title:
Gravitino, Axino, Kaluza-Klein Graviton Warm and Mixed Dark Matter and
  Reionisation

abstract:
  Stable particle dark matter may well originate during the decay of long-lived
relic particles, as recently extensively examined in the cases of the axino,
gravitino, and higher-dimensional Kaluza-Klein (KK) graviton. It is shown that
in much of the viable parameter space such dark matter emerges naturally
warm/hot or mixed. In particular, decay produced gravitinos (KK-gravitons) may
only be considered cold for the mass of the decaying particle in the several
TeV range, unless the decaying particle and the dark matter particle are almost
degenerate. Such dark matter candidates are thus subject to a host of
cosmological constraints on warm and mixed dark matter, such as limits from a
proper reionisation of the Universe, the Lyman-alpha forest, and the abundance
of clusters of galaxies.. It is shown that constraints from an early
reionsation epoch, such as indicated by recent observations, may potentially
limit such warm/hot components to contribute only a very small fraction to the
dark matter.


title:
Interactions of ultrahigh-energy cosmic rays with photons in the
  galactic center

abstract:
  Ultrahigh-energy cosmic rays passing through the central region of the Galaxy
interact with starlight and the infrared photons. Both nuclei and protons
generate secondary fluxes of photons and neutrinos on their passage through the
central region. We compute the fluxes of these secondary particles, the
observations of which can be used to improve one's understanding of origin and
composition of ultrahigh-energy comic rays, especially if the violation of the
Greisen--Zatespin--Kuzmin cutoff is confirmed by the future data.


title:
Star Formation Rates in Cooling Flow Clusters: A UV Pilot Study with
  Archival XMM-Newton Optical Monitor Data

abstract:
  We have analyzed XMM-Newton Optical Monitor (OM) UV (180-400 nm) data for a
sample of 33 galaxies, of which 30 are cluster members. Nine of these are
central cluster galaxies (CCGs) in cooling flow clusters, having mass
deposition rates which span a range of 8 to 525 solar masses per year. Using
the ratio of UV to 2MASS J band flux, we find a significant UV excess in many,
but not all, cooling flow CCGs. This UV excess is a direct indication of the
presence of young massive stars, and therefore recent star formation, in these
galaxies. Using the Starburst99 spectral energy distribution (SED) model of
continuous star formation over a 900 Myr period, we derive star formation rates
of 0.2 to 219 solar masses per year for the cooling flow sample. For 2/3 of
this sample it is possible to equate Chandra/XMM cooling flow mass deposition
rates with UV inferred star formation rates, for a combination of starburst
lifetime and IMF slope. This is a pilot study of the well populated XMM UV
cluster archive and a more extensive follow up study is currently underway.


title:
Induced two-photon decay of the 2s level and the rate of cosmological
  hydrogen recombination

abstract:
  Induced emission due to the presence of soft CMB photons slightly increases
the two-photon decay rate of the 2s level of hydrogen defining the rate of
cosmological recombination. This correspondingly changes the degree of
ionization, the visibility function and the resulting primordial temperature
anisotropies and polarization of the CMB on the percent level. These changes
exceed the precision of the widely used CMBFAST and CAMB codes by more than one
order of magnitude and can be easily taken into account.


title: Optimized Data Loading for a Multi-Terabyte Sky Survey Repository

abstract:
  Advanced instruments in a variety of scientific domains are collecting
massive amounts of data that must be post-processed and organized to support
scientific research activities. Astronomers have been pioneers in the use of
databases to host highly structured repositories of sky survey data. As more
powerful telescopes come online, the increased volume and complexity of the
data collected poses enormous challenges to state-of-the-art database systems
and data-loading techniques. When the data source is an instrument taking
ongoing samples, the database loading must, at a minimum, keep up with the
data-acquisition rate. These challenges are being faced not only by the
astronomy community, but also by other scientific disciplines interested in
building scalable databases to house multi-terabyte archives of complex
structured data. In this paper we present SkyLoader, our novel framework for
fast and scalable data loading that is being used to populate a multi-table,
multi-terabyte database repository for the Palomar-Quest sky survey. Our
framework consists of an efficient algorithm for bulk loading, an effective
data structure to support data integrity and proper error handling during the
loading process, support for optimized parallelism that matches the number of
concurrent loaders with the database host capabilities, and guidelines for
database and system tuning. Performance studies showing the positive effects of
the adopted strategies are also presented. Our parallel bulk loading with array
buffering technique has made fast population of a multi-terabyte repository a
reality, reducing the loading time for a 40-gigabyte data set from more than 20
hours to less than 3 hours. We believe our framework offers a promising
approach for loading other large and complex scientific databases.


title: On Rapidly Rotating Magnetic Core-Collapse Supernovae

abstract:
  We have analyzed the magnetic effects that may occur in rapidly rotating core
collapse supernovae. We consider effects from both magnetic turbulence and the
formation of magnetic bubbles. For magnetic turbulence we have made a
perturbative analysis for our spherically symmetric core-collapse supernova
model that incorporates the build up of magnetic field energy in the matter
accreting onto the proto-neutron star shortly after collapse and bounce. This
significantly modifies the pressure profile and increases the heating of the
material above the proto-neutron star resulting in an explosion even in
rotating stars that would not explode otherwise. Regarding magnetic bubbles we
show that a model with a modest initial uniform magnetic field and uniform
angular velocity of ~0.1 rad/s can form magnetic bubbles due to the very non
homologous nature of the collapse. It is estimated that the buoyancy of the
bubbles causes matter in the proto-neutron star to rise, carrying neutrino-rich
material to the neutron-star surface. This increases the neutrino luminosity
sufficiently at early times to achieve a successful neutrino-driven explosion.
Both magnetic mechanisms thus provide new means for initiating a Type II
core-collapse supernova.


title: Stellar Populations in the Local Group of Galaxies

abstract:
  The characteristics and properties of the stellar populations and
evolutionary histories of Local Group galaxies are summarized and compared to
predictions of cosmological models. No clear signature of the re-ionization
epoch is observed; in particular, there is no cessation of star formation
activity in low-mass dwarf galaxies at the end of re-ionization. Arguments
against the morphological transformation of dwarf irregular into dwarf
spheroidal galaxies are derived from their pronounced evolutionary differences
at early epochs as evidenced by the offset in the metallicity-luminosity
relation between gas-rich and gas-poor dwarfs. While there is increasing
evidence for past and ongoing accretion events the overall importance of dwarf
galaxies as building blocks remains unclear considering their differences in
modes of star formation and detailed chemistry.


title:
Analysis of variability in the burst oscillations of the accreting
  millisecond pulsar XTE J1814-338

abstract:
  The accreting millisecond pulsar XTE J1814-338 exhibits oscillations at the
known spin frequency during Type I X-ray bursts. The properties of the burst
oscillations reflect the nature of the thermal asymmetry on the stellar
surface. We present an analysis of the variability of the burst oscillations of
this source, focusing on three characteristics: fractional amplitude, harmonic
content and frequency. Fractional amplitude and harmonic content constrain the
size, shape and position of the emitting region, whilst variations in frequency
indicate motion of the emitting region on the neutron star surface. We examine
both long-term variability over the course of the outburst, and short-term
variability during the bursts. For most of the bursts, fractional amplitude is
consistent with that of the accretion pulsations, implying a low degree of fuel
spread. There is however a population of bursts whose fractional amplitudes are
substantially lower, implying a higher degree of fuel spread, possibly forced
by the explosive burning front of a precursor burst. For the first harmonic,
substantial differences between the burst and accretion pulsations suggest that
hotspot geometry is not the only mechanism giving rise to harmonic content in
the latter. Fractional amplitude variability during the bursts is low; we
cannot rule out the hypothesis that the fractional amplitude remains constant
for bursts that do not exhibit photospheric radius expansion (PRE). There are
no significant variations in frequency in any of the bursts except for the one
burst that exhibits PRE. This burst exhibits a highly significant but small
($\approx 0.1$Hz) drop in frequency in the burst rise. The timescale of the
frequency shift is slower than simple burning layer expansion models predict,
suggesting that other mechanisms may be at work.


title:
The 2MASS Wide-Field T Dwarf Search. V. Discovery of a T Dwarf via
  Methane Imaging

abstract:
  We present the discovery of a T dwarf, 2M2151-4853, via differential imaging
through methane filters. The filters are designed to highlight the strong
absorption in the H band, due to methane found in the atmospheres of T dwarfs,
and provide a very efficient means of searching for them. Subsequent J and H
band spectroscopy confirms 2M2151-4853 as a T dwarf of type T4.5. It has an
estimated spectrophotometric distance of 18 +/- 3 pc, and an estimated
tangential velocity of v=50 +/- 10 km/s.


title:
The 2MASS Wide-Field T Dwarf Search. IV Unting out T dwarfs with Methane
  Imaging

abstract:
  We present first results from a major program of methane filter photometry
for low-mass stars and brown dwarfs. The definition of a new methane filter
photometric system is described. A recipe is provided for the differential
calibration of methane imaging data using existing 2MASS photometry. We show
that these filters are effective in discriminating T dwarfs from other types of
stars, and demonstrate this with Anglo-Australian Telescope observations using
the IRIS2 imager. Methane imaging data and proper motions are presented for ten
T dwarfs identified as part of the 2MASS "Wide Field T Dwarf Search" -- seven
of them initially identified as T dwarfs using methane imaging.
  We also present near-infrared moderate resolution spectra for five T dwarfs,
newly discovered by this technique. Spectral types obtained from these spectra
are compared to those derived from both our methane filter observations, and
spectral types derived by other observers. Finally, we suggest a range of
future programs to which these filters are clearly well suited: the winnowing
of T dwarf and Y dwarf candidate objects coming from the next generation of
near-infrared sky surveys; the robust detection of candidate planetary-mass
brown dwarfs in clusters; the detection of T dwarf companions to known L and T
dwarfs via deep methane imaging; and the search for rotationally-modulated
time-variable surface features on cool brown dwarfs.


title:
CCD photometric search for peculiar stars in open clusters. VI. NGC
  1502, NGC 3105, Stock 16, NGC 6268, NGC 7235 and NGC 7510

abstract:
  In a sample of six young open clusters we investigated 1753 objects using the
narrow band, three filter Delta a photometric system resulting in the detection
of eleven bona-fide magnetic chemically peculiar (CP) stars and five Be or
metal-weak stars. The results for the distant cluster NGC 3105 is most
important because of the still unknown influence of the global metallicity
gradient of the Milky Way. These findings confirm that CP stars are present in
open clusters of very young ages (log t > 6.90) at galactocentric distances up
to 11.4 kpc. For all programme clusters the age, reddening, and distance
modulus were derived using the corresponding isochrones. Some additional
variable stars within Stock 16 could be identified by comparing different
photometric studies.


