dense halo and
dense disk that can form spiral arms, and then adding lower density halo and
disk material over time. Bars that form early in such small, dense, gas-rich
disks should disperse more quickly than bars that form later in fully developed
disks.


title: Bars, Spiral Structure, and Secular Evolution in Disk Galaxies

abstract:
  Simulations and observations of galactic bars suggest they do not commonly
evolve into bulges, although it is possible that the earliest bars formed
bulges long ago, when galaxies were smaller, denser, and had more gas. The most
highly evolved of today's bars may become lenses over a Hubble time. Most
galaxies in the early Universe are extremely clumpy, with 10^8-10^9 Msun blue
clumps that resemble in color and magnitude the isolated field objects nearby.
The presence of blue and irregular bars at high redshift suggests that some
bars formed primarily in the gas phase accompanied by giant starbursts, rather
than in pure stellar disks like most models. Secular and non-secular processes
that cause galaxies to evolve are summarized.


title:
Ensemble Learning Independent Component Analysis of Normal Galaxy
  Spectra

abstract:
  In this paper, we employe a new statistical analysis technique, Ensemble
Learning for Independent Component Analysis (EL-ICA), on the synthetic galaxy
spectra from a newly released high resolution evolutionary model by Bruzual &
Charlot. We find that EL-ICA can sufficiently compress the synthetic galaxy
spectral library to 6 non-negative Independent Components (ICs), which are good
templates to model huge amount of normal galaxy spectra, such as the galaxy
spectra in the Sloan Digital Sky Survey (SDSS). Important spectral parameters,
such as starlight reddening, stellar velocity dispersion, stellar mass and star
formation histories, can be given simultaneously by the fit. Extensive tests
show that the fit and the derived parameters are reliable for galaxy spectra
with the typical quality of the SDSS.


title: The low-power nucleus of PKS 1246-410 in the Centaurus Cluster

abstract:
  We present Chandra, Very Large Array (VLA), and Very Long Baseline Array
(VLBA) observations of the nucleus of NGC 4696, a giant elliptical in the
Centaurus cluster of galaxies. Like M87 in the Virgo cluster, PKS 1246-410 in
the Centaurus cluster is a nearby example of a radio galaxy in a dense cluster
environment. In analyzing the new X-ray data we have found a compact X-ray
feature coincident with the optical and radio core. While nuclear emission from
the X-ray source is expected, its luminosity is low, <10^{40} erg/s. We
estimate the Bondi accretion radius to be 30 pc and the accretion rate to be
0.01 M_sun/yr which under the canonical radiative efficiency of 10% would
overproduce by 3.5 orders of magnitude the radiative luminosity. Much of this
energy can be directed into the kinetic energy of the jet, which over time
inflates the observed cavities seen in the thermal gas. The VLBA observations
reveal a weak nucleus and a broad, one-sided jet extending over 25 parsecs in
position angle -150 degrees. This jet is deflected on the kpc-scale to a more
east-west orientation (position angle of -80 degrees).


title: HI Observations of Flat Galaxies

abstract:
  We present the HI observations of 94 flat spiral galaxies from RFGC (the
Revised Flat Galaxy Catalog) and 14 galaxies from 2MFGC (the 2MASS selected
Flat Galaxy Catalog) performed with the 100-m radio telescope in Effelsberg
(Germany). HI fluxes, heliocentric radial velocities, and HI line widths are
given for 65 detected galaxies. We present a mosaic of HI profiles. We
calculated some of the global parameters of the galaxies and analyzed the
linear correlations between them. The ratios of the total (indicative) masses
of the galaxies to their luminosities lie within the range 0.4 with a mean of
3.8 ($M_{\sun}/L_{\sun}$), and the mean mass fraction of neutral hydrogen is
13%. Upper limits are given for the radio fluxes from 43 undetected galaxies.


title: Metallicity dependent calibrations of flux based SFR tracers

abstract:
  We present new calibrations of the widely used H_alpha, [OII], and UV
luminosity vs. star formation rate (SFR) relations. Using our evolutionary
synthesis code GALEV we compute the different calibrations for 5 metallicities,
from 1/50 solar up to 2.5 solar. We find significant changes in the
calibrations for lower metallicities compared to the standard calibrations
using solar input physics.


