title: A 150MG magnetic white dwarf in the cataclysmic variable RX J1554.2+2721

abstract:
  We report the detection of Zeeman-split Lalpha absorption pi and sigma+ lines
in the far-ultraviolet Hubble Space Telescope/Space Telescope Imaging
Spectrograph spectrum of the magnetic cataclysmic variable RX J1554.2+2721.
Fitting the STIS data with magnetic white dwarf model spectra, we derive a
field strength of B~144MG and an effective temperature of 17000K<Teff<23000K.
This measurement makes RX J1554.2+2721 only the third cataclysmic variable
containing a white dwarf with a field exceeding 100MG. Similar to the other
high-field polar AR UMa, RX J1554.2+2721 is often found in a state of feeble
mass transfer, which suggests that a considerable number of high-field polars
may still remain undiscovered.


title: Demodulation of RHESSI count rates by an unbiased linear Bayes estimator

abstract:
  The RHESSI experiment uses rotational modulation for x- and gamma ray imaging
of solar eruptions. In order to disentangle rotational modulation from
intrinsic time variation, an unbiased linear estimator for the spatially
integrated photon flux is proposed. The estimator mimics a flat instrumental
response under a gaussian prior, with achievable flatness depending on the
counting noise. The amount of regularization is primarily given by the
modulation-to-Poisson levels of fluctuations, and is only weakly affected by
the Bayesian prior. Monte Carlo simulations demonstrate that the mean relative
error of the estimator reaches the Poisson limit, and real-data applications
are shown.


title:
High energy gamma rays from the massive black hole in the Galactic
  Center

abstract:
  Accreting black holes are believed to be sites of possible particle
acceleration with favorable conditions also for effective gamma-ray production.
However, because of photon-photon pair production, only low energy (MeV)
gamma-rays can escape these compact objects with typically very large
compactness parameter, given that in most cases the accretion disks within 10
Schwarzschild radii radiate with a power exceeding 10 percent of the Eddington
luminosity. Therefore, the high-energy gamma-ray emission of these objects
(both stellar mass and supermassive BHs) is generally suppressed, and
consequently the unique information on possible particle acceleration process
near the event horizon of the BH is essentially lost. Fortunately, this is not
the case for the super-massive BH located at the dynamical center of our Galaxy
(Sgr A*) which, thanks to its extraordinary low bolometric luminosity is
transparent fo gamma-rays up to very high energies, about 10 TeV. We discuss
different scenarios of gamma-ray production in Sgr A* and show that for a
reasonable set of parameters one can expect detectable gamma-ray fluxes of both
hadronic and electronic origin. Some of these scenarios are applicable not only
for the TeV gamma-ray emission recently reported from the direction of Galactic
Center, but may have broader implications relevant to highly variable
nonthermal emission of Sgr A* in radio, IR and X-ray bands.


title: Spatial Correlation Function of X-ray Selected AGN

abstract:
  We present a detailed description of the first direct measurement of the
spatial correlation function of X-ray selected AGN. This result is based on an
X-ray flux-limited sample of 219 AGN discovered in the contiguous 80.7 deg^2
region of the ROSAT North Ecliptic Pole (NEP) Survey. Clustering is detected at
the 4 sigma level at comoving scales in the interval r = 5-60 h^-1 Mpc. Fitting
the data with a power law of slope gamma=1.8, we find a correlation length of
r_0 = 7.4 (+1.8, -1.9) h^-1 Mpc (Omega_M=0.3, Omega_Lambda=0.7). The median
redshift of the AGN contributing to the signal is z_xi=0.22. This clustering
amplitude implies that X-ray selected AGN are spatially distributed in a manner
similar to that of optically selected AGN. Furthermore, the ROSAT NEP
determination establishes the local behavior of AGN clustering, a regime which
is poorly sampled in general. Combined with high-redshift measures from optical
studies, the ROSAT NEP results argue that the AGN correlation strength
essentially does not evolve with redshift, at least out to z~2.2. In the local
Universe, X-ray selected AGN appear to be unbiased relative to galaxies and the
inferred X-ray bias parameter is near unity, b_X~1. Hence X-ray selected AGN
closely trace the underlying mass distribution. The ROSAT NEP AGN catalog,
presented here, features complete optical identifications and spectroscopic
redshifts. The median redshift, X-ray flux, and X-ray luminosity are z=0.41,
f_X=1.1*10^-13 cgs, and L_X=9.2*10^43 h_70^-2 cgs (0.5-2.0 keV), respectively.
Unobscured, type 1 AGN are the dominant constituents (90%) of this soft X-ray
selected sample of AGN.


title: XMM-Newton and Chandra Observations of the Central Region of M31

abstract:
  The archival XMM-Newton data of the central region of M31 were analyzed for
diffuse X-ray emission. Point sources with the 0.5--10 keV luminosity exceeding
$\sim 4 \times 10^{35}$ erg s$^{-1}$ were detected. Their summed spectra are
well reproduced by a combination of a disk black-body component and a
black-body component, implying that the emission mainly comes from an assembly
of luminous low-mass X-ray binaries. After excluding these point sources,
spectra were accumulated over a circular region of $6\arcmin$ (1.2 kpc)
centered on the nucleus. In the energy range above 2 keV, these residual
spectra are understood mainly as contributions of unresolved faint sources and
spill-over of photons from the excluded point sources. There is in addition a
hint of a $\sim 6.6$ keV line emission, which can be produced by a hot
(temperature several keV) thin-thermal plasma. Below 2 keV, the spectra involve
three additional softer components expressed by thin-thermal plasma emission
models, of which the temperatures are $\sim 0.6$, $\sim 0.3$, and $\sim 0.1$
keV. Their 0.5--10 keV luminosities within 6$\arcmin$ are measured to be $\sim
1.2 \times 10^{38}$ erg s$^{-1}$, $\sim 1.6 \times 10^{38}$ erg s$^{-1}$, and
$\sim 4 \times 10^{37}$ erg s$^{-1}$ in the order of decreasing temperature.
The archival Chandra data of the central region of M31 yielded consistent
results. By incorporating different annular regions, all the three softer
thermal components were confirmed to be significantly extended. These results
are compared with reports from previous studies. A discussion is presented on
the origin of each thermal emission component.


title:
On the nature of the circumstellar medium of the remarkable type Ia/IIn
  supernova, SN 2002ic

abstract:
  We present results from the first high resolution, high S/N, spectrum of SN
2002ic. The resolved Halpha line has a P Cygni-type profile, clearly
demonstrating the presence of a dense, slow-moving (100 km/s) outflow. We have
additionally found a huge near-IR excess, hitherto unseen in type Ia SNe. We
argue that this is due to an IR light-echo arising from the pre-existing dusty
circumstellar medium. We deduce a CSM mass probably exceeding 0.3Msun produced
by a mass loss rate greater than several times 10^-4 Msun/yr. For the
progenitor, we favour a single degenerate system where the companion is a
post-AGB star. As a by-product of our optical data, we are able to provide a
firm identification of the host galaxy of SN 2002ic.


title: Visibility-Based Demodulation of Rhessi Light Curves

abstract:
  The Reuven Ramaty High Energy Spectroscopic Solar Imager (RHESSI) uses the
rotational modulation principle to observe temporally, spatially, and
spectrally resolved hard X ray and gamma ray images of solar flares. In order
to track the flare evolution on time scales that are commensurate with
modulation, the observed count rates must be demodulated at the expense of
spatial information. The present paper describes improvements of an earlier
demodulation algorithm, which decomposes the observed light curves into
intrinsic source variability and instrumental modulation.


title: The V1647 Ori (IRAS 05436-0007) Protostar and its Environment

abstract:
  We present Sloan Digital Sky Survey and United States Naval Observatory
observations of the V1647 Ori protostar and surrounding field near NGC 2068.
V1647 Ori, the likely driving source for HH 23, brightened significantly in
November 2003. Analysis of SDSS imaging acquired in November 1998 and February
2002 during the quiescent state, recent USNO photometry, and published 2MASS
and Gemini data shows that the color changes associated with brightening
suggest an EXor outburst rather than a simple dust clearing event.


title:
Small-Scale Structure of O VI Interstellar Gas in the Direction of the
  Globular Cluster NGC 6752

abstract:
  In order to study the small-scale structure of the hot interstellar gas, we
obtained Far Ultraviolet Spectroscopic Explorer interstellar O VI interstellar
absorption spectra of 4 four post-extreme horizontal branch stars in the
globular cluster NGC 6752 [(l,b) = (336.50,-25.63), d = 3.9 kpc, z= -1.7 kpc].
The good quality spectra of these stars allow us to measure both lines of the O
VI doublet at 1031.926 \AA and 1037.617 \AA. The close proximity of these stars
permits us to probe the hot interstellar gas over angular scale of only
$2\farcm2 - 8\farcm9$, corresponding to spatial scales $\la 2.5-10.1$ pc. On
these scales we detect no variations in the O VI column density and velocity
distribution. The average column density is log <N(O VI)> = 14.34 \pm 0.02 (log
<N_\perp(O VI)> = 13.98). The measured velocity dispersions of the O VI
absorption are also indistinguishable. Including the earlier results of Howk et
al., this study suggests that interstellar O VI is smooth on scales $\Delta
\theta \la 12\arcmin$, corresponding to a spatial scale of less than 10 pc, and
quite patchy at larger scales. Although such small scales are only probed in a
few directions, this suggests a characteristic size scale for the regions
producing collisionally-ionized O VI in the Galaxy.


title: The Origin of Cosmic Rays - A 96-Year-Old Puzzle Solved?

abstract:
  There is mounting evidence that long duration gamma ray bursts (GRBs) are
produced by ultra-relativistic jets of ordinary matter which are ejected in
core collapse supernova (SN) explosions. Such jets are extremely efficient
cosmic ray (CR) accelerators which can accelerate the swept up ambient
particles on their way to the highest observed CR energies. The bulk of the jet
kinetic energy is used to accelerate CRs while only a tiny fraction is used to
produce the GRB and its afterglow. Here we use the remarkably successful
cannonball (CB) model of GRBs to show that the bipolar jets from SN explosions,
which produce GRBs most of which are not beamed towards Earth, can be the main
origin of cosmic rays at all energies. The model explains very simply the
elemental composition of CRs and their observed spectra at all energies. In
particular it explains the origin of the CR knees and ankle. Above the CR
ankle, the Galactic magnetic fields can no longer delay the free escape of
ultra-high energies CRs (UHECR) from the Galaxy, and the CRs from the
intergalactic medium (IGM), which were injected there by SN jets from all the
galaxies and isotropized there by the IGM magnetic fields, dominate the
Galactic CR spectrum. A Greisen-Zatsepin-Kuzmin (GZK) effect due to the
interaction of UHECRs with the microwave background radiation is expected. The
CR nuclei which diffuse out of galaxies, or are directly deposited in the IGM
by the relativistic SN jets, may be the origin of the IGM magnetic fields.
Inverse Compton scattering of the cosmic microwave background radiation (MBR)
by the CR electrons in the IGM produces the diffuse extragalactic gamma-ray
background radiation (GBR).


