title:
Simulations and Analytic Calculations of Bubble Growth During Hydrogen
  Reionization

abstract:
  We present results from a large volume simulation of Hydrogen reionization.
We combine 3d radiative transfer calculations and an N-body simulation,
describing structure formation in the intergalactic medium, to detail the
growth of HII regions around high redshift galaxies. Our simulation tracks
1024^3 dark matter particles, in a box of co-moving side length 65.6 Mpc/h.
This large volume allows us to accurately characterize the size distribution of
HII regions throughout most of the reionization process. At the same time, our
simulation resolves many of the small galaxies likely responsible for
reionization. It confirms a picture anticipated by analytic models: HII regions
grow collectively around highly-clustered sources, and have a well-defined
characteristic size, which evolves from a sub-Mpc scale at the beginning of
reionization to R > 10 Mpc towards the end. We present a detailed statistical
description of our results, and compare them with a numerical scheme based on
the analytic model by Furlanetto, Zaldarriaga, and Hernquist. We find that the
analytic calculation reproduces the size distribution of HII regions and the 21
cm power spectrum of the radiative transfer simulation remarkably well. The
ionization field from the simulation, however, has more small scale structure
than the analytic calculation, owing to Poisson scatter in the simulated
abundance of galaxies on small scales. We propose and validate a simple scheme
to incorporate this scatter into our calculations. Our results suggest that
analytic calculations are sufficiently accurate to aid in predicting and
interpreting the results of future 21 cm surveys. In particular, our fast
numerical scheme is useful for forecasting constraints from future 21 cm
surveys, and in constructing mock surveys to test data analysis procedures.


title:
Magnetic draping of merging cores and radio bubbles in clusters of
  galaxies

abstract:
  Sharp fronts observed by Chandra satellite between dense cool cluster cores
moving with near-sonic velocity through the hotter intergalactic gas, require
strong suppression of thermal conductivity across the boundary. This may be due
to magnetic fields tangential to the contact surface separating two plasma
components. We point out that a super-Alfvenic motion of a plasma cloud (a core
of a merging galaxy) through a weakly magnetized intercluster medium leads to
"magnetic draping", formation of a thin, strongly magnetized boundary layer
with a tangential magnetic field. For supersonic cloud motion, M_s > 1,
magnetic field inside the layer reaches near-equipartition values with thermal
pressure. Typical thickness of the layer is L /M_A^2 << L, where L is the size
of the obstacle (plasma cloud) moving with Alfven Mach number M_A >> 1. To a
various degree, magnetic draping occurs both for sub- and supersonic flows,
random and ordered magnetic fields and it does not require plasma
compressibility. The strongly magnetized layer will thermally isolate the two
media and may contribute to the Kelvin-Helmholtz stability of the interface.
Similar effects occur for radio bubbles, quasi-spherical expanding cavities
blown up by AGN jets; in this case the thickness of the external magnetized
layer is smaller, L /M_A^3 << L.


title:
Weak Lensing of the Cosmic Microwave Background by Foreground
  Gravitational Waves

abstract:
  Weak lensing distortion of the background cosmic microwave background (CMB)
temperature and polarization patterns by the foreground density fluctuations is
well studied in the literature. We discuss the gravitational lensing
modification to CMB anisotropies and polarization by a stochastic background of
primordial gravitational waves between us and the last scattering surface.
While density fluctuations perturb CMB photons via gradient-type deflections
only, foreground gravitational waves distort CMB anisotropies via both
gradient- and curl-type displacements. The latter is a rotation of background
images, while the former is related to the lensing convergence. For a
primordial background of inflationary gravitational waves, with an amplitude
corresponding to a tensor-to-scalar ratio below the current upper limit of
$\sim$ 0.3, the resulting modifications to the angular power spectra of CMB
temperature anisotropy and polarization are below the cosmic variance limit. At
tens of arcminute angular scales and below, these corrections, however, are
above the level at which systematics must be controlled in all-sky anisotropy
and polarization maps with no instrumental noise and other secondary and
foreground signals.


title:
Near-UV Observations of HD221170: New Insights into the Nature of
  r-Process-Rich Stars

abstract:
  Employing high resolution spectra obtained with the near-UV sensitive
detector on the Keck I HIRES, supplemented by data obtained with the McDonald
Observatory 2-d coude, we have performed a comprehensive chemical composition
analysis of the bright r-process-rich metal-poor red giant star HD221170.
Analysis of 57 individual neutral and ionized species yielded abundances for a
total of 46 elements and significant upper limits for an additional five. Model
stellar atmosphere parameters were derived with the aid of ~200 Fe-peak
transitions. From more than 350 transitions of 35 neutron-capture (Z > 30)
species, abundances for 30 neutron-capture elements and upper limits for three
others were derived. Utilizing 36 transitions of La, 16 of Eu, and seven of Th,
we derive ratios of log epsilon(Th/La) = -0.73 (sigma = 0.06) and log
epsilon(Th/Eu) = -0.60 (sigma = 0.05), values in excellent agreement with those
previously derived for other r-process-rich metal-poor stars such as
CS22892-052, BD+17 3248, and HD115444. Based upon the Th/Eu chronometer, the
inferred age is 11.7 +/- 2.8 Gyr. The abundance distribution of the heavier
neutron-capture elements (Z >= 56) is fit well by the predicted scaled solar
system r-process abundances, as also seen in other r-process-rich stars. Unlike
other r-process-rich stars, however, we find that the abundances of the lighter
neutron-capture elements (37 < Z < 56) in HD221170 are also statistically in
better agreement with the abundances predicted for the scaled solar r-process
pattern.


title: The early X-ray afterglows of optically bright and dark Gamma-Ray Bursts

abstract:
  A systematical study on the early X-ray afterglows of both optically bright
and dark gamma-ray bursts (B-GRBs and D-GRBs) observed by Swift has been
presented. Our sample includes 25 GRBs. Among them 13 are B-GRBs and 12 are
D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes
($F_{X}$), the gamma-ray fluxes ($S_{\gamma}$), and the ratio ($R_{\gamma, X}$)
for both the D-GRBs and B-GRBs are similar. The differences of these
distributions for the two kinds of GRBs should be statistical fluctuation.
These results indicate that the progenitors of the two kinds of GRBs are the
same population. Their total energy explosions are comparable. The suppression
of the optical emissions from D-GRBs should results from circumburst but not
their central engine.


title:
Synthesis Imaging of Dense Molecular Gas in the N113 HII Region of the
  Large Magellanic Cloud

abstract:
  We present aperture synthesis imaging of dense molecular gas in the Large
Magellanic Cloud, taken with the prototype millimeter receivers of the
Australia Telescope Compact Array (ATCA). Our observations of the N113 HII
region reveal a condensation with a size of ~6" (1.5 pc) FWHM, detected
strongly in the 1-0 lines of HCO+, HCN and HNC, and weakly in C_2H. Comparison
of the ATCA observations with single-dish maps from the Mopra Telescope and
sensitive spectra from the Swedish-ESO Submillimetre Telescope indicates that
the condensation is a massive clump of ~10^4 solar masses within a larger ~10^5
solar mass molecular cloud. The clump is centered adjacent to a compact,
obscured HII region which is part of a linear structure of radio continuum
sources extending across the molecular cloud. We suggest that the clump
represents a possible site for triggered star formation. Examining the
integrated line intensities as a function of interferometer baseline length, we
find evidence for decreasing HCO+/HCN and HCN/HNC ratios on longer baselines.
These trends are consistent with a significant component of the HCO+ emission
arising in an extended clump envelope and a lower HCN/HNC abundance ratio in
dense cores.


title:
First Detection of Near-Infrared Intraday Variations in the Seyfert 1
  Nucleus NGC4395

abstract:
  We carried out a one-night optical V and near-infrared JHK monitoring
observation of the least luminous Seyfert 1 galaxy, NGC4395, on 2004 May 1, and
detected for the first time the intraday flux variations in the J and H bands,
while such variation was not clearly seen for the K band. The detected J and H
variations are synchronized with the flux variation in the V band, which
indicates that the intraday-variable component of near-infrared continuum
emission of the NGC4395 nucleus is an extension of power-law continuum emission
to the near-infrared and originates in an outer region of the central accretion
disk. On the other hand, from our regular program of long-term optical BVI and
near-infrared JHK monitoring observation of NGC4395 from 2004 February 12 until
2005 January 22, we found large flux variations in all the bands on time scales
of days to months. The optical BVI variations are almost synchronized with each
other, but not completely with the near-infrared JHK variations. The color
temperature of the near-infrared variable component is estimated to be
T=1320-1710 K, in agreement with thermal emission from hot dust tori in active
galactic nuclei (AGNs). We therefore conclude that the near-infrared variation
consists of two components having different time scales, so that a small K-flux
variation on a time scale of a few hours would possibly be veiled by large
variation of thermal dust emission on a time scale of days.


title: 4C 39.29 - extended emission around a powerful Type 2 quasar

abstract:
  We present new X-ray and optical spectroscopy of a Type 2 quasar candidate
selected from a follow-up program of hard, optically-dim, serendipitous Chandra
sources. The source is confirmed to be a Type 2 quasar at z=0.536 with an
intrinsic 2-10 keV luminosity L_{2-10}=5x10^{44} h_{0.7}^{-2} erg/s, an
absorbing column density N_H=8x10^{23} cm^{-2} and a neutral Fe K alpha line
detected by XMM-Newton EPIC-MOS1 as well as Chandra ACIS-S. An extended optical
forbidden emission line cloud is detected at the same redshift, and at about 15
kpc in projected separation. This cloud lies in close proximity to the peak of
the compact steep spectrum radio source 4C+39.29, which has previously been
identified with a foreground galaxy in the cluster Abell 963. We present
evidence to show that 4C+39.29 is associated with the background X-ray Type 2
quasar. The radio luminosity is dominated by lobes with complex structure and
the radio core is weak in comparison to narrow-line radio galaxies at the same
X-ray luminosity. The morphology and emission line properties of the extended
region are consistent with an on-going jet-cloud interaction. 4C+39.29
possesses a combination of high power and high absorbing column density
compared with other X-ray Type 2 quasars in the literature. These observations
highlight the efficacy of using X-rays to identify the primary energy source of
complex radio sources and distant obscured AGN.


title:
Magnetorotational Instability in Electrically Driven Flow of Liquid
  Metal: Spectral Analysis

abstract:
  The spectral stability of liquid metal differentially rotating in transverse
magnetic field is studied numerically by solving the eigenvalue problem with
rigid-wall boundary conditions. The equilibrium velocity profile used in
calculations corresponds to the electrically driven flow in circular channel
with the rotation law \Omega(r)~1/r^2. This type of flow profile is planned to
be used in new experimental device to test the magnetorotational instability
(MRI) in laboratory. Our analysis includes calculations of the eigen-frequency
spectra for both axisymmetric and non-axisymmetric modes. It is found that for
chosen device parameters the flow is always spectrally unstable due to MRI with
the fastest growth rate corresponding to the axisymmetric mode.