title: Transit flow models for low and high mass protostars

abstract:
  In this work, the gas infall and the formation of outflows around low and
high mass protostars are investigated. A radial self-similar approach to model
the transit of the molecular gas around the central object is employed. We
include gravitational and radiative fields to produce heated pressure-driven
outflows with magneto-centrifugal acceleration and collimation. Outflow
solutions with negligible or vanishing magnetic field are reported. They
indicate that thermodynamics is a sufficient engine to generate an outflow. The
magnetized solutions show dynamically significant differences in the axial
region, precisely where the radial velocity and collimation are the largest.
They compare quantitatively well with observations. The influence of the
opacity on the transit solutions is also studied. It is found that, when dust
is not the dominant coolant, such as in the primordial universe, mass infall
rates have substantial larger values in the equatorial region. This suggests
that star forming in a dust-free environment should be able to accrete much
more mass and become more massive than present day protostars.It is also
suggested that molecular outflows may be dominated by the global transit of
material around the protostar during the very early stages of star formation,
especially in the case of massive or dust-free star formation.


title:
Effects of mirror reflection versus diffusion anisotropy on particle
  acceleration in oblique shocks

abstract:
  Cosmic ray particles are more rapidly accelerated in oblique shocks, with the
magnetic field inclined with respect to the shock normal direction, than in
parallel shocks, as a result of mirror reflection at the shock surface and
slower diffusion in the shock normal direction. We investigate quantitatively
how these effects contribute to reducing the acceleration time over the whole
range of magnetic field inclinations. It is shown that, for quasi-perpendicular
inclination, the mirror effect plays a remarkable role in reducing the
acceleration time; whereas, at relatively small inclination, the anisotropic
diffusion effect is dominant in reducing that time. These results are important
for a detailed understanding of the mechanism of particle acceleration by an
oblique shock in space and heliosphereic plasmas.


title: The Discordance of Mass-Loss Estimates for Galactic O-Type Stars

abstract:
  We have determined accurate values of the product of the mass-loss rate and
the ion fraction of P^{4+}, Mdot q(P^{4+}), for a sample of 40 Galactic O-type
stars by fitting stellar-wind profiles to observations of the P V resonance
doublet obtained with FUSE, ORFEUS/BEFS, and Copernicus. When P^{4+} is the
dominant ion in the wind, Mdot q(P^{4+}) approximates the mass-loss rate to
within a factor of 2. Theory predicts that P^{4+} is the dominant ion in the
winds of O7-O9.7 stars, though an empirical estimator suggests that the range
from O4-O7 may be more appropriate. However, we find that the mass-loss rates
obtained from P V wind profiles are systematically smaller than those obtained
from fits to Halpha emission profiles or radio free-free emission by median
factors of about 130 (if P^{4+} is dominant between O7 and O9.7) or about 20
(if P^{4+} is dominant between O4 and O7). These discordant measurements can be
reconciled if the winds of O stars in the relevant temperature range are
strongly clumped on small spatial scales. We use a simplified two-component
model to investigate the volume filling factors of the denser regions. This
clumping implies that mass-loss rates determined from "density squared"
diagnostics have been systematically over-estimated by factors of 10 or more,
at least for a subset of O stars. Reductions in the mass-loss rates of this
size have important implications for the evolution of massive stars and
quantitative estimates of the feedback that hot-star winds provide to their
interstellar environments.


