title: HST Imaging of MEGA Microlensing Candidates in M31

abstract:
  We investigate $HST$/ACS and WFPC2 images at the positions of five candidate
microlensing events from a large survey of variability in M31 (MEGA). Three
closely match unresolved sources, and two produce only flux upper limits. All
are confined to regions of the color-magnitude diagram where stellar
variability is unlikely to be easily confused with microlensing. Red variable
stars cannot explain these events (although background supernova are possible
for two). If these lenses arise in M31's halo, they are due to masses $0.15 < m
/ M_\odot < 0.49$ (95% certainty, for a $\delta$-function mass distribution),
brown dwarfs for disk lenses, and stellar masses for bulge lenses.


title: Spectroscopic Observations and Analysis of the Unusual Type Ia SN 1999ac

abstract:
  We present optical spectra of the peculiar Type Ia supernova (SN Ia) 1999ac.
The data extend from -15 to +42 days with respect to B-band maximum and reveal
an event that is unusual in several respects. Prior to B-band maximum, the
spectra resemble those of SN 1999aa, a slowly declining event, but possess
stronger SiII and CaII signatures (more characteristic of a spectroscopically
normal SN). Spectra after B-band maximum appear more normal. The expansion
velocities inferred from the Iron lines appear to be lower than average;
whereas, the expansion velocity inferred from Calcium H and K are higher than
average. The expansion velocities inferred from SiII are among the slowest ever
observed, though SN 1999ac is not particularly dim. The analysis of the
parameters v_10, R(SiII), dv(SiII)/dt, and d_m15 further underlines the unique
characteristics of SN 1999ac. We find convincing evidence of CII 6580 in the
day -15 spectrum with ejection velocity v > 16,000 km/s, but this signature
disappears by day -9. This rapid evolution at early times highlights the
importance of extremely early-time spectroscopy.


title: Is the Universe odd?

abstract:
  We investigate the point-parity and mirror-parity handedness of the large
angle anisotropy in the cosmic microwave background (CMB). In particular we
consider whether the observed low CMB quadrupole could more generally signal
odd point-parity, i.e. suppression of even multipoles. Even though this feature
is ``visually'' present in most renditions of the WMAP dataset we find that it
never supports parity preference beyond the meagre 95% confidence level. This
is fortunate as point parity handedness implies almost certainly a high level
of galactic contamination. Mirror reflection parity, on the contrary, is
related to the emergence of a preferred axis, defining the symmetry plane. We
use this technique to make contact with recent claims for an anisotropic
Universe, showing that the detected preferred axis is associated with positive
(even) mirror parity. This feature may be an important clue in identifying the
culprit for this unexpected signal.


title: On the equation of state of Dark Energy

abstract:
  The formalism in order to obtain the Dark Energy equation of state is
extended to non-flat universes and we consider the inequalities that must be
satisfied by Phantom Dark Energy in this case. We show that due to a
non-vanishing spatial curvature satisfying the observational bounds, the
uncertainty on the determination of the Dark Energy equation of state parameter
$w$, when it is taken constant, can be significant and that it is minimal for
some redshift $z_{cr}\sim 3$. We consider the potential of future measurements
of the gravitational waves emitted by binaries at high redshifts $z>z_{cr}$ to
reduce this uncertainty. Results obtained here should also be relevant for a
weakly varying equation of state with $w\approx -1$.


title: Time-Dependent MHD Shocks and Line Emission: The Case of the DG Tau Jet

abstract:
  The line emission from a growing number of Herbig-Haro jets can be observed
and resolved at angular distances smaller than a few arcseconds from the
central source. The interpretation of this emission is problematic, since the
simplest model of a cooling jet cannot sustain it. It has been suggested that
what one actually observes are shocked regions with a filling factor of $\sim
1%$. In this framework, up to now, comparisons with observations have been
based on stationary shock models. Here we introduce for the first time the
self-consistent dynamics of such shocks and we show that considering their
properties at different times, i.e. locations, we can reproduce observational
data of the DG Tau microjet. In particular, we can interpret the spatial
behavior of the [SII]6716/6731 and [NII]/[OI]6583/6300 line intensity ratios
adopting a set of physical parameters that yield values of mass loss rates and
magnetic fields consistent with previous estimates. We also obtain the values
of the mean ionization fraction and electron density along the jet, compare
these values with the ones derived from observations using the sulfur doublet
to constrain the electron density (e.g. Bacciotti et al. 1995).


title: On the Submillimeter Opacity of Protoplanetary Disks

abstract:
  Solid particles with the composition of interstellar dust and power-law size
distribution dn/da propto a^{-p} for a < a_max with a_{max} > 3 lambda and 3 <
p < 4 will have submm opacity spectral index beta(lambda) = dln(kappa)/dln(nu)
approx (p-3) beta_{ism}, where beta_{ism} approx 1.7 is the opacity spectral
index of interstellar dust material in the Rayleigh limit. For the power-law
index p approx 3.5 that characterizes interstellar dust, and that appears
likely for particles growing by agglomeration in protoplanetary disks, grain
growth to sizes a > 3 mm will result in beta(1 mm) < ~1. Grain growth can
naturally account for beta approx 1 observed for protoplanetary disks, provided
that a_{max} > ~ 3 lambda.


title: Representations of spectral coordinates in FITS

abstract:
  Greisen & Calabretta describe a generalized method for specifying the
coordinates of FITS data samples. Following that general method, Calabretta &
Greisen describe detailed conventions for defining celestial coordinates as
they are projected onto a two-dimensional plane. The present paper extends the
discussion to the spectral coordinates of wavelength, frequency, and velocity.
World coordinate functions are defined for spectral axes sampled linearly in
wavelength, frequency, or velocity, linearly in the logarithm of wavelength or
frequency, as projected by ideal dispersing elements, and as specified by a
lookup table.


title: Multigroup Models of the Convective Epoch in Core Collapse Supernovae

abstract:
  Understanding the explosion mechanism of core collapse supernovae is a
problem that has plagued nuclear astrophysicists since the first computational
models of this phenomenon were carried out in the 1960s. Our current theories
of this violent phenomenon center around multi-dimensional effects involving
radiation-hydrodynamic flows of hot, dense matter and neutrinos. Modeling these
multi-dimensional radiative flows presents a computational challenge that will
continue to stress high-performance computing beyond the teraflop to the
petaflop level. In this paper we describe a few of the scientific discoveries
that we have made via terascale computational simulations of supernovae under
the auspices of the SciDAC-funded Terascale Supernova Initiative.


title: The FIRST-Optical-VLA Survey for Lensed Radio Lobes

abstract:
  We present results from a survey for gravitationally lensed radio lobes.
Lensed lobes are a potentially richer source of information about galaxy mass
distributions than lensed point sources, which have been the exclusive focus of
other recent surveys. Our approach is to identify radio lobes in the FIRST
catalog and then search optical catalogs for coincident foreground galaxies,
which are candidate lensing galaxies. We then obtain higher-resolution images
of these targets at both optical and radio wavelengths, and obtain optical
spectra for the most promising candidates. We present maps of several radio
lobes that are nearly coincident with galaxies. We have not found any new and
unambiguous cases of gravitational lensing. One radio lobe in particular, FOV
J0743+1553, has two hot spots that could be multiple images produced by a
z=0.19 spiral galaxy, but the lensing interpretation is problematic.


title:
Cooling flows within galactic haloes: the kinematics and properties of
  infalling multi-phase gas

abstract:
  We study the formation of disks via the cooling flow of gas within galactic
haloes using smoothed particle hydrodynamics simulations. These simulations
resolve mass scales of a few thousand solar masses in the gas component for the
first time. Thermal instabilities result in the formation of numerous warm
clouds that are pressure confined by the hot ambient halo gas. The clouds fall
slowly onto the disk through non-spherical accretion from material flowing
preferentially down the angular momentum axis. The rotational velocity of the
infalling cold gas decreases as a function of height above the disk, closely
resembling that of the extra-planar gas recently observed around the spiral
galaxy NGC 891.


title: White Dwarfs in NGC 6791: Avoiding the Helium Flash

abstract:
  We propose that the anomalously bright white dwarf luminosity function
observed in NGC 6791 (Bedin et al 2005) is the consequence of the formation of
0.5 Msun white dwarfs with Helium cores instead of Carbon cores. This may
happen if mass loss during the ascent of the Red Giant Branch is strong enough
to prevent a star from reaching the Helium flash. Such a model can explain the
slower white dwarf cooling (relative to standard models) and fits naturally
with scenarios advanced to explain Extreme Horizontal Branch stars, a
population of which are also found in this cluster.


title: Dusty Infrared Galaxies: Sources of the Cosmic Infrared Background

abstract:
  The discovery of the Cosmic Infrared Background (CIB) in 1996, together with
recent cosmological surveys from the mid-infrared to the millimeter have
revolutionized our view of star formation at high redshifts. It has become
clear, in the last decade, that a population of galaxies that radiate most of
their power in the far-infrared (the so-called ``infrared galaxies'')
contributes an important part of the whole galaxy build-up in the Universe.
Since 1996, detailed (and often painful) investigations of the high-redshift
infrared galaxies have resulted in the spectacular progress covered in this
review. We outline the nature of the sources of the CIB including their
star-formation rate, stellar and total mass, morphology, metallicity and
clustering properties. We discuss their contribution to the stellar content of
the Universe and their origin in the framework of the hierarchical growth of
structures. We finally discuss open questions for a scenario of their evolution
up to the present-day galaxies.


title:
Lucky Imaging: High Angular Resolution Imaging in the Visible from the
  Ground

abstract:
  We use a Lucky Imaging system to obtain I-band images with much improved
angular resolution on a ground-based 2.5m telescope. We present results from a
10-night assessment campaign on the 2.56m Nordic Optical Telescope and quantify
the performance of our system in seeings better than 1.0''. In good seeing we
have acquired near diffraction-limited images; in poorer seeing the angular
resolution has been routinely improved by factors of 2.5-4. The system can use
guide stars as faint as I=16 with full performance and its useful field of view
is consistently larger than 40" diameter. The technique shows promise for a
number of science programmes, both galactic (eg. binary candidates, brown
dwarfs, globular cluster cores) and extragalactic (eg. quasar host galaxies,
damped Lyman-alpha absorbers).


title: Dark Matter from Early Decays

abstract:
  Two leading dark matter candidates from supersymmetry and other theories of
physics beyond the standard model are WIMPs and weak scale gravitinos. If the
lightest stable particle is a gravitino, then a WIMP will decay into it with a
natural lifetime of order a month ~ M_{pl}^2/M_{weak}^3. We show that if the
bulk of dark matter today came from decays of neutral particles with lifetimes
of order a year or smaller, then it could lead to a reduction in the amount of
small scale substructure, less concentrated halos and constant density cores in
the smallest mass halos. Such beneficial effects may therefore be realized
naturally, as discussed by Cembranos, Feng, Rajaraman, and Takayama, in the
case of supersymmetry.


