title: From Galaxy-Galaxy Lensing to Cosmological Parameters

abstract:
  Galaxy-galaxy lensing measures the mean excess surface density DS(r) around a
sample of lensing galaxies. We develop a method for combining DS(r) with the
galaxy correlation function xi_gg(r) to constrain Omega_m and sigma_8, going
beyond the linear bias model to reach the level of accuracy demanded by current
and future measurements. We adopt the halo occupation distribution (HOD)
framework, and we test its applicability to this problem by examining the
effects of replacing satellite galaxies in the halos of an SPH simulation with
randomly selected dark matter particles from the same halos. The difference
between dark matter and satellite galaxy radial profiles has a ~10% effect on
DS(r) at r<1 Mpc/h. However, if radial profiles are matched, the remaining
impact of individual subhalos around satellite galaxies and environmental
dependence of the HOD at fixed halo mass is <5% in DS(r) for 0.1<r<15 Mpc/h. We
develop an analytic approximation for DS(r) that incorporates halo exclusion
and scale-dependent halo bias, and we demonstrate its accuracy with tests
against a suite of populated N-body simulations. We use the analytic model to
investigate the dependence of DS(r) and the galaxy-matter correlation function
xi_gm(r) on Omega_m and sigma_8, once HOD parameters for a given cosmological
model are pinned down by matching xi_gg(r). The linear bias prediction is
accurate for r>2 Mpc/h, but it fails at the 30-50% level on smaller scales. The
scaling of DS(r) ~ Omega_m^a(r) sigma_8^b(r) approaches the linear bias
expectation a=b=1 at r>10 Mpc/h, but a(r) and b(r) vary from 0.8 to 1.6 at
smaller r. We calculate a fiducial DS(r) and scaling indices a(r) and b(r) for
two SDSS galaxy samples; galaxy-galaxy lensing measurements for these samples
can be combined with our predictions to constrain Omega_m and sigma_8.


title:
The Evolution of Rest-Frame K-band Properties of Early-Type Galaxies
  from z=1 to the Present

abstract:
  We measure the evolution of the rest-frame K-band Fundamental Plane from z=1
to the present by using IRAC imaging of a sample of early-type galaxies in the
Chandra Deep Field-South at z~1 with accurately measured dynamical masses. We
find that $M/L_K$ evolves as $\Delta\ln{(M/L_K)}=(-1.18\pm0.10)z$, which is
slower than in the B-band ($\Delta\ln{(M/L_B)}=(-1.46\pm0.09)z$). In the B-band
the evolution has been demonstrated to be strongly mass dependent. In the
K-band we find a weaker trend: galaxies more massive than
$M=2\times10^{11}M_{\odot}$ evolve as $\Delta\ln{(M/L_K)}=(-1.01\pm0.16)z$;
less massive galaxies evolve as $\Delta\ln{(M/L_K)}=(-1.27\pm0.11)z$. As
expected from stellar population models the evolution in $M/L_K$ is slower than
the evolution in $M/L_B$. However, when we make a quantitative comparison, we
find that the single burst Bruzual-Charlot models do not fit the results well,
unless large dust opacities are allowed at z=1. Models with a flat IMF fit
better, Maraston models with a different treatment of AGB stars fit best. These
results show that the interpretation of rest-frame near-IR photometry is
severely hampered by model uncertainties and therefore that the determination
of galaxy masses from rest-frame near-IR photometry may be harder than was
thought before.


title: Metal Enrichment Discriminators of Cold Fronts

abstract:
  Cold fronts are sharp surface brightness discontinuities characterized by a
jump in gas temperature accompanied by a decline in X-ray surface brightness
such that the gas pressure remains continuous across the front and, thus, these
structures differ from bow shocks. Models suggest that cold fronts can be
generated by external mechanisms involving the accretion of a subsystem with a
remnant "cold core". However, internal mechanisms can also create cold fronts,
such as gravitational scattering of subclumps or cD oscillation around the
bottom of the potential well. These competing models for their formation can be
discriminated through the measurements of the SN Type contamination across the
front, which in turn can be determined from metal abundance ratios as measured
from an ensemble of elements. Here we present the preliminary results of such
analysis using a sample of clusters observed with Chandra.


title: Hot Jupiters: Lands of Plenty

abstract:
  In late August 2005, 80 researchers from more than 15 countries convened for
a 4-day conference entitled ``The Tenth Anniversary of 51 Peg b: Status and
Prospects for Hot Jupiter Studies''. The meeting was held at l'Observatoire de
Haute-Provence, the location of the 1.93-m telescope and ELODIE spectrograph
used to discover the planetary companion to 51 Peg roughly 10 years ago. I
summarize several dominant themes that emerged from the meeting, including (i)
recent improvements in the precision of radial velocity measurements of nearby,
Sun-like stars, (ii) the continued value of individual, newly-discovered
planets of novel character to expand the parameter space with which the theory
must contend, and (iii) the crucial role of space-based observatories in
efforts to characterize hot Jupiter planets. I also present the returns of an
informal poll of the conference attendees conducted on the last day of the
meeting, which may be amusing to revisit a decade hence.


title: Nucleosynthesis in Neutrino-Driven Supernovae

abstract:
  Core collapse supernovae are the leading actor in the story of the cosmic
origin of the chemical elements. Existing models, which generally assume
spherical symmetry and parameterize the explosion, have been able to broadly
replicate the observed elemental pattern. However, inclusion of neutrino
interactions produces noticeable improvement in the composition of the ejecta
when compared to observations. Neutrino interactions may also provide a
supernova source for light p-process nuclei.


title: A Double-Mode RR Lyrae Star with a Strong Fundamental Mode Component

abstract:
  NSVS 5222076, a thirteenth magnitude star in the Northern Sky Variability
Survey, was identified by Oaster as a possible new double-mode RR Lyrae star.
We confirm the double-mode nature of NSVS 5222076, supplementing the survey
data with new V band photometry. NSVS 5222076 has a fundamental mode period of
0.4940 day and a first overtone period of 0.3668 day. Its fundamental mode
light curve has an amplitude twice as large as that of the first overtone mode,
a ratio very rarely seen. Data from the literature are used to discuss the
location in the Petersen diagram of double-mode RR Lyrae stars having strong
fundamental mode pulsation. Such stars tend to occur toward the short period
end of the Petersen diagram, and NSVS 5222976 is no exception to this rule.


title: Weak compressible magnetohydrodynamic turbulence in the solar corona

abstract:
  This Letter presents a calculation of the power spectra of weakly turbulent
Alfven waves and fast magnetosonic waves ("fast waves") in low-beta plasmas. It
is shown that three-wave interactions transfer energy to high-frequency fast
waves and, to a lesser extent, high-frequency Alfven waves. MHD turbulence is
thus a promising mechanism for producing the high-frequency waves needed to
explain the anisotropic heating of minor ions in the solar corona.


title: Transient radio bursts from rotating neutron stars

abstract:
  The `radio sky' is relatively unexplored for transient signals, although the
potential of radio-transient searches is high, as demonstrated recently by the
discovery of a previously unknown type of source which varies on timescales of
minutes to hours. Here we report a new large-scale search for radio sources
varying on much shorter timescales. This has revealed 11 objects characterized
by single, dispersed bursts having durations between 2 and 30 ms. The average
time intervals between bursts range from 4 minutes to 3 hours, with radio
emission typically detectable for < 1 s per day. From an analysis of the burst
arrival times, we have identified periodicities in the range 0.4 - 7 s for ten
of the 11 sources, suggesting a rotating neutron star origin. Despite the small
number of sources presently detected, their ephemeral nature implies a total
Galactic population which significantly exceeds that of the regularly pulsing
radio pulsars. Five of the ten sources have periods greater than 4 s, and
period derivatives have been measured for three of the sources, with one having
a very high inferred magnetic field of 5e13 G, suggesting that this new
population is related to other classes of isolated neutron stars observed at
X-ray and gamma-ray wavelengths.


title:
The Energetics and Environment of the Short-GRB Afterglows 050709 and
  050724

abstract:
  We use the available radio, optical and X-ray measurements for the afterglows
of the short bursts 050709 and 050724 to constrain the blast-wave energy, its
collimation and the density of the circumburst medium. For GRB 050709 (whose
duration was 0.07 s), we identify two models: i) a high-density solution, where
the ejecta are collimated in a jet of half-angle theta_{jet} > 6 deg and
interact with a medium of particle density 10^{-4}/cc < n < 0.1/cc, and ii) a
low-density solution with theta_{jet} > 2 deg and n < 10^{-5}/cc. These density
ranges are compatible with those expected in the vicinity of the host galaxy
and in the intergalactic medium, lending support to the hypothesis that the
progenitor of GRB 050907 is a NS-NS or NS-BH merger. For GRB 050724 (which last
3 s), we obtain 0.1/cc < n < 1000/cc and theta_{jet} > 8 deg. The range of
allowed densities shows that this burst occurred in the intragalactic
environment. The dynamical parameters of the high-density model for the GRB
afterglow 050709 are similar to those for 050724. If these parameters are
representative for short-GRB outflows, then these jets are less collimated and
have a lower kinetic energy than those of long bursts, which suggests that GRB
jets are not magnetically collimated and are powered by the gravitational
energy of the torus. Evidently, the analysis of more short-GRB afterglows is
required for a more robust conclusion.


title: Submillimeter studies of circumstellar disks in Taurus and Orion

abstract:
  We highlight two recent studies of circumstellar disks in the Taurus and
Orion star forming regions. Using the JCMT and CSO, we measure disk fluxes in
Taurus over a wide range of submillimeter wavelengths and determine the
frequency dependence of the dust opacity. We find clear evidence for a
systematic change in its behavior with time, most readily explained by grain
growth. Using the SMA, we observed the protoplanetary disks (proplyds) in the
Orion Trapezium cluster. The combination of high resolution, high frequency,
and high sensitivity that this instrument provides made it possible to resolve
disks from one another, distinguish their emission from background cloud
material and surrounding ionized gas, and to detect thermal dust emission. This
allowed us to make the first mass measurements of the proplyds and to assess
their viability for planet formation.


