title:
The effective temperature scale of FGK stars. I. Determination of
  temperatures and angular diameters with the infrared flux method

abstract:
  The infrared flux method (IRFM) has been applied to a sample of 135 dwarf and
36 giant stars covering the following regions of the atmospheric parameters
space: 1) the metal-rich ([Fe/H]>0) end (consisting mostly of planet-hosting
stars), 2) the cool (Teff<5000 K) metal-poor (-1<[Fe/H]<-3) dwarf region, and
3) the very metal-poor ([Fe/H]<-2.5) end. These stars were especially selected
to cover gaps in previous works on Teff vs. color relations, particularly the
IRFM Teff scale of A. Alonso and collaborators. Our IRFM implementation was
largely based on the Alonso et al. study (absolute infrared flux calibration,
bolometric flux calibration, etc.) with the aim of extending the ranges of
applicability of their Teff vs. color calibrations. In addition, in order to
improve the internal accuracy of the IRFM Teff scale, we recomputed the
temperatures of almost all stars from the Alonso et al. work using updated
input data. The updated temperatures do not significantly differ from the
original ones, with few exceptions, leaving the Teff scale of Alonso et al.
mostly unchanged. Including the stars with updated temperatures, a large sample
of 580 dwarf and 470 giant stars (in the field and in clusters), which cover
the ranges: 3600 K<Teff<8000 K, -4.0<[Fe/H]<+0.5, have Teff homogeneously
determined with the IRFM. (Abridged)


title:
Can black hole MACHO binaries be detected by the Brazilian spherical
  antenna?

abstract:
  Different studies show that dark matter of non-baryonic origin might exist.
There have been experimental evidences that at least one form of dark matter
has been detected through microlensing effects. This form of dark matter is
named MACHOs (Massive Astrophysical Compact Halo Objects). The MACHO
collaboration estimated that the masses of these objects are to be in the range
0.15-0.95 solar masses, where the most probable mass is of 0.5 solar masses.
Some authors argue that MACHOs could be black holes, and that they could form
binary systems, BHMACHO binaries. As is well known binary systems are sources
of gravitational waves. The Brazilian spherical antenna will operate in the
frequency band of 3.0-3.4 kHz, sensitive to binaries of a pair of 0.5 solar
mass black holes just before coalescing. In the present work we study the
detectability of these putative BHMACHO binaries by the Brazilian spherical
antenna Mario Schenberg.


title:
The effective temperature scale of FGK stars. II. Teff : color : [Fe/H]
  calibrations

abstract:
  We present up-to-date metallicity-dependent temperature vs. color
calibrations for main sequence and giant stars based on temperatures derived
with the infrared flux method (IRFM). Seventeen colors in the following
photometric systems: UBV, uvby, Vilnius, Geneva, RI(Cousins), DDO,
Hipparcos-Tycho, and 2MASS, have been calibrated. The spectral types covered
range from F0 to K5 (7000 K<Teff<4000 K) with some relations extending below
4000 K or up to 8000 K. Most of the calibrations are valid in the metallicity
range -3.5<[Fe/H]<0.4, although some of them extend to as low as [Fe/H]=-4.0.
All fits to the data have been performed with more than 100 stars; standard
deviations range from 30 K to 120 K. Fits were carefully performed and
corrected to eliminate the small systematic errors introduced by the
calibration formulae. Tables of colors as a function of Teff and [Fe/H] are
provided. (Abridged)


title: Comparison of White Dwarf Mass Determinations

abstract:
  White dwarf masses can be determined in several ways. Here we compare masses
obtained from Balmer line spectroscopy with those derived from trigonometric
parallax measurements for an ensemble of cool hydrogen-atmosphere white dwarfs.


title: Detailed Spectroscopic and Photometric Analysis of DQ White Dwarfs

abstract:
  We present an analysis of spectroscopic and photometric data for cool DQ
white dwarfs based on improved model atmosphere calculations. In particular, we
revise the atmospheric parameters of the trigonometric parallax sample of
Bergeron et al.(2001), and discuss the astrophysical implications on the
temperature scale and mean mass, as well as the chemical evolution of these
stars. We also analyze 40 new DQ stars discovered in the first data release of
the Sloan Digital Sky Survey.


title: An Initial Look at the FIR-Radio Correlation within M51a using Spitzer

abstract:
  We present an initial look at the FIR-radio correlation within the
star-forming disk of M51a using {\it Spitzer} MIPS imaging, observed as part of
the {\it Spitzer} Infrared Nearby Galaxies Survey (SINGS), and WSRT radio
continuum data. At an estimated distance of 8.2 Mpc, we are able to probe the
variations in the 70$\micron$/22cm ratios across the disk of M51a at a linearly
projected scale of 0.75 kpc. We measure a dispersion of 0.191 dex, comparable
to the measured dispersion of the global FIR-radio correlation. Such little
scatter in the IR/radio ratios across the disk suggests that we have yet to
probe physical scales small enough to observe a breakdown in the correlation.
We also find that the global 70$\micron$/22cm ratio of M51a is 25% larger than
the median value of the disk, suggesting that the brighter disk regions drive
the globally measured ratio.


title:
X-ray Observations of the Boundary Layer in Dwarf Novae at Low Accretion
  Rates

abstract:
  We present a spectral analysis of XMM-Newton data of ten dwarf novae, nine of
which were observed during a quiescent state. The X-ray spectra indicate the
presence of a hot, optically thin plasma with a temperature distribution
consistent with a simple, isobaric cooling flow. The likely origin of the X-ray
emission is cooling plasma in the boundary layer settling onto the white dwarf.
Using a cooling flow model, we derive the temperatures, accretion rates,
rotational velocities, and elemental abundances of the X-ray emitting gas. We
discuss the implications of our findings for the structure of the boundary
layer. A comparison of X-ray and ultraviolet luminosities finds no evidence of
underluminous boundary layers in any of the quiescent dwarf novae. The X-ray
spectrum of EI UMa differs significantly from those of the other objects,
showing a strong fluorescent Fe K-alpha line and a strong O VII line triplet.
Based on the observational evidence, we argue that EI UMa is most likely an
intermediate polar and not as previously thought a dwarf nova.


title: A Northern Survey of Gamma-Ray Blazar Candidates

abstract:
  In preparation for GLAST, we have compiled a sample of blazar candidates to
increase the pool of well studied AGN from which GLAST counterparts will be
drawn. Sources were selected with our Figure of Merit (FoM) ranking; thus, they
have radio and X-ray properties very similar to the EGRET blazars.
Spectroscopic confirmation of these candidates is in progress, and more than
70% of these objects have been identified as flat spectrum radio quasars and BL
Lac objects. We present ~250 new optical blazar identifications based on
McDonald Observatory spectroscopy, 224 with redshifts. Of these, 167 are in our
FoM-selected set.
  To motivate the Gamma-ray nature of these objects, we analyzed the current
release of the EGRET data for possible point sources at their radio positions.
We develop two distinct methods to combine multiple EGRET observations of a sky
position into a single detection significance. We report a detection of the
signal of the set of blazar candidates in the EGRET data at the > 3 sigma level
by both techniques. We predict that the majority of these blazar candidates
will be found by GLAST due to its increased sensitivity, duty cycle and
resolving power.


title: Constraints on z~10 Galaxies from the Deepest HST NICMOS Fields

abstract:
  We use all available fields with deep NICMOS imaging to search for J dropouts
(H<28) at z~10. Our primary data set for this search were the two J+H NICMOS
parallel fields taken with the ACS HUDF. The 5 sigma limiting mags were 28.6 in
J and 28.5 in H. Several shallower fields were also used: J+H NICMOS frames
available over the HDF North, the HDF South NICMOS parallel, and the ACS HUDF.
The primary selection criterion was (J-H)>1.8. 11 such sources were found in
all search fields using this criterion. 8 of these were clearly ruled out as
credible z~10 sources, either as a result of detections (>2 sigma) blueward of
J or their colors redward of the break (H-K~1.5). The nature of the 3 remaining
sources could not be determined from the data. The number appears consistent
with the expected contamination from low-z interlopers. Analysis of the stacked
images for the 3 candidates also suggests contamination. Regardless of their
true redshifts, the actual number of z~10 sources must be <=3. To assess the
significance of these results, two lower redshift samples (a z~3.8 B-dropout
and z~6 i-dropout sample) were projected to z~8-12 using a (1+z)^{-1} size
scaling. They were added to the image frames, and the selection repeated,
giving 15.6 and 4.8 J-dropouts, respectively. This suggests that to the limit
of this probe (0.3 L*) there has been evolution from z~3.8 and possibly from
z~6. This is consistent with the strong evolution already noted at z~6 and
z~7.5 relative to z~3-4. Even assuming that 3 sources from this probe are at
z~10, the rest-frame continuum UV (~1500 A) luminosity density at z~10
(integrated down to 0.3 L*) is just 0.19_{-0.09}^{+0.13}x that at z~3.8 (or
0.19_{-0.10}^{+0.15}x including cosmic variance). However, if none of our
sources is at z~10, this ratio has a 1 sigma upper limit of 0.07. (abridged)


title:
A Self-Absorption Census of Cold HI Clouds in the Canadian Galactic
  Plane Survey

abstract:
  We present a 21cm line HI self-absorption (HISA) survey of cold atomic gas
within Galactic longitudes 75 to 146 degrees and latitudes -3 to +5 degrees. We
identify HISA as spatially and spectrally confined dark HI features and extract
it from the surrounding HI emission in the arcminute-resolution Canadian
Galactic Plane Survey (CGPS). We compile a catalog of the most significant
features in our survey and compare our detections against those in the
literature. Within the parameters of our search, we find nearly all previously
detected features and identify many new ones. The CGPS shows HISA in much
greater detail than any prior survey and allows both new and
previously-discovered features to be placed into the larger context of Galactic
structure. In space and radial velocity, faint HISA is detected virtually
everywhere that the HI emission background is sufficiently bright. This ambient
HISA population may arise from small turbulent fluctuations of temperature and
velocity in the neutral interstellar medium. By contrast, stronger HISA is
organized into discrete complexes, many of which follow a longitude-velocity
distribution that suggests they have been made visible by the velocity reversal
of the Perseus arm's spiral density wave. The cold HI revealed in this way may
have recently passed through the spiral shock and be on its way to forming
molecules and, eventually, new stars. This paper is the second in a series
examining HISA at high angular resolution. A companion paper (Paper III)
describes our HISA search and extraction algorithms in detail.


