title: A blind estimation of the power spectrum of CMB anisotropy from WMAP

abstract:
  Accurate measurements of angular power spectrum of Cosmic Microwave
Background (CMB) radiation has lead to marked improvement in the estimates of
different cosmological parameters. This has required removal of foreground
contamination as well as detector noise bias with reliability and precision. We
present the estimation of CMB angular power spectrum from the multi-frequency
observations of WMAP using a novel {\em model-independent} method. The primary
product of WMAP are the observations of CMB in 10 independent difference
assemblies (DA) that have uncorrelated noise. Our method utilizes maximum
information available within WMAP data by linearly combining all the DA maps to
remove foregrounds and estimating the power spectrum from cross power spectra
of clean maps with independent noise. We compute 24 cross power spectra which
are the basis of the final power spectrum. The binned average power matches
with WMAP team's published power spectrum closely. A small systematic
difference at large multipoles is accounted for by the correction for the
expected residual power from unresolved point sources. The correction is small
and significantly tempered. Previous estimates have depended on foreground
templates built using extraneous observational input. This is the first
demonstration that the CMB angular spectrum can be reliably estimated with
precision from a *self contained analysis* of the WMAP data.


title: On Random Walks with a General Moving Barrier

abstract:
  Random walks with a general, nonlinear barrier have found recent applications
ranging from reionization topology to refinements in the excursion set theory
of halos. Here, we derive the first-crossing distribution of random walks with
a moving barrier of an arbitrary shape. Such a distribution is shown to satisfy
an integral equation that can be solved by a simple matrix inversion, without
the need for Monte Carlo simulations, making this useful for exploring a large
parameter space. We discuss examples in which common analytic approximations
fail, a failure which can be remedied using the method described here.


title: Broadband modeling of gamma-ray burst afterglows

abstract:
  According to the fireball model gamma-ray burst (GRB) afterglows are the
result of a shock pushed into the surrounding medium by an extremely
relativistic outflow from the GRB. By modeling the broadband spectrum, ranging
from X-ray to radio wavelengths, on time scales of hours to years after the
GRB, we can determine several burst parameters, e.g. the burst energy, the
circumburst medium density (and its gradient) and the energy contained in
electrons and the magnetic field. We have developed a code to do broadband
modeling and determine the model parameters. We also performed Monte Carlo
simulations with synthetic data sets in order to derive an estimate of the
accuracy of the best fit parameters. GRB970508 was taken as a case study and we
present our fitting results. We also present our WSRT radio observations of
GRB030329 at centimeter wavelengths and the results from modeling this
afterglow. The low frequency WSRT radio observations provide a unique
possibility to study the late stages of the fireball evolution and examine the
jet structure.


title:
Frequency-Dependent Shift in the Image Centroid of the Black Hole at the
  Galactic Center as a Test of General Relativity

abstract:
  The inferred black hole in the Galactic center spans the largest angle on the
sky among all known black holes. Forthcoming observational programs plan to
localize or potentially resolve the image of Sgr A* to an exquisite precision,
comparable to the scale of the black hole horizon. Here we show that the
location of the image centroid of Sgr A* should depend on observing frequency
because of relativistic and radiative transfer effects. The same effects
introduce a generic dependence of the source polarization on frequency. Future
detection of the predicted centroid shift and the polarization dependence on
frequency can be used to determine the unknown black hole spin and verify the
validity of General Relativity.


title: Spectroscopic abundance analysis of dwarfs in young open cluster IC 4665

abstract:
  We report a detailed spectroscopic abundance analysis for a sample of 18 F-K
dwarfs of the young open cluster IC 4665. Stellar parameters and element
abundances of Li, O, Mg, Si, Ca, Ti, Cr, Fe and Ni have been derived using the
spectroscopic synthesis tool SME (Spectroscopy Made Easy). Within the
measurement uncertainties the iron abundance is uniform with a standard
deviation of 0.04 dex. No correlation is found between the iron abundance and
the mass of the stellar convective zone, and between the Li abundance and the
Fe abundance. In other words, our results do not reveal any signature of
accretion and therefore do not support the scenario that stars with planets
(SWPs) acquire their on the average higher metallicity compared to field stars
via accretion of metal-rich planetary material. Instead the higher metallicity
of SWPs may simply reflect the fact that planet formation is more efficient in
high metallicity environs. However, since that many details of the planet
system formation processes remain poorly understood, further studies are needed
for a final settlement of the problem of the high metallicity of SWPs.
  The standard deviation of [Fe/H] deduced from our observations, taken as an
upper limit on the metallicity dispersion amongst the IC 4665 member stars, has
been used to constrain proto-planetary disk evolution, terrestrial and giant
planets formation and evolution processes. Our results do not support the
possibility that the migration of gas giants and the circularization of
terrestrial planets' orbits are regulated by their interaction with a residual
population of planetesimals and dust particles.


title: Three-dimensional MHD Simulations of Jets from Accretion Disks

abstract:
  We report the results of 3-dimensional magnetohydrodynamic (MHD) simulations
of a jet formation by the interaction between an accretion disk and a large
scale magnetic field. The disk is not treated as a boundary condition but is
solved self-consistently. To investigate the stability of MHD jet, the
accretion disk is perturbed with a non-axisymmetric sinusoidal or random
fluctuation of the rotational velocity. The dependences of the jet velocity
$(v_z)$, mass outflow rate $(\dot{M}_w)$, and mass accretion rate $(\dot{M}_a)$
on the initial magnetic field strength in both non-axisymmetric cases are
similar to those in the axisymmetric case. That is, $v_z \propto B_0^{1/3}$,
$\dot{M}_w \propto B_0$ and $\dot{M}_a \propto B_0^{1.4}$ where $B_0$ is the
initial magnetic field strength. The former two relations are consistent with
the Michel's steady solution, $v_z \propto (B_0^2/\dot{M}_w)^{1/3}$, although
the jet and accretion do not reach the steady state. In both perturbation
cases, a non-axisymmetric structure with $m=2$ appears in the jet, where $m$
means the azimuthal wave number. This structure can not be explained by
Kelvin-Helmholtz instability and seems to originate in the accretion disk.
Non-axisymmetric modes in the jet reach almost constant levels after about 1.5
orbital periods of the accretion disk, while all modes in the accretion disk
grow with oscillation. As for the angular momentum transport by Maxwell stress,
the vertical component, $<B_\phi B_z/4\pi>$, is comparable to the radial
component, $<B_\phi B_r/4\pi>$, in the wide range of initial magnetic field
strength.


title:
Performance of the Fluorescence Detectors of the Pierre Auger
  Observatory

abstract:
  Fluorescence detectors of the Pierre Auger Observatory have been operating in
a stable manner since January 2004. After a brief review of the physical
characteristics of the detectors, the associated atmospheric monitoring, the
calibration infrastructure and the detector aperture, we will describe the
steps required for the reconstruction of fluorescence event data, with emphasis
on the shower profile parameters and primary energy.


title: N-body simulations of the Magellanic Stream

abstract:
  A suite of high-resolution N-body simulations of the Magellanic Clouds --
Milky Way system are presented and compared directly with newly available data
from the HI Parkes All-Sky Survey (HIPASS). We show that the interaction
between Small and Large Magellanic Clouds results in both a spatial and
kinematical bifurcation of both the Stream and the Leading Arm. The spatial
bifurcation of the Stream is readily apparent in the HIPASS data, and the
kinematical bifurcation is also tentatively identified. This bifurcation
provides strong support for the tidal disruption origin for the Magellanic
Stream. A fiducial model for the Magellanic Clouds is presented upon completion
of an extensive parameter survey of the potential orbital configurations of the
Magellanic Clouds and the viable initial boundary conditions for the disc of
the Small Magellanic Cloud. The impact of the choice of these critical
parameters upon the final configurations of the Stream and Leading Arm is
detailed.


title: 511 keV line from Q balls in the Galactic Center

abstract:
  The 511 keV photons from the galactic center can be explained by positrons
produced through Q-ball decay. In the scheme of gauge-mediated supersymmetry
breaking, large Q balls with lepton charge are necessarily long-lived. In
particular, the lifetime can be as long as (or even longer than) the age of the
universe. If kinematically allowed, such large Q balls decay into positrons,
which eventually annihilate with electrons into 511 keV photons. Our scenario
is realized within the minimal supersymmetric standard model in the
inflationary universe, which is very plausible.


title: VGCF Detection of Galaxy Systems at Intermediate Redshift

abstract:
  We continue the development of our Voronoi Galaxy Cluster Finder (VGCF)
technique by applying it to galaxy catalogs obtained with B and R band
observations of four high galactic latitude fields of 0.5x0.5 square degrees
each. These fields are deep R_lim ~23, B_lim ~26 and partially overlap the
Palomar Distant Cluster Survey (PDCS) fields at 0h and 2h. We run the VGCF also
on the original V and I bands PDCS galaxy catalogs.
  We identify a total of 48 clusters that are particularly reliable being
detected in at least two bands. The analysis of color-magnitude diagrams and,
in a few cases, spectroscopic observations allow us to further increase the
reliability of 25 of the 48 clusters. For these 26 clusters we also estimate
redshifts that fall in the approximate range 0.2 < z < 0.6.
  We detect 41 VGCF clusters within the strict limits of the PDCS fields at 0h
and 2h. The PDCS catalog for the same regions consists of 28 clusters. The two
catalogs have 20 clusters in common. These clusters together with the remaining
PDCS and VGCF clusters lead to a total number of 46 "independent" clusters. The
total number of clusters is therefore 20% larger than the number of VGCF
clusters and more than 60% larger than the number of PDCS clusters. These
results confirm a) that the VGCF is a competitive algorithm for the
identification of optical clusters, and b) that a combined catalog of
matched-filter and VGCF clusters constitutes a significant progress toward a
more complete selection of clusters from bidimensional optical data.


title:
Density waves in the shearing sheet V. Feedback cycle for swing
  amplification by non-linear effects

abstract:
  Non-linear effects in the dynamical evolution of a shearing sheet made of
stars are studied. First the implications of hitherto neglected non-linearities
of the Boltzmann equation for the dynamical evolution of the shearing sheet are
investigated. Using a formalism developed previously on the basis of the
linearized Boltzmann equation it is demonstrated that the inclusion of the
non-linear term leads to a feedback cycle for swing amplified density waves in
the unbounded shearing sheet. Such a feedback is unique to star disks and is
not known for gas disks. In order to present concrete examples of the
non-linear feedback cycle a SCF code was developed and numerical simulations of
the dynamical evolution of the shearing sheet are performed. The numerical
results seem to confirm the theoretical predictions. The evolution of the
shearing sheet resembles closely and might actually explain the recurrent
spiral instabilities found in large-scale numerical simulations of the
dynamical evolution of galactic disks.