title:
Thermal X-Ray Iron Line Emission from the Galactic Center Black Hole
  Sagittarius A*

abstract:
  We model thermal X-ray emission from the accreting supermassive black hole
Sagittarius A* at the Galactic Center. For the region inside
$1.^{\prime\prime}5$ of the center, we use a {generalized} radiatively
inefficient accretion flow (RIAF) model, and for the region out to
$10^{\prime\prime}$ we use published models of the ambient hot gas. We
calculate the equivalent widths of Hydrogen-like and Helium-like emission lines
of various elements, notably iron. We predict that a strong Helium-like iron
line with an equivalent width $\sim1$ keV should be emitted by both the
external medium and the RIAF. The equivalent width in the external medium is
sensitive to the metallicity $Z$ of the gas as well as the mean temperature.
For reasonable choices of these parameters, the calculated results agree with
Chandra's detection of an iron line with an equivalent width of 1.3 keV within
$10^{\prime\prime}$. The emission from within $1.^{\prime\prime}5$ is not
sensitive to the external temperature, but is sensitive to the density and,
especially, temperature profile inside the Bondi radius. For the range of
profiles we consider, we calculate the equivalent width of the iron line to be
$\sim0.6-1.5 (Z/Z_\odot)$ keV, where $Z_\odot$ is the solar metallicity. We
present a new Chandra spectrum of the quiescent emission within
$1.^{\prime\prime}5$ of Sgr A*. The measured equivalent width of the iron line
is 0.7 keV. Although this measurement has a large uncertainty, it is consistent
with our predictions, provided the metallicity of the gas is approximately
solar.


title:
TeVeS Cosmology : Covariant formalism for the background evolution and
  linear perturbation theory

abstract:
  A relativistic theory of gravity has recently been proposed by Bekenstein,
where gravity is mediated by a tensor, a vector and a scalar field, thus called
TeVeS. The theory aims at modifying gravity in such a way as to reproduce
Milgrom's MOdified Newtonian Dynamics (MOND) in the weak field,
non-relativistic limit, which provides a framework to solve the missing mass
problem in galaxies without invoking dark matter. In this paper I apply a
covariant approach to formulate the cosmological equations for this theory, for
both the background and linear perturbations. I derive the necessary perturbed
equations for scalar, vector and tensor modes without adhering to a particular
gauge. Special gauges are considered in the appendix.


title: The large-scale angular correlations in CMB temperature maps

abstract:
  Observations show that the Cosmic Microwave Background (CMB) contains tiny
variations at the 10^{-5} level around its black-body equilibrium temperature.
The detection of these temperature fluctuations provides to modern Cosmology
evidence for the existence of primordial density perturbations that seeded all
the structures presently observed. The vast majority of the cosmological
information is contained in the 2-point temperature function, which measures
the angular correlation of these temperature fluctuations distributed on the
celestial sphere. Here we study such angular correlations using a recently
introduced statistic-geometrical method. Moreover, we use Monte Carlo simulated
CMB temperature maps to show the equivalence of this method with the 2-point
temperature function (best known as the 2-Point Angular Correlation Function).
We also investigate here the robustness of this new method under possible
divisions of the original catalog-data in sub-catalogs. Finally, we show some
applications of this new method to simple cases.


title:
First Results from a Photometric Survey of Strong Gravitational Lens
  Environments

abstract:
  Many strong gravitational lenses lie in complex environments, such as poor
groups of galaxies, that significantly bias conclusions from lens analyses. We
are undertaking a photometric survey of all known galaxy-mass strong lenses to
characterize their environments and include them in careful lens modeling, and
to build a large, uniform sample of galaxy groups at intermediate redshifts for
evolutionary studies. In this paper we present wide-field photometry of the
environments of twelve lens systems with 0.24 < z_lens < 0.5. Using a
red-sequence identifying technique, we find that eight of the twelve lenses lie
in groups, and that ten group-like structures are projected along the line of
sight towards seven of these lenses. Follow-up spectroscopy of a subset of
these fields confirms these results. For lenses in groups, the group centroid
position is consistent with the direction of the external tidal shear required
by lens models. Lens galaxies are not all super-L_* ellipticals; the median
lens luminosity is < L_*, and the distribution of lens luminosities extends 3
magnitudes below L_* (in agreement with theoretical models). Only two of the
lenses in groups are the brightest group galaxy, in qualitative agreement with
theoretical predictions. As in the local Universe, the highest
velocity-dispersion groups contain a brightest member spatially coincident with
the group centroid, whereas lower-dispersion groups tend to have an offset
brightest group galaxy. This suggests that higher-dispersion groups are more
dynamically relaxed than lower-dispersion groups and that at least some evolved
groups exist by z ~ 0.5.


title: A Spectroscopic Study of the Environments of Gravitational Lens Galaxies

abstract:
  (Abridged) We present the first results from our spectroscopic survey of the
environments of strong gravitational lenses. The lens galaxy belongs to a poor
group of galaxies in six of the eight systems in our sample. We discover three
new groups associated with the lens galaxies of BRI 0952-0115 (five members),
MG 1654+1346 (seven members), and B2114+022 (five members). We more than double
the number of members for another three previously known groups around the
lenses MG 0751+2716 (13 total members), PG 1115+080 (13 total members), and
B1422+231 (16 total members). We determine the kinematics of the six groups,
including their mean velocities, velocity dispersions, and projected spatial
centroids. The velocity dispersions of the groups range from 110 +170, -80 to
470 +100, -90 km/s. In at least three of the lenses -- MG0751, PG1115, and
B1422 -- the group environment significantly affects the lens potential. These
lenses happen to be the quadruply-imaged ones in our sample, which suggests a
connection between image configuration and environment. The lens galaxy is the
brightest member in fewer than half of the groups. Our survey also allows us to
assess for the first time whether mass structures along the line of sight are
important for lensing. We first show that, in principle, the lens potential may
be affected by line-of-sight structures over a wide range of spatial and
redshift offsets from the lens. We then quantify real line-of-sight effects
using our survey and find that at least four of the eight lens fields have
substantial interloping structures close in projection to the lens, and at
least one of those structures (in the field of MG0751) significantly affects
the lens potential.


title: Introduction to neutrino cosmology

abstract:
  I review the basics of neutrino cosmology, from the question of neutrino
decoupling and the presence of sterile neutrinos to the effects of neutrinos on
the cosmic microwave background and large scale structure. Particular emphasis
is put on cosmological neutrino mass measurements, both the present bounds and
the future prospects.


title:
Power transfer in nonlinear gravitational clustering and asymptotic
  universality

abstract:
  We study the non linear gravitational clustering of collisionless particles
in an expanding background using an integro-differential equation for the
gravitational potential. In particular, we address the question of how the
nonlinear mode-mode coupling transfers power from one scale to another in the
Fourier space if the initial power spectrum is sharply peaked at a given scale.
We show that the dynamical equation allows self similar evolution for the
gravitational potential $\phi_{\bf k}(t)$ in Fourier space of the form
$\phi_{\bf k}(t) = F(t)D({\bf k}) $ where the function $F(t)$ satisfies a
second order non-linear differential equation. We provide a complete analysis
of the relevant solutions of this equation thereby determining the asymptotic
time evolution of the gravitational potential and density contrast. The
analysis shows that both $F(t) $ and $D({\bf k})$ have well defined asymptotic
forms indicating that the power transfer leads to a universal power spectrum at
late times. The analytic results are compared with numerical simulations
showing good agreement.


title: Air-Shower Spectroscopy at horizons

abstract:
  Horizontal and Upward air-showers are suppressed by deep atmosphere opacity
and by the Earth shadows. In such noise-free horizontal and upward directions
rare Ultra High Cosmic rays and rarer neutrino induced air-showers may shine,
mostly mediated by resonant PeVs interactions in air or by higher energy Tau
Air-showers originated by neutrino tau skimming the Earth. At high altitude
(mountains, planes, balloons) the air density is so rarefied that nearly all
common air-showers might be observed at their maximal growth at a tuned
altitude and directions. The arrival angle samples different distances and the
corresponding most probable primary cosmic ray energy. The larger and larger
distances (between observer and C.R. interaction) make wider and wider the
shower area and it enlarge the probability to be observed (up to three order of
magnitude more than vertical showers); the observation of a maximal
electromagnetic shower development may amplify the signal by two-three order of
magnitude (respect suppressed shower at sea level); the peculiar altitude-angle
range may disentangle at best the primary cosmic ray energy and composition.
Even from existing mountain observatory the up-going air-showers may trace,
above the horizons, PeV-EeV high energy cosmic rays and, below the horizons,
PeV-EeV neutrino astronomy: their early signals may be captured in already
existing gamma telescopes as Magic at Canarie, while facing the Earth edges
during (useless) cloudy nights.


title:
Star Formation in Distant Red Galaxies: Spitzer observations in the
  Hubble Deep Field South

abstract:
  We present Spitzer 24micron imaging of 1.5 < z < 2.5 Distant Red Galaxies
(DRGs) in the 10arcmin by 10arcmin Extended Hubble Deep Field South of the
Multiwavelength Survey by Yale-Chile. We detect 65% of the DRGs with K_AB <
23.2 mag at S_24micron > 40uJy, and conclude that the bulk of the DRG
population are dusty active galaxies. A mid-infrared (MIR) color analysis with
IRAC data suggests that the MIR fluxes are not dominated by buried AGN, and we
interpret the high detection rate as evidence for a high average star formation
rate of <SFR> = 130+/-30 M/yr. From this, we infer that DRGs are important
contributors to the cosmic star formation rate density at z ~ 2, at a level of
\~0.02 M/yr/Mpc^3 to our completeness limit of K_AB = 22.9 mag


title:
Polarization characteristics of the Crab pulsar's giant radio pulses at
  HFCs phases

abstract:
  We discuss our recent discovery of the giant radio emission from the Crab
pulsar at its high frequency components (HFCs) phases and show the polarization
characteristic of these pulses. This leads us to a suggestion that there is no
difference in the emission mechanism of the main pulse (MP), interpulse (IP)
and HFCs. We briefly review the size distributions of the Crab giant radio
pulses (GRPs) and discuss general characteristics of the GRP phenomenon in the
Crab and other pulsars.


title: Propeller-driven Outflows and Disk Oscillations

abstract:
  We report the discovery of propeller-driven outflows in axisymmetric
magnetohydrodynamic simulations of disk accretion to rapidly rotating
magnetized stars. Matter outflows in a wide cone and is centrifugally ejected
from the inner regions of the disk. Closer to the axis there is a strong,
collimated, magnetically dominated outflow of energy and angular momentum
carried by the open magnetic field lines from the star. The ``efficiency'' of
the propeller may be very high in the respect that most of the incoming disk
matter is expelled from the system in winds. The star spins-down rapidly due to
the magnetic interaction with the disk through closed field lines and with
corona through open field lines. Diffusive and viscous interaction between
magnetosphere and the disk are important: no outflows were observed for very
small values of the diffusivity and viscosity. These simulation results are
applicable to the early stages of evolution of classical T Tauri stars and to
different stages of evolution of cataclysmic variables and neutron stars in
binary systems. As an example, we have shown that young rapidly rotating
magnetized CTTSs spin-down to their present slow rotation in less than 10^6
years.