title: Observing Baryon Oscillations with Cosmic Shear

abstract:
  A cosmic shear survey, spanning a significant proportion of the sky, should
greatly improve constraints on a number of cosmological parameters. It also
provides a unique opportunity to examine the matter power spectrum directly.
However, the observed lensing signal corresponds to a weighted average of the
power spectrum across a range of scales, and so the potential to resolve the
baryon oscillations has been somewhat neglected. These features originated
prior to recombination, induced by the acoustics of the photon-baryon fluid.
Recent galaxy surveys have detected the imprints, and in the future such
measurements may even be used to refine our understanding of dark energy.
Without redshift information, cosmic shear is an ineffective probe of the
baryon oscillations. However, by implementing a novel multipole-dependent
selection of photometric redshift bins, sensitivity is improved by an order of
magnitude, bringing the "wiggles" within reach of future surveys. As an
illustration, we show that data from surveys scheduled within the next ten
years will be able to distinguish a smoothed power spectrum at the two sigma
level.


title: Spin-Induced Disk Precession in Sagittarius A*

abstract:
  In Sgr A* at the Galactic center, by far the closest and easiest supermassive
black hole we can study, the observational evidence is increasingly pointing to
the presence of a compact, hot, magnetized disk feeding the accretor. In such
low-Mach-number plasmas, forces arising, e.g., from pressure gradients in the
plasma, can altogether negate the warping of disks around Kerr black holes
caused by the Bardeen-Petterson effect and can lead to coherent precession of
the entire disk. In this Letter, we present for the first time highly detailed
3D SPH simulations of the accretion disk evolution in Sgr A*, guided by
observational constraints on its physical characteristics, and conclude that
indeed the Bardeen-Petterson effect is probably absent in this source. Given
what we now understand regarding the emission geometry in this object, we
suggest that a ~ 50-500-day modulation in Sgr A*'s spectrum, arising from the
disk precession, could be an important observational signature; perhaps the ~
106-day period seen earlier in its radio flux, if confirmed, could be due to
this process. On the other hand, if future observations do not confirm this
long modulation in Sgr A*'s spectrum, this would be an indication that either
the disk size or orientation is very different from current estimates, or that
the black hole is not spinning at all (unlikely), or that our current
understanding of how it produces its radiative output is incorrect.


title: The SFH of the LMC: The CMD approach vs. integrated colors and spectra

abstract:
  We present results of a study aiming at shedding light on the specific
advantages and limitations of methods to derive star formation histories (SFH)
in galaxies using resolved stellar populations and using integrated light,
respectively. For this purpose, we analyse the integrated-light spectrum of a
field in the LMC bar, for which highly resolved HST images are available as
well. To be compared with the SFH derived from the color magnitude diagram
(CMD) of this field (Smecker-Hane et al. 02), we have performed a set of
simulations of galaxies with systematically varying SFHs, but constant
metallicity (Z=0.008). We investigate to which extent different SF scenarios
can be discriminated on the basis of their photometric and spectral properties,
respectively, and determine in how far the detailed SFH obtained by the CMD
approach can be reproduced by results based upon integrated properties.
Comparing both methods for this nearby field we want to learn about the
specific character of both methods and understand to what precision SFHs can be
determined for distant galaxies only observable in integrated light. All
simulations are performed using our evolutionary synthesis code GALEV.


title: Cygnus X-3 and the problem of the missing Wolf-Rayet X-ray binaries

abstract:
  Cygnus X-3 is a strong X-ray source (L_X about 10^38 erg/s) which is thought
to consist of a compact object, accreting matter from a helium star. We find
analytically that the estimated ranges of mass-loss rate and orbital-period
derivative for Cyg X-3 are consistent with two models: i) the system is
detached and the mass loss from the system comes from the stellar wind of a
massive helium star, of which only a fraction that allows for the observed
X-ray luminosity is accreted, or ii) the system is semidetached and a
Roche-lobe-overflowing low- or moderate-mass helium donor transfers mass to the
compact object, followed by ejection of its excess over the Eddington rate from
the system. These analytical results appear to be consistent with evolutionary
calculations. By means of population synthesis we find that currently in the
Galaxy there may exist ~1 X-ray binary with a black hole that accretes from a
>~ 7 MSun Wolf-Rayet star and ~1 X-ray binary in which a neutron star accretes
matter from a Roche-lobe-overflowing helium star with mass <~ 1.5 MSun. Cyg X-3
is probably one of these systems.


title:
Deriving star formation histories from integrated light: Colors and
  indices

abstract:
  We present results of a detailed study aiming at understanding to what
precision star formation histories (SFHs) can be determined for distant
galaxies observable in integrated light only. Using our evolutionary synthesis
code, we have performed a set of simulations of galaxies with a wide range of
different SFHs. By analysing the resulting colors, spectra and Lick indices, we
investigate to which extent different SF scenarios can be discriminated on the
basis of their photometric and spectral properties, respectively. We find the
robust result that no later than 4 Gyrs after the latest episode of enhanced
star formation all scenarios exhibit very similar colors and indices; in
practice, it is not possible to distinguish different scenarios of star
formation which have evolved for more than 1, at the utmost 3-4 Gyrs since the
last star forming event, even when using spectral indices. For how long
different SF scenarios can be disentangled highly depends on the range of
colors available and absorption lines considered, as well as on the details of
the SFHs to be compared.


title: UV Continuum Spectroscopy of a 6L* z=5.5 Starburst Galaxy

abstract:
  We have obtained a high S/N (22.3 hr integration) UV continuum VLT FORS2
spectrum of an extremely bright (z_850 = 24.3) z = 5.515 +/- 0.003 starforming
galaxy (BD38) in the field of the z = 1.24 cluster RDCS 1252.9-2927. This
object shows substantial continuum (0.41 +/- 0.02 \muJy at \lambda1300) and
low-ionization interstellar absorption features typical of LBGs at lower
redshift (z ~ 3); this is the highest redshift LBG confirmed via metal
absorption spectral features. The equivalent widths of the absorption features
are similar to z ~ 3 strong Ly\alpha absorbers. No noticeable Ly\alpha emission
was detected (F <= 1.4 * 10^-18 ergs cm^-2 s^-1, 3\sigma). The half-light
radius of this object is 1.6 kpc (0\farcs25) and the star formation rate
derived from the rest-frame UV luminosity is SFR_UV = 38 h^-2_0.7 M_sun yr^-1
(142 h^-2_0.7 M_sun yr^-1 corrected for dust extinction). In terms of recent
determinations of the z ~ 6 UV luminosity function, this object appears to be
6L*. The Spitzer IRAC fluxes for this object are 23.3 and 23.2 AB mag
(corrected for 0.3 mag of cluster lensing) in the 3.6\mu and 4.5\mu channels,
respectively, implying a mass of 1-6 * 10^10 M_sun from population synthesis
models. This galaxy is brighter than any confirmed z ~ 6 i-dropout to date in
the z_850 band, and both the 3.6\mu and 4.5\mu channels, and is the most
massive starbursting galaxy known at z > 5. -- Abstract Abridged


title: Baryon oscillations

abstract:
  The coupling of photons and baryons by Thomson scattering in the early
universe imprints features in both the Cosmic Microwave Background (CMB) and
matter power spectra. The former have been used to constrain a host of
cosmological parameters, the latter have the potential to strongly constrain
the expansion history of the universe and dark energy. Key to this program is
the means to localize the primordial features in observations of galaxy spectra
which necessarily involve galaxy bias, non-linear evolution and redshift space
distortions. We present calculations, based on mock catalogues produced from
particle-mesh simulations, which show the range of behaviors we might expect of
galaxies in the real universe. We find that non-linearity, galaxy bias and
redshift space distortions all introduce important modifications to the basic
picture. Both the galaxy bias and the (isotropic) redshift space distortions
lead to relatively smooth modulations in power on the scales of interest to
baryon oscillations. The halo and galaxy power spectra exhibit low order
structure beyond the acoustic oscillations over the range of scales of
relevance. Fitting a cubic polynomial to the ratio of galaxy to dark matter
power reduces any remaining structure in the range 0.03<k<0.3 h/Mpc below the 2
per cent level, which is close to the error in our calculations.


title: The Ups and Downs of Baryon Oscillations

abstract:
  Baryon acoustic oscillations, measured through the patterned distribution of
galaxies or other baryon tracing objects on very large (100 Mpc) scales, offer
a possible geometric probe of cosmological distances. Pluses and minuses in
this approach's leverage for understanding dark energy are discussed, as are
systematic uncertainties requiring further investigation. Conclusions are that
1) BAO offer promise of a new avenue to distance measurements and further study
is warranted, 2) the measurements will need to attain ~1% accuracy (requiring a
10000 square degree spectroscopic survey) for their dark energy leverage to
match that from supernovae, but do give complementary information at 2%
accuracy. Because of the ties to the matter dominated era, BAO is not a
replacement probe of dark energy, but a valuable complement.


title: Iron-Line Emission as a Probe of Bardeen-Petterson Accretion Disks

abstract:
  In this work we show that Bardeen-Petterson accretion disks can exhibit
unique, detectable features in relativistically broadened emission line
profiles. Some of the unique characteristics include inverted line profiles
with sharper red horns and softer blue horns and even profiles with more than 2
horns from a single rest-frame line. We demonstrate these points by
constructing a series of synthetic line profiles using simple two-component
disk models. We find that the resultant profiles are very sensitive to the two
key parameters one would like to constrain, namely the Bardeen-Petterson
transition radius r_{BP} and the relative tilt \beta between the two disk
components over a range of likely values [10 < r_{BP}/(GM/c^2) < 40 ; 15deg <
\beta < 45deg]. We use our findings to show that some of the ``extra'' line
features observed in the spectrum of the Seyfert-I galaxy MCG--6-30-15 may be
attributable to a Bardeen-Petterson disk structure. Similarly, we apply our
findings to two likely Bardeen-Petterson candidate Galactic black holes - GRO
J1655-40 and XTE J1550-564. We provide synthetic line profiles of these systems
using observationally constrained sets of parameters. Although we do not
formally fit the data for any of these systems, we confirm that our synthetic
spectra are consistent with current observations.