title: The host of GRB/XRF 030528 - an actively star forming galaxy at z=0.782

abstract:
  An important parameter for the distinction of X-ray flashes, X-ray rich
bursts and Gamma-ray bursts in the rest frame is the distance to the explosion
site. Here we report on the spectroscopic redshift determination of the host
galaxy of XRF/GRB 030528 using the ESO VLT FORS2 instrument. From the strong
oxygen and hydrogen emission lines the redshift was measured to be
z=0.782+-0.001. Obtaining the line luminosities and ratios we find that the
host is consistent with being an actively star forming galaxy with sub-solar
metallicity. With a stellar mass of ~10E10 Msun the host is placed among the
most massive GRB host galaxies at a similar redshift. Estimating the redshifted
properties of the prompt emission, we find that XRF/GRB 030528 would be
classified as an X-ray rich bursts in the rest frame rather than an X-ray flash
in the typically used observer frame.


title:
Trans-ethyl methyl ether in space - A new look at a complex molecule in
  selected hot core regions

abstract:
  An extensive search for the complex molecule trans-ethyl methyl ether towards
several hot core regions has been performed. Using the IRAM 30m telescope and
the SEST 15m we looked at several frequencies where trans-ethyl methyl ether
has strong transitions, as well as lines which are particularly sensitive to
the physical conditions in which the molecule can be found. We included G34.26,
NGC6334(I), Orion KL, and W51e2 which have previously been proven to have a
rich chemistry of complex molecules. Our observations cannot confirm the
tentative Orion KL detection made by Charnley et al. (2001) within their stated
column density limits, but we confirm the existence of the trans-ethyl methyl
ether towards W51e2 with a column density of 2x10^14 cm-2. The dimethyl
ether/methanol ratio of 0.6 as well as the newly found ethyl methyl
ether/ethanol ratio of 0.13 indicate relative high abundances of ethers toward
W51e2. Furthermore, the observation of ethyl methyl ether also confirms the
importance of ethanol as a grain mantle constituent. We present new upper
limits of around 8x10^13 cm-2 for the column densities of the molecule toward
Orion KL, G34.26, NGC6334(I) and estimate the column density towards SgrB2(N)
to be of the same order. The W51e2 observations are discussed in more detail.


title: The HI content of the recently discovered field dwarf galaxy APPLES1

abstract:
  We present observations in a search for neutral hydrogen associated with the
recently detected field dwarf galaxy APPLES1, performed with the Parkes
radiotelescope. The observed radio spectrum shows no evident (> 3sigma rms)
line emission indicating an upper limit for the HI content of the galaxy of ~
10E6 solar masses and providing an upper value for the M(HI)/L(B) ratio equal
to 2.4 solar masses/solar luminosities. The low value of the HI content
suggested by the observations, together with the galaxy optical morphology,
might indicate that APPLES1 is a dwarf spheroidal. This indication is in
contrast with the evidence of recent star formation, which is typical for dwarf
irregular galaxies. This may suggest that APPLES1 belongs to the class of mixed
dwarf irregular/spheroidal transition-type galaxies. We also conclude that the
relatively low neutral gas mass in APPLES1 can be explained by an extended and
inefficient star formation process, without the need for a dramatic event such
as enhanced star formation or a past encounter with a massive galaxy or galaxy
group.


title:
The radio afterglow of GRB 030329 at centimeter wavelengths: evidence
  for a structured jet or non-relativistic expansion

abstract:
  We present our centimeter wavelength (1.4, 2.3 and 4.8 GHz) light curves of
the afterglow of GRB 030329, which were obtained with the Westerbork Synthesis
Radio Telescope. Modeling the data according to a collimated afterglow results
in a jet-break time of 10 days. This is in accordance with earlier results
obtained at higher radio frequencies. However, with respect to the afterglow
model, some additional flux at the lower frequencies is present when these
light curves reach their maximum after 40-80 days. We show that this additional
flux can be modeled with two or more components with progressively later jet
breaks. From these results we infer that the jet is in fact a structured or a
layered jet, where the ejecta with lower Lorentz factors produce additional
flux that becomes visible at late times in the lowest frequency bands. We show
that a transition to non-relativistic expansion of the fireball at late times
can also account for the observed flux excess, except for the lowest frequency
(1.4 GHz) data.


title:
Cosmic ray neon, Wolf-Rayet stars, and the superbubble origin of
  galactic cosmic rays

abstract:
  The abundances of neon isotopes in the galactic cosmic rays (GCRs) are
reported using data from the Cosmic Ray Isotope Spectrometer (CRIS) aboard the
Advanced Composition Explorer (ACE). We compare our ACE-CRIS data for neon and
refractory isotope ratios, and data from other experiments, with recent results
from two-component Wolf-Rayet (WR) models. The three largest deviations of GCR
isotope ratios from solar-system ratios predicted by these models are indeed
present in the GCRs. Since WR stars are evolutionary products of OB stars, and
most OB stars exist in OB associations that form superbubbles, the good
agreement of these data with WR models suggests that superbubbles are the
likely source of at least a substantial fraction of GCRs.


title: Instant nonthermal leptogenesis

abstract:
  We propose an economical model of nonthermal leptogenesis following inflation
during ``instant'' preheating. The model involves only the inflaton field, the
standard model Higgs, and the heavy ``right-handed'' neutrino.


title:
A Catalogue of Potential Adaptive Optics Survey Fields from the UKIRT
  Archive

abstract:
  We present a multicolour catalogue of faint galaxies situated close to bright
stars, V<15, with the aim of identifying high-redshift galaxies suitable for
study with adaptive optics-equipped near-infrared imagers and spectrographs.
The catalogue is constructed from archival calibration observations of UKIRT
Faint Standard stars with the UFTI camera on UKIRT. We have analysed the
deepest 16 fields from the archive to provide a catalogue of galaxies brighter
than K~20.3 lying within 25" of the guide stars. We identify 111 objects in a
total survey area of 8.7 sq. arcmin, of these 87 are classified as galaxies
based on their light profiles in our ~0.5" median seeing K-band images. Of
these, 12 galaxies have (J-K)>2.0 consistent with them lying at high-redshifts,
z~2. These 12 very red galaxies have K-band magnitudes of K=18.1-20.1 and
separations from the guide stars of 4-20" and hence are very well-suited to
adaptive optics studies to investigate their morphologies and spectral
properties on sub-kpc scales. We provide coordinates and JHK photometry for all
catalogued objects.


title: Going Nonlinear with Dark Energy Cosmologies

abstract:
  We propose an efficient method for generating high accuracy (~1%) nonlinear
power spectra for grids of dark energy cosmologies. Our prescription for
matching matter growth automatically matches the main features of the cosmic
microwave background anisotropy power spectrum, thus naturally including ``CMB
priors''.


title:
First tests of wavefront sensing with a constellation of laser guide
  beacons

abstract:
  Adaptive optics to correct current telescopes over wide fields, or future
very large telescopes over even narrow fields, will require real-time wavefront
measurements made with a constellation of laser beacons. Here we report the
first such measurements, made at the 6.5 m MMT with five Rayleigh beacons in a
2 arcmin pentagon. Each beacon is made with a pulsed beam at 532 nm, of 4 W at
the exit pupil of the projector. The return is range-gated from 20-29 km and
recorded at 53 Hz by a 36-element Shack-Hartmann sensor. Wavefronts derived
from the beacons are compared with simultaneous wavefronts obtained for
individual natural stars within or near the constellation. Observations were
made in seeing averaging 1.0 arcsec with 2/3 of the aberration measured to be
from a ground layer of mean height 380 m. Under these conditions, subtraction
of the simple instantaneous average of the five beacon wavefronts from the
stellar wavefronts yielded a 40% rms reduction in the measured modes of the
distortion over a 2 arcmin field. We discuss the use of multiple Rayleigh
beacons as an alternative to single sodium beacons on 8 m telescopes, and the
impact of the new work on the design of a multi-sodium beacon system for the 25
m Giant Magellan Telescope.


title: Disk evolution since z=1 in a CDM Universe

abstract:
  Increasingly large populations of disk galaxies are now being observed at
increasingly high redshifts, providing new constraints on our knowledge of how
such galaxies evolve. Are these observations consistent with a cosmology in
which structures form hierarchically? To probe this question, we employ
SPH/N-body galaxy scale simulations of late-type galaxies. We examine the
evolution of these simulated disk galaxies from redshift 1 to 0, looking at the
mass-size and luminosity-size relations, and the thickness parameter, defined
as the ratio of scale-height to scale-length. The structural parameters of our
simulated disks settle down quickly, and after redshift z=1 the galaxies evolve
to become only slightly flatter. Our present day simulated galaxies are larger,
more massive, less bright, and redder than at z=1. The inside-out nature of the
growth of our simulated galaxies reduces, and perhaps eliminates, expectations
of evolution in the size-mass relation.


title: Effect of the radiative background flux in convection

abstract:
  Numerical simulations of turbulent stratified convection are used to study
models with approximately the same convective flux, but different radiative
fluxes. As the radiative flux is decreased, for constant convective flux: the
entropy jump at the top of the convection zone becomes steeper, the temperature
fluctuations increase and the velocity fluctuations decrease in magnitude, and
the distance that low entropy fluid from the surface can penetrate increases.
Velocity and temperature fluctuations follow mixing length scaling laws.


title: On the discovery of the first 350 micron-selected galaxy

abstract:
  We report the detection of a 3.6sigma 350micron-selected source in the Bootes
Deep Field. The source, the first Short-wavelength Submillimeter-selected
Galaxy (SSG 1), was discovered as part of a blank field extragalactic survey
using the 350micron-optimised Submillimeter High Angular Resolution Camera
(SHARC II) at the Caltech Submillimeter Observatory. With multiwavelength
photometry from NOAO-NDWFS (R and I band), FLAMEX (J and K_s), Spitzer (IRAC
and MIPS) and the Westerbork 1.4GHz Deep Survey (radio upper limit), we are
able to constrain the photometric redshift using different methods, all of
which suggest a redshift of close to 1. In the absence of long-wavelength
submillimeter data we use SED templates to infer that this source is an
ultraluminous infrared galaxy (ULIRG) with a dust temperature of 30+/-5 K,
occupying a region of luminosity-temperature space shared by modarate redshift
ISO-selected ULIRGs (rather than high redshift SCUBA-selected SMGs). SHARC II
can thus select SMGs with moderately "warm'' dust that might be missed in
submillimeter surveys at longer wavelengths.