title: Neutrinos from Supernovas and Supernova Remnants

abstract:
  Supernovae (SN) and supernova remnants (SNR) have key roles in galaxies, but
their physical descriptions is still incomplete. Thus, it is of interest to
study neutrino radiation to understand SN and SNR better. We will discuss: (1)
The ~10 MeV thermal neutrinos that arise from core collapse SN, that were
observed for SN1987A, and can be seen with several existing or planned
experiments. (2) The 10-100 TeV neutrinos expected from galactic SNR (in
particular from RX J1713.7-3946) targets of future underwater neutrino
telescopes.


title: A Dark Galaxy in the Virgo Cluster Imaged at 21-cm

abstract:
  Dark Matter supposedly dominates the extragalactic, yet no totally dark
structure of galactic proportions has ever been convincingly identified.
Earlier (Minchin et al. 2005) we suggested that VIRGOHI 21, a 21-cm source we
found in the Virgo Cluster at Jodrell Bank using single-dish observations
(Davies et al. 2004), was probably such a dark galaxy because of its broad
line-width (~ 200 km/s) unaccompanied by any visible gravitational source to
account for it. Now we have managed to image VIRGOHI 21 in the neutral-hydrogen
line, and indeed we find what appears to be a dark, edge-on, spinning disc with
the mass and diameter of a typical spiral galaxy. Moreover the disc has
unquestionably interacted with NGC 4254, a luminous spiral with an odd
one-armed morphology, but lacking the massive interactor invariably responsible
for such a feature. Published numerical models (Vollmer, Huchtmeier & van Driel
2005) of NGC 4254 call for a close interaction ~ 10^8 years ago with a
perturber of 10^11 solar masses. This we take as completely independent
evidence for the massive nature of VIRGOHI 21.


title: First detection of dust emission in a High-Velocity Cloud

abstract:
  By comparing sensitive Spitzer Space Telescope (SST) infrared and Green Bank
Telescope 21 cm observations, we are able to report the first detection of dust
emission in Complex C, the largest High Velocity Cloud in the sky. Dust in the
region of Complex C studied here has a colder temperature
($T=10.7^{+0.9}_{-0.8}$ K - 1$\sigma$) than the local interstellar medium
($T=17.5$ K), in accordance with its great distance from the Galactic plane.
Based on the metallicity measurements and assuming diffuse Galactic
interstellar medium dust properties and dust/metals ratio, this detection could
imply gas column densities more than 5 times higher than observed in HI. We
suggest that the dust emission detected here comes from small molecular clumps,
spatially correlated with the HI but with a low surface filling factor. Our
findings imply that the HVCs' mass would be much larger than inferred from HI
observations and that most of the gas falling on the Milky Way would be in cold
and dense clumps rather than in a diffuse phase.


title:
A hard X-ray survey of the Crux Galactic spiral arm tangent. A catalog
  of sources

abstract:
  This work is part of a large solid angle hard X-ray survey. We analized a
number of observations by the IBIS telescope aboard the INTEGRAL observatory
covering the Crux Galactic spiral arm tangent. We have detected 46 hard X-ray
sources, with 15 of them being new. Among the identified sources there are 12
AGNs, 11 HMXBs, 6 LMXBs and 2 active stars. 13 sources remain unidendified.


title: Cosmological structure formation in a homogeneous dark energy background

abstract:
  There is now strong evidence that the current energy density of the Universe
is dominated by dark energy with an equation of state w<-1/3, which is causing
accelerated expansion. The build-up of structure within such Universes is
subject to significant ongoing study, particularly through the spherical
collapse model. This paper aims to review and consolidate progress for
cosmologies in which the dark energy component remains homogeneous on the
scales of the structures being modelled. The equations presented are designed
to allow for dark energy with a general time-varying equation of state w(a). In
addition to reviewing previous work, a number of new results are introduced: A
new fitting formula for the linear growth factor in constant w cosmologies is
given. A new formalism for determining the critical density for collapse is
presented based on the initial curvature of the perturbation. The commonly used
approximation to the critical density for collapse based on the linear growth
factor is discussed for a general dark energy equation of state. Virialisation
within such cosmologies is also considered, and the standard assumption that
energy is conserved between turn-around and virialisation is questioned and
limiting possiblities are presented.


title: Are WC9 Wolf-Rayet stars in colliding-wind binaries?

abstract:
  We present results from a spectroscopic search for massive companions to
dust-making Galactic WC9 stars as a step to testing the paradigm that dust
formation in these systems requires colliding winds to produce over densities.
We find evidence for OB companions to the WC9 stars WR 59 and WR 65, but not WR
121 or WR 117. We identify lines of N III-V and possibly N II in the spectrum
of WR 88, one of the few Galactic WC9 stars which do not make circumstellar
dust, and suggest that WR 88 is a transitional WN-WC9 object and less evolved
than the other WC9 stars. On the other hand, the possible identification of a
strong emission line at 4176A in the spectrum of WR 117 with Ne I suggests that
this star is more evolved than other WC9 stars studied.


title:
Star Formation and AGN in the Core of the Shapley Supercluster: A VLA
  Survey of A3556, A3558, SC1327-312, SC1329-313, and A3562

abstract:
  The core of the Shapley supercluster (A3556, A3558, SC1327-312, SC1329-313,
and A3562) is an ideal region in which to study the effects of cluster mergers
on the activity of individual galaxies. This paper presents the most
comprehensive radio continuum investigation of the region, relying on a
63-pointing mosaic obtained with the Very Large Array yielding an areal
coverage of nearly 7 square degrees. The mosaic provides a typical sensitivity
of about 80 uJy at a resolution of 16", enabling detection of galaxies with
star formation rates as low as 1 solar mass per year. The radio data are
complemented by optical imaging in B and R, producing a catalog of 210
radio-detected galaxies with m_R <= 17.36 (M_R <= -19). At least 104 of these
radio-detected galaxies are members of the supercluster on the basis of public
velocity measurements. Across the entire core of the supercluster, there
appears to be a significant deficit of radio galaxies at intermediate optical
magnitudes (M_R between -21 and -22). This deficit is offset somewhat by an
increase in the frequency with which brighter galaxies (M_R less than -22) host
radio sources. More dramatic is the highly significant increase in the
probability for fainter galaxies (M_R between -20 and -21) in the vicinity of
A3562 and SC1329-313 to be associated with radio emission. The radio and
optical data for these sources strongly suggest that these active galaxies are
powered by star formation. In conjunction with recent X-ray analysis, this is
interpreted as young starbursts related to the recent merger of SC1329-313 with
A3562 and the rest of the supercluster.


title: X-ray observations of Clusters of Galaxies

abstract:
  X-ray observations of clusters provide key information on the dark matter, on
the formation of structures in the Universe, and can be used to constrain the
cosmological parameters. I review our current knowledge, with emphasis on
recent XMM and Chandra results.


title: Scalelengths in Dark Matter Halos

abstract:
  We investigate a hypothesis regarding the origin of the scalelength in halos
formed in cosmological N-body simulations. This hypothesis can be viewed as an
extension of an earlier idea put forth by Merritt and Aguilar. Our findings
suggest that a phenomenon related to the radial orbit instability is present in
such halos and is responsible for density profile shapes. This instability sets
a scalelength at which the velocity dispersion distribution changes rapidly
from isotropic to radially anisotropic. This scalelength is reflected in the
density distribution as the radius at which the density profile changes slope.
We have tested the idea that radially dependent velocity dispersion anisotropy
leads to a break in density profile shape by manipulating the input of a
semi-analytic model to imitate the velocity structure imposed by the radial
orbit instability. Without such manipulation, halos formed are approximated by
single power-law density profiles and isotropic velocity distributions. Halos
formed with altered inputs display density distributions featuring scalelengths
and anisotropy profiles similar to those seen in cosmological N-body
simulations.


title:
The dynamical influence of cooling in the envelope of prestellar and
  protostellar cores

abstract:
  We compute numerical simulations of spherical collapse triggered by a slow
increase in external pressure. We compare isothermal models to models including
cooling with a simple but self-consistent treatment of the coupling between
gas, grains and radiation field temperatures. The hydrostatic equilibrium
appears to hold past the marginally stable state, until the collapse proceeds.
The last hydrostatic state before collapse has a lower central gas temperature
in the centre due to the enhanced coupling between gas, grains and radiation
field. This results in slightly lower pressure gradients in the bulk of the
envelope which is hence slightly more extended than in the isothermal case. Due
to the sensitivity of the collapse on these initial conditions, protostellar
infall velocities in the envelope turn out to be much slower in the case with
cooling.Our models also compute the radiative transfer and a rather large
chemical network coupled to gas dynamics. However, we note that the
steady-state chemisorption of CO is sufficient to provide an accurate cooling
function of the gas. This justifies the use of post-processing techniques to
account for the abundance of observed molecules. Existing observations of
infall signatures put very stringent constraints on the kinematics and
temperature profile of the class 0 protostar IRAM 04191+1522. We show that
isothermal models fail to account for the innermost slow infall motions
observed, even with the most hydrostatic initial conditions. In contrast,
models with cooling reproduce the general shape of the temperature profile
inferred from observations and are in much better agreement with the infall
signatures in the inner 3000 AU.


title:
Newly Discovered Variable Stars in the Globular Clusters NGC 5634, Arp 2
  and Terzan 8

abstract:
  We report the discovery of a sizeable, previously unknown variable star
population in the Sagittarius dwarf spheroidal globular clusters NGC 5634, Arp
2 and Terzan 8. Location, preliminary pulsation periods and B-band light curves
in relative flux units are provided for all these stars.


title:
The Radiative Transport of Dust in Primordial Galaxies and
  Second-Generation Star Formation

abstract:
  We investigate the radiative transport of dust in primordial galaxies in the
presence of the UV radiation field from the first metal-free stars. We find
that dust created in the first supernova (SN) explosions can be driven through
the interior of the SN remnant to accumulate in the SN shells, where
second-generation stars may form from compressed cooling gas. This scenario
requires metal-free stars to form continuously over timescales of up to 10 Myr,
consistent with recent estimates. Silicate and graphite grains, as well as
iron-bearing magnetites, are transported to the shells for reasonable parameter
assumptions, but their relative yields from primordial SNe is an important
factor in the resulting abundance ratios. We compare the results of segregated
grain transport with the current nucleosynthetic data on extremely metal-poor
Galactic halo stars. Fossil signatures of this process may already have been
detected in those iron-poor stars with enhanced carbon and silicate elements
such as magnesium, silicon and oxygen. We discuss the implications of our
results for the transition from first- to second-generation star formation in
primordial galaxies, and the role played by the radiative transport of dust in
this process.