title:
A "Missing" Supernova Remnant revealed by the 21-cm Line of Atomic
  Hydrogen

abstract:
  Although some 20--30,000 supernova remnants (SNRs) are expected to exist in
the Milky Way, only about 230 are presently known. This implies that most SNRs
are ``missing''. Recently, we proposed that small ($\simlt 1^\circ$), faint,
high-velocity features seen in large-scale 21-cm line surveys of atomic
hydrogen ({\sc Hi}) in the Galactic plane could be examples of such {\it
missing} old SNRs. Here we report on high-resolution \schi observations of one
such candidate, FVW 190.2+1.1, which is revealed to be a rapidly expanding
($\sim 80$ \kms) shell. The parameters of this shell seem only consistent with
FVW 190.2+1.1 being the remnant of a SN explosion that occurred in the
outermost fringes of the Galaxy some $\sim 3\times 10^5$ yr ago. This shell is
not seen in any other wave band suggesting that it represents the oldest type
of SNR, that which is essentially invisible except via its \schi line emission.
FVW 190.2+1.1 is one of a hundred "forbidden-velocity wings" (FVWs) recently
identified in the Galactic plane, and our discovery suggests that many of these
are likely to be among the oldest SNRs. We discuss the possible link between
FVWs and fast-moving atomic clouds in the Galaxy.


title:
Supernova remnant energetics and magnetars: no evidence in favour of
  millisecond proto-neutron stars

abstract:
  It is generally accepted that Anomalous X-ray Pulsars (AXPs) and Soft
Gamma-ray Repeaters (SGRs) are magnetars, i.e. neutron stars with extremely
high surface magnetic fields ($B > 10^{14}$ G). The origin of these high
magnetic fields is uncertain, but a popular hypothesis is that magnetars are
born with an initial spin period not much exceeding the convective overturn
time (~3ms), which results in a powerful dynamo action, amplifying the seed
magnetic field to $> ~10^{15}$ G. Part of this rotation energy is then expected
to power the supernova through rapid magnetic braking. It is therefore possible
that magnetars creation is accompanied by supernovae that are an order of
magnitude more energetic than normal supernovae, provided their initial spin
period is ~1 ms. However, we list here evidence that the explosion energies of
these supernova remnants associated with AXPs and SGRs -- Kes 73 (AXP 1E
1841-045), CTB 109 (AXP 1E2259+586) and N49 (SGR 0526-66) -- are close to the
canonical supernova explosion energy of $10^{51}$~erg, suggesting an initial
spin period of > ~5ms.
  We therefore do not find evidence that magnetars are formed from rapidly
rotating proto-neutron stars, allowing for the possibility that they descend
from stellar progenitor with high magnetic field cores, and we discuss the
merits of both formation scenarios.
  In an appendix we describe the analysis of XMM-Newton observations of Kes 73
and N49 used to derive the explosion energies for these remnants.


title:
Coronal density diagnostics with Si X: CHANDRA/LETGS observations of
  Procyon, $\alpha$ Cen A$&$B, Capella and $\epsilon$ Eri

abstract:
  Electron density diagnostics based on a line intensity ratio of Si X are
applied to the X-ray spectra of Procyon, $\alpha$ Cen A$&$B, Capella and
$\epsilon$ Eri measured with the Low Energy Transmission Grating Spectrometer
(LETGS) combined with High-resolution Camera (HRC) on board the {\it Chandra
X-ray Observatory}. The ratio $R_1$ of the intensities of the Si X lines at
50.524 \AA and 50.691 \AA is adopted. A certain of the temperature effect in
$R_1$ appears near the low-density limit region, which is due to the
contamination of Si X line at 50.703 \AA . Using the emission measure
distribution (EMD) model derived by Audard et al. (2001) for Capella and
emissivities calculated with APEC model by Smith et al. (2001), we successfully
estimate contributions of Fe XVI lines at 50.367 \AA and 50.576 \AA (73% and
62%, respectively). A comparison between observed ratios and theoretical
predictions constrains the electron densities (in logarithmic) for Procyon to
be 8.61$^{+0.24}_{-0.20}$ cm$^{-3}$, while for $\alpha$ Cen A$&$B, Capella and
$\epsilon$ Eri to be 8.81$^{+0.27}_{-0.23}$ cm$^{-3}$, 8.60$^{+0.39}_{0.32}$
cm$^{-3}$, 9.30$_{-0.48}$ cm$^{-3}$ and 9.11$^{+1.40}_{-0.38}$ cm$^{-3}$,
respectively. The comparison of our results with those constrained by the
triplet of He-like carbon shows a good agreement. For normal stars, our results
display a narrow uncertainty, while for active stars, a relatively larger
uncertainty, due to the contamination from Fe XVI lines, is found. Another
possible reason may be that the determination of the continuum level, since the
emission lines of Si X become weak for the active stars. For $\epsilon$ Eri, an
electron density in the C V forming region was estimated firstly through Si X
emissions.


title: Mapping and Mass Measurement of the Cold Dust in NGC 205 with Spitzer

abstract:
  We present observations at 3.6, 4.5, 5.8, 8, 24, 70 & 160um of NGC 205, the
dwarf elliptical companion of M31, obtained with the Spitzer Space Telescope.
The point sources subtracted images at 8 and 24um display a complex and
fragmented infrared emission coming from both very small dust particles and
larger grains. The extended dust emission is spatially concentrated in three
main emission regions, seen at all wavelengths from 8 to 160um. These regions
lie approximately along NGC 205's semi-major axis and range from ~100 to 300 pc
in size. Based on our mid-to-far infrared flux density measurements alone, we
derive a total dust mass estimate of the order of 3.2e4 solar masses, mainly at
a temperature of ~20K. The gas mass associated with this component matches the
predicted mass returned by the dying stars from the last burst of star
formation in NGC 205 (~0.5 Gyr ago). Analysis of the Spitzer data combined with
previous 1.1mm observations over a small central region or "Core'' (18"
diameter), suggest the presence of very cold (~12K) dust and a dust mass about
sixteen times higher than is estimated from the Spitzer measurements alone.
Assuming a gas to dust mass ratio of 100, these two datasets, i.e.with and
without the millimeter observations, suggest a total gas mass range of 3.2e6 to
5e7 solar masses.


title: Microlensing in phase space II: Correlations analysis

abstract:
  Applications of the phase space approach to the calculation of the
microlensing autocorrelation function are presented. The continuous propagation
equation for a random star field with a Gaussian velocity distribution is
solved in the leading non-trivial approximation using the perturbation
technique. It is shown that microlensing modulations can be important in the
interpretation of optical and shorter-wavelength light curves of pulsars, power
spectra of active galactic nuclei and coherence estimates for quasi-periodic
oscillations of dwarf novae and low-mass X-ray binaries. Extra scatter in the
brightness of type Ia supernovae due to gravitational microlensing is shown to
be of order up to 0.2 stellar magnitudes depending on the extent of the light
curves.


title:
Common Correlations between 60, 100 and 140 um Intensities in the
  Galactic Plane and Magellanic Clouds

abstract:
  We investigate the far-infrared SED of the Galaxy and the Magellanic Clouds
by using the COBE (COsmic Background Explorer) / DIRBE (Diffuse InfraRed
Background Experiment) ZSMA (Zodi - Subtracted Mission Average) maps at
wavelengths of 60 um, 100 um and 140 um. We analyze three regions: the Galactic
plane region with the Galactic latitude |b|<5 degree, the Large Magellanic
Cloud (LMC) region, and the Small Magellanic Cloud (SMC) region. Because the
dust optical depth is much smaller in the far-infrared than in the visible, we
may observe cumulative far-infrared radiation from regions with various
interstellar radiation field (IRSF) in a line of sight. As consequence of
considering such an effect, we find a common far-infrared color correlation
between the 140 - 100 um and 60 - 100 um intensity ratios in all the three
galaxies. Although this color correlation cannot be explained by any existing
model, it fits very well the far-infrared color of nearby star forming
galaxies.


title:
Stochastic Acceleration in Turbulent Electric Fields Generated by 3-D
  Reconnection

abstract:
  Electron and proton acceleration in three-dimensional electric and magnetic
fields is studied through test particle simulations. The fields are obtained by
a three-dimensional magnetohydrodynamic simulation of magnetic reconnection in
slab geometry. The nonlinear evolution of the system is characterized by the
growth of many unstable modes and the initial current sheet is fragmented with
formation of small scale structures. We inject at random points inside the
evolving current sheet a Maxwellian distribution of particles. In relatively
short time (less than a millisecond) the particles develop a power law tail.
The acceleration is extremely efficient and the electrons absorb a large
percentage of the available energy in a small fraction of the characteristic
time of the MHD simulation, suggesting that resistive MHD codes, used
extensively in the current literature, are unable to represent the full extent
of particle acceleration in 3D reconnection.


title:
XMM-Newton observation of the Be/neutron star system RX J0146.9+6121: a
  soft X-ray excess in a low luminosity accreting pulsar

abstract:
  We report on the XMM-Newton observation of the Be/neutron star X-ray binary
system RX J0146.9+6121, a long period (~ 23 m) pulsar in the NGC 663 open
cluster. The X-ray luminosity decreased by a factor two compared to the last
observation carried out in 1998, reaching a level of ~ 10^34 erg/s, the lowest
ever observed in this source. The spectral analysis reveals the presence of a
significant excess at low energies over the main power-law spectral component.
The soft excess can be described by a black-body spectrum with a temperature of
about 1 keV and an emitting region with a radius of ~ 140 m. Although the
current data do not permit to ascertain whether the soft excess is pulsed or
not, its properties are consistent with emission from the neutron star polar
cap. This is the third detection of a soft excess in a low luminosity (~ 10^34
erg/s) pulsar, the other being X Per and 3A 0535+262, suggesting that such
spectral component, observed up to date in higher luminosity systems, is a
rather common feature of accreting X-ray pulsars. The results on these three
sources indicate that, in low luminosity systems, the soft excess tends to have
a higher temperature and a smaller surface area than in the high luminosity
ones.


title:
On the Mass of Dense Star Clusters in Starburst Galaxies from
  Spectro-Photometry

abstract:
  The mass of unresolved young star clusters derived from spectro-photometric
data may well be off by a factor of 2 or more once the migration of massive
stars driven by mass segregation is accounted for. We quantify this effect for
a large set of cluster parameters, including variations in the stellar IMF, the
intrinsic cluster mass, and mean mass density. Gas-dynamical models coupled
with the Cambridge stellar evolution tracks allow us to derive a scheme to
recover the real cluster mass given measured half-light radius, one-dimensional
velocity dispersion and age. We monitor the evolution with time of the ratio of
real to apparent mass through the parameter eta. When we compute eta for rich
star clusters, we find non-monotonic evolution in time when the IMF stretches
beyond a critical cutoff mass of 25.5 solar mass. We also monitor the rise of
color gradients between the inner and outer volume of clusters: we find trends
in time of the stellar IMF power indices overlapping well with those derived
for the LMC cluster NGC 1818 at an age of 30 Myr. We argue that the core region
of massive Antennae clusters should have suffered from much segregation despite
their low ages. We apply these results to a cluster mass function, and find
that the peak of the mass distribution would appear to observers shifted to
lower masses by as much as 0.2 dex. The star formation rate (SFR) derived for
the cluster population is then underestimated by from 20 to 50 per cent.


