title:
Gravity-mode pulsations in subdwarf B stars: a critical test of stellar
  opacity

abstract:
  The identification of non-radial g-mode oscillations as the cause of
variability in cool subdwarf B stars (PG1716 variables) has been frustrated by
a 5 000 K discrepancy between the observed and theoretical blue edge of the
instability domain (Fontaine et al. 2003). A major component in the solution to
this problem has been identified} by (a) using updated OP instead of OPAL
opacities and (b) considering an enhancement of nickel, in addition to that of
iron, in the driving zone. The reason for this success is that, in OP, the
``Fe-bump'' contributions from iron and nickel occur at higher temperatures
than in OPAL. As well as pointing to a solution of an important problem in
stellar pulsation theory, this result provides a critical test for stellar
opacities and the atomic physics used to compute them.


title:
On the dipole straylight contamination in spinning space missions
  dedicated to CMB anisotropy

abstract:
  We present an analysis of the dipole straylight contamination (DSC) for
spinning space-missions designed to measure CMB anisotropies. Although this
work is mainly devoted to the {\sc Planck} project, it is relatively general
and allows to focus on the most relevant DSC implications. We first study a
simple analytical model for the DSC in which the pointing direction of the main
spillover can be assumed parallel or not to the spacecraft spin axis direction
and compute the time ordered data and map. The map is then analysed paying
particular attention to the DSC of the low multipole coefficients of the map.
Through dedicated numerical simulations we verify the analytical results and
extend the analysis to higher multipoles and to more complex (and realistic)
cases by relaxing some of the simple assumptions adopted in the analytical
approach. We find that the systematic effect averages out in an even number of
surveys, except for a contamination of the dipole itself that survives when
spin axis and spillover directions are not parallel and for a contamination of
the other multipoles in the case of complex scanning strategies. In particular,
the observed quadrupole can be affected by the DSC in an odd number of surveys
or in the presence of survey uncompleteness or over-completeness. Various
aspects relevant in CMB space projects (such as implications for calibration,
impact on polarization measurements, accuracy requirement in the far beam
knowledge for data analysis applications, scanning strategy dependence) are
discussed.


title:
Spitzer Observations of the Prototypical Extremely Red Objects HR10 and
  LBDS53W091: Separating Dusty Starbursts from Old Elliptical Galaxies

abstract:
  We present Spitzer Space Telescope observations of the well-studied extremely
red objects (EROs) HR10 and LBDS53W091 from 3.6 to 160 microns. These galaxies
are the prototypes of the two primary classes of EROs: dusty starbursts and
old, evolved galaxies, respectively. Both galaxies, as well as LBDS53W069,
another example of an old, quiescent galaxy, are well-detected out to 8
microns. However, only the dusty starburst HR10 is detected in the
far-infrared. All three EROs have stellar masses of a few times 10^11 M(sun).
Using evolutionary model fits to their multiband photometry, we predict the
infrared colors of similar EROs at 1<z<2. We find that blueward of observed 10
microns, the two ERO classes are virtually indistinguishable photometrically.
Deep spectroscopy and 24 micron data allow the classes to be separated.


title:
CMB quadrupole suppression: I. Initial conditions of inflationary
  perturbations

abstract:
  We investigate the issue of initial conditions of curvature and tensor
perturba- tions at the beginning of slow roll inflation and their effect on the
power spectra. Renormalizability and small back reaction constrain the high k
behavior of the Bogoliubov coefficients that define these initial conditions.We
introduce a transfer function D(k) which encodes the effect of generic initial
conditions on the power spectra. The constraint from renormalizability and
small back reaction entails that D(k) < mu^2/k^2 for large k, implying that
observable effects from initial conditions are more prominent in the low
multipoles. This behavior affects the CMB quadrupole by the observed amount
\~10-20% when mu is of the order of the energy scale of inflation. The effects
on high l-multipoles are suppressed by a factor ~1/l^2 due to the fall off of
D(k) for large wavevectors k. We show that the determination of generic initial
conditions for the fluc- tuations is equivalent to the scattering problem by a
potential V(eta) localized just prior to the slow roll stage. Such potential
leads to a transfer function D(k) which automatically obeys the
renormalizability and small backreaction constraints. We find that an
attractive potential V(eta) yields a suppression of the lower CMB
multipoles.Both for curvature and tensor modes, the quadrupole suppression
depends only on the energy scale of V(eta) and on the time interval where
V(eta) is nonzero. A suppression of the quadrupole for curvature pertur-
bations consistent with the data is obtained when the scale of the potential is
of the order of k^2_Q where k_Q is the wavevector whose physical wavelength is
the Hubble radius today.


title:
Chromo-thermal oscillations and collapse of strange stars to black holes
  : Astrophysical Implications

abstract:
  The effects of temperature on strange stars are studied and it is found that
the maximum mass of the star decreases with the increase of temperature since
at high temperatures the equations of state become softer. Moreover, if the
temperature of a strange star increases, keeping its baryon number fixed, its
gravitational mass increases and radius decreases. This leads to a limiting
temperature where it turns into a black hole. These features are due to a
combined effect of the change of gluon mass and the quark distribution with
temperature. We report a new kind of radial oscillations of strange stars
driven by what we call chromo-thermal instability. We also discuss the
relevance of our findings in the astrophysics of core collapse supernovae and
gamma ray bursts.


title: Cosmic Acceleration and Modified Gravity

abstract:
  I briefly discuss some attempts to construct a consistent modification to
General Relativity (GR) that might explain the observed late-time acceleration
of the universe and provide an alternative to dark energy. I mention the issues
facing extensions to GR, illustrate these with two specific examples, and
discuss the resulting observational and theoretical obstacles. This article
comprises an invited talk at the NASA workshop {\it From Quantum to Cosmos:
Fundamental Physics Research in Space}


title:
A Spectacular Radio Flare from XRF 050416a at 40 days and Implications
  for the Nature of X-ray Flashes

abstract:
  We present detailed optical, near-infrared, and radio observations of the
X-ray flash 050416a obtained with Palomar and Siding Springs Observatories as
well as HST and the VLA, placing this event among the best-studied X-ray
flashes to date. In addition, we present an optical spectrum from Keck LRIS
from which we measure the redshift of the burst, z=0.6528. At this redshift the
isotropic-equivalent prompt energy release was about 10^51 erg, and using a
standard afterglow synchrotron model we find that the blastwave kinetic energy
is a factor of 10 larger, E_K,iso ~ 10^52 erg. The lack of an observed jet
break to t ~ 20 days indicates that the opening angle is larger than 7 deg and
the total beaming-corrected relativistic energy is larger than 10^50 erg. We
further show that the burst produced a strong radio flare at t ~ 40 days
accompanied by an observed flattening in the X-ray band which we attribute to
an abrupt circumburst density jump or an episode of energy injection (either
from a refreshed shock or off-axis ejecta). Late-time observations with HST
show evidence for an associated supernova with peak optical luminosity roughly
comparable to that of SN 1998bw. Next, we show that the host galaxy of XRF
050416a is actively forming stars at a rate of at least 2 M_solar per year with
a luminosity of L_B ~ 0.5L* and metallicity of Z ~ 0.2-0.8 Z_solar. Finally, we
discuss the nature of XRF 050416a in the context of short-hard gamma-ray bursts
and under the framework of off-axis and dirty fireball models for X-ray
flashes.


title:
The DEEP2 Galaxy Redshift Survey: Evolution of the Color-Density
  Relation at 0.4 < z < 1.35

abstract:
  Using a sample of 19,464 galaxies drawn from the DEEP2 Galaxy Redshift
Survey, we study the relationship between galaxy color and environment at 0.4 <
z < 1.35. We find that the fraction of galaxies on the red sequence depends
strongly on local environment out to z > 1, being larger in regions of greater
galaxy density. At all epochs probed, we also find a small population of red,
morphologically early-type galaxies residing in regions of low measured
overdensity. The observed correlations between the red fraction and local
overdensity are highly significant, with the trend at z > 1 detected at a
greater than 5-\sigma level. Over the entire redshift regime studied, we find
that the color-density relation evolves continuously, with red galaxies more
strongly favoring overdense regions at low z relative to their red-sequence
counterparts at high redshift. At z ~ 1.3, the red fraction only weakly
correlates with overdensity, implying that any color dependence to the
clustering of ~ L* galaxies at that epoch must be small. Our findings add
weight to existing evidence that the build-up of galaxies on the red sequence
has occurred preferentially in overdense environments (i.e., galaxy groups) at
z < 1.5. The strength of the observed evolutionary trends at 0 < z < 1.35
suggests that the correlations observed locally, such as the morphology-density
and color-density relations, are the result of environment-driven mechanisms
(i.e., "nurture'') and do not appear to have been imprinted (by "nature'') upon
the galaxy population during their epoch of formation.


title:
A Time Delay for the Largest Gravitationally Lensed Quasar: SDSS
  J1004+4112

abstract:
  We present 426 epochs of optical monitoring data spanning 1000 days from
December 2003 to June 2006 for the gravitationally lensed quasar SDSS
J1004+4112. The time delay between the A and B images is 38.4+/-2.0 days in the
expected sense that B leads A and the overall time ordering is C-B-A-D-E. The
measured delay invalidates all published models. The models failed because they
neglected the perturbations from cluster member galaxies. Models including the
galaxies can fit the data well, but strong conclusions about the cluster mass
distribution should await the measurement of the longer, and less substructure
sensitive, delays of the C and D images. For these images, a CB delay of
681+/-15 days is plausible but requires confirmation, while CB and AD delays of
>560 days and > 800 days are required. We clearly detect microlensing of the
A/B images, with the delay-corrected flux ratios changing from B-A=0.44+/-0.01
mag in the first season to 0.29+/-0.01 mag in the second season and 0.32+/-0.01
mag in the third season.


title:
HD 203030B: an Unusually Cool Young Sub-Stellar Companion near the L/T
  Transition

abstract:
  We present the discovery of a brown-dwarf companion to the 130-400 Myr-old G8
V star HD 203030. Separated by 11.9" (487 AU in projection) from its host star,
HD 203030B has an estimated mass of 0.023 (+0.008;-0.011) solar masses. The
K-band spectral type of L7.5+/-0.5 places HD 203030B near the critical L/T
transition in brown dwarfs, which is characterized by the rapid disappearance
of dust in sub-stellar photospheres. From a comparative analysis with
well-characterized field L/T transition dwarfs, we find that, despite its young
age, HD 203030B has a bolometric luminosity similar to the >1 Gyr-old field
dwarfs. Adopting a radius from current models of sub-stellar evolution, we
hence obtain that the effective temperature of HD 203030B is only 1206
(+74;-116) K, markedly lower than the ~1440 K effective temperatures of field
L/T transition dwarfs. The temperature discrepancy can be resolved if either:
(1) the ages of field brown dwarfs have been over-estimated by a factor of
\~1.5, leading to under-estimated radii, or (2) the lower effective temperature
of HD 203030B is related to its young age, implying that the effective
temperature at the L/T transition is gravity-dependent.


