title: Anisotropy of the Cosmic Neutrino Background

abstract:
  The cosmic neutrino background (CNB) consists of low-energy relic neutrinos
which decoupled from the cosmological fluid at a redshift z ~ 10^{10}. Despite
being the second-most abundant particles in the universe, direct observation
remains a distant challenge. Based on the measured neutrino mass differences,
one species of neutrinos may still be relativistic with a thermal distribution
characterized by the temperature T ~ 1.9K. We show that the temperature
distribution on the sky is anisotropic, much like the photon background,
experiencing Sachs-Wolfe and integrated Sachs-Wolfe effects.


title: Entropy of gas and dark matter in galaxy clusters

abstract:
  On the basis of a large scale 'adiabatic', namely non-radiative and
non-dissipative, cosmological smooth particle hydrodynamic simulation we
compare the entropy profiles of the gas and the dark matter (DM) in galaxy
clusters. The quantity K_g = T_g \rho_g^{-2/3} provides a measure for the
entropy of the intra-cluster gas. By analogy with the thermodynamic variables
of the gas the velocity dispersion of the DM is associated with a formal
temperature and thereby K_DM = \sigma_DM^2 \rho_DM^{-2/3} is defined. This DM
entropy is related to the DM phase space density by K_DM \propto Q_DM^{-2/3}.
In accord with other studies the DM phase space density follows a power law
behaviour, Q_DM \propto r^{-1.82}, which corresponds to K_DM \propto r^{1.21}.
The simulated intra-cluster gas has a flat entropy core within (0.8 \pm 0.4)
R_s, where R_s is the NFW scale radius. The outer profile follows the DM
behaviour, K_g \propto r^{1.21}, in close agreement with X-ray observations.
Upon scaling the DM and gas densities by their mean cosmological values we find
that outside the entropy core a constant ratio of K_g / K_{DM} = 0.71 \pm 0.18
prevails. By extending the definition of the gas temperature to include also
the bulk kinetic energy the ratio of the DM and gas extended entropy is found
to be unity for r > 0.8 R_s. The constant ratio of the gas thermal entropy to
that of the DM implies that observations of the intra-cluster gas can provide
an almost direct probe of the DM.


title:
Optical Intensity Interferometry with Atmospheric Cherenkov Telescope
  Arrays

abstract:
  In the 1970s, the Narrabri intensity interferometer was used to measure 32
stellar diameters; some as small as 0.4 milli-arc-seconds (mas). The
interferometer consisted of a pair of 6.5m telescopes with relatively crude
optics, similar to those currently in use as Atmospheric Cherenkov Telescopes
(ACT). We explore the possibility of implementing a modern intensity
interferometer on an ACT array. Developments in fast digital signal processing
technology now make such a system relatively easy to implement, and provide
improved sensitivity. Allowing measurements at short wavelength (<400nm), with
long baselines (> 100m), which are still challenging for Michelson
interferometers, present ACT arrays could be used to probe angular structures
as small as ~0.2mas, and smaller with large array projects already being
discussed. This would provide measurements of stellar diameters, binary
systems, circumstellar environments and, possibly, stellar surface features.
ACT arrays could be used as intensity interferometers during bright moon
periods, providing valuable scientific output for little expense and no impact
on the gamma-ray observing schedule.


title:
Minimal Stereoscopic Analysis for Imaging Atmospheric Cherenkov
  Telescope Arrays

abstract:
  The trajectory of a primary gamma-ray detected with an array of at least four
atmospheric Cherenkov imaging telescopes can be reconstructed from the shower
image centroid positions and geometrical considerations independent of the
primary energy. Using only the image centroid positions some cosmic-ray
discrimination is also possible. This minimal approach opens the possibility of
pushing the analysis threshold to lower values, close to the hardware
threshold.


title: Cascading of Fast-Mode Balanced and Imbalanced Turbulence

abstract:
  We study the cascading of fast MHD modes in magnetically dominated plasma by
performing one-dimensional (1D) dynamical simulations. We find that the
cascading becomes more efficient as an angle between wave vector and underlying
magnetic field increases and fast mode becomes more compressive. We also study
imbalanced turbulence, in which wave packets propagating in one-direction have
more power than those in the opposite direction. Unlike imbalanced \Alfvenic
turbulence, the imbalanced fast mode turbulence shows faster cascading as the
degree of imbalance increases. We find that the spectral index of the velocity
and magnetic field, which are carried by the fast-mode turbulence, quickly
reaches stationary value of -2. Thus we conclude that the dissipation of fast
mode, at least in 1D case, happens not due to weak or strong turbulent
cascading, but mostly due to nonlinear steepening. The density fluctuations,
which are carried by slow-mode perturbation in the larger scale and
entropy-mode perturbation in the smaller scale, depend on initial driving
spectrum and a ratio of specific heat.


title: What is the Total Deuterium Abundance in the Local Galactic Disk?

abstract:
  Analyses of spectra obtained with the Far Ultraviolet Spectroscopic Explorer
(FUSE) satellite, together with spectra from the Copernicus and IMAPS
instruments, reveal an unexplained very wide range in the observed
deuterium/hydrogen (D/H) ratios for interstellar gas in the Galactic disk
beyond the Local Bubble. We argue that spatial variations in the depletion of
deuterium onto dust grains can explain these local variations in the observed
gas-phase D/H ratios. We present a variable deuterium depletion model that
naturally explains the constant measured values of D/H inside the Local Bubble,
the wide range of gas-phase D/H ratios observed in the intermediate regime (log
N(H I} = 19.2-20.7), and the low gas-phase D/H ratios observed at larger
hydrogen column densities. We consider empirical tests of the deuterium
depletion hypothesis: (i) correlations of gas-phase D/H ratios with depletions
of the refractory metals iron and silicon, and (ii) correlation with the
molecular hydrogen rotational temperature. Both of these tests are consistent
with deuterium depletion from the gas phase in cold, not recently shocked,
regions of the ISM, and high gas-phase D/H ratios in gas that has been shocked
or otherwise heated recently. We argue that the most representative value for
the total (gas plus dust) D/H ratio within 1 kpc of the Sun is >=23.1 +/- 2.4
(1 sigma) parts per million (ppm). This ratio constrains Galactic chemical
evolution models to have a very small deuterium astration factor, the ratio of
primordial to total (D/H) ratio in the local region of the Galactic disk, which
we estimate to be f_d <= 1.19 +/-0.16 (1 sigma) or <= 1.12 +/- 0.14 (1 sigma)
depending on the adopted light element nuclear reaction rates.


title:
Infrared 2-4 Micron Spectroscopy and Millimeter Interferometric HCN and
  HCO+ Observations of the Individual Merging Components of Arp299

abstract:
  We present ground-based infrared K- (2-2.5 micron) and L-band (2.8-4.1
micron) spectroscopy, as well as interferometric observations at 3mm, for the
individual merging components (A, B, and C) of the luminous infrared galaxy Arp
299. We investigate the presence and location of the putative buried active
galactic nucleus (AGN) inferred from previous X-ray observations at E > 10 keV.
Our sub-arcsec-resolution infrared spectra clearly reveal that the putative
buried AGN resides in the nucleus B1 (a subcomponent of B), based on a very low
equivalent width of 3.3 micron polycyclic aromatic hydrocarbon emission, a weak
2.3 micron CO absorption feature, and a large time variation of the K- and
L-band continuum fluxes. In component C, we find strong 3.1 micron ice
absorption at L and weak 2.3 micron CO absorption at K, as expected in a buried
AGN; however, a centrally concentrated young super star cluster is an
alternative possibility because of the modest infrared luminosity and
non-galaxy-nucleus nature of this component. The infrared K- and L-band spectra
of the infrared brightest nucleus, A, are typical of a normal starburst with no
explicit AGN signatures. Our interferometric observations simultaneously obtain
HCN (J=1-0) and HCO+ (J=1-0) emission lines with 4 arcsec resolution, and we
find the HCN to HCO+ brightness-temperature ratios to be as low as those found
in starburst nuclei in all the major merging components of Arp 299. The low
ratio even in the AGN-hosting nucleus B may be due to the presence of a large
amount of high-density molecular gas whose chemistry is dominated by coexisting
starbursts and/or shocks, rather than by the central strong X-ray-emitting AGN.


title: Discovery of a possible X-ray counterpart to HESS J1804-216

abstract:
  Suzaku deep observations have discovered two highly significant nonthermal
X-ray sources, Suzaku J1804$-$2142 (Src 1) and Suzaku J1804$-$2140 (Src 2),
positionally coincident with the unidentified TeV $\gamma$-ray source, HESS
J1804$-$216. The X-ray sources are not time variable and show no counterpart in
other wavebands, except for the TeV source. Src 1 is unresolved at Suzaku
spatial resolution, whereas Src 2 is extended or composed of multiple sources.
The X-ray spectra are highly absorbed, hard, and featureless, and are well
fitted by absorbed power-law models with best-fit photon indices and absorption
columns of $-0.3_{-0.5}^{+0.5}$ and $0.2_{-0.2}^{+2.0}\times 10^{22}$ cm$^{-2}$
for Src 1, and $1.7_{-1.0}^{+1.4}$ and $1.1_{-0.6}^{+1.0}\times 10^{23}$
cm$^{-2}$ for Src 2. The measured X-ray absorption to the latter source is
significantly larger than the total Galactic neutral hydrogen column in that
direction. The unabsorbed 2--10 keV band luminosities are $7.5\times
10^{32}(d/{\rm 5 kpc})^2$ ergs s$^{-1}$ (Src 1) and $1.3\times 10^{33}(d/{\rm 5
kpc})^2$ ergs s$^{-1}$ (Src 2), where $d$ is the source distance. Among the
handful of TeV sources with known X-ray counterparts, HESS J1804$-$216 has the
largest ratio of TeV $\gamma$-ray to hard X-ray fluxes. We discuss the nature
of the emission and propose the Suzaku sources as plausible counterparts to the
TeV source, although further observations are necessary to confirm this.


title: Chandra Smells a RRAT: X-ray Detection of a Rotating Radio Transient

abstract:
  "Rotating RAdio Transients" (RRATs) are a newly discovered astronomical
phenomenon, characterised by occasional brief radio bursts, with average
intervals between bursts ranging from minutes to hours. The burst spacings
allow identification of periodicities, which fall in the range 0.4 to 7
seconds. The RRATs thus seem to be rotating neutron stars, albeit with
properties very different from the rest of the population. We here present the
serendipitous detection with the Chandra X-ray Observatory of a bright
point-like X-ray source coincident with one of the RRATs. We discuss the
temporal and spectral properties of this X-ray emission, consider counterparts
in other wavebands, and interpret these results in the context of possible
explanations for the RRAT population.


