title:
The O VI Absorbers Toward PG0953+415: High Metallicity, Cosmic-Web Gas
  Far From Luminous Galaxies

abstract:
  The spectrum of the low-redshift QSO PG0953+415 shows two strong, intervening
O VI absorption systems. To study the nature of these absorbers, we have used
the Gemini Multiobject Spectrograph to conduct a deep spectroscopic galaxy
redshift survey in the 5' x 5' field centered on the QSO. This survey is fully
complete for r' < 19.7 and is 73% complete for r' < 21.0. We find three
galaxies at the redshift of the higher-z O VI system (z = 0.14232) including a
galaxy at projected distance rho = 155 kpc. We find no galaxies in the Gemini
field at the redshift of the lower-z O VI absorber (z = 0.06807), which
indicates that the nearest galaxy is more than 195 kpc away or has L < 0.04 L*.
Previous shallower surveys covering a larger field have shown that the z =
0.06807 O VI absorber is affiliated with a group/filament of galaxies, but the
nearest known galaxy has rho = 736 kpc. The z = 0.06807 absorber is notable for
several reasons. The absorption profiles reveal simple kinematics indicative of
quiescent material. The H I line widths and good alignment of the H I and metal
lines favor photoionization and, moreover, the column density ratios imply a
high metallicity: [M/H] = -0.3 +/- 0.12. The z = 0.14232 O VI system is more
complex and less constrained but also indicates a relatively high metallicity.
Using galaxy redshifts from SDSS, we show that both of the PG0953+415 O VI
absorbers are located in large-scale filaments of the cosmic web. Evidently,
some regions of the web filaments are highly metal enriched. We discuss the
origin of the high-metallicity gas and suggest that the enrichment might have
occurred long ago (at high z).


title: CMB Anisotropies at Second Order I

abstract:
  We present the computation of the full system of Boltzmann equations at
second-order describing the evolution of the photon, baryon and cold dark
matter fluids. These equations allow to follow the time evolution of the Cosmic
Microwave Background (CMB) anisotropies at second-order at all angular scales
from the early epoch, when the cosmological perturbations were generated, to
the present through the recombination era. This paper sets the stage for the
computation of the full second-order radiation transfer function at all scales
and for a a generic set of initial conditions specifying the level of
primordial non-Gaussianity. In a companion paper, we will present the
computation of the three-point correlation function at recombination which is
so relevant for the issue of non-Gaussianity in the CMB anisotropies.


title:
Proposing a Experimental Astronomical Test to the Existence of the
  Quantum Strings

abstract:
  It is proposed a model of Kaluza Klein that does make the quantification of
the electric charges without magnetic monopoles. This model of Kaluza Klein
allows to calculate de radius of compactation proposed for Klein. The model is
of Kaluza Klein, but it has consequences in the theory of the quantum strings,
and it is possible to indicate a manner of to test the existence of the quantum
strings.The model indicates that: if the quantum strings exist really, the
cosmological variation of the fine structure constant would do quantum jumps.
If this variation is continuous, the quantum strings does not exist.It is
possible to the astronomers to decide this.


title: On Universal Halos and the Radial Orbit Instability

abstract:
  The radial orbit instability drives dark matter halos toward a universal
structure. This conclusion, first noted by Huss, Jain, and Steinmetz, is
explored in detail through a series of numerical experiments involving the
collapse of an isolated halo into the non-linear regime. The role played by the
radial orbit instability in generating the density profile, shape, and orbit
structure is carefully analyzed and, in all cases, the instability leads to
universality independent of initial conditions. New insights into the
underlying physics of the radial orbit instability are presented.


title: A Hot DQ White Dwarf in the Open Star Cluster M35

abstract:
  We report the discovery of a hot DQ white dwarf, NGC 2168:LAWDS 28, that is a
likely member of the 150-Myr old cluster NGC 2168 (Messier 35). The spectrum of
the white dwarf is dominated by CII features. The effective temperature is
difficult to estimate but likely > 20,000 K based on the temperatures of hot
DQs with similar spectra. NGC2168:LAWDS 28 provides further evidence that hot
DQs may be the ``missing'' high-mass helium-atmosphere white dwarfs. Based on
published studies, we find that the DBA WD LP 475-242 is likely a member of the
Hyades open cluster, as often assumed. These two white dwarfs are the entire
sample of known He-atmosphere white dwarfs in open clusters with turnoff masses
>2 solar masses. Based on the number of known cluster DA white dwarfs and a
redetermination of the H-atmosphere:He-atmosphere ratio, commonly known as the
DA:DB ratio, we re-examine the hypothesis that the H- to He-atmosphere ratio in
open clusters is the same as the ratio in the field. Under this hypothesis, we
calculate that five He-atmosphere WDs are expected to have been discovered,
with a probability of finding fewer than three He-atmosphere white dwarfs of
0.08, or at the ~ 2-sigma level.


title:
Vegetation signature in the observed globally-integrated spectrum of
  Earth: Modeling the red edge strength using simultaneous cloud data and
  application for extrasolar planets

abstract:
  The vegetation's ``red edge'', an intensity bump in the Earth's spectrum near
700 $nm$ when sunlight is reflected from greenery, is often suggested as a tool
in the search for life in terrestrial-like extrasolar planets. Here, through
ground-based observations of the Earth's spectrum, satellite observations of
clouds, and an advanced atmospheric radiative transfer code, we determine the
temporal evolution of the vegetation signature of Earth. The excellent
agreement between models and observations motivated us to probe more deeply
into the red edge detectability using real cloud observations at longer time
scales. Overall, we find the evolution of the red edge signal in the
globally-averaged spectra to be weak, and only attributable to vegetation
changes when the real land and cloud distributions for the day are known.
However, it becomes prominent under certain Sun-Earth-Moon orbital geometries,
which are applicable to the search for life in extrasolar planets. Our results
indicate that vegetation detection in Earth-like planets will require a
considerable level of instrumental precision and will be a difficult task, but
not as difficult as the normally weak earthshine signal might seem to suggest.


title: Discovery of 14 radio pulsars in a survey of the Magellanic Clouds

abstract:
  A systematic survey of the Large and Small Magellanic Clouds for radio
pulsars using the Parkes radio telescope and the 20-cm multibeam receiver has
resulted in the discovery of 14 pulsars and the redetection of five of the
eight previously known spin-powered pulsars believed to lie in the Magellanic
Clouds. Of the 14 new discoveries, 12 are believed to lie within Clouds, three
in the Small Cloud and nine in the Large Cloud, bringing the total number of
known spin-powered pulsars in the Clouds to 20. Averaged over all positions
within the survey area, the survey had a limiting flux density of about 0.12
mJy. Observed dispersion measures suggest that the mean free electron density
in the Magellanic Clouds is similar to that in the disk of our Galaxy. The
observed radio luminosities have little or no dependence on pulsar period or
characteristic age and the differential luminosity function is consistent with
a power-law slope of -1 as is observed for Galactic pulsars.


title: Strangeness in Neutron Stars

abstract:
  It is generally agreed on that the tremendous densities reached in the
centers of neutron stars provide a high-pressure environment in which several
intriguing particles processes may compete with each other. These range from
the generation of hyperons to quark deconfinement to the formation of kaon
condensates and H-matter. There are theoretical suggestions of even more exotic
processes inside neutron stars, such as the formation of absolutely stable
strange quark matter. In the latter event, neutron stars would be largely
composed of strange quark matter possibly enveloped in a thin nuclear crust.
This paper gives a brief overview of these striking physical possibilities with
an emphasis on the role played by strangeness in neutron star matter, which
constitutes compressed baryonic matter at ultra-high baryon number density but
low temperature which is no accessible to relativistic heavy ion collision
experiments.


title: Secondary Star Formation in a Population III Object

abstract:
  We explore the possibility of subsequent star formation after a first star
forms in a Pop III object, by focusing on the radiation hydrodynamic (RHD)
feedback brought by ionizing photons as well as H2 dissociating photons. For
the purpose, we perform three-dimensional RHD simulations, where the radiative
transfer of ionizing photons and H2 dissociating photons from a first star is
self-consistently coupled with hydrodynamics based on a smoothed particle
hydrodynamics method. As a result, it is shown that density peaks above a
threshold density can keep collapsing owing to the shielding of H2 dissociating
radiation by an H2 shell formed ahead of a D-type ionization front. But, below
the threshold density, an M-type ionization front accompanied by a shock
propagates, and density peaks are radiation hydrodynamically evaporated by the
shock. The threshold density is dependent on the distance from a source star,
which is $\approx 10^2 cm^{-3}$ for the source distance of 30pc. Taking into
consideration that the extent of a Pop III object is $\approx 100$pc and
density peaks within it have the density of $10^{2-4}$cm$^{-3}$, it is
concluded that the secondary star formation is allowed in the broad regions in
a Pop III object.


title: Magnetic Jets from Swirling Disks

abstract:
  A broad swathe of astrophysical phenomena, ranging from tubular planetary
nebulae through Herbig-Haro objects, radio-galaxy and quasar emissions to
gamma-ray bursts and perhaps high-energy cosmic rays, may be driven by
magnetically-dominated jets emanating from accretion disks. We give a
self-contained account of the analytic theory of non-relativistic magnetically
dominated jets wound up by a swirling disk and making a magnetic cavity in a
background medium of any prescribed pressure, p(z). We solve the time-dependent
problem for any specified distribution of magnetic flux P(R,0) emerging from
the disk at z=0, with any specified disk angular velocity Omega_d(R). The
physics required to do this involves only the freezing of the lines of force to
the conducting medium and the principle of minimum energy.


title: GRB 990413: Insight into the thermal phase evolution

abstract:
  GRB 990413 shows a very hard spectrum (with a low energy spectral component
F(E) \propto E^{2.49}) which is well represented by a black body model with
characteristic temperature ~70 keV. It thus belongs to the subset of GRBs which
might be revealing a thermal phase. We find that the temperature/luminosity
evolution is consistent with that found in the other ``thermal'' GRBs. The time
resolved spectral analysis indicates the presence of a second non--thermal
component contributing (for about 1 s) up to 30 per cent of the total flux.
Differently from the other thermal GRBs, GRB 990413 shows significantly high
level of variability and the evolution of the thermal/non--thermal spectral
components is strongly correlated with the flux variations. This GRB thus
offers the unique opportunity to test the standard fireball photospheric and
internal shock phases and their reciprocal influence. GRB 990413 was not
selected on the basis of its spectrum and thus hints to the possibility that
this early behavior might be more common than currently known.