title: Ultra high energy neutrinos: the key to ultra high energy cosmic rays

abstract:
  We discuss the relation between the acceleration spectra of extragalactic
cosmic ray protons and the luminosity and cosmological evolution of their
sources and the production of ultra high energy cosmogenic neutrinos in their
propagation from the sources to us.


title:
Direct Detection of the Brown Dwarf GJ 802B with Adaptive Optics Masking
  Interferometry

abstract:
  We have used the Palomar 200" Adaptive Optics (AO) system to directly detect
the astrometric brown dwarf GJ 802B reported by Pravdo et al. 2005. This
observation is achieved with a novel combination of aperture masking
interferometry and AO. The dynamical masses are 0.175$\pm$0.021 M$_\odot$ and
0.064$\pm$0.032 M$_\odot$ for the primary and secondary respectively. The
inferred absolute H band magnitude of GJ 802B is M$_H$=12.8 resulting in a
model-dependent T$_\mathrm{eff}$ of 1850 $\pm$ 50K and mass range of
0.057--0.074 M$_\odot$.


title: Self-regulated reionization

abstract:
  Recently, we have presented the first large-scale radiative transfer
simulations of reionization. Here we present new simulations which extend the
source halo mass range downward to 10^8M_solar, to capture the full range of
halo masses thought to be primarily responsible for reionization by their star
formation following atomic hydrogen radiative cooling and gravitational
collapse. Haloes below about 10^9M_solar, however, are subject to Jeans-mass
filtering in the ionized regions, which suppresses their baryonic content and
their ability to release ionizing radiation. By including these smaller-mass
haloes but accounting for their suppression, too, we find that reionization is
``self-regulating,'' as follows. As the mean ionized fraction rises, so does
the fraction of the volume within which suppression occurs. Hence, the degree
of suppression is related to the mean ionized fraction. Since low-mass haloes
with high emissivity achieve a given mean ionized fraction earlier than do
those with low efficiency, Jeans-mass filtering compensates for the difference
in the emissivity of the suppressible haloes in these two cases. As a result,
in the presence of lower-mass source haloes, reionization begins earlier, but
the later stages of reionization and the time of overlap are dictated by the
efficiency of the higher-mass haloes, independent of the efficiency of the
suppressible, lower-mass haloes. Reionization histories consistent with current
observational constraints are shown to be achievable with standard stellar
sources in haloes above 10^8M_solar. Neither minihalos nor exotic sources are
required, and the phenomenon of ``double reionization'' previously suggested
does not occur. (abridged)


title: Minor Merger Origin for the Circumnuclear Starburst in NGC 7742

abstract:
  We present an emission-line diagnostic analysis of integral-field
spectroscopic observations that cover the central kiloparsec of NGC 7742. This
Sa galaxy hosts a spectacular nuclear starburst ring and nuclear regions
characterized by low-ionization emission. The gas in the ring rotates in the
opposite sense to the stars in the galaxy, suggesting a recent merging or
acquisition event. The combination of integral-field measurements for the
H-alpha + [NII] emission lines from DensePak and the H-beta and [OIII] emission
from Sauron allow the construction of diagnostic diagrams that highlight the
transition from star formation in the nuclear ring to excitation by
high-velocity shocks or by a central AGN towards the center. DensePak
measurements for the [SII] line ratio reveal very low gas densities in the
nuclear ring, Ne < 100 per cm^3, characteristic of massive HII regions.
Comparison with MAPPINGS III models for starbursts with low gas densities show
that the ring is of roughly solar metallicity. This suggests that the gas in
the nuclear ring originated in a stellar system capable of substantially
enriching the gas metallicity through sustained star formation. We suggest that
NGC 7742 cannibalised a smaller galaxy rich in metal-poor gas, and that star
formation episodes in the ring have since increased the metallicity to its
present value.


title: X-ray Observations of the Bipolar PNe NGC 2346 and NGC 7026

abstract:
  We have obtained X-ray observations of the bipolar planetary nebulae (PNe)
NGC 2346 and NGC 7026 with XMM-Newton. These observations detected diffuse
X-ray emission from NGC 7026 but not from NGC 2346. The X-ray emission from NGC
7026 appears to be confined within the bipolar lobes of the PN and has spectral
properties suggesting a thermal plasma emitting at a temperature of 1.1
+0.5/-0.2 times 10^6 K. The X-ray spectrum of NGC 7026 is modeled using nebular
and stellar abundances to assess whether a significant amount of nebular
material has been mixed into the shocked-wind, but the results of this
comparison are not conclusive owing to the small number of counts detected.
Observations of bipolar PNe indicate that diffuse X-ray emission is much less
likely detected in open-lobed nebulae than closed-lobed nebulae, possibly
because open-lobed nebulae do not have strong fast winds or are unable to
retain hot gas.


title: A fixed point in Coptic Chronology: the solar eclipse of 10 March, 601

abstract:
  We reconsider the description of a solar eclipse in the Coptic ostracon in
the Egyptian museum, Turin, confirming its identification with the solar
eclipse of 10 march 601. This provides one of very few fixed dates in Coptic
chronology. We comment on the rarity of such descriptions.


title:
Inverse Compton scattering on solar photons, heliospheric modulation,
  and neutrino astrophysics

abstract:
  We study the inverse Compton scattering of solar photons by Galactic
cosmic-ray electrons. We show that the gamma-ray emission from this process is
substantial with the maximum flux in the direction of the Sun; the angular
distribution of the emission is broad. This previously-neglected foreground
should be taken into account in studies of the diffuse Galactic and
extragalactic gamma-ray emission. Furthermore, observations by GLAST can be
used to monitor the heliosphere and determine the electron spectrum as a
function of position from distances as large as Saturn's orbit to close
proximity of the Sun, thus enabling unique studies of solar modulation. This
paves the way for the determination of other Galactic cosmic-ray species,
primarily protons, near the solar surface which will lead to accurate
predictions of gamma rays from pp-interactions in the solar atmosphere. These
albedo gamma rays will be observable by GLAST, allowing the study of deep
atmospheric layers, magnetic field(s), and cosmic-ray cascade development. The
latter is necessary to calculate the neutrino flux from pp-interactions at
higher energies (>1 TeV). Although this flux is small, it is a "guaranteed
flux" in contrast to other astrophysical sources of neutrinos, and may be
detectable by km^3 neutrino telescopes of the near future, such as IceCube.
Since the solar core is opaque for very high-energy neutrinos, directly
studying the mass distribution of the solar core may thus be possible.


title:
Long-term evolution of orbits about a precessing oblate planet. 2. The
  case of variable precession

abstract:
  We continue the study undertaken in Efroimsky (2005a) where we explored the
influence of spin-axis variations of an oblate planet on satellite orbits.
Near-equatorial satellites had long been believed to keep up with the oblate
primary's equator in the cause of its spin-axis variations. As demonstrated by
Efroimsky and Goldreich (2004), this opinion had stemmed from an inexact
interpretation of a correct result by Goldreich (1965). Though Goldreich (1965)
mentioned that his result (preservation of the initial inclination, up to small
oscillations about the moving equatorial plane) was obtained for non-osculating
inclination, his admonition has been persistently ignored for forty years.
  It was explained in Efroimsky and Goldreich (2004) that the equator
precession influences the osculating inclination of a satellite orbit already
in the first order over the perturbation caused by a transition from an
inertial to an equatorial coordinate system. It was later shown in Efroimsky
(2005a) that the secular part of the inclination is affected only in the second
order. This fact, anticipated by Goldreich (1965), remains valid for a constant
rate of the precession. It turns out that non-uniform variations of the
planetary spin state generate changes in the osculating elements, that are
linear in the planetary equator's total precession rate, rate that includes the
equinoctial precession, nutation, the Chandler wobble, and the polar wander.
  We work out a formalism which will help us to determine if these factors
cause a drift of a satellite orbit away from the evolving planetary equator.


title: Dynamics of Rarefaction Waves in General-Relativistic Collapsing Clouds

abstract:
  Formation and evolution of general relativistic collapse inhomogeneity is
investigated. It is shown that a rarefaction wave forms at initial collapse
stages and propagates inside from the cloud boundary to its center. The
focusing time of the rarefaction wave is found. In massive clouds, the
rarefaction wave focusing time equals the free-fall time. The collapse of such
clouds leads to black hole formation. In low-mass clouds, the rarefaction wave
focusing time is less than the free-fall time. After focusing, the collapse of
such clouds becomes fully inhomogeneous and can be sufficiently decelerated by
the pressure gradient.


title: The Fifth VLBA Calibrator Survey: VCS5

abstract:
  This paper presents the fifth part of the Very Long Baseline Array (VLBA)
Calibrator Survey (VCS), containing 569 sources not observed previously with
very long baseline interferometry in geodetic or absolute astrometry programs.
This campaign has two goals: (i) to observe additional sources which, together
with previous survey results, form a complete sample, (ii) to find new strong
sources suitable as phase calibrators. This VCS extension was based on three
24-hour VLBA observing sessions in 2005. It detected almost all extragalactic
flat-spectrum sources with correlated flux density greater than 200 mJy at 8.6
GHz above declination -30 degrees which were not observed previously. Source
positions with milliarcsecond accuracy were derived from astrometric analysis
of ionosphere-free combinations of group delays determined from the 2.3 GHz and
8.6 GHz frequency bands. The VCS5 catalog of source positions, plots of
correlated flux density versus projected baseline length, contour plots and
FITS files of naturally weighted CLEAN images, as well as calibrated visibility
function files are available on the Web at http://vlbi.gsfc.nasa.gov/vcs5


title: Nonminimal Inflation and the Running Spectral Index

abstract:
  We study a class of models in which the inflaton is minimally coupled to
gravity with a term $f(R)\vp^2$. We focus in particular on the case when $f\sim
R^2$, the expansion of the scale factor is driven by the usual potential
energy, while the rolling of the inflaton is driven by the nonminial coupling.
We show that the power spectrum is in general blue, and the problem of getting
a running spectral index is eased. However, the inflaton potential must have a
large second derivative in order to get a large running.


