title: The Universal Rotation Curve of Spiral Galaxies

abstract:
  The observed strong dark-to-luminous matter coupling is described by a bias
relation between visible and dark matter sources. We discuss the bias which
emerges in the case where the topological structure of the Universe at very
large distances does not match properly that of the Friedman space. With the
use of such "topological" bias, we construct the Universal Rotation Curve (URC)
for spirals which occurs to be in a striking agreement with the empirically
known URC. We also show that the topological bias explains the origin of the
Tully-Fisher relation ($ L\sim V^{4}$) and predicts peculiar oscillations in
the URC with a characteristic length $\sim \sqrt{L}$.


title: The Nature of SS433 and the Ultraluminous X-ray Sources

abstract:
  The periodic precession (162--day) and nodding (6.3--day) motions of the jets
in SS433 are driven in the outer regions of the disc, whereas the jets
themselves, being relativistic, are launched near the black hole at the disc
centre. Given that the nutation period is comparable to the dynamical timescale
in the outer regions of the disc, it seems unlikely that these periods can be
communicated efficiently to the disc centre. Here we propose that the massive
outflow observed in SS433 is launched at large radii in the disc, about 1/10 of
the outer disc edge, and that it is this outflow which responds to the
oscillations of the outer disc and determines the direction of the jets. The
massive outflow is launched at large radius because the mass transfer rate is
hyper-Eddington. This implies not only that the total luminosity of SS433
exceeds $\le$ by a considerable factor, but also that the radiative output is
collimated along the outflow. We thus suggest that SS433 is an ultraluminous
X-ray source (ULX) viewed `from the side'. We also suggest that the obscured
{\it INTEGRAL} sources may be SS433--like objects, but with slightly lower mass
transfer rates.


title: The yield of air fluorescence induced by electrons

abstract:
  The fluorescence yield for dry air and pure nitrogen excited by electrons is
calculated using a combination of well-established molecular properties and
experimental data of the involved cross sections. Particular attention has been
paid to the role of secondary electrons from ionization processes. At high
pressure and high energy, observed fluorescence turns out to be proportional to
the ionization cross section which follows the Born-Bethe law. Predictions on
fluorescence yields in a very wide interval of electron energies (eV - GeV) and
pressures (1 and 1013 hPa) as expected from laboratory measurements are
presented. Experimental results at energies over 1 MeV are in very good
agreement with our calculations for pure nitrogen while discrepancies of about
20% are found for dry air, very likely associated to uncertainties in the
available data on quenching cross sections. The relationship between
fluorescence emission, stopping power and deposited energy is discussed.


title:
The Globular Cluster System of NGC 5846 Revisited: Colours, Sizes and
  X-Ray Counterparts

abstract:
  NGC 5846 is a giant elliptical galaxy with a previously well studied globular
cluster system (GCS), known to have a bimodal colour distribution with a
remarkably high red fraction. Here we revisit the central galaxy regions
searching for new globular cluster (GC) candidates, and measuring, magnitudes,
colours and sizes for them. We also search for their X-ray counterparts. We use
archival Hubble Space Telescope WFPC2 images, from which we modelled and
subtracted the host light distribution and increased the available sample of
GCs. We performed photometry on the central objects, and measured sizes and
equatorial coordinates for the entire system known in this galaxy. We detect
two dozen previously unknown GC candidates in the central regions. Reliable
sizes are obtained for about 60 GCs; their typical effective radii are in the
range 3-5 pc. The largest clusters are located in the central regions. We find
7 X-ray counterparts to globular clusters, most of them in the central region.
They are among the most luminous X-ray sources in NGC 5846. They are also
optically luminous, compact and belong to the red subpopulation.


title:
On the Fueling of Massive Black Holes and the Properties of their Host
  Spheroids

abstract:
  We study the relation between nuclear massive black holes and their host
spheroid gravitational potential. Using simple models, we analyze how gas is
expected to be transported in the nuclear regions of galaxies. When we couple
it with the expected gas lifetime given by the Kennicutt-Schmidt Law, this
naturally leads to the `M_BH - M_virial' and `M_BH - sigma' relations. We also
numerically test, using AMR simulations, our simple models for the mass
transport with satisfactory results.


title:
3-D Photoionization Structure and Distances of Planetary Nebulae III.
  NGC 6781

abstract:
  Continuing our series of papers on the three-dimensional (3-D) structures of
and accurate distances to Planetary Nebulae (PNe), we present our study of the
planetary nebula NGC6781. For this object we construct a 3-D photoionization
model and, using the constraints provided by observational data from the
literature we determine the detailed 3-D structure of the nebula, the physical
parameters of the ionizing source and the first precise distance. The procedure
consists in simultaneously fitting all the observed emission line morphologies,
integrated intensities and the 2-D density map from the [SII] line ratios to
the parameters generated by the model, and in an iterative way obtain the best
fit for the central star parameters and the distance to NGC6781, obtaining
values of 950+-143pc and 385 Lsun for the distance and luminosity of the
central star respectively. Using theoretical evolutionary tracks of
intermediate and low mass stars, we derive the mass of the central star of
NGC6781 and its progenitor to be 0.60+-0.03 Msun and 1.5+-0.5 Msun
respectively.


title: Precise radial velocities of giant stars: I. Stable stars

abstract:
  Context: Future astrometric missions such as SIM PlanetQuest need very stable
reference stars. K giants have large luminosities, which place them at large
distances and thus the jitter of their photocenters by companions is relatively
small. Therefore K giants would be best suited as references. To confirm this
observationally a radial velocity survey is performed to quantify the level of
intrinsic variability in K giants.
  Aims: From this radial velocity survey we present 34 K giants with an
observed standard deviation of the radial velocity of less than 20 m/s. These
stars are considered ``stable'' and can be used as radial velocity standards.
  Methods: The radial velocity survey contains 179 K giants. All K giants have
a declination between -30 and +65 degrees and visual magnitude of 3-6 mag. The
Coude Auxiliary Telescope (CAT) at UCO/Lick Observatory is used to obtain
radial velocities with an accuracy of 5-8 m/s. The number of epochs for the 34
stable stars ranges from 11 to 28 with a total timespan of the observations
between 1800 and a little over 2200 days.
  Results: The observational results of the 34 ``stable'' stars are shown
together with a discussion about their position in the M_{V} vs. B-V diagram
and some conclusions concerning the radial velocity variability of K giants.
These results are in agreement with the theoretical predictions. K giants in a
certain range of the M_{V} vs. B-V diagram are suitable reference stars.


title:
Fluorine Abundance Variations as a Signature of Enhanced Extra Mixing in
  Red Giants of the Globular Cluster M4

abstract:
  We show that enhanced extra mixing in low-mass red giants can result in a
fluorine abundance that is correlated with abundance variations of other
elements participating in H burning, such as C, N, O and Na. This finding is
used to explain the fluorine abundance variations recently found in bright red
giants of the globular cluster M4.


title:
Time-Dependent Stochastic Particle Acceleration in Astrophysical
  Plasmas: Exact Solutions Including Momentum-Dependent Escape

abstract:
  Stochastic acceleration of charged particles due to interactions with
magnetohydrodynamic (MHD) plasma waves is the dominant process leading to the
formation of the high-energy electron and ion distributions in a variety of
astrophysical systems. Collisions with the waves influence both the
energization and the spatial transport of the particles, and therefore it is
important to treat these two aspects of the problem in a self-consistent
manner. We solve the representative Fokker-Planck equation to obtain a new,
closed-form solution for the time-dependent Green's function describing the
acceleration and escape of relativistic ions interacting with Alfven or
fast-mode waves characterized by momentum diffusion coefficient $D(p)\propto
p^q$ and mean particle escape timescale $t_esc(p) \propto p^{q-2}$, where $p$
is the particle momentum and $q$ is the power-law index of the MHD wave
spectrum. In particular, we obtain solutions for the momentum distribution of
the ions in the plasma and also for the momentum distribution of the escaping
particles, which may form an energetic outflow. The general features of the
solutions are illustrated via examples based on either a Kolmogorov or
Kraichnan wave spectrum. The new expressions complement the results obtained by
Park and Petrosian, who presented exact solutions for the hard-sphere
scattering case ($q=2$) in addition to other scenarios in which the escape
timescale has a power-law dependence on the momentum. Our results have direct
relevance for models of high-energy radiation and cosmic-ray production in
astrophysical environments such as $\gamma$-ray bursts, active galaxies, and
magnetized coronae around black holes.


title: Cosmology and the Bispectrum

abstract:
  The present spatial distribution of galaxies in the Universe is non-Gaussian,
with 40% skewness in 50 Mpc/h spheres, and remarkably little is known about the
information encoded in it about cosmological parameters beyond the power
spectrum. In this work we present an attempt to bridge this gap by studying the
bispectrum, paying particular attention to a joint analysis with the power
spectrum and their combination with CMB data. We address the covariance
properties of the power spectrum and bispectrum including the effects of beat
coupling that lead to interesting cross-correlations, and discuss how baryon
acoustic oscillations break degeneracies. We show that the bispectrum has
significant information on cosmological parameters well beyond its power in
constraining galaxy bias, and when combined with the power spectrum is more
complementary than combining power spectra of different samples of galaxies,
since non-Gaussianity provides a somewhat different direction in parameter
space. In the framework of flat cosmological models we show that most of the
improvement of adding bispectrum information corresponds to parameters related
to the amplitude and effective spectral index of perturbations, which can be
improved by almost a factor of two. Moreover, we demonstrate that the expected
statistical uncertainties in sigma8 of a few percent are robust to relaxing the
dark energy beyond a cosmological constant.


title: Close Galaxy Counts as a Probe of Hierarchical Structure Formation

abstract:
  Standard LCDM predicts that the major merger rate of galaxy-size dark matter
halos rises rapidly with redshift. The average number of close companions per
galaxy, Nc, is often used to infer the galaxy merger rate, however, recent
observational studies suggest that Nc evolves very little with redshift. Here
we use a "hybrid" N- body simulation plus analytic substructure model to
predict Nc directly. We identify dark matter subhalos with galaxies and show
that the observed lack of close pair count evolution arises because the high
merger rate per halo at early times is counteracted by a decrease in the number
of halos massive enough to host a galaxy pair. We compare our results to data
compiled from the DEEP2, SSRS2, and the UZC redshift surveys. Observed pair
counts match our predictions if we assume a monotonic mapping between galaxy
luminosity and the maximum circular velocity that each subhalo had when it was
first accreted onto its host halo. This suggests that satellite galaxies are
significantly more resilient to destruction than are dissipationless dark
matter subhalos. We argue that while Nc does not provide a direct measure of
the halo merger rate, it offers a powerful means to constrain the Halo
Occupation Distribution and the spatial distribution of galaxies within halos.
Interpreted in this way, close pair counts provide a useful test of galaxy
formation processes on < 100 kpc scales.