title: The UKIRT Infrared Deep Sky Survey (UKIDSS)

abstract:
  We describe the goals, design, implementation, and initial progress of the
UKIRT Infrared Deep Sky Survey (UKIDSS), a seven year sky survey which began in
May 2005, using the UKIRT Wide Field Camera. It is a portfolio of five survey
components covering various combinations of the filter set ZYJHK and H_2. The
Large Area Survey, the Galactic Clusters Survey, and the Galactic Plane Survey
cover approximately 7000 square degrees to a depth of K~18; the Deep
Extragalactic Survey covers 35 square degrees to K~21, and the Ultra Deep
Survey covers 0.77 square degrees to K~23. Summed together UKIDSS is 12 times
larger in effective volume than the 2MASS survey. The prime aim of UKIDSS is to
provide a long term astronomical legacy database; the design is however driven
by a series of specific goals -- for example to find the nearest and faintest
sub-stellar objects; to discover Population II brown dwarfs, if they exist; to
determine the substellar mass function; to break the z=7 quasar barrier; to
determine the epoch of re-ionisation; to measure the growth of structure from
z=3 to the present day; to determine the epoch of spheroid formation; and to
map the Milky Way through the dust, to several kpc. The survey data are being
uniformly processed, and released in stages through the WFCAM Science Archive
(WSA : http://surveys.roe.ac.uk/wsa). Before the formal survey began, UKIRT and
the UKIDSS consortium collaborated in obtaining and analysing a series of small
science verification (SV) projects to complete the commissioning of the camera.
We show some results from these SV projects in order to demonstrate the likely
power of the eventual complete survey. Finally, using the data from the First
Data Release we assess how well UKIDSS is meeting its design targets so far.


title:
Modelling the Galactic Interstellar Extinction Distribution in Three
  Dimensions

abstract:
  The Two Micron All Sky Survey, along with the Stellar Population Synthesis
Model of the Galaxy, developed in Besancon, is used to calculate the extinction
distribution along different lines of sight. By combining many lines of sight,
the large scale distribution of interstellar material can be deduced. The
Galaxy model is used to provide the intrinsic colour of stars and their
probable distances, so that the near infrared colour excess, and hence the
extinction, may be calculated and its distance evaluated. Such a technique is
dependent on the model used, however we are able to show that moderate changes
in the model parameters result in insignificant changes in the predicted
extinction. This technique has now been applied to over 64000 lines of sight,
each separated by 15 arcmin, in the inner Galaxy (|l|<=100 deg, |b|<=10 deg).
Using our extinction map, we have derived the main characteristics of the large
scale structure of the dust distribution: scale height and warp of the ISM disc
as well as the angle of the dust in the Galactic Bar. This resulting extinction
map will be useful for studies of the inner Galaxy and its stellar populations.


title: Hamilton's Eccentricity Vector Generalised to Newton Wonders

abstract:
  The vectorial velocity is given as a function of the position of a particle
in orbit when a Newtonian central force is supplemented by an inverse cubic
force as in Newton's theorem on revolving orbits. Such expressions are useful
in fitting orbits to radial velocities of orbital streams. The
Hamilton-Laplace-Runge-Lenz eccentricity vector is generalised to give a
constant of the motion for these systems and an approximate constant for orbits
in general central potentials. A related vector is found for Hooke's centred
ellipse.


title:
Parametric modelling of the 3.6um to 8um colour distributions of
  galaxies in the SWIRE Survey

abstract:
  We fit a parametric model comprising a mixture of multi-dimensional Gaussian
functions to the 3.6 to 8um colour and optical photo-z distribution of galaxy
populations in the ELAIS-N1 and Lockman Fields of SWIRE. For 16,698 sources in
ELAIS-N1 we find our data are best modelled (in the sense of the Bayesian
Information Criterion) by the sum of four Gaussian distributions or modes (C_a,
C_b, C_c and C_d). We compare the fit of our empirical model with predictions
from existing semi-analytic and phenomological models. We infer that our
empirical model provides a better description of the mid-infrared colour
distribution of the SWIRE survey than these existing models. This colour
distribution test is thus a powerful model discriminator and complementary to
comparisons of number counts. We use our model to provide a galaxy
classification scheme and explore the nature of the galaxies in the different
modes of the model. C_a consists of dusty star-forming systems such as ULIRG's.
Low redshift late-type spirals are found in C_b, where PAH emission dominates
at 8um. C_c consists of dusty starburst systems at intermediate redshifts. Low
redshift early-type spirals and ellipticals dominate C_d. We thus find a
greater variety of galaxy types than one can with optical photometry alone.
Finally we develop a new technique to identify unusual objects, and find a
selection of outliers with very red IRAC colours. These objects are not
detected in the optical, but have very strong detections in the mid-infrared.
These sources are modelled as dust-enshrouded, strongly obscured AGN, where the
high mid-infrared emission may either be attributed to dust heated by the AGN
or substantial star-formation. These sources have z_ph ~ 2-4, making them
incredibly infrared luminous, with a L_IR ~ 10^(12.6-14.1) L_sun.


title: Neutrino Astronomy and Cosmic Rays Spectroscopy at Horizons

abstract:
  A new air-showering physics may rise in next years at horizon, offering at
different angles and altitudes a fine tuned filtered Cosmic Rays astrophysics
and an upward Neutrino induced air-showering astronomy. Most of this
opportunity arises because of neutrino masses, their mixing and the consequent
replenishment of rarest tau flavor during its flight in Space. Horizontal air
atmosphere act as a filter for High energy Cosmic Rays (CR) and as a beam dump
for Ultra High Energy (UHE) neutrinos and a powerfull amplifier for its tau
decay in air by its wide showering areas. Earth sharp shadows plays the role of
a huge detector volume for UHE neutrino and a noise-free screen for upcoming
EeVs tau air-showers (as well PeVs anti-neutrino electron air interactions).
Projects for Tau Airshowers are growing at the top of a mountains or at the
edge of a cliff. ASHRA in Hawaii and CRNTN in Utah are tracking fluorescence
lights, while other novel projects on Crown array detectors on mountains, on
balloons and satellites are elaborated for Cherenkov lights. AUGER, facing the
Ande edges, ARGO located within a deep valley are testing inclined showers;
MILAGRO (and MILAGRITO) may be triggered by horizontal up-going muon bundles
from the Earth edges; HIRES and AUGER UHECR detectors, linking twin array
telescopes along their axis may test horizontal Cerenkov blazing photons. MAGIC
(Hess, Veritas) and Shalon Telescopes may act already like a detector for few
PeVs and Glashow resonance neutrino events; MAGIC pointing downward to
terrestrial ground acts as a massive tens of km^3 detector, making it the most
sensitive dedicated neutrino telescope. MAGIC facing the sea edges must reveal
mirrored downward UHECR Air-showers Cherenkov flashes. Magic-crown systems may
lead to tens km^3, neutrino detectors.

categories: astro-ph gr-qc hep-ph nucl-ex nucl-th physics.space-ph


title:
Cosmological viability of f(R)-gravity as an ideal fluid and its
  compatibility with a matter dominated phase

abstract:
  We show that f(R)-gravity can, in general, give rise to cosmological viable
models compatible with a matter-dominated epoch evolving into a late
accelerated phase. We discuss the various representations of f(R)-gravity as an
ideal fluid or a scalar-tensor gravity theory, taking into account conformal
transformations. We point out that mathematical equivalence does not
correspond, in several cases, to the physical equivalence of Jordan frame and
Einstein frame. Finally, we show that wide classes of f(R)-gravity models,
including matter and accelerated phases, can be phenomenologically
reconstructed by means of observational data. In principle, any popular
quintessence models could be "reframed" as an f(R)-gravity model.


title: The Environments around Long-Duration Gamma-Ray Burst Progenitors

abstract:
  Gamma-ray burst (GRB) afterglow observations have allowed us to significantly
constrain the engines producing these energetic explosions. Te redshift and
position information provided by these afterglows have already allowed us to
limit the progenitors of GRBs to only a few models. The afterglows may also
provide another observation that can place further constraints on the GRB
progenitor: measurements telling us about the environments surrounding GRBs.
Current analyses of GRB afterglows suggest that roughly half of long-duration
gamma-ray bursts occur in surroundings with density profiles that are uniform.
We study the constraints placed by this observation on both the classic
``collapsar'' massive star progenitor and its relative, the ``helium-merger''
progenitor. We study several aspects of wind mass-loss and find that our
modifications to the standard Wolf-Rayet mass-loss paradigm are not sufficient
to produce constant density profiles. Although this does not rule out the
standard ``collapsar'' progenitor, it does suggest a deficiency with this
model. We then focus on the He-merger models and find that such progenitors can
fit this particular constraint well. We show how detailed observations can not
only determine the correct progenitor for GRBs, but also allow us to study
binary evolution physics.


title: GRB030406 an extremely hard burst outside of the INTEGRAL field of view

abstract:
  Using the IBIS Compton mode, the INTEGRAL satellite is able to detect and
localize bright and hard GRBs, which happen outside of the nominal INTEGRAL
telescopes field of view. We have developed a method of analyzing such INTEGRAL
data to obtain the burst location and spectra. We present the results for the
case of GRB030406. The burst is localized with the Compton events, and the
location is consistent with the previous Interplanetary Network position. A
spectral analysis is possible with the detailed modeling of the detector
response for such a far off-axis source with the offset of 36.9 $^\circ$. The
average spectrum of the burst is extremely hard: the photon index above 400
\kev is -1.7, with no evidence of a break up to 1.1 \mev at 90% confidence
level.


title: The origin and fate of short-period low-mass black-hole binaries

abstract:
  We present results of a population synthesis study for semidetached short
orbital period binaries which contain low-mass(<1.5 Msun) donors and black hole
(>4 Msun) accretors. Evolution of these binaries is determined by nuclear
evolution of the donors and/or orbital angular momentum loss due to magnetic
braking by the stellar wind of the donors and gravitational wave radiation.
According to our model, the estimated total number of this type of black-hole
binaries in the Galaxy is about 10000. If the magnetic braking is described by
the Verbunt & Zwaan formula, the model predicts around 3000 transient systems
with periods >2 hours and around 300 luminous stable systems with periods
between 3 and 8 hours. Several dozens of these bright systems should be above
the RXTE ASM sensitivity limit. The absence of such systems implies that
angular momentum losses are reduced by a factor more than 2 with respect to the
Verbunt & Zwaan prescription. We show that it is unlikely that the transient
behaviour of black-hole short-period X-ray binaries is explained by the evolved
nature of the stellar companion. A substantial fraction of black-hole binaries
with periods >3 hours could be faint with truncated, stable cold accretion
discs as proposed by Menou et al. Most of the semidetached black-hole binaries
are expected to have periods shorter than ~2 hours. Properties of such, still
to be observed, very small mass-ratio (q<0.02) binaries are different from
those of their longer period cousins.