title: 3A 0535+262 in outburst

abstract:
  The Be/X-ray binary 3A 0535+262 has the highest magnetic field determined by
cyclotron line studies of all accreting X-ray pulsars, despite an open debate
if the fundamental line was rather at ~50 or above 100 keV as observed by
different instruments in past outbursts. The source went into quiescence for
more than ten years since its last outbursts in 1994. Observing during a
`normal' outburst August/September 2005 with Integral and RXTE we find a strong
cyclotron line feature at ~45 keV and have for the first time since 1975
determined the low energy pulse profile.


title:
The effects of moderately fast shellular rotation on adiabatic
  oscillations

abstract:
  We investigate adiabatic oscillations for delta Scuti star models, taking
into account a moderate rotation velocity ~100 \km/s. The resulting oscillation
frequencies include corrections for rotation up to second order in the rotation
rate including those of near degeneracy. Effects of either a uniform rotation
or a rotation profile assuming local angular momentum conservation of the form
Omega=Omega(r) on oscillation frequencies are compared. As expected, important
differences (around 3 microHz) are obtained in the $g$ and mixed mode regions.
For higher frequency p modes, differences range between 1 microHz and 3
microHz. Such differences are likely to be detectable with future space
missions such as COROT, where precisions in frequency around 0.5 microHz will
be reachable.


title:
Towards a working model for the abundance variations within Globular
  Clusters stars

abstract:
  A popular self--enrichment scenario for the formation of globular clusters
assumes that the abundance anomalies shown by the stars in many clusters are
due to a second stage of star formation occurring from the matter lost by the
winds of massive asymptotic giant branch (AGB) stars. Until today, the
modellizations of the AGB evolution by several different groups failed, for
different reasons, to account for the patterns of chemical anomalies. Here we
show that our own modelling can provide a consistent picture if we constrain
the three main parameters which regulate AGB evolution: 1) adopting a high
efficiency convection model; 2) adopting rates of mass loss with a high
dependence on the stellar luminosity; 3) assuming a very small overshooting
below the formal convective regions during the thermal pulse (TP) phase. The
first assumption is needed to obtain an efficient oxygen depletion in the AGB
envelopes, and the second one is needed to lose the whole stellar envelope
within few thermal pulses, so that the sum of CNO elements does not increase
too much, consistently with the observations. The third assumption is needed to
fully understand the sodium production. We also show that the Mg - Al
anticorrelation is explained adopting the higher limit of the NACRE rates for
proton captures by Mg25 and Mg26, and the models are consistent with the
recently discovered F-Al correlation. Problems remain to fully explain the
observed Mg isotopes ratios.


title: A refined position catalog of the Swift XRT afterglows

abstract:
  We present a catalogue of refined positions of 68 gamma ray burst (GRB)
afterglows observed by the Swift X-ray Telescope (XRT) from the launch up to
2005 Oct 16. This is a result of the refinement of the XRT boresight
calibration. We tested this correction by means of a systematic study of a
large sample of X-ray sources observed by XRT with well established optical
counterparts. We found that we can reduce the systematic error radius of the
measurements by a factor of two, from 6.5" to 3.2" (90% of confidence). We
corrected all the positions of the afterglows observed by XRT in the first 11
months of the Swift mission. This is particularly important for the 37 X-ray
afterglows without optical counterpart. Optical follow-up of dark GRBs, in
fact, will be more efficient with the use of the more accurate XRT positions.


title: The refill of superbubble cavities

abstract:
  In this paper we study the late evolution of model galaxies after a single
episode of star formation of different durations. The aim of the paper is to
discover the timescale needed to refill with cold gas the center of the galaxy.
This timescale strongly depends on the amount of gas initially present inside
the galaxy and ranges between 125 and 600 Myr. A HI hole can therefore survive
several hundred Myrs after the last SNII has exploded. If, as a consequence of
the refill of the center of the galaxy, a second episode of star formation
occurs, it pollutes the surrounding medium in a very short timescale (of the
order of 10--15 Myr), at variance with what happens if the center of the galaxy
is still occupied by hot and tenuous gas.


title: High redshift FRII radio galaxies: X-ray properties of the cores

abstract:
  We present an extensive X-ray spectral analysis of the cores of 19 FRII
sources in the redshift range 0.5<z<1.0 which were selected to be matched in
isotropic radio power. The sample consists of 10 radio galaxies and 9 quasars.
We compare our results with the expectations from a unification model that
ascribes the difference between these two types of sources to the viewing angle
to the line of sight, beaming and the presence of a dust and gas torus. We find
that the spectrum of all the quasars can be fitted with a single power law, and
that the spectral index flattens with decreasing angle to the line of sight. We
interpret this as the effect of increasingly dominant inverse Compton X-ray
emission, beamed such that the jet emission outshines other core components.
For up to 70 per cent of the radio galaxies we detect intrinsic absorption;
their core spectra are best fitted with an unabsorbed steep power law of
average spectral index $\Gamma=2.1$ and an absorbed power law of spectral index
Gamma=1.6, which is flatter than that observed for radio-quiet quasars. We
further conclude that the presence of a jet affects the spectral properties of
absorbed nuclear emission in AGN. In radio galaxies, any steep-spectrum
component of nuclear X-ray emission, similar to that seen in radio-quiet
quasars, must be masked by a jet or by jet-related emission.


title: A SAURON study of stars and gas in Sa bulges

abstract:
  We present results from our ongoing effort to understand the morphological
and kinematical properties of early-type galaxies using the integral-field
spectrograph SAURON. We discuss the relation between the stellar and gas
morphology and kinematics in our sub-sample of 24 representative Sa spiral
bulges. We focus on the frequency of kinematically decoupled components and on
the presence of star formation in circumnuclear rings.


title: SOAR BVI Photometry of the Metal-Poor Bulge Globular Cluster NGC 6642

abstract:
  We present BVI photometry of the globular cluster NGC 6642 using the SOI
imager at the SOAR Telescope. The Colour Magnitude Diagrams (CMD) reach
$\approx$1.5mag in V below the main sequence turn-off. A comparison of the
overall sequences, and in particular the Red Giant Branch slope of NGC 6642
with that of M~5 indicates that the two clusters must have a similar
metallicity of [Fe/H]$\approx$-1.3. We also obtain for NGC 6642 a reddening
E(B-V)=0.42$\pm$0.03, and a distance from the Sun of d$_{\odot}$=7.2$\pm$0.5
kpc. Therefore NGC 6642 is a moderately metal-poor globular cluster, spatially
located in the bulge, at a galactocentric distance of R$_{\rm GC}$$\approx$1.7
kpc. The comparison of CMDs of NGC 6642 with those of M~5 shows that there is a
very good match of magnitude difference between turn-off and horizontal branch,
suggesting comparable ages. M~5 has an age typical of the halo globulars, and
consequently NGC 6642 is coeval with the halo. NGC 6642 is a good candidate to
be one of the few genuine metal-poor and old {\it bulge} clusters, and might be
one of the most ancient fossils in the Galaxy.


title:
Simulations of thermally broadened HI Lya absorption arising in the
  warm-hot intergalactic medium

abstract:
  Recent far-ultraviolet (FUV) absorption line measurements of low-redshift
quasars have unveiled a population of intervening broad HI Lya absorbers (BLAs)
with large Doppler parameters (b> 40 km/s). If the large width of these lines
is dominated by thermal line broadening, the BLAs may trace highly-ionized gas
in the warm-hot intergalactic medium (WHIM) in the temperature range T ~
10^5-10^6 K, a gas phase that is expected to contain a large fraction of the
baryons at low redshift. In this paper we use a hydrodynamical simulation to
study frequency, distribution, physical conditions, and baryon content of the
BLAs at z=0. From our simulated spectra we derive a number of BLAs per unit
redshift of (dN/dz)_BLA ~ 38 for HI absorbers with log (N(cm^-2)/b(km/s))>10.7,
b>40 km/s, and log N(HII)<20.5. The baryon content of these systems is
Omega_b(BLA)=0.0121/h_65, which represents ~25 percent of the total baryon
budget in our simulation. Our results thus support the idea that BLAs represent
a significant baryon reservoir at low redshift. BLAs predominantly trace
shock-heated collisionally ionized WHIM gas at temperatures log T~4.4-6.2.
About 27 percent of the BLAs in our simulation originate in the photoionized
Lya forest (log T<4.3) and their large line widths are determined by
non-thermal broadening effects such as unresolved velocity structure and
macroscopic turbulence. Our simulation implies that for a large-enough sample
of BLAs in FUV spectra it is possible to obtain a reasonable approximation of
the baryon content of these systems solely from the measured HI column
densities and b values.


title:
The bulk Lorentz factor crisis of TeV blazars : evidence for an
  inhomogeneous pileup energy distribution ?

abstract:
  There is growing evidence that the estimations of the beaming Doppler factor
in TeV BL Lac object based on the Self Synchrotron Compton (SSC) models are in
strong disagreement with those deduced from the unification models between
blazars and radio galaxies. When corrected from extragalactic absorption by the
diffuse infrared background (DIrB), the SSC one-zone models require very high
Lorentz factor (around 50) to avoid strong gamma-gamma absorption. However, the
statistics on beamed vs. unbeamed objects, as well as the luminosity contrast,
favors much lower Lorentz factor of the order of 3. In this paper, we show that
for the special case of Markarian 501, the need for very high Lorentz factor is
unavoidable for all one-zone models where all photons are assumed to be
produced at the same location at the same time. Models assuming a double
structure with two different beaming patterns can partially solve the problem
of luminosity contrast, but we point out that they are inconsistent with the
statistics on the number of detected TeV sources. The only way to solve the
issue is to consider inhomogeneous models, where low energy and high energy
photons are not produced at the same place, allowing for much smaller Lorentz
factors. It implies that the jet is stratified, but also that the particle
energy distribution is close to a monoenergetic one, and that pair production
is likely to be significant. The implications on relativistic jet physics and
particle acceleration mechanism are discussed.