title:
Spectroscopic study of blue compact galaxies V. oxygen abundance and the
  metallicity-luminosity relation

abstract:
  This is the fifth paper in a series studying the stellar components, star
formation histories, star formation rates and metallicities of a blue compact
galaxy (BCG) sample. Based on our high-quality ground-based spectroscopic
observations, we have determined the electron temperatures, electron densities,
nitrogen abundances and oxygen abundances for 72 star-forming BCGs in our
sample, using different oxygen abundance indicators. The oxygen abundance
covers the range 7.15 < 12 + log (O/H)< 9.0, and nitrogen is found to be mostly
a product of secondary nucleosynthesis for 12 + log (O/H)>8.2 and apparently a
product of primary nucleosynthesis for 12 + log (O/H)< 8.2. To assess the
possible systematic differences among different oxygen abundance indicators, we
have compared oxygen abundances of BCGs obtained with the Te method, R23
method, P method, N2 method and O3N2 method. The oxygen abundances derived from
the Te method are systematically lower by 0.1-0.25 dex than those derived from
the strong line empirical abundance indicators, consistent with previous
studies based on region samples. We confirm the existence of the
metallicity-luminosity relation in BCGs over a large range of abundances and
luminosities. Our sample of galaxies shows that the slope of the
metallicity-luminosity relation for the luminous galaxies (~-0.05) is slightly
shallower than that for the dwarf galaxies (~-0.17). An offset was found in the
metallicity-luminosity relation of the local galaxies and that of the
intermediate redshift galaxies. It shows that the metallicity-luminosity
relation for the emission line galaxies at high redshift is displaced to lower
abundances, higher luminosities, or both.


title:
Electron Positron Capture Rates and the Steady State Equilibrium
  Condition for Electron-Positron Plasma with Nucleons

abstract:
  The reaction rates of the beta processes for all particles at arbitrary
degeneracy are derived, and an {\it analytic} steady state equilibrium
condition $\mu_n=\mu_p+2\mu_e$ which results from the equality of electron and
positron capture rates in the hot electron-positron plasma with nucleons is
also found, if the matter is transparent to neutrinos. This simple analytic
formula is valid only if electrons are nondegenerate or mildly degenerate,
which is generally satisfied in the hot electron-positron plasma. Therefore, it
can be used to efficiently determine the steady state of the hot matter with
plenty of positrons. Based on this analytic condition, given the baryon number
density and the temperature, if the nucleons are nondegenerate, only one
algebraic equation for determining the electron fraction is obtained, which
shows the great advantage of the analytic equilibrium condition.


title: Observational constraints on hyperons in neutron stars

abstract:
  The possibility that neutron stars may contain substantial hyperon
populations has important implications for neutron-star cooling and, through
bulk viscosity, the viability of the r-modes of accreting neutron stars as
sources of persistent gravitational waves. In conjunction with laboratory
measurements of hypernuclei, astronomical observations were used by Glendenning
and Moszkowski [Phys. Rev. Lett. 67, 2414 (1991)] to constrain the properties
of hyperonic equations of state within the framework of relativistic mean-field
theory. We revisit the problem, incorporating recent measurements of high
neutron-star masses and a gravitational redshift. We find that only the
stiffest of the relativistic hyperonic equations of state commonly used in the
literature is compatible with the redshift. However, it is possible to
construct stiffer equations of state within the same framework which produce
the observed redshift while satisfying the experimental constraints on
hypernuclei, and we do this. The stiffness parameter that most affects the
redshift is not the incompressibility but rather the hyperon coupling.
Nonrelativistic potential-based equations of state with hyperons are not
constrained by the redshift, primarily due to a smaller stellar radius.


title: Taylor-Couette flow: MRI, SHI and SRI

abstract:
  The linear stability theory of Taylor-Couette flows (unbounded in_z_) is
described including magnetic fields, Hall effect or a density stratification in
order to prepare laboratory experiments to probe the stability of differential
rotation in astrophysics. If an axial field is present then the
magnetorotational instability (MRI) is investigated also for small magnetic
Prandtl numbers. For rotating outer cylinder beyond the Rayleigh line
characteristic minima are found for magnetic Reynolds number of the order of 10
and for Lundquist numbers of order 1. The inclusion of extra toroidal
current-free fields leads to new oscillating solutions with rather low Reynolds
numbers and Hartmann numbers. The Hall effect establishes an unexpected
`shear-Hall instability' (SHI) where shear and magnetic field have opposite
signs. In this case even rotation laws increasing outwards may become unstable.
Recently global solutions have been found for the Taylor-Couette flows with
density stratified in axial directions (`stratorotational instability', SRI).
They exist beyond the Rayleigh line for Froude numbers of moderate order but
also not for too flat rotation laws with \hat\eta^2 < \hat\mu <\hat \eta.


title: Homeoidally striated density profiles. II. Anisotropy and rotation

abstract:
  With regard to homeoidally striated Jacobi ellipsoids, a unified theory of
systematically rotating and peculiar motions is developed, where both real and
imaginary rotation are considered. The effect of positive or negative residual
motion excess, is shown to be equivalent to an additional real or imaginary
rotation, respectively. Then it is realized that a homeoidally striated Jacobi
ellipsoid with assigned velocity distribution, always admits an adjoint
configuration i.e. a classical Jacobi ellipsoid of equal mass and axes. In
addition, further constraints are established on the amount of residual
velocity anisotropy along the principal axes, for triaxial configurations.
Special effort is devoted to investigating sequences of virial equilibrium
configurations in terms of normalized parameters, including the effects of both
density and velocity profile. In particular, it is shown that bifurcation
points from axisymmetric to triaxial configurations occur as in classical
Jacobi ellipsoids, contrary to earlier results. The reasons of the above
mentioned discrepancy are also explained. An interpretation of recent results
from numerical simulations on stability (Meza 2002), is provided in the light
of the model. A physical interpretation of the early Hubble sequence is shortly
reviewed and discussed from the standpoint of the model, according if
elliptical galaxies are considered as isolated systems or embedded within dark
matter haloes. In any case, a lower limit to the flattening of oblate-like
configurations is established. On the other hand, it is found no lower limit to
the elongation of prolate-like configurations, and observed lack of elliptical
galaxies more elongated than E7 needs a different physical interpretation, such
as the fully investigated bending instabilities.


title:
The discovery of a galaxy-wide superwind from a young massive galaxy at
  redshift z~3

abstract:
  High-velocity galactic outflows, driven by intense bursts of star formation
and black hole accretion, are invoked by current theories of galaxy formation
to terminate star formation in the most massive galaxies and to deposit heavy
elements in the intergalactic medium. From existing observational evidence on
high-redshift galaxies, it is unclear whether such outflows are localized to
regions of intense star formation just a few kiloparsecs in extent, or whether
they instead have a significant impact on the entire galaxy and its
surroundings. Here we present two-dimensional spectroscopy of a star-forming
galaxy at redshift z=3.09 (seen 11.5 Gyr ago, when the Universe was 20 per cent
of its current age): its spatially extended Ly-alpha emission appears to be
absorbed by HI in a foreground screen covering the entire galaxy, with a
lateral extent of at least 100 kpc and remarkable velocity coherence. It was
plausibly ejected from the galaxy during a starburst several 1E8 yr earlier and
has subsequently swept up gas from the surrounding intergalactic medium and
cooled. This demonstrates the galaxy-wide impact of high-redshift superwinds.


title:
Kiloparsec-Scale Jets in FR I Radio Galaxies and the Gamma-Ray
  Background

abstract:
  We discuss the contribution of kiloparsec-scale jets in FR I radio galaxies
to the diffuse gamma-ray background radiation. The analyzed gamma-ray emission
comes from inverse-Compton scattering of starlight photon fields by the
ultrarelativistic electrons whose synchrotron radiation is detected from such
sources at radio, optical and X-ray energies. We find that these objects, under
the minimum-power hypothesis (corresponding to a magnetic field of 300 muG in
the brightest knots of these jets), can contribute about one percent to the
extragalactic gamma-ray background measured by EGRET. We point out that this
result already indicates that the magnetic fields in kpc-scale jets of
low-power radio galaxies are not likely to be smaller than 10 muG on average,
as otherwise the extragalactic gamma-ray background would be overproduced.


title: Radiative Habitable Zones in Martian Polar Environments

abstract:
  The biologically damaging solar ultraviolet (UV) radiation (quantified by the
DNA-weighted dose) reaches the Martian surface in extremely high levels.
Searching for potentially habitable UV-protected environments on Mars, we
considered the polar ice caps that consist of a seasonally varying CO2 ice
cover and a permanent H2O ice layer. It was found that, though the CO2 ice is
insufficient by itself to screen the UV radiation, at 1 m depth within the
perennial H2O ice the DNA-weighted dose is reduced to terrestrial levels. This
depth depends strongly on the optical properties ofthe H2O ice layers (for
instance snow-lile layes). The Earth-like DNA-weighted dose and
Photosynthetically Active Radiation (PAR) requirements were used to define the
upper and lower limits of the nortern and southern polar radiative habitable
zone (RHZ) for which a temporal and spatial mapping was performed. Based on
these studies we conclude that phtosynthetic life might be possible within the
ice layers of the polar regions. The thickness varies along each Martian polar
spring and summer between 1.5 m and 2.4 m for H2= ice-like layers, and a few
centimeters for snow-like covers. These Martian Earth-like radiative habitable
environments may be primary targets for future Martian astrobiological
missions. Special attention should be paid to planetary protection, since the
polar RHZ may also be subject to terrestrial contamination by probes.


title:
SnIa Constraints on the event-horizon Thermodynamical model of Dark
  Energy

abstract:
  We apply the thermodynamical model of the cosmological event horizon of the
spatially flat FLRW metrics to the study of the recent accelerated expansion
phase and to the coincidence problem. This model, called "ehT model" hereafter,
led to a dark energy (DE) density $\Lambda $ varying as $r^{-2},$ where $r$ is
the proper radius of the event horizon. Recently, another model motivated by
the holographic principle gave an independent justification of the same
relation between $\Lambda $ and $r$. We probe the theoretical results of the
ehT model with respect to the SnIa observations and we compare it to the model
deduced from the holographic principle, which we call "LHG model" in the
following.Our results are in excellent agreement with the observations for
$H\_{0}=64kms^{-1}Mpc^{-1}$, and $\Omega \_{\Lambda
}^{0}=0.63\_{-0.01}^{+0.1}$, which leads to $q\_{0}=-0.445$ and $z\_{T}\simeq
0.965$.


title:
Neptune's Migration into a Stirred-Up Kuiper Belt: A Detailed Comparison
  of Simulations to Observations

abstract:
  Nbody simulations are used to examine the consequences of Neptune's outward
migration into the Kuiper Belt, with the simulated endstates being compared
rigorously and quantitatively to the observations. These simulations confirm
the findings of Chiang et al. (2003), who showed that Neptune's migration into
a previously stirred-up Kuiper Belt can account for the Kuiper Belt Objects
(KBOs) known to librate at Neptune's 5:2 resonance. We also find that capture
is possible at many other weak, high-order mean motion resonances, such as the
11:6, 13:7, 13:6, 9:4, 7:3, 12:5, 8:3, 3:1, 7:2, and the 4:1. The more distant
of these resonances, such as the 9:4, 7:3, 5:2, and the 3:1, can also capture
particles in stable, eccentric orbits beyond 50 AU, in the region of phase
space conventionally known as the Scattered Disk. Indeed, 90% of the simulated
particles that persist over the age of the Solar System in the so-called
Scattered Disk zone never had a close encounter with Neptune, but instead were
promoted into these eccentric orbits by Neptune's resonances during the
migration epoch. This indicates that the observed Scattered Disk might not be
so scattered. This model also produced only a handful of Centaurs, all of which
originated at Neptune's mean motion resonances in the Kuiper Belt. We also
report estimates of the abundances and masses of the Belt's various
subpopulations (e.g., the resonant KBOs, the Main Belt, and the so-called
Scattered Disk), and also provide upper limits on the abundance of Centaurs and
Neptune's Trojans, as well as upper limits on the sizes and abundances of
hypothetical KBOs that might inhabit the a>50 AU zone.