title: Gravitational lensing in fourth order gravity

abstract:
  Gravitational lensing is investigated in the weak field limit of fourth order
gravity in which the Lagrangian of the gravitational field is modified by
replacing the Ricci scalar curvature R with an analytical expression $f(R)$.
Considering the case of a pointlike lens, we study the behaviour of the
deflection angle in the case of power law Lagrangians, i.e. with f(R) = f_0
R^n. In order to investigate possible detectable signatures, the position of
the Einstein ring and the solutions of the lens equation are evaluated
considering the change with respect to the standard case. Effects on the
amplification of the images and the Paczynski curve in microlensing experiments
are also estimated.


title:
Measuring proton energies and fluxes using EIT (SOHO) CCD areas outside
  the solar disk images

abstract:
  An indirect proton flux measuring tool based on discrimination of the energy
deposited by protons in 128 x 128 pixel EIT CCD areas outside the solar disk
images is presented. Single pixel intensity events are converted into proton
incident energy flux using modeled energy deposition curves for angles of
incidence 60 deg in four EIT spatial areas with different proton stopping
power. The extracted proton flux is corrected for both the loss of one-pixel
events in the range of angles of incidence as well as for the contribution to
the single pixel events resulting from scattered middle-energy protons
(low-energy or high-energy particles are stopped by the EIT components or pass
through them, accordingly). A simple geometrical approach was found and applied
to correct for a non-unique relation between the proton-associated CCD output
signal and the incident proton energy. With this geometrical approximation four
unique proton incident energy ranges were determined as 45--49, 145--154,
297--335, and 390--440 MeV. The indirect proton flux measuring tool has been
tested by comparing Solar Energetic Particles (SEP) flux temporal profiles
extracted from the EIT CCD frames and downloaded from the GOES database for the
Bastille Day (BD) of 2000 July 14 and the more recent 2005 January 20 events.
The SEP flux temporal profiles and proton spectra extracted from the EIT in the
relatively narrow energy ranges between 45 and 440 MeV reported here are
consistent with the related GOES profiles. The four additional EIT extracted
ranges provide higher energy resolution of the SEP data.


title:
High Energy Neutrino Flashes from Far-Ultraviolet and X-ray Flares in
  Gamma-Ray Bursts

abstract:
  The recent observations of bright optical and x-ray flares by the Swift
satellite suggest these are produced by the late activities of the central
engine. We study the neutrino emission from far-ultraviolet and x-ray flares
under the late internal shock model. We show that the efficiency of pion
production in the highest energy is comparable to or higher than the unity, and
the contribution from such neutrino flashes to a diffuse very high energy
neutrino background can be larger than that of prompt bursts if the total
baryonic energy input into flares is comparable to the radiated energy of
prompt bursts. These signals may be detected by IceCube and are very important
because they have possibilities to probe the nature of flares (the baryon
loading, the photon field, the magnetic field and so on).


title: Nova V4743 Sagittarii 2002: An Intermediate Polar Candidate

abstract:
  We present the results of 11 nights of CCD unfiltered photometry of V4743 Sgr
(Nova Sgr 2002 # 3) from 2003 and 2005. We find two periods of 0.2799 d ~ 6.7 h
and 0.01642 d ~ 24 min in the 2005 data. The long period is also present in the
2003 data, but only weak evidence of the shorter period is found in this year.
The 24-min period is somewhat longer than the 22-min period, which was detected
from X-ray observations. We suggest that the 6.7-h periodicity represents the
orbital period of the underlying binary system and that the 24-min period is
the beat periodicity between the orbital period and the X-ray period, which is
presumably the spin period of the white dwarf. Thus, V4743 Sgr should be
classified as an intermediate polar (DQ Her star). About six months after the
nova outburst, the optical light curve of V4743 Sgr seemed to show
quasi-periodic oscillations, which are typical of the transient phase in
classical nova. Therefore, our results support the previous suggestion that the
trans ition phase in novae may be related to intermediate polars.


title: Antimatter from Microscopic Black Holes

abstract:
  The spectrum of positrons and antiprotons produced by the outflow of high
temperature matter surrounding microscopic black holes is calculated for
energies between five GeV and the Planck energy. The results may be applicable
for the last few hours and minutes of a microscopic black hole's lifetime.


title:
Comment on: Protecting Life in the Milky Way: Metals Keep the GRBs Away
  by Stanek et al

abstract:
  Stanek et al. (astro-ph/0604113) have noted that the four low-redshift
long-duration gamma-ray bursts (LSB) observed to date all occurred in faint,
metal-poor galaxies. Given this selection, they argue that it is improbable
that there has been a substantial population of Milky Way galaxy bursts
sufficiently recently to affect life on Earth. This argument ignores the
heterogeneity of stellar populations in the Milky Way, with evidence for
continuing mergers with low-metallicity dwarf galaxies; observational analysis
that points to LSBs being hosted by such galaxies undergoing interaction; and
the existence of a likely recent GRB remnant in our galaxy.

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


title:
Cosmic Neutrinos and the Energy Budget of Galactic and Extragalactic
  Cosmic Rays

abstract:
  Although kilometer-scale neutrino detectors such as IceCube are discovery
instruments, their conceptual design is very much anchored to the observational
fact that Nature produces protons and photons with energies in excess of
10^{20} eV and 10^{13} eV, respectively. The puzzle of where and how Nature
accelerates the highest energy cosmic particles is unresolved almost a century
after their discovery. We will discuss how the cosmic ray connection sets the
scale of the anticipated cosmic neutrino fluxes. In this context, we discuss
the first results of the completed AMANDA detector and the science reach of its
extension, IceCube.


title:
The Survey for Ionization in Neutral Gas Galaxies- II. The Star
  Formation Rate Density of the Local Universe

abstract:
  We derive observed Halpha and R band luminosity densities of an HI-selected
sample of nearby galaxies using the SINGG sample to be l_Halpha' = (9.4 +/-
1.8)e38 h_70 erg s^-1 Mpc^-3 for Halpha and l_R' = (4.4 +/- 0.7)e37 h_70 erg
s^-1 A^-1 Mpc^-3 in the R band. This R band luminosity density is approximately
70% of that found by the Sloan Digital Sky Survey. This leads to a local star
formation rate density of log(SFRD) = -1.80 +0.13/-0.07(random) +/-
0.03(systematic) + log(h_70) after applying a mean internal extinction
correction of 0.82 magnitudes. The gas cycling time of this sample is found to
be t_gas = 7.5 +1.3/-2.1 Gyr, and the volume-averaged equivalent width of the
SINGG galaxies is EW(Halpha) = 28.8 +7.2/-4.7 A (21.2 +4.2/-3.5 A without
internal dust correction). As with similar surveys, these results imply that
SFRD(z) decreases drastically from z ~ 1.5 to the present. A comparison of the
dynamical masses of the SINGG galaxies evaluated at their optical limits with
their stellar and HI masses shows significant evidence of downsizing: the most
massive galaxies have a larger fraction of their mass locked up in stars
compared with HI, while the opposite is true for less massive galaxies. We show
that the application of the Kennicutt star formation law to a galaxy having the
median orbital time at the optical limit of this sample results in a star
formation rate decay with cosmic time similar to that given by the SFRD(z)
evolution. This implies that the SFRD(z) evolution is primarily due to the
secular evolution of galaxies, rather than interactions or mergers. This is
consistent with the morphologies predominantly seen in the SINGG sample.


title: How Rare is the Bullet Cluster?

abstract:
  The galaxy cluster 1E 0657-56 has a bullet-like subcluster that is moving
away from the centre of the main cluster at high speed. Markevitch et al.
(2004) recently estimated a relative velocity of V_bullet = 4500 +1100/-800
km/s, based on observations of the bow shock in front of the subcluster. The
weak lensing analysis of Clowe et al. (2004) indicates that a substantial
secondary mass peak is associated with this subcluster. We estimate the
likelihood of such a configuration by examining the distribution of subhalo
velocities for clusters in the Millennium Run, a large LCDM cosmological
simulation. We find that the most massive subhalo has a velocity as high as
that of the bullet subcluster in only about 1 out of every 100 cluster-sized
halos. This estimate is strongly dependent on the precise velocity adopted for
the bullet. One of the ten most massive subhalos has such a high velocity about
40% of the time. We conclude that the velocity of the bullet subcluster is not
exceptionally high for a cluster substructure, and can be accommodated within
the currently favoured LCDM comogony.


title:
The Survey for Ionization in Neutral Gas Galaxies: I. Description and
  Initial Results

abstract:
  We introduce the Survey for Ionization in Neutral Gas Galaxies (SINGG), a
census of star formation in HI-selected galaxies. The survey consists of
H-alpha and R-band imaging of a sample of 468 galaxies selected from the HI
Parkes All Sky Survey (HIPASS). The sample spans three decades in HI mass and
is free of many of the biases that affect other star forming galaxy samples. We
present the criteria for sample selection, list the entire sample, discuss our
observational techniques, and describe the data reduction and calibration
methods. This paper focuses on 93 SINGG targets whose observations have been
fully reduced and analyzed to date. The majority of these show a single
Emission Line Galaxy (ELG). We see multiple ELGs in 13 fields, with up to four
ELGs in a single field. All of the targets in this sample are detected in
H-alpha indicating that dormant (non-star forming) galaxies with M(HI) > ~3e7
M_sun are very rare. A database of the measured global properties of the ELGs
is presented. The ELG sample spans four orders of magnitude in luminosity
(H-alpha and R-band), and H-alpha surface brightness, nearly three orders of
magnitude in R surface brightness and nearly two orders of magnitude in H-alpha
equivalent width (EW). The surface brightness distribution of our sample is
broader than that of the Sloan Digital Sky Survey spectroscopic sample, the
(EW) distribution is broader than prism-selected samples, and the morphologies
found include all common types of star forming galaxies (e.g. irregular,
spiral, blue compact dwarf, starbursts, merging and colliding systems, and even
residual star formation in S0 and Sa spirals). (abridged)


title: Low-Mass Binary Induced Outflows from Asymptotic Giant Branch Stars

abstract:
  A significant fraction of planetary nebulae (PNe) and proto-planetary nebulae
(PPNe) exhibit aspherical, axisymmetric structures, many of which are highly
collimated. The origin of these structures is not entirely understood, however
recent evidence suggests that many observed PNe harbor binary systems, which
may play a role in their shaping. In an effort to understand how binaries may
produce such asymmetries, we study the effect of low-mass (< 0.3 M_sun)
companions (planets, brown dwarfs and low-mass main sequence stars) embedded
into the envelope of a 3.0 M_sun star during three epochs of its evolution (Red
Giant Branch, Asymptotic Giant Branch (AGB), interpulse AGB). We find that
common envelope evolution can lead to three qualitatively different
consequences: (i) direct ejection of envelope material resulting in a
predominately equatorial outflow, (ii) spin-up of the envelope resulting in the
possibility of powering an explosive dynamo driven jet and (iii) tidal
shredding of the companion into a disc which facilitates a disc driven jet. We
study how these features depend on the secondary's mass and discuss
observational consequences.