title:
Primordial Gravitational Waves and Inflation: CMB and Direct Detection
  With Space-Based Laser Interferometers

abstract:
  The curl-modes of Cosmic Microwave Background (CMB) polarization probe
horizon-scale primordial gravitational waves related to inflation. A
significant source of confusion is expected from a lensing conversion of
polarization related to density perturbations to the curl mode, during the
propagation of photons through the large scale structure. Either high
resolution CMB anisotropy observations or 21 cm fluctuations at redshifts 30
and higher can be used to delens polarization data and to separate
gravitational-wave polarization signature from that of cosmic-shear related
signal. Separations based on proposed lensing reconstruction techniques for
reasonable future experiments allow the possibility to probe inflationary
energy scales down to 10^15 GeV. Beyond CMB polarization, at frequencies
between 0.01 Hz to 1 Hz, space-based laser interferometers can also be used to
probe the inflationary gravitational wave background. The confusion here is
related to the removal of merging neutron star binaries at cosmological
distances. Given the low merger rate and the rapid evolution of the
gravitational wave frequency across this band, reliable removal techniques can
be constructed. We discuss issues related to joint constraints that can be
placed on the inflationary models based on CMB polarization information and
space-based interferometers such as the Big Bang Observer.


title:
An Automated Method for the Detection and Extraction of HI
  Self-Absorption in High-Resolution 21cm Line Surveys

abstract:
  We describe algorithms that detect 21cm line HI self-absorption (HISA) in
large data sets and extract it for analysis. Our search method identifies HISA
as spatially and spectrally confined dark HI features that appear as negative
residuals after removing larger-scale emission components with a modified CLEAN
algorithm. Adjacent HISA volume-pixels (voxels) are grouped into features in
(l,b,v) space, and the HI brightness of voxels outside the 3-D feature
boundaries is smoothly interpolated to estimate the absorption amplitude and
the unabsorbed HI emission brightness. The reliability and completeness of our
HISA detection scheme have been tested extensively with model data. We detect
most features over a wide range of sizes, linewidths, amplitudes, and
background levels, with poor detection only where the absorption brightness
temperature amplitude is weak, the absorption scale approaches that of the
correlated noise, or the background level is too faint for HISA to be
distinguished reliably from emission gaps. False detection rates are very low
in all parts of the parameter space except at sizes and amplitudes approaching
those of noise fluctuations. Absorption measurement biases introduced by the
method are generally small and appear to arise from cases of incomplete HISA
detection. This paper is the third in a series examining HISA at high angular
resolution. A companion paper (Paper II) uses our HISA search and extraction
method to investigate the cold atomic gas distribution in the Canadian Galactic
Plane Survey.


title: Signatures of Cosmic Strings in the Cosmic Microwave Background

abstract:
  We report a search for signatures of cosmic strings in the the Cosmic
Microwave Background data from the Wilkinson Microwave Anisotropy Probe. We
used a digital filter designed to search for individual cosmic strings and
found no evidence for them in the WMAP CMB anisotropies to a level of $\Delta
T/T \sim 0.29$ mK. This corresponds to an absence of cosmic strings with $ G\mu
\ga 1.07 \times 10^{-5}$ for strings moving with velocity $v = c/\sqrt{2}$.
Unlike previous work, this limit does not depend on an assumed string
abundance. We have searched the WMAP data for evidence of a cosmic string
recently reported as the CSL-1 object, and found an ``edge'' with 2$\sigma$
significance. However, if this edge is real and produced by a cosmic string, it
would have to move at velocity $\ga$ 0.94c. We also present preliminary limits
on the CMB data that will be returned by the PLANCK satellite for comparison.
With the available information on the PLANCK satellite, we calculated that it
would be twice as sensitive to cosmic strings as WMAP.


title:
Polarization from a Strongly Magnetized Accretion Disks: Asymptotic
  Wavelength Behaviour

abstract:
  We calculate the polarization of radiation from thick accretion disks with
vertically averaged global magnetic field. The polarization arises as a result
of the radiation scattering by free electrons in magnetized plasma of a disk.
We consider as a basic effect the Faraday rotation of polarization plane along
the photon propagation in a magnetized disk. The various models of optically
thick accretion disk with a vertically averaged magnetic field are considered.
The main goal of this paper is to obtain simple asymptotic formulae for the
polarization of radiation when the Faraday rotation angle >> 1 at the Thomson
optical length ~1. The results of our calculation allows us to estimate the
magnetic field magnitude near the marginally stable orbit region of a black
hole via the data of polarimetric observations including the expected future
X-ray polarimetric observations. The wavelength dependence of polarization is
strongly dependent on various models of an accretion disks and thus allows to
choose a real model from the polarization data.


title: Neutrino Astrophysics in the cold: Amanda, Baikal and IceCube

abstract:
  This talk review status and results from the two presently operating
underwater/ice neutrino telescopes, NT-200 in Lake Baikal and Amanda-II at the
South Pole. It also gives a description of the design and the expected
performance of Icecube, the next-generation neutrino telescope at South Pole.


title:
Constraint on Cosmological Model with Matter Creation Using
  Complementary Astronomical Observations

abstract:
  The universe with adiabatic matter creation is considered. It is thought that
the negative pressure caused by matter creation can play the role of a dark
energy component, and drive the accelerating expansion of the universe. Using
the Type Ia supernovae (SNe Ia) data, the observational Hubble parameter data,
the Cosmic Microwave Background (CMB) data and the Baryonic Acoustic
Oscillation (BAO) data, we make constraints on the cosmological parameters,
assuming a spatially flat universe. Our results show that the model with matter
creation is consistent with the SNe Ia data, while the joint constraints of all
these observational data disfavor this model. If the cosmological constant is
taken into account, a traditional model without matter creation is favored by
the joint observations.


title: Intra-day Variability of Sagittarius A* at 3 Millimeters

abstract:
  We report observations and analysis of flux monitoring of Sagittarius A* at
3-mm wavelength using the OVRO millimeter interferometer over a period of eight
days (2002 May 23-30). Frequent phase and flux referencing (every 5 minutes)
with the nearby calibrator source J1744-312 was employed to control for
instrumental and atmospheric effects. Time variations are sought by computing
and subtracting, from each visibility in the database, an average visibility
obtained from all the data acquired in our monitoring program having similar uv
spacings. This removes the confusing effects of baseline-dependent, correlated
flux interference caused by the static, thermal emission from the extended
source Sgr A West. Few-day variations up to ~20% and intra-day variability of
\~20% and in some cases up to ~40% on few-hour time scales emerge from the
differenced data on SgrA*. Power spectra of the residuals indicate the presence
of hourly variations on all but two of the eight days. Monte Carlo simulation
of red-noise light curves indicates that the hourly variations are well
described by a red-noise power spectrum with P(f) ~ f^(-1). Of particular
interest is a ~2.5 hour variation seen prominently on two consecutive days. An
average power spectrum from all eight days of data reveals noteworthy power on
this time scale. There is some indication that few-hour variations are more
pronounced on days when the average daily flux is highest. We briefly discuss
the possibility that these few-hour variations are due to the dynamical
modulation of accreting gas around the central supermassive black hole, as well
as the implications for the structure of the SgrA* photosphere at 3 mm.
Finally, these data have enabled us to produce a high sensitivity 3-mm map of
the extended thermal emission surrounding SgrA*.


title: Resolving the mystery of the dwarf galaxy HIZSS003

abstract:
  The nearby galaxy HIZSS003 was recently discovered during a blind HI survey
of the zone of avoidance (Henning et al. 2000). Follow up VLA as well as
optical and near-IR imaging and spectroscopy (Massey et al. 2003; Silva et al.
2005) confirm that it is a low metallicity dwarf irregular galaxy. However
there were two puzzling aspects of the observations, (i) current star
formation, as traced by H$\alpha$ emission, is confined to a small region at
the edge of the VLA HI image and (ii) the metallicity of the older RGB stars is
higher than that of the gas in HII region. We present high spatial and velocity
resolution Giant Meterwave Radio Telescope (GMRT) observations that resolve
these puzzles by showing that HIZSS003 is actually a galaxy pair and that the
HII region lies at the center of a much smaller companion galaxy (HIZSS003B) to
the main galaxy (HIZSS003A). The HI emission from these two galaxies overlaps
in projection, but can be separated in velocity space. HIZSS003B has an HI mass
of 2.6 X 10^6 M$_\odot$, and a highly disturbed velocity field. Since the
velocity field is disturbed, an accurate rotation curve cannot be derived,
however, the indicative dynamical mass is ~5 X 10^7 M$_\odot$. For the bigger
galaxy HIZSS003A we derive an HI mass of 1.4 X 10^7 M$_\odot$. The velocity
field of this galaxy is quite regular and from its rotation curve we derive a
total dynamical mass of ~6.5 X 10^8 M$_\odot$.


title: Reconstruction of Objects by Direct Demodulation

abstract:
  High resolution reconstruction of complicated objects from incomplete and
noisy data can be achieved by solving modulation equations iteratively under
physical constraints. This direct demodulation method is a powerful technique
for dealing with inverse problem in general case. Spectral and image
restorations and computerized tomography are only particular cases of general
demodulation. It is possible to reconstruct an object in higher dimensional
space from observations by a simple lower dimensional instrument through direct
demodulation. Our simulations show that wide field and high resolution images
of space hard X-rays and soft gamma rays can be obtained by a collimated
non-position-sensitive detector without coded aperture masks.


title:
Open Cluster Birth Analysis and Multiple Spiral Arm Sets in the Milky
  Way

abstract:
  The Milky Way spiral arm dynamics is studied using the birth place of open
clusters. We separately study the nearby spiral arms, and find evidence for
multiple spiral sets. In particular, the Sagittarius-Carina arm appears to be a
superposition of two sets. The first has a pattern speed of
Omega_P,Carina,1=16.5^{+1.2}_{-1.4sys}+/-1.1_{stat} (km/s)/kpc, while the
second has Omega_P,Carina,2=29.8^{+0.6}_{-1.3sys}+/-1.3_{stat} (km/s)/kpc. The
Perseus arm located at larger galactic radii exhibits only one clear set with
Omega_P,Perseus=20.0^{+1.7}_{-1.2sys}+/-1.6_{stat} (km/s)/kpc. The Perseus and
"slower" Carina arms are most probably part of an m=4 set. The Orion "armlet"
appears to have a pattern speed of Omega_P,Orion=28.9
^{+1.3}_{-1.2sys}+/-0.8_{stat} (km/s)/kpc. In other words, both the "faster"
Carina arm and the Orion arm are nearly corotating with the solar system.