title:
Cataclysmic and Close Binaries in Star Clusters. V. Erupting Dwarf
  Novae, Faint Blue Stars, X-ray sources, and the Classical Nova in the Core of
  M80

abstract:
  Large populations of cataclysmic variables (CVs) in globular clusters have
long been predicted, but the number of absolutely certain cluster CVs known in
globulars is still less than 10. HST and Chandra observers have recently found
dozens of cataclysmic variable candidates in several populous globular
clusters. Confirmation and characterization of these candidates are extremely
difficult, thus identification of unambiguous CVs remains important. We have
searched all archival HST images of the dense globular cluster M80 for erupting
dwarf novae (DN), and to check the outburst behaviors of two very blue objects
first identified a decade ago. Two new erupting dwarf novae were found in 8
searched epochs, making M80 a record holder for erupting DN. The quiescent
classical nova in M80 varies by no more than a few tenths of a magnitude on
timescales of minutes to years, and a similar faint, blue object varies by a
similar amount. Simulations and completeness tests indicate that there are at
most 3 erupting DN like SS Cyg and at most 9 U Gem-like DN in M80. Either this
very dense cluster contains about an order of magnitude fewer CVs than theory
predicts, or most M80 CVs are extremely faint and/or erupt very infrequently
like WZ Sge. We have detected a sequence of 54 objects running parallel to the
main sequence and several tenths of a magnitude bluewards of it. These blue
objects are significantly more centrally concentrated than the main sequence
stars, but not as centrally concentrated as the blue stragglers. We suggest
that these objects are white dwarf--red dwarf binaries, and that some are the
faint CV population of M80.


title:
The Gemini Deep Deep Survey. VII. The Redshift Evolution of the
  Mass-Metallicity Relation

abstract:
  We have investigated the mass-metallicity (M-Z) relation using galaxies at
0.4<z<1.0 from the Gemini Deep Deep Survey and Canada-France Redshift Survey.
Deep K and z' band photometry allowed us to measure stellar masses for 69
galaxies. From a subsample of 56 galaxies, for which metallicity of the
interstellar medium is also measured, we identified a strong correlation
between mass and metallicity, for the first time in the distant Universe. This
was possible because of the larger base line spanned by the sample in terms of
metallicity (a factor of 7) and mass (a factor of 400) than in previous works.
This correlation is much stronger and tighter than the luminosity-metallicity,
confirming that stellar mass is a more meaningful physical parameter than
luminosity. We find clear evidence for temporal evolution in the M-Z relation
in the sense that at a given mass, a galaxy at z=0.7 tends to have lower
metallicity than a local galaxy of similar mass. We use the z=0.1 SDSS M-Z
relation, and a small sample of z=2.3 Lyman break galaxies with known mass and
metallicity, to propose an empirical redshift-dependent M-Z relation, according
to which the stellar mass and metallicity in small galaxies evolve for a longer
time than in massive galaxies. This relation predicts that the generally metal
poor damped Lyman-alpha galaxies have stellar masses of the order of 10^8.8
M_sun (with a dispersion of 0.7 dex) all the way from z=0.2 to z=4. The
observed redshift evolution of the M-Z relation can be reproduced remarkably
well by a simple closed-box model where the key assumption is an e-folding time
for star formation which is higher or, in other words, a period of star
formation that lasts longer in less massive galaxies than in more massive
galaxies. Such a picture supports the downsizing scenario for galaxy formation.


title:
The Araucaria Project: The effect of blending on the Cepheid distance to
  NGC 300 from Advanced Camera for Surveys images

abstract:
  We have used the Advanced Camera for Surveys aboard the Hubble Space
Telescope to obtain F435W, F555W and F814W single-epoch images of six fields in
the spiral galaxy NGC 300. Taking advantage of the superb spatial resolution of
these images, we have tested the effect that blending of the Cepheid variables
studied from the ground with close stellar neighbors, unresolved on the
ground-based images, has on the distance determination to NGC 300. Out of the
16 Cepheids included in this study, only three are significantly affected by
nearby stellar objects. After correcting the ground-based magnitudes for the
contribution by these projected companions to the observed flux, we find that
the corresponding Period-Luminosity relations in V, I and the Wesenheit
magnitude W_I are not significantly different from the relations obtained
without corrections. We fix an upper limit of 0.04 magnitudes to the systematic
effect of blending on the distance modulus to NGC 300.
  As part of our HST imaging program, we present improved photometry for 40
blue supergiants in NGC 300.


title: Statistics of Extinct Radio Pulsars

abstract:
  We study the statistical distribution of extinct radio pulsars -- isolated
neutron stars, that just crossed the death line. An important element that
distinguishes our study from other works is a consistent allowance for the
evolution of the angle between the magnetic and spin axes. We find the
distribution of extinct radio pulsars in spin period for two models: the model
with hindered particle escape from the neutron star surface and the model with
free particle escape. The total number of extinct radio pulsars is shown to be
much smaller than for the model in which the evolution of an inclination angle
is disregarded. The decrease in total number of extinct radio pulsars arises
from the fact, that account for evolution of the inclination angle allows the
transition of a neutron star to the propeller stage appear at much smaller
periods (P~5-10 s) than it is commonly assumed.


title:
Finite source effect on the polarization degree induced by a single
  microlens

abstract:
  We investigate the effect of a single microlens on Stokes parameters.
  Semi-analytical formulae of the microlensed Stokes parameters are derived.
The formulae not only reduce the double integrals in the estimations of those
quantities but can also be approximated to a useful form in the bypass case. By
using our formulation, we show that a combination of polarimetric data with
photometric data enables us to estimate not only the finite source effect but
also the direction of the microlens motion.


title:
Approximate Consistency Condition from Running Spectral Index in
  Slow-Roll Inflationary Models

abstract:
  Density perturbations generated from inflation almost always have a spectral
index n_s which runs (varies with the wavelength). We explore a running
spectral index scenario in which the scalar spectral index runs from blue (n_s
>1) on large length scales to red (n_s<1) on short length scales. Specifically,
we look for a correlation between the length scale at which n_s-1=0 and the
length scale at which tensor to scalar ratio T/S reaches a minimum for single
field slow roll inflationary models. By computing the distribution of length
scale ratios, we conclude that there indeed is a new approximate consistency
condition that is characteristic of running spectral index scenarios that run
from blue to red. Specifically, with strong running, we expect 96% of the slow
roll models to have the two length scales to be within a factor of 2, with the
length scale at which the tensor to scalar ratio reaching a minimum longer than
the wavelength at which n_s-1=0.


title: Repeated X-ray Flaring Activity in Sagittarius A*

abstract:
  Investigating the spectral and temporal characteristics of the X-rays coming
from Sagittarius A* (Sgr A*) is essential to our development of a more complete
understanding of the emission mechanisms in this supermassive black hole
located at the center of our Galaxy. Several X-ray flares with varying
durations and spectral features have already been observed from this object.
Here we present the results of two long XMM-Newton observations of the Galactic
nucleus carried out in 2004, for a total exposure time of nearly 500 ks. During
these observations we detected two flares from Sgr A* with peak 2-10 keV
luminosities about 40 times (L ~ 9x10^34 erg s−1) above the quiescent
luminosity: one on 2004 March 31 and another on 2004 August 31. The first flare
lasted about 2.5 ks and the second about 5 ks. The combined fit on the Epic
spectra yield photon indeces of about 1.5 and 1.9 for the first and second
flare respectively. This hard photon index strongly suggests the presence of an
important population of non-thermal electrons during the event and supports the
view that the majority of flaring events tend to be hard and not very luminous.


title: Background radiation from sterile neutrino decay and reionization

abstract:
  Sterile neutrinos are one of the most promising Warm Dark Matter candidates.
By considering their radiative- and pion-decay channels, we derive the allowed
contribution of sterile neutrinos to the X-ray, optical and near-infrared
cosmic backgrounds. The X-ray background puts a strong constraint on the mass
of radiatively decaying neutrinos (m <= 14 keV), whereas the allowed mass range
for pion-decay neutrinos (for a particle lifetime > 4 X 10^17 s) is 150 <=
m/MeV <= 500. Taking into account these constraints, we find that sterile
neutrinos do not significantly contribute to the optical and near-infrared
background. We further consider the impact of sterile neutrinos on
reionization. We find that the Thomson optical depth due to sterile neutrinos
is tau_e = (0.4-3) X 10^-2 in the case of radiative decays, and it is ~10^-3
for the pion-decay channel. We conclude that these particles must have played
only a minor role in cosmic reionization history.


title:
A New Apsidal Motion Determination of the Eclipsing Binary Star V459
  Cassiopeiae: A Possible Discrepancy Between the Theory and the Observation

abstract:
  Photometric and spectroscopic observations and analysis of the eccentric
eclipsing binary V459 Cassiopeiae (e=0.0244) were performed by Lacy et al.
(2004). Observations of minimum light show the presence of apsidal motion. In
order to find the observed rate of apsidal motion, I followed the procedure
described by Guinan & Maloney (1985). A new observed rate of apsidal motion of
15.2/100 yr with a period of 2400 yr is computed which is not in agreement with
the one reported earlier. Also the advance of the periastron is calculated
theoretically by taking into account the Newtonian (classical) and
general-relativistic effects according to the physical and orbital parameters
of the system. The theoretical value of 2.64/100 yr is obtained which is 5.75
times smaller than the observed rate of the apsidal motion.


title:
The magnetic structure of neutron stars and their surface-to-core
  temperature relation

abstract:
  We study the relation between the mean effective surface temperature T_s and
the internal temperature T_b for magnetic neutron stars, assuming that the
magnetic field near the surface has a presumably small-scale structure. The
heavy-element (iron) and light-element (accreted) heat-blanketing envelopes are
considered, and the results are compared with the case of a dipole magnetic
field. We argue that the difference in the T_b(T_s)-relation for different
magnetic configurations is always much smaller than a possible difference
caused by variations of the chemical composition in the envelope.


title:
C^2-Ray: A new method for photon-conserving transport of ionizing
  radiation

abstract:
  We present a new numerical method for calculating the transfer of ionizing
radiation, called C^2-Ray=Conservative, Causal Ray-tracing method. The method
is explicitly photon-conserving, so the depletion of ionizing photons by
bound-free opacity is guaranteed to equal the photoionizations these photons
caused. As a result, grid cells can be large and very optically-thick without
loss of accuracy. The method also uses an analytical relaxation solution for
the ionization rate equations for each time step which can accommodate time
steps which greatly exceed the characteristic ionization and ionization front
crossing times. Together, these features make it possible to integrate the
equation of transfer along a ray with many fewer cells and time steps than
previous methods. For multi-dimensional calculations, the code utilizes
short-characteristics ray tracing. C^2-Ray is well-suited for coupling
radiative transfer to gas and N-body dynamics methods, on both fixed and
adaptive grids, without imposing additional limitations on the time step and
grid spacing. We present several tests of the code involving propagation of
ionization fronts in one and three dimensions, in both homogeneous and
inhomogeneous density fields. We compare to analytical solutions for the
ionization front position and velocity, some of which we derive here for the
first time.