title: The ISO-2MASS AGN survey: On the type-1 sources

abstract:
  We combined the ISOCAM Parallel Mode Survey at 6.7 micron (LW2 filter) with
the Two Micron All Sky Survey in order to obtain a powerful tool to search for
AGN independent of dust extinction. Using moderate colour criteria H-K>0.5 and
K-LW2>2.7 we have selected a sample of 77 AGN candidates in an effective area
of about 10 square degrees. By means of optical spectroscopy we find 24 (30%)
type-1 QSOs at redshifts 0.1<z<2.3; nine of them have z>0.8. About one third of
the ISO-2MASS QSOs show so red optical colours, that they are missed in optical
and UV AGN surveys like SDSS, 2DF, or HES. With a surface density of about 2
deg^(-2) down to R<18 mag the ISO-2MASS QSOs outnumber the 1.35 deg^(-2) of the
SDSS quasar survey by 50%; we find a combined optical-IR QSO surface density of
2.7 deg^(-2). Since only two of the ISO-2MASS QSOs have also J-K>2, the
inclusion of the ISO mid-infrared photometry significantly extends the
capabilities of the pure 2MASS red AGN survey. We suggest that the newly found
red AGN resemble young members of the quasar population, and that quasars spend
much of their lifetime in a dust enshrouded phase.


title: XMM-Newton spectral properties of the Ultraluminous IRAS Galaxy Mrk 273

abstract:
  We present a 23 ks XMM-Newton observation of the ULIRG Mrk 273. The hard
X-ray spectrum can be modeled by a highly absorbed power law plus an Fe Kalpha
emission line. The iron line is broad, suggesting possible superposition of a
neutral iron line at 6.4 keV, and a blend of ionized iron lines from Fe XXV and
Fe XXVI. Given the relatively short exposure, the three line components can not
be singularly resolved with high statistical significance: the neutral
component is detected at ~2.5sigma and the Fe XXV line at ~2sigma c.l., while
for the Fe XXVI line we can only estimate an upper limit. The broad band
spectrum requires, in addition to a highly absorbed power law, at least three
collisionally ionized plasma components, which may be associated with
star-forming regions. The temperatures of the three plasmas are about 0.3, 0.8
and 6 keV, where the highest of the three is sufficient to produce ionized iron
emission lines. An alternative interpretation for the origin of the soft
emission might also be given in terms of reflection off some photoionized gas,
as has been observed in a number of nearby Compton-thick Seyfert 2 galaxies. A
hot gas, photoionized by the primary, continuum can also produce ionized iron
lines. Unfortunately, given the limited statistics and the lack of high
resolution spectroscopy, it is not possible to distinguish between the two
models investigated. We further compare the XMM-Newton findings with the
Chandra data obtaining consistent spectral results. The absorption corrected
hard X-ray (2-10 keV) luminosity of Mrk 273 corresponds to ~0.2% of the far-IR
luminosity, similar to typical values found in pure starbursts. The thermal
contribution to the soft X-ray luminosity is ~0.2-0.7x10^42 erg s^-1,
comparable to those found in NGC 6240 and other starburst dominated ULIRGs.


title: Which cosmological model with dark energy -- phantom or LambdaCDM

abstract:
  In cosmology many dramatically different scenarios with the past (big bang
versus bounce) and in the future (de Sitter versus big rip) singularities are
compatible with the present day observations. This difficulty is called the
degeneracy problem. We use the Akaike and Bayesian information criteria of
model selection to overcome this degeneracy and to determine a model with such
a set of parameters which gives the most preferred fit to the SNIa data. We
consider seven representative scenarios, namely: the CDM models with the
cosmological constant, with topological defect, with phantom field, with
bounce, with bouncing phantom field, with brane and model with the linear
dynamical equation of state parameter. Applying the model selection information
criteria we show that AIC indicates the flat phantom model while BIC indicates
both flat phantom and flat $\Lambda$CDM models. Finally we conclude that the
number of essential parameters chosen by dark energy models which are compared
with SNIa data is two.


title: A search for changing-look AGN in the Grossan catalog

abstract:
  We observed with XMM-Newton 4 objects selected from the Grossan catalog, with
the aim to search for new 'changing-look' AGN. The sample includes all the
sources which showed in subsequent observations a flux much lower than the one
measured with HEAO A-1: NGC 7674, NGC 4968, IRAS 13218+0552 and NGC 1667. None
of the sources was caught in a high flux state during the XMM-Newton
observations, whose analysis reveal they are all likely Compton-thick objects.
We suggest that, for all the sources, potential problems with the HEAO A-1
source identification and flux measurement prevent us from being certain that
the HEAO A-1 data represent a putative 'high' state for these objects.
Nonetheless, based on the high flux state and Compton-thin spectrum of its
GINGA observation, NGC 7674 represents probably the sixth known case of a
'changing-look' Seyfert 2 galaxy. From the X-ray variability pattern, we can
estimate a likely lower limit of a few parsec to the distance of the inner
walls of the torus in this object. Remarkably, IRAS 13218+0552 was not detected
by XMM-Newton, despite being currently classified as a Seyfert 1 with a large
[OIII] flux. However, the original classification was likely to be affected by
an extreme velocity outflow component in the emission lines. The object likely
harbors an highly obscured AGN and should be re-classified as a Type 2 source.


title: A closer look at the spectrum and small scale anisotropies of UHECRs

abstract:
  We present results of numerical simulations of the propagation of ultra high
energy cosmic rays (UHECRs) over cosmological distances, aimed at quantifying
the statistical significance of the highest energy data on the spectrum and
small scale anisotropies as detected by the AGASA experiment. We assess the
significance of the lack of a GZK feature and its compatibility with the
reported small scale anisotropies.
  Assuming that UHECRs are protons from extragalactic sources, we find that the
small scale anisotropies are incompatible with the reported spectrum at a
probability level of $2 \times 10^{-5}$. Our analysis of the AGASA results
shows the power of combining spectrum and small scale anisotropy data in future
high statistics experiments, such as Auger.


title: Anti-GZK effect in UHECR spectrum

abstract:
  In this paper we discuss the anti-GZK effect that arises in the framework of
the diffusive propagation of Ultra High Energy (UHE) protons. This effect
consists in a jump-like increase of the maximum distance from which UHE protons
can reach the observer. The position of the jump is independent of the
Intergalactic Magnetic Field (IMF) strength and depends only on the energy
losses of protons, namely on the transition energy from adiabatic and
pair-production energy losses. The Ultra High Energy Cosmic Rays (UHECR)
spectrum presents a low-energy steepening approximately at this energy, which
is very close to the position of the observed second knee. The dip, seen in the
universal spectrum as a signature of the proton interaction with the Cosmic
Microwave Background (CMB) radiation, is also present in the case of diffusive
propagation in magnetic fields.


title: Blue Luminescence and the Presence of Small PAHs in the ISM

abstract:
  Blue Luminescence (BL) was first discovered in a proto-planetary nebula, the
Red Rectangle (RR) surrounding the post-AGB star HD 44179. BL has been
attributed to fluorescence by small, 3-4 ringed neutral polycyclic aromatic
hydrocarbon (PAH) molecules, and was thought to be unique to the RR environment
where such small molecules are actively being produced and shielded from the
harsh interstellar radiation by a dense circumstellar disk. In this paper we
present the BL spectrum detected in several ordinary reflection nebulae
illuminated by stars having temperatures between 10,000 -- 23,000 K. All these
nebulae are known to also exhibit the infrared emission features called
aromatic emission features (AEFs) attributed to large PAHs. We present the
spatial distribution of the BL in these nebulae. In the case of Ced~112, the BL
is spatially correlated with mid-IR emission structures attributed to AEFs.
These observations provide evidence for grain processing and possibly for
in-situ formation of small grains and large molecules from larger aggregates.
Most importantly, the detection of BL in these ordinary reflection nebulae
suggests that the BL carrier is an ubiquitous component of the ISM and is not
restricted to the particular environment of the RR.


title:
Measurement of the Energy Release Rate and the Reconnection Rate in
  Solar Flares

abstract:
  By using the method presented by Isobe et al. (2002), the non-dimensional
reconnection rate Vin/Va has been determined for the impulsive phase of three
two-ribbon flares, where Vin is the velocity of the reconnection inflow and Va
is the Alfven velocity. The non-dimensional reconnection rate is important to
make a constraint on the theoretical models of magnetic reconnection. In order
to reduce the uncertainty of the reconnection rate, it is important to
determine the energy release rate of the flares from observational data as
accurately as possible. To this end, we have carried out one dimensional
hydrodynamic simulations of a flare loop and synthesized the count rate
detected by the soft X-ray telescope (SXT) aboard Yohkoh satellite. We found
that the time derivative of the thermal energy contents in a flare arcade
derived from SXT data is smaller than the real energy release rate by a factor
of 0.3 - 0.8, depending on the loop length and the energy release rate. The
result of simulation is presented in the paper and used to calculate the
reconnection rate. We found that reconnection rate is 0.047 for the X2.3 flare
on 2000 November 24, 0.015 for the M3.7 flare on 2000 July 14, and 0.071 for
the C8.9 flare on 2000 November 16. These values are similar to that derived
from the direct observation of the reconnection inflow by Yokoyama et al.
(2001), and consistent with the fast reconnection models such as that of
Petschek (1964).


title: Multi-Thread Hydrodynamic Modeling of a Solar Flare

abstract:
  Past hydrodynamic simulations have been able to reproduce the high
temperatures and densities characteristic of solar flares. These simulations,
however, have not been able to account for the slow decay of the observed flare
emission or the absence of blueshifts in high spectral resolution line
profiles. Recent work has suggested that modeling a flare as an sequence of
independently heated threads instead of as a single loop may resolve the
discrepancies between the simulations and observations. In this paper we
present a method for computing multi-thread, time-dependent hydrodynamic
simulations of solar flares and apply it to observations of the Masuda flare of
1992 January 13. We show that it is possible to reproduce the temporal
evolution of high temperature thermal flare plasma observed with the
instruments on the \textit{GOES} and \textit{Yohkoh} satellites. The results
from these simulations suggest that the heating time-scale for a individual
thread is on the order of 200 s. Significantly shorter heating time scales (20
s) lead to very high temperatures and are inconsistent with the emission
observed by \textit{Yohkoh}.