title:
Detection of ultra high energy neutrinos with an underwater very large
  volume array of acoustic sensors: A simulation study

abstract:
  This thesis investigates the detection of ultra high energy (E > 1 EeV)
cosmic neutrinos using acoustic sensors immersed in water. The method is based
on the thermoacoustic model describing the production of microsecond bipolar
acoustic pulses by neutrino-induced particle cascades. These cascades locally
heat the medium which leads to rapid expansion and a short sonic pulse
detectable in water with hydrophones over distances of several kilometres. This
makes acoustic detection an approach complementary to todays optical Cerenkov
and radio Cerenkov detectors, and could help to reduce the respective
systematic uncertainties. In this work a complete simulation / reconstruction
chain for a submarine acoustic neutrino telescope is developed, and the
sensitivity of such a detector to a diffuse flux of ultra highenergy cosmic
neutrinos is estimated.


title: No supernovae associated with two long-duration gamma ray bursts

abstract:
  It is now accepted that long duration gamma-ray bursts (GRBs) are produced
during the collapse of a massive star. The standard "collapsar" model predicts
that a broad-lined and luminous Type Ic core-collapse supernova (SN)
accompanies every long-duration GRB. This association has been confirmed in
observations of several nearby GRBs. Here we present observations of two nearby
long-duration GRBs that challenge this simple view. In the GRBs 060505 and
060614 we demonstrate that no SN emission accompanied these long-duration
bursts, down to limits hundreds of times fainter than the archetypal SN 1998bw
that accompanied GRB 980425, and fainter than any Type Ic SN ever observed.
Multi-band observations of the early afterglows, as well as spectroscopy of the
host galaxies, exclude the possibility of significant dust obscuration and show
that the bursts originated in star-forming regions. The absence of a SN to such
deep limits is qualitatively different from all previous nearby long GRBs and
suggests a new phenomenological type of massive stellar death. From the
supplementary material: Now we have observed SN-less GRBs in star-forming
regions, suggesting that a non-detection of a SN does not preclude a massive
progenitor. The position of the GRB, i.e. in a star-forming region or in an
older component, may be the only way to discriminate between merging compact
objects and massive stars as progenitors. In fact, several host galaxies for
short GRBs have been found to be as actively star-forming as some host galaxies
of long-duration GRBs. The GRB labels "long" and "short" have become synonymous
with "massive stars" and "other progenitors". These distinctions may need to be
relaxed.


title:
The Influence of Magnetic Field on Oscillations in the Solar
  Chromosphere

abstract:
  Two sequences of solar images obtained by the Transition Region and Coronal
Explorer in three UV passbands are studied using wavelet and Fourier analysis
and compared to the photospheric magnetic flux measured by the Michelson
Doppler Interferometer on the Solar Heliospheric Observatory to study wave
behaviour in differing magnetic environments. Wavelet periods show deviations
from the theoretical cutoff value and are interpreted in terms of inclined
fields. The variation of wave speeds indicates that a transition from dominant
fast-magnetoacoustic waves to slow modes is observed when moving from network
into plage and umbrae. This implies preferential transmission of slow modes
into the upper atmosphere, where they may lead to heating or be detected in
coronal loops and plumes.


title:
Correlation between the Peak Spectral Energy of Gamma-Ray Bursts and the
  Peak Luminosity of the Underlying Supernovae: Implication for the Nature of
  GRB-SN Connection

abstract:
  In this paper we present a correlation between the peak spectral energy of
gamma-ray bursts (GRBs) and the peak bolometric luminosity of the underlying
supernovae (SNe), based on a sample of four pairs of GRBs-SNe with
spectroscopically confirmed connection. Combining it with the well-known
relation between the peak spectral energy and the isotropic equivalent energy
of GRBs, we obtain an upper limit on the isotropic energy of GRBs, which is
\approx 10^{52} erg (L_{SN,peak}/10^{43} erg s^{-1})^{10}, where L_{SN,peak} is
the peak bolometric luminosity of the SNe. Our results suggest that the
critical parameter determining the GRB-SN connection is the peak luminosity of
SNe, rather than the feature of the SN spectra and/or the SN explosion energy
as commonly hypothesized. Since it is generally believed that the peak
luminosity of SNe powered by radioactive decays is related to the amount of
56Ni produced in the SN explosion, the mass of 56Ni may be a key physical
factor for understanding the nature of GRBs and their connection with SNe.
Application of our relation to Type Ibc SNe with normal peak luminosities
indicates that if those normal SNe have GRBs accompanying them, the GRBs would
be extremely soft and sub-energetic in gamma-rays, and hence easier to detect
with X-ray or UV detectors than with gamma-ray detectors.


title: Neutron star binaries and long duration gamma-ray bursts

abstract:
  Cosmological long-duration gamma-ray bursts (LGRBs) are thought to originate
from the core collapse to black holes of stripped massive stars. Those with
sufficient rotation form a centrifugally-supported torus whose collapse powers
the GRB. We investigate the role of tidal locking within a tight binary as a
source of the necessary angular momentum. We find that the binary orbit must be
no wider than a few solar radii for a torus to form upon core collapse.
Comparing this criterion to the observed population of binaries containing two
compact objects suggests that rotation may have been important in the formation
of up to 50% of the observed systems. As these systems created a neutron star
and not a black hole they presumably did not produce highly luminous GRBs. We
suggest instead that they make the subset of GRBs in the relatively local
universe which have much lower luminosity.


title: Strange Exotic States and Compact Stars

abstract:
  We discuss the possible appearance of strange exotic multi-quark states in
the interior of neutron stars and signals for the existence of strange quark
matter in the core of compact stars. We show how the in-medium properties of
possible pentaquark states are constrained by pulsar mass measurements. The
possibility of generating the observed large pulsar kick velocities by
asymmetric emission of neutrinos from strange quark matter in magnetic fields
is outlined.


title: Mysteries on Universe's Largest Observable Scales

abstract:
  We review recent findings that the universe on its largest scales shows hints
of the violation of statistical isotropy, in particular alignment with the
geometry and direction of motion of the solar system, and missing power at
scales greater than 60 degrees. We present the evidence, attempts to explain it
using astrophysical, cosmological or instrumental mechanisms, and prospects for
future understanding.


title:
Incompatibility of long-period neutron star precession with creeping
  neutron vortices

abstract:
  Aims: To determine whether ``vortex creep'' in neutron stars, the slow motion
of neutron vortices with respect to pinning sites in the core or inner crust,
is consistent with observations of long-period precession. Methods: Using the
concept of vortex drag, I discuss the precession dynamics of a star with
imperfectly-pinned (i.e., "creeping'') vortices. Results: The precession
frequency is far too high to be consistent with observations, indicating that
the standard picture of the outer core (superfluid neutrons in co-existence
with type II, superconducting protons) should be reconsidered. There is a slow
precession mode, but it is highly over-damped and cannot complete even a single
cycle. Moreover, the vortices of the inner crust must be able to move with
little dissipation with respect to the solid.


title:
XMM-NEWTON Detection of X-ray Emission from the Compact Steep Spectrum
  Radio Galaxy 3C303.1

abstract:
  Using XMM we detect faint unresolved X-ray emission from the Compact Steep
Spectrum radio galaxy 3C303.1. We detect a thermal component at kT = 0.8 keV
which seems likely to be produced in the ISM of the host galaxy. There is
evidence for a second component in the spectrum whose nature is currently
ambiguous. Plausible hypotheses for the second component include (1) hot gas
shocked by the expansion of the radio source, and (2) Synchrotron self-Compton
emission from the southern radio lobe if the magnetic field is below the
equipartition value by a factor of about 3.5.


title:
Extraordinarily Hot X-ray Emission from the 09 Emission Line Star HD
  119682

abstract:
  We present new optical and X-ray observations to show that the X-ray source 1
WGA J1346.5--6255 previously associated with the SNR G309.2--0.6 can be
unequivocally identified with the emission line star HD 119682 located in the
foreground open cluster NGC 5281. Images from Chandra in the X-ray band as well
as from Magellan in the narrow optical H-alpha band show a coincidence of the
source positions within 0.5". The X-ray source appears extremely hot for an
OB-star identified as of O9.7e type. XMM-Newton spectra show plasma
temperatures of 1 keV and >8 keV with an X-ray luminosity of 6.2E32 +/-0.1E32
erg/s. The optical and X-ray properties are very reminiscent of the prototype
emission line star Gamma-Cas. We discuss the ramifications of this similarity
with respect to very early type emission line stars as a new class of hard
X-ray sources.


title:
An enigmatic long-lasting gamma-ray burst not accompanied by a bright
  supernova

abstract:
  Gamma-ray bursts (GRBs) are short, intense flashes of soft gamma-rays coming
from the distant Universe. Long-duration GRBs (those lasting more than ~2 s)
are believed to originate from the deaths of massive stars, mainly on the basis
of a handful of solid associations between GRBs and supernovae. GRB 060614, one
of the closest GRBs discovered, consisted of a 5-s hard spike followed by
softer, brighter emission that lasted for ~100 s. Here we report deep optical
observations of GRB 060614 showing no emerging supernova with absolute visual
magnitude brighter than M_V = -13.7. Any supernova associated with GRB 060614
was therefore at least 100 times fainter, at optical wavelengths, than the
other supernovae associated with GRBs. This demonstrates that some long-lasting
GRBs can either be associated with a very faint supernova or produced by
different phenomena.


title: The Automated Palomar 60-Inch Telescope

abstract:
  We have converted the Palomar 60-inch telescope (P60) from a classical night
assistant-operated telescope to a fully robotic facility. The automated system,
which has been operational since September 2004, is designed for moderately
fast (t <~ 3 minutes) and sustained (R <~ 23 mag) observations of gamma-ray
burst afterglows and other transient events. Routine queue-scheduled
observations can be interrupted in response to electronic notification of
transient events. An automated pipeline reduces data in real-time, which is
then stored on a searchable web-based archive for ease of distribution. We
describe here the design requirements, hardware and software upgrades, and
lessons learned from roboticization. We present an overview of the current
system performance as well as plans for future upgrades.


title: Cosmological Implications of the Second Parameter of Type Ia Supernovae

abstract:
  Theoretical models predict that the initial metallicity of the progenitor of
a Type Ia supernova (SN Ia) affects the peak of the supernova light curve. This
can cause a deviation from the standard light curve calibration employed when
using SNe Ia as standardizable distance candles and, if there is a systematic
evolution of the metallicity of SN Ia progenitors, could affect the
determination of cosmological parameters. Here we show that this metallicity
effect can be substantially larger than has been estimated previously, when the
neutronisation in the immediate pre-explosion phase in the CO white dwarf is
taken into account, and quantitatively assess the importance of metallicity
evolution for determining cosmological parameters. We show that, in principle,
a moderate and plausible amount of metallicity evolution could mimic a
lambda-dominated, flat Universe in an open, lambda-free Universe. However, the
effect of metallicity evolution appears not large enough to explain the high-z
SN Ia data in a flat Universe, for which there is strong independent evidence,
without a cosmological constant. We also estimate the systematic uncertainties
introduced by metallicity evolution in a lambda-dominated, flat Universe. We
find that metallicity evolution may limit the precision with which Omega_m and
w can be measured and that it will be difficult to distinguish evolution of the
equation of state of dark energy from metallicity evolution, at least from SN
Ia data alone.


