title: The Origin, Composition, and Energy Source for the Sun

abstract:
  Heterogeneous supernova debris formed the solar system. Cores of inner
planets formed in the central iron rich region. The Sun formed on the collapsed
supernova core. Lighter elements and the lighter isotopes of each element are
enriched at the solar surface. The most abundant nuclide in the Sun is Iron 56,
the decay product of doubly magic Nickel 56. Doubly magic Oxygen 16 is next
most abundant. The least abundant elements, Li, Be, and B, have loosely bound
nucleons. Abundance is linked with nuclear stability, except for an over
abundance of H from neutron emission and neutron decay near the core. The main
elements in the Sun, Fe, Ni, O, Si, S, Mg, and Ca, comprise 99 percent of
meteorites. Neutron emission from the SN core triggers a series of reactions
that produce solar luminosity, solar neutrinos, excess H, and an annual
outpouring of 2.7 E 43 Hydrogen atoms in the solar wind.


title:
Mass Segregation and the Initial Mass Function of Super Star Cluster
  M82-F

abstract:
  We investigate the Initial Mass Function and mass segregation in super star
cluster M82-F with high resolution Keck/NIRSPEC echelle spectroscopy.
Cross-correlation with template supergiant spectra provides the velocity
dispersion of the cluster, enabling measurement of the kinematic (virial) mass
of the cluster when combined with sizes from NICMOS and ACS images. We find a
mass of 6.6 +/- 0.9 x 10^5 M_sun based on near-IR light and 7.0 +/- 1.2 x 10^5
M_sun based on optical light. Using PSF-fitting photometry, we derive the
cluster's light-to-mass ratio in both near-IR and optical light, and compare to
population synthesis models. The ratios are inconsistent with a normal stellar
initial mass function for the adopted age of 40 to 60 Myr, suggesting a
deficiency of low-mass stars within the volume sampled. King model light
profile fits to new HST/ACS images of M82-F, in combination with fits to
archival near-IR images, indicate mass segregation in the cluster. As a result,
the virial mass represents a lower limit on the mass of the cluster.


title: Searching for a Solution to the Age Problem of the Universe

abstract:
  We present here a phenomenological cosmological model under perfect fluid
distribution with a stiff equation of state $p=\rho$. The erstwhile
cosmological constant is assumed to be a time dependent variable, i.e.,
$\Lambda = \Lambda(t)$ in our study. It has been shown that the estimates of
different cosmological parameters from this model are in good agreement with
the experimental results, especially 13.79 Gyr as the age of the universe is
quite satisfactory. The behavior and relation of $\Lambda$-stiff fluid model
with dust, viscous fluid and variable $G$ have also been investigated in
detail.


title: Quintessence as k-essence

abstract:
  Quintessence and k-essence have been proposed as candidates for the dark
energy component of the universe that would be responsible of the currently
observed accelerated expansion. In this paper we investigate the degree of
resemblance between those two theoretical setups, and find that every
quintessence model can be viewed as a k-essence model generated by a kinetic
linear function. In addition, we show the true effects of k-essence begin at
second order in the expansion of the kinetic function in powers of the kinetic
energy.


title:
Molecular hydrogen in damped Ly-alpha systems: clues to interstellar
  physics at high-redshift

abstract:
  In order to interpret H2 (molecular hydrogen) quasar absorption line
observations of damped Ly-alpha systems (DLAs) and sub-DLAs, we model their H2
abundance as a function of dust-to-gas ratio, including H2 self-shielding and
dust extinction against dissociating photons. Then, we constrain the physical
state of gas by using H2 data. Using H2 excitation data for DLA with H2
detections, we derive a gas density 1.5 < log n [cm^-3] < 2.5, temperature 1.5
< log T [K] < 3, and internal UV radiation field (in units of the Galactic
value) 0.5 < log \chi < 1.5. We then find that the observed relation between
molecular fraction and dust-to-gas ratio of the sample is naturally explained
by the above conditions. However, it is still possible that H2 deficient DLAs
and sub-DLAs with H2 fractions less than ~ 10^-6 are in a more diffuse and
warmer state. The efficient photodissociation by the internal UV radiation
field explains the extremely small H2 fraction (< 10^-6) observed for \kappa <
1/30 (\kappa is the dust-to-gas ratio in units of the Galactic value); H2
self-shielding causes a rapid increase and the large variations of H2 abundance
for \kappa > 1/30. We finally propose an independent method to estimate the
star formation rates of DLAs from H2 abundances; such rates are then critically
compared with those derived from other proposed methods. The implications for
the contribution of DLAs to the cosmic star formation history are briefly
discussed.


title:
First Results of Fast One-dimensional Hybrid Simulation of EAS Using
  CONEX

abstract:
  A hybrid simulation code is developed that is suited for fast one-dimensional
simulations of shower profiles, including fluctuations. It combines the Monte
Carlo simulation of high energy interactions with a fast numerical solution of
cascade equations for the resulting distributions of secondary particles.
Results obtained with this new code, called CONEX, are presented and compared
to CORSIKA predictions.


title: Far-Infrared detection of methylene

abstract:
  We present a clear detection of CH2 in absorption towards the molecular cloud
complexes Sagittarius B2 and W49 N using the ISO Long Wavelength Spectrometer.
These observations represent the first detection of its low excitation
rotational lines in the interstellar medium. Towards Sagittarius B2, we detect
both ortho and para transitions allowing a determination of the total CH2
column density of N(CH2)=(7.5+/-1.1)x10^14 cm^-2. We compare this with the
related molecule, CH, to determine [CH/CH2]=2.7+/-0.5. Comparison with chemical
models shows that the CH abundance along the line of sight is consistent with
diffuse cloud conditions and that the high [CH/CH2] ratio can be explained by
including the effect of grain-surface reactions.


title: Branon dark matter: an introduction

abstract:
  This is a brief introduction to branon physics and its role in the dark
matter problem. We pay special attention to the phenomenological consequences,
both in high-energy particle physics experiments and in astrophysical and
cosmological observations.


title:
[alpha/Fe] in the thin and the thick disk towards an automatic
  parametrization of stellar spectra

abstract:
  We test an automatic procedure to measure [Fe/H] and [alpha/Fe] on high
resolution spectra. The test sample is the intersection of the ELODIE library
and a catalogue of 830 stars having well determined abundances.


title:
Introducing adapted Nelder & Mead's downhill simplex method to a fully
  automated analysis of eclipsing binaries

abstract:
  Eclipsing binaries are extremely attractive objects because absolute physical
parameters (masses, luminosities, radii) of both components may be determined
from observations. Since most efforts to extract these parameters were based on
dedicated observing programs, existing modeling code is based on interactivity.
Gaia will make a revolutionary advance in shear number of observed eclipsing
binaries and new methods for automatic handling must be introduced and
thoroughly tested. This paper focuses on Nelder & Mead's downhill simplex
method applied to a synthetically created test binary as it will be observed by
Gaia.


title:
On the gravitational potential of an inhomogeneous ellipsoid of
  revolution (spheroid)

abstract:
  It is shown that the gravitational potential outside an inhomogeneous
ellipsoid of revolution (spheroid) whose isodensity surfaces are confocal
spheroids is identical to the gravitational potential of a homogeneous spheroid
of the same mass.

categories: astro-ph math-ph math.MP physics.class-ph


title: The Bicoherence as a Diagnostic for Models of High Frequency QPOs

abstract:
  We discuss the use of the bicoherence - a measure of the phase coupling of
oscillations at different frequencies - as a diagnostic between different
models for high frequency quasi-periodic oscillations from Galactic black hole
candidates. We show that this statistic is capable of finding qualitative
distinctions between different hot spot models which produce nearly identical
Fourier power density spectra. Finally, we show that proposed new timing
missions should detect enough counts to make real use of this statistic.


title:
Calculated spectra for HeH+ and its effect on the opacity of cool metal
  poor stars

abstract:
  The wavelength and Einstein A coefficient are calculated for all
rotation-vibration transitions of $^4$He$^1$H$^+$, $^3$He$^1$H$^+$,
$^4$He$^2$H$^+$ and $^3$He$^2$H$^+$, giving a complete line list and the
partition function for $^4$HeH$^+$ and its isotopologues. This opacity is
included in the calculation of the total opacity of low-metallicity stars and
its effect is analysed for different conditions of temperature, density and
hydrogen number fraction. For a low helium number fraction (as in the Sun), it
is found that HeH$^+$ has a visible but small effect for very low densities
($\rho\leq 10^{-10}$g cm$^{-3}$), at temperatures around 3500 K. However, for
high helium number fraction, the effect of HeH$^+$ becomes important for higher
densities ($\rho\leq 10^{-6}$g cm$^{-3}$), its effect being most important for
a temperature around 3500 K. Synthetic spectra for a variety of different
conditions are presented.


title:
Rain and clouds in brown dwarf atmospheres: A coupled problem from small
  to large

abstract:
  The large scale structure of a brown dwarf atmosphere is determined by an
interplay of convection, radiation, dust formation, and gravitational settling,
which possibly provides an explanation for the observed variability. The result
is an element depletion of the dust forming regions and an element enrichment
of the dust evaporating sites. The formation of dust cloud structures in
substellar atmospheres is demonstrated based on a consistent theoretical
description of dust formation and destruction, gravitational settling, and
element depletion including the effect of convective overshoot.
  Since the viscosity is small in brown dwarf atmospheres, the convection
creates a turbulent environment with fluctuations of all thermodynamic state
variables on a wide range of spatial scales. Hence, the classical turbulent
closure problem needs to be tackled in connection with dust formation in
substellar objects, because a complete three-dimensional and time-dependent
solution of the model equations is simply not possible. Structure formation may
be seeded on the smallest scales, when chemical processes are involved. In
order to understand the interaction of turbulence and dust formation, we have
performed investigations of the smallest scale regimes in 1D and in 2D in order
to identify the governing processes of the unresolved scale regime.


title: Mg II Absorbing Galaxies: Morphologies and Kinematics

abstract:
  In this contribution, we review our current knowledge of the properties of
galaxies, and their extended halos, selected by MgII absorption in the spectra
of background quasars. We then describe recent efforts to quantify the
morphologies and orientations of galaxies and explore how these relate to the
gas kinematics. In a sample of 26 galaxies, we find no clear connection between
the orientation of the quasar line of sight through the galaxy and the velocity
spread of the gas. However, it appears that the quantity of gas "stirred up" in
the halo may be correlated to asymmetry in the galaxy morphology. Since the
galaxies have fairly normal morphologies, this connection may suggest that
galaxies with extended halos experienced an interaction or merging event a few
dynamical times prior to the epoch of observation.