title: The Draco dwarf galaxy in the near-infrared

abstract:
  With the William Herschel Telescope in La Palma we made IJKs observations of
an area of about 40'x30' of the Local Group galaxy Draco. This allows us to
describe Draco's late-type stellar population across the whole galaxy at a
photometric level 2 mag deeper than the 2MASS survey. We detected the red giant
branch (RGB) and measured the magnitude of the tip of the RGB in the three
bands. From that in the I band we obtain a distance modulus of
(m-M)_0=19.49+/-0.06(stat)+/-0.15(sys), in excellent agreement with a
measurement from RR Lyrae stars. The peak of the (J-Ks)_0 histogram at
different M_Ks suggests that Draco has a mean [Fe/H]=-1.95+/-1.26 while
fiducial RGB tracks of Galactic globular clusters indicate a mean
[Fe/H]=-1.33+/-0.72 where the error corresponds to the spread around the mean
value. There are significant differences between the colour-magnitude diagrams
of stars in the inner, medium and outer areas of the galaxy. A metal poor
(Z=0.0004) intermediate-age population (about 1.6 Gyr old) is clearly present
and emerges in particular between 6' and 12' from the centre of the galaxy. A
few additional carbon star candidates have been identified from both their
location in the colour-magnitude diagram and from an indication of variability.
The large scale distribution of late-type stars is smooth but irregular in
shape; this points at a variation of inclination with radius.


title: Model Simulations of a Shock-Cloud Interaction in the Cygnus Loop

abstract:
  We present optical observations and 2D hydrodynamic modeling of an isolated
shocked ISM cloud. H$\alpha$ images taken in 1992.6 and 2003.7 of a small
optical emission cloud along the southwestern limb of the Cygnus Loop were used
to measure positional displacements of $\sim$ $0 \farcs 1$ yr$^{-1}$ for
surrounding Balmer dominated emission filaments and $0\farcs025 - \farcs055$
yr$^{-1}$ for internal cloud emission features. These measurements imply
transverse velocities of $\simeq$ 250 km s$^{-1}$ and $\simeq$ 80 -- 140 km
s$^{-1}$ for ambient ISM and internal cloud shocks respectively. The complex
shock structure visible within the cloud indicates that the cloud's internal
density distribution is two phased: a smoothly varying background density which
is populated by higher density clumps. We present model results for a shock
interacting with a non-uniform ISM cloud. We find that this cloud can be well
modeled by a smoothly varying power law core surrounded by a low density
envelope with a Lorentzian profile. The lack of sharp density gradients in such
a model inhibits the growth of Kelvin-Helmholtz instabilities, consistent with
the cloud's appearance. Our model results also suggest that cloud clumps have
densities $\sim$ 10 times the ambient ISM density and account for $\sim$ 30% of
the total cloud volume. Moreover, the observed spacing of internal cloud shocks
and model simulations indicate that the distance between clumps is $\sim$ 4
clump radii.


title:
Anisotropy Studies Around the Galactic Center at EeV Energies with Auger
  Data

abstract:
  The Pierre Auger Observatory data have been analyzed to search for excesses
of events near the direction of the galactic center in several energy ranges
around EeV energies. In this region the statistics accumulated by the
Observatory are already larger than that of any previous experiment. Using both
the data sets from the surface detector and our hybrid data sets (events
detected simultaneously by the surface detector and the fluorescence detector)
we do not find any significant excess. At our present level of undestanding of
the performance and properties of our detector, our results do not support the
excesses reported by AGASA and SUGAR experiments. We set an upper bound on the
flux of cosmic rays arriving within a few degrees from the galactic center in
the energy range from 0.8-3.2 EeV. We also have searched for correlations of
cosmic ray arrival directions with the galactic plane and with the
super-galactic plane at energies in the range 1-5 EeV and above 5 EeV and have
found no significant excess.


title: Theoretical Aspects of Gravitational Lensing in TeVeS

abstract:
  Since Bekenstein's (2004) creation of his Tensor-Vector-Scalar theory
(TeVeS), the Modified Newtonian dynamics (MOND) paradigm has been redeemed from
the embarrassment of lacking a relativistic version. One primary success of
TeVeS is that it provides an enhancement of gravitational lensing, which could
not be achieved by other MONDian theories. Following Bekenstein's work, we
investigate the phenomena of gravitational lensing including deflection angles,
lens equations and time delay. We find that the deflection angle would maintain
its value while the distance of closest approach vary in the MOND regime, this
coincides with the conclusion of Mortlock and Turner's (2001) intuitional
approach. Moreover, the scalar field, which is introduced to enhance the
deflection angle in TeVeS, contributes a negative effect on the potential time
delay. Unfortunately this phenomenon is unmeasurable in lensing systems where
we can only observe the time delay between two images for a given source.
However, this measurable time delay offers another constraint on the mass ratio
of the DM and MOND scenarios, which in general differs from that given by the
deflection angle. In other words, for a lensing system, if two masses, m_gN and
m_gM, are mutually alternatives for the deflection angles in their own
paradigm, regarding the time delay they are in general in an exclusive
relation.


title: UHE neutrino damping in a thermal gas of relic neutrinos

abstract:
  We present a calculation of the damping of an ultra-energetic (UHE) cosmic
neutrino travelling through the thermal gas of relic neutrinos, using the
formalism of finite-temperature field theory. From the self-energy diagram due
to Z exchange, we obtain the annihilation cross section for an UHE neutrino
interacting with an antineutrino from the background. This method allows us to
derive the full expressions for the UHE neutrino transmission probability,
taking into account the momentum of relic neutrinos. We compare our results
with the approximations in use in the literature. We discuss the effect of
thermal motion on the shape of the absorption dips for different UHE neutrino
fluxes as well as in the context of relic neutrino clustering. We find that for
ratios of the neutrino mass to the relic background temperature $10^2$ or
smaller, the thermal broadening of the absorption lines could significantly
affect the determination of the neutrino mass and of the characteristics of the
population of UHE sources.


title: The Central Laser Facility at the Pierre Auger Observatory

abstract:
  The Central Laser Facility is located near the middle of the Pierre Auger
Observatory in Argentina. It features a UV laser and optics that direct a beam
of calibrated pulsed light into the sky. Light scattered from this beam
produces tracks in the Auger optical detectors which normally record nitrogen
fluorescence tracks from cosmic ray air showers. The Central Laser Facility
provides a "test beam" to investigate properties of the atmosphere and the
fluorescence detectors. The laser can send light via optical fiber
simultaneously to the nearest surface detector tank for hybrid timing analyses.
We describe the facility and show some examples of its many uses.


title:
Radiative Hydrodynamic Models of the Optical and Ultraviolet Emission
  from Solar Flares

abstract:
  We report on radiative hydrodynamic simulations of moderate and strong solar
flares. The flares were simulated by calculating the atmospheric response to a
beam of non-thermal electrons injected at the apex of a one-dimensional closed
coronal loop, and include heating from thermal soft X-ray, extreme ultraviolet
and ultraviolet (XEUV) emission. The equations of radiative transfer and
statistical equilibrium were treated in non-LTE and solved for numerous
transitions of hydrogen, helium, and Ca II allowing the calculation of detailed
line profiles and continuum emission. This work improves upon previous
simulations by incorporating more realistic non-thermal electron beam models
and includes a more rigorous model of thermal XEUV heating. We find XEUV
backwarming contributes less than 10% of the heating, even in strong flares.
The simulations show elevated coronal and transition region densities resulting
in dramatic increases in line and continuum emission in both the UV and optical
regions. The optical continuum reaches a peak increase of several percent which
is consistent with enhancements observed in solar white light flares. For a
moderate flare (~M-class), the dynamics are characterized by a long gentle
phase of near balance between flare heating and radiative cooling, followed by
an explosive phase with beam heating dominating over cooling and characterized
by strong hydrodynamic waves. For a strong flare (~X-class), the gentle phase
is much shorter, and we speculate that for even stronger flares the gentle
phase may be essentially non-existent. During the explosive phase, synthetic
profiles for lines formed in the upper chromosphere and transition region show
blue shifts corresponding to a plasma velocity of ~120 km/s, and lines formed
in the lower chromosphere show red shifts of ~40 km/s.


title:
On the Limb Darkening, Spectral Energy Distribution, and Temperature
  Structure of Procyon

abstract:
  We have fit synthetic visibilities from 3-D (CO5BOLD + PHOENIX) and 1-D
(PHOENIX, ATLAS 12) model stellar atmospheres of Procyon (F5 IV) to
high-precision interferometric data from the VLTI Interferometer (K-band) and
from the Mark III interferometer (500 nm and 800 nm). These data sets provide a
test of theoretical wavelength dependent limb-darkening predictions. The work
of Allende Prieto et al. has shown that the temperature structure from a
spatially and temporally averaged 3-D hydrodynamical model produces
significantly less limb darkening at 500 nm relative to the temperature
structure of a 1-D MARCS model atmosphere with a standard mixing-length
approximation for convection. Our direct fits to the interferometric data
confirm this prediction. A 1-D ATLAS 12 model with ``approximate overshooting''
provides the required temperature gradient. We show, however, that 1-D models
cannot reproduce the ultraviolet spectrophotometry below 160 nm with effective
temperatures in the range constrained by the measured bolometric flux and
angular diameter. We find that a good match to the full spectral energy
distribution can be obtained with a composite model consisting of a weighted
average of twelve 1-D model atmospheres based on the surface intensity
distribution of a 3-D granulation simulation. We emphasize that 1-D models with
overshooting may realistically represent the mean temperature structure of
F-type stars like Procyon, but the same models will predict redder colors than
observed because they lack the multicomponent temperature distribution expected
for the surfaces of these stars.


title:
A Two-Component Explosion Model for the Giant Flare and Radio Afterglow
  from SGR1806-20

abstract:
  The brightest giant flare from the soft $\gamma$-ray repeater (SGR) 1806-20
was detected on 2004 December 27. The isotropic-equivalent energy release of
this burst is at least one order of magnitude more energetic than those of the
two other SGR giant flares. Starting from about one week after the burst, a
very bright ($\sim 80$ mJy), fading radio afterglow was detected. Follow-up
observations revealed the multi-frequency light curves of the afterglow and the
temporal evolution of the source size. Here we show that these observations can
be understood in a two-component explosion model. In this model, one component
is a relativistic collimated outflow responsible for the initial giant flare
and the early afterglow, and another component is a subrelativistic wider
outflow responsible for the late afterglow. We also discuss triggering
mechanisms of these two components within the framework of the magnetar model.