title: Problems and Progress in Flare Fast Particle Diagnostics

abstract:
  Recent progress in the diagnosis of flare fast particles is critically
discussed with the main emphasis on high resolution Hard X-Ray (HXR) data from
RHESSI and coordinated data from other instruments. Spectacular new photon data
findings are highlighted as are advances in theoretical aspects of their use as
fast particle diagnostics, and some important comparisons made with
interplanetary particle data. More specifically the following topics are
addressed
  (a) RHESSI data on HXR (electron) versus gamma-ray line (ion) source
locations.
  (b) RHESSI hard X-ray source spatial structure in relation to theoretical
models and loop density structure.
  (c) Energy budget of flare electrons and the Neupert effect.
  (d) Spectral deconvolution methods including blind target testing and results
for RHESSI HXR spectra, including the reality and implications of dips inferred
in electron spectra
  (e) The relation between flare in-situ and interplanetary particle data.


title:
Solar Flare Hard X-ray Spectra Possibly Inconsistent with the
  Collisional Thick Target Model

abstract:
  Recent progress in solar Hard X-ray (HXR) observations with RHESSI data and
methods for spectral inversion allow us to study model-independent mean
electron flux spectra in solar flares. We report several hard X-ray events
observed by RHESSI in which the photon spectra $I(\epsilon)$ are such that the
inferred source mean electron spectra are not consistent with the standard
model of collisional transport in solar flares. The observed photon spectra are
so flat locally that the recovered mean electron flux spectra show a dip around
17-31 keV. While we note that alternative explanations, unrelated to electron
transport, have not been ruled out, we focus on the physical implications of
this tentative result for the collisional thick-target model.


title: Simple Models for the Distribution of Dark Matter

abstract:
  We introduce a simple family of models for representing the dark matter in
galaxies. The potential and phase space distribution function are all
elementary, while the density is cusped. The models are all hypervirial, that
is, the virial theorem holds locally, as well as globally. As an application to
dark matter studies, we compute some of the properties of gamma-ray sources
caused by neutralino self-annihilation in dark matter clumps.


title: Prevalence of compact nuclear starbursts in nearby Seyfert galaxies

abstract:
  We present an imaging survey of the CO(1--0), HCN(1--0), and HCO$^+$(1--0)
lines in the nearby Seyfert galaxies using the Nobeyama Millimeter Array and
RAINBOW Interferometer. Some of the observed Seyfert galaxies including NGC
1068, NGC 1097, NGC 5033, and NGC 5194 exhibit strong HCN(1--0) emission on a
few 100 pc scales. The observed HCN(1--0)/CO(1--0) and HCN(1--0)/HCO$^+$(1--0)
line ratios in the Seyfert nuclei ($>$0.2 and $>$1.8, respectively) have never
been observed in the central regions of nuclear starburst galaxies. On the
other hand, the molecular line ratios in the nuclei of NGC 3079, NGC 3227, NGC
4051, NGC 6764, NGC 7479, and NGC 7469 are comparable with those in the nuclear
starburst galaxies. We propose that the elevated HCN emission originates from
the X-ray irradiated dense molecular tori or XDRs close to the active nuclei.
Our HCN/CO and HCN/HCO$^+$ diagrams will provide a new powerful diagnostic of
the nuclear power source in active galaxies. Based on our diagnostic, we
observe 3 of 5 type-1 Seyferts (6 of 10 in total) host compact nuclear
starbursts. Our results are also supported by observations at other wavelengths
such as those by L-band PAH spectroscopy. The proposed method will be crucial
for investigating extremely dusty nuclei, such as ULIRGs and high-z submm
galaxies, because these molecular lines are devoid of dust extinction. As an
example, we present the HCN and HCO$^+$ observations of the LIRG NGC 4418,
which suggests the presence of a buried active nucleus.


title: High Mass Starless Cores

abstract:
  We report the identification of a sample of potential High-Mass Starless
Cores (HMSCs). The cores were discovered by comparing images of the fields
containing candidate High-Mass Protostellar Objects (HMPOs) at 1.2mm and
mid-infrared (8.3um; MIR) wavelengths. While the HMPOs are detected at both
wavelengths, several cores emitting at 1.2mm in the same fields show absorption
or no emission at the MIR wavelength. We argue that the absorption is caused by
cold dust. The estimated masses of a few 10^2Msun - 10^3 Msun and the lack of
IR emission suggests that they may be massive cold cores in a pre-stellar
phase, which could presumably form massive stars eventually. Ammonia (1,1) and
(2,2) observations of the cores indicate smaller velocity dispersions and lower
rotation temperatures compared to HMPOs and UCHII regions suggesting a
quiescent pre-stellar stage. We propose that these newly discovered cores are
good candidates for the HMSC stage in high-mass star-formation. This sample of
cores will allow us to study the high-mass star and cluster formation processes
at the earliest evolutionary stages.


title: Preferred sunspot longitudes: Non-axisymmetry and differential rotation

abstract:
  As recently found, the distribution of sunspots is non-axisymmetric and spot
group formation implies the existence of two persistent active longitudes
separated by 180 degrees. Here we quantitatively study the non-axisymmetry of
sunspot occurrence. In a dynamic reference frame inferred from the differential
rotation law, the raw sunspot data show a clear clustering around the
persistent active longitudes. The differential rotation describing the dynamic
frame is quantified in terms of the equatorial angular velocity and the
differential rotation rate, which appear to be significantly different from
those for individual sunspots. This implies that the active longitudes are not
linked to the depth of sunspot anchoring. In order to quantify the observed
effect, we introduce a measure of the non-axisymmetry of the sunspot
distribution. The non-axisymmetric component is found to be highly significant,
and the ratio of its strength to that of the axisymmetric one is roughly 1:10.
This provides additional constraints for solar dynamo models.


title: The Metallicity Distribution Function of the Halo of the Milky Way

abstract:
  We report on the distribution of metallicities, [Fe/H], for very metal-poor
stars in the halo of the Galaxy. Although the primary information on the nature
of the Metallicity Distribution Function (MDF) is obtained from the two major
recent surveys for metal-poor stars, the HK survey of Beers and collaborators,
and the Hamburg/ESO Survey of Christlieb and collaborators, we also discuss the
MDF derived from the publicly available database of stellar spectra and
photometry contained in the third data release of the Sloan Digital Sky Survey
(SDSS DR-3). Even though the SDSS was not originally planned as a stellar
survey, significant numbers of stars have been observed to date -- DR-3
contains spectroscopy for over 70,000 stars, at least half of which are
suitable for abundance determinations. There are as many very metal-poor
([Fe/H] < -2.0) stars in DR-3 as have been obtained from all previous survey
efforts combined. We also discuss prospects for significant expansion of the
list of metal-poor stars to be obtained from the recently funded extension of
the SDSS, which includes the project SEGUE: Sloan Extension for Galactic
Understanding and Exploration.


title:
Near IR diffraction-limited integral-field SINFONI spectroscopy of the
  Circinus galaxy

abstract:
  Using the adaptive optics assisted near infrared integral field spectrometer
SINFONI on the VLT, we have obtained observations of the Circinus galaxy on
parsec scales. The morphologies of the H_2(1-0)S(1) 2.12um and Br_gamma 2.17um
emission lines are only slightly different, but their velocity maps are similar
and show a gradient along the major axis of the galaxy, consistent with
rotation.Since V_rot/sigma is approximately 1 suggests that random motions are
also important, it is likely that the lines arise in a rotating spheroid or
thickened disk around the AGN. Comparing the Br_gamma flux to the stellar
continuum indicates that the star formation in this region began almost 10^8 yr
ago. We also detect the [SiVI] 1.96um,[AlIX] 2.04um and [CaVIII] 2.32um coronal
lines. In all cases we observe a broad blue wing, indicating the presence of
two or more components in the coronal line region. A correlation between the
ionisation potential and the asymmetry of the profiles was found for these high
excitation species.


title: Fiber optic interferometry: Statistics of visibility and closure phase

abstract:
  Interferometric observations with three telescopes or more provide two
observables: closure phase information together with visibilities measurements.
When using single-mode interferometers, both observables have to be redefined
in the light of the coupling phenomenon betwe en the incoming wavefront and the
fiber. We introduce in this paper the estimator of both so-called modal
visibility and modal closure phase. Then, we compute the statistics of the two
observables in presence of partial correction by Adaptive Optics. From this
theoretical analysis, data reduction process using classical least square
minimization is investigated. In the framework of the AMBER instrument, the
three beams recombiner of the VLTI, we simulate the observation of a single
Gaussian source and we study the performances of the interferometer in terms of
diameter measurements. We show that the observation is optimized, i.e. that the
Signal to Noise Ratio (SNR) of the diameter is maximal, when the full width
half maximum (FWHM) of the source is roughly 1/2 of the mean resolution of the
interferometer. We finally point out that in the case of an observation with 3
telescopes, neglecting the correlation between the measurements leads to
overestimate the SNR by a factor of $\sqrt{2}$. We infer that in any cases,
this value is an upper limit.


title:
Jets, Structured Outflows, and Energy Injection in GRB Afterglows:
  Numerical Modelling

abstract:
  We investigate numerically the ability of three models (jet, structured
outflow, energy injection) to accommodate the optical light-curve breaks
observed in 10 GRB afterglows (980519, 990123, 990510, 991216, 000301c, 000926,
010222, 011211, 020813, and 030226), and the relative intensities of the radio,
optical, and X-ray emissions of these afterglows. We find that the jet and
structured outflow models fare much better than the energy injection model in
accommodating the multiwavelength data of the above 10 afterglows. For the
first two models, a uniform circumburst medium provides a better fit to the
optical light-curve break than a wind-like medium with a r^{-2} stratification.
However, in the only two cases where the energy injection model may be at work,
a wind medium is favoured (an energy injection is also possible in a third
case, the afterglow 970508, whose optical emission exhibited a sharp rise but
not a steepening decay). The best fit parameters obtained with the jet model
indicate an outflow energy of 2-6 E50 ergs and a jet opening of 2-3 degrees.
Structured outflows with a quasi-uniform core have a core angular size of
0.7-1.0 degrees and an energy per solid angle of 0.5-3 E53 erg/sr, surrounded
by an envelope where this energy falls-off roughly as theta^{-2} with angle
from the outflow axis, requiring thus the same energy budget as jets.
Circumburst densities are found to be typically in the range 0.1-1 per cc, for
either model. We also find that the reverse shock emission resulting from the
injection of ejecta into the decelerating blast wave at about 1 day after the
burst can explain the slowly decaying radio light-curves observed for the
afterglows 990123, 991216, and 010222.