title: Heating of the Solar Corona by Dissipative Alfven Solitons

abstract:
  Solar photospheric convection drives myriads of dissipative Alfven solitons
(hereinafter called alfvenons) capable of accelerating electrons and ions to
energies of hundreds of keV and producing the X-ray corona. Alfvenons are exact
solutions of two-fluid equations for a collisionless plasma and represent
natural accelerators for conversion of the electromagnetic energy flux driven
by convective flows into kinetic energy of charged particles in space and
astrophysical plasmas. Their properties have been experimentally verified in
the magnetosphere, where they accelerate auroral electrons to tens of keV.


title:
Gamma-Hadron Separation Methods for the VERITAS Array of Four Imaging
  Atmospheric Cherenkov Telescopes

abstract:
  Ground-based arrays of imaging atmospheric Cherenkov telescopes have emerged
as the most sensitive gamma-ray detectors in the energy range of about 100 GeV
and above. The strengths of these arrays are a very large effective collection
area on the order of 100,000 square meter, combined with excellent single
photon angular and energy resolutions. The sensitivity of such detectors is
limited by statistical fluctuations in the number of Cosmic Ray initiated air
showers that resemble gamma-ray air showers in many ways. In this paper, we
study the performance of simple event reconstruction methods when applied to
simulated data of the Very Energetic Radiation Imaging Telescope Array System
(VERITAS) experiment. We review methods for reconstructing the arrival
direction and the energy of the primary photons, and examine means to improve
on their performance. For a software threshold energy of 300 GeV (100 GeV), the
methods achieve point source angular and energy resolutions of sigma[63%]= 0.1
degree (0.2 degree) and sigma[68%]= 15% (22%), respectively. The main emphasis
of the paper is the discussion of gamma-hadron separation methods for the
VERITAS experiment. We find that the information from several methods can be
combined based on a likelihood ratio approach and the resulting algorithm
achieves a gamma-hadron suppression with a quality factor that is substantially
higher than that achieved with the standard methods used so far.


title: Hot Accretion With Conduction: Spontaneous Thermal Outflows

abstract:
  Motivated by the low-collisionality of gas accreted onto black holes in Sgr
A* and other nearby galactic nuclei, we study a family of 2D advective
accretion solutions with thermal conduction. While we only impose global
inflow, the accretion flow spontaneously develops bipolar outflows. The role of
conduction is key in providing the extra degree of freedom (latitudinal energy
transport) necessary to launch these rotating thermal outflows. The sign of the
Bernoulli constant does not discriminate between inflowing and outflowing
regions. Our parameter survey covers mass outflow rates from ~ 0 to 13% of the
net inflow rate, outflow velocities from ~0 to 11% of the local Keplerian
velocity and outflow opening angles from ~ 0 to 60 degs. As the magnitude of
conduction is increased, outflows can adopt a conical geometry, pure inflow
solutions emerge, and the limit of 2D non-rotating Bondi-like solutions is
eventually reached. These results confirm that radiatively-inefficient, hot
accretion flows have a hydrodynamical propensity to generate bipolar thermal
outflows.


title:
GRB 060218/SN 2006aj: Prompt Emission from Inverse-Compton Scattering of
  Shock Breakout Thermal Photons

abstract:
  The gamma-ray burst (GRB) 060218/SN 2006aj is a peculiar event, with the
second lowest redshift, low luminosity, long duration, chromatic lightcurve
features, and in particular, the presence of a thermal component in the X-ray
and UV-optical spectra. Thanks to detailed temporal and spectral coverage of
the {\em Swift} observatory, the abundant data allow the GRB prompt emission to
be modelled in great detail for the first time. The low flux of prompt
UV/optical emission disfavors the conventional internal shock/synchrotron
radiation models, which generally predict strong UV/optical emission. Here we
show that the unusual prompt emission of GRB 060218 can be produced by
inverse-Compton scattering of shock-accelerated relativistic electrons off the
detected thermal photons. A pair of (forward plus reverse) shocks form when a
relativistic outflow interacts with a preexisting slower shell. The observed
gamma-ray emission and X-ray emission arise from the reverse-shocked and
forward-shocked regions, respectively. A fit to the data requires an initially
increasing outflow luminosity, which is consistent with the prediction of the
popular collapsar model.


title: Optical polarimetric monitoring of the type II-plateau SN 2005af

abstract:
  Aims. Core-collapse supernovae may show significant polarization that implies
non-spherically symmetric explosions. We observed the type II-plateau SN 2005af
using optical polarimetry in order to verify whether any asphericity is present
in the supernova temporal evolution. Methods. We used the IAGPOL imaging
polarimeter to obtain optical linear polarization measurements in R (five
epochs) and V (one epoch) broadbands. Interstellar polarization was estimated
from the field stars in the CCD frames. The optical polarimetric monitoring
began around one month after the explosion and lasted ~30 days, between the
plateau and the early nebular phase. Results. The weighted mean observed
polarization in R band was [1.89 +/- 0.03]% at position angle (PA) 54 deg.
After foreground subtraction, the level of the average intrinsic polarization
for SN 2005af was ~0.5% with a slight enhancement during the plateau phase and
a decline at early nebular phase. A rotation in PA on a time scale of days was
also observed. The polarimetric evolution of SN 2005af in the observed epochs
is consistent with an overall asphericity of ~20% and an inclination of ~30
deg. Evidence for a more complex, evolving asphericity, possibly involving
clumps in the SN 2005af envelope, is found.


title:
Power Spectrum Analysis of Far-IR Background Fluctuations in 160 Micron
  Maps From the Multiband Imaging Photometer for Spitzer

abstract:
  We describe data reduction and analysis of fluctuations in the cosmic far-IR
background (CFIB) in observations with the Multiband Imaging Photometer for
Spitzer (MIPS) instrument 160 micron detectors. We analyzed observations of an
8.5 square degree region in the Lockman Hole, part of the largest low-cirrus
mapping observation with this instrument. We measured the power spectrum of the
CFIB in these observations by fitting a power law to the IR cirrus component,
the dominant foreground contaminant, and subtracting this cirrus signal. The
CFIB power spectrum in the range 0.2 arc min^{-1} <k< 0.5 arc min^{-1} is
consistent with previous measurements of a relatively flat component. However,
we find a large power excess at low k, which falls steeply to the flat
component in the range 0.03 arc min^{-1} <k< 0.1 arc min^{-1}. This low-k power
spectrum excess is consistent with predictions of a source clustering
"signature". This is the first report of such a detection in the far-IR.


title: Polarised views of the drifting subpulse phenomenon

abstract:
  I review recent results concerning the shape of drifting subpulse patterns,
and the relationship to model predictions. While a variety of theoretical
models exist for drifting subpulses, observers typically think in terms of a
spatio-temporal model of circulating beamlets. Assuming the model is correct,
geometric parameters have been inferred and animated "maps" of the beam have
been made. However, the model makes very specific predictions about the
curvature of the drift bands that have remained largely untested. Work so far
in this area indicates that drift bands tend not to follow the prediction, and
in some cases discontinuities are seen that are suggestive of the superposition
of out of phase drift patterns. Recent polarimetric observations also show that
the drift patterns in the two orthogonal polarisation modes are offset in
phase. In one case the pattern in one of the modes shows a discontinuity
suggesting no less than three superposed, out-of-phase drift patterns! I advise
caution in the interpretation of observational data in the context of overly
simplistic models.


title:
Determining Distances to Clusters of Galaxies using Resonant X-ray
  Emission Lines

abstract:
  Bright clusters of galaxies can be seen out to cosmological distances, and
thus they can be used to derive cosmological parameters. Although the continuum
X-ray emission from the intra-cluster gas is optically thin, the optical depth
of resonant lines of ions of heavy elements can be larger than unity. In this
Letter we study the feasibility of deriving distances to clusters of galaxies
by determining the spatial distribution of the intra-cluster gas from X-ray
imaging and the optical depth from resonant emission lines (the XREL method).
We solve the radiative transfer problem for line scattering in the hot
intra-cluster gas using Monte Carlo simulations. We discuss the spatial and
spectral resolutions needed to use the XREL method for accurate determination
of distances, and hence cosmological parameters, and show that accurate
distances will be obtained by applying this technique with the next generation
of high resolution X-ray spectrometers.


title:
On the Putative Detection of z>0 X-ray Absorption Features in the
  Spectrum of Markarian 421

abstract:
  In a series of papers, Nicastro et al. have reported the detection of z>0
OVII absorption features in the spectrum of Mrk421 obtained with the Chandra
Low Energy Transmission Grating Spectrometer (LETGS). We evaluate this result
in the context of a high quality spectrum of the same source obtained with the
Reflection Grating Spectrometer (RGS) on XMM-Newton. The data comprise over
955ks of usable exposure time and more than 26000 counts per 50 milliAngstrom
at 21.6 Angstroms. We concentrate on the spectrally clean region (21.3 < lambda
< 22.5 Angstroms) where sharp features due to the astrophysically abundant OVII
may reveal an intervening, warm--hot intergalactic medium (WHIM). We do not
confirm detection of any of the intervening systems claimed to date. Rather, we
detect only three unsurprising, astrophysically expected features down to the
Log(N_i)~14.6 (3 sigma) sensitivity level. Each of the two purported WHIM
features is rejected with a statistical confidence that exceeds that reported
for its initial detection. While we can not rule out the existence of fainter,
WHIM related features in these spectra, we suggest that previous discovery
claims were premature. A more recent paper by Williams et al. claims to have
demonstrated that the RGS data we analyze here do not have the resolution or
statistical quality required to confirm or deny the LETGS detections. We show
that our careful analysis resolves the issues encountered by Williams et al.
and recovers the full resolution and statistical quality of the RGS data. We
highlight the differences between our analysis and those published by Williams
et al. as this may explain our disparate conclusions.