title:
Air-Showers in Space and Z-Showers in Universe for Neutrino Astronomy
  and Spectroscopy

abstract:
  Amplified Tau-airshower at horizons may well open a novel powerful windows,
at PeV-EeV energy, to Neutrino Astronomy. Neutrino induced air-showering
astronomy rise because of neutrino masses, their mixing and the consequent
replenishment of tau flavor during neutrino flight into spaces; Tau-Air-Showers
escaping the Earth are the main traces amplified by its millions muon, billions
gamma and thousand billions photon secondaries. Earth edges and its sharp
shadows is the huge beam-dump detector for UHE neutrino and the almost
noise-free screen for tau air-showers (as well as for PeVs anti-neutrino
electron scattering on air electrons by resonant interactions). Crown array
detectors for horizontal Cherenkov signals on mountains, on balloons and
satellites widening the solid angle view are being elaborated; deep and wide
valleys are considered. MAGIC Telescopes pointing downward to terrestrial
grounds acts, for EeV Tau neutrino air-showers astronomy, as a massive tens of
km^3 water equivalent detector, making (in a given direction) it at present the
most powerful dedicated neutrino telescope at PeVs. MAGIC facing the sea edges
must also reveal mirrored downward UHECR Air-showers (Cherenkov) flashes.
Magic-crown systems may lead to largest neutrino detectors in near future. They
maybe located on top mountains, on planes or balloons or in satellite arrays.
They may be screened in deep valleys. MILAGRO (and past MILAGRITO or future
larger detectors) on a mountain top might already hide records of horizontal
up-going muon bundles due to far UHECR and less far (but rarer) tau air-showers
at EeV. UHE neutrino may also scatter on relic light (0.1-0.2 eV) ones,
showering in the Universe at ZeV energies Cosmic Rays.


title: Neutrino-Neutrino Interactions and Flavor Mixing in Dense Matter

abstract:
  An algebraic approach to the neutrino propagation in dense media is
presented. The Hamiltonian describing a gas of neutrinos interacting with each
other and with background fermions is written in terms of the appropriate SU(N)
operators, where N is the number of neutrino flavors. The evolution of the
resulting many-body problem is formulated as a coherent-state path integral.
Some commonly used approximations are shown to represent the saddle-point
solution of the path integral for the full many-body system.


title:
The Chandra X-ray Spectrum of the 10.6 s Pulsar in Westerlund 1: Testing
  the Magnetar Hypothesis

abstract:
  Two sensitive Chandra X-ray observations of the heavily-reddened galactic
starburst cluster Westerlund 1 in May and June 2005 detected a previously
unknown X-ray pulsar (CXO J164710.20-455217). Its slow 10.6 s pulsations,
moderate X-ray temperature kT $\approx$ 0.5 keV, and apparent lack of a massive
companion tentatively suggest that it is an Anomalous X-ray Pulsar (AXP). An
isothermal blackbody model yields an acceptable spectral fit but the inferred
source radius is much less than that of a neutron star, a result that has also
been found for other AXPs. We analyze the X-ray spectra with more complex
models including a model that assumes the pulsar is a strongly magnetized
neutron star (``magnetar'') with a light element atmosphere. We conclude that
the observed X-ray emission cannot be explained as global surface emission
arising from the surface of a cooling neutron star or magnetar. The emission
likely arises in one or more localized regions (``hot spots'') covering a small
fraction of the surface. We discuss these new results in the context of both
accretion and magnetar interpretations for the X-ray emission.


title: Seeing the sky through Hubble's eye: The COSMOS SkyWalker

abstract:
  Large, high-resolution space-based imaging surveys produce a volume of data
that is difficult to present to the public in a comprehensible way. While
megapixel-sized images can still be printed out or downloaded via the World
Wide Web, this is no longer feasible for images with 10^9 pixels (e.g., the
Hubble Space Telescope Advanced Camera for Surveys [ACS] images of the Galaxy
Evolution from Morphology and SEDs [GEMS] project) or even 10^10 pixels (for
the ACS Cosmic Evolution Survey [COSMOS]). We present a Web-based utility
called the COSMOS SkyWalker that allows viewing of the huge ACS image data set,
even through slow Internet connections. Using standard HTML and JavaScript, the
application successively loads only those portions of the image at a time that
are currently being viewed on the screen. The user can move within the image by
using the mouse or interacting with an overview image. Using an astrometrically
registered image for the COSMOS SkyWalker allows the display of calibrated
world coordinates for use in science. The SkyWalker "technique" can be applied
to other data sets. This requires some customization, notably the slicing up of
a data set into small (e.g., 256^2 pixel) subimages. An advantage of the
SkyWalker is the use of standard Web browser components; thus, it requires no
installation of any software and can therefore be viewed by anyone across many
operating systems.


title:
Long-term evolution of orbits about a precessing oblate planet. 3. A
  semianalytical and a purely numerical approach

abstract:
  Construction of a theory of orbits about a precessing oblate planet, in terms
of osculating elements defined in a frame of the equator of date, was started
in Efroimsky and Goldreich (2004) and Efroimsky (2005, 2006). We now combine
that analytical machinery with numerics. The resulting semianalytical theory is
then applied to Deimos over long time scales. In parallel, we carry out a
purely numerical integration in an inertial Cartesian frame. The results agree
to within a small margin, for over 10 Myr, demonstrating the applicability of
our semianalytical model over long timescales. This will enable us to employ it
at the further steps of the project, enriching the model with the tides, the
pull of the Sun, and the planet's triaxiality. Another goal of our work was to
check if the equinoctial precession predicted for a rigid Mars could have been
sufficient to repel the orbits away from the equator. We show that for low
initial inclinations, the orbit inclination reckoned from the precessing
equator of date is subject only to small variations. This is an extension, to
non-uniform precession given by the Colombo model, of an old result obtained by
Goldreich (1965) for the case of uniform precession and a low initial
inclination. However, near-polar initial inclinations may exhibit considerable
variations for up to +/- 10 deg in magnitude. Nevertheless, the analysis
confirms that an oblate planet can, indeed, afford large variations of the
equinoctial precession over hundreds of millions of years, without repelling
its near-equatorial satellites away from the equator of date: the satellite
inclination oscillates but does not show a secular increase. Nor does it show
secular decrease, a fact that is relevant to the discussion of the possibility
of high-inclination capture of Phobos and Deimos.


title:
Does Unruh radiation accelerate the universe? A novel approach to dark
  energy

abstract:
  In braneworld scenario, the brane accelerates in the bulk, and hence it
perceives a thermal bulk filled with Unruh radiation. We put forward that there
may be an energy exchange between Unruh radiation in the bulk and the dark
matter confined to the brane, which accelerates the universe.


title: Two-Component Cosmological Fluids with Gravitational Instabilities

abstract:
  A survey of linearized cosmological fluid equations with a number of
different matter components is made. To begin with, the one-component case is
reconsidered to illustrate some important mathematical and physical points
rarely discussed in the literature. The work of some previous studies of
two-component systems are examined and re-analyzed to point out some
deficiencies of solutions, and further solutions and physical interpretation
are then presented. This leads into a general two-component model with variable
velocity dispersion parameters and mass density fractions of each component.
The equations, applicable to both hot dark matter (HDM) and cold dark matter
(CDM) universes are solved in the long wavelength limit. This region is of
interest, because some modes in this range of wavenumbers are Jeans unstable.
The mixture Jeans wavenumber of the two-component system is introduced and
interpreted, and the solutions are discussed, particularly in comparison to
analogous solutions previously derived for plasma modes. This work is
applicable to that region in the early Universe ($20 < z < 140$), where large
scale structure formation is thought to have occurred.


title:
Short Wavelength Analysis of the Evolution of Perturbations in a
  Two-component Cosmological Fluid

abstract:
  The equations describing a two-component cosmological fluid with linearized
density perturbations are investigated in the small wavelength or large $k$
limit. The equations are formulated to include a baryonic component, as well as
either a hot dark matter (HDM) or cold dark matter (CDM) component. Previous
work done on such a system in static spacetime is extended to reveal some
interesting physical properties, such as the Jeans wavenumber of the mixture,
and resonant mode amplitudes. A WKB technique is then developed to study the
expanding universe equations in detail, and to see whether such physical
properties are also of relevance in this more realistic scenario. The Jeans
wavenumber of the mixture is re-interpreted for the case of an expanding
background spacetime. The various modes are obtained to leading order, and the
amplitudes of the modes are examined in detail to compare to the resonances
observed in the static spacetime results. It is found that some conclusions
made in the literature about static spacetime results cannot be carried over to
an expanding cosmology.


title:
High-Resolution Spectroscopy in Tr37: Gas Accretion Evolution in Evolved
  Dusty Disks

abstract:
  Using the Hectochelle multifiber spectrograph, we have obtained
high-resolution (R~34,000) spectra in the Halpha region for a large number of
stars in the 4 Myr-old cluster Tr 37, containing 146 previously known members
and 26 newly identified ones. We present the Halpha line profiles of all
members, compare them to our IR observations of dusty disks (2MASS/JHK + IRAC +
MIPS 24 micron), use the radial velocities as a membership criterion, and
calculate the rotational velocities. We find a good correlation between the
accretion-broadened profiles and the presence of protoplanetary disks, noting
that a small fraction of the accreting stars presents broad profiles with
Halpha equivalent widths smaller than the canonical limit separating CTTS and
WTTS. The number of strong accretors appears to be lower than in younger
regions, and a large number of CTTS have very small accretion rates
(dM/dt<10^{-9} Msun/yr). Taking into account that the spectral energy
distributions are consistent with dust evolution (grain growth/settling) in the
innermost disk, this suggests a parallel evolution of the dusty and gaseous
components. We also observe that about half of the "transition objects" (stars
with no IR excesses at wavelengths shorter than ~6 micron) do not show any
signs of active accretion, whereas the other half is accreting with accretion
rates <10^{-9} Msun/yr. These zero or very low accretion rates reveal important
gas evolution and/or gas depletion in the innermost disk, which could be
related to grain growth up to planetesimal or even planet sizes. Finally, we
examine the rotational velocities of accreting and non accreting stars, finding
no significant differences that could indicate disk locking at these ages.


title:
Membership Determination of Open Cluster M48 Based on BATC Thirteen-Band
  Photometry

abstract:
  Beijing-Arizona-Taiwan-Connecticut (BATC) multi-band photometric data in the
field of open cluster M48 are used to determine its membership. By comparing
observed spectral energy distributions (SEDs) of stars with theoretical ones,
membership probabilities of 750 stars with limiting magnitude of 15.0 in BATC
$c$ band ($\lambda_{eff}=4194$ \AA) are determined. 323 stars with membership
probabilities higher than 30% are considered as candidate members of M48.
Comparing membership probabilities of 229 common stars obtained by the present
method and the proper-motion based methods, a 80% agreement among these methods
is obtained.


title: Reaction Rate Uncertainties: NeNa and MgAl in AGB Stars

abstract:
  We study the effect of uncertainties in the proton-capture reaction rates of
the NeNa and MgAl chains on nucleosynthesis due to the operation of hot bottom
burning (HBB) in intermediate-mass asymptotic giant branch (AGB) stars. HBB
nucleosynthesis is associated with the production of sodium, radioactive Al26
and the heavy magnesium isotopes, and it is possibly responsible for the O, Na,
Mg and Al abundance anomalies observed in globular cluster stars.
  We model HBB with an analytic code based on full stellar evolution models so
we can quickly cover a large parameter space. The reaction rates are varied
first individually, then all together. This creates a knock-on effect, where an
increase of one reaction rate affects production of an isotope further down the
reaction chain. We find the yields of Ne22, Na23 and Al26 to be the most
susceptible to current nuclear reaction rate uncertainties.