title:
Halos of Spiral Galaxies. I. The Tip of the Red Giant Branch as a
  Distance Indicator

abstract:
  We have imaged the halo populations of a sample of nearby spiral galaxies
using the Wide Field Planetary Camera 2 on broad the Hubble Space Telescope
with the aim of studying the stellar population properties and relating them to
those of the host galaxies. In four galaxies, the red-giant branch is
sufficiently well populated to measure the magnitude of the tip of the
red-giant branch (TRGB), a well-known distance indicator. Using both the Sobel
edge-detection technique and maximum-likelihood analysis to measure the
$I$-band magnitude of the red giant branch tip, we determine distances to four
nearby galaxies: NGC 253, NGC 4244, and NGC 4945, NGC 4258. For the first three
galaxies, the TRGB distance determined here is more direct, and likely to be
more accurate, than previous distance estimates. In the case of NGC 4258, our
TRGB distance is in good agreement with the the geometrical maser distance,
supporting the the Large Magellanic Cloud distance modulus $(m-M)_0 = 18.50$
that is generally adopted in recent estimates of the Hubble constant.


title: Halos of Spiral Galaxies. II. halo metallicity-luminosity relation

abstract:
  Using the Hubble Space Telescope, we have resolved individual red-giant
branch stars in the halos of eight nearby spiral galaxies. The fields lie at
projected distances between 2 and 13 kpc along the galaxies' minor axes. The
data set allows a first look at the systematic trends in halo stellar
populations. We have found that bright galaxies tend to have broad red-giant
branch star color distributions with redder mean colors, suggesting that the
heavy element abundance spread increases with the parent galaxy luminosity. The
mean metallicity of the stellar halo, estimated using the mean colors of
red-giant branch stars, correlates with the parent galaxy luminosity. The
metallicity of the Milky Way halo falls nearly 1 dex below this
luminosity-metallicity relation, suggesting that the halo of the Galaxy is more
the exception than the rule for spiral galaxies; i.e., massive spirals with
metal-poor halos are unusual. The luminosity-halo stellar abundance relation is
consistent with the scaling relation expected for stellar systems embedded in
dominant halos, suggesting that the bulk of the halo stellar population may
have formed in situ.


title: Halos of Spiral Galaxies. III. Metallicity Distributions

abstract:
  (Abriged) We report results of a campaign to image the stellar populations in
the halos of highly inclined spiral galaxies, with the fields roughly 10 kpc
(projected) from the nuclei. We use the F814W (I) and F606W (V) filters in the
Wide Field Planetary Camera 2, on board the Hubble Space telescope. Extended
halo populations are detected in all galaxies. The color-magnitude diagrams
appear to be completely dominated by giant-branch stars, with no evidence for
the presence of young stellar populations in any of the fields. We find that
the metallicity distribution functions are dominated by metal-rich populations,
with a tail extending toward the metal poor end. To first order, the overall
shapes of the metallicity distribution functions are similar to what is
predicted by simple, single-component model of chemical evolution with the
effective yields increasing with galaxy luminosity. However, metallicity
distributions significantly narrower than the simple model are observed for a
few of the most luminous galaxies in the sample. It appears clear that more
luminous spiral galaxies also have more metal-rich stellar halos. The
increasingly significant departures from the closed-box model for the more
luminous galaxies indicate that a parameter in addition to a single yield is
required to describe chemical evolution. This parameter, which could be related
to gas infall or outflow either in situ or in progenitor dwarf galaxies that
later merge to form the stellar halo, tends to act to make the metallicity
distributions narrower at high metallicity.


title:
Modeling Supernova-like Explosions Associated with Gamma-ray Bursts with
  Short Durations

abstract:
  There is now good evidence linking short-hard GRBs with both elliptical and
spiral galaxies at relatively low redshifts, redshift of about 0.2. This
contrasts with the average redshift of about 2 of long-duration events, which
also occur only in star-forming galaxies. The diversity of hosts is reminiscent
of type Ia supernovae, which are widely (but not universally) believed to
originate from the coalescence of white dwarfs. By analogy, it has been
postulated that short-hard bursts originate from neutron star mergers. Mergers,
as well as stellar core-collapse events (type II SNe and long-duration GRBs)
are accompanied by long-lived sub-relativistic components powered by
radioactive decay of unstable elements produced in the explosion. It is
therefore interesting to explore whether short duration events also have ejecta
powered by radioactivity (i.e. that are supernova-like). Observations already
inform us that any supernova like component in the first few well studied short
hard bursts must be fainter than those typical of type Ia or core-collapse
supernovae. Rather than refer to weaker supernova-like component as
``mini-super nova'', an etymologically indefensible term, I use the term {\it
macronova}. I investigate the observability of macronovae powered by neutron
decay and by radioactive Nickel. Separately, I note that a macronova will
reprocess energetic emission arising from a long lived central source. I find
that surprisingly interesting limits on the basic parameters of macronovae can
be obtained provided observations are obtained with current 10-m class
telescopes over a range of one hour to one day following the burst.