title:
High Resolution Spectroscopy of 4U 1728-34 from a Simultaneous
  Chandra-RXTE Observation

abstract:
  We report on a simultaneous Chandra and RossiXTE observation of the LMXB
atoll bursting source 4U 1728-34 performed on 2002 March 3-5. We fitted the
1.2-35 keV continuum spectrum with a blackbody plus a Comptonized component. An
overabundance of Si by a factor of ~2 with respect to Solar abundance is
required for a satisfactory fit. Large residuals at 6-10 keV can be fitted by a
broad (FWHM ~ 1.6 keV) Gaussian emission line, or, alternatively, by absorption
edges associated with Fe I and Fe XXV at ~7.1 keV and ~9 keV, respectively. In
this interpretation, we find no evidence of a broad, or narrow Fe Kalpha line,
between 6 and 7 keV. We tested our alternative modeling of the iron Kalpha
region by reanalyzing a previous BeppoSAX observation of 4U 1728-34, finding a
general agreement with our new spectral model.


title: XMM-Newton Observations of the 2003 X-ray Minimum of Eta Carinae

abstract:
  The XMM-Newton X-ray observatory took part in the multi-wavelength observing
campaign of the massive, evolved star Eta Carinae in 2003 during its recent
X-ray minimum. This paper reports on the results of these observations, mainly
from the aspect of spectral change. Hard X-ray emission from the point source
of Eta Carinae was detected even during the minimum. During the minimum the
observed flux above 3 keV was ~3e-12 ergs cm-2 s-1, which is about one percent
of the flux before the minimum. Changes in the spectral shape revealed two
X-ray emission components in the central point source. One component is
non-variable and has relatively cool plasma of kT~1 keV and moderate
absorption, NH~5e22 cm-2. The plasma is probably located far from the star,
possibly produced by the high speed polar wind from Eta Carinae. The other high
temperature component has kT~5 keV and is strongly variable. This component
shows an increase in the apparent column density from 5e22 cm-2 to 2e23 cm-2,
probably originating near the heart of the binary system. These changes in NH
were smaller than expected if the minimum is produced solely by an increase of
hydrogen column density. The X-ray minimum seems to be dominated by a decrease
of the apparent emission measure, suggesting that the brightest part of the
X-ray emitting region is completely obscured during the minimum in the form of
an eclipse. A ``partial covering'' model might explain the residual emission
seen during the minimum.


title:
PAH emission variations within the resolved starbursts of NGC253 and
  NGC1808

abstract:
  (ABRIDGED) We have undertaken a programme of 3 micron narrowband imaging of a
sample of nearby template galaxies covering a wide range of metallicity, star
formation activity, and nuclear activity. In the present paper we present first
results: high spatial resolution images of PAH emission and the adjacent
continuum emission from the central regions of the nearby starburst galaxies
NGC253 and NGC1808. Globally, the PAH emission is seen to peak on the central
starburst regions of both sources. On smaller scales, however, we see no
general spatial correlation or anti-correlation between the PAH emission and
the location of sites of recent star formation, suggesting that the degree to
which PAH emission traces starburst activity is more complicated than
previously hypothesized based on results from data with lower spatial
resolution. We do find spatial correlations, though, when we consider the
PAH-to-continuum ratio, which is low at the positions of known super star
clusters in NGC1808 as well as at the position of the IR peak in NGC253. We
take this to imply a decrease in the efficiency of PAH emission induced by the
star formation, caused by mechanical energy input into the ISM or
photoionisation or photodissociation of the PAH molecules. All three hypotheses
are discussed. In addition, for the first time we present observations of PAH
emission in the superwind of a starbursting system (NGC253), providing strong
support that winds are heavily mass-loaded and entrain substantial amounts of
ambient ISM. We have also found a plausible connection between observed NaD
absorption, H2, and PAHs above the plane of NGC253. This observation has
important implications for enriching galaxy halos and possibly the
intergalactic medium with small dust grains.


title: On the Effects due to a Decaying Cosmological Fluctuation

abstract:
  We present the initial conditions for a decaying cosmological perturbation
and study its signatures in the CMB anisotropies and matter power spectra. An
adiabatic decaying mode in presence of components which are not described as
perfect fluids (such as collisionless matter) decays slower than in a
perfect-fluid dominated universe and displays super-Hubble oscillations. By
including a correlated decaying mode with a red or a scale invariant spectrum,
the anisotropy pattern shows super-imposed oscillations before the first
Dopplear peak, while with a blue spectrum the amplitude of the secondary peaks
relative to the first one and the matter power spectrum can be altered. WMAP
first year data constrain the decaying to growing ratio of scale invariant
adiabatic fluctuations at the matter-radiation equality to less than 10%.


title:
XMM-Newton observations of the interacting galaxy pairs NGC7771/0 and
  NGC2342/1

abstract:
  We present XMM-Newton X-ray observations of the interacting galaxy pairs
NGC7771/7770 and NGC2342/2341. In NGC7771, for the first time we are able to
resolve the X-ray emission into a bright central source (L(X)~10^41 erg/s),
plus two (L(X)>10^40 erg/s) ultraluminous X-ray sources (ULXs) located either
end of the bar. The soft emission of the central source is well-modelled by a
two-temperature thermal plasma with kT=0.4/0.7 keV. The hard emission is
modelled with a flat absorbed power-law (Gamma~1.7, NH~10^22 cm^2), and this
together with a low-significance (1.7 sigma) ~300 eV equivalent width emission
line at ~6 keV are the first indications that NGC7771 may host a low-luminosity
AGN. For the bar ULXs, a power-law fit to X-1 is improved at the 2.5 sigma
level with the addition of a thermal plasma component (kT~0.3 keV), while X-2
is improved only at the 1.3 sigma level with the addition of a disc blackbody
component with T(in)~0.2 keV. Both sources are variable on short time-scales
implying that their emission is dominated by single accreting X-ray binaries
(XRBs). The three remaining galaxies, NGC7770, NGC2342 and NGC2341, have
observed X-ray luminosities of 0.2, 1.8 & 0.9x10^41 erg/s respectively (0.3-10
keV). Their integrated spectra are also well-modelled by multi-temperature
thermal plasma components with kT=0.2-0.7 keV, plus power-law continua with
slopes of Gamma=1.8-2.3 that are likely to represent the integrated emission of
populations of XRBs as observed in other nearby merger systems. A comparison
with other isolated, interacting and merging systems shows that all four
galaxies follow the established correlations for starburst galaxies between
X-ray, far-infrared and radio luminosities, demonstrating that their X-ray
outputs are dominated by their starburst components.


title:
Demographic and Citation Trends in Astrophysical Journal papers and
  Preprints

abstract:
  We have used data from ADS, AAS, and astro-ph, to study the publishing,
preprint posting, and citation patterns for papers published in the ApJ in 1999
and 2002. This allowed us to track statistical trends in author demographics,
preprint posting habits, and citation rates for ApJ papers as a whole and
across various subgroups and types of ApJ papers. The most interesting results
are the frequencies of use of the astro-ph server across various subdisciplines
of astronomy, and the impact that such posting has on the citation history of
the subsequent ApJ papers. By 2002 72% of ApJ papers were posted as astro-ph
preprints, but this fraction varies from 22-95% among the subfields studied. A
majority of these preprints (61%) were posted after the papers were accepted at
ApJ, and 88% were posted or updated after acceptance. On average, ApJ papers
posted on astro-ph are cited more than twice as often as those that are not
posted on astro-ph. This difference can account for a number of other,
secondary citation trends, including some of the differences in citation rates
between journals and different subdisciplines. Preprints clearly have
supplanted the journals as the primary means for initially becoming aware of
papers, at least for a large fraction of the ApJ author community. Publication
in a widely-recognized peer-reviewed journal remains as the primary determinant
of the impact of a paper, however. For example, conference proceedings papers
posted on astro-ph are also cited twice as frequently as those that are not
posted, but overall such papers are still cited 20 times less often than the
average ApJ paper. These results provide insights into how astronomical
research is currently disseminated by authors and ingested by readers.


title: Halo Mass Function: Low-mass Stars in Deep Fields

abstract:
  Deep fields are unique probes of the Galactic halo. With a limiting magnitude
of, e.g., I = 30 mag, all stars down to the hydrogen-burning limit are detected
out to distances of 10 kpc, while stars with 0.5 solar masses could be traced
out to distances of 400 kpc. Thus deep fields provide an opportunity to study
both the structure of the Galactic halo and the mass function of population
(Pop) II and Pop III stars. I summarize previous work on the Galactic stellar
halo utilizing the Hubble Deep Fields North and South, supplemented by a
preliminary analysis of the recently released Hubble Ultra-Deep Field.


title:
The Hot Intergalactic Medium - Galaxy Connection: Two Strong Absorbers
  in the Sightline Toward PG 1211+143

abstract:
  We present HST/STIS and FUSE spectra of the QSO PG 1211+143 (z_em = 0.081)
and a galaxy survey of the surrounding field. This sightline shows two strong
intergalactic absorption systems at cz ~ 15,300 and 19,300. This sightline
addresses the nature and origin of the OVI absorbers, and their connection to
galaxies. We explore the relationship of these absorbers to the nearby galaxies
and compare them to other OVI-bearing absorbers in diverse environments. At
15,300 km s^-1, we find four distinct HI components and associated CII, CIII,
CIV, SiII, SiIII, SiIV, NV, and OVI, lying near a spiral-dominated galaxy group
with a bright member galaxy 137 h_70^-1 kpc from the sightline. The observed
ions of C, Si, and N are likely to be photoionized, but the OVI is more
consistent with collisional ionization. The ion ratios in this absorber
resemble the highly-ionized Galactic HVCs; it may also trace the hot intragroup
medium gas or the unbound wind of an undiscovered dwarf galaxy. At 19,300 km
s^-1, we find five HI components and associated CIII, SiIII, and
collisionally-ionized OVI lying 146 h_70^-1 kpc from an isolated galaxy. The
properties of the OVI-bearing gas are consistent with an origin in strong
shocks between low-metallicity gas (>= 2 - 6 % solar) and one or more of the
warm photoionized components. It is likely that these absorbers are related to
the nearby galaxies, perhaps by outflows or gas stripped from unseen satellite
galaxies by interactions. However, we cannot reject completely the hypothesis
that they reside in the same large-scale structure in which the galaxies are
embedded but are otherwise not directly related.


title: Ionising stellar populations in circumnuclear star forming regions

abstract:
  We present a study of the stellar populations and gas physical conditions in
Circumnuclear Star Forming Regions (CNSFRs) based on spectrophotometric data,
including the 7000 angstroms to 1 micron spectral range, which is of great
interest to the whole diagnostic of the ionized gas. The properties of CNSFRs
as a class are inferred from a comparison with those of other star forming
emission-line objects: low excitation disc HII regions and HII galaxies.


title: Binaries among Ultra-cool Dwarfs and Brown Dwarfs

abstract:
  Observations of brown dwarfs provide important feedback on theories of
atmospheres and inner structure of substellar objects. Brown dwarf binary
systems furthermore offer the unique opportunity to determine the mass of
individual brown dwarfs, which is one of the fundamental astrophysical
quantities.