title: Low-mass companions to Hyades stars

abstract:
  It is now well established that a large fraction of the low-mass stars are
binaries or higher order multiples. Similarly a sizable fraction have giant
planets. In contrast to these, the situation for brown dwarf companions is
complicated: While close systems seem to be extremely rare, wide systems are
possibly more common. In this paper, we present new results on a survey for
low-mass companions in the Hyades. After measuring precisely the radial
velocity of 98 Hyades dwarf stars for 5 years, we have selected all stars that
show low-amplitude long-period trends. With AO-observations of these 14 stars
we found companion candidates around nine of them, where one star has two
companions. The two companions of HIP 16548 have masses between 0.07 to 0.08
Mo, and are thus either brown dwarfs or very low mass stars. In the case of HAN
172 we found a companion with a mass between 0.08 to 0.10 Mo, which is again
between a star and a brown dwarf. The other seven stars all have stellar
companions. In two additional cases, the RV-variations are presumably caused by
stellar activity, and in another case the companion could be a short-period
binary. The images of the remaining two stars are slightly elongated, which
might imply that even these are binaries. Because at least 12 of the 14 stars
showing low-amplitude RV trends turn out to have companions with a mass greater
than 70 MJupiter, or are just active, we finally estimate the number of
companions with masses between 10 MJupiter and 70 MJupiter within 8 AU of the
host stars in the Hyades as less equal 2%.


title:
The effect of non-isothermality on the gravitational collapse of
  spherical clouds and the evolution of protostellar accretion

abstract:
  We investigate the role of non-isothermality in gravitational collapse and
protostellar accretion by explicitly including the effects of molecular
radiative cooling, gas-dust energy transfer, and cosmic ray heating in models
of spherical hydrodynamic collapse. Isothermal models have previously shown an
initial decline in the mass accretion rate \dot{M}, due to a gradient of infall
speed that develops in the prestellar phase. Our results show that: (1) in the
idealized limit of optically thin cooling, a positive temperature gradient is
present in the prestellar phase which effectively cancels out the effect of the
velocity gradient, producing a near constant \dot{M} in the early accretion
phase; (2) in the more realistic case including cooling saturation at higher
densities, \dot{M} may initially be either weakly increasing or weakly
decreasing with time, for low (T_d ~ 6 K) and high dust temperature (T_d ~ 10
K) cases, respectively. Hence, our results show that the initial decline in
\dot{M} seen in isothermal models is definitely not enhanced by non-isothermal
effects, and is often suppressed by them. In all our models, \dot{M} does
eventually decline rapidly due to the finite mass condition on our cores and a
resulting inward propagating rarefaction wave. Thus, any explanation for a
rapid decline of $\dot{M}$ in the accretion phase likely needs to appeal to the
global molecular cloud structure and possible envelope support, which results
in a finite mass reservoir for cores.


title: How did it all begin?

abstract:
  How did it all begin? Although this question has undoubtedly lingered for as
long as humans have walked the Earth, the answer still eludes us. Yet since my
grandparents were born, scientists have been able to refine this question to a
degree I find truly remarkable. In this brief essay, I describe some of my own
past and ongoing work on this topic, centering on cosmological inflation. I
focus on
  (1) observationally testing whether this picture is correct and
  (2) working out implications for the nature of physical reality (e.g., the
global structure of spacetime, dark energy and our cosmic future, parallel
universes and fundamental versus environmental physical laws).
  (2) clearly requires (1) to determine whether to believe the conclusions. I
argue that (1) also requires (2), since it affects the probability calculations
for inflation's observational predictions.


title: The discovery of two new galaxy-galaxy lenses from the SDSS

abstract:
  The gravitational lens configuration where a background galaxy is closely
aligned with a foreground galaxy, can provide accurate measurement of the dark
matter density profile in the foreground galaxy, free of dynamical assumptions.
Currently only three such galaxy-galaxy lenses are known where the lensed
source has a confirmed redshift and is reasonably bright at optical
wavelengths, and therefore suitable for observations with the HST Advanced
Camera for Surveys (ACS). Two of these were discovered by noting an anomalous
emission line (from the source) in the spectrum of a massive early-type galaxy
(the lens). To find further galaxy-galaxy lenses suitable for ACS imaging we
have looked for anomalous emission lines in the luminous red galaxy (LRG)
subsample of the SDSS DR3 spectroscopic database. Our search methodology has
similarities to that applied by Bolton et al. (which has had recent success),
but extends the upper redshift limit for lensed sources to z=1.4. Here we
report follow-up imaging and spectroscopic observations of two candidates,
confirmed as gravitational lenses by the detection of multiple images in the
line of [OII]3726,3729. In the first system, J145957.1-005522.8, the lens at
z=0.58, consists of two LRGs. The anomalous emission line is confirmed as [OII]
by the detection of the corresponding H-gamma line, providing a source redshift
of z=0.94. In the second system, J230946.3-003912.9, the lens is a single LRG
at z=0.29, and the source redshift is z=1.00, confirmed by partially resolving
the [OII] doublet.


title: XMM-Newton view of the ultra-luminous X-ray sources in M51

abstract:
  (Abridged) We present results based on XMM-Newton observation of the nearby
spiral galaxy M51 (NGC5194 and NGC5195). Two ULXs in NGC5194 show evidence for
short-term variability, and all but two ULXs vary on long time scales (over a
baseline of 2.5 years), providing strong evidence that these are accreting
sources. One ULX in NGC5194, source 69, shows possible periodic behavior in its
X-ray flux. We derive a period of 5925\pm200s at a confidence level of 95%,
based on three cycles. This period is lower than the period of 7620\pm500s
derived from a Chandra observation in 2000. The higher effective area of
XMM-Newton enables us to identify multiple components in the spectra of ULXs.
Most ULXs require at least two components -- a power law and a soft X-ray
excess component which is modeled by an optically thin plasma or multicolor
disk blackbody (MCD). However, the soft excess emission, inferred from all ULXs
except source 69, are unlikely to be physically associated with the ULXs as
their strengths are comparable to that of the surrounding diffuse emission. The
soft excess emission of source 69 is well described either by a two temperature
mekal plasma or a single temperature mekal plasma kT~690eV) and an MCD
(kT~170eV). The MCD component suggests a cooler accretion disks compared to
that in Galactic X-ray binaries and consistent with that expected for
intermediate mass black holes (IMBHs). An iron line (EW 700eV) or K absorption
edge at 7.1keV is present in the EPIC PN spectrum of source 26. The spectrum of
the ULX in NGC5195, source 12, is consistent with a simple power law.


title: Long Type I X-ray Bursts and Neutron Star Interior Physics

abstract:
  Superbursts are very energetic Type I X-ray bursts discovered in recent years
by long term monitoring of X-ray bursters, believed to be due to unstable
ignition of carbon in the deep ocean of the neutron star. A number of
"intermediate duration" bursts have also been observed, probably associated
with ignition of a thick helium layer. We investigate the sensitivity of these
long X-ray bursts to the thermal profile of the neutron star crust and core. We
first compare cooling models of superburst lightcurves with observations, and
derive constraints on the ignition mass and energy release, and then calculate
ignition models for superbursts and pure helium bursts, and compare to
observations. The superburst lightcurves and ignition models imply that the
carbon mass fraction is approximately 20% or greater in the fuel layer,
constraining models of carbon production. However, the most important result is
that when Cooper pairing neutrino emission is included in the crust, the
temperature is too low to support unstable carbon ignition at the observed
column depths. Some additional heating mechanism is required in the
accumulating fuel layer to explain the observed properties of superbursts. If
Cooper pair emission is less efficient than currently thought, the observed
ignition depths for superbursts imply that the crust is a poor conductor, and
the core neutrino emission is not more efficient than modified URCA. The
observed properties of helium bursts support these conclusions, requiring
inefficient crust conductivity and core neutrino emission.


title: XMM-Newton timing mode observations of Mrk 421

abstract:
  We present the results of a detailed temporal analysis of the bright BL Lac
object Mrk 421 using the three available long timing mode observations by the
EPIC PN camera. This detector mode is characterized by its long life time and
is largely free of photon pile-up problems. The source was found in different
intensity and variability states differing by up to more than a factor of three
in count rate. A time resolved cross correlation analysis between the soft and
hard energy bands revealed that the characteristics of the correlated emission,
with lags of both signs, change on time scales of a few thousand seconds.
Individual spectra, resolved on time scales of a few hundread seconds, can be
quite well fitted by a broken power law. We find significant spectral
variations on time scales as short as 500-1000 sec. Both the hard and the soft
band spectral indices show a non-linear correlation with the source flux. A
comparison of the observed light curves with numerical results from
relativistic hydrodynamic computer simulations of the currently favored
shock-in-jet models indicates that any determination of the jet's physical
parameters from `simple' emission models must be regarded with caution: at any
time we are seeing the emission from several emission regions distinct in space
and time, which are connected by the complex hydrodynamic evolution of the
non-uniform jet.


title: Polar ring galaxies and warps

abstract:
  Polar ring galaxies, where matter is in equilibrium in perpendicular orbits
around spiral galaxies, are ideal objects to probe the 3D shapes of dark matter
halos. The conditions to constrain the halos are that the perpendicular system
does not strongly perturb the host galaxy, or that it is possible to derive
back its initial shape, knowing the formation scenario of the polar ring. The
formation mechanisms are reviewed: mergers, tidal accretion, or gas accretion
from cosmic filaments. The Tully-Fisher diagram for polar rings reveals that
the velocity in the polar plane is higher than in the host plane, which can
only be explained if the dark matter is oblate and flattened along the polar
plane. Only a few individual systems have been studied in details, and 3D
shapes of their haloes determined by several methods. The high frequency of
warps could be explained by spontaneous bending instability, if the disks are
sufficiently self-gravitating, which can put constraints on the dark matter
flattening.