title: Chandra Observations of Six QSOs at z $\approx$ 3

abstract:
  We report the results of our Chandra observations of six QSOs at $z\sim 3$
from the Palomer Transit Grism Survey. Our primary goal is to investigate the
possible systematic change of $\alpha_{ox}$ between $z>4$ and $z\sim 3$,
between which a rapid rise of luminous QSO number density with cosmic time is
observed. The summed spectrum showed a power-law spectrum with photon index of
$\Gamma \approx 1.9$, which is similar to other unabsorbed AGNs. Combining our
$z\sim 3$ QSOs with X-ray observations of QSOs at $z>4$ from literaure/archive,
we find a correlation of $\alpha_{\rm ox}$ with optical luminosity. This is
consistent with the fact that the luminosity function slope of the luminous end
of the X-ray selected QSOs is steeper than that of optically-selected QSOs. We
discuss an upper limit to the redshift dependence of $\alpha_{ox}$ using a
Monte-Carlo simulation. Within the current statistical errors including the
derived limits on the redshift dependence of $\alpha_{\rm ox}$, we found that
the behaviors of the X-ray and optically-selected QSO number densities are
consistent with each other.


title: Radiative Transfer Effects on the Lya Forest

abstract:
  Strong observational evidence for a fluctuating ultraviolet background (UVB)
has been accumulating through a number of studies of the HI and HeII Lya forest
as well as accurate IGM metallicity measurements. UVB fluctuations could arise
both from the inhomogeneous distribution of the ionizing sources and/or from
radiative transfer (RT) through the filamentary IGM. In this study we
investigate, via numerical simulations, the role of RT effects such as
shadowing, self-shielding and filtering of the ionizing radiation, in giving
raise to a fluctuating UVB. We focus on possible detectable signatures of these
effects on quantities derived from Lya forest spectra, as photoionization rate
fluctuations, eta parameter (the HeII to HI column density ratio) distributions
and the IGM temperature at redshift about 3. We find that RT induces
fluctuations up to 60% in the UVB, which are tightly correlated to the density
field. The UVB mean intensity is progressively suppressed toward higher
densities and photon energies above 4 Ryd, due to the high HeII opacity.
Shielding of overdense regions (Delta > 5) from cosmic HeII ionizing radiation,
produces a decreaseing trend of eta with overdensity. Furthermore we find that
the mean eta value inferred from HI-HeII Lya forest observations can be
explained only by properly accounting for the actual IGM opacity. We outline
and discuss several implications of our findings.


title: The Cosmological Unimportance of Low Surface Brightness Galaxies

abstract:
  We have searched for Type Ia supernovae (SNe Ia) in the local (d < 60 Mpc)
Universe using Northern Sky Variability Survey (NSVS) data collected from the
nightly optical surveys of the Robotic Optical Transient Search Experiment}
(ROTSE) Telescope. It was hoped that SNe Ia would provide a means to find
previously-unknown low surface brightness (LSB) galaxies or displaced stars
that would otherwise be very difficult to detect. The ROTSE data allowed us to
survey 19,000 square degrees at declinations north of 0 degrees, but we did not
find a single SN Ia in a period of time covering roughly one year. Using known
SNe Ia rates in bright galaxies, we set an upper limit on the optical
luminosity density, L_B, of LSBs in the local Universe. Using mean LSB baryonic
and dynamical mass-to-light ratios, we find 95% upper limits for LSBs of L_B
\le 2.53 x 10^8 L_{B, solar} Mpc^{-3}, Omega_b \le 0.0040, and Omega_m \le
0.036. We conclude that LSBs and displaced stars are not a major constituent of
matter in the local Universe.