title: Baryonic acoustic oscillations in simulated galaxy redshift surveys

abstract:
  Baryonic acoustic oscillations imprinted in the galaxy power spectrum provide
a promising tool for probing the cosmological distance scale and dark energy.
We present results from a suite of cosmological N-body simulations aimed at
investigating possible systematic errors in the recovery of cosmological
distances. We show the robustness of baryonic peaks against nonlinearity,
redshift distortions, and mild biases within the linear and quasilinear region
at various redshifts. While mildly biased tracers follow the matter power
spectrum well, redshift distortions do partially obscure baryonic features in
redshift space compared to real space. We calculate the statistical constraints
on cosmological distortions from N-body results and compare these to the
analytic results from a Fisher matrix formalism. We conclude that the angular
diameter distance will be constrained as well as our previous Fisher matrix
calculations while the Hubble parameter will be less constrained because of
nonlinear redshift distortions.


title:
Vectorization and Parallelization of the Adaptive Mesh Refinement N-body
  Code

abstract:
  In this paper, we describe our vectorized and parallelized adaptive mesh
refinement (AMR) N-body code with shared time steps, and report its performance
on a Fujitsu VPP5000 vector-parallel supercomputer. Our AMR N-body code puts
hierarchical meshes recursively where higher resolution is required and the
time step of all particles are the same. The parts which are the most difficult
to vectorize are loops that access the mesh data and particle data. We
vectorized such parts by changing the loop structure, so that the innermost
loop steps through the cells instead of the particles in each cell, in other
words, by changing the loop order from the depth-first order to the
breadth-first order. Mass assignment is also vectorizable using this loop order
exchange and splitting the loop into $2^{N_{dim}}$ loops, if the cloud-in-cell
scheme is adopted. Here, $N_{dim}$ is the number of dimension. These
vectorization schemes which eliminate the unvectorized loops are applicable to
parallelization of loops for shared-memory multiprocessors. We also
parallelized our code for distributed memory machines. The important part of
parallelization is data decomposition. We sorted the hierarchical mesh data by
the Morton order, or the recursive N-shaped order, level by level and split and
allocated the mesh data to the processors. Particles are allocated to the
processor to which the finest refined cells including the particles are also
assigned. Our timing analysis using the $\Lambda$-dominated cold dark matter
simulations shows that our parallel code speeds up almost ideally up to 32
processors, the largest number of processors in our test.


title:
Nucleosynthesis of PopIII Core Collapse Supernovae and the Abundances of
  Extremely Metal Poor Stars

abstract:
  We present a new analysis of the abundances observed in extremely metal poor
stars based on both a new generation of theoretical presupernova models and
explosions of zero metallicity massive stars and a new abundance analysis of an
homogeneous sample of stars having [Fe/H]<-2.5 (Cayrel et al. 2004).


title: Heavy element abundances in DAO white dwarfs measured from FUSE data

abstract:
  We present heavy element abundance measurements for 16 DAO white dwarfs,
determined from Far-Ultraviolet Spectroscopic Explorer {FUSE} spectra. Evidence
of absorption by heavy elements was found in the spectra of all the objects.
Measurements were made using models that adopted the temperatures, gravities
and helium abundances determined from both optical and FUSE data by Good et al.
(2004). Despite the different evolutionary paths that the types of DAO white
dwarfs are thought to evolve through, their abundances were not found to vary
significantly, apart from for the silicon abundances. Abundances measured when
the FUSE derived values of temperature, gravity and helium abundance were
adopted were, in general, a factor 1-10 higher than those determined when the
optical measure of those parameters was used. Satisfactory fits to the
absorption lines were achieved in approximately equal number. The models that
used the FUSE determined parameters seemed better at reproducing the strength
of the nitrogen and iron lines, while for oxygen, the optical parameters were
better.


title:
HS0139+0559, HS0229+8016, HS0506+7725 and HS0642+5049: Four new
  long-period cataclysmic variables

abstract:
  We present time-resolved optical spectroscopy and photometry of four
relatively bright (V~14.0-15.5) long-period cataclysmic variables (CVs)
discovered in the Hamburg Quasar Survey: HS0139+0559, HS0229+8016, HS0506+7725
and HS0642+5049. Their respective orbital periods, 243.69+-0.49min,
232.550+-0.049min, 212.7+-0.2min and 225.90+-0.23min are determined from radial
velocity and photometric variability studies. HS0506+7725 is characterised by
strong Balmer and He emission lines, short-period (~10-20min) flickering and
weak X-ray emission in the ROSAT All Sky Survey. The detection of a deep low
state (~18.5) identifies HS0506+7725 as a member of the VY Scl stars.
HS0139+0559, HS0229+8016 and HS0642+5049 display thick-disc like spectra and no
or only weak flickering activity. HS0139+0559 and HS0229+8016 exhibit clean
quasi-sinusoidal radial velocity varations of their emission lines but no or
very little orbital photometric variability. In contrast, we detect no radial
velocity variation in HS0642+5049 but a noticeable orbital brightness
variation. We identify all three systems either as UX UMa-type novalike
variables or as Z Cam-type dwarf novae. Our identification of these four new
systems underlines that the currently known sample of CVs is rather incomplete
even for bright objects. The four new systems add to the clustering of orbital
periods in the 3-4h range found in the sample of HQS selected CVs, and we
discuss the large incidence of magnetic CVs and VY Scl/SW Sex stars found in
this period range among the known population of CVs.


title: Stellar evolution with rotation XIII: Predicted GRB rates at various Z

abstract:
  We present the evolution of rotation in models of massive single stars
covering a wide range of masses and metallicities. These models reproduce very
well observations during the early stages of the evolution (in particular WR
populations and ratio between type II and type Ib,c at different metallicities,
see Meynet & Maeder 2005).
  Our models predict the production of fast rotating black holes. Models with
large initial masses or high metallicity end their life with less angular
momentum in their central remnant with respect to the break-up limit for the
remnant. Many WR star models satisfy the three main criteria (black hole
formation, loss of hydrogen-rich envelope and enough angular momentum to form
an accretion disk around the black hole) for gamma-ray bursts (GRB) production
via the collapsar model (Woosley 1993). Considering all types of WR stars as
GRB progenitors, there would be too many GRBs compared to observations. If we
consider only WO stars (type Ic supernovae as is the case for
SN2003dh/GRB030329, see Matheson et al. 2003) as GRBs progenitors, the GRBs
production rates are in much better agreement with observations. WO stars are
produced only at low metallicities in the present grid of models. This
prediction can be tested by future observations.


title: Spatially Resolved Spectral Analysis of Vela Shrapnel D

abstract:
  The ROSAT all-sky survey discovered several `shrapnels', showing boomerang
structures outside the Vela supernova remnant. We observed shrapnel D with the
XMM-Newton satellite. There is an X-ray bright ridge structure in our FOV
running from north to south. Applying the VNEI model to X-ray spectra of
various regions, we find that the plasma in the eastern part from the X-ray
ridge is significantly different from that in the western part. The X-ray
spectra in the western part can be represented by a single-temperature
component. The abundances of heavy elements are almost uniform, whereas they
are heavily overabundant, except for Fe; the relative abundances to the solar
values are O about 5, Ne about 10, Mg about 10, Fe about 1. This indicates that
shrapnel D originated from the ejecta of the supernova. We find that the plasma
in the eastern part from the ridge consists of two components with different
temperatures; the hot component comes from the ejecta, while the cold component
comes from the interstellar matter. These two components are considered to be
in contact with each other, forming a contact discontinuity. Around the
northern part of the contact discontinuity, we find wave-like structures of
which the typical scale are comparable with that of the Rayleigh--Taylor
instability.


title:
The nature of the red disk-like galaxies at high redshift: dust
  attenuation and intrinsically red stellar populations

abstract:
  We investigate which conditions of dust attenuation and stellar populations
allow models of dusty, continuously star-forming, bulge-less disk galaxies at
0.8<z<3.2 to meet the different colour selection criteria of high-z ``red''
galaxies (e.g. Rc-K>5.3, Ic-K>4, J-K>2.3). As a main novelty, we use stellar
population models that include the thermally pulsating Asymptotic Giant Branch
(TP-AGB) phase of stellar evolution. The star formation rate of the models
declines exponentially as a function of time, the e-folding time being longer
than 3 Gyr. In addition, we use calculations of radiative transfer of the
stellar and scattered radiation through different dusty interstellar media in
order to explore the wide parameter space of dust attenuation. We find that
synthetic disks can exhibit red optical/near-infrared colours because of
reddening by dust, but only if they have been forming stars for at least about
1 Gyr. Extremely few models barely exhibit Rc-K>5.3, if the inclination i=90
deg and if the opacity 2*tauV>6. Hence, Rc-K-selected galaxies at 1<z<2 most
probably are either systems with an old, passively evolving bulge or
starbursts. Synthetic disks at 1<z<2 exhibit 4<Ic-K<4.8, if they are seen edge
on (i.e. at i about 90 deg) and if 2*tauV>0.5. This explains the large fraction
of observed, edge-on disk-like galaxies with Ks<19.5 and F814W-Ks>4. Finally,
models with 2<z<3.2 exhibit 2.3<J-K<3, with no bias towards i about 90 deg and
for a large range in opacity (e.g. 2*tauV>1 for i about 70 deg). In conclusion,
red disk-like galaxies at 0.8<z<3.2 may not necessarily be dustier than nearby
disk galaxies (with 0.5<2*tauV<2) and/or much older than about 1 Gyr. This
result is due both to a realistic description of dust attenuation and to the
emission contribution by TP-AGB stars... (Abridged)


title: Neutrinos and Cosmology: an update

abstract:
  We review the current cosmological status of neutrinos, with particular
emphasis on their effects on Big Bang Nucleosynthesis, Large Scale Structure of
the universe and Cosmic Microwave Background Radiation measurements.


title: Absolute Calibration of the Auger Fluorescence Detectors

abstract:
  Absolute calibration of the Pierre Auger Observatory fluorescence detectors
uses a light source at the telescope aperture. The technique accounts for the
ombined effects of all detector components in a single measurement. The
calibrated 2.5 m diameter light source fills the aperture, providing uniform
illumination to each pixel. The known flux from the light source and the
response of the acquisition system give the required calibration for each
pixel. In the lab, light source uniformity is studied using CCD images and the
intensity is measured relative to NIST-calibrated photodiodes. Overall
uncertainties are presently 12%, and are dominated by systematics.