title: Noncommutative chaotic inflation and WMAP three year results

abstract:
  Noncommutative inflation is based upon the consideration of some effects of
the space-time uncertainty principle motivated by ideas from string/M theory.
The CMB anisotropies may carry a signature of this very early Universe
correction from the space-time uncertainty principle and can be used to place
constraints on the parameters of the noncommutative inflation model. In this
paper we analyze the noncommutative chaotic inflation model by means of the
WMAP three year results. We show that the noncommutative chaotic inflation
model can produce a large negative running of spectral index within a
reasonable range of $e$-folding number $N$, provided that the value of $p$ in
the potential $V(\phi)\propto \phi^p$ is enhanced roughly to $p\sim 12-18$.
Applying a likelihood analysis to the WMAP results, we find the best-fit values
of parameters for the noncommutative chaotic inflation model. In addition, this
model predicts a rather big gravitational wave which may be tested by the
upcoming experiments.


title: The $\dot{M} - M$ relationship in pre-main sequence stars

abstract:
  We examine the recent data and analysis of Natta et al. concerning the
accretion rate on to young stars as a function of stellar mass, and conclude
that the apparently steep dependence of accretion rate on mass is strongly
driven by selection/detection thresholds. We argue that a convincing
demonstration of a physical relationship between accretion and stellar mass
requires further studies which, as is the case for Natta et al., include
information on upper limits, and which quantify the possible incompleteness of
the sample, at both low and high accretion rates. We point out that the
distribution of detections in the ($M, \dot{M}$)-plane can in principle be used
to test conventional accretion disc evolutionary models, and that higher
sensitivity observations might be able to test the hypothesis of accelerated
disc clearing at late times.


title:
Observation of VHE Gamma Radiation from HESS J1834-087/W41 with the
  MAGIC Telescope

abstract:
  Recently, the HESS array has reported the detection of gamma-ray emission
above a few hundred GeV from eight new sources located close to the Galactic
Plane. The source HESS J1834-087 is spatially coincident with SNR G23.3-0.3
(W41). Here we present MAGIC observations of this source, resulting in the
detection of a differential gamma-ray flux consistent with a power law,
described as dN/(dA dt dE) = (3.7 +/- 0.6)*10^(-12) (E/TeV)^(-2.5 +/- 0.2) \
cm^(-2)s^(-1)TeV^(-1). We confirm the extended character of this flux. We
briefly discuss the observational technique used, the procedure implemented for
the data analysis, and put this detection in the perspective of the molecular
environment found in the region of W41. We present 13CO and 12CO emission maps
showing the existence of a massive molecular cloud in spatial superposition
with the MAGIC detection.


title:
Barium even-to-odd isotope abundance ratios in thick disk and thin disk
  stars

abstract:
  We present the Ba even-to-odd isotope abundance ratios in 25 cool dwarf stars
with the metallicity [Fe/H] ranged between 0.25 and --1.35. Our method takes
advantage of the hyperfine structure (HFS) affecting the \ion{Ba}{ii} resonance
line of the odd isotopes. The fractional abundance of the odd isotopes of Ba is
derived from a requirement that Ba abundances from the resonance line $\lambda
4554$ and subordinate lines $\lambda 5853$ and $\lambda 6496$ must be equal.
The results are based on NLTE line formation and analysis of high resolution (R
$\sim60000$) high signal-to-noise (S/N $\ge 200$) observed spectra. We find
that the fraction of the odd isotopes of Ba grows toward the lower Ba abundance
(or metallicity) and the mean value in the thick disk stars equals 33 $\pm$ 4%.
This indicates the higher contribution of the $r-$process to barium in the
thick disk stars compared to the solar system matter. The obtained fraction
increases with the [Eu/Ba] abundance ratio growth in agreement with
expectations. A significant fraction of the \emph{even} isotopes of Ba found in
old Galactic stars (the thick disk stars), $\sim67$%, is in contrast to the
prediction of the "classical" model of the $s-$process and favors the value
predicted by the "stellar" models of Arlandini et al. (1999) and Travaglio et
al. (1999).


title:
Prospects for Lunar Satellite Detection of Radio Pulses from Ultrahigh
  Energy Neutrinos Interacting with the Moon

abstract:
  The Moon provides a huge effective detector volume for ultrahigh energy
cosmic neutrinos, which generate coherent radio pulses in the lunar surface
layer due to the Askaryan effect. In light of presently considered lunar
missions, we propose radio measurements from a Moon-orbiting satellite. First
systematic Monte Carlo simulations demonstrate the detectability of Askaryan
pulses from neutrinos with energies above 10^{20} eV, i.e. near and above the
interesting GZK limit, at the very low fluxes predicted in different scenarios.


title: Models of inflation with primordial non-Gaussianities

abstract:
  We present a class of models in which the primordial metric fluctuations do
not necessarily obey Gaussian statistics. These models are realizations of
mechanisms in which non-Gaussianity is first generated by a light scalar field
and then transferred into curvature fluctuations during or at the end of
inflation. For this class of models we present generic results for the
probability distribution functions of the metric perturbation at the end of
inflation. It is stressed that finite volume effects can induce non trivial
effects that we sketch.


title: Evolutionary Status of SNR 1987A at the Age of Eighteen

abstract:
  $\sim$18 yr after the supernova explosion, the blast wave of SNR 1987A is
entering the main body of the equatorial circumstellar material, which is
causing a dramatic brightening of the remnant. We recently reported the
observational evidence for this event from our {\it Chandra} data (Park et al.
2005b; P05 hereafter). We present here the temporal evolution of the X-ray
emitting shock parameters and the detailed description of the spectral and
image analysis of SNR 1987A, on which P05 was based. While the remnant becomes
brighter, the softening of the overall X-ray spectrum continues and is enhanced
on around day $\sim$6200 (since the explosion). The two-component shock model
indicates that the electron temperatures have been changing for the last
$\sim$6 yr. The X-ray spectrum is now described by $kT$ $\sim$ 0.3 keV and 2.3
keV thermal plasmas which are believed to characteristically represent the
shock-heated density gradient along the boundary between the H{\small II}
region and the dense inner ring. As the blast wave sweeps through the inner
circumstellar ring shining in X-rays, we expect that the shock parameters
continue to change, revealing the density and abundance structure of the inner
ring. Follow-up {\it Chandra} observations will thus uncover the past history
of the progenitor's stellar evolution. The origin of the relatively faint hard
X-ray emission ($E$ $>$ 3 keV) from SNR 1987A is still unclear (thermal vs.
nonthermal). Considering the continuous brightening of the hard band intensity,
as well as the soft band flux, follow-up monitoring observations will also be
essential to reveal the origin of the hard X-ray emission of SNR 1987A.


title: Halos and voids in a multifractal model of cosmic structure

abstract:
  On the one hand, the large scale structure of matter is arguably scale
invariant, and, on the other hand, halos and voids are recognized as prominent
features of that structure. To unify both approaches, we propose to model the
dark matter distribution as a set of fractal distributions of halos of
different kinds. This model relies on the concept of multifractal as the most
general scaling distribution and on a plausible notion of halo as a singular
mass concentration in a multifractal. Voids arise as complementary to halos,
namely, as formed by regular mass depletions. To provide halos with definite
size and masses, we coarse-grain the dark matter distribution, using the length
given by the lower cutoff to scaling. This allows us to relate the halo mass
function to the multifractal spectrum. Hence, we find that a log-normal model
of the mass distribution nicely fits in this picture and, moreover, the
Press-Schechter mass function can be recovered as a bifractal limit.
  To support our model of fractal distributions of halos, we perform a
numerical study of the distribution produced in cosmological N-body
simulations. In the Virgo L-CDM GIF2 simulation, we indeed find fractal
distributions of halos with various dimensions and a halo mass function of
bifractal type. However, this mass function is not of Press-Schechter's type,
and we interprete it instead as caused by the undersampling of the distribution
at the scale of halos, due to discretization.


title:
Core Structure of Intracluster Gas: Effects of Radiative Cooling on Core
  Sizes

abstract:
  We investigate the core structure of radiatively cooling intracluster gas,
using a hydrodynamics code. We calculate evolution of model clusters of the
initial core radii 160--300 kpc until the initial central cooling time, and
analyze the resultant clusters using the double beta-model as done by
observational studies. It is found that the core-size distribution thus
obtained shows two peaks \sim 30--100 kpc and \sim 100--300 kpc and marginally
can reproduce the observed distribution which exhibits two distinct peaks
around \sim 50 kpc and \sim 200 kpc. This result may suggest radiative-cooling
origin for small cores, while cooling is yet insignificant in the clusters of
large cores. It should be noted that the small core peak is reproduced by
clusters that are still keeping quasi-hydrostatic balance before the initial
central cooling time has elapsed.


title:
The CMB Initial Data and Fundamental Operator Quantization of General
  Relativity

abstract:
  The observational data on CMB radiation revealed that our Universe can be an
ordinary physical object moving with respect to the Earth observer with the
occasional initial data. This fact allows us to apply the theory of irreducible
unitary representations of the Poincare group in order to describe the Universe
in the framework of the fundamental operator quantization of General Relatvity
and Standard Model of elementary particles. The simplest fit of the
observational CMB data is given that includes occasional gauge-invariant and
frame-covariant initial data and their units of measurement.


title: The dynamical state of massive galaxy clusters

abstract:
  We study the mass distribution of a sample of 24 X-ray bright Abell clusters
through weak gravitational lensing. This method is independent of the dynamical
state of the galaxy cluster. Hence, by comparing dynamical and lensing mass
estimators, we can access the dynamical state of these clusters. We have found
that clusters with ICM temperatures above 8 keV show strong deviations from the
relaxation, as well as the presence of prominent sub-structures. For the
remaining clusters (the majority of the sample) we have found agreement among
the several mass estimators, which indicates that most of the clusters are in
or close to a state of dynamical equilibrium.