title:
The Classical and Quantum Inflaton: the Precise Inflationary Potential
  and Quantum Inflaton Decay after WMAP

abstract:
  We clarify classical inflaton models by considering them as effective field
theories `a la Ginzburg-Landau. In this approach, the WMAP statement excluding
the pure phi^4 potential implies the presence of an inflaton mass term at the
scale m ~ 10^{13}GeV.Chaotic, new and hybrid inflation models are studied in an
unified manner.In all cases the inflaton potential takes the form V(phi)=m^2
M_{Pl}^2 v(phi/M_{Pl}), where all coefficients in v(varphi) are of order one.If
such potential corresponds to supersymmetry breaking, the susy scale is sqrt{m
M_{Pl}}~10^{16}GeV which coincides with the GUT scale. For red tilted spectrum
new inflation turns to be favoured while for blue tilted spectrum, hybrid
inflation turns to be the best choice.In both cases, we find an analytic
formula relating the inflaton mass with r (tensor/scalar ratio) and the scalar
spectral index ns: 10^6 m/M_{Pl} = 127 sqrt{r|1-n_s|} where the numerical
coefficient follows from the WMAP amplitude. We review quantum phenomena during
inflation which contribute to relevant observables in the CMB anisotropies and
polarization and we focus on inflaton decay.The deviation from the scale
invariant power spectrum is measured by a small parameter Delta.Delta regulates
the infrared divergences too.In slow roll inflation, Delta is a simple function
of the slow roll parameters. The quantum fluctuations can selfdecay in the
inflationary expansion through processes forbidden in Minkowski. We compute the
self-decay of the inflaton quantum fluctuations during slow roll:superhorizon
fluctuations decay as eta^{Gamma} in conformal time where the new scaling
dimension Gamma is expressed in terms of the amplitude, n_s and r. we discuss
the implications for scalar and tensor perturbations as well as for non
gaussianities.


title: Runaway collisions in young star clusters. I. Methods and tests

abstract:
  We present the methods and preparatory work for our study of the collisional
runaway scenario to form a very massive star (VMS, M > 400 Msun) at the centre
of a young, compact stellar cluster. In the first phase of the process, a very
dense central core of massive stars (M =~ 30-120 Msun) forms through mass
segregation and gravothermal collapse. This leads to a collisional stage,
likely to result in the formation of a VMS (itself a possible progenitor for an
intermediate-mass black hole) through a runaway sequence of mergers between the
massive stars. In this paper we present the runaway scenario in a general
astrophysical context. We then explain the numerical method used to investigate
it. Our approach is based on a Monte Carlo code to simulate the stellar
dynamics of spherical star clusters using a very large number of particles (a
few 1e5 to several 1e6). Finally, we report on test computations carried out to
ensure that our implementation of the important physics is sound. In a second
paper, we present results from more than 100 cluster simulations realized to
determine the conditions leading to the collisional formation of a VMS and the
characteristics of the runaway sequences.


title: Runaway collisions in young star clusters. II. Numerical results

abstract:
  We present a new study of the collisional runaway scenario to form an
intermediate-mass black hole (IMBH, MBH > 100 Msun) at the centre of a young,
compact stellar cluster. The first phase is the formation of a very dense
central core of massive stars (Mstar =~ 30-120 Msun) through mass segregation
and gravothermal collapse. Previous work established the conditions for this to
happen before the massive stars evolve off the main sequence (MS). In this and
a companion paper, we investigate the next stage by implementing direct
collisions between stars. Using a Monte Carlo stellar dynamics code, we follow
the core collapse and subsequent collisional phase in more than 100 models with
varying cluster mass, size, and initial concentration. Collisions are treated
either as ideal, ``sticky-sphere'' mergers or using realistic prescriptions
derived from 3-D hydrodynamics computations. In all cases for which the core
collapse happens in less than the MS lifetime of massive stars (~3 Myr), we
obtain the growth of a single very massive star (VMS, Mstar =~ 400-4000 Msun)
through a runaway sequence of mergers. Mass loss from collisions, even for
velocity dispersions as high as sigma1D ~ 1000 km/s, does not prevent the
runaway. The region of cluster parameter space leading to runaway is even more
extended than predicted in previous work because, in clusters with sigma1D >
300 km/s, collisions accelerate (and, in extreme cases, drive) core collapse.
Although the VMS grows rapidly to > 1000 Msun in models exhibiting runaway, we
cannot predict accurately its final mass. This is because the termination of
the runaway process must eventually be determined by a complex interplay
between stellar dynamics, hydrodynamics, and the stellar evolution of the VMS.
[abridged]


title:
The Chandra Observation of the Shell of Nova Persei 1901 (GK Persei):
  Detection of localized Non-thermal X-ray Emission from a Miniature Supernova
  Remnant

abstract:
  I present the data of the shell of classical Nova Persei (1901) obtained by
the Advanced CCD Imaging Spectrometer S3 detector on-board \cha Observatory.
The X-ray nebula is affected mostly by the complex interstellar medium around
the nova and has not developed a regular shell with bulk of emission coming
from the southwestern quadrant. The part of the bright zone that is co-spatial
with the brightest non-thermal radio emission region, is found to be a source
of non-thermal X-ray emission with a power law photon index of
2.3$^{+1.5}_{-0.9}$ and alpha=0.68^${+0.03}_{-0.15}$ at about a flux of
1.7x10^{-13} erg cm^{-2} s^{-1}. There are strong indications for nonlinear
diffusive shock acceleration occurring in the forward shock/transition zone
with an upper limit on the non-thermal X-ray flux of 1.0\times 10^{-14} erg
cm^{-2} s^{-1}.The total X-ray spectrum of has two components of emission. The
component dominant below 2 keV is most likely a non-equilibrium ionization
thermal plasma of kT_s=0.1-0.3 keV with an X-ray flux of 1.6x10^{-11} erg
cm^{-2} s^{-1}. There is also a higher temperature, kT_s=0.5-2.6 keV, embedded,
N_H=(4.0-22.0)x10^{22} cm^{-2}, emission component prominent above 2 keV. The
unabsorbed X-ray flux from this component is 1.5x10^{-10} erg cm^{-2} s^{-1}.
The X-ray emitting plasma is of solar composition except for enhancement in the
elemental abundances (mean abundances over the remnant)of Ne/Ne$_{\odot}$ and
N/N$_{\odot}$ in a range 13-21 and 1-5, respectively. A distinct emission line
of neon, He-like Ne IX, is detected which reveals a distribution of several
emission knots/blobs and shows a cone-like structure with wings extending
toward NW and SE at expansion velocities about 2600 km s^{-1} in the X-rays.


title:
A Deep Chandra Survey of the Globular Cluster 47 Tucanae: Catalog of
  Point Sources

abstract:
  We have detected 300 X-ray sources within the half-mass radius (2.79') of the
globular cluster 47 Tucanae in a deep (281 ks) Chandra exposure. We perform
photometry and simple spectral fitting for our detected sources, and construct
luminosity functions, X-ray color-magnitude and color-color diagrams.
Eighty-seven X-ray sources show variability on timescales from hours to years.
Thirty-one of the new X-ray sources are identified with chromospherically
active binaries from the catalogs of Albrow et al. The radial distributions of
detected sources imply roughly 70 are background sources of some kind. Most
source spectra are well-fit by thermal plasma models, except for quiescent
low-mass X-ray binaries (qLMXBs, containing accreting neutron stars) and
millisecond pulsars (MSPs). We identify three new candidate qLMXBs with
relatively low X-ray luminosities. One of the brightest cataclysmic variables
(CVs, X10) shows evidence (a 4.7 hour period pulsation and strong soft X-ray
emission) for a magnetically dominated accretion flow as in AM Her systems.
Most of the bright CVs require intrinsic N_H columns of order 10^{21} cm^-2,
suggesting a possible DQ Her nature. A group of X-ray sources associated with
bright (sub)giant stars also requires intrinsic absorption. By comparing the
X-ray colors, luminosities, variability, and quality of spectral fits of the
detected MSPs to those of unidentified sources, we estimate that a total of
\~25-30 MSPs exist in 47 Tuc (<60 at 95% confidence), regardless of their radio
beaming fraction. We estimate that the total number of neutron stars in 47 Tuc
is of order 300, reducing the discrepancy between theoretical neutron star
retention rates and observed neutron star populations in globular clusters.
(Abstract truncated.)


title: X-ray Binaries in the Globular Cluster 47 Tucanae

abstract:
  Chandra observations of globular clusters provide insight into the formation,
evolution, and X-ray emission mechanisms of X-ray binary populations. Our
recent (2002) deep observations of 47 Tuc allow detailed study of its
populations of quiescent LMXBs, CVs, MSPs, and active binaries (ABs). First
results include the confirmation of a magnetic CV in a globular cluster, the
identification of 31 additional chromospherically active binaries, and the
identification of three additional likely quiescent LMXBs containing neutron
stars. Comparison of the X-ray properties of the known MSPs in 47 Tuc with the
properties of the sources of uncertain nature indicates that relatively few
X-ray sources are MSPs, probably only ~30 and not more than 60. Considering the
\~30 implied MSPs and 5 (candidate) quiescent LMXBs, and their canonical
lifetimes of 10 and 1 Gyr respectively, the relative birthrates of MSPs and
LMXBs in 47 Tuc are comparable.


title: The Southern Galactic Plane Survey: HI Observations and Analysis

abstract:
  We describe the HI component of the Southern Galactic Plane Survey (SGPS).
The SGPS is a large-scale project to image at arcminute resolution the HI
spectral line and 21 cm continuum emission in parts of the plane of the Milky
Way. The survey covers Galactic longitudes 253 deg < l < 358 deg and latitudes
|b| <1.5 deg (SGPS I), plus a first quadrant extension covering 5 deg < l < 20
deg and |b| <1.5 deg (SGPS II). The survey combines data from the Australia
Telescope Compact Array and the Parkes Radio Telescope for sensitivity to
angular scales ranging from 2 arcminutes to several degrees. The combined data
cover 325 sq-deg and have an rms sensitivity of 1.6 K. Here we describe the HI
observations and data reduction in detail, and present examples from the final
data products. The complete dataset is publicly available through the Australia
Telescope National Facility's HI Surveys archive. This dataset provides an
unprecedented view of the neutral component of interstellar hydrogen in the
inner Milky Way.


title: Simulations of Dust in Interacting Galaxies I: Dust Attenuation

abstract:
  A new Monte-Carlo radiative-transfer code, Sunrise, is used in conjunction
with hydrodynamic simulations of major galaxy mergers to calculate the effects
of dust in such systems. The simulations are in good agreement with
observations of dust absorption in starburst galaxies, and the dust has a
profound effect on their appearance. The dust attenuation increases with
luminosity such that at peak luminosities ~90% of the bolometric luminosity is
absorbed by dust. In general, the detailed appearance of the merging event
depends on the stage of the merger and the geometry of the encounter. The
fraction of bolometric energy absorbed by the dust, however, is a robust
quantity that can be predicted from the intrinsic properties bolometric
luminosity, baryonic mass, star-formation rate, and metallicity of the system.
This paper presents fitting formulae, valid over a wide range of masses and
metallicities, from which the absorbed fraction of luminosity (and consequently
also the infrared dust luminosity) can be predicted. The attenuation of the
luminosity at specific wavelengths can also be predicted, albeit with a larger
scatter due to the variation with viewing angle. These formulae for dust
attenuation appear to be valid for both isolated and interacting galaxies, are
consistent with earlier studies, and would be suitable for inclusion in
theoretical models, e.g. semi-analytic models of galaxy formation.