title:
On the observed disc temperature of accreting intermediate mass black
  holes

abstract:
  Some ultraluminous X-ray sources in nearby galaxies show soft components
resembling thermal disc emission. Calculations based on blackbody emission then
indicate that the accreting black holes at the centres of these discs have
masses of 100s to 1000s Msun. Establishing the existence of such intermediate
mass black holes is of considerable importance so the assumptions and
approximations lying behind blackbody spectral fits must be examined. We study
here the basic assumption that the thermal emission is well-characterised by a
multi-temperature blackbody spectrum. Since the opacity in the surface layers
of a disc decreases at high energies the emergent spectrum is hardened. We
compute the observed spectra from discs around a non-spinning 1000 Msun black
hole and fit them over the XMM-Newton pn band with multi-colour disc models.
The typical overall spectra hardening factor usually adopted for discs around
stellar mass black hole (assuming an inclination of 60 deg and including
relativistic effects for a non-spinning black hole) is found to be appropriate.


title: Weightlessness of photons: A quantum effect

abstract:
  Contrary to general belief, the Fraunhofer lines have been found to be plasma
redshifted and not gravitationally redshifted, when observed on Earth. Quantum
mechanical effects cause the photons' gravitational redshift to be reversed as
the photons move from the Sun to the Earth. The designs of the experiments,
which were thought to have proven the gravitational redshift of photons, are
all in the domain of classical physics, and make it impossible to detect the
reversal of the gravitational redshifts. The solar redshift experiments,
however, are in the domain of quantum mechanics; and the reversal of the
redshift is easily detected, when the plasma redshift is taken into account.
The photons are found to be weightless relative to a local observer, but
repelled relative to a distant observer. The weightlessness of the photons in
the gravitational field relative to a local observer is inconsistent with
Einstein's equivalence principle. This together with the plasma redshift has
profound consequences for the cosmological perspectives. This article gives a
theoretical explanation of the observed phenomena, proper interpretation of the
many gravitational redshift experiments, and an understanding of how we missed
observing the reversal of photons' gravitational redshift. The present analysis
indicates that although the photons are weightless in a local system of
reference, the experimental evidence indicates that quasi-static
electromagnetic fields are not weightless, but adhere to the principle of
equivalence.


title:
A Possible Explanation for the Size Difference of Red and Blue Globular
  Clusters

abstract:
  Most observations of the projected half-light radii of metal-rich globular
clusters in a variety of galaxies have shown them to be ~20% smaller than those
of their metal-poor counterparts. We show using multi-mass isotropic
Michie-King models that the combined effects of mass segregation and the
dependence of main sequence lifetimes on metallicity can account for this
difference, under the assumption that clusters with similar central potentials
have the same distribution of half mass radii. If confirmed, this would
represent a new constraint on theories of globular cluster formation and
evolution.


title:
Polarization Signals of the 21 cm Background from the Era of
  Reionization

abstract:
  While emission and absorption lines of the 21 cm spin-flip transition of
neutral Hydrogen are intrinsically unpolarized, a magnetic field creates left-
and right-handed polarized components through the Zeeman effect. Here we
consider the resulting polarization of the redshifted 21 cm background from the
intergalactic medium before reionization. The polarization is detectable in
regions with a strong gradient in the mean brightness temperature. In
principle, this can open a new window on the evolution of intergalactic
magnetic fields. One possible approach is an extended integration of an
individual target during this era, such as the Mpc-scale HII regions inferred
to surround quasars at z ~ 6.5. The differential intensity between the two
polarization states can be used as a probe of the magnetic field at the edge of
the HII region. We estimate that the SKA could (ignoring systematics) detect B
\~ 200 (10) \muG coherent over several kiloparsecs with an observational
bandwidth of 100 (2) kHz. Beyond individual sources, the statistical properties
of wide-field 21 cm polarization maps, such as the angular power spectrum, can
be used to constrain the large-scale magnetic field. In this case, the SKA can
detect $B \sim 100 \mu$G fields coherent over many megaparsecs. The magnetic
field can be measured in any epoch over which the 21 cm background changes
rapidly (for example because the ionized fraction or spin temperature change).
Although the resulting constraints with SKA are relatively weak compared to
theoretical expectations, they nevertheless offer a unique direct probe of
magnetic fields in the high-redshift universe.


title: The cluster-scale AGN outburst in Hydra A

abstract:
  Deep Chandra observations of the Hydra A Cluster reveal a feature in the
X-ray surface brightness that surrounds the 330 MHz radio lobes of the AGN at
the cluster center. Surface brightness profiles of this feature and its close
association with the radio lobes argue strongly that it is a shock front driven
by the expanding radio lobes. The Chandra image also reveals other new
structure on smaller scales that is associated with the radio source, including
a large cavity and filament. The shock front extends 200 - 300 kpc from the AGN
at the cluster center and its strength varies along the front, with Mach
numbers in the range ~ 1.2 - 1.4. It is stronger where it is more distant from
the cluster center, as expected for a shock driven by expanding radio lobes.
Simple modeling gives an age for the shock front ~ 1.4\times10^8 y and a total
energy driving it of ~ 10^{61} erg. The mean mechanical power driving the shock
is comparable to quasar luminosities, well in excess of that needed to regulate
the cooling core in Hydra A. This suggests that the feedback regulating cooling
cores is inefficient, in that the bulk of the energy is deposited beyond the
cooling core. In that case, a significant part of cluster "preheating" is a
byproduct of the regulation of cooling cores.


title: Cosmological Distances and Fractal Statistics of Galaxy Distribution

abstract:
  This paper studies the effect of the distance choice in radial (non-average)
statistical tools used for fractal characterization of galaxy distribution.
After reviewing the basics of measuring distances of cosmological sources,
various distance definitions are used to calculate the differential density
$\gamma$ and the integral differential density $\gamma^\ast$} of the dust
distribution in the Einstein-de Sitter cosmology. The main results are as
follows: (1) the choice of distance plays a crucial role in determining the
scale where relativistic corrections must be taken into account, as both
$\gamma$ and $\gamma^\ast$ are strongly affected by such a choice; (2)
inappropriate distance choices may lead to failure to find evidence of a galaxy
fractal structure when one calculates those quantities, even if such a
structure does occur in the galaxy distribution; (3) the comoving distance and
the distance given by Mattig's formula are unsuitable to probe for a possible
fractal pattern as they render $\gamma$ and $\gamma^\ast$ constant for all
redshifts; (4) a possible galaxy fractal system at scales larger than 100Mpc (z
\~ 0.03) may only be found if those statistics are calculated with the
luminosity or redshift distances, as they are the ones where $\gamma$ and
$\gamma^\ast$ decrease at higher redshifts; (5) C\'el\'erier and Thieberger's
(2001) critique of Ribeiro's (1995: astro-ph/9910145) earlier study are
rendered impaired as their objections were based on misconceptions regarding
relativistic distance definitions.


title: Nonthermal Activity and Particle Acceleration in Clusters of Galaxies

abstract:
  Evidence for nonthermal activity in clusters of galaxies is well established
from radio observations of synchrotron emission by relativistic electrons, and
new windows (in EUV and Hard X-ray ranges) have provided more powerful tools
for its investigation. The hard X-ray observations, notably from Coma, are
summarized and results of a new RXTE observations of a high redshift cluster
are presented. It is shown that the most likely emission mechanisms for these
radiations is the inverse Compton scattering of the cosmic microwave background
photons by the same electrons responsible for the radio radiation. Various
scenarios for acceleration of the electrons are considered and it is shown that
the most likely model is episodic acceleration by shocks or turbulence,
presumably induced by merger activity, of high energy electrons injected into
the intercluster medium by galaxies or active galactic nuclei.


title: Simulation of Relativistic Force-free Magnetohydrodynamic Turbulence

abstract:
  We present numerical studies of 3-dimensional magnetohydrodynamic (MHD)
turbulence in a strongly magnetized medium in the extremely relativistic limit,
in which the inertia of the charge carriers can be neglected. We have focused
on strong Alfvenic turbulence in the limit. We have found the following
results. First, the energy spectrum is consistent with a Kolmogorov spectrum:
$E(k)\sim k^{-5/3}$. Second, turbulence shows a Goldreich-Sridhar type
anisotropy: $k_{\|} \propto k_{\perp}^{2/3}$, where $k_{\|}$ and $k_{\perp}$
are wavenumbers along and perpendicular to the local mean magnetic field
directions, respectively. These scalings are in agreement with earlier
theoretical predictions by Thompson & Blaes.


title:
Stellar evolution with rotation XI: Wolf-Rayet star populations at
  different metallicities

abstract:
  Grids of models of massive stars ($M \ge$ 20 $M_\odot$) with rotation are
computed for metallicities $Z$ ranging from that of the Small Magellanic Cloud
(SMC) to that of the Galactic Centre. The hydrostatic effects of rotation, the
rotational mixing and the enhancements of the mass loss rates by rotation are
included. The evolution of the surface rotational velocities of the most
massive O--stars mainly depends on the mass loss rates and thus on the initial
$Z$ value. The minimum initial mass for a star for entering the Wolf--Rayet
(WR) phase is lowered by rotation. For all metallicities, rotating stars enter
the WR phase at an earlier stage of evolution and the WR lifetimes are
increased, mainly as a result of the increased duration of the eWNL phase.
Models of WR stars predict in general rather low rotation velocities ($ < 50$
km s$^{-1}$) with a few possible exceptions, particularly at metallicities
lower than solar where WR star models have in general faster rotation and more
chance to reach the break--up limit.The properties of the WR populations as
predicted by the rotating models are in general in much better agreement with
the observations in nearby galaxies. The observed variation with metallicity of
the fractions of type Ib/Ic supernovae with respect to type II supernovae as
found by Prantzos & Boissier (\cite{Pr03}) is very well reproduced by the
rotating models, while non--rotating models predict much too low ratios.


title: Evolution of the Most Massive Stars

abstract:
  We discuss the physics of the $\Omega \Gamma$-- Limit, i.e. when the star is
unbound as a result of {\emph{both}} rotation and radiation pressure. We
suggest that the $\Omega \Gamma$-- Limit is what makes the Humphreys--Davidson
Limit. Stellar filiations are discussed, with an emphasis on the final stages,
in particular on the final masses, their angular momentum and the chemical
yields with account of rotation. A possible relation between WO stars and GRB
is emphasized.