title:
A Sensitive Search for Variability in Late L Dwarfs: The Quest for
  Weather

abstract:
  We have conducted a photometric monitoring program of 3 field late-L brown
dwarfs looking for evidence of non-axisymmetric structure or temporal
variability in their photospheres. The observations were performed using
Spitzer/IRAC 4.5 and 8 micron bandpasses and were designed to cover at least
one rotational period of each object. One-sigma RMS (root mean squared)
uncertainties of less than 3 mmag at 4.5 micron and around 9 mmag at 8 micron
were achieved. Two out of the three objects studied exhibit some modulation in
their light curves at 4.5 micron - but not 8 micron - with periods of 7.4 hr
and 4.6 hr and peak-to-peak amplitudes of 10 mmag and 8 mmag. Although the lack
of detectable 8 micron variation suggests an instrumental origin for the
detected variations, the data may nevertheless still be consistent with
intrinsic variability since the shorter wavelength IRAC bandpasses probe more
deeply into late L dwarf atmospheres than the longer wavelengths. A cloud
feature occupying a small percentage (1-2 %) of the visible hemisphere could
account for the observed amplitude of variation. If, instead, the variability
is indeed instrumental in origin, then our non-variable L dwarfs could be
either completely covered with clouds or objects whose clouds are smaller and
uniformly distributed. Such scenarios would lead to very small photometric
variations. Followup IRAC photometry at 3.6 and 5.8 micron bandpasses should
distinguish between the two cases. In any event, the present observations
provide the most sensitive search to date for structure in the photospheres of
late-L dwarfs at mid-IR wavelengths, and our photometry provides stringent
upper limits to the extent to which the photospheres of these transition L
dwarfs are structured.


title: Wide Field CCD photometry around nine open clusters

abstract:
  In this paper we study the evolution of core and corona of nine open clusters
using the projected radial density profiles derived from homogeneous CCD
photometric data obtained through the 105-cm Kiso Schmidt telescope. The age
and galactocentric distance of the target clusters varies from 16 Myr to 2000
Myr and 9 kpcto 10.8 kpc respectively. Barring Be 62, which is young open
cluster, other clusters show a uniform reddening across the cluster region. The
reddening in Be 62varies from $E(B-V)_{min}$= 0.70 mag to $E(B-V)_{max}$= 1.00
mag. The corona of six of the clusters in the present sample is found to be
elongated, however on the basis of the present sample it is not possible to
establish any correlation between the age and shape of the core. The elongated
core in the case of young cluster Be 62 may reflect the initial conditions in
the parental molecular cloud. The other results of the present study are (i)
Core radius `$r_c$' and corona size $`r_{cn}$'/cluster radius $`r_{cl}$' are
linearly correlated. (ii) The $r_c/r_{cn}/r_{cl}$ are linearly correlated with
the number of stars in that region. (iii) In the age range 10-1000 Myr, the
core and corona shrink with age. (iv) We find that in the galactocentric
distance range 9 - 10 kpc, the core and corona/cluster extent of the clusters
increase with the galactocentric distance.


title: Clusters and the Cosmic Web

abstract:
  We discuss the intimate relationship between the filamentary features and the
rare dense compact cluster nodes in this network, via the large scale tidal
field going along with them, following the cosmic web theory developed Bond et
al. The Megaparsec scale tidal shear pattern is responsible for the contraction
of matter into filaments, and its link with the cluster locations can be
understood through the implied quadrupolar mass distribution in which the
clusters are to be found at the sites of the overdense patches. We present a
new technique for tracing the cosmic web, identifying planar walls, elongated
filaments and cluster nodes in the galaxy distribution. This will allow the
practical exploitation of the concept of the cosmic web towards identifying and
tracing the locations of the gaseous WHIM. These methods, the Delaunay
Tessellation Field Estimator (DTFE) and the Morphology Multiscale Filter (MMF)
find their basis in computational geometry and visualization.


title:
Observations of Thick Disks in the Hubble Space Telescope Ultra Deep
  Field

abstract:
  The vertical profiles of chain and spiral galaxies in the Hubble Space
Telescope Ultra Deep Field (UDF) are fit to sech^2(z/z_0) functions convolved
with stellar profiles in order to measure the disk scale heights z_0 in four
passbands. The bulge regions of the spirals are avoided. Photometric redshifts
give absolute scales. The rms heights of the giant clumps in these galaxies are
also measured. The results indicate that UDF disks are thick with an average
z_0 of 1.0\pm0.4 kpc. The ratio of radial exponential scale length to z_0 is
\~3\pm1.5. The scale heights are only 20% larger than the radii of the giant
star-forming clumps and a factor of ~10 larger than the rms clump deviations
around the midplanes. This suggests the clumps formed from midplane gas and
dissolved to make the thick disks. Redshifted stellar population models suggest
ages of ~1 Gy and mass column densities from 4 to 40 Msun pc^{-2}. The UDF
disks look like young versions of modern thick disks. This resemblance is
difficult to understand if galaxies grow over time or if subsequent accretion
of thin disks gravitationally shrinks the observed thick disks. More likely,
high redshift disks are thick because their mass column densities are low; a
velocity dispersion of only 14 km/s reproduces the observed thickness. Modern
thick disks require more heating at high redshift. This is possible if the gas
that eventually makes the thin disk is in place before the youngest age of a
modern thick disk, and if the existing stars are heated during the delivery of
this gas.


title: Infrared Observations of The Helix Planetary Nebula

abstract:
  We have mapped the Helix (NGC 7293) planetary nebula (PN) with the IRAC
instrument on the Spitzer Space Telescope. The Helix is one of the closest
bright PN, and therefore provides an opportunity to resolve the small-scale
structure in the nebula. The emission from this PN in the 5.8 and 8 micron IRAC
bands is dominated by the pure rotational lines of molecular hydrogen, with a
smaller contribution from forbidden line emission such as [Ar III] in the
ionized region. The IRAC images resolve the "cometary knots" which have been
previously studied in this PN. The "tails" of the knots and the radial rays
extending into the outer regions of the PN are seen in emission in the IRAC
bands. IRS spectra on the main ring and the emission in the IRAC bands are
consistent with shock-excited H2 models, with a small (~10%) component from
photodissociation regions. In the Northeast Arc, the H2 emission is located in
a shell outside of the H alpha emission.


title: How Well Can Weak Lensing Measure the Mass of Galaxy Clusters?

abstract:
  The technique of weak-lensing aperture mass densitometry, so called the
zeta-statistic, has recently been popular in actual observations for
measurement of individual cluster mass. It has however been anticipated that
the line-of-sight projection by foreground and background matter can adversely
affect the cluster mass determination with not only substantial error
dispersion but also a sizable positive systematic bias. Additionally, the
finite number of background galaxies even at a reasonable observing depth can
also introduce Poisson noise to the mass estimate. In this paper, we
quantitatively investigate the degree of errors separately contributed by the
two sources to the mass determination of those galaxy clusters with
M_{200}>10^{14}M_{\odot}. We find that the aperture mass of zeta-statistic
turns out to be a mass estimator of much reduced systematic bias, due to the
cancellation by the positively biased local background mass sheet. However, the
error dispersion of M_{200} arising from both projection effect and Poisson
noise is found to be still sizable (40%-90%), even for the shear-selected,
clean sample where multiple clusters located within a suitable projected
aperture are removed. We also investigate how to remedy this large-error
problem in weak lensing measurements, and propose a plausible alternative mass
estimator, M(<theta_{1000}), an aperture mass measured within about half the
virial radius. The aperture mass M(<theta_{1000}) is free of bias and has a
substantially reduced error dispersion, 39% for the worst case of high-z,
low-mass clusters, that can be smaller than the error dispersion of M_{200} as
much as a factor 3.


title: Ultra-high energy cosmic rays: from GeV to ZeV

abstract:
  Cosmic ray (CR) particles arrive at the top of the Earth's atmosphere at a
rate of around 1000 per square meter per second. They are mostly ionized nuclei
- about 90% protons, 9% alpha particles traces of heavier nuclei and
approximately 1% electrons. CRs are characterized by their high energies: most
cosmic rays are relativistic, having kinetic energies comparable to or somewhat
greater than their rest masses. A very few of them have ultra-relativistic
energies extending beyond 100 EeV (tens of joules). In this series of lectures,
delivered at the 2005 Mexican School of Astrophysics, an overview of the main
experimental characteristics of the CR flux and their astrophysical
significance is given. Particular emphasis is given to the upper end of the CR
energy spectrum. Unfortunately, due to space limitations, only a fraction of
the original content of the lectures is included in the present manuscript. In
particular, the production mechanisms are not included and the fundamental
topic of anisotropies is only dealt with in a very superficial way.


title:
Collimated Jet or Expanding Outflow: Possible Origins of GRBs and X-Ray
  Flashes

abstract:
  We investigate the dynamics of an injected outflow propagating in a
progenitor in the context of the collapsar model for gamma-ray bursts (GRBs)
through two dimensional axisymmetric relativistic hydrodynamic simulations.
Initially, we locally inject an outflow near the center of a progenitor. We
calculate 25 models, in total, by fixing its total input energy to be 10^{51}
ergs s^{-1} and radius of the injected outflow to be $7\times 10^7$ cm while
varying its bulk Lorentz factor, $\Gamma_{0} = 1.05\sim 5$, and its specific
internal energy, $\epsilon_0/c^2 = 0.1\sim 30$. The injected outflow propagates
in the progenitor and drives a large-scale outflow or jet. We find a smooth but
dramatic transition from a collimated jet to an expanding outflow among
calculated models. The maximum Lorentz factor is, on the other hand, sensitive
to both of $\Gamma_0$ and $\epsilon_0$; roughly $\Gamma_{\rm max} \sim \Gamma_0
(1+\epsilon_0/c^2)$. Our finding will explain a smooth transition between the
GRBs, X-ray rich GRBs (XRRs) and X-ray Flashes (XRFs) by the same model but
with different $\epsilon_0$ values.