title:
Flux-transport dynamos with Lorentz force feedback on differential
  rotation and meridional flow: Saturation mechanism and torsional oscillations

abstract:
  In this paper we discuss a dynamic flux-transport dynamo model that includes
the feedback of the induced magnetic field on differential rotation and
meridional flow. We consider two different approaches for the feedback:
meanfield Lorentz force and quenching of transport coefficients such as
turbulent viscosity and heat conductivity. We find that even strong feedback on
the meridional flow does not change the character of the flux-transport dynamo
significantly; however it leads to a significant reduction of differential
rotation. To a large degree independent from the dynamo parameters, the
saturation takes place when the toroidal field at the base of the convection
zone reaches between 1.2 an 1.5 T, the energy converted intomagnetic energy
corresponds to about 0.1 to 0.2% of the solar luminosity. The torsional
oscillations produced through Lorentz force feedback on differential rotation
show a dominant poleward propagating branch with the correct phase relation to
the magnetic cycle. We show that incorporating enhanced surface cooling of the
active region belt (as proposed by Spruit) leads to an equatorward propagating
branch in good agreement with observations.


title: Implications of WMAP 3 Year Data for the Sources of Reionization

abstract:
  New results on the anisotropy of the cosmic microwave background (CMB) and
its polarization based on the first 3 years of data from the Wilkinson
Microwave Anisotropy Probe (WMAP) have revised the electron scattering optical
depth downward from tau_es=0.17+0.08-0.07 to tau_es=0.09+/-0.03. This implies a
shift of the effective reionization redshift from z_r~17 to z_r~11. Previous
attempts to explain the high redshift of reionization inferred from the WMAP 1
year data have led to widespread speculation that the sources of reionization
must have been much more efficient than those associated with the star
formation observed at low redshift. This is consistent, for example, with the
suggestion that early star formation involved massive, Population III stars
that early on produced most of the ionizing radiation escaping from halos. It
is therefore tempting to interpret the new WMAP results as implying that we can
now relax those previous high demands on the efficiency of the sources of
reionization and perhaps even turn the argument around as evidence against such
high efficiency. We show that this is not the case, however. The new WMAP
results also find that the primordial density fluctuation power spectrum has a
lower amplitude, sigma_8, and departs substantially from the scale-invariant
spectrum. We show that these effects combine to cancel the impact of the later
reionization implied by the new value of tau_es on the required ionizing
efficiency per collapsed baryon. The delay of reionization is surprisingly well
matched by a comparable delay (by a factor of ~1.4 in scale factor) in the
formation of the halos responsible for reionization.


title: Astronomy: Trouble at first light

abstract:
  The question of how much light the first stars produced is fundamental to
models of the Universe's development. But observations have so far failed to
agree: is the answer a lot, or not very much at all?


title:
Color and Variability Characteristics of Point Sources in the Faint Sky
  Variability Survey

abstract:
  We present an analysis of the color and variability characteristics for point
sources in the Faint Sky Variability Survey (FSVS). The FSVS cataloged ~23
square degrees in BVI filters from ~16--24 mag to investigate variability in
faint sources at moderate to high Galactic latitudes. Point source completeness
is found to be >83% for a selected representative sample (V=17.5--22.0 mag,
B-V=0.0--1.5) containing both photometric B, V detections and 80% of the
time-sampled V data available compared to a basic internal source completeness
of 99%. Multi-epoch (10--30) observations in V spanning minutes to years
modeled by light curve simulations reveal amplitude sensitivities to
0.015--0.075 mag over a representative V=18--22 mag range. Periodicity
determinations appear viable to time-scales of an order 1 day or less using the
most sampled fields (~30 epochs). The fraction of point sources is found to be
generally variable at 5--8% over V=17.5--22.0 mag. For V brighter than 19 mag,
the variable population is dominated by low amplitude (<0.05 mag) and blue
(B-V<0.35) sources, possibly representing a population of gamma Doradus stars.
Overall, the dominant population of variable sources are bluer than B-V=0.65
and have Main Sequence colors, likely reflecting larger populations of RR
Lyrae, SX Phe, gamma Doradus, and W UMa variables.


title: First Year Performance of The IceCube Neutrino Telescope

abstract:
  The first sensors of the IceCube neutrino observatory were deployed at the
South Pole during the austral summer of 2004-05 and have been producing data
since February 2005. One string of 60 sensors buried in the ice and a surface
array of 8 ice Cherenkov tanks took data until December 2005 when deployment of
the next set of strings and tanks began. We have analyzed these data,
demonstrating that the performance of the system meets or exceeds design
requirements. Times are determined across the whole array to a relative
precision of better than 3 nanoseconds, allowing reconstruction of muon tracks
and light bursts in the ice, of air-showers in the surface array and of events
seen in coincidence by surface and deep-ice detectors separated by up to 2.5
km.


title:
Solar differential rotation and meridional flow: The role of a
  subadiabatic tachocline for the Taylor-Proudman balance

abstract:
  We present a simple model for the solar differential rotation and meridional
circulation based on a mean field parameterization of the Reynolds stresses
that drive the differential rotation. We include the subadiabatic part of the
tachocline and show that this, in conjunction with turbulent heat conductivity
within the convection zone and overshoot region, provides the key physics to
break the Taylor-Proudman constraint, which dictates differential rotation with
contour lines parallel to the axis of rotation in case of an isentropic
stratification. We show that differential rotation with contour lines inclined
by 10 - 30 degrees with respect to the axis of rotation is a robust result of
the model, which does not depend on the details of the Reynolds stress and the
assumed viscosity, as long as the Reynolds stress transports angular momentum
toward the equator. The meridional flow is more sensitive with respect to the
details of the assumed Reynolds stress, but a flow cell, equatorward at the
base of the convection zone and poleward in the upper half of the convection
zone, is the preferred flow pattern.


title: Radial Kinematics of Isolated Elliptical Galaxies

abstract:
  Ellipticals in very low density environments are extremely rare but hold
important clues about galaxy formation and evolution. In this paper we continue
our study of isolated elliptical galaxies, presenting results on the radial
stellar kinematics for 13 isolated early-type galaxies. We derive radial
rotation velocity, velocity dispersion and hermite terms to ~1 effective
radius. We observe a dichotomy in kinematic properties similar to that in the
elliptical population as a whole, where low luminosity ellipticals tend to be
rotationally supported. For all galaxies the V/sigma ratio increases with
radius. We find kinematically distinct cores (KDCs), or velocity substructure,
in ~40% of the galaxies for which we have major axis spectra. Such a fraction
is similar to that observed for ellipticals in higher density environments.
Most galaxies in the sample reveal kinematic evidence for a nuclear disk. The
non-relaxed kinematics in several galaxies suggests that they have undergone a
merger or accretion event. Isolated ellipticals generally follow the
fundamental plane defined by cluster ellipticals -- exceptions being those
galaxies with evidence for young stellar populations. Overall, we find isolated
ellipticals have similar kinematic properties to their counterparts in higher
density environments.


title:
Solar-like oscillations in the metal-poor subgiant nu Indi: constraining
  the mass and age using asteroseismology

abstract:
  Asteroseismology is a powerful method for determining fundamental properties
of stars. We report the first application to a metal-poor object, namely the
subgiant star nu Ind. We measured precise velocities from two sites, allowing
us to detect oscillations and infer a large frequency separation of Delta_nu =
24.25 +/- 0.25 microHz. Combining this value with the location of the star in
the H-R diagram and comparing with standard evolutionary models, we were able
to place constraints on the stellar parameters. In particular, our results
indicate that nu Ind has a low mass (0.85 +/- 0.04 M_sun) and is at least 9 Gyr
old.


title: Diffuse Far-ultraviolet Observation of the Lupus Loop Region

abstract:
  Diffuse far-ultraviolet (FUV) emissions from the Lupus Loop region (SNR
330.0+15.0) have been observed with Spectroscopy of Plasma Evolution from
Astrophysical Radiation (SPEAR), also known as Far-ultraviolet IMaging
Spectrograph (FIMS). We have detected several important ionic lines, including
Si II*, C IV, and N IV], which characterize the warm, hot ionized gas in this
region. The spatial variations in the line intensities of Si II* and C IV have
also been studied in comparison with X-ray and dust observations. The result
shows that they originate from the interface between the hot gas seen in the
X-ray and the cooler H I shell with which dust is associated. The interface is
rather diffuse, and the gases with different temperatures seem to co-exist in
this region. A shock may exist upfront in the interface, but its velocity
should be very small as no shock-related distinguished feature is seen in Ha.


title:
Observations of the intense and ultra-long burst GRB041219a with the
  Germanium Spectrometer on INTEGRAL

abstract:
  GRB041219a is the brightest burst localised by INTEGRAL. The intense burst
occurred about ~250s after the precursor and the long delay enabled optical and
near infrared telescopes to observe the prompt emission. We present
comprehensive results of the temporal and spectral analyses, including line and
afterglow searches using the spectrometer, SPI, aboard INTEGRAL, BAT on Swift
and ASM on RXTE. We avail of multi-wavelength data to generate broadband
spectra of GRB041219a and afterglow. Spectra for the burst and sub-intervals
were fit by the Band model and also by the quasithermal model. The high
resolution Germanium spectrometer data were searched for emission and
absorption features and for gamma-ray afterglow. The overall burst and
sub-intervals are well fit by the Band model. The photon index below the break
energy shows a marked change after the quiescent time interval. In addition the
spectra are well described by a black body component with a power law. The
burst was detected by BAT and ASM during the long quiescent interval in SPI
indicating the central engine might not be dormant but that the emission occurs
in different bands. No significant emission or absorption features were found
and limits of 900 eV and 120 eV are set on the most significant features. No
gamma-ray afterglow was detected from the end of the prompt phase to ~12 hours
post-burst. Broadband spectra of the prompt emission were generated in 7 time
intervals using gamma-ray, x-ray, optical and near-infrared data and these were
compared to the high-redshift burst GRB050904. The optical and gamma-ray
emission are correlated in GRB041219a. The spectral lag was determined using
data from the BAT and it changes throughout the burst. A number of
pseudo-redshifts were evaluated and large dispersion in values was found.