title: The Ultimate Energy Density of Observable Cold Matter

abstract:
  We demonstrate that the largest measured mass of a neutron star establishes
an upper bound to the energy density of observable cold matter. An equation of
state-independent expression satisfied by both normal neutron stars and
self-bound quark matter stars is derived for the largest energy density inside
stars as a function their masses. The largest observed mass sets the lowest
upper limit to the density. Implications from existing and future neutron star
mass measurements are discussed.


title: Numerical Simulations of the MRI and Real Disks

abstract:
  Numerical MHD codes have become extraordinarily powerful tools with which to
study accretion turbulence. They have been used primarily to extract values for
the classical $\alpha$ parameter, and to follow complex evolutionary
development. Energy transport, which is at the heart of classical disk theory,
has yet to be explored in any detail. Further topics that should be explored by
simulation include nonideal MHD, radiation physics, and outburst behavior
related to the temperature sensitivity of the resistivity.


title: Star-Forming Complexes in Galaxies

abstract:
  Star complexes are the largest globular regions of star formation in
galaxies. If there is a spiral density wave, nuclear ring, tidal arm, or other
well-defined stellar structure, then gravitational instabilities in the gaseous
component produce giant cloud complexes with a spacing of about three times the
width. These gas complexes form star complexes, giving the familiar beads on a
string of star formation along spiral arms, or nuclear hotspots in the case of
a ring. Turbulence compression, supernovae, and self-gravitational contraction
inside the giant clouds produce a nearly scale-free structure, including giant
molecular clouds that form OB associations and molecular cloud cores that form
clusters. Without stellar density waves or similar structures, random
gravitational instabilities form flocculent spirals and these fragment into
star complexes, OB associations and star clusters in the same way. The largest
coherent star-forming regions are the flocculent arms themselves. At the core
of the hierarchy are the very dense clumps in which individual and binary stars
form. The overall star formation rate in a galaxy appears to be regulated by
gravitational collapse on large scales, giving the Kennicutt/Schmidt law
scaling with density, but the efficiency factor in front of this scaling law
depends on the fraction of the gas that is in a dense form. Turbulence
compression probably contributes to this fraction. The CO version of the
Schmidt law, recently derived by Heyer et al. (2004), follows from the
turbulent hierarchy as well, as do the local efficiencies of star formation in
OB associations and clusters. The efficiency of star formation increases with
cloud density, and this is why most stars form in clusters that are initially
self-bound.


title: Particle Dark Energy

abstract:
  We explore the physics of a gas of particles interacting with a condensate
that spontaneously breaks Lorentz invariance. The equation of state of this gas
varies from 1/3 to less than -1 and can lead to the observed cosmic
acceleration. The particles are always stable. In our particular class of
models these particles are fermions with a chiral coupling to the condensate.
They may behave as relativistic matter at early times, produce a brief period
where they dominate the expansion with w<0 today, and behave as matter at late
time. There are no small parameters in our models, which generically lead to
dark energy clustering and, depending on the choice of parameters, smoothing of
small scale power.


title: Terrestrial Ozone Depletion Due to a Milky Way Gamma-Ray Burst

abstract:
  Based on cosmological rates, it is probable that at least once in the last Gy
the Earth has been irradiated by a gamma-ray burst in our Galaxy from within 2
kpc. Using a two-dimensional atmospheric model we have performed the first
computation of the effects upon the Earth's atmosphere of one such impulsive
event. A ten second burst delivering 100 kJ/m^2 to the Earth penetrates to the
stratosphere and results in globally averaged ozone depletion of 35%, with
depletion reaching 55% at some latitudes. Significant global depletion persists
for over 5 years after the burst. This depletion would have dramatic
implications for life since a 50% decrease in ozone column density results in
approximately three times the normal UVB flux. Widespread extinctions are
likely, based on extrapolation from UVB sensitivity of modern organisms.
Additional effects include a shot of nitrate fertilizer and NO2 opacity in the
visible providing a cooling perturbation to the climate over a similar
timescale. These results lend support to the hypothesis that a GRB may have
initiated the late Ordovician mass extinction (Melott et al. 2004).

categories: astro-ph physics.ao-ph physics.geo-ph physics.space-ph q-bio.PE


title: A Keck/HIRES Doppler Search for Planets Orbiting Metal-Poor Dwarfs

abstract:
  We present results from our ongoing spectroscopic search for giant planets
within 1 AU around a well-defined sample of metal-poor stars with HIRES on the
Keck 1 telescope. We have achieved an rms radial velocity precision of $\sim 8$
m/s over a time-span of 1.5 years. The data collected so far build toward
evidence of the absence of very short-period ($< 1$ month) giant planets.
However, about 7% of the stars in our sample exhibits velocity trends
indicative of the existence of companions. We place preliminary upper limits on
the detectable companion mass as a function of orbital period, and compare them
with the performance of ESA's future space-borne high-precision astrometric
observatory Gaia.


title:
XMM-Newton Observation of an X-ray Trail Between the Spiral Galaxy
  NGC6872 and the Central Elliptical NGC6876 in the Pavo Group

abstract:
  We present XMM-Newton observations of a trail of enhanced X-rayemission
extending along the 8'.7 X 4' region between the spiral NGC6872 and the
dominant elliptical NGC6876 in the Pavo Group,the first known X-ray trail
associated with a spiral galaxy in a poor galaxy group and, with projected
length of 90 kpc, one of the longest X-ray trails observed in any system. The
X-ray surface brightness in the trail region is roughly constant beyond ~20 kpc
of NGC6876 in the direction of NGC6872. The trail is hotter (~ 1 keV) than the
undisturbed Pavo IGM (~0.5 keV) and has low metal abundances (0.2 Zsolar). The
0.5-2 keV luminosity of the trail, measured using a 67 X 90 kpc rectangular
region, is 6.6 X 10^{40} erg/s. We compare the properties of gas in the trail
to the spectral properties of gas in the spiral NGC6872 and in the elliptical
NGC6876 to constrain its origin. We suggest that the X-ray trail is either IGM
gas gravitationally focused into a Bondi-Hoyle wake, a thermal mixture of ~64%
Pavo IGM gas with ~36% galaxy gas that has been removed from the spiral NGC6872
by turbulent viscous stripping, or both, due to the spiral's supersonic motion
at angle xi ~ 40 degrees with respect to the plane of the sky, past the Pavo
group center (NGC6876) through the densest region of the Pavo IGM. Assuming xi
= 40 degrees and a filling factor eta in a cylindrical volume with radius 33
kpc and projected length 90 kpc, the mean electron density and total hot gas
mass in the trail is 9.5 X 10^{-4}*eta^{-1/2} cm^{-3} and 1.1 X
10^{10}*eta^{1/2} Msolar, respectively.


title: The influence of gravitational lensing on the spectra of lensed QSOs

abstract:
  We consider the influence of (milli/micro)lensing on the spectra of lensed
QSOs. We propose a method for the observational detection of microlensing in
the spectra of lensed QSOs and apply it to the spectra of the three lensed QSOs
(PG 1115+080, QSO 1413+117 and QSO 0957+561) observed with Hubble Space
Telescope (HST). We find that the flux ratio between images A1 and A2 of PG
1115+080 is wavelength-dependent and shows differential magnification between
the emission lines and the continuum. We interpret this magnification as
arising from millilensing. We also find that the temporal variations in the
continuum of image C of QSO 1413+117 may be caused by microlensing, while the
temporal variation observed in QSO 0957+561 was probably an intrinsic one.


title: Inferring hot-star-wind acceleration from Line Profile Variability

abstract:
  The migration of profile sub-peaks identified in time-monitored optical
emission lines of Wolf-Rayet star spectra provides a direct diagnostic of the
dynamics of their stellar winds via a measured line-of-sight velocity change
per unit time. Inferring the associated wind acceleration scale from such an
apparent acceleration then relies on the adopted intrinsic velocity of the wind
material at the origin of this variable pattern. We develop radiative transfer
tools to characterise the Line Emission Region (LER) of the program lines,
including turbulence and line-optical depth effects. We find that
monitored-lines can be fitted well with a pure optically thin formation
mechanism, line-broadening resulting from the finite velocity extent of the LER
rather than turbulence.Our new estimates of LER velocity centroids are
systematically shifted outwards closer to terminal velocity compared to
previous determinations, now suggesting WR-wind acceleration length scales of
ca. 10-20Rsun, a factor of a few smaller than previously inferred. Based on
radiation-hydrodynamics simulations of the line-driven-instability mechanism,
we compute synthetic line profile variability for CIII5696A, for WR111 The
results match well the measured observed migration of 20-30 m/s2, However, our
model stellar radius of 19 Rsun, typical of an O-type supergiant, is a factor
2--10 larger than generally expected for WR core radii.Such small radii leave
inferred acceleration scales to be more extended than expected from dynamical
models of line driving, but the severity of the discrepancy is substantially
reduced compared to previous analyses. We conclude with a discussion of how
using lines formed deeper in the wind would provide a stronger constraint on
the key wind dynamics as well as information on the onset of wind clumping.


title:
A Chandra observation of the z=2.285 galaxy FSC10214+4724: Evidence for
  a Compton-thick quasar?

abstract:
  We present a ~20 ks Chandra ACIS-S observation of the strongly lensed z=2.285
ultra-luminous infrared galaxy FSC10214+4724. Although this observation
achieves the equivalent sensitivity of an up-to ~4 Ms Chandra exposure (when
corrected for gravitational lensing), the rest-frame 1.6-26.3 keV emission from
FSC10214+4724 is weak (L_X~2E42 erg/s for a lensing boost of ~100); a
significant fraction of this X-ray emission appears to be due to vigorous
star-formation activity. If FSC10214+4724 hosts a quasar, as previously
suggested, then it must be obscured by Compton-thick material. We compare
FSC10214+4724 to high-redshift SCUBA galaxies and discuss the X-ray
identification of Compton-thick AGNs at high redshift.


title: SOAP and the Interstellar Froth

abstract:
  We investigate, whether the alleged failure of standard photoionization codes
of the Diffuse Ionized Gas (DIG) is simply caused by geometrical effects and
the insufficient treatment of the radiative transfer. Standard photoionization
models are applicable only to homogeneous and spherical symmetric nebulae with
central ionizing stars, whereas the geometry of disk galaxies requires a 3D
distribution of ionizing sources in the disk which illuminate the halo. This
change in geometry together with a proper radiative transfer model is expected
to substantially influence ionization conditions. Therefore, we developed a new
and sophisticated 3D Monte Carlo photoionization code, called SOAP (Simulations
Of Astrophysical Plasmas), by adapting an existing 1D code for HII-regions
(Och, Lucy, & Rosa 1998) such, that it self-consistently models a 3D disk
galaxy with a gaseous DIG halo. First results from a simple (dust-free) model
with exponentially decreasing gas densities are presented and the predicted
ionization structure of disk and halo is discussed. Theoretical line ratios
agree well with observed ones, e.g,. for the halo of NGC891. Moreover, the
fraction of ionizing photons leaving the halo of the galaxy is plotted as a
function of varying gas densities. This quantity will be of particular
importance for forthcoming studies, because rough estimates indicate that about
7% ionizing photons escape from the halo and contribute to the ionization of
the IGM. Given the relatively large number density of normal spiral galaxies,
OB-stars could have a much stronger impact on the ionization of the IGM than
AGN or QSOs.