title: Evidence of Orbital Motion in the Binary Brown Dwarf Kelu-1AB

abstract:
  We have resolved Kelu-1 into a binary system with a separation of ~290 mas
using the Laser Guide Star Adaptive Optics system on the Keck II telescope. We
have also re-analyzed a 1998 HST observation of Kelu-1 and find that the
observed PSF is best fit by a binary object separated by 45 mas. Observations
on multiple epochs confirm the two objects share a common proper motion and
clearly demonstrate the first evidence of orbital motion. Kelu-1B is fainter
than Kelu-1A by 0.39+/-0.01 magnitudes in the K' filter and 0.50+/-0.01
magnitudes in the H filter. We derive spectral types of L2+/-1 and L3.5+/-1 for
Kelu-1A and B, respectively. The separation of flux into the two components
rectifies Kelu-1's over-luminosity problem that has been known for quite some
time. Given the available data we are able to constrain the inclination of the
system to >81 degrees and the orbital period to >~40 years.


title: An 850 micron survey for dust around solar mass stars

abstract:
  We present the results of an 850 micron JCMT/SCUBA survey for dust around 13
nearby solar mass stars. The dust mass sensitivity ranged from 0.005 to 0.16
Earth masses. Three sources were detected in the survey, one of which (HD
107146) has been previously reported. One of the other two submillimeter
sources, HD 104860, was not detected by IRAS and is surrounded by a cold,
massive dust disk with a dust temperature and mass of Tdust = 33 K and Mdust =
0.16 Mearth. The third source, HD 8907, was detected by IRAS and ISO at 60-87
microns, and has a dust temperature and mass Tdust = 48 K and Mdust = 0.036
Mearth. We find that the deduced masses and radii of the dust disks in our
sample are roughly consistent with models for the collisional evolution of
planetesimal disks with embedded planets. We also searched for residual gas in
two of the three systems with detected submillimeter excesses and place limits
on the mass of gas residing in these systems.
  When the properties measured for the detected excess sources are combined
with the larger population of submillimeter excess sources from the literature,
we find strong evidence that the mass in small grains declines significantly on
a ~200 Myr timescale, approximately inversely with age. However, we also find
that the characteristic dust radii of the population, obtained from the dust
temperature of the excess and assuming blackbody grains, is uncorrelated with
age. This is in contrast to self-stirred collisional models for debris disk
evolution which predict a trend of radius increasing with age, t ~ R^3. The
lack of agreement suggests that processes beyond self-stirring, such as giant
planet formation, play a role in the evolutionary histories of planetesimal
disks.


title:
The Bar--Halo Interaction--I. From Fundamental Dynamics to Revised
  N-body Requirements

abstract:
  Only through resonances can non-axisymmetric features such as spiral arms and
bars exert torques over large scales and change the overall structure of a
near-equilibrium galaxy. We describe the resonant interaction mechanism in
detail and derive explicit criteria for the particle number required to
simulate these dynamical processes accurately using N-body simulations and
illustrate them with numerical experiments. To do this, we perform direct
numerical solution of perturbation theory and make detailed comparisons with
N-body simulations. The criteria include: sufficient particle coverage in phase
space near the resonance and enough particles to minimize gravitational
potential fluctuations that will change the dynamics of the resonant encounter.
Some of our more surprising findings are as follows. First, the
Inner-Lindblad-like resonance (ILR), responsible for coupling the bar to the
central halo cusp, requires almost 10^9 equal mass particles within the virial
radius for a Milky-Way-like bar in an NFW profile. Second, orbits that linger
near the resonance receive more angular momentum than orbits that move through
the resonance quickly. Small-scale fluctuations present in state-of-the-art
particle-particle simulations can knock orbits out of resonance, preventing
them from lingering and, thereby, decrease the torque. The required particle
numbers are sufficiently high for scenarios of interest that apparent
convergence in particle number is misleading: the convergence is in the
noise-dominated regime. State-of-the-art simulations are not adequate to follow
all aspects of secular evolution driven by the bar-halo interaction. We present
a procedure to test the requirements for individual N-body codes for the actual
problem of interest. [abridged]


title:
Determining the Properties and Evolution of Red Galaxies from the Quasar
  Luminosity Function

abstract:
  (Abridged) We study the link between quasars and the red galaxy population
using a model for the self-regulated growth of supermassive black holes in
mergers involving gas-rich galaxies. Using a model for quasar lifetimes and
evolution motivated by hydrodynamical simulations of galaxy mergers, we
de-convolve the observed quasar luminosity function at various redshifts to
determine the rate of formation of black holes of a given final mass.
Identifying quasar activity with the formation of spheroids in the framework of
the merger hypothesis, this enables us to deduce the corresponding rate of
formation of spheroids with given properties as a function of redshift. This
allows us to predict, for the red galaxy population, the distribution of galaxy
velocity dispersions, the mass function, mass density, star formation rates,
the luminosity function in many observed wavebands (NUV, U, B, V, R, I, J, H,
K), the total red galaxy number density and luminosity density, the
distribution of colors as a function of magnitude and velocity dispersion for
several different wavebands, the distribution of mass to light ratios vs. mass,
the luminosity-size relations, and the typical ages and distribution of ages
(formation redshifts) as a function of both mass and luminosity. For each of
these quantities, we predict the evolution from redshift z=0-6. Each of our
predictions agrees well with existing observations, without the addition of
tunable parameters; the essential observational inputs come from the observed
quasar luminosity function. These predictions are skewed by several orders of
magnitude if we adopt simpler, traditional models of quasar lifetimes in which
quasars turn on/off or follow simple exponential light curves, instead of the
more complicated evolution implied by our simulations.


title: Screening of the Magnetic Field of Disk Accreting Stars

abstract:
  An analytical model is developed for the screening of the external magnetic
field of a rotating, axisymmetric neutron star due to the accretion of plasma
from a disk. The decrease of the field occurs due to the electric current in
the infalling plasma. The deposition of this current carrying plasma on the
star's surface creates an induced magnetic moment with a sign opposite to that
of the original magnetic dipole. The field decreases independent of whether the
star spins-up or spins-down. The time-scale for an appreciable decrease (factor
of $>100$) of the field is found to be $\sim 1.6 \times 10^7$ yr, for a mass
accretion rate $\dot{M}=10^{-9} M_\odot/$yr and an initial magnetic moment
$\mu_i = 10^{30}{\rm G cm}^3$ which corresponds to a surface field of $10^{12}
$G if the star's radius is $10^6$ cm. The time-scale varies approximately as
$\mu_i^{3.8}/\dot{M}^{1.9}$. The decrease of the magnetic field does not have a
simple relation to the accreted mass. Once the accretion stops the field leaks
out on an Ohmic diffusion time scale which is estimated to be $ > 10^9$ yr.


title:
Near-Infrared photometry and spectroscopy of NGC 6539 and UKS 1: two
  intermediate metallicity Bulge Globular Clusters

abstract:
  Using the SofI imager at ESO/NTT and NIRSPEC spectrograph at KeckII, we have
obtained J,K images and echelle spectra covering the range 1.5 - 1.8 micron for
the intermediate metallicity Bulge globular clusters NGC6539 and UKS1. We find
[Fe/H]=-0.76 and -0.78, respectively, and an average alpha-enhancement of +0.44
dex and +0.31 dex, consistent with previous measurements of metal rich Bulge
clusters, and favoring the scenario of rapid chemical enrichment. We also
measure very low 12C/13C=4.5 +/-1 isotopic ratios in both clusters, suggesting
that extra-mixing mechanisms due to cool bottom processing are at work during
the evolution along the Red Giant Branch. Finally, we measure accurate radial
velocities of <v_r>=+31 +/-4Km/s and <v_r>=+57 +/-6Km/s and velocity dispersion
of about 8 Km/s and 11 Km/s for NGC6539 and UKS1, respectively.


title:
Using the seismology of non-magnetic chemically peculiar stars as a
  probe of dynamical processes in stellar interiors

abstract:
  Chemical composition is a good tracer of hydrodynamical processes that occur
in stars as they often lead to mixing and particle transport. By comparing
abundances predicted by models and those observed in stars we can infer some
constraints on those mixing processes. As pulsations in stars are often very
sensitive to chemical composition, we can use asteroseismology to probe the
internal chemical composition of stars where no direct observations are
possible. In this paper I focus on main sequence stars Am, lambda bootis, and
HgMn stars and discuss what we can learn of mixing processes in those stars
from seismology.


abstract:
  A new single-dynamical-scalar-field model of dark energy is proposed, in
which either higher derivative terms nor structures of extra dimension are
needed. With the help of a fixed background vector field, the parameter for the
effective equation of state of dark energy may cross $w=-1$ in the evolution of
the universe. After suitable choice of the potential, the crossing $w=-1$ and
transition from decelerating to accelerating occur at $z\approx 0.2$ and
$z\approx 1.7$, respectively.


title: HI Signal from Reionization Epoch

abstract:
  We investigate the all-sky signal in redshifted atomic hydrogen (HI) line
from the reionization epoch. HI can be observed in both emission and absorption
depending on the ratio of Lyman-$\alpha$ to ionizing flux and the spectrum of
the radiation in soft xray. We also compute the signal from pre-reionization
epoch and show that within the uncertainty in cosmological parameters, it is
fairly robust. The main features of HI signal can be summarized as: (a) The
pre-ionized HI can be seen in absorption for $\nu \simeq 10\hbox{--}40 \rm
MHz$; the maximum signal strength is $\simeq 70\hbox{--}100 \rm mK$. (b) A
sharp absorption feature of width $\la 5 \rm MHz$ might be observed in the
frequency range $\simeq 50 \hbox{--}100 \rm MHz$, depending on the reionization
history. The strength of the signal is proportional to the ratio of the
Lyman-$\alpha$ and the hydrogen-ionizing flux and the spectral index of the
radiation field in soft xray (c) At larger frequencies, HI is seen in emission
with peak frequency between $60\hbox{--}100 \rm MHz$, depending on the
ionization history of the universe; the peak strength of this signal is $\simeq
50 \rm mK$. From Fisher matrix analysis, we compute the precision with which
the parameters of the model can be estimated from a future experiment: (a) the
pre-reionization signal can constrain a region in the $\Omega_b h^2$--$\Omega_m
h^2$ plane (b) HI observed in emission can be used to give precise, $\la 1 %$,
measurement of the evolution of the ionization fraction in the universe, and
(c) the transition region from absorption to emission can be used as a probe of
the spectrum of ionizing sources; in particular, the HI signal in this regime
can give reasonably precise measurement of the fraction of the universe heated
by soft x-ray photons.


title: Magnetic fields from reionisation

abstract:
  We present a complementary study to a new model for generating magnetic
fields of cosmological interest. The driving mechanism is the photoionisation
process by photons provided by the first luminous sources. Investigating the
transient regime at the onset of inhomogeneous reionisation, we show that
magnetic field amplitudes as high as $2 \times 10^{-16}$ Gauss can be obtained
within a source lifetime. Photons with energies above the ionisation threshold
accelerate electrons, inducing magnetic fields outside the Stroemgren spheres
which surround the ionising sources. Thanks to their mean free path, photons
with higher energies propagate further and lead to magnetic field generation
deeper in the neutral medium. We find that soft X-ray photons could contribute
to a significant premagnetisation of the intergalactic medium at a redshift of
z=15.