title: Proto-Brown Dwarf Disks as Products of Protostellar Disk Encounters

abstract:
  The formation of brown dwarfs via encounters between proto-stars has been
confirmed with high-resolution numerical simulations with a restricted
treatment of the thermal conditions. The new results indicate that young brown
dwarfs (BDs) formed this way are disk-like and often reside in multiple
systems. The newly-formed proto-BDs disks are up to 18 AU in size and spin
rapidly making small-scale bipolar outflows, fragmentation and the possible
formation of planetary companions likely as have recently been observed for
BDs. The object masses range from 2 to 73 Jupiter masses, distributed in a
manner consistent with the observed sub-stellar initial mass function. The
simulations usually form multiple BDs on eccentric orbits about a star. One
such system was hierarchical, a BD binary in orbit around a star, which may
explain recently observed hierarchical systems. One third of the BDs were
unbound after a few thousand years and interactions among orbiting BDs may
eject more or add to the number of binaries. Improvements over prior work
include resolution down to a Jupiter mass, self-consistent models of the
vertical structure of the initial disks and careful attention to avoid
artificial fragmentation.


title: Structure of Magnetic Tower Jets in Stratified Atmospheres

abstract:
  Based on a new approach on modeling the magnetically dominated outflows from
AGNs (Li et al. 2006), we study the propagation of magnetic tower jets in
gravitationally stratified atmospheres (such as a galaxy cluster environment)
in large scales ($>$ tens of kpc) by performing three-dimensional
magnetohydrodynamic (MHD) simulations. We present the detailed analysis of the
MHD waves, the cylindrical radial force balance, and the collimation of
magnetic tower jets. As magnetic energy is injected into a small central volume
over a finite amount of time, the magnetic fields expand down the background
density gradient, forming a collimated jet and an expanded ``lobe'' due to the
gradually decreasing background density and pressure. Both the jet and lobes
are magnetically dominated. In addition, the injection and expansion produce a
hydrodynamic shock wave that is moving ahead of and enclosing the magnetic
tower jet. This shock can eventually break the hydrostatic equilibrium in the
ambient medium and cause a global gravitational contraction. This contraction
produces a strong compression at the head of the magnetic tower front and helps
to collimate radially to produce a slender-shaped jet. At the outer edge of the
jet, the magnetic pressure is balanced by the background (modified) gas
pressure, without any significant contribution from the hoop stress. On the
other hand, along the central axis of the jet, hoop stress is the dominant
force in shaping the central collimation of the poloidal current. The system,
which possesses a highly wound helical magnetic configuration, never quite
reaches a force-free equilibrium state though the evolution becomes much slower
at late stages. The simulations were performed without any initial
perturbations so the overall structures of the jet remain mostly axisymmetric.


title:
High-Resolution Spectroscopy of GRB030226: Features of a Massive Star
  Progenitor or Intervening Absorption Systems?

abstract:
  We present a high-resolution Keck/ESI spectrum of GRB, which exhibits four
absorption systems at z=1.04329, 1.95260, 1.96337, and 1.98691. The two highest
redshift systems, separated by about 2400 km/s, have been previously suspected
as kinematic features arising in the circumstellar wind around the progenitor
star. However, the high column densities of low-ionization species (including
possibly neutral hydrogen) in the blue-shifted system, are inconsistent with
the expected highly ionized state of the circumstellar wind from the massive
progenitor star, even prior to the GRB explosion. This conclusion is also
supported by the lack of detectable absorption from fine-structure transitions
of SiII and FeII. Instead we conclude that the two redshift systems are similar
to multiple DLAs found in QSO sight lines with a similar velocity separation
and chemical abundance of [Cr/Fe] and [Zn/Fe]. The absorption system at
z=1.96337 is likely an intervening low-mass galaxy, possibly related to the GRB
host as part of a forming large-scale structure.


title: Bayesian Model Selection and Extrasolar Planet Detection

abstract:
  Radial velocity (RV) planet searches are increasingly finding planets with
small velocity amplitudes, with long orbital periods, or in multiple planet
systems. Bayesian inference has the potential to improve the interpretation of
existing observations, the planning of future observations and ultimately
inferences concerning the overall population of planets. In recent years, the
refinement of Markov chain Monte Carlo (MCMC) algorithms has made it practical
to accurately characterize orbital parameters and their uncertainties from RV
observations of single-planet and weakly interacting multiple-planet systems.
Unfortunately, MCMC is not sufficient for Bayesian model selection, i.e.,
comparing the marginal posterior probability of models, as is necessary to
determine how strongly the observational data favor a model with n+1 planets
over a model with just n planets. Many of the obvious estimators for the
marginal posterior probability suffer from poor convergence properties. We
compare several estimators of the marginal likelihood and feature those that
display desirable convergence properties based on the analysis of a sample data
set for HD 88133b. We find that methods based on importance sampling are most
efficient, provided that a good analytic approximation of the posterior
probability distribution is available. We present a simple algorithm for using
a sample from the posterior to construct a mixture distribution that
approximates the posterior and can be used for importance sampling and Bayesian
model selection. We conclude with some suggestions for the development and
refinement of computationally efficient and robust estimators of marginal
posterior probabilities.


title: Errors in kinematic distances and our image of the Milky Way Galaxy

abstract:
  Errors in the kinematic distances, under the assumption of circular gas
orbits, were estimated by performing synthetic observations of a model disk
galaxy. It was found that the error is < 0.5 kpc for most of the disk when the
measured rotation curve was used, but larger if the real rotation curve is
applied. In both cases, the error is significantly larger at the positions of
the spiral arms. The error structure is such that, when kinematic distances are
used to develope a picture of the large scale density distribution, the most
significant features of the numerical model are significantly distorted or
absent, while spurious structure appears. By considering the full velocity
field in the calculation of the kinematic distances, most of the original
density structures can be recovered.


title:
"The Perfect Slope": A new robust low-scatter X-ray mass indicator for
  clusters of galaxies

abstract:
  This presentation is a Moriond version of our recent paper (Kravtsov,
Vikhlinin & Nagai astro-ph/0603205) where we discussed X-ray proxies for the
total cluster mass, including the spectral temperature (Tx), gas mass measured
within r500 (Mg), and the new proxy, Yx, which is a simple product of Tx and
Mg. We use mock Chandra images constructed for a sample of clusters simulated
with high resolution in the concordance LambdaCDM cosmology. The simulated
clusters exhibit tight correlations between the considered observables and
total mass. The normalizations of the M500-Tx, Mg-Tx, and M500-Yx relations
agree to better than =~ 10-15% with the current observational measurements of
these relations. Our results show that Yx is the best mass proxy with a
remarkably low scatter of only =~ 5-7% in M500 for a fixed Yx, at both low and
high redshifts and regardless of whether clusters are relaxed or not. In
addition, we show that redshift evolution of the Yx-M500 relation is close to
the self-similar prediction, which makes Yx a very attractive mass indicator
for measurements of the cluster mass function from X-ray selected samples.


title: Asteroseismic Diagnostics of Stellar Convective Cores

abstract:
  We present a detailed study of the small frequency separations as diagnostics
of the mass of the convective core and evolutionary stage of solar-type stars.
We demonstrate how the small separations can be combined to provide sensitive
tests for the presence of convective overshoot at the edge of the core. These
studies are focused on low degree oscillation modes, the only modes expected to
be detected in distant stars. Using simulated data with realistic errors, we
find that the mass of the convective core can be estimated to within 5% if the
total stellar mass is known. Systematic errors arising due to uncertainty in
the mass could be up to 20%. The evolutionary stage of the star, determined in
terms of the central hydrogen abundance using our proposed technique, however,
is much less sensitive to the mass estimate.


title:
Bright Metal-Poor Stars from the Hamburg/ESO Survey. I. Selection and
  Follow-up Observations from 329 Fields

abstract:
  We present a sample of 1777 bright (9<B<14) metal-poor candidates selected
from the Hamburg/ESO Survey (HES). Despite saturation effects present in the
red portion of the HES objective-prism spectra, the data were recoverable and
quantitative selection criteria could be applied to select the sample. Analyses
of medium-resolution (~2 A) follow-up spectroscopy of the entire sample,
obtained with several 2 to 4 m class telescopes, yielded 145 new metal-poor
stars with metallicity [Fe/H]<-2.0, of which 79 have [Fe/H]<-2.5, and 17 have
[Fe/H]<-3.0. We also obtained C/Fe estimates for all these stars. From this, we
find a frequency of C-enhanced ([C/Fe]>1.0) metal-poor ([Fe/H]<-2.0) giants of
9% +- 2%, which is lower than previously reported. However, the frequency
raises to similar (>20%) and higher values with increasing distance from the
Galactic plane. Although the numbers of stars at low metallicity are falling
rapidly at the lowest metallicities, there is evidence that the fraction of
carbon-enhanced metal-poor stars is increasing rapidly as a function of
declining metallicity. For ~60 objects, high-resolution data have already been
obtained; one of these, HE 1327-2326, is the new record holder for the most
iron-deficient star known.


title: Submillimetre Emission from Eta Carinae

abstract:
  We present critical, long-wavelength observations of Eta Carinae in the
submillimetre using SCUBA on the JCMT at 850 and 450 um to confirm the presence
of a large mass of warm dust around the central star. We fit a two-component
blackbody to the IR-submm spectral energy distribution and estimate between
0.3-0.7 solar masses of dust exists in the nebula depending on the dust
absorption properties and the extent of contamination from free-free emission
at the SCUBA wavelengths. These results provide further evidence that Eta
Carinae's circumstellar nebula contains > 10 solar masses of gas, although this
may have been ejected on a longer timescale than previously thought.


title:
Diamonds and PAHs in the Circumstellar Environment of the Herbig Ae/Be
  Star Elias 1

abstract:
  We report long-slit spectroscopic observations of the Herbig Ae/Be star Elias
1 in the 3.2-3.6 mum region covering the C-H stretch emission features of
hydrogen-terminated diamonds and PAHs. The data were recorded at UKIRT using
UIST and yield information on the profiles and intensities of the bands as a
function of offset along the N-S and E-W axes centred on the close binary. The
diamond and nearby IR continuum emission arises from a symmetrical inner core
region (< 0.34 arcsec or 48 AU). The 3.3 mum PAH emission is extended along the
E-W axis up to ~ 100 AU each side of the star. This result supports a
suggestion of Haas, Leinert & Richichi (1997) of an E-W oriented bipolar nebula
in Elias 1.


title: A Hard X-ray View on Scorpius X-1 with INTEGRAL: non-Thermal Emission ?