title: Multi-Resolution Radiative Transfer for Line Emission

abstract:
  We present describe a new computer code that solves the radiative transfer
problem on multi-resolution grids. If the cloud model is from an MHD simulation
on a regular cartesian grid, criteria based for example on local density or
velocity gradients are used to refine the grid by dividing selected cells into
sub-cells. Division can be repeated hierarchically. Alternatively, if the cloud
model is from an MHD simulations with adaptive mesh refinement, the same
multi-resolution grid used for the MHD simulation is adopted in the radiative
transfer calculations. High discretization is often needed only in a small
fraction of the total volume. This makes it possible to simulate spectral line
maps with good accuracy, also minimizing the total number of cells and the
computational cost (time and memory). Multi-resolution models are compared with
models on regular grids. In the case of moderate optical depths (tau ~ a few)
an accuracy of 10% can be reached with multi-resolution models where only 10%
of the cells of the full grid are used. For optically thick species (tau~100),
the same accuracy is achieved using 15% of the cells. The relation between
accuracy and number of cells is not found to be significantly different in the
two MHD models we have studied. The new code is used to study differences
between LTE and non-LTE spectra and between isothermal and non-isothermal cloud
models. We find significant differences in line ratios and individual spectral
line profiles of the isothermal and LTE models relative to the more realistic
non-isothermal case. The slope of the power spectrum of integrated intensity is
instead very similar in all models.


title: Evolution at very low and zero Z

abstract:
  Rotation deeply affects the evolution of very metal poor massive stars.
Indeed, even moderately rotating stars reach the break--up limit during the
Main--Sequence (MS) phase, they evolve rapidly to the red after the core
H--burning phase and important surface enrichment in CNO elements occurs at the
supergiant stage. High rotation and the self enrichment in heavy elements $Z$
tend to enhance the quantity of mass lost by stellar winds. As a numerical
example, we obtain that a 60 M$_\odot$ at $Z=0.00001$, with an initial rotation
corresponding to 0.7 of the critical velocity, loses half of its initial mass
during its lifetime. The ejected material, enriched in helium and CNO elements,
has interesting consequences for the early chemical evolution of galaxies.


title:
A new proof for non-occurrence of trapped surfaces and information
  paradox

abstract:
  We present here a very simple, short and new proof which shows that no
trapped surface is ever formed in spherical gravitational collapse of isolated
bodies. Although this derivation is of purely mathematical nature and without
any assumption, it is shown, in the Appendix, that, physically, trapped
surfaces do not form in order that the 3 speed of the fluid as measured by an
observer at a fixed circumference coordinate $R$ (a scalar), is less than the
speed of light $c$. The consequence of this result is that, mathematically,
even if there would be Schwarzschild Black Holes, they would have unique
gravitational mass M=0. Recall that Schwazschild BHs may be considered as a
special case of rotating Kerr BHs with rotation parameter a=0. If one would
derive the Boyer-Lindquist metric [1] in a straight forward manner by using the
Backlund transformation[2], one would obtain a= M sin phi where phi is the
azimuth angle. This relation demands that BHs have unique mass M=0 (along with
a=0) which in turn confirms that there cannot be any trapped surface in
realistic gravitational collapse where the fluid has real pressure and density.
Since there is no trapped surface and no horizon there is no Information
Paradox in the first place.


title:
Analytical representations of unified equations of state of neutron-star
  matter

abstract:
  Analytical representations are derived for two equations of state (EOSs) of
neutron-star matter: FPS and SLy. Each of these EOSs is unified, that is, it
describes the crust and the core of a neutron star using the same physical
model. Two versions of the EOS parametrization are considered. In the first
one, pressure and mass density are given as functions of the baryon density. In
the second version, pressure, mass density, and baryon density are given as
functions of the pseudo-enthalpy, which makes this representation particularly
useful for 2-D calculations of stationary rotating configurations of neutron
stars.


title: Properties and environment of the molecular complex near Holmberg IX

abstract:
  This paper is aimed at providing new insight into the nature and origin of
the molecular complex situated near the line of sight toward Holmberg IX in the
M81 group of galaxies. The first high resolution CO maps of the complex as well
as single dish 13CO(1-0), 12CO(3-2) and millimeter continuum observations and
the results of a survey of 12CO in the region are presented. These data
together with the available HI, optical and X-ray observations are analyzed to
study the properties and environment of the complex. We confirm there is no
unobscured massive star formation inside the complex and from the millimeter
constraint on the extinction it must have a low star formation rate or be
forming only low mass stars. According to the CO line ratios the abundances and
physical conditions could be similar to that of cold gas in spirals. We find
from its dynamics (no rotation) and its mass (2--6 million solar masses) that
it resembles a massive GMC. Also, re-inspecting N-body simulations of the M81
group and the HI data we find that it might be located inside the extreme outer
disk of M81 and be cospatial with the HI feature known as Concentration I. The
negative result of the CO survey suggests that the complex is unique in this
region and calls for a peculiar local formation process. We find that the
distribution of the CO emission in the data cube is asymmetrical in a way
similar to a cometary object. The optical observations of the nearby supershell
MH9/10 suggest the existence of an outflow toward the complex. We consider the
possibility that the molecular complex is related to this hypothetical outflow.


title: Nuclear Spirals and Supermassive Black Holes

abstract:
  We have performed SPH simulations for the response of the gaseous disks to
the imposed potentials including those from bars and SMBHs. Evolution of the
nuclear regions of gaseous disks depends critically on the masses of SMBHs as
well as the sound speeds in the gas.


title:
Probing the obscuring medium around active nuclei using masers: The case
  of 3C403

abstract:
  We report the first detection of a water megamaser in a radio-loud galaxy,
3C403, and present a follow-up study using the VLA. 3C403 has been observed as
a part of a small sample of FRII galaxies with evidence of nuclear obscuration.
The isotropic luminosity of the maser is ~1200 solar luminosities. With a
recessional velocity of cz~17680 km/s it is the most distant water maser so far
reported. The line arises from the densest (> 10^(8) cm^(-3)) interstellar gas
component ever observed in a radio-loud galaxy. Two spectral features are
identified, likely bracketing the systemic velocity of the galaxy. Our
interferometric data clearly indicate that these arise from a location within
0.1" (~110 pc) from the active galactic nucleus. We conclude that the maser
spots are most likely associated with the tangentially seen parts of a nuclear
accretion disk, while an association with dense warm gas interacting with the
radio jets cannot yet be ruled out entirely.


title: Tidal interactions of close-in extrasolar planets: the OGLE cases

abstract:
  Close-in extrasolar planets experience extreme tidal interactions with their
host stars. This may lead to a reduction of the planetary orbit and a spin-up
of stellar rotation. Tidal interactions have been computed for a number of
extrasolar planets in circular orbits within 0.06 AU, namely for OGLE-TR-56 b.
We compare our range of the tidal dissipation value with two dissipation models
from Sasselov (2003) and conclude that our choices are equivalent to these
models. However, applied to the planet OGLE-TR-56 b, we find in contrast to
Sasselov (2003) that this planet will spiral-in toward the host star in a few
billion years. We show that the average and maximum value of our range of
dissipation are equivalent to the linear and quadratic dissipation models of
Sasselov (2003). Due to limitations in the observational techniques, we do not
see a possibility to distinguish between the two dissipation models as outlined
by Sasselov (2003). OGLE-TR-56 b may therefore not serve as a test case for
dissipation models. The probable existence of OGLE-TR-3 b at 0.02 AU and the
discovery of OGLE-TR-113 b at 0.023 AU and OGLE-TR-132 b at 0.03 AU may also
counter Sasselovs (2003) assumption of a pile-up stopping boundary at 0.04 AU.


title: X-rays from the Mira AB Binary System

abstract:
  We present the results of XMM-Newton X-ray observations of the Mira AB binary
system, which consists of a pulsating, asymptotic giant branch primary and
nearby (~0.6'' separation) secondary of uncertain nature. The EPIC CCD (MOS and
pn) X-ray spectra of Mira AB are relatively soft, peaking at ~1 keV, with only
very weak emission at energies > 3 keV; lines of Ne IX, Ne X, and O VIII are
apparent. Spectral modeling indicates a characteristic temperature T_X ~ 10^7 K
and intrinsic luminosity L_X ~ 5x10^29 erg s^{-1}, and suggests enhanced
abundances of O and, possibly, Ne and Si in the X-ray-emitting plasma. Overall,
the X-ray spectrum and luminosity of the Mira AB system more closely resemble
those of late-type, pre-main sequence stars or late-type, magnetically active
main sequence stars than those of accreting white dwarfs. We conclude that Mira
B is most likely a late-type, magnetically active, main-sequence dwarf, and
that X-rays from the Mira AB system arise either from magnetospheric accretion
of wind material from Mira A onto Mira B, or from coronal activity associated
with Mira B itself, as a consequence of accretion-driven spin-up. One (or both)
of these mechanisms also could be responsible for the recently discovered,
point-like X-ray sources within planetary nebulae.


title: Heavy elements and chemical enrichment in globular clusters

abstract:
  High resolution (R > 40 000) and high S/N spectra have been acquired with
UVES on the VLT-Kueyen (Paranal Observatory, ESO Chile) for several main
sequence turnoff stars (V ~ 17 mag) and subgiants at the base of the Red Giant
Branch (V ~ 16 mag) in three globular clusters (NGC 6397, NGC 6752 and 47
Tuc/NGC 104) at different metallicities (respectively [Fe/H] = -2.0; -1.5;
-0.7$). Spectra for a sample of 25 field halo subdwarves have also been taken
with equal resolution, but higher S/N. These data have been used to determine
the abundances of several neutron-capture elements in these three clusters:
strontium, yttrium, barium and europium. This is the first abundance
determination of these heavy elements for such unevolved stars in these three
globular clusters. These values, together with the [Ba/Eu] and [Sr/Ba]
abundance ratios, have been used to test the self-enrichment scenario. A
comparison is done with field halo stars and other well known Galactic globular
clusters in which heavy elements have already been measured in the past, at
least in bright giants (V > 11-12 mag). Our results show clearly that globular
clusters have been uniformly enriched by r- and s-process syntheses, and that
most of them seem to follow exactly the same abundance patterns as field halo
stars, which discards the ``classical'' self-enrichment scenario for the origin
of metallicities and heavy elements in globular clusters.


title: Evidence for a Black Hole in the X-ray transient GS 1354-64 (=BW Cir)

abstract:
  We present the first radial velocity curve of the companion star to BW Cir
which demonstrates the presence of a black hole in this X-ray transient which
recorded outbursts in 1987 and 1997 (and possibly 1971-2). We identify weak
absorption features corresponding to a G0-5III donor star, strongly veiled by a
residual accretion disc which contributes 61-65 % of the total light at lambda
6300. The Doppler motions of these features trace an orbit of P=2.54448 days
(or its 1-yr alias of P=2.56358 days) and velocity semi-amplitude K2=279 +- 5
km/s (or K2=292 +- 5 km/s). Both solutions are equally possible. The mass
function implied by the shorter period solution is f(M)= 5.75 +- 0.30 Msun
which, combined with the rotational broadening of the tidally locked companion
(V sin i =71 +- 4 km/s), yields a compact object mass of M1 sin3 i = 7.34 +-
0.46 Msun. This is substantially above the mass of a neutron star under any
standard equation of state of nuclear matter. The companion star is probably a
G subgiant which has evolved off the main sequence in order to fill its Roche
lobe. Remarkably, a distance of > 27 kpc is inferred by the companion's
luminosity and this is supported by the large observed systemic velocity (gamma
= 103 +- 4 km/s) which requires such a distance in order to be consistent with
the Galactic rotation curve.