title: The Cosmic Near Infrared Background: Remnant Light from Early Stars

abstract:
  The redshifted ultraviolet light from early stars at z ~ 10 contributes to
the cosmic near infrared background. We present detailed calculations of its
spectrum with various assumptions about metallicity and mass spectrum of early
stars. We show that if the near infrared background has a stellar origin,
metal-free stars are not the only explanation of the excess near infrared
background; stars with metals (e.g. Z=1/50 Z_sun) can produce the same amount
of background intensity as the metal-free stars. We quantitatively show that
the predicted average intensity at 1-2 microns is essentially determined by the
efficiency of nuclear burning in stars, which is not very sensitive to
metallicity. We predict \nu I_\nu / \dot{\rho}_* ~ 4-8 nW m^-2 sr^-1, where
\dot{\rho_*} is the mean star formation rate at z=7-15 (in units of M_sun yr^-1
Mpc^-3) for stars more massive than 5 M_sun. On the other hand, since we have
very little knowledge about the form of mass spectrum of early stars,
uncertainty in the average intensity due to the mass spectrum could be large.
An accurate determination of the near infrared background allows us to probe
formation history of early stars, which is difficult to constrain by other
means. While the star formation rate at z=7-15 inferred from the current data
is significantly higher than the local rate at z<5, it does not rule out the
stellar origin of the cosmic near infrared background. In addition, we show
that a reasonable initial mass function, coupled with this star formation rate,
does not over-produce metals in the universe in most cases, and may produce as
little as less than 1 % of the metals observed in the universe today.


title: The Progenitor Stars of Gamma-Ray Bursts

abstract:
  Those massive stars that, during their deaths, give rise to gamma-ray bursts
(GRBs) must be endowed with an unusually large amount of angular momentum in
their inner regions, one to two orders of magnitude greater than the ones that
make common pulsars. Yet the inclusion of mass loss and angular momentum
transport by magnetic torques during the precollapse evolution is known to sap
the core of the necessary rotation. Here we explore the evolution of very
rapidly rotating, massive stars, including stripped down helium cores that
might result from mergers or mass transfer in a binary, and single stars that
rotate unusually rapidly on the main sequence. For the highest possible
rotation rates (about 400 km/s), a novel sort of evolution is encountered in
which single stars mix completely on the main sequence, never becoming red
giants. Such stars, essentially massive "blue stragglers", produce
helium-oxygen cores that rotate unusually rapidly. Such stars might comprise
roughly 1% of all stars above 10 solar masses and can, under certain
circumstances retain enough angular momentum to make GRBs. Because this
possibility is very sensitive to mass loss, GRBs will be much more probable in
regions of low metallicity.


title: A Potential Supernova Remnant/X-ray Binary Association in M31

abstract:
  The well-studied X-ray/Optical/Radio supernova remnant DDB 1-15 (CXOM31
J004327.8+411829; r3-63) in M31 has been investigated with archival XMM-Newton
and Chandra observations. The timing data from XMM-Newton reveals a power
density spectrum (PDS) characteristic of accreting compact objects in X-ray
binaries (XRBs). The PDS shows features typical of Roche lobe overflow
accretion, hinting that the XRB is low-mass. The Chandra observations resolve
the SNR into a shell and show a variable count rate at the 94% confidence level
in the northwest quadrant. Together, these XMM-Newton and Chandra data suggest
that there is an XRB in the SNR r3-63 and that the XRB is located in the
northwestern portion of the SNR. The currently-available X-ray and optical data
show no evidence that the XRB is high-mass. If the XRB is low-mass, r3-63 would
be the first SNR found to contain a low-mass X-ray binary.


title:
Cosmological and astrophysical parameters from the SDSS flux power
  spectrum and hydrodynamical simulations of the Lyman-alpha forest

abstract:
  (abridged) The flux power spectrum of the Lyman-alpha forest in quasar (QSO)
absorption spectra is sensitive to a wide range of cosmological and
astrophysical parameters and instrumental effects. Modelling the flux power
spectrum in this large parameter space to an accuracy comparable to the
statistical uncertainty of large samples of QSO spectra is very challenging. We
use here a coarse grid of hydrodynamical simulations run with GADGET-2 to
obtain a ``best guess'' model around which we calculate a finer grid of flux
power spectra using a Taylor expansion of the flux power spectrum to first
order. We find that the SDSS flux power spectrum alone is able to constrain a
wide range of parameters including the amplitude of the matter power spectrum
sigma_8, the matter density Omega_m, the spectral index of primordial density
fluctuations n, the effective optical depth tau_eff and its evolution. The
thermal history of the Intergalactic Medium (IGM) is, however, poorly
constrained and the SDSS data favour either an unplausibly large temperature or
an unplausibly steep temperature-density relation. By enforcing a thermal
history of the IGM consistent with that inferred from high-resolution QSO
spectra, we find the following values for the best fitting model (assuming a
flat Universe with a cosmological constant and zero neutrino mass): Omega_
m=0.28 \pm 0.03, n=0.95\pm0.04, \sigma_8=0.91\pm0.07 (1\sigma error bars).We
argue that the major uncertainties in this measurement are still systematic
rather than statistical.


title:
Stellar Winds and Embedded Star Formation in the Galactic Center
  Quintuplet and Arches Clusters: Multifrequency Radio Observations

abstract:
  A multi-frequency, multi-configuration study has been made of the compact
radio sources in the Galactic Center Quintuplet and Arches stellar clusters
using the Very Large Array. Ten radio sources have been detected in the
Quintuplet cluster. The majority of these radio sources have rising spectral
indices and are positionally coincident with young massive stars that are known
to have powerful stellar winds. We conclude that the three most compact of
these sources are produced by stellar wind emission; thus, mass-loss rates can
be derived and have an average value of 3 x 10^-5 solar masses/year. The
remainder of the sources are likely to be a combination of stellar wind
emission and free-free emission from surrounding ionized gas. In three cases,
the radio sources have no stellar counterpart and the radio emission is thought
to arise from compact or ultra-compact HII regions. If so, these sources would
be the first detections of embedded massive stars to be discovered in the
Galactic center clusters. The radio nebula associated with the Pistol star
resembles the nebula surrounding the LBV star Eta Carina and may be related to
the stellar wind of the Pistol star. Ten compact radio sources are detected in
the Arches cluster and are interpreted to be stellar wind sources, consistent
with previous findings. Several of the sources show moderate variability
(10-30%) in their flux density, possibly related to a nonthermal component in
the wind emission. A number of radio sources in both clusters have X-ray
counterparts, which have been interpreted to be the shocked, colliding winds of
massive binary systems.


title:
Spectroscopy of i-Dropout Galaxies with an NB921-Band Depression in the
  Subaru Deep Field

abstract:
  We report new spectroscopy of two star-forming galaxies with strong Ly_alpha
emission at z=6.03 and z=6.04 in the Subaru Deep Field. These two objects are
originally selected as i'-dropouts (i'-z' > 1.5) showing an interesting
photometric property, the ``NB921 depression''. The NB921-band (centered at
9196A) magnitude is significantly depressed with respect to the z'-band
magnitude. The optical spectra of these two objects exhibit asymmetric
emission-lines at lambda_obs ~ 8540A and ~ 8560A, suggesting that these objects
are Ly_alpha emitters at z~6. The rest-frame equivalent widths of the Ly_alpha
emission of the two objects are 94A and 236A; the latter one is the Ly_alpha
emitter with the largest Ly_alpha equivalent width at z > 6 ever
spectroscopically confirmed. The spectroscopically measured Ly_alpha fluxes of
these two objects are consistent with the interpretation that the NB921
depression is caused by the contribution of the strong Ly_alpha emission to the
z'-band flux. Most of the NB921-depressed i'-dropout objects are thought to be
strong Ly_alpha emitters at 6.0 < z < 6.5; Galactic L and T dwarfs and
NB921-dropout galaxies at z > 6.6 do not dominate the NB921-depressed
i'-dropout sample. Thus the NB921-depression method is very useful for finding
high-z Ly_alpha emitters with a large Ly_alpha equivalent width over a large
redshift range, 6.0 < z < 6.5. Although the broadband-selected sample at z ~ 3
contains only a small fraction of objects with a Ly_alpha equivalent width
larger than 100A, the i'-dropout sample of the Subaru Deep Field contains a
much larger fraction of such strong Ly_alpha emitters. This may imply a strong
evolution of the Ly_alpha equivalent width from z > 6 to z ~ 3.


title: Chemistry and Star Formation in the Host Galaxies of Type Ia Supervovae

abstract:
  We study the effect of environment on the properties of type Ia supernovae by
analyzing the integrated spectra of 57 local type Ia supernova host galaxies.
We deduce from the spectra the metallicity, current star formation rate, and
star formation history of the host and compare these to the supernova decline
rates. Additionally, we compare the host properties to the Hubble residuals for
each SN. Our results indicate a statistically insignificant correlation in the
direction higher metallicity spiral galaxies host fainter type Ia supernovae.
However, we present qualitative evidence suggesting progenitor age is more
likely than metallicity to be the source of variability in supernova peak
luminosities. We do not find a correlation between the supernova decline rate
and both host galaxy absolute B magnitude and current/past host galaxy star
formation rate. A tenuous correlation is observed between the supernova Hubble
residuals and host galaxy metallicities. Finally, we characterize the
environmental property distributions for type Ia supernova host galaxies
through a comparison with two larger, more general galaxy distributions using
Kolmogorov-Smirnov tests. The results show the host galaxy metallicity
distribution to be similar to the metallicity distributions of the galaxies of
the NFGS and SDSS. Significant differences are observed between the SN Ia
distributions of absolute B magnitude and star formation histories and the
corresponding distributions of galaxies in the NFGS and SDSS. Among these is an
abrupt upper limit observed in the distribution of star formation histories of
the host galaxy sample suggesting a type Ia supernovae characteristic delay
time lower limit of approximately 2.0 Gyrs. Other distribution discrepancies
are investigated and the effect on the supernova properties are discussed.