title:
An exact analytic spectrum of relic gravitational waves in an
  accelerating universe

abstract:
  An exact analytic calculation is presented for the spectrum of relic
gravitational waves in the scenario of accelerating Universe
$\Omega_{\Lambda}+\Omega_m = 1$. The spectrum formula contains explicitly the
parameters of acceleration, inflation, reheating, and the (tensor/scalar)
ratio, so that it can be employed for a variety of cosmological models. We find
that the spectrum depends on the behavior of the present accelerating
expansion. The amplitude of gravitational waves for the model
$\Omega_{\Lambda}=0.65$ is about $\sim 50 %$ greater than that of the model
$\Omega_{\Lambda}=0.7$, an effect accessible to the designed sensitivities of
LIGO and LISA. The spectrum sensitively depends on the inflationary models with
$a(\tau) \propto |\tau|^{1+\beta}$, and a larger $\beta$ yields a flatter
spectrum, producing more power. The current LIGO results rule out the
inflationary models of $\beta \geq -1.8$. The LIGO with its design sensitivity
and the LISA will also be able to test the model of $\beta=-1.9$. We also
examine the constraints on the spectral energy density of relic gravitational
waves. Both the LIGO bound and the nucleosynthesis bound point out that the
model $\beta=-1.8$ is ruled out, but the model $\beta=-2.0$ is still alive. The
exact analytic results also confirm the approximate spectrum and the numerical
one in our previous work.


title: Coincidence Problem in YM Field Dark Energy Model

abstract:
  The coincidence problem is studied in the effective Yang-Mills condensate
dark energy model. As the effective YM Lagrangian is completely determined by
quantum field theory, there is no adjustable parameter in this model except the
energy scale, and the cosmic evolution only depends on the initial conditions.
For generic initial conditions with the YM condensate subdominant to the
radiation and matter, the model always has a tracking solution, the Universe
transits from matter-dominated into the dark energy dominated stage only
recently $z\sim 0. 3$, and evolve to the present state with $\Omega_{y}\sim
0.73$ and $\Omega_m\sim 0.27$.


title: Relic gravitational waves and their detection

abstract:
  As the strong evidence for inflation, the relic gravitational waves (RGW)
have been extensively studied. Although, it has not been detected, yet some
constraints have been achieved by the observations. Future experiments for the
RGW detection are mainly two kinds: the CMB experiments and the laser
interferometers. In this paper, we study these current constraints and the
detective abilities of future experiments. We calculate the strength of RGW
$\Omega_g(k)$ in two methods: the analytic method and the numerical method by
solving the inflationary flow equations. By the first method we obtain a bound
$\Omega_g<3.89\times10^{-16}$ at $\nu=0.1$Hz, where we have used the current
constraints on the scalar spectral index, the tensor-scalar ratio, furthermore,
we have taken into account of the redshift-suppression effect, the accelerating
expansion effect, the neutrino damping effect on the RGW. But the analytic
expression of $\Omega_g(k)$ depends on the specific inflationary models and not
well applies for the waves with very high frequencies. The numerical method is
more precise for the waves with high frequencies and applies to any
single-field inflationary model. It gives a bound
$\Omega_g<8.62\times10^{-14}$, which is independent of the inflationary
parameters, and applies to any single-field slow-roll inflationary model. After
considering the current constraints on the inflationary parameters, this bound
becomes $\Omega_g<2\times10^{-17}$ (see text).


title:
Quintessence models with an oscillating equation of state and their
  potentials

abstract:
  In this paper, we investigate the quintessence models with an oscillating
equation of state (EoS) and their potentials. From the constructed potentials,
which have the EoS of $\omega_{\phi}=\omega_0+\omega_1\sin z$, we find they are
all the oscillating functions of the field $\phi$, and the oscillating
amplitudes are decreasing (or increasing) with $\phi$. From the evolutive
equation of the field $\phi$, we find this is caused by the expansion of the
universe. This also makes that it is very difficult to build a model whose EoS
oscillates forever. However one can build a model with EoS oscillating for a
period. Then we discuss three quintessence models, which are the combinations
of the invert power law functions and the oscillating functions of the field
$\phi$. We find they all follow the oscillating EoS.


title: Quintom models with an equation of state crossing -1

abstract:
  In this paper, we investigate a kind of special quintom model, which is made
of a quintessence field $\phi_1$ and a phantom field $\phi_2$, and the
potential function has the form of $V(\phi_1^2-\phi_2^2)$. This kind of quintom
fields can be separated into two kinds: the hessence model, which has the state
of $\phi_1^2>\phi_2^2$, and the hantom model with the state
$\phi_1^2<\phi_2^2$. We discuss the evolution of these models in the
$\omega$-$\omega'$plane ($\omega$ is the state equation of the dark energy, and
$\omega'$ is its time derivative in unites of Hubble time), and find that
according to $\omega>-1$ or $<-1$, and the potential of the quintom being
climbed up or rolled down, the $\omega$-$\omega'$ plane can be divided into
four parts. The late time attractor solution, if existing, is always
quintessence-like or $\Lambda$-like for hessence field, so the Big Rip doesn't
exist. But for hantom field, its late time attractor solution can be
phantom-like or $\Lambda$-like, and sometimes, the Big Rip is unavoidable. Then
we consider two special cases: one is the hessence field with an exponential
potential, and the other is with a power law potential. We investigate their
evolution in the $\omega$-$\omega'$ plane. We also develop a theoretical method
of constructing the hessence potential function directly from the effective
equation of state function $\omega(z)$. We apply our method to five kinds of
parametrizations of equation of state parameter, where $\omega$ crossing -1 can
exist, and find they all can be realized. At last, we discuss the evolution of
the perturbations of the quintom field, and find the perturbations of the
quintom $\delta_Q$ and the metric $\Phi$ are all finite even if at the state of
$\omega=-1$ and $\omega'\neq0$.


title:
Detection of Wolf-Rayet stars in host galaxies of Gamma-Ray Bursts
  (GRBs): are GRBs produced by runaway massive stars ejected from high stellar
  density regions ?

abstract:
  We have obtained deep spectroscopic observations of several nearby gamma-ray
burst (GRB) host galaxies revealing for the first time the presence of
Wolf-Rayet (WR) stars and numerous O stars located in rich and compact clusters
or star forming regions. Surprisingly, high spatial resolution imaging shows
that the GRBs and the associated supernovae did not occur in these regions, but
several hundreds of parsec away. Considering various scenarios for GRB
progenitors, we do not find any simple explanation of why they should be
preferentially born in regions with low stellar densities. All the examined
GRBs and associated SNe have occurred 400 to 800 pc from very high density
stellar environments including large numbers of WR stars. Such distances can be
travelled through at velocities of 100 km/s or larger, assuming the travel time
to be the typical life time of WR stars. It leads us to suggest that GRB
progenitors may be runaway massive stars ejected from compact massive star
clusters. The ejection from such super star clusters may lead to a spin-up of
these stars, producing the loss of the hydrogen and/or helium envelopes leading
to the origin of the type Ibc supernovae associated with GRBs. If this scenario
applies tocd text/Sc all GRBs, it provides a natural explanation of the very
small fraction of massive stars that emit a GRB at the end of their life. An
alternative to this scenario could be a binary origin for GRBs, but this still
requires an explanation of why it would preferentially occur in low stellar
density regions.


title: Magnetic Field Seeding by Galactic Winds

abstract:
  The origin of intergalactic magnetic fields is still a mystery and several
scenarios have been proposed so far: among them, primordial phase transitions,
structure formation shocks and galactic outflows. In this work we investigate
how efficiently galactic winds can provide an intense and widespread "seed"
magnetisation. This may be used to explain the magnetic fields observed today
in clusters of galaxies and in the intergalactic medium (IGM). We use
semi-analytic simulations of magnetised galactic winds coupled to high
resolution N-body simulations of structure formation to estimate lower and
upper limits for the fraction of the IGM which can be magnetised up to a
specified level. We find that galactic winds are able to seed a substantial
fraction of the cosmic volume with magnetic fields. Most regions affected by
winds have magnetic fields in the range -12 < Log B < -8 G, while higher seed
fields can be obtained only rarely and in close proximity to wind-blowing
galaxies. These seed fields are sufficiently intense for a moderately efficient
turbulent dynamo to amplify them to the observed values. The volume filling
factor of the magnetised regions strongly depends on the efficiency of winds to
load mass from the ambient medium. However, winds never completely fill the
whole Universe and pristine gas can be found in cosmic voids and regions
unaffected by feedback even at z=0. This means that, in principle, there might
be the possibility to probe the existence of primordial magnetic fields in such
regions.


title: Millimetric Properties of Gamma Ray Burst Host Galaxies

abstract:
  We present millimetre (mm) and submillimetre (submm) photometry of a sample
of host galaxies of Gamma Ray Bursts (GRBs), obtained using the MAMBO2 and
SCUBA bolometer arrays respectively. These observations were obtained as part
of an ongoing project to investigate the status of GRBs as indicators of star
formation. Our targets include two of the most unusual GRB host galaxies,
selected as likely candidate submm galaxies: the extremely red (R-K approx 5)
host of GRB 030115, and the extremely faint (R>29.5) host of GRB 020124.
Neither of these galaxies is detected, but the deep upper limits for GRB 030115
impose constraints on its spectral energy distribution.
  As a framework for interpreting these data, and for predicting the results of
forthcoming submm surveys of Swift-derived host samples, we model the expected
flux and redshift distributions based on luminosity functions of both submm
galaxies and GRBs, assuming a direct proportionality between the GRB rate
density and the global star formation rate density. We derive the effects of
possible sources of uncertainty in these assumptions, including an
anticorrelation between GRB rate and the global average metallicity.


title:
Dynamical Masses of Young Star Clusters: Constraints on the Stellar IMF
  and Star-Formation Efficiency

abstract:
  Many recent works have attempted to constrain the stellar initial mass
function (IMF) inside massive clusters by comparing their dynamical mass
estimates to the measured light. These studies have come to different
conclusions, with some claiming standard Kroupa-type IMFs, while others have
claimed extreme non-standard IMFs. However, the results appear to be correlated
with the age of the clusters, as older clusters (>80 Myr) all appear to be well
fit by a Kroupa-type IMF whereas younger clusters display significant scatter
in their best fitting IMF. Here we show that this is likely due to the fact
that young clusters are out of virial equilibrium and therefore cannot be used
for such studies. Hence only the older clusters are suitable for IMF studies.
Using only these clusters we find that the IMF does not vary significantly. The
youngest clusters can be used instead to constrain the star-formation
efficiency (SFE) within clusters. We find that the SFE varies between 20 and
60% and we conclude that approximately 60% of young clusters are unbound and
will not survive for more than a few 10's of Myr (i.e. "infant mortality").