title: Power-law Parameterized Quintessence Model

abstract:
  We introduce a power-law parameterized quintessence model for the dark energy
which accelerate universe at the low redshifts while behaves as an ordinary
matter for the early universe. We construct a unique scalar potential for this
parameterized quintessence model. As the observational test, the Supernova Type
Ia (SNIa) Gold sample data, size of baryonic acoustic peak from Sloan Digital
Sky Survey (SDSS), the position of the acoustic peak from the CMB observations
and structure formation from the 2dFGRS survey are used to constrain the
parameters of the quintessence model. The best fit parameters indicates that
the equation of state of this model at the present time is less than one
$(w_0<-1)$ which violates the energy condition in General Relativity. Finally
we compare the age of old objects with age of universe in this model.


title: The science of PAMELA space mission

abstract:
  Many different mechanisms can contribute to antiprotons and positrons
production, ranging from conventional reactions up to exotic processes like
neutralino annihilation. The open problems are so fundamental (i.e.: is the
universe symmetric in matter and antimatter ?) that experiments in this field
will probably be of the greatest interest in the next years. Here we will
summarize the present situation, showing the different hypothesis and models
and the experimental measurements needed to lead to a more established
scenario.


title:
A SCUBA imaging survey of ultracompact HII regions: The environments of
  massive star formation

abstract:
  We present a SCUBA submillimetre (450 & 850 micron) survey of the environment
of 105 IRAS point sources, selected from the Wood & Churchwell (1989a) and
Kurtz, Churchwell & Wood (1994) radio ultracompact (UC) HII region surveys. We
detected a total of 155 sub-mm clumps associated with the IRAS point sources
and identified three distinct types of object: ultracompact cm-wave sources
that are not associated with any sub-mm emission (sub-mm quiet objects), sub-mm
clumps that are associated with ultracompact cm-wave sources (radio-loud
clumps); and sub-mm clumps that are not associated with any known ultracompact
cm-wave sources (radio-quiet clumps). 90% of the sample of IRAS point sources
were found to be associated with strong sub-mm emission. We consider the sub-mm
colours, morphologies and distance-scaled fluxes of the sample of sub-mm clumps
and show that the sub-mm quiet objects are unlikely to represent embedded UC
HII regions unless they are located at large heliocentric distances. Many of
the 2.5 arcmin SCUBA fields contain more than one sub-mm clump, with an average
number of companions (the companion clump fraction) of 0.90. The clumps are
more strongly clustered than other candidate HMPOs and the mean clump surface
density exhibits a broken power-law distribution with a break at 3 pc. We
demonstrate that the sub-mm and cm-wave fluxes of the majority of radio-loud
clumps are in excellent agreement with the standard model of ultracompact HII
regions. We speculate on the nature of the radio-quiet sub-mm clumps and,
whilst we do not yet have sufficient data to conclude that they are in a pre-UC
HII region phase, we argue that their characteristics are suggestive of such a
stage.


title: Non-Gaussian Inflationary Perturbations from the dS/CFT Correspondence

abstract:
  We use the dS/CFT correspondence and bulk gravity to predict the form of the
renormalized holographic three-point correlation function of the operator which
is dual to the inflaton field perturbation during single-field, slow-roll
inflation. Using Maldcaena's formulation of the correspondence, this correlator
can be related to the three-point function of the curvature perturbation
generated during single-field inflation, and we find exact agreement with
previous bulk QFT calculations. This provides a consistency check on existing
derivations of the non-Gaussianity from single-field inflation and also yields
insight into the nature of the dS/CFT correspondence. As a result of our
calculation, we obtain the properly renormalized dS/CFT one-point function,
including boundary contributions where derivative interactions are present in
the bulk. In principle, our method may be employed to derive the n-point
correlators of the inflationary curvature perturbation within the context of
(n-1)th-order perturbation theory, rather than nth-order theory as in
conventional approaches.


title: Determining the H+ Region/PDR Equation of State in Star Forming Regions

abstract:
  The emission line regions of starburst galaxies and active nuclei reveal a
wealth of spectroscopic information. A unified picture of the relationship
between ionized, atomic, and molecular gas makes it possible to better
understand these observations. We performed a series of calculations designed
to determine the equation of state, the relationship between density,
temperature, and pressure, through emission-line diagnostic ratios that form in
the H+ region and PDR. We consider a wide range of physical conditions in the
H+ region. We connect the H+ region to the PDR by considering two constant
pressure cases, one with no magnetic field and one where the magnetic field
overwhelms the thermal pressure. We show that diagnostic ratios can yield the
equation of state for single H+ regions adjacent to single PDRs, with the
results being more ambiguous when considering observations of entire galaxies.
As a test, we apply our calculations to the Orion H+/PDR region behind the
Trapezium. We find the ratio of thermal to magnetic pressure in the PDR to be
\~1.2. If magnetic and turbulent energy are in equipartition, our results mean
the magnetic field is not the cause of the unexplained broadening in M 42, but
may significantly affect line broadening in the PDR. Since Orion is often used
to understand physical processes in extragalactic environments, our
calculations suggest magnetic pressure should be considered in modeling such
regions.


title: The Millennium Galaxy Catalogue: a census of local compact galaxies

abstract:
  We use the Millennium Galaxy Catalogue (MGC) to study the effect of compact
galaxies on the local field galaxy luminosity function. Here we observationally
define as `compact' galaxies that are too small to be reliably distinguished
from stars using a standard star-galaxy separation technique. In particular, we
estimate the fraction of galaxies that are misclassified as stars due to their
compactness. We have spectroscopically identified all objects to B_MGC = 20 mag
in a 1.14 deg^2 sub-region of the MGC, regardless of morphology. From these
data we develop a model of the high surface brightness incompleteness and
estimate that ~1 per cent of galaxies with B_MGC < 20 mag are misclassified as
stars, with an upper limit of 2.3 per cent at 95 per cent confidence. However,
since the missing galaxies are preferentially sub-L* their effect on the faint
end of the luminosity function is substantially amplified: we find that they
contribute ~6 per cent to the total luminosity function in the range -17 < M_B
< -14 mag, which raises the faint end slope alpha by 0.03^{+0.02}_{-0.01}.
Their contribution to the total B-band luminosity density is ~2 per cent.
Roughly half of the missing galaxies have already been recovered through
spectroscopy of morphologically stellar targets selected mainly by colour. We
find that the missing galaxies mostly consist of intrinsically small, blue,
star-forming, sub-L* objects. In combination with the recent results of Driver
et al. (2005) we have now demonstrated that the MGC is free from both high and
low surface brightness selection bias for giant galaxies (M_B <~ -17 mag).
Dwarf galaxies, on the other hand, are significantly affected by these
selection effects. To gain a complete view of the dwarf population will require
both deeper and higher resolution surveys.


title: The H+ Region Contribution to [C II] 158 Micron Emission

abstract:
  The [C II] 158 micron line is an important emission line diagnostic in
Photodissociation Regions (PDRs), but this emission line can also emerge from
ionized gas. This work calculates the contribution of [C II] emission from
ionized gas over a wide range of parameter space by considering the simplified
case of an H+ region and PDR in pressure equilibrium. Additionally, these
calculations also predict the strong correlation observed between [N II] 205
micron emission and [C II] discussed by previous authors. Overall, the results
of these calculations have wide-ranging applications to the interpretation of
[C II] emission in astrophysical environments.


title:
SiO in C-rich circumstellar envelopes of AGB stars: effects of non-LTE
  chemistry and grain adsorption

abstract:
  New SiO multi-transition millimetre line observations of a sample of carbon
stars, including J=8-7 observations with the APEX telescope, are used to probe
the role of non-equilibrium chemistry and the influence of grains in
circumstellar envelopes of carbon stars. A detailed radiative transfer
modelling, including the effect of dust emission in the excitation analysis, of
the observed SiO line emission is performed. A combination of low- and
high-energy lines are important in constraining the abundance distribution. It
is found that the fractional abundance of SiO in these C-rich environments can
be several orders of magnitude higher than predicted by equilibrium stellar
atmosphere chemistry. In fact, the SiO abundance distribution of carbon stars
closely mimic that of M-type (O-rich) AGB stars. A possible explanation for
this behaviour is a shock-induced chemistry, but also the influence of dust
grains, both as a source for depletion as well as production of SiO, needs to
be further investigated. As observed for M-type AGB stars, a clear trend that
the SiO fractional abundance decreases as the mass-loss rate of the star
increases is found for the carbon stars. This indicates that SiO is accreted
onto dust grains in the circumstellar envelopes.


title: Implications of a Running Spectral Index for Slow Roll Inflation

abstract:
  We analyze the weak (2 sigma) evidence for a running spectral index seen in
the three-year WMAP dataset and its implications for single field, slow roll
inflation. We assume that the running is comparable to the central value found
from the WMAP data analysis, and use the Hubble Slow Roll formalism to follow
the evolution of the slow roll parameters. For all parameter choices consistent
with a large, negative running, single field, slow roll inflation lasts less
than 30 efolds after CMB scales leave the horizon. Thus, a definitive
observation of a large negative running would imply that any inflationary phase
requires multiple fields or the breakdown of slow roll. Alternatively, if
single field, slow roll inflation is sources the primordial fluctuations, we
can expect the observed running to move much closer to zero as the CMB is
measured more accurately at small angular scales.


title: Neutrino Coannihilation on Dark-Matter Relics?

abstract:
  High-energy neutrinos may resonate with relic background neutralinos to form
short-lived sneutrinos. In some circumstances, the decay chain that leads back
to the lightest supersymmetric particle would yield few-GeV gamma rays or
charged-particle signals. Although resonant coannihilation would occur at an
appreciable rate in our galaxy, the signal in any foreseeable detector is
unobservably small.