title:
Collimation of astrophysical jets - the role of the accretion disk
  magnetic field distribution

abstract:
  We have applied axisymmetric MHD simulations to investigate the impact of the
accretion disk magnetic flux profile on the jet collimation. Using the ZEUS-3D
code modified for magnetic diffusivity, our simulations evolve from an initial
hydrostatic equilibrium state in a force-free magnetic field. Considering a
power law for the disk poloidal magnetic field profile Bp ~ r^{-mu} and for the
disk wind density profile rho ~ r^{-mu_rho} we performed a systematic study
over a wide parameter range mu and mu_rho. We find a degree of collimation
(ratio of mass flow rates in axial and lateral direction) decreasing for
steeper disk magnetic field profiles (increasing mu). Varying the total
magnetic flux doesn't change the degree of jet collimation substantially, it
only affects the time scale of outflow evolution and the terminal jet speed. As
our major result we find a general relation between the collimation degree with
the disk wind magnetization power law exponent. Outflows with high collimation
degree resulting from a flat disk magnetic field profile tend to be unsteady,
producing axially propagating knots as discussed earlier. Depending slightly on
the inflow density profile this unsteady behavior sets in for mu < 0.4. We also
performed simulations of jet formation with artificially enhanced decay of the
toroidal magnetic field in order to investigate the idea of a purely "poloidal
collimation" discussed in the literature. These outflows remain weakly
collimated and propagate with lower velocity. Thanks to our large numerical
grid size (7x14 AU for protostars), we may apply our results to recently
observed hints of jet rotation (DG Tau) indicating a relatively flat disk
magnetic field profile, mu ~ 0.5. In general, our results are applicable to
both stellar and extragalactic sources of MHD jets.


title: To probe into pulsar's interior through gravitational waves

abstract:
  The gravitational radiation from compact pulsar-like stars depends on the
state of dense matter at supranuclear densities, i.e., the nature of pulsar
(e.g., either normal neutron stars or quark stars). The solid quark star model
is focused for the nature of pulsar-like compact objects. Possible
gravitational emission of quark stars (either fluid or solid) during the birth
and later lifetime is discussed. Several observational features to distinguish
various models for pulsar-like stars are proposed. It is suggested that the
gravitational wave behaviors should be mass-dependent. Based on the data from
the second LIGO science run, the upper limits of R.theta^{1/5} and thus
M.theta^{3/5} (M: mass, R: radius, and theta: wobble angle) are provided for
those targets of millisecond pulsars.


title: Monopole-charged pulsars and relevant issues

abstract:
  The aligned pulsars whose rotation axes and magnetic dipole axes are parallel
should be positively charged. The total charge of pulsars is calculated after
considering the electromagnetic field in and out the star under a specific
condition. The statistical relation between the pulsar's rotation energy loss
rate (or the period derivative) and the period may hint that the millisecond
radio pulsars with small periods could be low-mass bare strange stars.


title:
Variability and periodicity of field M dwarfs revealed by multichannel
  monitoring

abstract:
  We present simultaneous, multiband monitoring of 19 field M dwarfs (spectral
types M2-M9). Significant variability was found in seven objects in at least
one out of the three channels I, R and G. Two objects, LHS370 (M5V) and
2M1707+64 (M9V), show periods of 5.9+-2.0 and 3.65+-0.1 hours respectively. On
account of the agreement with the typical values of v*sin(i) published for M
dwarfs (Mohanty & Basri 2003), we claim these to be the objects' rotation
periods. In the case of 2M1707+64 we furthermore find evidence for the presence
of magnetically-induced cool spots as the reason for the observed variability
(at a temperature contrast of 4-8 percent, with a projected surface coverage
factor of less than 0.075) and can rule out the scenario of dust clouds (as
represented by the COND or DUSTY models). Comparing the frequency of occurrence
of variability in this and various L dwarf samples published over the past few
years, we find that variability is more common in field L dwarfs than in field
M dwarfs. This implies a change in the physical nature and/or extent of surface
features when moving from M to L dwarfs.


title: Bulk viscous cosmology: statefinder and entropy

abstract:
  The statefinder diagnostic pair is adopted to differentiate viscous cosmology
models and it is found that the trajectories of these viscous cosmology models
on the statefinder pair $s-r$ plane are quite different from those of the
corresponding non-viscous cases. Particularly for the quiessence model, the
singular properties of state parameter $w=-1$ are obviously demonstrated on the
statefinder diagnostic pair planes. We then discuss the entropy of the viscous
/ dissipative cosmology system which may be more practical to describe the
present cosmic observations as the perfect fluid is just a global approximation
to the complicated cosmic media in current universe evolution. When the bulk
viscosity takes the form of $\zeta=\zeta_{1}\dot{a}/a$($\zeta_{1}$ is
constant), the relationship between the entropy $S$ and the redshift $z$ is
explicitly given out. We find that the entropy of the viscous cosmology is
always increasing and consistent with the thermodynamics arrow of time for the
universe evolution. With the parameter constraints from fitting to the 157 gold
data of supernova observations, it is demonstrated that this viscous cosmology
model is rather well consistent to the observational data at the lower
redshifts, and together with the diagnostic statefinder pair analysis it is
concluded that the viscous cosmic models tend to the favored $\Lambda$CDM model
in the later cosmic evolution, agreeable to lots of cosmological simulation
results, especially to the fact of confidently observed current accelerating
cosmic expansion.


title:
Dimensional Analysis applied to Spectrum Handling in Virtual Observatory
  Context

abstract:
  The handling of units in an automated way by software systems can be a
cumbersome procedure when the units are parsed as strings. Software systems
parsing units have to take into account extensive tables of unit names, not
always identical between different standards. In the Virtual Observatory
context, the transfer of metadata in access protocols is specially critical for
the understanding of the content of the data (many of which are legacy data).
Driven by this issue, we present a way to handle units automatically which is
based in dimensional analysis considerations. Although the approach presented
here can be valid to any other branch of physics, we concentrate mainly in the
application to spectrum handling in the VO context, and show how the proposed
solution has been implemented in the VOSpec, a tool to handle VO-compatible
spectra.


title: Underwater Acoustic Detection of Ultra High Energy Neutrinos

abstract:
  We investigate the acoustic detection method of 10^18-20 eV neutrinos in a
Mediterranean Sea environment. The acoustic signal is re-evaluated according to
dedicated cascade simulations and a complex phase dependant absorption model,
and compared to previous studies. We detail the evolution of the acoustic
signal as function of the primary shower characteristics and of the acoustic
propagation range. The effective volume of detection for a single hydrophone is
given taking into account the limitations due to sea bed and surface boundaries
as well as refraction effects. For this 'benchmark detector' we present
sensitivity limits to astrophysical neutrino fluxes, from which sensitivity
bounds for a larger acoustic detector can be derived. Results suggest that with
a limited instrumentation the acoustic method would be more efficient at
extreme energies, above 10^20 eV.


title: 51 Eri and GJ 3305: A 10-15 Myr old binary star system at 30 parsecs

abstract:
  Following the suggestion of Zuckerman et al. (2001, ApJ, 562, L87), we
consider the evidence that 51 Eri (spectral type F0) and GJ 3305 (M0),
historically classified as unrelated main sequence stars in the solar
neighborhood, are instead a wide physical binary system and members of the
young beta Pic moving group (BPMG). The BPMG is the nearest (d < 50 pc) of
several groups of young stars with ages around 10 Myr that are kinematically
convergent with the Oph-Sco-Cen Association (OSCA), the nearest OB star
association. Combining SAAO optical photometry, Hobby-Eberly Telescope
high-resolution spectroscopy, Chandra X-ray data, and UCAC2 catalog kinematics,
we confirm with high confidence that the system is indeed extremely young. GJ
3305 itself exhibits very strong magnetic activity but has rapidly depleted
most of its lithium. The 51 Eri/GJ 3305 system is the westernmost known member
of the OSCA, lying 110 pc from the main subgroups. The system is similar to the
BPMG wide binary HD 172555/CD -64d1208 and the HD 104237 quintet, suggesting
that dynamically fragile multiple systems can survive the turbulent
environments of their natal giant molecular cloud complexes, while still being
imparted high dispersion velocities. Nearby young systems such as these are
excellent targets for evolved circumstellar disk and planetary studies, having
stellar ages comparable to that of the late phases of planet formation.


title:
Chandra Observation of the Magellanic Cloud Supernova Remnant 0454-672
  in N9

abstract:
  A Chandra observation has defined the extent of the SNR B 0454-692 in the LMC
H II region N9. The remnant has dimension 2.3" x 3.6" and is elongated in the
NS direction. The brightest emission comes from a NS central ridge which
includes three bright patches. There is good agreement between X-ray and [O
III] and [S II] morphology. The remnant is old enough so that optical data give
more information about dynamics than do the X-ray data. The SN energy release
was >= 4 x 10^50 ergs and the age is ~3 x 10^4 years. There are several
unresolved sources nearby but none are clearly associated with the remnant. The
X-ray spectrum is soft and indicates enhanced Fe abundance in the central
region, consistent with a Type Ia SN origin, but a Type II origin cannot be
ruled out.


title:
Increase of the electron-positron Hawking radiation from Schwarzschild
  black holes by Dirac monopoles

abstract:
  An algorithm for numerical computation of the barrier transparency for the
potentials surrounding Schwarzschild black holes is described for massive
spinor particles. It is then applied to calculate the total (including
electronic neutrino and the contributions of twisted field configurations
connected with Dirac monopoles) luminosity for the electron-positron Hawking
radiation from a Schwarzschild black hole with mass $M=10^{15}$ g. It is found
that the contribution due to monopoles can be of order 12% of the total
electron-positron luminosity.


title: Galactic Corona or Local Group Intergalactic Medium?

abstract:
  Cosmological hydrodynamic simulations predict that the low redshift universe
comprises a web of warm-hot intergalactic gas and galaxies, with groups of
galaxies and clusters forming at dense knots in these filaments. Our own Galaxy
being no exception is also expected to be surrounded by the warm-hot
intergalactic medium, filling the Local Group. Some theoretical models also
predict the existence of a hot Galactic corona. With X-ray and FUV observations
of extragalactic sources, we can probe the warm-hot gas through absorption
lines of highly ionized elements. Indeed, Chandra, XMM and FUSE observations
have detected z=0 absorption lines toward many sightlines. The debate that has
emerged is over the interpretation of these observations: are the z=0
absorption systems from the halo of our Galaxy or from the extended Local Group
environment? This has important implications for our understanding of the mass
of the Local Group, the physical conditions in the intergalactic medium, the
structure of the Galaxy and galaxy formation in general. We will present the
current status of the debate and discuss our ongoing observing program aimed at
understanding the z=0 absorption systems, with an emphasis on the high quality
Chandra spectra of the Mrk 421 and Mrk 279 sightlines.