title: The Intrinsic Alignment of Dark Halo Substructures

abstract:
  We investigate the intrinsic alignments of dark halo substructures with their
host halo major-axis orientations both analytically and numerically.
Analytically, we derive the probability density distribution of the angles
between the minor axes of the substructures and the major axes of their host
halos from the physical principles, under the assumption that the substructure
alignment on galaxy scale is a consequence of the tidal fields of the host halo
gravitational potential. Numerically, we use a sample of four cluster-scale
halos and their galaxy-scale substructures from recent high-resolution N-body
simulations to measure the probability density distribution. We compare the
numerical distribution with the analytic prediction, and find that the two
results agree with each other very well. We conclude that our analytic model
provides a quantitative physical explanation for the intrinsic alignment of
dark halo substructures. We also discuss the possibility of discriminating our
model from the anisotropic infall scenario by testing it against very large
N-body simulations in the future.


title:
Evaporation and Condensation of HI clouds in thermally bistable
  interstellar media: semi-analytic description of isobaric dynamics of curved
  interfaces

abstract:
  We analyze the evaporation and condensation of spherical and cylindrical HI
clouds of the cold neutral medium surrounded by the warm neutral medium.
Because the interstellar medium including those two phases is well described as
a thermally bistable fluid, it is useful to apply pattern formation theories to
the dynamics of the interface between the two phases. Assuming isobaric
evolution of fluids and a simple cubic form of the heat-loss function, we show
the curvature effects of the interface. We find that approximate solutions for
spherical clouds are in good agreement with numerically obtained solutions. We
extend our analysis to general curved fronts taking into account the curvature
effects explicitly. We find that the curvature effects always stabilise curved
interfaces under assumptions such as isobaric evolution we adopt in this
Letter.


title: RApid Temporal Survey - RATS I: Overview and first results

abstract:
  We present the aim and first results of the RApid Temporal Survey (RATS) made
using the Wide Field Camera on the Isaac Newton Telescope. Our initial survey
covers 3 square degrees, reaches a depth of V~22.5 and is sensitive to
variations on timescales as short as 2 minutes: this is a new parameter space.
Each field was observed for over 2 hours in white light, with 12 fields being
observed in total. Our initial analysis finds 46 targets which show significant
variations. Around half of these systems show quasi-sinusoidal variations: we
believe they are contact or short period binaries. We find 4 systems which show
variations on a timescale less than 1 hour. The shortest period system has a
period of 374 sec. We find two systems which show a total eclipse. Further
photometric and spectroscopic observations are required to fully identify the
nature of these systems. We outline our future plans and objectives.


title: A Bayesian approach to filter design: detection of compact sources

abstract:
  We consider filters for the detection and extraction of compact sources on a
background. We make a one-dimensional treatment (though a generalization to two
or more dimensions is possible) assuming that the sources have a Gaussian
profile whereas the background is modeled by an homogeneous and isotropic
Gaussian random field, characterized by a scale-free power spectrum. Local peak
detection is used after filtering. Then, a Bayesian Generalized Neyman-Pearson
test is used to define the region of acceptance that includes not only the
amplification but also the curvature of the sources and the a priori
probability distribution function of the sources. We search for an optimal
filter between a family of Matched-type filters (MTF) modifying the filtering
scale such that it gives the maximum number of real detections once fixed the
number density of spurious sources. We have performed numerical simulations to
test theoretical ideas.


title:
Near-Infrared Observations of RR Lyrae variables in Galactic Globular
  Clusters: I. The case of M92

abstract:
  We present near-infrared J,H, and K-band time series observations of the
Galactic Globular Cluster (GGC) M92. On the basis of these data, we derived
well-sampled light curves for eleven out of the seventeen cluster RR Lyrae
variables, and in turn, accurate mean near-infrared (NIR) magnitudes. The
comparison between predicted and empirical slopes of NIR Period-Luminosity (PL)
relations indicates a very good agreement. Cluster distance determinations
based on independent theoretical NIR $PL$ relations present uncertainties
smaller than 5% and agree quite well with recent distance estimates based on
different distance indicators. We also obtained accurate and deep NIR
color-magnitude diagrams (CMDs) ranging from the tip of the Red Giant Branch
(RGB) down to the Main Sequence Turn-Off. We detected the RGB bump and the NIR
luminosities of this evolutionary feature are, within theoretical and empirical
uncertainties, in good agreement with each other.


title:
Star formation in unbound giant molecular clouds: the origin of OB
  associations?

abstract:
  We investigate the formation of star clusters in an unbound GMC, where the
supporting kinetic energy is twice as large as the cloud's self-gravity. This
cloud manages to form a series of star clusters and disperse, all within
roughly 2 crossing times (10 Myr), supporting recent claims that star formation
is a rapid process. Simple assumptions about the nature of the star formation
occurring in the clusters allows us to place an estimate for the star formation
efficiency at about 5 to 10 %, consistent with observations. We also propose
that unbound clouds can act as a mechanism for forming OB associations. The
clusters that form in the cloud behave as OB subgroups. These clusters are
naturally expanding from one another due to unbound nature of the flows that
create them. The properties of the cloud we present here are are consistent
with those of classic OB associations.


title:
Electromagnetic waves with negative phase velocity in Schwarzschild-de
  Sitter spacetime

abstract:
  The propagation of electromagnetic plane waves with negative phase velocity
(NPV) is considered in Schwarzschild-(anti-)de Sitter spacetime. It is
demonstrated that NPV propagation occurs in Schwarzschild-de Sitter spacetime
at lower values of the cosmological constant than is the case for de Sitter
spacetime. Furthermore, we report that neither is NPV propagation observed in
Schwarzschild-anti-de Sitter spacetime, nor is it possible outside the event
horizon of a Schwarzschild blackhole.


title:
An Extended Grid of Nova Models: II. The Parameter Space of Nova
  Outbursts

abstract:
  This paper is a sequel to an earlier paper devoted to multiple, multicycle
nova evolution models (Prialnik & Kovetz 1995, first paper of the series),
which showed that the different characteristics of nova outbursts can be
reproduced by varying the values of three basic and independent parameters: the
white dwarf mass-M_{WD}, the temperature of its isothermal core-T_{WD} and the
mass transfer rate-Mdot. Apart from being the largest computational classical
novae parameter-space survey, we show here that the parameter space is
constrained by several analytical considerations and find its limiting
surfaces. Consequently, we extend the grid of multicycle nova evolution models
presented in Paper I almost to its limits, adding multicycle nova outburst
calculations for a considerable number of new parameter combinations. In
particular, the extended parameter pace that produces nova eruptions includes
low mass transfer rates down to 5e-13 Msun/yr, and more models for low T_{WD}.
Resulting characteristics of these runs are added to the former parameter
combination results, to provide a full grid spanning the entire parameter space
for Carbon-Oxygen white dwarfs. The full grid covers the entire range of
observed nova characteristics, even those of peculiar objects, which have not
been numerically reproduced until now. Most remarkably, runs for very low Mdot
lead to very high values for some characteristics, such as outburst amplitude
A>~20, high super-Eddington luminosities at maximum, heavy element abundance of
the ejecta Z_{ej}~0.63 and high ejected masses m_{ej}~7e-4 Msun.


title: X-rays from accretion shocks in T Tauri stars: The case of BP Tau

abstract:
  We present an XMM-Newton observation of the classical T Tauri star BP Tau. In
the XMM-Newton RGS spectrum the O {\sc vii} triplet is clearly detected with a
very weak forbidden line indicating high plasma densities and/or a high UV flux
environment. At the same time concurrent UV data point to a small hot spot
filling factor suggesting an accretion funnel shock as the site of the X-ray
and UV emission. Together with the X-ray data on TW Hya these new observations
suggest such funnels to be a general feature in classical T Tauri stars.


title:
Temporal Correlation of Hard X-rays and Meter/Decimeter Radio Structures
  in Solar Flares

abstract:
  We investigate the relative timing between hard X-ray (HXR) peaks and
structures in metric and decimetric radio emissions of solar flares using data
from the RHESSI and Phoenix-2 instruments. The radio events under consideration
are predominantly classified as type III bursts, decimetric pulsations and
patches. The RHESSI data are demodulated using special techniques appropriate
for a Phoenix-2 temporal resolution of 0.1s. The absolute timing accuracy of
the two instruments is found to be about 170 ms, and much better on the
average. It is found that type III radio groups often coincide with enhanced
HXR emission, but only a relatively small fraction ($\sim$ 20%) of the groups
show close correlation on time scales $<$ 1s. If structures correlate, the HXRs
precede the type III emissions in a majority of cases, and by 0.69$\pm$0.19 s
on the average. Reversed drift type III bursts are also delayed, but
high-frequency and harmonic emission is retarded less. The decimetric
pulsations and patches (DCIM) have a larger scatter of delays, but do not have
a statistically significant sign or an average different from zero. The time
delay does not show a center-to-limb variation excluding simple propagation
effects. The delay by scattering near the source region is suggested to be the
most efficient process on the average for delaying type III radio emission.


title: Galaxy Clusters and Dark Matter Properties

abstract:
  Laboratory experiments, large-scale computer simulations and observational
cosmology have begun to make progress in the campaign to identify the particle
responsible for gravitationally-inferred dark matter. In this contribution we
discuss the dark matter density profiles in the cores of nearby galaxy clusters
and estimate the gamma-ray flux expected for MSSM dark matter over a range of
neutralino masses.


title: Statistical Properties of Dissipative MHD Accelerators

abstract:
  We use exact orbit integration to investigate particle acceleration in a
Gauss field proxy of magnetohydrodynamic (MHD) turbulence. Regions where the
electric current exceeds a critical threshold are declared to be `dissipative'
and endowed with super-Dreicer electric field ${\bf E}_\Omega = \eta {\bf j}$.
In this environment, test particles (electrons) are traced and their
acceleration to relativistic energies is studied. As a main result we find that
acceleration mostly takes place within the dissipation regions, and that the
momentum increments have heavy (non-Gaussian) tails, while the waiting times
between the dissipation regions are approximately exponentially distributed
with intensity proportional to the particle velocity. No correlation between
the momentum increment and the momentum itself is found. Our numerical results
suggest an acceleration scenario with ballistic transport between independent
`black box' accelerators.


title:
Filter design for the detection of compact sources based on the
  Neyman-Pearson detector

abstract:
  This paper considers the problem of compact source detection on a Gaussian
background in 1D. Two aspects of this problem are considered: the design of the
detector and the filtering of the data. Our detection scheme is based on local
maxima and it takes into account not only the amplitude but also the curvature
of the maxima. A Neyman-Pearson test is used to define the region of
acceptance, that is given by a sufficient linear detector that is independent
on the amplitude distribution of the sources. We study how detection can be
enhanced by means of linear filters with a scaling parameter and compare some
of them (the Mexican Hat wavelet, the matched and the scale-adaptive filters).
We introduce a new filter, that depends on two free parameters (biparametric
scale-adaptive filter). The value of these two parameters can be determined,
given the a priori pdf of the amplitudes of the sources, such that the filter
optimizes the performance of the detector in the sense that it gives the
maximum number of real detections once fixed the number density of spurious
sources. The combination of a detection scheme that includes information on the
curvature and a flexible filter that incorporates two free parameters (one of
them a scaling) improves significantly the number of detections in some
interesting cases. In particular, for the case of weak sources embedded in
white noise the improvement with respect to the standard matched filter is of
the order of 40%. Finally, an estimation of the amplitude of the source is
introduced and it is proven that such an estimator is unbiased and it has
maximum efficiency. We perform numerical simulations to test these theoretical
ideas and conclude that the results of the simulations agree with the
analytical ones.