title:
Kinematics of W UMa-type binaries and evidences on the two types of
  formation

abstract:
  The kinematics of 129 W UMa binaries is studied and its implications on the
contact binary evolution is discussed. The sample is found to be heterogeneous
in the velocity space that kinematically younger and older contact binaries
exist in the sample. Kinematically young (0.5 Gyr) sub-sample (MG) is formed by
selecting the systems which are satisfying the kinematical criteria of moving
groups. After removing the possible MG members and the systems which are known
to be members of open clusters, the rest of the sample is called Field Contact
Binaries (FCB). The FCB has further divided into four groups according to The
orbital period ranges. Then a correlation has been found in the sense that
shorter period less massive systems have larger velocity dispersions than the
longer period more massive systems. Dispersions in the velocity space indicates
5.47 Gyr kinematical age for the FCB group. Comparing with the field
chromospherically active binaries (CAB), presumably detached binary progenitors
of the contact systems, the FCB appears to be 1.61 Gyr older. Assuming an
equilibrium in the formation and destruction of CAB and W UMa systems in the
Galaxy, this age difference is treated as empirically deduced lifetime of the
contact stage. Since the kinematical ages of the four sub groups of FCB are
much longer than the 1.61 Gyr lifetime of the contact stage, the pre-contact
stages of FCB must dominantly be producing the large dispersions. The
kinematically young (0.5 Gyr) MG group covers the same total mass, period and
spectral ranges as the FCB. But, the very young age of this group does not
leave enough room for pre-contact stages, thus it is most likely that those
systems were formed in the beginning of the main-sequence or during the
pre-main-sequence contraction phase.


title: Flatness in disc galaxy dynamics without MOND or dark matter

abstract:
  In previous work (astro-ph/0306228) we have established that a particular
quasi-classical theoretical viewpoint about the nature of gravitation in galaxy
discs provides extremely high concordance (comparable with MOND) with the
observed dynamics in optical discs.
  In this paper, we consider the possibility that the optical disc and the flat
radio disc represent distinct dynamical regions which are inherently described
by distinct phases of the same over-arching theory of which the quasi-classical
theory is but one phase. This is a defining moment for the theory under
discussion since the only natural generalization available is that from the
existing quasi-classical (one-clock) model into a quasi-relativistic
(two-clock) model. The quasi-relativistic disc turns out to be a stationary
hyperbolic disc within which information propagates along characteristics and
within which the rotation curve is necessarily exactly flat.
  The transition between the two components of the disc is managed by
physically determined jump conditions which are represented by a set of
non-linear algebraic equations. These equations predict the existence of a
forbidden region within the parameter space which coincides exactly with that
part of the parameter space in which there is an already observed highly
significant underpopulation of galaxy discs (astro-ph/0107300).


title:
The Gaussian cell two-point "energy-like" equation: Application to large
  scale galaxy redshift and peculiar motion surveys

abstract:
  We introduce a simple linear equation relating the line-of-sight peculiar
velocity and density contrast correlation functions. The relation, which we
call the "Gaussian cell two-point energy-like equation", is valid in the
distant-observer-limit and requires Gaussian smoothed fields. In the variance
case, i.e., at zero lag, the equation is similar in its mathematical form to
the Layzer-Irvine cosmic energy equation. \beta estimation with this equation
from the PSC$z$ redshift galaxy survey and the SEcat catalogue of peculiar
velocities is carried out, returning a value of \beta = 0.44+-0.08. The
applicability of the method for the 6dF galaxy redshift and peculiar motions
survey is demonstrated with mock data where it is shown that beta could be
determined with ~5% accuracy. The prospects for constraining the dark energy
equation of state with this method from the kinematic and thermal
Sunyaev-Zel'dovich cluster surveys are discussed. The equation is also used to
construct a nonparametric mass density power spectrum estimator from peculiar
velocity data.


title:
Turbulent thermal diffusion of aerosols in geophysics and laboratory
  experiments

abstract:
  We discuss a new phenomenon of turbulent thermal diffusion associated with
turbulent transport of aerosols in the atmosphere and in laboratory
experiments. The essence of this phenomenon is the appearance of a nondiffusive
mean flux of particles in the direction of the mean heat flux, which results in
the formation of large-scale inhomogeneities in the spatial distribution of
aerosols that accumulate in regions of minimum mean temperature of the
surrounding fluid. This effect of turbulent thermal diffusion was detected
experimentally. In experiments turbulence was generated by two oscillating
grids in two directions of the imposed vertical mean temperature gradient. We
used Particle Image Velocimetry to determine the turbulent velocity field, and
an Image Processing Technique based on an analysis of the intensity of Mie
scattering to determine the spatial distribution of aerosols. Analysis of the
intensity of laser light Mie scattering by aerosols showed that aerosols
accumulate in the vicinity of the minimum mean temperature due to the effect of
turbulent thermal diffusion. Geophysical applications of the obtained results
are discussed.


title: Phase Transitions In Compact Stars

abstract:
  We report on a three--month research project for undergraduate students about
the mass-radius relation of compact stars. The equation of state used is
constrained at low densities by well-established equations of state of the
nuclear phase (the solid crust) and then extended to higher densities with a
phenomenological, parametric approach. A first order phase transition from
hadronic matter to a phase of higher density, assumed to be quark matter is
studied in addition. The mass-radius relation is obtained by solving
numerically the Tolman-Oppenheimer-Volkoff equation. We derive some conditions
for the existence of a third family of compact stars on the form of the
equation of state and its different global properties.


title:
Mid-infrared imaging and modelling of the dust shell around post-AGB
  star HD 187885 (IRAS 19500-1709)

abstract:
  We present 10 and 20 micron images of IRAS 19500-1709 taken with the
mid-infrared camera, OSCIR, mounted on the Gemini North Telescope. An extended
circumstellar envelope is detected, with the N band image indicating an
elongation in a NE-SW direction. We use a dust radiation transport code to fit
the spectral energy distribution from UV to sub-mm wavelengths, with a detached
dust shell model. A good fit is achieved using dust composed of amorphous
carbon, silicon carbide and magnesium sulphide. We derive estimates for the
inner and outer radius, density and mass of the dust in the shell. The inner
radius is not resolved in our OSCIR imaging, giving an upper limit of 0.4
arcsec. With this constraint, we conclude that IRAS 19500-1709 must be at least
4 kpc away in order to have the minimum luminosity consistent with a post-AGB
status.


title: The nature and origin of Seyfert warm absorbers

abstract:
  We collate the results of recent high resolution X-ray spectroscopic
observations of 23 AGN, and use the resulting information to try to provide
answers to some of the main open questions about warm absorbers: where do they
originate, what effect do they have on their host galaxies, and what is their
importance within the energetics and dynamics of the AGN system as a whole? We
find that the warm absorbers of nearby Seyferts and certain QSOs are most
likely to originate in outflows from the dusty torus, and that the kinetic
luminosity of these outflows accounts for well under 1% of the bolometric
luminosities of the AGN. Our analysis supports, however, the view that the
relativistic outflows recently observed in two PG quasars have their origin in
accretion disc winds, although the energetic importance of these outflows is
similar to that of the Seyfert warm absorbers. We find that the observed soft
X-ray absorbing ionisation phases fill less than 10% of the available volume.
Finally, we show that the amount of matter processed through an AGN outflow
system, over the lifetime of the AGN, is probably large enough to have a
significant influence on the evolution of the host galaxy and of the AGN
itself.


title:
Integral Field Spectroscopy of the Central Regions of 3C 120: Evidence
  of a Past Merging Event

abstract:
  IFS combined with HST WFPC imaging were used to characterize the central
regions of the Seyfert 1 radio galaxy 3C 120. We carried out the analysis of
the data, deriving intensity maps of different emission lines and the continua
at different wavelengths from the observed spectra. Applying a 2D modeling to
the HST images we decoupled the nucleus and the host galaxy, and analyzed the
host morphology. The host is a highly distorted bulge dominated galaxy, rich in
substructures. We developed a new technique to model the IFS data extending the
2D modeling. Using this technique we separated the Seyfert nucleus and the host
galaxy spectra, and derived a residual data cube with spectral and spatial
information of the different structures in 3C 120. Three continuum-dominated
structures (named A, B, and C) and other three extended emission line regions
(EELRs, named E1, E2 and E3) are found in 3C 120 which does not follow the
general behavior of a bulge dominated galaxy. We also found shells in the
central kpc that may be remnants of a past merging event in this galaxy. The
origin of E1 is most probably due to the interaction of the radio-jet of 3C 120
with the intergalactic medium. Structures A, B, and the shell at the southeast
of the nucleus seem to correspond to a larger morphological clumpy structure
that may be a tidal tail, consequence of the past merging event. We found a
bright EELR (E2) in the innermost part of this tidal tail, nearby the nucleus,
which shows a high ionization level. The kinematics of the E2 region and its
connection to the tidal tail suggest that the tail has channeled gas from the
outer regions to the center.


title: Energy Emission by Quantum Systems in an Expanding FRW Metric

abstract:
  Bound quantum mechanical systems not expanding with the comoving frame of an
expanding, flat FRW metric are found to release energy at a rate linearly
proportional to the local Hubble constant ($H_{o}$) and the systems' binding
energy ($E_{b}$); {\em i.e.}, $\dot{E} = H_{o} E_{b}$. Three exemplary quantum
systems are examined. For systems with early cosmological condensation times |
notably hadrons | time-integrated energy release could have been significant
and could account for an appreciable fraction of the dark matter inventory.


title:
The stellar content of the Hamburg/ESO survey. III. Field
  horizontal-branch stars in the Galaxy

abstract:
  We present a sample of 8321 candidate Field Horizontal-Branch (FHB) stars
selected by automatic spectral classification in the digital data base of the
Hamburg/ESO objective-prism survey. The stars are distributed over 8225 square
degrees of the southern sky, at |b| > 30 deg. The average distance of the
sample, assuming that they are all FHB stars, is 9.8 kpc, and distances of up
to ~30 kpc are reached. Moderate-resolution spectroscopic follow-up
observations and UBV photometry of 125 test sample stars demonstrate that the
contamination of the full candidate sample with main-sequence A-type stars is <
16%, while it would be up to 50% in a flux-limited sample at high galactic
latitudes. Hence more than ~6800 of our FHB candidates are expected to be
genuine FHB stars. The candidates are being used as distance probes for
high-velocity clouds and for studies of the structure and kinematics of the
Galactic halo.