title:
Morphological Dependence of Star Formation Properties for the Galaxies
  in the Merging Galaxy Cluster A2255

abstract:
  The merging cluster of galaxies A2255 is covered by the Sloan Digital Sky
Survey (SDSS) survey. In this paper we perform a morphological classification
on the basis of the SDSS imaging and spectral data, and investigate the
morphological dependence of the star formation rates (SFRs) for these member
galaxies. As we expect, a tight correlation between the normalized SFR by
stellar mass (SFR/M$_*$) and the H$\alpha$ equivalent width is found for the
late-type galaxies in A2255. The correlation of SFR/M$_*$ with the continuum
break strength at 4000 \AA is also confirmed. The SFR/M$_*$ - M$_*$ correlation
is found for both the early- and late-type galaxies, indicating that the star
formation activity tends to be suppressed when the assembled stellar mass
M$_*$) increases, and this correlation is tighter and steeper for the late-type
cluster galaxies. Compared with the mass range of field spiral galaxies, only
two massive late-type galaxies with M$_*>10^{11}$ M$_{\odot}$ are survived in
A2255, suggesting that the gas disks of massive spiral galaxies could have been
tidally stripped during cluster formation. Additionally, the SFR variation with
the projected radial distance are found to be heavily dependent upon galaxy
morphology: the early-type galaxies have a very weak inner decrease in
SFR/M$_*$, while the inner late-type galaxies tend to have higher SFR/M$_*$
values than the outer late-types. This may suggest that the galaxy-scale
turbulence stimulated by the merging of subclusters might have played different
roles on early- and late-type galaxies, which leads to a suppression of the
star formation activity for E/S0 galaxies and a SFR enhancement for spiral and
irregular galaxies.


title:
Detecting a physical difference between the CDM halos in simulation and
  in nature

abstract:
  Numerical simulation is an important tool to help us understand the process
of structure formation in the universe. However many simulation results of cold
dark matter (CDM) halos on small scale are inconsistent with observations: the
central density profile is too cuspy and there are too many substructures. Here
we point out that these two problems may be connected with a hitherto
unrecognized bias in the simulation halos. Although CDM halos in nature and in
simulation are both virialized systems of collisionless CDM particles,
gravitational encounter cannot be neglected in the simulation halos because
they contain much less particles. We demonstrate this by two numerical
experiments, showing that there is a difference on the microcosmic scale
between the natural and simulation halos. The simulation halo is more akin to
globular clusters where gravitational encounter is known to lead to such
drastic phenomena as core collapse. And such artificial core collapse process
appears to link the two problems together in the bottom-up scenario of
structure formation in the $\Lambda$CDM universe. The discovery of this bias
also has implications on the applicability of the Jeans Theorem in Galactic
Dynamics.


title: ROTSE observations of the young cluster IC 348

abstract:
  CCD observations of stars in the young cluster IC 348 were obtained from 2004
August to 2005 January with a 0.45 m ROTSEIIId robotic reflecting telescope at
the Turkish National Observatory site, Bakirlitepe, Turkey. The timing analysis
of selected stars whose X-Ray counterpart were detected by Chandra X-Ray
Observatory were studied. The time series of stars were searched for rotational
periodicity by using different period search methods. 35 stars were found to be
periodic with periods ranging from 0.74 to 32.3 days. Eighteen of the 35
periodic stars were new detections. Four of the new detections were CTTSs and
the others were WTTSs and G type (or unknown spectral class) stars. In this
study, we confirmed the stability of rotation periods of TTauri stars. The
periods obtained by Cohen et al. and us were different by 1%. We also confirmed
the 3.24 h pulsation period of H254 which is a delta Scuti type star as noted
by Ripepi et al. but the other periods detected by them were not found. We
examined correlation between X-ray luminosity and rotational period of our
sample of TTSs. There is a decline in the rotational period with X-ray
luminosity for late type TTSs.


title: Merger-origin of radio galaxies investigated with H I observations

abstract:
  We present results of an HI study of a complete sample of nearby radio
galaxies. Our goal is to investigate whether merger or interaction events could
be at the origin of the radio-AGN activity. Around five of our radio galaxies,
hosted mainly by early-type galaxies, we detect extended HI in emission. In
most cases this HI is distributed in large (up to 190 kpc) and massive (up to
M(HI) ~ 10^10 M(sun)) disk- or ring-like structures, that show fairly regular
rotation around the host galaxy. This suggests that in these systems a major
merger did occur, but at least several Gyr ago. For the HI-rich radio galaxy B2
0648+27 we confirm such a merger origin through the detection of a
post-starburst stellar population that dominates the visible light throughout
this system. The timescale of the current episode of radio-AGN activity in our
HI-rich radio galaxies is many orders of magnitude smaller than the merger
timescales. Therefore the radio-AGN activity either started late in the
lifetime of the merger event, or is not directly related to the merger event at
all. Another intriguing result is that the HI-rich (> 10^9 M(sun)) radio
galaxies in our sample all have compact radio sources, while none of the
extended radio sources contain these amounts of extended HI. This strongly
suggests that there is a relation between the size of the radio jet and the
presence of large amounts of neutral gas associated with the host galaxy.


title:
Evidence for surface cooling emission in the XMM-Newton spectrum of the
  X-ray pulsar PSR B2334+61

abstract:
  We report on the first XMM-Newton observation of the Vela-like pulsar PSR
B2334+61. Spectral analysis reveals soft X-ray emission, with the bulk of the
photons emitted at energies below ~1.5 keV. We find that the spectrum has a
thermal origin and is well-fitted with either a blackbody or a magnetized, pure
H atmospheric model. In the latter case, for a neutron star with a radius of 13
km and a magnetic field of 10e13 G, the best-fit gives an hydrogen column
density nH = 0.33 x 10^22 cm^-2 and an effective temperature T_eff^infinity =
0.65 x 10^6 K, as measured at Earth. A comparison of the surface temperature of
PSR B2334+61 obtained from this fit with cooling curves favor a medium mass
neutron star with M ~ 1.45 solar masses or M ~ 1.6 solar masses, depending on
two different models of proton superfluidity in the interior. We do not detect
any pulsed emission from the source, and determine an upper limit of 5% for the
modulation amplitude of the emission on the pulsar's radio frequency.


title: A relativistic model of the radio jets in NGC 315

abstract:
  We apply our intrinsically symmetrical, decelerating relativistic jet model
to deep VLA imaging of the inner 140 arcsec of the giant low-luminosity radio
galaxy NGC 315. An optimized model accurately fits the data in both total
intensity and linear polarization. We infer that the velocity, emissivity and
field structure in NGC 315 are very similar to those of the other
low-luminosity sources we have modelled, but that all of the physical scales
are larger by a factor of about 5. We derive an inclination to the line of
sight of 38 degrees for the jets. Where they first brighten, their on-axis
velocity is approximately v/c = 0.9. They decelerate to v/c = 0.4 between 8 and
18 kpc from the nucleus and the velocity thereafter remains constant. The speed
at the edge of the jet is roughly 0.6 of the on-axis value where it is best
constrained, but the transverse velocity profile may deviate systematically
from the Gaussian form we assume. The proper emissivity profile is split into
three power-law regions separated by shorter transition zones. In the first of
these, at 3 kpc (the flaring point) the jets expand rapidly at constant
emissivity, leading to a large increase in the observed brightness on the
approaching side. At 10 kpc, the emissivity drops abruptly by a factor of 2.
Where the jets are well resolved their rest-frame emission is
centre-brightened. The magnetic field is modelled as random on small scales but
anisotropic and we rule out a globally ordered helical configuration. To a
first approximation, the field evolves from a mixture of longitudinal and
toroidal components to predominantly toroidal, but it also shows variations in
structure along and across the jets, with a significant radial component in
places. Simple adiabatic models fail to fit the emissivity variations.


title:
Detecting gamma-ray bursts with the Pierre Auger Observatory using the
  single particle technique

abstract:
  During the past ten years, gamma-ray bursts (GRB) have been extensively
studied in the keV-MeV energy range but the high energy emission still remain
mysterious. Ground based observatories have the possibility to investigate
energy range around one GeV using the "single particle technique". The aim of
the present study is to investigate the capability of the Pierre Auger
Observatory to detect the high energy emission of GRBs with such a technique.
According to the detector response to photon showers around one GeV, and making
reasonable assumptions about the high energy emission of GRBs, we show that the
Pierre Auger Observatory is a competitive instrument for this technique, and
that water tanks are very promising detectors for the single particle
technique.


title: Statistics of Neutron Stars at the Stage of Supersonic Propeller

abstract:
  We analyze the statistical distribution of neutron stars at the stage of a
supersonic propeller. An important point of our analysis is allowance for the
evolution of the angle of inclination of the magnetic axis to the spin axis of
the neutron star for the boundary of the transition to the supersonic propeller
stage for two models: the model with hindered particle escape from the stellar
surface and the model with free particle escape. As a result, we have shown
that a consistent allowance for the evolution of the inclination angle in the
region of extinct radio pulsars for the two models leads to an increase in the
total number of neutron stars at the supersonic propeller stage. This increase
stems from he fact that when allowing for the evolution of the inclination
angle $\chi$ for neutron stars in the region of extinct radio pulsars and,
hence, for the boundary of the transition to the propeller stage, this
transition is possible at shorter spin periods (P~5-10 s) than assumed in the
standard model.


title:
An Observational Pursuit for Population III Stars in a Ly_alpha Emitter
  at z=6.33 through HeII Emission

abstract:
  We present a very deep near-infrared spectroscopic observation of a strong
Ly_alpha emitter at z=6.33, SDF J132440.6+273607, which we used to search for
HeII 1640. This emission line is expected if the target hosts a significant
number of population III stars. Even after 42 ksec of integration with the
Subaru/OHS spectrograph, no emission-line features are detected in the JH band,
which confirms that SDF J132440.6+273607 is neither an active galactic nucleus
nor a low-$z$ emission-line object. We obtained a 2sigma upper-limit of
9.06e-18 ergs/s/cm^2 on the HeII 1640 emission line flux, which corresponds to
a luminosity of 4.11e42 ergs/s. This upper-limit on the HeII 1640 luminosity
implies that the upper limit on population III star-formation rate is in the
range 4.9--41.2 M_sun/yr if population III stars suffer no mass loss, and in
the range 1.8--13.2 M_sun/yr if strong mass loss is present. The non-detection
of HeII in SDF J132440.6+273607 at z=6.33 may thus disfavor weak feedback
models for population III stars.


title: Superbursts from Strange Stars

abstract:
  Recent models of carbon ignition on accreting neutron stars predict
superburst ignition depths that are an order of magnitude larger than observed.
We explore a possible solution to this problem, that the compact stars in low
mass X-ray binaries that have shown superbursts are in fact strange stars with
a crust of normal matter. We calculate the properties of superbursts on strange
stars, and the resulting constraints on the properties of strange quark matter.
We show that the observed ignition conditions exclude fast neutrino emission in
the quark core, for example by the direct Urca process, which implies that
strange quark matter at stellar densities should be in a color superconducting
state. For slow neutrino emission in the quark matter core, we find that
reproducing superburst properties requires a definite relation between three
poorly constrained properties of strange quark matter: its thermal
conductivity, its slow neutrino emissivity and the energy released by
converting a nucleon into strange quark matter.