title:
Ionization States and Plasma Structures of Mixed-morphology SNRs
  Observed with ASCA

abstract:
  We present the results of a systematic study using ASCA of the ionization
state for six ``mixed-morphology'' supernova emnants (MMSNRs): IC 443, W49B,
W28, W44, 3C391, and Kes 27. MMSNRs show centrally filled thermal X-ray
emission, which contrasts to shell-like radio morphology, a set of
haracteristics at odds with the standard model of SNR evolution (e.g., the
Sedov model). We have therefore studied the evolution of the MMSNRs from the
ionization conditions inferred from the X-ray spectra, independent of X-ray
morphology. We find highly ionized plasmas approaching ionization equilibrium
in all the mmsnrs. The degree of ionization is systematically higher than the
plasma usually seen in shell-like SNRs. Radial temperature gradients are also
observed in five remnants, with cooler plasma toward the limb. In IC 443 and
W49B, we find a plasma structure consistent with shell-like SNRs, suggesting
that at least some MMSNRs have experienced similar evolution to shell-like
SNRs. In addition to the results above, we have discovered an ``overionized''
ionization state in W49B, in addition to that previously found in IC 443.
Thermal conduction can cause the hot interior plasma to become overionized by
reducing the temperature and density gradients, leading to an interior density
increase and temperature decrease. Therefore, we suggest that the
``center-filled'' X-ray morphology develops as the result of thermal
conduction, and should arise in all SNRs. This is consistent with the results
that MMSNRs are near collisional ionization equilibrium since the conduction
timescale is roughly similar to the ionization timescale. Hence, we conclude
that MMSNRs are those that have evolved over$\sim10^4$ yr. We call this phase
as the ``conduction phase.''


title: Faraday Rotation Measure Synthesis

abstract:
  We extend the rotation measure work of Burn (1966) to the cases of limited
sampling of lambda squared space and non-constant emission spectra. We
introduce the rotation measure transfer function (RMTF), which is an excellent
predictor of n-pi ambiguity problems with the lambda squared coverage. Rotation
measure synthesis can be implemented very efficiently on modern computers.
Because the analysis is easily applied to wide fields, one can conduct very
fast RM surveys of weak spatially extended sources. Difficult situations, for
example multiple sources along the line of sight, are easily detected and
transparently handled. Under certain conditions, it is even possible to recover
the emission as a function of Faraday depth within a single cloud of ionized
gas. Rotation measure synthesis has already been successful in discovering
widespread, weak, polarized emission associated with the Perseus cluster (De
Bruyn and Brentjens, 2005). In simple, high signal to noise situations it is as
good as traditional linear fits to polarization angle versus lambda squared
plots. However, when the situation is more complex or very weak polarized
emission at high rotation measures is expected, it is the only viable option.


title: Scalar phantom energy as a cosmological dynamical system

abstract:
  Phantom energy can be visualized as a scalar field with a (non-canonical)
negative kinetic energy term. We use the dynamical system formalism to study
the attractor behavior of a cosmological model containing a phantom scalar
field $\phi$ endowed with an exponential potential of the form $V(\phi)=V_0
\exp(-\lambda \kappa \phi)$, and a perfect fluid with constant equation of
state $\gamma$; the latter can be of the phantom type too. As in the canonical
case, three characteristic solutions can be identified. The scaling solution
exists but is either unstable or of no physical interest. Thus, there are only
two stable critical points which are of physical interest, corresponding to the
perfect fluid and scalar field dominated solutions, respectively. The most
interesting case arises for $0> \gamma > -\lambda^2/3$, which allows the
coexistence of the three solutions. The main features of each solution are
discussed in turn.


title: Diffuse polarized emission associated with the Perseus cluster

abstract:
  We report on full-polarization radio observations of the Perseus cluster
(Abell 426) using the Westerbork Synthesis Radio Telescope (WSRT) at
wavelengths from 81-95 cm. We have employed a novel technique, Rotation Measure
synthesis (Brentjens and de Bruyn, 2005) to unravel the polarization properties
of the emission across the full field of view and detect polarized emission
over a wide range of RM from about 0 to 90 rad m^-2. The low RM emission is
associated with our Galaxy, while the high RM emission is associated with the
Perseus cluster. The latter reaches typical surface brightness levels of 0.5-1
mJy per beam and must be rather highly polarized. Most of the peripheral
polarized emission appears too bright, by about 1-2 orders of magnitude, to be
explainable as Thomson scattered emission of the central radio source off the
thermal electrons in the cluster. The bulk of the emission associated with the
Perseus cluster is probably related to buoyant bubbles of relativistic plasma,
probably relics from still active or now dormant AGN within the cluster. A
lenticular shaped structure measuring 0.5-1 Mpc is strikingly similar to the
structures predicted by Ensslin et al. (1998). At the western edge of the
cluster, we detect very long, linear structures that may be related to shocks
caused by infall of gas into the Perseus cluster.


title: On the metallicity dependence of Wolf-Rayet winds

abstract:
  We have performed a pilot study of mass loss predictions for late-type
Wolf-Rayet (WR) stars as a function of metal abundance, over a range between
10^{-5} < (Z/Zsun) < 10. We find that the winds of nitrogen-rich Wolf-Rayet
stars are dominated by iron lines, with a dependence of mass loss on Z similar
to that of massive OB stars. For more evolved, carbon-rich, WR stars the wind
strength is also found to be dependent on the Fe abundance, so that they depend
on the chemical environment of the host galaxy, but with a mass loss
metallicity dependence that is less steep than for OB stars. Our finding that
WR mass loss is Z-dependent is a new one, with important consequences for black
hole formation and X-ray population studies in external galaxies. A further
finding of our study is that the Z dependence of C-rich WR stars becomes weaker
at metallicities below Z/Zsun < 1/10, and mass loss no longer declines once the
metal abundance drops below (Z/Zsun) = 10^{-3}. This is the result of an
increased importance of radiative driving by intermediate mass elements, such
as carbon. In combination with rapid rotation and/or proximity to the Eddington
limit -- likely to be relevant for massive Population III stars -- this effect
may indicate a role for mass loss in the appearance and evolution of these
objects, as well as a potential role for stellar winds in enriching the
intergalactic medium of the early Universe.


title:
A Homogeneous Sample of Sub-DLAs III: Total Gas Mass Omega_(HI+HeII) at
  z>2

abstract:
  Absorbers seen in the spectrum of background quasars are a unique tool to
select HI-rich galaxies at all redshifts. In turns, these allow to determine
the cosmological evolution of the HI gas, Omega_HI+HeII, a possible indicator
of gas consumption as star formation proceeds. The Damped Lyman-alpha systems
(DLAs with N(HI) > 10^20.3 cm^-2), in particular, are believed to contain a
large fraction of the HI gas but there are also indications that lower column
density systems, named ``sub-Damped Lyman-alpha'' systems play a role at
high-redshift. Here we present the discovery of high-redshift sub-DLAs based on
17 z>4 quasar spectra observed with the Ultraviolet-Visual Echelle Spectrograph
(UVES) on VLT. This sample is composed of 21 new sub-DLAs which, together with
another 10 systems from previous ESO archive studies, make up a homogeneous
sample. The redshift evolution of the number density of several classes of
absorbers is derived and shows that all systems seem to be evolving in the
redshift range from z=5 to z~3. This is further used to estimate the redshift
evolution of the characteristic radius of these classes of absorbers assuming a
Holmberg relation and one unique underlying parent population. DLAs are found
to have R_* ~ 20 h_100^-1 kpc, while sub-DLAs have R_* ~ 40 h_100^-1 kpc. The
redshift evolution of the column density distribution, f(N,z), down to N(HI) =
10^19 cm^-2 is also presented. A departure from a power law due to a flattening
of f(N,z) in the sub-DLA regime is present in the data. f(N,z) is further used
to determine the HI gas mass contained in sub-DLAs at z>2. The complete sample
shows that sub-DLAs are important at all redshifts from z=5 to z=2. Finally,
the possibility that sub-DLAs are less affected by the effects of dust
obscuration than classical DLAs are discussed.


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

abstract:
  We present a detailed analysis of the intrinsic X-ray absorption in the
Seyfert 1 galaxy NGC 4151 using Chandra/HETGS data obtained 2002 May, as part
of a program which included simultaneous UV spectra using HST/STIS and FUSE.
NGC 4151 was in a relatively low flux state during the observations reported
here, although roughly 2.5 times as bright in the 2 --10 keV band as during a
Chandra observation in 2000. The soft X-ray band was dominated by emission
lines, which show no discernible variation in flux between the two
observations. The 2002 data show the presence of a very highly ionized
absorber, in the form of H-like and He-like Mg, Si, and S lines, as well as
lower ionization gas via the presence of inner-shell absorption lines from
lower-ionization species of these elements. The former is too highly ionized to
be radiatively accelerated in a sub-Eddington source such as NGC 4151. We find
that the lower ionization gas had a column density a factor of ~ 3 higher
during the 2000 observation. If due to bulk motion, we estimate that this
component must have a velocity of more than 1250 km/sec transverse to our
line-of-sight. We suggest that these results are consistent with a
magneto-hydrodynamic flow.


title: Discovery of a Nearly Edge-On Disk Around HD 32297

abstract:
  We report the discovery of a nearly edge-on disk about the A0 star HD 32297
seen in light scattered by the disk grains revealed in NICMOS PSF-subtracted
coronagraphic images. The disk extends to a distance of at least 400 AU (3.3")
along its major axis with a 1.1 micron flux density of 4.81 +/-0.57 mJy beyond
a radius of 0.3" from the coronagraphically occulted star. The fraction of 1.1
micron starlight scattered by the disk, 0.0033 +/- 0.0004, is comparable to its
fractional excess emission at 25 + 60 micron of ~ 0.0027 as measured from IRAS
data. The disk appears to be inclined 10.5 degrees +/- 2.5 degrees from an
edge-on viewing geometry, with its major axis oriented 236.5 degrees +/- 1
degree eastward of north. The disk exhibits unequal brightness in opposing
sides and a break in the surface brightness profile along NE-side disk major
axis. Such asymmetries might implicate the existence of one or more (unseen)
planetary mass companions.


title: Constraints on the Formation of the Planet Around HD188753A

abstract:
  The claimed discovery of a Jupiter-mass planet in the close triple star
system HD 188753 poses a problem for planet formation theory. A circumstellar
disk around the planet's parent star would be truncated close to the star,
leaving little material available for planet formation. In this paper, we
attempt to model a protoplanetary disk around HD 188753A using a fairly simple
alpha-disk model, exploring a range of parameters constrained by observations
of T Tauri-type stars. The disk is truncated to within 1.5 to 2.7 AU, depending
on model parameters. We find that the in situ formation of the planet around HD
188753A is implausible.


title:
The Sensitivity of First Generation Epoch of Reionization Observatories
  and Their Potential for Differentiating Theoretical Power Spectra

abstract:
  Statistical observations of the epoch of reionization (EOR) power spectrum
provide a rich data set for understanding the transition from the cosmic "dark
ages" to the ionized universe we see today. EOR observations have become an
active area of experimental cosmology, and three first generation
observatories--MWA, PAST, and LOFAR--are currently under development. In this
paper we provide the first quantitative calculation of the three dimensional
power spectrum sensitivity, incorporating the design parameters of a planned
array. This calculation is then used to explore the constraints these first
generation observations can place on the EOR power spectrum. The results
demonstrate the potential of upcoming power spectrum observations to constrain
theories of structure formation and reionization.