title:
Globular Clusters in NGC 4365: New K-band Imaging and a Reassessment of
  the Case for Intermediate-age Clusters

abstract:
  We study the globular cluster (GC) system of the Virgo giant elliptical
galaxy NGC 4365, using new wide-field VIK imaging. The GC colour distribution
has (at least) two peaks, but the colours of the red GCs appear more strongly
weighted towards intermediate colours compared to most other large ellipticals
and the integrated galaxy light. The intermediate-color/red peak may itself be
composed of two sub-populations, with clusters of intermediate colours more
concentrated towards the centre of the galaxy than both the blue and red GCs.
Nearly all intermediate-colour and red GCs in our sample show an offset towards
red V-K and/or blue V-I colours compared to SSP models for old ages in a
(V-K,V-I) diagram. This has in the past been interpreted as evidence for
intermediate ages. We also combine our VIK data with previously published
spectroscopy. The differences between observed and model colour-metallicity
relations are consistent with the offsets observed in the two-colour diagram,
with the metal-rich GCs being too red (by about 0.2 mag) in V-K and too blue
(by about 0.05 mag) in V-I compared to the models at a given metallicity. These
offsets cannot easily be explained as an effect of younger ages. We conclude
that, while intermediate GC ages cannot be definitively ruled out, an
alternative scenario is more likely whereby all the GCs are old but the
relative number of intermediate-metallicity GCs is greater than typical for
giant ellipticals. The main obstacle to reaching a definitive conclusion is the
lack of robust calibrations of integrated spectral and photometric properties
for stellar populations with near-solar metallicity. In any case, it is
puzzling that the intermediate-colour GCs in NGC 4365 are not accompanied by a
corresponding shift of the integrated galaxy light towards bluer colours.


title: Detecting the Transition From Pop III to Pop II Stars

abstract:
  We discuss the cosmological significance of the transition from the Pop III
to Pop II mode of star formation in the early universe, and when and how it may
occur in primordial galaxies. Observations that could detect this transition
include those of element abundances in metal-poor Galactic halo stars, and of
the helium reionization and associated heating of the intergalactic medium. We
suggest that gamma-ray bursts may be a better probe of the end of the
first-stars epoch than of Pop III stars.


title: Fluorescence in damp air and comments on the radiative life time

abstract:
  Photon yields in damp air excited by an electron using a Sr90 $\beta$ source
are compared withthose in dry air. Water vapors considerably reduce the yields,
however, a further study is needed to evaluate the effects on the energy
estimation of ultrahigh-energy cosmic rays. The relation of fluorescence
efficiency to the life time of de-excitation by radiation is discussed.


title: Robust Reconstruction from Chopped and Nodded Images

abstract:
  In ground based infrared imaging a well-known technique to reduce the
influence of thermal and background noise is chopping and nodding, where four
different signals of the same object are recorded from which the object is
reconstructed numerically. Since noise in the data can severely affect the
reconstruction, regularization algorithms have to be implemented. In this paper
we propose to combine iterative reconstruction algorithms with robust
statistical methods. Moreover, we study the use of multiple chopped data sets
with different chopping amplitudes and the according numerical reconstruction
algorithm. Numerical simulations show robustness of the proposed methods with
respect to noisy data.


title: A Data Exchange Standard for Optical (Visible/IR) Interferometry

abstract:
  This paper describes the OI Exchange Format, a standard for exchanging
calibrated data from optical (visible/infrared) stellar interferometers. The
standard is based on the Flexible Image Transport System (FITS), and supports
storage of the optical interferometric observables including squared visibility
and closure phase -- data products not included in radio interferometry
standards such as UV-FITS. The format has already gained the support of most
currently-operating optical interferometer projects, including COAST, NPOI,
IOTA, CHARA, VLTI, PTI, and the Keck Interferometer, and is endorsed by the IAU
Working Group on Optical Interferometry. Software is available for reading,
writing and merging OI Exchange Format files.


title:
The properties of Ly-alpha emitting galaxies in hierarchical galaxy
  formation models

abstract:
  We present detailed predictions for the properties of Ly-alpha-emitting
galaxies in the framework of the Lambda-CDM cosmology, calculated using the
semi-analytical galaxy formation model GALFORM. We explore a model which
assumes a top-heavy IMF in starbursts, and which has previously been shown to
explain the sub-mm number counts and the luminosity function of Lyman-break
galaxies at high redshift. We show that this model, with the simple assumption
that a fixed fraction of Ly-alpha photons escape from each galaxy, is
remarkably successful at explaining the observed luminosity function of
Ly-alpha emitters over the redshift range 3<z<6.6. We also examine the
distribution of Ly-alpha equivalent widths and the broad-band continuum
magnitudes of emitters, which are in good agreement with the available
observations. We look more deeply into the nature of Ly-alpha emitters,
presenting predictions for fundamental properties such as the stellar mass and
radius of the emitting galaxy and the mass of the host dark matter halo. The
model predicts that the clustering of Ly-alpha emitters at high redshifts
should be strongly biased relative to the dark matter, in agreement with
observational estimates. We also present predictions for the luminosity
function of Ly-alpha emitters at z>7, a redshift range which is starting to be
be probed by near-IR surveys and using new instruments such as DAzLE.


title: Five WC9 stars discovered in the AAO/UKST H-alpha Survey

abstract:
  We report the discovery of 5 massive Wolf-Rayet (WR) stars resulting from a
programme of follow-up spectroscopy of candidate emission line stars in the
AAO/UKST Southern Galactic Plane H-alpha survey. The 6195-6775 angstrom spectra
of the stars are presented and discussed. A WC9 class is assigned to all 5
stars through comparison of their spectra with those of known late-type WC
stars, bringing the known total number of Galactic WC9 stars to 44. Whilst
three of the five WC9 stars exhibit near infrared (NIR) excesses characteristic
of hot dust emission -- as seen in the great majority of known WC9 stars -- we
find that two of the stars show no discernible evidence of such excesses. This
increases the number of known WC9 stars without NIR excesses to 7. Reddenings
and distances for all 5 stars are estimated.


title: Properties of five low-contrast open clusters in the third quadrant

abstract:
  We derive photometric, structural and dynamical evolution-related parameters
of five as yet unstudied low-contrast open clusters located in the third
quadrant using 2MASS data. The target clusters are Czernik 31, Czernik 32,
Haffner 9, Haffner 11 and Trumpler 13. We apply a statistical field-star
decontamination procedure to infer on the intrinsic CMD morphology which is
critical for such low-contrast objects. Consequently, it became possible to
derive accurate reddening, age, distance from the Sun and Galactocentric
distance for the five clusters. In the structural and luminosity/mass-function
analyses we apply a colour-magnitude filter which encompasses the cluster
evolutionary CMD sequences and excludes stars with discrepant colours. Using
this procedure we derive core and limiting radii, mass function slope, total
mass, mass density and relaxation time. We derive ages in the range 140 -- 1
100 Myr, Galactocentric distances within 7.7 -- 11.4 kpc, and total masses
within 360--2 900 \ms. Reflecting large-scale mass segregation, the MF slope in
the core is significantly flatter than that in the halo of the five clusters.
Although some of the present clusters are relatively younger than the Gyr-old
clusters, they present evidence of advanced dynamical evolution. This kind of
study has become possible because of the photometric uniformity and spatial
coverage of 2MASS which allows a proper subtraction of the field-star
contamination on the target CMDs. The present study indicates that low-contrast
clusters can be studied with 2MASS, particularly after field-star subtraction,
which is important since most of the unstudied open clusters belong to this
class.


title:
The trail of discrete X-ray sources in the early-type galaxy NGC4261:
  anisotropy in the globular cluster distribution?

abstract:
  Chandra images of the elliptical galaxy NGC4261 have revealed an anisotropy
in the spatial distribution of the off-nuclear X-ray sources, interpreted by
Zezas et al. as evidence of an association with a young stellar population. Our
independent analysis of archive X-ray (Chandra) and optical (INT and HST)
observations confirms the anisotropy of the X-ray sources but conducts to a
different interpretation for their origin. We find that nearly half of the
X-ray sources are associated to a globular cluster (optical counterpart)
suggesting that they are accreting low-mass X-ray binaries. Where color index
information is available, the X-ray sources are found to reside in red
(metal-rich) systems. The luminosity function of the X-ray sources is also
consistent with the one drawn from a population of Low Mass X-ray Binaries. We
further investigate the properties of the sample of point-like sources obtained
from archival optical images that we suggest are good globular cluster
candidates and for which we find that the projected spatial distribution is
non-homogeneous. In addition, we show that the distributions of the optical and
X-ray populations are very similar, which leads us to conclude that the spatial
anisotropy of the X-ray sources in NGC4261 is mostly a reflection of the
anisotropy of the globular cluster population.


title:
Gravitational signals due to tidal interactions between white dwarfs and
  black holes

abstract:
  In this paper we compute the gravitational signal emitted when a white dwarf
moves around a black hole on a closed or open orbit using the affine model
approach. We compare the orbital and the tidal contributions to the signal,
assuming that the star moves in a safe region where, although very close to the
black hole, the strength of the tidal interaction is insufficient to provoque
the stellar disruption. We show that for all considered orbits the tidal signal
presents sharp peaks corresponding to the excitation of the star non radial
oscillation modes, the amplitude of which depends on how deep the star
penetrates the black hole tidal radius and on the type of orbit. Further
structure is added to the emitted signal by the coupling between the orbital
and the tidal motion.


title:
A Millimeter Continuum Survey for Massive Protoclusters in the Outer
  Galaxy

abstract:
  Our search for the earliest stages of massive star formation turned up twelve
massive pre-protocluster candidates plus a few protoclusters. For this search,
we selected 47 FIR-bright IRAS sources in the outer Galaxy. We mapped regions
of several square arcminutes around the IRAS source in the millimeter continuum
in order to find massive cold cloud cores possibly being in a very early stage
of massive star formation. Masses and densities are derived for the 128
molecular cloud cores found in the obtained maps. We present these maps
together with near-infrared, mid-infrared, and radio data collected from the
2MASS, MSX, and NVSS catalogs. Further data from the literature on detections
of high-density tracers, outflows, and masers are added. The multi-wavelength
datasets are used to characterize each observed region. The massive cloud cores
(M>100 M_sun) are placed in a tentative evolutionary sequence depending on
their emission at the investigated wavelengths. Candidates for the youngest
stages of massive star formation are identified by the lack of detections in
the above-mentioned near-infrared, mid-infrared, and radio surveys. Twelve
massive cores prominent in the millimeter continuum fulfill this requirement.
Since neither FIR nor radio emission have been detected from these cloud cores
massive protostars must be very deeply embedded in these cores. Some of these
objects may actually Pre-Proto-cluster cores: an up to now rare object class,
where the initial conditions of massive star formation can be studied.