title: Ten milliparsec-scale structure of the nucleus region in Centaurus A

abstract:
  We present the results of a VLBI Space Observatory Programme (VSOP)
observation of the subparsec structure in Centaurus A at 4.9 GHz. Owing to its
proximity, our Centaurus A space-VLBI image is one of the highest spatial
resolution images of an AGN ever made -- 0.01 pc per beam. The elongated core
region is resolved into several components over 10 milli-arcseconds long (0.2
pc) including a compact component of brightness temperature 2.2x10^10K. We
analyze the jet geometry in terms of collimation. Assuming the strongest
component to be the core, the jet opening angle at ~ 5,000 r_s (Schwarzchild
radii) from the core is estimated to be ~ 12 degree, with collimation of the
jet to ~ 3 degree continuing out to ~ 20,000 r_s. This result is consistent
with previous studies of the jet in M87, which favor MHD disk outflow models.
Future space VLBI observations at higher frequencies will probably be able to
image the collimation region, within 1,000 r_s of the center of Centaurus A,
together with the accretion disk itself.


title:
H$_2$O maser emission from bright rimmed clouds in the northern
  hemisphere

abstract:
  We report the results of a multi-epoch survey of water maser observations at
22.2 GHz with the Medicina radiotelescope from 44 bright rimmed clouds (BRCs)
of the northern hemisphere identified by Sugitani et al. (1989) as potential
sites of star formation. The data span 16 years of observations and allow to
draw conclusions about the maser detection rate in this class of objects. In
spite of the relatively high far-infrared luminosities of the embedded sources
($L_{\rm FIR}\ga 10^2$ L$_\odot$), H$_2$O maser emission was detected towards
three globules only. Since the occurrence of water masers is higher towards
bright IRAS sources, the lack of frequent H$_2$O maser emission is somewhat
surprising if the suggestion of induced intermediate- and high-mass star
formation within these globules is correct. The maser properties of two BRCs
are characteristic of exciting sources of low-mass, while the last one (BRC~38)
is consistent with an intermediate-mass object. We argue that most BRCs host
young stellar objects of low-luminosity, likely in an evolutionary phase later
than the protostellar Class 0 sources, and that a significant contribution to
the observd IRAS luminosity comes from warm dust heated by the radiation from
the bright rim.


title:
The clustering of the luminosities of optical afterglows of long Gamma
  Ray Bursts

abstract:
  We studied the optical afterglows of the 24 pre-Swift Gamma-Ray Bursts with
known spectroscopic redshift and published estimates of the optical extinction
in the source frame. We find an unexpected clustering of the optical afterglow
luminosities measured 12 hours (source frame time) after the trigger. For 21
out of 24 bursts, the distribution of the optical luminosities is narrower than
the distribution of the X-ray luminosities, and even narrower than the
distribution of the ratio between the monochromatic optical luminosities and
the total isotropic emitted prompt energy. Three bursts stand apart from the
distribution of the other sources, being underluminous by a factor ~15. We
compare this result with the somewhat analogous result concerning the
luminosity of the X-ray afterglows studied by Gendre & Boer. For all our GRBs
we construct the optical to X-ray spectral energy distribution. For all but a
minority of them, the optical and the X-ray emissions are consistent with being
produced by the same radiation process. We discuss our results in the framework
of the "standard" external shock synchrotron model. Finally, we consider the
behavior of the first GRBs of known redshifts detected by Swift. We find that
these Swift GRBs entirely confirm our findings.


title: Wolf-Rayet and O Star Runaway Populations from Supernovae

abstract:
  We present numerical simulations of the runaway fractions expected amongst O
and Wolf-Rayet star populations resulting from stars ejected from binaries by
the supernova of the companion. Observationally the runaway fraction for both
types of star is similar, prompting the explanation that close dynamical
interactions are the main cause of these high-velocity stars. We show that,
provided that the initial binary fraction is high, a scenario in which
two-thirds of massive runaways are from supernovae is consistent with these
observations. Our models also predict a low frequency of runaways with neutron
star companions and a very low fraction of observable Wolf-Rayet--compact
companion systems.


title:
Stellar Model Analysis of the Oscillation Spectrum of eta Bootis
  Obtained from MOST

abstract:
  Eight consecutive low-frequency radial p-modes are identified in the G0 IV
star eta Bootis based on 27 days of ultraprecise rapid photometry obtained by
the MOST (Microvariability & Oscillations of Stars) satellite. The MOST data
extend smoothly to lower overtones the sequence of radial p-modes reported in
earlier groundbased spectroscopy by other groups. The lower-overtone modes from
the MOST data constrain the interior structure of the model of eta Boo. With
the interior fit anchored by the lower-overtone modes seen by MOST, standard
models are not able to fit the higher-overtone modes with the same level of
accuracy. The discrepancy is similar to the discrepancy that exists between the
Sun's observed p-mode frequencies and the p-mode frequencies of the standard
solar model. This discrepancy promises to be a powerful constraint on models of
3D convection.


title: Evidence for a Cosmological Phase Transition on the TeV Scale

abstract:
  Examining the reverse evolution of the universe from the present, long before
reaching Planck density dynamics one expects major modifications from the
de-coherent thermal equations of state, suggesting a prior phase that has
macroscopic coherence properties. The assumption that the phase transition
occurs during the radiation dominated epoch, and that zero-point motions drive
the fluctuations associated with this transition, specifies a class of
cosmological models in which the cosmic microwave background fluctuation
amplitude at last scattering is approximately $10^{-5}$. Quantum measurability
constraints (eg. uncertainly relations) define cosmological scales whose
expansion rates can be at most luminal. Examination of these constraints for
the observed dark energy density establishes a time interval from the
transition to the present. It is shown that the dark energy can consistently be
interpreted as due to the vacuum energy of collective gravitational modes which
manifest as the zero-point motions of coherent Planck scale mass units prior to
the gravitational quantum de-coherence of the cosmology. A scenario is
suggested that connects microscopic physics to the relevant cosmological scale.


title: The BeppoSAX view on the galactic high-mass X-ray binary 4U 0114+65

abstract:
  A pointed observation on the galactic high-mass X-ray binary 4U 0114+65 was
carried out with BeppoSAX in order to compare the X-ray spectral and timing
characteristics observed by this satellite over the broadest range of energies
ever (1.5-100 keV) with the information previously obtained with other
spacecraft. The light curve of 4U 0114+65 shows a large flare at the beginning
of the BeppoSAX pointing and no significant hardness evolution either during
the flare or in the low state occurring after the flare itself. The modulation
at about 2.7 hours, attributed to the accreting neutron star (NS) spin
periodicity, is not significantly detected in our data, although fluctuations
with timescales of about 3 hours can be seen in the 2-10 keV light curve.
Shorter modulations down to timescales of minutes, are also found and
interpreted as due to accretion of matter onto the NS. The flaring and the low
state spectra of 4U 0114+65 can be equally well fitted either with a power law
modulated by a high-energy exponential cutoff or with a Comptonization model.
During the low state the presence, although tentative, of a thermal component
(with kT around 0.3 keV) at low energies, possibly produced by an ionized
plasma cloud around the NS, cannot be excluded. Contrary to previous claims, a
cyclotron resonant feature in absorption at about 22 keV was not detected in
the BeppoSAX spectroscopic data, whereas evidence for a Fe emission line around
6.4 keV is found only during the low state emission. Using all of the above
information, a scenario for the system in which the NS is embedded in, and
accreting from, a low angular momentum gas cloud is envisaged.


title:
Dust distribution in protoplanetary disks - Vertical settling and radial
  migration

abstract:
  We present the results of a three dimensional, locally isothermal,
non-self-gravitating SPH code which models protoplanetary disks with two
fluids: gas and dust. We ran simulations of a 1 Msun star surrounded by a 0.01
Msun disk comprising 99% gas and 1% dust in mass and extending from 0.5 to ~300
AU. The grain size ranges from 0.001 mm to 10 m for the low resolution (~25 000
SPH particles) simulations and from 0.1 mm to 10 cm for the high resolution
(~160 000 SPH particles) simulations. Dust grains are slowed down by the
sub-Keplerian gas and lose angular momentum, forcing them to migrate towards
the central star and settle to the midplane. The gas drag efficiency varies
according to the grain size, with the larger bodies being weakly influenced and
following marginally perturbed Keplerian orbits, while smaller grains are
strongly coupled to the gas. For intermediate sized grains, the drag force
decouples the dust and gas, allowing the dust to preferentially migrate
radially and efficiently settle to the midplane. The resulting dust
distributions for each grain size will indicate, when grain growth is added,
the regions when planets are likely to form.


title: Tycho 2 stars with infrared excess in the MSX Point Source Catalogue

abstract:
  Stars of all evolutionary phases have been found to have excess infrared
emission due to the presence of circumstellar material. To identify such stars,
we have positionally correlated the infrared MSX point source catalogue and the
Tycho 2 optical catalogue. A near/mid infrared colour criteria has been
developed to select infrared excess stars. The search yielded 1938 excess
stars, over half (979) have never previously been detected by IRAS. The excess
stars were found to be young objects such as Herbig Ae/Be and Be stars, and
evolved objects such as OH/IR and carbon stars. A number of B type excess stars
were also discovered whose infrared colours could not be readily explained by
known catalogued objects.


title:
The 7Be(d,p)2alpha cross section at Big Bang energies and the primordial
  7Li abundance

abstract:
  The WMAP satellite, devoted to the observations of the anisotropies of the
Cosmic Microwave Background (CMB) radiation, has recently provided a
determination of the baryonic density of the Universe with unprecedented
precision. Using this, Big Bang Nucleosynthesis (BBN) calculations predict a
primordial 7Li abundance which is a factor 2-3 higher than that observed in
galactic halo dwarf stars. It has been argued that this discrepancy could be
resolved if the 7Be(d,p)2alpha reaction rate is around a factor of 100 larger
than has previously been considered. We have now studied this reaction, for the
first time at energies appropriate to the Big Bang environment, at the CYCLONE
radioactive beam facility at Louvain-la-Neuve. The cross section was found to
be a factor of 10 smaller than derived from earlier measurements. It is
concluded therefore that nuclear uncertainties cannot explain the discrepancy
between observed and predicted primordial 7Li abundances, and an alternative
astrophysical solution must be investigated.


title:
Stellar Evolution with Rotation and Magnetic Fields IV: The Solar
  Rotation Profile

abstract:
  We examine the generation of a magnetic field in a solar-like star and its
effects on the internal distribution of the angular velocity. We suggest that
the evolution of a rotating star with magnetic fields leads to an equilibrium
value of the differential rotation. This equilibrium is determined by the
magnetic coupling, which favours a constant rotation profile, and meridional
circulation which tends to build differential rotation. The global equilibrium
stage is close to solid body rotation between about 0.7 and 0.2 R_sun, in good
agreement with helioseismic measurements.