title:
Virgo cluster early-type dwarf galaxies with the Sloan Digital Sky
  Survey. I. On the possible disk nature of bright early-type dwarfs

abstract:
  We present a systematic search for disks in 476 Virgo cluster early-type
dwarf (dE) galaxies. Disk features (spiral arms, edge-on disks, or bars) were
identified by applying unsharp masks to a combined image from three bands (g,
r, i), as well as by subtracting the axisymmetric light distribution of each
galaxy from that image. 14 objects are unambiguous identifications of disks, 10
objects show 'probable disk' features, and 17 objects show 'possible disk'
features. The number fraction of these galaxies, for which we introduce the
term dEdi, reaches more than 50% at the bright end of the dE population, and
decreases to less than 5% for magnitudes B>16. The luminosity function of our
full dE sample can be explained by a superposition of dEdis and ordinary dEs,
strongly suggesting that dEdis are a distinct type of galaxy. This is supported
by the projected spatial distribution: dEdis show basically no clustering and
roughly follow the spatial distribution of spirals and irregulars, whereas
ordinary dEs are distributed similarly to the strongly clustered E/S0 galaxies.
While the flattening distribution of ordinary dEs is typical for spheroidal
objects, the distribution of dEdis is significantly different and agrees with
their being flat oblate objects. We therefore conclude that the dEdis are not
spheroidal galaxies that just have an embedded disk component, but are instead
a population of genuine disk galaxies. Several dEdis display well-defined
spiral arms with grand design features that clearly differ from the flocculent,
open arms typical for late-type spirals that have frequently been proposed as
progenitors of early-type dwarfs. This raises the question of what process is
able to create such spiral arms - with pitch angles like those of Sab/Sb
galaxies - in bulgeless dwarf galaxies. (Abridged)


title:
Redshift-Space Distortions with the Halo Occupation Distribution II:
  Analytic Model

abstract:
  We present an analytic model for the galaxy two-point correlation function in
redshift space. The model is constructed within the framework of the Halo
Occupation Distribution (HOD), which quantifies galaxy bias on linear and non-
linear scales. We model one-halo pairwise velocities by assuming that satellite
galaxy velocities follow a Gaussian distribution with dispersion proportional
to the virial dispersion of the host halo. Two-halo velocity statistics are a
combination of virial motions and host halo motions. The velocity distribution
function (DF) of halo pairs is a complex function with skewness and kurtosis
that vary substantially with scale. Using a series of collisionless N-body
simulations, we demonstrate that the shape of this DF is determined primarily
by the distribution of local densities around a halo pair, and at fixed density
the velocity DF is close to Gaussian and nearly independent of halo mass. We
calibrate a model for the conditional probability function of densities around
halo pairs on these simulations. With this model, the full shape of the halo
velocity DF can be accurately calculated as a function of halo mass, radial
separation, angle, and cosmology. The HOD approach to redshift-space
distortions utilizes clustering data from linear to non-linear scales to break
the standard degeneracies inherent in previous models of redshift-space
clustering. The parameters of the occupation function are well constrained by
real-space clustering alone, separating constraints on bias and cosmology. We
demonstrate the ability of the model to separately constrain Omega_m, sigma_8,
and galaxy velocity bias in models that are constructed to have the same value
of beta at large scales as well as the same finger-of-god distortions at small
scales. [Abridged]


title: Feedback from Clustered Sources During Reionization

abstract:
  The reionization history of the intergalactic medium (IGM) at high redshift
(z > 6) was likely strongly shaped by several global feedback processes.
Because the earliest ionizing sources formed at the locations of the rare
density peaks, their spatial distribution was strongly clustered. Here we
demonstrate that this clustering significantly boosts the impact of feedback
processes operating at high redshift. We build a semi-analytical model to
include feedback and clustering simultaneously, and apply this model to the
suppression of star-formation in minihalos due to photoionization. The model is
built on the excursion-set-based formalism of Furlanetto, Zaldarriaga and
Hernquist (2004), which incorporates the clustering of ionizing sources, and
which we here extend to include suppression of star formation in minihalos. We
find that clustering increases the mean HII bubble size by a factor of several,
and it dramatically increases the fraction of minihalos that are suppressed, by
a factor of up to 60 relative to a randomly distributed population. This
enhanced suppression can significantly reduce the electron scattering optical
depth, as required by the three-year data from the Wilkinson Microwave
Anisotropy Probe (WMAP). We argue that source clustering is likely to similarly
boost the importance of a variety of other feedback mechanisms.


title:
A Survey of Kiloparsec-Scale Radio Outflows in Radio-Quiet Active
  Galactic Nuclei

abstract:
  Seyfert galaxies commonly host compact jets spanning 10-100 pc scales, but
larger structures (KSRs) are resolved out in long baseline, aperture synthesis
surveys. We report a new, short baseline Very Large Array (VLA) survey of a
complete sample of Seyfert and LINER galaxies. Out of all of the surveyed
radio-quiet sources, we find that 44% (19 / 43) show extended radio structures
at least 1 kpc in total extent that do not match the morphology of the disk or
its associated star-forming regions. The KSR Seyferts stand out by deviating
significantly from the far-infrared - radio correlation for star-forming
galaxies, and they are more likely to have a relatively luminous, compact radio
source in the nucleus; these results argue that KSRs are powered by the AGN
rather than starburst. KSRs probably originate from jet plasma that has been
decelerated by interaction with the nuclear ISM. We demonstrate the jet loses
virtually all of its power to the ISM within the inner kiloparsec to form the
slow KSRs.


title:
The Nearby Damped Lyman-alpha Absorber SBS 1543+593: A Large HI Envelope
  in a Gas-Rich Galaxy Group

abstract:
  We present a Very Large Array (VLA) HI 21cm map and optical observations of
the region around one of the nearest damped Lyman-alpha absorbers beyond the
local group, SBS 1543+593. Two previously uncataloged galaxies have been
discovered and a redshift has been determined for a third. All three of these
galaxies are at the redshift of SBS 1543+593 and are ~185 kpc from the damped
Lyman-alpha absorber. We discuss the HI and optical properties of SBS 1543+593
and its newly identified neighbors. Both SBS 1543+593 and Dwarf 1 have baryonic
components that are dominated by neutral gas -- unusual for damped Lyman-alpha
absorbers for which only ~5% of the HI cross-section originates in such
strongly gas-dominated systems. What remains unknown is whether low mass
gas-rich groups are common surrounding gas-rich galaxies in the local universe
and whether the low star-formation rate in these systems is indicative of a
young system or a stable, slowly evolving system. We discuss these evolutionary
scenarios and future prospects for answering these questions.


title:
Laboratory Plasma Dynamos, Astrophysical Dynamos, and Magnetic Helicity
  Evolution

abstract:
  The term ``dynamo'' means different things to the laboratory fusion plasma
and astrophysical plasma communities. To alleviate the resulting confusion and
to facilitate interdisciplinary progress, we pinpoint conceptual differences
and similarities between laboratory plasma dynamos and astrophysical dynamos.
We can divide dynamos into three types: 1. magnetically dominated helical
dynamos which sustain a large scale magnetic field against resistive decay and
drive the magnetic geometry toward the lowest energy state, 2. flow-driven
helical dynamos which amplify or sustain large scale magnetic fields in an
otherwise turbulent flow, and 3. flow-driven nonhelical dynamos which amplify
fields on scales at or below the driving turbulence. We discuss how all three
types occur in astrophysics whereas plasma confinement device dynamos are of
the first type. Type 3 dynamos requires no magnetic or kinetic helicity of any
kind. Focusing on type 1 and 2 dynamos, we show how different limits of a
unified set of equations for magnetic helicity evolution reveal both types. We
explicitly describe a steady-state example of a type 1 dynamo, and three
examples of type 2 dynamos: (i) closed volume and time dependent; (ii)
steady-state with open boundaries; (iii) time dependent with open boundaries.


title:
Spitzer IRS spectra of a large sample of Seyfert galaxies: a variety of
  infrared SEDs in the local AGN population

abstract:
  We are conducting a large observing program with the Spitzer Space Telescope
to determine the mid-to-far infrared spectral energy distributions of a
well-defined sample of 87 nearby, 12 micron-selected Seyfert galaxies. In this
paper we present the results of IRS low-resolution spectroscopy of a
statistically representative subsample of 51 of the galaxies (59%), with an
analysis of the continuum shapes and a comparison of the Seyfert types. We find
that the spectra clearly divide into groups based on their continuum shapes and
spectral features. Some spectral features are clearly related to a starburst
contribution to the IR spectrum, while the mechanisms producing observed
power-law continuum shapes, attributed to an AGN component, may be dust or
non-thermal emission. The infrared spectral types appear to be related to the
Seyfert types. Principal component analysis results suggest that the relative
contribution of starburst emission may be the dominant cause of variance in the
observed spectra. We find that Sy 1's have higher ratios of IR/radio emission
than Sy 2's, as predicted by the unified model if the torus is optically thick
in the mid-IR. However, smooth-density torus models predict a much larger
difference between type 1's and 2's than observed in our sample. Our
observations may be consistent with clumpy torus models containing a steep
radial distribution of optically thick dense clumps. (Abridged)


title: The 21 Centimeter Forest

abstract:
  We examine the prospects for studying the pre-reionization intergalactic
medium (IGM) through the so-called 21 cm forest in spectra of bright
high-redshift radio sources. We first compute the evolution of the mean optical
depth for models that include X-ray heating of the IGM gas, Wouthuysen-Field
coupling, and reionization. Under most circumstances, the spin temperature T_S
grows large well before reionization begins in earnest. As a result, the
optical depth is less than 0.001 throughout most of reionization, and
background sources must sit well beyond the reionization surface in order to
experience measurable absorption. HII regions produce relatively large
"transmission gaps" and may therefore still be observable during the early
stages of reionization. Absorption from sheets and filaments in the cosmic web
fades once T_S becomes large and should be rare during reionization. Minihalos
can produce strong (albeit narrow) absorption features. Measuring their
abundance would yield useful limits on the strength of feedback processes in
the IGM as well as their effect on reionization.


title:
A sample of low-redshift BL Lacertae objects. II. EVN and MERLIN data
  and multi-wavelength analysis

abstract:
  We present new radio observations of 9 members of a sample of 29 nearby (z <
0.2) BL Lac objects. The new data have been obtained with the European VLBI
Network and/or the MERLIN at 1.6 and 5 GHz and complement previous
observations. For one object, the TeV source Mrk 421, we also present deep
multi-epoch VLBA and Global VLBI data, which reveal a resolved diffuse jet,
with clear signatures of limb brightening. We use the new and old data to
estimate physical parameters of the jets of the sample from which the subset
with new radio data is drawn. We derive Doppler factors in the parsec scale
radio jet in the range ~2 < delta < ~9. Using HST data, we separate the
contribution of the host galaxy from that of the active core. From the measured
and de-beamed observables, we find a weak correlation between radio power and
black hole mass, and a tight correlation between radio and optical core
luminosities. We interpret this result in terms of a common synchrotron origin,
with little contribution from a radiatively efficient accretion disk. The BL
Lacs in our sample have de-beamed properties similar to low power radio
galaxies, including the fundamental plane of black hole activity.


title:
Non-existence of self-similar solutions containing a black hole in a
  universe with a stiff fluid or scalar field or quintessence

abstract:
  We consider the possible existence of self-similar solutions containing black
holes in a Friedmann background with a stiff fluid or a scalar field. We
carefully study the relationship between the self-similar equations in these
two cases and emphasize the crucial role of the similarity horizon. We show
that there is no self-similar black hole solution surrounded by an exact or
asymptotically flat Friedmann background containing a massless scalar field.
This result also applies for a scalar field with a potential, providing the
universe is decelerating. However, if there is a potential and the universe is
accelerating (as in the quintessence scenario), the result only applies for an
exact Friedmann background. This extends the result previously found in the
stiff fluid case and strongly suggests that accretion onto primordial black
holes is ineffective even during scalar field domination. It also contradicts
recent claims that such black holes can grow appreciably by accreting
quintessence. Appreciable growth might be possible with very special matter
fields but this requires {\it ad hoc} and probably unphysical conditions.