title:
Particle-In-Cell Simulations of a Nonlinear Transverse Electromagnetic
  Wave in a Pulsar Wind Termination Shock

abstract:
  A 2.5-dimensional particle-in-cell code is used to investigate the
propagation of a large-amplitude, superluminal, nearly transverse
electromagnetic (TEM) wave in a relativistically streaming electron-positron
plasma with and without a shock. In the freestreaming, unshocked case, the
analytic TEM dispersion relation is verified, and the streaming is shown to
stabilize the wave against parametric instabilities. In the confined, shocked
case, the wave induces strong, coherent particle oscillations, heats the
plasma, and modifies the shock density profile via ponderomotive effects. The
wave decays over $\gtrsim 10^2$ skin depths; the decay length scale depends
primarily on the ratio between the wave frequency and the effective plasma
frequency, and on the wave amplitude. The results are applied to the
termination shock of the Crab pulsar wind, where the decay length-scale (at
least 0.05") might be comparable to the thickness of filamentary, variable
substructure observed in the optical and X-ray wisps and knots.


title:
Ejection of high-velocity stars from the Galactic Center by an
  inspiraling Intermediate-Mass Black Hole

abstract:
  The presence of young stars in the immediate vicinity and strong tidal field
of SgrA* remains unexplained. One currently popular idea for their origin
posits that the stars were bused in by an Intermediate-Mass Black Hole (IMBH)
which has inspiraled into the Galactic Center a few million years ago.
  Yu and Tremaine (2003) have argued that in this case some of the old stars in
the SgrA* cusp would be ejected by hard gravitational collisions with the IMBH.
Here we derive a general expression for the phase-space distribution of the
ejected high-velocity stars, given the distribution function of the stars in
the cusp. We compute it explicitly for the Peebles-Young distribution function
of the cusp, and make a detailed model for the time-dependent ejection of stars
during the IMBH inspiral. We find that (1) the stars are ejected in a burst
lasting a few dynamical friction timescales; if the ejected stars are detected
by Gaia they are likely to be produced by a single inspiral event, (2) if the
inspiral is circular than in the beginning of the burst the velocity vectors of
the ejected stars cluster around the inspiral plane, but rapidly isotropise as
the burst proceeds, (3) if the inspiral is eccentric, then the stars are
ejected in a broad jet roughly perpendicular to the Runge-Lenz vector of the
IMBH orbit. In a typical cusp the orbit will precess with a period of \sim 10^5
years, and the rate of ejection into our part of the Galaxy (as defined by e.g.
the Gaia visibility domain) will be modulated periodically. Gaia, together with
the ground-based follow-up observations, will be able to clock many
high-velocity stars back to their ejection from the Galactic Center, thus
measuring some of the above phenomena. This would provide a clear signature of
the IMBH inspiral in the past 10--20 Myr.


title:
On the Production and Survival of Carbon Fuel for Superbursts on
  Accreting Neutron Stars: Implications for Mass Donor Evolution

abstract:
  (abridged) We have investigated the physical conditions under which accreting
neutron stars can both produce and preserve sufficient quantities of carbon
fuel to trigger superbursts. Our models span the plausible ranges of neutron
star thermal conductivities, core neutrino emission mechanisms, and areal
radii, as well as the CNO abundances in the accreted material. We find that
neutron stars that accrete hydrogen-rich material with CNO mass fractions <~
that of the Sun will not exhibit superbursts under any circumstances. Neutron
stars that accrete material with CNO mass fractions >~ 4 times that of the Sun
will exhibit superbursts at accretion rates in the observed range. On this
basis, we suggest that the mass donors of superburst systems must have enhanced
CNO abundances. The accreted CNO acts only as a catalyst for hydrogen burning
via the hot CNO cycle, and therefore it is only the sum of the three elements'
mass fractions that is important. Systems that exhibit superbursts are observed
to differ from those that do not exhibit superbursts in the nature of their
helium-triggered Type I X-ray bursts: the bursts have shorter durations and
much greater alpha-values. Increasing the CNO abundance of the accreted
material in our models reproduces both of these observations. Many compact
binary systems have been observed in which the abundances of the accreting
material are distinctly non-solar. Though abundance analyses of the systems
that exhibit superbursts currently do not exist, Bowen fluorescence blend
profiles of 4U 1636-536 and Ser X-1 suggest that the mass donor stars may
indeed have non-solar CNO metallicities. More detailed abundance analyses of
the accreting matter in systems that exhibit superbursts are needed to verify
our assertion that the matter is rich in CNO elements.


title:
Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal
  Metallicity Distributions and the Nature of the High-Luminosity Clusters

abstract:
  We present new (B,I) photometry for the globular cluster systems in eight
Brightest Cluster Galaxies (BCGs), obtained with the ACS/WFC camera on the
Hubble Space Telescope. In the very rich cluster systems that reside within
these giant galaxies, we find that all have strongly bimodal color
distributions All the BCGs show population gradients, with much higher relative
numbers of red clusters within 5 kpc of their centers, consistent with their
having formed at later times than the blue, metal-poor population. A striking
new feature of the color distributions emerging from our data is that for the
brightest clusters (M_I < -10.5) the color distribution becomes broad and less
obviously bimodal. we suggest that it may be a characteristic of many BCGs.
Furthermore, the blue (metal-poor) clusters become progressively redder with
increasing luminosity, following a mass/metallicity scaling relation Z ~
M^0.55. We argue that these GCS characteristics are consistent with a
hierarchical-merging formation picture in which the metal-poor clusters formed
in protogalactic clouds or dense starburst complexes with gas masses in the
range 10^7 - 10^10 M_Sun, but where the more massive clusters on average formed
in bigger clouds with deeper potential wells where more pre-enrichment could
occur.


title:
Astro-ph communication: Simulations of the WMAP Internal Linear
  Combination sky map

abstract:
  Following this astro-ph communication, we release a set of 10,000 WMAP ILC
simulations, produced as described by Eriksen et al. (2004). We strongly
encourage that an analysis of these simulations accompanies any scientific
analysis of the observed ILC map, in order to assess the stability of the
results. For examples of such analyses, we refer the reader to our original
paper. In particular, Figure 1c) and d) show the bias and uncertainty induced
by the ILC method, and Figure 7 shows a sobering examples of a low-l analysis;
the reconstructed quadrupole-octopole alignment is plotted against the true
input alignment, and the correlation is underwhelming. It can hardly be
emphasized too strongly -- the heavily processed full-sky WMAP maps are not
reliable for quantitative analysis, neither at large nor small scales, and they
should only, at best, be used as supportive evidence. We hope that these
simulations will reduce some of the confusion regarding these maps that
currently exists in the community.


title:
Gamma-Ray Burst Selected High Redshift Galaxies: Comparison to Field
  Galaxy Populations to z~3

abstract:
  We study the internal structural properties of 37 long duration gamma-ray
burst (GRB) host galaxies imaged with the Hubble Space Telescope. Fitting
exponential disk and r^1/4 models to the surface brightness profiles of eight z
< 1.2 bright host galaxies, we find that the disk model is slightly preferred
for most hosts, although two galaxies are fit best with an r^1/4 profile. We
furthermore measure the central concentrations and asymmetries of all 37 host
galaxies using the CAS system, and compare with field galaxies in the Hubble
Deep Field. Our first main conclusion is that GRB hosts exhibit a surprisingly
high diversity of galaxy types. A significant fraction (68%) of host galaxies
are situated in a region of the concentration-asymmetry diagram occupied by
spirals or peculiar/merging galaxies. Twelve hosts (32%) are situated in the
region occupied by elliptical galaxies, having high concentration indices. We
also find some evidence for evolution in GRB host galaxy morphology, such that
hosts at z > 1 have a relatively high light concentration, indicating that
these systems are perhaps progenitors of massive galaxies, or are compact blue
star forming galaxies. We find that GRB hosts at z > 1 are different from the
general field population at z > 1 in terms of light concentration at >99.5%
confidence, yet have sizes similar to the general z > 1 population. This is the
opposite of the effect at z < 1 where GRB hosts are smaller than average. We
argue that GRB hosts trace the starburst population at high redshift, as
similarly concentrated galaxies at z > 1 are undergoing a disproportionate
amount of star formation for their luminosities. Our results show that GRBs are
perhaps ideal tracers of typical galaxies undergoing star formation at any
epoch.


title:
VLBI phase-reference observations of the gravitational lens JVAS
  B0218+357

abstract:
  We present the results of phase-referenced VLBA+Effelsberg observations at
five frequencies of the double-image gravitational lens JVAS B0218+357, made to
establish the precise registration of the A and B lensed image positions. The
motivation behind these observations is to investigate the anomalous variation
of the image flux density ratio (A/B) with frequency - this ratio changes by
almost a factor of two over a frequency range from 1.65 GHz to 15.35 GHz. We
investigate whether frequency dependent image positions, combined with a
magnification gradient across the image field, could give rise to the anomaly.
Our observations confirm the variation of image flux ratio with frequency. The
results from our phase-reference astrometry, taken together with the lens mass
model of Wucknitz et al. (2004), show that shifts of the image peaks and
centroids are too small to account for the observed frequency-dependent ratio.


title: Morphology and kinematics of the ionised gas in early-type galaxies

abstract:
  We present results of our ongoing study of the morphology and kinematics of
the ionised gas in 48 representative nearby elliptical and lenticular galaxies
using the SAURON integral-field spectrograph on the 4.2m William Herschel
Telescope. Making use of a recently developed technique, emission is detected
in 75% of the galaxies. The ionised-gas distributions display varied
morphologies, ranging from regular gas disks to filamentary structures.
Additionally, the emission-line kinematic maps show, in general, regular
motions with smooth variations in kinematic position angle. In most of the
galaxies, the ionised-gas kinematics is decoupled from the stellar counterpart,
but only some of them present signatures of recent accretion of gaseous
material. The presence of dust is very common in our sample and is usually
accompanied by gas emission. Our analysis of the [OIII]/Hbeta emission-line
ratios, both across the whole sample as well as within the individual galaxies,
suggests that there is no unique mechanism triggering the ionisation of the
gas.


title: Imaging redshifts of BL Lac objects

abstract:
  The HST snapshot imaging survey of 110 BL Lac objects (Urry et al. 2000) has
clearly shown that the host galaxies are massive and luminous ellipticals. The
dispersion of the absolute magnitudes is sufficiently small, so that the
measurement of the galaxy brightness becomes a valuable way of estimating their
distance. This is illustrated constructing the Hubble diagram of the 64
resolved objects with known redshift. By means of this relationship we estimate
the redshift of five resolved BL Lacs of the survey, which have no
spectroscopic z. The adopted method allows us also to evaluate lower limits to
the redshift for 13 objects of still unknown z, based on the lower limit on the
host galaxy magnitude. This technique can be applied to any BL Lac object for
which an estimate or a lower limit of the host galaxy magnitude is available.
Finally we show that the distribution of the nuclear luminosity of all the BL
Lacs of the survey, indicates that the objects for which both the redshift and
the host galaxy are undetected, are among the most luminous, and possibly the
most highly beamed.