title: Effect of Rossby and Alfv\'{e}n waves on the dynamics of the tachocline

abstract:
  To understand magnetic diffusion, momentum transport, and mixing in the
interior of the sun, we consider an idealized model of the tachocline, namely
magnetohydrodynamics (MHD) turbulence on a $\beta$ plane subject to a large
scale shear (provided by the latitudinal differential rotation). This model
enables us to self-consistently derive the influence of shear, Rossby and
Alfv\'{e}n waves on the transport properties of turbulence. In the strong
magnetic field regime, we find that the turbulent viscosity and diffusivity are
reduced by magnetic fields only, similarly to the two-dimensional MHD case
(without Rossby waves). In the weak magnetic field regime, we find a crossover
scale ($L\_R$) from a Alfv\'{e}n dominated regime (on small scales) to a Rossby
dominated regime (on large scales). For parameter values typical of the
tachocline, $L\_R$ is larger that the solar radius so that Rossby waves are
unlikely to play an important role in the transport of magnetic field and
angular momentum. This is mainly due to the enhancement of magnetic
back-reaction by shearing which efficiently generates small scales, thus strong
currents.


title:
Self-consistent theory of turbulent transport in the solar tachocline.
  III. Gravity waves

abstract:
  To understand the fundamental physical processes important for the evolution
of solar rotation and distribution of chemical species, we provide theoretical
predictions for particle mixing and momentum transport in the stably stratified
tachocline. By envisioning that turbulence is driven externally in the
tachocline (e.g. by plume penetration), we compute the amplitude of turbulent
flow, turbulent particle diffusivities, and eddy viscosity, by incorporating
the effect of a strong radial differential rotation and stable stratification.
We identify the different roles that the shear flow and stable stratification
play in turbulence regulation and transport. Particle transport is found to be
severely quenched due to stable stratification as well as radial differential
rotation, especially in the radial direction with an effectively more efficient
horizontal transport. The eddy viscosity is shown to become negative for
parameter values typical of the tachocline, suggesting that turbulence in the
stably stratified tachocline leads to a non-uniform radial differential
rotation. Similar results also hold in the radiative interiors of stars, in
general.


title:
Arcfinder: An algorithm for the automatic detection of gravitational
  arcs

abstract:
  We present an efficient algorithm designed for and capable of detecting
elongated, thin features such as lines and curves in astronomical images, and
its application to the automatic detection of gravitational arcs. The algorithm
is sufficiently robust to detect such features even if their surface brightness
is near the pixel noise in the image, yet the amount of spurious detections is
low. The algorithm subdivides the image into a grid of overlapping cells which
are iteratively shifted towards a local centre of brightness in their immediate
neighbourhood. It then computes the ellipticity for each cell, and combines
cells with correlated ellipticities into objects. These are combined to graphs
in a next step, which are then further processed to determine properties of the
detected objects. We demonstrate the operation and the efficiency of the
algorithm applying it to HST images of galaxy clusters known to contain
gravitational arcs. The algorithm completes the analysis of an image with
3000x3000 pixels in about 4 seconds on an ordinary desktop PC. We discuss
further applications, the method's remaining problems and possible approaches
to their solution.


title:
Energy dependent gamma-ray morphology in the Pulsar wind nebula
  HESSJ1825-137

abstract:
  Detailed morphological and spatially resolved spectral studies reveal the
very high-energy (VHE) gamma-ray aspects of this object with unprecedented
precision. We confirm previous results obtained in a survey of the Galactic
Plane in 2004. The gamma-ray emission extends asymmetrically to the south and
south-west of the energetic pulsar PSR J1826-1334, that is thought to power the
pulsar wind nebula. The differential gamma-ray spectrum of the whole emission
region is measured over more than two orders of magnitude, from 270 GeV to 35
TeV, and shows indications for a deviation from a pure power law. Spectra have
also been determined for spatially separated regions of HESS J1825-137. The
photon indices from a power-law fit in the different regions show a softening
of the spectrum with increasing distance from the pulsar and therefore an
energy dependent morphology. This is the first time that an energy dependent
morphology has been detected in the VHE gamma-ray regime. The VHE gamma-ray
emission of HESS J1825-137 is phenomenologically discussed in the scenario
where the gamma-rays are produced by VHE electrons via Inverse Compton
scattering. The high gamma-ray luminosity of the source cannot be explained on
the basis of constant spin-down power of the pulsar and requires higher
injection power in past.


title:
The Distances to Open Clusters from Main-Sequence Fitting. III. Improved
  Accuracy with Empirically Calibrated Isochrones

abstract:
  We continue our series of papers on open cluster distances with a critical
assessment of the accuracy of main-sequence fitting using isochrones that
employ empirical corrections to the color-temperature relations. We use four
nearby open clusters with multicolor photometry and accurate metallicities and
present a new metallicity for Praesepe ([Fe/H] = +0.11 +/- 0.03) from
high-resolution spectra. The internal precision of distance estimates is about
a factor of 5 better than the case without the color calibrations. After taking
into account all major systematic errors, we obtain distances accurate to about
2%-3% when there exists a good metallicity estimate. Metallicities accurate to
better than 0.1 dex may be obtained from BVIcKs photometry alone. We also
derive a helium abundance for the Pleiades of Y = 0.279 +/- 0.015, which is
equal within the errors to the Sun's initial helium abundance and that of the
Hyades. Our best estimates of distances are (m - M)_0 = 6.33 +/- 0.04, 8.03 +/-
0.04, and 9.61 +/- 0.03 to Praesepe, NGC 2516, and M67, respectively. Our
Pleiades distance at the spectroscopic metallicity, (m - M)_0 = 5.66 +/- 0.01
(internal) +/- 0.05 (systematic), is in excellent agreement with several
geometric distance measurements. We have made calibrated isochrones for -0.3 <=
[Fe/H] <= +0.2 available at http://www.astronomy.ohio-state.edu/iso/ .


title:
The K-band Spectrum of The Hot Star in IRS~8: An Outsider in the
  Galactic Center?

abstract:
  Using adaptive optics at the Gemini North telescope we have obtained a K-band
spectrum of the star near the center of the luminous Galactic center bowshock
IRS8, as well as a spectrum of the bowshock itself. The stellar spectrum
contains emission and absorption lines characteristic of an O5-O6 giant or
supergiant. The wind from such a star is fully capable of producing the
observed bowshock. However, both the early spectral type and the apparently
young age of the star, if it is single, mark it as unique among hot stars
within one parsec of the center.


title:
A Multi-wavelength study of 1WGA J1346.5-6255: a new $\gamma$ Cas analog
  unrelated to the background supernova remnant G309.2-00.6

abstract:
  1WGA J1346.5-6255 is a ROSAT X-ray source found within the radio lobes of the
supernova remnant (SNR) G309.2-00.6. This source also appears to coincide with
the bright and early-type star HD 119682, which is in the middle of the
galactic open cluster NGC 5281. The radio morphology of the remnant, consisting
of two brightened and distorted arcs of emission on opposite sides of the 1WGA
J1346.5-6255 source and of a jet-like feature and break in the shell, led to
the suggestion that 1WGA J1346.5-6255/G309.2-00.6 is a young analog of the
microquasar SS 433 powering the W50 nebula. This motivated us to study this
source at X-ray and optical wavelengths. We here present new Chandra
observations of 1WGA J1346.5-6255, archival XMM-Newton observations of
G309.2-00.6, and optical spectroscopic observations of HD 119682, in order to
search for X-ray jets from 1WGA J1346.5-6255, study its association with the
SNR, and test for whether HD 119682 represents its optical counterpart. We do
not find evidence for jets from 1WGA J1346.5-6255 down to an unabsorbed flux of
2.6E-13 ergs/cm2/s (0.5-7.5 keV), we rule out its association with G309.2-00.6,
and we confirm that HD 119682 is its optical counterpart. We derive a distance
of 1.2+/-0.3 kpc, which is consistent with the distance estimate to NGC 5281
(1.3+/-0.3 kpc), and much smaller than the distance derived to the SNR
G309.2-00.6. We discuss the nature of the source, unveil that HD 119682 is a Be
star and suggest it is a new member of the recently proposed group of
$\gamma$-Cas analogs. The Chandra and XMM X-ray lightcurves show variability on
timescales of hundreds of seconds, and the presence of a possible period of
about 1500 s that could be the rotational period of an accreting neutron star
or white dwarf in this $\gamma$-Cas analog.


title:
Weak Lensing by Galaxies in Groups and Clusters: I.--Theoretical
  Expectations

abstract:
  Galaxy-galaxy lensing is rapidly becoming one of the most promising means to
accurately measure the average relation between galaxy properties and halo
mass. In order to obtain a signal of sufficient signal-to-noise, one needs to
stack many lens galaxies according to their property of interest, such as
luminosity or stellar mass. Since such a stack consists of both central and
satellite galaxies, which contribute very different lensing signals, the
resulting shear measurements can be difficult to interpret. In the past,
galaxy-galaxy lensing studies have either completely ignored this problem, have
applied rough isolation criteria in an attempt to preferentially select
`central' galaxies, or have tried to model the contribution of satellites
explicitely. However, if one is able to {\it a priori} split the galaxy
population in central and satellite galaxies, one can measure their lensing
signals separately. This not only allows a much cleaner measurement of the
relation between halo mass and their galaxy populations, but also allows a
direct measurement of the sub-halo masses around satellite galaxies. In this
paper, we use a realistic mock galaxy redshift survey to show that galaxy
groups, properly selected from large galaxy surveys, can be used to accurately
split the galaxy population in centrals and satellites. Stacking the resulting
centrals according to their group mass, estimated from the total group
luminosity, allows a remarkably accurate recovery of the masses and density
profiles of their host haloes. In addition, stacking the corresponding
satellite galaxies according to their projected distance from the group center
yields a lensing signal that can be used to accurate measure the masses of both
sub-haloes and host haloes. (Abridged)


title: Pair emission from bare magnetized strange stars

abstract:
  The dominant emission from bare strange stars is thought to be
electron-positron pairs, produced through spontaneous pair creation (SPC) in a
surface layer of electrons tied to the star by a superstrong electric field.
The positrons escape freely, but the electrons are directed towards the star
and quickly fill all available states, such that their degeneracy suppresses
further SPC. An electron must be reflected and gain energy in order to escape,
along with the positron. Each escaping electron leaves a hole that is
immediately filled by another electron through SPC. We discuss the collisional
processes that produce escaping electrons. When the Landau quantization of the
motion perpendicular to the magnetic field is taken into account,
electron-electron collisions can lead to an escaping electron only through a
multi-stage process involving higher Landau levels. Although the available
estimates of the collision rate are deficient in several ways, it appears that
the rate is too low for electron-electron collisions to be effective. A simple
kinetic model for electron-quark collisions leads to an estimate of the rate of
pair production that is analogous to thermionic emission, but the work function
is poorly determined.


title:
Existence of black holes in Friedmann-Robertson-Walker universe
  dominated by dark energy

abstract:
  We study the existence of black holes in a homogeneous and isotropic
expanding Friedmann-Robertson-Walker (FRW) universe dominated by dark energy.
We show that black holes can exist in such a universe by considering some
specific McVittie solutions. Although these solutions violate all three energy
conditions, the FRW background does satisfy the weak energy condition.