title:
An X-ray Outburst from the Rapidly Accreting Young Star That Illuminates
  McNeil's Nebula

abstract:
  Young, low-mass stars are luminous X-ray sources whose powerful X-ray flares
may exert a profound influence over the process of planet formation. The origin
of such emission is uncertain. Although many or perhaps most recently formed,
low-mass stars emit X-rays as a consequence of solar-like coronal activity, it
has also been suggested that X-ray emission may be a direct result of mass
accretion onto the forming star. Here we report X-ray imaging spectroscopy
observations which reveal a factor ~50 increase in the X-ray flux from a young
star that is presently undergoing a spectacular optical/IR outburst. The
outburst is thought to be due to the sudden onset of a phase of rapid
accretion. The coincidence of a surge in X-ray brightness with the optical/IR
eruption demonstrates that strongly enhanced high-energy emission from young
stars can occur as a consequence of high accretion rates. We suggest that such
accretion- enhanced X-ray emission from erupting young stars may be
short-lived, because intense star-disk magnetospheric interactions are quenched
rapidly by the subsequent accretion flood.


title:
Age Constraints for an M31 Globular Cluster from Main Sequence
  Photometry

abstract:
  We present a color-magnitude diagram (CMD) of the globular cluster SKHB-312
in the Andromeda galaxy (M31), obtained with the Advanced Camera for Surveys on
the Hubble Space Telescope. The cluster was included in deep observations taken
to measure the star formation history of the M31 halo. Overcoming a very
crowded field, our photometry of SKHB-312 reaches V ~ 30.5 mag, more than 1 mag
below the main sequence turnoff. These are the first observations to allow a
direct age estimate from the turnoff in an old M31 cluster. We analyze its CMD
and luminosity function using a finely-spaced grid of isochrones that have been
calibrated using observations of Galactic clusters taken with the same camera
and filters. The luminosity difference between the subgiant and horizontal
branches is ~0.2 mag smaller in SKHB-312 than in the Galactic clusters 47 Tuc
and NGC 5927, implying SKHB-312 is 2-3 Gyr younger. A quantitative comparison
to isochrones yields an age of 10 +2.5/-1 Gyr.


title:
Average UV Quasar Spectra in the Context of Eigenvector 1: A Baldwin
  Effect Governed by Eddington Ratio?

abstract:
  We present composite UV spectra for low redshift Type 1 AGN binned to exploit
the information content of the Eigenvector 1 (E1) parameter space. Composite
spectra allow a decomposition of the CIV1549 line profile - one of the
strongest high-ionization lines. The simplest CIV decomposition into narrow
(NLR), broad (BLR) and very broad (VBLR) components suggests that different
components have an analog in Hb with two major exceptions. VBLR emission is
seen only in population B (FWHM(Hb)>4000 km/s) sources. A blue
shifted/asymmetric BLR component is seen only in pop. A (FWHM(Hb)<4000 km/s)
HIL such as CIV. The blueshifted component is thought to arise in a wind or
outflow. Our analysis suggests that such a wind can only be produced in pop. A
(almost all radio-quiet) sources where the accretion rate is relatively high.
Comparison between broad UV lines in radio-loud (RL) and radio-quiet (RQ)
sources shows few significant differences. Clear evidence is found for a narrow
CIV component in most radio-loud sources. We find also some indirect
indications that the black hole (BH) spin, rather than BH mass or accretion
rate is a key trigger in determining whether an object will be RL or RQ. We
find a ten-fold decrease in EW CIV with Eddington ratio (decreasing from ~1 to
\~0.01) while NV shows no change. These trends suggest a luminosity-independent
"Baldwin effect" where the physical driver may be the Eddington ratio.


title:
Dwarf Novae with Newly Determined Parallaxes: Model Analyses of VY
  Aquari, RU Pegasi, and T Leonis

abstract:
  Using newly determined parallaxes for dwarf novae, we have derived outburst
accretion rates for VY Aqr, RU Peg and T Leo and for T Leo during quiescence.
The two short-period dwarf novae, VY Aqr and T Leo, show good agreement with
optically thick steady-state accretion disks in outburst, whereas RU Peg shows
a significant departure from a steady-state disk. We have determined that the
white dwarf in T Leo has T$_{eff} = 16,000 \pm 1000$ K, a value consistent with
long term compressional heating when gravitational wave emission drives mass
transfer. The white dwarf in T Leo has a temperature in the same narrow range
as other WZ Sge-like dwarf novae.


title:
Structure of the Periphery of the Large Magellanic Cloud Revealed by
  2MASS

abstract: This paper has been withdrawn.


title: A Compact Starburst Core in the Dusty Lyman Break Galaxy Westphal-MD11

abstract:
  Using the IRAM Plateau de Bure Interferometer, we have searched for CO(3-2)
emission from the dusty Lyman break galaxy Westphal-MD11 at z = 2.98. Our
sensitive upper limit is surprisingly low relative to the system's 850 um flux
density and implies a far-IR/CO luminosity ratio as elevated as those seen in
local ultraluminous mergers. We conclude that the observed dust emission must
originate in a compact structure radiating near its blackbody limit and that a
relatively modest molecular gas reservoir must be fuelling an intense nuclear
starburst (and/or deeply buried active nucleus) that may have been triggered by
a major merger. In this regard, Westphal-MD11 contrasts strikingly with the
lensed Lyman break galaxy MS1512-cB58, which is being observed apparently
midway through an extended episode of more quiescent disk star formation.


title: The Hubble Constant from Gravitational Lens Time Delays

abstract:
  Present day estimates of the Hubble constant based on Cepheids and on the
cosmic microwave background radiation are uncertain by roughly 10% (on the
conservative assumption that the universe may not be PERFECTLY flat).
Gravitational lens time delay measurements can produce estimates that are less
uncertain, but only if a variety of major difficulties are overcome. These
include a paucity of constraints on the lensing potential, the degeneracies
associated with mass sheets and the central concentration of the lensing
galaxy, multiple lenses, microlensing by stars, and the small variability
amplitude typical of most quasars. To date only one lens meets all of these
challenges. Several suffer only from the central concentration degeneracy,
which may be lifted if one is willing to assume that systems with time delays
are either like better constrained systems with non-variable sources, or
alternatively, like nearby galaxies.


title:
X-ray/Optical/Radio Observations of a Resolved Supernova Remnant in NGC
  6822

abstract:
  The supernova remnant (SNR), Ho 12, in the center of the dwarf irregular
galaxy NGC 6822 was previously observed at X-ray, optical, and radio
wavelengths. By using archival Chandra and ground-based optical data, we found
that the SNR is spatially resolved in X-rays and optical. In addition, we
obtained a ~5" resolution radio image of the SNR. These observations provide
the highest spatial resolution imaging of an X-ray/optical/radio SNR in that
galaxy to date. The multi-wavelength morphology, X-ray spectrum and
variability, and narrow-band optical imagings are consistent with a SNR. The
SNR is a shell-shaped object with a diameter of about 10" (24 pc). The
morphology of the SNR is consistent across the wavelengths while the Chandra
spectrum can be well fitted with a nonequilibrium ionization model with an
electron temperature of 2.8 keV and a 0.3-7 keV luminosity of 1.6e37 erg/s. The
age of the SNR is estimated to be 1700-5800 years.


title: Triggering the Formation of Halo Globular Clusters with Galaxy Outflows

abstract:
  We investigate the interactions of high-redshift galaxy outflows with
low-mass virialized (Tvir < 10,000K) clouds of primordial composition. While
atomic cooling allows star formation in larger primordial objects, such
"minihalos" are generally unable to form stars by themselves. However, the
large population of high-redshift starburst galaxies may have induced
widespread star formation in these objects, via shocks that caused intense
cooling both through nonequilibrium H2 formation and metal-line emission. Using
a simple analytic model, we show that the resulting star clusters naturally
reproduce three key features of the observed population of halo globular
clusters (GCs). First, the 10,000 K maximum virial temperature corresponds to
the ~ 10^6 solar mass upper limit on the stellar mass of GCs. Secondly, the
momentum imparted in such interactions is sufficient to strip the gas from its
associated dark matter halo, explaining why GCs do not reside in dark matter
potential wells. Finally, the mixing of ejected metals into the primordial gas
is able to explain the ~ 0.1 dex homogeneity of stellar metallicities within a
given GC, while at the same time allowing for a large spread in metallicity
between different clusters. To study this possibility in detail, we use a
simple 1D numerical model of turbulence transport to simulate mixing in
cloud-outflow interactions. We find that as the shock shears across the side of
the cloud, Kelvin-Helmholtz instabilities arise, which cause mixing of enriched
material into > 20% of the cloud. Such estimates ignore the likely presence of
large-scale vortices, however, which would further enhance turbulence
generation. Thus quantitative mixing predictions must await more detailed
numerical studies.


title:
Uranus's anomalously low excess heat constrains strongly interacting
  dark matter

abstract:
  Dark matter annihilations can generate significant amounts of internal heat
inside planets if dark matter consists mainly of particles with nuclear cross
sections in the micro-barn range or larger (SIMPs). By considering a detailed
model of Uranus's interior, we calculate upper limits on the S-wave
annihilation cross section for these particles as a function of their mass.
These upper limits, together with other experimental and theoretical
constraints, rule out SIMPs with masses between 150 MeV and $10^{4}$ GeV.


title:
Metal Abundances of KISS Galaxies III. Nebular Abundances for Fourteen
  Galaxies and the Luminosity-Metallicity Relationship for HII Galaxies

abstract:
  We report results from the third in a series of nebular abundance studies of
emission-line galaxies from the KPNO International Spectroscopic Survey (KISS).
Galaxies with coarse metallicity estimates of 12 + log(O/H) less than 8.2 dex
were selected for observation. Spectra of 14 galaxies, which cover the full
optical region from [OII]3727,3729 to beyond [SII]6717,6731, are presented, and
abundance ratios of N, O, Ne, S, and Ar are computed. The auroral [OIII]4363
line is detected in all 14 galaxies. Oxygen abundances determined through the
direct electron temperature T_e method confirm that the sample is metal-poor
with 7.61 <= 12 + log(O/H) <= 8.32. By using these abundances in conjunction
with other T_e-based measurements from the literature, we demonstrate that HII
galaxies and more quiescent dwarf irregular galaxies follow similar
metallicity-luminosity (L-Z) relationships. The primary difference is a
zero-point shift between the correlations such that HII galaxies are brighter
by an average of 0.8 B magnitudes at a given metallicity. This offset can be
used as evidence to argue that low-luminosity HII galaxies typically undergo
factor of two luminosity enhancements, and starbursts that elevate the
luminosities of their host galaxies by 2 to 3 magnitudes are not as common. We
also demonstrate that the inclusion of interacting galaxies can increase the
scatter in the L-Z relation and may force the observed correlation towards
lower metallicities and/or larger luminosities. This must be taken into account
when attempting to infer metal abundance evolution by comparing local L-Z
relations with ones based on higher redshift samples since the fraction of
interacting galaxies should increase with look-back time.