title: Evidence for alignment of the rotation and velocity vectors in pulsars

abstract:
  We present strong observational evidence for a relationship between the
direction of a pulsar's motion and its rotation axis. We show carefully
calibrated polarization data for 25 pulsars, 20 of which display linearly
polarized emission from the pulse longitude at closest approach to the magnetic
pole. Such data allow determination of the position angle of the linear
polarisation which in turn reflects the position angle of the rotation axis. Of
these 20 pulsars, 10 show an offset between the velocity vector and the
polarisation position angle which is either less than 10\degr or more than
80\degr, a fraction which is very unlikely by random chance. We believe that
the bimodal nature of the distribution arises from the presence of orthogonal
polarisation modes in the pulsar radio emission. In some cases this orthogonal
ambiguity is resolved by observations at other wavelengths so that we conclude
that the velocity vector and the rotation axis are aligned at birth.
Strengthening the case is the fact that 4 of the 5 pulsars with ages less than
3 Myr show this relationship, including the Vela pulsar. We discuss the
implications of these findings in the context of the Spruit & Phinney
(1998)\nocite{sp98} model of pulsar birth-kicks. We point out that, contrary to
claims in the literature, observations of double neutron star systems do not
rule out aligned kick models and describe a possible observational test
involving the double pulsar system.


title:
Neutral hydrogen in radio galaxies: results from nearby, importance for
  far away

abstract:
  The study of neutral hydrogen emission and absorption in radio galaxies is
giving new and important insights on a variety of phenomena observed in these
objects. Such observations are helping to understand the origin of the host
galaxy, the effects of the interaction between the radio jet and the ISM, the
presence of fast gaseous outflows as well as jet-induced star formation. Recent
results obtained on these phenomena are summarized in this review. Although the
HI observations concentrate on nearby radio galaxies, the results also have
relevance for the high-z objects as all these phenomena are important, and
likely even more common, in high-redshift radio sources.


title:
Theory and Modeling of the Zeeman and Paschen-Back effects in Molecular
  Lines

abstract:
  This paper describes a very general approach to the calculation of the Zeeman
splitting effect produced by an external magnetic field on the rotational
levels of diatomic molecules. The method is valid for arbitrary values of the
total electronic spin and of the magnetic field strength -that is, it holds for
molecular electronic states of any multiplicity and for both the Zeeman and
incomplete Paschen-Back regimes. It is based on an efficient numerical
diagonalization of the effective Zeeman Hamiltonian, which can incorporate
easily all the contributions one may eventually be interested in, such as the
hyperfine interaction of the external magnetic field with the spin motions of
the nuclei. The reliability of the method is demonstrated by comparing our
results with previous ones obtained via formulae valid only for doublet states.
We also present results for molecular transitions arising between non-doublet
electronic states, illustrating that their Zeeman patterns show signatures
produced by the Paschen-Back effect.


title:
Fast neutral outflows in powerful radio galaxies: a major source of
  feedback in massive galaxies

abstract:
  We report the detection of fast (~ 1000 km/s), massive outflows of neutral
gas observed -- using the WSRT -- as 21-cm HI absorption against the strong
radio continuum of seven radio sources. The neutral outflows occur, in at least
somes cases, at kpc distance from the nucleus, and they are most likely driven
by the interactions between the expanding radio jets and the gaseous medium
enshrouding the central regions. We estimate that the associated mass outflow
rates are up to ~50 M_sun/yr, comparable (although at the lower end of the
distribution) to the outflow rates found for starburst-driven superwinds in
Ultra Luminous IR Galaxies (ULIRG). This suggests that massive, jet-driven
outflows of neutral gas in radio-loud AGN can have as large an impact on the
evolution of the host galaxies as the outflows associated with starbursts. A
radio-loud phase of the AGN is likely a relatively common, albeit short, phase
in the life of many (or even all) massive ellipticals. Jet-driven neutral
outflows may represent one of the main feedback mechanisms in these galaxies.