abstract:
  We present here simultaneous INTEGRAL/RXTE observations of Sco X-1, and in
particular a study of the hard X-ray emission of the source and its correlation
with the position in the Z-track of the X-ray color-color diagram. We find that
the hard X-ray (above about 30 keV) emission of Sco X-1 is dominated by a
power-law component with a photon index of ~3. The flux in the power-law
component slightly decreases when the source moves in the color-color diagram
in the sense of increasing inferred mass accretion rate from the horizontal
branch to the normal branch/flaring branch vertex. It becomes not significantly
detectable in the flaring branch, where its flux has decreased by about an
order of magnitude. These results present close analogies to the behavior of GX
17+2, one of so-called Sco-like Z sources. Finally, the hard power law in the
spectrum of Sco X-1 does not show any evidence of a high energy cutoff up to
100 - 200 keV, strongly suggesting a non-thermal origin of this component.


title: The Water Vapor Abundance in Orion KL Outflows

abstract:
  We present the detection and modeling of more than 70 far-IR pure rotational
lines of water vapor, including the 18O and 17O isotopologues, towards Orion
KL. Observations were performed with the Long Wavelength Spectrometer
Fabry-Perot (LWS/FP; R~6800-9700) on board the Infrared Space Observatory (ISO)
between ~43 and ~197 um. The water line profiles evolve from P-Cygni type
profiles (even for the H2O18 lines) to pure emission at wavelengths above ~100
um. We find that most of the water emission/absorption arises from an extended
flow of gas expanding at 25+-5 kms^-1. Non-local radiative transfer models show
that much of the water excitation and line profile formation is driven by the
dust continuum emission. The derived beam averaged water abundance is
2-3x10^-5. The inferred gas temperature Tk=80-100 K suggests that: (i) water
could have been formed in the "plateau" by gas phase neutral-neutral reactions
with activation barriers if the gas was previously heated (e.g. by shocks) to
>500 K and/or (ii) H2O formation in the outflow is dominated by in-situ
evaporation of grain water-ice mantles and/or (iii) H2O was formed in the
innermost and warmer regions (e.g. the hot core) and was swept up in ~1000 yr,
the dynamical timescale of the outflow.


title:
Very Massive Close Binaries and the Puzzling Temporal Evolution of 14N
  in the Solar Neighbourhood

abstract:
  Low metallicity very massive stars with an initial mass between 140 Mo and
260 Mo can be subdivided into two groups: those between 140 Mo and 200 Mo which
produce a relatively small amount of Fe, and those with a mass between 200 Mo
and 260 Mo where the Fe-yield ejected during the supernova explosion is
enormous. We first demonstrate that the inclusion of the second group into a
chemical evolutionary model for the Solar Neighbourhood predicts an early
temporal evolution of Fe which is at variance with observations whereas it can
not be excluded that the first group could have been present. We then show that
a low metallicity binary with very massive components (with a mass
corresponding to the first group) can be an efficient site of primary 14N
production through the explosion of a binary component that has been polluted
by the pair instability supernova ejecta of its companion. When we implement
these massive binary 14N yields in a chemical evolution model, we conclude that
very massive close binaries may be important sites of 14N enrichment during the
early evolution of the Galaxy.


title: Pinning Down Gravitational Settling

abstract:
  We analyse high-resolution archival UVES data of turnoff and subgiant stars
in the nearby globular cluster NGC 6397 ([Fe/H] = -2). Balmer-profile analyses
are performed to derive reddening-free effective temperatures. Due to the
limited S/N and uncertainties related to blaze removal, we find the data
quality insufficient to exclude the existence of gravitational settling. If the
newly derived effective temperatures are taken as a basis for an abundance
analysis, the photospheric iron (Fe II) abundance in the turnoff stars is 0.11
dex lower than in the (well-mixed) subgiants.


title:
Dielectronic recombination of Fe 3p^q ions: a key ingredient for
  describing X-ray absorption in active galactic nuclei

abstract:
  We have carried-out multi-configuration Breit-Pauli AUTOSTRUCTURE
calculations for the dielectronic recombination (DR) of Fe^{8+} - Fe^{12+}
ions. We obtain total DR rate coefficients for the initial ground-level which
are an order of magnitude larger than those corresponding to radiative
recombination (RR), at temperatures where Fe 3p^q (q=2-6) ions are abundant in
photoionized plasmas. The resultant total (DR+RR) rate coefficients are then an
order of magnitude larger than those currently in use by photoionized plasma
modeling codes such as CLOUDY, ION and XSTAR. These rate coefficients, together
with our previous results for q=0 and 1, are critical for determining the
ionization balance of the M-shell Fe ions which give rise to the prominent
unresolved-transition-array X-ray absorption feature found in the spectrum of
many active galactic nuclei. This feature is poorly described by CLOUDY and
ION, necessitating an ad hoc modification to the low-temperature DR rate
coefficients. Such modifications are no longer necessary and a rigorous
approach to such modeling can now take place using these data.


title: Recent Results from Kascade-Grande

abstract:
  KASCADE-Grande is a new extensive air shower experiment co-located to the
KASCADE site at Forschungszentrum Karlsruhe. The multi-detector system allows
to investigate the energy spectrum, composition, and anisotropies of cosmic
rays with unprecedented prevision in the energy range from 10^{14}-10^{18} eV.
The primary goals besides investigating the origin of the knee at E ~ 3 *
10^{15} eV, are to verify the existence of the second knee at E ~ 10^{17} eV
and to measure the composition in the expected transition region of galactic to
extragalactic cosmic rays. The performance of the apparatus and shower
reconstruction methods will be discussed on the basis of detailed Monte Carlo
simulations and first data. First results based on slightly more than a year of
data taking are presented.


title:
Sensitivity of p-Process Nucleosynthesis to Nuclear Reaction Rates in a
  25 Solar Mass Supernova Model

abstract:
  The astrophysical p process, which is responsible for the origin of the
proton rich stable nuclei heavier than iron, was investigated using a full
nuclear reaction network for a type II supernova explosion when the shock front
passes through the O/Ne layer. Calculations were performed with a multi-layer
model adopting the seed of a pre-explosion evolution of a 25 solar mass star.
The reaction flux was calculated to determine the main reaction path and
branching points responsible for synthesizing the proton rich nuclei. In order
to investigate the impact of nuclear reaction rates on the predicted p-process
abundances, extensive simulations with different sets of collectively and
individually modified neutron-, proton-, alpha-capture and photodisintegration
rates have been performed. These results are not only relevant to explore the
nuclear physics related uncertainties in p-process calculations but are also
important for identifying the strategy and planning of future experiments.


title: The Evolution of Lyman alpha Absorbers in the Redshift Range 0.5<z<1.9

abstract:
  We investigate the evolution and the statistical properties of the Lya
absorbers of the intergalactic medium (IGM) in the largely unexplored redshift
range z=0.5-1.9. We use high-resolution (R > 30,000) UV (STIS) and optical
(VLT/UVES and Keck/HIRES) spectra of nine bright quasars with z_em < 1.94. The
main results for the combined Lya line sample are summarized as follows: 1. The
evolution of the number density of the absorbers can be described by the power
law dn/dz ~ (1+z)^gamma. The number density of the low column density lines
decreases with decreasing z with gamma=0.74+-0.31 in the interval z=0.7-1.9. A
comparison with results at higher redshifts shows that it is decelerated in the
explored redshift range and turns into a flat evolution for z -> 0. The
stronger absorbers thin out faster (gamma=1.50+-0.45). The break in their
evolution predicted for z=1.5-1.7 cannot be seen down to z=0.7. On the other
hand, a comparison with values from the literature for the local number density
gives a hint that this break occurs at lower redshift. 2. The distribution of
the column densities of the absorbers is complete down to N_HI=10^12.90 cm^-2.
It can be approximated by a single power law with the exponent beta=1.60+-0.03
over almost three orders of magnitude. beta is redshift independent. 3. The Lya
lines with lower column densities as well as the higher column density lines
show marginal clustering with a 2 sigma significance over short distances
(Delta v < 200 km/s and Delta v < 100 km/s, respectively). We do not see any
difference in the clustering with either column density or redshift.


title: Mass Distribution and Bulge Formation in the Milky Way Galaxy

abstract:
  In its first part, this paper summarizes recent work on the mass and shape of
the Galactic dark halo. The second part presents a review of the large-scale
structure of the Milky Way, and of the evidence that the inner Galaxy is
dominated by baryonic matter. This is briefly compared with the predictions of
LCDM and MOND. Finally, a summary is given of bulge formation from clumpy,
gas-rich disks, a process which may give rise to old, disk-like, alpha-rich
bulges similar to the Galactic bulge.


title:
The rapid formation a large rotating disk galaxy three billion years
  after the Big Bang

abstract:
  [Abridged] Over the past two decades observations and theoretical simulations
have established a global frame-work of galaxy formation and evolution in the
young Universe. Galaxies formed as baryonic gas cooled at the centres of
collapsing dark matter halos. Mergers of halos led to the build up of galaxy
mass. A major step forward in understanding these issues requires well resolved
physical information on individual galaxies at high redshift. Here we report
adaptive optics, spectroscopic observations of a representative luminous star
forming galaxy when the Universe was only twenty percent of its age. The
superior angular resolution of these data reveals the physical and dynamical
properties of a high redshift galaxy in unprecedented detail. A large and
massive rotating proto-disk is channelling gas towards a growing central
stellar bulge hosting an accreting massive black hole.


title: Quark Matter in Neutron Stars: An apercu

abstract:
  The existence of deconfined quark matter in the superdense interior of
neutron stars is a key question that has drawn considerable attention over the
past few decades. Quark matter can comprise an arbitrary fraction of the star,
from 0 for a pure neutron star to 1 for a pure quark star, depending on the
equation of state of matter at high density. From an astrophysical viewpoint,
these two extreme cases are generally expected to manifest different
observational signatures. An intermediate fraction implies a hybrid star, where
the interior consists of mixed or homogeneous phases of quark and nuclear
matter, depending on surface and Coulomb energy costs, as well as other finite
size and screening effects. In this brief review article, we discuss what we
can deduce about quark matter in neutron stars in light of recent exciting
developments in neutron star observations. We state the theoretical ideas
underlying the equation of state of dense quark matter, including color
superconducting quark matter. We also highlight recent advances stemming from
re-examination of an old paradigm for the surface structure of quark stars and
discuss possible evolutionary scenarios from neutron stars to quark stars, with
emphasis on astrophysical observations.


title:
Ionisation and dissociation of cometary gaseous organic molecules by
  solar wind particles I: Formic Acid

abstract:
  In order to simulate the effects of energetic charged particles present in
the solar wind colliding with the cometary gaseous formic acid molecule
(HCOOH), laboratory experiments have been performed. The absolute ionisation
and dissociation cross sections for this molecule interacting with solar wind
particles were measured employing fast electrons in the energy range of 0.5 to
2 keV and energetic protons with energies varying from 0.128 to 2 MeV. Despite
the fact that both projectiles lead to a very similar fragmentation pattern,
differences in the relative intensities of the fragments were observed. Formic
acid survives about 4-5 times more to the proton beam than to the energetic
electron collision.The minimum momentum transfer in the electron impact case
was estimated to be 3-38% larger than the minimum momentum transfer observed
with the equivelocity protons. The UV photodissociation rates and half-lives
for HCOOH are roughly closer to the values obtained with energetic electrons.
It is consequently important to take electron impact data into account when
developing chemical models to simulate the interplanetary conditions.