title: Spitzer Observations of High Redshift Radio Galaxies

abstract:
  We present the results of a comprehensive Spitzer survey of 70 radio galaxies
across 1<z<5.2. Using IRAC, IRS and MIPS imaging we determine the rest-frame
AGN contribution to the stellar emission peak at 1.6um. The stellar
luminosities are found to be consistent with that of a giant elliptical with a
stellar mass of 10^11-12Msun. The mean stellar mass remains constant at
\~10^11.5Msun up to z=3 indicating that the upper end of the mass function is
already in place by this redshift. The mid-IR luminosities imply bolometric IR
luminosities that would classify all sources as ULIRGs. The mid-IR to radio
luminosity generally correlate implying a common origin for these emissions.
The ratio is higher than that found for lower redshift, ie z<1, radio galaxies.


title:
Colour Dependence of the Distribution of IRAS Galaxies revealed by
  Multifractal Measures

abstract:
  Multifractal measures are applied to three IRAS galaxy subsamples selected by
colour from the PSCz catalogue. As shown by generalised dimension spectrum, hot
IRAS galaxies are found less clustered than cold galaxies, but the difference
is very weak. An alternative tool, the conditional multifractal dimension
spectrum reveals apparent peculiarity of the distribution of hot galaxies,
especially at high orders. The conditional multifractal measure is basically
measuring the environment of selected galaxies. A detailed analysis of the
distribution of galaxies with their number of neighbours turns out that cold
galaxies are more likely living in over dense regions than hot galaxies.
Further studies suggest that, since the colour of IRAS galaxies is a good trace
of star formation rate, it is possible that we have statistical evidence here
for enhanced star formation rate due to galaxy interactions


title: Note on Redshift Distortion in Fourier Space

abstract:
  We explore features of redshift distortion in Fourier analysis of N-body
simulations. The phases of the Fourier modes of the dark matter density
fluctuation are generally shifted by the peculiar motion along the line of
sight, the induced phase shift is stochastic and has probability distribution
function (PDF) symmetric to the peak at zero shift while the exact shape
depends on the wave vector, except on very large scales where phases are
invariant by linear perturbation theory. Analysis of the phase shifts motivates
our phenomenological models for the bispectrum in redshift space. Comparison
with simulations shows that our toy models are very successful in modeling
bispectrum of equilateral and isosceles triangles at large scales. In the
second part we compare the monopole of the power spectrum and bispectrum in the
radial and plane-parallel distortion to test the plane-parallel approximation.
We confirm the results of Scoccimarro (2000) that difference of power spectrum
is at the level of 10%, in the reduced bispectrum such difference is as small
as a few percents. However, on the plane perpendicular to the line of sight of
k_z=0, the difference in power spectrum between the radial and plane-parallel
approximation can be more than 10%, and even worse on very small scales. Such
difference is prominent for bispectrum, especially for those configurations of
tilted triangles. The non-Gaussian signals under radial distortion on small
scales are systematically biased downside than that in plane-parallel
approximation, while amplitudes of differences depend on the opening angle of
the sample to the observer. The observation gives warning to the practice of
using the power spectrum and bispectrum measured on the k_z=0 plane as
estimation of the real space statistics.


title: New Observations and Models of the Kinematics of the Zodiacal Dust Cloud

abstract:
  We report on new observations of the motion of zodiacal dust using optical
absorption line spectroscopy of zodiacal light. We have measured the change in
the profile shape of the scattered solar Mg I 5184 line toward several lines of
sight in the ecliptic plane as well as the ecliptic pole. The variation in line
centroid and line width as a function of helio-ecliptic longitude show a clear
prograde signature and suggest that significant fraction of the dust follows
non-circular orbits that are not confined to the ecliptic plane. When combined
with dynamical models, the data suggest that the zodiacal dust is largely
cometary, rather than asteroidal, in origin.


title: The first year of SN 2004dj in NGC 2403

abstract:
  New BVRI photometry and optical spectroscopy of the Type IIp supernova 2004dj
in NGC 2403, obtained during the first year since discovery, are presented. The
progenitor cluster, Sandage 96, is also detected on pre-explosion frames. The
light curve indicates that the explosion occured about 30 days before
discovery, and the plateau phase lasted about +110 \pm 20 days after that. The
plateau-phase spectra have been modelled with the SYNOW spectral synthesis code
using H, NaI, TiII, ScII, FeII and BaII lines. The SN distance is inferred from
the Expanding Photosphere Method and the Standard Candle Method applicable for
SNe IIp. They resulted in distances that are consistent with each other as well
as earlier Cepheid- and Tully-Fisher distances. The average distance, D = 3.47
\pm 0.29 Mpc is proposed for SN 2004dj and NGC 2403. The nickel mass produced
by the explosion is estimated as 0.02 \pm 0.01 M_o. The SED of the progenitor
cluster is reanalysed by fitting population synthesis models to our observed
BVRI data supplemented by U and JKH magnitudes from the literature. The
chi^2-minimization revealed a possible "young" solution with cluster age T_{cl}
= 8 Myr, and an "old" solution with T_{cl} = 20 - 30 Myr. The "young" solution
would imply a progenitor mass M > 20 M_o, which is higher than the previously
detected progenitor masses for Type II SNe.


title: Particle decay in the early universe: predictions for 21 cm

abstract:
  The influence of ultra-high energy cosmic rays (UHECRs) and decaying dark
matter particles on the emission and absorption characteristics of neutral
hydrogen in 21 cm at redshifts $z = 10-50$ is considered. In presence of UHECRs
21 cm can be seen in absorption with the brightness temperature $T_b=-(5-10)$
mK in the range $z=10-30$. Decayng particles can stimulate a 21 cm signal in
emission with $T_b\sim 50-60$ mK at $z =50$, and $T_b \simeq 10$ mK at $z \sim
20$. Characteristics of the fluctuations of the brightness temperature, in
particular, its power spectrum are also calculated. The maps of the power
spectrum of the brightness temperature on the plane {\it wavenumber-redshift}
are shown to be sensitive to the parameters of UHECRs and decaying dark matter.
Observational possibilities to detect manifestations of UHECRs and/or decaying
particles in 21 cm with the future radio telescopes (LOFAR, 21CMA and SKA), and
to distinguish contributions from them are briefly discussed.


title:
The role of the LIRG and ULIRG phases in the evolution of Ks-selected
  galaxies

abstract:
  We investigate the role of the luminous infrared galaxy (LIRG) and
ultra-luminous infrared galaxy (ULIRG) phases in the evolution of Ks-selected
galaxies and, in particular, Extremely Red Galaxies (ERGs). With this aim, we
compare the properties of a sample of 2905 Ks<21.5 (Vega mag) galaxies in the
GOODS/CDFS with the sub-sample of those 696 sources which are detected at 24
microns. We find that LIRGs constitute 30% of the galaxies with stellar mass
M>1x10^{11} Msun assembled at redshift z=0.5. A minimum of 65% of the galaxies
with M>2.5x10^{11} Msun at z~2-3 are ULIRGs at those redshifts. 60% of the
ULIRGs in our sample have the characteristic colours of ERGs. Conversely, 40%
of the ERGs with stellar mass M>1.3x10^{11} Msun at 1.5<z<2.0 and a minimum of
52% of those with the same mass cut at 2.0<z<3.0 are ULIRGs. The average
optical/near-IR properties of the massive ERGs at similar redshifts that are
identified with ULIRGs and that are not have basically no difference,
suggesting that both populations contain the same kind of objects in different
phases of their lives.
  LIRGs and ULIRGs have an important role in galaxy evolution and mass
assembly, and, although they are only able to trace a fraction of the massive
(M>1x10^{11} Msun) galaxies present in the Universe at a given time, this
fraction becomes very significant (>50%) at redshifts z>~2.


title: X-ray number counts of normal galaxies

abstract:
  We use the number counts of X-ray selected normal galaxies to explore their
evolution by combining the most recent wide-angle shallow and pencil-beam deep
samples available. The differential X-ray number counts, dN/dS, for early and
late-type normal galaxies are constructed separately and then compared with the
predictions of the local X-ray luminosity function under different evolution
scenarios. The dN/dS of early type galaxies is consistent with no evolution out
to z~0.5. For late-type galaxies our analysis suggests that it is the sources
with X-ray--to--optical flux ratio logfx/fopt>-2 that are evolving the fastest.
Including these systems in the late-type galaxy sample yields evolution of the
form ~(1+z)^{2.7} out to z~0.4. On the contrary late-type sources with
logfx/fopt<-2 are consistent with no evolution. This suggests that the
logfx/fopt>-2 population comprises the most powerful and fast evolving
starbursts at moderate and high-z. We argue that although residual
low-luminosity AGN contamination may bias our results toward stronger
evolution, this is unlikely to modify our main conclusions.


title:
Two extremely metal-poor emission-line galaxies in the Sloan Digital Sky
  Survey

abstract:
  We present spectroscopic observations with the 3.6m ESO telescope of two
emission-line galaxies, J2104-0035 and J0113+0052, selected from the Data
Release 4 (DR4) of the Sloan Digital Sky Survey (SDSS). From our data we
determine the oxygen abundance of these systems to be respectively 12+logO/H =
7.26+/-0.03 and 7.17+/-0.09, making them the two most metal-deficient galaxies
found thus far in the SDSS and placing them among the five most metal-deficient
emission-line galaxies ever discovered. Their oxygen abundances are close to
those of the two most metal-deficient emission-line galaxies known,
SBS0335-052W with 12+logO/H = 7.12+/-0.03 and I Zw 18 with 12+logO/H =
7.17+/-0.01.


title: Stochastic wake field particle acceleration in Gamma-Ray Bursts

abstract:
  Gamma-Ray Burst (GRB) prompt emission can, for specific conditions, be so
powerful and short-pulsed to strongly influence any surrounding plasma. In this
paper, we briefly discuss the possibility that a very intense initial burst of
radiation produced by GRBs satisfy the intensity and temporal conditions to
cause stochastic wake-field particle acceleration in a surrounding plasma of
moderate density. Recent laboratory experiments clearly indicate that powerful
laser beam pulses of tens of femtosecond duration hitting on target plasmas
cause efficient particle acceleration and betatron radiation up to tens of MeV.
We consider a simple but realistic GRB model for which particle wake-field
acceleration can first be excited by a very strong low-energy precursor, and
then be effective in producing the observed prompt X-ray and gamma-ray GRB
emission. We also briefly discuss some of the consequences of this novel GRB
emission mechanism.


title:
Spitzer/MIPS 24 micron galaxies: the link to near-IR galaxies and the
  cosmic IR background

abstract:
  We present the results of our most recent works on Spitzer/MIPS 24 micron
galaxies. Through a multiwavelength analysis, we study different properties
(redshifts, luminosities, stellar masses) characterising the sources which
produce the bulk of the mid-IR background. From a comparative study with the
total population of Ks-selected galaxies, we determine that 24 micron sources
account for an important fraction of the most massive galaxies present at
different redshifts. On the other hand, we determine that 24 micron galaxies
also produce most of the energy contained in the far-IR cosmic background at 70
and 160 microns. Furthermore, we are able to set tight constraints on the
Cosmic Infrared Background (CIB) spectral energy distribution (SED). Our
results help to clarify the links between these presumably different IR galaxy
populations.