title: Detection of point sources on two-dimensional images based on peaks

abstract:
  This article considers the detection of point sources in two dimensional
astronomical images. The detection scheme we propose is based on peak
statistics. We discuss the example of the detection of far galaxies in Cosmic
Microwave Background experiments throughout the paper, although the method we
present is totally general and can be used in many other fields of data
analysis. We assume sources with a Gaussian profile --that is a fair
approximation of the profile of a point source convolved with the detector beam
in microwave experiments-- on a background modeled by a homogeneous and
isotropic Gaussian random field characterized by a scale-free power spectrum.
Point sources are enhanced with respect to the background by means of linear
filters. After filtering, we identify local maxima and apply our detection
scheme, a Neyman-Pearson detector that defines our region of acceptance based
on the a priori pdf of the sources and the ratio of number densities. We study
the different performances of some linear filters that have been used in this
context in the literature: the Mexican Hat wavelet, the matched filter and the
scale-adaptive filter. We consider as well an extension to two dimensions of
the biparametric scale adaptive filter (BSAF). The BSAF depends on two
parameters which are determined by maximizing the number density of real
detections while fixing the number density of spurious detections. For our
detection criterion the BSAF outperforms the other filters in the interesting
case of white noise.


title: X-ray sources in globular clusters of other galaxies

abstract:
  A large number of X-ray sources in globular clusters of galaxies other than
the Milky Way has been found with Chandra. We discuss three issues relating to
these sources. The X-ray luminosity function (XLF) of the sources in globular
clusters of M31 is marginally compatible with the XLF of globular clusters of
the Milky Way. The individual XLFs of a dozen elliptical galaxies, after
correction for incompleteness, are compatible with one another and show no
break; however, the XLF found by adding the individual XLFs of elliptical
galaxies has a break at L_x about 5x10(38) ergs/s. For the moment there is no
evidence for a difference between the XLFs of sources inside and outside
globular clusters of elliptical galaxies. It is not (yet?) possible to decide
which fraction of low-mass X-ray binaries in elliptical galaxies outside
globular clusters have formed inside globular clusters.


title: QPOs in Cataclysmic Variables and in X-ray Binaries

abstract:
  Recent observations, reported by Warner and Woudt, of Dwarf Nova Oscillations
(DNOs) exhibiting frequency drift, period doubling, and 1:2:3 harmonic
structure, can be understood as disc oscillations that are excited by
perturbations at the spin frequency of the white dwarf or of its equatorial
layers. Similar quasi-periodic disc oscillations in black hole low-mass X-ray
binary (LMXB) transients in a 2:3 frequency ratio show no evidence of frequency
drift and correspond to two separate modes of disc oscillation excited by an
internal resonance. Just as no effects of general relativity play a role in
white dwarf DNOs, no stellar surface or magnetic field effects need be invoked
to explain the black hole QPOs.


title:
MOJAVE: Monitoring of Jets in AGN with VLBA Experiments - I. First-Epoch
  15 GHz Linear Polarization Images

abstract:
  We present first-epoch, milliarcsecond-scale linear polarization images at 15
GHz of 133 jets associated with AGN in the MOJAVE survey (Monitoring of Jets in
Active Galactic Nuclei with VLBA Experiments). The sample consists of all known
AGN with galactic latitude |b| > 2.5 deg., J2000 declination > -20 deg., and 15
GHz VLBA flux density exceeding 1.5 Jy (2 Jy for sources with declination < 0)
at any epoch during the period 1994-2003. Because of strong selection effects,
the sample primarily consists of blazars with parsec-scale morphologies
consisting of a bright core component at the extreme end of a one-sided jet. At
least one third of the compact cores are completely unresolved on the longest
VLBA baselines, indicating brightness temperatures above 10^{11} K. The
unresolved cores tend to have electric vectors that are aligned with the inner
jet direction, suggesting the presence of a stationary transverse shock near
the base of the jet. Many of the extended jet regions display exceedingly high
fractional polarizations (> 50%) and electric vectors aligned with the jet
ridge line, consistent with optically thin emission from transverse shocks.
Both weak- and strong-lined blazars show a general increase in fractional
polarization with distance down the jet, but BL Lac jets are generally more
polarized and have electric vectors preferentially aligned with the local jet
direction. We show that these differences are intrinsic to the jets, and not
due to sample bias. Distinct features in the jets of gamma-ray loud (EGRET)
blazars are typically twice as luminous as those in non-EGRET blazars, and are
more polarized. These differences can be adequately explained if EGRET blazars
have slightly higher Doppler boosting factors than those not yet detected in
gamma-rays.


title: A Virgo high-resolution Halpha kinematical survey: I. NGC 4438

abstract:
  New Halpha emission-line observations of the Virgo cluster galaxy NGC 4438
are presented. Fabry-Perot interferometry data at an effective angular
resolution of
  ~2" are used to map the kinematics of the ionized gas in the galaxy. For the
first time we obtain a velocity field covering a large area in NGC 4438, much
larger than that deduced from previous HI and CO maps. The kinematics of the
extended, low surface brightness Halpha filaments to the West of the galactic
disk is discussed. We report on the discovery of a northern Halpha structure
which is clumpier than the other filaments. Evidence for multiple spectral
components through the data-cube are presented in a nuclear shell and in the
approaching half of the disk. The role of VCC 1040, a dwarf elliptical galaxy
located to the South of NGC 4438, is presented to investigate the origin of a
small-scale stellar tail of NGC 4438. It could be due to a minor tidal
interaction between the two galaxies.


title:
A deep Chandra observation of the Centaurus cluster: bubbles, filaments
  and edges

abstract:
  X-ray images and gas temperatures taken from a deep ~200 ks Chandra
observation of the Centaurus cluster are presented. Multiple inner bubbles and
outer semicircular edges are revealed, together with wispy filaments of soft
X-ray emitting gas. The frothy central structure and eastern edge are likely
due to the central radio source blowing bubbles in the intracluster gas. The
semicircular edges to the surface brightness maps 32kpc to the east and 17.5kpc
to the west are marked by sharp temperature increases and abundance drops. The
edges could be due to sloshing motions of the central potential, or are
possibly enhanced by earlier radio activity. The high abundance of the
innermost gas (about 2.5 times Solar) limits the amount of diffusion and mixing
taking place.


title: Properties of galactic B[e] supergiants. IV. Hen3-298 and Hen3-303

abstract:
  We present the results of optical and near-IR spectroscopic and near-IR
photometric observations of the emission-line stars Hen3-298 and Hen3-303.
Strong emission in the H-alpha line is found in both objects. The presence of
Fe II and [O I] emission lines in the spectrum of Hen3-298 indicates that it is
a B[e] star. The double-peaked CO line profiles, found in the infrared spectrum
of Hen3-298, along with the optical line profiles suggest that the star is
surrounded by a rotating circumstellar disk. Both objects also show infrared
excesses, similar to those of B[e] stars. The radial velocities of the
absorption and emission lines as well as a high reddening level suggest that
the objects are located in the Norma spiral arm at a distance of 3-4.5 kpc. We
estimated a luminosity of log (L/L_sun) ~ 5.1 and a spectral type of no earlier
than B3 for Hen3-298. Hen3-303 seems to be a less luminous B-type object (log
(L/L_sun) ~ 4.3), located in the same spiral arm.


title: Tracing the Nuclear Accretion History of the Red Galaxy Population

abstract:
  We investigate the evolution of the hard X-ray luminosity of the red galaxy
population using a large sample of 3316 red galaxies selected over a wide range
in redshift (0.3<z<0.9) from a 1.4 deg^2 region in the Bootes field of the NOAO
Deep Wide-Field Survey (NDWFS). The red galaxies are early-type,
bulge-dominated galaxies and are selected to have the same evolution corrected,
absolute R-band magnitude distribution as a function of redshift to ensure we
are tracing the evolution in the X-ray properties of a comparable optical
population. Using a stacking analysis of 5-ks Chandra/ACIS observations within
this field to study the X-ray emission from these red galaxies in three
redshift bins, we find that the mean X-ray luminosity increases as a function
of redshift. The large mean X-ray luminosity and the hardness of the mean X-ray
spectrum suggests that the X-ray emission is largely dominated by AGN rather
than stellar sources. The hardness ratio can be reproduced by either an
absorbed (N_H ~2 x 10^22 cm^-2) Gamma=1.7 power-law source, consistent with
that of a population of moderately obscured Seyfert-like AGN, or an unabsorbed
Gamma=0.7 source suggesting a radiatively inefficient accretion flow (e.g., an
advection-dominated accretion flow). We also find that the emission from this
sample of red galaxies constitutes at least 5% of the hard X-ray background.
These results suggest a global decline in the mean AGN activity of normal
early-type galaxies from z~1 to the present, which indicates that we are
witnessing the tailing off of the accretion activity onto SMBHs in early-type
galaxies since the quasar epoch.


title: Seismic constraints on open clusters

abstract:
  We derive knowledge on the global and structural parameters of low-mass stars
using asteroseismology and taking advantage of the stellar collective behavior
within open clusters. We build stellar models and compute the seismic signal
expected from main sequence objects in the 0.8-1.6 Msun range. We first
evaluate apparent magnitudes and oscillations-induced luminosity fluctuations
expected in the Hyades, the Pleiades and the alpha Persei clusters. The closest
cluster presents a feasible challenge to observational asteroseismology in the
present and near future. We combine seismological and classical computations to
address three questions: what can be inferred about 1) mass, 2) composition and
3) extension of outer convection zones of solar analogs in the Hyades. The
first issue relies on the strong sensitivity of the large separation to mass.
Then large separations and second differences are used to respectively
constrain metal and helium fractions in the Hyades.When plotted for several
masses, the relation of effective temperature vs large separation is found to
be strongly dependent on the metal content. Besides this the second difference
main modulation is related to the second ionization of helium.The second
difference modulations are also partly due to the discontinuity in stellar
stratification at the convective envelope / radiative core transition. They
permit direct insight in the stellar structure. We compute acoustic radii of
the convective bases for different values of the mixing length theoryparameter
alpha_MLT in convection modelling, i.e. different convective efficiency in the
superadiabatic layers. For a given effectivetemperature we show that the
acoustic radius changes with convection efficiency.