title:
Search for Small-Scale Anisotropy of Cosmic Rays above 10^19 eV with
  HiRes Stereo

abstract:
  We present the results of a search for small-scale anisotropy in the
distribution of arrival directions of cosmic rays above 10^19 eV measured in
stereo by the High Resolution Fly's Eye (HiRes) experiment. Performing an
autocorrelation scan in energy and angular separation, we find that the
strongest correlation signal in the HiRes stereo data set recorded between
December 1999 and January 2004 is consistent with the null hypothesis of
isotropically distributed arrival directions. These results are compared to
previous claims of significant small-scale clustering in the AGASA data set.


title: Constraining Dark Energy with DEEP2

abstract:
  The DEEP2 survey has now completed half of its planned three-year lifespan,
and we have collected approximately 50% of the data, putting us exactly on
schedule. The survey plan calls for spectroscopic coverage by July of 2005 of
\~60,000 galaxies over 3.5 square degrees to a limiting magnitude of
R_{AB}=24.1; the great majority of these objects are at 0.7<z<1.4. We describe
here one method by which DEEP2 can set constraints on the equation of state
parameter of the Dark Energy, w. By counting the number of virialized groups
and clusters we find in redshift space as a function of their redshift and
internal velocity dispersion, we probe both the volume element and the growth
of structure at z~1, each of which depends on w. Studies of early DEEP2 data
indicate that the method is likely to work, and preliminary indications are
that a total of ~250 small groups will be counted in the full survey, leading
to a constraint \delta w ~ 0.1 if combined with both the velocity dispersion
distribution of z~0 clusters from the Sloan Digital Sky Survey and an
independent measurement of \sigma_8. We also provide a general description of
the DEEP2 observations and target selection, including the algorithm by which
galaxies are placed on slitmasks, to provide context for discussion of DEEP2
cluster samples.


title: Some Like it Hot: The X-Ray Emission of The Giant Star YY Mensae

abstract:
  (Abridged abstract) We present an analysis of the X-ray emission of the
rapidly rotating giant star YY Mensae observed by Chandra HETGS and XMM-Newton.
Although no obvious flare was detected, the X-ray luminosity changed by a
factor of two between the XMM-Newton and Chandra observations taken 4 months
apart. The coronal abundances and the emission measure distribution have been
derived from three different methods using optically thin collisional
ionization equilibrium models. The abundances show an inverse first ionization
potential (FIP) effect. We further find a high N abundance which we interpret
as a signature of material processed in the CNO cycle. The corona is dominated
by a very high temperature (20-40 MK) plasma, which places YY Men among the
magnetically active stars with the hottest coronae. Lower temperature plasma
also coexists, albeit with much lower emission measure. Line broadening is
reported, which we interpret as Doppler thermal broadening, although rotational
broadening due to X-ray emitting material high above the surface could be
present as well. We use two different formalisms to discuss the shape of the
emission measure distribution. The first one infers the properties of coronal
loops, whereas the second formalism uses flares as a statistical ensemble. We
find that most of the loops in the corona of YY Men have their maximum
temperature equal to or slightly larger than about 30 MK. We also find that
small flares could contribute significantly to the coronal heating in YY Men.
Although there is no evidence of flare variability in the X-ray light curves,
we argue that YY Men's distance and X-ray brightness does not allow us to
detect flares with peak luminosities Lx <= 10^{31} erg/s with current
detectors.


title:
Can WIMP Spin Dependent Couplings explain DAMA data, in light of Null
  Results from Other Experiments?

abstract:
  We examine whether the annual modulation found by the DAMA dark matter
experiment can be explained by Weakly Interacting Massive Particles (WIMPs), in
light of new null results from other experiments. CDMS II has already ruled out
most WIMP-nucleus spin-independent couplings as an explanation for DAMA data.
Hence we here focus on spin-dependent (axial vector; SD) couplings of WIMPs to
nuclei. We expand upon previous work by (i) considering the general case of
coupling to both protons and neutrons and (ii) incorporating bounds from all
existing experiments. We note the surprising fact that CMDS II places one of
the strongest bounds on the WIMP-neutron cross-section, and show that SD
WIMP-neutron scattering alone is excluded. We also show that SD WIMP-proton
scattering alone is allowed only for WIMP masses in the 5-13 GeV range. For the
general case of coupling to both protons and neutrons, we find that, for WIMP
masses above 13 GeV and below 5 GeV, there is no region of parameter space that
is compatible with DAMA and all other experiments. In the range (5-13) GeV, we
find acceptable regions of parameter space, including ones in which the
WIMP-neutron coupling is comparable to the WIMP-proton coupling.


title: Junction conditions of cosmological perturbations

abstract:
  The behavior of perturbations is studied in cosmological models which consist
of two different homogeneous regions connected in a spherical shell boundary.
The junction conditions for the metric perturbations and the displacements of
the shell boundary are analyzed and the surface densities of the perturbed
energy and momentum in the shell are derived, using Mukohyama's gauge-invariant
formalism and the Israel discontinuity condition. In both homogeneous regions
the perturbations of scalar, vector and tensor types are expanded using the
3-dimensional harmonic functions, but the model coupling among them is caused
in the shell by the inhomogeneity. By treating the perturbations with odd and
even parities separately, it is found, however, that we can have consistent
displacements and surface densities for given metric parturbations


title: Evidence for Intrinsic Redshifts in Normal Spiral Galaxies

abstract:
  The Tully-Fisher Relationship (TFR) is utilized to identify anomalous
redshifts in normal spiral galaxies. Three redshift anomalies are identified in
this analysis: (1) Several clusters of galaxies are examined in which late type
spirals have significant excess redshifts relative to early type spirals in the
same clusters, (2) Galaxies of morphology similar to ScI galaxies are found to
have a systematic excess redshift relative to the redshifts expected if the
Hubble Constant is 72 km s-1 Mpc-1, (3) individual galaxies, pairs, and groups
are identified which strongly deviate from the predictions of a smooth Hubble
flow. These redshift deviations are significantly larger than can be explained
by peculiar motions and TFR errors. It is concluded that the redshift anomalies
identified in this analysis are consistent with previous claims for large
non-cosmological (intrinsic) redshifts.


title: Correlation Function in Deep Redshift Space as a Cosmological Probe

abstract:
  Recent development of galaxy surveys enables us to investigate the deep
universe of high redshift. We quantitatively present the physical information
extractable from the observable correlation function in deep redshift space in
a framework of the linear theory. The correlation function depends on the
underlying power spectrum, velocity distortions, and the Alcock-Paczy\'nski
(AP) effect. The underlying power spectrum is sensitive to the constituents of
matters in the universe, the velocity distortions are sensitive to the galaxy
bias as well as the amount of total matter, and the Alcock-Paczy\'nski effect
is sensitive to the dark energy components. Measuring the dark energy by means
of the baryonic feature in the correlation function is one of the most
interesting applications. We show that the ``baryon ridge'' in the correlation
function serves as a statistically circular object in the AP effect. In order
to sufficiently constrain the dark energy components, the redshift range of the
galaxy survey should be as broad as possible. The survey area on the sky should
be smaller at deep redshifts than at shallow redshifts to keep the number
density as dense as possible. We illustrate an optimal survey design that are
useful in cosmology. Assuming future redshift surveys of $z\simlt 3$ which are
within reach of the present-day technology, achievable error bounds on
cosmological parameters are estimated by calculating the Fisher matrix.
According to an illustrated design, the equation of state of dark energy can be
constrained within $\pm 5%$ error assuming that the bias is unknown and
marginalized over. Even when all the other cosmological parameters should be
simultaneously determined, the error bound for the equation of state is up to
$\pm 10%$.


title: Gamma Ray Bursts: new rulers to measure the Universe

abstract:
  The best measure of the Universe should be done using a standard "ruler" at
any redshift. Type Ia Supernovae (SN Ia) probe the universe up to z$\sim$1.5,
while the Cosmic Microwave Background (CMB) primary anisotropies concern
basically $z\sim$1000. Apparently, Gamma--Ray Bursts (GRBs) are all but
standard candles. However, their emission is collimated and the
collimation--corrected energy correlates tightly with the frequency at which
most of the radiation of the prompt is emitted, as found by Ghirlanda et al.
(2004). Through this correlation we can infer the burst energy accurately
enough to probe the intermediate redshift ($z<10$) Universe. Using the best
known 15 GRBs we find very encouraging results that emphasize the cosmological
GRB role. A combined fit with SN Ia yields $\Omega_{\rm M}=0.37\pm0.10$ and
$\Omega_{\Lambda}=0.87\pm 0.23$. Assuming in addition a flat Universe, the
parameters are constrained to be $\Omega_{\rm M}=0.29\pm0.04$ and
$\Omega_{\Lambda}=0.71\pm 0.05$. GRBs accomplish the role of "missing link"
between SN Ia and CMB primary anisotropies. They can provide a new insight on
the cosmic effects of dark energy, complementary to the one supplied by CMB
secondary anisotropies through the Integrated Sachs Wolfe effect. The
unexpected Standard Candle cosmological role of GRBs motivates the most
optimistic hopes for what can be obtained when the GRB-dedicated satellite,
Swift, will be launched.


title: HD 52452: New BVRI Photometry

abstract:
  In this paper we report the multi-band BVRI photometry of HD 52452. The
comparison of our data with previous observations reported by Messina et al.
(2001) shows that there is a variation in amplitude, but the phases of the two
minima, thus the positions of the spot, are quite stable during our
observations.


title:
AcDc - A new code for the NLTE spectral analysis of accretion discs:
  application to the helium CV AM CVn

abstract:
  We present a recently developed code for detailed NLTE calculations of
accretion disc spectra of cataclysmic variables and compact X-ray binaries.
Assuming a radial structure of a standard alpha-disc, the disc is divided into
concentric rings. For each disc ring the solution of the radiation transfer
equation and the structure equations, comprising the hydrostatic and radiative
equilibrium, the population of the atomic levels as well as charge and particle
conservation, is done self-consistently. Metal-line blanketing and irradiation
by the central object are taken into account. As a first application, we show
the influence of different disc parameters on the disc spectrum for the helium
cataclysmic variable AM CVn.


title:
Preliminary analysis of photometric variations of central star of
  planetary nebula Sh 2-71

abstract:
  We confirmed the presence of regular UBVRIc light variations of the object in
the centre of planetary nebula Sh 2-71, the improved period of them being P
=(68.132+/-0.005) days. The shapes and amplitudes of light curves in particular
colours are briefly discussed.