title:
The Separation/Period Gap in the Distribution of Extrasolar Planets
  around Stars with Masses M >= 1.2 Msolar

abstract:
  The evidence for a shortage of exosolar planets with semimajor axes -1.1 <=
log (a/AU) <= -0.2 is investigated. It is shown that this valley results from a
gap in the radial distribution of planets, orbiting stars with masses M >= 1.2
Msolar (the high-mass sample, HMS). No underabundance is found for planets
orbiting stars with smaller masses. The observational data also indicate that
within the HMS population it is preferentially the more massive planets with M
sin(i) >= 0.8 M_J that are missing. Monte-Carlo simulations of planet formation
and migration are presented that reproduce the observed shortage of planets in
the observed radius regime. A dependence on the disk depletion timescale
tau_dep is found. The gap is more pronounced for tau_dep = 10^6 - 10^7 yrs than
for tau_dep = 3*10^6 - 3*10^7 yrs. This might explain the observed trend with
stellar mass if disks around stars with masses M* >= 1.2 Msolar have shorter
depletion timescales than those around less massive stars. Possible reasons for
such a dependence are a decrease of disk size and an increase of stellar EUV
flux with stellar mass.


title: Solar Oscillation Frequency Changes on Time Scales of Nine Days

abstract:
  We establish that global solar p-mode frequencies can be measured with
sufficient precision on time scales as short as nine days to detect
activity-related shifts. Using ten years of GONG data, we report that mode-mass
and error-weighted frequency shifts derived from nine days are significantly
correlated with the strength of solar activity and are consistent with long
duration measurements from GONG and the MDI/SOHO instrument. However, the
correlation varies from year to year and appears to be a complex phenomena. For
the short-duration observations, the analysis indicates a higher sensitivity to
activity. We also find that magnetic indices behave differently in the rising
and falling phases of the activity cycle.


title:
Empirical Corrections for Charge Transfer Inefficiency and Associated
  Centroid Shifts for STIS CCD Observations

abstract:
  A variety of on-orbit imaging and spectroscopic observations are used to
characterize the Charge Transfer Efficiency (CTE) of the Charge-Coupled Device
(CCD) of the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble
Space Telescope. A set of formulae is presented to correct observations of
point sources for CTE-related loss of signal. For data taken in imaging mode,
the CTE loss is parametrized in terms of the location of the source on the CCD,
the source signal level within the measurement aperture, the background level,
and the time of observation. For spectroscopic data, it is found that one
additional parameter is needed to provide an adequate calibration of the CTE
loss, namely the signal in the point spread function located between the signal
extraction box and the read-out amplifier. The effect of the latter parameter
is significant for spectra taken using the G750L or G750M gratings of STIS. The
algorithms presented here correct flux calibration inaccuracies due to CTE
losses as large as 30% to within ~ 1.5% RMS throughout the wavelength range
covered by the STIS CCD modes. This uncertainty is similar to the Poisson noise
associated with a source detected at a signal level of about 2500 electrons per
resolution element. Using bi-directional CCD readouts, centroid shifts incurred
due to CTE loss are also derived. A tight correlation is found between the CTE
loss and the centroid shift (both for imaging and spectroscopic modes), thus
enabling one to correct for both effects of imperfect charge transfer to STIS
CCD observations.


title: Does a Galaxy Fly?

abstract:
  Disk galaxies in a cluster of galaxies are moving in hot gas filling the
cluster. Generally, they are moving at transonic or supersonic velocities. If
ram-pressure stripping is insufficient to destroy the gas disk, the galaxies
should be affected by the wind of the surrounding hot gas similar to an
airfoil. In this paper, I consider whether the aerodynamic interaction can be
strong enough to force a disk galaxy to deviate from the orbit that it would
have been in. I find that while the lift force is not effective, the drag force
could affect face-on disk galaxies in poor clusters on long timescales.


title:
The impact of neutrino masses on the determination of dark energy
  properties

abstract:
  Recently, the Heidelberg-Moscow double beta decay experiment has claimed a
detection for a neutrino mass with high significance. Here we consider the
impact of this measurement on the determination of the dark energy equation of
state. By combining the Heidelberg-Moscow result with the WMAP 3-years data and
other cosmological datasets we constrain the equation of state to -1.67< w
<-1.05 at 95% c.l., ruling out a cosmological constant at more than 95% c.l..
Interestingly enough, coupled neutrino-dark energy models may be consistent
with such equation of state. While future data are certainly needed for a
confirmation of the controversial Heildelberg-Moscow claim, our result shows
that future laboratory searches for neutrino masses may play a crucial role in
the determination of the dark energy properties.


title: Deficit of wide binaries in the eta Chamaeleontis young cluster

abstract:
  We have carried out a sensitive high-resolution imaging survey of stars in
the young (6-8 Myr), nearby (97 pc) compact cluster around eta Chamaeleontis to
search for stellar and sub-stellar companions. Given its youth and proximity,
any sub-stellar companions are expected to be luminous, especially in the near
infrared, and thus easier to detect next to their parent stars. Here, we
present VLT/NACO adaptive optics imaging with companion detection limits for 17
eta Cha cluster members, and follow-up VLT/ISAAC near-infrared spectroscopy for
companion candidates. The widest binary detected is ~0.2", corresponding to the
projected separation 20 AU, despite our survey being sensitive down to
sub-stellar companions outside 0.3", and planetary mass objects outside 0.5".
This implies that the stellar companion probability outside 0.3" and the brown
dwarf companion probability outside 0.5" are less than 0.16 with 95%
confidence. We compare the wide binary frequency of eta Cha to that of the
similarly aged TW Hydrae association, and estimate the statistical likelihood
that the wide binary probability is equal in both groups to be < 2e-4. Even
though the eta Cha cluster is relatively dense, stellar encounters in its
present configuration cannot account for the relative deficit of wide binaries.
We thus conclude that the difference in wide binary probability in these two
groups provides strong evidence for multiplicity properties being dependent on
environment. In two appendices we derive the projected separation probability
distribution for binaries, used to constrain physical separations from observed
projected separations, and summarize statistical tools useful for multiplicity
studies.


title: What aspects of galaxy environment matter?

abstract:
  We determine what aspects of the density field surrounding galaxies most
affect their properties. For Sloan Digital Sky Survey galaxies, we measure the
group environment, meaning the host group luminosity and the distance from the
group center (hereafter, ``groupocentric distance''). For comparison, we
measure the surrounding density field on scales ranging from 100 kpc/h to 10
Mpc/h. We use the relationship between color and group environment to test the
null hypothesis that only the group environment matters, searching for a
residual dependence of properties on the surrounding density. Generally, red
galaxies are slightly more clustered on small scales (about 100--300 kpc/h)
than the null hypothesis predicts, possibly indicating that substructure within
groups has some importance. At large scales (> 1 Mpc/h), the actual projected
correlation functions of galaxies are biased at less than the 5% level with
respect to the null hypothesis predictions. We exclude strongly the converse
null hypothesis, that only the surrounding density (on any scale) matters.
These results generally encourage the use of the halo model description of
galaxy bias, which models the galaxy distribution as a function of host halo
mass alone. We compare these results to proposed galaxy formation scenarios
within the Cold Dark Matter cosmological model.


title:
Discovery of an eclipsing X-ray binary with a 32.69 hour period in M101:
  an analog of Her X-1 or LMC X-4?

abstract:
  We report the discovery of an eclipsing X-ray binary in M101, the first such
system to be discovered outside the Local Group. Based on a sequence of 25
Chandra observations that sample a wide range of orbital phases, we find a
period of 32.688 $\pm$ 0.002 hours, which we interpret as an orbital period.
The folded light curve exhibits an eclipse lasting about 8 hours, suggesting a
compact orbit in an nearly edge-on configuration. The X-ray binary has an
average luminosity of $L_X(0.3-8 {\rm keV}) \approx 1.3\times10^{38}$ erg/sec,
with only one out of the 25 observations significantly lower in flux than the
average light curve.The presence of the eclipse and the $\sim$ 1.4-day orbital
period suggests that this source is an analog of the well studied eclipsing
X-ray binary pulsars Her X-1 or LMC X-4. Combining the Chandra data and the HST
ACS/WFC images, we have identified several possible optical counterparts,
including an O5-O3 star with V = 25.0. Follow-up optical monitoring
observations should be able to identify the donor and further constrain the
orbital properties.


title: Evolution of Giant Planets in Eccentric Disks

abstract:
  We investigate the interaction between a giant planet and a viscous
circumstellar disk by means of high-resolution, two-dimensional hydrodynamical
simulations. We consider planet masses that range from 1 to 3 Jupiter masses
(Mjup) and initial orbital eccentricities that range from 0 to 0.4. We find
that a planet can cause eccentricity growth in a disk region adjacent to the
planet's orbit, even if the planet's orbit is circular. Disk-planet
interactions lead to growth in a planet's orbital eccentricity. The orbital
eccentricities of a 2 Mjup and a 3 Mjup planet increase from 0 to 0.11 within
about 3000 orbits. Over a similar time period, the orbital eccentricity of a 1
Mjup planet grows from 0 to 0.02. For a case of a 1 Mjup planet with an initial
eccentricity of 0.01, the orbital eccentricity grows to 0.09 over 4000 orbits.
Radial migration is directed inwards, but slows considerably as a planet's
orbit becomes eccentric. If a planet's orbital eccentricity becomes
sufficiently large, e > ~0.2, migration can reverse and so be directed
outwards. The accretion rate towards a planet depends on both the disk and the
planet orbital eccentricity and is pulsed over the orbital period. Planet mass
growth rates increase with planet orbital eccentricity. For e~0.2 the mass
growth rate of a planet increases by approximately 30% above the value for e=0.
For e > ~0.1, most of the accretion within the planet's Roche lobe occurs when
the planet is near the apocenter. Similar accretion modulation occurs for flow
at the inner disk boundary which represents accretion toward the star.