categories: astro-ph gr-qc hep-ph hep-th math-ph math.MP


title: The influence of baryons on the mass distribution of dark matter halos

abstract:
  Using a set of high-resolution N-body/SPH cosmological simulations with
identical initial conditions but run with different numerical setups, we
investigate the influence of baryonic matter on the mass distribution of dark
halos when radiative cooling is NOT included. We compare the concentration
parameters of about 400 massive halos with virial mass from $10^{13}$ \Msun to
$7.1 \times 10^{14}$ \Msun. We find that the concentration parameters for the
total mass and dark matter distributions in non radiative simulations are on
average larger by ~3% and 10% than those in a pure dark matter simulation. Our
results indicate that the total mass density profile is little affected by a
hot gas component in the simulations. After carefully excluding the effects of
resolutions and spurious two-body heating between dark matter and gas
particles, we conclude that the increase of the dark matter concentration
parameters is due to interactions between baryons and dark matter. We
demonstrate this with the aid of idealized simulations of two-body mergers. The
results of individual halos simulated with different mass resolutions show that
the gas profiles of densities, temperature and entropy are subjects of mass
resolution of SPH particles. In particular, we find that in the inner parts of
halos, as the SPH resolution increases the gas density becomes higher but both
the entropy and temperature decrease.


title: Slow rolling, inflation and quintessence

abstract:
  We comment on the choice of the quintessence potential, examining the
slow-roll approximation in a minimally coupled theory of gravity. We make some
considerations on the potential behaviors, the related \gamma parameter, and
their relationships to phantom cosmology.


title:
Inverse Compton Scenarios for the TeV Gamma-Ray Emission of the Galactic
  Centre

abstract:
  The intense Compton cooling of ultra-relativistic electrons in the
Klein-Nishina regime in radiation dominated environments, such as that found in
the Galactic Centre, may result in radically different electron spectra than
those produced by Synchrotron cooling. We explore these effects and their
impact on the X-ray and gamma-ray spectra produced in electron accelerators in
this region in comparison to elsewhere in our galaxy. We discuss the broad-band
emission expected from the newly discovered pulsar wind nebula G 359.95-0.04
and the possible relationship of this X-ray source to the central TeV gamma-ray
source HESS J1745-290. Finally we discuss the possible relationship of the
Galactic Centre INTEGRAL source IGR J1745.6-2901 to the TeV emission.


title: The evolution of massive stars in the context of V838 Monocerotis

abstract:
  The aim of this paper is to look at the evolution of massive stars in order
to determine whether or not the progenitor of V838 Mon may be a massive star.
In the first part of this paper, the evolution of massive stars around solar
metallicity is described, especially the evolution in the Hertzsprung-Russell
(HR) diagram. Then, using the observational constraints, the probable
progenitors (and their evolution) are described. Using models of single stars,
no progenitor can be found amongst massive stars that can satisfy all the
observational constraints. Wolf-Rayet stars (stars with initial masses above
about 30 solar masses, which have lost their hydrogen rich envelopes) could
explain 10 to 100 solar masses of circumstellar material but they are very
luminous (L > 100,000 solar luminosities). Main sequence stars crossing the HR
diagram and becoming red supergiants (RSG) can have very low effective
temperatures but take thousands of years to cross over. Be stars (fast rotating
stars with a mass around 10 solar masses), which form disk or B stars accreting
matter from a binary companion of a similar mass would need to be compared in
detail with the observational constraints. In the future, there will hopefully
be further observational constraints on the models coming from the mass and
nature (interstellar or circumstellar) of the material producing the light echo
and from a frequency estimate of spectacular objects such as V838 Mon.


title:
A deep wide survey of faint low surface brightness galaxies in the
  direction of the Coma cluster of galaxies

abstract:
  We report on a search for faint (R total magnitude fainter than 21) and low
surface brightness galaxies (R central surface brightness fainter than ~24)
(fLSBs) in a 0.72x0.82 deg2 area centered on the Coma cluster. We analyzed deep
B and R band CCD imaging obtained using the CFH12K camera at CFHT and found 735
fLSBs. The total B magnitudes, at the Coma cluster redshift, range from -13 to
-9 with B central surface brightness as faint as 27 mag/arcsec2. Using empty
field comparisons, we show that most of these fLSBs are probably inside the
Coma cluster. We present the results of comparing the projected fLSB
distributions with the distributions of normal galaxies and with known X-ray
over densities. We also investigate their projected distribution relative to
their location in the color magnitude relation. Colors of fLSBs vary between
B-R~0.8 and ~1.4 for 2/3 of the sample and this part is consistent with the
known CMR red-sequence for bright (R<18) ellipticals in Coma. These fLSBs are
likely to have followed the same evolution as giant ellipticals, which is
consistent with a simple feedback/collapse formation and a passive evolution.
These fLSBs are mainly clustered around NGC4889. We found two other distinct
fLSB populations. These populations have respectively redder and bluer colors
compared to the giant elliptical red-sequence and possibly formed from stripped
faint ellipticals and material stripped from spiral in-falling galaxies.


title:
Formation of methyl formate and other organic species in the warm-up
  phase of hot molecular cores

abstract:
  Aims: The production of saturated organic molecules in hot cores and corinos
is not well understood. The standard approach is to assume that, as
temperatures heat up during star formation, methanol and other species
evaporate from grain surfaces and undergo a warm gas-phase chemistry at 100 K
or greater to produce species such as methyl formate, dimethyl ether, and
others. But a series of laboratory results shows that protonated ions, typical
precursors to final products in ion-molecule schemes, tend to fragment upon
dissociative recombination with electrons rather than just ejecting a hydrogen
atom. Moreover, the specific proposed reaction to produce protonated methyl
formate is now known not to occur at all. Methods: We utilize a gas-grain
chemical network to probe the chemistry of the relatively ignored stage of hot
core evolution during which the protostar switches on and the temperature of
the surrounding gas and dust rises from 10 K to over 100 K. During this stage,
surface chemistry involving heavy radicals becomes more important as surface
hydrogen atoms tend to evaporate rather than react. Results: Our results show
that complex species such as methyl formate, formic acid, and dimethyl ether
can be produced in large abundance during the protostellar switch-on phase, but
that both grain-surface and gas-phase processes help to produce most species.
The longer the timescale for protostellar switch-on, the more important the
surface processes.


title: Metal-rich Damped/sub-Damped Lyman-alpha Quasar Absorbers at z<1

abstract:
  Damped Lyman-alpha absorbers (DLAs), seen in absorption against a background
quasar, provide the most detailed probes available of element abundances in the
Universe over > 90 % of its age. DLAs can be used to observationally measure
the global mean metallicity in the Universe and its evolution with time.
Paradoxically, these observations are more difficult at lower redshifts, where
the absorber rest-frame UV spectra are cut-off due to the atmospheric
absorption. We present here high-resolution VLT/UVES observations of several
elements contained in three DLAs and one sub-DLA with 0.6<z_abs<0.9. We detect
Mg I, Mg II, Fe II, Zn II, Cr II, Mn II, Ti II and Ca II. Our observations more
than double the high-resolution sample of [Zn/H] at z<1. We also report the
discovery of three metal-rich systems, whereas most previous measurements show
low N(HI)-weighted mean metallicity projecting to about 1/6th solar level at
z=0. We derive [Zn/H]=-0.11+/-0.04 at z_abs=0.725, [Zn/H]=-0.54+/-0.20 at
z_abs=0.740 and [Zn/H]=-0.49+/-0.22 at z_abs=0.652, plus one additional upper
limit ([Zn/H]<-0.36 at z_abs=0.842). These measurements confirm the existence
of quasar absorbers with relatively high metallicities based on abundance
estimates free from the effect of dust depletion. Possible implications of
these results for the metallicity of neutral gas phase in the past ~ 8 Gyr are
presented and compared with models.


title:
Spitzer observations of the Orion OB1 association: second generation
  dust disks at 5-10 Myr

abstract:
  We report new Spitzer observations of intermediate mass stars in two regions
of the Orion OB1 association located in the subassociations OB1a ($\sim$10 Myr)
and OB1b ($\sim$5 Myr). In a representative sample of stars earlier than F5 of
both stellar groups, we find a population of stars surrounded of debris disks,
without excess in the IRAC bands and without emission lines in their optical
spectra, but with a varying degree of 24{\micron} excess. Comparing our samples
with 24{\micron} observations of intermediate mass stars in other stellar
groups, spanning a range of ages from 2.5 Myr to 150 Myr, we find that debris
disks are more frequent and have larger 24{\micron} excess at 10 Myr (OB1a).
This trend agrees with predictions of models of evolution of solids in the
outer regions of disks ($>$30 AU), where large icy objects ($\sim$1000 Km)
begin to form at $\sim$10 Myr; the presence of these objects in the disk
initiates a collisional cascade, producing enough dust particles to explain the
relatively large 24 {\micron} excess observed in OB1a. The dust luminosity
observed in the stellar groups older than 10 Myr declines roughly as predicted
by collisional cascade models. Combining Spitzer observations, optical spectra
and 2MASS data, we found a new Herbig Ae/Be star (HD290543) and a star
(HD36444) with a large 24 {\micron} excess, both in OB1b. This last object
could be explained as a intermediate stage between HAeBe and true debris
systems or as a massive debris disk produced by a collision between two large
objects ($>$1000 Km).


title: Gamma-rays from halos around stars and the Sun

abstract:
  Inverse Compton scattering by relativistic electrons produces a major
component of the diffuse emission from the Galaxy. The photon fields involved
are the cosmic microwave background and the interstellar radiation field from
stars and dust. Calculations of the inverse Compton distribution have usually
assumed a smooth ISRF, but in fact a large part of the Galactic luminosity
comes from the most luminous stars which are rare. Therefore we expect the
ISRF, and hence the inverse Compton emission, to be clumpy at some level which
could be detectable by instruments such as GLAST. Even individual nearby
luminous stars could be detectable assuming just the normal cosmic-ray electron
spectrum. We present the basic formalism required and give possible candidate
stars to be detected, and make predictions for GLAST. Then we apply the
formalism to OB associations and the Sun, showing that the IC emission produced
is not negligible compared to the sensitivity of current or coming detectors.
We estimate that the gamma-ray flux from the halo around the Sun contributes to
the diffuse background emission at about the few percent level.


title: Neutrino Scattering in Heterogeneous Supernova Plasmas

abstract:
  Neutrinos in core collapse supernovae are likely trapped by neutrino-nucleus
elastic scattering. Using molecular dynamics simulations, we calculate neutrino
mean free paths and ion-ion correlation functions for heterogeneous plasmas.
Mean free paths are systematically shorter in plasmas containing a mixture of
ions compared to a plasma composed of a single ion species. This is because
neutrinos can scatter from concentration fluctuations. The dynamical response
function of a heterogeneous plasma is found to have an extra peak at low
energies describing the diffusion of concentration fluctuations. Our exact
molecular dynamics results for the static structure factor reduce to the Debye
Huckel approximation, but only in the limit of very low momentum transfers.