title: K-luminous galaxies at z~2. Metallicity and B stars

abstract:
  We present the results from the analysis of the composite spectrum of five
near-IR luminous (K < 20) galaxies at z~2. Several of the strongest absorption
lines are present in the merging galaxy NGC 6090 UV spectrum and are not
present in the spectra of Lyman Break Galaxies at z~3. They were identified as
SiIII 1296, CIII 1428, SiII 1485, and Fe 1380 which are photospheric lines
typical of B stars. A metallicity higher than solar is suggested by comparing
the pure photospheric lines known as the 1425AA index (SiIII, CIII, FeV) with
Starburst99 models. The evidence of high metallicity, together with the high
masses, high star-formation rates, and possibly strong clustering, suggest that
these galaxies are candidates to become massive spheroids.


title: The Galaxy Evolution Explorer: A Space Ultraviolet Survey Mission

abstract:
  We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer
Mission launched on April 28, 2003. GALEX is performing the first space UV
sky-survey, including imaging and grism surveys in two bands (1350-1750
Angstroms and 1750-2750 Angstroms). The surveys include an all-sky imaging
survey (m[AB] ~ 20.5), a medium imaging survey of 1000 square degrees (m[AB] ~
23), a deep imaging survey of 100 square degrees (m[AB] ~ 25), and a nearby
galaxy survey. Spectroscopic grism surveys (R=100-200) are underway with
various depths and sky coverage. Many targets overlap existing or planned
surveys. We will use the measured UV properties of local galaxies, along with
corollary observations, to calibrate the UV-global star formation rate
relationship in local galaxies. We will apply this calibration to distant
galaxies discovered in the deep imaging and spectroscopic surveys to map the
history of star formation in the universe over the redshift range 0 < z < 1.5,
and probe the physical drivers of star formation in galaxies. The GALEX mission
includes a Guest Investigator program supporting the wide variety of programs
made possible by the first UV sky survey.


title:
A Short Characteristic Solution for the 2.5D Transfer Equation in the
  Envelopes of O and B Stars

abstract:
  We discuss work toward developing a 2.5D non-LTE radiative transfer code. Our
code uses the short characteristic method with modifications to handle
realistic 3D wind velocities. We also designed this code for parallel computing
facilities by representing the characteristics with an impact parameter vector
p. This makes the interpolation in the radiation angles unnecessary and allows
for an independent calculation for characteristics represented by different p
vectors. The effects of the velocity field are allowed for by increasing, as
needed, the number of grid points along a short characteristic. This allows us
to accurately map the variation of the opacities and emissivities as a function
of frequency and spatial coordinates. In the future we plan to use this
transfer code with a 2D non-LTE stellar atmosphere program to self-consistently
solve for level populations, the radiation field and temperature structure for
stars with winds and without spherical symmetry.


title:
GALEX observations of the UV surface brightness and color profiles of
  the Local Group elliptical galaxy M32 (NGC221)

abstract:
  M32, the compact elliptical-galaxy companion to the Andromeda spiral galaxy
has been imaged by the Galaxy Evolution Explorer (GALEX) in two ultraviolet
bands, centered at ~1500 (FUV) and 2300 Angstroms (NUV). The imaging data have
been carefully decomposed so as to properly account for the complicated
background contamination from the disk of M31. We have derived the surface
brightness and color profiles finding a slightly positive color gradient of
Delta(FUV-B)/Delta log(r)=+0.15+/-0.03 within one effective radius. Earlier
data from the Ultraviolet Imaging Telescope suggested that M32 had an extremely
large (negative) FUV-optical color gradient (Delta(FUV-B)/Delta log(r)<-2),
inverted with respect to the majority of gradients seen in giant elliptical
galaxies. Our new results show that, despite of its very low UV-upturn, M32 has
similar UV properties to those observed in luminous elliptical galaxies.


title:
The Ultraviolet Luminosity Function of GALEX Galaxies at Photometric
  Redshifts Between 0.07 and 0.25

abstract:
  We present measurements of the UV galaxy luminosity function and the
evolution of luminosity density from GALEX observations matched to the Sloan
Digital Sky Survey (SDSS). We analyze galaxies in the Medium Imaging Survey
overlapping the SDSS DR1 with a total coverage of 44 deg^2. Using the combined
GALEX+SDSS photometry, we compute photometric redshifts and study the LF in
three redshift shells between z=0.07 and 0.25. The Schechter function fits
indicate that the faint-end slope alpha is consistent with -1.1 at all
redshifts but the characteristic UV luminosity M* brightens by 0.2 mag from
z=0.07 to 0.25. In the lowest redshift bin, early and late type galaxies are
studied separately and we confirm that red galaxies tend to be brighter and
have a shallower slope alpha than blue ones. The derived luminosity densities
are consistent with other GALEX results based on a local spectroscopic sample
from 2dF and the evolution follows the trend reported by deeper studies.


title: Recent Star Formation in the Extreme Outer Disk of M83

abstract:
  Ultraviolet imaging with the Galaxy Evolution Explorer (GALEX) has revealed
an extensive sample of UV-bright stellar complexes in the extreme outer disk of
M83, extending to about four times the radius where the majority of HII regions
are detected (R_HII = 5.1' or 6.6 kpc). These sources are typically associated
with large-scale filamentary HI structures in the warped outer disk of M83, and
are distributed beyond the galactocentric radii at which molecular ISM has yet
been detected. We present measured properties of these stellar complexes,
including FUV and NUV magnitudes and local gas surface density. Only a subset
of the outer disk UV sources have corresponding HII regions detected in H-alpha
imaging, consistent with a sample of mixed age in which some sources are a few
Myr old and others are much more evolved (~ 10^8 yr).


title: The Star Formation Rate Function of the Local Universe

abstract:
  We have derived the bivariate luminosity function for the far ultraviolet
(1530Angstroms) and far infrared (60 microns). We used matched GALEX and IRAS
data, and redshifts from NED and PSC-z. We have derived a total star formation
luminosity function phi(L_{tot}), with L_{tot} = L_{FUV}+L_{FIR}. Using these,
we determined the cosmic ``star formation rate'' function and density for the
local universe. The total SFR function is fit very well by a log-normal
distribution over five decades of luminosity. We find that the bivariate
luminosity function phi(L_{FUV},L_{FIR}) shows a bimodal behavior, with L_{FIR}
tracking L_{FUV} for L_{TOT}< 10^10 L_sun, and L_{FUV} saturating at 10^10
L_sun, while L_{TOT} L_{FIR} for higher luminosities. We also calculate the SFR
density and compare it to other measurements.


title:
The Ultraviolet Galaxy Luminosity Function from GALEX data: Color
  Dependent Evolution at Low Redshift

abstract:
  We present measurements of the FUV (1530A) and NUV (2310A) galaxy luminosity
functions (LF) at low redshift (z<0.2) from GALEX observations matched to the
2dF Galaxy Redshift Survey. We split our FUV and NUV samples into two UV-bj
color bins and two redshift bins. As observed at optical wavelengths, the local
LF of the bluest galaxies tend to have steeper faint end slopes and fainter
characteristic magnitudes M* than the reddest subsamples. We find evidence for
color dependent evolution at very low redshift in both bands, with bright blue
galaxies becoming dominant in the highest redshift bin. The evolution of the
total LF is consistent with an 0.3 magnitude brightening between z=0 and 0.13,
in agreement with the first analysis of deeper GALEX fields probing adjacent
and higher redshifts.


title: GALEX Observations of the Ultraviolet Halos of NGC 253 and M82

abstract:
  We present Galaxy Evolution Explorer (GALEX) images of the prototypical
edge-on starburst galaxies M82 and NGC253. Our initial analysis is restricted
to the complex of ultraviolet (UV) filaments in the starburst-driven outflows
in the galaxy halos. The UV luminosities in the halo are too high to be
provided by shock-heated or photoionized gas except perhaps in the brightest
filaments in M82, suggesting that most of the UV light is the stellar continuum
of the starburst scattered into our line of sight by dust in the outflow. This
interpretation agrees with previous results from optical imaging polarimetry in
M82. The morphology of the UV filaments in both galaxies shows a high degree of
spatial correlation with H-alpha and X-ray emission. This indicates that these
outflows contain cold gas and dust, some of which may be vented into the
intergalactic medium (IGM). UV light is seen in the ``H-alpha cap'' 11 kpc
North of M82. If this cap is a result of the wind fluid running into a
pre-existing gas cloud, the gas cloud contains dust and is not primordial in
nature but was probably stripped from M82 or M81. If starburst winds
efficiently expel dust into the IGM, this could have significant consequences
for the observation of cosmologically distant objects.


title: The On-Orbit Performance of the Galaxy Evolution Explorer

abstract:
  We report the first year on-orbit performance results for the Galaxy
Evolution Explorer (GALEX), a NASA Small Explorer that is performing a survey
of the sky in two ultraviolet bands. The instrument comprises a 50 cm diameter
modified Ritchey-Chretien telescope with a 1.25 degree field of view,
selectable imaging and objective grism spectroscopic modes, and an innovative
optical system with a thin-film multilayer dichroic beam splitter that enables
simultaneous imaging by a pair of photon counting, microchannel plate, delay
line readout detectors. Initial measurements demonstrate that GALEX is
performing well, meeting its requirements for resolution, efficiency,
astrometry, bandpass definition and survey sensitivity.


title: Panoramic GALEX FUV and NUV imaging of M31 and M33

abstract:
  We present Galaxy Evolution Explorer (GALEX) far-UV and near-UV mosaic
observations covering the entirety of M31 and M33. For both targets, we measure
the decline of surface brightness (in FUV and NUV) and changes in FUV--NUV
color as a function of galactocentric radius. These UV radial profiles are
compared to the distribution of ionized gas traced by H-alpha emission. We find
that the extent of the UV emission, in both targets, is greater than the extent
of the observed HII regions and diffuse ionized gas. We determine the
ultraviolet diffuse fraction in M33 using our FUV observations and compare it
to the H-alpha diffuse fraction obtained from wide-field narrow-band imaging.
The FUV diffuse fraction appears to be remarkably constant near 0.65 over a
large range in galactocentric radius, with departures to higher values in
circumnuclear regions and, most notably, at the limit of the H-alpha disk. We
suggest that the increase in FUV diffuse fraction at large galactocentric radii
could indicate that a substantial portion of the diffuse emission beyond this
point is not generated in situ but rather scattered from dust, after
originating in the vicinity of the disk's outermost HII regions. Radial
variation of the H-alpha diffuse fraction was also measured. We found the
H-alpha diffuse fraction generally near 0.4 but rising toward the galaxy
center, up to 0.6. We made no attempt to correct our diffuse fraction
measurements for position-dependent extinction, so the quoted values are best
interpreted as upper limits given the plausibly higher extinction for stellar
clusters relative to their surroundings.