title:
A census of the Wolf-Rayet content in Westerlund 1 from near-infrared
  imaging and spectroscopy

abstract:
  New NTT/SOFI imaging and spectroscopy of the Wolf-Rayet population in
Westerlund 1 are presented. Narrow-band near-IR imaging together with follow up
spectroscopy reveals four new WR stars, of which three were independently
identified recently by Groh et al., bringing the confirmed WR content to 24 (23
excluding source S) [..] A quantitative near-IR spectral classification scheme
for WR stars is presented and applied to members of Westerlund 1. Late subtypes
are dominant, with no subtypes earlier than WN5 or WC8 for the nitrogen and
carbon sequences, respectively. A qualitative inspection of the WN stars
suggests that most (75%) are highly H-deficient. The WR binary fraction is high
(>62%), on the basis of dust emission from WC stars, in addition to a
significant WN binary fraction from hard X-ray detections according to Clark et
al. We exploit the large WN population of Westerlund 1 to reassess its distance
(~5.0kpc) and extinction (A_Ks ~ 0.96 mag), such that it is located at the edge
of the Galactic bar, [..]. The observed ratio of WR stars to red and yellow
hypergiants, N(WR)/N(RSG+YHG)~3, favours an age of 4.5-5.0 Myr, with individual
WR stars descended from progenitors of initial mass ~ 40-55 Msun. Qualitative
estimates of current masses for non-dusty, H-free WR stars are presented,
revealing 10-18 Msun, such that ~75% of the initial stellar mass has been
removed via stellar winds or close binary evolution. We present a revision to
the cluster turn-off mass for other Milky Way clusters in which WR stars are
known, based upon the latest temperature calibration for OB stars. Finally,
comparisons between the observed WR population and subtype distribution in
Westerlund 1 and instantaneous burst evolutionary synthesis models are
presented.


title:
The Initial Conditions for Gravitational Collapse of a Core: An
  Extremely Young Low-Mass Class 0 Protostar GF9-2

abstract:
  We present a study of the natal core harboring the class 0 protostar GF9-2 in
the filamentary dark cloud GF 9 (d = 200 pc). GF9-2 stands unique in the sense
that it shows H2O maser emission, a clear signpost of protostar formation,
whereas it does not have a high-velocity large-scale molecular outflow
evidenced by our deep search for CO wing emission. These facts indicate that
GF9-2 core is early enough after star formation so that it still retains some
information of initial conditions for collapse. Our 350 um dust continuum
emission image revealed the presence of a protostellar envelope in the center
of a molecular core. The mass of the envelope is ~0.6 Msun from the 350 um flux
density, while LTE mass of the core is ~3 Msun from moleuclar line
observations. Combining visibility data from the OVRO mm-array and the 45m
telescope, we found that the core has a radial density profile of
$\rho(r)\propto r^{-2}$ for 0.003 < r/pc < 0.08 region. Molecular line data
analysis revealed that the velocity width of the core gas increases
inward,while the outermost region maintains a velocity dispersion of a few
times of the ambient sound speed. The broadened velocity width can be
interpreted as infall. Thus, the collapse in GF9-2 is likely to be described by
an extension of the Larson-Penston solution for the period after formation of a
central star. We derived the current mass accretion rate of ~3E-05 Msun/year
from infall velocity of ~ 0.3 km/s at r~ 7000 AU. All results suggest that
GF9-2 core has been undergoing gravitational collapse for ~ 5000 years since
the formation of central protostar(s), and that the unstable state initiated
the collapse ~2E+05 years (the free-fall time) ago.


title: The small dispersion of the mid IR -- hard X-ray correlation in AGN

abstract:
  Context: We investigate mid-infrared and X-ray properties of the dusty torus
in unification scenarios for active galactic nuclei.
  Aims: We use the relation between mid IR and hard X-ray luminosities to
constrain AGN unification scenarios.
  Methods: With VISIR at the VLT, we have obtained the currently highest
angular resolution (0".35 FWHM) narrow-band mid infrared images of the nuclei
of 8 nearby Seyfert galaxies. Combining these observations with X-ray data from
the literature we study the correlation between their mid IR and hard X-ray
luminosities.
  Results: We find that the rest frame 12.3 mircon (L_MIR) and 2-10 keV (L_X)
luminosities are correlated at a highly significant level. The best fit
power-law to our data is log L_MIR \propto (1.60 \pm 0.22) log L_X, showing a
much smaller dispersion than earlier studies.
  Conclusions: The similarity in the og L_MIR / log L_X ratio between Sy1s and
Sy2s even using high angular resolution MIR data implies that the similarity is
intrinsic to AGN and not caused by contamination from extra-nuclear emission.
This supports clumpy torus models. The exponent of the correlation constrains
the inner geometry of the torus.


title: What is a planet?

abstract:
  A planet is an end product of disk accretion around a primary star or
substar. I quantify this definition by the degree to which a body dominates the
other masses that share its orbital zone. Theoretical and observational
measures of dynamical dominance reveal a gap of four to five orders of
magnitude separating the eight planets of our solar system from the populations
of asteroids and comets. The proposed definition dispenses with upper and lower
mass limits for a planet. It reflects the tendency of disk evolution in a
mature system to produce a small number of relatively large bodies (planets) in
non-intersecting or resonant orbits, which prevent collisions between them.


title:
Dense Matter in Compact Stars: Theoretical Developments and
  Observational Constraints

abstract:
  We review theoretical developments in studies of dense matter and its phase
structure of relevance to compact stars. Observational data on compact stars,
which can constrain the properties of dense matter, are presented critically
and interpreted.


title: Chang-Refsdal Microlensed Type Ia Supernova Light Curves

abstract:
  A description of the light curves of microlensed Type Ia supernovae (SNe Ia)
as extended and expanding sources is presented. We give examples of what
microlensing by stellar-mass Chang-Refsdal lenses can do to a small percentage
of supernova light curves. We find that in addition to overall brightening,
significant changes in light--curve shapes can also occur. Peaks can be
distorted, plateaus can appear, and even secondary peaks can be formed. The
effects of both the relative motion of the lens and the supernova and the
expansion of the supernova are given and compared. The effects of relative
motion are more pronounced when a distant supernova ($z_s \sim 1$) impacts well
within the Einstein ring of a nearby microlens ($z_d \sim 0.05$) and are less
important for more distant deflectors. We also find that the increase in shear
that comes with increased deflector distance tends to reduce the time
variability of microlensing. We briefly discuss the probability of observing
these effects.


title: Coronagraphic Search for Extra-Solar Planets around epsilon Eri and Vega

abstract:
  We present the results of a coronagraphic imaging search for extra-solar
planets around the young main-sequence stars, epsilon Eri and Vega.
Concentrating the stellar light into the core of the point spread function by
the adaptive optic system and blocking the core by the occulting mask in the
coronagraph, we have achieved the highest sensitivity for point sources in
close vicinity of the both central stars. Nonetheless we had no confidential
detection of a point source around the stars. The observations give the upper
limits on the masses of the planets to 4 -- 6 Jupiter mass and 5 -- 10 Jupiter
mass at a few arcsecond from epsilon Eri and Vega, respectively. Diffuse
structures are also not detected around both stars.


title:
Gamma-Ray Burst Spectral Correlations: Photospheric and Injection
  Effects

abstract:
  We present a physical framework that can account for most of the observed
spectral properties of the prompt gamma-ray burst emission. This includes the
variety of spectral shapes, shape evolutions, and spectral correlations between
flux and spectral peak, within bursts described by Borgonovo & Ryde, and among
bursts described by Amati/Ghirlanda. In our proposed model the spectral peak is
given by the photospheric emission from a relativistic outflow for which the
horizon length is much smaller than the radial width. The observed duration of
the thermal flash will be given by the radial light-crossing time. This then
gives that the typical emission site is at ~10e11 cm from the center, with a
Lorentz factor of ~300. This emission is accompanied by non-thermal emission
from dissipation locations outside the photosphere. The relative strength of
these two components depend on injection effects at the central engine leading
to varying relative location of the saturation and photospheric radii. The
total emission can then reproduce the observed variety. The spectral
correlations are found by assuming that the amount of energy dissipated depends
non-linearly on the averaged particle density. Beside the spectral correlations
this also gives a description of how the relative strength of the thermal
component varies with temperature within a burst.


title: XMM-Newton observations of Soft Gamma-ray Repeaters

abstract:
  All the confirmed Soft Gamma-ray Repeaters have been observed with the EPIC
instrument on the XMM-Newton satellite. We review the results obtained in these
observations, providing the most accurate spectra on the persistent X-ray
emission in the 1-10 keV range for these objects, and discuss them in the
context of the magnetar interpretation.


title:
Scale dependence of the primordial spectrum from combining the
  three-year WMAP, Galaxy Clustering, Supernovae, and Lyman-alpha forests

abstract:
  We probe the scale dependence of the primordial spectrum in the light of the
three-year WMAP (WMAP3) alone and WMAP3 in combination with the other
cosmological observations such as galaxy clustering and Type Ia Supernova
(SNIa). We pay particular attention to the combination with the Lyman $\alpha$
(Ly$\alpha$) forest. Different from the first-year WMAP (WMAP1), WMAP3's
preference on the running of the scalar spectral index on the large scales is
now fairly independent of the low CMB multipoles $\ell$. A combination with the
galaxy power spectrum from the Sloan Digital Sky Survey (SDSS) prefers a
negative running to larger than 2$\sigma$, regardless the presence of low
$\ell$ CMB ($2\le \ell \le 23$) or not. On the other hand if we focus on the
Power Law $\Lambda$CDM cosmology with only six parameters (matter density
$\Omega_m h^2$, baryon density $\Omega_b h^2$, Hubble Constant $H_0$, optical
depth $\tau$, the spectral index, $n_s$, and the amplitude, $A_s$, of the
scalar perturbation spectrum) when we drop the low $\ell$ CMB contributions
WMAP3 is consistent with the Harrison-Zel'dovich-Peebles scale-invariant
spectrum ($n_s=1$ and no tensor contributions) at $\sim 1\sigma$. When assuming
a simple power law primordial spectral index or a constant running, in case one
drops the low $\ell$ contributions ($2\le \ell \le 23$) WMAP3 is consistent
with the other observations better, such as the inferred value of $\sigma_8$.
We also find, using a spectral shape with a minimal extension of the running
spectral index model, LUQAS$+$ CROFT Ly$\alpha$ and SDSS Ly$\alpha$ exhibit
somewhat different preference on the spectral shape.


title:
The Chemical Evolution of Helium in Globular Clusters: Implications for
  the Self-Pollution Scenario

abstract:
  We investigate the suggestion that there are stellar populations in some
globular clusters with enhanced helium (Y from 0.28 to 0.40) compared to the
primordial value. We assume that a previous generation of massive Asymptotic
Giant Branch (AGB) stars have polluted the cluster. Two independent sets of AGB
yields are used to follow the evolution of helium and CNO using a Salpeter
initial mass function (IMF) and two top-heavy IMFs. In no case are we able to
produce the postulated large Y ~ 0.35 without violating the observational
constraint that the CNO content is nearly constant.


title: On the low-mass planethood criterion

abstract:
  We propose a quantitative concept for the lower planetary boundary, requiring
that a planet must keep its atmosphere in vacuum. The solution-set framework of
Pecnik and Wuchterl (2005) enabled a clear and quantitative criterion for the
discrimination of a planet and a minor body. Using a simple isothermal
core-envelope model, we apply the proposed planetary criterion to the large
bodies in the Solar System.