title: Afterglow calculation in the electromagnetic model for gamma-ray bursts

abstract:
  We compute the afterglow of gamma-ray bursts produced by purely
electromagnetic outflows to see if it shows characteristic signatures differing
from those obtained with the standard internal/external shock model. Using a
simple approach for the injection of electromagnetic energy to the forward
shock we obtain the afterglow evolution both during the period of activity of
the central source and after. Our method equally applies to a variable source.
Afterglow light curves in the visible and X-ray bands are computed both for a
uniform medium and a stellar wind environment. They are brighter at early times
than afterglows obtained with the internal/external shock model but relying
only on these differences to discriminate between models is not sufficient.


title:
SDSS J2125-0813: the evidence for the origination of optical FeII
  emission lines from accretion disk near central black hole

abstract:
  We report on the radio quiet quasar SDSS J2125-0813 which obviously emits
optical FeII emission lines and double-peaked broad Balmer emission lines.
Using the accretion disk model for double-peaked broad low-ionization emission
lines, we reproduce the composite line spectra at the optical band between
4100$\AA$ and 5600$\AA$. Broad FeII emission lines can be fit simultaneously
with the broad H$\beta$ and MgI lines, such that all broad lines have an
elliptical disk profile with the same disk parameters. This results indicates
that the optical FeII emission lines originate from the accretion disk near the
central black hole which produces the double-peaked broad Balmer emission
lines. Furthermore, we find that the object has dimensionless accretion rate
$\dot{m}\sim0.4-0.6$ which is much larger than accretion rate for ADAF mode,
and that the energy budget of the accretion disk is enough to power the
double-peaked broad Balmer emission lines.


title:
An empirical temperature calibration for the Delta a photometric system.
  II. The A-type and mid F-type star

abstract:
  With the Delta a photometric system, it is possible to study very distant
galactic and even extragalactic clusters with a high level of accuracy. This
can be done with a classical color-magnitude diagram and appropriate
isochrones. The new calibration presented in this paper is a powerful
extension. For open clusters, the reddening is straightforward for an
estimation via Isochrone fitting and is needed in order to calculate the
reddening-free, temperature sensitive, index (g1-y)0. As a last step, the
calibration can be applied to individual stars. Because no a-priori
reddening-free photometric parameters are available for the investigated
spectral range, we have applied the dereddening calibrations of the Stromgren
uvbybeta system and compared them with extinction models for the Milky Way. As
expected from the sample of bright stars, the extinction is negligible for
almost all objects. As a next step, already established calibrations within the
Stromgren uvbybeta, Geneva 7-color, and Johnson UBV systems were applied to a
sample of 282 normal stars to derive a polynomial fit of the third degree for
the averaged effective temperatures to the individual (g1-y)0 values with a
mean of the error for the whole sample of Delta T(eff) is 134K, which is lower
than the value in Paper I for hotter stars. No statistically significant effect
of the rotational velocity on the precision of the calibration was found.


title: A closure model with plumes I. The solar convection

abstract:
  Oscillations of stellar p modes, excited by turbulent convection, are
investigated. We take into account the asymmetry of the up and downflows
created by turbulent plumes through an adapted closure model. In a companion
paper, we apply it to the formalism of excitation of solar p modes developed by
Samadi & Goupil 2001. Using results from 3D numerical simulations of the upper
most part of the solar convection zone, we show that the two-scale-mass-flux
model (TFM) is valid only for quasi-laminar or highly skewed flows (Gryanik &
Hartmann 2002). We build a generalized-Two-scale-Mass-Flux Model (GTFM) model
which takes into account both the skew introduced by the presence of two flows
and the effects of turbulence in each flow. In order to apply the GTFM to the
solar case, we introduce the plume dynamics as modelled by Rieutord & Zahn
(1995) and construct a Closure Model with Plumes (CMP). When comparing with 3D
simulation results, the CMP improves the agreement for the fourth order
moments, by approximatively a factor of two compared with the use of the
quasi-normal approximation or a skewness computed with the classical TFM. The
asymmetry of turbulent convection in the solar case has an important impact on
the vertical-velocity fourth-order moment which has to be accounted for by
models. The CMP is a significant improvement and is expected to improve the
modelling of solar p-mode excitation.


title:
Discovery of Very High Energy Gamma-Ray Emission from the BL Lac Object
  H2356-309 with the H.E.S.S. Cherenkov Telescopes

abstract:
  The extreme synchrotron BL Lac object H2356-309, located at a redshift of z =
0.165, was observed from June to December 2004 with a total exposure of approx.
40 h live-time with the H.E.S.S. (High Energy Stereoscopic System) array of
atmospheric-Cherenkov telescopes (ACTs). Analysis of this data set yields, for
the first time, a strong excess of 453 gamma-rays (10 standard deviations above
background) from H2356-309, corresponding to an observed integral flux above
200 GeV of I(>200GeV) = (4.1+-0.5) 10^12 cm^-2.s^-1 (statistical error only).
The differential energy spectrum of the source between 200 GeV and 1.3 TeV is
well-described by a power law with a normalisation (at 1 TeV) of N_0 = (3.00 +-
0.80_stat +- 0.31_sys) 10^-13 cm^-2.s^-1.TeV^-1 and a photon index of Gamma =
3.09 +- 0.24_stat +- 0.10_sys. H2356-309 is one of the most distant BL Lac
objects detected at very-high-energy gamma-rays so far. Results from
simultaneous observations from ROTSE-III (optical), RXTE (X-rays) and NRT
(radio) are also included and used together with the H.E.S.S. data to constrain
a single-zone homogeneous synchrotron self-Compton (SSC) model. This model
provides an adequate fit to the H.E.S.S. data when using a reasonable set of
model parameters.


title:
A closure model with plumes II. Application to the stochastic excitation
  of stellar p modes

abstract:
  Our goal is to improve the theoretical modelling of stochastic excitation of
p modes by turbulent convection. With the help of the closure model with plume
(CMP) developed in a companion paper, we refine the theoretical description of
the excitation by the turbulent Reynolds stress term. The CMP is generalized
for two-point correlation products so as to apply it to the formalism developed
by Samadi & Goupil (2001). The excitation source terms are then computed with
this improvement, and a comparison with solar data from the GOLF instrument is
performed. The present model provides a significant improvement when comparing
absolute values of theoretical ampplitudes with observational data. It gives
rise to a frequency dependence of the power supplied to solar p modes, which
agrees with GOLF observations. It is shown that the asymmetry of the turbulent
convection zone (up- and downflows) plays a major role in the excitation
processes. Despite an increase in the Reynolds stress term contribution due to
our improved description, an additional source of excitation, identified as the
entropy source term, is still necessary for reproducing the observational data.
Theoretical excitation rates in the frequency range [2.5 mHz, 4 mHz] now are in
agreement with the observational data from the GOLF instrument. However, at
lower frequencies, it exhibits small discrepancies at the maximum level of a
few per cent. Improvements are likely to come from a better physical
description of the excitation by entropy fluctuations in the superadiabatic
zone.


title:
The Transit Light Curve (TLC) Project. I. Four Consecutive Transits of
  the Exoplanet XO-1b

abstract:
  We present RIz photometry of four consecutive transits of the newly
discovered exoplanet XO-1b. We improve upon the estimates of the transit
parameters, finding the planetary radius to be R_P = 1.184 +0.028/-0.018
R_Jupiter and the stellar radius to be R_S = 0.928 +0.018/-0.013 R_Sun,
assuming a stellar mass of M_S = 1.00 +/- 0.03 M_Sun. The uncertainties in the
planetary and stellar radii are dominated by the uncertainty in the stellar
mass. These uncertainties increase by a factor of 2-3 if a more conservative
uncertainty of 0.10 M_Sun is assumed for the stellar mass. Our estimate of the
planetary radius is smaller than that reported by McCullough et al. (2006) and
yields a mean density that is comparable to that of TrES-1 and HD 189733b. The
timings of the transits have an accuracy ranging from 0.2 to 2.5 minutes, and
are marginally consistent with a uniform period.


title: A high redshift detection of the integrated Sachs-Wolfe effect

abstract:
  We present evidence of a large angle correlation between the cosmic microwave
background measured by WMAP and a catalog of photometrically detected quasars
from the SDSS. The observed cross correlation is (0.30 +- 0.14) microK at zero
lag, with a shape consistent with that expected for correlations arising from
the integrated Sachs-Wolfe effect. The photometric redshifts of the quasars are
centered at z ~ 1.5, making this the deepest survey in which such a correlation
has been observed. Assuming this correlation is due to the ISW effect, this
constitutes the earliest evidence yet for dark energy and it can be used to
constrain exotic dark energy models.


title:
Complex stellar populations in massive clusters: trapping stars of a
  dwarf-disc galaxy in a newborn stellar super-cluster

abstract:
  Some of the most massive globular clusters of our Milky Way, such as for
example omega-Centauri, show a mixture of stellar populations spanning a few
Gyr in age and 1.5 dex in metallicities. In contrast, standard formation
scenarios predict that globular and open clusters form in one single star-burst
event of duration less than about 10 Myr and therefore should exhibit only one
age and one metallicity in its stars. Here, we investigate the possibility that
a massive stellar super-cluster may trap older galactic field stars during its
formation process that are later detectable in the cluster as an apparent
population of stars with a very different age and metallicity. With a set of
numerical N-body simulations, we are able to show that, if the mass of the
stellar super-cluster is high enough and the stellar velocity dispersion in the
cluster is comparable to the dispersion of the surrounding disc stars in the
host galaxy, then up to about 40 per cent of its initial mass can be
additionally gained from trapped disc stars. We also suggest that a
super-cluster may capture in excess of its own mass under certain conditions.


title: Models for Nonthermal Photon Spectra

abstract:
  We describe models of nonthermal photon emission from a homogeneous
distribution of relativistic electrons and protons. Contributions from the
synchrotron, inverse Compton, nonthermal bremsstrahlung and neutral-pion decay
processes are computed separately using a common parameterization of the
underlying distribution of nonthermal particles. The models are intended for
use in fitting spectra from multi-wavelength observations and are designed to
be accurate and efficient. Although our applications have focused on Galactic
supernova remnants, the software is modular, making it straightforward to
customize for different applications. In particular, the shapes of the particle
distribution functions and the shape of the seed photon spectrum used by the
inverse Compton model are defined in separate modules and may be customized for
specific applications. We assess the accuracy of these models by using a
recurrence relation and by comparing them with analytic results and with
previous numerical work by other authors.