title:
Photometric Typing Analyses of Three Young Supernovae with the Robotic
  Palomar 60-Inch Telescope

abstract:
  We present photometric typing analyses of three young supernovae observed
with the Robotic 60-inch Telescope at Palomar Observatory (P60). This
represents the first time that such photo-typing has been attempted, in a blind
fashion, on newly-discovered supernovae. For one of the target supernovae,
SN2004cs, our photometry provided the first constraint on the SN type, which we
predicted would be type Ia. To the contrary, however, our subsequent Keck
spectroscopy shows it to be an unusual type II supernova. For each of the other
two supernovae, SN2004dh (type II) and SN2004dk (type Ib), our photo-typing
results are consistent with the known type of the event as determined from
ground-based spectroscopy; however, the colors of SN2004dk are also consistent
with a type Ic or type II classification. We discuss our approach to the
challenges of photo-typing - contamination by host galaxy light and the unknown
photometric quality of the data - in the case where it is desirable to complete
the analysis with just one night of observations. The growing interest in the
properties and behavior of very young supernovae, and the increased discovery
rate for such events, mean that prompt photo-typing analyses can provide useful
input to observational campaigns. Our results demonstrate the value and
feasibility of such a project for P60, at the same time illustrating its chief
inherent shortcoming: an inability to identify new and unusual events as such
without later spectroscopic observations.


title: A Lack of Radio Emission from Neutron Star Low Mass X-ray Binaries

abstract:
  We report strict upper limits to the radio luminosities of three neutron star
low-mass X-ray binaries obtained with the Very Large Array while they were in
hard X-ray states as observed with the Rossi X-ray Timing Explorer: 1E
1724-307, 4U 1812-12, and SLX 1735-269. We compare these upper limits to the
radio luminosities of several black hole binaries in very similar hard states,
and find that the neutron star systems are as faint as or fainter than all of
the black hole candidates. The differences in luminosities can partly be
attributed to the lower masses of the neutron star systems, which on
theoretical and observational grounds are expected to decrease the radio
luminosities as M^0.8. However, there still remains a factor of 30 scatter in
the radio luminosities of black hole and neutron star X-ray binaries,
particularly at X-ray luminosities of a few percent Eddington. We find no
obvious differences in the X-ray timing and spectral properties that can be
correlated with the radio luminosity. We discuss the implications of these
results on current models for the relationship between accretion and jets.


title:
Internal rotation of subdwarf B stars: limiting cases and
  asteroseismological consequences

abstract:
  Observations of the rotation rates of horizontal branch (HB) stars show
puzzling systematics. In particular, cooler HB stars often show rapid rotation
(with velocities in excess of 10 km/s), while hotter HB stars typically show
much smaller rotation velocities. Simple models of angular momentum evolution
of stars from the main sequence through the red giant branch fail to explain
these effects. In general, evolutionary models in all cases preserve a rapidly
rotating core. The observed angular velocities of HB stars require that some of
the angular momentum stored in the core reaches the surface.
  To test the idea that HB stars contain such a core, one can appeal to
detailed computations of trace element abundences and rotational mixing.
However, a more direct probe is available to test these limiting cases of
angular momentum evolution. Some of the hottest horizontal branch stars are
members of the pulsating sdB class. They frequently show rich pulsation spectra
characteristic of nonradially pulsating stars. Thus their pulsations probe the
internal rotation of these stars, and should show the effects of rapid rotation
in their cores. Using models of sdB stars that include angular momentum
evolution, we explore this possibility and show that some of the sdB pulsators
may indeed have rapidly rotating cores.


title: Improved phenomenological equation of state in the chemical picture

abstract:
  I present an overview of an equation of state, being developed in the
chemical picture, and based on the very successful MHD equation of state. The
flexibility of the chemical picture combined with the free-energy minimization
procedure, makes it rather straight-forward, albeit laborious, to include new
effects in the model free-energy, simply by adding new terms.
  The most notable additions to the original MHD equation of state, are
relativistic effects, quantum effects, improved higher order Coulomb terms and
a long list of molecules other than the H2 and H2+ treated so far.


title: Processing of 24 Micron Image Data at the Spitzer Science Center

abstract:
  The 24 micron array on board the Spitzer Space Telescope is one of three
arrays in the Multi-band Imaging Photometer for Spitzer (MIPS) instrument. It
provides 5.3 x 5.3 arcmin images at a scale of ~2.5 arcsec per pixel
corresponding to sampling of the point spread function which is slightly better
than critical (~0.4\lambda/D). A scan-mirror allows dithering of images on the
array without the overhead of moving and stabilizing the spacecraft. It also
enables efficient mapping of large areas of sky without significant compromise
in sensitivity. We present an overview of the pipeline flow and reduction steps
involved in the processing of image data acquired with the 24 micron array.
Residual instrumental signatures not yet removed in automated processing and
strategies for hands-on mitigation thereof are also given.


title: Number Counts of GALEX Sources in FUV (1530A) and NUV (2310A) Bands

abstract:
  Number Counts of galaxies in two GALEX bands (FUV: 1530A and NUV: 2310A, both
in AB magnitudes) are reported. They provide for the first time in the
literature homogeneously calibrated number counts of UV galaxies covering
continuously a very wide range of UV magnitude (14 -- 23.8). Both the FUV and
NUV counts are inconsistent with a non-evolution model, while they are in good
agreement with evolution models (essentially luminosity evolution) derived from
the high-z UV luminosity functions of Arnouts et al. (2004). It is found that
the contribution from galaxies detected by GALEX to the UV background is
0.68+-0.10 nW m-2 sr-1 at 1530A and 0.99+-0.15 nW m-2 sr-1 at 2310A. These are
66+-9% and 44+-6% of the total contributions of galaxies to the the UV
background at 1530A, respectively, as estimated using the evolution models. ...


title:
The Look-back Time Evolution of Far-UV Flux from Elliptical Galaxies:
  The Fornax Cluster and Abell 2670

abstract:
  In order to investigate the origin of the far-UV (FUV) flux from the
early-type galaxies, Galaxy Evolution Explorer (GALEX) is collecting the UV
data for the elliptical-rich clusters at moderate redshifts (z < 0.2) where the
dominant FUV source is predicted to be hot horizontal-branch (HB) stars and
their post-HB progeny. Here we present our first result for the early-type
galaxies in Abell 2670 at z = 0.076. Compared to NGC 1399, a nearby giant
elliptical galaxy in the Fornax cluster, it appears that the rest-frame FUV - V
color of the giant ellipticals gets redder by ~ 0.7 mag at the distance of
Abell 2670 (z = 0.076; look-back time ~ 1.0 Gyr). Although a detailed
comparison with the models is postponed until more cluster data are
accumulated, it is interesting to note that this value is consistent with the
variation predicted by the population synthesis models where the mean
temperature of HB stars declines rapidly with increasing look-back time.


title: UV emission and Star Formation in Stephan's Quintet

abstract:
  we present the first GALEX UV images of the well known interacting group of
galaxies, Stephan's Quintet (SQ). We detect widespread UV emission throughout
the group. However, there is no consistent coincidence between UV structure and
emission in the optical, H\alpha, or HI. Excluding the foreground galaxy
NGC7320 (Sd), most of the UV emission is found in regions associated with the
two spiral members of the group, NGC7319 and NGC7318b, and the intragroup
medium starburst SQ-A. The extinction corrected UV data are analyzed to
investigate the overall star formation activity in SQ. It is found that the
total star formation rate (SFR) of SQ is 6.69+-0.65 M_\sun/yr. Among this,
1.34+-0.16 M_sun/yr is due to SQ-A. This is in excellent agreement with that
derived from extinction corrected H\alpha luminosity of SQ-A. The SFR in
regions related to NGC 7319 is 1.98+-0.58 M_\sun/yr, most of which(68%) is
contributed by the disk. The contribution from the 'young tail' is only 15%. In
the UV, the 'young tail' is more extended (~100 kpc) and shows a loop-like
structure, including the optical tail, the extragalactic HII regions recently
discovered in H\alpha, and other UV emission regions discovered for the first
time. The UV and optical colors of the 'old tail' are consistent with a single
stellar population of age t ~10^{8.5+-0.4} yrs. The UV emission associated with
NGC 7318b is found in a very large (~80 kpc) disk, with a net SFR of 3.37+-0.25
M_sun/yr. Several large UV emission regions are 30 -- 40 kpc away from the
nucleus of NGC7318b. Although both NGC7319 and NGC7318b show peculiar UV
morphology, their SFR is consistent with that of normal Sbc galaxies,
indicating that the strength of star formation activity is not enhenced by
interactions.


title: Scintillation in the Circinus Galaxy water megamasers

abstract:
  We present observations of the 22 GHz water vapor megamasers in the Circinus
galaxy made with the Tidbinbilla 70m telescope. These observations confirm the
rapid variability seen earlier by Greenhill et al (1997). We show that this
rapid variability can be explained by interstellar scintillation, based on what
is now known of the interstellar scintillation seen in a significant number of
flat spectrum AGN. The observed variability cannot be fully described by a
simple model of either weak or diffractive scintillation.


title: What are the Building Blocks of Our Universe?

abstract:
  We are told that we are living in a Golden Age of Astronomy. Cosmological
Parameters are found with un precedented accuracy. Yet, the known form of
matter forms only a small fraction of the total energy density of the universe.
Also, a mysterious dark energy dominates the universe and causes acceleration
in the rate of expansion.


title:
A Robust Algorithm for the Pointing Refinement and Registration of
  Astronomical Images

abstract:
  We present a generic algorithm for performing astronomical image registration
and pointing refinement. The method is based on matching the positions and
fluxes of available point sources in image overlap regions. This information is
used to compute a set of image offset corrections by globally minimizing a
weighted sum of all matched point-source positional differences in a
pre-specified reference image frame. A fast linear sparse matrix solver is used
for the minimization. From these corrections, the pointings and orientations of
images can be refined in either a relative sense where pointings become fixed
(registered) relative to a single input image, or, in an absolute sense (in the
ICRS) if absolute point source information is known. The latter provides
absolute pointing refinement to an accuracy depending on the robustness of
point source extractions, match statistics, and accuracy of the astrometric
catalog used. The software is currently used in the Spitzer image processing
pipelines, although it is adaptable to any astronomical imaging system which
uses the FITS image format and WCS pointing standard. We test the algorithm
using Monte Carlo simulations and compare them to image data acquired with the
Infrared Array Camera (IRAC) on board the Spitzer Space Telescope.