title: Fireball and cannonball models of gamma ray bursts confront observations

abstract:
  The two leading contenders for the theory of gamma-ray bursts (GRBs) and
their afterglows, the Fireball and Cannonball models, are compared and their
predictions are confronted, within space limitations, with key GRB
observations, including recent observations with SWIFT


title: The effect of minihaloes on cosmic reionization

abstract:
  One of the most debated issues in the theoretical modeling of cosmic
reionization is the impact of small-mass gravitationally-bound structures. We
carry out the first numerical investigation of the role of such sterile
`minihaloes', which serve as self-shielding screens of ionizing photons.
Minihaloes are too small to be properly resolved in current large-scale
cosmological simulations, and thus we estimate their effects using a sub-grid
model, considering two cases that bracket their effect within this framework.
In the `extreme suppression' case in which minihalo formation ceases once a
region is partially ionized, their effect on cosmic reionization is modest,
reducing the volume-averaged ionization fraction by an overall factor of less
than 15%. In the other extreme, in which minihalo formation is never
suppressed, they delay complete reionization as much as Delta z~2, in rough
agreement with the results from a previous semi-analytical study by the
authors. Thus, depending on the details of the minihalo formation process,
their effect on the overall progress of reionization can range from modest to
significant, but the minihalo photon consumption is by itself insufficient to
force an extended reionization epoch.


title: Perturbations of self-similar Bondi accretion

abstract:
  The question of stability of steady spherical accretion has been studied for
many years and, recently, the concept of spatial instability has been
introduced. Here we study perturbations of steady spherical accretion flows
(Bondi solutions), restricting ourselves to the case of self-similar flow, as a
case amenable to analytic treatment and with physical interest. We further
restrict ourselves to its acoustic perturbations. The radial perturbation
equation can be solved in terms of Bessel functions. We study the formulation
of adequate boundary conditions and decide for no matter-flux-perturbation
conditions (at the Bondi radius and at r=0). We also consider the problem of
initial conditions and time evolution, in particular, of radial perturbations.
No spatial instability at r=0 is found. The time evolution is such that
perturbations eventually become ergodic-like and show no trace of instability
or of acquiring any remarkable pattern.


title:
Observing Dark Energy Dynamics with Supernova, Microwave Background and
  Galaxy Clustering

abstract:
  Observing dark energy dynamics is the most important aspect of the dark
energy research. In this paper we perform an analysis of the constraints on the
property of dark energy from the current astronomical observations. We pay
particular attention to the effects of dark energy perturbations. Using the
data from SNIa (157 "gold" sample), WMAP and SDSS we find that the best fitting
dark energy model is given by the dynamical model with the equation of state
across -1. Nevertheless the standard \LambdaCDM models are still a very good
fit to the current data and evidence for dynamics is currently not very strong.
We also consider the constraints from SNLS.


title: The Sunyaev-Zeldovich Effect

abstract:
  This brief, general review the Sunyaev-Zeldovich (S-Z) effect includes a
description of the calculation of the total intensity change and polarization
components, a discussion of the basic properties of the S-Z power spectrum and
cluster number counts, and a summary of the main observational results.


title: Large-Scale Simulations of Reionization

abstract:
  We use cosmological simulations to explore the large-scale effects of
reionization. Since reionization is a process that involves a large dynamic
range - from galaxies to rare bright quasars - we need to be able to cover a
significant volume of the universe in our simulation without losing hte
important small scale effects from galaxies. Here we have taken an approach
that uses clumping factors derived from small scale simulations to approximate
the radiative transfer on the sub-cell scales. Using this technique, we can
cover a simulation size up to $1280 h^{-1} Mpc$ with $10 h^{-1} Mpc$ cells.
This allows us to construct synthetic spectra of quasars similar to observed
spectra of SDSS quasars at high reshifts and compare them to the observational
data. These spectra can then be analyzed for HII region sizes, the presence of
the Gunn-Peterson trough and the Lyman-$\alpha$ forest.


title:
Do recent supernovae Ia observations tend to rule out all the
  cosmologies?

abstract:
  Dark energy and the accelerated expansion of the universe have been the
direct predictions of the distant supernovae Ia observations which are also
supported, indirectly, by the observations of the CMB anisotropies,
gravitational lensing and the studies of galaxy clusters. Today these results
are accommodated in what has become the `concordance cosmology': a universe
with flat spatial sections t=constant with about 70% of its energy in the form
of Einstein's cosmological constant \Lambda.
  However, we find that as more and more supernovae Ia are observed, more
accurately and towards higher redshift, the probability that the data are well
explained by the cosmological models decreases alarmingly, finally ruling out
the concordance model at more than 95% confidence level. This raises doubts
against the `standard candle'-hypothesis of the supernovae Ia and their use to
constrain the cosmological models. We need a better understanding of the entire
SN Ia phenomenon in order to have cosmological consequences from them.


title: Pseudo-$C_\ell$ estimators which do not mix E and B modes

abstract:
  Pseudo-$C_\ell$ quadratic estimators for CMB temperature and polarization
power spectra have been used in the analysis pipelines of many CMB experiments,
such as WMAP and Boomerang. In the polarization case, these estimators mix E
and B modes, in the sense that the estimated B-mode power is nonzero for a
noiseless CMB realization which contains only E-modes. Recently, Challinor &
Chon showed that for moderately sized surveys ($f_{sky} \sim 0.01$), this
mixing limits the gravity wave B-mode signal which can be detected using
pseudo-$C_\ell$ estimators to $T/S \sim 0.05$. We modify the pseudo-$C_\ell$
construction, defining ``pure'' pseudo-$C_\ell$ estimators, which do not mix E
and B modes in this sense. We study these estimators in detail for a survey
geometry similar to that which has been proposed for the QUIET experiment, for
a variety of noise levels, and both homogeneous and inhomogeneous noise. For
noise levels $\simle 20$ $\mu$K-arcmin, our modification significantly improves
the B-mode power spectrum errors obtained using pseudo-$C_\ell$ estimators. In
the homogeneous case, we compute optimal power spectrum errors using a Fisher
matrix approach, and show that our pure pseudo-$C_\ell$ estimators are roughly
80% of optimal, across a wide range of noise levels. There is no limit, imposed
by the estimators alone, to the value of $T/S$ which can be detected.


title:
Production and Evolution of Perturbations of Sterile Neutrino Dark
  Matter

abstract:
  Sterile neutrinos, fermions with no standard model couplings [SU(2)
singlets], are predicted by most extensions of the standard model, and may be
the dark matter. I describe the nonthermal production and linear perturbation
evolution in the early universe of this dark matter candidate. I calculate
production of sterile neutrino dark matter including effects of Friedmann
dynamics dictated by the quark-hadron transition and particle population, the
alteration of finite temperature effective mass of active neutrinos due to the
presence of thermal leptons, and heating of the coupled species due to the
disappearance of degrees of freedom in the plasma. These effects leave the
sterile neutrinos with a non-trivial momentum distribution. I also calculate
the evolution of sterile neutrino density perturbations in the early universe
through the linear regime and provide a fitting function form for the transfer
function describing the suppression of small scale fluctuations for this warm
dark matter candidate. The results presented here differ quantitatively from
previous work due to the inclusion here of the relevant physical effects during
the production epoch.


title: Cosmic rays, lithium abundance and excess entropy in galaxy clusters

abstract:
  We consider the production of $^6$Li in spallation reactions by cosmic rays
in order to explain the observed abundance in halo metal-poor stars. We show
that heating of ambient gas by cosmic rays is an inevitable consequence of this
process, and estimate the energy input required to reproduce the observed
abundance of $^6$Li/H$\sim 10^{-11}$ to be of order a few hundred eV per
particle. We draw attention to the possibility that this could explain the
excess entropy in gas in galaxy groups and clusters. The evolution of $^6$Li
and the accompanying heating of gas is calculated for structures collapsing at
the present epoch with injection of cosmic rays at high redshift. We determine
the energy required to explain the abundance of $^6$Li at $z \sim 2$
corresponding to the formation epoch of halo metal-poor stars, and also an
increased entropy level of $\sim 300$ keV cm$^2$ necessary to explain X-ray
observations of clusters. The energy budget for this process is consistent with
the expected energy output of radio-loud AGNs, and the diffusion length scale
of cosmic-ray protons responsible for heating is comparable to the size of
regions with excess entropy. We also discuss the constraints imposed by the
extragalactic gamma-ray background.


title:
Testing Dark Energy with the Advanced Liquid-Mirror Probe of Asteroids,
  Cosmology and Astrophysics

abstract:
  The Advanced Liquid-Mirror Probe of Asteroids, Cosmology and Astrophysics
(ALPACA) is a proposed 8-meter liquid mirror telescope surveying 1000 square
degree of the southern-hemisphere sky. It will be a remarkably simple and
inexpensive telescope, that nonetheless will deliver a powerful sample of
optical data for studying dark energy. The bulk of the cosmological data
consists of nightly, high signal-to-noise, multiband light curves of SN Ia. At
the end of the three-years run ALPACA is expected to collect 100,000 SNe Ia up
to z~1. This will allow us to reduce present systematic uncertainties affecting
the standard-candle relation. The survey will also provide several other
datasets such as the detection of baryon acoustic oscillations in the matter
power spectrum and shear weak lensing measurements. In this preliminary
analysis we forecast constraints on dark energy parameters from SN Ia and
baryon acoustic oscillations. The combination of these two datasets will
provide competitive constraints on the dark energy parameters under minimal
prior assumptions. Further studies are needed to address the accuracy of weak
lensing measurements.


title: Mesolensing: I. High Probability Lensing Without Large Optical Depth

abstract:
  In a variety of astronomical situations, there is a relatively high
probability that a single isolated lens will produce a detectable event. The
high probability is caused by some combination of a large Einstein angle, fast
angular motion, and a dense background field. We refer to high-probability
lenses as mesolenses. The mesolensing regime is complementary to the regime in
which the optical depth is high, in that it applies to isolated lenses instead
of to dense lens fields. Mesolensing is complementary to microlensing, because
it is well suited to the study of different lens populations, and also because
different observing and analysis strategies are required to optimize the
discovery and study of mesolenses. Planetary and stellar masses located within
1-2 kpc are examples of mesolenses. We show that their presence can be detected
against a wide variety of background fields, using distinctive signatures of
both time variability and spatial effects. Time signatures can be identical to
those of microlensing, but can also include baseline jitter, extreme apparent
chromaticity, events well fit by lens models in which several independent
sources are simultaneously lensed, and sequences of events. Spatial signatures
include astrometric lensing of surface brightness fluctuations, as well as
patterns of time variability that sweep across the background field as the lens
moves. Wide-field monitoring programs, such as Pan-STARRS and LSST, are
well-suited to the study of mesolensing. In addition, high resolution
observations of the region behind a known mass traveling across a background
field can use lensing effects to measure the lens mass and study its
multiplicity.