title:
Spatial fluctuations in the spectral shape of the UV background at 2<z<3
  and the reionization of helium

abstract:
  The low density hydrogen and helium in the IGM probed by QSO absorption lines
is sensitive to the amplitude and spectral shape of the metagalactic UV
background. We use realistic HI and HeII Ly-alpha forest spectra, constructed
from state-of-the-art hydrodynamical simulations of a Lambda-CDM Universe, to
confirm the reliability of using line profile fitting techniques to infer the
ratio of the metagalactic HI and HeII ionization rates. We further show that
the large spatial variations and the anti-correlation with HI absorber density
observed in the ratio of the measured HeII to HI column densities can be
explained in a model where the HI ionization rate is dominated by the combined
UV emission from young star forming galaxies and QSOs and the HeII ionization
rate is dominated by emission from QSOs only. In such a model the large
fluctuations in the column density ratio are due to the small number of QSOs
expected to contribute at any given point to the HeII ionization rate. A
significant contribution to UV emission at the HeII photoelectric edge from hot
gas in galaxies and galaxy groups would decrease the expected fluctuations in
the column density ratio. Consequently, this model appears difficult to
reconcile with the large increase in HeII opacity fluctuations towards higher
redshift. Our results further strengthen previous suggestions that observed
HeII Ly-alpha forest spectra at z~2-3.5 probe the tail end of the reionization
of HeII by QSOs.


title:
Estimation of Carbon Abundances in Metal-Poor Stars. I. Application to
  the "Strong G-band" stars of Beers, Preston, & Shectman

abstract:
  We develop and test a method for the estimation of metallicities ([Fe/H]) and
carbon abundance ratios ([C/Fe]) for carbon-enhanced metal-poor (CEMP) stars,
based on application of artificial neural networks, regressions, and synthesis
models to medium-resolution (1-2 A) spectra and J-K colors. We calibrate this
method by comparison with metallicities and carbon abundance determinations for
118 stars with available high-resolution analyses reported in the recent
literature. The neural network and regression approaches make use of a
previously defined set of line-strength indices quantifying the strength of the
CaII K line and the CH G-band, in conjuction with J-K colors from the 2MASS
Point Source Catalog. The use of near-IR colors, as opposed to broadband B-V
colors, is required because of the potentially large affect of strong molecular
carbon bands on bluer color indices. Using these methods we are able to
reproduce the previously-measured [Fe/H] and [C/Fe] determinations with an
accuracy of ~ 0.25 dex for stars in the metallicity interval -5.5 <= [Fe/H]} <=
-1.0, and with 0.2 <= (J-K)o <= 0.8. At higher metallicity the CaII K line
begins to saturate, especially for the cool stars in our program, hence this
approach is not useful in some cases. As a first application, we estimate the
abundances of [Fe/H] and [C/Fe] for the 56 stars identified as possibly
carbon-rich, relative to stars of similar metal abundance, in the sample of
"strong G-band" stars discussed by Beers, Preston, & Shectman. (abridged)


title: The intriguing giant bow shocks near HH 131

abstract:
  Using the High Dispersion Spectrograph at the Subaru Telescope, echelle
spectra of two giant arcs, i.e. nebulosities Cw and L associated with HH 131 in
Orion are presented. Typical emission lines of Herbig-Haro objects have been
detected towards Cw. With the 2.16 m telescope of National Astronomical
Observatories, spectra of Nebu. C, L and K are obtained, which also show strong
[SII]6717/6731, H$\alpha$ and [NII]6583 emission lines. Position-velocity
distributions of Cw and L are analyzed. The fastest radial velocity of Cw is
V_r ~ -18.0 km/s. When the flow at L goes to the south, it slows down. The
fastest radial velocity of L has been observed of -45.0 km/s and the slowest
value is about -18.3 km/s. The similarity of the velocities and their
positional connection indicate that Cw and L are physically associated. The
entire flow tends to become less excited and less ionized when going further to
the south (i.e., from Nebu. K, L to C). The electron densities of all the
observed nebulosities are low (n_e ~ 10^2 cm^-3). Double kinematic signatures
have been found in Cw from its [NII]6583 profiles while the observed H$\alpha$
profiles of Cw are almost symmetric. Bow shock models appear to agree with the
observed position-velocity diagrams of the [NII spectra better than H$\alpha$
spectra. With the suggestion that these arcs are HH shocks possibly ejected out
of the Orion A molecular cloud by an uncertain source, their spectra show low
to intermediate excitation from their diagnostic line ratios.


title:
The kinetic temperature of a molecular cloud at redshift 0.7: Ammonia in
  the gravitational lens B0218+357

abstract:
  Using the Effelsberg 100-m telescope, absorption in the (J,K) = (1,1), (2,2)
and (3,3) inversion lines of ammonia (NH_3) was detected at a redshift of z =
0.6847 toward the gravitational lens system B0218+357. The lambda ~ 2cm
absorption peaks at 0.5-1.0 % of the continuum level and appears to cover a
smaller fraction of the radio continuum background than lines at millimeter
wavelengths. Measured intensities are consistent with a rotation temperature of
~35K, corresponding to a kinetic temperature of ~55K. The column density toward
the core of image A then becomes N(NH_3) ~ 1 * 10^(14)cm^(-2) and fractional
abundance and gas density are of order X(NH_3)~10^(-8) and n(H_2)~5 *
10^(3)cm^(-3), respectively. Upper limits are reported for the (2,1) and (4,4)
lines of NH_3 and for transitions of the SO, DCN, OCS, SiO, C_3N, H_2CO, SiC_2,
HC_3N, HC_5N, and CH_3OH molecules. These limits and the kinetic temperature
indicate that the absorption lines are not arising from a cold dark cloud but
from a warm, diffuse, predominantly molecular medium. The physical parameters
of the absorbing molecular complex, seen at a projected distance of ~2 kpc to
the center of the lensing galaxy, are quite peculiar when compared with the
properties of clouds in the Galaxy or in nearby extragalactic systems.


title: Modes of star formation along the Hubble Sequence and beyond

abstract:
  I assess the similarities and differences between the star-formation modes in
quiescent spiral galaxies versus those in violent starburst regions. As opposed
to the quiescent star-formation mode in spiral galaxies, current empirical
evidence on the star-formation processes in the extreme, high-pressure
environments induced by galaxy encounters strongly suggests that star CLUSTER
formation is an important and perhaps even the dominant mode of star formation
in such starburst events. The sizes, luminosities, and mass estimates of the
young massive star clusters (YMCs) are entirely consistent with what is
expected for young Milky Way-type globular clusters (GCs). Recent evidence
lends support to the scenario that GCs, which were once thought to be the
oldest building blocks of galaxies, are still forming today. One of the key
unanswered questions in this field relates to their possible survival chances
for a Hubble time, and thus to the potential evolutionary connection between
YMCs and GCs.


title:
Discovery of Fast X-ray Oscillations During the 1998 Giant Flare from
  SGR 1900+14

abstract:
  We report the discovery of complex high frequency variability during the
August 27, 1998 giant flare from SGR 1900+14 using the Rossi X-ray Timing
Explorer (RXTE). We detect an 84 Hz oscillation (QPO) during a 1 s interval
beginning approximately 1 min after the initial hard spike. The modulation
amplitude is energy dependent, reaching a maximum of 26% (rms) for photons
above 30 keV, and is not detected below 11 keV, with a 90% confidence upper
limit of 14% (rms). Remarkably, additional QPOs are detected in the average
power spectrum of data segments centered on the rotational phase at which the
84 Hz signal was detected. Two signals, at 53.5 and 155.1 Hz, are strongly
detected, while a third feature at 28 Hz is found with lower significance.
These QPOs are not detected at other rotational phases. The phenomenology seen
in the SGR 1900+14 flare is similar to that of QPOs recently reported by Israel
et al. from the December 27, 2004 flare from SGR 1806-20, suggesting they may
have a common origin, perhaps torsional vibrations of the neutron star crust.
Indeed, an association of the four frequencies (in increasing order) found in
SGR 1900+14 with l = 2, 4, 7, and 13 toroidal modes appears plausible. We
discuss our findings in the context of this model and show that if the stars
have similar masses then the magnetic field in SGR 1806-20 must be about twice
as large as in SGR 1900+14, broadly consistent with magnetic field estimates
from pulse timing.


title:
The 2dF Galaxy Redshift Survey: correlation with the ROSAT-ESO Flux
  Limited X-ray (REFLEX) galaxy cluster survey

abstract:
  The ROSAT-ESO Flux Limited X-ray (REFLEX) galaxy cluster survey and the 2dF
Galaxy Redshift Survey (2dFGRS) respectively comprise the largest, homogeneous
X-ray selected cluster catalogue and completed galaxy redshift survey. In this
work we combine these two outstanding datasets in order to study the effect of
the large-scale cluster environment, as traced by X-ray luminosity, on the
properties of the cluster member galaxies. We measure the LX-sigma relation
from the correlated dataset and find it to be consistent with recent results
found in the literature. Using a sample of 19 clusters with LX>=0.36*10^44 erg
s^-1 in the (0.1-2.4 keV) band, and 49 clusters with lower X-ray luminosity, we
find that the fraction of early spectral type (eta<=-1.4), passively-evolving
galaxies is significantly higher in the high-LX sample within R200. We extend
the investigation to include composite bJ cluster luminosity functions, and
find that the characteristic magnitude of the Schechter-function fit to the
early-type luminosity function is fainter for the high-LX sample compared to
the low-LX sample (Delta M*=0.58+/-0.14). This seems to be driven by a deficit
of such galaxies with M_bJ ~ -21. In contrast, we find no significant
differences between the luminosity functions of star-forming, late-type
galaxies. We believe these results are consistent with a scenario in which the
high-LX clusters are more dynamically evolved systems than the low-LX clusters.


title: A deeper understanding of white dwarf interiors

abstract:
  A detailed record of the physical processes that operate during
post-main-sequence evolution is contained in the internal chemical structure of
white dwarfs. Global pulsations allow us to probe the stellar interior through
asteroseismology, revealing the signatures of prior nuclear burning, mixing,
and diffusion in these stars. I review the rapid evolution of structural models
for helium-atmosphere variable (DBV) white dwarfs over the past five years, and
I present a new series of model-fits using recent observations to illustrate
the relative importance of various interior structures. By incorporating
physically motivated C/O profiles into double-layered envelope models for the
first time, I finally identify an optimal asteroseismic model that agrees with
both diffusion theory and the expected nuclear burning history of the
progenitor. I discuss the implications of this fundamental result, and I
evaluate the prospects for continued progress in the future.


title: The energetic Universe

abstract:
  In this paper I review the main topics on the energetic Universe that have
been put forward as main science goals in the Cosmic Vision 2015-2025 exercise.
I discuss the study of matter under extreme conditions (both under strong
gravity and at ultra-high densities), the cosmology of baryons (assembly of
ordinary matter in dark-matter dominated structures and the creation of heavy
elements) and the co-eval growth of super-massive black holes and stars in
galaxies along cosmic history. Most of these topics can be addressed with a
large-aperture deep Universe X-ray space observatory that can be flown soon
after 2015, complemented by gravitational wave observatories (LISA), a
focussing gamma-ray observatory, a far infrared high-sensitivity observatory
and an X-ray survey telescope.