title: The Ne/O abundance ratio in the quiet Sun

abstract:
  Aims: To determine the neon-to-oxygen abundance in the quiet Sun, a proxy for
the photospheric abundance ratio.
  Method: An emission measure method applied to extreme ultraviolet emission
lines of Ne IV-VI and O III-V ions observed by the Coronal Diagnostic
Spectrometer on the SOHO satellite.
  Results: The average Ne/O abundance ratio in supergranule cell centre regions
is 0.18 +/- 0.05, while in supergranule network regions is 0.16 +/- 0.04. A
photospheric Ne/O ratio of 0.17 +/- 0.05 is suggested, in good agreement with
the most recent compilation of solar photospheric abundances, but discrepant
with a recent Ne/O ratio derived from stellar X-ray spectra and revised neon
abundances suggested from solar interior models.


title:
Collisional dissipation of Alfv\'{e}n waves in a partially ionised solar
  chromosphere

abstract:
  Certain regions of the solar atmosphere are at sufficiently low temperatures
to be only partially ionised. The lower chromosphere contains neutral atoms,
the existence of which greatly increases the efficiency of the damping of waves
due to collisional friction momentum transfer. More specifically the Cowling
conductivity can be up to 12 orders of magnitude smaller than the Spitzer
value, so that the main damping mechanism in this region is due to the
collisions between neutrals and positive ions. Using values for the gas density
and temperature as functions of height taken from the VAL C model of the quiet
Sun, an estimate is made for the dependance of the Cowling conductivity on
height and strength of magnetic field. Using both analytic and numerical
approaches the passage of Alfven waves over a wide spectrum through this
partially ionised region is investigated. Estimates of the efficiency of this
region in the damping of Alfven waves are made and compared for both
approaches. We find that Alfven waves with frequencies above 0.6Hz are
completely damped and frequencies below 0.01 Hz unaffected.


title: Cosmological Constraints from Weak Lensing Surveys

abstract:
  Focusing on the well motivated aperture mass statistics $\Map$, we study the
possibility of constraining cosmological parameters using future space based
SNAP class weak lensing missions. Using completely analytical results we
construct the covariance matrix for estimators based on two-point and
three-point statistics. Our approach incorporates an accurate modelling of
higher-order statistics to describe cosmic variance as well as various sources
of discrete noise at small angular scales. These results are then fed into a
Fisher matrix based analysis to study cosmological parameter degeneracies.
Joint and independent analysis, with or without redshift binning, for various
parameter combinations are presented. An analytical modelling of the covariance
matrix opens up the possibility of testing various approximations which are
often used in derivations of semi-analytical results. These include how
inclusion of full non-Gaussian terms in covariance matrix affects parameter
estimation. Inclusion of three-point information and how such information can
enhance the accuracy with which certain parameters can be estimated is also
studied in detail. It is shown that broad correlation structure among various
angular scales in such circumstances implies reduction in number of available
angular scales which carry completely independent information. On the other
hand, the effect of theoretical inaccuracies, in modelling either the
power-spectrum or bi-spectrum evolution, onto the measure of cosmological
parameters from weak lensing surveys is also considered. Several cosmological
parameters, $\Om$, $\sigma_8$, spectral index $n_s$, running of spectral index
$\alpha_s$ and equation of state of the dark energy $\wde$ are included in the
analysis.


title: Broad-band Spectral Properties of Accreting X-ray Binary Pulsars

abstract:
  Broad-band spectra of accreting X-ray binary pulsars can be fit by a
phenomenological model composed by a power law with a high energy rollover
above 10 keV, plus a blackbody component with a temperature of few hundred eV.
While, at least qualitatively, the hard tail can be explained in terms of
(inverse) Compton scattering, the origin of the soft component cannot find a
unique explanation. Recently a qualitative picture able to explain the overall
broad band-spectrum of luminous X-ray pulsars was carried out by taking into
account the effect of bulk Comptonization in the accretion column. After a
review on these recent theoretical developments, I will present a case study of
how different modelization of the continuum affect broad features, in
particular the cyclotron resonance features in Vela X-1.