title:
Variability Profiles of Millisecond X-Ray Pulsars: Results of
  Pseudo-Newtonian 3D MHD Simulations

abstract:
  We model the variability profiles of millisecond period X-ray pulsars. We
performed three-dimensional magnetohydrodynamic simulations of disk accretion
to millisecond period neutron stars with a misaligned magnetic dipole moment,
using the pseudo-Newtonian Paczynski-Wiita potential to model general
relativistic effects. We found that the shapes of the resulting funnel streams
of accreting matter and the hot spots on the surface of the star are quite
similar to those for more slowly rotating stars obtained from earlier
simulations using the Newtonian potential. The funnel streams and hot spots
rotate approximately with the same angular velocity as the star. The spots are
bow-shaped (bar-shaped) for small (large) misalignment angles. We found that
the matter falling on the star has a higher Mach number when we use the
Paczynski-Wiita potential than in the Newtonian case.
  Having obtained the surface distribution of the emitted flux, we calculated
the variability curves of the star, taking into account general relativistic,
Doppler and light-travel-time effects. We found that general relativistic
effects decrease the pulse fraction (flatten the light curve), while Doppler
and light-travel-time effects increase it and distort the light curve. We also
found that the light curves from our hot spots are reproduced reasonably well
by spots with a gaussian flux distribution centered at the magnetic poles. We
also calculated the observed image of the star in a few cases, and saw that for
certain orientations, both the antipodal hot spots are simultaneously visible,
as noted by earlier authors.


title: Time dependent non-LTE calculations of ionisation in the early universe

abstract:
  We present a new implicit numerical algorithm for the calculation of the time
dependent non-Local Thermodynamic Equilibrium of a gas in an external radiation
field that is accurate, fast and unconditionally stable for all spatial and
temporal increments. The method is presented as a backward difference scheme in
1-D but can be readily generalised to 3-D. We apply the method for calculating
the evolution of ionisation domains in a hydrogen plasma with plane-parallel
Gaussian density enhancements illuminated by sources of UV radiation. We
calculate the speed of propagation of ionising fronts through different ambient
densities and the interaction of such ionising fronts with density
enhancements. We show that for a typical UV source that may be present in the
early universe, the introduction of a density enhancement of a factor ~10 above
an ambient density 10^{-4} atoms/cm^3 could delay the outward propagation of an
ionisation front by millions of years. Our calculations show that within the
lifetime of a single source (~a few million years), and for ambient
intergalactic densities appropriate to redshifts z~6-20, neutral fractions of
of ~10^{-3}-10^{-5} can be achieved within its zone of influence. We also
present calculations which demonstrate that once started, ionisation will
proceed very efficiently as multiple sources are subsequently introduced, even
if the time between the appearence of such sources may be much longer than
their lifetimes.


title:
Discovery of Multiply Imaged Galaxies behind the Cluster and Lensed
  Quasar SDSS J1004+4112

abstract:
  We have identified three multiply imaged galaxies in Hubble Space Telescope
images of the redshift z=0.68 cluster responsible for the large-separation
quadruply lensed quasar, SDSS J1004+4112. Spectroscopic redshifts have been
secured for two of these systems using the Keck I 10m telescope. The most
distant lensed galaxy, at z=3.332, forms at least four images, and an Einstein
ring encompassing 3.1 times more area than the Einstein ring of the lensed QSO
images at z=1.74, due to the greater source distance. For a second multiply
imaged galaxy, we identify Ly_alpha emission at a redshift of z=2.74. The
cluster mass profile can be constrained from near the center of the brightest
cluster galaxy, where we observe both a radial arc and the fifth image of the
lensed quasar, to the Einstein radius of the highest redshift galaxy, ~110 kpc.
Our preliminary modeling indicates that the mass approximates an elliptical
body, with an average projected logarithmic gradient of ~-0.5. The system is
potentially useful for a direct measurement of world models in a previously
untested redshift range.


title: The Luminosity Dependence of Quasar Clustering

abstract:
  We investigate the luminosity dependence of quasar clustering, inspired by
numerical simulations of galaxy mergers that incorporate black hole growth.
These simulations have motivated a new interpretation of the quasar luminosity
function. In this picture, the bright end of the quasar luminosity function
consists of quasars radiating nearly at their peak luminosities, while the
faint end consists mainly of very similar sources, but at dimmer phases in
their evolution. We combine this model with the statistics of dark matter halos
that host quasar activity. We find that, since bright and faint quasars are
mostly similar sources seen in different evolutionary stages, a broad range in
quasar luminosities corresponds to only a narrow range in the masses of quasar
host halos. On average, bright and faint quasars reside in similar host halos.
Consequently, we argue that quasar clustering should depend only weakly on
luminosity. This prediction is in qualitative agreement with recent
measurements of the luminosity dependence of the quasar correlation function
(Croom et al. 2005) and the galaxy-quasar cross-correlation function
(Adelberger & Steidel 2005). Future precision clustering measurements from SDSS
and 2dF, spanning a large range in luminosity, should provide a strong test of
our model.


title: A Gamma-Ray Burst Mission to Investigate the Properties of Dark Energy

abstract:
  [Abridged] Very recently, relations between the peak energy of Gamma-Ray
Burst burst spectra, the isotropic-equivalent energy of the burst, and the
radiated energy of the burst have been found. In a way that is exactly
analogous to the way in which the relation between the peak luminosity and the
rate of decline of the light curve of Type Ia supernovae can be used to make
Type Ia supernovae excellent standard candles for cosmology, so too, the
relations between Epk, Eiso, and Egamma point toward a methodology for using
GRBs as excellent standard candles for cosmology. In addition, GRBs occur over
the broad redshift range from z=0.1 to at least z=4.5, and both they and their
afterglows are easily detectable out to z > 8. Thus GRBs show great promise as
cosmological ``yardsticks'' to measure the rate of expansion of the universe
over time, and therefore the properties of dark energy (i.e., Omega_M,
Omega_Lambda, w_0, and w_a).
  We describe a concept for a possible MIDEX-class mission dedicated to using
GRBs to constrain the properties of dark energy that would obtain these
quantities for > 800 bursts in the redshift range 0.1 >~ z <~ 10 during a
2-year mission. This burst sample would enable both Omega_M and w_0 to be
determined to +/- 0.07 and +/- 0.06 (68% CL), respectively, and w_a to be
significantly constrained.


title: Detection of SiO Maser Emission in V838 Mon

abstract:
  We report on the detection of 43 GHz SiO maser emission in V838 Mon, a
prototype of a new class of eruptive variables, in which a red supergiant was
formed after the nova-like eruption in 2002. The detection of SiO masers
indicates that the star formed after the eruption is indeed a kind of cool
mass-losing object with circumstellar masers. The measured radial velocity and
the intensity of maser emission are consistent with the object being located at
the distance of about 7 kpc from the sun. It also suggests that a considerable
percentage of SiO masing objects in the Galaxy are formed in the same mechanism
as that created V838 Mon.


title: The very local Hubble flow: Simulating transition from chaos to order

abstract:
  The physical nature of the very local (<3 Mpc) Hubble flow is studied on the
basis of the recent high precision observations in the Local Volume. A model
including both analytical treatment and computer simulations describes the flow
dynamical evolution from a chaotic Little Bang initial state to the present-day
state of a quasi-regular expansion. The two major observational parameters of
the flow, which are the rate of expansion and the velocity dispersion, find a
clear qualitative and quantitative explanation in the model.


title:
Three-body encounters in the Galactic centre: the origin of the
  hypervelocity star SDSS J090745.0+024507

abstract:
  Hills (1988) predicted that runaway stars could be accelerated to velocities
larger than 1000 km/s by dynamical encounters with the supermassive black hole
(SMBH) in the Galactic center. The recently discovered hypervelocity star SDSS
J090745.0+024507 (hereafter HVS) is escaping the Galaxy at high speed and could
be the first object in this class. With the measured radial velocity and the
estimated distance to the HVS, we trace back its trajectory in the Galactic
potential. Assuming it was ejected from the center, we find that a $\sim$ 2
mas/yr proper motion is necessary for the star to have come within a few
parsecs of the SMBH. We perform three-body scattering experiments to constrain
the progenitor encounter which accelerated the HVS. As proposed by Yu &
Tremaine (2003), we consider the tidal disruption of binary systems by the SMBH
and the encounter between a star and a binary black hole, as well as an
alternative scenario involving intermediate mass black holes. We find that the
tidal disruption of a stellar binary ejects stars with a larger velocity
compared to the encounter between a single star and a binary black hole, but
has a somewhat smaller ejection rate due to the greater availability of single
stars.


title:
Neutrino from extragalactic cosmic ray interactions in far infrared
  background

abstract:
  Diffuse background of high energy neutrinos arising from interactions of
cosmic ray protons with far infrared radiation background in extragalactic
space is calculated. It is assumed that cosmic ray spectrum at superhigh
energies has extragalactic origin and is proton dominated.The cosmological
evolution of extragalactic sources of cosmic ray protons as well as
infrared-luminous galaxies is taken into account in the calculation.


title:
Revised equipartition & minimum energy formula for magnetic field
  strength estimates from radio synchrotron observations

abstract:
  The commonly used classical equipartition or minimum-energy estimate of total
magnetic fields strengths from radio synchrotron intensities is of limited
practical use because it is based on the hardly known ratio K of the total
energies of cosmic ray protons and electrons and also has inherent problems. We
present a revised formula, using the number density ratio K for which we give
estimates. For particle acceleration in strong shocks K is about 40 and
increases with decreasing shock strength. Our revised estimate for the field
strength gives larger values than the classical estimate for flat radio spectra
with spectral indices of about 0.5-0.6, but smaller values for steep spectra
and total fields stronger than about 10 muG. In very young supernova remnants,
for example, the classical estimate may be too large by up to 10x. On the other
hand, if energy losses of cosmic ray electrons are important, K increases with
particle energy and the equipartition field may be underestimated
significantly. Our revised larger equipartition estimates in galaxy clusters
and radio lobes are consistent with independent estimates from Faraday rotation
measures, while estimates from the ratio between radio synchrotron and X-ray
inverse Compton intensities generally give much weaker fields. This may be
explained e.g. by a concentration of the field in filaments. Our revised field
strengths may also lead to major revisions of electron lifetimes in jets and
radio lobes estimated from the synchrotron break frequency in the radio
spectrum.


title: CMBR anisotropy: theoretical approaches

abstract:
  The version of the cosmological perturbation theory based on exact resolution
of energy constraint is developed in accordance with the diffeomorphisms of
general relativity in the Dirac Hamiltonian approach. Such exact resolution
gives one a possibility to fulfil the Hamiltonian reduction and to explain the
``CMBR primordial power spectrum'' and other topical problems of modern
cosmology by quantization of the energy constraint and quantum cosmological
origin of matter.