title:
The vacuum energy excitations due to gravitational field as a possible
  candidate of dark matter in galaxies

abstract:
  In this Letter we point out to the possibility that the cloud of the vacuum
energy excitations in gravitation fields surrounding galaxies forms a component
of dark matter. These clouds of the vacuum energy excitations interact
gravitationally with the baryonic matter of galaxies changing their dynamical
and kinematical properties. In four model galaxies we show that the dynamic
changes due to the vacuum energy excitations of these galaxies are comparable
with data. This shows that vacuum energy excitations created in the gravitation
field of galaxies may be considered as one of the candidates of dark matter.


title: A Chandra ACIS view of the Thermal Composite Supernova Remnant 3C391

abstract:
  We present a 60 ks Chandra ACIS-S observation of the thermal composite
supernova remnant 3C391. The southeast-northwest elongated morphology is
similar to that previously found in radio and X-ray studies. This observation
unveils a highly clumpy structure of the remnant. Detailed spatially resolved
spectral analysis for the small-scale features reveals that the interior gas is
generally of normal metal abundance and has approached or basically reached
ionization equilibrium. The hydrogen column density increases from southeast to
northwest. Three mechanisms, radiative rim, thermal conduction, and cloudlet
evaporation, may all play roles in the X-ray appearance of 3C391 as a "thermal
composite" remnant, but there are difficulties with each of them in explaining
some physical properties. Comparatively, the cloudlet evaporation model is
favored by the main characteristics such as the highly clumpy structure and the
uniform temperature and density distribution over most of the remnant. The
directly measured postshock temperature also implies a young age, about 4 kyr,
for the remnant. The postshock gas pressure derived from the NE and SW rims,
which harbor maser spots, is consistent with the estimate for the maser
regions. An unresolved X-ray source is observed on the northwest border and its
spectrum is best fitted by a power-law.


title: The proper motion of the isolated neutron star RX J1605.3+3249

abstract:
  We obtained deep optical imaging of the thermally emitting X-ray bright and
radio-quiet isolated neutron star RX J1605.3+3249 with the Subaru telescope in
1999 and 2003. Together with archival HST images acquired in 2001 these data
reveal a proper motion of mu = 144.5 +/- 13.2 mas/yr. This implies a relatively
high spatial velocity and indicates that the star is unlikely to be re-heated
by accretion of matter from the interstellar medium. Assuming that RX
J1605.3+3249 is a young (10^5-10^6 yr) cooling neutron star, its apparent
trajectory is consistent with a birth in the nearby Sco OB2 OB association at a
location close to that derived for RX J1856.5-3754 and perhaps also to that of
RX J0720.4-3125. This suggests that the X-ray bright part of ROSAT-discovered
isolated neutron stars is dominated by the production of the Sco OB2 complex
which is the closest OB association and a part of the Gould belt. The B and R
magnitudes of the faint optical counterpart did not vary from 1999 to 2003 at B
= 27.22 +/- 0.10. Its B-R colour index of +0.32 +/- 0.17 is significantly
redder than that of other isolated neutron stars and the optical flux lies a
factor 11.5 above the extrapolation of the X-ray blackbody-like spectrum. The
red optical colour reveals the presence of an additional emitting component in
the optical regime over the main neutron star thermal emission. We also
discovered a small elongated Halpha nebula approximately centered on the
neutron star and aligned with the direction of motion. The width of the nebula
is unresolved and smaller than ~ 0.4" for a length of about 1". The shape of
the Balmer emitting nebula is very different from those seen close to other
neutron stars and should be confirmed by follow-up observations. We shortly
discuss the possible mechanisms which could give rise to such a geometry.


title:
Cataclysmic variables from the Calan-Tololo-Survey -- I. Photometric
  periods

abstract:
  In a search for cataclysmic variables in the Calan-Tololo Survey we have
detected 21 systems, 16 of them previously unknown. In this paper we present
detailed time-series photometry for those six confirmed cataclysmic variables
that show periodic variability in their light curves. Four of them turned out
to be eclipsing systems, while the remaining two show a modulation consisting
of two humps. All derived periods are below, or, in one case, just at the lower
edge of the period gap.


title: A new estimation of the Archeops angular power spectrum

abstract:
  We present a refined angular power spectrum of the Cosmic Microwave
Background (CMB) anisotropies using the Archeops last flight data. The
estimation of the Cl described here is performed using Xspect, a method which
uses the cross-power spectra of the maps of 6 different detectors. It covers
multipole range from l=10 to l=700 in 25 bins and confirms a strong evidence of
a plateau followed by the presence of two Doppler peaks. Archeops was conceived
as a precursor of the Planck HFI instrument by using the same optical design
and the same technology for the detectors and their cooling. Since last
publication, specific methods have been developed, extra bolometers were used
and the sky coverage, of about 20%, is almost twice larger. We also present a
comparison with first-year WMAP data both using individually spectra and by
computing the cross-power spectrum of the two experiments.


title: Precision Cosmology

abstract:
  The good agreement between large-scale observations and the predictions of
the now-standard $\Lambda$CDM theory gives us hope that this will become a
lasting foundation for cosmology. After briefly reviewing the current status of
the key cosmological parameters, I summarize several of the main areas of
possible disagreement between theory and observation: big bang nucleosynthesis,
galaxy centers, dark matter substructure, and angular momentum, updating my
earlier reviews [1]. The issues in all of these are sufficiently complicated
that it is not yet clear how serious they are, but there is at least some
reason to think that the problems will be resolved through a deeper
understanding of the complicated astrophysics involved in such processes as gas
cooling, star formation, and feedback from supernovae and AGN. Meanwhile,
searches for dark matter are dramatically improving in sensitivity, and gamma
rays from dark matter annihilation at the galactic center may have been
detected by H.E.S.S.


title:
Concerning the existence of a 'turbulent' magnetic field in the quiet
  Sun

abstract:
  We report on the a5F-y5F* multiplet of Ti I and its interest for the study of
'turbulent' magnetic fields in the quiet solar photosphere. In particular, we
argue that the sizable scattering polarization signal of the 4536 \AA line
(whose lower and upper levels have Land\'e factors equal to zero), relative to
the rest of the lines in the multiplet, gives direct evidence for the existence
of an ubiquitous, unresolved magnetic field. We cannot determine precisely the
strength of the magnetic field, but its very existence is evidenced by the
differential Hanle effect technique that this Ti I multiplet provides.


title:
CHORIZOS: a CHi-square cOde for parameteRized modelIng and
  characteriZation of phOtometry and Spectrophotometry

abstract:
  We have developed a CHi-square cOde for parameteRized modelIng and
characteriZation of phOtometry and Spectrophotometry (CHORIZOS). CHORIZOS can
use up to two intrinsic free parameters (e.g. temperature and gravity for
stars; type and redshift for galaxies; or age and metallicity for stellar
clusters) and two extrinsic ones (amount and type of extinction). The code uses
chi-square minimization to find all models compatible with the observed data in
the model N-dimensional (N=1,2,3,4) parameter space. CHORIZOS can use either
correlated or uncorrelated colors as input and is especially designed to
identify possible parameter degeneracies and multiple solutions. The code is
written in IDL and is available to the astronomical community. Here we present
the techniques used, test the code, apply it to a few well-known astronomical
problems, and suggest possible applications. As a first scientific result from
CHORIZOS, we confirm from photometry the need for a revised
temperature-spectral type scale for OB stars previously derived from
spectroscopy.


title:
Mass Profiles of Galaxy Cluster Cores: Implications for Structure
  Formation and Self-Interacting Dark Matter

abstract:
  We present a spectroscopic deprojection analysis of a sample of ten relaxed
galaxy clusters. We use an empirical F-test derived from a set of Markov Chain
Monte Carlo simulations to determine if the core plasma in each cluster could
contain multiple phases. We derive non-parametric baryon density and
temperature profiles, and use these to construct total gravitating mass
profiles. We compare these profiles with the standard halo parameterizations.
We find central density slopes roughly consistent with the predictions of LCDM:
$-1 \lesssim d\log(\rho)/d\log(r) \lesssim -2$. We constrain the core size of
each cluster and, using the results of cosmological simulations as a
calibrator, place an upper limit of ~0.1 cm^2/g = 0.2 b(GeV/c^2)^{-1} (99%
confidence) on the dark matter particle self-interaction cross section.


title:
The Nebular Environment and Enigmatic Hard X-ray Emission of the Hot DO
  White Dwarf KPD 0005+5106

abstract:
  We have detected an ionized nebula around the hot DO white dwarf KPD
0005+5106, and used the [OIII]/H-alpha ratios and nebular velocities to
separate this nebula from the background HII region of AO Cas. The angular size
of the [OIII] nebula of KPD 0005+5106 is ~3 deg. The velocity of this nebula is
similar to those of the local interstellar HI gas and the
interstellar/circumstellar absorption lines in UV spectra of KPD 0005+5106, but
has a large offset from those of the stellar photospheric lines. The mass of
the ionized nebula, ~70 Msun, indicates that it consists of interstellar
material and that the velocity offset between the star and the ambient medium
should not be interpreted as a wind outflow. We have also analyzed the ROSAT
PSPC observation of KPD 0005+5106 to determine its hard X-ray luminosity. Using
the L_X/L_bol relation for late-type stars and the lack of obvious near-IR
excess of KPD 0005+5106, we exclude the possible existence of a binary
companion with coronal activity. Without a wind outflow, the presence of
stellar OVIII emission requires that X-rays at energies greater than 0.871 keV
are present in the vicinity of KPD 0005+5106. This hard X-ray emission is most
puzzling as neither photospheric emission at such high energies nor a
high-temperature corona is expected from current stellar atmospheric models of
KPD 0005+5106. X-ray observations with high angular resolution and sensitivity
are needed to confirm the positional coincidence and to enable X-ray spectral
analyses for constraining the physical origin of the hard X-ray emission from
KPD 0005+5106.


title: The Crystal Method: Asteroseismology of BPM 37093

abstract:
  More than 40 years have passed since Ed Salpeter and others predicted that
the carbon/oxygen cores of the coolest white dwarf stars in our Galaxy will
theoretically crystallize. This effect has a dramatic impact on the calculated
ages of cool white dwarfs, but until recently we have had no way of testing the
theory. In 1992, pulsations were discovered in the massive potentially
crystallized white dwarf BPM 37093, and in 1999 the theoretical effects of
crystallization on the pulsation modes were determined. Observations from two
Whole Earth Telescope campaigns in 1998 and 1999, combined with a new
model-fitting method using a genetic algorithm, are now giving us the first
glimpse inside of a crystallized star.