title: Warm-hot intergalactic medium contribution to baryonic matter

abstract:
  Hydrodynamical simulations indicate that substantial fraction of baryons in
the Universe remains in a diffuse component - Warm-Hot Intergalactic Medium
(WHIM). To determine physical properties (spatial distribution, temperature and
density) of the WHIM, spatial structure of the soft extended X-ray emission
surrounding field galaxies is carefully investigated using the XMM-Newton
EPIC/MOS observations. Angular correlations between the galaxy distribution and
the soft X-ray background extending over several arcmin are determined. The
correlations at large scales result from the clustering of galaxies. At small
scales (below ~2 arcmin) the excess of the soft flux is interpreted as the
genuine emission from halos of the WHIM surrounding individual galaxies. Bulk
parameters of the average WHIM halos associated with galaxies in the sample are
estimated. Typical halo has a characteristic radius of ~0.3 Mpc and a mass of 4
- 7 x 10^11 M_sun. The average density of the WHIM in the local universe
amounts to 7 - 11 x 10^{-32} g cm^{-3} (Omega_WHIM = 0.7 - 1.2 %). Observations
of the X-ray WHIM emission are in good agreement with the numerical
simulations, but accuracy of the observational material is insufficient to
constrain the theory of WHIM. A series of deep observations of a moderately
numerous sample of low redshift galaxies with high resolution instruments of
Chandra would significantly improve our estimates of the WHIM parameters.


title:
Discovery of a 3.6-hr Eclipsing Luminous X-Ray Binary in the Galaxy NGC
  4214

abstract:
  We report the discovery of an eclipsing X-ray binary with a 3.62-hr period
within 24" of the center of the dwarf starburst galaxy NGC 4214. The orbital
period places interesting constraints on the nature of the binary, and allows
for a few very different interpretations. The most likely possibility is that
the source lies within NGC 4214 and has an X-ray luminosity of up to 7 e38
ergs/s. In this case the binary may well be comprised of a naked He-burning
donor star with a neutron-star accretor, though a stellar-mass black-hole
accretor cannot be completely excluded. There is no obvious evidence for a
strong stellar wind in the X-ray orbital light curve that would be expected
from a massive He star; thus, the mass of the He star should be <3-4 solar
masses. If correct, this would represent a new class of very luminous X-ray
binary -- perhaps related to Cyg X-3. Other less likely possibilities include a
conventional low-mass X-ray binary that somehow manages to produce such a high
X-ray luminosity and is apparently persistent over an interval of years; or a
foreground AM Her binary of much lower luminosity that fortuitously lies in the
direction of NGC 4214. Any model for this system must accommodate the lack of
an optical counterpart down to a limiting magnitude of 22.6 in the visible.


title: Global Dynamics in Galactic Triaxial Systems I

abstract:
  In this paper we present a theoretical analysis of the global dynamics in a
triaxial galactic system using a 3D integrable Hamiltonian as a simple
representation. We include a thorough discussion on the effect of adding a
generic non--integrable perturbation to the global dynamics of the system. We
adopt the triaxial Stackel Hamiltonian as the integrable model and compute its
resonance structure in order to understand its global dynamics when a
perturbation is introduced. Also do we take profit of this example in order to
provide a theoretical discussion about diffussive processes taking place in
phase space.


title: Spectral line variability amplitudes in AGNs

abstract:
  We present the results of a long-term variability campaign of very broad-line
AGNs with line widths broader than FWHM $>$ 5000 kms$^{-1}$. The main goal of
our investigation was to study whether the widths of the optical broad emission
lines are correlated with the optical intensity variations on timescales of
years. Our AGN sample consisted of 10 objects. We detected a significant
correlation between optical continuum variability amplitudes and H$\beta$
emission line widths (FWHM) and, to a lesser degree, between H$\beta$ line
intensity variations and H$\beta$ equivalent widths. We add the spectroscopic
data of variable AGNs from the literature to supplement our sample. The AGNs
from other optical variability campaigns with different line-widths helped to
improve the statistical significance of our very broad-line AGN sample. After
including the data on 35 additional galaxies, the correlation between optical
continuum variability amplitudes and H$\beta$ emission line widths becomes even
more significant and the probability that this is a random correlation drops to
0.7 percent.


title:
Modeling the Large Scale Structures of Astrophysical Jets in the
  Magnetically Dominated Limit

abstract:
  We suggest a new approach that could be used for modeling both the large
scale behavior of astrophysical jets and the magnetically dominated explosions
in astrophysics. We describe a method for modeling the injection of magnetic
fields and their subsequent evolution in a regime where the free energy is
magnetically dominated. The injected magnetic fields, along with their
associated currents, have both poloidal and toroidal components, and they are
not force free. The dynamic expansion driven by the Lorentz force of the
injected fields is studied using 3-dimensional ideal magnetohydrodynamic
simulations. The generic behavior of magnetic field expansion, the interactions
with the background medium, and the dependence on various parameters are
investigated.


title: LP 400-22, A very low-mass and high-velocity white dwarf

abstract:
  We report the identification of LP 400-22 (WD 2234+222) as a very low-mass
and high-velocity white dwarf. The ultraviolet GALEX and optical photometric
colors and a spectral line analysis of LP 400-22 show this star to have an
effective temperature of 11080+/-140 K and a surface gravity of log g =
6.32+/-0.08. Therefore, this is a helium core white dwarf with a mass of 0.17
M_solar. The tangential velocity of this white dwarf is 414+/-43 km/s, making
it one of the fastest moving white dwarfs known. We discuss probable
evolutionary scenarios for this remarkable object.


title:
Explosive Nucleosynthesis from GRB and Hypernova Progenitors: Direct
  Collapse versus Fallback

abstract:
  The collapsar engine behind long-duration gamma-ray bursts extracts the
energy released from the rapid accretion of a collapsing star onto a
stellar-massed black hole. In a collapsing star, this black hole can form in
two ways: the direct collapse of the stellar core into a black hole and the
delayed collapse of a black hole caused by fallback in a weak supernova
explosion. In the case of a delayed-collapse black hole, the strong
collapsar-driven explosion overtakes the weak supernova explosion before shock
breakout, and it is very difficult to distinguish this black hole formation
scenario from the direct collapse scenario. However, the delayed-collapse
mechanism, with its double explosion, produces explosive nucleosynthetic yields
that are very different from the direct collapse scenario. We present
1-dimensional studies of the nucleosynthetic yields from both black hole
formation scenarios, deriving differences and trends in their nucleosynthetic
yields.


title: Exploring the spectroscopic diversity of Type Ia Supernovae

abstract:
  The velocities and equivalent widths (EWs) of a set of absorption features
are measured for a sample of 28 well-observed Type Ia supernovae (SN Ia)
covering a wide range of properties. The values of these quantities at maximum
are obtained through interpolation/extrapolation and plotted against the
decline rate, and so are various line ratios. The SNe are divided according to
their velocity evolution into three classes defined in a previous work of
Benetti et al.: low velocity gradient (LVG), high velocity gradient (HVG) and
FAINT. It is found that all the LVG SNe have approximately uniform velocities
at B maximum, while the FAINT SNe have values that decrease with increasing
Delta m_15(B), and the HVG SNe have a large spread. The EWs of the Fe-dominated
features are approximately constant in all SNe, while those of Intermediate
mass element (IME) lines have larger values for intermediate decliners and
smaller values for brighter and FAINT SNe. The HVG SNe have stronger Si II
6355-A lines, with no correlation with Delta m_15(B). It is also shown that the
Si II 5972 A EW and three EW ratios, including one analogous to the R(Si II)
ratio introduced by Nugent et al., are good spectroscopic indicators of
luminosity. The data suggest that all LVG SNe have approximately constant
kinetic energy, since burning to IME extends to similar velocities. The FAINT
SNe may have somewhat lower energies. The large velocities and EWs of the IME
lines of HVG SNe appear correlated with each other, but are not correlated with
the presence of high-velocity features in the Ca II infrared triplet in the
earliest spectra for the SNe for which such data exist.


title: Active Galaxies in the UV

abstract:
  In this article we present different aspects of AGN studies demonstrating the
importance of the UV spectral range. Most important diagnostic lines for
studying the general physical conditions as well as the metalicities in the
central broad line region in AGN are emitted in the UV. The UV/FUV continuum in
AGN excites not only the emission lines in the immediate surrounding but it is
responsible for the ionization of the intergalactic medium in the early stages
of the universe. Variability studies of the emission line profiles of AGN in
the UV give us information on the structure and kinematics of the immediate
surrounding of the central supermassive black hole as well as on its mass
itself.


title:
Simulations of Mixed Morphology Supernova Remnants With Anisotropic
  Thermal Conduction

abstract:
  We explore the role of anisotropic thermal conduction on the evolution of
supernova remnants through interstellar media with a range of densities via
numerical simulations. We find that a remnant expanding in a dense environment
can produce centre-bright hard x-ray emission within 20 kyr, and centre-bright
soft x-ray emission within 60 kyr of the supernova event. In a more tenuous
environment, the appearance of a centre-bright structure in hard x-rays is
delayed until about 60 kyr. The soft x-ray emission from such a remnant may not
become centre bright during its observable lifetime. This can explain the
observations that show that mixed-morphology supernova remnants preferentially
occur close to denser, molecular environments. Remnants expanding into denser
environments tend to be smaller, making it easier for thermal conduction to
make larger changes in the temperatures of their hot gas bubbles. We show that
the lower temperatures make it very favorable to use high-stage ions as
diagnostics of the hot gas bubbles in SNRs. In particular, the distribution of
O VIII transitions from shell-bright at early epochs to centre-bright at later
epochs in the evolution of an SNR expanding in a dense ISM when the physics of
thermal conduction is included.


title: A toy model of a fake inflation

abstract:
  Discontinuities in non linear field theories propagate through null geodesics
in an effective metric that depends on its dynamics and on the background
geometry. Once information of the geometry of the universe comes mostly from
photons, one should carefully analyze the effects of possible nonlinearities on
Electrodynamics in the cosmic geometry. Such phenomenon of induced metric is
rather general and may occurs for any nonlinear theory independently of its
spin properties. We limit our analysis here to the simplest case of non linear
scalar field. We show that a class of theories that have been analyzed in the
literature, having regular configuration in the Minkowski space-time background
is such that the field propagates like free waves in an effective deSitter
geometry. The observation of these waves would led us to infer, erroneously,
that we live in a deSitter universe.


title: Gravitational lensing effects on the gamma-ray burst Hubble diagram

abstract:
  Gamma-Ray Bursts (GRBs) offer a potential way to extend the Hubble diagram to
very high redshifts and to constrain the nature of dark energy in a way
complementary to distant type Ia supernovae. However, gravitational lensing
systematically brightens distant GRBs through the magnification bias, in
addition to increasing the dispersions of distance measurements. We investigate
how the magnification bias limits the cosmological usage of GRBs. We perform
Monte-Carlo simulations of Swift GRBs assuming a cosmological constant
dominated universe and then constrain the dark energy equation of state
neglecting gravitational lens effects. The originally assumed model is
recovered with 68% confidence limit even when the dispersion of inferred
luminosities is comparable to that of type Ia supernovae. This implies that the
bias is not so drastic for Swift GRBs as to change constraints on dark energy
and its evolution. However, the precise degree of the bias in cosmological
parameter determinations depends strongly on the shape of the luminosity
function of GRBs. Therefore, an accurate determination of the shape of the
luminosity function is required to remove the effect of gravitational lensing
and to obtain an unbiased Hubble diagram.