title: The pattern of accretion flow onto Sgr A*

abstract:
  The material accreting onto Sgr A* most probably comes from the nearby stars.
We analyze the pattern of this flow at distances of a fraction of a parsec and
we argue that the net angular momentum of this material is low but
non-negligible, and the initially supersonic disk accretion changes into
subsonic flow with constant angular momentum. Next we estimate the flow
parameters at a distance $R_{BHL}$ from the black hole and we argue that for
the plausible parameter range the accretion flow is non-stationary. The inflow
becomes supersonic at distance of $\sim 10^4 R_g$ but the solution does not
continue below the horizon and the material piles up forming a torus, or a
ring, at a distance of a few up to tens of Schwarzchild radii. Such a torus is
known to be unstable and may explain strong variability of the flow in Sgr A*.
Our considerations show that the temporary formation of such a torus seems to
be unavoidable.
  Our best fitting model predicts a rather large accretion rate of around $4
\cdot 10^{-6} M_{\odot}/yr$ directly on Sgr A*. We argue that magnetic fields
in the flow are tangled and this allows our model to overcome the disagreement
with the Faraday rotation limits.


title:
Dark Energy as a Born-Infeld Gauge Interaction Violating the Equivalence
  Principle

abstract:
  We investigate the possibility that dark energy does not couple to
gravitation in the same way than ordinary matter, yielding a violation of the
weak and strong equivalence principles on cosmological scales. We build a
transient mechanism in which gravitation is pushed away from general relativity
by a Born-Infeld gauge interaction acting as an "Abnormally Weighting" (dark)
Energy. This mechanism accounts for the Hubble diagram of far-away supernovae
by cosmic acceleration and time variation of the gravitational constant while
accounting naturally for the present tests on general relativity.


title: Composite Dark Matter and its Charged Constituents

abstract:
  Stable charged heavy leptons and quarks can exist and hide in elusive atoms,
bound by Coulomb attraction and playing the role of dark matter. However, in
the expanding Universe it is not possible to recombine all the charged
particles into such atoms, and the positively charged particles, which escape
this recombination, bind with electrons in atoms of anomalous isotopes with
pregalactic abundance, exceeding substantially the terrestrial upper limits.
This abundance can not be reduced in the dense matter bodies, if negatively
charged particles have charge -1. Therefore composite dark matter can involve
only negatively charged particles with charge -2, while stable heavy particles
with charge -1 should be excluded. Realistic scenarios of composite dark
matter, avoiding this problem of anomalous isotope over-production, inevitably
predict the existence of primordial "atoms", in which primordial helium traps
all the free negatively charged heavy constituents with charge -2. Study of the
possibility for such primordial heavy $\alpha$ particle with compensated charge
to exist as well as the search for the stable charged constituents in cosmic
rays and accelerators provide crucial test for composite dark matter scenarios.


title:
The O VII X-ray forest toward Markarian 421: Consistency between
  XMM-Newton and Chandra

abstract:
  Recently the first detections of highly ionised gas associated with two
Warm-Hot Intergalactic Medium (WHIM) filaments have been reported. The evidence
is based on X-ray absorption lines due to O VII and other ions observed by
Chandra towards the bright blazar Mrk 421. We investigate the robustness of
this detection by a re-analysis of the original Chandra LETGS spectra, the
analysis of a large set of XMM-Newton RGS spectra of Mrk 421, and additional
Chandra observations. We address the reliability of individual spectral
features belonging to the absorption components, and assess the significance of
the detection of these components. We also use Monte Carlo simulations of
spectra. We confirm the apparent strength of several features in the Chandra
spectra, but demonstrate that they are statistically not significant. This
decreased significance is due to the number of redshift trials that are made
and that are not taken into account in the original discovery paper. Therefore
these features must be attributed to statistical fluctuations. This is
confirmed by the RGS spectra, which have a higher signal to noise ratio than
the Chandra spectra, but do not show features at the same wavelengths. Finally,
we show that the possible association with a Ly-alpha absorption system also
lacks sufficient statistical evidence. We conclude that there is insufficient
observational proof for the existence of the two proposed WHIM filaments
towards Mrk 421, the brightest X-ray blazar on the sky. Therefore, the highly
ionised component of the WHIM still remains to be discovered.


title: E- and B-mode mixing from incomplete knowledge of the shear correlation

abstract:
  Aims. We quantify the mixing of the measured cosmic-shear E- and B-modes
caused by the lack of shear-correlation measurements on small and large scales,
arising from a lack of close projected galaxy pairs and the finite field size,
respectively.
  Methods. We calculate the aperture-mass statistics <M_{ap, perp}^2> and the
E-/B-mode shear-correlation functions xi_{E, B +/-} where small- and
large-scale cutoffs are taken into account. We assess the deviation of the
obtained E-mode to the true E-mode and the introduction of a spurious B-mode.
  Results. The measured aperture-mass dispersion is underestimated by more than
10% on scales smaller than 12 times the lower cutoff. For a precise measurement
of the E- and B-modes at the percent level using a combination of xi_{E, B +}
and xi_{E, B -}, a field as large as 7 (2.4) degrees is necessary for
ground-based (space-based) observations.


title: Radio Constraints on Activity in Young Brown Dwarfs

abstract:
  We report on searches for radio emission from three of the nearest known
young brown dwarfs using the Very Large Array. We have obtained sensitive upper
limits on 3.6cm emission from 2MASSW J1207334-393254, TWA~5B and SSSPM
J1102-3431, all of which are likely members of the $\sim$8-Myr-old TW Hydrae
association. We derive constraints on the magnetic field strength and the
number density of accelerated electrons, under the assumption that young brown
dwarf atmospheres are able to produce gyrosynchrotron emission, as seems to be
indicated in older brown dwarfs. For the young brown dwarf TWA~5B, the ratio of
its detected X-ray luminosity to the upper limit on radio luminosity places it
within the expected range for young stars and older, active stars. Thus, its
behavior is anomalous compared to older brown dwarfs, in which radio luminosity
is substantially enhanced over the expected relationship. Our observations
deepen the conundrum of magnetic activity in brown dwarfs, and suggest that a
factor other than age is more important for determining radio emission in cool
substellar objects.


title: Josephson junctions and dark energy

abstract:
  In a recent paper Beck and Mackey [astro-ph/0603397] argue that the argument
we gave in our paper [Phys. Lett. B 606, 77 (2005)] to disprove their claim
that dark energy can be discovered in the Lab through noise measurements of
Josephson junctions is incorrect. In particular, they emphasize that the
measured noise spectrum in Josephson junctions is a consequence of the
fluctuation dissipation theorem, while our argument was based on equilibrium
statistical mechanics. In this note we show that the fluctuation dissipation
relation does not depend upon any shift of vacuum (zero-point) energies, and
therefore, as already concluded in our previous paper, dark energy has nothing
to do with the proposed measurements.


title:
Rolling down from the 30 keV peak: modelling the hard X-ray and
  gamma-ray backgrounds

abstract:
  We will briefly discuss the importance of sensitive X-ray observations above
a few tens of keV for a better understanding of the physical mechanisms
associated to the Supermassive Black Hole primary emission in both radio quiet
and radio loud AGN and to the cosmological evolution of the most obscured
sources.


title:
Feedback and metal enrichment in cosmological SPH simulations - II. A
  multiphase model with supernova energy feedback

abstract:
  We have developed a new scheme to treat a multiphase interstellar medium in
smoothed particle hydrodynamics simulations of galaxy formation. This scheme
can represent a co-spatial mixture of cold and hot ISM components, and is
formulated without scale-dependent parameters. It is thus particularly suited
to studies of cosmological structure formation where galaxies with a wide range
of masses form simultaneously. We also present new algorithms for energy and
heavy element injection by supernovae, and show that together these schemes can
reproduce several important observed effects in galaxy evolution. Both in
collapsing systems and in quiescent galaxies our codes can reproduce the
Kennicutt relation between the surface densities of gas and of star formation.
Strongly metal-enhanced winds are generated in both cases with ratios of
mass-loss to star formation which are similar to those observed. This leads to
a self-regulated cycle for star formation activity. The overall impact of
feedback depends on galaxy mass. Star formation is suppressed at most by a
factor of a few in massive galaxies, but in low-mass systems the effects can be
much larger, giving star formation an episodic, bursty character. The larger
the energy fraction assumed available in feedback, the more massive the
outflows and the lower the final stellar masses. Winds from forming disks are
collimated perpendicular to the disk plane, reach velocities up to 1000 km/s,
and efficiently transport metals out of the galaxies. The asymptotically
unbound baryon fraction drops from >95 per cent to ~30 per cent from the least
to the most massive of our idealised galaxies, but the fraction of all metals
ejected with this component exceeds 60 per cent regardless of mass. Such winds
could plausibly enrich the intergalactic medium to observed levels.


title:
Analysis of the chemical evolution of the Galactic disk via dynamical
  simulations of the open cluster system

abstract:
  For several decades now, open clusters have been used to study the structure
and chemical evolution of the disk of our Galaxy. Due to the fact that their
ages and metallicities can be determined with relatively good precision, and
since they can be observed even at great distances, they are excellent tracers
of the variations in the abundance of heavy chemical elements with age and
position in the Galactic disk. In the present work we analyze the star
formation history and the chemical evolution of the disk of the Galaxy using
numerical simulations of the dynamical evolution of the system of open clusters
in the Milky Way. Starting from hypotheses on the history of cluster formation
and the chemical enrichment of the disk, we model the present properties of the
Galactic open cluster system. The comparison of these models with the
observations allows us to examine the validity of the assumed hypotheses and to
improve our knowledge about the initial conditions of the chemical evolution of
the Galactic disk.


title: Cosmological Structure Formation Creates Large-Scale Magnetic Fields

abstract:
  This paper examines the generation of seed magnetic fields due to the growth
of cosmological perturbations. In the radiation era, different rates of
scattering from photons induce local differences in the ion and electron
density and velocity fields. The currents due to the relative motion of these
fluids generate magnetic fields on all cosmological scales, peaking at a
magnitude of ~ 10^{-24} Gauss at the epoch of recombination. Magnetic fields
generated in this manner provide a promising candidate for the seeds of
magnetic fields presently observed on galactic and extra-galactic scales.


title: Constraints on the Nature of Jets from kpc Scale X-ray Data

abstract:
  Motivated by the large number of jets detected by the Chandra X-ray
Observatory, and by the inverse Compton X-ray emission model (IC/CMB) for
relativistic jets, we revisit two basic questions: ``If the medium that carries
the jet's energy consists of hot electrons, can we use the physical length of
the jet to constrain the maximum electron energy?'' and ``Why do jets have
knots?'' Based on the two non-thermal emission processes for X-rays from jets,
we consider constraints on the jet medium and other properties from these two
simple questions. We argue that hot pairs cannot be the dominant constituent of
the medium responsible for the jet's momentum flux and that some mechanisms for
producing fluctuating brightness along jets (rather than a monotonically
decreasing intensity) are precluded by observed jet morphologies.