title:
Disk-Jet Coupling in Black Hole Accretion Systems I: General
  Relativistic Magnetohydrodynamical Models

abstract:
  General relativistic numerical simulations of magnetized accretion flows
around black holes show a disordered electromagnetic structure in the disk and
corona and a highly relativistic, Poynting-dominated funnel jet in the polar
regions. The polar jet is nearly consistent with the stationary paraboloidal
Blandford-Znajek model of an organized field threading the polar regions of a
rotating black hole. How can a disordered accretion disk and corona lead to an
ordered jet? We show that the polar jet is associated with a strikingly simple
angular-integrated toroidal current distribution $dI_\phi/dr \propto r^{-5/4}$,
where $I_\phi(r)$ is the toroidal current enclosed inside radius $r$. We
demonstrate that the poloidal magnetic field in the simulated jet agrees well
with the force-free field solution for a non-rotating thin disk with an
$r^{-5/4}$ toroidal current, suggesting rotation leads to negligible
self-collimation. We find that the polar field is confined/collimated by the
corona. The electromagnetic field in the disk also scales as $r^{-5/4}$, which
is consistent with some Newtonian accretion models that assume rough
equipartition between magnetic and gas pressure. However, the agreement is
accidental since toward the black hole the magnetic pressure increases faster
than the gas pressure. This field dominance near the black hole is associated
with magnetic stresses that imply a large effective viscosity parameter
$\alpha\sim 1$, whereas the typically assumed value of $\alpha\sim 0.1$ holds
far from the black hole.[abridged]


title:
Disk-Jet Coupling in Black Hole Accretion Systems II: Force-Free
  Electrodynamical Models

abstract:
  In paper I, we showed that time-dependent general relativistic
magnetohydrodynamic (GRMHD) numerical models of accretion disks, although being
highly turbulent, have surprisingly simple electromagnetic properties. In
particular, the toroidal current density in the disk takes the form $dI_\phi/dr
\propto r^{-5/4}$. Guided by this simplicity, we use a time-dependent general
relativistic force-free electrodynamics (GRFFE) code to study an idealized
problem in which the accretion disk is replaced by an infinitely thin rotating
equatorial current sheet. We consider both an $r^{-5/4}$ current profile and an
$r^{-1}$ profile, the latter corresponding to the paraboloidal model of
Blandford & Znajek (1977). The force-free magnetosphere we obtain with the
$r^{-5/4}$ current sheet matches remarkably well to the Poynting-dominated jet
seen in GRMHD numerical models. By comparing to the non-rotating force-free
model studied in paper I, rotation is seen to lead to mild decollimation of the
jet suggesting that hoop-stress forces nearly cancel centrifugal forces. In
order to study the process that generates the corona and disk wind and destroys
the ordered field in the corona in GRMHD numerical models, the force-free field
with the $r^{-5/4}$ current distribution is embedded in an accretion disk and
followed in a GRMHD simulation. Reconnection and magnetic stresses contribute
to a magnetized, thermal wind without the aid of an ordered field threading the
disk.


title: Measuring Statistical Isotropy of CMB Anisotropy

abstract:
  The statistical expectation values of the temperature fluctuations and
polarization of cosmic microwave background (CMB) are assumed to be preserved
under rotations of the sky. We investigate the statistical isotropy (SI) of the
CMB maps recently measured by the Wilkinson Microwave Anisotropy Probe (WMAP)
using the bipolar spherical harmonic formalism proposed in Hajian & Souradeep
2003 for CMB temperature anisotropy and extended to CMB polarization in Basak,
Hajian & Souradeep 2006. The Bipolar Power Spectrum (BiPS) had been measured
for the full sky CMB anisotropy maps of the first year WMAP data and now for
the recently released three years of WMAP data. We also introduce and measure
directional sensitive reduced Bipolar coefficients on the three year WMAP ILC
map. Consistent with our published results from first year WMAP data we have no
evidence for violation of statistical isotropy on large angular scales.
Preliminary analysis of the recently released first WMAP polarization maps,
however, indicate significant violation of SI even when the foreground
contaminated regions are masked out. Further work is required to confirm a
possible cosmic origin and rule out the (more likely) origin in observational
artifact such as foreground residuals at high galactic latitude.


title:
The effects of cosmic rays and solar flares on the IRAC detectors: the
  first two years of in-flight operation

abstract:
  The Infrared Array Camera (IRAC) is a four-channel camera on the Spitzer
Space Telescope, one of three focal plane science instruments. IRAC uses two
pairs of 256x256 pixel InSb and Si:As IBC detectors to provide simultaneous
imaging at 3.6, 4.5, 5.8, and 8 microns. IRAC experiences a flux of cosmic rays
and solar protons that produce transient effects in science images from each of
the arrays, with 4-6 pixels per second being affected during each integration.
During extreme solar flares, IRAC experiences a much higher rate of transients
which affects the science data quality. We present cosmic ray rates and
observed detector characteristics for IRAC during the first two years of
science operation, and rates observed in a period of elevated solar proton flux
during an intense solar flare in January 2005. We show the changes to the IRAC
detectors observed since launch, and assess their impacts to the science data
quality.


title: Rings and Bent Chain Galaxies in the GEMS and GOOD Fields

abstract:
  Twenty-four galaxies with rings or partial rings were studied in the GEMS and
GOODS fields out to z~1.4. Most resemble local collisional ring galaxies in
morphology, size, and clumpy star formation. Clump ages range from 10^8 to 10^9
yr and clump masses go up to several x10^8 Msun, based on color evolution
models. The clump ages are consistent with the expected lifetimes of ring
structures if they are formed by collisions. Fifteen other galaxies that
resemble the arcs in partial ring galaxies but have no evident disk emission
were also studied. Their clumps have bluer colors at all redshifts compared to
the clumps in the ring and partial ring sample, and their clump ages are
younger than in rings and partial rings by a factor of ~10. In most respects,
they resemble chain galaxies except for their curvature; we refer to them as
``bent chains.'' Several rings are symmetric with centered nuclei and no
obvious companions. They could be outer Lindblad resonance rings, although some
have no obvious bars or spirals to drive them. If these symmetric cases are
resonance rings, then they could be the precursors of modern resonance rings,
which are only ~30% larger on average. This similarity in radius suggests that
the driving pattern speed has not slowed by more by ~30% during the last ~7 Gy.
Those without bars could be examples of dissolved bars.


title:
Restframe Optical Spectroscopic Classifications for Submillimeter
  Galaxies

abstract:
  We report the results of a systematic near-infrared spectroscopic survey
using the Subaru, VLT and Keck Telescopes of a sample of high redshift
Ultra-luminous Infrared Galaxies (ULIRGs) mainly composed of
submillimeter-selected galaxies. Our observations span the restframe optical
range containing nebular emission lines such as H_beta, [OIII], and [OII],
which are essential for making robust diagnostics of the physical properties of
these ULIRGs. Using the H_alpha/H_beta emission line ratios, we derive internal
extinction estimates for these galaxies similar to those of local
ULIRGs:A_v~2.9+-0.5. Correcting the H_alpha estimates of the star formation
rate for dust extinction using the Balmer decrement, results in rates which are
consistent with those estimated from the far-infrared luminosity. The majority
(>60%) of our sample show spectral features characteristic of AGN, with ~65%
exhibiting broad Balmer emission lines. A proportion of these sources show
relatively low [OIII]/H_beta line ratios, which are similar to those of Narrow
Line Seyfert 1 galaxies suggesting small mass black holes which are rapidly
growing. In the subsample of our survey with both [OIII] and hard X-ray
coverage, at least ~60% show an excess of [OIII] emission, by a factor of 5-10
times, relative to the hard X-ray luminosity compared to the correlation
between these two properties seen in Seyferts and QSOs locally. From our
spectral diagnostics, we propose that the strong [OIII] emission in these
galaxies arises from shocks in dense gaseous regions in this vigorously
star-forming population.


title: The Spectral Energy Distribution of the High-Z Blazar Q0906+693

abstract:
  We describe further observations of QSO J0906+6930, a z=5.48 blazar likely to
be detected in gamma-rays. New radio and X-ray data place significant
constraints on any kpc-scale extension of the VLBA-detected jet. Improved
optical spectroscopy detects absorption from an intervening galaxy at z=1.849
and raise the possibility that this distant, bright source is lensed. We
combine the new data into an improved SED for the blazar core and comment on
the Compton keV-GeV flux component.


title: A survey for redshifted molecular and atomic absorption lines I

abstract:
  We are currently undertaking a large survey for redshifted atomic and
molecular absorption ... only one clear and one tentative detection were
obtained: HI absorption at z = 0.097 in PKS 1555-140 and OH absorption at z
=0.126 in PKS 2300-189, respectively... In order to determine why no clear
molecular absorption was detected in any of the 13 sources searched, we
investigate the properties of the five redshifted systems currently known to
exhibit OH absorption. In four of these, molecules were first detected via
millimetre-wave transitions and the flat radio spectra indicate compact
background continuum sources, which may suggest a high degree of coverage of
the background source by the molecular clouds in the absorber. Furthermore, for
these systems we find a relationship between the molecular line strength and
red optical--near infrared (V-K) colours, thus supporting the notion that the
reddening of these sources is due to dust, which provides an environment
conducive to the formation of molecules. Upon comparison with the V-K colours
of our sample, this relationship suggests that, presuming the reddening occurs
at the host galaxy redshift at least in some of the targets, many of our
observations still fall short of the sensitivityrequired to detect OH
absorption, although a confirmation of the ``detection'' of OH in 2300-189
could contravene this.


title: Evidence for Heating of Neutron Stars by Magnetic Field Decay

abstract:
  We show the existence of a strong trend between neutron star surface
temperature and the dipolar component of the magnetic field extending through
three orders of field magnitude, a range that includes magnetars, radio-quiet
isolated neutron stars, and many ordinary radio pulsars. We suggest that this
trend can be explained by the decay of currents in the crust over a time scale
of few Myr. We estimate the minimum temperature that a NS with a given magnetic
field can reach in this interpretation.


title:
The Effects of Rotation Rate on Deep Convection in Giant Planets with
  Small Solid Cores

abstract:
  We study how the pattern of thermal convection and differential rotation in
the interior of a giant gaseous planet is affected by the presence of a small
solid core as a function of the planetary rotation rate. We show, using 2D
anelastic, hydrodynamic simulations, that the presence of a small solid core
results in significantly different flow structure relative to that of a fully
convective interior only if there is little or no planetary rotation.


title: The Dependence of Galaxy Type on Host Halo Mass

abstract:
  We examine the relation between galaxy properties and environment in the SDSS
DR2, quantifying environment in terms of the mass of the host halo, which is
obtained with a new iterative group finder. We find that galaxy type fractions
scale strongly and smoothly with halo mass, but, at fixed mass, not with
luminosity. We compare these findings with the semi-analytical galaxy formation
model of Croton et al. (2006). The discrepancies we find can be explained with
an oversimplified implementation of strangulation, the neglect of tidal
stripping, and shortcomings in the treatments of dust extinction and/or AGN
feedback.