title:
A Search for TeV Gamma-Ray Emission from High-Peaked Flat Spectrum Radio
  Quasars Using the Whipple Air-Cherenkov Telescope

abstract:
  Blazars have traditionally been separated into two broad categories based
upon their optical emission characteristics; BL Lacs, with faint or no emission
lines, and flat spectrum radio quasars (FSRQs) with prominent, broad emission
lines. The spectral energy distribution of FSRQs has generally been thought of
as being more akin to the low-peaked BL Lacs, which exhibit a peak in the
infrared region of the spectrum, as opposed to high-peaked BL Lacs (HBLs),
which exhibit a peak in UV/X-ray region of the spectrum. All blazars currently
confirmed as sources of TeV emission are HBLs. Recent surveys have found
several FSRQs exhibiting spectral properties similar to HBLs, particularly the
synchrotron peak frequency. These objects are potential sources of TeV emission
according to several models of blazar jet emission and blazar evolution.
Measurements of TeV flux or upper limits could impact existing theories
explaining the links between different blazar types and could have a
significant impact on our understanding of the nature of objects that are
capable of TeV emission. In particular, the presence (or absence) of TeV
emission from FSRQs could confirm (or cast doubt upon) recent evolutionary
models that expect intermediate objects in a transitionary state between FSRQ
and BL Lac. The Whipple 10 meter imaging air-Cherenkov gamma-ray telescope is
well suited for TeV gamma-ray observations. Using the Whipple telescope, we
have taken data on a small selection of nearby(z<0.1 in most cases),
high-peaked FSRQs. Although one of the objects, B2 0321+33, showed marginal
evidence of flaring, no significant emission was detected. The implications of
this paucity of emission and the derived upper limits are discussed.


title:
Millisecond and Binary Pulsars as Nature's Frequency Standards. III.
  Fourier Analysis and Spectral Sensitivity of Timing Observations to
  Low-Frequency Noise

abstract:
  This paper discusses spectral sensitivity of solitary and binary pulsars to a
low-frequency (colored) noise. It is a third paper in a series of papers
devoted to analysis of the low-frequency noise in pulsar timing observations
and its impact on observable fitting parameters of timing model.


title:
Evolved Galaxies at z > 1.5 from the Gemini Deep Deep Survey: The
  Formation Epoch of Massive Stellar Systems

abstract:
  We present spectroscopic evidence from the Gemini Deep Deep Survey (GDDS) for
a significant population of color-selected red galaxies at 1.3 < z < 2.2 whose
integrated light is dominated by evolved stars. Unlike radio-selected objects,
the z > 1.5 old galaxies have a sky density > 0.1 per sq. arcmin. Conservative
age estimates for 20 galaxies with z > 1.3; <z> = 1.49, give a median age of
1.2 Gyr and <z_f> = 2.4. One quarter of the galaxies have inferred z_f > 4.
Models restricted to abundances less than or equal to solar give median ages
and z_f of 2.3 Gyr and 3.3, respectively. These galaxies are among the most
massive and contribute approximately 50% of the stellar mass density at 1 < z <
2. The derived ages and most probable star formation histories suggest a high
star-formation-rate (300-500 solar masses per year) phase in the progenitor
population. We argue that most of the red galaxies are not descendants of the
typical z=3 Lyman break galaxies. Galaxies associated with luminous sub-mm
sources have the requisite star formation rates to be the progenitor
population. Our results point toward early and rapid formation for a
significant fraction of present day massive galaxies.


title: VLA H92 Alpha and H53 Alpha Radio Recombination Line Observations of M82

abstract:
  We present high angular resolution (0.6'') observations made with the VLA of
the radio continuum at 8.3 and 43 GHz as well as H92 Alpha and H53 Alpha radio
recombination lines from the nearby (3 Mpc) starburst galaxy M82. In the
continuum we report 19 newly identified sources at 8.3 GHz and 5 at 43 GHz that
were unknown previously. The spatial distribution of the H92 Alpha line is
inhomogeneous; we identify 27 features. The line and continuum emission are
modeled using a collection of HII regions at different distances from the
nucleus assuming a single-density component and two-density components. The
high-density component has a density of 4 X 10^{4} cm^{-3}. However, the bulk
of the ionization is in regions with densities which are typically a factor 10
lower. The gas kinematics, using the H92 Alpha line, confirms the presence of
steep velocity gradient (26 km s^{-1} arcsec^{-1}) in the nuclear region. As
this steep gradient is observed not only on the major axis but also at large
distances along a band of PA of 150 degrees, the interpretation in terms of x2
orbits elongated along the minor axis of the bar, which would be observed at an
angle close to the inclination of the main disk, seems inadequate. Ad-hoc
radial motions must be introduced to reproduce the pattern of the velocity
field. Different families of orbits are indicated as we detect a signature in
the kinematics at the transition between the two plateaus observed in the NIR
light distribution. The H92 Alpha line also reveals the base of the outflow
where the injection towards the halo on the Northern side occurs. The
kinematical pattern suggests a connection between the gas flowing in the plane
of M82 towards the center; this behavior most likely originates due to the
presence of a bar and the outflow out of the plane.


title:
Sub-GeV galactic cosmic-ray antiprotons from primordial black holes in
  the Randall-Sundrum braneworld

abstract:
  We investigate cosmic-ray antiprotons emitted from the galactic primordial
black holes in the Randall-Sundrum type-2 braneworld. The recent results of the
BESS antiproton observation implies the existence of exotic primary sub-GeV
antiprotons, one of whose most probable origin is PBHs in Our Galaxy. We show
that the magnitude of antiproton flux from PBHs in the RS braneworld is
proportional to negative power of the AdS radius, and immediately find that a
large extra-dimension can relax upper-limits on the abundance of the Galactic
PBHs. If actually there are more PBHs than the known upper-limit obtained in
the pure 4D case, they set a lower bound on the size of the extra dimension
above at least 10^{20} times 4D Planck-length to avoid inconsistency. On
completion of the numerical studies, we show that these constraints on the AdS
radius is comparable to those obtained from the diffuse photon background by
some of the authors in the previous paper. Moreover, in the low accretion-rate
case, only antiprotons can constrain the braneworld. We show that we will
detect signatures of the braneworld as a difference between the flux of the
antiprotons predicted in 4D and 5D by future observations in sub-GeV region
with a few percent precision.


title: On the Hipparcos parallaxes of O stars

abstract:
  We compare the absolute visual magnitude of the majority of bright O stars in
the sky as predicted from their spectral type with the absolute magnitude
calculated from their apparent magnitude and the Hipparcos parallax. We find
that many stars appear to be much fainter than expected, up to five magnitudes.
We find no evidence for a correlation between magnitude differences and the
stellar rotational velocity as suggested for OB stars by Lamers et al. (1997),
whose small sample of stars is partly included in ours. Instead, by means of a
simulation we show how these differences arise naturally from the large
distances at which O stars are located, and the level of precision of the
parallax measurements achieved by Hipparcos. Straightforwardly deriving a
distance from the Hipparcos parallax yields reliable results for one or two O
stars only. We discuss several types of bias reported in the literature in
connection with parallax samples (Lutz-Kelker, Malmquist) and investigate how
they affect the O star sample. In addition, we test three absolute magnitude
calibrations from the literature (Schmidt-Kaler et al. 1982; Howarth & Prinja
1989; Vacca et al. 1996) and find that they are consistent with the Hipparcos
measurements. Although O stars conform nicely to the simulation, we notice that
some B stars in the sample of Lamers et al. (1997) have a magnitude difference
larger than expected.


title: Simulations of Jets Driven by Black Hole Rotation

abstract:
  The origin of jets emitted from black holes is not well understood, however
there are two possible energy sources, the accretion disk or the rotating black
hole. Magnetohydrodynamic simulations show a well-defined jet that extracts
energy from a black hole. If plasma near the black hole is threaded by
large-scale magnetic flux, it will rotate with respect to asymptotic infinity
creating large magnetic stresses. These stresses are released as a relativistic
jet at the expense of black hole rotational energy. The physics of the jet
initiation in the simulations is described by the theory of black hole
gravitohydromagnetics.


title: Disk-averaged synthetic spectra of Mars

abstract:
  The principal goal of the NASA Terrestrial Planet Finder (TPF) and ESA Darwin
mission concepts is to directly detect and characterize extrasolar terrestrial
(Earth-sized) planets. This first generation of instruments is expected to
provide disk-averaged spectra with modest spectral resolution and
signal-to-noise. Here we use a spatially and spectrally resolved model of the
planet Mars to study the detectability of a planet's surface and atmospheric
properties from disk-averaged spectra as a function of spectral resolution and
wavelength range, for both the proposed visible coronograph (TPF-C) and
mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our
model is a spectrum-resolving (line-by-line) atmospheric/surface radiative
transfer model which uses observational data as input to generate a database of
spatially-resolved synthetic spectra for a range of illumination conditions
(phase angles) and viewing geometries. Results presented here include disk
averaged synthetic spectra, light-curves and the spectral variability at
visible + mid-IR wavelengths for Mars as a function of viewing angle,
illumination, season. We also considered the appearance of an increasingly
frozen Mars and simulated its detection versus real Mars with TPF-C and TPF-I
as a function of spectral resolving power, signal-to-noise, integration time.


title: The evolution of Ks-selected galaxies in the GOODS/CDFS deep ISAAC field

abstract:
  We present estimated redshifts and derived properties for a sample of 1663
galaxies with Ks <= 22 (Vega), selected from 50.4 sq.arcmin of the GOODS/CDFS
field with deep ISAAC imaging, and make an extensive comparison of their
properties with those of the extremely red galaxies (ERGs) selected in the same
field. We study in detail the evolution of Ks-selected galaxies up to redshifts
z ~ 4 and clarify the role of ERGs within the total Ks-band galaxy population.
We compute the total Ks-band luminosity function (LF) and compare its evolution
with the ERG LF. Up to <z_phot>=2.5, the bright end of the Ks-band LF shows no
sign of decline, and is progressively well reproduced by the ERGs with
increasing redshift. We also explore the evolution of massive systems present
in our sample: up to 20%-25% of the population of local galaxies with assembled
stellar mass M>1x10^11 Msun has been formed before redshift z ~ 4, and contains
  ~ 45% to 70% of the stellar mass density of the Universe at that redshift.
Within our sample, the comoving number density of these massive systems is then
essentially constant down to redshift z ~ 1.5, by which point most of them have
apparently evolved into (I-Ks)-selected ERGs. The remaining massive systems
observed in the local Universe are assembled later, at redshifts z <= 1.5. Our
results therefore suggest a two-fold assembly history for massive galaxies, in
which galaxy/star formation proceeds very efficiently in high mass haloes at
very high redshift.


title: Fragmentation of a high-mass star-forming core

abstract:
  At the earliest evolutionary stages, massive star-forming regions are deeply
embedded within their natal cores and not observable at optical and
near-infrared wavelengths. Interferometric high-spatial resolution mm dust
continuum observations of one very young high-mass star-forming region
disentangle its cluster-like nature already at the very beginning of the star
formation process. The derived protocluster mass function is consistent with
the stellar IMF. Hence, fragmentation of the initial massive cores may
determine the IMF and the masses of the final stars. This implies that stars of
all masses can form via accretion, and coalescence of protostars appears not to
be necessary.