title:
Comment on "187Re(gamma,n) cross section close to and above the neutron
  threshold"

abstract:
  The work of M\"uller et al. [Phys. Rev. C 73, 025804 (2006);
astro-ph/0512603] provides interesting experimental data on neutron emission by
photodisintegration of 187Re. However, the comparison to theory and the
discussed implications for the Re/Os clock require considerable amendment.


title:
Spitzer/IRAC and ISOCAM/CVF insights on the origin of the Near to Mid-IR
  Galactic diffuse emission

abstract:
  We measure IRAC colors of extended emission in several fields covering a
range of Galactic latitudes and longitudes outside of star forming regions. We
determine the nature of the Galactic diffuse emission in Spitzer/IRAC images by
combining them with spectroscopic data. We show that PAH features make the
emission in the IRAC 5.8 and 8.0 $\mu$m channels, whereas the 3.3 $\mu$m
feature represents only 20 to 50% of the IRAC 3.6 $\mu$m channel. A NIR
continuum is necessary to account for IRAC 4.5 $\mu$m emission and the
remaining fraction of the IRAC 3.6 $\mu$m emission. This continuum cannot be
accounted by scattered light. It represents 9% of the total power absorbed by
PAHs and 120% of the interstellar UV photon flux. The 3.3 $\mu$m feature is
observed to vary from field-to-field with respect to the IRAC 8.0 $\mu$m
channel. The continuum and 3.3 $\mu$m feature intensities are not correlated.
We present model calculations which relate our measurements of the PAHs
spectral energy distribution to the particles size and ionization state. Cation
and neutral PAHs emission properties are inferred empirically from
\object{NGC7023} observations. PAHs caracteristics are best constrained in a
line of sight towards the inner Galaxy, dominated by the Cold Neutral Medium
phase : we find that the PAH cation fraction is about 50% and that their mean
size is about 60 carbon atoms. A significant field-to-field dispersion in the
PAH mean size, from 40 to 80 carbon atoms, is necessary to account for the
observed variations in the 3.3 $\mu$m feature intensity relative to the IRAC
8.0 $\mu$m flux. However, one cannot be secure about the feature interpretation
as long as the continuum origin remains unclear.


title: Galactic Warp in the overdensity of the Canis Major Region

abstract:
  Bellazzini et al. (2006b) claim that Lopez-Corredoira et al.'s (2002) warp
model is totally unable to reproduce the Canis Major structure in the red clump
stars. However, slight variations in the azimuth of the Lopez-Corredoira et al.
(2002) warp model, justified by the uncertainties in the parameter as well as
the local irregularities with respect to the average model, derive a result
much closer to the observations of the overdensity south/north. The bump of red
clump stars with m_K=13-13.5 around l=241 deg., b=-8.5 deg. and the depth of
the Canis Major structure are also explainable in terms of the warp with an
appropriate extrapolation of constant height between galactocentric radii of 13
and 16 kpc, as observed roughly in the southern warp, instead of a
monotonically increasing height like the northern warp; and the observed
velocity distribution of stars cannot exclude the warp possibility. A warp
model is therefore still a possible explanation of the Canis Major overdensity,
and the hypothesis of the existence of a dwarf galaxy is unnecessary, although
still a possibility too.


title: Extinction techniques and impact on dust property determination

abstract:
  The near infrared extinction powerlaw index ($\beta$) and its uncertainty is
derived from three different techniques based on star counts, colour excess and
a combination of them. We have applied these methods to 2MASS data to determine
maps of $\beta$ and near infrared extinction of the small cloud IC 1396 W. The
combination of star counts and colour excess results in the most reliable
method to determine $\beta$. It is found that the use of the correct
$\beta$-map to transform colour excess values into extinction is fundamental
for column density profile analysis of clouds. We describe how artificial
photometric data, based on the model of stellar population synthesis of the
Galaxy (Robin et al. 2003), can be used to estimate uncertainties and derive
systematic effects of the extinction methods presented here. We find that all
colour excess based extinction determination methods are subject to small but
systematic offsets, which do not affect the star counting technique. These
offsets occur since stars seen through a cloud do not represent the same
population as stars in an extinction free control field.


title:
Bisectors of the cross-correlation function applied to stellar spectra.
  Discriminating stellar activity, oscillations and planets

abstract:
  Aims: We investigate whether bisectors derived from cross-correlation
functions (CCF) of single-exposure spectra can be used to provide information
on stellar atmospheres, and whether they can be used to discriminate between
radial velocity changes caused by planets, magnetic activity and oscillations.
  Methods: Using a sample of bright stars observed with the HARPS spectrograph,
we examine the shapes of the bisectors of individual strong spectral lines in
summed spectra, comparing with similar studies in the literature. Moreover, we
examine four different quantitative CCF bisector measures for correlations with
radial velocity and stellar parameters.
  Results: We show that CCF bisector measures can be used for quantitative
analysis, employing both the absolute values and the variations. From absolute
values, log g and absolute magnitude can be approximated, and from the
correlations with radial velocity one can distinguish between magnetic
activity, oscillations and orbiting planets as the probable cause of radial
velocity variations. We confirm that different isolated spectral lines show
different bisector shapes, even between lines of the same element, calling for
caution in trying to derive global stellar properties from the bisector of a
CCF. For the active star HR 1362 we suggest from the bisector shape an extra
photospheric heating caused by the chromosphere of several hundred degrees. We
confirm the fill-in of spectral lines of the Sun taken on the daylight sky
caused by Rayleigh-Brillouin and aerosol scattering, and we show for the first
time that the fill-in has an asymmetric component.


title:
An Observational Test for the Anthropic Origin of the Cosmological
  Constant

abstract:
  The existence of multiple regions of space beyond the observable Universe
(within the so-called "multiverse") where the vacuum energy density takes
different values, has been postulated as an explanation for the low non-zero
value observed for it in our Universe. It is often argued that our existence
pre-selects regions where the cosmological constant is sufficiently small to
allow galaxies like the Milky Way to form and intelligent life to emerge. Here
we propose a simple empirical test for this anthropic argument within the
boundaries of the observable Universe. We make use of the fact that dwarf
galaxies formed in our Universe at redshifts as high as z~10 when the mean
matter density was larger by a factor of ~10^3 than today. Existing technology
enables to check whether planets form in nearby dwarf galaxies and globular
clusters by searching for microlensing or transit events of background stars.
The oldest of these nearby systems may have formed at z~10. If planets are as
common per stellar mass in these descendents as they are in the Milky Way
galaxy, then the anthropic argument would be weakened considerably since
planets could have formed in our Universe even if the cosmological constant was
three orders of magnitude larger than observed. For a flat probability
distribution, this would imply that the probability for us to reside in a
region where the cosmological constant obtains its observed value is lower than
\~10^{-3}. A precise version of the anthropic argument could then be ruled-out
at a confidence level of ~99.9%, which constitutes a satisfactory measure of a
good experimental test.


title:
ACIS-I observations of NGC2264. Membership and X-ray properties of PMS
  stars

abstract:
  We analyze a deep, 100 ksec long, Chandra ACIS observation of NGC2264. We
detect 420 sources, 85% of which are associated with known optical and NIR
counterparts. More than 90% of these counterparts are NGC2264 members, thus
significantly increasing the known low mass cluster population by about 100
objects. Among the sources without counterpart, ~50% are likely members,
several of which we expect to be previously unknown protostellar objects. We
confirm several previous findings on the X-ray activity of low mass PMS stars:
X-ray luminosity is related to stellar mass, although with a large scatter;
L_X/L_bol is close to but almost invariably below the saturation level, 1e-3. A
comparison between CTTS and WTTS shows several differences: CTTS are on average
less active than WTTS; their emission may also be more time variable and is on
average slightly harder. However, we find evidence in some CTTS of extremely
cool, ~0.1-0.2 keV, plasma which we speculate is heated by accretion shocks. We
conclude that activity in low mass PMS stars, while generally similar to that
of saturated MS stars, may be affected by mass accretion in several ways:
accretion is likely responsible for very soft X-ray emission directly produced
in the accretion shock; it may reduce the average energy output of solar-like
coronae, at the same time making them hotter and more dynamic.


title: Can the thermal instability drive turbulence?

abstract:
  The thermal instability with a piecewise power law cooling function is
investigated using one- and three-dimensional simulations with periodic and
shearing-periodic boundary conditions in the presence of constant thermal
diffusion and kinematic viscosity coefficients. Consistent with earlier
findings, the flow behavior depends on the average density, <rho>. When
$\bra{\rho}$ is in the range 1-5 x 10^{-24} g cm^{-3} the system is unstable
and segregates into cool and warm phases with temperatures of roughly 100 and
10^4 K, respectively. However, in all cases the resulting average pressure <p>
is independent of <rho> and just a little above the minimum value. For a
constant heating rate of 0.015 erg g^{-1} s^{-1}, the mean pressure is around
24 x 10^{-14} dyn (corresponding to p/k_B ~ K cm^{-3}). Cool patches tend to
coalesce into bigger ones. In all cases investigated there is no sustained
turbulence, which is in agreement with earlier results. Simulations in which
turbulence is driven by a body force show that when rms velocities of between
10 and 30 km/s are obtained, the resulting dissipation rates rates are
comparable to the thermal energy input rate. The resulting mean pressures are
then about 30 x 10^{-14} dyn, corresponding to p/k_B ~ 2170 K cm^{-3}. This is
comparable to the value expected for the Galaxy. Differential rotation tends to
make the flow two-dimensional, that is, uniform in the streamwise direction,
but this does not lead to instability.


title:
Direct measurement of the size of 2003 UB313 from the Hubble Space
  Telescope

abstract:
  We have used the Hubble Space Telescope to directly measure the angular size
of the large Kuiper belt object 2003 UB313. By carefully calibrating the point
spread function of a nearby field star, we measure the size of 2003 UB313 to be
34.3$\pm$1.4 milliarcseconds, corresponding to a diameter of 2400$\pm$100 km or
a size $\sim5$% larger than Pluto. The V band geometric albedo of 2003 UB313 is
$86\pm7$%. The extremely high albedo is consistent with the frosty methane
spectrum, the lack of red coloring, and the lack of observed photometric
variation on the surface of 2003 UB313. Methane photolysis should quickly
darken the surface of 2003 UB313, but continuous evaporation and redeposition
of surface ices appears capable of maintaining the extreme alebdo of this body.