title: Galaxy properties from Voids to Clusters in the SDSS-DR4

abstract:
  We investigate the environmental dependence of galaxy population properties
in a complete volume-limited sample of 91566 galaxies in the redshift range
0.05 <= z <= 0.095 and with M_r <= -20.0, selected from the Sloan Digital Sky
Survey (SDSS) Data Release 4. Our aim is to search for systematic variations in
the properties of galaxies with the local galaxy density. In particular, we
analize how the (u - r) color index and the morphological type of galaxies (the
latter evaluated through the SDSS Eclass and FracDev parameters) are related to
the environment and to the luminosity of galaxies, in order to find hints that
can be related to the presence of a ''void'' galaxy population. Void galaxies
are identified through a highly selective criterion, which takes also into
account redshift and allows us to exclude from the sample all the galaxies that
are not really close to the center of underdense regions. We study the (u - r)
color distribution for galaxies in different luminosity bins, and we look for
correlations of color with the environment, the luminosity, and the
morphological type of the galaxies. We find that galaxies in underdense regions
(voids) have lower luminosity (M_r > -21) and are bluer than cluster galaxies.
The transition from overdense to underdense environments is smooth, the
fraction of late-type galaxies decreases while the fraction of early-type
galaxies increases smoothly from underdense to dense environments. We do not
find any sudden transition in the galaxy properties with density, which,
according to a suggestion by Peebles (2001), should mark the transition to a
population of "void" galaxies in LCDM models. On the contrary, our results
suggest a continuity of galaxy properties, from voids to clusters.


title: Reliable Shapelet Image Analysis

abstract:
  Aims: We discuss the applicability and reliability of the shapelet technique
for scientific image analysis. Methods: We quantify the effects of
non-orthogonality of sampled shapelet basis functions and misestimation of
shapelet parameters. We perform the shapelet decomposition on artificial galaxy
images with underlying shapelet models and galaxy images from the GOODS survey,
comparing the publicly available IDL implementation with our new C++
implementation. Results: Non-orthogonality of the sampled basis functions and
misestimation of the shapelet parameters can cause substantial
misinterpretation of the physical properties of the decomposed objects.
Additional constraints, image preprocessing and enhanced precision have to be
incorporated in order to achieve reliable decomposition results.


title: The DART imaging and CaT survey of the Fornax Dwarf Spheroidal Galaxy

abstract:
  As part of the DART project we have used the ESO/2.2m Wide Field Imager in
conjunction with the VLT/FLAMES GIRAFFE spectrograph to study the detailed
properties of the resolved stellar population of the Fornax dwarf spheroidal
galaxy out to and beyond its tidal radius. We re-derived the structural
parameters of the Fornax dwarf spheroidal using our wide field imaging covering
the galaxy out to its tidal radius, and analysed the spatial distribution of
the Fornax stars of different ages as selected from Colour-Magnitude Diagram
analysis. We have obtained accurate velocities and metallicities from spectra
in the CaII triplet wavelength region for 562 Red Giant Branch stars which have
velocities consistent with membership in Fornax dwarf spheroidal. We have found
evidence for the presence of at least three distinct stellar components: a
young population (few 100 Myr old) concentrated in the centre of the galaxy,
visible as a Main Sequence in the Colour-Magnitude Diagram; an intermediate age
population (2-8 Gyr old); and an ancient population (> 10Gyr),which are
distinguishable from each other kinematically, from the metallicity
distribution and in the spatial distribution of stars found in the
Colour-Magnitude Diagram. From our spectroscopic analysis we find that the
``metal rich'' stars ([Fe/H]> -1.3) show a less extended and more concentrated
spatial distribution, and display a colder kinematics than the ``metal poor''
stars ([Fe/H<-1.3). There is tentative evidence that the ancient stellar
population in the centre of Fornax does not exhibit equilibrium kinematics.
This could be a sign of a relatively recent accretion of external material.


title:
Electron thermal conductivity owing to collisions between degenerate
  electrons

abstract:
  We calculate the thermal conductivity of electrons produced by
electron-electron Coulomb scattering in a strongly degenerate electron gas
taking into account the Landau damping of transverse plasmons. The Landau
damping strongly reduces this conductivity in the domain of ultrarelativistic
electrons at temperatures below the electron plasma temperature. In the inner
crust of a neutron star at temperatures T < 1e7 K this thermal conductivity
completely dominates over the electron conductivity due to electron-ion
(electron-phonon) scattering and becomes competitive with the the electron
conductivity due to scattering of electrons by impurity ions.


title: Magnetar Corona

abstract:
  Persistent high-energy emission of magnetars is produced by a plasma corona
around the neutron star, with total energy output of ~10^{36}erg/s. The corona
forms as a result of occasional starquakes that twist the external magnetic
field of the star and induce electric currents in the closed magnetosphere.
Once twisted, the magnetosphere cannot untwist immediately because of its
self-induction. The self-induction electric field lifts particles from the
stellar surface, accelerates them, and initiates avalanches of pair creation in
the magnetosphere. The created plasma corona maintains the electric current
demanded by curl(B) and regulates the self-induction e.m.f. by screening. This
corona persists in dynamic equilibrium: it is continually lost to the stellar
surface on the light-crossing time and replenished with new particles. In
essence, the twisted magnetosphere acts as an accelerator that converts the
toroidal field energy to particle kinetic energy. The voltage along the
magnetic field lines is maintained near threshold for ignition of pair
production, in the regime of self-organized criticality. The voltage is found
to be about 1 GeV which is in agreement with the observed dissipation rate
\~10^{36}erg/s. The coronal particles impact the solid crust, knock out
protons, and regulate the column density of the hydrostatic atmosphere of the
star. The transition layer between the atmosphere and the corona is the likely
source of the observed 100-keV emission from magnetars. The corona also emits
curvature radiation up to 10^{14}Hz and can supply the observed IR-optical
luminosity.


title:
Current bombardment of the Earth-Moon system: Emphasis on cratering
  asymmetries

abstract:
  We calculate the current spatial distribution of projectile delivery to the
Earth and Moon using numerical orbital dynamics simulations of candidate
impactors drawn from a debiased Near-Earth-Object (NEO) model. Surprisingly, we
find that the average lunar impact velocity is 20 km/s, which has ramifications
for converting observed crater densities to impactor size distributions. We
determine that current crater production on the leading hemisphere of the Moon
is 1.29 +/- 0.01 that of the trailing when considering the ratio of craters
within 30 degrees of the apex to those within 30 degrees of the antapex and
that there is virtually no nearside-farside asymmetry. As expected, the degree
of leading-trailing asymmetry increases when the Moon's orbital distance is
decreased. We examine the latitude distribution of impactor sites and find that
for both the Earth and Moon there is a small deficiency of time-averaged impact
rates at the poles. The ratio between deliveries within 30 degrees of the pole
to that of a 30 degree band centered on the equator is nearly unity for Earth
(<1%)(0.992 +/- 0.001) but detectably non-uniform for the Moon (~10%)(0.912 +/-
0.004). The terrestrial arrival results are examined to determine the degree of
AM/PM asymmetry to compare with meteorite fall times (of which there seems to
be a PM excess). Our results show that the impact flux of objects derived from
the NEOs in the AM hours is ~2 times that of the PM hemisphere, further
supporting the assertion that meteorite-dropping objects are recent ejections
from the main asteroid belt rather than young fragments of NEOs.


title:
A weakly nonlinear analysis of the magnetorotational instability in a
  model channel flow

abstract:
  We show by means of a perturbative weakly nonlinear analysis that the
axisymmetric magnetorotational instability (MRI) of a viscous, resistive,
incompressible rotating shear flow in a thin channel gives rise to a real
Ginzburg-Landau equation for the disturbance amplitude. For small magnetic
Prandtl number (${\cal P}_{\rm m}$), the saturation amplitude is $\propto
\sqrt{{\cal P}_{\rm m}}$ and the resulting momentum transport scales as ${\cal
R}^{-1}$, where $\cal R$ is the {\em hydrodynamic} Reynolds number. Simplifying
assumptions, such as linear shear base flow, mathematically expedient boundary
conditions and continuous spectrum of the vertical linear modes, are used to
facilitate this analysis. The asymptotic results are shown to comply with
numerical calculations using a spectral code. They suggest that the transport
due to the nonlinearly developed MRI may be very small in experimental setups
with ${\cal P}_{\rm m} \ll 1$.


title:
Molecular Cloud Evolution II. From cloud formation to the early stages
  of star formation in decaying conditions

abstract:
  We study the formation of giant dense cloud complexes and of stars within
them by means of SPH numerical simulations of the mildly supersonic collision
of gas streams (``inflows'') in the warm neutral medium (WNM). The resulting
compressions cause cooling and turbulence generation in the gas, forming a
cloud that then becomes self-gravitating and undergoes global collapse.
Simultaneously, the turbulent, nonlinear density fluctuations induce fast,
local collapse events. The simulations show that: a) The clouds are not in a
state of equilibrium. Instead, they undergo secular evolution. Initially, their
mass and gravitational energy |Eg| increase steadily, while the turbulent
energy Ek reaches a plateau. b) When |Eg| becomes comparable to Ek, global
collapse begins, causing a simultaneous increase in both that maintains a
near-equipartition condition |Eg| ~ 2 Ek. c) Longer inflow durations delay the
onset of global and local collapse, by maintaining a higher turbulent velocity
dispersion in the cloud over longer times. d) The star formation rate is large
from the beginning, without any period of slow and accelerating star formation.
e) The column densities of the local star-forming clumps are very similar to
reported values of the column density required for molecule formation,
suggesting that locally molecular gas and star formation occur nearly
simultaneously. The MC formation mechanism discussed here naturally explains
the apparent ``virialized'' state of MCs and the ubiquitous presence of HI
halos around them. Within their assumptions, our simulations support the
scenario of rapid star formation after MCs are formed, although long (>~ 15
Myr) accumulation periods do occur during which the clouds build up their
gravitational energy, and which are expected to be spent in the atomic phase.


title:
Hiding Cusps in Cores: Kinematics of Disk Galaxies in Triaxial Dark
  Matter Halos

abstract:
  We study the kinematics of gaseous disks in triaxial dark matter halos using
the closed-loop orbit solutions in non-axisymmetric potentials. The orbits are
in general non-circular and, for given triaxiality, their ellipticity depends
on the ratio of escape to circular velocities, V_esc^2/V_c^2. This ratio
increases steeply towards the center for cold dark matter (CDM) halo density
profiles, implying that even minor deviations from spherical symmetry may
induce large deviations from circular orbits in the velocity field of a gaseous
disk, especially near the center. This result suggests that caution should be
exercised when interpreting constraints on the presence of density cusps in the
dark halo derived from the innermost velocity profile. Simulated long-slit
rotation curves vary greatly in shape, depending primarily on the viewing angle
of the disk and on its orientation relative to the principal axes of the
potential. "Solid-body" rotation curves - typically interpreted as a signature
of a constant density core in the dark matter distribution - are often obtained
when the slit samples velocities near the major axis of the closed loop orbits.
Triaxial potentials imprint specific symmetries in 2D velocity fields,
generally inducing "twists" in the isovelocity contours and anti-symmetric
patterns in opposite quadrants. We suggest that triaxial halos may be
responsible for the variety of shapes of long-slit rotation curves of low
surface brightness (LSB) galaxies, as well as for the complex central
kinematics of LSBs, which are sometimes ascribed to the presence of "radial
motions" in the gas. We argue that LSB rotation curves might be reconciled with
the structure of CDM halos once the effects of halo triaxiality on the dynamics
of gaseous disks are properly taken into account.