title: GALEX Ultraviolet Photometry of Globular Clusters in M31

abstract:
  We present ultraviolet photometry for globular clusters (GCs) in M31 from 15
square deg of imaging using the Galaxy Evolution Explorer (GALEX). We detect
200 and 94 GCs with certainty in the near-ultraviolet (NUV; 1750 - 2750
Angstroms) and far-ultraviolet (FUV; 1350 - 1750 Angstroms) bandpasses,
respectively. Our rate of detection is about 50% in the NUV and 23% in the FUV,
to an approximate limiting V magnitude of 19. Out of six clusters with
[Fe/H]>-1 seen in the NUV, none is detected in the FUV bandpass. Furthermore,
we find no candidate metal-rich clusters with significant FUV flux, because of
the contribution of blue horizontal-branch (HB) stars, such as NGC 6388 and NGC
6441, which are metal-rich Galactic GCs with hot HB stars. We show that our
GALEX photometry follows the general color trends established in previous UV
studies of GCs in M31 and the Galaxy. Comparing our data with Galactic GCs in
the UV and with population synthesis models, we suggest that the age range of
M31 and Galactic halo GCs are similar.


title: Cosmological weak lensing with the HST GEMS survey

abstract:
  We present our cosmic shear analysis of GEMS, one of the largest wide-field
surveys ever undertaken by the Hubble Space Telescope. Imaged with the Advanced
Camera for Surveys (ACS), GEMS spans 795 square arcmin in the Chandra Deep
Field South. We detect weak lensing by large-scale structure in high resolution
F606W GEMS data from ~60 resolved galaxies per square arcminute. We measure the
two-point shear correlation function, the top-hat shear variance and the shear
power spectrum, performing an E/B mode decomposition for each statistic. We
show that we are not limited by systematic errors and use our results to place
joint constraints on the matter density parameter Omega_m and the amplitude of
the matter power spectrum sigma_8. We find sigma_8(Omega_m/0.3)^{0.65}=0.68 +/-
0.13 where the 1sigma error includes both our uncertainty on the median
redshift of the survey and sampling variance.
  Removing image and point spread function (PSF) distortions are crucial to all
weak lensing analyses. We therefore include a thorough discussion on the degree
of ACS PSF distortion and anisotropy which we characterise directly from GEMS
data. Consecutively imaged over 20 days, GEMS data also allows us to
investigate PSF instability over time. We find that, even in the relatively
short GEMS observing period, the ACS PSF ellipticity varies at the level of a
few percent which we account for with a semi-time dependent PSF model. Our
correction for the temporal and spatial variability of the PSF is shown to be
successful through a series of diagnostic tests.


title:
The Calan-Yale Deep Extragalactic Research (CYDER) Survey: Optical
  Properties and Deep Spectroscopy of Serendipitous X-ray Sources

abstract:
  We present the first results from the Cal\'an-Yale Deep Extragalactic
Research (CYDER) survey. The main goal of this survey is to study serendipitous
X-ray sources detected by Chandra in an intermediate flux range
($10^{-15}-10^{-12}$ ergs s$^{-1}$) that comprises most of the X-ray
background. 267 X-ray sources spread over 5 archived fields were detected. The
$\log N-\log S$ distribution obtained for this sample is consistent with the
results of other surveys. Deep $V$ and $I$ images were taken of these fields in
order to calculate X-ray-to-optical flux ratios. Identifications and redshifts
were obtained for 106 sources using optical spectroscopy from 8-m class
telescopes to reach the optically faintest sources, to the same level as deeper
X-ray fields like the Chandra Deep Fields, showing that the nature of sources
detected depends mostly on the optical limit for spectroscopy. In general,
sources optically classified as obscured Active Galactic Nuclei (AGNs) have
redder optical colors than unobscured AGN. A rough correlation between
$f_X/f_{\rm opt}$ and hard X-ray luminosity was found for obscured AGN
confirming the prediction by existing models that in obscured AGN the optical
light is completely dominated by the host galaxy. The previously claimed
decrease of the obscured to unobscured AGN ratio with increasing X-ray
luminosity is observed. However, this correlation can be explained as a
selection effect caused by the lower optical flux of obscured AGN. Comparison
between the observed $N_H$ distribution and predictions by existing models
shows that the sample appears complete up to $N_H<3\times 10^{22}$ cm$^{-2}$,
while for more obscured sources incompleteness plays an important role in the
observed obscured to unobscured AGN ratio.


title:
A Spatial and Spectral Study of Nonthermal Filaments in Historical
  Supernova Remnants: Observational Results with Chandra

abstract:
  The outer shells of young supernova remnants (SNRs) are the most plausible
acceleration sites of high-energy electrons with the diffusive shock
acceleration (DSA) mechanism. We studied spatial and spectral properties close
to the shock fronts in four historical SNRs (Cas A, Kepler's remnant, Tycho's
remnant, and RCW 86) with excellent spatial resolution of {\it Chandra}. In all
of the SNRs, hard X-ray emissions were found on the rims of the SNRs, which
concentrate in very narrow regions (so-called "filaments"); apparent scale
widths on the upstream side are below or in the order of the point spread
function of {\it Chandra}, while 0.5--40 arcsec (0.01--0.4 pc) on the
downstream side with most reliable distances. The spectra of these filaments
can be fitted with both thermal and nonthermal (power-law and {\tt SRCUT})
models. The former requires unrealistic high temperature ($\ga$2 keV) and low
abundances ($\la$1 solar) for emission from young SNRs and may be thus
unlikely. The latter reproduces the spectra with best-fit photon indices of
2.1--3.8, or roll-off frequencies of (0.1--28)$\times 10^{17}$ Hz, which
reminds us of the synchrotron emission from electrons accelerated via DSA. We
consider various physical parameters as functions of the SNR age, including the
previous results on SN 1006 \citep{bamba2003b}; the filament width on the
downstream side increases with the SNR age, and the spectrum becomes softer
keeping a nonthermal feature. It was also found that a function, that is the
roll-off frequency divided by the square of the scale width on the downstream
side, shows negative correlation with the age, which might provide us some
information on the DSA theory.


title:
GALEX UV Color-Magnitude Relations and Evidence for Recent Star
  Formation in Early-type Galaxies

abstract:
  We have used the GALEX UV photometric data to construct a first
near-ultraviolet (NUV) color-magnitude relation (CMR) for the galaxies
pre-classified as early-type by SDSS studies. The NUV CMR is a powerful tool
for tracking the recent star formation history in early-type galaxies, owing to
its high sensitivity to the presence of young stellar populations. Our NUV CMR
for UV-weak galaxies shows a well-defined slope and thus will be useful for
interpreting the restframe NUV data of distant galaxies and studying their star
formation history. Compared to optical CMRs, the NUV CMR shows a substantially
larger scatter, which we interpret as evidence of recent star formation
activities. Roughly 15% of the recent epoch (z < 0.13) bright (M[r] < -22)
early-type galaxies show a sign of recent (< 1Gyr) star formation at the 1-2%
level (lower limit) in mass compared to the total stellar mass. This implies
that low level residual star formation was common during the last few billion
years even in bright early-type galaxies.


title:
An XMM-Newton Observation of the Seyfert 2 Galaxy NGC 6300. I. The
  Nucleus

abstract:
  We present results from a half-day observation by XMM-Newton of the nucleus
of the nearby Seyfert 2 galaxy NGC 6300. The X-ray spectrum of the nucleus
consists of a heavily absorbed hard component dominating the 3--10 keV band and
a soft component seen in the 0.2--2 keV band. In the hard band, the spectrum is
well fitted by a power-law model with photon index of 1.83+/-0.08 attenuated by
a Compton-thin absorber (N_H \simeq 2.2 x 10^{23} cm^{-2}). A narrow iron line
is detected at 6.43_{-0.02}^{+0.01} keV with an equivalent width of ~150 eV;
the line velocity width is marginally resolved to be \sigma~60eV. The soft
emission can be modeled as a power-law and may be emission scattered by
surrounding plasma. Rapid and high-amplitude variability is observed in the
hard X-ray band, whereas both the iron line and the soft emission show no
significant variability. It is suggested that the nucleus has experienced an
overall long-term trend of decreasing hard X-ray intensity on a timescale of
years. We discuss the origins of the spectral components.


title:
Giant Radio Sources in View of the Dynamical Evolution of FRII-type
  Population. I. The Observational Data, and Basic Physical Parameters of
  Sources Derived from the Analytical Model

abstract:
  The time evolution of giant lobe-dominated radio galaxies (with projected
linear size D>1 Mpc if H_{0}=50 km/s/Mpc and q_{0}=0.5 is analysed on the basis
of dynamical evolution of the entire FRII-type population. Two basic physical
parameters, namely the jet power Q_{0} and central density of the galaxy
nucleus rho0 are derived for a sample of giants with synchrotron ages reliably
determined, and compared with the relevant parameters in a comparison sample of
normal-size sources consisting of 3C, B2, and other sources. Having the
apparent radio luminosity P and linear size D of each sample source, Q_{0} and
rho_{0} are obtained by fitting the dynamical model of Kaiser et al. (1997). We
find that: (i) there is not a unique factor governing the source size; they are
old sources with temperate jet power (Q_{0}) evolved in a relatively
low-density environment (rho_{0}). The size is dependent, in order of
decreasing partial correlation coefficients, on age; then on Q_{0}; next on
rho_{0}. (ii) A self-similar expansion of the sources' cocoon seems to be
feasible if the power supplied by the jets is a few orders of magnitude above
the minimum-energy value. In other cases the expansion can only initially be
self-similar; a departure from self-similarity for large and old sources is
justified by observational data of giant sources. (iii) An apparent increase of
the lowest internal pressure value observed within the largest sources' cocoon
with redshift is obscured by the intrinsic dependence of their size on age and
the age on redshift, which hinders us from making definite conclusions about a
cosmological evolution of intergalactic medium (IGM) pressure.


title:
Giant Radio Sources in View of the Dynamical Evolution of FRII-type
  Population. II. The Evolutionary Tracks on the P-D and u_{c}-E_{tot} Planes

abstract:
  The time evolution of `fiducial' radio sources derived from fitting the
dynamical model of Kaiser et al. (1997) is compared with the observational data
for the `clan' sources found in the sample of giant and normal-size FRII-type
sources published Paper I (Machalski et al. 2004). Each `clan' comprises 3, 4
or 5 sample sources having similar values of the two basic physical parameters:
the jet power Q_{0} and central density of the galaxy nucleus rho_{0}
(determined in Paper I) but different ages, radio luminosities and axial
ratios. These sources are considered as the `same' source observed at different
epochs of its lifetime and used to fit the evolutionary luminosity-size (P-D)
and energy density-total energy (u_{c}-E_{tot}) tracks derived from the model
for a `fiducial' source with Q0 and rho_{0} equal to the means of relevant
values obtained for the `clan' members, as well as to constrain the
evolutionary model of the source dynamics used. In the result we find that (i)
The best fit is achieved when the Kaiser et al.'s model is modified by allowing
an evolution of the sources' cocoon axial ratio with time as suggested by
Blundell et al. (1999). (ii) A slow acceleration of the average expansion speed
of the cocoon along the jet axis is suggested by the `clan' sources. We argue
that this acceleration, although minor, may be real and some supporting
arguments come from the well known hydrodynamical considerations.