title: Radial Velocities of Newly Discovered Globular Clusters in NGC 5128

abstract:
  We present radial velocity measurements for 74 globular clusters (GCs) in the
nearby giant elliptical NGC 5128, of which 31 are newly discovered clusters.
All the GC candidates were taken from the list of possible new clusters given
in the Harris, Harris, & Geisler (2004) photometric survey. In addition to the
newly confirmed clusters, we identified 24 definite foreground stars and 31
probable background galaxies. From a combined list of 299 known GCs in NGC 5128
with measured radial velocities and metallicity-sensitive (C - T_1) photometric
indices, we construct a new metallicity distribution function (MDF) for the
cluster system. The MDF shows an approximately bimodal form, with centroids at
[Fe/H] = -1.46 and -0.53, and with nearly equal numbers of metal-poor and
metal-rich clusters in the two modes. However, there are many
intermediate-color clusters in the distribution, and the fainter clusters tend
to have a higher proportion of red clusters. These features of the MDF may
indicate a widespread age range within the cluster system as well as an
intrinsically broad metallicity spread.


title:
Cepheid Calibrations from the Hubble Space Telescope of the Luminosity
  of Two Recent Type Ia Supernovae and a Re-determination of the Hubble
  Constant

abstract:
  We report observations of two nearby Type Ia supernovae (SNe Ia) for which
observations of Cepheid variables in the host galaxies have been obtained with
the Hubble Space Telescope: SN 1994ae in NGC 3370 and SN 1998aq in NGC 3982.
For NCG 3370, we used the Advanced Camera for Surveys to observe 64 Cepheids
that yield a distance of 29 Mpc, the farthest direct measurement of Cepheids.
We have measured emission lines from H II regions in both host galaxies which
provide metallicity-dependent corrections to their period-luminosity relations.
These two SNe Ia double the sample of ``ideal'' luminosity calibrators: objects
with well-observed and well-calibrated light curves of typical shape and with
low reddening. By comparing them to all similarly well-measured SNe Ia in the
Hubble flow, we find that H_0 = 73 +/- 4 (statistical) +/- 5 (systematic). A
detailed analysis demonstrates that most of the past disagreement over the
value of H_0 as determined from SNe Ia is abated by the replacement of past,
problematic data by more accurate and precise, modern data.


title: Second Order Geodesic Corrections to Cosmic Shear

abstract:
  We consider the impact of second order corrections to the geodesic equation
governing gravitational lensing. We start from the full second order metric,
including scalar, vector and tensor perturbations, and retain all relevant
contributions to the cosmic shear corrections that are second order in the
gravitational potential. The relevant terms are: the nonlinear evolution of the
scalar gravitational potential, the Born correction, and lens-lens coupling. No
other second order terms contribute appreciably to the lensing signal. Since
ray-tracing algorithims currently include these three effects, this derivation
serves as rigorous justification for the numerical predictions.


title: On the variation of the fine-structure constant in Friedmann Universes

abstract:
  The fine-structure constant alpha does not vary as Friedmann Universes
evolve, a conclusion based on assessments of quantum mechanics and
electrodynamics. alpha = e^2/(4pi epsilon hbar c), where e is the charge of the
electron, epsilon is vacuum permittivity, c is the speed of light, and hbar is
Planck's constant divided by 2pi. This inquiry was motivated by Schrodinger's
(1939) prediction that all quantum wave functions coevolve with Friedmann
geometry and a similar prediction by Sumner (1994) for vacuum permittivity. The
functional form of variations in quantum wave functions found by Schrodinger is
enough to show that alpha does not vary. Electrodynamics also predicts that
alpha does not vary. Evolutionary changes in c exactly cancel those in vacuum
permittivity and other factors in alpha do not change. Since alpha appears in
all first-order perturbation formulas for atomic energy levels, comparisons of
the atomic spectra of distant atoms with those in laboratories provide an
experimental measure of this prediction. Most experiments find changes in alpha
that are either statistically zero or very small. These results and estimates
of the Hubble constant and deceleration parameter from precision
redshift/magnitude data support a major assumption of this paper that the
Friedmann solution to Einstein's theory of general relativity without
cosmological constant is an adequate approximation to spacetime geometry and
its long term evolution at quantum scales.


title: A Thermal Graviton Background from Extra Dimensions

abstract:
  Inflationary cosmology predicts a low-amplitude graviton background across a
wide range of frequencies. This Letter shows that if one or more extra
dimensions exist, the graviton background may have a thermal spectrum instead,
dependent on the fundamental scale of the extra dimensions. The energy density
is shown to be significant enough that it can affect nucleosynthesis in a
substantial way. The possibility of direct detection of a thermal graviton
background using the 21-cm hydrogen line is discussed. Alternative explanations
for the creation of a thermal graviton background are also examined.


title:
Gravitational cooling and density profile near caustics in collisionless
  dark matter haloes

abstract:
  Cold dark matter haloes are populated by high-density structures with
sharply-peaked profiles known as caustics which have not yet been resolved by
3-dimensional numerical simulations. Here, we derive semi-analytic expressions
for the density profiles near caustics in haloes which form by self-similar
accretions of dark matter with infinitesimal velocity dispersion. A simple
rescaling shows that similarly to the case of absolutely cold medium these
profiles are universal: they are valid for all caustics and irrespective of
physical parameters of the halo. We derive the maximum density of the caustics
and show that it depends on the velocity dispersion and the caustic location.
We show that both the absolute and relative thickness of the caustic
monotonically decrease toward the center of the halo while the maximum density
grows. This indicates that the radial component of the thermal velocities
decreases in the inner streams, i.e. the collisionless medium cools down in the
radial direction descending to the center of the halo. Finally, we demonstrate
that there can be a significant contribution to the emission measure from dark
matter particle annihilation in the caustics.


title:
The Assembly History of Field Spheroidals: Evolution of Mass-to-light
  Ratios and Signatures of Recent Star Formation

abstract:
  We present a comprehensive catalog of high signal-to-noise spectra obtained
with the DEIMOS spectrograph on the Keck II telescope for a sample of
F850LP<22.43 (AB) field spheroidal (E+S0s; 163) and bulge dominated disk (61)
galaxies in the redshift range 0.2<z<1.2. We examine the zero point, tilt and
scatter of the Fundamental Plane (FP) as a function of redshift and
morphological properties, carefully accounting for luminosity-dependent biases
via Montecarlo simulations. The evolution of the overall FP can be represented
by a mean change in effective mass-to-light ratio given by <d \log (M/L_{\rm
B})/dz>=-0.72^{+0.07}_{-0.05}\pm0.04. However, this evolution depends
significantly on the dynamical mass, being slower for larger masses as reported
in a previous letter. In addition, we separately show the intrinsic scatter of
the FP increases with redshift as d(rms(M/L_{\rm B}))/dz=0.040\pm0.015.
Although these trends are consistent with single burst populations which formed
at $z_f>2$ for high mass spheroidals and z_{f}~1.2 for lower mass systems, a
more realistic picture is that most of the stellar mass formed in all systems
at z>2 with subsequent activity continuing to lower redshifts (z<1.2). The
fraction of stellar mass formed at recent times depend strongly on galactic
mass, ranging from <1% for masses above 10^{11.5} M_{\odot} to 20-40% below
10^{11} M_{\odot}. Independent support for recent activity is provided by
spectroscopic ([\ion{O}{2}] emission, H\delta) and photometric (blue cores and
broad-band colors) diagnostics. Via the analysis of a large sample with many
independent diagnostics, we are able to reconcile previously disparate
interpretations of the assembly history of field spheroidals. [Abridged]


title:
Comparative Direct Analysis of Spectra of Type Ia Supernovae. I. SN
  1994D

abstract:
  As the first step in a comprehensive, comparative, direct analysis of the
spectra of Type Ia supernovae (SNe Ia), we use the parameterized supernova
synthetic-spectrum code, SYNOW, to interpret 26 spectra of the well-observed SN
1994D. Our results are consistent with the traditional view that the
composition structure (element abundance fractions versus ejection velocity) is
radially stratified. We find that resonance-scattering features due to
permitted lines of Ca II, Na I, and Fe II persist to more than 100 days after
explosion. The fitting parameters for SN 1994D, together with those to be
determined for other SNe Ia, will provide an internally consistent
quantification of the spectroscopic diversity among SNe Ia, and shed light on
how the various manifestations of observational diversity are related to their
physical causes.


title: The influence of non-uniform reionization on the CMB

abstract:
  We investigate the impact of spatial variations in the ionized fraction
during reionization on temperature anisotropies in the CMB. We combine
simulations of large scale structure to describe the underlying density field
with an analytic model based on extended Press-Schechter theory to track the
reionization process. We find that the power spectrum of the induced CMB
anisotropies depends sensitively on the character of the reionization epoch.
Models that differ in the extent of the "patchy phase" could be distinguished
by future experiments such as the Atacama Cosmology Telescope (ACT) and the
South Pole Telescope (SPT). In our models, the patchy signal peaks at $l\simeq
2000$, where it can be four times larger than the kinetic Sunyaev-Zel'dovich
(kSZ)/Ostriker-Vishniac (OV) signal ($\Delta T_{\rm tot} \simeq 2.6 \mu K$). On
scales beyond $l \simeq 4000$ the total Doppler signal is dominated by kSZ/OV,
but the patchy signal can contribute up to 30% to the power spectrum. The
effect of patchy reionization is largest on scales where the primordial CMB
anisotropies dominate. Ignoring this contribution could lead to significant
biases in the determination of cosmological parameters derived from CMB
temperature measurements. Improvements in the theoretical modeling of the
reionization epoch will become increasingly important to interpret the results
of upcoming experiments.


title:
Turbulence driven by outflow-blown cavities in the molecular cloud of
  NGC 1333

abstract:
  Outflows from young stellar objects have been identified as a possible source
of turbulence in molecular clouds. To investigate the relationship between
outflows, cloud dynamics and turbulence, we compare the kinematics of the
molecular gas associated with NGC 1333, traced in 13CO(1-0), with the
distribution of young stellar objects (YSOs) within. We find a velocity
dispersion of ~ 1-1.6 km/s in 13CO that does not significantly vary across the
cloud, and is uncorrelated with the number of nearby young stellar outflows
identified from optical and submillimeter observations. However, from velocity
channel maps we identify about 20 cavities or depressions in the 13CO intensity
of scales > 0.1-0.2 pc and velocity widths 1-3 km/s. The cavities exhibit limb
brightened rims in both individual velocity channel maps and position velocity
diagrams, suggesting that they are slowly expanding. We interpret these
cavities to be remnants of past YSO outflow activity: If these cavities are
presently empty, they would fill in on time scales of a million years. This can
exceed the lifetime of a YSO outflow phase, or the transit time of the central
star through the cavity, explaining the the absence of any clear correlation
between the cavities and YSO outflows. We find that the momentum and energy
deposition associated with the expansion of the cavities is sufficient to power
the turbulence in the cloud. In this way we conclude that the cavities are an
important intermediary step between the conversion of YSO outflow energy and
momentum into cloud turbulent motions.