title: Minimal Noncanonical Cosmologies

abstract:
  We demonstrate how much it is possible to deviate from the standard
cosmological paradigm of inflation-assisted LambdaCDM, keeping within current
observational constraints, and without adding to or modifying any theoretical
assumptions. We show that within a minimal framework there are many new
possibilities, some of them wildly different from the standard picture. We
present three illustrative examples of new models, described phenomenologically
by a noncanonical scalar field coupled to radiation and matter. These models
have interesting implications for inflation, quintessence, reheating,
electroweak baryogenesis, and the relic densities of WIMPs and other exotics.


title: Galactic Warps Induced By Cosmic Infall

abstract:
  Recent ideas for the origin and persistence of the warps commonly observed in
disc galaxies have focused on cosmic infall. We present N-body simulations of
an idealized form of cosmic infall onto a disc galaxy and obtain a warp that
closely resembles those observed. The inner disc tilts remarkably rigidly,
indicating strong cohesion due to self-gravity. The line of nodes of the warp
inside $R_{26.5} ~ 4.5 \Rd$ is straight, while that beyond $R_{26.5}$ generally
forms a loosely-wound, leading spiral in agreement with Briggs's rules. We
focus on the mechanism of the warp and show that the leading spiral arises from
the torques from the misaligned inner disc and its associated inner oblate
halo. The fact that the line of nodes of most warps forms a leading spiral
might imply that the disc mass is significant in the centre. If the line of
nodes can be traced to very large radii in future observations, it may reveal
information on the mass distribution of the outer halo. The warp is not
strongly damped by the halo because the precession rate of the inner disc is
slow and the inner halo generally remains aligned with the inner disc. Thus
even after the imposed quadrupolar perturbation is removed, the warp persists
for a few Gyrs, by which time another infall event can be expected.


title:
Evidence for TP-AGB stars in high redshift galaxies, and their effect on
  deriving stellar population parameters

abstract:
  We explore the effects of stellar population models on estimating star
formation histories, ages and masses of high redshift galaxies. The focus is on
the Thermally-Pulsing Asymptotic Giant Branch (TP-AGB) phase of stellar
evolution, whose treatment is a source of major discrepancy among different
evolutionary population synthesis. In particular, besides the models usually
adopted in the literature, we use models (by Maraston 2005), in which the
contribution of the TP-AGB phase is observationally calibrated and is the
dominant source of near-IR energy for stellar populations in the age range 0.2
to 2 Gyr. We use a sample of high-z galaxies in the HUDF, with spectroscopic
redshifts, and Spitzer IRAC and MIPS photometry from GOODS. We find that the
TP-AGB phase plays a key role in the interpretation of Spitzer data for high-z
galaxies, when the rest-frame near-IR is sampled. When fitting without dust
reddening, the models with the empirically-calibrated TP-AGB phase always
reproduce better the observed spectral energy distributions (SEDs). Allowing
for dust reddening improves the fits with literature models in some cases. In
both cases, the results from Maraston models imply younger ages by factors up
to 6 and lower stellar masses (by ~60 % on average). The observed strengths of
the MgUV spectral feature compare better to the predicted ones in the case of
the Maraston models, implying a better overall consistency of SED fitting.
Finally, we find that photometric redshifts improve significantly using these
models on the SEDs extending over the IRAC bands. This work provides the first
direct evidence of TP-AGB stars in the primeval Universe.


title:
A Very High Spectral Resolution Study of Ground-State OH Masers in
  W3(OH)

abstract:
  We present VLBA observations of the ground-state hydroxyl masers in W3(OH) at
0.02 km s-1 spectral resolution. Over 250 masers are detected, including 56
Zeeman pairs. Lineshapes are predominantly Gaussian or combinations of several
Gaussians, with normalized deviations typically of the same magnitude as in
masers in other species. Typical FWHM maser linewidths are 0.15 to 0.38 km s-1
and are larger in the 1665 MHz transition than in the other three ground-state
transitions. The satellite-line 1612 and 1720 MHz masers show no evidence of
sigma^+/-2,3 components. The spatial positions of most masers are seen to vary
across the line profile, with many spots showing clear, organized positional
gradients. Equivalent line-of-sight velocity gradients in the plane of the sky
typically range from 0.01 to 1 km s-1 AU-1 (i.e., positional gradients of 1 to
100 AU (km s-1)-1). Small velocity gradients in the 1667 MHz transition support
theoretical predictions that 1667 MHz masers appear in regions with small
velocity shifts along the amplification length. Deconvolved maser spot sizes
appear to be larger in the line wings but do not support a spherical maser
geometry.


title: X-ray Spectral Variability of TeV Blazars during Rapid Flares

abstract:
  The spectral energy distribution (SED) of TeV blazars peaks both at keV and
TeV energies. The X-ray emission is generally believed to originate in the
synchrotron emission from relativistic electrons (and positrons) in the jet of
these sources, while the origin of the gamma-ray emission is still being
debated. We report results from a systematic study of X-ray spectral
variability of Mrk 421 and Mrk 501 during individual flares that last for
several days, making use of some of the high-quality data that have recently
become available. The X-ray spectra of the two sources fall on the opposite
sides of the synchrotron peak of their respective SEDs, so they together may
offer additional insights into the physical origin of X-ray variability. We
modeled each of the time-resolved X-ray spectra over a {\em single} flare by
adopting a homogeneous spatial distribution and an instantaneous power-law
spectral distribution for the emitting particles. We focused on the variation
of four key parameters: particle spectral index, maximum Lorentz factor, energy
density, and magnetic field. While there is considerable degeneracy in the
fits, we show that, in order to account for the X-ray spectral variability
observed in Mrk 421, at least three of the parameters are required to vary in
most cases, with the spectral index being one of them. The observations of Mrk
501 support the conclusion, although the quality of the data is not as good. We
discuss the implications of the results.


title: Stellar Rotation: A Clue to the Origin of High Mass Stars?

abstract:
  We present the results of a study aimed at assessing whether low and high
mass stars form similarly. Our approach is (1) to examine the observed
projected rotational velocities among a large sample of newly-formed stars
spanning a range in mass between 0.2 and 50 M ; and (2) to search for evidence
of a discontinuity in rotational properties that might indicate a difference in
the stellar formation process at some characteristic mass. Our database
includes both recently published values of v sin i for young intermediate- and
low- mass stars in Orion, as well as new observations of O stars located in
young clusters and OB associations. We find that the median of the quantity
v_obs/v_c (observed rotational speed/equatorial breakup velocity) is typically
about 0.15 and shows no evidence of a discontinuity over the full range of
stellar masses, while the quantity Jsini/M (derived angular momentum per unit
mass) exhibits a slow, monotonic rise with increasing mass with no evidence of
a discontinuity. We suggest that these observations are most simply interpreted
as indicative of a single stellar formation and angular momentum regulation
mechanism: one that results in rotation rates well below breakup, and angular
momenta per unit mass that differ systematically by no more than a factor of
3-4 over a mass range spanning a factor of 250.


title: On the Evolutionary History of Stars and their Fossil Mass and Light

abstract:
  The total extragalactic background radiation can be an important test of the
global star formation history (SFH). Using direct observational estimates of
the SFH, along with standard assumptions about the initial mass function (IMF),
we calculate the total extragalactic background radiation and the observed
stellar density today. We show that plausible SFHs allow a significant range in
each quantity, but that their ratio is very tightly constrained. Current
estimates of the stellar mass and extragalactic background are difficult to
reconcile, as long as the IMF is fixed to the Salpeter slope above 1 Msun. The
joint confidence interval of these two quantities only agrees with that
determined from the allowed range of SFH fits at the 3-sigma level, and for our
best-fit values the discrepancy is about a factor of two. Alternative energy
sources that contribute to the background, such as active galactic nuclei
(AGN), Population III stars, or decaying particles, appear unlikely to resolve
the discrepancy. However, changes to the IMF allow plausible solutions to the
background problem. The simplest is an average IMF with an increased
contribution from stars around 1.5--4 Msun. A ``paunchy'' IMF of this sort
could emerge as a global average if low mass star formation is suppressed in
galaxies experiencing rapid starbursts. Such an IMF is consistent with
observations of star-forming regions, and would help to reconcile the fossil
record of star formation with the directly observed SFH.


title: Cosmic-Ray proton spectrum below 100 TeV in the local region

abstract:
  The propagation of cosmic-ray protons in the Galaxy is discussed under the
framework of a three dimensional convection-diffusion model. Starting with the
assumption of a uniform and continuous distribution of cosmic-ray sources
injecting CRs continuously in the Galaxy and by invoking a supernova explosion
at various distances from the Earth, it is found that only those sources
located within a distance of ~ 1.5 kpc can produce appreciable temporal
fluctuations in the CR proton flux observed at the Earth. So, the construction
of the local CR proton spectrum is discussed by seperating the contributions of
the distant sources from that of the nearby sources. The contribution from the
distant sources is treated in the framework of a continuous source distribution
model both in space as well as time, but that of the nearby sources in a
discrete space-time source model. The study predicts the presence of at least
one old nearby source with a characteristic age of ~ 10^5 yrs located at a
distance of ~ 0.1 kpc to explain the observed proton flux below ~ 100 GeV.


title:
Effects of Rotation on Thermal-Gravitational Instability in the
  Protogalactic Disk Environment

abstract:
  Thermal-gravitational instability (TGI) is studied in the protogalactic
environment. We extend our previous work, where we found that dense clumps
first form out of hot background gas by thermal instability and later a small
fraction of them grow to virialized clouds of mass M_c >~ 6X10^6 M_sun by
gravitational infall and merging. But these clouds have large angular momentum,
so they would be difficult, if not impossible, to further evolve into globular
clusters. In this paper, through three-dimensional hydrodynamic simulations in
a uniformly rotating frame, we explore if the Coriolis force due to rotation in
protogalactic disk regions can hinder binary merging and reduce angular
momentum of the clouds formed. With rotation comparable to the Galactic
rotation at the Solar circle, the Coriolis force is smaller than the pressure
force during the early thermal instability stage. So the properties of clumps
formed by thermal instability are not affected noticeably by rotation, except
increased angular momentum. However, during later stage the Coriolis force
becomes dominant over the gravity, and hence the further growth to
gravitationally bound clouds by gravitational infall and merging is prohibited.
Our results show that the Coriolis force effectively destroys the picture of
cloud formation via TGI, rather than alleviate the problem of large angular
momentum.