title: Black-Hole Accretion Disc as an Analogue Gravity Model

abstract:
  We formulate and solve the equations governing the transonic behaviour of a
general relativistic black-hole accretion disc with non-zero advection
velocity. We demonstrate that a relativistic Rankine-Hugoniot shock may form
leading to the formation of accretion powered outflow. We show that the
critical points of transonic discs generally do not coincide with the
corresponding sonic points. The collection of such sonic points forms an
axisymmetric hypersurface, generators of which are the acoustic null geodesics,
i.e. the phonon trajectories. Such a surface is shown to be identical with an
acoustic event horizon. The acoustic surface gravity and the corresponding
analogue horizon temperature $T_{AH}$ at the acoustic horizon are then computed
in terms of fundamental accretion parameters. Physically, the analogue
temperature is associated with the thermal phonon radiation analogous to the
Hawking radiation of the black-hole horizon.Thus, an axisymmetric black-hole
accretion disc is established as a natural example of the classical analogue
gravity model, for which two kinds of horizon exist simultaneously. We have
shown that for some values of astrophysically relevant accretion parameters,
the analogue temperature exceeds the corresponding Hawking temperature. We
point out that acoustic {\it white holes} can also be generated for a
multi-transonic black-hole accretion with a shock. Such a white hole, produced
at the shock, is always flanked by two acoustic black holes generated at the
inner and the outer sonic points. Finally, we discuss possible applications of
our work to other astrophysical events which may exhibit analogue effects.


title: Radio-Excess IRAS Galaxies: IV. Optical Spectroscopy

abstract:
  This is the fourth in our series of papers investigating radio-excess
galaxies, which have radio emission associated with an active nucleus but which
do not fit into the traditional categories of either radio-loud or radio-quiet
active galaxies. In this paper, we present optical spectra of our sample of
FIR-luminous radio-excess galaxies. Optical emission line diagnostics are used
to determine the dominant source of the ionizing radiation. We find that radio
excess is an excellent indicator of the presence of an active nucleus: the
radio-excess sample contains a much higher fraction of AGN than samples
selected on FIR luminosity alone, or using other criteria such as warm FIR
colors. Several objects have ambiguous classifications and are likely to be
composite objects with mixed excitation. The type of optical spectrum appears
to be associated with the radio-loudness: radio-loud objects may be more `pure'
AGN than radio-intermediate objects. We find strong evidence for interaction
between the radio plasma and the surrounding gas. The jet energy fluxes of the
radio-excess objects, inferred from the [O III] luminosities, are lower than in
powerful radio sources, consistent with our previous results. We conclude that
the jets of radio-intermediate sources are intrinsically weaker than those in
sources with more powerful radio emission. A significant fraction of the sample
spectra show post-starburst stellar continuum, with A-star absorption lines,
consistent with the large fraction of merging or disturbed host galaxies in the
sample. The ages of the radio sources are significantly less than those of A
stars indicating that, if the radio sources are associated with merging
activity, there is a delay between the interaction and the initiation of the
radio activity. (Abridged.)


title:
Where are the z=4 Lyman Break Galaxies? Results from Conditional
  Luminosity Function Models of Luminosity-dependent Correlation Functions

abstract:
  Using the conditional luminosity function (CLF) -- the luminosity
distribution of galaxies in a dark matter halo -- as a way to model galaxy
statistics, we study how z=4 Lyman Break Galaxies (LBGs) are distributed in
dark matter halos. For this purpose, we measure luminosity-dependent clustering
of LBGs in the Subaru/XMM-Newton Deep Field by separating a sample of 16,920
galaxies to three magnitude bins in i'-band between 24.5 and 27.5. Our models
fits to data show a possible trend for more luminous galaxies to appear as
satellites in more massive halos. The satellite fraction of galaxies at z=4 in
these magnitude bins is 0.13 to 0.3, 0.09 to 0.22, and 0.03 to 0.14,
respectively, where the 1 sigma ranges account for differences coming from two
different estimates of the z=4 LF from the literature. To jointly explain the
LF and the large-scale linear bias factor of z=4 LBGs as a function of rest-UV
luminosity requires central galaxies to be brighter in UV at z =4 than
present-day galaxies in same dark matter mass halos. Moreover, UV luminosity of
central galaxies in halos with total mass greater than roughly 10^{12} M_sun
must decrease from z=4 to today by an amount more than the luminosity change
for galaxies in halos below this mass. This mass-dependent luminosity evolution
is preferred at more than 3 sigma confidence level compared to a
pure-luminosity evolution scenario where all galaxies decrease in luminosity by
the same amount from z=4 to today. The scenario preferred by the data is
consistent with the ``down-sizing'' picture of galaxy evolution.


title:
The spectral energy distribution of PKS 2004-447: a compact
  steep-spectrum source and possible radio-loud narrow-line Seyfert 1 galaxy

abstract:
  (abridged) The spectral energy distribution (SED) of the compact steep
spectrum (CSS) source and possible radio-loud narrow-line Seyfert 1 galaxy
(NLS1), PKS2004-447, is presented. Five out of six well studied RL NLS1 share
this dual classification (optically defined as a NLS1 with radio definition of
a CSS or giga-hertz peaked spectrum (GPS) source). The SED is created from
simultaneous observations at radio (ATCA), optical/NIR (Siding Spring) and
UV/X-ray (XMM-Newton) wavelengths. The X-ray data show evidence of short-term
variability, a possible soft excess, and negligible absorption. Together with
the rest of the SED, the X-ray emission is excessive in comparison to
synchrotron plus synchrotron self-Compton (SSC) models. The SED can be
described with a two component model consisting of extended synchrotron/SSC
emission with Comptonisation in the X-rays, though SSC models with a very high
electron-to-magnetic energy density ratio cannot be excluded either. The peak
emission in the SED appears to be in the near infrared, which can be attributed
to thermal emission from a dusty torus. Analysis of a non-contemporaneous, low
resolution optical spectrum suggests that the narrow-line region (NLR) is much
more reddened than the X-ray emitting region suggesting that the gas-to-dust
ratio in PKS2004-447 may be very different then in our own Galaxy. Long-term
radio monitoring of PKS2004-447 shows a rather constant light curve over nearly
a six month period with the exception of one outburst when the 6.65GHz flux
increased by ~35% over 19 days. In comparison to general samples of GPS
sources, which appear to be X-ray weak, NLS1-CSS/GPS sources possess stronger
X-ray emission relative to radio, and lower intrinsic absorption than GPS
sources of similar X-ray luminosity.


title: Unveiling the nature of INTEGRAL sources through optical spectroscopy

abstract:
  Since its launch on October 2002 the INTEGRAL satellite is performing an deep
survey of the hard X-ray sky with unprecedented sensitivity and positional
accuracy. This allowed pinpointing, through positional cross-correlation with
catalogs at longer wavelengths, possible optical/near-infrared candidates for
the hard X-ray sources of still unknown nature. In this presentation I will
describe this work as well as the observational activities aimed at
determining, through optical spectroscopy, the nature of the unknown INTEGRAL
sources, along with the main results of this search. Future prospects about
this identification program will also be illustrated.


title:
Unveiling the nature of INTEGRAL objects through optical spectroscopy.
  IV. A study of six new hard X-ray sources

abstract:
  We present further results from our ongoing optical spectrophotometric
campaign at the Astronomical Observatory of Bologna in Loiano (Italy) on
unidentified hard X-ray sources detected by INTEGRAL. We observed
spectroscopically the putative optical counterparts of the INTEGRAL sources IGR
J00234+6141, IGR J01583+6713, IGR J06074+2205, IGR J13091+1137 and IGR
J20286+2544. We find that the first two are Galactic objects, namely a
Cataclysmic Variable at a distance of about 300 pc and a Be/X transient
High-Mass X-ray Binary (HMXB) located at about 6.4 kpc, respectively, whereas
the last one is identified with MCG +04-48-002, a Starburst/HII galaxy at
redshift z = 0.013 hiding a Seyfert 2 nucleus. We identify IGR J13091+1137 as
the (likely Seyfert 2 type) active nucleus of galaxy NGC 4992, which we
classify as an X-ray Bright, Optically Normal Galaxy; this is the first example
of this type of object to be detected by INTEGRAL, and one of the closest of
this class. We moreover confirm the possible Be/X nature of IGR J06074+2205,
and we estimate it to be at a distance of about 1 kpc. We also reexamine the
spectrum of the z = 0.087 elliptical radio galaxy PKS 0352-686, the possible
counterpart of the INTEGRAL source IGR J03532-6829, and we find that it is a BL
Lac. Physical parameters for these sources are also evaluated by discussing our
findings in the context of the available multiwavelength information. These
identifications further stress the importance of INTEGRAL in the study of the
hard X-ray spectrum of Active Galactic Nuclei, HMXBs and Cataclysmic Variables.


title: Heating and cooling of the intergalactic medium by resonance photons

abstract:
  During the epoch of reionization a large number of photons were produced with
frequencies below the hydrogen Lyman limit. After redshifting into the closest
resonance, these photons underwent multiple scatterings with atoms. We examine
the effect of these scatterings on the temperature of the neutral intergalactic
medium (IGM). Continuum photons, emitted between the Ly_alpha and Ly_gamma
frequencies, heat the gas after being redshifted into the H Ly_alpha or D
Ly_beta resonance. By contrast, photons emitted between the Ly_gamma and
Ly-limit frequencies, produce effective cooling of the gas. Prior to
reionization, the equilibrium temperature of ~100 K for hydrogen and helium
atoms is set by these two competing processes. At the same time, Ly_beta
resonance photons thermally decouple deuterium from other species, raising its
temperature as high as 10^4 K. Our results have important consequences for the
cosmic 21-cm background and the entropy floor of the early IGM which can affect
star formation and reionization.


title: Reconstructing holographic quintessence

abstract:
  The holographic dark energy model is an attempt for probing the nature of
dark energy within the framework of quantum gravity. The dimensionless
parameter $c$ determines the main property of the holographic dark energy. With
the choice of $c\geq 1$, the holographic dark energy can be described
completely by a quintessence scalar field. In this paper, we show this
quintessential description of the holographic dark energy with $c\geq 1$ and
reconstruct the potential of the quintessence as well as the dynamics of the
scalar field.