title:
Light Element Signatures of Sterile Neutrinos and Cosmological Lepton
  Numbers

abstract:
  We study primordial nucleosynthesis abundance yields for assumed ranges of
cosmological lepton numbers, sterile neutrino mass-squared differences and
active-sterile vacuum mixing angles. We fix the baryon-to-photon ratio at the
value derived from the cosmic microwave background (CMB) data and then
calculate the deviation of the 2H, 4He, and 7Li abundance yields from those
expected in the zero lepton number(s), no-new-neutrino-physics case. We
conclude that high precision (< 5% error) measurements of the primordial 2H
abundance from, e.g., QSO absorption line observations coupled with high
precision (< 1% error) baryon density measurements from the CMB could have the
power to either: (1) reveal or rule out the existence of a light sterile
neutrino if the sign of the cosmological lepton number is known; or (2) place
strong constraints on lepton numbers, sterile neutrino mixing properties and
resonance sweep physics. Similar conclusions would hold if the primordial 4He
abundance could be determined to better than 10%.


title: AEGIS: Galaxy Spectral Energy Distributions from the X-Ray to Radio

abstract:
  The All-wavelength Extended Groth Strip International Survey (AEGIS) team
presents broad-band spectral energy distributions (SEDs), from X-ray to radio
wavelengths, for 71 galaxies spanning the redshift range 0.55-1.16 (<z>~0.7).
Galaxies with secure redshifts were selected from a small (22 arcminute-square)
sub-section of the Keck/DEIMOS galaxy redshift survey in the Extended Groth
Strip field that has also been targeted for deep panchromatic imaging by
Chandra (X-ray), GALEX (ultraviolet), Canada-France-Hawaii Telescope (optical),
Hubble Space Telescope (optical/near infrared), Palomar Observatory (near
infrared), Spitzer (mid/far infrared), and the Very Large Array (radio.) The
absolute magnitude of the typical galaxy in our sample is M_B=-19.82. The
ultraviolet to mid-infrared portion of their spectral energy distributions
(SEDs) are found to be bracketed by two stellar-only model SEDs: an early burst
followed by passive evolution and a constant star-formation rate since early
times; this suggests that few of these galaxies are undergoing major
starbursts. Approximately half the galaxies show a mid- to far-infrared excess
relative to the model SEDs, consistent with thermal emission from interstellar
dust. Two objects have power-law SEDs, indicating that they are dominated by
active galactic nuclei; both are detected in X-rays. The galaxies are grouped
by rest-frame color,quantitative optical morphology, and [OII] emission line
strength (possible indicator of star formation). On average, the panchromatic
SEDs of the galaxies, from the ultraviolet to the infrared, follow expected
trends: redder SEDs are associated with red U-B, early-type morphology, and low
[OII] emission, and vice versa for blue SEDs.


title:
A Simple Test of the External Shock Model for the Prompt Emission in
  Gamma-Ray Bursts

abstract:
  It is demonstrated here that if the prompt GRB emission is produced by the
simplest version of the external shock model, a specific relation should
prevail between the observed duration, isotropic equivalent energy, and photon
peak energy. In essence, this relation arises because both the burst duration
and the typical energy of the emitted synchrotron photons depend on the same
combination of the, usually poorly constrained, external density at the
deceleration radius, $n_{dec}$, and initial bulk Lorentz factor, $\Gamma_0$.
This has the fortunate consequence of making the relation independent of both
$\Gamma_0$ and $n_{dec}$. Unless the efficiency of electron acceleration is
very low, synchrotron gamma-rays from the external shock would fail to meet the
current observational constraints for the vast majority of GRBs, including
those with a smooth, single peak temporal profile. This argues either against
an external shock origin for the prompt emission in GRBs or for changes in our
understanding of the microphysical and radiation processes occurring within the
shocked region.


title:
The DEEP2 Galaxy Redshift Survey: AEGIS Observations of a Dual AGN at
  z=0.7

abstract:
  We present evidence for a dual Active Galactic Nucleus (AGN) within an
early-type galaxy at z=0.709 in the Extended Groth Strip. The galaxy lies on
the red sequence, with absolute magnitude M_B=-21.0 (AB, with h=0.7) and
rest-frame color U-B=1.38. Its optical spectrum shows strong, double-peaked
[OIII] emission lines and weak Hbeta emission, with Seyfert-like line ratios.
The two narrow peaks are separated by 630 km/s in velocity and arise from two
distinct regions, spatially resolved in the DEIMOS spectrum, with a projected
physical separation of 1.2 kpc. HST/ACS imaging shows an early-type (E/S0)
galaxy with hints of disturbed structure, consistent with the remnant of a
dissipationless merger. Multiwavelength photometric information from the AEGIS
consortium confirms the identification of a dust-obscured AGN in an early-type
galaxy, with detections in X-ray, optical, infrared and radio wavebands. These
data are most readily explained as a single galaxy harboring two AGN--the first
such system to be observed in an otherwise typical early-type galaxy.


title:
AEGIS: Host Galaxy Morphologies of X-ray and Infrared-selected AGN at
  0.2 < z < 1.2

abstract:
  We visually and quantitatively determine the host galaxy morphologies of 94
intermediate redshift (0.2 < z < 1.2) active galactic nuclei (AGN), selected
using Chandra X-ray and Spitzer mid-infrared data in the Extended Groth Strip.
Using recently developed morphology measures, the second-order moment of the
brightest 20% of a galaxy's flux (M_{20}) and the Gini coefficient, we find
that X-ray-selected AGN mostly reside in E/S0/Sa galaxies (53^{+11}_{-10}%),
while IR-selected AGN show no clear preference for host morphology.
X-ray-selected AGN hosts are members of close pairs more often than the field
population by a factor of 3.3+/-1.4, but most of these pair members appear to
be undisturbed early-type galaxies and do not tend to show direct evidence of
gravitational perturbations or interactions. Thus, the activation mechanism for
AGN activity remains unknown, even for pair members.


title: AEGIS: Chandra Observation of DEEP2 Galaxy Groups and Clusters

abstract:
  We present a 200 ksec Chandra observation of seven spectroscopically
selected, high redshift (0.75 < z < 1.03) galaxy groups and clusters discovered
by the DEEP2 Galaxy Redshift Survey in the Extended Groth Strip (EGS). X-ray
emission at the locations of these systems is consistent with background. The
3-sigma upper limits on the bolometric X-ray luminosities (L_X) of these
systems put a strong constraint on the relation between L_X and the velocity
dispersion of member galaxies sigma_gal at z~1; the DEEP2 systems have lower
luminosity than would be predicted by the local relation. Our result is
consistent with recent findings that at high redshift, optically selected
clusters tend to be X-ray underluminous. A comparison with mock catalogs
indicates that it is unlikely that this effect is entirely caused by a
measurement bias between sigma_gal and the dark matter velocity dispersion.
Physically, the DEEP2 systems may still be in the process of forming and hence
not fully virialized, or they may be deficient in hot gas compared to local
systems. We find only one possibly extended source in this Chandra field, which
happens to lie outside the DEEP2 coverage.


title:
Simultaneous Ultraviolet and X-ray Observations of the Seyfert Galaxy
  NGC 4151. II. Physical Conditions in the UV Absorbers

abstract:
  We present a detailed analysis of the intrinsic absorption in the Seyfert 1
galaxy NGC 4151 using UV spectra from the HST/STIS and FUSE, obtained 2002 May
as part of a set of contemporaneous observations that included Chandra/HETGS
spectra. In our analysis of the Chandra spectra, we determined that the soft
X-ray absorber was the source of the saturated UV lines of O VI, C IV, and N V
associated with the absorption feature at a radial velocity of ~ -500 km/sec,
which we referred to as component D+E. In the present work, we have derived
tighter constrains on the the line-of-sight covering factors, densities, and
radial distances of the absorbers. We find that the Equivalent Widths (EWs) of
the low-ionization lines associated with D+E varied over the period from 1999
July to 2002 May. The drop in the EWs of these lines between 2001 April and
2002 May are suggestive of bulk motion of gas out of our line-of-sight. If
these lines from these two epochs arose in the same sub-component, the
transverse velocity of the gas is ~ 2100 km/sec. Transverse velocities of this
order are consistent with an origin in a rotating disk, at the roughly radial
distance we derived for D+E.


title:
A new interpretation of the remarkable X-ray spectrum of the symbiotic
  star CH Cyg

abstract:
  We have reanalysed the ASCA X-ray spectrum of the bright symbiotic star CH
Cyg, which exhibits apparently distinct hard and soft X-ray components. Our
analysis demonstrates that the soft X-ray emission can be interpreted as
scattering of the hard X-ray component in a photo-ionised medium surrounding
the white dwarf. This is in contrast to previous analyses in which the soft
X-ray emission was fitted separately and assumed to arise independently of the
hard X-ray component.
  We note the striking similarity between the X-ray spectra of CH Cyg and
Seyfert 2 galaxies, which are also believed to exhibit scattering in a
photo-ionised medium.


title:
The Effects of Dark Matter Decay and Annihilation on the High-Redshift
  21 cm Background

abstract:
  The radiation background produced by the 21 cm spin-flip transition of
neutral hydrogen at high redshifts can be a pristine probe of fundamental
physics and cosmology. At z~30-300, the intergalactic medium (IGM) is visible
in 21 cm absorption against the cosmic microwave background (CMB), with a
strength that depends on the thermal (and ionization) history of the IGM. Here
we examine the constraints this background can place on dark matter decay and
annihilation, which could heat and ionize the IGM through the production of
high-energy particles. Using a simple model for dark matter decay, we show
that, if the decay energy is immediately injected into the IGM, the 21 cm
background can detect energy injection rates >10^{-24} eV cm^{-3} sec^{-1}. If
all the dark matter is subject to decay, this allows us to constrain dark
matter lifetimes <10^{27} sec. Such energy injection rates are much smaller
than those typically probed by the CMB power spectra. The expected brightness
temperature fluctuations at z~50 are a fraction of a mK and can vary from the
standard calculation by up to an order of magnitude, although the difference
can be significantly smaller if some of the decay products free stream to lower
redshifts. For self-annihilating dark matter, the fluctuation amplitude can
differ by a factor <2 from the standard calculation at z~50. Note also that, in
contrast to the CMB, the 21 cm probe is sensitive to both the ionization
fraction and the IGM temperature, in principle allowing better constraints on
the decay process and heating history. We also show that strong IGM heating and
ionization can lead to an enhanced H_2 abundance, which may affect the earliest
generations of stars and galaxies.