title:
An unified model for superluminal motion and state transition on
  microquasars and quasars

abstract:
  Superluminal motion has been interpreted as relativistically moving out flow.
The increasing observations of such sources provide chance to investigate their
mechanism in detail. This paper proposes that superluminal motion may be jet
precession induced blob motion. This model can interpret a number of
observational phenomena which are not well understood under the scenario of
bulk motion, such as the absence of the receding blob after the outburst and
the receding blob becomes brighter than the approaching one in XTE J1550-564 .
Moreover the compton scattering of photos from a warped accretion disk may form
a structured jet. And the precession of the structured jet may lead to the
complicated state transitions observed in microquasars like GRS 1915+105.
Applying to AGNs, the model may explain the scales of length and time of the
phenomena proportioning to the mass of the black hole. The new model can be
tested easily on microquasars, i.e., XTE J1550-564, on which the previous
receding blob should move towards the core instead of away from it after 2002,
and the previous approaching blob shall disappear. %For GRS 1915+105 the
vibration of the two blobs should be observed in both %the time scales of year
and days.


title:
Atmospheric scintillation at Dome C, Antarctica: implications for
  photometry and astrometry

abstract:
  We present low-resolution turbulence profiles of the atmosphere above Dome C,
Antarctica, measured with the MASS instrument during 25 nights in March-May
2004. Except for the lowest layer, Dome C has significantly less turbulence
than Cerro Tololo and Cerro Pachon. In particular, the integrated turbulence at
16 km is always less than the median values at the two Chilean sites. From
these profiles we evaluate the photometric noise produced by scintillation, and
the atmospheric contribution to the error budget in narrow-angle differential
astrometry. In comparison with the two mid-latitude sites in Chile, Dome C
offers a potential gain of about 3.6 in both photometric precision (for long
integrations) and narrow-angle astrometry precision. These gain estimates are
preliminary, being computed with average wind-speed profiles, but the validity
of our approach is confirmed by independent data. Although the data from Dome C
cover a fairly limited time frame, they lend strong support to expectations
that Dome C will offer significant advantages for photometric and astrometric
studies.


title:
Superclusters of galaxies from the 2dF redshift survey. II. Comparison
  with simulations

abstract:
  We investigate properties of superclusters of galaxies found on the basis of
the 2dF Galaxy Redshift Survey, and compare them with properties of
superclusters from the Millennium Simulation. We study the dependence of
various characteristics of superclusters on their distance from the observer,
on their total luminosity, and on their multiplicity. The multiplicity is
defined by the number of Density Field (DF) clusters in superclusters. Using
the multiplicity we divide superclusters into four richness classes: poor,
medium, rich and extremely rich. We show that superclusters are asymmetrical
and have multi-branching filamentary structure, with the degree of asymmetry
and filamentarity being higher for the more luminous and richer superclusters.
The comparison of real superclusters with Millennium superclusters shows that
most properties of simulated superclusters agree very well with real data, the
main differences being in the luminosity and multiplicity distributions.


title:
Spatially Resolved Spitzer Spectroscopy of the Starburst Nucleus in NGC
  5253

abstract:
  We present new Spitzer Space Telescope data on the nearby, low-metallicity
starburst galaxy NGC 5253, from the Infrared Array Camera IRAC and the Infrared
Spectrograph IRS. The mid-IR luminosity profile of NGC 5253 is clearly
dominated by an unresolved cluster near the center, which outshines the rest of
the galaxy at longer wavelengths. We find that the [NeIII]/[NeII] ratio
decreases from $\sim8.5$ at the center to $\sim2.5$ at a distance of $\sim250$
pc. The [SIV]/[SIII] follows the [NeIII]/[NeII] ratio remarkably well, being
about 4-5 times lower at all distances. Our spectra reveal for the first time
PAH emission feature at 11.3$\mu$m and its equivalent width increases
significantly with distance from the center. The good anti-correlation between
the PAH strength and the product between hardness and luminosity of the UV
radiation field suggests photo-destruction of the PAH molecules in the central
region. The high-excitation [OIV]25.91$\mu$m line was detected at
$0.42\times10^{-20}$W cm$^{-2}$. Our results demonstrate the importance of
spatially resolved mid-IR spectroscopy.


title:
Ground-Based CCD Astrometry with Wide Field Imagers. I. [Observations
  just a few years apart allow decontamination of field objects from members in
  two Globular clusters.]

abstract:
  This paper is the first of a series of papers in which we will apply the
methods we have developed for high-precision astrometry (and photometry) with
the Hubble Space Telescope to the case of wide-field ground-based images. In
particular, we adapt the software originally developed for WFPC2 to
ground-based, wide field images from the WFI at the ESO 2.2m telescope. In this
paper, we describe in details the new software, we characterize the WFI
geometric distortion, discuss the adopted local transformation approach for
proper-motion measurements, and apply the new technique to two-epoch archive
data of the two closest Galactic globular clusters: NGC 6121 (M4) and NGC 6397.
The results of this exercise are more than encouraging. We find that we can
achieve a precision of ~7 mas (in each coordinate) in a single exposure for a
well-exposed star, which allows a very good cluster-field separation in both
M4, and NGC 6397, with a temporal baseline of only 2.8, and 3.1 years,
respectively.


title:
The multi-phase gaseous halos of star forming late-type galaxies - II.
  Statistical analysis of key parameters

abstract:
  In Paper I we showed that multi-phase gaseous halos of late-type spiral
galaxies, detected in the radio continuum, in Halpha, and in X-rays, are
remarkably well correlated regarding their morphology and spatial extent. In
this work we present new results from a statistical analysis in order to
specify and quantify these phenomenological relations. This is accomplished by
investigating soft X-ray (0.3-2.0keV) luminosities, FIR, radio continuum,
Halpha, B-band, and UV luminosities for a sample of 23 edge-on late-type spiral
galaxies. Typical star formation indicators, such as SFRs, are determined and a
statistical correlation analysis is carried out. We find strong linear
correlations, covering at least two orders of magnitude, between star formation
indicators and integrated (disk+halo) luminosities in all covered wavebands. In
addition to the well established L_FIR/L_1.4GHz-relation, we show new and
highly significant linear dependencies between integrated soft X-ray
luminosities and FIR, radio continuum, Halpha, B-band, and UV luminosities.
Moreover, integrated soft X-ray luminosities correlate well with SFRs and the
energy input into the ISM by SNe. The same holds if these quantities are
plotted against soft halo X-ray luminosities. Only a weak correlation exists
between the dust mass of a galaxy and the corresponding X-ray luminosity. Among
soft X-ray luminosities, baryonic, and HI-gas masses, no significant
correlations are found. There seems to exist a critical input energy by SNe
into the ISM or a SFR threshold for multi-phase halos to show up. It is still
not clear whether this threshold is a physical or an instrument dependent
sensitivity limit. These findings strongly support our previous results, but
conflict with the concept of halos being due to infalling gas from the IGM.


title: The milliarcsecond-scale jet of PKS 0735+178 during quiescence

abstract:
  We present polarimetric 5 GHz to 43 GHz VLBI observations of the BL Lacertae
object PKS 0735+178, spanning March 1996 to May 2000. Comparison with previous
and later observations suggests that the overall kinematic and structural
properties of the jet are greatly influenced by its activity. Time intervals of
enhanced activity, as reported before 1993 and after 2000 by other studies, are
followed by highly superluminal motion along a rectilinear jet. In contrast the
less active state in which we performed our observations, shows subluminal or
slow superluminal jet features propagating through a twisted jet with two sharp
bends of about 90 deg. within the innermost three-milliarcsecond jet structure.
Proper motion estimates from the data presented here allow us to constrain the
jet viewing angle to values < 9 deg., and the bulk Lorentz factor to be between
2 and 4.


title: Energy Ranking Preservation in a N-Body Cosmological Simulation

abstract:
  In this paper we present a study of the cosmic flow from the point of view of
how clusterings at different dynamical regimes in an expanding universe evolve
according to a `coarse-grained' partitioning of their ranked energy
distribution. By analysing a Lambda-CDM cosmological simulation from the Virgo
Project, we find that cosmic flows evolve in an orderly sense, when tracked
from their coarse-grained energy cells, even when nonlinearities are already
developed. We show that it is possible to characterize scaling laws for the
Pairwise Velocity Distribution in terms of the energy cells, generally valid at
the linear and nonlinear clustering regimes.


title:
Formation of Pillars at the Boundaries between H II Regions and
  Molecular Clouds

abstract:
  We investigate numerically the hydrodynamic instability of an ionization
front (IF) accelerating into a molecular cloud, with imposed initial
perturbations of different amplitudes. When the initial amplitude is small, the
imposed perturbation is completely stabilized and does not grow. When the
initial perturbation amplitude is large enough, roughly the ratio of the
initial amplitude to wavelength is greater than 0.02, portions of the IF
temporarily separate from the molecular cloud surface, locally decreasing the
ablation pressure. This causes the appearance of a large, warm HI region and
triggers nonlinear dynamics of the IF. The local difference of the ablation
pressure and acceleration enhances the appearance and growth of a multimode
perturbation. The stabilization usually seen at the IF in the linear regimes
does not work due to the mismatch of the modes of the perturbations at the
cloud surface and in density in HII region above the cloud surface. Molecular
pillars are observed in the late stages of the large amplitude perturbation
case. The velocity gradient in the pillars is in reasonably good agreement with
that observed in the Eagle Nebula. The initial perturbation is imposed in three
different ways: in density, in incident photon number flux, and in the surface
shape. All cases show both stabilization for a small initial perturbation and
large growth of the second harmonic by increasing amplitude of the initial
perturbation above a critical value.


title:
Rare-earth elements in the atmosphere of the magnetic chemically
  peculiar star HD 144897. New classification of the Nd III spectrum

abstract:
  We have obtained a UVES spectrum of a slowly rotating strongly magnetic Ap
star, HD 144897, that exhibits very large overabundances of rare-earth
elements. Here we present a detailed spectral analysis of this object, also
taking into account effects of non-uniform vertical distribution
(stratification) of chemical elements. We have determined the photospheric
abundances of 40 ions. For seven elements (Mg, Si, Ca, Ti, Cr, Mn, Fe), we have
obtained a stratification model that allow us to produce a satisfactory fit to
the observed profiles of spectral lines of various strength. REEs abundances,
that for the first time in the literature have been determined from the lines
of the first and second ions, have been found typically four dex larger than
solar abundances. Our analysis of REE spectral lines provide a strong support
to the laboratory line classification and determination of the atomic
parameters. The only remarkable exception is Nd III, for which spectral
synthesis was found to be inconsistent with the observations. We have therefore
performed a revision of the Nd III classification. We have confirmed the
energies for 11 out of 24 odd energy levels classified previously, and we have
derived the energies for additional 24 levels of Nd III, thereby increasing
substantially the number of classified Nd III lines with corrected wavelengths
and atomic parameters.