title: The Trigger System of the H.E.S.S. Telescope Array

abstract:
  H.E.S.S. -- The High Energy Stereoscopic System-- is a new system of large
atmospheric Cherenkov telescopes for GeV/TeV Gamma-ray astronomy. This paper
describes the trigger system of H.E.S.S. with emphasis on the multi-telescope
array level trigger. The system trigger requires the simultaneous detection of
air-showers by several telescopes at the hardware level. This requirement
allows a suppression of background events which in turn leads to a lower system
energy threshold for the detection of Gamma-rays. The implementation of the
H.E.S.S. trigger system is presented along with data taken to characterise its
performance.


title: The HDF-North SCUBA Super-map II: Multi-wavelength properties

abstract:
  We present radio, optical and X-ray detected counterparts to the sub-mm
sources found using SCUBA in the Hubble Deep Field North region (GOODS-N). A
new counterpart identification statistic is developed to identify properties of
galaxies detected at other wavelengths that can be used to aid counterpart
identification. We discriminate between criteria that can be used to pre-select
sub-mm bright objects, and those that identify the counterpart to a known
sub-mm object. Optically faint galaxies detected in the deepest 1.4 GHz radio
continuum maps are the only effective way of pre-selecting SCUBA galaxies, and
radio sources are the best way to identify counterparts to known sub-mm
detections. Looking at radio spectral indices, only the steeper sources
(indicative of star formation) are detected in the sub-mm. Although we find
several X-ray identifications, we show that deep Chandra images do not
contribute to counterpart identifications, since in all cases they are already
detected in the more easily obtained VLA radio maps. We also find find no
evidence for clustering between Chandra and SCUBA sources in this field. For a
known SCUBA position, the reddest source tends to be the correct association,
although we can find no cut on colour, magnitude, or clustering property that
efficiently pre-selects for SCUBA sources. 15 micron ISO sources are
statistically detected by SCUBA, but the limiting mid-IR flux is not low enough
to provide useful constraints. We present postage stamp strips for each SCUBA
detection in separate bands from X-ray to radio, providing direct visual
evidence that approximately half of the sub-mm sources in this field remain
unidentified, despite an abundance of deep multi-wavelength data.


title: Particle Acceleration in Pair-Starved Pulsars

abstract:
  We investigate the physical situation above the pulsar polar cap (PC) where
the accelerating primaries (electrons) are not capable of producing sufficient
numbers of electron-positron pairs at low altitudes (within 1-2 stellar radii
above the PC surface) to screen the accelerating electric field, and continue
accelerating up to, at least, very high altitudes nearly approaching the light
cylinder. We derive an analytic solution for the parallel electric field valid
at high altitudes. The solution is based on the physical condition of
asymptotic vanishing of the rotationally induced transverse electric field
within the magnetic flux tube. This condition constrains the asymptotic value
of the effective space charge that determines the distribution of the parallel
electric field within the magnetic tube. Our estimates of low- to high-altitude
values of the parallel electric field imply the occurrence of a regime of
primary acceleration (with the characteristic Lorentz factor up to 1-2 X 10^7)
all the way from the PC to the light cylinder limited by curvature-radiation
reaction. In this model the primary outflow becomes asymptotically force-free,
and may turn into a relativistic wind beyond the light cylinder. Such a
solution will apply to both older pulsars producing only inverse Compton
scattering pairs and younger very high B pulsars (magnetars). We suggest that
pulsars, which are lying below the pair death line, may be radio-quiet
gamma-ray sources.


title: New northern common proper motion pairs

abstract:
  A list of 705 new Northern Celestial Hemisphere common proper motion pairs as
derived from the Second U.S. Naval Observatory CCD Astrograph Catalog is
presented, along with details of their separation, motion, brightness and
colour. Objects of particular interest are noted, and the use of the catalogue
for such work gauged.


title: The Large-Scale Structure of the Universe in One Dimension

abstract:
  (Abridged) I investigate statistical properties of one-dimensional fields in
the universe such as the Lyman alpha forest and inverted line-of-sight
densities. Because of gravitational clustering, the cosmic density field is
already quite non-Gaussian on scales below 10 Mpc/h at redshift z=3. The
covariance of the one-dimensional mass power spectrum indicates that Fourier
modes in the cosmic density field are highly correlated and that the variance
of the measured one-dimensional mass power spectrum is much higher than the
expectation for Gaussian random fields. It is found that rare high-density
structures contribute significantly to the covariance. The window function due
to the length of lines of sight introduces additional correlations between
different Fourier modes. In practice, one observes quasar spectra instead of
one-dimensional density fields. I show that the nonlinear transform between
density and flux quenches the fluctuations so that the flux power spectrum is
less sensitive to cosmological parameters than the one-dimensional mass power
spectrum. Finally, I provide a method for inverting Lyman alpha forests and
obtaining line-of-sight densities, so that statistics can be measured from
one-dimensional density fields directly.


title: Carbon-Enhanced Metal-Poor Stars in the Early Galaxy

abstract:
  Very metal-deficient stars that exhibit enhancements of their carbon
abundances are of crucial importance for understanding a number of issues --
the nature of stellar evolution among the first generations of stars, the shape
of the Initial Mass Function, and the relationship between carbon enhancement
and neutron-capture processes, in particular the astrophysical s-process. One
recent discovery from objective-prism surveys dedicated to the discovery of
metal-deficient stars is that the frequency of Carbon-Enhanced Metal-Poor
(CEMP) stars increases with declining metallicity, reaching roughly 25% for
[Fe/H] < -2.5. In order to explore this phenomenon in greater detail we have
obtained medium-resolution (2 A) spectroscopy for about 350 of the 413 objects
in the Christlieb et al. catalog of carbon-rich stars, selected from the
Hamburg/ESO objective prism survey on the basis of their carbon-enhancement,
rather than metal deficiency. Based on these spectra, and near-IR JHK
photometry from the 2MASS Point Source Catalog, we obtain estimates of [Fe/H]
and [C/Fe] for most of the stars in this sample, along with reasonably accurate
determinations of their radial velocities. Of particular importance, we find
that the upper envelope of carbon enhancement observed for these stars is
nearly constant, at [C/H] ~ -1.0, over the metallicity range -4.0 < [Fe/H] <
-2.0; this same level of [C/H] applies to the most iron-deficent star yet
discovered, HE 0107-5240, at [Fe/H] = -5.3.


title: Efficient Searches for r-Process-Enhanced, Metal-Poor Stars

abstract:
  Neutron-capture-enhanced, metal-poor stars are of central importance to
developing an understanding of the operation of the r-process in the early
Galaxy, thought to be responsible for the formation of roughly half of all
elements beyond the iron peak. A handful of neutron-capture-rich, metal-poor
stars with [Fe/H] < -2.0 have already been identified, including the well known
r-process-enhanced stars CS 22892-052 and CS 31082-001. However, many questions
of fundamental interest can only be addressed with the assemblage of a much
larger sample of such stars, so that general properties can be distinguished.
We describe a new effort, HERES: The Hamburg/ESO R-Process-Enhanced Star
survey, nearing completion, which will identify on the order of 5-10 additional
highly r-process-enhanced, metal-poor stars, and in all likelihood, a similar
or greater number of mildly r-process-enhanced, metal-poor stars in the halo of
the Galaxy. HERES is based on rapid "snapshot" spectra of over 350 candidate
halo giants with [Fe/H] < -2.0, obtained at moderately high resolution, and
with moderate signal-to-noise ratios, using the UVES spectrograph on the
European VLT 8m telescope.


title:
Bar Evolution Over the Last Eight Billion Years: A Constant Fraction of
  Strong Bars in GEMS

abstract:
  One third of present-day spirals host optically visible strong bars that
drive their dynamical evolution. However, the fundamental question of how bars
evolve over cosmological times has yet to be addressed, and even the frequency
of bars at intermediate redshifts remains controversial. We investigate the
frequency of bars out to z~1.0 drawing on a sample of 1590 galaxies from the
GEMS survey, which provides morphologies from HST ACS two-color images, and
highly accurate redshifts from the COMBO-17 survey. We identify spiral galaxies
using the Sersic index, concentration parameter, and rest-frame color. We
characterize bars and disks by fitting ellipses to F606W and F850LP images,
taking advantage of the two bands to minimize bandpass shifting. We exclude
highly inclined (i>60 deg) galaxies to ensure reliable morphological
classifications, and apply completeness cuts of M_v <= -19.3 and -20.6. More
than 40% of the bars that we detect have semi major axes a<0.5" and would be
easily missed in earlier surveys without the small PSF of ACS. The bars that we
can reliably detect are fairly strong (with ellipticities e>=0.4) and have a in
the range ~1.2-13 kpc. We find that the optical fraction of such strong bars
remains at ~(30% +- 6%) from the present-day out to look-back times of 2-6 Gyr
(z~0.2-0.7) and 6-8 Gyr (z~0.7-1.0); it certainly shows no sign of a drastic
decline at z>0.7. Our findings of a large and similar bar fraction at these
three epochs favor scenarios in which cold gravitationally unstable disks are
already in place by z~1, and where on average bars have a long lifetime (well
above 2 Gyr). The distributions of structural bar properties in the two slices
are, however, not statistically identical and therefore allow for the
possibility that the bar strengths and sizes may evolve over time.


title: The Fueling and Evolution of AGN: Internal and External Triggers

abstract:
  In this chapter, I review the fueling and evolution of active galactic nuclei
(AGN) under the influence of internal and external triggers, namely intrinsic
properties of host galaxies (morphological or Hubble type, color, presence of
bars and other non-axisymmetric features, etc) and external factors such as
environment and interactions. The most daunting challenge in fueling AGN is
arguably the angular momentum problem as even matter located at a radius of a
few hundred pc must lose more than 99.99 % of its specific angular momentum
before it is fit for consumption by a BH. I review mass accretion rates,
angular momentum requirements, the effectiveness of different fueling
mechanisms, and the growth and mass density of black BHs at different epochs. I
discuss connections between the nuclear and larger-scale properties of AGN,
both locally and at intermediate redshifts, outlining some recent results from
the GEMS and GOODS HST surveys.


title:
Stellar Activity and the Stromgren Photometric Metallicity Calibration
  of Intermediate-Type Dwarf Stars

abstract:
  We consider the effect of stellar activity, as measured by X-ray luminosity,
on metallicities of Solar-neighborhood F and G dwarfs derived from Stromgren
photometry. Rocha-Pinto & Maciel found evidence that Stromgren colors
systematically underpredict [Fe/H] for stars with extremely high Ca II H & K
emission. We investigate whether a recent photometric metallicity calibration
derived by Martell & Laughlin might be subject to this effect, and whether the
amount of underprediction could reliably be expressed as a function of log
(L_X/L_bol). Among those calibration stars used by Martell & Laughlin which are
also in the Bright Star Catalogue and detected in the ROSAT All-Sky Survey
there is no evidence for a correlation between photometric metallicity and
stellar activity. However, many of the "very active stars" on which the
Rocha-Pinto & Maciel result was based are members of interacting binaries or
are very young in age, and are not included in the X-ray sample that we are
using. Among normal dwarf stars it appears that stellar activity has little
effect on the metallicity calibration of Stromgren colors.