title: On the Growth of Perturbations as a Test of Dark Energy

abstract:
  The strongest evidence for dark energy comes presently from geometric
techniques such as the supernova distance-redshift relation. By combining the
measured expansion history with the Friedmann equation one determines the
energy density and its time evolution, hence the equation of state of dark
energy. Because these methods rely on the Friedmann equation which has not been
independently tested it is desirable to find alternative methods that work for
both general relativity and other theories of gravity.
  Assuming that sufficiently large patches of a perturbed Robertson-Walker
spacetime evolve like separate Robertson-Walker universes, that shear stress is
unimportant on large scales and that energy and momentum are locally conserved,
we derive several relations between long-wavelength metric and matter
perturbations. These relations include generalizations of the initial-value
constraints of general relativity. For a class of theories including general
relativity we reduce the long-wavelength metric, density, and velocity
potential perturbations to quadratures including curvature perturbations,
entropy perturbations, and the effects of nonzero background curvature. When
combined with the expansion history measured geometrically, the long-wavelength
solution provide a test that may distinguish modified gravity from other
explanations of dark energy.


title:
Ion dynamics and the magnetorotational instability in weakly-ionized
  discs

abstract:
  The magnetorotational instability (MRI) of a weakly ionized, differentially
rotating, magnetized plasma disk is investigated in the multi-fluid framework.
The disk is threaded by a uniform vertical magnetic field and charge is carried
by electrons and ions only. The inclusion of ion dynamics causes significant
modification to the conductivity tensor in a weakly ionized disk. The parallel,
Pedersen and Hall component of conductivity tensor become time dependent
quantities resulting in the AC and DC part of the conductivity. The
conductivity may change sign leading to the significant modification of the
parameter window in which MRI may operate.
  The effect of ambipolar and Hall diffusion on the linear growth of the MRI is
examined in the presence of time dependent conductivity tensor. We find that
the growth rate in ambipolar regime can become somewhat larger than the
rotational frequency, especially when the departure from ideal MHD is
significant. Further, the instability operates on large scale lengths. This has
important implication for the angular momentum transport in the disk.


title: The Central Engines of 19 LINERs as Viewed by Chandra

abstract:
  Using archival Chandra observations of 19 LINERs we explore the X-ray
properties of their inner kiloparsec to determine the origin of their nuclear
X-ray emission, to investigate the presence of an AGN, and to identify the
power source of the optical emission lines. The relative numbers of LINER types
in our sample are similar to those in optical spectroscopic surveys. We find
that diffuse, thermal emission is very common and is concentrated within the
central few hundred parsec. The average spectra of the hot gas in spirals and
ellipticals are very similar to those of normal galaxies. They can be fitted
with a thermal plasma (kT~0.5 keV) plus a power law (photon index of 1.3-1.5)
model. There are on average 3 detected point sources in their inner kiloparsec
with L(0.5-10 keV)~10^37-10^40 erg/s. The average cumulative luminosity
functions for sources in spirals and ellipticals are identical to those of
normal galaxies. In the innermost circle of 2.5" radius in each galaxy we find
an AGN in 12 of the 19 galaxies. The AGNs contribute a median of 60% of the
0.5-10 keV luminosity of the central 2.5" region, they have luminosities of
10^37-10^39 erg/s (Eddington ratios 10^-8 to 10^-5). The ionizing luminosity of
the AGNs is not enough to power the observed optical emission lines in this
particular sample. Thus, we suggest that the lines are powered either by the
mechanical interaction of an AGN jet (or wind) with the circumnuclear gas, or
by stellar processes, e.g. photoionization by post-AGB stars or young stars.


title: On the one loop corrections to inflation and the CMB anisotropies

abstract:
  We investigate the one loop effective potential of inflation in a standard
model of chaotic inflation. The leading one loop corrections to the effective
inflaton potential are evaluated in the quasi de Sitter background, and we
estimate the one loop correction to the two-point function of the inflaton
perturbations in the Hartree approximation. In this approximation, the one loop
corrections depends on the total number of e-foldings of inflation and the
maximal effect is estimated to be a correction to the power spectrum of a few
percent. However, such a correction may be difficult to disentangle from the
background in the simplest scenario.


title:
Radio observations of comet 9P/Tempel 1 with the Australia Telescope
  facilities during the Deep Impact encounter

abstract:
  We present radio observations of comet 9P/Tempel 1 associated with the Deep
Impact spacecraft collision of 2005 July 4. Weak 18-cm OH emission was detected
with the Parkes 64-m telescope, in data averaged over July 4 to 6, at a level
of 12 +/- 3 mJy km/s, corresponding to OH production rate 2.8 x 10^{28}
molecules/second (Despois et al. inversion model, or 1.0 x 10^{28} /s for the
Schleicher & A'Hearn model). We did not detect the HCN 1-0 line with the Mopra
22-m telescope over the period July 2 to 6. The 3 sigma limit of 0.06 K km/s
for HCN on July 4 after the impact gives the limit to the HCN production rate
of < 1.8 x 10^{25} /s. We did not detect the HCN 1-0 line, 6.7 GHz CH_3OH line
or 3.4-mm continuum with the Australia Telescope Compact Array (ATCA) on July
4, giving further limits on any small-scale structure due to an outburst. The 3
sigma limit on HCN emission of 2.5 K km/s from the ATCA around impact
corresponds to limit < 4 x 10^{29} HCN molecules released by the impact.


title: Structure formation in the quasispherical Szekeres model

abstract:
  Structure formation in the Szekeres model is investigated. Since the Szekeres
model is an inhomogeneous model with no symmetries, it is possible to examine
the interaction of neighboring structures and its impact on the growth of a
density contrast. It has been found that the mass flow from voids to clusters
enhances the growth of the density contrast. In the model presented here, the
growth of the density contrast is almost 8 times faster than in the linear
approach.


title: Gravitational Field of Fractal Distribution of Particles

abstract:
  In this paper we consider the gravitational field of fractal distribution of
particles. To describe fractal distribution, we use the fractional integrals.
The fractional integrals are considered as approximations of integrals on
fractals. Using the fractional generalization of the Gauss's law, we consider
the simple examples of the fields of homogeneous fractal distribution. The
examples of gravitational moments for fractal distribution are considered.

categories: astro-ph nlin.CD physics.class-ph physics.space-ph


title:
Einstein and Jordan frames reconciled: a frame-invariant approach to
  scalar-tensor cosmology

abstract:
  Scalar-Tensor theories of gravity can be formulated in different frames, most
notably, the Einstein and the Jordan one. While some debate still persists in
the literature on the physical status of the different frames, a frame
transformation in Scalar-Tensor theories amounts to a local redefinition of the
metric, and then should not affect physical results. We analyze the issue in a
cosmological context. In particular, we define all the relevant observables
(redshift, distances, cross-sections, ...) in terms of frame-independent
quantities. Then, we give a frame-independent formulation of the Boltzmann
equation, and outline its use in relevant examples such as particle freeze-out
and the evolution of the CMB photon distribution function. Finally, we derive
the gravitational equations for the frame-independent quantities at first order
in perturbation theory. From a practical point of view, the present approach
allows the simultaneous implementation of the good aspects of the two frames in
a clear and straightforward way.


title:
A Survey of Merger Remnants III: Are Merger Remnants Supported by
  Rotation or Anisotropy

abstract:
  A growing body of observational evidence suggests that the luminosity,
photometric shape and amount of rotational or anisotropical support in
elliptical galaxies may provide vital clues to how they formed. Elliptical
galaxies appear to fall into two distinct categories based on these parameters:
bright, boxy shaped, with little or no rotation, and less luminous, disky
shaped with significant rotation. One viable formation scenario is the ``Merger
hypothesis,'' in which two disk galaxies merge to form a new elliptical galaxy.
A comparison of the luminosity, photometric shape, and amount of rotation in
advanced merger remnants may shed more light on the possible formation
scenarios of elliptical galaxies. Yet, little observational data exists for
such merger remnants. This paper is the third in a series investigating the
photometric and kinematic properties of a sample of 51 optically selected
advanced merger remnants. Presented here are K-band isophotal shapes and
spatially resolved kinematics for a sub-sample of 37 merger remnants. The
results show that ~ 11% of the sample are boxy, and anisotropically supported
while ~ 47% are disky, and rotationally supported. The remainder of the sample
show variations among expected correlations between shape and rotation. This
may suggest that the isophotal shapes are still ``in flux.'' There does appear
to be a lower limit to the amount of anisotropy observed in the merger
remnants. This may provide an observational diagnostic for discriminating among
formation scenarios in elliptical galaxies.


title: Molecular outflows around high-mass young stellar objects

abstract:
  We present a study of molecular outflows using high-resolution mapping of the
CO (1-0) line emission toward eight relatively nearby 6.7 GHz methanol masers,
which are associated with massive star forming regions. Outflows were detected
in seven out of eight sources, and five of them clearly show bipolar or
multiple outflow morphologies. These outflows have typical masses of a few
solar masses, momenta of tens of $M_{\odot}$ km s$^{-1}$, kinetic energies of
$\sim$ 10$^{45}$ ergs, and the mass entrainment rate of a few $10^{-5}
M_{\odot}$ yr$^{-1}$. They have significantly more mass and kinetic energy than
their low-mass counterparts. In some of the sources, the massive outflow is
obviously associated with a particular massive star in the cluster, while in
others the origin remains uncertain. The high detection rate of outflows toward
methanol masers suggests that the outflow phase of massive protostars
encompasses the methanol maser phase.


title:
An Association in the Aquila Star-Forming Region: High Resolution
  Infrared Spectroscopy of T Tauri Stars

abstract:
  We present the properties of a group of young stars associated with the
well-studied T Tauri star system AS 353, located in the Aquila star-forming
region. The association is identified using radial velocity measurements of
sample objects selected from the Herbig and Bell Catalog based on their spatial
proximity to AS 353. Radial velocities of nine objects were measured from
multi-epoch high-resolution (R~30,000) H-band spectra obtained with NIRSPEC on
Keck II. High-resolution K-band spectra were also obtained for most of the
sample objects. Spectral types and rotational velocities are determined for all
objects in the sample. The multi-epoch H-band spectra were examined for radial
velocity variations in order to detect possible spectroscopic binaries. Eight
of the nine objects have radial velocities that are consistent within the
1-sigma scatter of the sample. From their mean of -8.6 km/s these eight objects
have a standard deviation of 2 km/s, which suggests that the sample stars are
related. The ninth object shows significant radial velocity variations between
epochs, characteristic of a spectroscopic binary. The overall multiplicity of
the sample is high; we observed 13 stars in seven systems, identifying three
new candidate binary components in this project. Many of the spectra reveal
hydrogen emission lines typical of strong accretion processes, indicating that
most of these objects harbor circumstellar disks and are less than a few
million years old. We discuss possible interpretations of the enigmatic pure
emission line spectrum of HBC 684. This work represents the highest spectral
resolution infrared observations to date of these intriguing, nearby young
stars.