title:
Likelihood methods for the combined analysis of CMB temperature and
  polarisation power spectra

abstract:
  We consider the shape of the likelihood and posterior surfaces to be used
when fitting cosmological models to CMB temperature and polarisation power
spectra measured from experiments. In the limit of an all-sky survey with
Gaussian distributed pixel noise we show that the true combined likelihood of
the four CMB power spectra (TT, TE, EE & BB) has a Wishart distribution and we
discuss the properties of this function. We compare various fits to the
posterior surface of the Cls, both in the case of a single auto-power spectrum
and for a combination of temperature and polarisation data. In the latter case,
it is important that the fits can accurately match the Wishart distribution in
the limit of near full-sky coverage. Simple extensions of auto-power spectrum
fits to include polarisation data generally fail to match correlations between
the different power spectra in this limit. Directly fitting pixel values on
large scales, as undertaken by the WMAP team in their analysis of the 3 year
data, avoids the complications of characterising the shape of the posterior for
the power spectra. Finally we demonstrate the importance of the likelihood
distribution on analytic marginalisation, and provide a formula for analytic
marginalisation over a calibration error given an all-sky survey.


title:
LANNDD - A line of liquid argon TPC detectors scalable in mass from 200
  Tons to 100 Ktons

abstract:
  A scalable line of liquid argon TPC detectors is described, based on a three
dimensional cubic frame array immersed on a common liquid argon volume. The
paper describes general lines, main construction criteria, crucial points,
parameters and required preliminary R&D activities for the construction of
detectors with active mass ranging from 200 ton to 100 kTon. Such detectors
appear as unique for supernova detection, proton decay, LBL neutrino physics
and other astropaticle physics applications.


title:
Gas stripping in galaxy groups - the case of the starburst spiral NGC
  2276

abstract:
  Ram pressure stripping of galactic gas is generally assumed to be inefficient
in galaxy groups due to the relatively low density of the intragroup medium and
the small velocity dispersions of groups. To test this assumption, we obtained
Chandra X-ray data of the starbursting spiral NGC 2276 in the NGC 2300 group of
galaxies, a candidate for a strong galaxy interaction with hot intragroup gas.
The data reveal a shock-like feature along the western edge of the galaxy and a
low-surface-brightness tail extending to the east, similar to the morphology
seen in other wavebands. Spatially resolved spectroscopy shows that the data
are consistent with intragroup gas being pressurized at the leading western
edge of NGC 2276 due to the galaxy moving supersonically through the intragroup
medium at a velocity ~850 km/s. Detailed modelling of the gravitational
potential of NGC 2276 shows that the resulting ram-pressure could significantly
affect the morphology of the outer gas disc but is probably insufficient to
strip large amounts of cold gas from the disc. We estimate the mass loss rates
due to turbulent viscous stripping and starburst outflows being swept back by
ram pressure, showing that both mechanisms could plausibly explain the presence
of the X-ray tail. Comparison to existing HI measurements shows that most of
the gas escaping the galaxy is in a hot phase. With a total mass loss rate of
roughly 5 M_Sun/yr, the galaxy could be losing its entire present HI supply
within a Gyr. This demonstrates that the removal of galactic gas through
interactions with a hot intragroup medium can occur rapidly enough to transform
the morphology of galaxies in groups. Implications of this for galaxy evolution
in groups and clusters are briefly discussed.


title:
Mapping stellar kinematics across the Galactic bar: HST measurements of
  proper motions in 35 fields

abstract:
  We present a proper motion mini-survey of 35 fields in the vicinity of Baade
window, (l, b) = (1 deg, -4 deg), sampling roughly a 5 x 2.5 deg region of the
Galactic bar. Our second epoch observations collected with the ACS/HRC
instrument on board the Hubble Space Telescope were combined with the archival
WFPC2/PC images. The resulting time baselines are in the range of 4 - 8 years.
Precise proper motions of 15,863 stars were determined in the reference frame
defined by the mean motion of stars with magnitudes between I_F814W = 16.5 -
21.5 along the line of sight. We clearly detect small gradients in proper
motion dispersions (sigma_l, sigma_b) ~ (3.0, 2.5) mas/yr, and in the amount of
anisotropy (sigma_l/sigma_b ~ 1.2). Both the longitude dispersion sigma_l and
its ratio to the vertical motion sigma_b increase toward the Galactic plane.
The decline of the anisotropy ratio sigma_l/sigma_b toward the minor axis of
the bulge is mostly due to increasing sigma_b. We also find, for the first
time, a significant negative covariance term in the transverse velocity field
sigma_lb/(sigma_l*sigma_b) ~ -0.10. Our results extend by a factor of ~15 the
number of the Galactic bar fields with good proper motion dispersions.


title:
Constraining the Adaptive Optics Point-Spread Function in Crowded
  Fields: Measuring Photometric Aperture Corrections

abstract:
  The point-spread function (PSF) of an adaptive optics (AO) system is often
poorly known. This ignorance can lead to significant systematic errors in
photometry. Since the degree of AO correction is sensitive to the observing
conditions: seeing, wind speed, brightness of the wavefront reference, etc., it
would be desirable to estimate the PSF from the data themselves. We have
developed a method to estimate the PSF delivered by an AO system in the case
where the scene consists of a crowded star field. We model the modulation
transfer function (MTF) of several key components of the imaging system. The
power spectrum of the image, even a dense star field, can then be used to
constrain our model, which in turn can be used to reconstruct the PSF. We show
that the method yields reasonable fit parameters and a useful approximation to
the PSF when applied to data from laser guide star (LGS) AO system at the Keck
Observatory. Comparison of Keck LGS/AO and HST/NICMOS data shows that
photometric accuracy of a few percent can be achieved for data with Strehl
ratios as low as 4%.


title:
A Survey for "Normal" Irregular Satellites Around Neptune: Limits to
  Completeness

abstract:
  We surveyed 1.75 square degrees of sky near Neptune to an R-band 50%
detection efficiency of 25.8 mags (corresponding to radii of about 17 km for an
assumed albedo of 0.04). We discovered one new outer satellite, Psamathe
(S/2003 N1), about 20 km in radius and having a distant retrograde orbit and
moderate eccentricity. Until 2003 Neptune was only known to have two satellites
which exhibited orbital signatures indicative of capture. Both of these, Triton
and Nereid, are unusual when compared to the irregular satellites of other
giant planets. With recent discoveries of four additional satellites by Holman
et al. (2004) it is now apparent that Neptune has a distant ``normal''
irregular satellite system in which the satellites have radii and orbital
properties similar to those of the satellites of other giant planets. We find
that the satellite size distribution at Neptune is not well determined given
the few objects known to date, being especially sensitive to the inclusion of
Triton and Nereid in the sample. Finally, we note that Psamathe and S/2002 N4
have similar semi-major axes, inclinations and eccentricities. They may be
fragments of a once larger satellite.


title:
A Revised Model for the Formation of Disk Galaxies: Low Spin and
  Dark-Halo Expansion

abstract:
  We use observed rotation velocity-luminosity (VL) and size-luminosity (RL)
relations to single out a specific scenario for disk galaxy formation in the
LCDM cosmology. Our model involves four independent log-normal random
variables: dark-halo concentration c, disk spin lam_gal, disk mass fraction
m_gal, and stellar mass-to-light ratio M/L_I. A simultaneous match of the VL
and RL zero points with adiabatic contraction requires low-c halos, but this
model has V_2.2~1.8 V_vir (where V_2.2 and V_vir are the circular velocity at
2.2 disk scale lengths and the virial radius, respectively) which will be
unable to match the luminosity function (LF). Similarly models without
adiabatic contraction but standard c also predict high values of V_2.2/V_vir.
Models in which disk formation induces an expansion rather than the commonly
assumed contraction of the dark-matter halos have V_2.2~1.2 V_vir which allows
a simultaneous fit of the LF. This may result from non-spherical, clumpy gas
accretion, where dynamical friction transfers energy from the gas to the dark
matter. This model requires low lam_gal and m_gal values, contrary to naive
expectations. However, the low lam_gal is consistent with the notion that disk
galaxies predominantly survive in halos with a quiet merger history, while a
low m_gal is also indicated by galaxy-galaxy lensing. The smaller than expected
scatter in the RL relation, and the lack of correlation between the residuals
of the VL and RL relations, respectively, imply that the scatter in lam_gal and
in c need to be smaller than predicted for LCDM halos, again consistent with
the idea that disk galaxies preferentially reside in halos with a quiet merger
history.


title:
The Stellar Masses and Star Formation Histories of Galaxies at z ~ 6:
  Constraints from Spitzer Observations in the Great Observatories Origins Deep
  Survey

abstract:
  Using the deep Spitzer IRAC observations of the Great Observatories Origins
Deep Survey (GOODS), we study the stellar masses and star formation histories
of galaxies at z ~ 6. Our study is based on the i-band dropout sample selected
from the GOODS southern and northern fields (~ 330 arcmin^2 in total), several
of which already have spectroscopic confirmations. In total, we derive stellar
masses for 53 i-band dropouts that have robust IRAC detections. These galaxies
have typical stellar masses of ~ 1e10 M_sun and typical ages of a couple of
hundred million years, consistent with earlier results based on a smaller
sample of z ~ 6 galaxies in the HUDF. We also study 79 i-band dropouts that are
invisible in the IRAC data and find that they are typically less massive by a
factor of ten. Based on our mass estimates, we derive a lower limit to the
global stellar mass density at z ~ 6. Considering the range of systematic
uncertainties in the derived stellar masses, this lower limit is 1.1--6.7e6
M_sun/Mpc^3 (co-moving), which is 0.2--1.1% of the present-day value. The
prospect of detecting the progenitors of the most massive galaxies at yet
higher redshifts is explored: a deep, wide-field near-IR survey using our
current technology could possibly result in positive detections at z > 7. We
also investigate the implication of our results for reionzation, and find that
the progenitors of the galaxies comparable to those in our sample, even in the
most optimized (probably unrealistic) scenario, cannot sustain the reionization
for a period longer than ~ 2 million years. Thus most of the photons required
for reionization must have been provided by other sources, such as the
progenitors of the dwarf galaxies that are far below our current detection
capability. (Abridged)


title:
Formation of Galactic Systems in Light of the Magnesium Abundance in
  Field Stars: The Thin Disk

abstract:
  We analyze the relations between the relative magnesium abundances in stars
and their metallicities, Galactic orbital elements, and ages. The relative
magnesium abundances in metal-poor ([Fe/H] < -0.4) thin-disk stars have been
found to systematically decrease with increasing stellar orbital radii in such
a way that magnesium over abundances ([Mg/Fe]>0.2 dex) are essentially observed
only in the stars whose orbits lie almost entirely within the solar circle. At
the same time, the range of metallicities in magnesium-poor stars is displaced
from (-0.5<[Fe/H]<+0.3 dex) to (-0.7<[Fe/H]<+0.2 dex) as their orbital radii
increase. This behavior suggests that, first, the star formation rate decreases
with increasing Galactocentric distance and, second, there was no star
formation for some time outside the solar circle while this process was
continuous within the solar circle. The decrease in the star formation rate
with increasing Galactocentric distance is responsible for the existence of a
negative radial metallicity gradient (grad_{R}[Fe/H]=(-0.05 \pm 0.01) kpc^{-1})
in the disk, which shows a tendency to increase with decreasing age. At the
same time the relative magnesium abundance exhibits no radial gradient. We have
confirmed the existence of a steep negative vertical metallicity gradient
(grad_Z [Fe/H]=(-0.29 \pm 0.06) kpc^{-1}) and detected a significant positive
vertical gradient in relative magnesium abundance (grad_Z [Mg/Fe]=(0.13 \pm
0.02) kpc^{-1}); both gradients increase appreciably in absolute value with
decreasing age. We have found that there is not only an age-metallicity
relation, but also an age-magnesium abundance relation in the thin disk.