title: Structure formation in the DGP cosmological model

abstract:
  The DGP brane-world model provides an alternative to the standard LCDM
cosmology, in which the late universe accelerates due to a modification of
gravity rather than vacuum energy. The cosmological constant $\Lambda$ in LCDM
is replaced by a single parameter, the crossover scale $r_c$, in DGP. The
Supernova redshift observations can be fitted by both models, with $\Lambda\sim
H_0^2$ and $r_c \sim H_0^{-1}$. This degeneracy is broken by structure
formation, which is suppressed in different ways in the two models. There is
some confusion in the literature about how the standard linear growth factor is
modified in DGP. While the luminosity distance can be computed purely from the
modified 4-dimensional Friedman equation, the evolution of density
perturbations requires an analysis of the 5-dimensional gravitational field. We
show that if the 5-dimensional effects are inappropriately neglected, then the
4-dimensional Bianchi identities are violated and the computed growth factor is
incorrect. By using the 5-dimensional equations, we derive the correct growth
factor.


title: Galactic Globular Clusters with Luminous X-Ray Binaries

abstract:
  Luminous X-ray binaries (>1E34 erg/s, LMXBs) have a neutron star or black
hole primary, and in globular clusters, most of these close binaries are
expected to be have evolved from wider binaries through dynamical interactions
with other stars. We sought to find a predictor of this formation rate that is
representative of the initial properties of globular clusters rather than of
the highly evolved core quantities. Models indicate the half-light quantities
best reflect the initial conditions, so we examine whether the associated
dynamical interaction rate, proportional to L^1.5 r^-2.5, is useful in
understanding the presence of luminous LMXBs in the Galactic globular cluster
system. We find that while LMXB clusters with large values of L^1.5 r^-2.5
preferentially host LMXBs, the systems must also have half-mass relaxation
times below about 1E9 yr. This relaxation time effect probably occurs because
several relaxation times are required to modify binary separations, a timescale
that must be shorter than cluster ages. The frequency of finding an LMXB
cluster is enhanced if the cluster is metal-rich and if it is close to the
bulge region. The dependence upon metallicity is most likely due either to
differing initial mass functions at the high mass end, or because bulge systems
evolve more rapidly from tidal interactions with the bulge. This approach can
be used to investigate globular cluster systems in external galaxies, where
core properties are unresolved.


title: New optical polarization measurements of the Crab pulsar

abstract:
  The Crab nebula and its pulsar have been observed for about 3 hours with the
high-speed photo-polarimeter OPTIMA in January 2002 at the Calar Alto 3.5m
telescope. The Crab pulsar intensity and polarization are determined at all
phases of rotation with higher statistical accuracy than ever. Therefore, we
were able to separate the so-called 'off-pulse' phase emission (with an
intensity of about 1.2% compared to the main peak, assumed to be present at all
phases) from the pulsed emission and show the 'net' polarization of the pulsed
structures. Recent theoretical results indicate that the measured optical
polarization of the Crab pulsar is similar to expectations from a two-pole
caustic emission model or a striped pulsar wind model.


title: First Light and Reionization: A Conference Summary

abstract:
  The search for the first illuminated astronomical sources in the universe is
at the edge of the cosmic frontier. Promising techniques for discovering the
first objects and their effects span the electromagnetic spectrum and include
gravitational waves. We summarize a workshop on discovering and understanding
these sources which was held in May 2005 through the Center for Cosmology at
the University of California, Irvine.


title: Observations of IC348: The Disk Population at 2-3 Million Years

abstract:
  We present near and mid-infrared photometry obtained with the Spitzer Space
Telescope of 300 known members of the IC348 cluster. We merge this photometry
with existing ground-based optical and near-infrared photometry in order to
construct optical-infrared spectral energy distributions (SEDs) for all the
cluster members and present a complete atlas of these SEDs. We employ these
observations to both investigate the frequency and nature of the circumstellar
disk population in the cluster. The observations are sufficiently sensitive to
enable the first detailed measurement of the disk frequency for very low mass
stars at the peak of the stellar IMF. Using measurements of infrared excess
between 3.6 and 8 microns we find the total frequency of disk-bearing stars in
the cluster to be 50 +/- 6%. However, only 30 +/- 4% of the member stars are
surrounded by optically thick, primordial disks, while the remaining
disk-bearing stars are surrounded by what appear to be optically thin,anemic
disks. The disk fraction appears to be a function of spectral type and stellar
mass. The disk longevity and thus conditions for planet formation appear to be
most favorable for stars which are of comparable mass to the sun. The optically
thick disks around later type (> M4) stars appear to be less flared than the
disks around earlier type stars. This may indicate a greater degree of dust
settling and a more advanced evolutionary state for the late M disk population.
Finally we find that the presence of an optically thick dust disk is correlated
with gaseous accretion as measured by the strength of Halpha emission. These
results suggest that it is more likely for dust disks to persist in the absence
of active gaseous accretion than for active accretion to persist in the absence
of dusty disks.


title: Precession of neutrino-cooled accretion disks in gamma-ray burst engines

abstract:
  We study the precession of accretion disks in the context of gamma-ray burst
inner engines. With an accretion disk model that allows for neutrino cooling,
we evaluate the possible periods of disk precession and nutation due to the
Lense-Thirring effect. Assuming jet ejection perpendicular to the disk midplane
and a typical intrinsic time dependence for the burst, we find possible
gamma-ray light curves with temporal microstructure similar to what is observed
in some subsamples. We conclude that the precession and nutation of a
neutrino-cooled accretion disk in the burst engine might be responsible for
some events, especially those with a slow rise and a fast decay.


title: A Near-Infrared Spectral Template for Quasars

abstract:
  We present a near-infrared quasar composite spectrum spanning the wavelength
range 0.58 - 3.5 um. The spectrum has been constructed from observations of 27
quasars obtained at the NASA IRTF telescope and satisfying the criteria Ks <
14.5 and Mi < -23; the redshift range is 0.118 < z < 0.418. The signal-to-noise
is moderate, reaching a maximum of 150 between 1.6 and 1.9 um. While a
power-law fit to the continuum of the composite spectrum requires two breaks, a
single power-law slope of alpha=-0.92 plus a 1260 K blackbody provides an
excellent description of the spectrum from H-alpha to 3.5 um, strongly
suggesting the presence of significant quantities of hot dust in this
blue-selected quasar sample. We measure intensities and line widths for ten
lines, finding that the Paschen line ratios rule out Case B recombination. We
compute K-corrections for the J, H, K, and Spitzer 3.6 um bands which will be
useful in analyzing observations of quasars up to z=10.


title: High Energy Neutrinos: Sources and Fluxes

abstract:
  We discuss briefly the potential sources of high energy astrophysical
neutrinos and show estimates of the neutrino fluxes that they can produce. A
special attention is paid to the connection between the highest energy cosmic
rays and astrophysical neutrinos.


title:
Big Bang Nucleosynthesis with an Evolving Radion in the Brane World
  Scenario

abstract:
  We consider the big bang nucleosynthesis (BBN) in the Brane world scenario,
where all matter fields are confined on our 3-brane and the radion of the Brane
evolves cosmologically. In the Einstein frame fundamental fermion masses vary
and the results of standard BBN (SBBN) are modified. We can thus use the
observational primordial element abundances to impose constraints on the
possible variations of the radion. The possibility of using the evolving radion
to resolve the discrepancies between the Wilkinson Microwave Anisotropy Probe
(WMAP) and SBBN values of the baryon-to-photon ratio ($\eta$) is also
discussed. The results and constraints presented here are applicable to other
models in which fundamental fermion masses vary.


title:
The investigation of ELAIS field by Vega photometry: Absolute -
  magnitude dependent on the Galactic model parameters

abstract:
  We estimate the density laws of the Galactic stellar populations as a
function of absolute magnitude in a near-polar Galactic field. The density laws
are determined by the direct fit to photometric parallaxes from Vega photometry
in the ELAIS (l=84.27, b=+44.90; 6.571 deg^2) field both independently for each
population and simultaneously for all stellar populations. Stars have been
separated into different populations based on their spatial location. The thick
disc and halo best fit by an exponential. However, the thin disc best fits by
using a sech^2 law for stars at faint absolute magnitudes, (10,11], (11,12] and
(12,13], whereas an exponential law for stars at relatively bright absolute
magnitudes, (5,6], (6,7], (7,8], (8,9] and (9,10]. The scaleheights for the
sech^2 density laws are the equivalent exponential scaleheights. Galactic model
parameters are absolute magnitude dependent: The scaleheight for thin disc
decreases monotonically from stars at bright absolute magnitudes to stars at
faint absolute magnitudes in the range 363-163 pc, except the minimum H=211 pc
at (9,10] where sech density law fits better. Its local density is flat at
bright absolute magnitudes but it increases at faint absolute magnitudes. For
thick disc, the scaleheight is flat within the uncertainties. The local space
density of thick disc relative to the local space density for the thin disc is
almost flat at absolute magnitude intervals (5,6] and (6,7], 7.59 and 7.41%
respectively, whereas it decreases down to 3.31% at absolute magnitude interval
(7,8]. The axial ratio for the halo is e=0.60, 0.73 and 0.78 for the absolute
magnitude intervals (4,5], (5,6] and (6,7] respectively, and its local space
density relative to the local space density for the thin disc is 0.06 and 0.04%
for the intervals (5,6], and (6,7] respectively.


title:
The chemical composition of metal-poor emission-line galaxies in the
  Data Release 3 of the Sloan Digital Sky Survey

abstract:
  We have re-evaluated empirical expressions for the abundance determination of
N, O, Ne, S, Cl, Ar and Fe taking into account the latest atomic data and
constructing an appropriate grid of photoionization models with state-of-the
art model atmospheres. Using these expressions we have derived heavy element
abundances in the $\sim$ 310 emission-line galaxies from the Data Release 3 of
the Sloan Digital Sky Survey (SDSS)with an observed Hbeta flux F(Hbeta)> 1E-14
erg s^{-1} cm^{-2} and for which the [O III] 4363 emission line was detected at
least at a 2sigma level, allowing abundance determination by direct methods.
The oxygen abundance 12 + log O/H of the SDSS galaxies lies in the range from ~
7.1 (Zsun/30) to 8.5 (0.7 Zsun). The SDSS sample is merged with a sample of 109
blue compact dwarf (BCD) galaxies with high quality spectra, which contains
extremely low-metallicity objects. We use the merged sample to study the
abundance patterns of low-metallicity emission-line galaxies. We find that
extremely metal-poor galaxies (12 + log O/H < 7.6, i.e. Z < Zsun/12) are rare
in the SDSS sample. The alpha element-to-oxygen abundance ratios do not show
any significant trends with oxygen abundance, in agreement with previous
studies, except for a slight increase of Ne/O with increasing metallicity,
which we interpret as due to a moderate depletion of O onto grains in the most
metal-rich galaxies. The Fe/O abundance ratio is smaller than the solar value,
by up to 1 dex at the high metallicity end. (abridged)


title:
A Blue Straggler Binary System with at least Three Progenitors in the
  Core of a Globular Cluster?