title: Stellar and total mass in early-type lensing galaxies

abstract:
  For 18 well-observed gravitationally lensed QSOs, we compare new
non-parametric mass profiles for the lensing galaxies with stellar-population
models derived from published HST photometry. The large volume of parameter
space searched -- with respect to the possible star formation histories --
allows us to infer robust estimates and uncertainties for the stellar masses.
The most interesting results are: (1) the transition from little or no dark
matter in the inner regions (<r_e) to dark matter dominating on the ~5r_e scale
(~20 kpc) is clearly seen in massive ellipticals; (2) Such a trend is not seen
in lower-mass galaxies, so that the stellar content dominates the mass budget
out to ~5r_e; (3) the radial gradient in the dark-matter fraction for these
intermediate redshift galaxies agrees with published data on nearby galaxies.
This result can help reconcile the discrepancies found in recent estimates of
dark matter in elliptical galaxies using different techniques (e.g. Planetary
nebulae versus X-ray). The observed trend suggests the stellar component in
massive galaxies extends further out in terms of the dark matter scale radius.


title: The Phantom of the OPRA

abstract:
  The Observed Perlmutter-Riess Acceleration (OPRA) implies that the expansion
of the Universe is currently increasing and is motivation for the so-called
phantom energy models. We consider the dynamics of phantom scalar field models.
An important physical time constraint, which can be used to rule out many
cosmological models, is obtained from the condition that all forms of energy
density, including the field causing OPRA (e.g., the phantom field), must be
non-negligible for an extended period, which is conservatively estimated to be
of the order of a few $Gyr$. We find that this physical time constraint cannot
be satisfied in conventional phantom cosmological models.


title: Large Scale Structure at 24 Microns in the SWIRE Survey

abstract:
  We present initial results of galaxy clustering at 24um by analyzing
statistics of the projected galaxy distribution from counts-in-cells. This
study focuses on the ELAIS-N1 SWIRE field. The sample covers ~5.9
square-degrees and contains 24,715 sources detected at 24um to a 5.6-sigma
limit of 250 micro-Jy (in the lowest coverage regions). We have explored
clustering as a function of 3.6 - 24um color and 24um flux density using
angular-averaged two-point correlation functions derived from the variance of
counts-in-cells on scales 0.05-0.7 degrees. Using a power-law parameterization,
$w_{2}(\theta)=A(\theta/deg)^{1-\gamma}$, we find [A,\gamma] =
[(5.43\pm0.20)\times10^{-4},2.01\pm0.02] for the full sample (1-sigma errors
throughout). We have inverted Limber's equation and estimated a spatial
correlation length of $r_{0}=3.32\pm0.19 h^{-1}$Mpc for the full sample,
assuming stable clustering and a redshift model consistent with observed 24um
counts. We also find that blue [f(24)/f(3.6)<=5.5] and red [f(24)/f(3.6)>=6.5]
galaxies have the lowest and highest $r_{0}$ values respectively, implying that
redder galaxies are more clustered (by a factor of ~3 on scales >0.2 degree).
Overall, the clustering estimates are smaller than those derived from optical
surveys, but in agreement with results from IRAS and ISO in the mid-infrared.
This extends the notion to higher redshifts that infrared selected surveys show
weaker clustering than optical surveys.


title: Constraints on the distance to SGR 1806-20 from HI absorption

abstract:
  The giant flare detected from the magnetar SGR 1806-20 on 2004 December 27
had a fluence more than 100 times higher than the only two other SGR flares
ever recorded. Whereas the fluence is independent of distance, an estimate for
the luminosity of the burst depends on the source's distance, which has
previously been argued to be ~15 kpc. The burst produced a bright radio
afterglow, against which Cameron et al. (2005) have measured an HI absorption
spectrum. This has been used to propose a revised distance to SGR 1806-20 of
between 6.4 and 9.8 kpc. Here we analyze this absorption spectrum, and compare
it both to HI emission data from the Southern Galactic Plane Survey and to
archival 12-CO survey data. We confirm ~6 kpc, as a likely lower limit on the
distance to SGR 1806-20, but argue that it is difficult to place an upper limit
on the distance to SGR 1806-20 from the HI data currently available. The
previous value of ~15 kpc thus remains the best estimate of the distance to the
source.


title: Is the Number of Giant Arcs in LCDM Consistent With Observations?

abstract:
  We use high-resolution N-body simulations to study the galaxy-cluster
cross-sections and the abundance of giant arcs in the $\Lambda$CDM model.
Clusters are selected from the simulations using the friends-of-friends method,
and their cross-sections for forming giant arcs are analyzed. The background
sources are assumed to follow a uniform ellipticity distribution from 0 to 0.5
and to have an area identical to a circular source with diameter $1\arcsec$. We
find that the optical depth scales as the source redshift approximately as
$\tau_{1''} = 2.25 \times 10^{-6}/[1+(\zs/3.14)^{-3.42}]$ ($0.6<\zs<7$). The
amplitude is about 50% higher for an effective source diameter of $0.5\arcsec$.
The optimal lens redshift for giant arcs with the length-to-width ratio ($L/W$)
larger than 10 increases from 0.3 for $\zs=1$, to 0.5 for $\zs=2$, and to
0.7-0.8 for $\zs>3$. The optical depth is sensitive to the source redshift, in
qualitative agreement with Wambsganss et al. (2004). However, our overall
optical depth appears to be only $\sim$ 10% to 70% of those from previous
studies. The differences can be mostly explained by different power spectrum
normalizations ($\sigma_8$) used and different ways of determining the $L/W$
ratio. Finite source size and ellipticity have modest effects on the optical
depth. We also found that the number of highly magnified (with magnification
$|\mu|>10$) and ``undistorted'' images (with $L/W<3$) is comparable to the
number of giant arcs with $|\mu|>10$ and $L/W>10$. We conclude that our
predicted rate of giant arcs may be lower than the observed rate, although the
precise `discrepancy' is still unclear due to uncertainties both in theory and
observations.


title: Non-Thermal Emission from AGN Coronae

abstract:
  Accretion disk coronae are believed to account for X-ray emission in Active
Galactic Nuclei (AGNs). In this paper the observed emission is assumed to be
due to a population of relativistic, non-thermal electrons (e.g. produced in a
flare) injected at the top of an accretion disk magnetic loop. While electrons
stream along magnetic field lines their energy distribution evolves in time
essentially because of inverse Compton and synchrotron losses. The
corresponding time dependent emission due, in the X-ray energy range, to the
inverse Compton mechanism, has been computed. Since the typical decay time of a
flare is shorter than the integration time for data acquisition in the X-ray
domain, the resulting spectrum is derived as the temporal mean of the real,
time-dependent, emission, as originated by a series of consecutive and
identical flares. The model outcome is compared to both the broad band BeppoSAX
X-ray data of the bright Seyfert 1 NGC 5548, and to a few general X-ray
spectral properties of Seyfert 1s as a class. The good agreement between model
and observations suggests that the presently proposed non-thermal,
non-stationary model could be a plausible explanation of AGN X-ray emission, as
an alternative to thermal coronae models.


title: Effects of a solid surface on jet formation around neutron stars

abstract:
  We present two numerical simulations of an accretion flow from a rotating
torus onto a compact object with and without a solid surface -- representing a
neutron star and a black hole -- and investigate its influence on the process
of jet formation. We report the emergence of an additional ejection component,
launched by thermal pressure inside a boundary layer (BL) around the neutron
star and examine its structure. Finally, we suggest improvements for future
models.


title: Generating cosmological perturbations with mass variations

abstract:
  We study the possibility that large scale cosmological perturbations have
been generated during the domination and decay of a massive particle species
whose mass depends on the expectation value of a light scalar field. We discuss
the constraints that must be imposed on the field in order to remain light and
on the annihilation cross section and decay rate of the massive particles in
order for the mechanism to be efficient. We compute the resulting curvature
perturbations after the mass domination, recovering the results of Dvali,
Gruzinov, and Zaldarriaga in the limit of total domination. By comparing the
amplitude of perturbations generated by the mass domination to those originally
present from inflation, we conclude that this mechanism can be the primary
source of perturbations only if inflation does not rely on slow-roll
conditions.


title:
A concise reference to (projected) Sersic R^{1/n} quantities, including
  Concentration, Profile Slopes, Petrosian indices, and Kron Magnitudes

abstract:
  Given the growing use of Sersic's (1963, 1968) R^{1/n} model for describing
the stellar distributions in galaxies, and the lack of any single reference
that provides the various associated mathematical expressions, we have
endeavoured to compile such a resource here. We present the standard intensity
profile, and its various guises such as the luminosity, surface-brightness, and
aperture-magnitude profile. Expressions to transform the effective surface
brightness into the mean effective and central surface brightness are also
given, as is the expression to transform between effective radii and
exponential scale-lengths. We additionally provide expressions for deriving the
`concentration' of an R^{1/n} profile, and two useful equations for the
logarithmic slope of the light-profile are given. Petrosian radii and fluxes
are also derived for a range of Sersic profiles and compared with the effective
radii and total flux. Similarly, expressions to obtain Kron radii and fluxes
are presented as a function of the Sersic index n and the number of effective
radii sampled. Illustrative figures are provided throughout. Finally, the
core-Sersic model, consisting of an inner power-law and an outer-Sersic
function, is presented.


title: Core depletion from coalescing supermassive black holes

abstract:
  New measurements of the stellar-mass deficits at the centers of luminous
elliptical galaxies are presented. These were derived considering the following
observational facts. Firstly, ``core'' galaxies, which are thought to have had
their inner region depleted from the coalesence of supermassive black holes,
show an abrupt downward deviation of their inner light-profile relative to
their outer Sersic profile. Second, ``power-law'' galaxies, having undisturbed
profiles and no partially depleted core, have inner light-profiles that display
no departure from the inward extrapolation of their outer Sersic profile. The
central stellar deficits have therefore been derived from the difference in
flux between the HST-observed galaxy light-profiles and the inward
extrapolation of each galaxy's outer Sersic profile. This approach gives flux
deficits ~0.1% of the total galaxy light, and mass deficits that are ~2 times
each galaxy's central supermassive black hole mass. These results are in
agreement with the theoretical expectations of mass ejection from binary black
hole mergers and also with popular LCDM models of hierarchical galaxy
formation. It is also explained why this result is some 10 times smaller than
current observational estimates of the central mass deficit, and therefore
implies a merger history for giant elliptical galaxies that is one order of
magnitude less violent than previously suggested.


title: Prospects for Extrasolar "Earths" in Habitable Zones

abstract:
  We have shown that Earth-mass planets could survive in variously restricted
regions of the habitable zones (HZs) of most of a sample of nine of the 102
main-sequence exoplanetary systems confirmed by 19 November 2003. In a
preliminary extrapolation of our results to the other systems, we estimate that
roughly a half of these systems could have had an Earth-mass planet confined to
the HZ for at least the most recent 1000 Ma. The HZ migrates outwards during
the main-sequence lifetime, and so this proportion varies with stellar age.
About two thirds of the systems could have such a planet confined to the HZ for
at least 1000 Ma at sometime during the main-sequence lifetime. Clearly, these
systems should be high on the target list for exploration for terrestrial
planets. We have reached this conclusion by launching putative Earth-mass
planets in various orbits and following their fate with mixed-variable
symplectic and hybrid integrators. Whether the Earth-mass planets could form in
the HZs of the exoplanetary systems is an urgent question that needs further
study.