title:
Can Ejecta-Dominated Supernova Remnants be Typed from their X-ray
  Spectra? The Case of G337.2-0.7

abstract:
  In this paper we use recent X-ray and radio observations of the ejecta-rich
Galactic supernova remnant (SNR) G337.2-0.7 to determine properties of the
supernova (SN) explosion that formed this source. H I absorption measurements
from the Australia Telescope Compact Array (ATCA) constrain the distance to
G337.2-0.7 to lie between 2.0 +/- 0.5 and 9.3 +/- 0.3 kpc. Combined with a
clear radio image of the outer blast-wave, this distance allows us to estimate
the dynamical age (between 750 and 3500 years) from the global X-ray spectrum
obtained with the XMM-Newton and Chandra observatories. The presence of ejecta
is confirmed by the pattern of fitted relative abundances, which show Mg, Ar
and Fe to be less enriched (compared to solar) than Si, S or Ca, and the ratio
of Ca to Si to be 3.4 +/- 0.8 times the solar value (under the assumption of a
single electron temperature and single ionization timescale). With the addition
of a solar abundance component for emission from the blast-wave, these
abundances (with the exception of Fe) resemble the ejecta of a Type Ia, rather
than core-collapse, SN. Comparing directly to models of the ejecta and
blast-wave X-ray emission calculated by evolving realistic SN Ia explosions to
the remnant stage allows us to deduce that one-dimensional delayed detonation
and pulsed delayed detonation models can indeed reproduce the major features of
the global spectrum. In particular, stratification of the ejecta, with the Fe
shocked most recently, is required to explain the lack of prominent Fe-K
emission.


title: The B-Supergiant Components of the Double-Lined Binary HD1383

abstract:
  We present new results from a study of high quality, red spectra of the
massive binary star system HD 1383 (B0.5 Ib + B0.5 Ib). We determined radial
velocities and revised orbital elements (P = 20.28184 +/- 0.0002 d) and made
Doppler tomographic reconstructions of the component spectra. A comparison of
these with model spectra from non-LTE, line blanketed atmospheres indicates
that both stars have almost identical masses (M_2/M_1 = 1.020 +/- 0.014),
temperatures (T_eff = 28000 +/- 1000 K), gravities (log g = 3.25 +/- 0.25), and
projected rotational velocities (V sin i < 30 km/s). We investigate a number of
constraints on the radii and masses of the stars based upon the absence of
eclipses, surface gravity, stellar wind terminal velocity, and probable
location in the Perseus spiral arm of the Galaxy, and these indicate a range in
probable radius and mass of R/R_sun = 14 - 20 and M/M_sun = 16 - 35,
respectively. These values are consistent with model evolutionary masses for
single stars of this temperature and gravity. Both stars are much smaller than
their respective Roche radii, so the system is probably in a pre-contact stage
of evolution. A fit of the system's spectral energy distribution yields a
reddening of E(B-V)=0.55 +/- 0.05 and a ratio of total-to-selective extinction
of R=2.97 +/- 0.15. We find no evidence of H-alpha emission from colliding
stellar winds, which is probably the consequence of the low gas densities in
the colliding winds zone.


title: Scalar Perturbations in Two-Temperature Cosmological Plasmas

abstract:
  We study the properties of density perturbations of a two-component plasma
with a temperature difference on a homogeneous and isotropic background. For
this purpose we extend the general relativistic gauge invariant covariant (GIC)
perturbation theory to include a multi-fluid with a particular equations of
state (ideal gas) and imperfect fluid terms due to the relative energy flux
between the two species. We derive closed sets of GIC vector and subsequently
scalar evolution equations. We then investigate solutions in different regimes
of interest. In particular, we study long wavelength and arbitrary wavelength
Langmuir and ion-acoustic perturbations. The harmonic oscillations are
superposed on a Jeans type instability. We find a generalised Jeans criterion
for collapse in a two-temperature plasma, which states that the species with
the largest sound velocity determines the Jeans wavelength. Furthermore, we
find that within the limit for gravitational collapse, initial perturbations in
either the total density or charge density lead to a growth in the initial
temperature difference. These results are relevant for the basic understanding
of the evolution of inhomogeneities in cosmological models.


title:
Numerical simulation of small perturbation on an accretion disk due to
  the collision of a star with the disk near the black hole

abstract:
  In this paper, perturbations of an accretion disk by a star orbiting around a
black hole are studied. We report on a numerical experiment, which has been
carried out by using a parallel-machine code originally developed by D\"{o}nmez
(2004). An initially steady state accretion disk near a non-rotating
(Schwarzschild) black hole interacts with a "star", modeled as an initially
circular region of increased density. Part of the disk is affected by the
interaction. In some cases, a gap develops and shock wave propagates through
the disk. We follow the evolution for order of one dynamical period and we show
how the non-axisymetric density perturbation further evolves and moves
downwards where the material of the disk and the star become eventually
accreted onto the central body.
  When the star perturbs the steady state accretion disk, the disk around the
black hole is destroyed by the effect of perturbation. The perturbed accretion
disk creates a shock wave during the evolution and it loses angular momentum
when the gas hits on the shock waves. Colliding gas with the shock wave is the
one of the basic mechanism of emitting the $X-$rays in the accretion disk. The
series of supernovae occurring in the inner disk could entirely destroy the
disk in that region which leaves a more massive black hole behind, at the
center of galaxies.


title:
A New Measurement of the Stellar Mass Density at z~5: Implications for
  the Sources of Cosmic Reionization

abstract:
  We present a new measurement of the integrated stellar mass per comoving
volume at redshift 5 determined via spectral energy fitting drawn from a sample
of 214 photometrically-selected galaxies with z'<26.5 in the southern GOODS
field. Following procedures introduced by Eyles et al. (2005), we estimate
stellar masses for various sub-samples for which reliable and unconfused
Spitzer IRAC detections are available. A spectroscopic sample of 14 of the most
luminous sources with <z>=4.92 provides a firm lower limit to the stellar mass
density of 1e6 Msun/Mpc^3. Several galaxies in this sub-sample have masses of
order 10^11 Msun implying significant earlier activity occurred in massive
systems. We then consider a larger sample whose photometric redshifts in the
publicly-available GOODS-MUSIC catalog lie in the range 4.4 <z 5.6. Before
adopting the GOODS-MUSIC photometric redshifts, we check the accuracy of their
photometry and explore the possibility of contamination by low-z galaxies and
low-mass stars. After excising probable stellar contaminants and using the z'-J
color to exclude any remaining foreground red galaxies, we conclude that 196
sources are likely to be at z~5. The implied mass density from the unconfused
IRAC fraction of this sample, scaled to the total available, is 6e6 Msun/Mpc^3.
We discuss the uncertainties as well as the likelihood that we have
underestimated the true mass density. Including fainter and quiescent sources
the total integrated density could be as high as 1e7 Msun/Mpc^3. Using the
currently available (but highly uncertain) rate of decline in the star
formationhistory over 5 <z< 10, a better fit is obtained for the assembled mass
at z~5 if we admit significant dust extinction at early times or extend the
luminosity function to very faint limits. [abridged]


title:
Surface Brightness Profiles of Galactic Globular Clusters from Hubble
  Space Telescope Images

abstract:
  Hubble Space Telescope allows us to study the central surface brightness
profiles for globular clusters at unprecedented detail. We have mined the HST
archives to obtain 38 WFPC2 images of galactic globular clusters with adequate
exposure times and filters, which we use to measure their central structure. We
outline a reliable method to obtain surface brightness profiles from integrated
light that we test on an extensive set of simulated images. Most clusters have
central surface brightness about 0.5 mag brighter than previous measurements
made from ground-based data, with the largest differences around 2 magnitudes.
Including the uncertainties in the slope estimates, the surface brightness
slope distribution is consistent with half of the sample having flat cores and
the remaining half showing a gradual decline from 0 to -0.8
(dlog(Sigma)/dlogr). We deproject the surface brightness profiles in a
non-parametric way to obtain luminosity density profiles. The distribution of
luminosity density logarithmic slopes show similar features with half of the
sample between -0.4 and -1.8. These results are in contrast to our theoretical
bias that the central regions of globular clusters are either isothermal (i.e.
flat central profiles) or very steep (i.e. luminosity density slope ~-1.6) for
core-collapse clusters. With only 50% of our sample having central profiles
consistent with isothermal cores, King models appear to poorly represent most
globular clusters in their cores.


title: Spitzer Observations of Red Galaxies at High Redshifts

abstract:
  I discuss constraints on star formation and AGN in massive, red galaxies at
z~1-3 using Spitzer observations at 3-24 micron. In particular I focus on a
sample of distant red galaxies (DRGs) with J - K > 2.3 in the southern Great
Observatories Origins Deep Survey (GOODS-S) field. The DRGs have typical
stellar masses >10^11 solar masses. Interestingly, the majority (>50%) of these
objects have 24 micron flux densities >50 micro-Jy. At these redshifts massive
galaxies undergo intense (and possibly frequent) IR-active phases, which is in
constrast to lower-redshift massive galaxies. If the 24 micron emission in
these z~1-3 galaxies is attributed to star formation, then it implies star
formation rates (SFRs) in excess of ~100 solar masses per year. These galaxies
have specific SFRs equal to or exceeding the global average value at that
epoch. Thus, this is an active period in their assembly. Based on their X-ray
luminosities and near-IR colors, as many as 25% of the massive galaxies at
z>1.5 host AGN, suggesting that the growth of supermassive black holes
coincides with massive-galaxy assembly.


title:
Bringing VY Canis Majoris Down to Size: An Improved Determination of Its
  Effective Tempeature

abstract:
  The star VY CMa is a late-type M supergiant with many peculiarities, mostly
related to the intense circumstellar environment due to the star's high
mass-loss rate. Claims have been made that would suggest this star is
considerably more luminous (L = 5 x 10^5 Lo) and larger (R=2800 Ro) than other
Galactic red supergiants (RSGs). Indeed, such a location in the H-R diagram
would be well in the "Hayashi forbidden zone" where stars cannot be in
hydrostatic equilibrium. These extraordinary properties, however, rest upon an
assumed effective temperature of 2800-3000 K, far cooler than recent work have
shown RSGs to be. To obtain a better estimate, we fit newly obtained
spectrophotometry in the optical and NIR with the same MARCS models used for
our recent determination of the physical properties of other RSGs; we also use
$V-K$ and $V-J$ from the literature to derive an effective temperatures. We
find that the star likely has a temperature of 3650 K, a luminosity L = 6 x
10^4 Lo, and a radius of 600Ro. These values are consistent with VY CMa being
an ordinary evolved 15 Mo RSG, and agree well with the Geneva evolutionary
tracks. We find that the circumstellar dust region has a temperature of 760 K,
and an effective radius of approximately 130 AU, if spherical geometry is
assumed for the latter. What causes this star to have such a high mass-loss,
and large variations in brightness (but with little change in color), remains a
mystery at present, although we speculate that perhaps this star (and NML Cyg)
are simply normal RSGs caught during an unusually unstable time.