abstract:
  We show that the X-ray source W31 in the core of the globular cluster 47
Tucanae is physically associated with the bright blue straggler BSS-7. The two
sources are astrometrically matched to 0.061\arcsec, with a chance coincidence
probability of less than 1%. We then analyse optical time-series photometry
obtained with the {\em Hubble Space Telescope} (HST) and find that BSS-7
displays a 1.56 day periodic signal in the I band. We also construct a
broad-band (far-ultraviolet through far-red) spectral energy distribution for
BSS-7 and fit this with single and binary models. The binary model is a better
fit to the data, and we derive the corresponding stellar parameters.
  All of our findings are consistent with BSS-7 being a detached binary
consisting of a blue straggler primary with an X-ray-active,
upper-main-sequence companion. The formation of such a system would necessarily
involve at least three stars, which is consistent with recent N-body models in
which blue stragglers often form via multiple encounters that can involve both
single and binary stars. However, we cannot yet entirely rule out the
possibility that BSS-7 descended directly from a binary system via mass
transfer. The system parameters needed to distinguish definitively between
these scenarios may be obtainable from time-resolved spectroscopy.


title: Cosmological evolution of cosmic string loops

abstract:
  The existence of a scaling evolution for cosmic string loops in an expanding
universe is demonstrated for the first time by means of numerical simulations.
In contrast with what is usually assumed, this result does not rely on any
gravitational back reaction effect and has been observed for loops as small as
a few thousandths the size of the horizon. We give the energy and number
densities of expected cosmic string loops in both the radiation and matter
eras. Moreover, we quantify previous claims on the influence of the network
initial conditions and the formation of numerically unresolved loops by showing
that they only concern a transient relaxation regime. Some cosmological
consequences are discussed.


title:
Apparent Hubble acceleration from large-scale electroweak domain
  structure

abstract:
  The observed luminosity deficit of Type Ia supernovae (SNe Ia) at high
redshift z can be explained by partial conversion to weak vector bosons of
photons crossing large-scale electroweak domain boundaries, making Hubble
acceleration only apparent and eliminating the need for a cosmological constant
> 0.


title: ACS imaging of 25 galaxies in nearby groups and in the field

abstract:
  We present HST/ACS images and color-magnitude diagrams for 25 nearby galaxies
with radial velocities V_LG < 500 km/s. Distances are determined based on the
luminosities of stars at the tip of the red giant branch that range from 2 Mpc
to 12 Mpc. Two of the galaxies, NGC 4163 and IC 4662, are found to be the
nearest known representatives of blue compact dwarf (BCD) objects. Using
high-quality data on distances and radial velocities of 110 nearby field
galaxies, we derive their mean Hubble ratio to be 68 km/(s Mpc) with standard
deviation of 15 km/(s Mpc). Peculiar velocities of most of the galaxies, V_pec
= V_LG - 68 D, follow a Gaussian distribution with sigma_v = 63 km/s, but with
a tail towards high negative values. Our data displays the known correlation
between peculiar velocity and galaxy elevation above the Local Supercluster
plane. The small observed fraction of galaxies with high peculiar velocities,
V_pec < -500 km/s, may be understood as objects associated with nearby groups
(Coma I, Eridanus) outside the Local volume.


title: Results from the KASCADE, KASCADE-Grande, and LOPES experiments

abstract:
  The origin of high-energy cosmic rays in the energy range from 10^14 to 10^18
eV is explored with the KASCADE and KASCADE-Grande experiments. Radio signals
from air showers are measured with the LOPES experiment. An overview on results
is given.


title: Towards testing interacting cosmology by distant type Ia supernovae

abstract:
  We investigate the possibility of testing cosmological models with
interaction between matter and energy sector. We assume the standard FRW model
while the so called energy conservation condition is interpreted locally in
terms of energy transfer. We analyze two forms of dark energy sectors: the
cosmological constant and phantom field. We find a simple exact solution of the
models in which energy transfer is described by a Cardassian like term in the
relation of $H^{2}(z)$, where $H$ is Hubble's function and $z$ is redshift. The
considered models have two additional parameters $(\Omega_{\text{int}},n)$
(apart the parameters of the $\Lambda$CDM model) which can be tested using SNIa
data. In the estimation of the model parameters Riess et al.'s sample is used.
We also confront the quality of statistical fits for both the $\Lambda$CDM
model and the interacting models with the help of the Akaike and Bayesian
informative criteria. Our conclusion from standard best fit method is that the
interacting models explains the acceleration of the Universe better but they
give rise to a universe with high matter density. However, using the tools of
information criteria we find that the two new parameters play an insufficient
role in improving the fit to SNIa data and the standard $\Lambda$CDM model is
still preferred. We conclude that high precision detection of high redshift
supernovae could supply data capable of justifying adoption of new parameters.


title: Dynamical friction on satellite galaxies

abstract:
  For a rigid model satellite, Chandrasekhar's dynamical friction formula
describes the orbital evolution quite accurately, when the Coulomb logarithm is
chosen appropriately. However, it is not known if the orbital evolution of a
real satellite with the internal degree of freedom can be described by the
dynamical friction formula. We performed N-body simulation of the orbital
evolution of a self-consistent satellite galaxy within a self-consistent parent
galaxy. We found that the orbital decay of the simulated satellite is
significantly faster than the estimate from the dynamical friction formula. The
main cause of this discrepancy is that the stars stripped out of the satellite
are still close to the satellite, and increase the drag force on the satellite
through two mechanisms. One is the direct drag force from particles in the
trailing tidal arm, a non-axisymmetric force that slows the satellite down. The
other is the indirect effect that is caused by the particles remaining close to
the satellite after escape. The force from them enhances the wake caused in the
parent galaxy by dynamical friction, and this larger wake in turn slows the
satellite down more than expected from the contribution of its bound mass. We
found these two have comparable effects, and the combined effect can be as
large as 20% of the total drag force on the satellite.


title: The AMIGA sample of isolated galaxies - II. Morphological refinement

abstract:
  We present a complete POSS II-based refinement of the optical morphologies
for galaxies in the Karatchenseva's Catalog of Isolated Galaxies that forms the
basis of the AMIGA project. Comparison with independent classifications made
for an SDSS overlap sample of more than 200 galaxies confirms the reliability
of the early vs. late-type discrimination and the accuracy of spiral subtypes
within DeltaT = 1-2. CCD images taken at the OSN were also used to solve
ambiguities. 193 galaxies are flagged for the presence of nearby companions or
signs of distortion likely due to interaction. This most isolated sample of
galaxies in the local Universe is dominated by 2 populations: 1) 82% spirals
(Sa-Sd) with the bulk being luminous systems with small bulges (63% between
types Sb-Sc) and 2) a significant population of early-type E-S0 galaxies (14%).
Most of the types later than Sd are low luminosity galaxies concentrated in the
local supercluster where isolation is difficult to evaluate. The late-type
spiral majority of the sample spans a luminosity range M_B-corr = -18 to -22
mag. Few of the E/S0 population are more luminous than -21.0 marking an absence
of, an often sought, super L* merger (eg fossil elliptical) population. The
rarity of high luminosity systems results in a fainter derived M* for this
population compared to the spiral optical luminosity function (OLF). The E-S0
population is from 0.2 to 0.6 mag fainter depending how the sample is defined.
This marks the AMIGA sample as almost unique among samples that compare early
and late-type OLFs separately. In other samples, which always involve galaxies
in higher density environments, M*(E/S0) is almost always 0.3-0.5 mag brighter
than M*(S), presumably reflecting a stronger correlation between M* and
environmental density for early-type galaxies.


title:
Interferometric Measurements of Variable 340 GHz Linear Polarization in
  Sagittarius A*

abstract:
  Using the Submillimeter Array, we have made the first high angular resolution
measurements of the linear polarization of Sagittarius A* at submillimeter
wavelengths, and the first detection of intra-day variability in its linear
polarization. We detected linear polarization at 340 GHz (880um) at several
epochs. At the typical resolution of 1.4"x2.2", the expected contamination from
the surrounding (partially polarized) dust emission is negligible. We found
that both the polarization fraction and position angle are variable, with the
polarization fraction dropping from 8.5% to 2.3% over three days. This is the
first significant measurement of variability in the linear polarization
fraction in this source. We also found variability in the polarization and
total intensity within single nights, although the relationship between the two
is not clear from these data. The simultaneous 332 and 342 GHz position angles
are the same, setting a one-sigma rotation measure (RM) upper limit of 7x10^5
rad/m^2. From position angle variations and comparison of "quiescent" position
angles observed here and at 230 GHz we infer that the RM is a few times 10^5
rad/m^2, a factor of a few below our direct detection limit. A generalized
model of the RM produced in the accretion flow suggests that the accretion rate
at small radii must be low, below 10^{-6} to 10^{-7} M_{sun}/year depending on
the radial density and temperature profiles, but in all cases below the gas
capture rate inferred from X-ray observations.


title:
FRII sources at z>0.5: X-ray properties of the core and extended
  emission

abstract:
  Active galaxies are the most powerful engines in the Universe for converting
gravitational energy into radiation, and their study at all epochs of evolution
is therefore important. Powerful radio-loud quasars and radio galaxies have the
added advantage that, since their radio jets need X-ray-emitting gas as a
medium in which to propagate, the sources can be used as cosmological probes to
trace significant atmospheres at high redshift. The radio emission can be used
as a measure of source orientation, and sensitive X-ray measurements,
especially when used in combination with multi-wavelength data, can be used to
derive important results on the physical structures on a range of sizes from
the cores to the large-scale components. In this paper we present new results
on a significant sample of powerful radio galaxies and quasars at z > 0.5,
drawn from the 3CRR catalogue and selected to sample a full range of source
orientation. Using high-quality observations from XMM-Newton and Chandra, we
discuss the X-ray properties of the cores, jets, lobes and cluster gas, and,
through the incorporation of multi-wavelength data, draw conclusions about the
nature of the emission from the different components.


title: Gravitational Structure Formation

abstract:
  We discuss the formation of the first structures in gravitational N-body
simulations. The role of two-body interaction is found to be a crucial element
and an analogy with the dynamics of the Coulomb lattice, well-studied in solid
state physics, is discussed.