title:
86 GHz SiO maser survey of late-type stars in the Inner Galaxy III.
  Interstellar extinction and colours of the SiO targets

abstract:
  We have determined extinction corrections for a sample of 441 late-type stars
in the inner Galaxy, which we previously searched for SiO maser emission, using
the 2MASS near-infrared photometry of the surrounding stars. From this, the
near-infrared extinction law is found to be approximated by a power law
A$_\lambda \propto \lambda^{-1.9\pm0.1}$. Near- and mid-infrared colour-colour
properties of known Mira stars are reviewed. From the distribution of the
dereddened infrared colours of the SiO target stars we infer mass-loss rates
between $10^{-7}$ and $10^{-5}$ M$_\odot$ yr$^{-1}$.


title:
Monitoring of the prompt radio emission from the unusual supernova
  2004dj in NGC2403

abstract:
  Supernova 2004dj in the nearby spiral galaxy NGC2403 was detected optically
in July 2004. Peaking at a magnitude of 11.2, this is the brightest supernova
detected for several years. Here we present Multi-Element Radio Linked
Interferometer Network (MERLIN) observations of this source, made over a four
month period, which give a position of R.A. = 07h37m17.044s, Dec
=+65deg35'57.84" (J2000.0). We also present a well-sampled 5 GHz light curve
covering the period from 5 August to 2 December 2004. With the exception of the
unusual and very close SN 1987A, these observations represent the first
detailed radio light curve for the prompt emission from a Type II-P supernova.


title:
Tentative detection of warm intervening gas towards PKS 0548-322 with
  XMM-Newton

abstract:
  We present the results of a long (~93 ksec) XMM-Newton observation of the
bright BL-Lac object PKS 0548-322 (z=0.069). Our Reflection Grating
Spectrometer (RGS) spectrum shows a single absorption feature at an observed
wavelength lambda=23.33 A, which we interpret as OVI Ka absorption at z=0.058,
i.e., ~3000 km/s from the background object. The observed equivalent width of
the absorption line ~30 mA, coupled with the lack of the corresponding
absorption edge in the EPIC pn data, implies an OVI column density ~ 2 10^{16}
cm-2 and turbulence with a Doppler velocity parameter b>100 km/s. Within the
limitations of our RGS spectrum, no OVII or OV Ka absorption are detected.
Under the assumption of ionisation equilibrium by both collisions and the
extragalactic background, this is only marginally consistent if the gas
temperature is ~250,000 K, with significantly lower or higher values being
excluded by our limits on OV or OVII. If confirmed, this would be the first
X-ray detection of a large amount of intervening warm absorbing gas through OVI
absorption. The existence of such a high column density absorber, much stronger
than any previously detected one in OVI, would place stringent constraints on
the large-scale distribution of baryonic gas in the Universe.


title: Axial Symmetry and Rotation in the SiO Maser Shell of IK Tauri

abstract:
  We observed v=1, J=1-0 43-GHz SiO maser emission toward the Mira variable IK
Tauri (IK Tau) using the Very Long Baseline Array (VLBA). The images resulting
from these observations show that SiO masers form a highly elliptical ring of
emission approximately 58 x 32 mas with an axial ratio of 1.8:1. The major axis
of this elliptical distribution is oriented at position angle of ~59 deg. The
line-of-sight velocity structure of the SiO masers has an apparent axis of
symmetry consistent with the elongation axis of the maser distribution.
Relative to the assumed stellar velocity of 35 km/s, the blue- and red-shifted
masers were found to lie to the northwest and southeast of this symmetry axis
respectively. This velocity structure suggests a NW-SE rotation of the SiO
maser shell with an equatorial velocity, which we determine to be ~3.6 km/s.
Such a NW-SE rotation is in agreement with a circumstellar envelope geometry
invoked to explain previous water and OH maser observations. In this geometry,
water and OH masers are preferentially created in a region of enhanced density
along the NE-SW equator orthogonal to the rotation/polar axis suggested by the
SiO maser velocities.


title:
An Assessment of the Fe XVIII and Fe XIX Line Ratios from the Chandra
  Grating Observations of Capella

abstract:
  Observations of Fe XVIII and Fe XIX X-ray, EUV, and FUV line emission, formed
at the peak of Capella's (alpha Aurigae) emission measure distribution and
ubiquitous in spectra of many cool stars and galaxies, provide a unique
opportunity to test the robustness of Fe XVIII and Fe XIX spectral models. The
Astrophysical Plasma Emission Code (APEC) is used to identify over 35 lines
from these two ions alone, and to compare model predictions with spectra
obtained with the Chandra Low Energy Transmission Grating and High Energy
Transmission Grating Spectrometers, the Far Ultraviolet Spectroscopic Explorer,
and the Extreme Ultraviolet Explorer. Some flux discrepancies larger than
factors of two are found between observations of Fe XVIII and Fe XIX lines and
predictions by APEC and other models in common usage. In particular the X-ray
resonance lines for both ions are stronger than predicted by all models
relative to the EUV resonance lines. The multiwavelength observations
demonstrate the importance of including dielectronic recombination and proton
impact excitation, and of using accurate wavelengths in spectral codes. These
ions provide important diagnostic tools for 10^7 K plasmas currently observed
with Chandra, XMM-Newton, and FUSE.


title:
The depolarisation properties of powerful extragalactic radio sources as
  a function of cosmic epoch

abstract:
  We use the observed polarisation properties of a sample of 26 powerful radio
galaxies and radio-loud quasars to constrain the conditions in the Faraday
screens local to the sources. We adopt the cosmological redshift, low-frequency
radio luminosity and physical size of the large-scale radio structures as our
`fundamental' parameters. We find no correlation of the radio spectral index
with any of the fundamental parameters. The observed rotation measure is also
independent of these parameters. The difference between the rotation measures
of the two lobes of an individual source as well as the dispersion of the
rotation measure show significant correlations with the source redshift, but
not with the radio luminosity or source size. Thus the small-scale structure
observed in the rotation measure is caused by a Faraday screen local to the
sources. The observed asymmetries between the lobes of our sources show no
significant trends with each other or other source properties. Finally, we show
that the commonly used model for the depolarisation of synchrotron radio
emission by foreground Faraday screens is inconsistent with our observations.
We apply alternative models to our data and show that they require a strong
increase of the dispersion of the rotation measure inside the Faraday screens
with cosmological redshift. Correcting our observations with these models for
redshift effects, we find a strong correlation of the depolarisation measure
with redshift and a significantly weaker correlation with radio luminosity. All
our results are consistent with a decrease in the order of the magnetic field
structure of the Faraday screen local to the sources for increasing
cosmological redshift. (abridged)


title:
Cross Correlations of X-ray and Optically Selected Clusters With Near
  Infrared and Optical Galaxies

abstract:
  We compute the real-space cluster-galaxy cross-correlation xi_cg(r) using the
ROSAT-ESO Flux Limited X-ray (REFLEX) cluster survey, a group catalogue
constructed from the final version of the 2dFGRS, and galaxies extracted from
2MASS and APM surveys. This first detailed calculation of the cross-correlation
for X-ray clusters and groups, is consistent with previous works and shows that
xi_cg(r) can not be described by a single power law. We analyse the clustering
dependence on the cluster X-ray luminosity L_X and virial mass M_vir thresholds
as well as on the galaxy limiting magnitude. We also make a comparison of our
results with those obtained for the halo-mass cross-correlation function in a
LambdaCDM N-body simulation to infer the scale dependence of galaxy bias around
clusters. Our results indicate that the distribution of galaxies shows a
significant anti-bias at highly non-linear small cluster-centric distances
(b_cg(r) ~ 0.7), irrespective of the group/cluster virial mass or X-ray
luminosity and galaxy characteristics, which show that a generic process
controls the efficiency of galaxy formation and evolution in high density
regions. On larger scales b_cg(r) rises to a nearly constant value of order
unity, the transition occuring at approximately 2 Mpch^(-1) for 2dF groups and
5 Mpch^(-1) for REFLEX clusters.


title: Probing the precession of the inner accretion disk in Cygnus X-1

abstract:
  We show that changes in the orientation of the inner accretion disk of Cygnus
X-1 affect the shape of the broad Fe K$\alpha$ emission line emitted from this
object, in such a way that eV-level spectral resolution observations (such as
those that will be carried out by the {\it ASTRO-E2} satellite) can be used to
analyze the dynamics of the disk. We here present a potential diagnostic tool,
supported by numerical simulations, by which a few observations of Cygnus X-1,
separated in time, can determine whether its accretion disk actually precesses,
and if so, determine its period and precession angle. This approach could also
be used for similar studies in other microquasar systems.


title: One-armed Spiral Instability in a Low T/|W| Postbounce Supernova Core

abstract:
  A three-dimensional, Newtonian hydrodynamic technique is used to follow the
postbounce phase of a stellar core collapse event. For realistic initial data
we have employed post core-bounce snapshots of the iron core of a 20 solar mass
star. The models exhibit strong differential rotation but have centrally
condensed density stratifications. We demonstrate for the first time that such
postbounce cores are subject to a so-called low-T/|W| nonaxisymmetric
instability and, in particular, can become dynamically unstable to an m=1 -
dominated spiral mode at T/|W| ~ 0.08. We calculate the gravitational wave
emission by the instability and find that the emitted waves may be detectable
by current and future GW observatories from anywhere in the Milky Way.


title: Massive young clusters in the disc of M31

abstract:
  We have studied the properties of a sample of 67 very blue and likely young
massive clusters in M31 extracted from the Bologna Revised Catalog of globular
clusters, selected according to their color [(B-V) < 0.45] and/or to the
strength of their Hbeta spectral index (Hbeta > 3.5 A). Their existence in M31
has been noted by several authors in the past; we show here that these Blue
Luminous Compact Clusters (BLCCs) are a significant fraction (>~ 15%) of the
whole globular cluster system of M31. Compared to the global properties of the
M31 globular cluster system, they appear to be intrinsically fainter,
morphologically less concentrated, and with a shallower Balmer jump and
enhanced $H\beta$ absorption in their spectra.
  Empirical comparison with integrated properties of clusters with known age as
well as with theoretical SSP models consistently indicate that their typical
age is less than ~2 Gyr, while they probably are not so metal-poor as deduced
if considered to be old. Either selecting BLCCs by their (B-V) colors or by the
strength of their Hbeta index the cluster sample turns out to be distributed
onto the outskirts of M31 disc, sharing the kinematical properties of the thin,
rapidly rotating disc component.
  If confirmed to be young and not metal-poor, these clusters indicate the
occurrence of a significant recent star formation in the thin disc of M31,
although they do not set constraints on the epoch of its early formation.