title:
Protostellar holes: Spitzer Space Telescope observations of the
  protostellar binary IRAS16293-2422

abstract:
  Mid-infrared (23-35 micron) emission from the deeply embedded "Class 0"
protostar IRAS16293-2422 is detected with the Spitzer Space Telescope infrared
spectrograph. A detailed radiative transfer model reproducing the full spectral
energy distribution (SED) from 23 micron to 1.3 mm requires a large inner
cavity of radius 600 AU in the envelope to avoid quenching the emission from
the central sources. This is consistent with a previous suggestion based on
high angular resolution millimeter interferometric data. An alternative
interpretation using a 2D model of the envelope with an outflow cavity can
reproduce the SED but not the interferometer visibilities. The cavity size is
comparable to the centrifugal radius of the envelope and therefore appears to
be a natural consequence of the rotation of the protostellar core, which has
also caused the fragmentation leading to the central protostellar binary. With
a large cavity such as required by the data, the average temperature at a given
radius does not increase above 60-80 K and although hot spots with higher
temperatures may be present close to each protostar, these constitute a small
fraction of the material in the inner envelope. The proposed cavity will also
have consequences for the interpretation of molecular line data, especially of
complex species probing high temperatures in the inner regions of the envelope.


title: Galactic and Cosmic Chemical Evolution with Hypernovae

abstract:
  We provide new nucleosynthesis yields depending on metallicity and energy
(i.e., (normal supernovae and hypernovae), and show the evolution of heavy
element abundances from C to Zn in the solar neighborhood. We then show the
chemodynamical simulation of the Milky Way Galaxy and discuss the G-dwarf
problem. We finally show the cosmological simulation and discuss the galaxy
formation and chemical enrichment.


title: Polarization in the inner region of Pulsar Wind Nebulae

abstract:
  We present here the first effort to compute synthetic synchrotron
polarization maps of Pulsar Wind Nebulae (PWNe). Our goal is to highlight how
polarization can be used as an additional diagnostic tool for the flow
structure in the inner regions of these nebulae. Recent numerical simulations
suggest the presence of flow velocities ~0.5 c in the surroundings of the
termination shock, where most of the high energy emission comes from. We
construct polarization maps taking into account relativistic effects like
Doppler boosting and position angle swing. The effect of different bulk
velocities is clarified with the help of a toy-model consisting of a uniformly
emitting torus. We also present a map based on recent numerical simulations of
the entire nebula and compare it with presently available data. The comparison
with upcoming high resolution observations could provide new insight into the
inner structure of the nebula and put constraints on the geometrical properties
of the magnetic field.


title: GCRT J1745-3009 as a Transient White Dwarf Pulsar

abstract:
  A transient radio source in the direction of the Galactic Center, GCRT
J1745-3009, exhibited 5 peculiar consecutive outbursts at 0.33 GHz with a
period of 77.13 minutes and a duration of ~10 minutes for each outburst. It has
been claimed to be the prototype of a hitherto unknown class of transient radio
sources. We interpret it as a transient white dwarf pulsar with a period of
77.13 minutes. The ~10-minute flaring duration corresponds to the epoch when
the radio beam sweeps our line of sight. The bursting epoch corresponds to the
episodes when stronger sunspot-like magnetic fields emerge into the white dwarf
polar cap region during which the pair production condition is satisfied and
the white dwarf behaves like a radio pulsar. It switches off as the pair
production condition breaks down.


title:
A Multistep Algorithm for the Radiation Hydrodynamical Transport of
  Cosmological Ionization Fronts and Ionized Flows

abstract:
  Radiation hydrodynamical transport of ionization fronts in the next
generation of cosmological reionization simulations holds the promise of
predicting UV escape fractions from first principles as well as investigating
the role of photoionization in feedback processes and structure formation. We
present a multistep integration scheme for radiative transfer and hydrodynamics
for accurate propagation of I-fronts and ionized flows from a point source in
cosmological simulations. The algorithm is a photon-conserving method which
correctly tracks the position of I-fronts at much lower resolutions than
non-conservative techniques. The method applies direct hierarchical updates to
the ionic species, bypassing the need for the costly matrix solutions required
by implicit methods while retaining sufficient accuracy to capture the true
evolution of the fronts. We review the physics of ionization fronts in
power-law density gradients, whose analytical solutions provide excellent
validation tests for radiation coupling schemes. The advantages and potential
drawbacks of direct and implicit schemes are also considered, with particular
focus on problem timestepping which if not properly implemented can lead to
morphologically plausible I-front behavior that nonetheless departs from
theory. We also examine the effect of radiation pressure from very luminous
central sources on the evolution of I-fronts and flows.


title: Tidal Destruction of The First Dark Microhalos

abstract:
  We point out that the usual self-similarity in cold dark matter models is
broken by encounters with individual normal galactic stars on sub-pc scale.
Tidal heating and stripping must have redefined the density and velocity
structures of the population of the Earth-mass dark matter halos, which are
likely to have been the first bound structures to form in the Universe. The
disruption rate depends strongly on {\it galaxy types} and the orbital
distribution of the microhalos; in the Milky Way, stochastic radial orbits are
destroyed first by stars in the triaxial bulge, microhalos on non-planar
retrograde orbits with large pericenters and/or apocenters survive the longest.
The final microhalo distribution in the {\it solar neighborhood} is better
described as a superposition of filamentry microstreams rather than as a set of
discrete spherical clumps in an otherwise homogeneous medium. We discuss its
important consequences to our detections of microhalos by direct recoil signal
and indirect annihilation signal.


title:
Galaxy Morphologies in the Hubble Ultra Deep Field: Dominance of Linear
  Structures at the Detection Limit

abstract:
  Galaxies in the Hubble Ultra Deep Field (UDF) larger than 10 pixels (0.3
arcsec) have been classified according to morphology and their photometric
properties are presented. There are 269 spirals, 100 ellipticals, 114 chains,
126 double-clump, 97 tadpole, and 178 clump-cluster galaxies. We also
catalogued 30 B-band and 13 V-band drop-outs and calculated their star
formation rates. Chains, doubles, and tadpoles dominate the other types at
faint magnitudes. The fraction of obvious bars among spirals is ~10 percent, a
factor of 2-3 lower than in other deep surveys. The distribution function of
axial ratios for elliptical galaxies is similar to that seen locally,
suggesting that ellipticals relaxed quickly to a standardized shape. The
distribution of axial ratios for spiral galaxies is significantly different
than locally, having a clear peak at ~0.55 instead of a nearly flat
distribution. The fall-off at small axial ratio occurs at a higher value than
locally, indicating thicker disks by a factor of ~2. The fall-off at high axial
ratio could be from intrinsic triaxial shapes or selection effects. Inclined
disks should be more highly sampled than face-on disks near the surface
brightness limit of a survey. Simple models and data distributions demonstrate
these effects. The decreased numbers of obvious spiral galaxies at high
redshifts could be partly the result of surface brightness selection.


title: Diffuse Light in the Virgo Cluster

abstract:
  We present deep optical imaging of the inner 1.5 x 1.5 degrees of the Virgo
cluster to search for diffuse intracluster light (ICL). Our image reaches a 1
sigma depth of mu_v=28.5 mag/arcsec^2 -- 1.5 mag/arcsec^2 deeper than previous
surveys -- and reveals an intricate web of diffuse intracluster light. We see
several long (>100 kpc) tidal streamers, as well as a myriad of smaller-scale
tidal tails and bridges between galaxies. The diffuse halo of M87 is traced out
to nearly 200 kpc, appearing very irregular on these scales, while significant
diffuse light is also detected around the M84/M86 pair. Several galaxies in the
core are embedded in common envelopes, suggesting they are true physical
subgroups. The complex substructure of Virgo's diffuse ICL reflects the
hierarchical nature of cluster assembly, rather than being the product of
smooth accretion around a central galaxy.


title: Mass transfer and the period decrease in RXJ0806.3+1527

abstract:
  We examine the nature of RXJ0806.3+1527 and show that it is possible to
reconcile the observed period decrease and X-ray luminosity with the transfer
of mass between two white dwarfs provided that: either the system is (i) still
in the early and short-lived (less than ~100yr) stages of mass transfer due to
atmospheric Roche-lobe overflow, or (ii) in a standard, long-term,
quasi-stationary mass-transfer phase that is significantly (~90%)
non-conservative and the conversion of accretion energy to X-rays is quite
inefficient. In either of the two cases and for a wide range of physical
parameters, we find that orbital angular momentum is lost from the system at a
rate that is a factor of a few (less than ~4) higher than the rate associated
with the emission of gravitational waves. Although the physical origin of this
extra angular momentum loss is not clear at present, it should be taken into
account in the consideration of RXJ0806.3+1527 as a verification Galactic
source for LISA.


title:
The ACS Virgo Cluster Survey X. Half-light Radii of Globular Clusters in
  Early-Type Galaxies: Environmental Dependencies and a Standard Ruler for
  Distance Estimation

abstract:
  We have measured half-light radii, r_h, for globular clusters (GCs) belonging
to the 100 early-type galaxies observed in the ACS Virgo Cluster Survey and the
elliptical galaxy NGC 4697. An analysis of the dependencies of the measured r_h
on both the properties of the GCs themselves and their host galaxies reveals
that the average r_h increases with increasing galactocentric distance or,
alternatively, with decreasing galaxy surface brightness. For the first time,
we find that the average r_h decreases with the host galaxy color. We also show
that there is no evidence for a variation of r_h with the luminosity of the
GCs. Finally, we find in agreement with previous observations that the average
r_h depends on the color of GCs, with red GCs being ~17% smaller than their
blue counterparts. We show that this difference is probably a consequence of an
intrinsic mechanism, rather than projection effects, and that it is in good
agreement with the mechanism proposed in Jordan (2004). We discuss these
findings in light of two simple pictures for the origin of the r_h of GCs and
show that both lead to a behavior in rough agreement with the observations.
After accounting for the dependencies found we show that the average GC
half-light radii <r_h> can be successfully used as a standard ruler for
distance estimation. We outline the methodology, and provide a calibration for
its use. We find <r_h> = 2.7 +- 0.35 pc for GCs with (g-z)=1.2 mag in a galaxy
with color (g-z)_{gal}=1.5 mag and at an underlying surface z-band brightness
of mu_z = 21 mag arcsec^{-2}. Using this technique, we place an upper limit of
3.4 Mpc on the 1-sigma line-of-sight depth of the Virgo Cluster. Finally, we
examine the form of the r_h distribution for our sample galaxies and provide an
analytic expression which successfully describes this distribution. (Abridged)