title: The role of HeH+ in cool helium rich white dwarfs

abstract:
  HeH$^+$ is found to be the dominant positive ion over a wide range of
temperatures and densities relevant to helium rich white dwarfs. The inclusion
of HeH$^+$ in ionization equilibrium computations increases the abundance of
free electrons by a significant factor. For temperatures below 8000 K, He$^-$
free-free absorption is increased by up to a factor of 5, by the inclusion of
HeH$^+$. Illustrative model atmospheres and spectral energy distributions are
computed, which show that HeH$^+$ has a strong effect upon the density and
pressure structure of helium rich white dwarfs with teff < 8000 K. The
inclusion of HeH$^+$ significantly reddens spectral energy distributions and
broad band color indices for models with Teff < 5500 K. This has serious
implications for existing model atmospheres, synthetic spectra and cooling
curves for helium rich white dwarfs.


title:
Subaru/HDS Abundances in Three Giant Stars in the Ursa Minor Dwarf
  Spheroidal Galaxy

abstract:
  With the HDS (High Dispersion Spectrograph) on the Subaru telescope, we
obtained high resolution optical region spectra of three red giant stars (cos
4, cos 82, and cos 347) in the Ursa Minor dwarf spheriodal galaxy. Chemical
abundances in these stars have been analysed for 26 elements including alpha-,
iron-peak, and neutron capture elements. All three stars show low abundances of
alpha-elements (Mg, Si, and Ca) and two stars (cos 82 and cos 347) show high
abundance of Mn compared to Galactic halo stars of similar metallicity. One
star (cos 4) has been confirmed to be very metal deficient ([Fe/H]=-2.7) and
found to show anomalously low abundances of Mn, Cu, and Ba. In another star cos
82 ([Fe/H]=-1.5), we have found large excess of heavy neutron-capture elements
with the general abundance pattern similar to the scaled solar system r-process
abundance curve. These observational results are rather puzzling: low
abundances of alpha-elements and high abundance of Mn seem to sugggest a
significant contribution of SNe Ia at low metallicity, while there is no hint
of s-process (i.e., AGB stars) contribution even at [Fe/H]=-1.5, suggesting a
peculiar nucleosynthetic history of the UMi dSph galaxy.


title: Science with Virtual Observatory Tools

abstract:
  The Virtual Observatory is now mature enough to produce cutting-edge science
results. The exploitation of astronomical data beyond classical identification
limits with interoperable tools for statistical identification of sources has
become a reality. I present the discovery of 68 optically faint, obscured
(i.e., type 2) active galactic nuclei (AGN) candidates in the two GOODS fields
using the Astrophysical Virtual Observatory (AVO) prototype. Thirty-one of
these sources have high estimated X-ray powers (>10^44 erg/s) and therefore
qualify as optically obscured quasars, the so-called QSO 2. The number of these
objects in the GOODS fields is now 40, an improvement of a factor > 4 when
compared to the only 9 such sources previously known. By going ~ 3 magnitudes
fainter than previously known type 2 AGN in the GOODS fields the AVO is
sampling a region of redshift -- power space much harder to reach with
classical methods. I also discuss the AVO move to our next phase, the EURO-VO,
and our short-term plans to continue doing science with the Virtual
Observatory.


title:
From Detailed Galaxy Simulations to a Realistic End-of-Mission Gaia
  Catalogue

abstract:
  We address the problem of identifying remnants of satellite galaxies in the
halo of our galaxy with Gaia data. We make use of N-body simulations of dwarf
galaxies being disrupted in the halo of our galaxy combined with a Monte Carlo
model of the Milky Way galaxy. The models are converted to a simulated Gaia
catalogue containing a realistic number ($\sim10^8$--$10^9$) of stars. The
simulated catalogue can be used to study how to handle the large data set that
Gaia will provide and to study issues such as how to best retrieve information
on substructure in the Galactic halo. The techniques described are applicable
to any set of N-body simulations of (parts of) the Galaxy.


title: Be/X-ray binaries: An observational approach

abstract:
  Be/X-ray binaries are the most numerous class of X-ray binaries. They
constitute an excellent tracer of star formation and can be used to study
several aspects of astrophysics, from mass loss in massive stars to binary
evolution. This short review, intended for the non-specialist, presents a
summary of their basic observational properties and outlines the physical
mechanisms giving rise to these characteristics.


title:
A comparative study of the spatial distribution of ultraviolet and
  far-infrared fluxes from M 101

abstract:
  The total ultraviolet (UV) flux (from 1412 to 2718 AA) of M 101 is compared
on a pixel-to-pixel basis with the total far-infrared (FIR) flux (from 60 to
170 micron), using the maps of the galaxy taken by GALEX in the near-UV and
far-UV and by ISOPHOT at 60, 100 and 170 micron. The main result of this
investigation is the discovery of a tight dependence of the FIR/UV ratio on
radius, with values monotonically decreasing from around 4 in the nuclear
region to nearly zero towards the edge of the optical disk.
  Although the tightness of this dependence is in part attributable to
resolution effects, the result is consistent with the presence of a large-scale
distribution of diffuse dust having a face-on optical depth which decreases
with radius and which dominates over the more localized variations in opacity
between the arm and interarm regions. We also find a trend for the FIR/UV ratio
to take on higher values in the regions of diffuse interarm emission than in
the spiral-arm regions, at a given radius. This is interpreted quantitatively
in terms of the escape probability of UV photons from spiral arms and their
subsequent scattering in the interarm regions, and in terms of the larger
relative contribution of optical photons to the heating of the dust in the
interarm regions.


title: FUSE spectroscopy of PG1159 Stars

abstract:
  PG1159 stars are hot hydrogen-deficient post-AGB stars with effective
temperatures within a range from 75000 K up to 200000 K. These stars are
probably the result of a late helium-shell flash that had occurred during their
first descent from the AGB. The lack of hydrogen is caused by flash-induced
envelope mixing and burning of H in deeper regions. Now the former intershell
matter is seen on the surface of the stars. Hence the stellar atmospheres show
metal abundances drastically different from the solar values. Our sample
comprises ten PG1159 stars with effective temperatures between 85000 K and
170000 K. We present first results of our spectral analysis based on FUV
spectra obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE).


title: Propagation of High Energy Galactic Cosmic Rays

abstract:
  We explore several aspects related to the propagation of high energy cosmic
rays (CRs) of galactic origin (i.e. in the range $E\simeq 10^{15}- 10^{18}$
eV). In particular, we study in detail the diffusion/drift scenario, a
rigidity-dependent model that explains the origin of the knee and the second
knee of the CR spectrum, as well as the most recent observations of composition
and anisotropies. Moreover, the behavior of the diffusion tensor for charged
particles propagating in highly turbulent magnetic fields is determined
numerically. We also investigate the high energy neutrino fluxes induced by
CRs, and we show that a rigidity-dependent scenario for the CR knee reduces the
background of atmospheric neutrinos, hence encouraging the search for
astrophysical neutrino sources. After exploring this effect in the detection
channel of lepton tracks, we investigate the less studied ``shower'' channel,
which turns out to be particularly effective for isolating the prompt
atmospheric neutrino component. Finally, we consider in detail the nuclear
photodisintegration model as an alternative explanation for the knee in the CR
spectrum, in which CR nuclei emitted by a source are disintegrated during their
propagation through a surrounding optical/UV photon field. In this case, the
composition is predicted to turn lighter across the knee, in constrast to the
results obtained in rigidity-dependent scenarios.


title: Extreme Gravitational Lensing near Rotating Black Holes

abstract:
  We describe a new approach to calculating photon trajectories and
gravitational lensing effects in the strong gravitational field of the Kerr
black hole. These techniques are applied to explore both the imaging and
spectral properties of photons that perform multiple orbits of the central mass
before escaping to infinity. Viewed at large inclinations, these higher order
photons contribute $\sim 20 %$ of the total luminosity of the system for a
Schwarzschild hole, whilst for an extreme Kerr black hole this fraction rises
to $\sim 60 %$. In more realistic models these photons will be re-absorbed by
the disc at large distances from the hole, but this returning radiation could
provide a physical mechanism to resolve the discrepancy between the predicted
and observed optical/UV colours in AGN. Conversely, at low inclinations, higher
order images re-intercept the disc plane close to the black hole, so need not
be absorbed by the disc if this is within the plunging region. These photons
form a bright ring carrying approximately 10% of the total disc luminosity for
a Schwarzchild black hole. The spatial separation between the inner edge of the
disc and the ring is similar to the size of the event horizon. This is
resolvable for supermassive black holes with proposed X-ray interferometery
missions such as MAXIM, so has the potential to provide an observational test
of strong field gravity.


title:
XMM-Newton observations of the Lockman Hole: III. A relativistic Fe line
  in the mean X-ray spectra of type-1 and type-2 AGN

abstract:
  Using the 770 ksec XMM-Newton survey of the Lockman Hole field in combination
with extensive optical identifications of the AGN population, we derive an
average rest-frame spectrum of AGN types-1 and 2. The most prominent feature in
the averaged spectrum is a strong fluorescent Fe line. In both type-1 and
type-2 AGN, a clear relativistic line profile is rev ealed. A laor line profile
with an inner disk radius smaller than the last stabl e orbit of a
Schwarzschild black hole is most consistent with the data, indicati ng that the
average supermassive black hole has significant spin. Equivalent wid ths of the
broad relativistic lines range between 400--600 eV. We used the disk reflection
model to compare the observed strength of the line with the amplitude of the
reflection component, concluding that to consistently describe the observations
the average iron abundance should be about three times the solar value.


title:
Beam Test of a Prototype Detector Array for the PoGO Astronomical Hard
  X-Ray/Soft Gamma-Ray Polarimeter

abstract:
  Polarization measurements in the X-ray and gamma-ray energy range can provide
crucial information on massive compact objects such as black holes and neutron
stars. The Polarized Gamma-ray Observer (PoGO) is a new balloon-borne
instrument designed to measure polarization from astrophysical objects in the
30-100 keV range, under development by an international collaboration with
members from United States, Japan, Sweden and France. To examine PoGO's
capability, a beam test of a simplified prototype detector array was conducted
at the Argonne National Laboratory Advanced Photon Source. The detector array
consisted of seven plastic scintillators, and was irradiated by polarized
photon beams at 60, 73, and 83 keV. The data showed a clear polarization
signal, with a measured modulation factor of $0.42 \pm 0.01$. This was
successfully reproduced at the 10% level by the computer simulation package
Geant4 after modifications to its implementation of polarized Compton/Rayleigh
scattering. Details of the beam test and the validation of the Geant4
simulations are presented.