title:
Morphological Studies of the SWIRE Galaxy Population in the UGC 10214
  HST/ACS field

abstract:
  We present results of a morphological analysis of a small subset of the
Spitzer Wide-area InfraRed Extragalactic survey (SWIRE) galaxy population. The
analysis is based on public ACS data taken inside the SWIRE N1 field, which are
the deepest optical high-resolution imaging available within the SWIRE fields
as of today. Our reference sample includes 156 galaxies detected by both ACS
and SWIRE. Among the various galaxy morphologies, we disentangle two main
classes, spheroids (or bulge-dominated galaxies) and disk-dominated ones, for
which we compute the number counts as a function of flux. We then limit our
sample to objects with IRAC fluxes brighter than 10 microJy, estimated ~90%
completeness limit of the SWIRE catalogues, and compare the observed counts to
model predictions. We find that the observed counts of the spheroidal
population agree with the expectations of a hierarchical model while a
monolithic scenario predicts steeper counts. Both scenaria, however,
under-predict the number of late-type galaxies. These observations show that
the large majority (close to 80 per cent) of the 3.6 and 4.5 micron galaxy
population, even at these moderately faint fluxes, is dominated by spiral and
irregular galaxies or mergers.


title: The Proper Motion of the Large Magellanic Cloud using HST

abstract:
  We present a measurement of the systemic proper motion of the Large
Magellanic Cloud (LMC) from astrometry with the High Resolution Camera (HRC) of
the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). We
observed LMC fields centered on 21 background QSOs that were discovered from
their optical variability in the MACHO database. The QSOs are distributed
homogeneously behind the central few degrees of the LMC. With 2 epochs of HRC
data and a ~2 year baseline we determine the proper motion of the LMC to better
than 5% accuracy: mu_W = -2.03 +/- 0.08 mas/yr; mu_N = 0.44 +/- 0.05 mas/yr.
This is the most accurate proper motion measurement for any Milky Way satellite
thus far. When combined with HI data from the Magellanic Stream this should
provide new constraints on both the mass distribution of the Galactic Halo and
models of the Stream.


title: Massive Protostars in the Infrared Dark Cloud MSXDC G034.43+00.24

abstract:
  We present a multiwavelength study of the infrared dark cloud MSXDC
G034.43+00.24. Dust emission, traced by millimeter/submillimeter images
obtained with the IRAM, JCMT, and CSO telescopes, reveals three compact cores
within this infrared dark cloud with masses of 170--800 Msun and sizes < 0.5
pc. Spitzer 3.6-8.0 um images show slightly extended emission toward these
cores, with a spectral enhancement at 4.5 um that probably arises from shocked
H2. In addition, the broad line widths (Delta V ~ 10 km/s) of HCN (4-3), and CS
(3-2), and the detection of SiO (2-1), observed with the JCMT and IRAM
telescopes, also indicate active star formation. Spitzer 24 um images reveal
that each of these cores contains a bright, unresolved continuum source; these
sources are most likely embedded protostars. Their millimeter to mid-IR
continuum spectral energy distributions reveal very high luminosities,
9000-32,000 Lsun. Because such large luminosities cannot arise from low-mass
protostars, MSXDC G034.43+00.24 is actively forming massive (~ 10 Msun) stars.


title: Gravitational Radiation from Primordial Helical Turbulence

abstract:
  In present talk I show that primordial helical turbulence produced during a
first-order phase transition induces circularly polarized cosmological
gravitational waves (GWs). The degree of polarization as well as the
characteristic frequency and the amplitude of these GWs depend crucially on
phase-transition model of primordial turbulence. I present a brief discussion
on the possibility of detection.


title: Structural Parameters of Thin and Thick Disks in Edge-On Disk Galaxies

abstract:
  We analyze the global structure of 34 late-type, edge-on, undisturbed, disk
galaxies spanning a wide range of mass. We measure structural parameters for
the galaxies using two-dimensional least-squares fitting to our $R$-band
photometry. The fits require both a thick and a thin disk to adequately fit the
data. The thick disks have larger scale heights and longer scale lengths than
the embedded thin disks, by factors of ~2 and ~1.25, respectively. The observed
structural parameters agree well with the properties of thick and thin disks
derived from star counts in the Milky Way and from resolved stellar populations
in nearby galaxies. We find that massive galaxies' luminosities are dominated
by the thin disk. However, in low mass galaxies (Vc < 120 km/s), thick disk
stars contribute nearly half of the luminosity and dominate the stellar mass.
Thus, although low mass dwarf galaxies appear blue, the majority of their stars
are probably quite old.
  Our data are most easily explained by a formation scenario where the thick
disk is assembled through direct accretion of stellar material from merging
satellites while the thin disk is formed from accreted gas. The baryonic
fraction in the thin disk therefore constrains the gas-richness of the merging
pre-galactic fragments. If we include the mass in HI as part of the thin disk,
the thick disk contains <10% of the baryons in high mass galaxies, and ~25-30%
of the baryons in low-mass galaxies. We discuss how our trends can be explained
by supernova-driven outflow at early times as well as the possibilities for
predicting abundance trends in thick disks, and for removing discrepancies
between semi-analytic galaxy formation models and the observed colors of low
mass galaxies. (abstract abridged)


title: A Nested Sampling Algorithm for Cosmological Model Selection

abstract:
  The abundance of new cosmological data becoming available means that a wider
range of cosmological models are testable than ever before. However, an
important distinction must be made between parameter fitting and model
selection. While parameter fitting simply determines how well a model fits the
data, model selection statistics, such as the Bayesian Evidence, are now
necessary to choose between these different models, and in particular to assess
the need for new parameters. We implement a new evidence algorithm known as
nested sampling, which combines accuracy, generality of application and
computational feasibility, and apply it to some cosmological datasets and
models. We find that a five-parameter model with Harrison-Zel'dovich initial
spectrum is currently preferred.


title: The Spin Periods and Rotational Profiles of Neutron Stars at Birth

abstract:
  We present results from an extensive set of one- and two-dimensional
radiation-hydrodynamic simulations of the supernova core collapse, bounce, and
postbounce phases, and focus on the protoneutron star (PNS) spin periods and
rotational profiles as a function of initial iron core angular velocity, degree
of differential rotation, and progenitor mass. For the models considered, we
find a roughly linear mapping between initial iron core rotation rate and PNS
spin. The results indicate that the magnitude of the precollapse iron core
angular velocities is the single most important factor in determining the PNS
spin. Differences in progenitor mass and degree of differential rotation lead
only to small variations in the PNS rotational period and profile. Based on our
calculated PNS spins, at ~ 200-300 milliseconds after bounce, and assuming
angular momentum conservation, we estimate final neutron star rotation periods.
We find periods of one millisecond and shorter for initial central iron core
periods of below ~ 10 s. This is appreciably shorter than what previous studies
have predicted and is in disagreement with current observational data from
pulsar astronomy. After considering possible spindown mechanisms that could
lead to longer periods we conclude that there is no mechanism that can robustly
spin down a neutron star from ~ 1 ms periods to the "injection" periods of tens
to hundreds of milliseconds observed for young pulsars. Our results indicate
that, given current knowledge of the limitations of neutron star spindown
mechanisms, precollapse iron cores must rotate with periods around 50-100
seconds to form neutron stars with periods generically near those inferred for
the radio pulsar population.


title: Deriving the mass distribution of M87 from globular clusters

abstract:
  We describe a maximum-likelihood method for determining the mass distribution
in spherical stellar systems from the radial velocities of a population of
discrete test particles. The method assumes a parametric form for the mass
distribution and a non-parametric two-integral distribution function. We apply
the method to a sample of 161 globular clusters in M87. We find that the mass
within 32 kpc is $(2.4\pm0.6)\times 10^{12} $M${_\odot}$, and the exponent of
the density profile $\rho\propto r^{-\alpha}$ in the range 10-100 kpc is
$\alpha=1.6\pm0.4$.The energy distribution suggests a few kinematically
distinct groups of globular clusters. The anisotropy of the globular-cluster
velocity distribution cannot be determined reliably with the present data.
Models fitted to an NFW potential yield similar mass estimates but cannot
constrain the concentration radius $r_c$ in the range 10-500 kpc.


title:
Weibel Filament Decay and Thermalization in Collisionless Shocks and
  Gamma-Ray Burst Afterglows

abstract:
  Models for the synchrotron emission of gamma-ray burst afterglows suggest
that the magnetic field is generated in the shock wave that forms as
relativistic ejecta plow through the circum-burst medium. Transverse Weibel
instability efficiently generates magnetic fields near equipartition with the
post-shock energy density. The detailed saturated state of the instability, as
seen in particle-in-cell simulations, consists of magnetically self-pinched
current filaments. The filaments are parallel to the direction of propagation
of the shock and are about a plasma skin depth in radius, forming a
quasi--two-dimensional structure. We use a rudimentary analytical model to
argue that the Weibel filaments are unstable to a kink-like mode, which
destroys their quasi--two-dimensional structure. For wavelengths longer than
than the skin depth, the instability grows at the rate equal to the speed of
light divided by the wavelength. We calculate the transport of collisionless
test particles in the filaments experiencing the instability and show that the
particles diffuse in energy. This diffusion marks the beginning of
thermalization in the shock transition layer, and causes initial magnetic field
decay as particles escape from the filaments. We discuss the implications of
these results for the structure of the shock and the polarization of the
afterglow.


title:
Extragalactic cosmic-ray source composition and the interpretation of
  the ankle

abstract:
  We consider the stochastic propagation of high-energy protons and nuclei in
the cosmological microwave and infrared backgrounds, using revised photonuclear
cross-sections and following primary and secondary nuclei in the full 2D
nuclear chart. We confirm earlier results showing that the high-energy data can
be fit with a pure proton extragalactic cosmic ray (EGCR) component if the
source spectrum is $\propto E^{-2.6}$. In this case the ankle in the cosmic ray
(CR) spectrum may be interpreted as a pair-production dip associated with the
propagation. We show that when heavier nuclei are included in the source with a
composition similar to that of Galactic cosmic-rays (GCRs), the pair-production
dip is not present unless the proton fraction is higher than 85%. In the mixed
composition case, the ankle recovers the past interpretation as the transition
from GCRs to EGCRs and the highest energy data can be explained by a harder
source spectrum $\propto E^{-2.2}$-- $E^{-2.3}$, reminiscent of relativistic
shock acceleration predictions, and in good agreement with the GCR data at
low-energy and holistic scenarios. While the expected cosmogenic neutrino
fluxes at high energy are very similar for pure proton and mixed composition
hypothesis, the two scenarii predict very different elongation rates from
$10^{17.5}$ to $10^{20}$ eV.