title:
Terrestrial Consequences of Spectral and Temporal Variability in
  Ionizing Photon Events

abstract:
  Gamma-Ray Bursts (GRBs) directed at Earth from within a few kpc may have
damaged the biosphere, primarily though changes in atmospheric chemistry which
admit greatly increased Solar UV. However, GRBs are highly variable in spectrum
and duration. Recent observations indicate that short (~0.1 s) burst GRBs,
which have harder spectra, may be sufficiently abundant at low redshift that
they may offer an additional significant effect. A much longer timescale is
associated with shock breakout luminosity observed in the soft X-ray (~10^3 s)
and UV (~10^5 s) emission, and radioactive decay gamma-ray line radiation
emitted during the light curve phase of supernovae (~10^7 s). Here we
generalize our atmospheric computations to include a broad range of peak photon
energies and investigate the effect of burst duration while holding total
fluence and other parameters constant. The results can be used to estimate the
probable impact of various kinds of ionizing events (such as short GRBs, X-ray
flashes, supernovae) upon the terrestrial atmosphere. We find that the ultimate
intensity of atmospheric effects varies only slightly with burst duration from
10^-1 s to 10^8 s. Therefore, the effect of many astrophysical events causing
atmospheric ionization can be approximated without including time development.
Detailed modeling requires specification of the season and latitude of the
event. Harder photon spectra produce greater atmospheric effects for spectra
with peaks up to about 20 MeV, because of greater penetration into the
stratosphere.

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


title: Minkowski's Object: A Starburst Triggered by a Radio Jet, Revisited

abstract:
  We present neutral hydrogen, ultraviolet, optical and near-infrared imaging,
and optical spectroscopy, of Minkowski's Object (MO), a star forming peculiar
galaxy near NGC 541. The observations strengthen evidence that star formation
in MO was triggered by the radio jet from NGC 541. Key new results are the
discovery of a 4.9E8 solar mass double HI cloud straddling the radio jet
downstream from MO, where the jet changes direction and decollimates; strong
detections of MO, also showing double structure, in UV and H-alpha; and
numerous HII regions and associated clusters in MO. In UV, MO resembles the
radio-aligned, rest-frame UV morphologies in many high redshift radio galaxies
(HzRGs), also thought to be caused by jet-induced star formation. MO's stellar
population is dominated by a 7.5 Myr-old, 1.9E7 solar mass instantaneous burst,
with current star formation rate 0.52 solar masses per year (concentrated
upstream from where the HI column density is high). This is unlike the
jet-induced star formation in Centaurus A, where the jet interacts with
pre-existing cold gas; in MO the HI may have cooled out of a warmer, clumpy
intergalactic or interstellar medium as a result of jet interaction, followed
by collapse of the cooling clouds and subsequent star formation (consistent
with numerical simulations). Since the radio source that triggered star
formation in MO is much less luminous, and therefore more common, than powerful
HzRGs, and because the environment around MO is not particularly special in
terms of abundant dense, cold gas, jet-induced star formation in the early
universe might be even more prevalent than previously thought.


title:
A Likelihood Method for Measuring the Ultrahigh Energy Cosmic Ray
  Composition

abstract:
  Air fluorescence detectors traditionally determine the dominant chemical
composit ion of the ultrahigh energy cosmic ray flux by comparing the averaged
slant depth of the shower maximum, $X_{max}$, as a function of energy to the
slant depths expect ed for various hypothesized primaries. In this paper, we
present a method to make a direct measurement of the expected mean number of
protons and iron by comparing the shap es of the expected $X_{max}$
distributions to the distribution for data. The advantages of this method
includes the use of information of the full distribution and its ability to
calculate a flux for various cosmic ray compositi ons. The same method can be
expanded to marginalize uncertainties due to choice of spectra, hadronic models
and atmospheric parameters. We demonstrate the technique with independent
simulated data samples from a parent sample of protons and iron. We accurately
predict the number of protons and iron in the parent sample and show that the
uncertainties are meaningful.


title:
Millisecond Pulsar Emission Altitude from Relativistic Phase Shift: PSR
  J0437-4715

abstract:
  We have analyzed the profile of the millisecond pulsar PSR J0437-4715 at 1440
MHz by fitting the Gaussians to pulse components, and identified its 11
emission components. We propose that they form a emission beam with 5 nested
cones centered on the core. Using the phase location of component peaks, we
have estimated the aberration--retardation (A/R) phase shift. Due to A/R phase
shift, the centroid of intensity profile and the inflection point of
polarization angle swing are symmetrically shifted in the opposite directions
with respect to the meridional plane, which is defined by the rotation and
magnetic axes. By recognizing this fact, we have been able to locate the phase
location of meridional plane and estimate the absolute altitude of emission of
core and conal components relative to the neutron star center. Using the more
exact expression for phase shift given recently by Gangadhara (2005), we find
that the radio emission comes from a range of altitude starting from the core
at 7% of light cylinder radius to outer most cone at 30%.


title: Quasars and Galactic Nuclei,a Half-Century Agitated Story

abstract:
  I recall how the discovery of quasars occurred more than forty years ago, and
the strong debates marking out their story. It led to the discovery of Massive
Black Holes, which are now known to be present in almost all galaxies, and it
opened on a coherent physical model and on a new vision of galaxy evolution.


title: The large-scale structure of the Universe

abstract:
  Research over the past 25 years has led to the view that the rich tapestry of
present-day cosmic structure arose during the first instants of creation, where
weak ripples were imposed on the otherwise uniform and rapidly expanding
primordial soup. Over 14 billion years of evolution, these ripples have been
amplified to enormous proportions by gravitational forces, producing
ever-growing concentrations of dark matter in which ordinary gases cool,
condense and fragment to make galaxies. This process can be faithfully mimicked
in large computer simulations, and tested by a variety of observations that
probe the history of the Universe starting from just 400,000 yr after the Big
Bang.


title: Short Gamma-Ray Bursts from Binary Neutron Star Mergers

abstract:
  We present the results from new relativistic hydrodynamic simulations of
binary neutron star mergers using realistic non-zero temperature equations of
state. We vary several unknown parameters in the system such as the neutron
star (NS) masses, their spins and the nuclear equation of state. The results
are then investigated with special focus on the post-merger torus-remnant
system. Observational implications on the Gamma-ray burst (GRB) energetics are
discussed and compared with recent observations.


title: The HI content of E+A galaxies

abstract:
  We present deep single-dish HI observations of a sample of six nearby E+A
galaxies (0.05<z<0.1). A non-negligible fraction of a local sample of E+As are
detected in HI. In four galaxies, we have detected up to a few times 10^9 Msun
of neutral gas. These E+A galaxies are almost as gas-rich as spiral galaxies
with comparable luminosities. There appears to exist no direct correlation
between the amount of HI present in an E+A galaxy and its star-formation rate
as traced by radio continuum emission. Moreover, the end of the starburst does
not necessarily require the complete exhaustion of the neutral gas reservoir.
Most likely, an intense burst of star formation consumed the dense molecular
clouds, which are the sites of massive star formation. This effectively stops
star formation, even though copious amounts of diffuse neutral gas remain. The
remaining HI reservoir may eventually lead to further episodes of star
formation. This may indicate that some E+As are observed in the inactive phase
of the star-formation duty cycle.


title:
Structure and Stability of Phase Transition Layers in the Interstellar
  Medium

abstract:
  We analyze the structure and stability of the transition layer (or front)
that connects the cold neutral medium and warm neutral medium in the
plane-parallel geometry. Such fronts appear in recent numerical simulations of
a thermally bistable interstellar medium. The front becomes an evaporation or
condensation front depending on the surrounding pressure. The stability
analysis is performed in both long- and short-wavelength approximations. We
find that the plane-parallel evaporation front is unstable under corrugational
deformations, whereas the condensation front seems to be stable. The
instability is analogous to the Darrieus-Landau instability in combustion
front. The growth rate of the instability is proportional to the speed of the
evaporation flow and the corrugation wavenumber for modes with wavelength much
longer than the thickness of the front, and it is suppressed at scales
approximately equal to the thickness of the front. The timescale of the
instability is smaller than the cooling timescale of the warm neutral medium
($\sim 1$ Myr), and can be as small as the cooling timescale of the cold
neutral medium ($\sim 0.01-0.1$ Myr). Thus, this instability should be one of
the processes for driving the interstellar turbulence.


title:
Stellar populations of early-type galaxies in different environments I.
  Line-strength indices

abstract:
  Aims: This paper commences a series devoted to the study of the stellar
content of early-type galaxies. The goal of the series is to set constraints on
the evolutionary status of these objects.
  Methods: In this paper we describe the details of the galaxy sample, the
observations, and the data reduction. Line-strength indices and velocity
dispersions sigma are measured in 98 early-type galaxies drawn from different
environments, and the relation of the indices with the velocity dispersion
analysed in detail.
  Results: The present sample indicates that some of the index-sigma relations
depend on galaxy environment. In particular, the slope of the relation between
Balmer lines and sigma is steeper for galaxies in the Virgo cluster, small
groups, and in the field than for galaxies in the Coma cluster. In several
indices there is also a significant offset in the zero point between the
relations defined by the different subsamples. The slopes of the index-sigma
relation for the Virgo and low-density environment galaxies are explained by a
variation of both age and metallicity with velocity dispersion, as previously
noted in other studies. For the galaxies in the Coma cluster, however, the
relation of the indices with sigma only requires a variation of the abundance
along the sigma sequence. In agreement with other studies we find that the
models that better reproduce the slopes are those in which the alpha elements
vary more than the Fe-peak elements along the sigma sequence, while, at a given
sigma, older galaxies show an higher alpha/Fe ratio.
  Conclusions: The results can be explained assuming that galaxies in the Coma
cluster have experienced a truncated star formation and chemical enrichment
history compared to a more continuous time-extended history for their
counterparts in lower density environments.