title:
The VIMOS-VLT Deep Survey - The evolution of galaxy clustering per
  spectral type to z~1.5

abstract:
  We measure the evolution of clustering for galaxies with different spectral
types from 6495 galaxies with 17.5<=I_AB<=24 and measured spectroscopic
redshift in the first epoch VIMOS-VLT Deep Survey. We classify our sample into
4 classes, based on the fit of well-defined galaxy spectral energy
distributions on observed multi-color data. We measure the projected function
wp(rp) and estimate the best-fit parameters for a power-law real-space
correlation function. We find the clustering of early-spectral-type galaxies to
be markedly stronger than that of late-type galaxies at all redshifts up to
z<=1.2. At z~0.8, early-type galaxies display a correlation length
r_0=4.8+/-0.9h^{-1}Mpc, while late types have r_0=2.5+/-0.4h^{-1}Mpc. The
clustering of these objects increases up to r_0=3.42+/-0.7h^{-1}Mpc for z~1.4.
The relative bias between early- and late-type galaxies within our
magnitude-limited survey remains approximately constant with b~1.7-1.8 from
z~=0.2 up to z~=1, with indications for a decrease at z>1.2, due to the growth
in clustering of the star-forming population. We find similar results when
splitting the sample into `red' and `blue' galaxies using the observed color
bi-modality. When compared to the expected linear growth of mass fluctuations,
a natural interpretation of these observations is that: (a) the assembly of
massive early type galaxies is already mostly complete in the densest dark
matter halos at z~=1; (b) luminous late-type galaxies are located in
higher-density, more clustered regions of the Universe at z~=1.5 than at
present, indicating that star formation activity is progressively increasing,
going back in time, in the higher-density peaks that today are mostly dominated
by old galaxies.


title: Dust and Gas Debris Around Main Sequence Stars

abstract:
  Debris disks are dusty, gas-poor disks around main sequence stars (Backman &
Paresce 1993; Lagrange, Backman & Artymowicz 2000; Zuckerman 2001).
Micron-sized dust grains are inferred to exist in these systems from
measurements of their thermal emission at infrared through millimeter
wavelengths. The estimated lifetimes for circumstellar dust grains due to
sublimation, radiation and corpuscular stellar wind effects are typically
significantly smaller than the estimated ages for the stellar systems,
suggesting that the grains are replenished from a reservoir, such as
sublimation of comets or collisions between parent bodies. Since the color
temperature for the excess emission is typically Tgr ~ 110 - 120 K, similar to
that expected for small grains in the Kuiper Belt, these objects are believe to
be generated by collisions between parent bodies analogous to Kuiper Belt
objects in our solar system; however, a handful of systems possess warm dust,
with Tgr > 300 K, at temperatures similar to the terrestrial planets. We
describe the physical characteristics of debris disks, the processes that
remove dust from disks, and the evidence for the presence of planets in debris
disks. We also summarize observations of infalling comets toward beta Pictoris
and measurements of bulk gas in debris disks.


title:
Thick fireballs and the steep decay in the early X-ray afterglow of
  gamma-ray bursts

abstract:
  We study the early afterglows of gamma-ray bursts produced by geometrically
thick fireballs, following the development of the external shock as energy is
continually supplied to the shocked material. We study the dependence of the
early afterglow slope on the luminosity history of the central engine. The
resulting light curves are modeled with power-law functions and the importance
of a correct choice of the reference time t_0 is investigated. We find that
deviations from a simple power-law are observed only if a large majority of the
energy is released at late times. The light curve in this case can be described
as a simple power-law if the reference time is set to be close to the end of
the burst. We applied our analysis to the cases of GRB 050219a and GRB 050315.
We show that the early steep decay of the afterglow cannot result from the
interaction of the fireball with the ambient medium. We conclude that the early
X-ray afterglow emission is associated with the prompt phase and we derive
limits on the radius at which the prompt radiation is produced.


title:
Candidate Isolated Neutron Stars and Other Optically Blank X-ray Fields
  Identified from the ROSAT All-Sky and Sloan Digital Sky Surveys

abstract:
  Only seven radio-quiet isolated neutron stars (INSs) emitting thermal X rays
are known, a sample that has yet to definitively address such fundamental
issues as the equation of state of degenerate neutron matter. We describe a
selection algorithm based on a cross-correlation of the ROSAT All-Sky Survey
(RASS) and the Sloan Digital Sky Survey (SDSS) that identifies X-ray error
circles devoid of plausible optical counterparts to the SDSS g~22 magnitudes
limit. We quantitatively characterize these error circles as optically blank;
they may host INSs or other similarly exotic X-ray sources such as radio-quiet
BL Lacs, obscured AGN, etc. Our search is an order of magnitude more selective
than previous searches for optically blank RASS error circles, and excludes the
99.9% of error circles that contain more common X-ray-emitting subclasses. We
find 11 candidates, nine of which are new. While our search is designed to find
the best INS candidates and not to produce a complete list of INSs in the RASS,
it is reassuring that our number of candidates is consistent with predictions
from INS population models. Further X-ray observations will obtain pinpoint
positions and determine whether these sources are entirely optically blank at
g~22, supporting the presence of likely isolated neutron stars and perhaps
enabling detailed follow-up studies of neutron star physics.


title: Troubles for observing the inflaton potential

abstract:
  Robustness of the solutions to the inflaton potential inverse problem based
on the slow-roll approximation is addressed. With that aim it is introduced a
measure of the difference of the outputs obtained using first and second order
respectively in the horizon-flow expansion. The evolution of this measure is
determined by a second order linear non-autonomous non-homogeneous differential
equation. Boundedness of the general solutions to this equation is analyzed. It
is shown that they diverge for most of the physically meaningful cases.
Examples for typical inflationary models are presented. It is argued that this
lack of robustness is due to the limitations of the slow-roll expansion for
probing the scale-dependence of the inflationary spectra.


title: A Class of Exact Solution to the Blandford-Znajek Process

abstract:
  We analyze the constraint equation giving allowed solutions describing fields
and currents in a force-free magnetosphere around a rotating black hole.
Utilizing the divergence properties of the energy and angular-momentum fluxes
for physically allowed solutions, we conclude that poloidal surfaces are
independent of the radial coordinate for large values of $r$. Using this fact
and the Znajek regularity condition, we explicitly derive all possible exact
solutions admitted by the constraint equation for $r$ independent poloidal
surfaces, which are given in terms of the electromagnetic angular velocity
function $\Omega = 1/a\sin^2\theta$, where $a$ is the angular momentum per unit
mass of the black hole.


title:
Gamma-Ray Burst Synthetic Spectra from Collisionless Shock PIC
  Simulations

abstract:
  The radiation from afterglows of gamma-ray bursts is generated in the
collisionless plasma shock interface between a relativistic outflow and a
quiescent circum-burst medium. The two main ingredients responsible for the
radiation are high-energy, non-thermal electrons and a strong magnetic field.
In this Letter we present, for the first time, synthetic spectra extracted
directly from first principles particle-in-cell simulations of relativist
collisionless plasma shocks. The spectra are generated by a numerical Fourier
transformation of the electrical far-field from each of a large number of
particles, sampled directly from the particle-in-cell simulations. Both the
electromagnetic field and the non-thermal particle acceleration are
self-consistent products of the Weibel two-stream instability. We find that the
radiation spectrum from a $\Gamma=15$ shock simulation show great resemblance
with observed GRB spectra -- we compare specifically with that of GRB000301C.


title:
ISM gas removal from starburst galxies and the premature death of star
  clusters

abstract:
  Recent observational studies of the age distribution of star clusters in
nearby merging galaxies and starburst (SB) galaxies indicate a premature death
of the young clusters. The fate of an evolving star cluster crucially depends
of its gas content. This behaves like a glue that helps to keep the star system
gravitationally bound. In SB systems where the rate of supernovae (SNe)
explosions is elevated one should expect an efficient heating of the gas and
its complete removal which could then favor the rapid dissociation of the
evolving star clusters. Based on a contemporaneous study of the dynamical
evolution of the interstellar gas in SB environments (Melioli & de Gouveia Dal
Pino 2004) where it has been considered also the presence of dense clouds that
may inhibit the heating efficiency of the interstellar gas by the SNe, we have
here computed the timescales for gas removal from young clusters embedded in
these systems and found that they are consistent with the very short timescales
for cluster dissolution which are inferred from the observational studies
above. Our results indicate that typical SB proto-clusters should start to
disperse after less than 5 Myr. For a given total gas mass content, this result
is nearly insensitive to the initial star formation efficiency.


title:
The Fastest Relativistic Jets: VLBA Observations of Blazars with
  Apparent Speeds Exceeding 25c

abstract:
  We have measured peak apparent speeds of 25.6 +/- 7.0c, 25.6 +/- 4.4c, and
28.2 +/- 6.6c in the jets of 0235+164, 0827+243, and 1406-076, respectively,
based on six epochs of high-sensitivity VLBA observations at 22 and 43 GHz
during 2002 and 2003 (H_{0}=71 km/(s Mpc), Omega_{m}=0.27, and
Omega_{Lambda}=0.73). These blazars had been identified as potentially having
apparent speeds exceeding 40c in an earlier VLBA survey of EGRET blazars by
Jorstad et al. We therefore confirm (with high confidence in 0827+243, and
lower confidence in 0235+164 and 1406-076) the presence of highly relativistic
pattern speeds in these three jets, although not at the >40c levels reported by
Jorstad et al. The lower limit to the bulk Lorentz factor implied by the
observed apparent speeds is Gamma>25-30 in these three sources, if the pattern
speeds are equal to or slower than the bulk flow speed.


title:
An Atlas of H-alpha and R Images and Radial Profiles of 29 Bright
  Isolated Spiral Galaxies

abstract:
  Narrow-band H-alpha+[NII] and broadband R images and surface photometry are
presented for a sample of 29 bright (M_B < -18) isolated S0-Scd galaxies within
a distance of 48 Mpc. These galaxies are among the most isolated nearby spiral
galaxies of their Hubble classifications as determined from the Nearby Galaxies
Catalog (Tully 1987a).


title: Mapping the large-scale anisotropy in the WMAP data

abstract:
  Analyses of recent cosmic microwave background (CMB) observations have
provided increasing indications for the existence of large scale anisotropy in
the universe. Given the far reaching consequences of such an anisotropy for our
understanding of the universe, it is important to employ alternative indicators
in order to determine whether the reported anisotropy is cosmological in
origin, and if so extract further information that may be helpful for
identifying its causes. Here we propose a new directional indicator, based on
angular-separation histograms of pairs of pixels with similar temperatures in
the CMB map, which provides a measure of departure from statistical isotropy.
The main advantage of this indicator is that it can be used to generate a sky
map of large-scale anisotropies in the CMB temperature map, thus allowing a
possible additional window into their causes. Using this indicator, we find a
statistically significant (at 95% CL) preferred direction in the CMB data and
discuss how it compares with other such axes recently reported. We also show
that our findings are robust with respect to both the details of the method
used, and the choice of the WMAP CMB maps employed, including the three-year
CMB data released recently.