title:
Supernovae and Radio Galaxies Probing Gurzadyan-Xue Cosmological Models
  with Dark Energy

abstract:
  In the previous papers we derived cosmological equations for models with
Gurzadyan-Xue dark energy, have performed their qualitative analysis and,
particularly, have revealed a remarkable hidden invariance in the models with
respect to the separatrix $\Omega_{sep}$ in their phase portraits. Now, new
analytic solutions for these models are obtained, showing additional symmetries
at various curvatures. The likelihood analysis with supernovae and radio
galaxies data and their characteristics (age, the deceleration parameter),
again demonstrate the crucial role of the $\Omega_{sep}$ for all models, in
spite of the diversity of both, the initial equations and their solutions.


title: FISICA: The Florida Image Slicer for Infrared Cosmology & Astrophysics

abstract:
  We report on the design, fabrication, and on-sky performance of the Florida
Image Slicer for Infrared Cosmology and Astrophysics (FISICA)- a
fully-cryogenic all-reflective image-slicing integral field unit for the
FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15,
FISICA with FLAMINGOS provides R \sim 1300 spectra over a 16x33-arcsec
field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a
6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran
Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three
sets of "monolithic" powered mirror arrays, each with 22 mirrored surfaces cut
into a single piece of aluminum. We review the optical and opto-mechanical
design and fabrication of FISICA, as well as laboratory test results for FISICA
integrated with the FLAMINGOS instrument. Finally, we present performance
results from observations with FISICA at the KPNO 4-m telescope and comparisons
of FISICA performance to other available IFUs on 4-m to 8-m-class telescopes.


title:
Stellar populations of early-type galaxies in different environments II.
  Ages and metallicities

abstract:
  This is the second paper of a series devoted to study the stellar content of
early-type galaxies. The goal of the series is to set constraints on the
evolutionary status of these objects. We use a new set of models which include
an improved stellar library (MILES) to derive simple stellar population
(SSP)-equivalent parameters in a sample of 98 early-type galaxies. The sample
contains galaxies in the field, poor groups, and galaxies in the Virgo and Coma
clusters.We find that low-density environment galaxies span a larger range in
SSP age and metallicity than their counterparts in high density environments,
with a tendency for lower sigma galaxies to be younger. Early-type galaxies in
low-density environments appear on average ~1.5 Gyr younger and more metal rich
than their counterparts in high density environments. The sample of low-density
environment galaxies shows an age metallicity relation in which younger
galaxies are found to be more metal rich, but only when metallicity is measured
with a Fe-sensitive index. Conversely, there is no age-metallicity relation
when the metallicity is measured with a Mg sensitive index. The
mass-metallicity relation is only appreciable for the low-density environment
galaxies when the metallicity is measured with a Mg-sensitive index and not
when the metallicity is measured with other indicators. On the contrary, this
relation exists for the high-density environment galaxies independently of the
indicator used to measure the metallicity. This suggests a dependence of the
mass-metallicity relation on the environment of the galaxies. Our data favour a
scenario in which galaxies in low density environments have suffered a more
extended star formation history than the galaxies in the Coma cluster, which
appear to host more homogenous stellar populations.


title: Curvature perturbation from symmetry breaking the end of inflation

abstract:
  We consider a two-field hybrid inflation model, in which the curvature
perturbation is predominantly generated at the end of inflation. By finely
tuning the coupling of the fields to the waterfall we find that we can get a
measurable amount of non-gaussianity.


title: VLBI Images of 49 Radio Supernovae in Arp 220

abstract:
  We have used a Very Long Baseline Interferometry (VLBI) array at 18cm
wavelength to image the nucleus of the luminous IR galaxy Arp 220 at ~1 pc
linear resolution, and with very high sensitivity. The resulting map has an rms
of 5.5 microJy/beam, and careful image analysis results in 49 confirmed point
sources ranging in flux density from 1.2 mJy down to ~60 microJy. Comparison
with high sensitivity data from 12 months earlier reveals at least four new
sources. The favored interpretation of these sources is that they are radio
supernovae, and if all new supernovae are detectable at this sensitivity, a
resulting estimate of the supernova rate in the Arp 220 system is 4 +/- 2 per
year. The implied star formation rate is sufficient to power the entire
observed far-infrared luminosity of the galaxy. The two nuclei of Arp 220
exhibit striking similarities in their radio properties, though the western
nucleus is more compact, and appears to be ~3 times more luminous than the
eastern nucleus. There are also some puzzling differences, and differential
free-free absorption, synchrotron aging and expansion losses may all be playing
a role. Comparison with the nearby starburst galaxy M82 supports the hypothesis
that the activity in Arp 220 is essentially a scaled-up version of that in M82.


title:
Stellar populations of early-type galaxies in different environments
  III. Line-strength gradients

abstract:
  We present line-strength gradients for 22 spectral indices measured in a
sample of 82 early-type galaxies in different environments,including the
high-density core of the Coma cluster, the Virgo cluster,poor groups,and field
galaxies. We derive age and metallicity gradients, and compare the mean values
with the predictions of different galaxy formation models. We explore the
behaviour of individual chemical species by deriving the metallicity gradient
with different indicators.We find that the strength of the metallicity gradient
inferred from stellar population models depends on the specific Lick index
employed. In particular, metallicity gradients obtained with CN2 and C4668
combined with Hb are steeper than when measured using Ca4227 or Fe4383. The
correlation of the metallicity gradients with other parameters also depends on
the specific index employed. If the metallicity gradient is obtained using CN2
and Mgb then it correlates with the central age of the galaxies. On the
contrary, if Fe4383 or Ca4227 are used, the metallicity gradient correlates
with the velocity dispersion gradient.This may suggests that several mechanism
have helped to set the age and metallicity gradients in early-type galaxies.
While we do not find any correlation between the metallicity gradient and the
central velocity dispersion for galaxies in low-density environments, we find a
marginal correlation between the metallicity gradient and the mass for galaxies
in the centre of the Coma cluster. We also find a trend for which galaxies in
denser environments show a steeper metallicity gradient than galaxies in less
dense environments.We interpret these results in light of the different models
to explain the differences between galaxies as a function of environment.


title: Spectroscopy of Massive Stars

abstract:
  Although rare, massive stars, being the main sources of ionizing radiation,
chemical enrichment and mechanical energy in the Galaxy, are the most important
objects of the stellar population. This review presents the many different
aspects of the main tool used to study these stars, i.e. spectroscopy. The
first part consists in an introduction on these objects and their physical
properties (mass, wind, evolution, relation with their environment). Next, the
spectral behaviour of single massive stars is investigated, in the visible as
well as in the X-ray domain. Finally, the last part of this paper deals with
massive binaries, especially those exhibiting a colliding wind phenomenon.


title: Gravitational collapse of magnetized clouds. I. Ideal MHD accretion flow

abstract:
  We study the self-similar collapse of an isothermal magnetized rotating cloud
in the ideal magnetohydrodynamic (MHD) regime. In the limit of small distance
from the accreting protostar we find an analytic solution that corresponds to
free-fall onto a central mass point. The density distribution is not
spherically symmetric but depends on the mass loading of magnetic field lines,
which can be obtained by matching our inner solution to an outer collapse
solution previously computed by Allen, Shu & Li. The concentration of magnetic
field trapped by the central mass point under field-freezing, independent on
the details of the starting state, creates a split monopole configuration where
the magnetic field strength increases as the inverse square of the distance
from the center. Under such conditions, the inflow eventually becomes
subalfvenic and the outward transfer of angular momentum by magnetic braking
very efficient, thus preventing the formation of a centrifugally supported
disk. Instead, the azimuthal velocity of the infalling gas decreases to zero at
the center, and the gas spirals into the star. Therefore, the dissipation of
dynamically important levels of magnetic field is a fundamental requisite for
the formation of protoplanetary disks around young stars.


title:
Gravitational collapse of magnetized clouds II. The role of Ohmic
  dissipation

abstract:
  We formulate the problem of magnetic field dissipation during the accretion
phase of low-mass star formation, and we carry out the first step of an
iterative solution procedure by assuming that the gas is in free-fall along
radial field lines. This so-called ``kinematic approximation'' ignores the back
reaction of the Lorentz force on the accretion flow. In quasi steady-state, and
assuming the resistivity coefficient to be spatially uniform, the problem is
analytically soluble in terms of Legendre's polynomials and confluent
hypergeometric functions. The dissipation of the magnetic field occurs inside a
region of radius inversely proportional to the mass of the central star (the
``Ohm radius''), where the magnetic field becomes asymptotically straight and
uniform. In our solution, the magnetic flux problem of star formation is
avoided because the magnetic flux dragged in the accreting protostar is always
zero. Our results imply that the effective resistivity of the infalling gas
must be higher by several orders of magnitude than the microscopic electric
resistivity, to avoid conflict with measurements of paleomagnetism in
meteorites and with the observed luminosity of regions of low-mass star
formation.


title:
Resonance scattering, absorption and off-centre abundance peaks in
  clusters of galaxies

abstract:
  A possible explanation for the central abundance dips found from
spatially-resolved X-ray spectroscopy of several groups and clusters of
galaxies is resonance scattering. A number of the prominent iron emission lines
are resonance lines. We construct a unique spectral model which takes account
of resonance scattering for several thousand resonance lines, projection
effects, photoelectric absorption, and allows direct spectral fitting. We apply
our model to Chandra observations of two clusters with pronounced central
abundance dips, Centaurus and Abell 2199. The results show that the effect of
resonance scattering on emission from the centre of the cluster can be as much
as 30 per cent for the Fe-K resonance lines, and 10 per cent for several Fe-L
lines, if turbulence is low. The change to the metallicities obtained by
fitting low resolution CCD spectra is at most 10 per cent. Accounting for
resonance scattering does not remove the central dip. Allowing for internal
absorption within the Centaurus significantly improves the quality of the fits,
indicating the presence of absorbing material within the inner 40 kpc of NGC
4696.